加热炉热过程动态操作数学模型

根据加热炉生产特点,建立了钢坯加热过程的动态操作数学模型,分析了待轧时间变化时炉内钢坯温度分布情况。并针对加热炉待轧的灰色性,采用多目标灰色局势决策方法,得出了相应合理的待轧优化控制策略。模拟结果表明:该方法具有良好的动态性能,适合于在线控制。     

Effects of barium on the nonlinear electrical characteristics and dielectric properties of SnO2-based varistors

The effects of barium on electrical and dielectric properties of the SnO_2·Co_2O_3·Ta_2O_5 varistor system sintered at 1250℃ for 60min were investigated. It is found that barium significantly improves the nonlinear properties. The breakdown electrical field increases from 378.0 to 2834.5V/mm, relative dielectric constant (at 1kHz) falls from 1206 to 161 and the resistivity (at 1kHz) rises from 60.3 to 1146.5kΩ·cm with an increase of BaCO_3 concentration from 0mol% to 1.00mol%. The sample with 1.00mol% barium has the best nonlinear electrical property and the highest nonlinear coefficient (α=29.2). A modified defect barrier model is introduced to illustrate the grain-boundary barrier formation of barium-doped SnO_{2}-based varistors.     

Low-threshold, high-efficiency, high-repetition-rate optical parametric generator based on periodically poled LiNbO3

We report a high-repetition-rate optical parametric generator (OPG) with a periodically poled lithium niobate (PPLN) crystal pumped by an acousto-optically Q-switched CW-diode-end-pumped Nd:YVO_4 laser. For the maximum 1064nm pump power of 970mW, the maximum conversion efficiency is 32.9% under the conditions of 250℃, 1064nm pulse repetition rate of 22.6kHz and pulse width of 12ns, and the PPLN OPG threshold in the collinear case is less than 23.7μJ. The output power increases with the increase of the crystal temperature. The 1485－1553nm signal wave and 3383－3754nm idler wave are obtained by changing the temperature and the angle of the PPLN crystal.     

Fenton 试剂处理2,4-D废水研究

利用Fenton试剂(Fe2+/H2O2)处理含有除草剂2,4-二氯苯氧乙酸(2,4-D)的模拟废水.结果显示,Fenton试剂对2,4-D有很好的去除效果.Fe2+和H2O2的摩尔比为1:20,在H2O2为1/2Qth理论投加量的条件下处理30mtn,2,4-D去除率达到80.0%.考察了Fe2+投加量、Fe2+和H2O2投加比、2,4-D初始浓度和pH等因素对2,4-D降解的影响.通过GC-MS和HPLC检测到反应中间产物有2,4-二氯苯酚、邻氯苯酚和对氯苯酚,氯离子在这些中间产物上释放.通过离子色谱检测到进一步氧化的产物还有小分子酸,如乙醇酸、乙醛酸、顺丁烯二酸,提出了Fenton降解2,4 -D的可能途径.     

The influence of hard‐segments on two‐phase structure and shape memory properties of PCL‐based segmented polyurethanes

Poly(ε‐caprolactone)‐based segmented polyurethanes (PCLUs) were prepared from poly(ε‐caprolactone) diol, diisocyanates (DI), and 1,4‐butanediol. The DIs used were 4,4′‐diphenylmethane diisocyanate (MDI), 2,4‐toluenediisocyanate (TDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI). Differential scanning calorimetry, small‐angle X‐ray scattering, and dynamic mechanical analysis were employed to characterize the two‐phase structures of all PCLUs. It was found that HDI‐ and MDI‐based PCLUs had higher degree of microphase separation than did IPDI‐ and TDI‐based PCLUs, which was primarily due to the crystallization of HDI‐ and MDI‐based hard‐segments. As a result, the HDI‐based PCLU exhibited the highest recovery force up to 6 MPa and slowest stress relaxation with increasing temperature. Besides, it was found that the partial damage in hard‐segment domains during the sample deformation was responsible for the incomplete shape‐recovery of PCLUs after the first deformation, but the damage did not develop during the subsequent deformation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 557–570, 2007     

