bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating the Mechanical Properties of 3D Woven Carbon-Epoxy Composite Materials Using Experimental Data and FEA Methods
Authors: Farahikia Mahdi , Macwan Sunilbhai , Delfanian Fereidoon , Hu Zhong
Published: August 2012

A series of tensile, compression and shear tests were carried out on carbon-epoxy composite materials to evaluate their mechanical properties. The experiments were set upin accordance with ASTM standards that best corresponded to the test specifications. Specimens were categorized into groups according to their dimensions and shape. Based on testing requirements, some were cut into rectangular and others into dog bone specimens to determine the effects of stress concentration. A number of specimens were reinforced at both ends by means of tabs which were bonded on both faces to reduce the effects of the external pressure exerted on them through the grips of the testing machines, and the rest of them were tested without any reinforcement tabs. All the specimens were tested until failure. Load, elongation (displacement) and strain data were recorded by means of strain gages and data acquisition systems. The experimental results obtained from similar tests on different groups are compared to examine the conformity of the results regardless of dimension and geometry, and are also verified by Finite Element Analysis (FEA). In addition, FEA is used to study different conditions, such as geometry, that could affect the final results. The experimental data are analyzed and effects of fiber direction on failure method are studied. It was concluded that shape and geometry factors as well as fiber direction influenced the failure method. The work, however, is still in progress and tests under conditions, such as elevated temperature, will be conducted to study other effects on the mechanical properties of 3D woven carbon-epoxy composites.
Microfluidic Chip for Particle-Liquid Separation
Authors: Bhardwaj Priyank , Bagdi Piyush , Sharma Ashish S. , Sen Ashis K.
Published: August 2012

This paper presents theoretical analysis, design, fabrication and test of a microfluidic device (‘Micro hydrocyclone’) for separation of micron and sub-micron size solid particles from liquid in a particle-liquid mixture. A theoretical analysis of the micro hydrocyclone is performed to understand the physics and develop suitable design models. The structure of the proposed device is designed based on Bradley model, as it offers lower cut-size thus making it suitable for microfluidics applications. The operational parameters are derived from the dimensional group model. The device is fabricated with SU-8 photoresist on PMMA substrate using a combination of photolithography and micro-milling. Experiments are performed to demonstrate particle-liquid separation using polystyrene microbeads suspended in PBS as the feed sample. The influence of inlet velocity and particle size on particle separation efficiency is investigated. The proposed device can be easily integrated with micro-environments thus is suitable for lab-on-chip and microsystems development. The device may have applications in chemical analysis, materials research, point-of-care, blood sample preparation and other biomedical applications.
Experimental Study of Nanoadditives for Biofuel Combustion Improvement
Authors: Li Calvin Hong
Published: August 2012

An experimental investigation of the combustion behavior of nano-aluminum (n-Al) and nano-aluminum oxide (n-Al2O3) particles, stably suspended in biofuel (ethanol) as a secondary energy carrier was conducted. The heat of combustion (HoC) was studied using a modified static bomb calorimeter system. Combustion element composition and surface morphology were evaluated using a SEM/EDS system. N-Al and n-Al2O3 particles of 50 nm and 36 nm diameters, respectively, were utilized in this investigation. Combustion experiments were performed with volume fractions of 1%, 3%, 5%, 7%, and 10% for n-Al, and 0.5%, 1%, 3%, and 5% for n-Al2O3. The results indicate that the amount of heat released from ethanol combustion increases almost linearly with n-Al concentration. N-Al volume fractions of 1% and 3% did not show enhancement in the average volumetric heat of combustion, but higher volume fractions of 5%, 7%, and 10% increased the volumetric heat of combustion by 5.82%, 8.65%, and 15.31%, respectively. N-Al2O3 and heavily passivated n-Al additives did not participate in combustion reactively, and there was no contribution from Al2O3 to the HoC in the tests. A combustion model that utilized Chemical Equilibrium with Applications (CEA) was conducted as well and was shown to be in good agreement with the experimental results.
Approximate Analysis for Darcy-Flow Convection in Cylindrical Porous Media With Zero Fluid Conduction
Authors: Dukhan Nihad
Published: August 2012

Contemporary porous media that are used in cooling designs include metal and graphite foam. These materials are excellent heat transfer cores due to their large surface area density and the relatively high conductivity of the solid phase. Engineering models for convection heat transfer in such media are needed for thermal system design. When the cooling fluid has a low conductivity, e.g., air, its conduction can be set to zero. Engineering analysis for the fully-developed convection heat transfer inside a confined cylindrical isotropic porous media subjected to constant heat flux is presented. The analysis considers the Darcy flow model and high Pe´clet number. The non-local-thermal equilibrium equations are significantly simplified and solved. The solid and fluid temperatures decay in what looks like an exponential fashion as the distance from the heated wall increases. The effects of the Biot number and the Darcy number are investigated. The results are in qualitative agreement with more complex analytical and numerical results in the literature. The solution is of utility for initial heat transfer designs, and for more complex numerical modeling of the heat transfer phenomenon in porous media.
An Equivalent Method for Optimised Design of Nested Tube Energy Absorber Under Space Constraints
Authors: Sun Lingyu , Leng Dingxin , Chen Weiwei , Xu Bin , Wang Xiaojie , Lin Yi , Hu Dayong , Shi Jiangxia
Published: August 2012

