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Showing 102 results for mahmoudi
Volume 21, Issue 9 (September 2021)
Abstract
Roll motion is one of the most important and dangerous motions of the ship and can even result in capsizing of the vessel. Therefore, its control has been always of interest for marine industry researchers. Among the various methods and equipment for controlling the roll motion, the use of free surface anti-roll tanks has been one of the most important methods and which used in many cases due to its simplicity in construction and design. The high efficiency of these tanks at all speeds and even without speed is another strength of these tanks. This study investigates the effect of the free surface anti-roll tank on the roll motion numerically and experimentally. In the numerical simulation, a CFD sloshing solver, based on the “Open source Field Operation And Manipulation”, known in short as Open-FOAM, and assuming 2D laminar flow conditions, is customized to calculate the sloshing loads from the tank. The predicted roll damping and moments due to the anti-roll tank are validated against experimental results. This simulator could be used as a sloshing simulator to couple with seakeeping solvers.
Volume 22, Issue 3 (March 2022)
Abstract
The use of non-destructive tests on composite materials to inspect, identify and observe defects to locate discontinuities or defects has received much attention in recent years. Among the existing methods, the use of a non-contact digital image correlation system for troubleshooting composites has been considered because of its advantages. In this study, using the digital image correlation method, the shape, position, and area of the failure area in six-layer glass/epoxy samples with impact damage with different energies under different loading amounts have been investigated. Five composite specimens with impact energies of 5, 10, 20, 30, and 40 joules were tested. At 5 joules of energy, the damage to the piece was very small, and at 40 joules, the amount of damage to the piece was such that the bullet was stuck inside the piece and the impact site remained as a hole in the piece. The areas obtained for the impact area in the strain contours at 40% load have values close to the actual area of damage. By comparing the area obtained from the strain contour at 40% load and the actual area of damage, for 10 joules, 20 joules, and 30 joules, the difference in areas obtained is about 2.3%, about 2.5%, and 3.1%, respectively.
Volume 22, Issue 3 (March 2022)
Abstract
In this research, the turbulent isotropic flow has been experimentally investigated. Hence, two different grids are made and a contraction channel is installed behind it inside the subsonic wind tunnel to generate an isotropic turbulence flow. The grids with mesh sizes of 2/54 cm and 5/08 cm were cut on the wood with obstruction ratio of 0/34 and 0/17, respectively. One-dimensional hot wire was used to determine the perturbation velocities in the direction of flow, and an approximation was used to determine the components of other directions. At speeds of 5 m/s and 10 m/s, experiments were performed for each of the grids, which range from a Reynolds number of 8500 to about 33000. To determine the onset of the isotropic location, methods of velocity skewness, kurtosis, turbulence intensity, dissipation rate, and longitudinal scales such as Kolmogorov and Taylor lengths were used. For skewness and kurtosis, the numbers show 0 and 3, respectively, which indicate the isotropic flow. Results showed that with increasing the velocity, the isotropy of the flow was delayed. Also, in a grid with a lower obstruction ratio, the intensity of turbulence will be less near the grid, but as it moves away from the grid, the intensity of turbulence will increase.
Volume 22, Issue 3 (5-2022)
Abstract
A significant number of engineering structures around the world are exposed to fire on a daily basis. The most important effect of fire on the structure is elevated temperatures, which may reach more than 1000 degrees Celsius and cause not only thermal stresses and deformations but also diminished mechanical properties of materials comprising the structure. Fire-related collapses have been observed in numerous structural fires. However, many reinforced concrete structures exposed to fire do not demonstrate notable apparent damage and survive despite having experienced elevated temperatures before the fire is put out. Estimating the residual strength of such structures is of critical importance when deciding whether such structures can be safely used after fire. Moreover, in many industrial applications, there is a need to concrete that can withstand repeated long-term cycles of elevated temperatures without diminished mechanical properties. The objective of this paper is to investigate the effects of silica fume and fly ash as two widely used supplementary cementitious materials on the residual strength of concrete exposed to elevated temperatures and evaluate while such materials can be of benefit in improving the strength retention in case of heat exposure. Using 19 mix designs, a series of 570 concrete cylinders was fabricated using different water to cement ratios (0.35, 0.5, and 0.65), silica fume replacement ratios (0, 10, and 15 percent), and fly ash replacement ratios (0, 10, 20, and 30 percent). The specimens were cured in water for 56 days, after which they were placed in a rate-controlled large-scale electrical furnace, and their residual compressive and tensile strengths were measured before heat, and after heat exposure for 2-, 12-, and 24-hour heating cycles with temperatures reaching 200, 400, and 600 degrees Celsius. To eliminate the risk of explosive spalling, all specimens were preheated at a temperature of 100 degrees for 24 hours before the main heating cycle. Results showed that the compressive and tensile strengths did not reduce noticeably after exposure to 200 degrees but demonstrated a significant drop after exposure to 400- and 600-degree cycles. In many cases, the residual compressive and tensile strengths of specimens were found to be smaller than those predicted in previous studies. The square root equation widely used in the literature was found to provide a reasonable lower-bound estimate of the residual splitting tensile strength of concrete from the residual compressive strength; however, a linear trend was identified to provide a more accurate estimate for the results of this study. Moreover, due to less scatter, the splitting tensile strength was found to be a better indicator of heat damage in the structure than the compressive strength. The use of silica fume did not result in a meaningful trend in the residual compressive strength but reduced the residual tensile strength of specimens. Fly ash, on the other hand, could increase the residual compressive strength of the specimens but reduces the residual tensile strength. The results suggest that generally, and with few exceptions, these two supplementary cementitious materials are not recommendable choices for improving the strength retention of concrete in case of heat exposure.
