Dynamic Performance Characteristics Research Articles

Economic Analysis and Implementation Strategies for SOFC Systems in Residential Applications

In this study, we installed and evaluated a 1.5 kW Solid Oxide Fuel Cell (SOFC) with Micro-CHP (combined heat and power) system as a Distributed Generation (DG) prime mover in a residential application. Both steady state and dynamic operating conditions were evaluated. With the steady state and dynamic performance characteristics of the SOFC CHP system, and the latest capital cost and performance data garnered from the ENE FARM Program (Japan) and ene. field Program (Europe), we carried out an economic analysis taking into account the daily and seasonal energy production, residential utility rates, fiscal incentives by state, and effective photovoltaic (PV) capacity integration. Various operation strategies that focus on 1) reduced energy use, 2) reduced peak demand, 3) PV integration at the residence, and 4) qualifications for fiscal incentive programs are evaluated. From the customer perspective, this study generates a guideline for the user to make decisions regarding SOFC system capacity, operating strategy and CHP configuration, while providing guidance regarding the breakeven costs of SOFC systems under various scenarios in various regions.

Dynamic Performance Characteristics of Pervious Concrete Pile Composite Foundations under Earthquake Loads

AbstractWith the advantages of both granular piles and rigid piles, pervious concrete piles (PCPs) are especially suitable for improving ground bearing capacity. To study the dynamic performance ch...

Dynamic Performance Characteristics of Pre-Stressed Cable RC Truss Floor System under Human-Induced Loads

Excessive floor vibrations in slender structural systems due to human activity are becoming more prevalent. This may result in serviceability problems such as discomfort to occupants and even subsequent public panic. This paper describes the experimental and analytical studies on the vibration performance of a long-span pre-stressed cable RC truss (PCT) floor system, along with an extensive comparison between the present results and the current vibration design criteria used in the USA and China. The dynamic responses of this floor system under heel-drop, falling-into-seats, and jumping loads were obtained through on-site tests. The test results show good agreement in natural frequencies of the PCT floor system with others, but there are obvious differences in peak accelerations and damping ratios. A method based on the classical plate theory was adopted to determine the fundamental frequency of the system. Dynamic magnification factors (DMFs) under different loads were calculated using the inversion technique and then compared with the results available from others. Some of the conclusions achieved may be incorporated into the structural design of the system of concern to improve safety and serviceability. They can also serve as the basis for developing the relevant design guideline.

Investigation of parasitic resistance and capacitance effects in nanoscaled FinFETs and their impact on static random-access memory cells

A thorough investigation of the parasitic resistance and capacitance (RC) effects of a single-fin FinFET on logic CMOS devices and circuits is presented. As parasitic RC effects become increasingly prominent in nanoscaled FinFET technologies, they are critical to the overall device and circuit performance. In addition, the effects of dummy patterns as well as multifin structures are analyzed and modeled in detailed. By incorporating parasitic resistance and capacitance extracted by both measurement and simulation, the static and dynamic performance characteristics of standard six transistor static random-access memory (6T-SRAM) cells are comprehensively evaluated as an example of parasitic RC effects in this investigation.

A new lever-type variable friction damper for freight bogies used in heavy haul railway

To overcome defects caused by the complex structure and unstable damping performance of the wedge-type damper, a new lever-type friction damper has been developed for use in freight bogies; the design allows the advantages of traditional three-piece bogies to be retained. A detailed description of the structure and mechanism of the lever-type damper is provided, followed by a stress analysis using the finite element method. Dynamic performance characteristics of the lever-type damper and the wedge-type damper are compared in terms of the nonlinear critical speed, riding index, and curve negotiation. The results indicate that the maximum stress of the lever remains below its yield limit. The lever-type car has higher running performance reliability, and achieves similar nonlinear critical speed, riding index, and curve negotiation when compared with the wedge-type car.

Dynamics study of ethanol adsorption on microporous activated carbon for adsorptive cooling applications

The present paper reports the experimental characterization of dynamic performance of three Ad-HEx configurations based on the activated carbon/ethanol working pair. The kinetic behavior of ethanol adsorption onto activated carbon was studied by the LTJ (Large Temperature Jump) method that reproduces the real conditions of isobaric stages of adsorptive cooling cycles. The study consists of two main parts: the first one is related to the adsorption kinetics of the Flat Adsorbent Bed configuration, composed of loose adsorbent grains placed on the metal support. While the second one describes the performance evaluation of finned flat – tube HEx configurations loaded with adsorbent grains. The effects of the grain size, the ratio S/m of heat transfer surface to the adsorbent mass and the Ad-HEx geometry are explored in detail in order to find the main factors affecting the adsorption dynamics. On the base of the main findings obtained, the practical recommendations on optimization of the Ad-HEx unit are formulated in order to enhance the specific cooling power of an adsorptive chiller. Furthermore, a comparison of the adsorption characteristic times between the activated carbon and a properly synthesized porous composite, composed of LiBr inside a silica gel host matrix is shown.

