ALMOST α-COSYMPLECTIC f-MANIFOLDS ENDOWED WITH A SEMI-SYMMETRIC NON-METRIC CONNECTION

( Selahattin Beyendi ),( Nesip Aktan ),( Ali Ihsan Sivridağ ) 호남수학회 2020 호남수학학술지 Vol.42 No.1

In this paper, we introduce almost α-Cosymplectic f-manifolds endowed with a semi-symmetric non-metric connection and give some general results concerning the curvature of such connection. In particular, we study some curvature properties of an almost α-cosymplectic f-manifold equipped with semi-symmetric non-metric connection.

Characteristics of traps in TlInS2 single crystals

Selahattin Ozdemir,Mahmut Bucurgat 한국물리학회 2013 Current Applied Physics Vol.13 No.9

Characteristics of charge traps in TlInS2 single crystals are investigated by the use of thermally stimulatedcurrent (TSC) technique. The TSC spectra of the sample from 80 K to 300 K are recorded at a constantheating rate. The spectra reveal that there are several trapping levels associated with the complexstructure of overlapping peaks. The experimental results indicate that the traps in TlInS2 associated withthe spectra in the measuring range of temperature obey the monomolecular (first order) kinetics. Thus,the spectra are resolved into first order shaped peaks by the use of computerized best fit procedure. Thetrapping parameters; such as the energy depth, temperature dependent frequency factor and capturecross section, together with concentrations of the corresponding six discrete levels are computed. Thesecenters all having low capture cross sections with strong temperature dependence are found to be at theenergies of 0.11 eV, 0.22 eV, 0.25 eV, 0.26 eV, 0.29 eV and 0.30 eV with high concentrations of 6.6 x 1016,2.0 x 1017, 3.3 x 1017, 9.6 x 1016, 2.3 x 1017 and 4.0 x 1017 cm-3, respectively.

MAC Protocols for Energy Harvesting Wireless Sensor Networks: Survey

Selahattin Kosunalp 한국전자통신연구원 2015 ETRI Journal Vol.37 No.4

Energy harvesting (EH) technology in the field of wireless sensor networks (WSNs) is gaining increasing popularity through removing the burden of having to replace/recharge depleted energy sources by energy harvester devices. EH provides an alternative source of energy from the surrounding environment; therefore, by exploiting the EH process, WSNs can achieve a perpetual lifetime. In view of this, emphasis is being placed on the design of new medium access control (MAC) protocols that aim to maximize the lifetime of WSNs by using the maximum possible amount of harvested energy instead of saving any residual energy, given that the rate of energy harvested is greater than that which is consumed. Various MAC protocols with the objective of exploiting ambient energy have been proposed for energy-harvesting WSNs (EH-WSNs). In this paper, first, the fundamental properties of EH-WSN architecture are outlined. Then, several MAC protocols proposed for EH-WSNs are presented, describing their operating principles and underlying features. To give an insight into future research directions, open research issues (key ideas) with respect to design trade-offs are discussed at the end of this paper.

Practical Implementation and Stability Analysis of ALOHA-Q for Wireless Sensor Networks

Selahattin Kosunalp,Paul Daniel Mitchell,David Grace,Tim Clarke 한국전자통신연구원 2016 ETRI Journal Vol.38 No.5

This paper presents the description, practical implementation, and stability analysis of a recently proposed, energy-efficient, medium access control protocol for wireless sensor networks, ALOHA-Q, which employs a reinforcement-learning framework as an intelligent transmission strategy. The channel performance is evaluated through a simulation and experiments conducted using a real-world test-bed. The stability of the system against possible changes in the environment and changing channel conditions is studied with a discussion on the resilience level of the system. A Markov model is derived to represent the system behavior and estimate the time in which the system loses its operation. A novel scheme is also proposed to protect the lifetime of the system when the environment and channel conditions do not sufficiently maintain the system operation.

