bluuebunny/crossref_metadata_2025 huggingface dataset:
The Phonon Thermal Conductivity of Single-Layer Graphene From Complete Phonon Dispersion Relations
Authors: Gu Yunfeng , Ni Zhonghua , Chen Minhua , Bi Kedong , Chen Yunfei
Published: May 2012

In this paper, the phonon scattering mechanisms of single-layer graphene are investigated based on the complete phonon dispersion relations. According to the selection rules that a phonon scattering process should obey the energy and momentum conservation conditions, the relaxation rates of combining and splitting umklapp processes can be calculated by integrating the intersection lines between different phonon mode surfaces in the phonon dispersion relation space. The dependence of the relaxation rates on the wave vector directions is presented with a three-dimensional surface over the first Brillouin zone. It is found that the reason for the optical phonons contributing little to heat transfer is attributed to the strong umklapp processes but not to their low phonon group velocities. The combining umklapp scattering processes involving the optical phonons mainly decrease the acoustic phonon thermal conductivity, while the splitting umklapp scattering processes of the optical phonons mainly restrict heat conduction by the optical phonons themselves. Neglecting the splitting processes, the optical phonons can contribute more energy than that carried by the acoustic phonons. Based on the calculated phonon relaxation time, the thermal conductivities contributed from different mode phonons can be evaluated. At low temperatures, both longitudinal and in-plane transverse acoustic phonon thermal conductivities have T2 temperature dependence, and the out-of-plane transverse acoustic phonon thermal conductivity is proportion to T3/2. The calculated thermal conductivity is on the order of a few thousands W/(m K) at room temperature, depending on the sample size and the edge roughness, and is in agreement well with the recently measured data in the temperature range from about 350 K to 500 K.
Boubaker Polynomials Expansion Scheme Solution to the Heat Transfer Equation Inside Laser Heated Biological Tissues
Authors: Aweda M. A. , Agida M. , Dada M. , Awojoyogbe O. B. , Isah K. , Faromika O. P. , Boubaker K. Ben Mahmoud , De K. , Ojambati O. S.
Published: May 2012

In this study, an analytical solution to the heat transfer equation in biological tissues during laser heating is presented. The results were compared to recently published numerical simulations.
Analytical Study of the Convection Heat Transfer From an Isothermal Wedge Surface to Fluids
Authors: Bachiri M. , Bouabdallah A.
Published: May 2012

In this work, we attempt to establish a general analytical approximation of the convection heat transfer from an isothermal wedge surface to fluids for all Prandtl numbers. The flow has been assumed to be laminar and steady state. The governing equations have been written in dimensionless form using a similarity method. A simple ad hoc technique is used to solve analytically the governing equations by proposing a general formula of the velocity profile. This formula verifies the boundary conditions and the equilibrium of the governing equations in the whole spatial region and permits us to obtain analytically the temperature profiles for all Prandtl numbers and for various configurations of the wedge surface. A comparison with the numerical results is given for all spatial regions and in wide Prandtl number values. A new Nusselt number expression is obtained for various configurations of the wedge surface and compared with the numerical results in wide Prandtl number values.
Barometric Compensation of a Pendulum
Authors: Drumheller Douglas S.
Published: May 2012

For centuries, accurate pendulum clocks were of strategic scientific and military importance. Environmental factors such as temperature and pressure affect the rate of a pendulum. Without temperature compensation, accuracy is limited to about 10 s per day. With it, however, a secondper month is possible. Barometric compensation is required for additional improvement. Indeed, highly accurate pendulum clocks, such as Shortt-Synchronome Pendulums, are placed in controlled partial vacuums to avoid this unsolved problem. We model the pendulum as a Duffing oscillator to account for the effects of circular deviation, buoyancy, virtual mass, and aerodynamic drag. The application of routine perturbation methods reveals a simple and elegant solution to the problem of barometric compensation, an arc of motion where a balance is achieved. The results are confirmed by comparison to experiment.
Design Methodology of Solar Powered Load Controller Using Sensor Assisted Remote Battery State of Charge Estimator
Authors: Roy Chowdhury Joydeb , Chatterjee Aditya , Basu Saikat , Goswami Sayan , Saha Suvradipta , Poddar Surajit , Bhattacharjee Anup
Published: May 2012

One of the main problems of a solar PV plant is low generation of electricity during bad weather condition when the generated power is less than the claimed demand of power. Under this condition it is not possible to generate more electricity as per demand once the power plant is designed. When the supply of electricity to the consumers reduces drastically and when there is no option for manipulation of power — a blackout out or load shedding is the inevitable. Online demand regulation i.e. regulating the claimed demand of the individual consumer depending on predicted power generation is an alternate option in this constrained situation. The present paper will address this particular problem through probabilistic duration estimation power against a critical load using statistical model. Our goal is to design a predictive model considering the environmental fluctuation of solar clarity index into consideration and incorporates a policy of meeting the critical base load primarily and loads exceeding the base load secondarily depending on predicted energy generation. A modified model of MARS (Multi variate adaptive regression spline) is developed and finally used for prediction of battery state of health from a remote end using sunlight intensity (similar to clarity index) using remote sensor technology. We use Multivariate adaptive smoothing spline with adaptive smoothing features of noisy data available from light sensor.
Engineering Ethics: A Necessary Attribute for Papua New Guinea Engineers
Authors: Pumwa J.
Published: May 2012

