bluuebunny/crossref_metadata_2025 huggingface dataset:
The Second Law of Thermodynamics and Heat Release to the Global Environment by Human Activities
Authors: Wong Kau-Fui Vincent
Published: May 2012

It is the postulate of the current work that all human activities do add heat to the global environment. The basis used is the concept of thermodynamic entropy and the second law of thermodynamics. It has been discussed and shown that human activities do release heat to the global environment. There is no claim and not the objective in the current work to make any statement about climate change or global warming. It is suggested that all significant human-related activities have been included in the discussion, and hence the proof and deduction. The approach used is in accordance with the manner in which the laws of thermodynamics were derived, which is empirical.
Measurement of Weld Dimensions of Butt Joint Welding in Thin Plates Using Superimposed Laser Sources
Authors: Wu Tsun-Yen , Ume I. Charles
Published: May 2012

Gas Metal Arc Welding (GMAW) is one of the primary techniques used to join thin structures together. The quality of the weld plays an important role in structure integrity and product safety. Weld dimensions in butt joint welding of thin plates such as penetration depth, bead width, and reinforcement height are key to the quality of welds. Therefore, it is very crucial to accurately measure them. In this paper, a system that uses laser generated Lamb waves and electromagnetic acoustic transducer (EMAT) reception is used to inspect welds. Lamb waves are widely used in structural integrity inspection and defect detection in thin structures because of their potentials to inspect large areas and their abilities to detect various kinds of defects. The use of lasers to generate Lamb waves is beneficial due to its noncontact nature. However, due to the fact that laser generated Lamb waves in thin structures are broadband and dispersive, the complexity of ultrasonic signals is greatly increased. A method named superimposed laser sources technique is applied to reduce the complexity of signals. By using superimposed laser sources, one would have the flexibility to generate a desired wavelength of Lamb waves. The advantage of generating narrowband Lamb waves with a fixed wavelength is that the dominant frequency contents and traveling speeds of different wave modes can be determined from the dispersion curves. A signal processing procedure that combines wavenumber-frequency domain filtering and continuous wavelet transform is also applied to further simplify received signals. Reflection of ultrasounds occurs due to the presence of weld joint and reflection coefficients of different Lamb wave modes and wavelengths can be measured and used to quantify weld dimensions. In addition, the effects of welding parameters such as contact tip to work distance (CTWD), welding speed, arc voltage, and wire feed rate on weld dimensions is investigated. The correlation between these reflection coefficients and weld dimensions is studied, and empirical regression models are developed as well. This research results in a new non-destructive and non-contact sensing technique for measuring important weld dimensions of butt joint welding in thin structures. It will help to improve the quality and efficiency of the GMAW process, and reduce material waste and associated costs.
Logarithmic Superposition in Airway Smooth Muscle Dynamics
Authors: Ijpma G. , Al-Jumaily A. M. , Sieck G. C.
Published: May 2012

Airway smooth muscle contraction is the main driving mechanism in asthma. However, in the dynamic environment of the ASM passive dynamics play an important role. The main aim of this research is to investigate the relative contribution of passive dynamics to ASM tissue dynamics and to characterize this behavior. The major finding of this study is the ability of the principle of logarithmic superposition to describe a wide range of dynamic behavior in relaxed (unstimulated) ASM and to a lesser extend in contracted ASM. The ability of this model to describe the force response to length oscillations in contracted muscle shows that cross-bridge cycling in ASM when fully contracted is not affected by oscillations. We hypothesize that this could be caused either by a very slow cross-bridge cycling rate, or by a large degree of non-contractile cross-linking which results in a greatly increased passive force.
A Multi-Criteria Simulation Framework for Civil Aircraft Trajectory Optimisation
Authors: Zolata Hasan , Celis Cesar , Sethi Vishal , Singh Riti , Zammit-Mangion David
Published: May 2012

Over the past few years, great concern has been raised about the impact of commercial aviation on the environment. In a Business As Usual approach, the expected growth in air traffic is going to affect climate change even more unless mitigation policies are devised and implemented. Although there is a tendency to focus on long-term technological solutions and breakthroughs, short-term improvements applicable to existing aircraft/engine configurations are also very important to fully realise the benefits of new technologies. Aircraft trajectory optimisation presents the opportunity to effectively reduce fuel consumption and pollutants emitted providing a feasible short-term strategy to be applied to the existing aircraft fleet. The present study focuses on preliminary results obtained using a multi-disciplinary aircraft trajectory optimisation simulation framework. Three in-house computational models are implemented in the framework to model the aircraft and engine performance, as well as to predict the level of gaseous emissions produced. A commercially available optimiser is integrated within the framework to analyse and optimise single flight path elements (e.g., climb), as well as the entire flight profile. For the purpose of this study, the climb and the whole flight profile are divided in four and eight segments respectively. Trajectory optimisation processes are then carried out in order to minimise three different objective functions: flight time, fuel burned, and mass of oxides of nitrogen (NOx) emitted. The results of the trajectory optimisation processes performed confirm the validity, effectiveness, and flexibility of the methodology proposed. In future, it is expected that these types of approaches are utilised to efficiently compute complete, optimum and ‘greener’ aircraft trajectories, which help to minimise the impact of commercial aviation on the environment. Other computational models that simulate several other aspects such as aircraft and engine noise, weather conditions and contrails formation, among others, need to be also included in the optimisation processes.
Forecasting the Impact of Plug-In Hybrid Electric Vehicles Penetration on Ontario’s Electricity Grid
Authors: Ahmadi Lena , Unbangluang Woramon , Croiset Eric , Elkamel Ali , Douglas Peter L. , Entchev Evgueniy , Ku Hong-Ming
Published: May 2012

