Numerical simulation of flow field dynamics characteristics for a novel twin screw kneader

The numerical simulation for dynamic characteristics of the flow field of a novel twin screw kneader is carried out. The numerical simulation model of twin screw kneader is established,and the three dimensional,isothermal and steady numerical analyses of non newtonian fluid are presented based on computational fluid dynamics(CFD)theory,and the characteristics under the conditions of different speeds and center distances,such as the distribution of pressure and velocity field,the maximum shear stress,the mass flow rate and so on,are studied. The research results show that：with increasing speed,the maximum flow pressure,the mass flow rate and the maximum shear stress increase; the maximum shear stress increases first and then decreases with increasing of center distance of the screw rotors,while the mass flow rate increases with increasing of center distance; but when the center distance reaches a certain degree,the mass flow rate is negative and the material appears serious reflux which can make the kneader stop working. The results provide a theoretical basis for performance prediction and reasonable designing for the novel twin screw kneader.     

苹果园芬兰真绥螨种群的空间动态分析

应用5种聚集度指标和Iwao法分析了芬兰真绥螨在苹果树冠的发生动态和空间格局.结果表明:叶螨和镰螯螨是芬兰真绥螨的主要猎物,7月中旬到8月中旬为其种群发生高峰期,种群数量主要随着镰螯螨数量增加而增加;树冠上层、北面和内膛,芬兰真绥螨种群个体间相互排斥;在树冠中层、下层、东面、南面和西面,芬兰真绥螨种群个体间相互吸引,分布的个体成分是个体群;在树冠垂直方向和水平方向上芬兰真绥螨种群均呈现聚集分布;从7月到10月,芬兰真绥螨种群表现低聚集度,10月1日到10月中旬聚集度有增长的趋势.     

藏系绵羊瘤胃古菌季节动态分析

在不同季节分别随机选取3只藏系绵羊,采用PCR-DGGE技术对12只藏系绵羊瘤胃内容物中的细菌区系进行分子生态学分析.对古菌16SrDNA的V2～V4可变区的扩增产物进行DGGE图谱分析、相似性分析和Shannon多样指数分析.结果表明:瘤胃内容物中古菌群落多样性指数冬季与春季间差异不显著(P>0.05),但冬季显著高于夏季(P<0.05),并极显著高于秋季(P<0.01);春季与夏季差异不显著(P>0.05),春季显著高于秋季(P<0.05);夏、秋季之间差异不显著(P>0.05).各季间瘤胃古菌区系组成结构相似性高于94%.冬、春季节,由于牧草中的纤维性物质含量增高,导致瘤胃古菌群落多样性增加,不同季节牧草中粗蛋白和酸性洗涤纤维含量的变化可以引起特异性的古菌群落发育,可能导致不同的优势种群.     

氯吡嘧磺隆在玉米植株及土壤中的消解动态研究

利用超高效液相色谱-质谱法建立了氯吡嘧磺隆在玉米植株和土壤中的残留分析方法,并研究了氯吡嘧磺隆在玉米植株和土壤中的残留消解动态,对影响残留分析方法的主要参数进行了优化。结果表明,氯吡嘧磺隆标准溶液的线性方程为y=66 535x+747.06(r2=0.999 9),线性范围为10～1 000ng/mL。残留样品采用丙酮提取,乙酸乙酯萃取净化,超高效液相色谱分离,质谱仪检测,外标法定量。该方法在玉米植株和土壤中的最低检测限(LOQ)均为0.002mg/kg,当样品中氯吡嘧磺隆的添加水平为0.05～0.2mg/kg时,采用该方法测得植株和土壤中的平均回收率分别为85.16%～88.13%和87.65%～91.37%,相对标准偏差(RSD)分别为1.92%～2.09%和1.16%～2.61%。消解动态试验表明,氯吡嘧磺隆的残留量随时间延长而降低,消解动态曲线符合一级动力学方程,在植株和土壤中半衰期分别为0.78～0.97d和7.00～16.90d。试验结果显示,氯吡嘧磺隆在玉米田中属较易降解的农药。     

不同水肥优化模式对冬小麦生长发育及产量的影响

【目的】在渭北旱塬有限灌溉条件下,优化小麦水氮管理,为渭北旱塬冬小麦高产及资源高效利用提供理论依据。【方法】通过大田试验,研究了优化施氮补灌、秸秆覆盖和有机无机肥结合对冬小麦群体动态、干物质量及产量的影响。【结果】各处理小麦从出苗开始群体数量不断增加,到返青期达最大后开始下降;返青期以前,各处理之间没有显著差异,且群体数量和干物质量都以农户模式2（农户传统施肥灌溉处理）最高;返青期后经拔节期追氮补灌,小麦群体数量和干物质量存在显著差异,以优化模式3-1（优化水氮管理并结合秸秆覆盖和配施有机肥）最高,施氮和灌水均提高了小麦的群体总茎（穗）数和干物质量。各处理产量以优化模式3-1最高,为5 542 kg/hm²,较对照、农户模式1（不灌水的农户传统施肥处理）和农户模式2分别显著提高了110.8%,72.1%和17.8%。【结论】在渭北旱塬有限灌溉条件下,优化模式3-1不仅节约大量水资源,而且显著提高了小麦产量。     

