Investigation of wall flexibility effects on seismic behavior of cylindrical silos

Ramazan Livaoğlu,Ayşegül Durmuş 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.1

This paper is concerned with effects of the wall flexibility on the seismic behavior of groundsupported cylindrical silos. It is a well-known fact that almost all analytical approximations in the literatureto determine the dynamic pressure stemming from the bulk material assume silo structure as rigid. However, it is expected that the horizontal dynamic material pressures can be modified due to varying horizontal extensional stiffness of the bulk material which depends on the wall stiffness. In this study, finite element analyses were performed for six different slenderness ratios according to both rigid and flexible wall approximations. A three dimensional numerical model, taking into account bulk material-silo wall interaction, constituted by ANSYS commercial program was used. The findings obtained from the numerical analyses were discussed comparatively for rigid and flexible wall approximations in terms of the dynamic material pressure, equivalent base shear and bending moment. The numerical results clearly show that the wall flexibility may significantly affects the characteristics behavior of the reinforced concrete (RC) cylindrical silos and magnitudes of the responses under strong ground motions.

Evaluation of wind loads and the potential of Turkey's south west region by using log-normal and gamma distributions

Ramazan Özkan,Faruk Sen,Serkan Balli 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.4

In this study, wind data such as speeds, loads and potential of Muğla which is located in the southwest of Turkey were statistically analyzed. The wind data which consists of hourly wind speed between 2010 and 2013 years, was measured at the 10-meters height in four different ground stations (Datça, Fethiye, Marmaris, Köyceğiz). These stations are operated by The Turkish State Meteorological Service (T.S.M.S). Furthermore, wind data was analyzed by using Log-Normal and Gamma distributions, since these distributions fit better than Weibull, Normal, Exponential and Logistic distributions. Root Mean Squared Error (RMSE) and the coefficients of the goodness of fit (R2) were also determined by using statistical analysis. According to the results, extreme wind speed in the research area was 33 m/s at the Datça station. The effective wind load at this speed is 0.68 kN/m2. The highest mean power densities for Datça, Fethiye, Marmaris and Köyceğiz were found to be 46.2, 1.6, 6.5 and 2.2 W/m2, respectively. Also, although Log-normal distribution exhibited a good performance i.e., lower AD (Anderson – Darling statistic (AD) values) values, Gamma distribution was found more suitable in the estimation of wind speed and power of the region.

Fabrication and properties of in-situ Al/AlB₂ composite reinforced with high aspect ratio borides

Ramazan Kayikci,Ömer Savaş 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.3

Production and properties of metal matrix composites reinforced with an in-situ high aspect ratio AlB2 flake have been investigated. Boron 2.2wt.% was dissolved in pure Al and Al-Cu alloy at 1300℃ by adding directly boron oxide which resulted in 4 vol.% reinforcing phase. The in-situ AlB2 flake concentration was increased up to 30 vol.% in order to increase the tensile strength of the composites. Hardness, compressive strength and tensile strength of the composite were measured and compared with their matrix. Results showed that 30 vol.% A1B2/Al composite show a 193% increase in the compressive strength and a 322% increase in compressive yield strength. Results also showed that ductility of composites decreases with adding AlB2 reinforcements.

An assessment of machine learning models for slump flow and examining redundant features

Ramazan Ünlü 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.25 No.6

Over the years, several machine learning approaches have been proposed and utilized to create a prediction model for the high-performance concrete (HPC) slump flow. Despite HPC is a highly complex material, predicting its pattern is a rather ambitious process. Hence, choosing and applying the correct method remain a crucial task. Like some other problems, prediction of HPC slump flow suffers from abnormal attributes which might both have an influence on prediction accuracy and increases variance. In recent years, different studies are proposed to optimize the prediction accuracy for HPC slump flow. However, more state-of-the-art regression algorithms can be implemented to create a better model. This study focuses on several methods with different mathematical backgrounds to get the best possible results. Four well-known algorithms Support Vector Regression, M5P Trees, Random Forest, and MLPReg are implemented with optimum parameters as base learners. Also, redundant features are examined to better understand both how ingredients influence on prediction models and whether possible to achieve acceptable results with a few components. Based on the findings, the MLPReg algorithm with optimum parameters gives better results than others in terms of commonly used statistical error evaluation metrics. Besides, chosen algorithms can give rather accurate results using just a few attributes of a slump flow dataset.

