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Harmonics - Science topic

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Can we do harmonic balance simulation in CST schematic or do we have to transfer the model to ADS for that purpose for non-linear analysis? Whats the way of doing that? I need to perform power sweep simulations for FSS.
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You can do that.
New task, spectral lines. Here we go
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Do harmonics exist in DC Microgrids? What are the sources?
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Harmonics are of ac fundamental, though in DC switching harmonics would exists for short time depending on time constant (T)of circuit….
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Hi everyone,
I have a very naive question. Can we consider a Fabry-Perot cavity/resonator as a High harmonics generator, since it exhibits an infinite number of both odd and even harmonics ?. Sincerely.
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I don‘t think that is how I would look at it. Specifically you use the word “generator“. The cavity supports a wide range of harmonic resonant frequencies, but, by itself, it won’t take one frequency and couple it into lots of others nor will it spontaneously generate all of its frequencies. Now you may place something within the cavity that generates a range of harmonic frequencies (laser gain) or couples one frequency into one or more other frequencies (nonlinear material). In those cases the cavity will determine which frequencies survive and which don’t. However by itself the etelon will not generate the harmonic frequencies. Think of it more as a filter, it permits some frequencies while disallowing others. But it doesn’t couple the frequencies together resulting in mixing nor does it spontaneously generate them.
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There was observed a temperature hysteresis of a resistance of gas sensing thin PdO films received by thermal oxidation and used in regime of long time (5 min) harmonic temperature modulation when minimum resistance takes place after passing the maximum temperature. There were observed also loops in the resistance temperature behavior in the presence of ozon which are more distinctive the greater O3-concentration.
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There is an assumption that such hysteresis is a manifestation of the topological properties of the material which some scientists consider as a topological semimetal.
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For example, in developing countries, having national standards aligned with international requirements accelerates the process of joining the World Trade Organization.
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The peculiarities of domestic context and problems may not call for a unified frameworks for resolution
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What are the most effective methods to measure and calculate the harmonic contribution from both the utility and the customers at the PCC? Which methods are commonly used in industries and power systems, and could you suggest useful references on this topic?
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Post-installation harmonic compliance assessments are crucial to ensuring that electrical systems remain within harmonic limits specified by standards (e.g. IEEE 519, IEC 61000-3-6).
1. The Recent methods for post-installation harmonic compliance assessment are Real-Time Monitoring and Continuous Assessment; DSP techniques like Fourier Transform, Wavelet Transform, and Hilbert Transform; Modern power quality analyzers can perform harmonic analysis in real time, measuring voltage and current distortions; and Machine learning algorithms.
2. The general formula used in harmonic compliance assessment) includes the calculation of Total Harmonic Distortion (THD) and individual harmonic contributions, focusing on voltage and current limits.
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I am studying the representation of atomic environments in disordered materials and am particularly interested in how the atomic neighbor density function can be expressed in terms of spherical harmonics. I understand that this approach is important for analyzing the angular characteristics of atomic arrangements.
Could someone explain how to derive the atomic neighbor density equation in terms of spherical harmonics, including any relevant mathematical formulations or concepts that are typically involved in this derivation?
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Dear Prof. Ashwani Kushwaha
Please, you can try to look at the following classical monograph:
Models of disorder: the theoretical physics of homogeneously disordered systems by Prof. J. M. Ziman, 1979. Cambridge University Press.
Best Regards.
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I am designing a high frequency filter using a loop resonator, one of the main goals is to achieve a reflection loss (S11) of -20db in a bandwidth of at least 500Mhz around 13.5 Ghz.
I used CST studio suite to simulate and design the filter, I used a frequency window of 0 - 20 Ghz at first, and achieved the desired filter (picture 1). I tried to simulate the same filter using a window of 0 - 30 Ghz(picture 2) and observed a harmonic at 27 Ghz, which is natural, but the first peak is now reduced to only -11db, the goal is not achieved. the question is, why is my first peak affected when I only changed the the frequency window ? which one of the two simulations would match measurements in case of a real produced and measured filter ?
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Youssef Hassab can you share the solution ?
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The Fast Wave package I developed for calculating the time-independent wave function of a Quantum Harmonic Oscillator now includes a new module for arbitrary precision wave function calculations. This module retains the functionality of the original but utilizes Python’s mpmath (https://mpmath.org/) package to control precision. Check it out: https://github.com/fobos123deimos/fast-wave/tree/main/src/fast_wave
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Adding new modules to your Fast Wave package can further enhance its functionality and usability. Here are some ideas for new modules you could consider:
1. Visualization Module
  • Purpose: Create plots of wave functions and probability densities.
  • Libraries: Use matplotlib or plotly for 2D and 3D visualizations.
  • Functionality: Allow users to visualize wave functions at different quantum numbers or precision levels.
2. Numerical Integration Module
  • Purpose: Provide tools for numerical integration of wave functions.
  • Libraries: Utilize scipy.integrate for accurate integration methods.
  • Functionality: Implement methods for integrating over various domains and handling boundary conditions.
3. Quantum Number Analysis
  • Purpose: Analyze and provide statistical information about quantum numbers.
  • Libraries: Use numpy and pandas for data analysis.
  • Functionality: Compute statistics and distributions of quantum numbers and their impact on wave functions.
4. Interaction with Other Potential Models
  • Purpose: Extend functionality to include other quantum models (e.g., potential wells, barriers).
  • Libraries: Depending on the model, you may use numpy, scipy, or custom implementations.
  • Functionality: Allow users to calculate wave functions for various potential models beyond the harmonic oscillator.
5. Parallel Computing Module
  • Purpose: Enhance performance for large-scale calculations by leveraging parallel computing.
  • Libraries: Use joblib, multiprocessing, or dask.
  • Functionality: Implement parallel computation for wave function calculations to handle large datasets more efficiently.
6. Unit Testing and Validation
  • Purpose: Ensure the accuracy and reliability of calculations.
  • Libraries: Use unittest or pytest for testing.
  • Functionality: Include a suite of test cases to validate the functionality and precision of the new module.
7. User Interface (UI) Module
  • Purpose: Provide a graphical or web-based interface for easier interaction with the package.
  • Libraries: Use tkinter for desktop applications or Flask/Django for web applications.
  • Functionality: Allow users to interact with the package through a user-friendly interface, enabling easier configuration and visualization.
8. Documentation and Tutorials
  • Purpose: Improve user guidance and support.
  • Libraries: Use Sphinx or MkDocs for generating documentation.
  • Functionality: Include comprehensive documentation and tutorials to help users understand and utilize the new module effectively.
Adding these modules can make your Fast Wave package more versatile and user-friendly, expanding its applications and improving the overall user experience.
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The delicate balance between competing demands for water resources remains a formidable challenge in the pursuit of sustainability. Engage with us as we navigate the complexities of water allocation, exploring strategies to harmonize the needs of agriculture, industry, and domestic consumption while ensuring the long-term resilience of our water systems—remains an indispensable academic inquiry.
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This seems to duplicate another ResearchGate site: see Jamel Chahed site on water. It is certainly an important issue, but does duplication help?
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Discussion:
This discussion explores the inherent limitations of the Lorentz transformation, a cornerstone of special relativity, particularly concerning its treatment of acceleration. While the Lorentz transformation adeptly describes relativistic effects such as time dilation, length contraction, and mass increase, it falls short in directly accommodating acceleration. This discrepancy becomes pronounced when the velocity-dependent Lorentz transformation fails to reconcile velocities between rest and inertial frames without the presence of acceleration, thus highlighting a significant gap in its applicability.
