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Now showing items 1 - 16 of 38

  • Energy Savings and Economic Impact of Green Roofs: A Pilot Study

    Celik, Serdar   Binatli, Ayla Ogus  

    This study focuses on the energy savings and economic impact of green roof systems applied to Central Bodrum, a district in southwestern Turkey. Energy savings of the buildings were evaluated based on the added thermal resistance on the roofs and corresponding heat transmission through the roofs. Four different scenarios, two without green financing and two with green consumer loans for retrofitting financed by the central government via the state-owned banks, were studied. The economic impact of this activity on the economy is estimated based on sectoral employment multipliers for a period of 10years. Based on the scenario analysis and the priorities of the Turkish economy, given the employment benefits and energy savings which would reduce the energy demand in the area in the peak season, we propose that the government implements green consumer loans for retrofitting through the state-owned banks.
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  • The histopathological correlation of Bosniak 3 cyst sub-classification

    Sefik, Ertugrul   Bozkurt, Ibrahim Halil   Adibelli, Zehra Hilal   Aydin, Mehmet Erhan   Celik, Serdar   Oguzdogan, Gülsen Yucel   Basmaci, Ismail   Gorgel, Sacit Nuri   Vardar, Enver   Gunlusoy, Bulent   Degirmenci, Tansu  

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  • The Histopathologic Correlation of Bosniak 3 Cyst Subclassification

    Sefik, Ertugrul   Bozkurt, Ibrahim Hall   Adibelli, Zehra Hilal   Aydin, Mehmet Erhan   Celik, Serdar   Oguzdogan, Gulsen Yucel   Basmaci, Ismail   Gorgel, Sacit Nuri   Vardar, Enver   Gunlusoy, Bulent   Degirmenci, Tansu  

    OBJECTIVE To evaluate the histopathologic correlation of recently described subclassification of Bosniak category 3 cysts (3s and 3n). MATERIALS AND METHODS A total of 106 patients who underwent partial/radical nephrectomy due to a complex renal cyst (>=3D Bosniak 3) were retrospectively reviewed. All the scans of the patients were reevaluated by 2 experienced uroradiologists. Bosniak 3 cysts were reclassified as 3n (nodularity on the cyst wall/septae) and 3s (septated cysts without nodularity) as described in a recently published paper. Group 1 consisted of patients with Bosniak 3s, Group 2 consisted of patients with Bosniak 3n, and Group 3 consisted of patients with Bosniak 4 cysts. Three groups were compared according to patients' characteristics, radiological findings, histopathologic results, and survival outcomes. RESULTS There were 52 patients in Bosniak 3 group and 54 patients in Bosniak 4 group. Mean follow-up was 35.3 months. Among Bosniak 3 cysts, 37 lesions were classified in 3s and 15 were classified in 3n. Malignancy was higher in 3n group than 3s (86.7% vs 54.1%, P=3D .026). Lesion size was significantly lower for malignant cysts compared to benign ones in the patients with Bosniak 3 lesions (44.2 +/- 27.5 vs 80 +/- 55.9 P=3D .005). In the subgroups, malignant lesions were significantly smaller than benign lesions in 3s group similar to general Bosniak 3 group. Most of the Bosniak 3 lesions were organ confined and low grade. CONCLUSION The subclassification of Bosniak 3 cysts as 3s and 3n can help to differentiate highly suspicious malignant lesions from the relatively less suspicious ones. (C) 2019 Elsevier Inc.
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  • Energy Savings and Economic Impact of Green Roofs: A Pilot Study

    Celik, Serdar   Ogus Binatli, Ayla  

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  • Octagonal Halbach Magnet Array Design for a Magnetic Refrigerator