This paper investigates the relationship of energy absorption between individual tube and nested tubes system in order to provide an equivalent design method for engineers. Firstly, both analytical and numerical methods were presented to analyze single tube under lateral point-loading compression, and the influences of material model and tube dimensions on energy absorption was studied. Secondly, an energy absorption system consisted of nested tubes was equivalently modeled by the combination of single tube in parallels or/and in series, and the resultant deformation and energy absorption were derived analytically by the present method. Several typical examples were verified numerically. It also discussed the relationship between structural effectiveness and solidity ratio for tube system and its components. Finally, a nested tubes system was optimized based on the requirements of installation space, crush distance and energy absorption capability.
In-Process Weighing Systems
Authors: Elbeltagi Rami , Ben-Tal Alona , Potgieter Johan , Chang Jen-Yuan James
Published: August 2012

In-process electronic high speed weighing systems play an important role in the highly automated, continuously evolving industrial world of today. They are an essential component in sorting, grading and quality control within a diverse range of industries, including; robotics, automotive and food. Load cells are considered to be the definitive force sensor for industrial weighing systems. Load cell output is in the form of an oscillatory response in which the measurand contributes to the response parameters. Current methods require the oscillatory response to settle in order to achieve an accurate measurement. This is time consuming and speed limiting. The focus of this paper is to find alternative weighing analysis methods for a system which utilises two load cells, placed either side of a carrier travelling on a chain conveyor, running at speeds of 10 items a second. It is necessary to determine the value of the measurand in the fastest time possible to speed up the process and increase throughput. This has been approached by mathematically modelling the system to allow accurate prediction of the weights passing the load cells before the settling time of the oscillatory response. Simple models of harmonic motion have been considered for the motion of a load cell. An experimental system was built and weighing data collected for different speeds and loads. Power spectra of the weighing data was analysed to determine dominant frequencies and estimate system parameters. This paper describes the work done to date on load cell modelling and improving an in-process electronic weighing system by successfully predicting the weight during the transient period of the oscillatory response. The assumptions and results of both simulations and experimental data are presented.
An Empirical Model for the Prediction of Hemodialysis System Performance
Authors: Kang Jane , Jariwala Amit , Rosen David W.
Published: August 2012

The examination of steady state behavior of hemodialysis treatment using the analytical model created by Olson et al. revealed that for each set of hemodialysis conditions, a fixed time constant exists that dictates how quickly the patient’s waste level cycle reaches a steady state condition. They also revealed that initial waste level does not affect the final steady state waste level. In this study, an empirical model for the time constant and the final steady state maximum waste level were found that lumps hemodialysis inputs such as flow rates, dialyzer properties, and patient waste generation by conducting a parametric study on a previous hemodialysis model from Olson et al. [1] The empirical model is validated by comparing the curve that predicts how the peak waste level of each cycle changes over time with the analytical model’s results. For all the tested input values which cover most of practical hemodialysis treatments, the curve closely matched the numerical model’s results with R2 value higher than .9973. The empirical model created in this study provides a much simpler prediction method without the use of complex numerical simulations. In addition, the Olson model cannot be used to run an inverse simulation to determine optimal inputs for desired outputs. This limitation is overcome by our empirical model, which further allows much easier and more extended exploration of different therapies (dose length and schedule) for both doctors and renal replacement system designers.
Electrokinetic Microscope for Imaging Three-Dimensional Surface Topography and Heterogeneity
Authors: Kwon Gi Hwan , Kim Tae Young , Kim Sung Jin
Published: August 2012

We introduce the concept of electrokinetic microscope (EKM) which is an imaging technique based on hydrodynamics and electrokinetics. The EKM can provide information of the three-dimensional surface topography and heterogeneity using a syringe pump, pressure sensor, and electrometer. The three-dimensional surface topography is obtained from the relation between the flow impedance and a relative distance of a probe from a specimen, and the surface heterogeneity is obtained by measuring streaming potential or current electrokinetically generated by a surface material. Experimental results show that streaming potential and current depend not only on the relative distance between the probe and specimen, but also on surface materials. The major advantages of the EKM are that it does not need direct physical contact between the probe and specimen, and the surface topography and heterogeneity of the specimen are measured simultaneously. EKM micrographs of microscale patterns with various materials and linewidths are presented. The lateral resolution of the EKM strongly depends on the inner diameter of the probe.
Atomistic Mechanisms of Enhancing Energy Conversion Efficiency of Nanostructured Thermoelectrics
Authors: Hu Ming , Zhang Xiaoliang , Giapis Konstantinos P. , Poulikakos Dimos
Published: August 2012

