Advances in Mechanical Engineering The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Effects of Annealing on TiN Thin Film Growth by DC Magnetron Sputtering Thu, 24 Jul 2014 14:09:07 +0000 We have reviewed the deposition of titanium nitride (TiN) thin films on stainless steel substrates by a DC magnetron sputtering method and annealing at different annealing temperatures of 500, 600, and 700°C for 120 min in nitrogen/argon atmospheres. Effects of annealing temperatures on the structural and the optical properties of TiN films were investigated using X-ray diffraction (XRD), atomic force microscope (AFM), field emission scanning electron microscopy (FESEM), and UV-VIS spectrophotometer. Our experimental studies reveal that the annealing temperature appreciably affected the structures, crystallite sizes, and reflection of the films. By increasing the annealing temperature to 700°C crystallinity and reflection of the film increase. These results suggest that annealed TiN films can be good candidate for tokamak first wall due to their structural and optical properties. Azadeh Jafari, Z. Ghoranneviss, A. Salar Elahi, M. Ghoranneviss, N. Fasihi Yazdi, and A. Rezaei Copyright © 2014 Azadeh Jafari et al. All rights reserved. Applications of the Exponential Function of the Euclidean Motion Group to the Theory of Gearing Thu, 24 Jul 2014 12:51:31 +0000 The present paper provides a first step to a new approach to the theory of gearing, which uses modern differential geometry in order to ensure a strict and coordinate-independent formulation. Here, we are mainly concerned with a basic equation, namely, the equation of meshing, of two rotating surfaces in mesh. Since we are able to solve this equation by the time parameter, we derive parameterizations of the mating pinion from a bevel gear as well as a parameterization for gears produced by special machine tools. Baozhen Lei, Harald Löwe, and Xunwei Wang Copyright © 2014 Baozhen Lei et al. All rights reserved. Experimental Research and Numerical Simulation of Wing Boxes under Pure Bending Load Thu, 24 Jul 2014 00:00:00 +0000 Two full-scale wing boxes with different types of butt joints were investigated under pure bending load, and numerical methods, including global analysis and detailed analysis, were proposed to determine the reasons for failure of the wing boxes. Wing boxes were tested under bending loads applied by a multichannel force control system. The experimental results showed that the region of the butt joint was the weakest location of the wing boxes, and the damage loads were far less than the design load. The global analysis and detailed analysis were carried out on the wing boxes, focusing on the region of the butt joint, to determine the reasons for failure. Global analysis in explicit dynamic modulus was adopted to simulate the loading process of the two wing boxes. Meanwhile, detailed finite element models created in Patran/Nastran were used to evaluate the stability. Comparing experimental results with numerical counterparts, it is shown that the failure of the wing boxes is induced by local buckling occurring around the butt joint. In addition, the wing box that uses butt joints with lap jointed sheets is more rigid than that without lap jointed sheets, and the stress distribution is more uniform. The numerical analysis proposed by the paper can help with structure design in preliminary assessment. Peiyan Wang, Shile Yao, Xinmei Wang, and Zhufeng Yue Copyright © 2014 Peiyan Wang et al. All rights reserved. The Effects of Different Fuels on Wear between Piston Ring and Cylinder Wed, 23 Jul 2014 12:52:10 +0000 In internal combustion engines, mechanical friction occurs between engine components in contact with each other, leading to wear and important loss of efficiency. Mechanical energy absorbed by piston ring-cylinder pair in piston engines accounts for the largest portion of efficiency losses due to mechanical friction. Different engine lubrication regimes significantly affect wear and friction. In addition to selection of compatible materials, improvement of operational conditions and the properties of lubricants and fuels are of great importance to minimize wear. This study investigated the effects of oil, diesel fuel, oil + diesel fuel, and two different biodiesel fuels (SOME: sunflower oil methyl ester and TSOME: tobacco seed oil methyl ester) as engine lubricants and their effects on wear in piston ring-cylinder pair. The tests were carried out at different engine speeds and loads. Minimum wear occurred when using engine oil as lubricant, and maximum wear occurred when using diesel fuel as lubricant. The use of SOME and TSOME lubricant resulted in half the amount of engine wear, on average, compared to diesel. İdris