Tsinghua Science and Technology

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Volume 12 No. 3
20 March 2007

Applications of Digital Correlation Method to Structure Inspection

2007, 12(3): 237-243. doi:10.1016/S1007-0214(07)70035-4

Abstract ( 109 ) ( 37 )

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In structure inspections, applications of optical techniques are rare, but the advantages of a non-contact, full field technique using a simple apparatus are attractive. The main requirements for structure inspection are the full-field strain measurement with the required precision and on-site measurement ability. The digital correlation method (DCM), a new optical deformation measurement tool, can satisfy all of the requirements for structure inspection. A smoothing algorithm which can greatly ...

Multi-Dimensional Piece-Wise Self-Affine Fractal Interpolation Model

2007, 12(3): 244-251. doi:10.1016/S1007-0214(07)70036-6

Abstract ( 106 ) ( 18 )

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Iterated function system (IFS) models have been used to represent discrete sequences where the attractor of the IFS is piece-wise self-affine in

A Note on Natural Coordinates and Frenet Frames

2007, 12(3): 252-255. doi:10.1016/S1007-0214(07)70037-8

Abstract ( 186 ) ( 31 )

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This paper discusses the relationship between natural coordinates in fluid mechanics and orthogonal curvilinear coordinates. Since orthogonal curvilinear coordinates have some excellent mathematical properties, natural coordinates can be applied more widely if they can be transformed to orthogonal curvilinear coordinates. Frenet formulas which describe the differential properties of natural coordinates were compared with the derivative formulas of orthogonal curvilinear coordinates to show that ...

Russian Nuclear Rocket Engine Design for Mars Exploration

2007, 12(3): 256-260. doi:10.1016/S1007-0214(07)70038-X

Abstract ( 295 ) ( 29 )

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This paper is to promote investigation into the nuclear rocket engine (NRE) propulsion option that is considered as a key technology for manned Mars exploration. Russian NRE developed since the 1950s in the former Soviet Union to a full-scale prototype by the 1990s is viewed as advantageous and the most suitable starting point concept for manned Mars mission application study. The main features of Russian heterogeneous core NRE design are described and the most valuable experimental performance ...

Micro-Friction and Adhesion Measurements for Si Wafer and TiB₂ Thin Film

2007, 12(3): 261-268. doi:10.1016/S1007-0214(07)70039-1

Abstract ( 166 ) ( 36 )

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An apparatus was specifically developed for micro-friction and adhesion measurements. The force measurement range is 10–2000 μN with a horizontal speed of 10–400 μm/s. The apparatus was tested using a 0.7-mm diameter steel ball as the upper specimen to measure the micro friction and adhesion behaviour of a Si (100) wafer and a TiB₂ film. The effects of rest time, speed, and load were studied. The results show that the maximum static and sliding friction forces of both the ...

Optimal Kinematic Design of a 2-DOF Planar Parallel Manipulator

2007, 12(3): 269-275. doi:10.1016/S1007-0214(07)70040-8

Abstract ( 189 ) ( 61 )

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Closed-form solutions were developed to optimize kinematics design of a 2-degree-of-freedom (2-DOF) planar parallel manipulator. The optimum design based on the workspace was presented. Meanwhile, a global, comprehensive conditioning index was introduced to evaluate the kinematic designs. The optimal parallel manipulator is incorporated into a 5-DOF hybrid machine tool which includes a 2-DOF rotational milling head and a long movement worktable. The results show that the planar parallel manipula...

Products Made from Nonmetallic Materials Reclaimed from Waste Printed Circuit Boards

2007, 12(3): 276-283. doi:10.1016/S1007-0214(07)70041-X

Abstract ( 158 ) ( 46 )

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Printed circuit boards (PCBs) are in all electronic equipment, so with the sharp increase of electronic waste, the recovery of PCB components has become a critical research field. This paper presents a study of the reclaimation and reuse of nonmetallic materials recovered from waste PCBs. Mechanical processes, such as crushing, milling, and separation, were used to process waste PCBs. Nonmetallic materials in the PCBs were separated using density-based separation with separation rates in excess ...

Phase-Plane Invariant Analysis of Pressure Fluctuations in Fluidized Beds

2007, 12(3): 284-289. doi:10.1016/S1007-0214(07)70042-1

Abstract ( 151 ) ( 45 )

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Partial agglomeration is a major problem in fluidized beds. A chaotic analytical method based on the phase-plane invariant of the pressure fluctuations in the fluidized beds has been used to warn of agglomeration at an early stage. Cold tests (no combustion) and hot tests (combustion) in fluidized beds show that the phase-plane invariant of the pressure fluctuations can distinguish the dynamic behavior of fluidized beds with different flow rates in cold tests. With combustion, when the flow rate...

Side Structure Sensitivity to Passenger Car Crashworthiness During Pole Side Impact

2007, 12(3): 290-295. doi:10.1016/S1007-0214(07)70043-3

Abstract ( 235 ) ( 45 )

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Side impact accidents of passenger cars with fixed poles may result in severe injuries to the vehicle occupants. In this paper, side structure intrusion was considered as the criterion for passenger cars crashworthiness during side impact with a pole. The relationship between side intrusions and the side structure stiffness was analyzed. The acceleration of the unstruck side vehicle body was selected as the criterion for studying the influence of different side structure components on the side s...