Nonequilibrium molecular dynamics (NEMD) simulations are performed to investigate possible mechanisms for enhancing the energy conversion efficiency of thermoelectric nanowires, including 1) surface roughening, 2) incorporating nano-particles on the surface or inclusions in the nanowires, and 3) inducing interfacial interference by covering the nanowire surface with other coatings. The enhancement in energy conversion efficiency is measured in terms of thermal conductivity of the nanowire, which is obtained by imposing a one-dimensional heat flux in the longitudinal direction of the nanowire. Our simulation results show that, compared to pristine nanowires, all generated nanocomposite structures proposed above were found to have considerably lower thermal conductivity (up to 78% reduction was achieved), implying ∼ 5 times enhancement in the ZT coeficient. The realizable approaches herein, open up new fundamental ways to improve markedly the energy conversion efficiency of nanostructured thermoelectrics.
The Influence of the Roller Forming Path on the Neck-Spinning Process of Tube at Elevated Temperature
Authors: Huang Chi-Chen , Hung Jung-Chung , Lo Cheng-Chan , Lin Chia-Rung , Hung Chinghua
Published: August 2012

The tube spinning process is a metal forming process used in the manufacture of axisymmetric products, and has been widely used in various applications. In this paper, the neck-spinning process was applied to form the neck part of the tube end at an elevated temperature. The spun tube was used as a high pressure CO2 vessel, which is a component of motorcycle airbag jackets. An uneven surface will occur on the tube surface if the thickness distribution of the tube is not uniform after the neck-spinning process. This is because different thicknesses result from different contractions during the cooling stage. For this reason, the aim of this research was to numerically investigate the roller forming path to improve the thickness distribution of the tube during the neck-spinning process. The finite element method was used to simulate the neck-spinning process of the tube at an elevated temperature. For the construction of the material model, special uni-axial tensile tests were conducted at elevated temperatures and various strain rates, because the material is sensitive to strain rates at high temperatures. This paper compares the experimental and simulation results of the thickness distribution and the outer contour of the spun tube. The validated finite element model was used to investigate the influence of the roller forming path on the thickness distribution of the tube. The thickness distribution of the tube formed by a curved path was found to be more uniform than for the tube formed by a straight path. Finally, the optimization technique was used to find the optimal forming path, and the optimal result was verified experimentally.
An Analytical Elastic-Plastic Contact Model
Authors: Brake M. R.
Published: August 2012

This paper presents a new formulation for elastic-plastic contact in the normal direction between two round surfaces that is solely based on material properties and contact geometries. The problem is formulated as three separate domains: the elastic regime, mixed elastic-plastic behavior, and unconstrained (fully plastic) flow. Solutions for the force-displacement relationship in the elastic regime follow from Hertz’s classical solution. In the fully plastic regime, two assumptions are made: that there is a uniform pressure distribution and that there is conservation of volume. The force-displacement relationship in the intermediate, mixed elastic-plastic regime is approximated by enforcing continuity between the elastic and fully plastic regimes. Transitions between the three regimes are determined based on empirical quantities: the von Mises yield criterion is used to determine the initiation of mixed elastic-plastic deformation, and Brinell’s hardness for the onset of unconstrained flow. Unloading from each of these three regimes is modeled as an elastic process with different radii of curvature based on the regime in which the maximum force occurred. Simulation results explore the relationship between the impact velocity and coefficient of restitution. Further comparisons are made between the model, experimental results found in the literature, and other existing elastic-plastic models.
Microstructure and Mechanical Properties of Electron Beam Deposits of AISI 316L Stainless Steel
Authors: Wang Liang , Felicelli Sergio D. , Coleman Jacob , Johnson Rene , Taminger Karen M. B. , Lett Ratessiea L.
Published: August 2012

Electron beam freeform fabrication (EBF3) is a process that uses an electron beam and wire feedstock to fabricate metallic parts inside a vacuum chamber. In this study, single and multiple layer linear deposits of AISI 316L stainless steel were produced with the EBF3 machine at NASA Langley Research Center (LaRC). EBF3 process parameters, including beam current, translation speed, and wire feed rate, were investigated in order to consider their effects on the resulting steel deposit geometry, microstructure and mechanical properties. Results indicate that the EBF3 process can produce pore-free, fully dense material within the range of process parameters used in this study. The electron beam deposited stainless steel has a solidification microstructure with fine columnar grains within most parts of the deposit due to the high cooling rate during the deposition, with some small homogeneous equiaxed grains at the top of the deposit. The mechanical properties of the deposits are comparable to those of wrought metal, which is attributed to the homogeneous fine-grained microstructure.
Experimentally Validated Computational Simulation of Lumbar Spine Intervertebral Disc Puncture
Authors: Lipscomb Kristen E. , Sarigul-Klijn Nesrin
Published: August 2012

