Reverse supply chain is a process dealing with the backward flows of used/damaged products or materials. Reverse supply chain includes activities such as collection, inspection, reprocess, disposal and redistribution. A well-organized reverse supply chain can provide important advantages such as economic and environmental ones. In this study, we propose a general framework and formulate a mathematical model for product return in reverse supply chain. We consider a multilayer, multi-product for the model. The main objective of the paper is minimizing the total COSTS of reverse supply chain including transportation, fixed opening, OPERATION, maintenance and remanufacturing COSTS of centers. To validate the mathematical model, a numerical example is solved using Lingo 9 software and the results are reported.

Tree felling is one of the most important components among tree harvesting components which consists of cutting and felling, limbing and bucking sub-stages. Tree limbing using chainsaw in hardwood forest is much effective and important. This research was carried out in two compartments of Namkhaneh district, in Kheyrud Forest for assessment of limbing sub-stage. The objectives of this study were time study of tree limbing OPERATION, estimating the productivity and COSTS of chainsaw and developing regression model. Factor affecting total limbing time regression model was dbh of harvested tree. The hourly production of chainsaw limbing with and without delay time were 11.1 m3/h (4 tree/h) and 14.8 m3/h (5 tree/h), respectively. Productivity of chainsaw tree limbing is increasing with dbh as power. The unit cost of chainsaw limbing with and without delay time were 14710 and 11020 Rials/m3, respectively. Total tree limbing cycle time without delay averaged 12.37 minutes and with delay time averaged 16.51 minutes and also with reducing personal delay, work efficiency can be increased.

Objective: Selecting suppliers of industrial systems equipment to minimize the total construction and OPERATION COSTS and implement it for Feed Water Multi-state System (FWS) of Heat Recovery Steam Generator (HRSG) boilers in Mapna Company. Methods: Using the Markov chain model results in a mathematical programming model and then analyzing the sensitivity of this model. First, using the Markov chain, different system states are drawn. Then, using the state transfer rate (failure rate and repair rate) of the equipment, the probability of the system being in any of these states is determined parametrically. Then, the Markov chain model results are added to the other constraints of a mathematical model the problem and solved by GAMS software. The effect of cost parameter changes on the optimal solution is calculated individually and then compared in a general graph. Results: The highest construction and OPERATION COSTS are in ascending order: 1-the equipment purchasing price, 2-the production capacity reduction cost, 3-the system construction delay penalty, and 4-the system shutdown cost. Also, the relationship between the optimal solution to these parameters is linear in a wide range of changes. Conclusion: All COSTS have a direct effect on the design of the Feed Water System (purchase, delay, capacity reduction, and shutdown), but the cost of purchasing equipment has the most significant effect on the total cost. It is therefore recommended to focus entirely on reducing this cost.

The utilization of distributed generators such as the renewable energies together with electrical vehicle are increasing because of the environmental and economic challenges. Irregular and yet large-scale use of either of these two technologies can have devastating effects on electrical grid. However, with planning and appropriate management of these technologies along with energy storage resources can reduce their detrimental effects. In this regard, integrated cumulative effect of electrical vehicles to the grid for the process of charging or discharging and also network instability caused by that – in particular during peak times-have been discussed as a fundamental challenge of utilizing these vehicles. Inconsistent and uncontrolled charging in these vehicles at the large scale on traditional grids can lead to overload, bigger fluctuations in generator speed, rise in voltage deviation of distribution buses, and increased power losses; which these consequences result in lower reliability and smart grid security. Thus, management of production or consumption in these vehicles are investigated. This study adopts Genetic algorithm (GA) to optimize uncoordinated and coordinated PEVs charging stations with renewable distributed generation resources. The proposed model is applied to IEEE 33– bus network. The output results have shown the efficiency and robustness of the proposed model.

Background and Aim: Different surgical techniques have been proposed for crown exposure among patients under orthodontic treatment. The aim of this study was to investigate periodontal indices in closed flap OPERATION technique used for impacted teeth crown exposure.Materials and Methods: In this descriptive study (2001-2003) 20 patients (15 females and 5 males), age ranging from 15 to 20 years, were participated. Following the performance of closed flap OPERATION technique, in 12 patients impacted canine and central incisors were exposed and treated orthodontically. Periodontal parameters including sulcular depth, width of keratinized gingiva and attachment loss were recorded. Results: The mean of gingival sulcus depth was 1.50±0.43, the means of keratinized gingival in central incisors and canines were 3.07±0.53 and 2.30±0.42, respectively. In one patient, attachment loss was reported.Conclusion: Considering the optimal sulcular depth and keratinized gingiva, the closed flap OPERATION technique seems suitable.

Power system restructuring has increased the take part distribution side of power system in providing power. Extensive influence of distribution resources for generation power in distribution side of power system and transferring power electricity between retailer and household consumers are the reason of that.Among different types of distributed resources, micro combined heat and power systems (m-CHP) have a large acceptability for using by retail household consumers, high efficiency, using the heat output and controllable output. In this paper, COSTS of annual electric and heat energy providing for a household consumer has been calculated under two conditions: without using m-CHP (purchasing electric power demand from electricity retailer and providing heat demand by boiler) and using m-CHP, then the two types compared.The output of m-CHP considering two types of controllers, modified heat led controller and price-based controller for showing the effect of controlling system in operating m-CHP has been determined to reduce the COSTS of electric energy providing for a household consumer.

In this research, the production rate and cost of felling and processing in the first thinning of Tyrum rood forest located in northern Iran has been studied in 2013. The study area was reforested by species such as Populus spp., Cupressus sempervirens var. horizontalis, Alnus subcordata, Acer velutinum in 1984. Overall, 132 cycles of felling and processing were recorded. Time study technique was used for calculating hourly production. After defining work phase elements, the influencing variable on each element was determined using stepwise multivariate regression. The results showed that the time consumption of felling and processing was as a function of influencing variables such as diameter, volume, and tree’s distance. The average production rate for all species was 2.8 m3 per hour. The average unit production cost obtained 61522 Rials per m3. Overall, unit cost of felling and processing OPERATION mostly depends on the tree size and tree branching size and structure. As a general rule, as tree size increases, the unit cost decreases, therefore Populus spp was more economical than other above mentioned species.