Cesur, Vezir Ayhan, Adnan Parlak, Ömer Savaş, and Zafer Aydin Copyright © 2014 İdris Cesur et al. All rights reserved. Design Optimization of Composite Elliptical Deep-Submersible Pressure Hull for Minimizing the Buoyancy Factor Wed, 23 Jul 2014 08:38:18 +0000 The design of deep submersible pressure hull’s structural is one of the core technologies of submersible development of human history. Submersible pressure hulls with fiber-reinforced multilayer constructions have been developed in the recent years as substitutes for classical metallic ring-stiffened pressure hulls; strength and stability are its top priority. This paper investigates the optimum design of a composite elliptical deep-submerged pressure hull under hydrostatic pressure to minimize the buoyancy factor of the submersible pressure hull under constraints on the failure criteria and the buckling strength of the hulls to reach the maximum operating depth. The thickness and the fiber orientation angles in each layer, the radii of the ellipse, and stringers dimensions were taken as design variables and determined in the design process. The optimization procedures are performed using commercial finite element analysis software ANSYS. Additionally, a sensitivity analysis is performed to study the influence of the design variables on the structural optimum design. Results of this study provide a valuable reference for designers of underwater vehicles. Elsayed Fathallah, Hui Qi, Lili Tong, and Mahmoud Helal Copyright © 2014 Elsayed Fathallah et al. All rights reserved. The Numerical Investigation of Temperature and Velocity Distribution in the High-Bay Depot Wed, 23 Jul 2014 07:17:40 +0000 High-bay depot plays an important role in the storage industry. Due to large and high space of high-bay depot, it is difficult to make temperature distribution uniform, which will influence the storage time of raw materials. In this paper, the aim is to find the reasonable air supply and energy-saving method; a supply-air method of high-bay depot is investigated as an example. The results show the radius and spacing of the supply-air inlet have great influence on temperature distribution. The temperature nonuniformity coefficient of summer is smaller than that of winter. The investigated results can provide a theoretical reference for the high-bay depot design and economic operation. Xuehong Wu, Jianbiao Dai, Hao Meng, Yanli Lu, and Zhijuan Chang Copyright © 2014 Xuehong Wu et al. All rights reserved. Modeling and Parameter Identification of the Vibration Characteristics of Armature Assembly in a Torque Motor of Hydraulic Servo Valves under Electromagnetic Excitations Wed, 23 Jul 2014 00:00:00 +0000 The resonance of the armature assembly is the main problem leading to the fatigue of the spring pipe in a torque motor of hydraulic servo valves, which can cause the failure of servo valves. To predict the vibration characteristics of the armature assembly, this paper focuses on the mathematical modeling of the vibration characteristics of armature assembly in a hydraulic servo valve and the identification of parameters in the models. To build models more accurately, the effect of the magnetic spring is taken into account. Vibration modal analysis is performed to obtain the mode shapes and natural frequencies, which are necessary to implement the identification of damping ratios in the mathematical models. Based on the mathematical models for the vibration characteristics, the harmonic responses of the armature assembly are analyzed using the finite element method and measured under electromagnetic excitations. The simulation results agree well with the experimental studies. Jinghui Peng, Songjing Li, and Yongbo Fan Copyright © 2014 Jinghui Peng et al. All rights reserved. Heat Transfer Enhancement by Using Different Types of Inserts Wed, 23 Jul 2014 00:00:00 +0000 Heat transfer enhancement has been always a significantly interesting topic in order to develop high efficient, low cost, light weight, and small heat exchangers. The energy cost and environmental issue are also encouraging researchers to achieve better performance than the existing designs. Two of the most effective ways to achieve higher heat transfer rate in heat exchangers are using different kinds of inserts and modifying the heat exchanger tubes. There are different kinds of inserts employed in the heat exchanger tubes such as helical/twisted tapes, coiled wires, ribs/fins/baffles, and winglets. This paper presents an overview about the early studies on the improvement of the performance of thermal systems by using different kinds of inserts. Louvered strip insert had better function in backward flow compared to forward one. Modifying the shape of twisted tapes led to a higher