Interest in engineering ethics education has developed significant momentum in almost all advanced countries. The developing countries have not yet paid enough attention to such critical issues and Papua New Guinea is no different. This is probably the reason why corruption activities have become part of the normal activities of politicians, senior public servants and many other higher office holders as reported in the daily news media. As engineering work becomes more complex and diverse, an understanding of engineering ethics becomes an important attribute for adequate and ethical preparation of engineers along with their technical knowledge. This basically means that engineering students have to learn about their ethical obligations towards society, their employers, fellow engineers and themselves. This paper discusses the needs and reasons for integrating ethics into the education of undergraduate engineering students in Papua New Guinea.
Investigation of the Transition Character for Duffing System by Employing Periodicity Ratio and Lyapunov Exponents
Authors: Han Lu , Dai Liming , Zhang Huayong
Published: May 2012

The transition characters from periodicity to chaos and periodicity to quasi-periodicity have been detected for a Duffing equation which is a representative nonlinear dynamic system who has complicated, diverse transition characters. Specifically, Lyapunov exponents and periodicity ratio method are both employed to diagnose the transition routes. By combining the two methods together, it is very efficient to classify different types of transition of a nonlinear differential system. It can be found that the transition routes from periodicity to chaos can be more divergent than other routes from periodicity to quasi-periodicity. Therefore, some predications can be made about the occurrence of the chaos by observing the divergence or convergence of the transition routes. Further more, the new symmetrical transition characters from periodicity to quasi-periodicity can be displayed in terms of the periodicity Ratio. Comparing to Lyapunov Exponents, the Periodicity Ratio can disclose more detailed transition information.
Acoustic Holographic Analysis of Vehicle Side Mirror Power-Fold Actuator for Sound Quality Control
Authors: Wang Xu , Subic Aleksandar , Jazar Reza
Published: May 2012

The possibility of application of acoustic holographic analysis with statistical envelope analysis algorithm for vehicle side mirror power-fold (PF) noise diagnostic is explored. The aim of this paper is to establish whether the sound visualization contours derived from the measurements can be used as a basis for the power-fold quality differentiation, and whether the results of noise source localization can suggest the best locations for signal sensor placement(s). With use of the acoustic camera, the diagnostic algorithm of the statistical envelope analysis is developed and validated using a large number of power-fold actuators comprising of subjectively ‘good’ and ‘bad’ samples. These power-fold actuators were tested and measured for the sound pressure spectra over the 1/3rd octave band over the frequency range up to 6300 Hz. Power-fold noise was measured by use of the microphone array. For given frequency limits of 1/3rd octave bands, sound pressure levels are measured on given power-fold actuators, an envelope algorithm was formed for the subjectively ‘good’ actuators, thus allowing to develop a quality control acceptance boundary envelope, with which, sound pressure spectrum amplitude of each individual actuator was compared. When the actuators have sound pressure spectrum amplitude curves falling within this boundary envelope, a pass status is obtained, and when the sound pressure spectrum amplitude curves stay outside of this envelope, a fail status is given.
New Numerical Simulation by the FEM of Residual Stresses in Random Structure Elastically Homogeneous Composites
Authors: Buryachenko Valeriy , Brun Michele
Published: May 2012

We consider a linearly elastic composite medium, which consists of a homogeneous matrix containing statistically inhomogeneous random set of noncanonical inclusions. The elastic properties of the matrix and the inclusions are the same, but the stress-free strains are different. The new general volume integral equation (VIE) proposed by Buryachenko (2010a, 2010b) is implemented. This equation is obtained by a centering procedure without any auxiliary assumptions such as, e.g., effective field hypothesis implicitly exploited in the known centering methods. The results of this abandonment are quantitatively estimated for some modeled composite with homogeneous fibers of nonellipsoidal shape. Some new effects are detected that are impossible in the framework of a classical background of micromechanics.
Geometric Optimization of Crack Arresting Holes in an Operational Component
Authors: Scott-Emuakpor Onome , George Tommy , Cross Charles
Published: May 2012

