bluuebunny/crossref_metadata_2025 huggingface dataset:
The Quantification of Seal-Interface Leakage of an Elastomer Face Seal
Authors: Garafolo Nicholas G. , Daniels Christopher C.
Published: August 2012

Current gas leak rate prediction methods for elastomeric face seals rely heavily on the assumption that all leakage is permeation, rather than leakage across the seal interface [1–3]. To date, there has been no definitive evidence that this is indeed the case. It is essential to investigate the magnitude of interface leakage to facilitate the validation of the current compressible permeation model and to quantify the interfacial leakage for the design of future state-of-the-art face seals. To this end, a series of leak rate experiments is presented on a square-ring seal, manufactured from silicone elastomer S0383-70. The unique experimental design affords the ability to quantify both a metal-elastomer interface, as well as an elastomer-elastomer interface. The experiments utilized two square-ring test specimens, each with a common width but different in height. The test apparatus consisted of stainless steel platens, near-hermetic plumbing, programmable environmental chamber, and the required instrumentation. The initial data reduction was accomplished by the mass point leak rate technique; whereas mass was calculated through measurements of gas pressure, temperature, and volume and a regression analysis yielded the leak rate of the seal. A secondary reduction of the leak rates in the unique experimental configuration further distinguished the total leakage into permeation and interface leak components, accomplished through the algebraic solution of the design of experiments guided matrix. Results showed that, with modest contact pressure, permeation was the largest component of the total leakage. In addition, the interface leakage for the various seal mating conditions (i.e., seal-on-flange, seal-on-seal) was quantified for the contact pressure investigated. Contrary to previous conclusions, the interface leakages were found to be significant. In the application of space docking seals, a common example of elastomeric face seals, the significance of quantifying the interfacial leakages guides the design of the seal for incomplete seal compression conditions as well has for the androgynous docking configuration.
Performance and Emission Characteristics of a Small Scale Gas Turbine Engine Fueled With Propanol/Jet A Blends
Authors: Mendez Carlos J. , Parthasarathy Ramkumar N. , Gollahalli Subramanyam R.
Published: August 2012

Alcohols serve as an alternate energy resource to the conventional petroleum-based fuels. The objective of this study was to document the performance and emission characteristics of blends of n-propanol and Jet A fuel in a small-scale gas turbine engine. The experiments were conducted in a 30kW gas turbine engine with a single-stage centrifugal flow compressor, annular combustion chamber and a single-stage axial flow turbine. In addition to neat propanol and Jet A fuel, three blends, with 25%, 50% and 75% of propanol by volume, were used as the fuels. The thrust, thrust-specific fuel consumption, and the concentrations of CO and NOx in the exhaust were measured and compared with those measured with Jet A fuel. The engine was operated at the same throttle settings with all the fuels. The operational range of engine rotational speed was shifted downwards with the addition of propanol due to its lower heating value. The thrust specific fuel consumption increased with the addition of propanol, while the CO emission index increased and NOx emission index decreased.
Temperature Effect on Ballistic Impact of Hybrid Woven Composites
Authors: Budhoo Yougashwar , Liaw Benjamin , Delale Feridun
Published: August 2012

This paper investigates the effect of temperature on the ballistic limit of hybrid woven composite panels (6in×4in×0.25in) at three different temperatures: R.T, 75°C and 125°C. Studies were also done on the stacking sequence and its effect on the ballistic limit at the above stated temperature. The studies were conducted by combining experimental and 3-D dynamic finite element approaches. The specimens tested were made of plain-weave hybrid S2 glass-IM7graphite fibers/toughened epoxy. The composite panels were impacted using an in-house gas gun. The time-histories of impact-induced dynamic strains was recorded. The damaged specimens were inspected visually and using the ultrasonic C-scan method. A 3-D dynamic finite element (FE) software, with Chang-Chang composite damage model, was then used to simulate the experimental results of the ballistic impact tests. Good agreement between experimental and FE results has been achieved.
Wavelet Analysis of Oscillating Motions in an Oscillating Heat Pipe
Authors: Zhao Nannan , Ma Hongbin , Pan Xinxiang
Published: August 2012

The heat to be removed from the electronic components or systems can be used to excite the oscillating motion of a train of liquid plugs and bubbles in the oscillating heat pipe (OHP). The oscillating motion in the OHP can significantly enhance heat transfer. The wavelet transform (WT) analysis is used to analyze the oscillating motions occurring in the OHP. It is found that a number of waveforms exist, which indicates that the oscillating motions in an OHP are resulted from a number of sources. Results of the investigation will provide a better understanding of oscillating motion mechanisms occurring in the OHP.
Advanced Procedure Used for Determining the Absorption Coefficient of Sonic-Absorbent Materials
Authors: Pop Petru A. , Ungur Patricia A. , Lazar Liviu , Marcu Florin M.
Published: August 2012