efficiency in most of the cases excpet for perforated twisted tape and notched twisted tape. Combination of various inserts and tube with artificial roughness provided promising results. In case of using various propeller types, heat transfer enhancement was dependent on higher number of blades and blade angle and lower pitch ratio. S. Tabatabaeikia, H. A. Mohammed, N. Nik-Ghazali, and B. Shahizare Copyright © 2014 S. Tabatabaeikia et al. All rights reserved. Drag Reduction by Microvortexes in Transverse Microgrooves Wed, 23 Jul 2014 00:00:00 +0000 A transverse microgrooved surface was employed here to reduce the surface drag force by creating a slippage in bottom layer in turbulent boundary layer. A detailed simulation and experimental investigation on drag reduction by transverse microgrooves were given. The computational fluid dynamics simulation, using RNG k- turbulent model, showed that the vortexes were formed in the grooves and they were a main reason for the drag reduction. On the upside of the vortex, the revolving direction was consistent with the main flow, which decreased the flow shear stress by declining the velocity gradient. The experiments were carried out in a high-speed water tunnel with flow velocity varying from 17 to 19 m/s. The experimental results showed that the drag reduction was about 13%. Therefore, the computational and experimental results were cross-checked and consistent with each other to prove that the presented approach achieved effective drag reduction underwater. Bao Wang, Jiadao Wang, Gang Zhou, and Darong Chen Copyright © 2014 Bao Wang et al. All rights reserved. Comparison of Measured Residual Stress Distributions in Extra-Thick Butt Welds Joined by One-Pass EGW and Multipass FCAW Tue, 22 Jul 2014 10:08:21 +0000 This study is to measure the welding residual stress distributions in a 70 mm-thick butt weld by one-pass electron gas welding using both the inherent strain method and neutron diffraction method, respectively. Based on the measurement results, the characteristics of residual stress distribution through thickness were compared between one-pass electron gas welding and multipass flux-cored arc welding. Residual stresses in the specimens of electron gas welding measured by the inherent strain method and neutron diffraction method were well matched. The longitudinal residual stress in the multi-pass flux-cored arc welding is tensile through all thicknesses in the welding fusion zone. Meanwhile, longitudinal residual stress in electron gas welding is tensile on both surfaces and compressive at the inside of the plate. The magnitude of residual stresses due to electron gas welding is lower than that due to flux-cored arc welding. Jeong-Ung Park, GyuBaek An, Wan Chuck Woo, Jae-hyouk Choi, and Ninshu Ma Copyright © 2014 Jeong-Ung Park et al. All rights reserved. Theoretical Simulation Study on Controlling Factors in Horizontal Well CO2 Stimulation of Heavy Oil Tue, 22 Jul 2014 00:00:00 +0000 Since CO2 Stimulation in Horizontal Wells can avoid the problem of steam flooding, clay swelling, and sand production, it has been carried out in many fields. To improve the research on the controlling factors and their influence and establish a specific reservoir selecting method, this paper founded the components and geology model according to typical heavy oil reservoirs firstly. Comparing with pilot test, the theoretical model result could give expression to the characteristic of large water ratio descend rang, long period of validity, and high rounds effectiveness. Secondly, this study designed simulation scheme including factors of geology, development, and stimulation technology, to filter the controlling factors of the oil incremental and well reopened water cut and describe their influence. Based on it, we proposed a quick filter criterion to choose heavy oil reservoirs for CO2 stimulation. Tongjing Liu, Pengxiang Diwu, Baoyi Jiang, Liwu Jiang, and Rui Liu Copyright © 2014 Tongjing Liu et al. All rights reserved. Large Eddy Simulation of the Subcritical Flow over a U-Grooved Circular Cylinder Tue, 22 Jul 2014 00:00:00 +0000 With the aim of numerically replicating a drag reduction phenomenon induced by grooves presence, this paper presents a comparative large eddy simulation study of the flow over a smooth circular cylinder, and the flow over a U-grooved cylinder, at , which is near transition between the subcritical and critical flow regimes. The grid densities were 2.6 million cells and 20.7 million cells for the smooth and the U-grooved cylinder, respectively. Both meshes were composed of hexahedral cells disposed in a structured form with additional refinements in near-wall regions, in order to obtain values. The cases were simulated during 25 vortex