Vehicle emissions are a major concern in the development of new automobiles. Plug-in hybrid electric vehicles (PHEVs) have a large potential to reduce greenhouse gases emissions and increase fuel economy and fuel flexibility. PHEVs are propelled by the energy from both gasoline and electric power sources. Penetration of PHEVs into the automobile market affects the electrical grid and increasing the electricity demand has not been fully investigated. This paper studies effects of the wide spread adoption of PHEVs on peak and base load demands in Ontario, Canada. Long-term forecasting models of peak and base load demands and the number of light-duty vehicles sold are developed. To create proper forecasting models, both linear regression (LR) and non-linear regression (NLR) techniques are employed, considering different ranges in the demographic, climate and economic variables. The results from the LR and NLR models (LRM and NLRM) are compared and the most accurate one is selected. Furthermore, forecasting the effects of PHEVs penetration is done through consideration of various scenarios of penetration levels, such as mild, normal and aggressive ones. Finally, the additional electricity demand on the Ontario electricity grid from charging PHEVs is incorporated for electricity production planning purposes.
The Energy Return on Investment for Algal Biocrude: Results for a Research Production Facility
Authors: Beal Colin M. , Hebner Robert E. , Webber Michael E. , Ruoff Rodney S. , Seibert A. Frank
Published: May 2012

This study is an experimental determination of the energy return on investment (EROI) for algal biocrude production at a research facility at the University of Texas at Austin (UT). During the period of this assessment, algae were grown at several cultivation scales and processed using centrifugation for harvesting, electromechanical cell lysing, and lipid separation in an enhanced coalescence membrane. The separated algal lipids represent a biocrude product that could be refined into fuel. To determine the EROI, a second order analysis was conducted, which includes direct and indirect energy flows, but does not consider capital energy expenses. At the time that the data in this study was collected, the research program was focused on improving biomass and lipid productivity. As a result, some higher efficiency processing steps were replaced by lower efficiency ones to permit other experiments. Although the production process evaluated here was energy negative, the majority of the energy consumption resulted from non-optimized growth conditions. Therefore, the experimental results do not represent an expected typical case EROI for algal fuels, but rather outline the important parameters to consider in such an analysis. The results are the first known experimental energy balance for an integrated algal biocrude production facility. A Reduced Case is presented that speculates the energy use for a similar system in commercial-scale production. In addition, an analytical model that is populated with data that have been reported in the literature is presented. For the experiments, the Reduced Case, and Literature Model, the estimated EROI was 1.3 × 10−3, 0.13, and 0.57, respectively (refining energy requirements are not included in the experimental or Reduced Case EROI value). These results were dominated by growth inputs (96.59%, 94.15%, and 76.32% of the total energy requirement, respectively). For the experiments and Literature Model, lipid separation was the most energy intensive processing step (2.47% and 10.06%, respectively), followed by harvesting, refining, and then electromechanical cell lysing.
Pump Design for a Portable Renal Replacement System
Authors: Kang Jane , Scholz Tamera , Weaver Jason , Ku David N. , Rosen David W.
Published: May 2012

This work proposes a small, light, valve-less pump design for a portable renal replacement system. By analyzing the working principle of the pump and exploring the design space using an analytical pump model, we developed a novel design for a cam-driven finger pump. Several cams sequentially compress fingers, which compress flexible tubes, thus eliminating valves. Either changing the speed of the motor or size of the tube can control the flow rate. In vitro experiments conducted with whole blood using the pump measured Creatinine levels over time, and the results verify the design for the portable renal replacement system. The proposed pump design is smaller than 153 cm3 and consumes less than 1W while providing a flow rate of more than 100ml/min for both blood and dialysate flows. The smallest pump of a portable renal replacement system in the literature uses check valves, which considerably increase the overall manufacturing cost and possibility of blood clotting. Compared to that pump, the proposed pump design achieved reduction in size by 52% and savings in energy consumption by 89% with the removal of valves. This simple and reliable design substantially reduces the size requirements of a portable renal replacement system.
Failure Locus of the Anterior Cruciate Ligament Disruption at 25° Knee Flexion: 3D Finite Element Analysis
Authors: Homyk Andrew , Canavan Paul K. , Orsi Alexander , Wibby Story , Yang Nicholas , Nayeb-Hashemi Hamid
Published: May 2012