Crack-growth arrest is analyzed in this study with the simulation of real-life fatigue of a structure during service. Unlike conventional crack-growth arrest studies, this research does not analyze an opening mode (Mode I) crack extension from an induced crack-tip specimen. The work in this analysis focuses on designing drill-holes into a structure, without a preexisting crack, that will operate under cyclic loads. The purpose of the holes is to prevent through-crack propagation if a crack initiates during service of the structure. Prevention reduces the possibility of a phenomenon like Foreign Object Damage (FOD) by a fragment of a fractured structure in heavy operating machinery and over-looked cracks during routine inspections. The drill-hole design procedure for crack growth arrest explores the use of two, three and four-hole configurations as well as the effect of inserting hard Viton-rubber pins into each drill hole of a square plate test specimen. Each specimen configuration is geometrically designed with the following in mind: minimized the hole-to-fatigue zone stress ratio, minimize damping loss between the original and the new designs with holes and pins, and experimentally validating the theory of the crack arresting methods. The geometric optimization for the square plate specimen was developed in accordance with a vibration-based fatigue testing method for uniaxial bending, which is the benchmark method for this study.
An Elastic Cloak Model Based on Coordinate Transformation
Authors: Brun M. , Guenneau S. , Movchan A. B.
Published: May 2012

We propose a class of cylindrical cloaks for elastic waves which are deduced from geometric transform. In particular we implement a radially symmetric linear geometric transform which depends upon a parameter and depending upon the value of such parameter, the transform is applied to the design of neutral (invisibility) cloaks and to obtain mirage effects. Interestingly, the cloaking device has been designed for fully-coupled in-plane shear and pressure waves and, moreover, the chosen reparameterization is such that the elasticity equations maintain their initial form under the transformation, which is generally untrue in the elasticity case.
Modeling and Simulation of Medium-Duty Tactical Truck for Fuel Economy Improvement
Authors: Liao Y. Gene , Yeh Chih-Ping , Quail Allen M.
Published: May 2012

The impact of the vehicle fuel economy in tactical convey is amplified due to the fact that much of the present logistics support is devoted to moving fuel. Fuel economy improvement on medium-duty tactical truck has and continues to be a significant initiative for the U. S. Army. The focus of this study is the investigation and analysis of Automated Manual Transmissions (AMT) that have potential to improve the fuel economy of the 2.5-ton cargo trucks. The current platform uses a seven-speed automatic transmission. This study utilized a combination of on-road experimental vehicle data and analytical vehicle model and simulation. This paper presented the results of (1) establishment of a validated, high fidelity baseline analytical vehicle model, (2) modeling and simulation of two AMTs and their control strategy, and (3) optimization of transmissions shift schedules to minimize the fuel consumption. The fuel economy discrepancy between experimental average and the baseline simulation result was 2.87%. The simulation results indicated a 12.2% and 14.5% fuel economy improvement for the 12-speed and 10-speed AMT respectively.
Coordination in Collective Product Innovation
Authors: Panchal Jitesh H.
Published: May 2012

Collective innovation is based on connected, open, and collaborative processes to generate, develop, prioritize, and execute new ideas. While collective innovation is gaining significant attention by organizations, research on fundamental understanding of mechanisms enabling collective innovation is still in its infancy. One of the questions in enabling successful collective product innovation is: “How can activities of a large number of independent participants be coordinated?” Various researchers have studied coordination problems in traditional product realization processes, where the emphasis is on managing the dependencies between activities and resources. However, existing approaches for coordinating product development have limited applicability for collective product innovation because they are based on self-organizing communities as opposed to traditional hierarchies. To address this limitation, there is a need to understand how self-organization based coordination can be achieved in collective product innovation. In this paper, two key aspects of self-organization based coordination are highlighted: decentralization and evolution. A conceptual framework for understanding self-organization based coordination in collective product innovation is discussed. The framework highlights the dependencies between products, processes, individuals and organizational structures, which are important for coordination in collective product innovation. Various coordination mechanisms are required to manage these dependencies, thereby achieving decentralized, evolutionary coordination. For illustrative purposes, examples of such mechanisms used in open-source software development are discussed. Finally, an agent-based model is presented to quantitatively study the mechanisms for achieving decentralized evolutionary coordination. The conceptual framework and the agent-based model are used to derive insights for designing novel coordination mechanisms.
Prediction of the Cutting Temperatures of Turning Stainless Steels With Nose Radius Worn Tools
Authors: Chang Chung-Shin
Published: May 2012

To study the cutting forces and the carbide tip’s surface temperatures of stainless steel (SUS 304) with a chamfered main cutting edge nose radius worn tools. A new cutting temperature model incorporating tool worn factor and using the variations of shear and friction plane areas occurring in tool worn situations are presented in this paper. The heat partition factor between the tip and chip is solved by using g the inverse heat transfer analysis, which utilizes temperature on the carbide tip’s surface measured by infrared as the input. The tip’s carbide surface temperature is determined by finite element analysis (FEA) and compared with temperatures obtained from experimental measurements; good agreement demonstrates the proposed model.
Detection of Arteries by Using Diffuse Reflectance Photoplethysmography
Authors: Ota Shinichiro , Yasuda Toshitaka , Saito Takashi
Published: May 2012

