bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and Theoretical Study of the Cone-Jet for Electrospray
Authors: Si Bui Quang Tran , Byun Doyoung , Lee Sukhan
Published: May 2009

The interference effect on an array of electrospray emitters is analytically and experimentally investigated. An analytical model is presented to predict the behavior of the operating voltage with respect to emitter spacing in an array of emitters. The basic idea of these models is to superimpose the electric potential of individual emitters together in an array of emitters. If only one of the emitters operates and no liquid is supplied through the neighboring emitters, the potential required to form a stable cone-jet generally increases as the emitters move closer to each other due to electrical shielding. However, at very close spacing the required potential decreases. If all the emitters operate simultaneously, the operating voltage required for cone-jet spraying increases as the emitter spacing decreases; furthermore, there is no decrease in potential when the spacing is very close. The results of the analytical electrostatic interference model agree well with the experimental data.
Metal Hydride Heat Storage Technology for Directed Energy Weapon Systems
Authors: Park Chanwoo , Tang Xudong , Kim Kwang J. , Gottschlich Joseph , Leland Quinn
Published: May 2009

Directed Energy Weapon (DEW) systems in a pulse operation mode dissipate excessively large, transient waste heat because of their inherent inefficiencies. The heat storage system can store such a pulsed heat load not relying on oversized systems and dissipate the stored heat over time after the pulse operation. A compressor-driven metal hydride heat storage system was developed for efficient, compact heat storage and dissipation of the transient heat from the DEW systems. The greater volumetric heat storage capacity of metal hydride material was realized into more compact design than conventional Phase Change Material (PCM) systems. Other exclusive advantages of the metal hydride system were fast thermal response time and active heat pumping capability required for precision temperature control and on-demand cooling. This paper presented the operating principle and heat storage performance results of the compressor-driven metal hydride heat storage system through system modeling and prototype testing. The modeling and test results showed that the metal hydride system can store the average heat of 4.4kW during the heat storage period of 250 seconds and release the stored heat during the subsequent regeneration period of 900 seconds.
Heat Transfer Enhancement in Pipe Flow Problems of a Magnetic Fluid
Authors: Kaloni P. N. , Lin F. , Rankin G. W.
Published: May 2009

Analytical solutions are presented for the temperature distribution and heat transfer coefficient in the forced convection of a magnetic fluid in cylindrical pipe flow. The theory of a ferro-fluid with internal rotation of magnetic particles is employed. Effects of the conventional dissipation term along with the dissipation reflecting the effect of internal rotation are considered and discussed. By computing the Nusselt number in various cases, the influence that different parameters have on the flow are revealed.
Comparison of Stone Comminution Produced by Two Different Reflector Configurations in an HM-3 Lithotripter
Authors: Qin Jun , Simmons W. Neal , Zhong Pei
Published: May 2009

Clinical experience has demonstrated that the performance of the 2nd and 3rd generation shock wave lithotripters in terms of stone comminution has become inferior to the 1st generation Dornier HM-3 lithotripter. A primary change in the design of the newer generation lithotripters is the enlarged aperture of the shock source, leading to a higher peak pressure with a smaller focal area. To evaluate the effect of beam size on stone comminution in the same lithotripter, we developed a reflector insert for the HM-3 that can substantially increase the peak pressure while concomitantly tightening the beam size of the lithotripter field. Using a light spot hydrophone, we have characterized the acoustic fields produced by the two reflector configurations at 20 kV. The peak positive pressure and the −6dB beam size were found to be 87 MPa and 4 mm for the HM-3 with the reflector insert, which are significantly different than the corresponding values (51 MPa and 13 mm) for the original reflector. In contrast, the peak tensile pressure and the total acoustic energy of the lithotripter pulse were found to be similar (−12 MPa and 59 mJ with the reflector insert, −11 MPa and 52 mJ for the original reflector). Stone comminution was evaluated in four different holders in order to determine the effect of lateral spreading of residual fragments on lithotripsy outcome. After 250 shocks, the results of stone comminution in a mesh holder of D = 15 mm (63% vs. 61%) were similar. However, the corresponding values produced by the HM-3 with reflector insert in a finger cot of D = 15 mm (45%) and in a membrane holder of D = 30 mm (14%) were significantly lower than those produced by the original reflector (56% and 26%). Further, the efficiencies of stone comminution in both the mesh holder and the finger cot were much higher than that in the membrane holder. These results suggest that a wide beam size in the original HM-3 may increase stone comminution efficiency when the fragments are spread out to a large area during lithotripsy. In contrast, when the fragments are confined during lithotripsy the beam size may not influence significantly the treatment outcome.
Performance of an Adaptive Magnetorheological Fluid Mount
Authors: Ciocanel Constantin , Nguyen The , Schroeder Christopher , Elahinia Mohammad H.
Published: May 2009

