bluuebunny/crossref_metadata_2025 huggingface dataset:
Siloxanes as Working Fluids for Mini-ORC Systems Based on High-Speed Turbogenerator Technology
Authors: Uusitalo Antti , Turunen-Saaresti Teemu , Honkatukia Juha , Colonna Piero , Larjola Jaakko
Published: March 2013

This paper presents a study aimed at evaluating the use of siloxanes as the working fluid of a small-capacity (≈10kWe) ORC turbogenerator based on the “high-speed technology” concept, combining the turbine, the pump, and the electrical generator on one shaft, whereby the whole assembly is hermetically sealed, and the bearings are lubricated by the working fluid. The effects of adopting different siloxane working fluids on the thermodynamic cycle configuration, power output, and on the turbine and component design are studied by means of simulations. Toluene is included into the analysis as a reference fluid in order to make comparisons between siloxanes and a suitable low molecular weight hydrocarbon. The most influential working fluid parameters are the critical temperature and pressure, molecular complexity and weight, and, related to them, the condensation pressure, density and specific enthalpy over the expansion, which affect the optimal design of the turbine. The fluid thermal stability is also extremely relevant in the considered applications. Exhaust gas heat recovery from a 120 kW diesel engine is considered in this study. The highest power output, 13.1 kW, is achieved with toluene as the working fluid, while, among siloxanes, D4 provides the best simulated performance, namely 10.9 kW. The high molecular weight of siloxanes is beneficial in low power capacity applications, because it leads to larger turbines with larger blade heights at the turbine rotor outlet, and lower rotational speed if compares, for instance, to toluene.
Influence of Molecular Complexity on Nozzle Design for an Organic Vapor Wind Tunnel
Authors: Guardone Alberto , Spinelli Andrea , Dossena Vincenzo
Published: March 2013

A novel blow-down wind tunnel is currently being commissioned at the Politecnico di Milano, Italy, to investigate real-gas behavior of organic fluids operating at subsonic-supersonic speed in the proximity of the liquid-vapor critical point and the saturation curve. The working fluid is expanded from a high-pressure reservoir, where it is kept at controlled super-heated or super-critical conditions, into a low-pressure reservoir, where the vapor is condensed and pumped back into the high-pressure reservoir. Expansion to supersonic speeds occurs through a converging-diverging Laval nozzle. Siloxane fluid MDM (octamethyltrisiloxane-C8H24O2Si3) is to be tested during the first experimental trials. A standard method of characteristics is used here to assess the influence of the molecular complexity of the working fluid on the design of the supersonic portion of the nozzle by considering different fluids at the same real-gas operating conditions, including linear and cyclic siloxanes, refrigerant R245fa, toluene, and ammonia. The thermodynamic properties of these fluids are described by state-of-the-art thermodynamic models. The nozzle length and exit area are found to increase with increasing molecular complexity due to the nonideal dependence of the speed of sound on density along isentropic expansion of organic fluids.
Thermal Properties of Couple-Stress Fluid Flow in an Asymmetric Channel With Peristalsis
Authors: Abd elmaboud Y. , Mekheimer Kh. S. , Abdellateef A. I.
Published: March 2013

The heat transfer characteristics of a couple-stress fluid (CSF) in a two-dimensional asymmetric channel is analyzed. The channel asymmetry is produced by choosing the peristaltic wave train on the walls to have different amplitudes and phase. Mathematical modeling corresponding to the two-dimensional couple stress fluid is made. Analytical expressions for the axial velocity, stream function, heat transfer, and the axial pressure gradient are established using long wavelength assumption. Numerical computations have been carried out for the pressure rise per wavelength. The influence of various parameters of interest is seen through graphs on frictional forces, pumping and trapping phenomena, and temperature profile.
Wear Simulation of Metal-on-Metal Hip Replacements With Frictional Contact
Authors: Mattei Lorenza , Di Puccio Francesca
Published: March 2013

Preclinical wear evaluation is extremely important in hip replacements, wear being one of the main causes of failure. Experimental tests are attractive but highly cost demanding; thus predictive models have been proposed in the literature, mainly based on finite element simulations. In such simulations, the effect of friction is usually disregarded, as it is considered not to affect the contact pressure distribution. However, a frictional contact could also result in a shift of the location of the nominal contact area, which can thus modify the wear maps. The aim of this study is to investigate this effect in wear prediction for metal-on-metal implants. Wear assessment was based on a purpose-developed mathematical model, extension of a previous one proposed by the same authors for metal-on-plastic implants. The innovative aspect of the present study consists in the implementation of a modified location of the nominal contact point due to friction, which takes advantage of the analytical formulation of the wear model. Simulations were carried out aimed at comparing total and resurfacing hip replacements under several gait conditions. The results highlighted that the adoption of a frictional contact yields lower linear wear rates and wider worn areas, while for the adopted friction coefficient (f=0.2), the total wear volume remains almost unchanged. The comparison between total and resurfacing replacements showed higher scaled wear volumes (wear volume divided by wear factor) for the latter, in agreement with the literature. The effect of the boundary conditions (in vivo versus in vitro) was also investigated remarking their influence on implant wear and the need to apply more physiological-like conditions in hip simulators. In conclusion although friction is usually neglected in numerical wear predictions, as it does not affect markedly the contact pressure distribution, its effect in the location of the theoretical contact point was observed to influence wear maps. This achievement could be useful for increasing the correlation between numerical and experimental simulations, usually based on the total wear volume. In order to improve the model reliability, future studies will be devoted to implement the geometry update by combining the present model to finite element analyses. On the other hand, further experimental investigations are required to get out from the wide dispersion of wear factors reported in the literature.
Mixed Convection Three-Dimensional Flow in the Presence of Hall and Ion-Slip Effects
Authors: Nawaz M. , Hayat T. , Alsaedi A.
Published: March 2013

