等离子体电弧炉内流动与传热数值模拟

本文采用磁流体动力学(MHD)模型对直流等离子体自由燃烧电弧和电弧炉内部的流动与传热进行了数值模拟研究. 通过对基于磁矢量势描述的电磁场方程组和流体力学方程组的耦合迭代计算, 求解得到了流体的温度场和速度场等, 计算结果清晰地反映出等离子体电弧的高温阴极射流现象, 并与同行的实验和数值结果进行了对比. 本模拟方法和结果对于电弧炉的工业应用和优化设计有重要的指导意义.

~(157)YB的形状共存和Vi_(13/2)带的结构演变

利用在束γ谱学技术,通过反应144Sm（16O,3n）研究了157Yb的高自旋态,其中16O束流的能量为90MeV.采用门套BGO（AC）HPGe探测器进行了长时间的γ-γ-t符合测量.基于γ-γ符合关系、γ射线的各向异性度和DCO系数的测量结果,首次建立了157Yb的高自旋能级纲图.围绕157Yb的能级纲图着重讨论了此核的形状共存和Vi13/2能带随着角动量增加的结构演变,另外还比较了N=87同中子素链的Vi13/2转动带结构的系统性.

A proposal design of a multi-hit two-dimensional position-sensitive energy spectrum detector

A new non-linear comparison method of charge-division readout scheme is conceived and the first design of a multi-hit two-dimensional position-sensitive energy spectrum Si(Au) surface barrier detector with a continuous sensitive area is proposed.

Thermochemical and thermal analysis on N-(p-methylphenyl)-N '-(2-pyridyl)urea

Low temperature heat capacities of N-(p-methylphenyl)-N'-(2-pyridyl)urea were determined by adiabatic calorimetry method in the temperature range from 80 to 370 K. It was found that there was not any heat anomaly in this temperature region. Based on the experimental data, some thermodynamic function results were obtained. Thermal stability and decomposition characteristics analysis of N-(p-methylphenyl)-N'-(2-pyridyl)urea were carried out by DSC and TG. The results indicated that N-(p-methylphenyl)-N'-(2-pyridyl)urea started to melt at ca. 426 K (153degreesC) and the melting peak located at 447.01 K (173.86degreesC). The melting enthalpy was 204.445 kJ mol(-1) (899.6 J g(-1)). The decomposition peak of N-(p-methylphenyl)-N'-(2-pyridyl)urea was found at 499.26 K (226.11degreesC) from DSC curve. This result was similar with that from TG and DTG experiment, in which the mass loss peak was determined as 500.4 K (227.2degreesC).

腐植酸复合肥在春小麦上的增产效果

<正> 目前,对化学肥料进行二次加工,发展多元复合专用肥料,是世界肥料发展的大趋势,根据FAO(联合国粮农组织)肥料年鉴的统计数字,1989年、1990年度世界发达国家以复混肥料形态的N、P_2O_5、K_2O分别占肥料消费施用总量的20.4％-87.8％、79.2％-98.3％和36.5％-99.6％,而1992年,我国复混肥料施用量占化肥总量的15.8％,尚低于世界平均水平,而且主要是依赖进口。针对上述情况以及三江平原岗平地白浆土“板、瘦、硬”的具体特点,八五二农场天华腐植酸

西部开发 科技先行——在生态环境建设中发挥科学技术支撑作用

在国家决定实施西部大开发战略之际 ,朱基总理 1 999年 8月视察陕西等省区 ,提出了“退田还林 (草 ) ,封山绿化 ,个体承包 ,以粮代赈”的生态环境建设重大措施。以植被建设为中心带动农村经济结构调整的生态环境建设 ,作为西部开发的重要基础工程即将全面启动。同年 8月 7日 ,朱基总理视察水土保持研究所时 ,针对黄土高原水土保持与生态环境建设问题 ,对科技人员提出了明确的要求和殷切的期望 ,充分肯定了科学技术在环境建设中的重要地位。现就如何充分发挥科学技术在生态环境建设中支撑作用的问题谈几点看法。1　科研单位与科技人员应直接切入水土流失治理与生态环境建设工程在生态环境建设中 ,为增加科技含量 ,提高治理水平 ,应使专业研究机构作为技术依托单位参加规划 ,鼓励科技人员直接投入生态环境建设。这样 ,既有利于已有科研成果的推广 ,又能及时研究并解决治理中关键的科学技术问题 ,也有利于解决科研单位游离于建设项目之外的局面 ,促进科研体制深化改革。在大规模的生态建设中 ,从规划到实施的全过程 ,均对科学技术有迫切的需求。一些地县领导针对过去植被建设的经验教训 ,已经清醒地意识到 ,必须加强科技的投入 ,才能克...

