bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive Integral Base Sliding Mode Tracking Control of Piezoelectric Actuators
Authors: Sheikh Sofla Mohammad , Rezaei Seyed Mehdi , Zareinejad Mohammad
Published: July 2010

This paper presents an adaptive integral sliding mode control scheme for precise trajectory tracking of piezoelectric actuators (PEAs). This control methodology is proposed considering the problems of unknown or uncertain system parameters, hysteresis nonlinearity, and external load disturbances. The hysteretic behavior is represented by Bouc–Wen hysteresis model. It is shown that the nonlinear response of the model due to the hysteresis effect, acts as a bounded disturbance. Then base on this fact an adaptive robust controller is proposed, where an integral sliding surface is utilized to achieve the desired tracking performance. By using the proposed control approach the asymptotical stability in displacement tracking and robustness to the dynamic load disturbance can be provided. Finally, Experimental results are illustrated to verify the efficiency of the proposed method for tracking in various range of frequency and load which are common in practical applications.
Determination of Optimum Insulation Thickness for Different Climatic Zones of Turkey
Authors: Ku¨rekci Nuri Alpay , Ag˘ra O¨zden , Emanet O¨zlem
Published: July 2010

Turkey has dynamic economic development and rapid population growth. It also has macro-economic and especially, monetary instability. The net effect of these factors is that Turkey’s energy demand has grown rapidly almost every year and is expected to continue growing. Since 1990, energy consumption has increased at an annual average rate of 4.3%. The energy consumption is distributed among four main sectors which are industrial, building (residential), transportation and agriculture. Approximately 33% of total energy consumption in Turkey is used by residential sector. This situation makes it more important to insulate buildings in our country where fuel prices are too high. Turkey is divided into four climatic zones depending on average temperature degree days of heating. In this study, the four different cities of Turkey, Izmir, Istanbul, Ankara and Erzurum are selected to determine the optimum insulation thickness of the external wall of buildings. Optimum insulation thickness for six different energy sources (Soma coal, natural gas, coal, LPG, fuel-oil, diesel fuel) and two different insulants (extruded polystyrene, rock wool) is calculated and compared to each other. In addition, by using life cycle cost analysis method. Pay back period is calculated for each zone.
VARTM Process Improvement for Repeatable and Improved Mechanical Properties of Composite Laminates
Authors: Sharma Sanjay , Siginer Dennis A.
Published: July 2010

Quality of laminates produced by Seeman Composite Resin Infusion Molding Process (SCRIMP) is studied by comparing their Fiber Volume fraction and void content. SCRIMP is a variant of Vacuum Assisted Resin Transfer Molding (VARTM). Manufacturing process parameters are then identified and varied to study the impact on mechanical properties of laminated composites. Modification to SCRIMP is carried out by infusing the resin under additional pressure. Optimal process parameters for this modified SCRIMP process are suggested to yield laminates that are repeatable and consistent in quality. Void content is reduced in the composite laminates by altering the vacuum pressure level. Thickness gradient commonly found in SCRIMP processed laminates is eliminated by allowing longer de-bulking time. Final laminate quality is measured using ASTM standardized mechanical testing.
A Classroom Experience in Control Systems Following an Intensive Nonlinear Control Design Research Project: Two Perspectives
Authors: Taylor Carrie-Anne , McDonald Dale B.
Published: July 2010

It has been well documented in the engineering education literature that introductory linear control systems courses present unique pedagogical challenges. Similarly, it has been reported that engaging undergraduate students in control systems research is challenging. The control of nonlinear systems is the focus of much research; Therefore, a paradox exists; research programs involving undergraduate students are often conducted in a “nonlinear before linear” fashion. Prior research by the authors approached this paradox by investigating whether a meaningful research project in nonlinear control systems could be conducted. While the author and co-author were willing to execute this research (despite the intense time commitment), this type of project is not sustainable long-term unless the significant time invested results in Item 1) illumination of new pedagogical techniques that generalize to each student in the linear control systems course (not just participants in the research project). This manuscript will describe in detail Item 1). Given the student and faculty mentors experience in the nonlinear controls research project and the student’s experience in the linear control systems course, pedagogical insights gained through this endeavor will be detailed by the faculty member. These are meant to close the loop of instructor assessment of the course during preparation for future offerings. Therefore, the undergraduate student directly provides an accounting of the experiences throughout the research program and introductory control systems course. The result is a proposed pedagogical approach to be implemented by three distinct methodologies. Methodology (1) Traditional lecture format, Methodology (2) Targeted physical or hands-on experiences where students are exposed to a controlled system/process commonly seen in industry, and Methodology (3) Direct student participation in the design of certain aspects of course materials.
Patterns of Secondary Flow Field in a Circular Tube Caused by Corona Wind Using the Method of Characteristics
Authors: Baghaei Lakeh Reza , Molki Majid
Published: July 2010