shedding cycles with the purpose of obtaining significant statistic data through the commercial software FLUENT V.12.1, which solved the Navier-Stokes equations in their unsteady and incompressible forms. Regarding the U-grooved cylinder flow, parameters such as the drag coefficient, lengths of recirculation, the transition from subcritical to critical flow, and the formation of a wake formed by secondary vortices of smaller sizes were predicted satisfactorily by the LES technique. From the manner in which the flow separates at different angles for both valleys and peaks of the U-grooves, a distinctive transitional mechanism induced by grooves presence is conjectured. A. Alonzo-García, C. del C. Gutiérrez-Torres, and J. A. Jiménez-Bernal Copyright © 2014 A. Alonzo-García et al. All rights reserved. Development of Delta Wing Aerodynamics Research in Universiti Teknologi Malaysia Low Speed Wind Tunnel Mon, 21 Jul 2014 11:04:39 +0000 This paper presents wind tunnel experiment on two delta wing configurations which are differentiated by their leading edge profiles: sharp and round-edged wings. The experiments were performed as a part of the delta wing aerodynamics research development in Universiti Teknologi Malaysia, low speed tunnel (UTM-LST). Steady load balance and flow visualization tests were conducted at Reynolds numbers of 0.5, 1, and 1.5 × 106, respectively. The flow measurement at low Reynolds number was also performed at as low as speed of 5 m/s. During the experiments, laser with smoke flow visualizations test was performed on both wings. The study has identified interesting features of the interrelationship between the conventional leading edge primary vortex and the occurrence and development of the vortex breakdown above the delta wings. The results conclude the vortex characteristics are largely dependent on the Reynolds number, angle of attack, and leading-edge radii of the wing. Shabudin Mat, I. S. Ishak, Tholudin Mat Lazim, Shuhaimi Mansor, Mazuriah Said, Abdul Basid Abdul Rahman, Ahmad Shukeri Mohd. Kamaludim, and Romain Brossay Copyright © 2014 Shabudin Mat et al. All rights reserved. Optimization Design of a Double-Channel Pump by Means of Orthogonal Test, CFD, and Experimental Analysis Mon, 21 Jul 2014 08:45:14 +0000 A new approach to optimizing a double-channel pump was presented, based on combined use of orthogonal test, computational fluid dynamics (CFD), and experimental analysis. First, a preliminary pump was designed according to design specifications, implementing the traditional design method. Later, a standard (34) orthogonal table including 9 representative design schemes was implemented to find the best parameter combination for the impeller of the pump. Reynolds averaged Navier-Stokes equations accompanied by Smith modified turbulence model were solved to obtain the inner flow fields of the pump as well as its hydraulic performance for each design scheme. The optimized design scheme was obtained after range analysis. Finally, CFD analyses and experiments were carried out to evaluate the optimized design. The results show that the characteristics of the optimized pump were obviously improved, and the simulated pump head and efficiency increased by 3.622% and 9.379%, respectively. This research not only provides an effective way to improve the hydraulic design of double-channel pumps, but also has certain reference value in multiobjective optimization design of other pumps. Binjuan Zhao, Douhua Hou, Huilong Chen, Yu Wang, and Jing Qiu Copyright © 2014 Binjuan Zhao et al. All rights reserved. Cloud Manufacturing Service Paradigm for Group Manufacturing Companies Sun, 20 Jul 2014 11:22:16 +0000 The continuous refinement of specialization requires that the group manufacturing company must be constantly focused on how to concentrate its core resources in special sphere to form its core competitive advantage. However, the resources in enterprise group are usually distributed in different subsidiary companies, which means they cannot be fully used, constraining the competition and development of the enterprise. Conducted as a response to a need for cloud manufacturing studies, systematic and detailed studies on cloud manufacturing schema for group companies are carried out in this paper. A new hybrid private clouds paradigm is proposed to meet the requirements of aggregation and centralized use of heterogeneous resources and business units distributed in different subsidiary companies. After the introduction of the cloud manufacturing paradigm for enterprise group and its architecture, this paper presents a derivation from the abstraction of paradigm and framework to the application of a practical evaluative working mechanism. In short, the paradigm establishes an effective working mechanism to translate collaborative business process composed by the activities into cloud manufacturing process composed by services so as to create a foundation resulting in mature traditional project monitoring and scheduling technologies being able to be used in cloud manufacturing project management. Jingtao Zhou and Mingwei Wang Copyright © 2014 Jingtao Zhou and Mingwei Wang. All rights reserved. 