Journal Staff

This master's thesis aims to investigate how fuzzy logic can be used to adapt the tuning of a speed control law during certain conditions such as turbulence. The objective is to lower the speed overshoot caused by the auto-thrust function as well as the general engine agitation. The main modifications studied are direct lowering of the closed loop gains, hybridisation and filtering of the longitudinal acceleration estimation. Finally, saturations or limits on the control signal as well as on the coordination with the longitudinal control law are studied in order to cope with the possible consequences of a softer control law. To detect the turbulence, an already existing turbulence detector is used. In addition, a wind gradient detector is designed in order to increase the gain during such wind conditions to counter ramp errors. It is found that a general lowering of the closed loop gain in combination with a slow hybridisation, all proportional to the detected turbulence level, together with a limitation of the coordination gives a satisfactory result. In scenarios including severe turbulence and wind gradients, the forced limits are shown to be indispensable. A conclusion is drawn that the fuzzy tuning is better adapted to turbulent conditions but that the wind gradient detection and the forced limits must be studied further. It is also concluded that the coupling between the closed loop gain and the acceleration hybridisation can be interesting to investigate. Moreover, additional realistic scenarios should be simulated in order to further validate the design. For future studies on the subject; it is recommended that the controller tuning is validated with the help of expert knowledge. Alternatively, the tuning could be handled by an ANFIS (Adaptive Neuro Fuzzy Inference System). Finally the tuning of the controller should be validated for a wider range of flight points, most importantly the forced limits since the engine response varies a lot between different points in the flight envelope

Use of thermodynamic properties of metal-gas systems as low-pressure standards

Modified version of Sievert's apparatus accurately calibrates low pressure measuring instruments. Metal-gas system is composed of hydrogen in two-phase equilibrium with erbium to obtain reproducible hydrogen pressures

Does cooperation improve implementation? Central-local governnment relations in active labour market policy in Sweden

Theory suggests that relations between authorities affect implementation. This article studies the link between central and local government agencies in the Swedish labour market sector. The analysis is based on new quantitative data. The results indicate that central and local government agencies have very different priorities, but they nonetheless cooperate to a considerable extent. However, cooperation and ‘good’ implementation only coincide under certain conditions. If the collaborative endeavours are explicitly designed to lead to implementation of a specific and demanding task, cooperation is positively related to implementation performance. Agencies that collaborate to a considerable extent at a general level do not, however, perform better than others. Thus, I argue that theories should be developed and tested to indicate when cooperation between public authorities will promote implementation, instead of assuming that cooperation, in general, is a ‘good thing’.Implementation; cooperation; public employment services; municipalities; active labour market policy

Has Import Disciplined Swedish Manufacturing Firms in the 1990s?

This paper analyses how increased integration and the ongoing enlargement of European Union’s internal market affected the performance of Swedish manufacturing firms. The pro-competitive effect of international trade, in terms of intensified import competition on domestic firms’ market power, has been investigated extensively at industry level. In contrast to previous studies, this analysis is based on detailed firm-level information. Import data are divided into an EU member group and a group of recently proved EU member candidates. It focuses on how imports from these groups, together with imports from other non-European trading partners, impact on firm profitability, while taking firm-specific efficiency effects into account. The findings are that import from the new EU-candidates seems to have a substantial disciplinary effect on Swedish firm profits, whereas import from EU-member countries only appears to have an impact on firms with large market shares and in highly concentrated industries.Import discipline; Market structure; Market share; Firm-level efficiency

Import Competition, Product Differentiation and Mark-Ups - Microeconomic evidence from Swedish manufacturing in the 1990s

This paper examines how import competition from different origins and the presence of product differentiation affect market power of Swedish manufacturing firms during the 1990s. Applying Roeger’s method (1995), I perform the empirical analysis based on detailed firm-level data and estimate an average mark-up level of Swedish manufacturing firms. The general finding is that imports from both European countries and other highincome countries outside Europe impose disciplinary effects on price-cost margin of Swedish manufacturing firms. The strongest effect is from the recent EU member countries. However, the competitive pressure associated with import is relaxed in the presence of product differentiation.Import competition; Mark-up; Market structure; Product differentiation

A study of metal oxygen and metal nitrogen systems for use as reduced pressure standards

Metal-oxygen and metal-nitrogen systems for use as reduced pressure standards using Sieverts apparatu

A bicentennial agenda for America

A commencement address is presented. Topics reviewed include politics, technological developments in science as a whole, and the effects of science on human progress. The social ramifications of satellite technology are also reviewed