    Celik, Serdar   Kural, Mehmet Hamdi  

    An effective magnet array design for magnetic refrigeration systems is crucial given the space limitations and need for maintaining the required cooling capacity. Here, Halbach permanent magnet arrays (HPMA) in an octagonal orientation are studied using NdFeB permanent magnets. Gadolinium is selected as the magnetocaloric material (MCM) for the aperture inside the octagonal HPMA. The optimum outer-to-inner radii ratio for the octagonal HPMA and MCM system is found to be 2, at which the cooling energy per volume of magnet has a peak. For this ratio, the effect of using soft magnetic material, which in this study is FeVCo, inside and outside the HPMA is evaluated over a range of material thicknesses. The optimum soft magnetic material thickness outside the HPMA is obtained to be 3% of the external radius. At this thickness, soft magnetic material is also placed inside the array as a concentrator. It is found that although using soft magnetic material inside the magnet array increases the average flux, cooling energy is decreased due to using less MCM inside the aperture because of the space occupied by the soft magnetic material.
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  • Octagonal Halbach Magnet Array Design for a Magnetic Refrigerator

    Celik, Serdar   Kural, Mehmet Hamdi  

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  • Analysis of perlite and pumice based building insulation materials

    Celik, Serdar   Family, Roxana   Menguc, M. Pinar  

    Insulation panels composed of perlite, pumice, and cement were fabricated. Perlite and pumice were used to achieve high thermal resistance, and low density. Experimentation was conducted for determining R-values of perlite-pumice-cement (PPC) panels at different moisture content values. Dry and moist sample panels were tested with and without soil and moss at the top where the one with the soil and plant coupling represents a green roof. Reverse heat leak method was used in determination of the R-values of the samples. Verification of theory was achieved via experimentation with an acceptable error range. Thermal diffusivity values of the developed samples were measured using flash method. (c) 2016 Elsevier Ltd. All rights reserved.
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  • Analysis of perlite and pumice based building insulation materials

    Celik, Serdar   Family, Roxana   Menguc, M. Pinar  

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  • Green Roof Storm-Water Runoff Quantity and Quality

    Morgan, Susan   Celik, Serdar   Retzlaff, William  

    The design of a green roof plays a significant role in performance. In a ground-level field study, 28 built-in-place green roof models, four modular units, and four roof decks with standard black membrane were arranged in a completely randomized design. Storm-water runoff quantity and quality were monitored from September 2005 through June 2008. Results indicate that green roof systems significantly reduced storm-water runoff and that system design, growth media depth, and presence of plants impacted storm-water retention. In a second study on a building roof, two modular systems were used to evaluate water loss through evapotranspiration. Water loss of both systems was significant and influenced by system design, growth media type, and presence of plants. Finally, runoff quality analyses from the ground-level field study and from a laboratory pot experiment indicate that nitrate, total suspended solids, and turbidity are generally low in runoff after a first-flush event. Runoff water quality was also influenced by system design, growth media type, and presence of plants. DOI: 10.1061/(ASCE)EE.1943-7870.0000589. (C) 2013 American Society of Civil Engineers.
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  • Performance evaluation of a variable speed DC compressor

    Ekren, Orhan   Celik, Serdar   Noble, Brad   Krauss, Ryan  

    Direct current compressors are strong candidates to be employed in energy-efficient refrigeration systems, especially for renewable energy powered units, as these compressors do not require additional components such as a power inverter that an alternative current compressor would require. This study represents experimental performance analysis of a direct current type refrigeration compressor implemented in a 79 L refrigerator. Energy usage reduction and operational improvement potential of the direct current compressor via variable speed operation were investigated. Experiments were carried out at variable speed operation and four different constant speed operation modes of the compressor. Temperature, pressure, and power input measurements were obtained every 30 s. The experimental data were analyzed in terms of energy and exergy efficiencies. The comparison showed that variable speed operation of the direct current compressor can be much more efficient than constant speed operation of the direct current compressors, especially at higher speeds. (C) 2012 Elsevier Ltd and IIR. All rights reserved.
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  • Performance analysis of a refrigerating system with a grooved-tube evaporator

    Celik, Serdar   Nsofor, Emmanuel C.  

