Enhancement of the hydrogen storage properties of Mg/C nanocomposites prepared by reactive milling with molybdenum

The effect of Mo on the morphology, crystal structure and hydrogen sorption properties of Mg/C composites prepared by reactive milling was studied. Transmission electron microscopic(TEM) observation shows that Mg/C composites prepared with the addition of Mo are of nanoscale with particle size about 20-120 nm after 3 h of milling under 1 MPaH_2. MgH_2 of tetrahedral crystal structure predominates in the materials with the geometric shape of oblique hexagonal prism. From X-ray diffraction(XRD) and hydrogen content studies, Mo and crystallitic carbon have a synergistic effect on promoting the hydrogenation rate in the reactive milling process. From differential scanning calorimetric(DSC) studies, the dehydrogenation peak temperature of the Mg/C materials with Mo is lowered to 299-340 ℃.     

A novel tuned heave plate system for heave motion suppression and energy harvesting on semi-submersible platforms

Deepwater offshore structures such as semi-submersible platforms suffer powerful ocean waves due to their location and site condition. The long distance away from the shore also brings many difficulties to energy supply for the platform operation. How to reduce the response of the platform and convert the wave energy into electrical power is a meaningful topic. In this paper, a tuned heave plate system (THP) is presented and designed to be employed on a semi-submersible platform for heave motion suppression and energy harvesting. This THP system is composed of spring supports, a power take-off system (PTO), and a heave plate. The PTO system is a permanent magnet linear generator (PMLG), which could directly convert the kinetic energy of the heave plate into electronic power. The stiffness of the spring supports is designed based on the principle of the tuned mass damper (TMD). The numerical model of the platform and the THP system is established according to the hydrodynamic analysis results of the platform. The model is tested and modified by scale model tests on the platform in the wave tank. A parameter study, including the size, tuned period, and damping ratio of the THP system, is conducted systematically based on the numerical model. The optimal parameters of the THP are selected due to the maximum heave motion reduction under severe wave conditions in South China Sea. The performance of the semi-submersible with and without the THP system under different wave conditions is analyzed. It is demonstrated that this novel tuned heave plate system could reduce the heave motion of the semi-submersible platform significantly and generate considerable power, which makes the THP system have a broad prospect for development.     

能量有效的频谱感知与接入策略联合优化算法

针对认知无线电网络中次用户节点能量受限问题,提出了一种联合考虑频谱感知和接入策略的能量有效优化算法。根据主用户非时隙接入信道可能与次用户发生碰撞的特点,基于连续时间马尔科夫理论对次用户的频谱感知和接入策略进行建模,在满足碰撞概率约束的条件下,通过合理设置次用户的感知时间和接入概率实现了感知性能与传输能效的有效折衷。仿真结果表明,相对于仅考虑感知时间或接入概率的传统优化算法,所提算法可使次用户的能量有效性得到显著提高。     

纳豆芽孢杆菌菌剂的制备工艺

采用单因素及正交试验对纳豆芽孢杆菌发酵培养基、pH、温度、发酵时间等条件进行了考察,利用喷雾干燥法制备菌剂,考察了β-环糊精、蔗糖、可溶性淀粉及脱脂奶粉作为保护剂对菌剂制备的影响,并研究了储藏时间及条件对菌剂发酵活力的影响.研究结果表明:纳豆芽孢杆菌发酵培养基为黄豆浸汁培养基:黄豆以5倍水体积浸泡8~14h,121℃~126℃,0.1~0.15MPa处理1h,滤除黄豆,取豆水,加入5%的葡萄糖和0.02%的K2HPO4,调节pH至7.0;最优发酵工艺:初始pH7.0,37℃发酵10h;喷雾干燥最佳保护剂为5%脱脂奶粉;菌剂4℃冷藏180d以内不影响发酵活力.上述工艺下所制得的纳豆芽孢杆菌菌剂活菌数为6.5×108 CFU/g,发酵生产纳豆激酶性能良好.发酵生产纳豆激酶酶活为2 000~2 200IU/g.本研究为纳豆芽孢杆菌菌剂制备提供了一条较为合理的工艺路线.     

