bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics and Thermodynamics of a Free-Piston Expander-Compressor
Authors: Kornhauser Alan A.
Published: August 2012

In a free-piston expander-compressor (FPEC) the work of an expanding gas or vapor is used to compress another gas or vapor through a direct connection of one piston-cylinder assembly to another, without rotary motion. Each section of the FPEC operates like the piston-cylinder of a shaft-connected reciprocating machine. The expander section operates like that of a steam engine: high-pressure gas or vapor is freely admitted through part of the expansion process, but stopped at the “cutoff” part way through the expansion. The compressor section is like that of a shaft-driven reciprocating compressor: low-pressure gas is admitted during the intake stroke, compressed during the compression stroke, and then discharged when it has reached the downstream high pressure. The design of an FPEC is complicated by the fact that the expander and compressor have different relationships between force and position. The force on the expander piston decreases as the stroke progresses, while that on the compressor piston increases. The force difference must be made up by momentum change of the pistons and connecting rod, which accelerate in the early part of the stroke and decelerate in the latter part. The balance between the expanding fluid, the moving mass, and the compressed fluid can be described either dynamically (force and momentum) or thermodynamically (work and energy). It is shown that the mechanical design (piston areas, stroke, oscillating mass, and frequency) of an idealized FPEC is highly constrained by the thermodynamics of the high-pressure stream expansion and the low-pressure stream compression. For simple cases, dynamic models in differential equation form can be compared to thermodynamic analyses in algebraic form. The thermodynamic models provide a baseline design point for an ideal FPSE. The dynamic models can then be used to study non-ideal cases.
A Study on Measuring the Lateral Motion of a Long Tube Subject to Impulse Loads Using Accelerometers and Mechanical Filters
Authors: Choi Won-yeong , Yoo Seong-yeol , Cha Ki-up , Kim Sung-Soo , Noh Myounggyu
Published: August 2012

In many respects, accelerometers are convenient for measuring the lateral vibrations of a long tube under impulse loads. Reliable measurements by accelerometers must overcome two issues: exceedingly large acceleration at high frequencies due to stress wave and the elimination of drifts accumulating through the integration of acceleration signals. In this paper, we use a mechanical filter that reduces the effect of stress wave. Also, we propose a new double integration algorithm based on multi-resolution wavelet decomposition. Using a test-rig, we measure the vibration characteristics of commercially-available damping materials. Based on the test results, we design a mechanical filter and experimentally verify the performance of the filter. The proposed double integration algorithm is shown to be as effective as other existing algorithms without arbitrary selection of parameters.
Mechanical Engineering Design-for-Reliability
Authors: Wessels William R.
Published: August 2012

This paper presents a design-for-reliability approach for mechanical design. Reliability analysis in part design, indeed the very definition of reliability, has been focused towards the electronic and digital disciplines since the emergence of reliability engineering in the late 1940’s. That focus dictates that parts fail in time; that all parts have a constant failure rate, and that part failure is modeled by the exponential mass density function. This paper presents current research that proposes that reliability in mechanical design is not characterized by ‘best practices’ reliability analyses. One premise investigated is that time does not cause failure in mechanical design; only failure mechanisms do. Mechanical parts experience wear-out and fatigue, unlike electronic and digital parts. Mechanical design analysis for part design investigates material strength properties required to survive failure mechanisms induced by part operation and by part exposure to external failure mechanisms. Such failure mechanisms include physical loads, thermal loads, and reactivity/corrosion. Each failure mechanism acting on a mechanical part induces one or more part failure modes, and each part failure mode has one or more failure effects on the part and the upper design configurations in which the part is integrated. The second premise investigated is that mechanical part failure is modeled by the Weibull mass density function in terms of stress, not time. A reliability math model for tensile strength in composite materials is presented to illustrate the two premises.
Identification of the Coherent Structures in Multiple Impinging Jets
Authors: Draksler Martin , Koncˇar Bosˇtjan
Published: August 2012

An array of impinging jets is characterized by high heat removal capability. As such it is used as a cooling technique in various industrial applications, i.e. paper drying, turbine blades cooling etc. The objective of the current study is to analyze the coherent structures in the interaction region of impinging jets and relate them to the local heat transfer. Since they play the major role in the local heat enhancement, their proper identification is crucial for the understanding of the heat transfer mechanisms. Three different methods for identification of flow structures in the jet interaction region are discussed in the paper. Heat transfer capability of different jet arrangements (in-line and hexagonal) are compared and analyzed in the context of flow structures comparison. The numerical simulations were performed with the CFD code ANSYS-CFX, solving Reynolds Averaged Navier-Stokes Equations (RANS approach). For the turbulence modeling Shear Stress Transport (SST) turbulence model was used.
A Biomimetic Elastic Cable Driven Quadruped Robot: The RoboCat
Authors: Kljuno Elvedin , Zhu J. Jim , Williams Robert L. , Reilly Stephen M.
Published: August 2012

