联合收割机生产率计算模型与适宜作业路线分析

提高农业机械生产率可大大节约农业生产成本。本文将田间试验与数值模拟相结合,首先在综合分析收割机作业时间构成的基础上,构建了不同作业路线下收割机生产率计算模型;其次实测了3种型号收割机在不同田块条件下整个收割过程中各个作业环节的时间及其工作特性参数;最后基于计算模型和实测参数,采用MATLAB进行编程,模拟分析了不同型号收割机、作业路线和田块面积下收割机生产率的变化规律。结果表明,收割机生产率随田块长宽比、田块面积和割台幅宽的增大而增大;采用"回"形和"U"形相结合的收割机作业路线,可提高收割机生产率8%以上。该结果可为农机实际作业路线选择和农田系统优化布局提供参考。     

基于线性自抗扰的稻田除草对行控制系统设计与试验

为降低水稻机械除草的行间伤苗率,该文基于线性自抗扰技术开展水稻田间除草对行控制系统研究。在苗带信息获取的基础上,针对水田作业环境设计了一种基于线性自抗扰的对行液压控制系统。采用内、外滑梁结构,实现对行执行机构对除草部件作业路径的避苗调控。应用Amesim与Matlab联合仿真方法,构建了对行液压控制系统仿真平台,分别对线性自抗扰算法和PID算法进行了控制器设计及仿真比较,仿真结果表明:在加入扰动情况下,线性自抗扰控制系统达到期望的对行调控时间比PID减少0.1s,且抗干扰性及鲁棒性均优于PID控制算法。田间试验结果表明:行进速度和作业深度对伤苗率影响显著,最优作业参数组合为行进速度0.5 m/s,调节间距60 cm,作业深度20 cm,此时伤苗率为3.6%;性能比较试验表明:有对行控制系统的平均伤苗率为3.9%,没有对行系统控制的伤苗率为18.6%。该系控制统满足机械除草对行控制的要求,可为水田作业环境下的精准控制问题提供借鉴。     

用优化方法求韦布尔参数的最优估计

在求解韦布尔参数的图解法基础上，提出了通过线性拟合与一维优化来求解韦布尔参数的新方法，理论上其求解结果应为韦布尔参数的最优估计，实例计算结果表明其求解精度较图解法大为提高。此方法对零件的可靠性设计与寿命预估很有参考价值     

智能化田间土壤水分测定仪的研制

该在简要的介绍了笔研制的土壤水分传感器的基础上，着重介绍以单片微机为基础，适用于田间野外工作的智能化土壤水分测定仪的软硬件及特点。     

深松旋耕组合作业机的研制与试验研究

根据国内中等功率拖拉机配套农机具的研究现状，以机组匹配理论为依据，研制了与中型拖拉机配套的深松旋耕组合作业机，并进行了单独深松、单独旋耕和组合工况的试验。试验表明所研制的机具在作业时能充分发挥拖拉机的动力性，减少拖拉机的功率消耗。机具配置的深松铲和旋耕刀片排列合理，深松扰动影响宽度和旋耕宽度相匹配，作业时波动范围较小，偏牵矩对拖拉机方向的稳定性基本没有影响。机具的研制也为与大功率拖拉机配套新型农机具的开发提供了借鉴。     

黄河中游地区机械修梯田机具研制及配套作业试验研究

根据现有梯田施工机具性能和黄土区修梯田作业特点,在协作试验研究中,进行了推土机改装和八字松推铲等铲刀的研制,改进了推土机的作业性能;研制的铲抛机、破冻土机和液压翻转犁等,可分别用于连续横向抛土、冬季揭冻层和往返向下翻土修梯田。在梯田施工机具中,侧向连续运土机具较正向运土机具工效高,但对地面起伏的仿形性强。机组配套联合作业试验表明,不同机具相互配合、扬长避短,可提高综合施工工效。     

