Damping factor

In this paper, an equivalent combination of series and parallel R-L-C high-pass filter circuit is derived for a nano (quantum) antenna for the Internet of thing (IoT) based sensors for speedy data or organ image displaying in medical line surgeries. The proposed method utilized the sample frequency behavior of characteristics mode to develop a fundamental building block that superimposes to create the complete response. The resonance frequency, input impedance, and quality factor have been evaluated along with basic and higher-order resonating modes. The relation between quality factor, bandwidth, resonance frequency, and selectivity for higher order, increases the quantum circuits in terms of increased order of a filter, quality factor, and odd and even harmonics factors. Therefore, the basic circuits derivation factor of frequency coefficients are expanded in terms of polynomials and then they are expressed as a simple rational function from which the basic circuit parameters are c...

In this paper, an equivalent combination of series and parallel R-L-C high-pass filter circuit is derived for a nano (quantum) antenna for the Internet of thing (IoT) based sensors for speedy data or organ image displaying in medical line surgeries. The proposed method utilized the sample frequency behavior of characteristics mode to develop a fundamental building block that superimposes to create the complete response. The resonance frequency, input impedance, and quality factor have been evaluated along with basic and higher-order resonating modes. The relation between quality factor, bandwidth, resonance frequency, and selectivity for higher order, increases the quantum circuits in terms of increased order of a filter, quality factor, and odd and even harmonics factors. Therefore, the basic circuits derivation factor of frequency coefficients are expanded in terms of polynomials and then they are expressed as a simple rational function from which the basic circuit parameters are c...

En viviendas de concreto de baja altura se emplean usualmente muros delgados con baja resistencia del concreto, cuantias minimas de refuerzo y mallas de alambre soldado para refuerzo a cortante en el alma. Con base en la respuesta sismica medida durante el ensayo en mesa vibratoria de seis muros de concreto de baja altura se evalua el factor de amortiguamiento que se utiliza usualmente en el analisis dinamico especificado en los reglamentos. Las variables estudiadas fueron el tipo de concreto (peso normal y ligero), la cuantia —0,125% y 0,25%— y el tipo de refuerzo a cortante en el alma —barras corrugadas y malla de alambre soldado— y el efecto de aberturas (puerta y ventana). Tomando en cuenta las ventajas de los sistemas de identificacion en el dominio de la frecuencia, las propiedades dinamicas se evaluaron utilizando el metodo de ajuste de amplitud de la funcion de transferencia dinamica. En el articulo se discute el efecto del modo de falla sobre el factor de amortiguamiento y ...

This paper derives two kinds of Q factor formulas for use in estimating frequency stability of sinusoidal oscillators. To cover various circuit topologies, we consider a general black-box model having DC input and RF output ports. Assuming a small deviation in DC supply voltage or RF load impedance, the frequency shift caused by such deviation is formulated by a perturbation technique. As a versatile criterion to indicate the tolerance of circuit itself, we introduce oscillator Q against each deviation. Since the theory is described in the linear impedance domain, it gives oscillator designers a clear vista on the stability of practical circuits.

In 1981, famous engineer William F. Egan conjectured that a higher-order type 2 PLL with an infinite hold-in range also has an infinite pull-in range, and supported his conjecture with some third-order PLL implementations. Although it is known that for the second-order type 2 PLLs the hold-in range and the pull-in range are both infinite, this brief shows that the Egan conjecture is not valid in general. We provide an implementation of the third-order type 2 PLL, which has an infinite hold-in range and experiences stable oscillations. This implementation and the Egan conjecture naturally pose a problem, which we will call the Egan problem: to determine a class of type 2 PLLs for which an infinite hold-in range implies an infinite pullin range. Using the direct Lyapunov method for the cylindrical phase space we suggest a sufficient condition of the pull-in range infiniteness, which provides a solution to the Egan problem.

In this paper an algorithm for frequency and damping factor estimation of a real-valued noisy damped sinusoid is proposed. It is an extension of the three-point Interpolated Discrete Fourier Transform (3p-IpDFT) undamped sinusoid frequency estimator based on Maximum Sidelobe Decay (MSD) windows. Analytical expressions for the frequency and the damping factor estimators are provided and the related estimation errors due to the contribution of the spectral image component are derived and compensated. The accuracies of the proposed algorithm and other stateof-the-art frequency-domain based algorithms are compared to each other through computer simulations.

