Bifurcation control in a delayed two-neuron fractional network

The issue of bifurcation control for a delayed fractional network involving two neurons is concerned. Delay-dependent stability conditions and the bifurcation point are established by discussing the associated characteristic equation of the proposed network. Then, a delayed feedback controller is firstly designed to stabilize the Hopf bifurcation, and desirable dynamics is achieved. It is indicated that the designed controller is extremely effective which can postpone the onset of bifurcation by carefully selecting the feedback gain. Finally, simulation results are given to verify the efficiency of the theoretical results.     

对象间差异度的限制非对称相似关系模型

经典Rough集理论主要是利用了不可分辨关系对完备信息系统进行分析的。对现有粗糙集模型进行扩充后,才可以应用于不完备信息系统。容差关系、非对称相似关系、基于对象间完备度的限制容差关系、限制非对称相似关系等是现有的扩充模型。通过分析其优点和不足之处,提出一种新的模型——对象间差异度的限制非对称相似关系模型,在该模型中,给出的知识粒度更精确,更符合实际。实例结果也证明新模型可以从不完备信息系统获取更加精确的知识粒度。     

企业信息安全防护体系的构筑

企业信息系统的安全保障体系可以分为三个层次:一是基本安全环节,通常由系统平台(如操作系统或者数据库)本身提供,有效的发挥这些安全机制的作用十分有效;其次是对基本安全要素的增强环节,能够为系统带来更可靠的保护作用;再次是扩充的安全机制,提供更强的安全监测和防御能力,是对安全有很高要求的信息系统应该考虑的成分。     

Surface tension calculation of the Ni3S2---FeS---Cu2S mattes

The surface tension of the Ni₃S₂-FeS-Cu₂S ternary mattes have been calculated from those of the Ni₃S₂-FeS·FeS-Cu₂S and Cu₂S-Ni₃S₂ pseudo-binary boundary systems by using geometric models (Kohler and Toop model) and a general solution model (Chou model). Taking account of the experimental accuracy of ±2.5%, the respective calculated results are in agreement with the experimental data. At the same time, surface tensions of molten Ni₃S₂-FeS-Cu₂S mattes and their pseudo-binary boundary systems are predicted based on Butler's original treatment with great attention to the model parameter β. The predicted results also agree with the experimental data. Therefore, the resulting iso-surface tension curves in molten Ni₃S₂-FeS-Cu₂S mattes at 1473K, especially calculated by using Kohler, Toop and Chou models, are generally acceptable.     

Simulation and fabrication of piezoresistive membrane type MEMS strain sensors

Two piezoresistive (n-polysilicon) strain sensors on a thin Si₃N₄/SiO₂ membrane with improved sensitivity were successfully fabricated by using MEMS technology. The primary difference between the two designs was the number of strips of the polysilicon patterns. For each design, a doped n-polysilicon sensing element was patterned over a thin 3 μm Si₃N₄/SiO₂ membrane. A 1000×1000 μm² window in the silicon wafer was etched to free the thin membrane from the silicon wafer. The intent of this design was to fabricate a flexible MEMS strain sensor similar in function to a commercial metal foil strain gage. A finite element model of this geometry indicates that strains in the membrane will be higher than strains in the surrounding silicon. The values of nominal resistance of the single strip sensor and the multi-strip sensor were 4.6 and 8.6 kΩ, respectively. To evaluate thermal stability and sensing characteristics, the temperature coefficient of resistance [TCR=(ΔR/R₀)/ΔT] and the gage factor [GF=(ΔR/R₀)/] for each design were evaluated. The sensors were heated on a hot plate to measure the TCR. The sensors were embedded in a vinyl ester epoxy plate to determine the sensor sensitivity. The TCR was 7.5×10⁻⁴ and 9.5×10⁻⁴/°C for the single strip and the multi-strip pattern sensors. The gage factor was as high as 15 (bending) and 13 (tension) for the single strip sensor, and 4 (bending) and 21 (tension) for the multi-strip sensor. The sensitivity of these MEMS sensors is much higher than the sensitivity of commercial metal foil strain gages and strain gage alloys.     

Design, construction, and application of a generic visual languagegeneration environment

The implementation of visual programming languages (VPLs) and their supporting environments is time-consuming and tedious. To ease the task, researchers have developed some high-level tools to reduce the development effort. None of these tools, however, can be easily used to create a complete visual language in a seamless way as the lex/yacc tools do for textual language constructions. This paper presents the design, construction and application of a generic visual language generation environment, called VisPro. The VisPro design model improves the conventional model-view-controller framework in that its functional modules are decoupled to allow independent development and integration. The VisPro environment consists of a set of visual programming tools. Using VisPro, the process of VPL construction can be divided into two steps: lexicon definition and grammar specification. The former step defines visual objects and a visual editor, and the latter step provides language grammars with graph rewriting rules. The compiler for the VPL is automatically created according to the grammar specification. A target VPL is generated as a programming environment which contains the compiler and the visual editor. The paper demonstrates how VisPro is used by building a simple visual language and a more complex visual modeling language for distributed programming     

遗传算法求解邮递员问题的探讨

邮递员问题是目前一个尚未完全解决的图论问题,而遗传算法则是一个比较好的全局搜索算法,本文提出了一种换方法,以此为基础,用遗传算法实现了对有向图邮递员问题的求解,较传统方法更加容易实现,在求解大规模复杂网络时,其效率更高。     

氰戊菊酯剂型加工研究进展

综述了近年来氰戊菊酯剂型加工研究进展，重点介绍了其混合制剂的发展情况。     

A Piecewise Grey System Model for Study the Effects of Anthropogenic Activities on Karst Hydrological Processes

Sustainable groundwater development must rely on a good understanding of hydrological processes, especially under effects of anthropogenic activities. This paper develops a piecewise analysis based on grey system model for study effects of anthropogenic activities on hydrological processes. The time series of precipitation and spring discharge were segmented into three time periods depending on whether variations are due to climate variation: the predevelopment stage, the transition stage, and the new equilibrium stage. Then we modeled hydrological process of the predevelopment stage and new equilibrium stage by the grey system model. By comparing the model results, we can quantify the effects of human activities on hydrological processes. We applied the model to Liulin Springs China. The results indicated that the hydraulic response time of the spring discharge to precipitation from the predevelopment stage to the new equilibrium stage, ranges from less than 1 year to up to 4 years. The results revealed that human activities slow the groundwater flow. GM (1,N) models of Liulin Springs discharge showed that the driving coefficients of precipitation to the spring discharge decreased from 0.012272 in the predevelopment stage to 0.007753 in the new equilibrium stage, which means that groundwater recharge ability has reduced about 36.82 %. Human activities in Liulin Springs have drastically changed the groundwater system. Piecewise grey system model is a robust method for hydrological process simulation.