Fire and explosion hazard analysis of the urea synthesisproduction process

On the basis of identifying and analyzing harmful risk factors in the urea synthesis production process of a factory, the production process is assessed and analyzed using the Dow chemical company fire and explosion index method. The related indexes are f     

Dynamic responses of ultra high voltage transmission line ice shedding

Numerical models of typical 500 kV ultra high voltage (UHV) transmission lines are set up in ABAQUS/CAE software. The dynamic response of the transmission lines with different structure parameters under various ice shedding load cases are analyzed, and th     

Design of subretinal artificial chip based on standard CMOS technology

A chip with smaller size and higher pixel density was designed to increase the chip’s pixel density in subretinal prosthesis. This chip was designed on 0.35 μm standard CMOS(complementary metal oxide semiconductor) technology of CHRT company, while the double inverter relaxation oscillator was chosen as the basic pixel circuit. By creating layout on Cadence software, the circuit was debugged and simulated. The experiment results show that the pixel circuit provide effective pulse signals whose values and frequencies can vary with photocurrent to stimulate retinal nerve cells. For the simulated layout, the pulse width was 0.26 ms, the frequency was 18～503 Hz, the pixel size was 65 μm×65 μm, and the chip size was 1.1 mm×1.1 mm. All of the parameters can satisfy the requirement to stimulate retinal nerve cells in physiology. The experiment results provide a good foundation for the following research.     

Experimental Study on Channel Characteristic and Refrigerating Effect in Vortex Tubes

Taking compressed air as the working medium, the performances of energy separation and temperature distribution in various kinds of vortex tubes are experimentally studied. Temperature distribution and refrigerating effect curve in vortex tubes are attained. The results show that the refrigerating effect of vortex tube with four nozzles is better than the other three kinds of vortex tube under the condition of ordinary temperature and 0.7 MPa pressure, and the refrigerating effect of vortex tube with six nozzles is worst in the four kinds of vortex tube. The refrigerating effect of nozzle with Achimid curve is best compared with other kinds of curves. The experiment shows that there is a boundary between cold and hot airflow at 0.7R of the tube, where cold airflow is inside the boundary and hot airflow is outside the boundary.     

Hybrid field network simulation of temperature in a building fire

A connecting platform between the field model and network model has been constructed, based on a multi functional building model. The field model is used to simulate the fire smoke in certain special compartments (the fire room and specific large space rooms), while the network model is used to simulate the uniform compartments. When combining the simulation results of the field model and network model as the interface boundary conditions for the each other, a hybrid field and network model is presented. The hybrid field network model can provide more detailed physical information of the fire smoke properties under a specific fire scenario for the specially confined compartments. In addition, the hybrid model can predict the fire smoke flow properties in the building accurately.     

Simulation and analysis of all terrain vehicle ride comfort

A multi rigid body dynamic model of an all terrain vehicle (ATV) is established in MSC.ADAMS. The model takes into consideration the body, suspension, frame and the steering system. According to the method of superposition of harmonic wave, a Grade B road file is created in ADAMS for the riding comfort test. The engine excitation is analyzed. The infliction for engine excitation to ADAMS is achieved. The ATV ride comfort simulation is carried out with the excitation of the engine, and the seat vibration is evaluated using an evaluation method programmed via MATLAB. It has laid a good foundation for further analysis.     

Performance analysis and comparison of IEEE 802.11 distributed coordination function and improved schemes

To improve the media access control mechanism and enhance the performance of large scale wireless LANs, the distributed coordination function of IEEE802.11 standard and two typical improved schemes are studied extensively. Compared with the distributed coordination function, the fast collision resolution mechanism greatly enhances the throughput, but deteriorates the delay jitter and fairness of wireless LANs. The new self adaptive distributed coordination function markedly improves the delay jitter and fairness performance, while enhancing the throughput of wireless LANs to a certain degree. Hence, with further improvement, the new self adaptive distributed coordination function is more suitable for large scale wireless LANs for multimedia information transmission.     

Analysis of the Kinetic Theory of Submerged Abrasive Water Jets

Abrasive water jets can incise objects with strong rigidity under water. The analytical means of kinetic theory is optimal for theoretical problems of submerged abrasive water jets. The flow characteristics in submerged abrasive water jets were analyzed based on kinetic theory for multiphase flows. The impact characteristics of every phase in submerged abrasive water jets was analyzed and continuity and momentum equations subsequently were developed for solid, gas and liquids in submerged abrasive water jets. It is shown that if the distributing function of every phase were given, the law of its movement could be ascertained.     

Numeric Analysis of the Dynamic Performance of a Prestressed Concrete Beam

The finite element of a prestressed concrete (PSC) beam is analyzed in a case of diverse prestressing forces. The mechanical model applied is that advanced by Clough for a concrete beam bearing axial force. The results indicate that the beam frequencies decrease with increasing prestressing force. A dynamic experiment of a non bonded PSC beam was carried out to validate the veracity of the finite element analysis. Test beam frequencies increase with increasing prestressing force. The analysis model thus is unfit for frequency analysis of a PSC beam. The determinant factor of frequencies is analyzed, and the dynamic model is modified according to experimental results. The modified model analysis result shows that: the calculated frequencies of mode 1 agree with the test results well; the frequencies of mode 2 posses some errors; and, the modified model can reflect the direction of frequency change along with the change of prestressing force well.     

Deformation Properties of Backfill Grouting in Shield Tunnel

Utilizing the self made unit body model test apparatus, the deformation laws of backfill grouting were studied under different grouting pressures, different soil conditions and different ground water pressures. It was shown that high grout pressures can accelerate the consolidation rate of grout drainage and increase final deformation amount. And soil permeability coefficient was an important factor to grout deformation. The ground water pressure was more important for sand soil while the grout pressure was for clay soil. The proposed apparatus can truly reflect stress status of grout injected to tail void. And grout deformation properties were helpful to clarify the stratum stress release and stratum deformation of backfill grouting. 