bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechatronic Integration in the Design of Ambulatory Rehabilitation Device
Authors: Shetty Devdas , Fast Avital , Campana Claudio , Manzione Lou
Published: May 2012

Increasing demands on the productivity and growing technological complexity will require the application of new methods in the product development process. A smart machine is one that can make decisions about the mechanical motion and respond to the commands in real time. It is possible to arrive at ways of optimizing the design of the structural components, the construction of the feed drives or the controller strategy. The distinguishing feature of mechatronic systems is the achievement of system functionality through intensive integration. That allows a better understanding of the dynamic behavior and interactions of the components. This paper shows that the simulation results from the mechatronic model of the rehabilitation equipment. The rehabilitation device is an apparatus developed with the intent of aiding in the rehabilitation of hospital patients learning to walk again. It is comprised of a gantry system which provides motion in the horizontal (x, y) plane and vertical axis (z). The z axis motion is provided by a hoist motor which is actively controlled using feedback from strain gauge sensors. As the patient walks around within the confines of the room-sized gantry, the hoist will follow the patient around. The closed loop motor control reacts to feedback from multi-axis tilt sensors on the hoist line. If ever the patient were to fall, the hoist system would to keep the patient in place. This paper shows how the sensor is integrated to the system in order to ensure the required control accuracy and precision in combination with enhanced motion dynamics, the interactions between a rehabilitation patient and tilt-sensor, the influence of the control system and the control process.
Robust Stable Control of Haptic Devices Based on Transparency Maximization
Authors: Tajaddodianfar Farid , Ahmadian Mohammadtaghi , Vossoughi Gholamreza
Published: May 2012

Performance of a haptic device is evaluated based on the concept of transparency. Stability of a haptic device prevalently has been evaluated based on the passivity criterion. Due to conservativeness of passivity, it appears as an obstacle to improve transparency. In this paper, passivity is suggested to be replaced by the complementary stability criterion which accounts for the robust stability of the interaction in the presence of uncertain user hand dynamics. In this respect, an algorithm is proposed which guarantees transparency of the haptic device in a stable manner. Assuming that the dynamics of the device is known, a certain compensatory structure is assigned. This special structure guarantees transparency of the device by compensating for dynamics of the device and its control loop. The design objective is to obtain a stabilizing controller which achieves robust interaction stability in the presence of parametric uncertainties of user hand dynamics and other sources of uncertainties. An iterative method is implemented, in conjunction with the D-K iteration algorithm, to derive controller dynamics. The algorithm is applied to a series elastic actuator based haptic device. This results in a widened frequency range of transparent impedance emulation. Simulation results confirm enhanced transparency and robust stability.
Analysis of a High Temperature Gas-Cooled Reactor Powered High Temperature Electrolysis Hydrogen Plant
Authors: McKellar M. G. , Harvego E. A. , Gandrik A. M.
Published: May 2012

An updated reference design for a commercial-scale high-temperature electrolysis (HTE) plant for hydrogen production has been developed. The HTE plant is powered by a high-temperature gas-cooled reactor (HTGR) whose configuration and operating conditions are based on the latest design parameters planned for the Next Generation Nuclear Plant (NGNP). The current HTGR reference design specifies a reactor power of 600 MWt, with a primary system pressure of 7.0 MPa, and reactor inlet and outlet fluid temperatures of 322°C and 750°C, respectively. The reactor heat is used to produce heat and electric power for the HTE plant. A Rankine steam cycle with a power conversion efficiency of 44.4% was used to provide the electric power. The electrolysis unit used to produce hydrogen includes 1.1 million cells with a per-cell active area of 225 cm2. The reference hydrogen production plant operates at a system pressure of 5.0 MPa, and utilizes a steam-sweep system to remove the excess oxygen that is evolved on the anode (oxygen) side of the electrolyzer. The overall system thermal-to-hydrogen production efficiency (based on the higher heating value of the produced hydrogen) is 42.8% at a hydrogen production rate of 1.85 kg/s (66 million SCFD) and an oxygen production rate of 14.6 kg/s (33 million SCFD). An economic analysis of this plant was performed with realistic financial and cost estimating The results of the economic analysis demonstrated that the HTE hydrogen production plant driven by a high-temperature helium-cooled nuclear power plant can deliver hydrogen at a competitive cost. A cost of $3.03/kg of hydrogen was calculated assuming an internal rate of return of 10% and a debt to equity ratio of 80%/20% for a reactor cost of $2000/kWt and $2.41/kg of hydrogen for a reactor cost of $1400/kWt.
Effects of Starch Volume Expanders on Blood Viscosity and Vascular Endothelial Markers
Authors: Walker Andrew M. , Lee Kogan , Rinker Kristina D. , Shepherd Robert D. , Dobson Gary M. , Johnston Clifton R.
Published: May 2012

