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Taha Toros Arşivi, Dosya Adı: Ahmet Cevat Paşa-Cevat Şakir Kabaağaçl

Atmospheric nutrient inputs to the northern levantine basin from a long-term observation: sources and comparison with riverine inputs

Aerosol and rainwater samples have been collected at a rural site located on the coastline of the Eastern Mediterranean, Erdemli, Turkey between January 1999 and December 2007. Riverine sampling was carried out at five Rivers (Ceyhan, Seyhan, Göksu, Berdan and Lamas) draining into the Northeastern Levantine Basin (NLB) between March 2002 and July 2007. Samples have been analyzed for macronutrients of phosphate, silicate, nitrate and ammonium (PO<sub>4</sub><sup>3−</sup>, Si<sub>diss</sub>, NO<sub>3</sub><sup>−</sup> and NH<sub>4</sub><sup>+</sup>). Phosphate and silicate in aerosol and rainwater showed higher and larger variations during the transitional period when air flows predominantly originate from North Africa and Middle East/Arabian Peninsula. Deficiency of alkaline material have been found to be the main reason of the acidic rain events whilst high pH values (>7) have been associated with high Si<sub>diss</sub> concentrations due to sporadic dust events. In general, lowest nitrate and ammonium concentrations in aerosol and rainwater have been associated with air flow from the Mediterranean Sea. Comparison of atmospheric with riverine fluxes demonstrated that DIN and PO<sub>4</sub><sup>3−</sup> fluxes to NLB have been dominated by atmosphere (~90% and ~60% respectively) whereas the input of Si was mainly derived from riverine runoff (~90%). N/P ratios in the atmospheric deposition (233); riverine discharge (28) revealed that NLB receives excessive amounts of DIN and this unbalanced P and N inputs may provoke even more phosphorus deficiency. Observed molar Si/N ratio suggested Si limitation relative to nitrogen might cause a switch from diatom dominated communities to non-siliceous populations particularly at coastal NLB

Investigation of metallo beta lactamases and oxacilinases in carbapenem resistant acinetobacter baumannii strains isolated from inpatients

Background: Resistance to beta-lactam antibiotics is widespread among Acinetobacter strains. Plasmid-mediated metallo beta lactamases (MBL) are responsible for carbapenem resistance, as are oxacillinases (OXA). In recent years, MBL producing carbapenem-resistant strains have been reported in the world and in Turkey in increasing rates. In our country, besides the OXA 51- like enzyme which is inherent in A. baumannii strains, OXA 58-like and OXA 23-like carbapenemases producing strains have also been widely detected. In addition, Verona Imipenemase (VIM) and (IMP)-type MBL have been reported in some centers. Aims: The aim of our study was to investigate the presence of carbapenemases in Acinetobacter strains isolated from hospitalized patients in Edirne. Study Design: Cross-sectional study. Methods: A total of 52 imipenem-resistant A. baumannii strains isolated between January and March 2013 were investigated. The presence of MBL was described phenotypically by the combined disk diffusion test (CDDT), double disk synergy test (DDST), MBL E- test (only performed in 28 strains) and modified Hodge test. blaIMP , blaVIM, blaGIM, blaSIM, blaSPM genes and blaOXA-23, blaOXA-51, blaOXA-40, blaOXA-58 genes were inves- tigated by multiplex polymerase chain reaction (PCR). The blaNDM-1 gene was determined by PCR. Results: By modified Hodge test, 50 strains (96%) were found to be MBL positive. Positivity of MBL was 21% by both CDDT (0.1 M EDTA) and DDST. Twen- ty-four of 28 strains (85.7%) were positive by MBL E-test. OXA 23-like and OXA 51-like carbapenemases were detected in all strains, but OXA 58-like and OXA 40-like carbapenemases-producing A. baumannii were not detected. Also, MBL genes were not detected by genotypic methods. Conclusion: Only OXA 23-like carbapenemase was responsible for carbapenem resistance in carbapenem- resistant Acinetobacter strains in Edirne. The MBL- producing Acinetobacter strain is not yet a problem in our hospital. MBL resistance was found by phenotyp- ing tests, which must be confirmed by genotypic meth- ods; multiplex PCR tests can be easily used for screen- ing MBL