The paper investigates the response of a magnetorheological (MR) fluid based mount that combines the squeeze and flow modes in operation. The mount governing equations are introduced and the effect of system parameters on its performance is analyzed. The proposed design yields a high static and a low dynamic stiffness in the working frequency range of the mount. The overall vibration isolation characteristic of the mount is enhanced if compared to that of existing hydraulic mounts. Displacement and/or force transmissibility can be isolated or significantly reduced, in real time, by controlling the MR fluid yield stress. An embedded electromagnet is used to activate the MR fluid that can work in either squeeze or flow modes, or in both simultaneously. The results indicate that the flow mode is less effective in reducing transmissibility than the squeeze mode. However, when the flow and squeeze modes are both activated, the effect of the flow mode becomes more obvious.
Building-Integrated Thermoelectrics as Active Insulators and Heat Pumps
Authors: Headings Leon M. , Washington Gregory N.
Published: May 2009

Heating, ventilation, and air conditioning (HVAC) accounts for 40% to 60% of residential and commercial building energy consumption, making this a critical component of energy usage in the face of rising energy prices. Building-integrated thermoelectrics (BITE) may provide a step towards adaptive homes and buildings that offer significantly improved efficiency and comfort. Integrating thermoelectrics into thermal mass and resistance (insulation) wall systems presents a fundamental shift from optimizing heating and cooling source efficiencies and minimizing building-envelope energy losses to a new regime where an active envelope is optimized to most efficiently eliminate those losses. This approach not only offers improved energy efficiency, but improves the uniformity and consistency of temperature, eliminates the need for all other heating and air conditioning equipment including thermal energy transport, and provides the platform for adaptive zone heating and cooling which can provide additional efficiency gains. Because of the solid-state nature of thermoelectrics, such a system would be reliable, low maintenance, silent, and clean. This paper examines various wall configurations and sizing for thermal mass, resistance, and thermoelectric components. A dynamic simulation is used to demonstrate how proper system design of thermal resistance and capacitance elements with existing thermoelectric materials may improve the typically low coefficient of performance of thermoelectric devices, making it competitive with traditional building systems. The results for different wall configurations are shown as a basis for future configuration design and optimization.
The Research on the Fault Mechanism of Port Plate/Cylinder Block Frictional Pair in Axial Piston Pump
Authors: Li Lan , Wang Shaoping , Shi Shuai , Liu Hongmei
Published: May 2009

The problem of vibration and noise in axial piston pump has been intensively studied in the past; however, recently the interest about this problem grew because of great requirement for designing excellent performance axial piston pump having high pressure, high rotating speed and high flow characteristics etc. One of the most important noise and vibration sources is the flow distribution noise caused by the shock pressure of flow distribution and cavitations in the process of the regulation of working conditions, and the vibration caused by wearing of the port plate frictional pair. A lot of methods have been developed to reduce the flow distribution impulsion and the port plate wearing by improving the design of port plate as well as the materials of axial piston pump. However, the current research level remains incomplete and there are still noise and vibration existing in the axial piston pump. So it is very important to develop efficient diagnosis methods for online monitoring the hydraulic pump which helps to increase the reliability of the whole fluid power system. In the present paper the structure and working principle of port plate in axial piston pump is discussed first. Then this paper proposes a fault diagnosis method based on vibration signals after analyzing the fault mechanism of the port plate frictional pair. And it verifies the diagnosis method through experiment and gives out the analysis result. The result indicates that the vibration signal is sensitive to the port plate frictional pair’s wearing fault.
A Numerical Study of Natural Convection in a Cavity With Two Fins Attached to Its Vertical Walls
Authors: Sheikhzadeh G. A. , Pirmohammadi M. , Ghassemi M.
Published: May 2009

Numerical study natural convection heat transfer inside a differentially heated square cavity with adiabatic horizontal walls and vertical isothermal walls is investigated. Two perfectly conductive thin fins are attached to the isothermal walls. To solve the governing differential mass, momentum and energy equations a finite volume code based on Pantenkar’s simpler method is developed and utilized. The results are presented in form of streamlines, isotherms as well as Nusselt number for Rayleigh number ranging from 104 up to 107. It is shown that the mean Nusselt number is affected by the position of the fins and length of the fins as well as the Rayleigh number. It is also observed that maximum Nusselt number occurs about the middle of the enclosure where Lf is grater the 0.5. In addition the Nusselt number stays constant and does not varies with width of the cavity (lf) when Lf is equal to 0.5 and Rayleigh number is equal to 104 and 107 as well as when Lf is equal to 0.6 and low Rayleigh numbers.
In-Situ Multi-Mode Sensing With Embedded Piezoelectric Wafer Active Sensors for Critical Pipeline Health Monitoring
Authors: Yu Lingyu , Giurgiutiu Victor , Chao Yuh , Pollock Patrick
Published: May 2009

