Radio astronomy with very large arrray

The construction of the Very Large Array of radio telescopes has been completed, and this new research instrument is now being used to make radio images of astronomical objects with a resolution comparable to or better than that of ground-based optical telescopes. The role of the Very Large Array in current and future research is discussed both in principle and in terms of a sample of observing projects.     

几种淡水小型鱼类吞食粘性鱼卵的初步观察

通过在室内进行８种淡水小型鱼类吞食鱼卵的试验观察表明：小型鱼吞食鱼卵带有普遍性，吞食强度依次为宽鳍、麦穗鱼、马口鱼、虎鱼、棒花鱼、鱼旁鱼皮、银鱼句、，其中７种鱼具有昼夜摄食节律，高峰期各异，但每天皆有１６ｈ的停食期．由此可见，小型鱼类通过摄食鱼卵，对能够在湖泊水库中自然繁殖的经济鱼类及凶猛鱼类的种群具有一定调控作用，对公鱼等孵化期较长的鱼类移植效果产生不良影响     

Galactic X-rays: Variable Sources in Hydromagnetic Waves

Galactic sources of x-rays fluctuating in intensity are explained as being small regions, of enhanced gas density and temperature, emitting thermal Coulomb bremsstrahlung of kiloelectron-volt energies. Hydromagnetic wave motions, of the magnetic fields in the galactic spiral arms, produce the enhanced regions by compressing the clouds of ionized gas to which they are tied by their high electrical conductivity. From the observed periods of fluctuation of a few months, together with the hydromagnetic velocity, it is estimated that the average size of sources does not exceed 10(16) centimeters. By using the formula for Coulomb bremsstrahlung and requiring that the sources shall produce the observed x-ray fluxes, one finds a second estimate of size of sources in agreement at about 1016 centimeters. Such regions are too small to be observable radio sources with current radio telescopes.     

Origins

The farthest of the galaxies that can be seen through the large ground-based telescopes of modern astronomy, such as those on La Palma in the Canary Islands, are so far away that they appear as they did close to the time of the origin of the universe, perhaps some 10 billion years ago. Much has been learned, and much has still to be learned, about the young universe from optical and radio telescopes, but these instruments cannot be used to look directly at the universe in its first few hundred thousand years. Instead, they are used to search the relatively recent past for relics of much earlier times. Together with experiments planned for the next generation of elementary particle accelerators, astronomical observations should continue to extend what is known about the universe backward in time to the Big Bang and may eventually help to reveal the origins of the physical laws that govern the universe.     

New Instruments Shed Light On Astronomy's Future

KONA, HAWAII-The snowy 14,000-foot summit of Mauna Kea, with its bevy of powerful telescopes including the just-completed Keck, provided an appropriate backdrop for a recent ocean-side gathering of astronomers and engineers to discuss "Astronomical Telescopes and Instrumentation for the 21st Century." Last month's meeting was organized by the Society of Photo-Optical Instrumentation Engineers, and included a status report on liquid mirror telescopes, discussion of a space observatory that may make optical and x-ray astronomers best friends, and a modest proposal to cover the globe with a network of small, automated telescopes.     

Active optics, adaptive optics, and laser guide stars

Optical astronomy is crucial to our understanding of the universe, but the capabilities of ground-based telescopes are severely limited by the effects of telescope errors and of the atmosphere on the passage of light. Recently, it has become possible to construct inbuilt corrective devices that can compensate for both types of degradations as observations are conducted. For full use of the newly emerged class of 8-meter telescopes, such active corrective capabilities, known as active and adaptive optics, are essential. Some physical limitations in the adaptive optics field can be overcome by artificially created reference stars, called laser guide stars. These new technologies have lately been applied with success to some medium and very large telescopes.     

Laser ranging retro-reflector: continuing measurements and expected results

After successful acquisition in August of reflected ruby laser pulses from the Apollo 11 laser ranging retro-reflector (LRRR) with the telescopes at the Lick and McDonald observatories, repeated measurements of the round-trip travel time of light have been made from the McDonald Observatory in September with an equivalent range precision of +/-2.5 meters. These acquisition period observations demonstrated the performance of the LRRR through lunar night and during sunlit conditions on the moon. Instrumentation activated at the McDonald Observatory in October has yielded a precision of +/-0.3 meter, and improvement to +/-0.15 meter is expected shortly. Continued monitoring of the changes in the earth-moon distance as measured by the round-trip travel time of light from suitably distributed earth stations is expected to contribute to our knowledge of the earth-moon system.     

