平板边界层转捩的数值模拟

对于自由湍流引起的压力梯度为零的平板边界层转捩过程的数值模拟,本文提出了一个单方程湍流模型 (VL M模型),对湍流粘性系数和湍流长度尺度都进行了修正以正确引入低雷诺数效应。数值计算表明,该模型在自由来流湍流度为 0.03～8%的大范围内能正确模拟边界层转捩全过程,包括转捩区起点位置和转捩区长度、边界层内的平均及脉动参数分布等。本文还提出了上述转捩过程的时均化五阶段模型。      

Order out of Randomness: Self-Organization Processes in Astrophysics

Self-organization is a property of dissipative nonlinear processes that are governed by a global driving force and a local positive feedback mechanism, which creates regular geometric and/or temporal patterns, and decreases the entropy locally, in contrast to random processes. Here we investigate for the first time a comprehensive number of (17) self-organization processes that operate in planetary physics, solar physics, stellar physics, galactic physics, and cosmology. Self-organizing systems create spontaneous “order out of randomness”, during the evolution from an initially disordered system to an ordered quasi-stationary system, mostly by quasi-periodic limit-cycle dynamics, but also by harmonic (mechanical or gyromagnetic) resonances. The global driving force can be due to gravity, electromagnetic forces, mechanical forces (e.g., rotation or differential rotation), thermal pressure, or acceleration of nonthermal particles, while the positive feedback mechanism is often an instability, such as the magneto-rotational (Balbus-Hawley) instability, the convective (Rayleigh-Bénard) instability, turbulence, vortex attraction, magnetic reconnection, plasma condensation, or a loss-cone instability. Physical models of astrophysical self-organization processes require hydrodynamic, magneto-hydrodynamic (MHD), plasma, or N-body simulations. Analytical formulations of self-organizing systems generally involve coupled differential equations with limit-cycle solutions of the Lotka-Volterra or Hopf-bifurcation type.     

New Horizons: Anticipated Scientific Investigations at the Pluto System

The New Horizons spacecraft will achieve a wide range of measurement objectives at the Pluto system, including color and panchromatic maps, 1.25–2.50 micron spectral images for studying surface compositions, and measurements of Pluto’s atmosphere (temperatures, composition, hazes, and the escape rate). Additional measurement objectives include topography, surface temperatures, and the solar wind interaction. The fulfillment of these measurement objectives will broaden our understanding of the Pluto system, such as the origin of the Pluto system, the processes operating on the surface, the volatile transport cycle, and the energetics and chemistry of the atmosphere. The mission, payload, and strawman observing sequences have been designed to achieve the NASA-specified measurement objectives and maximize the science return. The planned observations at the Pluto system will extend our knowledge of other objects formed by giant impact (such as the Earth–moon), other objects formed in the outer solar system (such as comets and other icy dwarf planets), other bodies with surfaces in vapor-pressure equilibrium (such as Triton and Mars), and other bodies with N₂:CH₄ atmospheres (such as Titan, Triton, and the early Earth).     

Amino acids from ion-irradiated nitrile-containing ices

Solid CH(3)CN and solid H(2)O + CH(3)CN were ion irradiated near 10 K to initiate chemical reactions thought to occur in extraterrestrial ices. The infrared spectra of these samples after irradiation revealed the synthesis of new molecules. After the irradiated ices were warmed to remove volatiles, the resulting residual material was extracted and analyzed. Both unhydrolyzed and acid-hydrolyzed residues were examined by both liquid and gas chromatographic-mass spectral methods and found to contain a rich mixture of products. The unhydrolyzed samples showed HCN, NH(3), acetaldehyde (formed by reaction with background and atmospheric H(2)O), alkyamines, and numerous other compounds, but no amino acids. However, reaction products in hydrolyzed residues contained a suite of amino acids that included some found in carbonaceous chondrite meteorites. Equal amounts of D- and L-enantiomers were found for each chiral amino acid detected. Extensive use was made of (13)C-labeled CH(3)CN to confirm amino acid identifications and discriminate against possible terrestrial contaminants. The results reported here show that ices exposed to cosmic rays can yield products that, after hydrolysis, form a set of primary amino acids equal in richness to those made by other methods, such as photochemistry.     

