bluuebunny/crossref_metadata_2025 huggingface dataset:
An Energy Consumption Rewards System to Incentivize Environmentally Conscious Social Behavior
Authors: Godre Atishay , Nikolaev Alexander , Rai Rahul
Published: April 2014

This paper outlines an idea of creatively incentivizing home-owners to conserve electricity through a socially competitive lottery-based rewards system. The core idea of this work is in leveraging the power of social network influence to make consumers participate and compete in a lottery so that the resulting engagement consistently enhances the population’s energy spending awareness. The potential value of such a system in generating energy and monetary savings/revenue is investigated via simulation of social influence processes in an agent based simulation framework. The study encompasses three analysis cases: a lottery system with no communication between consumers, a system with the added social influence, and a “fall-back” scenario where people may return to their old habits of not conserving electricity while still communicating among themselves. To model these analysis cases, a standard independent cascade model is employed with influence success thresholds varied between 1% and 10%. The paper concludes by summarizing the simulation results. Pertinent aspects such as generation of lottery prize money, and expected impact on energy savings is also discussed.
Integral Effect Test on Operational Performance of the PAFS (Passive Auxiliary Feedwater System) for a SGTR (Steam Generator Tube Rupture) Accident
Authors: Park Yusun , Bae Byoung-Uhn , Kim Seok , Cho Yun-Je , Kang Kyoung-Ho
Published: April 2014

The PAFS is one of the advanced safety features adopted in the APR+ (Advanced Power Reactor Plus) which is intended to completely replace a conventional active auxiliary feedwater system. The PAFS cools down the steam generator secondary side and eventually removes the decay heat from the reactor core by adopting a natural convection mechanism; i.e., condensing steam in nearly-horizontal U-tubes submerged inside the PCCT (Passive Condensation Cooling Tank). With an aim of verifying the operational performance of the PAFS, the experimental program of an integral effect test is in progress at KAERI (Korea Atomic Energy Research Institute). The test facility, ATLAS-PAFS was constructed to experimentally investigate the thermal hydraulic behavior in the primary and secondary systems of the APR+ during a transient when the PAFS is actuated.

Since the ATLAS-PAFS facility simulates a single train of the PAFS, the anticipated accident scenarios in the experiment include FLB (Feedwater Line Break), MSLB (Main Steam Line Break), and SGTR (Steam Generator Tube Rupture). Among them, SGTR was considered as one of the design basis accidents having a significant impact on safety in a viewpoint of radiological release. Therefore, the SGTR test was determined to be the integral effect test item in the frame of the ATLAS-PAFS experimental program.

In this study, the PAFS-SGTR-HL-02 test was performed to simulate a double-ended rupture of a single U-tube in the hot side of the steam generator of the APR+. The three-level scaling methodology was taken into account to determine the test conditions of the steady-state and the transient. The pressures and temperatures of the system and the data related to the PAFS operation were collected with the measurement of the break flow.

The initial steady-state conditions and the sequence of event of SGTR scenario for the APR+ were successfully simulated with the ATLAS-PAFS facility. And it was shown that the pressure and the temperature of the primary system were continuously decreased during the heat removal by the PAFS operation. The water pool in the PCCT was heated up to the saturation condition and the evaporation of the water made a decrease of the PCCT water level.

It could be concluded from the present experimental result that the APR+ has the capability of coping with the hypothetical SGTR scenario with adopting the PAFS and the proper set-points of its operation.
Direct Transmission Loss Calculation of Simplified Muffler Configurations Using a Lattice-Boltzmann Method
Authors: Mann Adrien , Pérot Franck
Published: April 2014

Lattice-Boltzmann Method (LBM) is broadly used for the simulation of aeroacoustics problems. This time-domain CFD/CAA approach is transient, explicit and compressible and offers an accurate and efficient solution to simultaneously resolve turbulent flows and their corresponding flow-induced noise radiation. Some examples of applications are ground transportation wind-noise problems, buffeting, Heating, Ventilation, and Air Conditioning (HVAC), fan noise, etc. As shown in previous studies, LBM can also be used to accurately handle linear acoustics problems if the source of noise is not a flow but a simple acoustic source. This set of capabilities makes LBM a suitable candidate for evaluating the acoustics performances of exhaust systems and mufflers.

Compared to other traditional acoustics methods, LBM presents the advantage to skip tedious volume meshing operations since the mesh generation is fully automatic. Furthermore, considering that all geometrical details are included in the simulation domain and that LBM is explicit, high frequencies mechanisms up to 10–20 kHz can be captured. The upper frequency limit is indeed solely driven by the spatial resolution used to discretize the system.

In this paper, three academic 3-D geometries representative of production muffler systems are studied. Transmission Loss (TL) measurements are performed on three configurations and these experiments are reproduced numerically with LBM.

