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Proceedings of 2013 10th International Bhurban Conference on Applied Sciences & Technology (IBCAST)最新文献

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Experimental investigation of filament-wound composite tubes for mechanical characterization by internal pressure testing 纤维缠绕复合材料管力学性能内压试验研究
T. Rasheed, S. Akbar, S. Mirza
This paper presents method for the characterization of composite tubes produced by filament winding technique. The aim of this study is to investigate the mechanical properties by tensile test and under internal pressure loads. For this purpose specimens produced with different orientation having the same reinforcement with two different matrix systems. Data produced experimentally by measuring the mechanical properties like longitudinal tensile and hoop tensile properties, strain in hoop direction and maximum hoop stresses during the hydraulic testing. In order to investigate these parameters, internal pressure tests are done on the filament-wound composite tubes having internal diameter 64.5± 0.5 mm and length 320± 2.0 mm according to ASTM D 1599-99 standard. The tubes for the testing are manufactured by wet filament winding methods of [± 60°] E-glass/Epoxy of various wall thicknesses. Hydraulic tests revealed that the tubes with winding orientation [± 60°]2[±90°]2 exhibits better burst performance compared with others orientations. In addition, factors affecting the behavior of the tubes like buckling, stress variation through wall thickness are discussed.
本文介绍了长丝缠绕复合材料管的表征方法。本研究的目的是通过拉伸试验和内压载荷来研究其力学性能。为此,用两种不同的基体体系制作具有不同取向、相同配筋的试样。通过测量水力测试期间的纵向拉伸和环向拉伸性能、环向应变和最大环向应力等力学性能的实验数据。根据ASTM D 1599-99标准,对内径64.5±0.5 mm、长度320±2.0 mm的丝绕复合材料管进行了内压试验。用于测试的管是用不同壁厚的[±60°]e -玻璃/环氧树脂湿长丝缠绕法制造的。水力试验结果表明,缠绕方向为[±60°]2[±90°]2的管具有较好的爆破性能。此外,还讨论了影响管的屈曲、应力随壁厚变化等因素。
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引用次数: 1
Multiphase flow modeling using Lattice Boltzmann method 基于点阵玻尔兹曼方法的多相流建模
S. Mushtaq, R. Basit
To model the Multiphase flow along with phase transition process is a challenging task. In the present paper, capability of Lattice Boltzmann method (LBM) to simulate flow through complex geometries and multiphase flow has been discussed. LBM is an innovative computational fluid dynamics (CFD) approach based on kinetic models. It describes the physical system as an artificial micro-world of the particles in which the particles simply propagate, collide and interact. To check the validity of LBM, simulations have been performed for two dimensional Poisuelle flow as a test problem and compared with analytical result. Then simulations results for various geometries resembling the porous media, introduced in the flow have also been presented. For the simulation of multiphase flow involving phase transition Shan and Chen model has been used. Periodic boundary conditions have been applied in all directions. Then gravity has been introduced as the driving force. Phase transition occur spontaneously whenever the interaction strength between the particles exceeds its threshold limit. Results have been verified by Laplace law. Finally, it has been concluded that LBM is a simulation method of choice for simulating flow through porous media and multiphase flow.
