The Development of Friction Pairs for Intermediate to Very High Duty Railway Applications

1994 ◽  
Vol 208 (2) ◽  
pp. 109-113
Author(s):  
K D Dolbear ◽  
J C Watson
Keyword(s):  
High Speed ◽  
High Performance ◽  
Point Of View ◽  
Railway Vehicle ◽  
Vehicle Design ◽  
Large Spread ◽  
Challenges And Opportunities ◽  
Ceramic Interfaces ◽  
Very High

Railway vehicle service speeds are set to increase from the present 300 km/h. These developments are being spearheaded by the French, German, Italian and Japanese railways. It is also clear in other less glamorous areas such as freight and suburban operations, that the trends in vehicle design are going to put severe burdens on the braking technology available today. These initiatives included the advanced suburban bogie for British Railways. While it will be possible to squeeze some further improvements out of conventional products, it has become essential to initiate work on new materials which not only meet the immediate demands but address the requirements of the middle- and long-term. Some proposals such as carbon/carbon may be impractical from a cost point of view on anything other than exotic high-speed vehicles but studies involving ceramic to ceramic interfaces are proving interesting with a real possibility of providing high performance at an economical cost for a large spread of applications. The paper will discuss some of the challenges and opportunities to be grasped and solved.

The Air-to-air Missile Matra 530

1969 ◽  
Vol 73 (701) ◽  
pp. 449-452
Author(s):  
J. E. Cadoux
Keyword(s):  
Air Force ◽  
High Performance ◽  
First Generation ◽  
Second Generation ◽  
Point Of View ◽  
Ground Control ◽  
Close Link ◽  
Pure Pursuit ◽  
Very High ◽  
Pursuit Curve

The Matra 530 is currently called a second generation air-to-air missile. Indeed the first generation of air-to-air missiles was represented in France by the Nord 5103 which was command-guided, or the Matra 511 which was a semi-active, pure pursuit curve missile. In the second part of the 1950's the requirement was obvious for a sophisticated interception system capable of coping with the high and medium altitude threat represented by heavy and medium bombers. The destruction of this threat required a close link with an interception system composed of ground radars, ground control equipment, sophisticated high performance interceptor aircraft and, as a last link, a very high performance missile. From the French Air Force point of view, the two main characteristics of this missile as the last link of an interceptor system, were first its flexibility in different weather environment and counter measure environment; second, its capability to decrease to the maximum the penetration of the enemy bomber, which meant that the missile should be capable of attacking not only in the rear sector but also in frontal attack and in fact in all sectors around the attacking bomber.

4H-SIC Dmosfets for High Frequency Power Switching Applications

2003 ◽  
Vol 764 ◽  
Author(s):  
Sei-Hyung Ryu ◽  
Anant K. Agarwal ◽  
James Richmond ◽  
John W. Palmour
Keyword(s):  
High Voltage ◽  
High Speed ◽  
High Performance ◽  
High Frequency Power ◽  
Power Devices ◽  
Power Switching ◽  
High Speed Switching ◽  
Unipolar Devices ◽  
Very High ◽  
Frequency Power

AbstractVery high critical field, reasonable bulk electron mobility, and high thermal conductivity make 4H-Silicon carbide very attractive for high voltage power devices. These advantages make high performance unipolar switching devices with blocking voltages greater than 1 kV possible in 4H-SiC. Several exploratory devices, such as vertical MOSFETs and JFETs, have been reported in SiC. However, most of the previous works were focused on high voltage aspects of the devices, and the high speed switching aspects of the SiC unipolar devices were largely neglected. In this paper, we report on the static and dynamic characteristics of our 4H-SiC DMOSFETs. A simple model of the on-state characteristics of 4H-SiC DMOSFETs is also presented.

scholarly journals Enzymatic treatment of long-term human marrow cultures reveals the preferential location of primitive hemopoietic progenitors in the adherent layer