The intravenous fluid of choice for acute blood volume replacement remains controversial. We focus here on the two hydroxyethyl (HES) available in Canada: HES 130/0.40 (Voluven®) and HES 260/0.45 (Pentaspan®). Although information regarding their pharmacokinetic and risk/benefit profiles are available, how the infusion of these fluids could affect blood viscosity and vascular endothelial function in humans is largely unknown. Dynamic viscosity was measured at 21°C and 37°C through capillary viscometry. The HES solutions were driven through a closed flow loop at room temperature (21°C). Viscosity at 21°C was 7.62 centipoise (cP) for HES 260/0.45 and 2.73 cP for HES 130/0.40 decreasing to 4.23 cP for HES 260/0.45 and 1.72 cP for HES 130/0.40 at 37°C. Analysis of viscous behaviour through pipe flow found that HES 260/0.45 displayed marginal variations in viscosity suggesting Newtonian behaviour across our range of Re measured. HES 130/0.40 displayed an appreciable increase in viscosity at higher Re suggesting the presence of shear thickening behaviour. Human aortic endothelial cells (HAEC) and human microvascular endothelial cells (HMVEC) were exposed to the HES solutions and saline to identify chemical effects on vascular endothelium. Western blot quantification showed that E-selectin was the leukocyte adhesion receptor that was most strongly affected, and this was not dose dependent. Interestingly, HAEC and HMVEC had different responses to HES treatment, suggesting that different vascular tissues may have different outcomes to HES infusion. Protein expression in HMVEC decreased when exposed to both HES solutions.
Maximum Distance Throwing Simulation and Analysis
Authors: Kim Joo H.
Published: May 2012

This paper proposes a numerical framework that generates maximum distance throwing motions and the associated dynamic results for a whole-body human mechanism. Multibody dynamic models of actuation, ground reaction force, and balance are incorporated into an optimization formulation. The algorithm outputs include the motion, required actuator torques, release parameters, and object projectile. Realistic human-like motions of maximum distance throwing are generated, which demonstrate valid kinematic and dynamic cause-effect relations. The maximum distance throw is associated with active movement of the arm and torso with larger ranges of motion.
Nonadiabatic Chemical to Electrical Energy Conversion in Planar Schottky Nanostructures
Authors: Karpov Eduard G. , Nedrygailov Ievgen
Published: May 2012

Nonadiabatic energy dissipation by electron subsystem of nanostructured solids unveil interesting opportunities for the solid-state energy conversion and sensor applications. We found that planar Pd/n-SiC, Pt/n-GaP and Pd/n-GaP Schottky structures with nanometer thickness metallization demonstrates a nonadiabatic channel for the conversion into electricity the energy of a catalytic hydrogen-to-water oxidation process on the metal layer surface. The observed abovethermal current greatly complements the usual thermionic emission current, and its magnitude is linearly proportional to the rate of formation and desorption of product water molecules from the nanostructure surface. The possibilities and advantages of utilizing the nonadiabatic functionality in a novel class of chemical-to-electrical energy conversion devices are discussed. The technology has a potential for a very high volumetric energy density due to the intrinsically planar device architecture.
Nonlinear Modelling and Unknown Input Estimation of an Electro-Hydraulic System for a Dual Clutch Transmission
Authors: Mustafa Rashad , Kassel Tobias , Alvermann Gunther , Ku¨c¸u¨kay Ferit
Published: May 2012

The paper describes the concepts of nonlinear complex modelling of the electro-hydraulic dual clutch transmission. In addition, a method to estimate the unknown electric current input based on the measurable clutch pressure output is presented. The estimation method is based on the classical inverse problem theory. The inverse problem consists of using the actual result of some measurements to infer the values of the parameters that characterize the system. In this method, prior information is obtained from the measurements (clutch pressures). After that, the prior information is used to estimate the unknown input (electric current) using the concepts of nonlinear functional analysis. Experiments performed on a test vehicle, confirm that the proposed model is able to describe the actuators and identify the behavior during a shifting process. The derived model can be useful for an early and accelerated start of the application process in the development phase especially as a simulation tool for gear shift control by means of Software in the Loop (SiL). This method can also be used also in a model fault detection applied on a transmission control system which relies on mathematical descriptions of the system. In addition, this method can be used for determining the optimal electric current supplied to the valve based on the optimal control pressure.
Dispersion Relation for Generally Damped Periodic Materials
Authors: Frazier Michael J. , Hussein Mahmoud I.
Published: May 2012

In this paper, we present a theoretical formalism for the study of damped periodic materials. First we consider a lumped parameter model consisting of two masses in the unit cell whereby the masses are connected by springs and dashpot viscous dampers. We then extend our analysis to the study of a two-dimensional phononic crystal, modeled as an elastic continuum, and consisting of a periodic arrangement of square inclusions distributed in a matrix base material. For our damping model, we consider both proportional damping and general damping. Our results demonstrate the effects that damping have on the dispersion relation and damping ratio band structure.
Fault Detection of a Water Loop Refrigerating System Using Multivariate Statistics
Authors: Posada Jose´ , Solano Jose´ , Sanjuan Marco
Published: May 2012

