bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical and Experimental Investigation on Performance of Dual Fuel D87 Engine
Authors: Gharehghani A. , Jazayeri A. , Mirsalim M. , Ghanbari M.
Published: May 2012

Conventional compression ignition internal combustion engines can easily be converted to a dual fuel mode of operation using natural gas as the main fuel and diesel oil injection as pilot to initiate the mixture or as a part of main fuel to improve the power output by changing the percentage of diesel oil to natural gas. Natural gas is abundant and relatively cheap alternative fuel with capability of reducing emission levels considerably. In order to examine the combustion characteristic of a heavy duty diesel engine which is locally produced, called D87, in dual fuel mode of operation. A detail performance analysis has been carried out where the main fuel is natural gas and diesel oil is as pilot injection. A reduced detailed chemical kinetics combustion model is combined with a partially stirred combustion model which is inserted in KIVA3V2 code to predict the knock and performance characteristics of the engine. Also, interaction between fuels during the combustion has been studied. Influence of parameters such as intake pressure and temperature on occurrence of knock and the effect of initial swirl ratio on engine performance parameters such in cylinder heat release rate, temperature-pressure and emission levels have been investigated. Appropriate computational grid for KIVA has been generated by ANSYS ICEM CFD commercial software. The developed model results are compared and validated with experimental results available during development tests.
Characteristics and Effects on a Machine-Tool Due to Grazing Motions of a Friction Boundary
Authors: Gegg Brandon C. , Suh Steve S.
Published: May 2012

The machine-tool interactions are studied with respect to the chip/tool friction boundary on the tool-piece rake face. The grazing motions with this chip/tool friction boundary are the focus of the study and how the effects are identified quantitatively. This study considers the transient motion of the machine-tool and will provide a framework for prediction of such grazing motions. The proposed study will include prediction through a range of excitation and system parameters. The significance of this lay within the application and the general approach to the definition of grazing via discontinuous systems theory.
Numerical Approach to Nonlinear Temporal Stability of Visco-Plastic Lubrication
Authors: Hormozi S. , Wielage-Burchard K. , Frigaard I. A. , Martinez D. M. , Grecov D.
Published: May 2012

A mixed finite element/finite volume method is used to study the entry/start-up flow of core-annular and channel configurations, with a Newtonian central fluid surrounded by a Bingham lubricating fluid. The established flow is known to be temporally stable. Here we explore issues relating to establishing the flow in realistic geometries. Using transient simulation we show that these flows may be stably achieved for a range of flow parameters and explore the development/entry lengths of the steady established flow. We show that three different development lengths can be defined and explain the variations in development/entry length with the dimensionless parameters. Also, nonlinear temporal stability to axisymmetric perturbations is studied numerically to understand structural aspects of the flow stability, not easily extracted from the energy stability method.
Experimental Studies of Visco-Elastic Flow Using Visco-Plastic Lubricant
Authors: Hormozi S. , Martinez D. M. , Frigaard I. A. , Grecov D.
Published: May 2012

Multi-layer shear flows of viscous fluids are frequently vulnerable to interfacial instabilities. In the case of a duct flow, it is known that use of a yield stress fluid as the lubricating fluid, coupled with maintaining a plug region at the interface, can lead to flows that are hydrodynamically stable: linearly and nonlinearly, both theoretically and in laboratory experimental studies; see [1],[2], and [3]. Whether the same technique is effective in stabilizing multi-layer duct flows with a visco-elastic core fluid is unknown and also relevant to many potential applications. In this paper we provide an experimental study by using viscoelastic fluid (Polyethylene Oxide solution) in the core region and visco-plastic fluid (Carbopol Solution) with yield stress as lubricant. The experiments have been carried out in axisymmetric configuration with different size of inner pipes. Via control of the individual fluid flow rates, it is also possible to vary the inner fluid radius over a significant range, which suggests utility for various industrial processes.
Computational Simulation of the Deformation of Neuronal Cells
Authors: Cao Guoxin , Zhou You , Lee Jeong Soon , Lim Jung Yul , Ganpule Shailesh , Chandra Namas
Published: May 2012

A numerical simulation (finite element method (FEM)) is used to determine the local mechanical response of a neuron based on the real neuron geometry. The real 3D geometry of a neuron can be constructed from the 2D confocal image stack which is taken per micron along the thickness direction from the top surface of neuron to the substrate. By matching the simulated deformation of the neuron with the measured results from the confocal microscopy images, the relative strength of the neuron components can be determined based on the reverse analysis of FEM. Then, the neuron local mechanical response and the relationship between the local response and the global applied deformation can be obtained, which will be the first step of building the mechanical injury model of neuron.
Energy Payback Optimization of Thermoelectric Power Generator Systems
Authors: Yazawa Kazuaki , Shakouri Ali
Published: May 2012