State of the art legged robots, such as the Honda’s series of bipedal robots ending in the latest advanced walking robot ASIMO, and the series of bipedal robots of Waseda University including the latest advanced robot WABIAN, employ joint-mount motors, which simplifies the analysis/design and traces the route for an effective control system, but results in legs that are heavy and bulky. Cable-driven robots overcome this shortcoming by allowing the motors to be mounted on or near the torso, thereby reducing the weight and inertia of the legs, resulting in lower overall weight and power consumption. To facilitate analysis and design, typical cable-driven robots use non-stretchable cables, which require at least n+1 motors for an n Degree-of-Freedom (DoF) joint. Therefore, for a robot with N joints, at least N additional motors are needed comparing to joint-mount motor drives. Moreover, the drive train of both joint-mount and cable-driven designs are rigid, which cannot effectively absorb ground impact shocks nor transfer potential energy to kinetic energy and vice versa when the robot is in motion, as biologic animals do. In this paper we present the design and test of a cat-size quadruped robot called RoboCat, which employs stretchable elastic cable-driven joints as inspired by biological quadruped animals. Although it complicates kinematics and dynamics analysis and design, the elastic cables allow n motors to be used for an n-DoF joint, thereby eliminating N motors for a robot with N joints comparing to non-stretchable cables, further realizing the weight and power savings of the cable driven design. Moreover, the elastic cable driven joints not only effectively absorb ground contact shock, but also effectively transfer potential and kinetic energy during walking or running, thereby improving the robot motion performance and energy efficiency. In the paper we will discuss the kinematics and dynamics analysis of elastic cable driven joints, implementation of elastic cable-driven joints on the Ohio University RoboCat, and control.
The Analytical Solutions for Heat Transfer in Thin Film Evaporation With Disjoining Pressure
Authors: Yan Chunji , Ma Hongbin
Published: August 2012

A mathematical model predicting heat transfer and film thickness in thin film region is developed. Utilizing the dimensionless analysis, analytical solutions of the heat flux distribution, the total heat transfer rate per unit width, the location of the maximum heat flux and the ratio of the conduction thermal resistance to the convection thermal resistance in evaporating film region have been obtained. The analytical solutions obtained herein indicate that the maximum dimensionless heat flux is constant which is independent on the superheat. For a given thin film region, its maximum total heat transfer rate is determined. The ratio of the conduction thermal resistance to the convection thermal resistance is a function of dimensionless film thickness. This work will lead to a better understanding of heat transfer and fluid flow occurring in the evaporating film region.
Clamp Load Retention of Bolted Joints Under Alternating and Superposed Thermal Stress
Authors: Duchardt Markus , Berger Christina , Wuttke Ulrich
Published: August 2012

Current efforts for using lighter materials are essentially determined by economic and ecological parameters. The automotive industry can expect a 8 to 10 percent improvement in fuel usage with a mere 10 percent reduction in vehicle weight. Lighter vehicles facilitate easier braking, and reduced collision impact, thereby creating a superior driving experience for consumers. Magnesium and aluminium alloys are common materials for a wide range of applications including engine and power train components, as well as under-hood applications with operating temperatures of up to 150°C. Today’s state-of-the-art joining method for lightweight materials is the use of aluminium fasteners. Several studies have been conducted to describe and analyze the static load behaviour of bolted joints; to date, however, the pre-load retention behaviour under alternating as well as superposed thermal stress has yet to be characterized. The current research project investigates effect of alternating stress on the bolted joint while also considering such variables as different material combinations, varying levels of load, and changes in temperature. Our main focus is on the embedding amounts and the surface pressure limits of the substrate(s), with special consideration made for time-dependent deformation mechanisms. Furthermore, based on the generated material parameters, the deformation behaviour will be reproduced and simulated.
Fitting Discrete-Time Models to Frequency Responses for Systems With Transport Delay
Authors: Butterworth Jeffrey A. , Pao Lucy Y. , Abramovitch Daniel Y.
Published: August 2012

Fitting discrete-time models to frequency-response functions without addressing existing transport delay can yield higher-order models including additional non-physical nonminimum-phase (NMP) zeros beyond those that may appear as a result of sampling. These NMP zeros can be attributed to a discrete-time representation of a Pade´ approximation to account for the transport delay [1, 2]. Here, we explore this idea in greater detail and this discussion motivates the main contribution of this paper, the presentation of a procedure for fitting a discrete-time model to experimentally measured frequency response data. The appearance of NMP zeros in a system model can complicate controller design and limits the desired closed-loop performance. This discrete-time model-fitting procedure presents a technique that will help yield a model that reflects the measured frequency-response functions accurately, while minimizing the presence of non-physical NMP zeros. The key benefit being that, with respect to previous model fits, it may be possible to eliminate all NMP zeros in the discrete-time model. In the case of model-inverse-based control design, this will allow the stable inversion of the model without the use of approximation methods to account for NMP zeros.
Low-Frequency Electrical Noise Thermometry for Micro- and Nano-Scale Devices
Authors: Sayer Robert A. , Engerer Jeffrey D. , Sen Sudeshna , Vidhyadhiraja N. S. , Fisher Timothy S.
Published: August 2012

