bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Meta-Modeling Approaches for Optimization
Authors: Devanathan Srikanth , Koch Patrick N.
Published: August 2012

Understanding and optimizing complex design problems involves analyzing mathematical models that simulate real-world systems. When such simulations require an enormous amount of time to evaluate a design point, approximation models are created that are simpler and quicker and allow exploration of the design space. Approximation models are also referred to surrogate models or meta-models. Kriging, response surface models, neural networks such as radial basis functions are examples of such approximation methods. The quality of approximations obtained using these methods is dependent upon: (1) the type of approximation technique, (2) the distribution of sample points, namely the sampling strategy, (3) number of sample points available for approximation and (4) the topography of the function being approximated. The quality and performance of an approximation method are measured using prediction errors and time taken to fit respectively. In this work, we present a study of the quality and performance of polynomial regression (general and orthogonal polynomials), Radial basis functions (RBF), Elliptical basis functions (EBF), and Kriging (ordinary and blind) for functions with different topographies. Specifically, the objective of this benchmark is to study the following effects on the accuracy of approximation techniques for comparison: 1. Effect of sampling strategy, 2. Effect of number of points, 3. Effect of function topography. Results indicate that Kriging approximation is best suited for cases where there are few sample points that are uniformly spaced (typically from Optimal Latin Hypercube sampling). Elliptical or Radial Basis Function neural networks are fast, robust and accurate enough to be used for any sampling strategy. For factorial sampling, Chebyshev polynomials have higher accuracy compared to simple polynomial regression.
Bolted Joints-Stochastic Modeling
Authors: Amir Yosef
Published: August 2012

In general, prediction behavior of bolted joints is very complex due to the uncertainty nature parameters involved in the design. Particularly, bolted Joints under shear load; the coefficient of friction plays a big role in prediction of joint movement. The analytical method of the Extreme Value method is utilized by applying a well-known worst case scenario like VDI 2230 and is sufficient for most of general purpose bolted joint analysis. However, there are cases of bolted joints where this method could leads to a false prediction of bolted joint failures. This paper applies stochastic method in the design of bolted joint modeling. As an example of this method case study of a critical bolted joint to safety presented, the model simulation assumed probabilistic functions for sensitive variables with significant variance like coefficient of friction, preload scatter, and embedment. The simulation presented the prediction of the preload required to sustaining the joint members of no relative movement with a level of 99.97% confidence. Comparisons of extreme value method to stochastic highlighted the cases of benefit to use both methods.
Estimation of Local Viscoelasticity of Lungs Based on Surface Waves
Authors: Dai Zoujun , Peng Ying , Mansy Hansen A. , Royston Thomas J. , Sandler Richard H.
Published: August 2012

The viscoelastic properties of lung tissue are of interest in medicine as they have been shown to be affected by various pathologies. Identifying the mechanical properties of lung tissue first requires a means of quantitatively measuring phenomena, such as mechanical wave motion, that are affected by these properties. In the present study, lung surface motion is measured on excised pig lungs to determine suitable viscoelastic models. The relation between the surface wave speed and the frequency is analyzed and different viscoelastic models are used to fit this relation. Also a more comprehensive method to evaluate the frequency-dependent shear modulus of the pig lung measuring the propagation of surface waves on the surface of the lung is presented and viscoelastic models (both of integer and fractional order) are compared to experimental results over the frequency range of 100–500 Hz.
The Effect of Orifice Angle and Cavity Dimension on Rectangular Synthetic Jet Actuators
Authors: Kabiri Pooya , Bohl Douglas G. , Ahmadi Goodarz
Published: August 2012

In the last decade, a great deal of interest has been focused on the application of synthetic jet actuators (SJA) for active flow control. SJAs delay separation by injecting vortex pairs into the cross flow and energizing the turbulent boundary layer. The goal of this study was to investigate the effects of the orifice angle on the performance of axisymmetric SJAs. The SJAs used in this experiment were composed of a piezoelectric (PZT) membrane, cavities and orifices. SJA’s with either a straight (90°) or angled (60°) orifices were characterized using hot-wire anemometry and Particle Image Velocimetry (PIV). It was found that the structure of the jet flow changed depending on the angle of the orifice with differences in the resulting vortical structure observed. The peak jet speed was found to be higher for the straight orifice than for the angled orifice contradicting the analytic prediction based on cavity dimension.
Thickness and Temperature Dependent Thermal Conductivity of Nanoscale Tin Films
Authors: Kaul Pankaj B. , Prakash Vikas
Published: August 2012