Anterior cruciate ligament (ACL) disruption is a common injury that is detrimental to an athlete’s quality of life. Determining the mechanisms that cause ACL injury is important in order to develop proper interventions. This study was conducted to provide insight into the specific knee orientations associated with ACL injuries. A failure locus for the ACL was developed by simulating multiple loading scenarios using a 3-D finite element analysis (FEA) model of the knee. The results indicated varus and valgus were more dominant to the ACL injury compared to femoral rotation. The order of MCL failure, ACL failure, and maximum meniscus stress was also determined with respect to time during loading. The results of this study could be used to develop training programs focused on the avoidance of the described combination of movements, which may lead to ACL injury.
Nonlinear Dynamics of MEMS Arches
Authors: Alkharabsheh Sami , Younis Mohammad
Published: May 2012

In this paper, the dynamic response of electrostatically actuated clamped-clamped arch microbeam is investigated when excited by a DC load superimposed to an AC harmonic load. The dynamic analysis is carried out using a Galerkin-based reduced order model along with a shooting technique to find periodic motions and analyzing its stability using a Floquet theory. Results are presented for the cases of primary and super harmonic resonances. We found several nonlinear dynamic phenomena due to the inherent nonlinear electrostatic force and geometric nonlinearity of the arch. These include frequency-amplitude dependence, jumps, tangent bifurcations, coexistence of solutions, and softening and hardening behaviors. The shooting technique showed high robustness in capturing both the stable and unstable states of the system. Hence, it helped clarify vague behaviors that were previously reported using longtime integration of the equations of motion.
Analytical Investigation of Microwave Heating
Authors: Hossan Mohammad Robiul , Dutta Prashanta
Published: May 2012

Microwave heating is very popular and widely used for warming up foodstuffs quickly. However, non-uniform temperature distribution obtained from microwave heating is a major limiting factor for its application outside the food industry. The rapid decay of incident microwave and the potential existence of standing wave are responsible for non-uniform heating. Therefore, it is important to study the coupling between microwave propagation and energy transfer in the system to predict temperature distribution. In this paper, a closed-form analytical solution is presented to predict the temperature distribution within a cylindrical shape foodstuff under microwave heating by solving an unsteady energy equation. The simplified Maxwell’s equation is solved for electric field distribution; Poynting theorem is employed to calculate microwave power from electric field. The results show that the temperature in the body is very sensitive to size and time. This analytical solution can be used to investigate the influence of various parameters on microwave heating.
A Green Heat Transfer Design Project to Introduce Globalization and Society Awareness
Authors: Fleischmann Shirley , Sozen Mehmet , Mokhtar Wael
Published: May 2012

Energy, environmental issues and society awareness are three of the main components in many engineering problems. Engineering Schools use general education courses to address these issues. However, the bridge between the engineering skills and these issues is still a challenge. In the present work, an open-ended design project was used in a senior level Heat Transfer course to address this need. The students were asked to work in teams to design and build a one- or two-person shelter that is built from recycling material and has no active heat source. The shelter should be portable and easily assembled and disassembled using limited tools to match the use in the time of crises or in developing countries. The details of the project are presented and supported by samples from the students’ work.
The Study on PLLA-Nanodiamond Composites for Surgical Fixation Devices
Authors: Zhang Qingwei , Mochalin Vadym , Neitzel Ioannis , Gogotsi Yury , Lelkes Peter I. , Zhou Jack
Published: May 2012

Biopolymers have a great potential in biomedical engineering, having been used as scaffolds for hard and soft tissues, such as bone and blood vessels for many years. More recently biopolymers have also found applications in surgical fixation devices. Compared with conventional metal fixation devices, bone grafts and organ substitutes, biopolymer products have advantages of no long-term implant palpability or temperature sensitivity, predictable degradation to provide progressive bone loading and no stress shielding, all of which leads to a better bone healing, reduced patient trauma and cost, elimination of second surgery for implant removal, and fewer complications from infections. However lack of initial fixation strength and bioactivity are two major concerns which limited more widespread applications of biopolymers in orthopedic surgery. Nanodiamond is attractive for its use in reinforcement of composite materials due to their outstanding mechanical, chemical and biological properties. Nanotechnology shows us many innovations and it is generally accepted view that many could be further developed and applied in tissue engineering. In this work, we conduct poly(L-lactic acid) (PLLA) and octadecylamine functionalized nanodiamond (ND-ODA) composite research to optimize the polymer/ND interface, thus to reinforce the mechanical strength. Composites comprising PLLA matrix with embedded ND-ODA were prepared by mixing PLLA/chloroform solution with chloroform suspension of nanodiamonds at concentrations of 0–10 by weight percent. The dispersion of ND-ODA was observed by transmission electron microscopy (TEM). TEM micrographs show that ND-ODA can disperse uniformly in PLLA till 10% wt. Nanoindentation result shows the mechanical strength of ND-ODA/PLLA composites improving following increasing the concentration of ND-ODA in composites. The noncytotoxicity of ND-ODA was demonstrated on 7F2 Osteoblasts. To test the usefulness of ND-ODA/PLLA composites as scaffolds for supporting cell growth, 7F2 Osteoblasts were cultured on scaffolds for 6 days. The attachment and proliferation of 7F2 on all scaffolds were assessed by fluorescent nuclear staining with Hoechst 33258 and Alamar BlueTM assay. The results showed that the adding ND-ODA does small influence cell growth, which indicates the composites have good biocompatibility. The morphology of 7F2 cells growing on all ND-ODA/PLLA composite scaffolds was determined by SEM, which confirms the Osteoblasts spread on the scaffolds. All these results combined suggest that ND-ODA/PLLA might provide a novel composite suitable for surgical fixation devices.
I35W Bridge Collapse: Design Issues in Past and Challenges Revealed for Future
Authors: Halo Su
Published: May 2012