Volume 22, Issue 3 (5-2022)
Abstract
The problem of determining the prestressing force in the tendons of prestressed concrete structures and monitoring the non-exceedance of prestressing drops is an issue that has been addressed by many researchers over the past decades and has provided methods in this field. Today, pre-installation sensors are installed in important prestressed concrete structures to monitor prestressing loss. However, due to the unpredictability of such equipment in older structures, monitoring of these forces requires destructive or non-destructive testing but is inaccurate. Therefore, in this paper, a method is presented that without the need for these sensors and destructive tests, only by measuring static displacement, is able to detect the amount of prestressing loss in the cross-sectional tendons of a prestressed concrete beam. In this regard, an algorithm in the Python program environment based on genetic algorithm as well as modeling in the finite element analysis program is provided. The numerical example presented in this research shows that the proposed algorithm detects the values of prestressing loss with good accuracy even in spite of 10% of the intentional error due to measurement. In recent years, the use of prestressing methods has become much simpler and more effective, and its materials have been optimized. Today, a high percentage of structures under construction worldwide are built using this technology, and the advance has found wide applications in the construction of office buildings, residential, commercial, parking lots, sports stadiums, concrete tanks and special structures such as piers. Therefore, in recent years, for long-term monitoring of prefabricated structures, equipment and sensors sensitive to force drop, such as fiber optic sensors and FBG sensors in the construction phase are predicted and installed in the desired locations. [13] However, since the above equipment requires a lot of money and it is not possible to use them in old structures, the need for a technique that shows the amount and location of force reduction in all tendons without using them remains. Therefore, in this paper, a method is presented that, while using the simplest tools, provides the most accurate results only by measuring static displacements under the effect of various loading scenarios and using an artificial intelligence algorithm based on genetic algorithm. The proposed method is based on computer analysis and comparison of the results of two prestressed concrete beams with the same geometry, loading and arrangement of tendons. First, a specific prestressing beam is modeled in the SAP2000 analysis program and the desired prestressing forces are applied to it, and then these forces are reduced in some of the studied tendons. This deliberate change in prestressing values is considered as failure and the technique presented in this mapping tries to discover the extent and location of failure of this beam. In other words, this paper is the determination of the amount of prestressing force in prestressed concrete beams in which force measuring sensors are not predicted without the need for destructive testing and only by measuring the static displacement under load. In the form of a numerical example on a prestressed concrete beam consisting of 6 steel tendons and using a genetic algorithm, it was shown that the displacement is a function of the amount of prestressing and its location and amount of reduction by the technique used. It was correctly detected with 93% accuracy when 10% of the deliberate error due to displacement field measurement was applied. As a suggestion for future work, this research will be able to be developed in the simultaneous diagnosis of prestressing reduction and beam concrete failure.
Volume 22, Issue 4 (6-2020)
Abstract
Human well-being is one of the main goals of sustainable rural development. Indeed, human well-being demonstrates rural societies’ quality of life. This concept consists of objective and subjective well-being dimensions. Although it is assumed that objective well-being is rationally related to subjective well-being, this relationship has not been fully confirmed in past studies. Three main reasons including the geographical level of assessment, the type of data used, and different epistemological perspectives have separated objective well-being assessment from the subjective one. We used the same geographical level, type of data used, as well as epistemological perspective in order to evaluate the relationship between objective well-being and subjective well-being among rice farmers. Using a questionnaire, a survey was carried out among 384 rice farmers (Response rate= 92.3%) in the main rice cultivation areas in Iran. The study sample was chosen by a two-stages cluster random sampling technique. Face to face personal interview was also used as the form of data collection. The results of structural equation modeling illustrated that farmers’ perception of economic, social, and environmental well-being as objective well-being domains significantly explained their subjective well-being constructs including happiness as well as life satisfaction. In fact, life satisfaction and happiness would be changed once farmers mentally perceive objective well-being domains. Therefore, objective well-being indicators can affect subjective well-being constructs, including life satisfaction and happiness, if they are assessed based on farmers’ self-evaluation.
Volume 23, Issue 1 (1-2021)
Abstract
This research aimed to analyze the influence of probiotic bacteria on the microbiological, physico-chemical, technological, and sensory characteristics of goat yogurt during 28 days of refrigerated storage. Results revealed that the incorporation of two probiotic bacteria did not significantly influence (P> 0.05) the physico-chemical characteristics such as pH, lactic acidity, total solids, syneresis, water holding capacity and protein, color, viscosity and texture parameters and sensory properties of the inoculated samples, compared to the control. Similarly, the probiotic viability was maintained at all stages of storage at the rate of 108 CFU g-1. Therefore, this research shows that yogurt is an appropriate vehicle for probiotic bacteria and provides new insights regarding their impact on the metabolism of this functional food while preserving its quality.
Volume 23, Issue 4 (7-2021)
Abstract
In this research, production of a probiotic drink based on jujube extract by means of fermentation with Lactobacillus plantarum and Lactobacillus delbrueckii as probiotic lactic acid bacteria was studied. The fermentation was performed for 72 hours at 37°C. The changes in microbial population, pH and titratable acidity as well as sugar and organic acid metabolism during the fermentation period were evaluated. In addition, before and after fermentation, the changes in total phenolic compounds and antioxidant activity in the extract were also investigated. Eventually, different drink formulations were developed employing fermented and non-fermented jujube extract, carbonatation, and sour cherry concentrate. Then, sensory properties of the formulated drinks were evaluated. Appropriate growth of L. plantarum and L.delbruckii resulted in an increase in acidity to 1.86 and 1.75, and a decline in pH to 3.4 and 3.56, respectively, after 72 hours. Glucose and fructose were significantly consumed by the strains. Citric acid concentration dropped to 1.12 and 5.8 g L-1 in the extract fermented by L. plantarum and L. delbrueckii, respectively, after 72 hours. At the end of fermentation, 23.8 and 11.4 g L-1 lactic acid was produced by L. plantarum and L. Delbrueckii, respectively. The contents of phenolic compounds and antioxidant activity in jujube extract after fermentation were significantly increased.The results of sensory evaluation of different drink formulations showed that the carbonated drink containing jujube extract fermented by L.plantarum mixed with sour cherry concentrate obtained the highest score among different drink formulations.