Performance behaviour of elliptical-bore journal bearings lubricated with solid granular particulates

Journal bearings operating in hot environments and at high temperatures experience accelerated degradation of lubricating oils. In such situations, dry granular particulates have emerged as potential media for providing lubrication in journal bearings in place of lubricating oils. Granular particulates do not degrade thermally, even at considerably high temperatures. This work explores the static and dynamic performance characteristics of elliptical-bore journal bearings lubricated with granular particulates. It is found that a bearing lubricated with a larger size (2μm) particles offers better performance compared with that using smaller size (1μm) particles. Bore ellipticity reduces the load-carrying capacity and increases side leakage and the coefficient of friction; however, rotor stability is marginally improved at low eccentricity ratios (<0.6), followed by significant improvement at high eccentricity ratios (>0.6).

Analysis of the dynamic performance of a variable-frequency induction motor drive using various control structures and algorithms

A comparative analysis of the dynamic characteristics of field-oriented induction motor drive control systems relying on the main magnetic flux linkage vector reference, space-vector pulse width modulation (SVPWM) of the voltage inverter output, and direct torque control (DTC) is carried out using the Matlab/Simulink program package, with the parameters of the induction motor model used being the same. A changeover from stepless vector control systems to systems using microprocessors and modern controllable frequency converters operating on the principle of relay control entails possible changes in the properties of the electric drives being controlled. In this connection, there is a need to compare the dynamic performance characteristics of an electric drive with a slave vector control system (with an idealized frequency converter), referred to as electric drive 1 (ED1), an electric drive with a DTC system (ED2), and an electric drive using direct torque control and SVPWM (ED3). Modeling has shown that the response time of the torque control loop in all the control systems considered is the same, the time delay being no more than 0.01 s. On the whole, speed control transients in all of the above systems take their course in one and the same way. The differences in flux linkage control transients between ED2 and ED3, on the one hand, and ED1, on the other hand, are due to the differences between the methods used to form the electromagnetic torque. No provision is made in the above control systems for the stabilization of the magnitude of the flux linkage vector. At low loads, the flux linkage automatically follows the load. In an ED3 with direct torque control, the calculation of the necessary instant magnitudes of the voltage vector projections and the SVPWM based formation of the voltages applied to the motor allows implementation of a fast-response control system with minimal harmonic distortions and torque pulsations. The control system coefficients are calculated beforehand. The speed controller is adjusted to the technical optimum. In the main flux linkage oriented control system, it is also desirable to use an SVPWM-based formation of the motor voltage.

Dynamic performance characteristics of an innovative Cable Supported Beam Structure–Concrete Slab Composite Floor System under human-induced loads

An innovative Cable Supported Beam Structure–Concrete Slab Composite Floor System (CSBS–CSCFS) with a desirable large span capacity was developed in this study to meet the large interior space requirement of public buildings. This new system has excellent merits over conventional floor structures, particularly in terms of span capacity, strength-to-weight ratio, and thin-walled floor. Despite awareness of these advantages, this type of system is not fully utilized because of the potential disadvantage of excessive vibration under human-induced loads. To investigate the dynamic behavior of this system under human-induced loads, field tests were conducted on the floor of the recently built Hebei Normal University Gymnasium, to which the CSBS–CSCFS was applied for the first time. Two types of experimental tests were conducted: free and human-induced vibration tests, in which the vertical acceleration responses of the floor structure were measured under several types of human-induced loads (e.g., stepping, jumping, walking, running, and random activities). Human perception of vibration during the tests was also determined through questionnaires. Results of the free vibration tests showed that the first three natural frequencies of the structure are 2.30Hz, 2.69Hz and 3.06Hz. Moreover, the floor has a damping ratio with a value of 1.54%. This result implies that the structure has relatively low natural frequencies, and its performance may be affected by human activities. Results of human-induced vibration tests indicated that the human-induced vibration of the CSBS–CSCFS is influenced by several factors, namely, dynamic characteristics of the structure, type of human-induced load, stationary people occupying the floor, synchronism of activities, crowd size, and load frequency. The dynamic responses of the structure were compared with International Organization for Standardization (ISO) and American Institute of Steel Construction (AISC) criteria. Meanwhile, human perception of vibration was also summarized. The comparison and summary implied that the vibration of the floor should be attenuated to improve human comfort, although doing so is unnecessary in normal usage. A passive dynamic control system is an efficient method to achieve this goal.

