Showing 5 results for Coa
F. Sereshki, S.a. Hosseini, N. Aziz , I. Porter ,
Volume 19, Issue 5 (7-2008)
Abstract
The Outburst can be defined as a sudden release of coal and rock accompanied by large quantities of gas into the underground coal mine workings which represents a major hazard in underground coal mines. Gas drainage has been proven to be successful in reducing outburst hazards by decreasing the in-situ gas pressure. One of aspect of gas drainage from coal seams is coal matrix volume changes. Current study is primarily concerned with experimental studies related to coal volume change (coal shrinkage) under various gas types and pressures. Two types of tests were conducted on each sample, the adsorption test for coal swelling and the desorption test for coal shrinkage. The gases used in the study were CH4, CO2, CH4/CO2 (50-50% volume), and N2. In this research, tests were conducted with respect to volumetric change behavior in different gases and their corresponding comparative results were presented.
S. Rastegari, Z. Salehpour , Bakhshi , H. Arabi,
Volume 19, Issue 5 (7-2008)
Abstract
Formation mechanism of silicon modified aluminide coating applied on a nickel base super alloy IN-738 LC by pack cementation process was the subject of investigation in this research. Study of the microstructure and compositions of the coating was carried out, using optical and scanning electron microscopes, EDS and X-ray diffraction (XRD) techniques. The results showed that due to low partial pressure of silicon halide in Pack process, the amount of soluble silicon in the coating can not exceed 1 wt % of the total coating composition, although the Si content of the particles present within the outer coating sub-layer could reach as far as 5 wt%. Thus, the small amount of soluble Si within the coating could not provide the necessary conditions for formation of any intermetallic and it seems that the formation and growth behavior of various sub-layers in Si-modified aluminide coating is similar to that of simple aluminide coating. Three sub-layers were detected in the coating structure after being subjected to diffusion heat treatment. They were an outer Ni-rich NiAl sub-layer a middle Ni-rich NiAl and an inter diffusion sub-layers. The details of formations and growth mechanism of these sub-layers has been discussed in this research.
Mohammad Mahdi Nasiri, Nafiseh Shamsi Gamchi, Seyed Ali Torabi,
Volume 27, Issue 4 (12-2016)
Abstract
Hubs are critical elements of transportation networks. Location of hubs and allocation of demands to them are of high importance in the network design. The most important purpose of these models is to minimize the cost, but path reliability is also another important factor which can influence the location of hubs. In this paper, we propose a P-center hub location model with full interconnection among hubs while there are different paths between origins and destinations. The purpose of the model is to determine the reliable path with lower cost. Unlike the prior studies, the number of hubs in the path is not limited to two hubs. The presented model in this paper is bi-objective and includes cost and reliability to determine the best locations for hubs, allocation of the demands to hubs and the best path. In order to illustrate our model, a numerical example is presented and solved using the Cuckoo Optimization Algorithm.
Nataliia Demchuk, Iuliia Masiuk2, Anastasiia Donskykh, Iryna Kadyrus,
Volume 31, Issue 4 (11-2020)
Abstract
The aim of the study is to develop theoretical and methodological foundations, scientific and practical recommendations for improving the management and evaluation of public debt in Ukraine. The methodological foundations of the study are a systematic approach to the analysis of the relationship of financial phenomena and processes, creative reflection on the works of Ukrainian and foreign scientists on public debt, and its role in the context of macro-financial stabilization. Specific scientific theoretical and applied developments by the applicant were obtained using the following methods: graphical financial analysis (for studying the tendencies of debt formation); statistical-economic (to identify the impact of public debt on socio-economic processes); economic-mathematical modeling (to determine the relationship between public debt and macroeconomic indicators). On the basis of the research, it was revealed that the selected macroeconomic indicators have a significant impact on the government debt, and there are difficulties in coordinating international, regional economic integration or creating a broad separation based on stable international competitiveness. In order to test the impact of some macroeconomic indicators on the size of public debt, the World Bank's economic indicators have been taken as the main material for research. The analyzed period of time is 2001-2017 years.
The recommendations provided in this article will contribute to the development of public debt management and the associated increase in the living standards of the country's population. Based on the analysis conducted, there are every reason to assert that effective management of public debt can contribute to the development of the national economy. The scientific novelty of the study is to determine the impact of some macroeconomic indicators on public debt management at the current stage of Ukraine's development.
Shahla Zandi, Reza Samizadeh, Maryam Esmaeili,
Volume 33, Issue 4 (12-2022)
Abstract
A coalition loyalty program (CLP) is a business strategy employed by for-profit companies to increase or retain their customers. One of the operational challenges of these programs is how to choose the mechanism of coordination between business partners. This paper examines the role of revenue sharing contracts in the loyalty points supply chain of a CLP with stochastic advertising-dependent demand where the program operator (called the host) sells loyalty points to the partners of the program. The purpose of the study is to examine the effect of this coordination mechanism on the decisions and profits of the members of the chain using the Stackelberg game method and determine whether the presence of revenue sharing contracts benefits the chain members when the advertising is done by the host and when the advertising cost is shared between the host and its partners. The results show that when the host gives bonus points to end customers (advertising), revenue sharing contracts become a powerful incentive for the profitability of the host and its partners. The findings provide new insights into the management of CLPs, which can benefit business decision-makers.
