农业物料细观力学研究进展及农产品加工中的应用

农业物料细观力学性质的研究为宏观力学在农业工程中的应用奠定了基础,为设计农产品加工机械、农业生产系统装备、检测系统设计等方面的应用提供了理论支持。通过对有限元法、解析细胞模型和图像处理技术等方法解决农业物料细观力学问题的研究进展进行分析,较为全面地综述了农业物料细观力学的研究现状、发展趋势和解决农产品加工实际问题的应用概况,旨在为研究运用农业物料细观力学提供参考。     

农业物料电磁特性的研究与应用

综述了目前国内外对于农业物料电磁特性的研究与应用情况。介绍了高压脉冲电场的应用及其试验装置的设计,并对静电技术和等离子体技术在农业工程领域中的应用作了较为详尽的阐述,在对磁处理种子和磁化水的作用机理进行分析的基础上,着重对相关试验装置的设计进行了介绍。提出了今后在农产品加工等领域的研究重点和发展方向。     

茶叶抖筛设备筛分数学模型的讨论

茶叶抖筛设备是筛分机械中的一种。多年来,茶叶抖筛设备的设计与研制都以筛分数学模型为主要指导原理。筛分作业在散体物料处理工艺中具有极其重要的地位,筛面上细粒及条状物料的透筛过程以概率论的原理为基础。茶叶筛分过程是一个复杂的物料透筛过程。运用筛分数学模型和力学模型去分析茶叶筛分的实质,对今后茶叶抖筛设备的研制有很大的指导意义。     

渐变刚度钢板弹簧建模方法对比

为更好地分析钢板弹簧刚度特性,对钢板弹簧建模方法进行了对比研究。依据钢板弹簧国家标准GB/T 19844-2005,针对某型渐变刚度钢板弹簧分别在有限元软件Hypermesh和多体动力学软件Adams中建立其有限元模型和离散梁模型,并进行了仿真,得到刚度特性。将仿真结果与试验值进行了比较。结果表明,在针对该钢板弹簧的刚度分析中,运用离散梁法得到的刚度特性更加接近试验值。     

黑龙江农业可持续发展系统动力学模型仿真

为实现黑龙江省农业可持续性发展,运用复杂系统的观点研究分析了农业发展的特点,将黑龙江农业发展系统划分为农业经济、农业技术、农村社会、农业环境4个子系统。在此基础上,通过分析各子系统间的关联及影响机理,利用Vensim DSS软件及《黑龙江省统计年鉴》等历史数据,经过参数估计及有效性检验,从而建立并完善了黑龙江农业可持续发展的系统动力学模型。然后对黑龙江省2005—2020年农业各子系统发展的可持续性进行仿真模拟与预测。结果发现黑龙江省的农业经济可持续度发展最好,农业技术次之,农业社会与生态环境可持续性最差。     

农业物料介电特性的测试及影响

在进行农业物料相关品质检测与加工时,往往需要测定其许多参数,其中介电特性随物料种类的不同而体现出差异性,可以根据这一特性对不同物料的物性进行表达。此外,同种物料本身的介电特性又与许多因素有关,利用影响因素与介电特性的相关性,可以对物料的品质因素进行判定,对加工过程进行实时监测和优化控制。综述分析了国内外农业物料介电特性的相关研究,介绍了生物电学模型及介电特性的各种测试方法,并概括了各种测试方法的优缺点,总结了不同方法的适用条件以及受约因素。综述农业物料(特别是果蔬)的介电特性受到电磁场参数、温度、物料外形参数以及水和离子行为的影响,为研究果蔬介电特性在果蔬干燥、保鲜、品质检测等方面的应用提供参考。     

DSSAT模型在中国农业与气候变化领域应用进展

为了掌握农业转移支持决策系统(Decision Support System for Agrotechnology Transfer, DSSAT)模型在国内农业与气候变化领域的研究进展,更好地让模型在今后气候变化对农业生产影响评估和适应研究中应用,本文以近年来国内的研究和实践为基础,通过梳理模型应用的相关研究案例、方法和成果,从DSSAT 模型本地化适用性验证、数据库构建、参数订正和优化方案、气候变化影响评估及适应的应用等方面全面总结了模型的应用进展。结果表明：DSSAT模型在我国应用比较广泛,包括不同地区和不同作物之间;利用DSSAT模型研究气候变化对农业生产的影响的研究较多,研究结果比较丰富。但模型在应用中存在研究方法和结果比较分散、应用的作物种类有限、数据需求量大而实验数据有限等问题,这些都需要在今后的研究中不断完善解决。     