This paper describes the use of statistical fault detection techniques to improve energy management in a large water loop refrigerating system (WLRS). The water loop has one centrifugal chiller with specified capacity of 420TR in parallel with another screw chiller with specified capacity of 420 TR, feeding several buildings to control the temperature inside them through condenser units. Multivariate statistical fault detection techniques such as Principal Component Analysis (PCA) were used, in order to analyze the historical data from the system to detect abnormal situations, by means of statistical measures such as Square Prediction Error (SPE) and T2., Finally, using this expertise of plant engineers were used to determine the fault causes, and results will be used to prevent future abnormal conditions.
Design of a Wireless, Passive, Single-Use Emergency Call System
Authors: Staats Wayne L. , Lorenc Dan P. , Zhang Zihao , Huwe Ethan L. , Barineau Mark M. , Slocum Alexander H.
Published: May 2012

In order to improve patient access to nurses during emergencies, a wireless wrist-mounted call button system was developed. The goal of this project was to create a simple, easy-to-use system that features a completely passive, wireless call button. Three major problems in existing systems — inability for patients to locate or reach the button, unnecessary user interface complexity, and the introduction of a potential vector for hospital-contracted illness — were addressed in the design. The wireless nature of the device ensures that it is always near the patient. A single-button interface considerably simplifies its use in comparison to multi-button systems, eliminating the possibility of incorrect button presses. Finally, the proposed call button uses inexpensive technologies and can be manufactured for such a low cost that it can be offered as a single-use device, eliminating the possibility of patient-to-patient disease transmission. Using radio-frequency identification (RFID) technology, patients are able to call for hospital staff from any location in the hospital that is covered by readers. The call button uses a passive RFID tag that can be turned on or off by a mechanical switch. A second tag is used to notify the system when a patient is out of range. The design was prototyped and tested, and future improvements are suggested.
Numerical Test Method for Random Chopped Fiber Composites
Authors: Pan Yi , Pelegri Assimina A.
Published: May 2012

A two-scale approach for numerical determination of composite material constants using a finite element model is developed. A representative volume element is numerically generated using a modified sequential adsorption algorithm. To determine the strength of the composite material, progressive material degradation models are adopted for the matrix, fiber and the fiber/matrix interface. The epoxy resin is modeled with a modified von Mises criterion in which the effect of hydrostatic stress on yield is accounted for. The resin’s elastic constants degrade with increasing loading application. The glass fiber is modeled as an isotropic material whose failure is governed by the maximum strain criterion. A traction-separation type cohesive zone model is applied at the fiber/matrix interface. Validation of the presented model is achieved by comparing numerical simulations with experimental data. The effective material constants that have been homogenized by the numerical test approach can be applied for future structural analysis.
Simulation and Dynamic Characterization of a 3-Layer Piezo-Actuated Valveless Micropump System
Authors: SadAbadi Hamid , Chandrasekaran Arvind , Packirisamy Muthukuraman , Wuthrich Rolf
Published: May 2012

In order to design the valveless micropump with a Piezo actuator, it is essential to understand the dynamic properties of the actuating system. Besides several other considerations in designing of microfluidic systems, the efficiency of valveless micropumps also strongly depends on parameters of the actuation system including the actuation frequency. Cleary, higher displacement of the diaphragm results in higher output flow rate of the pump. Thus, studying the dynamic behavior of the actuation system forms one of the important considerations for the design of micropumps. Three different models of the actuating system for the fabricated micropump system are proposed with different boundary conditions and are simulated by finite element method using ANSYS. Comparison of the experimental results and the simulation results of the natural frequencies of the system shows that the proposed simulation method can also be now used as a tool to optimize the design of the actuation system in terms of natural frequency of the system.
J-Strips: Haptic Joint Limit Warnings for Human-Robot Interaction
Authors: Parker Chris A. C. , Croft Elizabeth
Published: May 2012

The capabilities of humans and robots naturally compliment each other. Humans excel at spatial problem solving and fine manipulation tasks, whereas robots are good at supporting and stabilizing heavy loads. However, the typical impedance control strategy employed in this domain does not communicate any of a robot’s underlying physical constraints to its user. In this work, we propose j-strips, an anthromimetic haptic cue designed to convey stress in a robot manipulator to its human user. We hypothesize that when warned via j-strips that the robot is nearing a joint limit in this way, the human user will modify the path of the robot to avoid the limit. We present the results of a pilot study of three human subjects manipulating a robot arm that uses j-strips to warn its user when its elbow position limit is approached. Two of the subjects were found to significantly modify the manner in which they manipulated the robot, and both verbally reported that j-strips conveyed the intended message.
3-D CFD Simulation of Hydrogen Dispersion From a Fuel Cell Vehicle in an Indoor Environment
Authors: Zhang X. , Huang C. , Hernandez M. , Rossetto M. , Liu Z.-S. , Klomp R. , Meyer N. , Belzile M. A.
Published: May 2012

