bluuebunny/crossref_metadata_2025 huggingface dataset:
Global health and transfusion medicine: education and training in developing countries
Authors: Eichbaum Quentin , Shan Hua , Goncalez Thelma T. , Duits A.J. , Knox Patricia , Reilly Jim , Andrews David
Published: April 2014

Education and training in transfusion medicine have improved over the past decade in developing countries but are still generally deficient for the purpose of maintaining the safety of the global blood supply. In 2009, the World Health Organization global database on blood safety indicated that only 72% of countries in the world were able to meet their training needs necessary for maintaining the safety of their local blood supply. Educational approaches in transfusion medicine vary widely between continents and world regions. In this article, we summarize a session on global health education and training in developing countries that took place at the 2012 AABB conference. The panel consisted of transfusion representatives from South America (Brazil), Asia (China), Africa (South Africa), and the Caribbean (Curaçao), as well as a description of capacitation issues in postearthquake Haiti and the pivotal role of the US President's Emergency Plan for AIDS Relief (PEPFAR) in transfusion training and education in Africa. We present here summaries of each of these panel presentations.
Computational fluid dynamics modelling of different detention pond configurations in the interest of sustainable flow regimes and gravity sedimentation potential
Authors: Tsavdaris Alexandros , Mitchell Steve , Williams John B.
Published: April 2014

This study presents the results of the flow regime evaluation, by means of computational fluid dynamics (CFD), of a vegetated detention pond located at Waterlooville, Hampshire, UK. Alternative pond layouts were assessed for the same flow conditions on the basis of recommendations made in the literature. The results were validated by comparing the maximum computational velocities for the same case using different numbers of mesh elements. It was found that the development of a CFD model of detention ponds is intricate but feasible. The main findings were: (i) The present design performed well in terms of flood risk management, but the flow patterns could result in questionable treatment efficiency; (ii) vegetation seems to promote horizontal recirculation and turbulence; (iii) triangular and elliptical pond designs showed very poor performance; (iv) the most appropriate design for the given location and hydrological regime is an elliptical pond with a central emergent/submerged island.
First glyphosate‐resistant Lolium spp. biotypes found in a European annual arable cropping system also affected by ACCase and ALS resistance
Authors: Collavo A , Sattin M
Published: April 2014

In Europe, glyphosate‐resistant weeds have so far only been reported in perennial crops. Following farmers' complaints of poor herbicide efficacy, resistance to glyphosate as well as to ACCase and ALS inhibitors was investigated in 11 populations of Lolium spp. collected from annual arable cropping systems in central Italy. Field histories highlighted that farmers had relied heavily on glyphosate, often at low rates, as well as in a non‐registered crop. The research aimed at elucidating the resistance status, including multiple resistance, of Lolium spp. populations through glasshouse screenings and an outdoor dose–response experiment. Target‐site resistance mechanism was also investigated for the substitutions already reported for EPSPs, ALS and ACCase genes. Three different resistant patterns were identified: glyphosate resistant only, multiple resistant to glyphosate and ACCase inhibitors and multiple resistant to glyphosate and ALS inhibitors. Amino acid substitutions were found at position 106 of the EPSPs gene, at position 1781, 2088 and 2096 of the ACCase gene and at position 197 and 574 of the ALS gene. Not all populations displayed amino acid substitutions, suggesting the presence of non‐target‐site‐mediated resistance mechanisms. After 39 years of commercial availability of glyphosate, this is the first report of multiple resistance involving glyphosate selected in annual arable crops in Europe. Management implications and options are discussed.
Experimental Improvement of Ejector Performance Through Numerical Optimization of Nozzle Geometry
Authors: Sharifi Navid , Sharifi Majid
Published: April 2014

Ejectors are widely used in different applications such as refrigeration, propulsion, evacuation and aerospace. They use a pressurized flow as a motive stream to entrain a secondary flow or suction flow. In the current study, a malfunctioning steam ejector is studied experimentally to identify the sources of low compression ratio. This ejector was designed to operate under a motive pressure of 6 bar. However, the required vacuum in the system was not attained unless the pressure of motive steam was increased to 8 bar. The steam ejector was coupled with other unit operating facilities and hence, the ejector replacement was very costly. Therefore, the fastest and the most inexpensive way of improving the device performance was considered as replacing just the primary nozzle and without any further change in ejector’s geometry.