The discussion delves into the historical context of the Lorentz transformation, acknowledging its development by Mr. Lorentz and its status as a final form in science. However, it also underscores the expectation for accurate physics within its framework, especially considering the pre-existence of the concept of acceleration predating Mr. Lorentz. This expectation includes honouring Isaac Newton's second law, which governs the dynamics of accelerated motion in classical mechanics.
While the scientific community initially accepted the Lorentz transformation without questioning its treatment of acceleration, there is now a growing recognition of the importance of integrating principles from classical mechanics, such as Newton's second law, to address these limitations. The discussion emphasizes the need for a more comprehensive theoretical framework that harmonizes the principles of classical mechanics and relativity, thereby offering a more unified and accurate depiction of physical phenomena.
The Impact of Acceleration on Kinetic Energy in the Relativistic Lorentz Factor in Motion?
The Lorentz factor (γ) becomes relevant when the object attains its desired velocity and is in motion relative to the observer. Initially, when both reference frames are at rest, the object's energetic state reflects its lack of motion, resulting in zero kinetic energy (KE). As the frames separate, the moving object undergoes acceleration until it reaches its desired velocity. At this stage, the object's energetic state reflects its motion, and it possesses kinetic energy (KE) due to its acceleration. This acceleration is not accounted for in the Lorentz factor (γ). Once the object reaches its desired velocity, its energetic state reflects its motion, and it possesses kinetic energy (KE) due to its velocity. The Lorentz factor (γ) and kinetic energy (KE) play significant roles in relativistic motion. However, the acceleration component is not considered in the Lorentz factor (γ).
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The subject of discussion is really interesting. However, the author should have formulated his initial positions in an acceptable form - not so vague, but in generally accepted terms and comparisons.
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The harmonic mean $<x>$ of two positive numbers $x_1$ and $x_2$ can
be written as a weighted average $<x>=w_1 x_1+w_2 x_2$ where the
weights are $w_1=x_2/(x_1+x_2)$ and $w_2=x_1/(x_1+x_2)$. As such is
very responsible and respectful of different opinions. Can this
property be extended to more than two numbers?
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Dear Prof. Germano
You ask for the Ref. , which uses harmonic average in transition modeling. An Algebraic LCTM Model for Laminar–Turbulent Transition
Prediction by Menter et al.: Journal: Flow, Turbulence and Combustion
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The sustainability of the accounting profession is starting to be questioned. Will it still exist, or will it be replaced by technology ???
This chapter will provide a literature review on the relationship between accounting and artificial intelligence and harmonize them to maintain the sustainability of the accounting profession in Indonesia.
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The accounting profession is indeed facing significant transformations due to technological advancements, particularly with the rise of automation and AI-driven tools. However, while technology can streamline certain tasks, the role of accountants is unlikely to be fully replaced. Instead, accountants may need to adapt their skill sets to leverage technology effectively, focusing more on strategic analysis, advisory services, and complex decision-making. So, rather than being replaced, the profession is likely to evolve to incorporate AI as a complementary tool.
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After harmonizing and making all the radiometric corrections, I still get that Landsat 8 shows a wrong increase in vegetation intensity. Anybody with a similar problem that may have found a solution?
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Yes, Landsat 5 and Landsat 8 data are generally compatible with each other. Both satellites are part of the Landsat program and have similar imaging capabilities, although there are some differences in sensor characteristics and data processing methods. While Landsat 5 was operational until 2013 and used the Thematic Mapper (TM) sensor, Landsat 8, launched in 2013, carries the Operational Land Imager (OLI) sensor. Despite these differences, efforts are made to ensure data continuity and compatibility between different Landsat missions, allowing for consistent analysis and comparison of imagery collected over time. However, it's always a good practice to verify compatibility based on specific analysis requirements and any potential differences in data characteristics.
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I'm performing VPT2 calculations in a reaction mechanism to calculate rate coefficients by SCTST theory and perceived that some species presented unexpected negative frequencies after the VPT2 calculation. This was observed for transition structures and reactive intermediates bound by hydrogen bonds or other weak interactions. The example below shows my problem:
Fundamental Bands
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Mode(n) Status E(harm) E(anharm) Aa(x) Ba(y) Ca(z)
1(1) active 3763.110 3598.689 3.057697 0.123142 0.122807
H 2(1) active 2586.244 2577.498 3.060523 0.122682 0.122379
H 3(1) active 2585.777 2554.772 3.063117 0.122701 0.122411
4(1) active 2557.751 2524.031 3.054464 0.122649 0.122352
5(1) active 2418.710 2039.750 3.069775 0.120913 0.120608
6(1) active 1158.445 1122.073 3.141484 0.122739 0.122411
7(1) active 1150.289 1085.902 3.123672 0.122768 0.122499
8(1) active 1008.896 966.784 3.033002 0.122639 0.122347
H 9(1) active 1007.937 958.193 3.030136 0.122625 0.122394
10(1) active 992.893 899.923 3.068002 0.122841 0.122468
11(1) active 305.153 200.472 3.874636 0.122220 0.121213
12(1) active 277.188 187.185 2.355992 0.122516 0.123005
13(1) active 159.127 -393.075 3.079803 0.118279 0.117974
14(1) active 139.159 -112.063 3.112331 0.124439 0.124194
15(1) active 136.961 -99.655 3.098757 0.124517 0.124199
It is possible to see that the 13-14 modes are negative after the VPT2 procedure, while the harmonic frequencies are all positive. I have read that if the perturbation magnitude is higher than the harmonic frequency, and presents a negative value, it can result in a negative frequency. However, I don't know how to improve the calculation to avoid this error.
I'm will be very grateful if anyone has a clue about this issue or helps me to correct my calculations.
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@Keshav I think you miss his point slightly. The harmonic frequencies are positive, therefore we are at a minimum.
It is true that the VPT2 method can give negative frequencies. This happens as the anharmonic correction is far too large. In other words - our 0th order guess of a harmonic oscillator is crap for some modes. It is especially the low frequency-modes that are very sensitive to this issue.
You can select which modes to treat anharmonically by 'selectanharmonic' keyword. By not choosing the modes that are troublesome they are only treated harmonically and therefore should prevent negative frequencies.
Bear in mind that the 1 or 2 modes that turns out negative might not be the problem. Maybe it's actually another mode coupling to these that are the problem so you have to make some guestimates of which modes to include and which modes to leave out of the VPT2 treatment.
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hi,
I need a practical calculation and design for designing passive harmonic filter inductors.
and the information about core sizing and considerations for 3-phase system.
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Two books I found very good for inductor/transformer design and core selections are written by C. W. Mclyman:
1. Mclyman, C. W. M. T. (2004). Transformer and Inductor Design Handbook, (Third Edition) Marcel Dekker, Inc, 5(3)-5(20)
2. T. Mclyman, C. W. (1997). Magnetic Core Selection for Transformers and Inductors A User’s Guide to Practice and Specification (Second Edition). Taylor & Francis Group, 69, 93.
3. In my M.S thesis project, I worked on transformer design, and the thesis book titled, "Design, Analysis, and Simulation of an Isolated High Voltage DC Power Supply Based on Modular Converter and Cockcroft-Walton Voltage Multiplier Topology" is available in research gate. Although it is about transformer, many calculation shown on the book are also applicable for inductor design. Step by Step calculation for magnetic design is given there.
4. Sometimes, you will find application note, data sheet, core selection chart from the website of the magnetic core manufacture like FERROXCUBE, TDK. Those documents may also become helpful.
Hope these resources/ references will help. Best of luck.
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Does anyone have access to any of these articles? I have already tried to contact some of the authors, but without success. I don´t speak Mandarin so is very difficult with CNKI where they are available through payment. I can not understand even the payment method or if I would have access from Brazil. Thanks in advance for any help.
P.S. Even with google translator it was impossible understand the database.
