Morphological biodiversity and local use of the Himalayan pear (<Emphasis Type="Italic">Pyrus pashia</Emphasis>) in Central Bhutan

A survey was undertaken in two valleys of the Bumthang area in Central Bhutan to study the morphological diversity, farmers’ knowledge, management practices, yield and income generation potential of the neglected Himalayan Pear (Pyrus pashia Hamilton ex D. Don). For this study a total of 148 Pyrus pashia accessions were collected and 103 households interviewed. Three quantitative and 14 qualitative traits such as colour, size, shape and texture of fruits and tree habit were used for morphological characterization of the accessions. The results demonstrated a high morphological diversity within the P. pashia trees. Fruit shape varied widely from globose to pyriform, fruit skin colour from light yellow and glossy to brown and dull. The observed diversity is likely due to the fact that under farmers’ conditions trees are propagated through seedlings rather than by grafting. None of the characters were specific and correlated with region or altitude. Distinct local cultivars with specific characters were absent making it impossible to group the pears morphologically. Interviews revealed low numbers of trees per farmers, lacking marketability of the fruits and farmers’ subsequent preference for improved varieties as major obstacles for the in situ preservation of biodiversity in P. pashia in this area.     

桃叶卫矛种子休眠、催芽及芽苗移栽技术的探讨

桃叶卫矛是优良的观赏树种。作者揭示了它的种子休眠主要是由于种皮、胚乳含有抑制物。通过试验得出结论,低温层积30d或混雪层积40d,再转入高温催芽,效果最好。同时探讨了利用间苗时的芽苗移栽技术,以求经济、合理的利用种子,降低苗木成本。     

非保守系统的拟Hamilton原理及其应用

按照广义力和广义位移之间的对应关系,将弹性动力学的基本方程乘上相应的虚量,然后积分,代数相加,并考虑到体积力和面积力均为非保守力,建立了非保守弹性动力学系统的拟Hamilton原理和拟余Hamilton原理。应用拟Hamilton原理和拟余Hamilton原理研究不同性质的非保守动力系统的算例,表明不同性质的非保守动力系统的拟Hamilton原理和拟余Hamilton原理均可写成统一的形式。     

Dynamic modeling and control of a padder roller system

This is the first time in the literature dealing with the dynamic modeling and control of a rotating padder roller system. It is intended to design a control system with effective scheme and robustness to stabilize all vibration modes of a rotating padder roller system by using one set of sensor and actuator. The controller design depends on the specific pole-zero patterns. In practice, the pole-zero patterns remain the same, no matter how the physical system parameters are different. By properly placing the actuator and sensor, a realizable controller and sensor is designed to stabilize all the vibration modes and make the closed loop system absolutely stable. This will suppress the vibration without suffering from spillover and can eliminate an infinite number of vibration modes. The performance of this controller has been successfully implemented by computer simulation.     

变质量质系的哈密顿原理

在变质量系的第二类拉格朗日方程的基础上 ,进一步导出了原质点的结合与分离同时进行时 ,变质量质系哈密顿原理的表达式 ,其目的是导出哈密顿原理更具有普遍性的表达式 ,该表达式同样可以计算常质量系的问题     

关于无爪图中哈密尔顿圈的一个注记

证明了具有Hourglass和Dumbbell性质的3-连通的无爪图是哈密尔顿圈.     

捕食-食饵系统的捕获优化问题

对捕食-食饵系统的捕获模型进行了定性分析,并利用Pontrjagin最大值原理及最优控制理论,得到该系统的最优捕获策略。     

泊松括号与量子力学

本文证明了ｌｉｍ（Ａ，Ｂ）／ｉｎ＝（Ａ，Ｂ）成立的条件，并且对这个证明的物理意义了作讨论，结论是当ｈ→０时，泊松括号是保持海森伯方程与哈密顿方程形式不变的必要条件。     

Allozyme variation of hatchery and river populations of rohu (Labeo rohita, Hamilton) in Bangladesh

The genetic variations of rohu (Labeo rohita, Hamilton) sampled from five hatchery populations (Arabpur, Brahmaputra, Comilla, Kishorganj and Natore) and three major river populations (the Halda, the Jamuna and the Padma) were analysed by allozyme electrophoresis. Ten enzymes encoded by 11 loci were screened, and six were polymorphic. Alleles at three loci (Est‐1^*, Gpi‐1^* and Gpi‐2^*) proved variable for hatchery and river populations, and the Mdh‐2^* locus exhibited heterozygous genotypes for river populations only. Polymorphic loci per population (27.3±5.3%), heterozygous loci per individual (15.5±1.2%) and relative gene diversity (0.27±0.08) in river populations were higher than those for hatchery populations (25.5±1.8%, 10.7±1.6% and 0.25±0.01 respectively). Also, the observed heterozygosity (Ho) and expected heterozygosity (He) (0.09±0.03 and 0.14±0.04 respectively) in river populations were higher than those in hatchery populations (0.08±0.01 and 0.11±0.01 respectively). The lower levels of genetic variability in hatchery populations suggested the occurrence of inbreeding and/or genetic drift. The pairwise population differentiation (F_ST) values showed a lower level of genetic differentiation between hatchery and river population pairs. The unweighted pair‐group method with arithmetic mean dendrogram of Nei's genetic distances showed a relationship between the genetic distance and geographic distance. The populations were clustered into three groups: the Padma in one group, the Halda in second group and the Jamuna, including five hatcheries, in the third group. Highly diversified rohu individuals were observed in the Padma and Halda Rivers, whereas less genetically variable individuals were found in the Jamuna River and five hatcheries. These findings can be useful for rohu hatchery propagation to enhance the sustainable aquaculture production.     

运动项目排序中的优化算法

本文巧妙得将运动员参赛项目的排序问题转化为图论中经典的旅行商问题求解。以连续参加两项比赛的人次最少为目标,应用了最小生成树求解Ham ilton回路的方法,得到了题目的最优解。之后,经过严谨的分析,我们又增加了1个使连续比赛的事件尽量分散开的约束条件,即保证任何1位运动员至多出现1次连续比赛的情况的条件下,求得总连续比赛人次数最少的排序方案。这样得到结果就加强了比赛项目排序结果对每位运动员的公平性、合理性。改进后的约束模型,要求我们从一些近似最优解的结果中再挑选满足约束的最终解。针对这种算法,我们采取了解决这种问题更有效的遗传算法计算。两种算法各有利弊,得到的结果与理论分析保持一致。