Impact driving of piles is a complex process which depends on the interaction of the stress wave progressing down the pile and on the dynamic soil resistance along the shaft and at the toe. Pile driving vibrations can adversely affect adjacent structures, and the intensity of ground vibrations depends on the dynamic resistance along the pile rather than on the energy applied to the pile. The viscous damping factor, J c , is one of the fundamental parameters when the static pile resistance is determined from dynamic tests. Theoretical analyses and field observations show that the J c -factor is not solely a soil parameter, but a function of the ratio of pile impedance and soil impedance at the pile toe. Consequently, the pile toe damping factor for an open-toe pipe pile would be different when no plug develops in the pile and when the pile toe is fully plugged. Moreover, the mentioned aspect needs to be considered when the results of a test pile of one pile type are applied to a construction pile of a different type. Viscous damping along the pile shaft and at the pile toe is the source of ground vibrations. The vibration magnitude is governed by the interactive nature of dynamic pile-soil resistance, which is a function of the ratio between the pile impedance and the soil impedance for P-waves. It is shown that the vibration transmission efficacy and the dynamic resistance are inversely linearly proportional to the pile impedance, and that energy transmission efficacy correctly reflects the vibration emission from the pile to the surrounding soil layers. The literature includes several studies of comparisons between pile capacity determined in a static loading test to that determined in a CAPWAP analysis on dynamic records. Much of the agreement and non-agreement in such papers is due to that many of the comparisons include mistakes and a few sources of such are illustrated and explained. A case of over reliance on blow-count is presented.

The effect of adjusting damping factor α, from a small initial value α0 to the final desired αf value, upon then iterations needed for PageRank computation is observed. Adjustment of the damping factor is done in one or more steps. Results show no improvement in performance over a fixed damping factor based PageRank. Index terms — PageRank algorithm, Step-wise adjustment, Damping factor.

In this paper, impedance characteristics are determined for discrete movement. It explores the changes in impedance characteristics of human arm during a complete task. This study considered 3D spatial movement for horizontal adduction and abduction. The human arm is considered as mass-spring-damper system and the modelling is done accordingly. The model is solved for 3 degree of freedom (3DoF) spatial movement usually used for daily work. Inertia, stiffness and damping factor are the impedance characteristics considered in the model. Using position measuring device, the position data of elbow and wrist were obtained with respect to pre-defined references. The data were used to calculate velocity, acceleration and force. Then, the impedance characteristics were determined by solving the equation of motion of the mass-spring-damper system corresponding to different position of the wrist on the trajectory. These impedance factors were then plotted to map the characteristics. The mappi...

In this paper an algorithm for frequency and damping factor estimation of a real-valued noisy damped sinusoid is proposed. It is an extension of the three-point Interpolated Discrete Fourier Transform (3p-IpDFT) undamped sinusoid frequency estimator based on Maximum Sidelobe Decay (MSD) windows. Analytical expressions for the frequency and the damping factor estimators are provided and the related estimation errors due to the contribution of the spectral image component are derived and compensated. The accuracies of the proposed algorithm and other stateof-the-art frequency-domain based algorithms are compared to each other through computer simulations.

The atomically flat interface of Y3Fe5O12 (YIG) thin film and Gd3Ga5O12 (GGG) substrate play a vital role in obtaining the magnetization dynamics of YIG below and above the anisotropy field. Here, magneto-impedance (MI) is used to investigate the magnetization dynamics in fully epitaxial 45 nm YIG thin films grown on the GGG (001) substrates using a copper strip coil in the MHz-GHz frequency region. The resistance (R) and reactance (X), which are components of impedance (Z), allow us to probe the absorptive and dispersive components of the dynamic permeability, whereas a conventional spectrometer only measures the field derivative of the power absorbed. The distinct excitation modes arising from the uniform and non-uniform excitation of magnetization dynamics of the magnetization vector of YIG, above and below the anisotropy field, are observed. The magneto-dynamics clearly shows the visible dichotomy between two resonant fields below and above the anisotropy field and its motion as a function of the direction of the applied magnetic field. A low value of the damping factor ~ 4.7 6.1 10 is estimated for uniform excitation mode with anisotropy field of 65 ± 2 Oe. Investigation of anisotropy field dependent magneto-dynamics across these two different regimes, below and above anisotropy field, in the low-frequency mode can be used in designing the YIG based resonators, oscillators, filters, and magnonic devices.

