土壤水盐运移的简化数学模型在水盐动态预报上的应用研究

对土壤水盐运移的确定性数学模型 ,采用数值模拟的简化法 ,实现对方程的求解。并引入水分运动原理、质量守恒原理 ,根据地下水、土壤水盐运动的特点 ,建立土壤剖面含水量分布的概化模型和土壤盐储量的预报模型。以期从土壤水盐运动的机制出发 ,提出一种应用简化数值模拟方法来预报土壤水盐动态的途径。同时为适应大面积田间土壤盐分预报的特点 ,希望不通过方程的求解来达到应用简化数学模型实现水盐动态预报的目的。所建简化数学模型可为田间大面积土壤水盐动态预测预报提供参考     

蛋鸡福利化养殖模式及技术装备研究进展

自1999年欧洲福利法提出全面禁止传统笼养以来,世界各国开展了很多蛋鸡福利化养殖系统的研究,以保障蛋鸡福利,取得了很多方面的改进。然而,在世界上的主要蛋品生产国家中,福利化养殖设施所占蛋鸡养殖模式的比例仍然较低。随着人们对动物福利的重视和行业的可持续发展要求的提高,开发新型养殖设施的呼声日益高涨。根据国内养殖业建筑现状以及现代高产品种抗病力差的特点,发展福利化养殖装备提高蛋鸡鸡体本身的健康和福利,减少因药物使用带来的负面影响,中国开发福利化蛋鸡养殖设施以提高鸡体健康和福利以抵抗疾病,减少用药;同时促进舍内环境良好,创造适应现代鸡群的生存条件显得至关重要。该文通过概述世界现存的几种替代传统笼养的福利化养殖模式及装备,比较它们各自的特点以及它们在蛋鸡福利、生产性能及蛋品质、社会经济环境对它们产生的不同影响等方面的差异。提出并分析了不同养殖系统存在的主要问题。通过总结国外蛋鸡福利化养殖设施的优缺点,为国内蛋鸡福利化系统的开发提供参考。在改善行为福利的同时,还需要结合传统笼养鸡体与粪便分离、动物健康状况好、投资较低的优点,改变现有的福利化养殖装备系统设计。另外,该文展望了福利化养殖设施的发展方向,并提出了发展福利化养殖设施的新思路。     

小麦和玉米秸秆热解反应与热解动力学分析

为了对生物质快速热解液化设备进行分析和计算，该文用热重、差热分析仪分别对小麦和玉米秸秆在不同升温速率下进行了热分析研究。结果表明：小麦和玉米秸秆的热解特性基本一致，热解过程可以用同一种模型描述；随升温速率的提高，热解最高速率时的温度和热解最高速率明显提高。分析了小麦和玉米秸秆热解反应过程，提出了平行一阶反应动力学模型并计算出模型中各参数，将该模型的计算结果、现有一阶反应模型的计算结果分别和试验数据进行了对比，结果表明，平行一阶反应模型的准确程度比现有一阶反应模型有很大的提高。     

内蒙古河套灌区节水灌溉工程实施后地下水变化的BP模型预测

根据黄河河套灌区多年的水文、气象和地下水资料，应用不同的ANN—BP网络模型对灌区年、月地下水埋深的变化进行了模拟，预测了黄河河套灌区节水工程实施后未来灌区年平均地下水位下降的情况，从预测结果可以看出，河套灌区节水工程实施后灌区平均地下水位预计下降0.5 m左右。此外对BP模型的结构设计中隐含层数、隐含单元数和学习速率的合理确定作了具体分析，提出了学习速率取值范围lr=0.01～0.1，为河套灌区节水工程改造规划、设计和管理决策及BP模型的应用提供了参考依据。     

Environmental persistence of 2,3,7,8-tetrachlorodibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxin in soil around hardstand 7 at eglin air force base,Florida