Corona discharge is widely known as an effective method for improving the characteristics of the flow field and enhancing heat transfer. Distribution of charge density and electric field form a Coulomb body force which acts on the charged particles within the fluid and generates a secondary flow field. The thermal enhancing effects of corona wind are normally dominant in low Reynolds numbers or free convection problems. Although the governing differential equations of corona discharge are relatively simple, solving these equations by conventional computational methods does not yield a smooth solution for charge density and electric field. In particular, the results obtained from finite-volume method suffer from dispersion errors and fluctuations which lead to distorted values of electric body force, and consequently a distorted secondary flow. In this study, the corona discharge in a circular tube with the electrode positioned at the tube centerline is considered. An exact solution for charge density, electric field, and potential distribution along the radius of the tube has been derived analytically using a Lagrangian formulation for the charge density and the Method of Characteristics. It was found that the results of this method do not show any fluctuations or dispersion effects on charge density and electric field. The solution of the electric field provided a body force which was used in the Navier-Stokes equations to obtain the secondary flow in the cross section of the tube. In this paper, the electric and fluid flow fields are presented. The results are compared with those obtained by other computational methods and the differences are discussed.
Bubble Dynamics Under Forced Oscillation in Microgravity Environment
Authors: Movassat Mohammad , Ashgriz Nasser , Bussmann Markus
Published: July 2010

Two-dimensional numerical simulation of bubble dynamics in microgravity is performed employing a Volume of Fluid (VOF) solver. Shape oscillation and deformation of bubbles under forced vibration are studied. Coupling between the oscillatory translational motion and shape deformation results in nonlinear behavior of bubbles at high amplitudes and frequencies. As a result of oscillation of the buoyancy force, the pressure field around the bubbles oscillates and bubbles interact with each other. Effect of vibration frequency and amplitude and liquid to gas density ratio on the shape of bubbles and bubble-bubble interaction is studied. It is shown that the shape of the bubbles in response to the forced vibrations mainly depends on the acceleration of the vibration.
A Novel Bi-Stable Force Sensor: Theory and Modeling
Authors: Hassanpour Pezhman A. , Nieva Patricia M. , Khajepour Amir
Published: July 2010

In this paper, a novel sensing mechanism is introduced. This mechanism consists of a clamped-clamped beam and two parallel electrodes. An analytical model of the system, that takes into account the mechanical linear and nonlinear stiffnesses as well as the nonlinear electrostatic force, is developed. The time response of the system to a disturbance is derived while the applied voltage is increasing at a constant rate. It has been shown that the voltage, that destabilize the beam, can be used as a measure of the axial force in the beam. This technique can be used in the development of new type of sensors.
Integrated Automation System for Weighing and Blending Process Based on DCS
Authors: Ku Xiangchen , Ma Wei , Ling Ling , Li Jishun
Published: July 2010

Weighing and blending process is an important step of industrial and agricultural production. Traditionally, the simplest way of weighing and blending is to weigh the variety of raw materials manually and mix them together. There are some disadvantages of this method, such as measuring inaccurate, low productivity and labor-intensive. The comparatively advanced method is making use of the computer control technology to realize automatic weighing and blending according to predetermined formula. According to the production characteristics and technological requirements of a certain chemical product, an integrated control system of weighing and blending for liquid raw material based on DCS (Distributed Control System) is developed in this paper. The system is composed of IPC (Industrial Personal Computer), ADAM data acquisition modules, weighing sensor and execution unit. The 485 bus is adopted to transmit data between the different equipments. With the support of SQL Server 2000, the process control and production management of weighing and blending are realized with C++ builder 6.0. The integrated system can be divided into three subsystems, namely, the process control subsystem, the production monitoring subsystem and the production information management subsystem. The application result indicates that this system improves the production efficiency and stabilizes the production process.
Mechanical Properties of PBS Plastic Reinforced by Paper Using Waste Silk
Authors: Song Ruoyuan , Ino Haruhiro , Kimura Teruo
Published: July 2010

Considering the efficient recycling of waste silk resource, the biodegradable composite consisting of PBS matrix and pure silk paper was prepared by hot compression molding. Beating treatment is adopted to modify silk fibroin and enhance the composite, and the corresponding mechanical properties and morphologies were studied detailedly. The results showed that beating treatment could realize the fibrillation of fibroin and improve the paper’s tensile strength, and proper beating treatment to fibroin could also improve the mechanical properties of silk paper reinforced PBS composite. The tensile, flexural and impact resistance properties of this green composite were improved remarkably with fiber loading increasing. Especially for impact resistance, it was improved 154% at 40 wt% fiber loading compared with PBS control.
Natural Convection With Non-Newtonian Shear-Thinning Power Law Fluids in Inclined Two Dimensional Rectangular Cavities
Authors: Khezzar Lyes , Siginer Dennis
Published: July 2010

