bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of Heat Transfer by Nanoparticles Added to the Working Fluid of Swimming Pool Heat Exchangers
Authors: Ashrafi N. , Bashirzadeh Y.
Published: October 2013

The present experimental study reports on enhancement of heat transfer by addition of nanoparticles to the working fluid of commercial swimming pool heat exchangers under laminar flow condition. Three different concentrations of Titanium dioxide nanoparticles were added to the water as working fluid of a typical forced convective heat exchanger used to transfer heat to public swimming pools. The experimental setup is capable of measuring velocity, heat transfer rate, and temperature at different points. TiO2 nanoparticles with mean diameter of 20 nm were used. The effects of concentration of suspended nanoparticles and that of Reynolds number on forced convective heat transfer were investigated. It is observed that at 0.1%, 0.5% and 1% weight concentration of suspended TiO2 nanoparticles, the average convective heat transfer coefficient improved by 1.1%, 15.9% and 31.6% respectively. The coefficient is further increased at higher Reynolds numbers. The efficiency of heat exchanger is evaluated for different scenarios.
The Effect of Rolling Speed and Friction on Cold Rolling Mill Stability
Authors: Kim Y. S. , Zhang N. , Ji J. C. , Yuen W. Y. D.
Published: October 2013

In order to investigate the validity of a coupled mill vibration model presented in the dynamic rolling formulation, this paper presents the results of dynamic characteristics examining rolling force variations in response to rolling parameters. Under the given steady state rolling condition, the unstable vibrational modes with corresponding frequencies are identified and stability analysis is also performed to demonstrate that the proposed model is highly dependent on the rolling speed and friction coefficient with an assumed negative gradient of friction coefficient. To further find the transient characteristics and the direct influences of the friction coefficient and rolling speed on the mill chatter, the derived equations of motion of the system are solved using Runge-Kutta numerical integration method. Simulations are carried out to reveal the chatter sources, which gives rise to unstable rolling vibrations.
Correlation of Cutting Force and Power Consumption for Ultrasonic-Vibration-Assisted Cutting of Label Paper Stacks
Authors: Deibel Karl-Robert , Boos Jens , Weikert Sascha , Wegener Konrad
Published: October 2013

Experiments comparing conventional and ultrasonic vibration assisted guillotine cutting of paper stacks have been performed on plain and aluminum coated label paper. It is shown that ultrasonic vibration assisted cutting reduces the cutting force for both paper species. Reduction of the cutting force allows the down holder force to be decreased and lowers the compression of the paper stack necessary to prevent pull-out of the top sheets of paper. Using a higher amplitude setting on the ultrasonic generator further decreases the cutting force for the paper stack. For three different cutting speeds, it is shown that ultrasonic vibration assisted cutting force reduction depends on the average speed of the tool for both paper species. A linear regression with present experimental data is done to obtain an equation for the relation between input generator power and resulting cutting force. Finally, the quality of the cutting edge is examined, quality parameters are defined, and according to these the cutting edge quality is assessed.
Delayed Output Feedback Control for Nonlinear Systems With Fuzzy Observers
Authors: Karkoub Mansour , Wu Tzu Sung
Published: October 2013

In this paper, the design problem of delayed output feedback control scheme using two-layer interval fuzzy observers for a class of nonlinear systems with state and output delays is investigated. The Takagi-Sugeno type fuzzy linear model with an on-line update law is used to approximate the nonlinear system. Based on the fuzzy model, a two-layer interval fuzzy observer is used to reconstruct the system states according to equal interval output time delay slices. Subsequently, a delayed output feedback adaptive fuzzy controller is developed to override the nonlinearities, time delays, and external disturbances such that the H∞ tracking performance is achieved. The linguistic information is developped by setting the membership functions of the fuzzy logic system and the adaptation parameters to estimate the model uncertainties directly for using linear analytical results instead of estimating nonlinear system functions. The filtered tracking error dynamics are designed to satisfy the Strictly Positive Realness (SPR) condition. Based on the Lyapunov stability criterion and linear matrix inequalities (LMIs), some sufficient conditions are derived so that all states of the system are uniformly ultimately bounded and the effect of the external disturbances on the tracking error can be attenuated to any prescribed level and consequently an H∞ tracking control is achieved. Finally, a numerical example of a two-link robot manipulator is given to illustrate the effectiveness of the proposed control scheme.
Development and Validation of a Non-Linear Viscoelastic Viscoplastic Stress Model for a PFCB/PVDF Fuel Cell Membrane
Authors: Wright Jessica A. , Ellis Michael W. , Dillard David A. , Case Scott W. , Moore Robert B. , Li Yongqiang , Lai Yeh-Hung , Gittleman Craig S.
Published: October 2013

