bluuebunny/crossref_metadata_2025 huggingface dataset:
Trajectory Control of a Car-Like Wheeled Robot
Authors: Lee Ho-Hoon
Published: May 2012

This paper proposes a trajectory control method for a carlike four-wheeled mobile robot. First, a kinematic control scheme is designed based on the nonholonomic kinematic constraints of a mobile robot, in which reference driving speed and steering angle are computed for a given desired trajectory of the robot. This kinematic control scheme, generating the reference speed and steering angle, can be applied to unmanned vehicle control with a robot driver. Second, a new backstepping trajectory control scheme is designed based on the robot dynamics subject to the nonholonomic kinematic constraints, in which the desired driving force and steering torque are computed for a given desired trajectory. In this study, the Lyapunov stability theorem is used as a mathematical design tool. The proposed control guarantees asymptotic stability of the trajectory control while keeping all internal signals bounded. Finally, the validity of the theoretical results is shown by realistic computer simulations with one sampling delay in the control loop.
Flexible Multibody Dynamics Formulation by Hamilton’s Equations
Authors: Tong Martin M.
Published: May 2012

Numerical solution of the dynamics equations of a flexible multibody system as represented by Hamilton’s canonical equations requires that its generalized velocities q˙ be solved from the generalized momenta p. The relation between them is p = J(q)q˙, where J is the system mass matrix and q is the generalized coordinates. This paper presents the dynamics equations for a generic flexible multibody system as represented by p˙ and gives emphasis to a systematic way of constructing the matrix J for solving q˙. The mass matrix is shown to be separable into four submatrices Jrr, Jrf, Jfr and Jff relating the joint momenta and flexible body mementa to the joint coordinate rates and the flexible body deformation coordinate rates. Explicit formulas are given for these submatrices. The equations of motion presented here lend insight to the structure of the flexible multibody dynamics equations. They are also a versatile alternative to the acceleration-based dynamics equations for modeling mechanical systems.
Low Reynolds Number Flow Control Over an Airfoil Using Synthetic Jet Actuators
Authors: Goodfellow Sebastian D. , Yarusevych Serhiy , Sullivan Pierre
Published: May 2012

The influence of periodic excitation from synthetic jet actuators, SJA, on boundary layer separation and reattachment over a NACA 0025 airfoil at a low Reynolds number is studied. All experiments were performed in a low-turbulence recirculating wind tunnel at a Reynolds number of 100000 and angle of attack of α = 0°. Mounted just below the surface of the airfoil, the SJA consists of four (32.77mm diameter) piezo-electric ceramic diaphragms positioned in a single row. Flow visualization and hot wire tests were conducted with the SJA outside of the airfoil to characterize the exit flow. Results from flow visualization show a vertical jet pulse accompanied by two counter rotating vortices being produced at the exit of the simulated slot, with the vortices shed at the excitation frequency. Based on flow visualization results, the length scales of successive vortices were used to estimate the exit velocities. Hot-wire measurements determined the maximum jet velocity for a range of excitation frequencies (f = 50Hz–2.7kHz) and voltages (Vp–p = 50V–300V), which was used to characterize the excitation amplitude in terms of the momentum coefficient (cμ). With the SJA installed in the airfoil, preliminary flow visualization results show a reattachment of the boundary layer and a significant reduction in wake width.
Nano-Droplet Impingement Heat Transfer on a Solid Surface
Authors: Haas Geoffrey , Wemhoff Aaron P.
Published: May 2012

The reduction of electronic components towards the nano-scale drives the development of novel cooling methods to keep up with the increasing thermal demands of the electronics industry. Since transistor dimensions are shrinking to the order of 1–10 nm, pinpointed cooling may be required for maximum efficiency. Many nano-scale cooling methods are difficult to observe in direct experimentation, so simulation techniques present an attractive alternative approach. In this respect, molecular dynamics (MD) simulations of nano-droplet impingement on a solid surface is being investigated as a potential means for pinpointed cooling. Various observations of thermophysical phenomena associated with the impingement are discussed, including the temperature rise at the collision point, the acceleration of the droplet prior to impact, and and the ordering of molecules in the liquid due to the influence of the solid.
Average Droplet Diameter Spatial Distribution in a Spray After Gas-Assisted Atomization
Authors: Pougatch Konstantin , Salcudean Martha , McMillan Jennifer
Published: May 2012

