Showing papers by "University of Mannheim published in 1989"

F-logic: a higher-order language for reasoning about objects, inheritance, and scheme

Abstract: We propose a database logic which accounts in a clean declarative fashion for most of the “object-oriented” features such as object identity, complex objects, inheritance, methods, etc. Furthermore, database schema is part of the object language, which allows the user to browse schema and data using the same declarative formalism. The proposed logic has a formal semantics and a sound and complete resolution-based proof procedure, which makes it also computationally attractive.

Subexponential distributions and characterizations of related classes

Abstract: LetL(γ),γ≧0, γ≧0, denote the class of distributionsF satisfying $$\mathop {\lim }\limits_{x \to \infty } \bar F^{2*} (x)/\bar F(x) = 2\mathop \smallint \limits_0^\infty e^{\gamma y} dF(y)< \infty$$ (i) $$\mathop {\lim }\limits_{x \to \infty } \bar F^{2*} (x - y)/\bar F(x) = e^{\gamma y} \forall y \in \mathbb{R}.$$ (ii) The classesL(γ), for γ>0, are characterized by means of subexponential densities. As an application we derive a result on the asymptotic behaviour of densities of random sums. In particular for anM/G/1 queue, we relate the tail behaviour of the stationary waiting time density to that of the service time distribution.

Estimation of ruin probabilities by means of hazard rates

Abstract: We show that the asymptotic behaviour of the hazard rate of the claim-size distribution determines not only the singular point of the moment generating function but can also be used to estimate the asymptotic ruin probability. We shall use these results to classify the relevant claim-size distributions and calculate the respective ruin probabilities. Hereby we shall concentrate on the case where Cramer's method does not work.

Neurophysiological aspects of penile erection: the role of the sympathetic nervous system.

Abstract: Recent studies have revealed that the initiation, maintenance and rigidity of penile erection are under parasympathetic and somatotopic control. The mechanism of penile detumescence is still under debate. Single and combined cavernous and hypogastric nerve stimulation was used to study the influence of the sympathetic nervous system on penile erection and to identify the mechanism of penile detumescence. Penile arterial flow and intracorporeal pressure recordings during various stimulation patterns indicated that erection induced by stimulation of the cavernous nerve could be blocked by excitation of the upper hypogastric nerves. Venous outflow studies demonstrated that the inhibitory effect of the sympathetic nervous system was due to active vaso- and corporeal smooth muscle constriction. It was concluded that subsidence and suppression of erection is a sympathetic function. Previous studies have shown that the neurophysiology of erection can be explained by 3 major inhibitory (sympathetic). Our findings are of clinical importance, since a better appreciation of the basic erectile mechanism is essential for successful management of erectile dysfunction.

Computer Integrated Manufacturing as a Two‐edged Sword

Abstract: The favourable prospects of computer integrated manufacturing (CIM) are widely recognised. Based on a case study and relevant literature some of the risks associated with CIM are outlined. It is argued that the technological orientation of the CIM vision unwarrantably underestimates organisational and social problems of implementing and applying computerised manufacturing systems. Specifically, it is shown how disregard of uncertainty and of applicants′ divergent motivations may lead to serious friction. The attempt to realise the CIM vision may trigger a social dynamic which impedes the realisation of potential results. Finally, several implications of the research are described.

Temporary vs. permanent migration A decision theoretical approach

Abstract: The decision problem of the guest worker as a target saver is considered. He plans to accumulate capital in the host country for investment in the home country after return migration. As the worker is supposed to be incompletely informed about the economic variables in the host country he might prolong his stay unexpectedly provided the economic conditions in the host country are unfavourable. Explicit conditions for the economic variables are given such that temporary migration turns into permanent migration.

Positive homogeneity and multiplicativity of premium principles on positive risks

Abstract: In this note it is shown that the Swiss premium principle on positive risks is, under a mild regularity condition, positively homogeneous or multiplicative if and only if it is the net premium principle. A similar result is obtained for a generalized form of the Orlicz principle.

Public Opinion and Decision Making in the Community. Evaluation of Residents' Attitudes Towards Town Planning Measures:

Abstract: The relationship between political decision-making in the community, local public opinion and residents' attitudes are examined with reference to a concrete local political issue in Mannheim (Feder...