Back pain is a debilitating medical condition, often with an unclear source. Over time, back pain can affect the work and lifestyle of an individual by reducing job productivity and time spent on enjoyable activities. Discography of the intervertebral disc (IVD) is often used to diagnose pathology of the disc and determine if it may be a source for chronic back pain. It has recently been suggested that discography may lead to IVD degeneration, and has been a cause of controversy among spine care physicians. Using the results from a cadaveric experimental model, a finite element model was first validated. Then, a study was conducted to better understand the changes caused by discography on human spine mechanics. An anatomically accurate L3-L5 lumbar spine model was developed using computed tomography scans. Discography was simulated in the model as an area in the disc affected by needle puncture. The material properties in the nucleus pulposus were adjusted to match experimental data both before and after puncture. The results show that puncture of the IVD leads to increased deformation as well as increased stresses in the disc. Pressure in the nucleus pulposus found to decrease after puncture, and was calculated in the course of this study. Puncturing the IVD changes disc mechanics and may lead to progressive spine issues in the future such as disc degeneration. While discography has been the gold standard to determine if the disc was a source of back pain in patients for many years, the potential long-term degenerative effects of the procedure are only now coming into light, and must be closely examined.
Transient Vapor Compression Refrigeration Cycle for Electronics Cooling: Part 1—Distributed Model Validation
Authors: Zhang TieJun , Catano Juan , Wen John T. , Jensen Michael K.
Published: August 2012

For high-power electronic systems, such as high-concentration photovoltaics arrays, laser diode arrays, and high-density data centers, two-phase cooling technologies are being explored to significantly reduce heat convection resistance from electronics’ wall to the ambient. Lower electronics surface or junction temperatures lead to higher energy conversion or computation efficiency; therefore, thermal management is a critical issue for energy efficient electronic system operation. In large-scale electronics cooling systems, there usually exist many distributed and transient heat sources. The non-uniform heat loads could cause severe flow mal-distribution problems and local device burn-out (i,e, a difficult thermal management challenge). Vapor compression refrigeration cycles have been identified as promising solutions to ultra high-power electronics cooling. A well-designed active refrigeration cooling system is expected to achieve higher transient cooling capability and energy efficiency. This paper presents a comprehensive first-principle dynamic refrigeration cycle model to understand its fundamental mass, energy, and momentum transport mechanisms in transient operation. Experimental validation results show the proposed distributed vapor compression cycle model has excellent steady-state and transient prediction performance. The proposed distributed dynamic model is able to provide valuable design and operation guidelines for energy-efficient electronics cooling systems under transient and non-uniform heating scenarios.
Transient Vapor Compression Refrigeration Cycle for Electronics Cooling: Part 2—Multi-Evaporator Dynamics and Control
Authors: Zhang TieJun , Wen John T. , Jensen Michael K.
Published: August 2012

For next-generation sustainable electronic systems, such as high-concentration photovoltaics arrays and high-density super-computers, two-phase cooling technologies are being explored to significantly reduce heat resistance from electronics’ surface to the ambient. Lower electronics operating temperatures lead to higher energy conversion or computation efficiency; therefore, thermal management, especially dynamic thermal management, is able to bring great potential to energy-efficient electronic system operation. These large-scale electronics cooling systems normally include multiple, distributed, and transient heat sources. Multi-evaporator vapor compression refrigeration cycle provides such a promising cooling solution. Due to the complexity of multiple evaporator structure, its transient analysis and active control become very challenging. This paper applies our previous distributed heat exchanger modeling techniques to study the dynamics of multi-evaporator refrigeration cycles. A comprehensive first-principle multi-evaporator vapor compression cycle model is formulated for its transient analysis. Some preliminary expansion valve control results are presented to show the excellent active electronics cooling capability. This general tool is expected to bring instructive guidelines for the optimal design and operation of energy-efficient transient electronics cooling systems with multiple heat loads and hot spots.
Reciprocating Bone Saw: Effect of Blade Speed on Cutting Rate
Authors: Lannin Timothy B. , Kelly Matthew P. , James Thomas P.
Published: August 2012

Power reciprocating saws are used in surgical procedures to cut bone. Improved cutting rates are desirable in order to reduce operative time and improve patient outcome. A fixture was developed to test the effect of blade speed on cutting rate of bovine cortical bone. It was hypothesized that the volumetric cutting rate would increase in a linear manner for a fixed stroke length and a constant thrust force. A 7.0 N thrust force was applied. The reciprocating stroke length was held constant at 3.0 mm. Using an 18 TPI blade, cutting rate was determined to increase in a slightly non-linear manner, with disproportionately higher cutting rate at higher blade speeds. The data implies that a higher reciprocating frequency may invoke more efficient cutting.
Modal Bifurcation in Integrally Bladed Rotors
Authors: Mubarak Rana Noman , Chang Jen-Yuan James
Published: August 2012

