• Clinical and Experimental Reproductive Medicine
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• 제43권3호
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• pp.157-163
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• 2016

Objective: The decision to use in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), or split insemination (IVF-ICSI) in the first cycle is based on the number of motile sperm. Hence, total fertilization failure (TFF) often occurs during IVF cycles, despite normozoospermia. To investigate whether the cumulative motile swim-up spermatozoa percentage at 22 hours post-insemination (MSPPI) is an indicator for ICSI, we analyzed TFF, fertilization, blastocyst development, chemical pregnancy, clinical pregnancy, and live birth rates. Methods: This prospective study was performed using data obtained from 260 IVF cycles. At 22 hours after insemination, the remaining swim-up spermatozoa were observed and divided into six groups according to MSPPI (<10%, 10% to <30%, 30% to <50%, 50% to <70%, 70% to <90%, and 90% to 100%). Results: Regardless of the ejaculated motile sperm concentration ($0.6-280{\times}10^6/mL$ motile spermatozoa), the incidence of TFF significantly increased when MSPPI was <10%, and the fertilization rate significantly decreased when MSPPI was <30%. We found that cumulative MSPPI correlated with the cumulative fertilization rate (Spearman correlation, 0.508, p<0.001). Regarding embryo development, we observed no significant differences in the rates of blastocyst development, chemical pregnancy, clinical pregnancy, or live birth among all groups. Conclusion: Our findings suggest that MSPPI is a viable indicator for split IVF-ICSI and ICSI. Taken together, by employing the MSPPI test in advance before IVF, ICSI, or split IVF-ICSI cycles, unnecessary split IVF-ICSI and ICSI may be avoided.

• 대한치과의사협회지
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• 제55권2호
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• pp.116-127
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• 2017

Objectives : The aim of this study was to evaluate the cumulative survival rates of the implants placed into grafted sinus and determine the effect of age, gender, smoking, and systemic disease on the implant cumulative survival rates. Materials and Methods : The retrospective study was performed on 51 implants placed in 26 patients by one dentist at the Dental Implant Center, Seoul National University Dental Hospital in the years 2000-2010. The cumulative survival rates were calculated by the Kaplan-Meier method. The differences within the factors were analyzed using log-rank test and the correlations between the factors and implant survival rates were analyzed using Cox proportional hazard model. Results : 1. Among the total of 51 implants placed in 26 patients, 7 implants failed and 44 implants remained stable. The 1-year, 5-year, and 10-year cumulative survival rates were 92%, 88%, and 85%, respectively. 2. Patients in their 50s and in their 70s showed statistically significant difference in the cumulative survival rates (P < 0.05). Gender and the existence of systemic disease did not show significant results. 3. In the implant treatment, smokers showed 7.5 times higher risk of implant failure than non-smokers (P < 0.05). Conclusion: Implants installed in combination with sinus elevation can be considered as a reliable treatment method.

• 한국신뢰성학회지:신뢰성응용연구
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• 제18권3호
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• pp.271-279
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• 2018

Purpose: Probabilistic safety analysis was performed to enhance the safety and reliability of nuclear power plants because traditional deterministic approach has limitations in predicting the risk of failure by crack growth. The study introduces a probabilistic approach to establish a basis for probabilistic safety assessment of passive components. Methods: For probabilistic modeling of fatigue crack growth rate (FCGR), various FCGR tests were performed either under constant load amplitude or constant ${\Delta}K$ conditions by using heat treated X-750 at low temperature with adequate cathodic polarization. Bayesian inference was employed to update uncertainties of the FCGR model using additional information obtained from constant ${\Delta}K$ tests. Results: Four steps of Bayesian parameter updating were performed using constant ${\Delta}K$ test results. The standard deviation of the final posterior distribution was decreased by a factor of 10 comparing with that of the prior distribution. Conclusion: The method for developing a probabilistic crack growth model has been designed and demonstrated, in the paper. Alloy X-750 has been used for corrosion fatigue crack growth experiments and modeling. The uncertainties of parameters in the FCGR model were successfully reduced using the Bayesian inference whenever the updating was performed.