In this paper an algorithm for frequency and damping factor estimation of a real-valued noisy damped sinusoid is proposed. It is an extension of the three-point Interpolated Discrete Fourier Transform (3p-IpDFT) undamped sinusoid frequency estimator based on Maximum Sidelobe Decay (MSD) windows. Analytical expressions for the frequency and the damping factor estimators are provided and the related estimation errors due to the contribution of the spectral image component are derived and compensated. The accuracies of the proposed algorithm and other stateof-the-art frequency-domain based algorithms are compared to each other through computer simulations.

This paper describes a novel method for proportional-integral-derivative controlled phase-locked loop model for communication system for better settling time during acquisition. A proportional-integral-derivative controlled block is inserted in place of a 4 th order loop filter of the phase-locked loop. The s-domain transfer function of the system is derived for linear analysis. The settling, phase margin, bandwidth and stability of the system are analyzed through behavioral simulation by using MATLAB platform. It is observed that the proportional-integral-derivative controlled phase-locked loop model reduces the settling time (~ nS) in comparison to phase-locked loop with 4 th order loop filter in the loop (~µS).

Contribution of step-in geometric discontinuity to the longitudinal coupling impedance has been obtained analytically using exact field matching. We assumed a perfectly conducting beam-pipe wall of two different radii connected coaxially at z¼ 0 so that the contribution to the longitudinal coupling impedance is purely due to the beam-pipe geometric discontinuity. We also obtained the longitudinal loss factor for a Gaussian beam as a function of beam energy and bunch length. Results have been analyzed numerically for some representative parameters close to real machine parameters. Analytical results have also been compared with numerical simulation from CST at relativistic beam energies. We found a very good agreement between theory and simulation.

This article exhaustively investigates the impedance characteristics of mid-infrared Quantum Cascade Lasers (QCLs). Also, the effect of device parameters namely optical confinement factor, mirror reflectivity and spontaneous emission factor on the impedance and modulation characteristics of QCLs are reported for the first time. The QCL considered for the study operates at 9 μm and contains 48 stages. Under standard operating conditions, the device provides an electrical bandwidth of 250 GHz with an intrinsic impedance of 2.07 mΩ. From the analysis results, it is inferred that maximum value of impedance is always achieved with minimum drive current. Moreover, the magnitude of maximum value of impedance (2.37 mΩ) is obtained at a mirror reflectivity (R) of 0.45. Further, maximum bandwidth of 335 GHz is achieved when optical confinement factor (Γ) is 0.45 and at a drive current of 3 A. The device also provides a flat impedance response with a value of around 1 mΩ over a wide band of frequencies from 1 to 20 GHz enabling its application in 5G wireless networks. Impedance characteristics of QCL will aid in designing proper matching circuits for reducing reflections and efficient operation.

This article exhaustively investigates the impedance characteristics of mid-infrared Quantum Cascade Lasers (QCLs). Also, the effect of device parameters namely optical confinement factor, mirror reflectivity and spontaneous emission factor on the impedance and modulation characteristics of QCLs are reported for the first time. The QCL considered for the study operates at 9 μm and contains 48 stages. Under standard operating conditions, the device provides an electrical bandwidth of 250 GHz with an intrinsic impedance of 2.07 mΩ. From the analysis results, it is inferred that maximum value of impedance is always achieved with minimum drive current. Moreover, the magnitude of maximum value of impedance (2.37 mΩ) is obtained at a mirror reflectivity (R) of 0.45. Further, maximum bandwidth of 335 GHz is achieved when optical confinement factor (Γ) is 0.45 and at a drive current of 3 A. The device also provides a flat impedance response with a value of around 1 mΩ over a wide band of frequencies from 1 to 20 GHz enabling its application in 5G wireless networks. Impedance characteristics of QCL will aid in designing proper matching circuits for reducing reflections and efficient operation.

This study proposes the modelling and behavioural simulation of a high-speed phased-locked loop for frequency synthesis. The authors consider the second-order active lag-lead as well as the standard feedback approach of loop filter design for the system model. The s-domain transfer functions of the model for both the cases under considerations are derived for its linear analysis, considering its elemental values. Transient behaviour and stability of the model is analysed using behavioural simulations in MATLAB (Version: 7.1) which shows excellent results. Here, the authors discuss in detail the procedure for mathematical derivation of the theoretical model, taking into account both active lag-lead and standard feedback approach for the loop in the PLL model, the various aspects of methodology for simulations and their results.

