A Comparison of Alternative Approaches for Numerical Solutions of GI/PH/1 Queues

1996 ◽  
Vol 8 (1) ◽  
pp. 74-85 ◽  
Author(s):  
Edward P. C. Kao
Keyword(s):  
Numerical Solutions ◽  
Alternative Approaches

Burnthrough Prediction for In-Service Welding: Past, Present and Future

2012 ◽  
Author(s):  
Matthew A. Boring
Keyword(s):  
Surface Temperature ◽  
Numerical Solutions ◽  
Computer Models ◽  
Operating Conditions ◽  
Inside Surface ◽  
Welding Parameters ◽  
Mechanical Approach ◽  
Alternative Approaches ◽  
Analysis Models ◽  
Determining Factor

The methods of determining burnthrough risk have changed over the years. The first burnthrough limits were developed experimentally and then, with the development of computers, came computer models. The first major advancement in computer models came at Battelle, in the early 1980s, with the development of the “Hot-Tap Thermal-Analysis Models.” The Battelle models use two-dimensional numerical solutions to predict the inside surface temperature as a function of the welding parameters, pipe parameters, and the operating conditions. The Battelle model considers an inside surface temperature of less than 1800°F (982°C) when using low-hydrogen electrodes, [1400°F (760°C) when using cellulosic-coated electrodes] to be safe. Since the release of the Battelle model, introduction other models have been developed which are based on Battelle’s logic as well as other approaches. PRCI, as well as others, has funded research to develop an alternative burnthrough prediction model which is based on a thermo-mechanical approach taking into account the stress associated with pressurized pipe. These alternative approaches differ from Battelle’s criteria which only uses the inside surface temperature as the lonely determining factor of safe welding practices.

SOLVING LARGE-SCALE RATIONAL-EXPECTATIONS MODELS

1997 ◽  
Vol 1 (1) ◽  
pp. 45-75 ◽  
Author(s):  
JESS GASPAR ◽  
KENNETH L. JUDD
Keyword(s):  
Numerical Methods ◽  
Rational Expectations ◽  
Large Scale ◽  
Numerical Solutions ◽  
Projection Methods ◽  
General Purpose ◽  
Asset Markets ◽  
Trade Offs ◽  
Incomplete Asset Markets ◽  
Alternative Approaches

We explore alternative approaches to numerical solutions of large rational-expectations models. We discuss and compare several current alternatives, focusing on the trade-offs in accuracy, space, and speed. The models range from representative-agent models with many goods and capital stocks, to models of heterogeneous agents with complete or incomplete asset markets. The methods include perturbation and projection methods. We show that these methods are capable of analyzing moderately large models even when we use only elementary, general-purpose numerical methods.

Alternative approaches to ultra-high resolution imaging

1991 ◽  
Vol 49 ◽  
pp. 650-651
Author(s):  
J.M. Cowley
Keyword(s):  
High Resolution ◽  
High Voltage ◽  
High Resolution Electron Microscopy ◽  
Crystal Defects ◽  
High Resolution Imaging ◽  
General Applicability ◽  
Resolution Electron ◽  
Radiation Resistant ◽  
Resolution Imaging ◽  
Alternative Approaches

By extrapolation of past experience, it would seem that the future of ultra-high resolution electron microscopy rests with the advances of electron optical engineering that are improving the instrumental stability of high voltage microscopes to achieve the theoretical resolutions of 1Å or better at 1MeV or higher energies. While these high voltage instruments will undoubtedly produce valuable results on chosen specimens, their general applicability has been questioned on the basis of the excessive radiation damage effects which may significantly modify the detailed structures of crystal defects within even the most radiation resistant materials in a period of a few seconds. Other considerations such as those of cost and convenience of use add to the inducement to consider seriously the possibilities for alternative approaches to the achievement of comparable resolutions.

Atomic Imaging of Crystals using Large-Angle Electron Scattering in STEM

1990 ◽  
Vol 48 (1) ◽  
pp. 74-75
Author(s):  
D.E. Jesson ◽  
S. J. Pennycook
Keyword(s):  
Wave Function ◽  
Electron Scattering ◽  
Numerical Solutions ◽  
Large Angle ◽  
Real Space ◽  
High Angle ◽  
Analytical Treatment ◽  
Order Zero ◽  
Experimental Conditions ◽  
Ewald Sphere

It is well known that conventional atomic resolution electron microscopy is a coherent imaging process best interpreted in reciprocal space using contrast transfer function theory. This is because the equivalent real space interpretation involving a convolution between the exit face wave function and the instrumental response is difficult to visualize. Furthermore, the crystal wave function is not simply related to the projected crystal potential, except under a very restrictive set of experimental conditions, making image simulation an essential part of image interpretation. In this paper we present a different conceptual approach to the atomic imaging of crystals based on incoherent imaging theory. Using a real-space analysis of electron scattering to a high-angle annular detector, it is shown how the STEM imaging process can be partitioned into components parallel and perpendicular to the relevant low index zone-axis.It has become customary to describe STEM imaging using the analytical treatment developed by Cowley. However, the convenient assumption of a phase object (which neglects the curvature of the Ewald sphere) fails rapidly for large scattering angles, even in very thin crystals. Thus, to avoid unpredictive numerical solutions, it would seem more appropriate to apply pseudo-kinematic theory to the treatment of the weak high angle signal. Diffraction to medium order zero-layer reflections is most important compared with thermal diffuse scattering in very thin crystals (<5nm). The electron wave function ψ(R,z) at a depth z and transverse coordinate R due to a phase aberrated surface probe function P(R-RO) located at RO is then well described by the channeling approximation;

Beyond GDP: The Quest for a Measure of Social Welfare. Part II

2012 ◽  
pp. 32-51 ◽  
Author(s):  
M. Fleurbaey
Keyword(s):  
Social Welfare ◽  
Social Relations ◽  
Well Being ◽  
Welfare Economics ◽  
Subjective Well Being ◽  
Alternative Approaches ◽  
Micro Level ◽  
Beyond Gdp

The second part of the paper is devoted to the non-monetary indicators of social welfare. Various approaches to the study of subjective well-being and happiness are described. The author shows what problems a researcher would encounter trying to analyze welfare on the micro-level and to take account of the cognitive and affective aspects of the individuals assessment of their well-being, as well as the relevance of social relations. The author also shows to what extent the alternative approaches, particularly the analysis of functionings and capabilities advanced by A. Sen are compatible to the modern welfare economics and what prospects the latter has.

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