bluuebunny/crossref_metadata_2025 huggingface dataset:
A Roadmap to Successful Implementation of Modular Manufacturing Equipment
Authors: Pattantyus Imre Andrew
Published: April 2008

The challenges of implementing modular systems go beyond basic economic models and overcoming technical hurdles. Industry personnel are “tooled” for traditional equipment; it’s what people are trained to support and there is a huge installed base. That kind of inertia is hard to overcome. Change must begin at the top. Executives and financial managers must first rethink the way they measure the effectiveness of their capital investments. They must then create a new environment for justification and implementation that does not exclude modular systems. Both the organization structure and the supportive systems must be “retooled” to properly support the modular system and assure success. Efficient modular systems will not emerge quickly or naturally from the research lab or the plant floor. Cooperation and teamwork, supported by the necessary management and measurement systems, will be needed to produce the best result. After the initial deployment, much work still remains to produce the manufacturing system that has the necessary refinements to be truly effective. Management must not only commit to and support the modular initiative, but must insist on success every step of the way.
New Dielectric Polymer Film Capacitors for Pulse Power Applications
Authors: Munshi M. Zafar A. , Ibrahim Ayad
Published: April 2008

High voltage pulse power technologies utilized by the Department of Defense applications such as armor/anti-armor, electromagnetic/electrothermal guns, lasers, high power microwave weapons, etc. are usually satisfied today by film capacitor technologies. Commercial applications extend to a.c. motors, lighting, and automotive and implantable and portable defibrillators, among others. Film capacitors based on polypropylene (PP) and polyester (PET) have the ability to operate at very high voltages and with good reliability. They also offer high breakdown voltages, inherent low losses, excellent frequency response, low dissipation factor (DF), and good self-healing abilities. Unlike most other circuit components, existing capacitor technologies now present a barrier to achieving significant packaging (size and weight) reductions and struggling to meet market-driven performance requirements. The energy density of commercial film capacitors is less than 1 J/cc. Polyvinylidene fluoride (PVDF) has a much higher dielectric constant (12) than commercial films such as polypropylene (PP) (2.5) and a practical energy density of about 2.4 J/cc. However, it has a number of drawbacks including non-linearity of the dielectric constant with voltage, very poor insulation resistance, poor clearing or self-healing ability, poor dissipation factor (DF), higher leakage currents, relatively lower breakdown voltages and is very costly. In recent SBIR Programs, Lithium Power Technologies demonstrated that by combining PP with PVDF in a polymer blend, one could obtain a material with a very high dielectric constant as well as other excellent electrical properties. Electrical data on biaxial oriented thin films and capacitors demonstrated very high breakdown voltages of 700 V/μm to over 1050 V/μm. In contrast, PP films and capacitors resulted in breakdown voltages of 220 to 560 V/±m. Preliminary energy density for the new dielectric capacitor was about 12 J/cc compared to less than 0.5 J/cc for PP. The frequency response data with respect to the DF demonstrated an almost negligible loss in dielectric activity at high frequencies. The new polymer dielectric offers a number of key advantages, including improved performance and lower cost per unit of energy. The technology is a promising candidate for the development of a higher energy density, high voltage metallized film capacitor for a large number of applications including, defense, aerospace, defibrillator, automotive, and electric power generation. This paper will discuss the development of this new technology and commercial potential.
Effectiveness of the Cryogenic Treatment of Tungsten Carbide Inserts on Tool Wear When in Full Production Operations
Authors: Arner Kenneth A. , Agosti Christopher D. , Roth John T.
Published: April 2008

As a cutting tool wears, the quality of the parts being produced by the tool are reduced. Therefore, it is important to change cutting tools whenever the wear on the tool begins to cause unacceptable or out-of-specification parts. However, frequent replacement of tooling is not only expensive, it also results in a loss of production throughput. Therefore, in order to lower tooling costs and increase production rates, it is vital to extend cutting tool life. Thus, this research focuses on establishing the effect that cryogenically treating carbide inserts has on the overall tool life when the tools are operating in production. To validate the effectiveness, multiple treated and untreated cutting tools for five styles of inserts are examined. The cutters are tested in production lines that are fabricating parts for an industrial partner where the only process variable that is changed is the cryogenic treatment of the tooling. For the five insert styles tested, each style provided very consistent changes in overall tool life. However, the amount of improvement was dependent on the tool style. One style was found to have its life doubled, whereas, another style had its life decreased. Possible causes for this difference in effectiveness of the treatment are presented, along with a discussion concerning the actual costs savings that the treatment represents for the industrial partner.
A Feedback Controlled Carbon Nanotube Based NEMS Device: Concept and Modeling
Authors: Ke Changhong , Espinosa Horacio D.
Published: April 2008

