This paper deals with the problem of the asymptotical stability for a class of linear systems with multiple time-delays. Using Lyapunov-Razumikhin theorem and the concept of matrix norm, the sufficient conditions of delay-independent stability and delay-dependent stability are derived to ensure that the linear systems with multiple time-delays are asymptotically stable. By comparing with the present theorem, it is obvious that the stability theorem in this paper could deal with the linear systems with constant delay and time-varying delay. Last, an example is given to illustrate that the new method is more effective than the present method and the delay bound obtained in this paper is of less conservative.
In this paper, the cycloid bearing type of connection structure for the giant die forging hydraulic press's movable beam eccentric torque test system are put forward to compare the static comprehensive error with the original movable slider structure. Through the MAC finite-element model analysis, the mode and vibration of the simultaneous balance detection bracket are obtained. The results show that the proposed type is superior to the original one.
In this paper, the dynamic least mean square(DLMS) algorithm is firstly proposed to reduce the computation of LMS. In the DLMS architecture, the redundant coefficients of LMS can be grouped automatically. The coefficient number of filter and the computation are reduced. Moreover, two modes of DLMS algorithm are employed analyzed. The DLMS-based line echo cancellation (LEC) is employed to evaluate the performance of DLMS. The experimental results confirm the good performance in DLMS algorithm. Moreover, the performance of mode-II is superior to the mode-I. Moreover than 44% of coefficient saving of LMS is achieved.
Switched converter (SC) DC/DC converters are new prototype of DC/DC Conversion technology. Since switched capacitor can be integrated into a power IC chip, consequently, these converters have small size and high power density. Switched capacitor can be used in voltage-lift technique to construct DC/DC converters. The clue is that for the converters operating in input current discontinuous mode (ICDM) the switched capacitors can be charged during the input current discontinuous period. The switched capacitors are charged to the source voltage during the switch-off period. They will join the conversion operation during switch-on period, and the stored energy in them will be delivered through further elements to the load. These converters are called switched-capacitorized DC/DC converters. Simulation and experimental results are provided for verification of this design.
In this paper, we examine the parameterization of all stabilizing multi-period repetitive controllers for multiple-input/multiple-output plants with the specified input-output frequency characteristic. The parameterization of all stabilizing multi-period repetitive controllers, those are used to improve the disturbance attenuation characteristics of the repetitive controller, for non-minimum phase systems was solved by Yamada et al. However, when we design a stabilizing multi-period repetitive controller using the parameterization by Yamada et al., the input-output frequency characteristic of the control system cannot be settled so easily, because 2(N +1) numbers of free parameters in the parameterization related to the input-output characteristic. This problem is solved by obtaining the parameterization of all stabilizing multi-period repetitive controllers with the specified input-output frequency characteristic, which is the parameterization when the input-output characteristic is settled beforehand. From this view point, the parameterization of all stabilizing multi-period repetitive controllers with the specified input-output frequency characteristic was proposed. However, the previous result did not clarify the parameterization of all stabilizing multi-period repetitive controllers for multiple-input/multiple-output plants with the specified input-output frequency characteristic. This work extends the previous results into the multiple-input/multiple-output plants.
It is presented a model of uncertain switched fuzzy systems, which each subsystem of switched system is an uncertain fuzzy system, and the robust reliable control problem is studied. When the actuators are serious failure - the residual part of actuators can not make original system stability, using switching technique depend on the states of observers and Lyapunov function method, dynamic fuzzy reliable controller is built to ensure the relevant closed-loop system is asymptotic stability. Moreover, observers switching strategy achieving observer errors decreasing uniformly asymptotically to zero of the uncertain switched fuzzy systems is given. A simulation shows the feasibility and the effectiveness of the method.
In this paper, the global exponential stability is discussed for Cohen-Grossgerg neural network with time varying delays. On the basis of the linear matrix inequalities (LMIs) technique, and Lyapunov functional method combined with the Bellman inequality and Jensen inequality technique, we have obtained two main conditions to ensure the global exponential stability of the equilibrium point for this system, one of which is dependent on the change rate of time varying delays, and the other is dependent on the upper bound of time varying delays. The proposed results are less restrictive than those given in the earlier literatures, easier to check in practice, and suitable of the cases of slow or fast time varying delays. Remarks are made with other previous works to show the superiority of the obtained results, and the simulation examples are used to demonstrate the effectiveness of our results.
