• 한국정밀공학회지
• /
• 제17권1호
• /
• pp.145-152
• /
• 2000

X-ray diffraction method detects change of crystal lattice distance under material surface using diffraction angle 2$\theta$. This technique can be applied to the behavior on slip band and micro crack due to material degradation. The relation between half-value breadth and number of cycle has three stages which constitute rapid decrease in initial number of cycles, slight decrease in middle number of cycles and rapid decrease in final number of cycles. The ratio of half-value breadth takes a constant value on B/B$_{0}$-N diagram with loading condition except early part of fatigue life. The ratio of half-value breadth B/B$_{0}$ with respect to number of cycle to failure N$_{f}$ has linear behavior on B/B$_{0}$-log N$_{f}$ diagram. Therefore, in this paper the estimation of fatigue life by average gradient method has much less estimated mean error than the estimation of fatigue life by log B/B$_{0}$-log N/N$_{f}$ relation.elation.ation.

• 한국축산식품학회지
• /
• 제34권4호
• /
• pp.482-495
• /
• 2014

The objectives of this study were to know the effect of repeated freeze-thaw cycles of beef on the sensory, physicochemical quality and microbiological assessment. The effects of three successive freeze-thaw cycles on beef forelimb were investigated comparing with unfrozen fresh beef for 75 d by keeping at $-20{\pm}1^{\circ}C$. The freeze-thaw cycles were subjected to three thawing methods and carried out to know the best one. As the number of freeze-thaw cycles increased color and odor declined significantly before cook within the cycles and tenderness, overall acceptability also declined among the cycles after cook by thawing methods. The thawing loss increased and dripping loss decreased significantly (p<0.05). Water holding capacity (WHC) increased (p<0.05) until two cycles and then decreased. Cooking loss increased in cycle 1 and 3, but decreased in cycle 2. pH decreased significantly (p<0.05) among the cycles. Moreover, drip loss, cooking loss and WHC were affected (p<0.05) by thawing methods within the cycles. 2-Thiobarbituric acid (TBARS) value increased (p<0.05) gradually within the cycles and among the cycles by thawing methods. Total viable bacteria, total coliform and total yeast-mould count decreased significantly (p<0.05) within and among the cycles in comparison to the initial count in repeated freeze-thaw cycles. As a result, repeated freeze-thaw cycles affected the sensory, physicochemical and microbiological quality of beef, causing the deterioration of beef quality, but improved the microbiological quality. Although repeated freeze-thaw cycles did not affect much on beef quality and safety but it may be concluded that repeated freeze and thaw should be minimized in terms of beef color for commercial value and WHC and tenderness/juiciness for eating quality.

• Clinical and Experimental Reproductive Medicine
• /
• 제42권3호
• /
• pp.118-125
• /
• 2015

Objective: The goal of this study was to evaluate the pregnancy potential of immature (metaphase I or germinal vesicle stage) oocytes retrieved in intracytoplasmic sperm injection (ICSI) cycles. Methods: A total of 1,871 couples with infertility underwent 2,984 ICSI cycles. Cycles in which three or fewer oocytes were retrieved were included in this study in order to evaluate the pregnancy potential of immature oocytes. Cycles were divided into five groups (group I-V), according to the maturation status of the oocytes at the time of cumulus cell removal and ICSI. The fertilization and pregnancy rates after ICSI were analyzed and compared among the study groups based on the maturation status of the retrieved oocytes. Results: The retrieval of only immature oocytes was associated with a significant decrease in the fertilization rate ($76.1%{\pm}37.3%$ vs. $49.0%{\pm}49.1%$, $66.7%{\pm}48.7%$; group I vs. group II, group III, respectively) and the average number of transferred embryos ($1.5{\pm}0.7$ vs. $1.1{\pm}0.4$, $1.1{\pm}0.6$). The cycle cancellation rate was significantly higher when only immature oocytes were retrieved. The clinical pregnancy rate decreased significantly when the transferred embryos had originated from immature oocytes (16.9% vs. 10.3%, 1.2%). Conclusion: In ICSI cycles, the fertilization potential and pregnancy potential of the immature oocytes retrieved in ICSI cycles were inferior to those of mature oocytes. Therefore, increasing the number of injectable oocytes and transferrable embryos by using immature oocytes after their spontaneous in vitro maturation does not necessarily improve pregnancy outcomes.

