Abstract:The principal stress rotation will be involved in these activities such as establishing lunar bases, exploring mineral resource and operating vehicles on Moon surface. Two sets of tests were performed using the hollow cylinder apparatus (HCA) at Tongji University, China to investigate the effects of principal stress rotation on the deformation behavior and non-coaxiality of dry TJ-1 lunar soil simulant. One set of tests enabled pure principal stress rotation at different constant levels of the intermediate stress parameter, while the deviatoric stress ratio and intermediate stress parameters were maintained as constant with a variation of mean stress in the other set. The test results show that intermediate stress parameters and mean stress have significant influence on deformation behavior of TJ-1 lunar soil simulant under the principal stress rotation. Their effects on the development of strain components and the volumetric strain, and the non-coaxiality of TJ-1 lunar soil simulant were studied.

Abstract:A modified Shanley method is proposed to study the post-buckling behavior of axially restrained steel columns under combined axial load and bending moment in a fire. The modified Shanley method considers the influence of the axial restraint, the axial temperature expansion and the plastic deformation of steel in high temperature, in which the strain of two limbs is an unknown quantity, to get the axial force-temperature relationship of the column. The critical temperature can be obtained by the contrast of the axial force-temperature relationship curve and the original axial force. The simplified calculation method is verified by an ABAQUS model. The critical temperatures predicated by the two methods agree well.The study shows that this model has the features of clear concept, fine analysis, and easy for the analysis of axial restrained column in a fire.

Abstract:Strands model or parallel model based on the assumption of parallel wire is helpless to semi parallel wire cable for its helical characteristics and complex structure. Based on the theory of Love’s curved bar, considering effects of the Poisson’s ratio and contact deflection between wires, introducing inter-wire contact force and friction, the mechanical model for multilayered semi parallel wire cables with symmetric wire breaks were updated. With some emphasis, axial force distribution of wires, magnification factors of axial force and axial stiffness of cable are discussed by numerical calculation. Numerical examples show that contact deformations aggravate nonuniform distribution of wires’ axial force and that the axial stiffness of cable falls much after wires break.

Abstract:Tests of reinforced concrete (RC) and prestressed reinforced concrete (PRC) beams with 500MPa steel bars were carried out in Tongji University in order to popularize the application of high strength steel bar. The results verified the equations from new code GB 50010-2010 in calculating short term flexural stiffness of concrete beams with high strength steel bars, and indicated that the deformational response of beams was influenced mainly by three parameters including initial elastic flexural stiffness, longitudinal reinforcement ratio and load level. Based on the tests, a simpler unified formula is suggested after theoretical analyses for predicting short term deformation of concrete beams using high strength steel bars. Comparison with calculations from different codes at home and abroad exhibits that the suggested formula is precise and practical for both RC and PRC beams. Keyword：cold-rolled ribbed steel wires; concrete slab; static load test; flexural behavior

Abstract:There are more and more high-rise buildings erected on soft soil. The structure-soil-structure interaction cannot be ignored. Through finite element method, a series of three-dimensional models of structures and soil were built to study on the influence of direction of seismic motion, spectrum composition, shear wave velocity and damping ratio of subsoil, foundation form and depth, number of floors on SSSI effect. The calculated result shows that, SSSI effect can be ignored with seismic motion perpendicular to buildings' orientation; SSSI effect is directly bound up with spectrum composition of seismic wave; SSSI effect is apparent if shear wave velocity was slow, damping ratio was small, foundation depth was shallow, and the numbers of floors of buildings were the same.

Abstract:The dynamic evolution process of frozen wall temperature in Tunnel Construction of Shanghai Yangtze is studied by finite element method. Considering the effect of heat radiation of tunnel lining and refrigerate battery, a three- dimensional solid element modal is built to simulate the construction process, in which latent heat of phase change is indicated by way of Enthalpy application. The law of frozen wall development, frozen wall closure, average temperature and effective thickness is summarized in this paper. Research demonstrates that the process of froze wall forming is successive and has some rules to follow. The time of frozen wall closure, average temperature and thickness agrees well with the on-site test data, which validates the numerical results. The result is of value to similar projects.

