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- 저자 : Tufan, (검색결과 36 건)
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Influence of wall flexibility on dynamic response of cantilever retaining walls
Tufan Cakir 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.1
A seismic evaluation is made of the response to horizontal ground shaking of cantilever retaining walls using the finite element model in three dimensional space whose verification is provided analytically through the modal analysis technique in case of the assumptions of fixed base, complete bonding behavior at the wall-soil interface, and elastic behavior of soil. Thanks to the versatility of the finite element model, the retained medium is then idealized as a uniform, elastoplastic stratum of constant thickness and semi-infinite extent in the horizontal direction considering debonding behavior at the interface in order to perform comprehensive soil-structure interaction (SSI) analyses. The parameters varied include the flexibility of the wall, the properties of the soil medium, and the characteristics of the ground motion. Two different finite element models corresponding with flexible and rigid wall configurations are studied for six different soil types under the effects of two different ground motions. The response quantities examined incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that the wall flexibility and soil properties have a major effect on seismic behavior of cantilever retaining walls and should be considered in design criteria of cantilever walls. Furthermore, the results of the numerical investigations are expected to be useful for the better understanding and the optimization of seismic design of this particular type of retaining structure.
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Tufan Tarcan,Cem Akbal,Çağrı A. Şekerci,Tuncay Top,Ferruh Şimşek 대한비뇨의학회 2014 Investigative and Clinical Urology Vol.55 No.4
Purpose: This was a prospective single-arm study to assess the efficacy and safety ofintradetrusor injections of onabotulinum toxin-A in children with urinary incontinenceassociated with neurogenic detrusor overactivity due to myelomeningocele. All patientshad failed the first-line treatment of a combination of oral antimuscarinics andintermittent catheterization. Materials and Methods: The study group consisted of 31 children with myelomeningocelewith a mean age of 7.95 years (range, 5–13 years) who were followed up for a meanof 29 weeks. The amount of onabotulinum toxin A injected was 10 U/kg with a maximaldose of 300 U. There were 20 to 30 injection sites with rigid cystoscopic guidance undergeneral anesthesia. Results: Thirty of 31 patients reported dryness between intermittent catheterizationintervals. The mean reduction in maximum detrusor pressure and the mean increasein maximum cystometric capacity from baseline were 53% and 51.5%, respectively, 6weeks after injection. We found a 324% increase in mean bladder compliance and a 57%increase in mean intermittent catheterization volumes. The mean duration of efficacywas 28 weeks with a single injection and 36 weeks for repeated injections (minimum,16 weeks; maximum, 52 weeks). The mean time interval between repeated onabotulinumtoxin-A injections was 7 months (maximum, 13 months). Intradetrusor injectionsof onabotulinum toxin-A were well tolerated. Conclusions: Onabotulinum toxin-A injections into the bladder wall provide a significantsymptomatic and urodynamic improvement in children with neurogenic detrusoroveractivity due to myelomeningocele who are on intermittent catheterization. The treatment seems to be safe and very well tolerated.
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Backfill and subsoil interaction effects on seismic behavior of a cantilever wall
Cakir, Tufan Techno-Press 2014 Geomechanics & engineering Vol.6 No.2
The main focus of the current study is to evaluate the dynamic behavior of a cantilever retaining wall considering backfill and soil/foundation interaction effects. For this purpose, a three-dimensional finite element model (FEM) with viscous boundary is developed to investigate the seismic response of the cantilever wall. To demonstrate the validity of the FEM, analytical examinations are carried out by using modal analysis technique. The model verification is accomplished by comparing its predictions to results from analytical method with satisfactory agreement. The method is then employed to further investigate parametrically the effects of not only backfill but also soil/foundation interactions. By means of changing the soil properties, some comparisons are made on lateral displacements and stress responses. It is concluded that the lateral displacements and stresses in the wall are remarkably affected by backfill and subsoil interactions, and the dynamic behavior of the cantilever retaining wall is highly sensitive to mechanical properties of the soil material.
