bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel Compressor Using Woven/Wound Composite Impeller
Authors: Lindberg Bruce E. , Papuka Kristen M. , Kharazi Amir A. , Mu¨ller Norbert
Published: April 2008

In the design of compressors, typical obstacles arise such as cost, size, weight, manufacturability, and structural integrity. Compression technology has different ways of addressing these challenges. One way to overcome these challenges is a novel multi-stage, axial, counter-rotating turbo compressor with a woven composite impeller. The compressor uses multiple stages to achieve higher pressure ratios. Several configurations are possible including ones with and without guide vanes. Axial compressors are inherently much smaller than radial or mix-flow compressors. A size reduction may result in decreasing costs and help with spatial constraints. The use of counter-rotating impellers allows for no swirl before and after each impeller. This eliminates the need for guide vanes, and thus reduces size, cost, and fluid losses in the compressor. A unique component of this novel compressor technology is the woven composite impeller. Impellers used in high performance compressors are typically required to be of a strong, lightweight material. These impellers are often made from titanium or formed composite sheets and have to be constructed component by component. This in turn is time consuming and incurs very high manufacturing costs. By using a readily available multiple axis winding machine, composite fibers can be wound using computer generated pattern into impellers with a wide variety of shapes. These shapes may include a shroud which can also be cut off if desired. The impellers can be both, rapidly prototyped and mass-produced without the need for expensive dies, molds, tooling or hand crafting. Because of this, the composite impellers are envisioned to reduce the cost of high-performance compressors extensively. The use of composite materials may also include the use of ceramic fiber and matrix material that can withstand high temperatures. In addition, the woven design allows for the interweaving of induction wires or magnetic material for motor, generator and electromagnetic bearing components integrated in the impeller in the same production step. While the paper focuses much on the compressor application especially as needed for compressing water vapor used as refrigerant (R718), this technology can also be adopted for other turbomachinery applications, such as pumps, fans, power generating turbines, in propulsion and more.
Hydrodynamic Load Support of a Slip Wedge
Authors: Wu C. W. , Ma G. J.
Published: April 2008

This paper studies the hydrodynamic load support generated by a slip wedge of a slider bearing. The surface slip property is optimized to obtain a maximum hydrodynamic load support. A multi-linearity method was used to approach the slip control equation of two-dimensional (2-D) wall slip. It is found that the hydrodynamic pressure generated in the slip wedge is greater than that of the traditional geometrical convergent-wedge. Even though the geometrical gap is a parallel or divergent sliding gap, the slip wedge still gives rise to a very big hydrodynamic pressure. The optimized slip wedge gives rise to a maximum hydrodynamic load support as large as 2.5 times of what the Classical Reynolds theory predicts for the geometrical convergent-wedge. Wall slip usually gives a small surface friction drag.
Young’s Modulus Measurement of Electroplated Nickel Using AFM
Authors: Kim Sang-Hyun , Boyd James G.
Published: April 2008

This paper addresses a relatively simple method of measuring Young's modulus of electroplated nickel using Atomic Force Microscope. Thin layer of nickel to be measured is electroplated onto the tip side of AFM silicon cantilever, whose Young's modulus and the geometric dimensions are defined from manufacturer. The resonant frequency and the quality factor of the electroplated AFM cantilever are measured by the tapping mode of AFM and its spring constant is calculated using Sader's method. The spring constant of the electroplated cantilever is also calculated by using the laminar composite beam theory. Comparing two spring constants, Young's modulus of the electroplated nickel is determined. The measured elastic modulus of nickel in each time step is in the range of between and the average elastic modulus is with relative uncertainty of less than 5%
Eigensystem Realization With Modified Genetic Algorithm for System Identification of Noise Corrupted Processes
Authors: Schoen Marco P. , Chinvorarat Sinchai , Kuo Chien-Hsun
Published: April 2008

The results of real world application of system identification (SI) algorithms are always affected by the process and measurement noise associated with the system to be identified and the measurement set-up. A small signal to noise ratio generally results into poor and sometimes unusable dynamical models. Missing system dynamics and characteristics in the inferred system model may cause undesirable and sometimes harmful control laws. Robust control is one avenue to avoid causing undesirable system performance due to the large model uncertainties. In this paper, an alternative approach is presented. In particular, a proof is given that no dynamic controller can reduce the noise influence in linear system identification. Eigensystem Realization Algorithms (ERA) used commonly in the Observer Kalman Filter Identification (OKID) algorithm allows for the discrimination between noise and system modes based on the magnitude of the singular values. Having a large noise content embedded in the input/output data is reflected by large singular values for the noise and system modes. This leaves them indistinguishable from each other. Hence the number and exact selection of the system modes using the traditional Eigensystem realization and the DC realization algorithm is impracticable. A new selection scheme is proposed for the Eigensystem realization portion of the OKID algorithm. The selection is done using a modified Genetic Algorithm (GA). The GA uses a cost function based on the step response, which is addition data to the random data collected from the experiment. The GA proposed adapts the probability density function for the selection scheme of the mating chromosomes based on the approximated cost gradient. Simulation results of the proposed algorithm in comparison with the traditional used method are presented. The results indicate an improved ability to extract system models from very noise data.
Cooperative Control of Autonomous Mobile Robots in Unknown Terrain
Authors: Ray Laura E. , Brande Devin , Murphy John , Joslin James
Published: April 2008