To achieve the required vacuum under the available motive pressure (i.e. 6 bar), a CFD–based optimization procedure was performed and different nozzle shapes were numerically investigated. The CFD Models were constrained to a fixed constant throat since the optimized nozzle shall not consume more flow rate than the former one. Ten different nozzle geometries were scrutinized in this numerical simulation and the one, which yields the highest entraining performance under the given boundary condition (i.e. motive flow pressure of 6 bar), was selected as the most optimized nozzle and manufactured. After installing the designed nozzle, an improved entrainment capability was observed and a desired vacuum level was attained under the nominal pressure of 6 bar.
Harvesting Downstream Energy to Improve Efficiency: Creating Apparent Discharge Coefficients of Jet Nozzles Greater Than 1.3
Authors: Surjaatmadja Jim B. , McDaniel Billy W. , Pawar Bharat B.
Published: April 2014

Fluid movement devices use upstream energy to move fluid from one location to another. Flow nozzles that slightly accelerate fluid motion, especially into the same direction, often exhibit discharge coefficients greater than 1.0. Jet nozzles, however, by definition, create a jet stream that is much faster than the upstream fluid, often exceeding 100-fold higher velocities. Energy used to move this fluid is often very high; jetting efficiencies are generally less than 1.0 and will only approach 1.0 if the shape of the entrance is such that there is no “vena contracta” within its flow regime inside the nozzle.

High-pressure nozzles require high horsepower to generate high-velocity fluids. As is commonly performed, power is created using high-powered pumping equipment. Oftentimes, nozzles are used to jet in locations that have high ambient pressures, such as at the bottom of the ocean or inside a deep oil well. At these locations, the hydrostatic pressures could be very high. Pressure at the upstream side of the nozzle would be even higher.

This paper discusses the design and use of a unique nozzle that uses the hydrostatic (potential) energy to accelerate the fluid velocity of the jet. In essence, the nozzle uses the downstream energy to perform part of its job, thus, substantially reducing the upstream pressure requirement. This phenomenon was proven to occur using CFD analysis. Laboratory tests have shown apparent discharge coefficients between 1.38 and 1.69, depending on the downstream pressure.
Hot Milling: A Proposal to Minimize Thermal Cracks Formation in Cemented Carbide Tools
Authors: Lima Ramsés Otto Cunha , Alves de Melo Anderson Clayton
Published: April 2014

It is well known that milling is a rotating and interrupted cutting process in which the milling cutter is made up of a number of inserts placed around its body and that each insert has the function of removing an amount of material from the workpiece per revolution. This feature induces the cyclic thermal loading in the cutting tool edge leading the insert to thermal fatigue, which induces nucleation and propagation of thermal cracks and accelerates the process of tool wear. This paper proposes a method to minimize this thermal cycling effect. In this case, hot air was blown into the idle phase of the milling cutter during face milling of an AISI 1045 steel with coated cemented carbide inserts. The main goal was to make the process quasi-continuous from the thermal viewpoint. Trials were carried out dry, at room temperature and with hot air applied at 100, 350 and 580°C, and wet at room temperature and 580°C. In this last case, an MQL (Minimum Quantity of Lubricant) system was used to create a spray of cutting fluid. After milling trials, the inserts were taken to a scanning electron microscope where the number of thermal cracks, wear and other damage was analyzed. It was observed that the heating of the idle phase helped reducing the number of thermal cracks and tool wear.
Study of Impact Properties of a Fluid-Filled Honeycomb Structure
Authors: Clark J. , Jenson S. , Schultz J. , Hoffman J. , Takak S. , Ali M. , Matthews Tessa
Published: April 2014

The work presented in this paper is a continuation of the study conducted on exploring impact properties of a functionally graded bio cellular structure found in a banana peel. The graded cellular structure with unfilled cells reacts intelligently to impact loading and crushes in a manner that results in a higher amount of energy absorption as compared to an equivalent regular honeycomb structure. In this paper, a non-Newtonian fluid is introduced into the cells of a regular honeycomb structure, and its effect on energy absorption properties are studied using an experimental approach. The results are compared with impact mitigation properties of an unfilled regular honeycomb structure. The introduction of non-Newtonian fluid significantly enhances the energy absorption capacity of regular honeycomb structure, and therefore, suggests that fluid inside a banana peel structure is playing a critical role in energy and impact absorption. A rudimentary relationship between the numbers of fluid filled layers and total energy absorption capacity of the structure is presented through a regression analysis.
Integration of Computer Aided Design Analysis Into the Engineering Design Process for Use by Engineering Designers
Authors: Petersson Håkan , Motte Damien , Eriksson Martin , Bjärnemo Robert
Published: April 2014

When developing products, engineering designers often face the problem that their candidate for a technical solution, ranging from a concept to a detailed design, needs to be analyzed by a design analyst before it is approved or rejected and the engineering designer can continue his/her activities within the product development process. If engineering designers have to send every solution candidate to a design analyst, a lot of time and money is lost. To avoid this, some Swedish companies have started to allow their engineering designers to use the analysis capabilities imbedded in modern CAD/CAE software.