Influence of Temperature on Creep Behavior of Ag Particle Enhancement SnCu Based Composite Solder

2007, 12(3): 296-301. doi:10.1016/S1007-0214(07)70044-5

Abstract ( 167 ) ( 59 )

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The creep properties of solder alloys are an important factor affecting the reliability of soldered joints in surface mount technologies. Particle-enhancement is one way to improve the properties of solder alloys. The temperature of the solder joint is one of the primary factors affecting the solder joint creep properties. Single shear lap creep specimens with a 1 mm² cross-sectional area were fabricated using Ag particle enhancement 99.3Sn0.7Cu based composite solder and 99.3Sn0.7Cu ...

Housing Price Fluctuations Across China: An Equilibrium Mechanism Perspective

2007, 12(3): 302-308. doi:10.1016/S1007-0214(07)70045-7

Abstract ( 159 ) ( 22 )

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The mechanisms affecting housing prices were studied using the equilibrium housing prices based on classic supply/demand theory. The fluctuations of the actual housing prices were then analyzed relative to the equilibrium prices. The equilibrium prices for each area were calculated from economic statistics and housing prices in 35 China metropolitan areas. The fluctuations of the actual prices are then manifested as functions of the equilibrium price, the mean reversion, and the autocorrelation ...

Urban Transport and Sustainable Transport Strategies: A Case Study of Karachi, Pakistan

2007, 12(3): 309-317. doi:10.1016/S1007-0214(07)70046-9

Abstract ( 142 ) ( 60 )

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The uncontrolled growth in urbanization and motorization generally contributes to an urban land use and transportation system that is socially, economically, and environmentally unsustainable. This paper uses Karachi as a case study, which is the largest urban and economic centre of Pakistan, passing through an uncontrolled phase of rapid urbanization and motorization. The paper first reviews research related to sustainable transportation systems to comprehend the concept of sustainable developm...

Bicycle Conversion Factor Calibration at Two-Phase Intersections in Mixed Traffic Flows

2007, 12(3): 318-323. doi:10.1016/S1007-0214(07)70047-0

Abstract ( 135 ) ( 46 )

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Chinese traffic is typically composed of bicycles and motor vehicles on the same road. The efficiency of bicycle traffic in time and space at intersections was investigated for eight typical intersections in the cities of Tianjin, Shenyang, and Changchun, all in China, by means of video recording. Models were developed to calculate the through bicycle traffic and the left-turn bicycle traffic conversion factors in intersections where bicycles and motor vehicles share the same road. The results i...

Transport of Yellow Sand in Stratified Flow over an Isolated Mountain Ridge

2007, 12(3): 324-331. doi:10.1016/S1007-0214(07)70048-2

Abstract ( 134 ) ( 43 )

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The transport of yellow sand over mountain regions in the presence of internal gravity waves has been investigated numerically. The motion of yellow sand particles has been simulated in a Lagrangian frame of reference by solving the time-dependent Reynolds averaged Navier-Stokes equations. An implicit time integration in a fitted body grid arrangement was used to simulate the stratified flow over an isolated ideally bell-shaped mountain. The transport and deposition of particles of various sizes...

Numerical Simulation on Stratified Flow over an Isolated Mountain Ridge

2007, 12(3): 332-336. doi:10.1016/S1007-0214(07)70049-4

Abstract ( 93 ) ( 47 )

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The characteristics of stratified flow over an isolated mountain ridge have been investigated numerically. The two-dimensional model equations, based on the time-dependent Reynolds averaged Navier-Stokes equations, are solved numerically using an implicit time integration in a fitted body grid arrangement to simulate stratified flow over an isolated ideally bell-shaped mountain. The simulation results are in good agreement with the existing corresponding analytical and approximate solutions. It ...

Investigation of Exact Truncated Data Image Reconstruction Algorithm on Parallel PI-Line Segments in Fan-Beam Scans

2007, 12(3): 337-344. doi:10.1016/S1007-0214(07)70050-0

Abstract ( 91 ) ( 28 )

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Some novel reconstruction algorithms have recently been proposed to solve the problem of reconstruction from transverse truncated projections of fan-beam scans. This paper introduced and reformulated the exact backprojection-filtration (BPF)-type reconstruction algorithm for fan-beam scans based on Zou and Pan's work. Subsequently, a legible and implementary BPF algorithm for region-of-interest (ROI) reconstruction is presented using projection data truncated not only in angle-scanning but also ...

Numerical Investigation of the Impact of Different Configurations and Aspect Ratios on Dense Gas Dispersion in Urban Street Canyons

2007, 12(3): 345-351. doi:10.1016/S1007-0214(07)70051-2

Abstract ( 106 ) ( 20 )

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The dispersion of chlorine gas in urban street canyons was numerically simulated using the fire dynamics simulator, a code developed by the National Institute of Standards and Technology of USA, which uses large eddy simulation coupled with the Smagorinsky sub-grid scale model. The unsteady flow fields were computed by solving the filtered incompressible Navier-Stokes equations under low Mach number approximation by the finite difference method. The studies analyzed the influence of different st...

Heterogeneous Beliefs, Trading Volume, and Seemingly Emotional Stock Market Behavior

2007, 12(3): 352-360. doi:10.1016/S1007-0214(07)70052-4

Abstract ( 62 ) ( 26 )

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Various information types and rational learning methods have shown that heterogeneous belief changes in a rational expectation model can explain many empirical findings in stock markets, such as momentum, contrarians, and technical trading. The methods have also shown that momentum and price movements can coexist in an asset market with only rational agents. The purpose of this paper is to provide a rational economic theory to explain these phenomena. Results of a dynamic programming model with ...