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.      

Performance of A Sludge Reduction System on Removal of Nitrogen and Phosphorous Controlled by Low Dissolved Oxygen

The influences of dissolved oxygen (DO) on the removal process of nitrogen and phosphorous in a sludge reduction system had been studied by controlling aeration amounts. It was found that under the conditions of low doses of 2,4,5trichlorophenol (TCP), endogenous sour values of activated sludge increased with the extension of low DO state duration in SBR system and the decrease of cyclic average DO, which led to a low DO environment favored the formation of simultaneous nitrification and denitrification(SND).TCP concentration was recommended as 2mg / L and cyclic average DO value in SBR system was kept at 2mg / L based on the impacts of TCP concentration on sludge reduction, removal of nitrogen and phosphorous and sludge performance. Compared with the control system, aeration amounts increased by 23% and the discharge of excess sludge decreased by 34.6%. The water quality in effluents was equivalent in the aeration sludge reduction system with 2mg/LTCP, which met the discharge standards. Therefore, it was indicated that the removal of nitrogen and phosphorous and sludge reduction can obtain excellent performance in TCP system under low DO state with removing Phosphrous rich sewage.     

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     

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.     

Design and application of hospital service info structurebased on medical knowledge flow

To counter deficient medical knowledge sharing and the low efficiency cooperative diagnosis between doctors, the knowledge flow from knowledge management (KM), knowledge acquisition and knowledge supply are established as the core info structure of a hospital KM model. This is done by combining heavy idea exchange, frequent updating, and intensive use of the medical knowledge. Three important knowledge flow(KF) operations (knowledge refreshing, knowledge migration and knowledge expansion) are proposed. By comparing hospital information management with hospital KM, a hospital KM method based on knowledge flow is constructed. The method emphasizes tracking, monitoring and controlling hospital wide comprehensive process of medical knowledge. A specific clinical diagnosis instance is given for detailed healthcare knowledge flow analysis.      

Generalized conforming quadrilateral membrane element with vertex rotational freedom

A new generalized conforming quadrilateral membrane element is developed by introducing additional rigid vertex rotational freedoms to the normal 4 node quadrilateral membrane element. The rotational stiffness of the present element is not zero so that the singularity of the stiffness matrix is avoided. Numerical analysis of the Cook problem cantilever beam shows that the EAE/Mem element passes the patch test and possesses good convergence, reliability, and precision without a zero energy mode. It provides a lock free solution to the MacNeal beam problem. Numerical results also show that the EAE/Mem element is insensitive to mesh distortion. The results demonstrate that the generalized conforming technique is an efficient tool for developing high performance finite element models.     

A mathematical description of the liquid flows inside blast furnaces

The knowledge of liquid flows in blast furnaces may play an important role in controlling the blast furnace process. Appropriate assumptions are given to represent the main characteristics of the liquid flow in blast furnaces, such as liquid streams being composed of unwetting liquid droplets, inertial force having little effect on the liquid flows, and mass exchange existing along the direction perpendicular to liquid flow. A mathematical model is built to predict the distribution of the liquid flow rate and the liquid flow range in packed beds. The scale of the numerical grid used to solve this model may not necessarily be reduced to the particle level. The predicted results of this model accord well with the observed data. This model is an alternative theory for the simulation of blast furnaces     

Stability of a nonlinear red tide dynamic model in a polluted environment

We develop a nonlinear red tide dynamic model to study the effect on a system of two harmful phytoplankton and zooplankton and of a toxicant emitted into the environment from external sources and a toxin excreted by phytoplankton. We use modern nonlinear dynamics to discuss stability and bifurcation, and obtain the thresholds of persistence and extinction for each species. Numerical simulations are used to validate the theoretical results. The results show that a sequence of Hopf bifurcations occur at the interior equilibrium as the delay increases or the growth rates increase.     

Application of GC FTIR technology in the analysis of SF6 decomposition products

The composition of SF6 decomposition products is directly associated with the safe operation of equipment. Through GC FTIR coupling technique,the SF6 decomposition products are divided, the qualitative analysis is made with FTIR to the outlier,and spectrogram was processed with subtract and searched the analogous one. Above data is used to generate the tridimensional atlas of infrared spectrum absorbance GC holding time. Single gas analysis is compared with local measurement, the foregoing method can make the qualitative analysis and quantitative analysis for the decomposition products, the fault features detected by gas composition and chroma is anastomotic with the actual fault, the result indicates that this method can be used in GIS fault diagnosis.