Electrical noise is inherent in all conductors; the magnitude of this noise is proportional to device temperature in some frequency bands. Shot noise thermometry is a self-calibrating measurement technique that relates statistical fluctuations in DC current across a device to temperature. Historically, low frequency bands that contain 1/f noise have been filtered out in noise thermometry analysis. We report a noise analysis that accounts for 1/f noise in temperature measurements, thus reducing the required bandwidth of the measurement system. Numerical simulation is used to show the efficacy of this approach. Computer-generated noise signals containing Johnson, shot and 1/f noise are randomly generated. Data processing is used to determine device temperature and Fano factor. The impact of important factors such as data averaging, 1/f noise magnitude, bias range, ambient temperature and Fano factor on the accuracy and precision of fit values is investigated. This technique is then applied to experimental measurements on a vertical single-walled carbon nanotube array.
Development of a Dementia-Specific Gait Profile: A Computational Approach
Authors: Karakostas Tasos , Hsiang Simon , Davis Boyd , Shenk Dena , Maclagan Margaret
Published: August 2012

The rate at which elderly are being diagnosed with dementia has accelerated over the recent years and it is alarming [1]. They are three times more likely to fall and over three times more likely to have severe injury compared to cognitively unimpaired elderly [2]. Consequently, recently there is an interest in the identification of biomarkers that can contribute towards, or establish, early detection and diagnosis of dementia.
Numerical Hemodynamics Analysis of Stented Cerebral Artery
Authors: Yang Hongcheon , Kim Kwang-Sun
Published: August 2012

Stroke is one of the most dangerous causes of a sudden death. It is generally caused by the blood clotting in the stenotic region of artery. Cerebrovascular and cardiovascular systems are blocked by plaques so that it can lead to occlusion of the artery. Stenosis in the cerebral artery can be cause of ischemic stroke, or even death if it doesn’t get treatment earlier. Ballooning and stent implementation are main methods to treat stenosis in the artery vascular. Stent implantation has widely been used for cardio-artery diseases and as nano-technology has been developed recently, stents can be produced at sufficiently small sizes, with sufficient delicacy for use in cerebral artery. The blood flow in the stented cerebral artery depends on biomechanical factors such as blood viscosity, blood velocity, vascular density, or body temperature. In this research, we investigated the effects of stent in different types of stented cerebral artery model. The result can be adapted for particular part of the blood vessel or new types of safer stent model. For numerical analysis, we used Solidworks 2010[1] and Star-CCM+[2] softwares for modeling and simulation. Then we compared the result to look into the differences of hemodynamic characteristics between the stenotic blood vessels and stented blood vessels.
Numerical Analysis of Inner Reaction Effects of Cylindrical Li-Ion Battery by Discharge Rates
Authors: Jang Kyung-min , Kim Kwang-Sun
Published: August 2012

The characteristics of the Li-ion batteries are to be assessed by SOC (State of Charge) or SOH (State of Health) and these two factors are found to be dependent on the inner temperatures. However, the most research reports on Li-ion battery performance are focused on the different surrounding temperatures. There are not many reports on effects of battery self-heating together with electro-chemical reaction. In this research we used FEM to analyze the exothermic problem of the Li-ion battery assuming Ohmic heat, reaction heat, and polarization heat. According to the previous reports, the Ohmic heat is the biggest heat source about 54%, the heat of electro chemical reaction is 30%, and the rest of heat source is the polarization heat. The battery in the energy storage system is generally used as a package connecting several cells together. For the connections of several cells, the surface temperature gradient is also different being compared to one cell. And it is figured out that there are considerable differences on battery performances for various discharge rates.
Numerical Analysis on Thermal Deformation of Linear Motor in Chip Mounter
Authors: Joo Kang-Woo , Kim Kwang-Sun , Kim Jun-Young , Beom Hee-Rak
Published: August 2012

In the semiconductor chip mounting process, the size of semiconductor chips is decreasing, while the number of mounting the chips per time are increasing, and this trend is being accelerated. The research activities to develop the chip mounters, which are able to mount rapidly and accurately, have been needed in the industry. With this background, the linear motor in the chip mounters has been an important part. The electro-magnetic type linear motor has many advantages such as direct linear reciprocating motion being compared with the rotary motor and the ball screw type linear motor. However, the electro-magnetic linear motor has thermal problems. These problems affect life and performance of motor and bring out the other problems such as thermal stress and deformation. The heat transfer analysis is difficult to solve thermal problems because the moving and fixed parts coexist. The trial & error methods have been therefore used under majority of cases. In this paper, we investigated the thermal deformation problems of linear motor in a chip mounter and the optimized parameters to design the motion parts of electro-magnetic linear motor were obtained.
Craig-Bampton Modal Reduction Applied to Human Tibia Tradeoff Between Accuracy and Speed
Authors: Kłodowski Adam , Valkeapa¨a¨ Antti , Mikkola Aki
Published: August 2012