Gas-assisted atomization is used in many industries to produce finely dispersed droplets. Knowledge about the droplet size distribution guides the design and development of the nozzle as well as of the whole processes. This knowledge can be obtained through experimental and modeling works that usually complement each another. In this paper we present an application of the mathematical model previously developed for gas-assisted atomization to the prediction of the average droplet diameter distribution in a spray and compare the results with experimental findings. The model is based on a two-fluid Eulerian-Eulerian treatment of the motion of the phases with a catastrophic phase inversion (atomization). It also includes the compressibility effects for the gaseous phase and can be applied to both the flow through the nozzle-atomizer and to the dispersion of the spray. The model accounts for the break-up and coalescence of bubbles and droplets due to interfacial shear and collisions. The diameter of the particle (bubble or droplet) is represented by its local mean average value that varies throughout the flow field. Simulations are conducted for the flow of air and water through the convergent-divergent nozzle, which is similar to the one used in commercial fluid cokers, a bitumen upgrading apparatus, for steam-assisted atomization of bitumen. It is found that while there are wide experimentally observed local distributions of the particle diameter, the concept of the average diameter still allows for satisfactory predictions of its average values and spatial variations. In agreement with the experiments, the numerical model demonstrated that the largest droplet diameter is located in the axial area, and the diameter values reduce towards the periphery of the jet. In addition, the average diameter increases slightly and its radial variation becomes more uniform as the distance from the nozzle orifice increases.
Effect of Asymmetric Jet Placement on Turbulent Flow Structure Inside a Jet-Stirred Reactor
Authors: Hammad Khaled J. , Milanovic Ivana M.
Published: May 2012

Particle Image Velocimetry (PIV) was used to investigate the turbulent flow structure inside a jet-stirred cylindrical vessel. The submerged jet issued vertically downward from a long pipe ensuring fully developed turbulent flow conditions at the outlet. The Reynolds number based on jet mean exit velocity was 15,000. The effect of symmetric and asymmetric nozzle placement within the vessel on the resulting flow patterns was also studied. The measured turbulent velocity fields are presented using Reynolds decomposition into mean and fluctuating components, which, for the selected flow configuration, inflow and boundary conditions, allow for straightforward assessment of turbulence models and numerical schemes. The flow field was subdivided into three regions: the jet, the jet-wall interaction and bulk of vessel. Proper Orthogonal Decomposition (POD) analysis was applied to identify the most energetic coherent structures of the turbulent flow field in the bulk of tank region. The swirling strength vortex identification technique was used to detect the existence and strength of vortical structures in the jet region.
Energy Harvesting From Bike Using Linear DC Motor
Authors: Sabzehgar Reza , Arzanpour Siamak
Published: May 2012

This paper investigates the application of a proposed energy harvesting mechanism to convert the vibrations in a bicycle tire to electricity. For this setting all tire spokes have been removed and two spring-damper links and one linear DC motor are used instead. The vibration analysis of the tire’s center of mass caused by bicycle motion is obtained using trigonometric relations. Moreover, the regenerated power by the linear motor is obtained analytically. This model together with the motion of the center of the mass of the tire are used to estimate the harvested power. The mechanical and electrical parameters are also optimized to harvest the maximize the power. Simulation results show the efficiency of proposed energy harvesting mechanism.
Stochastic Simulation of a Casimir Oscillator
Authors: Khoshnoud Farbod , Owhadi Houman , de Silva Clarence W.
Published: May 2012

Stochastic simulation of a Casimir Oscillator is presented in this paper. This oscillator is composed of a flat boundary of semiconducting oscillator parallel to a fixed plate separated by vacuum. In this system the oscillating surface is attracted to the fixed plate by the Casimir effect, due to quantum fluctuations in the zero point electromagnetic field. Motion of the oscillating boundary is opposed by a spring. The stored potential energy in the spring is converted into kinetic energy when the spring force exceeds the Casimir force, which generates an oscillatory motion of the moving plate. Casimir Oscillators are used as micro-mechanical switches, sensors and actuators. In the present paper, a stochastic simulation of a Casimir oscillator is presented for the first time. In this simulation, Stochastic Variational Integrators using a Langevin equation, which describes Brownian motion, is considered. Formulations for Symplectic Euler, Constrained Symplectic Euler, Stormer-Verlet and RATTLE integrators are obtained and the Symplectic Euler case is solved numerically. When the moving parts in a micro/nano system travel in the vicinity of 10 nanometers to 1 micrometer range relative to other parts of the system, the Casimir phenomenon is in effect and should be considered in analysis and design of such system. The simulation in this paper considers modeling such uncertainties as friction, effect of surface roughness on the Casimir force, and change in environmental conditions such as ambient temperature. In this manner the paper explores a realistic model of the Casimir Oscillator. Furthermore, the presented study of this system provides a deeper understanding of the nature of the Casimir force.
Analytical and Experimental Investigations of High Porosity Metallic Foams
Authors: Mudunuri Venkateswara Raju , Sudhini Goutham , Fakheri Ahmad
Published: May 2012

