深基坑锻锤基础冬期施工

在冬期施工，对于土方开挖、钢筋绑扎、人员的通行、砼的浇铸、砼的温度控制，基坑的保温等都带来一定困难，为此提出了深基坑锻锤基础才是最佳实践应用。     

Effects of weed control practices on surface-dwelling arthropod predators in tomato agroecosystems

Weed control, an important practice in agroecosystems to protect crop production, is usually achieved with herbicides. However, these pesticides are expensive, pose potential risks to the environment, may affect some beneficial organisms indirectly, and decrease overall arthropod biodiversity, including pests and their natural enemies, by removing weeds that might act as hosts or shelters for many organisms. The activity density response of important surface-dwelling arthropod predators (ground beetles [Coleoptera: Carabidae], ants [Hymenoptera: Formicidae] and spiders [Arachnida: Araneae]) to herbicides (trifluralin and paraquat), and to two alternative weed management practices (rye straw mulch and mechanical treatment to maintain weeds below threshold levels, in comparison with an untreated check), was assessed using pitfall traps. The mulch treatment had the greatest effect on activity density, reducing the number of predators trapped significantly (P<0.05). Herbicide use resulted in significant (P<0.05) reductions in the activity density of ground beetles. Most predators were trapped in the check plots — which had the highest weed biomass, followed in turn by numbers trapped in the threshold weed control treatment, the full herbicide application and the mulch treatment plots. http://www.phytoparasitica.org posting July 10, 2002.     

大通沼气池的应用及发展探讨

大通县依托林业重点工程,发展沼气,采用国内最先进的旋流布料自动循环式沼气,解决了高原冬季不产气的问题。取得了初步成效。受到农村广大用户的赞誉。     

钢支撑代替混凝土支撑可行性分析

在地铁深基坑施工中，围护结构对基坑的安全起着至关重要的作用。本文依据合肥地铁一号线明光路站，施工过程中，由于车站3号出入口为出土口，原计划的第一道钢筋混凝土支撑无法实现，更改为钢支撑，通过有限元分析软件MIDAS-GTS\NX，建立二维模型进行数值模拟，对围护结构的变形和地表沉降进行分析，结果表明：第一道支撑采用钢支撑代替钢筋混凝土支撑对围护结构的侧移值影响不大，钢筋混凝土支撑控制地表沉降的效果要比钢支撑好，对今后类似工程变更提供依据。     

洪江水电站闸门调度试验

以不同工况的消能复核和下游冲刷复核为控制,先通过模型试验确定洪江水电站左闸运行调度、右闸运行调度及左右闸联合泄洪调度的方式,再根据模型试验泄流数据的整理结果,分析闸门相对开启高度(he/H)与参数(q2/g H3)之间的关系,得出适应任何上游水位,任何洪水来量,任何机组运行台数的洪江水电站闸门调度粗估公式。     

Deformation of deep foundation pits due to excavation and dewatering considering the change of void ratio and permeability coefficient with current stress of soil

基于修正剑桥模型理论,推导了孔隙比e随土体当前应力变化的方程,同时比选了4组经典的描述渗透系数k随孔隙比变化的方程,选择了其中一组最佳的估算公式,编写ABAQUS用户子程序VOIDRI和USDFLD,以实现孔隙比和渗透系数随土体当前应力的变化。在此基础上,研究深基坑降水开挖所致的坑内外土体的变形、围护结构的变形及弯矩,得到以下结论：当考虑孔隙比随土体当前应力变化时,坑外地表沉降量、墙体的水平位移、地下连续墙的弯矩、坑底隆起量均大于孔隙比为定值时的情况;当考虑渗透系数随土体当前应力变化时,坑外地表沉降量、墙体的水平位移、地下连续墙的弯矩均小于渗透系数为定值时的情况,但同时考虑渗透系数和孔隙比变化情况时,其对坑底的隆起量的影响可以忽略不计。     

