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Harmonics - Science topic

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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
-----------------
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.
In a transition state structure, the frequency corresponding to the reaction coordinate is negative. This is the characteristic feature of the TS structure. it will not go away if your TS is correct.
For other negative frequencies in TS structure or other structures, you can simply remove them by adding displacement manually in the result manu--> vibrations --> manual displacement. Then reoptimize structures and recalculate vibretional frequencies. After a few trials, unwanted negative frequencies will be gone.
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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.
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?
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 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 ?
Did YOU get solution @youssef?
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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?
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
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
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?
Dear doctor
Go To
On mixed polynomials of bidegree (n, 1)
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.
Mr. Sadri, I have met the same question, How did you solve your problem? Thanks
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Distance x Size + Resonance = Harmonic "SOUND"; as with Earth Sun Moon
@108
#7.83
In certain cases, distance can indeed play a role in creating sound or affecting the perception of sound. One example is the phenomenon of resonance. When an object or a medium vibrates at its natural frequency or multiples of it, it can produce sound. Resonance occurs when an external force or stimulus matches the natural frequency of an object, causing it to vibrate and generate sound waves.
Regarding your mention of Earth, Sun, and Moon, they do not directly create sound in the conventional sense. However, their interactions can generate various waves or vibrations that are interpreted or detected as sound by scientific instruments. For example, solar flares or coronal mass ejections on the Sun can produce intense electromagnetic waves, including radio waves, which can be converted into sound waves for analysis and interpretation.
Similarly, the movement of the Earth's tectonic plates during earthquakes can generate seismic waves, which can be detected and converted into audible sounds by seismographs. These sounds are not audible to human ears directly but are converted into frequencies within the audible range for analysis.
In summary, while distance alone does not create sound, the interaction of objects, resonant properties, and other physical phenomena can generate vibrations and waves that we interpret as sound.
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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?
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
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?
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
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!
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
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?
thank you Divyansh Baranwal and Richard Lewis for your response. I will try these methods.
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Thanks
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
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?
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
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.
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?
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?
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..
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
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.
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?
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.
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?
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.
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 ??
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.?
Nazanin Fallahi
Hi,
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?
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 ?
42.11
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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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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?
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?
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 ?
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.
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.
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.
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?
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?
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.,
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,
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 ?
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?
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.
@, 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
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.
Best regards
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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?
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?
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.
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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I am doing vibrational analysis of mono-acetic acid after wavefunction and geometry optimisation. In the output file of vibrational analysis the following lines were present containing harmonic frequencies of mono-acetic acid.
****************************************************************
HARMONIC FREQUENCIES [cm**-1]:
-93.9446 -56.8345 -14.9036 79.1124
83.2432 123.7967 180.8622 415.9833
465.7580 564.8411 581.9038 795.9969
942.4123 1030.7040 1139.4888 1218.9753
1356.8784 1433.9457 1447.8727 1776.4078
2976.9823 3023.5483 3084.8354 3634.5117
PURIFICATION OF DYNAMICAL MATRIX
****************************************************************
HARMONIC FREQUENCIES [cm**-1]:
-55.0883 -0.0000 0.0000 0.0000
80.2766 101.0671 159.3476 415.9277
465.5977 564.8100 581.8316 795.9872
942.4062 1030.6968 1139.4801 1218.9731
1356.8769 1433.9456 1447.8725 1776.4022
2976.9823 3023.5483 3084.8354 3634.5117
ChkSum(FREQ) = 0.26286465E+05
Can some one help me understand what is meant by "Purification OF DYNAMICAL MATRIX" and interpret the above results CH3COOH should have 18 modes of vibrations (3N-6). but I am getting 20 modes of vibrations? Furthermore is -55.0883 cm-1 a false flag or is it because of incorrect optimisation of structure?
Getting all zeros for the first 6 modes enforces the requirement of invariance of the PES with respect to translation/rotation. Harmonic frequencies obtained by finite differences may often lead, for lack of numerical precision, to non-zero values in these modes. The "purification" should consist (at least if it is the same as in GAMESS) in a procedure of transforming back and forth the matrix between cartesian and internal coordinates, which effectively helps zeroing the freqs and IR absorptions of the translational and rotational modes.
The fact that you still get those -55. and +88. cm-1 is a possible sign of your structure not being close enough to a true minimum, but I can't be sure on this. In some cases, a solution is met by simply repeating the optimisation with increased numerical precision in the DFT integration scheme and/or SCF convergence.
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Application of these 3 Means (AM, GM and HM) individuality? where can we use this? welcome with research papers?
