bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimizing Selection of Appropriate Power Generation Systems in Indonesia By Using Distance Based Approach Method
Authors: Widiyanto Anugerah , Kato Seizo , Maruyama Naoki
Published: May 2004

A deterministic quantitative model has been developed to compare the technical, economical and environmental feature of various electric power generating plants. The model, which is based on matrix operations, is used in evaluating the various aspects of energy sources available for electricity generation systems in a developing country. Several energy sources which could be considered for production of electricity to meet current and future electricity demands have been chosen. These will include fossil fuel fired, nuclear, and natural-renewable energy power plants. And, a set of criteria for optimized selection includes five area of concerns: energy economy, energy security, environmental protection, socio-economic development and technological aspects for the electric power generations. The model developed in this study is applied to the Indonesian’s electric power sector development. Most of the data required are obtained from various sources related to power industry in Indonesia, such as the electricity generating authority of Indonesia (Perusahaan Listrik Negara, PLN), Government of Indonesia, World Bank, Asian Development Bank, United Nations, and other sources, both in published and public domains. The result of this study will be a ranking of energy sources for Indonesia power generation systems based on the Euclidean composite distance of each alternative to the designated optimal source of energy.
Prediction of Slug Length Distribution Along a Hilly Terrain Pipeline Using Slug Tracking Model
Authors: Al-safran Eissa M. , Taitel Yehuda , Brill James P.
Published: May 2004

Accurate prediction of slug length distribution and the maximum slug length in a hilly terrain pipeline is crucial for designing downstream separation facilities. A hilly terrain pipeline consists of interconnected uphill and downhill pipe sections, where slugs can dissipate in the downhill sections and grow in the uphill sections. Furthermore, new slugs can be generated at the dips (bottom elbows) and dissipate at the top elbows. Although existing steady-state models are capable of predicting the average slug length for pressure drop calculations and pipeline design, they are incapable of predicting detailed flow characteristics such as the maximum slug length expected at the exit of a hilly terrain pipeline. A transient slug tracking model based on a quasi-equilibrium formulation was developed to track the front and back of each individual slug, from which individual slug lengths are calculated. The model was verified with large-scale two-phase flow hilly terrain experimental data acquired at the Tulsa University Fluid Flow Projects (TUFFP). The results show a fairly accurate match between the model predictions and experimental data.
Convective Heat Transfer Near One-Dimensional and Two-Dimensional Wall Temperature Steps
Authors: Mukerji Debjit , Eaton John K. , Moffat Robert J.
Published: May 2004

Steady-state experiments with one-dimensional and two-dimensional calorimeters were used to study the convective heat transfer near sharp steps in wall temperature in a turbulent boundary layer. Data acquired under low and high freestream turbulence conditions indicated that spanwise turbulent diffusion is not a significant heat transport mechanism for a two-dimensional temperature step. The one-dimensional calorimeter heat transfer data were predicted within ±5 percent using the STAN7 boundary layer code for situations with an abrupt wall temperature step. The conventional correlation with an unheated starting length correction, in contrast, greatly under-predicts the heat transfer for the same experimental cases. A new correlation was developed that is in good agreement with near and far-field semi-analytical solutions and predicts the calorimeter heat transfer data to within ±2 percent for temperature step boundary condition cases.
Experiments on Heat Transfer in a Thin Liquid Film Flowing Over a Rotating Disk
Authors: Ozar B. , Cetegen B. M. , Faghri A.
Published: May 2004

An experimental study of heat transfer into a thin liquid film on a rotating heated disk is described. Deionized water was introduced at the center of a heated, horizontal disk with a constant film thickness and uniform radial velocity. Radial distribution of the disk surface temperatures was measured using a thermocouple/slip ring arrangement. Experiments were performed for a range of liquid flow rates between 3.0 lpm and 15.0 lpm. The angular speed of the disk was varied from 0 rpm to 500 rpm. The local heat transfer coefficient was determined based on the heat flux supplied to the disk and the temperature difference between the measured disk surface temperature and the liquid entrance temperature onto the disk. The local heat transfer coefficient was seen to increase with increasing flow rate as well as increasing angular velocity of the disk. Effect of rotation on heat transfer was largest for the lower liquid flow rates with the effect gradually decreasing with increasing liquid flow rates. Semi-empirical correlations are presented in this study for the local and average Nusselt numbers.
Spectral Emittance of Particulate Ash-Like Deposits: Theoretical Predictions Compared to Experimental Measurement
Authors: Bhattacharya S. P.
Published: May 2004

This note presents results of a theoretical and experimental investigation on the emittance of particulate deposits. A simple model based on independent and multiple scattering and using discrete ordinate method has been developed to predict the spectral hemispherical and normal emittance of particulate deposits. The model predictions are compared with measurements carried out under this study-controlled spectral emission measurements between wavelengths of 2 and 12 μm on deposits of ground synthetic ash particles having known composition and particle size. The trends from the predictions matched well with the measured values, except for some differences in the wavelength region below 4 μm, and between 8 μm and 12 μm wavelength. Possible reasons for these differences are discussed.
Effect of Double Stratification on Free Convection in a Darcian Porous Medium
Authors: Murthy P. V. S. N. , Srinivasacharya and D. , Krishna P. V. S. S. S. R.
Published: May 2004

