The evolution of binary stars into contact states

Good-quality empirical results on 62 short-period binary stars recently summarised by Hilditch & Bell (1987) and Hilditch, King & McFarlane (1988) are discussed in terms of evolutionary paths from detached to semi-detached and contact states. These data suggest two evolutionary paths to the contact binaries — from detached systems directly into contact to form initially shallow-contact systems, and via case A mass transfer to semi-detached states, thence to contact systems. These empirical results support previous arguments based on evolutionary models and less detailed observational data.Concern is expressed about the paucity of high-quality spectroscopic data, particularly for low-mass systems displaying EB-type light curves and the resultant limitations on analyses of those light curves. Such systems provide tests of evolution into contact for the first time, or of broken-contact phases for WUMa-type binaries. The crucial importance of long-term monitoring (decades) of times of minima as indicators of mass transfer rates amongst these interacting binaries is also noted.     

The evolution of binary stars into contact states

Good-quality empirical results on 62 short-period binary stars recently summarised by Hilditch & Bell (1987) and Hilditch, King & McFarlane (1988) are discussed in terms of evolutionary paths from detached to semi-detached and contact states. These data suggest two evolutionary paths to the contact binaries — from detached systems directly into contact to form initially shallow-contact systems, and via case A mass transfer to semi-detached states, thence to contact systems. These empirical results support previous arguments based on evolutionary models and less detailed observational data. Concern is expressed about the paucity of high-quality spectroscopic data, particularly for low-mass systems displaying EB-type light curves and the resultant limitations on analyses of those light curves. Such systems provide tests of evolution into contact for the first time, or of broken-contact phases for WUMa-type binaries. The crucial importance of long-term monitoring (decades) of times of minima as indicators of mass transfer rates amongst these interacting binaries is also noted.     

Automatic generation of binary feature detectors

The authors discuss the automatic generation of feature detectors, which is the major task in the design of classical pattern recognition systems. They present a software environment that, in place of human intuition, utilizes learning strategies and stochastic search procedures to guide the generation process. The environment allows the exploration of evolutionary learning processes and adaptive control mechanisms. A preliminary experiment with a two-class recognition system is described, and initial observations are discussed. The recognition task requires the classification of upper case English letters into two categories: target and nontarget     

Advanced Aircraft Electric System

The topics, advanced aircraft electric system and all-electric airplane, inspire a broad range of concepts from the evolutionary to the revolutionary. The revolutionary developments are exciting to the research and development community but find little encouragement or acceptance from airframe developers whose objective is to build an advanced technology airplane using only-off-the-shelf, proven equipment. Their anthem rings "We know how bad the ___________ is, but we have learned to live with it. We have only your vision of how good an advanced system will be and fear to chance it. "However, the cost of living with these known systems combined with the escalating cost of fuel and the military need to address advanced mission capability demands more than a patch called improved reliability and maintainability. The time is at hand to demonstrate an evolutionary approach to achieve a revolutionary improvement. This paper describes an advanced electric system, the life cycle cost improvement anticipated, and the evolutionary means to implementation.     

Massive close binaries: Observational characteristics

Theoretically predicted evolutionary phases of massive close binaries are compared with the observations. For the evolution up to the High-Mass X-ray Binary (HMXB) phase there is fair agreement between theory and observation. Beyond the HMXB phase there is much uncertainty. Notably it is puzzling why we observe so few systems consisting of a helium star and a neutron star (Cygnus X-3 is the only one found so far), and why the incidence of double neutron stars is so low. A better understanding of Common Envelope evolution is required in order to answer these questions. The role of velocity kicks imparted to neutron stars during supernova collapse is discussed. Such kicks might cause many runaway OB stars to be single.     

The future of military standards. A focus on electronics

The growing perception that with cutbacks in the military and the changing international economic environment, the military must rely on commercial industries in order to afford the next generation of high-performance and high-reliability military systems is discussed. One issue associated with the question of whether an industrial base for the military can be provided and maintained without major changes in the operation of both the government and commercial industry is examined, namely, whether commercial standards can effectively supplant military standards and still provide high performance and reliability for military missions     

基于多目标算法的空中作战任务规划框架研究

空中作战任务规划是一项复杂的任务,随着空中作战飞行器的种类、数量及其之间交互性的增加,任务规划也变得越来越复杂。任务规划人员必须在有限的时间内制定出最优的任务分配策略。决策支持工具可以辅助任务规划人员找到最优的规划方案。介绍了设计多目标进化算法以及在空中作战任务规划领域的框架和工作流程,具体的任务包括空中打击动态目标的定位问题和情报监视侦察（ISR）任务规划。总结了这些研究的经验教训,探讨了未来可能的发展方向。     

