bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-Dimensional Numerical Study of Two-Phase Flow (Gas-Liquid) in a Microchannel Mixer
Authors: Abdel-Salam Tarek , Bayraktar Tuba , Pidugu Srikanth
Published: May 2012

Microfluidic systems are important in a variety of applications such as DNA sequencing, cell separation, environmental monitoring, heat transportation in spacecraft and space station [1–2]. Micromixers are the most important component in microfluidic systems and they can be classified as active and passive micromixers [3]. In micro dimensions, surface forces dominate over body forces requiring special attention for problems involving two-phase flows with free surfaces which are often driven by capillary forces [4]. In the present work the flow and mixing process in a passive microchannel mixer were numerically investigated. Effects of velocity, surface tension, and contact angle on the two phase flow were studied. Numerical results are obtained with a finite volume CFD code and using structured grids. Different liquids-gas Reynolds number ratios (Reliquid/Regas) were used ranging from 4 to 42. In addition, five values of the contact-angle (0 – 120) and seven values of the liquid surface tension (0.02 – 0.1) were used. Results show that increasing Reliquid increases the rate of the development of the air bubble. Increased surface tension resulted in increased bubble length. Bubble length decreased with increased contact angle till 75 degrees and further increase resulted in increased bubble length.
Energy Absorption and Dissipation Performance in Cycloid Guided Pendulum Absorbers
Authors: Rashidi Younes , Arzanpour Siamak , Tabatabaian Mehrzad
Published: May 2012

The dynamic energy absorbers are auxiliary systems that are attached to the main structure and widely used as a simple solution for neutralization of vibrations. Among various types of pendulum vibration absorbers are preferable for high-rise buildings, bridges and other civil structures for suppression earthquake-excited vibrations. The problem in dissipating vibration of earthquake is its unknown characteristics such as excitation frequency and magnitude. As a result, designing of an effective self tuning vibration absorber that can adjust its performance according to the excitation frequency will be a challenge. The situation is to have an absorber that can respond at a single frequency for wide range of excitation amplitude so its parameter can be well adjusted for the maximum energy dissipation. It is shown [5] that period in cycloid pendulum is constant for large amplitude. This feature is a major advantage of cycloid pendulum absorbers that could be used in combination with an energy dissipation mechanism to reduce the induced motion in a structure. In this paper, two types of vibration absorbers, i.e., simple and cycloid pendulum are analytically compared. The simulation results demonstrate the superiority of the cycloid damper type in energy absorption/dissipation over a simple pendulum one.
Dynamic Response of Small Cantilever Beams in Viscous Media
Authors: Mishty A. , Stewart P. , Mian A.
Published: May 2012

We have considered two configurations of cantilever beam for characterization of rheological properties (density and viscosity) of viscous material. Both the beams are made of thin steel foils, having different free end condition. The beams were vibrated in various viscous fluids such as water and lubrication oils under sweeping modes, and the frequency response of the beam was measured using Polytec laser vibrometer. For both beam configurations, the resonance frequency decreased while the width of the resonance peak (related to Q-factor) increased with increasing viscosity and density. Thus, the viscosity and the density of a liquid can be determined simultaneously using the experimentally measured resonance frequency and peak width.
The Fatigue and Aging Effects on the Materials of the Nuclear Power Plant Components and Systems
Authors: Akbar Sajjad , Khalil M. Shahid
Published: May 2012

The first generation of nuclear power plants (NPP) parts, components, equipment and systems have completed their predicted trouble free operational life. Now their materials are posing fatigue and aging effects for the future useful applications in the NPP. For the reliable future operations, this study is made for the management of the fatigue and aging effects on the components/systems. The neutron irradiation and normal aging phenomena will cause deterioration in the properties of materials by increasing brittleness-ductile transition temperature. This would affect the reactor pressure vessel as well. For the design purpose as well as estimating the permissible service life of a reactor pressure vessel, it is essential to have reliable data regarding this effect. Considerable efforts have been made and data search carried out on this work. The routine and schedule maintenance programs are the prerequisite means of managing fatigue and aging effects. Therefore, these are monitored through collecting data on plant service condition, inspection, surveillance, testing and by regularly monitoring such programs. This paper presents the future course of actions, which are necessary in the enhancement of the useful and safe NPP operations throughout the world.
Diagnosis of Defected Rolling Bearings via Vibration Analysis Method
Authors: Hamedynia Majid , Rokni D. T. Hossein
Published: May 2012

The main function of rolling element bearings is to provide low friction conditions for supporting and guiding a rotating shaft. The rolling element bearing includes both ball bearings and roller bearings. Rolling element bearings operate with a rolling action whereas plain bearings operate with a sliding action. In various applications, these bearings are considered as critical mechanical components since defect in these components may lead to malfunction and catastrophic failure in some cases. Vibration analysis is one of the most established methods used to evaluate the condition of bearings in operating machines. In this paper, an abnormal detection structure, in which different types of abnormal detection routines can be applied, is proposed. Bearing fault modes and their effects on the bearing vibration are discussed. In order to achieve this purpose, a feature extraction method is developed to overcome the limitation of time domain features. Experimental data from bearings under different operating conditions are used to verify the proposed method.
Stability of Shear-Thickening Liquids Between Rotating Cylinders
Authors: Ashrafi Nariman , Karimi Haghighi Habib
Published: May 2012

