Der Einfluß des Atmosphärendruckes bei energiedispersiven Röntgenfluoreszenzanalysen leichter Elemente

Energiedispersive Röntgenspektrometer besitzen gegenüber wellenlängendispersiven Systemen den Vorteil einer wesentlich höheren Effektivität. Deshalb finden bei der energiedispersiven Röntgenfluoreszenzanalyse oft auch Nuklidquellen zur Anregung Verwendung. Die gebräuchlichsten Quellen dieser Art bestehen je nach Primäraktivität und Nuklid aus Scheiben mit einem Durchmesser zwischen 5 und 20 mm und einer Dicke von 5–10 mm. Damit wird von der Anregungsseite her ein einfacher Aufbau des Analysengerätes ermöglicht. Die Leistungsfähigkeit eines solchen Gerätes ist in vielen Fällen ausreichend, Spuren-elemente analytisch zu bestimmen. Deshalb ist auch die Notwendigkeit einer evakuierbaren Meßkammer oft noch umstritten. Besonders bei der Analyse leichter Elemente (mit Ordnungszahlen Z ? 20) macht sich jedoch die umgebende Atmosphäre störend bemerkbar. Dieser Einfluß ist am Beispiel des Schwefelnachweises (Z = 16) näher untersucht worden.     

活性炭吸附氦气式回热器的吸附特性研究

回热式低温制冷机在空间探测和地面实验中都有重要应用,但是在液氦温区工质氦气的体积比热容高于目前几乎所有的蓄冷材料,导致回热器效率低下.直接使用活性炭吸附一部分工质氦气作为蓄冷填料是一种潜在的解决方案.基于4～J10 K温度区间内吸附量的实验数据,建立了低温动态吸附计算模型,分析了液氦温区动态吸附特性对回热器性能参数的影...     

空气绕流诱发H型桥面振动的机理分析与模拟——————以Tacoma大桥风振致毁事故为例

以Tacoma大桥风振致毁事故为例, 研究H型桥面的风振机理. 分析了绕流场对称性的 破缺及其诱发桥面振动的情况; 并根据大桥实际尺寸, 采用Fluent软件进行了二维仿真计算. 结果表明: 桥面低压区从中部逐步形成并顺风向移动, 在上下桥面依次交替进行; 其二, 风 速越大, 桥面所受的阻力和升力变化周期越小, 周期变化速率也越小; 其三, 升力系数的变 化周期约为阻力系数变化周期的两倍, 在当时19m/s的风速条件下, 升力系数变化的周期约 为31.5s.     

The Cuntz semigroup and comparison of open projections

We show that a number of naturally occurring comparison relations on positive elements in a C^?-algebra are equivalent to natural comparison properties of their corresponding open projections in the bidual of the C^?-algebra. In particular we show that Cuntz comparison of positive elements corresponds to a comparison relation on open projections, that we call Cuntz comparison, and which is defined in terms of—and is weaker than—a comparison notion defined by Peligrad and Zsidó. The latter corresponds to a well-known comparison relation on positive elements defined by Blackadar. We show that Murray-von Neumann comparison of open projections corresponds to tracial comparison of the corresponding positive elements of the C^?-algebra. We use these findings to give a new picture of the Cuntz semigroup.     

外场作用下聚合物滞后生热效应

为了研究振动参数对聚合物黏弹性能及塑化成型过程的影响,深入分析了振动场的作用机理,揭示了相位角与滞后生热率之间的关系,得出了振动场作用下聚合物塑化成型速率表达式,最后通过聚对苯二甲酸乙二醇酯(PET)动态毛细管挤出以及多维振动塑化成型设备进行实例计算和实验研究,实验结果和理论计算值符合得很好,并得出结论: PET塑化速率随振动频率的增加呈先增加后减小的趋势,当激振频率趋向于材料固有频率时(振动频率约为15 Hz时),PET塑化速率达到最大值,当振幅为6 MPa时,其值约为22 g/min,为相同振幅下,频 关键词： 振动场 滞后生热 相位角 低温成型     