The experimental setup is described in a first part and the numerical details are given in a second part and third part. In particular, the method used to calculate the TL in the simulation and the convergence of the results with respect to the spatial resolution are shown. In a third part, the simulations are compared to the TL measurements and a numerical investigation of the effect of geometry details on the simulated results is proposed. This study highlights the sensitivity of acoustics measurements to geometry details.
Teaching Stress Transformation Through Laboratory Experiments
Authors: Aluko O.
Published: April 2014

This paper describes a hands-on laboratory solid mechanics project which was supervised as an independent study. The experimental study and analysis were focused on strain and stress transformation on cantilever beam subjected to bending within elastic range. A combination of five different metals and two types strain rosette arrangements were used in the experimentation. The project involves the design and construction of test facility and experimental analysis of tested piece. The samples of measured data and analysis are reported in this paper. The strains in rectangular and principal coordinates which were computed from measured strains enabled the stress in both coordinates to be determined. This analysis enables the students to determine experimentally, that the sum of normal strain and stresses are invariant. The teaching strategy employed to integrate fundamental theories with hands-on experiences is described. The effectiveness of the laboratory project in enhancing student learning of stress-strain transformation and project management skill was demonstrated by monitoring student performance improvements over the duration of the project. The success of this project leads to an experiment for teaching students stress-strain transformation in mechanics of materials laboratory.
A Parametric Study on Failure of Pin-Loaded Unidirectional-Woven Composite Joints
Authors: Aluko O.
Published: April 2014

An analysis was performed to predict the failure load of unidirectional and woven pinned loaded composite joints using the characteristic curve model. The characteristic dimensions used to determine the characteristic curve were evaluated from stress functions without experimental tests. A parametric study was carried out for different coefficient of friction ranging between 0 and 0.15 to evaluate the effect of friction on joints failure using Tsai-Wu failure criterion along the characteristic curve. A comparison of analytical results with the available experimental data showed that the friction coefficient of 0.05 generally gave the best prediction for the joint configurations evaluated.
Lithium-Ion Battery Cell Health Monitoring Using Vibration Diagnostic Test
Authors: Pham Huan L. , Dietz J. Eric , Adams Douglas E. , Sharp Nathan D.
Published: April 2014

With their superior advantages of high capacity and low percentage of self-discharge, lithium-ion batteries have become the most popular choice for power storage in electric vehicles. Due to the increased potential for long life of lithium-ion batteries in vehicle applications, manufacturers are pursuing methodologies to increase the reliability of their batteries. This research project is focused on utilizing non-destructive vibration diagnostic testing methods to monitor changes in the physical properties of the lithium-ion battery electrodes, which dictate the states of charge (SOC) and states of health (SOH) of the battery cell. When the battery cell is cycled, matter is transported from one electrode to another which causes mechanical properties such as thickness, mass, stiffness of the electrodes inside a battery cell to change at different states of charge; therefore, the detection of these changes will serve to determine the state of charge of the battery cell. As mass and stiffness of the electrodes change during charge and discharge, they will respond to the excitation input differently. An automated vibration diagnostic test is developed to characterize the state of charge of a lithium-ion battery cell by measuring the amplitude and phase of the kinematic response as a function of excitation frequency at different states of charge of the battery cell and at different times in the life of the cell. Also, the mechanical properties of the electrodes at different states of charge are obtained by direct measurements to develop a first-principles frequency response model for the battery cell. The correlation between the vibration test results and the model will be used to determine the state of charge of the cell.
Comparison of Different Preparation Processes and Final Surface Finishes of Metallographic Specimens
Authors: Sugimoto Takuya , Sakamoto Toshihiko , Kuwahara Yoshiaki , Koshino Tetsushi , Endo Atsushi , Takai Yuka , Goto Akihiko
Published: April 2014

The carburizing process requires metallurgical inspection by means of polished metallurgical mounts. Metallographic preparation for a metallurgical mount is an important process. The purpose of this study is to clarify the differences between expert and nonexpert executions of the grinding and polishing process and the consequent polished surface finishes. Three inspectors with 0.5, 2 and 20 years of experience in metallographic preparation were interviewed and their processes analyzed. As a result of the process analysis, the differences between an expert and a nonexpert were determined.
Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete
Authors: Di Carlo Tony , Khoshnevis Behrokh , Carlson Anders
Published: April 2014

