bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Interface and Depth on Hardness and Viscoelastic Modulus in Polycarbonate and Polyester Films
Authors: Ahuja Suresh
Published: May 2009

Hardness and modulus of a polymer is known to depend on its structure, molecular weight and number of segments between entanglements. Nano-indentation is used increasingly as a powerful tool to determine hardness and visco-elastic modulus of polymer surfaces linear, cross-linked or composites. Hysitron Nanoindenter was used in our investigation of contact deformation of surfaces of polyester and polycarbonate supported on an aluminum substrate. Bar coatings of polymer films were made from solutions and dried all at 110C for half an hour. The coatings were subjected to indentation including sinusoidal deformation at various contact depths and hardness as well as modulus is computed. The results show that hardness of surface of polycarbonate on polyester is higher than hardness of surface of polycarbonate, which in turn is higher than polyester surface. It appears that diffusion of polyester chains into compatible polycarbonate chains results in higher modulus of the surface than the modulus of either of the two polymers. Hardness and modulus of polycarbonate is found to decrease with contact depth and reaches a plateau around 600nm while that of polyester keeps on decreasing. Differences in contact deformation including the one arising from dynamic deformation between polycarbonate from that of polyester is analyzed in terms of morphology, molecular weight and entanglements.
Attenuation of Free Vibration Using Particle Impact Damper
Authors: Hamidzadeh Hamid R.
Published: May 2009

The particle impact damper is an effective vibration damping treatment that can be used in the cases where visco-elastic constrained layer damping fails due to excessive surrounding temperature. In this type of passive damping, particles move in a container attached to the vibrating system resulting in plastic impact with the container. In the presented theoretical study, the damping characteristics of free oscillation for a vertical system with an initial displacement are considered and a governing equation for the system under free vibration with a particle damper is derived. To evaluate the damping characteristics for the free vibrating system, the equivalent damping ratio is determined by considering both kinematics and kinetics of the particle motion and its impacts with the container. The presented solution concludes that in general damping effectiveness can be enhanced by increasing the mass of the particle in comparison with total mass of the system. Mathematical optimum clearance for the moving particle and the equivalent viscous damping ratio are determined for the best performance of the particle impact damper.
Elastoplastic Micromechanical Damage Mechanics for Composites With Progressive Partial Fiber Debonding and Thermal Residual Stress
Authors: Ju J. W. , Yanase K.
Published: May 2009

By incorporating interfacial damage and thermal residual stress, a novel elastoplastic damage model is proposed to predict the overall transverse mechanical behavior of fiber-reinforced ductile matrix composites within the framework of micromechanics. Based on the concept of fictitious inclusion, and taking the debonding angle into consideration, partially debonded isotropic fibers are replaced by equivalent orthotropic yet perfectly bonded elastic fibers. Up to three interfacial damage modes (no debonding, partial debonding and complete debonding) are considered. The Weibull’s probabilistic function is employed to describe the varying probability of progressive partial fiber debonding. The effective elastic moduli of four-phase composites, composed of a ductile matrix and randomly located yet unidirectionally aligned fibers (undamaged/damaged) are derived by a micromechanical formulation. Thermal residual stress is taken into account through the concept of thermal eigenstrain to study the effect of the manufacturing process-induced residual stress. Further, explicit exact formulation on the exterior point Eshelby’s tensor for elliptical fiber is utilized to investigate the effect on the inelastic mechanical responses of the composites due to the aspect ratio of elliptical fiber.
Safety Basis Design Development Challenges
Authors: Young Jonathan , Lowry Pete , Schmitt Bruce , Sullivan Robin , Mahoney Lenna , Ryan Grant
Published: May 2009

“Designing in Safety” is a desired part of the development of any new potentially hazardous system, process, or facility. It is a required part of nuclear safety activities as specified in the U.S. Department of Energy (DOE) Order 420.1B, Facility Safety. This order addresses the design of nuclear related facilities developed under federal regulation 10CFR830, Nuclear Safety Management. 10CFR830 requires that safety basis documentation be provided to identify how nuclear safety is being adequately addressed as a condition for system operation (e.g., the safety basis). To support the development of the safety basis, a safety analysis is performed. Although the concept of developing a design that addresses safety is simple, the execution can be complex and challenging. This paper addresses those complexities and challenges for the design activity of a system to treat sludge, a corrosion product of spent nuclear fuel, at DOE’s Hanford Site in Washington State. The system being developed is referred to as the Sludge Treatment Project (STP). This paper describes the portion of the safety analysis that addresses the selection of design basis events using the experience gained from the STP and the development of design requirements for safety features associated with those events. Specifically, the paper describes the safety design process and the application of the process for two types of potential design basis accidents associated with the operation of the system, 1) flashing spray leaks and 2) splash and splatter leaks. Also presented are the technical challenges that are being addressed to develop effective safety features to deal with these design basis accidents.
Interactions Between Bubbles in Close Proximity Under Uniform and Non-Uniform Electric Fields
Authors: Pearson Matthew R. , Seyed-Yagoobi Jamal
Published: May 2009