多相流与相变过程的建模是一项具有挑战性的任务。本文讨论了晶格玻尔兹曼法(Lattice Boltzmann method, LBM)模拟复杂几何流和多相流的能力。LBM是一种基于动力学模型的计算流体动力学(CFD)新方法。它将物理系统描述为粒子的人工微观世界,粒子在其中简单地传播、碰撞和相互作用。为了验证LBM的有效性,将二维泊威尔流作为测试问题进行了模拟,并与分析结果进行了比较。在此基础上,给出了流体中引入的类似多孔介质的各种几何形状的模拟结果。对于涉及相变的多相流的模拟,采用了Shan和Chen模型。周期边界条件在各个方向上都得到了应用。然后引入了重力作为驱动力。当粒子间的相互作用强度超过阈值时,相变就会自发发生。用拉普拉斯定律对结果进行了验证。最后,得出了LBM是模拟多孔介质流动和多相流的理想方法。
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引用次数: 0
Experimental study and CMFD modeling of transport processes in flow of two Immiscible liquids 两种不混相液体流动输运过程的实验研究与CMFD建模
M. Arshad, I. R. Chughtai, M. H. Inayat, A. Haq
Rectangular shaped sieve plate column was installed for study of transport parameters through high speed photography and image analysis. Two Immiscible liquids consisting of the dispersed phase (water) and continuous phase (kerosene oil) were introduced in countercurrent operation. Experiments were performed for dispersed and continuous phase superficial velocities 0.16-0.44 cm/sec and 0.37-0.47 cm/sec respectively, pulsation frequency 0.95 -1.72 rev/sec and pulsation amplitude 1cm. Upon increasing the superficial velocity of dispersed phase, its void fraction increases up to its asymptotic value and droplet velocity increase while the droplet size decreases. Upon increasing the pulsation frequency, its void fraction increases while the droplet size and droplet velocity decreases. A Computational Multi Fluid Dynamics simulation has been carried out in order to verify the experimental results using the FLUENT. The CMFD calculations for void fraction have been compared with the experimental results which have shown a maximum deviation of 2-3%.
安装矩形筛板柱,通过高速摄影和图像分析研究输送参数。逆流操作中引入了分散相(水)和连续相(煤油)两种不混相液体。脉动频率为0.95 ~ 1.72 rev/sec,脉动幅值为1cm,分散相表面速度为0.16 ~ 0.44 cm/sec,连续相表面速度为0.37 ~ 0.47 cm/sec。随着分散相表面速度的增加,其空隙率逐渐增大,直至其渐近值,液滴速度增大,液滴尺寸减小。随着脉动频率的增加,其空隙率增加,液滴尺寸和液滴速度减小。为了验证实验结果,利用FLUENT进行了计算多流体动力学仿真。将CMFD计算结果与实验结果进行了比较,结果显示最大偏差为2-3%。
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引用次数: 0
Hybrid type of broad-band microwave phase shifter using schiffman lines 希夫曼线混合型宽带微波移相器
I. Hussain, A. K. Rashid, H. Ullah
This paper presents a new hybrid type of phase shifter that employs basic Schiffman lines. Compared with conventional coupled line and Schiffman line phase shifters the new hybrid design shows advantage of optimally very small phase shift error of (±5°) over an entire band of 2.85-17.15 GHz (143% bandwidth). To validate the method, a 90° phase shifter is designed and simulated.
本文提出了一种采用基本希夫曼线的新型混合型移相器。与传统的耦合线移相器和希夫曼线移相器相比,新型混合移相器在2.85 ~ 17.15 GHz(143%带宽)的整个频段内的最佳相移误差为(±5°)。为了验证该方法,设计并仿真了一个90°移相器。
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引用次数: 2
Numerical simulation of pressure oscillations and instabilities in a solid propellant subscale motor 固体推进剂亚尺度发动机压力振荡和不稳定性的数值模拟
M. Ozair, M. N. Qureshi
It has been broadly reported in the literature that the large segmented solid rocket motors (SRMs), such as Ariane 5 solid booster (P230) and Space Shuttle RSRM (Re-designed SRM), experience undesirable pressure oscillations that lead to thrust oscillations during combustion due to a complex coupling between the combustion and the internal aerodynamics of the combustion chamber. These fluctuations adversely affect the rocket motor performance, could damage the payload and eventually cause mission failure. To investigate these instabilities, experiments on full-size motors are very expensive, complicated and time consuming, and are therefore not really suited for research. In this paper, LP6 motor, the 1/15- scale axisymmetric model of the Ariane 5 booster, is used to study the pressure oscillations and the vortex-shedding induced pressure instabilities. Computational Fluid Dynamics (CFD) simulations were carried out on a quadrilateral mesh of the LP6 geometry at the time of 6.4 s after ignition when the pressure oscillations were found to be almost peaked. Pressure oscillation frequencies and amplitudes obtained from CFD simulations are found to be in good agreement with experimental results obtained at ONERA (French National Aerospace Research Centre). From CFD simulations, it was also found that the potential source of instabilities and pressure oscillations in LP6 motor having no inhibitor rings or restrictors is the surface vortex shedding mechanism which is a phenomenon that has also been observed in the experiments. On the basis of the present study and results, CFD simulations can also be carried out for different geometric configurations and flow conditions in other SRMs to investigate the instabilities and pressure oscillations occurring in their combustion chambers.
