寻夏之旅

每年的6月21日或22日,为夏至日,此时太阳直射北回归线。这一天,在中国最北的漠河北极村,一天24小时几乎都是白昼。这一天,在中国南边的云南墨江、广东从化、广西桂平,正午时分"立竿无影"。这一天,山东的人在吃面,而广西的人在吃狗肉……从北至南,在夏至这一天,你会看到最不同的风俗,也会看到最特别的景致,所以,让我们马上开始一次寻夏之旅。     

Conjecture on superrotation in planetary atmospheres: A diffusion model with mixing length theory

Superrotation on Venus is discussed in the context of comparative planetary atmospheres. In our planetary system, the rigid shell component (global average) of superrotation is ubiquitous (Jupiter, Saturn, Earth, Venus, Mars, Titan). The largest equatorial values of the component are between 25 and 150 m/sec. We present a simplified, heuristic analysis, utilizing mixing length theory to describe the small scale non-linear advections of energy and angular momentum, thereby providing a closure of the dynamic system. This leads to the conjecture that the zonal velocity may be crudely estimated by

, approximating the observed planetary trends; with c the speed of sound, the parameter a being 1 or 2 for geostrophic or cyclostrophic conditions respectively, P_α an effective Prandtl number which becomes less than one when radiative cooling is important, S_o the average stability, Γ the adiabatic lapse rate and γ the ratio of specific heats.     

New technologies and data integration

The fourth workshop of the Earth Observation Data Policy and Europe (EOPOLE) project was held in Brussels, Belgium, 18–20 October 1999 at the offices of the European Commission DG Research, with Yves Reginster of Gere SA, Luxembourg, as guest speaker. The purpose of the workshop was to discuss the data policy issues raised by new technologies and by integrating Earth observation (EO) data with non-EO data. They included risks and reliability of output products, transfer of experience with new projects and intellectual property rights.     

Absolute Radiometer for the Flow Field of a Hypervelocity Projectile

As part of a hypervelocity instrumentation development program, it was desirable to include a radiometer system for measuring absolute radiation from projectile flow fields. A system employing a photomultiplier tube was designed, and laboratory and range experiments were conducted to investigate its performance characteristics. The laboratory experiments show that the linearity, saturation, and noise characteristics are suitable for this measurement; the system bandwidth is adequate to allow low frequency calibrations to be applied to high frequency measurements; and a derived expression for radiometer sensitivity variation as a function of photomultiplier supply voltage is reasonably correct. The results of the range experiments imply that the system response is sufficient to reproduce accurately input pulses as narrow as one microsecond and that a particular analytical technique for calculating the form of the radiative input to the radiometer from the projectile stagnation region is valid. Principles involved in the design of photomultiplier radiometer circuits of this type are discussed in detail.     

European perspectives on trends in public sector Earth observation data policies

The growing number of Earth observation satellites are producing ever increasing amounts of data. These data sets require adequate management to be widely exploited and to ensure preservation of what is a valuable information resource. Many Earth observation organisations have formulated or are developing policies related to how data are managed and distributed which encompass issues such as property rights, access and price of the data, exclusive data use and data archiving. European Earth observation is gaining more prominence in these developing policy issues. This paper is a review, from a largely European perspective, of current Earth observation data policies in operation by various public sector international, regional and national organisations in both the data providing and data user sectors. It will be demonstrated that certain trends exist between the various data policies but that differences in position are present in some key areas which may need to be reconciled in order for the Earth observation sector to reach maturity.     

Sample acquisition, processing and handling systems for future Mars missions

The next generation of Mars exploration robotics will have equipment to acquire subsurface samples, process and refine them, and transfer them to science instruments for observation. In 2003, MD Robotics and NORCAT, under contract with the Canadian Space Agency, designed, developed and tested building block technologies for a sample acquisition, processing and handling system for a future Mars mission. Four key technologies were developed to support this system: drill bit development for varied substrates, sample acquisition mechanisms to acquire cores at depth, material transport technologies to move waste material up the hole, and sample reduction technologies, studying the means to efficiently reduce samples into uniform particle sizes. This paper will discuss the technology development, the driving requirements and the test results.     

Earth observation and the public good

The term ‘public good’ is often used in satellite Earth observation to indicate that Earth observation data are of value or interest to the public. In fact, the term ‘public good’ has a more specific meaning, originating in the discipline of Economics, which carries with it a set of assumptions and implications about how markets operate. In this context a public good has two main characteristics: non-rivalry and non-excludability. In their most common digital format, Earth observation data can appear to be both non-rivalrous and non-excludable. However, it is not the digital medium itself which controls the ‘publicness’ of a good but the conditions of access to that good. This paper explores the meaning of the concept of public goods in an Earth observation context by, first, examining public good theory and related concepts of categories of goods and, second, applying the concepts to nine Earth observation missions, programmes and data.     

酷路泽的时尚精神

丰田FJ酷路泽正式上市已经5个多月的时间了,其时尚前卫的个性、超凡的越野性能,为国内SUV市场增添了些许别样的风景。疯狂的越野迷们也与FJ酷路泽一同,挑战了种种险路阻途。FJ迷们表示,无论是在高温炙烤的沙漠中跋涉沙海,还是在风雪中破冰击雪,FJ酷路泽都能,以金刚般的意念勇往直前。