A switchable carbon nanotube based nano-electromechanical systems (NEMS) device with close-loop feedback is examined. The device is made of a conductive multi-walled carbon nanotube (MWNT) placed as a cantilever over a micro-fabricated step. A bottom electrode, power supply and a resistor are also parts of the device circuit. The pull-in/pull-out and tunneling characteristics of the device are investigated by means of an electro-mechanical analysis. The model includes the concentration of electrical charge, at the end of the nanocantilever, and the van der Waals force. Finite kinematics accounting for large deformations of the cantilever is also included in the modeling. The result shows that the device has two well-defined stable equilibrium positions as a result of the tunneling and the incorporation of a feedback resistor to the circuit. The potential applications of the device include NEMS switches, random-access memory (RAM) elements, logic devices and electron-counters.
Slow Lamb Wave Generation and Reception With a Gold-on-PVDF Interdigitated PVDF Transducer
Authors: Lloyd George M. , Hua Gu , Wang Ming L.
Published: April 2008

Interdigitated surface and guided-wave transducers have only recently received attention as possible tools for non-destructive testing. This may be due in part to the increasing attention being paid to piezoelectric polymers as practical transduction materials for structural sensing and actuation. However, much remains to be done to produce a rugged, monolithic device oriented toward these sorts of applications, to characterize and optimize its passive and active response, to develop excitation strategies and signal processing algorithms that in tandem can be employed for arrayed structure monitoring applications. In this paper we confine ourselves to the first two topics and report on the development and proof-of-principle testing of a monolithic interdigitated polyvinyldine fluoride (PVDF) transducer. Specifically, we report on the design and response of an interdigitated transducer with relatively large finger spacings. The finger spacing yield measureable responses in the asymptotically slow single-mode region of Lamb wave dispersion behavior for frequency-thickness products which may be useful for nondestructive testing of many mechanical and civil structural systems.
Fracture Size Effect in Ultrananocrystalline Diamond: Weibull Theory Applicability
Authors: Peng B. , Espinosa H. D.
Published: April 2008

Strength characterization and analysis of fracture size effect in ultrananocrystalline diamond (UNCD) thin films are presented. In this work, we report the changes in mechanical properties of UNCD by the addition of nitrogen gas to the Ar/CH4 microwave plasma. Both undoped and doped UNCD films show a decrease in fracture strength with an increase in specimen size. The strength data, obtained by using the membrane deflection experiment (MDE) developed at Nothwestern University, is interpreted using Weibull statistics. The capability of the theory is examined in conjunction with detailed fractographic analysis. The Weibull parameters are estimated by maximum likelihood estimation (MLE) based on 480 tests when the specimen volume varies from 500 to 1600 cubic microns. The results show that one can predict the fracture strength of a component possessing any arbitrary volume to within ±3% from the fracture strength identified from the tested specimens. The failure mode of UNCD is suggested to be volume controlled.
Architectural Effect on ANFIS for Machine Condition Assessment
Authors: Sheng Shuangwen , Gao Robert X.
Published: April 2008

This paper investigates the architectural effect on adaptive neuro-fuzzy inference system (ANFIS) for machine condition assessment. The study was motivated by ANFIS’s limitation in adapting its architecture to map the modeled input output relationship. Based on the grid input space partition method, two elements in defining an ANFIS architecture were studied: the type of the membership function (MF) and the MF number assigned to ANFIS inputs. A new modeling accuracy index was introduced to address the limitation of the traditional root mean square error (RMSE) in describing the effect of the MF type. The analysis showed that wide core membership functions enabled a smaller RMSE than narrow core membership functions for machine defect severity classification. It is further shown that selecting appropriate MF number is critical to ensuring accuracy of ANFIS, considering the overfitting problem. These results were experimentally investigated on a bearing test bed, where defect severity classification and dynamic load estimation were evaluated. The experiments agreed well with the theoretical analysis.
Viscoelasticity of Growing Actin Networks
Authors: Chaudhuri Ovijit , Parekh Sapun H. , Liu Allen , Fletcher Daniel A.
Published: April 2008

Actin self-assembles to form filaments that can organize into dendritic networks through interactions with various actin binding proteins. Growing actin filament networks produce significant mechanical forces that play a key role in many dynamic cellular processes such as motility, cytokinesis, and phagocytosis. We investigated the mechanical properties of growing actin networks with atomic force microscopy and found the actin networks to behave as viscoelastic solids.
The Measure of the Machine: How Exposure to Current Technology Can Upgrade a Student’s Education
Authors: Conger Robert , Blum Amanda , Erickson Paul A.
Published: April 2008

Over the past decade there has been a distinct trend toward implementing computer technology in education. The advent of affordable, student accessible computing power has allowed engineering curricula to follow the trends of computer technology in the engineering workplace. The developments in hardware and software, combined with the explosive entrance of the Internet, have allowed design projects to evolve into elaborate and imaginative endeavors. The enhanced speed at which projects can now be completed allows students the opportunity to undertake tasks of greater magnitude, while the advanced tools now available permit students to solve more sophisticated and lifelike problems. The examination of a senior-level design course, in which students must design and build a maze-solving robot, serves to highlight the educational benefits that stand to be gained through the judicious application of technology. The evolutionary history of this design course demonstrates the remarkable progress that computer technology has allowed in educational settings.
Receptance Coupling Study of Tool-Length Dependent Dynamic Absorber Effect
Authors: Burns Timothy J. , Schmitz Tony L.
Published: April 2008

