A hybrid class- and prototype-based object model to support language-neutral structural intercession

ContextDynamic languages have turned out to be suitable for developing specific applications where runtime adaptability is an important issue. Although .Net and Java platforms have gradually incorporated features to improve their support of dynamic languages, they do not provide intercession for every object or class. This limitation is mainly caused by the rigid class-based object model these platforms implement, in contrast to the flexible prototype-based model used by most dynamic languages.ObjectiveOur approach is to provide intercession for any object or class by defining a hybrid class- and prototype-based object model that efficiently incorporates structural intercession into the object model implemented by the widespread .Net and Java platforms.MethodIn a previous work, we developed and evaluated an extension of a shared-source implementation of the .Net platform. In this work, we define the formal semantics of the proposed reflective model, and modify the existing implementation to include the hybrid model. Finally, we assess its runtime performance and memory consumption, comparing it to existing approaches.ResultsOur platform shows a competitive runtime performance compared to 9 widespread systems. On average, it performs 73% and 61% better than the second fastest system for short- and long-running applications, respectively. Besides, it is the JIT-compiler approach that consumes less average memory. The proposed approach of including a hybrid object-model into the virtual machine involves a 444% performance improvement (and 65% less memory consumption) compared to the existing alternative of creating an extra software layer (the DLR). When none of the new features are used, our platform requires 12% more execution time and 13% more memory than the original .Net implementation.ConclusionOur proposed hybrid class- and prototype-based object model supports structural intercession for any object or class. It can be included in existing JIT-compiler class-based platforms to support common dynamic languages, providing competitive runtime performance and low memory consumption.     

片状Nd1Ni5-xCx合金粉的电磁和微波吸收特性

利用电弧熔炼和行星球磨技术制备出片状Nd1Ni5-xCx(x=0.0,0.1,0.3,0.5)合金粉。利用X射线衍射仪(XRD)、扫描电镜(SEM)、振动样品磁强计(VSM)、矢量网络分析仪(VNA)等仪器对其结构、形貌和电磁特性进行检测。结果表明,随着C含量的增加,粉体的饱和磁化强度和矫顽力逐渐减小,并且反射损耗的吸收峰向高频移动。在C添加量为x=0.5时出现2个有效带宽,分别为8.28~9.82GHz和11.17~12.03GHz,有效改善了粉体的吸收带宽。另外,随着粉体厚度的变化,反射损耗可以在较大的频段内进行调整。可见该粉体有着广泛的应用前景。     

The territorial and landscape impacts of photovoltaic systems: Definition of impacts and assessment of the glare risk

The installation and operation of systems that exploit solar energy through photovoltaic conversion, recently promoted in some European countries by new sell-back tariffs, is a relevant transformation of the territory for various reasons (land use, elimination of the existing vegetation, visual impact on the components of the landscape, microclimate change, glare from the reflection of the direct sunlight). The weak energy intensity of the solar source coupled with the low conversion efficiency of the photovoltaic cells, make the physical dimensions of such systems relevant and, with them, also the environmental, territorial and landscape impacts that basically depend on the physical extent of the system. If it is well known that an incentive to the exploitation of renewable sources is one of the features of the policy of land conservation, including the one of the protected areas, at the same time the concerns of local communities and governments about the environmental, territorial and landscape impacts of this technology are increasing rapidly.Given this picture, this work is intended to clarify the territorial impacts of the ground mounted photovoltaic systems. Later, the paper concentrates on a specific impact, which is the assessment of the risk of glare by reflection of direct sunlight from the surfaces of photovoltaic modules. The methodologies that can be used to assess this impact and the outcomes of an evaluation carried out for a 5000 m² PV system currently designed on a hilly territory in Italy are presented.     

