蓝点马鲛(Scomberomorus niphonius)大网目流刺网参数优化研究

在对黄渤海区蓝点马鲛(Scomberomorus niphonius)流刺网进行10种网型主要参数分析和筛选的基础上,2013年4月10日—5月15日,使用鲁昌渔64068渔船在黄海中南部对蓝点马鲛大网目流刺网网片做了4种规格网目尺寸的优化对比实验。结果显示,120 mm 网目尺寸的网片渔获尾数和重量最大,单位捕捞努力量渔获量(Catch per unit effort, CPUE)为0.1696尾/片·日和373.78 g/片·日,渔获效果优于110、115、125 mm 的网目。2015年4月12日—5月27日,使用鲁昌渔64068和鲁莱州渔66287渔船分别在黄海中南部、烟威外海、莱州湾海域对蓝点马鲛大网目流刺网主要参数做了网型优化对比实验。结果显示,鲁昌渔64068渔船使用120 mm 网目尺寸网型捕获的蓝点马鲛平均叉长为764.18 mm,最大个体叉长为1000 mm,最小个体叉长为490 mm;平均重量为3623.27 g,最大重量为7500 g,最小重量为850 g;CPUE 分别为0.1379尾/片·日和517.65 g/片·日。鲁莱州渔66287渔船使用122 mm网目尺寸网型捕获的蓝点马鲛平均叉长为780.47 mm,最大个体叉长为910 mm,最小个体叉长为600 mm;平均重量为4065.17 g,最大重量为7400 g,最小重量为2000 g;CPUE分别为0.0778尾/片·日和283.35 g/片·日。120 mm 网目尺寸网型的渔获效果优于122 mm 网目尺寸的网型,春季捕捞大个体蓝点马鲛的流刺网网目尺寸以120 mm 左右适合当前的蓝点马鲛群体组成。120 mm 网目优化网型主要参数为：渔具主尺度33.00 m×18.54 m,网衣规格500目×175目,网目尺寸为120 mm,网线材料为直径0.48 mm 的尼龙单丝(PAM),横向缩结系数为0.55,静浮力配备为267.9 g/m,浮沉比为1.768∶1。120 mm 网目优化网型的另一特点为通过缩小上缘网网目尺寸,用上缘网替代上缘纲和浮子纲2根纲索,既保持了渔具主要结构和性能不变,又节约了渔具材料。设计方法为：上缘网的网目尺寸=主网衣网目尺寸×主网衣横向缩结系数。     

扇形雾喷头雾滴飘失机理

为了分析雾滴飘失机理和提出针对性的防飘措施,使用相位多普勒粒子分析仪( PDPA)对常规扇形雾喷头雾化产生的喷雾扇面中的雾滴粒径与运动速度分布进行了分析.结果表明:喷雾截面上雾滴体积中值直径(VMD)分布为中间低、边缘高的凹面形态,在喷雾扇面横向和纵向对称面上,VMD形态呈二次多项式分布;易飘失雾滴主要集中在距离喷头300～500 mm喷雾扇面的中心位置;喷雾扇面截面上的夹带气流速度符合高斯分布,气流分布与空气淹没射流类似;喷雾扇面中易飘失区域是喷雾扇面末端、喷雾扇面两翼、喷雾扇面迎流面外层.     

Rotary atomiser design requirements for optimum pesticide application efficiency

Pesticide application efficiency from aircraft could be increased substantially, and required downwind buffer distances to avoid drift damage reduced significantly, if sharp issuing points or pins were added to existing rotary cage atomizer designs. This would enable existing rotary cage units, already successfully deployed for Ultra Low Volume (ULV) applications of insecticides, to be also used for Large Droplet Placement (LDP) application of herbicides. Studies at Cranfield University using high speed photography and laser droplet sizing instrumentation demonstrated that the addition of fine pins to the final atomizing surface of the rotating cage would increase uniformity of droplet production, by promoting fluid atomization in the ligament mode. This would lead to a substantially increased percentage of droplets in the spray falling between 100 μm and 300 μm in size, suggested here as a biological/environmental droplet size optimum. Development of a ‘spinning pins’ rotary atomizer for aircraft would therefore be highly desirable for agricultural and other purposes. Investment in this technology has the potential to significantly reduce pollution of atmosphere, soil, fresh water and oceans with pesticides.     

超高地隙喷杆喷雾机风幕式防飘移技术研究

结合超高地隙喷雾机实际结构,应用ANSYS Fluent软件,采用标准k-ε湍流模型、离散相模型与Couple算法,建立了超高地隙喷杆喷雾机风幕式气流辅助施药技术雾滴沉积飘移分布模型,对飘移率与各影响因素之间的关系进行了仿真研究,确定了不同风机转速下雾滴飘移率与其各影响因素之间的函数关系,并对模拟研究结果的准确性进行了试验验证.研究结果表明,所建模拟模型能够比较准确地反映风幕系统各作业参数对雾滴飘移率的影响规律,其中辅助气流喷射角度、喷头水平安装位置、自然风风速、风机转速,以及辅助气流喷射角度和自然风风速、辅助气流喷射角度和风机转速、喷头水平安装位置和自然风风速、自然风风速和风机转速的交互作用都对飘移率有显著的影响.     

