The direct discrete method for the analysis magnetohydrodynamic equations

The Direct Discrete Method has been applied to derive the algebraic form of the Magnetohydrodynamic equations. It is shown that the method can be considered as a replacement for the various differential based discritization methods. This approach is based on the global variables that are used in two cell complexes- one dual of the other- to subdivide the 3D space. In this paper, using the discrete form of the differential operators, we discretized the magnetohydrodynamic equations directly into a set of algebraic equations. Using this method, an example of a 3D magnetohydrodynamic equilibrium problem as a case study has also been represented.Keywords: Direct Discrete Method, magnetohydrodynamic equations, cell complex, discretizatio

Reproduction characteristics of the Vimba vimba persa (Pallas, 1811), in coastal waters of the Caspian Sea

Some reproduction characteristics of the Caspian Vimba, Vimba vimba persa, were studied from Oct. 2008 to Sep. 2009 in coastal waters of the Caspian Sea (Mazandaran province). 994 specimens were monthly collected from 6 fish landing sites of Ramsar, Tonekabon, Chalus, Mahmood Abad, Sari and Behshahr. The fecundity was measured using 92 specimens. This species was found to have more abundance in spring (especially April and May). The samples composed of 397(42.6%) male, 537(57.4%) female; the sex ratio was M:F = 1:1.35. The advanced stages of maturity (4th & 5th) were found in April and May. The highest Gonadosomatic Index in females was in May and the lowest one was in July. The average of absolute and relative fecundities was 17198±7710 and 171.85±48.8, respectively

The effects of creosote on mortality rate and blood biochemical factors of stellate sturgeon (Acipenser stellatus)

The effects of creosote on stellate sturgeon (Acipenser stellatus) juveniles each weighing 3.6 ±1 grams was evaluated. Acute toxicity test was undertaken in static water quality at 22 degree C plus or minus 1 according to the OECD method at the Caspian Sea Ecology Institute in 2005. The effect was assessed based on the results of the acute toxicity test. For the test, the hematological and biochemical properties of one control and five experimental groups of the fish juveniles what were exposed to creosote were compared. The acute toxicity test lasting 96 h was performed in fully static water condition with aeration

Effect of Co-Driver on Job Content and Depression of Truck Drivers

Background: Since the presence of a co-driver can be considered as a companion, partner, or friend for a driver through eliminating driver's loneliness, it plays a significant role in health and safety of drivers. The objective of this study was to investigate the effect of co-drivers on depression and occupational stress on male truck drivers. Methods: This study was an interventional case-control study. Seventy truck drivers were selected and divided into two groups: case (33 truck drivers with co-drivers) and control (37 truck drivers without co-drivers). Two Goldberg depression inventories (for evaluating driver's depression) and the Karasek job content questionnaire (for evaluating driver's job stress) were used to collect data which were completed by interview. Results: The results showed that job content values for the case group were higher in all dimensions except job nature. The comparison of the percentages showed significant difference between two groups. Depression rate in drivers with co-driver is truly less than depression rate in drivers without co-driver. There was significant positive relationship between dimensions of job content and depression rate. Conclusion: According to the results of this study, it can be claimed that a co-driver decreases stress and loneliness of drivers, as well as increases work performance and job satisfaction, and, in turn, leads to a decrease in job-related depression. © 2018 The Author

Prevalence of food addiction in children and adolescents: A systematic review and meta-analysis

Food addiction (FA) has been as a construct that is associated with childhood obesity. However, relatively little is known regarding the prevalence of FA among children and adolescents. An instrument designed to assess FA among youth, the Yale Food Addiction Scale for Children and Adolescents (YFAS-C), has been developed and used to estimate FA prevalence among pediatric populations. The present systematic review and meta-analysis aimed to synthesize the results of FA prevalence among youth. Using keywords related to FA and children to search PubMed, Embase, Scopus, and Web of Science, we identified and analyzed 22 cross-sectional studies. No longitudinal studies were identified in the search. Meta-analysis with Freeman-Tukey Double Arcsine transformation was conducted to estimate FA prevalence. Meta-regression was applied to understand whether weight status (i.e., data from community samples vs. overweight/obese samples) is associated with FA. Eligible studies (N = 22) were analyzed using 6,996 participants. The estimated FA prevalence was 15% (95% CI 11-19%) for all samples, 12% (95% CI 8-17%) for community samples, and 19% (95% CI 14-26%) for overweight/obese samples. Meta-regression indicated that weight status was associated with FA severity (p = 0.002) and marginally with FA prevalence (p = 0.056). Healthcare providers should consider and address the high FA prevalence among pediatric population. Keywords: addictive behaviors; adolescent; child; food addiction; obesity; prevalence; systematic review

