气动激光器的稳定振荡条件与输出功率

本文直接由辐射场方程与边界条件导出了气动激光器的稳定振荡条件.由这一稳定振荡条件与资料的饱和增益公式导出了气动激光器的输出功率表达式,指出了在一定的近似下用迭代法可由该公式求出气动激光器的输出功率值,并导出了气动激光器的最佳耦合计算公式,指出了Rigrod公式对气动激光器的不适用性,用本文的方法对Gerry的典型实验进行了计算,计算结果与实验结果的一致证明了所提理论的可靠性.

One-dimensional improvement and two-dimensional and 3-dimensional treatments for stable oscillation condition, mode structure and power output in high-speed-flow lasers

For high-speed-flow lasers, the one-dimensional and first-order approximate treatment in[1] under approximation of geometrical optics is improved still within the scope of approx-imation of geometrical optics. The strict accurate results are obtained, and what is more,two- and three-dimensional treatments are done. Thus for two- and three-dimensional cases, thestable oscillation condition, the formulae of power output and analytical expression of modesunder approximation of geometrical optics (in terms of gain function) are derived. Accord-ing to the present theory, one-and two-dimensional calculations for the typical case of Gerry'sexperiment are presented. All the results coincide well with the experiment and are better thanthe results obtained in [1].In addition, the applicable scope of Lee's stable oscillation condition given by [1] is ex-panded; the condition for the approximation of gcometrical optics to be applied to mode con-structure in optical cavity is obtained for the first time and the difference between thiscondition and that for free space is also pointed out in the present work.

