bluuebunny/crossref_metadata_2025 huggingface dataset:
A Robust Lift Control Technique in Electro-Hydraulic Camless Valves Using System Average Model
Authors: Pournazeri Mohammad , Fazeli Amir , Khajepour Amir
Published: May 2012

In electro-hydraulic camless valvetrains, both valve timing and lift are simultaneously controlled through precise control of solenoid actuated servo-valves at each cycle. In fact, the desired maximum lift is obtained by accurate controlling of the servo-valve opening interval. However, at high engine speeds, due to the slow servo-valve response time, concurrent control of both timing and peak lift becomes more difficult and sometimes impossible. In this paper a new valve lift control technique is proposed based on the average model of the mechanism introduced in [1]. Using this method, it is possible to control the valve lift without precise control of the high pressure servo-valve opening interval and the servo-valves are only responsible for controlling the valve timings and duration. This eliminates the need for high precision servo-valves and measuring devices and consequently cut the system cost. In contrast to the existing lift control methods in which the maximum lift should be repeatedly controlled within each cycle, employing this technique, it is possible to adjust the maximum valve lift after few engine cycles. To this end, an average model of the system is developed based on system energy balance and a non-linear sliding mode controller is designed and implemented on the proposed mechanism. To compensate for the model uncertainties, the designed sliding mode controller is equipped with adaptive law. A conventional boundary layer method is used to solve the controller chattering problem. Finally, the performance of the proposed lift control technique is evaluated through simulation.
Dynamics Stability of a Translating String With a Sinusoidally Varying Velocity
Authors: Zhu W. D. , Song X. K. , Zheng N. A.
Published: May 2012

A new parametric instability phenomenon characterized by infinitely compressed, shock-like waves with a bounded displacement and an unbounded vibratory energy is discovered in a translating string with a constant length and tension and a sinusoidally varying velocity. A novel method based on the wave solutions and the fixed point theory is developed to analyze the instability phenomenon. The phase functions of the wave solutions corresponding to the phases of the sinusoidal part of the translation velocity, when an infinitesimal wave arrives at the left boundary, are established. The period number of a fixed point of a phase function is defined as the number of times that the corresponding infinitesimal wave propagates between the two boundaries before the phase repeats itself. The instability conditions are determined by identifying the regions in a parameter plane where attracting fixed points of the phase functions exist. The period-1 instability regions are analytically obtained, and the period-i (i > 1) instability regions are numerically calculated using bifurcation diagrams. The wave patterns corresponding to different instability regions are determined, and the strength of instability corresponding to different period numbers is analyzed.
Processing and Characterization for Implementation of Ni-Ti SMA Bending Actuators
Authors: Miller David A. , Denowh Chantz
Published: May 2012

This project is based on the predicated growth in the demand for high force/displacement NiTi SMA actuators and structural components for industrial and aerospace applications. As the use of SMAs has advanced, focus has shifted from intrinsic material behavior to identifying the influence of conditioning and processing of NiTi SMAs for actuators and structural components. While the uniaxial actuation of NiTi SMAs is rather mature, little data is available on their potential use as bending actuators. The difficulty encountered in thermomechanical conditioning of a NiTi SMA under an applied bending moment is the asymmetry of the tensile and compressive response, thus creating a shifting neutral axis. In this study, the uniaxial characteristics of 55 NiTi (49.9 at% Ni ∼50.1 at% Ti) are used to develop a process to maximize the actuation strain of a NiTi SMA bending actuator. The characterization includes monotonic tension/compression tests, tension/compression training, tension/compression actuation strains, and transformation temperatures. From these results, the most efficient thermomechanical training method for bending is identified as a cyclic temperature induced phase transformation under a constant flexural stress. The resulting actuation strains and deformation conditions are discussed in light of the complex loading path created by the bending stress. Predicted outcomes of the training methodology are made for comparison to future experimental results.
Deposition of Polypyrrole Onto a Novel Polymer Electrode for Use in a Biomimetic Artificial Excitable Cell Membrane
Authors: Haden Christina V. , Jordan Donald A. , Norris Pamela M.
Published: May 2012

A novel and inexpensive bucky gel electrode has been investigated for use as the electrode substrate for deposition of polypyrrole. The electroactive polymer membrane was successfully deposited and the surface morphology studied using scanning electron microscopy. Given the properties of the bucky gel electrode and its ability to conduct ions, this work establishes the first step towards a semi-solid ion-gating system to be used in further applications.
Vibration of a Microbeam Under Ultra-Short-Pulsed Laser Excitation Considering Momentum and Heating Effect
Authors: Pasharavesh Abdolreza , Alizadeh Vaghasloo Y. , Ahmadian M. T. , Moheimani Reza
Published: May 2012