An analytical approach to the acoustic input impedance of vibrating cylindrical pipes is considered. The variation in the acoustic impedance introduced by wall vibrations is calculated using the integro-modal method taking into account axisymmetric shell vibration. It is shown that this variation can be interpreted as a small correction in the acoustic input impedance when the walls of the shell do not influence the acoustics in the pipe. Special conditions such as the mechanical resonance condition and spatial coincidence effect lead to maximum values of the correction factor for the input impedance. The results allow us to determine particular shell parameters for which the input impedance is strongly affected by wall vibrations.

Although several research programs have investigated the performance of structural elements made of lightweight concrete, there is a limited understanding of the behavior of lightweight shear walls under seismic conditions. In this paper is summarized an experimental study that comprised quasi-static cyclic tests and shake table tests of twenty walls, conducted to provide information on the effect of lightweight and low-strength concrete on seismic performance of thin lightly-reinforced shear walls. Test results indicate that shear strength, drift ratios and energy dissipated at different limit states of lightweight concrete walls were larger in comparison to walls made of normalweight concrete. Measured performance also indicate that the reduction factor proposed by ACI 318-11 and NTC-C does not capture adequately the influence of lightweight and low-strength concrete. Thus, shear strength of thin lightly-reinforced, lightweight concrete shear walls can be calculated without any modification factor.

The acoustical impedance of the exhaust of an internal combustion engine is measured using the two microphone transfer function method according to ISO 10534-2. Some improvements are proposed to this procedure. The engine exhaust impedance is also simulated using electrical analog circuits, wherein geometrical data of the engine and the manifold is used. The simulation results correlates well with the measurement results. Some special cases are simulated, to determine the engine components which contribute primarily to its acoustical impedance.

A damping device, consisting of an annular tail-pipe, has been developed. It is applicable in situations wherein acoustic damping is required in combination with low flow resistance. The device consists of a central tube surrounded by a narrow slit. The central tube has an acoustic mass which impedance increases with frequency while the slit resistance remains constant. When the frequency has been increased sufficiently, a considerable part of the acoustic flow passes through the slit where it will be damped. In this way, acoustic energy can be dissipated while the flow experiences a low flow resistance. The acoustic properties of the device will be investigated using an electrical equivalent circuit. The impedance will be measured using an impedance measurement duct, from which the slit resistance will be deduced. The resulting slit resistance consists of a linear part depending on the air viscosity, and a non-linear part which is caused by the loss of kinetic energy of the fluidum through the slit. The presence of a laminar mean flow does not effect the acoustic performance of the annular tailpipe, only some minor effects are observed in the low frequency range. Even with a mean turbulent flow, the acoustic damping mechanism still remains intact.

A vital feature of modern web search engine is the ability to display relevant and reputable pages near the top of the list of query results. A well-used search engine nowadays is Google search engine, it is the world's most popular search engine, rely on PageRank technology to determine a website's ranking. We put our attention on important benefactions to improving the quality of rankings via the value which is called damping factor, commonly the original suggestion d=0.85 by Brin and Page is the most common choice. In this paper, we suggest a new value which plays an important role to rank web sites accurately, our work focuses on damping factor value which improves the efficiency of PageRank value for each website. Our results show that the suggested value can get greater performance. Finally, we will show satisfactory result without link spam and dangling node applying PageRank algorithm on graphs with over 5000 links.

Traditionally, inertia in power systems has been determined by considering all the rotating masses directly connected to the grid. During the last decade, the integration of renewable energy sources, mainly photovoltaic installations and wind power plants, has led to a significant dynamic characteristic change in power systems. This change is mainly due to the fact that most renewables have power electronics at the grid interface. The overall impact on stability and reliability analysis of power systems is very significant. The power systems become more dynamic and require a new set of strategies modifying traditional generation control algorithms. Indeed, renewable generation units are decoupled from the grid by electronic converters, decreasing the overall inertia of the grid. 'Hidden inertia', 'synthetic inertia' or 'virtual inertia' are terms currently used to represent artificial inertia created by converter control of the renewable sources. Alternative spinning reserves are then needed in the new power system with high penetration renewables, where the lack of rotating masses directly connected to the grid must be emulated to maintain an acceptable power system reliability. This paper reviews the inertia concept in terms of values and their evolution in the last decades, as well as the damping factor values. A comparison of the rotational grid inertia for traditional and current averaged generation mix scenarios is also carried out. In addition, an extensive discussion on wind and photovoltaic power plants and their contributions to inertia in terms of frequency control strategies is included in the paper.