Human bones adapt to external loading through bone growth and resorption processes (1). Strains within specific range induced by physical loading can lead to strengthening of affected bones. On the other hand, when external forces are too high, it can lead to bone fracture (2) or cause significant loads in the joints, which in turn can be damaging for the cartilage surfaces (3) and ligaments. Optimization of the gym equipment as well as the techniques of exercising is necessary to achieve bone growth stimulation without overloading the bones or the joints. This issue has been recently addressed with the use of flexible multibody simulations supported by modal reduction techniques. Although the strain output of the simulations is sound (4), it is necessary to understand the tradeoffs between accuracy and speed of the modal reduction methods. This paper presents a comparison of the tibial strains, stresses and global displacements obtained from modal representation of the bone and results obtained from the initial finite element model. Strains are obtained at the same nodes in both models during various static case loadings. Efficiency of both methods is compared by correlating computation times. Accuracy of modal representation is verified by using bending, torsion, tension and compression tests, which represent the possible physical loading conditions of tibia. Influence of the material models as well as discretization level has also been taken into account. Finally conclusions are drawn from the results providing guidelines for future work.
Posttest Calculations of PARAMETER-SF4 Experiment With Air Ingress and Water Reflood Using SOCRAT/V3 Computer Modeling Code
Authors: Vasiliev Alexander
Published: August 2012

The PARAMETER-SF4 test conditions simulated a severe LOCA (Loss of Coolant Accident) NPP (nuclear power plant) sequence in which the overheated up to 1700–2300K core would be reflooded from the bottom in occasion of ECCS (Emergency Core Cooling System) recovery. The test was successfully conducted at the NPO “LUTCH”, Podolsk, Russia, in July 21, 2009, and was the fourth of four experiments of series PARAMETER-SF. PARAMETER facility of NPO “LUTCH” (scientific and industrial association LUTCH), Podolsk, is designed for studies of the VVER fuel assemblies behavior under conditions simulating design basis, beyond design basis and severe accidents. The test bundle was made up of 19 fuel rod simulators. Heating was carried out electrically using tantalum heating elements installed in the center of the rods and surrounded by annular UO2 pellets. The rod cladding was identical to that used in VVER (water-water energetic reactor, Russian type of pressurized water reactor). After the maximum cladding temperature of about 1900K was reached in the bundle during PARAMETER-SF4 test, the bottom flooding was initiated. The important feature of PARAMETER-SF4 test was the air ingress phase during which the air was supplied to the working section of experimental installation. It is known that zirconium oxidation in the air proceeds in a different way in comparison to oxidation in the steam. The thermal hydraulic and SFD (Severe Fuel Damage) best estimate computer modeling code SOCRAT/V3 was used for the calculation of PARAMETER-SF4 experiment. Thermal hydraulics in PARAMETER-SF4 experiment played very important role and its adequate modeling is important for the thermal analysis. The results obtained by the complex SOCRAT/V3 were compared with experimental data concerning different aspects of air ingress phase and thermal hydraulics behavior during the reflood. The temperature experimental data were found to be in a good agreement with calculated results. It is indicative of the adequacy of modeling the complicated thermo-hydraulic behavior in the PARAMETER-SF4 test.
Characterizing Tensile Strength Properties in an E-Glass Composite With Fiber Waviness
Authors: Kendall Cory , Doud Greg R.
Published: August 2012

This report investigates failure properties of a unidirectional fiber-reinforced E-glass epoxy resin matrix (CYCOM 5216). This material is used in military and commercial helicopter blades and structures and is commonly used in engine nacelles. Testing and failure analysis is critical for these structures, which undergo vibratory and complex aerodynamic loading. Defined manufacturing methods were modified to produce thick samples containing wrinkle defects. Wrinkles were added to simulate realistic marcelling, which commonly occurs within complex structures. All samples were validated using volume fraction experiments. Static uniaxial tension and five-point bending testing was performed as strain was measured using a multi-axis strain gage or an axial extensometer. Tensile and shear moduli, tensile strength, and shear strength were all determined. Shear modulus was determined through the use of a reinforced five point bending apparatus. The effects of fiber waviness on static strength were observed by testing samples with wrinkles of varying amplitude in both shear and tension. Fatigue analysis in this study differs from previous finite element crack growth studies due to the introduction of fiber waviness. For this reason, previous mixed mode bending tests and analytical methods were used with finite element techniques to improve failure prediction methods.
Effect of Consolidation Mechanism on the Properties of Nanostructured WC-6, 9, 12 wt%Co Hardmetals
Authors: Laoui Tahar , Hakeem Abbas Saeed , Abdullahi Kachalla , Saheb Nouari , Al-Aqeeli Nasser
Published: August 2012