In this study, vibration of a microbeam excited by an ultra-short-pulsed laser considering the momentum and heating effect of the laser beam is investigated. When the laser impacts the microbeam, portion of the photons is absorbed by the beam and their energy will be transformed into heat while the others are reflected. The momentum change of the absorbed and reflected laser photons is considered and modeled as a distributed force on the beam. The absorbed thermal energy yields non-uniform thermal stress causing the beam to vibrate. According to short duration of laser pulse, the non-Fourier conduction equation which takes into account the finite propagation speed of thermal energy, is implemented to the problem and Euler-Bernoulli assumption is made for the beam. The coupled partial differential equations for the deflection and temperature are solved implementing the mode summation method and Laplace transform. Effect of reflectivity, pulse duration and absorption depth are investigated. It should be noted that depth of the thermal absorption and reflectivity can be managed to control the vibration amplitude and phase of the beam vibration.
Noise Source Identification and Noise Reduction of PDP TV Using Transfer Path Analysis
Authors: Kwak Hyung-Taek , Yoon Ji-Hyun , Yang In-Hyung , Lee Jung-Youn , Oh Jae-Eung
Published: May 2012

The module which is used for the operation of PDP TV consists of three main PCB board, X-board, Y-board, SMPS. Numerous studies on identifying noise sources of PDP TV, and reducing the noise have so far been done through experiments. However, it has been difficult to identify the exact noise sources due to correlations between sources as they are located close to each other. For that reason, Multi-Dimensional Spectral Analysis, MDSA, one of Transfer Path Analysis method, is increasingly required since it enables a quantitative analysis of each input signal’s contribution to the out signal to be carried out by eliminating the correlations of input signals. In this study, Transfer Path Analysis using MDSA is implemented to determine the quantitative noise contribution of each board. And the possibility of noise reduction is confirmed through the experimental method that isolates the most contributing board by adding sound-absorbing materials to it.
Robust Compensator Control of a Non-Resonant MEMS Gyroscope With Linear Quadratic Regulator
Authors: Cui Wei , Chen Xiaolin , Xue Wei
Published: May 2012

This paper presents a controller design for a four degrees-of-freedom (4-DOF) non-resonant gyroscope via the linear quadratic regulator (LQR) technique. Compared to conventional MEMS gyroscopes, non-resonant gyroscopes are less vulnerable to fabrication perturbations. However, closed-loop performance of non-resonant gyroscopes has not been investigated previously. The control of non-resonant gyroscopes involves consideration of high order systems. LQR, which achieves balances between a fast response and a low control effort, has proven to be effective for high order systems. Our simulation results show that the closed-loop 4-DOF non-resonant gyroscope presented in this paper is able to achieve faster response and higher robustness to parameter uncertainties than the open-loop device. Under the sinusoidal input, compared to an error of 11.06% for the open-loop system, the closed-loop scale factor uniformity error is reduced to 0.014% under ±10% parameter perturbations. The device performance is analyzed by the behavior modeling approach in CoventorWare. The results show that the closed-loop non-resonant gyroscope achieves better performance through the LQR. The method reported here is proven to be effective and can be used in a wide range of applications.
Driver Differentiation With Seat Settings: Part I—Component Selection
Authors: Flannagan Carol , Chen Shih-Ken , Litkouhi Bakhtiar
Published: May 2012

The addition of user-customizable features to automobiles increases the need to differentiate among drivers so that each driver’s custom settings can be automatically applied. This study explored the feasibility of using component adjustment settings (e.g., seat position or steering wheel angle) to differentiate among drivers. The primary consideration in the feasibility assessment is the ratio of the within- and between-driver variance in component adjustments. Differentiation is a function of the stature difference between sharing drivers. Simulation and analysis showed that H-point fore-aft position provides the best single-component differentiation, followed by H-point up-down, steering wheel telescope and steering wheel angle. Seatback angle and seat-cushion angle are less useful in driver differentiation.
Nonlinear Approach for Strain Energy Release Rate in Micro Cantilevers
Authors: Mousavi Arash Kheyraddini , Alaie Seyedhamidreza , Kashamolla Maheshwar R. , Leseman Zayd Chad
Published: May 2012

An analytical Mixed Mode I & II crack propagation model is used to analyze the experimental results of stiction failed micro cantilevers on a rigid substrate and to determine the critical strain energy release rate (adhesion energy). Using nonlinear beam deflection theory, the shape of the beam being peeled off of a rigid substrate can be accurately modeled. Results show that the model can fit the experimental data with an average root mean square error of less than 5 ran even at relatively large deflections which happens in some MEMS applications. The effects of surface roughness and/or debris are also explored and contrasted with perfectly (atomically) flat surfaces. Herein it is shown that unlike the macro-scale crack propagation tests, the surface roughness and debris trapped between the micro cantilever and the substrate can drastically effect the energy associated with creating unit new surface areas and also leads to some interesting phenomena. The polysilicon micro cantilever samples used, were fabricated by SUMMIT V™ technology in Sandia National Laboratories and were 1000 μm long, 30 μm wide and 2.6 μm thick.
Path Planning and Control for Underwater Vehicle Driven by an Ionic Polymer Metal Composite (IPMC) Actuator
Authors: Gutta Shivakanth , Yim Woosoon , Trabia Mohamed B.
Published: May 2012

