Fracture behavior and pore structure of concrete with metakaolin

Akcay, Burcu,Sengul, Cengiz,Tasdemir, Mehmet ali Techno-Press 2016 Advances in concrete construction Vol.4 No.2

Metakaolin, a dehydroxylated product of the mineral kaolinite, is one of the most valuable admixtures for high-performance concrete applications, including constructing reinforced concrete bridges and impact- and fire-resistant structures. Concretes produced using metakaolin become more homogeneous and denser compared to normal-strength concrete. Yet, these changes cause a change of volume throughout hardening, and increase the brittleness of hardened concrete significantly. In order to examine how the use of metakaolin affects the fracture and mechanical behavior of high-performance concrete we produced concretes using a range of water to binder ratio (0.42, 0.35 and 0.28) at three different weight fractions of metakaolin replacement (8%, 16% and 24%). The results showed that the rigidity of concretes increased with using 8% and 16% metakaolin, while it decreased in all series with 24% of metakaolin replacement. Similar effect has also been observed for other mechanical properties. While the peak loads in load-displacement curves of concretes decreased significantly with increasing water to binder ratio, this effect have been found to be diminished by using metakaolin. Pore structure analysis through mercury intrusion porosimetry test showed that the addition of metakaolin decreased the critical pore size of paste phases of concrete, and increasing the amount of metakaolin reduced the total porosity for the specimens with low water to binder ratios in particular. To determine the optimal values of water to binder ratio and metakaolin content in producing high-strength and high-performance concrete we applied a multi-objective optimization, where several responses were simultaneously assessed to find the best solution for each parameter.

Influence of deposition pressure and power on characteristics of RF-Sputtered Mo films and investigation of sodium diffusion in the films

N. Akcay,N. Akin Sonmez,E.P. Zaretskaya,S. Ozcelik 한국물리학회 2018 Current Applied Physics Vol.18 No.5

Mo films deposited by DC sputtering are widely used as back contact in CIGS and CZTS based thin film solar cells. However, there have been only a few studies on the deposition of Mo films by RF sputtering method. In this context, Mo films on SLG substrates were prepared as a function of deposition pressure and power by using RF magnetron sputtering method to contribute to this shortcoming. Mo films were deposited at 250 °C substrate temperature by using 20, 15, 10 mTorr Ar pressures at 120 W RF power and 10 mTorr Ar pressure at 100 W RF power. Structural, morphological and reflectivity properties of RF-sputtered Mo films were clarified by XRD, AFM, FE-SEM and UV–Vis measurements. In addition, due to sodium incorporation from SLG substrate to the absorber layer through Mo back contact layer is so essential in terms of improving the conversion efficiency values of CIGS and CZTS thin film solar cell devices, the effects of Na diffusion in the films were analyzed with SIMS depth profile. The electrical properties of the films such as mobility, carrier density and resistivity were determined by Hall Effect measurements. It was found that Mo films prepared at 120 W, 10 mtorr and 250 °C substrate temperature and then annealed at 500 °C for 30 min, had resistivity as low as 10−5 Ω cm, as well as higher amount of Na incorporation than other films.

Aggregate Restraining Effect on Autogenous Shrinkage of Cementitious Materials

Burcu Akcay 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.8

In this paper the restraining effect of aggregates on autogenous shrinkage of cementitious materials is investigated by usingdifferent maximum aggregate sizes. Experimental studies were conducted to determine the restraining effect of aggregates onautogenous shrinkage of composites with a paste to aggregate ratio of 70 to 30 by volume percent. It was shown that the autogenousshrinkage is reduced by addition of aggregate, and this effect can be predicted using Pickett’s expression. A comparison of the resultsof calculated autogenous shrinkage with that of experimental studies on cement paste, mortars, concrete, and also individualcomposites containing cement paste and different particle size of aggregate is presented. The use of the modulus of elasticity obtainedfrom the meso-mechanical modeling gave satisfactory predictions in calculating the autogenous shrinkage of cementitious materials. The microstructural characteristics of samples were identified using their pore size distributions that were determined by mercuryintrusion porosimetry tests. The results show that experimental and predicted values of autogenous shrinkage are in good agreements.

Evaluation of Left Atrial Electromechanical Delay and Left Atrial Phasic Functions in Surgical Early Menopause Patients

Murat Akcay,Metin Coksevim,Hasan Ulubaşoğlu,Omer Gedikli,Ozcan Yılmaz 한국심초음파학회 2019 Journal of Cardiovascular Imaging (J Cardiovasc Im Vol.27 No.2