Non-invasive measurement of the arterial pulse wave can be carried out by means of an optical sensor placed at the center of the artery. In this paper, we explore the possibility of using diffuse reflectance photoplethysmography (PPG) for the detection of arteries, a method that allows for the timely detection of changes in the blood pressure. It is believed that the light scattering intensity is affected by the presence of veins in the light path. The purpose of the present study is to elucidate the influence of veins on the accuracy of PPG. In this study, we used light scattering measurements to investigate the difference observed in the performance of PPG (wavelength: 810 and 530 nm) due to the presence of veins. On the basis of these results, we concluded that PPG at a wavelength of 810 nm is more susceptible to the presence of veins than at 530 nm. However, the influence of veins can be reduced by the measurement condition that surrounding veins are being crushed at a wavelength of 810 nm.
ProEmotion: A Tool to Tell Mobile Phone’s Gender
Authors: Wang William W. , Xu Xun W. , Hsiao Hsiang-Hung
Published: May 2012

Kansei engineering, also known as kansei ergonomics or emotional engineering, aims at analyzing and incorporating customer’s feeling and demands into product function and product design. The paper described a system called ProEmotion for the purpose of assessing the kansei aspects of a product by considering design attributes of a product. Neural network is used to process kansei words. The system has been successfully implemented to ascertain gender inclination of a mobile phone. Principal parameters of a mobile are considered, i.e. length, width, thickness and mass. The system can inform gender inclination of a mobile phone with accuracy up to 90%. This is based on a set of 92 mobile phone samples from the five major mobile phone manufacturers.
Student-Centered Microsystem and Nanotechnology Courses and Laboratories for Mechanical Engineering Students
Authors: Xue Wei
Published: May 2012

Modern society has been drastically changed by the rapid development of miniature science and engineering. In order to improve the microsystem and nanotechnology education, we developed a student-centered experimental module for two laboratory-intensive courses: Micro/Nano Technology and Microelectromechanical Systems (MEMS) Engineering. The experimental module emphasizes hands-on experience and it is seamlessly integrated into the course structures. The developed laboratory activities include photomask layout design, photolithography, isotropic and anisotropic wet etching, bulk micromachining, optical microscopy, surface profiling based on light interferometry, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The students benefit from gaining a better understanding of the course topics by designing their own structures that meet the design requirements and by fabricating their own devices. The laboratory results are satisfactory and show that the experimental module is effective in teaching microsystems and nanotechnology at both the undergraduate and graduate levels.
Study of the Dynamic Performance of Mechanical Systems With Multi-Clearance Joints
Authors: Megahed S. M. , Haroun A. F.
Published: May 2012

Joints’ clearance in mechanical systems such as linkage mechanisms and robots is an inevitable matter due to wear of mating parts. The presence of such clearance is a main source of impact forces resulting local deformation, wear and tear of such joints and consequently degradation of system performance. In this investigation, the effect of revolute joints’ clearance on the dynamic performance of mechanical systems is reported. The contact force between the pin (journal) and the bearing of the joint is modeled using Coulomb’s friction law, and contact force approach. This approach takes into consideration the elastic behavior of the collided bodies and the energy dissipated due to collision during the contact period. A computation algorithm is developed with the aid of SolidWorks/CosmosMotion software package. A crank-slider mechanism with one and two clearance-joints working in horizontal or vertical planes is studied. The simulation results point out that the presence of such clearance in the joints of the system understudy leads to high peaks in the characteristic curves of its dynamic and kinematic performance. The amplitudes of these peaks become higher as the number of clearance-joints included in the mechanism increases. For a multi-clearance joints mechanism, the maximum impact force at its joints takes its highest value at the nearest joint to the input link. This study also shows that, when the mechanism works in horizontal plane, the rate of impacts at each clearance-joint increases and consequently the clearance-joints and actuators will deteriorate faster. This means that working of the real mechanisms in vertical plan is more advantageous and improves their performance.
Feasibility of Integrating Multiple Types of Electroactive Polymers to Develop an Artificial Human Muscle
Authors: Spath William E. , Walter Wayne W.
Published: May 2012

Electroactive polymers (EAPs) have been labeled as the future stakeholder for artificial muscle technology and machine actuation. The US Armed Forces have seen an increased population of service members suffering from loss of limbs as a result of conflicts overseas. Civilian populations have suffered as well, due to muscle tissue deterioration brought on by injury or disease. Many prosthetic limbs have been engineered with rotary actuation, but do not mimic fluid motion as human muscles do. Through the research of biomimetics, imitating nature and applying those techniques to technology, electroactive polymers have been found to produce the fluid-like characteristics of biological muscles as needed for precise artificial simulation. These materials exhibit common traits of biological muscle tissue regarding potential energy storage. When activated by an electrical voltage potential, EAPs can produce characteristics such as: bending/axial strain or changes in viscosity. One classification of electroactive polymers, Ionic EAPs, exhibit bipolar activation under low voltages and can be found in various physical states; solid, liquid, and gel states. These characteristics make Ionic EAPs the most attractive materials to be used in low energy or mobile applications, such as exoskeletons and implants. For high strain and large load applications, electronic EAPs can be used. Electronic EAPs require high voltages which induces high rates of strain and large deformations. To date, it appears that various types of EAP materials are being used individually, as opposed to integrated with other types. Biological muscles are made of many different proteins organized in an optimized geometrical structure which yields a more efficient response combined than achieved individually. The focus of the current project is to integrate multiple EAP materials in a designed mechanical system to produce a closer representation of a biological muscle. The status of this RIT project; to design, fabricate, and test an integrated EAP-based artificial muscle will be discussed along with the conceptual thinking for design obtained to date.
Geometric Optimization of Aggressive Inter-Turbine Ducts
Authors: Hu Shuzhen , Zhang Xue Feng , Benner Michael , Gostelow Paul , Vlasic Edward
Published: May 2012