Pipelines are important infrastructures in petroleum and gas industries which are vital to the national economy. They are typically subjected to corrosion inside of the pipe and there is an urgent need for the development of a cost-effective, non-excavating, in-service, permanent critical pipeline damage detection and prediction system. In this paper, we proposed an in-situ multiple mode pipeline monitoring system by utilizing permanently installed piezoelectric wafer active sensors (PWAS). As an active sensing device, PWAS can be bonded to the structure or inserted into a composite structure, operated in propagating wave mode or electromechanical impedance mode. The small size and low cost (about ∼$10 each) make it a potential and unique technology for in-situ application. Additionally, PWAS transducers can operate at a temperature as high as 260°C which is sufficient for most critical pipeline systems used in gas/petroleum industry. This system can be used during in-service period, recording and monitoring the changes, such as cracks, impedance, wall thickness, etc., of the pipelines over time. Having the real-time data available, maintenance strategies based on these data can then be developed to ensure a safe and less expensive operation of the pipeline systems. The paper will first give an intensive literature review of current pipeline corrosion detection. Then, the basic principles of applying PWAS to in-situ SHM using in-plane propagation waves and impedance measurement for damage detection are studied and developed. Next, experiments were conducted to verify the corrosion detection and thickness measurement ability of PWAS sensor network in a laboratory setting and in water pipe with flowing fluid inside as well. In addition, the potential of PWAS application for high temperature pipeline thickness monitoring was also investigated.
Pseudo-Impellers in Supersonic Crypto-Steady Flow Induction
Authors: Zhang Hongfang , Garris Charles A.
Published: May 2009

This paper is motivated by a long-range goal of developing a new class of turbo-machine where fluid impellers, created through supersonic wave structures, replace mechanical impellers. This paper is an exploratory study to show how effectively supersonic wave structures can fulfill this goal, and to provide some fundamental insight as to the behavior. A novel device is presented which, by means of a free spinning rotor placed in front of a supersonic nozzle, causes a rotating interface to form between an energetic primary fluid and a secondary fluid to be compressed. This rotating interface is shown to act like a pseudo-impeller in driving the less energetic secondary fluid. A simple two-dimensional example is provided which helps understand the physical processes occurring in the three-dimensional configuration. A hypothesis is offered which contends that the use of pseudo-impellers has great potential in reducing the cost and size of turbomachinery in many applications, and in possibly improving efficiency.
CAD/CAM Library of Parts and Assemblies for Engineering Curricula
Authors: Zeid Abe , Kamarthi Sagar
Published: May 2009

Most often instructors and students are forced to search through a wide range of scattered resources, such as textbooks, archival journals, conference proceedings, Websites, and industry catalogs to identify parts/assemblies that demonstrate the CAD/CAM concepts of their interest. This long and tedious process is both a major impediment to student learning and a time-consuming distraction to effective teaching of CAD/CAM concepts. To address issues, this paper presents the concept of a CAD/CAM library of parts/assemblies of products for use in CAD/CAM related courses, to enhance student learning and critical thinking, and to increase the effectiveness of CAD/CAM teaching. The addition of pedagogical features to the CAD/CAM library will make it even more effective and useful. For every part/assembly, the CAD/CAM library has to provide not only geometric models with dimensions, but also has to include construction planning strategy, step-by-step creation procedure, modeling questions, and hands-on exercises that facilitate effective teaching and enhance student learning. In addition, the library has to offer its models in multiple formats so that they can be run on most of the commercial CAD systems. The library may have far-reaching impact on non-CAD/CAM areas, such as psychology and physics that require cognitive and 3D visualization studies. The paper presents the results and observation of using CAD/CAM library concept in teaching a CAD/CAM and design courses.
A Critical Review of Slag Properties of Chinese Coals for Entrained Flow Coal Gasifier
Authors: Liu Sheng , Hao Yingli
Published: May 2009

Numbers of entrained flow coal gasifiers have been built in China. In China, the coal types are various and the properties between coals from different collieries are quite different causing the properties of slag different too. The experimental data for slag properties of Chinese coal are collected and critically reviewed, especially for the conditions in entrained flow coal gasifiers. The most widely used models for predicting the fusion characteristics and viscosity of Chinese coal ash slags are compared. The most suitable models for fusion characteristics and viscosity of Chinese coal ash slags are recommended. For other properties, empirical models with widely suitability are also recommended.
Study on Ignition and Weak Flame in Heated Meso-Scale Channel
Authors: Tsuboi Yosuke , Yokomori Takeshi , Maruta Kaoru
Published: May 2009

