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Ti6Al4V titanium alloys are widely used in a variety of scientific and industrial fields. Laser beam welding is one of the most effective techniques for the joining of titanium plates. The main objective of this study was to investigate the influence of the most important laser parameters on welding performance of titanium alloy in two different physical environments such as air and water (i.e., serum) media. Specifically, the laser beam welding of 2 mm thick Ti6Al4V samples was applied using an Nd:YAG laser in open-air welding using argon as a shielding gas, and in wet welding using a serum environment. The deepest penetration was achieved at −3 mm focal position with 11 J of laser energy in both investigated media (i.e., air and serum). The maximum hardness (1130 HV) was achieved for the focal position of −4 mm in serum medium while it was 795 HV for a focal position of −5 mm in air medium. The minimum (1200 μm and 800 μm) and maximum (1960 μm and 1900 μm) weld widths were observed for air and serum medium, respectively. After the welding process, martensite, massif martensite, and transformed martensite were observed in the microstructure of Ti6Al4V. To the best of our knowledge, the underwater wet welding of titanium alloy was carried out and reported for the first time in this study.

Today, dueto the rapidly developing technology, new production techniques are used to utilize natural resources more efficiently. The rapid change and competition conditions brought about by technology cause occupational accidents as a result of some deficiencies and negative situationsin working life. In this study, the situation of mining activities in 5 different classes within occupational accidents was evaluated by using the statistics of Social Security Institution of Turkey (SSI)between the years 2010-2019. In addition, the current situation of mining activities in terms of occupational accidents and occupational diseases in other sectors was analyzed by examining the data of 5 other sectors together.The results ofpresent studyreveal that occupational accidents, related deathsand workday losses are high in the mining sectoramong other sectors.

Purpose: The aim of this study is to investigate the spatial dimensions of the convergence process in the agricultural and non-agricultural sectors, public expenditures, and migration in 81 provinces of Turkey for the 2008-2018 period.Design/methodology/approach: For this purpose, spatial panel data estimation methodology with Driscoll-Kraay estimator is used to capture the effect of space, which is a necessary condition to prevent biased estimates of convergence.Findings: It is clear that structural problems in the agricultural sector restrict interaction with the non-agricultural sector in the provinces and this limits the convergence effect on the agricultural sector. Limited convergence in agricultural sector causes continued income gap between rich and poor provinces in Turkey. In addition to this, migration from the agricultural sector to the non-agricultural sector has an impact on the convergence of both sectors between provinces. Moreover, public expenditures appears to have no direct, indirect or total effect on both agriculture and non-agricultural sectors.Originality/value: To the best of our knowledge, this study is the first to show the spatial dimensions of convergence at sectoral level for provinces of Turkey with relation to public expenditures and migration across agricultural and non-agricultural sectors.

In this study noise measurements were made in a quarry belonging to a private, company located in the boundaries of Karaomerler village, Konya (Turkey). Noise levels were measured at 42 points, in the operation field and equivalent noise levels were determined and the results were mapped using NetCad program. With the help of the obtained noise maps, it is recommended to take preventive measures, where necessary. Proper reading of maps is crucial for effective and sufficient measures in terms of occupational health and safety measures have to be taken.

Kömür oluşumu itibariyle heterojen bir yapıya sahiptir. Bundan dolayı kömürün gazlaşmasınıetkileyen birçok etken vardır. Isıl analiz kömürün gazlaşma özelliklerinin belirlenmesinde ve buetkenlerin kömürün gazlaşma özellikleri üzerindeki etkilerinin incelenmesinde en iyi yöntemlerdenbirisidir. Bu çalışmada Ilgın kömürlerinden alınan numunelerle belirlenen sıcaklıklarda dönüşümsüreleri ve gazlaşma hızları termogravimetrik analiz yöntemiyle belirlenmiş sıcaklığın bu faktörlerüzerindeki etkileri incelenmiştir. Ilgın kömürleri 700°C, 750°C, 800°C ve 850°C sıcaklıklardaCO2 atmosferinde termogravimetrik analiz cihazı kullanılarak gazlaştırılmış dönüşüm oranları vegazlaşma hızları incelenmiş ve numuneler arasında karşılaştırmalar yapılmıştır. Ilgın kömürünün800°C sıcaklıkta diğer sıcaklıklara göre daha kısa sürede dönüşümünün tamamlandığıgörülmüştür.