The problem of free convection heat and mass transfer from vertical surface embedded in a doubly stratified porous medium has been studied. The similarity solution is presented for the case of uniform heat and mass flux conditions when the thermal and solutal stratification of the medium are assumed to have the power function form x1/3. The flow, temperature and concentration fields are effected by the complex interactions among the diffusion ratio parameter Le and buoyancy ratio parameter N in addition to the flow driving Darcy-Rayleigh number Rax. The temperature and concentration profiles are effected due to double stratification of the medium and its effect on the Nusselt and Sherwood numbers is discussed.
A Numerical Model Coupling the Heat and Gas Species’ Transport Processes in a Tubular SOFC
Authors: Li Pei-Wen , Schaefer Laura , Chyu Minking K.
Published: May 2004

A numerical model is presented in this work that computes the interdependent fields of flow, temperature, and mass fractions in a single tubular solid oxide fuel cell (SOFC). Fuel gas from a pre-reformer is considered to contain H2, CO, CO2,H2O (vapor), and CH4, so reforming and shift reactions in the cell are incorporated. The model uses mixture gas properties of the fuel and oxidant that are functions of the numerically obtained local temperature, pressure, and species concentrations, which are both interdependent and related to the chemical and electrochemical reactions. A discretized network circuit of a tubular SOFC was adopted to account for the Ohmic losses and Joule heating from the current passing around the circumference of the cell to the interconnect. In the iterative computation, local electrochemical parameters were simultaneously calculated based on the local parameters of pressure, temperature, and concentration of the species. Upon convergence of the computation, both local details and the overall performance of the fuel cell are obtained. These numerical results are important in order to better understand the operation of SOFCs.
Advancements in Salinity Gradient Solar Pond Technology Based on Sixteen Years of Operational Experience
Authors: Lu Huanmin , Swift Andrew H. P. , Hein, Herbert D. , Walton John C.
Published: May 2004

The El Paso salinity gradient solar pond, initiated in 1983, has been in operation since 1985. Through 16 years of research and operation, the El Paso Solar Pond has successfully demonstrated applications including desalination, waste brine management, industrial process heat production, and electricity generation; and has developed and implemented key technical advancements to improve the technical viability and economic feasibility of salinity gradient solar ponds, including: 1) an automated instrumentation monitoring system, 2) a stability analysis strategy and high temperature (60–90°C) gradient maintenance methods, 3) a scanning injection technique for improved salinity gradient construction and maintenance, 4) new liner technology, and 5) an improved heat extraction system.
Generation of Hourly Ambient Temperature from Generalized Cumulative Frequency Distributions
Authors: Satyamurty V. V. , Ravikumar P.
Published: May 2004

The present article is devoted to make available a method to generate hourly ambient temperature values when the monthly average hourly ambient temperature, T¯ah is known. Cumulative frequency distributions for hourly ambient temperature have been developed employing normalized variables. The normalized variables used in the present study contain not only the monthly average hourly ambient temperature but also the maximum, Tah,max, and minimum, Tah,min. In order that the frequency distributions developed in the present study become available for the purpose of calculating hourly ambient temperature when T¯ah only is known, correlations to estimate Tah,max and Tah,min from known parameters have been presented. The ability of the present distributions to generate hourly ambient temperatures during a day has also been established. A large data base of 239 locations has been employed in developing and validating the distributions and the needed additional correlations. The predicted hourly ambient temperature values have been found to be in agreement with data values within a % rms difference of 0.30 (when Tah is in K) and the standard deviation has been found to be 0.85 K. The agreement between the predicted hourly ambient temperatures during a day employing the present distributions and the data values has been excellent.
Development of “Low-tech” Solar Thermal Water Pumps for Use in Developing Countries
Authors: Orda E. , Mahkamov K.
Published: May 2004

Solar water pumps, based on electro-mechanical pumps powered by PV arrays, are commonly used and commercially available. However, one of the difficulties for their wider application in developing countries, where there is a high average insolation, is their relatively excessive cost. This arises mainly due to the high cost of the PV elements. Hence, this paper describes some developmental work and results of experimental tests on “low-tech” solar thermal water pumps which were built on the basis of Stirling engines with fluid pistons coupled to flat-plate solar collectors. Temperatures and pressures in the cycle are comparatively low, thus cheap design materials, such as glass and plastic, and a simple technology, available in the majority of mechanical workshops, can be used for their manufacture and consequently reduce their cost. Several design modifications of the above solar thermal water pumps have been developed and tested. The results obtained demonstrate that existing installations can be effectively applied for water pumping with a dynamic head which varies between 2-5 m. Furthermore, data from experimental tests shows that the pulsating motion of water in channels of the flat-plate solar collectors increases the collector’s efficiency by approximately 8-10%, which is a considerable advantage when a pump is used as part of a house solar heating system.
On the Group Front and Group Velocity in a Dispersive Medium Upon Refraction From a Nondispersive Medium
Authors: Zhang Z. M. , Park Keunhan
Published: May 2004

