bluuebunny/crossref_metadata_2025 huggingface dataset:
Weakly-Singular Integral Equations for Steady State Flow in Anisotropic Porous Media Containing Discontinuity Surfaces
Authors: Rungamornrat Jaroon , Wheeler Mary F. , Gai Xiuli
Published: April 2008

In this paper, we present the development of the weakly-singular, weak-form fluid pressure and fluid flux integral equations for steady state Darcy’s flow in porous media. The integral equation for fluid flux is required for the treatment of flow in a domain which contains surfaces of discontinuities (e.g. cracks and impermeable surfaces), since the pressure integral equation contains insufficient information about the fluid flux on the surface of discontinuity. In this work, a systematic technique has been established to regularize the conventional fluid pressure and fluid flux integral equations in which the pressure equation contains a Cauchy singular kernel and the fluid flux equation contains both Cauchy and strongly-singular kernels. The key step in the regularization procedure is to construct a special decomposition for the fluid velocity fundamental solution and the strongly-singular kernel such that it is well-suited for performing an integration by parts via Stokes’ theorem. These decompositions involve weakly-singular kernels where their explicit form can be constructed, for general anisotropic permeability tensors, by the integral transform method. The resulting integral equations possess several features: they contain only weakly-singular kernels of order 1/r; their validity requires only that the pressure boundary data is continuous; and they are applicable for modeling fluid flow in porous media with a general anisotropic permeability tensor. A suitable combination of these weakly-singular, weak-form integral equations gives rise to a symmetric weak-form integral equation governing the boundary valued problem, thereby forming a basis for the weakly-singular, symmetric Galerkin boundary element method (SGBEM). As a consequence of that the integral equations are weakly-singular, the SGBEM allows standard C° elements to be employed everywhere in the discretization.
Study of Energy Methods to Strongly Nonlinear Vibrations in a Loudspeaker Cone-Shaped Shell
Authors: Zong F. D. , Zhang Z. L. , Fang J. W. , Yu Y. J. , Chen Q.
Published: April 2008

H. F. Olson points out that a loudspeaker cone-shaped shell, as a nonlinear oscillation system, can be described as the Classical Duffing Equation in low frequency range. Yoshinisa, a Japanese scholar, studied the nonlinear phenomena of the loudspeaker cone-shaped shell in low frequency range driven by a stable galvanic source, including the resonance frequency changing with amplitude and leap phenomena. But their research were not taken the influence of nonlinear magnetic field into account. Its work mostly related to getting solution of nonlinear differential equation by the Numerical Calculation, but it didn’t get approximate solutions. Through research and analysis of the experiment on the loudspeaker cone-shaped shell, we obtain the Generalized Duffing Equation that’s a strongly nonlinearity system which is used to describe the loudspeaker cone-shaped shell driven by a stable voltage source, it considers the nonlinearity of mechanical resilience and the magnetic field. This paper focuses on first finding the approximate solutions (limit cycles) of strongly nonlinear oscillations and nonlinear heteronomy of the loudspeaker cone-shaped shell in low frequency range by use of energy methods. They obtained the equation relating to the forced vibration amplitude with frequency and the corresponding relation about phase versus frequency, and analysed particularly complete stability of limit cycles belonged to the strongly nonlinear systems, and drew several important conclusions. (1) As to strongly nonlinear oscillations of the loudspeaker cone-shaped shell in low frequency range, it is only likely to appear main oscillation and odd-order sub-harmonic oscillations. But it cannot appear super-harmonic vibrations and even-order sub-harmonic vibrations. (2) As to strongly nonlinear oscillations of the loudspeaker cone-shaped shell in low frequency range, two cases about main oscillation and one third sub-harmonic oscillation whose approximate solutions accord with numerical solutions very well. (3) It is worthy to study strongly nonlinear oscillations of commonly thin shell structure such as a loudspeaker cone-shaped shell by use of energy methods, and we will continue to carry out this research.
Optimization of High Heat Flux Thermal Energy Storage With Phase Change Materials
Authors: Du Jianhua , Chow Louis C. , Leland Quinn
Published: April 2008

Future military systems such as high energy lasers and high power microwaves will require the development of high flux thermal energy storage (TES) systems to reduce the mass and volume of the thermal management system. Phase change materials (PCMs) should have a large latent heat of fusion. The PCM is usually impregnated into a solid matrix of high thermal diffusivity so that unacceptably large temperature increase at the heat source can be avoided. In this paper, a model was established for a TES medium with PCM filled channels. Two coupled one-dimensional transient heat conduction equations were solved to simulate the conjugated heat transfer in the wall and solid/liquid phase change in the PCM. A parametric study was conducted to investigate the effects of the channel configuration on the TES performance. An optimization study was carried out to minimize the temperature spike at the heating surface while maximizing the rate of heat absorption and specific storage capacity. The result of this study can also be used to provide an optimal design for a wax-filled carbon foam structure.
Innovative Laboratorial Teaching in Traditional Mechanical Courses
Authors: Yuan Yanhong , Yu Hong , Wang Wenzhong , Tang Zhedong , Hu Xudong
Published: April 2008

