Search

Electromagnetic radiation has become a great threat to human health. In this paper, ferrite and graphite were main absorbing agent, which were prepared to a new type of anti-electromagnetic radiation gypsum board. The results show that the microwave absorbing properties of ferrite/graphite mixed are better than with ferrite or graphite single-agent mixed. The gypsum board with the graphite content of 5wt% and the ferrite content of 25wt% has the best absorbing performance, The effective band width less than-5dB of the samples is 7.1311GHz, and the maximum absorption peak-18.467dB.

There were many problems when natural flake graphite was used in gypsum as an absorbing agent, such as absorbing large amount of water, a poor interfacial compatibility and so on. In this paper, polycarboxylate-based water reducer and AES (sodium alcohol ether sulphate) are used to modify graphite-gypsum system. The results show that both agents are effective to improve the properties of gypsum system and the former is best. Compared with the sample without any reagents, polycarboxylate-based water reducer can reduce the water-solid ratio from 1.1 to 0.9, increase the compressive strength from 0.106Mpa to 0.701Mpa and the flexural strength form 0.064Mpa to 0.312Mpa.

Using FGD gypsum as raw material, calcium sulfate whisker was prepared by hydrothermal synthesis method. Through testing the aspect ratio of calcium sulfate whisker, the effect of reaction temperature, reaction time, desulfurization gypsum slurry concentration and pH value on the growth of calcium sulfate whisker were deeply researched. The optimum conditions for the preparation were that the reaction temperature was 150 °C, reaction time was 270min, the slurry concentration was 10% and the slurry pH value was 6.

This paper introduces practical measurement of steel fiber distribution in steel fiber reinforced concrete (SFRC) which serves as the matrix of prestressed SFRC beams. Using digital image processing in mesos-copical mechanism of SFRC, “the Dynamic System of Measuring Steel Fiber Distribution” is developed. Compared with theoretical analysis, the system is practical and valid, and a new method is provided for guiding production technology of SFRC and controlling constructional quality.

In order to study the shear capacity enhancement effect of prestressed technology to steel fiber reinforced concrete, the practical formulas were proposed for evaluating the shear-strength of unbonded prestressed steel-fiber reinforced concrete beams (UPSFRCB) through the test and study of shear capacity of UPSFRCB with simply supported ends. Various factors affecting the shear strength of UPSFRCB, such as steel fiber, prestress and shear-span to depth ratio were analyzed. The result is of importance to the popularization and application of prestressed steel-fiber reinforced concrete.

The formation method of the intersecting hole nozzle, each hole is formed by the converging of two or more child holes, is proposed, for the purpose of accelerating the fuel-air mixing process of direct injection internal combustion engines. In order to examine the macro characteristics of intersecting hole nozzles, three single-orifice intersecting hole nozzles, with the intersecting point of the axes of child holes locating inside, outside, and right at the exit surface, were manufactured. And high speed photography was employed to visualize, thus to quantify the angle and penetration of, the spray from these intersecting hole nozzles in a vessel under ambient room temperature and pressure of 0.1 to 2.0 MPa. The experimental results showed that the spray from intersecting hole nozzles were fan-shaped, which were beneficial for prompting the fuel-air mixing. Particularly, when the intersecting points of the axes of child holes locate right at the exit surface, the longest spray penetration was obtained, and the spray front angle is slightly smaller than side angle. While the intersecting points of the axes of child holes locate inside or outside the exit surface, the spray penetration is shorter, and the spray front angles are extremely larger than side angles under pressure of 0.1 to 2.0 MPa. With the rising of ambient pressure, the differences between front angle and side angle of all the three intersecting hole nozzles become smaller in different degrees.

In order to improve the durability of the wood fiber reinforced external wall board, silica fume, a kind of inorganic silica material was added in the board. The properties of the boards containing different amount of silica fume were studied. The durability was effectively characterized by determining the fracture work and bending strength after wetting-drying cycles test of the board. The results showed that the fracture work and bending strength of the board obviously increased when the proportion of silica fume and cement was 1:9~1:3.

Gas permeability mechanism for the laminated salt rock gas storage is very complex. The key problem is to establish the permeability model and to propose the corresponding numerical method suitable for salt rock with weak interlayer based on seepage theory in porous media. An efficient and accurate method is proposed to model the flow in fracture and matrix. The fractures are regarded as boundaries among adjacent matrix blocks. Darcy’s law governs velocities in the matrix blocks, while the flow in the fracture on boundaries is set up by accounting for the fracture’s thickness. This model can reflect the fracture flow which is different from the equivalent medium model, and its computational complexity is less than that of double porous model. Combining with the field situation of Jintan gas storage in China, the pressure distributions of storage with different cyclic pressures for gas injection and production in five years are studied. It is concluded that the effect of permeability on gas pressure distribution is very important.

Asbestos is used as reinforcing fiber in nearly all the current external wall board manufacturing process, but it has harmful effects on the human body. In this paper, composite-fiber reinforced external wall board without asbestos was successfully prepared using plant fibers as reinforcing material instead of asbestos by compression molding. Effect of the content of wood fiber, wood powder, quartz sand and water on the density and mechanical properties of the board were studied in this work. Besides, the optimized preparation method for composite-fiber reinforced external wall board without asbestos was achieved.

Generally, a cell can trigger its self-defense mechanism in response to genomic stress under acute perturbations from outer environment. To investigate the dynamic kinetics of cellular repair mechanisms in fighting against genomic stress, a mathematical model of representing and analyzing DNA damage generation and repair process is proposed under acute Ion Radiation (IR) by using the Kinetic Theory of Active Particles (KTAP). In this paper, we focus on describing a mathematical framework of Cellular Repair System (CRS). We also present the dynamic processes of Double Strand Breaks (DSBs) and Repair Protein (RP) generating, DSB-protein complexes (DSBCs) synthesizing, and toxins accumulating under continuous radiation time.

The transient performance of engines is investigated in this paper. A mathematical model of single-cylinder engines is established and the friction torques produced by crankshaft bearing, piston assembly, pumping loss and other major factors are modeled. A dynamic simulation system is developed based on the MATLAB Simulink environment. Friction torques and instantaneous motion characteristics of the engine are predicted. The results show that crankshaft bearing, piston assembly, and pumping loss have a major effect on the transient performance of the engine, and the models described in this paper provide an effective tool to simulate engine processes.

To manufacture the complicated turbo molecular pumps (TMP) rotor by NC machine tool, a geometric modeling for unitary rotor of TMP is created by UG NX 4.0. Based on the optimized geometric parameters of turbo blades, the coordinate system was defined, the wheel and blades were created, and the unitary rotor was built, then the outline of rotor and blade root were modified by cylinder and arc on UG CAD platform. The geometric model of the TMP rotor will be used in the next manufacturing step: NC programming. The result of TMP rotor geometric modeling is shown that UG NX CAD is an available tool to design and manufacture TMP unitary rotor.

In order to ensure diesel engine operating reliably, need to forecast the performance parameters of diesel engine. Grey system theory, a method to research poor information and uncertain system, was approached to sequential turbocharged diesel engine. Grey forecast model of boost pressure of sequential turbocharged diesel engine was established. The precision of the forecast model was inspected by grey relation analysis, it is proved that the model has a good precision and is suitable to forecasting boost pressure. The relatively error of the forecast result is 2.5%. And it establishes the base for forecasting control and failure prediction of diesel engine sequential turbocharging system.