Thin films in general exhibit different thermal properties compared to bulk due to size effect [1–3]. In this study, the thermal conductivity of sputtered Sn films of thickness 500 nm ± 50 nm and 100 nm ± 20 nm are obtained from 55K to 300K and from 40K to 310K, respectively, using the three omega method. The thermal conductivity of 500 nm thin film at room temperature is 46.2 ±4.2 W/m-K, which is lower when compared to its bulk value of 63 W/m-K, and increases gradually as the temperature is lowered to 55K. In contrast, the thermal conductivity of the 100 nm thin film exhibits even reduced thermal conductivity, 36 ± 2.88 W/m-K at 300K, when compared to the 500 nm film, and decreases as the temperature is lowered. The reduction in thermal conductivity of Sn thin film may be due to the pronounced effects of electron scattering at the grain boundaries as well as the twin boundaries in addition to the scattering from the boundary surface at lower temperatures. These experimentally determined thermal conductivities are compared to models that take into account size effects on thermal conductivity of metallic films based on electronic scattering as proposed by Fuchs-Sondheimer (FS), Mayadas-Shatzkes (MS) and Qiu and Tien (QT). The experimentally measured thermal conductivity of Sn films is in good agreement with the MS model indicating the importance of the grain boundary scattering. Thickness measurements are obtained by ellipsometry and profilometer. The estimation of the mean grain size in both films and the evidence of twin boundaries are obtained by Atomic Force Microscopy.
Analysis of Large-Scale Ground Source Heat Pump Systems for Residential Heating and Cooling in Austin, TX
Authors: Fyffe John R. , Clayton Mary E. , Grosvenor Courtney E. , Webber Michael E.
Published: August 2012

This paper shares the results of an analysis of the energetic, emissions and economic balance of a simulated large-scale (multi-home) ground-source heat pump (GSHP) system in Austin, TX for heating and cooling. In contrast with traditional AC units and furnaces that use air outside of the house as a heat sink or source, GSHP systems use a ground loop heat exchanger to transfer heat to and from the soil where temperatures stay relatively constant throughout the year. GSHP systems operate more efficiently due to their use of the ground as a heat sink or source, whereas traditional AC units use the outside air. Consequently, GSHP systems typically use less energy than traditional HVAC units, but high capital costs have inhibited their widespread use. The monthly and annual energy costs for a home with a traditional AC unit-furnace are compared to a home with a GSHP system using hourly energy consumption data. The GSHP system modeled for the energy efficient home uses less energy (8.2 MMBtu) throughout the year compared to an efficient AC unit installed on the same home. Energy costs are lower using both the Austin Energy current rate schedule and for a proposed alternative schedule. Additionally, the GSHP system produces a net reduction in harmful emissions. Furthermore, GSHP systems reduce peak demand during the energy-intensive summer months, when air emissions are of greater concern. The installation costs for a large-scale residential GSHP system used in this research were based on interviews, current industry standards, and available pricing data. The analysis includes a sample case study of the cost of the GSHP system included with a home mortgage using a net monthly payment method and includes electricity price increases over time and federal tax incentives. If installed on a large scale, assuming best-case pricing with current federal tax incentives, the GSHP system case is $17 less per month than the traditional HVAC case. Federal tax incentives and high natural gas prices were found to make savings more significant for the GSHP system over time. Additionally, capital cost variability had a greater effect on savings than changes in electricity costs. Based on these analyses, large-scale GSHP systems are considered an economically feasible alternative to traditional HVAC units that will reduce energy consumption and air emissions.
Accurate Prediction of Transient Thermal Behavior of Electronic Systems With State-Space Models
Authors: Dogruoz M. Baris , Magargle Ryan , Shankaran Gokul
Published: August 2012

Accurate prediction of transient thermal behavior of electronic systems with the use of Computational Fluid Dynamics (CFD) requires large amount of CPU time. Even though steady state response of such systems is mostly of interest, transient thermal simulations with actual time dependent power cycles should be carried out to determine the steady-state behavior. Traditionally, power dissipation values are time-averaged to obtain steady-state characteristics, which may or may not be accurate. To overcome the large associated computational cost, several different approximate models were suggested and published in the literature. Among these models, Resistor-Capacitor (R-C) thermal network approaches have been popular in obtaining the transient response for the past few decades. These approaches require rigorous curve-fitting effort followed by an optimization process and are applicable to relatively simple systems. This study presents a state-space approach to determine transient and steady state behavior of electronic systems as accurately as possible without compromising the speed. This technique is applied to a sample graphics card system and the comparisons are made with the fully transient CFD model computations. It is shown that the temperature histories obtained from the state-space approach agree very well with those from the fully transient CFD simulations, where the CPU time for the former is radically (three to four orders of magnitude) smaller compared to that of the latter.
Design, Analysis and Manufacturing a Double Wishbone Suspension System With Variable Camber Angle by Pneumatics Mechanism
Authors: Pourshams M. , Mokhlespour M. I. , Keshavarzi A. , Hoviat Talab M.
Published: August 2012