The development of nanostructured materials has been exploited in enormous applications nowadays owing to the remarkable properties possessed by these advanced materials. Among these materials are tungsten carbide (WC)-based alloys, which have been widely used in a range of industrial applications including cutting and drilling tools, wear resistant components in wire drawing, and wear resistant surfaces in various equipments and dies. These alloys are processed using a variety of techniques in which powder metallurgy has been widely adopted. The key challenge lies in retaining the nanostructure of WC-based powders after the consolidation stage that is used to obtain dense parts following powder metallurgy processing. In the present study, the densification parameters, microstructural development and mechanical behavior of WC containing 6, 9 and 12wt. %Co powders in the range of nanometer to micron size of WC particles were investigated. Two types of consolidation techniques were considered namely spark plasma sintering (SPS) and microwave sintering (MW) for a comparative analysis as well as to explore the suitable process that will minimize grain growth. The consolidated (sintered) samples were characterized by X-ray diffraction, scanning electron microscopy, and hardness measurement.
Quantitative Analysis of Subunit Mismatch Arrangement in Staphylococcal Gamma-Hemolysin Heteroheptameric Transmembrane Pore
Authors: Tomita Noriko , Abe Kazuyo , Ohta Makoto
Published: August 2012

Pore-forming cytolytic proteins distributed in a wide variety of eukaryotic and prokaryotic organisms have been intensively studied in terms of pathophysiological functions and molecular architecture of transmembrane pores. These proteins are also being developed for various analytical applications such as detector of proteins and DNA by engineering the structure of the pore. Staphylococcal gamma-hemolysin (Hlg), a pore-forming protein, which consists of two separate proteins, LukF and Hlg2, has potential to be a useful tool as a multifunctional biosensor. However, the fine structure of the Hlg pore has not been clarified. Our previous studies revealed that LukF and Hlg2 assemble alternately on the membrane in a molar ratio of 3:4 and 4:3 and form cylindrical heteroheptameric transmembrane pores. In the present study, we conducted quantitative analysis of the subunit arrangement of the pore by using two-dimensional (2-D) image analysis based on high-resolution transmission electron microscopy (TEM) images. Results of this study suggest a new aspect of the characteristic structure in two-component pore-forming protein and can contribute to the engineering of the Hlg pore.
Analysis of Taylor Flow in Microchannels by the Phase Field Method
Authors: Ganapathy Harish , Al-Hajri Ebrahim , Ohadi Michael M.
Published: August 2012

The present paper reports a comprehensive study on the numerical simulation of Taylor flow in microchannels by the phase field method. Additionally, a comparative study was also performed against an alternative volume of fluid model based on which the phase field method was found to be more advantageous in key aspects such as the absence of unphysical interfacial pressure oscillations and the ability to account for variations in the surface tension force and thus predict several bubble lengths under constant flow conditions while observing the physics of homogeneous two-phase flow. Different bubble formation mechanisms were simulated and compared against experimental findings in literature. The simulation of a thin liquid film at the channel wall was found to be limitation of most works pertaining to Taylor flow, including the present. This was ascribed to be more likely due to limited dimensional and spatial resolution as well as inaccurate contact angle dynamics rather than limitations of the modeling approach itself. The effect of wall adhesion was studied with respect to the flow and pressure field in the channel. A validation of the model was achieved through a favorable comparison of the numerically predicted gas void fraction and bubble lengths with existing models and correlations. On the whole, the phase field method was concluded to have improved predictive accuracy with respect to certain aspects as compared to conventional multiphase flow models.
Synthesis of Zeolite A Crystals in the Presence of Crystal Growth Inhibitors by Microwave-Assisted Hydrothermal Technique
Authors: Baig Mirza Aqeel , Laoui Tahar , Fadhillah Farid , Muraza Oki , Khan Zafarullah
Published: August 2012

Zeolite A crystals were synthesized at 100°C from sodium metasilicate and aluminium foil by microwave assisted hydrothermal technique. It was confirmed by using X-ray diffraction technique that zeolite A was produced. The influence of heating rate on the zeolite crystal size was investigated using 2.5°C/min, 7.5°C/min, and 50°C/min. It was shown that the low heating rate resulted in larger crystal size with high crystallinity. To evaluate the effect of crystal growth inhibitors (GCIs) on the zeolite synthesis and crystal size, three types of CGIs, namely Poly Ethylene Glycol (PEG); Poly Ethylene Glycol-Methyl Ether (PEG-ME); and Brij-96, were utilized. It was found that PEG gave the best result in terms of zeolite size compared to the other two CGIs by resulting in reduction of the size of zeolite A crystals into about half compared to that without CGI.
Experimental Study of Entrainment Ratio of the Near Exit Region of High-Speed Jets
Authors: Saffaraval Farhad , Solovitz Stephen A.
Published: August 2012

