bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation of Power Density Enhancement for a Small Wind Turbine Augmented With a Novel Deflector
Authors: Tabatabaian Mehrzad , Goodwin Stuart B.
Published: May 2012

This paper explains a novel concept for wind power density enhancement through the use of specially shaped static wind deflector structures. The design and fabrication of the deflectors and the experimental results are explained. The general wind enhancement concept is further divided into two separate but related versions. The first deflector version discussed herein is a closed or constrained-flow device proposed for energy recapture from industrial-scale ventilation exhaust air. The second deflector version discussed herein is an open or unconstrained-flow device proposed for low wind velocity (< 4 m/s) applications and thus offers potential for wind power generation in built-up urban environments. Experiments associated with the two design adaptations were performed on a test-duct and in a wind tunnel, respectively. The test results showed velocity increases (factors of 3 and 1.7 respectively). The test-duct results for the constrained-flow device also showed turbine power output enhancement by a factor of approximately 20. Neglecting other losses, such a ratio would provide a theoretical power improvement of about 5 times over the base flow velocity. The term Wind Powered Deflector (WPD) was coined to describe the devices discussed herein.
Computer Simulation of Multibody Dynamical Systems in a TeraGrid Environment
Authors: Duan Shanzhong Shawn , Mohammed Abdul Muqtadir
Published: May 2012

Despite the great growth in capability of computer hardware, the system size, complexity of structures, and time scales present in virtual prototyping of multibody dynamical systems will continue to challenge the field of computational multibody dynamics for the foreseeable future. In this paper, the scientific problems in virtual prototyping of multibody dynamical systems are articulated. Implementation of an efficient parallelizable algorithm on TeraGrid computing systems is further discussed. Various simulation cases and computing results are presented to demonstrate impact of the TeraGrid to the performance of the algorithm.
Small Satellite Formations via Higher Velocity Deployment
Authors: McMullen Matthew G. , Alexander Tamara , Huang Adam
Published: May 2012

Small satellites can be constructed at a fraction of the cost of a full-size satellite. One full-size satellite can be replaced with a multitude of small satellites, which offers a benefit in covering more area at the same time, achievable through formations. However, the shortcoming to the smaller size is usually a lack of thrusting capabilities. Furthermore, current designs for small satellite deployment mechanisms are only capable of low deployment velocities (on the order of meters per second). Prior research in using a pneumatic launcher shows that it is possible to achieve higher deployment velocities (75–125 m/s). This is beneficial in that it opens the possibility for limited but useful orbit placement and small satellite formations. Achieving a formation is done by reformulating the classical orbital mechanics equations to find the required deployment velocity vectors that yield the desired formation.
Hygrothermally Stable Extension-Twist Coupled Laminates With Bending-Twist Coupling
Authors: Haynes Robert A. , Armanios Erian A.
Published: May 2012

The necessary and sufficient conditions for hygrothermal curvature stability of laminated composite plates have been derived in a prior publication and shown to be material independent. From within these conditions, various couplings are being investigated to determine any improvements over previously known optima. Extension-twist and bending-twist coupling have been investigated in previous work, and significant improvements over the previous state-of-the-art are demonstrated. In this work, the combined effect of extension-twist and bending-twist couplings is investigated to determine the level of twist achievable with a single laminate. Hygrothermal stability is taken to be a constraint. Results for laminates consisting of five through ten plies are presented. A Monte Carlo simulation investigates the robustness of the six-ply laminate to errors in ply angle stacking sequence.
An Update to the Merchant Orthogonal Force Diagram (MFD)
Authors: Payton Lewis N.
Published: May 2012

Metal cutting as a science remains more art than science. A truly predictive model for use in quantitative modeling has eluded researchers to date, leading the noted mathematician, R. Hill [1] to observe that “it is notorious that the extant theories of the mechanics of machining do not agree well with experiment”. Extensive experiments with a videographic quick stop device (VQSD) by the author indicate an extremely simple reason for these disagreements. A simple correction that is applicable to all of the classic orthogonal models of metal cutting is presented. A detailed application to the classic Merchant Force Diagram is presented.
Effects of Alternative Metal Working Fluids Upon Tool Face Wear
Authors: Payton Lewis N. , Sripathi Prajwal
Published: May 2012

Orthogonal metal cutting allows the collection of force data in the laboratory in an analytical manner not practical during industrial applications. Orthogonal tube turning (OTT) allows the collection of force data at much higher speeds than the original methods used by Ernst and Merchant. An orthogonal tube turning apparatus was constructed and validated in order to study the effects of rake angle, uncut chip thickness and cutting environments on the tool forces and the wear of the tool face itself. Although there have been many studies which characterized the forces and the surface finish of the part machined, along with some version of tool life, this study is unique in that the wear of the tool face itself is characterized in a detailed analysis of variance (ANOVA) study. A widely utilized commercial water based product performed less well than either nitrogen gas or cold shop compressed air. Surface roughness of the tool was used to parameterize tool surface finish for cutting each factor level combination of the experiment.
The Influence of Soil Heat Imbalance on Ground-Coupled Heat Pump System and Strategy
Authors: Fan Rui , Gao Yan , Song Yingqian , Long Weiding
Published: May 2012