Dynamic and steady state performance comparison of line-start permanent magnet synchronous motors with interior and surface rotor magnets

Abstract A comprehensive comparison of the dynamic and steady state performance characteristics of permanent magnet synchronous motors (PMSM) with interior and surface rotor magnets for line-start operation is presented. The dynamic model equations of the PMSM, with damper windings, are utilized for dynamic studies. Two typical loading scenarios are examined: step and ramp loading. The interior permanent magnet synchronous motor (IPMSM) showed superior asynchronous performance under no load, attaining faster synchronism compared to the surface permanent magnet synchronous motor (SPMSM). With step load of 10 Nm at 2 s the combined effect of the excitation and the reluctance torque forced the IPMSM to pull into synchronism faster than the SPMSM which lacks saliency. The ability of the motors to withstand gradual load increase, in the synchronous mode, was examined using ramp loading starting from zero at 2 s. SPMSM lost synchronism at 12 s under 11 Nm load while the IPMSM sustained synchronism until 41 seconds under 40 Nm load. This clearly suggests that the IPMSM has superior load-withstand capability. The superiority is further buttressed with the steady state torque analysis where airgap torque in IPMSM is enhanced by the reluctance torque within 90° to 180° torque angle.

Advanced Dynamic & Crash Simulation of Lightweight Profiles for Design of Roadside Infrastructure

Many research works recently have attempted to use different computational and numerical simulation techniques to model the material thermal large deformation processes for the design of high performance profiles in new roadside infrastructure designs. The material processes for the lightweight crash-capable parts are among the most delicate processes for the material scientist and designing engineers. The forming and extrusion of lightweight alloys involves thermal effects, large deformation, complex geometries and free surface boundaries. The conventional approach towards the simulation of extrusion process using Finite Element (FE) or Finite Volume (FV) has serious short comes even when updated Lagrangian, Eulerian or ALE techniques are employed. During past decades, there has been considerable effort to simulate the whole extrusion process by splitting it into steady state (using Eulerian technique) and transient (using Updated Lagrangian technique) processes.The damage initiation, progression and also failure of lightweight hollow profiles during crash are a result of accumulated damage under plastic deformation. Based on the damage theories, as the loading condition is changing for the material, a plastic deformation may take place which would progressively increase the damage in the component. The accumulated damage would ultimately result in the failure of the cross-section. There are different numerical models to calculate the damage evolution, fracture initiation and also its propagation using continuum and/or discrete damage techniques. In the present study, following an in-depth study of material processing and its absorption capacities, folding modes and geometric/production constrains; a frame work has been setup to develop and test an optimised aluminium extruded profiles for best dynamic and crash performance characteristics. The numerical dynamic simulations (including fatigue, vehicle buffeting …) and virtual crash performance of lightweight hollow profiles have been considered for the design of new generation of roadside signals, lighting posts… for future.The complicated mathematical basis of large deformations, plasticity, contact and folding have been developed and special attention has been devoted to the plastic deformation, rate dependency and tailored yield locus. To assess the dynamic performance and energy absorption of these profiles, a full transient dynamic analysis can be performed using a time history dynamic loading. The new absorbing component design has been checked and verified using a result of carefully-setup experiments work and also advanced explicit simulation runs. One of the main contributions of this paper is to show the applicability and reliability of the numerical simulation approach for the crash performance of new lightweight roadside entities.

Development of a Novel Control for a Matrix Converter Interfaced Wind Energy Conversion System for Dynamic Performance Enhancement

This article presents the development of a novel control for matrix converter interfaced permanent magnet wind energy conversion system. Here, an adaptive fuzzy control algorithm incorporated with a reversed matrix converter is proposed to yield maximum energy with enhanced dynamic performance and low harmonic characteristics. The control algorithm is implemented using a dSPACE DS1104 real-time board (dSPACE, Paderborn, Germany). Feasibility of the proposed system has been verified through simulation and experiment results using a laboratory 1.2-kW prototype of a wind energy conversion system under dynamic conditions.

The effect of performance trend on performance ratings occurs through observer attributions, but depends on performance variability

AbstractResearch regarding the influence of dynamic performance characteristics on performance ratings suggests that raters are remarkably susceptible to observed trends in performance over time, such that systematic trends or patterns in performance can have an undue influence on how performance is evaluated. However, research in this domain has not fully explained how dynamic performance characteristics influence performance judgments. Drawing on attribution theory, we introduce a model whereby the impact of dynamic performance characteristics on subsequent performance judgments occurs through attributions for performance. Then, in three experimental studies, we show that dynamic performance characteristics influence attributions for performance, which in turn affect performance ratings.