玉米去雄机去雄作业控制系统设计与试验

为推动中国玉米制种去雄机械化的进程,针对中国农业大学协助研制的去雄机,该文设计了一套包括主控板、显示屏和控制面板的去雄作业控制系统。系统可通过按钮操作实现去雄机构高度的手动调整,也可通过玉米穗高度信息的采集,控制算法的推导实现去雄机构高度的自动调整。系统控制参数由去雄机构的运动分析、车辆的作业车速和液压系统特性获得,并通过显示屏进行设置和显示。田间试验结果表明:去雄机安装本系统进行去雄作业,去雄效率是人工的18倍,去雄率达到96.16%,且去雄误差小于5%,满足去雄作业要求。该系统的设计为玉米去雄机的研制提供参考。     

智能地面测温仪的研制

用热电偶、热敏电阻组成的地面温度测量探头,运用先进的微机技术进行自动采样处理,进行了地面温度的观测、对比试验和理论计算的探讨。研究结果表明:该系统灵敏度高,测量精度高和资料代表性优越,能够满足地面温度的观测要求。微机系统具有较好的实用性和改进性。理论研究表明:智能地面测温仪,其测量资料能够代表地面的温度状况,因而可以认为该食品的研制是具有理论基础的,并为它的实际应用提供了可行性论证。     

农业物料力学—流变学性质测试系统的研究

研制了一个完整物料力学性质测试系统；设计了微机测试处理系统软件；能进行力—变形关系、应力松弛、蠕变等各类性质测试；具有拉伸、压缩、剪切、弯曲等试验功能，力—变形数据经传感器转化为电压量经过Ａ／Ｄ模数转换输入电子计算机，进行数据采集，绘出力、变形、时间关系曲线，通过微机测试软件进行数据处理，获得必要的力学性质参数信息。     

水平摘锭式采棉机采摘头传动系统优化与试验

为了提高水平摘锭式采棉机的作业效率,针对国产采棉机在高速作业过程中存在采摘速比系数匹配不当、采摘头传动系统不合理的问题,该研究根据水平摘锭式采棉机采摘头结构与工作原理,对采摘头传动系统、采棉机采摘机理进行分析,根据传动系统传动要求和采棉机采摘条件,建立目标函数与约束条件,运用遗传算法和1stOpt软件对采摘头传动系统进行优化分析。优化结果为:滚筒动力齿轮齿数为72,离合器上齿轮变位系数为-0.14,滚筒动力齿轮变位系数为1.208,齿轮顶隙系数为1.25。结合采棉机作业要求搭建棉花采摘性能试验台,选取采摘滚筒转速113～143 r/min、作业速度5.93～7.20km/h,对优化前后采摘头的作业性能进行验证试验。结果表明:优化后的采摘头作业速度由6.4km/h提升至7.2 km/h,工作效率由4.86 hm~2/h提升至5.47 hm~2/h,提高了12.5%;优化后的采摘头在7.2 km/h的作业速度下,采净率由90.4%提升至93.7%,采净率提高了3.6%,含杂率由10.28%降至9.72%,含杂率降低了5.4%,验证了传动系统优化结果的合理性。该研究可为国产采棉机采摘头的研发提供参考。     

Modeling cumulative evidence for freedom from disease with applications to BSE surveillance trials

This investigation deals with the question of when a particular population can be considered to be disease-free. The motivation is the case of BSE where specific birth cohorts may present distinct disease-free subpopulations. The specific objective is to develop a statistical approach suitable for documenting freedom of disease, in particular, freedom from BSE in birth cohorts. The approach is based upon a geometric waiting time distribution for the occurrence of positive surveillance results and formalizes the relationship between design prevalence, cumulative sample size and statistical power. The simple geometric waiting time model is further modified to account for the diagnostic sensitivity and specificity associated with the detection of disease. This is exemplified for BSE using two different models for the diagnostic sensitivity. The model is furthermore modified in such a way that a set of different values for the design prevalence in the surveillance streams can be accommodated (prevalence heterogeneity) and a general expression for the power function is developed. For illustration, numerical results for BSE suggest that currently (data status September 2004) a birth cohort of Danish cattle born after March 1999 is free from BSE with probability (power) of 0.8746 or 0.8509, depending on the choice of a model for the diagnostic sensitivity.     

