1,200 research outputs found
Photovoltaic System Efficiency Enhancement With Thermal Management: Phase Changing Materials (pcm) With High Conductivity Inserts
No full textThe electrical conversion efficiency of photovoltaic cells from solar radiation heavily depends on the cell temperature. Here we propose a novel thermal management strategy to keep the cell temperature in the same order to attain maximum efficiency. The comparative study presented is based on four solar module configurations: a conventional photovoltaic module (PVT module), a conventional module with PCM layer underneath (PVT/PCM-I), a configuration where fins embedded into PCM (PVT/PCM-II), and configuration where the bottom of the PCM layer in PVT/PCM-II was cooled via convection (PVT/PCM-III). The developed 3D numerical model is solved via ANSYS software involving the solar ray tracing radiation model for incident solar radiations and a transient melting-solidification thermo-fluid model to cater for PCM phase transition. Results from the numerical model were validated via a comparison of experimentally studied results presented in the literature. After 120 minutes, results show that the conversion efficiency of PV cells becomes 16.84%, 18.65%, 18.83%, and 18.98% after 120 minutes for PVT module, PVT/PCM-I, PVT/PCM-II, and PVT/PCM-III with an inlet velocity of 3m/s, respectively. For the respective configurations, the specific electrical power per unit area produced reaches 75.30W/m2, 83.39W/m2, 84.19W/m2, and 89.42W/m2 for solar radiation of 540W/m2 and 26°C ambient temperature. Results reveal that a 5 mm increase in the fin height for PVT/PCM-II results in a 0.22% increase in efficiency while a 0.5m/s increase in the inlet velocity of the cooling air for PVT/PCM-III results in about 0.06% increase in efficiency. © 2021, ilhami Colak. All rights reserved
Enhanced transmission of electromagnetic waves through a subwavelength aperture using metamaterials at microwave regime
No full textA PROMOTER POLYMORPHISM IN THE PON1 GENE IS ASSOCIATED WITH ESSENTIAL HYPERTENSION
No full textColak, Ertugrul/0000-0003-3251-1043; Colak, Emine/0000-0002-6293-2909; Cosan, Didem Turgut/0000-0002-8488-6405Objective:
Increased vascular oxidative stress, the main risk factor of cardiovascular diseases, is seen as a role in the pathophysiology of essential hypertension. Genetic factors also play an important role in the formation of hypertension
Properties of ZnO nanostructures produced by mechanochemical-solid state combustion method using different precursors
No full textNanostructured zinc oxide (ZnO) samples were produced by the mechanochemical-solid state combustion method using different precursors, namely citric acid, maleic acid, sodium oxalate, salicylic acid, tartaric acid and urea. The ZnO samples were characterised by XRD. The average crystallite sizes of the samples were found to be between 18 and 67 nm and from 43 to 69 nm for synthesis temperatures of 400 and 600 degrees C, respectively. The morphology of the samples was investigated by SEM, and their particle sizes were found to be between 25 and 223 nm and from 38 to 339 nm for synthesis temperatures at 400 and 600 degrees C, respectively. The electrical conductivity measurements of the samples were performed via the four probe method. The ZnO samples produced at 600 degrees C have higher electrical conductivity than those produced at 400 degrees C. Also, the optical absorbances of the ZnO samples were measured via Uv/vis spectrophotometer. (C) 2017 Elsevier B.V. All rights reserved
Organisering av ekonomiskt bistånd – Perspektiv på en integrerad och en specialiserad kommun
No full textAuthor: Merima Colak Title: Organization of financial assistance - Perspective on an integrated and a specialized municipality [translated title] Supervisor: Håkan Johansson Assessor: Staffan Blomberg The purpose of this study was to examine how specialized and integrated social services manage their social assistance. In addition to this the aim was to examine how social workers and officials working within these two forms of organizations experience discretion. Furthermore, a goal of this paper was also to examine if the social workers felt that any of these two organizational forms had any impact on the workload and how that in such case manifested. The study was conducted through a qualitative research method. Six social workers and officials were interviewed for the study. The results from the study demonstrated that the employees in the integrated organization had more general work tasks and that those in the specialized