The accuracy of multi dimensional simulation of vehicle dynamics has been significantly increased for both passive and active vehicles which are equipped with advanced electronic components. Recently, one of the subjects that has been considered is increasing the car safety in design. Therefore, many efforts have been done to increase vehicle stability especially during the turn. It is also very important in three wheel car. One of the most important efforts is adjusting the camber angle in the car suspension system. Camber angle as well as the vehicle stability has major effects on the wheel slip, reducing rubber abrasion, acceleration and braking. Since the increase or decrease in the camber angle impacts on the stability of three wheel vehicles, in this paper, a car suspension system mechanism is introduced by which camber angle could be adjusted furthermore the mechanism is user friendly applicable and also economic. Actually, a passive double wishbone suspension system with variable camber angle has been designed, analyzed and subsequently manufactured. This mechanism was modeled in Visual Nastran software and kinematic analysis was presented. It can change camber angle from −5.5 to 5 degrees. In this work, two different modeling is presented, active geometry system (variable camber) and passive (conventional suspension system) then the rate of Roll and Yaw angle were discussed to investigate and compare models stability in same condition. Simulation and test results have shown that vehicle stability in active geometry model is sustained more than conventional models.
Experimental Investigation of Magnetically-Induced Thermal Conductance Variations in a Ferromagnetic Nanofluid
Authors: Gardner Alexander M. , Seshadri Indira , Ramanath Ganpati , Borca-Tasciuc Theodorian
Published: August 2012

Ferrofluids have been the subject of great interest in engineering because of their unique flow characteristics under magnetic fields (Rosensweig, 1987). However, there are limited experiments which show the potential of ferrofluids to undergo controlled changes in thermal conductivity (Philip et al., 2008) under magnetic fields. The purpose of this experiment is to investigate thermal transport in ferrofluids. A test apparatus was designed and the thermal resistance of a commercially available ferromagnetic fluid within a test cell was measured as a function of the applied magnetic field.
A Linear Model of Stationary Elevator Traveling and Compensation Cables
Authors: Ren H. , Zhu W. D.
Published: August 2012

Based on a recent asymptotic analysis of a nonlinear model of elevator traveling and compensation cables, a computationally efficient, linear model is developed for calculating the natural frequencies, mode shapes, and dynamic responses of stationary elevator traveling and compensation cables. The linear cable model consists of two vertical cable segments connected by a half circular loop at the bottom. The two vertical cable segments are modeled as a string with a variable tension due to the weight of the cable. The horizontal displacements of the cable segments consist of boundary induced displacements and internal displacements, where the boundary induced displacements are interpolated from the displacements of the two ends of the cable segments, and the internal displacements satisfy the corresponding homogeneous boundary conditions of the cable segments. The horizontal displacement of the lower loop is interpolated from those of the two lower ends of the two cable segments, and the bending stiffness of the lower loop is represented by a spring with a constant stiffness, which can be calculated from the nonlinear model. Given a car position, the natural frequencies and mode shapes of an elevator traveling or compensation cable are calculated using the linear model and compared with those from the nonlinear model. The calculated natural frequencies are also compared with those from a full-scale experiment. In addition, the dynamic responses of a cable under a boundary excitation are calculated and compared with those from the nonlinear model. There is a good agreement between the predictions from the linear and nonlinear models and between the measured natural frequencies from a full-scale experiment and the corresponding calculated ones.
Texture Modification and Ductility Enhancement in Mg Alloy Through Friction Stir Processing
Authors: Yu Zhenzhen , Feng Zhili , Choo Hahn , Vogel Sven
Published: August 2012

The effects of friction stir processing (FSP) parameters, i.e., rotation and travel rates of the processing tool, on the texture modification and ductility enhancement of an Mg alloy AZ31B were investigated. With the systematic change in processing parameters as a function of the Zener-Hollomon parameter, a transition of different crystallographic texture was observed through neutron diffraction measurement, which correlated well with the changes in deformation and recrystallization mechanism activated during the processing. The variation in the texture leads to dramatic changes in the strength and ductility in the stir zone of the processed Mg plate. A maximum of three-fold increase in the ductility was achieved in the Mg alloy through FSP when the Zener-Hollomon parameter exceeds 1012 s−1 which is associated with low rotation speed and high travel speed processing conditions.
Multi-Objective Optimization of Functionally Graded Hollow Cylinders
Authors: Nabian M. , Ahmadian M. T.
Published: August 2012

In this study, two physical properties of simply supported hollow cylinders made of functionally graded materials are investigated. These two properties are mass and first natural frequency which is desirable to be minimized and maximized respectively in mechanical applications. The functionally graded material properties are assumed to vary continuously through the thickness of the cylinder. In this multi-objective optimization problem the first natural frequency of the FGM cylinders as well as its mass are formulated in terms of the volume fraction of the constituents, then by using Genetic algorithm optimization method the continuous volume fraction function of the constituents has been derived to minimize the mass and maximize the first natural frequency simultaneously.
Dynamic Analysis of a Delaminated Composite Beam due to a Moving Oscillatory Mass
Authors: Ahmadian Mohammad-Taghi , Kargarnovin Mohammad-Hosein , Jafari-Talookolaei Ramazan-Ali
Published: August 2012

