Transitivity of Commutativity for Linear Time-Varying Physical Systems

Koksal Mehmet Emir 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.2

In this contribution, the transitivity property of commutative fi rst-order linear time-varying systems with and without initial conditions is investigated. It is proven that transitivity property of fi rst-order systems holds with and without initial conditions. On the base of impulse response function, transitivity of commutation property is formulated for any triplet of commutative linear time-varying relaxed systems. Transitivity proves are given for some special combinations of fi rst and second-order linear time-varying systems which are initially relaxed.

A failure criterion for RC members under triaxial compression

Koksal, Hansan Orhun Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.24 No.2

The reliable pushover analysis of RC structures requires a realistic prediction of moment-curvature relations, which can be obtained by utilizing proper constitutive models for the stress-strain relationships of laterally confined concrete members. Theoretical approach of Mander is still a single stress-strain model, which employs a multiaxial failure surface for the determination of the ultimate strength of confined concrete. Alternatively, this paper introduces a simple and practical failure criterion for confined concrete with emphasis on introduction of significant modifications into the two-parameter Drucker-Prager model. The new criterion is only applicable to triaxial compression stress state which is exactly the case in the RC columns. Unlike many existing multi-parameter criteria proposed for the concrete fracture, the model needs only the compressive strength of concrete as an independent parameter and also implies for the influence of the Lode angle on the material strength. Adopting Saenz equation for stress-strain plots, satisfactory agreement between the measured and predicted results for the available experimental test data of confined normal and high strength concrete specimens is obtained. Moreover, it is found that further work involving the confinement pressure is still encouraging since the confinement model of Mander overestimates the ultimate strength of some RC columns.

Analgesic and Antiinflammatory Activities of Some New Mannich Bases of 5-Nitro-2-Benzoxazolinones

Koksal, Meric,Kupeli, Esra,Yesilada, Erdem,Erdogan, Hakki,Gokhan, Mesrin 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.4

In this study, the synthesis of a novel series Mannich bases of 5-nitro-3-substituted piperazino-methyl-2-benzoxazolinones are described. The structures attributed to compounds 3a-3k were elucidated using IR, $^1$H-NMR spectroscopic techniques besides elemental analysis. The compounds were examined for their in vivo antiinflammatory and analgesic activities in two different bioassays, namely, carrageenan-induced hind paw edema and p-benzoquinone-inducedabdominal constriction tests in mice, respectively. In addition, the ulcerogenic effects of the compounds were determined. Among the tested derivatives most promising results were obtained for the compounds bearing electron-withdrawing substituents (F, Cl, COCH$_3$) in the ortho/para position of the phenyl nucleus on the piperazine ring at 3 position of benzoxazoli-none moiety (3a, 3b, 3c, 3d, 3h). The analgesic activities of all compounds are higher than their antiinflammatory activities. Antiinflammatory inhibitory ratios for all compounds were above 30% for the last two measurements. Because of this compounds 3a,3b,3c,3d deserve attention and may be considered for further evaluation.

Computational material modeling of masonry walls strengthened with fiber reinforced polymers

Koksal, H. Orhun,Jafarov, Oktay,Doran, Bilge,Aktan, Selen,Karakoc, Cengiz Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.5

This paper aims to develop a practical approach to modeling of fiber reinforced polymers (FRP) strengthened masonry panels. The main objective is to provide suitable relations for the material characterization of the masonry constituents so that the finite element applications of elasto-plastic theory achieves a close fit to the experimental load-displacement diagrams of the walls subjected to in-plane shear and compression. Two relations proposed for masonry columns confined with FRP are adjusted for the cohesion and the internal friction angle of both units and mortar. Relating the mechanical parameters to the uniaxial compression strength and the hydrostatic pressure acting over the wall surface, the effects of major and intermediate principal stresses ${\sigma}_1$ and ${\sigma}_2$ on the yielding and the shape of the deviatoric section are then reflected into the analyses. Performing nonlinear finite element analyses (NLFEA) for the three walls tested in two different studies, their stress-strain response and failure modes are eventually evaluated through the comparisons with the experimental behavior.

