Papers by Necmettin Şahin
Journal of The Faculty of Engineering and Architecture of Gazi University, Jan 6, 2023
LED lighting fixture for M1 and M2 class roads Optical design of COB LED road lighting fixtur... more LED lighting fixture for M1 and M2 class roads Optical design of COB LED road lighting fixture Development of COB LED+lens module in accordance with international road lighting standards Figure A shows how the extension of the ray emitted from an LED light source and parallel to the principal axis of a concave lens passes through the focal point (f) and then follows. This phenomenon is known as diffraction of light. Figure A. Diffraction of light in a concave lens Purpose: The purpose of this study; optical design and analysis of a COB LED road lighting fixture model suitable for M1 and M2 lighting class roads. Theory and Methods: One of the most important and critical parts of luminaire design is the optical design process. With a welldesigned optical design, the rays emanating from the light source can be fine controlled. Optical systems are arranged in multiple layers to ensure sufficient brightness and luminous integrity in the event of a possible LED failure. In this study, a spherical concave-convex lens compatible with COB LED was designed to transmit the rays emitted from the light source to the desired area without loss and to keep the efficiency of the rays at the maximum level. In the LightTools program, the lens and the LED were combined at three different distances and three different luminaire models were developed. It was carried out the simulation studies on these models and light distribution curves were obtained. The light distribution curves which were obtained transferred to the lighting calculation program. Design verification studies have been carried out in the lighting calculation program. Results: In the study, the light distribution curves belonging to three different luminaire models were transferred to the DIALux lighting calculation program. Lighting parameters of light distribution curves were simulated according to M1 and M2 road conditions in the DIALux lighting calculator program and design verification studies were carried out. During the optimization phase, COB LED and lens distance of the luminaire model optimized which was developed considering compliance with M1 and M2 road lighting criteria. When the DIALux results of the study were examined, it was seen that the developed luminaire model within the scope of this study met the M1 and M2 road lighting criteria. As a result, with this study, the optical design and design verification of a completely original COB LED road lighting fixture model for the solution of a lighting problem needed in our country have been successfully completed. Conclusion: The luminaire designed by using a concave-convex spherical lens and a COB LED suitable for the lens, ensures that the rays emanating from the light source are transmitted to the desired area with minimal loss. In this way high energy efficient and original model has been developed that can better meet the lighting needs.
Bu çalışmada, $ThSi_2$ yakıtlı flibe $(Li_2BeF_4)$ soğutuculu bir füzyon-fisyon hibrid reaktörde ... more Bu çalışmada, $ThSi_2$ yakıtlı flibe $(Li_2BeF_4)$ soğutuculu bir füzyon-fisyon hibrid reaktörde trityum üretim bölgesinde $Li_2TiO_3$, $Li_2ZrO_3$, $Li_4SiO_4$ ve $Li_2O$ gibi dört farklı Li bileşikleri kullanılmıştır. Füzyon nötron kaynağı olarak 14.1 MeV ortalama enerjili nötronlar üreten D-T reaksiyonları kullanılmış ve $\Delta t=10$ gün olmak üzere 4 yıllık çalışma süresince reaktörde füzyon nötron kaynağı için gerekli fusil yakıt üretimi, fisil izotop üretimi, fisyon enerjisi üretimi ve nükleer güç üretiminin değişimleri incelenmiştir. Tritiyum üretim bölgesinde $Li_2O$ kullanıldığında en yüksek fusil yakıt üretimi elde edilirken, fisil üretimde ve fisyon enerjisi üretiminde $Li_2TiO_3$ ve Li2ZrO3 bileşiklerinin kullanıldığı mantolarda en iyi sonuçlara ulaşılmıştır.In this work, in a $ThSi_2$ fuelled-flibe moderated fusion-fission reactor in the tritium breeding zones of the reactor are used four different Li compound, respectively, $Li_2TiO_3$, $Li_2ZrO_3$, $Li_4SiO_4$ and $L...
