bluuebunny/crossref_metadata_2025 huggingface dataset:
About Some Problems of the Surface Accuracy and Quality Increase of Ti-6Al-4V Alloys at Pulse ECM
Authors: Zaytsev A. N. , Zhitnikov V. P. , Idrisov T. R. , Gimaev N. Z.
Published: April 2008

Here we present the procedure and results of the electrode process research in electrochemical machining (ECM) by microsecond pulses of titanium and its alloys. These researches have allowed us to determine the conditions of the process localization increase and improvement of surface quality (reduction of surface roughness, pitting and hydrogenation of the surface stratum). The results of the experiments on checking of the conditions described above are presented.
Geometric Non Linear Analysis of Composite Shells Under Thermomechanical Load
Authors: Sutharson B. , Perumal A. Elaya , Thangarathanam R. Kari
Published: April 2008

Geometric nonlinear analysis of composite shells under thermomechanical load is reported here. From the literature, it may be seen that the thermal stress analysis of structural elements has continued to remain a research topic for a couple of decades. No one computationally verified the geometric non-linear buckling of composite shells under thermomechanical load using semiloof element. In this work, linear buckling analysis of Kari Thangaratnam (2) is extended to geometric non-linear analysis of composite shells under thermomechanical load. A general shell element called the semiloof shell element has been extended to thermal stress analysis of laminated shells. The formulation is based on nonlinear theory and the finite element method using semiloof element. The validation checks on the program are carried out using results on homogeneous isotropic shells available in the literature. The parameters considered in analysis are (1) number of layers in the laminate, (2) Lay-up sequence (symmetry, antisymmetry, cross-ply etc.), (3) Fibre orientation angle, (4) Different aspect ratios, (5) Orthotrophy ratio, (6) Boundary conditions (simply supported, clamped and combination of boundary conditions).
Modeling and Identification of Hysteresis in Piezoelectric Actuators
Authors: Yeh T.-J. , Lu Shin-Wen , Wu Ting-Ying
Published: April 2008

In this paper, a model and the associated identification procedure are proposed to precisely portray the hysteresis behavior in piezoelectric actuators. The model, presented in bond graphs, consists of basic physical elements and utilizes a Maxwell-slip structure to describe the hysteresis. By analyzing the model, the influence of the initial strain/charges on the hysteresis behavior is revealed. It is also found that if all the spring elements in the model are linear, the resultant hysteresis loop is anti-symmetric and does not match the experimental behavior. To account for this mismatch, a nonlinear spring element is included into the model. The constitutive relation of the nonlinear spring and the parameters of the basic elements in the model are identified from the experimental data using linear programming. Simulations of the identified model indicate that the model can reproduce the major as well as the minor hysteresis loops. An inverse control is further implemented to validate the accuracy of the identified model. Experiments show that the hysteresis is effectively cancelled and accurate tracking of a reference trajectory is achieved.
An Experimental Study on Saturated Liquid Nitrogen’s Boiling Under Transient Pulsed Laser Irradiation
Authors: Dong Zhaoyi , Huai Xiulan , Wang G.-X.
Published: April 2008

Liquid nitrogen (LN2) was widely applied in many areas, but researches on the boiling behavior under the transient high heat flux have not been reported. In this paper, the high power short pulse duration laser was used to heat the saturated LN2 rapidly, and the high-speed photography aided by the spark light system was employed to take series of photos which displayed the process of LN2’s boiling behavior under such conditions. At the same time, a special temperature measuring system was applied to record the temperature variation of the heating surface. The experimental result disclosed that at the earlier stage of laser heating, an explosive boiling would happen within LN2. After the newly-defined changeover time, the conventional boiling behavior would follow. Therefore the changeover time became an important index to distinguish these two kinds of boiling behaviors. By analyzing the temperature variation of the heating surface, it is found that the latent heat released by the crack of bubbles in explosive boiling is an important factor that greatly influences the boiling heat transfer mechanism.
Investigating the Propelling Wheelchair Behavior Against Various Loads
Authors: Suzuki Tatsuto , Uchiyama Hironobu , Kurata Junichi , Grattan Kenneth T. V.
Published: April 2008

The purpose of this study is to solve an attendant’s daily propelling wheelchair behavior, which is based on propelling force and walking speed against loads, for design of wheelchairs and other carts to handle materials. To obtain the propelling behavior, we proposed the model of the attendant propelling the wheelchair, such as the attendant is a motor, and the wheelchair is a load. Along with the model, we carried out experiments to solve the propelling behavior. The experiments were carried out on the ground and on a new type of a treadmill, which can generate various resistant forces. As the result, the propelling force increased and the walking speed decreased gradually with increasing the resistant force. This change is mostly along on a line. We also define a mechanical power of the propelling behavior and calculated the power. It was about 50W on daily use. The power of the propelling wheelchair is very small, therefore the comfortable design of attendant’s wheelchair must be done with the ability of attendant’s propelling.
Thermoeconomic Synthesis of District Heating Networks
Authors: Verda V. , Ciano C. , Cali` M.
Published: April 2008

