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Determination of local site soil conditions by microtremor measurements for sustainable buildings
(Proceedings of 3rd International Sustainable Buildings Symposium (ISBS 2017), 2018) Subaşı, Ozan; Özaslan, Bilal; Haşal, Murat Emre; Hiroaki, Yamanaka; Chimoto, Kosuke
As well known, local soil condition at a specific site affects the significant features of strong ground motion such as amplitude, frequency range and time duration. The effects of site condition depend on the properties of the motion characteristics, material properties, topography and geometry of the field. The bedrock slope at the basin sides also is one of the most important factors in the response analyzing of a specific site in geotechnical earthquake engineering applications. The reflection and refraction waves from the basin edges induce the wave transmission and two dimensional effects. In this case two dimensional site response analyses are required to estimate the behavior of the soil layers. So, local geotechnical site condition should be into account in the design of earthquake resistant building. The bedrock slope of the basin edges should be determined for suitable method in two dimensional dynamic response analyses. In this study, the result of a specific site response based on shear wave velocity profiles determined by microtremor array measurements are presented. The geotechnical properties of the soil layers were obtained from the previous subsurface explorations. Seismic bedrock depth and bedrock slope of the edge were defined by microtremor array measurements. Shear wave velocity value is from ten to hundred meters was obtained from passive surface wave method by employed Spatial Auto Correlation algorithm. Established variation of shear wave velocity with depth models were examined in terms of local site amplification. In order to verify consistency of obtained amplification numbers, empirical and measuremental results were compared for each site. As a conclusion, dynamic properties of local site conditions under earthquake excitation were described in terms of maximum amplification, resonance frequency and predominant period.
Fiscal spending multipliers over the household leverage cycle
(Elsevier, 2022) Polattimur, Hamza; Klein, Mathias; Winkler, Roland
This paper investigates household leverage-dependent fiscal policy effects in a two-agent New Keynesian DSGE model with occasionally binding borrowing constraints. Our model successfully replicates empirical evidence showing that fiscal policy’s effectiveness differs significantly across the household leverage cycle. Fiscal multipliers are persistently above unity when government spending rises at the peak of the household leverage cycle. In contrast, increases in government spending at the trough of the household leverage cycle imply fiscal multipliers below unity. We test the model’s predictions on post-WWII U.S. data.
Improvement of thermal stability and gamma-rayabsorption in microwave absorbable poly(methylmethacrylate)/graphene nanoplatelets nanocomposite
(Journal of Applied Polymer Science, 2021) Gül, Furkan Berke; Bel, Tayfun; Muhammettursun, Mahmut; Kocacinar, Elif; Erman, Ecem; Doğan, Emre; Celep, Murat; Baydoğan, Nilgün
The graphene nanofiller (2 wt%) was dispersed in poly(methyl methacrylate) byin situ polymerization method. The optimum high frequency (microwave)absorption was evaluated at X-band due to changes in the scattering parameters(determined by using a vector network analyzer). The slight improvement hasbeen attained in gamma attenuation coefficient of the polymer nanocompositeby using gamma transmission technique. The addition of graphene nanoplatelets(2 wt%) resulted in a thermal improvement from 196.73 to 243.00 C (with 5%weight loss) in TGA analysis. The graphene nanoplatelets provided an optimumdecrease in scattering of the microwaves due to the elimination of the defectsand the prevention of the agglomeration of the graphene nanoplates. Theimprovement of microwave absorption (between 8 and 12 GHz) suggested thatthe nanocomposite was a suitable candidate as a microwave absorbing material.This multipurpose nanocomposite has provided thermal stability and it hasensured the optimum gamma-ray and microwave absorption depending on thedevelopment of the structural properties. The development of these physicalcharacteristics has enabled to improve the electrical conductivity as a result ofthe progress in the structural properties.