This paper presents a distributed control framework for groups of wheeled mobile robots with significant (non-negligible) vehicle dynamics driving on terrain with variable performance characteristics. A dynamic model of a high-speed robot is developed with attention to representation of wheel-terrain performance characteristics. Using this model, aspects of distributed, cooperative control on unknown terrain are investigated. A potential function path planning and cooperative control algorithm is combined with a local slip controller on each robot to provide high-speed control of vehicle formation. Local slip control is shown to reduce sensitivity of the distributed path planning and control method to tire-terrain performance variation and its resulting effect on dynamic behavior of the robots. Computationally efficient methods for real-time assessment of force-slip characteristics are presented to provide slip setpoints for this control architecture.
Performance of Gaseous Parallel-Flow Micro Heat Exchangers
Authors: Asako Y. , Hong C. , Miwa J. , Faghri M.
Published: April 2008

Heat exchangers performance of two-stream parallel-flow gas-gas type micro-heat exchangers is investigated numerically. The flow passages of the micro-heat exchangers are parallel-plate channels with heights in the range of 10 to 100 μm and selected lengths of 12.7 and 25.4 mm. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian method. The computations were performed to find the effects of capacity ratio, channel height and length on the heat exchange characteristics of micro heat exchangers. The results are presented in form of temperature contours, bulk temperatures, total temperatures and heat flux variation along the channel. Also, the correlation between the effectiveness and Ntu is discussed.
Research on Variable Speed Electro-Hydraulic Control System Based on Energy Regulating Strategy
Authors: Haikuo Shen , Bo Jin , Chen Ying
Published: April 2008

A new type of variable speed electro-hydraulic control system is developed in this paper. In this system, a fixed displacement hydraulic pump is driven by an electrical motor which is controlled by a frequency inverter, so the discharge of the pump can be modified by changing the speed of the motor. A proportional directional valve is used to acquire higher low-speed control precision and faster dynamic response while the system is decelerating. In order to improve the dynamic response while the system is accelerating, an energy regulation device is employed in the system. The experiment results show that this system has higher efficiency than valve control system. Further more it has faster dynamic response and higher low-speed control precision than normal variable speed hydraulic control system.
Determination of Transition Curves for a Gear System With Coulomb Friction
Authors: Saryazdi Maryam Gh. , Durali Mohammad
Published: April 2008

This paper discusses the determination of the transition curves for a pair of spur gear with coulomb friction. Transition curves are the loci of periodic response of parametrically excited systems and separate the stable and unstable solutions. A discrete model of a pair of spur gear is developed and the friction forces are calculated base on instantaneous dynamic force between gear teeth. The dynamic equation of the system is a linear ordinary differential equation with periodic coefficients. Periodic friction torque, as the parametric excitation is represented by Fourier series. The loci of periodic solutions are determined in μ-Γ plane (coefficient of friction-contact ratio) by strained parameters method. The influence of angular velocity on transition curves and stability zones is examined. Finally, stable and unstable zones are determined and the existence of periodic solutions on transition curves is verified by numerical analysis.
Pressure Drop and Mass Transfer Studies in Liquid Fluidized Beds
Authors: Murthy Bhagavatula Venkata Ramana
Published: April 2008