Volume 23, Issue 4 (10-2023)
Abstract
Unreinforced masonry buildings are quite popular in many countries such as Iran, even though they are prone to significant damage against even moderate seismic excitations. In 2003, 26000 people lost their lives and 30000 were injured in southeastern Iran during Bam earthquak. The regional investigations showed an almost total overall collapse of all adobe and masonry buildings. Even to this day, notable number of buildings in Iran is masonry buildings due to low costs, especially in rural areas. Hence, the popularity despite the poor performance has sought researchers to study efficient ways to improve the URM buildings. Generally speaking, masonry buildings are classifed into unreinforced and reinforced; the latter usually beneft from horizontal and vertical steel bars which signifcantly improve strength, ductility and energy dissipation capacity of such walls. Masonry buildings can also be categorized as confned and unconfned. Using horizontal and/or vertical ties usually in the form of lightly reinforced concrete members at the perimeter of walls, their intersection with perpendicular walls and if necessary, around large openings can considerably enhance their ductility and in some cases their strength. Unlike other masonry construction types, the behavior of Confned unreinforced Masonry (referred to CM hereafter) buildings has not yet been fully formulated. This is mainly because of more sophisticated behavioral characteristics of CM walls compared to unconfned Unreinforced Masonry (referred to URM hereafter) buildings. CM is the only masonry system that has been allowed practicing by the Iranian Code of Practice for Seismic Resistant Design of Buildings (Standard 2800) in seismic-prone areas. When it comes to seismic retrofitting of masonry buildings, there are a rather wide variety of available options, e.g. shotcrete, adding steel or FRP sheets on the wall, adding Reinforced Concrete (RC) ties, changing the arrangement and size of the openings, and using Near Surface Mounted (NSM) rods on the walls. Considering the significant number of two-story URM school buildings in Iran, there is a need to provide instructions for the type of improvement plan of these buildings. In response to this need, the Organization of Renovation, Development and Equipping of Schools of Iran developed a guideline for the purpose of typifying the improvement plan of these buildings with the shotcrete method in 2021. In this research, based on the results obtained from five two-story URM schools, the accuracy of this guideline is evaluated. For this purpose, the investigated buildings in the two cases of flexible roof without ties and rigid roof with ties in ETABS software using shell elements and spectral dynamic analysis method, once based on the requirements of the guideline and once based on the Code 360 was evaluated and retrofitted using Shotcrete. The results of this research show that the guideline in the case of flexible roofs leads to minimum vulnerability of the walls of the studied buildings. In the case of a rigid roof, the results show that according to this guideline, some of improved and unimproved walls are vulnerable in both direction; In such a way that the average percentage of vulnerable walls in terms of relative length for the first floor is 63% in the longitudinal direction and 38% in the transverse direction, and for the ground floor in the longitudinal direction is 56% and in the transverse direction is 17%.
Volume 24, Issue 1 (Spring 2020)
Abstract
1. Introduction
This study investigates the impact of a variety of attributes or ‘characteristics’ on the rates charged for hotel rooms in Iran. The aim of this paper is to provide information for tourist destinations through an analysis of the valuation of the location implicit in the price of accommodation. Using OLS model (that is, taking into account that demand valuation can vary along the hotel price distribution), the authors find that huge price differences between 5-star hotels and the rest, is coupled with practically of no difference between 1-star and 2-star hotels. Other attributes with a significant effect on price are towns. With regard to the valuation of location, a hotel in Tehran location is valued much more at higher percentiles.
The study of hotel-room pricing is complex because of seasonality, different price regimes (full-board, half-board, bed & breakfast), and discounts and supplements on various grounds (additional bed for children, single room, view of the sea, additional room equipment such as air-conditioning, television, or mini-bar).
The value of attributes and characteristics are unobserved, as they are not separately traded in any market. Only the overall prices of hotel rooms, including particular combinations of attributes are observed. Our analysis draws upon the hedonic-prices tradition of fitting statistical models to estimate the effect of attributes on price (early theoretical developments in hedonic prices are those of Lancaster 1966; Rosen, 1974.
Empirical applications in the tourist sector are found in Andersson, 2010; Chen and Rothschild, 2010; Castro and Ferreira, 2014; and Espinet, Coenders, and Fluvia 2003). The product a given hotel H is offering can be regarded as a set of attributes, which may consist of services (such as swimming pool, garden, television in the room), or characteristics (star category, town, year of first opening, number of rooms, etc):
Hi = (qi1, qi2, qi3,…, qik,…, qim ) (1)
Where i= 1 … n represents the hotel and qik (k=1,…, m) each of its attributes.
Thus, the hedonic price function for each hotel is represented as:
Pi = P(qi1, qi2, qi3,…,qik,…, qim ) (2)
2. Methodology
This regression model offers us estimates of the homogeneous parameters between individuals and its application is justified by hedonic price theory. In the context of tourism, it is also easy to appreciate that the valuations individuals make of the physical characteristics (destination and time) of their accommodation differ according to their price. That is, it would be interesting to know the behavior of the explanatory variables along the price distribution. For this, an estimator is required that allows heterogeneous responses: the estimator stemming from the linear regression (βi). Furthermore, a median-based estimator is also attractive because it is less sensitive to outliers than a mean-based estimator. Therefore, the bias from unobserved characteristics (quality, renovation) should be smaller.
Dependent variable: Price
The per night price of a room in the case of hotels and of an entire unit in the case of hotel.
Explanatory variables:
- Resort
Esfahan: a dummy variable that takes a value of one if the accommodation is located in Esfahan and zero otherwise.
Tabriz: a dummy variable that takes a value of one if the accommodation is located in Tabriz and zero otherwise.
Tehran: a dummy variable that takes a value of one if the accommodation is located in Tehran and zero otherwise.
Mashhad: a dummy variable that takes a value of one if the accommodation is located in Mashhad and zero otherwise, and etc.