This paper deals with the dynamic analysis of a delaminated composite beam under the action of moving oscillatory mass. The beam is analyzed as four interconnected sub-beams using the delamination limits as their boundaries. The constrained model is used to model the delamination region. The continuity and equilibrium conditions are satisfied between the adjoining beams. The beam response variation due to the delamination with respect to the intact beam has been investigated. Furthermore, the possible separation of the moving oscillator from the beam during the course of the motion is investigated by monitoring the contact force between the oscillator and the beam. The effect of the parameters such as the oscillator axial velocity and the size, depth and spanwise location of the delamination on the dynamic response of the beam and on the oscillator separation from the delaminated beam has been studied. It is shown that the delamination has significant influence on the dynamic response of the beam and on the oscillator separation from the beam.
The Effects of Blood Flow on the Iceball Evolution During a Multiple Probes Cryosurgery
Authors: He Zhi Zhu , Liu Jing
Published: August 2012

This paper presents a three dimensional numerical study to investigate the effects of blood flow in thermally significant blood vessels on the iceball evolution during cryosurgery of target tissue using multiple cryoprobes. Discretization of the Pennes’ bioheat equation, which should include convection term for blood vessel, was obtained using an alternate direction implicit finite difference (ADI-FD) scheme combined with an adaptive grid approach. The iceball front is then characterized by temperature profile. A comprehensive analysis of the influence of blood velocity, blood vessel size and the number of multiple cryoprobe on iceball evolution within target tissue undergoing cryosurgery is presented in detail. This work may enhance current understanding of the factors for determining the effects of cryosurgery.
Far-Infrared Imaging Method for Non-Contact Monitoring of Ice Valve Array in Controlling Micro/Nano Fluidics
Authors: Yang Yang , Liu Jing
Published: August 2012

Ice valve is a unique kind of micro valve without any moving elements and leakage. While in its operational process, appropriate control on the valve depends on well knowing the working statues of the valve system. In order to develop a quick and convenient method for guiding the operation of the ice valve, this paper is dedicated to establish a non-contact image way for monitoring the ice valve during controlling the micro fluid. The far-infrared thermal imaging system was adopted to detect and map the surface temperature distribution of the ice valve, which consequently could help achieve the non-contact monitoring of the ice valve.
Multiscale Modeling of Random Lattices: Critical Issues on Continuum Approximation
Authors: Zhao Haifeng , Rodin Gregory J.
Published: August 2012

In this work, we are concerned that transmission of various boundary conditions through irregular lattices. The boundary conditions are parameterized using trigonometric Fourier series, and it is shown that, under certain conditions, transmission through irregular lattices can be well approximated by that through classical continuum. It is determined that such transmission must involve the wavelength of at least 12 lattice spacings; for smaller wavelength classical continuum approximations become increasingly inaccurate.
On Extension of Boundary Algebraic Equations to Irregular Lattices
Authors: Zhao Haifeng , Rodin Gregory J.
Published: August 2012

This study is concerned with extending the use of boundary algebraic equations (BAEs) to problems involving irregular rather than regular lattices. Such an extension would be indispensable for solving multiscale problems defined on irregular lattices, as BAEs provide seamless bridging between discrete and continuum models. BAEs share many features with boundary integral equations and are particularly effective for solving problems involving infinite domains. However, it is shown that, BAEs for irregular lattices containing certain terms may require the same amount of computational effort as the original problem for which the equations are formulated. In this paper, we formulate a BAE for a model problem and expose the fundamental obstacle that prevents us from using that BAE as an effective tool. It is shown that, in contrast to regular lattices, BAEs for irregular lattices require a statistical rather than deterministic treatment. This is a very interesting direction for future research.
Assessment of Resistance of a Damaged Member Jacket Type Offshore Platform to Boat Impact
Authors: Naderi Banafsheh , Aghakouchak A. A.
Published: August 2012

In many optimized offshore platforms, initial failure of a member seldom represents the ultimate capacity of the structure. This is due to the fact that this type of structure possesses strength reserves beyond those recognized in traditional design. It is observed that although the damage in members may does not play an important role in the ultimate strength of the structure in a nonlinear static analysis, it may have an important effect on structural performance in vessel collision. The principle objective of this paper is to assess how damage in members within the splash zone may increase the vulnerability of platform in the event of ship impact. The structure under study is a Production Platform jacket located in Persian Gulf. The loading on the structure includes functional and environmental loads. The analysis is carried out under displacement control. In this paper, first, the structure is evaluated by pushover analysis in intact and damaged conditions. Therefore, the jacket is subjected to impact from a conventional supply vessel. Subsequently, the ability of the damaged structure to dissipate impact energy is investigated and is compared with that of the intact condition. Two types of damage namely “Local Denting” and “Out of Straightness” as well as total removal of critical members are considered.
Pulsating and Bouncing off of Dropwise Condensate on Superhydrophobic Surface
Authors: Ma Xuehu , Wang Sifang , Lan Zhong , Peng Benli , Bai Tao , Ma Hongbin
Published: August 2012