When the coal is heated, conversion process starting with moisture loss passes through pyrolysis, burning and gasification processes depending on the atmosphere, temperature rise rates, final tempe...

International audience; The study of magnetic bubble configuration in Co/Ni multilayers circular dots under in-plane magnetic field enlightens two magnetic force microscopy (MFM) measurement artifacts. We demonstrate that any tilt of the magnetic field producing out-of-plane field component due to the inhomogeneity of the MFM set up strongly affects the shape and size of the magnetic bubble independently of the in-plane field component intensity. Furthermore, MFM signal variations for in-plane magnetic field larger than 0.1 Tesla can only be understood considering MFM tip magnetization rotation. These two artifacts can have strong impact on MFM images and need to be carefully checked for reliable results in imaging skyrmionic structures with MFM under-field.

Strain modulation during a two-way shape memory effect (TWSME) in a sputtered nitinol NiTi is used to reliably induce and switch by 90° a uniaxial magnetic anisotropy of a 20 nm thick Ni film during the thermal cycle from 300 K to 400 K. NiTi strain and its distribution are carefully measured by digital image correlation during tensile prestrain and subsequent temperature cycles in order to compare with Ni strain extracted from the magnetometry measurement and from transmission electron microscopy. In a NiTi/Ni bilayer, a variation of 2.7% strain in NiTi during the TWSME generates 1.3% strain in Ni, which results in a transition from −2 × 104 J/m3 in-plane magnetic anisotropy to +1 × 105 J/m3. Such a composite system offers a way to timely ease writability while maintaining high thermal stability at rest in magnetic media.

Recently discovered exotic magnetic configurations, namely magnetic solitons appearing in the presence of bulk or interfacial Dzyaloshinskii-Moriya Interaction (i-DMI), have excited scientists to explore their potential applications in emerging spintronic technologies such as race-track magnetic memory, spin logic, radio frequency nano-oscillators and sensors. Such studies are motivated by their foreseeable advantages over conventional micro-magnetic structures due to their small size, topological stability and easy spin-torque driven manipulation with much lower threshold current densities giving way to improved storage capacity, and faster operation with efficient use of energy. In this work, we show that in the presence of i-DMI in Pt/CoFeB/Ti multilayers by tuning the magnetic anisotropy (both in-plane and perpendicular-to-plane) via interface engineering and postproduction treatments, we can stabilize a variety of magnetic configurations such as N\'eel skyrmions, horseshoes and most importantly for the first time, the recently predicted isolated radial vortices at room temperature and under zero bias field. Especially, the radial vortex state with its absolute convergence to or divergence from a single point can potentially offer exciting new applications such as particle trapping/detrapping in addition to magnetoresistive memories with efficient switching, where the radial vortex state can act as a source of spin-polarized current with radial polarization., Comment: 26 pages, 5 figures

The development of catalysts as an alternative to platinum group metals (PGMs) has great importance to improve the efficiency of hydrogen evolution reaction (HER). Herein, the novel amorphous ternary refractory metal selenides (MWSex; M = Co and Ni), which were synthesized by hot-injection approach, were firstly investigated on the electrocatalytic HER in alkaline media. Optical, electrochemical and magnetic properties of the electrocatalysts were explored, as well as the chemical structures and morphologies. These results clearly show that the obtained materials are having the amorphous crystal structure and are shaped as spherical and rod-like structures. Moreover, the addition of Ni and Co metals into the WSex structure were raised the catalytic activity of HER comparing to that of only WSex. This work paves the way for the exploration of copper-based amorphous selenides as electrocatalysts for the hydrogen evolution in order to replace noble metal Pt. © 2019 Elsevier B.V., 32-M-16 Türkiye Bilimler Akademisi 215M309, The authors would like to thank TUBITAK (The Scientific and Technological Research Council of Turkey ) (Grant number: 215M309 ), Karamanoglu Mehmetbey University , Scientific Research Foundation (Grand Number: 32-M-16 ) and Turkish Academy of Sciences via a TUBA-GEBIP fellowship for supporting this work. Appendix A