3D Acoustic Modelling of Dissipative Silencers with Nonhomogeneous Properties and Mean Flow Sun, 20 Jul 2014 08:05:15 +0000 A finite element approach is proposed for the acoustic analysis of automotive silencers including a perforated duct with uniform axial mean flow and an outer chamber with heterogeneous absorbent material. This material can be characterized by means of its equivalent acoustic properties, considered coordinate-dependent via the introduction of a heterogeneous bulk density, and the corresponding material airflow resistivity variations. An approach has been implemented to solve the pressure wave equation for a nonmoving heterogeneous medium, associated with the problem of sound propagation in the outer chamber. On the other hand, the governing equation in the central duct has been solved in terms of the acoustic velocity potential considering the presence of a moving medium. The coupling between both regions and the corresponding acoustic fields has been carried out by means of a perforated duct and its acoustic impedance, adapted here to include absorbent material heterogeneities and mean flow effects simultaneously. It has been found that bulk density heterogeneities have a considerable influence on the silencer transmission loss. E. M. Sánchez-Orgaz, F. D. Denia, J. Martínez-Casas, and L. Baeza Copyright © 2014 E. M. Sánchez-Orgaz et al. All rights reserved. Hemodynamics Modeling and Simulation of Anterior Communicating Artery Aneurysms Thu, 17 Jul 2014 12:27:03 +0000 It is a general agreement that hemodynamics plays very important role in the initiation, growth, and rupture of cerebral aneurysms and hemodynamics in the anterior communicating artery aneurysms is considered the most complex in all cerebral aneurysms and it is difficult to find some reasonable relationship between the hemodynamics parameters and the rupture risk. In this paper, the 3D geometries of four anterior communicating artery aneurysms were generated from the CTA data and the computational models with bilateral feeding arteries for the four aneurysms were constructed. The blood flow was simulated by computational fluid dynamics software and the hemodynamics parameters such as velocity, wall shear stress, and oscillatory shear index were calculated. The following results were observed: one of the four models only needs the left feeding artery; the max normalized wall shear stress locates at the aneurysmal neck of the largest aneurysm; the max oscillatory shear index locates at the aneurysmal sac of the largest aneurysm. The conclusion was drawn that the anterior communicating artery aneurysm has higher rupture risk from the hemodynamics viewpoint if the max wall shear stress locates at the neck and the max oscillatory shear index locates at the dome. Jianjun Li, Shengzhang Wang, Gang Lu, and Xiaolong Zhang Copyright © 2014 Jianjun Li et al. All rights reserved. Prediction of Mass Transfer Time Relaxation Parameter for Boiling Simulation on the Shell-Side of LNG Spiral Wound Heat Exchanger Thu, 17 Jul 2014 10:47:37 +0000 The objective of this present study is to propose an approach to predict mass transfer time relaxation parameter for boiling simulation on the shell-side of LNG spiral wound heat exchanger (SWHE). The numerical model for the shell-side of LNG SWHE was established. For propane and ethane, a predicted value of mass transfer time relaxation parameter was presented through the equivalent evaporation simulations and was validated by the Chisholm void fraction correlation recommended under various testing conditions. In addition, heat transfer deviations between simulations using the predicted value of mass transfer time relaxation parameter and experiments from Aunan were investigated. The boiling characteristics of SWHE shell-side were also visualized based on the simulations with VOF model. The method of predicting mass transfer time relaxation parameter may be well applicable to various phase change simulations. Zhi-Yong Wu, Wei-Hua Cai, Guo-Dong Qiu, and Yi-Qiang Jiang Copyright © 2014 Zhi-Yong Wu et al. All rights reserved. Flow of a Maxwell Fluid between Two Porous Disks Rotating about Noncoincident Axes Thu, 17 Jul 2014 09:24:31 +0000 This paper is concerned with the steady flow of a Maxwell fluid between two porous disks rotating with the same angular