The chatter-free material removal rate during high-speed machining of aluminum using long, slender endmills is limited by the cutting system dynamics, which changes with the tool length. Traditional stability-lobe diagrams that predict the maximum allowable chip width for a given spindle speed are determined using the tool point frequency response function. A brief review is given of a combined analytical and experimental method that uses receptance coupling substructure analysis (RCSA) for the rapid prediction of the tool-point frequency response as the tool length is varied. The basic idea of the method is to combine the measured direct displacement vs. force receptance (i.e., frequency response) at the free end of the spindle-holder system with analytical expressions for the tool receptances. The method is then used to provide an explanation for the dynamic absorber effect that has been observed in the context of tool-length tuning.
A Review of Wave Rotor Technology and Its Applications
Authors: Akbari Pezhman , Nalim Razi , Mu¨ller Norbert
Published: April 2008

The objective of this paper is to provide a succinct review of past and current research in developing wave rotor technology. This technology has shown unique capabilities to enhance the performance and operating characteristics of a variety of engines and machinery utilizing thermodynamic cycles. Although there have been numerous efforts in the past dealing with this novel concept, this technology is not yet widely used and barely known to engineers. Here, an attempt is made to summarize both the previously reported work in the literature and ongoing efforts around the world. The paper covers a wide range of wave rotor applications including the early attempts to use wave rotors, its successful commercialization as supercharges for car engines, research and development for gas turbine topping, and other developments. The review also pays close attention to more recent efforts: utilization of such devices in pressure-gain combustors, ultra-micro gas turbines, and water refrigeration systems, highlighting possible further efforts on this topic. Observations and lessons learnt from experimental studies, numerical simulations, analytical approaches, and other design and analysis tools are presented.
Hydraulic Components Contribution to Total Power Losses and Acceleration of an Open Loop System With Long Hose
Authors: Westman Michael , Isaksson Ove
Published: April 2008

This paper is concerned with forest logging machinery. A great deal of final felling in cut-to-length method done by harvester, which fells, delimbs and cuts the trees to pre-selected lengths. Two important criteria of a harvester head are that it has to be energy efficient and it has to be as fast as possible. To minimize losses in hydraulic systems the main demand is to reduce pressure losses in high power valves and outer components as much as possible. Each orifice in the flow path results in power losses. This work is an experimental study on power losses and acceleration of hydraulic motor in a system with long hoses. Main hydraulic components included are hydraulic pump, cartridge valve, pipe line and hydraulic motor. The results show that pre-activating the pump improves the system speed. To reduce losses, optimization of valve block, cartridge valve orifices are needed. Accumulators are favourable if combined with high stand-by pressure.
Vibratory and Acoustic Behavior of Orchestral Bell Plates
Authors: Dai Liming , Caswell Daryl J. , Ma Yong
Published: April 2008

This investigation is on design and assessment of the vibratory and acoustical behavior of a bell plate in imitating the sound of a bell to be used in a classical orchestral piece. In the investigation, the characteristics of the bell plate developed are compared to the real bell and a more traditional style of thin bell plate in four areas: the determination of the fundamental frequency, the spacing of the frequency partials, the relative strength of the partials and the decay envelope of the sound. The goal of this research is to gain further control over the four key components of the bell sound by capitalizing on beneficial constraints imposed on a metal plate by its material and three-dimensional geometry. The investigation led to the discovery of a small window of dimension that suppresses the undesirable vibrational modes and components of acoustic response of the freely suspended metal plate while at the same time emphasizes the bell-like qualities of the sound. The large aspect ratio of the plates leads to the use of the classical Rayleigh-Ritz method with beam functions to design the dimensions of the bell plates. A finite element method is employed to analyze the frequencies and vibrational modes of the bell plates. Numerous experiments are also carried out with steel plates of various geometrical dimensions for identifying the vibratory and acoustical behavior of the bell and plates and for evaluating the sound qualities of the bell plates to be developed. The effects of the methods of hanging the plates are analyzed and the hanging locations that provide the least effects to the vibrations and vibration modes of the bell plates are also determined. The experimental of the investigation measurements compare well with the numerical results obtained from the mathematical model and from the FEM model. An instrumental bell plate covering a full chromatic range from D3 to E4 is developed on the basis of the findings of the investigation. The instrument provides the desired bell sound of high strength, prominent smoothness and low decay rate over a sufficiently long decay period.
Optimal Tolerance Allocation for a Sliding Vane Compressor
Authors: Huang Yuan Mao , Shiau Ching-Shin
Published: April 2008