The steam dropwise condensation (DWC) characteristics on superhydrophobic plates were investigated experimentally in the presence of a high concentration noncondensable gas (NCG, >80mol%). The behaviors of condensate droplets on the roughness-induced superhydrophobic surface were observed with a photron high speed camera attached to a microscope. Pulsating features are found during droplets coalescence movement. Bouncing off of coalesced droplet was also observed induced by the strong effect of pulsating motion to overcome the pinning effect of the surface micro-nanostructures. Induced by the pulsating effect of droplets coalescence, the droplet can move at a long distance to join a coalesced droplet.
Gas Mass Flow Rate Measurement in T-Shaped Microchannels in Slip Flow Regime
Authors: Li Yongli , Barrot Christine , Baldas Lucien , Colin Ste´phane , Brandner Ju¨rgen J. , Newport David
Published: August 2012

A new setup was developed for gas mixing analysis in T-shaped microchannels. The principle of the flow rate measurement was based on the Constant Volume (CV) method [1]. The mass flow rate measurements of two gases N2 / CO2 mixing in a T mixer were carried out in the slip flow regime and followed by a simulation work for comparison. The mass flow rate has a magnitude of 10−8 or 10−7 kg/s and has good agreement with simulation for the lowest inlet over outlet pressures ratios and moderate agreement for the highest inlet over outlet pressures ratios.
Pre-Test CFD Calculations for a Bypass Flow Standard Problem
Authors: Johnson Richard W.
Published: August 2012

The bypass flow in a prismatic high temperature gas-cooled reactor (HTGR) is the flow that occurs between adjacent graphite blocks. Gaps exist between blocks due to variances in their manufacture and installation and because of the expansion and shrinkage of the blocks from heating and irradiation. Although the temperature of fuel compacts and graphite is sensitive to the presence of bypass flow, there is great uncertainty in the level and effects of the bypass flow. The Next Generation Nuclear Plant (NGNP) program at the Idaho National Laboratory has undertaken to produce experimental data of isothermal bypass flow between three adjacent graphite blocks. These data are intended to provide validation for computational fluid dynamic (CFD) analyses of the bypass flow. Such validation data sets are called Standard Problems in the nuclear safety analysis field. Details of the experimental apparatus as well as several pre-test calculations of the bypass flow are provided. Pre-test calculations are useful in examining the nature of the flow and to see if there are any problems associated with the flow and its measurement. The apparatus is designed to be able to provide three different gap widths in the vertical direction (the direction of the normal coolant flow) and two gap widths in the horizontal direction. It is expected that the vertical bypass flow will range from laminar to transitional to turbulent flow for the different gap widths that will be available.
Failure Mode Clustering is Electronic Assemblies Using Sammon’s Mapping With Supervised Training of Perceptrons
Authors: Lall Pradeep , Gupta Prashant , Goebel Kai
Published: August 2012

An anomaly detection and failure mode classification method has been developed for electronic assemblies with multiple failure modes. The presented prognostic health management method targets the pre-failure space of the electronic assembly life to trigger repair or replacement of impending failures. Presently, health monitoring systems focus on reactive diagnostic detection of failure modes. Examples of diagnostic detection include the built in self test and on-board diagnostics. In this paper, damage pre-cursors from time-spectral measurements of the electronic assemblies has been measured under applied vibration and shock stimulus. The time-evolution of spectral content of the damage pre-cursors has been studied using joint time frequency analysis in a full-field manner on the printed circuit assembly. Frequency moments have been used to build a feature vector. Evolution of the feature vector with damage initiation and progression has been studied under shock and vibration. The feature vector from multiple locations in the board assemblies has been mapped into a de-correlated feature space using Sammon’s mapping. Several chip-scale packages have been studied, with SAC305 and SAC405 leadfree second-level interconnects. Transient strain has been measured during the drop-event using digital image correlation and high-speed cameras operating at 100,000 fps. Continuity has been monitored simultaneously for failure identification. In addition, explicit finite element models have been developed and various kinds of failure modes have been simulated such as solder ball cracking, trace fracture, package falloff and solder ball failure. The neural net has been trained using simulated data-sets created from error-seeded models with specific failure modes. The neural net has then been used to identify and classify the failure modes in board assemblies experimentally. Supervised learning of multilayer neural net in conjunction with parity has been used to identify the hard-separation boundaries between failure mode clusters in the de-correlated feature space. The assemblies have been cross-sectioned to verify the identified failure modes. Cross-sections indicate that the experimentally measured failures modes correlate well with the position of the cluster in the de-correlated feature space.
Accrued Damage and Remaining Life in Field Extracted Assemblies Under Sequential Thermo-Mechanical Loads
Authors: Lall Pradeep , Harsha Mahendra , Suhling Jeff , Goebel Kai , Jones Jim
Published: August 2012

