A MULTI-OBJECTIVE APPROACH FOR DETERMINING THE NUMBER OF BLADES ON A NACA MARINE PROPELLER

This paper numerically discusses how the performance of a NACA marine propeller is affected by the number of blades, which is one of the most crucial geometrical parameters determining the performance of a propeller. Results are presented in terms of the hydrodynamic and structural parameters. The results show that changing the number of blades changes the hydrodynamic efficiency, torque, thrust, cavitation behaviour and structural stiffness of the propeller nonlinearly. Furthermore, it is shown that the propellers structural lifetime is shortened by increasing the number of blades. Hence, the propeller’s number of blades is a multi-objective function and will be discussed in this research. The applied tool which is used to study the hydrodynamic performance of the propellers is a RANS-based CFD one and the FEM is considered to study the structural behaviour of the propellers

Electrocaloric Response of Ferroelectric Material Applicable as Electrothermal Transducer

Electrocaloric response of the PMN-10PT is measured experimentally and compared with the numerical results. Based on the compatibility of the experimental and numerical results, feasibility of using ferroelectric materials as an electrothermal transducer has been investigated. In this study, electrocaloric response of three different ferroelectric capacitors (PMN-10PT, PMN-25PT, and PZN-4.5PT) under an applied periodic electric field have been investigated. Alternative switching of the electrocaloric elements with specific boundary conditions generates a directed heat flux. It can be concluded that each ferroelectric material can be used as a transducer in a special temperature range that in which it has good electrocaloric response

Francis Turbine Draft Tube Troubleshooting during Operational Conditions Using CFD Analysis

Hydropower plant vibrations due to pressure fluctuations and their troubleshooting methods are some of the most challenging issues in power plant operation and maintenance. This paper targets these fluctuations in a prototype turbine in two geometries: the initially approved design and the as-built design. Due to topographic conditions downstream, these geometries slightly differ in the draft tube height; the potential effect of such a slight geometrical change on the applicability of troubleshooting techniques is investigated. Therefore, the water flow was simulated using the CFD scheme at three operating points based on the SST k–ω turbulence model, while the injection of water/air was examined to decrease the pressure fluctuations in the draft tube, and the outputs were compared with no-injection simulations. The results show that a slight change in draft tube geometry causes the pressure fluctuations to increase 1.2 to 2.8 times after 4 s injecting at different operating points. The modification in the location of the air injection also could not reduce the increase in pressure fluctuations and caused a 3.6-fold increase in pressure fluctuations. Therefore, the results show that despite water/air injection being a common technique in the hydropower industry to reduce pressure fluctuations, it is effective only in the initially approved design geometry. At the same time, it has a reverse effect on the as-built geometry and increases the pressure fluctuations. This research highlights the importance of binding the construction phase with the design and troubleshooting stages and how slight changes in construction can affect operational issues.<br/