智能化稻麦考种自动测试仪

本文叙述了智能化稻麦考种自动测试仪的系统原理结构和微机处理框图及程序。该微机系统由四个部分组成:计数;计重;测长及由8031单片微机组成的控制和数据处理部分。其中计数是采用光电原理,并有清杂扬谷功能。称重传感器是采用压敏控制器,计长则采用光栅和光电脉冲的采样部件。数据处理的功能是将采集到的大量数据进行处理,计算总和、均值及预测谷物的亩产等。其检测结果均由打印或数码显示输出。     

玉米氮高效品种的生物学特征

提高氮肥利用率依赖于氮肥优化管理及作物氮素营养效率的遗传改良。本文分析了作物氮高效的定义,并以玉米为例,分析了氮高效的生物学机制,提出了玉米氮高效品种的生物学特征。本文认为,玉米氮高效品种的生物学特征为:(1)在开花前,维持稳定的氮吸收,并将所吸收的氮素高效利用于穗的发育,提高小花结实率,为产量形成过程中的碳、氮积累提供较大的库;根系生长发育能力强,能建成较大的根系,以满足籽粒生长期氮素吸收的要求;有较强的叶片扩展能力,保持较大的叶面积。(2)在开花后,充分利用前期建成的根系,高效吸收土壤中的矿化氮,用于籽粒生长所需,从而减少叶片中氮素的输出,减缓叶片衰老(保绿性强),维持叶片较高的光合效率,为籽粒灌浆提供碳化合物。因此,在氮高效育种中,应注重穗部性状(大穗,结实能力强)、根系性状(发达的根系,功能期长)与叶片性状(保绿性好)的结合。     

Gas chromatographic determination of pentachlorophenol in gelatin

A method is described for the determination of pentachlorophenol (PCP) in gelatin. The method employs acid and heat to hydrolyze the gelatin matrix, a base partition and wash for separation and cleanup, and a reacidification and extraction with hexane for direct determination of PCP, without preparation of a derivative, using gas chromatography (GC) with a 1% SP- 124ODA liquid phase and a 63Ni electron capture detector. Recoveries averaged 106% for fortifications between 0.02 and 1.0 ppm. The limit of quantitation is 20 ppb. The limit of detection is 4-6 ppb. The method, which has undergone a successful intralaboratory trial, is simple and rapid, and requires only general laboratory reagents and equipment. GC of the acetate derivative of PCP is used for confirmation of identity.     

A Varying Coefficients Model For Estimating Finite Population Totals: A Hierarchical Bayesian Approach

In some finite sampling situations, there is a primary variable that is sampled, and there are measurements on covariates for the entire population. A Bayesian hierarchical model for estimating totals for finite populations is proposed. A nonparametric linear model is assumed to explain the relationship between the dependent variable of interest and covariates. The regression coefficients in the linear model are allowed to vary as a function of a subset of covariates nonparametrically based on B-splines. The generality of this approach makes it robust and applicable to data collected using a variety of sampling techniques, provided the sample is representative of the finite population. A simulation study is carried out to evaluate the performance of the proposed model for the estimation of the population total. Results indicate accurate estimation of population totals using the approach. The modeling approach is used to estimate the total production of avocado for a large group of groves in Mexico.     