Investigation of Cu whisker growth by molecular beam epitaxy
(Walter de Gruyter, 2021) Elibol, Çağatay; Strunk, Horst Paul
There is a trend towards smaller and smaller structures (nanostructures/miniaturization) which is well known in microelectronic, energy and semiconductor applications. Nanoengineering is expected to lead to significant improvements in the intrinsic properties of structures, e. g., in energy storage for supercapacitors. In this context, a deeper understanding of the growth mechanisms of the thinnest crystal layers is of crucial importance for the controlled growing of nanowhiskers with outstanding properties. In the present study, we consider a simple whisker growth model based on the surface energy (i. e., wettability) of the components and investigate the effect of the carbon interlayer deposited on a Si (111) wafer using the magnetron sputtering technique on the whisker formation during the subsequent molecular beam epitaxy process in the Si-C-Cu system. In the present study, the topographic holes in the carbon layer which are the preferred nucleation areas of whiskers were identified by a series of scanning tunneling microscopy analyses, and the natural hole density was statistically determined. Using atomic force microscopy, the surface roughness of the carbon layer was characterized. The results of our investigations indicate that there is a correlation between the hole density in the carbon layer and the density of Cu nanowhiskers. This may validate the supposition that the holes in the carbon layer are the preferred nucleation sites for whiskers - an effect that could be relevant for future works on the growth of nanowhiskers at predefined positions.
Simple processes for the preparation of superhydrophobic polymer surfaces
(Elsevier, 2016) Söz, Çağla; Yılgör, Emel; Yılgör, İskender
Two simple processes; (i) spin-coating, and (ii) doctor blade coating of silica/polymer dispersions are described for the preparation of superhydrophobic polymer surfaces. To demonstrate the versatility and broad applicability of the processes, polymeric surfaces modified included a thermoplastic resin, polystyrene (PS) and a thermoset, crosslinked epoxy resin (ER). Micro/nano hierarchical nature of the surface topographies obtained were demonstrated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and white light interferometry (WLI) studies. Roughness factor (r) and average surface roughness (Ra) values, which are critical in obtaining superhydrophobic surfaces were determined for each polymeric system. It was clearly demonstrated that increased (r) and (Ra) values resulted in superhydrophobic behavior with very high static, advancing and receding water contact angles, well above 150° and contact angle hysteresis values of less than 10°. Incorporation of small amounts (1.0% by weight) of a silicone copolymer or a perfluoroether glycol oligomer reduced the contact angle hysteresis in the epoxy resin system well below 10° and produced truly superhydrophobic surfaces.
Fumed silica filled poly(dimethylsiloxane-urea) segmented copolymers: Preparation and properties
(Elsevier, 2011) Yılgör, Emel; Yılgör, İskender; Eynur, Tuğba; Söz, Çağla; Malay, Özge; Menceloğlu, Yusuf Ziya; Wilkes, Garth L.
Novel fumed silica filled thermoplastic poly(dimethylsiloxane-urea) (TPSU) segmented copolymers were synthesized and characterized. TPSU copolymers were prepared from a cycloaliphatic diisocyanate, aminopropyl terminated PDMS oligomers with number average molecular weights of 3,200, 10,800 and 31,500 g/mol and 2-methyl-1,5-diaminopentane chain extender. Two different types of fumed silica HDK H2000 (hydrophobic) and HDK N20 (hydrophilic) were utilized and incorporated into silicone-urea copolymers in amounts of 1–60% by weight. Influence of the silica type (hydrophilic versus hydrophobic), amount of silica loading and the PDMS soft segment molecular weight on the morphology, tensile properties and modulus-temperature behavior of the nanocomposites were determined. Major observations of this study were: (i) under the blending conditions used, incorporation of silica does not seem to interfere significantly with the hydrogen bonding between urea groups, (ii) incorporation of silica does not affect the glass transition temperature of PDMS, (iii) incorporation of silica influences the tensile and thermomechanical properties of silicone-urea segmented copolymers significantly, (iv) average molecular weight of the PDMS soft segment in the silicone-urea copolymer plays a critical role on the improvement of the tensile properties of the fumed silica/TPSU composites.