黄土高原肥水坑施技术下苹果树根系及土壤水分布

为了解黄土丘陵区雨养条件下山地老果园布设肥水坑(water-wertilizer pit,WFP)技术对红富士老果树(Malus pumila Mill)根系及土壤水分空间分布特征的影响,以无肥水坑处理为对照(CK),利用管式TDR系统监测0~300 cm土层土壤含水率,利用根钻法获得21a生旱地果园0~300 cm土层的根系干质量密度。结果表明:WFP能够显著增加果园含水率低值区间(≥40~80 cm土层)土壤含水率,WFP60(60 cm坑深)处理土壤平均含水率增量(145.4%)最显著。WFP40(40 cm坑深)根际土壤湿润区主要集中在≥40~100cm土层,WFP60在≥20~140 cm土层,WFP80(80 cm坑深)主要集中在深层土壤≥140 cm土层。在0~200cm试验土层,WFP60处理土壤多次平均含水率值都最高,为11.02%,依次为WFP40(10.67%)和WFP80(9.80%)。总根系质量密度WFP60处理最大(594.76 g/m3),WFP40(579.08 g/m3)和WFP80(491.82 g/m3)次之,CK最小(372.12 g/m3)。根系在0~100、≥100~200和≥200~300 cm土层中的分配比例为:CK(69.88%、13.74%和16.38)、WFP40(66.04%、14.26%和19.70%)、WFP60(70.35%、24.08%和5.58%)和WFP80(46.54%、15.04%和38.42%),其根系分布与水分分布正相关。该研究表明WFP能够显著改变土壤水分在不同土层深度的分布,坑深越大向下湿润的土体范围也越深;从而显著促进果树根系的生长和根系在不同湿润土层的分配比例关系。总体而言,WFP60处理效果显著好于WFP40和WFP80处理。研究结果将对黄土高原旱地果园集雨和灌溉制度的制定和肥水坑技术的推广提供参考。     

提高耐磨与破碎性的仿生凹坑形磨辊设计与试验

为了提高水泥辊压机磨辊的耐磨性与破碎性,以仿生非光滑理论为指导,在磨辊表面设计并加工出具有不同直径、不同深度、不同轴向间距及周向个数的仿生凹坑形结构,根据正交表编制试验方案并对磨辊进行磨损及破碎性试验。试验结果表明,仿生凹坑形结构可以有效提高磨辊的耐磨性与破碎性。相对于标准磨辊,其耐磨性最大提高29.06%,破碎性最大提高18.7%。当仿生磨辊的凹坑直径为8 mm、凹坑深度为2 mm、轴向凹坑间距为16 mm、周向凹坑个数为12时,是兼具耐磨性及破碎性的最优辊。通过有限元方法对磨辊所受应力进行分析时发现,合理的仿生凹坑形结构可以优化磨辊表层受力,减少磨辊磨损;磨辊挤压石英砂破碎时受到的最大挤压力是影响其破碎性的重要因素。通过单颗粒石英砂破碎试验可知,仿生凹坑形结构减少了石英砂对其表面的刻划,分散了石英砂对其表面的挤压力,提高了磨辊的耐磨性及破碎性。     

Antipredator behaviour of naïve Arctic charr young in the presence of predator odours and conspecific alarm cues

Abstract –  We investigated how Arctic charr young respond behaviourally to olfactory cues from skin-damaged conspecifics, charr-fed pikeperch, and the combination of food-deprived pikeperch and skin-damaged conspecific cues in a two-channel Y-maze fluviarium test arena. Significant antipredator responses were found to skin-damaged conspecifics in three behavioural traits, to charr-fed pikeperch in two traits and to the combination of pikeperch and skin-damaged conspecific cues in all six behaviours investigated. The combination of predator and conspecific cues significantly increased spatial avoidance and cautiousness to approach the source of scent compared with odours from charr-fed predators. The results suggest that damage-released alarm cues exist in charr, and they strengthen the antipredator responses in conspecifics. As the charr used different behaviours and levels of response in the presence of different cues, they seem to have sophisticated skills to distinguish between different odour combinations and be able to adjust their behaviour according to the current predation risk level.     

Do lethal trap devices threaten foot-hold trap capture efficacy?

Foot-hold trapping is an important tool used in pest management programs in countries such as Australia, New Zealand and in North America. Research on humane trapping methods including the addition of sedatives (Tranquilizer Trap Device) and toxins (Lethal Trap Device) to foot-hold traps to improve the welfare of trapped pest animals is important. Lethal Trap Devices (LTD) are being tested in Australia to determine if deploying a toxin with a foot-hold trap is effective at delivering a lethal dose of toxin to trapped predators. This study aimed to test whether fitting an LTD to two different foot-hold jaw traps (Victor Soft catch #3 and Bridger #5) would affect the jaw closure time and as such affect capture rates. We found that two spring Victor Soft catch traps were faster (20.91, SD 0.72 ms) than four spring Bridger #5 traps (26.79, SD 0.48 ms) even when fitted with a Lethal Trap Device. Fitting a Lethal Trap Device to either of these trap models did not affect closure time and as such would not have any effect on capture efficacy.