Power factor correction converters with a programmable harmonic input impedance can be used to reduce the harmonic distortion in the utility grid. Whereas previously proposed controllers tried to obtain a resistive behaviour of the converter with a constant input impedance for all frequencies, including the fundamental, another recently proposed control strategy allows the setting of a harmonic input resistance independent of the fundamental input impedance. Although previous papers showed the usefulness of this approach, the analysis and verification of the input impedance of the converter in a broad frequency spectrum is focussed here. The characteristics of the current controller will determine the input impedance of the converter in the frequency domain. The implementation of the control strategy with a programmable harmonic resistance on a digitally controlled full-bridge bidirectional converter is described. Experimental tests on a 1-kW prototype show that with the proposed implementation good concordance with the theoretical input impedance curves is obtained.

Ground vibrations are an important design consideration for piles driven by impact hammers. The first task is to determine allowable vibration levels; the second task is to predict the intensity of ground vibrations during driving and the attenuation of ground vibrations with increasing distance. The paper describes the Swedish vibration standard which is applicable for pile driving. Commonly used vibration parameters, associated with the evaluation of vibration measurements, are discussed. The importance of pile impedance for ground vibrations is highlighted. A simplified calculation method is proposed which can be used to estimate vertical ground vibration velocity as a function of distance from the driven pile. Two case histories have been evaluated and compared with theoretical predictions, using the proposed method of analysis.

The estimation of load impedance spectrum is required in the research and applications of electrical engineering. Some of the current applications are the grid impedance estimation of active filters, the research of the propagation of EMI (Electro Magnetic Interference) and power line communication. The direct measurement of load impedance, in the frequency range in question, requires synchronous voltage and current measurement, which can be difficult. Compared to the direct impedance spectrum measurement, the measurement of impedance amplitude spectrum is a simple and low-cost method since e.g. only peak or RMS (Root-Mean-Square) value of current and voltage for each measured frequency is required. This article presents a method and a tool based on the method that allows one to compute the phase spectrum estimate for the impedance amplitude spectrum. The method is based on the maximum entropy model (MEM). The applicability of the tool is demonstrated with input impedance measuremen...

Impact driving of piles is a complex process which depends on the interaction of the stress wave progressing down the pile and on the dynamic soil resistance along the shaft and at the toe. Pile driving vibrations can adversely affect adjacent structures, and the intensity of ground vibrations depends on the dynamic resistance along the pile rather than on the energy applied to the pile. The viscous damping factor, Jc, is one of the fundamental parameters when the static pile resistance is determined from dynamic tests. Theoretical analyses and field observations show that the J c-factor is not solely a soil parameter, but a function of the ratio of pile impedance and soil impedance at the pile toe. Consequently, the pile toe damping factor for an open-toe pipe pile would be different when no plug develops in the pile and when the pile toe is fully plugged. Moreover, the mentioned aspect needs to be considered when the results of a test pile of one pile type are applied to a construction pile of a different type. Viscous damping along the pile shaft and at the pile toe is the source of ground vibrations. The vibration magnitude is governed by the interactive nature of dynamic pile-soil resistance, which is a function of the ratio between the pile impedance and the soil impedance for P-waves. It is shown that the vibration transmission efficacy and the dynamic resistance are inversely linearly proportional to the pile impedance, and that energy transmission efficacy correctly reflects the vibration emission from the pile to the surrounding soil layers. The literature includes several studies of comparisons between pile capacity determined in a static loading test to that determined in a CAPWAP analysis on dynamic records. Much of the agreement and non-agreement in such papers is due to that many of the comparisons include mistakes and a few sources of such are illustrated and explained. A case of over reliance on blow-count is presented.

This paper describes the impedance characteristics of the human arm during passive movement. The arm was moved in the desired trajectory. The motion was actuated by a 1-degree-of-freedom robot system. Trajectories used in the experiment were minimum jerk (the rate of change of acceleration) trajectories, which were found during a human and human cooperative task and optimum for muscle movement. As the muscle is mechanically analogous to a spring-damper system, a second-order equation was considered as the model for arm dynamics. In the model, inertia, stiffness, and damping factor were considered. The impedance parameters were estimated from the position and torque data obtained from the experiment and based on the "Estimation of Parametric Model". It was found that the inertia is almost constant over the operational time. The damping factor and stiffness were high at the starting position and became near zero after 0.4 seconds.

