A Reduced Reachability Tree for a Class of Unbounded Petri Nets

As a powerful analysis tool of Petri nets, reachability trees are fundamental for systematically investigating many characteristics such as boundedness, liveness and reversibility. This work proposes a method to generate a reachability tree, called ωRT for short, for a class of unbounded generalized nets called ω-independent nets based on new modified reachability trees (NMRTs). ωRT can effectively decrease the number of nodes by removing duplicate and ω-duplicate nodes in the tree, and verify properties such as reachability, liveness and deadlocks. Two examples are provided to show its superiority over NMRTs in terms of tree size.      

四川盆地上三叠统划分对比研究

四川盆地上三叠统对比长期存在混乱，给盆地整体评价带来困难。通过岩石地层、地震地层、事件地层及高分辨率旋回地层等多种方法讨论了须家河组与香溪群各岩性段的对比关系，得出了全盆地上三叠统的对比关系；指出须四段底可近似看成等时界面；须家河组下部地层自西向东、向南逐层超覆在雷口坡组之上，上部地层在盆地西北部自东南向西北方向剥蚀层位渐次变老。文章建议四川盆地上三叠统废除“香溪群”，统一使用“须家河组”，以利于对全盆地上三叠统进行油气资源整体评价与深化研究。     

现代化工分离技术讲座

<正>第十一章离子液体在分离过程中的应用(上接第2006年第5期) 5．2有机/生物/生物燃料分子的离子液体萃取由于带电有机物在离子液体中的高溶解性,促进了离子液体回收有机物的发展。如表11-7所示,在IL-H_2O两相体系中进行了一些取代苯衍生物的相分配研究。     

Antenna-array pattern nulling using a differential evolution algorithm

A new method based on the differential evolution (DE) algorithm is proposed for antenna-array pattern synthesis with prescribed nulls. The array excitation amplitudes are the only controlling parameters, and the objectives are to synthesize array patterns with nulls imposed on directions of interferences while keeping the sidelobe levels (SLLs) below prescribed levels. Many factors such as the excitation dynamic range ratio, null depth level, null width, and SLLs are taken into account in the synthesis. Simulation results of several typical problems are compared with published results to illustrate the effectiveness of the proposed method. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 57–63, 2004.     

抗乙肝病毒表面抗原PreS1(20-47)的单链抗体在转基因烟草根分泌物中的初步表达

为探索利用植物根分泌表达重组蛋白的可行性，构建了含有抗乙肝病毒表面抗原PreS1(20—47)单链抗体(ScFv)基因的表达载体。该ScFv基因转化烟草后在烟草根部细胞的细胞质和内质网中获得表达。实验结果表明，5’端融合ER导向信号肽的重组ScFv可通过根分泌表达。