BACKGROUND: This study evaluated the atrial electromechanical delay (AEMD) and the left atrial (LA) mechanical functions in patients with surgical early menopause. METHODS: A total of 62 patients were included in the study: 33 patients with surgical early menopause and 29 age- and sex-matched healthy controls. The duration distance from the start of the P wave to the beginning of the A wave for the lateral mitral annulus, septal mitral annulus, and lateral tricuspid annulus was assessed by tissue Doppler echocardiography. The differences in these durations were used to calculate the inter- and intra-atrial mechanical delays. LA volumes were evaluated using the biplane area-length technique, and LA mechanical function values were measured. RESULTS: The baseline laboratory and clinical characteristics were similar between the two groups. Surgical early menopause patients displayed increased static atrial electromechanical connection (PA′) times for the septal mitral annulus and lateral tricuspid annulus compared to the controls. However, the lateral mitral annulus, the inter-atrial, the intra-LA, and the right atrial EMD PA′ times were not significantly altered in surgical early menopause patients compared to controls. Importantly, the LA volume index (28.1 ± 8.17 vs. 24.89 ± 7.96 mL/m2, p = 0.019), the maximal LA volume (49.6 ± 14.1 vs. 42.9 ± 16.1 mL, p = 0.004), the minimal LA volume (18.4 ± 7.0 vs. 15.2 ± 9.0 mL, p = 0.022), and the atrial precontraction LA volume (31.0 ± 10.9 vs. 24.9 ± 10.1 mL, p = 0.006) were higher in the patients with surgical early menopause compared to the controls. The LA reservoir, conduit and pumping functions and the total, passive, and active emptying volumes were all comparable between the two groups (p = 0.09; 0.06; 0.68; 0.06; 0.48; 0.07, respectively). CONCLUSIONS: Patients with surgical early menopause demonstrated impaired atrial electrical delay and electromechanical functions.

Autogenous Shrinkage, Pozzolanic Activity and Mechanical Properties of Metakaolin Blended Cementitious Materials

Burcu Akcay,Mehmet Ali Tasdemir 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.11

In the literature, there are some conflicting results regarding the influence of metakaolin (MK) addition on autogenous shrinkage behavior of cementitious materials. In this study, with the aim of identifying how the use of MK changes the properties of cementitious materials, cement was partially replaced by MK in different proportions (8%, 16%, and 24%) in pastes produced with variable water/binder ratios (w/b; 0.28, 0.35 and 0.42). The temperature development and calcium hydroxide consumption by thermogravimetric analysis were observed to better characterize the effects of MK on the autogenous shrinkage behavior. The mechanical properties such as compressive strength and flexural strength were experimentally investigated. The results show that the addition of MK has contrasting effects on autogenous shrinkage during early ages depending on the w/b ratio. Thermogravimetric analysis showed that the amount of stratlingite was smaller in pastes with low w/b ratios than in pastes with high w/b ratio. The calcium hydroxide consumption with the pozzolanic reaction of MK was significant even at 2 days, but consumption ratios with respect to the reference paste slowed down at 7 to 28 days.

Pomegranate Wine Has Greater Protection Capacity Than Red Wine on Low-Density Lipoprotein Oxidation

Yasemin Delen Akcay,Ebru Demirel Sezer,Bilal Ilanbey,Hatice Kalkan Yıldırım,Eser Yıldırım Sozmen 한국식품영양과학회 2007 Journal of medicinal food Vol.10 No.2

Although there is a large body of evidence on the main role of red wine in protection of low-density lipopro-tein (LDL) against oxidation, there are few data on the role of pomegranate juice, which has high phenolic content. We con-ducted this study considering the possible importance of pomegranate wine as an antioxidant and in order to make a com-parison between red and pomegranate wines. The phenol levels of pomegranate and red wines (4,850 mg/L gallic acidequivalents and 815 mg/L gallic acid equivalents, respectively) were in accordance with their total antioxidant activity (39.5%and 33.7%, respectively). Both wines decreased LDL-diene levels following a 30-minute incubation period compared withcontrols (145. 3.2 .mol/mg of LDL protein). However, pure pomegranate wine demonstrated a greater antioxidant effect(P. .01) on diene level (110. 4.6 .mol/mg of LDL protein) than pure red wine (124. 3.2 .mol/mg of LDL protein). Inconclusion, we suggest that pomegranate wine has potential protective effects toward LDL oxidation, and it may be a dietarychoice for people who prefer fruit wines.

Comparison of Pain between First and Second Operated Eyelids after Upper Eyelid Blepharoplasty

Mehmet Icoz(Mehmet Icoz ),Bilge Tarım(Bilge Tarım ),Sule Gokcek Gurturk Icoz(Sule Gokcek Gurturk Icoz ),Emine Kalkan Akcay(Emine Kalkan Akcay ) 대한안과학회 2023 Korean Journal of Ophthalmology Vol.37 No.3