Field deployed electronics may accrue damage due to environmental exposure and usage after finite period of service but may not often have any macro-indicators of failure such as cracks or delamination. A method to interrogate the damage state of field deployed electronics in the pre-failure space may allow insight into the damage initiation, progression, and remaining useful life of the deployed system. Aging has been previously shown to effect the reliability and constitutive behavior of second-level leadfree interconnects. Prognostication of accrued damage and assessment of residual life can provide valuable insight into impending failure. In this paper, field deployed parts have been extracted and prognosticated for accrued damage and remaining useful life in an anticipated future deployment environment. A subset of the field deployed parts have been tested to failure in the anticipated field deployed environment to validate the assessment of remaining useful life. In addition, some parts have been subjected to additional know thermo-mechanical stresses and the incremental damage accrued validated with respect to the amount of additional damage imposed on the assemblies. The presented methodology uses leading indicators of failure based on micro-structural evolution of damage to identify accrued damage in electronic systems subjected to sequential stresses of thermal aging and thermal cycling. Damage equivalency methodologies have been developed to map damage accrued in thermal aging to the reduction in thermo-mechanical cyclic life based on damage proxies. The expected error with interrogation of system state and assessment of residual life has been quantified. Prognostic metrics including α-λ metric, sample standard deviation, mean square error, mean absolute percentage error, average bias, relative accuracy, and cumulative relative accuracy have been used to compare the performance of the damage proxies.
Liquid Cooling of a Stacked Quad-Core Processor and DRAM Using Laminar Flow in Microchannels
Authors: Chauhan Anjali , Sammakia Bahgat , Afram Furat F. , Ghose Kanad , Refai-Ahmed Gamal , Agonafer Dereje
Published: August 2012

Three dimensional (3D) stacking of the processor and memory components in high computing applications reduces the communication delay in multicore system-on-a-chip (SoCs) owing to reduced system size and shorter interconnects. The shorter interconnection length between the processing and memory components in a multicore system lowers the overall system access latencies and boosts the system performance. However, this 3D integration of the processors and memory exacerbates the reliability and thermal problems due to high thermal resistance of the stacked designs. Liquid cooling is the most promising solution to overcome this thermal problem arising in the 3D multicore systems. In this paper, we provide a 3D simulation model comprising of quad-core processor, dynamic random-access-memory (DRAM), liquid cooled microchannel heat sink and air-cooled heat sink. The thermal resistance offered by the silicon oxide layer and thermal interface material (TIM) has also been taken into account. The model assumes the integration of the thermal as well as electrical vias and considers the modified thermal conductivity of the materials in the stack. The cores of the quad-core processor are identical, have non-uniform power dissipation and are arranged in a symmetric layout. The quad-core layouts are based on the traditional and optimized floor plan of a single-core microprocessor. The paper reports the results for both planar flow and impingement flow in the microchannels. The thermal efficiency of the 3D design is evaluated on the basis of the hot spot temperature, hot spot spread and number of hot spots on the surface of the chip as well as DRAM.
A New Field Unbalance Estimation Method for Flexible Rotors
Authors: Zhang Y. , Mei X. S. , Zou D. L. , Sun N. G. , Zhang J. J.
Published: August 2012

Current field unbalance estimation methods regards “flexible rotors with lumped mass” as the main research object, and most of them need a stop running to take trial weights. Due to its test speed closing to the critical speed, the process of balance is really complicated and dangerous. This paper concerns rotors which unbalance state shows a continuous spatial distribution. Firstly, a dynamic finite element (FE) model of the rotor system is built, the inherent relations and differences between the dynamics transfer matrix and influence coefficient (IC) matrix are analyzed, and then, an extended dynamics matrix with arbitrary dimension is obtained based on the principle of IC balancing method. Secondly, the continuous distribution mass eccentricity curve is represented as mass eccentricity point on each FE model node, and the unbalance forces imposing on each FE model node are identified by the extended dynamics matrix. Finally, the theoretic analysis and experiment is presented to verify this method, and the result shows that unbalance forces on all FE model nodes can be identified accurately with less measuring points, and higher order modal components of the distributed unbalance are balanced effectively.
A Mathematical Model to Decrease Obesity in the UAE
Authors: Azzeh Sara , Alhussain Omar , Abu Samra Sara
Published: August 2012

