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Number of results: 4
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Abstract

The article presents the possibility of using the Cobb-Douglas production function for planning in a turbulent environment. A case study was carried out – the Cobb-Douglas function was used to examine the condition of the Polish hard coal mining industry and the progress which has been made after undertaking certain activities aimed at increasing the competitiveness of coal companies over recent years. Only the correct and confirmed identification of the causes of irregularities in the production process can allow for the introduction of effective remedies. The effectiveness of the solutions proposed by the author has been confirmed thanks to the simulation during which the impact of the proposed production strategy on the parameters of the CD function was examined. Three variants of production functions models were created and production productivity rates and marginal substitution rates were determined. The results enabled the verification of the progress of restructuring as well as identification of the origin of the observed problems and comparison of the current state with the results of analyses carried out in previous years. Scenarios of possible trend developments for the factors introduced into the function model in order to present remedial measures that could improve the process of hard coal extraction were created. The scenarios were created using the ARIMA class models. Which scenario is the most favourable was determined. A computer program, created by the author, for optimising the level and use of labor resources at the level of the entire coal company has been presented.
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Abstract

Ludwigite is the main available boron-bearing resource in China. In order to enrich the theory system and optimize its utilization processes, this paper study the mechanism and kinetics on non-isothermal decomposition of ludwigite in inert atmosphere by means of thermal analysis. Results show that, the decomposition of serpentine and szajbelyite is the main cause of mass loss in the process. At the end of decomposition, hortonolite and ludwigite are the two main phases in the sample. The average E value of structural water decomposition is 277.97 kJ/mol based on FWO method (277.17 kJ/mol based on KAS method). The results is proved to be accurate and reliable. The mechanism model function of structural water decomposition is confirmed by Satava method and Popescu method. The form of the most probable model function is G(α) = (1 – α)–1 – 1 (integral form) and f (α) = (1 – α)2 (differential form), and its mechanism is chemical reaction. This is verified by the criterion based on activation energy of model-free kinetics analysis.
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Abstract

The paper considers the modeling and estimation of the stochastic frontier model where the error components are assumed to be correlated and the inefficiency error is assumed to be autocorrelated. The multivariate Farlie-Gumble-Morgenstern (FGM) and normal copula are used to capture both the contemporaneous and the temporal dependence between, and among, the noise and the inefficiency components. The intractable multiple integrals that appear in the likelihood function of the model are evaluated using the Halton sequence based Monte Carlo (MC) simulation technique. The consistency and the asymptotic efficiency of the resulting simulated maximum likelihood (SML) estimators of the present model parameters are established. Finally, the application of model using the SML method to the real life US airline data shows significant noise-inefficiency dependence and temporal dependence of inefficiency.
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Abstract

This paper presents the construction of adequate 3-D computer models for simulation research and analysis of dynamic aspects of caliper disc brakes, as well as of drum brakes, actuated by a short stroke electromagnet or a hydraulic thruster, when these brake types are used in the hoisting mechanism of cranes. The adequacy of the 3-D models has been confirmed by comparing their simulation results with results from an experiment and from classic computational models. The classic computational models, related to the study of main dynamic features of friction brakes, are layouts that are based on a number of assumptions, such as that the braking force instantly reaches its steady-state value, the clearance between the friction lining and the disc/drum is neglected, etc. These assumptions lead to a limitation of research options. The proposed 3-D computer models improve the research layouts by eliminating a number of the classic model assumptions. The improvements are related to the determination of the braking time, braking torque, normal force and other dynamic aspects of the brakes by performing simulations that take into account: the braking force as a function of time, the presence of clearance between the friction lining and the disc/drum, etc.
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