Thermal preference and tolerance of green abalone Haliotis fulgens (Philippi, 1845) and pink abalone Haliotis corrugata (Gray, 1828)

The thermoregulatory behaviour of green abalone Haliotis fulgens and pink abalone H. corrugata was investigated. Haliotis fulgens juveniles ranging in wet weight from 3.0 to 3.3 g and from 28.7 to 30.5 mm shell length and of H. corrugata 2.0 g and 25.7 mm in shell length were exposed to 19°C for 30 days in a flow‐through water system. Temperature preference was determined in a horizontal thermal gradient and was found to be 25.4°C for green abalone and 25.0°C for pink abalone. Displacement velocity was 4.3 cm h⁻¹ for H. fulgens and 12.8 cm h⁻¹ for H. corrugata. The optimum temperature for growth calculated for both abalone species was 24.6 and 24.5°C respectively. The critical thermal maxima (CTMax) of H. fulgens and H. corrugata were determined as a measure of thermal tolerance. Abalones were subjected to increasing water temperatures at a rate of 1°C on 30 min until they detached from the substrate. The CTMax at 50% were 33.6 and 32.0°C for green and pink abalone respectively. The results are discussed in relation to site selection and commercial rearing.     

微小迷宫流道中的沙粒沉积规律

为了分析迷宫型微小流道中沙粒沉积规律,通过计算流体动力学软件FLUENT对灌水器内部流场进行了分析,研究了灌水器中沙粒运动轨迹及沉积规律。研究表明：碰撞反弹系数对沙粒沉积规律影响很大,灌水器各流道单元速度场分布相似,压力场差异较大,沙粒运动轨迹基本不受各单元压力场变化的影响;粒径是影响沙粒沉积的最主要因素,粒径越大,沙粒的沉积危险系数越大;灌水器入口压力越大,沙粒的沉积危险系数越小。对沙粒沉积规律的研究,有利于深入地了解灌水器的堵塞机理,为灌水器抗堵塞设计提供一定的依据。     

农村基础设施投资效益评价的关键指标遴选

农村基础设施对中国的农业增长、农村经济发展及脱贫意义重大。但中国目前尚没有完善相关设施的评价体系,尤其此类评价体系中的评价指标更是缺少。该研究旨在建立一套客观评价农村基础设施投资效益的关键指标体系（CAIs）。针对农村基础设施投资效益评价指标,通过对政府、高校和研究机构、咨询企业专家展开两轮问卷调查,进而采用蒙特卡罗模拟（MCS）分析问卷调查反馈的数据,并根据模拟结果运用模糊集合理论选取关键评价指标,总共选取了8个关键指标。研究表明,MCS可以有效克服数据源不足的缺陷,而模糊集合理论可以应对问卷调查中专家意见的模糊性。遴选出的8个关键指标与已有的零星研究相印证,为政府在农村基础设施投资提供依据。     

稻田水肥资源高效利用与调控模拟

水和肥是影响作物产量与生态环境的重要因素。为揭示稻田水肥利用规律,以达到稻田节水、省肥、高产、减排的目标,该文以湖北省漳河团林实验站稻田水肥耦合灌溉与控制排水试验观测数据为基础,联合运用作物生长模型ORYZA 2000和田间水文模型DRAINMOD 6.0,模拟分析不同降水、节灌、施肥、控排条件下的水稻产量与稻田排水量响应关系,得出了稻田水肥调控的临界条件,即采用稻田间歇灌溉方式,灌水定额30 mm,施氮量170 kg/hm2左右,控制排水水位20 cm时,节水12.5%～18.87%、省肥35.1%、增产11%、减排19.9%。本研究对加强农田水肥科学管理,提高水氮生产效率,防治农业面源污染,促进灌区可持续发展具有重要意义。     