Comparison of morphometric and meristic attributes of bream (Abramis brama orientalis), in Caspian Sea and Aras Dam Reservoir

Morphometric and meristic specifications of Abramis brama orientalis of the Caspian Sea and Aras Dam Reservoir was studied in the year 2002. For this purpose, 40 morphometric attributes, 16 meristic attributes and 37 specifications in relation to the proportions of speciality of morphometric attributes of the Abramis brama orientalis were evaluated from the two habitats. Anova, factor and discriminant function analyses were conducted on the data. According to results the average coefficient of variation in morphometric, meristic and proportion of speciality of morphometric attributes for Abramis brama orientalis of Caspian Sea was 22.85, 3.24 and 7.68 and for Abramis brama orientalis of Aras Dam Reservoir was 17.45, 3.53 and 15.27. The Abramis brama orientalis of the two areas showed meaningful differences in 35 morphometric factors, 6 meristic factors and 25 factor of proportion of the speciality of the age had significand differences (P<O.05). Factor analysis showed that the Abramis brama orientalis of the two habitats had 80.62% of changes in 7 factors of first morphometric attributes, 73.65% of changes in the 9 factors of the first proportion of morphometric specialities and 46.52% of changes in the 4 factors of the first meristic attribute. We showed that, fork length, standard length, proportion of head length to the standard length, number of scales of the lateral line, number of scales under the lateral line, number of scales above the lateral line, radius of dorsal fin and number of dorsal fins can be used to separate population of the fish from the two habitats. The first two factors of proportion of speciality of morphometric and meristic attributes causes total separation of the two populations. We found different in morphometric specialities between the two specialities of morphometric and meristic attributes. It is suggested that different environmental conditions have led to the differences in the populations of the fish in the Caspian Sea and Aras Dam Reservoir

Free vibration analysis and design optimization of SMA/Graphite/Epoxy composite shells in thermal environments

Composite shells, which are being widely used in engineering applications, are often under thermal loads. Thermal loads usually bring thermal stresses in the structure which can significantly affect its static and dynamic behaviors. One of the possible solutions for this matter is embedding Shape Memory Alloy (SMA) wires into the structure. In the present study, thermal buckling and free vibration of laminated composite cylindrical shells reinforced by SMA wires are analyzed. Brinson model is implemented to predict the thermo-mechanical behavior of SMA wires. The natural frequencies and buckling temperatures of the structure are obtained by employing Generalized Differential Quadrature (GDQ) method. GDQ is a powerful numerical approach which can solve partial differential equations. A comparative study is carried out to show the accuracy and efficiency of the applied numerical method for both free vibration and buckling analysis of composite shells in thermal environment. A parametric study is also provided to indicate the effects of like SMA volume fraction, dependency of material properties on temperature, lay-up orientation, and pre-strain of SMA wires on the natural frequency and buckling of Shape Memory Alloy Hybrid Composite (SMAHC) cylindrical shells. Results represent the fact that SMAs can play a significant role in thermal vibration of composite shells. The second goal of present work is optimization of SMAHC cylindrical shells in order to maximize the fundamental frequency parameter at a certain temperature. To this end, an eight-layer composite shell with four SMA-reinforced layers is considered for optimization. The primary optimization variables are the values of SMA angles in the four layers. Since the optimization process is complicated and time consuming, Genetic Algorithm (GA) is performed to obtain the orientations of SMA layers to maximize the first natural frequency of structure. The optimization results show that using an optimum stacking sequence for SMAHC shells can increase the fundamental frequency of the structure by a considerable amount