篮球运动竞技参赛过程特征研究

采用文献资料法,专家调查法和数理统计法,解析篮球竞技参赛过程,分析篮球运动竞技参赛过程主要特征,以确定篮球项目竞技参赛过程的主要环节和重点要素。研究结果表明：篮球运动竞技参赛过程中,参赛方案制订、比赛技能应用、训练条件保障、参赛准备总结、比赛名次评价、掌控局势能力、比赛体能分配、阵容配备能力、特定战术演练和参赛控制总结等要素权重依次排序前十位,是篮球运动竞技参赛过程的重点要素。     

Hydrophobically modified melamine-formaldehyde sponge used for conformance control and water shutoff during oil production

Polymer or polymer gels have been widely used to control excessive water during oil production by homogenizing injection profile and reducing water cut in the produced fluids. However, the gels used are generally unable to selectively minimize water production, and face the challenge of syneresis of gels under high temperature and high salinity environment. In this work, melamine-formaldehyde sponge was modified with AlCl₃ solution, rendering a transition from hydrophilic to hydrophobic state with a water contact angle of 130° on the surface of the modified product. Filtration results show that mineral oil and water can be selectively separated with the hydrophobically modified sponge powders. Simulated water shutoff experiments demonstrated the blockage efficiency against water was 30% higher than that against oil, and the oil production was increased 7.4% after blocking. The parallel profile control tests confirmed that the fraction flow of high permeable channel decreased about 75%, accompanied with 60% rise of oil recovery factor. These results indicated that such hydrophobic materials can significantly reduce excessive water production, and this work provided a new idea to offer a low-cost hydrophobic material for conformance control and water shutoff during oil production.     

脉冲MIG焊接电弧的闭环控制

作者研究成功了一种用于脉冲MIG焊接电弧的闭环控制系统,称为QH-ARC-102控制法。它具有优异的静态及动态品质。无论脉冲或者维弧阶段,电弧的工作点均位于三极管焊接电源阶梯形外特性的恒流段上。因此,电弧稳定,始终保持喷射过渡,飞溅极少,电流的调节范围也较宽广.在每个脉冲期间,均对弧长讯号进行采样以实现对弧长的闭环控制。因此电弧具有很强的抗弧长干扰能力,而且其脉冲工艺参数能够自动优化,可以适应送丝速度大范围的突变。本控制系统对脉动送丝或程序送丝MIG 焊接新工艺比较适用。如用于实现全位置焊接、焊缝成型控制、线能量控制以及熔深的闭环自动控制等,特别是对机器人焊接更为适用。文章论述了本系统的工作原理,介绍了实用的电路图,并且给出了一些焊接结果。     

Ti和V对Fe中氢与位错交互作用的影响

研究了Fe-0.5wt-%Ti和Fe-0.5wt-%V合金中由氢与位错交互作用所形成的氢致冷加工内耗峰(H-CWP)。实验结果表明:合金元素对H-CWP、对氢与位错之间的交互作用有显著的影响,与氢作用愈强的元素,对H-CWP的影响愈大,内耗实验结果与力学性能之间存在着一定的联系.     

加入WTO给当代大学生带来的若干思考

入世对大学人才培养目标、社会人才需求、大学生知识结构、学习理念、就业市场等提出了新的要求，当代大学生必须提高自身的综合素质，培养创新能力，开阔国际视野，重视非智力因素的培养等，以此来适应WTO对人才的需求。     

储油缸塑件圆周抽芯注射模设计

分析了储油缸的塑件工艺特点，主要分析了点浇口注射模成型且带侧向抽芯机构制品的工艺特点．介绍了带转盘的注射模结构，为保证外观质量，综合地处理好产品外观要求与浇口位置及脱模方式之间的问题，简化模具结构，减低制造成本，提高了生产效率。