In order to reduce green house gases, hydrogen fueled vehicles are expected to be commercialized in the near future. Hydrogen is nontoxic, but it is flammable. A relatively low ignition energy can ignite a hydrogen-air mixture when the concentration of hydrogen is within a flammable range. Therefore safety concerns related to possible leakage from hydrogen fueled vehicles need to be addressed. In this study, we focus on the distribution of the lower flammability limit (LFL) of a hydrogen cloud when hydrogen is released from a fuel cell vehicle. CFD techniques, using FLUENT, are applied to the simulation of hydrogen dispersion from a parked vehicle’s tailpipe. We analyzed several hydrogen release scenarios to investigate the hydrogen cloud formation, thermal effects and transient behaviors. We also simulated the effects of the inclination of the garage ceiling and forced ventilation on hydrogen dispersion. We found that the configuration of indoor space affects the hydrogen cloud formation in certain ways. The simulation results can be further applied to define the codes, standards and recommended safety practices related to possible hydrogen leakage and the risk of ignition.
High Temperature Endurance of FRP Composites With Polymeric Thermal Barrier Coatings
Authors: Igiede Edwin , Mensah Patrick F. , Akwaboa Stephen
Published: May 2012

High Temperature exposure and the corresponding thermo-mechanical behavior of cylindrical polymer composite pipe using CFD simulation has been investigated in this study. The software FLUENT was employed for the analysis of heat transfer, by coupling equations of energy and motion. Analysis was done based on applied external boundary temperature profile, change in internal energy, the total surface heat flux and surface heat transfer rate in order to evaluate the extent of thermal damage. FLUENT compatible program written in C++ language in the form of user define functions (UDF) has been developed and used to specify the time dependent heat flux generated temperature as well as temperature dependent thermal properties of density, thermal conductivity and specific heat. Available furnace test experimental data from (ASTM 1173-95) database were used as outer surface boundary condition in the model setup by developing it into UDF correlation equations. The outputs of the FLUENT simulations are predictions of transient temperature distribution through the thickness of the pipe wall that were then used in evaluating the thermal stresses of the composite pipe. Validation of the simulation results is done with existing data available in the literature. Using the wall generated temperatures, internal energy, the rate of change of the temperature dependent properties and the heat transfer rate, the thermal endurance of each of the coatings materials has been predicted in this work. At the same time knowledge of the thermal performance of these materials is essential for the optimum design of protection based on the composite application.
Modeling Fractal-Like Branching Microchannel Heat Exchangers
Authors: Heymann Douglas B. , Pence Deborah V.
Published: May 2012

A one-dimensional model for single-phase flow in a fractal-like branching microchannel heat exchanger was developed to estimate bulk fluid temperature and pressure distributions in co-flow and counter-flow configurations. The model assumes incompressible flow with thermally and hydrodynamically developing boundary layers. An existing correlation for the heat transfer coefficient in the simultaneously developing boundary layer region was found to adequately describe results from a three-dimensional computational analysis of conjugate heat transfer and fluid flow using the commercial software package Star-CCM+. Additionally, the fin efficiency was found to be an important descriptor of the difference in performance between a heat exchanger made of low and high thermal conductivity material. A parametric study was performed with the one-dimensional model to assess the influence of flow conditions and flow network characteristics on performance measures, including the benefit-to-cost ratio, which is defined as the heat transfer divided by flow power. Results of heat transfer versus log-mean temperature difference and effectiveness versus number of transfer units are compared between branching and straight microchannel heat exchangers.
Stiffness of Locking and Conventional Plates in Fixation of Distal Fibula Fractures: A Finite Element Study
Authors: Patel Bipin , Gustafson Peter A. , Jastifer James
Published: May 2012

The objective of this study is to establish and differentiate the stiffness of conventional and fixed angle screw constructs for the treatment of distal fibula fractures. Two plate types are examined; a fibular neutralization plate and a lateral periarticular distal fibular plate with fixed angle (locked) screws. The neutralization plate is considered with two construct types; conventional and locked screws. Several comparisons were made to differentiate the stiffness of the plate constructs. First, the neutralization plate is examined with conventional and locked screws when used for fixation of Danis-Weber B and comminuted fractures. Second, neutralization and periarticular plates are compared with locked screws for the same fracture patterns. The stiffnesses of the constructs are computed with the finite element method based on several load cases. The type of screw construct is found to have minimal effect on the stiffness, whereas the plate type is found to have a larger influence due to geometrical differences. The comparison is limited to stiffness; the strength of the constructs should be examined in future work.
Synthesis of Ultra-Thin Superhydrophilic Titanium Oxide Film and its Effects on the Capillary of Microchannels
Authors: Zhang Min , Zhang Bo , Cui Tianhong
Published: May 2012