云南晚第三纪化石木研究及其古气候意义

本论文研究了我国云南龙陵大坝和镇安、昌宁红星晚上新世以及楚雄洲吕合晚中新世191个化石木标本，鉴定出7种化石木类型，其中越桔型木属为新属，越桔型木、常绿杜鹃型木和龙陵杜鹃型木为新种。并利用化石木的现存种或现存亲缘种的生态环境对化石产地的气候和环境进行了讨论。 木材种类的特征如下： 华山松（Pinus armandii Franchet）：生长轮明显，早材至晚材渐变。交叉场纹孔主为窗格型。木射线具单列射线和纺锤状射线。射线管胞内壁平滑或微锯齿状。具正常轴向和径向树脂道，由薄壁泌脂细胞组成。 云南铁杉（Tsuga dumosa Eicher）：生长轮明显，早材至晚材略急变至渐变。管胞径壁具缘纹孔单列;具缘纹孔膜上明显具棒状延伸;纹孔膜下具缘纹孔外表面具明显的瘤状层，瘤状突起大小相近。交叉场纹孔式柏木型。木射线主为单列;由射线薄壁细胞和射线管胞组成;射线细胞水平壁厚，纹孔明显，数多;端壁节状加厚明显。轴向木薄壁组织细胞数少，轮界状;其端壁节状加厚明显。 柳杉型木（Taxodioxylon cryptomeripsoides Schonfeld）：生长轮明显，早材至晚材略急变。管胞径壁纹孔1列，偶尔成疏松排列的2列;晚材弦壁纹孔明显可见。交叉场具1-4枚杉木型纹孔。轴向木薄壁组织细胞数多，星散状或有时成短弦线状;端壁节状不明显或略现。木射线单列，全由射线薄壁细胞组成;射线细胞水平壁薄，纹孔缺乏，端壁平滑。 杉木型木（Taxodioxylon cunninghamioides Watari）：生长轮明显，早材至晚材渐变。管胞径壁纹孔1-2列;晚材弦壁纹孔明显可见。交叉场1-4枚杉木型纹孔。轴向木薄壁组织丰富，星散状或有时成短弦线状;端壁节状不明显或略现。木射线单列全由射线薄壁细胞组成;射线细胞水平壁薄;端壁薄，平滑。 龙陵杜鹃型木（新种）（Ericaceoxylon longlingense sp. nov.）：生长轮明显，散孔材。导管横切面为多角形，单管孔，散生。螺纹加厚仅出现导管分子尾端。梯状穿孔为主。管间纹孔式为对列或梯状对列。轴向薄壁组织量少，疏环管状。纤维分子细胞壁厚度中等。射线宽1-6细胞。多列射线的中部多为横卧细胞，边缘有1-4（6）行直立和/或方形细胞。射线导管间纹孔式梯状对列，类似导管间纹孔式。 常绿杜鹃型木（新种）（Ericaceoxylon hymenanthesoides sp. nov.）：生长轮明显，半环孔材。导管横切面为多角形，单管孔，散生。螺纹加厚出现整个导管分子壁上。复穿孔，梯状穿孔为主。管间纹孔式为互列。轴向薄壁组织量少，疏环管状;端壁节状加厚不明显。纤维分子细胞壁厚度中等;径壁和弦壁均具有具缘纹孔。射线宽1-4细胞;多列射线的中部多为横卧细胞，边缘有1-9行直立和/或方形细胞。射线导管间纹孔式互列，类似导管间纹孔式。 常绿杜鹃型木（相似种）（Ericaceoxylon cf. hymenanthesoides）：生长轮明显，半环孔材。单管孔;导管散生。梯状穿孔板;管间纹孔式为互列;射线导管间纹孔式多对列，类似导管间纹孔式。螺纹加厚出现在导管分子壁上。木纤维细胞壁中等厚度。射线宽1-3细胞。 越桔型木（新种）（Vacciniaceoxylon vacciniumoides sp. nov.）：生长轮略明显，散孔材。单管孔，散生;整个导管分子上具螺纹加厚。网状和梯状穿孔。轴向薄壁组织量少，星散状或疏环管状。纤维分子径壁和弦壁都具有具缘纹孔。射线多列和单列射线组成，两种大小，1-4细胞宽。射线导管间纹孔式互列，纹孔有明显的纹孔缘。 化石木植物群及其所反映的古植被和古气候如下： 楚雄吕合化石木植物群4个标本中鉴定出两种木材类型—柳杉型木和杉木型木。由于化石标本少，不足以反映植被面貌，两种杉科植物的出现反映其生长地为亚热带温暖湿润环境。 龙陵大坝和镇安化石木植物群95个标本中鉴定出四种木材类型：华山松、常绿杜鹃型木、越桔型木和龙陵杜鹃型木。他们反映的古植被为针阔混交林，生长于亚热带温凉湿润的山地气候环境中，当时当地的海拔高度在1800-3000米之间。 昌宁红星化石木植物群92个标本中鉴定出三种木材类型：华山松、云南铁杉、常绿杜鹃型木（相似种）。他们反映的古植被为针阔混交林，生长于亚热带温凉湿润的山地气候环境中，当时当地的海拔在2200-3000米之间。