To reduce the harmful effects of aviation on the environment, aircraft gas turbine manufacturers continue to focus on producing engines with lower specific fuel consumption and weight. To address the engine weight challenges, R&D efforts continue to center around extending aerodynamic design limits, thus enabling reduced airfoil/stage count, reducing engine length or some combination thereof. The inter-turbine transition duct (ITD), located between the high-pressure (HP) and low-pressure (LP) turbines, is one of the components for which potentially significant weight reduction can be achieved through aggressive aerodynamic designs. Such ducts could have larger HP-to-LP radial offset and/or shorter length resulting in Aggressive Inter-Turbine Ducts (AITD). This paper presents a geometry optimization process to design AITD with minimum total pressure losses. Geometry optimizations were performed using the built-in optimization process in NUMECA Fine/Turbo 8.7. To evaluate the optimization process, one baseline ITD geometry was first generated with the same inlet and outlet coordinates as an existing ITD. The performance of the optimized ITD was studied numerically in comparison with the existing ITD. After the evaluation study, a second ITD geometry with more aggressive parameters, equivalent to increasing mean rising angle by 25% was optimized. Based on the studies of those two optimized geometries, a generic design rule of ITD with mild parameters was developed and the third ITD geometry with increased 20% area ratio (AR) was designed. The performance of designed ITDs was investigated numerically and the results are discussed in the paper.
Numerical Study of the Flow in the Wake of an Impulsively Started Rotating and Translating Circular Cylinder
Authors: Ghosh S. K. , Mukherjea S. K. , Datta B. N.
Published: May 2012

In the present work, a detailed investigation in the wake region of the flow for the case of a two dimensional, laminar, incompressible flow past a rotating and translating circular cylinder has been carried out by applying a second order time accurate finite difference method using primitive variable formulation for different values of α ranging between 0 and 8 for Re = 200, where α is a nondimensional peripheral velocity of the cylinder. It has been observed that lift coefficient increases monotonically with α. But the effect of rotational speed on the steadiness of the flow is found significantly critical. Within the present range of α it is found that there have been back and forth regimes of unsteadiness in the flow. The flow remains unsteady for α ≤ 1.95, becomes steady for 1.95 ≤ α ≤ 4.33 and is unsteady again for 4.33 ≤ α ≤ 4.73. For α > 4.73 the flow is again steady. It is found that while the first steady regime of flow is characterised by two oppositely rotating static vortices, the second steady regime is characterised by only one rotating static vortex wrapping around the cylinder. It is also found that the nature of two unsteady regimes are not same. Detailed investigation reveals that in the first mode of vortex shedding, vortices are shed alternatively from both top and bottom surfaces, while in the second mode, the shedding occurs only from the bottom surface. Investigation also explains the cause behind increase of lift, decrease of drag with respect to α. From FFT analysis it can be concluded that lift curves corresponding to the first unsteady regime are simple sinusoidal waves, while those corresponding to the second unsteady regime are combinations of different harmonics. On the other hand, simple sinusoidal nature of the drag variation is found only when α is zero. By tracking the vortex shedding process closely, it is observed that during the process of formation, a small anticlockwise vortex is formed inside a large anticlockwise wrapping vortex around the cylinder to result into a higher pressure stagnation region just below the cylinder which in turn, effects maximum lift and detaches the small vortex from the lower surface of the cylinder resulting into vortex shedding from the bottom surface.
Experimental Studies on Fire Spread Over Glass Fac¸ade
Authors: Chow C. L. , Chow W. K.
Published: May 2012

There are concerns on the behaviour of glass fac¸ade under a big fire. Real-scale experiments on a single-skin fac¸ade were carried out at a large laboratory of a sizable aluminum manufacturing plant in Southern China. Burning behaviour of a three-storey high single-skin glass fac¸ade with double glazing due to an adjacent big room fire was studied. Part of the fac¸ade of width 12 m and height 13 m was installed in a testing tower. A glass pane of the fac¸ade was taken out with a model fire chamber placed next to the opening. Flashover in the chamber was set up by burning a 2 MW gasoline fire. Flame and smoke spread from the chamber would move up along the glass fac¸ade. Air temperature outside the glazing above the fire chamber was measured. It is observed that flame spread out of the opening will be attached to the upper levels. The glass fac¸ade at that level will be heated up and broken. Flame can spread to the room at the upper level. Another flashover fire will then occur with adequate air supply. This scenario on having a post-flashover fire in an adjacent upper room should be included in hazard assessment in buildings with glass fac¸ade.
Predicting Two Phase Flow Pressure Drop With CFD and ANN
Authors: Teke I˙smail , Ag˘ra O¨zden , Demir Hakan , Atayılmaz S¸. O¨zgu¨r
Published: May 2012