Steady two-dimensional natural convection in rectangular cavities has been investigated numerically. The conservation equations of mass, momentum and energy under the assumption of a Newtonian Boussinesq fluid have been solved using the finite volume technique embedded in the Fluent code for a Newtonian (water) and three non Newtonian carbopol fluids. The highly accurate Quick differential scheme was used for discretization. The computations were performed for one Rayleigh number, based on cavity height, of 105 and a Prandtl number of 10 and 700, 6,000 and 1.2×104 for the Newtonian and the three non-Newtonian fluids respectively. In all of the numerical experiments, the channel is heated from below and cooled from the top with insulated side-walls and the inclination angle is varied. The simulations have been carried out for one aspect ratio of 6. Comparison between the Newtonian and the non-Newtonian cases is conducted based on the behaviour of the average Nusselt number with angle of inclination. Both Newtonian and non-Newtonian fluids exhibit similar behavior with a sudden drop around an angle of 50° associated with flow mode transition from multi-cell to single-cell mode.
A Basic Numerical Study of the Effect of a Hot Air Vent on the Heat Transfer Rate From a Cold Window
Authors: Oosthuizen Patrick H.
Published: July 2010

In colder climates hot air vents are often mounted below a cold window to improve thermal comfort of the occupants. The presence of the vent alters the rate of convective heat transfer to the window and changes the air-flow pattern near the window and this has here been numerically studied. The situation considered in this study is an approximate model of most real situations. The window is represented by a plane isothermal section recessed into the wall, this window section being colder than the room air far from the window. The vent is assumed to be placed against the wall and to have a uniform discharge velocity which is normal to the vent surface. The vent has been assumed to be centrally located below the window. The flow has been assumed to be steady and both laminar and turbulent flows have been considered. The fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being dealt with using the Boussinesq approach. The governing equations have solved using the commercial cfd code FLUENT, the k-epsilon turbulence model with buoyancy force effects fully accounted for having been used in the turbulent flow calculations. The solution has the following parameters: the Rayleigh number, the Reynolds number based on the vent discharge velocity, the dimensionless depth that the window is recessed, the dimensionless window-to-undisturbed-air temperature difference, the Prandtl number, the dimensionless width of the window, the dimensionless depth and width of the hot air vent, and the dimensionless vent discharge temperature-to-undisturbed-air temperature difference. Results have only been obtained for a Prandtl number of 0.7. The effects of the other dimensionless variables on the window Nusselt number and on the flow pattern and air temperature distribution near the window have been numerically determined.
Co-Current Stratified Gas-Liquid Flow in a Horizontal Pipe With Discharging Branches
Authors: Bowden Robert , Saleh Wael F. , Hassan Ibrahim
Published: July 2010

Experiments were performed in an adiabatic horizontal pipe with co-current stratified gas-liquid flow and a single discharge oriented at either 0, 45, or 90 degrees from horizontal. The study used air and water as the two fluid phases, operating at 312 kPa. The test section was scaled down from a typical CANDU header-feeder bank and used a pipe and discharge diameter of 50.8 mm and 6.35 mm, respectively. The objectives of the study were to provide quantitative two-phase measurements of the mass flow rate and quality at the pipe inlet, outlet, and discharge branch.
On Mutual Deflection for the Radial Rotating Jet Pressure Exchange Mechanism
Authors: Umar Muhammad , Garris Charles A.
Published: July 2010

The “Pressure exchange” is a novel concept in turbomachinery whereby two fluids, at different energy levels, come in direct contact with each other to transfer energy and momentum between them through non-steady interface pressure forces. The rotating jets of the high pressure primary fluid, often referred to as pseudoblades, resemble solid blades on the impeller of a conventional turbomachine. The low pressure secondary fluid, ahead of the pseudoblades, is pressurized by the action of interface pressure forces. The current paper seeks to provide an insight into the complex flow phenomena occurring inside the radial flow pressure exchange ejector. The primary mechanisms controlling the process are pressure exchange and mixing. The angular deviation, between an actual pseudoblade and the pseudoblade with no secondary fluid, was calculated for the first time. The results revealed that the angular deviation is small in the near field, where pressure exchange dominates, and becomes larger in the far field as the mixing layer tends to grow. If this new concept is shown to be viable for gas compression at sufficiently high pressure ratios, then, in refrigeration applications, it would enable environmentally benign refrigerants to replace the harmful chlorofluorocarbons (CFC) and reduce the effluence of greenhouse gases. Applications in many other areas, where conventional ejectors are currently used, are also possible.
Performance Based Cost Modeling of Phase Change Thermal Energy Storage for High Temperature Concentrating Solar Power Systems
Authors: Muren Russell , Arias Diego A. , Luptowski Brian
Published: July 2010