The effects of nonlinearities on the stability are explored for shear thickening fluids in the narrow-gap limit of the Taylor-Couette flow. It is assumed that shear-thickening fluids behave exactly as opposite of shear thinning ones. A dynamical system is obtained from the conservation of mass and momentum equations which include nonlinear terms in velocity components due to the shear-dependent viscosity. It is found that the critical Taylor number, corresponding to the loss of stability of Couette flow becomes higher as the shear-thickening effects increases. Similar to the shear thinning case, the Taylor vortex structure emerges in the shear thickening flow, however they quickly disappear thus bringing the flow back to the purely azimuthal flow. Naturally, one expects shear thickening fluids to result in inverse dynamical behavior of shear thinning fluids. This study proves that this is not the case for every point on the bifurcation diagram.
Multidisciplinary Visualization Aspects in European R&D Projects
Authors: Vucinic Dean
Published: May 2012

The paper addresses Scientific Visualization (SV) aspects in the Modeling and Simulation (M&S) environments, experienced by the author in the multidisciplinary European Research and Development (R&D) projects, which are expect to meet the challenges in the growing complexity of software tools and their visualization features, considered as an essential factor to improve their quality and efficient use. The visualization tools are considered as the natural integration mechanism to evidence the complexity and to provide missing integration solutions. Today’s visualization tools are equipped with highly interactive visual aids, which allow analysis and inspection of complex numerical data generated from high-bandwidth data sources such as simulation software, experimental rigs, satellites, scanners, etc… Such tools help scientist and engineers in data extraction, visualization, interpretation and analysis tasks, enabling them to experience high degree of interaction and effectiveness in solving their design problems. Today, the modern engineering design is, and has to be based on the M&S principles, as the key enabler to combine multidisciplinary workflows to manage and to structure such highly complex industrial solutions, which heavily include generic M&S tools and open standards solutions. The author experience, gained in solving the M&S problems in European R&D projects is presented throughout a time-span of last two-decades, where the software technologies have been researched and demonstrated, especially addressing the SV software evolution in engineering, and in addition, the information visualization in general.
A New Method for Protecting Pipeline in Summer Monsoon
Authors: Jia Shaohui , Guo Lei , Feng Qingshan , Zhou Lijian , Huang Yan
Published: May 2012

In annual summer monsoon, geo-hazard is common. Monsoon-caused casualties and economic losses throughout the year accounted for 70% ∼ 80% of the total annual losses. Also, geo-hazard is a serious threat for pipeline operators to manage. Over 12,000 kilometers of pipelines with crude oil, gas, and refined oil are operated by PetroChina Pipeline Company. The pipelines, through sixteen provinces and cities, have been operated for over forty years. Geographic Information System (GIS) technology, as an effective spatial analysis tool, provides advanced analysis for pipeline geo-hazard prediction and early warning during summer monsoon based on field data and historical precipitation records. After many years of research and application of our prediction model of pipeline geo-hazard, an important link between geo-hazard and rainfall is understood. Rainfall is the main triggering factor of geo-hazards such as landslide and debris flow leading to heavy losses, especially rainstorm and heavy rainstorm. We use GIS technology to perform spatial analysis with predicted rainfall data the next twenty-four hours and the data of pipeline geo-hazard susceptibility, and predict the severity of pipeline impacts caused by geo-hazards during the next twenty-four hours. Finally, the result is modified by existed geo-hazards data. The pipeline geo-hazard early warning is divided into five ranks which are displayed by different colors, and pipelines damaged by geo-hazards and protection measures are also proposed. During July 16 and 17 of 2009 years, we released geo-hazard early warning four rank of Lanzhou-Chengdu-Chongqing Oil Pipeline through PetroChina Pipeline Company web page and the communication software of Instant Messaging. The Lanzhou-Chengdu-Chongqing Oil Pipeline Company acted promptly with a detailed deployment and emergency plan to ensure pipeline safety.
Experimental Determination of Parameters to Avoid Arcing in Electrical Discharge Machining of Titanium Diboride Particulate Reinforced Ferrous Matrix Composite
Authors: Pandey Akash B. , Brahmankar Prakash K. , Purohit Harsh S.
Published: May 2012