Effect ofL/DRatio on the Performance of Two-Lobe Pressure Dam Bearing: Micropolar Lubricated

Two-lobe pressure dam bearings are commonly used in high speed rotating machineries. Their use is considered more stable than plain cylindrical bearings. Such bearings have a dam in the upper half whereas the lower half is provided with a relief track. Performance of two-lobe pressure dam bearings under micropolar fluid is evaluated. Finite element method is used to solve the modified Reynolds equation. Fluid film pressures are obtained by solving modified Reynolds equation. Thus pressure obtained is used to find performance characteristics of this bearing. The dynamic performance characteristics are studied at variousL/Dratios. ThreeL/Dratios are considered 1.6, 2.0, and 2.4 for the analysis purpose. Results obtained are presented for various micropolar parameters. Results show that stability of two-lobe pressure dam bearings increases with decrease in aspect ratio (L/D).

FORECASTING OF SUBJECTIVE COMFORT IN TRAM USING ORDINAL LOGISTIC REGRESSION AND MANIFOLD LEARNING

Comfort in a vehicle has a very important role to play as one of the most important dynamic performance characteristics of rail vehicles. It is the factor of ever-increasing importance, even creating a specialized branch of engineering associated with relation between human limitations and designing of machines: human–factors engineering. The vibration is known to be a major factor that affects and deteriorates ride comfort. For evaluating ride comfort in rail vehicles, there have been developed methods resulting in the creation of many standards and multiple criteria used and even standardized in different countries. One of the authors, J. Szczygie · designed and performed a passive experiment to collect data describing physical conditions of ride and associated subjective assessments of comfort. Panel of fourteen people during the tram ride made synchronous subjective assessments of comfort, assessing it on a discrete ordinal scale of 0 to 5, using electronic panels connected to the computer. At the same time computer through sensors recorded values of acceleration in three perpendicular axes. It made possible to correlate the fuzzy subjective evaluations with objective physical measurements. Because of the discrete type of fuzzy ratings of comfort, natural way of modelling is the ordinal logistic regression. The classic form of the ordinal logistic regression assumes that in the space of explanatory factors there are parallel activation hyper-planes slightly disturbed by unknown or uncontrolled noise factors. In fact, the assumption of linearity is a very strong idealization and leads to considerable misclassifications. The original space of explanatory factors is 11-dimensional with ten continuous dimensions and one discrete. Then the multivariate method, principal component analysis (PCA), was used to identify principal components, which are responsible most to the variability of the studied set. The scree plot was used to identify the number of significant PCA factors. The use of PCA revealed that the area occupied by the data set is approximately 6-dimensional. However, the dimensionality reduction of explanatory variables set did not lead to better forecasting accuracy. A more subtle analysis involving discretization techniques showed that activation hyperplanes are highly curved in the six-dimensional area identified by PCA but their dimensionality is much lower. The details of the procedure are described in the article. The article conclusion is that is necessary to introduce curvilinear coordinate system embedded into the shapes of activation hyper-planes to obtain better classification.

THE DYNAMICS THE ASSEMBLY INCLUDING LIGHT TRAILER - VEHICLE WITH COMBUSTION ENGINE OR HYBRID DRIVING

The rising greenhouse gas emissions at a global level have caused the increasing interest in cleaner and less oildependent transportation sources. It has been carried out a lot of researches on the alternative energy sources, like biofuels, fuel cells, wind farms, etc. and on the clean vehicles (hybrids). Most major manufacturers have successfully introduced hybrid automobiles utilizing electric motors and an internal combustion engine to improve their gas mileage. To decrease the use of gasoline even further, some hybrids are being retrofitted to allow them to be pluggedinto a standard i.e. 120-volt socket to charge the batteries and potentially to provide power back to the electric grid when needed. Plug-in Hybrid Cars offer the fuel-efficiency benefits of hybrid cars with the added feature of being able to plug-in to household electricity during rest. This allows the increased mileage and fuel savings. Plug-ins requires larger batteries than normal hybrids, which drives up their cost. Lithium-ion batteries are smaller, have a higher output of energy but are more expensive than rechargeable nickel metal hydride (NiMh), still used in hybrid vehicles. Improvement in battery storage capacity is of the most importance for the plug-ins. Plug-in technology is developed by the major auto manufacturers, with working prototypes of both plug-in hybrid electric vehicles (PHEV) and plug-in electric vehicles possessing small backup gas generators. The aim of the paper has been to assess the dynamic performance characteristics of the assembly light trailer �” car with classic combustion engine (in the first case) or PHEV (in the second case), using mathematical models and numerical simulations of standard driving cycles and to investigate algorithms for charging the stock battery pack.