Implementation issues impacting system designer utilization ofwireless technologies

Wireless technologies provide the missing link for automating a wide spectrum of applications which previously were not computerized due to constraints of their environment. For example, remote flight line support, outdoor sporting events, and one-time events such as conferences, all could be well served through computer aided support and resources. However, the costs associated with, even solely, the physical labor required to lay conventional cabling for such an event is prohibitive. Weatherproofing and time constraints also come into play; but before wireless technologies can become ubiquitous, many implementation issues must be addressed. This paper provides an overview of these issues and the current trends     

A study of a complete soft X-ray selected sample of AGN

We present preliminary results from analyses of hard X-ray and optical observations of a soft X-ray selected sample. We created a small but complete sample with 20 of the softest and brightest objects with low Galactic absorption from the ROSAT bright soft X-ray selected radio-quiet AGN sample. This sample consists of 10 narrow-line Seyfert 1 galaxies and 10 broad-line Seyfert galaxies. We analyze ASCA data in the 0.6–10 keV band and optical spectra from ground-based telescopes. We investigate the photon indices in the hard X-ray band, soft excesses in the ASCA band, and optical emission line properties. The photon indices in the 2–10 keV band are nominal for both narrow-line Seyfert 1 galaxies and broad-line Seyfert 1 galaxies in each class compared with other heterogeneous samples. All of the narrow-line Seyfert 1 galaxies show soft excesses, but this component seems to be less significant for broad-line Seyfert 1 galaxies. There seems to be a trend of steeper X-ray spectra to be accompanied by narrower Hβ for narrow-line Seyfert 1 galaxies, but this is not extended to the larger velocity width regime of broad-line Seyfert 1 galaxies, and no clear trend is seen among them.     

Source processes in the high-latitude ionosphere

Space Science Reviews -     

绿色航空产业的未来

综述 由于航油价格波动，全球各航空公司面对的商业前景正经历着巨大变化，多家公司需要解决短期和长期债务的清偿问题。然而，形势并非不可挽回，航空公司还有机会在业务模式和投资领域采取短期的战略行动，构建超越竞争对手的优势，保障各自的生存能力。通过投资开发燃油效率更高的技术、可替代新能源，并在短期内优化业务模式等办法，航空公司的航油消耗减负势在必行。     

A glimpse from the inside of a space suit: What is it really like to train for an EVA?

The beauty of the view from the office of a spacewalking astronaut gives the impression of simplicity, but few beyond the astronauts, and those who train them, know what it really takes to get there. Extravehicular Activity (EVA) training is an intense process that utilizes NASA’s Neutral Buoyancy Laboratory (NBL) to develop a very specific skill set needed to safely construct and maintain the orbiting International Space Station. To qualify for flight assignments, astronauts must demonstrate the ability to work safely and efficiently in the physically demanding environment of the space suit, possess an acute ability to resolve unforeseen problems, and implement proper tool protocols to ensure no tools will be lost in space. Through the insights and the lessons learned by actual EVA astronauts and EVA instructors, this paper will take you on a journey through an astronaut’s earliest experiences working in the space suit, termed the Extravehicular Mobility Unit (EMU), in the underwater training environment of the NBL. This work details an actual Suit Qualification NBL training event, outlines the numerous challenges the astronauts face throughout their initial training, and the various ways they adapt their own abilities to overcome them. The goal of this paper is to give everyone a small glimpse into what it is really like to work in a space suit.     

NASA Human Health and Performance Center: Open innovation successes and collaborative projects

In May 2007, what was then the Space Life Sciences Directorate published the 2007 Space Life Sciences Strategy for Human Space Exploration, setting the course for development and implementation of new business models and significant advances in external collaboration over the next five years. The strategy was updated on the basis of these accomplishments and reissued as the NASA Human Health and Performance Strategy in 2012, and continues to drive new approaches to innovation for the directorate. This short paper describes the successful execution of the strategy, driving organizational change through open innovation efforts and collaborative projects, including efforts of the NASA Human Health and Performance Center (NHHPC).