It is widely known that dielectrophoretic force can be harnessed to enhance the separation of liquid and vapor phases, with several known benefits in heat transfer enhancement. It has been shown that, when the electrode spacing and the bubble radius are of the same order of magnitude, the presence of the electric field can significantly deform the bubble, and this deformation can significantly affect the bubble’s behavior. Additionally, the presence of a bubble can provide significant, local distortion of the electric field. Consequently, the existence of multiple bubbles in close proximity may generate interactions that serve to further affect bubble deformation and motion behavior. Of course, nucleate boiling involves the generation of several bubbles in close proximity, and it is useful to understand whether these interactions may favorably or adversely affect the potential for heat transfer enhancement. This numerical study simulates the behavior of two and three bubbles within an external, electric field. The geometric deformation of the bubbles due to the electric field and the distortion of the electric field due to the existence of the bubbles are both incorporated into the mathematical model. The numerical results provide information about the effect that one bubble can have on the others’ motion, and also illustrate any tendencies of the bubbles to attract or repel each other when subject to various electric fields. Based on the numerical results, conclusions are drawn on the implications that the observed phenomenon may have on heat transfer enhancement applications.
Statistical Analysis on High Strain Rate Tensile Strength of T700 Carbon Fiber
Authors: Wang Yang , Zhou Yuanxin , Xia Yuanming , Jeelani Shaik
Published: May 2009

Tensile mechanical behavior of T700 fiber bundles have been studied in the strain rate range from 0.001 l/s to 1000 l/s and complete stress strain curves were obtained. Results show that both ultimate strength and failure strain are strain rate insensitive, and T700 carbon fiber can be regarded as strain rate insensitive materials. On basis of the fiber bundles model and the statistic theory of fiber strength, a statistical constitutive model based on Weibull distribution function has been developed to describe mechanical behavior of T700 fiber. And a method for determine the statistic parameters of fibers by tensile tests of fiber bundles is established, too. The simulated stress strain curves from the model are in good agreement with the test data. Simulated results show that the strength of T700 fiber can be described by single Weibull distribution function.
Non-Linear Dynamic Pulse Response of Plates and Cylindrical Panels
Authors: Thoppul Srinivasa D. , Ari-Gur Judah
Published: May 2009

The dynamic response of plates and cylindrical panels with various curvatures under external lateral pressure pulse was studied. Nonlinearities due to large deflections were included and the dynamic response was analyzed using a finite element code. Effects of shell curvatures, pulse durations and load intensities were investigated. The observed dynamic behavior included also non-linear shell buckling due to the compressive stresses under the external pressure on the cylindrical panels. The results, when compared to the linear response, show the effects of the increased load intensity and the resulting non-linear behavior on the response to various pulse durations. Also, the differences between the static and the dynamic behaviors for similar load intensities were studied. Non-dimensional processing of the results, including in the large deflection range, highlights the effects of high load intensities on the structural stiffness and in turn on the changing characteristics of the response under a given pulse duration.
Swing Up Control of the Pendubot Through Energy Management of the Underactuated Link
Authors: Albahkali Thamer , Mukherjee Ranjan , Das Tuhin
Published: May 2009

The control problem of the pendubot refers to the task of stabilizing its equilibrium configuration with the highest potential energy. Linearization of the dynamics of the pendubot about this equilibrium results in a completely controllable system and allows a linear controller to be designed for local asymptotic stability. Therefore, the real challenge is to design a control law for the underactuated system that will swing up both the links and brings the configuration variables of the system within the region of attraction of the equilibrium. This paper provides a method for swing-up control based on a series of start and stop maneuvers of the first link about its vertically upright configuration. The start and stop maneuvers are designed such that each maneuver results in a net gain in the energy of the second link. This results in swinging up of the second link and the pendubot configuration reaching the region of attraction of the desired equilibrium. A three step algorithm is provided for swing up control followed by stabilization. Simulation results are presented to demonstrate the efficacy of the approach.
Thermodynamics as a General Science That Applies to All Systems and All States: Fundamental and Pedagogical Aspects of a New Paradigm
Authors: von Spakovsky Michael R.
Published: May 2009