An optimization model has been built with consideration of required reliability, minimum machining cost and quality loss. The normal and the lognormal distributions of the tolerances that depend on the production types of components are used in the reliability model. Cost-tolerance data obtained from Bjo̸rke is used to calculate the machining cost. The asymmetric quadratic quality loss model is used to calculate the quality loss caused by the deviation and the mean-shift of distributions. The tolerance allocation of a sliding vane compressor is optimized for reliability, cost and quality loss, and the optimum tolerances of components are recommended. The results show that high accuracies of the slot length, the vane thickness and the slot width are required. Hence, their tolerances are smaller than other components. If the correlation coefficient of the bottom cover plate and the top cover plate and the correlation coefficient of the front cover plate and the rear cover plate are equal, the effect of correlation coefficients on the cost is insignificant.
Dean Instability in Non-Newtonian Fluids
Authors: Fellouah H. , Castelain C. , El Moctar A. Ould , Peerhossaini H.
Published: April 2008

We present a numerical study of Dean instability in non-Newtonian fluids in a laminar 180° curved-channel flow of rectangular cross section. A methodology based on the Papanastasiou model [1] was developed to take into account Bingham-type rheological behavior. After validation of the numerical methodology, simulations were carried out (using Fluent CFD code) for Newtonian and non-Newtonian fluids in curved channels of square and rectangular cross section and of large aspect and curvature ratios. A criterion based on the axial velocity gradient was defined to detect the instability threshold. This criterion is used to optimize the grid geometry. The effects of curvature and aspect ratios on the instability are studied for all fluids, Newtonian and non-Newtonian. In particular, we show that the critical value of the Dean number decreases with increasing duct curvature ratio. The variation of the critical Dean number with duct aspect ratio is less regular. The results are compared with those for Newtonian fluids to emphasize the effect of the power-law index and the Bingham number. The onset of Dean instability is delayed with increasing power-law index. The same delay is observed in Bingham fluids when the Bingham number is increased.
Considerations on Flow Classification Criteria
Authors: Thompson Roney L. , Souza Mendes Paulo R.
Published: April 2008

Flow classification is still an open problem in continuum mechanics. Among the presently available flow criteria, there are two that have an outstanding importance, namely, Tanner and Huilgol (1975) and Astrarita (1979). While the former is restricted to MWCSH, the latter was shown by Huilgol (1980) to fail for certain 3-D kinematics. In the present work we suggest a generalization of Tanner-Huilgol’s classification to encompass motions other then MWCSH. We also establish both the range of applicability of Astarita’s criterion and the relationship between the two criteria. The application to the Doubly Superposed Viscometric Flow of these two criteria and also of the one recently proposed by Thompson and Souza Mendes (2004), shows that it is advantageous to adopt the persistence-of-straining parameter proposed by Thompson and Souza Mendes (2004).
Thawing of Bio-Compounds in Frozen Microplates
Authors: Lund Kurt O.
Published: April 2008

Libraries of pharmaceutical compounds are typically stored in solvents and frozen in microplates, which consist of 96 or more wells of about 1 ml, each well capable of retaining a distinct compound. In current practice, when the microplates are removed from the storage freezer, the entire microplate with all wells is allowed to thaw in ambient air or water bath, thus permitting extraction of liquid solution from the wells. This results in the thawing of all compounds, even if only one or several were selected for retrieval from that microplate. This process is inefficient as well as damaging to the nonselected compounds that are refrozen. For the present work we consider thawing in an individual well, independent of all other wells in the microplate, which is surrounded by a metallic sleeve; this effects time-dependent, radial heat transfer from the sleeve to the frozen compound. Partial differential equations are formulated to describe the phase-change thawing process. Regimes of the process are identified as solid-sensible, latent, and liquid-sensible. Semi-analytical solutions are obtained which indicate rapid thawing for a specified, safe sleeve temperature. The thermal system is investigated experimentally for a well containing frozen DMSO. A typical sleeve in thermal contact with the well is fitted with a heater and thermal sensor, and digital feedback control is achieved using a PID algorithm in conjunction with a P/C computer and A/D conversion. Experimental results are found to agree with theory for the conditions tested. It is concluded that the use of thermal sleeves greatly enhances the rate of thawing of compounds in microplates, and that individual wells can be safely and gently thawed independent of other wells in the plate.
Mechanical Simulation for the Robust Design of RF-MEMS Switches
Authors: Qian Zhengfang , Tomase Joe , Lian Keryn
Published: April 2008

Mechanical models and analytical solutions have been developed for the RF-MEMS switches under electrical actuation, forced vibration, and shock/impact loading conditions. The basic structure based on cantilever beam switches has been used as model system to illustrate the static and dynamic responses. Analytical solutions for folded beam structures have been furthermore derived and combined with the model system as an effective beam. These characterizations are used to define reliability and performance criteria for the robust design, performance evaluation, and rapid reliability assessment of RF-MEMS switch devices. It was found that the actuation voltage depends on several key design parameters and material properties. Actual acceleration to tiny switch structure is found only one portion of applied acceleration under shock/impact conditions, depending on system stiffness.
Modal Analysis of an Ultra-Flexible, Self-Rigidizing Toroidal Satellite Component
Authors: Ruggiero Eric J. , Tarazaga Pablo A. , Inman Daniel J.
Published: April 2008