Surgical Excition of Spinal Intradural Meningiomas through a Single-Sided Minimally Invasive Approach: Key-Hole Laminotomy

Ramazan Alper Kaya 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.2

Study Design: Eight patients who underwent surgery through a single-sided keyhole laminotomy due to intradural extramedullary (IDEM) meningiomas were retrospectively investigated. Purpose: To present the surgical outcomes of single-sided keyhole laminotomies aimed to excise large ventral IDEM spinal cord menengiomas. Overview of Literature: Less invasive procedures, such as laminotomies and osteoplastic laminotomies, have been previously described in the literature, but an approach that interferes with spinal stability to an even lesser extent would be more desirable. Methods: Tumors were removed through a slit-like space between the dura and spinal cord without retraction of the spinal cord. The neurological conditions of patients were evaluated pre- and postoperatively with the Nurick grading system. Pathologic subtypes, preoperative symptom duration, tumor location on the sagittal and axial planes, and the percentage of tumor occupying the intradural space were investigated. On follow-up, magnetic resonance imaging was conducted to evaluate whether the tumor had recurred. Results: All tumors were localized either ventrally or ventrolaterally. Of the spinal menengiomas, four were cervical and four were thoracic. All lesions were completely excised, and the neurological condition improved in six patients. The remaining two patients already had preoperative Nurick grades of 0, and this score was maintained postoperatively. Neither kyphotic changes nor instability developed in any patient during the follow-up period. Conclusions: Total resection of anterior and anterolateral IDEM menengiomas, without introducing new neurological deficits, can be performed by an isolated posterior approach through a single-sided keyhole laminotomy. However, this approach should be applied cautiously and with a thorough understanding of its limitations.

A Path Stretching Model for Effective Terminal Airspace Management

Ramazan Kursat Cecen 한국항공우주학회 2022 International Journal of Aeronautical and Space Sc Vol.23 No.5

This study presents a mathematical model to optimize the total fuel consumption per aircraft for the aircraft landing problem (ALP) using the path stretching (PS) method. The PS model applies vector maneuver (VM), speed reduction (SR), and flight path angle (FPA) change methods for aircraft operation. In addition, two different mixed-integer linear programming models utilizing the point merge system (PMS) are presented to compare the PS model as PMS is a widely used method in ALP. The first PMS model uses the VM to handle arrival traffic and solve aircraft conflicts. The second one implements the VM and the SR techniques. Furthermore, an exact solution algorithm is selected to obtain the optimal solution. The PS model aims to increase the number of continuous descent operations by eliminating the level flights. Two different linear regression equations are generated to calculate the fuel consumption and flight time values in descent operations considering realistic aircraft parameters, FPA, and average airspeed. The results demonstrate that the PS model can reduce the total fuel consumption per aircraft by 8.94% and 3.45% compared to the PMS models.

Approximation by interpolating polynomials in Smirnov-Orlicz class

Ramazan Akg\,Daniyal M. Israfilov 대한수학회 2006 대한수학회지 Vol.43 No.2

Let $\Gamma $ be a bounded rotation (BR) curve without cusps in the complex plane $\mathbb{C}$ and let $G:=\operatorname{int}\Gamma $. We prove that the rate of convergence of the interpolating polynomials based on the zeros of the Faber polynomials $F_{n}$ for $\overline{G}$ to the function of the reflexive Smirnov-Orlicz class $E_{M}\left( G\right) $ is equivalent to the best approximating polynomial rate in $E_{M}\left( G\right) $.

A novel method for high-frequency transgenic shoot regeneration via Agrobacterium tumefaciens in flax (Linum usitatissimum L.)