1. DC Bias and Saturation Protection of Converter Transformer
WEN Ji-feng,ZHANG Xiao-yu,CHENG Xiao,XIONG Hui,LI Hai-ying,CHEN Song-lin(Nanjing NARI-relays Electric Co.Ltd.,Nanjing 211102,China)
This paper analyzes main causes of DC bias of converter transformer,and summarizes electrical characteristics of exciting current during DC bias of converter transformer and the mechanism of DC bias leading to damage of converter transformer.In addition,the principle of saturation protection of converter transformer and the implement method of the protection are introduced.Finally,points for attention in the engineering application of overexcitation protection of converter transformer are discussed.
2. Analysis on maintenance and operation of earth electrode shared by some HVDC systems
Lei X.,China Electric Power Research Institute | Li X.,China Electric Power Research Institute | Lin S.,China Electric Power Research Institute | Sun X.,China Electric Power Research Institute | And 4 more authors.
Dianwang Jishu/Power System Technology | Year: 2015
There are many inconveniences of maintenance and operation for HVDC systems with sharing earth electrode. When earth electrode line maintenance is implementing, personal security may be at risk because of DC current flowing through earth electrode line. As an example of sharing earth electrode of two HVDC systems, DC current distributions of earth electrode line and effect factors were analyzed according theoretical analysis and the actual project parameters. And operation suggestions of HVDC systems were proposed during earth electrode line maintenance. The results show that DC current distributions of earth electrode line are mainly affected by earth electrode resistance, earth electrode line resistance, maintenance grounding location and soil conditions. Besides, DC bias of converter transformers may be affected by DC current from earth electrode line, in serious condition, HVDC systems are blocked because of saturation protection action of converter transformer. © 2015, Power System Technology Press. All right reserved.
3. Analysis on the Transformer Saturation Protection in Fengxian Converter Station
LI Yueting,HAO Yuedong,LI Tengliang(Shanghai Management Office,Grid Operation Branch of State Grid Corporation of China,Shanghai 201413,China)
Fengxian Station is the receiving end of ± 800 kV Xiangjiaba–Shanghai UHVDC transmission project,and the transformer DC saturation protection(TSP) in the station has alarmed and even triped under the unbalanced operation mode while the transformer was charged.This paper introduces the operation principle of TSP,and analyzes its action logic and the rationality of its settings,and then discusses the cause of leading to TSP maloperation and related solution for the manufacturer.
4. The Influence of DC Bias and Harmonic on Sympathetic Inrush of Converter Transformer
Lingfeng Xia;Xiangfei Sun;Junwei He;Jianping Zhou;Kunming University of Science and Technology;
Compared with common transformer, converter transformer shows some differences from the perspectives of DC bias and harmonic and so on, which has significant influences on sympathetic inrush. There are few researches about that. Therefore, taking the characteristics of converter transformer as the starting point, this thesis analyzes the influence of DC bias and harmonic on sympathetic inrush of converter transformer. Emulation proof is processed with utilization of PSCAD/EMTDC and MATLAB. It's found by study that the influences of DC bias on sympathetic inrush mainly depend on its relationship with the direction of the magnetic linkage of transformer. Content of characteristic harmonic in sympathetic inrush is relatively high and the content of each subharmonic has linear correlation with the intensity of DC bias.
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Hello, Cheng Li . Could you please assist me in obtaining the listed articles? I appreciate it in advance.
1) Journal of the Chinese Society of Rare Earths. 2022(01) Page:24-37Core
A Review on Research of Rare Earths Separation and Purification TechnologyChinese Full TextEnglish Full Text (MT)
Zhang Wenjie;Tong Xiong;Xie Xian;Feng Dongxia;Du Yunpeng;Song Qiang;Faculty of Land and Resources Engineering,Kunming University of Science and Technology,Yunnan Province Engineering Research Center for Reutilization of Metal Tailings Resources;Yunnan Yuankuang Technology Development Co.,Ltd.;
2) Journal of the Chinese Society of Rare Earths. 2017(01) Page:1-8Core
Review and Recent Progresses on Theory of Countercurrent ExtractionChinese Full TextEnglish Full Text (MT)
Liao Chunsheng;Cheng Fuxiang;Wu Sheng;Yan Chunhua;China Minmetals (Beijing)Research Institute of RE Co.,Ltd;Beijing National Laboratory for Molecular Sciences,State Key Laboratory of Rare Earth Materials Chemistry and Applications,PKU-HKU Joint Lab on Rare Earth Materials and Bioinorganic Chemistry,Peking University;
3) Journal of the Chinese Society of Rare Earths. 2021(03) Page:490-503
Construction and Application of Design Theory for Hyperlink Extraction Separation ProcessChinese Full TextEnglish Full Text (MT)
Cheng Fuxiang;Wu Sheng;Liao Chunsheng;Yan Chunhua;China Minmetals (Beijing) Research Institute of RE Co., Ltd.;College of Chemistry and Molecular Engineering, Peking University, State Key Laboratory of Rare Earth Materials Chemistry and Applications, Beijing National Laboratory for Molecular Sciences;
4) Journal of the Chinese Society of Rare Earths. 2022(06) Page:909-919
Development of Countercurrent Extraction Theory and Technological Progress in Rare Earth Separation IndustryChinese Full TextEnglish Full Text (MT)
Liao Chunsheng;Cheng Fuxiang;Wu Sheng;Yan ChunHua;China Minmetals(Beijing)Research Institute of RE Co.,Ltd;College of Chemistry and Molecular Engineering of Peking University,State Key Laboratory of Rare Earth Materials Chemistry and Applications,Beijing National Laboratory for Molecular Sciences;
5) Journal of the Chinese Society of Rare Earths. 2018(03) Page:292-300
Countercurrent Extraction Theory: Process Design of Hyperlink Extraction Separation Ⅰ:Adjacent Stage Impurity Ratio of Countercurrent Extraction SeparationChinese Full Text
Cheng Fuxiang;Wu Sheng;Liao Chunsheng;Yan Chunhua;China Minmetals ( Beijing) Research Institute of RE Co.,Ltd.;State Key Laboratory of Rare Earth Materials Chemistry and Applications,PKU-HKU Joint Lab on Rare Earth Materials and Bioinorganic Chemistry,Peking University;
6) Journal of the Chinese Society of Rare Earths. 2023(03) Page:623-630
Simulation System of Mixer-Settlers in Rare Earth Extraction SeparationChinese Full TextEnglish Full Text (MT)
Chang Zhiduo;Wu Sheng;Cheng Fuxiang;Liao Chunsheng;Yan Chunhua;China Minmetals (Beijing) Research Institute of RE Co., Ltd.;China Rare Earth Group Co., Ltd.;College of Chemistry and Molecular Engineering,Peking University, State Key Laboratory of Rare Earth Materials Chemistry and Applications, Beijing National Laboratory for Molecular Sciences;
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If resonant frequencies were determined using Ansys modal, and the system is excited at those resonant frequencies with some force, it should vibrate with an increasing amplitude, do we have any way to get a graph of this increasing amplitude with time in Ansys harmonic?
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I think you need transient analysis you can check the videos and search about on this way
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Who else seeks to further harmonize the world while admitting that imperfections will always exist? How? Why?
How I recommend harmony:
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Individuals, organizations, and movements seeking global harmony while acknowledging imperfections often do so for reasons like global citizenship, humanitarian values, cultural exchange, environmental stewardship, peacebuilding, interfaith dialogue, social justice, and education. Despite recognizing flaws, these efforts aim to create positive change and understanding in the world.
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I am designing pseudo-Doppler direction finder and trying to observe Doppler shift, but I am not able to get it. My system consists of 4 antennas shifted by RF switch. Test signal is 433MHz CW.
