关于林业数学模型中参数的取值问题

针对国内林业期刊文献中普遍存在的数学模型参数取值不规范的问题，提出林业数学模型的参数取值，应遵循小数位统一和有效数统一的原则，而且有效数统一原则应该成为最高准则；同时还对与这两项原则有关的某些特定林业数表模型中参数的取值和估计问题进行讨论。     

山东农业科技期刊学术影响力分析与动态评估

利用动态评估模型对2008~2012年山东13种农业科技期刊的学术影响力进行分析。结果显示,2008~2012年中,13种农业类科技期刊的总被引频次和影响因子总体呈上升趋势,5年间,平均总被引频次增加了84.85%,平均影响因子增加了47.35%;平均学术影响力呈快速增长趋势,5年间增长了268%。各期刊发展不均衡,其中,《山东农业科学》和《中国烟草科学》学术影响力分别位居第一和第二,且发展态势良好。     

Design and Experiment of Slave Computer Control System for Applying Variable-rate Liquid Fertilizer

In order to increase the applying rate of liquid fertilizer and reduce environmental pollution, a slave computer control system for applying variable-rate liquid fertilizer was designed. The system used SMC as core processor and electrically controlled pressure regulator as execution component. The characteristic equation of the system was obtained by using classical control theory. Results indicated that the characteristic equation met the requirements of routh-criterion, which indicated the working process of the system was stable. Performance of the slave computer was verified via bench tests. Results demonstrated that there was no significant influence on the response from interclass error. The fertilization error was less than 0.9, and the fertilization accuracy was larger than 97%. The liquid fertilizer emitted by the fertilizing devices had no significant difference in uniformity, which met the demands of the slave computer control system for applying variable-rate liquid fertilizer.     

Comparison of dietary essential amino acid requirements determined from group‐housed versus individually‐housed juvenile bluegill,Lepomis macrochirus

Two 60‐day experiments were conducted sequentially to determine (i) lysine requirement of juvenile bluegill, Lepomis macrochirus based on the dose–response method, (ii) requirements for other essential amino acids (EAAs) using whole‐body amino acid profile and (iii) whether differences in growth rates of group‐housed versus individually‐housed bluegills lead to different lysine requirement levels because of the presence and absence, respectively, of social hierarchies. Seven, semi‐purified, experimental diets (isonitrogenous, isocaloric) were prepared to contain graded levels of digestible lysine (10–31 g kg⁻¹). Experiment‐1 involved group‐housed bluegills (approximately 27 g, n = 10 fish/chamber, 4 chambers/diet) whereas experiment‐2 involved individually‐housed bluegills (approximately 30 g, n = 1 fish/chamber, 14 chambers/diet). Fish were fed twice daily to apparent satiation. Bluegill growth responses in both experiments generally improved (P < 0.05, anova ) with increasing dietary lysine levels from 10 to 16 g kg⁻¹, and then levelled off with further increase in lysine level (P > 0.05). Optimal dietary lysine level (digestible basis) was estimated to be 15 g kg⁻¹ based on broken‐line regression analyses of relative growth rate and feed conversion ratio with no differences being observed between the two rearing methods. Determined dietary requirement levels for other EAAs ranged from 2.4 g kg⁻¹ (tryptophan) to 15.3 g kg⁻¹ (leucine).     

保健食品中原花青素测定的不确定度评定

对保健食品中原花青素的测定进行不确定度的评定,建立不确定度评定程序和方法。依据《保健食品检验与评价技术规范》建立数学模型,进行不确定度的计算并合成不确定度。找出了影响保健食品中原花青素测定的主要因素,分析归纳了不确定度分量的主要来源。评定程序和方法符合规范要求,适用于同类型试验不确定度评定。     

食用菌产品线下体验线上销售新模式应用探究

基于O2O与电子商务的理论背景,分析了线下体验线上销售模式应用于食用菌产品运营中的可行性,运用SWOT方法分析了该方法的优势、劣势、机会和威胁,构建了食用菌产品线下体验线上销售平台,并从财务成本管理的角度对该模式的成本与盈利进行了简要分析。结果表明,线下体验线上销售模式的应用会使得企业内部成本控制得到进一步优化,能降低促销成本,改变企业的分销战略,增加企业的营业外收入,降低交易成本。     