神光Ⅱ与神光Ⅲ原型上的辐射驱动小收缩比内爆靶设计

本文建立辐射驱动小收缩比(5至10倍)的内爆靶丸的设计方法,并利用辐射流体力学程序Multi-1d对神光Ⅱ和神光Ⅲ原型装置的辐射驱动小收缩比内爆靶丸进行模拟计算,设计出小收缩比内爆靶丸的构形,计算结果给出压缩比、中子产额、压缩面密度随燃料压力变化等内爆物理参量.神光Ⅱ装置上的内爆靶燃料分别采用DD气体和DT气体两种;神光Ⅲ原型装置的内爆靶燃料采用DD气体.神光Ⅱ上小收缩比内爆实验结果与模拟结果基本一致,表明Multi-1d用于设计此类实验的可靠性. 关键词： 辐射驱动 小收缩比 内爆 面密度     

Regulation of phosphorylase kinase by low concentrations of Ca ions upon muscle contraction: the connection between metabolism and muscle contraction and the connection between muscle physiology and Ca-dependent signal transduction

It had long been one of the crucial questions in muscle physiology how glycogenolysis is regulated in connection with muscle contraction, when we found the answer to this question in the last half of the 1960s. By that time, the two principal currents of muscle physiology, namely, the metabolic flow starting from glycogen and the mechanisms of muscle contraction, had already been clarified at the molecular level thanks to our senior researchers. Thus, the final question we had to answer was how to connect these two currents. We found that low concentrations of Ca ions (10(-7)-10(-4) M) released from the sarcoplasmic reticulum for the regulation of muscle contraction simultaneously reversibly activate phosphorylase kinase, the enzyme regulating glycogenolysis. Moreover, we found that adenosine 3',5'-monophosphate (cyclic AMP), which is already known to activate muscle phosphorylase kinase, is not effective in the absence of such concentrations of Ca ions. Thus, cyclic AMP is not effective by itself alone and only modifies the activation process in the presence of Ca ions (at that time, cyclic AMP-dependent protein kinase had not yet been identified). After a while, it turned out that our works have not only provided the solution to the above problem on muscle physiology, but have also been considered as the first report of Ca-dependent protein phosphorylation, which is one of the central problems in current cell biology. Phosphorylase kinase is the first protein kinase to phosphorylate a protein resulting in the change in the function of the phosphorylated protein, as shown by Krebs and Fischer. Our works further showed that this protein kinase is regulated in a Ca-dependent manner. Accordingly, our works introduced the concept of low concentrations of Ca ions, which were first identified as the regulatory substance of muscle contraction, to the vast field of Ca biology including signal transduction.     

悬臂梁压电振子宽带低频振动能量俘获的随机共振机理研究

研究了利用系统非线性来提高悬臂梁压电振子宽带低频振动能量俘获效率的随机共振机理,通过增加一对矩形永磁铁对传统线性悬臂梁压电振子结构进行了改进,结果揭示:在外部非线性磁力作用以及合适的磁铁间距条件下,这种外加磁力悬臂梁压电振子会构成一个双稳系统,在外部宽带低频随机振动源激励下发生随机共振现象,且发生随机共振时的输出电压明显增大,从而可以扩展悬臂梁压电振子的共振频率范围、提高低频振动能量的转化输出. 关键词： 压电悬臂粱 振动能量俘获 宽带低频 随机共振     

常温制备形貌可控中空羟基磷灰石的研究

利用锂钙硼玻璃(LCB)微球在磷酸盐溶液中的原位转化反应,在常温下制备中空的羟基磷灰石(HA)微球,研究了玻璃微球的组分、磷酸盐浸泡液的浓度及热处理等工艺参数对微球的形貌影响。研究结果表明,常温下反应得到的产物微球为晶型较好具有中空结构的羟基磷灰石,随着玻璃微球组分中CaO含量的升高,中空微球的球壁逐渐变厚,当CaO含量达到30%时,微球变为实心结构。磷酸盐溶液浓度较低时,中空微球的球壁容易形成层状结构。