District Heating (DH) is an efficient way to provide heat to residential users since it can allow recuperation of waste heat or can be coupled with cogenerative plants and very efficient boilers, achieving overall energy savings and thus allowing reductions in the system’s global emissions. Notwithstanding all of these benefits, the question if DH is to be preferred to other solutions, such as micro-cogenerative plants or conventional boilers feeding single or small groups of buildings, has its answer not only in technical and environmental evaluations, but also in economical ones, involving the district heating network (DHN) as a determinant parameter, being largely the most important investment. An important problem to be solved when planning a district heating system in a municipality is the extension of the network, which does not necessarily involve the whole town. The determination of optimal configuration, formulated as a synthesis problem, should allow one to decide which areas could be effectively and conveniently fed trough the DHN and which ones through distributed systems. Such design criterion should be always formulated as a first step of the decisional project, since, once the main network is designed, further developments are technically difficult or even impossible if not planned. In this paper thermoeconomic analysis is used as the key-factor for the system synthesis. This procedure does not guarantee to obtain the true optimal network structure; nevertheless a quasi-optimal configuration is always determined. In this case, the result can be improved by coupling this approach with other optimization algorithms, which increases the probability of reaching the true optimum. The use of the thermoeconomic approach (although combined with other optimization algorithms) reduces sensibly the computational efforts with respect to the direct application of other optimization procedures. In case of large systems, where the number of possible structures is extremely large, the use of this procedure is a strategy to make the problem resolvable. The theoretical developments are here applied to the town of Turin, where a district heating network operates. The optimal network is determined and compared with the existing one.
Modeling of the Broadband Noise Radiated by an Airfoil
Authors: Fedala Djaafer , Kouidri Smai¨ne , Bakir Farid , Rey Robert
Published: April 2008

The mechanisms of noise generation due to the turbulent flow around an airfoil are complex phenomena. In this paper, a prediction method of the broadband noise is presented then validated. The aim of this work is to develop tools of noise prediction in turbomachinery engaged by the laboratory since several years. The modeling presented is based on the unsteady aerodynamic linearized theory of an airfoil. An acoustic calculation based on the formulation of Amiet determines the far field acoustic power spectral density produced by an airfoil. It shows the importance of the noise due to the interaction of incident turbulence flow with the leading edge. The results obtained are compared with the experimental results available in the literature.
Study on Stiffness and Resonant Frequency of a Parylene Suspended Structure
Authors: Aoyagi Seiji , Yoshikawa Dai-ichiro , Makihira Kenji , Tai Yu-Chong
Published: April 2008

Parylene has intrinsic tensile stress on account of mismatch of thermal coefficient of expansion (TCE) between the substrate and the deposited film. Therefore, the stiffness k of the Parylene suspended structure under tensile stress is much higher than that under no stress, which also leads to its higher resonant frequency fr. These mechanical characteristics are investigated in this study. First, FEM simulation is employed, and it is proved that k is decreased in proportional to the first power of the beam length l, while it is decreased in proportional to the third power of l under no stress according to the theory of strength of materials. Considering this, a structure with spiral shaped beams is proposed for lowering k. Second, practical Parylene suspended structures are fabricated. The vibrations of them are observed by LDV (Laser Doppler Vibrometer) and their experimental resonant frequencies obtained. They coincide well with simulated ones.
DesignSpace Embossing Method for Basic Design Plans of a Vehicle Suspension System
Authors: Yu Qiang , Kageyama Yusuke , Minami Hiroki
Published: April 2008

In general, vehicle structure design processes, like a suspension system, are performed in three stages, the concept design, the basic design, and the detailed design processes. There is incessant demand to shorten the design time required for all three of these stages. An abundance of CAE technologies have been developed for the detailed design process, serving as powerful tools to improve design quality and efficiency. However, the concept design process is still performed using classic approaches, such as experience and know-how. By implementing a quantitative analysis method to evaluate design information, design engineers can improve their design concept or basic design plans. Unfortunately, the early design stages involve numerous design factors and extensive design ranges, making it difficult for design engineers to fully understand the extent of their design capacity. This paper introduces a new approach called the Design Space Embossing Method. This method uses CAE technology to efficiently search for promising design spaces for complicated basic design processes. Having this information will enable engineers to visually comprehend the design capabilities in the early phases of the design process. When this method is implemented, the number of necessary samples can be drastically reduced while providing a satisfactory result for even complicated multiple maximum problems. In this paper, the proposed method has been applied to the basic design process of a vehicle suspension system. The results show that the design spaces generated by this method could help design engineers understand the basic behavior of the system.
Utility of Projection Network for Air-Craft-Engine Fault Diagnosis
Authors: Jansuwan Chaiyakorn , Li C. James
Published: April 2008