- Category
One star: a dummy variable that takes a value of one if the hotel is one-star and zero otherwise.
Two stars: a dummy variable that takes a value of one if the hotel is two-star and zero otherwise, and etc.
- Type of room (Single, Double and Suite).
Rooms: number of hotel/apartment rooms.
- Swimming pool: a dummy variable that takes a value of one if the hotel has a swimming pool and zero otherwise.
- Car park: a dummy variable that takes a value of one if the hotel has a car park and zero otherwise.
- Garden/terrace: a dummy variable that takes a value of one if the hotel has a garden/terrace and zero otherwise.
3. Results and Discussion
One of the most relevantcharacteristics ratios of a hotel to its price is star category. Figure 1 clearly shows that the greatest differences in price occur for 5-star hotels, while those with 1 and 2 stars hardly vary. Given the marked differences among the towns under study, the town in which the hotel is situated is another potentially very relevant variable.
4. Conclusion
This article has identified some variables that affect the price paid by tourists in Iran hotels. The attributes or characteristics that allow hotels to increase price can also be seen as attributes that contribute to the differentiation of their offers.
The use of hedonic functions has allowed us to quantify the effects of each of the significant variables (town, star category, number of rooms, and availability of parking place) on price. Thus, hotel managers can make economic estimates of the impact of decisions concerning changes in these variables. This should make the results very useful to hotel managers, and to a lesser extent, to tour operators and public authorities
This study investigates the impact of a variety of attributes or ‘characteristics’ on the rates charged for hotel rooms in Iran. The aim of this paper is to provide information for tourist destinations through an analysis of the valuation of the location implicit in the price of accommodation. Using OLS model (that is, taking into account that demand valuation can vary along the hotel price distribution), the authors find that huge price differences between 5-star hotels and the rest, is coupled with practically of no difference between 1-star and 2-star hotels. Other attributes with a significant effect on price are towns. With regard to the valuation of location, a hotel in Tehran location is valued much more at higher percentiles.
The study of hotel-room pricing is complex because of seasonality, different price regimes (full-board, half-board, bed & breakfast), and discounts and supplements on various grounds (additional bed for children, single room, view of the sea, additional room equipment such as air-conditioning, television, or mini-bar).
The value of attributes and characteristics are unobserved, as they are not separately traded in any market. Only the overall prices of hotel rooms, including particular combinations of attributes are observed. Our analysis draws upon the hedonic-prices tradition of fitting statistical models to estimate the effect of attributes on price (early theoretical developments in hedonic prices are those of Lancaster 1966; Rosen, 1974.
Empirical applications in the tourist sector are found in Andersson, 2010; Chen and Rothschild, 2010; Castro and Ferreira, 2014; and Espinet, Coenders, and Fluvia 2003). The product a given hotel H is offering can be regarded as a set of attributes, which may consist of services (such as swimming pool, garden, television in the room), or characteristics (star category, town, year of first opening, number of rooms, etc):
Hi = (qi1, qi2, qi3,…, qik,…, qim ) (1)
Where i= 1 … n represents the hotel and qik (k=1,…, m) each of its attributes.
Thus, the hedonic price function for each hotel is represented as:
Pi = P(qi1, qi2, qi3,…,qik,…, qim ) (2)
2. Methodology
This regression model offers us estimates of the homogeneous parameters between individuals and its application is justified by hedonic price theory. In the context of tourism, it is also easy to appreciate that the valuations individuals make of the physical characteristics (destination and time) of their accommodation differ according to their price. That is, it would be interesting to know the behavior of the explanatory variables along the price distribution. For this, an estimator is required that allows heterogeneous responses: the estimator stemming from the linear regression (βi). Furthermore, a median-based estimator is also attractive because it is less sensitive to outliers than a mean-based estimator. Therefore, the bias from unobserved characteristics (quality, renovation) should be smaller.
Dependent variable: Price
The per night price of a room in the case of hotels and of an entire unit in the case of hotel.
Explanatory variables:
- Resort
Esfahan: a dummy variable that takes a value of one if the accommodation is located in Esfahan and zero otherwise.
Tabriz: a dummy variable that takes a value of one if the accommodation is located in Tabriz and zero otherwise.
Tehran: a dummy variable that takes a value of one if the accommodation is located in Tehran and zero otherwise.
Mashhad: a dummy variable that takes a value of one if the accommodation is located in Mashhad and zero otherwise, and etc.
- Category
One star: a dummy variable that takes a value of one if the hotel is one-star and zero otherwise.
Two stars: a dummy variable that takes a value of one if the hotel is two-star and zero otherwise, and etc.
- Type of room (Single, Double and Suite).
Rooms: number of hotel/apartment rooms.
- Swimming pool: a dummy variable that takes a value of one if the hotel has a swimming pool and zero otherwise.
- Car park: a dummy variable that takes a value of one if the hotel has a car park and zero otherwise.
- Garden/terrace: a dummy variable that takes a value of one if the hotel has a garden/terrace and zero otherwise.
3. Results and Discussion
One of the most relevant
4. Conclusion
This article has identified some variables that affect the price paid by tourists in Iran hotels. The attributes or characteristics that allow hotels to increase price can also be seen as attributes that contribute to the differentiation of their offers.
The use of hedonic functions has allowed us to quantify the effects of each of the significant variables (town, star category, number of rooms, and availability of parking place) on price. Thus, hotel managers can make economic estimates of the impact of decisions concerning changes in these variables. This should make the results very useful to hotel managers, and to a lesser extent, to tour operators and public authorities
Volume 24, Issue 1 (spring 2024)
Abstract
رIntroduction
The tourism sector plays a pivotal role in national economic development because it promotes the development of related industries such as transportation. The boosting effect of tourism on economic growth is more obvious in developing countries with abundant tourism resources (Dieke, 2003). However, tourism development undergoes great dynamic changes due to complex and volatile external environments, such as global climate change and social disturbances with a high degree of uncertainty (Nguyen et al., 2020; Scott et al., 2019). thus, the tourism economy has become very fragile and has a weak ability to withstand risks from various sources (Wang et al., 2022). Therefore, this study attempts to examine the Indirect impact of tourism on economic vulnerability and other factors affecting economic vulnerability in selected developing countries over the period 1995-2021 by using a panel smooth transition regression model.