Fluidized beds are widely used in industries for mixing solid particles with liquids as the solid is vigorously agitated by the liquid passing through the bed and the mixing of the solid ensures that there are practically no temperature gradients in the bed even with exothermic or endothermic reactions (Mixing and the segregation in a liquid fluidized of particles with different sizes and densities", The Canadian Journal of Chemical Engineering, 1988). The violent motion of the solid particles also gives high heat transfer rates to the wall or to cooling tubes immersed in the bed. Because of the fluidity of the solid particles, it is easy to pass solid from one vessel to another. In the present experimental work, the relative density between solid and liquid phases on pressure drop under fluidized condition has been studied using the solid-liquid systems namely, glass beads-water, glass beads-kerosene, plastic beads-kerosene and diamond sugar-kerosene. Pressure drop - liquid velocity and void fraction - liquid velocity relationships have been found for all the mentioned solid-liquid systems under fluidized condition and results have been noted. The effect of the nature of the fluid on the minimum fluidization velocity and the pressure drop has been studied. In addition to the pressure drop studies, mass transfer studies have also been conducted with diamond sugar-water system with and without fluidization and results have been obtained. In addition to these, comparison of bed voidage, pressure drop and minimum fluidization velocity between denser and lighter liquids have been studied and the results have been obtained. Also, the value of rate of mass transfer with fluidization is compared that without fluidization for diamond sugar-water system and the results have been obtained.
The Influence of Specific Heats Variability on Heat Release Analysis Using Two-Zone Models
Authors: Brusca S. , Collura S. , Lanzafame R. , Messina M.
Published: April 2008

Heat release and burn rate analysis in Internal Combustion Engines (ICEs) are usually based on a zero-dimensional application of First-Law of thermodynamics. In order to evaluate the heat release models available in literature use the differential form of the energy conservation equation, generally neglecting specific heats derivative terms. In this work the effects of specific heats derivative terms on a two-zone heat release model, for a Spark Ignition (SI) engine, have been evaluated. Results obtained with and without considering specific heats derivative terms have been compared. These comparisons show that proposed modifications allow to obtain more regular curves especially for mass fraction burned and heat release according to the combustion phenomenology. Besides, taking into account the specific heats derivative terms, the model's calibration constants do not need to be tuned, and the combustion efficiency can be evaluated directly by the mathematical model (otherwise experimentally measured).
Uncertainties in Spectral Fatigue Damages and an Efficient Simple-Reliability Calculation of Offshore Structures
Authors: Karadeniz H.
Published: April 2008

This paper presents uncertainties in spectral fatigue damages of offshore structures firstly. Then, attention is given to the formulation and procedure of a fast and efficient computation of fatigue reliability estimates. Most of uncertainties are embedded in response characteristics of the stress process and the damage-model used. Uncertainties in stress statistical characteristics are associated with the modeling of structures and random wave environment as well as wave loading and the analysis used. Uncertainties arising from degradation of member stiffness, wave-current and water-structure interactions can be considered in the modeling of structures, wave environment and loading. In the fatigue damage, there are additional uncertainties arising from the modeling of damage-mechanism. These uncertainties are due to experimental fatigue data and structural joint configurations. All these uncertainties can be classified into aleatory (naturally inherent) and epistemic (due to lack of knowledge) categories. The second part of the paper is devoted to a fast and efficient computation of fatigue reliability. This algorithm eliminates repetitive execution of spectral analysis procedure. It is performed only once for all reliability iterations. In this technique, a suitable spectral formulation of the stress process is used and a new uncertainty parameter is introduced to represent most of uncertainties in the stress spectrum. A detailed modeling of the fatigue-related uncertainties is presented. The failure function of the reliability analysis is expressed independently of the spectral analysis. The advanced FORM reliability method is used to calculate the reliability index and to identify important uncertainty parameters. The procedure is demonstrated by an example jacket structure and the results are compared with previously available ones.
Regenerative Flow Pumps and Compressors (RFP/RFC) Applications for Water as Refrigerant
Authors: Elkacimi Younes , Mu¨ller Norbert
Published: April 2008

This paper presents some preliminary design consideration of Regenerative Flow Pumps and Compressors (RFP/RFC) and their application in chillers that use water (R718) as the sole refrigerant. A brief overview of the fundamentals and hypothesis of the operation of RFP/RFC is presented. A one-dimensional (1-D) performance prediction code of an RFP/RFC model is developed using geometric parameters as input. Results of a sensitivity analysis are briefly discussed as they are validated using CFD analysis and suggest design changes for performance enhancement. Finally the RFC may be considered as an interesting alternative solution for R718-chiller application especially for smaller capacities and operation with lower speed.
Abrasion Under Humide Condition for Tool Steels H-13 and AISI D-2
Authors: Hilerio I. , Vite M. , Barro´n M. A. , Jime´nez H. , Alva´rez G. D.
Published: April 2008

In the present work, is developed the tribologic characterization of steels AISI H-13 and D-2, submitted to nitruration ionic process to determine wear resistance in aqueous conditions. Wear test are realized with an abrasion wear tool in an aqueous environment, designed and constructed by SEPI, ESIME, IPN, according to the norm ASTM G105-89. The aim of this investigation is to use a new material at lower prize which has an excellent wear resistance properties for high abrasion in aqueous environments, as occurs in several cases as mining industry equipments.
Experimental Identification of Nonlinear Continuous Vibratory Systems Using Nonlinear Principal Component Analysis
Authors: Kamiya Keisuke , Mizuno Yuichi , Yasuda Kimihiko
Published: April 2008