4 receiving magnetic base monopole antennas are positioned on the disc with 25cm diameter. Switching frequency is 251kHz.
The issue that I unable to see doppler shift at all. As spectrogram shows 433MHz frequency spike isn't showing any shift and doesn't appear to move at all. As I zoom in even with way much smaller RBW no difference. I can see only switching frequency harmonics around my carrier.
As I understand I should see carrier moving around centre frequency as I switching the antennas.
Thank you for your help.
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I did not find the link you mentioned to be very helpful, so I went in search of original source materials. I first tried Wikipedia: https://en.wikipedia.org/wiki/Doppler_radio_direction_finding . Their explanation of how pseudo-Doppler DF worked was that the technique used phase differences. They also referenced a 1987 book [1], which also mentioned on p. 122 that the technique, pseudo-Doppler DF, was also called "sequential phase" DF. Chapter 9 of this book shows one how to actually build such a DF, and it mentions a number of pitfalls when trying to get such a circuit to work: 1) multipath (p. 136), and 2) grounding of the non-active antennas (the non-active antennas must float, electrically, if they are grounded they tend to reradiate the incoming signal, see p. 130).
[1] also referenced a 1981 article by David C. Cunningham on desining and building a pseudo-Doppler DF, see [2]. The article also mentioned that Cunningham had patented his design. I looked up his US patent (granted on Novmeber 5, 1985), US Patent No. 4,551,727, on the following URL: https://ppubs.uspto.gov/pubwebapp/static/pages/ppubsbasic.html To obtain a PDF of a US patent, simply enter the patent number, without its commas, in the "Quick lookup" field at the top of the page. Cunningham's patent cites the June 28, 1941 US patent, US Patent No. 2,414,798, by Horace T. Budenbom showing the rotating antenna DF - the word 'Doppler' was not used. The antenna at the edge of the rotating disk phase modulates the incoming signal. Cunningham's patent also cites the 1947 article discussing the square array of electronically commutated aerials [3], notice the title of this article.
[1] Joseph D. Moell, Thomas N. Curlee; Transmitter Hunting, Radio Direction Finding Simplified; TAB Books; 1987; see Chapter 9 Doppler DF Units, pp. 120-141; URL: https://archive.org/details/curlee-t.-n.-moell-j.-d.-transmitter-hunting-radio-direction-finding-simplified-1987-tab-books
[2] David Cunningham; DF Breakthrough!; 73 Magazine; Vol ...; No. ...; June 1981; pp. 32-46; URL: https://archive.org/details/73-magazine-1981-06
[3] C. W. Earp, R. M. Godfrey; Radio direction-finding by the cyclical differential measurement of phase; Journal of the Institution of Electrical Engineers, Part IIIA: Radiocommunication; Vol. 94; No. 15; March-April 1947; pp. 705-721.
Regards,
Thomas Cuff
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I am currently working on an air compressor unit. I have already done the simulation and testing for modal analysis on the compressor(static condition). Now I want to do a Harmonic response simulation using the imbalance in the rotor because until now I think that is the only parameter that will be causing a harmonic excitation force. but my question is how can I verify the simulation with testing.
Till now I have figured out I can do a vibration test on a running compressor and verify the results. but are there any other tests that I can do to verify the results from simulation?
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You could perform a transient vibration recording during the start (or shut-down) of the compressor until it reaches its nominal speed and visualise (waterfall display) the dominant harmonics (maybe the unbalance is not the predominant one?) and if they evolve smoothly with the square RPM (if they trigger some structural resonance you will see bumps in the waterfall)
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I have read 1 article and they said:
1. "frequency analysis calculations to be minima or transition states."
2. "using the gas phase ... harmonic frequencies."
What are those calculation in Gaussian software and what is the input code for those?
Thanks in advance.
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The keyword FREQ requires the calculation of frequencies in the harmonic approximation and FREQ=anharmonic in the anharmonic approximation. See details here https://gaussian.com/freq/
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We have implemented and installed a grid-connected PV inverter in two different locations. In the first location, it works well, but in the second location, the line voltage to the cubicle body increases and the inverter surge arrester burns. The earth resistance in both cases is below 1 ohm, which indicates that the earthing system is good. I know that high-frequency harmonics are generated by power electronic devices and can cause leakage currents and neutral-earth voltage, but I cannot find the difference between the two conditions. I would appreciate any suggestions you may have.
in the attached pic :
Yellow: line to cubicle body ( which is earthed)
Blue: line-to-line voltage
Green: inverter current
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Please check the surroundings. If the earth around inverter is having many installations with leakage currents the Ground potential itself increases.
Check system Ground/neutral voltage wrt Earth at both locations. This may give hint.
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Attached image shows plot of Fast fourier transform of ECG that had applied a lowpass filter to (15 Hz, zero-phase shift FIR with 24 dB/octave roll-off). The frequency bands increase in increments of 0.03125Hz from 0 to 15 Hz. HRV (< 0.4 Hz) and HR (~1.5 Hz) peaks are clear, but I'm unsure what the harmonics are specifically or their significance. I've found suggestions they are related to subtle variations in the PQRST waveform but find very little literature detailing their significance or meaning, besides a preprint Kotriwar, Y., Kachhara, S., Harikrishnan, K. P. & Ambika, G. Higher order spectral analysis of ECG signals. arXiv (2018) doi:10.48550/arxiv.1809.08451.
Any advice or further references related to these harmonics and their meaning would be greatly appreciated. Thanks
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Thanks Stephen, I see Patrick has done a lot on pulse wave so perhaps he has some info on ECG also and Ive messaged him.
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I have tried to find the discriminant for complex-valued harmonic polynomial by using the following options:
1. Real part of the equation=Imaginary part of the equation=Jacobian with respect to equation=0
2. Using singular method.
The problem is these two methods are too slow to compute the discriminant.
My question is can I have another option to compute the discriminant?
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Dear doctor
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On mixed polynomials of bidegree (n, 1)
Mohamed Elkadi and André Galligo
December 17, 2014
"Abstract Specifying the bidegrees (n, m) of mixed polynomials P(z, z¯) of the single complex variable z, with complex coefficients, allows to investigate interesting roots structures and counting; intermediate between complex and real algebra. Multivariate mixed polynomials appeared in recent papers dealing with Milnor fibrations, but in this paper we focus on the univariate case and m = 1, which is closely related to the important subject of harmonic maps. Here we adapt, to this setting, two algorithms of computer algebra: Vandermonde interpolation and a bissection-exclusion method for root isolation. Implemented in Maple, they are used to explore some interesting classes of examples."
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Hi
I did a Frequency analysis in Abaqus. And in next step i create a Modal dynamics to analyse a harmonic pressure which is function of position and time thereafter i used of DLOAD subroutine but my problem is TIME and KINC variables of DLOAD subroutine does not change never and TIME(1) and TIME(2) are equal to "Time increment" of step always and KINC is equal to 1.
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Mr. Sadri, I have met the same question, How did you solve your problem? Thanks
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I have a periodic signal of frequency Fs that is measured, sampled with frequency Fo. How is it possible to recover the shape of the Fs signal, especially if Fo and Fs or their harmonics are close to resonance conditions, when beats effect realized?
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Thank you,
Rana Hamza Shakil
and Mostak Ahamed for your proposals. I'd like to tell you that I know very well about interpolation. But please, read again my question. Interpolation works correctly for the case when frequencies of signal and its sampling are very different.
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I am calculating dynamic hyperpolarizability values for a set of organic derivatives using DFT. I want to plot harmonic light intensity as a function of polarization angle as reported by several authors. How can do this? Please help me.