In this study, the several well known two-phase viscosity models were used for predicting two-phase flow pressure drop in a smooth tube using Computational Fluid Dynamics (CFD) software at homogenous flow conditions. Pressure drop for two different mass flux values (300 and 650 kg/m2s) for R134a with a saturation temperature of 45 °C in a smooth tube has been modeled according to the homogenous flow model and the results have been compared with the analytical formulas and experimental data from the literature. Three different average viscosity correlations were used. It is seen that the numerical results are in a good agreement with the homogenous flow model and fall in ± 30% band. Also, the results derived from the average viscosity expression are in a good agreement with the results calculated using separated two-phase flow correlations. In addition to this, Artificial Neural Networks (ANNs) were employed for predicting the pressure drop in a horizontal smooth pipe. The trained network gives the best values over the correlations with less than 1% mean relative error.
Experimental Characterization of a Small-Scale Downdraft Gasifier for Biomass Waste
Authors: Emmerson Vaughn M. , Diaz Gerardo
Published: May 2012

Biomass is essentially organic garbage obtained from many sources of dead or live vegetation including yard waste. According to recent data, approximately sixty million bone dry tons of biomass are produced in California each year [1]. Of this, only five million tons are used for the generation of electricity. At a global scale, 8700 Tg of biomass (dry matter) were burned without energy recovery in 1991. This number has increased especially in developing countries with the main sources being the savannas, agricultural waste, tropical forests, and fuel wood. Inefficient burning of waste, through combustion in open-air or in open dumps are a significant source of pollutants leading to possible health effects. An alternative to open air combustion is gasification, which involves the conversion of biomass to generate synthesis gas (syngas) by adding heat and limited amounts of oxygen. Several gasifying agents can be utilized, but air is commonly used in small-scale gasifiers. The use of air causes a large molar fraction of nitrogen in the syngas composition. This papers shows the experimental results obtained with a commercially available small-scale downdraft gasifier. Woodchips obtained from a nearby landfill are used as input to the gasifier and temperatures, flow rates, and syngas composition are reported and analyzed.
Dielectrophoretic Assembly of Organized Carbon Nanotubes and Thin Films
Authors: Li Pengfei , Xue Wei
Published: May 2012

In this paper, we investigate the dielectrophoretic assembly of organized carbon nanotube (CNT) and CNT thin films. Both single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) are employed in our experiments. Electrodes with “teeth”-like patterns are fabricated to study the influence of electrode width on CNT deposition and alignment. The entire fabrication process is compatible with optical lithography based techniques. Therefore, the fabrication cost is low and the resulting devices are inexpensive. SWNT and MWNT solutions are prepared with different concentrations. The alignment of SWNT/MWNT thin films and small bundles are achieved under the optimized experimental conditions. The electrical properties of these samples are characterized. The results demonstrate that the controlled deposition of CNT thin films using dielectrophoresis is highly repeatable. The alignment of small nanotube bundles can only be achieved using narrow electrodes and low-concentration solutions. Our investigation shows that it is possible to deposit a controllable amount of CNTs in desirable locations using dielectrophoresis. This research has the potential to enable the development of practical and inexpensive CNT devices that can be used in a wide range of applications: nanoelectronics, nano-bioelectronics, nanoelectromechanical systems (NEMS), and energy devices.
Kinematic Analysis of a Motorcyclist Impact on Concrete Barriers Under Different Road Conditions
Authors: Moradi Rasoul , Ramamurthy Shashikumar , Thorbole Chandrashekhar K. , Bhonge Prasannakumar S. , Lankarani Hamid M.
Published: May 2012

In many countries, motorcycle crashes constitutes a significant proportion of road crash injuries. Several roadside guard systems such as concrete barriers, wire road barriers and steel guard rails are used to protect cars or heavy trucks occupants, yet motorcycle riders are vulnerable to these barriers and guard systems, resulting in major injuries. The road and climatic conditions also have a major impact on motorcyclists’ accidents. The safety measures can be successful only if more attention is devoted to this issue. The aim of this study is to understand the most influential factors causing motorcycle accidents. For this, a multi-body motorcycle model with a Hybrid III 50th percentile male dummy rider is developed under normal road condition in the MADYMO 6.3. The motorcycle model as well as the motorcycle and rider model has been validated using full scale crash test of a motorcycle with a rider available in a literature. Motorcycle kinematics, rider kinematics and the rider injury criteria are validated with the test results. The simulations results are found to be in a reasonable agreement with the experimental data. A parametric study is then conducted to investigate the nature of crash injuries for various impact speeds, different impact angles and for normal and icy road conditions to assess rider kinematics and potential injuries. The results from this study can help in designing road barriers and guard systems in order to protect the occupants of cars and motorcycles. The results from the parametric study indicate a significant difference on the motorcycle and rider kinematics when compared the icy road conditions to normal road conditions. It is also observed that the head injury risk is the major mode of injury in motorcycle accident.
Numerical Simulations on Airflow to the Double-Skin Fac¸ade Cavity by an Adjacent Room Fire
Authors: Chow C. L.
Published: May 2012