If the flame temperature and the reaction speed can be controlled arbitrarily, it is of great help for energy saving through effective utilization of heat generated by combustion. In order to examine the possibility of such mild or moderate combustion, we tried to identify possible weakest flames experimentally with heated meso-scale channel, that is, combustion with controlled heat balance. Results show that the lowest flame speed may exist even though heat loss is compensated by the external heating. For the case of low flow velocity condition, the temperature difference between heated channel wall surface and flame measured by using thermocouple became smaller and smaller with decreasing flow velocity. It implies that there is the lowest flame temperature which corresponds to ignition temperature. To further examine existence and its mechanism of the lowest flame speed, 1-D computations with detailed chemistry were conducted. Computational results show a limit of stable solution in the low velocity region as well as experimental results. Furthermore, diffusive mass transfer was dominant compared to convective mass transfer in the low velocity region. It is probably related to the existence of the lowest flame speed, since the radical species, which is vital for chain reaction, diffuse out from reaction zone.
Current Trends of Hydroforming Process Into Automotive Body Structure and Chassis Applications
Authors: Koganti Ramakrishna , Balzer Jason , Hertell Klaus
Published: May 2009

Recent low emission, lightweight, safety requirements, automotive manufacturers are implementing lighter and stronger materials and new manufacturing processes into body structural components. Typical widely used forming process in automotive body structures is stamping process. Other forming processes currently used in body structural applications are hydroforming, Rollforming and hot stamping processes. Initially, hydroforming process was used for chassis applications. Few applications of chassis are cross members, engine cradle, instrument panel (IP) beams, and bumper beams. Recently, a few automotive manufacturers are already implemented the hydroforming process into front end structures. Hydroform process gives more part consolidation, and perhaps even weight reduction. However, depending on applications some brackets may be needed to attach other components. Some of the issues related to bracket attachments can be avoided in the design phase. Audi A2, and Chrysler Pacifica have implemented roof rails in the body structures arena. Latest developments are even pushing the hydroforming process into High Strength Steels arena. Pontiac Solstice and Saturn Sky implemented Dual Phase 600 material on the chassis rails. In this paper, current trends of hydroforming process with advanced high strength steels (AHSS) will be discussed. Hydroforming process involves, bending, preforming (low pressure), and final forming (high pressure) with mechanical properties of DP780 material at various stages of the hydroforming process will be discussed.
Thermo-Chemical Energy Conversion Using Supplementary Animal Wastes With Coal
Authors: Annamalai K. , Carlin N. T. , Oh H. , Gordillo Ariza G. , Lawrence B. , Arcot V. U. , Sweeten J. M. , Heflin K. , Harman W. L.
Published: May 2009

Researchers at Texas A&M University have studied properties of cattle biomass (CB or manure) fuels and their possible utility in combustion systems. Larger, more concentrated animal feeding operations (CAFO) and farms make manure disposal more difficult. At the same time, due to the concentration of the manure, the CAFOs can be a source of a more feasible and reliable CB feedstock for fossil fuel supplementation and emissions reduction technologies. This paper reviews the history of work conducted on animal biomass fuels and current research and experiments undertaken by Texas A&M University (TAMU) System research personnel. Feedlot biomass (FB), dairy biomass (DB), and chicken litter biomass (LB) are considered here. When cofiring with coal under rich conditions, the CB has the potential to reduce NOx and Hg emissions. Reburning coal with CB can be just as effective as and possibly more economical than reburning with conventional fuels like natural gas. In addition to cofiring and reburning, another possible energy conversion method is gasification of cattle biomass with air and air-steam oxidizing agents that can produce synthetic gases which can then be used in a variety of different combustion systems. The economic feasibility of utilizing animal-based biomass on existing coal-fired power plants is greatly dependent on the relative cost of coal, the biomass transportation distance to the combustion facility, and numerous other factors. Even though most of the methodologies and procedures, in this paper, deal with CB, similar schemes can be undertaken for most other animal or solid wastes.
Urea Mixing in Selective Catalytic Reduction Systems
Authors: Fadul Fawaz , Nelli Amarnath , Fakheri Ahmad
Published: May 2009

The tightening of emission standards mandates NOx and particulate emissions to be reduced by more than 90 percent by 2010 in Europe, United States, and Japan. Selective Catalyst Reduction (SCR) using Urea as the NOx reducing agent is fast becoming the preferred technology. This paper provides an overview of the state of art on the topic. It also examines the use of urea vapor instead of spraying an aqueous mixture and the impact of different spraying strategies on mixing. It is shown that by injecting urea vapor opposite to direction of the exhaust gas flow, better mixing with the exhaust and thus better conversion can be achieved as compared with injecting the urea vapor parallel to the gas. The increase in pressure drop does not appear significant.
The Frictional Properties of Galvannealed Coatings With Different Annealing Temperatures at Low Normal Loads
Authors: Lee Jungmin , Ko Daecheol , Kim Byungmin
Published: May 2009