In the literature on product development and on computer based design analysis (CBDA) both processes are fairly well described. However, this cannot be said about the interaction between the two processes. This is a growing issue as it represents core knowledge for developing efficient and effective integration concepts, which in turn can be developed into likewise efficient and effective approaches on how to assist the engineering designer to perform parts of the CBDA process on his/her own. Note that when we refer to CBDA here, this is confined to the use of FEM in the development of products, primarily based on working principles originating from the area of Mechanical Engineering.

Since we have been working on a process model for the integration between engineering design and design analysis, this has inspired us to utilize findings from these efforts to propose a conceptual model for a design analysis process driven by the engineering designer to be integrated into the product development process.

The proposed design analysis process model is based on the use of predefined analysis methods or templates. Templates are also utilized for QA (Quality Assurance) and monitoring of the analysis activities. Responsible for the development of the analysis methods and the templates are expert design analysts, who develop these tools within a technology development process. Before allowing the engineering designers access to them, these tools need to be approved by relevant bodies within the industrial enterprise and/or by external sources such as those responsible for certification and risk management.

In this paper we present the development of the proposed integrated design analysis process model and an industrial case study, which incorporates a non-linear design analysis activity, utilizing the FEM-program Abaqus within the CAD-software Catia V5 and its imbedded optimization module.
Numerical Investigations of the Positive Effects of Vehicle Dynamics Control Systems on Vehicle Crash
Authors: Elkady Mustafa , Elmarakbi Ahmed , MacIntyre John , El-Hage Hicham
Published: April 2014

This paper focuses on the use of vehicle dynamics control systems (VDCS) to mitigate vehicle collisions in case of offset frontal vehicle-to-barrier crash scenario. A unique six-Degree-of-Freedom (6-DOF) vehicle dynamics/crash mathematical model is developed and analysed in this paper. The model is used to define the vehicle body crash parameters by integrating a vehicle dynamics model with a vehicle front-end structure model. In this model, the anti-lock braking system (ABS) and the active suspension control system (ASC) are co-simulated with the full car vehicle dynamics model and integrated with the front-end structure. The associated equations of motion of the model are developed and solved numerically.

In this study, different crash scenarios are simulated with different cases of VDCS to investigate their influences on the vehicle collision improvement. ABS, ASC, and anti-pitch control (APC) systems as well as an under pitch control (UPC) technique are applied in this paper, and their results are compared with free rolling crash scenarios. This study shows that the vehicle dynamics/crash response is captured and analysed quickly and accurately. Furthermore, it is shown that the VDCS affect the crash characteristics positively.
Effect of Different Italian Regulatory Frameworks on the Energetic Assessment of CHP Plants: A Comparative Design and Experimental Condition Analysis
Authors: Badami Marco , Bocci Giacomo , Camillieri Francesco , Pagliarulo Davide , Portoraro Armando , Vigliani Elisa
Published: April 2014

Since a Combined Heat and Power (CHP) plant can offer high economic benefits when a certain energy savings value is obtained, it is very interesting to consider the requirements foreseen by legislation to meet this target. The paper deals with an energetic assessment of eleven industrial CHP power plants, based on different prime mover technologies installed and in operation in Italy. The analysis has been carried out considering not only the nominal design data of the plants, but also experimental ones, in order to highlight their real operational performances.

The aim of the study was to compare the effects of two legislations on the calculation of the primary energy savings: the first is the Italian legislation that was in force when the power plants were designed, and the second is the current European Directive, which was issued a few years later when the plants were already in operation. The results of the study show as the subsidy mechanism introduced by the new legislation is stricter than the previous one, and could have a significant effect on the economic profitability of a cogeneration plant installation. More critical comments on the overall regulatory framework are presented in the paper.
Study to Reduce Heat Loss From Solar Thermal Collector by Diminishing Natural Convection With High-Porosity Porous Medium
Authors: Hirasawa Shigeki , Tsubota Ryohei , Kawanami Tsuyoshi , Shirai Katsuaki
Published: April 2014

We studied the reduction of natural convection heat loss from a solar thermal collector by placing a high-porosity porous medium above the collector plate in a solar thermal collector system. It is known that natural convection can be diminished in a porous medium. In order to use a porous medium in a solar thermal collector, it is necessary to minimize the shading effect of solar radiation caused by the porous medium. In this work, we used a series of offset wire screens made of fine nylon fishing lines of 0.05 mm in diameter with 2-mm pitch and a porosity of 0.999. The experimental apparatus consisted of a copper 300 mm × 300 mm collector plate with a selective absorption film on the surface. We measured the inlet solar radiation, the absorbed solar radiation on the collector plate and the collected heat to cooling water under actual sun radiation, and obtained the reduction rate of the convection heat loss from the collector plate and the shading effect. We changed the condition of the porous medium, the temperature of the collector plate, and the inclined angle of the collector plate. Experimental results of the Nusselt number of natural convection in the high-porosity porous medium agreed with the equation proposed by Gupta et al. [10]. The effect of the inclined angle on the Nusselt number was small. The net reduction rate of natural convection heat loss was 7% by placing the high-porosity porous medium above the collector plate when the temperature of the collector plate was 100°C.
Small Scale Prototype Biomass Drying System for Co-Combustion With Coal
Authors: Roberts Heather , Favrow Mitch , Coatney Jesse , Yoe David , Langness Chenaniah , Depcik Christopher
Published: April 2014