Regards
Dr. Renjith R
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To plot harmonic light intensity as a function of the polarization angle Ψ by two-dimensional and polar representations, you can follow these steps:
  1. Define the intensity equation for the harmonic light. For example, if the electric field of the harmonic light is given by E = E0 cos(ωt), the intensity can be calculated as I = (1/2)ε0c|E|^2, where ε0 is the electric constant, c is the speed of light, and |E|^2 is the magnitude squared of the electric field.
  2. Write the intensity equation in terms of the polarization angle Ψ. The polarization angle is the angle between the polarization direction of the light and a reference axis. For example, if the polarization direction is along the x-axis, then Ψ = 0.
  3. Use trigonometric identities to express the intensity equation in terms of cos(Ψ) and sin(Ψ). For example, if the polarization direction is along an axis that makes an angle φ with the x-axis, then E = E0 cos(ωt - φ), and I = (1/2)ε0c|E|^2 = (1/2)ε0cE0^2 [cos^2(ωt - φ)].
  4. Plot the intensity as a function of the polarization angle Ψ using a two-dimensional representation. This can be done by plotting I as a function of cos(Ψ) or sin(Ψ), depending on the form of the intensity equation.
  5. Plot the intensity as a function of the polarization angle Ψ using a polar representation. This can be done by plotting I as a function of Ψ on a polar plot. The intensity values can be plotted as lines or as a color map, depending on the desired visualization.
Note that the specific details of the plotting method will depend on the software or programming language being used. However, the general approach outlined above should be applicable to most cases.
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In your experience, how has the alignment or misalignment between strategic thinking and organizational culture impacted an organization's ability to innovate, adapt, and achieve long-term success?
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alignment or misalignment between strategic thinking and organizational culture impacted an organization's ability to innovate, adapt, and achieve long-term success,
my opinion: this is relate to knowlegde management.
if an organization want to innovate, adapt an achieve long-term success, first the company need to be aligned the strategic thinking with organization culture.
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I should experimentally determine the second and third harmonic generation in quantum dot
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Thank you for your attention.
Yes I am exciting a GaAs quantum dot with light in visible ranges to study the spin-orbit interactions effects. I have studied theoretically. If I can investigate experimentally, I can compare their results. Unfortunately I don't have experimental information.
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Hello all:
I have a random signal whose time domain is from 0s to 0.01s. I hope to simplify this signal so that it has the following two characteristics:
1. a infinite time domain
2. a certain funtion which could express this signal
Therefore, I wonder if I could approximate the random signal to the superposition of harmonic signals.
Any information will be appreciated!
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From your description, I suppose you know the random signal value (denoted by r(t)) within the time interval from 0 to T=0.01 seconds, but don't know (or, do not care) the signal value outside this interval. In order to approximate this signal as a superposition of harmonic signals, you may try the following.
1) Define a signal s(t) which is equal to r(t) within the interval from 0 to T, but is zero outside this interval.
2) Define a signal x(t) which is a sum of s(t-kT), where k is integers from minus infinity to infinity.
In this way, x(t) is an infinitely long periodic signal with its value same as the random signal r(t) within the interval from 0 to T, and, it can be expressed as a superposition of harmonic signals since x(t) is periodic.
Hope it helps. Good luck.
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published paper on Studying and Mitigating the Effects of Harmonics in HVDC Transmission line Converter
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There are several ways to mitigate the harmonics on the HVDC converter station. However, the most common methods are:
1. Using AC harmonic filters. They create low-impedance paths to ground for specific harmonic frequencies which should be mitigated, and
2. Canceling out harmonics by using different converter configurations. Typically, 12 or 24 pulse bridges are deployed. 12 pulse bridge, for example, consists of two six-pulse bridges connected in series or parallel, with their AC connections supplied from a converter transformer that produces a 30° phase shift between the bridges.
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I want to calculate PECD spectra and in order to do so I require calculated electron density in terms of symmetry adopted spherical harmonic basis functions. How should I do that?
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thank you Divyansh Baranwal and Richard Lewis for your response. I will try these methods.
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what is your opinion about this question?
Thanks
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International treaties are binding on all parties who sign and ratify them since they are agreements between sovereign governments. Yet, depending on each nation's legal system, the process of integrating international treaties with national constitutions and laws may be complicated.
In general, there are two main ways in which international treaties can be harmonized with national constitutions and laws: through incorporation and transformation.
The process through which international treaties are immediately incorporated into domestic law is referred to as incorporation. Monist and dualist systems are both viable options for achieving this. International law is automatically absorbed into domestic law and has the same status as domestic law in monist systems. International law must be implemented through a different mechanism, such as parliamentary ratification or adoption by executive decree, in dualist regimes because it is distinct from domestic law.
Transformation refers to the process by which international treaties are translated into national law, often through the enactment of implementing legislation. This may involve adapting the content of the treaty to the legal system of the country, clarifying ambiguous provisions, and ensuring that the treaty is compatible with the country's constitution and other domestic laws.
The particular procedure for bringing international treaties into compliance with national constitutions and laws will vary depending on each nation's legal framework and the specific requirements of the relevant treaty. The relationship between international law and national law may occasionally be shaped by the courts in order to interpret and apply international treaties in domestic legal issues.
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Frequency synthesizers are quite expensive especially for double conversion RF systems. Maybe there are cheaper solutions instead of VCO that might be not such precise. A while ago I was analyzing one repeater that was using RS485 driver for LO. Maybe you have similar experience and can suggest something. For double conversion two individual frequency synthesizers are required or is there any solutions to utilise single one (using) it harmonics or something more exotic. Thank you in advance
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Thank you very much Joerg Fricke . Thats basically what I was searching for. If anybady have cheaper solution please feel free to share. Thank you in advance.
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How to calculate and design LCL filter for harmonic reduction in matlab simulink?
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Initially, we need to design the circuit components and draw the circuit. You may use any software like proteus for this purpose. Then, open the simulink in matlab and select the components as it is in your circuit design. The specifications also need to be given for each component. Finally, run the design to get output.
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Hi everyone,
I am trying to place Piezoelectric ceramic patch as strain sensor for substrate structural element. I am confused about the components of the conditioning circuit needed to measure voltage signal induced in the sensor due to harmonic mechanical strain affecting substrate structure . I would be so appreciated if any one illustrated this circuit to me with schematic drawing or pictures from lab setting.
Regards
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Why would you prefer a voltage amplifier? The output voltage depends on the total capacitance (incl. connecting cable), because voltage = charge/capacitance.
Of course you can do this, but it depends on the frequency you want to measure. The voltage amplifier must have the highest possible input resistance, which is usually achieved by a JFET or MOSFET input. This is because the voltage measurement has an additional disadvantage compared to the charge amplifier: The total capacitance C of the piezo and the cable, together with the input resistance R, form a high-pass filter with a time constant T=R*C.
This means that you can only measure frequencies that are significantly above (10x) the cut-off frequency.
You can find further explanations on my website:
or
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I'm working on a vibration combined simulation, and I need the different modes of vibration formulation, I've been using harmonic mode but I need further formulation like that.
Any recommendation is greatly appreciated.
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dear Matin,
don't trust formulas for modelizing the vibration of industrial structures! The reason relate to the fact that what matters are your assumptions on the "boundary conditions": formulas work perfectly for a beam in really free (or perfectly clamped) conditions, but you have nothing like that in reality...
So my recommendation is to start with EXPERIMENTAL modal analysis then try to learn how this behaviour can be approached by simple formulas if any. Then you can safer try to modelize other structures of similar construction... The same if you uses FEM. Stuctural dynamics remain an art more than a science!
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Standard tuning for guitar E A D G B E comes around frequently but the old lute tuning E A D G C F is rarely if ever used.