Methodology
In this study, the nonlinear threshold effect of tourism on economic vulnerability in selected developing countries is examined using a PSTR model. For this purpose, following Gonzalez et al. (2005) and Colletaz & Hurlin (2006), a PSTR model with two regimes and a transition function is defined. according to the study of Colletaz & Hurlin (2006), can be chosen among the explanatory variables, the lag of the dependent variable, or any other variable outside the model that is theoretically related to the model under study and causes a nonlinear relationship.
As mentioned earlier, another salient feature of the PSTR model is that it provides a parametric approach to cross-country heterogeneity and time instability of the slope coefficients, allowing the parameters to change smoothly as a function of the threshold variable
It is worth noting that the estimation of the parameters of the PSTR model consists in eliminating the individual effects by removing the individual means and then applying nonlinear least squares (NLS) to the transformed model (see for details, Gonzalez et al., 2005). This method is equivalent to maximum likelihood (ML) estimation in the case of normal errors.
Following Gonzalez et al. (2005), Colletaz & Hurlin (2006), and Jude (2010), the estimation steps of a PSTR model are as follows: First, the linearity test against PSTR is performed using Wald Tests (
Results and Discussion:
The results show that in the first regime, trade openness has a negative effect on economic vulnerability, which has decreased and turned positive after crossing the threshold location in the second regime. Government expenditure has a positive effect on economic vulnerability, and after crossing the threshold location and entering the second regime, its effect gradually decreased and became positive. Inflation coefficients in the regime had a negative and insignificant effect on economic vulnerability, which after crossing the threshold location and entering the second regime, its effect gradually decreased and became positive, but it was significant at the 10 percent level.
Also, the results show that before the threshold location and at low levels of tourism income, the logarithm of financial development has a negative and significant effect on economic vulnerability, and after the threshold location and entering the second regime, this effect is still negative and increases. The coefficients of the logarithm of total unemployment have a negative effect on economic vulnerability in the first regime and before the threshold location. By crossing the threshold location and entering the second regime, this effect decreases and becomes positive.
Conclusion
In this study, the threshold and Indirect effect of tourism on economic vulnerability in selected developing countries during 1995-2021 was investigated. For this purpose, the PSTR model provided and developed by Gonzalez et al. (2005) and Colletaz & Hurlin (2006) was used. The estimation results suggested a nonlinear relationship between trade openness, financial development, government spending, total unemployment, inflation and economic vulnerability. Moreover, considering a threshold with two regimes or a transition function is sufficient to investigate nonlinear behaviors. The results show that the threshold of the transition variable is equal to 3.1378 and the slope parameter is equal to 33.8978, which include only one transition function and only one threshold.
Considering the positive impact of tourism on financial development and government spending, it can be said that the development of tourism income can indirectly reduce the economic vulnerability of developing countries by increasing financial development and national income and adjusting industrial structures, while this mediating effect at the level Social does not appear. Therefore, it is suggested that considering that in developing countries where the overall economic strength of a country is weak, with low economic development, the development of international tourism should be cautious. The main task should be to create infrastructure and stimulate domestic consumption. Investment should be focused on industries such as manufacturing and financial development to increase the growth of GDP and improve people's quality of life. Physical needs are the most important factor to maintain economic stability and prevent economic vulnerability. For these countries, attention should be paid to domestic tourism by strengthening the construction of tourism service facilities, adjusting the structure of the tourism industry and ensuring the sustainable development of international tourism, while accelerating the development of domestic tourism.
From an institutional perspective, creating active employment policies to create preferential employment conditions for low-income people can further ensure the positive impact of low-level international tourism on economic vulnerability. Finally, regardless of the level of economic development, one should have a clear understanding of the performance of the tourism industry based on the state of the country. This is possible by correctly positioning the tourism industry and not exaggerating the role of tourism and not giving up on its development due to some negative factors. Economic vulnerability can be effectively reduced only by combining tourism with other industries and focusing on overall economic development.
Volume 24, Issue 2 (summer 2024)
Abstract
Introduction
The occurrence of various shocks affects economic variables and change their course over time. Knowing the effecst of such shocks on economic variables is necessary for proper policy making in the economy. Therefore, many researches are conducted in this field in the world. Policy-making without recognizing these effects can result into tremendous challenges. One of the most effective shocks in the Iranian economy is the sanctions, especially the nuclear ones, which have had extensive effects on the behavior of brokers and consequently on the country's economic variables.
Economic sanctions cause a change in the exchange rate by creating a chaotic atmosphere and confusion in the economy, followed by a change in the supply and demand of housing. Therefore, the purpose of this research is to investigate the effect of economic sanctions on the supply and demand of housing through the exchange rate channel. For this purpose, provincial seasonal data for the period of 2011-2021 have been used and Seemingly Unrelated Regression (SUR) model has been used to analyze the data.
Methodology
Different methods can be used to estimate the model of the equations of this study, such as single equation methods or methods of solving simultaneous equations, whose estimates are different. The most common methods of solving simultaneous equations are the two-stage and three-stage least squares regression methods, as well as Seemingly Unrelated Regression, which is used when there is a relationship between the error part of the equations or there is a simultaneous correlation. The method discussed in this research is Seemingly Unrelated Regression (SUR) model or Seemingly Unrelated Regression Equations (SURE), which was proposed in 1962 in econometrics.
Findings
The findings show that provincial gross domestic product, housing prices, and inflation have a positive effect on demand. The variables of stock market index, exchange rate and sanctions have had a negative effect on housing demand. On the supply side, housing price variables, the number of building permits issued, and inflation have a positive effect on the housing supply, while the exchange rate, sanctions, and the price of construction materials have a negative effect on the housing supply. Imports and embargoes have increased the exchange rate and exports have decreased the exchange rate. On this basis, the embargo has both a direct effect and an indirect effect through the exchange rate on the reduction of housing supply and demand.
