In two level modeling, random effect and error's normality assumption is one of the basic assumptions. Violating this assumption leads to incorrect inference about coefficients of the model. In this paper, to resolve this problem, we use skew normal distribution instead of normal distribution for random and error components. Also, we show that ignoring positive (negative) skewness in the model causes overestimating (underestimating) in intercept estimation and underestimating (overestimating) in slope estimation by a simulation study. Finally, we use this model to study relationship between shift work and blood cholesterol.

Acronyming is one of the word-formation processes. In general terms, there are two types of acronyms; initialisms and word acronyms. An initialism is read and pronounced as a spelling or as a sequence of letters, while a word acronym is pronounced as a single ordinary word. Two-level word acronym is a type of word acronym used by organizations and social groups to suggest some aspect of their purpose or objective. Two-level word acronym expresses meaning on two levels, i.e., as an acronym and as a simple word. This research aimed at the introduction and analysis of some Persian two-level word acronyms whose application is increasing among Iranian organizations and social groups. Furthermore, in this paper, it is argued that the formation of two-level word acronyms which makes the written form and the pronunciation of an actual word and an acronym the same as each other, is a type of semantic extension in the form of polysemy.

Bilevel programming, a tool for modeling decentralized decision problem, consists of the objective of the leader at its first level and that of the follower at the second level. Bilevel programming has been proved to be an Np-hard problem. Numerous algorithms have been developed for solving bilevel programming problems. These algorithms lack the required efficiency for solving a real problem. In this paper, attempts have been made to develop an algorithm based Simulated Annealing (SA) Approach. This algorithm is efficient enough to find a near optimal solution. The proposed method is compared with the one developed by Mathieu et al [1] through application of both to a number of different problems.  

Bilevel programming is the model for hierarchical optimization problems in which there are two decision makers that have different objective functions, variables and constraints. Alves et al in [1], proposed a method for computing the Pareto frontier of bilevel linear problem with biobjective at the upper level and a single objective function at the lower level. In this paper, we extend their method for the situation in which there exists more than two objective function at both levels, and then by using a suitable exchange variable, we proposed a new method for computing the Pareto frontier of bilevel linear problem with fractional multi-objective at the upper level. Finally we will show the efficiency of the propsed approaches by solving a few numerical examples and comparing the results with other methods.

The purpose of this study is to analyze oil and tax revenues in the Iranian economy. Applying the stochastic dynamic general equilibrium approach, a model for the oil exporting economy was simulated. In order to recover the tax system, oil and tax revenues added to the model as a part of government’s revenue. The present study applies Dynare software with Matlab to estimate the model’s parameters by Bayesian statistical techniques based on Monte Carlo method with Markov chain in the form of Metropolis-Hastings algorithm. The period of study is from 1368 to 1396 in a quarterly setting. In order to analyze the shocks, two scenarios were designed. In the first scenario, it was assumed that the government has oil revenues and all oil revenues are spent by the government so that the government does not rely on tax revenues. In the second scenario, it is assumed that 40% of the government's oil revenues are injected into the Development Fund and a percentage of it, is allocated to facilitate the production sector, and the government mostly relies on the taxes. The results show that the tax and oil shock by reducing dependence on oil and reliance on tax revenues, has negative impact on macroeconomic variables in the short term, but in the long run, with increasing tax revenues, production and, consequently, investment, consumption, employment has increased. JEL classification: H21 C13، E17، G5

In this paper, a new kind of ring damper composed of three rings is introduced and investigated numerically and experimentally. The proposed damper combined three steel ring damper in order to dissipate energy of two different level of predefined excitation such as moderate and severe one. first fuse (outer pipe) and second fuse (inner pipes) can absorb energy in moderate and severe earthquakes respectively. To evaluate the introduced damper, numerical finite element models are developed to clarify the effect of thickness and diameter variation of main fuse. Results of force-displacement curves obtained from cyclic loading confirmed the two level performance of models. Stiffness and fore increase improved the energy dissipation capacity after the predefined displacement gap. Also, damping ratio are calculated for all samples and results showed that equivalent damping ratio have been improved when main fuse was engaged. Two experimental samples have been constructed based on numerical models and examined under cyclic loading. Defined results of experiments showed that samples could tolerate 20 cycles of 10 times of yield displacement amplitude. Good agreement between numerical model and experimental samples results have been achieved.

استراتژی دریایی یکی از مهمترین ابعاد استراتژی ملی قدرت های بزرگ به حساب می آید. این مساله اگرچه با تحول ماهوی قدرت در سیاست جهانی، اهمیتی را که آلفرد ماهان در «تاثیر و نفوذ قدرت دریایی در تاریخ» مطرح کرده بود را از دست داده است اما در دو دهه اخیر مجددا به عرصه رقابت ژئوپلیتیک قدرت های بزرگ بازگشته است. در این میان، اقیانوس هند و شکل گیری ائتلاف بندی های جدیدی مانند کواد و آکوس در آن را می توان نقطه عزیمت جدیدی در بازی قدرت های جهانی دانست. در این راستا، این مقاله به این سوال اصلی پرداخته است که اقیانوس هند چه جایگاهی در معادلات ژئوپلیتیک قدرت های دریایی با تاکید بر گروه بندی های کواد و آکوس دارد؟ یافته های این پژوهش که به روش توصیفی- تحلیلی صورت گرفته نشان دهنده انتقال تدریجی مرکز ثقل اقتصاد و سیاست جهانی از اقیانوس اطلس به اقیانوس هند-آرام است که در پرتو ائتلاف بندی های نظامی و امنیتی جدید به تشدید رقابت و تنش میان قدرت های بزرگ دریایی منجر خواهد شد.