bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study on Energy Harvesting From Salinity Gradient by Reverse Electrodialysis in Ag/AgCl Deposited AAO Nanochannel Array
Authors: Kang Byeongdong , Kim Moojoong , Joo Hyungmin , Kim Hyun Jung , Kim Dong-Kwon
Published: April 2014

Reverse electrodialysis (RED) is energy conversion phenomena which generates electricity from concentration gradient energy by mixing the ions in sea water with fresh water through ion-selective nanochannel. When nanochannels are filled with an aqueous solution, the surface of nanochannels is charged by ionization, ion adsorption, and ion dissolution. Therefore, co-ions are repelled from the nanochannels and only counter-ions can be transported through the nanochannels. As a result, the electric current can be generated by selective ion transport through the nanochannels from sea water to fresh water. Recently, solid-state nanochannels or nanopores have received attention because they have potential to replace polymer ion-selective membranes. Especially, anodic aluminum oxide (AAO) nanochannel array has advantage of easiness of pore size control and high pore density. In the present study, to collect electric current generated by the nanochannels, we deposited the porous silver layer on both front and rear surface of the AAO nanochannel array by using e-beam evaporation and changed the silver layer to the silver/silver chloride layer by chemical oxidation with aqueous FeCl3. Finally, we conduct an experimental investigation for the power generation from the AAO nanochannel arrays placed between two potassium chloride solutions with various combinations of concentrations.
Functional Modeling: A Key Point in CAD Systems
Authors: Ferrise Francesco , Bordegoni Monica , Cugini Umberto
Published: April 2014

For more than 40 years the development of Computer Aided Design (CAD) tools has been focused on the description of the geometry of products. More recently, CAD tools have evolved in tools to support the Product Lifecycle Management (PLM), which are more oriented to support the management aspects of the product development process than the design process itself. Recently, it has been introduced a new design method that adopts a top-down approach, which starts from the definition of a Functional MockUp (FMU) allowing to simulate the overall behavior and the use of the concept level before the detailed design. This method is closer to the typical logical sequence of design, where the designer has at first an overall view of a system and of its sub-components, and then he takes care of the details. This method is supported by commercial tools, as the LMS-Amesim suite, or by open-source software tools based on the Modelica language. This is an open-source language allowing designers to integrate and describe at functional level several aspects of a system, including mechanical, electrical, thermal, hydraulic, control and others allowing to simulate all together. The paper analyses this methodological approach and presents some applications where some systems are designed using a functional modeling approach.
A Study on Power Uprating of a Steam Injected Gas Turbine Cogeneration System by Compressor Discharge Air Bypass
Authors: Kang Do Won , Jang Hyuck Jun , Kim Tong Seop
Published: April 2014

Gas turbines are widely used for cogeneration systems. In general, electricity and heat demands are not constant throughout the year. In cooling seasons, generally, heat demand decreases but electricity demand increases. In small gas turbine cogeneration systems, steam injection is a good way to respond to the demand variation. However, steam injection causes compressor discharge pressure to rise. This means a reduction in compressor surge margin, which is a critical operational parameter. Hence, even though thermal energy demand decreases considerably as is the case in cooling seasons, the surplus exhaust heat cannot be utilized for the steam injection in the conventional operation. In this study, a modified steam injected operation is suggested, which uprates electric power output without damaging a minimum allowable surge margin. This can be realized by extracting some of compressor discharge air and supplying it to the turbine exhaust side. The modified operation allows more steam to be injected into the combustor in comparison to the conventional steam injected operation while it guarantees the same compressor surge margin. The modified operation concept provides another merit of modulating the heat to power generation ratio by controlling both the amount of air bypass and the steam injection rate. In particular, pure power generating operation, where full amount of generated steam is injected and thus no heat output is available, is possible without decreasing the surge margin below a desired minimum value.
System Identification of a Grinding Machine Excited by an Active Tool Holding Device
Authors: Boldering Alexander L. , Borchert Gunnar , Raatz Annika , Dröder Klaus
Published: April 2014

Reducing the cost of manufacturing products can be realized by high performance, precise and productive machine tools. This goal is often obtained by the user increasing the adjustable machine parameters, which include the feed rate or the cut depth. Both will increase the grinding force during the grinding process, which can result in an excitation of the machine structure. If the excitation is too high, the machine structure can show an undesired dynamic behavior, which can cause the machine to vibrate. These vibrations can result in chatter marks on the work piece surface and if large enough can result in a production stop. One possibility to minimize the chance of excessive vibration is a conservative choice of machine parameters which are well below the optimal set for a particular machine. This paper presents an approach which shows the first results of an active tool holding device aimed at reducing unwanted vibrations resulting from an aggressive parameter choice.
Prototyping a New Lightweight Passenger Seat
Authors: Yüce C. , Karpat F. , Yavuz N. , Kaynaklı Ö. , Dolaylar E. , Şendeniz G.
Published: April 2014