Laboratorial teaching (Lab time) is very important during a four year learning for an engineering student. Innovative lab equipments play a part in the teaching. The goal of lab time is to offer students a insight into the basic theory of mechanism, to practice their ability of approaching a real machine. Display visually the phenomena of mechanical foundation is also another aim of the teaching phase. Traditional lab equipment is very limited in China. The typical teaching methodology is to show students the experimental result by a faculty adviser. Seldom do the students have the chance to involve in the experiments [1]. So the teaching results are not as good as expected. During the ten year reformation of the teaching method, authors developed a series of innovative laboratorial equipment, which are microcontroller embedded and connected to a computer. The list of the equipment includes: Typical Mechanical Motion, Gear Transmission, Belt Transmission, Chain Transmission, Dynamic Characteristic of Bolt Connection, Dynamic Characteristic of Machine, Balance of Cylinder, etc. With the help of that equipment, students can do their experiments by themselves now. They can gain enough “hands on” experience during the Lab time. Further more, all of the experimental results can be displayed in the computer in analytical format. It helps students to insight the mechanics that hide out in the physical phenomena. This paper describes the effort of author’s works. And results we got will be evaluated here.
Automated Guided Vehicle Systems Trends in Technology and Application
Authors: Schulze L. , Lucas M. , Baumann A.
Published: April 2008

The automation of transportation in the production, trade and service sector is a key point in the optimization of logistics. For this task Automated Guided Vehicle Systems (AGVS) provide special benefits. Main points of these systems are the central controlled Automated Guided Vehicles (AGV). In the beginning, the vehicles were guided by optical or inductive guidelines. The main disadvantages of guidelines are the inflexibility regarding the modification and changing of the routing and the necessity of installations on or in the ground. New developments result in guidance without guidelines. An example of this development is the laser guidance for the AGV. The AGVs have a high individuality. They are usually developed and constructed for the demands of a special application and are therefore unique. Due to this individuality a special problem is the wide variety of maintenance and part logistics. Research and development leads to new approaches to this question. Examples are the implementation of the modulation of AGV and the implementation of construction kits. Further points are the reduction of complexity of the modules and the establishment of compatibility between various AGVS-producers. Another main direction of the development is the supplementary automation of standard fork lift trucks. At the Department of Planning and Controlling of Transport Systems and Warehouses, University of Hanover (PSLT), an AGV was developed and established for further research. This AGV is used for verification and validation of new hardware and software components, like safety, navigation or controlling parts. It is strictly modular composed and offers a high adaptation in different directions. Based on the AGVS-Statistic Europe, which is created and administrated by the department PSLT, the main application of AGVS and the industrial sectors in which they are used are analyzed. With this database developments and current trends in the AGVS-sector are identified. More and more the AGVS-producers have to offer their products in a global competition. The relevance of AGVS in the area of automation will increase in the future.
Trajectory Tracking Control of Flexible Manipulators Considering Modeling Discrepancy
Authors: Kilicaslan S. , Ider S. K. , Ozgoren M. K.
Published: April 2008

A new method is proposed for the end-effector motion control of flexible manipulators. The dynamic equations of flexible robot manipulators are partitioned as pseudostatic equilibrium equations and deviations from them. The pseudostatic equilibrium considered here is defined as a hypothetical state where the end-effector motion variables have their desired values while the elastic deformations are instantaneously constant. Then, the control torques for the pseudostatic equilibrium are computed and the feedback stabilization of the deviation equations is achieved using strain gage and joint variable or tip point variable measurements. A planar two link robot with flexible forearm is taken into consideration for demonstration of the method. The elasticity of the forearm is approximately described by the first two modes and a controller is designed using this two-mode model. Furthermore, in order to investigate the effects of modeling discrepancies, a “submodel controller” is considered using a model that has only the first mode. The performances of these two controllers are compared by means of simulations. It is observed that the proposed control method does not seem to be sensitive to the number of modes included in the model of the manipulator.
Parametric Study of Temperature Field During the Cooling Stage for Extrusion Blow Molded Part
Authors: Yin Zhan-Song , Huang Hon-Xiong
Published: April 2008

A mathematical model of the transient heat transfer during the cooling and solidification of extrusion blow molded part was developed. The temperature profiles were obtained by using finite element (FE) code POLYFLOW to solve the mathematical model. The influences of blow mold material, internal heat transfer coefficient, part thickness, and initial parison temperature on cooling were analyzed. An orthogonal experimental design was applied to determine the significance of four process parameters on the time for opening the mold. The calculated results were estimated by analysis of variance (ANVOA). An artificial neural network (ANN) model based on the numerical simulation data was developed to build for predicting the temperature distribution across thickness. The results showed that ANN approach was an effective method for analyzing the cooling of blow molded part.
A Stress-Dependent Hysteresis Model for Ferromagnetic Transducer Materials
Authors: Smith Ralph C. , Dapino Marcelo J.
Published: April 2008