velocity about noncoincident axes normal to the disks. An exact solution to the problem depending on the Deborah number, the suction/injection velocity parameter, and the Reynolds number is obtained. It is shown that the core of fluid tends to rotate about the -axis that characterizes the line in equal distance to the two axes of rotation when the Deborah and Reynolds numbers increase and a thinner boundary layer occurs in the region adjacent to the top disk when the axial velocity of fluid that is based on the suction/injection velocity parameter is upward. In addition, an approximate solution is presented for small Deborah numbers. The comparison between the exact and approximate solutions is given and found to be in excellent agreement. H. Volkan Ersoy Copyright © 2014 H. Volkan Ersoy. All rights reserved. Flow Mode Magnetorheological Dampers with an Eccentric Gap Thu, 17 Jul 2014 07:54:35 +0000 This paper analyzes flow mode magnetorheological (MR) dampers with an eccentric annular gap (i.e., a nonuniform annular gap). To this end, an MR damper analysis for an eccentric annular gap is constructed based on approximating the eccentric annular gap using a rectangular duct with a variable gap, as well as a Bingham-plastic constitutive model of the MR fluid. Performance of flow mode MR dampers with an eccentric gap was assessed analytically using both field-dependent damping force and damping coefficient, which is the ratio of equivalent viscous field-on damping to field-off damping. In addition, damper capabilities of flow mode MR dampers with an eccentric gap were compared to a concentric gap (i.e., uniform annular gap). Young-Tai Choi and Norman M. Wereley Copyright © 2014 Young-Tai Choi and Norman M. Wereley. All rights reserved. Direct Numerical Simulation and Visualization of Biswirling Jets Thu, 17 Jul 2014 00:00:00 +0000 Two parallel swirling/rotating jets with a distance between them are termed biswirling jets here, which have important and complicated vortex structures different from the single swirling jet due to the negligible vortex-vortex interactions. The visualization of vortex-vortex interaction between the biswirling jets is accomplished by using direct numerical simulation. The evolution of vortex structures of the biswirling jets is found rather complicated. The turbulent kinetic energy and turbulence dissipation in the central convergence region are augmented locally and rather strongly. The modulation of turbulent kinetic energy by jet-jet interaction upon different scales of vortices is dominated by the swirling levels and the distance between the jets. The turbulent kinetic energy upon intermediate and small scale vortices in bijets with not very high swirling level and at a very close distance is smaller than that in single swirling jets, whereas the opposite is true under a far distance, and so forth. Jie Yan, Nan Gui, Gongnan Xie, and Jinsen Gao Copyright © 2014 Jie Yan et al. All rights reserved. Dynamic Characteristics Analysis of Power Shift Control Valve Wed, 16 Jul 2014 12:50:42 +0000 In order to study the influence that dynamic performance of shift control valve has on shifting process of construction machinery, the paper introduces working principle of the shift control valve and sets up the dynamically mathematical model and corresponding simulation model with simulation software LMS Imagine. Lab AMESim. Based on simulation, the paper analyzes the influence of pressure variation characteristics and buffering characteristics acting on vehicle performance during the process of shifting, meanwhile conducting experiments to verify the simulation. The results indicate that the simulation model is accurate and credible; the performance of the valve is satisfactory, which indeed reduces impact during shifting. Furthermore, the valve can meet the demand of other construction machineries in better degree by suitable matching between control spring stiffness and damping holes diameter. Feng Ren, Xinhui Liu, Jinshi Chen, Ping Zeng, Boliang Liu, and Qinmeng Wang Copyright © 2014 Feng Ren et al. All rights reserved. Advances in Cable-Driven Parallel Manipulators Wed, 16 Jul 2014 12:40:06 +0000 Xiaoqiang Tang, Dengfeng Sun, and Yuanying Qiu Copyright © 2014 Xiaoqiang Tang et al. All rights reserved. The Optimum Wavelet Base of Wavelet Analysis in Coal Rock Microseismic Signals Wed, 16 Jul 2014 12:39:28 +0000 Coal rock rupture microseismic signal is characterized by time-varying, nonstationary, unpredictability, and transient property. Wavelet transform is an important method in microseismic signals processing. However, different wavelet bases yield different results when analyzing the same signal. To study the comparability of different wavelet bases in analyzing microseismic