A kind of composite magnetic field for flow control in slab mold is proposed, in which an electromagnetic stirring (EMS) is carried out near the meniscus and an electromagnetic braking (EMBr) is carried out near the outlet of the submerged entry nozzle (SEN), simultaneously. The yoke for the EMS and the EMBr is made independent from each other, with a ruler type for the EMBr. A three-dimensional model of the magnetic field calculation is established. The simulation results show that the magnetic induction intensity generated with the EMS mainly concentrates in the EMS area. The magnetic induction intensity generated with the EMBr has a large component in the EMS results, which has little effect on the flow of this area. Based on the composite magnetic field calculation results, the three-dimensional numerical simulation of the flow field is carried out, and the flow field obtained is compared to that without the magnetic field but with the EMS and the EMBr only, respectively. The results show that under the composite magnetic field, EMBr and EMS can play their respective roles well under certain conditions, the impact of the jet flow on the narrow face is reduced, and the stirring beneath the meniscus is intensified.

The function of immature Leydig cells is regulated by hormones, such as androgen and luteinizing hormone (LH). However, the regulation of this process is still unclear. The objective of this study was to determine whether luteinizing hormone (LH) or androgens contribute to this process. Immature Leydig cells were purified from 35-day-old male Sprague Dawley rats and cultured with LH (1 ng/ml) or androgen (7α-methyl-19- nortestosterone, MENT, 100 nM) for 2 days. LH or MENT treatment significantly increased the androgens produced by immature Leydig cells in rats. Microarray and qPCR and enzymatic tests showed that LH up-regulated the expression of Scarb1, Cyp11a1, Cyp17a1, and Srd5a1 while down-regulated the expression of Sult2a1 and Akr1c14. On the contrary, the expression of Cyp17a1 was up-regulated by MENT. LH and MENT regulate Leydig cell function through different sets of transcription factors. We conclude that LH and androgens participate in the regulation of rat immature Leydig cell function through different transcriptional pathways.

对不同年级学生同时进行了冶金概论课程PBL教学改革实践.讨论了学生已有知识经验和教学背景对课程PBL教学中项目完成效果的影响,为不同年级全面开展PBL教学提供支持和经验积累.实践表明,已有知识经验和教学背景对项目的选题影响最大,但在学生能力和高层思维培养上没有差别,PBL的教学模式可以适应各年级知识体系,同时在不同年级开展教学活动.

提出了一种用于板坯流动控制的复合磁场,在弯月面附近施加电磁搅拌,在浸入式水口附近施加电磁制动,以形成对流场及温度场的复合控制.使用Fluent软件建立了结晶器内复合磁场作用下的钢液流场与温度场三维计算模型.通过与无磁场作用的钢液流动及传热行为进行对比,揭示了复合磁场对结晶器钢液流场和温度场的作用规律.结果表明:复合磁场在一定电磁参数条件下可以减弱水口出流主流股对窄面的冲击,冲击位置处的最大湍动能值降低62％,减少下返流侵入深度;弯月面附近得到了充分的搅拌,结晶器壁面附近的钢液流速增强30％,有利于凝固前沿的冲刷;同时结晶器壁面附近温度提高了1～2 K,均匀了结晶器内温度分布.结晶器电磁搅拌与电磁制动的流场控制优势得以同时发挥.

Abnormal mold level fluctuation is frequently observed in high-speed casting, especially for peritectic steels, which has been shown to severely deteriorate product quality. Both an online electromagnetic sensor and an ibaAnalyzer are used to analyze the frequency and amplitude of massive mold level fluctuation data from the slab casting process of different steel grades using different casting speeds, slab widths and physical parameters of mold flux. The results show that in the slab continuous casting process of peritectic steels, the main frequency and equivalent amplitude of abnormal mold level fluctuations first increase and then decrease with increasing the carbon content. In the production of various grades of steel, the main frequency of abnormal mold level fluctuation and the equivalent amplitude increase with increasing the casting speed, while the main frequency of abnormal mold level fluctuation changes little with increasing the casting width. The main frequency of abnormal mold level fluctuation is positively related to the surface tension of the mold flux. Based on these results, a new mechanism has been presented. It is shown that the abnormal mold level fluctuation is mainly induced by shell bulging while moving through the rollers, and resonance occurs when the frequency approaches the natural frequency of the molten steel in mold, which results in a large amplitude of the abnormal mold level fluctuation. Based on this mechanism, a new equation for the resonance frequency of molten steel is proposed. The improved method based on this mechanism has proved to be effective in controlling abnormal mold fluctuations.