Solving the acoustical problem and improving the impact indoor environmental quality represents a priority for many researchers and manufacturers of materials with a high noise reduction of coefficient rating. The paper presents a real solution for determination the sound-absorption coefficient of materials with acoustical properties from the gypsum family. The procedure used for test is standing wave method into a Kundt tube. The experiment setup used a complex installation of a Kundt tube containing a loudspeaker for emitting the sound waves at a well-defined frequency by a first PC, a microphone for detecting and transmitting the signal to a second PC for analyzing and processing the data. All of these were performed by using MATLAB Programs. Tests were conducted with two material samples with original receipts, one from gypsum and other from special gypsum plaster with sound-absorbent properties. The frequency was set separately for each material from 50 Hz to 1250 Hz to determine their sound-absorption coefficients. The result of experiments shows the efficiency of installation and superiority of special gypsum plaster vs. gypsum along entire frequency range of testing that can be carrying on to other materials with sound properties.
Comparative Study Among Hybrid Ground Source Heat Pump System, Complete Ground Source Heat Pump and Conventional HVAC System
Authors: Zhu Jiang , Tao Yong
Published: August 2012

In this paper, a hotel with hybrid geothermal heat pump system (HyGSHP) in the Pensacola is selected and simulated by the transient simulation software package TRNSYS [1]. To verify the simulation results, the validations are conducted by using the monthly average entering water temperature, monthly facility consumption data, and etc. Three types of HVAC systems are compared based on the same building model and HVAC system capacity. The results are presented to show the advantages and disadvantages of HyGSHP compared with the other two systems in terms of energy consumptions, life cycle cost analysis.
Analysis of Heat-Spreading Thermal Management Solutions for Lithium-Ion Batteries
Authors: Khasawneh Hussam , Neal John , Canova Marcello , Guezennec Yann , Wayne Ryan , Taylor Jonathan , Smalc Martin , Norley Julian
Published: August 2012

The analysis and optimization of thermal performance of Li-ion battery packs are topics of great interest today. Most Li-ion batteries for motive, vehicular, backup power and utility energy storage applications are fitted with a microprocessor-controlled thermal management system including an array of temperature and voltage sensors and an active cooling system. However, as the complexity of the thermal management system increases, so does its weight, volume and parasitic power consumption, all factors that adversely affect the vehicle’s performance. In this sense, an improved thermal management system based on including passive solutions such as phase change materials or heat spreading technologies could decrease the load on active components and ultimately the weight and costs of the system. This paper describes an experimental and simulation study aimed at evaluating the effectiveness of flexible graphite materials for heat spreaders in battery thermal management systems. A commercial Li-ion battery pack for power tools applications was adopted as a case study. The electro-thermal behavior of the battery pack was characterized through combined experimental investigation and 3D FEM modeling to determine the heat generation rate of the battery cells during utilization and to evaluate the thermal behavior of the battery pack. A thermal management solution based on flexible graphite heat spreading material was then designed and implemented. The paper presents a comparative study conducted in simulation to evaluate the improvements in the pack thermal behavior.
Parametric Study of Ground Source Heat Pump System for Hot and Humid Climate
Authors: Zhu Jiang , Tao Yong
Published: August 2012

The U-tube sizes and varied thermal conductivity with different grout materials are studied based on the benchmark residential building in Hot-humid Pensacola, Florida. In this study, the benchmark building is metered and the data is used to validate the simulation model. And a list of comparative simulation cases with varied parameter value are simulated to study the importance of pipe size and grout to the ground source heat pump energy consumption. The simulation software TRNSYS [1] is employed to fulfill this task. The results show the preliminary energy saving based on varied parameters. Future work needs to be conducted for the cost analysis, include the installation cost from contractor and materials cost.
Development and Validation of a Subject-Specific Finite Element Model for Skull Fracture Assessment
Authors: Huang James , Raymond David , Shen Weixin , Stuhmiller James , Crawford Gregory , Bir Cynthia
Published: August 2012

Due to the frequent occurrence of skull fractures from unintended head impacts from kinetic energy weapons, there is an immediate need to develop injury assessment tools for evaluating the risk of skull fracture under the high speed projectile impacts. Skull fracture tolerance has been shown to be dependent on impactor characteristics such as size and shape, as well as subject-specific anatomy. Accurate strain data collected at the fracture location has historically been difficult to measure, which has led to the use of finite element models. Prior research however has used generic finite element (FE) models of the head to determine skull strain and establish FE-based fracture criteria and thus may not be reflective of actual strain in the experimental tests, leading to inaccurate criteria. Additionally, prior FE models have not demonstrated the ability to accurately model fracture patterns. This study reports on two blunt ballistic temporo-parietal head impacts carried out to a post-mortem human subject (PMHS) and the development and validation of a subject-specific FE model. A nine-accelerometer array was mounted to the frontal bone to measure linear and rotational head accelerations. Three rectangular Rosette-style strain gauges were utilized to collect bone strain data surrounding the impact sites. A rigid, flat-faced 38.1 mm diameter projectile with a mass of 0.1 kg was used for all impacts. An accelerometer was mounted to the rear aspect of the projectile for measurement of impactor acceleration and from which impact force was calculated using the projectile mass and applying Newton’s Second Law. A subject-specific finite element head model was developed from the PMHS CT images. Results demonstrated good correlation between experimentally collected strain and accelerometer data to the FE model. The fracture patterns predicted from the model also demonstrated good agreement to fractures observed in the PMHS.
Diesel Particulate Filter Model With Detailed Permeability Analysis
Authors: Sprouse Charles E. , Mangus Michael D. , Depcik Christopher D.
Published: August 2012