This research explores the structural properties of fresh concrete. The work is relevant wherever green, or uncured, concrete must be load-bearing. In traditional concreting, rigid forms mold and protect young concrete, and these forms are not removed until the maturing material has developed considerable load-bearing strength. Conversely, an automated construction technology under development at the University of Southern California, proposes to rapidly fabricate civil structures additively — layering continuous ribbons of fresh unconfined concrete — the freshly layered concrete must be load-bearing immediately upon placement. This is an unprecedented structural requirement, and little has been done to substantiate uncured concrete in such a load-bearing capacity. With emphasis on expedient experimental techniques, early maturity, and time-dependent constitutive modeling, this research develops the engineering necessary to erect these structures safely.
Environmental Effects on Flexural Over-Strength Factor of Epoxy Resin Materials
Authors: Fard Masoud Yekani , Chattopadhyay Aditi , Raji Brian
Published: April 2014

Polymer composite structures are usually subjected to large flexural loadings during their life-span of the structures, so the flexural behavior of these structures and their constituents in different environmental conditions are critical to their use. A novel analytical approach for epoxy resin semi-brittle materials with strain softening model in tension and compression has been developed to investigate the flexural behavior of these materials. The value of the flexural over-strength factor which is the ratio of the flexural strength to the strength obtained from tension and compression stress strain models depends on stress gradient, size and loading system and it has already been evaluated at the laboratory condition. The mechanical properties of epoxy resin materials are sensitive to environmental effects at which they are loaded. The influence of temperature 60°C and humidity 90% Rh on tension, compression and flexural behavior of epoxy resin polymeric materials PRI and PR 520 have been investigated. Digital image correlation system was used for material characterization. The effects of heat and humidity on softening localization in flexural response were considered. The influence of heat and humidity on the flexural over-strength factor was evaluated.
Fracture Mechanics Based Total Fatigue Life Behavior for Stitch-Bonded Polymer Matrix Composites
Authors: Fard Masoud Yekani , Raji Brian , Chattopadhyay Aditi
Published: April 2014

Stitch-bonded biaxial polymer matrix composite is a compromise between unidirectional composite and woven composite materials. In this paper, fatigue delamination behavior of stitch-bonded biaxial polymer matrix composites was investigated. The delamination growth rate in three domains of subcritical, linear, and unstable growth rate were studied. The effects of increased fracture resistance due to fiber bridging, multiple cracks, separation, and matrix cracking were considered in fatigue behavior of the composite. The fatigue onset life test was conducted to determine the threshold energy release rate. The total life delamination growth rate of stitch-bonded polymer matrix composites was characterized and presented.
Contact Glow Discharge Electrolysis as an Efficient Means of Generating Steam From Liquid Waste
Authors: Sharma Neeraj , Diaz Gerardo
Published: April 2014

The present study focuses on the performance evaluation of contact glow discharge electrolysis as a potential means for efficient generation of steam from liquid waste in the form of cooling tower blowdown produced at the campus of the University of California at Merced. The cooling tower blowdown, which acts as an electrolyte is fed into a stainless steel electrolytic cell connected to a DC power supply. After describing the transition from normal electrolysis to contact glow discharge electrolysis, the electrolytic cell is run in glow discharge mode for a specific duration of time and data for current, voltage, and rate of steam generation are recorded. Steam generation efficiency as high as 87% is obtained. High efficiency of steam generation makes it a practical method of generating steam from liquid waste.
Influence of Process Parameters on the Dimensions of the Channels Prepared Using Abrasive Water Jet Machining
Authors: Gupta T. V. K. , Tandon Puneet , Ramkumar J. , Vyas Nalinaksh S.
Published: April 2014

Preparation of micro/macro channels using unconventional machining methods/processes on hard to machine materials is increasingly in demand in the micro machining industry. AWJM is one such process that can be used for the creation of these channels. Achieving the dimensional accuracy is a challenge because process is influenced by large set of process parameters and further in depth milling process, it is much more challenging than anticipated unlike in conventional machining process. The current research is an attempt to create a channel with varying operating parameters (abrasive size, flow rate, standoff distance and traverse speed) and address the issues of 3D shape generation which is nothing but an overlap of channels for a specific freeform surface. The paper presents the variations in the dimensions of the channel with process parameters. Traverse speed decides the exposure time of the material to the jet and also the erosion capabilities. The experimental results reveal that the channel dimensions are dependent on the standoff distance which leads to the abrasive particle velocity distributions. Results obtained reveals that depth of cut is mainly dependent on the traverse speed followed by particle size. The width of the cut is dependent on the jet diameter which changes with standoff distance. The taper cut is mainly because of the particle distribution which is governed by the abrasive size and the abrasive flow rate. Proceeding in this way, we can understand the influence of process parameters on the dimensional characteristics and further to establish a base for creating complex shapes using AWJM.
Electrostatically Actuated MEMS Cantilevers of Linear Thickness Variation
Authors: Caruntu Dumitru I. , Fath El-Den Mostafa M.
Published: April 2014