Specific Binding of Angiotensin II and Atrial Natriuretic Factor in Non-nephropathic Type I Diabetes Mellitus

Abstract: We examined ten patients with type I diabetes mellitus and ten age- and sex-matched healthy controls. Median duration of diabetes was 7 years (range 0.5-24). None of the diabetic patients had hypertension, microalbuminuria, or proliferative retinopathy. Maximal specific binding capacity for angiotensin II to thrombocytes was significantly increased in diabetics (Bmax 11.9 +/- 1.6 sites per cell vs 7.0 +/- 0.9 in controls; P less than 0.01). In contrast, maximal binding for atrial natriuretic factor tended to be lower in type I diabetics (8.84 +/- 1.25 sites per cell vs 16.8 +/- 2.97; P less than 0.07). There was no difference of apparent dissociation constant (KD) for either receptor. Angiotensin II values (RIA) were greater in diabetics (16.2 +/- 1.5 pg/ml vs 8.5 +/- 1.4 in controls; P less than 0.02) and concentrations of atrial natriuretic factor (RIA) were not significantly different. The data suggest increased angiotensin II binding despite high angiotensin II concentrations in non-nephropathic type I diabetic patients. These findings may be relevant when considering the evolution of hypertension and microangiopathy lesions.

Life feeling scales for use in German and American samples

Abstract: This paper describes an effort to construct social life feeling scales (self-determination, trust, future outlook, and so forth) for use in both American and German samples. Unidimensional scales (as defined) based on American respondents were modified as required to meet the same criteria in a German sample. Scales based on the German sample were modified as required to meet the same criteria among the American respondents. These modified scales were combined in order to meet given criteria of unidimensionality in both samples. Although combined scales meet (approximately) criteria of unidimensionality in both samples (German and American), the question of whether the feelings underlying these scales are identical in both populations remains.

Productivity Gaps and Capacity Utilization in the Manufacturing Sectors of Five OECD Countries, 1963 - 1982

Abstract: The purpose of this paper is to apply some novel features in the theory of productivity indexes to the measurement of productivity gaps. It advances the proposition that one reason for the persistence of productivity gaps might be that the methodology of measuring gaps does not separate shifts of the production function due to intercountry efficiency from shifts due to intercountry differences in capacity utilization.

Gefühle und soziale Konventionen

Abstract: Dieser Beitrag basiert nicht auf eigenen Untersuchungsergebnissen und ist weitgehend spekulativ. Er handelt von der konventionalen Vorpragung einer Klasse von Gefuhlen und zugleich davon, welche Rolle diese Klasse von Gefuhlen in konventional fundierten Handlungsregulationen spielt. Die konventionale Einbettung und regulative Funktion von Emotionen scheinen mir in ihrer Tragweite von der gegenwartigen Psychologie nicht hinreichend berucksichtigt zu werden, und schon diese Sachlage durfte auch sehr provisorische und spekulative Uberlegungen der von mir beabsichtigten Art rechtfertigen. Freilich ersetzen aber solche Spekulationen keine beharrliche psychologische Forschungsarbeit und auch nicht einen umfassenden Import von gesicherten Erkenntnisresultaten aus unseren Nachbarwissenschaften.

Mineral composition of sedimentary formations in the North Atlantic Ocean

Abstract: Sedimentary formations established in the western North Atlantic basin byJansa et al. (1979) and their coeval counterparts from the eastern North Atlantic were studied for their mineral composition using X-ray powder diffractometry. More than thousand samples from different legs of the Deep Sea Drilling Project were analysed semiquantitatively. The results are presented as diagrams of about thirty five different mineral phases versus depth/stratigraphy in the single boreholes. Sites 105, 106, 386, 387, 391, 417, and 418 were studied from the western North Atlantic, and Sites 367, 369, 370, 415, and 416 from the eastern North Atlantic off W-Africa. Specific mineral spectra were found from most of the formations which can thus be additionally characterized. The change of mineral composition along the formation boundaries is in most cases sharp but along some of the boundaries it is transitional. Local variations of mineral spectra within the same formation can mainly be referred to distance from source areas. The sedimentary section studied from the western North Atlantic basin ranges in age from Oxfordian to Quaternary. It consists of: argillaceous limestones (Cat Gap Formation); limestones (Blake-Bahama Formation); claystones and shales (Hatteras Formation); zeolitic claystones (Plantagenet Formation); nanno-marls (Crescent Peaks Member); siliceous oozes, clays, and cherts (Bermuda Rise Formation), and hemipelagic muds (Blake Ridge Formation) with locally redeposited shallow-water carbonates (Great Abaco Member). A corresponding section in the eastern North Atlantic is only developed at Site 367 where similar mineral assemblages could be found. At Sites 369, 370, 415, and 416 the sediment sequence is dominated by turbiditic influx of terrigenous components alternating with pelagic sediments; this can clearly be depicted from the mineral suites but it is not possible to establish sedimentary formations which can be paralleled to those within the western North Atlantic. Seismically mappable reflectors which were calibrated at the sediment sequence of the drillsites, are in most cases related to lithological changes and mineral composition. These acoustic horizons are very often coincident with formation boundaries. Besides different mineral composition, changes in grain size and diagenesis but also erosional unconformities are responsible for the impedance contrasts leading to the reflectors as already pointed out byTucholke (1979).