Over the past few years, much research has been performed on understanding the dynamics of an ultra-large, flexible toroidal satellite component subject to an internal pressure. However, the harsh environment of space is no place for inflated, membrane-like materials for fear of micro meteorite bombardment and subsequent puncture. Addressing this issue directly, United Applied Technologies (Huntsville, AL) has developed a novel, thin film casting approach to create a self-rigidizing torus. Once inflated, the torus structure is able to support its own shape, thus eliminating the need for any internal pressure. The self-rigidizing torus is extremely flexible, much more so than its pressurized predecessors. Such compliancy makes modal testing extremely difficult. However, through careful application of traditional modal testing techniques (shaker and accelerometer testing), the damped natural frequencies and mode shapes of the self-rigidizing torus can be discerned in the frequencies and mode shapes of the self-rigidizing torus can be discerned in the frequency bandwidth of interest, 1–12 Hz.
Adiabatic Temperature Rise and Heat Release Rates for Concrete With Application to a Large-Scale Multi-Step Grouting Process
Authors: O’Brien J. E. , Johnson R. W. , Siahpush A. S. , Stoots C. M.
Published: April 2008

An experimental study has been performed in order to determine the thermal characteristics of a specific concrete formula to be used for a large-scale tank-grouting project. The experimental results were incorporated into finite-element numerical simulations aimed at predicting local concrete temperatures over the duration of multiple concrete pours. The pours will occur in a stepwise fashion whereby each additional concrete layer will be added while the previous layers are still undergoing the curing process. The experimental portion of the project included a series of laboratory-scale tests aimed at determining the time-dependent adiabatic temperature rise of several concrete samples and the corresponding time-dependent concrete internal heating rates. Results of the experiments were incorporated directly into the finite-element thermal model. The finite-element simulations indicated that the pour schedule did not have a strong influence on the maximum temperature in the concrete.
Shape Memory Alloy Tuned Vibration Absorbers: Robustness Analysis
Authors: Elahinia Mohammad H. , Koo Jeong-Hoi , Ahmadian Mehdi
Published: April 2008

A conventional passive tuned vibration absorber (TVA) is effective when it is precisely tuned to the frequency of a vibration mode; otherwise, it may amplify the vibrations of the primary system. In many applications, the frequency often changes over time. For example, adding or subtracting external mass on the existing primary system results in changes in the system’s natural frequency. The frequency changes of the primary system can significantly degrade the performance of TVA. To cope with this problem, many alternative TVAs (such as semiactive, adaptive, and active TVAs) have been studied. As another alternative, this paper investigates the use of Shape Memory Alloys (SMAs) in passive TVAs in order to improve the robustness of the TVAs subject to mass change in the primary system. The proposed SMA-TVA employs SMA wires, which exhibit variable stiffness, as the spring element of the TVA. This allows us to tune effective stiffness of the TVA to adapt to the changes in the primary system’s natural frequency. The stimulation model, presented in this paper, contains the dynamics of the TVA along with the SMA wire model that includes phase transformation, heat transfer, and the constitutive relations. The robustness analysis is then performed on both the SMA-TVA and the equivalent passive TVA. For our robustness analysis, the mass of the primary system is varied by 30% of its nominal mass. The simulation results show that the SMA-TVA is more robust than the equivalent passive TVA in reducing peak vibrations in the primary system subject to change of its mass.
Compact Analytical Models of Effective Thermal Conductivity of Rough Spheroid Packed Beds
Authors: Bahrami M. , Yovanovich M. M. , Culham J. R.
Published: April 2008

New compact analytical models for predicting the effective thermal conductivity of regularly packed beds of rough spheres immersed in a stagnant gas are developed. Existing models do not consider either the influence of the spheres roughness or the rarefaction of the interstitial gas on the conductivity of the beds. Contact mechanics and thermal analyses are performed for uniform size spheres packed in SC and FCC arrangements and the results are presented in the form of compact relationships. The present model accounts for the thermophysical properties of spheres and the gas, contact load, spheres diameter, spheres roughness and asperities slope, and temperature and pressure of the gas. The present model is compared with experimental data for SC and FCC packed beds and good agreement is observed. The experimental data cover a wide range of the contact load, surface roughness, interstitial gas type, and gas temperature and pressure.
Performance Evaluation of Occupant Classification Systems
Authors: Lichtenberg Glen , Carr Kirsten
Published: April 2008