Supplemental Material, supplementary_data for The effect of polyurethane and carnauba wax on the ... more Supplemental Material, supplementary_data for The effect of polyurethane and carnauba wax on the mechanical and physicochemical properties of acrylonitrile butadiene nitrile rubber coating working gloves by Necmi Düşünceli, Lalehan Akyüz, Necmettin Şahin, and Hatice Duru in Journal of Elastomers & Plastics
Bitlis Eren Üniversitesi Fen Bilimleri Dergisi, 2020
Öz Spor tesislerinin aydınlatması, aydınlatma uygulamasının özel bir kategorisidir. Oyunun türüne... more Öz Spor tesislerinin aydınlatması, aydınlatma uygulamasının özel bir kategorisidir. Oyunun türüne ve seviyesine göre farklı aydınlatma seviyelerine ihtiyaç duyulmaktadır. Sporcuların ve seyircilerin görsel ihtiyaçlarının karşılaması amacıyla spor sahalarında yüksek miktarda enerji tüketilmektedir. Bunun için spor tesislerinin aydınlatılmasında ekonomik ve sürdürülebilir yöntemlere ihtiyaç duyulmaktadır. Ayrıca spor tesislerinde elverişli ve sağlıklı görme koşullarının sağlanması sporcuları hem fizyolojik hem de psikolojik açıdan etkilemektedir. Elverişli ve sağlıklı görme koşullarının sağlanması uygun ve elverişli aydınlatma araçlarının ve standartlarının kullanılması ile gerçekleştirilebilir. Spor tesislerinin aydınlatmasında Türkiye'de EN 12193 Işık ve Aydınlatma-Spor Aydınlatması standartları kullanılmaktadır. Bu standartlar sporcular, hakemler, seyirciler ve TV iletimi için uygun görsel koşulları sağlamayı amaçlamaktadır. Çalışmada, spor tesislerindeki aydınlatma ve EN 12193 aydınlatma standartları ile ilgili temel bilgiler verilmiştir. Ayrıca çalışmada sürdürülebilir ve ekonomik aydınlatma araçları olan LED'lerin spor tesislerindeki kullanımlarından bahsedilmiştir.
World Journal of Engineering, 2015
Progressive decline in world energy resources, rising costs, on behalf of the various studies has... more Progressive decline in world energy resources, rising costs, on behalf of the various studies has led businesses to use energy resources efficiently. This work is at the top of the exergy analysis. In this study, using data from Eregli Sugar Factory 2010–2011 campaign year for sugar production processes, the first law of thermodynamics (energy analysis) and analysis of these condlaw (exergy analysis) were conducted. Depending on there sults of this analysis of the sugar production process yields the first and these cond law is calculated. Obtained in the light of the secalculation stoin crease theen ergy efficiency of the plant, was tetoprovide energy to gainth embackand give direction to the development of new technologies Eregli Sugar Factory recommendations were made.
Kerntechnik, 2006
Abstract Nuclear waste actinides can be used as a booster fissile fuel material in form of mixed ... more Abstract Nuclear waste actinides can be used as a booster fissile fuel material in form of mixed fuel with thorium in a CANDU reactor in order to assure the initial criticality at startup. Two different fuel compositions have been found useful to provide sufficient reactor criticality over a long operation period: 1) 95% thoria (ThO2)+5% minor actinides MAO2 and 2) 90% ThO2+5% MAO2+5% UO2. The latter allows a higher degree of nuclear safeguarding through denaturing the new 233U fuel with 238U. The temporal variation of the criticality k∞ and the burn-up values of the reactor have been calculated by full power operation for a period of 10 years. The criticality starts by k∞>1.3 for both fuel compositions. A sharp decrease of the criticality has been observed in the first year as a consequence of rapid plutonium burnout in the actinide fuel. The criticality becomes quasi constant after the 2nd year and remains close to k∞ = ∼1.06 for ∼10 years. After the 2nd year, the CANDU reactor begins to operate practically as a thorium burner. Very high burn up could be achieved with the same fuel material (up to 200000 MW.D/MT), provided that the fuel rod claddings would be replaced periodically (after every 50000 or 100000 MW.D/MT). The reactor criticality can be maintained until a great fraction of the thorium fuel is burnt up. This would reduce fuel fabrication costs and nuclear waste mass for final disposal per unit energy drastically.
