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Reflection and transmission coefficients of multiple chiral layers

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Science China(Technological Sciences) 2006年第4期49卷 457-467页

作者： SABAH Cumali uckun savas Electrical and Electronics Engineering Department Engineering Faculty University of Gaziantep Gaziantep 27310 Turkey

This paper presents a general analysis of reflection and transmission coeffi- cients of multiple chiral layers in detail. Reflection and transmission coefficients through multiple chiral layers are computed and presented particularly for the incident wave of parallel polarization for a number of cases―a wide range of incidence angle, neigh- boring center frequency and different chirality parameters. Transfer matrix method is used in the analysis. From the numerical results, it can be seen that multiple chiral layers may be used as a polarization-conversion transmission filter and antireflection filter at the fre- quency band around the central frequency.

关键词： multiple chiral, reflection, transmission, polarization, filters.

Computational and Empirical Investigation of Propeller Tip Vortex Cavitation Noise

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China Ocean Engineering 2020年第2期34卷 232-244页

作者： savas SEZEN Sakir BAL aDepartment of Naval Architecture and Marine Engineering Yildiz Technical UniversityIstanbul 34349Turkey bDepartment of Naval Architecture and Marine Engineering Istanbul Technical UniversityIstanbul 34469Turkey

In this study,non-cavitating and cavitating flow around the benchmark DTMB 4119 model propeller are solved using both viscous and potential based *** and non-cavitating propeller radiated noises are then predicted by using a hybrid method in which RANS(Reynolds-averaged Navier-Stokes)and FWH(Ffowcs Williams Hawkings)equations are solved together in open water *** cavitation on the propeller blades is modelled by using a VOF(Volume of Fiuld)method equipped with Schnerr-Sauer cavitation ***,tip vortex cavitation noise is estimated by using two different semi-empirical techniques,namely Tip Vortex Index(TVI,based on potential flow theory)and Tip Vortex Contribution(TVC).As the reference distance between noise source and receiver is not defined in open water case for TVI technique,one of the outputs of this study is to propose a reference distance for TVI technique by coupling two semi-empirical techniques and ITTC distance *** the defined distance,the starting point of the tip vortex cavitation is determined for different advance ratios and cavitation numbers using potential flow ***,it is examined that whether the hybrid method and potential flow solver give the same noise results at the inception point of tip vortex *** show that TVI method based on potential flow theory is reliable and can practically be used to replace the hybrid method(RANS with FWH approach)when tip vortex cavitation starts.

关键词： FWH equation propeller noise tip vortex cavitation TVI TVC

Evaluation of relative tectonic activity along the Priene-Sazli Fault(Soke Basin,southwest Anatolia):Insights from geomorphic indices and drainage analysis

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Journal of Mountain Science 2019年第4期16卷 909-923页

作者： savas TOPAL Pamukkale University Department of Geological EngineeringKinikli Campus

The West Anatolia Extensional Zone, which has a width of about 300 km, is located within the Alpine-Himalayan belt and is one of the regions with intense seismic activity in the world. The most important geomorphological structures in this area are three main graben structures resulting from regional N-S extension since the Early Miocene. These structures are the E-W trending Büyük Menderes, Kü?ük Menderes, and Gediz grabens. S?ke Basin is located at the SW end of the Büyük Menderes graben. The lineaments which control the NW of S?ke Basin have a length of approximately 40 km and have been defined as the Priene-Sazl? Fault(PSF). The PSF is seismically active, and the last large earthquake(the S?ke-Balat earthquake; Ms: 6.8) was produced on July 16 th of 1955. The ancient city of Priene, which was located in the study area, suffered from destructive earthquakes(in the 4 th century and 2 nd century BC, in the 2 nd century AD, during the Byzantine period and after the 12 th century BC). This study aims to reveal the effect of the PSF on the morphotectonic evolution of the region and the relative tectonic activity of the fault. To this end, it was the first time the stream length gradient index(SL: 130-1303), mountain-front sinuosity(Smf: 1.15-1.96), valley floor height and valley width ratio(Vf: 0.27-1.66), drainage basin asymmetry(AF: 0.15-0.76), hypsometric curve(HC) and hypsometric integral(HI: 0.22-0.86) and basin shape index(Bs: 1.04-5.75) along the mountain front that is formed by the PSF. Using a combination of the mountain-front sinuosity(Smf), valley floor height and valley width ratio(Vf), it is found that the uplift ratio in the region is not less than 0.05 mm/yr and the relative tectonic activity of PSF is high. According to the relative tectonic activity index(Iat) obtained from geomorphic indices, the southwest part of the PSF is relatively more active than the northeast part. As a result, I posit that the PSF has the potential to produce earthquakes in t