Profitability is the key concern for transport companies. Costs are increased due to the rising fuel prices and technological investments. As well as new legal restrictions on the emission rates have forced the sector different fuel efficient technologies. Reducing weight is one of the most important methods of improving fuel efficiency and cutting CO2 emissions. Accordingly lighter, more fuel efficient, environmentally sustainable and safety vehicles are in the priority list of European authorities. And also the future of hybrid and electric vehicles depends on the lightweighting. The seat structure was chosen as the area for study which presented the best opportunity for weight reduction by the use of new materials. A seat provides comfort and safety of an occupant’s while travelling. In the event of crash, the passenger seat is exposed many different forces. For this reason it should be designed sufficient strength and stiffness. Therefore an optimized seat design should be aesthetically pleasing, ergonomic, light and meet the safety requirements. Seats play an important role in mass of buses and coaches due to number of seats per vehicle. In this project, finite element analysis, together with topology and free-size optimization is used to design a lightweight passenger seat for new generation commercial vehicles.

The seat CAD models were created with CATIA V5 and then imported into HyperMesh for finite element model creation and analysis. Results from the nonlinear analysis provide an accurate prediction of the material yielding and load path distribution on the seat structural frame components. In the end, the verification tests which were determined by ECE are applied the new seat and results were compared with the FEA results.

In this study, the lightweight passenger seat prototypes have developed. High strength steel and fiber-reinforced plastic parts are used. An overall 20% weight reduction is achieved including the structural frame, cushion, armrest, and pillar. And also the new passenger seat provides ECE safety norms.
High Efficiency Propeller Design Based on the Betz Minimum Induced Loss Condition and CFD Validation on an APC 8″ Propeller
Authors: Albert Sven , Epple Philipp , Willinger Bettina , Delgado Antonio
Published: April 2014

Betz [1] described the wake flow conditions for a propeller of minimum induced loss. The condition is somewhat similar to the elliptic circulation distribution of a finite wing, which was found by Prandtl [2]. Larrabee [3] reworked the theory in his 1979 paper Practical Design of Minimum Induced Loss Propellers, allowing for a step by step design of a propeller of specified RPM, advance velocity, diameter and thrust. In the present work the Larrabee model was programmed in VBA utilizing MS Excel and applied to a series of selected propellers. The minimum induced loss condition can be met for a chosen propeller duty point only. In order to evaluate off design points the blade element theory according to Glauert [4] was applied and implemented in the design tool. The tool itself offers complete freedom over the propeller parameters, including the choice of blade sections. Also a geometry export function into the ANSYS curve format was implemented to allow for a fast CFD computation of the current propeller design. For theory evaluation purposes a commercially available RC model propeller with 8″ in diameter was chosen as a reference. This propeller is listed in the wind tunnel measurements database of the University of Illinois [5]. CFD computations of the reference propeller design showed very good agreement with the experimental data, therefore indicating an accurate CFD setup. The theory of minimum induced loss is based on the distribution of circulation along the propeller’s blades, which was also investigated using CFD. Satisfying the minimum induced loss condition, several design strategies are shown and evaluated, ultimately leading to a design which proved to be superior to the actual reference design. Hence the validity of the loss condition could be shown. Also deep insights into the circulation along propeller blades were gained which in turn allow for a further refinement of theory and design tool.
Insights on Centrifugal Pendulum Vibration Absorber: Part Two — Behaviour of a FWD Powertrain With a CPVA on its Clutch’s Flange
Authors: Simionatto Vinícius G. S. , Miyasato Hugo H. , Dias Júnior Milton
Published: April 2014

This work is the second and last part of a study whose aim is to present the vibrational aspects of a system with a centrifugal pendulum vibration absorber (i.e. CPVA). The aim of this work, specifically, is to develop a mathematical model of a front engine–front wheel drive powertrain to study gear rattle phenomenon, and to install on its clutch disk’s flange a CPVA in order to understand what are the effects of this device on the dynamics of this system.

Results from the linear analysis show that the eigenfrequencies of the system vary with the engine speed. They oscillate between the eigenvalues of the system without the CPVA and, for regions away from the tuning frequency of the pendulum, which is the second order of rotation of the engine, the behaviour of the system remains the same. However, near the tuning frequency of the pendulum, the behaviour of the system varies very much, and the amplitude of vibration of the gearbox’s inner parts diminishes.

