Robustness of strong stability of discrete semigroups

In this paper we study the robustness of strong stability of a discrete semigroup on a Hilbert space under bounded perturbations. As the main result we present classes of perturbations preserving the strong stability of the semigroup.     

P-反演半群上的部分核正规系

设S(P)为P-反演半群.首先介绍了S(P)上的正则P-同余和部分核正规系的概念.然后借助于部分核正规系给出了S(P)上正则P-同余的一个抽象刻画,给出了互不相交的S(P)的子集B={Bi∶i∈I}是以P∩Bi为C-集的S(P)的部分核正规系的充分必要条件.由此推出了P-正则半群上的每个P-同余完全是由其包含幂等元的部分核正规系所决定的.     

Accelerated development of CuSbS2 thin film photovoltaic device prototypes

Development of alternative thin film photovoltaic technologies is an important research topic because of the potential of low‐cost, high‐efficiency solar cells to produce terawatt levels of clean power. However, this development of unexplored yet promising absorbers can be hindered by complications that arise during solar cell fabrication. Here, a high‐throughput combinatorial method is applied to accelerate development of photovoltaic devices, in this case, using the novel CuSbS₂ absorber via a newly developed three‐stage self‐regulated growth process to control absorber purity and orientation. Photovoltaic performance of the absorber, using the typical substrate CuIn_xGa_{1 − x}Se₂ (CIGS) device architecture, is explored as a function of absorber quality and thickness using a variety of back contacts. This study yields CuSbS₂ device prototypes with ~1% conversion efficiency, suggesting that the optimal CuSbS₂ device fabrication parameters and contact selection criteria are quite different than for CIGS, despite the similarity of these two absorbers. The CuSbS₂ device efficiency is at present limited by low short‐circuit current because of bulk recombination related to defects, and a small open‐circuit voltage because of a theoretically predicted cliff‐type conduction band offset between CuSbS₂ and CdS. Overall, these results illustrate both the potential and limits of combinatorial methods to accelerate the development of thin film photovoltaic devices using novel absorbers. Copyright © 2016 John Wiley & Sons, Ltd.     

核电主管道锻件心部裂纹缺陷性质分析

核电主管道锻造毛坯在中心棒套料加工过程中发现中心棒的一段出现裂纹,并伴有大量碎块。对中心棒及碎块金属进行化学成分分析、低倍、高倍检验和能谱分析,并采用Jmatpro对316LN钢平衡析出相进行了计算。结果表明,裂纹区域存在的大量条状和粒状α-Cr析出相导致局部塑性降低,变形不协调,在锻造过程中形成了裂纹。     

Photoactive Earth‐Abundant Iron Pyrite Catalysts for Electrocatalytic Nitrogen Reduction Reaction

The generation of ammonia, hydrogen production, and nitrogen purification are considered as energy intensive processes accompanied with large amounts of CO₂ emission. An electrochemical method assisted by photoenergy is widely utilized for the chemical energy conversion. In this work, earth‐abundant iron pyrite (FeS₂) nanocrystals grown on carbon fiber paper (FeS₂/CFP) are found to be an electrochemical and photoactive catalyst for nitrogen reduction reaction under ambient temperature and pressure. The electrochemical results reveal that FeS₂/CFP achieves a high Faradaic efficiency (FE) of ≈14.14% and NH₃ yield rate of ≈0.096 µg min^?1 at ?0.6 V versus RHE electrode in 0.25 m LiClO₄. During the electrochemical catalytic reaction, the crystal structure of FeS₂/CFP remains in the cubic pyrite phase, as analyzed by in situ X‐ray diffraction measurements. With near‐infrared laser irradiation (808 nm), the NH₃ yield rate of the FeS₂/CFP catalyst can be slightly improved to 0.1 µg min^?1 with high FE of 14.57%. Furthermore, density functional theory calculations demonstrate that the N₂ molecule has strong chemical adsorption energy on the iron atom of FeS₂. Overall, iron pyrite‐based materials have proven to be a potential electrocatalyst with photoactive behavior for ammonia production in practical applications.     

2014年新安江水库特丰来水预测

新安江水库来水年际变化大，水库特丰来水年预报对水库发电、防洪等综合利用功能的发挥具有重要意义。文中以新安江特丰来水年为研究对象，基于可公度预测理论，应用三元、五元预测模型进行计算分析。预测结果显示2014年新安江水库来水特丰，有发生类似于1983年特丰来水的可能;同时预报新安江水库2012年为丰水年。     

Approximations in a semigroup by using a neighbourhood system

Let S be a semigroup. We consider the relation γ and its transitive closure γ*. The relation γ is the smallest equivalence relation on S so that S/γ* is a commutative semigroup. Based on the relation γ, we define a neighbourhood system for each element of S, and we present a general framework of the study of approximations in semigroups. The connections between semigroups and operators are examined.     

富水风化花岗岩地层工程特性试验研究

以云南凯腾锡矿斜井施工工程为例,对富水风化花岗岩基本物理力学指标和水稳定性能进行了试验研究,并对试验结果数据进行了分析;总结了富水风化类岩体施工特性,为在该类岩层进行地下工程开挖和支护等提供了科学的依据.