陕西关中出土木材的研究

研究人类历史时期遗留木材是一项涵盖植物解剖学、植物地理学、环境科学和考古学等多学科的综合工作。通过对历史时期木材的研究，一方面可以了解当时的植物类群组成、地理分布和植被面貌，并可通过植物作为气候代用指标，重建历史时期环境，反映气候变迁。另一方面可以了解人类对木材的认识、选择和使用的历史，并反映当时的人类活动、及其在建筑、文化艺术和风格等诸多方面的建树。 本工作对陕西关中地区出土的神禾塬战国古墓木椁、秦始皇陵兵马俑坑棚架和凤栖原西汉古墓木椁、木炭的原木材进行识别和鉴定，研究结果如下 1、古木组成 神禾塬战国古墓木椁全部由裸子植物松科中的冷杉属（Abies）、云杉属（Picea）、铁杉属（Tsuga）和松属（Pinus）木材组成；秦始皇陵兵马俑棚架木材由裸子植物松科冷杉属、云杉属和铁杉属木材，以及被子植物樟科楠木属（Phoebe）木材组成，包括前人在兵马俑坑中发现了榆科的木材，综合分析可以看出，秦始皇陵兵马俑坑棚架主要是以裸子植物为主，占木材总量的95%，被子植物仅占5%。凤栖原西汉古墓木椁为松科松属木材组成，在其木椁周围填充的木炭中发现有胡桃科化香树属（Platycarya）的木材。 2、木材来源 1）木材类群的分布 冷杉属、云杉属和松属现仍然分布在秦岭北坡、关中地区及其以北的地方，而铁杉属、楠木属和化香树属植物类群则是亚热带成分，现分布在秦岭以南的地区。不过也有报道，铁杉属在秦岭北坡还能看到它残留的个别植株，枯枝以及保存在过去地层中的花粉。这似乎可以说，历史时期铁杉属植物在秦岭北坡有过分布。 2）、气候的影响 各种气候记录、考古数据显示，中国5000年来发生过多次冷暖变化。春秋至秦汉时期、唐朝初期均是历史上温暖湿润的适宜时期，那时关中地区的温度比现在要高出1-2°C。最近有人在兵马俑坑中，报道野桐属（Mallotus）的孢粉，该类群现在广泛分布在亚热带及热带地区。这似乎说明兵马俑坑修建时，关中地区的气候较现在温暖。秦岭现在南北坡的温度之差恰好也是2°C。可以设想现在分布在秦岭以南的亚热带植物的成分，如：楠木、化香树等亚热带植物在历史上温暖湿润的时期有可能分布到了秦岭的北坡和关中地区。 3）、用材的特点 在兵马俑坑棚架中出土的木材粗细不均，长短不一，种类不同，这种种迹象表明秦人在修建兵马俑坑时有可能是就近取材。另外，在兵马俑坑出土的楠木和其他种类的木材一样作棚木用，并没有见到其特殊的用途。而同样在关中地区出土的汉代、唐朝的楠木也未见其特殊的作用，与其他木材混在一起使用。此外，凤栖原西汉古墓防潮用的木炭中的化香树也未见其特殊的用途。因此推测包括楠木和化香树在内的所有木材都有可能是就地取材。

Molecular and functional characterization of a c-type lysozyme from the Asian corn borer, Ostrinia furnacalis

Some lepidopteran lysozymes have been reported to display activity against Gram-positive and Gram-negative bacteria, in contrast to most lysozymes that are active only against Gram-positive bacteria. OstrinLysC, a c-type lysozyme, was purified from the As

Phylogeny and biogeography of the Petaurista philippensis complex (Rodentia : Sciuridae), inter- and intraspecific relationships inferred from molecular and morphometric analysis

With modified DNA extraction and Purification protocols, the complete cytochrome b gene sequences (1140 bp) were determined from degraded museum specimens. Molecular analysis and morphological examination of cranial characteristics of the giant flying squirrels of Petaurista philippensis complex (P. grandis, P. hainana, and P. yunanensis) and other Petaurista species yielded new insights into long-standing controversies in the Petaurista systematics. Patterns of genetic variations and morphological differences observed in this study indicate that P. hainana, P. albiventer, and P. yunanensis can be recognized as distinct species, and P. grandis and P. petaurista are conspecific populations. Phylogenetic relationships reconstructed by using parsimony, likelihood, and Bayesian methods reveal that, with P. leucogenys as the basal branch, all Petaurista groups formed two distinct clades. Petaurista philippensis, P. hainana, P. yunanensis, and P. albiventer are clustered in the same clade, while P. grandis shows a close relationship to P. petaurista. Deduced divergence times based on Bayesian analysis and the transversional substitution at the third codon suggest that the retreating of glaciers and upheavals or movements of tectonic plates in the Pliocene-Pleistocene were the major factors responsible for the present geographical distributions of Petaurista groups. (c) 2005 Elsevier Inc. All rights reserved.

