• Structural Engineering and Mechanics
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• v.34 no.3
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• pp.367-376
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• 2010

In this paper, an experimental investigation of the mechanical behavior and buckling failure of sharp-notched circular tubes subjected to cyclic bending is discussed. The unnotched and sharp-notched circular tubes of SUS 304 stainless steel were tested under symmetric curvature-controlled cyclic bending. It was found from moment-curvature curves that the loops show cyclic hardening and gradually steady after a few cycles for all tested tubes. The ovalization-curvature curves show an unsymmetric, ratcheting and increasing manner with the number of cycles. In addition, it was found that six almost parallel lines corresponding to unnotched and five different notch-depth (0.2, 0.4, 0.6, 0.8 and 1.0 mm) tubes were noted from the experimental relationship between the cyclic controlled curvature and the number of cycles necessary to produce buckling on a log-log scale. An empirical formulation was proposed so that it could be used for simulating the aforementioned relationship. By comparing with the experimental finding, the simulation was in good agreement with the experimental data.

• Clinical and Experimental Reproductive Medicine
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• v.49 no.3
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• pp.202-209
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• 2022

Objective: The aim of this study was to assess the correlation of oocyte number with serum anti-Müllerian hormone (AMH) levels measured by two automated methods (Access or Elecsys) in fresh stimulated in vitro fertilization (IVF) cycles. Methods: In this retrospective study at a university hospital, data were collected from 243 fresh stimulated IVF cycles performed from August 2016 to December 2020. The serum AMH level was measured by Access in 120 cycles and by Elecsys in 123 cycles. The cut-off of serum AMH for prediction of poor responders (three or fewer oocytes) or high responders (15 or more oocytes) was calculated by the receiver operating characteristic curve analysis. Results: For the two automated methods, the following equations were derived: total oocyte number=2.378+1.418×(Access-AMH) (r=0.645, p<0.001) and total oocyte number=2.417+2.163×(Elecsys-AMH) (r=0.686, p<0.001). The following combined equation could be derived: (Access-AMH)=0.028+1.525×(Elecsys-AMH). To predict poor responders, the cut-off of Access-AMH was 1.215 ng/mL (area under the curve [AUC], 0.807; 95% confidence interval [CI], 0.730-0.884; p<0.001), and the cut-off of Elecsys-AMH was 1.095 ng/mL (AUC, 0.848; 95% CI, 0.773-0.923; p<0.001). To predict high responders, the cut-off of Access-AMH was 3.450 ng/mL (AUC, 0.922; 95% CI, 0.862-0.981; p<0.001), and the cut-off of Elecsys-AMH was 2.500 ng/mL (AUC, 0.884; 95% CI, 0.778-0.991; p<0.001). Conclusion: Both automated methods for serum AMH measurement showed a good correlation with oocyte number and good performance for predicting poor and high responders in fresh stimulated IVF cycles. The Access method usually yielded higher measured serum AMH levels than the Elecsys method.

• Clinical and Experimental Reproductive Medicine
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• v.16 no.1
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• pp.81-91
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• 1989

It has been suggested that the prognosis for fertility of the infertile patients with healed pelvic tuberculosis is very poor. Total 60 patients(77 cycles) with previous history of pelvic tuberculosis who underwent IVF-ET from January 1988 to March 1989 at SNUH were classified into three groups according to the principal histopathological lesions : tuberculous endometritis group(N=20, 28 cycles), tuberculous salpingitis group(N=32, 37 cycles) and pelvic peritoneal tuberculosis group(N=8, 12 cycles). To evaluate the effects of previous pelvic tuberculous lesions on ovarian follicular growth and development in controlled ovarian hyperstimulation for IVF-ET and its final outcome, serum E2 levels on the day of hCG administration(Day 0) and the day after hCG administration(Day +1), the number of ovarian follicles with mean diamete ${\geqq}$ 12 mm on Day 0, the number of oocytes retrieved by transvaginal aspiration, and pregnancy rate per cycle were measured and compared with control group(N=123, 161 cycles). There were no significant differences in cancellation rate during controlled ovarian hyperstimulation, total dosage of FSH and hMG administrated, menstrual cycle date(MCD) of hCG injection, serum E2 levels, the number of ovarian follicles with mean diameter ${\geqq}$ 15 mm, and the number of oocytes retrieved between pelvic tuberculosis group and control group. But in pelvic tuberculosis group, the number of ovarian follicles with mean diameter 12-14 mm, total number of ovarian follicles(${\geqq}$ 12 mm), and pregnancy rate per cycle were significantly decreased. These data suggest that previous pelvic tuberculous lesions have no significant adverse effects on the ovarian response to gonadotropin stimulation. IVF-ET proved to be an useful treatment modality for infertile patients with previous history of pelvic tuberculosis in spite of its relatively lowered pregnancy rate.