System Characterization of MAHI EXO-II: A Robotic Exoskeleton for Upper Extremity Rehabilitation.

This paper presents the performance characterization of the MAHI Exo-II, an upper extremity exoskeleton for stroke and spinal cord injury (SCI) rehabilitation, as a means to validate its clinical implementation and to provide depth to the literature on the performance characteristics of upper extremity exoskeletons. Individuals with disabilities arising from stroke and SCI need rehabilitation of the elbow, forearm, and wrist to restore the ability to independently perform activities of daily living (ADL). Robotic rehabilitation has been proposed to address the need for high intensity, long duration therapy and has shown promising results for upper limb proximal joints. However, upper limb distal joints have historically not benefitted from the same focus. The MAHI Exo-II, designed to address this shortcoming, has undergone a static and dynamic performance characterization, which shows that it exhibits the requisite qualities for a rehabilitation robot and is comparable to other state-of-the-art designs.

Dynamic Performance Characteristics of Floating-Ring Bearings With Varied Oil-Injection Swirl-Control Angles

Hydrodynamic instability is a prime causative of performance irregularities and violent vibrations in floating-ring bearing (FRB) supported turbosystems. The quest for energy-efficient solutions to this has stimulated the development of diverse FRB design-geometries, dimensional relationships, and surface-contours. Unfortunately, these modifications are characterized mainly by model-predictors, which results lack sufficient test-data to benchmark their authenticities. This work presents the concept and the test-data of flow redirection in FRBs by using an oil-injection swirl-control mechanism (OISCM) to attenuate rotordynamic instabilities. FRBs with radius ratio = 1.75 and clearance ratio = 1.5 are tested for various OISCM angles (0 deg, 30 deg, and 60 deg) and under a specific load = 50 kN/m2. The test results indicate that FRBs with OISCM demonstrate substantial improvements in damping and stability characteristics. Their whirl-frequency-ratio (WFR) and cross-coupled forces are lower because of improved symmetry of films' pressure-forces (Kxx ≈ Kyy). Although the magnitudes of direct damping are higher (|Cxx| = 16.92 kN s/m for 60 deg and 6.03 kN s/m for 0 deg), the load capacity (Kxx) is slightly lower than the normal (0 deg), injection. Nonetheless, this discrepancy in load capacities becomes insignificant for speeds above 22 krpm. The WFR and subsynchronous amplitudes, which are graphic reflections of the bearing-based instability, become progressively smaller with increasing OISCM angle. However, this advantage at elevated speeds can only be sustained by a corresponding increase in oil-supply pressure to circumvent the advent of a starved inner-film and its attendant imbalance response and thermal growth. In closure, the OISCM bearing is more effective for mitigating rotordynamic instabilities in turborotors than conventional FRBs.

Research on the PID Control Strategy in BP Neural Network of Terrain Detector-Milling Cutting Depth System

Targeting at the nonlinear, time-varying characteristics of terrain detector-milling cutting depth electro-hydraulic servo system in soil milling collection machines, this paper proposed the PID control menthod in BP neural network of terrain detector - milling cutting depth system and designed PID controller in BP neural network and conducted simulation analysis by programming with Matlab. The results show that, when compared with conventional PID control, BP neural network compounded with PID control would enable the system better dynamic performance and follow-up characteristics, therefore, it is an effective control strategy.

A trigonometric series expansion based method for the research of static and dynamic characteristics of eccentric seals

Static and dynamic characteristics of labyrinth seals are important in the prediction of the stability of turbomachinery. The paper presents an effective numerical method to predict the static and dynamic performance characteristics of seals at off-center conditions with different rotor whirling frequency. Modifications are introduced for the traditional turbulent bulk flow model to consider the circumferentially varying flow. A trigonometric series expansion method is used to approximate parameters such as pressure and velocity in seals cavity. Numerical simulations show that 8–10 series terms with 5–10 iterations are enough for the solution of this set of nonlinear equations. The resulting nonlinear algebraic equations can be solved rapidly. The analytical results are verified by comparison with the simulated CFD results. Parametric investigations showing the influence of eccentricity and whirling frequency on seals dynamics are also presented. The results show that the trigonometric series expansion based method gives an effective prediction of the static and dynamic characteristics of the eccentric seals.