Effect of soft segment molecular weight on tensile properties of poly(propylene oxide) based polyurethaneureas
(Elsevier, 2012) Ertem, Sedef Pırıl; Yılgör, Emel; Söz, Çağla; Wilkes, Garth L.; Zhang, Mingqiang; Yılgör, İskender
Influence of soft segment molecular weight and hard segment content on the morphology, thermomechanical and tensile properties of homologous polyurethaneurea copolymers based on narrow molecular weight poly(propylene oxide)glycol (PPG) oligomers were investigated. A series of polyurethaneureas with hard segment contents of 12–45% by weight and PPG number average molecular weights of 2000 to 11,800 g/mol were synthesized and characterized structurally by SAXS and mechanically by DMA and stress strain analysis. Bis(4-isocyanatocyclohexyl)methane and 2-methyl-1,5-diaminopentane were used as the diisocyanate and the chain extender respectively. All copolymers displayed microphase separation by SAXS and DMA. The critical entanglement molecular weight (Me) of PPG is reported to be around 7700 g/mol. Our mechanical results suggest that when copolymers possess similar hard segment contents and are compared to those based on soft segments with number average molecular weights (Mn) greater than Me, they generally displayed higher tensile strengths and particularly lower hysteresis and creep than those having soft segment molecular weights below Me. These results imply that soft segment entanglements in thermoplastic polyurethaneureas may provide a critical contribution to the tensile properties of these copolymers – particularly in the range where the soft segment content is dominant.
Polyurethaneurea–silica nanocomposites: Preparation and investigation of the structure–property behavior
(Elsevier, 2013) Malay, Özge; Oğuz, Oğuzhan; Söz, Çağla; Yılgör, Emel; Yılgör, İskender; Menceloğlu, Yusuf Ziya
Nanocomposites consisting of thermoplastic polyurethane–urea (TPU) and silica nanoparticles of various size and filler loadings were prepared by solution blending and extensively characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermal analysis, tensile tests, and nanoindentation. TPU copolymer was based on a cycloaliphatic diisocyanate and poly(tetramethylene oxide) (PTMO-2000) soft segments and had urea hard segment content of 20% by weight. TPU/silica nanocomposites using silica particles of different size (29, 74 and 215 nm) and at different loadings (1, 5, 10, 20 and 40 wt. %) were prepared and characterized. Solution blending using isopropyl alcohol resulted in even distribution of silica nanoparticles in the polyurethane–urea matrix. FTIR spectroscopy indicated strong interactions between silica particles and polyether segments. Incorporation of silica nanoparticles of smaller size led to higher modulus and tensile strength of the nanocomposites, and elastomeric properties were retained. Increased filler content of up to about 20 wt. % resulted in materials with higher elastic moduli and tensile strength while the glass transition temperature remained the same. The fracture toughness increased relative to neat TPU regardless of the silica particle size. Improvements in tensile properties of the nanocomposites, particularly at intermediate silica loading levels and smaller particle size, are attributed to the interactions between the surface of silica nanoparticles and ether linkages of the polyether segments of the copolymers.
Influence of the average surface roughness on the formation of superhydrophobic polymer surfaces through layer-by-layer spin-coating with hydrophobic fumed silica
(Elsevier, 2015) Söz, Çağla; Yılgör, Emel; Yılgör, İskender
Formation of superhydrophobic polymer surfaces were investigated through successive spin-coating of hydrophobic fumed silica dispersed in an organic solvent onto polymer films. Two different polymers, a hydrophobic segmented silicone-urea copolymer (TPSC) and hydrophilic poly(methyl methacrylate) (PMMA) were used as model substrates. Influence of the polymer type and structure, silica concentration and the number of silica layers applied on the topography, average roughness and the wetting behavior of the surfaces were determined. Polymer surfaces obtained were characterized by scanning electron microscopy, white light interferometry, atomic force microscopy and advancing and receding water contact angle measurements. It was possible to obtain superhydrophobic surfaces displaying hierarchical micro/nano features both for TPSC and PMMA. A close correlation was observed between the number of silica layers applied and average surface roughness obtained. It was demonstrated that an average surface roughness value of 125–150 nm was necessary for the formation of superhydrophobic surfaces, both for TPSC and PMMA. Chemical structure and nature of the polymeric substrate seem to play a significant role on the topography and average roughness of the silica coated surfaces formed. Superhydrophobic surfaces displayed static and advancing water contact angles well above 150° and fairly small contact angle hysteresis.