Abstract:According to the movement mechanism of snow particles, the numerical simulation for a single saltating particle’s trajectory is carried out by using the Lagrange method. At the same time, some of parameters that affect the movement, such as particle diameter, the friction velocity and particle density are analyzed, based on the characteristics of forces applying to the particle. The results show that as the snow particle diameter or particle density increases, the ratio of particle vertical force to gravity decreases and the particle’s saltation height increases. The ratio of horizontal force to gravity varies with the particle’s liftoff velocity, thereby affecting its horizontal saltation length. Based on empirical formula, the relationship between the mass flux of snow surface erosion and the number of saltation particles is established to calculate the mass transport rate of snow particle. And the comparison is made with the calculated results from the classically empirical formula. It is shown that, with the growth of snow particle diameter and friction velocity, particle mass transport rate increases; particle mass transport rate decreases with the increase of the threshold friction speed. The present results in this paper coincide well with Iversen’s empirical formula.

Abstract:One of the important factors causing urban expressway congestion was traffic flow breakdown at bottlenecks, which resulted from mutual effects of traffic demand, driving behavior and road geometry. Aiming at probabilistic nature of breakdown at urban expressway recurring bottlenecks, survival analyses models of breakdown were proposed based on the detector data. Firstly, breakdowns were identified according to speed and density thresholds. Secondly, traffic parameters during and before breakdown were counted, and relationship between probability of breakdown and bottleneck capacity was described by survival function. Finally, factors of bottleneck breakdown were analyzed by COX regression models. 277 breakdown events were collected from three typical two-lane recurring bottlenecks (Guangzhong on-ramp in inner-circle, Wuning on-ramp in inner-circle and outer-circle) at inner-ring expressway in Shanghai. Analyses results showed when the probability of breakdown was less than 50%, the single lane capacities of the three bottlenecks were 1341veh/h, 1552veh/h and 1662veh/h respectively. It can effectively protect breakdown of bottlenecks to adjust or control speed of main lane and ramp volume. The probabilistic capacity of bottleneck would be quantified more precisely according to the proposed method, which also could supply the scientific basis for active traffic management strategies design.

Abstract:Incidents on congested expressways lead to roadway capacity reduction and commuter time loss. Incident data of Shanghai inner-ring and middle-ring expressways in Pu’xi by video monitoring were employed in this study. An analysis was made of the monthly change, weekly change and daily change of incident occurrence on segments with different ramp types, and the relationship was explored between the incident occurrence and traffic flow characteristics. Negative binomial regression was adopted to establish the frequency estimation model to explore temporal heterogeneity. Results show that holiday is significant for both types of incidents while temperature only has a significant impact on disabled vehicles. The effect of weather varies among different expressways, time periods and incident types.

Abstract:Subgrade stresses and strains for a two-layer pavement structure under dual wheels are firstly studied. In different axles, loading positions and multilayer structure cases, the rules of compressive stresses and strains at subgrade depth are then analyzed. By introducing the concepts of side wheel coefficient ξ, adjacent axle coefficient ζ, position coefficient φ and generalizing approximate regression equations of them, universal and high precision computation expressions of subgrade vertical compressive stresses and strains under pavement structure are established.

Abstract:Gradient acid dissolve tests were used to divide geopolymer and hydration product quantificationally. The feasibility of gradient acid dissolve test was investigated through dissolution rates of geopolymer/hydration product and XRD, FT-IR analyses. The results show the behaviors of dissolution between geopolymer and hydration product in the same gradient acid are different, the acid point to divide geopolymer and hydration product is pH=3. The gradient acid dissolve test is an effective method to divide geopolymer and hydration product. It will lay a theoretical basis for further mechanism research on the chemical composition and structure of the main products and on the role of each composition in the geopolymeric system.

Abstract:The paper presents a summary of the key technologies for the design of a cruciform biaxial tensile machine and specimen.The Abaqus software was resoted to a comparative study of the stress distribution and plastic strain range of three classic specimens under the same loading ratio and different loading ratios. Study results show that the movement of the central region of specimen under control is a guarantee; A minimized extra bending momentum is a need; and a cooperation of loadings for different directions is a must. To increrase the plastic deformation in the central region and enlarge the uniform stress field range as well as to diminish the stress concentration are critical for the design of a specimen.Of the three specimens being analyzed, Kuwabara specimen is of the worse stress uniformity; the Mankinde specimen is of the best stress uniformity; Müller specimen is of the least stress concentration and the smallest plastic deformation region. And the plastic deformation in Müller specimen is more sensitive to the change of the load ratio.