In identifying machines and structures, one sometimes encounters cases in which the system should be regarded as a nonlinear continuous system. The governing equations of motion of a nonlinear continuous system are described by a set of nonlinear partial differential equations and boundary conditions. Determining both of them simultaneously is a quite difficult task. Thus, one has to discretize the governing equations of motion, and reduce the order of the equations as much as possible. In analysis of nonlinear vibratory systems, it is known that one can reduce the order of the system by using the nonlinear normal modes preserving the effect of the nonlinearity accurately. The nonlinear normal modes are description of motion by nonlinear functions of the coordinates for analysis. In identification it is expected that an accurate mathematical model with minimum degree of freedom can be determined if one can express the response as nonlinear functions of the coordinates for identification. Based on this idea, this paper proposes an identification technique which uses nonlinear principal component analysis by a neural network. Applicability of the proposed technique is confirmed by numerical simulation.
Exergy Transfer Effectiveness on Heat Exchanger
Authors: Wu Shuang-Ying , Yuan Xiao-Feng , Li You-Rong , Cui Wen-Zhi , Quan Liao
Published: April 2008

In this paper, the concept of exergy transfer effectiveness is put forward firstly and the expressions involving relevant variables for the exergy transfer effectiveness, the heat transfer units number and the ratio of cold and hot fluids heat capacity rate have been derived for the high and low temperature heat exchangers. Taking the parallel flow, counter flow and cross flow heat exchangers as examples, the numerical results of exergy transfer effectiveness are given and the comparison of exergy transfer effectiveness with heat transfer effectiveness is analyzed.
Actuating Performance of Non-Passivated Micro Heaters
Authors: Kim Min Soo , Lee Yong Soo , Lee Bang Weon , Sohn Dong Kee , Kuk Keon
Published: April 2008

Effects of thin film layers have been investigated on the actuating performance of micro heaters. Bubble behaviors on micro heaters were observed experimentally. Nine (9) kinds of tantalum nitride (TaN) micro heaters were prepared to have different thin film layers with same planar size of 22 μm by 22 μm. Step-stress test (SST) showed that maximum endurable voltage levels in the non-passivated heaters are less than 50% of those in the passivated heaters. Bubble test was carried out using de-ionized (DI) water as working fluid in an open pool. The results showed that the non-passivated heaters can produce comparable bubbles with only 20 to 50% of the input energy required for the passivated heaters. However, the non-passivated heaters could be operated only in a narrow range of driving voltage. Applicability of non-passivated heaters as promising micro actuators needs further investigation from the viewpoints of robustness and reliability.
From Traditional to Virtual Design of Machine-Tools: A Long Way to Go ... Part 1 — Problem Identification and Model Validation
Authors: Bedini Raffaele , Tani Giovanni , Fortunato Alessandro , Gallorini Giovanni , Mantega Claudio
Published: April 2008

This paper reports the final results of research devoted to providing a package of tools for the Virtual Design of Machining Centers for an Italian manufacturer involved until today with traditional design procedures. The general thematics of Virtual Design have been realistically defined and focalised on the topics of particular interest for the firm; these constraints are analysed and the chosen solutions discussed. The paper also reports on the experimental validation of some complex parameters of the models of the Machining Centers already set up.
A Collision Dynamics Model of a Multi-Level Train
Authors: Priante Michelle , Tyrell David , Perlman Benjamin
Published: April 2008

In train collisions, multi-level rail passenger vehicles can deform in modes that are different from the behavior of single level cars. The deformation in single level cars usually occurs at the front end during a collision. In one particular incident, a cab car buckled laterally near the back end of the car. The buckling of the car caused both lateral and vertical accelerations, which led to unanticipated injuries to the occupants. A three-dimensional collision dynamics model of a multi-level passenger train has been developed to study the influence of multi-level design parameters and possible train configuration variations on the reactions of a multi-level car in a collision. This model can run multiple scenarios of a train collision. This paper investigates two hypotheses that could account for the unexpected mode of deformation. The first hypothesis emphasizes the non-symmetric resistance of a multi-level car to longitudinal loads. The structure is irregular since the stairwells, supports for tanks, and draglinks vary from side to side and end to end. Since one side is less strong, that side can crush more during a collision. The second hypothesis uses characteristics that are nearly symmetric on each side. Initial imperfections in train geometry induce eccentric loads on the vehicles. For both hypotheses, the deformation modes depend on the closing speed of the collision. When the characteristics are non-symmetric, and the load is applied in-line, two modes of deformation are seen. At low speeds, the couplers crush, and the cars saw-tooth buckle. At high speeds, the front end of the cab car crushes, and the cars remain in-line. If an offset load is applied, the back stairwell of the first coach car crushes unevenly, and the cars saw-tooth buckle. For the second hypothesis, the characteristics are symmetric. At low speeds, the couplers crush, and the cars remain in-line. At higher speeds, the front end crushes, and the cars remain in-line. If an offset load is applied to a car with symmetric characteristics, the cars will saw-tooth buckle.
Hydrodynamics and Heat Transfer in Heat Exchanger Channels With Spherical Holes
Authors: Leontiev A. I. , Popov I. A. , Gortyshov Yu. F. , Olympiev V. V. , Schelchkov A. V. , Kaskov S. I.
Published: April 2008