Thin walls having low concrete strength, minimum web steel ratios and web shear reinforcement made of welded wire meshes are commonly used in low-rise concrete housing. The damping factor commonly used for code-based dynamic analysis was evaluated based on seismic response measured during shake table tests of six low-rise concrete walls. The variables studied were the type of concrete (normal and lightweight), the web steel shear ratio (0.125% and 0.25%), the type of web shear reinforcement (deformed bars and welded wire meshes) and the effect of openings (doors and windows). Dynamic properties were evaluated considering the advantages of frequency-domain system identification, using the dynamic transfer function amplitude fitting method. The effect of failure mode on damping factor is discussed. An equation for estimating damping associated with a particular vibration period value is also proposed. It was observed that a 5% damping factor (assumed for dynamic analysis of concrete housing in the range of lineal elastic behaviour) was consistent with the values measured here.

Thin walls having low concrete strength, minimum web steel ratios and web shear reinforcement made of welded wire meshes are commonly used in low-rise concrete housing. The damping factor commonly used for code-based dynamic analysis was evaluated based on seismic response measured during shake table tests of six low-rise concrete walls. The variables studied were the type of concrete (normal and lightweight), the web steel shear ratio (0.125% and 0.25%), the type of web shear reinforcement (deformed bars and welded wire meshes) and the effect of openings (doors and windows). Dynamic properties were evaluated considering the advantages of frequency-domain system identification, using the dynamic transfer function amplitude fitting method. The effect of failure mode on damping factor is discussed. An equation for estimating damping associated with a particular vibration period value is also proposed. It was observed that a 5% damping factor (assumed for dynamic analysis of concrete housing in the range of lineal elastic behaviour) was consistent with the values measured here.

As it is widely recognized, seismic design parameters used in most current codes are mainly intended for designing concrete walls in medium-or high-rise buildings. In low-rise concrete housing, thin walls with low concrete strength, web steel ratio smaller than the minimum ratio prescribed by codes, and in many cases, shear web reinforcement made of welded wire meshes are commonly used. In this paper, a simplified equation for estimating the period of vibration of low-rise concrete housing is proposed. The equation is based on response measured during shaking table tests of solid walls and walls with openings, on the results derived from conventional spectral analysis of ambient vibration tests, as well as on results obtained from mathematical models using the wide-column analogy and the finite element method. Statistical analysis of the ratios of predicted-to-measured periods demonstrated that predicted periods were very similar to those observed, and the scatter is also lower than in existing equations. The proposed equation is useful for seismic design, as well as for assessing the adequacy of available equations in current codes.

This paper compares the performance of four isolated reinforced concrete (RC) walls with openings: two prototype walls tested under quasi-static cyclic (QSC) loading, and two models tested under shaking table excitation. The variables studied were the web steel ratio, the type of web reinforcement, and the testing method. By means of the measured response, it was verified that loading history of the QSC testing ignores the foremost dynamic effects observed in structures subjected to earthquake loads. When dynamic and QSC responses were compared, it was apparent that stiffness and strength degradation properties depend on the loading rate, the strength mechanisms associated to the failure modes, number of cycles, and cumulative parameters such as ductility demand and energy dissipated. We deducted that data obtained from QSC tests cannot always be safely assumed to be a lower limit of the expected capacity. Stiffness and strength degradation models for RC walls with openings subjected to earthquake-type loading are also proposed.

The results of a study of the variation of three-phase induction machines' input impedance with frequency are proposed. A range of motors were analysed, both two-pole and four-pole, and the magnitude and phase of the input impedance were obtained over a wide frequency range of 20 Hz-1 MHz. For test results that would be useful in the prediction of the performance of induction machines during typical use, a test procedure was developed to represent closely typical three-phase stator coil connections when the induction machine is driven by a threephase inverter. In addition, tests were performed with the motor's cases both grounded and not grounded. The results of the study show that all induction machines of the type considered exhibit a multiresonant impedance profile, where the input impedance reaches at least one maximum as the input frequency is increased. Furthermore, the test results show that the grounding of the motor's case has a significant effect on the impedance profile. Methods to exploit the input impedance profile of an induction machine to optimise machine and inverter systems are also discussed.

