应用于鱼道设计的新疆木扎提河斑重唇鱼的游泳能力测试

为了探究斑重唇鱼的游泳能力,给过鱼设施设计和鱼类游泳行为学研究提供基础参数,本研究以木扎提河野生斑重唇鱼(全长TL=12～16 cm)为研究对象,测定了其在(16.6±1.6)℃水温下的感应流速、临界游泳速度、爆发游泳速度及持续与耐久游泳能力。结果显示,斑重唇鱼感应流速为(0.18±0.02)m/s,相对感应流速为(1.40±0.23) BL/s (BL为体长);临界游泳速度为(1.02±0.15) m/s,相对临界游泳速度为(8.58±1.65) BL/s;爆发游泳速度为(1.39±0.17) m/s,相对爆发游泳速度为(10.92±1.86) BL/s;最大持续游泳速度为0.87 m/s,最大耐久游泳速度为1.37 m/s,与平均爆发游泳速度相近。其持续游泳时间与流速呈负相关(l g T=?5:136X+8:504)。当以斑重唇鱼为主要过鱼对象时,建议为吸引鱼类进入鱼道,进口流速设计为1.02～1.39 m/s,休息池主流设计为0.20～1.02 m/s,鱼道竖缝处流速宜低于0.85 m/s。鱼道长度为1 000 m时,鱼道内平均水流速度应低于0.78m/s。本研究结果可为新疆木扎...     

Harmonic radar: efficacy at detecting and recovering insects on agricultural host plants

BACKGROUND: In pest management research, harmonic radar systems have been largely used to study insect movement across open or vegetation‐poor areas because the microwave signal is attenuated by the high water content of vegetation. This study evaluated whether the efficacy of this technology is sufficient to track insects in vegetative landscapes. RESULTS: Field efficacy data were collected using portable harmonic microwave radar and electronic dipole tags mounted on adults of three economically important pests: Leptinotarsa decemlineata (Say), Diabrotica virginifera virginifera (LeComte) and Conotrachelus nenuphar Herbst. Detection and recovery of tagged Colorado potato beetles, plum curculios and western corn rootworms was high within and among potato plants, moderate within apple trees and high within, but not between, corn plants respectively. The efficacy of the radar depends on the ability of the operator to move around the host, scanning for a signal ‘sightline’ with the tagged insect among plant structures. CONCLUSION: The detection rate of tagged insects by harmonic radar systems is high enough to track the walking path of pests through low row crops such as potato, tall row crops such as corn or tall but well‐separated trees of orchard‐type crops by adapting the scanning procedure to the vegetative architecture. Copyright © 2010 Crown in the right of Canada. Published by JohnWiley & Sons, Ltd     

六盘山北侧生长季内华北落叶松树干液流速率研究

2006年5～10月在宁夏六盘山北侧叠叠沟林场,运用德国Ecomatik公司生产的SF-L树干液流仪研究了9株华北落叶松的树干液流变化过程及其对环境因子(气象条件、土壤水分)的响应.结果表明:华北落叶松的树干液流昼夜变化明显,呈不太典型双峰型曲线,晴天变化幅度大(0.087～0.348cm/min),阴天变化幅度小(0.087～0.281cm/min).树干液流速率在生长季内呈现逐渐降低的趋势.对环境因子影响树干液流速率的偏相关分析表明:日液流速率(SFV)与太阳辐射(ESR)、土壤水分(Ps)各影响因子均存在显著正相关,而与温度因子(Tamean)的相关系数较低.经回归分析,建立了日液流速率与各环境因子的线性回归模型:SFV=0.106 0.000141Ps 0.00214ESR 0.00218Tamcan-00043P(R=0.883).     

用于梯形渠道的仿翼形便携式量水槽水力性能

机翼形量水设施水力条件优、量水精度高,但翼形曲线的复杂性制约其推广,为此,该研究基于结构简单的仿翼形便携式量水槽,探究其在末级梯形渠道的适用性。模型试验设计5组收缩比、7组流量进行水力性能试验,在此基础上,基于FLOW-3D软件对比分析仿翼形与机翼形量水槽水力性能的差异,深入研究不同收缩比对仿翼形量水槽水力性能的影响。研究结果表明：数值模拟与试验结果的水深数据吻合,误差小于4.91%,数值模拟的方法准确可靠;简化后未改变机翼形过流顺畅、雍水高度小等特点;所有工况上游佛汝德数均小于0.5,雍水高度小于7.6 cm,满足测流精度和渠道安全的要求,收缩比在0.60~0.64范围时,量水槽水力性能最优;基于能量方程及临界流原理建立的流量公式精度较高,平均测流误差为2.75%。该研究表明仿翼形保持了原机翼形良好的水力性能,测流精度高且曲线形式简单,便于推广,对于促进灌区末级梯形渠道便携式量水槽的推广具有实用价值。     