An analytic model for optimizing thermoelectric power generation system is developed and utilized for parametric studies. This model takes into account the external thermal resistances with hot and cold reservoirs. In addition, the spreading thermal resistance in the module substrates is considered to find the impact of designing small fraction of thermo elements per unit area. Previous studies are expanded by a full optimization of the electrical and thermal circuits. The optimum condition satisfies both electrical load resistance match with the internal resistance and the thermal resistance match with the heat source and the heat sink. Thermoelectric element aspect ratio and fill factor are found to be key parameters to optimize. The optimum leg length and the maximum output power are determined by a simple formula. The output power density per mass of the thermoelectric material has a peak when thermo elements cover a fractional area of ∼1%. The role of the substrate heat spreading for thermoelectric power generation is equally significant as thermoelement. For a given heat source, the co-optimization of the heat sink and the thermoelectric module should be performed. Active cooling and the design of the heat sink are customized to find the energy payback for the power generation system. The model includes both the air cooled heat sinks and the water cooled micro channels. We find that one can reduce the mass of thermoelement to around 3∼10% of that in commercial modules for the same output power, as long as the module and elements are designed properly. Also one notes that higher heat flux sources have significantly larger energy payback and reduced cost per output power.
Simplified Approaches for Solar Energy Modeling and Tracking
Authors: Naraghi Mohammad H.
Published: May 2012

Use of spreadsheets to model complex solar radiation calculations is described. The solar tracking equations are presented and the equations are used to determine shading on a fenestration by external horizontal and vertical shades. The orientation of window and dates were changed to observe their effect on the percentage of shades on the fenestration. Additionally, a spreadsheet based on the monthly clearness index method was used to determine monthly and annual solar radiation on an arbitrarily oriented surface. The solver of the spreadsheet was utilized to obtain the surface orientation for the maximum annual insolation.
Robust Multi-Robot Cooperation Using an Idiotypic Model of Artificial Immune Systems
Authors: Khan Muhammad Tahir , Imanuel Toar , Gabo Yelnil , de Silva C. W.
Published: May 2012

The human immune system is a network of cells, tissues, and other organs that defend the body against foreign invaders called antigens. Jerne’s Idiotypic network theory concerns how an antibody in the immune system stimulates or suppresses another antibody and recognizes an antigen. Based on the principles of the human immune system and Jerne’s idiotypic network theory this paper presents a method for cooperation among robots in a multi-robot system. The developed cooperative multi-robot system is fully autonomous and distributed. In the present paper, cooperation is not assumed a priori. If a robot is unable to complete a task alone, the system autonomously chooses the appropriate number of suitable and most capable robots in the fleet to cooperate with each other in carrying out a global task. The approach developed in the paper incorporates robustness and fault tolerance in immune system–based multi-robot cooperation.
Replacing a Power Plant Control Room Simulation Laboratory for an Engineering Technology Program
Authors: Cote´ Mark A.
Published: May 2012

Industry-centered education has been an integral part of the educational program at Maine Maritime Academy (MMA) since the founding of the college in 1941. This has included extensive use of laboratories and cooperative education as part of all MMA academic programs. Employers, graduates, and potential students describe MMA’s “hands-on” focus, reflected in the laboratory and cooperative education experiences, to be one of the main advantages of an MMA education, including the Power Engineering Technology (PET) program. In 1993, the MMA Engineering Department decided to build on this strength for the PET program by adding a personal computer-based, power plant control room simulator laboratory. The simulators were integrated into the PET Capstone experience, a two-course, nine credit hour sequence, that included both individual and team projects. The simulators were used to provide additional realistic, “hands–on” training as the students completed their degree. Over the course of the past fifteen years, while the simulators have continued to be a valued tool for the PET Program, the simulators were reaching the end point of their viable use due to hardware obsolescence. Since the simulator software was hardware specific, it had become impossible to procure replacement hardware for the simulators. In 2008, it was decided to replace the simulators and new simulator hardware and software have been procured and will be integrated into the PET Program beginning in the fall 2010 semester. This paper will describe the process used to determine the scope of the replacement process, the parameters for the new simulation systems, the procedure for determining the systems selected, and the process of integrating these new resources, including the assessment methods using the simulators, into the PET Program.
Characteristic Analysis of Anti-Reflective Subwavelength Cross Gratings Fabricated With Holographic Technique
Authors: Zhao Fengmei , Zhang Xiangsu , Liu Shou , Ren Xuechang
Published: May 2012

The paper presents the investigation on anti-reflection property of subwavelength cross-gratings with relief profile close to pyramid or cone. Such gratings are polarization independent and have effective refractive index increasing gradually from the top to the substrate. Theoretical analysis indicates that, to obtain good anti-reflection effect, for normally incident lights in visible band (400 ∼ 700 nm) the grating period should not be larger than 266 nm. Cross gratings with different periods were fabricated using holographic double-exposure method on photoresist. Measurements show that the grating with 255 nm period has higher transmittance compared with the gratings with the periods larger than 266 nm. Measurements also show that larger grating depth results in higher transmittance. The experimental results are in good agreement with the theoretical analysis.
Analysis of Geometric Characteristics of Scroll Compression Chamber for Scroll Fluid Machine
Authors: Qiang Jianguo
Published: May 2012