A novel analytical model is developed to examine the temperature distribution of high porosity metallic foams. The foam is modeled as small fins, which results in a set of equations similar to those obtained in finite difference representation of the energy equation, from which foam temperature can be evaluated. These equations are solved simultaneously along with the energy equation for the fluid. The parameters needed to determine the performance of the foam are average strut length (dp) and strut diameter (df) which can be obtained from the knowledge of foam Porosity (ε) and Pore Density (PPI). To validate the analytical model, the temperature distribution of an Aluminum 6101-T6 alloy foam with porosity 92% and pore density (10 PPI) is measured in a wind tunnel for different air velocities. There is close agreement between analytical and experimental results.
A Numerical Methodology for Thermo-Mechanical Characterization of High Power Electronic Packages
Authors: Park S. B. , Nguyen T. T. , Goo N. S.
Published: May 2012

In this study, an effective numerical methodology that combines computational fluid dynamics (CFD) and finite element method (FEM) modeling is presented for thermo-mechanical characterization of electronic packages in transient state under a forced convection environment. Experiments were performed on a thermal test chip under a power cycling condition to measure transient temperature distribution in the package. A power profile was designed and applied to the test die to generate a typical temperature profile of a high power electronic package under field use conditions which includes ramp up, mini-cycle, dwell, and ramp down periods. CFD model was then built with the Icepak software to simulate the performed experiment. The CFD simulation reproduced the experimentally-obtained temperature profile accurately. The nodal heat flux and heat transfer coefficients (HTC) were extracted from the CFD simulation results. Then, a separate thermal FEM model which contains all the components of the package except the heat sink was built in ANSYS. The heat flux from the package to the heat sink obtained from the CDF simulation results was applied to the thermal FEM model as the boundary conditions (BC) at the top surface of the package. The HTC from the CFD were used for BC’s at all other surfaces. This equivalent BC’s eliminated the necessity of complex modeling for forced convection. Transient temperature distribution obtained from this simplified model thermal FEM simulation matched very well with that of CFD simulations. Consequently, a structural simulation was performed with temperature distribution obtained from this thermal FEM simulation as the thermal loading. Strains, stresses, strain energy density, and other mechanical index were obtained and used for reliability assessments of the package. The proposed methodology enables to assess reliability of high power packages under real power cycling conditions with any desired power and temperature patterns efficiently.
Conjugate Effect of Hygro and Thermo-Mechanical Behavior in MEMS Packages
Authors: Park Seungbae , Kwak Jae , Zhang Haojun , Zhang Xin , Ng Siu-Lung
Published: May 2012

This paper is to study the combined behavior of plastic encapsulated MEMS package under humid and elevated temperature environments. Although thermal-induced stress for the materials used in the MEMS package is already fully understood, moisture-induced stress is still not well studied. To cope with humidity effects on the MEMS package, the moisture-induced properties of mold compound are obtained from the proposed experiments. From the weight gain/loss measurement, saturated moisture content and diffusivity were obtained by curve fitting following Fick’s law. In addition, using digital image correlation (DIC) together with precision weight scale, coefficient of hygroscopic swelling (CHS) could also be obtained at different temperatures. The experimental results show that the diffusion coefficient of mold compound material follows Arrhenius’s equation well. Also, it is shown that the CHS of mold compound increases as temperature increases. Finally, using these experimentally obtained moisture properties, conjugated behavior (thermo-hygro-mechanical) of MEMS package under high temperature and humid environment could be estimated through numerical analysis by adopting classical analogy method. The numerical result was also validated by comparing with experimentally obtained warpage of MEMS package at elevated temperatures.
The Effects of Neck Stiffness Properties on Brain Response Under Impact Loads
Authors: Dirisila Venkata , Karami Ghodrat , Ziejewski Mariusz
Published: May 2012

One primary concerns in computational modeling of brain under external loads is to defining the realistic boundary conditions and the head-neck junction stiffness. Neck is a complex structure with cervical spine, neck muscle and ligaments, when considered anatomically. The major mechanical function of the anatomical neck is to support the head through the cervical vertebrae. Few studies have focused on studying the response of head with neck and without neck. In this paper we examine the behavior of head under impact loadings with a simulated neck with elastic foundation-type stiffness. In this FE head–neck model, a three dimensional detailed head model is presented, while for neck, a simplified model of linear elastic springs is considered. The paramount interest is laid in modeling the mechanical functionality of the neck, rather than the modeling of the complete anatomical neck. Determining the exact stiffness properties for the springs, in order to (replicate) duplicate the neck functionality is the most complex aspect in this model. By considering the existing literature stiffness values of neck ligaments and cervical discs, four neck stiffness values ranging from zero stiffness to high stiffened neck have been chosen. A computational parametric examination of the varying the above considered neck stiffness properties are conducted to examine the impact of impact on the head model. Impact loading responses are examined against the Nahum’s cadaver experiments. Numerical intracranial coup and contre-coup pressure histories during impact loading show good correlation with the respective experimental results. Brain intracranial pressure, maximum shear stress and strain response under impact are presented. A significant effect on the magnitude and pattern of brain shear stress and strains can be detected in comparison with the intracranial coup pressure response, with varying neck stiffness properties. Biomechanical multiscale studies on brain reveal that distortional strain is one of the main causes for the axonal injury, and this shear strain pattern significantly varies with neck stiffness properties. Thereby, it the extent of the role of the stiffness of the neck in predicting axonal injury can be examined.
Design of Composite Water Turbine in Free Stream Using CFD
Authors: Wang Jifeng , Vagani Marco , Mu¨ller Norbert
Published: May 2012