This paper is designed to investigate the frictional and powdering characteristics of coating layer on a galvannealed sheet steel with different annealing temperatures of 465, 505, 515 and 540°C. Estimations of powdering and friction were done using a 60°bending test and flat-friction test. In order to clearly understand the effect of each coating on friction, a cross-section of the coatings before and after the friction tests was observed using SEM. The results show that powdering of the coatings increased with the increase of the annealing temperature and that the friction characteristics greatly depend on their powdering, which leads to an increase of the real contact area between the tools and coatings.
1-D Model and Experimental Tests of Pressure Wave Supercharger
Authors: Pohorˇelsky´ Ludeˇk , Obernesser Philippe , Va´vra Jirˇi , Kli´r Vojteˇch , Macek Jan
Published: May 2009

In this contribution, a pressure wave supercharger (PWS) is investigated both at diesel engine and at combustion chamber test bench using 1-D simulation and experimental measuring. Moreover, a combustion engine supercharged by PWS has been compared using 1-D simulation to turbocharged one at steady state and transient operations. A pressure wave supercharger is simulated using a detailed model based on the partial differential equations capturing non-linear effects of gas dynamics. The work has been performed using the commercial 1-D code GT-Power. A concept of modeling used enables to integrate the PWS model with all other models which are already created in the commercial codes (like more precise model of combustion, vehicle model, etc.). The PWS takes advantage of the direct pressure and enthalpy exchange between exhaust gases and fresh air in narrow channels to provide boost pressure. Due to the direct contact between exhaust gas and fresh air, a mixing occurs. Nevertheless, this internal recirculation of exhaust gas can be used for lowering of NOx emissions, but at the same time it could deteriorate engine power as the result of a lack of oxygen. The internal mixing has been investigated using 1-D simulation and different possibilities to avoid mixing have been tested. The PWS has showed during the simulation work behavior it could fulfill demand on a modern car propulsion system. Finally, PWS measurements with a combustion chamber have been undertaken and compared to the 1-D simulation results. Using the results of PWS measurement at the test bench and the 1-D simulation the usage of PWS in fuel cell applications is discussed, as well. This work results from the collaboration between Josef Bozˇek Research Center and Renault SA.
An Advanced CMC Thermal Protection System Flight Experiment on the FOTON-M2 Mission
Authors: Reimer T.
Published: May 2009

In June 2005 the re-entry module of the Russian FOTON-M2 spacecraft made a successful landing after a microgravity mission in space. On board was also the “KERAMIK” experiment by the Institute of Structures and Design of the German Aerospace Center (DLR) in Stuttgart, Germany. The re-entry technology experiment had performed a flight of a Thermal Protection System (TPS) with it’s structural components designed and manufactured fully in C/C-SiC, a Ceramic Matrix Composite (CMC) material developed by DLR. The experiment had a surface diameter of 340 mm and was located on the exterior of the re-entry spacecraft embedded into the ablative heat shield. The emphasis of the experiment was on the system aspects of the TPS design. It included two stiffened surface panels each fixed to three structural posts with a special fastener type, all components made from the C/C-SiC material. The experiment deliberately included a gap between the panels and a surrounding close-out ring to test the performance of a dedicated seal in that area. In addition to the structural aspects of the experiment, a set of different oxidation protection coatings was applied to the surface of one of the panels to conduct a comparative test under flight conditions. The position of the experiment was carefully selected with regard to the aerothermodynamic environment. Since the experiment technology aims at re-usable vehicles, a position in the stagnation area of the ballistic re-entry module would have resulted in excessive heat loads. Therefore a location was preferred at an angle of almost 90° relative to the flight direction. The temperature data that was measured during re-entry shows that the surface temperature was close to 1500°C, which was in the targeted range. The structural components on the surface of the experiment were in an excellent condition as a visual inspection immediately after landing revealed.
Top-Down Decomposition of Multi-Product Requirements Onto Locator Tolerances
Authors: Lo¨o¨f Johan , So¨derberg Rikard
Published: May 2009

The tolerance allocation problem consists of choosing tolerances on dimensions of a complex assembly so that they combine into an ‘optimal state’ while fulfilling certain requirements on an allowed variation. This optimal state often coincides with the minimum manufacturing cost of the product. Sometimes it is balanced with an artificial cost that the deviation from target induces on the quality of the product. This paper suggests a multiobjective formulation of the tolerance allocation problem to automatically decompose requirements for an allowed variation on a set of critical product dimensions. This formulation is demonstrated using a rear lamp on a car with multiple requirements on allowed variation. In this case only the tolerances on locators that locates the lamp on the body are considered. The paper also reviews a selection of work that has been made on solving tolerance allocation problems.
Viscoplastic Behavior of Hypo-Eutectic Sn3.0Ag0.5Cu Pb-Free Alloy Under Creep Loading Conditions
Authors: Cuddalorepatta Gayatri , Dasgupta Abhijit
Published: May 2009