The AC magnetic susceptibility is a fundamental method in materials science,
which allows to probe the dynamic magnetic response of magnetic materials and
superconductors. The LAMPS laboratory at the Laboratori Nazionali di Frascati
of the INFN hosts an AC multi-harmonic magnetometer that allows performing
experiments with an AC magnetic field ranging from 0.1 to 20 Gauss and in the
frequency range from 17 to 2070 Hz. A DC magnetic field from 0 to 8 T produced
by a superconducting magnet can be applied, while data may be collected in the
temperature range 4.2-300 K using a liquid He cryostat under different
temperature cycles setups. The first seven AC magnetic multi-harmonic
susceptibility components can be measured with a magnetic sensitivity of 1x10-6
emu and a temperature precision of 0.01 K. Here we will describe in detail
about schematic of the magnetometer, special attention will be dedicated to the
instruments control, data acquisition framework and the user-friendly
LabVIEW-based software platform.
In Ad Hoc networks, route failure may occur due to less received power,
mobility, congestion and node failures. Many approaches have been proposed in
literature to solve this problem, where a node predicts pre-emptively the route
failure that occurs with the less received power. However, this approach
encounters some difficulties, especially in scenario without mobility where
route failures may arise. In this paper, we propose an improvement of AODV
protocol called LO-PPAODV (Link Quality and MAC-Overhead aware Predictive
Preemptive AODV). This protocol is based on new metric combine more routing
metrics (Link Quality, MAC Overhead) between each node and one hop neighbor.
Also we propose a cross-layer networking mechanism to distinguish between both
situations, failures due to congestion or mobility, and consequently avoiding
unnecessary route repair process. The LO-PPAODV was implemented using NS-2. The
simulation results show that our approach improves the overall performance of
the network. It reduces the average end to end delay, the routing overhead, MAC
errors and route errors, and increases the packet delivery fraction of the
Supply Chain coordination has become a critical success factor for Supply
Chain management (SCM) and effectively improving the performance of
organizations in various industries. Companies are increasingly located at the
intersection of one or more corporate networks which are designated by "Supply
Chain". Managing this chain is mainly based on an 'information sharing' and
redeployment activities between the various links that comprise it. Several
attempts have been made by industrialists and researchers to educate
policymakers about the gains to be made by the implementation of cooperative
relationships. The approach presented in this paper here is among the works
that aim to propose solutions related to information systems distributed Supply
Chains to enable the different actors of the chain to improve their
performance. We propose in particular solutions that focus on cooperation
between actors in the Supply Chain.
The Time Projection Chamber of the ALICE experiment at the CERN Large Hadron
Collider features highly integrated on-detector read-out electronics. It is
following the general trend of high energy physics experiments by placing the
front-end electronics as close to the detector as possible -- only some 10 cm
away from its active volume. Being located close to the beams and the
interaction region, the electronics is subject to a moderate radiation load,
which allowed us to use commercial off-the-shelf components. However, they
needed to be selected and qualified carefully for radiation hardness and means
had to be taken to protect their functionality against soft errors, i.e. single
Here we report on the first measurements of LHC induced radiation effects on
ALICE front-end electronics and on how they attest to expectations.
Dimensionality reduction (DR) of image features plays an important role in
image retrieval and classification tasks. Recently, two types of methods have
been proposed to improve the both the accuracy and efficiency for the
dimensionality reduction problem. One uses Non-negative matrix factorization
(NMF) to describe the image distribution on the space of base matrix. Another
one for dimension reduction trains a subspace projection matrix to project
original data space into some low-dimensional subspaces which have deep
architecture, so that the low-dimensional codes would be learned. At the same
time, the graph based similarity learning algorithm which tries to exploit
contextual information for improving the effectiveness of image rankings is
also proposed for image class and retrieval problem. In this paper, after above
two methods mentioned are utilized to reduce the high-dimensional features of
images respectively, we learn the graph based similarity for the image
classification problem. This paper compares the proposed approach with other
approaches on an image database.
Understanding the behavior of concrete and reinforced concrete at high strain rates is of critical importance in a range of application. The behavior of concrete and reinforced concrete at strain rates of the order of 104/s and pressure up to 1.5 GPa are studied experimentally. The concrete analyzed has the same composition and processing conditions as the matrix phase in the reinforced concrete. The dynamic compression experiments of reinforced concrete are carried out by one-stage light gas gun apparatus which subjects the reinforced concrete to deformation at strain rates of the order of 104/s with confining pressures of 1–1.5 GPa. The voltage–time signals are recorded by the manganin pressure gauges embedded in the target. The stress–strain curves of reinforced concrete with different impact velocities are obtained using Lagrangian analysis, from which the distribution regulations of other mechanical parameters such as specific internal energy and specific volume in the flow field are acquired. Experimental results indicate that the load-carrying capacities of concrete and reinforced concrete increase significantly with strain rate. The concrete and reinforced concrete are non-linear, rate-sensitive and pressure-dependent.