Effects on structure designs on free vibrations of integrated bladed rotor (IBR) have been conducted in this research through finite element simulations. Migration of natural frequencies is characterized through parameter studies considering changes of blade angle and blade thickness on an underlying uniform axis-symmetric rotor. Recurring coupled repeated doublet modes, defined as replica modes, has been observed in this study by characterizing blade’s vibrations in-phase or out-of-phase to disk’s vibrations. Veering and cluster of replica modes’ natural frequencies are observed with respect to the blade design parameters. Fourier content for low frequency replica component is found to be sensitive and tunable to blade angle design, which has implications on forced response of spinning IBR in engineering applications.
Piezo-Elastic Actuation for Micro-Positioning of Lateral Tape Motion
Authors: Chang Jen-Yuan James
Published: August 2012

In this paper, development of a prototypical microcontroller controlled ultrasonic actuator system incorporating a plate-like piezoelectric actuator is discussed to provide an alternative means in actively guiding the tape laterally. Structural vibration modes are first experimentally examined through standard modal analyses. Method of modal superposition is used in programming the micro-controller so as to provide excitations to the PZT actuator resulted in traveling waves in the plate-like structure. Promising results are demonstrated in the proposed system that have rich implications in providing active guiding mechanism to minimize and even actively control the tape’s lateral motion.
Dynamic Simulation of a HRSG System for a Given Start-Up/Shut Down Curve
Authors: Cha Hun , Song Yoo Seok , Kim Kyu Jong , Kim Jung Rae , KIM Sung Min
Published: August 2012

An inappropriate design of HRSG (Heat Recovery Steam Generator) may lead to mechanical problems including the fatigue failure caused by rapid load change such as operating trip, start-up or shut down. The performance of HRSG with dynamic analysis should be investigated in case of start-up or shutdown. In this study, dynamic analysis for the HRSG system was carried out by commercial software. The HRSG system was modeled with HP, IP, LP evaporator, duct burner, superheater, reheater and economizer. The main variables for the analysis were the temperature and mass flow rate from gas turbine and fuel flow rate of duct burner for given start-up (cold/warm/hot) and shutdown curve. The results showed that the exhaust gas condition of gas turbine and fuel flow rate of duct burner were main factors controlling the performance of HRSG such as flow rate and temperature of main steam from final superheater and pressure of HP drum. The time delay at the change of steam temperature between gas turbine exhaust gas and HP steam was within 2 minutes at any analysis cases.
The Power Generation With Vegetable Oils: A Case Study
Authors: Calabria Alfonso , Capata Roberto , Di Veroli Mario
Published: August 2012

The utilization of vegetable oils, and in particular the palm oil, as fuel in the power generation has had a remarkable development in the last few years. Generally the vegetable oil can be used with a particular marine-derived diesel ICE, with low rpm and an electric conversion efficiency of about 40%. The efficiency is strictly connected to the size of the plant. Moreover, the considerable amount of the required vegetable oil to feed the system forces to import the fuel. This is one of the most critical elements as the palm oil is subject to continuous and wide variations in prices. Due to this variation it is difficult to obtain a stable and convenient fuel supply over a long period of time. The present work is aimed at evaluating and estimating the economic, technical and environmental feasibility of a 20 MW plant for the stationary power generation fed with palm oil, enlightening the system solution (technical constructive aspects) and the economic appraisal, on the basis of variations in oil prices. Finally, the economic sensibility analysis based on the fuel cost and the European mechanisms of biomass incentives.
3D Microfabrication Using Bulk Lithography
Authors: Gandhi Prasanna , Bhole Kiran
Published: August 2012

Microstereolithography (MSL) has been a promising technology for fabrication of three-dimensional (3D) microstructure using layer-by-layer photopolymerization. However, this process produces 3D microstructures with a step corresponding to each layer. We propose in this paper a novel way, termed as ‘Bulk Lithography’, of generating 3D microstructures in single-pass scanning of laser beam over the photopolymer resin of unconstraint depth. In the proposed method, laser energy exposure, being one of the important parameters affecting cured depth, is varied along the line scan to enable fabrication of varying depth structure. Test structure is fabricated with proposed method to illustrate the capability of the proposed process. Lesser fabrication time and step-free 3D microfabrication in the direction perpendicular to the scan plane (z-axis) are the key features of the proposed method.
Metamodel-Assisted Ice Detection for Wind Turbine Blades
Authors: Malave´ Veruska , Turner Cameron J.
Published: August 2012

