必要条件

The necessary conditions for a ternary alloy phase to form in nanometer powders are that the components can compound or solid solute each other,and there is a proper composition range for the master alloy.

三种组元间能够相互化合或固溶是在纳米粉末中形成三元化合物相的必要条件。此外，母合金的成分范围还必须合适。

This paper discusses singularities, inflection points and convexity of FB-spline curves in terms of their control polygons, and gives the necessary and sufficient conditions for testing when FB-spline curves have one or two inflection points, or a cusp, or a loop, or none of the above points by the envelope theory and the topological mapping method.

文章利用包络理论和拓扑映射的方法，讨论了FB-样条曲线的奇拐点和曲线性质，并给出了依据控制多边形判断FB-样条曲线出现1个或2个拐点、1个尖点、1个二重点以及处处为凸的充分必要条件；最后给出了FB-样条曲线的奇点、拐点以及二重点在λ-μ平面上的分布图。

In this paper the equivalent of the various topologies on the closed setlattice of a topological space is investigated a sufficient and necessary condition for their equivalent is given.

本文对拓扑空间闭集格上的各种拓扑的等价性进行了研究，得到了它们等价的一个充分必要条件

In order to research topological vector space,the relations between strong lower K-semi continuity and continuity and K- continuity are investigated.

研究了序拓扑向量空间映射的强下K-半连续性与连续性及K-连续性之间的关系，得到了一些充分条件和必要条件

In this paper the equivalent of the various topologies on the closed setlattice of a topological space is investigated a sufficient and necessary condition for theirequivalent is given.

本文对拓扑空间闭集格上的各种拓扑的等价性进行了研究，得到了它们等价的一个充分必要条件

Then as one of the three elements of it, the ethnic cultural touristy resources are one of the most important factors and the necessary conditions that ensure ethnic culture tourism become successful.

而作为其发展三要素之一的民族文化旅游资源，是旅游地吸引游客的最重要因素，是确保民族文化旅游开发成功的必要条件之一。

Considering linear and O-linear predictable variables, the author investigates optimal prediction problems by the trace of matrix. A few necessary conditions are derived and accordingly optimal linear and optimal O-linear unbiased predictors, which are unique with probabitity one, are obtained respectively by the author.

对于一类线性可预测变量和Φ-线性可预测变量，作者在矩阵迹意义下研究了一般增长曲线模型中最优预测问题，找到了其存在最优预测的几个必要条件，并在给定的条件下分别得到了最优线性无偏预测和最优Φ-线性无偏预测，而且还证明了它们在几乎处处意义下的唯一性。

The scientific intergovernmental transfer payment system is the prerequisite of the perfect market economy system.

科学的政府间转移支付制度是市场经济体制具备完善性的必要条件。

In chapter 4, we studythe cyclic edge connectedness of regular half vertex transitive graphs, we showthat a connected k(≥4)-regular half vertex transitive graph X with girthg≥6 isλ_c-optimal, and we also obtain a su?cient and necessary conditionfor a connected k(≥4)-regular half vertex transitive graph X with girth 4 tobeλ_c-optimal.

第四章，我们研究了正则半点传递图的圈边连通性问题，主要结果是证明了一个围长为g≥6的k(≥4)-正则连通半点传递图X是λ_c-最优的，并且得到了一个围长为g = 4的k(≥4)-正则连通半点传递图X是λ_c-最优的充分必要条件。

This paper, which focused on the structure optimization theory and method, has finished such studies as follows: The three dimension model has been built, which provide the necessary conditions for the building of the dynamics equivalent model. By the launch dynamics simulation, the loads of the key joints when the rocket is launched has been got, which provide the necessary data for the finite element analysis and the structure optimization. The finite element model of the excess weight parts of the rocket has been built, buy the finite element intension analysis of the model in two conditions, the displacement and the stress of the key points have been got, which make us know the distributing of the stress and the transmogrification of the part. To satisfy the intension and the precision design request and to decrease the weight of the part as many as possible, the part has been topology optimized by the structure optimization theory and method. After that, the new model has been analysis in structure and launch dynamics. The contrast of the character change of the old part and the new part and the influence on the rocket system have been studied.

本文以结构优化理论和方法为核心，主要做了以下工作：建立了某自行火箭炮全炮三维实体模型，为建立该火箭炮系统的动力学等效模型提供了必要条件，进行了发射动力学仿真，得到该火箭炮发射装置各关键连接部位在发射状态下的载荷，为有限元分析和结构优化提供了必需的数据；建立了该火箭炮发射装置超重部分的有限元模型，分两种工况，对模型进行了有限元强度分析，得出了关键部位的位移和应力值，对其的应力和变形分布有了具体的了解；运用结构优化的理论和方法，对该火箭炮发射装置超重部分进行了拓扑优化，使其在满足强度和精度的要求下尽可能多地减轻重量，对优化后得到的模型进行了结构分析和发射动力学分析，对比了该部件优化前后的特性变化以及对火箭炮系统的影响。

Singer Leona Lewis and former Led Zeppelin guitarist Jimmy Page emerged as the bus transformed into a grass-covered carnival float, and the pair combined for a rendition of "Whole Lotta Love".

歌手leona刘易斯和前率领的飞艇的吉他手吉米页出现巴士转化为基层所涵盖的嘉年华花车，和一双合并为一移交&整个lotta爱&。

This is Kate, and that's Erin.

这是凯特，那个是爱朗。