The objective of this paper is to investigate the performance of composite material axial water turbines in a free stream using Fluent, a Finite Volume based commercial CFD package. Based on three dimensional numerical flow analysis and fluid-structure interaction, the flow characteristics of water turbines including a nozzle, impeller and diffuser are predicted. The extracted power coefficient is calculated for water turbines of different tip speed ratios in a free stream of water with inlet velocity of 2.5m/s. The extracted powers of one single turbine unit and an array with ten turbine units are analyzed and compared for different rotating speeds and water inlet velocities. The calculated results will provide a fundamental understanding of the impeller as a water turbine, and this design method is used to shorten the design process and improve the water turbine’s performance.
Visualization of Actin Fibers in a Living Osteoblast Under Shear Deformation
Authors: Shiraishi Toshihiko , Sakata Kazuhiro , Morishita Shin , Takeuchi Ryohei
Published: May 2012

Bone cells are adaptive to surrounding mechanical conditions. Osteoblasts, one of bone cells, have been reported to be sensible to mechanical stimulation and change the generated bone mass. Activation of the signaling molecules in relation to the initial mechanoreception appears to be mediated though changes in the cytoskeleton. In this study, we propose a method to visualize cytoskeletal actin fibers in a living osteoblast under applied shear deformation and measure the local deformation of actin fibers. Transfection of MC3T3-E1, which is an osteoblast-like cell line, with GFP-actin was performed using a transfection reagent. Shear deformation was applied to the cell using a micropipette. As a result of the experiment, it is shown to be able to recognize the specific points such as points crossed by the actin fibers and obtain the local deformation vectors of the actin fiber network at the specific points in the cell. The present method contributes to not only obtaining the deformation distribution of actin fibers in cells but also understanding the mechanotransduction mechanisms.
Numerical Simulation of Fluid Flow and Heat Transfer in U-Shape Microchannels
Authors: Zhang Tiantian , Jia Li , Zhang Jingru , Jaluria Yogesh
Published: May 2012

An experimental system on the fluid flow in microchannels with heat generation at the bottom has been set up. This system approximates the use of microchannel flow for the cooling of electronic components. The fabrication procedure of the test section is introduced briefly. Then, different flow rates and heat input have been proposed to study the effect of these parameters experimentally. Several numerical models have been given to simulate this process. By comparing the results from these models and the experimental data, it is found that the “two channel model”, which employ two channels with periodic boundary conditions, is the best model to simulate the overall heat transfer performance. The study considers the use of combined experimental and numerical simulation for an accurate and realistic modeling of such complex microchannel systems.
An Integrated Computer-Aided Engineering Approach for Parametric Investigation of Locked Plating Systems Design
Authors: Arnone Joshua C. , El-Gizawy A. Sherif , Crist Brett D. , Della Rocca Gregory J. , Ward Carol V.
Published: May 2012

Locked plating systems have emerged in recent years as effective devices for treating and stabilizing femoral fractures. Nevertheless, clinical failures due to plate yielding and fracture have been observed — particularly with distal femoral plates. The majority of failures are attributed to improper placement, fixation techniques, or plate selection, and to premature weight-bearing by the patient. While the mechanical function of plating systems is well-understood, the optimum design parameters that lead to efficient stability and fracture healing, such as plate geometry, material properties, and fixation techniques (e.g. screw configuration and the use of hole inserts), are unknown. The present paper presents an integrated computer-aided engineering (CAE) approach combining digital imaging, solid modeling, robust design methodology, and finite element analysis in order to conduct a parametric investigation of the design of locked plating systems. The present study allows for understanding the contributions of different design parameters on the biomechanics and reliability of these systems. Furthermore, the present approach will lead to exploration of optimum design parameters that will result in robust system performance. Three-dimensional surface models of cortical and cancellous femoral bone were derived via digital CT image processing techniques and a medical imaging analysis program. A nine orthogonal array matrix simulation (L9) was conducted using finite element methods to study the effects of the various design parameters on plate performance. The technique was demonstrated on a case study using a Smith & Nephew PERI-LOC distal femur locking plate where the plate thickness and material, the use of screw hole inserts, and the use of an oblique screw angled distally and medially were the design parameters. After creating a distal fracture with bone loss and stabilizing the femur with the plating system, the impact force due to walking was simulated on each of the nine fracture models. Results showed that increasing the plate’s thickness, using titanium alloy for fabrication, and using screw hole inserts in proximity to the fracture site will maximize the overall factor of safety.
Gyrosonics: Signature Analysis and Reduced-Order Models
Authors: Roy Mahapatra D. , Chakraborty N. , Bandopadhyay S. , Balachandran B.
Published: May 2012