Turbine engines are frequently used in critical systems including the power plants and propulsion systems of aircrafts and ships. Frequent inspection and periodic maintenance have been necessary to ensure their proper functionality. Condition based maintenance of jet engines can significantly reduce their operational and maintenance costs, and, in the mean time, enhance safety and reliability. This study investigates the feasibility of establishing the utility of a dynamic network, i.e., projection network, to recognize hot air pass faults from measurements of e.g., fan speed, core speed, compressor inlet and exit temperatures and pressures, turbine exit temperatures, etc. Projection network is a nonlinear dynamic network architecture that provides stable oscillatory or non-oscillatory attractors. In contrast to the static mapping provided by e.g., neural networks and fuzzy systems, the projection network offers more functionality through its rich dynamics. When properly setup, its nonlinear dynamics can filter out noise from measurements, and classify/recognize complex patterns. This study established the utility of projection network for detection and diagnosis of several aircraft engine faults. This paper will also describe methods for both structure training and parameter tuning. Using these methods, projection networks were setup to recognize baseline, fan damage, high pressure turbine fault, and customer bleed valve fault.
Solution of Similarity Transformation Equations for Boundary Layers Using Spreadsheets
Authors: Naraghi Mohammad H. N.
Published: April 2008

A spreadsheet based solution of the similarity transformation equations of laminar boundary layer equations is presented. In this approach the nonlinear third order differential equations, for both the hydrodynamic and the thermal boundary layer equations, are discretesized using a simple finite difference approach which is suitable for programming spreadsheet cells. This approach was implemented to solve the similarity transform equations for a flat plate (Blasius equations). The thermal boundary layer result was used to obtain the heat transfer correlation for laminar flow over a flat plate in the form of Nu = Nu(Pr,Re). The relative difference between results of the present approach and those of published data are less than 1%. This approach can be easily covered in the undergraduate. Fluid Mechanics and Heat Transfer courses. Also, it can be incorporated in graduate Viscous Fluid Mechanics and Convection Heat Transfer courses. Application of the present approach is not limited to the flat plat boundary layer analysis. It can be used for the solution of a number of similarity transformation equations, including wedge flow problem and natural convection problems that are covered in graduate level courses.
Measurement of Molecular Mobility in Mammalian Cells
Authors: Aksan Alptekin , Toner Mehmet
Published: April 2008

Preservation of mammalian cells requires establishing a reversible stasis condition by reducing the intra/extracellular molecular mobility ensuring reduced chemical reaction and deterioration rates. Molecular mobility may be reduced by various techniques. For example, in cryopreservation, mobility within and surrounding the cell is reduced through freezing the free water that constitutes 70–90% of the cell’s composition. In dried-state preservation applied successfully to preserve seeds, pharmacological materials and foodstuff (mimicking the anhydrobiosis phenomenon seen in nature), reduction in molecular mobility is established by removing intra/extracellular water. Certain carbohydrates (such as trehalose and sucrose) can be artificially uploaded into mammalian cells to replace the removed water and to form an intra/extracellular glass. In this research, a fluorescent rotor is utilized to determine the changes in intracellular molecular mobility during carbohydrate uploading of mammalian cells. It was shown that using this technique, it is feasible to make real-time mobility measurements at a single cell level.
Effects of a Void Beneath a Kapton Heater Patch in a Vacuum
Authors: Schmidt Ryan A.
Published: April 2008

The vacuum of space can lead to some interesting heater problems. In many space applications, heater patches consisting of Inconel elements joined together with Teflon sandwiched together between two Kapton layers are bonded to a structure (substrate) to provide thermal control. A void between the heater patch and the substrate can lead to a hot spot due to the loss of conduction path from the heater to the substrate. When the heater is in a vacuum with a void beneath it, heat is transferred to the substrate by radiation and fin effects through the heater and then to the substrate. The localized hot spot can cause heater layers to separate and further reduce the conduction pathway from the affected area and eventually burnout the heater. A large enough void combined with high heater heat fluxes and substrate temperatures can induce heater failures. For this paper the sensitivity of peak temperature with respect to heat flux (power density), substrate temperature, void size, and void location is considered.
Data Acquisition During the Entire Product Life Cycle as a Basis for the Maintenance, Dismantling and Product Recycling Processes
Authors: Mu¨ehlenbruch Helge , Nyhuis P.
Published: April 2008

The planning and control of recycling and disassembly processes depends to a great extent on information about the product and its usage. A substantial amount of information about products is provided on delivery, but a continuous and systematic recording of information during a product life is normally not carried out. Repairs, disassembly and product recycling are however dependent on decentralised and information-intensive processes and can only be facilitated through the recording of life-cycle information. All information which is generated during the product life is first integrated into a newly created information model for life-cycle documentation. The paper presents a new integrated approach that guarantees consistent data storage and data structuring during the entire product life. An innovative information system is introduced which can provide any required information to all product user groups at any point in the product life. One module of this model is the electronic life-cycle memory for data storage on the product itself of the life-cycle documentation. It is done using Radio Frequency Identification Technology (RFID) for the first time in this field. Subsequently, the integration of the life-cycle memory into the entire information system is described. The paper closes with a practical case from industry.
Dielectrophoresis of Nanoparticles
Authors: John Kadaksham Arun Thankamony , Singh Pushpendra , Aubry Nadine
Published: April 2008

