High speed propulsion: Performance advantage of advanced materials

High-speed air breathing propulsion systems have many attractive military and civil applications. The high propulsive efficiency of these systems allows the exploitation of speed, distance, and bigger payloads, or any combination of the three. The severe operating conditions of these systems require particular attention to overall thermal management of the engine/air-frame. Fuel-cooling the engine structure is a viable way of maintaining thermal balance over a range of flight conditions. Air Force applications have focused on using endothermic hydrocarbon fuels to address this issue because of their compatibility with the military operations. Recent ground tests of scramjet engines have demonstrated adequate performance utilizing state-of-the-art technology in materials. This progress has paved the way for an expendable flight test vehicle in the near future. In order to take full advantage of the capabilities of this propulsion system, advances in fuel-cooled structures, high temperature un-cooled materials, and increased heat capacity of hydrocarbon fuels will be needed to enable expendable systems to reach higher Mach numbers. An additional benefit would be realized in future reusable systems.     

Biapenem versus imipenem/cilastatin in the treatment of complicated intra-abdominal infections: report from a Swedish Study Group

The objective of this study is to describe usual medical management and costs associated with recurrent respiratory infections in subjects with chronic obstructive bronchitis in France. A prospective survey was performed in Autumn 1994 on a national sample of private practice pulmonologists (N = 71). Two hundred forty-four patients, presenting at least one infection of the lower respiratory tract, were included. Bronchitis was the most frequent acute exacerbation observed (94%). Pneumonia concerned 9% of the patients. Biological tests, X-rays and pulmonary function tests were prescribed for, respectively, 59, 65 and 45% of the patients. Following the visit, 15 patients were hospitalized (6%). The direct medical cost per acute exacerbation was estimated 3,289 francs (1994 value) of which 60% were hospital-related. An average 10.4 day sick-leave was prescribed to 21% of patients in employment. For those patients, this sick-leave was associated to an extra-cost of 1,264-1,876 francs for Social Security and of 0-2,553 francs out of pocket per episode varying according to their Benefit Regimen.     

IEEE standard 802.16: a technical overview of theWirelessMANTM air interface for broadband wirelessaccess

The broadband wireless access industry, which provides high-rate network connections to stationary sites, has matured to the point at which it now has a standard for second-generation wireless metropolitan area networks. The IEEE standard 802.16, with its WirelessMAN^TM air interface, sets the stage for widespread and effective deployments worldwide. This article overviews the technical medium access control and physical layer features of this new standard     

Neural fuzzy logic programming

A foundational development of propositional fuzzy logic programs is presented. Fuzzy logic programs are structured knowledge bases including uncertainties in rules and facts. The precise specifications of uncertainties have a great influence on the performance of the knowledge base. It is shown how fuzzy logic programs can be transformed to neural networks, where adaptations of uncertainties in the knowledge base increase the reliability of the program and are carried out automatically.     

Consensus design of repeat proteins

Consensus design is a valuable protein-engineering method that is based on statistical information derived from sequence alignments of homologous proteins. Recently, consensus design was adapted to repeat proteins. We discuss the potential of this novel repeat-based approach for the design of consensus repeat proteins and repeat protein libraries and summarize recent results from such experiments.     

Self-organized porous TiO2 and ZrO2 produced by anodization

The present work investigates the electrochemical formation of self-organized high aspect ratio TiO₂ and ZrO₂ nanotube layers. The formation and growth of a self-organized porous layer can be achieved directly by anodization without any templates in fluoride containing electrolytes. The morphology of the porous layers is affected by the electrochemical conditions such as the electrolyte composition, the pH and the exact polarization treatment (such as the potential sweep rate from the open-circuit potential to the anodizing potential). For Ti, nanotube layers are formed with diameters varying from approx. 20 nm to 100 nm and lengths from approx. 0.25 μm to 2.5 μm depending on the electrolytes and pH. On the other hand, for Zr, tubes of 50 nm in diameter and up to approx. 17 μm in length can be grown—a key parameter in this case is the potential sweep rate. The large difference between Ti and Zr in the achievable thickness of nanotube layers indicates a difference in the growth mechanism which may be based on the different chemical dissolution rates of electrochemically formed oxides.     

Relationships between ergonomics and quality in assembly work

Several studies indicate a relationship between ergonomic work conditions and the quality of the work. The purpose of this study was to evaluate relationships between a number of ergonomic conditions and product quality in car assembly. The most physically demanding tasks, the tasks with the most difficult parts to assemble, and the most psychologically demanding tasks, were identified by interviews with experienced assembly workers. Information on quality deficiencies was obtained from the internal quality statistics of the company and from interviews with quality control personnel. The results showed that the quality deficiencies were three times as common for the work tasks with ergonomics problems, compared with the other tasks. An increased risk of quality deficiencies was seen for all three categories of ergonomics problems investigated. Direct causes of quality deficiencies were identified, such as discomfort from strained parts of the body, organizational factors and time pressure. The analyses pointed to certain types of task that were more likely than others to cause quality problems. The results also showed that an important factor for job satisfaction was the possibility for the workers to perform their tasks with high quality. The study therefore confirms close relationships between ergonomics and quality, and thereby points to the possibility of conducting integrated change programmes aimed at improving work quality and work conditions simultaneously.     

Sorting and disposing of waste at recycling centres - A users perspective

This paper investigates Swedish recycling centres from the users' perspective. The aim was to describe the characteristics and experiences of the users and their activities when sorting and disposing of waste, and to identify improvements for the users. The typical recycling centre user is a recently retired man, living in a house with a garden, having travelled 5 km alone in his own car. The users requested longer opening hours and better information available at home and at the recycling centre. The major difficulty for the users is to understand which fraction their waste belongs to, and consequently into which container they should throw it. The most important sources of sorting information, in addition to experience from earlier visits, are signs and asking the personnel. Although the service at recycling centres is perceived positively by a majority of users, substantial improvements can still be made, and a number of such suggestions are given.