It is well noticed that imbalance between winter heat requirement and summer heat gain in soil has an effect on heat transfer characteristic of ground heat exchanger (GHE), which results into the decrease of operation efficiency of ground-coupled heat pump system year by year. Therefore, the research on heat transfer characteristic of GHE for different heat imbalance rate is firstly presented in the article, and then, based on numerical model of heating conduction and groundwater heat advection, the influence of groundwater flow rate is analyzed. Finally, several suggestions such as auxiliary cool and heat source, GHE adjustment strategy are put forward for better and efficient operation of system.
Investigation of Thermal Characteristics on Simultaneous Snow and Melt in Road
Authors: Huang Yong , Gao Qing , Liu Yan , Yan Y. Y.
Published: May 2012

An automatically controlled hydronic ice-snow melting (HISM) technology in road coupled with slab solar collection (SSC) and underground thermal energy storage (UTES) has become an increasingly sustainable and important measure in road engineering and heat engineering An experiment on the hydronic snow melting system with coil pipe imbedded in road was implemented to investigate the thermal characteristics of simultaneous snow and melt in road. Research focused on the active sync process of road snow melting in the different pitch pipe, snow melt patterns, surface temperature, unit area heat consumption and unit length temperature difference, etc, and explored factors of impact characteristics, and recognized a synchronous process. The result shows that the smaller pipe pitch of dense arrangement is, the higher snow free area ratio is and the effect of snow removal is better. Actually the short duration of snow melting needs big heat load and heat consumption. The arrangement of small pitch can support big heating intensity. In the simultaneous snow and melt, a short duration of snow melting and timely melting must be fulfilled as quickly as possible and it can significantly shorten the lifetime of snow accumulated on road. But a big heating system will be required and it leads to a large initial investment.
Quantifying Acoustic and Pressure Sensing for In-Pipe Leak Detection
Authors: Khalifa Atia E. , Chatzigeorgiou Dimitris M. , Youcef-Toumi Kamal , Khulief Yehia A. , Ben-Mansour Rached
Published: May 2012

Experiments were carried out to study the effectiveness of using inside-pipe measurements for leak detection in plastic pipes. Acoustic and pressure signals due to simulated leaks, opened to air, are measured and studied for designing a detection system to be deployed inside water networks of 100 mm (4 inch) pipe size. Results showed that leaks as small as 2 l/min can be detected using both hydrophone and dynamic pressure transducer under low pipe flow rates. The ratio between pipe flow rate and leak flow rate seems to be more important than the absolute value of leak flow. Increasing this ratio resulted in diminishing and low frequency leak signals. Sensor location and directionality, with respect to the leak, are important in acquiring clean signal.
Demonstration of Continuous Electrowetting Actuation
Authors: Lynch Corey M. , Khodayari Mehdi , Volinsky Alex A. , Crane Nathan B.
Published: May 2012

Electrowetting is the change in apparent surface energy of a liquid in an applied electric field. It has shown great promise in diverse applications including lab-on-a-chip and electronic displays. The electrowetting response is typically considered independent of the actuation voltage polarity. This paper describes a new approach that achiees actuation in different directions for positive and negative voltage polarities using the electrochemical characteristics of aluminum electrodes. This paper presents a concept for continuous actuation of a droplet using a single electrode and DC voltage based on this effect. Initial experiments demonstrate that droplet motion is possible. Measurements of voltage drop across aluminum electrodes confirms the polarity-dependent response of the electrodes.
Structural Modeling of the Human Musculoskeletal System for Clinical Treatment by Applying Joint-Connected Multibody Dynamics and System Approach
Authors: Kayo Munehiro Michael , Ohkami Yoshiaki
Published: May 2012