灌浆期六旋翼无人机喷幅和喷液量对玉米群体内雾滴沉积分布、漂移特性的影响

采用大疆T30无人机在玉米灌浆期进行喷施作业,探讨喷幅和喷液量对雾滴在群体内沉积分布影响。采用两因素试验设计,设置3个喷幅[4(G1)、5(G2)、6.5 m (G3)]和5个喷液量[15、30、45、60、75 L/hm²(R1～R5)],将玉米群体从上至下分为5层(A～E)。结果表明,在不同喷幅和喷液量处理组合下,随着喷液量增加,雾滴总沉积量、覆盖率、覆盖密度显著增加,随着喷幅的升高呈先增后降的趋势,其中G2R5、G3R5和G1R5处理的雾滴总沉积量较大,但雾滴的地面损失量增多、沉积量均匀性和穿透性不佳、漂移加重,总体上G2喷幅下各叶层的雾滴沉积分布较优。在实际生产中喷液量选择不宜过大,应结合施药属性及农田环境等因素,确定适宜的喷液量。     

闽东海区流刺网渔业的现状分析

根据2000－2001年对闽东地区流刺网渔业的社会调查资料，研究分析了闽东海区流刺网渔业的利用现状，存在问题和发展趋势。提出了控制内湾，沿岸海域小网目流刺网作业的数量规模；调整近海捕捞结构，优化捕捞资源的合理配置；优先扶持，达量发展近海和外海大中型流刺网作业管渔业管理意见。     

Shear tests of double shear plate connector joints in sugi—Japanese larch composite glulam beams

To study the shear strength of structural joints in sugi (Cryptomeria japonica D. Don) — Japanese larch (Larix kaempferi Carriere) composite glulam beams using structural connectors with double shear plates, shear tests were conducted on two types of joint (post-beam and girder-beam). Two types of the composite beam (240 and 300 mm depth) were prepared for the tests. Ordinary sugi glulam beam and Japanese larch glulam beam were also used as control specimens. The load—displacement curves of joints in composite beams were somewhere between those of sugi and Japanese larch glulam beams. The shear strength of joints in composite beams was higher than that in the sugi glulam beam control. However, the allowable loads of the joints in composite beams were lower than those in the sugi beam with 240 mm depth. Large variation of maximum load of the joints in the composite beams resulted in lower allowable load.     

影响随机保种理论的随机遗传因素分析

本文运用计算机模拟的方法分析了畜禽随机保种理论的主要影响因素——近交及遗传漂变的效应,以俾从理论和实践上对随机保种理论进行深入分析,为畜禽保种新理论与方法的研究提供科学依据。     

改进双圆弧罩盖减少雾滴飘失试

通过计算流体力学软件Fluent的仿真模拟,分析现有双圆弧罩盖喷雾的流场和雾滴运动轨迹,并针对存在的问题提出了罩盖的改进方案.与改进前罩盖喷雾、常规喷雾进行了流场、雾滴运动轨迹和沉积率的仿真对比以及雾滴沉积率的风洞试验对比.仿真结果表明,改进后罩盖的流场有利于雾滴向靶标的沉降,当风速为3 m/s时 ,安装改进罩盖喷雾的雾滴沉积率为76.88%,高于改进前的63.26%和常规喷雾的50.16%.风洞试验结果表明,当风速为3 m/s时,改进罩盖的雾滴沉积率为73.35%,高于改进前的66.90%和常规喷雾的49.95%.     

Post-fire hillslope erosion response in a sub-alpine environment, south-eastern Australia

This paper examines post-fire erosion response in a sub-alpine environment in south-eastern Australia for a period of 2.2 years. Few studies have examined fire impacts on sediment transfer in this environment. Erosion pins were used in grids located at upper, mid and lower slope positions on adjacent burnt and unburnt hillslopes to assess fire effects on the extent of surface level change. The results indicated that there was a significant difference between the surface level change regimes on the burnt and unburnt hillslopes. Estimated erosion rates for the burnt slope over the study period ranged from 2.7 to 94.3 t ha^− 1, which could be considered low given the high slope angles, high precipitation and moderate fire severity. Slope position was critical in modifying post-fire erosion response, as it controlled slope angle and the rate of surface cover regrowth. Analysis of lower slope sites, for which more detailed data was available, indicated a second delayed erosion peak after the initial elevated post-fire response during the following spring snowmelt period. Surface recovery on the lower burnt site was slow, with vegetation cover still comparatively low 2.3 years after the fire. Evidence of post-fire sediment supply limitation was found on this site, with a declining rate of increase in the magnitude of total surface level change, despite limited regrowth and an increasing number of precipitation events > 20 mm for measurement intervals since the fire. Modification of the hillslope surface by fire leads to changing hillslope erosion process dominance in this environment. The post-fire hillslope undergoes erosion by direct rain-drop impact and overland flow, whereas the unburnt slope rarely experiences overland flow due to the thick ground cover. As a result surface level change on the unburnt slope was largely influenced by wetting–drying effects rather than sediment transfer by surface flow. Downslope biotransfer appears to be the dominant sediment movement process in the unburnt sub-alpine forest environment.