This work is accomplished to investigate the Hall and ion-slip effects on mixed convection three-dimensional flow of a Maxwell fluid over a stretching vertical surface. The problem is first formulated and then nondimensionalized by using suitable variables. The solutions are computed by homotopy analysis method (HAM). The results are compared with the already limiting results. The convergence of derived series solutions is studied. The velocity components and temperature have been examined for several important parameters. Numerical computations for Nusselt number are presented and analyzed.
Experiment of Heat Transfer to Supercritical Water Flowing in Vertical Annular Channels
Authors: Yang Zhendong , Bi Qincheng , Wang Han , Wu Gang , Hu Richa
Published: March 2013

An experimental study of heat transfer to supercritical water has been performed at Xi'an Jiaotong University with a vertical annular tube. The annular test sections were constructed with an annular gap of 2 mm and an internal heater of 8 mm outer diameter. Experimental parameter covered pressures of 23 and 25 MPa, mass fluxes of 700 and 1000 kg/m2s, and heat fluxes of 200–1000 kW/m2. Experimental data were acquired from downward flow and upward flow, respectively. There were differences of heat-transfer characteristics between the two flow directions. Compared to upward flow, the heat-transfer coefficient increased at downward flow. A strong effect of spacer on heat transfer is observed at locations downstream of the device in the annuli regardless of flow direction. The spacer effect impaired the buoyancy effect at low heat flux, but not for large heat flux. Complex of forced convection and mixed convection in supercritical water is due to various thermophysical properties and the gravity. The affected zone of the spacer effect depends on the flow conditions. The buoyancy effect was analyzed qualitatively in this study and the criterion Gr¯/Re2.7<10-5 for negligible heat-transfer impairment was discussed. Four correlations were compared with the experimental data; the Swenson correlation predicted nearly the experimental data but overpredicted slightly the heat-transfer coefficients.
A Possible Role of Nanostructured Ridges on Boiling Heat Transfer Enhancement
Authors: Maroo Shalabh C. , Chung J. N.
Published: March 2013

Evaporation of a nanoscale meniscus on a nanostructured heater surface is simulated using molecular dynamics. The nanostructures, evenly spaced on the surface, are ridges with a width and height of 0.55 nm and 0.96 nm, respectively. The simulation results show that the film breaks during the early stages of evaporation due to the presence of nanostructures and no nonevaporating film forms (unlike a previous simulation performed in the absence of nanostructures where nonevaporating film forms on the smooth surface). High heat transfer and evaporation rates are obtained. We conclude that heat transfer rates can be significantly increased during bubble nucleation and growth by the presence of nanostructure ridges on the surface as it can break the formation of nonevaporating film. This causes additional chaos and allows the surrounding cooler liquid to come in contact with the surface providing heat transfer enhancements.
Homotopy Perturbation Method for Nonlinear Vibration Analysis of Functionally Graded Plate
Authors: Yazdi Ali A.
Published: March 2013

In this paper, the Homotopy perturbation method (HPM) is used to analysis the geometrically nonlinear vibrations of thin rectangular laminated functionally graded material (FGM) plates. The Von Karman's strain-displacement relations have been employed to model structural nonlinearity of the system. The material properties of the plate are assumed to be graded continuously in direction of thickness. The effects of initial deflection, aspect ratio and material properties are investigated. Based on the results of this study, the first order approximation of the HPM leads to highly accurate solutions for geometrically nonlinearity vibration of FGM plates. Moreover, HPM in comparison with other traditional analytical methods (e.g., perturbation methods) has excellent accuracy for the whole range of oscillation amplitude and initial conditions.
Optimized Expanding Microchannel Geometry for Flow Boiling
Authors: Miner Mark J. , Phelan Patrick E. , Odom Brent A. , Ortiz Carlos A. , Prasher Ravi S. , Sherbeck Jon A.
Published: March 2013

This study discusses the simulation of flow boiling in a microchannel and numerically predicts the effects of channel geometry variation along the flow direction. Experimental studies by Pan and collaborators and suggestions from Mukherjee and Kandlikar have generated interest in expanding the cross section of a microchannel to improve boiling heat transfer. The motivation for this geometry change is discussed, constraints and model selection are reviewed, and Revellin and Thome's critical heat flux criterion is used to bound the simulation, via matlab, of separated flow in a heated channel. The multiphase convective heat-transfer coefficient is extracted from these results using Qu and Mudawar's relationship and is compared to reported experimental values. Expanding channel geometry permits higher heat rates before reaching critical heat flux.
Knowledge Support System for Aesthetics in Product Design
Authors: Soni Sitaram , Khanna Pritee , Tandon Puneet
Published: March 2013