The time-dependent viscoplastic behavior of hypoeutectic Sn3.0Ag0.5Cu (SAC305) solder is presented. Mechanical shear tests are conducted at room and high temperatures, using a custom-built thermo-mechanical-microscale (TMM) test system. This test system uses a modified Iosipescu shear specimen with a 180 microns wide solder joint. Creep deformation is measured at constant stress levels between 3 MPa to 20 MPa, at different temperatures. The creep results are fit using Garofalo’s secondary creep model and a generalized exponential primary creep model. Secondary creep measurements from the current work are higher than those reported in literature. Discrepancies in the curve fits based on the chosen continuum creep models are discussed. Possible sources of the discrepancies are discussed. In future work the primary and secondary creep constants measured from this work will be used in viscoplastic finite element models to compare with stress relaxation behavior measured earlier on the TMM specimens at various temperatures and strain levels [1].
Development of a Simultaneous Cooling and Heating Absorption Chiller for Combined Heat and Power Systems
Authors: Wagner Timothy C. , Rog Lynn , Jung Sung-Han
Published: May 2009

The objective of this investigation was the development and testing of a waste heat-driven chiller capable of simultaneously generating chilled and heated water. In addition to simultaneous operation, the ability to seamlessly change from chilling to heating eliminates the seasonal changeover which is typical in existing absorbers. These enhancements significantly increase the flexibility and utilization of the chiller. In this paper, the design of the chiller will be described along with presentation of results from testing of a 140 RT full-scale prototype chiller. A case study for a hospital in New Jersey will also be presented to show the additional energy utilization provided by the simultaneous capability.
A New Approach for the Study of Reliability for MEMS Magnetic Actuator
Authors: Berkcan E. , Chandrasekaran S.
Published: May 2009

This paper presents a summary of the design for reliability and the reliability test procedures used for the design, fabrication and testing of a MEMS magnetic actuator. The MEMS device reliability is determined incorporating device structure, its fabrication process, the packaging, & their interacting contributions. The goal of the MEMS actuator reliability design task is to increase the probability of failure free operation of a MEMS based system for a specified time period and the use environment. The design for reliability and the subsequent reliability testing procedures are used to determine the reliability of the MEMS actuator and enable the determination of the reliability of the final product that the MEMS device is becoming part of.
Increasing Experiential Learning in Freshman Engineering Through a Microfabrication Project
Authors: Hegab H. , Hall D.
Published: May 2009

A hands-on microfabrication project was developed and piloted for Louisiana Tech’s integrated freshman engineering curriculum. The project involves the design and fabrication of a simple nickel resistance temperature detector (RTD). The project is part of a series of hands-on projects being developed for the freshman engineering curriculum as part of a “Living with the Lab” concept that utilizes the BASIC Stamp Board-of-Education (BoE-bot) kit (a microcontroller-based robotics kit) to increase experiential learning. The project was piloted in two sections of a freshman engineering course taken by all engineering majors at Louisiana Tech. The temperature sensor was used by the students as part of a control systems project to monitor and control the temperature and salinity of a water tank. The project included the direct application of fundamental engineering topics as well as applied technical skills that are part of the freshman curriculum. It also provided an opportunity to introduce the students to some common microfabrication techniques. The RTDs were fabricated using optical lithography and etching of a nickel coated Kapton© film. Students designed the geometry of the RTD based upon the resistivity of nickel. They created masks patterns using a commercial CAD package. They participated in a lab demonstration of the processing steps in performing photolithography to create the RTD pattern on the nickel coated Kapton© film. They then used their BoE-bot microcontrollers to measure the resistance of their RTD sensors and to calibrate the sensors. The project is being refined to be implemented this next academic year for the entire freshman engineering student body.
The Role of Atomizing Medium in the Effectiveness of Water-Oil Emulsions to Reduce Unburned Carbon Particles
Authors: Diego-Marin Antonio , Melendez-Cervantes Carlos , Mani-Gonzalez Alejandro
Published: May 2009

Two older boilers were burning low grade heavy fuel oil (number 6) and emitting large amounts of unburned carbon particles. Owing to the short life remaining of the units and economic constrains, it was not possible to change to a better fuel or install new burners. To contribute to the solution of this problem, an experimental program was carried out by emulsifying water in the fuel oil. Tests were performed in a scale furnace (0.35MWth) and the emulsions that produced the best results were assessed in the two boilers, 28 and 34 MWe capacity with Y-jet atomizer type. The system to prepare the emulsion was very simple: water was added into the oil before the fuel oil pump, no chemical products were added and a static mixed was used to improve the water size distribution, which 90% ranged from 1 to 9 micron. In the pilot furnace the emulsions were prepared with 5 and 10% water and atomized with compressed air. Particle reductions of 43 and 67% were obtained compared with the net heavy fuel oil. In the boilers, the emulsions were prepared with the same amount of water, and were atomized with saturated steam. In the 28 MWe boiler, a similar particle reduction was obtained to that of the scale furnace. However, in the 34 MWe boiler there was no particle abatement. By using a commercial fluid dynamic computer code, it was found that the combustion air transferred heat to the steam raising its temperature. Thus, in the mixing chamber of the Y-jet atomizers, the steam was superheated and destroyed the water droplets of the emulsion. Compressed air and saturated steam as atomizing medium of the emulsions had similar effect on the unburned particle reduction. However, the effectiveness of the emulsions may be affected by the steam. Care should be taken to avoid the use of steam with a temperature higher than the saturated water temperature.
Analysis of In-Scattering Effects on Laser Induced Incandescence Measurements Through Backwards Monte Carlo
Authors: Daun K. J. , Thomson K. A. , Liu F.
Published: May 2009

