液下泵内部非定常流动及噪声特性

为研究液下泵内部流动的非定常特性及噪声规律,通过采用计算流体动力学软件ANSYS CFX15.0与LMS Virtual.lab声学仿真软件相结合的一种间接混合计算方法,对液下泵内部流场及其声场进行求解.在该计算方法中,对流场进行求解得到监测点的非定常压力脉动,从而获得非稳态的压力脉动频域特性规律;基于声学边界元法,对液下泵蜗壳偶极子内场噪声和叶片偶极子内场噪声进行求解,获得了边界元表面的声压级分布以及典型场点的声压频率曲线.计算结果表明:叶片扫掠过程中与蜗壳隔舌的相互作用产生较大的压力脉动,隔舌附近的噪声是流动噪声的主要噪声源;声压级在叶片通过频率及其谐频时达到极大值,随频率的增大,声压级极大值都呈现衰减状态.研究结果可为液下泵的后续降噪分析提供一定的理论基础.     

选举观察的制度引入与基层选举监督的创新路径——基于村委会选举观察员制度运行的分析

国内村委会选举观察员制度运行的成效和问题为选举观察制度的普遍引入提供了发展方向和问题警示。总结国内村委会选举观察员制度运行的得失,认为当今我国基层民主监督在理论与实践上的双重弱化状态和地方政治发展的实际需要是选举观察制度引入的基本条件,公众和媒体的参与、专家学者的推动等多重社会力量是促使选举观察制度运行的动力。选举观察制度的法制建设、政府部门的相对淡出、民间观察的介入与激励是选举观察制度完善与基层选举监督创新的基本路径。     

四明湖水库浮游生物现状调查及评价

2006-2007年分4次对余姚四明湖水库水质理化指标、浮游生物群落结构进行了调查,并进行了多样性指数分析及渔产潜力估算。结果表明,四明湖水库浮游植物种类共计8门、47种（属）,其中以绿藻为最优势类群,占总密度的36.2%;浮游动物共计3大类、30种,其中原生动占40%;浮游植物年均生物量为10.20mg/L,浮游动物年均生物量2.36mg/L。从水体理化指标数据来看,四明湖水库水质属于II～IV类;从浮游植物群落结构和多样性指数分析结果来看,水库属于富营养水平;根据相关公式估算四明湖水库的鱼产潜力为20     

我国农村居民收入水平与幸福感关系研究综述

通过对国内外涉及收入水平与幸福感关系的研究进行元分析,研究了收入水平与幸福感间的关系。结果表明,收入水平和幸福感之间的关系呈类似于倒＂U＂型曲线,且可以从适应、社会比较和心理预期3方面进行解释。最后,就如何在提高农村居民收入水平的的同时能提高我国农村居民的幸福感提出相应的政策性建议：缩小城乡居民收入分配差距;淡化人们对金钱和物质地位的竞争;完善农村社会保障体系;努力创造农村居民各尽其能的条件。     

努力提高农科院所党的建设科学化水平

该文结合中国农科院及其所属研究所党建工作的情况,按照提高党的建设科学化水平的新要求,以科学发展观为指导,深刻理解和正确把握党的建设的科学化内涵,进一步深化对党的建设和执政规律的认识。此外,该文联系实际,分析农科院所党建工作的新特点,找准党建工作着力点,坚持以人为本,加强组织建设,深化创先争优,构建和谐院所,充分发挥党组织的政治核心作用等方面提高党建工作的科学化水平。     

Incubation success and habitat selection of shore‐spawning kokanee Oncorhynchus nerka: effects of water‐level regulation and habitat characteristics

Changes to water‐level regimes have been known to restructure fish assemblages and interfere with the population dynamics of both littoral and pelagic species. The effect of altered water‐level regimes on shore‐spawning kokanee Oncorhynchus nerka incubation success was evaluated using a comprehensive in situ study in Lake Pend Oreille, ID, USA. Survival was not related to substrate size composition or depth, indicating that shore‐spawning kokanee do not currently receive a substrate‐mediated survival benefit from higher winter water levels. Substrate composition also did not differ among isobaths in the nearshore area. On average, the odds of an egg surviving to the preemergent stage were more than three times greater for sites in downwelling areas than those lacking downwelling. This study revealed that shoreline spawning habitat is not as limited as previously thought. Downwelling areas appear to contribute substantially to shore‐spawning kokanee recruitment. This research illustrates the value of rigorous in situ studies both for testing potential mechanisms underlying population trends and providing insight into spawning habitat selection.     