Influence of the coating method on the formation of superhydrophobic silicone–urea surfaces modified with fumed silica nanoparticles
(Elsevier, 2015) Söz, Çağla; Yılgör, Emel; Yılgör, İskender
Effect of the coating method on the formation of superhydrophobic polydimethylsiloxane–urea copolymer (TPSC) surfaces, modified by the incorporation of hydrophobic fumed silica nanoparticles was investigated. Four different coating methods employed were: (i) layer-by-layer spin-coating of hydrophobic fumed silica dispersed in an organic solvent onto TPSC films, (ii) spin-coating of silica–polymer mixture onto a glass substrate, (iii) spray coating of silica/polymer mixture by an air-brush onto a glass substrate, and (iv) direct coating of silica–polymer mixture by a doctor blade onto a glass substrate. Influence of the coating method, composition of the polymer/silica mixture and the number of silica layers applied on the topography and wetting behavior of the surfaces were determined. Surfaces obtained were characterized by scanning electron microscopy (SEM), white light interferometry (WLI) and advancing and receding water contact angle measurements. It was demonstrated that superhydrophobic surfaces could be obtained by all methods. Surfaces obtained displayed hierarchical micro-nano structures and superhydrophobic behavior with static and advancing water contact angles well above 150° and fairly low contact angle hysteresis values.
Effect of filler content on the structure-property poly(ethylene oxide) based polyurethaneurea-silica nanocomposites
(Wiley, 2017) Oğuz, Oğuzhan; Şimsek, Eren; Söz, Çağla; Kasli Heinz, Özge; Yılgör, Emel; Yılgör, İskender; Menceloğlu, Yusuf Ziya
Poly(ethylene oxide) (PEO) based polyurethaneurea?silica nanocomposites were prepared by solution blending and characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Differential Scanning Calorimetry and tensile testing. The colloidal silica nanoparticles with an average size of 50 nm were synthesized by modified Stöber method in isopropanol. Silica particles were incorporated into three cycloaliphatic polyurethaneurea (PUs) copolymers based on PEO oligomers with molecular weights of 2,000, 4,600, and 8,000 g/mol. Hard segment content of PUs was constant at 30% by weight. Silica content of the PU nanocomposites varied between 1 and 20% by weight. Soft segment (SS) glass transition and melting temperatures slightly increased with increasing filler content for all the copolymers. Degree of SS crystallinity first increased with 1% silica incorporation and subsequently decreased by further silica addition. Elastic modulus and tensile strengths of PU copolymers gradually increased with increasing amount of the silica filler. Elongation at break values gradually decreased in PEO?2000 based PU copolymer with increasing silica content, whereas no significant change was observed in PUs based on PEO?4600 and PEO?8000. Enhancement in tensile properties of the materials was mainly attributed to the homogeneous distribution of silica filler in polymer matrices and strong polymer?filler interactions.
