292 resultados para 196-1173


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本文是根据云南星云湖、杞麓湖中所产大头鲤进行一些生态习性的研究。大头鲤的年龄鉴定是依据鳞片上环片切割现象。依星云湖的标本实测平均体长,Ⅰ龄为135.12毫米,Ⅱ龄鱼为196.93毫米,Ⅲ龄鱼为241.92毫米,Ⅳ龄焦为288毫米。星云湖和杞麓湖大头鲤体长和体重的关系式分别为:W=0.00001283L~(3.0719),W=0.00002181L~(2.9895)。食性极为单纯,主要是以枝角类和桡足类为食。不同大小个体的食性差异不大。Ⅰ龄鱼部分达到性成熟,Ⅱ龄鱼全部性成熟。其中性成熟最小个体雌鱼体长为14

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<正> 关于寄生鳢属鱼类原生动物的研究,外国已有不少的文献,但在我国还没有关于这方面的资料。作者进行这一研究工作,目的是了解斑鳢(Ophiocephalus maculatus)和乌鳢(O.argus)两种淡水鱼的孢子虫种类的形态学,以及对寄主的关系,以供鱼病防治和有关寄生虫学方面工作者在理论和实践上的参考。本文记述的孢子虫共22种,其中已见于文献的6种,新种16种,并包括粘孢子虫一新属。其分类系统如下:

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<正> 一、绪言关于中国淡水鱼类的研究,如果从C.Linnaeus的记载算起,至今已超过一个半世纪了。在这个时期内,特别是前100年,全部工作几乎只限于种类的筒单描述。进行这些工作的鱼类学者,大抵都是外国人,他们绝大多数没有到过中国,一般仅凭从中国采得的少数标本,予以鉴定研究。个别早期作者,甚至往往只根据一幅鱼的绘图,就进行描述鉴定,创立新种。到二十世纪三十年代,才有我国学者从事本国鱼类的研究,开始比较系统的在全国一些主要河流进行鱼类调查。到四十年代止,可以说除边远地区外,我国的主要经济鱼类资源基本上都有

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A new genus and species of freshwater monostiliferous hoplonemertean, Limnemertes poyangensis gen. et sp. nov., from Poyang Lake, People's Republic of China, is described and illustrated. The taxon is compared and contrasted with previously described freshwater hoplonemerteans. This is the fourth species of freshwater nemertean to be described from China and the first recorded from Poyang Lake.

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We investigate the spin relaxation time of holes in an ultrathin neutral InAs monolayer (1.5 ML) and compare with that of electrons, using polarization-dependent time-resolved photoluminescence (TRPL) experiments. With excitation energies above the GaAs gap, we observe a rather slow relaxation of holes (tau(1h) = 196 +/- 17 ps) that is in the magnitude similar to electrons (tau(1e) = 354 +/- 32 ps) in this ultrathin sample. The results are in good agreement with earlier theoretical prediction, and the phonon scattering due to spin-orbit coupling is realized to play a dominant role in the carrier spin kinetics.

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Electrolyte electroreflectance spectra of the near-surface strained-layer In0.15Ga0.85As/GaAs double single-quantum-well electrode have been studied at different biases in non-aqueous solutions of ferrocene and acetylferrocene. The optical transitions, the Franz-Keldysh oscillations (FKOs) and the quantum confined Stark effects (QCSE) of In0.15Ga0.85As/GaAs quantum well electrodes are analyzed. Electric field strengths at the In0.15Ga0.85As/GaAs interface are calculated in both solutions by a fast Fourier transform analysis of FKOs. A dip is exhibited in the electric field strength versus bias (from 0 to 1.2 V) curve in ferrocene solution. A model concerning the interfacial tunneling transfer of electrons is used to explain the behavior of the electric field. (C) 2001 Elsevier Science B.V. All rights reserved.

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The effects of InP substrate orientations on self-assembled InAs quantum dots (QDs) have been investigated by molecular beam epitaxy (MBE). A comparison between atomic force microscopy (AFM) and photoluminescence (PL) spectra shows that a high density of smaller InAs islands can be obtained by using such high index substrates. On the other hand, by introducing a lattice-matched underlying In0.52Al0.24Ga0.24As layer, the InAs QDs can be much more uniform in size and have a great improvement in PL properties. More importantly, 1.55-mu m luminescence at room temperature (RT) can be realized in InAs QDs deposited on (001) InP substrate with underlying In0.52Al0.24Ga0.24As layer. (C) 2000 Elsevier Science B.V. All rights reserved.