Simulations of the powertrain without and with the nonlinear model of the studied device show that its presence reduces dramatically the vibrations inside the gearbox and its nonlinear character does not influence the effectiveness of this solution.
Development of a Virtual Coil Model for Blood Flow Simulation in Coil-Embolized Aneurysms
Authors: Otani Tomohiro , Ii Satoshi , Fujinaka Toshiyuki , Hirata Masayuki , Kuroda Junko , Shibano Katsuhiko , Wada Shigeo
Published: April 2014

Hemodynamics is considered to be one of the indices to evaluate the effects of the treatment by coil embolization for cerebral aneurysms. For the sake of detailed analysis of hemodynamics in coil-embolized aneurysms, we develop a virtual coil model based on the mechanical theory that the coil deforms toward minimizing the elastic energy, and represent a realistic configuration of the embolized coils in the aneurysm by the insertion simulation. Then, the blood flow analysis is done by solving the N.S. and continuity equations numerically with the finite volume method using polyhedral mesh. The coil insertion simulation demonstrated that almost uniform distribution of the coil in the aneurysm was achieved at over 10% packing density of the coil. The blood flow analysis using the virtual coil model showed that the flow momentum inside the aneurysm was reduced to less than 10% by coil embolization with a packing density over 20%. In comparison to the simulation results using a porous media model for the embolized coil, there was no significant difference in the reduction ratio of the flow momentum in the aneurysm by coil embolization. However, local flow dynamics evaluated by the flow vorticity was different in the virtual coil model and the porous media model, in particular at the neck region of the aneurysm.
Numerical Investigation of the Pressure Drop Through Micro-Pillar Arrays for a Wide Range of Aspect Ratios
Authors: Taher Ahmed M. , Jones Benjamin , Adam Ihab G. , Lagae Liesbet
Published: April 2014

Accurate prediction of the pressure drop through micropillar arrays is essential for many micro total analysis system (μTAS) applications (e.g., liquid chromatography and filtration). Minimizing the pressure drop for such applications is often vital for performing their primary functions efficiently.

In this paper, numerical investigation of pressure drop through square micropillar arrays with different pillar diameter and pitch was conducted. Finite volume discretization method was employed for the numerical simulations using commercial code. Simulation results were validated against experimental data from the literature. A parametric study of geometric variables (pillar diameter, pitch, and height) was performed. Models available from the literature for predicting the permeability of a 2D micropillar array were accessed by comparison to the numerical results. Both dimensional analysis and simulation results were used to develop a new model for square arrangements of micropillar arrays which shows good agreement with numerical simulation results for both 2D and 3D cases. The maximum absolute error between the 3D simulation results and predicted value of the pressure drop has been decreased from 67.3% using a model from the literature to only 1.9% using the proposed model.
A Passive Progressive Damping Design for Ride and Handling
Authors: Moshchuk Nikolai , Namuduri Chandra , Nardi Flavio , Ryu Jihan , Golpe William , Knoll Richard
Published: April 2014

This article presents a method of synthesizing the non-linear compression damping curve to more effectively control the suspension behavior over roads that generate maximum wheel displacements, while maintaining good ride quality on normal roads. One degree of freedom (1DOF) nonlinear mechanical system is used to develop the optimal compression damping curve. All findings obtained using this 1DOF system are then confirmed using a quarter car model, full vehicle ADAMS model, and vehicle tests. The article addresses only the jounce portion of the damping curve which significantly influences the wheel displacement and shock tower load during a pothole event.
Electrohydrodynamic Patterning of Micro/Nano-Structures on Thin Polymer Films
Authors: Yang Qingzhen , Li Ben Q. , Ding Yucheng
Published: April 2014

Electrohydrodynamic (EHD) patterning provides an alternative to fabricate the controllable polymeric micro/nano-structures, which have wide applications in industry. Both steady state and dynamic development of EHD patterning structures are discussed in this paper. For the steady state modeling, a discontinuous boundary element coupled with finite element method is applied. Numerical results reveal that a critical voltage exists, below which a small amplitude structure is obtained and above which polymer evolves into patterns with a large height/width ratio. The transient process of EHD patterning is represented by the numerical solution of the phase field equation coupled with the electric field and Navier-Stokes equation. The computer model is capable of describing the dynamic development of the electrically-induced transport and surface deformation phenomena during EHD patterning. The coupled multi-field equations are discretized in finite difference with an enhancement by parallel computing. For structured templates, the application of an electric field creates the conformal structures in the polymer film with the periodicity and aspect ratios of the polymer structures controlled by template patterns and applied electric fields. Analysis indicates that the interaction between the applied field and the fluids leads to an occurrence of complex flow structures and free surface deformation and plays an important role in determining the dynamics of an EHD patterning process.
Mechanical Property and Degradation in Hot Water of Injection Molded Glass Short Fiber/Wood Powder/Polypropylene Hybrid Composites
Authors: Kong Xujie , Yu Ying , Yang Yuqiu , Li Jungang , Liao Mengyuan , Nomura Manabu
Published: April 2014

As well known, natural fibers absorb water easily that will affect the mechanical property considerably and there exists a problem of incompatibility which leads the weak interfacial adhesion between the fiber and the resin matrix because of the hygroscopic nature of natural fibers. Therefore, conducting hot water immersion and tensile test is necessary to study the mechanical property and degradation. In this study, glass fiber/wood powder/pp. hybrid composites were prepared by injection molding process at a fixed reinforcement to matrix ratio of 51:49. 3 kinds of hybrid specimens with glass fiber/wood powder ratios of 51:0, 21:30, and 0:51 were fabricated. The hydrothermal aging performance was investigated during the 80°C hot water immersion experiment with a series of immersion time and the effect of hot water immersion on the mechanical properties of composites have been evaluated based on the tensile test.