Titanium diboride (TiB2) particles are most popular reinforcement along with tungsten carbide for ferrous matrices for developing composites with high specific modulus, improved wear resistance and hardness while providing good fatigue properties as well. The hardness of such composites poses a problem in conventional machining in terms of very fast wear rates of tools and very high cutting forces. Non-conventional processes like electrical discharge machining (EDM) are very popular for machining of conductive composites like TiB2 reinforced ferrous matrix composites. However, there are a large number of process parameters for EDM which need to be selected and controlled carefully for satisfactory machining performance. Parameter settings which lead to arcing are specifically investigated and avoided as this phenomenon leads to uncontrolled machining through short circuit conditions and large energy discharges. In this paper, an experimental approach to determine the parameter settings which will lead to arcing during EDM machining of TiB2 particulate reinforced ferrous matrix composite is discussed. Values of major EDM process parameters are selected in roughing, intermediate and finishing domains. Experimental trials using L27 design of experiment are conducted and parameter combinations leading to arcing are recorded and the zone of parameters that can lead to arcing is identified.
Increasing the Diesel and Brayton Cycle Efficiency With Thermoelectric Materials
Authors: Sarnacki W. Peter , Wallace Travis T. , Wlodkowski Paul A.
Published: May 2012

Thermoelectric materials, utilizing the Seebeck effect, have the potential of augmenting the thermal efficiency of all types of internal combustion engines and in particular, a simple cycle gas turbine, as well as the combined steam and gas turbine cycles. Current research and development at Maine Maritime Academy (MMA) has successfully demonstrated the conversion of waste exhaust heat into electrical power from a marine diesel and micro gas turbine. While the automotive industry has been investigating the utility of thermoelectric materials in passenger vehicles for a number of years, the authors believe that the marine and stationary power industries would be the significant beneficiaries of this technology given economies of scale and greater ability to generate higher thermal gradients. This paper examines both the application of thermoelectric generation on marine diesel propulsion systems, and a micro gas turbine. Research and development at MMA highlights the ability to supersede existing thermal efficiency barriers encountered by each power producer.
Enhancing Mechanical Properties of AZ31 Magnesium Alloy Through Simultaneous Addition of Aluminum and Nano-Al2O3
Authors: Han S. , Alam M. E. , Hamouda A. M. S. , Nguyen Q. B. , Gupta M.
Published: May 2012

In the present study, AZ31-Al2O3-Al magnesium nano-composites were successfully synthesized using an innovative disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization studies revealed uniaxial grain size, reasonably uniform distribution of particulates/intermetallics in the matrix and minimal porosity. Physical properties characterization revealed that addition of both nano-Al2O3 and Al reduced the coefficient of thermal expansion (CTE) of monolithic AZ31. The presence of both Al2O3 particulates and aluminum also assisted in improving overall mechanical properties including microhardness, UTS, ductility and work of fracture of AZ31. The results suggest that these composites have significant potential in diverse engineering applications when compared to AZ31 alloy.
Optimization of Machining Parameters for Surface Roughness in EDM of AISI 1045 Based on Taguchi Technique
Authors: Kumar Subodh , Agarwal Sanjay
Published: May 2012

Electrical discharge machining (EDM) is a nontraditional manufacturing technique that has been widely used in the production of tools and dies throughout the world in recent years. The most important performance measure in EDM is the surface roughness. In this study, the effect and optimization of machining parameters on surface roughness in an EDM operation was investigated by using the Taguchi method. The experimental studies were conducted under varying discharge current, duty cycle and pulse-duration. An orthogonal array, the signal-to-noise (S/N) ratio, and the analysis of variance (ANOVA) were employed to the study the surface roughness in the EDM of AISI 1045 tool steel. It was observed that the discharge current was the most influential factors on the surface roughness. To validate the study, confirmation experiment has been carried out at optimum set of parameters and predicted results have been found to be in good agreement with experimental findings.
Remote Measurement and Heat Demand Control of CHP System With Heat Storage at Sapporo City University
Authors: Kurata Osamu , Iki Norihiko , Matsunuma Takayuki , Maeda Tetsuhiko , Hirano Satoshi , Kadoguchi Katsuhiko , Takeuchi Hiromi , Yoshida Hiro
Published: May 2012

Combined heat and power (CHP) systems are widely used to prevent global warming and reduce energy costs. Both high efficiency of the elements and good coordination of the systems are considered as the points to solve. A microturbine CHP with a latent heat storage system was demonstrated at Sapporo City University. The heat exchanger of the CHP and an economizer were located in parallel downstream a bypass-dumper of the exhaust gas. The latent heat storage tank was located downstream the economizer. The bypass-dumper released exhaust gas when the boiler water in the heat exchanger exceeded 90°C. It is very important to use the heat supply of hot water as much as possible. At Sapporo City University, the winter term heat demand from 6pm to 7pm was somewhat smaller than that from 8am to 6pm. We tested a partial load from 6pm to 7pm to observe how it would respond to the heat demand. The heat supply from the microturbine CHP from 6pm to 7pm was shown to be controllable with heat storage. The heat supply from the microturbine CHP at the lowest power was larger than the heat demand so without the heat storage it was uncontrollable.
Efficient Probabilistic Analysis and Design Optimization Using Data Classification Decision Boundaries
Authors: Wang Liping , Subramaniyan Arun K. , Beeson Don
Published: May 2012

