Applied Mechanics and Materials Vols. 52-54

Abstract: In this study, the volume-acceleration model was introduced to determine the initial condition for bubble motion during underwater explosion. Subroutines, which defined the initial and boundary conditions of the fluid field, were developed based on MSC.DYTTAN software. Numerical simulations were compared with the results of validated experimental data. From the basic phenomenon of interaction between a bubble and a vertical rigid wall, the dynamic behavior of a bubble near a vertical rigid wall was simulated and analyzed. The dynamic behavior of bubble and the jet were studied systematically and summarized relative to the law that both of the motion of bubble and water jet are closely related with the standoff distance parameter. The results of this study have valuable implications for correlative theory research and engineering calculation.

Abstract: A model for a moderately deep underwater explosion bubble was developed in inviscid and irrotational fluid. Considering the effects of gravity, buoyancy, drag to the motion of bubble, the equations of motion (EOM) for bubble in inviscid and irrotational fluid near a free surface were established by introducing the potential-flow theory, energy equation and Hamilton principle. The displacement of the center of bubble, the radius-time histories and impulse periods of bubble were acquired by solving the EOM. The calculated results were compared with the experimental and numerical results. The compared results show that the former is consistent with the latter. The research has value to correlative theory research and engineering calculation.

Abstract: With dynamic stress intensity factor (DSIF) as a characteristic parameter, this paper makes an analysis on the effect of parameters variation of vehicle speed, asphalt overlay thickness, modulus and old cement concrete pavement joint width on asphalt overlay reflective crack by investigating the variation law of reflective crack of asphalt overlay structure suffer wheel load. The results show that: the maximum dynamic stress intensity factor decreases with the increase of speed. Numerical value of maximum dynamic stress intensity factor is larger than the corresponding value of the static load. The longer the initial crack, the less the times of sustaining load of the same extending length. The increase of asphalt overlay thickness can reduce the value of dynamic stress intensity factor to a certain extent. With the augmentation of asphalt overlay modulus, the effect of dynamic load on reflective crack can be reduced in some degree. Dynamic stress intensity factor increases with the increase of joint width.

Abstract: Due to the concrete self-shrinkage, frequent load application and temperature fluctuation, and so on，the gap formed between the inner tube wall and the core concrete surfaces would decrease the performance of concrete-filled steel tube (CFST). To prevent this cavity problem, various types of expansive agents and aggregates were used in this study to improve the volume stability of core concrete. Comparative experiments with mortars and concrete were carried out respectively under standard curing condition and under enclosed curing condition which simulated the environment in steel tube. The results could be summarized as follows: ● Two types of expansive agents, ZY type expansive agent mainly containing sulfates and aluminates and M type expansive agent mainly containing magnesium oxide, presented different expansive behaviors with curing ages in mortar and concrete. Two types of expansive agents combined with each other could produce complementary and superimposition effects to improve continuously the volume stability of mortar and concrete. ● Sufficient water supply is the key factor for the formation and maintenance of expansion. The volume change caused by the self-shrinkage effect of core concrete could not be effectively off-set with whether two types expansive agents or their compounds under enclosed environment in which water was scarce and could not be supplied from outside. ● When some water-saturated ceramsite were used to partially replace aggregates in core concrete,the volume expansion performance of core concrete improved dramatically with the water storage and supply effects of water-saturated ceramsite.

Abstract: In ACFM, the measured signal is very weak and always inevitably includes the noises and the unwanted signal. Make use of lock-in amplifier technology to have designed a disturbance magnetic field testing circuit which includes eliminating 2.5 volt DC circuit, amplifying and filtering circuit, phase-shifting circuit and switching voltage multiplier. This circuits designed can performe the measurement and do-nosing for weak magnetic signal of ACFM. The experiment indicated that make use of lock-in amplifier technology to design and optimize ACFM detection circuit is an effective method

Abstract: According to the characteristics of design and production for digital maps, a methodology for developing popular science tour digital map is proposed in respect with the reality of popular science tour resources in Northeast. A popular science tour digital map in Northeast was made with the MapX controls, which is a popular GIS development tool designed from the VB program language. Several key technologies for the design and production of the electrical map were discussed. The development of popular science tour digital map in Northeast has practical values for tourism developments.

Abstract: To calculate soot for a high-pressure common rail diesel engine a new soot model (TP model) is presented.. In soot source term phase, when zone temperature T<1500K, gas-phase kinetics is considered and the soot precursors –PAHs (Polycyclic aromatic hydrocarbons) is calculated. When zone temperature T ≥ 1500K, the gas-phase chemistry and soot source terms are calculated. The soot model integrated with the new auto-ignition models is then applied in multidimensional simulations. The TP model is then implemented in KIVA code instead of original model to carry out optimizing. The results of soot with variation of injection time, variation of rail pressure and variation of speed among TP model, KIVA standard model and experimental data are analyzed. The results indicate that the TP model can carry out optimization and CFD (computational fluid dynamics) and can be a tool to calculate for a high-pressure common rail directed injection diesel engine.

Abstract: To improve the utilization ratio of resources and the complete number of tasks, a kind of a new grid resource scheduling algorithm TWMQC (based on Task Weight and Multi-QoS Constraint) integrating multi-QoS constraint with task weight was proposed. The accomplished process of grid resource scheduling algorithm was transformed multi attribute constraints of resource and task, according to the parametric resource information and task information, classified different task weight sets based on the priority of tasks. Multi-QoS constraints of deadline of gridlets, bandwidth and CPU were defined, and the correlative algorithms were simulated by the GridSim toolkits. The simulation results show that algorithm TWMQC, which integrating multi-QoS constraint and tasks weight is superior in solving such kind of issues by comparing and analyzing the result data.

Abstract: The band structures of in-plane elastic waves propagating in two-dimensional phononic crystals with one-dimensional aperiodicity are analyzed in this paper. The localization of wave propagation is discussed by introducing the concept of the localization factor that is calculated by the plane-wave-based transfer-matrix method. By treating the aperiodicity as the deviation from the periodicity in a special way, two kinds of aperiodic phononic crystals that have Thue-Morse and Rudin-Shapiro sequence in one direction and translational symmetry in the other direction are considered. The transmission coefficients based on eigenmode match theory are also calculated and the results show the same behaviors as the localization factor does. In the case of Thue-Morse and Rudin-Shapiro structures, the band structures of Thue-Morse sequence exhibit similarities with quasi-periodic sequence not present in the results of Rudin-Shapiro sequence.

Abstract: Many methods of fire detection in video have been carried out on PC. Generally it needs long cables to transmit images and processes videos on computers. That system is too dependent on computers, and costs a lot using cables to transmission. We would rather use a portable device to detect fire, which will bring us much more convenience. This paper designed a portable system to detect fire using DSP. The system integrates video acquisition, image processing and fire alarm together in a circuit board. Then we develop algorithms to recognize fire, and transplant them into DSP. Finally put it into use after commissioning test. This portable system can work independently. Users can put into their requirements through user-interface, and system will output the fire pictures and alarm by wireless communication or internet. This system is applicable to various places, such as indoor and outdoor, large and open spaces, forest, etc.