Influence of thermal pretreatments on dimensional change and humidity sensitivity of densified spruce and poplar wood

The effect of thermal pretreatments on the dimensional change and humidity sensitivity of densified spruce (Picea orientalis) and poplar (Populus nigra) wood were investigated. A thermal pretreatment was applied on the wood specimens at 140 °C, 160 °C, 180 °C, and 200 °C for 7 h and 9 h. Wood specimens were then compressed at ratios of 20 % and 40 % at a temperature of 150 °C. The results showed that spring-back and thickness swelling increased in all specimens (thermally pre-treated and untreated) depending on the increase in compression ratio. However, set-recovery was determined higher at 20 % compression ratio. The equilibrium moisture content values ​​of untreated specimens and thermally pre-treated specimens at low temperatures (140 ºC and 160 ºC) were found lower than uncompressed specimens. The impact of compression ratio on equilibrium moisture content was not clear. Thermal pretreatments significantly affected the dimensional stability and hygroscopicity of densified specimens (especially poplar wood). Depending on the increase in thermal pretreatment temperature and duration, spring-back, set-recovery and thickness swelling in wood specimens decreased up to 31 %, 67 % and 62 %, respectively. In addition, equilibrium moisture content and water absorption decreased with the increase in thermal pretreatment temperature and duration. Moreover, the thermal treatment temperature was more important than duration on the investigated properties

HASTANE ÇALIŞANLARINDA KONTROL ODAĞININ ÖZ VE KOLEKTİF YETERLİLİK ÜZERİNE ETKİSİ

Kontrol odağı kavramı kişilerin yaptıkları bir işin sonucunu üstlenme durumu ile ilgilenirken; öz ve kolektif yeterlilik kavramları yapacakları işi yapabilme noktasında kendilerinde oluşan inanç ile ilgilenmektedir. Sağlık sektörünün sürekli gelişim içinde olan ve büyük sorumluluk gerektiren bir hizmet sektörü olması, bu nedenle de bu sektörde çalışanların hem yaptığı şeylerin sonuçlarının sorumluluğunu üstlenmesi hem de çalışanların görevini yaparken kendisine olan güveninin tam olması daha iyi bir hizmet verilmesi için önemlidir. Bu araştırmada hastane çalışanlarında kontrol odağı algısının öz ve kolektif yeterlilik algıları üzerine etkisinin araştırılması hedeflenmiştir. Araştırma da kontrol odağı boyutlarının bazılarının hastane çalışanlarının öz ve kolektif yeterlilik algıları üzerinde pozitif yönde etki yaparken bazılarının ise öz ve kolektif yeterlilik algıları üzerinde negatif etkiye sahip olduğu sonucuna ulaşılmıştır

Determination of some physical and mechanical properties of heat treated and thermo-mechanical densified eastern spruce (Picea orientalis) and black poplar (Populus nigra) woods

YÖK Tez No: 561390Bu çalışmada, farklı sıcaklık ve sürelerde ısıl işlem uygulandıktan sonra termo-mekanik olarak yoğunlaştırılmış ağaç malzemelerin bazı fiziksel, mekanik ve teknolojik özelliklerinin belirlenmesi amaçlanmıştır. Doğu ladini (Picea orientalis) ve kara kavak (Populus nigra) odunlarından hazırlanmış olan örnekler, atmosferik basınç ortamında dört farklı sıcaklık (140 °C, 160 °C, 180 °C ve 200 °C) ve iki farklı sürede (7 ve 9 saat) ısıl işleme tabi tutulmuştur. Isıl işlemli örnekler daha sonra hidrolik bir pres kullanılarak 150 °C sıcaklıkta %20 ve %40 sıkıştırma oranları ile yoğunlaştırılmıştır. Deney örneklerinin fiziksel özelliklerini belirlemek için geri esneme oranı, hava kurusu yoğunluk, su alma (absorpsiyon) oranı ve sıkıştırma yönü (radyal) şişme oranı; mekanik direnç özelliklerini belirlemek için ise statik eğilme direnci, eğilmede elastikiyet modülü, liflere paralel basınç direnci ve Brinell sertlik testleri gerçekleştirilmiştir. Çalışma sonuçlarına göre, ısıl işlemli örneklerde yoğunluk ve mekanik direnç özellikleri genel olarak işlem sıcaklığı ve süresindeki artışa bağlı olarak azalmıştır. Yoğunlaştırılmış örneklerde ise, ön ısıl işlemler sayesinde geri esneme oranı ile su alma oranı azalmış ve boyutsal stabilitede %60'a kadar bir iyileşme sağlanmıştır. Diğer taraftan, direnç kayıpları yaşanan ısıl işlemli örneklerde, yoğunlaştırma modifikasyonu sonrası yoğunluk, mekanik direnç ve sertlik özellikleri sıkıştırma oranına bağlı olarak önemli ölçüde artış göstermiştir. Elde edilen sonuçlara göre, hem ısıl işlem hemde yoğunlaştırma modifikasyonunun ağaç malzeme üzerindeki olumsuz etkilerini bertaraf etmek için bu iki yöntemin birlikte kullanılması önerilebilir. Anahtar sözcükler: Ağaç malzeme, Fiziksel ve mekanik özellikler, Isıl işlem, Yoğunlaştırma.In this study, it was aimed to determine some physical, mechanical and technological properties of thermo-mechanical densified wood materials after heat treatment at different temperatures and durations. Specimens prepared from Eastern spruce (Picea Orientalis) and black poplar (Populus nigra) woods were subjected to heat treatment in atmospheric pressure environment at four different temperatures (140 °C, 160 °C, 180 °C and 200 °C) and two different duration (7 and 9 h). Heat-treated samples were then densified using a hydraulic press at 150 °C with compression ratios of 20% and 40%. In the test specimens, the spring-back ratio, air-dry density, water absorption and compression direction (radial) swelling ratio were performed to determine the physical properties while static bending strength, modulus of elasticity, compression strength parallel to fibers and Brinell hardness tests were performed in order to determine mechanical properties. According to the results of the study, the density and mechanical strength properties of the heat treated specimens decreased in general due to the increase in the process temperature and duration. In the densified specimens, the spring-back and the water absorption decreased due to the heat pre-treatments and an improvement of up to 60% in dimensional stability was achieved. On the other hand, in heat treated specimens where strength losses occurred, density, mechanical strength and hardness properties after densification modification demonstrated a significant increase depending on compression ratio. According to the obtained results, it can be suggested to use these two methods together in order to eliminate the negative effects of both heat treatment and densification modification on the wood material

