泵用圆形压电双晶片弯曲变形分析

为了准确获得压电泵泵腔容积的变化量,需要对压电振子的变形特性进行理论分析．将压电双晶片的受力模型分成2部分,即中间压电陶瓷和金属基板的3层复合部分,以及外部的金属基板部分．应用弹性薄板的小挠度弯曲变形理论,推导出固定边界条件下双晶片振动时的容积变化方程．结果表明:压电双晶片振动时容积变化的大小,是与双晶片的几何参数、材料的性能参数以及驱动电压有关的量．为了验证理论推导的正确性,对铜基板直径为35 mm、压电陶瓷直径为29 mm的压电双晶片,在不同直流电压驱动下中心点振幅进行非接触式激光测试,并将测试结果与理论计算值进行比较,结果表明:理论计算值要略大于实际测试值,两者之间存在20％左右的误差,但存在着一致性．应用泵腔容积变化量的理论计算方法,计算得到利用该压电振子制作的单腔压电泵在110 V,200 Hz正弦电压信号的作用下,泵腔每次振动产生的容积变化量约为12881 mm3,理论上最大输出流量为3 091 mL／min．     

Phytase and sodium diformate supplementation in a plant‐based diet improves protein and mineral utilization in rainbow trout (Oncorhynchus mykiss)

A basal isonitrogenous and isoenergetic plant‐based diet (Control) was supplemented with either 10 g kg^?1 sodium diformate (NaDF), 4000 FTU kg^?1 phytase (Phy) or a combination of both additives (NaDF + Phy). Three hundred juvenile rainbow trout with an average weight of 120 g were randomly distributed into 12 fibreglass tanks (300 L). After 65 days of trial, fish fed diets containing phytase, NaDF or the combination of both additives showed a higher growth rate (P < 0.05) compared to fish fed Control diet. NaDF increased feed intake (P = 0.032), while phytase inclusion resulted in a better feed conversion ratio (P < 0.0001) and a higher N retention efficiency (P = 0.02) compared with the Control. Apparent digestibility of P, Ca, Mg and Zn was improved by the use of phytase (P < 0.005) as well as P, Ca and Mg retention efficiency in fish (P < 0.0001). Using 4000 FTU kg^?1 phytase in plant‐based diets resulted in a 13% and 50% reduction in N and P loadings, respectively. The use of NaDF in combination with phytase in a plant‐based diet for rainbow trout resulted in a higher weight gain than that when NaDF was used alone.     

Broodstock diet with water and astaxanthin improve condition and egg output of brood fish and larval survival in Atlantic cod,Gadus morhua L.

Broodstock of Atlantic cod were fed with three diets; astaxanthin supplemented (100 ppm kg^?1) hydrated diet (30% water) (HWHAs), no additional astaxanthin supplemented (50 ppm kg^?1) hydrated diet (30% water) (HWLAs) and a control diet (50 ppm kg^?1 astaxanthin and 10% water). Throughout the spawning period, eggs were collected daily and fertilization success and proportion of embryos with normal cleavage were recorded. Larvae were reared using standard culture methods. Larval growth was recorded every 10 days and larval survival was recorded at 50 days post hatch. In general, broodstock fed with diets containing higher water content (HWHAs and HWLAs) and higher astaxanthin (HWHAs) had higher egg production and efficiency of egg output, lower egg incubation mortality and higher larval growth and survival. Broodstock fed with higher water content diets consumed less feed compared to control group. Also, broodstock fed with HWHAs and HWLAs recovered faster in terms of body condition than the control group. The egg bound mortality of female fish was significantly higher in control broodstock compared to broodstock fed with HWHAs and HWLAs. Broodstock fed with higher astaxanthin (HWHAs) had significantly higher fertilization success than other two groups however; no differences were found in proportion embryos with normal cleavage among different groups. Larval survival was significantly higher in HWHAs broodstock compared to other two groups. Our results showed that increased water content and astaxanthin levels in the diet could improve the condition and fecundity of Atlantic cod broodstock.     

财政投入与林业总产出关系研究——基于湖南林业投入产出的实证分析

财政投入是湖南林业投资中的重要构成,充分有效的财政投入能够保证林业的长期健康发展。根据湖南省2000~2014年林业财政投入和林业总产值的统计数据,利用格兰杰因果关系检验分析了林业的财政投入与林业总产值之间的相关关系。随后采用滞后变量模型发现了林业财政投入对林业总产值的增长具有正效应,短期内财政投入资金对林业总产值增长的影响不显著,但从长期来看,财政投入与林业总产值的增加之间的相关性比较明显。因此,为了促进林业经济的发展,必须完善林业财政投入的长效机制、加大林业财政投入、拓宽资金使用渠道、提高资金使用率以及引入社会资本。     

安徽省固定资产投资与农业经济增长关系的实证研究

基于C—D生产函数和已有的理论基础,选取1990—2014年安徽省16个地级市的面板数据,分别构建农业经济增长的静态和动态面板模型,利用“异方差—序列相关—截面相关”稳健型协方差矩阵来估计静态面板模型系数的标准误,同时基于二步系统GMM法对动态面板模型系数进行估计,结果表明：我省各地级市农业产出呈现逐渐增大的趋势,农业经济增长的波动是一个连续的动态调整过程;我省各地级市的固定资产投资所带来的直接边际产出效应相对较小,但影响非常显著;而农业劳动力投入对农业经济增长的边际产出较大,但影响不够显著。建议加大公共性农业投入;加快农村劳动向非农产业转移,提升农业产出的规模效益,促进农业经济持续稳定增长。     

