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In this paper bus scheduling problem under the constraints that the total number of buses needed to perform all trips is known in advance and the energy level of buses is limited, is considered. Each depot has a different time processing cost. The goal of this problem is to find a minimum cost feasible schedule for buses. A mathematical formulation of the problem is developed. When there are two depots, a polynomial time algorithm is developed for the problem and theoretical results about the complexity and correctness of the algorithm is presented. Also, several examples are introduced for illustrating validity of the algorithm.

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Natural gas is a critical energy source that substantially contributes to meeting national energy demand. Iran possesses the world's second-largest natural gas reserves. In South Khorasan province, natural gas coverage is extensive, reaching 100% of urban households, 99.9% of rural households, and a large proportion of industrial facilities. This study examines the effects of natural gas supply to agricultural and production centers on production efficiency and economic profitability. The research is applied and employs a descriptive–survey design with a mixed-methods approach, combining structured questionnaires and expert interviews. The sample consisted of 165 respondents from the agricultural sector and 150 respondents from the production sector. Results indicate that supplying natural gas to agricultural and production centers enhances resource utilization, reduces energy costs, improves operational efficiency, and diminishes air pollution and greenhouse gas emissions.