A new technique for performing probabilistic analysis and optimization design using data classification methods is investigated. The approach is based on nonlinear decision boundaries constructed from data classification methods. A statistical learning tool known as support vector machine (SVM) is used to construct the boundaries. An adaptive sampling technique is used to generate samples and update the approximated decision function. The proposed approach is demonstrated with several benchmark and engineering problems.
Evaluation of Circuit Models for an IPMC Sensor to Effectively Detect the Bending Angles of a Body
Authors: Park Kiwon , Yoon Myung-Keun
Published: May 2012

Ionic Polymer-Metal Composite (IPMC) consists of an ion conductive membrane plated by metallic electrodes on both surfaces. When it bends, a voltage is generated between two electrodes. Since IPMC is flexible and thin, it can be easily mounted on the various surfaces of a body. Moreover, IPMC can produce output voltages without attenuation under large deflections. The present study investigates a sensor system using IPMC to effectively detect the bending angles applied on IPMC sensor. The paper evaluates existing R and C circuit models of IPMC and selects the best model for the detection of angles. The circuit models describe the relationship between input bending angles and output voltages. The identification of R and C values was performed by minimizing the error between the real output voltages and the simulated output voltages from the circuit models of IPMC sensor. Then the output signal of a sensor was fed into the inverse model of the identified model to reproduce the bending angles. In order to support the validation of the model, the output voltages from an arbitrary bending motion were also applied to the selected inverse model, which successfully reproduced the arbitrary bending motion. On-going work includes investigation of the selected circuit model to better understand the dynamics of the sensor as well as the relationships between electric and physical parameters of the sensor.
Performance of Solid-Liquid Two Phase Jet Pump Vacuuming Up Beach Sand
Authors: Itoh K. , Nishigaki S. , Honda I. , Yoshida T. , Boda A. , Kumamaru H. , Shimogonya Y.
Published: May 2012

The performance of the water-sand two phase jet pump has been evaluated for developing environmental sand purification systems. Three types of throat diameter, D = 26, 31, 37 mm, are tested with constant nozzle-exit diameter 20 mm in order to vary the cross section ratio of nozzle exit to throat, R = 0.59, 0.42 and 0.29. The coarse and fine natural sands extracted at Hirase-higashi beach and artificial crushed sand, of which the fineness modulus are 2.71, 2.03 and 2.88 respectively, are mixed in the secondary water flow. The concentration of sand is less than 18% in the present experiment. It is confirmed that the dependences of two-phase efficiency curve and of two-phase flow rate ratio curve upon cross section ratio R agrees with those of single phase flow. On the other hand, the effect of particle size appears in the range of decrement of pump efficiency. That is, it is found that the deviation between two phase and single phase efficiency is 10% on average for coarse sand, whereas the deviation is almost zero for fine sand.
Computational Fluid Dynamics Modeling of Redundant Stent-Graft Configurations in Endovascular Aneurysm Repair
Authors: Tse Leonard W. , Shek Tina L. T. , Nabovati Aydin , Amon Cristina H.
Published: May 2012

An aneurysm is a bulge or localized dilation of an artery that can result in rupture, rapid blood loss, and death. Endovascular aneurysm repair (EVAR) is a minimally-invasive surgical technique that involves delivery of a stent-graft from within the blood vessels. The metallic stents anchor and support the graft (fabric tube), through which blood flow is contained and directed. This relieves the pressure on the weakened aneurysm wall. When the stent-graft is too long for a given patient, the redundant (extra) length adopts a convex configuration in the aneurysm. Based on clinical experience, we hypothesize that redundant stent-graft configurations increase the downward force acting on the device thereby increasing the risk of device dislodgement and failure. This work numerically studies both steady-state and physiologic pulsatile blood flow in redundant stent-graft configurations. Computational fluid dynamics simulations predicted peak downward displacement force for the zero-, moderate- and severe-redundancy configurations of 7.49, 7.65 and 8.04 N, respectively for steady-state flow; and 7.55, 7.70 and 8.31 N, respectively for physiologic pulsatile flow. These results suggest that redundant stent-graft configurations in EVAR do increase the downward force acting on the device, but the clinical consequence depends significantly on device-specific resistance to dislodgement.
Piezo Thermoelastic Model for Quality Factor Optimization of Resonant Rings
Authors: Vigevani Gabriele , Myers David R. , Pisano Albert P.
Published: May 2012

In this work an analytical model for the computation of thermoelastic losses for piezoelectric resonant rings vibrating in flexural mode is presented. The analytical model is based on the classic dynamic balance equations for ring structures [1] and considers the constitutive equations for piezoelectric and pyroelectric materials. The approximations of this work are based on the recent analysis for thermoelastic beams by Lifshitz and Roukes [6] and its application to isotropic rings in [10] and [11]. This work shows that for isotropic thermoelastic materials the ultimate Q-factor is determined by the geometry of the vibrating ring. However, for piezoelectric and pyroelectric materials the Q-factor is penalized by 15%.
Analysis of Frequency Band Gaps in a Plate With Periodic Stubbed Surface
Authors: Huang Zi-Gui
Published: May 2012