In this paper, the authors study the structure of a novel binaural sound with a certain phase and amplitude modulation and the response to this excitation when it is applied to natural rewarding circuit of human brain through auditory neural pathways. This novel excitation, also referred to as gyrosonic excitation in this work, has been found to have interesting effects such as stabilization effects on the left and right hemispheric brain signaling as captured by Galvanic Skin Resistance (GSR) measurements, control of cardiac rhythms (observed from ECG signals), mitigation of psychosomatic syndrome, and mitigation of migraine pain. Experimental data collected from human subjects are presented, and these data are examined to categorize the extent of systems disorder and reinforcement reward due to the gyrosonic stimulus. A multi-path reduced-order model has been developed to analyze the GSR signals. The filtered results are indicative of complicated reinforcing reward patterns due to the gyrosonic stimulation when it is used as a control input for patients with psychosomatic and cardiac disorders.
Using Dynamic Infrared Imaging to Detect Melanoma: Experiments on a Tissue-Mimicking Phantom
Authors: Pirtini C¸etingu¨l M. , Herman C.
Published: May 2012

In this paper we investigated how the surface temperature distribution reflects the properties of malignant lesions such as the metabolic activity level, the location, and size of lesions, by conducting an extensive experimental study on a skin tissue mimicking phantom developed to validate our numerical model. Experiments were conducted for different dimensions and depths of the thermistor simulating the heat generating lesion. The rate of heat generation was also varied. We found that times immediately after the removal of the cooling stress (up to 2 minutes) are critical for the identification of masses beneath the surface. Additionally, the results indicate that the surface temperature distributions are sensitive to thermistor size. These findings are consistent with the findings of our numerical model.
A Study of Vehicle Ride Performance Using a Quarter Car Model and Half Car Model
Authors: Alam Firoz , Faheem Ahmad , Jazar Reza , Smith Lloyd V.
Published: May 2012

This paper studies the responses of a quarter car and a half car model. The vehicle ride performance was assessed at the design stage by simulating the vehicle response to road excitation. This required the development of a vehicle model to analyze its responses. The disturbances from the road were assumed to be constant or step function and the time responses and frequency responses of the sprung and unsprung masses have been studied. Simple yet, in practice, meaningful state-space formulations of the optimal suspension control problem for a half-car 2-D and 4-D vehicle model are given. Using an efficient equivalent representation, a complete analytical solution of the system was obtained. The optimal solution here was the damping, which has been optimised with the given set of fixed parameters. This paper provides insight on the suspension dynamics of the two most extensively used models in vehicle dynamics with their complete state space realization, simulated using the MATLAB platform.
Conjugate Mixed Convection With Surface Radiation and Substrate Conduction in Laminar Channel Flow With Discrete Flush-Mounted Heat Sources
Authors: He Jing , Jacobi Anthony M.
Published: May 2012

Thermal analysis employing a full conjugation model is performed in this study for laminar airflow in a parallel-plate channel with discrete flush-mounted heat sources. The numerical model accounts for mixed convection, surface radiation, and two-dimensional conduction in the substrate. The effects of Reynolds number, surface emissivity of walls and heat sources, as well as thickness and thermal conductivity of the substrate, are analyzed in detail. It is shown that participation of radiation brings the wall temperatures closer, and the trend of temperature variation along the top wall is drastically altered. Such effects are pronounced for black enclosures and diminished for high Reynolds numbers. The influence of substrate conductivity and thickness is very similar in that a large value for both parameters would facilitate redistribution of heat and tend to yield a uniform temperature field in the substrate. For highly conductive or thick substrate, the ‘hot spot’ cools down and may move upstream to the penultimate source. Radiation loss to the ambient increases with substrate conductivity and thickness due to the elevated temperature near the inlet and outlet, yet the total heat transfer over the bottom surface by convection and radiation remains unaltered.
Prediction of On-Stride Walking for Pregnant Women
Authors: Yang Jingzhou James , Zou Qiuling
Published: May 2012

Pregnant women’s size, shape, and weight changes have significant effects on their walking stability. Traditionally, experiments are used to study the effects of subjects, but it is time consuming and expensive. This paper presents an optimization-based pregnant women walking simulation with one-stride formulation. The pregnant woman’s model with 55 degrees of freedom (DOFs) is used, including 6 global DOF’s and 49 human body DOF’s. The dynamic equations of motion are based on the recursive dynamics. Without the constraint of symmetry of the human body between two steps within one walking cycle, the study is based on bio-mechanical, human kinematic, and dynamic properties to perform the one-stride simulation, which represent the holonomic and non-holonomic constraints in walking simulation. This forms a nonlinear optimization problem. The summation of all joint actuator torques squared within one stride is the cost function. Nine determinant DOF’s are used to analyze the kinematics and three for dynamics. Three cases (non-pregnancy, 6 month, and 9 month pregnancy) are adopted for the test and investigation. The simulation results show that during the course of pregnancy, pregnant women’s bodies dynamic and kinematic properties change and thus affect their walking and stability.
CFD Analysis of Flow and Heat Transfer in a Novel Heat Sink for Electronic Devices
Authors: Ramos-Alvarado Bladimir , Li Peiwen , Liu Hong , Hernandez-Guerrero Abel
Published: May 2012