The past several decades can be remembered as the most successful period for engineering, which has also brought up great challenges to engineers to digest rapidly-developed ideas, new tools, and novel methodologies while to assure industrial designs and daily operations being safe, economic, and technologically advancing. This article discusses some particular issues in structural design, focused on the lessons learned from the highway I35W Bridge’s collapse that occurred at August 1st, 2007, based on a preliminary analysis of this disaster and an associated report submitted to the related administrative agencies [27]. By comparing the results in that report with the materials’ evidences of National Safety Transportation Safety Board (NTSB) official investigation [1,2] and the recent in-depth analyses [28,29], it seems that the issues addressed early may still have certain significance for the safety assessments of those similarly-structured steel bridges today. A bridge’s service life is 75 years or longer. According to a NTSB’s document [37], there are more than hundreds this kind of bridges still on service [4].
The Effect of Thermal Field on the Deposition of Fe-TiC on Carbon Steel Using Laser Cladding
Authors: Alimardani Masoud , Emamian Ali , Khajepour Amir , Corbin Stephen F.
Published: May 2012

In this paper, a numerical and experimental method is used to investigate the effect of thermal fields on the deposition of Fe-TiC using the laser cladding process. Since in laser cladding temperature distributions and consequent rapid cooling rates determine the microstructure and final physical properties of the deposited layers, a 3D time-dependent numerical model is used to simulate the cladding process parallel to experimental analysis. The numerical results are used to study the temperature distributions and their evolutions throughout the deposition process. The experimental and verified numerical outcomes are then employed to study the variations of the microstructures of the deposited material as well as correlation between the formed microstructures and temperature distributions across the deposition domain. The numerical and experimental investigations are conducted through the deposition of Fe-TiC on the substrate of AISI 1030 carbon steel using a 1.1 kW fiber laser. The experimental results confirm that by increasing the substrate temperature throughout the process the distribution of the TiC particles changes along with the deposited tracks and the TiC particles start forming clusters at the top of the clad.
A Fatigue Test to Assess the Deformation Behavior of Dental Implants
Authors: Lee Choongryeong , Jeong Hyun-Yong
Published: May 2012

A purpose of this paper is to analyze the effects of material properties and design of a jig on fatigue test results of dental implants. An implant fatigue test method is specified in ISO14801 [1], but it is not described well about the fatigue test jig. The jig of ISO14801 has to firmly hold the fixture, and the elastic modulus of the jig should be more than 3 GPa. These requirements are not sufficient enough to represent the dental implant in the jawbone because the fixture is osseointegrated in the jawbone that is made up with the cortical bone and cancellous bone. In this paper three different materials were used for the jig, and two different fixation methods to hold the fixture were examined in several FE (Finite Element) simulations and fatigue tests. From the simulation and test results, the effects of material properties and design of the jig were evaluated in the light of fatigue life of dental implants.
Energy Efficiency of a Quasi CPC Concentrating Solar PV/T System
Authors: Cui Wenzhi , Zhao Long , Wu Wei , Wang Ke , Jen Tien-Chien
Published: May 2012

Compound parabolic concentrator (CPC) is a typical non-tracking ideal concentrator sharing the advantages of simple structure and no need of complicated and expensive continue sun-tracking systems, making the system economically attractive in the practical applications. In order to avoid the use of expensive curved mirror, usually used in standard CPC, a quasi CPC consisting of multiple flat mirror segments has been designed. This CPC concentrator is combined with a photovoltaic and thermal (PV/T) collector to be a CPC-PV/T system. The characteristics of solar concentrating and the performance of photovoltaic and photo-thermal energy conversion of the quasi CPC-PV/T have been experimentally studied. The test results show that solar concentrating decreases the electric efficiency of PV module. The total electric output, however, increases. The integrated energy efficiency of this system is above 70%.
Investigation of Interstitial Velocity Field Inside Micro-Porous Media
Authors: Sen Debjyoti , Abdolrazaghi Mona , Nobes David S. , Mitra Sushanta K.
Published: May 2012