• Communications of the Korean Mathematical Society
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• v.32 no.4
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• pp.805-810
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• 2017

Let $C_n$ be the cycle graph of order n on the vertices $v_0,v_1,{\ldots},v_n$ and $C^k_n$ be the k-th power of $C_n$. In this article we determine the hull-number of $C^k_n$.

• Geomechanics and Engineering
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• v.12 no.4
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• pp.611-626
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• 2017

The research reported herein is concerned with the model testing of piles socketed in soft rock which was simulated by cement, plaster, sand, water and concrete hardening accelerator. Model tests on a single pile socketed in simulated soft rock under axial cyclic loading were conducted and the bearing capacity and accumulated deformation characteristics under different static, and cyclic loads were studied by using a device which combined oneself-designed test apparatus with a dynamic triaxial system. The accumulated deformation of the pile head, and the axial force, were measured by LVDT and strain gauges, respectively. Test results show that the static load ratio (SLR), cyclic load ratio (CLR), and the number of cycles affect the accumulated deformation, cyclic secant modulus of pile head, and ultimate bearing capacity. The accumulated deformation increases with increasing numbers of cycles, however, its rate of growth decreases and is asymptotic to zero. The cyclic secant modulus of pile head increases and then decreases with the growth in the number of cycles, and finally remains stable after 50 cycles. The ultimate bearing capacity of the pile is increased by about 30% because of the cyclic loading thereon, and the axial force is changed due to the applied cyclic shear stress. According to the test results, the development of accumulated settlement is analysed. Finally, an empirical formula for accumulated settlement, considering the effects of the number of cycles, the static load ratio, the cyclic load ratio and the uniaxial compressive strength, is proposed which can be used for feasibility studies or preliminary design of pile foundations on soft rock subjected to cyclic loading.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.104-107
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• 2004

The crack widths of reinforced concrete flexural members are influenced by repetitive fatigue loadings. The bond stress-slip relation is necessary to estimate these crack widths realistically. The purpose of the present study is, therefore, to propose a realistic model for bond stress-slip relation under repeated loading. To this end, several series of tests were conducted to explore the bond-slip behavior under repeated loadings. Three different bond stress levels with various number of load cycles were considered in the tests. The present tests indicate that the bond strength and the slip at peak bond stress are not influenced much by repeated loading if bond failure does not occur. However, the values of loaded slip and residual slip increase with the increase of load cycles. The bond stress after repeated loading approaches the ultimate bond stress under monotonic loading and the increase of bond stress after repeated loading becomes sharper as the number of repeated loads increases. The bond stress-slip relation after repeated loading was derived as a function of residual slip, bond stress level, and the number of load cycles. The models for slip and residual slip were also derived from the present test data. The number of cycles to bond slip failure was derived on the basis of safe fatigue criterion, i.e. maximum slip criterion at ultimate bond stress.

