Microwave Edge Diffraction by Features in Saturn's Rings: Observations with Voyager 1

Classical edge diffraction patterns are formed at centimeter wavelengths by several features of Saturn's rings. These patterns were discovered in 3.6-and 13-centimeter radio signals from Voyager 1 during occultation by the rings. The observed shapes are in agreement with theoretical patterns computed for screens of perfectly abrupt edges having large but finite opacity. Comparison with models in which the opacity at the edge tapers to zero from a finite value sets a new bound of less than about 200 meters on the microwave edge thickness. Certain features of the data suggest a smaller upper bound of about 130 meters on the edge thickness.     

Macroscopic hierarchical surface patterning of porphyrin trimers via self-assembly and dewetting

The use of bottom-up approaches to construct patterned surfaces for technological applications is appealing, but to date is applicable to only relatively small areas (approximately 10 square micrometers). We constructed highly periodic patterns at macroscopic length scales, in the range of square millimeters, by combining self-assembly of disk-like porphyrin dyes with physical dewetting phenomena. The patterns consisted of equidistant 5-nanometer-wide lines spaced 0.5 to 1 micrometers apart, forming single porphyrin stacks containing millions of molecules, and were formed spontaneously upon drop-casting a solution of the molecules onto a mica surface. On glass, thicker lines are formed, which can be used to align liquid crystals in large domains of square millimeter size.     

一种互补式LVTSCR的CMOS芯片ESD保护方法

为实现对CMOS芯片进行ESD防护提出了一种互补式LVTSCR结构,给出了该结构横切面电路模型以及等效电路,分析了工作原理及可行性,并与现有的ESD保护结构进行对比分析,采用ISE-TCAD工具进行仿真实验.结果表明：该结构具有占用面积小,单位面积防护效率高的特性,可有效降低成本.     

单船海上视觉搜寻水上人员的搜寻方式效率比较

分析了单船海上扩展方形和扇形视觉搜寻水上人员两种方式,通过建立衡量单船海上视觉搜寻水上人员两种高效搜寻方式的数学模型并结合《国际航空和海上搜寻救助手册》对其进行定量分析,得出在搜寻半径为2～5 n mile的较小搜寻区域内,扩展方形视觉搜寻方式的效率高于扇形视觉搜寻方式的结论,为海上视觉搜寻决策者进行科学决策提供依据。     

浅谈城市广场

按照广场的功能、用途及在城市交通系统中所处的位置可分为集会广场(包括市民广场、纪念广场、生活广场、文化广场、游憩广场等)交通广场、商业广场等。这种分类是相对的,实际上每一类广场都具备其他类型广场的某些功能。因此城市广场的分类,从一定程度上描述了广场的功能。近几年,许多城市兴建了不少广场,但有些广场仅是以草坪道路为主,缺乏人群活动休息的空间,忽视了人的行为需求,使得广场的草坪屡遭破坏。     

不同种植方式对花生生育及产量的影响

针对黑龙江省花生栽培技术落后,生产水平低等问题,研究了不同种植方式对花生生育及产量的影响.研究结果表明,花生大垄双行栽培模式的适宜密度为40株·m-2,比密度32株·m-2的处理增产14.7%,两种密度处理的花生产量在1%水平上差异显著;花生小垄单行栽培模式的适宜密度为30株·m-2,比密度26株·m-2的处理增产8.4%,两种密度处理的花生产量没有显著差异;花生大垄双行栽培模式(密度为40株·m-2)的产量比花生小垄单行栽培模式(密度为30株·m-2)增产37.5%,两种模式处理的花生产量在1%水平上差异显著.应用本项研究取得的成果,集成组装了寒地花生大垄双行高产栽培模式,对推动黑龙江省花生生产的发展具有重要意义.     

The first chemical enrichment in the universe and the formation of hyper metal-poor stars

The recent discovery of a hyper-metal-poor (HMP) star, with a metallicity Fe/H smaller than 1/100,000 of the solar ratio, together with one earlier HMP star, has raised a challenging question whether these HMP stars are the actual first-generation, low-mass stars of the universe. We argue that these HMP stars are second-generation stars formed from gases that were chemically enriched by the first-generation supernovae. The key to this solution is the very unusual abundance patterns of these HMP stars and the similarities and differences between them. We can reproduce these abundance features with core-collapse "faint" supernova models that include extensive matter mixing and fallback during explosions.     

