جستجوی مقالات مرتبط با کلیدواژه « demand estimation » در نشریات گروه « علوم انسانی »

Considering the large volume of mineral resources in Iran and the geographical extent of mines and related industries in the country, its transportation is of particular importance. Although this product is known as a rail-friendly product in terms of transportation mode, but the 39% share of the rail transportation industry is far from the capabilities and expectations of this field. Therefore, in order to increase the share of rail transportation, it is necessary to identify the factors in the attractiveness of rail transport compared to road one. Identifying the factors in mode choice of transportation is one of the most important issues that has always been of interest to researchers in this field. Several studies have been conducted on understanding the behavior of customers to choose the mode of transport. In this paper, the most important factors that affect the mode choice have been identified and the demand function for minerals rail transport is estimated.

For this purpose, at first step, the affective factors in choosing the mode of transportation have been identified with the revealed preference method through literature review and background studies. Using the multiple regression model and the SPSS software, the correlation between the dependent variable (share or demand) and independent variables have been measured and a list of variables that effect on attracting demand and have a significant presence has been identified. In the end, using the double logit model and NLOGIT software, the rail utility function has been estimated to absorb the demand for minerals. The logit model is a discrete choice model, which in this research includes a utility function with different choice options and parameters affecting them. The structure of these models is of the probability type and in it the behavior of the decision maker and his efforts to maximize the utility resulting from the choice are modeled through mathematical relationships. The "forward selection" method has been used to build the model. In this method, the independent variables are entered into the model one by one in the order of their influence on the dependent variable and are evaluated, and at each stage, according to their t test statistic sign, chi-square test statistic and model fit. The next step is to obtain the final model of the utility function. Finally, the validity of the model was measured by the in-sample method, which shows a 3% error in demand forecasting

The results show that the most important factors affecting the choice of mineral transportation method are the ratio of rail transportation tariff to road tariff per ton, the bulk of the mine load, and the accessibility of the origin and destination to the rail network. This means that with the increase in the price of the rail tariff compared to the road, the desirability of rail transportation decreases and the probability of transferring cargo to the road increases. Also, having origin and destination access to the rail network was identified as one of the favorable factors for the rail transportation. This can be included in network development policies for investing in connecting major cargo centers to the network. On the other hand, the lack of access to the network increases the cost of combined transportation, which, in addition to wasting time, causes additional time and unloading and loading operations, which will lead to a decrease in the attractiveness of rail. Load accumulation with a threshold of 200 million ton-km increases the possibility of attracting demand to the rail side. Also, by increasing the ratio of rail to road distance on a fixed route, the possibility of rail and road competition decreases.

The results of this model help the transportation service providers to focus on improving the identified factors that lead to the growth of their performance in the transportation market of this product.

Extended Abstract
Among different areas of tourism, health tourism has received a lot of attention due to creating threefold currency compared to other types of tourism, capabilities and competitive advantages. Advances and medical achievements and the high level of health care equipment in Iran have created new possibilities and opportunities for the field of medical tourism. Iran due to its specialized doctors, low treatment costs, natural resources and suitable climate, proximity to Arab countries and similarity of culture and dialect with some neighboring countries have advantages in the field of attracting medical tourists from these countries despite the obstacles and weaknesses such as the presence of competitors in the region. Iran's share of the health tourism market is small despite its high capacity for medicine and healthcare. Therefore, Iran, as one of the regions and centers of medical tourism in the world, has potential therapeutic and medical capacities.
 
The research area includes four tourism zones with comparative medical advantage, according to the report of land use planning (2018). These 4 zones of land use planning include zone 2 (West Azerbaijan, East Azerbaijan, Ardabil and Kurdistan), zone 4 (Isfahan, Chaharmahal and Bakhtiari and Khuzestan), zone 6 (Tehran, Qom and Alborz), and zone 9 (South, North and Razavi Khorasan). Medical tourism demand was estimated by the Almost Ideal Demand. According to the studies of Walsh (1996), Uysal and Crampton (1984) due to insufficient access to data, problems related to compound alignment, etc., the factors affecting the tourist were selected separately for medical tourism demand in areas with medical system. Based on the Almost Ideal Demand, ten effective factors on the demand of medical tourism in zones with a medical system, including services and visa duration, relative prices (exchange rates), disposable personal income, entry and exit regulations and facilities, political and communication conditions with Iran, cost of accommodation, cost of treatment, waiting time for service, physician reputation and specialization were estimated. A random sample of 183 foreign tourists was selected by referring to the relevant customs.
 