Thermoelectric power plants burn thousands of tons of non-renewable resources every day to heat water and create steam, which drives turbines that generate electricity. This causes a significant drain on local resources by diverting water for irrigation and residential usage into the production of energy. Moreover, the use of fossil reserves releases significant amounts of greenhouse and hazardous gases into the atmosphere. As electricity consumption continues to grow and populations rise, there is a need to find other avenues of energy production while conserving water resources. Co-combusting biomass with coal is one potential route that promotes renewable energy while reducing emissions from thermoelectric power plants. In order to move in this direction, there is a need for a low-energy and low-cost system capable of drying materials to a combustion appropriate level in order to replace a significant fraction of the fossil fuel used. Biomass drying is an ancient process often involving the preservation of foods using passive means, which is economically efficient but slow and impractical for large-scale fuel production. This effort, accomplished as an undergraduate capstone design project, instead implements an active drying system for poplar wood using theorized waste heat from the power plant and potentially solar energy. The use of small-scale prototypes demonstrate the principles of the system at a significantly reduced cost while allowing for calculation of mass and energy balances in the analysis of drying time, Coefficient of Performance, and the economics of the process. Experimental tests illustrate the need to distribute air and heat evenly amongst the biomass for consistent drying. Furthermore, the rotation of biomass is critical in order to address the footprint of the system when placing next to an existing thermoelectric power plant. The final design provides a first step towards the refinement and development of a system capable of efficiently returning an amount of biomass large enough to replace non-renewable resources. Finally, an innovative methodology applied to the dryer is discussed that could recover water evaporated from the biomass and utilize it for agricultural purposes or within the power plant thermodynamic cycle.
Investigation of Thermal Cycle and Hardness Distribution in the Laser Cladding of AISI H13 Tool Steel Produced by a High Power Direct Diode Laser
Authors: Farahmand Parisa , Balu Prabu , Kong Fanrong , Kovacevic Radovan
Published: April 2014

Laser cladding (LC) of tool steel has significant application in rapid tooling, and surface coating for worn-out components in different industries. During the LC process, several phase transformations influence the microstructural and mechanical properties of the deposited layer. In order to successfully implement the LC process, it is essential to understand the relationship between the thermal cycle (heating and cooling), phase transformations, and the output quantities of the deposited layer. In this study a direct diode laser with a power of up to 8 kW was used to deposit AISI H13 tool steel on mild steel grade A36 substrate to enhance its surface properties. Primarily, an experimentally verified three-dimensional (3-D) heat transfer analysis was developed based on the finite element method to compute temperature history during the cladding and cooling process. Next, the computed thermal cycles were coupled with a semi-empirical thermo-kinetic model to estimate the hardness of deposited layers based on different cooling cycles in a time-temperature-transformation (TTT) diagram. Further, the microstructural details obtained from the cross-sections of the clad were correlated with the estimated thermal cycles and hardness. A good correlation between the modeled and experimental results revealed that the developed model can be used to estimate the microstructural characteristics and mechanical properties of the H13 layer produced by the LC process.
Parametric Analysis of Single-Phase and Two-Phase Models of a Microfluidic Direct Methanol Fuel Cell
Authors: Tohid Usama , Pacheco-Vega Arturo
Published: April 2014

We perform numerical simulations of single-phase and two-phase models of a direct methanol microfluidic fuel cell (μ-DMFC). The focus of this study is on the parametric analysis of a single channel of the system, for specific sets of operating conditions, in order to map the dependence of the cell performance with respect to the geometrical parameters. Different geometries, ranging from 500 μm to 4 mm in width, and 500 μm to 4 cm in length, along with membrane thicknesses from 50 μm to 500 μm, were considered. The mathematical models are given in terms of the Navier-Stokes, the Butler-Volmer and the Maxwell-Stefan equations, along with Darcy’s equation for the flow across the membrane. The difference between the single- and two-phase flow models lies upon the specific constitutive equations used. For each geometry and operating condition, the two-dimensional equations were solved by a finite element method. The conditions of operation include: flow rates and inlet weight fractions of methanol at the anode and oxygen the cathode. The results from this analysis, presented as polarization curves and power densities, indicate that fuel-cell systems with higher flow rates and inlet weight fraction of methanol achieve the best performance. However, when the concentration of methanol exceeds 2M the cell performance is negatively impacted due to crossover. Comparison of the results indicates that the two-phase model has a more restrictive domain for both the geometrical parameters and operating conditions.
Large Amplitude Vibrations of Thin Hyperelastic Plates: Neo-Hookean Model
Authors: Breslavsky Ivan , Amabili Marco , Legrand Mathias
Published: April 2014