Investigation of risk factors for community-acquired urinary tract infections caused by extended-spectrum beta-lactamase Escherichia coli and Klebsiella species

Eda Koksal,Necla Tulek,Meliha Cagla Sonmezer,Fatih Temocin,Cemal Bulut,Cigdem Hatipoglu,Fatma Sebnem Erdinc,Gunay Ertem 대한비뇨의학회 2019 Investigative and Clinical Urology Vol.60 No.1

Purpose: The aim of this study was to determine the prevalence and risk factors for community-acquired urinary tract infections (CA-UTIs) caused by extended-spectrum β-lactamase (ESBL) producing Escherichia coli and Klebsiella species. Materials and Methods: The patients diagnosed with CA-UTIs caused by E. coli or Klebsiella spp. were included in the study. All of the patients were compared to demographic characteristics, underlying diseases, urinary tract pathology, history of hospitalization, use of antibiotics according to ESBL positivity. Results: A total of 322 urine isolates were studied. Sixty-six patients (37.1%) of a total of 178 patients were ESBL positive E. coli and Klebsiella spp. Being over the age of sixty (odds ratio [OR], 1.90; p=0.03), history of renal stone (OR, 3.00; p=0.03), urinary tract anatomical of physiological disorder (OR, 2.17; p=0.01), urologic intervention (OR, 3.43; p<0.001), history of urinary tract surgery (OR, 3.10; p=0.01), history of urinary catheterization (OR, 3.43; p<0.001), and hospitalization for last 1 year (OR, 3.70; p=0.01) and antibiotic usage in the last 3 months (OR, 1.90; p=0.04) were found as significant risk factors for the producing of ESBL. However, gender and underlying disease were not related for ESBL production. Conclusions: In present study, high rate of ESBL positivity was detected in CA-UTIs. The increasing of infections caused by ESBL positive E. coli and Klebsiella spp. are bringing together a lot of the problem, such as antibiotic resistance and reducing treatment options for outpatients. Identification of underlying risk factors would be important for the development of preventive strategies.

Fresh, flexural and mechanical performance of polyamide and polypropylene based macro-synthetic fiber-reinforced concretes

Fuat Koksal,Cem Bacanli,Ahmet Benli,Osman Gencel 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.1

The brittleness of concrete can be overcome by fiber reinforcement that controls the crack mechanisms of concrete. Corrosion-related durability issues can be prevented by synthetic fibers (SFs), while macro synthetic fibers have proven to be particularly effective to provide ductility and toughness after cracks. This experimental study has been performed to investigate the comparative flexural and mechanical behavior of four different macro-synthetic fiber-reinforced concretes (SFRCs). Two polyamide fibers (SF1 and SF2) with different aspect ratios and two different polypropylene fiber types (SF3 and SF4) were used in production of SFRCs. Four different SFRCs and reference concrete were compared for their influences on the toughness, compressive strength, elastic modulus, flexural strength, residual strength and splitting tensile strength. The outcomes of the study reveal that the flowability of reference mixture decreases after addition of SFs and the air voids of all SFRC mixtures increased with the addition of macro-synthetic fibers except SFRC2 mixture whose air content is the same as the reference mixture. The results also revealed that with the inclusion of SFs, 11.34% reduction in the cube compressive strength was noted for SFRC4 based on that of reference specimens and both reference concrete and SFRC exhibited nearly similar cylindrical compressive strength. Results illustrated that SFRC1 and SFRC4 mixtures consistently provide the highest and lowest flexural toughness values of 36.4 joule and 27.7 joule respectively. The toughness values of SFRC3 and SFRC4 are very near to each other.