The applications and researches of so-called photonic crystals raise the exciting researches of acoustic wave propagation and frequency band gaps in phononic crystals. The photonic crystal structure can be modeled in two different forms, namely the periodically-repeated dual materials, or a single medium with periodically-repeated stubbed surface. This paper presents the results of the tunable band gaps of acoustic waves in a plate with periodic stubbed surface using the finite element method. Band gaps variations of the plate modes due to different oriented angles of periodic stubbed surface are calculated and discussed. The results show that the elastic band gaps for plate modes can be enlarged or reduced by adjusting the orientation of stubbed surface. The phenomena in this idea can potentially be utilized for the design of new resonance frequency devices.
The Investigation of 3D Embedded Microchannel Networks for 3D IC Cooling, Vacuum Packaging and THz Passive Device Applications
Authors: Miao Min , Zhang Jing , Zhang Yang , Han Bo , Jin Yufeng
Published: May 2012

This Paper reports the design, simulation and test of 3D microchannel networks intended for the 3D IC stackup cooling, vacuum building and even THz passive device applications. Recently, the prominent advantages of 3D IC integration, including reduction in system size, interconnect delay, power dissipation and enabling hyper-integration of chips from disparate process technologies, have drive the relentless research effort worldwide. Although various low-power methodologies are exploited, rapid increasing in device packing density in 3D stacking of chips have demanded revolutionary heat removal technologies, as high performance chips projected to dissipate more than 100W/cm2 and require more than 100A of supply current are frequently integrated. Besides, high data rate and bandwidth interconnects are urgently needed as an efficient data transfer backbone between the chips comprising 3D ICs. To address these limits, the authors investigated 3D microchannel networks with various layouts such as fractal tree, which is embedded into stackup structures for highly efficient cooling, and as THz (terahertz) range waveguides. The 3D microchannel networks, with water as working medium are designed and simulated with computational fluidic dynamic methodology, which reveals both the flow and temperature fields and verifies their effectiveness in 3D stackup structure cooling. The 3D microchannels are further experimentally validated on a fast microsystem prototyping platform based on laminating multiple layers of Low Temperature Cofired Ceramic plates, which is capable of quickly realizing a complex exterior or interior 3D structures, for experimental validation. A testing system is set up, consisting of resistive heating source, temperature pickup device and microfluidic metering pumping devices. The temperature rises for samples with or without 3D microchannels with different configurations under various heat flux are obtained and compared with simulated results. The testing results shows that this embedded microfluidic cooling technique may effectively realized a decrease of around 60 centigrade at a heat flux of 1W/cm2 and increase with the flux, confirming the effectiveness of this 3D microchannel in cooling a stackup structure and that of the simulation and modeling. Beside the microchannel, combined with sealed pipe I/O joints may effectively act as a ventilation pumping path for the vacuum buildup, adjustment and vacuum level inspection for 3D IC vacuum packaging. In addition, the authors present the investigations of the conceptional design of waveguide and functional structures operating at terahertz frequencies, together with the simulation results which demonstrate the prosperity of this simple structure for high data rate transmission in 3D IC stackups.
CFD Simulation of Flow in a Circular Pipe With Percina Rex Fish
Authors: Bangaru Sreekanth , Cui Jie
Published: May 2012

We tried to correlate the fish behavior observed in the laboratory during the development of the exhaustion threshold curves with flow field in the fish passage with culverts and other impediments. In particular, we focused on aspects of fish behavior which may have exploited the velocity and turbulence fields in a circular passage. Roanoke logperch ( Percina rex ), the largest of the Virginia’s darters are federally endangered species. Logperch of different sizes were tested during the development of the exhaustion threshold curves at different velocities ranging from 40 to 70 cm/s in the laboratory in a circular pipe. The pipe was divided into four quadrants in the streamwise direction. Simulations were run at velocities 40 and 70 cm/s using Computational Fluid Dynamics (CFD) software Fluent with fish at center and bottom of the pipe. The velocity and turbulence kinetic energy contours of all the positions of the fish were compared to correlate the fish behavior observed in the laboratory.
Steam Condensation in Parallel Channels of Plate Heat Exchangers
Authors: Bobbili Prabhakara Rao , Sunden Bengt
Published: May 2012

An experimental investigation has been carried out to find the nature of temperature profiles of the process and cooling fluids during steam condensation across the port to channel in plate heat exchangers (PHEs). In the present study, low corrugation angle (30°) plates have been used for different plate package of PHEs with 41 and 81 plates. The process steam entered at 1 bar with a small degree of superheat. Water has been used as the cold fluid. A traverse temperature probe is inserted into both inlet and outlet ports of the plate heat exchanger. The temperature of the process steam and cooling fluid have been measured and recorded at the location of first, middle and last channels for different inlet and exit flow conditions for each plate package of the heat exchanger. Also, the overall pressure drop has been measured at different conditions at the outlet of the process steam, i.e., full and partial condensation. The traverse temperature measurements have indicated that there is a considerable variation in temperature along inlets and outlets of process steam and cooling fluid, due to flow maldistribution. The experimental data has been analyzed to show how the flow distribution on the cooling side affects the condensation of steam in plate heat exchangers. The present results will help to study further the nature of steam condensation in parallel channels of heat exchangers.
Modeling Competitive Adsorption in Urea-SCR Catalysts for Effective Low Temperature NOx Control
Authors: Devarakonda Maruthi , Tonkyn Russell , Tran Diana , Lee Jong H. , Herling Darrell
Published: May 2012