Fusion Engineering and Design, 2001
Production of denaturated fissile fuel in a thorium fusion breeder has been investigated by mixin... more Production of denaturated fissile fuel in a thorium fusion breeder has been investigated by mixing the fertile fuel with natural-UO 2 and LWR (light water reactors) spent nuclear fuel. Four different coolants (pressurised helium, Flibe 'Li 2 BeF 4 ', natural lithium and Li 17 Pb 83 eutectic) are selected for the nuclear heat transfer. In order to obtain a power flattening in the fissile-fertile zone, the UO 2-or the spent fuel-fraction in the mixed oxide (MOX) fuel has been gradually increased in radial direction. Power plant operation periods between 13 and 29 months are evaluated to achieve a fissile fuel enrichment 4%, under a first-wall fusion neutron energy current of 5 MW m − 2 (plant factor of 100%). For a plant operation over 4 years, enrichment grades between 6.0 and 11.5% are calculated for the investigated MOX fuel and coolant compositions. The 238 U component of natural-UO 2 can provide a limited proliferation hardening only for the 233 U component, whereas, the homogenous mixture of ThO 2 with a small quantity of (\ 4%) LWR spent nuclear fuel remains all-over non-prolific for both, uranium and plutonium components.
gazi university journal of science, 2018
In this study, in order to provide heat dissipation of the high power LEDs to be used for street ... more In this study, in order to provide heat dissipation of the high power LEDs to be used for street illumination, U-shaped cylindrical copper heat pipes are used. Thermal analysis of this system was carried out numerically in the ANSYS Fluent software. Firstly, thermal analysis was performed for different numbers, diameters and lengths of heat pipes and optimum values were obtained. Afterwards, the optimum materials to be used as components of LED packages were determined. In addition, the effect of the power applied to the LED chip and of ambient temperature on the temperature distribution of the whole system was examined.
Bu calismada, ThSi 2 yakitli flibe (Li 2 BeF 4 ) sogutuculu bir fuzyon-fisyon hibrid reaktorde tr... more Bu calismada, ThSi 2 yakitli flibe (Li 2 BeF 4 ) sogutuculu bir fuzyon-fisyon hibrid reaktorde trityum uretim bolgesinde Li 2 TiO 3 , Li 2 ZrO 3 , Li 4 SiO 4 ve Li 2 O gibi dort farkli Li bilesikleri kullanilmistir. Fuzyon notron kaynagi olarak 14.1 MeV ortalama enerjili notronlar ureten D-T reaksiyonlari kullanilmis ve Dt=10 gun olmak uzere 4 yillik calisma suresince reaktorde fuzyon notron kaynagi icin gerekli fusil yakit uretimi, fisil izotop uretimi, fisyon enerjisi uretimi ve nukleer guc uretiminin degisimleri incelenmistir. Tritiyum uretim bolgesinde Li 2 O kullanildiginda en yuksek fusil yakit uretimi elde edilirken, fisil uretimde ve fisyon enerjisi uretiminde Li 2 TiO 3 veLi 2 ZrO 3 bilesiklerinin kullanildigi mantolarda en iyi sonuclara ulasilmistir.
