Research of {0001} crystal orientation for magnesium alloys solidified in a fashion of cellular crystals

The magnesium alloy grew in a fashion of cellular crystals during the process of unidirectional solidification, and the {0001} crystal face orientation in the cast ingot of the magnesium alloy was studied. The theoretical model and methodology were set up, and a corresponding experiment was carried out to verify the theoretical analysis results. The experimental results indicate that the {0001} crystal face of magnesium crystals parallels to the width direction for the thin-plate cast ingot when the magnesium grows in a manner of cellular crystals. The separation angle between the {0001} crystal face of magnesium crystals and the vertical axis line of the cast ingot is about 62° for the circular column cast ingot, which distributes in cone-type. The theoretical analysis results are basically in agreement with the experimental ones of previous literatures and this paper.     

Physical model of fluid flow characteristics in RH-TOP vacuum refining process

To understand the characteristic of circulation flow rate in 250-t RH-TOP vacuum refining process, the l:4 water model test was established through the bubble behavior and gas holdup in the up-leg to investigate the effects of different processes and equipment parameters on the RH circulation flow rate. With the increases of lifting gas flow rate, lifting bubble travel, and the internal diameter of the up-leg, and the decrease of nozzle diameter, the work done by bubble floatage and the circulation flow rate increase. The expression of circulation flow rate was derived from the regression analysis of experiment data. Meanwhile, the influences of vacuum chamber pressure and nozzle blockage situation on the circulation flow rate were discussed in detail by the bubble behavior and gas holdup in the up-leg. It is necessary to maintain a certain vacuum chamber liquid level in the molten steel circulation flow. Compared with a nozzle with symmetrical blockage in the up-leg, when a nozzle with non-symmetrical blockage is applied, the lifting gas distribution is non-uniform, causing a great effect on the molten steel circulation flow and making the circulation flow drop largely.     

Research on TDM approach of sharing BRT-lane supported by vehicle-infrastructure integration

In order to increase the availability of the part-time idle bus rapid transit lane (BRT-lane),a time divi-sion multiplexing (TDM) method to share BRT-lane with the vehicles besides BRT buses is propose...     

Large scale patterns of forage yield and quality across Chinese grasslands

Understanding the patterns of forage quantity and quality and investigating the factors influencing these patterns are essential for the development of animal husbandry.However,there is very little field evidence focused on these issues at a large spatial scale.In the current study,we analyzed forage quantity and quality at 177 sites distributed in all the major grassland types across China,and explored the relationship between forage quantity and quality based on consistent sampling protocols.We also investigated potential factors influencing forage quality patterns across China.Our study indicates the Tibetan grasslands had both higher quantity and quality forage than the Inner Mongolian grasslands,and alpine meadow had the best quantity and quality forage because of the meadow’s high productivity and the crude protein and nitrogen free extract content of the meadow forage.For the main vegetation formations,Kobresia tibetica meadows and Achnatherum splendens steppes had the highest quantity,while Kobresia pygmaea meadows and Kobresia humilis meadows had the best quality.We also found that although environmental factors,such as temperature and soil fertility,could affect physiological processes and so influence forage quality,the large scale patterns of change were mainly a result of the differences in vegetation types.Finally,we reported a negative relationship between forage quantity and quality:higher forage quantity means more crude fiber but less ether extract and crude protein.These findings improve our understanding on the spatial patterns of forage quantity and quality,and provide solid evidence related to the future development of animal husbandry.     

生物柴油高效合成方法研究

采用连续流动式、碱催化和超声辅助强化等手段,研究了一种新的生物柴油合成方法.优化了温度、催化荆用量和反应时间等影响酯交换反应的因素.采用核磁共振(NMR)分析方法,研究了在不同反应条件下的酯交换率.结果表明,当流动式反应盘管长为130 cm,甲醇与大豆油以9:1的摩尔比混合,反应温度为40℃,反应时间为13 min,NaOH用量在油重的0.5%的实验条件下酯交换率可达到99.9%以上.     

Numerical simulation of the temperature fields of stainless steel with different roller parameters during twin-roll strip casting

The temperature field of stainless steel during twin-roll strip casting was simulated by experiment and a finite element (FE) model. By comparing the measured result with the simulated values, it is found that they fit close to each other, which indicates this FE model is effective. Based on this model, the effects of roll gap (t) and roll radius (R) on solidification were simulated. The simulated results give the relationship between t or R and the position of the freezing point. The larger the t is and the smaller the R is, the closer the position of the freezing point is to the exit.     