小型和微型无人机的气动特点和设计

讨论了当前包括固定翼、扑翼和微型旋翼的小型无人驾驶飞行器(SUAV)和微型无人驾驶飞行器(MAV)的进展和未来发展可能涉及的技术问题。讨论了低雷诺数空气动力特性,包括分离气泡和展弦比的影响。介绍了用于拍动翼的非定常空气动力特性和高升力机理。讨论了目前存在的2种设计方法——多学科/多目标优化设计和探索式/进化式的设计方法,以及在设计中柔性翼和主动智能控制的重要性。     

应用混合演化策略的机翼气动优化设计

把基于实数编码的遗传算法与可变容差法相结合,建立了数值优化设计中的混合演化策略(HES),并将其与机翼的气动分析相结合进行跨音速机翼的气动优化设计.与基准机翼相比,优化设计的机翼其气动性能有较大程度的改善,表明了混合演化策略在机翼优化设计中的有效性.与单纯的遗传算法(GA)相比,应用混合演化策略的气动优化设计具有更高的优化效率和优化质量.     

Evolution of massive close binaries

This paper briefly reviews the competition between massive single star and massive close binary evolution the last two decades. The status of the binary evolutionary model is summarized, the assumptions and simplifications are critically discussed. Using all computations performed since 1970, general conclusions are drawn and a comparison with massive single star evolution is presented. Special attention is given at the assumptions behind the commonly accepted model for the mass gainer and a new accretion model is proposed. The binary results in combinarion with single star evolution are compared with observations of massive stars with emphasis on the HR diagram, star number counts, WR stars, SN 1987A, OBN and OBC stars.     

Possible Applications of Communications Satellites to Offshore Systems

Expanding offshore operations have generated an increased need for communications in both international and domestic areas. The capabilities of communications satellites are presented both as currently existing and as envisioned in the future. The possibilities of using these capabilities in offshore communications systems are discussed especially with regard to the potential of new services brought about by the latest generation of satellites currently under production. Two potentially new types of services are hypothesized. Lastly, progress on the development of a small earth station of low cost suitable for such services is reported. It is concluded that communications satellites hold potential both currently and in the future for various offshore operations.     

Reverse Algols

An Algol is a binary system having a semidetached configuration where the less massive component is in contact with the critical equipotential surface. A reverse Algol is a binary system having a semidetached configuration where the more massive component is in contact with the critical equipotential surface. In 1985, Leung suggested 5 reverse Algol systems at the Beijing Colloquium. Two more such systems have been discovered recently. The spectral types of these systems range from early B to mid G. There is also a wide spread in mass ratio among these systems. There appear to be two types of reverse Algols, hot and cool systems. The hot systems have their more massive components as the hotter stars and the cool systems their more massive components as the cooler stars. The mass-radius relation of the reverse Algols is very similar to that of the contact and near-contact systems. It is believed that reverse Algols represent the pre-mass-reversal semidetached phase of close binary evolution. Since selection effects apply to both the regular Algols and reversed Algols in a similar manner, the evolutionary time scale between them would be simply the ratio of the number of confirmed systems of these two types of Algols.     

Spacecraft Application of Expert Systems

Artificial Intelligence (AI) will play a major role in future spacecraft operation. Because the technology has not matured, knowledge-based systems will be incorporated in an evolutionary manner, with increasing responsibility as their performance is proven. Internal research at Boeing Aerospace Company has demonstrated that AI software development techniques, knowledge-based systems in particular, can be used to provide limited spacecraft subsystem automation. This capability represents a first step toward an evolutionary path to spacecraft automation. A likely progression will proceed to integrated subsystem control, automated planning and scheduling, plan execution, anomoly handling, and eventually to autonomous spacecraft operation. Although this paper is written in the context of Space Station the ideas and techniques identified should be easily transferable to spacecraft automation in general.     

Correlation of Multiple-Site Track Data

Tactical air defense systems often require the interchange of target tracking data between two radar sites. This paper presents a systematic and effective procedure, employing correlation gates, for associating , or correlating, track information from one site with that from the other. Using the correlation equation, gate sizes are selected, based on remote and local tracking accuracies, target separation, the number of track coordinates investigated, and the number of successive correlation attempts made, to maximize the selected measure of correlation accuracy. The modeling of physical encounters is discussed and a representative situation is selected for analysis. A variety of correlation procedures are compared in terms of correlation accuracy and ease of implementation.     