Proton exchange membranes (PEMs) in operating fuel cells are subjected to varying thermal and hygral loads while under mechanical constraint imposed within the compressed stack. Swelling during hygrothermal cycles can result in residual in-plane tensile stresses in the membrane and lead to mechanical degradation or failure through thinning or pinhole development. Numerical models can predict the stresses resulting from applied loads based on material characteristics, thus helping to guide the development of more durable membrane materials. In this work, a non-linear viscoelastic stress model based on the Schapery constitutive formulation is used with a Zapas-Crissman viscoplastic term to describe the response of a novel membrane material comprised of a blend of perfluorocyclobutane (PFCB) ionomer and polyvinylidene fluoride (PVDF). Uniaxial creep and recovery tests are used to establish the time dependent linear viscoelastic modulus as well as the fitting parameters for the non-linear viscoelastic viscoplastic model. The stress model is implemented in a commercial finite element code, Abaqus®, to predict the response of a membrane subjected to mechanical loads. The stress model is validated by comparing predicted and experimental responses for membranes subjected to stress relaxation and multiple step creep loads in uniaxial tension.
Model Development and Analysis of a Cricket Filiform Hair Socket Under Low Velocity Air Currents
Authors: Joshi Kanishka , Mian Ahsan , Miller John
Published: October 2013

Cricket filiform hairs are very sensitive to air currents in the animal’s immediate environment generated by movement of other animals or objects. When an air current is experienced by the animal, filiform hairs located on a pair of abdominal appendages called cerci deflect from their original position, activating the sensing mechanism. Though the flow sensing mechanism of the hair has been studied previously and flow sensors have been fabricated based on the same principle, the socket structure in which the hair base sits and which encompasses the hair below the skin of the cricket has not been characterized in terms of deformation and stress transfers. This paper presents a preliminary study on the response of the socket under a given loading or displacement the hair experiences. If the socket is characterized well, the mechanical principles can be applied in the design of a highly-responsive MEMS senor.
Application of Cartesian Cut Cell Method for Incompressible Flow on High Lift Devices
Authors: Ghmati Ramadan , Jawad Badih , Arslan Selin
Published: October 2013

With advances in computing power and Computational Fluid Dynamics (CFD) algorithms, the complexity of CutCell based simulation models has significantly increased. In this study three dimensional numerical simulations were created for steady incompressible flow around an airfoil shape. The authors extended their work [39] on more complex geometries; NACA-23012 Wing with 20 percent C clark Y Flap was used for this study. Boundary layer thickness, mesh expansion ratio, and mesh density variation parameters were examined. Drag and lift coefficients were compared to measured data. Use of the CutCell method produces fair agreement between CFD results and measured data.
Uncertainty Analysis of Solid-Liquid-Vapor Phase Change of a Metal Particle Subject to Nanosecond Laser Heating
Authors: Peng Hao , Zhang Yuwen , Pai P. Frank
Published: October 2013

Effects of uncertainties of various parameters, including laser fluence, diameter of metal powder articles, laser pulse width and initial temperature of metal particles, on solid-liquid-vapor phase change processes of metal particles under nanosecond laser heating are investigated in this paper. A systematic approach of simulating phase change with uncertain parameters are presented and a sample-based stochastic model are established to investigate the influence of different uncertain parameters on maximum surface temperature of metal particles, maximum solid-liquid interface location, maximum liquid-vapor interface location, maximum saturation temperature and maximum recoil pressure, and time needed to reach maximum solid-liquid interface location. The results show that the mean value and standard deviation of laser fluence have dominant effects on all output parameters.
Improving Energy Efficiency Through Thermal Control of a Modular Data Center
Authors: Guinn John , Gondipalli Srujan
Published: October 2013

As the IT industry’s demand for greater power density racks grows, the operating cost associated with power and cooling IT equipment remains an ever present concern facing data centers. A key component in reducing Total Cost of Ownership (TCO) for a facility is to optimize their cooling system design. Hewlett-Packard has developed a self contained enclosure for high density servers and mass storage devices called a Modular Data Center (MDC). This unit is intended to reduce issues that have plagued large scale data centers by increasing cooling capacity and efficiency. This paper takes a look at the thermal control logic for the MDC and explains ways to decrease energy costs by developing a thermal control scheme centered on optimizing Power Usage Efficiency (PUE).

Tests were conducted to understand the relationships between fan power and fan speed, facility power and thermal capacity. Areas of large power drains were isolated and analyzed. Tests showed that there are two parts in managing power usage on the MDC, system and facility control. In the development of a smarter control algorithm, the fans and water valve (“system”) performance curves provided a road map to the hardware’s capability. This was accomplished by understanding how key variables such as inlet water temperature, water flow rate and fan speed impact the behavior of server inlet air temperature and cooling capacity.

Facility control comes from optimizing what equipment is in place to support the MDC (i.e. dedicated chiller, campus chiller, pumps, etc…) within a data center. A significant goal of this project was to minimize the dependency MDC has on external cooling by optimizing the variables that affect facility power. For instance controlling heat removal rate and exiting water temperature affects chiller power; while water flow rate affects pump power. Knowledge of your system and facility’s capabilities directly impacts power management.