One- and Two-Mode Combination Squeezing Operator for Two Harmonic Oscillators with Coordinate-Momentum Coupling

By virtue of the technique of integration within an ordered product of operators, we derive the normal ordering expansion of a one- and two-mode combination squeezing operator for two harmonic oscillators with coordinatemomentum coupling. It turns out that this squeezing operator just diagonalizes the Hamiltonian H = p21/2m1 m1ω21x21/2 p22/2m2 m2ω22x22/2 - λx2p1, so its ground state is a one- and two-mode combination squeezed state.Quantum fluctuation in the ground state is calculated.     

光纤复合型油气井下压力温度测量系统

针对目前广泛使用的电子式油气井下压力温度测量系统可靠性低、高温环境漂移大的不足,设计了一种基于非本征型F-P干涉仪(EFPI)和光纤布喇格光栅(FBG)的复合型油气井下压力、温度测量系统,详细说明了其工作原理、传感器组成和信号解调方法,初步试验结果表明,该测量系统不仅克服了电子测量方式的不足,而且具有复用性好、测量精度高等优点.     

回填材料膨润土对放射性气体滞留能力模拟研究

利用各种分析手段对膨润土的物理特性进行了表征 .X射线衍射分析表明钠基膨润土呈典型的六方晶胞 ,晶胞参数是 :a轴 4 .913,c轴 5 .4 0 5 ;差热分析曲线在低温区和高温区有明显的吸热峰出现 ;元素分析钠、钾离子的含量大于钙、镁离子的含量 ,在性能上表现为钠质膨润土具有较强的离子交换能力 ;显微分析表明其表面呈皱隙状 ,测定比表面积高达 2 4 .5 2m2 /g;吸水率测定表明膨胀率大 ,说明它具有密封功能 ,可有效阻滞地下水的渗入 .利用SF6示踪技术 ,通过采集不同时间段取样池样品 ,分析样品中示踪气体浓度 ,绘制取样池示踪气体浓度随时间的变化关系曲线 ,根据费克扩散定律计算扩散系数 .实验结果表明 ,随着压实膨润土密度的增大 ,示踪气体扩散系数迅速减小 ,当密度大于 1.8g/cm3 时 ,扩散系数降至 10 -9m2 /s.研究结果表明 ,膨润土性能优化是通过在膨润土中添加适量的活性炭 ,可明显改善其对气体的阻滞能力 ;增加其对放射性气体滞留能力 ;添加少量的石英砂增加其机械性能、导热性和减少蠕变性 ,将引起对气体阻滞能力的下降 .综合考虑 ,在膨润土中各添加 5 %活性炭和石英砂 ,既对气体具有较好的滞留能力 ,又具有较好的工程特性 .     

CreditRisk+模型下商业银行经济资本配置研究

对金融资产风险的度量与经济资本的分配应该体现分散化效应,传统的V aR方式不能保证分散化效应的次可加性.本文讨论了基于T a ilV aR这一新的风险度量与经济资本分配标准,并在违约率均值不变情况下,对C red itR isk+模型下的商业银行经济资本分配进行了实证分析.     

Experimental 511 W Composite Nd：YAG Ceramic Laser

We demonstrate a 511 W laser diode pumped composite Nd：YAG ceramic laser. The optical pumping system is consisted of five laser diode stacked arrays arranged in a pentagonal shape around the ceramic rod whose size is φ6.35×144mm. When the pumping power is 1600 W, the cw laser output up to 511 W at 1064nm can be obtained with a linear piano-piano cavity, and the optical-to-optical efficiency is 31.9%. To our knowledge, this is the highest value of laser output by using a newly invented composite Nd：YAG ceramic rod as the gain medium.