A numerical scheme based on the distributed Lagrange multiplier method (DLM) is used to study the motion of nano sized particles of dielectric suspensions subjected to uniform and nonuniform electric fields. Particles are subjected to both electrostatic and hydrodynamic forces, as well as Brownian motion. The results of the simulations presented in this paper show that in the case of uniform electric fields the evolution of the particle structures depends on the ratio of electrostatic particle-particle interactions and Brownian forces. For solids fraction of the order 0.01, when this ratio is of the order of a hundred or more particles form stable chains and columns whereas when this ratio is of the order ten the particles are distributed in a random manner. For the non uniform electric field cases considered in this paper, the relative magnitude of Brownian forces is in the range such that it does not influence the eventual collection of particles by dielectrophoresis and the particular locations where the particles are collected. However, Brownian motion is observed to influence the transient particle trajectories. The deviation of the particle trajectories compared to those determined by the electrostatic and hydrodynamic forces alone is characterized by the ratio of Brownian and dielectrophoretic forces.
Regulation of Cell Adhesion and De-Adhesion Proteins in Veins Perfused Under Arterial Conditions Ex-Vivo
Authors: El-Kurdi Mohammed S. , Van Epps J. Scott , Toth Robert J. , Hamilton Douglas W. , Wu Chuanyue , Vipperman Jeffrey S. , Vorp David A.
Published: April 2008

Failure of veins employed as arterial bypass grafts via intimal hyperplasia (IH) often occurs within 5 years after implantation, requiring re-operation in 60% of all cases1. IH is characterized by de-adhesion, followed by migration of medial and adventitial smooth muscle cells (SMCs) and myofibroblasts into the intima, where they demonstrate uncontrolled proliferation. It is thought that this process may be induced by the abrupt exposure of the veins to the dynamic mechanical environment of the arterial circulation2. Veins are much thinner walled and more distensible than arteries. Therefore, the SMCs within the vein wall are exposed to significantly higher levels of stress and strain than they are accustomed2. The tissue responds to this perceived injury by thickening, which is thought to be an attempt to return the stress and strain to venous levels. However, when this response is uncontrolled it can over-compensate, leading to stenosis instead of the desired thickening or “arterialization” of the vein segment. Cellular de-adhesion, which refers to a change from a state of stronger adherence to a state of weaker adherence, is involved in the earliest response and therefore was the focus of this study. While there are many important proteins involved in the regulation of cellular adhesion, we focus our attention here to matricellular proteins, which function as adaptors and modulators of cell-matrix interactions3,4, and intracellular adhesion proteins, which have been shown to localize to cellular focal adhesion sites5,6. Tenascin-C (TN-C), thrombospondin-1,2 (TSP), and secreted protein acidic and rich in cysteine (SPARC) are matricellular proteins that exhibit highly regulated expression during development and cellular injury7. Mitogen inducible gene 2 (Mig-2) and integrin linked kinase (ILK) are intracellular proteins involved in cellular shape modulation5 and integrin-mediated signal transduction8, respectively. It is well known that many intracellular and extracellular matrix proteins are regulated by mechanical stress9,10. The purpose of this work was to explore the hypothesis that intact vein segments exposed to arterial hemodynamics will alter their expression of TN-C, TSP, SPARC, Mig-2 and ILK within 24 hours. This may induce a modulation of the level of cell adhesion, which could contribute to IH.
Compact Actuation Through Magnetorheological Flow Control and Rectification of Magnetostrictive Vibrations
Authors: Nosse David , Burton Brett , Dapino Marcelo
Published: April 2008

There is currently a need for compact actuators capable of producing large deflections, large forces, and broad frequency bandwidth. In all existing transducer materials, large force and broadband responses are obtained at small displacements and methods for transmitting very short transducer element motion to large deformations need to be developed. This paper addresses the development of a hybrid actuator which provides virtually unlimited deflections and large forces through magnetorheological (MR) flow control and rectification of the resonant mechanical vibrations produced by a magnetostrictive Terfenol-D pump. The device is a compact, self-contained unit which produces large work output concurrently with stiffness and damping control and is self-locking when unpowered. To increase the output force, hydraulic advantage is created by implementing a driven piston diameter that is larger than the drive piston. Since the pump operates at high speeds in the low kHz range, a fast-acting MR fluid valve is required. The paper presents a four-port MR fluid valve in which the fluid controls its own flow while carrying the full transducer load. A multi-domain systems model for the coupled dynamics of the valve is presented. A four-port valve was constructed and tested for purposes of proof-of-the-concept validation, model verification and system parameter identification. The combined experimental and model results demonstrate the feasibility of the proposed transducer concept.
The Attachment of Carbon Nanotube on a Blunt AFM Tip Using Electric Fields
Authors: Lee Hyung Woo , Kwon Soon Geun , Kim Soo Hyun , Kwak Yoon Keun , Han Chang Soo
Published: April 2008