Sizing and cost models were developed for thermal energy storage (TES) systems utilizing cascaded phase change materials (PCM) as the storage media in a variety of configurations. The sizing model is based on an energy balance around a characteristic fundamental element of the system, consisting of a steel pipe embedded in a matrix of phase change material. Due to the transient behavior PCM system, the sizing model requires time and space integrations. The model accounts for decreases in thermal performance caused by precipitate formation on the surface of the pipe and predicts the resulting transient power output. The model calculates the required tank and pipe sizes, the amounts of heat transfer fluid and PCM, as well as the land area for the configuration. Using a cost metric approach, the cost of each system component is estimated. Furthermore, the effect of several technological pitfalls, including: pinch point heat transfer, precipitate buildup, and transient energy output have been investigated. Prices are shown to depend heavily on system configuration. Specifically, prices are shown to be most dependent on precipitate formation during discharge and consequently the size of the necessary heat transfer area of heat exchangers. The cost of different configurations vary from $40/kWh to $100/kWh.
Comparison of Numerical Modeling to Experimental Data in a Small, Low Power Data Center Test Cell
Authors: Cruz Ethan , Joshi Yogendra , Iyengar Madhusudan , Schmidt Roger
Published: July 2010

As the performance of Information Technology (IT) equipment continues to rise, so do the power dissipated and overall power density. Air cooling this increasing power has proved a significant challenge even at the data center level. In order to combat this challenge, Computational Fluid Dynamics and Heat Transfer (CFD/HT) models have been employed as the dominant technique for the design and optimization of both new and existing data centers. This study is a continuation of earlier comparisons of CFD/HT models to experimentally measured temperature and flow fields in a small data center test cell. It compares previously unpublished experimentally collected data for the 11 kW dissipation cases using three different layouts of perforated tiles to a CFD/HT model using eight turbulence models and a laminar flow model. Insight into the location of the deviation between the different turbulence models and experimental data are discussed, along with the computational effort involved in running the CFD/HT models. It was found that the laminar flow model and the Spalart-Allamaras turbulence model produced the smallest deviations from experimental data, but the former required only one twentieth of the computational effort of the latter.
A Fractal Approach for Modeling SOFC Electrode Mass Transport
Authors: Nelson George J. , Haynes Comas , Wepfer William
Published: July 2010

Fractal modeling approaches are common in the study of porous media and may be applied to describe pore surface morphology and network topology within a porous medium. Fractal structures can serve as templates for the pore structure and allow for the more detailed examination of diffusion phenomena within pore structures. In the present work a fractal pore morphology model is applied toward modeling diffusion within the electrochemically active region of an SOFC electrode. The porous electrode is separated into bulk and electrochemically active regions. Within the bulk electrode a one-dimensional model is applied based on the dusty-gas formalism assuming volume average microstructural parameters. The electrochemically active region is modeled using a two-dimensional finite element model based on a Koch pore cross-section as a fractal template. This fractal model is compared to a one-dimensional transport model applying the common assumption of a planar reaction zone. Performance variations that may exist for electrodes with the same average bulk properties are investigated in initial studies. These studies allow for exploration of the merits of fractal approaches in modeling diffusive transport within porous SOFC electrodes.
A Comparative Study of Different Control Strategies for a Magnetorheological Haptic System
Authors: Zakeri Vahid , Arzanpour Siamak
Published: July 2010

Magnetorheological (MR) dampers are a new generation of adjustable dampers that can generate large resistive forces against motion with low power. This feature is a unique characteristic that idealizes them for many applications including haptics. A haptic interface system is developed that includes a magnetorheological (MR) damper on the master side and a linear DC motor on the slave side. In this system, the slave motion follows the master and the force experienced by the slave is reflected to the master. The major challenge in this arrangement is control of the MR damper to create the desired resistive force. This paper investigates the different strategies for controlling the MR damper. In haptics, rather than the perfect tracking of a desired force, it is more convenient to generate a force in the master that is ‘similar’ to the actual force sensed by the slave. In addition, in many applications of MR dampers such as suspension systems, seismic response reduction, etc., perfect tracking is unneeded. Considering all of these factors, this paper proposes the concept of ‘similarity’ between the desired force and the resistive force of the MR damper. ‘Similarity’ means whenever the desired force is large, the resistive force should also be large, and whenever the desired force is small, the resistive force should then be small. Based on this concept, three controllers are applied and tested in both open loop and closed loop schemes: a gain controller, a fuzzy logic controller, and a lookup table controller. The results of these controllers are evaluated and compared to each other with respect to smaller time delays and smaller and smoother control inputs. In the absence of major differences in the results, the closed loop gain controller appeared to be a suitable choice for control because of its simple scheme and its ease of application.
High Temperature SiC Power Module Packaging
Authors: Rowden Brian , Mantooth Alan , Ang Simon , Lostetter Alex , Hornberger Jared , McPherson Brice
Published: July 2010

