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.

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.

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.

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

Dosimetric and Clinical Predictors of Acute Esophagitis in Lung Cancer Patients in Turkey Treated with Radiotherapy

Etiz, Durmus,Bayman, Evrim,Akcay, Melek,Sahin, Bilgehan,Bal, Cengiz Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.7

Background: The purpose of this study was to determine the clinical and dosimetric factors associated with acute esophagitis (AE) in lung cancer patients treated with conformal radiotherapy (RT) in Turkey. Materials and Methods: In this retrospective review 104 lung cancer patients were examined. Esophagitis grades were verified weekly during treatment, and at 1 week, and 1 and 2 months afterwards. The clinical parameters included patient age, gender, tumor pathology, number of chemotherapy treatments before RT, concurrent chemotherapy, radiation dose, tumor response to RT, tumor localization, interruption of RT, weight loss, tumor and nodal stage and tumor volume. The following dosimetric parameters were analyzed for correlation of AE: The maximum ($D_{max}$) and mean ($D_{mean}$) doses delivered to the esophagus, the percentage of esophagus volume receiving ${\geq}10$ Gy ($V_{10}$), ${\geq}20$ Gy ($V_{20}$), ${\geq}30$ Gy ($V_{30}$), ${\geq}35$ Gy ($V_{35}$), ${\geq}40$ Gy ($V_{40}$), ${\geq}45$ Gy ($V_{45}$), ${\geq}50$ Gy ($V_{50}$) and ${\geq}60$ Gy ($V_{60}$). Results: Fifty-five patients (52.9%) developed AE. Maximum grades of AE were recorded: Grade 1 in 51 patients (49%), and Grade 2 in 4 patients (3.8%). Clinical factors had no statistically significant influence on the incidence of AE. In terms of dosimetric findings, correlation analyses demonstrated a significant association between AE and $D_{max}$ (>5117 cGy), $D_{mean}$ (>1487 cGy) and $V_{10-60}$ (percentage of volume receiving >10 to 60 Gy). The most significant relationship between RT and esophagitis were in $D_{max}$ (>5117 cGy) (p=0.002) and percentage of esophageal volume receiving >30 Gy ($V_{30}$ >31%) (p=0.008) in the logistic regression analysis. Conclusions: The maximum dose esophagus greater than 5117 cGy and approximately one third (31%) of the esophageal volume receiving >30 Gy was the most statistically significant predictive factor associated with esophagitis due to RT.