The Impact of Learning Curve on Flap Thickness Outcome in Femtosecond Laser-assisted Laser In Situ Keratomileusis Performed with New LenSx Dual Platform

Bilgehan Sezgin Asena,Oya Donmez 대한안과학회 2022 Korean Journal of Ophthalmology Vol.36 No.3

The use of neural networks in concrete compressive strength estimation

M. Bilgehan,P. Turgut 사단법인 한국계산역학회 2010 Computers and Concrete, An International Journal Vol.7 No.3

Testing of ultrasonic pulse velocity (UPV) is one of the most popular and actual non-destructive techniques used in the estimation of the concrete properties in structures. In this paper, artificial neural network (ANN) approach has been proposed for the evaluation of relationship between concrete compressive strength, UPV, and density values by using the experimental data obtained from many cores taken from different reinforced concrete structures with different ages and unknown ratios of concrete mixtures. The presented approach enables to find practically concrete strengths in the reinforced concrete structures, whose records of concrete mixture ratios are not yet available. Thus, researchers can easily evaluate the compressive strength of concrete specimens by using UPV values. The method can be used in conditions including too many numbers of the structures and examinations to be done in restricted time duration. This method also contributes to a remarkable reduction of the computational time without any significant loss of accuracy. Statistic measures are used to evaluate the performance of the models. The comparison of the results clearly shows that the ANN approach can be used effectively to predict the compressive strength of concrete by using UPV and density data. In addition, the model architecture can be used as a non-destructive procedure for health monitoring of structural elements.

Analysis of Radiofrequency Ablation of Small Renal Tumors in Patients at High Anesthetic and Surgical Risk: Urologist Experience with Follow-up Results in the Initial Six Months

Yuksel, Mehmet Bilgehan,Karakose, Ayhan,Gumus, Bilal,Tarhan, Serdar,Atesci, Yusuf Ziya,Akan, Zafer Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.11

Background: To evaluate the results of various types of radiofrequency ablation (RFA) treatment of renal tumors in patients with excessive anesthetic and surgical risk. Materials and Methods: Data for RFA performed in in high risk patients were retrospectively evaluated. Other RFA applications in patients with no anesthetic and/or surgical risk were excluded. RFA was by ultrasound or CT guided percutaneous (USG/CT-PRFA) and retroperitoneally or transperitoneally laparoscopic (R/T-LRFA) techniques under general or local anethesia. Follow-up data of enhanced CT or MRI after 1, 3 and 6 months were analysed for twelve RFA applications. Results: The RFA applications included 4 (40%) left-sided, 5 (50%) right-sided and 1 (10%) bilaterally RFA (simultaneously 1 right and 2 left). The localizations of tumors were 2 (16.6%) upper, 5 (41.6%) mid and 5 (41.6%) lower pole. The RFA applications included 9 (75%) USG-PRFA, 1 (8.3%) CT-PRFA, 1 (8.3%) T-LRFA and 1 (8.3%) R-LRFA. The mean age was $65.3{\pm}8.5$ (52-76) years. The mean tumor size was $29.6{\pm}6.08$ (15-40) mm. No complications related to the RFA were encountered in any of the cases. Failure (residual tumour) was determined in 8.3% (1/12) of USG-RFA application. The success rate was thus 91.7% (11/12). Other 1st, 3rd and 6th months follow-up data revealed no residua and recurrence. Conclusions: RFA application appears to be safe as a less invasive and effective treatment modality in selected cases of small renal tumors in individuals with excessive anesthetic and also surgical risk.

Sepsis and Meningitis due to Listeria Monocytogenes

Orhan Yildiz,Bilgehan Aygen,Duygu Esel,Uner Kayabas,Emine Alp,Bulent Sumerkan,Mehmet Doganay 연세대학교의과대학 2007 Yonsei medical journal Vol.48 No.3

