Änderungen der Fugenfläche und ihr Einfluß auf die Scherfestigkeit von Leimverbindungen

Ohne Zusammenfassung     

A Geometric Approach to Solving Problems of Control Constraints: Theory and a DAE Framework

The paper deals with controlled mechanical systems in which the number of control inputs is equal to the number of desired system outputs, and is smaller than the number of degrees of freedom of the system. The determination of control input strategy that force the underactuated system to complete the partly specified motion is a challenging problem. In the present formulation, the outputs (performance goals), expressed in terms of system states, are treated as constraints on the system—called control or program constraints as distinct from contact constraints in the classical sense, and a mathematical resemblance of the inverse control problem to the constrained system dynamics is exploited. However, while the reactions of contact constraints act in the directions orthogonal to the respective constraint manifold, the available control reactions may have arbitrary directions with respect to the program constraint manifold, and in the extreme may be tangent. A specific methodology must then be developed to find the solution of such singular problems, related to a class of control tracking problems such as position control of elastic joint robots, control of cranes, and aircraft control in prescribed trajectory flight. The governing equations of the problem arise as a set of differential-algebraic equations (DAEs), and an effective method for solving the DAEs, based on backward Euler method, is proposed. The open-loop control formulation obtained this way is then extended by a closed-loop control law to provide stable tracking of the required reference trajectories in the presence of perturbations. Some examples of applications of the theory and results of numerical simulations are reported.     

Structural Determinants of Workforce Participation after Retirement in Poland

In this paper, we aim to analyse selected structural determinants of workforce participation after retirement in Poland. By structural determinants we mean characteristics of one’s socio-economic position that (a) result from the interplay of social conditions (mechanisms of power, differentiated access to resources) and individual agency, and (b) restrict or facilitate individuals’ choices. We conceptualise workforce participation as engaging in either part- or full-time paid employment despite receiving the old-age pension. Our general hypothesis is that working in older age is not only a matter of motivation or psychological traits but also a complex interplay of structural characteristics, accumulated by individuals during their life course. In the paper, we test a number of hypotheses about the role of specific components of socio-economic status (SES), i.e. occupational prestige, education, and wealth, for workforce participation among retirees. We argue that, in case of retirees, the prestige of the last job before retirement is a more reliable measure of the social position than education. Hence, we conduct a more detailed analysis of the role of occupational prestige for the chances of being employed after retirement. The analysis was based on data gathered in the years 2013–2014 within the sixth wave of the Polish Panel Survey POLPAN (www.polpan.org). We extracted a subsample of retirees from this dataset and used logistic regression to test the hypotheses described above. We found that both occupational prestige of the last job before retirement and educational attainments are strong predictors of being in paid work after retirement, however the impact of occupational prestige varies across the groups with the lowest and higher level of retirement pension. We also found that there are horizontal differences in the occupational structure of the chances for workforce participation after retirement and additionally found that being a farm owner increases the propensity to engage in economic activity after retirement. The paper contributes to the field of studies on the relationship between SES and workforce participation after retirement in line with the cumulative advantage/disadvantage theory and shows that resources that individuals have accumulated during the life course can determine their chances of working after retirement just as individual motivations or organisational characteristics do.     

The Role of the Mizar Mathematical Library for Interactive Proof Development in Mizar

The Mizar system is one of the pioneering systems aimed at supporting mathematical proof development on a computer that have laid the groundwork for and eventually have evolved into modern interactive proof assistants. We claim that an important milestone in the development of these systems was the creation of organized libraries accumulating all previously available formalized knowledge in such a way that new works could effectively re-use all previously collected notions. In the case of Mizar, the turning point of its development was the decision to start building the Mizar Mathematical Library as a centrally-managed knowledge base maintained together with the formalization language and the verification system. In this paper we show the process of forming this library, the evolution of its design principles, and also present some data showing its current use with the modern version of the Mizar proof checker, but also as a rich corpus of semantically linked mathematical data in various areas including web-based and natural language proof presentation, maths education, and machine learning based automated theorem proving.     

Strong and uniform equivalence of nonmonotonic theories – an algebraic approach

We show that the concepts of strong and uniform equivalence of logic programs can be generalized to an abstract algebraic setting of operators on complete lattices. Our results imply characterizations of strong and uniform equivalence for several nonmonotonic logics including logic programming with aggregates, default logic and a version of autoepistemic logic. This work was partially supported by the NSF grant IIS-0325063.     

Atomicity failure and the retrenchment atomicity pattern

The issues surrounding the question of atomicity, both in the past and nowadays, are briefly reviewed, and a picture of an ACID (atomic, consistent, isolated, durable) transaction as a refinement problem is presented. An example of a simple air traffic control system is introduced, and the discrepancies that can arise when read-only operations examine the state at atomic and finegrained levels are handled by retrenchment. Non-ACID timing aspects of the ATC example are also handled by retrenchment, and the treatment is generalised to yield the Retrenchment Atomicity Pattern. The utility of the pattern is confirmed against a number of different case studies. One is the Mondex Electronic Purse, its protocol treated as a conventional atomic transaction. Another is the recovery protocol of Mondex, viewed as a compensated transaction (leading to the view that compensated transactions in general fit the pattern). A final one comprises various unruly phenomena occurring in the implementations of software transactional memory systems, which can frequently display non-ACID behaviour. In all cases the Atomicity Pattern is seen to perform well.     

Some Remarks on the Role of Minimal Length of Positive Maps in Constructing Entanglement Witnesses

The main objective of this paper is to discuss correspondence between the concept of entanglement witnesses (self-adjoint operators on a composite Hilbert space that are, in general, not positive, but are positive on separable states) and positive maps which are not completely positive. The notion of minimal length of linear positive map is introduced and the role of this quantity in the constructing of entanglement witnesses is explained.Presented at the 36th Symposium on Mathematical Physics, ‘Open Systems & Quantum Information’, Toruń, Poland, June 9-12, 2004.Supported by the Grant PBZ-MIN-008/P03/2003.     

Interpretable segmentation of medical free-text records based on word embeddings

Journal of Intelligent Information Systems - Medical free-text records store a lot of useful information that can be exploited in developing computer-supported medicine. However, extracting the...     

A wave-packet technique to simulate resonant X-ray scattering cross sections

This article describes algorithms and a program implementation for wave packet calculations of resonant X-ray scattering cross sections of molecules with one active internal degree of freedom. The program uses a time-dependent formalism and a grid representation of the wave packets. The potentials of ground, core-excited and final states can be specified by analytical expressions or by discrete sets of energies on arbitrary grids allowing for interfacing with electronic structure packages. The theory on which the program is founded is briefly reviewed. The implemented numerical algorithm is described in detail together with usage instructions and a sample application.