This paper presents an approach for trajectory planning and control of an underwater vehicle within obstacles. The vehicle is driven by a single IPMC actuator that goes through oscillatory locomotion. The presented work is divided into kinematic path planning and trajectory control sections. In the kinematic path planning phase, the vehicle is approximated by a rectangle that encloses the largest deformation of the oscillating IPMC actuator. Obstacles are approximated by polygonal shapes that approximate their actual dimensions. To simplify the problem of collision detection, vehicle is shrunk to a line while obstacles are expanded by a half width of the rectangle representing the vehicle. Path planning problem is formulated as a nonlinear programming problem that minimizes the error between current and goal configurations of the vehicle. The objective function combines the distance to target and the orientation of the vehicle. A penalty term is added to the objective function to ensure that the vehicle is not colliding with obstacles. The obtained path is discretized with respect to time, and controlled simultaneously for the yaw angle and speed of the vehicle. These two controllers are designed based on the simulation data from the dynamic model of the IPMC propelled vehicle. This proposed approach can be used in real time implementation of vehicle trajectory control in the presence of obstacles.
Use of Radiation Pressure to Calibrate Sub Micro-Newton Forces and Damping Ratios
Authors: Abbas Khawar , Alaie Seyedhamidreza , Hossein-Zadeh Mani , Leseman Zayd C.
Published: May 2012

We present a noncontact method to calibrate micro/nanostructures using sub-nN forces. In this work, a microcantilever’s material properties as well as damping ratio are determined using two independent laser systems. A continuous wave laser system is used as a heterodyne interferometer to determine displacements while another laser system is pulsed in order to produce radiation pressure. A noncontact method is preferred while calibrating sub-μN forces since no material is transferred between the calibrating apparatus and (NEMS/MEMS) to be calibrated. The incidence force is calculated from the optical properties of Si cantilever. Simulations presented in this work shows that thermal gradient along the length of the cantilever beam is very small to affect its physical properties due to the difference in time scales on which both operate.
Surrogate Skull-Brain Response to a Pressure Wave
Authors: Ford Matthew , Bagchi Amit , Simmonds Kirth , Gauvin John , Matic Peter
Published: May 2012

In current US Military operations, warfighters are frequently subjected to blast events, which can lead to traumatic brain injury (TBI). The causes of mild and moderate TBI are not yet well understood by the medical community, and current diagnoses rely on identifying behavioral or physiological symptoms. Characterizing the brain response to various threats should provide a better understanding of possible injury mechanisms, and this knowledge could be applied to equipment design for prevention of TBI.
Mechanical Properties of Three-Dimensional Microstructures Infiltrated by Carbon Nanotube/Epoxy Nanocomposite Under Shear Flow
Authors: Farahani Rouhollah Dermanaki , Dalir Hamid , Le´vesque Martin , Therriault Daniel
Published: May 2012

Three-dimensional interconnected microfluidic channels fabricated by the direct-write method were infiltrated with SWCNT/epoxy nanocomposites under high shear flow to mechanically characterize the effect of single-walled carbon nanotubes (SWCNTs) spatial orientation in thermosetting-matrix nanocomposites. The micron-size fugitive ink filaments were deposited layer by layer in order to form a scaffold followed by its encapsulation by an epoxy resin. Three-dimensional interconnected microfluidic channels were then obtained by heat curing the encapsulated epoxy followed by fugitive ink removal by liquefying it at high temperature under vacuum. To debundle the Laser-ablated single-walled carbon nanotubes (La-SWNTs), nitric acid treatment following introduction of protoporphyrin IX as surfactant were done to prevent reclustering of the CNTs after separation. La-SWNTs were then mixed with ultraviolet-curable epoxy using a three-roll mill machine to achieve a well-dispersed nanocomposite. The nanocomposites were then infiltrated within the empty channels at high pressures to induce shear. High shear flow infiltration of nanocomposites will cause the CNTs to be aligned in the direction of the channels where an increase in shear leads to an increase in CNT alignments. Finally, in order to mechanically investigate the effectiveness of the infiltration technique and the orientation of SWCNTs, tensile and three-point bending tests were done.
UV-Assisted Direct-Write Assembly of Scaffold-Templated Nanoclay Composites via Biotin-Streptavidin Interactions
Authors: Dalir Hamid , Farahani Roohollah Dermanaki , Le´vesque Martin , Therriault Daniel
Published: May 2012

Three-dimensional epoxy scaffolds with abundant active epoxy groups on surfaces were fabricated through UV-assisted direct-write manufacturing process. The prepared scaffolds composed of cylindrical filaments (diameter ∼100 μm) were aminated by reacting the epoxy groups with 1, 3-diaminopropane. The resulting aminated scaffolds were subsequently biotinylated and then successfully applied to immobilize biotinylated nanoclay conjugates via a specific, strong and rapid binding of biotin and streptavidin. In another approach, the same amount of nanoclays was properly dispersed in epoxy by three-roll mill machine inducing high shear mixing. The nanoclay-epoxy filaments were then deposited by a computerized-control robot in a 3D micro structure scaffold form. Tensile mechanical tests were performed with a dynamic mechanical analysis (DMA) using a film tension clamp on three microstructures: nanoclay-epoxy scaffolds, aminated-biotinylated nanoclays coated on unloaded epoxy scaffolds and finally unloaded epoxy scaffolds (used as a reference). DMA tensile measurements indicated a slight improvement in modulus (by ∼5%), but significant increase in strength (by ∼24%), fracture strain (by ∼21%) and fracture energy (by ∼38%) by introducing biotin-streptavidin strong bonds among epoxy scaffolds and nanoclays in comparison with those of mixed nanoclay-epoxy scaffolds. These mechanical improvements are attributed to the strong biotin and streptavidin bonds between the epoxy scaffolds and nanoclays.
Foot Injury Patterns With Protective Footwear After Lift Truck Impact
Authors: Bussone William R. , Baxter Jill N. , Mkandawire Chimba
Published: May 2012