Characterizing the spatial pattern of Abutilon theophrasti seedling patches

Spatial biology of weed populations is the study of weed patches and their relevant patch-level processes. In this context, a patch was defined as an area in which individuals are aggregated into discrete subdivided populations. Four Abutilon theophrasti seedling patches in two continuous maize production fields were surveyed using a contiguous grid of quadrats between 1995 and 1997. Surveyed area was dependent on patch size and ranged from 96 m² to 1134 m². Within each area, all seedlings were counted in each 1 m × 0.75 m quadrat in June, just before post-emergence weed control, and in mid-July after all weed control practices were completed. The spatial pattern observed in the seedling distribution maps was single or multiple focal points of high seedling density that decreased with distance from the focal point. Two-directional correlograms corroborated this visual observation, such that A. theophrasti seedling density in neighbouring quadrats was spatially autocorrelated, and correlation strength decreased with distance separating quadrats. Autocorrelation coefficients decreased at a greater rate across crop rows than parallel to crop rows. Visually, patch shape was elliptical and oriented in the direction of field traffic. Factors affecting patch-level processes of spatial aggregation, stability and edge dynamics were considered.     

紫薇长斑蚜发生规律及防治研究

紫薇长斑蚜是紫薇叶面上最严重的害虫，还经常诱发紫薇煤污病。该虫在贵阳最多可产生２６代。正常条件下成蚜都是有翅蚜，当紫薇进入落叶休眠期，气温明显下降时，产生无翅成蚜，并以此为越冬虫态。若蚜历期相当于全代历期（通常为５～７ｄ），当天羽化的成蚜当天产若虫。成虫寿命、产蚜量及发育速率的回归式建立。虫口周年变化为单峰曲线。药剂防治，全年３～５次即可。     

大白杜鹃与露珠杜鹃杂交亲和性及其杂交果实发育动态研究

以大白杜鹃为母本,露珠杜鹃为父本进行杂交试验,通过测算露珠杜鹃与大白杜鹃的花柱长度比进行杂交可行性分析,利用荧光显微镜观察授粉后露珠杜鹃花粉管的生长状况确定杂交亲和性,并对温室和露天两种条件下的杂交果实的纵横径动态变化情况进行观测。研究结果显示,露珠杜鹃与大白杜鹃的花柱长度比为0.98,推测两种杜鹃杂交容易成功。露珠杜鹃花粉管在授粉后9 d进入大白杜鹃胚珠并完成受精,证实两种杜鹃杂交亲和。温室和露天条件下的杂交果实形态成熟时间均约180 d,其中,授粉后0~9 d为第1次缓慢生长期,授粉后9~105 d为第1次迅速生长期,授粉后105~135 d为第2次缓慢生长期,授粉后135~180 d为第2次迅速生长期;果实纵径和横径的生长动态变化过程相似,但横径的生长动态曲线较纵径平缓。温室条件下的杂交果实纵横径大小明显高于露天条件下的杂交果实。研究认为,大白杜鹃与露珠杜鹃杂交亲和,杂交果实生长动态曲线为"双S"型,其形态成熟时的纵横径大小与其栽培条件直接相关。     

The role of lysimeters in the development of our understanding of soil water and nutrient dynamics in ecosystems

This paper considers the development of lysimeters and their role in the evolution of our understanding of the dynamics of water and plant nutrients in ecosystems. Lysimeters are delineated volumes of soil. They can be divided into those filled with repacked soil, and those enclosing an undisturbed monolith. The original repacked lysimeter was developed to investigate the concept that all life stems from water, and is considered to be the first quantitative experiment in history. It focussed on the growth of a willow tree and how much of the increment was derived from the soil solids. From this start some 360 years ago lysimeters quickly contributed to the quantification of the transpiration stream and the differentiation of water loss by evaporation from the soil from loss via the leaves of plants. Chronologically, further development began about 210 years ago with the exploration of whether precipitation could account for all the water moving from the land to the oceans, and was the origin of springs. In part, this required a careful quantification of soil evaporation, runoff and deep drainage. This in turn led to the quantification of the soil water balance. As a result, we are able to predict indices, such as crop water use efficiency, drainage and irrigation requirements, contributions to stream flow, groundwater recharge and nutrient loss by leaching. Recognition that the quantification of drainage and leaching required soils of natural structure and profile integrity resulted in the building of the first monolith lysimeter and the development of ‘pan’ or ‘Ebermayer’ lysimeters. Improved technology allowed a better understanding of the role of soil in the regional water balance through the development of small diameter lysimeters that could be transported to a central location subject to the same climatic variables. In contrast, other technological changes allowed the impact of typical soil management operations carried out using regular machinery to be applied on field‐scale lysimeters. The contribution of the different types of lysimeter to the development of our understanding of soil use and management is considered.     

南京幕府山矿区废弃地恢复植被的群落种群动态研究

通过南京幕府山地区矿区植被恢复的群落种群的调查,对植物群落的组成、主要植物种群径级、垂直结构、密度等进行了分析,总结了群落种群动态规律。对模拟自然植被恢复,恢复植被的管理,建设幕府山矿区废弃地生态恢复工程具有重要的意义。