Although the SCR technology exhibits higher NOx reduction efficiency over a wider range of temperatures among the lean NOx reduction technologies, further improvement in low-temperature performance is required to meet the future emission standards and to lower the system cost. In order to improve the catalyst technologies and optimize the system performance, it is critical to understand the reaction mechanisms and catalyst behaviors with respect to operating conditions. For example, it is well known that the ammonia coverage on catalyst surface is critical for NOx reduction efficiency. However, the level of ammonia storage is influenced by competitive adsorption by other species, such as H2O and NO2. Moreover, hydrocarbon species that slip through the upstream DOC during the cold-start period can also inhibit the SCR performance, especially at low temperatures. Therefore, a one-dimensional kinetic model that can account for the effects of such competitive adsorption has been developed based on steady state surface isotherm tests on a commercial Fe-zeolite catalyst. The model is developed as a C language S-function and implemented in Matlab/Simulink environment. Rate kinetics of adsorption and desorption of each of the adsorbents are determined from individual adsorption tests and validated for a set of test conditions that had all the adsorbents in the feed gas. Using the competitive adsorption model, a kinetic model for standard-SCR reaction involving NH3 and H2O is developed and validated.
Deep Drawing Height Analysis of Rectangular Cup Drawing
Authors: Colorado Alonso Francisco J. , Medelli´n Castillo Hugo I. , Garci´a Zugasti Pedro de J. , de Lange Dirk F.
Published: May 2012

The deep drawing process is widely used in industry because it allows the production of parts with reduced weight and good mechanical properties. However, the deep drawing process of non-cylindrical shapes still relies on experimental and trial and error methods, leading to high costs and long development times. The deformation mechanism of non-cylindrical cup drawing is theoretically very complex because of the large elasto-plastic stress and strain, and contact conditions between the tools and the sheet metal involved. In particular, several attempts have been tried in the past to perform theoretical and numerical analysis of rectangular cups. This paper presents an analysis of the allowable deep drawing height (DDH) of rectangular cups. The aim of this paper is twofold: 1) to analyze and estimate the allowable DDH of rectangular parts using theoretical, numerical (FEM) and experimental methods, and 2) identify the theoretical expression that predicts with the highest accuracy the allowable DDH of rectangular parts. A new theoretical expression for predicting this DDH is also proposed. To perform the study FEM is used together with the experimental data from industrial parts. The results show the accuracy of each theoretical expression in predicting the allowable DDH of rectangular parts.
A Study on the Interaction of Brain Impact With the Grounds of Different Material Types
Authors: Paka Parshuram , Karami Ghodrat , Ziejewski Mariusz
Published: May 2012

This paper proposes a parametric study of the response of brain, to human head impact with varied velocities as well as with the grounds of different material properties. The human head and its constituents are modeled using three-dimensional finite elements. The brain is made up of various elements that are modeled with a viscoelastic behavior. The ground is also assembled by finite elements. Five different velocities of impacts are considered based on realistic scenarios of human body falling due to gravity from five different heights. Three different materials for ground including wood, soil and rubber are considered. The simulation is run for a time history of 10ms after the incident. The intracranial coup pressure and shear stresses in the brain and various parts of the head are recorded. At the time of impact the peaks of the coup pressure and shear stress are observed to be proportional to the velocity of head and stiffness of the ground. Studies are conducted on the influence of the material of the impacting ground.
Comparison of Enabling Wafer Bonding Techniques for TSV Integration
Authors: Kim Bioh , Matthias Thorsten , Wimplinger Markus , Kettner Paul , Lindner Paul
Published: May 2012

In this study are compared the technical merits and demerits of three bonding methods suitable for manufacturing 3D-ICs. Patterned metal thermo-compression bonding facilitates fine-pitch, high-density TSV stacking with lower electrical resistance and higher mechanical strength. Direct Cu-Cu bonding is preferred over transient liquid phase bonding with Sn or Sn alloys, but reliable Cu-Cu bonds result only from high process temperature and long process time. Both bonding temperature and post-bond annealing temperature have the most significant influence on Cu-Cu bond properties. The pre-bonding of silicon oxide bonds occurs at room temperature and thus does not induce any run-out errors in wafer alignment, resulting in higher post-bond alignment accuracy. Subsequent heating to high temperatures is necessary to achieve covalent bonds, but modifying the surface chemistry by plasma activation allows the formation of strong chemical bonds at significantly lower annealing temperatures (200–400°C). Adhesive bonding has such advantages as low bonding temperature and process time compared to metal bonding, the tolerance to wafer topography and surface conditions, and the ability to join any wafer materials. However, the material reflow imposes some challenges for maintaining the alignment accuracy and another major concern is the reliability of polymer adhesives during the post-bond processes.
Vibration Studies of Cylindrical Thick Shells Using 3D Elasticity and Finite Elements
Authors: Wang W. , Qatu M. S.
Published: May 2012