This paper focuses on the development of a model which characterizes the nonlinear and hysteretic stress-dependence inherent to magnetic transducer materials operating in high drive regimes. The model builds upon a previous ferromagnetic characterization framework based on energy analysis at the lattice level in combination with stochastic homogenization techniques. Aspects of the stress-dependent magnetomechanical model are illustrated through comparison with experimental steel data.
Non-Linear Vibrations of Plates Under Thermal and Mechanical Loads
Authors: Ribeiro P.
Published: April 2008

The geometrically non-linear vibrations of plates under the combined effect of thermal fields and mechanical excitations are analyzed. With this purpose, an accurate model based on a p-version, hierarchical, first-order shear deformation finite element is employed. The constitutive material of the plates is linear elastic and isotropic. The equations of motion are solved in the time domain by an implicit time integration method. The temperature and the amplitude of the mechanical excitation are varied, and transitions from periodic to non-periodic motions are found.
Improved Scheme of Analysis and Stress Computation in Lap Welded Joints With Fillet Welds Tranverselly and Longitudinally Loaded
Authors: Goytisolo Rafael , Hernandez Hernan , Moya Jorge , Jackson Inga M.
Published: April 2008

In this paper, a new scheme of analysis is used for the stress calculation in the throat area of the weld in lap joints with fillet welds transversely and longitudinally loaded. New calculation expressions are obtained that belong together better than the classic expressions with relationship to the values obtained by the Finite Elements Analysis.
A Hybrid Rapid Microfluidic Mixer Utilizing Electrokinetic Relay and Asymmetric Flow Geometries for Lab-on-a-Chip Applications
Authors: Wang Yiou , Zhe Jiang , Dutta Prashanta , Cheng Gary J.
Published: April 2008

Numerical study on a rapid micromixer based on hybrid electrokinetic relay and asymmetric serpentine structures is presented. Effective mixing of liquids is essential in many applications such as drug delivery, DNA analysis/sequencing, pheromone synthesis in micro bioreactors, and biological/chemical agent detections. Rapid mixing can reduce the analysis time and permit high throughput in lab-on-a-chip or micro total analysis systems (μTAS). The proposed hybrid mixing takes advantages of both mixing enhancements induced by asymmetric flow geometries and the electrokinetic relay actuating. Simulation results show that the micro mixer is able to achieve high mixing efficiencies (94.3%) in short time (1.2s). Effects of relay frequency, electric field and channel geometry on micro-mixing have been conducted. Numerical results show that electrokinetic relay at an appropriate frequency causes effective micromixing. Moreover asymmetric flow geometries are critical for ultra effective mixing.
Scavenging Energy From Piezoelectric Materials for Wireless Sensor Applications
Authors: Green Christopher , Mossi Karla M. , Bryant Robert G.
Published: April 2008

Wireless sensors are an emerging technology that has the potential to revolutionize the monitoring of simple and complex physical systems. Prior research has shown that one of the biggest issues with wireless sensors is power management. A wireless sensor is simply not cost effective unless it can maintain long battery life or harvest energy from another source. Piezoelectric materials are viable conversion mechanisms because of their inherent ability to covert vibrations to electrical energy. Currently a wide variety of piezoelectric materials are available and the appropriate choice for sensing, actuating, or harvesting energy depends on their characteristics and properties. This study focuses on evaluating and comparing three different types of piezoelectric materials as energy harvesting devices. The materials utilized consisted on PZT 5A, a single crystal PMN 32%PT, and a PZT 5A composite called Thunder. These materials were subjected to a steady sinusoidal vibration provided by a shaker at different power levels. Gain of the devices was measured at all levels as well as impedance in a range of frequencies was characterized. Results showed that the piezoelectric generator coefficient, g33, predicts the overall power output of the materials as verified by the experiments. These results constitute a baseline for an energy harvesting system that will become the front end of a wireless sensor network.
Prediction of the Sugar Mill Shaft Failure Using a Fracture Mechanics Method
Authors: Arzola Nelson , Goytisolo Rafael , Perez Ramon , Fernandez Ariel
Published: April 2008

A fracture mechanics based method and a new analysis scheme is presented for determining the residual life of sugar mill shafts with semi elliptical cracks. Due to the multiaxial stress field, an equivalent strain energy release rate stress intensity solution is used in the Paris law to predict crack growth. Ultrasonic inspection intervals for the shafts are established. The crack zone evaluated is located in the shoulder of the bearing nearest to the square box coupling where about 85% of the service failure these types of shafts are observed [1, 2, 3].
Analysis of Common Accident Reconstruction Operations
Authors: Kimbrough Scott
Published: April 2008