针对板坯连铸结晶器铜板冷却水槽的结构优化,将三维传热模型应用于结晶器铜板导热过程,并采用有限元方法进行了模拟,计算并比较了水槽结构优化前后结晶器宽面铜板热面温度分布情况.结果表明:水槽结构优化后铜板螺栓处温度较优化前降低6℃,弯月面处温度降低10℃;优化前和优化后铜板在螺栓处和弯月面处的温度波动幅度分别为3、1.5℃和8、2℃,水槽结构优化后铜板传热能力和冷却均匀性有明显提高.

以某钢厂板坯连铸机生产高碳钢BJS55C为研究对象,结合钢种高温力学实验,优化了高碳钢BJS55C连铸生产工艺.其中对铸机弯曲段二次冷却强度减弱,调整各区冷却水分配,使板坯通过矫直区避开了脆性温度区间,板坯角部裂纹发生率降低41％;优化动态轻压下压下区间,压下量在原有基础上增加15％,板坯低倍指数由2.6改善到2.0;高碳钢保护渣熔点由1 100℃降低到980℃,保护渣黏度(Pa·s,1 300℃)由0.14降低到0.08,保护渣熔化效果与透气性得到明显改善.解决了板坯连铸生产高碳钢的一些关键难题,实现了高碳钢连铸的批量稳定生产.

In an attempt to explore high efficient and cheap electrocatalyst for water splitting hydrogen production, small molybdenum carbide nanoparticles with the size about 3-6 nm are loaded on three-dimensional N-doped carbon matrix successfully with ammonium heptamolybdate ((NH4)(6)Mo7O24 center dot 4H(2)O) and filter paper as precursor by pyrolysis. Due to its small size, large surface area and high conductivity, this electrocatalyst shows excellent activity in hydrogen evolution reaction (HER). In acid media, its overpotential to achieve a current density of 10 mA.cm(-2) is as low as 167 mV, with Tafel slope is only 73 mV.dec(-1). The electrocatalyst also shows large exchange current density (j(0) ) with the value 0.15 mA.cm(-2). Furthermore, it shows excellent durability after 1000 cycles of long-term test, and the catalytic current remains stable over 10 h at fixed overpotential. This work elucidates a feasible strategy to obtain efficient electrocatalysts with cheap and naturally sustainable material as precursor and shed some light on the exploration and optimization of electrocatalysts in energy chemistry. The HER of this electrocatalyst is studied and the results illustrate it exhibits a stable hydrogen evolution rate of 44.5 mu mol.h(-1) with faradaic efficiency about 100%.

Many reports have established that the action of Nerve growth factor (NGF) is not restricted to the nervous system but can affect a broad range of non-neuronal cells. There are increasing evidences for a broader physiological role of NGF effects on the testis. Leydig cells is of particular interest. Leydig cells can secrete androgens which is a steroid hormone, synthesized in Leydig cells from cholesterol, the testosterone from Leydig cells, is of the main circulating androgen in the body. Local functions for NGF have been demonstrated in the developing and mature testis of rodents. The testis have the presence of nerve growth factor (NGF), as well as neurotrophin receptors p75NTR, TrkA and immunohistochemical analyses, carried out on prenatal human testis, identified a broad expression of NGF and NGF receptors, predominantly localized to Leydig cells. NGF performs function through NGF/TrkA/p75 system, which main expression sites are in germ cells, sertoli cells and Leydig cells. NGF may be a potential regulator of steroidogenesis in Leydig cell. Moreover, these regulations may involve in several different pathway. Here we present the presently available data on the distribution of possible local activities of NGF and its receptors in Leydig cells, provides further information about effect of NGF on the Leydig cell function and development.