signals, the current paper uses the microseismic signals released from coal rock bursting as the research subject. Through the analysis of the properties of commonly used wavelet basis functions and the characteristics of coal rock microseismic signals, the current study found that Coiflet and Symlet wavelets are suitable for analyzing coal rock microseismic signals. Sym 8 and Coif 2 wavelets were found to be suitable for analyzing and denoising coal rock microseismic signals. After Sym 8 wavelet denoising, signal-to-noise ratio (SNR) and the root mean square error were 30.4184 and , respectively. After Coif 2 wavelet denoising, the SNR and the root mean square error values were 35.2176 and , respectively. The results will aid in the analysis and extraction of coal rock microseismic signals. Shoufeng Tang, Minming Tong, and Xinmin He Copyright © 2014 Shoufeng Tang et al. All rights reserved. A Method to Characterize the Quality of a Polymer Laser Sintering Process Wed, 16 Jul 2014 12:02:32 +0000 The reproducibility and reliability of quality aspects are an important challenge of the polymer laser sintering process. However, existing quality concepts and standardization activities considering influencing factors along the whole process chain have not been validated experimentally yet. In this work, these factors are analyzed and kept constant to obtain a reliable material data set for different layer thicknesses and testing temperatures. In addition, material qualities regarding powder ageing effects are analyzed using different build heights and layer thicknesses: while an increase of the layer thickness reduces mechanical part strength and density, it also results in a less intense thermal ageing of unmolten powder due to shorter build times. Stefan Rüsenberg, Stefan Josupeit, and Hans-Joachim Schmid Copyright © 2014 Stefan Rüsenberg et al. All rights reserved. A Numerical Approach to Determine Attitude Dynamics of Floating Bodies with Irregular Configurations Wed, 16 Jul 2014 11:58:03 +0000 This study acquires the attitude dynamics of floating bodies with irregular configurations using an effective computational model, which has been validated theoretically and verified by experiments. By comparison a correlation formula was described to predict inclinations for the floating slender body imitating an excise torpedo. Thereafter a computational model was developed to account for bodies with attitudes in more general situations. For demonstration, a submersible was simulated to reveal that the inclinations vary abruptly around certain longitudinal locations of center of gravity. The property variations during water ingress assumption were presented. Similar to the virtue tank, an innovative concept of building the numerical data base for a specific floating body has been proposed, by which the position of its center of gravity can be obtained by interpolation from attitude data in tables as determined by the present computational model. Jiann-Lin Chen, Li-Ming Chu, and Chan-Chuan Wen Copyright © 2014 Jiann-Lin Chen et al. All rights reserved. On the Flow Instabilities and Turbulent Kinetic Energy of Large-Scale Francis Hydroturbine Model at Low Flow Rate Conditions Wed, 16 Jul 2014 11:46:11 +0000 This paper is to make a better understanding of the flow instabilities and turbulent kinetic energy (TKE) features in a large-scale Francis hydroturbine model. The flow instability with aspect of pressure oscillation and pressure-velocity correlation was investigated using large eddy simulation (LES) method along with two-phase cavitation model. The numerical simulation procedures were validated by the existing experimental result, and further the TKE evolution was analyzed in a curvilinear coordinates. By monitoring the fluctuating pressure and velocities in the vanes’ wake region, the local pressure and velocity variations were proven to have a phase difference approaching , with a reasonable cross-correlation coefficient. Also the simultaneous evolution of pressure fluctuations at the opposite locations possessed a clear phase difference of , indicating the stresses variations on the runner induced by pressure oscillation were in an odd number of nodal diameter. Considering the TKE generation, the streamwise velocity component contributed the most to the TKE, and thus the normal stress production term and shear stress production term imparted more instability to the flow than other production terms. Wen-Tao Su, Xiao-Bin Li, Feng-Chen Li, Xian-Zhu Wei, Jin-Tao Liu, and Yu-Lin Wu Copyright © 2014 Wen-Tao Su et al. All rights reserved. Advances in Propulsive Bionic Feet and Their Actuation Principles Wed, 16 Jul 2014 10:25:33 +0000 In the past decades, researchers have deeply studied