Recent legislation of engine exhaust Particulate Matter (PM) emission levels cannot be met with in-cylinder PM reduction techniques, thus resulting in the need for a Diesel Particulate Filter (DPF). Modern DPFs use a honeycomb of long channels with porous walls in order to filter PM with near 100% efficiency. They must be designed to balance trapping efficiency and pressure drop, as flow restriction decreases engine efficiency. This paper describes the construction of two Matlab models in order to predict properties within the filter. Two methods for simultaneously solving the differential conservation equations along with the algebraic ideal gas law in the inlet and outlet channels have been developed. The first method solves the channel equations by transforming the differential algebraic equations (DAEs) into an ordinary differential equation (ODE) system. In addition, a second method is developed that directly solves DAE systems of index-one. In order to link the inlet and outlet channel profiles, modeling of the wall flow is necessary. Four permeability models from different disciplines are used in Darcy’s law to determine their applicability in calculating DPF wall velocity profiles. The resulting inlet, wall, and outlet parameters are compared with published results to demonstrate each model’s accuracy.
Evaluation of Hydrous Ethanol Combustion in a Swirl-Stabilized Combustor
Authors: Breaux Baine B. , Karmakar Srinibas , Zhu Shengrong , Acharya Sumanta
Published: August 2012

The use of commercial hydrous ethanol reduces the energy cost of producing that fuel, and results in a larger net energy gain per dollar invested. Current production of commercial grade ethanol contains 5% water, and is used routinely in gasoline engines, primarily as an additive, and is currently being considered for use in gas turbines. In this study ethanol is burned in a swirl-stabilized combustor, air is introduced at a constant flow rate through a dump diffuser, and fuels ranging from 0%–20% water in ethanol are injected via pressure-orifice atomizing nozzles. The goal of the study is to examine the combustion characteristics of hydrous ethanol and to make an assessment of its suitability for a gas turbine engine. The flame structure is observed using high speed OH and CH radical chemiluminescence imaging. These observations, combined with overall metrics such as lean blowout, flame holding, heat release and emissions, are a necessity in obtaining the complete picture of hydrous ethanol combustion and are required to fully evaluate hydrous fuel as an option in continuous flame applications.
A Novel Plating Technique for Realizing Copper Filled TSVs in Silicon Wafers
Authors: Adanur Emir , Ellis Charles , Dean Robert N. , Tuck Eric , Strembicke Derek
Published: August 2012

Through-Silicon-Vias (TSVs) continue to stand out as the most promising technology for electrical interconnections in the microelectronics industry. As package size continues to decrease, TSVs offer an elegant and robust solution for vertical interconnects. They facilitate 3D die stacking while minimizing or even eliminating area consuming planar packaging, allowing for direct signal and power paths through the substrate itself. TSVs can also be fabricated from different materials to desired dimensions to handle the required current level. Plated copper is emerging as the material of choice for TSVs. In this work, electroplated copper TSVs were fabricated successfully and evaluated using cutting and polishing techniques in preparation for image capture. The detailed fabrication process and analysis of the resulting TSVs are presented in this work.
An Improved Mathematical Model to Predict the Real Time Transient Performance of a Large Steel Reheating Furnace
Authors: Jenkins Joanna , Ward John , Tan C. K. , Broughton Jonathan
Published: August 2012

This paper describes the development and application of a two-dimensional model based on the zone method of radiation analysis to simulate the thermal behaviour of a large steel reheating furnace at Tata Steel. The furnace has a maximum throughput of 160 t/hr of steel blooms and is equipped with a total of 75 burners firing a mixture of combustible fuel gases arising from the steelmaking process. The model was validated for two different furnace throughput rates using experimental and plant data supplied by Tata Steel. Following validation it was then used to assess the furnace performance at a wider range of throughputs as well as examining the effect of the distribution of heat input along the furnace on furnace efficiency and stock temperature uniformity. The model differs from previous work since it takes into account the radiation interchange between the top and bottom firing sections of the furnace and also allows for enthalpy exchange due to the flows of combustion products between these sections. The results to-date showed that the model predictions are in good agreement with typical heating profile of the stock encountered in the actual furnace and are potentially suitable for incorporation into a model based furnace control system due to its relatively fast computing time.
The Influence of Heat Spreading on the Thermal Control of Photonics Integrated Circuits
Authors: Hickey Se´amus , Punch Jeff , Daly John , Jeffers Nicholas
Published: August 2012