黑龙江省农村居民消费水平与消费结构分析

为深入了解黑龙江农村居民消费率持续走低的原因,挖掘农村居民消费潜力,基于黑龙江2000—2012年时间序列数据,运用统计分析方法,对黑龙江农村居民的消费水平、消费结构及其变化趋势进行分析。结果表明:城乡居民收入和消费差距均很大,农村居民内部收入差距较大,但消费差距不大,虽然消费倾向高,但购买力较弱,仍以生存型消费为主,消费受政策影响明显。最后结合黑龙江的实际情况提出了积极深化和扩展各种惠农、利农政策和拓宽农村居民的收入渠道等建议。     

东海和黄海南部七星底灯鱼摄食习性的研究

根据2008年5月至2009年2月东海和黄海南部4个航次大面调查所获得的七星底灯鱼(Benthosema pterotum)胃含物样本,对其食物组成、摄食强度、食物多样性程度及营养级进行了研究.结果表明,东海和黄海南部七星底灯鱼属浮游动物食性,桡足类是其最主要的食物类群,其％ IRI值、质量百分比和个数百分比分别为75...     

供氮水平对田间桑树叶片产量及其生理特性的影响

为了探寻龙桑一号的适宜施氮量,从而指导桑农科学施用氮肥,以桑树品种龙桑一号为试验材料,在大田条件下研究了不同供氮(纯氮)水平(0、48.3、96.6、144.9、193.2和241.5kg.hm-2)对桑树叶片产量及其生理特性的影响情况。结果表明:当施氮量为0～193.2kg.hm-2时,桑树单株枝条数、单枝叶片数、单叶面积、单叶质量和单株产叶量均随供氮水平的增加而增加,而当施氮量达到241.5kg.hm-2时,桑树单叶面积、叶片质量和单株产叶量反而有所降低;施氮量在0～144.9kg.hm-2范围内,桑树叶片中的全氮(N)和全磷(P)含量均随施氮量的增加而提高,而当施氮量超过144.9kg.hm-2时,叶片中的全氮和全磷含量随着施氮量的增加反而有所降低,这说明施氮量过高反而降低了桑树对N和P的吸收;随着供氮水平的增加,桑树叶片中的叶绿素含量、可溶性蛋白和可溶性糖含量均随施氮量的增加而增加。从氮肥对桑树产叶量及其生理特性的影响情况来看,桑树品种龙桑一号田间的最佳施氮量为144.9～193.2kg.hm-2。     

Low levels of Aflatoxin B1 could cause mortalities in juvenile hybrid sturgeon,Acipenser ruthenus ♂×A. baeri♀

Toxicity of aflatoxin B₁ (AFB₁) was investigated in juvenile hybrid sturgeon Acipenser ruthenus ♂ × A. baeri♀, an important coldwater finfish farmed in China and other countries. Seven experimental diets (Diet A–G) containing different levels of AFB₁ (0, 1, 5, 10, 20, 40 and 80 μg kg^?1 diet) were fed to juvenile sturgeon weighing 10.53 ± 0.17 g kg^?1 to determine its effect on survival, growth, feed consumption, hematocrit, liver histology as well as muscular and hepatic toxin accumulation. The experiment lasted for 35 days and was conducted in two periods of 25 and 10 days each. No external changes or unusual behaviour was observed in the fish fed diets with AFB₁. Mortality was observed in fish fed with highest levels of AFB₁ (80 μg kg^?1– Diet G) from day 12 onwards. After 25 days, fish fed the diet of 80 μg AFB₁ kg^?1 showed significant lower survival (50 ± 5.77%) followed by those fed 40 μg AFB₁ kg^?1 diet (80 ± 5.77%) and 20 μg AFB₁ kg^?1 diet (86.66 ± 3.33%). No significant difference was observed in specific growth rate (SGR) or hepatosomatic index (HSI) between groups. Hematocrit was significantly higher in the fish fed the diet of highest AFB₁. The fish were weighed at day 25 in some treatments (Diets F and G) because of high mortality. However, feeding was continued for another 10 days to observe mortality or behavioural changes if any in the other groups. After 35 days, survival in the fish fed Diet F (40 μg AFB₁ kg^?1) was 40% and those fed Diet E (20 μg AFB₁ kg^?1) was 36.2%. Significant histopathological changes including nuclear hypertrophy, hyperchromasia, extensive biliary hyperplasia, focal hepatocyte necrosis and presence of inflammatory cells were observed in the liver of fish fed high levels of aflatoxin (40 and 80 μg kg^?1). AFB₁ accumulation in fish muscle and liver increased with increased dietary AFB₁ levels. It could be confirmed that 10 μg AFB₁ kg^?1 diet was the maximum allowable level in hybrid sturgeon diet.