Stabilization of symmetric formations to motion around convex loops

We provide a cooperative control algorithm to stabilize symmetric formations to motion around closed curves suitable for mobile sensor networks. This work extends previous results for stabilization of symmetric circular formations. We study a planar particle model with decentralized steering control subject to limited communication. Because of their unique spectral properties, the Laplacian matrices of circulant graphs play a key role. We illustrate the result for a skewed superellipse, which is a type of curve that includes circles, ellipses, and rounded parallelograms. © 2007 Elsevier B.V. All rights reserved.

Delayed control of a Moore-Greitzer axial compressor model

Several feedback control laws have appeared in the literature concerning the stabilization of the nonlinear Moore-Greitzer axial compression model. Motivated by magnitude and rate limitations imposed by the physical implementation of the control law, Larsen et al. studied a dynamic implementation of the S-controller suggested by Sepulchre and Kokotović. They showed the potential benefit of implementing the S-controller through a first-order lag: while the location of the closed-loop equilibrium achieved with the static control law was sensitive to poorly known parameters, the dynamic implementation resulted in a small limit cycle at a very desirable location, insensitive to parameter variations. In this paper, we investigate the more general case when the control is applied with a time delay. This can be seen as an extension of the model with a first-order lag. The delay can either be a result of system constraints or be deliberately implemented to achieve better system behavior. The resulting closed-loop system is a set of parameter-dependent delay differential equations. Numerical bifurcation analysis is used to study this model and investigate whether the positive results obtained for the first-order model persist, even for larger values of the delay.

人工诱导异源四倍体、新四倍体及异源三倍体白鲫的细胞遗传学研究

作者比较了第一代异源四倍体鱼、异源三倍体鱼、新四倍体鱼与亲本白鲫、红鲫及其杂交一代的染色体组型。三种亲本的二倍体染色体数均为100，但其组型分组各有差异，白鲫染色体组型公式：12m＋36sm＋32st十20t,NF＝148，在亚中着丝点组中有一对特大的标记染色体；红鲫染色体组型：20m＋34sm＋26st＋20t,NF＝154；白鲫×红鲫杂种染色体组型：16m＋35sm＋29st＋20t,NF＝151，有一条与白鲫相似的特大标记染色体，证实其组型由白鲫和红鲫各提供一套染色体组组成。异源三倍体的染色体数为1

Structural analysis of plate-type fuel assemblies and development of a non-destructive method to assess their integrity

This work is concerned with the structural behaviour and the integrity of parallel plate-type nuclear fuel assemblies. A plate-type assembly consists of several thin plates mounted in a box-like structure and is subjected to a coolant flow that can result in a considerable drag force. A finite element model of an assembly is presented to study the sensitivity of the natural frequencies to the stiffness of the plates' junctions. It is shown that the shift in the natural frequencies of the torsional modes can be used to check the global integrity of the fuel assembly while the local natural frequencies of the inner plates can be used to estimate the maximum drag force they can resist. Finally a non-destructive method is developed to assess the resistance of the inner plates to bear an applied load. Extensive computational and experimental results are presented to prove the applicability of the method presented. © 2013 Elsevier B.V. All rights reserved.

华鳈的繁殖生物学

根据野外调查和室内养殖的结果,华鳈一龄即达性成熟,绝对怀卵量在1040—5580粒之间,相对怀卵量为83.3—209.6;繁殖季节为4月下旬至7月中旬,繁殖高峰期在5月中下旬;繁殖群体主要由一、二龄组成,雌雄性比为1:1;精母细胞和卵母细胞都有分批成熟现象;卵分批产于流水中,为漂流性。最后对其繁殖习性进行了较为详细的分析。

江豚背部小齿的超微结构与功能

长江江豚背部皮肤表面有一长条小齿,由1—3排组成。它是由表皮向体表突起而成。小齿区皮肤中的乳头深深伸入表皮,几达表面,它的高度在成体约占整个表皮厚度的70—80％,新生幼儿为84.6％。经研究,我们发现在小齿区皮肤中存在着大量类似于人类皮肤中的环层小体那样的被囊神经末梢和几种有鞘神经纤维束。根据这些结构,我们认为小齿是一种感觉器官,它并不能起到防止幼儿从母体背部滑落的作用。

Polychromatic single-shot spectroscopy on SOI-FET trapped electrons

The behavior of trapped electrons, in a dielectric close to the channel of a silicon SOI-FET, is studied by cryogenic microwave spectroscopy. On-resonance microwave excitation causes one of these trapped electrons to undergo spatial Rabi oscillations between widely separated trap sites. This charge displacement causes a change in the drain current of the transistor, resulting in high quality factor resonances in continuous wave spectroscopy. The potential of this effect for non-classical information processing is investigated through polychromatic single-shot spectroscopy, using on-resonance and difference frequencies. Interaction between different trapped electrons is seen in the post excitation behavior and the possibilities of quantum gate operations are discussed. © The Electrochemical Society.