3D coffee stain
(Royal Society of Chemistry, 2017) Doğru, Itır Bakış; Söz, Çağla; Press, Daniel Aaron; Melikov, Rustamzhon; Begar, Efe; Çonkar, Deniz; Fırat Karalar, Elif Nur; Yılgör, Emel; Yılgör, İskender
When a liquid droplet (e.g., coffee, wine, etc.) is splattered on a surface, the droplet dries in a ring-shaped stain. This widely observed pattern in everyday life occurs due to the phenomenon known as a coffee stain (or coffee ring) effect. While the droplet dries, the capillary flow moves and deposits the particles toward the pinned edges, which shows a 2D ring-like structure. Here we demonstrate the transition from a 2D to a 3D coffee stain that has a well-defined and hollow sphere-like structure, when the substrate surface is switched from hydrophilic to superhydrophobic. The 3D stain formation starts with the evaporation of the pinned aqueous colloidal droplet placed on a superhydrophobic surface that facilitates the particle flow towards the liquid–air interface. This leads to spherical skin formation and a cavity in the droplet. Afterwards the water loss in the cavity due to pervaporation leads to bubble nucleation and growth, until complete evaporation of the solvent. In addition to the superhydrophobicity of the surface, the concentration of the solution also has a significant effect on 3D coffee stain formation. Advantageously, 3D coffee stain formation in a pendant droplet configuration enables the construction of all-protein lasers by integrating silk fibroin with fluorescent proteins. No tools, components and/or human intervention are needed after the construction process is initiated; therefore, 3D coffee-stains hold promise for building self-assembled and functional 3D constructs and devices from colloidal solutions.
Wetting behavior of superhydrophobic poly(methyl methacrylate)
(Elsevier, 2018) Yılgör, Emel; Söz, Çağla; Yılgör, İskender
Superhydrophobic PMMA surfaces were prepared by spin-coating and doctor blade coating of PMAA/hydrophobic silica (1/10 by weight) dispersions in toluene onto glass substrates. Influence of the number of coating layers applied and gauge thickness of the doctor blade used on surface properties were investigated. Formation of dual scale, micro/nano surface topographies were demonstrated by scanning electron microscopy, atomic force microscopy and white light interferometry studies. Roughness factor (r) and average surface roughness (Ra) values of the surfaces were determined. Wetting behavior of superhydrophobic PMMA surfaces obtained by introducing micro-nano, hierarchical roughness to inherently hydrophilic smooth PMMA films cannot be explained by Wenzel model. Therefore, wetting behavior of these surfaces were analyzed using Cassie-Baxter model and area fraction of surface protrusions were estimated.
Analysis of correlation between white matter changes and functional responses in thalamic stroke: a DTI & EEG study
(Springer, 2015) Duru, Adil Deniz; Göksel Duru, Dilek; Yumerhodzha, Sami; Bebek, Nerses
Diffusion tensor imaging (DTI) allows in vivo structural brain mapping and detection of microstructural disruption of white matter (WM). One of the commonly used parameters for grading the anisotropic diffusivity in WM is fractional anisotropy (FA). FA value helps to quantify the directionality of the local tract bundle. Therefore, FA images are being used in voxelwise statistical analyses (VSA). The present study used Tract-Based Spatial Statistics (TBSS) of FA images across subjects, and computes the mean skeleton map to detect voxelwise knowledge of the tracts yielding to groupwise comparison. The skeleton image illustrates WM structure and shows any changes caused by brain damage. The microstructure of WM in thalamic stroke is investigated, and the VSA results of healthy control and thalamic stroke patients are reported. It has been shown that several skeleton regions were affected subject to the presence of thalamic stroke (FWE, p < 0.05). Furthermore the correlation of quantitative EEG (qEEG) scores and neurophysiological tests with the FA skeleton for the entire test group is also investigated. We compared measurements that are related to the same fibers across subjects, and discussed implications for VSA of WM in thalamic stroke cases, for the relationship between behavioral tests and FA skeletons, and for the correlation between the FA maps and qEEG scores.Results obtained through the regression analyses did not exceed the corrected statistical threshold values for multiple comparisons (uncorrected, p < 0.05). However, in the regression analysis of FA values and the theta band activity of EEG, cingulum bundle and corpus callosum were found to be related. These areas are parts of the Default Mode Network (DMN) where DMN is known to be involved in resting state EEG theta activity. The relation between the EEG alpha band power values and FA values of the skeleton was found to support the cortico-thalamocortical cycles for both subject groups. Further, the neurophysiological tests including Benton Face Recognition (BFR), Digit Span test (DST), Warrington Topographic Memory test (WTMT), California Verbal Learning test (CVLT) has been regressed with the FA skeleton maps for both subject groups. Our results corresponding to DST task were found to be similar with previously reported findings for working memory and episodic memory tasks. For the WTMT, FA values of the cingulum (right) that plays a role in memory process was found to be related with the behavioral responses. Splenium of corpus callosum was found to be correlated for both subject groups for the BFR.