基于Agent技术的玉米生产管理协同决策系统研究

针对传统农业信息系统在解决分布式网络环境下的复杂决策问题的不足,利用多Agent技术智能性、交互性、协作性的优点,应用基于UML的面向Agent的系统分析方法,提出了基于Agent技术的作物生产管理协同决策系统的设计思想和实现方法,用于实现分布式环境下的作物信息共享、软件共享、协同工作和群决策支持;本文以玉米为实验对象,结合玉米生长模拟模型和玉米知识模型,实现预测功能和决策功能的有机耦合与集成。通过开发实践分析,多Agent作物协同决策模型及系统为解决农业系统复杂问题的决策提供了新的技术手段和方法,提高了作物生长预测和栽培决策的精确性。     

尾矿坝变形细观力学机理的颗粒流数值模拟

以新建四川省盐源县平川铁矿黄草坪尾矿库为工程背景,通过堆坝模型试验与室内土工试验,获得尾矿坝干滩面几何特征、颗粒分布规律及尾矿力学性质。基于离散元理论,采用PFC 2D数值模拟软件进行双轴试验,与土工试验结果对比,得到尾矿细观力学参数,并分析尾矿坝颗粒接触力分布、颗粒位移与坝体结构变形特征。结果显示：1)初期坝中颗粒间接触力较大,形成的力链大致呈45°倾斜向上;坝体尾矿颗粒接触力随着埋深的增加而增大,在基岩凸起处接触力较大且集中。2)初期坝颗粒位移不明显,堆积坝少数尾矿颗粒沿坡面向下滚动,具有较大位移;尾矿堆积坝存在较为典型的滑移面,滑移面上部区域颗粒位移较大。3)初期坝结构变化不明显,尾矿堆积坝中靠近初期坝内坡面附近结构变形显著。     

智慧农业系统让农民坐在办公室里种田

正智慧农业就是将物联网技术运用到传统农业中去,运用传感器和软件,通过移动平台或者电脑平台对农业生产进行控制,使传统农业更具"智慧"。智慧农业起源于上世纪60年代,国外相关科学家将计算机技术应用到农业领域。上世纪80年代,我国有关专家用计算机技术模拟动植物的生长过程,用数字化进行农业生产决策。但是,当时计算机的计算能力较弱,一个简单的模型进行一次运算的时间都很长,稍复杂的甚至长达一周或更久。     

Object-oriented FEM Program for Three-dimensional Convection Diffusion Problems

According to an analysis of three-dimensional convection diffusion problems and object-oriented programming method,the classes of finite element models for convection diffusion problems are designed in C++.There are vector classes,matrix classes,element classes,material classes and method classes of finite element among these classes.On the basis of these classes,an object-oriented finite element program for three-dimensional convection diffusion problems is accomplished,which is able to simulate similar problems.The program's reuse,maintenance expansion and integration with other ones are easier than traditional ones which are designed with structural language,it can be applied to a large universal computational software for science and engineering.     

填充床中细小颗粒渗流行为的DEM模拟

为进一步探索COREX过程固体物料的运动状态,对COREX过程中涉及到的细小颗粒渗流行为进行了DEM模拟。考察不同颗粒直径比、阻尼系数及滑动摩擦系数对细小颗粒渗流行为的影响,特别是计算得到不同模拟参数下细小颗粒在填充床内的运动轨迹。模拟结果显示,渗流过程中细小颗粒的平均渗流速度为一定值。随着颗粒直径比的增加,颗粒竖直方向的渗流速度逐渐减小,停留时间与径向弥散逐渐变大。随着颗粒间阻尼系数的增加,颗粒渗流速度逐渐增加,停留时间逐渐减小,径向弥散逐渐变小。滑动摩擦系数对细小颗粒的渗流行为影响较小。从细小颗粒运动轨迹分析可知,颗粒直径比变大时,细小颗粒易在空隙中缓慢移动,易趋于静止床层中,导致颗粒沉积。随着颗粒间阻尼系数变小,颗粒运动轨迹向填充床边缘发展,偏离床层中心。     

中国作物化控栽培工程技术研究进展及展望

新世纪条件下如何进一步挖掘作物产量潜力，实现作物高产、优质、高效及可持续发展，将是中国农业科技的一项长期艰巨任务。作物化控与传统栽培技术革新相互融合，产生了新型模式的栽培技术体系，即为作物化控栽培工程，它是当前农业研究中十分活跃的新领域之一，已经融入作物栽培生产各个方面。概述了作物化控栽培工程技术研究和应用的历史及进展，并强调了新世纪下发展作物化控栽培工程技术的必要性，指出作物化控栽培工程技术在中国农业发展中起到不可代替的作用，同时对作物化控栽培工程技术研究和应用作了进一步研究展望。     

Design Method for the Individual Anatomical Hip Joint Endoprosthesis

A new design method for the individual hip joint endoprostheses is proposed. By picking up the contour lines from the femur's CT images and making them closed and smoothed, a solid model of the femur is reconstructed using the contour lines by CAD software. An individual anatomical hip joint endoprosthesis is designed with the inner contour curves of the medulla cavity in CAD software. Utilizing the APDL(ANSYS Parametric Design Language) and the CT value per pixel in the CT image for developing a program through which every element of the bone can get its own material property. The finite element model's anisotropy and inhomogeneity of bone material are realized, then the endoprosthesis and the femur-stem contact finite element model can be built in ANSYS. Based on this, calculation on the contact model can be processed. It is feasible to checkout the rationality of the design by comparing the stress distribution in the femur with the situation before replacement. And the results reveal that the method is more reasonable and reliable.     