Results showed that both the strength and modulus of hybrid composite decrease obviously as the immersion time increase, which can be considered that the hydroscopic property of natural fiber would decrease the durability of composite in humidity environment. And the skin-core structure comes from injection molded process contributes to the better hydrothermal aging property of Glass/PP composite.
Microfluidic Molecular Trap: Probing Extracellular Signaling by Selectively Blocking Exchange of Specific Molecules in Cell-Cell Interactions
Authors: Brewer Bryson M. , Gao Yandong , Sappington Rebecca M. , Li Deyu
Published: April 2014

Communication among cell populations is achieved via a wide variety of soluble, extracellular signaling molecules [1]. In order to investigate the role of specific molecules in a cellular process, researchers often utilize in vitro cell culture techniques in which the molecule under question has been removed from the signaling pathway. Traditionally, this has been accomplished by eliminating the gene in the cell that is responsible for coding the targeted ligand/receptor by using modern DNA technology such as gene knockout; however, this process is expensive, time-consuming, and labor intensive. Previously, we have demonstrated a microfluidic platform that uses a semi-permeable barrier with embedded receptor-coated nanoparticles to selectively remove a specific molecule or ligand from the extracellular signaling pathway in a cell co-culture environment [2]. This initial proof-of-principle was conducted using biotinylated nanoparticles and fluorescently tagged avidin molecules, as the avidin/biotin complex is the strongest known non-covalent interaction between a protein and a ligand (Dissociation constant kd = 10−15 M). Also, the trap was only effective for short time periods (<15 min) because the high concentration of fluorescently tagged avidin molecules required for visualization quickly saturated the barrier. However, nearly all biologically relevant ligand-receptor interactions have lower binding affinities than the avidin-biotin complex, with dissociation constants that are larger by several orders of magnitude. In addition, many in vitro cell culture experiments are conducted over multiple hours or days. Thus, a practically useful molecular trap device must be able to operate in a lower binding affinity regime while also lasting for extended time periods. Here we present results in which a biotinylated-particle barrier was used to successfully block lower concentrations of fluorescently tagged avidin for multiple days, showcasing the applicability of the device for long term experiments. In addition, we introduce a modified molecular trap in which the protein A/goat IgG complex was used to demonstrate the effectiveness of the platform for lower binding affinity protein-ligand interactions. These results indicate the potential usefulness of the microfluidic molecular trap platform for probing extracellular signaling pathways.
Exergoeconomic Evaluation of a Solid-Oxide Fuel-Cell-Based Combined Heat and Power Generation System
Authors: Lee Young Duk , Ahn Kook Young , Morosuk T. , Tsatsaronis G.
Published: April 2014

An exergoeconomic evaluation has been conducted for a 100kW-class SOFC power generation system, in order to evaluate the cost effectiveness of the system. The exergoeconomic analysis is an appropriate combination of an exergy analysis and an economic analysis. Through an exergoeconomic analysis, we obtain the real cost associated with each stream and component in a system. We also can calculate the portion of the cost that is associated with the exergy destruction within each component.

The analyzed system, a 100kW SOFC power generation system, consists of SOFC stack, reformer, catalytic combustor, heat exchangers, pumps, blowers, inverter, and HRSG for heat recovery.

As a first step, mass, energy, and exergy balances were formulated. Then a conventional exergetic analysis (based on the concept of exergy of fuel/exergy of product) was performed. Next, a levelized cost for each component was calculated based on the purchased equipment costs using the Total Revenue Requirement (TRR) method with appropriate economic assumptions. Finally, the cost structure of the SOFC was figured out through an exergoeconomic evaluation. Finally suggestions have been made for reducing the cost associated with the product of the system.
Modeling Transient Churn-Annular Flows in a Long Vertical Pipe
Authors: Alves M. V. C. , Barbosa J. R. , Waltrich P. J. , Falcone G.
Published: April 2014

A mathematical model is presented to describe the behavior of transient gas-liquid flows involving the churn and annular flow patterns in a long vertical tube. The HyTAF (Hyperbolic Transient Annular Flow) code, developed specifically for this study, is based on the one-dimensional multi-fluid formulation and takes account of hydrodynamic non-equilibrium flow conditions by means of relationships for the rates of droplet entrainment and deposition. A finite difference algorithm is employed to solve the hyperbolic system of mass, momentum and energy equations via the Split Coefficient Matrix Method. The modeling results are compared with experimental data for steady-state annular and churn flows obtained from the literature and with pressure and flow rate induced transient churn-annular flow data generated in a large scale facility (48-mm ID, 42-m long test section).
Effect of Flexible Damped Bearing-Supports on the Dynamic Stability of High-Speed Turbochargers
Authors: Alsaeed A. , Kirk G. , Bashmal S.
Published: April 2014