We report a simple, low cost, reliable technique of making carbon nanotube (CNT) modified atomic force microscopy (AFM) tip. We used the dielectrophoresis and the electrophoresis to align and deposit carbon nanotubes on the end of the AFM tip. From the simulation and the various experiments, we obtained the optimal electric condition, 0.32Vpp/μm. Also, we found that the blunt shape of the tip’s apex is more effective than sharpened one. Through the experiments, we verified that the blunt shape is more effective over 50% than the sharpened one in the attachment of CNTs. By comparing the scanning results between the CNT modified tip and a normal AFM tip, we obtained the improvement in efficiency of 23%.
Contact Modelling in Method of Influence Coefficient for Variation Simulation of Sheet Metal Assemblies
Authors: Dahlstro¨m Stefan , Lindkvist Lars
Published: April 2008

Sheet metal assembly is a common manufacturing process for several products such as automobiles and airplanes. Since all manufacturing processes are affected by variation and products need to have a high geometric quality, geometry related production problems must be analyzed during early design phases. Often, the analysis is done by using FEA (Finite Element Analysis) to include the compliant behavior of the parts. There are many variables that affect the geometric quality and to include many of them in a FEA simulation is often very time-consuming. One way of performing the simulations relatively fast is to establish linear relationships between part deviation and assembly spring-back deviation by using Method of Influence Coefficient (MIC). However, one limitation with the method is that the method does not consider contact between the parts. This means that the parts are allowed to penetrate each other. In some cases when contact occurs, this method will not simulate the real behavior of the assembly. This paper presents a contact modeling technique that can be implemented in the MIC. The contact modeling procedure consists of a contact detection algorithm and a solution algorithm for finding the position of equilibrium. When implemented, the MIC still only requires two FEA calculations. This paper describes the steps in the contact algorithm and how it can be used in MIC, finally a case study is analyzed.
The Effect of the Accuracy of Various Measuring Devices on Recorded Joint Kinematics
Authors: Moore Susan M. , Gabriel Mary T. , Thomas Maribeth , Zeminski Jennifer , Woo Savio L.-Y. , Debski Richard E.
Published: April 2008

Knowledge of joint kinematics contributes to the understanding of the function of soft tissue restraints, injury mechanisms, and can be used to evaluate surgical repair techniques. (Tibone, McMahon et al. 1998; Karduna, McClure et al. 2001; Abramowitch, Papageorgiou et al. 2003) Previous studies have measured joint kinematics using a variety of non-invasive methods that include: optical tracking, magnetic tracking, and mechanical linkage systems. (Rudins, Laskowski et al. 1997; Apreleva, Hasselman et al. 1998; Gabriel, Wong et al. 2004) These measurement devices report kinematics of rigid bodies with respect their own global coordinate system. However, it is often useful to understand these kinematics in terms of a coordinate system whose axes coincide with the degrees of freedom of each specific joint (anatomical coordinate systems). Once the kinematics are obtained with respect to the global coordinate system of the measurement device, the joint kinematics can be calculated with respect to anatomical coordinate systems if the relationship between the measurement device and the anatomical coordinate systems are known. Although the accuracy of these kinematic measurement devices is provided by the manufacturer, the effect of their accuracy on joint kinematics reported with respect to anatomical coordinate systems must be determined. (Panjabi, Goel et al. 1982; Crisco, Chen et al. 1994) For example, small errors in orientation of the measurement system could lead to large errors in position for an anatomical coordinate system located at some distance away. As researchers report joint kinematics with respect to the anatomical coordinate systems, understanding the errors produced by one’s measurement device with respect to the anatomical coordinate systems is necessary. Further, a great deal of interest exists for studying knee joint kinematics. (Sakane, Livesay et al. 1999; Lephart, Ferris et al. 2002; Ford, Myer et al. 2003) Within our research center our goal is to collect knee joint kinematics of a cadaver and reproduce them with respect to the anatomical coordinate systems using robotic technology. Therefore, the objective of this study was to determine the effect of the accuracy of three measurement devices (optical tracking device-OptoTrak® 3020, magnetic tracking device-Flock of Birds®, instrumented spatial linkage-EnduraTec Corp.) on knee joint kinematics reported with respect to an anatomical coordinate system.
PZT-Actuated In-Flight Deicing With Simultaneous Shear and Impulse Forces
Authors: Venna Suresh V. , Lin Y. J.
Published: April 2008