Thermal performance testing of the heat exchanger in the MDC provided insight into how increasing thermal efficiency at the heat exchanger produced an overall drop in facility power. Tests revealed that the optimized thermal control system achieved an infrastructure energy savings up to 33% with a PUE improvement from 1.35 to 1.23 for a 100KW IT heat load. The results show that characterizing and incorporating the behavior of the fans and heat exchanger into the thermal control system produced an improved Power Usage Efficiency (PUE) and a smarter control method.
Size Scale Effect on Generated Electric Potential of Nano Composite Electrical Generators
Authors: Momeni Kasra
Published: October 2013

A multiscale approach is pursued for modeling the size-scale effect on generated electric potential by nanocomposite electrical generators of ZnO nanowires. A core-surface model is used for capturing the effect of size-scale on elastic modulus of ZnO NWs. In this model, a surface with different elastic modulus as of the core of NW was considered. Using linear elasticity and axisymmetric configuration of this problem, closed form governing equations are derived in cylindrical coordinate system. Parametric studied are performed for sample cases to demonstrate application of the developed model. It is shown that ZnO nanowires with larger aspect ratio and smaller diameters have higher performance and can produce higher electric potential.
Thermal Characterization of Aluminum and Steel Foams
Authors: Playford James D. , Midturi S. , Pidugu S. B.
Published: October 2013

Metallic foams are a new class of ultra-lightweight materials with potential applications in such industries as automobile, aerospace, and energy industries. These materials when realized in product form can serve as efficient heat exchanges, energy absorbers, and thermal protective and hydrogen storage devices. Accurate determination of thermal conductivity and understanding of heat transfer characteristics is important in designing such products incorporating metal foams. The present research characterizes the effective thermal conductivity and heat transfer characteristics of DUOCEL AL 6106-T6 and Stainless Steel 314 open cell foams by experiments at near room temperature conditions. The effective thermal conductivity of these materials has been determined experimentally. Thermal conductivity of metal foams increased with increasing mechanical stress. The effect of porosity on the thermal conductivity of ERG supplied aluminum and NASA-GRC supplied SS 314 are also studied and compared with the published data in literature, however, in our studies systematic dependency of porosity is not observed. Experiments also conducted to quantify forced convective heat transfer characteristics under laminar flow conditions. Heat transfer coefficient increases with increased Reynolds number but results are not conclusive in case of natural convection.
High Sensitivity MEMS Biosensor for Monitoring Cell Attachment
Authors: Liu Fei , Li Fang , Spray David C. , Nordin Anis Nurashikin , Voiculescu Ioana
Published: October 2013

This paper presents the fabrication and testing of a novel microelectromechanical (MEMS) biosensor based on live cells. The biosensor combines two biosensing techniques; resonant frequency measurements and electric cell-substrate impedance sensing (ECIS) on a single device. The sensor is based on the innovative placement of the working microelectrode for ECIS technique as the upper electrode of a quartz crystal microbalance (QCM) resonator. This hybrid biosensor was tested with bovine aortic endothelial cells with different seeding densities. The cell attachment and spreading was monitored with both sensors; the QCM and the ECIS technique. After the cells form a monolayer the values of the impedance and resonant frequency measurements are constant. The optimal cell seeding density with minimal time required to attach and form a monolayer was observed to be 1.5×104 cells/cm2. This biosensor monitors the cells attachment and viability and could be used for screening toxicants in drinking water.
Effect of the Heat Recovery System to the Performance of Air Handling Unit of a Shopping Centre
Authors: Kelasovali Furkan , Celen Ali , Kayaci Nurullah , Dalkilic Ahmet Selim , Wongwises Somchai
Published: October 2013

In today’s world, the efficient use of energy is very important due to short of energy sources. In order to use energy efficiently, some methods/devices have been developed recently. One of them is heat recovery systems which are used for energy saving in the Heating Ventilating and Air Conditioning applications. Air handling units (AHUs) equipped with heat recovery system can be used applications for energy saving. Not only this paper presents information about rotary heat exchangers which is one of the air to air heat recovery systems but also it investigates their effects to system when they are used in an application. In the study, a shopping centre, which is located in the capital city of Turkey, is taken consideration. The shopping centre has an air handling unit having 54567 m3/h fresh air flow rate, 640 kW heating and 41 kW cooling capacity. Calculations are performed for AHU of the shopping centre both equipped with rotary heat exchanger and without rotary heat exchanger. In order to compare performance of AHUs, annual energy saving, initial investment cost, annual operating expenses, payback time and profit parameters are calculated for each month. According to the results, heating battery power in the heating season and cooling battery power in the cooling season is significantly decreased by using heat recovery system and total annual energy saving is calculated as $83,444. Consequently, it is found that the use of rotary heat exchanger improves performance of system in terms of the reduction in required powers and costs.
Hyperelastic and Viscoelastic Properties of Brain Tissue in Tension
Authors: Rashid Badar , Destrade Michel , Gilchrist Michael D.
Published: October 2013

Mechanical characterization of brain tissue at high loading velocities is particularly important for modelling Traumatic Brain Injury (TBI). During severe impact conditions, brain tissue experiences a mixture of compression, tension and shear. Diffuse axonal injury (DAI) occurs in animals and humans when the strains and strain rates exceed 10% and 10/s, respectively. Knowing the mechanical properties of brain tissue at these strains and strain rates is thus of particular importance, as they can be used in finite element simulations to predict the occurrence of brain injuries under different impact conditions.