Laser-induced incandescence (LII) measurements carried out on aerosols having a large particle volume fraction must be corrected for extinction between the energized aerosol particles and the detector, called signal trapping. While standard correction techniques have been developed for signal trapping by absorption, signal trapping due to scattering requires further investigation, particularly the case of highly anisotropic scattering. This paper examines this effect in an aerosol containing highly-aggregated soot particles by simulating LII signals using a backwards Monte Carlo analysis; the signals are then used to recover a pyrometric beam temperature and soot volume fraction. The results show that in-scattered radiation is a substantial component of the LII signal under high soot loading conditions, which can strongly influence the properties derived from these measurements. Correction techniques based on Bourguer’s law are shown to be effective in mitigating the effect of scatter on the LII signals.
Characterization of Laser Assisted Maskless Micro-Deposition Technology for Fabrication of Conductive Micro Systems
Authors: Alemohammad Hamidreza , Toyserkani Ehsan
Published: May 2009

Laser assisted maskless micro-deposition (LAMM) is a recently developed technology for deposition of thin films with micro-scale feature sizes. It can be used for deposition of a large number of materials such as, electronic inks/pastes, conductive polymers, insulators, adhesives, and biological materials. This process is a combination of liquid atomization, micro-deposition and laser sintering. The present study is concerned with the process characterization for the deposition of silver thin films on silica. The deposited material is in the form of nano-particles dispersed in liquid, known as nano-past. In the present research work, deposition patterns are produced with different process parameters. Afterwards, the effects of process parameters, e.g., laser power and laser scanning speed, are investigated by examining the quality of the deposited material.
On a Process Modeling Framework for Sustainable Manufacturing: A Machining Perspective
Authors: Jayal Anshu D. , Balaji A. K.
Published: May 2009

Sustainability and economic factors are increasingly pushing industry towards environmentally friendly manufacturing methods. However, the implications of processing level changes, which are being introduced at a significant rate, for overall, environmental impact need better characterization. In the first half of this paper, a simplified framework for enhancing sustainability in manufacturing, by enabling rapid assessment of approximate life-cycle implications of competing process-level alternatives, is introduced. This framework relies on developing or enhancing manufacturing process models in such a way that a superior quantitative evaluation of the environmental and economic impacts of decisions made in manufacturing process planning can be established. In the second half of this paper, the specific case of metal machining is presented. In machining the maximum attention has been directed towards reducing the traditional profligate use of metalworking fluids. Consequently, a significant quantity of research work has been directed towards developing dry and near-dry, or Minimal Quantity Lubrication (MQL), machining techniques. A review of available literature shows that several outcomes of these techniques for product life-cycle assessment need to be addressed — i.e., some environmental tradeoffs are often involved in their implementation. Avenues for further research in sustainable machining, including some ideas for advancing dry and near-dry machining without resorting to chemical action for extreme-pressure lubrication, are also presented.
Simulation of Reinforced Concrete Structures Under Blast and Penetration Through Lattice Discrete Particle Modeling
Authors: Cusatis Gianluca , Pelessone Daniele , Mencarelli Andrea , Baylot James T.
Published: May 2009

In this study, the Lattice Discrete Particle Model (LDPM), a recently developed three-dimensional meso-level model for concrete, is used to simulate the behavior of reinforced concrete under severe loading conditions. LDPM simulates concrete through an assemblage of particles (coarse aggregate pieces) connected through a lattice mesh. In order to simulate steel reinforcement, a mesh of plastic beams is embedded in the lattice system. Nonlinear concrete-reinforcement bond is also included in the formulation. The effectiveness of the approach is demonstrated through the simulation of projectile penetration into reinforced concrete slabs and blast spallation of dividing walls.
Parametric Study of Hybrid Cooling Solution for Thermal Management of Data Centers
Authors: Mulay Veerendra , Karajgikar Saket , Agonafer Dereje , Schmidt Roger , Iyengar Madhusudan
Published: May 2009