Accidents occur when the circumstances (i.e. the inputs) leading up to an accident map through the physical processes involved, to produce an undesirable result, namely the accident (i.e., the outputs). What the accident reconstructionist has to work with is the evidence left behind, and he then strives to determine the circumstances that led to the accident, based upon that evidence. In accident investigation there is often a deficit of physical evidence, and it is impossible, based on the available physical evidence alone, to pinpoint the circumstances that led to the accident. In practice, computer programs are often used to run simulations to find a set (or sets) of circumstances that is consistent with the evidence, and then the discovered set (or sets) of circumstances is presented as the answer. But this approach ignores some important questions related to whether the mapping being used (e.g., the computer simulation) is invertible and whether the circumstances leading to the evidence can be identified in a unique way, or whether the mapping is not invertible and the most that can be achieved is to identify whole sets in the input space of circumstances that might have led to the accident. Analysis offers the tools to probe such questions.
Internal Condensing Flows Inside a Vertical Pipe: Experimental/Computational Investigations of Effects of Constrained and Natural Exit Conditions
Authors: Narain A. , Siemionko A. , Kurita J. H. , Ng T. W. , Kim N. , Opella K. , Sweger P. O.
Published: April 2008

The flow and heat transfer rates inside a condenser depend on the specification of inlet, wall, and exit conditions. For steady/quasi-steady internal condensing flows (that involve compressible vapor at low Mach Numbers), the vapor’s ability to change its density — and hence interfacial mass transfer rates and associated locations of the interface — allows the flow to have a rather significant dependence on exit conditions. Both experimental and direct computational simulation results presented here show that this is indeed the case for flows of pure vapor experiencing film condensation on the inside walls of a vertical tube. In applications, the totality of boundary conditions are determined not only by the condenser; but also by the flow-loop (or the system) — of which the condenser is only a part. Therefore, the results outlined here should contribute towards a better understanding of the behavior (particularly the extent to which vapor compressibility effects affect the flow regimes of operation — i.e. annular, plug/churn, etc.) and response (transients due to start-up, system instabilities, etc.) of condensers in application systems (e.g. Rankine Cycle power plants, Capillary Pumped Loops, Looped Heat Pipes, etc.). In this connection, an experimental example of a relevant system instability is presented here. In summary, the experimental results presented here, and computational results presented elsewhere, reinforce the fact that there exist multiple steady solutions (with different heat transfer rates) for different exit conditions and that there also exists a “natural” steady solution for straight vertical condensers (circular and rectangular cross-sections).
A General Geometric Framework for Control of Electrostatically-Actuated MEMS and NEMS
Authors: Maithripala D. H. S. , Kawade B. D. , Berg J. M. , Dayawansa W. P.
Published: April 2008

This paper presents a geometric framework for the modeling and stabilization of a general class of electrostatically-actuated mechanical systems. The class of devices under study consists of a movable, rigid, grounded electrode, with a variety of allowable rotational and/or translational degrees of freedom, and a set of multiple, fixed, independently-addressable, drive electrodes. Previous work has placed the general electrostatic forces and the electrical system in a framework suitable for passivity-based control. This paper generalizes this result further by allowing the electrical part of the model to incorporate current leakage between electrodes. With respect to this model a stabilizing dynamic feedback control laws is derived in terms of coordinate-independent geometric formulas. To obtain controllers for a specific device it is then necessary only to evaluate these formulas. Appropriate approximations may be applied to make the computations more tractable. Performance may be improved using dynamic output feedback, but additional information is needed, typically in the form of a model relating electrode capacitances to the system configuration. We demonstrate the controller computations on a representative MEMS, and validate performance using ANSYS simulations.
Experimental Evaluation of the Thermal Behavior of a Vertical Solar Tank Using Energy and Exergy Analysis
Authors: Dehghan Ali A. , Hosni Mohammad H. , Shiryazdi S. Hoda
Published: April 2008

The thermal performance of a Thermosyphon Domestic Solar Water Heater (DSWH) with a vertical storage tank is investigated experimentally. The system is installed on a roof - top of a four person family house and its thermal characteristics is evaluated by means of carefully measuring the temperature distribution of water inside the storage tank, solar collector flow rate and its inlet and outlet temperatures as well as load/consumption outlet and inlet temperatures and the corresponding water flow rate under a realistic operating conditions. The measurements are conducted every hour starting from morning until late night on a daily basis and continued for about 120 days during August until November 2004. It is seen that thermal stratification is well established inside the tank from 11 AM until 10 PM especially during August to September enabling the tank to provide the necessary amount of hot water at an acceptable temperature. However, thermal stratification is observed to start degrading from mid-night until morning when there is no hot water supply from the collector and due to the diffusion of heat from the top hot water layers to the bottom cold region and conduction through tank’s wall. The thermal behavior of the storage tank is also assessed based on both energy and exergy analysis and its first and second law efficiencies are calculated. It is observed that the storage tank under study has an average first law efficiency of 47.8% and is able to supply the required amount of hot water at a proper temperature. The average second law efficiency of the storage tank is observed to be 28.7% and, although is less than its first low efficiency, but is high enough to ensure that the quality of the hot water supply is well preserved. The proper level of second law efficiency is due to the preservation of the thermal stratification inside the storage tank, leading to supply of hot water at highest possible temperature and hence highest possible energy potential. Experiments are also done for no-load conditions when the storage tank only interacts with the collector, without hot water withdrawal from the tank. It is seen that for no-load condition, thermal stratification continuously develops from morning until around 16 PM after which no noticeable changes in the temperature distribution inside the tank is observed.
Double Laser Crystallization (DLC) of 50 Nanometer and 20 Nanometer Amorphous Silicon Film for Thin Film Transistors (TFTS) Application
Authors: Xu Li , Griogoropoulos Costas P.
Published: April 2008