Based on the general geometrical model of scroll compression chamber for scroll fluid machine, the geometric characteristics of scroll compression chamber, such as width, length, volume, and comprehensive curvature radius at the mesh point, and their variation as well are comprehensively analyzed. It is shown by the analysis that among all of the geometric characteristics, the width variation is the most complicated one; the comprehensive variation of the width together with the length can be used to determine the deformation processes of the chamber. The variability of its length, volume, and comprehensive curvature radius at meshing points should be taken as its basic deformation characteristics. For a scroll compression chamber with involute of circle, its deformation efficiency is higher and dynamic stability is excellent. At the same time, the scroll wrap with involute of circle is easy to fabricate and the profile with involute of circle is used widely for the major part of the scroll profile.
A Coarse-Grained Molecular Dynamics Model for Sickle Hemoglobin Fibers
Authors: Li He , Lykotrafitis George
Published: May 2012

The intracellular polymerization of deoxy sickle cell hemoglobin (HbS) has been identified as the main cause of sickle cell disease. Therefore, the material properties and biomechanical behavior of polymerized HbS fibers have been a topic of intense research interest. A solvent-free coarse-grained molecular dynamics (CGMD) model has been developed and it represents a single hemoglobin fiber with four tightly bonded chains, each of which comprises soft particles. A harmonic spring potential, a bending potential, a torsional potential, and a Lennard-Jones potential are introduced along with a Langevin thermostat to simulate the behavior of a polymerized HbS fiber in the cytoplasm. The parameters of the potentials are identified via comparison of the simulation results with the experimentally measured values of bending and torsional rigidity of single HbS fibers. The proposed model is able to very efficiently simulate HbS fibers of 20 nm diameter and on the order of μm length-scale and μs time-scale. The model is validated by comparison with published experimental results and then it is used to investigate the interaction between two HbS fibers, and to study the fiber zippering process during heterogeneous fiber growth.
Health Monitoring Method for Load Assessment and Cooling Performance Degradation of Printed Circuit Boards
Authors: Hirohata Kenji , Hisano Katsumi , Hisakuni Yousuke , Omori Takahiro , Mukai Minoru
Published: May 2012

Health monitoring technologies, which can evaluate the performance degradation, load history and degree of fatigue, have the potential to improve the maintenance, the reliability design method and the availability in improper use conditions of electronic equipment. In this paper, we propose a method to assess the cooling performance degradation and load history of printed circuit boards in electronic equipment by use of a hierarchical Bayes model based on CAE (Computer Aided Engineering) results of thermal stress simulation and experiment data from actual measurements. We applied this method to a notebook PC that can monitor the device load factor and revolution number of cooling fan. It is shown that this method can estimate the temperature and deformation distribution of the printed circuit board from monitoring variables through latent variables such as thermal dissipation of the device and thermal boundary condition by use of the hierarchical Bayes model. And it is confirmed that the statistical load assessment concerning thermal cyclic load and the maximum load distribution can be conducted using the estimated temperature and deformation data. We verified that the cooling performance degradation can be assessed, if the temperature difference per unit thermal value between two suitable points on the printed circuit board can be obtained. Furthermore, we attempted the estimation method based on the hierarchical Bayes model to dynamic load assessment such as cyclic drop impact for PCB. The assessment method for the strain range distribution of the solder joints on the PCB was conducted to lead to the conservative results for reliability design. It is concluded that the proposed method can be effective to assess the field load history and cooling performance degradation.
Techno-Economic Evaluation of Pressurized Oxy-Fuel Combustion Systems
Authors: Hong Jongsup , Ghoniem Ahmed F. , Field Randall , Gazzino Marco
Published: May 2012

Oxy-fuel combustion coal-fired power plants can achieve significant reduction in carbon dioxide emissions, but at the cost of lowering their efficiency. Research and development are conducted to reduce the efficiency penalty and to improve their reliability. High-pressure oxy-fuel combustion has been shown to improve the overall performance by recuperating more of the fuel enthalpy into the power cycle. In our previous papers, we demonstrated how pressurized oxy-fuel combustion indeed achieves higher net efficiency than that of conventional atmospheric oxy-fuel power cycles. The system utilizes a cryogenic air separation unit, a carbon dioxide purification/compression unit, and flue gas recirculation system, adding to its cost. In this study, we perform a techno-economic feasibility study of pressurized oxy-fuel combustion power systems. A number of reports and papers have been used to develop reliable models which can predict the costs of power plant components, its operation, and carbon dioxide capture specific systems, etc. We evaluate different metrics including capital investments, cost of electricity, and CO2 avoidance costs. Based on our cost analysis, we show that the pressurized oxy-fuel power system is an effective solution in comparison to other carbon dioxide capture technologies. The higher heat recovery displaces some of the regeneration components of the feedwater system. Moreover, pressurized operating conditions lead to reduction in the size of several other critical components. Sensitivity analysis with respect to important parameters such as coal price and plant capacity is performed. The analysis suggests a guideline to operate pressurized oxy-fuel combustion power plants in a more cost-effective way.
Near Three Half Natural Frequency Resonance of Electrostatically Actuated MEMS Resonators
Authors: Caruntu Dumitru I. , Knecht Martin W.
Published: May 2012