The objective of this paper is to establish a concise structural model of the human musculoskeletal system (HMS) that can be used to clinically treat malfunctions or distortions of the human body. This model must be uncomplicated for therapists to identify the problematic areas of the human body with adequate visualization while maintaining a theoretical thoroughness in mechanics. To achieve this objective, a system theory approach called the Interpretive Structural Modeling (ISM) has been applied to bridge multi-body dynamics and clinical observations. From a mechanical engineering viewpoint, this HMS system can be treated as a collection of joint connected 15 rigid bodies in a topological tree configuration with 35 Degrees-of-Freedom (DOF). Alternatively, from a clinical viewpoint, the functioning of the joints is a major concern since most malfunctions or distortions take place around the joints. Based on 20 years of accumulated clinical observation data, we have discovered that all HMS movements can be constructed by a combination of 35 fundamental motion elements, all having a certain degree of interaction with each other. By applying the ISM for a matrix representation of the HMS system, we have obtained the following results: 1) The association between the rotation of the joints and the fundamental motion elements is represented by a square matrix of dimension N, where N is twice of the DOF 2) The determinant of this matrix, corresponding to the N-square matrix in SE terminology, gives an evaluation criteria in selecting the fundamental elements; 3) Application of the ISM reveals a distinction between an active motion element with intention versus an associated motion element that is induced by another motion element(s). In addition, the ISM yields a tiered structure of the fundamental motion elements according to the degree of activeness; and 4) most important, an overall investigation of the matrix characteristics gives a means to identify imbalances or distortions within the HMS. With the help of a motion diagram for the purpose of visualization, this research can eventually be applied to clinical observations whereby an automated identification of malfunctioning parts can be achieved with computer software. The above stated results will contribute to a holistic and non-invasive approach for medical care and rehabilitation.
Simulation of Nonlinear Heat Transfer and Residual Stress for Multi-Pass Welding
Authors: Li Hong , Li Hongliang , Gao Xiang , Ni Yongliang
Published: May 2012

Welding residual plastic strains and stresses of welded structures are complicated and they will cause errors during the assembly of the structure and reduce the strength of the structure. Based on an elastic-plastic-model, a 3D finite element numerical simulation of a representative penetration assembly with loop welding line is carried out in this paper. The method of join for penetration structure and base plate is multi-pass welding. The transient temperature field and the real-time dynamic stresses field of the structure are obtained due to different welding sequences during multi-pass welding. In the process of analysis, the heat source is modeled as a moving heat flux along girth welds following a double ellipsoid distribution and the temperature-dependent properties of materials are considered. Being compared with the analysis results of other’s and the theory study, which provide instruction to the numerical simulation of welding process on similar components, the simulated results show mostly conformity.
The Entropy Analysis on NH3/CO2 Cascade Refrigeration Cycle
Authors: Xie Yingbai , Cui Kuikui , Zong Luxiang , Wang Zhichao
Published: May 2012

This paper introduces a cascade refrigeration cycle that uses natural refrigerants of CO2 and NH3 at low temperature. It introduces the character of CO2 and NH3, besides analyzes the cascade refrigeration cycle. The optimal intermediate temperature of NH3/CO2 cascade refrigeration cycle is determined by the entropy production minimization method. We analyze the four processes entropy production in both CO2 cycle (LT side) and NH3 cycle (HT side) and research how the total entropy production changes in the conditions of different T0, different TCL and different ΔT. We also find that in order to enhance the efficiency of NH3/CO2 cascade refrigeration cycle, it is necessary to reduce ΔT. It can be concluded that NH3/CO2 cascade refrigeration cycle has a good future.
Control of Vibration Amplitude, Frequency and Damping of an Electrostatically Actuated Microbeam Using Capacitive, Inductive and Resistive Elements
Authors: Pasharavesh Abdolreza , Alizadeh Vaghasloo Y. , Fallah A. , Ahmadian M. T.
Published: May 2012

In this study vibration amplitude, frequency and damping of a microbeam is controlled using a RLC block containing a capacitor, resistor and inductor in series with the microbeam. Applying this method all of the considerable characteristics of the oscillatory system can be determined and controlled with no change in the geometrical and physical characteristics of the microbeam. Euler-Bernoulli assumptions are made for the microbeam and the electrical current through the microbeam is computed by considering the microbeam deflection and its voltage. Considering the RLC block, the voltage difference between the microbeam and the substrate is calculated. Two coupled nonlinear partial differential equations are obtained for the deflection and the voltage. The one parameter Galerkin method is employed to transform the equations of motion to a set of nonlinear coupled ordinary differential equations. Differential quadrature method (DQM) is implemented to solve the governing nonlinear ordinary differential equations. The effect of the controller parameters such as capacitance, resistance and inductance on the amplitude, frequency and damping is studied. Also the internal resonance between the electrical and mechanical parts of the system is studied. Results indicate using these elements, amplitude, frequency and damping can be controlled as desired by the user.
An Experimental Study on the Kinematics of a Skilled Service in Playing Tennis
Authors: Ahmadi Seyed Mohammad , Shirzad Elham , Sajadi Banafsheh , Cheraghi Mehdi , Haghighi Khashayar
Published: May 2012

This paper studies the effective parameters of a skilled service in playing tennis and determines their relationship with skill deals. Effective service in tennis plays an important role in gaining more desirable result and the most important factor of success in getting scores depends on the player’s skills in serving an effective service. The characteristics of a good service are the high speed of the ball and the precision of landing the ball. The several parameters affecting on these two characteristic in the service, are studied in this paper. Therefore, the Kinematic parameters of 8 Iranian professional tennis athletes of first division tennis league and also 8 non-professional Iranian athletes who exercise about 3 sessions a week were extracted. After land marking these athletes, by use of two high-frequency cameras, pictures were recorded when the tennis players were serving the services. The investigation on the results of these tests is performed by three dimensional motion analyses. The pictures are analyzed with the WinAnalyze software. Therefore, in this paper, the most important effective parameters in serving a successful service are detected.
Effect of Entrance Position on Particle Dispersion in the Vortex Engine
Authors: Dehghani S. R. , Saidi M. H. , Mozafari A. A. , Ghafourian A.
Published: May 2012