Icing is a complex atmospheric phenomenon that causes airflow disruption and degrades aerodynamically the original performance of the wind turbine blades (WTBs). This is due to blade sensitivity to minor changes in the airfoil geometry. Aerodynamic distortions induced by ice decrease the lift-to-draft ratio and pitch moment, increase the airfoil weight, and adversely alter the effectiveness of position angle and velocity. Typically, wind turbines exposed to all-weather conditions are equipped with icing prevention systems (IPS). However at the present time, no ice-detection technique has been proven effective, and the implementation of new strategies that effectively detect and mitigate blade icing adverse effects are needed. In this work, a WTB ice-detection technique that consists of a numerical design tool using Matlab/Simulink models and non-uniform rational B-spline (NURBs) based metamodeling algorithms is examined. This is carried out in terms of the blade icing effects on turbine aerodynamic performance in accordance to condition-based maintenance (CBM) and prognostics health management (PHM) techniques.
Polymerization Shrinkage and Adhesion in UV-Nanoimprint Lithography
Authors: Amirsadeghi Alborz , Lee Jae Jong , Park Sunggook
Published: August 2012

Ultraviolet nanoimprint lithography (UV-NIL) is a molding-based nanofabrication technique utilizing the change in viscosity of a UV resist upon UV irradiation and is one of the most promising candidates for mass-production lithography [1]. The biggest challenge, however, in UV-NIL is demolding, a process to remove the stamp from the molded substrate. Numerous efforts have been made to make the demolding process easier with the main goal being the reduction in adhesion at the stamp/resist interface. However, it is not only the adhesion at the stamp/resist interface that produces stress during demolding. The force applied to the sidewalls of stamp structures by resist shrinkage occurring during UV curing also contributes to demolding force. Experimental methods such as bilayer beam deflection [2] have been employed to measure stress generated in a thin resist layer during UV curing. However, the stress measured by these methods does not represent the real UV-NIL process in which the resist is locally confined within the stamp structures. To the best of our knowledge, there has been no attempt to experimentally determine the stress by polymerization shrinkage in the actual UV-NIL system.
Effects of Rotation of Material Axes on Free Flexural Vibrations of Centrally Bonded Symmetric Double Doubler Joint in Composite Mindlin Plates or Panels
Authors: Yuceoglu U. , Gu¨vendik O.
Published: August 2012

The present study investigates the serious effects of rotation of material axes on the free dynamic response of composite plates or panels with “Bonded Double Doubler Joint Systems”. The “Plate Adherends” and the “Upper and Lower Doubler Plates” are connected through the relatively very thin adhesive layers. The “Bonded Double Doubler Joint System” is considered in terms of the “System.1” and the “System.2”. In the “System.1”, the material directions of “Plate Adherends” are rotated 90° (about z-axis) while there is no change in the material axes of the “Double Doubler Plates”. In the “System.2”, the material directions of the “Double Doubler Plates” are rotated 90° (about z-axis), while there is no change in the material axes of the “Plate Adherends”. All plate elemnts of the “System.1” and the “System.2” are assumed to be dissimilar “Orthotropic Mindlin Plates” with the transverse shear deformations and the transverse (or bending) moments of inertia and the rotary moments of inertia. The upper and lower adhesive layers are linearly elastic continua with dissimilar material properties and with unequal thicknesses. The damping effects in all plate elements and also in adhesive layers are neglected. The entire theoretical analysis for both “Systems.1 and 2” is based on the “Orthotropic Mindlin Plate Theory”. For this purpose, the dynamic equations of the left and the right “Plate adherends” and of the “Upper and Lower Doubler Plates” and the equations of the adhesive layers are combined to-gather with the stress resultant – displacement expressions of the plate elements. Then, after some algebric manipulations and combinations, and with the “Classical Levy’s Solutions” the original dynamic equations are finally reduced into the two new sets of the “Governing System of the First Order O.D.E’s” in compact matrix forms with the “state vectors” for the “System.1” and “System.2”, respectively. In this way, the original “Initial and Boundary Value Problem” (or the free vibrations problem) is converted to the “Multi–Point Boundary Value Problem” of Mechanics and Physiscs. In the case of both “Systems.1 and 2”, these results facilitate the direct application of the present method of solution that is the “Modified Transfer Matrix Method (MTMM) (with Interpolation Polynomials)”. The aforementioned “Governing Equations” for both “Systems.1 and 2” are numerically integreted by making use of the “ (MTMM) (with Interpolation Polynomials)”. Thus, the natural frequencies and the mode shapes of the “Systems.1” and the “System.2” are graphically presented for the same “Support Conditions”. The comparison of the numerical results corresponding to each “System.1” and “System.2” for the same “Support Conditions” is considered leading to some very important conclusions.
Modeling and Control for Cooling Management of Data Centers With Hot Aisle Containment
Authors: Zhou Rongliang , Wang Zhikui , Bash Cullen E. , McReynolds Alan
Published: August 2012