Static deflection and large amplitude vibrations of a rubber plate are analyzed. Both the geometrical and physical (material) nonlinearities are taken into account. The properties of the plate hyperelastic material are described by the Neo-Hookean law. A method for building a local model, which approximates the plate behavior around a deformed configuration, is proposed. This local model takes the form of a system of ordinary differential equations with quadratic and cubic nonlinearities. The results obtained with the help of this local model are compared to the solution of the exact model, and are found to be accurate. The difference between the model retaining both physical and geometrical non-inearities and a model with only geometrical nonlinearities is also analyzed. It is found that influence of physically induced nonlinearities at moderate strains is significant.
A Study of a New Cooling Device Based on the Electrocaloric Effect
Authors: Sato Wataru
Published: April 2014

We describe our study on a new cooling device based on the electrocaloric effect (ECE). The ECE causes increases and decreases in the temperature of dielectric material by changing the electric field. We used a multilayer ceramic capacitor (MLC) to demonstrate the temperature change on the basis of the ECE. The temperature change in commercial MLCs can be controlled by applying a voltage to them, and the maximum change is 0.55 K when 300 V are used. However, these changes are sequentially caused by applying and removing the voltage. Therefore, this phenomenon to a cooling device was difficult to apply. We used a heat pipe that had an anisotropic heat conduction feature to separate the heating and cooling. We developed a cooling device consisting of MLCs and a heat pipe containing acetone as the working fluid. The MLCs were set in the bottom of the heat pipe to create the cold side and the other side of the heat pipe was attached to a heatsink for the hot side. Only the heat from the ECE in this device was transferred to the heatsink. The temperature of the cold side decreased due to voltage being periodically applied and removed. This device revealed that the temperature of an MLC dropped 0.49 K when 300 V were used at a 0.1-Hz frequency.
Structural-Feature-Attribute-Based Segmentation of Optical Images of Bone Slices Using Optimized Pulse Coupled Neural Networks (PCNN)
Authors: Hage Ilige S. , Hamade Ramsey F.
Published: April 2014

In this work, we apply an image segmentation technique that uses pulse coupled neural networks to automatically discern the micro-features of cortical bone histology. In order to properly identify them, we exploit the geometric attributes of these micro features namely shape (i.e., circular or elliptical). These micro-constituent attributes are used as targets for the fitness function of the optimization method (particle swarm optimization, PSO) that was combined with PCNN along with an adaptive threshold, (T) that finds the best value for T between two segmented regions. The result is an optimal set of PCNN parameters that was found in this work to yield good-quality segmented pulses of the various micro-features of 2 different cortical bone images.
Carbon Fiber Composite Materials in Modern Day Automotive Production Lines: A Case Study
Authors: Petersson Håkan , Motte Damien , Bjärnemo Robert
Published: April 2014

New and innovative production equipment can be developed by introducing lightweight materials in modern day automotive industry production lines. The properties of these new materials are expected to result in improved ergonomics, energy savings, increased flexibility and more robust equipment, which in the end will result in enhanced productivity. Carbon composite materials are one such alternative that has excellent material properties. These properties are well documented, and the market for carbon composite materials is growing in many areas such as commercial aircrafts, sporting goods and wind turbines. However, when studying the use of carbon composite materials for production equipment in the automotive industry, it was found that there were few, if any, such examples.

This paper focuses on innovative ways of making carbon composite materials available for designing automotive industry production equipment by introducing a design and material concept that combines flexibility, relatively low costs and high functionality. By reducing the weight by 60%, it was obvious that the operators were very positive to the new design. But just as important as the improvement of the ergonomic feature, the combination of low weight and material properties resulted in a more robust design and a more stable process of operation. The two main designs (two versions of the steel-based design were constructed) were developed sequentially, making it difficult to compare development costs since knowledge migrated from one project to the next. In this study, the gripper was manufactured in both carbon composite material and steel. The different designs were compared with reference to design costs, functionality, robustness, product costs and ergonomics. The study clearly shows that the composite material represents a favorable alternative to conventional materials, as the system combines superior properties without significantly increasing the cost of the equipment. This paper describes the approach in detail.
A Study of the Planar Serial-Parallel Mechanism With Various Stiffness for a Biotic Compliant Fish
Authors: Zuo Cui , Hong-zhou Jiang
Published: April 2014