Particle dispersion in the vortex flow has been one of the most interesting subjects in recent years. Bidirectional vortex flow field is an industrial sample of the rotating flow which is used to obtain advantages of better mixing and combustion. In this work penetration and dispersion quality of the particles which are entering from various positions on the vortex engine walls have been numerically predicted. Head side, end side, and sidewall are considered as the entering positions. The particle has been assumed to be a rigid sphere. Initial velocity, diameter, and density of entering the particles are assumed to be known. If the particle length scale is considered not to be comparable with the chamber length and if the particle number density is low, then influence of the particle on the flow field is negligible and one-way solution is applicable. The solutions in each case are carried out for estimating the particle trajectory and their affecting parameters. Governing equation includes affecting forces on the particle and consequently the movement of particle and velocity. The governing equation is converted to a set of nonlinear, coupled, second order of ordinary differential equation (ODE), and solved by a numerical scheme. Results present axial and radial trajectory of the particles in the vortex engine from the point of entering position to the wall. They show that a high centrifugal force pushes the particles towards the sidewall. This pushing force becomes more powerful when the particles approach the chamber centerline. The results imply that the best injection arrangement in the vortex engine is not the head side. The sidewall and the end side composition arrangement of the injection can be the best.
Stabilizing Periodic Orbits of the Fractional Order Chaotic Van Der Pol System
Authors: Rahimi Mohammad A. , Salarieh Hasan , Alasty Aria
Published: May 2012

In this paper, stabilizing the unstable periodic orbits (UPO) in a chaotic fractional order system called Van der Pol is studied. Firstly, a technique for finding unstable periodic orbit in chaotic fractional order systems is stated. Then by applying this technique to the van der Pol system, unstable periodic orbit of system is found. After that, a method is presented for stabilization of the discovered UPO based on theories stability of the linear integer order and fractional order systems. Finally, a linear feedback controller was applied to the system and simulation is done for demonstration of controller performance.
Study on Structure Optimization and Evaluation Index of Cooling Capacity in a Bi-Layer Coolant Jacket of Cylinder Head
Authors: Wang Zhaowen , Deng Peng , Li Wei , Huang Ronghua
Published: May 2012

To solve problems such as thermal overload in the cylinder head of a 6-cylinder heavy-duty diesel engine and the thermal cracks in the valve-bridge of the engine. Structure of the coolant jacket was optimized from monolayer to bi-layer, and structures of upper nozzles were also optimized using the orthogonal experimental design method in this paper. At present, the cooling capacity of the coolant jacket in cylinder head is mainly judged by the coolant velocity. In this paper, the coolant heat transfer coefficient (HTC) was adopted as the criterion to evaluate the heat transfer process in cylinder head. Both of the velocity and HTC were used as the evaluation indexes to obtain the optimum schemes respectively. To determine which evaluation index fits the actual heat transfer process better, and which optimized schemes should be adopted, the temperatures in the bottom of the cylinder head were measured. The experimental results show that it is better to evaluate the cooling capacity of coolant jackets by HTC. HTC reflects the actual heat transfer process much better than velocity.
Mixing in a Rotating Micro-Channel
Authors: Leung Wallace Woon-Fong , Ren Yong
Published: May 2012

Mixing of liquids in rotating micro-channel is studied as it has important applications in portable diagnostic devices in rotating lab-on-a-chip. The latter utilizes rotation to pump liquid samples and reagents, and to actuate mixing between different liquids during transport in the channel using secondary flow generated from rotation. Experiments have been carried out on a rotating platform wherein two liquids are directed from their respective reservoirs through small capillaries into a common channel when the centrifugal force generated from rotation exceeds the capillary force which initially traps the liquid in their respective reservoirs. As two liquids are combined to flow through a common channel directed radially outward, Coriolis acceleration which is proportional to the rotation speed and relative radial velocity of the fluids, induces a tangential acceleration and thus velocity component that directs opposite to the direction of rotation. As this cross-flow, predominantly with maximum effect at the center of the channel, intercepts the far wall (i.e. pressure face) it splits up into two streams returning the flow back to the leading (in direction of rotation) face of the channel. This produces two main vortices/circulations for the channel and smaller vortices at the four corners for a channel with a rectangular cross-section. These vortices specifically the two main vortices are responsible for mixing of momentum, mass and energy in the cross-flow direction as the throughflow moves radially outward along the channel from small to a large radius. In the reference frame of the rotating channel, the combination of throughflow and crossflow results in two cork screw-shaped helical flow pattern streaming down the rotating channel. Connected with a microscope to view in details of the mixing in a small area, a rotating camera, mounted to the rotating platform, is used to take video of the mixing at various locations along a radial channel 30-mm in length and 1 mm width. This test is repeated for other observation locations along the channel. All the tests under identical rotation speed are grouped together to provide a full record of the mixing in the entire channel. These results can also be examined as mixing under same rotation speed but different channel lengths. Obviously, increasing length enhances mixing especially at small channel lengths under 5–10 mm. However, between 10–30 mm downstream mixing is diminished. It was also found that higher rotation speed can indeed produces better mixing with a modest increase.
The Stories Statistics Don’t Tell: Using Qualitative Data to Enhance Findings About Student Learning
Authors: Vernon Tanya M.
Published: May 2012

