A formal architectural model for logical agent mobility

The process of agent migration is the major difference between logical code mobility of software agents and physical mobility of mobile nodes in ad hoc networks. Without considering agent transfer, it would make little sense to mention the modeling of strong code mobility, which aims to make a migrated agent restarted exactly from the state when it was stopped before migration. From the perspective of system's architecture, this paper proposes a two-layer approach for the formal modeling of logical agent mobility (LAM) using predicate/transition (PrT) nets. We view a mobile agent system as a set of agent spaces and agents could migrate from one space to another. Each agent space is explicitly abstracted to be a component, consisting of an environmental part and an internal connector dynamically binding agents with their environment. We use a system net, agent nets, and a connector net to model the environment, agents, and the connector, respectively. In particular, agent nets are packed up as parts of tokens in system nets, so that agent transfer and location change are naturally captured by transition firing (token game) in Petri nets. Agent nets themselves are active only at specific places and disabled at all the other places in a system net. The semantics of such a two-layer LAM model is defined by transforming it into a PrT net. This facilitates the analysis of several properties about location, state, and connection. In addition, this paper also presents a case study of modeling and analyzing an information retrieval system with mobile agents.     

SPS烧结M42粉末冶金高速钢的显微组织与性能

采用放电等离子烧结技术(SPS)制备了M42粉末冶金高速钢,研究了SPS烧结M42粉末冶金高速钢及其热处理后的显微组织与性能。结果表明:与普通粉末冶金高速钢相比,SPS烧结制备的M42粉末冶金高速钢显微组织均匀、晶粒细小、无碳化物偏析。经过在1180℃×5min×550℃×1h的热处理后,硬度比普通粉末冶金高速钢提高1～2HRC。     

基于免疫否定选择算法的机场航班延误状态检测与实现

把免疫算法中的否定选择算法运用到航班延误状态的诊断检测与预测中,将生物免疫系统机制与机场航班运行机制联系起来,建立了相应的自体集合、检测细胞、抗原信息及它们之间的匹配模型,给出了检测方法。首先根据机场航班运行数据生成航班检测的成熟检测器和记忆检测器,然后用否定选择算法和航班数据对检测器进行训练和改进,最后利用检测器中的信息对机场航班状态分段进行预测,获得每个时段的航班延误状况,为机场有关部门对航班延误应急处理提供决策支持。仿真实验表明,该方法能较准确地预测航班的延误状态,且实时性好。     

The characteristics of waves around an entrance of a lagoon in South China Sea

The characteristics of the waves around a lagoon entrance in South China Sea were observed during the past one and half years based on the wave measurements.The...     

222Rn在大气输运研究中的示踪应用

本文简要回顾了222Rn及其子体示踪应用的主要方面,介绍了国内外对利用222Rn及其子体在预报地震和大气物质输运研究这两方面的工作.对这些示踪应用而言,要进行准确的定量分析和数值模拟,必须对222Rn及其子体在大气中的输运规律有细致的了解,这一点可以通过研究其动力学特征,建立输运模型来实现.本文中列举了部分对222Rn及其子体输运模式的研究,对比上层大气中的简单输运模型,一个比较全面的222Rn输运模型还需要考虑地表层结大气中的复杂的动力学因素,并将其作为222Rn在上层大气输运模型中的下垫面边界条件.     

一种新型设备用断路器——NDB3的结构原理及应用

介绍了液压-电磁式设备用断路器的工作原理、产品特点及其在典型行业中的应用,阐述了这一区别于传统热磁式断路器的优点,及在通信行业中的典型应用。     

一种飞机目标暴露面积的简易工程计算方法

任意威胁方向的暴露面积计算是进行飞机目标易损性评估的基础,本文提出了一种计算暴露面积的简易工程计算方法;利用AUTOCAD软件建立实体模型,通过视点设置,直接形成目标平行投影结果.利用图像处理技术,结合球体投影,计算任意形状图形的像素点,回算目标部件的投影面积.此方法操作简单,可计算任意形状的飞机暴露面积,计算误差可控制在2%以下,满足工程计算要求.     

Physicochemical properties and osteogenic activity of radiopaque calcium silicate–gelatin cements

The purpose of this study is to evaluate the physicochemical properties and in vitro osteogenic activity of radiopaque calcium silicate–gelatin cements. The radiopacity, setting time, working time, flow, diametral tensile strength, pH value, washout resistance and morphology of the cements with gelatin (0, 5 and 10 % by weight) were measured, which compared to a popular endodontic material, ProRoot white-colored mineral trioxide aggregate (WMTA). The cell morphology, cell attachment and proliferation, alkaline phosphatase and osteocalcin levels on the cements were measured by culturing the specimens with dental pulp cells. The results indicated that the presence of gelatin significantly (P < 0.05) reduced radiopacity and diametral tensile strength and prolonged setting time. Nevertheless, the 5 wt% gelatin cement had a radiopacity (5.1 mm of Al thickness) higher than ISO 6876:2001 standards (3 mm of Al thickness). The setting time (33 min), working time (9 min) and flow value (17.4 mm) of the 5 wt% gelatin cement were significantly (P < 0.05) better than those of WMTA (corresponding 165, 6 min and 14.2 mm). The fresh WMTA completely degraded after soaking in a physiological solution for 1 h, while the gelatin cements resisted washout, showing no noticeable breakdown even after 1 day of soaking. The gelatin cement enhanced the higher expression of cell attachment, proliferation and differentiation as compared to WMTA. It was concluded that the 5 wt% gelatin–calcium silicate hybrid cement appears to be promising as a radiopaque biomaterial for medical applications such as endodontics and vertebroplasty.     

用于内窥光学相干层析成像探头的小型化及焦深拓展技术

小型化探头是内窥光学相干层析成像(Optical coherence tomography,OCT)中的普遍需求。介绍了包括基于球透镜、光纤透镜、自聚焦光纤、自由曲面透镜、无透镜的OCT技术的发展历程,总结和比较了各种技术的优劣,为探头的小型化设计提出了建议。研究探头的焦深拓展技术对分辨人体内细胞的在体成像的发展具有重要意义。介绍了几种重要的适用于小型化探头的焦深拓展技术,其中基于模式干涉的探头由于易于制作、结构紧凑、传输效率高,同时具有可以优化工作距离、焦深和轴向光强均匀性的优点,在拓展小型化探头的焦深方面具有一定的发展潜力。