Previous biological experiments show that the fish use their muscles to stiffen their bodies for improving the swimming performance. Inspired by that, we propose a planar model of oscillatory propulsor with variable stiffness using hyper redundant serial-parallel mechanisms to mimic a fish. Our goal in the paper is to identify the swimming characteristics with respect to the body stiffness. Moreover, a simulation model is presented and its results show that the swimming performance is largely dependent on the body stiffness and the driven frequency. Our primary conclusions include: 1) when the driven frequency is closed to the design frequency, the robotic fish with the calculated body stiffness has a super swimming performance. 2) Driven at the design frequency, the forward speed of robotic fish is linearly proportional to the driving frequency and the Strouhal number is consistent with the experiment results 0.25<St<0.35.
Numerical Investigation to Evaluate the Performance of Helical Coiled Tube Heat Exchanger With and Without Nanofluid
Authors: Mahdi Qasim Saleh , Fattah Sahar A. , Jumia Firas
Published: April 2014

A numerical analysis presented out to simulate internal forced convection and temperature distribution in helical coil tube with and without nanofluid. An ANSYS FLUENT package 14.1 commercial copy with SOLID WORK and GAMBIT software program is employed. The flow pattern and temperature distribution in helical coil tube heat exchanger is studied with and without nanofluid. Numerical work included two parts: the first is included helical coil heat exchanger with optimum curvature ratio (17). An optimum helical coil pitch has been used to study the temperature distribution and flow pattern difference along the turns without nanofluid. The second part included studying the effect of using (Oxide Titanium TiO2) nanoparticle powder with 20 nm diameter dispersed in distilled water with 0.6 % volume concentrations on the same above variables. Temperature contours showed that the temperature decreased along the coil. Also there is difference in temperature between turns. After turn nine the difference become less. The results showed enhancement in the heat flow for fluid with nanofluid compared to without nanofluid.
Comprehensive Comparisons of Random Space Transformation Methods Between Rackwitz-Fiessler and Nataf-Pearson in Theory and Algorithm
Authors: Zhou Sheng-Tong , Zhong Zuo-Yang , Li Hong-Guang , Li Cheng
Published: April 2014

Rackwitz-Fiessler method and Nataf-Pearson method are two most widely used random space transformation methods. However, unlike Nataf-Pearson method, Rackwtitz-Fissler method is always used when random variables are independent due to its difficulties of accounting for dependency variation. So in present article, we discussed the transformation ways and linear correlation variations of these two methods. And found that the same isoprobabilitic transformation principle was followed by the forward transformation of Rackwitz-Fiessler method like that of the Nataf-Pearson method, so the same Pearson linear correlation matrix should also be possessed by the transformed random vector after the Rackwitz-Fiessler method. In addition, the backward transformations, algorithm realizations, computation cost and efficiency were also discussed between these two methods. Finally, combined with standard Hasofer-Lind FORM method, we presented two numerical examples to illustrate the actual differences and similarities of these two transformation methods in their reliability applications.
Flat-Plate Solar Collector in Transient Operation: Modeling and Measurements
Authors: Saleh Ahmad M. , Mueller Donald W. , Abu-Mulaweh Hosni I.
Published: April 2014

Solar energy is a viable alternative to limited fossil fuel resources. One of the simplest and most direct applications of this energy is the conversion of solar radiation into thermal energy with a flat-plate solar collector which can be used in water-heating systems. This paper presents a mathematical model for simulating the transient processes which occur in liquid flat-plate solar collectors. A discrete nodal model that represents the flat-plate solar collector’s layers and the storage tank is employed. The model is based on solving a system of coupled differential equations which describe the energy conservation for the glass cover, air gap, absorber, fluid, insulation, and the storage tank. Inputs to the model include the time-varying liquid flow rate, incident solar radiation, and ambient air temperature, as well as the volume of liquid in the storage tank and initial temperature of the solar collector and tank. The system of differential equations is solved iteratively using an implicit, finite-difference formulation executed with MATLAB software. In order to verify the proposed method, an experiment was designed and conducted on different days with variable ambient conditions and flow rates. The comparison between the time-varying computed and measured fluid temperature at the collector outlet shows good agreement.

The proposed method is extremely general and flexible accounting for variable ambient conditions and flow rates, as well as allowing for a geometrical and thermophysical description of all essential components of the solar collector system, including the storage tank. The validated and verified, general model is suitable to investigate the effectiveness of various components without the necessity of carrying out experimental work, and the flexible computational scheme is useful for transient simulations of energy systems.
The Molecular Dynamics Study for Detection of ssDNA by Monolayer Graphene Nanopore
Authors: Si Wei , Sha Jingjie , Liu Lei , Zhang Yin , Chen Yunfei
Published: April 2014