Wide band gap semiconductors such as silicon carbide (SiC) provide the potential for significant advantages over traditional silicon alternatives including operation at high temperatures for extreme environments and applications, higher voltages reducing the number of devices required for high power applications, and higher switching frequencies to reduce the size of passive elements in the circuit and system. All of these attributes contribute to increased power density at the device and system levels, but the ability to exploit these properties requires complementary high temperature packaging techniques and materials to connect these semiconductors to the system around them. With increasing temperature, the balance of thermal, mechanical, and electrical properties for these packaging materials becomes critical to ensure low thermal impedance, high reliability, and minimal electrical losses. A primary requirement for module operation at high temperatures is a suitable high temperature attachment technology at both the device and module levels. This paper presents a transient liquid phase (TLP) attachment method implemented to provide lead-free bonding for a SiC half-bridge power module. This module was designed for continuous operation above 250 °C for use as a building block for multiple system level applications including hybrid electric vehicles, distributed energy resources, and multilevel converters. A silver-based TLP system was used to accommodate the device and substrate bond with a single TLP system compatible with the device metallurgy. A SiC power module was built using this system and electrically tested at a 250 °C continuous junction temperature. The TLP bonding process was demonstrated for multiple devices in parallel and large substrate bonding surfaces with traditional device and substrate metallization and no requirements for surface planarization or treatment. The results are presented in the paper.
Transformative Learning Opportunities Help Prepare Students for Their Future Careers
Authors: Scho¨nning M. Alexandra
Published: July 2010

A large percentage of the mechanical engineering students at the University of North Florida have been extensively exposed to transformative learning opportunities over the past five years. Through collaborative efforts with local industry and other institutions, the students have had the opportunity to utilize their engineering knowledge in real-world applications. Students engaged in these projects have improved several of their technical skills in, for example, computer-aided engineering, design, mechanical testing, and analysis. Nontechnical objectives of these projects include improving communication skills, learning how an engineering firm functions, and learning how to research relevant data. Technical and non-technical objectives were met by students working on engineering projects sponsored by partnering collaborators. The collaborators defined the engineering project and the students, under the supervision of faculty, carried out the project tasks. This paper discusses a number of different transformative learning opportunities for students; it discusses the educational objectives and skills developed for each project, and it describes how the students are better prepared for their future careers through their involvement with the program. Many of the students have found rewarding engineering careers and a few have continued to pursue graduate degrees. Furthermore, the paper discusses how the efforts of this program are aligned with the mission of the University in that it heavily emphasizes transformational learning opportunities for the whole university community.
A Case Study on Course-Based Outcomes Assessment to Enhance Student Learning and Course Delivery in the Engineering Sciences Core Curriculum
Authors: Hensel Edward , Ghosh Amitabha
Published: July 2010

A formal two-loop learning outcomes assessment process has been implemented in the mechanical engineering department at Rochester Institute of Technology. The outer loop establishes high-level outcomes and objectives for the program, while the inner loop provides assessment of achievement and feedback for improvement. Planning for the two-loop assessment process was initiated in academic year 2005–06 with the establishment of four faculty workgroups, with each group assigned responsibility for conducting outcomes assessment on a subset of the ME core curriculum. The engineering science core curriculum inner loop assessment process was initiated in AY2006–07 and continues today. Results of a three year longitudinal study of the engineering science course learning outcomes assessment and the details of the assessment and continuous improvement process are described herein. The three year study period encompassed 83 sections of five courses, with a cumulative student enrollment of 2,853 individuals. Sample data from the longitudinal study of the fluid mechanics course (reviewing 19 sections with a cumulative enrollment of 619 students) is presented, to illustrate improvement of student learning through refinement of the course delivery. A discussion of the assessment process, lessons learned, and conclusions are presented.
Machine Design Project and Mechanics Education
Authors: Atiqullah Mir M.
Published: July 2010

Traditional machine design is essentially applied mechanics and builds upon engineering mechanics topics: strength of materials, statics and dynamics. The current Mechanical Engineering Technology program includes a sequence of mechanics courses leading to the upper level course of Machine Design. Our program emphasizes strong background in computer aided modeling and drafting as well as manufacturing, a combination much appreciated by the employers in the region. Thus our senior class is well prepared for the capstone machine design course which requires not only an electronic design solution but also a prototype. A design group was assigned the design of a beam testing device which would load an instrumented beam in various ways and the results will be measured in terms of stress and deflection. Moreover the group was charged with the task of visualizing this device being used in the junior level strength of materials laboratory class. It would require the student team to conceive, design, model using CAD, analyze, prototype, test and finally develop a set of laboratory experiments. The project will not only train the design team with the design process and modern analysis and simulation tools, but also the mechanics education behind beam loading and resulting stress will be reinforced. Developing the Instructor’s User Manual was also an exercise in thoughtful insight into the mechanics of beams. The completed rig is being used in our Strength of Materials laboratory class which virtually eliminated the 15 feet beam that was used earlier. The test rig made it possible to simulate multiple loading conditions and tested within one lab session which was impossible using the large beams. The design team took special interest and pride in completing this ‘practical’ project. This paper describes the design course, the prerequisite structure, the design project format and expectations, the design and engineering specifications and summary features of the test rig. Limited usability survey data demonstrates the ease and versatility of the new rig compared to the large beam testing setup.
Workspace and Singularity Characteristics of 3-DOF Planar Parallel Robots
Authors: Huang Ming
Published: July 2010

