普物教学中如何讲述电磁场变换

从洛伦兹力公式和运动电荷磁场出发，导出了两惯性系间电磁场的变换关系．     

气井携液临界流量计算方法研究

目前水平井中气液两相流动携液临界流量的计算方法仅考虑了水平井段的携液情况而没有考虑直井段与斜井段对携液的影响,所以在直井段和斜井段中未完全携带出的残余流体还是会流到井底,从而在水平井中产生积液.本文对液滴在水平井中直井段,斜井段和水平段进行受力分析发现,在不同的井段液滴因为受力不同从而产生不同的形变,从而计算的携液临界流量也不相同。基于携液理论与气液两相流型理论,根据不同位置的受力情况分别推导了液滴处于直井段,斜井段和水平段时的携液临界流量公式.而水平井的携液临界流量应该为液滴从直井段,斜井段和水平段流过时携液临界流量的最大值。最后通过理论计算与实验结果验证了方法的正确性.     

键阻断原理构建中孔A型沸石

采用不同类型的有机硅烷化SiO₂作为基本合成单元, 制备了具有晶内中孔的A型沸石。考察了反应碱度、Si/Al比、晶化时间等合成条件对产品的影响。结果表明, 甲氨基丙基三甲氧基硅烷是合成中孔A型沸石的最佳硅烷化试剂;硅烷化试剂的应用, 使中孔沸石晶化过程可以通过“键阻断原理”有效控制;沸石的中孔尺寸可以通过不同类型的有机硅烷化试剂进行调控; 一定范围内, 其外比表面积、中孔体积随SiO₂表面硅烷化度的增加而增加。通过沸石晶化过程中的“键阻断”, 可以制备具有晶内中孔的A型沸石。     

Neutron powder diffraction and high-pressure synchrotron x-ray diffraction study of tantalum nitrides

Tantalum nitride(TaN) compact with a Vickers hardness of 26 GPa is prepared by a high-pressure and hightemperature(HPHT) method. The crystal structure and atom occupations of WC-type TaN have been investigated by neutron powder diffraction, and the compressibility of WC-type TaN has been investigated by using in-situ high-pressure synchrotron x-ray diffraction. The third-order Birch–Murnaghan equation of state fitted to the x-ray diffraction pressure–volume(P–V) sets of data, collected up to 41 GPa, yields ambient pressure isothermal bulk moduli of B'_0= 369(2) GPa with pressure derivatives of B 0= 4 for the WC-type TaN. The bulk modulus of WC-type TaN is not in good agreement with the previous result(B_0= 351 GPa), which is close to the recent theoretical calculation result(B_0= 378 GPa). An analysis of the experiment results shows that crystal structure of WC-type TaN can be viewed as alternate stacking of Ta and N layers along the c direction, and the covalent Ta–N bonds between Ta and N layers along the c axis in the crystal structure play an important role in the incompressibility and hardness of WC-type TaN.     

SiO2气凝胶中ZnS∶Mn纳米微晶的发光性质

利用溶胶 凝胶法在SiO2 气凝胶中制得了ZnS∶Mn纳米微晶 ,并对微晶的X射线衍射谱、激发 发射光谱、发光效率、时间分辨光谱进行了研究 ,讨论了发光性质变化的原因。实验表明 ,Mn2 + 在纳米微晶中的发光效率相对于体材料有明显的提高 ,弛豫时间也比在体材料中缩短了约一个数量级     

Solid state reaction synthesis of filled skutterudite compounds (Ce or Y)yFexCo4-xSb12 and the effect of filling atoms Ce or Y on lattice thermal conductivity

The synthesis of filled skutterudite compounds (Ce or Y)_y(Fe)_x(Co)_(4x)(Sb)_(12), through a solidstate reaction using chloride of Ce or Y,high purity powder of Co, Fe, and Sb as starting materials,was investigated. (Ce or Y)_y(Fe)_x(Co)_(4x)(Sb)_(12) (x=0--1.0, y=0--0.15) compounds were obtained at850--1 123 K. The results of Rietveld analysis demonstrate that (Ce or Y)_y(Fe)_x(Co)_(4x)(Sb)_12synthesized by a solid state reaction possesses a filled skutterudite structure. The filling fraction ofCe or Y obtained by Rietveld analysis agrees well with the composition obtained by chemicalanalysis. The lattice constant of (Ce)_y(Fe)_x(Co)_(4x)(Sb)_(12) increases with increasing substitution of Fe at Cosites, and with an increasing Ce filling fraction in the Sb-dodecahedron voids. The lattice thermalconductivity of (Ce or Y)_y(Fe)_x(Co)_(4x)(Sb)_(12) decreases significantly with an increasing Ce or Y fillingfraction in the voids and with substitution of Fe at Co sites.     

填充式skutterudite化合物：BayFexCo4-xSb12的多步固相反应合成及结构

以Ba为填充原子,在x=0—3.0,y=0—0.7的组成范围内,用多步固相反应法合成了单相Ba_yFe_xCo_4-xSb₁₂化合物.用Rietveld方法对结构的精确化结果表明：合成的Ba_yFe_xCo_4-xSb₁₂化合物具有填充式skutterudite结构,Ba的热振动参数(B)比Sb,Fe/Co的大,表明在Ba_y关键词： 填充式skutterudite化合物 固相反应     

根霉胞外羧甲基纤维素酶和β－葡糖苷酶的纯化研究

采用柱层析等步骤纯化了根霉Ｇ７的羧甲基纤维素酶及β－葡糖苷酶，回收率分别为４．５％和１９．６％．二种酶的最适酶反应温度都为５５°Ｃ，并都能在较大ｐＨ范围内保持稳定，其中羧甲基纤维素酶具有很高的耐热性，在１００°Ｃ水浴中保持１ｈ也仍可检测出约２０％的酶活性，最适反应ｐＨ为７．０～７．５；而β－葡糖苷酶的热稳性较差，其最适反应ｐＨ为５．０．该两种酶的分子量分别为２．５×１０４和９．５×１０４，而Ｋｍ值则分别为７．４０ｍｇｍＬ－１和０．２１３ｍｇｍＬ－１．     

脂环族环氧树脂和螺环原碳酸酯的光引发正离子共聚合

<正> 无收缩单体-1,6,8,13-四氧螺[7,7]十三碳烷(SOC_7)和3,4-环氧基环己烷甲酸3',4'-环氧基环己烷甲酯(ERL-4221)的光引发正离子共聚合的研究结果表明,少量SOC_7加到ERL-4221体系中可抑制固化收缩没有明显降低热性能。ERL-4221对SOC_7的合适克分子比为4比1,由此得到T_g为203℃而聚合时体积收缩为4.4％的交联共聚物。