Piezoelectric actuations for simultaneous generation of shear and impulse forces for effective and energy efficient deicing applications are proposed. Aircraft leading edge structures is considered for the analysis. Adhesive shear bond between the ice layer and the substrate, which is more than ten times weaker than the normal bond, is targeted to achieve deicing. Piezoelectric actuators consisting of high normal to shear coupling factor(d15) are considered at the inner surface of the leading edge at the locations where highest amount of ice accretion is occurred. Simultaneous shear and impulse force generation can be achieved with actuators consisting of two sets of electrodes, one arranged in parallel to the poling direction and the other perpendicular to the poling direction to generate shear forces and normal forces respectively. Appropriate piezoelectric material configuration is chosen, so that enough shear forces are generated to weaken the bond of the ice-substrate interface which is weak in shear. Once the shear bond is weakened, applied normal impulses force the ice layer come off the surface. Finite element model of the leading edge structure with ice accretion layer and piezoelectric actuators are constructed. Simulations of the deicing process are performed and the actuator locations, electric charge applied and impulse duration are optimized. This method employs single actuator for both shear and impulse generation and consumes far less power than any existing in-flight deicing methods.
Design and Convergence of a Time-Varying Iterative Learning Control Law
Authors: Tharayil Marina , Alleyne Andrew
Published: April 2008

This paper presents a novel linear time-varying (LTV) iterative learning control law that can provide additional performance while maintaining the robustness and convergence properties comparable to those obtained using traditional frequency domain design techniques. Design aspects of causal and non-causal linear time-invariant (LTI), along with the proposed LTV, ILC update laws are discussed and demonstrated using a simplified example. Asymptotic as well as monotonic convergence, robustness and performance characteristics of such systems are considered, and an equivalent condition to the frequency domain convergence condition is presented for the time-varying ILC. Lastly the ILC algorithm developed here is implemented on a Microscale Robotic Deposition system to provide experimental verification.
Burning Speed Measurement of JP-8 Air Flames
Authors: Parsinejad Farzan , Arcari Christian , Shirk Edwin , Metghalchi Hameed
Published: April 2008

Burning speed measurement and structure of JP-8 air mixtures at a wide range of temperature and pressure have been studied using two matched constant volume chambers. The experimental facilities include a spherical chamber and cylindrical vessel with glasses at the end caps to enable us visualizing flame structure. Cylindrical vessel is located in a Schlieren set up including spherical mirrors and a high speed CCD camera. Facilities also include and oven which can raise the initial temperature of the mixtures in spherical vessel to 500 K and similar heating elements that perform the same task in cylindrical chamber. A thermodynamic model has been developed to calculate burning speeds using dynamic pressure rise in the chamber. The model considers a central burned gas core of variable temperature surrounded by an unburned gas shell with uniform temperature with a thermal boundary layer at the wall. Burning speed and flame structure of different gaseous fuel-air mixtures have been investigated. Autoignition characteristics of JP-8 air mixtures have also been determined by the sudden pressure rise in spherical vessel.
Calculation of Polymer Flow Using Micro-Macro Simulations
Authors: Feigl Kathleen , Senaratne Deepthika C.
Published: April 2008

A micro-macro simulation algorithm for the calculation of polymeric flow is developed and implemented. The algorithm couples standard finite element techniques to compute velocity and pressure fields with stochastic simulation techniques to compute polymer stress from simulated polymer dynamics. The polymer stress is computed using a microscopic-based rheological model which combines aspects of network and reptation theory with aspects of continuum mechanics. The model dynamics include two Gaussian stochastic processes each of which is destroyed and regenerated according to a survival time randomly generated from the material’s relaxation spectrum. The Eulerian form of the evolution equations for the polymer configurations are spatially discretized using the discontinuous Galerkin method. The algorithm is tested on benchmark contraction domains for a polyisobutylene (PIB) solution. In particular, the flow in the abrupt die entry domain is simulated and the simulation results are compared with experimental data. The results exhibit the correct qualitative behavior of the polymer and agree well with the experimental data.
Effects of a Cryoprotective Agent on Thermal Properties of Solutions at Subzero Temperatures
Authors: Choi Jeung Wan , Han Bumsoo , Bischof John C.
Published: April 2008

The study focuses on evaluating the effects of adding a cryoprotective agent (CPA) on the thermal properties of solutions. Preliminary results for Phosphate Buffered Saline (PBS) with glycerol at subzero temperatures are reported. A Differential Scanning Calorimeter (DSC) was used to measure the specific heat and to observe latent heat release. Cryomicroscopy was performed using a cryostage to control the cooling and heating rate of the sample and visually observe microscopic changes. The specific heat data obtained from the DSC is also used for predicting bulk thermal conductivity by a transient heat transfer model using a thermistor. Thermal properties measurement results show opposing trends prior to and after devitrification and melting events with respect to glycerol concentration.
Pulse Combustion in a Traveling Wave Thermoacoustic Engine
Authors: Weiland Nathan T. , Zinn Ben T.
Published: April 2008