Evaluating grassed waterway efficiency in southeastern Iowa using WEPP

Properly calibrated, single storm event, model simulations can be valuable quantitative tools for evaluating the effectiveness of grassed waterways (GWWs) and identifying a threshold length for an effective GWW. Current specifications for GWW lengths in Iowa are lacking. The key objective of this study is to employ the well-established Water Erosion Prediction Project model (WEPP) for determining an effective (or threshold) GWW length for reducing runoff and sediment yields under a wide range of hydrologic and management conditions in an agricultural Iowa watershed, namely Clear Creek, IA. The advantage of this physically based, distributed-parameter model is its ability to replicate processes at the hillslope scale where GWW performance is mostly evaluated. Overall, 84 WEPP runs were performed for assessing (i) the effect that GWW length has on reducing runoff and sediment yields within a representative test hillslope, and (ii) the effect of the gradient of the drainage area on GWW efficiency. Results show that the GWW efficiency for all GWW lengths is governed by hydrology, expressed as Q_peak. The results suggest that the threshold length for an effective GWW is 500 m for the hydrologic conditions in this study and for a representative drainage area of approximately 27 ha. For all storm events, a threshold drainage area gradient of approximately 3% was found above which the GWW efficiency was independent of topographic steepness. The results demonstrate similar trends to other studies although the relative increases in reduction in runoff and sediment delivery differ between sites and are very much dictated by Q_peak and hydrologic soil group. The effectiveness of models to evaluate GWW efficiency for nearly saturated conditions and shallow flows is discussed.     

深基坑土钉墙内部稳定性计算新方法——最危险滑裂面复合遗传进化 …

高层建筑深基坑土钉墙内部稳定性分析的关键是如何确定最危险滑裂面的位置并计算与相对应的安全系数，这可归结为一类非线性优化问题。为克服传统优化分析方法容易陷于局部最优解的缺点，作者利用从模拟自然进化过程的遗传进化算法和求解约束优化问题的复杂形法而发展起来的复合遗传算法来搜索最危险滑动面，提出了一种深基坑土钉墙内部稳定性分析的复合遗传进化调优算法，它是一种全局优化分析方法，且比一般的遗传算法寻优效率要高     

恒定加热量时热油管道工作特性研究

通过对热油管道工作特性的研究,发现在加热站加热量恒定时热油管道存在临界输量,当输量小于临界输量时,管道运行将进入不稳定工作区。对恒定加热量管道临界输量的影响因素进行了分析,指出总传热系数降低、加热量的增大和加热站上游来油进站温度升高都将使恒定加热量管道临界输量降低。     

淮河上游冬小麦生长关键期旱涝灾害阈值研究

利用淮河上游地区1961-2015年13个气象站逐日降水数据,计算冬小麦生长关键期(2、3、4月)1个月尺度及3个月尺度SPI值,结合冬小麦产量数据,确定生长关键期对产量灾损率影响的具体时段,在此基础上分析了降水量变化及旱涝灾害空间分布,建立了SPI值与产量灾损率之间的定量关系。结果表明,(1)生长关键期(SPI3)和4月(SPI1_4)SPI值均与产量灾损率相关性程度高,分别通过0.01和0.05显著性水平检验;2个时段降水量变化整体呈减少趋势,且旱涝灾害空间分布存在一定的差异;(2)当SPI3值和SPI1_4值分别为-2.23和-1.82时,达到决定发生旱灾时产量灾损的阈值;(3)SPI3值和SPI1_4值与产量灾损率相关系数分别为0.94和0.82,在典型涝灾年,SPI值与产量灾损率具有线性关系。     

方斑东风螺对盐度适应性的研究

通过实验生态学的方法，在温度28．2～29．7℃、pH7．6—8．3的条件下，研究了养殖方斑东风螺（Babylonia areolata）的适宜、最适生存盐度及适宜、最适生长盐度，以期为养殖生产提供科学依据。生存临界盐度界定为120h50％死亡的盐度（120hLS50），其范围为适宜生存盐度；生长临界盐度界定为增长率为最佳一组30％所对应的盐度，其范围为适宜生长盐度；把经过多重比较结果显示无显著差异的存活率或13生长量最高的几个实验组所对应的盐度范围作为最适生存或生长盐度。研究结果表明，方斑东风螺适宜生存盐度为19．18～41．39，最适生存盐度为26．0—34．4；适宜生长盐度为19．28～39．96，最适生长盐度为26．0—31．6。当盐度变化超出最适范围时，养殖方斑东风螺对低盐更为敏感。     

肉类腐败变质时菌落总数(SPC)临界值的研究

本研究各用五组猪、牛、羊肉、在常温下置放，然后比较其感官指标、微生物指标、理化指标、测定肉类腐败变质时的菌落总角定其腐败变质时的临界值，借以快速确定肉类商品的货架期是否已经结束。