Hot deformation behavior of a Cr-containing low carbon steel in the ferrite range

A low carbon steel with Cr addition of 0.46wt% combined with trace elements of Mn and Ti was studied. The apparent activation energy of deformation and the hot deformation equation of the steel in the ferritic range were determined by means of single hot compression tests. The hot-rolled strip of 3 mm in thickness rolled in the ferritic range was obtained using a laboratory hot rolling mill. The mechanical properties show that the values of yield strength and ultimate tensile strength are 230 and 330 MPa, respectively, and the elongation is 33%. The average r-value is 1.1. Large polygonal ferrite recrystallization grains with about 40 grn in size and the strong { 111 } recrystallization texture can be obtained in the hot-rolled strip.     

Status and prospects of intermediate temperature solid oxide fuel cells

Compared with conventional electric power generation systems, the solid oxide fuel cell (SOFC) has many advantages because of its unique features. High temperature SOFC has been successfully developed to its commercial applications, but it still faces many problems which hamper large-scale commercial applications of SOFC. To reduce the cost of SOFC, intermediate temperature solid oxide fuel cell (IT-SOFC) is presently under rapid development. The status of IT-SOFC was reviewed with emphasis on discussion of their component materials.     

Corrosion behaviors of NdFeB magnets prepared by spark plasma sintering

The spark plasma sintering (SPS) technique was introduced into the field of NdFeB preparation due to its own advantages.High property NdFeB magnets with fine grains were prepared by SPS method. The corrosion behaviors of SPS NdFeB were studied by electrochemical measurements and 92% RH hyther tests at 353 K. The results were compared with those of the traditional sintered NdFeB magnets. It shows that both the SPS NdFeB and the traditional sintered NdFeB have good corrosion resistance in alkaline environment due to surface passivation; while, the fine grain microstructure of SPS NdFeB results in a more homogeneous phase composition distribution and thus reduces the electrochemical inhomogenity between the ferromagnetic phase and the Nd-rich intergranular phase in the magnet. Therefore, the SPS NdFeB exhibits better corrosion resistance than the traditional sintered NdFeB in neutral and weak acidic environment.     

Preparation of Zn-doped TiO2 nanotubes electrode and its application in pentachlorophenol photoelectrocatalytic degradation

Zn-doped titanium oxide （TiO2） nanotubes electrode was prepared on a titanium plate by direct anodic oxidation and immersing method in sequence. Field emission scanning electron microscopy （FESEM） showed that the Zn-doped TiO2 nanotubes were well aligned and organized into high density uniform arrays with diameter ranging from 50 to 90 nm. The length and the thickness were about 200 and 15 nm respectively. TiO2 anatase phase was identified by X-ray diffraction （XRD）. X-ray photoelectronspectroscopy （XPS） indicated that Zn ions were mainly located on the surface of TiO2 nanotubes in form of ZnO clusters. Compared with TiO2 nanotubes electrode, about 20 nm red shift in the spectrum of UV-vis absorption was observed. The degradation of pentachlorophenol （PCP） in aqueous solution under the same condition （initial concentration of PCP： 20 mg/L; concentration of Na2SO4：0.01 mol/L and pH： 7.03） was carried out using Zn-doped TiO2 nanotubes electrode and TiO2 nanotubes electrode. The degradation rates of PCP using Zn-doped TiO2 nanotubes electrode were found to be twice and 5.8 times as high as that using TiO2 nanotubes electrode by UV radiation （400 μw/cm^2） and visible light radiation （4500 μw/cm^2）, respectively. 73.5% of PCP was removed using Zn-doped TiO2 nanotubes electrode against 45.5% removed using TiO2 nanotubes electrode in 120 min under UV radiation. While under visible light radiation, the degradation efficiency of PCP was 18.4% using Zn-doped TiO2 nanotubes electrode against 3.2% using TiO2 nanotubes electrode in 120 min. The optimum concentration of Zn doping was found to be 0.909%. The PCP degradation efficiencies of the 10 repeated experiments by Zn-doped TiO2 nanotubes electrode were rather stable with the deviation within 3.0%.