A study of commuter air service

A regionally oriented overview of the commuter air service industry is provided. A framework for an eventual assessment of potential technology directions that may be of benefit to the industry is presented. Data are provided on the industry's market characteristics, service patterns, patronage characteristics, aircraft and airport needs, economic characteristics and institutional issues. Using personal interview and literature survey methods, investigation of a considerable cross-section of the industry was made

Small V/STOL aircraft analysis, volume 1

A study has been made of the economic viability of advanced V/STOL aircraft concepts in performing general aviation missions. A survey of general aviation aircraft users, operators, and manufacturers indicated that personnel transport missions formulated around business executive needs, commuter air service, and offshore oil supply are the leading potential areas of application using VTOL aircraft. Advanced VTOL concepts potentially available in the late 1970 time period were evaluated as alternatives to privately owned contemporary aircraft and commercial airline service in satisfying these personnel transport needs. Economic analysis incorporating the traveler's value of time as the principle figure of merit were used to identify the relative merits of alternative VTOL air transportation concepts

Urban space and the social control of incivilities: perceptions of space influencing the regulationof anti-social behaviour

Contemporary cities are increasingly governed through space. In this article,we examine how urban space and perceptions thereof can influence the social control inthe area of incivilities. To this end, we first inspect the existing literature, in particularthe socio-spatial studies that emphasise the importance of culture and values in theinteraction with social control. Partly drawing on examples from our previous studies,we suggest that people’s perceptions of urban space (influenced by cultural symbols,social and media representations, aesthetics and other values) affect their perceptions ofincivilities, while the latter often determine or at least importantly contribute to theshaping of the social control of incivilities. We further highlight the role of gentrifica-tion as a medium and a tool of social control. The paper concludes by discussingimplications of this for the possible future, more integrated and interdisciplinaryresearch on the social control of incivilities in the city

Towards a Framework for Comparing Process Modelling Languages

The increasing interest in process engineering and application integration has resulted in the appearance of various new process modelling languages. Understanding and comparing such languages has therefore become a major problem in information systems research and development. We suggest a framework to solve this problem involving several instruments: a general process metamodel with a table, an analysis of the event concept, and a classification of concepts according to the interrogative pronouns: what, how, why, who, when, and where. This framework can be used for several purposes, such as translating between languages or verifying that relevant organisational aspects have been captured. To validate the framework, three different process modelling languages have bee

Solvent-Free Reactive Extrusion As an Innovative and Efficient Process for the Synthesis of Polyimides

International audiencePolyimides are commonly synthesized in a 2-step solution polymerization process. Such process requires long reaction times as well as specific care due to the use of potentially harmful solvents. In the present study, the total reaction time for producing polyimides has been lowered to less than 10 min by using a solvent-free continuous reactive extrusion process. The proof of concept was determined with the system based on 3,3′,4,4′-benzophenone-tetracarboxylic dianhydride (BTDA) and an aliphatic diamine, Jeffamine D-230 within a microextruder. Degrees of conversion to polyimide, determined with 13C NMR and DSC analysis, are over 90 mol % after 5 min of extrusion at 180 °C, 200 °C, and 225 °C, respectively. These syntheses were then transferred to a twin-screw extruder to form linear aliphatic-aromatic polyimides with two types of dianhydride: BTDA and pyromellitic dianhydride (PMDA). Comparison with a conventional solution polymerization process showed no significant differences in the polymers characteristics. The polyimides produced with this method presented glass transition temperatures ranging from 5 to 90 °C. The number-average molar masses measured were between 11 000 and 15 000 g·mol–1

Four Issues Concerning the Semantics of Message Flow Graphs

We discuss four issues concerning the semantics of Message Flow Graphs (MFGs). MFGs are extensively used as pictures of message-passing behavior. One type of MFG, Message Sequence Chart (MSC) is ITU Standard Z.120. We require that a system described by an MFG has global states with respect to its message-passing behavior, with transitions between these states effected by atomic message-passing actions. Under this assumption, we argue (a) that the collection of global message states defined by an MFG is finite (whether for synchronous, asynchronous, or partially-asynchronous message-passing); (b) that the unrestricted use of `conditions' requires processes to keep control history variables of potentially unbounded size; (c) that allowing `crossing' messages of the same type implies certain properties of the environment that are neither explicit nor desirable, and (d) that liveness properties of MFGs are more easily expressed by temporal logic formulas over the control states than by Buc..