Molecular dynamics simulations are performed to provide valuable information about the translocation of four single-stranded DNAs with ten identical bases through graphene nanopore with diameter of 2 nm. The monolayer graphene nanopore is highly sensitive to ssDNA translocation events and the 10-base resolution detection can be realized by electrophoreticly threading ssDNA through graphene nanopore. Due to the similar sizes of the four nucleotides, the blockage current is unlikely to provide a distinguishable signal. However, by simply monitoring and analyzing the translocation time of poly(dA)10, poly(dC)10, poly(dG)10 and poly(dT)10 though graphene pore, each ssDNA can be identified and characterized.
A Study on the Influence of the Suction Arrangement on the Performance of Twin Screw Compressors
Authors: Pascu Maria , Heiyanthuduwage Manoj , Mounoury Sebastien , Cook Graeme , Kovacevic Ahmed
Published: April 2014

Screw compressors are complex flow systems, but operate upon simple considerations: they are positive displacement machines consisting of meshing rotors contained in a casing to form a working chamber, whose volume depends only on the angle of rotation. Their performance is highly affected by leakages, which is dependent on various clearances and the pressure differences across these clearances. Nowadays, the manufacturing and profiling techniques have matured so much, that rotors of even the most complex shapes can be manufactured to tolerances in the order of few microns, resulting in high efficiencies. With manufacturing tolerances this tight, there is only small amount of improvement expected from further exploration of this venue, and a rather different direction for analysis may be more rewarding, i.e. other components of the screw compressor, like the suction and discharge areas. While the available literature includes several references on improvements of the compressor performance based on the analysis of the discharge port and discharge chamber, the investigation of the suction arrangement and inlet port remains fairly unexplored. This is the area of concern for the present paper, where the influence of the port shape and suction arrangement on the overall compressor performance is investigated. Two suction models were investigated for a standard screw compressor by means of CFD, which allowed in-depth analyses and flow visualizations, confirmed by the experimental investigation carried out on the actual compressor.
Dredged Sediments as Materials in Tunnel Construction
Authors: Kazi Aoual-Benslafa Fatiha , Kerdal Djemal , Mekerta Belkacem , Semcha Abdelaziz
Published: April 2014

The actual shortage of land aggregates and environmental concerns raised by dumping at sea of dredged sediments (DS), more than ever, DS could constitute a new source of building materials. This experimental study investigates the potential of using DS from harbour of Oran in tunnel construction; the first objective is to determine their chemical, physical and mineralogical characteristics. The concept of enhancing building material characteristics based on the component characteristics of DS is considered. Thus, the treatment by the leaching and the natural decantation is used to decrease their salt and water content. Finally, the influence of various percentages of DS (from 20%, to up to 35% of sand mass by DS) in the mechanical behaviour of mortars was analyzed. Compressive strengths of a first set of mortar specimens were determined after 7, 28, 60 and 90 days of moist curing. The second set of mortar specimens, that were submitted to chemical attacks and elevated temperatures, had their residual compressive strengths determined at 118 days and 150 days. So far, laboratory results show that partial replacement of 20% or 25% of sand by DS in mortars give good results.
What Lean Teaches Us About Ethics in Engineering
Authors: Flumerfelt Shannon , Alves Anabela C. , Kahlen Franz-Josef
Published: April 2014

This theoretical paper provides a comprehensive examination of the need for the ethical development of the engineering student. A review of the literature regarding the need for the teaching of ethics in the Academy and of the need for ethics in the engineering workplace is described. The Toyota Education Model based on respect for people is presented as a viable method for the Academy’s consideration.
Thin Film Evaporation Model With Retarded van der Waals Interaction
Authors: Hanchak Michael S. , Vangsness Marlin D. , Gheorghiu Nadina , Ervin Jamie S. , Byrd Larry W. , Jones John G.
Published: April 2014

In phase change heat transfer equipment, three-phase contact regions exist that consist of a solid wall and the liquid and vapor phases of a working fluid. When the working fluid fully wets the solid wall, a microscopic thin film adjoining the meniscus is present called the adsorbed film. Upon heating, a non-uniform evaporative flux profile develops with a maximum value occurring within the transition between the adsorbed film and the intrinsic meniscus. It is important to study the heat transfer characteristics of this region to gain better fundamental understanding and useful design principles. The adsorbed film occurs when the driving potential for evaporation is opposed by the presence of intermolecular forces, represented analytically by the disjoining pressure, which acts to thicken a wetting film. The model presented includes lubrication theory of the liquid flow within the film, heat conduction across the film from the heated wall to the liquid-vapor interface, kinetic theory evaporation from the interface to the vapor phase, and disjoining pressure based on a retarded van der Waals interaction. The retarded van der Waals interaction is derived from Hamaker theory, the summation of retarded pair potentials for all molecules for a given geometry. When combined, the governing equations form a third-order, nonlinear differential equation for the film thickness versus distance, which is solved numerically using iteration of the initial film curvature in order to match the far-field curvature of the meniscus. Also, iteration is required at each length step to determine the liquid-vapor interface temperature. Useful outputs of the model include the liquid-vapor interface temperature and the evaporative mass flux profile. The model is calibrated to in-house experiments that employ an axisymmetric capillary feeder to provide a thin film of n-octane onto a substrate of silicon, where the gas phase is air saturated with vapor. The film thickness versus radial distance is measured using reflectometry and interferometry.
Zone of Intrusion for F-Shape and Single-Slope Concrete Barriers
Authors: Reid John D. , Stolle Cale
Published: April 2014