In this paper we establish some spectral conditions for a graph to be
Hamilton-connected in terms of the spectral radius of the adjacency matrix or
the signless Laplacian of the graph or its complement. For the existence of
Hamiltonian paths or cycles in a graph, we also give a sufficient condition by
the signless Laplacian spectral radius.
We develop a novel constitutive modeling approach for the analysis of
fracture propagation in quasi-brittle materials using the Material Point
Method. The kinematics of constitutive models is enriched with an additional
mode of localized deformation to take into account the strain discontinuity
once cracking has occurred. The crack details therefore can be stored at
material point level and there is no need to enrich the kinematics of finite
elements to capture the localization caused by fracturing processes. This
enhancement also removes the drawback of classical smeared crack approach in
producing unphysical snapping back constitutive responses when the spatial
resolution is not fine enough. All these facilitate the implementation of the
new approach in the Material Point Method for analysis of large scale problems.
Numerical examples of fracture propagation are used to demonstrate the
effectiveness and potentials of the new approach.
By the covariance intersection (CI) fusion method, the covariance intersection fusion steady-state Kalman filter is presented
for two-sensor system with unknown cross-covariances between local filter errors. It is proved that its accuracy is higher
than that of each local filtering, and is lower than that of the optimal fuser with known cross-covariances. A Monte-Carlo
simulation result shows that its accuracy is approximates to that of the optimal fuser.
KeywordsInformation fusion Kalman filter–steady-state Kalman filter–covariance intersection fusion–unknown cross-covariances–covariance ellipse
This paper is concerned with methods to determine the resultant impact load pulse on test structures during gas gun tests. The muzzle of a gas gun carries an instrumented target support designed to measure force-time-pulses of the impact event on structures mounted on the device. The target during impact is supported on two long slender metallic bars with axial strain gauges. By measuring the impact strain pulses in the support bars and assuming longitudinal wave propagation, it is possible to determine the impact load pulse on the target. The paper describes the strain measuring device and methods for determining the impact loads during impact. Gas gun test results with different projectiles are presented and the load pulses compared with a direct load measurement from a target load cell. The paper discusses possibilities and limitations of the device for quantitative force pulse measurements.
A testing device in turning including, in particular, a six-component dynamometer, is used to measure the complete torque of the cutting actions, in a case of self-excited vibrations. For the tests, the used tool was a noncoated carbide tool (TNMA 160412) without chip breaker. The cutting material is a chrome molybdenum alloy type (ASI 4140). The cylindrical test tubes have a diameter of 120 mm and a length of 30 mm. For the first time, we present an analysis of forces and moments for different depths of cut and different feed rates.
In the air conditioning (AC) industry chilled water storage (CWS) systems are one form of cool thermal storage technology that can be used to time shift the electrical load of the system from the peak day periods to off peak night time periods. In this paper the data for the actual exported and generated electrical energy obtained for the power stations has been used to estimate the electrical energy consumption and the peak electrical load of AC systems. Since the chiller in an air cooled AC system represent more than 75% of the total electrical power consumed by an AC system during the peak demand period, the impact of using CWS systems with alternative operating strategies including partial(load leveling ), partial (demand limiting) and full load has been investigated. In our conclusions we estimate that approximately 45% of the total annual exported electrical energy is consumed solely by AC systems as a result of the very high ambient temperatures. Furthermore, it is estimated AC systems represent about 62% of the peak electrical load. The results demonstrate that CWS can reduce the peak electrical load of a chiller in an air cooled AC system by up to 100% and reduce the nominal chiller size by up to 33% depending up on the operating strategy adopted. This is achieved with only a 4% increase in power consumption of the chiller for all CWS strategies except for full storage where the energy consumption actually decreases by approximately 4%.
Treatment of printing and dyeing wastewater by the device of high gradient magnetic separation (HGMS)developed by author was tested. The results showed that printing and dyeing wastewater contained varied chemical composition and whose initial concentration of chromaticity and COD were 800 and 565mg/L respectively can be well cleaned by Fenton oxidation¡ªmagnetic seed coagulation¡ªHGMS. The removal rate of chromaticity and COD was up to92.6% and 79.5% respectively. The effluent can meet the national drainage criterion. The optimum technological parameters are as follows: pH=6, [FeSO4¡¤7H2O]=250mg/L, [H2O2]=1.3ml/L, [PAM]=0.75 mg/L, dose of magnetic particle W=150mg/L, current intensity I=8A, current velocity U=2.420L/min, packing density of stainless steel wire R=1.00%-1.43%. Recovery rate of magnetic particle was up to90% by regenerated technique of chemistry in combination with physics.