In this paper, the author illustrates several techniques for deriving findings from qualitative data. Data collected in this way can be used to enhance, but not necessarily take the place of, quantitative data which are routinely collected metrics of student performance. In this paper, the author suggests how to utilize naturalistic methods such as observation, interviews and blogs to represent “student stories” (or case studies). The paper has the following outcomes: 1) recognizing and using elements of good interviews, 2) knowing how to relate qualitative methods and findings to quantitative information and 3) understanding appropriate analysis for qualitative data. For this paper, the author draws upon her PhD research undertaken 2003–2007.
Fuzzy Sliding Mode Control of Multi-Agent Systems Using Artificial Potentials
Authors: Roshanghalb F. , Mortazavi J. , Alasty A. , Sayyaadi H.
Published: May 2012

In this paper a fuzzy control strategy of autonomous multi-agent systems is presented. The main purpose is to obtain an improvement on the results of designed sliding mode controllers in previous articles using supervisory fuzzy controller. Similarly, a quasi-static swarm model in n-dimensional space is introduced wherein the inter-individual interactions are based on artificial potential functions; and the motions of members are in direction with the negative gradient of the combined potentials which are the result of a balance between inter-individual interactions and the simultaneous interactions of the swarm members with their environment. Then a general model for vehicle dynamics of each agent has been studied. The aim is to reach the desirable formation of swarm by forcing agent’s motion to follow the quasi-static model. In literature a sliding mode controller is used to perform this task. In this work, same control structure is applied with a difference in control parameters. In this paper, fuzzy rules are introduced for some major control parameters which are efficacious on the results in order to get better performances along with less error during the formation control approach.
Experimental Validation of the COMPACT Code in Data Centers
Authors: Toulouse Michael M. , Lettieri David , Carey Van P. , Bash Cullen E.
Published: May 2012

This paper summarizes the comparison of predictions by a compact model of air flow and transport in data centers to temperature measurements of an operational data center. The simplified model and code package, referred to as COMPACT (Compact Model of Potential Flow and Convective Transport), is intended as an alternative to the use of time-intensive full CFD thermofluidic models as a first-order design tool, as well as a potential improvement to plant-based controllers. COMPACT is based on potential flow and combined with an application of convective energy equations, using sparse matrix solvers to seek flow and temperature solutions. Full-room solutions can be generated in 15 seconds on a commercially available laptop, and an accompanying graphical user interface has also been developed to allow quick configuration of data center designs and analysis of flow and temperature results. Experiments for validation of the model were conducted at the HP Labs data center in Palo Alto, CA, which is in a traditional configuration consisting of inlet floor tiles feeding cold air between two rows of multiple server racks. Subsequently, air exits either through ceiling tiles or direct room-return to CRAC units located on the side of the room. Temperatures were recorded at multiple points along entering and exiting flow faces within the room, as well as at various points in cold and hot aisles, and are presented and compared to model predictions to assess their accuracy. Areas of greater and lesser accuracy are analyzed and presented, in addition to conclusions as to the strengths and weaknesses of the model. For some cases, the average predicted temperature along in-flowing rack faces was within one degree of the average measured temperature. However, the differences in temperature are not evenly distributed. The most pronounced variations between the model and room measurements were located in areas above server racks where recirculation was shown to most likely occur. In these areas, the predicted temperature was higher than experimental values; this can likely be attributed to the absence of buoyancy effects in the simplified potential flow model. Adaptations of the model and its configuration standards for more accurate temperature distributions are proposed, as well as investigations into the effect on temperature comparisons to idealized model output by unaccounted heat sources or flow phenomena.
LMI-Based Decentralized PID Controller Design With Application to the Shape Control of Magnetic Fluid Deformable Mirrors
Authors: Wu Zhizheng , Iqbal Azhar , Ben Amara Foued
Published: May 2012