Ramazan Beyaz,E. Selcen Darçın,Murat Aycan,Mustafa Kayan,Mustafa Yıldız 한국식물생명공학회 2016 JOURNAL OF PLANT BIOTECHNOLOGY Vol.43 No.2

In this study, routinely used transformation method, which includes transferring explants onto co-cultivation medium after inoculating them with bacterial solution for a while, was compared with 3 different inoculation methods. In every 3 methods, hypocotyl explants excised from 7-day-old sterile flax seedlings having cotyledon leaves and no root system dried under air flow in sterile cabin for 35 min were inoculated with different volumes of bacterial solution at different inoculation periods. GV2260 line of Agrobacterium tumefaciens having ‘pBIN 19’ plasmid containing npt II (neomycin phosphotransferase II) gene and GUS reporter gene was used in transformation studies. After inoculation, hypocotyl segments of seedlings (0.5 cm in length) - were excised and left to co-cultivation for 2 days. Then, explants were transferred to regeneration medium supplemented with different antibiotics. The presence of npt-II and GUS genes in transformants was confirmed by PCR and GUS analysis. The highest results in all characters examined in all cultivars were obtained from the 2 inoculation method in which hypocotyls excised from seedlings inoculated with 500 μl of bacterial solution after drying in sterile cabin for 35 min were used.

Variations in the Origin of Inferior Phrenic Arteries and Their Relationship to Celiac Axis Variations on CT Angiography

Ramazan Aslaner,Yeliz Pekcevik,Hilal Sahin,Onur Toka 대한영상의학회 2017 Korean Journal of Radiology Vol.18 No.2

Objective: Knowing the origin of the inferior phrenic artery (IPA) is important prior to surgical interventions and interventional radiological procedures related to IPA. We aimed to identify variations in the origin of IPA and to investigate the relationship between the origin of IPA and celiac axis variations using computed tomography angiography (CTA). Materials and Methods: The CTA images of 1000 patients (737 male and 263 female, the mean age 60, range 18–94 years) were reviewed in an analysis of IPA and celiac axis variations. The origin of IPA was divided into two groups, those originating as a common trunk and those originating independently without a truncus. The relationship between the origin of IPA and celiac axis variation was analyzed using Pearson’s chi-square test. Results: Both IPAs originated from a common trunk in 295 (29.5%) patients. From which the majority of the common trunk originated from the aorta. Contrastingly, the inferior phrenic arteries originated from different origins in 705 (70.5%) patients. The majority of the right inferior phrenic artery (RIPA) and the left inferior phrenic artery (LIPA) originated independently from the celiac axis. Variation in the celiac axis were detected in 110 (11%) patients. The origin of IPA was found to be significantly different in the presence of celiac axis variation. Conclusion: The majority of IPA originated from the aorta in patients with a common IPA trunk, while the majority of RIPA and LIPA originating from the celiac axis in patients without a common IPA trunk. Thus, the origin of IPA may widely differ in the presence of celiac axis variation.

Highly Sensitive and Reliable Electrospun Polyaniline Nanofiber Based Biosensor as a Robust Platform for COX-2 Enzyme Detections

Ramazan Asmatulu,Zeinab Veisi,Md. Nizam Uddin,Anil Mahapatro 한국섬유공학회 2019 Fibers and polymers Vol.20 No.5

Highly sensitive, reliable and practical detection of Cyclooxygenase-2 (COX-2) as an important enzyme in painbiomarkers, inflammation, and cancer cell proliferation is of great importance. This study demonstrates the feasibility ofdeveloping nanobiosensor (or biosensor) platforms for sensitive COX-2 biomarker detection from phosphate buffer saline(PBS) and human serum samples. Highly porous polyaniline nanofibers were fabricated in four different average diametersusing electrospinning process. They were then integrated as the main sensing component into interdigitated goldmicroelectrodes to develop label-free electrochemical nanobiosensors. The performance of the nanobiosensors was evaluatedin comparison with a plain control biosensor using electrochemical impedance spectroscopy (EIS). Significant improvementwas observed in the sensitivity of the nanofiber-based biosensors revealing the remarkable capability of electrospunpolyaniline nanofiber in robust and rapid detection of the COX-2 biomarker. The fabricated nanofiber-based biosensors wereable to detect the target antigen with concentrations as low as 0.01 pg/ml in PBS and human serum samples, respectively. High sensitivity, as well as remarkable selectivity towards COX-2 analyte, suggested the excellent potential of this nanofiberbasedplatform for reliable COX-2 analyte detection.