An investigation of interstitial velocity field within a micro porous media is studied using a three component three dimensional (3C3D) μ-PIV system. The porous media is formed by packing of micro glass beads of size 400 μm inside a flow cell. The two component two dimensional (2C2D) velocity fields in micro pore region are obtained near the wall. 3C3D velocity field is obtained by scanning through 100 μm inside the porous media using the scanning μ-PIV system. Cross flow pattern and flow recirculation is observed within the micro pore region.
Experimental Investigation of Film Cooling Effectiveness for a New Shaped Hole at the Leading Edge
Authors: Elnady T. , Hassan I. , Kadem L. , Lucas T.
Published: May 2012

An experimental investigation has been performed to study the film cooling of a smooth expansion exit at the leading edge of a gas turbine vane. A two-dimensional cascade has been employed to measure the cooling performance of the proposed expansion using a transient Thermochromatic Liquid Crystal technique. One row of cylindrical holes, located on the stagnation line, is investigated with two expansion levels at the hole exit, 2d and 4d, in addition to the standard cylindrical exit. The air is injected at 0° and 30° inclination angles with the mainstream direction at four blowing ratios ranging from 1 and 2 and a 0.9 density ratio. The Mach number and the Reynolds number based on the cascade exit velocity and the axial chord are 0.23 and 1.4E5, respectively. The detailed local cooling effectiveness over both the pressure side and the suction side are presented in addition to the lateral-averaged cooling effectiveness. The proposed expansion enhances the coolant distribution over the leading edge, particularly over the suction side. The cooling effectiveness increases with the increase of the blowing ratio due to the decrease in the jet lift-off, hence higher cooling capacity is provided. The complete confrontation between both streams on the 0° inclination angle causes a strong dispersion to the coolant, yielding a significant reduction in the effectiveness.
Development of LIGA-Like Process With Positive Photoresist and SU-8
Authors: Lee Yongsu , Kim Jinha , Lee Seokwoo , Lee Seungsub
Published: May 2012

LIGA-Like techniques allows the fabrication of structures with high aspect ratio. SU-8 is a well-known thick photoresist used in this process. However, the remainder of highly cross-linked epoxy after photolithography process is difficult to remove without damage or alteration to electroplated metal due to the high aspect ratio of the structure. Different from SU-8, positive photoresist is easily removed, yet has limitation of fabricating structures with high aspect ratio. In this paper, we present novel LIGA-Like process with positive photoresist to improve above mentioned difficulties. In order to increase a height of positive photoresist, we have introduced SU-8 into the system. SU-8 is used for cast to control the thickness of positive photoresist, and AZ9260 (positive photoresis) is used for electroplating mold. In this suggested process, Donut-shaped SU-8 cast is patterned on the border of substrate to control and increase total height of positive photoresist. AZ9260, a kind of positive photoresist, fills the center of vacant area, and the thickness of the AZ9260 is controlled by height of SU-8 cast during the process of slow spin coating. After spin coating, the system is exposed to natural atmospheric condition for hours to improve surface planarization. The soft baking is carried out in two steps. The purpose of first prebaking is to evaporate large amount of solvent, and second prebaking is to enhance aspect ratios of photoresist. In the process of prebaking, the AZ9260 coated wafer is covered with chalet due to the fast dry process causes wrinkle and bubble on the surface. Through extensive experiments, we have established the condition of spin coating, exposure doses, prebaking and development process in each structure of 150, 200 and 240 μm thickness. Different from the case of SU-8, AZ9260 mold can be effectively removed after electroplating treatment. Finally, we obtain metal structures of 150, 200, 240μm heights corresponding to the mold height (AZ9260). It is shown that SU-8 can be successfully replaced by positive photoresist in LIGA-Like process. Therefore, the suggested fabrication method can be applied to materialize the positive photoresist structures with high aspect ratio in UV lithography process.
Impact Strength Degradation of Adhesive Joints Under Heat and Moisture Environmental Conditions
Authors: Goda Yasuhiro , Sawa Toshiyuki , Himuro Katsuya , Yamamoto Ken-ichi
Published: May 2012

The effects of environmental degradations on the deformation behavior of an epoxy resin for structural adhesive are experimentally examined using an INSTRON-type material testing machine. The effects of environmental degradations on the shear strength of adhesive joints are also examined using an INSTRON-type material testing machine and a split Hopkinson pressure bar apparatus. The results of quasi-static tensile tests for an epoxy resin for structural adhesive shows that the effect of the resistant to heat degradations tests is small on the deformation behavior, while it seems that the yield stress decreases and the elongation after the rupture increases as the degradations day increases in the resistant to moisture degradation tests. The results of quasi-static and impact shear tests for the adhesive joints shows that the effect of the resistant to heat degradations tests is small on the joint strength, while the shear strength decreases as the degradations day increases at any strain rate in the resistant to moisture degradation tests. In addition, the stress distributions at the adhesive interface of adhesive joints are examined using finite element stress analysis. From the numerical results, it is assumed that the joint strength increases as Young’s modulus of the adhesive decreases and the adhesive thickness is 0.25 mm. For verification of the FEA, the loading responses between the experimental and the numerical results are compared. A fairly good agreement is found between the experimental and the numerical results.
An Iterative Feedback Tuning Scheme for the Multiloop PID Control of a UAV
Authors: Ramirez Juan A. , Gutierrez Luis B. , Vasquez Rafael E.
Published: May 2012