Ultra-large grain poly-crystalline silicon has been formed in 20 nm and 50 nm amorphous silicon films by the double laser crystallization (DLC) method. Surface reflection properties of such thin films upon laser irradiation were calculated. In-situ images were captured to monitor the transient melting and solidification process of 50 nm silicon film in order to understand the crystallization induced by steep laser intensity gradients. SEM (scanning electron microscope) images of crystallized 50 nm film after Secco etch revealed grain size up to 10 m while plane-view TEM (transmission electron microscope) images of 50 nm film also showed perfect crystalline structure inside the grains. AFM (atomic force microscope) images were also taken to show the topology of the grain structure and RMS of 20 nm film.
Temperature and Strain History Measurement During an Arc Welding Process
Authors: Davoud Mohammad S.
Published: April 2008

Evaluation of weld temperature field history, strain field history, and residual stress distribution are essential in predicting the performance of weldment during service. During an arc welding process electromagnetic field, radiation, and high temperature gradient away from the centerline of weldment affects measurement of temperature and strain history. The important and critical issues regarding temperature history measurement using thermocouples and strain history measurement using strain gages during the Gas Metal Arc Welding (GMAW) process are explored and overviewed. Guidance is provided to properly select sensors and to reduce the measurement errors in such severe environments during GMAW. Results of experimental temperature and strain history during GMAW are presented.
Experimental Investigation of a Pilot Compression Chiller With Alternatives Refrigerants R401a and R134a
Authors: Fatouh M.
Published: April 2008

This paper reports the results of an experimental investigation on a pilot compression chiller (4 kW cooling capacity) working with R401a and R134a as R12 alternatives. Experiments are conducted on a single-stage vapor compression refrigeration system using water as a secondary working fluid through both evaporator and condenser. Influences of cooling water mass flow rate (170–1900 kg/h), cooling water inlet temperature (27–43°C) and chilled water mass flow rate (240–1150 kg/h) on performance characteristics of chillers are evaluated for R401a, R134a and R12. Increasing cooling water mass flow rate or decreasing its inlet temperature causes the operating pressures and electric input power to reduce while the cooling capacity and coefficient of performance (COP) to increase. Pressure ratio is inversely proportional while actual loads and COP are directly proportional to chilled water mass flow rate. The effect of cooling water inlet temperature, on the system performance, is more significant than the effects of cooling and chilled water mass flow rates. Comparison between R12, R134a and R401a under identical operating conditions revealed that R401a can be used as a drop-in refrigerant to replace R12 in water-cooled chillers.
Condensation Heat Transfer Characteristics of R134A on Smooth or Finned Horizontal Tube
Authors: Fatouh M.
Published: April 2008

The present work aimed at determining the condensation heat transfer characteristics of R134a on single horizontal smooth and finned tubes under different parameters. These are saturated temperature (36°C and 43°C), inlet coolant temperature (25°C and 30°C) and coolant mass flow rate (100: 800 kg/h) for smooth and finned tubes. In the case of finned tubes, the pitch to height ratio varies from 0.5 to 3.08. Experimental condensation heat transfer characteristics for R134a and R12 on a smooth tube are compared. Experimental results confirmed that the heat flux and the overall heat transfer coefficient for R134a increase when coolant mass flow rate, saturation temperature and fin height increase or as both coolant inlet temperature and fin height decrease. The influence of fin pitch, on condensation heat flux and overall heat transfer, is lower than that of fin height. However, the heat flux and the overall heat transfer coefficient for R134a are correlated with the investigated parameters. Finally, the comparison between R12 and R134a revealed that the condensation heat transfer characteristics for R134a are better than those of R12.
Accuracy and Computational Complexity Analysis of Design Models Created by Virtual Sculpting
Authors: Zhang Weihan , Peng Xiaobo , Leu Ming C. , Blackmore Denis
Published: April 2008

We have developed an experimental virtual sculpting system with haptic interface, which allows the user to create a freeform model interactively. The virtual sculpting method is based on the metaphor of carving a solid block into a 3D freeform object. The PHANToM™ manipulator is used to provide the position and orientation data of the sculpting tool and to generate haptic sensation to the user’s hand during the sculpting process. The goal is to provide a high-fidelity simulation system with real-time performance and adequate accuracy of the generated model. In order to understand the limitations on the geometric details that can be generated, we perform an accuracy analysis in different aspects. The computational complexity due to various parameters of the virtual sculpting system is also analyzed. Numerical data are presented to verify the analytical results.
Novel Manufacturing Process of Nanocomposite Hydrogel For Bio-Applications
Authors: Haraguchi Kazutoshi , Takehisa Toru
Published: April 2008