    A grooved-tube heat exchanger was developed and applied as an evaporator of a refrigerating system. Studies were carried out to evaluate the performance of the refrigerator. Isobutane (R-600a) was employed as the working fluid. Same studies were performed on the system but with the same size of a regular-tube evaporator. The two refrigerating systems were compared in terms of heat exchanger effectiveness, coefficient of performance (COP), and two-phase pressure drop. The heat exchanger effectiveness of the grooved-tube evaporator was found to be higher compared to the regular-tube evaporator. COP of the system with the grooved-tube evaporator was also observed to be higher. Although the pressure drop for the grooved-tube evaporator was slightly higher than that for the regular-tube evaporator, the compressor demand for this increase was not very significant. (C) 2014 Elsevier Ltd. All rights reserved.
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  • Performance analysis of a refrigerating system with a grooved-tube evaporator

    Celik, Serdar   Nsofor, Emmanuel C.  

    A grooved-tube heat exchanger was developed and applied as an evaporator of a refrigerating system. Studies were carried out to evaluate the performance of the refrigerator. Isobutane (R-600a) was employed as the working fluid. Same studies were performed on the system but with the same size of a regular-tube evaporator. The two refrigerating systems were compared in terms of heat exchanger effectiveness, coefficient of performance (COP), and two-phase pressure drop. The heat exchanger effectiveness of the grooved-tube evaporator was found to be higher compared to the regular-tube evaporator. COP of the system with the grooved-tube evaporator was also observed to be higher. Although the pressure drop for the grooved-tube evaporator was slightly higher than that for the regular-tube evaporator, the compressor demand for this increase was not very significant. (C) 2014 Elsevier Ltd. All rights reserved.
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  • COMBINED-LOOP MAGNETIC REFRIGERATION SYSTEM

    A magnetic refrigeration system having a magnetocaloric material for adjusting the temperature of a transfer fluid is disclosed. The magnetic refrigeration system includes tubing filled with the transfer fluid that flows in a first pass through a heat exchanger having a magnetocaloric material that is magnetized by one or more electromagnets and heats the transfer fluid. The magnetocaloric material is magnetized and demagnetized by one or more electromagnets controlled by a timer/controller device. A three-way solenoid valve controls the flow of heated transfer fluid from the heat exchanger and directs the heated transfer fluid to a warm heat exchanger for cooling of the transfer fluid. The cooled transfer fluid is then passed a second time through the heat exchanger in which the magnetocaloric material is demagnetized for further cooling of the cooled transfer fluid.
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  • A systematic approach for assessment of renewable energy using analytic hierarchy process

    Budak, Gercek   Chen, Xin   Celik, Serdar   Ozturk, Berk  

    Background Cities around the world face a great challenge in establishing a long-term strategy for the development of energy alternatives. Previous research tried to identify renewable energy across many different cities. Because each city has unique characteristics in terms of geographic and environmental conditions, population, economic development, and social and political environment, the most sustainable energy source for one city might be the least sustainable for another. Methods This research develops and implements a systematic approach to assess renewable energy and identify the energy alternatives for a city using the analytic hierarchy process. The methodology integrates experts' input and data analytics and helps decision-makers form long-term strategies for renewable energy development. Results The decision support system is applied to three cities, Chengdu in China, Eskisehir in Turkey, and Chicago in the United States of America. Results show that improving energy efficiency and development of solar and wind energy are the most preferred energy alternatives whereas nuclear and hydroelectric are the least preferred energy alternatives for these three cities. Conclusions The results of this study are in line with decades of research and development in energy alternatives and show a clear direction for the future development of energy alternatives around the world. There are differences in the rankings of energy alternatives for different cities, indicating that it is necessary to apply the decision support system developed in this study to help form customized energy strategies for cities with unique characteristics.
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  • Studies on the flow-induced noise at the evaporator of a refrigerating system

    Celik, Serdar   Nsofor, Emmanuel C.  