The objective of this study was to evaluate the properties and kinematics of an ASTM steel toe cage during quasi-static loading and forklift runover. Example ASTM F2413-05-compliant steel-toed shoes were loaded via forklift and via mechanical test device, and examined visually for external damage and fluoroscopically for internal displacement and damage of the steel-toed cage. Resulting displacement was quantified and analyzed to assess likely foot injuries and their location sustained by the wearer. When loaded by a lift truck, an ASTM F2413-05-compliant steel toe supported the weight without crushing, but the structure of the shoe around the steel cup did not, causing the steel toe to rotate and translate fore-aft or laterally, depending on the direction of loading. The survival of the steel toe combined with the failure of the shoe around it may lead to sparing of the toes, with crushing of the distal midfoot due either to direct or induced loading of the foot. Steel-toed shoes are unlikely to prevent injury to the midfoot or proximal phalanges when loaded by a forklift.
Development and Evaluation of a Micro-Cogeneration Prototype for Residential Applications
Authors: Ferreira Ana C. M. , Madureira Francisco , Nunes Manuel L. , Lea˜o Celina P. , Teixeira Senhorinha F. C. F. , Teixeira Jose´ C. F. , Martins Lui´s B.
Published: May 2012

Combined heat and power (CHP) units use heat that would otherwise be wasted in a conventional power plant, and may reach an overall efficiency above 90% (LHV), which is well above to the 40% achieved by reference plants. This paper presents the design and development of a micro-cogeneration prototype (<6kWe) for single family households. The unit is based on a commercially available internal combustion engine (ICE) and generator, optimized and modified to be fuelled by natural gas, coupled to a two-step exhaust heat recuperating system. The work starts with the thermodynamic analysis of the ICE operating cycle and the assessment of thermal energy that can be recovered from the exhaust gases and through the engine cooling system. The analysis included the study of gas-mixture composition, combustion, heat loss to engine walls and water-vapor mass transfer. The main innovation is the exhaust gases heat recovery system, developed in two stages. The first stage consists on a direct heat exchanger where water is heated by direct contact with hot jets of exhaust gases, while the second stage heat exchanger involves further cooling of the saturated gases and condensation of evaporated water. The results showed the potential for significant gains in engine performance. The effective thermal power recovered in the recuperating system is reasonable, since the CHP system is able to produce 6.58 kWe of electrical energy and 11.16 kW of thermal energy.
Effect of Ultrasound and Strain Rate on Tensile Behavior of Neat Thermoplastic Polyurethane Thin Films
Authors: Balakrishnan Anandh , Saha Mrinal C.
Published: May 2012

Thermoplastic Polyurethane (TPU) thin films have many applications in engineering and biomedical fields. Examples include moisture sensors, load cells, optical element and biocompatible stens. The TPU is a block copolymer naturally phase segregates into thermodynamically incompatible hard- and soft-segments. The size of the segments and their spatial distribution can significantly affect the microstructure and mechanical properties of the TPU. In this paper, we propose to investigate the effect of ultrasound energy on mechanical properties of TPU thin films fabricated via a solution route utilizing Tetra Hydro Furan (THF) as a solvent. The times of sonication was fixed at 60 minutes whilst all films were fabricated at average thickness of 20+/-5 um. The primary objective of the study was to understand the influence of ultrasound and strain rates on the material microstructure and the resulting mechanical properties. Mechanical tests have been conducted at two different displacement rates, namely 5 and 10 mm/min. Our preliminary results indicate that ultrasound improves the strength of the neat TPU films. We also see that strain hardening is displacement or strain rate dependent. We attribute these results to changes in the hard (H) and soft (S) domain structure. To further understand these microstructural variations, we propose to conduct Differential Scanning Calorimetry (DSC). The data has been interpreted in conjunction with our mechanical test data.
A Case Study in “Total Beauty” Design: An Experience Through Sustainable Product Design
Authors: Flores-Caldero´n Alejandro , Borja Vicente , Lo´pez-Parra Marcelo , Rami´rez-Reivich Alejandro
Published: May 2012