This paper deals with nonuniform linear thickness variation and constant width MEMS cantilever resonators electrostatically actuated through AC voltage near half natural frequency. The frequency response of the structure is investigated. Nonlinearities in the system arise from the electrostatic force. The electrostatic actuation introduces parametric coefficients in both linear and nonlinear parts of the governing equation. The method of multiple scales (MMS) is used to obtain the phase-amplitude relationship of the system, and the steady-state solutions. Parameters’ influences are reported.
An Overview of Solid-Like Electrolytes for Supercapacitors
Authors: Fang Xudong , Yao Donggang
Published: April 2014

Supercapacitors with an electric double-layer design have attracted great attention in the recent years because they are promising energy storage devices for a number of applications, particularly for portable electronics and electric automobiles. They utilize the interface between the electrode and the electrolyte to store energy, resulting in energy storage devices with high power density but low energy density compared to batteries. To improve the performance and reduce the cost, researchers have made significant progress in increasing energy density, electrode voltage, and cycle life. The increase of the energy density is considered to be achieved mainly by increasing the effective specific interface between the electrodes and the electrolyte. Various electrodes with porous structure have been attempted to increase the specific surface area. The increase of electrode voltage is realized primarily via the change of liquid electrolytes to gel, solid and composite ones. In this overview, they are summarized as solid-like electrolytes. This paper reviews the materials adopted and the processing methods developed for solid-like electrolytes, as well as the general characteristics of supercapacitors employing such electrolytes.
Reduced Order Model of CNT Cantilever Resonators Under AC Voltage Near Half Natural Frequency
Authors: Caruntu Dumitru I. , Luo Le
Published: April 2014

This paper deals with electrostatically actuated Carbon Nano-Tubes (CNT) cantilevers using Reduced Order Model method. The system consists of a CNT parallel to a ground plate. An alternating current (AC) voltage is considered between the two. The CNT undergoes an oscillatory motion due to the electrostatic force generated by the voltage. Another two forces act on the CNT, namely a damping force, and a van der Waals force due to gaps less than 50 nm. The Method of Multiple Scales (MMS) and the Reduced Order Model (ROM) method (using AUTO solver) are used to investigate the system under soft excitations and/or weak nonlinearities. The frequency response is found in the case of AC near half natural frequency.
Atmospheric Icing Effects on Aerodynamics of Wind Turbine Blade
Authors: Myong Rho Shin
Published: April 2014

A significant degradation in the aerodynamic performance of wind turbine system can occur by ice accretion on the surface of blades operated in cold climate. The ice accretion can result in performance loss, overloading due to delayed stall, excessive vibration associated with mass imbalance, ice shedding, instrumental measurement errors, and, in worst case, complete wind turbine system shutdown. In this study, the similarity and difference between atmospheric icing (wind turbine) and inflight icing (aircraft) are first identified. In particular, nature of cloud, iced area, ice sensor location, and efficient anti/de-icing systems for wind turbine are discussed. Then the impact of ice accretions on the aerodynamic characteristics of wind turbine blade sections is investigated on the basis of modern CFD method. It is shown that the thickness of ice accretion increases from the root to the tip and the effects of icing conditions such as relative wind velocity play significant role in the shape of ice accretion. Finally, the computational results are used to predict three-dimensional aerodynamic characteristics of wind turbine blade through the blade element momentum method.
Modelling of Effective Thermal Conductance of Metal Foam Contact Thermal Interfaces
Authors: Trifale Ninad , Yazawa Kazuaki , Nauman Eric
Published: April 2014

We present a modeling study of the effective thermal conductance of metal foams as a thermal interface focusing on the electronics cooling applications. Metal foam material as a porous media has been considered for several applications because of its significantly large surface area for a given volume. In the electronics cooling, aluminum porous heat sinks have been well studied. It is not only cost effective due to the unique production process, but also attractive for the theoretical modeling study to determine the performance. In the past studies, effective thermal conductivity for heat transfer through solid with the tetrahedral geometry, while the pores, assumed to have vacant volumes, has been modeled. Instead of allowing the refrigerant flow through the connected pores in the porous medium, we considered the vacant space filled with stationary air. The major transport of the heat is considered to flow through the solid bridges, which connect the onside to the other side directly. Thus, the porous density for our application shall be relatively lower than the best value for heat sink applications. It must, however, be in a specific range such that it is mechanically compliant to make proper contact to both, the cooling target surface and the heat sink surface. It is obvious that the smaller pore ratio makes the metal foam stiffer. We model the contact thermal performance with considering the mechanical stiffness as a function of pore ratio as well as an intrinsic thermal conductance across the metal foam. Due to the limited literature of the variation of the pore size, we present the first order analysis assuming a fixed and uniform pore size.
Robustness Analysis of Two-Speed Electric Vehicles
Authors: Roser Holger , Walker Paul D. , Zhang Nong
Published: April 2014

This paper presents the findings of a theoretical analysis of a two-speed Dual-Clutch Transmission (DCT) for electric vehicle applications. Electric drives incorporating DCTs can offer improved driving economy and range, acceleration and climbing gradeability, with potentially smaller electric motors (EMs). Overall powertrain performance is simulated with different standard driving cycles, including urban, extra-urban, and constant speed driving, and different EM power ratings. Simulation results are compared against equivalent single-speed powertrain, including a conceptual evaluation of powertrain bulk, weight and cost.