The new FMVSS 208 Federal Regulation requires restraint systems to focus on occupants other than the 50th percentile male. The new focus includes small adults and children. As a result, restraint systems may need to perform differently for several occupant classes, thereby creating a need for occupant classification systems (OCS). A typical regulation compliance strategy is to suppress the restraint system when a child occupies the front passenger seat and to enable the restraints when an adult occupies the seat. The regulation provides specific weight and height ranges to define these classes of seat occupants. The evolution of OCS technologies produced a need for test methodologies and objective metrics to measure classification system capability. The application of the statistical one-sided tolerance interval to OCS systems has proven invaluable in measuring classification performance and driving system improvements. The one-sided tolerance method is based on a single continuous variable, such as weight. A single common threshold, or tolerance limit, is used to compare two competing populations, such as 6-year-old versus 5th percentile female populations. Output of the method produces graphics demonstrating reliability as a function of potential threshold that objectively characterizes a system’s classification performance level. This paper also discusses the importance of applying the one-sided tolerance interval method to performance data that captures the noise sources that impact system performance. For occupant classification systems, noise sources include differences in test subjects’ sizes, how they sit in the seat, and how the seat is set-up. This paper also discusses the importance of sample size selection. Two methods of determining a sample size are presented. The first method uses the one-sided tolerance interval method equation directly. The second method simulates a noise source and selects a sample size where the noise standard deviation converges to its population variance. Once the mean, standard deviation, and sample size for each test case is known, the proposed method computes the reliability of each test case evaluated for a range of potential thresholds. A review of the resulting reliability curves characterizes classification performance. If an acceptable range of thresholds exists, the resulting range is referred to as a “threshold window.” System improvements can be directed toward those test cases that constrain the “threshold window.” This paper proposes a statistical method that can provide a solid measure of the robust capability of an OCS that classifies based on a single continuous variable (such as weight) to distinguish between occupant classes. This statistical method enables the careful balance necessary in setting thresholds.
Simulation of Mist Transport for Gas Turbine Inlet Air Cooling
Authors: Wang Ting , Li Xianchang , Pinninti Venu
Published: April 2008

The output and efficiency of gas turbines are reduced significantly during the summer. Gas turbine inlet air-cooling is considered a simple and effective method to increase the power output as well as thermal efficiency. Among various cooling schemes, fog cooling (a direct evaporative cooling) has gained increasing popularity due to its simplicity and low installation cost. During fog cooling, water is atomized to micro-scaled droplets (or mist) and introduced into the inlet airflow. The inlet air temperature is reduced through water evaporation. To investigate the mist transport in the entrance duct, numerical study is performed in this paper. Different fundamental geometries are considered first, which include a straight tunnel, a diffuser, a contraction, and a 90° bend. These geometries are used to investigate the effect of acceleration, deceleration, and centrifugal force on mist transport and cooling effectiveness, respectively. Lastly, a duct representing a real application is used. The effects of droplet size, droplet distribution, and humidity on cooled air temperature distribution are examined. Analysis on droplet history (trajectory and size) is employed to interpret the mechanism of droplet dynamics under influence of acceleration, diffusion, and body forces.
Frequency-Based Partial and Total Decomposition Approaches for Trajectory Planning of Robotic Systems With Variable Dynamic Responses
Authors: Podder Tarun K. , Sarkar Nilanjan
Published: April 2008

In this paper, we present a frequency-based trajectory planning approach that considers the variable dynamic bandwidth of any multibody system having different dynamic subsystems. This approach provides us with important motion planning methodology for a variety of robotic systems including land-based mobile robots, space robots, and underwater robots, where the vehicles have much slower response as compared to the manipulators. The proposed method has been improvised for an Autonomous Underwater Vehicle-Manipulator System (UVMS) which is a heterogeneous dynamic system having vehicle’s natural frequency much lower than that of the manipulator. This motion-planning algorithm not only considers the variability in dynamic bandwidth of such a complex system but also generates kinematically admissible as well as dynamically feasible reference trajectories. Additionally, the proposed algorithm exploits the inherent kinematic redundancy of the system and provides reference trajectories that accommodate several other important criteria such as thruster/actuator fault and saturation; it also minimizes hydrodynamic drag on the UVMS. Here, we have mainly compared the performance of two frequency-based decomposition approaches, namely: Partial Decomposition and Total Decomposition. The effectiveness of the proposed algorithm is verified with extensive computer simulations and the results are found quite promising.
A Laplace-Based Spiral Contouring Method for General Pocket Machining
Authors: Chuang Jui-Jen , Yang Daniel C. H.
Published: April 2008

In this paper, a method for generating boundary-conformed pocketing toolpaths is developed. Based on the 2D Laplace parameterization of pocket contours and the redistribution of the original Laplace isoparametrics, continuous toolpaths are generated. These generated toolpaths have neither thin walls nor leftover tool marks. Detailed algorithms are formulated in steps. The method can be applied to general pockets either with or without islands. Some examples are provided to demonstrate the applicability of this method. In most cases, the method can successfully generate satisfactory toolpaths for arbitrary shaped pockets. However, according to the shape of the pockets and the distribution of the islands, when use this method, over machining may occur in some narrow or bottlenecked areas. Further investigation on how to alleviate this problem is needed. We believe that this method provides an alternative choice for pocket machining.
Thermo-Hydraulic Model of a Twin-Screw Multiphase Pump
Authors: Nakashima Celso Y. , Oliveira Silvio , Caetano Elisio F.
Published: April 2008

