فهرست مطالب sharareh mohammadi

Boilers are one of the major energy consumers in the building. For this reason, increasing the efficiency of this device and improving its performance is an effective step in solving the problems in building energy and reducing waste energy. Due to the limited resources of fossil fuels and the increasing cost of energy in the world, manufacturers of these equipment are always working to improve the performance and use of appropriate control equipment. The purpose of this study is to increase the thermal recovery efficiency of steam energy in gases from shell and corrugated tubes condensing boilers. Numerical simulations are performed using commercial CFD code, ANSYS FLUENT 18.2. In this research, the effect of different arrangement of tubes in a shell and corrugated tubes condensing boiler are analyzed numerically. There are 10 tubes with three different arrangements inside the shell. The results show that the first model has clearly better heat recovery performance than the other two investigated models because of its irregular position of the tubes. The numerical model is validated by experimental results. According to the comparison of the results, the maximum difference is 6.9% and 8.9%. So simulation result shows good agreement and accuracy. Also, 10 pipes with 3 different configurations are used inside the tube. results reveal that nonlinear and irregular configuration is better than two other models.

Individuals performance at the workplace is affected by different adopted postures. Sitting postures are mostly used during office work. Improper sitting postures may cause muscle fatigue and discomfort in the spine and also result in mental workload. Poor posture may result in human errors and delay in information processing. Previous studies have demonstrated the relationship between static sitting postures and cognitive factors such as reaction time to an auditory stimulus. Also, some recent studies have demonstrated the effect of static postures on cognitive performance. To our knowledge, none of the studies had considered the sitting and standing postures effects on cognitive performance simultaneously. The aim of this study was to evaluate cognitive performance during three different static working postures: standard sitting, standing, and self-selected sitting postures.
This semi-experimental design study was conducted on the twenty-nine healthy students (aged 20-30 years). The non-probability sampling method was selected. All participants provided their written informed consent. Participants with no musculoskeletal disorders, heart disease, spine surgery, and history of depression and stress were selected. Their depression status and level of stress were measured using Beck questionnaire. The study was approved by the Ethics Committee of University of Social Welfare and Rehabilitation Sciences. Subjects performed complex Stroop test and typing activity in an office-like laboratory setting at the University of Social Welfare and Rehabilitation Sciences. Stroop test lasted about 9-12 minutes, and a typing task was also designed for approximately 5 minutes for all subjects. Three random postures were selected based on common postures used in the office. The effects of the postures (standard standing, standard sitting, and self-selected sitting posture) on dependent variables such as total test duration and reaction time to congruent and incongruent stimulus, number of typing words and number of typing error were assessed with Repeated Measures ANOVA. To examine the differences between groups, the paired t-test was used.
The results demonstrated that reaction time measure and number of typing error (accuracy) were affected by postures (P=0.001). Post hoc analysis demonstrated that reaction time was significantly different between self-selected sitting posture and standard sitting posture (P=0.001), self-selected sitting posture and standard standing posture (P=0.043), standard sitting posture and standard standing posture (P=0.001). With considering the average amount of reaction time to congruent and incongruent cases, it was observed that there is less reaction time in the standardized sitting posture (M=628.67 ms) compared to the self-selected sitting posture (M=689.41 ms) and standard standing posture (M= 675.16 ms). Also, among the three postures studied a significant difference was observed in the number of typing error words (P=0.001). The number of typing error (accuracy) was lower in this posture compared to the two other postures (M=1.58).
This study demonstrates that cognitive performance is affected by working postures. This study demonstrates that standard sitting posture is the best posture. Therefore, it is recommended that sitting posture can help in increasing cognitive performance in the workplace.

The aim of this study is to investigate on relationship between decision-making styles of managers and creativity and participatory management, in schools of Ghaem shahr city. The research method is a descriptive correlation. The statistical population of the study consists of all school's managers of Ghaemshahr city. The sample size consists of 78 subjects. Research instruments were three questionnaires of decision-making styles of Moghadam zade and Tehrani (1387), Participatory management of Moghimi (1381) and creativity of Sanatizade (1389). For analysis of data, descriptive statistics methods (frequency, percentage, mean, and standard deviation) and statistical illation (correlation coefficient test, t-test, stepwise regression and variance) is used.
The resualts showed that the components of the decision-making styles, Rational and annie components have a significant and positive relationship with creativity.Also Results showed that from the Components of decision-making styles, only intuitive has a significant positive relationship with Participatory management and There is a significant positive relationship between creativity and participatory management. Also Results showed that the components of a rational and Annie were the better predictor for creativity and also intuitive component is the better predictor for participatory management.

Security is one of the human needs. As human needs hierarchy of Maslow, the security is in the second level and it's after the physiologic needs. The scientists believe that the factors like social, economic, cultural and etc. effect on security.in the meantime we can mention indefensible space role. Target of this paper is applying of GIS for finding and analyzing of these spaces; until in this way have a better recognition about these spaces for recommended the appropriate solutions. This research applied spatial analyst (GIS) and analyzing indefensible spaces in case study (Pardis). The result shows that distinguishable spatial patterns can be fined and these situations are useful for defining the subject and action plans in case study.