Computational Simulation of Thermal and Spattering Phenomena and Microstructure in Selective Laser Melting of Inconel 625

AbstractComputational modelling of Laser Powder Bed Fusion (L-PBF) processes such as Selective laser Melting (SLM) can reveal information that is hard to obtain or unobtainable by in-situ experimental measurements. A 3D thermal field that is not visible by the thermal camera can be obtained by solving the 3D heat transfer problem. Furthermore, microstructural modelling can be used to predict the quality and mechanical properties of the product. In this paper, a nonlinear 3D Finite Element Method based computational code is developed to simulate the SLM process with different process parameters such as laser power and scan velocity. The code is further improved by utilizing an in-situ thermal camera recording to predict spattering which is in turn included as a stochastic heat loss. Then, thermal gradients extracted from the simulations applied to predict growth directions in the resulting microstructure

Three-Dimensional Finite Element analysis of the seismic behavior of pile foundations

Bu çalışmada; özellikle kayma modülleri arasında belirgin fark olan zemin tabakalarındaki zeminlerin doğrusal olmayan davranışlarının incelenebilmesi amacıyla deprem yükleri altındaki kazıklı temellerin doğrusal olmayan bir dinamik analiz işlemi başarıyla gerçekleştirilmiştir. Bu çalışmanın yardımıyla, deprem sarsıntıları sırasında kazıklarda meydana gelen gerilmelere, diğer yapısal ayrıntılar aynı kalırken, zemin şartlarında değişik koşulları temsil eden basitçe iki durum göz önünde bulundurularak, zemin tabakasının etkisinin çok belirgin olduğu gösterilmeye çalışılmıştır. Bu çalışmadan elde edilen sayısal sonuçlar, zayıf zemin koşullarındaki kazık tasarımlarında, yerin deformasyon davranışının etkilerini yeterince göz önünde bulundurulmasına gereksinim duyulduğunu sergilemektedir. Anahtar Kelimeler: Sonlu elemanlar, kazık-zemin etkileşimi, kazıklı temeller, üç boyutlu, sismik davranış, kesme kuvveti, eğilme momenti.In this study a general nonlinear dynamic analysis procedure for pile foundations has been applied successfully to investigate the nonlinear behaviors of soils, being particularly large at interfaces soil layers which sharply differing shear module, under earthquake loads. Generally, long piles penetrating deep layered deposit, particularly when there is a sudden change in soil stiffness are likely to be exerted by large ground response forces. However, such as ground forces are termed simply as "ground response effects" in dynamic pile-soil interaction, which are generally neglected in the pile design practice. Investigations on damage to piles during the past earthquakes provide some basic information concerning the nature of failures in piles at locations with deep soil deposit under strong ground shaking. Remarkably significant instance of the damage is reported to have occurred at deeper parts along the pile, particularly in relatively longer piles. Evidently, the location of pile damage at the intermediate part in longer piles also tends to coincide with changes in soil layering, giving rise to stiffness contrast interface. By means of this study, considering two simple variations in soil condition, other structural details remaining the same, it is shown that the influence of soil layering on the stresses developed in piles during earthquake shaking can bevery dominant. Numerical results obtained from this study show the need for adequate consideration of the ground deformation response effects in the pile design in relatively soil conditions. Keywords: Finite elements, pile-soil interaction, pile foundations, three dimensional, seismic behavior, shear force, bending moment

