Application of dye-partition technique to the determination of the rates of initiation in radical polymerization

Summary Dye-partition technique as an useful method of measuring kinetic chain length (v), rate of initiation (R _i ), initiator efficiency (f), and the parameter [=(2k _t)^1/2 k _p] etc. in radical polymerization using styrene and methylmethacrylate as monomers in dimethyl formamide medium and 4,4 azobis-4-cyanopentanoic acid as the initiator to produce dye responsive carboxyl ended polymers has been discussed. The values ofR _p,f and obtained by this method compare fairly well with those obtained by a standard method, viz., molecular weight method. The magnitude off much less than unity and constancy in its value under different concentrations of monomers and initiator indicate that almost all radicals surviving geminate recombination is captured by the monomers. The precautions necessary for applying this method have also been discussed.

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Zusammenfassung Farbstoff-Verteilungstechnik als nützliche Methode zur Messung der kinetischen Kettenlänge (v), Initiationsgeschwindigkeit (R _i ), des Initiator-Wirkungsgrades (f), und des Kennwertes (2k,^1/2 k _p ) (=) etc. bei der radikalischen Polymerisation von Styrol und Methylmethacrylat in Dimethylformamid-Medium mit 4,4'-Azobis-4-cyanopentansäure als Initiator zur Bildung von mit Farbstoffen reagierenden Carboxylatendgruppen in den Polymeren, wurde diskutiert. Die durch obengenannte Methode festgestellten Werte vonR _p ),f und sind ungefähr mit den durch übliche Methoden festgestellten Werten vergleichbar (durch Molekulargewicht-Methode).Die konstante Größenordnung von 'f, die viel weniger als eins beträgt, weist darauf hin, daß alle die paarweise Rekombination überlebenden Radikale von den Monomeren abgefangen werden. Die zur Anwendung dieser Methode nötigen Vorsichtsmaßnahmen sind auch diskutiert worden.

     

Head space gas chromatography with glass capillaries using an automatic electropneumatic dosing system

Head space GC using a special electropneumatic sampling system works well in combination with glass capillaries. Because a homogenous gas mixture is already present most problems inherent with inlet splitters are thus avoided. In cases where the high vapor pressure of the sample can cause problems with the pressure controlled sampling system, the use of narrow bore glass capillaries provides the necessary inlet pressure. The use of this powerful and convenient analytical tool for water pollution analysis, flavour analysis and the analysis of volatiles in crude oil samples is shown by examples.     

Balancing capacity and lot sizes

In many companies there is an on-going discussion about capacity, capacity utilization and capital tied up in inventories. However, traditional models such as the EOQ model only include capacity considerations in the set-up cost, or in the cost of a replenishment order. This implies e.g. that they do not consider the set-up time as a capacity constraint. Furthermore, in these models the set-up cost is usually treated as a constant, even though the opportunity cost for capacity in general is dependent upon the capacity utilization.The purpose of this paper is to derive an analytical model for the balancing of capacity and lot sizes. The model includes costs for capacity, work-in-process (queueing, set-up, and processing time), and finished goods inventory. The total costs are minimized with respect to capacity. Then, the corresponding, recommended lot sizes are determined. The model was tested with data from a Swedish manufacturing company. The results turned out to coincide with experiences of the company in many important respects. The model offers production management an opportunity to discuss the relationship between capacity, work-in-process, and lot sizes.     

TiMnSi2结构的高分辨电镜研究

利用高分辨电子显微镜（ＨＲＥＭ）研究了ＴｉＭｎＳｉ_２（硅化钛锰）相的原子结构及其平面缺陷。通过大角度倾转的电子衍射分析，揭示ＴｉＭｎＳｉ_２相具有简单正交结构，空间群为Ｐｂａｍ。高分辨电子显微分析发现，ＴｉＭｎＳｉ_２相具有３￣２４３４网格特征，并接近于五角σ相的网格特征。在ＴｉＭｎＳｉ_２相中还观察到Ｓｔｅｉｎｍｅｔｚ等提出的假想结构，并证实它具有类似于六角反棱锥并置的Ｈ相网格特征，但由于只有２～３层，因而只能看成是ＴｉＭｎＳｉ_２中的Ｕ、Ｄ层错。     

Optical studies of local flow behaviour of a non-Newtonian fluid inside a porous medium

In this study the local flow of a polymeric solution inside a porous medium is studied visually. While the flow is quite uniform for low volume flow rates it shows pronounced nonuniformity for higher volume flow rates. That is to say, only certain preferred passages are taken and these passages change in time (they fluctuate). This flow irregularity is the reason for increased resistance. Received: 28 April 1997 Accepted: 30 December 1997     

制备工艺对电子俘获材料性能的影响

利用等离子体质谱(ICP-MS)技术测试了硫化助熔剂法和稀土直接掺杂工艺合成电子俘获材料的化学计量比,结果表明,采用稀土直接掺杂工艺合成材料的化学计量比更接近设计值;通过分析电子俘获材料的发光机制和光谱测试结果,讨论了制备工艺条件对电子俘获材料中稀土离子化合价的影响.     

A levitation technique for determining particle hydrophobicity

A new technique designed to evaluate the hydrophobicity of fine particles is described. Results of the hydrophobicity measurements correlate well with those of the Hallimond tube flotation tests both in triply distilled water and in 1·10⁻³ mol dm⁻³ AlCl₃ solution. Experimental error analysis indicates that this technique is more sensitive for detecting small changes in the hydrophobicity than the Hallimond tube tests used for determining floatability.     

用于反坦克导弹研究的红外能量测试技术

简述红外能量测试技术在反坦克导弹研究上的应用,介绍其工作原理和测试方法。给出在实际测试应用中的例子,并提出有关测试和数据处理的技巧。     

悬置槽线行波相位调制器的特性分析

提出一种新颖的集成光波导行波相位调制器结构，它利用悬置槽线作为调制器的外调制电路，减小了光波和调制波之间的速度失配，提高了相位调制器的调制带宽。采用谱域等效传输线法分析了悬置槽线的传播特性．     

热重分析技术研究聚-α-甲基苯乙烯降解温度

采用热重分析技术研究了4种聚-α-甲基苯乙烯原料和其它微球壳层材料的热降解温度。研究表明,聚-α-甲基苯乙烯原料主要失重温度范围为220～340℃,等离子体辉光放电涂层材料的降解温度为350～450℃。升温速率在20℃/min和30℃/min时,降解温度基本相同,升温速率不影响降解的温度范围,低于20℃/min时,随着升温速率升高,降解温度升高。