沈阳市苔藓植物区系初步研究

对882份标本进行鉴定,共记录沈阳市苔藓植物30科67属143种及变种,其中辽宁省新纪录种36种,东北新纪录种18种.区系分析表明本区苔藓植物以北温带成分为主(51.16%),其次为东亚成分(16.28%)和中国特有成分(12.40%),具强烈的温带性质,与该区地理位置和气候条件等相吻合,与种子植物的区系分布特点也一致.同其他城市地区苔藓植物属和种的相似性系数分析表明,沈阳市与同处辽宁省的抚顺市和鞍山市苔藓植物的亲缘性较大,而与其他城市地区亲缘性较小.

渭北黄土高原刺槐林—草地景观界面土壤水分影响域及其动态变化规律研究

对渭北黄土高原刺槐林—草地景观界面土壤水分影响域及其时空动态变化规律进行了研究。采用移动窗口法分析得出刺槐林—草地景观界面土壤水分影响域为林内4 m到林外12 m之间,宽度16 m,为渐变型界面,由此可将刺槐林—草地景观划分为3个区域:草地区、界面区和刺槐林区。经典统计分析表明,历经3个区域,不同层次的土壤水分在水平方向上随着水平距离梯度的变化表现出不同的上升或下降的趋势,在界面区域土壤含水量变化最为显著。基于标准差和变异系数两个指标,可将草地和林地区域土壤剖面水分垂直变化划分为4层,界面区域划分为3层。3个区域土壤含水量的季节变化表现为基本一致的“高-低-高”规律,可以划分为3个时期,4~5月中旬为土壤水分贮存期,6~7月中旬为土壤水分消耗期,8~10月中旬土壤水分恢复期。水分在时间和空间上的这种变化主要受植被类型、根系分布、降水资源再分配的影响。

Influence of laser-glazing on hot corrosion resistance of yttria-stabilized zirconia TBC in molten salt mixture of V2O5 and Na2SO4

Plasma-sprayed 8YSZ (zirconia stabilized with 8 wt% yttria)/NiCoCrAlYTa thermal barrier coatings (TBCs) were laser-glazed using a continuous-wave CO2 laser. Open pores within the coating surface were eliminated and an external densified layer was generated by laser-glazing. The hot corrosion resistances of the plasma-sprayed and laser-glazed coatings were investigated. The two specimens were exposed for the same period of 100 h at 900 degrees C to a salt mixture of vanadium pentoxide (V2O5) and sodium sulfate (Na2SO4). Serious crack and spallation occurred in the as-sprayed coating, while the as-glazed coating exhibited good hot corrosion behavior and consequently achieved a prolonged lifetime. The results showed that the as-sprayed 8YSZ coating achieved remarkably improved hot corrosion resistance by laser-glazing.

Supramolecular isomerism in zinc hydroxide coordination polymers with pyridine-2,4-dicarboxylic acid: Two polymorphs with centrosymmetric two-dimensional and acentric three-dimensional coordination networks

Reactions of Zn(BF4)(2) and pyridine-2,4-dicarboxylic acid (2,4-pydcH(2)) in the presence of 1,2-bis( 4-pyridyl) ethylene or 1,3-bis(4-pyridyl) propane under hydro(solvo) thermal conditions yielded two polymorphic metal-organic coordination polymers formulated as Zn-2(OH)(2)(2,4-pydc) (1 and 2). Polymorph 1 features a two-dimensional (2-D) layer-like structure that is constructed by 2,4-pydc ligands bridging between the Zn-OH-Zn double-chain units. Each single Zn-OH-Zn chain is composed of mu(2)-OH groups connecting trigonal bipyramidal and tetrahedral Zn centers. Polymorph 2 is a 3-D coordination polymer containing 2-D Zn-OH-Zn sheets that consist of mu(2)- and mu(3)-OH groups and trigonal bipyramidal Zn centers. The sheets are pillared by 2,4-pydc ligands to form an acentric structural architecture. 1 and 2 are rare examples that the two polymorphs exhibit a centrosymmetric 2-D coordination network and an acentric 3-D coordination network, respectively. The different structures lead to differences in photoluminescent properties and thermal stabilities for 1 and 2.

席夫碱铝双核配合物的合成及其对ε-己内酯的催化作用

采用中性双席夫碱配体与异丙氧基铝反应制备了席夫碱铝配合物。经NMR和X射线晶体结构衍射分析证明,该配合物是双核结构。席夫碱配体上的氧和氮原子同时与铝原子配位形成独立单元。2个铝单元由甲氧基基团桥联形成双金属结构。其中铝原子与甲氧基氧原子构成一个平行四边形,它也包含该配合物分子的对称中心。该配合物可以催化ε-己内酯开环聚合。动力学研究表明,单体的转化率和聚合产物的数均分子量均随反应时间的延长而线性增加,并与理论计算值接近,而分子量分布没有明显变化,反应呈活性聚合的特征。NMR分析证明,寡聚物的端基为甲氧基和羟基,因此聚合反应为配位插入机理。