A novel class of nanocomposite hydrogels (NC gels) with a unique organic / inorganic network structure was synthesized by in-situ free-radical polymerization of N-isopropylacrylamide (NIPA) or N,N-dimethylacrylamide (DMAA) in the presence of inorganic clay (hectorite). Since NC gels are composed of a unique organic / inorganic network structure, which consists of exfoliated clay platelets uniformly dispersed in an aqueous medium with a number of flexible polymer chains linking them together, NC gels exhibit high transparency, high degrees of swelling, and superb mechanical properties with extraordinarily large deformations. Also, NC gels formed from thermo-sensitive polymers, e.g. PNIPA, exhibit rapid temperature-response in transparency and gel volume (de-swelling) at the lower critical solution temperature (LCST). All the properties of NC gels are very different from those of conventional, chemically-crosslinked hydrogels (OR gels). Here, we evaluated various properties of NC gels from a biomaterials point of view, such as mechanical toughness (capable of sewing), absorption (water and saline), purification and extraction, drying (effect of cover film), coexistence of absorption and drying, sterilization (by autoclave and γ-ray irradiation), preliminary implantation (implanted to rabbit intramuscularly) and blood compatibility. These results indicate that NC gels are promising as soft biomaterials with blood compatibility as well as high transparency, absorbing power and mechanical properties.
A Novel Independent Train Localization Method Based on Multi-Sensor Fusion
Authors: Zhou Datian , Tang Tao
Published: April 2008

Train localization system is a vital part of train control system. A novel independent train localization method based on multi-sensor fusion is proposed in this paper. In conventional train localization system, the position determination is dependent on the reference information source controlled by rail operator, such as track circuit and so on. In some new train localization systems on test[1][2][3][4], the localization methods based on Satellite Navigation are very popular, so that the system’s reliability and safety are put outside of the rail operators’ control actually. The localization method proposed in this paper uses inertial sensor gyrometer and conventional odometer, which is mounted on the locomotive’s driven axle. Gyrometer is used to measure train’s heading angular rate. And odometer is used to measure train’s velocity. Usually, the dead reckoning method independent of outside reference information is selected for these two sensors’ fusion. But an obvious disadvantage of this method is the position error is increasing linearly according to time, so that this method can not work independently. Therefore Satellite Navigation system is often used to restrict the increasing error to an acceptable range. The method proposed in this paper overcomes the disadvantage of dead reckoning. Because the rail route or train’s moving track is fixed, the route’s curvature-mile curve can be obtained. According to this curve it is obvious, in the area where route is straight, the curvature value is zero; in the area existing a turning, the value is not zero. DGPS equipment is mounted on the test train to get and record the position data on the test route. Then the curvature-mile curve can be calculated from these data. We use Hurst coefficient to get the characters of train track such as turning from the gyrometer and odometer’s data. By matching these characters and the known route’s curvature-mile curve, the train’s real-time position can be calculated. If the dual-direction communication channel such as GSM-R is available, virtual block or moving automatic block in train control system could be achieved. Details of this process are presented in this paper with some results to illustrate the effectiveness of the methods.
Cooperative Reconnaissance for Stationary and Moving Targets Using Mixed Integer Linear Programming
Authors: Ousingsawat Jarurat
Published: April 2008

This work focuses on the use of cooperative multi-vehicle systems in reconnaissance. A team of vehicles travels to collect information of targets such that their uncertainties are reduced. An approach is developed and employed to effectively plan paths of the vehicles. The high-level of a hierarchical control structure is considered. In prior works, the path optimization is generally constructed so that it can be used at any circumstances. While it offers many benefits, it is computationally intensive. It is proposed here to decompose the planning into 1)strategy planning and 2)task/path planning. Unlike other works, the two elements are separated. The paths are planned under the policy given by the strategy planning. The separation allows the policy to be adjusted based on the current environmental status. Therefore, the planner becomes more flexible and is able to tackle more complex situations such as moving targets and obstacles. The knowledge from an optimal planner is employed to provide an insight on the best policy. The simulations show the vehicles successfully observe multiple moving and stationary targets using relatively short run time.
Laser Scanning Vibrometer Studies of Electro-Active Papers
Authors: Sundaresan Mannur , Park Yongkun , Kim Jaehwan , Craft William J. , Song Kyo D. , Choi Sang H.
Published: April 2008

The paper presents the initial results on the performance of cellulose-based Electro-Active Papers (EAPap) as actuators. The electro-active papers depend on ion migration and dipole moment for the actuation. EAPap is fabricated by depositing gold electrodes on the top and bottom surfaces of cellophane sheets. Small sheet specimens measuring approximately 1 cm × 3 cm, suspended from the 1 cm width were tested in this study. The characteristics of EAPap are evaluated by applying electric fields at different exciting frequencies and humidity levels. The dynamic responses of the specimens were measured using a scanning Laser vibrometer. As expected, different plate modes are excited at different frequencies. Wide variations in the performance of the specimens were seen bat different levels of humidity. The results indicate the potential of EAPap for low power and lightweight actuation.
Improving Volume Resistivity of Epoxy Nanocomposites Using Electrospun Polyacrylonitrile-Based Carbon Nanofibers and Their Silver Modification
Authors: Sancaktar E. , Aussawasathien D.
Published: April 2008