U形渠道圆头量水柱测流影响因素试验及模拟

为研究U形渠道圆头量水柱的测流规律及影响因素,基于绕流理论和RNG k-?湍流模型,对18种体型圆头量水柱5种工况下的水力性能进行全流场数值计算,获得了时均流场、断面流速分布及柱后水流流态,并与实测值进行对比。同时,通过模型试验与数值仿真研究了V形尾翼对测流的影响。结果表明：水力参数的实测值与模拟值具有较好的一致性,渠道底坡为1/1 000,流量为45.01 L/s,收缩比及长宽比分别为0.50和2时,驻点处横断面最大流速模拟值与实测值相对误差为1.51%,水深15 cm位置剖面最大流速模拟值与实测值相对误差为0.45%。适宜长宽比的V形尾翼可以有效改善过槽水流：当收缩比为0.50～0.75时,建议长宽比为3/2～2;当收缩比＜0.50时,长宽比应相应增大,但不宜＞5/2。通过回归分析得到的圆头量水柱流量计算公式,在收缩比为0.63时最大测流误差为4.95%,平均误差仅为0.10%,该研究为圆头量水柱在中国北方灌区末级渠系的进一步应用提供参考。     

从儒教祭祀乐章看古代诗歌的作用

自汉至清,历代封建王朝不仅继承了原始宗教教义,而且也继承了以诗事神的古老传统。他们信奉"感天地,动鬼神,莫近乎诗"的古训,坚持"放郑近雅",以《诗经》雅颂为典范,大力创制与使用儒教祭祀乐章,旨在借助诗歌"感鬼神而通教化"的作用,为国家统治服务。在儒者看来,诗歌的主要作用是祀奉神祗,教化民众。认为祭祀诗歌是中国古代最重要的诗歌,也是最有价值的文学作品。     

Skating on thin ice: Identifying the need for species‐specific data and defined migration ecology of Rajidae spp.

Skates (class Chondrichthyes; subclass Elasmobranchii; order Rajiformes; family Rajidae) comprise one quarter of extant chondrichthyans, yet have received little attention in the scientific literature likely due to their relatively low economic value and difficulties in species identification. The absence of species‐specific information on catch, life history and migration of skates has often precluded the development of single‐species stock assessments and led to the use of cursory multispecies assessments, which lack the ability to track species‐specific catch and abundance trends. This has resulted in undetected local extirpations, as has been previously reported for common (Dipturus batis, Rajidae), white (Rostroraja alba, Rajidae) and long‐nose (Dipturus oxyrhinchus, Rajidae) skates in the Irish Sea. Here, we (a) use case studies to illustrate how the perception of skate population structure and stock status has historically been masked through multispecies assessment and management practices, (b) review current information on the movement of skates and identify gaps in knowledge, and (c) identify biases associated with the use of various tagging technologies, which have confounded our understanding of movement and migration ecology of skates. Considering that over 40% of extant Rajidae species are listed as “Data Deficient” by the International Union for Conservation of Nature, we illustrate a critical need to broaden the current understanding of skate life history, movement and migration ecology by providing recommendations on the further application of electronic tags and biogeochemical natural tags in movement studies and highlight the benefits that studies using these approaches have for novel management frameworks.     

含运动副间隙汽车摆振系统非线性动力学建模

机构运动副间隙对系统动力学响应有重要影响,有必要将转向机构运动副间隙引入汽车摆振系统动力学分析。基于非线性系统动力学,应用拉格朗日方程建立了考虑转向机构运动副间隙的六自由度摆振动力学模型。通过仿真分析讨论了车速对前轮摆振的影响,结果表明在特定车速范围内前轮会发生自激摆振,这与实际情况吻合,验证了模型的正确性。     

土壤重金属迁移模拟研究的现状与展望

随着工业发展和废弃物的排放不断增加,土壤重金属污染已经成为一个世界性环境问题。土壤重金属的分布转化以及污染修复的研究受到广泛关注,数学模型及计算机模拟研究成为重要的研究手段。该文对土壤重金属迁移的模拟研究的进展进行了回顾与归纳,集中阐述了对流弥散和经验随机两大类模型的特点和应用,并指出了研究中存在的问题及今后研究的发展方向。将数学模拟与土壤重金属信息系统及地理信息系统GIS的有机结合,将有可能为环境保护和农业决策提供新的重要依据。     

Movement and Distribution of Cryptolestes ferrugineus (Coleoptera: Laemophloeidae) Adults Under Different Temperature Differences in Different Lengths of Horizontal Grain Columns

Understanding insect movement and distribution is critical for developing an effective insect pest management protocol. Movement and distribution of adult Cryptolestes ferrugineus (Stephens) in response to nominal temperature differences of 5, 10, 15, and 20°C in 1- and 2-m horizontal columns filled with 12.5% moisture content wheat were studied in 24, 48, and 72 h of movement times. In the wheat columns without temperature differences, adults had a diffusion distribution pattern caused by their random movement. Adults showed bias movement to the warmer grain in wheat columns with temperature differences and preferred the warmer grain regardless of the magnitude of temperature differences in less than 24 h. Their distribution did not have significant differences among different movement times in 1- or 2-m columns. About 40% of adults moved to the warmer wheat located at 0.4 to 0.5 m in the 1 m column but did not move to the warmer wheat located at 0.9 to 1 m in the 2-m column. Therefore, length of grain column influenced detection of warmer grain by insects. Adults under different temperatures had a similar response as that under linear temperature gradients.