The stiffness of structural walls is a key parameter for seismic design because the distribution of shear forces depends on the relative stiffness of each wall of the structural system. The study of stiffness degradation of lowrise reinforced concrete walls has been focused on the description of the deterioration of such structural property. This study aims at proposing a semi-empirical model for assessing the lateral stiffness degradation in terms of drift ratio of thin and lightly reinforced concrete walls for low-rise and low-cost housing subjected to seismic demands. The variables of the study are the height-to-length ratio of walls (0.5, 1 and 2), type of concrete (normal-weight, lightweight and self-compacting), steel ratio of web shear reinforcement (0.125% and 0.25%), and the type of web shear reinforcement (deformed bars and welded-wire meshes). The experimental program comprises 23 walls tested under quasi-static reversed-cyclic loading. Lateral stiffness computed using measured response of walls are compared with stiffness computed using recommendations prescribed by codes or reported in a literature review. The effect of geometrical and mechanical properties of walls on stiffness is also assessed in the paper. In addition, the study proposes limit values of stiffness degradation for different limit states and performance levels.

The stiffness of structural walls is a key parameter for seismic design because the distribution of shear forces depends on the relative stiffness of each wall of the structural system. The study of stiffness degradation of lowrise reinforced concrete walls has been focused on the description of the deterioration of such structural property. This study aims at proposing a semi-empirical model for assessing the lateral stiffness degradation in terms of drift ratio of thin and lightly reinforced concrete walls for low-rise and low-cost housing subjected to seismic demands. The variables of the study are the height-to-length ratio of walls (0.5, 1 and 2), type of concrete (normal-weight, lightweight and self-compacting), steel ratio of web shear reinforcement (0.125% and 0.25%), and the type of web shear reinforcement (deformed bars and welded-wire meshes). The experimental program comprises 23 walls tested under quasi-static reversed-cyclic loading. Lateral stiffness computed using measured response of walls are compared with stiffness computed using recommendations prescribed by codes or reported in a literature review. The effect of geometrical and mechanical properties of walls on stiffness is also assessed in the paper. In addition, the study proposes limit values of stiffness degradation for different limit states and performance levels.

Aimed at better understanding the seismic behavior of reinforced concrete (RC) walls, typically used in one-to-two stories housing in several Latin American countries, a large investigation project has been carried out. Previous experimental programs considered the behavior of walls subjected to monotonically and cyclically increased loads. This paper compares and discusses displacement and shear strength capacities, as well as the dynamic characteristics of six RC walls tested under shaking table excitations. Variables studied were the wall geometry (solid walls and walls with openings), type of concrete (normalweight and lightweight), web steel reinforcement ratio (0.125% and 0.25%) and type of web reinforcement (deformed bars and welded-wire mesh). Shaking table tests were essential for assessing dynamic characteristics, such as changes in fundamental frequencies and damping factors of RC walls for low-rise housing.

Proportional damping is the most common approach to model dissipative forces in complex engineering structures and it has been used in various dynamic problems for more than 10 decades. One of the main limitation of the mass and stiffness proportional damping approximation comes from the fact that the arbitrary variation of damping factors with respect to vibration frequency cannot be modelled accurately by using this approach. Experimental results, however, suggest that damping factors can vary with frequency. In this paper a new generalized proportional damping model is proposed in order to capture the frequency-variation of the damping factors accurately. A simple identification method is proposed to obtain the damping matrix using the generalized proportional damping model. The proposed method requires only the measurements of natural frequencies and modal damping factors. Based on the proposed damping identification method, a general approach for modelling of damping in complex systems has been proposed. Examples are provided to illustrate the proposed method.

Thin walls having low concrete strength, minimum web steel ratios and web shear reinforcement made of welded wire meshes are commonly used in low-rise concrete housing. The damping factor commonly used for code-based dynamic analysis was evaluated based on seismic response measured during shake table tests of six low-rise concrete walls. The variables studied were the type of concrete (normal and lightweight), the web steel shear ratio (0.125% and 0.25%), the type of web shear reinforcement (deformed bars and welded wire meshes) and the effect of openings (doors and windows). Dynamic properties were evaluated considering the advantages of frequency-domain system identification, using the dynamic transfer function amplitude fitting method. The effect of failure mode on damping factor is discussed. An equation for estimating damping associated with a particular vibration period value is also proposed. It was observed that a 5% damping factor (assumed for dynamic analysis of concrete h...