An alternative for the steady-level flight control on an Unmanned Aerial Vehicle (UAV) is the use of decentralized multi-loop PID controllers for each controlled variable. PIDs are linear structured low order controllers which are not so easy to tune in the presence of complex dynamics such as multivariable, non-minimum phase, oscillatory and high-order plants; and the use of conventional design techniques based on linearized models usually does not end in satisfactory results. In this work a design scheme based on iterative feedback tuning (IFT) for the multivariable nonlinear model of the Condor Andino UAV (Andean Condor UAV) is addressed. The method proposes the optimization of a quadratic performance target function using the closed loop response obtained from simulations. In this case the characteristics of the model are not used directly in the controller tuning process, but in simulations and in some other numeric manipulations. The optimization process is made using a modified version of the Levenberg-Marquardt algorithm. The simulation results show that a set of controller parameters can be found such that the target function has a local minimum.
The Feasibility of Statistical Energy Analysis in the Modeling of Stringed Musical Instruments
Authors: Mansour Hossein
Published: May 2012

Stringed musical instruments are complex vibrating systems both from structural and fluid-structure coupling perspectives; hence, their modeling is one of the most challenging tasks in the area of vibration and acoustics. Making a reliable model not only broadens our knowledge of the physics of these instruments, but also it simplifies the procedure of structural modification and optimization on them. In this regard, a Finite Element Model has been previously made from Setar and is verified with the experimental results. Although that model could precisely simulate the instrument in lower frequencies (i.e. below 2.5 KHz), its results showed a weak correlation with reality in higher frequencies. In fact, unreliable results and high computational demand are common drawbacks of finite element method in higher frequencies. To avoid these problems, in this study Setar is modeled with Statistical Energy Analysis (SEA) approach. This method is more efficient in dealing with high degree of uncertainty in the system. SEA does this by averaging the response over the frequency and location to gain a more general and reliable result. Application of SEA in higher frequencies is, in fact, compatible with the nature of musical instruments where in higher frequencies we are mostly interested in the trend of the response rather than the location of each individual peak.
Multi-Pulse Chaotic Dynamics for Composite Laminated Plates
Authors: Zhang Jun-Hua , Zhang Wei , Wang Qian
Published: May 2012

The heteroclinic bifurcation and multi-pulse chaotic dynamics of a simply-supported symmetric cross-ply composite laminated rectangular plate with parametric and forcing excitations are investigated in this paper for the first time. The formulas of the simply-supported composite laminated rectangular plate are derived by using Hamilton’s principle and the Galerkin’s approach. The extended Melnikov method is improved to enable us to analyze directly the non-autonomous nonlinear dynamical system, which is applied to the non-autonomous governing equations of motion for the simply-supported composite laminated rectangular plate. The results obtained here indicate that the multi-pulse chaotic motions can occur in the simply-supported composite laminated rectangular plate. Numerical simulation is also employed to find the multipulse chaotic motions of the simply-supported composite laminated rectangular plate.
Powder Injection Molding of Copper and the Effect of Sintering Temperature on Its Mechanical Properties
Authors: Keshavarz Panahi Ali , Khoshkish Hossein
Published: May 2012

In this article, the fabrication steps of copper parts, using the powder injection molding method have been investigated. For the purpose of this study, first, several feedstocks were prepared by mixing copper powder (in volume percentages of 60, 64, 68, and 72%) and a thermoplastic binder. Due to the sensitivity of the mixing stage in the powder injection molding process, the Extrumixing method was utilized to appropriately mix the copper powder with the binder. Rheological characteristics of the different feedstocks were analyzed by means of a capillary rheometer. Based on this analysis, the feedstock having a 68 vol. % copper powder was selected as the optimum powder, out of which, samples shaped like tensile test specimens were successfully molded. These samples were later debinded by the solvent debinding method. Sintering of the pieces was carried out at different temperatures. Research showed that raising the sintering temperature leads to an increase of density and tensile strength of the specimens.
Variable Stiffness Tensioner for a Belt Driven Transmission System
Authors: Farshidi Reza , Mashatan Vahid , Zu Jean W.
Published: May 2012

