Showing papers by "Wolfgang Wagner published in 1993"

International Equations for the Saturation Properties of Ordinary Water Substance. Revised According to the International Temperature Scale of 1990. Addendum to J. Phys. Chem. Ref. Data 16, 893 (1987)

Abstract: Consistent with the latest experimental data and the internationally recommended values for the critical parameters we published in 1987, compact and accurate correlation equations are given for the following properties on the saturation line of ordinary (light) water substance: vapor pressure, density, and enthalpy and entropy of both the saturated liquid and the saturated vapor. As an addendum to a paper by A. Saul and W. Wagner, J. Phys. Chem. Ref. Data 16, 893 (1987), this paper brings all temperature values and adjusted coefficients in all correlation equations into agreement with the International Temperature Scale of 1990 (ITS‐90). The new equations form the basis of the ‘‘Revised Supplementary Release on Saturation Properties of Ordinary Water Substance’’ issued by the International Association for the Properties of Water and Steam (IAPWS). This revised release which contains all equations and coefficients adjusted with regard to the ITS‐90 is the main part of this paper.

Can representations explain social behaviour? a discussion of social representations as rational systems *

Abstract: Two propositions are presented in order to show that social representations cannot be regarded as explanations of behaviour: First it is argued that rational beliefs, decisions, and acting necessarily involve socially constructed knowledge which gains its evidence by collective consensus. Social Representations are considered as one form of collectively validated rational knowledge. Second it is shown that social psychological theories containing common-sense or everyday-rational knowl- edge cannot be interpreted as explanatory theories in the strict sense of the term. Additionally, experi- ments aimed at empirically proving hypotheses deduced from such theories are not a proof, but an "illustration" or "example" of the rational context. Taken together the two propositions lead to the conclusion that rational beliefs and rational behaviour are inseparable from each other, such that a specific belief cannot be used as an explanation of subsequent related behaviour. Equally, social repre- sentations do not explain, but describe related behaviour. One of the logical and methodological problems inherent in social representation theory is the relationship between representation and social behaviour. Usually social representations have been considered as being closely linked to behaviour (e.g. Jodelet, 1984, 1989). This link must be qualified in at least two ways. First, social representations do not account for the behaviour of individuals per se, but only for the behaviour of individuals qua members of social groups (Moscovici, 1982, p. 129). This characteristic is a consequence of their genesis in social discourse. Their socio-genesis of being collectively elaborated implies that social representations be valid systems of knowledge for groups as a whole and the respective group members. Second, social representations are not conceived as cognitions simply inter- vening between stimulus and behavioural response, but as symbolic structures comprising stimulus and behaviour in a simultaneous circular movement. As such, Moscovici (1984, p. 60f) holds, representations do not mediate stimuli but they are stimuli themselves and there- fore independent variables in empirical investigations, be they laboratory or field studies. The status of representations as independent variables makes them a prime candidate to explain collective behaviour on a group level or the behaviour of individuals qua representa- tives of social groups in research (e.g. Echebarria & Gonzales, 1992; Thommen et al., 1988; von Cranach, 1992, etc.). The use of representations as explanatory devices for subsequent behaviour, however, raises crucial epistemological questions. This understanding essentially implies a kind of "causal" link between representation and behaviour. This causal link then is explored in experimental or field studies showing that representation R precedes (the weak version) or causes (the strong version) subsequent behaviour B.

Special equations of state for methane, argon, and nitrogen for the temperature range from 270 to 350 K at pressures up to 30 MPa

Abstract: In order to describe the thermodynamic behavior of methane, argon, and nitrogen in the so-called “natural-gas region,” namely, from 270 to 350 K at pressures up to 30 MPa as accurate as possible with equations of a very simple form, new equations of state for these three substances have been developed. These equations are in the form of a fundamental equation in the dimensionless Helmholtz energy; for calculating the pressure or the density, the corresponding equations explicit in pressure are also given. The residual parts of the Helmholtz function representing the behavior of the real gas contain 12 fitted coefficients for methane, 8 for argon, and 7 for nitrogen. The thermodynamic relations between the Helmholtz energy and the most important thermodynamic properties and the needed derivatives of the equations are explicitly given; to assist the user there is also a table with values for computer-program verification. The uncertainties when calculating the density ρ, the speed of sound w, the isobaric specific heat capacity c p, and the isochoric specific heat capacity c v are estimated as follows. For all three substances it is Δρ/ρ≤±0.02 % for p≤ 12 MPa and Δρ/ρ ≤ ±0.05% for higher pressures. For methane it is Δw/w≤±0.02% for p≤10 MPa and Δw/w≤+-0.1% for higher pressures; for argon it is Δw/w≲-0.1 % for p≤ 7 MPa, Δw/w≤±0.3 % for 7

A random discrete velocity model and approximation of the Boltzmann equation

Abstract: An approximation procedure for the Boltzmann equation based on random choices of collision pairs from a fixed velocity set and on discrete velocity models is designed. In a suitable limit, the procedure is shown to converge to the time-discretized and spatially homogeneous Boltzmann equation.

Intra-operative monitoring during syringo-endoscopy: results of median nerve stimulated somatosensory evoked potentials in nine patients.

Abstract: Intra-operative SEP monitoring was performed in nine patients with cervical syringomyelia undergoing myelotomy and syringo-endoscopy. Several cortical and subcortical SEP components were evaluated. Pathological latency shifts of brain stem P14 were seen in two patients; other SEP components did not worsen nor recover intra-operatively. The clinical and pathophysiological significance of the data is briefly discussed.