Modelling programs by the notion of hypergraph

Abstract: Programs can be modelled by hypergraphs where the nodes of the hypergraph represent programming units, such as statements or operands/operators, and the edges contain units which are related to each other This approach gives new insights into the measurement of programs, either by the fact that the well known measures of lines of code, cyclomatic complexity and program length in software science are part of this model, or by definition of a new measure based on the number of cycles in a hypergraph

Remarks on exponential splines, in particular a contour integral representation of exponential B-splines

Abstract: In the present paper we consider spline functions which are piecewise exponential sums of the form Σ αμeμx. Using the notation of Schumaker [10], we construct recursively computable B-splines of this space, where we make use of a complex contour integral. Furthermore, it is shown that this definition of a B-spline coincides in a certain sense with the ‘usual’ ones. which are based on the concept of generalized divided differences (e.g. [3, 12]). Finally, some additional properties of exponential B-splines are presented, including a differential relation.

Duality and Regularization for INF-Sup Problems

Abstract: Zu dieser Veroffentlichung liegt kein Abstract vor. There is no abstract found for this paper.

Locking policies and predeclared transactions

Abstract: Locking is considered as a means to achieve serializable schedules of concurrent transactions. Transactions are assumed to be predeclared such that a pre-analysis for locking becomes feasible to increase concurrency. A condition for safety is introduced which, based on a pre-analysis, allows the design of policies strictly dominating known policies such as 2-phase locking. The static case, in which the complete set of transactions is known in advance, and the online case, in which a transaction is known when it is started, are considered. It is shown that a policy strictly dominating 2-phase locking and some other interesting pre-analysis policies can also be applied in an online environment.

A contour integral representation of linear extrapolation methods

Abstract: Extrapolation methods are well-known to be very efficient tools for the acceleration of the convergence of certain sequences of numbers or functions, cf. [2, 3, 4, 8, 9]. In this note we present a representation of linear extrapolation procedures in terms of complex contour integrals. For the proof we make use of a complete characterization of these procedures as linear functionals, which is itself of some interest and can be found, for example, in [2] or [8].

The Case for International Competition Among Economic Policy Makers

Abstract: How can governments and civil servants be controlled? Professor Roland Vaubel, of the University of Mannheim, explains how competition between nations improves economic policy.

Integritätsbewahrendes Prototyping von verteilten Systemen

Abstract: Fur den konzeptuellen Entwurf dynamischer Aspekte von verteilten Systemen sind Pradikate/Transitionen- Netze als formale Beschreibungssprache geeignet, da sie ermoglichen, neben sequentiell ablaufenden Aktivitaten auch unabhangig voneinander (nebenlaufig) stattfindende sowie sich gegenseitig ausschliesende Aktivitaten zu modellieren.

Error Bounds and Stopping Rules for Extrapolation Methods

Abstract: On presente deux types differents d'estimations d'erreurs pour l'approximation des fonctions par des methodes d'extrapolation appelees aussi methodes d'elimination. On traite des exemples numeriques

Gemeinwirtschaftliche Bedeutung der Telekommunikation

Abstract: Von Konfuzius stammt der Satz: “Zuerst verwirren sich die Worte, dann die Begriffe, und schlieslich die Sachen” Beim Wort “Gemeinwirtschaft” besteht diese Gefahr Das Wort lost im deutschen Sprachraum divergierende Assoziationen aus Die ruhren daher, das das Wort “Gemeinwirtschaft” sowohl positiv als auch negativ interpretiert wird Und was den Begriffswirrwarr (insbesondere auf einer internationalen Konferenz) verschlimmert: das Wort ist kaum in andere Sprachen ubersetz-bar1