The aim of this study is to analytically design flexible damped bearing-supports in order to improve the dynamic characteristics of the rotor-bearing system. The finite-element model of the turbocharger rotor with linearized bearing dynamic coefficients is used to solve for the logarithmic decrements and hence the stability map. The design process attempts to find the optimum dynamic characteristics of the flexible damped bearing-support that would give best dynamic stability of the rotor-bearing system. The method is successful in greatly improving the dynamic stability of the turbocharger and may also lead to a total linear stability throughout the entire speed range when used besides the enhanced-performance hydrodynamic bearings.
Numerical Study of Natural Convective Heat Transfer From a Very Short Isothermal Cylinder Mounted on a Flat Adiabatic Base
Authors: Oosthuizen Patrick H.
Published: April 2014

Natural convective heat transfer from a vertical isothermal cylinder mounted on a flat adiabatic base has been numerically studied. The cylinder has an exposed top surface. The cylinder is relatively very short, i.e., has a height that is equal to or less than the cylinder diameter. Both the cases where the cylinder is pointing upward and where it is pointing downward have been considered. The governing equations have been numerically solved using the commercial CFD solver ANSYS FLUENT©. Results have only been obtained for Prandtl number = 0.74. The mean heat transfer rates have been expressed in terms of a Nusselt number, consideration being given both to the heat transfer rate from the entire cylinder surface and to the heat transfer rates from the side and top surfaces of the cylinder. The effect of the dimensionless cylinder height–to–diameter ratio on the Nusselt number variation has been studied in detail.
Economic, Emissions, and Energy Benefits From Combined Heat and Power Systems by Location in the United States Based on System Component Efficiencies
Authors: Smith Amanda D. , Mago Pedro J.
Published: April 2014

A graphical evaluation is performed for combined heat and power (CHP) systems using screening parameters for optimized performance with respect to operating costs, emissions, and energy consumption. CHP systems have the potential to reduce operating costs, emissions, and primary energy consumption when compared with electricity purchased from the grid and thermal energy produced from a boiler, and these benefits have been shown to depend on the location where the system is to be installed as well as the characteristics of the system itself. A CHP system is analyzed in 9 U.S. cities in different climate zones which differ in both the local electricity generation fuel mix and local electricity prices. Its potential to produce economic, emissions, and energy savings is quantified based on the concepts of required spark spread, emissions spark spread, and primary energy spark spread. The corresponding parameters for cost ratio, carbon dioxide emissions ratio, and primary energy ratio are plotted on a 3-dimensional graph which illustrates these potential benefits simultaneously. The location of each point on the 3-D graph indicates for a given geographical location whether the system falls within a region of multiple potential benefits from CHP technology. The results are unique to the efficiencies of the CHP system components and the alternate heating system. A simple sensitivity analysis is then conducted to examine the influence of electrical generation efficiency, the percentage of heat recovered, and the heating system on the cost, emissions, and energy savings potential of CHP systems. Of the 9 cities analyzed, Duluth, MN, is shown to have the greatest potential to provide these three types of benefits by using a CHP system. The results are most sensitive to the values of two input parameters: CHP electrical efficiency and CHP thermal efficiency. Changes in the input efficiency values are most influential when the electrical efficiency is low, and as the amount of recovered heat goes to 0, the electrical efficiency becomes the most important factor in whether a CHP shows the potential for cost, emissions, and energy benefits.
Computation of Elastic Constants of Functionally Graded Materials Using Eigenfunction Virtual Fields Method
Authors: Nayakanti Nigamaa , Subramanian S. J.
Published: April 2014

The Virtual Fields Method (VFM) is a technique for computing material properties from full-field data. Recently, a variant of this technique, called Eigenfunction Virtual Fields Method (EVFM) has been proposed and applied to homogeneous linear elastic property evaluation. In this work, we extend this technique to heterogeneous materials by applying it to linear elastic material with exponentially varying elastic modulus. For such materials, there are three constitutive parameters to be evaluated: an elastic modulus, the Poisson’s ratio and a material length scale parameter β that controls spatial variation of the elastic modulus. We consider a plate made of such a material, with a circular hole, subjected to uni-axial tension in this study. The elasticity solution to this problem is synthesized using FEM, and strain fields in the vicinity of the hole are obtained on a rectangular grid. These strain component fields are assembled into an augmented strain matrix, whose eigenfunctions are obtained through Principal Components Analysis (PCA). EVFM is then performed using these eigenfunctions as virtual fields and solution of the resulting system of nonlinear equations yields values for the material parameters that are in excellent agreement with the true values.
A Gravity Driven Microfluidic Platform for DNA Enrichment
Authors: McCarthy Conor E. , Dalton Tara , Davies Mark
Published: April 2014