文献中广泛报道了大型分段固体火箭发动机(SRM),如阿丽亚娜5号固体助推器(P230)和航天飞机RSRM(重新设计的SRM),由于燃烧和燃烧室内部空气动力学之间的复杂耦合,在燃烧过程中经历了不良的压力振荡,导致推力振荡。这些波动对火箭发动机性能产生不利影响,可能损坏有效载荷并最终导致任务失败。为了研究这些不稳定性,在全尺寸电机上进行实验是非常昂贵、复杂和耗时的,因此并不真正适合研究。本文利用阿丽亚娜5型助推器1/15比例轴对称模型LP6电机,研究了该助推器的压力振荡和旋涡脱落引起的压力不稳定性。在点火后6.4 s的四边形网格上进行了计算流体动力学(CFD)模拟,发现压力振荡几乎达到峰值。通过CFD模拟得到的压力振荡频率和振幅与法国国家航空航天研究中心(ONERA)的实验结果非常吻合。通过CFD模拟还发现,在无阻环和节流器的情况下,LP6电机不稳定和压力振荡的潜在来源是表面涡脱落机制,这一现象在实验中也得到了观察。在本研究和结果的基础上,还可以对其他srm的不同几何构型和流动条件进行CFD模拟,以研究其燃烧室内发生的不稳定性和压力振荡。
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引用次数: 0
Detection of lung tumor in CE CT images by using weighted Support Vector Machines 基于加权支持向量机的CE CT图像肺肿瘤检测
U. Javed, M. Riaz, T. A. Cheema, H. Zafar
Lung tumor detection using Contrast Enhanced (CE) Computed Tomography (CT) images plays a key role in computer aided diagnosis and medical practice. Detection of a lung tumor and accurate segmentation is a very challenging task. One major task is to perform classification between a normal (healthy) lung tissue and abnormal (tumor) tissue. However this distribution of data is nonlinear and training a classifier on this kind of data is a difficult process. Limitation of existing approaches is that they assign equal importance to each input feature; this weight assessment is not true for all problems. In this paper we propose a novel method for assigning optimal weights for the calculated features. This proposed technique is tested on CE CT Lung images. Simulation results and analysis showed that our proposed system has shown better classification accuracy than the conventional SVM.
对比增强(CE)计算机断层扫描(CT)图像检测肺肿瘤在计算机辅助诊断和医疗实践中起着关键作用。肺肿瘤的检测和准确分割是一项非常具有挑战性的任务。一项主要任务是对正常(健康)肺组织和异常(肿瘤)组织进行分类。然而,这种数据的分布是非线性的,在这种数据上训练分类器是一个困难的过程。现有方法的局限性在于它们对每个输入特征分配同等的重要性;这种权重评估并不适用于所有问题。本文提出了一种为计算特征分配最优权重的新方法。该方法在CE CT肺部图像上进行了测试。仿真结果和分析表明,该系统比传统的支持向量机具有更好的分类精度。
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引用次数: 15
MIMO sliding mode controller design using inverse hyperbolic function 利用逆双曲函数设计MIMO滑模控制器
M. Asad, S. Iqbal, A. I. Bhatti
In this work a new reaching law (RL) is proposed that uses inverse hyperbolic function (IHF) instead of the Signum function for switching. The characteristic of this reaching law is that its switching gain is variable, during the reaching phase, which is governed by the parameters of IHF. Its gain decreases with the convergence of system states towards the sliding surface. The variable gain results in: (a) the considerable reduction of the phenomenon of chattering at the control inputs and (b) the decrease of the reaching phase of the sliding mode control (SMC).
