浅谈自育亲本在甘蔗杂交育种中的作用

统计分析了国内外主要育成品种及亲系，发现用自育品种和材料作为杂交亲本育成的品种在统计品种数中占有相当大的比例。台湾占85．7％、四川50．0％、江西42．9％、广东37．5％、云南占了27％、广西16．7％、福建6．7％。印度、美国、巴巴多斯、毛里求斯分别是100％、95．5％、92．9％和100％。说明使用自育品种和材料作为亲本在甘蔗杂交育种中有相当重要的作用。     

Estimation for the number of components in a mixture model using stepwise split-and-merge EM algorithm

The main difficulty with EM algorithm for mixture model concerns the number of components, say g. This is the question of model selection, and the EM algorithm itself could not estimate g. On the contrary, the algorithm requires g to be specified before the remaining parameters can be estimated. To solve this problem, a new algorithm, which is called stepwise split-and-merge EM (SSMEM) algorithm, is proposed. The SSMEM algorithm alternately splits and merges components, estimating g and other parameters of components simultaneously. Also, two novel criteria are introduced to efficiently select the components for split or merge. Experimental results on simulated and real data demonstrate the effectivity of the proposed algorithm.     

Response level crossing rate of a linear system excited by a partially specified Gaussian load process

The problem of determining the maximum mean response level crossing rate of a linear system driven by a partially specified Gaussian load process has been considered. The partial specification of the load is given only in terms of its total average energy. The critical input power spectral (PSD) function, which maximizes the mean response level crossing rate, is obtained. The critical input PSD turns out to be highly narrow-banded which fails to capture the erratic nature of the excitation. Consequently, the trade-off curve between the maximum mean response level crossing rate and the maximum disorder in the input process, quantified in terms of its entropy rate, has been generated. The method of Pareto optimization is used to tackle the conflicting objectives of the simultaneous maximization of the mean response level crossing rate and the input entropy rate. The non-linear multi-objective optimization has been carried out using a recently developed multi-criteria genetic algorithm scheme. Illustrative example of determining the critical input of an axially vibrating rod, excited by a partially specified stationary Gaussian load process, has been considered.     

蝶阀加工及装配工艺的研究

传统工艺加工阀体、活门时，对机床的性能要求较高，一般为数控镗床。介绍了一种采用普通镗床加工阀体、活门的工艺方法及蝶阀在厂内装配的工艺方法。     

杭-宁输气管道工程定向钻穿越设计浅析

杭州-宁波天然气输气管道工程（简称杭-宁输气管道工程）是浙江省天然气长输管网主干线之一，根据工程河流穿越众多、渠塘穿越频繁的特点，对杭-宁输气管道工程水域穿越的特点和穿越方式作了总结；重点分析了水域定向钻穿越设计及需要注意的问题，为今后浙江省天然气管网建设的水域穿越设计作了探讨。     

多排数翅片管空冷器风阻特性的数值模拟

本文对多排数翅片管空冷器空气侧的风阻特性进行了数值模拟.利用商用软件Fluent进行数值计算,结合经验公式和已有的实验数据,分析了不同入口风速下,阻力的变化规律以及流动阻力和温度变化对模拟计算的影响.     

On inversive maximal period polynomials over finite fields

Over finite field GF(q) withq a power of an odd primep, we characterize inversive maximal period polynomials in terms of polynomials of orderq + 1, and then we study some properties of polynomials of orderq + 1.This paper was written while the author was visiting the Institute of Information Processing, Austrian Academy of Sciences, AustriaThe author would like to thank the Institute of Information Processing, Austrian Academy of Sciences, Austria, for its hospitality and for using its facilities     

网络分解法的误差分析

网络分解法是求解电大尺寸复杂结构电磁问题的重要方法之一,关于网络分解法误差分析的研究有着重要的理论意义和实用价值.本文给出了网络分解法的误差估计,并对于脉冲基函数转换成三角基函数的情况给出了三角基函数个数的最优公式,数值结果表明了分析的正确性.     

On the number of broadcast schemes in networks

Broadcasting is the process of spreading one piece of information among a group of individuals connected by an interconnection network. In this paper we give exact lower and upper bounds for the number of broadcast schemes in arbitrary networks. Also, we give the exact value for complete bipartite graphs and an upper bound for regular networks. Based on the counting method we describe a new random algorithm for broadcasting in networks.