Novel flow channel configurations in heat sinks for electronics cooling were proposed in this paper. Computational analyses were carried out to better understand the heat transfer performance, the uniformity of temperature fields of the heat sinking surface, as well as the pressure losses and pumping power in the operation of heat sinks. Comparison of the overall performance regarding to temperature uniformity on the heat sink surface and pumping power consumption was made for heat sinks having novel flow channel configurations and having traditional flow channel configurations. It has been found that the novel flow channel configuration dramatically reduces the pressure loss in the flow field. Giving the same pumping power consumption of an electronics cooling process, the temperature difference on surface of the heat sink which has novel flow channel configuration can be much lower than that of the heat sinks which have traditional flow channel configurations.
Estimation of the Heat Generation and Dissipation for the Hydraulic System of a Medium Size Excavator Using One Dimensional Analysis
Authors: Kim Jin-Young , Lee Jae-Seok , Kim Hong-Won , Moon Weon-Sik
Published: May 2012

The heat generation and dissipation are important design parameters in the hydraulic system of an excavator which is composed of valves, pump, cylinders and cooler etc, for the evaluation of system efficiency, reliability and optimum design. Accurate estimation of heat generation is therefore required for the design of an excavator hydraulic system. In this study the hydraulic system of a medium size excavator is simulated using one dimensional transient network analysis method. To increase the accuracy of estimation, the pressure loss coefficients at the displacement valves calculated by computational fluid dynamics are applied. The simulated flow-rate pattern of the pump approximately coincides with the experimental data. And the temperature at the pump inlet with assumed solid surface heat dissipation rate is 2°C different compared to the experimental data.
A New Process for Configuration and Application of Complex Validation Environments Using the Example of Vehicle-in-the-Loop at the Roller Test Bench
Authors: Albers Albert , Du¨ser Tobias
Published: May 2012

Due to the increasing complexity of modern vehicle concepts new methods to integrate simulation and test on each level of the validation chain are required. Especially for the development of advanced driver assistant systems with focus on safety and energy efficiency the interaction between the unit under test, the driver and the environment like traffic, road topology, etc. are very important and must be considered in detail. To meet this challenge IPEK - Institute of Product Engineering at the Karlsruhe Institute of Technology (KIT) developed the X-in-the-Loop-Framework for drivetrain systems. Based on this approach the Vehicle-in-the-Loop technology was developed at a roller test bench. On the one hand this allows doing highly reproducible and automated tests with the whole vehicle in the loop considering the influences of different driver types and different environmental situations. On the other hand the task-oriented configuration and application of such an environment is very difficult but necessary. Complex vehicle concepts cause more complex development and validation environments. The X-in-the-Loop-Framework and the Vehicle-in-the-Loop technology are established in many projects at the IPEK and were publicized in different papers. A challenge is to define a process for the configuration and application because of the very different application areas of such a technology. This paper shall answer the question how a validation environment can be specified in very early stages of the product development to save time and costs. Starting with a use case for a validation task a functional model for the structure and the behavior is defined based on the system modeling language SysML. This allows estimation for chances and risks and ensures a sustainability for established configurations in future projects. Based on the functional description the input/output specification, new models and interfaces were generated and implemented. This process is demonstrated exemplary using a concrete application example on the roller test bench with Vehicle-in-the-Loop technology: an energy efficient working adaptive cruise control (Green ACC) for hybrid electric vehicles (HEV).
Development Concept for Non Conventional Hybrid Engine
Authors: Purohit Harsh , Shah Ankit , Parekh Nishant , Pandey Akash
Published: May 2012