The research described is the initial efforts to develop knowledge based support system to the aesthetic design in industrial products. The methodology takes into account the cognition process during the design generation and captures this behavior in a group theoretic structure. This approach leads to a mathematically robust model for the creative design generation during the product design. Based on this model, an artificial neural network (ANN) and genetic algorithm (GA) based framework is implemented to assess the validity and usefulness of the approach.
Heat Transfer Analysis of a Solid-Solid Heat Recuperation System for Solar-Driven Nonstoichiometric Redox Cycles
Authors: Lapp Justin , Davidson Jane H. , Lipiński Wojciech
Published: March 2013

Heat transfer is predicted for a solid-solid heat recuperation system employed in a novel directly-irradiated solar thermochemical reactor realizing a metal oxide based nonstoichiometric redox cycle for production of synthesis gas from water and carbon dioxide. The system is designed for continuous operation with heat recuperation from a rotating hollow cylinder of a porous reactive material to a counter-rotating inert solid cylinder via radiative transfer. A transient heat transfer model coupling conduction, convection, and radiation heat transfer predicts temperatures, rates of heat transfer, and the effectiveness of heat recovery. Heat recovery effectiveness of over 50% is attained within a parametric study of geometric and material parameters corresponding to the design of a two-step solar thermochemical reactor.
Precise Quantitative Analysis of Probabilistic Business Process Model and Notation Workflows
Authors: Herbert Luke , Sharp Robin
Published: March 2013

We present a framework for modeling and analysis of real-world business workflows. We present a formalized core subset of the business process modeling and notation (BPMN) and then proceed to extend this language with probabilistic nondeterministic branching and general-purpose reward annotations. We present an algorithm for the translation of such models into Markov decision processes (MDP) expressed in the syntax of the PRISM model checker. This enables precise quantitative analysis of business processes for the following properties: transient and steady-state probabilities, the timing, occurrence and ordering of events, reward-based properties, and best- and worst- case scenarios. We develop a simple example of medical workflow and demonstrate the utility of this analysis in accurate provisioning of drug stocks. Finally, we suggest a path to building upon these techniques to cover the entire BPMN language, allow for more complex annotations and ultimately to automatically synthesize workflows by composing predefined subprocesses, in order to achieve a configuration that is optimal for parameters of interest.
Characterization of Joint Quality in Ultrasonic Welding of Battery Tabs
Authors: Shawn Lee S. , Hyung Kim Tae , Jack Hu S. , Cai Wayne W. , Abell Jeffrey A. , Li Jingjing
Published: March 2013

Manufacturing of lithium-ion battery packs for electric or hybrid electric vehicles requires a significant amount of joining, such as welding, to meet the desired power and capacity needs. However, conventional fusion welding processes, such as resistance spot welding and laser welding, face difficulties in joining multiple sheets of highly conductive, dissimilar materials to create large weld areas. Ultrasonic metal welding overcomes these difficulties by using its inherent advantages derived from its solid-state process characteristics. Although ultrasonic metal welding is well-qualified for battery manufacturing, there is a lack of scientific quality guidelines for implementing ultrasonic welding in volume production. In order to establish such quality guidelines, this paper first identifies a number of critical weld attributes that determine the quality of welds by experimentally characterizing the weld formation over time using copper-to-copper welding as an example. Samples of different weld quality were cross-sectioned and characterized with optical microscopy, scanning electronic microscopy (SEM), and hardness measurements in order to identify the relationship between physical weld attributes and weld performance. A novel microstructural classification method for the weld region of an ultrasonic metal weld is introduced to complete the weld quality characterization. The methodology provided in this paper links process parameters to weld performance through physical weld attributes.
Thermal Response Modeling of Sheet Metals in Uniaxial Tension During Electrically-Assisted Forming
Authors: Jones Joshua J. , Mears Laine
Published: March 2013

For the current practice of improving fuel efficiency and reducing emissions in the automotive sector, it is becoming more common to use low density/high strength materials instead of costly engine/drivetrain technologies. With these materials there are normally many manufacturing difficulties that arise during their incorporation to the vehicle. As a result, new processes which improve the manufacturability of these materials are necessary. This work examines the manufacturing technique of electrically-assisted forming (EAF) where an electrical current is applied to the workpiece during deformation to modify the material's formability. In this work, the thermal response of sheet metal for stationary (i.e., no deformation) and deformation tests using this process are explored and modeled. The results of the model show good agreement for the stationary tests while for the deformation tests, the model predicts that all of the applied electrical current does not generate Joule heating. Thus, this work suggests from the observed response that a portion of the applied current may be directly aiding in deformation (i.e., the electroplastic effect). Additionally, the stress/strain response of Mg AZ31 under tensile forming using EAF is presented and compared to prior experimental work for this material.
A Proposed Technique to Acquire Cavity Pressure Using a Surface Strain Sensor During Injection-Compression Molding
Authors: Guan Wei-Sheng , Huang Han-Xiong
Published: March 2013