The twin-screw multiphase pump has been studied as an alternative equipment to substitute the conventional system (fluid separation, liquid pumping and gas compression) in petroleum boosting. By “pumping” gas and liquid together, the multiphase pump could reduce production costs, particularly in deepwater activity. This paper presents a thermo-hydraulic model of a twin-screw multiphase pump developed to determine important parameters such as: volumetric efficiency, absorbed power, discharge conditions, heat transfer and pressure and temperature profiles. The continuous movement from suction to the discharge of pump chambers is divided in small discretive steps. This division allows the calculation of energy and mass balances for each screw chamber. At each step, it is possible to calculate mass and energy that enters and leaves one chamber. With this balance, pressure and temperature for the next step can be calculated. Differently from previous model, it considers not only water-air but also hydrocarbon mixtures (including petroleum heavy fractions) as working fluids. Besides, inclusion of screw rotation influence over peripheral backflow is not neglected as in previous models.
Spectral Radiative Heat Transfer Analysis of the Planar SOFC
Authors: Damm David L. , Fedorov Andrei G.
Published: April 2008

Thermo-mechanical failure of components in planar-type solid oxide fuel cells (SOFCs) depends strongly on the local temperature gradients at the interfaces of different materials. Therefore, it is of paramount importance to accurately predict the temperature fields within the stack, especially near the interfaces. Because of elevated operating temperatures (of the order of 1000 K or even higher), radiation heat transfer could become a dominant mode of heat transfer in the SOFCs. In this study, we extend our recent work on radiative effects in solid oxide fuel cells (Journal of Power Sources, Vol. 124, No. 2, pp. 453–458) by accounting for the spectral dependence of the radiative properties of the electrolyte material. The measurements of spectral radiative properties of the polycrystalline yttria-stabilized zirconia (YSZ) electrolyte we performed indicate that an optically thin approximation can be used for treatment of radiative heat transfer. To this end, the Schuster-Schwartzchild two-flux approximation is used to solve the radiative transfer equation (RTE) for the spectral radiative heat flux, which is then integrated over the entire spectrum using an N-band approximation to obtain the total heat flux due to thermal radiation. The divergence of the total radiative heat flux is then incorporated as a heat sink into a 3-D thermo-fluid model of a SOFC through the user-defined function utility in the commercial FLUENT CFD software. The results of sample calculations are reported and compared against the baseline cases when no radiation effects are included and when the spectrally gray approximation is used for treatment of radiative heat transfer.
Finite Element Analysis of Positioning of Pin in Lapidus Procedure
Authors: Royyuru Haritha , Chen Yitung , Hsieh Hsuan-Tsung , Borgia Anthony V.
Published: April 2008

A finite element analysis was carried out to determine the optimum pin placement with the application of mini fixator in Lapidus procedure. Various parameters were considered for analysis like pin diameter, distance from fracture site, number of pins, distance of the rail from the fracture site, effect of width and length of the rail on gap closing, angle of fracture and pin angle. FEMLAB 2.3 is used for both modeling and analysis. A 2D model is constructed with the bone joint consisting of first metatarsal and cuneiform along with the fixation device. The dimensions of the model are taken similar to a prototype model of the foot and mini fixation device. Simple Static analysis is done as a beginning case which will be later developed to dynamic case.
Analytical and Experimental Study of Potential Heat Recovery From Household Refrigerators
Authors: Todd Jessica
Published: April 2008

Opportunities for waste recovery exist in many types of industrial devices as summarized by Kreith and West [1]. However, no experimental data regarding the potential of heat recovery from household refrigerators have been published in open literature. The decision to implement a heat recovery option depends mostly on convenience and cost. In some cases, however, the decision is difficult because there is a lack of reliable information of the payback for a potential application. This article provides useful information for the design and payback of a waste heat recovery system on a household refrigerator. This paper presents experimental and analytical results of energy recovery potential from the heat rejected by the condenser coils of a household refrigerator. Using a small heat exchanger affixed to the condenser coils, the heat thus recovered can preheat domestic tap water. The analytical study considered three designs: A heat exchanger with the refrigerant condensing on the outside of water pipes, refrigerant on the inside of a counter-flow heat exchanger, and the refrigerant condensing inside a serpentine coil enclosed by a container filled with household tap water. Considering economic feasibility and manufacturing ease, the serpentine coil design was chosen. Experimental data confirmed the heat recovery possibility from the condenser coils. The serpentine coil design can achieve a payback time of 2 to 10 years dependent on whether the domestic hot water uses electric or gas heating.
Prediction and Analysis of the Bubble Formation in Film Boiling
Authors: Agrawal A. , Biswas G. , Welch S. W. J. , Durst F.
Published: April 2008

