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10 February 2002, Volume 24 Issue 1
Around the mechanics
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2000-230
Abstract ( 1242 )   PDF (689KB) ( 649 )
Using the IFA-300 Hot Wire/Film Anemometer, the detailed measurement results are obtained on the effect of the nozzle-to-plate space on the free turbulent impinging jet flow field. The Reynolds number considered is 23000, and the space of nozzle-to-plate is set as 2D (D is the diameter of the pipe), 4D,6D,8D above the impingement plate, respectively. It is shown that the "damping"effect mainly exists in the zone of 0.5D from the impingement wall. Under a small nozzle-to-plate space, the radial velocity decreases more rapidly than that under a large one. And the velocity under the small space is somewhat smaller. In the area r/D ≤1.5, the trend and the quantity of the turbulent kinetic energy of the small and large spaces are quite different. For the other radial positions, the trend is the same though the quantity under a larger space is greater. It also shows that the flow structure is greatly changed when the nozzle-to-plate space is around Z/D=6, which is attributed to the effect of the potential core of the jet. Consequently, the turbulent kinetic energy keeps large at the end of the potential core and in the area of several diameters downstream of it.
Application study
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2000-255
Abstract ( 1285 )   PDF (554KB) ( 755 )
Based on the concrete $S$-$N$ curve, a model of residual strength degradation is established in this paper, and then both the fatigue life and its reliability are modeled and analyzed by using this degradation model and the three-parameter Weibull distribution under spectrum loading. The experiments show that the present method is reliable, the analysis and calculation is simple and effective.
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2000-296
Abstract ( 968 )   PDF (308KB) ( 536 )
The dynamic properties of the transmission wire of contact net were analysed and the stable response of the transmission wire was obtained by the modal analysis.
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2000-359
Abstract ( 970 )
In order to meet the field demand of reinforced concrete long post hoisting, a study on the hoisting procedure is made for double-hoist three-point lifting, and a mathematical model for the double-hoist three-point lifting is established. Software is developed to solve problems encountered in the double-hoist three-point lifting.
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2000-391
Abstract ( 1569 )   PDF (522KB) ( 1027 )
In this paper, the application of Mathematica in transfer matrix method was demonstrated by two examples. A method using reduce'' command was given to find the proper frequencies of a vibration system. The result obtained was compared with that in reference [2], which shows the effectiveness of this method.
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2000-419
Abstract ( 995 )   PDF (573KB) ( 655 )
Finite Element Method (FEM) was used to simulate the creep indentation testing on film/substrate systems. Based on the FEM simulation, a new method is proposed to derive the material creep properties (in Norton equation) from the indention creep experimental results (indentation stress-indenter depth-time) for thin film/substrate systems by the definition of effective' stress and effective' strain. In the simulation, a steady state was found and the steady state was used to construct the relationship between the traditional uniaxial tensile creep testing and indentation testing. In the simulation of the creep indentation testing, FEM-results showed that the experimental results would have some error from ignoring the influence of the substrates even if the indentation depth did not exceed 5%~10% depth of film.
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2000-424
Abstract ( 1071 )   PDF (698KB) ( 640 )
Based on the mathematical model of the forced vibration system of Duffing vibrator, this paper presents a computer simulation software of the dynamic system. An example of Duffing equation is analyzed; the relation between each parameter and chaos dynamic property in this equation is analyzed.
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2001-002
Abstract ( 1348 )   PDF (762KB) ( 807 )
A new method called $N$-point supply opening model for describing inlet boundary conditions of indoor airflow simulation is proposed to deal with perforated panels. Examples of two perforated panels under various inlet velocities are presented. Both the simulated results and experimental data of centerline velocity distribution, angle of divergence and jet velocity profile are discussed. Comparisons between predicted results and experimental data show that the new approach can well describe those rather complicated inlet boundary conditions of perforated panel in the indoor airflow simulation.
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2001-054
Abstract ( 1468 )   PDF (363KB) ( 684 )
In this paper, a kind of generalized Krylov function is defined and discussed. The analytic solution for Timoshenko beams on elastic foundations is given by generalized Krylov function.
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2001-235
Abstract ( 960 )   PDF (2222KB) ( 925 )
The research progress of geosynthetics and reinforced earth is reviewed in this paper. The focus for future research is pinpointed.
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2001-473
Abstract ( 851 )   PDF (562KB) ( 518 )
This ariticle discusses the theory and practice of improving the great resistance underdrain system of filter and it has been affirmed by the application in a project.
2002, 24(1):  0-0.  doi:10.6052/1000-0992-2002-002
Abstract ( 1407 )   PDF (2043KB) ( 1077 )
The paper briefly reviews the development of turbulence reseaech in 20$^{\rm th}$ century, in particular the recent achievement in past 30 years. A number of ideas are put forward on some hot spots in turbulence research.