Program clocks in small mammals

Complex patterns of time, direction, and speed of running by small nocturnal mammals in activity wheels sometimes are duplicated almost exactly from night to night. These activity pattern repetitions disclose: (i) previously unknown capabilities of biological clocks to act as sequence programmers for behavior; (ii) that animals can retain a record of the sequence and timing of their activities covering an entire night; and (iii) that the activities of one night can bias an animal toward similar behavior on subsequent nights.     

The most distant known galaxies

Ever since the proposal of the idea of an expanding universe more than 50 years ago, each generation of investigators has found that some current theory could be (marginally) tested by the properties of the most distant known galaxies. There has consequently been a continuing effort to identify very remote objects, especially to confront theories of the evolution of galaxies (since galaxies are seen as they were at prior epochs) and to confront cosmological theories (which make predictions about the overall dynamics of the expansion of the universe). These theories have yet to be definitively tested, but a new generation of optical telescopes and detectors provides hope for significant progress during this decade.     

农村小型水利工程建设管理思考

现代化的农村建设与诸多影响农村发展的因素紧密相连,而农村小型水利工程建设更与每个方面的发展因素有着密切的关系,所以对农村小型水利工程建设提出了新的层次的要求.相对于农村水利工程建设需要新建现代化农村小型水利工程.就针对传统农村小型水利工程建设管理中存在的问题进行分析,并且通过各方面的研究来提出农村小型水利工程建设管理相关改善措施.     

Mount Graham. Report finds squirrels survived 3 telescopes

In 1988 Congress allowed construction of three telescopes on Mount Graham, a desert "sky island" northeast of here, prompting the U.S. Forest Service to order a long-range study to monitor the population of an endangered subspecies of red squirrel that lives here. The results are now in. But the findings--that the work to date has had "no significant effect" on the rare rodents--have done little to resolve a debate that is expected to heat up again next year when the University of Arizona seeks permission to build four more telescopes.     

An intercontinental array--a next-generation radio telescope

It is difficult to estimate accurately the cost of constructing a large scientific instrument that involves many techniques. On the other hand, most of the component parts of the VLBA consist of antennas and electronic systems that already exist or are being fabricated. The kind of 25-m antennas being constructed for the VLA will cost about $900,000 each and will work at wavelengths as short as 1 cm. A multifrequency radiometer, hydrogen maser frequency standard, small control computer, control building, and wide-band instrumentation recorder bring the cost to about $1.5 million per element, or $15 million for a ten-element array using tape recorders. A multistation playback facility, with ten recorders and enough correlators to handle all interferometer pairs simultaneously, together with the necessary computers to control the processor and reduce the data, may add $5 million. The total cost is thus about $20 million at current prices, including an adequate supply of magnetic tape. This is comparable to the cost of existing large radio telescopes and arrays. An array that used a geostationary communication satellite to transmit the data to a real-time correlator would cost $30 million to $50 million more, but this is still within the price range of other space astronomy projects. It is thus feasible to construct at reasonable cost an intercontinental very long baseline array which has sub-milliarcsecond resolution. This would complement the Very Large Array now being constructed (4), which is much more sensitive to objects of low surface brightness. This next step would permit the study of the universe with unprecedented angular resolution.     

Interferometric coupling of the Keck telescopes with single-mode fibers

Here we report successful interferometric coupling of two large telescopes with single-mode fibers. Interference fringes were obtained in the 2- to 2.3-micrometer wavelength range on the star 107 Herculis by using the two Keck 10-meter telescopes, each feeding their common interferometric focus with 300 meters of single-mode fibers. This experiment demonstrates the potential of fibers for future kilometric arrays of telescopes and is the first step toward the 'OHANA (Optical Hawaiian Array for Nanoradian Astronomy) interferometer at the Mauna Kea observatory in Hawaii. It opens the way to sensitive optical imagers with resolutions below 1 milli-arc second. Our experimental setup can be directly extended to large telescopes separated by many hundreds of meters.     

