Application of Meshless Method in Dynamic Mechanics

As a new type of meshless method which has appeared in recent years, the Reproducing Kernel Particle Method has such meshless features as the need for nodes only without classified units, and is advantageous in the process of calculation. The present study introduces the Reproducing Kernel Particle Method and applies it to the research of nonlinear dynamic mechanics. The dynamic process involves different kinds of nonlinearity. The study assumes that deformation of dynamic analysis belongs to small one and that the material nonlinearity has been taken into account. When under small strain, the increment constitutive law and the total Lagrangian model of calculation are adopted to deduce the dynamic control equation by the Reproducing Kernel Particle Method. The instances of calculation demonstrate that this method is effective in the analysis of dynamic problems.     

Exact Integration of Biharmonic Equation In Boundary Element Method

The boundary integral in Boundary Element Method effects the precision and the speed of the method. The boundary integrals are composed of the normal integrals and singular integrals. The normal integrals are popularly calculated by exact integral, and the singular integrals by the Gauss numerical integral. The singular integrals are low in precision when the source points approach the element. This paper presents an alternative way to transform the double integral in Biharmonic Equation on 3-d into the linear integrals on the boundary of each subdomain, so that all the singular integrals and nonsingular integrals are calculated by analytical method. It makes the precision and the speed of BEM improve.     

A Non-overlapping Domain Decomposition Method for Scattering Problems

In this paper, a domain decomposition method for the exterior Helmholtz problem is investigated. The unboundary domain is divided into some non overlapping subdomains. The natural integral operator is used as the artificial boundary conditions on the exterior boundary of the computational domains. The convergence of the algorithm is given in the sense of energy norm. Finally, the discrete problem is discussed and some numerical examples are presented.     

The Convergence of a 2-Block AOR Method for Large-Scaled Least-Square Problems

A necessary and sufficient condition and some sufficient conditions concerning the convergence of a 2-block AOR method for large-scaled least-square problems are given. It is shown that, by appropriately selecting parameters, the 2-block AOR method is always convergent and the theorem in [3] is only a corollary of this paper.     

A Finite Element Method for Quasi Static Problems of Two phase Porous Media

For the quasi static problems of two phase porous media,the velocity variable of fluid phase can be eliminated as the viscosity of fluid is neglected.The corresponding governing equations,with displacement of solid phase and pore pressure as basic variables,as well as the boundary and initial conditions are given out.Finally a mixed finite element formula with u S-p variables is obtained with weighted residual method.This method has lesser nodal variables and higher accuracy of pressure distribution.     

Mixed Finite Element Method for Dynamic Problems of Fluid Saturated Biphasic Porous Media

Based on the fluid saturated biphasic porous media model deduced from mixture theory,a finite element formulation with u S u F p variables for dynamic response analysis is given out.This method overcomes the difficulty of choosing suitable penalty parameter in penalty finite element method,and the accuracy of pressure distribution obtained with the mixed finite element method is higher than the penalty finile element method.An iterative solution method is suggested to solve the system of equations whose coefficient matrices are non positive definite.It is concluded from patch test that the order of interpolation function for pressure variables must be higher than that of displacement variables of solid phase.     

甘蓝型油菜黄籽双低隐性核不育两系86AB的选育

通过以油研10号(82278 A×942 R)F1为基础,采用自交、测交的方法,并经连续夏繁加代选择,历经5年7代的选育于2003年育成稳定了甘蓝型油菜黄籽双低隐性细胞核雄性不育两型系86 AB.其芥酸均在1％以下,硫甙20.6～26.8 μmol/g,含油量46.6％ ～49.3％,种子蛋白质23.7％～25.1％.黄籽株率分别平均为98.9％,色级(粒色指数)在3.28 ～3.58之间,平均色级为3.5.全生育期在210 d左右,不育系株高适中,分枝多,分枝位较低,不育株天然结荚结实好,抗倒性强,在海拔386m的塘头地区10月上旬播种,密度8000株/667 m2的情况下,株高186.3 cm,一次分枝高度47.6 cm,一次分技数9.8个,单株有效角586.4角,角长5.3 cm,角粒数18.8粒,千粒重3.6g,单株产量25.1g.以该不育系组配的优质杂交油菜新组合NR 168于2006～2009年完成了贵州省预备区试、区试和生产试验,于2009年通过贵州省农作物品种审定委员会审定,命名为益油1号.     