In this paper, a novel early mode decision algorithm is proposed to reduce the complexity of the mode selection process for
enhancement layers in H.264 Scalable Video Coding. Generally, the proposed algorithm consists of the following three main
steps which are applied to the enhancement layer. Firstly all the macroblocks are divided into several cases according the
mode of neighboring macroblocks and collocated MBs in the base layer. Then different mode selection algorithms perform for
different cases. At last, if it is necessary to check more than one intra mode, a fast intra mode selection algorithm is performed.
Experiment results show that with this algorithm, 10%~40% encoding time can be saved with a negligible loss in BDSNR and very
little increment in BDBR compared to JSVM 9.18.
The frequent and excessive fluctuation of agricultural and livestock products price is not only harmful to residents square living, but also affects CPI (Consumer Price Index) values, and even leads to social crisis, which influences social stability. Therefore it is important to forecast the price of agriculture and livestock products. As a result, we made a research on the factors affecting agricultural and livestock products price, established a forecasted model of agricultural and livestock products price, and developed its early-warning system which is suitable to China. Considering the direct relationship between the price and the output, multiple linear regression method was adopted to study this problem. The model is composed of three sub-models. This paper puts forward the concept of price equilibrium coefficient C(0), which describes the degree to which people accepting the forecasted price. With the establishment of the standard for the influence of price fluctuation, the influence of price fluctuation is measured. Each range of the C(0) value corresponds with a specific result, which may informs the government with the danger of price fluctuation. As a result, the model can early-warn the price rising caused by crop reduction due to sudden natural disaster, which may induce social turmoil and crisis. If the forecasted price rises heavily, the government should take measures to avoid crisis. This paper offers the method to control future price. Finally, a forecasted model of pork price is calculated with simulated data. The forecasted result is in good agreement with actual situation.
From the perspective of selecting service by QoS attributes, a computation method of QoS expectation value, which is based on Algorithm Prim, was presented to provide support for selection of service. On the basis of the ability of service providers, by Algorithm Prim, this method succeeded in calculating a set of balanced expectation values of QoS. Selection of service based on these QoS values would be beneficial to optimization of system resources and protection of the users of those services. An example with analysis has been provided to demonstrate the feasibility and effectiveness of the method.
As an important tool to study practical problems of biology, engineering and image processing, the cellular neural networks
(CNNs) has caused more and more attention. Some interesting results about the existence of solution for cellular neural networks
have been obtained. In this paper, by means of iterative analysis, the existence of periodic solution and the uniform stability
of the equilibrium point of impulsive Hopfield cellular neural networks with time delays are considered. Some new results
To distinguish chatter gestation, chatter recognition method based on hybrid PCA(Principal Compenent Analysis) and SVM(Support Vector Machine) is proposed for dynamic patterns of chatter gestation in cutting process. At first, FFT features are extracted from the vibration signal of cutting process, then FFT vectors are presorted and introduced to PCA-SVM for machine learning and classification. Finally the results of chatter gestation recognition and chatter prediction experiments are presented and show that the method proposed is effective. If chatter is being gestated in the cutting process, information of chatter will be shown in the vibration signal of cutting process. We predict the latent chatter in the process of chatter gestation so that reasonable method can be taken to eliminate chatter in the early period of chatter gestation. Thus, recognition of chatter gestation is always paid attention to by experts, and there have been researches on features extracted from the vibration signal to predict latent chatter, chatter prediction and recognition based on dynamic signal of cutting force, and chatter monitor using AE sensor, etc(1). These methods are based on recognition of narrow-band feature from the spectrum. The availability of these methods highly relies on the rightness of feature
In this paper, with the ANSYS, stress distribution and safety factor of crankshaft were analyzed by using 3D finite element method. The results show that the exposed destructive position is the transition circular bead location of the crank web and the crankpin. Maximum stress is 123 MPa. Safety factor is 3.12. Maximum deformation is 0.711 mm Crankshaft satisfies the design requirement.