Recent research on ‘engineering design’ is expanding to consider methods, tools and frameworks aimed at assisting designers in the process of developing sustainable products. Some of these new approaches highlight the importance and advantages of applying biology, chemistry and human-environment health, concepts and principles at the design stage of the product development process. The successful application of these approaches also requires overcoming a number of challenges. Two particular issues currently being investigated are: 1) the contradictory and sometimes misleading use of concepts regarding what a sustainable product is; and 2) the lack of sustainable parameters to evaluate how sustainable a product is. This paper presents a synthesis of the Total-Beauty theoretical framework, based on the study reported in a previous paper. Then, a process to redesign products using BioThinking, is proposed followed by its application in the redesign of a product. The process is original because it shows how the core concepts are considered in all the steps of a design process and not just in the specification and evaluation steps. The redesign is used as a case study to show its utility. The paper includes the synthesis of evaluation parameters based on BioThinking to both assess the sustainability of products, and compare the redesigned product against the original design. In the end of the paper, a discussion of the design process and the results of the case study will be presented.
Development of an Economical System for Electrical Discharge Machining (EDM) in Water
Authors: Medelli´n Castillo Hugo I. , Loredo Rami´rez J. Abraham
Published: May 2012

Electrical discharge machining (EDM) is a non-traditional machining process which has been widely used to manufacture dies and molds in industries such as aerospace, automotive, and surgical. Since EDM does not make direct contact between the tool and the workpiece, mechanical stresses, chatter and vibration problems during machining are eliminated. Moreover, materials of any hardness can be machined as long as they can conduct electricity. However, the use of hydrocarbon oil (commonly used as dielectric in commercial EDM machines) liberates harmful vapours, which represents health and safe risk. Research in the last three decades has involved the use of water as dielectric and the advantages that this implies. Most of the equipment used to perform EDM in water is based on commercial EDM machines, originally designed for hydrocarbon oil as dielectric, and that have been modified to stand water. In this paper the development and design of an economical EDM machine to be used with water as dielectric is presented. The main objective was to design an economical, simple, and effective system with augmented capabilities to perform EDM in water. The EDM system has been developed and the design of the main components is described in this paper. Some experimental tests of EDM in water have been carried out and the results have proved the functionality of the system.
MEMS Based Fabry-Perot Sensor for Measuring Flow Velocity
Authors: Manjunath Vinay Kanive , Rahman Anisur
Published: May 2012

New MEMS based Fabry–Perot sensor has been proposed to measure the flow of a fluid.. The flow velocity will cause the oscillatory strain on the optical waveguide which will be detected by the Fabry-Perot Interferometer principle. The velocity of flow is found to be varied with the frequency induced by the vortex shedding of the fluid flow.
Mechanical Model of Neuronal Function Loss
Authors: Cao Guoxin , Zhou You , Lee Jeong Soon , Lim Jung Yul , Chandra Namas
Published: May 2012

The mechanism of mild traumatic brain injury (mTBI) is directly related to the relationship between the mechanical response of neurons and their biological/chemical functions since the neuron is the main functional component of brain.1 The hypotheses is that the external mechanical load will firstly cause the mechanical deformation of neurons, and then, when the mechanical deformation of neurons reaches to a critical point (the mechanical deformation threshold), it will initiate the chemical/biological response (e.g. neuronal function loss). Therefore, defining and measuring the mechanical deformation threshold for the neuronal cell injury is an important first step to understand the mechanism of mTBI. Typically, the mechanical response of neurons is investigated based on the deformation of in vitro model, in which the neurons are cultured on the elastic substrate (e.g. PDMS membranes). The elastic membrane is deformed by the external load, e.g. equibiaxial stretching. The substrate deformation is considered to be the deformation of neurons since the substrate is several orders stiffer than the neurons and the neurons are perfectly bonded with the substrate. The fluoresce method is typically used to test the cell injury, e.g. the cell vitality and the neuron internal ROS level.1, 2
Experimental Validation Technique for Constitutive Models Describing Behavior of Soft Tissue Surrogates During Projectile Penetration
Authors: Amborn Ericka K. , Muci-Ku¨chler Karim H. , Hinz Brandon J.
Published: May 2012

Numerical simulations of ballistic penetration of soft tissues are particularly difficult to validate because relevant experimental data is not readily available. Efficient, controlled, high strain rate experiments involving large deformations must be developed for that purpose. This paper proposes an axisymmetric experiment to validate constitutive models describing the bulk mechanical behavior of soft tissue surrogates. The need to use techniques such as element erosion and re-meshing or to consider material failure is avoided by using a cylindrical target with a small pre-made cylindrical channel along its axis. Cavitation is excited by firing a spherical projectile through the pre-made channel whose diameter is smaller than that of the projectile. The transient response of the channel is recorded using a high speed camera and the images collected are analyzed using a digital image tracking software to measure the channel deformations. As an example to demonstrate the usefulness of the proposed experiment, measurements from a test involving a ballistic gelatin cylinder are used to evaluate the quality of numerical results produced by finite element analyses performed with ABAQUS/Explicit. The mechanical behavior of the soft tissue surrogate is represented in the simulations using a single-term Ogden model. Different values are attempted for the required material properties and friction coefficient based on data available in the literature and simple sensitivity studies. The experimental results are used to assess the results corresponding to each set of model parameters.
Modeling and Exergy and Exergoeconomic Optimization of a Gas Turbine Power Plant Using a Genetic Algorithm
Authors: Fouladi Soheil , Saffari Hamid
Published: May 2012