A new technique was proposed and experimentally verified for the cavity pressure acquisition in the injection-compression molding (ICM). The surface strain of the fixed mold half and the cavity pressure were monitored simultaneously during ICM. In the compression stage, a directly proportional relationship between the cavity pressure and mold surface strain was found and determined via the regression analysis. By taking the advantage of this relationship, the cavity pressure profile with high accuracy was indirectly obtained from the nondestructive measurement of the mold surface strain. Moreover, the mold surface strain profile could indicate the part weight or thickness and the critical time when the part surface lost contact with the cavity surface in a large area. The monitoring of the mold surface strain could serve as an interesting alternative to the direct monitoring of the cavity pressure with respect to process and part quality control for ICM.
Size Reduction of Cellulosic Biomass in Biofuel Manufacturing: Separating the Confounding Effects of Particle Size and Biomass Crystallinity
Authors: Zhang Meng , Song Xiaoxu , Zhang Pengfei , Pei Z. J. , Deines T. W. , Wang Donghai
Published: March 2013

Increasing demands and concerns for reliable supply of liquid transportation fuels make it important to find alternative sources to petroleum-based fuels. Cellulosic biofuels provide one such alternative in the short to medium term. Size reduction is the first step for converting biomass into biofuels. In the literature, there are inconsistent reports about the effects of particle size and biomass crystallinity on sugar yield (proportional to biofuel yield). An important reason for this inconsistence is that particle formation in current size reduction methods is not well controlled, causing the effects of these two variables confounded. One paper investigating the confounding effects of particle size and biomass crystallinity using a metal-cutting (milling) process was previously published in this journal. This paper presents a follow-up study. In this study, a lathe was used to produce poplar wood particles with the same crystallinity but different sizes, making it possible to study the effects of particle size on biofuel yield independently without being confounded by the effects of biomass crystallinity. Results showed that, for the three levels of particle size used in this study, sugar yield increased as particle size became smaller. This study also revealed future research opportunities to understand the effects of size reduction and biomass crystallinity in cellulosic biofuel manufacturing.
On the Use of Shape Memory Alloy Studs to Recover Load Loss in Bolted Joints
Authors: Ould-Brahim Nazim , Bouzid Abdel-Hakim , Brailovski Vladimir
Published: March 2013

Creep is an important factor that contributes to the clamp load loss and tightness failure of bolted joints with and without gaskets over time. Retightening of the joint can be expensive and time consuming; therefore, it is an undesirable solution. Currently, most efforts are put towards reducing load losses directly by tightening to yield, improving material creep properties, or making joint less rigid. An alternative solution of current interest is the use of bolts in shape memory alloys (SMAs). However, very few experimental studies are available, which demonstrate the feasibility of these alloys. The objective of this study is to explore the benefit of shape memory and superelasticity behavior of an SMA stud to recover load losses due to creep and thermal exposure of a gasket in a bolted-joint assembly. This paper explores several venues to investigate and model the thermomechanical behavior of a bolted joint with a nickel–titanium SMA stud. A stiffness-based analytical model which incorporates the Likhachev model of SMA is used as a representation of an experimental bolted-joint assembly. Based on this model, the rigidity of the experimental setup is optimized to make the best use of the SMA properties of the stud. This analytical model is compared with a finite element model, which also implements the Likhachev's material law. Finally, an experimental test bench with a relatively low stiffness representative of standard flanges is used, with and without gaskets to demonstrate the ability of the SMA stud to recover load losses due to gasket creep.
Sloshing Analysis of Flowing Liquid in 3D Tank Using Boundary Elements Method
Authors: Firouz-Abadi R. D. , Borhan-Panah M. R.
Published: March 2013

A numerical model based on the boundary element method is proposed for the sloshing of a flowing liquid in a three-dimensional tank. Assuming a mean flow in the tank in addition to a perturbation flow, the nonlinear boundary conditions of the liquid free-surface are linearized. Using the boundary element method along with the modal analysis technique a reduced order model is obtained which is used to calculate the fundamental sloshing frequencies and modes in the tank with an inlet and outlet. The obtained results for a test case are compared with the literature data to validate the proposed model. The results are in a very good agreement with analytical results and show an acceptable comparison with experimental data. Then a rectangular tank is provided for further studies and the effects of flow inlet position and velocity on the sloshing frequencies and modes are investigated.
A Digital Micro Magnetofluidic Platform For Lab-on-a-Chip Applications
Authors: Hang Koh Wei , Seng Lok Khoi , Nguyen Nam-Trung
Published: March 2013