Elastoplastic Finite Element Analysis of Masonry Shear Walls

H. Orhun Koksal,Bilge Doran,A. Osman Kuruscu,Ali Kocak 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.2

Masonry is the most important construction material in Turkey. It has been used for public and residential buildings in the past several thousand years. A great number of well-preserved old masonry structures still exist proving that this form of construction can successfully resist loads and environmental impact. Traditionally, most major buildings were solid walled structures with the walls bearing directly on the ground. Engineers work hard to convert the highly indeterminate, ambiguous and nonlinear behavior of historic masonry construction into something which can be understood with mathematical certainty. Therefore, practical and accurate structural analysis techniques are needed for the preserve the historical monuments as a huge cultural heritage. This paper is focused on Nonlinear Finite Element (NLFE) modeling of masonry shear walls at a macro-level taking the geometric arrangement of constituents. In this study, 3D elasto-plastic Finite Element (FE) analysis for the masonry walls that subjected to the combinations of vertical and lateral loads, are determined to find a practical method. An original meshing procedure is introduced to consider the orthotropy along the two natural directions of the masonry while the material is still assumed to be isotropic. The paper further examines parameter studies carried out to show that the relation suggested for cohesion values of mortar joint masonry can also be adopted for the masonry walls with dry joints employing compressive stresses on the top surface of the wall despite using its compressive strength. The accuracy of the proposed approach is verified by simulating a series of experiments reported in the literature. Those papers include shear tests on masonry walls with both dry and mortar joints by Raijmakers and Vermeltfoort, Oliveira and Roca. Comparisons between the predicted and measured failure loads of the walls confirm that it is possible to reproduce the fundamental features of masonry shear walls with the proposed meshing scheme. Finally, the proposed approach is shown to fit quite well the experimental load-deformation plots of masonry walls with both dry- and mortar joint under shearcompression fracture.

Prevelance of Common YMDD Motif Mutations in Long Term Treated Chronic HBV Infections in a Turkish Population

Alagozlu, Hakan,Ozdemir, Ozturk,Koksal, Binnur,Yilmaz, Abdulkerim,Coskun, Mahmut Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.9

In the current study we aimed to show the common YMDD motif mutations in viral polymerase gene in chronic hepatitis B patients during lamivudine and adefovir therapy. Forty-one serum samples obtained from chronic hepatitis B patients (24 male, 17 female; age range: 34-68 years) were included in the study. HBV-DNA was extracted from the peripheral blood of the patients using an extraction kit (Invisorb, Instant Spin DNA/RNA Virus Mini Kit, Germany). A line probe assay and direct sequencing analyses (INNO-LIPA HBV DR v2; INNOGENETICS N.V, Ghent, Belgium) were applied to determine target mutations of the viral polymerase gene in positive HBV-DNA samples. A total of 41 mutations located in 21 different codons were detected in the current results. In 17 (41.5%) patients various point mutations were detected leading to lamivudin, adefovir and/or combined drug resistance. Wild polymerase gene profiles were detected in 24 (58.5%) HBV positive patients of the current cohort. Eight of the 17 samples (19.5%) having rtM204V/I/A missense transition and/or transversion point mutations and resistance to lamivudin. Six of the the mutated samples (14.6%) having rtL180M missense transversion mutation and resistance to combined adefovir and lamivudin. Three of the mutated samples (7.5%) having rtG215H by the double base substituation and resistance to adefovir. Three of the mutated samples (7.5%) having codon rtL181W due to the missense transversion point mutations and showed resistance to combined adefovir and lamivudin. Unreported novel point mutations were detected in the different codons of polymerase gene region in the current HBV positive cohort fromTurkish population. The current results provide evidence that rtL180M and rtM204V/I/A mutations of HBV-DNA may be associated with a poor antiviral response and HBV chronicity during conventional therapy in Turkish patients.