Bu calismada; (Th+233U)O2 yakit karisiminin CANDU reaktorlerinde kullanilabilirligi ve reaktor ba... more Bu calismada; (Th+233U)O2 yakit karisiminin CANDU reaktorlerinde kullanilabilirligi ve reaktor basariminaetkisi arastirilmistir. Bunun icin yakit olarak %98 ThO2 + %2 233UO2 yakit karisimi kullanilmistir. Notronikveriler, tek boyutlu SCALE 4.4a nukleer hesaplama kodu yardimiyla elde edilmistir. Reaktor kritiklik ve yanmaderecesi degerleri tam gucte 20 yil icin hesaplanmistir. Yapilan hesaplamalar sonucunda, reaktor kritikliginink∞=~1,3 le basladigi ve 2. yil sonundan itibaren 20 yil boyunca k∞=1,06 sinir degerinin uzerinde oldugugorulmustur. Yanma derecesi 2. yil sonunda 45.216 MW.D/MT ve 20. yilin sonunda 558.061 MW.D/MT gibicok yuksek bir deger elde edilmistir. Bu calisma, toryumun cok dusuk oranda (%2) fisil izotop karisimlariylaCANDU reaktorlerinde yakit olarak kullanilabilecegini gostermektedir.
Mühendislik Bilimleri ve Tasarım Dergisi, Mar 20, 2020
Bu çalışmada, sokak aydınlatmalarında kullanılan yüksek güçlü LED'lerin soğutulması için ısı boru... more Bu çalışmada, sokak aydınlatmalarında kullanılan yüksek güçlü LED'lerin soğutulması için ısı borulu soğutucu tasarımı yapılmıştır. Dört adet yüksek güçlü LED, dörtgensel alüminyum plaka üzerine yerleştirilmiş ve U şeklinde üç adet silindirik bakır ısı borusu, alüminyum plakanın içinden geçecek şekilde monte edilmiştir. Isı borusunun ısıyı doğal taşınım ile dış ortama aktarabilmesi için, ısı borusunun yoğuşturucu bölgesine kanatçıklı soğutucu plaka yerleştirilmiştir. Tasarlanan sistemin termal analizi, nümerik olarak ANSYS Fluent yazılımında yapılmıştır. Analizlerde sırasıyla, 15 W, 20 W ve 25 W'lık elektriksel giriş güçlerinin sistem sıcaklık dağılımına etkisi incelenmiştir. Buna ek olarak, sayısal analizlerde, çözüm metodu olarak farklı türbülans modeli ve duvar yaklaşımlarının sıcaklık dağılımına etkisi de incelenmiştir. Sayısal çözümlerin doğrulanması için deneysel çalışma yapılmıştır. Sayısal ve deneysel sonuçlar birbiriyle uyumlu olduğu gözlenmiştir.
... Nigde, Turkey. Email: Kadir Yıldız ([email protected]). *Correspondence: Kadir Yıldız, ... more ... Nigde, Turkey. Email: Kadir Yıldız ([email protected]). *Correspondence: Kadir Yıldız, Engineering Faculty, Department of Mechanical Engineering, Aksaray University,Aksaray, Turkey. Publication History. Issue published ...
Journal of Elastomers & Plastics
In this study, the effect of polyurethane (PU) and carnauba wax (CW) on the mechanical and physic... more In this study, the effect of polyurethane (PU) and carnauba wax (CW) on the mechanical and physicochemical properties of acrylonitrile butadiene nitrile rubber coating gloves was investigated. Thermal decomposition and morphological characterizations were carried out using Thermogravimetric analysis (TGA) and Scanning Electron Microscopy (SEM), respectively. Fourier-transform infrared spectroscopy (FTIR) analysis was done to determine the chemical interactions between NBR and PU in the polymer matrix. After the vulcanization of NBR, including PU and CW, thermal stability was increased. The spectrums of FTIR showed that carboxyl groups of NBR were linked to the PU to form stable complexes between polymeric chains via H-bonding. SEM images showed that because CW acted as a dispersant for the colloidal particles, the surface appeared smooth compared with the non-containing PU/CW samples. Tensile and tear strength and abrasion resistance tests were conducted using the specimens of vulcanized NBR including PU/CW under uniaxial loading. Test specimens were prepared using hydraulic mold according to EN 388 standards. Cross-head speeds were chosen as 100 mm min À1. The chemical and morphological changes due to PU/CW had no significant effects on the macromechanical responses of the tensile and tear strength. However, it was obviously determined that the abrasion resistance was enhanced by the increase in the amount of CW.