Results of classification of the existed data on hydrodynamics and heat transfer under forced convection in channels with spherical holes (SHs) are presented. Energy efficiency of the use of SHs under laminar and turbulent flow of a coolant is shown. Effects of regime and design parameters on heat transfer in such channels are studied. The flow-regime chart is developed.
Modeling of Micro-Cooling, Heating, and Power (Micro-CHP) for Residential or Small Commercial Building Applications
Authors: Mago P. J. , Chamra L. M. , Moran Alan
Published: April 2008

The increasing demand for electrical power as well as energy for heating and cooling of residences and small commercial buildings is a growing worldwide concern. Cooling, Heating, and Power (CHP) is a promising technology for increased energy efficiency through the use of distributed electric and thermal energy delivery systems at end-user sites. Micro-cooling, heating, and power (micro-CHP) is decentralized electricity generation coupled with thermally activated components for residential and small commercial applications. Micro-CHP systems, typically designated as less than thirty kilowatts electric, can simultaneously produce heat, cooling effects, and electrical power. The number of combinations of components and parameters in a micro-CHP system are too many to be designed through experimental work alone. Therefore, theoretical models for different micro-CHP components and complete micro-CHP systems are needed to facilitate the design of these systems and to study their performance. This paper presents a model for micro-CHP systems for residential and small commercial applications. Some of the results that can be obtained using the developed model include: the cost per month of operation of using micro-CHP versus conventional technologies, the amount of fuel per month required to run micro-CHP systems, the overall efficiency of micro-CHP systems, etc. Also, this model allows to evaluate micro-CHP systems using different type of fuels such as: natural gas, propane, biofuels, etc, to determine the fuel that provides the best performance.
A Technique to Characterize Rate-Dependent Failure Envelopes in Surface Mount Assemblies
Authors: Varghese J. , Dasgupta A.
Published: April 2008

This paper characterizes the fatigue failure envelopes for solder damage in Printed Wiring Assemblies (PWAs) subjected to dynamic loading. An empirical, rate-dependent, power-law durability model, motivated by mechanistic considerations, is used to characterize the failure envelopes in terms of PWA flexural strain and strain rate. Explicit nonlinear finite element analysis (FEA) is used to make the damage constants independent of the specimen geometry and characterize the durability in terms of the ratio of solder plastic strain to its failure strain. A case study, using a simple PWA specimen containing a single area array component, is presented to demonstrate the proposed approach.
Improving Learning Outcomes of a Course in Instrumentation
Authors: Rathod Mulchand S.
Published: April 2008

Many engineering educators have become sensitive to the improved outcome of student learning in their classes. This has been true for our colleagues in the colleges of education where teachers are prepared for the teaching pedagogy. In many cultures as well as ours, the teaching profession is upheld as a noble profession. At the same time, the university faculty are held with high esteem by the general population. Faculty teaching in undergraduate programs have begun to address the pedagogy of learning in recent years. There is a national trend towards helping in this phenomenon. Besides funding initiatives by organizations such as the National, Science Foundation, engineering professional societies continue to organize forums and awards to recognize and promote teaching and learning of engineering subject matter. This paper would address an experiment in improved learning by students of a subject matter that is laboratory based. The instrumentation course is a required course for engineering technology (ET) students pursuing mechanical, manufacturing/industrial, product design, and electromechanical majors at Wayne State University (WSU). Most engineering technology students are more comfortable with experimental techniques than with derivation of equations and formulas. Setting for this course was a multi-media distance learning classroom and a set of lab experiments. The teacher had an important task of not just covering the material, but to increase student interest to optimize their learning. Although all the teaching materials were prepared for presentation in power point, after discussion with the class it was decided to make the learning process different from the traditional teaching. The class was divided in three groups and each group was given a reading assignment covering one third of the material to be covered in each session. Each team met on a regular basis going over its assignment and breaking up the tasks for each team member to lead presentation and discussion for the whole class. Learning objectives addressed in the course included team work, effective communication, system design and testing, continued student participation, effective learning for long term retention besides the contents of the subject matter. Overall, student really felt they were learning a lot and new things. This paper summarizes a very positive experience of students and faculty dealing with learning pedagogy.
A Homogenization Scheme for Nonlinear Viscoelastic Behaviors of Particulate Reinforced Composites
Authors: Kim Jeong Sik , Muliana Anastasia , Khan Kamran
Published: April 2008