Encoding of mixtures in a simple olfactory system.

Natural odors are usually mixtures; yet, humans and animals can experience them as unitary percepts. Olfaction also enables stimulus categorization and generalization. We studied how these computations are performed with the responses of 168 locust antennal lobe projection neurons (PNs) to varying mixtures of two monomolecular odors, and of 174 PNs and 209 mushroom body Kenyon cells (KCs) to mixtures of up to eight monomolecular odors. Single-PN responses showed strong hypoadditivity and population trajectories clustered by odor concentration and mixture similarity. KC responses were much sparser on average than those of PNs and often signaled the presence of single components in mixtures. Linear classifiers could read out the responses of both populations in single time bins to perform odor identification, categorization, and generalization. Our results suggest that odor representations in the mushroom body may result from competing optimization constraints to facilitate memorization (sparseness) while enabling identification, classification, and generalization.

Encoding of mixtures in a simple olfactory system

Natural odors are usually mixtures; yet, humans and animals can experience them as unitary percepts. Olfaction also enables stimulus categorization and generalization. We studied how these computations are performed with the responses of 168 locust antennal lobe projection neurons (PNs) to varying mixtures of two monomolecular odors, and of 174 PNs and 209 mushroom body Kenyon cells (KCs) to mixtures of up to eight monomolecular odors. Single-PN responses showed strong hypoadditivity and population trajectories clustered by odor concentration and mixture similarity. KC responses were much sparser on average than those of PNs and often signaled the presence of single components in mixtures. Linear classifiers could read out the responses of both populations in single time bins to perform odor identification, categorization, and generalization. Our results suggest that odor representations in the mushroom body may result from competing optimization constraints to facilitate memorization (sparseness) while enabling identification, classification, and generalization

用浮游植物的生产量估算武昌东湖鲢鳙生产潜力与鱼种放养量的探讨

本文根据浮游植物生产量求得对鲢、鳙的供饵能力,并通过浮游植物对鲢、鳙转化效率的计算,估算出武昌东湖鲢、鳙的生产潜力,进而求得武昌东湖鲢、鳙的合理投放量。作者求得东湖浮游植物全年对鲢、鳙的供饵能力是61,153吨(鲜重);由此估算出东湖鲢、鳙的生产潜力是789公斤/公顷以上,每年鱼种(四寸以上)的合理投放量,鲢是 209万尾,鳙是 110万尾。

中国粒鲇属Akysis鱼类二新种

<正> 粒鲇科Akyisidae鱼类是分布在东南亚地区的小型鱼类,包括三个属。其中大粒鲇属Achrochodomchthys Bleeker只产于苏门答腊岛、爪哇岛和加里曼丹岛。狭尾粒鲇属Breitensteinia Steindachner只产于苏门答腊岛和加里曼丹岛。粒鲇属Akysis Bleeker鱼类已记录的有下列8种:Akysis variegatus(Bleeker),1846;Akysis macronemus Bleeker,1860;Akysis pictus Gnther,1883;A

黑龙江流域鲫鱼的种群变异和生态资料

<正> 黑龙江流域的鲫鱼,是渔获物中的主要粗成之一,约占总产量的20%。黑龙江流域的水利枢扭建成后,它将成为水库中的主要养殖对象,因此,调查研究鲫鱼的生活习性及其种群变异,对于今后的渔业利用是有很大益处的。一、种群的变异鲫鱼在黑龙江流域的分布极其广泛,各种不同的水体中都能棲息生存。在额尔古纳河,鲫鱼是捕捞的主要对象;在黑龙江,则主要是分布在干流相通的附属水体中。其它如达赖湖、镜泊湖、小兴凯湖、五大连池等湖泊里均有相当数量的鱼群。

中国淡水鱼寄生桡足类鳋科的研究

<正> 一.绪言桡足类的主要组成部分是自由生活的剑水溞(Cyclopoida)和镖水溞(Calanoida),它们都是鱼类的优良食料。另一部分就是营寄生生活的种类,其中有些对于鱼类的危害性很大。鳋科(Ergasilidae)是一群由自由生活的剑水溞演变成寄生生活的过渡类型,其幼虫及雄虫完全营自由生活,只有雌性的成虫始寄生在鱼体上。因此过去如 Gurney氏等认为它们是半寄生性的种类,是很正确的论断。