Search

Shrinkage porosity and segregation defects are often found in an air cooled jumbo steel ingot, which will influence the quality of the final rolled plates.The solidification behaviours for a 60t jumbo slab ingot under varied cooling conditions were simulated using the ProCast software.The influences of different cooling speed on dendrite distribution and segregation were studied.The results show the jumbo slab ingot could freeze layer by layer when the heat transfer coeffcients of mould increase to 1000W·K-1·m-2. The thick finer chill zone were achieved. At the same time, the columnar crystals grow preferentially parrelling to the density of heat flow, and finer equiaxied crystals are formed in the core of the ingot. They all improve the microstructure and decrease the composition segregation of jumbo slab ingot.

This paper is based on the FPGA-based realization of tail-biting convolutional coding and decoding in LTE system, including simulation, synthesis and board-level verification on the Virtex-6 chip. Implementation results show that, the encoding and decoding algorithm applied to the TD-LTE RF conformance testing instrument has advantages of high efficiency and good reliability.

In order to improve the efficiency of blind detection in receiving end, this paper deeply considered structure of the PDCCH multiplexing data and analyze the current algorithm. A more efficient algorithm based on preprocessing the PDCCH multiplexing data in certain search space is proposed in this paper. This algorithm ably reduces the blind detection times.

A pilot-scale nitrogen removal system composed of an anoxic area, an anaerobic area, a microaerobic area and an aerobic area (A2O2) was established to treat high strength ammonium wastewater from a nitrogenous fertilizer factory. The influences of key factors such as DO, pH, FA and temperature on partial nitrification in the microaerobic area were investigated. The results showed that in the DO concentration of 0.5~0.7mg/L, the stable and efficient nitrite accumulation could be realized. Meanwhile, the effluent NH3-N and TN quality was superior to the requirement of the《Synthetic ammonia industrial water contamination emission standard》(draft for comment). The optimal pH of 7.5~8.0 and the corresponding free ammonia (FA) concentration of around 0.95 mg/L limited the nitrobacteria activity selectively, thus favoring the stability of partial nitrification. The nitrite accumulation rate didn’t show obvious difference in wide temperature range (18~35°C) at given DO (0.5~0.7mg/L) and pH (7.5~8.0). But contrary to the usual partial nitrification obtained by high temperatures (>30°C), the effluent ammonium of A2O2system was substandard due to the inhibition of nitrobacteria activity caused by high temperature, which diminished the further removal of ammonium in the subsequent aerobic area.

Scattering spheres-embedding three-dimensional ordered macroporous (3DOM) titania(TiO2) was fabricated, by the route of colloidal spheres self-assembly, infiltration and template removal. The procedures of 3DOM structure preparation were characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD). The silica@PMMA core-shell spheres were prepared and self-assembled into colloidal crystal template. Solid material was deposited in the colloidal crystal template by spin-coating of titania nanoparticle dispersions. Subsequently, the samples were heated to 400 °C to form anatase TiO2and to remove the polymer of template, which resulted in macroporous structure with a silica sphere in each lattice pore. The conventional TiO2film, 3DOM TiO2photoanodes were also fabricated. It was found that SiO2-embedding 3DOM photoanode has the higher photocurrent efficiency than both of TiO2 film and 3DOM, because there are scattering spheres in its lattice pores which enhance the light scattering and improve the light harvest of the dye.

In this paper, the graphene oxide reducing by photochemical-thermal reduction and high-temperature thermal reduction was studied to get qualified graphene and avoid the re-aggregation. The results show that graphene obtained by both of the two reduction methods all maintained the original well-layered morphology of the graphene oxide. The graphene had smooth surface and high quality as completely reduced by high-temperature thermal method. However, the reduction the photochemical-thermal reaction was not sufficient and caused many vesicles on the graphene surface due to the low temperature and the lack of reaction time.