Overview and initial results of the very long baseline interferometry space observatory programme

High angular resolution images of extragalactic radio sources are being made with the Highly Advanced Laboratory for Communications and Astronomy (HALCA) satellite and ground-based radio telescopes as part of the Very Long Baseline Interferometry (VLBI) Space Observatory Programme (VSOP). VSOP observations at 1.6 and 5 gigahertz of the milli-arc-second-scale structure of radio quasars enable the quasar core size and the corresponding brightness temperature to be determined, and they enable the motions of jet components that are close to the core to be studied. Here, VSOP images of the gamma-ray source 1156+295, the quasar 1548+056, the ultraluminous quasar 0014+813, and the superluminal quasar 0212+735 are presented and discussed.     

我国开发小水电清洁发展机制项目的研究

通过对清洁发展机制的理论阐述,分析了小水电项目引入清洁发展机制（CDM）的可行性,以及小水电CDM项目带来的效益,提出了小水电CDM项目开发程序,并指出了应该注意的问题。     

Soft X-ray Images of the Solar Corona with a Normal-Incidence Cassegrain Multilayer Telescope

High-resolution images of the sun in the soft x-ray to extreme ultraviolet(EUV) regime have been obtained with normal-incidence Cassegrain multilayer telescopes operated from a sounding rocket in space. The inherent energy-selective property of multilayer-coated optics allowed distinct groups of emission lines to be isolated in the solar corona and the transition region. The Cassegrain telescopes provided images in bands centered at 173 and 256 angstroms. The bandpass centered at 173 angstroms is dominated by emission from the ions Fe IX Fe X. This emission is from coronal plasma in the temperature range 0.8 x 10(6) to 1.4 x 10(6)K. The images have angular resolution of about 1.0 to 1.5 arc seconds, and show no degradation because of x-ray scattering. Many features of coronal structure, including magnetically confined loops of hot plasma, coronal plumes, polar coronal holes, faint structures on the size scale of supergranulation and smaller, and features due to overlying cool prominences are visible in the images. The density structure of polar plumes, which are thought to contribute to the solar wind, has been derived from the observations out to 1.7 solar radii.     

小型水利工程管护中出现的问题与完善措施

最近几年以来,国家逐渐开始重视小型农田水利工程项目的建设,投入的建设资金越来越多,所以如何确保水利工程在建设完成之后能够正常的运行、管理和维护,发挥出最大的经济以及社会效应,已经成为目前急需解决的问题.基于此,本文主要对小型水利工程管护中出现的问题与完善措施进行了探讨.     

小水电清洁发展机制碳减排效益研究——以甘肃省南部为例

从碳排放权、适宜性、额外性、协同效应4个方面分析了甘肃省南部地区开展小水电项目的可能性,利用中国西北电网数量相当电量来探讨CDM减排效益。计算得出基准线综合排放因子,采用线性模型,将污染物的排放量和其他变量简化求得协同效应减排量,验证了CDM减排成果,得出不同阶段甘肃省南部小水电CDM减排效益。甘肃省南部地区开展小水电CDM项目存在着较大的发展潜力,要想取得最大化的减排效益,需要在保护生态环境的基础上推进CDM市场化减排,随着未来国际碳减排价格的增长,甘肃省南部地区小水电项目减排效益显著。     

Telescopes and automation

In stellar astronomy, the future of automation techniques lies in their application to the largest telescopes. In such a case, the cost of automation is small compared to that of the telescope project as a whole, and is well repaid in the savings in observing time. A "stand-alone" capability for manual operation in event of computer breakdown is usually provided for systems like this; an example is the 107-inch (272-cm) telescope under construction at the McDonald Observatory of the University of Texas, which will be associated with an IBM 1800 computer.     

黄土高原沟壑区小流域水土保持工程体系优化配置研究

采用优化规划的方法,把黄土高原沟壑区小流域水土保持工程视为一个系统,以生态、经济效益最大为目标,以塬(坡)面和沟道之间的水沙联系为纽带,把塬(坡)面工程和沟道工程统一起来,建立了小流域整个工程防治体系优化配置的数学模型.在此基础上,以淳化县泥河沟小流域为例对工程体系结构进行了优化配置.实践和优化结果的相互印证说明该优化模型较为可靠.