Predictive Role of Neutrophil Gelatinase-Associated Lipocalin in Early Diagnosis of Platin-Induced Renal Injury

Seker, Mehmet Metin,Deveci, Koksal,Seker, Ayse,Sancakdar, Enver,Yilmaz, Ali,Turesin, A. Kerim,Kacan, Turgut,Babacan, Nalan A. Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.2

Background: Acute kidney injury is an important issue in chemotherapy receiving patients an neutrophil gelatinase-associated lipocalin has been proposed as a novel marker. We here aimed to assess the role of urinary levels for assessment after platin exposure. Materials and Methods: Patients who had treated with cisplatin or carboplatin or oxaliplatin containg regimens were included in this study. Baseline and postchemotherapy serum urea, creatinine, urine neutrophil gelatinase-associated lipocalin and urine creatinine levels were determined. To avoid the effects of hydration during chemotherapy infusion the urinary neutrophil gelatinase-associated lipocalin/urine creatinine ratio was used to determine acute kidney injury. Results: Of a total of 42 patients receiving platin compounds,14 (33.3%) received cisplatin containing regimens, 14 (33.3%) received carboplatin and 14 (33.3%) oxaliplatin. The median age was 60 (37-76) years. Nineteen of the patients (45.2%) had lung cancer, 12 (28.6%) colorectal cancer and 11 (26.2%) others. The median pre and post chemotherapy urine neutrophil gelatinase-associated lipocalin/urine creatinin ratio was 15.6 ng/mg and 35.8 ng/mg (p=0.041) in the cisplatin group, 32.5 ng/mg and 86.3 ng/mg (p=0.004) in the carboplatin group and 40.9 ng/mg and 62.3 ng/mg (p=0.243) in the oxaliplatin group. Conclusions: Nephrotoxicity is a serious side effect of chemotherapeutic agentslike cisplatin and carbopaltin, but only to a lower extent oxaliplatin. All platin compounds must be used carefully and urine neutrophil gelatinase-associated lipocalin measurement seems to be promising in detecting acute kidney injury earlier than with creatinine.

Competitive Strategic Performance Benchmarking (CSPB) Model for International Construction Companies

Tugce Ercan,Almula Koksal 대한토목학회 2016 KSCE Journal of Civil Engineering Vol.20 No.5

Strategic performance management is an important tool in acquiring managerial superiority that affects international construction companies’ success. Most comparative analysis of company performance focus on construction site productivity or project management processes, while only few studies focuses on the issues of competitiveness. In this context the objective of this study is to develop a Competitive Strategic Performance Benchmarking (CSPB) model for large international construction companies. The model was developed in two stages. In the first stage, the key parameters of the strategic performance measurement system were developed. In the second state, international construction companies performed self-assessments of their strategic performances on the bases of the key parameters defined in the first stage. Binary logistic regression analysis was employed to develop the strategic performance scale. The findings of this research indicate that a company’s competitiveness based on profitability and sales growth are affected by the strength of strategies at the functional level whereas market share is influenced at the competitive level. Finally, a case study was conducted in order to present the applicability of the model for the practitioners. The CSPB model contributes to the managerial decision making process in construction companies and can be used as a tool for strategy formulation. Strategic performance management is an important tool in acquiring managerial superiority that affects international construction companies’ success. Most comparative analysis of company performance focus on construction site productivity or project management processes, while only few studies focuses on the issues of competitiveness. In this context the objective of this study is to develop a Competitive Strategic Performance Benchmarking (CSPB) model for large international construction companies. The model was developed in two stages. In the first stage, the key parameters of the strategic performance measurement system were developed. In the second state, international construction companies performed self-assessments of their strategic performances on the bases of the key parameters defined in the first stage. Binary logistic regression analysis was employed to develop the strategic performance scale. The findings of this research indicate that a company’s competitiveness based on profitability and sales growth are affected by the strength of strategies at the functional level whereas market share is influenced at the competitive level. Finally, a case study was conducted in order to present the applicability of the model for the practitioners. The CSPB model c