FLUID-STRUCTURE INTERACTION ON A FIXED FAN BLADE

High global electricity demand is pushing engineers towards providing hydropower electromagnetic generators with more resistant rotary equipment against well-known problems such as fatigue and vibrational cracking. The aim is to make power plants immune against high time and cost consuming refurbishments. In these systems, one of the rotating parts that is most susceptible to such failures is the ventilation fan. It is often an axial fan with blades distributed at one or two ends of the machine. The blades are attached to, and rotating with, the same shaft as the rotor, pushing the air through the rotor and stator towards the cooler. The blades are often manufactured by simple bent plates that are welded to the rotor, to keep the cost at minimum. They operate in an air flow that is highly restricted to the space that is available when the electromagnetic parts of the machine have been designed, causing temporally and spatially varying and non-ideal flow angles. For such conditions it is vital to study fluid-structure interaction on the blades to be able to avoid fan blade failures. Broken fan blades may cause severe damages to other parts of the machine, at enormous costs of repair and down-time. The present work provides a numerical study of the aeroelastic behaviour of a fixed blade resembling a blade of a double-sided axial fan of a hydropower generator. The focus is on flow-induced fluttering and resonance due to vortex shedding. The fluid-structure interaction is captured using the solids4Foam toolbox, which is an open source module for OpenFOAM, including specific solvers for solid and fluid mechanics and fluid-structure interaction. The turbulence is modelled using the scale-adaptive SAS model, which is able to capture vortex shedding with a combination of moderate computational costs and acceptable accuracy.Figure 1 shows the blade geometry, which has an extruded circular arc cross-section that is connected to a base plate at the lower side and has a thin clearance to a cover at the upper side. Iso-surfaces of the Q-criterion in the left picture, show the vortical structures at the tip and trailing edge. In the right picture, an instantaneous exaggerated deformed shape of the blade is shown under the working condition.AcknowledgementsThe research presented was carried out as a part of the Swedish Hydropower Centre (SVC). SVC is established by the Swedish Energy Agency, EnergiForsk and Svenska Kraftn\ue4t together with Lule\ue5 University of Technology, The Royal Institute of Technology, Chalmers University of Technology and Uppsala University, www.svc.nu. The computations were enabled by resources provided by the Swedish National Infrastructure for Computing (SNIC) at NSC and C3SE, partially funded by the Swedish Research Council through grant agreement no. 2018-05973.References[1]\ua0\ua0\ua0 OpenCFD, OpenFOAM: The Open Source CFD Toolbox. User Guide Version 1.4, OpenCFD Limited. Reading UK, Apr. 2007. [2]\ua0\ua0\ua0 C. W. Bergan, B. W.\ua0 Solemslie, P. 8stby, &amp; O. G. Dahlhaug, “Hydrodynamic damping of a fluttering hydrofoil in high-speed flows”,\ua0International Journal of Fluid Machinery and Systems, vol.\ua011, No. 2, pp. 146-153, April-June 2018, ISSN: 18829554. DOI: http://dx.doi.org/10.5293/IJFMS.2018.11.2.146

Comparison of the effects of direct and indirect education of sexually transmitted infections on knowledge and attitude of male nursing and medical students of Shahid Beheshti University of Medical Sciences, Tehran – Iran, 2018

Introduction: It is very important to prevent Sexually Transmitted Diseases (STIs) as they cause many other health problems with serious complications. In fact, prevention is the most effective mean of dealing with STIs. In saying that, the basic requirements of prevention include appropriate health education on the subject. This study compares the effectiveness of two health education programs regarding bacterial STIs among male students at Nursing and Medical Schools of Shahid Beheshti University of Medical Sciences and Health Services in Tehran. Materials and Methods: The quasi-experimental study included 430 male students aged between 18 and 30 who were majoring in nursing and medical field. Two faculties were selected through purposeful non-random sampling.  A valid and reliable researcher-made questionnaire was filled out in two steps (before and one month after the training). The training interventions in direct education group included a lecture along with a session of questions and answers (Q&amp;As) for one and a half hours. On the other hand, the indirect education only included a weblog on the topic of STIs. The statistical tests were employed to analyze the collected data in SPSS 22. Results: Generally, students’ knowledge and attitudes toward this subject were at a moderate level before the intervention, and only %18.4 of them were well-aware of bacterial STIs. In fact, %44 of the respondents had positive attitudes toward those diseases. The research results indicated that the educational intervention managed to increase the awareness and attitudes of the students in relation to STIs in the two case groups in comparison with the control group. However, the different methods of education produced similar results and had no significant differences. Moreover, attitudes increased in the weblog group slightly more than the lecture group. Conclusion: According to the findings of this research, The weblog intervention had more effects on their attitudes than the lecture intervention. Therefore, the modern training method based on the use of the internet (weblog) can be used effectively as an alternative or supplement to traditional training methods

Effects of Government Investment in Energy Sector on Growth, Employment and Private Investment in Iran

This research analyzes governmental investment effects in energy sector including subsectors of oil, gas and electricity on growth, private investment and employment in agriculture, industry and mining, and services during 1971-2013. We use vector autoregressive models in order to derive the response of variables, impulse response function and variance decomposition. The results indicate that governmental investment influence growth in agriculture, industries and mining, and services negatively but in median-term, it influences agriculture, and industries and mining positively. Effect of government investment is positive for private investment. In industries and mining sector, the relationship is positive in long term and negative in middle term. Keywords: Energy Sector, Government Investment, Economic Growth, Employment, Private Investment, Vector Autoregressive Method JEL Classifications: C01, O16, E24, 040, H54

Composición química de aceites de almendras (Prunus scoparia) y pistachos silvestres (Pistacia atlantica)