Abstract:A theoretical thermodynamic cycle model was established with the expansion ratio of constant temperature as a parameter. Based on an analysis of the thermodynamic cycle of typical the closed and open porous medium(PM) engine, a formula of the thermal efficiency and cycle net-work was derived. The relationship of thermodynamic cycle between the closed and open PM engine was defined with the compression ratio coefficient. Through calculation, six kinds of thermodynamic cycle of two types of traditional and the closed PM engine were studied, in which the variation and impact of thermal efficiency and cycle net-work with the change of other parameters were deduced. The analysis results show that the net-work of theoretical thermodynamic cycle of the closed PM engine is superior to that of the traditional engine. The high speed diesel engine cycle is found to be more suitable for PM technical scheme.

Abstract:Through the numerical simulation on cylinder flow, mixture formation and combustion process of a turbo-charged gasoline direct injection engine, meanwhile, with the help of break specific fuel consumption, emission and combustion data from engine test, the effect of start of injection timing on engine performance was studied. The results show, for 5000r/min condition, the case whose injection is started at 400ºCA obtains the optimal mixture formation. Because of the more uniform mixture distribution, higher turbulence kinetic energy around spark plug at spark time, shortest 10-90% burning duration and lower HC emission, it has the best fuel economy and combustion stability. While the best start of injection timing is retarded 30ºCA at 2000r/min. When injection is advanced, wall film increases, the decreased equivalence ratio and lower turbulence kinetic energy around spark lead to lower burning rate, so HC emissions, fuel economy and combustion stability may go bad. The same situation occurs in delayed injection, the mixture uniformity goes worsens at spark time because of insufficient mix, consequently engine performance is deteriorated.

Abstract:The form of non-smooth surfaces, which is ubiquitous in nature, is applied to automobiles and the feasibility of aerodynamic drag reduction on automobiles is studied by using computational fluid dynamics (CFD) simulation method. Meanwhile, by studying the composition of the air resistance and comparing the external flow field of automobiles with smooth or non-smooth surfaces, the effects of automobile with non-smooth surfaces on pressure drag, induced drag and frictional drag are analyzed together with the mechanism of drag reduction, which provides theoretical basis for a further study of reduction drag effect of non-smooth surfaces.

Abstract:Structural flexibility of wheelset due to bending vibration was taken into account. A simplified model of elastic wheelset was established with the axle considered as a Timoshenko beam, and the inclined angular displacement of wheel was derived from solving its equations of motion in the steady-state harmonic force via Green's function. According to the geometric constraint relationship of wheel-rail contact, the constrained equations of elastic wheelset-rail contact geometry were analytically derived. The geometric parameters of wheel-rail contact were calculated by solving those equations. Comparisons on wheel-rail contact parameters between elastic wheelset and rigid wheelset were carried out, and discussions about the influence of wheelset’s bending deformation on wheel-rail contact locations and contact parameters were performed, respectively. Results show that when the wheelset lateral displacement exceeds 5mm, the wheel-rail contact parameters change significantly due to wheelset structural flexibility; the simplified model is beneficial to wheel-rail contact calculation issues for elastic wheelset.

Abstract:The experiments were carried out to study the filtration performance of fibrous media during dust loading period. The influence of the aerosol characteristics on the dynamic parameters of fibrous media was analyzed. The relationships of pressure drop, filtration efficiency with the accumulative loading dust were described and the most penetrating particle size (MPPS) during the particle-loaded period was calculated. In addition, the calculating method for the dusty packing density α was developed and the empirical formula for pressure drop during dust loading period was identified based on the results of experiments. An improved method for calculating pressure drop was established by the regression analysis of Matlab.

Abstract:Multi-user interference occurs in an asynchronous time hopping impulse radio ultra-wide band (IR-UWB) multi-user system, therefore the asymptotic bandwidths of IR-UWB signal of dense network and extended network are derived respectively when the multi-user interference can be negligible with respect to output noise with high probability. The theoretic study results indicate that the obtained asymptotic bandwidth of IR-UWB signal is in direct proportion to the numbers of user. The asymptotic bandwidth of IR-UWB signal required by the dense network is much more than that by extended network. As the bandwidth of IR-UWB signal satisfies the obtained theoretic asymptotic bandwidth, the probability of error of the multi-user system is simplified to that of the single user system.

