混流泵内部流动不稳定特性的数值模拟

为了研究小流量工况下混流泵内存在的不稳定流动特性,基于大涡模拟亚格子尺度模型与滑移网格技术, 对包括进口管和出口弯管的混流泵全流场进行三维非定常湍流计算．外特性试验结果表明,在60％～85％最优工况范围内,扬程-流量特性曲线呈正斜率特性．数值模拟结果与试验结果误差控制在4％内,表明大涡模拟可以准确预估混流泵存在的扬程-流量正斜率不稳定特性．在此基础上,分析了混流泵产生正斜率不稳定特性的内流机理．分析结果表明,在小流量工况下叶轮入口切向速度呈明显的非对称性,叶轮与导叶流道内液流的失速效应使叶轮叶片表面和导叶叶片入口轮毂侧存在大尺度的旋涡结构．导叶流道内旋涡尺度较大,压力脉动沿导叶轴向呈明显的周期性波动,使旋涡区域从吸力面侧逐渐扩展到导叶流道,旋涡结构的涡核附着在压力脉动最小值的导叶吸力面中间叶高区,且涡核旋向与叶轮旋向相同．     

Production and isolation of azaspiracid-1 and -2 from Azadinium spinosum culture in pilot scale photobioreactors

Azaspiracid (AZA) poisoning has been reported following consumption of contaminated shellfish, and is of human health concern. Hence, it is important to have sustainable amounts of the causative toxins available for toxicological studies and for instrument calibration in monitoring programs, without having to rely on natural toxin events. Continuous pilot scale culturing was carried out to evaluate the feasibility of AZA production using Azadinium spinosum cultures. Algae were harvested using tangential flow filtration or continuous centrifugation. AZAs were extracted using solid phase extraction (SPE) procedures, and subsequently purified. When coupling two stirred photobioreactors in series, cell concentrations reached 190,000 and 210,000 cell · mL(-1) at steady state in bioreactors 1 and 2, respectively. The AZA cell quota decreased as the dilution rate increased from 0.15 to 0.3 day(-1), with optimum toxin production at 0.25 day(-1). After optimization, SPE procedures allowed for the recovery of 79 ± 9% of AZAs. The preparative isolation procedure previously developed for shellfish was optimized for algal extracts, such that only four steps were necessary to obtain purified AZA1 and -2. A purification efficiency of more than 70% was achieved, and isolation from 1200 L of culture yielded 9.3 mg of AZA1 and 2.2 mg of AZA2 of >95% purity. This work demonstrated the feasibility of sustainably producing AZA1 and -2 from A. spinosum cultures.     

荒漠区柽柳液流特征及其与环境因子的关系研究

干旱荒漠区植被水分传输状况决定着区域生态需水量,进而影响生态安全。植物的茎干液流量表征其蒸腾耗水量,能够准确反映单株植物的蒸腾作用和水分利用状况。本文以古尔班通古特沙漠南缘典型荒漠植被柽柳为研究对象,采用茎热平衡法,对区域典型荒漠植被柽柳茎干液流及其与环境因子的关系进行了研究,结果表明：①柽柳茎干液流日变化曲线呈多峰格型,日平均液流率为0．00399g／s,最大值为O．0135g／s。茎干液流7：00～15：00一直保持较高值（0．003g／s以上）,21：00左右液流速率降到极低值;②柽柳风速变化和茎干液流速率存在相关性,微风可加快茎干液流,强风对茎干液流有抑制作用,而冠层温度与茎干液流速率呈正相关,冠层空气湿度与茎干液流呈负相关。     

基于三维建模和数值模拟的CNG发动机进气系统分析

发动机进气系统的结构直接影响到发动机各缸的燃烧情况以及热负荷等各项性能,利用CFD技术建立三维流动模型,根据CFD计算经验将进气管内的气体流动视为三维可压缩定常流动。根据进气系统的CAD图利用GAMBIT软件建立三维模型并进行网格划分,最后用FLUENT软件进行三维流动的模拟计算,得到流场内各处流体速度的分布和变化情况,计算出各歧管出口处的流体质量流量,并分析了进气的不均匀性。     

Effects of Water Depth and Water Flow Duration on Growth and Survival of Juvenile Spotted Babylon (Babylonia areolata) Cultured in a Flow-Through System

