Matrix Transformation in Boron Containing High-Temperature Co–Re–Cr Alloys

An addition of boron largely increases the ductility in polycrystalline high-temperature Co–Re alloys. Therefore, the effect of boron on the alloy structural characteristics is of high importance for the stability of the matrix at operational temperatures. Volume fractions of ε (hexagonal close-packed—hcp), γ (face-centered cubic—fcc) and σ (Cr₂Re₃ type) phases were measured at ambient and high temperatures (up to 1500 °C) for a boron-containing Co–17Re–23Cr alloy using neutron diffraction. The matrix phase undergoes an allotropic transformation from ε to γ structure at high temperatures, similar to pure cobalt and to the previously investigated, more complex Co–17Re–23Cr–1.2Ta–2.6C alloy. It was determined in this study that the transformation temperature depends on the boron content (0–1000 wt. ppm). Nevertheless, the transformation temperature did not change monotonically with the increase in the boron content but reached a minimum at approximately 200 ppm of boron. A probable reason is the interplay between the amount of boron in the matrix and the amount of σ phase, which binds hcp-stabilizing elements (Cr and Re). Moreover, borides were identified in alloys with high boron content.     

Deterministic safety study of advanced molten salt nuclear systems for prospective nuclear power

The inter-comparative analysis of the deterministic safety potential of innovative molten salt systems with critical and sub-critical cores is presented for both fast and thermal neutron spectra. The analysis includes two aspects: the choice of an initial level of sub-criticality and the study of multiple unprotected transients which have been simulated on the basis of one-point kinetics and two-point thermo-hydraulic schemes considering realistic feedback effects. Our preliminary results show that even small levels of sub-criticality (2–3 dollars) of cores can improve their safety characteristics significantly.     

用动态规划神经网络模型研究多水库系统的水量分配(下)

为了分析多水库系统中两座水库之间灌溉用水的分配问题，建立了基到动态规划的神经网络模型。为了研究从一座上游水库取水在下游两座之库之间进行水量分配的问题，提出了3个状态变量和4个决策变量的改进的动态规划算法。采用神经网络模型，用3个状态变量动态规划算法得出调度原则，就所研究的多水库系统实例来说，新的动态规划神经网络模型的性能很好，将该模型的性能与临时凑合的标准调度原则和以前推荐使用的约束动态规划神经网络模型进行了比较。     

伊朗卡尔黑水利枢纽

伊朗卡尔黑多目标水利枢纽，首台机组于2002年9月投运。介绍了工程历史，并从导流系统遂洪道、渗漏控制和惟幕灌浆等方面介绍了工程的技术要求。     

河床变形对水电站动力设备工作条件的影响

水电站运行过程中河床变形会使河底高程逐渐降低。从而导致下游流量特性曲线下降以及水电站水头增大。水头增大使水电站气蚀特性发生变化，导致动力设备的正常工作条件受到破坏。并对其运行安全性和效率造成不利影响。以卡马河的沃特金水电站为例，阐述了河床变形对水电站动力设备工作条件的影响。     

关于21世纪的综合水管理(下)

必须利用水库多蓄水，另外再通过回灌把水蓄在含水层中供缺水时使用。城市废水也是一种重要水资源，但．必须加强规划和管理以防止造成对健康的负面影响，用于灌溉时则应防止污染地下水。长期以来地下水不仅受到非点源污染，还因对其开采超过回灌导致含水层减少。在灌区，地下水位必须通过排水或抽水系统加以控制，以防止水涝和土壤盐碱化。含盐的水排出后必须妥善处置。缺水的国家可以通过从其他国家进口大部分粮食和电力来节水，这往往比开发本国的水资源划算。本地水源就可用于更具社会、生态或经济回报的用途．或以备不时之需。     

Characteristics of planar diodes based on heavily doped GaAs/AlAs superlattices in the terahertz frequency region

Characteristics of ohmic InGaAs contacts in planar diodes based on semiconductor superlattices with a small-area active region (1–10 μm²) are studied. The diodes were formed on the basis of short (18 or 30 periods) heavily doped (10¹⁸ cm⁻³) GaAs/AlAs superlattices with a miniband width of 24.4 meV. The reduced resistance of the ohmic contact was equal to 2×10⁻⁷ Ω cm² at room temperature. It is shown that the properties of fabricated planar diodes make it possible to use these diodes later on in semiconductor devices that operate in the terahertz frequency region in a wide temperature range (4–300 K). __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 9, 2004, pp. 1141–1146. Original Russian Text Copyright ? 2004 by Pavel’ev, Demarina, Koshurinov, Vasil’ev, Semenova, Zhukov, Ustinov.     

An invitation to fiberwise topology: The general framework for multicolored images in pattern recognition and some of its artificial intelligence aspects

We present a short and rather informal account concerning a problem we posed in earlier work, recall our conjecture at the time, and report on our answer today. Specifically, our purpose is to draw attention to fiberwise topology as a possible mathematical tool for formalizing multi-colored images and other complex signals met in pattern recognition (P.R.), to provide some information concerning the mathematical background of the fiber topological machinery, and indicate how to use it. For a detailed technical study as well as a tentative hierarchical classification of topological images in growing order of complexity and the corresponding topological processing methods, the readers may consult Pavel [5]. The paper ends by mentioning some artificial intelligence (A.I.) aspects of the fiberwise imagery.