Search results

This chapter develops a growth model of a country under a Hobbesian environment with international conflicts in which national defense is the only way to prevent external predation. The long run growth path is determined by the equilibrium of a dynamic game with three players: the external predator, the government, and the family. The equilibrium growth path has three phases: submissive equilibrium, tolerant equilibrium, and full-protected equilibrium. Different defense strategies result in different growth prospects, and sustainable growth will endogenously induce adjustment of defense strategies.

THE following notes are being written solely for the benefit of ground engineers who are endeavouring to acquire the necessary knowledge to obtain a D licence. A licence in Category D demands a knowledge of the heat treatment of steels. Practical experience is, of course, quite as essential in this as in other and allied branches of engineering, but a theoretical study of the reasons for, and the results of, different heat treatment, is equally essential for a complete understanding of the subject.

1.1. Logical Necessity of the Three Dimensions as a Unit of Thought The mathematician does not look kindly on the simple question of why natural space should consist of precisely three dimensions. Instead of giving an answer he assumes a silent smile and shows us a version of space with an infinity of dimensions, as if space were some kind of toy for him to fiddle with to his heart's content.

Anecdotal discussions suggest that enterprise system (ES) user performance is low when such complex systems are introduced, and then improves over time. However, there is a dearth of scientific rigor and empirical evidence about the user performance over the lengthy lifecycles. Moreover, our scientific understanding of user performance phenomenon is further convoluted by the various user groups (i.e. operational, management and executive), who purport to have often conflicting objectives and priorities. Using a longitudinal study design of two surveys, gathering data twice from 465 respondents representing three organization, the purpose of this paper is to explore the changes in user performance of operational, management and executive staffs, across the key phases of the ES lifecycle.

A longitudinal study approach was followed, gathering data using two surveys. The two surveys were conducted six years apart, yielding data from 465 ES users. The respondents belong to operational, managerial and executive staffs of three organizations that were using the same market-leading ES, SAP.

The paper provides empirical insights on how user performance changes over time, across the ES lifecycle phases. Importantly, it was observed that the three user cohorts demonstrate substantial differences on their performance with the system.

The research results may lack generalizability due to homogeneity of the sample in terms of the types of the system, implementation partners and the industry sector the respondents belonged to.

Based on the study findings, organizations can introduce tailor-made management interventions for each user cohort for each ES lifecycle phase.

This paper provides empirical evidence for a phenomenon that still lacks scientific rigor and empirical evidence. By conducting a longitudinal survey of all ES user cohorts, the study provides insights into ES user performance.

Outlines the importance of dissociating change issues from transition issues within organizations. Presents some transition triggers and shows how they can affect people in their job. Describes a five‐stage model of the transition dynamic, with examples of how people live through organizational transitions. Gives some ideas for addressing these issues and building a transition management approach.

The purpose of this paper is to develop multi-physics computational model for the conventional gas metal arc welding (GMAW) joining process has been improved with respect to its predictive capabilities regarding the spatial distribution of the mechanical properties (strength, in particular) within the weld.

The improved GMAW process model is next applied to the case of butt-welding of MIL A46100 (a prototypical high-hardness armor-grade martensitic steel) workpieces using filler-metal electrodes made of the same material. A critical assessment is conducted of the basic foundation of the model, including its five modules, each dedicated to handling a specific aspect of the GMAW process, i.e.: first, electro-dynamics of the welding-gun; second, radiation/convection controlled heat transfer from the electric arc to the workpiece and mass transfer from the filler-metal consumable electrode to the weld; third, prediction of the temporal evolution and the spatial distribution of thermal and mechanical fields within the weld region during the GMAW joining process; fourth, the resulting temporal evolution and spatial distribution of the material microstructure throughout the weld region; and fifth, spatial distribution of the as-welded material mechanical properties.

The predictions of the improved GMAW process model pertaining to the spatial distribution of the material microstructure and properties within the MIL A46100 butt-weld are found to be consistent with general expectations and prior observations.

To explain microstructure/property relationships within different portions of the weld, advanced physical-metallurgy concepts and principles are identified, and their governing equations parameterized and applied within a post-processing data-reduction procedure.