In this paper, the thermodynamic modelling of a gas turbine power plant in Iran is performed. Also, a computer code has been developed based on Matlab software. Moreover, both exergy and exergoeconomic analysis of this power plant have been conducted. To have a good insight into this study, the effects of key parameters such as compressor pressure ratio, gas turbine inlet temperature (TIT), compressor and turbine isentropic efficiency on the total exergy destruction, total exergy efficiency as well as total cost of exergy destruction have been performed. The modelling results have been compared with an actual running power plant located in Yazd city, Iran. The results of developed code have shown reasonable agreement between the simulation code results and experimental data obtained from power plant. The exergy analysis revealed that the combustion chamber is the must exergy destructor in comparison with other components. Also, its exergy efficiency is less than other components. This is due to the high temperature difference between working fluid and burner temperature. In addition, it was found that by the increase of TIT, the exergy destruction of this component can be reduced. On the other hand, the cost of exergy destruction is high for the combustion chamber. The effects of design parameters on exergy efficiency have shown that increase in the air compressor ratio and TIT, increases the total exergy efficiency of the cycle. Furthermore, the results have revealed that by the increase of TIT by 350°C, the cost of exergy destruction is decreased about 22%. Therefore, TIT is the best option to improve the cycle losses. In addition, an optimization using a genetic algorithm has been conducted to find the optimal solution of the plant.
The Conceptual Speed-Bump: Losing Potential STEM Students in the Transition From Elementary School to Middle School
Authors: Floersheim Bruce , Johnston Jonathan
Published: May 2012

Many educators in the science, technology, engineering and math (STEM) disciplines hope to improve the number of students interested in and prepared for these more difficult disciplines through innovative teaching, demonstrations and hosted camps. Research has shown that motivation is a much smaller part of the issue; student learning outcomes are much more sensitive to fundamental academic ability. Current curriculum design fails most students miserably in helping them bridge the gap from concrete learning to abstract thought and understanding in the middle school years. Thus, they are ill-prepared to engage in the more advanced learning required to pursue the STEM disciplines, a result that no amount of innovative teaching can correct. This paper will review the performance data from industrial nations at the 4th Grade and 8th Grade levels and illustrate curriculum differences between industrial countries producing higher percentages of STEM graduates. Examination of the performance effects of many variables, including number and sequencing of topics studied, time spent on homework, teacher credentials, access to technology, class size and dollars allocated per student, yields some surprising results. The problem is not as sensitive to many of these variables as one might expect. However, the variables that seem to provide promise for significant improvement from the current state of STEM education are related to topic coverage and manner of presentation. Final recommendations include reduction in the number of topics introduced in any given year with a corresponding reorganization of the curricula, to allow STEM teachers in the middle school to focus on the transitional learning that must occur to prepare for more advanced studies.
CFD Simulations of Under Water Turbine in Gulf Stream Using RANS Method
Authors: Ghenai Chaouki , Oliver Ben
Published: May 2012

The principal objective of this numerical study is to investigate the hydrodynamic behavior of horizontal axis underwater turbine in the Gulf Stream. The CFD analysis provides detailed information about the local flow and the performance of the underwater turbine under varying flow conditions. Three dimensional simulations were performed using a 5.6 meter diameter turbine with 3 blades. The finite volume method was used to solve the equations of conservation of mass and momentum and turbulence (k-ε equations). The flow field, turbulence, pressure distribution on the turbine blades and turbine power were obtained for a range of water speed (1–6 m/s) and rotation speed of turbine (1–10 rad/s). The z-velocity profiles behind the turbine were used to calculate the induction factor a, the power coefficient Cp and the total power P from the turbine. The results show a turbine power coefficient of 33% to 37.5% with an induction factors between 0.10 and 0.12.
Combustion of Hydrogen Enriched Hydrocarbon Fuels in Vortex Trapped Combustor
Authors: Ghenai Chaouki , Zbeeb Khaled
Published: May 2012

Trapped vortex combustor represents an efficient and compact combustor for flame stability. Combustion stability is achieved through the use of cavities in which recirculation zones of hot products generated by the direct injection of fuel and air are created and acting as a continuous source of ignition for the incoming main fuel-air stream. Computational Fluid Dynamics analysis was performed in this study to test the combustion performance and emissions from the vortex trapped combustor when natural gas fuel (methane) is replaced with renewable and alternative fuels such as hydrogen and synthesis gas. The flame temperature, the flow field, and species concentrations inside the Vortex Trapped Combustor were obtained. The results show that hydrogen enriched hydrocarbon fuels combustion will result in more energy, higher temperature (14% increase when methane is replaced with hydrogen fuels) and NOX emissions, and lower CO2 emissions (50% decrease when methane is replaced with methane/hydrogen mixture with 75% hydrogen fraction). The NOX emission increases when the fraction of hydrogen increases for methane/hydrogen fuel mixture. The results also show that the flame for methane combustion fuel is located in the primary vortex region but it is shifted to the secondary vortex region for hydrogen combustion.
On the Overall Energy Efficiency of a High-Performance Solar Energy Residential Building
Authors: Wong Adam J. , Gonza´lez Jorge E. , Escobar Sergio , Aschheim Mark
Published: May 2012