The present study introduces a micromechanical model for predicting nonlinear viscoelastic responses of composite systems reinforced with solid spherical micro particles. The composite microstructures are simplified with uniformly distributed cubic particles over an infinite medium. The representative volume element (RVE) consists of a single particle embedded in the cubic matrix. One eighth unit-cell model with four particle and polymer subcells is generated. The solid spherical particle is modeled as linear elastic, while the polymer follows nonlinear viscoelastic material responses. The homogenized micromechanical relation is developed in terms of the average strains and stresses and satisfies traction continuity and displacement compatibility at the subcells' interfaces. The micromechanical model provides three-dimensional (3D) effective properties of homogeneous materials, while recognizing important micro-structural aspects and parameters of the heterogeneous medium. The micromechanical formulation is generalized to include an explicit time-scale for modeling time-dependent behavior and is designed to be compatible with general displacement based finite element (FE) analyses. Due to the nonlinear and time-dependent response in the polymeric matrix, the linearized micromechanical relations will often deviate from the nonlinear constitutive equations. Thus, the stress-strain correction scheme is formulated to satisfy both micromechanical and nonlinear constitutive relations. Experimental data and analytical models available in the literature are used to verify the capability of the above micromechanical model in predicting the overall nonlinear behaviors. Comparisons with detail unit-cell FE model are also presented.
The Effect of Dissolved and Entrained Gases on Flow Through a Process Control Valve
Authors: Riveland Marc L.
Published: April 2008

Process fluids flowing through control valves undergo thermodynamic throttling that induces a decrease in the mean fluid pressure. Substantial pressure reduction can result in the formation of a stable, secondary compressible phase within the liquid continuum. Without distinction this phenomenon is generally referred to as flashing, and may have a significant impact on the magnitude of flow through the control valve. The formation of the compressible phase may be the result of two different underlying sources: vaporization, wherein a small portion of the liquid undergoes a phase change from liquid to vapor; or out-gassing, wherein dissolved or entrained gases come out of solution. The industry standard equations used to determine an appropriate process control valve size include an adjustment for the effect of vaporization. Implicit in this method is the assumption that the fluid is vaporizing according to a corresponding states model. This paper distinguishes between the two compressible phase forming mechanisms and derives a comparable methodology that is appropriate to the out-gassing process. A revised prediction of the choked or limiting flow pressure differential is presented and density corrections are incorporated into the industry standard methodology.
Design of a Variable Conductance Heat Pipe for a Photonic Component
Authors: Cleary Martin , Grimes Ronan , Hodes Marc , North Mark T.
Published: April 2008

Thermoelectric modules (TEMs) are widely used to provide precision temperature control in photonic applications. A problem with TEMs, however, is that when they are subjected to a large range of ambient temperatures the power of consumption of TEMs can be excessive. This study proposes the replacement of the TEM based approach with a variable conductance heat pipe (VCHP). VCHPs offer reduced power consumption compared to TEMs whilst still offering precision temperature control of the device. Using existing theory this paper investigates the use of wicked and non-wicked reservoirs and the effect of reservoir volume on the sensitivity of the evaporator temperature to changes in both ambient temperature and heat load for both heated and unheated reservoirs. The paper also investigates the effectiveness of the use of a steel collar between the reservoir and the condenser in reducing the heat loss to ambient. The paper concludes that passive control of evaporator temperature can be achieved for the case of a variable heat load, but not for the case of a variable ambient temperature, that evaporator temperature is more sensitive to reservoir temperature for a wicked than a non-wicked reservoir, and that with the use of a steel collar between the reservoir and the condenser a VCHP provides a significant power consumption reduction when compared to a TEM.
The Development of a Terrain Severity Measurement System
Authors: Dembski Nicholas , Rizzoni Giorgio , Soliman Ahmed , Malmedahl Grant , Disaro' Lorenzo
Published: April 2008