pathological and nonpathological gait to understand the human ankle function during walking. These efforts resulted in the development of new lower limb prosthetic devices aiming at raising the 3C-level (control, comfort, and cosmetics) of amputees. Thanks to the technological advances in engineering and mechatronics, challenges in the field of prosthetics have become an important source of interest for roboticists. Currently, most of the bionic feet are still on a research level but show promising results and a preview of tomorrow's commercial prosthetic devices. In this paper, the authors present the current state-of-the-art and the latest advances in propulsive bionic feet with its actuation principles. The context of this review study is outlined followed by a brief description of the basics in human biomechanics and criteria for new prosthetic designs. A new categorization based on the actuation principle of propulsive ankle-foot prostheses is proposed. Based on simulations, the general principles and benefits of each actuation method are explained. The corresponding latest advances in propulsive bionic feet are presented together with their main characteristics and scientific outcomes. The authors also propose to the reader a comparison analysis of the presented devices with a discussion of the general tendencies in new prosthetic feet. Pierre Cherelle, Glenn Mathijssen, Qining Wang, Bram Vanderborght, and Dirk Lefeber Copyright © 2014 Pierre Cherelle et al. All rights reserved. Hemodynamic Influence of Different Pulmonary Stenosis Degree in Glenn Procedure: A Numerical Study Wed, 16 Jul 2014 08:50:07 +0000 Background. Single ventricle disease is treated by Glenn surgery. It is generally accompanied by stenosis on a pulmonary artery or its branches, which has great effect on hemodynamics. This study investigated the hemodynamic influence of different pulmonary stenosis degree in Glenn procedure. Materials. Four three-dimensional Glenn models with different left pulmonary artery stenosis rates as, respectively, 0% (model 1), 25% (model 2), 50% (model 3), and 75% (model 4) by the diameter were generated. Method. Geometric multiscale analysis method was used in the numerical simulations by coupling the lumped parameter model (LPM) and three-dimensional model. Results. During one cardiac cycle, the flow ratio between left pulmonary artery and superior vena cava was about 0.49 for models 1, 2, and 3, while the ratio decreased to 0.34 for model 4. On the other hand, hemodynamics parameters like power loss and oscillation shear index show complications of the stenosis to the postoperative development. Conclusion. When the stenosis rate is above 75%, it is suggested to treat stenosis before Glenn procedure, while when the stenosis rate is below 50%, there is no necessity to pay attention to it due to the little effect it makes. Liancai Ma, Youjun Liu, Xi Zhao, Xiaochen Ren, Fan Bai, Jinli Ding, Mingzi Zhang, Wenxin Wang, Jinsheng Xie, Hao Zhang, Zhou Zhao, and Hua Han Copyright © 2014 Liancai Ma et al. All rights reserved. Transducer Type and Design Influence on the Hearing Loss Compensation Behaviour of the Electromagnetic Middle Ear Implant in a Finite Element Analysis Wed, 16 Jul 2014 06:23:46 +0000 Several types of electromagnetic transducer for the middle ear implants (MEIs) have been developed as an alternative to conventional hearing aids for the rehabilitation of sensorineural hearing loss. Electromagnetic transducer type and design are thought to have a significant influence on their hearing compensation performance. To investigate these effects, a middle ear computational model was constructed based on a complete set of microcomputerized tomography section images of a human ear. Its validity was confirmed by comparing the model predicted motions with published experimental measurements. The result shows that the eardrum driving transducer (EDT) is superior to the floating mass transducer (FMT) in hearing compensation when the transducer mass is small but inferior to the FMT when the mass gets bigger. The incus body driving transducer (IBDT) is the most ineffective type of transducer for hearing compensation. Moreover, the masses of the EDT and the FMT decrease the transducer performance mainly at higher frequencies: the greater the transducer mass, the lower the displacement of the stapes excited by these transducers. On the other hand, the IBDT driving rod stiffness decreases transducer’s performance severely at low frequencies and its adverse effect on transducer performance increases with the decrease of the stiffness of the IBDT driving rod. Houguang Liu, Shirong Ge, Gang Cheng, Jianhua Yang, Zhushi Rao, and Xinsheng Huang Copyright © 2014 Houguang Liu et al. All rights reserved.