铸坯生产过程中参数的实时采集与准确定位是实现铸坯质最实时分析判定的基础,对典型铸坯生产过程进行研究得出了一种连铸坯质量相关生产过程参数定位方法,该方法能够将实时采集的铸坯生产过程参数精确定位到铸坯切片,克服了传统铸坯生产过程参数定位的缺陷与不足.此外该方法可利用数据库中的判定规则对铸坯生产过程参数异常诊断,利用众多铸坯切片信息组建立铸坯质量判定模型或判定铸坯切片质量缺陷,模型命中率达到了95.4％.

A nitrogen doped mesoporous carbon matrix supported oxygen vacancies rich tungsten oxide composite material, WO3-x@NC (1 > x > 0), has been fabricated successfully with chitosan and H3PW12O40 as precursors through calcination. In this composite material, WO3-x particles with the size about 10-15 nm disperse evenly in nitrogen doped mesoporous carbon matrix. WO3-x@NC presents low overpotentials (eta(10)) of 61 and 306 mV to reach a current density of 10 mA/cm(2) for HER and OER in 1.0 M KOH, respectively. With WO3-x@NC as both cathode and anode at the same time, an electrolyzer, WO3-x@NC//WO3-x@NC was constructed for overall water splitting, which only needs a cell voltage of 1.60 V to achieve a current of 10 mA/cm(2). During this process, WO3-x@NC//WO3-x@NC exhibits remarkable stability in 48 h. Moreover, besides HER and OER, WO3-x,@NC also shows striking catalytic activity for reductive conversion of 4-nitrophenol to 4-aminophenol. Oxygen vacancies from WO3-x and good electron transportation property of nitrogen doped carbon matrix play important roles in overall water electrocatalytic splitting and 4-nitrophenol reductive removal. We expect WO3-x@NC will find its way as a new resource for hydrogen energy as well as a promising material in 4-nitrophenol removal from water.

Flow behavior in the slab mold by optimized swirling flow generation in the submerged entry nozzle (SEN) is investigated. Therefore, hydromechanical model experiment was carried out to simulate this metallurgical process, the effect of turning around the nozzle with swirling and different bottom shape of nozzle is especially analyzed. The flow behavior in the mold was recorded by dye tracer and camera; The two dimension average velocity distribution in the slab mold was measured by the Ultrasound Doppler Velocimetry (UDV). The velocity distribution agrees well with flow pattern recorded by camera. The swirling flow in SEN can reduce the impinging to the narrow face and slag entrapment is inhibited by swirling. Furthermore, the flow in the mold was optimized with swirling in SEN as well as turning around the nozzle outlet in reverse, which avoids the impinging to both the wide and narrow faces of the mold at the same time. It is a potential technology for continuous casting.

In order to control the slab internal cracking during the production of 1 650 peritectic steel slab in Meisteel,a 3D mathematical model of the solidification of the 1 560 mm× 230 mm section peritectic steel slab was established according to the practical production of 1 650 continuous casting machine in Meisteel,which revealed the distribution laws of the slab temperature in mold and second cooling zones and the evolution behaviors of stress and strain during soft reduction.The results showed that the cooling intensity and the slab temperature gradient along the direction of casting speed and vertical direction in mold and the bender segment were large.The slab surface deformation and the stress of the center and the 1/4 position of slab wide face were similar,and the maximum plastic strain occurred on the solidification front near to the inner arc of the slab during soft reduction.Moreover,the largest stress occurred on the shell corner.The peritectic steel slabs in Meisteel were easily suffered to the internal cracks due to the current inadequacy soft reduction process.

The influence of the swirl flow on the fluid flow and inclusion behavior in the submerged entry nozzle (SEN) and mold was studied. This swirl flow was generated by using a half type electromagnetic ...