Environmental issues and the need for environment-friendly transport have always been a priority for the world due to ever increasing demand of modes of transport. So developing quick and eco friendly vehicle is the trend as of now with most manufacturers globally. There are numerous ways in which manufacturers have tackled these issues. Some of the common approaches undertaken are refinements of existing internal combustion engines. Like developing technologies such as direct injection, VVT (variable valve time), VTEC (variable valve time electronic lift), VGT (variable geometry turbines), reducing engine friction and weight, cam less engines, micro hybrids, etc But the best/optimum compromise between eco friendliness and urge to develop more power with good fuel economy and reduced emission is best met by the development of hybrid engines. Thermal and electric engines both have advantages and disadvantages that are often complementary. Combustion engines offer better range, power and ‘lunge’, but give out exhaust gas, although the current Euro IV norm place strict limits on these. Electric engines are zero-emission and offer very quick pick-up from a stopped position, but the batteries have low range and limited speed. So this complementation of both power trains is exploited in hybrid engines. Now conventional hybrids have many disadvantages such as being bulky with additional weight of battery packs and motors and other auxiliary transmission components, complex and dangerous electric systems, etc. So it is proposed to develop a non conventional hybrid engine which produces power at par with the conventional one and releases emission which is compatible with the stringent emission norms set for the conventional hybrids with considerably lucrative fuel economy comparable with the currently available hybrids in market and yet overcome the drawbacks of the conventional hybrid engines. Also the compact size of the hybrid engine that we propose makes it quite viable to fitted in small vehicles (like bikes, compact cars, etc) which further makes it a more promising technology that can be made available to common people across the globe and there by lead to a better transportation system for people of all class and need. The conceptualization basically includes modification of an inline twin cylinder or a v-twin 4-stroke gasoline engine as a preliminary step towards achieving the above proposed objectives.
Minimum Airflow of Single Duct VAV Terminal Boxes
Authors: Cho Young-Hum
Published: May 2012

Terminal boxes are the critical component of the VAV systems. The minimum airflow of terminal boxes is a key factor for comfort, indoor air quality (IAQ) and energy cost. If the minimum airflow is higher than required, terminal boxes will have significantly more simultaneous heating and cooling, and AHUs will consume more fan power. Buildings will have IAQ problems if the minimum airflow is less than required. A building simulation was conducted to evaluate the impact of energy consumption on the minimum airflow of single duct VAV terminal boxes. The results show that simulation data revealed that compared with the existing set point, the improved optimal minimum airflow set point exhibited an annual energy savings of 29%.
The Effect of SAS Materials and Modeling in Transferring Impact Loads to the Brain
Authors: Saboori Parisa , Sadegh Ali
Published: May 2012

While subarachnoid space (SAS) trabeculae play an important role in damping and reducing the relative movement of the brain with respect to the skull, thereby reducing traumatic brain injuries, their mechanical properties and modeling are not well established in the literature. A few studies, e.g., Zhang et al. (2002) and Xin Jin et al. (2008) have reported a wide range the elastic modulus of the trabeculae up to three orders of magnitudes. The histology of the trabeculae reveals a collagen based structure. Thus, a few investigators have estimated the mechanical properties of trabeculae based on collagen’s properties. The objective of this study is to determine the stress/strain changes in the brain as a function of the mechanical properties and modeling methodology of the trabeculae, when the loading and the boundary conditions of the model are kept the same. This study was performed through several modeling steps. A wide range of the mechanical properties of the trabeculae was employed and the transductions of blunt impact loads from the skull to the brain were determined. The mechanical properties of the SAS trabeculae were determined based on the validation of the models with experimental results of Sabet et al. (2009). The result indicated that when we use softer material properties for the trabeculae the meningeal layers absorb and damp the impact load. It is also concluded that the material properties of the trabeculae can be simulated by only tension element since the trabeculae buckles with minimal compressive load. Finally, an optimum material property of SAS was proposed.
Laser Ultrasonic Inspection of Solder Bumps in Flip Chip Packages Using Virtual Package Device as Reference
Authors: Ume I. Charles , Gong Jie , Ahmad Razid , Valdes Abel
Published: May 2012

Flip chip package is widely used in the electronic device manufacturing industry. The top side of a flip chip device is manufactured with solder bumps. The device is then flipped on its top so that the solder bumps can be bonded to a substrate, forming the mechanical and electrical connection between the device and substrate. As a result, the solder bumps are sandwiched between the silicon die and the substrate, making them no longer visible for usual inspection. A novel solder joint inspection system capable of evaluating the quality of the hidden solder bumps on a flip chip package has been developed using laser ultrasound techniques. The system pulses a laser onto the top surface of a chip package to generate ultrasonic waves in the package and excite structural vibrations which can then be measured using an interferometer. Since defective solder bumps cause changes in the transient vibration response of a tested sample, quality of the tested sample can be assessed by correlating its vibration responses to that of a known good device. A limitation of this implementation is the necessity of a known-good reference chip package, which typically involves expensive testing using alternate methods. In this paper, the development of a method capable of generating a virtual reference chip package is presented. This method, called Hybrid Reference Method, uses a statistical approach to find which packages in a sample set are most similar and then averages their time domain signals to generate a virtual chip package, known as the Hybrid Reference Package. The signals associated with Hybrid Reference Package are then correlated with the time domain signals obtained from the packages under inspection to obtain a quality signature. Finally, defective and non-defective chip packages are separated by estimating a beta distribution that fits the quality signature histogram of the inspected packages and then determining a cutoff threshold for an acceptable quality signature. This method was applied to two types of flip chip packages where no pre-established known-good reference package was available. The results of this quality analysis were validated by comparison with electrical test and X-ray results.
Instrumentation for Performance Measurements of Heat Pumps With Commercial Desuperheaters
Authors: Yilmaz Emin
Published: May 2012

