161 research outputs found
Spirodiepoxide application: psymberin ; Direct carbinolamide synthesis
No full textThe complete structure of Psymberin was determined with the application of the Universal NMR database approach. A formal synthesis of psymberin was completed with the application of spirodiepoxides. An assembly of a dihydroisocumarin ring was accomplished from a complex aldehyde and an anion derived from a pentasubstituted arene. A new condition to couple an aldehyde and an amide was achieved to reach a carbinolamide moiety. This condition was applied for the synthesis of analogs and hybrid structures. In a separate study, a metal and a ligand were investigated to promote the coupling between thioacids and azides.Ph.D.Includes bibliographical referencesby Sezgin Kire
Ecological modernization at the intersection of environment and energy
No full textSezgin, Zeynep (Dogus Author)Contemporary environmental policy is marked by an emphasis on the fight against climate change. Technological improvements for energy efficiency and transition to a low carbon economy are seen as principal environmental policy measures. Has this been the case 40 years ago when modern environmental policy took its first leap? Or has it been the result of a particular twist in the course of the development of environmental policy? Taking sides with the latter approach, it is argued that the intertwining of environmental and energy policy is attributable to ecological modernization that has become the dominant interpretation of sustainable development. Accordingly, this article focuses on ecological modernization theory and policy strategy in an aim to capture this turn. Empirical evidence will be provided through an analysis of European Union (EU) environmental policy. It will be demonstrated how EU environmental policy takes its direction from ecological modernization and how energy efficiency lies at its core
Research of the differences among the problem solving skills of the ninth grade students who have different learning styles
No full textYüksek Lisans TeziBu çalışmada, araştırmaya katılan lise dokuzuncu sınıf öğrencilerin öğrenme stilleri ile problem çözme becerileri arasındaki ilişki araştırılmış ve dokuzuncu sınıf öğrencilerinin rutin olmayan problem hakkındaki düşünceleri de araştırılmıştır. Bu kapsamda, araştırmaya katılan (N=563) dokuzuncu sınıf öğrencileri üzerinde öğrenme stillerinin belirlenmesi amacıyla Kolb Öğrenme Stili Envanteri sonra da matematiksel rutin ve rutin olmayan problemlerin çözümlerinde kullanılan stratejilerin incelenmesi amacıyla Matematik Problem Çözme Testi uygulanmıştır. Araştırmaya katılan dokuzuncu sınıf öğrencilerinden gönüllü olan öğrenciler (N=20) ile de rutin olmayan problemler ile ilgili yarı yapılandırılmış görüşmeler yapılmıştır. Bu araştırmada hem nitel hem de nicel yöntemlerle veriler elde edilmiş olup, veri analizleri MS Excel ve SPSS 18.0 programları ile yapılmıştır. Çalışmanın sonunda, araştırmaya katılan dokuzuncu sınıf öğrencilerinin öğrenme stilleri arasında farklılıklar bulunmuş olup; farklı öğrenme stillerine sahip dokuzuncu sınıf öğrencilerin matematik problem çözme başarıları arasında düşük düzeyde anlamlı bir ilişkinin olduğu anlaşılmıştır. Bununla birlikte; ayrıştıran ve değiştiren öğrenme stillerine sahip dokuzuncu sınıf öğrencilerinin problem çözme becerilerinin farklılaştığı tespit edilmiştir. Ayrıca öğrencilerin rutin olmayan matematik problemleri hakkındaki olumlu görüşleri de rapor edilmiştir.In this research, it was explored the relationship between learning styles of students and problem-solving skills styles of ninth grade students who participated in this research and it was examined ninth grade students' thoughts about non-routine problems. With this context, it was studied on the ninth grade students (N = 563) who participated in the research, Kolb Learning Style Inventory for determining learning style and after it was put into practice Mathmematic Problem Solving Test about routin and non-routin problem solving skills and problem solving strategies. And also it was interviewed with the volunteer students (N = 20) from ninth grade students who participated in the study about non-routine problems. In this research, both qualitative and quantitative data were obtained and the data were analyzed with MS Excel and SPSS 18.0. At the end of the study, it was found differences among the learning styles of the ninth grade students participating in the study; was understood that it was found that there was a low level meaningful relationship between mathematics problem solving sucseses and learning styles. However; The problem solving skills of the ninth grade students having converging and diverging learning styles were found to be different. Additionally, it was reported students's positive opinions about non-routine problems