Walking assist using Functional Electrical Stimulation (FES) has been studied for a quite long time to help paraplegic persons overcome their walking impairment. One of the problems of these devices is how to cope with individual dependent, time-varying, and nonlinear user's characteristics and external disturbances. In this study, Feedback Error Learning (FEL), a scheme that integrates feedback and feedforward control, was applied to FES control. As a first step, an inverted-pendulum model was used to examine the usefulness of this scheme. Next, the control of a swinging motion, using a leg model simulation, was performed. After the verification in the simulation models, an FES experiment was to investigate the applicability of this system. The data obtained from the FES experiments were used to construct a new simulation model for investigating the effect of FES in different condition. The results showed that, usability of the FEL scheme for different FES control strategies.
To grasp Complex characteristics of shortwave (HF) channel is the key and difficulty to research HF communication. On the premise of comprehending the ionosphere prediction method in the Asia Oceania region, HF frequency prediction method recommended by the International Telecommunication Union (ITU) is improved in this paper, and the engineering calculation method of predicting HF frequency in the Asia Oceania region is concluded and summarized. Comparing with the ITS (the Institute for Telecommunication Science) software's predicting result, the method is improved to some extent in time availability and SNR in the receiving point.
A design synthesis technique based on sensitivity for Micro-Electro-Mechanical Systems (MEMS) proposed. This new technique can be called Sensitivity-Based Direct Solution Algorithm (DSA) of design synthesis for MEMS with expected performance. Design synthesis with expected performance is regarded as a reverse problem of MEMS analysis. Behavior equation group can be educed from analysis equations. This behavior equation group can be solved using any solution algorithm of non-linear equation group. Newton Iteration Method based on sensitivity is adopted. Comparing with Genetic Optimization Algorithm (GA), computational workload of DSA is greatly decreased.
Maximal frequent itemsets are one of several condensed representations of frequent itemsets, which store most of the information contained in frequent itemsets using less space, thus being more suitable for stream mining. This paper focuses on mining maximal frequent itemsets approximately over a stream landmark model. A false negative method is proposed based on Chernoff Bound to save the computing and memory cost. Our experimental results on a real world dataset show that our algorithm is effective and efficient.
The optimization for petroleum high pressure wellhead gate valve stem is significant. Valve stem load calculation method is developed, and petroleum high pressure wellhead gate valve stem optimization model based on MATLAB is established, taking 2 9/16 inch 35MPa wellhead gate valve for an example, the stem weight decreases by 27%, consequently decreasing valve weight.
Multicast requires reliability in peer-to-peer or multiple-to-multiple communication services and such demand for reliability
becomes more and more an important factor to manage the whole network. Communication method for multicast is a way of communication
for a transmitter that provides multicast data to every registered member in the transmitter’s group, and it can be classified
into the traditional and the reliable communication methods in general. The traditional communication method is very fast
in connection but quality of service is poor. In contrast, the reliable communication method provides good quality in service
but its speed is somewhat poor. Thus to enhance such demerits, this paper proposes communication method of multicast by using
QCBT (Quality of Service Core Based Tree ) method. In this paper, a fair and practical bandwidth is used for data packet transmission
along with the use of QCBT. The bandwidth and data processing capability filters out the transmitted data from an QCBT router
through transmission packet and upgrades multimedia data packet more effectively. Therefore, recipients in various levels
receive the effective data packet and based on these facts, the study actualizes and evaluates efficiency of a router, which
is able to transmit the fair bandwidth from QCBT router in a simulation.
Although the integration of SIP-based systems with a network address translation (NAT) environment has been investigated extensively, SIP-based system operation in symmetric model NAT remains relatively unexplored. This paper studies the application of symmetric NAT traversal techniques to SIP-based systems. This study focuses on following the SIP process, a non-additive service server, and employs standard SIP commands such as "REGISTER," "INVITE," and "200 OK" to predict and deliver the IP addresses and port numbers of the local NAT. This study also implements RTP streaming in the client-to-client (C2C) mode. The symmetric NAT traversal method for the SIP increases the direct peer-to-peer connection rate. This approach also avoids the STUN and RTP-Relay server. Experimental results with 50 types of NAT indicate that symmetric NAT traversal performs better than the STUN solution. The RTP-Relay server bandwidth cost is likewise superior to the TURN solution. These finding have important implications for SIP-based system developers and carrier providers.
Purpose: The themes of the study are composite structural components. For this purpose have been designed and built several research positions.Design/methodology/approach: Using different structural materials to build new device components requires multiple tests of the components. Research posts were designed in the advanced graphical program CAx Siemens NX 7.5. Analysed samples were made from the glass fibre, aramid and carbon of various weights. Due to the specific use of composite materials it focuses on the elements in the form of plates and flat bars. For the examination of experimental strain gauge technique was used bead, the force sensor and displacement sensor. The experimental methods were compared with computer simulation using the FEM.Findings: The aim of this study was to determine the basic material constants and a comparison of the experimental method and the method of computer simulation.Research limitations/implications: Change the number of layers and how to connect the laminate with the steel plate changes mechanical properties of the structural component.Practical implications: The ultimate result will be knowledge on the different forms of laminates, such as material properties, the stresses in all layers, strain and comparing the results obtained by two methods.Originality/value: The expected outcome of the study will be the composition and method of joining composite laminate with a steel plate to the possible application in the repair and construction of structural elements of freight wagons.