The current project is an extension of the original “ETME 475-Mechanical Systems Design” course project with a new National Instruments data acquisition board, a newly developed LabVIEW data acquisition program, and with a more realistic heat transfer loop. The study covers performance of our heat pump operating in A/C mode as well as in heating mode with a commercial desuperheater (a cross-flow heat exchanger). For this project, the experimental set up consisted of a desuperheater spliced into Trane XL1000, 2-ton, 10-SEER heat pump and a heat transfer loop with a 72-liter hot water storage tank. The instrumentation consisted of seven copper-constantan thermocouples and a LabVIEW-based computer data acquisition system. The thermocouples were used to measure refrigerant, water, indoor air and ambient air temperatures. The LabVIEW based computer data acquisition system was used to record temperatures. Indoor airflow rate was previously measured using Alnor LoFlo balometer. Results indicate that, depending on the water temperature in the desuperheater, heat pump Coefficient of Performance (COP) dropped 6–18% in A/C mode and 8–38% in heating mode. Again depending on the average water temperature in the desuperheater, the desuperheater efficiencies ranged from 12% to 27% for cooling and 11% to 39% for heating. Although even modifying an existing LabVIEW program was a challenge, the student who worked on it and the author has gained very valuable experience and enjoyed the work.
Development and Validation of a 50th Percentile Male Pedestrian FE Model
Authors: El-Jawahri Raed E. , Ruan Jesse S. , Rouhana Stephen W. , Barbat Saeed D.
Published: May 2012

The objective of this study was to develop and validate a finite element (FE) human model that represents a 50th percentile adult pedestrian male. The geometry of the previously developed and well validated Ford Human Body (FHB) model was modified to change the posture from driving to standing. The femur, tibia, and fibula were validated against published test data of human bone specimens in different dynamic loading scenarios. The leg model was validated against dynamic, three-point bending test data of human legs from Post Mortem Human Subjects (PMHS). The kinematics and dynamics of the full pedestrian model was validated against PMHS car-pedestrian impact test data under different levels of severity. The model responses were compared with the corresponding published generalized response corridors. In all the component level and full body model simulations the responses from the model correlated well with both the generalized response corridors and the responses from the individual cadavers.
Process Heater Air Infiltration
Authors: Baukal Charles E. , Bussman Wesley R.
Published: May 2012

Process heaters are among the largest energy consumers in industry. Many of them were built years ago and often are not well sealed which leads to excessive air infiltration. Air leaks may be caused by cracks in the wall, by sight ports that are not properly sealed or may even be left open, failure to close air registers for burners that are out of service, improper sealing of penetrations through the heater walls, and by excessive draft levels in the heater. These leaks reduce energy efficiency and indirectly increase pollution emissions as more fuel must be consumed for a given production rate. Leaks may also directly cause NOx emissions to increase due to increased excess oxygen. Excessive air leakage can indirectly cause process burners to operate improperly. The excess oxygen level in a heater is normally controlled to a certain target value, typically about 2–3% by volume for gaseous fuels. Process burners are designed assuming that all of the air for combustion goes through the burner. However, if a significant amount of air is leaking into a heater, the measured excess oxygen level may be on target but not enough of the air is coming through the burner which can adversely affect performance. The flame length may be dramatically increased as the flame searches for air to complete combustion which often causes flame impingement on process tubes. The heat flux distribution may be shifted as the flame length increases. The flames may even become unstable if they are sufficiently starved for air. The draft level in a heater varies with elevation which means that air infiltration depends not only on the size of the leak opening, but also on its location. This paper will include an analysis of how excess air infiltration affects thermal efficiency and how the location of the leak and the heater draft level affect the amount of air infiltration. The impact of air infiltration on burner performance will be discussed. Techniques will be recommended for detecting air leaks and how to correct them.
Investigation of Stress Wave Propagation in Brain Tissues Through the Use of Finite Element Method
Authors: Zhang Biaobiao , Shepard W. Steve , Floyd Candace L.
Published: May 2012

Because axons serve as the conduit for signal transmission within the brain, research related to axon damage during brain injury has received much attention in recent years. Although myelinated axons appear as a uniform white matter, the complex structure of axons has not been thoroughly considered in the study of fundamental structural injury mechanisms. Most axons are surrounded by an insulating sheath of myelin. Furthermore, hollow tube-like microtubules provide a form of structural support as well as a means for transport within the axon. In this work, the effects of microtubule and its surrounding protein mediums inside the axon structure are considered in order to obtain a better understanding of wave propagation within the axon in an attempt to make progress in this area of brain injury modeling. By examining axial wave propagation using a simplified finite element model to represent microtubule and its surrounding proteins assembly, the impact caused by stress wave loads within the brain axon structure can be better understood. Through conducting a transient analysis as the wave propagates, some important characteristics relative to brain tissue injuries are studied.