A fundamental principle of materials engineering is that the microstructure of a material controls the properties. The phase transformation is an important phenomenon that determines the final microstructure. Recently, many analytical and numerical methods were used for modeling of phase transformation, but some limitations can be seen in relation to the choice of the shape of growing grains, introduction of varying grain growth rate and modeling of diffusion phenomena. There are also only few comprehensive studies that combine the final microstructure with the actual conditions of its formation. Therefore, the objective of the work is a development of a new hybrid model based on lattice Boltzmann method (LBM) and cellular automata (CA) for modeling of the diffusional phase transformations. The model has a modular structure and simulates three basic phenomena: carbon diffusion, heat flow and phase transformation. The purpose of this study is to develop a model of heat flow with consideration of enthalpy of transformation as one of the most important parts of the proposed new hybrid model. This is one of the stages in the development of the complex model, and the obtained results will be used in a combined solution of heat flow and carbon diffusion during the modeling of diffusion phase transformations.

Different values of overheating/overcooling affect different values in the enthalpy of transformation and thus the rate of transformation. CA and LBM are used in the hybrid model in part related to heat flow. LBM is used for modeling of heat flow, while CA is used for modeling of the microstructure evolution during the phase transformation.

The use of LBM and CA in one numerical solution creates completely new possibilities for modeling of phase transformations. CA and LBM in comparison with commonly used approaches significantly simplify interface and interaction between different parts of the model, which operates in a common domain. The CA can be used practically for all possible processes that consist of nucleation and grains growth. The advantages of the LBM method can be well used for the simulation of heat flow during the transformation, which is confirmed by numerical results.

The developed heat flow model will be combined with the carbon diffusion model at the next stage of work, and the new complex hybrid model at the final stage will provide new solutions in numerical simulation of phase transformations and will allow comprehensive modeling of the diffusional phase transformations in many processes. Heating, annealing and cooling can be considered.

The paper presents the developed model of heat flow (temperature module), which is one of the main parts of the new hybrid model devoted to modeling of phase transformation. The model takes into account the enthalpy of transformation, and the connection with the model of microstructure evolution was obtained.

PART II Analysis of the examination syllabuses Sixth‐form school chemistry is closely tied to the syllabuses of the GCE at ‘A/S’ level and in consequence the most practical method of judging whether textbooks provide the requirements of sixth‐form work is to compare them with the examination syllabuses. Recently this has been made difficult because of rather revolutionary changes in some of the GCE Boards syllabuses. Oxford, Oxford and Cambridge, and the Joint Matriculation Board of the Northern Universities, introduced modifications for the 1964 examination, the Southern Universities for the 1965 examination, and recently Cambridge has introduced an alternative syllabus (T) for the 1966 examination. The other Cambridge examination, now known as ‘Alternative N’, was modified to its present form in 1954. London are in the process of revision.

This paper aims to numerically study the compositional flow of two- and three-phase fluids in one-dimensional porous media and to make a comparison between several upwind and central numerical schemes.

Implicit pressure explicit composition (IMPEC) procedure is used for discretization of governing equations. The pressure equation is solved implicitly, whereas the mass conservation equations are solved explicitly using different upwind (UPW) and central (CEN) numerical schemes. These include classical upwind (UPW-CLS), flux-based decomposition upwind (UPW-FLX), variable-based decomposition upwind (UPW-VAR), Roe’s upwind (UPW-ROE), local Lax–Friedrichs (CEN-LLF), dominant wave (CEN-DW), Harten–Lax–van Leer (HLL) and newly proposed modified dominant wave (CEN-MDW) schemes. To achieve higher resolution, high-order data generated by either monotone upstream-centered schemes for conservation laws (MUSCL) or weighted essentially non-oscillatory (WENO) reconstructions are used.

It was found that the new CEN-MDW scheme can accurately solve multiphase compositional flow equations. This scheme uses most of the information in flux function while it has a moderate computational cost as a consequence of using simple algebraic formula for the wave speed approximation. Moreover, numerically calculated wave structure is shown to be used as a tool for a priori estimation of problematic regions, i.e. degenerate, umbilic and elliptic points, which require applying correction procedures to produce physically acceptable (entropy) solutions.

This paper is concerned with one-dimensional study of compositional two- and three-phase flows in porous media. Temperature is assumed constant and the physical model accounts for miscibility and compressibility of fluids, whereas gravity and capillary effects are neglected.

The proposed numerical scheme can be efficiently used for solving two- and three-phase compositional flows in porous media with a low computational cost which is especially useful when the number of chemical species increases.

A new central scheme is proposed that leads to improved accuracy and computational efficiency. Moreover, to the best of authors knowledge, this is the first time that the wave structure of compositional model is investigated numerically to determine the problematic situations during numerical solution and adopt appropriate correction techniques.