Molecular phylogeny and biogeography of woolly flying squirrel (Rodentia : Sciuridae), inferred from mitochondrial cytochrome b gene sequences

To investigate the genetic diversity between the populations of woolly flying squirrels (Eupetaurus) from the eastern and western extremes of the Himalayas, partial mitochondrial cytochrome b gene sequences (390-810bp) that were determined from the museum specimens were analyzed using maximum parsimony (MP) and maximum likelihood (ML) methods. The molecular data reveal that the two specimens that were collected in northwestern Yunnan (China) are members of the genus Eupetaurus. Reconstructed phylogenetic relationships show that the populations of Eupetaurus in the eastern and western extremes of the Himalayas are two distinct species with significant genetic differences (12%) and diverged about 10.8 million years ago. Eupetaurus is significantly different from Petaurista and Pteromys. The level of estimated pairwise-sequence divergence observed between Eupetaurus and Petaurista or Pteromys is greater than that observed between Eupetaurus and Trogopterus, Belomys, Glaucomys, or Hylopetes. Considering the divergence time of the two Eupetaurus groups, the glaciations and the uplift of the Himalayas and Qinghai-Tibet plateau during the Pliocene-Pleistocene period might be the major factors affecting the present distribution of Eupetaurus along the Himalayas. (C) 2004 Elsevier Inc. All rights reserved.

水污染对鱼类生态毒理影响研究的新进展

<正> 随着水污染的日趋严重,为适应水质监测、渔业等方面的需要,近年来,鱼类生态毒理学研究得到了迅速发展。有关鱼类生态毒理研究的进展情况,已分别有人就1975、1978年及1978～1979年作过综述报导。在此,作者对1984～1986年的鱼类生态毒理研究新进展作一综述。 一、概述 第二届国际海洋生物对污染物反应讨论会于1983年4月27日在美国明尼苏达州Woods Hole召开’会后由Stegeman,J.J.编辑出版了论文集《海洋生物对污染物

Long rectangle resonator 1550 nm AlGaInAs/InP lasers

1550 nm AlGaInAs/InP long rectangle resonator lasers with three sides surrounded by SiO2 and p electrode layers are fabricated by planar technology, and room-temperature continuous-wave lasing is realized for a laser with a length of 53 mu m and a width of 2 mu m. Multiple peaks with wavelength intervals of Fabry-Perot mode intervals and mode Q factors of about 400 and a lasing mode with a Q factor over 8000 are observed from the lasing spectrum at threshold current. The numerical results of the FDTD simulation indicate that the lasing mode may be a whispering-gallery mode, which is a coupled mode of two high-order transverse modes of the waveguide.

Investigation of mode radiation loss for microdisk resonators with pedestals by FDTD technique

Mode radiation loss for microdisk resonators with pedestals is investigated by three-dimensional (3D) finite-difference time-domain (FDTD) technique. For the microdisk with a radius of 1 mu m, a thickness of 0.2 mu m, and a refractive index of 3.4, on a pedestal with a refractive index of 3.17, the mode quality (Q) factor of the whispering-gallery mode (WGM) quasi-TE7,1 first increases with the increase of the radius of the pedestal, and then quickly decreases as the radius is larger than 0.75 mu m. The mode radiation loss is mainly the vertical radiation loss induced by the mode coupling between the WGM and vertical radiation mode in the pedestal, instead of the scattering loss around the perimeter of the round pedestal. The WG M can keep the high Q factor when the mode coupling is forbidden.

Mode characteristics of metallically coated square microcavity connected with an output waveguide

Mode characteristics of a square microcavity with an output waveguide on the middle of one side, laterally confined by an insulating layer SiO2 and a p-electrode metal Au, are investigated by two-dimensional finite-difference time-domain technique. The mode quality (Q) factors versus the width of the output waveguide are calculated for Fabry-Peacuterot type and whispering-gallery type modes in the square cavity. Mode coupling between the confined modes in the square cavity and the guided modes in the output waveguide determines the mode Q factors, which is greatly influenced by the symmetry behaviors of the modes. Fabry-Peacuterot type modes can also have high Q factors due to the high reflectivity of the Au layer for the vertical incident mode light rays. For the square cavity with side length 4 mu m and refractive index 3.2, the mode Q factors of the Fabry-Peacuterot type modes can reach 10(4) at the mode wavelength of 1.5 mu m as the output waveguide width is 0.4 mu m.