This paper investigates electrostatically actuated micro resonators response near three half natural frequency. Electrostatic force including fringe effect and Casimir force are included in the model. These forces introduce parametric nonlinear terms in the system. The partial-differential equation of motion of the system is solved by using the method of multiple scales. A direct approach of the problem is then used. Two approximation problems resulting from the direct approach are solved. Phase-amplitude relationship is obtained. Numerical results for electrostatically actuated uniform micro resonator sensors are provided.
Properties Evaluation of Metallic, Polymeric and Ceramic Packing Materials for the Emission Reduction to the Atmosphere From Burning Kilns
Authors: Salazar Araceli , Chavez Rosa-Hilda , Olea Oscar , Solis Dora
Published: May 2012

The climate change and its impact to the environment is a topic of general importance which in the last years has raised a growing interest, to such a degree that many groups have been created worldwide to analyze it. The use of structured packing materials in an absorption column for washing sour gases proceeding from brick kilns is a suitable way to determine the material of more mechanical and chemical resistant and efficient in the treatment of these gases. In this work, three materials were characterized, a ceramic, a polymer and a metal by means of hardness test and electron microscopy (morphology). These materials are used as gas-liquid contactors, or packing beds in the absorption column for the sour gases treatment. The hardness results indicated that the ceramic material is the hardest one and therefore the most weak mechanically, the polymeric one is the most ductile, and the mechanical behavior of the metal material is intermediate. This study focuses on the first experimental stage, which is before the contact with the gases and particles from the kilns. The initial properties of the above materials were studied before being introduced the absorption column. The resistance to corrosion or the deposition, from the treatment of the gases in real conditions will be evaluated in a second phase on the research. The hydrodynamic behaviors were determined in the absorption column in order to determine the ideal conditions of operation, usually in the turbulence or load region. It was found that the polymeric material can work with a wide range of liquid load: from 0 to 30.03 m3/m2h, while with the metallic material it is better to work with a liquid load of 27.16 m3/m2h, Also, a standard test of corrosion (TAFEL), was performed using a solution of sulphuric acid 1N.. This was done in agreement to the ASTM G5-1999 standard procedure and the methods ININ No. P, SC (LC)-05. It found that the polymeric material is the most resistance to corrosion.
Structural Dynamics of the Automotive Body: Effects of Rear Overhang on Ride Comfort
Authors: Sugirtharaj P. , Fard M. , Jazar R. , Subic A.
Published: May 2012

Most of the researches about vehicle ride comfort and effects of the car body vibration on vehicle occupant had little or no focus on the structural modal characteristics of the vehicle body while these characteristics can have large effects on the transmission of the vibration to the vehicle occupant. One of the issues of the automotive ride comfort is related to the transmission of the vibration from the rear suspension to the rear seat mounting and therefore the seat and the vehicle occupant. Since such vibration are mainly caused by the rear body structure torsion mode, more care is required to predict the characteristics of this torsion mode in early design phase of the car. When the predecessor platform is resized for using a new car, it is sometimes necessary to extend the rear overhangs of the car. This research shows that the length of rear overhang may have a large effect on the torsion mode of the body and therefore on the transmission of the vibration from the road or rear suspension (shock absorbers) to the rear seat mountings. When a same platform is used for two similar models with different lengths of rear overhangs, the rear seat vibration level can considerably be different for these two similar models. An automotive CAE concept beam model, here, is used to investigate the effects of rear overhang on the rear seat vibration and comfort level. CAE beam concept models for the car body are important tools are used to predict and optimize the structural dynamics, in early design phase where there is no enough detailed design data. Here, the results show that by extending the rear overhang, the dynamic stiffness of the rear/overhang bending decreases and this may considerably aggravates the transmission of the vibration to the seat.
Exergoeconomic Analysis of New High-Temperature District Heating System Based on Absorption Heat Pump Technology in Combined Heat and Power
Authors: Sun Fangtian , Fu Lin , Zhang Shigang
Published: May 2012

