Abstract:This study investigated the shear behavior of two reinforced thin-wall box girders with vertical prestressed tendon. Whether the vertical tendons were prestressed or not and the ducts were grouted or not were comparatively studied. The experimental study addressed diagonal cracking behaviors, crack patterns and width, load-deflection relationship, the web strain and stirrup strain, as well as ultimate shear capacity. The test results have shown that, the cracking load of box girder with prestressing force is about 16% higher than those without, and the effect of prestressing force only increases by about 2.3% for ultimate shear capacity. Meanwhile, the shear resistance of girder without grouting is about 9.3% lower than those with ducts well grouted. Through the comparison of test girders, it has been found that the vertical prestressing force can improve the diagonal cracking load and shear capacity. The grouting quality for vertical prestressed ducts is of great importance to the shear behavior of the box girder.

Abstract:Five groups of high strength concrete (HSC) specimens with a 28-day cubic compressive strength of 82.6 MPa and with fire insulation were tested, and the influence of the thickness of fire insulation on the chloride ion permeability of HSC after high temperature was discussed. Test results have shown that, in the case that the fire insulation thickness is 30 mm, the chloride ion permeability of HSC after high temperature is almost the same as that at room temperature; in the case that the fire insulation thickness is 20~25 mm, the chloride ion permeability of HSC after high temperature is still lower than that of C50 concrete at room temperature; and in the case that the fire insulation thickness is 15 mm, the chloride ion permeability of HSC after high temperature is relatively large. It can be concluded that fire insulation with a thickness of 20 mm is effective both for the inhibition of explosive spalling of HSC at elevated temperature and for the reduction of the chloride ion permeability of HSC after high temperature.

Abstract:The temperature response of geothermal heat exchangers (GHEs) can be described more accurately with heat transfer model with groundwater advection. Considering that the current analytical solution model is time-consuming in calculation, a new form of analytical solution of g-function was proposed, and the influence of groundwater flow on the heat transfer in GHEs was discussed. Computations indicate that the calculation efficiency of the new g-function has improved significantly while the reasonable accuracy is maintained, and the value of middle point temperature g-function is larger than that of integral mean temperature g-function. Groundwater advection can improve the effectiveness of GHEs significantly for the step heating flux. The temperature distribution of borehole area is influenced greatly by the arrangement of multiple boreholes.

Abstract:The conclusion may be blurred and subjective in the traditional fuzzy comprehensive evaluation of risk analysis because of the weight set over-reliance on expert scoring and subjective survey method. In response to these shortcomings, the introduction of rough set theory can help us to calculate the weight of the objective set and to avoid the "lost" phenomenon of the smaller weight factors. With 120 detailed tunnel collapse accident statistics in the past 15 years, we can identify the six major landslides risk factors, including geological factors, design and construction quality and so on. By the application of rough set theory in the decision table method, we can also calculate the factors of the objective weight and use the fuzzy theory to focus on the evaluation factors as normal membership function approach. Then, we can establish tunnel construction period collapse assessment method on the basis of the rough set theory and theory of barycenter of fuzzy set. Finally, using the assessment methods in the engineering project, we find this method can verify the applicability and it is more accurate, compared with the traditional fuzzy comprehensive evaluation and practical engineering analysis method.

Abstract:Wind tunnel tests of single 3D hilly terrain for eight slopes were carried out, and the wind speed spectrum in different places and the effect of the hill slope were studied. The results show that the effect of the hill at the windward and hilltop far away from the hill can be ignored; at the leeward under the height of 0.8 h, the peak value of the wind speed spectrum increases and peak frequency moves to a high frequency. There is a single peak and the frequency bandwidth becomes narrower. It is assumed that the fluctuant wind speed energy at the leeward is composed of the inflow turbulence energy and the vortex energy induced by the hill, so the vortex energy can be separated. The calculation model of the vortex spectrum was proposed by the fitting of the wind tunnel test data. The wind tunnel test of different hill slopes shows that the slope 0.5 is the critical slope where the vortex will appear.

Abstract:Traditional artificial potential field (APF) method can hardly be applied directly to intelligent vehicle local path planning, as it does not take into account the dynamics and kinematics constraints. A dynamic virtual obstacle based local path planning method was presented to solve this problem. Firstly, environment information, vehicle operation status and traffic rules were used to analyze driving safety, and the analytical expression of the virtual lane was deduced. Secondly, driving operation decision was made and constrained dynamic virtual obstacles were generated according to the decision. Finally, the local path was planned on the basis of an improved APF with dynamics and kinematics constraints. Simulation results show that the proposed method can achieve better planning performance at various initial speeds, relative speeds and relative distance under the condition of dynamics and kinematics constraints.