In 1976 and then again in 1984, a series of six groundbreaking papers were published (Hatsopoulos and Gyftopoulos, 1976; Beretta et al. 1984; Beretta, Gyftopoulos, and Park, 1985), presenting a new formulation of thermodynamics, which simply and elegantly extends in a unified fashion the concepts of thermodynamics to quantum mechanics and the concepts of quantum mechanics to thermodynamics. It does so without the bridge traditionally used, i.e. statistical mechanics, eliminating a number of the ambiguities, tautologies, and inconsistencies (including a built-in violation of the 2nd Law) inherent in the presentations of both classical and statistical thermodynamics. This new formulation, called the Unified Quantum Theory of Mechanics and Thermodynamics, generalizes thermodynamics so that it applies to all systems large or small (including one particle systems) either in a state of thermodynamic (i.e. stable) equilibrium or not in a state of thermodynamic equilibrium. Intrigued by both the scientific and pedagogical possibilities of this new theory, the author began his own study and application of this new formulation in 1998. The present paper focuses on the foundational and pedagogical aspects of this new non-statistically based paradigm of physics and thermodynamics, which uses as its primitives inertial mass, force, and time and introduces the laws of thermodynamics in the most unambiguous and general formulations found in the literature. Not only does this new formulation or paradigm provide a clearer understanding of thermodynamics to the student and the practitioner, but it has the potential for revolutionizing how we understand and synthesize/design systems at a microscopic level since this paradigm, unlike the predominant statistically based paradigm of the last century and a half, allows one to extend down to the microscopic such concepts as generalized available energy (i.e. a special case of this property is the exergy) and entropy, properties which are already effectively applied to systems at the macroscopic level.
Silicon Micro-Ring Gyroscopes
Authors: Chang Guo-En , Chang Chia-Ou , Chou Chan-Shin , Chang Chien Wen-Tien
Published: May 2009

The aim of this paper is to analysis a single-crystal microring gyroscope. It is found that Si(111) ring is in-plane isotropic but out-of-plane anisotropic, while Si(100) ring is fully anisotropic. Hamilton’s principle is used to derive the equations of vibration, which is a set of partial differential equations with variable coefficients. The exact solutions for frequencies and mode shapes are found. It is also found that the degeneracy of frequencies for isotropic ring splits for anisotropic ring. Then structure design and dynamic analysis of silicon resonant micro-ring gyroscope are presented. The perturbation method of multiple scales is used to find the explicit expression for the relationship between input (angular velocity) and output (nodal displacement of the ring). The effectiveness of phase-locking for enhancing the output signal is proved and quantitatively analyzed.
Adsorption Characteristics of Maxsorb-III + Methane Systems by Desorption Experiments
Authors: Saha Bidyut Baran , Srinivasan Kandadai , Chakraborty Anutosh , Habib Khairul , El-Sharkawy Ibrahim Ibrahim , Koyama Shigeru
Published: May 2009

The adsorption isotherms and kinetics of gaseous methane onto highly porous activated carbon (Maxsorb-III) at temperatures ranging from 278 to 333 K and at different equilibrium pressures between 0.1 and 2.0 MPa have been experimentally measured by the desorption method unlike volumetric or thermo-gravimetric apparatus. The thermophysical properties such as skeletal density, BET surface area, pore size, pore volume and the total porosity of Maxsorb-III have been determined. The Dubinin-Astakhov (DA) and Langmuir isotherm models are found to fit well all of the experimental data within the experimental errors. The experimental isotherms and the computed isosteric heat of adsorption are compared with the measurements of similar specimens of activated carbon of other researchers, and found to be consistent. The present isotherm and isosteric heat data are useful for designing environmentally benign adsorption cooling and storage systems.
Model Based Characterization of Transient Response of a Solid Oxide Fuel Cell System
Authors: Das Tuhin , Narayanan Sridharan , Mukherjee Ranjan
Published: May 2009

In this paper we perform transient analysis of a Solid Oxide Fuel Cell (SOFC) system. We consider a steam reformer based SOFC system with anode recirculation and with methane as fuel. For the analysis, we develop a control-oriented model that captures the details of heat and mass transfer, chemical kinetics and electrochemistry of the SOFC system. The coupled dynamics of the steam reformer and the fuel cell anode control volumes are extracted and through coordinate transformations we derive closed-form expressions characterizing the steady-state and transient behaviors of two critical performance variables of reformer-based SOFC systems, namely utilization and steam-to-carbon balance. Our analysis is supported by simulations. Using the results derived, we address steady-state fuel optimization by posing it as a problem in linear programming. Our results can be applied in predicting system response to step changes in current and will be useful in designing control strategies for SOFC based power plants.
Investigation of the Nanomechanical and Tribological Properties of Tooth-Fillings Materials
Authors: Al-Haik Marwan , Trinkle Shane , Sumali Hartono , Garcia Daniel , Yang Fan , Martinez Ulises , Miltenberger Scott
Published: May 2009

This study utilizes novel characterization techniques nanoindentation and nanoscratch for testing both the human enamel and dentine together with two biocompatible dental filling materials; epoxy nanocomposite and silver amalgam. Nanoindentation tests were performed to obtain accurate hardness and reduced modulus values for the enamel, dentin and two different fillers. We utilized Nano-scratch tests to obtain critical load in scratch test and resistance to sliding wear. Testing showed the silver amalgam filling has a higher modulus of elasticity, hardness and wear resistance compared to the nanocomposite. The novel mechanical characterization techniques utilized might assist in better understanding the mechanical behavior of the dental fillers and thus facilitate the design of robust fillers with excellent mechanical properties.
Inner Surface Cracking of an Aluminum Alloy in Small-Radius Bending
Authors: Li Zhuoqun , Wu Xin
Published: May 2009