Strategies for variety-independent genetic transformation of important cereals, legumes and woody species utilizing particle bombardment

Summary The limiting component in the creation of transgenic crops has been the lack of effective means to introduce foreign genes into elite germplasm. However, the development of novel direct DNA transfer methodology, by-passing limitations imposed by Agrobacterium-host specificity and cell culture constraints, has allowed the engineering of almost all major crops, including formerly recalcitrant cereals, legumes and woody species. The creation of transgenic rice, wheat, maize, barley, oat, soybean, phaseolus, peanut, poplar, spruce, cotton and others, in an efficient and in some cases, variety-independent fashion, is a significant step towards the routine application of recombinant DNA methodology to the improvement of most important agronomic crops. In this review we will focus on key elements and advantages of particle bombardment technology in order to evaluate its impact on the accelerated commercialization of products based on agricultural biotechnology and its utility in studying basic plant developmental processes and function through transgenesis. Fundamental differences between conventional gene transfer methods, utilizing Agrobacterium vectors or protoplast/suspension cultures, and particle bombardment will be discussed in depth.     

生鲜农产品冷链物流车辆配送路径优化研究

针对生鲜农产品易变质、易腐蚀的特性,探索冷链物流配送路径的优化方法。首先通过对固定成本、运输成本、货损成本、惩罚成本和能耗成本的研究,建立了以总成本最小为目标函数的农产品冷链物流车辆配送路径优化模型,然后采用改进的蚁群算法对模型进行设计,最后通过实例分析,运用MATLAB软件编写算法程序,求解结果验证了设计的模型的合理性和可行性。     

Face Stability Analysis of Shield Tunneling in Sandy Cobble Stratum

When shield crossed the sandy cobble stratum in Chengdu metro line 1, ground subsidence reached as high as dozens of times. The losing stability of excavation face caused excessive ground loss. Conditions of engineering geology and hydrogeology about sandy cobble stratum in Chengdu were analyzed. Mechanical characteristics of sandy cobble were obtained via large-scale triaxial test. According to the low cohesion and heavily discrete characteristics of sandy cobble, numerical computation was conducted by discrete element method. Based on numerical simulation of the large scale triaxial test, the micro parameters of the sandy cobble were calibrated. The influence of support pressure on shield excavation face deformation, surface settlement, max horizontal displacement and stress of soil was analyzed. The results show that: 1) Collapse pattern of excavation face by numerical simulation coincides with result of centrifuge model test in sand. 2) When supporting pressure is small, contact forces of particle in front of excavation face is low. The tendency of particle flow is apparent. Since over-excavation is easily brought out, cavity in the ground is caused after shield tunneling. 3)Soil arching effect in shield construction is obvious. Shield excavation forms cavity in deep ground and obvious earth surface collapse is not observed. This is main reason for lagged settlement phenomena of shield tunneling in Chengdu.     

Finite Element Simulation of Inhomogeneity and Anisotropy of Proximal Femur

To solve implant's looseness and subsidence, and to adapt for the requirement of custom-made hip endoprostheses' rapid automatic design and manufacture, a new method is presented for constituting the anisotropic and inhomogeneous model of proximal femur based on CT, CAD technology and finite element analysis during design of custom-made hip endoprostheses, Raw CT image data, 3-D modeling and finite element software is utilized to set up 3-D finite element model of proximal femur. The model is provided with anisotropy and inhomogeneity by self-developed specific software. The near true proximal femur model is structured and good biomechanics condition is provided for optimize design of custom-made hip endoprostheses. For simulating and analysing of proximal femur's structrue and material mechanics property, and determining stress ,strain and response after-operation under the action of physiological load more exactly, and supplying design of custom-made hip endoprostheses with data, the method can provide biomechanics condition for optimize design of custom-made hip prostheses.     

DEM模拟解析二元混合颗粒粒径偏析分布规律

颗粒粒径偏析分布是高炉炉顶布料过程中不可避免的现象,易造成炉喉处局部料层的空隙度降低和压差升高,影响煤气流的均匀分布,继而间接影响炉况的顺行。通过DEM离散单元法模拟研究二元混合颗粒的偏析分布规律,同时,提出一个偏析指数T,用以表征粒径偏析分布的相对程度。研究结果表明：同一T值图中,相邻区域颗粒的T值相差越大,则该区域颗粒的粒径偏析程度越大;不同T值图中,所有相邻T值之差的平均绝对值越大,则颗粒堆积整体粒径偏析程度越为严重。