Arithmetic mean is calculated by adding all the sample values followed by dividing it by the number of samples taken... Geometric mean is the square root of the product of the values of each sample and harmonic mean is the reciprocal of the arithmetic mean of the reciprocal of the values of the sample... example calculation of AM, GM and HM of the values A, B and C will be
AM= (A+B+C)/3
GM= √A×B×C
HM= 3/ {(1/A)+(1/B)+(1/C)}
Arithmetic mean is used for calculation of average of anything because it consider all the observations like plant height, average speed when time is fixed, calculation of so many yield attributes. It is frequently used in agriculture and will be most authentic average... Geometric mean is used to calculate bacterial growth, cell division etc...if one value is zero, then whole GM value will be zero, because product of the value is used here..In case of harmonic mean, average of small value can be used like Average of rate or ratio because we have take reciprocal values of each samples whereby taking reciprocal of very small values obtained value is comparatively larger..
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its like,why does the power system network still affected by effects of harmonics yet mitigation measure in place.
thanks
There are so many moving parts in the power system that have a lot to do with the mechanics of the system. Mitigations are there but most of them are physics related like the resistivity which is affected by the length of the wire and area then we can also look at overheating and this is because there is work done and magnetic fields hence we can control or reduce them but we can't get rid of them completely.
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Hello,
I am working on project that consists of analyzing power quality. The grid is connected to a nonlinear load which will evidently causes appearance of harmonics and potential swell and sag on the wave form of load current.
Basically, the measured voltage and current will be processed to determine and detect any possible disturbances, for instance swell and sag .
I am asking for an algorithm to do so(especially for sag/swell).
Thank you.
@abbas jamshidi Gahrouei, thanks for your response.
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Hi
Sir how is useful in power electronic system for measure harmonic is MATLAB or PLECS
If you build your power electronic model in Matlab/Simulink then you can calculate your current and voltage waveforms. One you get these waveforms use the tool box of the fast Fourier transform to resolve the waveform into its fundamental and harmonics sinusoids provided that you have to sample the waveform with a sampling frequency greater than 2 times the highest possible harmonic frequency.
You can also measure the waveform of any experimental circuit and acquire it by using data acquisition cards then store the waveforms and analyze them using the FFT tool box.
Best wishes
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i used CHARMM-GUI membrane builder module to prepare the necessary files for simulating a membrane using NAMD and while inspecting the configuration input files, i noticed that it uses collective variables (ColVar) to apply a harmonic potential on some atoms of the head groups of the lipids during equilibration only. why would i need to apply these potentials? and why selecting the centers values to be of these specific values (ex: 18 for the cholesterol lipid)?
these are the first and last colvar lines included in the first equilibration step:
Colvarstrajfrequency 100
Colvarsrestartfrequency 100
colvar {
distanceZ {
ref {
dummyAtom ( 0.000, 0.000, 0.000 )
}
main {
atomsCol B
atomsColValue 1.0
}
}
}
harmonic {
centers 18
forceConstant 5
}
....
....
....
colvar {
distanceZ {
ref {
dummyAtom ( 0.000, 0.000, 0.000 )
}
main {
atomsCol B
atomsColValue 1.0
}
}
}
harmonic {
centers -21
forceConstant 5
}
I think it is important to make some restraints on the membrane to not lose the bilayer configuration when preparing the system for the simulation.
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Please suggest any algorithm diagram for understanding the concept of an active power filter for removing harmonics.
For harmonic elimination only, the concept is that your reference current is described as the difference between the measured distorted load current minus the fundamental component of the measured distorted load current.
Assuming fixed dc bus voltage this reference can be used in a conventional inverter pwm scheme with feedback to apply the necessary correction.
In this idealized case the source current should be sinusoidal.
There are several techniques in the literature to achieve this, describe above is only the concept.
See: TC Green, JH Marks great review titled Control techniques for active power filters
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Hello,
I have a circular loop absorber with two dielectric substrates. I want to reduce the reflection at 3GHz. When i set the circumference to half of the effective wavelength, I got this simulation result.
My equation is why the second resonance is obtained at 12 GHz instead of the 2nd harmonic (6GHz)? And why is the reflection coefficient at 12 GHz smaller than at 3 GHz?!
I think you will need to provide a better description of your ring absorber, the direction it is illuminated from, and the polarization you used, if you want an explanation.
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In the attached file, the harmonic-like sequence is defined. Is this kind of a sequence known in the literature? Do you know any source with the properties of such numbers?
I don't need to do anything special, I just want to know if there are any properties of it.
The question comes from obtaining the formula from the attached file (omega function stands for prime omega function in number theory).
I don't get your observation about the derivative though (why did you change notation?). It doesn't really use any property of the sequence h_m^(r). Unless they do, but your anwser wasn't clear enough for me.
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Dear Lammps users, a vaste literature is available on the matter of molecular mechanics simulations of layers, “slabs”so to say, of different materials floating on each other. Typical examples are layers or bilayers of lipids on water.
In the final simulation, more often than not we may find a central water slab with two molecular layers symmetrically disposed adjacent to the opposite surfaces of the water slab, so, for example, the disposition in, let’s say the z direction, is “molecular layer A” – “water slab” – “molecular layer A”
Additionally, two empty spaces are added on top (and below) the molecular layers to avoid mutual interactions between the molecules of the layers. I forgot to clarify that the system is periodic in all 3 directions.