Conventional definitions of velocities associated with the propagation of modulated waves cannot clearly describe the behavior of the wave packet in a multidimensional dispersive medium. The conventional definition of the phase velocity, which is perpendicular to the wave front, is a special case of the generalized phase velocity defined in this work, since there exist an infinite number of solutions to the equation describing the wave-front movement. Similarly, the generalized group-front velocity is defined for the movement of a wave packet in an arbitrary direction. The group-front velocity is the smallest speed at which the group-front travels in the direction normal to the group front. The group velocity, which is the velocity of energy flow in a nondissipative medium, also satisfies the group-front equation. Because the group-front velocity and the group velocity are not always the same, the direction in which the wave packet travels is not necessarily normal to the group front. In this work, two examples are used to demonstrate this behavior by considering the refraction of a wave packet from vacuum to either a positive-index material (PIM) or a negative-index material (NIM).
Spatially Resolved Surface Heat Transfer for Parallel Rib Turbulators With 45 Deg Orientations Including Test Surface Conduction Analysis
Authors: Won S. Y. , Burgess N. K. , Peddicord S. , Ligrani P. M.
Published: May 2004

Spatially resolved Nusselt numbers, spatially-averaged Nusselt numbers, and friction factors are presented for a stationary channel with an aspect ratio of 4 and angled rib turbulators inclined at 45 deg with parallel orientations on two opposite surfaces. Results are given at different Reynolds numbers based on channel height from 9000 to 76,000. The ratio of rib height to hydraulic diameter is 0.078, the rib pitch-to-height ratio is 10, and the blockage provided by the ribs is 25 percent of the channel cross-sectional area. Nusselt numbers are determined with three-dimensional conduction considered within the acrylic test surface. Test surface conduction results in important variations of surface heat flux, which give decreased local Nusselt number ratios near corners, where each rib joins the flat part of the test surface, and along the central part of each rib top surface. However, even with test surface conduction included in the analysis, spatially-resolved local Nusselt numbers are highest on tops of the rib turbulators, with lower magnitudes on flat surfaces between the ribs, where regions of flow separation and shear layer re-attachment have pronounced influences on local surface heat transfer behavior. The augmented local and spatially averaged Nusselt number ratios (rib turbulator Nusselt numbers normalized by values measured in a smooth channel) decrease on the rib tops, and on the flat regions away from the ribs, especially at locations just downstream of the ribs, as Reynolds number increases. With conduction along and within the test surface considered, globally averaged Nusselt number ratios vary from 3.53 to 1.79 as Reynolds number increases from 9000 to 76,000. Corresponding thermal performance parameters also decrease as Reynolds number increases over this range.
Solar-Assisted Induced Ventilation of Small Field Structures
Authors: Oz S. , Fogel S. , Dubovsky V. , Ziskind G. , Letan R.
Published: May 2004

Induced passive ventilation was studied in a small field structure, about 60cm×30cm×85cm in size, heated by solar irradiation. The structure has three stories, connected by a vertical duct, which in turn is connected to a horizontal duct above the upper level of the structure. The outer walls of these two ducts are metal sheets painted on the outside with black matte paint and covered by glass sheets. The other outer walls and inner partitions of the structure are made of cardboard attached to a metal frame. Additional elements included in some experiments were a water tank, used for heat storage, and a chimney for enhancing air flow. The structure orientation was with its vertical metal sheet facing south-west. Experimental study, based on temperature and velocity measurement, and computer simulations, using the FLUENT software, were performed. During a typical experiment, the structure has been exposed to the sun for a full day in July through November. The ports of the system were either opened in the morning, or kept closed until about 13:45-14:00 and then opened. The results of the study indicate that effective ventilation has been achieved: the calculated rates of air change inside the stories were rather high, and the mean air temperatures were only about 1-2°C above the ambient in its lower stories and 2-3°C above the ambient in the upper story. Detailed comparison of the experimental and numerical results is presented and discussed.
Heat Transfer Enhancement Using Shaped Polymer Tubes: Fin Analysis
Authors: Li Zhihua , Davidson Jane H. , Mantell Susan C.
Published: May 2004

The use of polymer tubes for heat exchanger tube bundles is of interest in many applications where corrosion, mineral build-up and/or weight are important. The challenge of overcoming the low thermal conductivity of polymers may be met by using many small-diameter, thin-walled polymer tubes and this route is being pursued by industry. We propose the use of unique shaped tubes that are easily extruded using polymeric materials. The shaped tubes are streamlined to reduce form drag yet the inside flow passage is kept circular to maintain the pressure capability of the tube. Special treatment is required to predict convective heat transfer rates because the temperature distribution along the outer surface of the shaped tubes is nonuniform. The average forced convection Nusselt number correlations developed for these noncircular tubes can not be used directly to determine heat transfer rate. In this paper, heat transfer rates of shaped tubes are characterized by treating the tubes as a base circular tube to which longitudinal fin(s) are added. Numerical solution of an energy balance on the fin provides the surface temperature distribution and a shaped tube efficiency, which can be used in the same manner as a fin efficiency to determine the outside convective resistance. The approach is illustrated for three streamlined shapes with fins of lenticular and oval profile. The presentation highlights the effects of the geometry and the Biot number on the tube efficiency and heat transfer enhancement. Convective heat transfer is enhanced for the oval shaped tube for 2000⩽Re⩽20,000 when Bi<0.3. For polymeric materials, the Biot number in most applications will be greater than 0.3, and adding material to the base tube reduces the heat transfer rate. The potential benefit of reduced form drag remains.
Modelling, Identification, and Passivity-Based Robust Control of Piezo-actuated Flexible Beam
Authors: Gosavi S. V. , Kelkar A. G.
Published: May 2004