• Food Science of Animal Resources
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• v.35 no.6
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• pp.772-782
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• 2015

This study was performed to explore the deterioration of physicochemical quality of beef hind limb during frozen storage at −20℃, affected by repeated freeze-thaw cycles. The effects of three successive freeze-thaw cycles on beef hind limb were investigated comparing with unfrozen beef muscle for 80 d by keeping at −20±1℃. The freeze-thaw cycles were subjected to three thawing methods and carried out to select the best one on the basis of deterioration of physicochemical properties of beef. As the number of repeated freeze-thaw cycles increased, drip loss decreased and water holding capacity (WHC) increased (p<0.05) till two cycles and then decreased. Cooking loss increased in cycle one and three but decreased in cycle two. Moreover, drip loss, WHC and cooking loss affected (p<0.05) by thawing methods within the cycles. However, pH value decreased (p<0.05), but peroxide value (p<0.05), free fatty acids value (p<0.05) and TBARS value increased (p<0.05) significantly as the number of repeated freeze-thaw cycles increased. Moreover, significant (p<0.05) interactive effects were found among the thawing methods and repeated cycles. As a result, freeze-thaw cycles affected the physicochemical quality of beef muscle, causing the degradation of its quality.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.8
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• pp.1113-1116
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• 2009

The objective of this study was to compare the follicular population during spontaneous and $PGF_2{\alpha}$ induced oestrous cycles in Nili-Ravi buffaloes. In Exp.1, (n = 13 oestrous cycles) follicular population was monitored using ultrasonography on alternate days. Buffaloes were monitored for ovarian follicles from day 0 (first oestrus) until next oestrus. These animals were observed for oestrus twice daily using a teaser bull. Of 12 oestrous cycles, 9 (75%) had two waves of follicular activity and only 3 (25%) had three waves during the oestrous cycle. The mean number of small, medium and large follicles among various days of the oestrous cycle between two and three waves of follicular development were not significantly different (p>0.05). In Exp. 2, follicular population 3 days before oestrus was compared in buffaloes undergoing spontaneous (n = 12 oestrous cycles) and $PGF_2{\alpha}$ induced (n = 6) luteolysis. The mean number of small and large follicles increased (p<0.05) and the number of medium follicles decreased (p<0.05) during the 3 days before oestrus in buffaloes undergoing induced luteolysis as compared to those with spontaneous luteolysis. These results showed that the mean number of small, medium and large follicles among various days of the oestrous cycle were similar between the two and three waves of follicular development, and three days before oestrous the number of small, medium and large follicles altered due to induced luteolysis on day 9, compared to those with spontaneous luteolysis.

• Structural Engineering and Mechanics
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• v.86 no.5
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• pp.663-671
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• 2023

Freeze-thaw cycles induce strength loss at the frozen soil-concrete interface and deterioration of bonding, which causes construction engineering problems. To clarify the deterioration characteristics of the interface under the freeze-thaw cycle, a frozen soil-concrete sample was used as the research object, an interface scanning electron microscope test under the freeze-thaw cycle was carried out to identify the micro index information, and an interface shear test was carried out to explore the loss law of interface shear strength under the freeze-thaw cycle. The results showed that the integrity of the interface was destroyed, and the pore number and pore size of the interface increased significantly with the number of freeze-thaw cycles. The connection form gradually deteriorates from surface-to-surface contact to point-to-surface contact and point-to-point contact, and the interfacial shear strength decreases the most at 0-3 freeze-thaw cycles, with small decreases from to 3-8 cycles. After 12 freeze-thaw cycles, the interfacial shear strength tends to be stable, and shear the failure occurs internally in the soil.

• Tribology and Lubricants
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• v.16 no.5
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• pp.389-394
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• 2000

Scanning Probe Microscope (SPM) such as Scanning Tunneling Microscope (STM) and Atomic Force Microscope (AEM) was shown to be the powerful tool for nano-scale characterization of material surfaces. Using this technique, surface morphology of the cyclically deformed Cu or Cu-Al single crystal was observed. The surface became proportionately rough as the number of cycles increased, but after some number of cycles no further change was observed. Slip steps with the heights of 100 to 200 nm and the widths of 1000 to 2000 nm were prevailing at the stage. The slipped distance of one slip system at the surface was not uniform, and formation of the extrusions or intrusions was assumed to occur such place. By comparing the morphological change caused by crystallographic orientation, strain amplitude, number of cycles or stacking fault energy, some interesting results which help to clarify the basic mechanism of fatigue damage were obtained. Furthermore, applicability of the scanning tunneling microscopy to fatigue damage is discussed.