Photonics Integrated Circuits (PICs), a feature of contemporary optical communications technologies, can represent a stringent packaging challenge, particularly in terms of their requirements for thermal control. Devices such as laser arrays can demonstrate tight temperature limits, sub-ambient operating temperatures, moderate heat loads but high device-level heat fluxes. A key feature of many hybrid PICs is a multilayer substrate which offers mechanical support, electrical interconnection and heat spreading for the devices that it carries; such substrates are typically mounted on a thermoelectric (TE) module (TEM) to achieve thermal control. The objective of this paper is to examine the influence of heat spreader structures on the thermal behavior of PICs, with particular attention on maximizing TEM efficiency. To this end, closed-form analytical and numerical models are developed for a representative laser array PIC which captures the conductive heat transfer within the spreader, coupled with a constitutive representation of the TEM. A parametric study is conducted to illustrate the influence of the following parameters on the source temperature of the PIC for the application: effective conductivities and dimensions of the heat spreader; thermal interface resistances; and thermal resistance between the TEM and the ambient. The outcome of the paper is an enhanced understanding of the role of heat spreading in the stable and efficient operation of contemporary PICs. This paper represents the initial results of an extensive programme of work on packaging-related aspects of next-generation PICs.
A Solar-Powered Direct Steam Generation Boiler for an Educational Desktop Rankine Cycle
Authors: Toro Ximena , Compere Marc , Van Wie Bernard , Dikici Birce
Published: August 2012

This paper presents the design and hardware validation of a unique solar powered boiler for powering a desktop scale steam Rankine power cycle. The primary purpose of the desktop Rankine cycle is to improve engineering education through a hands-on laboratory learning approach. Within this context, we have designed and validated a novel, glass-enclosed boiling chamber that generates steam entirely from the sun. Using a solar concentrator, the sun’s heat is focused onto an absorber plate that acts as a heating element. The absorber plate receives solar power via radiation and heats the working fluid through convection. Since this is a direct steam generation boiler, the entering fluid is water that stratifies upon boiling into two steady-state flow regions with both liquid and gaseous phases. A thermal model is developed to characterize the concentrated solar power (CSP), chamber geometry, and heat transfer to the working fluid. A complete solar-to-steam efficiency analysis is presented and validated with the hardware. The boiler’s estimated efficiency is 27.7% for converting typical daily solar irradiance to steam. The solar water boiling process can clearly be observed and is an excellent educational tool for both concentrated solar power as well as Rankine cycle power systems.
A Genetic Algorithm for Optimizing Heat Recovery Steam Generators of Combined Cycle Power Plants
Authors: Carapellucci Roberto , Giordano Lorena
Published: August 2012

Improving performance of combined cycle power plants has been the target of numerous investigations. Most of the researchers have focused their attention on the heat recovery steam generator (HRSG), the connecting equipment between the gas turbine group and the steam section. On the other hand, almost all equipment in a combined cycle is a fairly standard design available from a manufacturer, while the HRSG is one of the few components that may be somewhat customized. In fact, the HRSG provides many different design options with respect to the layout of heat transfer sections and their operating parameters. The aim of this work is the development of a model for optimizing the main operating parameters of the heat recovery steam generator of a CCGT. The thermodynamic behaviour of the power plant has been simulated through the commercial software GateCycle, whereas the optimization has been carried out using a genetic algorithm. The objective function to be minimized is the cost of electricity, evaluated through a cash flow analysis in constant or in current dollars. Two CCGT power plant configurations, with one or three-pressure reheat HRSG, are simulated and optimized, evaluating the influence of fuel price variation on the optimal operating parameters of HRSG.
Bench-Scale Pyrolysis of Wood Pellets
Authors: Brown Alexander L. , Mowry Curtis D. , Borek Ted T.
Published: August 2012