In this paper, a decentralized robust PID controller design method is proposed for multi-input multi-output systems. The system model is first decoupled in the low frequency range, and only the diagonal entries in the DC-decoupled plant model are retained. To deal with the resulting unmodeled high frequency dynamics, a decentralized robust PID controller design method is proposed, where the robust stability and transient response performance of the resulting closed loop system are formulated as a multi-objective H∞/H2 static output feedback problem. The desired parameters of the PID controller are determined by solving a static output feedback problem using linear matrix inequalities (LMIs). Finally, the performance of the proposed control algorithm is experimentally evaluated on the adaptive optics system involving a prototype magnetic fluid deformable mirror (MFDM). The experimental results illustrate the effectiveness of the proposed control algorithm for the MFDM surface shape tracking in the closed loop adaptive optics system.
Spatial and Temporal Wall Temperature Fluctuations in Two-Phase Flow in Microgap Coolers
Authors: Sheehan Jessica , Bar-Cohen Avram
Published: May 2012

Heat transfer to an evaporating refrigerant and/or dielectric liquid in a microgap channel can provide very high heat transfer coefficients and volumetric cooling rates. Recent studies at Maryland have established the dominance of the annular flow regime in such microgap channels and related the observed high-quality peak of an M-shaped heat transfer coefficient curve to the onset of local dryout. The present study utilizes infrared thermography to locate such nascent dryout regions and operating conditions. Data obtained with a 210 micron microgap channel, operated with a mass flux of 195.2 kg/m2-s and heat fluxes of 10.3 to 26 W/cm2 are presented and discussed.
Thermal-Aware Power Migration in Many-Core Processors
Authors: Raghu Avinash , Karajgikar Saket , Agonafer Dereje , Sammakia Bahgat , Refai-Ahmed Gamal
Published: May 2012

The demand for greater performance in applications involving high levels of parallelism and sequential computation, has led to an increase in design complexity, has rendered the single-core processor obsolete for such applications and resulted in more cores being put onto a single chip. While improving performance, this has lead to increased power densities and, consequently, increased die temperature. Also, the power distribution across the die surface is not uniform, resulting in hot spots. The increase in die temperature results in decreased performance and reliability and increased leakage currents and cooling costs. Spreading activity across a multi-core chip is increasingly being considered as a way to contain chip temperatures while minimally degrading performance. This paper investigates power migration, or “core hopping,” which involves dynamic allocation of workload among the cores on a many-core processor. This work numerically analyzed core hopping for different configurations of a many-core processor, and performed the migration based on both time of activity and temperature of individual cores. Based on the analysis, this work demonstrated a notable drop in junction temperature of about 8°C.
Design, Fabrication and Calibration of Heat Transfer Gauges for Transient Measurement
Authors: Kumar Rakesh , Sahoo Niranjan , Kulkarni Vinayak
Published: May 2012

Transient measurements of surface heating rates are very important in many applications in the field of internal combustion engines, gas turbine engines, fluidized beds and high-speed flow environments. In most surface heat transfer mapping, very fast response sensors are used for dynamic temperature measurements in the flow. The surface heat fluxes are then estimated from the temperature history, analytically/numerically by various heat transfers modeling. Thin film gauges and thermocouples are most cost effective temperature sensors for dynamic measurements because the response time of these sensors are in the range of microseconds. The production of heat transfer gauges in the laboratory has always been an art rather than a method of manufacture. The present work is aimed at design and fabrication of fast response thermocouples and thin film gauges (TFG) in the laboratory. Three types of thermocouples have been fabricated (E-type, T-type and K-type) whereas platinum film is deposited on the insulating substrate (Pyrex and Macor) for thin film heat transfer gauge. Both thermocouples and thin film gauges are calibrated under same experimental conditions.
Experimental Investigations of Laminar, Transitional to Turbulent Gas Flow in a Micro-Channel
Authors: Hong Chungpyo , Yamada Toru , Asako Yutaka , Faghri Mohammad , Suzuki Koichi , Ueno Ichiro
Published: May 2012

This paper presents experimental results on flow characteristics of laminar, transitional to turbulent gas flows through micro-channels. The experiments were performed for three micro-channels. The micro-channels were etched into silicon wafers, capped with glass, and their hydraulic diameter are 69.48, 99.36 and 147.76 μm. The pressure was measured at seven locations along the channel length to determine local values of Mach number and friction factor for a wide range of flow regime from laminar to turbulent flow. Flow characteristics in transitional flow regime to turbulence were obtained. The result shows that f·Re is a function of Mach number and higher than incompressible value due to the compressibility effect. The values of f·Re were compared with f·Re correlations in available literature.
Performance Analysis of Thermally Regenerated Desiccant System Integrated With Chilled Beam for Warm Humid Climate
Authors: Wahed M. A. , Wong Y. W. , Toh K. C. , Ho H. K.
Published: May 2012