Influence of Densification on Mechanical Properties of Thermally Pretreated Spruce and Poplar Wood

WOS: 000493997400153The effects of mechanical densification on density, Brinell hardness, bending strength (MOR), modulus of elasticity (MOE), and compression strength (CS) of thermally pretreated spruce (Picea orientalis) and poplar (Populus nigra) wood samples were investigated. Thermal treatment was applied on the wood samples at four different temperatures (140 degrees C, 160 degrees C, 180 degrees C, and 200 degrees C) and two different durations (7 h and 9 h) under atmospheric pressure. Wood samples were then densified by compression at a temperature of 150 degrees C to two degrees (20% and 40%) of compression. The results indicated that the density, hardness, and MOR values of both compressed and non-compressed thermally pretreated spruce and poplar samples decreased with increasing treatment temperature and duration. At temperatures below 200 degrees C, the MOE was generally increased in thermally pretreated samples. However, the MOE was reduced in thermally pretreated samples at 200 degrees C compared to the untreated samples. Additionally, all thermal pretreatments increased CS values in compressed and non-compressed wood samples. The CS tended to decrease in thermally pretreated samples (especially 40% compressed) at 200 degrees C. After the densification, all of the strength properties tested in thermally pretreated samples increased significantly depending on the increase in compression ratio.Research Fund of Duzce UniversityDuzce University [BAP-2018.07.01.673]The authors are grateful for the support of the Research Fund of Duzce University, Grant No. BAP-2018.07.01.673

A Steep mountain to cross: an evaluation of the PH.D. proficiency process from the perspective of students

In Türkiye, postgraduate students are required to take the "Ph.D. proficiency exam" to pass the thesis stage and complete their education after completing their doctoral course period. The "proficiency process," which manifests itself as a long, difficult and stressful process, seems like a "steep mountain to cross" in the lives of doctoral students. This research examines the Ph.D. proficiency process from doctoral students' perspectives and determines the results. The interpretative phenomenological design, one of the qualitative research methods, was used; with the criterion sampling method, which is one of the purposive sampling methods, interviews were conducted with 9 participants and 55 pages of data were obtained, and the data were analyzed with thematic analysis. When the proficiency exam is evaluated as a whole, it has been determined that it has some positive and negative results. At the end of this whole process, the proficiency exam has gained meaning as a "compelling process," "learning and development process," "great exam," "understanding of inadequacy," and "an indescribable process." The information obtained from the research is a guide for students who will take the exam in the future. In addition, based on the research results, suggestions for students and suggestions for the exam are presented

Prevalence and predictors of gestational diabetes mellitus: a nationwide multicentre prospective study

Cetinkaya, Esra/0000-0003-2415-1236; Taskiran, Bengur/0000-0003-4842-450X; MELEKOGLU, RAUF/0000-0001-7113-6691; pekkolay, zafer/0000-0002-5323-2257; Ozer, Alev/0000-0002-0934-0226; kilinc, faruk/0000-0002-0198-2558; Aygun, Elif Ganime/0000-0003-3737-7250; KARAKILIC, ERSEN/0000-0003-3590-2656; Aydin, Hasan/0000-0003-4246-0681WOS: 000457530200011PubMed: 30402933Aim Prevalence rates of gestational diabetes mellitus (GDM) show considerable variation among different countries and regions of the world. The primary aim of this study was to determine the nationwide prevalence and predictors of GDM in Turkey. Methods We conducted prospective nationwide screening among pregnant women. Between August 2016 and November 2017, a total of 2643 pregnant women from 51 centres in 12 different regions were enrolled. A two-step screening method and Carpenter and Coustan criteria were used in the diagnosis of GDM. Clinical and biochemical data were obtained using electronic database software. Results The national prevalence of GDM was found to be 16.2% [95% confidence intervals (CI) 15.0% to 17.4%] without a significant difference between urban and rural regions. Women with GDM were older (mean age: 32 +/- 5 vs. 28 +/- 5 years, P < 0.001) and heavier (mean BMI: 27.2 +/- 5.1 vs. 24.7 +/- 4.7 kg/m(2), P < 0.001) than their counterparts without GDM. The prevalence of GDM tended to increase with age (< 25 years, 6.9%; 26-35 years, 15.6%; and 36-45 years, 32.7%; P < 0.001). Maternal age, maternal BMI, history of previous GDM and family history of diabetes mellitus were independent predictors of developing GDM (P < 0.05 for all). Low-risk women (age < 25 years, BMI < 25 kg/m(2), no family history of diabetes) comprised 10.7% of the total population and the prevalence of GDM in these women was 4.5% (95% CI 2.4% to 7.8%). Conclusion The results of this nationwide study indicate that GDM is very common, affecting one in seven pregnancies in Turkey. Implementation of international guidelines on screening and management of this public health problem is required