A study of workspace and singularity characteristics is presented for two common types of 3-DOF planar parallel robot manipulators. The robots considered feature a kinematic structure with 3 in-parallel actuated, R-R-R and R-P-R serial chain geometries. In this study, computer simulations aided with graphic visualization were used to characterize the complete pose workspace (for ranges of both position and orientation) and the singularity inherent to the systems. Parametric studies have also been performed to ascertain the way in which both characteristics vary with respect to various geometric parameters such as pivot location, link length, and platform size for end-effector. Results are shown by way of a unique composite ratio of the available workspace to the density of singularity within that workspace.
Control of a Robotic UV Curing Process With Thermal Vision Feedback Through Two IR Cameras
Authors: Zeng Fan , Ayalew Beshah , Omar Mohammed
Published: July 2010

Robotic ultra-violet (UV) curing is considered to be one of the effective ways to replace the current convection-based methods in various manufacturing processes due to its fast curing rate and high energy efficiency. This paper presents a closed-loop control of a robotic UV curing system by using thermal vision feedback through two infrared (IR) cameras. The proposed approach is developed based on a mathematical analysis of the fundamental UV curing process and the integration of the local and global IR cameras in a cascade manner. A computer simulation study is conducted to evaluate the proposed strategy by regarding two control variables: the radiant intensity of the UV heater and the sweeping speed of the robot end effector. The results indicate that controllers using either control variable can compensate for interferences and improve curing quality under this thermal-vision-based architecture.
Microengineered Surfaces for Thin Film Evaporation for Enhanced Heat Dissipation
Authors: Xiao Rong , Wang Evelyn N.
Published: July 2010

The increasing performance of integrated chips has introduced a growing demand for new thermal management technologies. While various thermal management schemes have been studied, thin film evaporation promises high heat dissipation rates (1000 W/cm2) with low thermal resistances. However, methods to form a thin liquid film including jet impingement and sprays have challenges associated with achieving the desired film thickness. In this work, we investigated novel microstructures to control the thickness of the thin film where the liquid is driven by capillarity. Micropillar arrays with diameters ranging from 2 μm to 10 μm, spacings between pillars ranging from 5 μm to 10 μm, and heights of 4.36 μm were studied. A semi-analytical model was developed to predict the propagation rate of the liquid film, which was validated with experiments. The heat transfer performance was investigated on the micropillar arrays with microfabricated heaters and temperature sensors. The behavior of the thin liquid film under varying heat fluxes was studied. This work demonstrates the potential of micro- and nanostructures to dissipate high heat fluxes via thin film evaporation.
A Conceptual Taxonomy Study of Sustainable Product Design Processes
Authors: Flores Caldero´n Alejandro , Borja Vicente , Lo´pez Parra Marcelo , Rami´rez Reivich Alejandro C.
Published: July 2010

The evolution of methods on sustainable product design has been wining a high level of maturity showing the possibility of being applied to different types of products. This paper shows a comparative study of recent sustainable product design approaches. The study was carried out developing a three level taxonomy to compare the approaches: sustainable development, sustainable product development and sustainable product design tasks. The compared approaches were selected because they were considered the most robust and referred in the literature. The study provides designers an overview of the methods, vision, purpose and concepts used by the selected approaches to sustainable product design.
Thermal Management of Telecommunication Cabinets Using Thermoelectric Coolers
Authors: Mariam Feroz Ahamed Iqbal , Mulay Veerendra , Karajgikar Saket , Agonafer Dereje , Hendrix Mark
Published: July 2010

Telecommunication cabinets are standalone outdoor enclosures, which houses electronic components and switching devices. These electronics are powered by DC power and have backup batteries to support them in the event of power supply failure. The heat loads on these cabinets are dependent not only on the heat dissipated by the internal components but also by solar heating. Therefore the ambient temperatures around the cabinet, based on the location and time of day can vary anywhere from −40°C to +50°C. The life of a battery is dependent on the nature of the load applied, recharging conditions and most importantly ambient temperatures. Batteries supporting the cabinet electronics are either housed within the cabinet or in compartments attached to the cabinet. For long standing battery life, the temperature inside these battery compartments should be kept below 25°C [1]. Active cooling using air-conditioners are often used to achieve this, but air-conditioners are difficult to backup and are high in maintenance. A more convenient way to cool the battery compartments are to use Thermo-electric Coolers (TEC) as they are less bulky and quite. This paper discusses the validation of results of numerical modeling of a telecommunication cabinet, which uses TEC to cool its battery compartment, with experimental data for the corresponding real world model.
Development and Testing of a Rotary-Vane Two-Phase Refrigerating Expander
Authors: Mahmoud A. M. , Sherif S. A. , Lear W. E.
Published: July 2010