The electrospinning technique was utilized to prepare non-woven fabric carbon nanofibers (CNFs) via polyacrylonitrile (PAN) precursor nanofibers. The volume resistivity (ρv) of non-woven mat CNFs containing the small size of beads and fiber diameters was lower than the ones possessing large beads and fiber diameters owing to the high specific surface area of the former. The ρv values of CNF mats prepared from 6.5 (fiber dia. ~120–250 nm) and 8.0 (fiber dia. ~250–600) wt% PAN solutions and carbonized at 950 °C were 0.32 and 1.33 Ω.cm, respectively. Additionally, the ρv value of CNF fabrics was improved by silver (Ag) modifications. The CNF mats containing Ag nanoparticles by in-situ preparing Ag nanoparticles in PAN solution prior to electrospinning and carbonization and Ag coating of CNF mats exhibited ρv values more or less 0.15 and 0.24 Ω.cm, respectively, even though the nanofiber diameter obtained from the former method was slightly larger than that of the latter. Effects of the fiber aspect ratio (L/D ratio) and the interconnecting network due to non-woven mat like fibers on the ρv were demonstrated by comparing the ρv of epoxy nanocomposites containing different forms of CNFs, non-woven fabric and short nanofibers. It was found that the ρv value of non-woven mat CNF/epoxy nanocomposite was much lower than that of short CNF/epoxy nanocomposite at 10 phr filler loading. Interestingly, the ρv values of non-woven mat CNF/epoxy nanocomposites dropped rapidly from 1010.5 Ω.cm at 0 phr filler content to 1.05 Ω.cm at about 10 phr filler content. Furthermore, the ρv values of non-woven mat CNF/epoxy nanocomposites leveled off to that of the filler itself or even lower at the filler dosage about 15 phr or higher, because the thickness of CNF mats impregnated in the epoxy composite was increased at high filler loading, thus yielding highly connected network inside the composite.
Risk-Informed Load and Resistance Factor Design (LRFD) Methods for Piping
Authors: Ayyub Bilal M. , Assakkaf Ibrahim A. , Avrithi Klieo , Gupta Abinav , Shah Nitin , Kotwicki Philip , Balkey Kenneth , Hill Ralph S.
Published: April 2008

The main objective of structural design is to insure safety, functional, and performance requirements of a structural system for selected target reliability levels, for specified period of time and for a specified environment. As this must be accomplished under conditions of uncertainty, risk and reliability analyses are deemed necessary in the development of such methods as risk-informed load and resistance factor design for piping. This paper provides a summary of the methodology and technical basis for reliability-based, load and resistance factor design suitable for the ASME Section III, Class 2/3 piping for primary loading, i.e., pressure, deadweight and seismic. The methodology includes analytical procedures, such as the First-Order Reliability Method (FORM) for calculating the LRFD-based partial safety factors for piping. These factors were developed in this paper for demonstration purposes, and they can be used ultimately in LRFD design formats to account for the uncertainties in strength and in the load effects. The technical basis provided in the paper is suitable for a proof-of-concept in that LRFD can be used in the design of piping with consistent reliability levels. Also, the results from additional projects in this area, including future research for piping secondary loads, will form the basis for future code cases.
Enhancement of Dimensional Stability of Polymer Composites Manufacturing Using Carbon Nanofibers
Authors: Gangireddy Sudhir , Hsiao Kuang-Ting
Published: April 2008

Process induced residual stress arises in polymer composites as a result of resin shrinkage during cure cycle. When a shell-like composite part is demolded, these residual stresses result in change of dimensions such as spring-in, which is a phenomenon that the enclosed angles of the composite part are reduced due to process-induced residual stress. To have good precision in the composite part, the dimensional instability of enclosed angles must be controlled and/or compensated. The traditional approach is to estimate the spring-in and consequently correct the mold geometry to counterbalance the predicted dimensional instability. The success of such mold design practice relies on the past experience or by costly trial and error approach. In this paper, we present a new approach to reduce the spring-in by using Carbon Nanofibers (CNF). CNF have remarkable physical and mechanical properties and have excellent dimensional stability and hence may be useful in improving the dimensional stability of polymer composites. In this experimental study, we dispersed different fractions of CNF into fiberglass/polyester composite parts with corner angles and compared their spring-in angles after the composite parts were demolded. The results show that the CNF can effectively restrain the undesired deformation and improve the dimensional stability of polymer composites during manufacturing process.
A New Method for Obtaining Non-Autonomous, Reduced-Order Model of Flow Using Proper Orthogonal Decomposition (POD) and Optimal Control of the Resultant Nonlinear Model
Authors: Fardisi S. , Shahamiri A. , Emdad H.
Published: April 2008