Ultra-thin superhydrophilic titanium oxide films were fabricated on silicon microchannels by an in situ reaction sol-gel method using titanium tetraisopropoxide as a starting material.. By changing the concentration of water in ethanol and reaction time, the thickness of synthesized TiO2 films can be controlled from around 10 nm to 80 nm. The contact angle of as-synthesized TiO2 films on flat silicon is around 20° and can be further decreased to zero by calcination at 700 °C in nitrogen atmosphere. X-ray diffraction spectra show the microstructure of the TiO2 films changed gradually from amorphous to anatase with the increase of calcination temperature. Surface morphology of the film before and after calcination also shows that a smoother coating with crystal structure was obtained by heat treatment. The flow velocity in the TiO2 coated channel reached around 0.03 m/s, almost ten times of that in PDDA/PSS coated channel and 4 times of that in SiO2 coated one. The ultra-thin superhydrophilic TiO2 films fabricated by this method show the ability to strongly increase the wettability of microchannels without affecting the morphology of the sidewall of the channels, indicating potential applications to biomolecule analysis and surface tension driven microfluidic systems.
Design of an Automated System for Shaping Paint-Brush Knots
Authors: Gorbashev Aleksandr , Bunai Christopher , Khalifeh Fadi , Thamire Chandrasekhar
Published: May 2012

The purpose of this paper is to describe the development of an automated assembly system to form filament in paint-brush knots. Currently this process is largely accomplished by hand. The solution proposed is reached through a formal design approach, including steps such as needs analysis, quality function deployment exercise, product design specification, functional decomposition, concept generation, concept evaluation, strength and dynamic analyses, failure modes and effect analysis, and concept testing. Results from studies performed for handling synthetic and natural filaments used to design and refine the system are presented in this paper. The system described in this paper uses in-process measurement sensors to determine the location of the assembly components prior to the assembly operations. Preliminary prototypes of the subsystems developed so far indicate that required production rates can be achieved at the desired quality.
Finite Element Simulation for Structural Response of U7Mo Dispersion Fuel Plates via Fluid-Thermal-Structural Interaction
Authors: Ozaltun Hakan , Shen Herman , Medvedev Pavel
Published: May 2012

This article presents numerical simulation of dispersion fuel mini plates via fluid-thermal-structural interaction performed by commercial finite element solver COMSOL Multiphysics to identify initial mechanical response under actual operating conditions. Since fuel particles are dispersed in Aluminum matrix, and temperatures during the fabrication process reach to the melting temperature of the Aluminum matrix, stress/strain characteristics of the domain cannot be reproduced by using simplified models and assumptions. Therefore, fabrication induced stresses were considered and simulated via image based modeling techniques with the consideration of the high temperature material data. In order to identify the residuals over the U7Mo particles and the Aluminum matrix, a representative SEM image was employed to construct a microstructure based thermo-elasto-plastic FE model. Once residuals and plastic strains were identified in micro-scale, solution was used as initial condition for subsequent multiphysics simulations at the continuum level. Furthermore, since solid, thermal and fluid properties are temperature dependent and temperature field is a function of the velocity field of the coolant, coupled multi-physics simulations were considered. First, velocity and pressure fields of the coolant were computed via fluid-structural interaction. Computed solution for velocity fields were used to identify the temperature distribution on the coolant and on the fuel plate via fluid-thermal interaction. Finally, temperature fields and residual stresses were used to obtain the stress field of the plates via fluid-thermal-structural interaction.
A Study on Nonlinear Population Dynamics Based on Energy Flow
Authors: Zhu Xinqiang , Zhang Huayong , Zhao Lei , Huang Tousheng , Han Lu
Published: May 2012

In considering energy flow between organism and environment, population dynamics for single species is studied in the present research. When the total available energy of environment is infinite, a model obeying the Malthusian law is obtained. Under the condition of limited total available energy, a model approximate Logistic Model is also established. These two models give a better comprehension on the ecological effects of growth rate and carry capacity of environment.
Jet Inlet Condition Effect on the Heat Transfer From a Circular Impinging Air Jet to a Flat Plate
Authors: Yan Terry X. , Streufert Patricia
Published: May 2012

Local turbulent convection heat transfer from a flat plate to a circular impinging air jet is investigated numerically, with emphases on the effect of inlet flow condition, i.e. velocity profiles, on the impingement jet heat transfer distribution on a flat plate. Reynolds-Averaged Navier-Stokes equations (RANS) and the energy equation are solved for axisymmetric, three-dimensional flow. Eddy viscosity k-ε (RNG) and V2F turbulence models are used with non-uniform meshes to obtain mesh-independent solutions. Three Reynolds numbers, i.e. 23,000, 50,000 and 75,000 and three geometries (jet-to-plate distance, L/D = 2, 4, & 6), and four inlet velocity profiles are used in the analysis. The numerical solutions obtained are compared with existing experimental heat transfer data. The results show that stagnation region heat transfer is most sensitive to inlet velocity profiles at small jet-to-plate distances. The Blasius and long pipe (P/D = 20) profiles have the best match with experimental data in the secondary heat transfer maximum region (r/D = 2). As Reynolds number increases, it’s very difficult to predict heat transfer in the region of secondary maximum, where flow transition takes place.
Fragility of Chaos in Multispecies Competition Influenced by Predation
Authors: Zhao Lei , Zhang Huayong , Huang Tousheng , Zhu Xinqiang , Han Lu
Published: May 2012