Discussion and Conclusion
The estimation results for the first equation show that the variables are significant. It can also be said that provincial GDP, housing prices and general price level index have a positive effect on housing demand and with the increase of these variables, housing demand increases. According to the findings of the research and the analysis of the available data, the inverse relationship between the stock market index, the sanctions index and the exchange rate with housing demand is confirmed. So, with the growth of the stock market index, sanctions index and exchange rate, the demand for housing decreases.
In the preliminary results, the estimate for the second equation of the average effect of labor wages as a part of the production cost was not significant. But in estimates, the effect of the price of construction materials is significant. This variable was removed from the model. It can be said that one of the reasons for the non-significance of the wage variable is its low relative growth compared to the growth of housing prices and the growth of construction materials. On the other hand, the share of wages in housing construction costs is much lower than the costs of materials and other costs. This causes the wage rate in Iran to be less effective in housing supply. It can also be said that an increase in the provincial GDP, housing prices and the number of building permits issued increases housing supply.
The results of the third equation show that exports, imports, sanctions index, liquidity volume and provincial GDP explain 99% of exchange rate changes. It is worth mentioning that any increase in exports and sanctions index increases the exchange rate, but with the increase in imports, the exchange rate decreases, which shows the negative relationship between the exchange rate and imports. Since the exchange rate increases under the influence of the sanctions and the exchange rate has a negative effect on the housing demand, it can be said that sanctions have a direct effect on the economic activities of supply and demand due to the disruption of security, certainty and economic stability. Housing has an effect on the supply and demand of housing due to the change in the exchange rate
The occurrence of various shocks affects economic variables and change their course over time. Knowing the effecst of such shocks on economic variables is necessary for proper policy making in the economy. Therefore, many researches are conducted in this field in the world. Policy-making without recognizing these effects can result into tremendous challenges. One of the most effective shocks in the Iranian economy is the sanctions, especially the nuclear ones, which have had extensive effects on the behavior of brokers and consequently on the country's economic variables.
Economic sanctions cause a change in the exchange rate by creating a chaotic atmosphere and confusion in the economy, followed by a change in the supply and demand of housing. Therefore, the purpose of this research is to investigate the effect of economic sanctions on the supply and demand of housing through the exchange rate channel. For this purpose, provincial seasonal data for the period of 2011-2021 have been used and Seemingly Unrelated Regression (SUR) model has been used to analyze the data.
Methodology
Different methods can be used to estimate the model of the equations of this study, such as single equation methods or methods of solving simultaneous equations, whose estimates are different. The most common methods of solving simultaneous equations are the two-stage and three-stage least squares regression methods, as well as Seemingly Unrelated Regression, which is used when there is a relationship between the error part of the equations or there is a simultaneous correlation. The method discussed in this research is Seemingly Unrelated Regression (SUR) model or Seemingly Unrelated Regression Equations (SURE), which was proposed in 1962 in econometrics.
Findings
The findings show that provincial gross domestic product, housing prices, and inflation have a positive effect on demand. The variables of stock market index, exchange rate and sanctions have had a negative effect on housing demand. On the supply side, housing price variables, the number of building permits issued, and inflation have a positive effect on the housing supply, while the exchange rate, sanctions, and the price of construction materials have a negative effect on the housing supply. Imports and embargoes have increased the exchange rate and exports have decreased the exchange rate. On this basis, the embargo has both a direct effect and an indirect effect through the exchange rate on the reduction of housing supply and demand.
Discussion and Conclusion
The estimation results for the first equation show that the variables are significant. It can also be said that provincial GDP, housing prices and general price level index have a positive effect on housing demand and with the increase of these variables, housing demand increases. According to the findings of the research and the analysis of the available data, the inverse relationship between the stock market index, the sanctions index and the exchange rate with housing demand is confirmed. So, with the growth of the stock market index, sanctions index and exchange rate, the demand for housing decreases.
In the preliminary results, the estimate for the second equation of the average effect of labor wages as a part of the production cost was not significant. But in estimates, the effect of the price of construction materials is significant. This variable was removed from the model. It can be said that one of the reasons for the non-significance of the wage variable is its low relative growth compared to the growth of housing prices and the growth of construction materials. On the other hand, the share of wages in housing construction costs is much lower than the costs of materials and other costs. This causes the wage rate in Iran to be less effective in housing supply. It can also be said that an increase in the provincial GDP, housing prices and the number of building permits issued increases housing supply.
The results of the third equation show that exports, imports, sanctions index, liquidity volume and provincial GDP explain 99% of exchange rate changes. It is worth mentioning that any increase in exports and sanctions index increases the exchange rate, but with the increase in imports, the exchange rate decreases, which shows the negative relationship between the exchange rate and imports. Since the exchange rate increases under the influence of the sanctions and the exchange rate has a negative effect on the housing demand, it can be said that sanctions have a direct effect on the economic activities of supply and demand due to the disruption of security, certainty and economic stability. Housing has an effect on the supply and demand of housing due to the change in the exchange rate
Volume 24, Issue 4 (Winter 2020)
Abstract
Introduction: Multi temporal changes in built up areas are mainly caused by natural disasters (such as floods and earthquakes) or urban sprawl. Detecting these changes which consist of construction, destruction and renovation of buildings can play an important role in updating three dimensional city models. Multi-temporal remote sensing data are one the powerful tools for detecting urban changes due to the increasing growth and then, for updating the three dimensional city models. Urban changes detection methods using various types of remotely sensed data have been proposed by many researchers to meet a wide range of applications (Singh, 1989). Considering the procedure of algorithms and the utilized multi-temporal remote sensing data, change detection algorithms can be divided into two dimensional and three dimensional categories (Qin et al., 2016). Many of the proposed urban change detection methodologies have utilized only the multi-spectral remote sensing data without considering digital elevation models, which caused some problems in buildings identification (Bouziani et al., 2010; Brunner et al., 2010; Huang et al., 2014; Vakalopoulou et al., 2015). Two dimensional changes detection methods have some serious problems such as high computational cost and inaccessible volumetric information due to the absence of altitude data. Moreover, as digital elevation models can be easily produced recently, the three dimensional changes detection methods are more concerned (Martha et al., 2010; Tian et al., 2014; Waser et al., 2008; Daniel & Doran, 2013; Gruen, 2013). Three dimensional change detection methods are suitable for identifying the changes of high altitude objects such as buildings and their results are more close to reality. Three dimensional change detection methods can be considered in one of the spectral-geometric analysis methods or geometric comparison (Qin et al., 2016).