Past work has demonstrated the feasibility of pyrolyzing biomass and condensing the resulting vapor to form a low quality combustible liquid. The product, often termed pyrolysis oil, bio-oil, or bio-crude, can be refined to a transportation grade fuel. Because the pyrolysis process is comparatively simple, we speculate that a mobile pyrolysis system might be able to process the biomass at the site of harvest, generating a dense liquid for transportation. This would be expected to result in improved transportation economics compared to transporting the raw biomass fuel. This technology is being considered for northern New Mexico forests that are presently managed by periodic thinning efforts with little utilization of the products. We have designed a bench-scale system and pyrolyzed biomass pellets, which function in these tests as surrogate material for the forest trimmings. The system features controllable furnace temperatures, augur feed, gas recirculation, and multi-stage condensation. We have analyzed gases, chars, and liquids resulting from various operating conditions and report product quantities and qualities through various standard chemical methods. Good liquid mass yields of over 50% of the original material are typically found, with varying product quality and quantity depending on the operating temperature. Our results suggest the current configuration gives better yields and functions more optimally at pyrolysis temperatures around 525°C. For a practical system, combustion of the non-condensable fuel gases may be able to replace the electrically heated furnace used in these tests.
Finite Element Modeling of Burnishing and the Effects of Process Parameters on Surface Integrity of Orthopedic Implants
Authors: Salahshoor M. , Guo Y. B.
Published: August 2012

Hydrostatic burnishing is mainly a ceramic ball supported by a pressurized cushion of hydraulic oil and pushed against the workpiece surface. As the ball rolls along the surface it produces a unique combination of three physical effects in the surface layer: i) work hardening and increased hardness, ii) burnishing and decreased roughness, and iii) increased compressive residual stresses. This process has gained an increasingly great attention in automotive, aerospace, and especially medical device manufacturing industries. However, most of the research in hydrostatic burnishing has been performed experimentally and there is still lack of numerical studies providing fundamental understanding of the mechanics and the way process parameters interact with surface integrity characteristics particularly surface roughness and residual stresses. Understanding the correlation between process parameters and surface integrity is critical in efficiently adjusting the surface integrity in order to achieve proper biodegradation rate in human body after implantation. In this study, the dynamic mechanical behavior of the material is simulated using internal state variable (ISV) plasticity model. A semi-infinite, two-dimensional, plane strain FE model is developed and the ISV material model is incorporated into it using a user defined material subroutine. The effects of burnishing pressure and feed on surface roughness and residual stresses are investigated. The simulation results are validated with experimental measurements of residual stresses and surface roughness.
Selective and Automated Detection of Airborne Asbestos Fibers Using Chrysotile-Adhesive Protein and High-Throughput Microscopy (HTM)
Authors: Cho Myoung-Ock , Chang Hyo Mi , Yu Yeon Gyu , Han Hwataik , Kim Jung Kyung
Published: August 2012

There are several methods to detect asbestos including phase contrast microscopy (PCM), polarized light microscopy, X-ray diffraction, and electron microscopy. Although the PCM method is widely used due to its simple process and relatively low cost, it is a time-consuming and laborious process that is manually performed by a human counter. We developed a high-throughput microscopy (HTM) system for automated counting of airborne asbestos fibers to automate the conventional PCM method. Our results show that automatic image acquisition by synchronization of charge-coupled device (CCD) camera with movement of stages, and image analysis using image processing software, significantly reduced time consumption and labor. In this study, we used DksA chrysotile-adhesive protein for the selective detection of asbestos. DksA, known as the protein that specifically attaches to chrysotile, was extracted from Escherichia coli through a recombinant protein technique. We tried to detect chrysotile selectively from other fibers or particles, and we developed a highly selective and automated low-cost device for automated identification and enumeration of airborne asbestos fibers based on the HTM method.
Intermediate Scale Composite Material Fire Testing
Authors: Brown Alexander L. , Dodd Amanda B. , Pickett Brent M.
Published: August 2012

Composite materials are increasingly being used in aviation applications. As the quantity of composite material increases, there is a corresponding need to develop a better understanding of composite material response in fire environments. We have recently developed a program to examine this problem experimentally and computationally. Although Sandia National Laboratories and Air Force Research Laboratories at Tyndall have slightly different focuses, we are collaborating to focus on understanding duration, intensity, and the underlying physics during composite fires, as well as the technology and procedures to safely manage composite fire events. In the past year, we have been performing both small and intermediate scale testing to understand the behavior of composite materials used in aviation applications. The current focus is on a set of intermediate scale tests to generate data useful for understanding the behavior of carbon fiber epoxy composites in adverse thermal environments. A series of tests has been performed in a 90 cm cubic enclosure with 25–40 kg of composite materials to generate a severe fire environment fueled mostly by the composites. Preliminary results of these tests will be reported to provide data on the severity of the environment in terms of thermal intensity, duration, and chemical products.
A Model to Predict Contact Resistance During Contact Solidification in Ribbon Growth on Substrate Process
Authors: McFall James , Ma Ronghui
Published: August 2012