Aluminum alloys, due to their low density, high strength to weight ratio and formability, are widely used in automotive components. At present, most of the sheet alloy being used is AA6111; an Al-Mg-Si alloy with addition of Cu. AA6111. These alloys contain micrometer sized inclusions and second phase particles, with good combination of strength and formability [1]. However, at the same time, the formability of AA6111 is also limited because of these micro-sized inclusions and second phase particles [2]. To improve the formability of sheet metal used as automotive body such as panels, a newer alloy AA6022 containing nano-sized strengthening precipitates and enhanced formability has been developed. A number of research works have been done on the precipitation sequences and phase development during aging of these alloys. Recently Miao and Laughlin have reported that the precipitation sequence in the AA6022 is in the following reaction: solid solution α → GP zones → β″ → β′ + lath-like precipitate ← β + Si [3, 4]. As to AA6111, the sequence of precipitation is believed to initiate with the metastable phases, β″ and β′ leading to the equilibrium β phase. The structure and composition of the β phase have been well established to be of the fluorite structure with a composition Mg2Si [5–7]. Recent works also report the presence of a quaternary phase, Q and its metastable precursor, Q′ in the precipitation sequence [8]. The aim of this report is to find the relationship between the microstructure and the failure of the hole expanded and small angle bended samples. We will report a finding of inner surface fracture during small-radius bending due to the tensile residual stress development in the inner surface.
Nanoparticle Heat Transfer and Its Application to Laser Hyperthermia
Authors: Li B. Q. , Mi C. , Liu C. , Cheng G. , Fu M. , Meadow G.
Published: May 2009

Nanoparticles-enabled laser hyperthermia holds a great promise as a new therapeutic treatment for cancer patients. This paper presents some preliminary data on the frequency tenability of nanostructures and on the heat transfer aspect of this process that results from the interaction between high frequency electromagnetic field and nanostructures. Maxwell equations are solved to predict heat generation from the surface plasma resonance excitation of a nano-sized particle or structure by a laser beam. An experimental system has also been setup to validate the concept of heat generation through particle-laser interaction. Results obtained on both model tissues and on mice are consistent with the model predictions. Experiments further show that concentrated local heating can be generated in cancerous cells for a thermal kill.
Structural and Mechanical Properties of Multilayer TiN/CrN Coatings
Authors: Konchady Manohar S. , Yarmolenko Sergey , Pai Devdas M. , Sankar Jag
Published: May 2009

Multilayer and superlattice coatings of TiN/CrN coating are deposited on Si(100) substrate at different modulation wavelength by reactive unbalanced magnetron sputtering and characterized using X-ray diffraction, nanoindentation, AFM. Nano-roughness of films is in good correlation with hardness and modulus and this effect has been used for optimization of deposition parameters. Preliminary results have shown slightly better mechanical properties for multilayered TiN/CrN coatings compared to single layer TiN and CrN coatings. The XRD results have shown a preferred orientation in <100> direction for TiN/CrN multilayer coatings at modulation wavelengths below 80 nm. At 100 nm layer thickness, TiN revealed small amount of crystals with <111> orientation and their content significantly increases with increase in layer thickness while CrN layers only show preferred orientation of <100>. Multilayered coatings exhibit better mechanical properties due to presence of large number of interfaces which act as barrier to dislocations. Fracture toughness and tribological properties of these coatings are also expected to show significant improvement and the investigation in this area is under progress.
Estimating the Thermal Properties of a Calorimeter Using Hierarchical Bayesian Inference With MCMC
Authors: Emery A. F. , Bardot D.
Published: May 2009

The accurate determination of the specific heat by placing of a sample in a bath of liquid and measuring the temperature change of the bath and the sample is dependent upon estimation of the heat lost to or gained from the calorimeter. This heat transfer is a complex function of the thermal characteristics of the calorimeter, the initial and ambient conditions, and the convective heat transfer between the bath and the calorimeter walls. This paper describes the estimation of the heat transfer and the determination of the uncertainties in the computed sample specific heat by using Bayesian inference.
A Coupled Solution Procedure for Zonal Radiative and Convective Heat Transfer in 3-D Enclosures With Blockages and Screens
Authors: Malikov German , Lisienko Vladimir , Malikov Yuri , Chudnovsky Yaroslav , Viskanta Raymond
Published: May 2009