Blood ◽  
1983 ◽  
Vol 62 (2) ◽  
pp. 291-297 ◽  
Author(s):  
L Coulombel ◽  
AC Eaves ◽  
CJ Eaves
Keyword(s):  
Stem Cells ◽  
Marrow Cell ◽  
Point Of View ◽  
Adherent Cell ◽  
Reproducible Method ◽  
Preferential Location ◽  
Very High ◽  
Marrow Cultures

Abstract Recent studies with long-term mouse marrow cultures have indicated the importance of the adherent layer as a primary reservoir of the most primitive stem cells, from which derivative stem cells and more differentiated progenitors are continuously generated. We have now examined the role of the adherent cell layer in long-term human marrow cultures from this point of view. Prerequisite to such an undertaking was the development of a nontoxic and reproducible method for detaching the adherent layer and making it into a single-cell suspension suitable for characterization by colony assays. Both trypsin and collagenase could be used to obtain suspensions that met these criteria. Lack of toxicity was demonstrated by the preservation of CFU-E, BFU-E, and CFU- C plating efficiency in fresh human marrow cell suspensions exposed to the same enzymatic treatments. Collagenase treatment of long-term marrow culture adherent layers was considered superior because it freed all hemopoietic colony-forming cells but left some of the other cells still adherent. Using this method, we found that CFU-C, BFU-E, and CFU- G/E were consistently detectable in the adherent layer for at least 8 wk, with the majority of the BFU-E and CFU-G/E being located in the adherent layer (70%-75% after 2–3 wk and more than 90% by 7–8 wk). Although corresponding numerical differences in adherent and nonadherent CFU-C populations were not observed, the colonies derived from them showed marked differences in the size they achieved; the adherent layer being the exclusive site of CFU-C, with a very high proliferative capacity. These findings emphasize the importance of assessing the progenitor content of the adherent layer of long-term human marrow cultures and provide an appropriate methodology.

Reflections on the Client—Consultant Relationship: Challenges and Opportunities in a Context of Organisational Change

2012 ◽  
Vol 37 (3) ◽  
pp. 1-19 ◽  
Author(s):  
Omar Belkhodja ◽  
Égide Karuranga ◽  
Guillaume Giasson Morin
Keyword(s):  
Information Technology ◽  
Change Agents ◽  
Organisational Change ◽  
Point Of View ◽  
Management Information ◽  
Challenges And Opportunities ◽  
Research Findings ◽  
Active Communication ◽  
Interpretive Frame

This paper investigates the determinants of success of the client-consultant relationship from the consultant's point of view. Ten consultants from various fields (e.g. change management, information technology, etc.) based in the province of Quebec in Canada were interviewed. They were asked to comment on issues relating to their roles in the consultancy project, expectations, and the determinants of success of the client–consultant relationship. Interview data were analysed using an interpretive frame. The research findings reveal that consultants perceive their contribution and role positively and perceive themselves as change agents and knowledge transmitters. Trust, active communication, and shared feedback were identified as the major determinants of success of the client–consultant relationship. The results support and help advance earlier research findings in the management consulting field. Consultants are conscious that a long-term relationship built on trust, active communication, and shared feedback, identified as major determinants of success in the client–consultant relationship, is essential. The qualitative findings of the study add to, and help support, earlier research findings on consultants' perception of their roles and contributions within client organisations.

III-V HETEROJUNCTION BIPOLAR TRANSISTORS FOR HIGH-SPEED APPLICATIONS

1990 ◽  
Vol 01 (03n04) ◽  
pp. 245-301 ◽  
Author(s):  
M.F. CHANG ◽  
P.M. ASBECK
Keyword(s):  
Integrated Circuits ◽  
Heterojunction Bipolar Transistors ◽  
High Speed ◽  
High Performance ◽  
Growth Parameters ◽  
Bipolar Transistors ◽  
System Requirements ◽  
Potential Impact ◽  
Computational Systems ◽  
Very High

Recent advances in communication, radar and computational systems demand very high performance electronic circuits. Heterojunction bipolar transistors (HBTs) have the potential of providing a more efficient solution to many key system requirements through intrinsic device advantages than competing technologies. This paper reviews the present status of GaAs and InP-based HBT technologies and their applications to digital, analog, microwave and multifunction circuits. It begins with a brief review of HBT device concepts and critical epitaxial growth parameters. Issues important for device modeling and fabrication technologies are discussed. The paper then highlights the performance and the potential impact of HBT devices and integrated circuits in various application areas. Key prospects for future HBT development are also addressed.