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High-density InAs nanowires embedded in an In0.52Al0.48As matrix are fabricated in situ by molecular beam epitaxy on (100) InP. The average cross section of the nanowires is 4.5 x 10 nm(2). The linear density is as high as 70 wires/mu m. The spatial alignment of the multilayer arrays exhibit strong anticorrelation in the growth direction. Large polarization anisotropic effect is observed in polarized photoluminescence measurements. (C) 1999 American Institute of Physics. [S0003-6951(99)04134-0].

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It was determined that oxygen concentration in heavily Sb-doped silicon was about 40% lower than that in the lightly doped Czochralski grown silicon and decreased with increasing content of Sb by means of coincident elastic recoil detection analysis. Through thermodynamic calculation, the oxygen loss by evaporation from the free surface of melt is only due to the formation of SiO, and Sb2O3 evaporation can be neglected. The basic reason for oxygen concentration reduction in heavily Sb-doped CZSi was that oxygen solubility decreased when element Sb with larger radius doped degenerately into silicon crystal. (C) 1999 Elsevier Science B.V. All rights reserved.

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A novel AlGaN/GaN/GaN/GaN double heterojunction high electron mobility transistors (DH-HEMTS) structure with an AlN interlayer on sapphire substrate has been grown by MOCVD. The structure featured a 6-10 nm In0.1Ga0.9N layer inserted between the GaN channel and GaN buffer. And wer also inserted one ultrathin. AlN interlayer into the Al/GaN/GaN interface, which significantly enhanced the mobility of two-dimensional electron gas (2DEG) existed in the GaN channel. AFM result of this structure shows a good surface morphology and a low dislocation density, with the root-mean-square roughness (RMS) of 0.196 nm for a scan area of 5 mu m x 5 mu m. Temperature dependent Hall measurement was performed on this sample, and a mobility as high as 1950 cm(2)/Vs at room temperature (RT) was obtained. The sheet carrier density was 9.89 x10(12) cm(2), and average sheet resistance of 327 Omega/sq was achieved. The mobility obtained in this paper is about 50% higher than other results of similar structures which have been reported. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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AlGaN/AlN/GaN/InGaN/GaN double heterojunction high electron mobility transistors (DH-HEMTs) structures with improved buffer isolation have been investigated. The structures were grown by MOCVD on sapphire substrate. AFM result of this structure shows a good surface morphology with the root-mean-square roughness (RMS) of 0.196 nm for a scan area of 5 mu mx5 mu m. A mobility as high as 1950 cm(2)/Vs with the sheet carrier density of 9.89x10(12) cm(-2) was obtained, which was about 50% higher than other results of similar structures which have been reported. Average sheet resistance of 327 Omega/sq was achieved. The HEMTs device using the materials was fabricated, and a maximum drain current density of 718.5 mA/mm, an extrinsic transconductance of 248 mS/mm, a current gain cutoff frequency of 16 GHz and a maximum frequency of oscillation 35 GHz were achieved.

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GaN nanorods with vertebra-like morphology were synthesized by nitriding Ga2O3/ZnO films at 1000 degrees C for 20min. Ga2O3 thin films and ZnO middle layers were pre-deposited in turn on Si(111) substrates by r.f. magnetron sputtering system. In the flowing ammonia ambient, ZnO was reducted to Zn and Zu sublimated at 1000 degrees C. Ga2O3 was reducted to Ga2O and Ga2O reacted with NH3 to synthesize GaN nanorods in the help of the sublimation of Zn. The structure and morphology of the nanorods were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), The composition of GaN nanorods was studied by energy dispersive spectroscopy (EDS) and fourier transform infrared (FTIR) system.

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该文对4轮MISTY和3轮双重MISTY两种结构进行了优化。在保持其安全性不变的情况下,把4轮MISTY结构中第1轮的伪随机置换,用一个XOR-泛置换代替,第2,第3轮采用相同的伪随机置换,3轮结构中第1轮的伪随机置换用XOR-泛置换代替,其它轮相同。伪随机置换的数量分别由原来的4个变为2个,3个变为1个,从而缩短了运行时间,节省了密钥量,大大降低了结构的实现成本。

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在简单介绍工作流管理系统一般概念的基础上,重点介绍了基于工作流技术实现的网上协同办公系统的体系结构、系统主要组成部分、各部门的实现方法以及需要注意的事项。