Background and Goal  A number of global events have generated intense scientific scrutiny and public concern of polychlorinated dibenzo-p-dioxins (dioxin). DIoxins have been associated with a range of adverse health effects. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is recognized as among the most dangerous of the dioxin compounds, and was a contaminant found In one of the herbicides used for vegetation control during the Vietnam conflict: Agent Orange. As a result of purging spray systems and leaking drums of Agent Orange concentrate, TCDD contamination occurred in the soils surrounding Hardstand 7 at Eglin Air Force Base, Florida. This research uses a multimedia model to estimate the TCDD concentrations in surface soil around Hardstand 7 for a 70-year time Interval beginning with observed surface soil concentrations 1984. Methods  Hardstand 7 is a nearly 40-m circular concrete and asphalt aircraft parking area. The hardstand was used as a staging area for spraying equipment used to disseminate herbicide In a test area called C-52A within EAFB. Concentrated herbicide was also stored in 208-L barrels for use with the equipment, and later, for disposal. In 1984, a field investigation characterized the extent of TCDD contamination in surface soils around Hardstand 7 using a radial sampling protocol. The 1984 observed concentrations and locations was used in a multimedia model, CalTOX, as an initial source term concentrations and locations to estimate expected concentrations during the subsequent 70-years. Results  The results indicate that more than 94% of the TCDD observed in surface soils 1984 will remain after a 70-year period. Access restrictions and remediation activities at the site eliminate bar verification of the CalTOX estimates. Conclusions. TCDD is highly persistent in the soil medium and natural attenuation may not produce a significant decrease In soil concentrations. Recommendation  Active remediation actions may be required to prevent exposure to TCDD contamination surface soils. Verifying CalTOX concentration estimates an Important step that should be performed, however, the, model provides an easy to use tool to estimate TCDD surface soil contamination at herbicide storage or dispersion staging sites.     

Integrating effects of hunting policy, catastrophic events, and inbreeding depression, in PVA simulation: the Scandinavian wolf population as an example

Focusing on the wolf Canis lupus in Scandinavia as an example, criteria are proposed and an analysis performed to assess the effect on extinction risk of various control policies, while accounting simultaneously for effects of inbreeding depression and potential catastrophic events. Each control policy is characterized by a hunting pressure (the increase caused by hunting of annual mortality rates) combined with a hunting threshold (the population size below which hunting is not permitted). Catastrophes are taken into account by including the persistence of a severe catastrophe in the criterion for population viability. Based on these criteria, the results suggest that only a very limited amount of hunting should be permitted at low population sizes. The results also illustrate the importance of including a long-term perspective in modelling threatened populations.     

水稻插秧机分插机构工作过程的计算机模拟与分析系统

对水稻插秧机连杆分插机构工作过程的计算机模拟与分析方法进行了深入的研究,并开发出相应的计算机软件系统。该文对这类系统的设计要求、数学模型的建立及系统的设计作了概括性的论述,建立了系统关键的数学模型,并提出了系统的总体设计方案。     

作物养分定量化模型原理及方法比较分析

本文比较分析了养分经验模型和动态模拟模型的原理和计算方法。比较典型的经验模型有肥料效应函数方程,目标产量法,以及基于土壤肥力指标的QUEFTS(QUantitative Evaluation of the Fertility of Trop ical Soils)养分模型等。经验模型的特点是简单易行,所需参数少,但模拟精度难免误差较大;动态模拟模型由于考虑到复杂因素对作物养分吸收的影响,以及植物营养的动态过程,更能反映的系统真实行为。然而,由于土壤养分运移和作物养分吸收过程的复杂性,目前除氮外,还很难做到其它养分的动态定量化模拟,这些都还有待于更深入的基础性研究。     

池-田蓄引水模式改善环渤海棉田水盐运移提高棉花产量

为探明环渤海“池-田”蓄引水模式下棉田水盐运移规律对棉花生产的影响,2017和2018年4－10月对未改造棉田（CK）及模式中的台田（A）、浅层地下水抽提棉田（B）、抑盐排涝棉田（C）进行土壤水分、盐分和pH值、棉花光合指标、产量进行测定,结果表明,模式中棉田0～80 cm土层盐分和pH值显著降低,A和B棉田盐分降至3.0 g/kg左右,pH值低于8.0;C棉田盐分低于5.0 g/kg,7－8月pH值低于8.0。A棉田土壤水分、盐分和pH值最低,滴灌条件下棉花光合性能长期保持高值,光合物质积累的直线增长持续时间和活跃期最长,籽棉产量超过3 500 kg/hm2。B棉田水分0～40 cm土层高于20%,光合性能高值较长,籽棉产量超过3 000 kg/hm2。C棉花7－8月光合性能明显提高,籽棉产量超过2 500 kg/hm2。环渤海“池-田”蓄引水模式显著改善棉田水盐运移,有利于棉花生产,从而提高产量。研究可为高效开发利用滨海盐碱地提供科学模式和理论基础。