This paper describes the energy performance of a solar house over its first year of monitoring. The 2007 Solar Decathlon house currently sits on Santa Clara University’s campus at 60.4 m2. The house is powered entirely by solar PV and solar thermal off the grid. This solar energy house is heavily instrumented with more than 100 sensors to measure temperatures, humidity, power consumption of electric appliances, lighting, water, and performance of a 7.2 kW solar PV array and a sophisticated HVAC system. The instrumentation includes a full weather station. The house is divided into two interconnected modules, and constructed with high thermal insulation and sustainable materials. The instrumentation also allows quantifying energy performance of individual components as well as the overall energy performance of the house. The paper focuses on the complete energy balance of the house as a function of weather conditions, and of the performance of individual components. Of particular interest is the performance of the solar PV and solar thermal systems. The solar thermal system includes an absorption air conditioning unit, integrated with a thermal storage tank to provide all energy needs for water consumption and heating. The I-V curves of the full PV array are reported, demonstrating peak, off-peak, and seasonal performance and deviations from manufacturers’ conditions. Similarly, the overall COP of the solar-driven HVAC system is reported for both cooling and heating modes. Finally, it is shown how data can be used to demonstrate improvement of simulation tools for solar building energy performance. Although data has been collected since March 2009, this paper focuses on performance during summer 2009.
A Practical Model Reduction Method for Complex Variable Identified System
Authors: Suk Jae Hyeuk , Fabien Brian C.
Published: May 2012

This paper presents a practical model order reduction method which can handle the complex variable state-space model. The proposed model reduction method is based upon an identified result which is from the Eigensystem Realization Algorithm (ERA) with a complex variable transformation (z = x + iy) in [1]. The biggest advantage of a complex variable transformation is the fact that transformation (i) eliminates skew-symmetric term in state-space model and (ii) reduces a number of system states. However, using the complex variable transformation causes the result that an identified system includes the complex variables. Therefore, a new model reduction method for a complex variables state-space model is required. In particular, it is shown results of selecting system order with experimental data of flywheel energy storage system and the proposed method. Finally, a comparison of system order which is chosen by the other model reduction methods is analyzed.
Computational Fluid Dynamics Analysis of Fluid Mixing in Single Use Bioreactors
Authors: Spall Robert , Jones Nephi , Staheli Clinton
Published: May 2012

CFD calculations were performed for a series of stirred, single use bioreactor vessels using both rotating reference frame and sliding mesh model approaches. Comparisons of quantities such as flow patterns, power numbers, and mixing times are presented. Calculations to predict mass transfer coefficients for a sparged 250L vessel were also performed using the rotating reference frame model. Results presented include those from a series of single, fixed bubble diameter calculations, and those which employed a population balance model consisting of 9 discrete bubble diameters.
Performance and Emission Evaluation of Low Heat Rejection Direct Injection Diesel Engine Fueled by Diesel–Turpentine Oil Blends
Authors: Anandavelu K. , Alagumurthi N. , Saravanan C. G.
Published: May 2012

Light Vegetable oils are a promising alternative among the different diesel fuel alternatives. Using Light Vegetable oils in diesel engine is not a new idea. The Vegetable oils have high energy content. However, the high viscosity, poor volatility and cold flow characteristics of vegetable oils can cause some problems such as severe engine deposits, piston ring sticking and thickening of lubrication oil due to long-term use in diesel engines. Diesel fueled engine have the disadvantage of producing Smoke, Particulate Matter and Nitrogen Oxides and are now subjected to increasingly severe legislation of Emission norms. The required levels are difficult to achieve through engine design alone. Even with high-grade fuels, catalytic systems are being extensively investigated to reduce the diesel engine emission. But there are still difficulties in operation of these. This leads to replacement of diesel fuel with renewable fuels has been set target worldwide to reduce the diesel exhaust pollution. The energy of the light vegetable oil can be released more efficiently with the concept of low heat rejection (LHR) engine. The aim of the study is to apply LHR engine for improving the engine performance and reducing the emission when light vegetable oil (turpentine oil) is used as an alternate fuel. The work was carried out in two stages. In first Stage, the turpentine oil (20, 40, 60, 80 & 100, v/v) with diesel blends used in direct injection diesel engine and to identify best blend with respect to performance and emission. In second Stage, the work has been carried out by the converting direct injection diesel engine in to a LHR engine and the effects of different blends of turpentine oil (20, 40, 60, 80 & 100, v/v) with diesel fuel used in LHR engine and its performance, emission and combustion characteristics have been investigated experimentally. From the experimental investigation, the combination of LHR engine with blended fuels shows the better performance when compared to diesel engine. The smoke density decreases for the diesel engine (without LHR) whereas with the effect of LHR, Oxides of Nitrogen will be reduced and heat release rate also reduces.
Correlation of Direct Evaporative Cooling Efficiency With Media Porosity
Authors: Walker James , Sheng Shenguang , Nnanna A. G. Agwu , Li Lincang
Published: May 2012