The architectural feature of double-skin fac¸ades has been proposed in green or sustainable buildings. However, there are potential fire risks and so the design was normally not accepted by the authorities having jurisdictions. The scenario of trapping heat and smoke in the fac¸ade cavity is identified as hazardous and should be better understood. Hot smoke flowing out of openings driven by an adjacent room fire to the double-skin fac¸ade cavity was simulated using computational fluid dynamics (CFD). A five-level building model was taken as an example. A fire occurred in a room at the third level under two different heat release rates of 1 MW and 5 MW, and cavity depths of 0.5 m, 1 m and 2 m were considered. Based on the simulation results, three stages of flame spreading from the room fire to the adjacent fac¸ade cavity were proposed in fire hazard assessment for this architectural feature. Results suggested that wider cavity depths would be more dangerous, having a greater chance to break the adjacent upper interior glass panes. Smoke or even flames can then spread to the upper levels.
An Experimental Investigation of Cavitating Jet Dynamic Power and Cavitation Intensity
Authors: Hutli Ezddin A. F. , Nedeljkovic Milos S. , Vojislav Ilic
Published: May 2012

The principal focus of this investigation were the effect of hydrodynamic and geometrical parameters on cavitating jet dynamic power and cavitation intensity under different flow conditions. Jet performance indicators were taken to be the erosion rate of the target surface and the size of the erosion area.. In addition, flow visualization was used as an additional tool to demonstrate the effect of dynamic power on the cavitating jet characteristics. The results show that the erosion rate can be used an indicator of the strength of the impinging jet to establish a correlation between the jet power and the pertinent experimental parameters. In addition, the importance of non-dimensional standoff distance was investigated and an analytical relationship established between it and the jet intensity. These expressions are proposed for calculating the efficiency of cavitating jets.
A Comprehensive Electrical Engineering Program Adapting an Active Teaching Method and Assuring the Continuation for Retention Plan
Authors: Al Shariff Samir M.
Published: May 2012

Electrical Engineering is one of the leading fields in the professional working world. Every day a novel idea is being adapted into the program to insure the progression of the students and to increase the possibility of the learning experience. Active Teaching methods are today’s leading approach in educational enhancement. We at Taibah University have successfully ran a course (GE 102: Introduction to Engineering Design) via the method of active teaching approach. Adopting these methods on Electric Circuit 1, Digital Design 1, Electronics 1, Signals and Systems, and Power System Analysis 1 courses at the second year program studies will advances the students learning capabilities. For those students who successfully complete these courses will advance into the third year at the program. To assure a 100% retention rate, we promote a gate in association with the vocational college to accept those students who would fail the completion of this year in a smooth manor with their program and graduate from the vocational college. [1,2,3,4]
Modeling of Temperature Distribution Inside a Current Transformer
Authors: Cui Jie , Mahajan Satish , Robalino Diego
Published: May 2012

Current transformer (CT) is a device that transfers the electrical energy from one circuit to another through a shared magnetic field. In a CT, heat is generated in the core, tank wall, primary and secondary windings. The performance of current transformer is well indicated by the temperature distribution inside a CT. In this study, numerical analysis was performed to predict the temperature distribution inside a CT at every instant under different load conditions. It was found that the numerical results obtained were in good agreement with the experimental measurements.
Autodriver Algorithm for Autonomous Vehicle
Authors: Jazar Reza N. , Simic Milan , Khazaei A.
Published: May 2012

In a recent research a superior algorithm has been introduced to design an autodriver to keep an autonomous vehicle on a given road using independent four-wheel-steering (4WS) system. The kinematic condition of steering sets the steer angles such that the kinematic center of rotation of the vehicle be controlled on a two dimensional space. The vehicle however, will turn about an actual point that is not necessarily at the road curvature center; because of the road, tire characteristics, and dynamics of the moving vehicle. The algorithm shows how the position of the dynamic turning center can be controlled by adjusting the steer angles such that it coincides with the road curvature center. Such a vehicle will move on the desired road autonomously. In this paper, the required facilities to apply the algorithm experimentally will be discussed.
Improved Mathematical Modeling of Thermal Effects in Flexural Microcantilever Resonators Dynamics
Authors: Jazar Reza N. , Takla Monir , Mahinfalah M.
Published: May 2012