Obesity is becoming a major problem all over the world, and it is severely affecting the United Arab Emirates (UAE). This inspired us to create a mathematical model that allows predicting the weight, as a function of time, based on two factors: diet and exercise. An early model dealing with diet only was used as a starting point, and then the exercise component was added based on an experiment we have performed where a group of students, wearing pedometers, have walked on a treadmill for thirty minutes in an average temperature between 20 to 25 degrees Celsius, with fixed speed. Data was collected and used to calculate the relation between weight and the energy burned, then Mathematica® was used to find how many days a person needs in order to reach his ideal weight calculated based on the Body Mass Index (BMI). Finally, we analyze the model, show that it is realistic with identified limitations, and we present future perspectives.
The Survival Spectrum: The Key to Transition Engineering of Complex Systems
Authors: Krumdieck Susan
Published: August 2012

This paper puts forward a simple idea describing the time, space and relationship scales of survival. The proposed survival spectrum concept represents a new way to think about sustainability that has clear implications for influencing engineering projects in all fields. The argument for the survival spectrum is developed sequentially, building on theory, definition, examples and history. The key idea is that sustainability can be effectively addressed by emergence of a new field, Transition Engineering. This is a parallel of safety engineering but with longer time scale, broader space scale, and more complex relationship scale. The past 100-year development of safety engineering is examined as a model for development of sustainability risk management and mitigation. The conclusion is that the new field, Transition Engineering, will emerge as the way our society will realize reduction in fossil fuel use and reduction in the detrimental social and environmental impacts of industrialization.
Applicability of Choking Flow Models for Subcooled Flashing Flow Through Tube Cracks
Authors: Wolf Brian , Revankar Shripad T. , Riznic Jovica R.
Published: August 2012

Recently there is some database available on choking flow through cracks relevant to steam generator (SG) tubes to model the critical flow. These data are used in assessing the key choking flow models. Based on this assessment a mechanistic choking model is developed. The model is used to predict the choking flow rates for various experimental conditions for subcooled flashing flow through narrow slits with L/D varying from small values (∼5) to large values (100). Results are presented on the effects of thermal and mechanical non-equilibrium on the choking flow for small L/D channels. A mechanistic model was developed to model two-phase choking flow through slits. A comparison of model results to experimental data shows that the homogeneous equilibrium based models markedly under predict choking flow rates in such geometries. As subcooling increases, and channel length decreases the non-equilibrium effects play a greater role in the choking phenomenon, therefore the difference in model predictions and experimental results increases.
Localization Effects in Bammann-Chiesa-Johnson Metals With Damage Delocalization
Authors: Enakoutsa Koffi , Ahad Fazle R. , Solanki Kiran N. , Tjiptowidjojo Yustianto , Bammann Douglas J.
Published: August 2012

The presence of softening in the Bammann-Chiesa-Johnson (BCJ) material model presents a major physical drawback: the unlimited localization of strain which results in spurious zero dissipated energy at failure. This difficulty resolves when the BCJ model is modified to incorporate a nonlocal evolution equation for the damage, as proposed by Pijaudier-Cabot and Bazant (1987). The objective of this work is to theoretically assess the ability of such a modified BCJ model to prevent unlimited localization of the strain. To that end, we investigate two localization problems in nonlocal BCJ metals: appearance of a spatial discontinuity of the velocity gradient in a finite, inhomogeneous body, and localization into finite bands. We show that in spite of the softening arising from the damage, no spatial discontinuity occurs in the velocity gradient. Also, we find that the dissipation energy is continuously distributed in nonlocal BCJ metals and therefore can not localize into zones of vanishing volume. As a result, the appearance of any vanishing width adiabatic shear band is impossible in a nonlocal BCJ metal. Finally, we study the finite element (FE) solution of shear banding in a rectangular mesh, deformed in plane strain tension and containing an imperfection, thereby illustrating the effects of imperfections on the localization of the strain.
Optimization of Ski Jumper’s Posture Considering Lift-to-Drag Ratio and Aerodynamic Stability in Pitch
Authors: Park Min-Jung , Lee Ki-Don , Kim Kwang-Yong
Published: August 2012

In the present study, an optimization of ski jumper’s posture using a surrogate model has been numerically performed to improve lift-to-drag ratio and to examine aerodynamic stability in pitch to ensure flight control and safety. Three-dimensional Reynolds-averaged Navier-Stokes equations are discretized by finite volume approximations for the flow analysis, and the shear stress transport turbulence model is used as the turbulence closure. Airfoil theory and principles of aircraft stability are used to examine the stability mechanism. To enhance aerodynamic stability in ski jumping, the ranges of design variables are determined to have a static margin value within 5∼25%. Two angles of ski jumper’s posture are chosen as design variables through a preliminary test and the lift-to-drag ratio is used as an objective function for the present optimization problem. Twelve design points within design spaces are selected by Latin hypercube sampling. To approximate the objective function in the design space, the Kriging model is constructed using the numerical results on the design points, and the optimal point is found by sequential quadratic programming. The predicted values of the design variables and the objective function for the optimal and the reference design, as well as corresponding results of numerical calculation. The Kriging model predicts the objective function values at the optimum points with only 1.61% error in comparison with the values obtained the RANS analysis. And, the optimum design shows not only improved lift-to-drag ratio but also increased longitudinal stability in ski jumping as compared to the reference design.
A Comparative Experimental Study on Tensile Properties of Three Types of High-Performance Polymer Fibers
Authors: Gao X.-L. , Zhou S.-S. , Bosselman S. E. , Zheng J. Q.
Published: August 2012