There is currently considerable interest in the development of microfluidic based lab-on-chip devices for sample preparation in next generation sequencing. One of these steps is DNA enrichment which often relies on conventional PCR to amplify the sample to detectable levels. To successfully automate this step, technologies are required whereby the samples are selectively inputted, thermocycled and selectively dispensed, all non invasively and therefore leading to no contamination issues. In this study such a system was created through the use of liquid-liquid plugs flowing in a gravity driven siphon. Plug generation was achieved through an innovative approach whereby a hydrophobic tube was traversed between two immiscible fluids (silicon oil and PCR reagents) and successful amplification was shown for Beta-2-Microfloblin (B2M).
Uncertainty Analysis Plus Importance in Severe Accident Calculations: Quantitative Evaluation of Important Parameters
Authors: Hoseyni Seyed Mohsen , Pourgol-Mohammad Mohammad , Abbaspour Tehranifard Ali , Yousefpour Faramarz
Published: April 2014

This paper describes a systematic framework for quantifying the degree of contribution of each parameter to the uncertainty of the output in severe accident assessment. This research is an extension of the recent work of the authors on uncertainty assessment of severe accident calculations where the main sources of uncertainty are identified through the so-called modified PIRT approach. The proposed methodology here utilizes uncertainty importance measures for the quantification of the effect of each input parameter on the output uncertainty. A response surface fitting approach is proposed for estimating the associated uncertainties with less calculation cost. The quantitative results are used to plan in reducing epistemic uncertainty in the input variable(s). The application of the proposed methodology is demonstrated for the ACRR MP-2 severe accident test facility.
Investigation of Conjugate Heat Transfer in Microchannels Using Variable Thermophysical Property Nanofluids
Authors: Kadja M. , Rezaiguia I.
Published: April 2014

We report the results of a study on heat transfer in microchannels. The fluid used is a nanofluid whose properties are temperature dependent. The energy dissipation is evaluated for various solid fraction contents along with the cooling effectiveness of this modern type of heat exchangers. The shape of the channels is also investigated. The evaluation parameter used for thermal energy dissipation is the Nusselt number while that used for cooling effectiveness is the static pressure drop between the inlet and the outlet of the microchannel. Conjugate convection-conduction energy conservation equations have been solved along with mass and momentum conservation equations in order to determine these parameters. The results obtained showed important heat transfer augmentation with solid fraction at the expense of an increased pressure drop, i.e high pumping cost (therefore low cooling effectiveness). The microchannel inlet section geometry was also found to contribute to the values of the Nusselt number and pressure drop. Among the tested geometries (elliptical, rectangular, trapezoidal) the rectangular section provided the best compromise between heat transfer augmentation and pumping cost. At the end of the study, a comparison was made between the results obtained by assuming Newtonian rheology and those obtained with non-Newtonian rheological behavior of the same nanofluid sample. It was found that the assumption of non-Newtonian rheological behavior of nanofluids gives higher Nusselt number values and much lower pressure drops.
Dissociation of Carbon Dioxide Using a Microdischarge Plasma Reactor
Authors: Taylan Onur , Berberoglu Halil
Published: April 2014

This paper reports an experimental study on dissociation of carbon dioxide using a microdischarge plasma reactor at ambient conditions. Carbon dioxide contributes to more than 80% of the greenhouse gas emissions in United States. The microdischarge plasmas can be a very promising method in dissociating gases, including carbon dioxide, due to their lack of need for catalysts, operating at temperatures lower than conventional thermochemical dissociation processes and ease of operation. A microhollow cathode discharge plasma reactor was designed and prototyped for CO2 dissociation. The reactor included metal electrodes that were attached to both sides of a dielectric material with a micro-size through hole. The electrodes and the dielectric material were placed perpendicular to flow direction for dissociation to occur as carbon dioxide passed through the hole. A set of experiments were conducted to investigate the effect of flow rate and applied voltage on the composition of the products, energy conversion efficiency and CO2-to-CO conversion yield of the microdischarge plasma reactor. Temperature of reactants and products were continuously measured; applied voltage was set using a high-voltage power supply; and molar composition of products for each case was analyzed using gas chromatography. Results showed that CO2 dissociation rate, energy conversion efficiency and CO2-to-CO conversion yield increased with applied voltage. Moreover, CO2 dissociation rate and conversion yield decreased while energy conversion efficiency increased with increasing flow rate.
Development and Implementation of an Engineering Course Guided by Involvement in University-Based Professional Development
Authors: Casto Mark , Zeid Ibrahim , Duggan Claire
Published: April 2014

Amesbury High School is a small suburban district located in the northeastern portion of Massachusetts. Amesbury High School offers a traditional science curriculum (biology, chemistry, and physics) blended with many elective courses. Recently added electives include microbiology, forensics, geology, environmental science, and meteorology to name a few. All of these courses offer students a chance to explore in-depth issues connected to each of these fields with a curriculum designed to address real-life connections, strengthen their problem solving skills, and provide opportunities for application of their knowledge. Based upon review of the Next Generation Science Standards, it became evident a need to offer students a STEM course that was strongly focused on problem-based learning, which bridged math and science content, and offered students a better understanding of the engineering field.