Ribbon Growth on Substrate (RGS) has emerged as a promising method for growing multicrystalline silicon wafer directly on a substrate for photovoltaic applications. In this method, the wafer forms as a substrate contacts molten silicon for a controlled period of time. Due to the surface roughness, a thin layer of air is trapped at the interface of the substrate and molten silicon, leading to a contact resistance to heat transfer. The interfacial heat transfer plays an important role in determining the subcooling rate and nucleation, which defines the structural characteristics of the wafer. The contact resistance has been identified as an important phenomenon that affects solidification at the interface. It is dependent on many factors such as the roughness and wetting of the substrate as well as the substrate pre-heating temperature. Quantitative knowledge of the interfacial heat transfer resistance is essential for control of the solidification process. A mathematical model is presented for quantification of the interfacial heat transfer resistance during the initial stage of the solidification for RGS process. A three dimensional unit cell is constructed to represent the contact geometry and interface characteristics. The surface roughness, the mean trapped air layer between the substrate and the liquid, the parameters of area density and the radius of contact spots will be included in the geometry of the unit cell. A microscale heat transfer model is developed to describe conduction and radiation across the interface to quantify the contact heat transfer resistance as a function of surface roughness, morphology and preheating temperatures of the substrate. The contact resistance is incorporated into a heat transfer model and predicts the temperature variation with time in the substrate during the initial stage of contact. The presented model provides a valuable tool to predict the effect of various process parameters and substrate surface roughness on wafer growth during the RGS process.
Surface Modification of Biodegradable Magnesium-Calcium Implants by Burnishing
Authors: Salahshoor M. , Guo Y. B.
Published: August 2012

Magnesium-Calcium (MgCa) alloys have shown very promising potential to make biodegradable metallic orthopedic implants. Biodegradable metallic implants relieve the need for second surgery and avoid stress shielding common with permanent metallic implants. Moreover, they provide enough strength in load carrying orthopedic applications as opposed to polymeric counterparts. High degradation rate of these alloys is the pressing issue resulting in subcutaneous hydrogen bubbles and high pH values and ultimately imbalance in physiological reactions. Surface modification techniques has been implemented to enhance the biocompatibility of these alloys by matching their corrosion rate with bone healing rate and absorption rate of corrosion by-products. Low plasticity burnishing (LPB) is a novel technique that makes wide range of surface integrity characteristics and consequently corrosion rates attainable. This is instrumental in developing proper degradation rates with respect to local healing and absorptions rates present in each application. Besides, LPB can be applied on already available CNC machining centers and in that sense is very flexible. Hence, studying the effects of LPB process parameters on surface integrity is important. In this paper, effects of burnishing passes and their pattern on surface topography, surface roughness, surface/subsurface microhardness, microstructure, and surface residual stresses of MgCa0.8 (wt%) implants are investigated.
Pool Boiling Enhancement via Micro Ratchets
Authors: Brumfield Lance Austin , Ok Jeong Tae , Park Sunggook
Published: August 2012

Preliminary experiments on nucleate pool boiling using asymmetric micro ratchets with de-ionized (DI) water as the working fluid were investigated. Two brass surfaces were tested for comparison; one surface was manually polished while the second was composed of asymmetric ratchets with 30μm height and 150 μm period. Small test aquariums (114.8 mm × 54 mm × 152.4 mm) were fabricated and tested on a hot plate. Results show that the ratchet surface made significant heat transfer improvements over the polished surface.
Reducing the Size of NURBs Controls Nets Using Genetic Algorithms and CUDA
Authors: O’Neal Matthew J. , Turner Cameron J.
Published: August 2012

The typical goals for defining a control net for a Non-Uniform Rations B-spline (NURBs) based metamodel from a given set of data the desired result is the smallest set of control points in the least possible time while minimizing local and/or global error. Current metamodel fitting algorithms iteratively find and eliminate the largest sources of local error, thus creating a very accurate control net with sub-optimal size. Since, control net size is directly related to the speed the control net can be searched for global optima, the size must be reduced as much as possible without increasing local or global error. Current algorithms can model discontinuous portions of data by clustering numerous control points close together. This is both inefficient to search and may cause the search algorithm to become numerically unstable and crash because of control points placed too closely together. Furthermore, many current algorithms do not take advantage of the weight property of each control point. In this paper, a Genetic Algorithm (GA) is used to optimize existing control nets as well as create new control nets from data sets. In order to offer a comparable creation time for the control net, parallel programming techniques are used incorporating the CUDA GPU Architecture. CUDA was chosen because it is low cost, highly parallel architecture available on millions of computers. The code is intended for a single desktop computer, running a maximum of 4 CUDA devices, not a CUDA cluster. This approach may have fitting applications to both metamodels and geometric fitting of NURBs objects.
Size Reduction of Poplar Wood Using a Lathe for Biofuel Manufacturing: A Preliminary Experiment
Authors: Song Xiaoxu , Zhang Meng , Pei Z. J. , Deines T. , Zhang Q. , Zhang P. F. , Wang D. H.
Published: August 2012