In this paper, the three dimensional (3D) elasticity theory is used to investigate the accuracy of shell and solid elements of typical commercial finite element analysis (FEA) software packages. This is done with thick cylindrical shells in mind. The FEA software ABAQUS® is used in modeling. A First order shear deformation thick shell theory is used as well to show that if an improved shell theory is used the accuracy of shell elements can be improved.
Thrust Measurements of Different Gases in a Micro Nozzle
Authors: Lee John , McMullen Matthew G. , Huang Adam
Published: May 2012

It is sought to determine the suitability of fluorine based gases, i.e. 1,1,1,2-Tetrafluoroethane (R-134a), for use in a micronozzle. Several experimental thrust measurements have already been made for micronozzles using air or nitrogen. However, air and nitrogen are too prohibitive in terms of transportation in nano/pico satellites. Fluorine based gases, although not as efficient, offer a huge payoff in terms of transportability. The efficiency of R-134a was found to be about 27% lower than that of nitrogen, while being multitudes better in terms of transportability. Unsteady flow was encountered for air and nitrogen, while completely unexpected behavior was exhibited by R-134a.
Interfacial Delamination Between Through Silicon Vias (TSVs) and Silicon Matrix
Authors: Lu Kuan Hsun , Ryu Suk-Kyu , Zhao Qiu , Huang Rui , Ho Paul S.
Published: May 2012

Recently, three-dimensional (3-D) integration with through silicon vias (TSVs) has emerged as an effective solution for interconnect structures beyond the 32-nm technology node in microelectronics. Among others, thermo-mechanical reliability is a key concern for the development of TSV structures used in 3-D interconnects. This paper examines the thermal stress-induced delamination between through silicon via (TSV) and the silicon matrix. First, the driving force for TSV delamination was derived for a long crack at the steady state, and then the analytical solutions were validated using finite element analysis (FEA). The analytical solutions and simulation results were found to be in good agreement at the steady state, and together they suggested a fracture mechanism to account for the TSV delamination observed. The analytical solution further provided a basic framework for studying the impact of materials, process and structural design on reliability of the TSV structure. In particular, we found that reducing the thermal mismatch and TSV diameter yield definite advantages in lowering the crack driving force for TSV delamination. Such driving force can also be controlled by introducing an annular metal filling or a dielectric liner between TSV and the Si matrix. Finally, the TSV protrusion phenomenon during thermal cycles was investigated. The interfacial delamination was found to initiate during a cooling process and to develop under a subsequent heating process, causing TSVs to protrude from the silicon matrix after repeated thermal cycles.
Study on the Solid Welding Conditions of Hollow Extrusion of 7075 Aluminum Alloy
Authors: Hsu Quang-Cherng , Shi Shu-Ping , Hsu Chi-Peng
Published: May 2012

Direct extrusion by port hole–bridge die configuration has been successfully used to fabricate products with hollow cross sections for 6000 series aluminum alloys. When these aluminum alloys flow through the upper die (with bridge and port hole) material flows separately. These separate materials contact together when they flow through the lower die (with welding chamber). The contacting and welding processes occurs naturally if the material temperature and contact pressure are suitable; then the product with hollow and complicated cross section will be obtained when the material flow through bearing regions in lower die. This solid welding process for 6000 series aluminum alloys is without any problem. However, if for 7000 series aluminum alloys this situation alerts since different alloy compositions such as Zn and Cu causing welding process in lower die failed. It will impede the success of industry application with light and high strength aluminum alloys. In order to determine the solid welding conditions during hollow extrusion with port-hole die structure for high strength aluminum alloy such as 7000 series, an easy tooling configuration has been designed. Based on this approach, two split and half die components with taper angle feature were inserted into an outer steel ring. In the beginning, some clearances happen between inner die and outer ring result from design in purpose. When the upper punch continues to press the testing billet, the clearance disappears gradually due to the designed taper angle of inner die and outer ring. However, when the pushing pressure from upper punch is over 350 Mpa and billet temperature is maintained at about 480C below melting temperature, small gaps between the two split half die components occur automatically. During this situation, two small flashes can flow into the opening gaps both from the upper and lower billets which then can weld together. However, these two upper and lower billets in direct pressing zone did not weld together. Several experiments at different pressure have been conducted and the best solid welding condition has been obtained. The proposed method (die configuration) is easy and cheap because there is no necessary to conduct experiment in controlled environment such as in vacuum chamber of Gleeble test or in a protective atmosphere. The grain size and grain structure as well as grain flow have been discussed in the proposed paper for testing parts in direct pressing zone and in flash zone. Some SEM photos and EDS analysis have been prepared and will be presented in this paper.
Study on the Guiding Chamber Effect on Welding Pressure in Hollow Extrusion Die Design
Authors: Hsu Quang-Cherng , Tsai Ping-Hsun
Published: May 2012