In the spring of 2012, a curriculum was written based upon experiences in Northeastern University’s Research Experience for Teachers Program and the CAPSULE Program which are both funded by NSF. Both of these programs offer rich professional development, is focused on engineering-based learning (EBL), have strong connections to University faculty, and provide teachers the opportunity to develop lessons and units that they can directly apply in their classrooms. The CAPSULE program provided extensive training in developing units based upon the engineering design process (EDP), offered intensive training in SolidWorks® (mechanical design software), and provided each of its participants with continued support through classrooms visits and online discussion forums.

Based upon participation in these programs, available support through University connections, and a deeper understanding of the field of engineering and the EDP, we anticipate the curriculum developed for our students will lead to a deeper understanding of STEM topics and lead to an increase in enrollment in our science and math classes. I also feel that the potential exists to have CAPSTONE projects become a requirement in the newly developed course.

This paper covers the details of the initial offering of the newly-developed course, the changes made for the upcoming school year, and the challenges faced throughout the process of implementation. It also addresses the grant writing successes and failures encountered and how the funding has been used to enhance components of the course. Included in the paper are student reactions and feedback that was considered in revising the course. Lastly, the paper summarizes my involvement in both of these professional development programs and how they are integral to developing leadership skills and confidence within the education profession.
Evaluating the Rate of Technological Improvement Necessary to Achieve Greenhouse Gas Reduction Targets
Authors: Miller C. Andrew
Published: April 2014

Considerable effort has been made to evaluate the technological improvement required to achieve global emission levels that are estimated to be needed to prevent the most serious impacts of climate change. While these analyses have highlighted the magnitude of technological change needed to meet target emission levels, the rate of such change has not been discussed as frequently. Application of the simple yet informative Kaya Identity, which relates emission levels to social and technological drivers, can be applied to gain insights into the required rate of technological change. This analysis shows that the current rate of technological improvement, as measured by the rate of change in energy intensity of economic growth (energy/dollar of GDP) and carbon intensity [carbon dioxide (CO2) emissions per unit energy], must be accelerated to reduce atmospheric CO2 levels to levels estimated to be needed to avoid serious climate impacts, even if population and economic activity were to remain constant. Given projected population growth and desired economic growth, the rate of technological change must accelerate by a factor of 5–8 times current levels and maintain that level of change for the foreseeable future. Such an accelerated pace of technological change has substantial implications for energy technology development, the need for technical expertise, and potentially the structure of the economy as a whole.
CFD Evaluation of Steam Properties Within Thermo-Compressors With Two Different Numerical Approches
Authors: Sharifi Navid , Sharifi Majid
Published: April 2014

Thermo-compressors are among the most important facilities in thermal desalination systems. Such devices are compressing and recycling the useless vapors and hence effectively enhancing the efficiency of desalination units. Since the connection between the evaporator box and suction surface is not perfectly symmetric, it is necessary to consider the effect of this curved path on pressure loss at the inlet boundary. In this study, a numerical procedure is developed to achieve reliable results in thermo-compressors through using CFD simulations. Two approaches are examined: axisymmetric and full three-dimensional method. The results are compared and the deviations of velocity, pressure and temperature are evaluated in both methods. The flow pattern in the steam collector is investigated afterwards. The distributions of velocity and pressure through this canal are illustrated and the critical point where pressure loss originates is revealed. In the meantime, the effect of this non-symmetric path on the flow is compared with the axisymmetric results. Finally, it is shown that the influence of the curved-shape inlet on flow properties is insignificant such that it can be neglected, because the flow swirl at the inlet is very negligible. Therefore, the axisymmetric model is capable of producing reliable results for thermo-compressors in a more advantageous way with a simpler mesh generation and reduced computational cost.
A Novel Passive Three-Dimensional Asymmetric Arc Micromixer Based on the Concept of Chaotic Advection and Unbalanced Splitting-Collision
Authors: Li Lin , Chen Qingde , Hou Liang , Sui Guodong , Tsai Chitay
Published: April 2014