Space heating area of district heating system of combined heat and power (CHP) accounts for approximately one third of total space heating area in Chinese northern cities. In the extraction condensing turbine combined heat and power system based on district heating network, there are a large number of low-grade waste heat in the condenser, and exergy loss in the steam-water heat exchanger and water-water heat exchanger. Based on absorption heat pump technology, a new high-temperature district heating technology (DHSAHP) was presented to improve the current district heating system of CHP. Absorption heat pumps are used to recycle low-temperature waste heat in condenser. Absorption heat pump type heat exchanger is used to reduce temperature of return water in primary heat network, and decrease irreversible loss. Where, DHSAHP was analyzed by thermodynamics and economics method, and evaluated by exergetic efficiency, exergetic output cost, exergetic cost difference and exergoeconomic factor. Compared with current district heating system of CHP, DHSAHP can decrease about 31.3% steam consumption, increase about 75% transmission and distribution capacity of the primary heating network. The evaluation results show that the exergetic efficiency of new district heating system of CHP based on the absorption cycle technology is higher 10.41% than that of current district heating system of CHP, whereas its exergetic cost is lower 36.6¥/GJ than that of the conventional district heating system. With the increase of annual heating time, economy efficiency of new district heating system of CHP becomes better. The DHSAHP has higher energy utilization efficiency and better economic benefits and provides a kind of better technological method to solve the main problems of cuurent district heating with CHP in China.
Enhancement of RF Ablation by Combined Use of Ultra-Low Temperature Fluid Cooling and Magnetic Nanoparticles
Authors: Deng Zhong-Shan , Liu Jing
Published: May 2012

Magnetic nanoparticles with high electrical conductivity have been proved to be effective in enhancing the efficacy of RF ablation. However, the possible carbonization of tissues is an unfavorable factor in achieving greater dimensions of necrosis, because carbonized tissue is a poor conductor, increases impedance and limits propagation area of RF energy. To prevent potential carbonization of tissues surrounding to the heating part of RF electrodes during RF ablation, a new method using ultra-low temperature fluid was proposed for cooling RF electrodes and tissues in the vicinity of RF electrodes in this study. To test its feasibility, the corresponding bioheat transfer process during RF ablation simultaneously applying this cooling method and magnetic nanoparticles was studied through numerical simulations. The results indicate that the cooling method by ultra-low temperature fluid can prevent carbonization of tissues resulted by local high temperature, significantly enlarge the effective heating area and thus actualize highly efficient thermal coagulation to tumor tissues during RF ablation with adjuvant use of magnetic nanoparticles.
Nano-Cryosurgery to Tackle the Deficiency in Conventional Freezing of Tumors With Large Blood Vessels
Authors: Deng Zhong-Shan , Liu Jing
Published: May 2012

Recently, nano-cryosurgery was proposed to improve freezing efficiency of the conventional cryosurgery. As is well known, the effect of thermally significant large blood vessel on temperature has long been a research focus for conventional cryosurgery, since the warm blood flowing through large vessel may result in insufficient freezing and tumor residual. However, there is little information concerning the effects of large vessels on the temperature distribution and freezing lesion in nano-cryosurgery. In this study, two typical vascular models were applied to investigate the effects of large blood vessels to the thermal distribution and freezing lesion during nano-cryosurgery. The numerical results indicated that, after localized introduction of nanoparticles, large vessels embedding in tumor tissues can be totally frozen during cryosurgery and thus the insufficient freezing region surrounding large vessels can be effectively eliminated. The results also suggested that adjuvant use of nanoparticles is expected to serve as a promising method to tackle the deficiency in conventional freezing of tumors with large blood vessels in future oncological clinics.
Two-Dimensional Elastohydrodynamic Lubrication Fluid Flow Modeling of Piston Top Ring Considering Elastic Deformation in Initial Engine Start Up
Authors: Malik M. Afzaal , Qasim Syed Adnan , Usman Ali , Mufti Riaz A.
Published: May 2012

The absence of Elastohydrodynamic Lubrication (EHL) between the first piston compression ring (top ring) and the liner surface in the initial engine startup causes adhesive wear whereas the presence of such a film enhances engine life by wear prevention. In the current work, a two dimensional model is presented for barrel-faced ring profile by considering elastic deformation and EHL. A non-axisymmetric elliptical cylinder bore and an elastic ring are considered to determine circumferential flow. The EHL film profile is generated by solving the two dimensional Reynolds equation using inverse solution technique and finite difference method in fully flooded lubrication condition. The results show that piston ring lubrication depends on the bore shape or bore out-of-roundness and lubricating film thickness due to which circumferential flow gets significantly reduced during the initial engine start up.
Viscoelastic Behaviour of the Human Spinal Disc
Authors: Ranu Harcharan Singh , Bhullar Aman Sweet , Zakaria Abdulrahim
Published: May 2012

An intradiscal pressure transducer (IDPT) and a set of intervertebral pressure transducer (IVPT) were developed to measure the pressures in the nucleus pulposus and around the annulus. Human lumbar spinal segments were loaded up to 2.0 kN and following parameters were recorded: applied compressive load as a function of time, intradiscal pressure as a function of time, intervertebral pressure as a function of time for anterior and lateral edges of the vertebra, strain as a function of time for anterior and lateral right and left sites of the vertebra, stress-relaxation of the complete segment as a function of time. All show very similar response to loading and stress-relaxation. However, annulus pressure did not respond to stress-relaxation. This was due to functional aspect of annulus.
The Effect of Using Nanofluids on Triangular Microchannel Heat Exchanger Performance
Authors: Bhaskaran G. , Mohammed H. A. , Shuaib N. H.
Published: May 2012

