Optimization of the power ascension path for a boiling water reactor using genetic algorithms

To ensure the core status can meet the requirements of thermal limits, stability and other constraints during the power ascension process of a nuclear power plant, operators usually gradually increase power based on onsite measurements and experience. To reduce the operator’s burden, this research develops a method to find an optimal power ascension path that can be followed by operators. The power ascension path is formulated as a multiobjective optimization problem with the following constraints: power ascension time, thermal limits, core stability and maximum rod line. A genetic algorithm is adopted to obtain the optimal power ascension path. The results show that using our approach full power can be achieved quickly, while maintaining reasonable margins of thermal limit and stability, in addition to satisfying maximum rod line criteria.     

Anomalous variations of OFF-State leakage current in poly-Si TFTunder static stress

Studies the anomalous variations of the OFF-state leakage current (I_OFF) in n-channel poly-Si thin-film transistors (TFTs) under static stress. The dominant mechanisms for the anomalous I_OFF can be attributed to (1) I_OFF increases due to channel hot electrons trapping at the gate oxide/channel interface and silicon grain boundaries and (2) I_OFF decreases due to hot holes accumulated/trapped near the channel/bottom oxide interface near the source region. Under the stress of high drain bias, serious impact ionization effect will occur to generate hot electrons and hot holes near the drain region. Some of holes will be injected into the gate oxide due to the vertical field (~(V_Gstress V_Dstress)/T _OX) near the drain and the others will be migrated from drain to source along the channel due to lateral electric field (~V_Dstress/L_CH)     

Expert system for dispatch control in restoration of ehv power system after complete blackout

Present-day power systems operate with high reliability, and it is rare that a blackout will extend over an entire system swiftly and securely. This paper considers automatic power supply to loads after a complete blackout of a system. First, taking into account characteristics of generators, loads, and initial power sources, a method is proposed of allocating several generators to each load in parallel to the system and supplying power to the load sequentially. Second, to remove the imbalance between supply and demand of power, a method is proposed of adjusting the amount of supply and generation according to a present imbalance and the sum of past ones. Third, to automatically issue orders for start-up, parallel, follow-up, stand-by, and stoppage of generators, several rules for each power station are set and an expert system is made based on them. Finally, the expert system is applied to a model power system, and it is verified that it can restore loads without any trouble for a complete blackout which occur at any time of a day and in any restoration pattern.     

Study on phase behavior–impact strength relationship of unsaturated polyester/polyurethane hybrid polymer network

The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties.     

A Survey on the Numerics and Computations for the Landau-Lifshitz Equation of Micromagnetism

The Landau-Lifshitz (LL)equation of micromagnetism governs rich variety of the evolution of magnetization patterns in ferromagnetic media. This is due to the complexity of physical quantities appearing in the LL equation. This complexity causes also an interesting mathematical properties of the LL equation: nonlocal character for some quantities,nonconvex side-constraints, strongly nonlinear terms. These effects influence also the numerical approximations. In this work, recent developments on the approximation of weak solutions, together with the overview of well-known methods for strong solutions,are addressed. Author is supported by the Fund for Scientific Research - Flanders FWO (Belgium).     

消失的房子

建筑人的家，却不谈设计，不谈美学。张基义叨叨絮絮讲的是，在城市里他看着星星入睡，或就着那亮眼的月光，坐在院子里拿着Notebook打起文章，直到凌晨两点…… 迷人的叙述里，如何让房子消失，是拥有大自然的秘诀。[编者按]     

锝化学研究 Ⅸ.脑显像剂Tc~(Ⅴ)ON_2S_2类配合物结构稳定性和价态的研究

采用改进的ＣＮＤＯ／２法模拟了ＢＡＴ类脑显像剂Ｔｃ（Ⅴ）Ｏ配合物价态的转换过程，发现Ｎ２Ｓ２类配体与Ｔｃ（Ⅴ）Ｏ核配位时，可能存在配位平衡离子Ｘ。在溶液中由于Ｘ离子的优先解络，瞬间存在＋１价对称性９９Ｔｃｍ配合物，并且，它又自动向相对稳定的０价不对称性９９Ｔｃｍ配合物转换，在动态转换过程中，将导致仅有一个配位Ｎ原子保留一个质子，这与实验结果一致。采用键级削弱百分数概念，表征配位过程的二个配位Ｎ原子上保留程度，解释了Ｔｃ（Ⅴ）Ｏ核、Ｔｃ（Ⅴ）≡Ｎ核Ｎ２Ｓ２类配合物两个Ｎ－Ｈ键上质子保留程度不同的原因，为今后设计不同价态锝配合物结构提供理论依据。     

Variations of physical properties in pellets containing alumina/carbon powder mixtures during reduction and nitridation

Surface area and porosity of pellets containing alumina/carbon powder mixtures during reduction and nitridation were determined. The experimental results indicated that surface area and porosity of solid samples were decreased by increasing the reaction temperature, grain size, forming pressure and the amount of catalyst. Increasing the molar ratio of C/Al₂O₃ and gas flow rate could decrease the surface area and increase the porosity of the solid sample.