Despite added complexity of including a DCT, the simulated driving range is increased by shifting the operating region of the electric motor to greater efficiency regions. This is shown to be more predominant during high-speed driving. In addition, satisfactory drive performance can be achieved with smaller EMs, compensating for added transmission bulk, weight and cost. An outline of further areas of two-speed electric drive research and applications conclude this paper.
Microfeature Edge Quality Optimization in Excimer Laser Ablation of Metallic Film
Authors: Akhtar Syed Nadeem , Ramkumar J. , Ramakrishna S. Anantha
Published: April 2014

Excimer laser ablation of thin films finds an advanced application in the manufacture of integrated circuits and it is desirable in the process that the size of the ablated region is close to the design and clean ablation takes place at the edges. In practice, the boundaries of the ablated region are irregular, the features are oversized and spattering is observed inside the ablated region. This work studies the edge roughness, channel width and boundary integrity as indicators of quality of ablation. Experiments are conducted with varying fluence, shot overlap and pitch (inter-channel distance) to generate different features. The edge roughness and channel width are found to have little dependence on spot overlap but are greatly influenced by the fluence. The overcut (channel width) is more at higher fluence but repetitive pulses do not affect the overcut. The range of parameters of ablation are identified from these experiments that lead to optimum edge roughness, channel width and boundary integrity.
Acceleration/Drift Feedback Control of MRD Connected Buildings
Authors: Chandiramani Naresh K. , Motra Gokarna B.
Published: April 2014

Seismic response control of buildings connected by a magnetorheological damper (MRD) is studied. The desired control force is obtained using Linear Quadratic Gaussian (LQG) control with feedback of estimated states, or Optimal Static Output Feedback (OSOF) control using direct feedback of outputs. The damper input voltage is predicted using a Recurrent Neural Network (RNN). Various sensor configurations and state weightings are considered to obtain effective control. Effective control is possible using few sensors (eg. a single accelerometer with LQG-RNN).
Micromechanical Modeling of Two-Dimensional Periodic Cellular Materials
Authors: Alzebdeh K. , Al-Shabibi A. , Pervez T.
Published: April 2014

The mechanical behavior of 2-D periodic cellular materials is investigated using a continuum-based modeling approach. Two micromechanical models are developed on the basis of representative unit cell concept in which skeleton of cellular material is modeled as elastic beams. The ANSYS finite element code is used to solve the beam model of skeleton. Elastic moduli of square and triangular networks comprising the microstructure of the cellular material are calculated based on an equivalent continuum model. This is achieved by equating the stored energy in skeleton of a unit cell to the strain energy of the equivalent continuum under a set of prescribed boundary conditions. A proper displacement-controlled (essential) boundary condition generates a uniform strain field in both models which corresponds to calculation of one elastic modulus at a time. Then, effective Young’s modulus and Poisson’s ratio of continuum are extracted from the calculated elastic moduli. The dependence of effective elastic constants on relative density and thickness to length ratio of the microstructure is investigated. Furthermore, the in-plane behavior of cellular solids in compression is explored with the help of current modeling. The proposed models may contribute to optimal designs of a new class of materials with tailored geometry and material properties which could be useful in a broad range of structural applications.
Heavy Truck Chassis Clamping Load Evaluation of the Bolted Joints Under External Loads
Authors: Cinar Ali
Published: April 2014

Bolted joints are frequently used in the automotive industry. Loosening of the joints under vibration has been an ongoing problem which is associated with many structural failure incidents. Finite element model of heavy truck chassis were used for the analysis. We performed static analysis by applying assembly loads to twenty priorly identified critical joints. Then, time varying external loads (impact loads) were applied to truck chassis fifth wheel. Abaqus explicit is used as the solver. We examined critical parameters for the clamping load variation under highly dynamic external loads.
Friction Self-Piercing Riveting (F-SPR) of AA6061-T6 to AZ31B
Authors: Li YongBing , Wei ZeYu , Li YaTing , Wang ZhaoZhao , Zhu Xiaobo
Published: April 2014