关键词： Geomorphic indices Tectonic activity Earthquake Priene-Sazli Fault Soke basin Western Anatolia

An axisymmetric model for draft tube flow at partial load

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Journal of Hydrodynamics 2016年第2期28卷 195-205页

作者： Hosein FOROUTAN savas YAVUZKURT Department of Mechanical and Nuclear Engineering The Pennsylvania State University

A new Reynolds-averaged Navier-Stokes （RANS） turbulence model is developed in order to correctly predict the mean flow field in a draft tube operating under partial load using 2-D axisymmetric simulations. It is shown that although 2-D axisymmetric simulations cannot model the 3-D unsteady features of the vortex rope, they can give the average location of the vortex rope in the draft tube. Nevertheless, RANS simulations underpredict the turbulent kinetic energy （TKE） production and diffusion near the center of the draft tube where the vortex rope forms, resulting in incorrect calculation of TKE profiles and, hence, poor prediction of the axial velocity. Based on this observation, a new k- c turbulence RANS model taking into account the extra production and diffusion of TKE due to coherent structures associated with the vortex rope formation is developed. The new model can successfully predict the mean flow velocity with significant improvements in comparison with the realizable k - c model. This is attributed to better prediction of TKE production and diffusion by the new model in the draft tube under partial load. Specifically, the new model calculates 31% more production and 46% more diffusion right at the shear layer when compared to the k - ~ model.

关键词： hydropower draft tube turbulence model computational fluid dynamics vortex rope

Numerical Prediction of Total Resistance Using Full Similarity Technique

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China Ocean Engineering 2019年第4期33卷 493-502页

作者： savas SEZEN Ferdi CAKICI Department of Naval Architecture and Marine Engineering Yildiz Technical University

Model tests are often conducted by researchers in a real or a numerical towing tank to calculate residuary resistance of a ship with the aid of Froude similarity. Common ITTC-1957 formula is usually employed to calculate frictional resistance. As computer technologies develop over time, CFD tools are used for calculating total resistance of a ship at full scale without establishing any dynamic similarities. In this paper, both Froude and Reynolds similarities are numerically implemented to four different model scales by using virtual fluids. The total resistance at different Fr numbers calculated by the numerical study is validated against the experimental data of DTMB 5512 (L=3.048 m) model hull. The results show that establishing Froude and Reynolds similarities together in numerical simulation is possible in principle. To determine whether it has advantages for prediction of full-scale ship total resistance by employing this method, it is also examined the model scale with the same number of elements and Reynolds number of the full-scale ship. Results show that numerical calculation of total resistance for a full-scale ship in a model scale by defining virtual fluids has only slight advantages on the prediction of residuary resistance. Additionally, no advantage in the calculation of frictional resistance is observed.

关键词： total resistance Froude and Reynolds similarities DTMB 5512 CFD

A NOTE ON GENERALIZED ABSOLUTE SUMMABILITY FACTORS FOR A TRIANGULAR MATRIX

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Acta Mathematica Scientia 2011年第4期31卷 1513-1516页

作者： Ekrem savas Department of Mathematics Istanbul Ticaret Universityskdar

In this paper, a general theorem on ｜ A, δ ｜k -summability factors of infinite series is proved under different conditions.