A new tensioner mechanism is designed for a belt driven transmission system with variable gear ratios. The preliminary design of such transmission system includes a morphing driver pulley, a driven pulley with constant radius, and a tensioner. With the aim of changing the gear ratio, the radius of the morphing pulley (driver) varies gradually through a stepwise shifting procedure. Hence, the geometry of the belt and pulley system, including the tensioner pulley position, changes noticeably while the shifts occur. A regular tensioner, commonly used in the belt and pulley systems, includes a linear spring, which is attached to an idler pulley. This type of tensioner is designed and installed in the transmission systems with respect to the geometry and loading condition in order to guarantee a certain value of static pretension in the belt. The longitudinal vibration of the belt and pulley system is also controlled by setting proper value of tensioner spring stiffness and other dynamic parameters. The regular tensioner is commonly modeled as a linear spring. These tensioners are mainly used for the belt and pulley systems with constant gear ratios. In the case of variable drive system, while the radius of the driver pulley changes, a large displacement in the tensioner pulley position is expected. This large displacement results in large variation into the belt static tension, and might cause unpredicted fatigue failure in the belt or pulleys. Lower values of static tension can cause belt dynamics instability in a belt driven system. [Wickert 1990] A new tensioner is proposed for the morphing pulley transmission system in order to control the static tension and the belt longitudinal vibrations for different gear ratios. The tensioner includes a linear spring that is connected to the tensioner pulley via a convertor mechanism. The convertor system consists of a traveling pin and guide rail mechanism. The traveling pin is connected to the tensioner pulley while the rail is attached to the linear spring. Using this mechanism, the tensioner system behaves like a variable spring element. By defining a proper curve, it is possible to maintain the static tension within the desired range and control the longitudinal vibration of the belt and pulley system. The design parameters of the tensioner system are investigated through a linear optimization process in order to minimize the longitudinal vibration of the belt as well as the pretension.
CFD Simulation of PWR Subchannel Void Distribution Benchmark
Authors: In Wang-Kee , Shin Chang-Hwan , Chun Tae-Hyun
Published: May 2012

A CFD study was performed to simulate the steady-state void distribution benchmark based on the NUPEC PWR Subchannel and Bundle Tests (PSBT). The void distribution benchmark provides measured void fraction data over a wide range of geometrical and operating conditions in a single subchannel and fuel bundle. This CFD study simulated the boiling flow in a single subchannel. A CFD code was used to predict the void distribution inside the single subchannel. The multiphase flow model used in this CFD analysis was a two-fluid model in which liquid (water) and vapor (steam) were considered as continuous and dispersed fluids, respectively. A wall boiling model was also employed to simulate bubble generation on a heated wall surface. The CFD prediction with a small diameter of vapor bubble shows a higher void fraction near the heated wall and a migration of void in the subchannel gap region. A measured CT image of void distribution indicated a locally higher void fraction near the heated wall for the test conditions of a subchannel averaged void fraction of less than about 20%. The CFD simulation predicted a subchannel averaged void fraction and fluid density which agree well with the measured ones for a low void condition.
Non-Newtonian Elastohydrodynamic Lubrication Fluid Flow Modeling of Piston Skirts Considering Low Speed Effects in Initial Engine Start Up
Authors: Qasim Syed Adnan , Malik M. Afzaal , Chaudhri Usman F. , Mufti Riaz A.
Published: May 2012

Elastohydrodynamic lubrication (EHL) is critically essential to minimize engine wear at low engine start up speeds. During the normal engine operations at medium to high speeds, non-Newtonian characteristics of multigrade engine lubricants enhance engine life by preventing adhesive wear. By incorporating viscoelastic effects of a non-Newtonian lubricant and focusing on different low engine start up speeds, this study models EHL fluid flow in the initial engine start up conditions. A 2-D non-Newtonian piston skirts lubrication model and analysis at the time of engine start up is presented based on the upper convected Maxwell viscoelastic model. The analysis of a non-Newtonian lubricant between piston and cylinder liner by using characteristic lubricant relaxation times in all order of magnitude analysis is done by using a perturbation method. The EHL film profile is predicted by solving the two-dimensional Reynolds equation using the inverse solution technique and the finite difference computational method in the fully flooded lubrication conditions. At different low engine start up speeds, the effect of viscoelasticity on lubricant velocity and pressure fields is examined and the influence of film thickness on lubricant characteristics is investigated. Numerical simulations show that piston eccentricities, EHD pressures and film thickness profiles are functions of low range of engine start up speeds. This study suggests that the initial engine start up speed at low range can be optimized as viscoelasticity produces a beneficial effect on piston skirt lubrication in the initial engine start up.
Belt Drive Mechanics With Absolute Nodal Coordinate Finite Element Verification
Authors: Hussein Muhammad M. , Metwalli Sayed M. , Mohamed Abdel-Nasser A. , Shabana Ahmed A.
Published: May 2012

This paper presents preliminary analytical and numerical procedures for the analysis of the motion of extensible belt/pulley systems. These procedures can be used to accurately predict the change in the belt velocity, tension force, normal force, friction force and the cross section deformations along the belt length at the steady state condition. The methods used in this paper relax the assumption of constant shear and internal moment along the belt length, leading to more accurate results as compared to the results obtained using previous models. The analytical solution obtained in this paper is validated by comparing it with the solution obtained using absolute nodal coordinate formulation (ANCF) finite elements. It is shown that considering the effect of the internal moment and assuming that the contact between the belt and the pulley has three stages lead to more realistic prediction of the belt system variables and more accurate values for the angles in the belt/pulley sliding zones. The change in the angular velocity of the driven pulley with respect to the driving pulley, the change in the cross section dimensions, and the belt stretch are predicted. The results obtained in this study also demonstrate that formulations presented in this paper lead to more accurate prediction for the belt tension, friction and normal forces. ANCF structural finite elements provide more general kinematic description that can be used to predict the cross section deformation and its coupling with the extension and bending of the belts and rubber chains.
Determination of Condensation Heat Transfer Characteristics of R134A by Means of Artificial Intelligence Method
Authors: Balcilar Muhammet , Dalkilic¸ Ahmet Selim , Wongwises Somchai
Published: May 2012