Project ‘Telma’: A scientific framework for conserving the world's peatlands

The world's peat resources are diminishing rapidly—a fact that is causing anxiety in some countries. Project ‘Telma’, initiated by IUCN and IBP, is concerned with international cooperation in the conservation of peatlands (mires). Because peatlands play a key rôle in certain biogeochemical cycles (especially the hydrological and carbon cycles), interest is being expressed in the part they may have in maintaining ecological balance in some regions, and thus in the need for a conservation policy for peatlands. But further research is required on this function of peatlands. However, the scientific argument for conserving them is more definitive and is largely based on the fact that they comprise an important source of ecological information. Some of the diversity and intrinsic importance of this information is demonstrated by studies of the European sub-group of boreal mires. The Telma classification was devised as a framework for gathering information for preparing lists of sites of international significance for science and education.     

DPTIMAL INTERPOLATION AND ISARITHMIC MAPPING OF SOIL PROPERTIES. IV SAMPLING STRATEGY

A sampling strategy is presented for soil survey in which an individual soil property is of interest and can be measured. It depends on first determining accurately the semi-variogram for the property, and this must be done in a prior reconnaissance stage of a survey. Then from the semi-variogram estimation variances can be found for any combination of block size and sampling density by the methods of kriging. Alternatively for a given block size the sampling density needed to achieve a predetermined precision (maximum estimation variance) can be determined. The strategy is optimal in the sense that the sampling effort is the least possible to achieve the precision desired. An equilateral triangular configuration of sampling points is best where variation is isotropic, but a square grid at the same density is very nearly as good, and will usually be preferred for convenience. Where there is simple anisotropic variation optimal sampling is achieved by choosing a rectangular grid with sides in the same proportion to one another as the slopes of the semi-variogram in the directions of maximum and minimum variation.     

Rapid multipoint method for quantification of various physiological groups of bacteria in soil

A modified multipoint method for enumeration of bacteria capable of various biochemical degradation reactions in soil is described. The method is a combination of multipoint inoculation of a dilution series and the most probable number (MPN) technique. Five serial soil dilutions are prepared and inoculated directly on plates containing different substrates. Five replicates of a constant amount of each dilution are transferred with a multipoint inoculator to plates suitable for visualization of the physiological groups involved. At least five replicate plates of each substrate are recommended. Degradation zones at the inoculation sites are scored, and a MPN method is used for enumeration of the bacterial groups in question. A MPN table is provided for the dilution series used. The inoculation method is rapid, allowing the same soil sample to be plated on many different substrates in a short time. The use of plates instead of tubes simplifies the method and allows long incubation periods, and only one plate is required for 25 inoculation sites. For comparison, a general isolation technique for evaluation of various physiological groups of bacteria in soil was conducted.     

水土严重流失的黄土丘陵区建立良性农业生态模式的探讨

长期来,由于建设方针上的失误,人口猛增,植被稀少,土壤瘠薄,“三料”俱缺,造成固原县水土流失相当严重,人民生活非常贫困。固原县经过1983—1985年的土地结构合理调整,生产力有较大提高,粮食产量明显增加,水土流失大幅度减少,群众收入净增两倍。结合全县的综合治理工作,确定了今后农林牧优化用地比例为1:1:3,农田中粮食作物、经济作物和牧草用地比例为5:1:2。建立良性农业生态模式的关键一环,是建立起一个合理高效的农林牧生态经济结构,孤立地就水土保持抓水土保持,解决不了这样一个全局性的问题。     

潋水流域产水产沙自然过程的计算机模拟 Ⅱ.模拟结果与分析

叙述了潋水河流域产水量、产沙量等自然过程的模拟结果，分析了它们的时间变化、空间分布与模拟精度。模拟初始有个热身（warm up）阶段，特别是对产沙量的模拟。模拟精度随模拟年份增长而降低：年模拟精度产水量3年平均为98．32％；8年平均为90．27％。产沙量2年平均为88．83％；8年平为82．51％。模拟年份长到7～8年后，结果趋于稳定。表明此方法可用于流域产水产沙量的中长期年际动态监测。至于月平均模拟精度，产水量3年为83．84％，8年为86．05％；产沙量3年为68．80％，8年为59．70％。此方法的模拟结果也可应用于流域自然资源管理。