关键词： absolute summability summability factors triangular matrix

Gastrointestinal endoscopy in pregnancy

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World Journal of Gastroenterology 2014年第41期20卷 15241-15252页

作者： Nurten savas Department of Gastroenterology Baskent Universitesi Hastanesi

Gastrointestinal endoscopy has a major diagnostic and therapeutic role in most gastrointestinal disorders; however, limited information is available about clinical efficacy and safety in pregnant patients. The major risks of endoscopy during pregnancy include potential harm to the fetus because of hypoxia, premature labor, trauma and teratogenesis. In some cases, endoscopic procedures may be postponed until after delivery. When emergency or urgent indications are present, endoscopic procedures may be considered with some precautions. United States Food and Drug Administration category B drugs may be used in low doses. Endoscopic procedures during pregnancy may include upper gastrointestinal endoscopy, percutaneous endoscopic gastrostomy, sigmoidoscopy, colonoscopy, enteroscopy of the small bowel or video capsule endoscopy, endoscopic retrograde cholangiopancreatography and endoscopic ultrasonography. All gastrointestinal endoscopic procedures in pregnant patients should be performed in hospitals by expert endoscopists and an obstetrician should be informed about all endoscopic procedures. The endoscopy and flexible sigmoidoscopy may be safe for the fetus and pregnant patient, and may be performed during pregnancy when strong indications are present. Colonoscopy for pregnant patients may be considered for strong indications during the second trimester. Although therapeutic endoscopic retrograde cholangiopancreatography may be considered during pregnancy, this procedure should be performed only for strong indications and attempts should be made to minimize radiation exposure.

关键词： Pregnancy Endoscopy Colonoscopy Endoscopic retrograde cholangiopancreatography Safety

Relational Logging Design Pattern

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Computers, Materials & Continua 2023年第4期75卷 51-65页

作者： savas Takan Gokmen Katipoglu Ankara University Ankara06560Turkey Kafkas University Kars36000Turkey

Observability and traceability of developed software are crucial to its success in software *** is the ability to comprehend a system’s internal state from the *** is used to determine what causes system problems and *** are among the most critical technology to guarantee observability and *** are frequently used to investigate software *** current log technologies,software events are processed independently of each ***,current logging technologies do not reveal ***,system events do not occur independently of one *** this perspective,our research has produced a new log design pattern that displays the relationships between *** the design we have developed,the hash mechanism of blockchain technology enables the display of the logs’*** created design pattern was compared to blockchain technology,demonstrating its performance through *** has been determined that the recommended log design pattern outperforms blockchain technology in terms of time and space for software engineering observability and *** this context,it is anticipated that the log design pattern we provide will strengthen the methods used to monitor software projects and ensure the traceability of relationships.

关键词： Blockchain logging software engineering data structure design pattern

Novel Metrics for Mutation Analysis

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Computer Systems Science & Engineering 2023年第8期46卷 2075-2089页

作者： savas Takan Gokmen Katipoglu Ankara University Ankara06100Turkey Kafkas University Kars36100Turkey

A measure of the“goodness”or efficiency of the test suite is used to determine the proficiency of a test *** appropriateness of the test suite is determined through mutation *** Finite State Machine(FSM)mutants are produced in mutation analysis by injecting errors against *** mutants serve as test subjects for the test suite(TS).The effectiveness of the test suite is proportional to the number of eliminated *** most effective test suite is the one that removes the most significant number of mutants at the optimal *** is difficult to determine the fault detection ratio of the *** it is difficult to identify the system’s potential flaws *** mutation testing,the Fault Detection Ratio(FDR)metric is currently used to express the adequacy of a test ***,there are some issues with this *** both test suites have the same defect detection rate,the smaller of the two tests is *** test case(TC)is affected by the same *** smaller two test cases with identical performance are assumed to have superior *** difficulty involves *** performance of numerous vehicles claiming to have a perfect mutant capture time is *** study developed three metrics to address these issues:FDR/|TS|,FDR/|TC|,and FDR/|Time|;In this context,most used test generation tools were examined and tested using the developed *** to the metrics we have developed,the research contributes to eliminating the problems related to performance measurement by integrating the missing parameters into the system.

关键词： Software engineering testing mutation analysis fault detection ratio metrics time