基于GIS技术的福建省烟区烤烟产量估测与分区

采用烟区代表性样点的烤烟产量和相关影响因素调查资料,在筛选出烤烟K326、云烟87(85)品种产量最佳估测模型的基础上,借助GIS与烤烟产量最佳估测模型集成技术开展福建烟区不同烤烟品种产量的估测与空间分区,揭示福建省烟区耕地不同烤烟品种产量的空间差异。结果表明,人工神经网络模型对K326和云烟87(85)产量的估测精度最高,分别高达99.48%和99.51%,可作为福建烟区烤烟产量预测的最佳模型。福建烟区K326、云烟87(85)高产量区面积分别为96 695.67和208 683.58 hm~2,集中分布于浦城、建阳、建瓯等县市;中产量区面积分别为121 879.70 hm~2和91 803.92 hm~2;低产量区面积分别为296 096.70 hm~2和214 184.60 hm~2,中产区主要分布于永定、宁化和上杭等县(市),表明福建省烟区种植云烟系列烤烟品种可获得更高的产量。     

The quandary of quota management in the Torres Strait rock lobster fishery

Islanders, commercial non‐indigenous fishers and Papua New Guinea fishers share the tropical rock lobster fishery, Panulirus ornatus (Fabricius) in Torres Strait. As the fishery is in the process of moving from input to output controls, a pre‐implementation understanding of indigenous fishers' perceptions of the potential impact of different quota management systems is gained. This study, based on workshops and interviews, considers the impact of competitive quota, community quota and a hybrid system with individually tradeable quota (ITQ), and broadens the current biological focus of fisheries management through consideration of economic, social and cultural aspects. The perceived quota system impact on indigenous lobster fishers largely mirrors the experience internationally, with unlimited access and self‐determination considered most important. The heterogeneity of the indigenous sector increases the management complexity for this fishery, but needs to be taken into consideration if unexpected consequences of the chosen quota management system are to be avoided.     

变速器设计专家系统开发与应用研究

介绍了运用MATLAB开发变速器设计专家系统并基于该专家系统进行拖拉机变速器设计计算的过程,阐述了专家系统的知识库建立和人—机界面设计时需要考虑的具体内容。知识库部分论述变速器设计计算模型建立、材料库的搭建和参数库的建立等具体问题的解决方案。人—机界面巧妙运用MATLAB的GUI技术,组织相关知识,保证了专家系统的知识库与人—机界面的一致性、布局的合理性。通过各种控件与用户进行对话、交流,使变速器设计计算变得简洁、直观、方便。最后,通过一个(4+1)挡拖拉机变速器的实例对专家系统的计算和分析进行了测试,结果表明,该变速器设计专家系统可以缩短变速器的设计时间和提高设计精度,达到了预期的目标。     

单振子双腔体V形管无阀压电泵的流场分析

为了提高泵送流量,获得连续、低脉动的输出特性,设计了一种单振子双腔体V形管无阀压电泵,并建立其几何模型,对其工作原理进行了简要介绍,采用Fluent软件的动网格模型对其内部流动进行数值分析．对压电泵内部流场进行动态模拟,得到不同时期压电泵内部的压力、速度及瞬时流量等动态特征,将双晶片压电振子的动态特征和流体的运动特征有机地结合在一起,结果与压电泵的工作原理相吻合,验证了动网格模型应用于压电泵数值模拟计算的可行性．通过大量的数值模拟研究了驱动频率、压电振子振幅、泵腔高度和V形管位置对单振子双腔体V形管无阀压电泵输出性能的影响．模拟结果表明：驱动频率为250Hz时单振子双腔体V形管无阀压电泵的出口流量最大;压电振子振幅越大,出口流量越大;合理选择一组振幅值、泵腔高度和管道位置,便可得到压电泵的最优输出性能．     

滴灌年限对土壤盐分分布及棉花的影响

针对新疆盐碱地的改良及土壤次生盐渍化的问题,定点监测了121团开荒应用膜下滴灌技术种植棉花从第2年到第4年连续3年的盐分变化,并与荒地盐分对比。结果表明:滴灌2年,各个土层土壤含盐量在生育期初与生育期末变化较小,积盐现象与荒地相比有所减轻;随着滴灌年限的增加,各个土层土壤含盐量均呈减少趋势;滴灌4年后各个土层土壤含盐量再分布比较明显,0～20cm土层及120～140cm土层含盐量最大,40～60cm与80～100cm土层土壤含盐量较小,棉花根系主要分布的40～60cm土层土壤含盐量最小;滴灌4年土壤含盐量基本满足种子出苗,平均成活率从6.9%,增加到94.5%,但是棉花平均株高、平均单株铃数及产量仅为正常棉花的66%、53%和57%,相对较低。对于滴灌4年后的盐碱地应继续加大水盐调控的力度。