In this research, uniaxial tensile tests at strain rates of 30, 60 and 90/s up to 30% strain and stress relaxation tests in tension at various strain magnitudes (10%–60%) with an average rise time of 24 ms were performed. The brain tissue showed a stiffer response with increasing strain rates, showing that hyperelastic models are not adequate and that viscoelastic models are required. Specifically, the tensile engineering stress at 30% strain was 3.1 ± 0.49 kPa, 4.3 ± 0.86 kPa, 6.5 ± 0.76 kPa (mean ± SD) at strain rates of 30, 60 and 90/s, respectively. The Prony parameters were estimated from the relaxation data. Numerical simulations were performed using a one-term Ogden model to analyze hyperelastic and viscoelastic behavior of brain tissue up to 30% strain. The material parameters obtained in this study will help to develop biofidelic human brain finite element models, which subsequently can be used to predict brain injuries under impact conditions.
Development of a Two-Dimensional Model of the Human Arm to Investigate the Biomimetic Substitution of Human Bicep Muscle With a Dielectric Electroactive Polymer Muscle Actuator
Authors: Spath William E. , Walter Wayne W.
Published: October 2013

Current prostheses are not able to meet the needs of patients. The authors have recently been investigating the feasibility of integrating multiple types of electroactive polymers (EAP) to develop an artificial muscle for prostheses and muscle implants; much like biological muscle is made up of multiple types of muscle fibers. The intent is to produce a lightweight device which has smooth fluid-like motion, in contrast to the jerky motion of current prostheses which use heavy rotary actuators. A human arm model, isolating the bicep muscle, was developed to better understand the requirements on force and strain that an artificial muscle must meet to replace biological muscle. This study was conducted with the assistance of orthopedic surgeons from the Rochester General Hospital. Bicep muscle characteristics were compared with those of dielectric elastomer electroactive polymers (DEAP), since they produce relatively high force and large strain during actuation. Results show that current characteristics of DEAPs will not allow for direct substitution of human muscle fibers with EAPs because their force and strain outputs are too low. To increase the force and strain output of DEAPs to that of human muscle fibers, the stiffness of the DEAP needs to be increased. The analysis done and results obtained are discussed in the paper, as well as possible ways to increase the stiffness of EAPs to better meet the requirements for biological muscle replacement.
Multifunctional Skin-Like Electronics for Long-Term Health Monitoring
Authors: Yeo Woon-Hong , Kim Yun-Soung , Lee Jongwoo , Rogers John A.
Published: October 2013

Conductive gel-based wet electrodes along with the skin preparation have been widely used for the measurement of electrophysiological signals on the skin in a health monitoring system. The use of conductive gels is necessary to reduce the contact impedance between the skin surface and electrode. However, it can cause skin irritation or allergic reactions. This issue originates from the mismatch between the soft, curvy skin epidermis and the rigid, flat metal electrode.

To address the issues of conventional electronics, we introduce a new class of ‘skin-like’ electronic system. The electronics can be conformally laminated on the epidermis, such that it ensures high-quality data recording without conductive gels. The skin-like electronics incorporates electrophysiological-, temperature-, and strain sensors in the system for multimodal functionality. To provide robust wearability for a week, a medical spray bandage is utilized to shield the sensor on the skin. The multifunctional sensor measures physiological signals and they are recorded with a commercial wireless data acquisition system along with a releasable, skin-like connector. This novel, multifunctional electronics on the skin can potentially replace the irritable and cumbersome wet electrodes for portable, long-term health monitoring at home.
Counting Failure Events for a Support System
Authors: Smith Curtis
Published: October 2013

An initiating event is a departure from a desired operational envelope to a system state where a control response is required either by human or machine intervention. In the case of a support system such as a cooling water or electrical distribution system, failure of this system represents the departure from normal operating conditions. Initiating event frequencies for probabilistic risk assessments are generally based on data collection. For rare, but potentially high consequence initiators representing the failure of support systems, this approach has a number of shortcomings. For example, since events are rare, there may not be any complete system failure events in the available data sets. Consequently, there is a desire to model system failures of initiating events since component-level failure events in the support systems are more frequent. Therefore, what is needed is a suitable method for calculating the initiating event frequency (expected number of system failures over some operating mission) from the relatively well known component failure rates. In this paper, we explore ways to develop and quantify models that represent the rates of failures for support systems. These failures of repairable systems can be represented by focusing on observables. Specifically, we can either count the number of failures in time t or count the times of failure. As part of the analysis, we will describe and evaluate a couple of typical redundant support systems. Included in the analysis will be considerations of dependent failure mechanisms.
The Design of a Yacht-Type Chiller
Authors: Kayki Mehmet , Celen Ali , Kayaci Nurullah , Dalkiliç Ahmet Selim , Wongwises Somchai
Published: October 2013