At present, climate change and rising energy prices motivate the researchers to focus on better utilization of energy for space cooling applications. The chilled beam system has already been widely used in Europe for better utilization of energy for space cooling. But, the condensation on the chilled ceiling panel limits its application in the hot and humid climates. Operating a chilled beam system for such warm and humid climate requires the integration of desiccant system, which needs to be regenerated thermally for the purpose of the indoor air quality control. This paper emphasis the performance analysis of a thermally regenerated desiccant system integrated with a building chilled beam system in Singapore. A TRNSYS simulation model of such system has been developed to investigate the thermal performance. In this model, the chilled beam system meets the sensible load of the cooling space, while the desiccant air handling system meets the latent load of the cooling space. To regenerate this desiccant system, different heat sources such as solar, electricity and waste heat are considered in the analysis. It has been found that this integrated desiccant system with active chilled beam meets the cooling load (space temperature 21°C to 25°C and relative humidity between 55% ∼ 65%) of an office building effectively. It has also been found that the utilization of solar energy as heat source for desiccant regeneration decreases the energy consumption of the system at about 20% and reduces the operating cooling cost at about 1.5 to 2.5 times than the conventional VAV system.
Cytotoxicity of Magnetic Nanocomposite Spheres for Possible Drug Delivery Systems
Authors: Asmatulu R. , Garikapati A. , Misak H. E. , Song Z. , Yang S.-Y. , Wooley P.
Published: May 2012

Cytotoxicity test is a rapid and standardized in vitro method to determine the harmful effects of materials used for biomedical purposes, such as drug carriers, implants and their coatings, biosensors and surgical/medical devices. In the present study, sol-gel driven nickel ferrite (NiFe2O4) and cobalt ferrite (CoFe2O4) nanoparticles (10–25 nm) at different concentrations were incorporated into biodegradable polymer, poly(lactic-co-glycolic acid) (PLGA), using oil-in-oil emulsion/solvent evaporation technique, and then the cytotoxicity of magnetic nanocomposite spheres was characterized using raw cells. The test provides the toxicity of the products prior to their real applications, which may limit animal experimentation, remove potential toxic compounds and reduce the downstream costs. The cytotoxicity results showed that both magnetic nanocomposite spheres were toxic at some degree to the raw cells; however, the cobalt ferrite nanoparticles in nanocomposite spheres are more toxic than the nickel ferrite nanoparticles.
Aerodynamic Performance Analysis of Three Bladed Savonius Wind Turbine With Different Overlap Ratios and at Various Reynolds Number
Authors: Rahman Mosfequr , Morshed Khandakar N. , Mian Ahsan
Published: May 2012

Considerable improvements in the aerodynamic performance of a vertical axis wind turbine (VAWT) can be achieved by integrating computational fluid dynamics (CFD) simulation and wind tunnel investigation in their design improvement. With the growing demand for energy worldwide, conventional sources are becoming more scarce and expensive. Wind is among the most popular and fastest growing sources of alternative energy in the world. It is an inexhaustible, indigenous resource, pollution-free, and available almost any time of the day, especially in coastal regions. Industry experts predict that, with proper development, wind energy could provide 20% of the nation’s energy needs. Vertical axis wind turbines (VAWTs) may be as efficient and practical as, and simpler, and significantly cheaper to build and maintain than, horizontal axis wind turbines (HAWTs). They have other inherent advantages; for example, they always face the wind. VAWTs include both a drag-type configuration, such as the Savonius rotor, and a lift-type configuration, such as the Darrieus rotor. The Savonius wind turbine is the simplest. Its operation depends on the difference in drag force when the wind strikes either the convex or concave part of its semi-cylindrical blades. It is good at self-starting and works independently of wind direction. However, its efficiency is relatively lower than that of the lift-type VAWTs. Due to its simple design and low construction cost, Savonius rotors are primarily used for water pumping and to generate wind power on a small scale and its large starting torque makes it suitable for starting other types of wind turbines that have inferior starting characteristics. Recently, some generators with high torque at low rotational speed, suitable for small-scale wind turbines, have been developed, suggesting that Savonius rotors may yet be used to generate electric power. The main goal of this research work is to improve the aerodynamic performance of the three bladed vertical axis Savonius wind turbine. Based on this goal, the objective of this project is to study the performance characteristics of the Savonius wind turbine scale models both experimentally and numerically. The turbine scale models will have different designs with different overlap ratios (ratio of gap between two adjacent blades and the rotor diameter) and without overlap within three blades. The experimental measurements and testing will be conducted in front of a low speed subsonic wind tunnel at different Reynolds number and the computational fluid dynamic (CFD) flow simulation around those design models will be performed by commercial CFD software FLUENT and GAMBIT.
Research on Influencing Factors of Surface Plasmon Resonance Glucose Detection Based on D-Galactose/D-Glucose Protein Immobilizied by Amine Coupling Method
Authors: Wu Peng , Li Dachao , Zhang Jingxin , Song Bing , Xu Kexin
Published: May 2012