. Energy consumption of HVAC&R could be reduced by integrating evaporative cooling device into air conditioning systems. Direct Evaporative Cooling (DEC) are suited for climates where the air is hot and humidity is low. In DEC, heat is absorbed whenever water is evaporated and converted to water vapor. By passing through or around a wetted surface, heat is removed from the surrounding air in the vaporization of the water. The process approximates the adiabatic-saturation process and the path lies on a constant wet-bulb temperature which is a constant enthalpy line. The wetted surface area in direct evaporative cooling depends on porosity and absorptivity of the media. This paper evaluates the effect of media porosity on performance of a Direct Evaporative Cooling system. In this experimental work, the porosity is varied by changing the packing density and volume of media. The packing material allows air and water to come in direct contact. Holding all other variables like mass flow rates and inlet dry-bulb temperature constant, the effect Porosity on DEC performance is studied. The performance of DEC system is a function of porosity, dry- and wet-bulb temperatures and relative humidity. Efficiency increases with porosity.
Design and Testing of Innovative Rotational Mould Heated by Thermal Fluid
Authors: Monzo´n M. D. , Beni´tez A. N. , Bordo´n P. , Herna´ndez P. M. , Marrero M. D. , Ortega Fernando
Published: May 2012

Rotomoulded plastic parts have no internal stresses, as it is a process carried out at lower temperatures than injection moulding and no pressure is applied. The main disadvantage is the high cycle times needed. This paper focuses on reducing this cycle time and in producing a mould using standardized parts. For cycle time reducing, it is proposed to heat the mould by thermal fluid in continuous circulation; heat transfer processes have been studied for over 20 different configurations of the oil’s inlet – outlet, obtaining acceptable results with a manifold with 25 perforations in the front and rear faces. This configuration has been optimized by computational fluids dynamics, allowing reducing heating and cooling time and improving the energetic efficiency and the uniformity of heating. Design, simulations and testing of a 100 mm3 cube have been carried out in order to produce a standardized mould; this mould consists in some standardized parts and a nickel shell, obtained by rapid prototyping and electroforming process. This shell can be removed from the rest of elements in the mould, allowing thus to obtain parts with any other geometry just by changing the nickel shell. An experimental machine for testing has been developed as well.
Simulation of Welding of Aluminum Parts Using High Energy Laser Beam
Authors: Jen Tien-Chien , Reikher Alexandre
Published: May 2012

A three dimensional finite difference model of the high energy laser beam welding process has been developed to predict temperature distribution. The calculations were performed using fixed grid enthalpy method, which does not require direct tracking of the solid–liquid interface and thus eliminates explicit reference to a moving boundary. As a result it allows utilizing standard solution method for the energy equation without any additional manipulations and transformations. Heat losses due to convection and radiation form the top surface of the workpiece, as well as effects of the natural convection in the liquid zone during welding operation has been accounted for in this study. Simulation results are in good agreement with published experimental measurements as well as with results obtained using commercial software Flow3D®.
Development of Dual Volume Cryogenic Hydrogen Storage System
Authors: Ledesma-Orozco Elias , Aceves Salvador M. , Espinosa-Loza Francisco
Published: May 2012

We are developing cryogenic capable pressure vessels with thermal endurance at least 5 times longer than conventional liquid hydrogen (LH2) tanks that can eliminate evaporative losses in routine use while providing high hydrogen storage weight and volume performance. The generation 2 vessel, installed onboard a Toyota Prius hydrogen hybrid experimental vehicle, has demonstrated the longest driving distance on a single LH2 tank and the longest LH2 hold time without evaporative losses. In addition to presenting the basic concept and recent progress on cryogenic capable pressure vessels, this paper describes the potential for greatly exceeding the hydrogen storage density of the generation 2 vessel through conformable dual volume containers that can better occupy box-shaped spaces onboard a vehicle. We present a design and analysis of a dual volume vessel that shows promise for delivering unprecedented hydrogen storage weight and volume performance. Future work will focus on demonstrating the technology onboard the experimental vehicle.
Experimental and Numerical Study of Transient Electronic Chip Cooling by Liquid Flow in Microchannel Heat Sink
Authors: Zhang Jingru , Zhang Tiantian , Jaluria Yogesh
Published: May 2012

Cooling of electronic chips has become a critical aspect in the development of electronic devices. Overheating may cause the malfunction or damage of electronics and the time needed for heat removal is important. In this paper, an experimental setup and numerical model was developed to test the effects of different parameters and their influence on the transient electronic chip cooling by liquid flow in microchannel heat sinks. The temperature change with time of the system for different heat fluxes at different flow was determined, from which the response time can be obtained. Three different configurations of multi-microchannel heat sinks were tested during the experiment. Numerical models were then developed to simulate the transient cooling for two of the configurations. A good agreement between the experimental data and numerical results showed that single-channel models are capable of simulating the thermal behavior of the entire heat sink by applying appropriate assumptions and boundary conditions.