Abstract:A model of urea-SCR system was built to simulate low temperature performances. The results reveal that, in the range of 150~250 ℃,gas hourly space velocity(GHSV) has more impact on DeNOx than at a higher temperature; when GHSV is smaller than a value, DeNOx can hardly change; and below 200 ℃,the NH3 should be less than NOx, or it will lead to waste and pollution. The impact of the oxygen on DeNOx depends on the NO content, and this trend becomes weaker when the temperature increases. When the oxygen content reaches 5%, the DeNOx in different temperatures has stable values.

Abstract:A two-degree-of-freedom (TDOF) fluid-type floating raft system was propoesd for vibration isolation based on anti-resonance mechanism, which enables completely isolate vibrations, including two frequency components. The mathematical model of TDOF fluid-type floating raft was derived under the assumption of small amplitude vibration. The isolation behavior of the floating raft was analyzed, and the expression of force transmissibility was obtained. The analysis indicates that TDOF fluid-type floating raft possess two anti-resonance frequencies, which can be tuned by changing the liquid level. The isolation behavior of TDOF fluid-type floating raft was compared with that of single-degree-of-freedom (SDOF) fluid-type floating raft and classical mass-spring isolation system. It shows that TDOF fluid-type floating raft has effect of vibration isolation at low frequency, and it also has better effect of vibration isolation than SDOF fluid-type floating raft when the two anti-resonance frequencies are equal to each other.

Abstract:This paper designed the mechanical and electrical structure of the underwater condenser cleaning robot. Considering the comprehensive influence caused by factors such as buoyance, flow resistance, etc, a dynamics model was established based on the complex work environment, and an adaptive control method was proposed. The structure of the control rule is simple and robust, which can overcome the uncertainties and the disturbances. The stability and convergence of the control system are ensured by using the Lyapunov method. Simulation results show the controller is very steady and can provides satisfactory tracking ability, which verifies the proposed model.

Abstract:By combining the field-weakening control principles of interior permanent magnet synchronous motor (IPMSM) with the space vector pulse width modulation (SVPWM), a novel field-weakening control strategy for IPMSM was proposed. The difference between the reference voltage updated by current regulator and the saturated voltage output by SVPWM is used for field-weakening control, which modifies the stator current phase angle. The d and q axis stator reference current component is redistributed, and finally, the speed operation range of IPMSM is extended. With this method, high-time speed field-weakening operation was realized, and the smooth transition of field-weakening stator current and fast response were also guaranteed. Moreover, since the proposed method utilizes the dc-link voltage more efficiently, it makes the motor generate higher output torque and has better adaptability in field-weakening operation region than conventional field-weakening control methods under the same voltage and current limitation. The effectiveness of the proposed field-weakening control method was verified with simulation and experimental results.

Abstract:Considering cable accessories structure and the characteristic that insulation failure easily occurs in internal attachment resulting in partial discharge, this paper designed a built-in UHF and UWB bowtie antennas sensor to detect partial discharge signal for cable accessories. Simulation results show that the effective bandwidth of the antenna is 350~585 MHz. Measurement results also show that the antenna sensor has high sensitivity and superior performance, and can be applied to PD UHF signal detection of cable accessories.

Abstract:When using traditional state equations to calculate and analyze nonlinear dynamic autonomous networks, there are some problems, such as limitations and calculation difficulties, especially the problem of calculating the time of the response crossing a boundary. To avoid these problems for the nonlinear dynamic autonomous networks, this paper presented a method based on canonical piece-wise linearization to obtain a set of canonical piece-wise-linear equations for dynamic units in nonlinear dynamic autonomous networks and the hybrid parameter equations of nonlinear dynamic autonomous networks. By resolving these equations, the simulation algorithm of fault response of nonlinear dynamic autonomous networks can be obtained. This paper used wavelet transform as a preprocessor to extract the fault features from the fault responses of nonlinear dynamic autonomous networks, and adopted Generic Algorithm to optimize the structure and parameters of BPNN. Then, the fault state features were fed to GABPNN to classify and determine the faults. Simulation results show that this fault diagnostic algorithm is an efficient analysis method.

Abstract:A simulation study has been carried out for the solidification process of liquid Ca50Zn50 alloy by using molecular dynamics method. The pair distribution function g(r) curves, bond-type index method, cluster-type index method (CTIM) and three-dimensional visualizing analysis method have been used to analyze the evolution properties of microstructures during the solidification process. The results show that, owing to the difference of atomic radius for Ca and Zn, the first peak of the total pair distribution function gtot(r) curve is split into three secondary peaks. With the decrease of temperature, the propability of Zn atoms being close to each other is increased obviously. In the system, the icosahedron basic cluster (12 0 12 0) consisting of 1551 bon-types plays a key role in forming amorphous structure. And the center atoms of basic clusters in the system are mainly the Zn atoms with smaller size. Most basic clusters with short-range order would be linked to each other in the manners of vertex-sharing(VS), edge-sha ring (ES) , face-sharing (FS) and intercross-sharing (IS) atoms. During the solidification process of forming amorphous state, most basic clusters would be linked with the manner of intercross-sharing (IS) atoms to form various larger clusters with different sizes, more tightness of connecting and more stability of structure.