Very High-Resolution Remote Sensing: Challenges and Opportunities [Point of View]

2012 ◽  
Vol 100 (6) ◽  
pp. 1907-1910 ◽  
Author(s):  
Jon Atli Benediktsson ◽  
Jocelyn Chanussot ◽  
Wooil M. Moon
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Point Of View ◽  
Challenges And Opportunities ◽  
Very High

scholarly journals Modelling of the shape of railway transition curves from the point of view of passenger comfort

2021 ◽  
Vol 60 (4) ◽  
pp. 205-217
Author(s):  
Krzysztof Zboiński ◽  
Piotr Woźnica ◽  
Yaroslav Bolzhelarskyi
Keyword(s):  
High Speed ◽  
Point Of View ◽  
Transition Curve ◽  
Optimum Shape ◽  
Railway Vehicle ◽  
Vehicle Model ◽  
Circular Arc ◽  
Passenger Comfort ◽  
Rail Vehicle ◽  
Transition Curves

In the past, railway transition curves were not used. Instead of it, a simple connection of the straight track and circular arc was applied. Nowadays, such simplicity is not allowed due to the increasing vehicle operating velocities. It is mainly visible in the high-speed train lines, where long curves are used. The article aims to develop a new shape of railway transition curves for which passenger travel comfort will be as high as possible. Considerations in this paper concern the polynomials of 9th- and 11th-degrees, which were adopted to the mathematical model of the mentioned shape of curves. The study's authors applied a 2-axle rail vehicle model combined with mathematically understood optimisation methods. The advanced vehicle model can better assign the dynamical properties of railway transition curves to freight and passenger vehicles. The mentioned model was adopted to simulate rail vehicle movement in both cases of the shape of transition curves and the shape of circular arc (for comparison of the results). Passenger comfort, described by European Standard EN 12299, was used as the assessment criterion. The work showed that the method using the 2-axle railway vehicle model combined with mathematically understood optimisation works correctly, and the optimisation of the transition curve shape is possible. The current study showed that the 3rd-degree parabola (the shape of the curve traditionally used in railway engineering) is not always the optimum shape. In many cases (especially for the long curves), the optimum shape of curves is between the standard transition curves and the linear curvature of the 3rd-degree parabola. The new shapes of the railway transition curves obtained when the passenger comfort is taken into account result in new railway transition curves shapes. In the authors' opinion, the results presented in the current work are a novelty in optimisation and the properties assessment of railway transition curves.

The Renewal of HTR Development in Europe

2002 ◽  
Author(s):  
Dominique Hittner
Keyword(s):  
High Performance ◽  
Nuclear Research ◽  
Reactor Physics ◽  
Coated Particles ◽  
Economic Competitiveness ◽  
Geologic Disposal ◽  
First Results ◽  
European Nuclear ◽  
Very High

The European HTR-Technology Network (HTR-TN), created in 2000, presently groups 20 organisations from European nuclear research and industry for developing the technologies of direct-cycle modular HTRs, which presently raise a large world-wide interest, because of their high potential for economic competitiveness, natural resource sparing, safety and minimisation of the waste impacts, in line with the goals of sustainable development of Generation IV. All aspects of HTR technologies are addressed by HTR-TN, from the reactor physics to the development of materials, fuel and components. Most of this activity is supported by the European Commission in the frame of its 5th Euratom Framework Programme. The first results of HTR-TN programme are given: the analysis of the reactor physics international benchmark on the commissioning tests of HTTR (Japan), the long term behaviour of spent HTR fuel in geologic disposal conditions, the preparation of a very high burnup fuel irradiation and the development of fabrication processes for producing high performance coated particles, etc.

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