Acute changes in electrophysiological brain dynamics in elite karate players
(Springer, 2020) Duru, Adil Deniz; Balcıoğlu, Taylan Hayri; Özcan Çakır, Canan Elif; Göksel Duru, Dilek
Regular physical exercise has enhanced effects on the human anatomy and functionality. Recently, an effect of a single set of exercise is shown to have positive effects on mood and on cognitive functioning. The aim of this study is to investigate the effect of a single bout of moderate exercise on the brain electrophysiological dynamics in resting-state condition and under the mental workload situation from elite-level athletes. For this purpose, electroencephalogram (EEG) is measured before and after the exercise sessions from 17 elite karate players who are members of the national karate team of Turkey. Blood lactate measurements are implemented to monitor the volunteers before EEG measurements. EEG data are analyzed using three metrics: conventional band power of each electrode, coherence metrics between electrodes for each band and source coherence values corresponding to each frequency band. Each metric is statistically analyzed between pre- and post-values, and results revealed that in all frequency bands, right parietal electrode had increased connection values which are thought to be related to ongoing sympathetic nervous system response observed during the recovery period. Another finding is the enhanced connectivity of frontal sources under the resting state as well as during the increased mental workload periods.
Application of self-organizing artificial neural networks on simulated diffusion tensor images
(Hindawi Publishing Corporation, 2013) Göksel Duru, Dilek; Özkan, Mehmed
Diffusion tensor magnetic resonance imaging (DTMRI) as a noninvasive modality providing in vivo anatomical information allows determination of fiber connections which leads to brain mapping. The success of DTMRI is very much algorithm dependent, and its verification is of great importance due to limited availability of a gold standard in the literature. In this study, unsupervised artificial neural network class, namely, self-organizing maps, is employed to discover the underlying fiber tracts. A common artificial diffusion tensor resource, named “phantom images for simulating tractography errors” (PISTE), is used for the accuracy verification and acceptability of the proposed approach. Four different tract geometries with varying SNRs and fractional anisotropy are investigated. The proposed method, SOFMAT, is able to define the predetermined fiber paths successfully with a standard deviation of (0.8–1.9) × 10?3 depending on the trajectory and the SNR value selected. The results illustrate the capability of SOFMAT to reconstruct complex fiber tract configurations. The ability of SOFMAT to detect fiber paths in low anisotropy regions, which physiologically may correspond to either grey matter or pathology (abnormality) and uncertainty areas in real data, is an advantage of the method for future studies.
Fachtagung der Hochschule für Fremdsprachen der Türkisch-Deutschen Universität zum Thema ,,sprach-und kulturkontakte im Deutsch-Türkischen kontext"
(2015) Yüce, Nilgün
Am 8. Mai 2015 fand im Konferenzsaal der Türkisch-Deutschen Universität in Beykoz eine Fachtagung der Hochschule für Fremdsprachen der Türkisch-Deutschen Universität zum Thema „Sprach- und Kulturkontakte im deutsch-türkischen Kontext“ statt. Dies war bereits die zweite internationale Tagung der Hochschule für Fremdsprachen der TDU, nachdem schon am 9. Mai 2013 eine erste Veranstaltung zum Thema „Sprach- und Fachsprachenunterricht – studienvorbereitender und studienbegleitender Deutschunterricht für fremdsprachige Studiengänge“ stattgefunden hatte. Die von Assoc. Prof. Dr. Aysel Uzuntaş (Türkisch-Deutsche Universität) und Prof. Dr. Uwe Koreik (Universität Bielefeld, K-TDU) gemeinsam organisierte Tagung beinhaltete die thematischen Schwerpunkte „Deutsch-Türkische Begegnungen“, „Türkisch-Deutsche Zweisprachigkeit“, „Deutsche und Türkische Kultur in der Literaturwelt“ und „Deutsch als Fremdsprache und kulturelle Perspektiven“.