In order to increase the welding pressure of the hollow Al7075 tube in extrusion process, a special die feature has been created. Several different proportions of chamber structure in outlet of extrusion die have been designed. The finite element analysis software DEFORM 3D to analyze various design parameters on the load–displacement and the welding pressure have been studied. Comparing to 6000 series, 7000 series aluminum alloy have good material properties, including excellent strength and toughness especially for hollow aluminum extrusion products in terms of Al7075. However, in extruded hollow aluminum alloy products, the industry’s common use is 6000 series material, except for indirectly extruded seamless pipe, Al7075 can be found. This is because of less welding pressure can be provided by using the traditional die structures in Al7075 hollow products. Therefore, to use the directly extruded seam tube of Al7075 in high-yield and high-quality, to increase the welding pressure and improve the quality of welding products becomes a very important issue. In this study, a different high proportion in material guiding chamber has been defined. The same angle both on the exit of female die and the bearing of male die which can be integrated into a material guiding chamber has been designed. Therefore, the welding pressure can be increased due to the change of metal flow behavior that is after a complete fill in material guiding chamber, and then metal can flow out of die bearing surface. The results showed that welding pressure can be increased rapidly if a suitable material guiding chamber has been built. Among them, the ratio of chamber height and length is 2:1; the increased welding pressure is most significant.
A Novel Pneumatic Non-Contact Suction Pad With Embedded Air Bearings
Authors: Renn Jyh-Chyang , Cheng Chin-Yi
Published: May 2012

In this paper, a novel suction pad based on CFD simulation and vortex levitation principle is proposed. To assure the absolute non-contact between the suction pad and the work-piece, four symmetrical air bearings are introduced and integrated into the design of the suction pad. In addition, the closed-loop gap control is applied to the operation of the suction pad, which avoids successfully the possible initial impact and maintains the desired gap between the suction pad and the work-piece. The vortex inside the suction pad serves to levitate the work-piece and the air bearings, on the contrary, try to push the work-piece away if the work-piece comes too close to the suction pad. Therefore, a proper function switching between the vortex and the air bearings is necessary. In this paper, a 5/3 pneumatic proportional directional control valve is utilized to switch these functions mentioned above. In the future, such a suction pad may find some potential application fields, like the pick-up and transportation devices for TFT-LCD, solar energy panels, etc.
An Unstructured Finite Volume Method for Structure-Electrostatics Interaction in MEMS
Authors: Das Shankhadeep , Mathur Sanjay R. , Murthy Jayathi Y.
Published: May 2012

Radio-frequency microelectromechanical systems (RF MEMS) are widely used for contact actuators and capacitative switches, and involve metal-dielectric contact. Proper understanding of structure-electrostatics interaction is necessary to prevent failure of these systems. In these devices, the structure is activated by an electrostatic force, whose magnitude changes as the gap closes. Accurate modeling of fluid-structure-electrostatics interaction is important to determine device dynamical behavior, and ultimately, device lifetime. It is advantageous to model fluid and structural mechanics and electrostatics within a single comprehensive numerical framework to facilitate coupling between them. In this paper, we extend a cell-based finite volume approach popularly used to simulate fluid flow to characterize structure-electrostatics interactions. The method employs fully-implicit second order finite volume discretization of the integral conservation equations governing elastic solid mechanics and electrostatics, and uses arbitrary convex polyhedral meshes. The electrostatic actuation is treated as a surface force, and is directly added to the force balance for the control volume. The resulting set of algebraic equations is solved using a biconjugate gradient stabilized (BCGSTAB) solver. Results are presented in this paper for a fixed-fixed beam under electrostatic actuation.
The Onset of Brinkman-Benard Ferroconvection in a Saturated Porous Layer With Internal Heat Generation
Authors: Nanjundappa C. E. , Prakash H. N.
Published: May 2012

The effect of internal heat generation on the criterion for the onset of thermomagnetic convection in a horizontal ferrofluid saturated porous layer in the presence of a uniform magnetic field is studied using the Brinkman-Lapwood extended Darcy flow model with fluid viscosity different from effective viscosity. The lower boundary is taken to be rigid – insulating and the upper surface is free and subject to the general thermal condition. The resulting eigenvalue problem is solved numerically using the Galerkin method with the Rayleigh number as the eigenvalue. The effect of increase in the value of dimensionless internal heat source strength Ns, magnetic number M1 and the non-linearity of fluid magnetization parameter M3 is to hasten, while increase in the value of inverse of Darcy number Da−1, viscosity ratio Λ, Biot number Bi and magnetic susceptibility χ is to delay the onset of thermomagnetic convection in a ferrofluid saturated porous layer. Further, increase in the value of Bi, Da−1 and Ns as well as decrease in Λ M1> and M3 is to diminish the dimension of convection cells.