• Clinical and Experimental Reproductive Medicine
• /
• 제42권1호
• /
• pp.8-13
• /
• 2015

Objective: Great advances have been made in the field of assisted reproductive technology (ART) since the first in vitro fertilization (IVF) baby was born in Korea. This study was designed to report on the current status of ART therapy in South Korea between January 1 and December 31 of 2010. Methods: A revised survey, originally developed by the International Committee Monitoring Assisted Reproductive Technologies, was sent to all available ART centers via email in 2013. Fresh embryo transfer (FET) cases were categorized into standard IVF or intracytoplasmic sperm injections. These cases, the thawing embryo transfer (TET) cases, and other related procedures were surveyed. Results: Data from 30,785 ART procedures were provided by 78 clinics. Of the 28,200 cycles in which oocytes were retrieved, 92.2% of these cycles were completely transferred. In addition, 8,075 cycles were confirmed to be clinical pregnancies in the FET cycles, which represent a pregnancy rate of 28.6% per oocyte pick-up and 31.1% per embryo transfer. The most common number of embryos transferred in the FET was three embryos (37.3%) followed by two embryos (36.3%) and one embryo (14.0%). Of the 6,648 TET cycles transferred, 2,356 clinical pregnancies were confirmed by ultrasonography. The most common number of embryos in the TET group was two embryos (43.4%) followed by three embryos (25.4%) and one embryo (18.9%). Conclusion: The clinical pregnancy rate per transfer in the FET cycles was similar in 2009 and 2010. Among the FET cycles where one or two embryos were transferred, the clinical pregnancy rate per transfer slightly increased from 2009 (28.7%) to 2010 (32.9%).

• 대한수학회보
• /
• 제49권2호
• /
• pp.359-365
• /
• 2012

Giving a planar graph G, let $x^'_l(G)$ and $x^{''}_l(G)$ denote the list edge chromatic number and list total chromatic number of G respectively. It is proved that if a planar graph G without 6-cycles with chord, then $x^'_l(G){\leq}{\Delta}(G)+1$ and $x^{''}_l(G){\leq}{\Delta}(G)+2$ where ${\Delta}(G){\geq}6$.

• 전자공학회논문지C
• /
• 제36C권3호
• /
• pp.17-25
• /
• 1999

본 논문에서는 기존의 bit-serial 방식 곱셈기 및 나눗셈기의 하드웨어 부담을 줄이고 동일한 연산 사이 클 수를 갖는 새로운 bit-serial 방식의 곱셈기 및 나눗셈기 아키텍쳐를 제안한다. 제안하는 bit-serial 곱셈 및 나눗셈기 아키텍쳐는 부분곱 또는 부분나머지를 구하기 위해 레지스터 및 가감산기의 비트 수를 2배 확장하지 않기 때문에 기존의 아키텍쳐에 비해 하드웨어의 부담을 줄였다. 또한 덧셈/뺄셈과 Shift 연산을 동시에 수행하므로써 {{{{ { N}_{ } }}}} 비트 곱셈 및 나눗셈 연산에 각각 ,{{{{ { N}_{ } }}}},{{{{ { N}_{ } }}}}＋ 2 사이클을 소모하며 이는 기존의 아키텍쳐와 동일한 연산 사이클 수를 지원한다. 제안하는 bit-serial 곱셈기 및 나눗셈기 아키텍쳐는 SliM Image Processor에 적용하여 실제 칩으로 구현하였으며 그 성능을 입증하였다.

• 공업화학
• /
• 제34권5호
• /
• pp.493-500
• /
• 2023

본 연구에서는 스크린 프린팅 공정을 통해 탄소 잉크 기반의 2상 전극을 제작하고, 전극 표면에 이리듐 산화물(IrO_x)을 코팅함으로써 전극의 분극 현상을 제어할 수 있는 임피던스 센서를 개발하였다. IrO_x는 순환 전압 전류법으로 탄소 전극의 표면 위에 순환 수(0~50 cycles)에 따라서 코팅되었다. 전자주사현미경을 이용하여 cycle 수가 증가할수록 IrO_x 입자의 크기와 수가 증가하는 경향성을 확인하였다. 전기화학 임피던스 분석을 이용하여 상기 제조된 센서들의 NaCl 농도에 따른 임피던스 변화 값을 조사하였다. 50 cycle에서 제조된 센서가 가장 우수한 결정계수와 재현성을 나타내었으며, 이는 분극 현상이 잘 제어되었기 때문이다. 실제 용액 샘플들을 이용한 삼투압 장비와 비교 측정 실험을 수행함으로써 IrO_x 기반 센서의 안구건조증 진단 센서로의 활용가치를 증명하였다.