This study mentioned a yacht-type chiller design working between 50 and 200 kW. Ventilation and air conditioning systems on a yacht provide the conditions necessary for the proper internal medium for the staff, passengers, cargo, machinery, and auxiliary systems. The conditions of the internal medium in a yacht are controlled by air conditioning, heating, cooling, humidification and dehumidification processes. Ventilation and air conditioning systems are primarily simple, reliable, and must be practical. Also, the ability to control noise and vibration caused by these systems and the maintenance costs should be lower. The power of the total air-conditioning and ventilation is calculated to be 105 kW for 15 rooms on a yacht. For the system to work efficiently, rather than a single system to 105 kW, 35 kW at 3 units, the establishment of a chiller system is preferred. The Mollier diagram of the system (refrigerant R-407C) is produced to accept an evaporation temperature of 1 °C (minimum) and a condensation temperature of 45 °C (maximum), and then the values of power, efficiency, and COP are calculated. By taking the design flow velocity in pipes of 12 m/s pipe diameter, the calculation is done for 3 basic lines (suction, discharge, and liquid). According to the calculated data, the suitable components were selected and assembled to establish a yacht type chiller. Necessary security checks were done for the system to work correctly, and finally, the system was ready for installation.
Numerical Investigation of the Effects of Different Overhang Configurations on the Wind-Driven Rain Wetting of Building Facades
Authors: Mohaddes Foroushani Seyed Sepehr , Naylor David , Ge Hua
Published: October 2013

The distribution of wind-driven rain loads on building facades is of high importance in evaluating the hygrothermal performance and durability of building envelopes. Wind-driven rain is known to be a major source of moisture loads on building facades and is responsible for numerous cases of facade failure. One of the classical solutions for preventing the building envelope from being extensively exposed to such loads is the use of overhangs. In this work, the effects of different overhang lengths on the distribution of wind-driven rain on building facades are investigated by numerical methods. To check validity, the results are compared to existing data reported in the literature. Calculated values of catch ratio at two sample positions on the front facade of a simple cubic building are in good agreement with previously published results. The protective effect of overhangs is shown by calculating catch ratio values for cases where rectangular overhangs were added to the cubic building. Results suggest that the introduction of the overhang can significantly change both the amount and the pattern of the wind-driven rain wetting of the facade. This change may, in certain points, be unfavourable.
Stability of Viscous Flow Driven by an Azimuthal Pressure Gradient Between Two Porous Concentric Cylinders With Radial Flow and a Constant Heat Flux at the Inner Cylinder
Authors: Deka R. K. , Paul A.
Published: October 2013

A linear analysis for the instability of viscous flow between two porous concentric circular cylinders driven by a constant azimuthal pressure gradient is studied, when a radial flow through the permeable walls of the cylinders is present. Also, a constant heat flux at the inner cylinder is applied. The linearized stability equations form an eigenvalue problem, which are solved by using Runge-Kutta-Fehlberg scheme combined with a shooting method, termed unit disturbance method. It is found that the constant heat flux parameter N, even for a radially weak outward flow has a strong stabilizing effect and the stabilization is more as the gap between the cylinders increases.
Thickness Evaluation of Insulated Pipelines and Pressure Vessels Using Pulsed Eddy Current Technology
Authors: Shameli Ehsan
Published: October 2013

Information about integrity of pipelines and pressure vessels is vital to the oil and gas industry. This emphasizes the need for fast and cost effective non-destructive testing solutions for monitoring and inspection of these components. However, due to reasons such as corrosion protection and temperature maintenance, pipelines and pressure vessels are usually coated throughout the oil and gas industry. These coatings also present a barrier to inspections and typically need to be removed prior to inspection with nondestructive evaluation (NDE) methods. This article presents a pulsed eddy current (PEC) system suitable for nondestructive evaluation of steel pipelines and pressure vessels without the need for removing the coating layers. A PEC probe was fabricated and a custom computer code with built in signal processing and data analysis functions was developed to collect the measurement signals and calculate thickness variations in the test objects. From a lift-off distance of 12mm, experiments were performed on eight SS304 stainless steel samples with thicknesses ranging from 1mm to 8mm. The SS304 steel was chosen as the test material to represent the steel type commonly used in the pipeline industry. A calibration curve based on the zero crossing time of initial measurements was obtained and implemented into the measurement software. Using the calibrated system, 25 measurements where performed on each sample. Statistical analysis of results showed that the proposed system can accurately detect thickness variations in the test samples with maximum measurement error of 3.3 percent.
Experimental Investigation of the Water Impact on Performance of Proton Exchange Membrane Fuel Cells (PEMFC) With Porous and Non-Porous Flow Channels
Authors: Karthikeyan P. , Li H. Calvin , Lipscomb G. , Neelakrishnan S. , Abby J. G. , Anand R.
Published: October 2013

