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This paper aims to investigate the problem of on-line orbit planning and guidance for an advanced upper stage.
The double impulse optimal transfer orbit is planned by the Lambert algorithm and the improved particle swarm optimization (IPSO) method, which can reduce the total velocity increment of the transfer orbit. More specially, a simplified formula is developed to obtain the working time of the main engine for two phases of flight based on the theorem of impulse. Subsequently, the true anomalies of the start position and the end position for both two phases are planned by the Newton iterative algorithm and the Kepler equation. Finally, the first phase of flight is guided by a novel iterative guidance (NIG) law based on the true anomaly update with respect to the geometrical relationship. Also, a completely analytical powered explicit guidance (APEG) law is presented to realize orbital injection for the second phase of flight.
Simulations including Monte Carlo and three typical orbit transfer missions are carried out to demonstrate the efficiency of the proposed scheme.
A novel on-line orbit planning algorithm is developed based on the Lambert problem, IPSO optimization method and Newton iterative algorithm. The NIG and APEG are presented to realize the designed transfer orbit for the first and second phases of flight. Both two guidance laws achieve higher orbit injection accuracies than traditional guidance laws.
The decade of the 1970s witnessed a phenomenon in the growing acceptance of online database searching and its integration with more traditional library services. Although accurate statistics on the extent of online use by type of library remain scarce, an estimated 400 academic libraries used online search systems in 1977. Martha Williams' annual surveys of online search volume in the United States and Canada demonstrate an explosive growth in five years from one million searches in 1975 to almost four million in 1980. Of the more than 500 data‐bases available publicly, over 165 are accessible through the big three “supermarket” search services — BRS, Lockheed, and SDC.
Today, the telecommunication issue in Europe is possibly the most important influence in the growth and establishment of the on‐line information market in that region. Europe is behind the USA in developing cheap, publicly available switched dial‐up networks on demand such as Tymnet and Telenet in America. The situation is complicated by the different regulations in each country and by the monopoly status afforded to the PTTs, the European postal, telegraph and telephone agencies. In Europe, it is illegal for a third party to access a network leased to any two parties. Thus, a circuit leased to Tymshare for communicating with its computers in Europe or the United States cannot be sold by Tymshare to any other party, although such ‘illegal’ access has been tolerated by the PTTs for some time. A number of PTTs, however, are now ‘legalizing’ the traffic by controlling third party access to Tymshare's nodes in Europe. As usual, the consumer has to pick up the tab for the added circuits, equipment, billing and overhead required for such control. It might be that, as the European countries develop their own networks, they will be motivated to encourage traffic by reducing charges and simplifying access. In the meantime On‐Line Review will monitor the scene which should really be the concern of the telecommunications experts, leaving our readers to get on with the business of accessing information efficiently and without restrictions. Here are some European telecommunications news items.
“A Canadian company required information on a process in Switzerland. Since data were too complicated to obtain by mail a vice‐president of the company was assigned to make a trip. The company librarian hearing of this situation accidentally made a search and produced the information from the company's own files.”
The following paper discusses the costs involved when a library adds online bibliographic searching to the services it offers to its patrons. Reviewed in the study are…
The following paper discusses the costs involved when a library adds online bibliographic searching to the services it offers to its patrons. Reviewed in the study are total online costs, comparisons of manual and online search results, various pricing policy alternatives, and some probable future changes for online bibliographic searching.
The most obvious symptom of the most obvious trend in the building of new libraries is the fact that, as yet, no spade has entered the ground of the site on Euston Road, London, upon which the new building for the British Library Reference Division has to be erected. Some twenty years of continued negotiation and discussion finally resulted in the choice of this site. The UK and much more of the world awaits with anticipation what could and should be the major building library of the twentieth century. The planning and design of a library building, however large or small, is, relatively speaking, a major operation, and deserves time, care and patience if the best results are to be produced.
INFOMART is an information retrieval service of the Southam Press Limited and the Torstar Corporation. It provides exclusive access in Canada to the Search Service of the…
INFOMART is an information retrieval service of the Southam Press Limited and the Torstar Corporation. It provides exclusive access in Canada to the Search Service of the System Development Corporation in Santa Monica, Calif., USA. The paper outlines the background and organization of INFOMART, its focus on marketing and sales, and its orientation to user education and training. Communication is cited as a significant factor in the arrangements between the two companies. The author concludes that INFOMART has been a welcome development in Canada, where commercial information activities have formerly been dominated by the USA.
THE COMPUTER was first applied to the processing of bibliographical information in 1961 when the Chemical abstracts service (CAS) produced Chemical titles (CT), a machine‐generated alphabetical subject index to the 600 most significant journals covered by the parent journal Chemical abstracts. The key‐word‐in‐context (KWIC) format devised for CT was quickly adopted by other secondary bibliographical services to alleviate the problems imposed by the phenomenal growth of the scientific and technical literature.
Examines the contentious area of charging for on‐line services.Covers both the theoretical aspects and the practical application of theservices through a review of library…
Examines the contentious area of charging for on‐line services. Covers both the theoretical aspects and the practical application of the services through a review of library practice, looking in detail at three libraries (two academic, one public) operating in Liverpool. Despite growing financial concerns, on‐line services are necessary. Competitors in the form of information brokers will corner the market if libraries do not extend their service by providing an on‐line facility. A compromise must be reached which benefits the user of the library and maintains the freedom of access to information.