This paper presents modelling, system identification, simulation, and experimental results for passivity-based robust control of piezo-actuated flexible beam. The flexible beam configuration considered is a cantilever aluminum beam with a piezoelectric transducer used as the actuator and tip-accelerometer as the sensor. The actuator and sensor are non-collocated. The Lagrangian formulation is used to obtain mathematical model of the flexible link dynamics with piezo actuator. For control design purposes, a finite dimensional approximate model is derived using assumed modes approach. It is shown that the approximate model compares very well with the experimentally identified model. Since the system is inherently not passive, passification techniques are used to render the system robustly passive which enables the use of passivity-based feedback control design. The controller design is validated both in simulation as well as in experiments. The simulation and experimental results demonstrate the effectiveness of controller in suppressing the tip vibrations of the link. The controller design is shown to be robust to both parametric uncertainties and unmodeled dynamics.
Using the Modal and Trigonometric Collocation Methods in Rotor Dynamic Systems
Authors: Malenovsky´ Eduard
Published: May 2004

This article deals with the computational modeling of nonlinear rotor dynamic systems. The theoretical basis of the modal method, and combination with the method of dynamic compliances supplemented by the method of trigonometric collocation, is presented. The main analysis is focused on the solutions of transient and steady state responses. The algorithms for solving this range of problems are presented. The finite element method is the basis for both methods. The theoretical analysis is supplemented with a solution of an example model.
Isolated Resonance Captures and Resonance Capture Cascades Leading to Single- or Multi-Mode Passive Energy Pumping in Damped Coupled Oscillators
Authors: Vakakis Alexander F. , McFarland D. Michael , Bergman Lawrence , Manevitch Leonid I. , Gendelman Oleg
Published: May 2004

We examine passive energy pumping in a system of damped coupled oscillators. This is a one-way, passive and irreversible energy flow from a linear main system to a nonlinear attachment that acts, in essence, as a nonlinear energy sink (NES). Energy pumping is caused by 1:1 resonance captures on resonant manifolds of the damped systems. We show that the NES is capable of absorbing significant portions of the energies generated by transient, broadband external excitations. By performing a series of numerical simulations we confirm that the energy dependence of the nonlinear normal modes (NNMs) of the underlying undamped, unforced system determines, in essence, the resonance capture and energy pumping dynamics in the corresponding damped system. We present numerical simulations of single- and multi-mode energy pumping, that involve isolated resonance captures or resonance capture cascades, respectively. In addition, we discuss methodologies for enhancing the nonlinear energy pumping phenomenon by properly selecting the system parameters. The described technique of passively localizing and locally eliminating externally induced energy provides a new paradigm for vibration and shock isolation of mechanical oscillators.
Micro-Control Actions and Location Sensitivity of Actuator Patches Laminated on Toroidal Shells
Authors: Tzou H. S. , Chai W. K. , Wang D. W.
Published: May 2004

Toroidal shell structures have been proposed for components of inflatable telescopes and space structures, etc. over the years. Thus, distributed control of toroidal shells becomes a critical issue in precision maneuver, operation, and reliability. The converse effect of piezoelectric materials has made it one of the best candidates for distributed actuators. The resultant control forces and micro-control actions induced by the distributed actuators depend on applied voltages, geometrical (e.g., spatial segmentation and shape) and material (i.e., various actuator materials) properties of the actuators. The purpose of this analysis is to study the spatial location effects of actuator placement and to evaluate the micro-control actions imposed upon toroidal shell structures. Mathematical models and governing equations of the toroidal shells laminated with distributed actuator patches are presented first, followed by formulations of distributed control forces and micro-control actions including meridional/circumferential membrane and bending control components. Spatially distributed electromechanical microscopic actuation characteristics and control effects resulting from various meridional and circumferential actions of actuator patches at various shell locations are evaluated.
Prediction of Time-Varying Vibroacoustic Energy Using a New Energy Approach
Authors: Sui F. , Ichchou M. N.
Published: May 2004

A new energetic approach is proposed to predict the time-varying dynamic response in the vibroacoustic field. This approach is based on the derivation and development of a hyperbolic type energy equation. It can be derived from the transport theory, or obtained by applying fundamental energy balance equation. The focus of this paper is to compare this new energy equation with the time-varying vibrational conductivity equation used extensively in recent study of energy approaches in mid-high frequency domain. The new energy equation is evaluated numerically by comparing its solutions with the diffusion equation and exact energy results. The comparative studies are applied to a beam subjected to a transverse unit impulse, and the dispersive effect is considered.
An Analytical Method for Expansion Chambers With Continuously Varying Cross-Sectional Area
Authors: Utsumi M.
Published: May 2004

