2,419 research outputs found
Solution of the problem of composite charge using R.D.38
No full textIn this paper the author has solved the problem of internal ballistics of composite charge using 'R.D.38' method which is based upon the usual isothermal approximation. A linear law of burning has been assumed
Author index
No full textThe articles have been scanned in colour with a HP Scanjet 5590; 300dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.This is a continuation of the "Author and Subject Index to the Onderstepoort Journal
of Veterinary Science and Animal Industry (1933- l950)" and the "Onderstepoort Journal
of Veterinary Research (1951 - 1968)" which appeared in June 1969 and covers the period
1969 to 1973, i.e. Volumes 36 to 40.
As from 1974 (Volume 41) it is intended to furnish an Author and Subject Index
in Number 4 of each volume covering all four numbers for that particular year
Noise due to unsteady flow past trailing edges
No full textThis paper presents two-dimensional direct numerical simulations (DNS) of noise generated at trailing edges (TE) with zero thickness. The simulations are conducted specifying either no-slip or slip walls in order to investigate viscous effects. In both cases, small amplitude disturbances are introduced close to the inflow boundary that serve as pressure disturbances at the TE. DNS data reveals that the unsteady Kutta condition is not satisfied, irrespective of the wall boundary condition. However, it appears that the validity of the unsteady Kutta condition is not essential for making an accurate prediction of the far field noise. The far field pressure is predicted as a function of the surface pressure difference using a 2-D modification of Amiet's classical theory, and compared with the far field pressure computed directly. Directivity plots provide evidence that the presence of boundary layers and noise generated by an unsteady wake in the no-slip cases lead to smearing of individual lobes, and that the downstream pointing lobes in no-slip wall cases are probably due to nonlinear noise generation in the wake. The simulations are conducted using a high-order accurate numerical method which is free of upwinding, artificial dissipation or any form of explicit filtering, and employs a novel boundary treatment
Characteristic distribution and scale interaction of turbulence in a boundary layer
No full textThis work revisits the concept of turbulent boundary layers from a novel perspective on scale transfer. Turbulence production and dissipation together with the energy budgets are analyzed in the velocity gradient invariant phase space. In combination with filtering, the mechanism of scale coupling is investigated and illustrated for different characteristic flow topologies. The understanding of the scale coupling is important to model turbulence. Turbulence models describe the complex interaction of the scales of motion in a simplified form. The essential task of turbulence modeling is to capture the coupling of the modeled and unmodeled scales as well as the evolution of the modeled scales within the unmodeled flow. This work characterizes the scale coupling by focusing on the interfaces between modeled and unmodeled flow such as production and dissipation. The mechanisms that govern the evolution of the modeled quantities are investigated for their core properties and universal features. Direct numerical simulation (DNS) is carried out to obtain data of a compressible zero pressure-gradient flat plate turbulent boundary layer flow. This flow topology allows to unveil the effect of a wall on the coupling of scales and evolution of turbulence
Informational Benefits of International Environmental Agreements
No full textGiven that it is difficult to monitor, and even more so to enforce, International Environmental Agreements, it is surprising that they are signed and implemented. This paper offers a theoretical model, which addresses the phenomena. The focus is on informational and coordination problems--a country which is unsure about the benefits of environmental policy may believe that the benefits are higher the greater the number of other countries which lean towards taking action. Whereas each country may individually take no environmental action, in equilibrium several countries may take environmental action if they expect others to. An International Environmental Agreement can thus be self-enforcing. Such effects can appear even if international environmental spillovers are absent, and even if monitoring and enforcement are infeasible. Our approach can explain additional phenomena: why a country that is known to care little about the environment may deeply influence other countries if it takes environmental action, why lags may appear between the signing of an agreement and its implementation, and how requirements for approval by several bodies within a country can increase support for environmental action.Environmental policy; International agreements; Signaling; Regulation
Informational benefits of international environmental agreements
No full textGiven the difficulty of monitoring, and even more so of enforcing, International Environmental Agreements, it is surprising that they are signed and implemented. This paper offers a theoretical model, which addresses this issue. The focus is on informational and coordination problems. A country which is unsure about the benefits of environmental policy may find that the benefits are higher the greater the number of other countries which lean towards taking action. Whereas each country may individually take weak environmental action, in equilibrium several countries may take strong action if they expect others to. An International Environmental Agreement can thus be selfenforcing. Such effects can appear even if international environmental spillovers are absent, and even if monitoring and enforcement are infeasible. Our approach can explain additional phenomena: why a country known to care little about the environment may deeply influence other countries if it takes strong environmental action, why lags may appear between the signing of an agreement and its implementation, and how requirements for approval by several bodies within a country can increase support for environmental action.Environmental policy, international agreements, signaling, regulation
Learning from One's Mistakes
No full textCreated by R.D. Lee for the Royal Statistics Society, this article describes an exercise, which highlights the effect of sampling without replacement in small populations, and leads to consideration of the relative importance of sample and population size when examining standard error. The author provides a number of exercises, an explanation of statistical errors and the importance of sample size. This is a brief, yet fine resource for those in the field of statistics
Informational benefits of international environmental agreements.
No full textGiven the difficulty of monitoring, and even more so of enforcing, International Environmental Agreements, it is surprising that they are signed and implemented. This paper offers a theoretical model, which addresses this issue. The focus is on informational and coordination problems. A country which is unsure about the benefits of environmental policy may find that the benefits are higher the greater the number of other countries which lean towards taking action. Whereas each country may individually take weak environmental action, in equilibrium several countries may take strong action if they expect others to. An International Environmental Agreement can thus be selfenforcing. Such effects can appear even if international environmental spillovers are absent, and even if monitoring and enforcement are infeasible. Our approach can explain additional phenomena: why a country known to care little about the environment may deeply influence other countries if it takes strong environmental action, why lags may appear between the signing of an agreement and its implementation, and how requirements for approval by several bodies within a country can increase support for environmental action.Environmental policy; International agreements; Signaling; Regulation;
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