• Proceedings of the KWS Conference
• /
• 1996.10a
• /
• pp.19-34
• /
• 1996

A review was made of fatigue failures of nuclear power plant components in Japan, which were experienced in service and during periodical inspection. No case has been recently reported of a service fatigue failure of a reactor pressure vessel itself, excluding nozzle corner cracks, that occurred many years ago. But, service fatigue failures have been occasionally experienced in piping systems, pumps, and valves, on which fatigue design seems to have been inadequately applied. The causes of fatigue failures can be divided into two categories: mechanical-vibration-induced fatigue and thermal-fluctuation-induced fatigue. Vibration-induced fatigue failure occurs more frequently than is generally thought. The lesson gleaned from the present survey is a recognition that a service fatigue failure may occur due to any one or a combination of the following factors: (1) lack of communication between designers and fabrication engineers, (2) lack of knowledge about a possibility of fatigue failure and poor consideration about the effects of residual stresses, (3) lack of consideration on possible vibration in the design and fabrication stages, and (4) lack of fusion or poor penetration in a welded joint.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.5
• /
• pp.769-774
• /
• 2010

It happened fractures on special bolt which supported main landing gear actuator up-lock rod of aircraft. Cracks were initiated mainly from the center hole and the external thread of the special bolt. To find out failure root causes, metallographic, fractographic analyses as well as test work were carried out. From the fractographic study by SEM work, fracture occurred by a brittle intergranular type failure. The fracture could be occurred primarily by solid-metal-induced embrittlement due to cadmium embrittler penetrated into the flaw existed after machining work for center hole and thread on the bolt during baking treatment processing to eliminate hydrogen. For its successful application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and make no more drilled center hole on the bolt to prevent same failure.

• The Korean journal of internal medicine
• /
• v.34 no.1
• /
• pp.11-43
• /
• 2019

Heart failure (HF) is an important cardiovascular disease because of its increasing prevalence, significant morbidity, high mortality, and rapidly expanding health care cost. The number of HF patients is increasing worldwide, and Korea is no exception. There have been marked advances in definition, diagnostic modalities, and treatment of HF over the past four decades. There is continuing effort to improve risk stratification of HF using biomarkers, imaging and genetic testing. Newly developed medications and devices for HF have been widely adopted in clinical practice. Furthermore, definitive treatment for end-stage heart failure including left ventricular assist device and heart transplantation are rapidly evolving as well. This review summarizes the current state-of-the-art management for HF and the emerging diagnostic and therapeutic modalities to improve the outcome of HF patients.

• Journal of Applied Reliability
• /
• v.3 no.2
• /
• pp.93-101
• /
• 2003

Life time data analysis requires some time-to-failure data to an extent. Some life tests result in few or no failure. In such cases, it is difficult to access reliability with traditional life tests that record only time to failure. Furthermore, with short product development time, reliability tests must be conducted with severe time constraints. For some devices, it is possible to obtain degradation measurements over time, and these measurements may contain useful information about product reliability. This article describes degradation reliability analysis methods to do inferences and predictions about a failure-time distribution by using software. In addition, the possibility of extension to CBM (Condition Based Maintenance) is suggested as an example of applied degradation data analysis.

• Journal of Hydrospace Technology
• /
• v.1 no.1
• /
• pp.75-88
• /
• 1995

Auto-Pilot System uses heading angle information via the position sensor and the rudder device to control the ship's direction. Most of the control logics are composed of the state estimation and control algorithms assuming that the measurement device and the actuator have no fault except the measurement noise. But such asumptions could bring the danger in real situation. For example, if the heading angle measuring device is out of order the control action based on those false position information could bring serious safety problem. In this study, the control system including improved method for processing the position information is applied to the Auto-Pilot System. To show the difference between general state estimator and F.D.F., BJDFs for the sensor and the actuator failure detection are designed and the performance are tested. And it is shown that bias error in sensor could be detected by state-augmented estimator. So the residual confined in the 2-dimension in the presence of the sensor failure could be unidirectional in output space and bias sensor error is much easier to be detected.

• Corrosion Science and Technology
• /
• v.20 no.5
• /
• pp.242-248
• /
• 2021

Unforeseen failures of boilers in power plants may affect the continuation of electricity generation. Main failures in boilers are influenced by the tube material, tube position, boiler service temperature and pressure, and chemical composition of the feed water and coal. This investigation was intended to find answers on the causes and mechanism of failure of the fire-side boiler water-wall tubes, due to perforation and corrosion. The tube conformed to the material requirements in terms of its chemical composition and hardness. Microscopic examination showed ferrite and pearlite indicating no changes in its microstructure due to the temperature variation. SEM test showed a single layer and homogenous film density particularly on the area far from perforation. However, layers of corrosion product were formed on the nearby perforation area. EDX showed that there were Na, Ca, S, and O elements on the failed surface. XRD indicated the presence of Fe₂O₃ oxide. The failure mechanism was identified as a result of significant localized wall thinning of the boiler water wall-tube due to oxidation.

• Archives of Plastic Surgery
• /
• v.46 no.5
• /
• pp.475-479
• /
• 2019

The Goldilocks technique for breast reconstruction utilizes redundant mastectomy flap tissue to construct a breast mound. This technique is suitable for women who decline, or are poor candidates for, traditional postmastectomy reconstruction. Moreover, this technique can be applied in secondary operations after the failure of initial reconstruction efforts. A 74-year-old patient underwent the Goldilocks procedure after reconstruction failure with an implant and acellular dermal matrix. At her 6-month follow-up, the cosmetic outcome of the procedure was satisfactory, and no complications were noted. Therefore, the Goldilocks procedure is a safe alternative to reconstruct breast mounds following reconstruction failure, especially in obese patients.

• Proceedings of the Korean Reliability Society Conference
• /
• 2002.06a
• /
• pp.35-86
• /
• 2002

No Abstract, See Full Text

• Proceedings of the Korean Reliability Society Conference
• /
• 2002.06a
• /
• pp.131-146
• /
• 2002

No Abstract, See Full Text

• Journal of National Security and Military Science
• /
• s.13
• /
• pp.1-41
• /
• 2016

US 8th Army in the attack on the Western Front was a situation that was frustrated by the 13th Corps Communist army. To this time support this, goals that have been granted to the US 1st Marine Division that initiated the attack in Mupyonri direction, lack the potential to achieve was not decisive. It was a operation specific erroneous judgment that occurred because there was no one accurately grasp the battlefield of the situation the wrong UN Forces Command. Tactical victory can be to maximize the operation outcomes. However, there is no possible failure of the operation is to expand the tactical success. This is because the failure of the operation, because directly linked to the success or failure of the war. Tactical victory can be to maximize the operation outcomes. However, operation specific failure is not it possible to expand the tactical victory. Therefore tactical success of the US 1st Marine Division, can not compensate for operation specific failure of the United Nations Forces Command. However, Chinese Communist Army 9th Corps is obsessed only victory of tactics to annihilate the US 1st Marine Division, by being fixation to the Chosin whole area, it was not possible to run a operational operation. Therefore tactical success df the US 1st Marine Division, Chinese Communist Army 9th Corps is to extinguish the ability to increase the number of the 13th Corps of the Western Front, 8th Army US have contributed to have escaped the crisis. In addition, the US 10th Corps while maintaining the combat force, by an important role to withdraw through the sea, was able to complement the misjudgment of the operation.