Looking at the gradients, standard tuning is 0 5 5 5 4 5 and the lute tuning is 0 5 5 5 5 5, so the strings in standard span two octaves 0 5 10 15 19 24, while the lute tuning 0 5 10 15 20 25 has one more note than standard.
Same number of points, different number of notes. That makes two different topologies, so we have a collection of guitar topologies that make a theory of guitar.
When guitar strings have one note in common, they have every note in common. Then the guitars have the same set of pitch values (since they can form a union in which every note sounds in tune) but two guitars may have a different number of notes. The notes may be located at different points on guitar.
The number of notes and the number of frets on the guitar is not critical to structure because the structure is basically the same the same with a few more or less but changing the tuning by just one note is critical because it completely changes utility of the structure.
So 0 5 5 5 4 5 is a very, very good number but 0 5 5 5 5 5 is bad number.
It is clear the lute tuning is not as rich as standard because the regularity of 0 5 5 5 5 5 means that the richness of harmonic structures is reduced. For instance, if a major chord moves across the guitar so the tonic falls on successively higher string sets, the structure of the chord in lute tuning does not change. Also, many chords are difficult to play in lute tuning, so a seventh chord is quite difficult to finger. In standard, moving an E chord to the next set of strings makes an A chord, then a D chord; Moving a G chord to higher strings gives a C chord, then F. So standard tuning has 6 different shapes for a major chord, where lute tuning has only one or two.
This shows the principle of least action acts on the guitar topology as a calculus. Action in stardard is far less constrained than lute tuning.
We have here only pitch values, strings, and frets so why isn't that triple a mathematic model?
Perhaps it is this: Mathematicians want to see mathematical proof. But we can hear when pitch is equal, when one pitch is greater or less than another, and when a pitch is multiplied by two.
We know when guitar are in tuning, but we must deduce when they have the same tuning. It would be relatively easy to distinguish guitar in standard and lute tuning, even if they play the same notes. The image of guitar music has the kernal of the tuning.
The topology of music is remarkable because only ordinary math is required to understand the added structure that makes harmony or guitar, but even a brief investigation leads to the realization that the mathematics of music is special and only applies to musical instruments.
I really can't understand why mathematicians and physics are not interested in music as a formal object of study. Doesn't it bug you when you can't understand an everyday object like guitar?
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I'm not sure exactly what your goal is here. My overview: if you know the tuning of the guitar (the absolute reference pitch of the lowest string and the intervals of the strings in standard tuning) you can determine the resulting pitches of any tablature depiction. I think most guitarists develop a schema or map of the neck that they learn to navigate to find specific notes and note combinations. Expert guitarists have a deeper understanding of the pitch space of the guitar neck than could be represented by tablature notation. Tablature is used primarily by guitarists who haven't developed that deeper understanding: it's a mechanical method to find particular sounds, it is not music notation in the strict sense of the word, it merely tells the player where to put their fingers, not the sounds that will be produced. Because there a single pitch can be found in several places on the neck, the topology of the guitar kind of "folds in on itself" in places, as opposed to a typical piano keyboard which is a simple low-to-high topology.
So, if you could clarify what your end goal is here, more useful comments could be made.
Referring to your final question: I think physicists and mathematicians ARE interested in music as an object, and I think musical instruments, like guitars, are objects of study. Read a few things: Hall, Donald E. Musical Acoustics, 3rd edition. Brooks/Cole, 2001; Partch, Harry, The Genesis of a Music, Da Capo Press; 2nd edition (August 22, 1979); and others for in depth explication of tuning and instrumentation. Partch is interesting because he created an intonation system and invented a whole set of instruments to play his music. You can find my masters thesis on Partch, 40 years old, here: https://www.academia.edu/84012831/Harry_Partch_And_on_the_Seventh_Day_Petals_Fell_on_Petaluma.
Anyway, perhaps I'm missing the point here. Please let me know how much I've missed the mark.
Matthew Nicholl
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I am working on a trend analysis of at-satellite temperatures (brightness temperature) using Landsat 5, 7 and 8 thermal bands. For the visual and infrared bands I used the sensor harmonization function proposed by Roy et al.
However, for the thermal bands no transformation coefficients were calculated. Is there the necessity to transform the thermal bands?
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From what I understand, yes, the infrared bands should still be harmonized. I had the same question and was unable to find any citations for how to do this. The most recent publication I found that mentions thermal harmonization says that this harmonization is "complicated" and leaves it at that. Harmonizing surface reflectance between Landsat-7 ETM + , Landsat-8 OLI, and Sentinel-2 MSI over China | SpringerLink
However, collection 2 level 2 data should have relatively minor errors when comparing between satellites. If the higest accuracy Landsat thermal data is required for something like a timeseries analysis, the best option is to use the ARD product provided by USGS. This dataset is (currently) only available for the United States with plans for a global release at an unspecified point in the future.
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I am aware of how fundamental frequency of bpf raises. but trying to understand physically causes to excite the harmonics of these fundamental.. this applicable to bearing harmonics, gear mesh harmonics, unbalance harmonics..
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Let me see if I understand your question. You state that you understand how the fundamental frequency, f0, of a BPF (Band Pass Filter?) increases. You then wonder how to physically explain how the fundamental frequency gives rise to harmonics due to excitation of the system. You also seem to imply that the system has many fundamental frequencies: "these fundamental [frequencies?]"; the word 'these' is the plural of the word 'this'. Do I understand your question correctly? If I have not paraphrased your quection correctly, would you, please, restate it in a different way.
Regards,
Thomas Cuff
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1) In utility-scale BESS, is there any minimum clearance requirement (outdoor) from one power conversion system (Inverter) to another PCS?
2) If two PCS requires to be connected on the LV side of one transformer (0.69/33 kV), are there any technical issues/limitations such as harmonic, voltage mismatch, etc?
It would be amazing to know your thoughts on that. Thanks in advance
#BESS
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Shaikat Debnath , I second the comments from Sacotte Michel
1) Clearance: more related to thermal dissipation than electrical requirements. If you have a 1MW PCS with 98% efficiency, that means 20kW of power dissipation. That is a lot of heat that you should get rid somehow. If you want a very compact solution, your are probably going for water cooling, on both PCS and transformer. From a practical perspective, safety regulations may require minimum clearances for escape routes, maintenance and so on.
2) Technical issues / limitations: there are certainly technical issues. If there is or not an active front end will influence how much reactive power is required and the size of the transformer. You may want to use one secondary for each PCS, preferably with different vector groups, so that commutations do not appear on the primary side concurrently. Transformers for converters must have their core and insulation oversized compared to regular utility transformers, and shielding between primary and secondary. Regarding harmonics, take a look at IEEE 519 or the limits imposed by the utility.
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i am working with spectral analyzer (35670a) with noise current amplifier (SR570), however, when i used to experiment about IGZO TFT's low frequency noise, i usually get a 60hz harmonic noise showed in picture.
i just wonder how to eliminate the 60Hz harmonic noise. Also, I will make an individual grounding box and conduct an experiment, but I wonder if this will be effective.
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60hz is the electronically service frequency in Korea.
if you change the AC to DC, eletonic noise we be loss.
AC to DC converter is well used in Car audio parts.
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For example, if I would like to calculate thermal conductivity of Si/Ge interface, and I have acquired the second order force constants of Si and Ge. But, How to mapping these force constants to construct dynamical matrix? Is there any code or other learning source?
I could not understand what the meaning of H_t,n or H_t,m is the regular harmonic matrix that links unit cells t and n(or m) because in my opinion, the harmonic matrix is separated for each single cell., how can it link unit cells?
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Is there any software or code can directly construct these dynamical matrix?
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I'm essentially looking at creating a 4 body harmonic potential where the stiffness constant can be represented as a stiffness matrix such as to allow for the direct dependency of one atom on the movement of all other atoms defined in the quartet.