The bubble formation and heat transfer on a horizontal surface have been numerically analyzed using a volume of fluid (VOF) based interface tracking method incorporated into a complete solution of the Navier-Stokes and the thermal energy equations. The numerical method took into account the effects of surface tension, the interface mass transfer and the corresponding latent heat. The computations demonstrated capability of the algorithm in generating quantitative information on unsteady periodic bubble release patterns and on the spatially and temporally varying film thickness. The computations also predict the transport coefficients on the horizontal surface.
Validating the Directional Performance of Multi-Wheeled Combat Vehicle Computer Simulation Models
Authors: Hillegass Matthew J. , Faller James G. , Bounds Mark S. , El-Gindy Moustafa , Joshi Abhishek S.
Published: April 2008

The dynamic performance of a multi-wheeled combat vehicle model specially developed in multi-body dynamics code was validated against measured data obtained on the U.S. Army Aberdeen Test Center’s (ATC) test courses. The multi-wheeled combat vehicle variant that was tested was developed in the modeling software TruckSim from Mechanical Simulation Corporation. Prior to validating the model, the vehicle weights, dimensions, tires and suspension characteristics were measured and referenced in the specially developed computer simulation model. Non-linear measured tire and suspension look-up tables were used in the simulation. The predictions of the vehicle handling characteristics and transient response during lane change at different vehicle speeds were compared with field tests results. Measured and predicted results are compared on the basis of vehicle steering, yaw rates, accelerations and handling diagrams. Statistical methods such as power spectral density, root mean square, skewness, and kurtosis are applied to validate the model. Validation tolerances are defined for each set of statistical results based on ATC’s experience.
A Novel On-Line Fault Detection Scheme Using Multivariable Zeros and Zero Directions
Authors: Pandey Amit , Jayasuriya Suhada
Published: April 2008

A new algorithm which generates a class of input signals corresponding to which the combination of plant outputs in the output zero direction is always zero irrespective of time, is proposed. Using this result and the results in MacFarlane and Karcanias (1976) we propose two tests to find the defective rows and the defective columns of a plant transfer function matrix. Our fault detection scheme is based on the following triple: the output zero direction of the plant, the transmission zero of the plant, and the input zero direction of the plant. Based on the faulty rows and columns we identify the faulty elements of the plant transfer function matrix. A system of four interconnected water tanks with two multivariable zeros and four stable poles was found ideal for illustrating the results obtained. The algorithm proposed is used to detect changes occurring in the four-tank setup. Each input channel is analyzed one at a time. In the latter part of the work we have analyzed the 4-tank system by measuring the new steady state output of the plant which is obtained after disturbing the plant from its previous equilibrium state by changing the inputs by a small quantity from their equilibrium values. The method helps in pin-pointing the defective elements of the plant transition matrix. The key advantage of this method lies in the fact that the changes can be found without having to restart the plant.
Thermal Contact Conductance Enhancement With Carbon Nanotube Arrays
Authors: Xu Jun , Fisher Timothy S.
Published: April 2008

The present work reports on an experimental study of carbon nanotube (CNT) arrays used for thermal contact conductance enhancement. Multiwall carbon nanotubes were synthesized directly on silicon wafers using plasma-enhanced chemical vapor deposition. Thermal contact conductance was experimentally measured with a steady-state contact conductance technique. To reduce heat losses and experimental uncertainty, testing occurred in a high-vacuum environment with radiation shielding, and temperature measurements were made with an infrared camera. In addition, results from other thermal interface materials (phase change material and metal foil) are presented, and the performance of combinations of these materials with CNT arrays are also reported.
Validation Studies for the Dual Optimization of Indentation Creep and Stress Relaxation of Biological Soft Tissues Using Biphasic Poroviscoelasticity: Potential Method for Brain Tissue
Authors: Olberding Joseph E. , Suh Jun-Kyo Francis
Published: April 2008

Traumatic brain injury (TBI) is highly fatal and has profound physical and psychological repercussions for survivors. Knowledge of the precise material properties of brain tissue is crucial in developing holistic computational models to predict and prevent TBI. Despite the recent proliferation of material models of brain tissue, none have utilized porous media theory to explicitly include the significant fluid component of the hydrated soft tissue. Furthermore, the delicate composition of brain tissue limits the number of suitable biomechanical testing methodologies. In order to incorporate these considerations, in situ indentation creep and stress relaxation tests and linear biphasic poroviscoelasticity (BPVE) [1] were proposed to characterize the material properties of cerebral brain tissue. The objective of the present study was to evaluate these experimental and computational protocols in which the data from indentation creep and stress relaxation tests were simultaneously curve-fitted using a dual-optimization technique to determine the material parameters of the linear BPVE model.