An analytical method is applied to predict the acoustic attenuation performance of expansion chambers with continuously varying cross-sectional area. A feature of the present method is the use of spherical coordinates whose origin is at the top of the cone that is tangent to the wall of the expansion chamber. By this means, the characteristic functions can be analytically determined despite the non-uniform geometry of the expansion chamber. Using the Galerkin method, a variational principle is transformed into linear algebraic equations that are solved to determine the transmission coefficient of the expansion chamber. Numerical results are provided for the case where broadband noise attenuation is achieved.
Solar Methane Reforming Using a New Type of Catalytically-Activated Metallic Foam Absorber
Authors: Kodama Tatsuya , Kiyama Atsushi , Moriyama Takuya , Mizuno Osamu
Published: May 2004

The solar reforming of methane with CO2 is investigated using a direct irradiated absorber subjected to solar flux levels in the range 180-250 kWm−2. This solar thermochemical process can upgrade the calorific value of the methane feed by 17% to produce hydrogen via the water-gas shift reaction. The volumetric receiver-reactor is best suited for this application because of its compactness and low thermal capacity. The new type of catalytically-activated “metallic foam” absorber–an Ni-Cr-Al-foam absorber applied with Ru/Al2O3–was found to have a superior thermal performance at relatively low solar fluxes when compared to conventional ceramic foam absorbers.
Structural Dynamics Optimization Based on a Hybrid Inverse Synthesis Method Using a Quadratic Approximation
Authors: Schorderet Alain , Gmu¨r Thomas
Published: May 2004

This paper lies within the framework of the so-called redesign problem of structures subjected to dynamic constraints. A hybrid synthesis algorithm is developed, combining the truncated modal basis of the initial system and the spatial or material co-ordinates of an added component, which is modelled with shell-type finite elements parameterized with respect to a shape factor. Based upon a quadratic inverse formulation, the proposed technique shows several advantages in comparison to other synthesis methods, such as a refined sensitivity strategy, a powerful modal synthesis approach and a simplified optimization phase. Numerical examples are provided illustrating the capabilities of the novel procedure.
Effect of Plant Interaction on Wind-Induced Crop Motion
Authors: Doare´ O. , Moulia B. , de Langre E.
Published: May 2004

Plant motion due to wind affects plant growth, a phenomenon called thigmomorphogenesis. Despite intensive studies of the turbulence over plant canopies, the study of plant motion induced by wind has often been limited to individual trees or cereal plants. Few models of global canopy motions are available. Moreover the numerical analysis of models that are based on individual stems becomes time consuming when dealing with crops. A model of motion within the canopies is proposed here using a wave propagation equation within a homogenized continuous medium, and a forcing function representing turbulent gusts advected over the canopy. This model is derived from a discrete model of a set of plant shoots represented as individual oscillators, including elastic contacts between shoots. Such contacts induce nonlinearities into the wave equation. A new experimental method to measure stem dynamical properties and elastic collision properties is presented with an illustration on alfalfa stems. Results obtained modeling plant motions in an alfalfa crop are presented.
Microstructural Mechanics of Collagen Gels in Confined Compression: Poroelasticity, Viscoelasticity, and Collapse
Authors: Chandran Preethi L. , Barocas Victor H.
Published: May 2004

Background: Collagen gels are important as platforms for in vitro study of cell behavior and as prototypical bioartificial tissues, but their mechanical behavior, particularly on the microscopic scale, is still poorly understood. Method of Approach: Collagen gels were studied in step (10% strain in 0.05 s) and ramp (0.1%/s strain rate for 100 s) confined compression. Real-time birefringence mapping gave the local collagen concentration and orientation along with piston stress. Variations in the retardation allowed material-point tracking and qualitative determination of the strain distribution. Results: Ramp tests showed classical poroelastic behavior: compression near the piston and relaxation to a uniform state. Step tests, however, showed an irreversibly collapsed region near the piston. Conclusions: Our results suggest that interstitial flow and fibril bending at crosslinks are the dominant mechanical processes during compression, and that fibril bending is reversible before collapse.
Measurement and Simulation of Water and Methanol Transport in Algal Cells
Authors: Walsh John R. , Diller Kenneth R. , Brand Jerry J.
Published: May 2004

