回龙阁水库大坝除险加固方案浅析

本文针对当前国内病险水库大坝存在的主要问题结合湖北省回龙阁水库这一典型工程,提出了一套技术可行、经济适用的加处理设计方案,为今后类似工程进行除险加固建设提供了重要的参考。     

化工过程非方瘦系统的串级控制系统结构设计

化工过程一般为多变量系统，其中输出变量个数多于输入变量个数的非方多变量系统称为瘦系统，现有的非方系统控制结构设计一般采用方形化处理方法，只能形成一个输入变量与一个输出变量配对的单回路控制，要么作为工艺控制指标的重要变量不能成为被控变量，要么次要变量未纳入反馈控制，无法满足控制要求。本文介绍了非方系统的平均频域相对增益阵，对瘦系统进行了变量配对分析，提出了一种瘦系统串级控制系统结构设计方法。这种方法在不添加输入变量的同时有效利用了所有的输出变量反馈，使系统反馈信息更完备，构造了重要变量与次要变量结合的串级控制系统。最后通过实例分析说明了瘦系统的串级控制系统结构设计方法不仅能够得到合理的变量配对，而且系统控制性能良好，尤其在进行干扰抑制的过程中体现出了快速性和高效性。     

新时代长江鱼类多样性保护的思考

长江是我国第一大河流,是世界生物多样性的热点区域,也是我国鱼类多样性最高的河流之一。在介绍长江鱼类主要生态习性生境条件的基础上,分析了导致鱼类多样性下降的主要因素——生境丧失和过度捕捞,并简要总结了目前已采取的保护措施及存在的问题,提出了关于新时期长江鱼类多样性保护的思考与建议:①建立以流域管理机构牵头,相关部门和地方共同组建流域生态保护机制;②有计划开展支流及通江湖泊的生态恢复,使支流的小水电逐步退出,使原本的通江湖泊恢复自然江湖关系;③提高民众环保意识,积极建立全流域禁捕机制和休闲垂钓机制,并让垂钓者成为渔政的管理者和监督者。     

The effects of run‐of‐river dam spill on Columbia River microplankton

Dams, increasingly common in riverine systems worldwide, are particularly prevalent on the Columbia River (CR) in the United States. Hydroelectric projects, including both storage and run‐of‐river (i.e., minimal storage) structures, on the mainstem CR highly manage water flow, often by releasing water over (rather than through) dams as “spill.” To test the effects of run‐of‐river dam spill on microplankton abundance and composition, we sampled above and below two dams in the lower CR before and during spill conditions in spring 2016 and during and after spill conditions in late summer 2007. We tested the effects of location (i.e., above vs. below dams), spill condition (i.e., before, during, and after spill), and their interaction on microplankton abundance. Generally, diatoms were most abundant during springtime, whereas cyanobacteria were most abundant in late summer. Most taxa were not significantly different in abundance above and below dams, regardless of spill status; although cyanobacteria abundance was marginally higher below dams in summer 2007 (p = .04). Abundances of all taxa were significantly different between pre‐spill and spill periods in spring 2016, whereas only diatom and flagellate abundances were significantly different between spill and post‐spill periods in summer 2007. We conclude that spill conditions may influence microplankton abundance, but are not likely to affect microplankton communities on either side of run‐of‐river dams on the CR. This is important information for dam managers concerned about ecosystem impacts of spill.     

Confined Transformation of UiO‐66 Nanocrystals to Yttria‐Stabilized Zirconia with Hierarchical Pore Structures for Catalytic Applications

Solid acids as a substitution for hazardous liquid acids (e.g., HF and H₂SO₄) can promote many important reactions in the industry, such as carbon cracking, to proceed in a more sustainable way. Starting from a zirconium‐based metal‐organic framework (UiO‐66 nanocrystals), herein a transformative method is reported to prepare micro/mesoporous yttria‐stabilized zirconia (YSZ) encapsulated inside a mesoporous silica shell. It is then further demonstrated that the resultant reactor‐like catalysts can be used for a wide range of catalytic reactions. The acidity of the YSZ phase is found with rich accessible Lewis acid and Brønsted acid sites and they display superior performances for esterification (acetic acid and ethanol) and Friedel‐Crafts alkylation (benzylation of toluene). After being loaded with different noble metals, furthermore, hydrogenation of CO₂ and a one‐pot cascade reaction (nitrobenzene and benzaldehyde to N‐benzylaniline) are used as model reactions to prove the versatility and stability of catalysts. Based on the findings of this work, it is believed that this class of reactor‐like catalysts can meet future challenges in the development of new catalyst technology for greener heterogeneous catalysis.     

Effects of airfoil-probe tubes on the flow field of a compressor cascade

To explore the effects of airfoil-probe tubes and its installment position on the flow field of the compressor cascade,and find out the mechanism that how the airfoil-probes affect the aerodynamic characteristics of the compressor cascade,this paper performed both numerical and experimental works on the same compressor cascade.The experiment mainly focused on the cases of low Mach number (Ma =0.1),and cases with different Mach numbers (0.1,0.3,0.7) and different incidence angles (-5,0,5) are investigated by the numerical method.The case without the airfoil-probe tube was referenced as the baseline,and other three cases with the airfoil-probe tubes installed in different chordwis positions (30％,50％,70％ of the chord length) were studied.The diameter of the airfoil-probe tube is 3ram,which is configured as 300％ amplification of some particular airfoil-probe according to the geometrical similarity principle.The results show that the airfoil-probe tubes have a negative influence on the flow capacity of the cascade at all investigation points.The separations and the large scale streamwise vortices that induced by the airfoil-probe tube on the pressure side cause most the losses at the high Mach number.The influence of the airfoil-probe tube on the flow field in the vicinity of the pressure side surface is local separation at the low Mach number.The airfoil-probe tubes also have a clearly effect on the leakage flow.It decreases the mass flow of the leakage flow and weakens the intensity of the leakage vortex,but enlarges the influence area.The total pressure loss of the case that the tube is installed at the half chordwise position is generally lower than other cases especially at the high Mach number,it can even decrease the losses compared with the basic case.     

Long-term performance and binder chemical structure evolution of elastomeric bituminous geomembranes

This paper presents the results of uniaxial tensile tests, flow-rate measurements, and size-exclusion chromatography (SEC), which are used to evaluate the ageing of elastomeric bituminous geomembranes (BGMs) that were installed 6, 10, 15, 20, and 30 years ago in ponds at two different sites in France. SEC was used to detect oxidation and the absence of polymer in the bitumen at the surface of the 20- and 30-year-old BGMs. The results indicate that, for BGMs exposed less than 20 years, there was no oxidation or degradation of the polymer at the core. However, the elastomeric polymer was altered at the core of the 30-year-old BGM, resulting in an embrittlement of the bitumen, but this did not affect the mechanical properties of the glass veil and nonwoven polyester geotextile in the BGM core. Lastly, the flow rates through the BGM measured according to EN 14150 are still below 10^?6 m³ m^?2 d^?1, which indicates that the elastomeric bituminous GM is still watertight after 30 years of exposure.     

老井复查评价技术在浅层油藏中的研究与应用

本文以靖安地区浅层老井为例,利用钻井、录井、测井、取心等资料,结合现代测井解释评价技术,对受当时技术条件限制被误判的储层进行再分析研究。制定可行的复查评价标准与流程,确定出油下限,优选补孔潜力井,并结合精细地质研究成果筛选建产目标区,达到挖潜增效和滚动增储的双重目的。对老区日后寻找新储量进行勘探开发具有十分重要的意义。