The measurement of road profiles is useful for many purposes, from the determination of road conditions, to terrain mapping, and so on. There are systems in which the profile measurement is taken utilizing of non-contact laser scanning technologies. In such systems, the measurements are relative and are referred to a moving reference frame. These measurements require the knowledge of the moving reference frame, which can be extracted from inertial measurements. Typically, each of these sensors is provided with an accelerometer, and the vertical distance travelled by each sensor is calculated by integrating this accelerometer signal twice. In this work, the errors associated with the measurement of the terrain profile are analyzed in order to identify the main causes of measurement error as well as the overall accuracy of the terrain severity measurement system.
Non-Continuum Mass Transport in Solid Oxide Fuel Cell Anodes by the Lattice Boltzmann Method
Authors: Joshi Abhijit S. , Grew Kyle N. , Peracchio Aldo A. , Chiu Wilson K. S.
Published: April 2008

At the length scales and temperatures present in a typical SOFC, both continuum and non-continuum transport of fuel and product species are important. Fuel and product transport through a representative, microscopic, two-dimensional (2D) channel present in the porous anode of a solid oxide fuel cell (SOFC) is examined. Non-continuum transport, which can be broken down into the slip, transition and free molecular regimes, is modeled for a ternary system (H2, H2O, and N2) using the Stefan-Maxwell (SM) model, the Dusty-Gas (DG) model and the lattice Boltzmann method (LBM). Results obtained show that the LBM can provide a suitable framework for continuum as well as non-continuum transport in a SOFC up to the transition regime. LBM can also handle complex porous geometries, which are currently intractable by other modeling approaches, e.g. SM and DG. However, further work is required to extend the range of application of the present LBM to the free-molecular flow regime.
A Conductivity Based Microfluidic Flow Sensor
Authors: Dutta Prashanta
Published: April 2008

A conductivity based on-chip flow sensor is introduced to measure the velocity of liquid-gas interface in microchannels for lab-on-a-chip applications. This sensor is used to evaluate the performance of planar electrokinetic micropumps formed on hybrid poly-di-methyl-siloxane (PDMS)-glass platform. In this study, the micropump thickness is varied between 3.5 and 10 microns, and the externally applied electric field of electrokinetic pump is ranged from 100 V/mm to 200 V/mm. For all channel dimensions and for all electric fields, fairly repeatable flow results are obtained from the speed of liquid-gas interface. Flow results obtained from this interface tracking method are compared to those of other existing flow measuring technique. The maximum error of this micro flow sensor is less than 5%, even in ultra low flow velocity.
Two-Dimensional Stress Analysis of Adhesive Butt Joints Filled With Elastic Circular Fillers in an Adhesive Subjected to Static Tensile Loadings
Authors: Sawa Toshiyuki , Akita Yosuke
Published: April 2008

This paper deals with a two-dimensional stress analysis of adhesive butt joints filled with elastic circular fillers in an adhesive subjected to an external tensile load. Similar adherends and an adhesive bond are replaced with finite strips in the analyses. Stress distributions in adhesive joints are analyzed exactly using the two-dimensional theory of elasticity. The effects of stiffness and number of fillers on the interfaces stress distributions and around the fillers with higher Young's modulus are shown in the numerical computations. It was seen that as an amount of number of fillers increased, the strength of joints was able to be more improved than that of the joints without a filler. For verification, experiments were carried out to measure the strains. The analytical results are in fairly good agreements with the experimental ones. In addition, for verification of the interface stress distribution, the analytical results are also compared with those obtained from the two-dimensional and three-dimensional FEM calculations. Fairly good agreements are seen between the analytical and the two-dimensional FEM results. However, the result from the present analysis is different from that of the three-dimensional FEM.
Swing Reduction of Ropeway Carriers by Means of Two-Ball Rolling Type Damping Equipment
Authors: Sato H. , Chishima M.
Published: April 2008

To enhance transport safety and reliability of ropeway systems, it is essential to reduce the swing of the carriers that results from wind, etc. As a means to lessen the swing of the carriers, we will propose damping equipment that uses two balls as the movable mass. We will also discuss the method for adjusting the design parameters for this equipment. Based on a simulation, we will determine the effect of this equipment. In addition, we will refer to the results of a model test to verify the effect of this damping equipment.
Design and Modeling of the Fowler Flap With Adaptive Elements
Authors: Kozlov Oleksandr
Published: April 2008

This paper describes the process of the designing of the Fowler flap with adaptive elements. Modern passenger and transport aircraft use high lift devices for take off and landing. Of great importance for the creation of high lift during take off and landing is the shape and size of the gap between wing and extended Fowler flap. To improve the deformation behaviour of the leading edge of this flap, and to improve the geometry of the gap, it was decided to use shape memory alloy (SMA) actuators in the flap structure. First, the complex finite element model of the passive flap was created and then this model was extended with active elements, which are modelling the SMA actuators. As a result, the complex finite element model of the active flap was obtained. This modelling was done using software MATLAB and a finite element model was created using software ANSYS. The main result of this work is that with help of SMA actuators integrated in the flap it was possible to influence and improve the geometry of the gap between the wing and the extended flap, resulting in the aerodynamic efficiency of this flap being increased.
Superlattice Analysis for Tailored Thermal Transport Characteristics
Authors: Landry E. S. , McGaughey A. J. H. , Hussein M. I.
Published: April 2008