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Just adding the answer myself since the resolution has been found. The best way is to make a new potential on LAMMPS.
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In the VIV process of a cylinder or a bridge, we can always find harmonic frequencies in the flow field. How does the harmonic frequency come into being and what does it mean? What does the harmonic frequencies represent and what effects can it bring?
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Harmonics are generated by nonlinearity via convolution theorem.
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Dear Researchers,
I am looking for methods to mesh a twisted blade in order to get more structure mesh.
I tried several mesh size yet the quality metric are a bit bad.
I am analyzing regarding the skewness and the orthogonal quality.
My objective will be performing modal and harmonic in order to determine the stress distribution adequate to the natural frequencies.
Thanks in advance for your advise.
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Mohammed Lamine Mekhalfia I didn't receive an email.
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Dear all,
I am trying to perform harmonic analysis with the forcing term which is not harmonic but periodic. I converted the forcing term to harmonic series of sine and cosine. Now the problem arises when I have to incorporate this force in ANSYS analysis.
Is there any way to input non harmonic forcing term, or the another way to input series of sine and cosine term ??
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I agree with Hiba Nadhim A. Al-Kaoaz . Harmonic response analysis simulates how a structure will respond to sinusoidally repeating dynamic loading. You can define load as a specific sin and cos function with domain and frequency to your model and harmonic analysis, but you should be done with modal analysis before that. Still, if you have a specific function for your forcing vibration, you can use it in the APDL program of your model.
regards;
Ehtisham
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I am currently working on my project of crack detection in cantilever beams using an Ansys, and I did modal analysis and harmonic response to find the natural frequencies and frequency response of the deformation.
I have found the maximum amplitude of all 6 modes and how does it really work in crack detection?
amplitude gets lower when frequencies get higher.?
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Nazanin Fallahi
Hi,
Thank you so much for your response and its so helpful.
I need to know about how it works with cracks detection?
absolutely the natural frequencies of the healthy and unhealthy varies.
also amplitude of the healthy and unhealthy varies as well. I need a clear idea about detection working?
it would be helpful if someone could clarifying this..
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I am trying to solve an isolator suspension problem in which a mass is suspended using 4 Nos of 3D springs(Isolators). I want to carryout response studies to find harmonic and random response on mass.
I tried using bushing element in ANSYS mechanical. Here in connections I have provided relevant stiffness and damping in matrix form for bushing elements.
Also overall damping ratio of 0.02 % is given as input under harmonic analysis tab.
Analysis shows that response is function only of harmonic damping ratio not one given in bushing element . Can anyone pls comment on this?
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Claudio Pedrazzi
How did you connect (RBE2 or RBE3) the bushing with the rectangular block? I guess that all DOFs of Node 4198 are suppressed. Am I right?
Where did you apply the harmonic load?
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hello everyone
i'm asking about any mathmatical methode that can calculate the(total harmonic distortion) for ramp function ?
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42.11
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Using Quantum espresso I was able to converge through SCF calculation for my structure. I have also optimized the geometry by vc-relax. Now I want to fit forcefield parameters for bond, angle, torsion, improper, non bonded Buckingham/coul potentials. How can I do so?
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The answer depends significantly upon which force field you intend to use. There is no unique definition of parameters like partial charges on atom types. Each force field's developers have adopted a strategy to provide consistent definitions within their own parameterization. Thus, one cannot copy a set of Amber parameters that you found somewhere and plug them into a Charmm calculation.
Generally, creating force field parameters is a lengthy, tedious process. Developers have also documented their processes. There are, alternatively, some more user-friendly, parameter-generating codes out there but I cannot speak to their veracity or accuracy. I always used the painful, tedious approach.
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Hello World,
I am trying to perform the modal analysis and harmonic response analysis for forced vibration in rotating cantilever beam through ANSYS. Is there any way to incorporate the rotational velocity and add Coriolis and centrifugal effect for the analysis?
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Hello Amrit Tiwari ,
You have not the possibility to insert a rotational velocity in the Harmonic Response, because this kind of analysis uses mode superposition in RESPONSE to a load. The rotational velocity has its effect on the modes of the structure, then the loads from Harmonic Response are "projected" onto the structures modes and the response is than rebuilt up form each mode response.
In the Harmonic response only periodic loads are accepted (a constant acceleration is considered a periodic load with 0 frequency, therefore it is acceptable).
I suggest to perform a static structural analysis and use the pre-stressed state as input to the modal analysis (see project schematic in the annexed archive .wbpz).
Warning: the prestressed structure must have results different from zero everywhere, otherwise, there will be no difference with respect to fixed beam.
See the different response with and without rotational velocity when the prestressed state is different from zero.
Last remark: when I toggle "Coriolis effect" to on, the prestressed solution is zero everywhere, therfore the rotational velocity is completely ineffective. I don't know why, this is unexpected.
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Hi there, I am running a targeted molecular dynamics job on NAMD and an error occurs, FATAL ERROR: Number of atoms in constraint constant PDB doesn't match coordinate PDB ,
in the procedure of minimization that I can't fix. it doesn't progress any further than making the "harmonic restraint" pdb. so, has any one ever encountered this error ?
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Dear Aria,
In addition to what Rezvan Marjani mentioned, You should check your equilibration.tcl script or if you're using simulation.tcl if it's not already messed up.
Alternatively, you should try and follow this tutorial. It will help you a lot.
Best regards
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I am trying to simulate harmonic dynamic loading applied on square machine foundation using ABAQUS. While doing experiment, I have used rotating mass type mechanical oscillator. The loading intensity of the same is dependent on the angular frequency(w), [F(t) = F_0.Sinwt = m_e.w^2.Sinwt]. In the numerical modeling, to apply the load on the footing I need to convert the load in terms of real and imaginary components. I am quite confused, how to do that. Can anyone explain, how to calculate the real and imaginary components of the dynamic load. I have mentioned the variation of force amplitude with the rotating frequency of the mechanical oscillator.
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Thank you Hassan Nasser for your answer.
I have earlier gone through the link that you have suggested. The page shows the procedures for the direct solution of steady state dynamics analysis. However, my concern is how to divide the force magnitude (amplitude vector) in terms of real and imaginary part. I am confused, how much load I should assign for the real part and how much for the imaginary part. Please see the image given. I have given the values in "CF3" since the dynamic load is acting Z direction.
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Hello all,
I want some recommendations for spectrometers of UV to near IR (230 nm to 900 nm), with High resolution, have a good price, can distinguish between second and third harmonic, and are easy to use.
Thank you.
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Avantes spectrometer is highly recomnded in terms of product price and benfits
you can perform easily spectral scanning.
If you are interested in photon counting and high resolution Andor is one posibility, but you should know your need for that.
Good luck,
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SNS is a feeding tube device provides babies supplemental feeding , it helps in inducing and maintaining lactation by triggering harmonal release. Any practical experience about the nursing system?
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There are photos of homemade supplementers in the WHO courses on breastfeeding.
If you are writing a paper or doing research take care with the term that you use, Supplementary nursing system (SNS) is a trademarked term for the Medela product. It is not a generic term.
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I have been trying to get a sub synchronous resonance scenario in the "Wind Farm - Detailed DFIG Model (available on mathworks website)" in Simulink as a part of my project. For that I have to identify the possible frequencies where the harmonics can occur. To identify these, an impedance scan/frequency sweep of the wind farm is required to understand. I have been trying to get give input perturbations to source voltage, measuring the ouput changes at windfarm terminals and then using script to calculate the Fourier Transform. But the results are not ok as my impedance scan actually shows lower impedance at higher frequencies.
Is there any other way to get an impedance scan for the wind farm in Simulink?