Background: Experimental data and a complementary biophysical model are presented to describe the dynamic response of a unicellular microalga to osmotic processes encountered during cryopreservation. Method of Approach: Chlorococcum texanum (C. texanum) were mounted on a cryoperfusion microscope stage and exposed sequentially to various solutions of sucrose and methanol. Transient volumetric excursions were determined by capturing images of cells in real time and utilizing image analysis software to calculate cell volumes. A biophysical model was applied to the data via inverse analysis in order to determine the plasma membrane permeability to water and to methanol. The data were also used to determine the elastic modulus of the cell wall and its effect on cell volume. A three-parameter (hydraulic conductivity Lp, solute permeability; (ω), and reflection coefficient, (σ)) membrane transport model was fit to data obtained during methanol perfusion to obtain constitutive property values. These results were compared with the property values obtained for a two coefficient (Lp and ω) model. Results: The three-parameter model gave a value for σ not consistent with practical physical interpretation. Thus, the two-coefficient model is the preferred approach for describing simultaneous water and methanol transport. The rate of both water and methanol transport were strongly dependent on temperature over the measured temperature range (25°C to −5°C) and cells were appreciably more permeable to methanol than to water at all measured temperatures. Conclusion: These results may explain in part why methanol is an effective cryoprotective agent for microalgae.
Particle-Hemodynamics Simulations and Design Options for Surgical Reconstruction of Diseased Carotid Artery Bifurcations
Authors: Hyun S. , Kleinstreuer C. , Longest P. W. , Chen C.
Published: May 2004

Based on the hypothesis that aggravating hemodynamic factors play a key role in the onset of arterial diseases, the methodology of “virtual prototyping” of branching blood vessels was applied to diseased external carotid artery (ECA) segments. The goals were to understand the underlying particle-hemodynamics and to provide various geometric design options for improved surgical reconstruction based on the minimization of critical hemodynamic wall parameters (HWPs). First, a representative carotid artery bifurcation (CAB) and then CABs with stenosed ECAs, i.e., a distally occluded ECA and an ECA stump, were analyzed based on transient three-dimensional blood flow solutions, employing a user-enhanced commercial finite volume code. Specifically, the HWPs, i.e., oscillatory shear index, wall shear stress angle gradient, near-wall residence time of monocytes, and near-wall helicity angle difference were evaluated to compare the merits of each design option, including a reconstructed near-optimal junction which generates the lowest HWP-values. The results provide physical insight to the biofluid dynamics of branching blood vessels and guide vascular surgeons as well as stent manufacturers towards interventions leading to high sustained patency rates.
Thermodynamic Nonequilibrium Phase Change Behavior and Thermal Properties of Biological Solutions for Cryobiology Applications
Authors: Han Bumsoo , Bischof John C.
Published: May 2004

Understanding the phase change behavior of biomaterials during freezing/thawing including their thermal properties at low temperatures is essential to design and improve cryobiology applications such as cryopreservation and cryosurgery. However, knowledge of phase change behavior and thermal properties of various biomaterials is still incomplete, especially at cryogenic temperatures ⩽−40°C. Moreover, in these applications, chemicals are often added to improve their outcome, which can result in significant variation in the phase change behavior and thermal properties from those of the original biomaterials. These chemical additives include cryoprotective agents (CPAs), antifreeze protein (AFP), or cryosurgical adjuvants like sodium chloride (NaCl). In the present study, phase change behavior and thermal properties of saline solutions–either water-NaCl or phosphate buffered saline (PBS)–with various chemical additives were investigated. The chemical additives studied are glycerol and raffinose as CPAs, an AFP (Type III, molecular weight=6500), and NaCl as a cryosurgical adjuvant. The phase change behavior was investigated using a differential scanning calorimeter (DSC) and a cryomicroscope. The specific and latent heat of these solutions were also measured with the DSC. The saline solutions have two distinct phase changes–water/ice and eutectic phase changes. During freezing, eutectic solidification of both water-NaCl and PBS are significantly supercooled below their thermodynamic equilibrium eutectic temperatures. However, their melting temperatures are close to thermodynamic equilibrium during thawing. These eutectic phase changes disappear when even a small amount (0.1 M glycerol) of CPA was added, but they are still observed after the addition of an AFP. The specific heats of these solutions are close to that of ice at very low temperatures ⩽−100°C regardless of the additives, but they increase between −100°C and −30°C with the addition of CPAs. The amount of latent heat, which is evaluated with sample weight, generally decreases with the addition of the additives, but can be normalized to approximately 300 J/g based on the weight of water which participates in the phase change. This illustrates that thermal properties, especially latent heat, of a biomaterial should be evaluated based on the understanding of its phase change behavior. The results of the present study are discussed in the context of the implications for cryobiology applications.
Manipulabilities of the Index Finger and Thumb in Three Tip-Pinch Postures
Authors: Yokogawa Ryuichi , Hara Kei
Published: May 2004

Tip-pinch, in which the tips of the index finger and thumb pick up and hold a very fine object, plays an important role in the function of the hand. The objective of this study was to investigate how human subjects affect manipulabilities of the tips of the index finger and thumb within the flexion/extension plane of the finger in three different tip-pinch postures. The index finger and thumb of twenty male subjects were modeled as linkages, based on measurement results obtained using two three-dimensional position measurement devices. The manipulabilities of the index finger and thumb were investigated in three tip-pinch postures, using three criteria indicating the form and posture of the manipulability ellipse of the linkage model. There were no significant differences (p>0.05, ANOVA) in each criterion of each digit across the subjects, except for two criteria of the thumb. The manipulabilities of the index finger and thumb were separately similar across all subjects in tip-pinch postures. It was found that the manipulability for the cooperation of the index finger and thumb of all the subjects in tip-pinch depended on the posture of the index finger, but not on the posture of the thumb. In two-dimensional tip-pinch, it was possible that the index finger worked actively while the thumb worked passively to support the manipulation of the index finger.
Changes in Foot Loading Following Plantar Fasciotomy: A Computer Modeling Study
Authors: Erdemir Ahmet , Piazza Stephen J.
Published: May 2004