Prediction of blood glucose based on measuring the glucose concentration in interstitial fluid is an effectively way to control diabetes. A surface plasmon resonance (SPR) system based on a miniature integrated SPR sensor is set up in this paper to measure the glucose concentration in interstitial fluid, and the D-galactose/D-glucose Binding Protein (GGBP) which can specifically absorb glucose is immobilized onto the SPR sensor surface by amine coupling method for higher sensitivity. The experiment result is affected by various factors, such as the grime on sensor surface, baseline, flow velocity, mass transfer effect, temperature, protein activity, bubbles. In this paper these factors are studied systemically by experiments and some solutions are proposed accordingly: (1) Make sure the sensor surface is clean before it is used. (2) Dynamic baseline can provide the best baseline location during the measurement. (3) Flow velocity of 10uL/min-30uL/min is supposed to be chosen. (4) The density of protein immobilized on the sensor surface should maintain lower to avoid the mass transfer effect. (5) Higher response is got when the temperature is between 26°C and 30°C and it is important to keep temperature constant during the experiment. (6) The protein should be preserved with a proper way and make sure it is active during the measurement. (7) The sample should be degassed and filtered before the experiment and make sure there is no air in the pipeline. Through optimizing the experiment conditions, the sensitivity and stability of the measurement are improved.
Mechanism of Re-Scaling Frequency Stochastic Resonance Based on Kramers Rate and its Application
Authors: Leng Yong-gang , Guo Yan
Published: May 2012

We develop and further explore the mechanism of re-scaling frequency stochastic resonance (RFSR) based on the Kramers rate. We find that when the input signal frequency for stochastic resonance (SR) exceeds the half the Kramers rate limit, a frequency-scale ratio of RFSR should be selected to re-scale the larger signal frequency to a small SR frequency. Within the SR frequency range, we compare the performance of two approaches of realizing SR, the method of adjusting system parameters and the method of frequency-scale ratio. We showed that the former makes the half the Kramers rate approaching the signal frequency, while the latter makes the signal frequency approaching the half the Kramers rate. An engineering example demonstrates excellent performance of the re-scaling frequency for SR in fault diagnosis.
Fabrication of Carbon Membrane X-Ray Mask for X-Ray Lithography
Authors: Noda Daiji , Takahashi Naoki , Tokuoka Atsushi , Katori Megumi , Hattori Tadashi
Published: May 2012

X-ray radiographic imaging techniques have been applied in many fields. Previously we proposed a method for X-ray phase imaging using X-ray Talbot interferometry which requires the use of X-ray gratings. In this work, we fabricated the X-ray gratings needed for X-ray Talbot interferometry using an X-ray lithography technique. For X-ray lithography the accuracy of the fabricated structure depends largely on the accuracy of the X-ray mask. Conventionally a resin material is used for the support membrane for large area X-ray masks. However, resin membranes have the disadvantage that they can sag after several cycles of X-ray exposure due to the heat generated by the X-rays. For our new proposal we used thin carbon wafers for the membrane material because carbon has an extremely small thermal expansion coefficient. This new type of X-ray mask is very easy to process, and it is expected that it will lead to more precise X-ray masks. We fabricated carbon membrane X-ray masks on 6 inch wafers with a 1:1 line-to-space ratio and a pitch of 5.3 μm, covering a large effective area of 100 × 100 mm2.
Effect of Channel Orientation on the Distribution of the Heat Transfer Coefficient in Smooth and Dimpled Rotating Rectangular Channels
Authors: Kim Seokbeom , Choi Eun Yeong , Kwak Jae Su
Published: May 2012

The detailed heat transfer coefficients on rotating smooth and dimpled rectangular channels were measured by the transient liquid crystal technique. The rotating speed of the channel was fixed at 500rpm and the tested Reynolds number based on the channel hydraulic diameter was varied from 10,000 to 30,000. A stationary case and two different channel rotating orientations of 90° and 120° were tested in order to investigate the effects of channel orientation on the distribution of the heat transfer coefficient in smooth and dimpled rotating surfaces. Results showed high and low heat transfer coefficient regions caused by flow separation and reattachment by dimple and Coriolis force induced flows. Also, measured data indicated that the heat transfer coefficients on the dimpled surface were strongly affected by the rotation and channel rotating orientation. In the dimpled cases, the higher heat transfer coefficient is showed in the 120° orientated channel rather than the 90° orientated channel.
Methods for Computing 3D Steady-State Vibrations of Composites Using Green’s Functions
Authors: Karmazin Alexander , Kirillova Evgenia , Seemann Wolfgang , Syromyatnikov Pavel
Published: May 2012

Spatial steady-state harmonic vibrations of an infinite layered composite plate with an arbitrary elastic anisotropy of each layer are considered in this paper. The required vector of mechanical displacements of arbitrary points for a layered structure can be represented in the form of a double inverse Fourier transform of the product of the Fourier transform of the Green’s matrix and the Fourier transform of the surface load vector. An algorithm for computing the Fourier inverse transform with the given load vector is presented. Reducing of the initial double integral to the repeated one and using Jordan’s lemma make it possible to present the displacement vector in terms of residues in real and complex poles of the Green’s matrix. The stationary phase method is applied for computing asymptotic representations of the displacement field in the far-field zone. Displacements on the surface of some various composites on the basis of graphite-epoxy material for two types of surface load were computed as numerical examples.