Poplar wood can be used as feedstocks for manufacturing of cellulosic biofuels (e.g., ethanol) as liquid transportation fuels. Producing ethanol from poplar wood involves reducing poplar wood into small particles, hydrolyzing cellulose inside poplar particles to fermentable sugars, and converting these sugars to ethanol. Size reduction is usually done by wood chipping and biomass milling. In the literature on poplar biofuels, there are no reports on particle formation mechanisms or effects of size reduction on sugar yield. One important reason for the lack of such knowledge is that particle formation in current size reduction methods is not well controlled. This paper presents the first attempt to use a lathe to generate poplar particles (or chips) with well controlled mechanisms of chip formation. The objective is to experimentally determine relations among chip thickness, uncut chip cross-section area, shear angle (representing the deformation severity of the chips), crystallinity index, and sugar yield.
Effects of Joint Preparation Angle of Single-Vee Butt Welds on the Tensile Strength of ASTM A36 Carbon Steel
Authors: McClure Matthew R. , Shahhosseini A. Mehran , Alberts Todd , Cochrane Phillip
Published: August 2012

Welding is a multi-faceted procedure of manufacturing and can occur at any point during the creation of a product. Quality issues in welding can have disastrous, or even deadly, consequences. The issue of weld preparation angle is one of several different elements that have a direct correlation on the quality of a welded joint. The purpose of this research centers on resultant tensile strength of a single-vee butt joint in carbon steel with various preparation angles. Preparation angles were machined on twenty-six pieces of ASTM A36 carbon steel in 5° increments in order to produce thirteen samples with included preparation angles ranging from 0° to 120°. Test samples were developed using an automated welding process that remained consistent for all of the welds. Each sample was plasma cut into ten coupons, which were machined to have a uniform cross section of the welded joint and surrounding parent material using a computer numerically controlled machining center. This yielded a total population of 130 coupons, which were tested to failure using a United Testing Systems stress/strain tensile tester. The empirical data were analyzed via the use of SPSS 18 statistical software. Initially, the level of population variance was assessed within groups and between groups by use of a one-way ANOVA test at the .05 alpha level. The result showed a statistically significant difference of the sample population. Secondly, a comparison of the data at various preparation angles to that of the industry standard angle of 60° was assessed using a Bonferroni multiple comparisons at the .05 alpha level, which resulted in one angle being statistically significant compared to the industry standard.
Optimization Design of an Axial-Flow Fan Used in Local Ventilation in Mining Industry
Authors: Desai Dhaval , Zhou Jiang
Published: August 2012

In a world where the increasing demand on developing energy-efficient systems is probably the most stringent design constraint, the trend in engineering research in recent years has been to optimize the existing technologies rather than to implement new ones. The present work addresses a robust axial-type fan design technique developed using an optimization technique. A fan is indispensable equipment for primary and local ventilation in mining industries. We always pursue the fan with high working efficiency and low noise. In this paper, an optimization method is developed to improve the pneumatic properties of the fan based on the blade element theory. A new type of fan used in local ventilation is designed with the help of computer. It is shown that the new design enhanced the efficient up to 88%. Numerical analysis is also conducted to validate the optimization design results.
Modeling of a Steam Turbine Including Partial Arc Admission for Use in a Process Simulation Software Environment
Authors: Liese Eric
Published: August 2012

A dynamic process model of a steam turbine, including partial arc admission operation, is presented. Models were made for the first stage and last stage, with the middle stages presently assumed to have a constant pressure ratio and efficiency. A condenser model is also presented. The paper discusses the function and importance of the steam turbines entrance design and the first stage. The results for steam turbines with a partial arc entrance are shown, and compare well with experimental data available in the literature, in particular, the “valve loop” behavior as the steam flow rate is reduced. This is important to model correctly since it significantly influences the downstream state variables of the steam, and thus the characteristic of the entire steam turbine, e.g., state conditions at extractions, overall turbine flow, and condenser behavior. The importance of the last stage (the stage just upstream of the condenser) in determining the overall flowrate and exhaust conditions to the condenser is described and shown via results.
Prediction and Validation of Performance of an Entrained Flow Gasifier Model
Authors: Roy Arnab , Ekkad Srinath V. , Vandsburger Uri
Published: August 2012

Computational fluid dynamics (CFD) simulation of a single stage, dry-feed entrained flow gasifier is carried out to predict several physical and chemical processes within the gasifier. The model is developed using a commercial software package FLUENT. The CFD model is based on an Eulerian-Lagrangian framework, where the continuous fluid phase is modeled in Eulerian approach and the particle flow trajectory is simulated in Lagrangian frame. The two phases are coupled by appropriate source terms in the conservation equations. The gasification process can be divided into the following sub-processes, which are inert heating, moisture release, coal devolatilization, char gasification and gas phase reactions. Discrete Phase Model (DPM) is used to model the coal particles and coupled with heterogeneous particle surface reactions in Species Transport module. The interaction between reaction chemistry and turbulence is described by Finite-rate/Eddy dissipation model. The simulation provides detailed information of temperature field and species concentration profile inside the gasifier. The temperature distribution clearly indicates the three different reaction zones for devolatilization, gasification and reduction. Steady state model predictions are compared with benchmark experimental data from literature. The trend of the predicted species mole fraction distribution is in good agreement within error bound of the experiment. The model thus provides a validated set of model parameters along with an insight to the underlying flow physics and chemical reactions of gasification process that can be employed to improve design of experiments. This study also develops the basis to achieve further accuracy incorporating complex effects such as detailed reaction kinetic mechanisms, proper devolatilization models, effect of ash-slag transition and particle deposition.
Forced Convection Heat Transfer Simulation Using Dissipative Particle Dynamics With Energy Conservation
Authors: Yamada Toru , Kumar Anurag , Asako Yutaka , Faghri Mohammad
Published: August 2012