The growth of volcanic plumes is highly dependent on entrainment ratio, which is a ratio of the radial mass inflow to a jet to its axial mass flow. This fraction is relatively constant in many conditions, and its magnitude is a factor in whether a volcanic column either becomes buoyant and rises or collapses. Under fully-developed, self-similar conditions, the value of this fraction is approximately 0.065 for neutrally buoyant-jets and 0.09 for buoyant jets. However, volcanic eruptions generally involve much higher pressures than these conditions, resulting in overpressured exit flows and supersonic speeds downstream, which likely impact entrainment. A small-scale laboratory model of a high-speed jet was developed, and particle image velocimetry was used to study the velocity fields both along the jet centerline and in the ambient atmosphere. The experiments consider exit speeds ranging from low subsonic levels up to overpressure ratios, K = pexit/patm, of approximately three. The resulting instantaneous fields were then integrated to determine the entrainment ratio. At these higher pressure conditions, the entrainment was significantly reduced downstream of the exit, with the mass flow more than 40% lower. This may have significant impact on analytical models of volcanic plume development, as the expected plume growth may be overpredicted.
Hybrid Solar-Geothermal Power Generation to Increase the Energy Production From a Binary Geothermal Plant
Authors: Manente Giovanni , Field Randall , DiPippo Ronald , Tester Jefferson W. , Paci Marco , Rossi Nicola
Published: August 2012

This article examines how hybridization using solar thermal energy can increase the power output of a geothermal binary power plant that is operating on geothermal fluid conditions that fall short of design values in temperature and flow rate. The power cycle consists of a subcritical organic Rankine cycle using industrial grade isobutane as the working fluid. Each of the power plant units includes two expanders, a vaporizer, a preheater and air-cooled condensers. Aspen Plus was used to model the plant; the model was validated and adjusted by comparing its predictions to data collected during the first year of operation. The model was then run to determine the best strategy for distributing the available geothermal fluid between the two units to optimize the plant for the existing degraded geofluid conditions. Two solar-geothermal hybrid designs were evaluated to assess their ability to increase the power output and the annual energy production relative to the geothermal-only case.
Coupled Computational Thermal and Mechanical Analysis of a Single Chip Flip Chip Module With Low-k Dielectric Medium
Authors: Mirza Fahad , Raman Thiagarajan , Ghalambor Saeed , Bastawros Ashraf , Agonafer Dereje
Published: August 2012

Miniaturization and more recently convergence have been driving the industry since the invention of the transistor and integrated circuit (IC). While gate delay has decreased with transistor scaling, the increase in the resistive capacitive (RC) delay due to shrinking interconnect dimensions has become a serious concern for the development of future-generation electronics. To reduce the delay due to resistance R, a major technology change was the replacement of Aluminum (Al) with Copper (Cu) interconnects. Recently, some investigators have suggested using low-k dielectric (having dielectric constant less than 4) instead of Silicon dioxide (k = 3.9) to reduce the capacitive component in the RC delay. Recent research has shown low-k materials to have characteristics such as low mechanical strength and adhesion. In this paper, thermo-mechanical analysis of a single chip flip-chip module (SCM) consisting of a die integrated with low-k dielectric medium, substrate, solder balls, and a printed circuit board (PCB) is performed. The analysis is done in two steps within the ANSYS finite element software to account for thermally induced stresses due to mismatch in thermal expansion coefficient. In the first step, the thermal analysis is carried out to derive the steady state temperature distribution within the package under the imposed power rating. In the second step, the evaluated temperature field is utilized in a coupled thermo-mechanical structural analysis. The developed framework is utilized to study the thermo-mechanical behavior of various low-k dielectrics, wherein the stresses and strain distributions within the chip region are quantified. The analysis has shown no change in the temperature distribution between the base case of Silicon dioxide (SiO2) and low-k materials. The maximum equivalent stress in the package, for all the four dielectric cases (SiO2, polyimide, Hydrogen Silsesquioxane, and Black diamond) is seen in the silicon region of the die and that it does not change with the dielectric materials. However, the maximum equivalent stress in the low-k/metal layers varies with the materials but is always few orders of magnitude less than their corresponding yield strengths. Comparative analysis between Silicon dioxide (SiO2) and different low-k materials will help in identifying the weak spots in low-k dielectric when exposed to standard user environments.
Analysis of Solar Organic Rankine Cycle for a Building in Hot and Humid Climate
Authors: Rayegan Rambod , Tao Yong X.
Published: August 2012

The objective of this paper is to model and analyze the solar Organic Rankine Cycle (ORC) engine for a geothermal air-conditioned net zero-energy building (NZEB) in a hot and humid climate. In the authors’ previous work, 11 fluids have been suggested to be employed in solar ORCs that use low or medium temperature solar collectors. In this paper, the system requirements needed to maintain the electricity demand of a commercial building have been compared for the 11 suggested fluids. The solar collector loop, building, and geothermal air conditioning system are modeled using TRNSYS with the required input for the ORC system derived from the previous study. The commercial building is located in Pensacola of Florida and is served by grid power. The building has been equipped with two geothermal heat pump units and a vertical closed loop system. The performance of the geothermal system has been monitored for 3 weeks. Monitoring data and available electricity bills of the building have been employed to calibrate the building and geothermal air conditioning system simulation. Simulation has been repeated for Miami and Houston in order to evaluate the effect of the different solar radiations on the system requirements.
Model Based Study of Stability Limits for Three Wheeled Vehicles Using ADAMS/Car
Authors: Rao Sughosh , Sidhu Anmol , Johnson Michael , Marquette Brooks , Heydinger Gary , Guenther Dennis
Published: August 2012