Experimental Study of Capture Effect for Medium Access Control with ALOHA

Selahattin Kosunalp,David Grace,Tim Clarke 한국전자통신연구원 2015 ETRI Journal Vol.37 No.2

In this paper, we investigate the capture effect through experiments conducted with Iris nodes equipped with AT86RF230 radio transceivers. It is shown that the first arriving packet in a collision can capture the radio channel for equal power transmissions and may be decoded depending on the amount of overlap. A new 3-packet-capture scenario is introduced and implemented. To be able to understand the impact of capture on the throughput performance of wireless sensor networks, we present an analysis of the capture coefficient using our practical results. For real-world implementations, the throughput of pure ALOHA considering a finite number of users is presented in analytical form. The capture coefficient is then applied to pure ALOHA as a case study. Using analytical and practical implementations of the capture effect on ALOHA, a very good match in channel throughput performance enhancement is demonstrated over the non-capture effect case. TinyOS-2.x is used to program the nodes and to observe data exchange on a computer through a base station.

Significance of Atypical Small Acinar Proliferation and High-Grade Prostatic Intraepithelial Neoplasia in Prostate Biopsy

Orhan Koca,Selahattin Çalışkan,Metin İshak Öztürk,Mustafa Güneş,Ihsan Karaman 대한비뇨의학회 2011 Investigative and Clinical Urology Vol.52 No.11

Purpose: In clinical practice, atypical small acinar proliferation (ASAP) and high-grade prostatic intraepithelial neoplasia (HGPIN) are two common findings on prostate biopsies. Knowing the frequency of a prostate cancer diagnosis on repeat biopsies would aid primary treating physicians regarding their decisions in suspicious cases. Materials and Methods: One hundred forty-three patients in whom biopsies revealed ASAP or HGPIN or both were enrolled in the present study; prostate cancer was not reported in the biopsy specimens and at least one repeat biopsy was performed. Age, digital rectal examination findings, prostate volumes, and free and total prostate-specific antigen (PSA) levels and the biopsy results of the patients were recorded. Results: Of the 97 patients with ASAP on the first set of biopsies, prostate cancer was diagnosed in the second and third biopsies of 32 and 6 patients, respectively. Prostate cancer was not detected in the second or third biopsies of the 40 patients with HGPIN in the first biopsy. Of the 6 patients with ASAP+HGPIN in the first biopsy, prostate cancer was detected in 3 patients in the second biopsy and in 1 patient in the third biopsy. Conclusions: The diagnosis of ASAP is a strong risk factor for prostate cancer. A repeat biopsy should be performed for the entire prostate subsequent to the diagnosis of ASAP. In patients with HGPIN according to the biopsy result, the clinical decision should be based on other parameters, such as PSA values and rectal examination, and a repeat biopsy should be avoided if the initial biopsy was performed with multiple sampling. Purpose: In clinical practice, atypical small acinar proliferation (ASAP) and high-grade prostatic intraepithelial neoplasia (HGPIN) are two common findings on prostate biopsies. Knowing the frequency of a prostate cancer diagnosis on repeat biopsies would aid primary treating physicians regarding their decisions in suspicious cases. Materials and Methods: One hundred forty-three patients in whom biopsies revealed ASAP or HGPIN or both were enrolled in the present study; prostate cancer was not reported in the biopsy specimens and at least one repeat biopsy was performed. Age, digital rectal examination findings, prostate volumes, and free and total prostate-specific antigen (PSA) levels and the biopsy results of the patients were recorded. Results: Of the 97 patients with ASAP on the first set of biopsies, prostate cancer was diagnosed in the second and third biopsies of 32 and 6 patients, respectively. Prostate cancer was not detected in the second or third biopsies of the 40 patients with HGPIN in the first biopsy. Of the 6 patients with ASAP+HGPIN in the first biopsy, prostate cancer was detected in 3 patients in the second biopsy and in 1 patient in the third biopsy. Conclusions: The diagnosis of ASAP is a strong risk factor for prostate cancer. A repeat biopsy should be performed for the entire prostate subsequent to the diagnosis of ASAP. In patients with HGPIN according to the biopsy result, the clinical decision should be based on other parameters, such as PSA values and rectal examination, and a repeat biopsy should be avoided if the initial biopsy was performed with multiple sampling.

SOME NOTES ON NEARLY COSYMPLECTIC MANIFOLDS

( MUSTAFA YILDIRIM ),( Selahattin Beyendi ) 호남수학회 2021 호남수학학술지 Vol.43 No.3

In this paper, we study some symmetric and recurrent conditions of nearly cosymplectic manifolds. We prove that Ricci-semisymmetric and Ricci-recurrent nearly cosymplectic manifolds are Einstein and conformal flat nearly cosymplectic manifold is locally isometric to Riemannian product R × N, where N is a nearly Kähler manifold.