    Studies were performed here to investigate the behaviour of flow-induced noise at the evaporator section of a refrigerating system located in an anechoic chamber. An x-ray system was used to visualize the refrigerant flow in the pertinent tubes of the system. The flow-induced noise under transient and steady-state operations of the system was studied using acoustic, pressure and temperature measurements. Calculations on the bubble size-resonant frequency and x-ray results agreed with the dominant frequency range obtained through acoustical measurements. One-third octave band analysis was performed for the 200-500 Hz frequency range as this frequency band was where the refrigerant-induced noise was found to be dominant in the system. Factors that influence the transient noise generated by the refrigerant flow were identified. Published by Elsevier Ltd.
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  • The role of cancer stem cells in immunotherapy for bladder cancer:An in vitro study

    Ozcan, Yegane   Caglar, Fulya   Celik, Serdar   Demir, Ayse Banu   Ercetin, Ayse Pinar   Altun, Zekiye   Aktas, Safiye  

    Objective: Bladder cancer is characterized by frequent recurrence and progression. CD44+ cancer stem cells (CSCs) might be one of the main reasons for recurrence. Although Bacillus Calmette Guerin (BCG) has become a gold standard immunotherapy, after treatment recurrence frequently occur. Based on this knowledge, the aim of this study was to evaluate the changes in cytokine and chemokine expressions in bladder cancer and CSCs cultures in vitro with BCG only and in combination with IL2 and lymphocyte (MNCs) applications. Material and methods: In this study, 3 cell lines of human bladder cancer cells with different characteristics (T24, 5637, and JMSU-1) and CD44+ bladder CSCs isolated by magnetic bead isolation (Miltenyl Magtech) were used. Bladder cancer cell lines and bladder CSCs in complete medium were cultured under humidified conditions of 37 degrees C temperature in 5% CO2. BCG only and its combination with IL2 and MNCs were applied to bladder cancer cell lines and bladder CSCs for 24, 48, and 72 hours. Annexin V-PI was used to detect the percentages of apoptotic and necrotic cells in treatment groups and control groups. After treatments, total RNAs were isolated and converted to cDNA for each group and controls. Quantitative fold changes in terms of gene expression were measured by RT2 PCR array and fold changes for expression levels of genes were compared among groups. Eighty-four genes were analyzed in standard array of chemokines and cytokines (Biorad). Results: BCG treatment with 7.32 mu g/ml dose alone and in combination with IL2 (1000 IU/ml) and MNCs (1000 cells/ml) were found to be most effective on bladder cancer cells. When BCG and its combinations were applied to CSCs of the 3 cell lines, BCG treatment showed cytotoxic effect on CSCs as well as cancer cells. CSCs of 3 cell lines over expressed CXCL5, CCL8, CNTF, and CSF2 compared with cancer cells. Cancer cells over expressed IL6, TNSFF11, FASLG, and CXCL9 compared with CSCs. In all 3 cell lines, BCG application increased expression of CXCL5 and LTB and also decreased CCL20 and IL6. When BCG was combined with IL2 and MNCs, CXCL10, CXCL5, and IFNG were increased and CXCL12, IL6, and TNSF11 were decreased. BCG treatment of CSCs caused increases in ADIPOQ, CXCL10, and XCL1 and a decrease in CCL8. When IL2 and MNCs were combined with BCG, the expression of many cytokines and chemokines decreased. Conclusion: BCG treatment changes the expression of many cytokines and chemokines in bladder cancer. The expression differs in 3 different cell lines and their CSCs. Immune modulation of each case differs from each other. The effectivity of BCG-based immunotherapy in bladder cancer on CSCs might decrease in combination with IL2. Our results indicate that recurrence after BCG treatment for bladder cancer may not occur mainly based on the CSCs hypothesis considering bladder cancer occurs at different loci of surface epithelium. (C) 2020 Elsevier Inc. All rights reserved.
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