Rotary-vane positive displacement machines have played an important role for many years in refrigeration and air compression applications because of their inherent simplicity and reliability. This paper details the development and testing of a rotary-vane two-phase expander for the purpose of work recovery in an air-cooled chiller. The paper describes the methodology used to design an expander for two-phase flow from a single-phase compressor and an air-motor. Input from detailed analytical models developed by the authors are used to improve the expander design with respect to internal leakage losses and friction. Controls and performance testing are also presented. Directions for future research are highlighted.
Thermal-Mechanical Analysis of Annular Target Design for High Volume Production of Molybdenum-99 Using Low-Enriched Uranium
Authors: Turner Kyler K. , Solbrekken Gary L. , Allen Charlie W.
Published: July 2010

Techenetium-99m is a diagnostic radioactive medical isotope that is currently used 30,000 times a day in the United States. All supplies of techenetium-99m’s parent isotope molybdenum-99 currently originate from nuclear reactor facilities located in foreign countries and use highly enriched uranium (HEU). In accordance with the Global Threat Reduction Initiative all uranium used in future molybdenum-99 production will use low enriched uranium (LEU). A design approach to using LEU in a cost-effective manner is to use a target that is based on LEU foil. A potential failure mode for the LEU foil based target is temperature excursion during irradiation due to poor thermal contact between the foil and the target cladding. The purpose of this study is to establish the theoretical basis for experimentally measuring the thermal contact resistance. Replicating in service heating conditions is nearly impossible when testing the thermal contact resistance as part of a study to establish LEU foil warpage tolerances, thus it is necessary to establish an alternate heating configuration that will allow a conservative estimate of the contact resistance. Thermal and mechanical analysis suggests that external heating of an annular target will place the interface into a state that will over-estimate the contact resistance relative to use conditions. Further, the magnitude of the heat load used for testing can be adjusted to control the degree of overestimation.
Interface Cracks Problems in Composites With Piezoelectric and Thermal Effects
Authors: Duduchava R. , Buchukuri T. , Chkadua O. , Natroshvili D.
Published: July 2010

We investigate three–dimensional interface crack problems (ICP) for metallic-piezoelectric composite bodies with regard to thermal effects. We give a mathematical formulation of the physical problem when the metallic and piezoelectric bodies are bonded along some proper parts of their boundaries where interface cracks occur. By potential methods the ICP is reduced to an equivalent strongly elliptic system of pseudodifferential equations (ψDEs) on overlapping manifolds with boundary, which have no analogues in mathematical literature. We study the solvability of obtained ψDEs on overlapping manifolds with boundary by reduction to ψDEs on non-overlapping manifolds with boundary in different function spaces. These general results are applied to prove the uniqueness and the existence theorems for the original ICP-Problem.
Seismic Evidence for Active Underplating Below the Megathrust Earthquake Zone in Japan
Authors: Kimura Hisanori , Takeda Tetsuya , Obara Kazushige , Kasahara Keiji
Published: July 2010

Quake Control

Large earthquakes occur at the margins of two colliding plates, where one plate subducts beneath the other at a shallow angle. These megathrust earthquakes often cause destructive tsunamis owing to the displacement of large volumes of water at the fault along the plate boundary. Two related studies of the seismic structure of subduction zones attempt to reveal the underlying mechanisms of megathrust earthquakes (see the Perspective by

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(p.
210
) compared seismic reflection images and microearthquake locations at the Philippine Sea plate where it subducts obliquely beneath Japan. The locations of repeating microearthquakes correspond to active transfer of material from the subducting plate to the continent—a process only previously assumed from exhumed metamorphic rocks.

Dean
et al.

(p.
207
) observe an expansive structure in the sea-floor sediment near the location of the 2004 and 2005 Sumatra earthquakes in Indonesia that suggests sediment properties may influence the magnitude of megathrust ruptures and their subsequent tsunamis.
Comment on “Differential Sensitivity to Human Communication in Dogs, Wolves, and Human Infants”
Authors: Marshall-Pescini S. , Passalacqua C. , Valsecchi P. , Prato-Previde E.
Published: July 2010

Topál
et al
. (Reports, 4 September 2009, p. 1269) showed that dogs, like infants but unlike wolves, make perseverative search errors that can be explained by the use of ostensive cues from the experimenter. We suggest that a simpler learning process, local enhancement, can account for errors made by dogs.
Mesoscopic Percolating Resistance Network in a Strained Manganite Thin Film
Authors: Lai Keji , Nakamura Masao , Kundhikanjana Worasom , Kawasaki Masashi , Tokura Yoshinori , Kelly Michael A. , Shen Zhi-Xun
Published: July 2010

Separating Under Strain

Complex oxides, such as cuprate superconductors and perovskites, often exhibit microscopic phase separation, where two or more phases coexist on the macroscopic scale but are spatially separated on the microscopic scale.