This paper reports the design and investigation of a digital micro magnetofluidic platform for lab-on-a-chip applications. The platform allows a ferrofluid droplet to be driven along a preprogrammed path. The platform consists of a programmable x-y-positioning stage, a permanent magnet and a glass plate coated with a thin layer of Teflon. First, the actuation of a stand-alone water-based ferrofluid droplet was investigated. Circular, rectangular, triangular and number-eight-shape trajectories were tested and analyzed. The speed of the droplet is evaluated from the position data of the black ferrofluid using a customized MATLAB program. The results show that better positioning accuracy and steady movement can be achieved with smooth trajectories. Next, the ferrofluid droplet as the driving engine for a cargo of other diamagnetic liquid droplets is demonstrated. The characteristics of different cargo volumes are investigated. Due to the liquid/liquid cohesion, a large cargo of five times the volume of a 3-μL ferrofluid droplet can be transported. If the cargo is larger than the driving ferrofluid droplet, the liquid system forms a long trail that faithfully follows the preprogrammed path. Various mixing experiments were carried out. The effectiveness of mixing in this system is demonstrated with a titration test as well as a chemiluminescence assay. The platform shows a robust, simple and flexible concept for implementing a complex analysis protocol with multiple reaction steps.
Uniform Flow Control for a Multipassage Microfluidic Sensor
Authors: Solovitz Stephen A. , Zhao Jiheng , Xue Wei , Xu Jie
Published: March 2013

Microfluidic sensors have been very effective for rapid, portable bioanalysis, such as in determining the pH of a sample. By simultaneously detecting multiple chemicals, the overall measurement performance can be greatly improved. One such method involves a series of parallel microchannels, each of which measures one individual agent. For unbiased readings, the flow rate in each channel should be approximately the same. In addition, the system needs a compact volume which reduces both the wasted channel space and the overall device cost. To achieve these conditions, a manifold was designed using a tapered power law, based on a concept derived for electronics cooling systems. This manifold features a single feed passage of varying diameter, eliminating the excess volume from multiple branch steps. The design was simulated using computational fluid dynamics (CFD), which demonstrated uniform flow performance within 2.5% standard deviation. The design was further examined with microparticle image velocimetry (PIV), and the experimental flow rates were also uniform with approximately 10% standard deviation. Hence, the tapered power law can provide a uniform flow distribution in a compact package, as is needed in both this microfluidic sensor and in electronics cooling applications.
Planar Multiplexing of Microfluidic Fuel Cells
Authors: Ho Bernard , Kjeang Erik
Published: March 2013

Microfluidic fuel cells eliminate the membrane by utilizing parallel colaminar flow of electrolyte between the anode and cathode electrodes. When operated on vanadium redox electrolyte, these cells also eliminate the need for catalyst. Hence, microfluidic fuel cells are promising contenders in terms of achieving useful performance levels for commercial applications while being cost-effective on a commercial scale. However, due to the inherent size of these devices the power output is relatively low and scale-up is a major challenge. In the present article, two planar cell multiplexing strategies are introduced, featuring a nonsymmetric unilateral design and a symmetric bilateral device architecture, both of which employ two cells with shared fluidic inlet ports. The fuel cell design is based on flow-through porous carbon electrodes using vanadium redox electrolytes as reactants. In both array architectures, the two cells are fluidically connected in parallel and electrically in series. The main challenge of achieving uniform flow distribution is assessed using laminar flow theory and computational fluid dynamics and validated experimentally. The normalized performance obtained with the two prototype array cells is found to be equivalent to previously reported data for single cells, in this case doubling the device level voltage and power output and reaching 820 and 1200 mW/cm2 peak power density for the nonsymmetric unilateral and symmetric bilateral array designs, respectively. It is, thus, demonstrated that both unilateral and bilateral planar multiplexing strategies are feasible for microfluidic fuel cell technologies and are shown to be particularly effective when the flow sharing between different cells is equal.
Experimental Techniques for Bubble Dynamics Analysis in Microchannels: A Review
Authors: Mohammadi Mahshid , Sharp Kendra V.
Published: March 2013

Experimental studies employing advanced measurement techniques have played an important role in the advancement of two-phase microfluidic systems. In particular, flow visualization is very helpful in understanding the physics of two-phase phenomenon in microdevices. The objective of this article is to provide a brief but inclusive review of the available methods for studying bubble dynamics in microchannels and to introduce prior studies, which developed these techniques or utilized them for a particular microchannel application. The majority of experimental techniques used for characterizing two-phase flow in microchannels employs high-speed imaging and requires direct optical access to the flow. Such methods include conventional brightfield microscopy, fluorescent microscopy, confocal scanning laser microscopy, and micro particle image velocimetry (micro-PIV). The application of these methods, as well as magnetic resonance imaging (MRI) and some novel techniques employing nonintrusive sensors, to multiphase microfluidic systems is presented in this review.
Towards New Methodologies for Manipulation of Colloidal Particles in a Miniaturized Fluidic Device: Optoelectrokinetic Manipulation Technique
Authors: Kwon Jae-Sung , Wereley Steven T.
Published: March 2013

The rapid electrokinetic patterning (REP) technique developed recently is a hybrid optoelectrokinetic one that manipulates micro- or nanocolloids in a microfluidic chip using the simultaneous application of a uniform ac electric field and laser illumination. Since its invention, the technique has been applied to many research fields with promising potential, but these applications are still in their early stages. In order to effectively complete and leverage the applications, this paper reviews the publications concerning the REP technique and discusses its underlying principles, applications, and future prospects.
Method and Tool Design for Passive Sheet Metal Hydroforming on Conventional Single Action Presses
Authors: Budai Alina F. , Achimaş Gheorghe , Neugebauer Reimund , Pröhl Marco
Published: March 2013