Layers are usually “built” alone and equilibrated (with either fix NVT or NPT) and subsequently combined to give rise to the above described system, which is then submitted to the desired simulation.
I tried several times to follow this procedure and the major issue was to avoid to have images conflict which immediately stops the simulation rising an error.
I found a trick which consists of preparing the water and organic molecules slabs separately by using fix addforce to constrain the molecules (water and organic) of each box inside a relatively narrow layer. This system is somehow equilibrated with fix NVT.
In a second step, with a specific program I wrote, the complete system A-water-A is submitted to simulation.
Actually, the simulation finally runs, even if I am getting an “inconsistent image flags warning” .
Honestly, I feel uneasy with my “trick”. It seems to me unphysical and I doubt that the authors in literature made use of such a cumbersome procedure.
I hope to find some “ultra-patient” and competent gentleman willing to comment on this.
My field of research is the regular synthesis of 2-dimensional polymers at the liquid-air interface.
MD simulations are an essential tool in my research.
Thanks a lot for your attention
Paolo Botto
p.s. herebelow please find the Lammps input script of a “toy” system of 16 molecules:
# LAMMPS INPUT SCRIPT M44 16 filename: in-M44-16-00
units real
boundary p p p
atom_style full
pair_style lj/cut/coul/cut 10 12
bond_style harmonic
angle_style harmonic
dihedral_style opls
improper_style cvff
atom_modify map array
pair_modify table 0
velocity all create 300 887723
fix mynve all nve
fix mylange all langevin 300 300 100 314159
group mygroup type 2 4 # force acts on Oxygen and Nitrogen only
region myregion1 block 1.0 10.0 -42.0 42.0 -42.0 42.0
fix myforce 1 mygroup addforce -1.0 0.0 0.0 region myregion1
region myregion2 block -10.0 -1.0 -42.0 42.0 -42.0 42.0
fix myforce2 mygroup addforce 1.0 0.0 0.0 region myregion2
neighbor 2 bin
neigh_modify delay 0 every 1 check yes page 100000 one 10000
thermo 1000 thermo_style custom cpu step etotal temp press density dump mydump all custom 1000 dump-M44-16-00 id type mol xs ys zs
restart 1000 rest1 rest2 run 500000
write_data dat-M44-16-00 write_restart restart-M44-16-00
Dear Sun, it is exactly as you say.
The way I build the system might affect results of later simulations.
Any recommendation?
Thanks
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I have completed the simulation of grid tied inverter and got voltage, current, harmonics distortion at PCC but i don't know how to extract features and process the simulation outputs for SVM training and classification in MATLAB
"A novel Multi-LSTM based deep learning method for islanding detection in the microgrid".
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Goldbach and Euler’s proof is a typical example of what some historians consider a misuse of divergent series  , for it starts by assigning a “value” to the harmonic series ∑1/n and proceeds by manipulating it by substraction and replacement of other series until the desired result is reached.
I totally agree with the teachers' opinions
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Is there a definitive way to determine the delay between the fundamental (800 nm) and it's second harmonic (400 nm) generated by a type 1 BBO?
Our Ti-Sapphire laser generates 800 nm pulses at 30 fs, a Mach–Zehnder interferometer is constructed. One arm is made to pass through a type 1 beta-BBO of 100 microns, while the other is not disturbed. The delay between 800 and 800 nm was determined quite easily before the type-1 BBO was placed, but a delay is introduced between the 800 and 400 nm pulses in one arm due to the type-1 BBO. Is there any way to determine the delay between them?
PS: The THG generation method was not advisable since control of individual intensities was not guaranteed in the said method.
I do not quite understand your conclusion that type-I phase matching will give rise to a delay between fundamental and SHG as both pulses travel at identical phase velocities in the crystal. Of course, this does not mean that group velocities are identical, too, but as the SHG becomes most intense during the final stretch of the propagation I would not expect much of a measurable delay from that effect.
You can theoretically investigate this by setting up the coupled propagation equations for fundamental and SHG, including a group velocity mismatch. If you want to measure this then you can certainly try to set up an auto/cross correlator with a broadband nonlinearity, e.g., tightly focusing on a quartz substrate using surface SHG/SFG. However, you would unavoidably see dispersive effects due to beam splitters, lenses and air paths rather than the delay incurred during the original SHG process. There are ways around this, but this would be a rather challenging experiment for an effect that probably does not even exist.
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Greetings all. I am writing an input file for my simulation but I get error on the improper_style. I used opls force field so I used 'harmonic' style for it. But, it gives out error like so:
ERROR: Incorrect args for improper coefficients (src/MOLECULE/improper_harmonic.cpp:219)
Does anyone know where it went wrong or how to fix this?