When dynamic performance of structures is assessed experimentally, most experimental studies consider variation in intensity by increasing the record of peak ground acceleration or displacement at different values. However, severity of earthquake motion is not only a function of the concerns instrumental intensity, but also the frequency content, duration and the amount of energy imposed on the structure. To fulfill dynamic test conditions, this paper describes and discusses a novel method for selecting several seismic events characterising the seismic area and fulfilling particular similitude requirements. The method included using an earthquake record as an empirical Green's function for simulating larger magnitude events. Three seismic events used for shake table testing of reinforced concrete walls for low-rise housing are presented and discussed to validate the proposed method's results.

Sinusoidal oscillation transmission through branched metabolic pathways is studied. Two systems are analyzed, which are composed of two convergent reaction branches and differ in the length of one of them. Linear kinetics is assumed first. Michaelis-Menten enzymes are then considered by using previous results that suggest their behavior with respect to propagation of oscillations is close to linearity around the mean input flux. As a result, there exist ways to modulate the activity of the enzymes so that propagation is equivalent for branched and specific unbranched pathways. Cells may have taken advantage of such a possibility in cases where oscillations have a biological role.

When dynamic performance of structures is assessed experimentally, most experimental studies consider variation in intensity by increasing the record of peak ground acceleration or displacement at different values. However, severity of earthquake motion is not only a function of the concerns instrumental intensity, but also the frequency content, duration and the amount of energy imposed on the structure. To fulfill dynamic test conditions, this paper describes and discusses a novel method for selecting several seismic events characterising the seismic area and fulfilling particular similitude requirements. The method included using an earthquake record as an empirical Green's function for simulating larger magnitude events. Three seismic events used for shake table testing of reinforced concrete walls for low-rise housing are presented and discussed to validate the proposed method's results.

Although several research programs have investigated the performance of structural elements made of lightweight concrete, there is a limited understanding of the behavior of lightweight shear walls under seismic conditions. In this paper is summarized an experimental study that comprised quasi-static cyclic tests and shake table tests of twenty walls, conducted to provide information on the effect of lightweight and low-strength concrete on seismic performance of thin lightly-reinforced shear walls. Test results indicate that shear strength, drift ratios and energy dissipated at different limit states of lightweight concrete walls were larger in comparison to walls made of normalweight concrete. Measured performance also indicate that the reduction factor proposed by ACI 318-11 and NTC-C does not capture adequately the influence of lightweight and low-strength concrete. Thus, shear strength of thin lightly-reinforced, lightweight concrete shear walls can be calculated without any modification factor.

Based on steel strains recorded during shake table tests of six wall specimens, the effect and contribution of steel reinforcement to peak shear strength and displacement capacity of low-rise concrete walls is assessed and discussed. The experimental program included four variables such as wall geometry, concrete type, web steel ratio and type of web reinforcement. Wall response was assessed through effective steel strains in vertical reinforcement, efficiency factors of wall reinforcement, contribution of web horizontal reinforcement to wall shear strength, and the effect of type of web reinforcement to wall displacement.

Using exact field matching, the longitudinal loss factor and impedance of a step-out in a round cylindrical beam-pipe at arbitrary beam energy have been obtained analytically. The beam-pipe sections have perfectly conducting walls which are connected coaxially at z ¼ 0 such that b 2 o b 1 , where b 2 and b 1 are the corresponding radii. Comparison between the step-out and step-in impedances at ultrarelativistic energies shows that both impedances peak at the same eigenmode frequencies. The imaginary parts of the step-out and step-in impedances are negative, slightly different in magnitude up to few Ohms, and have a similar frequency evolution. The real part of the step-out starts at positive values below the first cutoff , remains positive and tends toward a positive value at higher frequencies. At low frequencies below the first cutoff frequency, the real parts of the step-out and step-in impedances are equal in magnitude, shifted up to a positive value for the step-out and down below zero to the same value for the step-in. Numerical examples of the variation of step-out impedance with beam energy have also been given. The loss factor of the step-out is positive indicating energy loss, is higher in magnitude than the negative loss factor of the step-in, and therefore, the net effect will be a slowing down of the beam.