Experimental study on hollow section joints under impact loading

U ovom se radu analizira udarna otpornost čeličnih profila s četiri različite vrste priključaka. Za te je potrebe razvijeno ispitivanje uređajem s padajućim teretom. Ispitivanja otpornosti na udarno opterećenje provedena su za dvije razine energije. Izrađeni su i prikazani dijagrami ubrzanja i vremena, pomaka i vremena, udarnog opterećenja u vremenu te odnosa udarnog opterećenja i pomaka. Utvrđeno je da na ponašanje uzoraka utječe vrsta priključka i nanesena udarna energija. Do sloma oštećenjem dolazi ranije kod niže krutosti uzoraka te pri nanošenju više razine udarne energije.Steel sections with four different joint types, subjected to sudden impact, are investigated in this study. A drop weight test setup was developed for this purpose. Impact tests were performed for two different energy levels. Acceleration-time, displacement-time, impact load-time, and impact load-displacement graphs were developed and presented. It was established that the behaviour of test specimens is affected by joint types and impact energy applied. Failure damage situation occurs earlier when rigidity of specimens decreases and when higher level of impact energy is applied

Experimental and Numerical Investigation of Steel Sections under Impact Effect

U radu se analizira eksperimentalno i numeričko ponašanje čeličnih ispitnih uzoraka s različitim vrstama priključaka. U tu svrhu korišten je uređaj s padajućim utegom. Kako bi se primijenila ista količina udarne energije na ispitne uzorke, masa i visina udarnog utega uzete su kao konstante. Eksperimentalnim istraživanjem dobivene su vrijednosti ubrzanja, pomaka, udarnog opterećenja, broja ispusta i trajanja pada. Tijekom ispitivanja pratilo se i širenje oštećenja na ispitnim uzorcima. Provedena je i numerička analiza ponašanja uzoraka uslijed udarnog opterećenja pomoću računalnog programa Abaqus te je napravljena usporedba rezultata.Experimental and numerical behaviour of steel test specimens with various types of joints is investigated in this study. A drop weight test setup with necessary test equipment is used for this purpose. The mass and drop height of the hammer is taken to be constant so that the same impact energy can be applied on test specimens. The acceleration, displacement, impact load, drop numbers and drop durations, are obtained through experimental study. In addition, development of damage to test specimens is observed during tests. Numerical analyses of behaviour of test specimens under impact load are also conducted to verify test results using the Abaqus software, and a comparison of results is made

Comparative analysis of tripod offshore structure

Pomorske se konstrukcije u današnje vrijeme koriste za razne namjene. U ovom se radu analizira odobalna građevina tronožnog tipa ukupne visine šezdeset metara. Uz opterećenja vezana za samo funkcioniranje, konstrukcija građevine podvrgnuta je i opterećenjima uslijed djelovanja vjetra i valova. Za proračun sile vjetra korišten je profil brzine prema europskoj normi, a za određivanje sile valova Airyeva brzina valova. Model je izrađen pomoću programa za analizu konačnih elemenata, a sastoji se od fluidnog i konstrukcijskog dijela. Interakcija između tih dijelova postignuta je kombiniranim Euler-Lagrangeovim postupkom (CEL).Marine structures are nowadays used in a variety of ways. The analysis of a tripod-type offshore structure sixty m in total height is performed in this study. In addition to operation-related loads, the structure is also under the effect of wind and wave loads. While the Eurocode velocity profile is used to calculate wind forces, the Airy wave velocity profile is utilized to determine wave forces. The model is created by a finite elements analysis program, and is composed of fluid and structural parts. The interaction of the parts is ensured by Coupled Eulerian Lagrangian (CEL) technique

Simple models for scaling in phylogenetic trees

Many processes and models --in biological, physical, social, and other contexts-- produce trees whose depth scales logarithmically with the number of leaves. Phylogenetic trees, describing the evolutionary relationships between biological species, are examples of trees for which such scaling is not observed. With this motivation, we analyze numerically two branching models leading to non-logarithmic scaling of the depth with the number of leaves. For Ford's alpha model, although a power-law scaling of the depth with tree size was established analytically, our numerical results illustrate that the asymptotic regime is approached only at very large tree sizes. We introduce here a new model, the activity model, showing analytically and numerically that it also displays a power-law scaling of the depth with tree size at a critical parameter value.Comment: 7 pages, 4 figures. A new figure, with example trees, has been added. To appear in Int. J. Bifurcation and Chao