A comparative experimental study on tensile properties of three types of high-performance polymeric fiber yarns — AuTx™, Kevlar® KM2 600 denier and Twaron® 500 denier — is conducted. Tensile tests are performed on samples of the three kinds of fiber yarns at five testing temperatures (24, 50, 60, 70 and 80 °C) and three loading rates (100, 200 and 300 mm/min). The elastic modulus, breaking stress, and breaking strain are obtained for each type of fiber yarns under specified testing conditions as averages of measured values from 15 specimens. The experimental data reveal that the tensile properties of all three types of fiber yarns under investigation exhibit strong temperature dependence, with the elastic modulus and breaking stress decreasing with the temperature increase. However, the dependency of the properties on the loading rate is insignificant for the range considered. The measured tensile properties of the Kevlar® and Twaron® yarns are seen to be close, while the elastic modulus and breaking stress of the AuTx™ yarn are found to be, respectively, about 12% and 40% higher than those of the Kevlar® and Twaron® fiber yarns. It is also observed that the AuTx™ yarn degrades about two times faster than the other two yarns as temperature increases.
Energy Usage and Management at a Large Wastewater Treatment Facility in Boulder, Colorado
Authors: Douville Chris , Macknick Jordan
Published: August 2012

Wastewater treatment plants require substantial amounts of energy for pumping and treating water as well as for other plant operations. National and regional policy changes resulting in stricter water quality standards could result in an increase in energy requirements for treatment, as further treatment or more energy intensive technologies would be required. Given rises in energy costs, effective energy management plans are necessary for municipal wastewater treatment plants. Energy usage in wastewater treatment plants can be reduced through a number of different technology options without compromising water quality output. These different technology options vary in effectiveness, energy intensity, and upfront and operational costs, and the choice of technologies is often dependent upon local conditions and plant specific characteristics. Energy management can be improved also through electricity production on-site from the capture of methane gases released during treatment or from the inclusion of renewable electricity generating technologies. These technology options augment the creation of energy on-site while not necessarily reducing total energy demands. The objective of this paper is to, through use of a case study of a wastewater treatment facility in Boulder, Colorado, describe the most energy intensive processes of wastewater treatment, review various technology options for these processes, and discuss the opportunities and barriers to improving energy management at wastewater treatment plants. This paper is part of a topical session entitled “An Energy Appetite of U.S. Water Systems — what does it take to supply our water?”
Conquering Language Barriers and Cultural Gaps Between Japan and the West and Role of International Education: Lessons Learned From the Author’s Cases as International Student, Engineer and Energy Economist
Authors: Honda Hiroshi
Published: August 2012

The subject of paper discusses the author’s experiences as a graduate student at the Pennsylvania State University and in the United States, and international professional experiences thereafter, including the activities for the United Nations (UN), International Energy Agency (IEA), Asia Pacific Economic Cooperation (APEC) Energy Working Group, and ASME International. The international professional experiences involved energy economics, the environment and engineering issues, and teaching of industry, business, economy, energy, the environment and engineering focused courses and lectures, in English and Japanese, at universities and Institute for the International Education of Students (IES), among others. The author’s educational background in Japan is also introduced to describe the cultural differences and language barrier between Japan and the West, which the author has encountered for the past sixty years, to substantiate an academic report that it takes seven times as much time for a Japanese to become proficient in English as for a Spanish to reach the same level in English proficiency. The synergetic/collaborative approaches for the international education of both Japanese and international students, is also discussed, based on lessons learned from the author’s experiences.
Analyzing Compression and Buoyancy in Technical Swimming Suits
Authors: Halvorson Lori M.
Published: August 2012

This study entailed a scientific assessment of popular speculations related to technical (i.e. competition) swimming suits. Specific issues addressed include the effects that buoyancy and compression have on reducing the cross-sectional area of a swimmer’s body and thus reducing the form resistance and increasing the velocity of a swimmer. Analyses in this study were done for competitive female swimmers wearing a range of different technical suits. Body compression by the suits was quantified using the percent reduction of the cross-sectional area of a swimmer with each suit. Several race times swam in international competitions corresponded with the relative percent velocity increase for the corresponding suit. The buoyancy of each technical swimming suit was analyzed by determining the volume of air voids in each suit and the density of each suit. The volume and densities were used to calculate the reduced cross-sectional area of a swimmer’s body interacting with the water and the relative velocity increase for the least dense suit. It was found that the Jaked brand suit was the least dense but the overall reduction in the cross-sectional area of the swimmer’s body due to the swimmer floating slightly higher in the water did not indicate a significant speed advantage.