The most critical aspect of fuel cell water management is the delicate balance of membrane hydration and avoiding cathode flooding. Liquid water accumulation in the interfacial contact area between the flow channel landing and gas diffusion layer (GDL) can dramatically impact steady and transient performance of proton exchange membrane fuel cells (PEMFCs). In this concern, a porous landing could facilitate water removal in the cathode flow channel and significantly improve PEMFCs performance. In this work, an attempt has been made to fabricate the porous interdigitated cathode flow channels from a porous carbon sheet. Performance measurements have been made with nominally identical PEMFCs using non-porous (serpentine and interdigitated) and porous (interdigitated) cathode flow channels. PEMFCs with porous interdigitated flow channels had 48% greater power output than PEMFCs with non-porous interdigitated flow channels at high current densities. For the non-porous interdigitated flow channel, significant performance loss appears to arise from greatly reduced oxygen transport rates when the water generation rate exceeds the water removal rate, however for the porous interdigitated flow channel, the design removes the accumulated liquid water from the landing area through the capillarity of its porous structure and eliminates the stagnant regions under the landing, thereby reducing liquid flooding in the interface between landing and GDL area.
The Effect of Crystallographic Orientation on Material Removal Behavior of (001) Plane KDP Crystal in Nano-Scratch Test
Authors: Zhang C. L. , Feng P. F. , Wang D.
Published: October 2013

KDP crystal has been widely used in harmonic generation and optical parametric oscillators due to its good nonlinear optical properties and high laser damage threshold. However, because of its inherent properties, such as fragility, hygroscopic, anisotropy and low rigidity etc., KDP crystal is regarded as one of the most difficult machining materials. Nanoscratch tests were conducted in [100], [110] and [010] orientation of (001) plane KDP crystal at room temperature under a ramp loading condition from 40μN to 200 mN using with a nanomechanical test system in scratch mode to study the effects of crystallographic orientations on plastic deformation and brittle deformation features of KDP crystal. A spherical monocrystalline diamond indenter was employed in this study. Penetration depths and residual deformations of the scratch tracks were collected during the scratch process. Morphology characteristics of the scratch grooves in different scratch directions, including plastic deformation features and brittle deformation features, were observed by scanning electron microscopy. The experimental results clearly showed that there exist two distinct material deformation modes of each scratch process: plastic deformation mode, and brittle deformation mode. Comparative studies of surface depth profiles and scratch groove features induced in different crystallographic orientations revealed that the anisotropy of (001) plane KDP crystal has significant effects on the deformation features. It also presented that [110] orientation of (001) plane KDP crystal has the maximal critical load and critical depth, and can produce the highest proportion plastic deformation, which imply that [110] orientation can get adequate surface quality of KDP crystal for diamond cutting, grinding, and milling etc..
Experimental Investigation of Flat Tube-Louver Fin Heat Exchanger Performance Working as a Cooler in Dry and Wet Conditions
Authors: Popli Sahil , Hwang Yunho , Radermacher Reinhard
Published: October 2013

An experimental study has been conducted to evaluate the performance of a flat-tube louver-fin heat exchanger working as a cooler, with frontal area of 0.25 m2 in both dry and wet conditions. Deluge water cooling at different flow rates was achieved by incorporating perforated tube-type distributor on top of the heat exchanger. Water at 35°C temperature was used as heat transfer fluid at cooler inlet. Ambient air and deluge cooling water were both maintained at 22°C temperature. Heat exchanger capacity and air-side pressure drop were measured with the heat exchanger angle set at 0° and 21° from vertical, with a frontal air velocity of 1.4 m/s and 3.5 m/s without deluge water cooling, and a frontal air velocity of 1.2 m/s, 1.4 m/s with deluge water cooling. Significant capacity enhancement could be obtained both with the use of deluge water cooling and with the heat exchanger angle set at 21° from vertical. Furthermore, it was found that approximately same capacity was obtained at both 0° and 21° angle when wetting water flow rate was reduced from 0.17 kg/s to 0.063 kg/s, without significant reduction in air-side pressure drop. This study highlights the importance of wetting of heat transfer surfaces of compact flat tube heat exchangers and provides motivation for further research in this area.
Adaptive Neural-Fuzzy Controller (ANFC) Based Energy Management System for Battery/Ultracapacitor Electric Vehicle
Authors: Fung Eric H. K. , Wang Yiyun , Wong Y. K.
Published: October 2013

In order to improve fuel economy of electric vehicles, a battery/ultra-capacitor energy storage system is proposed and tested in AVL-Cruise. The battery is treated as the main power source of the vehicle, and the ultra-capacitor will store the energy when braking. In this paper, an adaptive neural-fuzzy controller is developed to control the energy system. It can split the power flow in a more efficient manner. The simulation result shows the new control strategy has a better fuel economy than the traditional fuzzy logic controller.
Cathode Catalyst Layer Model for Polymer Electrolyte Membrane Fuel Cell
Authors: Kamarajugadda Sai , Mazumder Sandip
Published: October 2013