Implementation of lightweight low-ductility materials such as aluminum alloys, magnesium alloys and composite materials has become urgently needed for automotive manufacturers to improve the competitiveness of their products. However, the hybrid use of these materials poses big challenges to joining processes. Self-piercing riveting (SPR) is currently the most popular technique for joining dissimilar materials and has been widely used in joining all-aluminum and multi-material vehicle bodies. However, in riveting magnesium alloys, cracks always occur for its low ductility. In this paper, a hybrid joining process named friction self-piercing riveting (F-SPR), which combines mechanical joining mechanism of SPR with solid-state joining mechanism of friction stir spot welding (FSSW) by making rivet rotating at high speed in riveting process, was proposed aiming at joining the low ductility materials. 1-mm-thick AA6061-T6 and 2-mm-thick AZ31B were used to validate the effectiveness of the F-SPR process. The results showed that the F-SPR process could significantly improve the rivetability of magnesium alloys, and greatly increase the joint strength, comparing with traditional SPR process.
Mechanical and Thermal Engineering for High Temperature Fuel Cell Systems
Authors: Salminen Pauli , Ahlgren Esa , Kuosmanen Petri
Published: April 2014

Solid Oxide Fuel Cell (SOFC) systems achieve high electrical efficiency and can utilize many types of fuels such as methanol or biogas. These systems operate at high temperatures up to 600–1000 °C. Due to high temperatures, mechanical engineering must be combined with thermal engineering through the design work.

System design for SOFC systems should take into account several functions such as mechanical support of components, thermal insulation, instrumentation, compensation for thermal expansion and heat recovery as well as conduction of gases through channels, piping or open cavities. One should note that many of these functions have strong interactions and cannot be designed without an effect on the system as a whole. When a system is designed to fulfill all the expectations, it will have a compact size, good thermal properties, small pressure losses and good overall performance together with a competitive price, long system lifetime and easy maintenance.

This article aims to improve the mechanical structure of SOFC systems. In addition, our aim is to give sophisticated recommendations for a system design. To achieve this, we have used systematic concept development tools and methodologies to investigate the interactions and relative importance of system requirements and functions.

Our key result from this study is that engineers must use a holistic approach when designing a high temperature system with strong interactions between system functions and components. Contrary to our former expectations, these systems could not be designed well by methods that are based on reductionism. In practice, this means that thermal engineering must be utilized from the very beginning. Thermal insulation concept should be selected during the first design steps since this has a great effect on system layout. Mechanical engineering is needed in system layout design in order to solve problems related to the thermal expansion and support of components. Combined thermal and structural analysis utilizing finite element methods can be used to develop or optimize mechanical key components and system layout. The best results can be achieved by using a holistic approach during the design process.

In addition, it is beneficial to keep the system as simple and compact as possible. To achieve this, the integration of functions and components must be increased. Thus, SOFC system performance is greatly dependent on system design, not only of its components alone. Findings obtained from this study can be used by researchers designing experimental apparatuses or by companies manufacturing full scale SOFC systems.
Study of the Cooling Performance of Oscillating Piezoelectric Fans
Authors: Bidakhvidi Mohammad Ahmadi , Shirzadeh Rasoul , Vanlanduit Steve
Published: April 2014

Piezoelectric vibrating fans operating at resonance are a viable cooling technology due to its easy scalability and low power consumption. This study focuses on the characterization and optimization of the thermal performance of these miniature flapping cooling systems. Different experiments in a miniature windtunnel are conducted to investigate the cooling performance of the oscillating fans. The Strouhal number is a dimensionless parameter describing wing kinematics of flying systems. The aerodynamic propulsive efficiency of these systems is high over a narrow range of Strouhal numbers. Different St numbers were obtained and investigated, by changing the flow velocity of the win-tunnel. In practical applications different St could be obtained by combining conventional axial fans with piezoelectric fans. Both the feasibility of a single fan and array of fans is studied. For a wide range of operating coditions, including distance from heat source, dynamic tip deflection and orientation, the heat transfer performance of the piezoelectric fans is characterized.
2D Phase-Field Analyses of Axonal Extension of Nerve Cell
Authors: Nakagawa K. , Takaki T. , Morita Y. , Nakamachi E.
Published: April 2014