• 한국환경복원기술학회지
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• 제21권1호
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• pp.133-143
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• 2018

In spite of the growing importance of landscaping trees, the rate of flawed and withered trees damaged by pest, disease, drought or frost is increasing. In order to evaluate the performance of the Tree Protective Pad, which are developed to reduce the failure ratio in landscape planting, the tree protective pad for 'digging', 'pest controlling', and 'insulating' are tested based on the five functional criteria; moisturizing effect, wither preventive effect, pest and disease control, thermal effect, tensile strength, and environmental performance. The result of this study is as follows. The moisturizing effect of the tree protective pad for digging is found to be outstanding. According to the result of testing the pad on trees, in particular, it is better than jute tape in wither preventive effect, which means it is expected to prevent flaw and wilt from planting during the improper seasons like summertime. The experiment of installing the protective tree pad for pest controlling to the trunk of Quercus mongolica shows that preventive effect of the pad from diseases and insects is superior, and it also has economical effect by reducing the use of agricultural chemicals. The comparative test of the pad for insulating and jute tape proves that the temperature of the pad is about $2^{\circ}C$ higher than outside. The rate of tensile strength and biodegradation of the pad exceeds the optimal level, so it is revealed that the pad may be the work efficient and environment-friendly product. Likewise, by timely irrigating trees, the tree protective pad economically prevents trees from pest, disease,drought or frost, which may be caused by improper seasonal or delayed planting. As a means of reducing the flaw and facilitating the growth of trees, the exceptional performance of the pad is expected to effectively used in landscape planting and management.

• 한국재료학회지
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• 제15권8호
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• pp.528-535
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• 2005

It is inclined to increase that use of hazardous substances such as lead(Pb), mercury (Hg), cadmium(Cd) etc. are prohibited in the electronics according to environmental friendly policies of an advanced nation for protecting environment of earth. As this reasons, many researches for ensuring the reliability were proceeding in Pb free soldering process. n the flux remains on the PCB(printed circuit board) in the soldering process or the electronics exposed to corrosive environment, it becomes the reasons of breakdown or malfunction of the electronics caused by corrosion. Therefore in this studies we researched the polarization and Tafel properties of Sn40Pb and SnCu system solders based on the electrochemical theory. The experimental polarization curves were measured in distilled ionized water and 1 mole $3.5 wt\%$ NaCl electrolyte of $40^{\circ}C$, pH 7.5. Ag/AgCl and graphite were utilized by reference and counter electrodes, respectively. To observe the electrochemical reaction, polarization test was conducted from -250mV to +250mV. From the polarization curves composed of anodic and cathodic curves, we obtained Tafel slop, reversible electrode potential(Ecorr) and exchange current density((cow). In these results, we compared the corrosion rate of SnPb and SnCu solders.

• 한국재료학회지
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• 제15권8호
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• pp.536-542
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• 2005

Recently European Council(EU) published the RoHS(restriction of the use of certain hazardous substances in electrical and electronic equipment) which is prohibit the use of Pb, Hg, Cd, $Cr^{+6}$, PBB or PBDE in the electrical and electronic equipments. So EU member States shall ensure that, from 1 July 2006, new electrical and electronic equipment put on the market does not contain 6 hazardous substances. The one of the most important in electronics manufacturing process is soldering. Soldering process use the chemical substances which are applied in fluxing and cleaning processes and it can generate the malfunction of electronics caused by corrosion in the fields conditions. Therefore this study researched on the polarization and Tafel properties of Sn40Pb and Sn3.0Ag0.5Cu(SAC) solder based on the electrochemical theory. We prepared SnPb specimens which was aged in $150^{\circ}C,\;180^{\circ}C$ for 15 minutes ana Sn3.0Ag0.5Cu specimens that was aged in $180^{\circ}C,\;220^{\circ}C$ for 10 minutes. Experimental polarization curves were measured in distilled ionized water and $3.5 wt\%$, 1 mole NaCl electrolyte of $40^{\circ}C$, pH 7.5. Ag/AgCl and graphite were utilized by reference and counter electrode, respectively. To observe the electrochemical reaction, polarization test was conducted from -250 mV to +250 mV. From the polarization curves that were composed of anodic and cathodic curves, we obtained Tafel slop, reversible electrode potential(Ecorr) and exchange current density(Icorr). In these results, corrosion rate for two specimen were compared Sn3.0Ag0.5Cu with SnPb solders

• 전기화학회지
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• 제6권3호
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• pp.212-216
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• 2003