Forward dynamic simulations of a toe-rise task were developed to explore the outcomes of plantar fasciotomy, a surgery commonly performed to relieve heel pain. The specific objectives of this study were to develop such a simulation, validate its predictions, and simulate rising on toes using a model from which the plantar fascia had been removed. Root-mean squared differences between the intact model and measurements of healthy subjects were found to be 0.009 body weights (BW) and 0.055 BW for the horizontal and vertical ground reaction forces and 7.1 mm, 11.3 mm, and 0.48 deg for the horizontal, vertical and rotational positions of the pelvis. Simulated plantar fasciotomy increased passive arch torques by 7.4%, increased metatarsal head contact forces by 18%, and resulted in greater toe flexor activity. These simulations may explain the mechanisms behind plantar fasciotomy complications when patients perform activities that require loading of the plantarflexors and the longitudinal arch.
Feasibility of Using Orthogonal Fluoroscopic Images to Measure In Vivo Joint Kinematics
Authors: Li, Guoan , Wuerz, Thomas H. , DeFrate Louis E.
Published: May 2004

Accurately determining in vivo knee kinematics is still a challenge in biomedical engineering. This paper presents an imaging technique using two orthogonal images to measure 6 degree-of-freedom (DOF) knee kinematics during weight-bearing flexion. Using this technique, orthogonal images of the knee were captured using a 3-D fluoroscope at different flexion angles during weight-bearing flexion. The two orthogonal images uniquely characterized the knee position at the specific flexion angle. A virtual fluoroscope was then created in solid modeling software and was used to reproduce the relative positions of the orthogonal images and X-ray sources of the 3-D fluoroscope during the actual imaging procedure. Two virtual cameras in the software were used to represent the X-ray sources. The 3-D computer model of the knee was then introduced into the virtual fluoroscope and was projected onto the orthogonal images by the two virtual cameras. By matching the projections of the knee model to the orthogonal images of the knee obtained during weight-bearing flexion, the knee kinematics in 6 DOF were determined. Using regularly shaped objects with known positions and orientations, this technique was shown to have an accuracy of 0.1 mm and 0.1 deg in determining the positions and orientations of the objects, respectively.
The Structure and Mechanical Properties of the Mitral Valve Leaflet-Strut Chordae Transition Zone
Authors: Chen Ling , Yin, M.D., Ph.D. Frank C-P. , May-Newman, Ph.D. Karen
Published: May 2004

Biaxial testing, histological measurements and theoretical continuum mechanics modeling were employed to investigate the structure and mechanical properties of the mitral valve leaflet-strut chordae transition zone (LCT). The results showed that geometry changes and collagen fiber angle distribution contribute to variations in mechanical properties in the LCT zone. A simple three-coefficient exponential constitutive law was able to simulate the variation in stress-stretch behavior in the LCT zone by spatially varying a single coefficient and incorporating collagen fiber angle and degree of alignment. This quantitative information can greatly improve the predictions from biomechanical valve models by incorporating regional variations of structure and properties in the mitral leaflet-chordae tendineae system. These data provide the foundation for a computational model for studying stress distributions before and following chordal rupture, which may indicate the underlying reasons for the development of valve insufficiency in patients.
Strain-Rate Sensitive Mechanical Properties of Tendon Fascicles From Mice With Genetically Engineered Alterations in Collagen and Decorin
Authors: Robinson Paul S. , Lin Tony W. , Reynolds Paul R. , Derwin Kathleen A. , Iozzo Renato V. , Soslowsky Louis J.
Published: May 2004

Tendons have complex mechanical behaviors that are nonlinear and time dependent. It is widely held that these behaviors are provided by the tissue’s composition and structure. It is generally thought that type I collagen provides the primary elastic strength to tendon while proteoglycans, such as decorin, play a role in failure and viscoelastic properties. This study sought to quantify such structure-function relationships by comparing tendon mechanical properties between normal mice and mice genetically engineered for altered type I collagen content and absence of decorin. Uniaxial tensile ramp to failure experiments were performed on tail tendon fascicles at two strain rates, 0.5%/s and 50%/s. Mutations in type I collagen led to reduced failure load and stiffness with no changes in failure stress, modulus or strain rate sensitivity. Fascicles without decorin had similar elastic properties to normal fascicles, but reduced strain rate sensitivity. Fascicles from immature mice, with increased decorin content compared to adult fascicles, had inferior elastic properties but higher strain rate sensitivity. These results showed that tendon viscoelasticity is affected by decorin content but not by collagen alterations. This study provides quantitative evidence for structure-function relationships in tendon, including the role of proteoglycan in viscoelasticity.
Comparison of a Multi-Layer Structural Model for Arterial Walls With a Fung-Type Model, and Issues of Material Stability
Authors: Holzapfel Gerhard A. , Gasser Thomas C. , Ogden Ray W.
Published: May 2004