The power trend for Server systems continues to grow thereby making thermal management of Data centers a very challenging task. Although various configurations exist, the raised floor plenum with Computer Room Air Conditioners (CRACs) providing cold air is a popular operating strategy. The air cooling of data center however, may not address the situation where more energy is expended in cooling infrastructure than the thermal load of data center. Revised power trend projections by ASHRAE TC 9.9 predict heat load as high as 5000W per square feet of compute servers’ equipment footprint by year 2010. These trend charts also indicate that heat load per product footprint has doubled for storage servers during 2000–2004. For the same period, heat load per product footprint for compute servers has tripled. Amongst the systems that are currently available and being shipped, many racks exceed 20kW. Such high heat loads have raised concerns over limits of air cooling of data centers similar to air cooling of microprocessors. A hybrid cooling strategy that incorporates liquid cooling along with air cooling can be very efficient in these situations. A parametric study of such solution is presented in this paper. A representative data center with 40 racks is modeled using commercially available CFD code. The variation in rack inlet temperature due to tile openings, underfloor plenum depths is reported.
Evaluating the Crack-Tip Bridging Stress in a Bovine Cortical Bone
Authors: Khandaker M. , Ekwaro-Osire S. , Afrin F.
Published: May 2009

Recent experimental studies on human and bovine cortical bone shows that fracture strength of a cortical bone cannot be characterized by a single value of fracture toughness, but rather by variable crack growth resistance values. The mechanism of resistance of a crack extension in a bone is generally defined by R-curve behavior, which can be expressed as the relation between crack growth resistance values and crack extension. Crack bridging stress in front of a crack has been shown to be the main source of this resistance of the bone crack extension. The calculation of this bridging stress is important for predicting fracture stress in cortical bone material. In this study, a theoretical model based on weight function was developed to evaluate the bridging stress in front of a cortical bone crack tip. The main goal of this research was to investigate the role of specimen orientation on bridging stress. The hypothesis used was that specimen orientation has significant influence on the bridging stress. Two specific aims are developed to support this hypothesis: determination of the bridging stress along a crack length and investigation of the orientation effect on bridging stress. A weight function formulation was used to calculate crack opening displacements. The bridging stress along a crack can be found by minimizing the experimental and calculated crack opening displacements using a least square formulation. Finally, the bridging stress variation along a crack extension was examined in the specimen along two different orientations. The developed analytical model produces a gradually increasing trend of bridging stress with crack extension which depends on the orientation of the specimen extraction.
To Study the High Temperature Effects on Ball Bonds Using Low K Material in Wire Bond Devices
Authors: Kudtarkar S. A. , Murcko R. , Srihari K. , Saiyed S.
Published: May 2009

Wire bonding is widely used as one of the main interconnect alternatives. This technique applies significant mechanical stresses on the bond pads along with heat and ultrasonic energy to form a bond. An interconnection of copper plus low k material has been a focus of the semiconductor industry with the goal of reducing interconnection delays. The material is below the wire bond pads and complicates the mechanical stability of the device during wire bonding. The low k materials that are suggested are very sensitive to these mechanical stresses. This generates a significant reliability concern for the underlying metal structures. In addition, the integrity of the bond formed may be negatively impacted from a reliability perspective because of the softer material properties of the dielectric. This research explores the ball bond integrity for die with SiO2 and low k dielectric underlying material respectively, using 0.8 mil thick (20 microns) gold wire. Accelerated tests, such as high temperature storage at 150°C and 175°C, were conducted to assess the reliability of these bonds. The results of this investigation reveal that the ball bond’s strength degrades after high temperature tests due to the occurrence of Kirkendall voids between the gold wire and the aluminum bond pad. The degradation recorded was more severe for regular die than its low k counterpart.
Nonlinear Control Techniques for a SMA Active Ankle Foot Orthosis
Authors: Tarkesh Ehsan , Elahinia Mohammad
Published: May 2009

This paper is aimed toward the development and evaluation of a novel active ankle foot orthosis (AAFO) based on shape memory alloy (SMA) actuators. This device intends to fill the gap in the existing research aimed at helping patients with drop foot muscle deficiencies as well as rehabilitation activities. To check the feasibility of this idea, a brief study is done on the dynamic behavior of ankle joint and then an SMA manipulator with a similar biological concept is used for experiment. Nonlinear behavior of SMA wires requires nonlinear control techniques such as Sliding Mode Controller (SMC) for tracking the desired ankle angle. Simulation results of three different techniques are compared (PID, SMC and SMC-PID) and finally the experimental result of a SMC-PID switching control is provided. This results shows that a switching control between simple PID and Sliding Mode Control can be a good alternative to follow the desired trajectory in slow walking cycles.
On Geometric Nonlinear Vibrations of Nonuniform Beams
Authors: Caruntu Dumitru I.
Published: May 2009

Nonlinear bending vibrations in the case of moderately large curvature are reported for a nonuniform cantilever beam of rectangular cross section and a sharp end. This is a beam of constant width and parabolic thickness variation. The method of multiple scales is directly applied to the governing partial-differential equation of motion and boundary conditions. The linear modes are obtained in terms of hypergeometric functions by using the factorization method. In the absence of internal resonance (weakly nonlinear systems) the nonlinear modes are taken to be perturbed versions of the linear modes. The nonlinear mode shapes and frequencies of the beam are reported.