Design criteria for a high energy Compton Camera and possible application to targeted cancer therapy
(Iop Publishing Ltd, 2015) Çonka Yıldız, Tuba; Nurdan, Kıvanç; Brill, Aaron B.; Walenta, A. H.
The proposed research focuses on the design criteria for a Compton Camera with high spatial resolution and sensitivity, operating at high gamma energies and its possible application for molecular imaging. This application is mainly on the detection and visualization of the pharmacokinetics of tumor targeting substances specific for particular cancer sites. Expected high resolution (< 0.5 mm) permits monitoring the pharmacokinetics of labeled gene constructs in vivo in small animals with a human tumor xenograft which is one of the first steps in evaluating the potential utility of a candidate gene. The additional benefit of high sensitivity detection will be improved cancer treatment strategies in patients based on the use of specific molecules binding to cancer sites for early detection of tumors and identifying metastasis, monitoring drug delivery and radionuclide therapy for optimum cell killing at the tumor site. This new technology can provide high resolution, high sensitivity imaging of a wide range of gamma energies and will significantly extend the range of radiotracers that can be investigated and used clinically. The small and compact construction of the proposed camera system allows flexible application which will be particularly useful for monitoring residual tumor around the resection site during surgery. It is also envisaged as able to test the performance of new drug/gene-based therapies in vitro and in vivo for tumor targeting efficacy using automatic large scale screening methods.
Single-shot full strain tensor determination with microbeam X-ray Laue diffraction and a two-imensional energy-dispersive detector
(Int Union Crystallography, 2017) Abboud, Ali; Kirchlechner, C.; Keckes, J.; Çonka Yıldız, Tuba; Send, S.; Micha, J. S.; Pietsch, U.
The full strain and stress tensor determination in a triaxially stressed single crystal using X-ray diffraction requires a series of lattice spacing measurements at different crystal orientations. This can be achieved using a tunable X-ray source. This article reports on a novel experimental procedure for single-shot full strain tensor determination using polychromatic synchrotron radiation with an energy range from 5 to 23 keV. Microbeam X-ray Laue diffraction patterns were collected from a copper micro-bending beam along the central axis (centroid of the cross section). Taking advantage of a two-dimensional energy-dispersive X-ray detector (pnCCD), the position and energy of the collected Laue spots were measured for multiple positions on the sample, allowing the measurement of variations in the local microstructure. At the same time, both the deviatoric and hydrostatic components of the elastic strain and stress tensors were calculated.
Green supplier evaluation with SWARA-TOPSIS integrated method to reduce ecological risk factors
(Springer, 2019) Akcan, Serap; Taş, Mehmet Ali
One of the most important agendas of the world is the topic of global warming. In order to protect the ecological balance, all organizations turning towards using natural resources more effectively and not harming the environment. Increasing social expectation, legal regulations, and diminishing natural resources necessitate the dissemination of these orientations in all areas. Enterprises' supply chain management applications are also affected by this situation, and the concept of green supply chain management which reflects the environmentalist perspective has emerged. One of the most important stages of this chain is to find suppliers who care about the environment. Choosing a green supplier is of great importance for both the business and the environment. In this study, 11 environmental criteria were defined for green supplier evaluation and SWARA-TOPSIS integrated method was used to determine the most suitable supplier. Furthermore, a case study for an international yachting company operating in Turkey was also presented in this study. Based on the results of the study, it was seen that supplier 2 was the most suitable among five prominent alternative suppliers, and "environmental management system", "senior management's support and commitment", and "green image" criteria were ranked as the top three criteria among the 11 determined criteria.

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