The present study investigates the best artificial neural network (ANN) approach to estimate the measured convective heat transfer coefficient of R134a flowing downward inside a vertical smooth copper tube having an inner diameter of 8.1mm and a length of 500mm during annular flow numerically. R134a and water are used as working fluids in the tube side and annular side of a double tube heat exchanger, respectively. Experimental data, used as the ANN training set, came from intube condensation tests including three different mass fluxes of R134a such as 260, 340 and 456 kg m−2s−1, two different saturation temperatures of R134a such as 40 and 50 °C and heat fluxes ranging from 10.83 to 50.89 kW m−2. Accuracy of the dataset was proven in many papers in the literature. The quality of the refrigerant in the test section is calculated considering the temperature and pressure obtained from the experiment. The pressure drop across the test section is directly measured by a differential pressure transducer. Measured values of test section such as mass flux, heat flux, the temperature difference between the tube wall and saturation temperature, average vapor quality are assigned as input of the ANNs, while the experimental condensation heat transfer coefficient and measured pressure drop are specified as the output in the analysis. The artificial neural network (ANN) methods of multi-layer perceptron (MLP), radial basis networks (RBFN), generalized regression neural network (GRNN) and adaptive neuro-fuzzy inference system (ANFIS) were used to decide the best approach for modeling condensation heat transfer characteristics of R134a. 183 data points obtained in the experiments are divided into two sets randomly. Sets of test and training/validation are including 33 and 120/30 data points respectively. In training phase, 5-fold cross validation is used for determine the best value of ANNs control parameters. The ANNs performances were measured by mean relative error criteria with the usage of unknown test sets. The performance of the method of multi layer perceptron (MLP) with 5-13-1 architecture and radial basis function networks (RBFN) with the spread coefficient (sp) of 40000 were found to be superior to other methods and architectures by means of satisfactory results with their deviations within the range of ±0.58% for the estimated condensation heat transfer coefficient and ±1.74% for the estimated pressure drop respectively.
Formability Limits and Microstructural Features of Parts Made by Single-Point Incremental Forming
Authors: Bosetti Paolo , Bruschi Stefania
Published: May 2012

Single-point incremental sheet forming processes represent today a promising alternative to traditional sheet forming operations for producing low batches or even prototypes without the use of expensive dies. Several investigations have been carried out in recent years to study the fundamental aspects of incremental sheet forming operations, with particular attention to determination of material formability. In this framework, the Authors propose to study the material tendency to be formed by incremental forming, called SPIFability, through different indicators, and to evaluate this tendency as a function of the process parameters, with particular regard to the relative velocity between the tool and the blank. Other reported studies — based on both experimental and numerical studies — have tried to give a comprehensive explanation of the deformation mechanisms that arise during incremental sheet forming, and that possibly affect the material formability. However, none of the proposed theories are today fully accepted by the scientific community. In order to study the relevant deformation mechanisms, the Authors propose to analyze the microstructural characteristics of the formed parts by means of optical microscopy and the fracture surfaces by means of scanning electron microscopy. The investigated case study is an axi-symmetric part characterized by a varying slope with depth, made from blanks of the aluminum alloy AA5182. The parts were formed on a CNC machine until the first crack appeared, and then were measured by means of a Coordinate Measuring Machine to evaluate their thickness profile and geometrical parameters.
Molecular/Mechanical Dynamics Simulations With Nonholonomic Constraints
Authors: Chen Po-Chih , Chang Chia-Ou , Chang Chien Wen-Tien , Chou Chan-Shin
Published: May 2012

In this paper a new method of incorporating linear/nonlinear nonholonomic constraints into the mechanical/molecular dynamical systems is presented. We first introduce the mass-weighted coordinates such that acceleration and forces are scaled to have the same units, and can be operated in the same space. Then we use the projector formalism and Gauss’s principle of least constraint to derive the constraint force in the explicit form so that the equations of motion are free of Lagrange multipliers. The use of mass-weighted coordinates enable the equation of the constraint forces to be expressed in terms of first generalized inverse of constraint matrix rather than the two-time generalized inverse of matrices used in the recent works. An algorithm of numerical integration for ensuring the satisfaction of constraint equations and avoiding the numerical drift is proposed. Two simple examples, constant kinetic energy (or temperature) and time-varying prescribed kinetic energy of three-particle dynamical system effectively verify our method.