• Wind and Structures
• /
• 제12권4호
• /
• pp.383-400
• /
• 2009

Low rise building roofs can be subjected to large fluctuating pressures during a tropical cyclone resulting in fatigue failure of cladding. Following the damage to housing in Tropical Cyclone Tracy in Darwin, Australia, the Darwin Area Building Manual (DABM) cyclic loading test criteria, that loaded the cladding for 10000 cycles oscillating from zero to a permissible stress design pressure, and the Experimental Building Station TR440 test of 10200 load cycles which increased in steps to the permissible stress design pressure, were developed for assessing building elements susceptible to low cycle fatigue failure. Recently the 'Low-High-Low' (L-H-L) cyclic test for metal roofing was introduced into the Building Code of Australia (2007). Following advances in wind tunnel data acquisition and full-scale wind loading simulators, this paper presents a comparison of wind-induced cladding damage, from a "design" cyclone proposed by Jancauskas, et al. (1994), with current test criteria developed by Mahendran (1995). Wind tunnel data were used to generate the external and net pressure time histories on the roof of a low-rise building during the passage of the "design" cyclone. The peak pressures generated at the windward roof corner for a tributary area representative of a cladding fastener are underestimated by the Australian/New Zealand Wind Actions Standard. The "design" cyclone, with increasing and decreasing wind speeds combined with changes in wind direction, generated increasing then decreasing pressures in a manner similar to that specified in the L-H-L test. However, the L-H-L test underestimated the magnitude and number of large load cycles, but overestimated the number of cycles in the mid ranges. Cladding elements subjected to the L-H-L test showed greater fatigue damage than when experiencing a five hour "design" cyclone containing higher peak pressures. It is evident that the increased fatigue damage was due to the L-H-L test having a large number of load cycles cycling from zero load (R=0) in contrast to that produced during the cyclone.

• 한국재료학회지
• /
• 제17권3호
• /
• pp.152-159
• /
• 2007

When the electronics are tested with thermal shock for Pb-free solder joint reliability, there are temperature conditions with use environment but number of cycles for test don't clearly exist. To obtain the long term reliability data, electronic companies have spent the cost and times. Therefore this studies show the test method and number of thermal shock cycles for evaluating the solder joint reliability of electronic components and also research bonding strength variation with formation and growth of intermetallic compounds (IMC). SMD (surface mount device) 3216 chip resistor and 44 pin QFP (quad flat package) was utilized for experiments and each components were soldered with Sn-40Pb and Sn-3.0 Ag-0.5 Cu solder on the FR-4 PCB(printed circuit board) using by reflow soldering process. To reliability evaluation, thermal shock test was conducted between $-40^{\circ}C\;and\;+125^{\circ}C$ for 2,000 cycles, 10 minute dwell time, respectively. Also we analyzed the IMCs of solder joint using by SEM and EDX. To compare with bonding strength, resistor and QFP were tested shear strength and $45^{\circ}$ lead pull strength, respectively. From these results, optimized number of cycles was proposed with variation of bonding strength under thermal shock.

• 한국농공학회:학술대회논문집
• /
• 한국농공학회 2003년도 학술발표논문집
• /
• pp.363-366
• /
• 2003

Concrete structures are becoming larger, higher, longer and more specialized. Currently, one of the biggest problems of concrete structures is the occurrence of cracks. Cracks are a serious structural problem that decreases durability and causes external damage leading to corrosion. The specimen without steel fiber fractured between 60-70% of the static ultimate strength (the fatigue strength to one million cycles on the number of cycles from the S-N curve was 73.7% and the fatigue strength to two million cycles was approximately 67.2%). The specimen with steel fiber fractured at 65-80% of the static ultimate strength, concluding fatigue strength to one million cycles around 74.6% and to two million cycles around 75%.