In this study, we aimed to develop a computer-aided simulation technique to predict the axonal extension in the neuronal network evolution processes for design new scaffolds to activate the nerve cell and promote the nerve regeneration. We developed a mathematical model of axonal extension by using phase-field method and evaluated the validity of the mathematical model by comparison with the experiments. In the previous experimental studies, the peripheral nerve scaffold has been introduced to guide the axonal extension. Damaged part of nerve was replaced by the artificial tube as the scaffold to induce the axonal growth through the artificial tube and regenerate the nerve network. However, the scaffold made of biodegradable materials has a problem that it is degraded and absorbed before the nerve regenerate, and then the nerve cannot regenerate. Therefore, there is a need for the design and development of a scaffold for nerve regeneration to promote nerve regeneration. For that purpose, it is necessary to understand the difference between the axonal extensions by the surrounding environment, such as the shape or materials of the scaffold for nerve regeneration. In particular, the numerical technique to analyze the remodeling process of the nerve in the scaffold is strongly required to be established because the in-vivo experimental observation technology at the micro scale, bioethical issues in the animal experiment and requires time and money are also remained as unresolved problems. In this study, we developed a new simulation code which employed the phase-field method to predict the two-dimensional dendritic and axonal growth processes of nerve cells on cultivation scaffolds. We curried out the phase-field analyses to make clear how the parameters of Kobayashi–Warren–Carter (KWC) phase-field model affected on the morphologic growths of dendrite and axon. Simultaneously, we had observed the axonal extension process by using the PC-12D cells with nerve growth factor (NGF) on two-dimensional cultivation dish. Based on these axonal extension observation results, we approximated the morphological changes and establish the phenomenological model for phase-field analysis. Finally, we confirmed the validity of our newly developed phase-field simulation scheme in two dimensions by comparison with the experiments.
An Offline-Signal Processing Algorithm for Combining Superior Excitation Methods for an Ultrasonic Piezo Motor
Authors: Borchert Gunnar , Dröder Klaus , Raatz Annika
Published: April 2014

Ultrasonic piezomotors have been applied as a drive concept in miniaturized robot systems for many years. They have various beneficial characteristics, such as low costs, high accuracy and velocity. This has been demonstrated, with instance, with APIS, a miniaturized robot developed at the Technische Universität Braunschweig. With the example of APIS, this contribution discusses the challenge of an offline signal processing techniques in order to combine different excitation methods for the piezomotors used in this robot. Since each excitation method influences the motor characteristic in a variety of ways, this research is motivated by desire for an optimal adaptation of certain features to a given trajectory, such as velocity, acceleration, moving direction or step resolution. Thus, our approach is to develop different ways to split a given trajectory into segments with regard to the requirements of the motor. So these segments can be linked to an excitation method which brings about the desired features. To this end, model trajectories are first generated and reasonable excitation methods for the piezomotor are identified and characterized. Key features are velocity, acceleration, moving direction and step resolution. Apart from defining key features, an assessment algorithm has been developed along with suitable weighting criteria. Offline signal algorithm means that the trajectory will be analyzed and that the arrangement of suitable excitation methods will be defined before the motion process starts.

Finally the results, that is, each model signal together with the associated excitation method, are shown and validated. To achieve better results, possibilities for future developments are identified.
Strengths and Limitations of Advanced Exergetic Analyses
Authors: Morosuk T. , Tsatsaronis G.
Published: April 2014

The exergetic analysis is a powerful tool for developing, evaluating and improving an energy conversion system.

The strengths and limitations of the so-called conventional exergetic analysis have already been discussed. An advanced exergetic analysis can significantly reduce some of the limitations of a conventional analysis by evaluating (a) the detailed interactions between components of the overall system, and (b) the real potential for improving a system component. The main objective of advanced exergy-based analyses is to provide engineers with additional useful information for better understanding and improving the design and operation of energy-conversion systems. This information cannot be supplied by any other approach. The weaknesses of an advanced exergetic analysis are associated with (a) the subjectivity that is associated with the calculation of avoidable exergy destruction and with the definition of both the ideal and the so-called hybrid processes, and (b) the large number of calculations that need to be conducted to obtain the avoidable endogenous and the avoidable exogenous values.
The Influence of the Roughness Parameters on the EHL Line Contact Using the Free Volume Model
Authors: D’Agostino V. , Petrone V. , Senatore A.
Published: April 2014

A numerical solution of elastohydrodynamic lubrication (EHL) contact between two rough surface cylinders is presented. In the theoretical approach the free-volume viscosity model is used to describe the piezo-viscous behavior of the lubricant in a Newtonian Elastohydrodynamic line contact [1,2]. Random rough surfaces with Gaussian and exponential statistics have been generated using a method outlined by Garcia and Stoll [3], where an uncorrelated distribution of surface points using a random number generator is convolved with a Gaussian filter to achieve correlation. This convolution is most efficiently performed using the discrete Fast Fourier Transform (FFT) algorithm, which in MATLAB is based on the FFTW library [4]. The maximum pressure and average film thickness are studied at different values of RMS, skewness, kurtosis, autocorrelation function and correlation length. Numerical examples show that skewness and kurtosis have a great effect on the parameters of EHD lubrication. Surface roughness, indeed, tends to reduce the minimum film thickness and it produces pressure fluctuations inside the conjunction which tend to increase the maximum stress. In this way the dynamic stress increases and tends to reduce the fatigue life of the components.