Molecular dynamics simulations and the Green-Kubo method are used to predict the thermal conductivity of binary Lennard-Jones superlattices and alloys. The superlattice thermal conductivity trends are in agreement with those obtained through the direct method, verifying that the Green-Kubo method can be used to examine thermal transport in heterostructures. The simulation temperature and the constituent species are fixed while the superlattice period structure is varied with the goals of (i) minimizing the cross-plane thermal conductivity and (ii) maximizing the ratio of in-plane to cross-plane thermal conductivities. The superlattice thermal conductivity in both the cross-plane and in-plane directions is found to be greater than the corresponding alloy value and less than the value predicted from continuum theory. The anisotropy of the thermal conductivity tensor is found to be at a maximum for a superlattice with a uniform layer thickness. Lattice dynamics calculations are used to investigate the role of optical phonons in the thermal transport.
3D Parametric Design: A Means for Lifting Standardisation to a Higher Level
Authors: Dierneder Stefan , Scheidl Rudolf
Published: April 2008

3D parametric design functionality of modern CAD systems offers the possibility to create some higher level standards for components or systems. Instead of picking out several of the many variants of a certain product class and declaring them standard, a family of variants is created which can be adapted to different requirements by adjusting a few parameters. The standard is represented by design rules especially by the relations between the dependent and the lead parameters. The challenging work is to create these relations, called the parameter model.
A SISO, Multi-Analyte Sensor Based on a Coupled Microresonator Array
Authors: Rhoads Jeffrey F. , DeMartini Barry E. , Shaw Steven W. , Turner Kimberly L.
Published: April 2008

This work details a preliminary analytical and experimental investigation of a new class of resonant, single input - single output (SISO) microsensors, which are capable of detecting multiple analytes. The key feature of these sensors is that they exploit vibration localization in a set of N microbeams, coupled indirectly through a common shuttle mass, to allow for the detection of N distinct resonance shifts (induced by the presence of up to N distinct analytes) using solely the shuttle mass' response. The work includes a brief overview of the proposed sensor design, the formulation and subsequent analysis of a representative lumped-mass model of the sensor, and details of a recently-completed simulated mass detection experiment, which verified the feasibility of the proposed sensor design. Where appropriate, practical design issues, essential to sensor development, are described.
Property Variation Within the Thin-Walled Magnesium Alloy Components
Authors: Subramanian Saravanan , Cooper Ronald , Blanchard Patrick , Houstan Dan , Warrior Nicholas , Chen Xiaoming
Published: April 2008

Utilization of magnesium alloys within the field of vehicle design offers substantial opportunity for mass reduction. This has resulted in a wide range of automotive applications. More recently, the scope of application has been extended to include components that are considered crash critical. However, the magnesium die casting process is widely reported as producing parts that exhibit large local variation in part properties. Hence, this introduces the technical challenge of how to design effectively based upon these constraints. In order to better understand this phenomenon, two large size thin walled production components were examined. Tensile test coupons were extracted from multiple locations. Micro and macro level investigations were also conducted in an effort to identify the root cause of property variation. This paper discusses the influences of porosity on mechanical property variation, specifically tensile strain to failure. Further discussion is also presented, detailing a proposed empirical model, for the prediction of local strain to failure.
Structural Health Assessment After an Impact
Authors: Martinez-Flores Rene , Haldar Achintya , Katkhuda Hasan
Published: April 2008

An innovative technique to assess structural health just after subjected to impulsive loadings (blasts, explosions, etc.) underdevelopment at the University of Arizona was experimentally verified and is presented in this paper. The authors called it the Generalized Iterative Least Square Extended Kalman Filter with Unknown Input (GILS-EKF-UI) method. The system is represented by finite elements and a Kalman filter-based system identification (SI) technique is used to identify the system. Some of the major characteristics of the method are that it does not require information on input excitation and can identify a system with limited noise-contaminated response information measured at few node points. To implement the Kalman-filter based algorithm, the information on the input excitation and the initial state vector must be available. The authors proposed a two-stage approach. In the first stage, based on the limited measured response information available at the locations of the sensors, a substructure is identified. After the completion of the first stage, the input excitation information that caused the responses and the stiffness of all the elements in the substructure can be evaluated. Then, in stage 2, the Kalman-filter based algorithm is used to identify the whole structure. The experimental verification of the method is emphasized in this paper.