Current sheet metal hydroforming processes require special equipment such as a hydroforming press with an external high pressure generator. This holds the barriers for entering the market high, especially for small and medium companies that cannot invest such an amount of money. In this article, a method and tool design is presented that allows setting up a sheet metal hydroforming process on single action presses without using special hydroforming equipment. The inner pressure for forming the part is generated by tool integrated pistons and results from the difference between ram and cushion force in relation to the part's projected surface. To explore the limits of the process, a tryout tool was manufactured for producing test samples of medical parts in DX54D and AlMg3 0.6 mm. After the experiments, the parts were measured and analyzed to investigate the accuracy of the process, in comparison with the simulation done beforehand. This work will enable small and medium enterprises (SMEs) to produce small series hydroformed parts in a cost efficient way on their conventional presses.
Toward System Architecture Generation and Performances Assessment Under Uncertainty Using Bayesian Networks
Authors: Moullec Marie-Lise , Bouissou Marc , Jankovic Marija , Bocquet Jean-Claude , Réquillard François , Maas Olivier , Forgeot Olivier
Published: March 2013

Architecture generation and evaluation are critical points in complex system design. Uncertainties concerning component characteristics and their impact onto overall system performance are often not taken into account in early design stages. In this paper, we propose a Bayesian network (BN) approach for system architecture generation and evaluation. A method relying on Bayesian network templates is proposed in order to represent an architecture design problem integrating uncertainties concerning component characteristics and component compatibility. These templates aim at modeling designers' knowledge concerning system architecture. We also propose an algorithm for architecture generation and evaluation related to the Bayesian network model with the objective of generating all possible architectures and filtering them in view to a defined confidence threshold. Within this algorithm, expert estimations on component compatibilities are used to estimate overall architecture uncertainty as a confidence level. The proposed approach is tested and illustrated on a case study of bicycle design. This first case shows how uncertainties concerning component compatibilities and components characteristics impact bicycle architecture generation. The method is, additionally, tested and implemented in the case of a radar antenna cooling system design in industry. Results highlight the relevance of the proposed approach in view to the generated solutions as well as other benefits such as reduced time for architecture generation, and a better overall understanding of the design problem. However, some limitations have been observed and call for enhancements like integration of designer's preferences and identification of possible trade-offs within the architecture. This method enables generation and evaluation of complex system architecture taking into account initial system requirements and designer's knowledge. Its usability and added-value have been verified on a large-scale system implemented in industry.
Classification and Fault Detection Methods for Fuel Cell Monitoring and Quality Control
Authors: Lowery Natalie L. H. , Vahdati Maria M. , Potthast Roland W. E. , Holderbaum William
Published: March 2013

In this paper, various types of fault detection methods for fuel cells are compared. For example, those that use a model based approach or a data driven approach or a combination of the two. The potential advantages and drawbacks of each method are discussed and comparisons between methods are made. In particular, classification algorithms are investigated, which separate a data set into classes or clusters based on some prior knowledge or measure of similarity. In particular, the application of classification methods to vectors of reconstructed currents by magnetic tomography or to vectors of magnetic field measurements directly is explored. Bases are simulated using the finite integration technique (FIT) and regularization techniques are employed to overcome ill-posedness. Fisher's linear discriminant is used to illustrate these concepts. Numerical experiments show that the ill-posedness of the magnetic tomography problem is a part of the classification problem on magnetic field measurements as well. This is independent of the particular working mode of the cell but influenced by the type of faulty behavior that is studied. The numerical results demonstrate the ill-posedness by the exponential decay behavior of the singular values for three examples of fault classes.
Microfluidics Underground: A Micro-Core Method for Pore Scale Analysis of Supercritical CO2 Reactive Transport in Saline Aquifers
Authors: Nguyen Phong , Fadaei Hossein , Sinton David
Published: March 2013

Carbon sequestration in microporous geological formations is an emerging strategy for mitigating CO2 emissions from fossil fuel consumption. Injection of CO2 in carbonate reservoirs can change the porosity and permeability of the reservoir regions, along the CO2 plume migration path, due to CO2-brine-rock interactions. Carbon sequestration is effectively a microfluidic process over large scales, and can readily benefit from microfluidic tools and analysis methods. In this study, a micro-core method was developed to investigate the effect of CO2 saturated brine and supercritical CO2 injection, under reservoir temperature and pressure conditions of 8.4 MPa and 40 °C, on the microstructure of limestone core samples. Specifically, carbonate dissolution results in pore structure, porosity, and permeability changes. These changes were measured by X-ray microtomography (micro-CT), liquid permeability measurements, and chemical analysis. Chemical composition of the produced liquid analyzed by inductively coupled plasma-atomic emission spectrometer (ICP-AES) shows concentrations of magnesium and calcium in the produced liquid. Chemical analysis results are consistent with the micro-CT imaging and permeability measurements which all show high dissolution for CO2 saturated brine injection and very minor dissolution under supercritical CO2 injection. This work leverages established advantages of microfluidics in the new context of core-sample analysis, providing a simple core sealing method, small sample size, small volumes of injection fluids, fast characterization times, and pore scale resolution.
Improvements to Common Data Reduction and Calibration Methods for Seven Hole Probes
Authors: Crawford James , Michael Birk A.
Published: March 2013