고분자전해질형 연료전지에 사용되는 외부 및 내부 가습기를 통과한 반응 기체의 상대습도와 온도를 측정한 자료가 실시간으로 컴퓨터에 입력되어지는 시스템을 자체적으로 구성하였다. 이 시스템을 이용하여 측정한 경우 10-20분이 경과한 후에 습도 값이 안정되었으므로 가습 측정치에 대한 신뢰성을 향상시킬 수 있었으며, 여러 가지 가습의 영향을 해석할 수 있었다. 측정 장비의 이상을 초래할 수 있는 상대 습도가 $100\%$부근의 영역에서 지속적으로 측정을 수행할 경우 센서의 오작동 내지 고장의 원인이 될 수 있었으므로 실험시 주의가 필요하였다. 가습기를 통과한 반응기체는 유량이 증가할수록 가습되는 양은 증가하나, 일정 유량 이상이 되면 그 증가폭이 감소하는 경향을 보였는데 이는 가습기 출 통과하는 기체의 체류 시간 영향에 기인한 것으로 추정되어진다.

• Journal of Electrochemical Science and Technology
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• 제10권2호
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• pp.223-230
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• 2019

A facile method for surface coating with $Li_2TiF_6$ which has a high lithium-ion conductivity, on $LiMn_2O_4$ spinel cathode material for high performance lithium ion batteries. The surface coating is performed by using a co-precipitation method with $Li_2CO_3$ powder and $H_2TiF_6$ solution under room temperature and atmospheric pressure without special equipment. Total coating amount of $Li_2TiF_6$ is carefully controlled from 0 to 10 wt.% based on the active material of $LiMn_2O_4$. They are evaluated by a systematic combination of analyses comprising with XRD, SEM, TEM and ICP. It is found that the surface modification of $Li_2TiF_6$ is very beneficial to high cycle life and excellent rate capability by reducing surface failure and supporting lithium ions transportation on the surface. The best coating condition is found to have a high cycle life of $103mAh\;g^{-1}$ at the 100th cycle and a rate capability of $102.9mAh\;g^{-1}$ under 20 C. The detail electrochemical behaviors are investigated by AC impedance and galvanostatic charge and discharge test.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3648-3658
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• 2023

The early localization of a fuel subassembly with a failed (wet rupture) fuel pin is very important in reactors to limit the associated radiological and operational consequences. This requires a fast and reliable system for failure detection and their localization in the core. In the Prototype Fast Breeder Reactor, the system specially designed for this purpose is Failed Fuel Location Modules (FFLM) housed in the control plug region. It identifies a failed sub-assembly by detecting the presence of delayed neutrons in the sodium from a failed sub-assembly. During the commissioning phase of PFBR, it is mandatory to demonstrate the FFLM effectiveness. The paper highlights the engineering and physics design aspects of FFLM and the integrated simulation towards its function demonstration with a source assembly containing a perforated metallic fuel pin. This test pin mimics a MOX pin of 1 cm² of geometrical defect area. At 10% power and 20% sodium flow rate, the counts rate in the BCCs of FFLM system range from 75 cps to 145 cps depending upon the position of DN source assembly. The model developed for the counts simulation is applicable to both metal and MOX pins with proper values of k-factor and escape coefficient.

• 한국ITS학회 논문지
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• 제13권1호
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• pp.86-98
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• 2014

현재 DSRC(Dedicated Short Range Communication)를 이용한 자동요금징수시스템(이하 ETCS, Electronic Toll Collection System)이 전국 영업소에 구축 되면서 많은 하이패스 단말기(이하 OBU, On-Board Unit)가 보급되었다. 이러한 ETCS 인프라와 전국호환카드를 활용한 ITS 서비스 분야가 연구개발 및 사업화 추진 중에 있다. ETCS에 전국호환카드 적용방안 연구가 많이 이루어지고 있지만 전국호환카드 적용방안 및 교통편의시설 결제에 대한 표준이 명확하게 이루어지지 않고 있다. 이에 국토교통부에서 고시한 "전국호환카드" 를 기존 DSRC기반 ETCS에 적용방안을 제안하고자 한다. 본 연구에서 제안하는 적용방안을 시범운영 사이트에서 시험차량 3대를 이용해 다양한 주행시험을 통해 시스템의 성능을 확인 하였다. 주행시험 결과 약 99%의 통신 성공률을 보였고 이를 통해 본 논문에서 제안한 표준 적용방안의 유효성을 확인하였으며, 약 1%의 실패를 통해 교통편의시설 전자결제 서비스 부분의 적용하여 발생할 수 있는 문제점을 분석하였다.