In order to study the stability of chaotic behaviors, a nonlinear dynamical model of the competing multispecies with a predator is investigated. A series of numerical simulations is demonstrated via wave diagram and phase diagram. The results show that the chaos can change into either oscillation or ordinary equilibrium as the attacking rate of the predator increases. Moreover, chaos in the system becomes fragile and even vanishes when the attacking rate reaches 0.0186. This study also exhibits the transformation in phase diagram from a strange attractor to a stable equilibrium.
A Study on the Hydraulic Resistance of Rigid Unsubmerged Vegetation in Floodplain
Authors: Li Fei , Wang Zhongyu , Zhang Huayong , Xu Weigang , Jing Yu , Yang Shoushan
Published: May 2012

The variations of water level and flow velocity distribution can be caused by the aquatic vegetation which plays an important role in flood plain. In this study, a series of laboratory experiments are carried out to simulate the floodplain flow under three discharge conditions and four reed densities. The flow state, water level variation and flow velocity distribution are investigated in the modeling floodplain. Also, the relationship between flow resistance and reed densities is discussed. The results provide a better insight into the flow resistance of rigid unsubmerged vegetation in floodplain.
A Matlab® GUI (Graphical User Interface) for Generating the Inverse Dynamic Model for Industrial Manipulator Until Five Degrees of Freedom
Authors: Valencia Guillermo E. , Turizo John C. , Sanjuan Marco E.
Published: May 2012

A Graphical User Interface program in Matlab® for generating the inverse dynamic non linear model of industrial manipulator in symbolic form is presented, that is, the joint torques required for a given set of joint angles, velocities and accelerations of the end -effector. The program, called RIDMD (Robotic Inverse Dynamic Modeling Deduction), is an application of Newton-Euler (NE) Recursive Methods to the derivation of closed form dynamic equations of robots, considered as a group of rigid bodies connected by suitable single degree-of-freedom (DOF) joints. The general procedure implemented in the program in order to calculated the model, begin estimating the Denavit-Hartenberg parameter, selecting a frame attached to each link of the robot arm and calculating the transformation matrix, which is a homogeneous transformation matrix that expresses the position and orientation of consecutives frames of reference for the robot. In addition, the kinematic inicial condition for the first link is determinate, and the kinematic variables transformation is developed, for prismatic or sliding joint. Finally, the force and torque transformation is solved with the program, which is transparent to the user and allows the symbolic calculation of dynamical models until five DOF.
Exploring Electrical Impedance Spectroscopy as an Innovative Tool for On-Chip Analysis of Human Trabecular Meshwork
Authors: Gu Wenwen , Kim Bongsu , Zhao Yi
Published: May 2012

This work reports the investigation of in vitro cultured human trabecular meshwork (TM) using electric impedance spectroscopy. The outflow facility of aqueous humor contains a three-dimensional network composed of TM endothelial cells and the extracellular matrix (ECM). The network is a critical determinant of intraocular pressure (IOP), the increase of which is the main cause of primary open angle glaucoma (POAG). Electric impedance spectroscopy was chosen over other technologies for on-chip TM cell study because of its non-invasive and label-free natures as well as the ease of on-chip integration. An array of interdigitated microelectrodes (IMEs) was fabricated for impedance sensing. Polydimethylsiloxane (PDMS) was used as the passivation layer and to form the cell culture wells. TM cell growth and proliferation under external stimuli can thus be in situ monitored. In this work, the utility of the impedance spectroscopy was demonstrated by treating TM cells with dexamethasone (DEX), a synthetic glucocorticoid which is found to increase the IOP. Electric impedance was monitored for 3 days during DEX treatment. The impedance measurement at 40 kHz showed that a smaller increase of impedance magnitude occurred in the DEX treated group than in the control group, which suggested that DEX inhibits the proliferation of TM cells. The higher the DEX concentration, the greater inhibition was observed. The measurement was validated using AlamarBlue proliferation assay and microscopic observation. The measurement provides a reasonable explanation of glucocorticoid induced glaucoma, where the glucocorticoid alters the metabolic and physiological functions of TM cells by inhibiting normal cell growth and proliferation.
A Study on Manning’s Coefficient of Rigid Unsubmerged Vegetation Under Open Channel Constant Gradual Flow Condition
Authors: Xu Weigang , Zhang Huayong , Jing Yu , Wang Zhongyu , Ji Changming , Zhang Hua
Published: May 2012