Purpose: This study focused on the effect of immuno-compromising conditions on the clinical presentation of severe listerial infection. Patients and Methods: Nine human listeriosis cases seen from 1991-2002 were reviewed. All adult patients, from whose blood, peritoneal fluid or cerebrospinal fluid (CSF) the L. monocytogenes was isolated, were included in this retrospective study. Results: Listeriosis presented as primary sepsis with positive blood cultures in 5 cases and meningitis with positive CSF cultures in 4 cases. All of these patients had at least one underlying disease, most commonly, hematologic malignancy, diabetes mellitus, amyloidosis and hepatic cirrhosis; 55.6% had received immunosuppressive or corticosteroid therapy within a week before the onset of listeriosis. The patients were adults with a mean age of 60 years. Fever, night sweats, chills and lethargy were the most common symptoms; high temperature (>38℃), tachycardia, meningeal signs and poor conditions in general were the most common findings on admission. The mortality rate was 33.3% and was strictly associated with the severity of the underlying disease. Mortality differences were significant between sepsis (20%) and meningitis (50%) patients. Conclusion: Listeriosis as an uncommon infection in our region and that immuno- suppressive therapy is an important pre-disposing factor of listeriosis. Sepsis and meningitis were more common in this group of patients and had the highest case-fatality rate for food-borne illnesses.

Understanding Hydrogen-Induced Strain Localization in Super Duplex Stainless Steel Using Digital Image Correlation Technique

Cem Örnek,Bilgehan M. Şeşen,Mustafa K. Ürgen 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.2

This paper provides a mechanistic understanding of hydrogen-microstructure-strain interactions in a finely-grained 25Cr–7Nisuper duplex stainless steel subjected to dynamic tensile loading. Miniature-sized tensile specimens were hydrogen-chargedfor up to nine days, and the microstructure was imaged, in-situ, during mechanical tensile testing. Digital image correlationanalysis of the recorded images revealed that the austenite phase underwent softening while the ferrite phase hardened due touptaken hydrogen. Severe strain localization occurred due to dissolved hydrogen in the microstructure resulting in hydrogeninducedcracks. Mobile hydrogen atoms caused softening of the microstructure while trapped hydrogen reasoned hardening. The austenite’s hydrogen absorption capacity is decisive for the susceptibility to hydrogen embrittlement.

Treatment of reactive dyebath wastewater by electrocoagulation process: Optimization and cost-estimation

Ahmet Aygun,Bilgehan Nas,Mehmet Faik Sevimli 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.9

Reactive dyestuff is commonly used in the textile industry. Reactive dyebath wastewater (RDW) was treated with a batch, monopolar, parallel lab scale electrocoagulation process (EC) having 0.042m2 effective electrode area. The effects of process parameters, such as initial pH, current density and electrolysis period on COD and color removal efficiency, were investigated by using response surface methodology (RSM). At the optimal conditions, 85.8% color and 76.9% COD removal were obtained with 1.84 €/m3 operating cost for Al electrode, while 92.0% decolorization and 80.9% COD removal were obtained with 1.56 €/m3 operating cost for an iron electrode. The iron electrode was found superior to aluminum as a sacrificial anode material in terms of COD and color removal with low cost. The cost of electrical energy, electrode, and chemical consumptions for electrocoagulation were considered to find an optimum and feasible solution. As a result, the operating cost consists of approximately 2% for energy, 28% for electrode and 70% for chemical consumption for both electrodes. Based upon the data, it is clearly seen that operating cost covers mostly for HCI to adjust pH due to the high pH and alkalinity of RDW, which was neglected in many studies. The first-order reaction kinetics with a higher slope for the color were well fitted, resulting in faster color removal than that of COD for both electrodes.

Application of sequencing batch biofilm reactor (SBBR) in dairy wastewater treatment

Ahmet Aygun,Arzu Ozturk,Bilgehan Nas 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.2

Application of lab-scale sequencing batch (SBR) and sequencing batch biofilm reactors (SBBR) for treatment of dairy wastewater was investigated under organic loading of 1,130-1,560 gBOD5/m3·d. The main characteristics of the dairy wastewater were: pH=4.9, chemical oxygen demand (COD)=16,264 mg/l; biological oxygen demand (BOD5)=10,536mg/l, PO4-P=342mg/l; total nitrogen (TN)=224mg/l. SBBR was filled with the Kaldnes K1 biocarrier at 30% of the volume of empty reactor. The SBR and SBBR were operated in fixed 24 h cycles, each consisting of 30 min fill up, 22 h aeration, 1.5 h settle, 30min decant, and idle with a hydraulic retention time (HRT) of 8 days. Operational parameters such as pH, dissolved oxygen (DO), mixed liquor suspended solid (MLSS), solids retention time (SRT) and sludge volume index (SVI) were monitored during the whole cycle. The effects of these parameters on the COD, nitrogen and phosphorus removal were discussed in this paper. As a result, adding biocarrier to the reactor had a positive effect on organic with COD removal of 63.5% for SBR and 81.8% for SBBR and nutrient removal with ammonium removal of 66.0% for SBR and 85.1% for SBBR in treatment of dairy wastewater.