Methodology: The objective of this study is to provide an effective method for three dimensional changes detection of buildings in urban areas based on Digital Elevation Models (DEMs). The proposed three dimensional building change detection algorithm in this research is considered for estimating the construction of new buildings in flat areas and renovation of low-rise buildings (up to three floors) in order to make high-rise ones (more than three floors). The proposed method in this paper consists of three main steps; 1) generating Digital Surface Model (DSM), Digital Terrain Model (DTM) and normalized DSM for two epochs, 2) performing object based image analysis consists of segmentation and structural classification of DEMs in order to generate multi temporal classification maps, 3) producing the change maps and analyzing the change percentages between various object classes.
Resullts & Discussion: The ability of the proposed algorithm is evaluated in a rapid developing urban area in Tehran, Iran in a 9-years interval. The obtained results represent that the ground and bare soil decreased for about -1.37% and low-rise buildings also decreased for about -9.7%. Moreover, the class of high-rise buildings increased for about +16.4% which conforms making new constructions in addition to renovation of low-rise buildings. As the objective of this research was to investigate the three aspects of changes in built up areas containing new constructions, destruction and renovation of buildings, some interesting results are obtained. The main changes occurred in this region are in the new construction category with 4.8% growth which is occurred to about 132680 square meters of the study area. Moreover, the renovation of low-rise buildings to high-rise ones is 3.05% of land use equivalent to 83889.5 square meters. The obtained results showed 3.89% destructions in the buildings which is occurred to 106896.25 square meters of this study area. Most of the destructions are in the low-rise building class which confirms decreasing the worn texture of the city and urban passages sweating.
Conclusion: According to the results, the construction of new buildings is faster than the vertical growth of the city and its destruction in this 9-years period. As it is clear from the results of this study, change detection in urban environment can help urban planners to manage land resources and prevent the growth of irregular constructions. As high-rise buildings prevent wind, disrupt the urban ecosystem and increase air pollution, it is important to control and manage the vertical growth of the cities.
Kay words: Three dimensional change detection, Building, Object Based Image Analysis, Segmentation, Normalized DSM
Volume 24, Issue 4 (12-2020)
Abstract
The purpose of this article is to develop and genesis the ethical-oriented corporate branding model in the confectionary industry in Iran and to predict and innuendo the ethical-oriented corporate branding construct in an exploratory study. After identifying the corporate branding ethical constructs in a qualitative study in this research, by interviewing 14 connoisseurs and analyzing the data that acquired from the interviews using the theme analysis method, in a quantitative study and collecting information through a questionnaire of 202 confectionery and chocolate marketers, the partial least squares approach to structural equation modeling has been used to estimate and calculate the relationships in the ethical-oriented corporate branding model. Also, employee based brand equity has been used as a variable of measurement for corporate branding of endogenous construct. Extracting the structural model of corporate branding by four corporate branding predictive constructs including Corporate Ethical Philosophy, Corporate Ethical Communication, Corporate Ethical Culture and Corporate Ethical Image and extracting the measurement model of corporate branding through 14 extracted variables to measure the constructs in a structural model are the results of this research.
Volume 24, Issue 4 (10-2024)
Abstract
Structures, including concrete bridges, may be exposed to gradual damage during operation due to environmental conditions such as corrosion, which will reduce their useful life. Knowing the amount of remaining useful life of the structures makes it possible to improve, strengthen or rebuild them at the right time. To determine the remaining useful life of a structure, there are three common methods under the titles of data-driven method, failure physics method and combined method. In this article, the combined method of determining the remaining useful life of structures has been studied. The purpose of this research is to propose a suitable method for predicting the remaining useful life of a bridge structure with a reinforced concrete deck under chloride ion corrosion using a Bayesian network. The remaining useful life of reinforced concrete parts under chloride attack includes two parts of the time related to the initial stage of corrosion and the time related to the release of chlorine ions. To determine the remaining useful life part related to the initial stage, various researches have been done and the American ACI365 committee has proposed a software called Life-365 for this purpose. There is no comprehensive research to determine the second part of the remaining life, which is related to the release stage. Based on the prepared Bayesian network and the formula obtained in this research, the remaining life of the chloride diffusion stage in concrete was estimated to be 9.116 years in the best conditions and 2.73 years in the worst conditions. Meanwhile, the number suggested by the ACI365 committee, in practical work, is usually equal to 6 years for the release stage. This issue clarifies the need for more research in this regard. In this article, using the data available in past researches and reproducing the data and using the Bayesian network, relationships are presented to determine the useful life of the bridge structure in both the initial and release stages.Based on the proposed method, using the Bayesian network, relationships can be obtained for each of the two parts of the remaining useful life of the structure under chloride corrosion, i.e., the corrosion initiation stage and the chloride release stage, in terms of factors affecting the remaining useful life in a specific project. . In these networks, the effect of various factors can be considered, which is one of the advantages of the proposed method.The remaining useful life has an inverse relationship with temperature. When the average temperature increases by 20 degrees, the remaining useful life decreases by an average of 30%.With the help of the proposed relationships, a parametric study was conducted to investigate the effect of different conditions of using pozzolanic compounds on the remaining life of the structure. In this regard, 17 states of different pozzolanic compounds with different concentrations were considered and the average remaining useful life due to different states was calculated. The average life obtained compared to the case where no pozzolan is used in concrete showed a 38% increase in life. In order to evaluate the results of the proposed relationships, the problem of determining the remaining useful life for a numerical model of a concrete bridge and several marine structures located in the Persian Gulf was investigated. The results of this research show that by using the proposed relationships, it is possible to improve the accuracy of estimating the remaining useful life of bridges with concrete decks exposed to chloride ion penetration, relying on the data obtained from the field inspections of the structure.