A series of experiments were carried out to study the hydraulic resistance of rigid unsubmerged vegetation in open constant gradual channel flow. Flow depth and velocity were measured in the density of 54, 108 and 202 reed stems per square meter within a range of discharge values. The results demonstrated that the back-up water height increases with the reed density, while the velocities show an opposite trend. The phenomenon can be explained by the relationship between Manning coefficient and the vegetation density parameters.
Water Utilization in Data Center Infrastructure
Authors: Sharma Ratnesh , Shih Rocky , McReynolds Alan , Bash Cullen , Patel Chandrakant , Christian Tom
Published: May 2012

Fresh water is one of the few resources which is scarce and has no replacement; it is also closely coupled to energy consumption. Fresh water usage for power generation and other cooling applications is well known and accounts for 40% of total freshwater withdrawal in the U. S[1]. A significant amount of energy is embedded in the consumption of water for conveyance, treatment and distribution of water. Waste water treatment plants also consume a significant amount of energy. For example, water distribution systems and water treatment plants consume 1.3MWh and 0.5MWh[2], respectively, for every million gallons of water processed. Water consumption in data centers is often overlooked due to low cost impact compared to energy and other consumables. With the current trend towards local onsite generation[3], the role of water in data centers is more crucial than ever. Apart from actual water consumption, the impact of embedded energy in water is only beginning to be considered in water end-use analyses conducted by major utilities[4]. From a data center end-use perspective, water usage can be characterized as direct, for cooling tower operation, and indirect, for power generation to operate the IT equipment and cooling infrastructure[5]. In the past, authors have proposed and implemented metrics to evaluate direct and indirect water usage using an energy-based metric. These metrics allow assessment of water consumption at various power consumption levels in the IT infrastructure and enable comparison with other energy efficiency metrics within a data center or among several data centers[6]. Water consumption in data centers is a function of power demand, outside air temperature and water quality. While power demand affects both direct and indirect water consumption, water quality and outside air conditions affect direct water consumption. Water from data center infrastructure is directly discharged in various forms such as water vapor and effluent from cooling towers. Classification of direct water consumption is one of the first steps towards optimization of water usage. Subsequently, data center processes can be managed to reduce water intake and discharge. In this paper, we analyze water consumption from data center cooling towers and propose techniques to reuse and reduce water in the data center.
Cylindrical Shell Control With Center- and Corner-Placed Photostrictive Skew-Quad Actuators
Authors: Jiang Jing , Yue Hong-Hao , Deng Zong-Quan , Tzou Horn-Sen
Published: May 2012

Light-driven photostrictive actuators can induce control actions capable of wireless non-contact actuation and control of precision structures and systems. Conventional distributed actuators laminated on shells and plates usually introduce only uniform control forces and moments. Structural actuation and control based on uniform control forces and moments have been investigated for over two decades. This paper is to exploit a new photostrictive actuator design, i.e., a skew-quad (SQ) actuator system and this new distributed SQ system laminated on shells and plates can introduce non-uniform control forces and moments. The new SQ actuator system is composed of four pieces of photostrictive materials and inner two edges of each piece are bonded to a cross fixture. Under the irradiation of high-energy lights, each piece generates non-uniform control forces and moments, due to its uneven nonsymmetrical boundary conditions. Modal actuation characteristics of a cylindrical shell coupled with a center-placed and corner-placed skew-quad actuator system are evaluated respectively. A paired-design regulating positive/negative control forces of each actuator region is proposed to improve the control effectiveness of the center-located skew-quad actuator system. Parametric analysis proves improved control effectiveness of unsymmetrical shell modes.
Performance and Testing of Novel Quantum Well Thermoelectric Devices
Authors: Jovanovic Velimir , Ghamaty Saeid , Elsner Norbert B. , Krommenhoek Daniel , Bass John C.
Published: May 2012

New nano-structured thermoelectric (TE) materials have been developed and fabricated that have much higher conversion efficiencies than the state-of-the-art (SOTA) bulk thermoelectrics. In these new quantum well (QW) materials, the carrier and barrier materials (in this case SiGe and Si) are confined in alternating layers less than 10 nm thick, and this confinement has been shown to result in greatly improved TE properties (Seebeck coefficient, electrical resistivity and thermal conductivity) leading to higher TE Figure of Merit, ZT, conversion efficiencies and Coefficient of Performance (COP) for cooling applications than for SOTA thermoelectrics. From the most recent QW test data, ZTs greater than 3 at room temperature have been obtained which constitutes a significant improvement over the SOTA bulk thermoelectrics which have ZTs less than 1. QW materials have the best measured TE power factor (Seebeck coefficient squared divided by electrical resistivity) and, combined with low thermal conductivity substrates, should provide very high efficiency TE modules. The QW TE materials with ZTs greater than 3 lead to conversion efficiencies greater than 20 percent, which allows for much wider commercial applications, particularly in the applications such as the waste-heat recovery from truck engines, refrigeration, and air conditioning, where the SOTA bulk TE modules were shown to be technically feasible but economically unjustified due to low conversion efficiencies. With higher efficiency QW materials, these applications become economically attractive. The above mentioned QW TE ZTs include the effect of the substrate which degrades the overall performance, and a new test technique was developed that eliminates the effect of the substrate and for just the QW films, ZTs greater than 6 have been measured. This illustrated the importance of using a low thermal conductivity substrate in order to achieve good TE performance. In a recent QW test, a conversion efficiency corresponding to 62 percent of the Carnot efficiency was measured and this is believed to be the highest such value ever measured for a TE material. For power generation applications, QW TE generators can be designed for capacities ranging from milliwatts to kilowatts and for cooling applications with capacities ranging from watts to several tons of refrigeration. The paper discusses the effects of the thermal and electrical contact resistances and of substrate thermal conductivity on the TE performance, the status of the prototype QW TE generators and coolers being designed and fabricated, and the latest test results.
Predicting the Effect of Pulse Duration on Fatigue During Electrical Stimulation
Authors: Marion M. Susan , Hull Maury L. , Wexler Anthony S.
Published: May 2012