According to the opinion of 183 foreign medical tourists in four zones od land use planning, the sensitivity of medical tourism demand to effective factors and types of medical tourism expenditures is measured. The results in all four medical tourism zones indicate the sensitivity of foreign tourists to various macro factors such as inflation and exchange rates. In addition, the variables of service and duration of visa, rules and facilities of entry and exit, political and communication conditions with Iran, cost of accommodation, cost of treatment, waiting time for service and the reputation of the doctor and special expertise all affect the tourist demand. Also, foreign tourists are highly sensitive to the costs and expenses of treatment in Iran and less sensitive to other costs such as accommodation and other expenses. All variables are at a stable level, so the level values of the variables were used to estimate the model in different regions, and out of 42 estimated parameters, 23 parameters were significant at the 95% confidence level. And since, according to Durbin-Watson statistics and the White test, all relationships have no autocorrelation and variance inequality, so the results are reliable. Therefore, the statistically significant coefficients indicate the sensitivity of tourists' demand to the corresponding variables of significant coefficients such as price, expenditure, exchange rate, inflation and so on. In other words, the significance of price coefficients for medical goods and services implies that the government can use these variables as a tool to achieve its economic goals in order to strengthen medical tourism.
 
Based on the results of estimating the almost ideal demand model for medical health tourism and considering the positive sign of the variable coefficient of tourists' opinions about the exchange rate and its significance in relation to the demand for medical services, it can be seen that an increase in the exchange rate leads to an increase the demand for medical services. Achieving this result based on trade theories such as Heckcher-Ohlin theory and the law of gravity is not far from expectation, and in fact this has led to cheaper Iranian domestic goods for foreigners, which is a tourist pull factor under the law of gravity. Based on the results of estimating the almost ideal medical tourism demand model and considering the negative sign of the variable coefficient of tourists' opinions about the waiting time for receiving services and its significance in relation to medical demand, it can be seen that increasing the growth of the health sector and service facilities, faster leads to an increase in demand for medical services. According to the results in all zones of land use planning, medical tourism demand is sensitive to service quality and visa duration, entry and exit regulations and facilities, political and communication conditions with Iran, cost of accommodation, cost of treatment, waiting time to receive services and doctor reputation and specialty. This means that foreign medical tourists who come to Iran are sensitive to the cost and quality of services in terms of income level and demand. In other words, the estimate indicates that the actual demand for medical services for foreigners is a necessary and non-luxury demand and therefore, increasing costs or reducing the quality of services will lead to a sharp decline in this demand.

In order to respond effectively to his clients, the National Gas Company needs to know about the amount of prevailing demand in every period. From the other hand, lack of information about the amount of subscription demand will in turn cause certain difficulties such as not knowing the number of required contractors, the absence of an appropriate inventory control for all kinds of needed gas consumption counters, etc.In the last few decades, economists and management specialists have frequently used econometric methods for estimating demand. Today, among the available estimation methods, they are using the artificial neural networks methods and fuzzy models in many areas of applications and each of them have its own merits and limitations. A successful combination of these two methods, with emphasis on learning power of neural networks and logical performance of fuzzy model, have been transformed into a very powerful instrument that are now being applied in different contexts.The main purpose of this article is to estimate the urban household gas subscription demand by using the ARIMA linear method and the fuzzy neural networks nonlinear method and to compare them on the basis of six performance criteria. The article concludes that, considering the six performance criteria, the fuzzy neural networks nonlinear method has supremacy over the ARIMA linear method for estimating the urban household gas subscription demand; therefore, it is more appropriate.