Paleomagnetic tests of pacific plate reconstructions and implications for motion between hotspots

The plate-motion circuit through the South Pacific and Antarctica is shown to fail paleomagnetic tests of consistency. These failures imply that reconstructions of Pacific basin plates relative to surrounding plates inferred from this circuit are systematically in error and that estimates of motion between hotspots inferred from this circuit are probably too large. Therefore, the motions between hotspots remain poorly known and may be much smaller than previously estimated.     

Large-scale, low-amplitude bedforms (chevrons) in the selima sand sheet, egypt

Landsat images of the Selima sand sheet in southwestern Egypt display alternating light and dark chevron-shaped patterns that occur downwind from low scarps and major dune fields. Images acquired between 1972 and 1988 indicate that these features move as discrete bedforms at a rate of up to 500 meters per year. Extremely long-wavelength (130 to 1200 meters), low-amplitude (10 to 30 centimeters) bedforms were measured in the field; the light chevrons seen in the orbital data may be thin accumulations of active sand sheet deposits in the lee of these bedforms. Dark chevrons contain an admixture of coarse-granule lag deposits that are continually winnowed by aeolian erosion on the windward sides of the large bedforms. Sediment transport budgets derived from orbital and field analyses suggest net movement of up to 83,000 cubic meters per year for a single light chevron; such measurements can be used as a check on similar calculations from dunes and other smaller scale features to determine sand transport budgets for large areas of the eastern Sahara.     

桁杆张网渔具菱形和方形网目网囊的选择性研究

使用套网法作为选择性试验方法,Logistic曲线作为选择性曲线模型,并运用极大似然估计法进行曲线参数估算,对桁杆张网渔具不同网目尺寸(25mm、30mm、35mm、40mm以及45mm网目大小)、不同网目形状(菱形网目和方形网目)的网囊选择性进行分析。结果显示:各菱形网目网囊对黄鲫和银鲳的50%选择体长(或叉长)比相应方形网目的大(分别为3.79%和31.25%),而对小黄鱼的50%选择体长比相应方形网目小(7.92%);各菱形网目对黄鲫、小黄鱼和银鲳的选择范围都比相应方形网目大(分别为20.76%、5.36%以及45.99%)。这与传统认为方形网目选择性优于菱形网目的观点存在差异。通过讨论,认为黄鲫和银鲳体形较扁,游泳能力较弱是造成这些差异的主要原因。因此,在进行网囊结构改革时,不能盲目遵循方形网目优于菱形网目的传统观点。     

桁杆张网渔具菱形和方形网目网囊的选择性研究

使用套网法作为选择性试验方法,Logistic曲线作为选择性曲线模型,并运用极大似然估计法进行曲线参数估算,对桁杆张网渔具不同网目尺寸(25mm、30mm、35mm、40mm以及45mm网目大小)、不同网目形状(菱形网目和方形网目)的网囊选择性进行分析。结果显示:各菱形网目网囊对黄鲫和银鲳的50%选择体长(或叉长)比相应方形网目的大(分别为3.79%和31.25%),而对小黄鱼的50%选择体长比相应方形网目小(7.92%);各菱形网目对黄鲫、小黄鱼和银鲳的选择范围都比相应方形网目大(分别为20.76%、5.36%以及45.99%)。这与传统认为方形网目选择性优于菱形网目的观点存在差异。通过讨论,认为黄鲫和银鲳体形较扁,游泳能力较弱是造成这些差异的主要原因。因此,在进行网囊结构改革时,不能盲目遵循方形网目优于菱形网目的传统观点。     

绥芬河市中心广场改造设计

文章简要介绍了绥芬河市中心广场的设计背景,依据合理组织空间,完善功能、"以人为本"体现对使用群体的尊重、注重地域特色的表达的原则对广场进行总体布局,将广场分为林荫广场、疏林草坪、休闲交流、中心广场四个区域并进行绿化设计。     

Minimum condition for stereopsis and anomalous contour

Horizontal borders were deleted progressively from square and circular dot patterns containing disparate forms. Stereoscopic depth and anomalous contour occur in the absence of horizontal borders and the form in depth does not always assume the shape of the dot patterns. The stereoscopic effects depend on a laterally disparate form in the stereogram.     

Short-period climatic fluctuations: effects on diatom biomass

An analysis of the weekly averages of diatom biomass measured near the coast of Southern California (32 degrees 50'N, 117 degrees 10'W) during the period from 1928 through 1939 indicates that three major blooms account for 85 percent of each year's diatom biomass. The average duration of a single bloom is 5.5 weeks. The diatom blooms coincide with upwelling, but their individual characteristics depend on the detailed features of the circulation patterns of the water masses. That is, if upwelling takes place after a large influx of subtropical or even tropical water because of the slackening California Current, the resulting diatom blooms are smaller by several orders of magnitude than those observed when the flow of the current is strong. This influx of subtropical water into the region is reflected in positive anomalies of temperature, salinity, and sea level.     