Electrocoagulation of Disperse Dyebath Wastewater: Optimization of Process Variables and Sludge Production

Aygun, Ahmet,Nas, Bilgehan,Sevimli, Mehmet Faik The Korean Electrochemical Society 2021 Journal of electrochemical science and technology Vol.12 No.1

This study was conducted to investigate the effect of initial pH, current density, and electrolysis time on process performance in terms of decolorization and chemical oxygen demand (COD) removal from disperse dyebath wastewater (DDW) by mono-polar parallel laboratory scale electrocoagulation (EC) process. COD reduction of 51.3% and decolorization of 92.8% were obtained with operating cost of 0.19 €/㎥ treated wastewater for Al-Al electrode pair, while 90.5% of decolorization and 49.2% of COD reduction were obtained with operating cost of 0.20 €/㎥ treated wastewater for an Fe-Fe electrode pair. The amount of sludge production were highly related to type of the electrode materials. At the optimum conditions, the amount of sludge produced were 0.18 kg/㎥ and 0.28 kg/㎥ for Al-Al and Fe-Fe electrode pairs, respectively. High decolorization can be explained by the hydrophobic nature of the disperse dye, while limited COD removal was observed due to the high dissolved organic matter of the DDW based on auxiliary chemicals. Energy, electrode, and chemical consumptions and sludge handling were considered as major cost items to find a cost-effective and sustainable solution for EC. The contribution of each cost items on operating cost were determined as 10.0%, 51.1%, 30.5% and 8.4% for Al-Al, and they were also determined as 9.0%, 38.0%, 40.5% and 12.5% for Fe-Fe, respectively. COD reduction and decolorization were fitted to first-order kinetic rule.

Serum Levels of Trace Elements in Patients with Prostate Cancer

Kaba, Mehmet,Pirincci, Necip,Yuksel, Mehmet Bilgehan,Gecit, Ilhan,Gunes, Mustafa,Ozveren, Huseyin,Eren, Huseyin,Demir, Halit Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.6

Background: Trace elements are major components of biological structures; however, excessive levels of these elements can be toxic. Materials and Methods: In the present study, serum levels of trace elements were measured in 30 patients with newly diagnosed as prostate cancer and 32 healthy volunteer by using furnace atomic absorption spectrophotometry. Results: It was found that there was an increase in serum levels of Co, Cu, Mg and Pb (p<0.05), whereas a decrease in serum levels of Fe, Mn, and Zn levels in patients with prostate cancer (p<0.05). Conclusions: These changes may be important in the pathogenesis of prostate cancers; however, further prospective studies are needed to identify relationships between prostate cancer and trace elements.

A comparison of the effect of SSI on base isolation systems and fixed-base structures for soft soil

Karabork, T.,Deneme, I.O.,Bilgehan, R.P. Techno-Press 2014 Geomechanics & engineering Vol.7 No.1

This study investigated the effect of soil-structure interaction (SSI) on the response of base-isolated buildings. Seismic isolation can significantly reduce the induced seismic loads on a relatively stiff building by introducing flexibility at its base and avoiding resonance with the predominant frequencies of common earthquakes. To provide a better understanding of the movement behavior of multi-story structures during earthquakes, this study analyzed the dynamic behavior of multi-story structures with high damping rubber bearing (HDRB) behavior base isolation systems that were built on soft soil. Various models were developed, both with and without consideration of SSI. Both the superstructure and soil were modeled linearly, but HDRB was modeled non-linearly. The behavior of the specified models under dynamic loads was analyzed using SAP2000 computer software. Erzincan, Marmara and Duzce Earthquakes were chosen as the ground motions. Following the analysis, the displacements, base shear forces, top story accelerations, base level accelerations, periods and maximum internal forces were compared in isolated and fixed-base structures with and without SSI. The results indicate that soil-structure interaction is an important factor (in terms of earthquakes) to consider in the selection of an appropriate isolator for base-isolated structures on soft soils.