Lai
et al.

(p.
190
) studied a configuration often found in technological applications, a strained manganite thin film placed on a substrate. Microwave impedance microscopy, which differentiates between conducting and insulating areas on the thin film, allowed visualization of the phase separation as the magnetic field was varied. A network of conducting domains was observed whose orientation and characteristic length scales suggest that the substrate-exerted strain was involved in network formation.
HIV Persistence and the Prospect of Long-Term Drug-Free Remissions for HIV-Infected Individuals
Authors: Trono Didier , Van Lint Carine , Rouzioux Christine , Verdin Eric , Barré-Sinoussi Françoise , Chun Tae-Wook , Chomont Nicolas
Published: July 2010

HIV infection can persist in spite of efficacious antiretroviral therapies. Although incomplete inhibition of viral replication may contribute to this phenomenon, this is largely due to the early establishment of a stable reservoir of latently infected cells. Thus, life-long antiviral therapy may be needed to control HIV. Such therapy is prone to drug resistance and cumulative side effects and is an unbearable financial burden for regions of the world hit hardest by the epidemic. This review discusses our current understanding of HIV persistence and the limitations of potential approaches to eradicate the virus and accordingly pleads for a joint multidisciplinary effort toward two highly related goals: the development of an HIV prophylactic vaccine and the achievement of long-term drug-free remissions in HIV-infected individuals.
Long Noncoding RNA as Modular Scaffold of Histone Modification Complexes
Authors: Tsai Miao-Chih , Manor Ohad , Wan Yue , Mosammaparast Nima , Wang Jordon K. , Lan Fei , Shi Yang , Segal Eran , Chang Howard Y.
Published: July 2010

A Lot of HOTAIR

The roles of several classes of small (<50 nucleotides) noncoding RNAs are beginning to be defined in molecular detail, whereas the function of most of the long (∼200+ nucleotides), intergenic noncoding (linc)RNAs found in most eukaryotic genomes remains something of a mystery. The HOTAIR lincRNA, which is transcribed from the mouse
HOXC
locus, binds to the Polycomb Repressive Complex 2 (PRC2) and recruits it to
HOXD
and other genes, where its histone methylase activity acts to repress gene transcription.

Tsai
et al.

(p.
689
, published online 8 July) now show that HOTAIR also binds to a histone demethylase enzyme, LSD1, part of the CoREST/REST repressor complex. LSD1 acts to remove transcription-activating histone marks, reinforcing the repressive activity of the PRC2 complex. HOTAIR thus functions as a platform for the coordinated binding of PRC2 and LSD1-containing complexes to genes, as revealed in a genome-wide analysis of PRC1/CoREST/REST co-regulated genes.
How Time Flies
From Eternity to Here
The Quest for the Ultimate Theory of Time

by Sean Carroll

Dutton, New York, 2010. 448 pp. $26.95, C$33.50. ISBN 9780525951339.
Authors: Jardine-Wright Lisa
Published: July 2010

Examining various explanations for why time has a direction, Carroll argues for the importance of conditions before the Big Bang.
The Legacy Plan
Authors: Couzin-Frankel Jennifer
Published: July 2010

After a long career, you're ready to close the lab and give away a lifetime's worth of specimens. Who will take them?
Tracing the Regional Rise of HIV
Authors: Cohen Jon
Published: July 2010

Detailed molecular analyses have revealed that HIV strains isolated in Belarus, Russia, Kazakhstan, and other countries in the former Soviet Union evolved from southern Ukrainian strains. But the factors behind the explosion of HIV in this region remain elusive.
Praised Russian Prevention Program Faces Loss of Funds
Authors: Cohen Jon
Published: July 2010

In 2006, then-President Vladimir Putin pledged increased support for HIV/AIDS programs, but the government recently declined to fund some key efforts.
Mannose-Binding Lectin Genotypes and Susceptibility to Epstein-Barr Virus Infection in Infancy
Authors: Friborg Jeppe T. , Jarrett Ruth F. , Koch Anders , Garred Peter , Freeland June M. L. , Andersen Andreas , Melbye Mads
Published: July 2010

In a cohort study of children <4 years of age in Greenland, mannose-binding lectin (MBL2) genotypes and Epstein-Barr virus (EBV) antibody levels were determined. EBV seropositivity was significantly lower and time to seroconversion increased in MBL-insufficient compared with MBL-sufficient children, indicating that MBL may be involved in primary EBV infection in infancy.