organization had their tasks divided on different units that were more specialized. Findings also showed that employees in each municipality interpret discretion differently. The social workers from the integrated organization interpreted discretion in terms of being able to affect their client’s case. The social workers from the specialized organization, on the other hand, defined discretion as being able to influence their own daily work tasks. Conclusively, the study showed that workload exists in both municipalities and that it was manageable in each of the municipalities, the workload was however higher in the specialized one but it was no burden on the employees in neither the specialized nor the integrated. Key words: Discretion, organizational structure, integrated and specialized organizations, social assistance, workload. Key words: handlingsutrymme, organisationsstruktur, integrerade och specialiserade organisationer, ekonomiskt bistånd, arbetsbelastning
The opinions of the pre-service teachers about e-democracy in Turkey
No full textToday, Internet has a widespread position in the world and the usage of electronic environments in the context of governance was begun. Because of the important role of e-democracy processes in 21(st) century and importance of the social studies pre-service teachers in training active citizens, in this study opinions of the social studies pre-service teachers about e-democracy are presented. The data has been collected from pre-service teachers through interviews. The data has been collected from pre-service teachers through interviews. (C) 2010 Elsevier Ltd. All rights reserved
Prevalence of Root Dilacerations in Central Anatolian Turkish Dental Patients
No full textBayraktar, Yusuf/0000-0001-6250-5651; Hamidi, Mehmet Mustafa/0000-0003-3461-7925; Colak, Hakan/0000-0001-8262-0913Objective: The aim of this study was to determine, retrospectively, the prevalence and distribution of the dilaceration of the root for each tooth-type in a sample of Central Anatolian Turkish population by using panoramic radiographs. Method: Panoramic radiograhs of 6912 patients (3860 women and 3052 men, mean age 29.04 years, range, 15 to 50 years) were examined for the presence of root dilacerations. Chi-square test was also used to compare the prevalence of dilacerations between male and female subjects and upper and lower jaws. Results: Data showed that 1108 (16.0%) of these subjects had one or more teeth that were dilacerated and these were detected in 466 (15.2%) males and 642 (16.6%) females. Statistical analysis (chi(2) test) showed a significant difference in the prevalence of dilaceration among male and female patients. Mandibular third molars were dilacerated most often (3.76%), followed by mandibular second molars (1.81%). Dilaceration was found in 1.23% of maxillary second premolars and 1.23% of mandibular second molars. Conclusion: Root dilacerations are not uncommon among Turkish dental patients, and their early detection could be important in treatment problems associated with it. However, further larger scale studies are required to assess its prevalence in the general population in order to compare it with other ethnic groups
Comparative analysis of on-load tap changing (OLTC) transformer topologies
No full textOld - EWI-ESE-DC&S DC systems & StorageElectrical Power Processin
Determination and mapping of cadmium accumulation in plant leaves on the highway roadside, Turkey
No full textThis study investigates cadmium (Cd) accumulation in the plant leaves of juglans regia (walnut) and cydonia oblanga (quince) trees related to traffic emissions on the highway roadside. The plant leaf samples were collected from 20 sites on the D-100 Highway roadside and washed with deionized water before analyzed. Determination of Cd was carried out using an inductively-coupled plasma-mass spectrometer after microwave digestion of the samples. Cd concentration on the plant leaves was found to be between 0.04-0.11 mg/kg. In order to determine the traffi c-based emissions, vehicles were counted and an emission inventory was prepared. 0.18 tons of Cd was found to be delivered into the atmosphere every day. Cd accumulation depends on traffic density because there were no residential area and industrial plants. The distribution of Cd accumulation caused by traffic emissions was mapped by using a geographic information system (GIS). The maps showed that the Cd accumulation was high in the areas near the highway and then gradually decreased by moving away from the highway
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