基于景观图式语言的龙溪古镇公共空间特征与保护研究

图式语言是揭示公共空间由景观要素、空间单元到空间组合的过程,在空间解读上存在直观性与逻辑性的优势.利用景观图式语言的研究方法,将龙溪古镇公共空间分为线型空间、类方型块状空间、自由型块状空间,总结出47种空间要素图式、 25种空间单元图式、 9种空间组合图式.分析图式语汇,得到了自由型图式最多的数量特征和类方型图式最具有人文价值的功能特征.分析词法,得到龙溪古镇公共空间在构成方式上以叠加型空间为主、街巷空间为骨架的特征.分析句法得到公共空间性质随时间变化,但中码头性质与街巷空间形态不变;公共空间秩序随时间变化更加丰富,封闭空间变多;枕山环水面屏的自然山水空间格局、两纵两横的公共空间格局与簇群建筑空间格局均稳定无变化的特征.结合以上公共空间特征,提出增加要素多样性、保留类方型空间而修整自然型空间、增加叠加型空间组合并大力保护街巷空间、尊重空间时态而增加空间序列、保护整体格局等保护发展措施.     

亚热带城市广场园林植物的配植:以贵阳市为例

为了探索城市广场中的植物如何配置,如何营造出各种不同风格的城市广场园林景观,从而使城市色彩更丰富,外观更美丽,使城市更富文化品味,体现出城市的历史文脉和精神风貌,对贵阳市6个城市广场的植物配植情况进行了调查分析。结果表明:贵阳市城市广场植物配植符合植物引种的规律性,布局合理,空间利用充分,整体效果好,视觉景观运用合理,营造出特有的亚热带景观。     

Scale dependence in plant biodiversity

The relationship between the number of species and the area sampled is one of the oldest and best-documented patterns in community ecology. Several theoretical models and field data from a wide range of plant and animal taxa suggest that the slope, z, of a graph of the logarithm of species richness against the logarithm of area is roughly constant, with z approximately 0.25. We collected replicated and randomized plant data at 11 spatial scales from 0.01 to 10(8) square meters in Great Britain which show that the slope of the log-log plot is not constant, but varies systematically with spatial scale, and from habitat to habitat at the same spatial scale. Values of z were low (0.1 to 0.2) at small scales (<100 square meters), high (0.4 to 0.5) at intermediate scales (1 hectare to 10 square kilometers), and low again (0.1 to 0.2) for the largest scale transitions (e.g., East Berks to all of Berkshire). Instead of one process determining changes in species richness across a wide range of scales, different processes might determine plant biodiversity at different spatial scales.     

中国传统民居建筑的生态文化

中国传统民居根植于农耕文化,具有丰富的思想和内涵。笔者通过分析传统民居建筑的生态思想和文化思想以期为现代民居建筑的设计提供参考。笔者认为：①传统民居建筑的生态思想包括＂天人合一＂的朴素生态观、＂负阴抱阳＂的风水观、＂因势利导＂的节能观。传统民居建筑多顺应自然地形而建,采用＂负阴抱阳、背山面水＂的择址原则,就近取材,由该地区环境、气候特点决定建筑形式,使民居具有冬暖夏凉、南向日照充足、通风隔热、防风祛湿的特性,为居住者提供自然的生态居住环境。②传统民居建筑的文化思想包括方正严明的哲理思想和丰富和谐的艺术思想。中国传统民居以严整的格局、强烈的秩序感来反映伦理规范,在空间格局上多具有明确的轴线,表现建筑群体中的层次与核心;传统民居建筑的建筑细部多使用抽象化的花、草、动物、人物图案,富有审美情趣。中国传统民居的形成与中国各地的社会、文化、居住习俗以及地理、水土、环境、气候、风土人情都有着密切的关系,对现代新型民居建筑的设计、改造具有重要参考价值。     

Experimental demonstration of guiding and bending of electromagnetic waves in a photonic crystal

The routing and interconnection of optical signals through narrow channels and around sharp corners are important for large-scale all-optical circuit applications. A recent computational result suggests that photonic crystals may offer a novel way of achieving this goal by providing a mechanism for guiding light that is fundamentally different from traditional index guiding. Waveguiding in a photonic crystal and near 100 percent transmission of electromagnetic waves around sharp 90 degree corners were observed experimentally. Bending radii were made smaller than one wavelength.