Application of Symmetric Galerkin Boundary Element Method in Limit Analysis of Plane Problems

Based on Melan's theorem, the symmetric Galerkin boundary element method (SGBEM) is used to discretize two dimensional structures and a computational formulation of structural limit analysis is established. The self equilibrium stress field is constructed by linear combination of several basic vectors, which are the stress differences between different iteration steps at the same increment using the traditional elastoplastic incremental method. Then the complex method is used to solve the nonlinear programming directly, so that the lower bound load multiplier of two dimensional structures is obtained. The validation of the present method has been confirmed by some numerical examples.     

Several Problems About Analyses of Finite Element Method on Coalbed Gas Seepage Flow

Based on the govering equation of gas seepage flow,this paper an alyzes;the re-lationship of the underground pressure and permeability of coal seams,discusses the averagedly dis-crete metheds of small terms of time variable which is related to mining progress of coal seams,and set up the element property form ulation on the basis of the weak statement of Galerk in integral e-quation.     

Constitutive Equations for Thermo-mechanical Coupling Problems

The conflict events that occurred in construction engineering project(CEP) bring about a lot of adverse influence on project implementation.Furthermore,there is a limitation for five modes used to deal with the conflicts in favor of the project management,which is proved by the practice.On the basis of investigation,the authors bring to light the multi-attributive characteristics of the conflict events through clustering analysis,and put forward a new concept as co-adaptability aiming at solving the conflict events in CEP,and building up a new project management mechanism based on the new concept and a new mode to deal with the conflict events based on the whole project benefit.So,this research offers not only a new idea but also a new method of solving conflict events in CEP.     

The BEM for Elliptic Unilateral Problems

Unilateral problems is a kind of important partial differential problems. It can be solved by treating it as a complementary problem. As the complementary conditions lie in the boundary of the region,it is suitable for BEM. This paper is based on the switching algorithm,which is first used by J. M. Aitchison for the Signorini Problems of Laplace operator,then extends it to the elliptic operator,and conjunct it with the BEM. At last the detail of the algorithm is given. The new algorithm is easy to be implied effectively and quickly. It only needs the minimal change of the BEM programming. The numerical tests show the algorithm is effective and conventional.     

Problems involved in breeding for resistance

At the start of a breeding programme mostly a cross is made between the resistant plant and a plant belonging to a commercial variety of the crop in question. If both belong to the same species the exchange of genes can be easily brought about. If, however, the resistance is present only in other more distantly related species, difficulties mostly arise.In consequence of successful breeding work races of the parasite able to break down the resistance can come to the fore. It is of the utmost importance to combine the genes for resistance from all available sources so as to produce barriers that cannot be broken down or at least only with great difficulty. Therefore not only the easy line of intraspecific crossing should be followed but also the much more difficult one of interspecific and even of intergeneric crossing.As in most cases resistance is dominant, the method of repeated backcrossing can be used with great profit. In each step of the backcross programme large numbers of seedlings should be raised, selecting very carefully the parent material that will be used for the next step, even if this selection takes several years. As a consequence the number of subsequent backcrosses can be restricted and the danger of loss of valuable genes for resistance and for other characters is very much reduced.If resistance is recessive the backcross method cannot be applied to its full extent. The F₁ is susceptible and by inbreeding more or less resistant seedlings can be obtained. If the resistant source is a wild species this program of outbreeding followed by inbreeding has to be repeated and progress will be very slow.A point of major importance is the availability of quick methods for mass-testing. These methods need not be more reliable than is demanded by the kind of material that has to be tested.