In a recent research the thermal dependency of material characteristics in dynamic response of microresonator systems is modeled using Lorentzian function and employing perturbation analysis. Thermal phenomena introduce two main effects: damping due to internal friction, and softening due to Young modulus-temperature relationship. The presented mathematical model provided effective equations to study the electrically actuated microbeam resonators. The mathematical model of thermal phenomena in microbeam vibration was introduced by Jazar (2009). In that analysis, using the Zener model, a positive frequency dependent damping and a negative frequency dependent stiffness terms were introduced to mode the effects of warming at resonance (Jazar 2009). In this investigation, the problem will be analyzed from a practical point of view. We introduce a better mathematical model by improving the presented model. The main difference would be including the strain distribution in the damping and stiffness model.
Numerical Evaluation of Energy Absorption for Composite Aluminium Tubes
Authors: Henning Petrus F. J. , Pretorius Leon , Laubscher Rolf
Published: May 2012

This paper describes a numerical evaluation of the energy absorption capabilities of Al 6063-T6 tubes arranged as tube–in tube with and without imperfections. Reaction force vs. displacement and energy vs. displacement graphs are presented for the different configurations. This work forms the basis for an energy absorber design with application in the transport industry.
A Tetraparametric Metamodel for the Simulation and Optimization of Bolting Sequences for Wind Generator Flanges
Authors: Abasolo Mikel , Aguirrebeitia Josu , Avile´s Rafael , Fernandez de Bustos Igor
Published: May 2012

In the bolted joints of wind generator flanges there is a gap between the contact surfaces of the flanges. This involves a nonlinear behavior of the system during the tightening sequence of the joint. This phenomenom, in addition with the elastic interaction, makes it difficult to achieve a uniform bolt preload at the end of the assembly process. This work presents a methodology which, based on a metamodel created for such purpose, enables the optimization of the tightening sequence; i.e. it calculates the load to be applied to each bolt in order to achieve a desired uniform preload at the end of the tightening sequence. This optimization is done with a minimum computational cost, avoiding costly experimental measurements or nonlinear FE simulations. Besides, the methodology also takes into account that the load for any bolt must be below its yield point, and therefore calculates a two-pass sequence if necessary.
Numerical Simulation for Compressible Supercavitating Flow Over Disk-Cavitator
Authors: Meng Qingchang , Zhang Zhihong , Liu Jubin , Gu Jiannong , Miao Tao
Published: May 2012

To deal with the effect of compressible fluid on the supercavitating flow over the subsonic disk cavitator of projectile, a finite volume method has been formulated based on the ideal compressible potential theory. By using the continuity equation and Tait state equation as well as Riabouchinsky closure model, an “inverse problem” solution has been presented for the supercavitating flow. According to the impenetrable condition on the surface of supercavity, a new iterative method for the supercavity shape has been designed to deal with the effect of compressibility on supercavity shape and pressure field. The supercavity shape changes from ellipse to taper, as well as the drag coefficient increases with Mach number increasing. The results compare well with the experiment data and empirical formula, and the numerical method is proven to be valid.
Birdstrike Analysis on Leading Edge of an Aircraft Wing Using a Smooth Particle Hydrodynamics Bird Model
Authors: Walvekar Vinayak , Thorbole Chandrashekhar K. , Bhonge Prasanna , Lankarani Hamid M.
Published: May 2012

With the increase in air travel, the recent occurrences of birdstrikes on aircraft pose a major threat to human life; hence, there is a need to develop aircraft structures with a high resistance to such occurrences. According to the Federal Aviation Regulation (FAR 25.571) on Damage-Tolerance and Fatigue Evaluation of Structure (Amdt. 25-96), an airplane must be capable of successfully completing a flight during which likely structural damage might occur as a result of impact with a four-pound (1.8 kg) bird at sea-level cruise velocity or 0.85 percent of cruise velocity at 8,000 feet (2,400 m). Since the actual physical testing of a birdstrike is expensive, time-consuming, and cumbersome, this paper presents a methodology, based on the use of analytical finite element modeling and analysis, to certify an aircraft for a birdstrike. In actual physical testing for birdstrikes the mass of the bird might not be accurate and hence for certification purpose the computational modelling technique is more accurate and standardizes the certification procedure. The modeling and simulations are carried out as follows: the bird is modeled using the smooth particle hydrodynamics (SPH) technique in the LS-Dyna nonlinear finite element code. To validate this model, birdstrikes are carried out on rigid and deformable plates. The results, including displacement, Von-Mises stresses, forces, impulse, squash time and rise time, are obtained from the simulation, and non-dimensional values are plotted and compared with results from the test data. The detailed CAD geometry of the leading edge of an aircraft is modeled in CATIA V5. Meshing, connections, and material properties are then defined in the Altair Hypermesh 9.0 program. The results obtained from the birdstrike simulations on this leading edge are compared to data from the experiments, and the process is validated. Parametric studies are carried out by designing the aircraft leading edge for different values of nose radius and by assigning appropriate thickness values for leading-edge components and impacting the SPH-modeled bird at different velocities. The methodology and results obtained from simulation can be utilized in the initial design stages as well as for “certification by analysis” of an aircraft for birdstrike requirements as per federal regulations.