The goals of this paper are (i) to re-examine the constitutive law for the description of the (passive) highly nonlinear and anisotropic response of healthy elastic arteries introduced recently by the authors, (ii) to show how the mechanical response of a carotid artery under inflation and extension predicted by the structural model compares with that for a three-dimensional form of Fung-type strain-energy function, (iii) to provide a new set of material parameters that can be used in a finite element program, and (iv) to show that the model has certain mathematical features that are important from the point of view of material and numerical stability.
Bi-directional Mechanical Properties of the Axillary Pouch of the Glenohumeral Capsule: Implications for Modeling and Surgical Repair
Authors: Moore Susan M. , McMahon Patrick J. , Debski Richard E.
Published: May 2004

The objective of this study was to determine the mechanical properties of the axillary pouch of the inferior glenohumeral ligament in the directions perpendicular (transverse) and parallel (longitudinal) to the longitudinal axis of the anterior band of the inferior glenohumeral ligament. A punch was used to excise one transverse and one longitudinal tissue sample from the axillary pouch of each cadaveric shoulder (n=10). Each tissue sample was preconditioned and then a load-to-failure test was performed. All tissue samples exhibited the typical nonlinear behavior reported for ligaments and tendons. Significant differences (p<0.05) were detected between the transverse and longitudinal tissue samples for ultimate stress (0.8±0.4 MPa and 2.0±1.0 MPa, respectively) and tangent modulus (5.4±2.9 MPa and 14.8±13.1 MPa, respectively). No significant differences (p>0.05) were observed between the ultimate strain (transverse: 23.5±11.5%, longitudinal: 33.3±23.6%) and strain energy density (transverse: 10.8±8.5 MPa, longitudinal: 21.1±15.4 MPa) of the transverse and longitudinal tissue samples. The ultimate stress determined for the longitudinal axillary pouch tissue samples was comparable to a previous study that reported it to be 5.5±2.0 MPa. The ratio of the longitudinal to transverse moduli (3.3±2.8) is considerably less than that of the medial collateral ligament of the knee (30) and interosseous ligament of the forearm (385), suggesting that the axillary pouch functions to stabilize the joint in more than just one direction. Future models of the glenohumeral joint and surgical repair procedures should consider the properties of the axillary pouch in its transverse and longitudinal directions to fully describe the behavior of the inferior glenohumeral ligament.
Electrical Impedance Tomography of Cell Viability in Tissue With Application to Cryosurgery
Authors: Davalos Rafael , Rubinsky Boris
Published: May 2004

Tissue damage that is associated with the loss of cell membrane integrity should alter the bulk electrical properties of the tissue. This study shows that electrical impedance tomography (EIT) should be able to detect and image necrotic tissue inside the body due to the permeabilization of the membrane to ions. Cryosurgery, a minimally invasive surgical procedure that uses freezing to destroy undesirable tissue, was used to investigate the hypothesis. Experimental results with liver tissue demonstrate that cell damage during freezing results in substantial changes in tissue electrical properties. Two-dimensional EIT simulations of liver cryosurgery, which employ the experimental data, demonstrate the feasibility of this application.
Infrared Spectroscopic Evidence for Protonated Water Clusters Forming Nanoscale Cages
Authors: Miyazaki Mitsuhiko , Fujii Asuka , Ebata Takayuki , Mikami Naohiko
Published: May 2004

Size-dependent development of the hydrogen bond network structure in largesized clusters of protonated water, H
+
(H
2
O)

n

(
n
= 4 to 27), was probed by infrared spectroscopy of OH stretches. Spectral changes with cluster size demonstrate that the chain structures at small sizes (
n
≲ 10) develop into two-dimensional net structures (∼10 <
n
< 21), and then into nanometer-scaled cages (
n
≥ 21).
EGFR
Mutations in Lung Cancer: Correlation with Clinical Response to Gefitinib Therapy
Authors: Paez J. Guillermo , Jänne Pasi A. , Lee Jeffrey C. , Tracy Sean , Greulich Heidi , Gabriel Stacey , Herman Paula , Kaye Frederic J. , Lindeman Neal , Boggon Titus J. , Naoki Katsuhiko , Sasaki Hidefumi , Fujii Yoshitaka , Eck Michael J. , Sellers William R. , Johnson Bruce E. , Meyerson Matthew
Published: May 2004

Receptor tyrosine kinase genes were sequenced in non–small cell lung cancer (NSCLC) and matched normal tissue. Somatic mutations of the epidermal growth factor receptor gene
EGFR
were found in 15of 58 unselected tumors from Japan and 1 of 61 from the United States. Treatment with the EGFR kinase inhibitor gefitinib (Iressa) causes tumor regression in some patients with NSCLC, more frequently in Japan.
EGFR
mutations were found in additional lung cancer samples from U.S. patients who responded to gefitinib therapy and in a lung adenocarcinoma cell line that was hypersensitive to growth inhibition by gefitinib, but not in gefitinib-insensitive tumors or cell lines. These results suggest that
EGFR
mutations may predict sensitivity to gefitinib.