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Samenvatting Bij de uitvoering van een kweekprogramma wordt altijd begonnen met het kruisen van de resistence plant met een plant uit het ras dat men wil verbeteren.Als beide planten tot dezelfde soort behoren kan de uitwisseling van genen gemakkelijk worden bewerkstelligd. Indien de resistentie echter alleen in andere meer of minder verwante soorten voorkomt, dan treden gewoonlijk complicaties op.Als gevolg van de verbouw van resistente rassen zijn fysio's van de parasiet, welke de resistentie kunnen doorbreken, in staat zich naar verhouding sterk te vermeerderen. Het is daarom van het grootste belang de resistentie-genen uit alle beschikbare bronnen te combineren, teneinde een barrière op te kunnen werpen die niet of slechts met grote moeite te doorbreken is. Men moet derhalve niet alleen de gemakkelijke weg van de raskruising volgen maar ook de veel moeilijker weg van de soortskruising en zelfs die van de geslachtskruising, teneinde ook die genen in het werk te betrekken die buiten de soort voorkomen.Daar de resistentie in de meeste gevallen dominant is kan de methode van de herhaalde terugkruising met voordeel worden toegepast.Bij iedere volgende stap in het terugkruisingsschema moeten grote aantallen zaailingen worden opgekweekt, terwijl het toekomstige oudermateriaal met grote zorg moet worden uitgezocht. Daardoor kan het aantal terugkruisingen worden beperkt en tevens het gevaar voor verlies van waardevolle genen.Als de resistentie recessief overerft kan de methode van de herhaalde terugkruising niet in volle omvang worden toegepast. De F₁ is vatbaar en door inteelt kunnen meer of minder resistente zaailingen worden verkregen. Als de bron van resistentie een wilde soort is dan moet dit programma van kruisen gevolgd door inteelt worden herhaald en zal er slechts langzaam vooruitgang optreden.Van veel belang is de mogelijkheid snelle methoden voor massale toetsing te ontwikkelen. Deze methoden behoeven niet betrouwbaarder te zijn dan door de aard van het te toetsen materiaal wordt geëist.

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Lecture read at the A-course Resistance in agriculture, 12–14 Jan. 1959, organised by the Royal Society of Agricultural Science and the Netherlands Society of Graduates in Agriculture at Wageningen.     

新品种展示工作存在的问题及对策

为了加快新审定品种的宣传和推广力度,延长其使用期,使其尽快转化为现实生产力,适应种植业结构调整的需要,推进育、繁、推一体化的进程,2001年全国农业技术推广中心在各地安排     

葡萄套袋中存在的问题与解决途径

在葡萄栽培生产中,对果穗进行套袋、实施物理隔离,可有效地降低农药等有害物质的残留和污染,改善和提高果品的外观品质,这项措施已成为一些主要葡萄品种(如红地球等)必不可少的栽培技术环节.但是葡萄果实套袋,由于起步晚、时间短,其应用过程中表现为"应用在先,研究滞后".因而,在果实袋销售市场中适宜各生产区的系列果袋少,低劣质袋充斥市场、配套技术缺乏,不合理使用套袋给果农带来损失的事件屡屡发生.为此,总结葡萄套袋中存在的问题、探索其解决途径,是当前葡萄生产中为贮藏保鲜做前期准备亟待解决的问题.     

水稻生产中的农田生态问题与可持续发展对策

从农田生态系统整体出发,分析水稻生产中的农田生态问题,并重点就水资源短缺、旱涝灾害日趋频繁,生物多样性减少、病虫暴发频率上升,化肥农药利用率低、化学品污染严重等问题,提出了建生态化农田、设生态化布局、行生态化栽培等水稻可持续生产对策。     

Problems for Township Construction Teams and Their Countermeasures

Under the condition of urbanization, the advantages and inferior positions that existed in town and township construction teams compared with those for city construction enterprises and serious problems the town and township construction teams faced with are discussed. The authors suggest some methods to solve these problems.     

Pyramidal Central Configurations for Spatial 5-Body Problems

In this paper,classifications are studied for all pyramidal central configurations with a regular trapezoid base.In fact,there are two such central configurations that the base is a regular trapezoid.From the results it is easy to obtain the classfications of pyramidal central configurations with rectangular base.     

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.     

凝固型酸乳常见问题的原因分析及控制措施

分析了凝固型酸乳常见质量问题的原因,并提出了相应的控制措施。