A new 3D method of modeling convective-diffusive (CDT) heat transfer and zonal radiation transfer (ZRT) employing different calculation schemes and multi-scale curvilinear grids is presented. The coarse multiblock unstructured grid calculation domain allows use of a conservative and an accurate zonal radiation transfer method with only modest computational effort that requires only a small fraction of total processor CPU time. The blockages (e.g., bars in a furnace) and screens have their own very coarse grids. This reduces the time for defining their intersections with rays. Structured fine grid is used for convective-diffusive (CDT) calculations. The main difficulty (i.e., in coupling between CDT and ZRT numerical computations) is successfully overcome using a simple algorithm. The zonal radiation transfer method is based on a fast algorithm for calculating view factors and total exchange areas. The present approach is fast, efficient and accurate for gas fired furnaces and complex internal configurations of the work pieces with many blockages and screens. The utility of the method is demonstrated by calculating the heating of a hundred round metal bars arranged in a continuous natural gas fired furnace. Good agreement between calculations and industrial experiments is demonstrated.
Non-Spherical Collapse of an Air Bubble Subjected to a Lithotripter Pulse
Authors: Johnsen Eric , Colonius Tim , Kreider Wayne , Bailey Michael R.
Published: May 2009

In order to better understand the contribution of bubble collapse to stone comminution in shockwave lithotripsy, the shock-induced and Rayleigh collapse of a spherical air bubble is investigated using numerical simulations, and the free-field collapse of a cavitation bubble is studied experimentally. In shock-induced collapse near a wall, it is found that the presence of the bubble greatly amplifies the pressure recorded at the stone surface; the functional dependence of the wall pressure on the initial standoff distance and the amplitude are presented. In Rayleigh collapse near a solid surface, the proximity of the wall retards the flow and leads to a more prominent jet. Experiments show that re-entrant jets form in the collapse of cavitation bubbles excited by lithotripter shockwaves in a fashion comparable to previous studies of collapse near a solid surface.
Effect of Board-Level Reflow on Adhesion Between Lead-Free Solder and Underfill in Flip-Chip BGA Packages
Authors: Tang Zhenming , Park Seungbae , Lee H. C. John , Chung Soonwan
Published: May 2009

The change in solder/underfill adhesion and its effect on fatigue life were investigated for Pb-free solder joints for which, during the reflow process, the solder has melted and resolidified inside the underfill cavities. The change in interfacial adhesion was simulated and its strength compared using button shear test. Surprisingly, the difference was found to be only about 11%. Suspecting the validity of the result, the study was extended to further investigate the adhesion effect on fatigue life under thermal cycles. The effect was assessed analytically using FEA model. Energy-based Darveaux’s fatigue life model [1] is used to calculate solder fatigue life under two extreme conditions: perfect adhesion (without delamination or void between underfill and solder) and non adhesion. The failure parameter, accumulated plastic work per cycle for non adhesion was significantly less than that for perfect adhesion case suggesting adverse effect of strong adhesion to the enhancement of structural integrity. In this simulation, the room temperature was taken as the stress free state.
Molecular Dynamics Prediction of the Thermal Conductivity of Si/Si1−xGex Superlattices
Authors: Landry E. S. , McGaughey A. J. H. , Hussein M. I.
Published: May 2009

Molecular dynamics simulations and the non-equilibrium direct method are used to predict the effective cross-plane thermal conductivity of Si/Si1−xGex superlattices modeled by the Stillinger-Weber potential. The experimentally observed thermal conductivity design space and the methodology of making the thermal conductivity prediction with the direct method are reviewed. Preliminary results for the thermal conductivity prediction of a Si/Si0.7Ge0.3 at a temperature of 500 K are discussed.
Sliding-Mode Control Algorithm for a Hard-Mounted Isolation System
Authors: Wang Yung-Peng , Tsao Jen-Chieh
Published: May 2009

It is well known that the trend of current technology development is microscopic and ultra-precision, especially in the areas of semiconductor manufacturing, ultra-precision machining, MEMS, microbiology and nanotechnology. Hence, vibration becomes a significant problem in those fields. There are two types of vibration control techniques. One is passive isolation system; the other is active isolation system. Passive isolation system can provide better performance for higher frequencies. Active isolation system is used to improve the isolation performance for lower frequencies. However, passive isolation system has bad performance around the natural frequency. In addition, it cannot eliminate the effects of onboard disturbances. Therefore, active isolation system becomes the major technology in the applications of microvibration control for precision equipment. In practice, all active isolation systems are based upon a hybrid concept, combining a passive isolator for higher frequencies and a servo control system for lower frequencies. This combination allows for two significantly different configurations, which can be categorized as: soft-mounted isolation systems and hard-mounted isolation systems. The soft-mounted systems are inherently insensitive to resonance in the main structure below the isolators. Yet, they are sensitive to resonances in the isolated platform. The hard-mounted systems are extremely stiff and allows for large onboard disturbance forces without excessive motion. However, the major drawback with a hard-mounted system is that vibration isolation performance suffers from the passive-active compromise and is unable to come up to the optimal performance. In this paper, a sliding-mode control algorithm is developed for a hard-mounted isolation system with a piezoactuator. Based on the bounds of environmental vibrations and onboard disturbances, the sliding-mode control algorithm can make the hard-mounted isolation system achieve the optimal and robust performance of low vibration transmissibility and high stiffness. The results are verified by the numerical simulations.
Parametric Study of the Tubular SOFC Power Cycle With a Thermodynamic Model
Authors: Ghassemi M. , Mostofi S. , Mollayi Barsi Y. , Pirmohammadi M.
Published: May 2009