Efficient Utilization of Orbit/Frequency for Satellite Broadcasting

In this paper some basic concepts involved in efficient orbit/spectrum utilization for broadcast satellites are discussed. A theoretical analysis leads to the determination of interference zones and minimum number of frequency channels required for homogeneous systems operating in the 800-MHz and 12-GHz bands. A crossed-beam arrangement of satellite systems is proposed, in which the beams from satellites to service areas cross each other. This arrangement has a more efficient orbit spectrum utilization compared to the identical-longitude approach, in which the subsatellite point has the same longitude as the center of the service area, Based upon practical considerations, the elemental number of frequency channels required for world-wide coverage has been calculated in relation to satellite orbital position, for single-beam and multibeam satellite systems, using the identical-longitude and crossed -beam arrangements.     

Satellite-Aided Search and Rescue (SAR) System

To carry out search and rescue of people in distress on the distressed aircrafts/vessels on land, at sea, or in a remote mountainous region, there are a number of different search and rescue systems and methods that are being used by the different national search and rescue organizations worldwide. Herein, the main terrestrial search and rescue (SAR) systems that are in use are discussed in brief and a satellite-aided search and rescue (SAR) system - COSPAS - SARSAT is discussed in detail highlighting its benefits over other SAR systems.     

Presupernova evolution of the most massive stars

Taking as example a 60M _⊙ star of solar metallicity, the state of the art of model calculations for very massive, from the main sequence to the supernova stage, is reviewed. It is argued that — due to the simple internal structure of Wolf-Rayet stars — the post main sequence evolutionary phases are currently those which are better understood. A brief discussion of the supernova outcome from very massive stars is given. Then, the more uncertain main sequence evolution is discussed. A first attempt to incorporate results about pulsational instabilities of very massive stars in stellar evolutionary calculations is performed. On its basis, a new type of evolutionary sequence for very massive stars is obtained, namely O-star → Of-star → H-rich WNL → LBV → H-poor WNL → WNE → WC → SN. This scenario is shown to correspond better to many observed properties of very massive stars than the standard one. It includes a model for the prototype LBV P Cygni.     

It is software process, stupid: next millennium software qualitykey

The economic impacts of software in our economy are discussed. The current economic state has been attributed to the Information Technology which has not only generated a large number of jobs but also contributed to the productivity and quality of the operations in our digital economy. The next millennium will be digital and obviously software has a very important role to play in our personal, national, and international scenes. Software will be essential in all our products from Space Station and airplanes to automobiles, television, pagers, and cellular telephones, For any organization, for that matter, even nations to succeed in the digital millennium software will be very essential. One who develops software better, cheaper, and faster will become the leader with enormous economic advantage. The key to success in software development will depend upon the software processes used to build them. Many national and international organizations have developed models based on processes to improve quality, productivity and cycle time of software development. Software Engineering Institute's Capability Maturity Model (CMM) is one such model. CMM helps in assessing the software processes and their capabilities and continuously improve them to higher levels of maturity. Similarly, ISO 9000 and the related ISO 9001 for software quality are based on software processes. This paper will bring out the importance of software processes particularly in managing the quality of software based on national and international initiatives     

离子推力器放电腔内等离子体流动规律的全粒子模型

为了详细描述等离子体在放电腔内的产生、演化过程,建立了放电腔内部等离子体流动的二维轴对称全粒子数值模型。在考虑壁面二次电子发射影响的前提下,模拟得到了稳态后放电腔内电磁场、电子与离子数密度,电流密度等一系列参数分布,且与相关实验数据进行了比较,吻合较好。模型得到了实验中难以观测到的放电腔内等离子体的产生、演化过程以及稳态下的分布规律,合理解释了放电腔工作的基本原理。     

Comparative analysis of energy storage media and techniques

Techniques for storing and converting energy from one form to another are examined. The parameters of interest are storage density (in terms of both energy and power), conversion efficiency, and number of steps in the conversion process. The techniques compared are electrostatic, magnetic, inertial, chemical, thermal, and nuclear. Each technique for storage is discussed in terms of the ease with which the energy can be converted to electricity for powering lightweight compact power systems for a variety of uses. The storage density associated with the various mechanisms spans an enormous range (~0.5 MJ/kg to ~10⁵ MJ/kg). The impact upon time-to-refuel within the context of mobile tactical army applications is discussed