The Zone of Intrusion (ZOI) is a measurement of the furthest protrusion of a vehicle component behind a permanent concrete barrier during a crash. Often, roadside objects or structures, such as luminaire poles or trees, are located within or near the ZOI of a barrier, posing a risk to the occupants of impacting vehicles. Due to the high costs of full-scale crash testing it is not practical to test for the ZOI of every size and shape of barrier. As an alternative, non-linear finite element simulation was used to develop ZOI guidelines for the 40-inch tall F-shape parapet and the 9.1-degree single-slope parapet (at heights of 36, 42 and 56 inches). Results showed a minimum ZOI of 0 inches for the 56-inch tall barrier and a maximum ZOI of 9 inches for the 36-inch one. The amount of vehicle structure overhanging the barriers was limited to the front corner of the hood, and under certain conditions, small portions of the fender. Tire friction, tire deflation, suspension component failures and combinations of those vehicle behaviors had little influence on the ZOI.
A New Method to Study the Joint Surfaces With Large Areas and its Application in Machine Tools
Authors: Zhou Anan , Wang Xiaopeng , Chen Tianning
Published: April 2014

In the finite element analysis (FEA) of machine tools, the study on contact parameters uses the data calculated by theory or identified by experiment directly, which may cause the great distinguish between the results obtained by FEA and by experiment. It is well known that the basic assumption on contact is the contact load of the joint surface stays the same throughout all areas. For the joint surfaces with small areas the loads are well-distributed and unchanged. But for the big joint surfaces the error will be very large with that assumption. A different method was proposed in this paper to calculate the parameters of joint surfaces with big areas. According to the different load conditions, we divided the joint surfaces into different parts and for each part the contact parameters were calculated respectively by the theory we established before. Substituting the parameters into the finite element model the result of FEA can be got. Moreover the methods on how to divide the joint surfaces into parts and how to apply the parameters to FEA of machine tools were also discussed. A dynamic experimental study on contact parameters was carried out. The first 3 natural frequencies and mode shapes of the experiment had a good agreement with the ones of FEA while the error was acceptable. As a result, for the joint surfaces with big areas such as those in machine tools, using the method proposed in this paper, the result of FEA will be more reasonable and the finite element model will be much closer to real one.
Multiscale Analysis of Multifunctional Composite Structures
Authors: Bahei-El-Din Yehia , Micheal Amany
Published: April 2014

In a truly multiscale analysis of multilayered composites, the underlying phenomena are represented and their effect on the overall behavior is determined considering the interaction between the different phases and between the laminas. The analysis gets more involved when multiple phenomena are considered since in this case not only the direct effects play a role but also the coupled effects contribute to the distribution of the local fields and the overall response. In a fibrous composite laminate reinforced with piezoelectric filaments, for example, passing an electric field in the fibers generates stresses and strains which propagate through the composite medium due to constraints that exist both at the micromechanical, ply level, and the macromechanical, laminate level. Pyroelectricity is another coupling phenomenon in which a temperature change is caused by an electric field, and hence leads to changes in the stress and strain fields throughout the composite medium.

The above phenomena have been considered by the authors in a unified, transformation field analysis (TFA) approach in which stresses and strains which cannot be removed by mechanical unloading are treated as transformation fields. Due to mutual constraints of the phases and the bonded plies, local transformations generate stresses at the micro and macro levels, which are computed by means of influence functions which depend on material geometry and properties. Treatment of damage follows the same scheme but the transformation fields are instead determined such that the local stresses in the affected phase are removed.

In the present paper, implementation of the TFA approach in a general purpose finite element code is described. This expands the multiscale analysis outlined above to composite structures where complex geometries can be modeled and the effect of local phenomena can be considered. This naturally comes at a much larger cost of the computations compared to finite element analysis with homogenized models but the benefit of obtaining a more realistic response is clear. Moreover, the availability of high performance computing and parallel processing overcomes the computation time barrier. In the present paper however, simple examples of laminated structures are given as proof of concept in which the results are compared to those of standalone routines. Since the TFA approach centers on treating the composite medium as elastic with induced local transformations, implementation in the finite element framework does not require generation of an overall instantaneous stiffness matrix, which saves tremendously on the computation time. Instead, overall transformation strains, or stresses, are computed through a multiscale model, which is implemented as a user routine, and treated in the general finite element solution as nonmechanical strains in the same way thermal strains are treated.