A study is presented into the effect of ultrasonic activation of the platen on the stressstrain relationship in compression tests on aluminium specimens. The aim is to gain some insights into the reported beneficial effects of ultrasonically excited tools in metal forming operations. The paper investigates the compression of aluminium specimens using a variety of different lubricants under conditions of constant crosshead velocity and superimposed longitudinal ultrasonic excitation of the platen. The study shows that the changes in the stress-strain relationship under ultrasonic excitation can be explained in terms of the superimposed oscillatory stress condition and that there is some evidence of small changes in the interfacial friction condition.
Recent NATO funded research on methods for detection and interpretation methodologies for damage detection in aircraft panel structures has motivated work on low-order nonlinear analytical modelling of vibrations in cracked isotropic plates, typically in the form of aluminium aircraft panels. The work applies fundamental aspects of fracture mechanics to define an elliptical crack, and the local stress field and loading conditions, arbitrarily located at some point in the plate, and then derives an analytical expression for this that can be incorporated into the PDE for an edge loaded plate with various possible boundary conditions. The plate PDE is converted into a nonlinear Duffing-type ODE in the time domain by means of a Galerkin procedure and then an arbitrarily small perturbation parameter is introduced into the equation in order to apply an appropriate solution method, in this case the method of multiple scales. This is used to solve the equation for the vibration in the cracked plate for the chosen boundary conditions, which, in turn, leads to an approximate analytical solution. The solution is discussed in terms of the perturbation approximations that have been applied and highlights the phenomenology inherent within the problem via the specific structures of the analytical solution.
Recent EPSRC funded research at Glasgow University, Swansea University, and Virginia Polytechnic and State University, and collaborative work with the Karlsruhe University of Applied Sciences, on the application of shape memory alloy (SMA) elements integrated within glass epoxy composite plates and shells is currently leading to the design of a novel smart bearing based on the principle of antagonistic action. In this system a ball bearing is fitted halfway down a glass epoxy composite tube, entering through one end of the tube. The tube has both ends rigidly built in to the support frame. The tube is divided into two regions, one on each side of the centrally located bearing. SMA strips are bonded in two independent sets of four, each set running axially along half the length of the tube and separated by 90° around the tube. The four strips in each set are electrically connected in series to a high current power supply that can be switched in or out, and the current set, as required. This provides a convenient and fast way of heating each set of SMA strips through the martensite-to-austenite transformation temperature, and provides a significant axial contraction load on the tube in either direction. Previous FE analysis has provided predictions for converting an axial contraction load into useful stiffening of the structure in the radial and hoop directions. This introduces the potential for modification of the dynamic performance of the flexible rotor. In addition to separate heating each half of the active bearing has its own independent forced-air cooling system. Previous work by one of the authors, and others, has shown that a single SMA/composite active bearing can be very effective in both altering the natural frequency of the fundamental whirl mode as well as the modal amplitude. The drawback with that design has been the disparity in the time constant between the relatively fast heating phase and the much slower cooling phase which is reliant on forced air, or some other form of cooling. This form of design means that die cooling phase of one half, still using forced air, is significantly assisted by switching the other half into its heating phase, and vice versa, thereby equalising the time constants, and giving a faster push-pull load on the centrally located bearing; a loading which is termed 'antagonistic' in this paper. The experimental system is discussed in terms of potential performance and control issues.
We present a nonlinear analysis of the dynamics of an automatic ball balancer (ABB) for rotors which are both eccentric and misaligned. The ABB consists of two or more ball bearings which are free to travel around a circular race at a fixed distance from the shaft. The balls, after a transient response, find a steady state which balances the rotor. Following the previous work of Green et al. at Bristol, we have included the effect of shaft misalignment which causes the rotor to precess. This can be countered by having two ABB races at different axial locations along the shaft. Mathematically, we use a Lagrangian approach to derive the equations of motion for the system. It is found that, contrary to the case of flexible rotors that are subject to eccentricity and shaft bending, there is no choice of co-ordinate system which leads to autonomous governing equations. Simulations are then computed which illustrate the role of the ball damping coefficient. EPSRC, Rolls-Royce plc.