In traditional raised-floor data center design with hot aisle and cold aisle separation, the cooling efficiency suffers from recirculation resulting from the mixing of cool air from the Computer Room Air Conditioning (CRAC) units and the hot exhaust air exiting from the back of the server racks. To minimize recirculation and hence increase cooling efficiency, hot aisle containment has been employed in an increasing number of data centers. Based on the underlying heat transfer principles, we present in this paper a dynamic model for cooling management in both open and contained environment, and propose decentralized model predictive controllers (MPC) for control of the CRAC units. One approach to partition a data center into overlapping CRAC zones of influence is discussed. Within each zone, the CRAC unit blower speed and supply air temperature are adjusted by a MPC controller to regulate the rack inlet temperatures, while minimizing the cooling power consumption. The proposed decentralized cooling control approach is validated in a production data center with hot aisles contained by plastic strips. Experimental results demonstrate both its stability and ability to reject various disturbances.
Performance Analysis of a Countercurrent Flow Heat Exchanger Placed on the Truck Compartment Roof
Authors: Lin Wamei , Yuan Jinliang , Sunde´n Bengt
Published: August 2012

Due to the increasing power requirement and the limited available space in vehicles, placing the heat exchanger at the roof or the underbody of vehicles might increase the possibility to handle the cooling requirement. A new configuration of the heat exchanger has to be developed to accommodate with the position change. In this paper, a countercurrent heat exchanger is developed for position on the roof of the vehicle compartment. In order to find an appropriate configuration of fins with high thermal performance on the air side, the CFD (computational fluid dynamics) approach is applied for a comparative study among louver fin, wavy fin, and pin fin by using ANSYS FLUENT software. It is found that the louver fin has high thermal performance and low pressure drop. Thus, the louver fin is chosen to be the configuration of the countercurrent heat exchanger, which presents higher heat transfer coefficient than a cross flow heat exchanger. For a specific case, the overall size and the air pumping power of the countercurrent flow heat exchanger is lower than that one for a cross flow heat exchanger. Several suggestions and recommendations are highlighted.
Directing Supervisory Control Towards Real HVAC System Integration
Authors: Wemhoff Aaron P. , Flaherty William
Published: August 2012

Heating, ventilating, and air conditioning (HVAC) systems comprise a significant portion of U. S. energy consumption. A supervisory control approach allows for the reduction of HVAC energy used. The authors previously developed and discussed the Master Controller (MC) method as a type of supervisory control that minimizes HVAC energy consumption for a given system. This paper provides two advancements towards the application of the MC method in a real system. First, airflow constraints are incorporated into the MC algorithm. Second, an approach is developed for incorporating transient system loads that are calculated via commercial software. The constrained MC method is shown to produce energy savings of approximately 40% compared to a traditional Variable Air Volume (VAV) method and VAV method with chiller control for reducing HVAC energy consumption for an example system.
Simulation of a Gas Turbine Engine With Performance Degradation Modeling
Authors: Campora Ugo , Carretta Mauro , Cravero Carlo
Published: August 2012

A simulation of performance degradation for an aeronautical gas turbine engine (Honeywell T55 L712) is presented. The effects of turbine (low and high pressure stages) erosion on the engine performance have been investigated in some detail. The behavior of the engine has been simulated using a dynamic model implemented in Matlab-Simulink. Using a throughflow code the LPT and HPT have been simulated and their performance maps have been obtained with a high level of accuracy. In order to understand the effects of turbine erosion nine degradation levels have been introduced and the LPT and HPT performance have been computed using the abovementioned throughflow code. The degradation levels have been based on stator erosion effects (increase of throat section and blade thickness reduction) only according to the experimental evidence from the engine tests from Piaggio Aero Industries. The introduction of the modified turbine characteristics into the Matlab-Simulink model has allowed the degradation effects on the overall engine performance to be tested and discussed. Finally, using experimental data from the industrial maintenance database, the link of each level of degradation with the number of the engine operational time (hours) has been obtained.
A Multi-Body Modeling and Design of Experiment Investigation of a Motorcyclist Impact on Roadside Barriers at Upright and Sliding Configurations
Authors: Moradi Rasoul , Lankarani Hamid M.
Published: August 2012

Roadside guard systems such as concrete and wire barriers and steel guard rails are mainly developed to protect occupants of the errant cars or trucks. Yet motorcycle riders are vulnerable to these barriers and guard systems, and impact on these barriers may result in major injuries. The objective of this study is to examine the major factors causing injuries in motorcycle-barriers accidents. A mathematical multi-body motorcycle model with a motorcycle anthropometric test device, MATD, is developed in the MADYMO 7.2 for this purpose. The motorcycle model as well as the motorcycle and rider model are validated using full-scale crash test data available in the literature. The simulations results are found to be in a reasonable agreement with the experimental data. A parametric study using the design of experiment (DOE) is then conducted to investigate the nature of crash injuries for various impact speeds, impact angles, different bike and rider positions to assess the rider kinematics and potential injuries. The results from this study can help in designing road barriers and guard systems in order to protect the motorcycle riders.
A Single Probe Transient Moving Line Source Method for Determining Thermal Conductivity, Thermal Diffusivity, and Superficial Flow Velocity of a Porous Material With Flow
Authors: Woods Kevin D. , Ortega Alfonso
Published: August 2012