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Experimental analysis on FEM definition of backfill-rectangular tank-fluid system
Cakir, Tufan,Livaoglu, Ramazan Techno-Press 2013 Geomechanics & engineering Vol.5 No.2
In the present study, the numerical and experimental investigations were performed on the backfill- exterior wall-fluid interaction systems in case of empty and full tanks. For this, firstly, the non-linear three dimensional (3D) finite element models were developed considering both backfill-wall and fluid-wall interactions, and modal analyses for these systems were carried out in order to acquire modal frequencies and mode shapes by means of ANSYS finite element structural analysis program. Secondly, a series of field tests were fulfilled to define their modal characteristics and to compare the results from proposed approximation in the selected structures. Finally, comparing the theoretical predictions from the finite element models to results from experimental measurements, a close agreement was found between theory and experiment. Thus, it can be easily stated that experimental verifications provide strong support for the finite element models and the proposed procedures themselves are the meritorious approximations to the real problem, and this makes the models appealing for use in further investigations.
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Influence of wall flexibility on dynamic response of cantilever retaining walls
Cakir, Tufan Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.1
A seismic evaluation is made of the response to horizontal ground shaking of cantilever retaining walls using the finite element model in three dimensional space whose verification is provided analytically through the modal analysis technique in case of the assumptions of fixed base, complete bonding behavior at the wall-soil interface, and elastic behavior of soil. Thanks to the versatility of the finite element model, the retained medium is then idealized as a uniform, elastoplastic stratum of constant thickness and semi-infinite extent in the horizontal direction considering debonding behavior at the interface in order to perform comprehensive soil-structure interaction (SSI) analyses. The parameters varied include the flexibility of the wall, the properties of the soil medium, and the characteristics of the ground motion. Two different finite element models corresponding with flexible and rigid wall configurations are studied for six different soil types under the effects of two different ground motions. The response quantities examined incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that the wall flexibility and soil properties have a major effect on seismic behavior of cantilever retaining walls and should be considered in design criteria of cantilever walls. Furthermore, the results of the numerical investigations are expected to be useful for the better understanding and the optimization of seismic design of this particular type of retaining structure.
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Mukhopadhyay, Tufan K.,Rock, Christopher L.,Hong, Mannkyu,Ashley, Daniel C.,Groy, Thomas L.,Baik, Mu-Hyun,Trovitch, Ryan J. American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.13
<P>We recently reported a bis(imino)pyridine (or pyridine diimine, PDI) manganese precatalyst, (<SUP>Ph2PPr</SUP>PDI)Mn (<B>1</B>), that is active for the hydrosilylation of ketones and dihydrosilylation of esters. In this contribution, we reveal an expanded scope for <B>1</B>-mediated hydrosilylation and propose two different mechanisms through which catalysis is achieved. Aldehyde hydrosilylation turnover frequencies (TOFs) of up to 4900 min<SUP>-1</SUP> have been realized, the highest reported for first row metal-catalyzed carbonyl hydrosilylation. Additionally, <B>1</B> has been shown to mediate formate dihydrosilylation with leading TOFs of up to 330 min<SUP>-1</SUP>. Under stoichiometric and catalytic conditions, addition of PhSiH<SUB>3</SUB> to (<SUP>Ph2PPr</SUP>PDI)Mn was found to result in partial conversion to a new diamagnetic hydride compound. Independent preparation of (<SUP>Ph2PPr</SUP>PDI)MnH (<B>2</B>) was achieved upon adding NaEt<SUB>3</SUB>BH to (<SUP>Ph2PPr</SUP>PDI)MnCl<SUB>2</SUB> and single-crystal X-ray diffraction analysis revealed this complex to possess a capped trigonal bipyramidal solid-state geometry. When 2,2,2-trifluoroacetophenone was added to <B>1</B>, radical transfer yielded (<SUP>Ph2PPr</SUP>PDI<B>·</B>)Mn(OC<B>·</B>(Ph)(CF<SUB>3</SUB>)) (<B>3</B>), which undergoes intermolecular C-C bond formation to produce the respective Mn(II) dimer, [(μ-<I>O</I>,<I>N</I><SUB>py</SUB>-4-OC(CF<SUB>3</SUB>)(Ph)-4-H-<SUP>Ph2PPr</SUP>PDI)Mn]<SUB>2</SUB> (<B>4</B>). Upon