Design of quantum cascade microcavity lasers based on Q factor versus etching depth

The choice of the etching depth for semiconductor microcavities is a compromise between a high Q factor and a difficult technique in a practical fabricating process. In this paper, the influences of the etching depth on mode Q factors for mid-infrared quantum cascade microcylinder and microsquare lasers around 4.8 and 7.8 mu m are simulated by three-dimensional (3D) finite-difference time-domain (FDTD) techniques. For the microcylinder and the microsquare resonators, the mode Q factors of the whispering-gallery modes (WGMs) increase exponentially and linearly with the increase in the etching depth, respectively Furthermore, the mode Q factors of some higher order transverse WGMs may be larger than that of the fundamental transverse WGM in 3D microsquares. Based on the field distribution of the vertical multilayer slab waveguide and the mode Q factors versus the etching depth, the necessary etching depth is chosen at the position where the field amplitude is 1% of the peak value of the slab waveguide. In addition, the influences of sidewall roughness on the mode Q factors are simulated for microsquare resonators by 2D FDTD simulation. (C) 2009 Optical Society of America

Equilateral-Triangle and Square Resonator Semiconductor Microlasers

The characteristics of equilateral-triangle resonator (ETR) and square resonator microlasers are reported, which are potential light sources in the photonic integrations. Based on the numerical simulations, we find that high-efficiency directional emission can be achieved for the triangle and square microlasers by directly connecting an output waveguide to the resonators. The electrically injected InP/InGaAsP ETR and square resonator microlasers with a 2-mu m-wide output waveguide were fabricated by standard photolithography and inductively coupled plasma etching techniques. Room-temperature continuous-wave (CW) operations were achieved for the ETR microlasers with the side length from 10 to 30 mu m and the square resonator microlasers with the side length of 20 mu m. The output power versus CW injection current and the laser spectra are presented for an ETR microlaser up to 310 K and a square resonator microlaser to 305 K. The lasing spectra with mode wavelength intervals as that of whispering-gallery-type modes and Fabry-Perot modes are observed for two square lasers, which can lase at low temperature and room temperature, respectively.

Investigation of mode coupling in a microdisk resonator for realizing directional emission

Mode coupling between the whispering-gallery modes (WGMs) is numerically investigated for a two-dimensional microdisk resonator with an output waveguide. The equilateral-polygonal shaped mode patterns can be constructed by mode coupling in the microdisk, and the coupled modes can still keep high quality factors (Q factors). For a microdisk with a diameter of 4.5 mu m and a refractive index of 3.2 connected to a 0.6-mu m-wide output waveguide, the coupled mode at the wavelength of 1490 nm has a Q factor in the order of 10(4), which is ten times larger than those of the uncoupled WGMs, and the output efficiency defined as the ratio of the energy flux confined in the output waveguide to the total radiation energy flux is about 0.65. The mode coupling can be used to realize high efficiency directional-emission microdisk lasers. (C) 2009 Optical Society of America

Mode Analysis for Equilateral-Triangle-Resonator Microlasers with Metal Confinement Layers

Mode characteristics are analyzed for electrically injected equilateral-triangle-resonator (ETR) semiconductor microlasers, which are laterally confined by insulating barrier SiO2 and electrode metals Ti-Au. For the ETR without metal layers, the totally confined mode field patterns are derived based on the reflection phase shifts, and the Q-factors are calculated from the far-field emission of the analytical near field distribution, which are agreement very well with the numerical results of the finite-difference time-domain (FDTD) simulation. The polarization dependence reflections for light rays incident on semiconductor-SiO2 -Ti-Au multi-layer structures are accounted in considering the confinement of TE and TM modes in the ETR with the metal layers. The reflectivity will greatly reduce with a Ti layer between SiO2 and Au for light rays with incident angle less than 30 especially for the TE mode, even the thickness of the Ti layer is only 10 nm. If the ETR is laterally confined by SiO2-Au layers without the Ti layer, the Fabry-Perot type modes with an incident angle of zero on one side of the ETR can also have high Q-factor. The FDTD simulation for the ETR confined by metal layers verifies the above analysis based on multi-layer reflections. The output spectra with mode intervals of whispering-gallery modes and Fabry-Perot type modes are observed from different ETR lasers with side length of 10 m, respectively.