This paper presents a method to determine the effective thermal conductivity and thermal diffusivity of a porous material, as well as the superficial flow velocity of fluid flowing through the porous matrix using a single probe transient moving line source method. The method transforms the transient analytical solution for a moving line source using differentiation to produce three independent equations to solve for the three unknowns. Empirical data are presented from a laboratory scale test apparatus for three test cases with known properties and flow rates to validate the method. The method is then applied to field data from a standing column well used in ground source heat pump systems to obtain the thermal and flow properties of the ground formation. The properties are inserted into the transient analytical solution for a moving line source and superimposed over the empirical data showing agreement between the model and the data. The method is more accurate than traditional methods for estimating thermal properties when flow conditions are present, and the implementation of the method does not require any additional thermal data.
Augmenting Probabilistic Risk Assessment With Malevolent Initiators
Authors: Smith Curtis , Schwieder David , Bjornard Trond
Published: August 2012

As commonly practiced, the use of probabilistic risk assessment (PRA) in nuclear power plants only considers accident initiators such as natural hazards, equipment failures, and human error. Malevolent initiators are ignored in PRA, but are considered the domain of physical security, which uses vulnerability assessment based on an officially specified threat (design basis threat). This work explores the implications of augmenting and extending existing PRA models by considering new and modified scenarios resulting from malevolent initiators. Teaming the augmented PRA models with conventional vulnerability assessments can cost-effectively enhance security of a nuclear power plant. This methodology is useful for operating plants, as well as in the design of new plants. For the methodology, we have proposed an approach that builds on and extends the practice of PRA for nuclear power plants for security-related issues. Rather than only considering “random” failures, we demonstrated a framework that is able to represent and model malevolent initiating events and associated plant impacts.
3D CFD Electrochemical and Heat Transfer Model of an Internally Manifolded Solid Oxide Electrolysis Cell
Authors: Hawkes Grant L. , O’Brien James E. , Tao Greg G.
Published: August 2012

A three-dimensional computational fluid dynamics (CFD) and electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in an internally manifolded planar solid oxide electrolysis cell (SOEC) stack. This design is being evaluated experimentally at the Idaho National Laboratory (INL) for hydrogen production from nuclear power and process heat. Mass, momentum, energy, and species conservation are numerically solved by means of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, operating potential, steam-electrode gas composition, oxygen-electrode gas composition, current density and hydrogen production over a range of stack operating conditions. Results will be presented for a five-cell stack configuration that simulates the geometry of five-cell stack tests performed at the INL and at Materials and System Research, Inc. (MSRI). Results will also be presented for a single cell that simulates conditions in the middle of a large stack. Flow enters the stack from the bottom, distributes through the inlet plenum, flows across the cells, gathers in the outlet plenum and flows downward making an upside-down “U” shaped flow pattern. Flow and concentration variations exist downstream of the inlet holes. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Contour plots of local electrolyte temperature, current density, and Nernst potential indicate the effects of heat transfer, reaction cooling/heating, and change in local gas composition. Results are discussed for using this design in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production, cell thermal efficiency, cell electrical efficiency, and Gibbs free energy are discussed and reported herein.
Characterization of SOI MEMS Sidewall Roughness
Authors: Phinney Leslie M. , McKenzie Bonnie B. , Ohlhausen James A. , Buchheit Thomas E. , Shul Randy J.
Published: August 2012

Deep reactive ion etching (DRIE) of silicon enables high aspect ratio, deep silicon features that can be incorporated into the fabrication of microelectromechanical systems (MEMS) sensors and actuators. The DRIE process creates silicon structures and consists of three steps: conformal polymer deposition, ion sputtering, and chemical etching. The sequential three step process results in sidewalls with roughness that varies with processing conditions. This paper reports the sidewall roughness for DRIE etched MEMS as a function of trench width from 5 μm to 500 μm for a 125 μm thick device layer corresponding to aspect ratios from 25 to 0.25. Using a scanning electron microscope (SEM), the surfaces were imaged detecting an upper region exhibiting a scalloping morphology and a rougher lower region exhibiting a curtaining morphology. The height of rougher curtaining region increases linearly with aspect ratio when the etch cleared the entire device layer. The surface roughness for two trench widths: 15 μm and 100 μm were further characterized using an atomic force microscope (AFM), and RMS roughness values are reported as a function of height along the surface. The sidewall roughness varies with height and depends on the trench width.