Abstract:Crystallization transformation kinetics of Cu45Zr45Ag7Al3 bulk metallic glasses in non-isothermal (continuous heating) modes were investigated by differential scanning calorimetry (DSC). Activation energy for crystallization at different crystallized volume fractions was analyzed in Kissinger method. Then non-isothermal transformation kinetics was described with the Kempen model. Under the condition of continuous heating, the characterization temperature Tg,Tx and Tp of amorphous alloy Cu45Zr45Ag7Al3 increase with the heating rate, and the super-cooled liquid phase zone also expands gradually. The activation energies of Cu45Zr45 Ag7 Al3 bulk metallic glasses are 431.1, 307.2, 339.5 kJ·mol-1 and the exponent n are 5.2 and 1.9. The results have indicated that the crystallization processes for all the glassy alloys are polymorphic crystallization controlled by interface.

Abstract:An asphaltene-degrading bacterium S, which can utilize asphaltene as the sole carbon source, was screened and isolated from oil production water. Strain S was showed 99 % probability of Bacillus subtilis Bsn5 by the result of the partial 16SrDNA analysis. The utilization of heavy oil containing abundant asphaltene by strain S was done, and the influence of biodegradation on the physical and chemical properties of heavy oil was analyzed. The results indicated that the surface appearance and structure of heavy oil were changed obviously after biodegradation. The alkane content increased while the asphaltene fractions decreased, compared with these components in heavy oil sample before biodegradation. The asphalt degradation rate is up to 34%, and the viscosity and density of heavy oil was reduced about 34.11% and 4.57% respectively. The physical and chemical properties of heavy oil have been improved by strain S.

Abstract:The efficiency and performing of external circulation up-flow anaerobic sludge blanket reactor (UASB) in dealing with algae-laden water from Taihu Lake was studied for the high organic matter concentration of algae-laden water. The test results showed that, using naturally decomposed algae-laden water for about 5~7 d as influent , the external circulation UASB could be completely started and remained stable, when the reactor ,which was inoculated sludge from municipal sewage treatment plant ,was operated at HRT of 5 d,temperature of （32 ±1） ℃. Based on declining HRT, increasing COD concentration phasedly, the organic load of the algae-laden water was increased to 3 kgCOD/(m3·d), with a stable COD removal of 75% and a gas production rate of 0.75 L/(L·d), indicating the stability and performance of the external circulation UASB treating the water. Observed by SEM, the granular sludge was found in the stabilization stage with coupled growing micro-organisms such as filamentous bacteria, rod-shaped bacteria, and spherical bacteria.

Abstract:In order to solve the problem that redundant rules in cooperative firewall will reduce the throughput, a bidirectional redundancy deletion approach to high-throughput cooperative firewall was presented to explore cooperative firewall with one administrative domain. This approach removes redundant rules of two firewalls in cooperative firewall by comparing the rules of two firewalls, and simultaneously enhance the throughput of whole cooperative firewall. The result of the simulation experiment shows that, redundancy rate of the approach reached 22.7%, and the cooperative firewall throughput was improved 8.2%. Compared with the existing methods, the approach benefits more in removing the redundancy rules of cooperative firewall and improving the cooperative firewall throughput.

Abstract:This paper first derived the function between the transmission time and the interference for given Bayesian risk value. On this basis, the following two interference constraint algorithms were proposed, i.e., the non-cooperative sensing mode frame length design algorithm to maximize system throughput and the cooperative sensing mode frame length design algorithm based on Newman-Pearson criterion. Simulations results have shown that, even if the Bayesian risk value is large, the proposed algorithm can achieved better throughput due to the optimization of the frame length, compared with the existing schemes.

Abstract:In order to improve the quality and efficiency of intelligent optimization algorithms for solving path planning, the framework of knowledge-conducting intelligent optimization algorithms for solving path planning was proposed. Considering the limitaion of the knowledge adopted previously, the framework does not adopt the knowledge mined from previous iterations, which is different from the conventional conducting evolution, but adopts the costomizing domain knowledge of path planning. In order to describe the conducting manner, the intelligent optimization algorithms is defined formally as a set composed of 3 conducting objects, and the conducting manner is divided into 7 kinds of form which are separated or combined accordingly. A corresponding conducting manner is adopted according to the characteristic of different costomizing domain knowledges of path planning, and these knowledges are transformd to structured meta-strategy which can improve the performance of the algorithm. The solving framework is verified by taking particle swarm optimization algorithm for instance. Simulation experiments results have indicated that the conducting of costomizing domain knowledge can improve the algorithm's global search capabilities, and the algorithm possesses better convergence rate.