Three-wheeled motor vehicles have been around for close to a half a century now, but they have largely remained in the realm of recreational or concept vehicles. Due to increasing fuel prices and an emphasis on fuel efficient design, the automotive industry is exploring the three-wheeled option now more than ever as a mainstream daily-use vehicle. The trend is evident from the Automotive X-Prize which featured six teams with three-wheeled vehicle designs to meet the fuel efficiency target [1]. A three-wheeled vehicle design offers vast potential for improvement in overall fuel efficiency over their four wheeled counterparts, as it lends itself to a tear-drop shape which is highly aerodynamic and is also likely to be lighter and have lower rolling resistance. These factors have considerable impact on improving fuel efficiency, but such a design also presents challenges in terms of vehicle stability and can be susceptible to roll-over or spin out in certain scenarios. The primary factor that determines the stability of a three-wheeled vehicle is its center of gravity (CG). This paper uses a model-based approach to explore the CG position limits for stable operation of a front wheel drive three wheel vehicle and aims to give an empirical basis for deciding CG position limits for future three wheel vehicle design. ADAMS/Car is used to model the vehicle and the model is validated using test data from a commercially available three-wheeled vehicle. The performance of the model is then studied for various CG positions and the limits of safe operation are established for this particular model.
Bioheat Transfer During Infrared Laser Irradiation of Tissue Phantoms for Replacing Traditional Moxibustion
Authors: Cho Jiyong , Lee Seungdeok , Kim Jung Kyung
Published: August 2012

Traditional moxibustion generates heat stimulation that expands blood vessels and promotes blood circulation. We developed a novel noncontact-type thermal therapeutic system using an infrared laser diode. The device allows direct interaction of laser light with the skin, thereby rendering a temperature distribution on both on the skin’s surface and deep under the skin. Optical and thermal properties—the absorption coefficient, specific heat, and thermal conductivity—are the three most important parameters for a tissue phantom used as a substitute for real skin. We found that these parameters could be manipulated using the concentration of agar gel, and we fabricated multi-layer tissue phantoms using combinations of agar gels with different concentrations. The temperature distribution inside the tissue phantom during laser irradiation was measured using inserted thermocouples and thermal imaging. The temperature increased with agar gel concentration, and could reach a maximum value under the surface of the tissue phantom. Further analysis of the temperature distribution yielded controllable parameters for laser irradiation (output power, spot size, wavelength, and pulse width) to induce a similar thermal effect with moxibustion therapy. With known compositions and the opto-thermal properties of a patient’s skin tissue, we manipulated the temperature distribution inside the tissue by optimizing the laser parameters, which will ultimately enable patient-specific thermal therapy.
Light Activated Shape Memory Polymers: Some Inhomogeneous Deformation Examples
Authors: Sodhi Jaskirat S. , Rao I. Joga
Published: August 2012

Shape memory polymers (SMP’s) belong to a large family of shape memory materials, which are defined by their capacity to store a deformed (temporary) shape and recover an original (parent) shape. SMP’s have the ability to change size and shape when activated through a suitable trigger. This trigger, which can be heating the polymer or exposing it to light of a specific frequency, is responsible for the new temporary shape. Return to the original shape can be achieved by a suitable reverse trigger. Light Activated Shape Memory Polymers (LASMP) are recently developed smart materials which are synthesized with special photosensitive molecules. These molecules when exposed to Ultraviolet (UV) light at specific wavelengths, form covalent crosslinks that are responsible for providing LASMP with their temporary shape. Light activation removes temperature constraints faced by thermoresponsive SMP for medical applications and also brings the added advantage of remote activation. Thus LASMP find use in a variety of applications ranging from MEMS devices to widespread usage for biomedical devices such as intravenous needles and stents. Furthermore, the aerospace industry has found use for these materials for applications ranging from easily deployable space structures to morphing wing aircraft. The authors have introduced a constitutive model to model the mechanics of these LASMP [1]. The modeling is done using a framework based on the theory of multiple natural configurations. A few homogenous and inhomogeneous examples were solved in [1], but with tacit understanding that the intensity of light and hence the extent of reaction is homogenous throughout the polymer sample. In this paper we use the developed model to solve the cases of inhomogeneous deformation with inhomogeneous exposure to light.
Overcoming the Limitations of Current Online Laboratory Systems Using Game-Based Virtual Environments
Authors: Chang Yizhe , Aziz El-Sayed , Esche Sven K. , Chassapis Constantin
Published: August 2012