The flooded agglomerate model has found prolific usage in modeling the oxygen reduction reaction within the cathode catalyst layer of a polymer electrolyte membrane fuel cell (PEMFC). The assumption made in this model is that the ionomer-coated carbon-platinum agglomerate is spherical in shape and that the spheres are non-overlapping. This assumption is convenient because the governing equations lend themselves to closed-form analytical solution when a spherical shape is assumed. In reality, micrographs of the catalyst layer show that the agglomerates are best represented by sets of overlapping spheres of unequal radii. In this article, the flooded agglomerate is generalized by considering overlapping spheres of unequal radii. As a first cut, only two overlapping spheres are considered. The governing reaction-diffusion equations are solved numerically using the unstructured finite-volume method. The volumetric current density is extracted for various parametric variations, and tabulated. This sub-grid-scale generalized flooded agglomerate model is first validated and finally coupled to a computational fluid dynamics (CFD) code for predicting the performance of the PEMFC. Results show that when the agglomerates are small (< 200 nm equivalent radius), the effect of agglomerate shape on the overall PEMFC performance is insignificant. For large agglomerates, on the other hand, the effect of agglomerate shape was found to be critical, especially for high current densities for which the mass transport resistance within the agglomerate is strongly dependent on the shape of the agglomerate, and was found to correlate well with the surface-to-volume ratio of the agglomerate.
Sliding Vane Rotary Compressor Energy Optimization
Authors: Cipollone Roberto , Bianchi Giuseppe , Contaldi Giulio
Published: October 2013

The reduction of the electrical energy for producing compressed air gives an important contribution to the overall energy saving in the industrial context. Among the different technologies, Sliding Vane Rotary Compressors (SVRC) demonstrate unforeseen potential in terms of energy saving due to some intrinsic features specifically related to this machine.

One of the most important contribution is given by cooling the air during compression; this could be achieved by a proper oil injection conceived for this purpose. A mathematical model describing the oil injection process is presented in this paper. It considers the main parameters which describe the spray formation, its penetration inside the cell till to the intersection with metallic surfaces and the resulting air cooling.

The influence of the most important design and operating injection parameters have been checked on the model and design rules are outlined in order to produce an oil injection potentially able to reduce mechanical work.
Reduced Order Model for MEMS Cantilever Resonators Under Soft AC Voltage Near Natural Frequency
Authors: Caruntu Dumitru I. , Martinez Israel
Published: October 2013

The nonlinear response of an electrostatically actuated cantilever beam microresonator is investigated. The AC voltage is of frequency near resonator’s natural frequency. A first order fringe correction of the electrostatic force and viscous damping are included in the model. The dynamics of the resonator is investigated using the Reduced Order Model (ROM) method, based on Galerkin procedure. Steady-state motions are found. Numerical results for the uniform microresonator are compared with those obtained via the Method of Multiple Scales (MMS).
Reduced Order Model of CNT Cantilever Resonators Under AC Voltage Near Half Natural Frequency
Authors: Caruntu Dumitru I. , Luo Le
Published: October 2013

This paper deals with electrostatically actuated Carbon Nano-Tubes (CNT) cantilevers using Reduced Order Model method. There are three kinds of forces acting on the CNT cantilever: electrostatic, elastostatic, and van der Waals. The van der Waals forces are significant for values of 50 nm or lower of the gap between the CNT and the ground plate. As both forceselectrostatic and van der Waals are nonlinear, and the CNT electrostatic actuation is given by AC voltage, the CNT undergoes nonlinear parametric dynamics. The Method of Multiple Scales (MMS), Reduced Order Model (ROM) and AUTO are used to investigate the system under soft excitations and/or weak nonlinearities. The frequency-amplitude and frequency-phase behaviors are found in the case of resonance near half natural frequency.
Neck Pain Participant’s Perception of Traction Forces During Chiropractic Manual Cervical Distraction
Authors: Gudavalli M. Ram , Henderson Charles N. R. , Vining Robert , Carber Lynne , Patwardhan Avinash G. , Goertz Christine
Published: October 2013

In this exploratory study, we measured applied traction forces during a chiropractic manual cervical distraction procedure for each of three “treatment” perceptions; (i) beginning to feel a stretch, (ii) stretch feels like it could be a treatment, and (iii) stretch definitely feels like a treatment. A single trained clinician performed manual cervical distraction procedures on 10 neck pain participants using a commercially available table that was embedded with force and motion sensors. Participants were prone on the table while manual distraction was applied with gradually increasing force. When the specified perception was experienced, the study participant depressed a hand switch. Data was summarized with descriptive statistics and plotted for graphical analysis. Point estimates and 95% confidence intervals were calculated for the distractive force associated with each of the 3 treatment perceptions. Mean traction forces with 95% confidence intervals, corresponding to each of the 3 perception levels were: i) beginning to feel a stretch 18.6 N (11.9–25.2 N), ii) stretch feels like it could be a treatment 25.5 N (18.3–32.6 N), and iii) stretch definitely feels like a treatment 36.2 N (26.2–46.1 N).
Optimization of Gait Trajectory of Bipedal Walking on Inclined Plane With Pitch and Roll Using Genetic Algorithm
Authors: Yu H. F. , Fung E. H. K. , Jing X. J.
Published: October 2013

