Showing papers by "Aalto University published in 1991"

Selecting a flexible manufacturing system using multiple criteria analysis

Abstract: A visual interactive decision support framework designed to aid the decision-maker, typically top management, in selecting the most appropriate technology and design when planning a flexible manufacturing system (FMS) is described. The framework can be used in the preinvestment stage of the planning process, after the decision in principle has been made to build an FMS. First, both qualitative and quantitative criteria are used to narrow the set of alternative system configurations under consideration down to a small number of most attractive candidates. After this prescreening phase, a multiobjective programming model is formulated for each remaining configuration, allowing the manager to explore and evaluate the costs and benefits of various different scenarios for each configuration separately by experimenting with different levels of batch sizes and production volumes. The system uses visual interaction with the decision-maker, graphically displaying the relevant trade-offs between such relevant perfo...

On the dynamics of renewable resource harvesting and pollution control

Abstract: The paper presents a dynamic partial equilibrium model which combines optimal renewable resource harvesting and optimal pollution control. Pollution accumulates as a slowly decaying stock and is assumed to affect the growth and the quality of the renewable resource stock. The aim is to maximize a social welfare functional which gives the present value of the difference between natural resource benefits and pollution control costs. The existence, uniqueness and the dynamic properties of the steady states are investigated. The analysis also gives a general result concerning the steady state of any two state variable optimal control problems.

Success of software packages in small businesses: an exploratory study

Abstract: In this paper we develop and use a framework for evaluating the success of microcomputer based integrated administrative software packages in small businesses. The results of an exploratory survey of 66 small business organizations show that small businesses have often been disappointed with their software packages. The disappointment is frequently a result of the inability of the package to adapt to the needs of the company, especially in small businesses of more than 50 employees. For small businesses of less than 20 employees the packages are too difficult to use. These findings indicate that small businesses should place more emphasis on the acquisition, especially the requirements specification, and developers should improve user-friendliness, the quality of support and documentation to fulfil the needs of the smallest of small businesses. The successful implementers—because of their experience—knew their needs, carefully acquired the package, and implemented various parts of it, benefiting from integration. There seem to be no shortcuts to success, but a determined and eager attitude of the personnel can produce success with any of the software packages in our study.

Approximation of delay systems—a case study

Abstract: The approximation of delay systems is studied. A numerically well-behaved method for computing Hankel optima) rational approximations for delay systems is presented based on certain properties of Hankel matrices and the theory of Laguerre polynomials. The CF method of Trefethen and certain Pade approximations of delay systems are also considered. The importance of a certain Wiener algebra property in the analysis of the rational approximation of an important class of delay systems in the L∞ norm and the Hankel norm is shown, completing certain results presented in the literature for systems satisfying certain nuclearity or absolute continuity conditions. A case study and numerical comparison is presented for the approximation of the parametric family of first-order stable delay systems G(s) = exp ( —τs)/(Ts + 1). Numerical experience indicates that L°° optimized CF approximations based on short truncated Maclaurin series give, in general, somewhat smaller L∞ approximation errors than Hankel optim...

The Bigger the Better? On the Dimensions of Welfare State Development: Social Expenditures versus Social Rights

Abstract: The purpose of this article is twofold First, focusing on sickness insurance programs in eighteen OECD countries, the article seeks to answer whether higher spending levels also are associated with higher quality of the benefits being provided The answer to this question is partly positive: there is a tendency that bigger also is better Second, by using pooled cross-sectional data for 1960-85, the study explores if the distinction between spending levels and 'social rights' makes a difference when analyzing the determinants of welfare state growth. The study demonstrates that the choice of dependent variable considerably affects the results. Estimates pertaining to various political factors are particularly sensitive to the choice of dependent variable In the case of benefit levels, political factors appear important, whereas when analyzing spending rates, their impact appears to be negligible. This finding may explain the many inconsistent results in recent research on the growth of the welfare state

Using harmonious houses for visual pairwise comparison of multiple criteria alternatives

Abstract: In this paper, we consider the problem of evaluating decision alternatives, which are described by means of several criteria. Our aim is to develop an approach which enables a decision-maker to present value information on the basis ofa visual representation. The underlying ideas used in the approach are based on the use of symmetry and harmony. These principles are operationalized by using “harmonious houses”. The theoretical approach is implemented as a decision support system, which makes pairwise comparisons possible between alternatives. To perform sensitivity analysis is also possible. In our pilot tests, the idea has proven very promising.

Transboundary air pollution between Finland and the USSR — A dynamic acid rain game

Abstract: We develop and analyse a two-country transboundary air pollution model in a dynamic game setting. Air pollution is mainly due to sulphur and nitrogen emissions that are partially deposited onto the ground in the emitter countries. However, due to transboundary transport of pollutants by winds, large amounts of the emissions fall on the ground in the neighboring countries as well. Sulphur and nitrogen compounds affect the properties of soil, surface water, and ground water, and hence, the pollution process is referred to as acidification. The acidification dynamics model is based on recent models of ion exchange dynamics in soil. The empirical data are based on the estimates of sulphur emissions as well as sulphur depositions in Finland and in four nearby regions in the USSR, namely the Estonian SSR, and the regions of Karelia, Leningrad and Kola. The main part of this paper is devoted to the identification of the structure and the dynamics of the acid rain game and to the estimation of the emission abatement costs and the benefits from emission reductions. We compare the non-cooperative and cooperative game solutions. The USSR loses from the environmental cooperation. Finland needs to compensate the USSR to negotiate a bilateral agreement on reductions of sulphur emissions.