Graphite oxide is of great importance in preparing graphene, the average layer of graphene depends on that of graphene oxide in some extent. In this paper, we prepared graphite oxide via H3PO4/H2SO4mixed acid, then which were dried by vacuum drying in a freezer dryer and drying oven respectively, the graphite oxide powder and thin film were obtained correspondingly. After dispersing the above two forms of graphite oxide in water by shaking, stirring or supersonic wave, they were reduced in the same condition. According to the XRD, AFM results, vacuum freeze-drying was inclined to gain few-lay graphene.

We prepared graphite oxide (GO) from natural graphite by the modified Hummers method. Then graphene was prepared by ultrasonically dispersing GO in the presence of hydrazine hydrate. The samples were characterized by FTIR, Raman, Scanning electron microscope (SEM) and Transmission electron microscope (TEM). The results suggest that the graphite is oxidized to covalent bond-type graphite intercalation compounds with various oxygen functional groups (C=O, C-OH, -COOH and C-O-C). Results show that the functional groups on graphite oxide surface are mostly removed by hydrazine hydrate and graphene presents translucent slide with curly edge.

The production of huge rectangular ingots becomes crying needs in the condition of lots of heavy plate mills more than 5m have been in operation. In this paper, we simulate the solidification of 60t Q235 huge rectangular ingot with ProCAST in different cooling conditions such as air cooling, forced air cooling and water cooling. The results show that solidification time in forced air cooling and water cooling shortened than that in air cooling respectively by 0.9 hours and 2.2 hours; The primary fine-grain area is large in the forced air cooling and water cooling. In forced air cooling , we can obtain the largest equiaxial crystal ratio and the minimum columnar crystal ratio; The shrinkage cavity position of the ingot in forced air cooling and water cooling is closer to riser than it is in air cooling, but the volumes of shrinkage cavities respectively increased to a greater extent than in air cooling.

A water model of 1/4 linear scale for 210t RH has been established. RH circulation flow rate is measured by a velocimeter. The influences of lifting gas flow rate, snorkel inner diameter, injection depth and nozzle inner diameter on circulation rate were discussed. The dimension correlation has been calculated for the prediction of circulation rate. The results showed that the formula of circulation rate is 5.434×10-6G0.356·D1.254·d -0.106·H 0.821. The best nozzles inner diameter in terms of circulation rate was 3mm.

In this paper, the solidification and heat transfer of a 60t huge rectangular ingot has been simulated. The solidification rate at pouring finish and the solidification times were simulated for air cooling, soft wind cooling, strong wind cooling, fog cooling, weak water cooling and strong water cooling. Mathematical simulation results tell us that by intensive cooling, the solidification time of the can be obviously shortened, internal soundness can be ensured and the surface quality could be improved.

In this paper the influence of snorkel length and snorkel inner diameter and lifting gas flow rate on inclusion removal rate are discussed. It is found that inclusion removal rate varies greatly with snorkel length and snorkel inner diameter. Prolonging the snorkel length is benefited for inclusions removal in RH and inclusion remove time is enhanced, but inclusion remove rate is decreased when snorkel inner diameter is reduced. There is a best lifting gas flow rate for inclusion removal.

Huge rectangular ingots becomes crying needs in the condition of lots of heavy plate mills more than 5m have been in operation. In this paper, a special method of wind cooling outside mould has been presented and applied to produce 60t rectangular ingot. Mathematical simulation results tell us that by wind cooling, the solidification time of the 60t ingot can be shortened by 67 minutes, internal soundness can be ensured. The wind cooling process can obviously improve microstructure and preventing skull patch by increasing the thickness of solidified shell. A 60 tons huge rectangular ingot is successfully produced by wind cooling, the surface quality of is very well and the internal soundness should be improved further.

In this paper the fluid flow and temperature are used together to optimize the 40 tons six strand tundish. Fluid flows in a six strand tundish have been investigated with physical modeling, then steady, three-dimensional temperature fields inside the six strand tundish are obtained. The physical modeling experiments give two optimal integrated tundish structural parameters of baffle holes. From the further study of temperature fields, the tundish should be optimized in the structural parameters of baffle holes in the condition of height 300mm, angel 30° and diameter 20mm.