A numerical study is performed to study the effects of using various types of nanofluids on a triangular shaped microchannel heat exchanger (MCHE). The performance of an aluminum MCHE with various types of nanofluids such as Al2O3, CuO, SiO2, Ag and TiO2 and diamond particles with particle volume fraction of 2% using water as base fluid is comprehensively analyzed. The three-dimensional steady, laminar developing flow and conjugate heat transfer of a balanced MCHE were solved using finite volume method. In order to maintain laminar flow in the microchannels, Re number was ranged from 100 to 800. The other parameters tested in this study include the effects of Reynolds number towards the temperature, effectiveness and pressure drop of the MCHE. It is found that nanofluids have improved the temperature profile and heat transfer rate of the MCHE. The increase in pressure drop was minimal while the thermal and hydrodynamic performance of the heat exchanger was enhanced.
The Effect of Memory in Observer Design for a DP System
Authors: Hajivand A. , Mousavizadegan S. H.
Published: May 2012

The behavior of marine structures is investigated in regular waves using various models in frequency and time domains. In normal practice, the differential form of motion equations are used with constant hydrodynamic coefficients. Those coefficients which are added masses and damping coefficients are frequency dependent due to the memory effect. The memory effect is usually represented by a convolution integral and hence it converts the motion equations into integro-differential forms. The presence of the convolution integral makes the equations complex. However, it is necessary to take into account the memory effect in ship motion control and specially in dynamic positioning system to enhance the accuracy and obtained a more precise controller. The motion equations are solved for a DP system with memory effect and compare with the conventional model. The computations show that memory effect is important as the wave frequency increases. A nonlinear observer has been design to solve the wave filtering and state estimation problems with the memory effect. The performance of the nonlinear observer is demonstrated by computer simulations.
Thermally Actuated Plastic Microfluidic Valves
Authors: Gu Pan , Pitchaiman Karthik , Liu Ke , Nishida Toshikazu , Fan Z. Hugh
Published: May 2012

This paper reports the design, fabrication, characterization, and integration of a thermally actuated microvalve. The valve is made of 4 plastic layers, consisting of a layer for temperature-sensitive fluid, flow channel substrate, elastomeric film and a plastic film patterned with microheaters. When the temperature-sensitive fluid is heated, its volumetric expansion deflects the elastomeric film into the microchannel, closing the valve. Heat supplied to the temperature-sensitive fluid comes from microfabricated heaters. The external power applied to the heaters can be controlled using a printed circuit board (PCB)-based controller. The main challenge of this design is to find a suitable elastomeric film that is both elastic and can be bonded with cyclic olefin copolymer (COC) substrates. Pressure-sensitive tape (PSA) was investigated as an elastomeric film for the valve. A valve using PSA was successfully fabricated and tested. A conductive solution (NaCl) was filled into a microfluidic channel containing the valve. The operation of the valve was investigated by measuring a change in the microchannel’s ionic conduction current mediated by the resistance variation corresponding to the deflection of the microvalve. In addition, we integrated an array of such valves with other components in a device and used the valves to control the introduction of different separation media for two-dimensional protein separation.
Normal and Prevention of Pedal Sequelae in Diabetic Patients: A 3-D Pressure Pattern Analysis
Authors: Ranu Harcharan Singh , Almejrad Ali
Published: May 2012

A 3-D Foot Print Device was developed to measure the plantar foot pressures for normal and diabetic patients with neurotrophic ulcers. The results show that patients with peripheral neuropathy develop very high forefoot pressures as compared to normal segment of the populations. Bubble technology and new memory biomaterials insoles were used to reduce these forefoot pressures combined with providing new custom made shoes.
Quasi-Variational Principles of Single Flexible Body Dynamics
Authors: Song Haiyan , Zhou Jiansheng , Liang Lifu , Liu Zongmin
Published: May 2012

The theoretical analysis of flexible multi-body system is a long-term and complicated problem. So the single flexible body dynamics should be studied firstly. Quasi-variational principle of non-conservative single flexible body dynamics is established under the cross-link of particle rigid body dynamics and deformable body dynamics. Some important problems are studied in quasi-variational principle of non-conservative single flexible body dynamics. The vibration problem of unrestrained beam can be solved very well by using quasi-variational principle.
Manipulation of Multibody Active Objects Using Simple Passive Manipulators
Authors: Beigzadeh Borhan , Meghdari Ali , Sohrabpour Saeed
Published: May 2012

In this paper, we study passivity in dynamic manipulation of active objects. Active object is a concept covering a variety of objects, which are not rigid and need to be controlled during manipulation process. In this work, we use multi-link mechanisms with sufficient actuators to be controlled as object and a series of simple 1-DoF passive manipulators to perform such a process. Control of the object, dynamic and motion planning of the system, and stability in presence of impact are significant issues in this study.
A New Approach for Computing the Normal Forms of High Dimensional Nonlinear Systems
Authors: Chen Shuping , Zhang Wei , Yao Minghui
Published: May 2012