A micromixer is an important component of microfluidic systems, which reveals wide and essential applications in the field of chemistry and biochemistry. In the micro scale, diffusive mixing is notoriously slow as fluid is in the form of laminar flow. Therefore, design of a high performance micromixer to mix fluids at short distance is essential for a successful development of microfluidic systems. A novel three-dimensional micromixer, which composed of several units of three dimensional asymmetric arc structures, was proposed. Mixing experiments and numerical studies were carried out and the experimental results showed a good agreement with the simulation results. For the normal fluid (viscosity is 9.7×10−4 kg/ms and diffusivity is 3.6×10−10 m2/s), the complete mixing lengths are less than 2 mm at the inlet velocity from 1.9×10−4m/s to 2.9 m/s. The complete mixing length gradually increases from 350μm to 2000μm when inlet velocity increases from 1.9×10−4 m/s to 1.9×10−2 m/s. However, the complete mixing length decreases to 700 μm while the inlet velocity continues increasing to 2.9m/s. The inlet velocity of 1.9×10−2 m/s is considered as a critical inlet velocity, where more chaotic advection occurs to enhance the mixing performance and reduce the complete mixing length when the inlet velocity is bigger than the critical value. For the fluid with viscosity of 0.186 kg/ms and diffusion rate of 9×10−13m2/s, no chaotic advection occurs and the complete mixing lengths are around 2200μm at the inlet velocity from 3.7×10−3m/s to 3.7m/s. The results show that this novel micromixer has extremely short mixing length even for difficult mixing fluids.
Zuber-Type Parameter Distributions for Non-Equilibrium Two-Phase Flows: Generalization for Annular Channel and Rod Cluster Geometries
Authors: Kornienko Y.
Published: April 2014

This study presents the main results of the analysis of the previously developed generalized hierarchical closed system of analytical closure relations for the distribution parameters (DPs) Cks (k = f - fluid or g - vapor; s = 0,1,2,3 - mass, energy, momentum) that are used in quasi-one-dimensional form of the conservation laws for mass, momentum and energy in non-equilibrium two-phase flows. The current method has been expanded to account for non-uniform in cross-section profile of void fraction. The main assumptions of the received quadrature relationships for DP are: (a) the use of the drift flux model, (b) the quasi-steady-state approximation, and (c) the power-mode approximations of the local distribution profiles of the variables. These DPs Cks quadrature are expressed in terms of elementary functions, they directly reflect the principle of superposition, generalize and unify not only the Zuber-Findlay method, but also Hancox-Nicoll and Hibiki-Ishii methods. The revealed complementarity properties are particularly useful for the purposes of testing, validating and verifying DPs.
Tunable Optical Properties of Graphene Quantum Dots by Centrifugation
Authors: Wei Junhua , Qiu Jenny
Published: April 2014

In this work, tunable optical properties of graphene quantum dots (GQDs) were achieved by centrifugation method. GQDs prepared through intercalating and exfoliating commercially available stacked graphene nanofibers were separated into two samples with different mean sizes by centrifugation. The separated GQD samples were characterized by transmission electron microscope (TEM). The optical properties of the GQD samples were measured by UV-visible and photoluminescence spectroscopy. The characterization results demonstrated that the UV and photoluminescence of GQDs were highly correlated with their sizes and surface chemistry. As the diameters of GQDs reduced, the UV peaks of the GQD blue shift, and the photoluminescence of PL red shift, indicating that the centrifugation method can be used to efficiently achieve tunable optical properties from as-synthesized GQD.
Experimental and Computational Model Comparisons of Thermal Profiles Within a Column Photobioreactor
Authors: Bari Ghazi S. , Anderson Gary A. , Suess Taylor N. , Gent Stephen P.
Published: April 2014

In a bubble column-based photobioreactor, sparger design and placement govern the bubble size distribution and gas hold-up. These factors in turn influence flow pattern, effective interfacial area, rates of mass and heat transfer, and mixing. Previous computational studies of the hydrodynamic and heat transfer effects within a column photobioreactor for one sparger row have found that bubble Nusselt number and heat transfer coefficient with respect to superficial velocity do not follow any particular pattern. This study evaluates the temperature distribution and heat transfer within a photobioreactor in an effort to explain the earlier study results. Experimental and computational studies will focus on the bubble flow pattern and heat transfer within a rectangular column photobioreactor (33.65 cm long × 30.48 cm wide × 33.97 cm tall) with a single row sparger located either lengthwise or widthwise at the center of the base (27.94 cm long × 1.27 cm wide). Temperature distribution and heat transfer for both sparger positions will be compared. Carbon dioxide, water, light photons, algal cells, and nutrients need to come together continuously for successful algal production, hence mixing of the nutrients, algal cells, and carbon dioxide is essential. Instead of a light source, a heat source is used in the system. Constant electric energy is supplied to the heating pad, which converts the electric energy to thermal energy. Thermocouples are placed inside the PBR to record temperature at 36 different spatial positions. The experimental results are compared with previously developed CFD simulations. The sparger not only effects the aeration inside the PBR, but also creates mixing in the PBR. Proper design and placement of the sparger ensures proper mixing in the PBR. The present study shows the effects bubble movement and flow pattern have on the temperature distribution and how well the simulation predicts the temperature distribution inside a PBR. The present research is a continuum of previous work aimed at pursuing the optimum design of a column PBR which is commercially viable and effective at producing algal biofuels and bioproducts.