Pulse characteristics should be considered when predicting the optimal stimulation strategy to minimize fatigue during Functional Electrical Stimulation. Our previous mathematical model of non-isometric muscle fatigue accounted for the effect of applied load, but not the effect of pulse duration. Therefore, our objectives were to: 1) further develop our model of non-isometric fatigue and 2) experimentally validate the model. A computer-controlled stimulator sent electrical pulses to surface electrodes on the thighs of 25 able-bodied human subjects. Isometric and non-isometric non-fatiguing and fatiguing leg extension ankle forces and/or knee angles were measured. The independent variable was pulse duration (170, 200, 250, 400, and 600 μs) and the dependent variables were angular excursion, velocity, and train duration. The model was fit to measurements from 13 subjects. The equation for one fatigue model parameter was modified. Two other fatigue model parameters were unnecessary and removed. The modified parameter is a function of other parameters within the model. To validate the model, we predicted fatigue at two other pulse durations using the same subjects, at all five pulse durations in a set of new subjects, and at one pulse duration but different applied loads in ten subjects from a previous study. More than 65% of the variability in the measurements was explained by the new force-fatigue model.
Evaluation of a Stacked Package Utilizing LGA Devices
Authors: Srinivasan G. , Iyer S. , Havens R. , Srihari K.
Published: May 2012

A Land Grid Array (LGA) is an area array component similar to a Ball Grid Array (BGA), but without solder balls attached to the bottom surface of the package. Due to the absence of solder balls, the LGA package has a lower thickness as compared to an equivalent BGA package. Accordingly, this reduces the thickness of the module assembly. This is a critical consideration especially for modules using stacked packages. On the other hand, the lower standoff height of the solder joints could have an impact on the performance of the package during temperature cycling. For high density modules, along with ‘minimizing’ the thickness, it is desirable to avoid increasing the package size in the length and width directions. This allows maintaining the same number of Inputs/Outputs (I/Os) as a comparable BGA device and accommodates the package on existing Printed Circuit Board (PCB) designs. For this reason, the LGA package used for the current research was identical to the BGA device that is currently used for the stacked package, but without solder balls on the bottom side. The stacked package utilizing these LGA devices and the modules were assembled using Sn3.8Ag0.7Cu lead-free solder. The reliability of the assembly was assessed using thermal cycling test. Based on the results, the first failure was recorded at the end of 1250 thermal cycles, whereas the comparable stacked package using BGA components was able to withstand 1500 cycles without failures. Dye & pry analysis was also performed on the failed stacked packages as a part of failure analysis.
Gas Metal Arc Welding (GMAW) Process Optimization of a 1.4 mm Uncoated Dual Phase 980 (DP980) Joint for Automotive Body Structural Applications
Authors: Koganti Ramakrishna , Elliott Adrian , Jiang Cindy
Published: May 2012

With the increasing demand for safety, energy saving and emission reduction, Advanced High Strength Steels (AHSS) have become very attractive steels for automobile makers. The usage of AHSS steels is projected to grow significantly in the next 5–10 years with new safety and fuel economy regulations. These new steels have significant manufacturing challenges, particularly for welding and stamping. Welding of AHSS remains one of the technical challenges in the successful application of AHSS in automobile structures due to heat-affected zone (HAZ) at the weld joint. In this study Gas Metal Arc Welding (GMAW) of a lap joint configuration consisting of 1.4 mm uncoated DP980 to itself was investigated. The objective of the study was to understand the wire feed rate and torch speed influence on lap joint tensile strength (static and fatigue). A two factor, two level, full factorial design of experiment (DOE) was conducted to understand the wire feed and torch speed influence on tensile and fatigue strength of the welded joints. In order to understand the curvature effect, a center point was also included in the experiment. Based on the statistical analysis, neither factor was significant on static tensile strength, however, a two way interaction between wire feed rate and torch speed was significant on static tensile strength. Metallurgical properties of the lap joints were evaluated using optical microscopy. A significant hardness drop of 40% was observed at the HAZ.