Dissipative particle dynamics (DPD) with energy conservation was applied to simulate forced convection in parallel-plate channels with boundary conditions of constant wall temperature (CWT) and constant wall heat flux (CHF). DPD is a coarse-grained version of molecular dynamics. An additional governing equation for energy conservation was solved along with conventional DPD equations where inter-particle heat flux accounts for changes in mechanical and internal energies when particles interact with surrounding particles. The solution domain was considered to be two-dimensional with periodic boundary condition in the flow direction. Additional layers of particles on top and bottom of the channel were utilized to apply no-slip velocity and temperature boundary conditions. The governing equations for energy conservation were modified based on periodic fully developed velocity and temperature conditions. The results were shown via velocity and temperature profiles across the channel cross section. The Nusselt numbers were calculated from the temperature gradient at the wall using a second order accurate forward difference approximation. The results agreed well with the exact solutions to within 2.3%.
Spectral Boundary Element Method for Liquid Bridge Dynamics Between Capillary and Substrate
Authors: Wang Yechun , Lutfurakhmanov Artur , Akhatov Iskander S.
Published: August 2012

Micro/Nanolithography is an emerging technique to create micro/nano features on substrate. New capillary based lithography method has been developed to overcome the limitations (e.g. directly contact of the substrate) of existing lithography techniques including dip-pen nanolithography nano-imprint lithography and electron-beam lithography. The understanding of the behavior of the liquid bridge formed between a capillary tube and a substrate is essential for the recently developed capillary based lithography method that is non-invasive to the substrate. A three-dimensional spectral boundary element method has been employed to describe the dynamics of liquid bridge. Starting with a steady-state liquid bridge shape, the transient bridge deformation is computed as the capillary tube is retracting away from the substrate. Several relations between the dynamic contact angle and contact line speed have been employed and discussed. The computational results are compared with experimental findings. The influences of liquid properties and retracting speed on the bridge dynamics are investigated.
Comparison of Deformation Analysis of a Biological Cell Under an Injection Force Using Analytical, Experimental and Finite Element Methods and Artificial Neural Network
Authors: Sarvi Masoud Nasiri , Ahmadian M. T.
Published: August 2012

Biological cell injection is a sensitive and important work which is implemented in injection of foreign materials into individual cells. Microinjection is significantly developed in the field of drug discovery and genetics so predicting the behavior of cell in microinjection is remarkably important because a tiny excessive manipulation force can destroy the tissue of the biological cell. There are a few analytical methods available to simulate the cell injection, hence the numerical methods such as FEM are suitable to be used to model the microinjection. In this study, a new spherical super element is presented to model the biological cells and deformation of a specific cell under an external force is performed. The relationship between the injection force and the deformation of biological cell is demonstrated by using super element formulations. For validating the model, results are compared with findings of analytical and experimental methods and an Artificial Neural Network (ANN) model. The advantage of this element is that only a few super elements can predict the static behavior of biological cell in microinjection properly instead of implementing a large number of conventional elements, so using the super element to model the cell can decrease the run time with suitable accuracy.
Assessment of Prototypic and Closed Loop Operation During Pulse Jet Mixer Tests With Non-Cohesive Solids to Develop Scale-Up Relationships
Authors: Bamberger Judith Ann , Minette Michael J. , Meyer Perry A. , Fort James A. , Baer Ellen B. K.
Published: August 2012

The Hanford Waste Treatment Plant (WTP) in Richland, Washington is applying pulse jet mixer (PJM) technology for slurry mixing applications requiring solids mixing, solids suspension, fluid blending, and release of gases generated by radiolysis and thermal processes. Experiments were conducted to investigate pulse jet mixer performance in two different experimental configurations: one using intermittent flow through the pulse tube with non-prototypic refill and the other with prototypic reciprocating flow. Models developed to predict the critical suspension velocity (UCS), cloud height, and concentration based on the intermittent flow data. This model under predicted the UCS condition for data obtained using prototypic reciprocating flow. When an adjustment to the settling velocity was incorporated into the model to address the effects of intermittent flow, the resulting reciprocating flow model more closely matched the experimental data.