The focus of this work is on the use of POD and perturbation method to develop non-autonomous, low-dimensional models for the dynamics of the flow evolution and optimal control of the resultant system. The main difficulty of the POD for control purposes is that, control inputs do not show up explicitly in the resulting system making it useless for control purposes. Most of the approaches which are presented to handle this issue make a use of superposition principle and are more appropriate for linear systems. In addition these methods don’t care about time varying nature of the system and consider a constant influence for the inputs on the system. The test bed was selected to be the unsteady, incompressible flow around a circular cylinder. Actuation was performed by two suction-blowing panels on the sides of the cylinder. It is obvious from the physical features of the problem, that the control inputs will not have a constant effect, but a periodic one on the system. The presented method uses perturbation method to account for some nonlinear characteristics of the problem and results in a non-autonomous, time-varying, simply-handled system which tries to capture the periodic influence of the inputs on the system and is expected to predict the Navier-Stokes response to external excitations more precisely. Finally, optimal control theory was employed to design a control law for the nonlinear reduced model, trying to minimize the vorticity content in the fluid domain. Simulations were performed to show the flow’s evolution with the control influence according to the low dimensional model.
Experimental Conditions for Minimum Critical Reynolds Number in Pipe Flow
Authors: Kanda Hidesada , Yanagiya Takayuki
Published: April 2008

From the results of many experiments carried out in the past, it is clear that the transition between laminar and turbulent flows occurs in the entrance region, and that the critical Reynolds number (Rc) is governed by the shape of the bellmouth entrance. To date, it has not been considered how a bellmouth-shaped entrance affects the flow in pipes. If it governs the transition, the turbulence can be controlled. These findings are verified by reproducing Reynolds color-dye experiments, in particular, varying the ratio of the bellmouth diameter to pipe diameter (BD/D). CASE I through IV are devised for natural disturbance conditions. We found that (i) there were two types of Rc, namely, Rc1 for the laminar to turbulent flow transition and Rc2 for the turbulent to laminar flow transition, (ii) each bellmouth-shaped entrance had a minimum value, Rc2(min, ent), which increased as BD/D increased, and (iii) when using a straight pipe, the Rc value of 2050 was obtained as a minimum value in CASE II and IV, and the Rc2(min) value was approximately 1750 in CASE III.
Change in Radiative Optical Properties of Tantalum Pentoxide Thin-Films Due to Material Compositional Changes at High Temperature
Authors: Chandrasekharan Ramesh , Prakash Shaurya , Masel R. I. , Shannon Mark A.
Published: April 2008

Thin films (0.85μm, 3μm) of Ta2O5 deposited on Si and SiO2 were heated to 900°C. Their reflectance in the infrared was measured using an FTIR (Fourier Transform Infrared Spectrometer) equipped with a multiple angle reflectometer before and after exposure to high temperature. An interfacial layer (TaSixOy) formed by the diffusion of Si from the substrate into the deposited film was observed using Auger depth profiling, and the effect of this interfacial layer on the reflectance was measured. Using a least squares optimization technique coupled with an optical admittance algorithm, the multiple angle reflectance data was used to calculate the optical constants of the as deposited Ta2O5 film, crystalline Ta2O5, and the interfacial layer in the 1.6μm to 10μm range. The interfacial layer formed due to exposure to high temperature was found to be more absorptive than the crystalline Ta2O5.
Research of Outer and Inner Parts for Reducing Noises in Rotary Compressors
Authors: Gao Yan , Zhang Haifeng , Cong Li , Huang Zisi , Geng Qiao
Published: April 2008

With the requirement of low noises in the airconditioner marketing, noise problems have been becoming an important task in the design of compressors. In this paper, the achievements of reducing compressor noises in our company are introduced and the impacts of outer and inner parts of the compressor, such as case’s thickness, foot’s shape and muffles, are discussed. Kinds of methods are used. Noise resources and the frequency of peak value are analyzed using theoretical calculation of professional software, such as CAE and SYSNOISE and phonometry of special instruments. On the basis, some modifications have been adopted. Finally the result of experiments shows that the noise of compressors reduces about 7 to 8 dBA.
Numerical Study of the Pusher-Type Billet Reheating Furnace
Authors: Zou Linjiang , Li Chaoxiang , Yuan Yinmei , Guo Wei , Yang Fan , Lu Yaxiong
Published: April 2008

In the present work, a commercial CFD software package, FLUENT, was used to develop a three-dimensional model of pusher-type billet reheating furnace for the second high speed wire rod plant of XiangTan Iron and steel Co. Ltd. The purpose of the study was to gain a better understanding of the gas flow and velocity and pressure distribution in the furnace. The results show that the numerical results are in agreement with the practice and the characteristics of the furnace configuration. The CFD model can be used to improve the performance and structure by analyzing and studying the behavior of the reheating furnace.