Normal form theory is very useful for direct bifurcation and stability analysis of nonlinear differential equations modeled in real life. This paper develops a new computation method for obtaining a significant refinement of the normal forms for high dimensional nonlinear systems. The method developed here uses the lower order nonlinear terms in the normal form for the simplifications of higher order terms. In the theoretical model for the nonplanar nonlinear oscillation of a cantilever beam, the computation method is applied to compute the coefficients of the normal forms for the case of two non-semisimple double zero eigenvalues. The normal forms of the averaged equations and their coefficients for non-planar non-linear oscillations of the cantilever beam under combined parametric and forcing excitations are calculated.
Preventing Conglomeration of Reduced Fine Powder in Solar Thermochemical Redox Cycles Based on Metals With Low Melting and High Boiling Points
Authors: Vishnevetsky Irina , Epstein Michael , Feldman Yishay
Published: May 2012

This paper describes a new method that enables avoiding conglomeration of small metal drops after reduction from their oxides. These solidified metal micro drops can be hydrolyzed with steam to generate hydrogen and close a solar redox cycle. Metals with low melting points and low vapor pressure at the reduction temperature do not evaporate and their drops tend to agglomerate. This phenomenon severely reduces the yield of the hydrogen production in the hydrolysis reaction. To avoid this agglomeration the mixture of metal oxide and carbon is blended with an additional small amount of inert ceramic powder that does not take a part in either reaction. This inert powder minimizes the amount of the reduction agent necessary for high conversion of the oxide and allows producing micron and submicron metal particles which are suitable for the hydrolysis step when performed in a fixed bed flow reactor. Experimental results with tin dioxide powder as a representative material are presented. Tests were done with different proportions of tin dioxide powder, charcoal and alumina powder as agglomeration retardant. Product morphology as a function of the components content was analyzed by TEM and SEM. Conversion was controlled by measuring of weight losses, amount of oxygen in output gases and X-ray Diffraction Quantitative Analysis.
Geometric Design of a Slotted Disc Spring for a Prescribed Load-Displacement Function
Authors: Fawazi Noor , Yoon Ji-Hyun , Oh Jae-Eung , Lee Jung-Youn
Published: May 2012

Geometric parameter design is an important stage in any product design. For example, by varying any of its geometric parameters, a slotted disc spring will show various defined nonlinear load-displacement behaviors. Therefore, these geometric parameters must be precisely designed to ensure the output spring design possesses a nonlinear load-displacement behavior that satisfies particular nonlinear criteria. More importantly, various engineering designs benefit from nonlinear behavior in order to meet certain engineering design requirements. Since each nonlinear spring application requires a unique load-displacement function, the spring geometric parameters must be precisely custom designed. However, there is no specific algorithm available to calculate such geometric design parameterization. The aim of this study is to propose a generalized algorithm for a slotted disc spring geometric design that ensures the output design exhibits identical load-displacement function with any prescribed one. A predicted geometric design algorithm for a slotted disc spring is proposed in this study. The design is characterized by a prescribed load-displacement function obtained from numerical model in the previous literature. The key feature of our proposed algorithm is that, the identified meeting point, which is defined from a prescribed function, can be used as a target point to match the predicted function with the prescribed function. Our proposed algorithm manipulates the slope characteristics of the established slotted disc spring numerical formulation to tune the predicted nonlinear function. This enables a geometric parameter design to be achieved. Improvements to the proposed geometric parameters were done by searching the best combination of optimum variables that produce minimum least mean square error between the prescribed and proposed nonlinear functions. The obtained numerical results demonstrate the effectiveness of the proposed algorithm to parameterize the geometric parameters for a slotted disc spring design.
On the Performances of High-Order Absorbing Boundary Conditions for Progressive and Standing Waves
Authors: Lancioni G. , Lenci S.
Published: May 2012

The performances of three different high order absorbing boundary conditions (ABCs) are investigated in the case of progressive and standing waves in a dispersive one-dimensional medium. Their accuracy is first analyzed with respect to the frequency of a single incident wave. Then they are submitted to a wave train characterized by a wide frequency spectrum, resulting from an impulsive force. The influence of both the order and the parameters of the ABCs on the accuracy is analyzed in detail.
Topology Optimization-Based Design of a Compliant Aircraft Wing for Morphing Leading and Trailing Edges
Authors: Podugu Pakeeruraju , Ananthasuresh G. K.
Published: May 2012