Abstract:Optical and SAR image registration has become a research focus in the area of multisensory image processing, because of their information complementarity and feature difference. Based on the structural similarity between images, registration via implicit similarity simplifies the traditional feature matching process as a migration of the feature points and the iterative search of registration parameters only on a single image. This provides a new idea for optical and SAR image registration. Based on the above ideas, this paper uses Canny operator to modify extraction process of feature points; introduces Joint Markov Model (JMM) to improve denoising quality of SAR image; optimizes the search process of registration parameters with modified Quantum Particle Swarm Optimization (QPSO) algorithm; achieves optical and SAR image registration at last. The experiment proves that: improved implicit similarity algorithm on optical and SAR image registration can reach a high accuracy of pixel level or even sub-pixel level.

Abstract:In order to make up the insufficiency of the single data source in the classification, the paper presents an approach that integrating LiDAR and aerial image, and implements the multistage complex urban ground object classification based on object-oriented and single pixel. Aerial image and LiDAR are merged and split some homogeneous regions as the research object by combining spectrum and spatial characteristics; ground points and non-ground points are separated by filtering LiDAR, and the altitude difference is obtained based on twice return pulse heights, and vegetation data from false-color aerial image, the classification rules are established and the segmentation objects are classified by adopting object-oriented method; and then the mistake objects are defined again based on above information, the second-stage classification based on single pixel is finished; further classification is put up to eliminate the mistake buildings by extracting the line segments of buildings. The result shows that the approach can automatically effectively separate buildings, woodland, grassland and road, the producer-accuracy and user-accuracy is respectively 92.53% and 95.79%, the whole classification accuracy is 89.62%, the study was a successful step in developing classification method for integrating LiDAR and aerial images.

Abstract:Previous efforts did not provide an accurate and fast way for generating true othorphoto. This paper tries to solve the problem by analyzing the complexity of algorithm processes and finding the optimum manner to allocate them. In this paper, an optimum segmentation number (OSN) for radial sweep is presented to achieve minimum complexity. First, the scan area, number of azimuth lines and visibility judgment area of radial sweep and spiral sweep method have been discussed with rigorous geometric theory, and then the algorithm complexity of both methods are estimated with mathematical computation theory. At last, minimum complexity of methods is obtained based on extreme point theory of differential calculus. Experiments have demonstrated that the proposed method has the best efficiency, and is efficient to avoid “M-potion” problem, and false occlusions and false visibilities caused by the rolling area, the incompatibility between the DSM and ground image resolution. The deduction and experiments indicate that the proposed method is a robust, accurate, fast and effective approach to generate high quality true orthophoto at a large scale.

Abstract:In this paper, a new method is put forward for Shield-attituded Automatic Measurement. With narrow space in underground tunnel and difficulty to measure more than 2 points by TPS, this paper takes advantage of integrated guidance method by TPS and clinometer , then pitch and scroll of shield obtained from clinometer as observed data would be processed error adjustment based on 3D datum transformation ,which solves multi-source data collection and process; With some successful application of this method on tunnel construction guidance in Shanghai Metro No.12 line and Hangzhou Metro No.1 line, this method proved to be reliable and practical.

Abstract:60 percent settlements were selected randomly from the 1452 prehistoric settlement in area of Songshan culture circle for settlement sites selection Preference zoning. The paper discussed the relationship between the settlement distribution and altitude, slope, river systems, topography, soil, climate by using GIS spatial analysis techniques. Weights of each index factor were calculated by using the method of variation coefficient. Prehistoric settlement sites preference level model was constructed by introducing space-weighted superposition method to divide study area into three classes: high level, medium level, low level. The model was validated by using remnant 40% settlements. The validation results showed that the accuracy of the model was relatively high. The model can be used to predict the geographical location of the settlements that are not found.

Abstract:An investigation was made into the effect of the time delay on the stability of the positive equilibrium of the gene-regulatory in cells and the periodic oscillatory phenomenon induced by it. Two cases of discrete and distributed delay were studied. By analyzing the associated characteristic equation, the conditions for absolute stability and conditional stability as well as the critical values of inducing periodic oscillation were obtained. At last, the numerical simulations were employed to support the theoretical results.

Abstract:In this paper, a class of LQ singular optimal control problems is investigated by an iteration process of Riccati differential equation for classical LQ optimal control problem. The convergence result is obtained to give an algorithm for computing the optimal value of this kind of problem. Moreover, three examples are given to illustrate the iteration process.