The aim of this study was to determine the fatty acids, sterols and triacylglycerol compositions as well as the amount of tocopherols, total phenols and pigments wild almond and cold pressed wild pistachio oils. Triacylglycerols, tocopherols and pigments were analyzed with HPLC, fatty acids and sterols with gas chromatography, and total phenols photometrically. The main fatty acids in both samples were oleic, linoleic and palmitic acids. The most predominant TAG species are SLL + PLO (21.83%) in wild pistachio oil and OOO (47.27%) in wild almond oil. Pheophytin a was the major pigment in wild pistachio oil. There were no pigments detected in wild almond oil. Total phenols were 57.6 mg kg-1 oil for wild pistachio and 45.3 mg kg-1 oil for wild almond oil.El objetivo de este estudio fue determinar la composición en ácidos grasos, esteroles, triglicéridos, así como tocoferoles, fenoles totales y pigmentos de aceites de almendras y pistachos silvestres prensados en frío. Triglicéridos (TAG), tocoferoles y pigmentos se analizaron mediante HPLC, los ácidos grasos y esteroles mediante cromatografía de gases, y los fenoles totales espectrofotométricamente. Los principales ácidos grasos de ambas especies fueron los ácidos oleico, linoleico y palmítico. Las especies de TAG predominantes son SLL + OLP (21,83%) en el pistacho silvestre y OOO (47,27%) en almendras silvestre. Feofitina a es un pigmento importante en los aceites de pistacho silvestre. No se detectó pigmentos en los aceites de almendras silvestres. Los fenoles totales fueron 57,6 mg kg-1 y 45,3 mg kg-1 en los aceites de pistacho silvestre y de almendra silvestre respectivamente

Analysis of urban form typology using urban heat island indicators: Case study of Ferdous neighborhood of Tabriz

Urbanization, with the acceleration of construction operations in cities, is the main reason for in-creasing the absorption of thermal energy in urban areas, which leads to climate change, especially urban form has responded differently depending on environmental dimension of urban context concerning the urban heat island intensity. In the last Studies, Researchers have not Codified the effect of urban form on heat islands in the form of a comprehensive model. It is necessary to examine each urban context according to its own conditions. Accordingly, this study aims to identify the effect of building form variability on reducing the intensity of heat islands in Ferdous context of Tabriz in the form of comprehensive modelling as a new task. The research gap is the effect of the form of buildings on the intensity of UHI, and the question will be asked whether it is possible to control the intensity of UHI by changing the form by influencing the climatic indicators. Our conceptual framework was based on urban form typologies in microscale affect the amount of energy intake and consumption, especially the intensity of heat islands, and whether the use of desirable types can be responsive to reducing the intensity of these islands? In this regard, using a quantitative analysis method in Rhinoceros software, especially using Grasshopper plugins, urban form is investigated. This analysis includes both the coldest and hottest days of the year. The results show that the optimal model is the cross typology

Costs of hospital-acquired infection for patients hospitalized in intensive care unit of an Iranian referral hospital

Background: Hospital infections have affected millions of people around the world and are considered as one of the most important issues related to patient safety. Therefore, this study was conducted to estimate the extra costs caused by hospital-acquired infections in hospitals. Methods: This retrospective cohort study was conducted in Tehran province, Iran, in 2017. Medical records of 235 patients hospitalized in one of Tehran hospitals were reviewed for the study. They were divided into case (90 patients) and control (145 patients) groups. Data were analyzed using SPSS and STATA software. Results: Results revealed no significant relationship between age and gender with the incidence of nosocomial infection (p > 0.05). However, the chance of nosocomial infection is most affected by length of hospital stay and costs paid by patients. Moreover, nosocomial infection increases the length of hospital stay up to 25 days. Our results revealed that the mean±SD hospital stay of infected and non-infected patients were 15.8 ± 17.2 and 40.8 ± 19.1 days, respectively. Furthermore, the total cost of patients without any hospital infection was 2451 ± 3098 USD (83 674 480 ± 105 765 500 Rials). On the other hand, the cost for infected patients was 3264±6078 USD (207 497 500±111 430 700 Rials). Conclusion: Hospital-acquired infections can impose great costs on both patients and the health system. The results of this study indicated the importance of taking specific measures for infection control in hospitals. © 2018, Iran University of Medical Sciences