Eight growth trials of juvenile B. areolata at different water depths (20 and 50 cm) and water flow durations (6, 12, 18, and 24 h) were conducted in a flow-through culture system over 5 months. One-way ANOVA performed on each growth data set showed that there were significant differences among water depth (WD) and water flow duration (WFD) treatments (P < 0.05). The highest weight gain (6.29 g /snail) was found in snails reared in the treatment of WD₅₀ /WFD₂₄, followed by those from WD₅₀ /WFD₁₈ (6.15 g/snail), WD₅₀/WFD₁₂ (5.90 g/snail), WD₅₀ /WFD₆ (5.83 g/snail), WD₂₀ /WFD₂₄ (5.86 g/snail), and WD₂₀ /WFD₁₈ (5.87 g /snail), while the lowest one was found in WD₂₀ /WFD₆ (5.52 g/snail) and WD₂₀ /WFD₁₂ (5.57 g/snail). The relative weight gain (RWG) and individual weight gain (IWG) of the snails showed similar trends as the weight gain. Final survival exceeded 95% for all treatments. Based on all criteria, the best growth performances of juvenile spotted babylon were found in the WD₅₀ /WFD₁₈ and WD₅₀ /WFD₂₄ treatments, followed by the treatments of WD₅₀/WFD₁₂, WD₅₀ /WFD₆, WD₂₀ /WFD₂₄, and WD₂₀ /WFD₁₈; the lowest growth was found in WD₂₀ /WFD₆ and WD₂₀ /WFD₁₂.     

新疆恰尔巴哈特桥设计流量的计算

桥梁洪水设计流量的计算在桥位设计中有非常重要的地位,为避免桥梁水毁,保证桥梁在设计标准的洪水频率下安全运营,必须在设计过程中对水文计算给予足够的认识。但由于水文系统是一个复杂不确定的系统,水文资料的获知相对有限。尤其是在新疆维吾尔族自治区,该地中低山区小河流沟渠数不胜数,且多数没有实测连续的水文记录,如何利用现有的、邻近的水文资料,推求该流域的设计流量就尤为重要。结合参加省道315公路的恰尔巴哈特桥设计工作的经验,探讨了新疆小流域桥梁洪水设计流量的确定。     

主要农作物转基因飘流频率和距离的数据调研与分析Ⅴ.油菜

转基因植物在批准商业化之前通常要求在控制条件下开展实验。我国规定转基因油菜田间试验的隔离距离为1 000 m,该距离大于世界上绝大多数国家和地区的规定。转基因油菜基因流研究的数据显示,自然条件下甘蓝型油菜品种间的天然异交率一般不超过3%,多数在1%以下,隔离距离和保护行可以显著降低异交率,隔离距离400 m处异交率低于0.01%。白菜型油菜、自交不亲和系和雄性不育系的异交率则要高得多。建议对转基因油菜的安全监管采取分类管理和阈值管理的原则,在0.1%允许阈值下,普通甘蓝型油菜的隔离距离可设为400 m,而以异花授粉为主的其他油菜（包括白菜型油菜与其他类型油菜的自交不亲和系和雄性不育系）的隔离距离可设为1 000 m。     

The role of river flow in the migration of adult Atlantic salmon,Salmo salar,through estuaries and rivers

An assumption of Atlantic salmon, Salmo salar L., management is that river flow influences their upstream migration; but the quantitative relationships between flow and movements are variable and inconsistent. A consensus has emerged that standard rules on salmon flow needs for water management across all rivers are unattainable. However, this does not preclude an underlying conceptual framework that should guide a consistent scientific basis to flow management for protecting salmon. This article examines the potential for a conceptual framework from a British Isles perspective, assuming that upstream migration is an emergent property from selection to optimise lifetime fitness. The template for this adaptation is the diversity of river types and hydro‐morphology in British rivers coupled with life‐history and migration adaptations that may be influenced by flow‐related factors. Models of adult salmon migration through estuaries and rivers are outlined that may provide a basis for developing generic guidance.     

The role of the UK conservation agencies in protecting river flows

Abstract An outline is given of the scale and nature of special wildlife designations in the UK river network, the general approach of the UK conservation agencies to their evaluation and management, and the specific way in which impacts of river flows are handled. The need for a holistic ecological and biodiversity view of water resource impacts on river systems is stressed, within which the specific needs of individual species, such as Atlantic salmon, Salmo salar L., can be framed. An approach founded on the provision of a natural flow regime within a natural physical channel not only provides the most suitable conditions for characteristic riverine wildlife to flourish but also provides the best local defence against global climate change. Arguments are made for a future focus on the generic evidence base for flow targets and its strengthening through strategic and demonstrably fit‐for‐purpose research. The practical constraints to an approach based on protection of the natural flow regime are discussed. Ultimately, transparent separation and consideration of what river ecosystems really need, and what can realistically be provided, is the key to shared ownership of the water resource dilemma.     

一种利用流式细胞术鉴定梨倍性的方法

流式细胞术鉴定植物染色体倍性的方法广泛应用于果树多倍体育种中,然而相关流式细胞术鉴定梨染色体倍性的方法还没有系统的研究。以梨树叶片为试材系统优化了各个流式细胞术关键实验节点,结果表明：实验材料选取当年春季新梢第3~5 片梨树嫩叶,尤其是大棚新梢嫩叶最好;叶片前处理时用蒸馏水、去离子水依次洗净叶片表面后,再用去离子水浸泡10 min;使用WPB解离液对梨叶片细胞核进行提取后,用500 目滤膜过滤2 次,离心1 次后用流式细胞仪进行检测可得到理想的实验结果。该方法步骤简单、结果可靠,是一种快速、高效的梨染色体倍性鉴定的方法,可广泛用于梨树多倍体鉴定。