Resistivity－temperature characteristics of sol gel YBa2Cu3Oy samples synthesized in flowing oxygen atmosphere

The relationship of resistivity versus synthesizing temperature of sol gel YBa_2Cu_3O_y samples was studied when prepared under flowing oxygen conditions. A set of high-temperature ρ－T curves was obtained for the whole process. After the sample finished the test measuring, its resistivity was ρ_{300}=9.83×10^{-3 }Ω·cm at room temperature. The ρ－T curve also showed that the orthorhombic－tetragonal phase transformation of sol-gel YBa_2Cu_3O_y sample occurred at 581℃ for the sample in the rising temperature process, but at 613℃ in the cooling process, lower than that of the samples made by using the conventional powder metallurgy methods.     

环境对MgB_2氧化过程中MgO晶须生长形状的影响

用扫描电镜研究了在 Mg B2 氧化过程中环境对 Mg O晶须生长形状的影响。仅有 Mg B2 时 ,在 80 0℃左右空气气氛中 ,可生长出纳米尺寸的 Mg O晶须。若把 Mg B2 添加到氧化铝陶瓷基体中 ,则生长成竹节状晶须。Mg O晶须生长形状的差别可能是由于氧浓度以及位错等因素造成的。     

碳纳米管阵列、捆束的三步升温工艺制备及其形貌与结构

使用结构简单的单温炉设备，通过三步升温热解二茂铁、三聚氰氨混合物方法，在二氧化硅、多晶陶瓷基底上分别合成了碳纳米管阵列、碳纳米管捆束.使用扫描电子显微镜、透射电子显微镜、电子能量损失谱和x射线光电子能谱对合成样品进行了结构和成分分析.结果显示：两种基底上合成的纳米管均为多壁纯碳管；生长于光滑二氧化硅表面的碳纳米管具有高度取向性和一致的外径，长度为10—40μm.碳纳米管采取催化剂顶端生长模式并展示出类杯状形貌；生长于粗糙多晶陶瓷表面的碳纳米管捆束随机取向，碳纳米管直径为15—80nm，长度在几百微米，展示 关键词： 碳纳米管 热解法 三步升温工艺     

基于遗传算法和指标满意度求解的第三方物流企业物流中心选址方法

本利用AHP和模糊综合评价法评价物流中心选址的定性指标、用量化选址模型结合遗传算法计算定量指标，再藉助指标满意度求解把定性和定量的指标进行综合，从而为决策对物流中心选址做出科学的决策提供支持。     

Influence of Mobile Phase Composition on the Enantioseparation of Meythoxyl Flavanones with Self—prepared CDMPC Column and Chiral Recogniton Mechanism

The influence of different alcohol modifiers in mobile phase on the chiral separation of 4‘‘‘‘‘‘‘‘-methoxyl flavanone,5-methoxyl flavanone and 6-methoxyl flavanone on cellulose tris(3,5-dimethylphenylcarbamate)(CDMPC)column was studied and the chiral recognition mechanism was discussed.Using hexane-tert-butanol(1.31molL^-1) as the mobile phase,those three methoxyl flavanones were excellently separated on CDMPC chiral column.     

T2铜的低温比热

在1.4—27K的温区内测量了纯度为99.9％的国产T_2铜的比热,得出了T_2铜的电子比热系数γ为0.68mJ·mol_(-1)·K_(-2),德拜温度θ_D为339.7K。与国外的比热数据比较,显然在纯度相同的条件下,比热数据是一致的,且可以互换。     

温度对PSⅡCP4 7/D1/D2/Cytb559复合物荧光光谱特性的影响

采用激励光源为514.5 nm的分幅扫描单光子计数荧光光谱装置对经20℃、42℃和48℃不同温度处理后的反应中心复合物CP47/D₁/D₂/Cyt b559的荧光光谱特性进行了研究.经解析,获得不同温度处理后,CP47/D₁/D₂/Cyt b559复合物最大峰值未发生变化,均在682 nm,说明Chla670的能量都由Chla682接收,但损耗愈来愈小,在48℃时,损耗程度最小,而其荧光百分比未发生多大变化.振动副带～700 nm和～740 nm的中心波长都发生蓝移,在不同温度下分别为:20℃ 703 nm,749 nm;42℃ 697 nm,744 nm;48℃ 694 nm,740 nm.因此可以推测温度的升高,影响了CP47/D₁/D₂/Cyt b559色素蛋白的二级结构以及色素分子的空间位置,使最大峰值处的荧光强度逐渐降低,振动副带逐渐蓝移.42℃的温度已造成影响,48℃影响较大.     

多结超导环在外磁场中的行为

分析和计算了双结超导环在无偏置电流时的磁通、环流、自由能与外磁场的关系.发现双结环与单结环在磁场中的行为有所不同.当两个结的Ic相等时，双结环在1＜β=2πLIcΦ0＜2时，若无偏置电流，总磁通Φ、环流I与外磁通Φe的关系仍然是非回滞的曲线.仅当β≥2时，曲线才出现回滞.另外双结环有两支解，并且每支解的周期为2Φ0. 关键词： 双结环 双支解 2Φ0周期 回滞     

Temperature-Dependent Dynamic Properties of LixMn2O4 in Monte Carlo Simulations

Monte Carlo (MC) simulations are used to simulate the voltage profile and the ionic conductivity s of Li ions in LixMn2O4 and its dependence on the lithium concentration x. The open circuit potential shows clearly the two plateaus in the charge/discharge curve, which agrees well with the experimental results. The two plateaus become more and more steep when the temperature is increased. The simulated ionic conductivity shows an M-shaped curve in the plot of ionic conductivity cr versus x when the simulation temperature is low. Interestingly,the minimum valley, which lies at the middle single-phase area near x=0.5, disappears gradually when the temperature increases to 453K.