This paper adopts Genetic Algorithm Optimized Fourier Series Formulation (GAOFSF) [1] to achieve stable walking on inclined plane with pitch and roll angle. The first section presents the physical configuration of bipedal robot. Also, kinematic model and inverse dynamic model are derived by Denavit-Hartenberg notation and iterative Newton-Euler dynamic algorithm respectively. Both of them consider the period of single support phase (SSP) only. Then, the formulae of the proposed trajectories which are represented by Truncated Fourier Series (TFS) are given. Moreover, the control objectives of genetic algorithm (GA) which are ZMP trajectories, strike velocity, desired step length and desired average trunk velocity are shown in the third section. Besides, the objective functions and constraints are clearly stated. In the final section, the performance of the proposed trajectories is analyzed based on the preset requirements. The optimized trajectory is found to be satisfactory since it can fulfill all the preset requirements.
Application of Optimal Control Method to Improve Kinematic Characteristics of Crank-Slider Mechanisms
Authors: Saeidi H. , Heidari M. , Zahiri M.
Published: October 2013

In this study two approaches are proposed to improve the kinematic characteristics of the conventional crank-slider transmission mechanism. The investigation presented here deals with the motion control of a crank-slider mechanism rather than driving the input crank at a uniform speed. The purpose is to decrease the maximum value of the slider acceleration by applying an optimal control theory and a genetic algorithm (GA) to the crank speed. Results show a reduction of 43.68% and 42.23% of the peak acceleration value of the slider in optimal mechanisms analyzed by optimal control theory and genetic algorithm respectively in comparison with a constant angular speed driven crank. Examples are given to illustrate the design procedure.
Effects of Equivalence Ratio on the Emission and Temperature Characteristics of Spray Flames of Jet A/Butanol Blends Under Lean Conditions
Authors: Ratul Tanjir H. , Parthasarathy Ramkumar N. , Gollahalli Subramanyam R.
Published: October 2013

Butanol is an attractive alternate fuel because it can be produced from renewable sources and has properties similar to those of petroleum fuels. Thus, blending butanol with petroleum fuels is a promising solution to reduce the dependence on petroleum fuels. In a previous study, we investigated the differences in the structure and emissions of Jet A and Butanol flames. The objective of this investigation was to study the emission and in-flame temperature characteristics of spray flames of Jet A/butanol blends at two equivalence ratios: 0.75 and 0.95. In addition to pure Jet A and pure butanol, blends of Jet A with 25%, 50% and 75% volumetric concentrations of butanol were used as fuel. The liquid fuel was atomized and combusted with air in a heated environment (479 K). The equivalence ratio was changed by altering the fuel flow rate, while maintaining the atomizing and coflow air flow rates constant, thus maintaining gas velocity field invariant. The global emission index of CO varied non-monotonically with the volume concentration of butanol in the blend at the lower equivalence ratio whereas the variation was gradual at the higher equivalence ratio. The global NOx emission index decreased monotonically as the butnaol content was increased at both equivalence ratios. The global NOx emission index level in the flames at equivalence ratio of 0.95 was higher than that at equivalence ratio of 0.75. At 25% flame height, the peak reaction zone was located off-axis; this radial location moved further away from the centerline as the equivalence ratio was increased. The peak temperatures were comparable in all the flames. The flames with butanol highlighted the effects of preferential vaporization of butanol.
Distributed Marine Biorefineries for Developing Economies
Authors: Golberg A. , Linshiz G. , Koudritsky M. , Chemodanov A. , Hillson N. J.
Published: October 2013

In the coming decades, developing countries will be responsible for significant increases in liquid fuel demand. There is an urgent need to develop alternative, preferably carbon-neutral, transportation fuels to supplement limited fossil fuel resources and minimize undesirable climatic change. While biofuels present a promising alternative to fossil fuels, sustainable biorefinery process design remains challenging. Efficiencies of scale realized by large centralized facilities are offset by increased feedstock collection and fuel distribution logistical costs. In this work, we use a thermodynamic balance approach to derive the optimal serviced territory size for a single biorefinery. We find that the optimal size decreases with increasing population density and per capita fuel consumption. We propose a modular, scalable, and sustainable biorefinery design based on the marine macro algae Ulva sp. To demonstrate the design principal, we provide an example marine biorefinery design for a coastal town of 20,000 inhabitants in rural India. Beyond basic biorefinery design, we consider biorefinery integration into distributed power sources and environmental impacts.