Current online laboratory systems based on either remotely operated hardware or pure software simulations are often criticized for lacking experimental setup experience and for being limited to the data collection and result analysis aspects of traditional hands-on laboratories. One possible solution for overcoming these shortcomings is to use a multi-player computer game engine for implementing interactive laboratory environments. Taking advantage of game technology, the students are enabled to simultaneously interact with laboratory equipment in the virtual laboratory and to communicate with each other through voice or chat. In particular, assembling the experimental equipment before using it in some experimental procedure can become part of the laboratory exercise. In this article, a virtual gear design laboratory environment for a junior-level undergraduate mechanical engineering course on mechanisms and machine dynamics is presented. This virtual laboratory environment implemented using a multiplayer computer game engine provides the students with the flexibility to perform various experiments related to the concepts of the fundamental law of gearing and to planetary motion of gears. In this environment, the students can work in teams to interactively select and cooperatively assemble gear train components piece by piece into a more complex experimental apparatus. This article describes the assembly logic that is used to combine individual components into experimental setups as part of the experimental procedure in student laboratories. Furthermore, the game environment can be equipped with functionality for monitoring the students’ progress and learning outcomes, thus enabling skill-based assessment.
High Flow Rate Device for Circulating Tumor Cell Capture
Authors: Park Taehyun , Park Daniel Sangwon , Murphy Michael C.
Published: August 2012

Circulating tumor cells (CTCs) were captured at high flow rates with a high recovery rate using a small footprint disposable polymer micro device. A new concept of target cell capture was introduced to break through the barriers limiting current approaches. Several potential designs were parametrically simulated using computational fluid dynamics (CFD) to achieve the best performance. The high flow rate device (HFRD) was fabricated in polymethyl methacrylate (PMMA) based on simulation results. Antibodies (anti-EpCAM) were immobilized on the PMMA device with surface treatments including UV modification and amine functionalization. A novel rare cell sample preparation method was established to provide an exact number of initial target cells to accurately test the rare cell performance. The precisely prepared samples of rare target tumor cells were spiked in a solution containing human erythrocytes, with a 40% hematocrit. The mean recovery rate with the HFRD was 85% at a 750 μL/min flow rate.
Numerical Modeling and Simulation of Condensation Heat Transfer in a Bundle of Transport Membrane Tubes for Waste Heat and Water Recovery
Authors: Lin Cheng-Xian Charlie , Wang Dexin , Bao Ainan
Published: August 2012

In this paper, a numerical study has been carried out to investigate the heat and mass transfer with condensation in a transport membrane tube bundle, which is used for recovering both heat and water from combustion flue gas. The tube wall is made of a specially designed porous material that is able to extract condensate liquid from the flue gas. The flue gas investigated consists of one condensable water vapor (H2O) and three noncondensable gases (CO2, O2, and N2). A simplified multi-species transport model was developed for the heat and mass transfer of flue gas. The condensation-evaporation process was simulated as a two-step chemical reaction. The RNG two-equation turbulence model was used for the turbulent flow. The numerical study was conducted within ranges of Reynolds number of 1.0×103–7×104 based on hydraulic diameter of flue gas channel, and 6.4×100–3.3×102 based on inner diameter of the water tube. Flue gas inlet temperature is within the range of 333.2–360.9 K, while the water inlet temperature is within the range of 293.9–316.7 K. Numerical results were compared with experimental data obtained in a parallel effort. It has been found that the developed multi-species transport model was able to predict the flue gas heat and mass transfer in the tube bundle with fairly good accuracy. The heat and mass depletion levels decrease with the increase of the flue gas Reynolds numbers. A new Nusselt number correlation was developed for flue gas convection in the tube bundle. Detailed results about temperature, mass fraction, enthalpy, and skin fraction factors are also presented and discussed.
Capillary Rise and Evaporative Heat Transfer in Nano-Structured Multi-Mode Wicks
Authors: Choi Changho , Chang Chih-hung , Krishnan Shankar , Hendricks Terry J. , TeGrotenhuis Ward
Published: August 2012

Nanostructured films were successfully deposited on various wick samples including conventional screen materials, engineered single and dual-mode wicks which are specially designed to augment boiling heat transfer performance. Microreactor-assisted nanomaterial deposition, MAND™, was employed with a flow cell to deposit the nanostructures on large wick shims (4.3cm × 10.7cm). Capillary rise experiments, height based measurement and weight gain method, were performed to characterize wicking dynamics in nano-coated and “bare” capillary wicks with water and ethanol. The results indicate that nanocoated wick is most efficient for ethanol in terms of the enhancement of capillary force. Analytical and numerical analyses based on Lucas Washburn equation were performed to model the capillary rise. Data from the height measurement were in a good agreement with both numerical and analytical solutions. Capillary rise of water on engineered multi-mode wicks displayed a step-rise in the wicking front. Flow boiling tests were also performed to characterize heat transfer from nano-coated wicks for application in energy conversion systems as compact evaporators. Experimental results indicate that the nanostructured wicks enhance heat transfer, reduce superheat required and operate stably when compared with “bare” wicks and conventional microchannels.