In this work, the placement of an electromagnetic swirl flow generator (EMSFG) around a submerged entry nozzle (SEN) was proposed as a method for generating a rotating electromagnetic field in a continuous casting (CC) process of steel. First, two kinds of a full type EMSFG and a half type EMSFG were designed based on mathematical modeling. Then, distributions of magnetic flux intensity in an EMSFG as well as distributions of Lorentz force in molten steel were simulated. It was found that the EMSFG structure and electromagnetic parameters have an important effect on magnetic flux intensity and Lorentz force distributions. For both a full type and a half type EMSFG, the magnetic flux intensity and Lorentz force increases as the magnetomotive force increases. Especially, for a full type EMSFG, the magnetic flux intensity is distributed evenly in molten steel. Moreover, the Lorentz force increases along a radial direction in the molten steel in the SEN. However, for a half type EMSFG, the magnetic flux intensity and Lorentz force decreases gradually towards the region without an EMSFG. Consequently, a full type EMSFG with a 44 000 AT magnetomotive force and a 50 Hz frequency is more suitable to apply in the operation of an EMSFG under actual production conditions.

In the preceding work, the inclusion behavior in a submerged entry nozzle (SEN) and mold induced by using a swirl flow has been investigated. The results showed that a swirl flow can effectively promote the inclusions removal to the meniscus as well as reduce the inclusions entrapment at the solidified shell wall. Moreover, that the swirl flow was generated by using a full type electromagnetic swirl flow generator (EMSFG). In the present work, a kind of a half type EMSFG was investigated, since it is easier to implement in a production scale. The influence of the stirrer on the fluid flow, heat transfer, and inclusion behavior in the SEN and mold was studied. Furthermore, a comparison between these two types of EMSFG from the aspects of flow field, temperature field, and inclusion behavior was done. In addition, the effect of different magnetomotive forces, inclusion sizes, densities as well as boundary conditions on the inclusion behavior was studied. The results show that the effect of a half type EMSFG (88000 AT) on the molten steel is very close to a full type case (44000 AT). More specifically, the flow pattern, temperature distribution as well as inclusion behavior in the SEN and mold look very similar. Also, it was found that from the viewpoints of the inclusions separation to the mold meniscus and the inclusions trapping at the solidified shell wall, better results could be obtained for a "Trap" boundary condition when using half type EMSFGs.

A new process for swling flow generaton in the submerged entry nozzle (SEN) in continuous casting process of steel was proposed. A rotating electromagnetic field was set up around the SEN to induce swirling flow by Lorentz force. The flow and temperature felds in the SEN and round bllet mold with electromagnetic swirling were numerically simulated and then verified by the electromagnetic swirling model experiment of low meting point alloy. The effects of divergent angle of the SEN on the flow and temperature fields in mold with electromagnetic swling were investigated. The electromagnetic swrling flow generator (EMSFG) could effectively induce swirling flow of molten steel in the SEN, which consequently improved greatly the flow and temperature fields in the mold. Below the nozzle outlet in mold, with the increase of divergent angle, the stream of bulk flow diverged more widely, the high temperature zone shifted up, and the temperature field became more uniform. Above the nozzle outlet in mold, with 350 A electromagnetic swirling, when the divergent angle of the SEN increased, the upward flow velocity and the meniscus temperature first increased and then decreased. With a divergent angle of 60°, the upward flow velocity and meniscus temperature reaced the largest value.

The fundamental researches show that, swirling flow in an immersion nozzle can effectively improve the uniformity and stability of the flow from the nozzle, and consequently improve the distribution of flow and temperature, reduce meniscus fluctuation in mold. In this study a new process is proposed, in which a rotating electromagnetic stirrer is set up around an immersion nozzle to induce a swirling flow in it by Lorentz force. The flow distribution in mold for round billet and square billet continuous casting process in a round electromagnetic swirling flow generator with 350 A electromagnetic swirling flow is numerically analyzed. The simulation results show that: for round billet, the electromagnetic swirling flow downward from the immersion nozzle can drive all the flow in mold swirling; for square billet, with electromagnetic swirling, a weak swirling flow can be observed at the corner of the meniscus, and the impinging depth of the flow becomes less while the upward flow velocity becomes larger.

The application of ANSYS and FLUENT in electromagnetic continuous casting of steel was introduced.And taking small square billet as an exmple,a three-dimensional numerical simulation was conducted on the magnetic field of the molten steel in the submerged nozzle,and the flow field in the nozzle and mold under the electromagnetic swirl device during electromagnetic swirl continuous casting of steel.