Purpose: To evaluate and compare intraoperative pain during upper eyelid blepharoplasty (UEB) between on first and second operated eyelids. Methods: In this cross-sectional observational study, the patients were divided into two groups, with group 1 representing 40 patients whose surgery was first started on the right and group 2 representing the other 40 patients who started surgery on the left first. UEB was performed to all patients by the same surgeon under the same and equal amount of local anesthesia. Degree of pain felt during surgery on first and second operated eyelid was evaluated with the visual analoge scale (VAS) and Wong-Baker Facial Pain Expression Scale (WBFPES) of all patients immediately after surgery and was compared using paired t-test. Results: There were 20 female and 20 male patients in both groups. In group 1, the VAS value was 2.8 ± 1.5 and WBFPES value was 2.7 ± 1.6 UEB in the first operated eyelid; the VAS value was 4.1 ± 1.8 and WBFPES value was 3.9 ± 1.8 UEB in the second operated eyelid. A significant difference was found between pains felt during first and second operated eyelid UEB regarding VAS and WBFPES values in group 1 (p = 0.003 and p = 0.002, respectively). In group 2, the VAS value was 1.9 ± 1.0 and WBFPES value was 2.0 ± 1.0 UEB in the first operated eyelid; the VAS value was 3.0 ± 1.5 and WBFPES value was 2.8 ± 1.6 UEB in the second operated eyelid. A significant difference was found between pains felt during first operated and second operated eyelid UEB regarding VAS and WBFPES values in group 2 (p = 0.009 and p = 0.005, respectively). Conclusions: To the best of our knowledge, this study is the first to evaluate which eyelid is more painful during surgery in UEB. Patients tend to feel more pain during surgery on the second operated eyelid. Therefore, surgeons should consider using local anesthetics with more volume or longer duration in the second operating eyelid in light of this information and patients should be given detailed information about pain.

Multi-Objective Design for Half-Car Active Suspensions

Semiha Turkay,Huseyin Akcay 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10

In this paper, multi-objective control of a half-car suspension system is formulated as a mixed H2/H∞ synthesis problem and this convex problem is solved using linear matrix inequalities. Then, the control design problem is re-formulated as a non-convex and non-smooth optimization problem with fixed order controllers and solved by using the recently developed HIFOO toolbox. Parametric studies show that tire damping can seriously impact closed-loop performance of actively controlled half-car models.

The use of infrared thermography to detect the stages of estrus cycle and ovulation time in anatolian shepherd dogs

( Kemal Tuna Olgac ),( Ergun Akcay ),( Beste Cil ),( Burak Mehmet Ucar ),( Ali Daskın ) 한국축산학회(구 한국동물자원과학회) 2017 한국축산학회지 Vol.59 No.10

Background: The aim of the study is to evaluate the effectiveness of thermographic monitoring, using the temperature changes of perianal and perivulvar areas for the determination of estrus in Anatolian Shepherd bitches. Fifteen bitches were used in the study. Blood and vaginal smear samples were collected and thermographic monitoring of perianal and perivulvar areas were carried out starting from proestrus to early diestrus. Also, external signs of estrus were investigated. Smear samples were evaluated by light microscopy after Diff-Quik staining method and superficial and keratinized superficial cells were determined as percentage (S + KS%). Progesterone and luteinizing hormone measurements were done by radioimmunoassay. The difference in temperature between perianal and perivulvar areas was evaluated through thermographic images by FLIR ResearchIR Software. Results: According to the results obtained from the study, differences between progesterone and S + KS% were statistically significant (P < 0,05). Although temperature showed increase and decrease with progesterone and S + KS%, the differences were not important statistically (P > 0,05). Serum luteinizing hormone levels did not sign any difference (P > 0,05). Conclusions: As a result, thermographic monitoring alone is not enough for estrus detection in Anatolian Shepherd bitches. However, it can be used to assist the actual estrus detection technique in terms of providing some foreknowledge by evaluating the differences in temperature

Timing of Thoracic Radiotherapy in Limited Stage Small Cell Lung Cancer: Results of Early Versus Late Irradiation from a Single Institution in Turkey

Bayman, Evrim,Etiz, Durmus,Akcay, Melek,Ak, Guntulu Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.15

Background: It is standard treatment to combine chemotherapy (CT) and thoracic radiotherapy (TRT) in treating patients with limited stage small cell lung cancer (LS-SCLC). However, optimal timing of TRT is unclear. We here evaluated the survival impact of early versus late TRT in patients with LS-SCLC. Materials and Methods: Follow-up was retrospectively analyzed for seventy consecutive LS-SCLC patients who had successfully completed chemo-TRT between January 2006 and January 2012. Patients received TRT after either 1 to 2 cycles of CT (early TRT) or after 3 to 6 cycles of CT (late TRT). Survival and response rates were evaluated using the Kaplan-Meier method and comparisons were made using the multivariate Cox regression test. Results: Median follow-up was 24 (5 to 57) months. Carboplatin+etoposide was the most frequent induction CT (59%). Median overall, disease free, and metastasis free survivals in all patients were 15 (5 to 57), 5 (0 to 48) and 11 (3 to 57) months respectively. Late TRT was superior to early TRT group in terms of response rate (p=0.05). 3 year overall survival (OS) rates in late versus early TRT groups were 31% versus 17%, respectively (p=0.03). Early TRT (p=0.03), and incomplete response to TRT (p=0.004) were negative predictors of OS. Significant positive prognostic factors for distant metastasis free survival were late TRT (p=0.03), and use of PCI (p=0.01). Use of carboplatin versus cisplatin for induction CT had no significant impact on OS (p=0.634), DFS (p=0.727), and MFS (p=0.309). Conclusions: Late TRT appeared to be superior to early TRT in LS-SCLC treatment in terms of complete response, OS and DMFS. Carboplatin or cisplatin can be combined with etoposide in the induction CT owing to similar survival outcomes.