The influence of calibration data sorting procedures and the order of polynomial curve fit used to calibrate seven hole pressure probes in subsonic, incompressible flow are discussed. It is shown that the inclusion of fourth order polynomial terms is necessary to properly model the physical response of the probe. It is also shown that the uniformity of probe response error is significantly affected by polynomial extrapolation near sector boundaries, and that the uniformity can be improved by using some calibration points in multiple sectors.
Experimental and Numerical Study of Flow Structures Associated With Low Aspect Ratio Elliptical Cavities
Authors: Khadivi Taravat , Savory Eric
Published: March 2013

The flow regimes associated with 2:1 aspect ratio elliptical planform cavities of varying depth immersed in a turbulent boundary layer at a Reynolds number of 8.7 × 104, based on the minor axis of the cavity, have been quantified from particle image velocimetry measurements and three-dimensional steady computational fluid dynamics simulations (Reynolds stress model closure). Although these elliptical cavity flows have some similarities with nominally two-dimensional and rectangular cases, three-dimensional effects due to the low aspect ratio and curvature of the walls give rise to features exclusive to low aspect ratio elliptical cavities, including formation of cellular structures at intermediate depths and vortex structures within and downstream of the cavity.
Effect of Gas Diffusion Layer With Double-Side Microporous Layer Coating on Polymer Electrolyte Membrane Fuel Cell Performance
Authors: Chang Hao-Ming , Chang Min-Hsing
Published: March 2013

In this study, the performance of a polymer electrolyte membrane fuel cell with double-side microporous layer (MPL) coating on gas diffusion layer (GDL) is investigated experimentally. A standard commercial SGL® 10BA carbon paper is used as the substrate and it is coated with MPL on both sides of the paper with different composition. Three different carbon powders are used in the experiments, including Vulcan XC-72R, Acetylene black, and Black Pearls 2000. The effect of polytetrafluoroethylene (PTFE) content is also considered. A single cell testing apparatus is constructed to measure the cell performance and evaluate the effect of GDL with double-side MPL coating. Accordingly, the optimal fabrication parameters of double-side MPL are determined. The result shows that under the same operating conditions, the performance of fuel cell using GDL with double-side MPL is better than that using general single-side MPL. The Acetylene black is found to give the best cell performance than the others. The optimal composition of MPL on the surfaces facing to the catalyst layer and flow-channel plate are 1.25 mg/cm2 and 0.25 mg/cm2, respectively. Besides, the optimal PTFE content is the same on both sides of MPL which is found to be 20 wt%.
Insight into the multicomponent nature of negative bias temperature instability
Authors: Nguyen Duc D. , Kouhestani Camron , Kambour Kenneth E. , Devine Roderick A. B.
Published: March 2013

A novel measurement technique is used to extract two physically distinct “permanent” (long lived on our experimental time scale, ≤12 000 s) and one recoverable charge components of the negative bias temperature instability in p-channel metal–oxide–semiconductor field effect transistors under inversion and n-channel devices under accumulation. The results suggest that the permanent components are present in both cases, while there is little, if any, recoverable charge present in the case of the n-channel device. A physical explanation is provided involving the band energy diagram to explain these observations.
Energy splitting of CdSe quantum dots induced by intense femtosecond laser excitation
Authors: Zhang Shengkun , Zeylikovich Iosif , Gayen Taposh , Alfano Robert , Tamargo Maria
Published: March 2013

Microscopic photoluminescence (PL) spectra of self-assembled CdSe quantum dots (QDs) grown by molecular beam epitaxy were investigated under excitation of intense femtosecond laser. Two samples with different QD sizes were fabricated. One had a single layer of larger CdSe QDs while the other had three layers of smaller QDs. The second harmonic radiation at 420 nm obtained from a mode-locked tunable Ti-Sapphire laser was used as the excitation source. The laser power density was in the order of kW cm−2 and the peak power density was in the order of GW cm−2 for the 150 fs laser pulse with a repetition rate of 78 MHz. The intense femtosecond laser pulses generated strong surface acoustic waves and modulated energy bands of electrons and holes of CdSe QDs. Increasing of the laser power resulted in the PL peak of the CdSe QDs splitting into four peaks for both QD samples: two peaks shifted to a lower energy side and the other two shifted to a higher energy side. The strong strain fields led to the mixing of heavy-hole state and light-hole state in the quantum dots. The strain fields further modulated the energy bands of electrons and holes and produced splitting of both electron–heavy hole (e-hh) transition and electron–light hole (e-lh) transition. For the sample with a single layer of smaller QDs, the energy splitting for both e-hh and e-lh transitions reached 23.5 meV at a peak power density of 0.32 GW cm−2. For the sample with three layers of larger QDs, the energy splitting was 19.9 meV for e-hh transition and 17.9 meV for e-lh transition at a peak power of 1.1 GW cm−2.
Epitaxial growth of engineered metals for mid-infrared plasmonics
Authors: Law Stephanie , Yu Lan , Wasserman Daniel
Published: March 2013