Bilateral Ureteral Stones and Spontaneous Perirenal Hematoma in a Patient with Chronic Idiopathic Thrombocytopenic Purpura

Mehmet Akyüz,Selahattin Çalışkan,Cevdet Kaya 대한비뇨의학회 2012 Investigative and Clinical Urology Vol.53 No.7

Idiopathic thrombocytopenic purpura (ITP) is an immune thrombocytopenia with a usually benign clinical course. Bleedings are mostly of the mucocutaneous type with mild symptoms. Massive bleedings requiring transfusion are rarely seen, unless the number of platelets decreases to extremely low levels. In this case, bilateral perirenal hematoma and bilateral distal ureteral stones were detected on a non-contrast computed tomography scan of a 57-year-old male patient who developed macroscopic hematuria during his treatment in the clinics of internal medicine because of left flank pain and diffuse petechial rashes all over his body. The patient, who had been receiving chronic ITP treatment for 1 year, had a very low platelet count (4,000/mm3). The patient was prescribed bed rest, and his platelet count increased to a safe level for surgical intervention of above 50,000/mm3 with administration of prednisolone, intravenous immune globulin, and platelet suspension. A stone-free state was achieved after bilateral ureterorenoscopy and pneumatic lithotripsy. A conservative approach was followed for the perirenal hematoma. Upon regression of the perirenal hematoma, the patient was discharged at 9 weeks postoperatively.

LAZHAR TYPE INEQUALITIES FOR p-CONVEX FUNCTIONS

Imdat Iscan,Tekin Toplu,Selahattin Maden 호남수학회 2022 호남수학학술지 Vol.44 No.3

The aim of this study is to establish some new Jensen and Lazhar type inequalities for p-convex function that is a generalization of convex and harmonic convex functions. The results obtained here are reduced to the results obtained earlier in the literature for convex andharmonic convex functions in special cases.

Regional climate simulations and future projections by COSMO-CLM in Istanbul

Cemre Yoruk Sonuc,Yurdanur Unal,Selahattin Incecik 한국대기환경학회 2021 한국대기환경학회 학술대회논문집 Vol.2021 No.10

Climate change can affect human health by making our air less healthy to breathe. Atmospheric warming associated with climate change has the potential to increase surface ozone levels, particularly in mid-latitude regions of the world. Rising ozone levels cause serious health problems, especially in summer, and may pose difficulties in complying with ozone air quality standards in the future. The study aims to investigate the ability of the COSMO-CLM model to reproduce the climate characteristics over Turkey and northwest of the country and emphasizing Istanbul to evaluate the projections of the regional climate model by determining the future changes in the temperature and precipitation variables. This study examines the present (1991-2005) and high-resolution climate projections for (2041-60) and (2071-90) over Istanbul and its surrounding areas at a spatial resolution of 0.0275o (2.8 km), employing the IPCC RCP 8.5 emission scenario by the COSMO-CLM_5.0 regional climate model forced by the earth system model MPI-ESM-LR. The performance of the model was validated by comparing simulation results to the observations. Climate projections show significant warming expected over the whole area in the period of 2041-2060 and especially in 2071-2090. Warming over Istanbul is around 1.25°C in the first period but, significantly higher in the case of the second period, which reaches up to 3.0°C. With the effect of Marmara at the south and the Black Sea on the north, warming increases in the coastline are higher than in the inner parts of the city. Moreover, in the spring and summer seasons, the north of Istanbul warms up more slowly than the south, the difference in the rate of temperature increase is expected to be more pronounced in the summer season. An increase in summer temperatures is expected especially in the southern coastal parts of the city. This will lead to an increase in ozone levels with the effect of land-sea breeze circulations. A significant reduction in precipitation is particularly evident at the end of the century over Istanbul. It is expected that the greatest decrease will occur in the spring season in both periods. The decrease in precipitation will lead to an increase in particulate pollution caused by Saharan dust transport, which affects Istanbul, especially in the spring season.