函数乘积的可导性

运用导数的定义,从理论上分析不同形式的函数乘积的可导性条件。     

Modeling of pedestrian evacuation under fire emergency based on an extended heterogeneous lattice gas model

An extended heterogeneous lattice gas (E-HLG) model is developed by introducing an altitude factor into the heterogeneous lattice gas (HLG) model. The altitude factor is used to describe the position height of lattice sites. Evacuation features from a terrace classroom are investigated through simulations using both the model and experiments. To study evacuation processes under fire emergency, an agent-based fire and pedestrian interaction (FPI) model is proposed. It is supposed that the possible moving directions of a pedestrian depend on the environmental temperature field, which is simulated by the software FDS. The walking speed reduction due to the visibility worsening in the FPI model is described by a multi-grid method. It is found that simulation results based on the extended HLG model are in good agreement with the experiments. The altitude factor plays a guidance role to the evacuation, and the fire notably delays the evacuation due to both the harmfulness of the high temperature field and the change of evacuation routes which results in frequent local jamming and clogging.     

二氧化硅负载磷钨酸铵催化苯酚氧化溴代反应

以溶胶-凝胶法制备的二氧化硅负载磷钨酸铵为催化剂,溴化钾为溴源,双氧水为氧化剂,冰醋酸为溶剂,实现了苯酚的催化氧化溴代反应。 探讨了催化剂负载量、催化剂用量和反应时间等反应参数对氧化溴代反应的影响。 结果表明,溶胶-凝胶法制备的负载磷钨酸铵仍具有典型的Keggin结构;在室温的温和条件下,该催化剂表现出较强的催化苯酚氧化溴代反应活性和较高的对溴苯酚选择性,在实验优化条件下,苯酚转化率达到95.4%,对邻比达到3.2;而且催化剂易回收,重复4次使用后,催化活性有所降低,苯酚转化率为87.4%,对邻比为1.6。     

A note on characterization of finite groups with some S-quasinormal subgroups

In this paper, firstly two examples are given to indicate that the main result in the paper “Characterization of Finite Groups with Some S-quasinormal Subgroups” (Asaad and Csörg? in Monatsh Math 146:263–266, 2005) are not correct. Secondly, a revised version of that theorem is obtained.     

Effect of aging time and salt on the viscosity behaviour of a Gemini cationic surfactant

Rheological properties of micellar solutions of a cationic Gemini surfactant, 2-hydroxypropyl-1,3-bis (dodecyldimethylammonium chloride), are studied as a function of aging time and salt addition. The results show that the self-aggregating behaviour in solution changes as a factor of time, probably due to intermolecular hydrogen bonds. The viscosity of the solution undergoes a series of visible changes so that the solution changes from a flow state to highly viscoelastic state, and finally, to a transparent solid, with a corresponding 4–6-fold increase in zero shear state viscosity. Rheology and freeze fracture transmission electron microscopy (FF-TEM) measurements show rod-like micelles at the beginning, which then change to wormlike micelles, and eventually to a quasi-gel-like network. Addition of an inorganic salt (NaCl) induces salting out, while the addition of an organic salt (NaSal) promotes micellar growth. At a fixed NaSal-to-surfactant molar ratio of 3:5, all solutions show Maxwell fluid behaviour and maximum zero-shear-rate viscosity; these trends can be attributed to the formation of a network structure between the cationic ions of the surfactant and Sal^– as the surfactant concentration increases. Crystal analysis further confirms the presence of structures linked by intermolecular hydrogen bonds.     

主链含羟基的芳杂环液晶共聚物聚对苯撑苯并二噁唑的 合成及性能研究

通过在聚合过程中添加少量2,5-二羟基对苯二甲酸(DHTA)部分替代对苯二甲酸(TPA)与4,6-二氨基间苯二酚(DAR)盐酸盐进行共聚, 合成了一系列大分子链上含有羟基基团的DHPBO共聚物, 并制得其初生纤维. 利用FTIR、接触角等分析手段对其化学结构和纤维表面性能进行了表征, 通过单丝拔出实验和SEM考察了DHPBO纤维与环氧树脂基体的界面剪切强度, 并采用轴向压缩弯曲实验和紫外光加速老化实验评价了羟基基团的引入对提高纤维压缩性能和抗紫外性能的影响. 结果表明, 羟基基团的引入使得DHPBO纤维的表面亲水性、与环氧树脂的界面剪切强度以及纤维的压缩性能和抗紫外性能都有了显著提高.     

磷酸二氢铵转化法测定硫酸钡含量

针对目前重晶石中硫酸钡含量测定方法研究不多、进展缓慢的问题,提出了一种对重晶石预处理后测定硫酸钡的方法,采用磷酸二氢铵与重晶石在700℃发生复分解反应,将不溶于水且不溶于酸的硫酸钡转化为可溶于酸的磷酸钡盐,最后依据确定的磷钡比关系,根据总磷含量间接得到钡含量。实验结果表明,磷酸二氢铵与硫酸钡的物质的量之比为2.0,并在700℃的条件下高温煅烧,可使硫酸钡全部转化完全,形成偏磷酸钡,再经过氢氧化钠、双氧水处理,转变为正磷酸氢钡并溶于盐酸中,与喹钼柠酮试剂形成磷钼酸喹啉沉淀,根据沉淀质量可准确计算出样品中硫酸钡的含量。测定的结果准确、方法可行。对测定重晶石中硫酸钡的含量提出一种新的思路和解决方案,具有实际意义。     

基于频率特征的薄膜损伤声学判别方法

利用声学法研究单层氧化硅薄膜在不同激光能量下的损伤情况,建立了激光致薄膜产生的声波采集系统,对其采集到的时域信号进行傅里叶变换,比较和分析薄膜损伤前后声波24~40 kHz高频段的曲线,提取频率特征,并提出用曲线相似函数进行薄膜损伤的识别方法。实验数据结果表明,该方法简单易行,可降低环境噪声的影响,既能实现在线检测,又能准确判别薄膜损伤。