Rediscovering a Lost Alchemical Text: The Risālat Mītāwus al-‘uẓmā
No full textIn 1971 and 1972, Fuat Sezgin and Manfred Ullmann drew attention to a peculiar alchemist mentioned in various texts, a certain Mītāwus, but whose works had not been preserved. Sezgin saw in the name of this character a corruption of the name of the alchemist Petasios, and Ullmann, more likely, a transcription of the name Matthaeus. In this paper, the author will present a text by this author that he found in an Iranian manuscript, and discuss its content and its attribution
Wear Behavior of Borided Cold-Rolled High Manganese Steel
No full textIn this study, a novel high-manganese steel (HMS) was borided at 850, 900 and 950 °C for 2, 4, and 6 h by the pack boriding process. Contrary to previous literature, borided HMS uncommonly exhibited saw-tooth morphology like low alloy steels, and manganese enhanced the boron diffusion. Another striking analysis is that the “egg-shell effect” did not occur. The present study demonstrated the silicon-rich zone for the first time in the literature by EDX mapping. Moreover, the formation mechanism of silicon-rich zones was explained and termed as “compact transfer of silicones (CTS)”. XRD analysis showed the existence of FeB, Fe2B, MnB and SiC phases. The boriding time and temperature increased the thickness of the boride layer from 31.41 μm to 117.65 µm. The hardness of the borided layer ranged from 1120 to 1915 HV0.05. The activation energy of borided HMS was found to be a very low result compared to high alloy steel investigated in the literature. The Daimler-Benz Rockwell-C adhesion test showed that adhesions of borided HMS surfaces are sufficient. The dry sliding wear tests showed that boriding treatment increased the wear resistance of untreated HMS by 5 times. The present study revealed that the boriding process extended the service life of HMS components
THE INVESTIGATION OF CORROSIVE AND WEAR PROPERTIES OF NITRIDED AND BORIDED HIGH MANGANESE STEEL
No full textBu çalışmada, yüksek manganlı bir çelik (YMÇ) döküm yapıldıktan sonra soğuk haddeli hali ve ısıl işlemli hali olmak üzere iki kısma ayrılmıştır. Isıl işlem, 1000 °C’de 30 dakika ısıtma ve sonrasında suda su vererek gerçekleştirilmiştir. Her iki gruptaki YMÇ‘lere, 850, 900 ve 950 °C’de 2, 4 ve 6 saat borlama işlemi; 520 ve 570 °C’de 12, 18 ve 24 saat gaz nitrasyon işlemi uygulanmıştır. Borlanmış ve nitrürlenmiş YMÇ’ler ile ana malzemelerin XRD analizleri yapılmış, SEM, EDS nokta analizi, EDS elementel haritalama ve optik mikroskopta mikroyapıları incelenmiş, oluşan tabakaların kalınlıkları ölçülmüştür. Daha sonra tabakaların mikrosertlik değerleri ölçülmüştür. VDI 3198 normuna göre adezyon testleri yapılarak tabakaların adezyon özellikleri incelenmiştir. Pürüzlülükleri incelenen numunelerin daha sonra 5, 10 ve 15 N yük altında aşınma testi ile aşınma hacim kayıpları, aşınma oranları ve sürtünme kat sayıları (COF) tespit edilmiştir. EDS elementel haritalama ve EDS çizgisel analiz ile aşınma izindeki elementel dağılımların değişimi tespit edilip, SEM görüntülerinden aşınma testi sonucu ortaya çıkan aşınma hasarları tespit edilerek analizleri yapılmıştır. Korozyon testleri %3,5 tuzlu su çözeltisinde potansiyodinamik polarizasyon ölçümü yapılarak korozyon hızları tespit edilmiştir. YMÇ alaşımlı bir çelik olmasına rağmen borlanmış numunelerde az alaşımlı ve az karbonlu çeliklerde görülen “testere diş morfolojisi” gözlemlenmiştir. Soğuk hadde sonrası gaz nitrürlenen numunelerde “genişlemiş martenzit” tabakası ile karşılaşırken ısıl işlem sonrası gaz nitrürlenmiş numunelerde “beyaz tabaka” meydana gelmiştir. Borlanmış YMÇ’lerde en yüksek sertlik 1915 HV0,05; gaz nitrürlenmiş YMÇ’lerde 1035 HV0,05 olarak tespit edilmiştir. Her iki işlem de ana malzemenin yüzey sertliklerini arttırdığı gözlemlenmiştir. Adezyon testleri yapılan borlanmış numuneler, VDI 3198 normuna göre HF1-HF3; gaz nitrürlenmiş numunelerin hepsinin HF1 kalite sınıfında oldukları tespit edilmiştir. Aşınma testinden önce yapılan pürüzlülük testlerinde en düşük pürüzlülüğe 0,267 µm ile soğuk haddeli orjinal malzeme sahipken en yüksek pürüzlülüğe 1,759 µm ile ısıl işlem ve 570 °C’de 12 saat gaz