This work focuses on modeling and performance evaluation of an anodic re-circulation system including ejector technology, pre-reformer and solid oxide fuel cells (SOFC). An improved one-dimensional dynamic model of a simple tubular SOFC cycle components in the engineering equation solver (EES) environment is presented. In this simulation, ejector and pre-reformer components are modeled thermodynamically and a simple electrochemical SOFC model is developed all these models are coupled together to predict the operation of the cycle. The goal is to predict the effect of input parameters such as fuel mixing ratio and temperature on output parameters (i.e. pressure ratio increase, outlet temperature and molar fractions). Therefore the model determines the pressure, temperature and fuel composition variations of each component and the complete cycle at different points. For instance the model for ejector predicts the effect of mixing ratio and temperature on the pressure ratio as well as outlet temperature (operating temperature of pre-reformer) of induced fluid. In addition the model for pre-reformer predicts the effect of input gas temperature on the shift and reforming reactions kinetic. The SOFC developed electrochemical model predicts the effects of electrical load variations on out put gas composition as well as its characteristics. Finally components model are coupled together to conduct a parametric study of the complete cycle. It is found that at the low mixing ratio the pressure variation with the mixing ratio is very sharp but at mixing ratios higher than 1.5 the outlet pressure curve will become smooth. And also it is observed that CH4 mole fraction decreases but H2 and CO2 mole fractions will increase as the input temperature augments.
Application of Single-Layered Graphene Sheets as Mass Sensors and Atomistic Dust Detectors
Authors: Sakhaee-Pour A. , Ahmadian M. T. , Vafai A.
Published: May 2009

Molecular structural mechanics is implemented to model vibrational behavior of defect free single-layered graphene sheets (SLGSs) at constant temperature. To mimic these two-dimensional layers, zigzag and armchair models with cantilever and bridge boundary conditions are adopted. Fundamental frequencies of these nano structures are calculated, and it is perceived that they are independent of the chirality and aspect ratio. Effects of point mass and atomistic dust on the fundamental frequencies are also considered in order to investigate the possibility of using SLGSs as sensors. Results of exhibit the principle frequencies are highly sensitive to the added mass in the order of 10−6fg.
Economic Optimization of a Cogeneration System for Apartments in Korea
Authors: Seo HyonUk , Sung Jinil , Oh Si-Doek , Oh Hoo-Suk , Kwak Ho-Young
Published: May 2009

A cogeneration system which can be used as a distributed generation source produces electricity and heat energy simultaneously from a single source of fuel. For industrial and domestic applications, where both kinds of energy are required, the cogeneration system can return fossil fuel energy savings up to 30%, and can reduce CO2 emissions correspondingly as compared with a conventional system. In this study, eight apartments with residential areas in the range of 7200 m2 to 18200 m2 were chosen to study how much energy savings can be achieved by adoption of the cogeneration system in those apartments. Based on the energy demand data for heat and electricity, an optimum configuration of the cogeneration system for each apartment was determined by a developed computer program. The economic gain achieved by introducing the cogeneration system in those apartments was estimated and the monitored values compared with the estimated ones. By adoption of the cogeneration system, the fossil fuel saved was more than 30% and an average economic gain of $3.6/m2 per year was obtained.
Characterization of Micro-Features in Polymeric Drug Delivery Devices Using FDM
Authors: Masood S. H. , Singh Shivdeep
Published: May 2009

This paper presents the results of the experimental work done in applying the Fused Deposition Modelling (FDM) rapid prototyping technique to fabricate and characterise the porous polymeric matrix for controlled drug delivery device (DDD). With FDM technique, both macro and micro level structures of the device matrix can be produced and controlled, which provide several advantages over the conventional techniques of DDD fabrication. The paper investigates effect of various FDM parameters viz. Raster Width, Contour Width, Air-gap and Raster Angle on the controlled drug release profiles, drug infiltration and porosity of fabricated device matrices. The paper concludes that effective DDD matrices with desired release regimes can be fabricated using FDM technology with careful selection of FDM control parameters.
Numerical Simulation of Coal Gasification in a 1 t/h Two-Stage Entrained Flow Gasifier
Authors: Du Min , Hao Yingli , Wang Yan
Published: May 2009

Coal gasification has received increasing attention in the past two decades due to the growing demand for clean gaseous fuels. Numerical simulations of the coal gasification process inside a two-stage dry feed entrained flow gasifier were carried out using the commercial CFD solver FLUENT. The predicted main product gas components and carbon conversion were in well agreement with the measured data, which verified the validity of the model. A series of calculations were carried out to investigate the effects of operating parameters on the performance of gasifier, including the coal particle size, coal type and coal feeding ratio between the first and the second stages. The flow field, coal particle deposition on the wall, gas temperature and mole fraction inside of the gasifier were analyzed. And the simulation results indicated that the performance of gasifier is improved with decreasing particle size. The low volatile component fraction or high ash content in coal is not propitious to the gasification performance. And the performance of gasifier of the case with coal distribution with 75% (first stage) vs. 25% (second stage) is better than the case with 50% (first stage) vs. 50% (second stage) and the case with 100% for the first stage. The calculation is helpful for designing the operating conditions of the gasifier.
The Effect of Turboset Bearing Misalignment Defect on the Bearing Journal and Bush Trajectory Pattern
Authors: Rybczynski Jozef
Published: May 2009

