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During the Industrial Revolution and particularly at the beginning of the Second World War, mathematicians and those involved in the industry became interested in the optimization models. The application of these model was specially developed in industry and services sector after the Second World War. Based on this, designing of the mathematical model for the transportation network of Islamic Republic of Iran’s Post Corporation, which is practically complicated as a result of the multiplicity of communication paths and the variation of transportation systems and vehicles as well as mail items, will be studied according to a multi-level model. First the transportation system’s data is loaded into the post corporation’s system of transportation data. After estimating the Function Utility of the system, the shortest time and path as well as the vehicle carrying the intended mail item between the two post offices (i & j) will be identified. Finally, the consignments will be transported through the selected paths and based on their weights. Therefore, besides reviewing the related literature, the history of transportation systems as well as postal transportation systems will be discussed. Finally, based on the methodology, the findings and proposals will be presented through a multi-level mathematical model.

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This research develops a two-level model based on hypotheses, which concern relationships among role ambiguity, role conflict, job involvement and salesperson performance at individual level and collective sale self efficacy, customer orientation and competitive climate at sale unit level in Iranian food industry. Data was drawn from 482 sales people in 30 companies , using a 51-item self-reported questionnaire. Research model was tested in disaggregation, aggregation and multilevel approaches. The results from three approaches were different. Multilevel modeling analysis revealed that role ambiguity and role conflict have negative effects, but collective sale self efficacy and job involvement have positive effects on sales person performance. Results also showed that collective sale self efficacy has positive moderation effect on the relationship between job involvement and sales person performance. Collective sale self efficacy indicated positive moderation effect on the relationship between job involvement and sales person performance and negative moderation effect on the relationship between role conflict and sales person performance.

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The advantages of structures equipped with bracing systems such as high lateral stiffness, light weight of the skeleton compared to flexural frames plus the weakness of flexural frame connections as well as high risk of the performance of these connections during earthquakes always place the bracing lateral stiffness system at equal level of the other seismic-resistant systems in the minds of designers. However, Experiences gained from the concentric brace frames performance during earthquakes showed the undesirable function and hysteresis loops of the bracing system. The early buckling of the brace members causes joint failure, instability and unpredictable seismic behavior of the frame. Researchers tried to avoid the buckling phenomenon by making some changes in brace members structure. Using energy dissipation systems like buckling restrained braces, viscose dampers, friction dampers and yielding dampers were the methods which have been investigated during years. yielding dampers due to their benefits like economic aspects, easy construction, available material, flexible design, durability and significant impact on the seismic responses were one of the devices which has been considered. Many researchers worked on different types of yielding dampers. they used parallel plates yielding dampers on top of the chevron braces and slit dampers along diagonal brace. despite of many researches has been done, but it seems more efficient projects can be achieved in this field. the yielding dampers constructed so far have several considerable problems: i) the existence of one or two-level behavior against earthquakes, ii) the implementation of the welding process in energy-absorbing parts causing premature rupture of steel, and iii) the lack of support system in the event of severe earthquakes or unusual loads outside the design leading to frame instability. This research tries to design a two-level yielding damper with parallel fuse plates using finite element sensitivity analyses on an effective component of these types of dampers. After that to assessment of the damper function, an OpenSees code developed to analyze the nonlinear time history of the seven far-field selected ground motions. All the ground motions selected according to the FEMA P-695 suggested ground motions with the site class of C and the base shear, roof acceleration, story velocity and drift nonlinear time history responses of a three-story braced frame compared with and without damper. To prevent buckling of the brace members, dampers with the capacity of 90% of brace members capacity designed to use at any story brace and the maximum displacement capacity of dampers adjusted to the maximum allowable drift of the building stories. Results showed that, there are some effective and less effective parameters whose variation such as geometrical parameters can seriously change the total energy absorption level and improve the damper hysteresis loops. Also, According to the flexible design of the presented damper, if it needs to be designed with a force bearing capacity and energy absorption in accordance with the seismic design of the desired frame, it is possible to achieve the desired capacity by making changes in the overall dimensions and number of energy absorbing plates. time history responses assessment showed that using the new damper has a significant decreasing effect on the seismic responses of the building.