The dynamic response of a pile group embedded in a layered poroelastic half space subjected to axial harmonic loads is investigated in this study. Based on Biot's theory and utilizing Muki's method, the second kind of Fredholm integral equations describing the dynamic interaction between the layered half space and the pile group is constructed. Numerical results show that in a two-layered half space, for the closely populated pile group with a rigid cap, the upper softer layer thickness has considerably different influence on the center pile and the corner piles, while for sparsely populated pile group; it has almost the same influence on all the piles.
The barrier effect of window, windowsill wall and balcony is significant on vertical spread of window spill plume along building exterior facade. Fire Simulation experiments are conducted in a full scale model, consisting one 4m x 4m x 4m fire compartment with five windows, five windowsill walls and five balconies like geometries in order to observe vertical spread of window spill plume along building exterior facade under different dimensions of windows, windowsill walls and balconies, and then the correlation between smoke temperature near the exterior facade and dimensions of window, windowsill wall and balcony is obtained by numerical fitting and dimensional analyses. Finally concluded:(l) window, windowsill wall and balcony play different degrees of barrier effect on vertical spread of window spill plume along building exterior facade, balcony playing dominant barrier effect; (2) When the elongation of the balcony is not less than 1.2m, the critical hazardous temperature (70 ‘C) does not spread to the exterior facade of fire room upper; (3) When the width of the window is less than 2.4m, the critical hazardous temperature does not spread to the exterior facade of fire room upper. These quantitative conclusions provide fire Prevention of the building exterior facade with a reference.
A finite element FEM reinforced concrete model has been analyzed by the author using ANSYS 9 finite element program for both unstrengthened and CFRP-strengthened beams using concrete element model 25 × 25 × 25 mm and discrete and smeared steel elements models was used. The CFRP has been modeled using Solid46 element. The obtained deflection results have been compared with other experimental and FE model results in which using concrete element 100 × 42.5 × 42.5 mm, smeared steel distribution, and modeling CFRP with ANSYS 5 program. The obtained results show a success for the author’s proposed model. Also, a parametric study has been done using the proposed model to analyze the maximum strains values for concrete and steel at failure loads, for different opening sizes, and compared them with the experimental data from other researchers, which shows the efficiency of the proposed models.
This paper describes a study of laser generated ultrasonic waves in an 2-layer elastic, isotropic biomaterial model, in order to establish a modelling technique to simulate the thermoelastic response of high-power short pulse laser beams in human skin. The theory proposed in this paper takes into consideration the fundamental understanding of the laser/material interface. A finite element model using the commercial finite element code ANSYS is used to study the effects of laser pulse duration and energy flux contribution to the surface waves. The simulation comprises a set of boundary conditions that approximate a heat flux point source located on top of the surface of the material. Because of the time scale of interest, the elastic effects do not feed back into the thermal problems, so that a sequential coupled-field analysis was performed where the thermal and elastodynamic fields are uncoupled and treated separately. The initial finite element analysis involves a transient thermal analysis using a heat flux with Gaussian spatial variation to simulate the laser pulse heating. The results from the thermal analysis were read and applied to the structural analysis where the out-of-plane displacements histories are analyzed in the skin model with varying thicknesses. Proceedings of the 4th International Conference on Advances in Experimental Mechanics, University of Southampton, 6th-8th September 2005 Advances in experimental mechanics IV / edited by J.M. Dulieu-Barton and S. Quinn. (ISBN13: 9780878499878)
Damaging temperature effects observed during ultrasonic cutting operations are typically a result of friction between the vibrating blade and material, and combustion of debris. In order to prevent the high temperatures causing damage, the ultrasonic blade has to cut with a sufficient speed. This can be achieved either by applying a relatively high static load or by increasing the working vibration amplitude of the cutting edge, however, the result can be poor operational control and exceeding the fatigue limit of the blade, respectively. In this paper, the effect of blade tip profile is considered, particularly with reference to the influence of the cutting edge contact area on temperature under different static loading conditions. Titanium blades, with different cutting edge profiles are tested in a series of experiments that monitor cutting speed, static load, temperature around the cut site, and vibration amplitude at the cutting edge. The blades are tested cutting bovine femur and artificial bone material, and the cut surfaces are examined for signs of damage after each test. The experimental data reveal that blades with a small cutting edge contact area cut at a lower temperature, and that signs of thermal damage are less evident.
