Abstract: In order to research that statics properties of concrete cylinder sample are influenced by micro-concrete material heterogeneity, by random aggregate models generated by different random number were established. By fixed aggregate size and constantly changing of the sample size, the concrete numerical model was simulated and Strength change of concrete samples was analyzed .So that strength influence of the aggregate location of the concrete random sample was study. Calculation shows that: the strength of concrete has been little effect by the aggregate random location, the size effect on concrete has been changed regularly, with the size effect ratio coefficient of aggregate and sample gradually increasing, the error square sum of strain was reduced and the brittlness of the samples becomes obvious.
Abstract: Indoor model experiments were made to study drag loads on two piles of side-by-side arrangements in the uniform flow. Take three different velocities of the flow, three different diameters of piles and five different distances of two piles in the experiments to get the variations of loads. Drag forces were measured by a two-component balance. Analysis on experiment results shows that drag forces increase with the increase of the pile diameter, the increase of the flow velocity and the decrease of the distance of two piles. The drag coefficient CD under different Reynolds numbers shows the same change law. The drag coefficient CD decreases with the increase of the distance of two piles and has good coherence to the ratio of the distance of two piles to the pile diameter.
Abstract: It is the key to guide rock-breaking design and engineering practice for how to obtain a reasonable test indicator to assess the cuttability of the rock. Some sandstone samples were tested by using the linear rock cutting machine in the school of mining engineering, University of New South Wales (UNSW), Australia. The curves characteristics for the weight percent of the broken debris with the mesh size distribution were obtained through the screening statistics. Furthermore, the fractal dimension of the specimen broken debris was derived through theoretical calculations and statistical analysis. The results showed that the rock cutting fragmentation is of significant fractal features under the mechanical shock loads. The broken debris fractal dimension of the structural integrity specimens is bigger, the range of the fractal dimension is smaller and the broken debris size distribution is more even than that of the poor structural integrity specimens. The fractal dimension is the ideal test indicator to assess and analysis the rock-breaking degree.
Abstract: A new test device, which can be used for measuring the stain and the displacement on the adhesive interface while the slip occurs within the reinforced concrete, is proposed and designed. With that, a comparative experiment is carried out on a group of the reinforced concrete columns bearing alternating load to obtain the τ-s curve. The hysteretic curves of these specimens are recorded timely. The result from the one-way repeated load is similar with several well-known expressions which are commonly cited at home and abroad. That from the low cycle load reveals some certain characteristic of the alternating slip, which there isn't in the static test. The experimental data could make contribution for the numerical simulation on bridge and seismic building.
Abstract: The finite element model for the basalt fiber reinforced concrete(BFRC)-roller compacted concrete(RCC) composite pavement structure is formed, by the model the influence of the BFRC and RCC panel thickness, elasticity modulus and foundation Equivalent Resilient Modulus on the complex road load stress can be summarized as: with the increasing of the composite pavement slab thickness, the stress at the end of the below plate shows decreasing trend, but the above end of the plate stress increased with the increasing of relative thickness of laminates; the increasing of concrete elastic modulus will make the stress in the end of this laminate increase, while the end of the adjacent laminates stress will reduce; with the increasing of the equivalent modulus of elasticity of roadbed top, the stress of laminates decreases. The results of the analysis are available as the reference to optimize the design of BFRC-RCC composite pavement.
Abstract: Wireless sensor networks (WSNs) based on ZigBee technology are currently popular low-energy, low-cost, short-distance communication technologies that can be applied in many areas, such as industry, environment, agriculture, etc. Energy efficiency is one of the most important research points for WSNs. In this paper, we analyze the existing WSNs protocols, especially LEACH, and propose an energy-efficient cluster head and router selecting protocol (EECRS). EECRS combines both cluster-based and energy-threshold routing protocols to balance the energy consumption of the sensor nodes in the whole network in order to extend the network lifetime. And through the simulation via NS2 software, it is shown that EECRS improves the network performance, network lifetime and data received per energy mount consumption, compared with LEACH protocol.
Abstract: Acoustic seabed sediment classification method is always important research contents in marine geology and marine acoustics because of its characters of low-cost and high efficiency. At present, there are mainly three types of acoustic seabed sediment classification methods:(1) the echo signal statistical characteristics classification; (2) image texture classification; (3) submarine acoustic parameter inversion method. The principles of anterior two classification methods are similar, which is based on statistics, unknown sediment type can be concluded according to the statistical characteristics of known sediment. There are many usable acoustic equipments and commercial classification software for the two kinds of methods. The third type method is based on suitable seabed sediment model. Seabed acoustic characteristic parameters are inversed and thus seabed sediment can be classified. At present, there are few usable acoustic equipment and commercial classification software for the third method, but it's more accurate than the anterior two classification methods.
Abstract: Due to the presence of nonlinear springback deformation, when the aviation piston hydraulic pump which is usually called sliding-shoe is formed by cold extrusion method, the surface of the sliding-shoe’s ball-socket becomes non-analytic curved surface. And this brings many difficulties to the measurement. In this paper, the precision measurement and fitting method to the inferior concave spherical surface of the sliding-shoe is discussed. And according to the deformation characteristics of the sliding-shoe, a meridian measurement method is established for the measurement. To a large number of discrete data, we fit it by least squares method and calculate it by VC++ Language program. Then we get the ball-socket’s center and radius. And fitting the sliding-shoe’s ball-socket to find out the contour error. It provides a reliable basis for the inspection of sliding-shoe.
Abstract: Synthetic Aperture Radar Interferometry (InSAR) provides a new tool to study geohazards.A map of the surface displacement with subcentimeter accuracy can be constructed using,if the Earth’s surface deformed between two radar image acquisitions.In this paper, the research examples of InSAR are introduced firstly.Then Merits and Demerits of InSAR Applicaion in Geohazards Study are reviewed.
Abstract: Because of the requirement of accurate measurement of projectile’s flying characteristics and limitations of the traditional attitude measuring methods, a new method based on three pairwise-orthogonal magnetic sensors only is presented for non-spinning projectiles. The characteristic ratio theory proposed in our earlier work is described in detail. In order to get the pitch angle with this theory, the mathematical relationship between magnetic sensors output and the theoretical extreme value is derived in this paper. Based on this relation, the extremum ratio method is expanded to be used in non-spinning projectiles. The measurement error of the attitude measuring method is also analyzed in theoy. At last, the simulation of the method is achieved under the given conditions to prove its effectiveness. The simulation experiment results indicate that the method is feasible and the calculating errors of the attitude angles are within ±1°.