Volume 25, Issue 3 (5-2023)
Abstract
This study aimed to evaluate the effect of Artemisia absinthium L. Essential Oil (EO) incorporation at various concentrations on the properties and oxidative stability of butter during 2 months of refrigerated storage. The obtained results on peroxide value, acidity, fatty acids, antiradical scavenging activity, and physical and microbiological properties confirmed the effectiveness of Artemisia EO incorporation in fat rich dairy foods. New produced butters can be classified as functional products due to their strong antioxidant activity, better oxidative stability, and richness in essential unsaturated fatty acids when compared to the control. All quality parameters were improved with Artemisia EO enrichment, however, descriptive sensorial analysis showed that the lowest concentration of about 45 ppm of the product was the most preferred in terms of color, odor, taste, firmness and overall acceptability. Due to its positive effects on all butter properties, Artemisia absinthium EO can be used as natural antioxidant and antimicrobial agent in food industries.
Volume 26, Issue 3 (9-2019)
Abstract
Democratic family, as a new phenomenon in Iran, is based on some fundamental principles such as liberty, equality, rule of law, and tolerance. In this article, some of the important aspects of a democratic family in Iran will be explained and evaluated by applying conceptual analysis and critical evaluation. The family, which is characterized by middle class, rights, population and urbanization, marriage and divorce, violence, and nuclear family, lead to reasonable decision-making through dialogue and cooperation. The patriarchal mode of management in Iranian family has gradually changed into a collective decision-making, in which, the role of boys and girls are significant. These characteristics indicate that Iranian democratic family is a transitional process of social and political development in Iran.
Volume 26, Issue 6 (11-2024)
Abstract
The current research aimed, first, to valorize Tunisian cork oak acorn starch extracted by water soaking method in dairy industry. The effect of its incorporation into milk on the evolution of rheological, sensorial and microbiological properties of stirred yogurt during refrigerated storage was, also, evaluated. No significant effect was observed on fermentation parameters of the acorn starch added product. During 28 days of refrigerated storage, the incorporation of acorn starch did not affect the post-acidification and the viability of the lactic starter cultures. Moreover, the treated stirred yogurt exhibited a lower syneresis value and a higher consistency when compared to the untreated control and that incorporated with industrial modified starch. The findings revealed that acorn starch incorporation extended the shelf life of the final product by about 6 days. Despite its less appreciated color (3.67±0.5), acorn-starch-added yogurt product gained the highest overall acceptability scores (4.11±0.6) by the panel.
Volume 27, Issue 1 (12-2025)
Abstract
This study aimed to evaluate the sensorial, physicochemical, rheological, and microbiological properties of yoghurt fortified with Artemisia absinthium leaf powder during refrigerated storage. The valorization of this plant in food industry was realized by the incorporation of its dried leaf powder at various concentrations in order to produce a new functional yoghurt. It is interesting to note that the fortified yoghurt with the lowest Artemisia dose (2%) was the most preferred by the panel. Furthermore, this fortification did not affect the fermentation parameters nor the viability of lactic starter. During storage, the incorporation of Artemisia powder reduced syneresis and improved the microbiological properties of fortified yoghurts. Besides, at the end of storage, it was noted that yoghurt fortified with 2% of Artemisia powder presented the highest consistency (8.98±0.04 Pa sn) and antioxidant activity (60.08±3.61%) when compared to the control yoghurt. Finally, the accelerated shelf-life test showed the efficiency of Artemisia absinthium powder incorporation by increasing the shelf life of yoghurt by about 4 days.
Volume 27, Issue 4 (Winter 2023)
Abstract
Achieving optimal acoustic conditions in urban public areas emerges as a crucial element in enhancing the overall well-being and satisfaction of inhabitants. Urban parks stand out as pivotal public spaces, with park benches playing a fundamental role as key pieces of furniture contributing to visitors' comfort. The primary aim of this study revolves around evaluating the suitability of existing acoustic comfort standards concerning the placement of seating facilities within parks. Employing a descriptive-analytical approach, the research focuses on Laleh Park in Tehran as a case study, where the sound levels at designated seating areas are quantified using a decibel meter, while subjective perceptions of acoustic comfort are gathered through a structured questionnaire. Through a spatial analysis integrating both objective and subjective data, areas with inadequate acoustic conditions are pinpointed. Notably, the calculated Pearson's correlation coefficient (0.692) highlights a significant association between objective and subjective assessments of acoustic comfort at seating locations within the park. Results reveal that southern seating areas, encompassing approximately 15 stations, exhibit substandard acoustic comfort mainly due to their proximity to the bustling Keshavarz Boulevard. Conversely, seating locations near Bazarche Laleh Park and the Tehran Museum of Arts are deemed satisfactory. Out of the 19 monitored stations, 14 feature bench seats, 4 offer backless seating, and 1 provides pavilions. Among the stations with moderate acoustic comfort, comprising 38 stations in total, bench seats are predominant (23 stations), followed by backless seats (10 stations) and pavilions (15 stations). Conversely, stations with superior acoustic comfort are predominantly situated in the northern section, adjacent to facilities catering to children and teenagers as well as the carpet museum. In conclusion, the acoustic comfort level at Laleh Park is moderate to subpar concerning its geographical setting. The study suggests considering the installation of acoustic-enhanced park chairs as a potential solution to improve overall maintenance, in conjunction with other pertinent factors.