International Journal of Hydrogen Energy, 2016
Energy Conversion and Management, 2000
The potential of a moderated hybrid reactor fueled with ThC2 or ThF4 is investigated by a PF (pla... more The potential of a moderated hybrid reactor fueled with ThC2 or ThF4 is investigated by a PF (plant factor) 75% under a first wall fusion neutron current load of 5 MW/m2. LWR (Light Water Reactor) fuel rods containing ThC2 or ThF4 are replaced in the fissile fuel zone of the hybrid reactor. It is considered that gas (He or CO2),
Nuclear engineering and …, 2006
Weapon grade plutonium is used as a booster fissile fuel material in the form of mixed ThO 2 /PuO... more Weapon grade plutonium is used as a booster fissile fuel material in the form of mixed ThO 2 /PuO 2 fuel in a Canada Deuterium Uranium (CANDU) fuel bundle in order to assure the initial criticality at startup. Two different fuel compositions have been used: (1) 97% thoria (ThO 2) + 3%PuO 2 and (2) 92% ThO 2 + 5% UO 2 + 3% PuO 2. The latter is used to denaturize the new 233 U fuel with 238 U. The temporal variation of the criticality k ∞ and the burn-up values of the reactor have been calculated by full power operation for a period of 20 years. The criticality starts by k ∞ = ∼1.48 for both fuel compositions. A sharp decrease of the criticality has been observed in the first year as a consequence of rapid plutonium burnout. The criticality becomes quasi constant after the second year and remains above k ∞ > 1.06 for ∼20 years. After the second year, the CANDU reactor begins to operate practically as a thorium burner. Very high burn up could be achieved with the same fuel material (up to 500,000 MW•D/T), provided that the fuel rod claddings would be replaced periodically (after every 50,000 or 100,000 MW•D/T). The reactor criticality will be sufficient until a great fraction of the thorium fuel is burnt up. This would reduce fuel fabrication costs and nuclear waste mass for final disposal per unit energy drastically.
Annals of Nuclear Energy, 2008
A CANDU reactor fueled with a mixed fuel made of thoria (ThO 2) and nuclear waste actinides has b... more A CANDU reactor fueled with a mixed fuel made of thoria (ThO 2) and nuclear waste actinides has been investigated. The mixed fuel composition has been varied in radial direction to achieve a uniform power distribution and fuel burn-up in the fuel bundle. The best fuel compositions with respect to power flattening as well as long term reactivity have been found by mixing thoria with 14% minor actinides in form of MAO 2 in the central fuel bundle and with a radially decreasing MAO 2 content at discrete levels down to 2% at the periphery. Furthermore, as an alternative fuel composition, 5% UO 2 has been added to the mixed fuel for the sake of a higher degree of nuclear safeguarding through denaturing the 233 U component with 238 U. The temporal variation of the criticality k 1 and the burn-up values of the reactor have been calculated for a period of 10 years, operated at full power. The criticality starts at time zero near to k 1 = $1.24 for both fuel compositions. A sharp decrease of the criticality has been observed during the first year as a consequence of rapid plutonium burnout in the actinide fuel. The criticality becomes quasi-constant after the 2nd year after sufficient 233 U is accumulated and remains close to k 1,end = $1.06 over $10 years. Quasi-uniform power generation density has been realized in the fuel bundle throughout the reactor operation. Very high burn-up could be achieved with the same fuel material (up to 200,000 MW D/MT), provided that the fuel rod claddings would be replaced periodically. This would reduce fuel fabrication costs and nuclear waste mass for final disposal per unit energy drastically.
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Papers by Necmettin Şahin