It can be seen that the pressures developed in the fluid film in the case of rough surfaces fluctuate with the same frequency of the surface roughness. These pressure ripples correspond to the asperity peaks. This indicates that surface roughness causes very high local contact pressures which may lead to local thinning of the film. A significant reduction has been also observed in the minimum film thickness due to surface roughness.
Real Time Measurement of Heat Flux by Directional Flame Thermometers Using Filter Form IHCP Method
Authors: Najafi Hamidreza , Woodbury Keith A. , Keltner Ned R. , Beck James V.
Published: April 2014

The real-time measurement of heat flux is an important challenge for several industrial applications including furnace control. For efficient operation of high-temperature process furnaces, accurate and stable temperature measurements are needed. Directional Flame Thermometers (DFTs) offer the ability to use both temperature and heat flux measurements for furnace control. Currently, analysis of dynamic temperature data from the DFTs to compute heat flux information must be performed off-line based on the gathered data by using a full-non-linear inverse heat conduction problem (IHCP) analysis. Availability of a near real-time algorithm for accurate reduction of the data will allow for continual monitoring of the furnace during operation. This will result in better furnace control and significant savings in energy and cost. The purpose of this paper is to provide a solution strategy based on filter concept for the inverse heat conduction problem associated with DFT. The filter based solution has the capability of heat flux estimation in a near real time manner. Two IHCPs are discussed and a coupled solution is proposed to estimate the unknown surface heat flux. The solution procedure is then validated using numerical test cases. Results are then computed using data from a physical experiment with DFT (see Reference [13]). The heat fluxes obtained are found in satisfactory agreement with those obtained from a full non-linear IHCP analysis.
Experimental Study on Natural Convection From Vertical Cylinders With Branched Fins
Authors: Park Kuen Tae , Kang Byeongdong , Kim Hyun Jung , Kim Dong-Kwon
Published: April 2014

Advances in semiconductor technology and trends in slim and light electronic systems have led to a significant increase in heat dissipation density of the electronic devices. Therefore, effective cooling technology is essential for reliable operation of electronic components. Among various cooling systems, natural convection heat sinks have been proven to be appropriate because of their inherent simplicity, reliability, and low long-term cost. The present study is focused on natural convective heat transfer from the cylindrical heat sink. Especially, the branched fins, which are motivated by the branched design of nature shown in trees and lungs, are used. The heating power and surface temperature are measured for various types of branched fins and numbers of fins. The result showed that the branched fin dissipates 20% more heat compared to the normal plate fins. Therefore, heat sinks with branched fins have a potential as a next-generation cooling device.
Analysis of Axisymmetric Cup Forming of Metal Foil and Micro Hydroforming Process
Authors: Sato Hideki , Manabe Ken-ichi , Wei Dongbin , Jiang Zhengyi
Published: April 2014

A novel forming method “micro hydromechanical deep drawing (MHDD)” is focused to improve the tribological property and forming limit. In this study, a theoretical model for MHDD is developed to investigate the size effect on deformation behavior in micro hydromechanical deep drawing. The effects of fluid pressure, the difference of friction coefficients at inner pockets and outer pockets are considered in the investigation on the size effect of tribological property. The friction force decreases as the scale factor decreases in MHDD process. It is also found that the tribological property in micro scale can be improved by applying the fluid pressure. The forming limit decreases as the relative punch diameter increases. However, it is clarified that the forming limit can be improved by decreasing the friction force in MHDD.
Swing Phase Lubrication Analysis of a Novel Artificial Hip Joint
Authors: Boedo S. , Coots S. A. , Booker J. F.
Published: April 2014

This paper investigates swing-phase cavitation formation and collapse in a novel artificial hip joint using a well-established transient mass-conserving finite element cavitation algorithm. Elastic elements and ellipsoidal cup surface geometry are incorporated into the new design to promote and enhance ‘squeeze-film’ action over ‘wedge-film’ action employed in conventional artificial hip joints. During the swing phase of the gait cycle, the lubricant film undergoes cavitation from normal separation of ball and cup surfaces. Reformation of a complete lubricant film is predicted over a wide range of sub-ambient cavitation threshold pressures, ball velocities, ellipticity specifications, and ball initial positions that are likely to be encountered in practice.
Numerical Study on the Diffusive-Ballistic Heat Transport in a Two-Dimensional Square Plate
Authors: Yamada Toru , Park Keunhan , Asako Yutaka , Faghri Mohammad , Sundén Bengt
Published: April 2014

The heat conduction in a two-dimensional square plate at nano/micro scales is investigated using numerical and semi-analytical methodologies which are energy conserving dissipative particle dynamics (DPDe) and Boltzmann transport equation (BTE) with the gray relaxation time approximation. The solution domain was considered to be a two-dimensional square plate surrounded by walls having constant temperatures. The numerical and semi-analytical results for different Knudsen numbers ranging from 0.1 to 10 are presented in form of temperature distributions in the solution domain. These results are compared with each other and the applicability of the DPDe model to two-dimensional structures is discussed.