Bu çalışmada, iş sağlığı ve güvenliği açısından çok önemli olan işyerlerinin aydınlatılması ile ilgili temel bilgiler verilerek iyi bir aydınlatmanın nasıl yapılması gerektiği açıklanmıştır. Yeraltı maden işletmelerinde yeterli aydınlatma koşullarının oluşturulmasının iş sağlığı ve güvenliği açısından önemi ifade edilmiştir. Ayrıca iki farklı yeraltı maden işletmesinde yapılan aydınlatma ölçümleri verilerek yasal sınırlamalar vurgulanmış, yetersiz aydınlatma durumunda yapılması gerekenler ve yaşanabilecek olumsuz durumlar hakkında bilgi verilmiştir, In the present work, an explanation how to make a good illumination is given together with the basic information about lighting. The importance of establishing sufficient lighting conditions in underground mines has been emphasized in terms of occupational health and safety. In addition, legal limitations are also declared by presenting illumination measurements made in two different underground mines and information about what to do in case of inadequate lighting and the possible negative situations are also mentioned

Resistance drift of the amorphous states of multilevel phase change memory (PCM) cells is currently a great challenge for the commercial implementation of a reliable multiple-bit-per-cell memory technology. This paper reports observation of a stable intermediate state for a multilevel PCM cell that is achieved through nonuniform heating with a square current injection top electrode. Drift coefficient of the intermediate state is an order of magnitude lower than reset and has weaker temperature dependence. Using finite-element simulations and an analytical model for the subthreshold current–voltage characteristics, based on thermally activated hopping of charge carriers across Coulombic donor-like traps, we conclude that the defect density is two orders of magnitude larger in the intermediate state. We attribute the low drift coefficient of the intermediate state to a large number of stable interfacial defects which dominate the electron transport. Current findings give way to a more stable ultrahigh-density PCM device.

A number of physical features of coal can be determined as the function of temperature by the utilization of thermal treatment applied to coal itself. The most common techniques encountered in literature on this matter are differential thermal analysis, thermogravimetric analysis, and differential thermogravimetric analysis. In this article, the thermogravimetric behavior and physicochemical characteristics of some Turkish coals have been defined. Additionally, the relationship between these characteristics of the coal samples has also been given in a statistical manner.

In this work, experiments were undertaken in an open field having 10,000 m2 area purified from any noise on 121 survey stations using the central frequencies of seven different octave bands with a single and double artificially formed sources of noise. Meteorological parameters such as temperature, humidity, atmospheric pressure, velocity and direction of wind were also taken into consideration. Additionally, the effect of reflecting waves from any surface was also experimentally examined. To evaluate the data obtained, the statistical program of SPSS 9.05 was utilized. From this research, an equation utilising all the parameters was developed. © Springer Science+Business Media B.V. 2008., Acknowledgement Support given to achieve this work by the scientific research fund of Selcuk University is greatly acknowledged.

The high contrast in the electrical resistivity between amorphous and crystalline states of a phase change material can potentially enable multiple memory levels for efficient use of a data storage medium. We report on our investigation of the role of the current injection site geometry (circular and square) in stabilizing such intermediate states within a nanoscale single-phase change material system (Ge2Sb2Te5). We have developed a three dimensional multiphysics model, which includes phase change kinetics, electrical, thermal, thermoelectric, and percolation effects, all as a function of temperature, using an iterative approach with coupled differential equations. Our model suggests that the physical origin of the formation of stable intermediate states in square top contact devices is mainly due to anisotropic heating during the application of a programming current pulse. Furthermore, the threshold current requirement and the width of the programming window are determined by crystallite nucleation and ...