Dimension Optimization for Silica Sand Based on the Analysis of Dynamic Absorption Efficiency in Microwave Drying

We propose a theoretical guideline for prediction of maximum microwave absorption in microwave drying by optimizing the thickness of a silica sand layer based on analysis of reflection loss (RL). The microwave RL of the silica sand layer was studied over the moisture content of 1% to 5% at 20°C and the silica sand (5% moisture content) in the temperature range of 20 to 100°C at 2.45 GHz. The calculated RL for various moisture contents and temperatures shows that the RL sensitively depends on the thickness of the silica sand. There are absorption peaks in the RL patterns, and the microwave absorption peak shifts towards a smaller thickness side as the moisture content and temperature of the silica sand increase. We also show that the intensity of microwave absorption peaks in the RL patterns of silica sand decrease with decreasing moisture content, and achieve the highest absorption at 60°C.     

基于反射的实时构件模型规约描述研究

以现有的构件模型为研究基点,应用反射技术,针对实时应用系统的开发,提出一类新的构件模型——反射式实时构件模型,由反射式实时构件语义模型和反射式实时构件语法模型组成。该模型在规约构件应有的功能需求特征的基础上,有效地标识构件的时间约束特征,使得与传统的功能性构件区别开来,能被系统开发者更好地选用。同时,该模型结合反射技术,能根据用户需求的变化,对实时构件进行动态修改,以便更准确地保障实时应用系统的构建与开发,并增强构件设计的活性,达到构件更好实现的效果。反射式实时构件模型既是一个构件理论模型,也是一个工程模型。     

轻量级开放式移动Agent系统：原理与实现

移动agent计算模式是一种灵活的基于Internet的分布式计算模式，但是“黑盒”式的设计和“单体”结构使得既有移动agent系统过于冗余，且不能随着用户需求和计算环境的变化动态修改系统的结构和行为。因此提出利用反射技术将移动agent系统“构件化”使其能够支持系统的“可定制”或“可裁剪”，并采用开放式的实现为移动agent系统的使用者提供扩展系统的能力。反射架构下的移动agent系统能够在运行时刻无需关闭系统动态加载或卸载特定模块；通过移动agent和底层平台的反射特性能自然地实现agent和agent平台的自适应。遵循这个途径开发了具有反射特性的Artemis-Mogent原型系统，并通过试验示范了新系统应用反射后的效果。     

空气中声波对电磁波的定向反射

以电磁波折射率具有周期性变化的层状结构来模拟空气中两个相距较远的相干声源干涉形成的中心区域,研究了结构对电磁波定向反射的特性。理论研究结果表明:尽管声波在空气中引起的电磁波折射率的振荡幅度非常小,但是在一定的条件下,声波的存在会对电磁波造成非常强烈的定向反射。文中给出了发生强烈定向反射时,声波波长、电磁波波长和入射角等应该满足的条件,并且计算了反射峰的宽度。     

EJB设计中一种动态会话外观模式的实现策略

会话外观是一种经典的EJB设计模式,其实现通常都是静态的,亦即要将EntityBean的LocalHome接口硬编码为会话外观SessionBean具体的实例变量,这在需要封装多个EntityBean时,会话外观SessionBean将变得异常复杂而难以实现和维护。本文通过对以上静态会话外观模式不足的分析,提出了一种基于Java反射机制和接口技术的、动态会话外观模式的实现策略,有效的解决了由单一会话外观来封装多个EntityBean的问题。     

EJB设计中一种动态会话外观模式的实现策略

会话外观是一种经典的EJB设计模式，其实现通常都是静态的，亦即要将EntityBean的LocalHome接口硬编码为会话外观SessionBean具体的实例变量，这在需要封装多个EntityBean时，会话外观SessionBean将变得异常复杂而难以实现和维护。本文通过对以上静态会话外观模式不足的分析，提出了一种基于Java反射机制和接口技术的、动态会话外观模式的实现策略，有效的解决了由单一会话外观来封装多个EntityBean的问题。     

基于Web Service的呼叫修理系统的设计和实现

介绍了利用WebService技术实现呼叫修理的方案，并提出了三层的软件体系结构模型，使得用WebService实现一个现代商业模式变得更为方便，而数据的更新、维护、管理更为有效，避免了许多不必要的重复劳动。