nitrasyon uygulanmış numune sahiptir. Aşınma testleri, soğuk hadde sonrası borlanmış bütün numunelerin bütün aşınma testi yüklerinde soğuk haddeli YMÇ ile mukayesesinde aşınma hacim kayıplarının düşük olduğu ve YMÇ’nin aşınma özelliklerini geliştirdiğini ortaya koymuştur. Isıl işlem sonrası borlanan numunlerin bazılarının 5 N yük altında yapılan aşınma testlerinde ısıl işlemli YMÇ’den daha yüksek; 10 ve 15 N yük altındaki testlerde daha düşük aşınma hacim kayıplarına sahip olduğu gözlemlenmiştir. Nitrürlenmiş bütün numuneler hem soğuk haddeli ve hem de ısıl işlemli numunelerden daha iyi aşınma performanlarına sahip oldukları gözlemlenmiştir. Dolayısıyla gaz nitrasyon, borlamaya göre YMÇ’nin aşınma direncini daha çok geliştirmiştir. Borlama ve nitrasyon işlemlerinin soğuk haddeli ve ısıl işlemli orjinal YMÇ’nin korozyon potansiyellerini daha pozitif yöne doğru çektiklerini tespit edilmiştir. Potansiyodinamik polarizasyon testinde, borlamanın genel olarak soğuk haddeli ve ısıl işlemli orjinal YMÇ’nin korozyon hızlarını düşürdükleri tespit edilmiştir. Gaz nitrasyon uygulanan numunelerin hepsinin korozyon hızı soğuk haddeli ve ısıl işlemli orjinal YMÇ’den daha düşük çıkmıştır. Bu da gaz nitrasyonun, borlamaya göre YMÇ’nin korozyon direncini daha iyi geliştirdiği göstermektedir.In this study, after a high manganese steel (HMS) was produced, it was clasiffied two parts as cold rolled and anealled. HMS was annealed at 1000 °C for 30 minutes and cooled in water. HMSs in both groups were borided at 850, 900 and 950 °C for 2, 4 and 6 hours and nitrided for 12, 18 and 24 hours at 520 and 570 °C by using gas nitriding method. XRD analyzes of all samples were carried out, microstructures were examined in SEM, EDS point analysis, EDS elemental mapping and optical microscope, boriding and nitriding layer thicknesses were measured with SEM. The microhardness values of the layers were measured. The adhesion properties of the borided and nitrided layers were investigated by performing adhesion tests according to the VDI 3198 norm. The roughness of sample was investigated. The wear volume losses, wear rates and coefficients of friction (COF) of the samples were determined by the wear test under 5, 10 and 15 N loads. With EDS elemental mapping and EDS linear analysis, the changes in the elemental distributions in the wear trace were determined, and the analyzes were carried out by detecting the wear damage resulting from the wear test from the SEM images. Corrosion tests were performed with potentiodynamic polarization measurement in 3.5% NaCl solution, and corrosion rates were determined. Although HMS is an alloy steel, the “saw tooth morphology” seen in low alloyed and low carbon steels was observed in boronized samples. While ""expanded martensite"" layers were observed at cold-rolled gas nitrided samples, ""white layer"" occured in annealed gas nitrided samples. While the highest hardness was determined in borided samples as 1915 HV0,05, the highest hardness was determined in gas nitrided samples as 1035 HV0,05. Both processes increased the surface hardness of the base material. Although borided samples are classified in HF1-HF3 adhesion quality, all gas nitrided samples are classified in HF1 adhesion quality according to VDI 3198 norm. The roughness tests showed that while unannealed base metal had the lowest roughness with 0.267 µm, HMS annealed and nitrided for 12 hours at 570 °C had highest roughness with 1.759 µm. Wear tests revealed that all nitrided and boronized samples had lower wear volume losses compared to unannealed base metal at all wear test loads and both of these surface treatment improved wear properties of HMS. All nitrided samples also had better wear performance than unannealed base metal and annealed base metal. Gas nitriding process improved the wear resistance of HMS more than boriding process. It has been determined that boriding and nitriding processes caused more nobler the corrosion potentials of unannealed base metal and annealed base metal. In the potentiodynamic polarization test, it was determined that boriding generally reduced the corrosion rates of unannealed base metal and annealed base metal. The corrosion rate of all nitrided samples was lower than unannealed base metal and annealed base metal. It has been observed that gas nitriding improves corrosion resistance better than boriding.
Farklı Sıcaklıklarda Isıl İşlem Uygulanmış Dp 600 Çeliğinin Mekanik Özelliklerinin İncelenmesi
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