The paper presents results of simulation of the bearing misalignment defect in a power turboset. The results are shown in the form of a set of journal and bush trajectories of all bearings in the turboset. The subject area of analysis was the vibrational effect of displacing two most vulnerable bearings in horizontal and vertical directions by a maximum permissible range calculated taking into account the permissible bearing vibration criterion. Relations were shown between the shape and dimensions of particular bearing trajectories on the one hand, and their location with respect to the misaligned bearing and direction of misalignment, on the other hand. It was indicated that the relative journal trajectories and absolute bush trajectories carry much more information about the dynamic state of the machine than vibration amplitudes measured by standard. The trajectories contain the information on the amplitudes of relative and absolute bearing vibrations in all directions, complemented by journal and bush trajectory shapes, indicating the way in which bearings are loaded. As a result trajectories can be a source of information on the position and direction of bearing displacements. The article indicates the potential of using trajectory patterns for diagnosing misalignment defects in rotating machines. Including a set of trajectories to the base of knowledge of a diagnostic system can extend its diagnostic abilities by including bearing misalignment defects, which are frequently recorded in these machines.
The Design and Experimental Validation of an Ultrafast SMART (SMA Resettable) Latch
Authors: Redmond John A. , Brei Diann , Luntz Jonathan , Browne Alan L. , Johnson Nancy L. , Strom Kenneth A.
Published: May 2009

Latches are an essential machine element utilized by all sectors (medical, military, industrial, etc.) and there is a growing need for active latches with automatic release and reset capabilities. Shape memory alloy (SMA), due to its high energy/power densities, is an attractive alternative actuation approach to conventional methods (electrical, hydraulic) because it is inexpensive, lightweight, compact and has a fast heating response times. This paper introduces the T-latch which is based upon a compact spooled SMA rotary actuator. The T-latch can engage passively, maintain a structural connection in multiple degrees of freedom with zero power consumption, actively release very quickly (< 20 ms) and then repeat operation with automatic reset. To provide the basis to apply this latch across sectors, operational behavioral models are summarized for the key states of engagement, retention, release and reset. To demonstrate the technology, a proof-of-concept prototype for automotive panel lockdown was designed, built and experimentally characterized for the basic operational states along with studies of the effects of power, seal and reset force. The results from this study indicate promising suitability of the T-latch technology for a broad range of industrial applications.
Online Wall Thickness Control for Blow Molded Part Using Fuzzy Iterative Learning Control Algorithm
Authors: Huang Geng-Qun , Huang Han-Xiong
Published: May 2009

Blow molded parts require a strict control of the wall thickness distributions so as to achieve the required mechanical performance and to minimize the usage of material. In this work, an online wall thickness control strategy for the extrusion blow molded part was presented. A multichannel ultrasonic thickness measuring system was used to obtain the part wall thickness. A feedback control system based on fuzzy iterative learning control (ILC) algorithm was designed and implemented to control the part thickness. Instead of using the pure numerical method, engineer knowledge and experience were combined in the control algorithm using fuzzy rules. The results showed that the online wall thickness control system developed in this work can automatically achieve the die gap profile and the resulting part thickness can satisfy the desire thickness distribution.
Computational Study of SiC Halide Chemical Vapor Deposition System
Authors: Wang Rong , Ma Ronghui , Dhanaraj Govindhan , Chen Yi , Dudley Michael
Published: May 2009

Halide CVD (HCVD) is recently employed to grow SiC epitaxial layers using SiCl4/C3H8/H2 mixtures in an effort to achieve high deposition rates. The introduction of the chlorinated species allows the formation of more stable species SiCl2 while maintaining high surface reactivity, thus avoiding the silicon gas phase nucleation that has been widely reported in conventional CVD process using SiH4/C3H8/H2. However, the difficulties in reducing defect density and controlling the electrical properties of the material present a significant technical obstacle for HCVD of SiC. In experimental growth, the electrical properties, defect densities and the growth rate of as-deposited SiC epitaxial films are, to a large extent, determined by processing parameters including temperature, pressure, flow rates of precursors and carrier gas. Optimization of growth conditions provides the opportunity to engineer films with desired film properties and qualities at high deposition rate but requires in-depth understanding the deposition process. In this study, we performed computational study to investigate the effects of main processing parameters in HCVD process on film growth. Numerical experiments were performed over a wide range of operational parameters to provide information on distributions of gas velocity, temperature, and chemical species’ concentrations in the reactor as well as the deposition rates on the substrate surface. Simulations were also carried out to address hot zone design and operational conditions.
Design and Experimental Validation of a Structural Health Monitoring Fastener
Authors: Rakow Alexi , Chang Fu-Kuo
Published: May 2009