本文提出了一种新的趋近律(RL),该趋近律使用逆双曲函数(IHF)代替Signum函数进行切换。该趋近律的特点是其在趋近相位的开关增益是可变的,它受IHF参数的控制。其增益随系统状态向滑动面收敛而减小。可变增益导致:(a)控制输入处的抖振现象显著减少,(b)滑模控制(SMC)的到达相位减少。
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引用次数: 0
Design and analysis of two-dimensional InAlAs/InGaAs Single Hetero-junction Bipolar Transistor 二维InAlAs/InGaAs单异质结双极晶体管的设计与分析
H. Nawaz, M. Rizwan
The paper presents an InAlAs/InGaAs Hetero-junction Bi-polar transistor structure. The structure formation and performance analysis has been carried out using SILVACO software. Parametric analysis is carried out and results are presented in correspondence with the theory. Doping profile of proposed HBT is optimized to achieve appropriate current gain and maintain possibly low resistance in the base region to avoid recombination. Emitter area of 5×5 μm2 is used to achieve low off set voltage and high gain of 62dB while low doping enabled the device to operate effectively at high frequencies that is up-till 80GHz. Energy band diagram and effects of different layers are discussed showing efficient workability of the proposed structure.
本文提出了一种InAlAs/InGaAs异质结双极晶体管结构。利用SILVACO软件进行了结构形成和性能分析。进行了参数分析,得到了与理论相符的结果。所提出的HBT的掺杂谱被优化,以获得适当的电流增益,并在基区保持可能的低电阻,以避免复合。利用5×5 μm2的发射极面积实现了62dB的低关断电压和高增益,而低掺杂使器件能够在高达80GHz的高频下有效工作。讨论了不同层的能带图和影响,表明了该结构的有效可操作性。
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引用次数: 0
Ranging using amplitude comparison of closely spaced time samples 使用距离很近的时间样本的振幅比较测距
N. Ahsan, Z. Haider, S. Sultan
This paper presents a new scheme for the range estimation of an unknown radar emitter. With the proposed algorithm, range of unknown radar emitter can be determined by amplitude comparison of closely spaced time samples. A mathematical model of this ranging method is discussed in detail and supported by computer simulations. For various scenarios, the standard deviation in range estimate has been estimated. For normal incidence, the simulation results indicate that standard deviation in range estimate is only 76m for a 20Km range considering 10dB SNR and observer position error of ±1m. The comparison of proposed method with traditional triangulation method has also been presented. The comparison indicates that for a single platform configuration, the proposed scheme provides more accurate range estimation in a short span of time. Therefore, making it a suitable choice for applications where fast update is required.
本文提出了一种未知雷达辐射源距离估计的新方案。利用该算法,可以通过近间隔时间样本的幅值比较来确定未知雷达辐射源的距离。详细讨论了该测距方法的数学模型,并进行了计算机仿真。对于各种情况,估计了距离估计的标准差。对于正态入射,在考虑10dB信噪比和±1m观测器位置误差的情况下,对20Km距离估计的标准差仅为76m。并将该方法与传统三角剖分方法进行了比较。对比表明,对于单一平台配置,该方案在短时间内提供了更准确的距离估计。因此,对于需要快速更新的应用程序来说,它是一个合适的选择。
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引用次数: 1
Comparative analysis of DSP and intel processors by implementing FFTs using parallel programming for underwater signal processing applications 利用并行编程实现fft在水下信号处理中的应用,对DSP和intel处理器进行了比较分析
U. Hamid, H. Shahzad, M. Irfan
This paper presents Fast Fourier Transform (FFT) benchmark results to measure and compare the performance of various DSP and Intel processors for underwater signal processing applications. This paper aims to show performance enhancement in Intel processors as compared to DSP processors by using parallel programming for implementing signal processing functions in real time. This paper provides results that show a significant decrease in FFT execution time on an Intel based Multicore processor using parallel programming. Therefore comparative analysis among different processor architectures presented in this paper will help the system designers in selecting an optimal processor for underwater signal processing applications.
本文给出了快速傅里叶变换(FFT)基准测试结果,用于测量和比较各种DSP和英特尔处理器在水下信号处理应用中的性能。本文旨在通过使用并行编程实现实时信号处理功能,展示英特尔处理器与DSP处理器相比的性能增强。本文提供的结果显示,使用并行编程在基于Intel的多核处理器上显著减少FFT执行时间。因此,本文所提出的不同处理器架构之间的比较分析将有助于系统设计者为水下信号处理应用选择最佳的处理器。
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引用次数: 0
期刊
Proceedings of 2013 10th International Bhurban Conference on Applied Sciences & Technology (IBCAST)
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