Correspondence of electron spectra from photoionization and nuclear internal conversion.

Abstract: Electron energy spectra have been measured that result from {ital K}-shell ionization of Kr by two different mechanisms: (1) photoionization and (2) internal conversion in the decay of the isomeric state of {sup 83}Kr. It is demonstrated experimentally that these spectra, including satellites on the low-energy side of the primary 1{ital s}-electron peak, are identical. A theoretical interpretation of the identity of the spectra is given. The spectra agree well with a relativistic many-electron calculation in which the satellites are attributed to excitation and ionization of {ital M} and {ital N} electrons during the {ital K}-ionization process.

Multifrequency observations of BL Lacertae in 1988

Abstract: Simultaneous multiwavelength observations of BL Lacertae were performed on two occasions separated by month in 1988 June and July, covering the radio, submillimeter, infrared, optical, ultraviolet, and X-ray wave bands. In the wide-band photon spectra, the X-ray flux lies clearly above the extension of radio ultraviolet continuum as expected. The slope of the X-ray spectra is significantly flatter than that at optical ultraviolet regimes, and its spectral index 0.7-1.0 corresponds to the slope at submillimeter band. Comparison with earlier observations, in fact, indicates that the X-ray flux is correlated with the submillimeter band, and not with the others, and supports the SSC model.

In Search of Explanations for Bank Performance — Some Finnish Data

Abstract: In this paper, our purpose is to discover the processes which generate bank performance. The study was carried out in two phases among banks of the SKOPBANK Group in Finland.The first phase is based on cross-sectional data consisting of a sample of 79 banks at the beginning of the 1980s. In this phase we have identified three different performance groups and found specific features characterizing them.The second phase is based on sixteen case banks representing these three performance groups. The data there comprise the documented development of the studied banks, and the interview data on the work histories of their managers. Our aim is to broaden and understand the findings based on the analysis of the cross-sectional data, and to develop more dynamic explanations for the variations in bank performance.The major finding of the statistical part of the study is that despite significant differences, there is no combination of environmental and organizational variables leading directly to superior or inferi...

Water flow and binder migration during drying of coated paper

Abstract: The aim of this study has been to develop a mathematical model for water flow and binder migration in coated paper. The model can be used for simulation of the stages starting after the coating applicator including infrared and air drying sections. On the basis of the model the moisture, temperature and binder distribution can be determined across the paper thickness. Approximating equations concerning the paper properties are used in the model. We have measured the diffusion coefficient between the water and binder substances. Representative numerical examples are presented for separate and combined infrared and air drying processes.

Two-phonon absorption by the real squashing mode in superfluid 3He-B.

Abstract: We have observed in superfluid {sup 3}He-{ital B} two-phonon absorption, which is one of the nonlinear effects recently predicted by McKenzie and Sauls. The {ital J}=2{sup +} real squashing mode was excited with two coincident sound pulses at the temperature {ital T}{sup +}, f{sub signal}+{ital f}{sub pump}={ital f}{sub rsq}({ital T}{sup +}), under 0, 2.7, and 3.5 bars pressure. The heights of the attenuation peaks scale almost linearly with the energy of the higher-intensity wave, in qualitative agreement with the theory. Furthermore, a satellite peak appears even in zero magnetic field, which originates from the reflected wave.

Charge-state-dependent relaxation and positron states at vacancy defects in GaAs

Abstract: The positron states in the perfect GaAs lattice and at fully relaxed vacancies with different total charges have been calculated. Moreover, the metastable configuration of the As anti-site in GaAs proposed as a model for the EL2 defect is considered. The atomic structures of the defects are taken from recent ab initio molecular dynamics calculations. The positron states and the ensuing positron annihilation rates and trap binding energies have been determined by the method based on the superposition of atomic electron densities. A comparison of the results with experimental data shows that, while the present theoretical approach gives a consistent and qualitative interpretation, it fails to reproduce the trapped state lifetimes quantitatively. It is shown that a localized positron can affect the lattice relaxations around the defect. Therefore, it is suggested that the positron should be treated fully self-consistently, simultaneously with electrons, in the ab initio molecular dynamics in order to determine the way in which the localized positron affects the electron structure and ionic relaxation near the vacancy.

Two Decision Support Systems for Continuous and Discrete Multiple Criteria Decision Making: VIG and VIMDA

Abstract: Two “free search” approaches and their implementations (WG and VIMDA) for solving continuous and discrete multiple criteria problems are considered. The systems are user-friendly and based on visual interaction. The user communicates with the respective systems using spreadsheets, menus, and graphics. The mathematical foundations are based on the reference direction approaches. The basic underlying ideas of the approaches are described and the use of the systems is demonstrated. Several real applications of WO will be discussed, for example, how to analyze input-output models from the perspective of economic defense.

Systems That Turn Manufacturing into Service

Abstract: Systems developed for flexible, computer integrated manufacturing are having an impact - they are turning manufacturing into service operations. They enable small productive and development units to link into inter-organizational networks and to act as independent suppliers and service providers. Customers expect more complete service in time, often relying on a long chain of value-adding partners. Service, once viewed as the peril of productivity, is now the stuff of strategy that wins customers and reshapes industries. This trend may be unsettling to managers and researchers who conventionally have emphasized the internal control and integration of manufacturing facilities. Systematic ways of thinking about the strategic impacts of information systems on manufacturing are starting to emerge. This paper suggests a model of service channels that opens up the manufacturing/services interface and examines the trade-offs of matching different organizations and systems technology.