This work describes the use of pulse combustion for increasing the acoustic power output of a thermoacoustic engine. Such engines directly convert thermal energy into acoustic energy, which is typically used to drive a thermoacoustic refrigeration process that can achieve cryogenic temperatures without the use of moving parts. After a brief overview of thermoacoustics, the design of the thermoacoustic engine is discussed, and a perturbation analysis of the thermoacoustic energy fluxes and pulse combustion process is presented to quantify the extent to which pulse combustion has the potential to add to the engine’s acoustic power output. Guided by this analysis and the requirements of the engine design, various active and passive combustion control strategies for the reactant injection configuration and combustion chamber design are discussed.
Surface Reconstruction From Dexel Data for Virtual Sculpting
Authors: Peng Xiaobo , Zhang Weihan , Asam Sai-Gowthami , Leu Ming C.
Published: April 2008

This paper presents a new method for surface reconstruction from dexel data for virtual sculpting. We are in the midst of developing a dexel model based sculpting system having the capability of interactive solid modeling with haptics interface. The geometric modeling of our sculpting system is based on the Sweep Differential Equation method to compute the boundary of the tool swept volume. Ray casting is used to perform Boolean operations between the tool swept volume and the virtual stock in dexel models to simulate the sculpting process. The dexel data are converted to a series of planar contours in parallel slices (i.e. cross sections). The overlapping ratio between two contour areas is used as the criterion for deciding on the corresponding contours in two adjacent slices. The tiling problem is tackled by using the rule of the shortest distance between points on two corresponding contours. The branching problem is solved by adding one line segment between two contours to form one composite contour. Examples are given to demonstrate the ability of the developed code to convert from dexel data to triangular meshes for the viewing of a sculpted model in different directions.
Development and Validation of a Finite Element Model of the Lower Limb
Authors: Untaroiu Costin , Darvish Kurosh , Crandall Jeff , Deng Bing , Wang J. T.
Published: April 2008

Pedestrians struck by a vehicle frequently sustain lower limb injuries. Moreover, the biomechanics of the lower limb under lateral impact influences the trajectory of the pedestrian and subsequent injuries to the pelvis, thorax, and head. In order to increase the understanding of injury mechanisms in the lower limb, a finite element (FE) model of the lower limb was developed. The geometry of the bones and flesh was originally obtained from the Visible Human Project Database and was scaled to a 50th percentile male. The geometry of the knee ligaments was originally obtained from the 3D-CAD-Browser Database and was scaled according to the published anatomical data to align with the bones and the corresponding insertion sites. The FE mesh consists mostly of hexahedral elements which was developed using a structural mesh generator. The material and failure properties were initially selected from the literature and were later tuned based on the validation tests. The FE model was validated using the literature data and several cadaveric component tests performed specifically for model development and evaluation. The validation tests included quasi-static and dynamic lateral three-point-bend tests of the femur and the leg with flesh, and lateral four-point-bend tests of the knee joint.
Performance Characteristics of a Microturbine-Double Effect Absorption Chiller CHP System
Authors: Wagner Timothy C. , Marler Mark E. , Jung Sunghan
Published: April 2008

A combined heat and power (CHP) system consisting of four natural gas-fired microturbines and a double effect absorption chiller/heater has been developed and tested. The system is designed to operate in one of three modes: Power Only, Power and Cooling, and Power and Heating. Depending on the operating mode, the system is capable of generating 240 kW of electrical power, 387 kW of cooling capacity, and 264 kW of heating capacity. This paper will present test results of the system performance, including power output, cooling and heating capacity, system fuel utilization, and sound levels for conditions representative of commercial buildings located in the United States.
A New Method for a Single Semi-Conducting Nanotube Device
Authors: Lee Hyung Woo , Kim Soo Hyun , Kwak Yoon Keun , Han Chang Soo
Published: April 2008

We report a new technology for the selective deposition of a semi-conducting single-walled carbon nanotube(SWNT) between two electrodes. This technology consists of two processes. First, to separate the most of metallic nanotubes from semi-conducting ones and align the nanotubes, we applied dc and ac voltage to the electrodes respectively. But, in spite of the separation of the metallic nanotubes from semi-conducting nanotubes, some of metallic nanotubes and semi-conducting nanotubes are still deposited together. The second process is to burn the metallic and semi-conducting nanotubes by applying the voltage between two electrodes which enable to obtain a single semi-conducting nanotube structure. We verified the trace of the burning by SEM images or AFM images, and checked the characteristic of semi-conducting nanotubes through the I-V characteristic graph.
Characterization of Heating, Movement and Visualization of Magnetic Nanoparticles for Biomedical Applications
Authors: Kalambur Venkatasubramaniam S. , Han Bumsoo , Kim Byeong-Su , Taton T. Andrew , Bischof John C.
Published: April 2008