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I don't know now if there's any other way to get a wind farm impedance scan in Simulink, but I recommend a few measurement systems located at different key points (inverter outputs) for monitoring (U, I, P, Q, S, Lambda , THD-I, THD-U etc.) and then try to analyze them according to the wind direction, temperature and humidity in that area in a certain range ...
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I understand there will be exact multiple of fundamental frequency based bearing rotation with respect to fundamental, based on gear rotation with respect to fundamental. But what exactly means for multiples of bearing rotations, multiples of blade passes like 1x, 2x, 3x etc.,
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Honestly, it depends...
It depends on the specific machinery and source mechanism.
It can be nonlinearities in the system (e.g., nonlinearities in linear drives like speakers), it can be (periodic) elements in the system (e.g. number of teeth in gears), it can be wear in components (which needs to be periodic on rotating parts, e.g. higher harmonics on railcar wheels - polygonalization), it can be impulsive behaviour triggered periodically by a rotating part (e.g. combustion impulses in internal combustion engines), it can be linearly moving parts that are not rotating (e.g. pistons), it can be some additional higher order torque components from inbalances, ...
The key point is that for all of these processes (except of some non-linearities that might generate subharmonics), you can only get integer multiples of the base period.
Nevertheless, it is important to mind the base period. For a 4-stroke engine, for example, this is 2 rotations, which is why you might also find "half orders" at internal combustion engines (and only full and half orders, no third or something...).
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Greetings,
I have modeled a faulty system (Bowed rotor) in MATLAB. By increasing the sampling frequency, a frequency component appeared in the FFT graph (after the 1X), but the location (frequency in which the component appeared) is constant, i.e., by changing the system's angular velocity, the coordinate of the X-axis (frequency) is constant and does not show a harmonic component (such as 2X or 3X) while the fault has been modeled as a harmonic force. On the other hand, by increasing defect severity the amplitude of this harmonic component has been raised. Now, does anybody know and could explain it physically, please.
Yours sincere,
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Hi dear Nima Rezazadeh ,
Perhaps the constant frequency component belongs to the fault harmonic force.
Best regards
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In the context of designig a VAR compensation system with switched capcitors and a TCR, due to the switching of these two components there will be harmonics introduced to the network, the in order to supress those harmonics one must use harmonic filters, but, ¿is it necessary to take in count the power consumption of those filters in order to calculate the size in VAr of the capacitor bank and reactor ?
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You can add traps filters to suppress the harmonics as a series resonance circuit.
This circuit must be act as a short circuit at the intended harmonic frequency. It is also called a notch filter. Which means it must have resonance at the intended harmonic frequency. At the fundamental frequency the filter will act as an effective capacitance. So, it can be share in improving the power factor of the grid in case of inductive loads or lag phase. Otherwise it will affect the reactive power by the energy stored in this equivalent capacitance. But its value is relatively small as it is combined with an inductor to resonate at the intended harmonic frequency.
Best wishes
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Hello everyone, I am analyzing the harmonic response of a beam in ANSYS workbench and I need to assign the loss factor (hysterisis or structural damping) to the beam I am studying . My question is is it possible, in my case, to add the following APDL command (MP,DMPS,MATID,0.01) below the object in the geometry branch?
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The command MP, defines a linear material property as a constant or a function of temperature. So I suppose you can use MP, DMPR to define constant material damping.
Also the discussion in the following link provides some useful information on this subject:
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Can anyone help me to write review article on harmonization topic ..special reference to India.....means giving outline ..which topic should be covered under this head..please help me..i think this topic should be address.
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@, samar..thank alot..i will try to use your given outline in preparation of my manuscript.
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Hello everybody
Is there any software other than Matlab to produce data for sinusoidal excitation with gradually increasing amplitude like attached plots?
Thanks
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You can do this with any programming software. for example LabVIEW, Python and ... .
You just have to multiply the sine function with the desired frequency by a function with gradually increasing amplitude.
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The stress strain curve of rubber is not linear and follows a curved line both as the strain increases and as it decreases again. Does this hysteresis lead to formation of harmonics or other non lienar phenomena in eg a vibration insulated system?
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My experience with elastomeric vibration isolators is limited by vibration control of precision instruments, that is, small vibrations (micron and sub-micron range). Hysteresis leads to dissipation of mechanical energy (damping) that can be described in terms of complex stiffness incorporating a (rather large) loss factor. In frame of this model, the dynamic reaction includes a phase shift but stays linear, described by complex transfer functions. See more in Vibration Control for Optomechanical Systems, by V.M. Ryaboy, World Scientific, 2021, ISBN 9789811237331, pages 132-137. https://www.amazon.com/Vibration-Control-Optomechanical-Systems-Vyacheslav/dp/9811237336/ ;
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What are the challenges and update s regarding harmonization among food safety rules in india and worldwide.
Kindly suggest articles and reviews.
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Hello everyone, I am analyzing the harmonic response of a beam in a frequency range [0-50 Hz] but I noticed that the results for the 0 Hz frequency are not provided by ANSYS workbench. would like to know is there a possibility to have the amplitude of the displacement of the beam for the frequency 0Hz?
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That's the least I could do.
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Hello all, i'm trying to analyse the vertical deflection of a beam traversed by a point load as shown in the figure. The load has the following format: F=Pcos( ωt+ϕ) where P is the load amplitude (N), ω is the radial frequency of the applied load (rad/sec), V is the speed of the moving load (m/s) and t is the time (s). ϕ is an initial phase applied to the load to ensure that for every frequency, it will arrive at the mid-span with maximum amplitude. Please guide me, how would I define that in Ansys workbench?
Thank you.
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Hi @Hajar Rhylane.
I would like to add a method to do this without programming using Ansys Workbench.
You may resort to solid modeling of the beam and create a body that has contact with the solid beam. The contact between the body and the solid beam should be only at one location along length at any point of time. The contact surface should be the solid beam surface and the target should be the edge of the body in contact with the solid beam. The acceleration can be applied on the body and should be adjusted to match the required contact force that has to be applied to the solid beam by contact. Hence the acceleration can be defined by a function something like a.cos(wt+phi). The type of contact can be defined as no separation contact. The linear velocity v cab be applied to the body directly.
However it has to be noted that the linear velocity v and the angular velocity w are not independent and cannot be defined arbitrarily because of the requirement that it has to arrive at the centre with the maximum amplitude. The relation between v and w can be determined by solving the two equations 1) wt1+phi = n.pi and 2) vt1= L/2. Where t1 is the time at which the body reaches the mid length of the beam. The parameter t1 can be eliminated to get the relation between w and v. The parameter n can take any whole number value.
And please remember to switch on finite sliding in the contact settings. Hope this helps.
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Although adopted by few scholars, Kinetic energy minimization could be a helpful approach to isolate vibration.
Suppose we have a plate under harmonic loading and vibration reduction with the help of an absorber is of interest. Personally speaking, I don't like vector quantities for this purpose. Having a positive or negative direction on a large number of nodes, these quantities cannot accurately determine the level of vibration. Because, the designer may use an average or RMS evaluation of a lot of nodal vector quantities which of each has some approximation error.
Thus, I am eager to get some feedback from the community of NVH engineers for considering Kinetic energy as the criterion to be minimized for vibration reduction (instead of vector quantities such as force, velocity or displacement).
Looking forward to your valuable comments!
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- If the system is isolated, energy conservation implies that the only thing you can do is to share it in a different way allowing to minimize it where you need and increase it where it remains harmless - e.g. by fitting a tuned vibration absorber (TVA) that will concentrate kinetic energy on its resonance
- If you introduces decoupling between your various structural components, then you increase the kinetic energy on the source side and you decrease it downstream the isolators (impedance mismatch reduces the coupling between the components) - you remain an isolated system as a whole