农村土地流转信托化的法律机制构建

从法律层面厘清了土地流转信托的概念,明晰了土地流转信托委托人、信托人及受益人的权利与义务,分析了我国土地流转信托在实践中存在的问题,如委托人权利缺乏维护,受托人过失缺乏追究,受益人权利缺乏保障,信托财产缺乏独立性,政府角色缺乏公立性,金融信贷缺乏畅通性。对此,提出了构建土地流转信托机制的设想:单独制定农村土地流转信托法律法规,加快土地流转信托确权登记颁证制度,强化政府的宏观调控职能,建立土地流转信托基金,加强金融合作,推行农村土地信托责任保险。     

凸齿镇压器作业过程的运动学与动力学分析

[目的]基于理论推导建立凸齿镇压器作业过程中的运动学和动力学模型。[方法]根据运动学中刚体做平面运动的瞬心定理和牵连运动为平动时质点的加速度合成定理,建立凸齿镇压器在不同工作阶段的运动参数模型;根据动力学中的动量定理、动能定理和冲量定理,建立凸齿镇压器工作状态中所需牵引力、凸齿与地面作用瞬间产生的冲击力和冲击能的参数模型。[结果]凸齿镇压器作业过程中所需的牵引力随着凸齿镇压器的自身质量和滚动阻力系数的增加而增大,而凸齿镇压器转动惯量的增加会降低凸齿镇压器所需牵引力;冲击过程中,凸齿镇压器的牵引速度越大、质量和转动惯量越大、冲击时间越短,则冲击力越大;凸齿镇压器冲击土壤时的冲击能随着凸齿的转动惯量、质量和质心竖直向下移动距离的提高而增加,而随土壤的弹性系数与土壤的塑性变形量的增加而减小。[结论]建立了凸齿镇压器在不同工作状态下运动学及动力学模型,分析并揭示了凸齿镇压器结构参数与运动参数间的相互联系,探索了凸齿镇压器冲击土壤的特征规律,为设计和优化其结构参数和运动参数提供了理论依据。     

Mapping soil salinity and pH across an estuarine and alluvial plain using electromagnetic and digital elevation model data

Increasing pressures from agriculture and urbanization have resulted in drainage of many floodplains along the eastern Australian coastline, which are underlain by sulphidic sediments, to lower water tables and reduce soil salinity. This leads to oxidation of the sediments with a rapid decline in pH and an increase in salinity. Accurately mapping soil salinity and pH in coastal acid sulphate soil (CASS) landscapes is therefore important. One required map is the extent of highly acidic (i.e. pH < 4.5) areas, so that the application of alkaline amendments (e.g. lime) to neutralize the acid produced can be specifically targeted to the variation in pH. One approach is to use digital soil mapping (DSM) using ancillary information, such as an EM38, digital elevation models (DEM – elevation) and trend surface parameters (east and north). We used an EM38 in the horizontal (EM38h) and vertical (EM38v) modes together with elevation data to develop multiple linear regressions (MLR) for predicting EC_1:5 and pH. For pH, best results were achieved when the EM38 EC_a data were log‐transformed. By comparing MLR models using REML analysis, we found that using all ancillary data was optimal for mapping EC_1:5, whereas the best predictors for pH were north, log‐EM38v and elevation. Using residual maximum likelihood (REML), the final EC_1:5 and pH maps produced were consistent with previously defined soil landscape units, particularly CASS. The DSM approach used is amenable for mapping saline soils and identifying areas requiring the application of lime to manage acidic soil conditions in CASS landscape.     

基于Lasso和支持向量机的组合预测及其应用

针对Lasso方法与支持向量机两者的联系与各自的优势，给出了基于Lasso与支持向量机的串联型、并联型和嵌入型三种组合预测，并将它们运用到我国粮食价格预测中.实证结果表明，与单一预测方法的预测结果相比，基于Lasso方法与支持向量机的串联型组合预测和嵌入型组合预测具有更高的预测精度.