Magnetic nanoparticles can be used for a variety of biomedical applications. They can be used in the targeted delivery of therapeutic agents, as contrast agents in MR imaging and in the hyperthermic treatment of cancers. Previous studies using these particles have not dealt with a quantitative characterization of movement and heating of these particles in biological environments. In the present study, the thermal characteristics of magnetic nanoparticles in water and collagen were investigated. In other studies, the movement of these particles in collagen in a known magnetic field was studied; infra-red (IR) imaging was used to visualize these particles in vitro. The results show that the amount of temperature rise increases with the concentration of nanoparticles regardless of the microenvironments. However, the amount of heating in collagen is significantly less than water at the same nanoparticle concentration. IR imaging can be used to visualize these particles in vitro over a wide range of concentrations of these nanoparticles.
Bridging Mechanical Stimulation of Cellular and Molecular Structure Through Lattice Based Computational Simulations
Authors: Puskar Kathleen , Apeltsin Leonard , Ta’asan Shlomo , Schwartz Russell , LeDuc Philip R.
Published: April 2008

Understanding the connection between mechanics and cell structure requires a critical exploration of molecular structure. One of these molecular bridges is known to be the cytoskeleton, which is involved with intracellular organization and mechanotransduction. In order to examine the structure in cells, we have developed a computational simulation that is able to probe the self-assembly of actin filaments through a lattice based Monte Carlo method. We have modeled the polymerization of these filaments based upon the interactions of globular actin through a probabilistic scheme with both inert and active proteins. The results show similar response to classic ordinary differential equations at low molecular concentrations, but a bi-phasic divergence at realistic concentrations for living mammalian cells. Further, these inert monomers have a limiting effect based upon their relative density ratios, which alter the polymerization process. Finally, by introducing localized mobility parameters, we are able to set up molecular gradients that are found in non-homogeneous protein distributions in vitro. This method and results have potential applications in cell and molecular biology as well as self assembly in inorganic systems.
Dynamic Response of Dielectric Elastomers
Authors: Mockensturm Eric M. , Goulbourne Nakhiah
Published: April 2008

Dielectric elastomers have received a great deal of attention recently for effectively transforming electrical energy to mechanical work. Their large strains and conformability make them enticing materials for many new types of actuators. Unfortunately, their non-linear material behavior and large deformations make actual devices difficult to model. However, the reason for this difficulty can also be used to design actuators that utilize these material and geometric non-linearities to obtain multiple stable equilibria. In this work, we investigate one of the simplest possible configurations, a spherical membrane, using a model that incorporates both mechanical and electrostatic pressure as well as inertial effects that become important when transitioning from one equilibrium to another.
Modeling and Characterization of Laser Drilling of Small Holes on Metal Sheets
Authors: Han Wei , Pryputniewicz Ryszard J.
Published: April 2008

Laser drilling is increasingly being used in fabrication of small components in various materials with applications in aerospace, automotive, electronics and medical industries, and it offers a unique combination of benefits for the contemporary manufacturing industry as a rapid, precise, clean, flexible, and efficient process. Laser drilling involves a stationary laser beam which uses its high power density to melt or vaporize material from the workpiece, and the process is governed by an energy balance between the irradiating energy from the laser beam, the conduction heat into the workpiece, the energy losses to the environment, and the energy required for phase change in the workpiece. There are three major mechanisms of removal of material from the beam interaction zone and consequent propagation of the melt front into the metal bulk. They are (1) melt ejection due to interaction between the melt and an assisting gas, (2) melt ejection by the vaporization-induced recoil force, and (3) melt evaporation. The results of laser drilling processes, such as the profile of the heat affected zone (HAZ) and the geometry of the holes, strongly depend on settings of the laser parameters such as peak power, pulse length, pulse repetition rate, number of pulses, focal condition, etc. In addition, the processing results are strongly influenced by geometrical and material properties of the workpiece. This paper presents theoretical and experimental studies of laser drilling of micrometer size holes on metal sheets using a pulsed Nd:YAG laser. A model of the temperature distribution and the motion of the melting front for laser drilling is presented and compared with experimental data. Effects of laser parameters on the resultant geometry of the hole are investigated and summarized, and an optimum procedure for laser drilling of small holes on metal sheets is outlined.
Linear Perturbation Adaptive Control of Hydraulically Driven Manipulators
Authors: Andersen Torben Ole , Hansen Michael Rygaard , Conrad Finn
Published: April 2008

A method for synthesis of a robust adaptive scheme for a hydraulically driven manipulator, that takes full advantage of any known system dynamics to simplify the adaptive control problem for the unknown portion of the dynamics is presented. The control method is based on adaptive perturbation control. Using the Lyapunov approach, under slowly time-varying assumptions, it is shown that the tracking error and the parameter error remain bounded. This bound is a function of the ideal parameters and a bounded disturbance. The control algorithm decouples and linearizes the manipulator so that each joint behaves as an independent second-order system with fixed dynamics.