The authors demonstrate the ability of high-quality epitaxial InAs films to be used as wavelength-flexible, low-loss, engineered plasmonic metals across the mid-infrared spectral range. Films are grown by molecular beam epitaxy and characterized by Hall effect measurements, atomic force microscopy, and infrared reflection and transmission spectroscopy. The losses of our plasmonic material are studied as a function of InAs doping density, growth rate, buffer layer type, and substrate type. High growth rates are shown to be integral to obtaining films with low losses and doping densities approaching 1×1020 cm−3.
Influence of plasma treatment on optical and electrical properties of a-InGaZnO films
Authors: Xifeng Li , Enlong Xin , Jifeng Shi , Chunya Li , Jianhua Zhang
Published: March 2013

Amorphous InGaZnO (a-IGZO) films were prepared by radio frequency magnetron sputtering, and as-deposited a-IGZO films were treated with plasma in plasma-enhanced chemical vapor deposition equipment. The effects of plasma surface treatment on the microstructure and the optical and electrical properties of IGZO films were investigated. X-ray diffraction analysis indicated that the IGZO films were amorphous. Results showed that plasma surface treatment have remarkable influence on the resistivity, carrier concentration, and carrier mobility of IGZO films. The analysis of x-ray photoelectron spectroscopy revealed a correlation between the electrical properties of IGZO films and plasma surface treatment. For all the samples, the average transmission in the visible region is more than 80%.
Physics for Diagnostic Radiology, Third Edition.
Authors: Sprawls Perry
Published: March 2013

Physics for Diagnostic Radiology, Third Edition., Dendy P., Heaton B., CRC Press, Taylor & Francis Group, FL, 2012. 720 pp. Price: $79.95. ISBN: 9781439896402 (hardcover).
Structural Basis for Molecular Recognition at Serotonin Receptors
Authors: Wang Chong , Jiang Yi , Ma Jinming , Wu Huixian , Wacker Daniel , Katritch Vsevolod , Han Gye Won , Liu Wei , Huang Xi-Ping , Vardy Eyal , McCorvy John D. , Gao Xiang , Zhou X. Edward , Melcher Karsten , Zhang Chenghai , Bai Fang , Yang Huaiyu , Yang Linlin , Jiang Hualiang , Roth Bryan L. , Cherezov Vadim , Stevens Raymond C. , Xu H. Eric
Published: March 2013

Dissecting Serotonin Receptors

Serotonin receptors are the targets for many widely used drugs prescribed to treat ailments from depression to obesity and migraine headaches (see the Perspective by

Palczewski and Kiser

).

C. Wang
et al.

(p.
610
, published online 21 March) and

Wacker
et al.

(p.
615
, published online 21 March) describe crystal structures of two members of the serotonin family of receptors bound to antimigraine medications or to a precursor of the hallucinogenic drug LSD. Subtle differences in the way particular ligands bind to the receptors cause substantial differences in the signals generated by the receptor and the consequent biological responses. The structures reveal how the same ligand can activate one or both of the two main serotonin receptor signaling mechanisms, depending on which particular receptor it binds.
Deciphering the Glycosylome of Dystroglycanopathies Using Haploid Screens for Lassa Virus Entry
Authors: Jae Lucas T. , Raaben Matthijs , Riemersma Moniek , van Beusekom Ellen , Blomen Vincent A. , Velds Arno , Kerkhoven Ron. M. , Carette Jan E. , Topaloglu Haluk , Meinecke Peter , Wessels Marja W. , Lefeber Dirk J. , Whelan Sean P. , van Bokhoven Hans , Brummelkamp Thijn R.
Published: March 2013

Viruses and Congenital Disorders

Mutations in genes involved in α-dystroglycan O-linked glycosylation result in posttranslation modifications associated with the congenital disease Walker-Warburg syndrome (WWS). This cellular modification is also required for efficient Lassa virus infection of cells.

Jae
et al.

(p.
479
, published online 21 March) screened for genes involved in O-glycosylation that affected Lassa virus infection and identified candidates involved in glycosylation. Individuals from different pedigrees exhibiting WWS had unique mutations among genes identified in the genetic screen. Thus, comprehensive forward genetic screens can be used to define the genetic architecture of a complex disease.
Draft Genome Sequence of the Chronic, Nonclonal Cystic Fibrosis Isolate Pseudomonas aeruginosa Strain 18A
Authors: Woo Jerry K. K. , McElroy Kerensa , Rice Scott A. , Kirov Sylvia M. , Thomas Torsten , Kjelleberg Staffan
Published: March 2013

Pseudomonas aeruginosa
strain 18A is a clinical, nonclonal isolate retrieved from the sputum of a chronically infected cystic fibrosis patient. The genome of 18A was sequenced for comparison with environmental and clinical isolates to identify genes that might facilitate its persistence during infection.
Complete Genome Sequence of the Probiotic Lactobacillus plantarum Strain ZJ316
Authors: Li Xuan , Gu Qing , Lou Xiuyu , Zhang Xiaomei , Song Dafeng , Shen Lei , Zhao Yizhen
Published: March 2013

Lactobacillus plantarum
strain ZJ316, a probiotic strain with several functions, was isolated from healthy newborn infant fecal samples. Here we report the finished and annotated genome sequence of this organism.