In this study a structural health monitoring (SHM) fastener, with built-in eddy current sensors for in-situ monitoring of fatigue cracks at hole locations in layered metallic joints was developed. This presents an optimal method of sensor integration for early stage detection of these cracks, which are among of the most common forms of damage in airframes. Thin, conformable eddy current sensors optimized for in-hole flaw detection [1] and a method of mechanical integration and complete data acquisition and software system are discussed. Results from fatigue tests of single layer and multi-layer specimens are presented in addition to results from bench-top flaw detection tests as a means of experimental validation of the system.
Laser Hybrid Welding of Advanced High Strength Steels (AHSS) for Automotive Body Construction
Authors: Koganti Ramakrishna , Angotti Sergio , Joaquin Armando , Stiles Eric
Published: May 2009

In response to demands for improved safety standards and fuel economy, automotive OEMs have shown an increased interest for using light weight materials with greater strength. Advanced High Strength Steels (AHSS) have gained popularity due to their superior mechanical properties and weight advantages, as compared to mild steel materials. Welding of AHSS materials remains one of the technical challenges in the successful application of AHSS in automobile structures, especially when durability of the welded structures is required. Currently, various fusion welding processes such as Metal Inert Gas (MIG), Laser and Laser Hybrid are used on mild steel applications. The Laser and Laser Hybrid weld processes continue to gain popularity in automotive applications due to their ability to provide structural integrity and manufacturing efficiency. In laser welding, only a light source is used to join materials together. In laser hybrid, both a light source and metal filler are used to join the materials. In this paper, the laser hybrid joining process on AHSS materials (DP780 and Boron) is investigated. Influence of heat from Laser Hybrid welding process and its effect on the steel is discussed.
Numerical Study of Liquid Slug Stability During Adiabatic Two Phase Flow Inside a Minichannel
Authors: Mukherjee A. , Allen J. S.
Published: May 2009

The present study is performed to analyze stability of a liquid meniscus inside a microchannel. A liquid plug is placed inside a microchannel and the shape and stability of upstream and downstream interfaces have been studied for different airflow rates. The thickness of the liquid plug and the contact angle has been varied systematically. In the numerical model the complete Navier-Stokes equations along with continuity equation are solved using the SIMPLER method. The liquid vapor interface is captured using the level set technique. The liquid plug is seen to move downstream along with the air and surface instabilities are noted at the upstream and downstream interfaces. At low contact angle, water is found to accumulate at the channel corners due to capillary forces causing the slug to disintegrate. The numerical results are found to be qualitatively similar to experimental data.
Combined Non-Luminous Flame Radiation and Surface Tension Effects During Methanol Droplet Combustion
Authors: Raghavan Vasudevan , Pope Daniel N. , Gogos George
Published: May 2009

The effect of non-luminous thermal radiation on suspended (constant relative velocity) methanol droplet combustion in a low temperature (300 K) and low pressure (1 atm) environment is discussed in detail. Numerical results are obtained using a predictive, transient, two-phase, axisymmetric numerical model that includes surface tension effects. Radiation is modeled using the optically thin approximation with the product species CO2 and H2O as the radiating species. Results for combustion in a quiescent atmosphere (initial Reynolds number 0.01) and initial droplet diameters in the range of 0.43 mm to 3 mm are presented. The results show that the effect of flame radiation is negligible when the initial droplet diameter is less than approximately 1 mm and becomes increasingly important for droplets with initial diameters greater than approximately 1 mm, as reported in previous literature. The average evaporation constant decreases with the initial droplet diameter. Both radiation and surface tension have a significant effect on the predicted extinction diameters of initially larger droplets. The extinction diameter presents a non-linear variation with the initial droplet diameter for initially larger droplets and agreement with experiments is good.
Analytical Homogenization for Microelectronic Substrates
Authors: Modi Mitul , Kulkarni Deepak , Bao Andy , Bekar Ibrahim , Cho Steve
Published: May 2009

Organic substrates used in microelectronic packages contain complex micro-via, plated-through-hole via, and copper networks in order to accommodate stringent electrical requirements of power delivery and I/O. These complex layouts can produce significant inhomogeniety in the in-plane and out-of-plane mechanical properties of the substrates. An analytical homogenization methodology has been established that uses substrate design geometries and material properties such as the copper density and via locations with two-phase micromechanics models to homogenize the substrate. In this paper the homogenization methodology is discussed and validated with experimental data. A comparison of the various two-phase micromechanics models commonly found in literature are reviewed and compared for their applicability to accurately homogenize organic substrates. Two case studies are provided to highlight the importance of accurately modeling the anisotropy of the substrates for temperature cycling and bend reliability predictions.