finding <B>3</B> to be inefficient and <B>4</B> to be inactive, kinetic trials were conducted to elucidate the mechanisms of <B>1</B>- and <B>2</B>-mediated hydrosilylation. Varying the concentration of <B>1</B>, substrate, and PhSiH<SUB>3</SUB> revealed a first order dependence on each reagent. Furthermore, a kinetic isotope effect (KIE) of 2.2 ± 0.1 was observed for <B>1</B>-catalyzed hydrosilylation of diisopropyl ketone, while a KIE of 4.2 ± 0.6 was determined using <B>2</B>, suggesting <B>1</B> and <B>2</B> operate through different mechanisms. Although kinetic trials reveal <B>1</B> to be the more active precatalyst for carbonyl hydrosilylation, a concurrent <B>2</B>-mediated pathway is more efficient for carboxylate hydrosilylation. Considering these observations, <B>1</B>-catalyzed hydrosilylation is believed to proceed through a modified Ojima mechanism, while <B>2-</B>mediated hydrosilylation occurs via insertion.</P> [FIG OMISSION]</BR>
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Assessment of effect of material properties on seismic response of a cantilever wall
Cakir, Tufan Techno-Press 2017 Geomechanics & engineering Vol.13 No.4
Cantilever retaining wall movements generally depend on the intensity and duration of ground motion, the response of the soil underlying the wall, the response of the backfill, the structural rigidity, and soil-structure interaction (SSI). This paper investigates the effect of material properties on seismic response of backfill-cantilever retaining wall-soil/foundation interaction system considering SSI. The material properties varied include the modulus of elasticity, Poisson's ratio, and mass density of the wall material. A series of nonlinear time history analyses with variation of material properties of the cantilever retaining wall are carried out by using the suggested finite element model (FEM). The backfill and foundation soil are modelled as an elastoplastic medium obeying the Drucker-Prager yield criterion, and the backfill-wall interface behavior is taken into consideration by using interface elements between the wall and soil to allow for de-bonding. The viscous boundary model is used in three dimensions to consider radiational effect of the seismic waves through the soil medium. In the seismic analyses, North-South component of the ground motion recorded during August 17, 1999 Kocaeli Earthquake in Yarimca station is used. Dynamic equations of motions are solved by using Newmark's direct step-by-step integration method. The response quantities incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that while the modulus of elasticity has a considerable effect on seismic behavior of cantilever retaining wall, the Poisson's ratio and mass density of the wall material have negligible effects on seismic response.
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Cervical Cancer Screening in an Early Diagnosis and Screening Center in Mersin, Turkey
Nayir, Tufan,Okyay, Ramazan Azim,Nazlican, Ersin,Yesilyurt, Hakki,Akbaba, Muhsin,Ilhan, Berrin,Kemik, Aytekin Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.16
Cancer is a major public health problem due to the jeavy disease burden, fatality and tendency for increased incidence. Of all cancer types, cervical cancer is reported to be the fourth most common cancer in women, and the seventh overall, with an estimated 528,000 new cases worldwide in 2012. It features a long preclinical phase with slowly progressing precancerous lesions such as CIN 2 and 3 and adenocarcinoma in situ. Therefore, screening programs such as with Pap smear tests may play an important role in cervical cancer prevention. The purpose of this study was to present results of a Pap smear screening survey for cervical cancer targeting women living in an urban area in the province of Mersin, located in the Mediterranean region of Turkey. This community-based descriptive study included women living at Akdeniz county of Mersin province. A total of 1,032 screened women between 30 and 65 ages within the routine screening programme constituted the study population. The mean age of the participants was $43.8{\pm}8.6$ (min. 30, max. 65) years. The percentage of the participants who had previously undergone smears was 40.6%. Epithelial cell changes were found in 26 (2.5%) participants, with ASC-US in 18 (1.7%), ASC-H in 2 (0.2%), LSIL in 5 (0.5%) and HSIL in 1 (0.1%). The most common clinical presentation together with epithelial changes was abnormal vaginal discharge. Taking into account the presence of women who had never undergone Pap test; it should be offered at primary level of health care in the form of a community-based service to achieve reduced morbidity and mortality rates.
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