In this paper, we present a methodology for designing a compliant aircraft wing, which can morph from a given airfoil shape to another given shape under the actuation of internal forces and can offer sufficient stiffness in both configurations under the respective aerodynamic loads. The least square error in displacements, Fourier descriptors, geometric moments, and moment invariants are studied to compare candidate shapes and to pose the optimization problem. Their relative merits and demerits are discussed in this paper. The ‘frame finite element ground structure’ approach is used for topology optimization and the resulting solutions are converted to continuum solutions. The introduction of a notch-like feature is the key to the success of the design. It not only gives a good match for the target morphed shape for the leading and trailing edges but also minimizes the extension of the flexible skin that is to be put on the airfoil frame. Even though linear small-displacement elastic analysis is used in optimization, the obtained designs are analysed for large displacement behavior. The methodology developed here is not restricted to aircraft wings; it can be used to solve any shape-morphing requirement in flexible structures and compliant mechanisms.
The Ca-PTH Curve: Mathematical Considerations
Authors: Shrestha Rajiv P. , Schmitt Claus P. , Hollot Christopher V. , Chipkin Stuart R. , Chait Yossi
Published: May 2012

The symmetrical reverse sigmoid Ca-PTH curve has been suggested as a potential bio-tool for assessing parathyroid gland function and calcium homeostasis in the human body. A recent paper, in the context of a new mathematical model for the acute Ca-PTH response, suggested that this curve may not be symmetrical. In this paper, we flesh out the flaw in the conventional method of constructing the Ca-PTH curve and then propose a formal procedure for quantifying this curve using a series of carefully designed calcemic clamp test. The asymmetrical nature of this curve is demonstrated using a Ca-PTH model, the parameters of which are estimated from clinical data.
A Numerical Study of Laminar and Turbulent Natural Convective Heat Transfer From an Isothermal Vertical Plate With a Wavy Surface
Authors: Oosthuizen Patrick H.
Published: May 2012

Natural convective heat transfer from a wide isothermal plate which has a wavy surface, i.e., has a surface which periodically rises and falls, has been numerically studied. The main purpose of the study was to examine the effect of the surface waviness on the conditions under which transition from laminar to turbulent flow occurred and to study the effect of the surface waviness on the heat transfer rate. The surface waves, which have a saw-tooth cross-sectional shape, are normal to the direction of flow over the surface and have a relatively small amplitude. The range of Rayleigh numbers considered in the present study extends from values that for a non-wavy plate would be associated with laminar flow to values that would be associated with fully turbulent flow. The flow has been assumed to be steady and fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being treated by means of the Boussinesq type approximation. A standard k-epsilon turbulence model with full account being taken of the effects of the buoyancy forces has been used in obtaining the solution. The solution has been obtained using the commercial CFD solver FLUENT. The solution has the following parameters: the Rayleigh number based on the plate height, the Prandtl number, the dimensionless amplitude of the surface waviness, and the dimensionless pitch of the surface waviness. Results have been obtained for a Prandtl number of 0.7 and for a single dimensionless pitch value for Rayleigh numbers between approximately 106 and 1012. The effects of Rayleigh number and dimensionless amplitude on the mean heat transfer rate have been studied. It is convenient in presenting the results to introduce two mean heat transfer rates, one based on the total surface area and the other based on the projected frontal area of the surface.
Enhanced Deterministic Design: Application to a Micro CNC Machine Design
Authors: Mekid S.
Published: May 2012

This paper introduces an enhanced deterministic design approach for the design of a micro mechanical system with the objective to achieve better accuracy through miniaturisation. The methodology of design encompasses optimisation using Taguchi technique, finite element modelling, and, added functions considering a number of micro physical problems that may characterise the micro mechanical system. Typical micro physical problems of a micro milling machine were enumerated with possibilities to include some of them within the overall methodology was observed. Micro physical effects may not all have a known model. An objective function was created to satisfy part of the specifications. An example of a vertical column of the micro mill was designed and evaluated within the concept of the proposed design methodology. Initial results and error assessment measured on the micro machine are presented.
Thermoelectric Coolers for Thermal Gradient Management on Chip
Authors: Sullivan Owen , Gupta Man Prakash , Mukhopadhyay Saibal , Kumar Satish
Published: May 2012

Site-specific and on-demand cooling of hot spots in the microprocessors can provide efficient cooling solution, improve its performance and increase its life time by reducing peak temperature and achieving more uniform thermal profile on the chip. Thermoelectric coolers (TEC) have the potential to provide such efficient cooling of hot spots on a chip. We investigate pulse cooling behavior of ultra-thin multiple TEC devices integrated inside the electronic package on the active side of a chip below the heat spreader. Various pulse profiles have been studied to obtain optimal shape of the current pulse in order to efficiently operate TECs considering crucial parameters such as the total energy consumed in TECs, peak temperature on the chip, temperature overshoot at hot spot and settling time during pulsed cooling of hot spots. The square root pulse profile is found to be most effective with maximum cooling and half the energy expenditure in comparison to a constant current pulse. It has been observed that high thermal contact resistances can entirely negate the transient cooling effect of the TECs. We analyze the operation of multiple TECs for cooling spatiotemporally varying hot spots. The analysis shows that the temperature of the hot spots can be retained below a threshold using transient current pulses through the TECs. This underlines the benefits of using multiple TECs for hot spot cooling in order to obtain favorable thermal profile on the chip in an energy efficient way.