In this paper, Imperialist Competitive Algorithm (ICA) and Genetic Algorithm (GA) are used to find the optimal form for torispherical dome ends under internal pressure load. According to fabrication and strength of material requirements, a group of compromised counters are studied. According to ASME Section VIII and BS5500 pressure vessel codes, a reasonable buckling pressure limit is proposed. Four-centered ellipse method is used to describe the geometry of the torispherical dome end that this method is commonly used in engineering drawing. A minimum weight optimization problem based on buckling pressure is studied. Two different size torispherical dome end examples are selected and studied. Imperialist Competitive Algorithm is found to be very efficient and easy to use for the applications, such as torispherical dome end and subjected to internally pressurized loading.
Modelling the dynamic performance of an elevator car system represents a complex task and forms an important step in the elevator system design procedure. The need to consider the behaviour of passengers travelling in the car complicates the procedure further. This paper presents an original approach to identify the stiffness and damping characteristics of an elevator car system in order to investigate the effect of passenger load on the dynamic response. A simplified model is developed and the experimental rig with a rectangular elevator platform fixed on the top of four silent blocks attached to a shaker is setup. The transmissibility measurements are carried out with a harmonic excitation applied first to a platform with no passenger load and then to the platform with one passenger within the frequency range of 1 – 20 Hz. A single person standing on the platform is employed in order to assess the passenger’s contribution to the dynamic behaviour of the elevator car system. Curve fitting technique implemented in MATLAB is used to determine the damping and stiffness coefficients both for the empty car system and the car-passenger system. Investigation on the tolerances for both parameters is carried out. An approach to simplify the experimental procedure and to reduce the number of individual tests is proposed.
The stresses and its distribution in complex shape chain plate geometry play a critical role in the fatigue life performance of a chain assembly. However, it is difficult to identify the stress distribution and stress concentration zones precisely using only the conventional industrial friendly tools such as routine quality control test, breaking load test and numerical computations. In this context the transmission photoelastic technique has made it possible to identify the stress distribution, its concentration and also to quantify the stress and strain at any point in the chain plate. This paper explains how transmission photoelastic technique is used to estimate the stress distribution and its concentration zones in a complex chain plate when it is loaded.
In this study, cocoa (Theobroma cacao) pod husk (CPH) fiber reinforced thermoplastic polyurethane (TPU) was prepared by melt compounding method using Haake Polydrive R600 internal mixer. The composites were prepared with different fiber loading: 20%, 30% and 40% (by weight), with the optimum processing parameters: 190 °C, 11 min, and 40 rpm for temperature, time and speed, respectively. Five samples were cut from the composite sheet. Mean value was taken for each composite according to ASTM standards. Effect of fiber loading on mechanical (i.e. tensile, flexural properties and impact strength) and morphological properties was studied. TPU/CPH composites showed increase in tensile strength and modulus with increase in fiber loading, while tensile strain was decreasing with increase in fiber loading. The composite also showed increase in flexural strength and modulus with increase in fiber content. Impact strength was deteriorated with increase in fiber loading. Morphology observations using Scanning Electron Microscope (SEM) showed fiber/matrix good adhesion.
This study was performed to investigate the effects of cylindrical and row trenched cooling holes with alignment angles of 0 degree and 90 degree at blowing ratio of 3.18 on the film cooling performance adjacent the endwall surface of a combustor simulator. In this research a three dimensional representation of Pratt and Whitney gas turbine engine was simulated and analyzed with a commercial finite volume package FLUENT 6.2. The analysis has been carried out with Reynolds-Averaged Navier-Stokes turbulence model (RANS) on internal cooling passages. This combustor simulator was combined with the interaction of two rows of dilution jets, which were staggered in the stream wise direction and aligned in the span wise direction. Film cooling was placed along the combustor liner walls. In comparison with the baseline case of cooling holes, the application of row trenched hole near the endwall surface doubled the performance of film cooling effectiveness.
Use of common parts for different products (commonality) is important methods for managing product variety and preserving competitiveness in the age of mass customization and supply chain competition. In literature, the advantages of inclusion of common components in a product family are well established. Unfortunately, most of the works have been conducted via simulation or conceptual thinking. The mathematical models in the premises are not adequate for production, planning and control in multistage production. This paper focuses on the advancement of venerable manufacturing resources planning models by incorporating the part commonality concept in a multi-product, multi-period and multi-stage manufacturing system under a deterministic situation. The models are validated with established MRPII models. The material requirement schedule for the basic MRP II and proposed models are compared. It is really a good matching shown between the two schedules. The later bearing additional information of the location where to be available the parts in a time frame. The effects of commonality on cost, capacity and requirement schedule are discussed based on the outcomes of the mathematical models executed with the available live data.