• 비파괴검사학회지
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• 제8권1호
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• pp.12-21
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• 1988

The behaviour of pressure vessel made of SS41 steel was investigated during hydrotest. AE tests were carried out for the vessels in as-manufactured, V-notched and weld-cracked state using microcomputer-based AE instrumentation. The following results were obtained: 1) In the case of source location using cylindrical program, to minimize the error of source location, the difference of max. Delta T values measured from each sensor should be kept as small as possible. 2) When crack grew, AE event rate increased continuously but AE event from the inclusions occurred intermittently, so by analyzing event rate, the source of AE could be derived. 3) From the spot welding part of supporter, many events with low energy occurred independent of Kaiser effect, which could be confirmed by analyzing energy parameter. 4) The b-value from the tensile specimen of was lower than that from normal specimen and the b-value from crack propagation was lower than that from deformation, so by analyzing peak amplitude distribution, the source mechanism could be derived from the b-value.

• 한국한의학연구원논문집
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• 제13권3호
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• pp.79-85
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• 2007

Objective : To investigate documented surveys about adverse events of acupuncture therapy. Methods: We searched Medline with the terms of 'acupuncture/adverse event(s)', 'acupuncture/side effect(s)' and 'CAM/adverse event(s)' using Pubmed and set the limits to human study. Results: There were 5 prospective studies, 3 reviews and 3 surveys in our searching. There were 3 reports about acupuncture related adverse events in UK ranging from 10.7% to 15% of which the rate of significant events were from 0.13% to 0.14%. In Germany, there were 11% of acupuncture related adverse events in one report and 7.5%(significant events were 45 in 190,924 patients) in another report. In Australia, one study reported that every adverse event associated with acupuncture occurred in 8-9 month per one practitioner. In Japan, 0.14% of acupuncture related adverse events in 48 practitioners were reported in one systemic review. A cumulative review about significant adverse events associated with acupuncture reported 715 adverse events of which most frequent accidents were pneumothorax and central nervous system injury. Conclusion : The risk of adverse event associated with acupuncture is far lower than that associated with other general medical interventions. However, some safety guidelines about the acupuncture performance are needed.

• 지질공학
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• 제6권2호
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• pp.59-64
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• 1996

암석 시료가 파괴될 때에 발생되는 AE신호는 미세한 균열 발생시의 갑작스런 변형에너지 해바에 기인한다. 압전 압력형 탐촉자와 다채널 기록장치를 이용하여 AE 신호파를 기록하여 분석하므로 외적인 하중조건과 그에 따른 미세균열의 특징에 대하여 연구하였다. 연구결과 미세균열의 체적은 수 $\mu\textrm{m}^3$ 내지 $150,000\mu\textrm{m}^3$로 산출되어서 그 크기가 넓은 범위로 분포하였고 인장형 미세균열이 대체적으로 전단형 보다 큰 체적을 보였다. 또한, 균열원에서의 에너지 강도는 모드 I 하중조건하에서 발생하는 AE 신호가 혼합모드 조건하에서 발생한 신호보다 약 3배정도 크게 나타났으나,시료가 파괴되는 동안 기록된 AE 신호의 숫자는 반대로 모드 I의 경우가 혼합모드의 25%에 불과하였다. 이러한 사실은 같은 크기의 파괴면을 형성하는데 필요한 에너지 요구량이 대체적으로 동일함을 암시하는 것으로 보인다.

• Korean Journal of Acupuncture
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• 제29권3호
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• pp.421-430
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• 2012

Objectives : We investigated the incidence rate and type of adverse events associated with RCTs(Randomized Controlled Trials) of acupuncture and moxibustion. Methods : This study included 949 patients who received acupuncture or moxibustion or usual care from 8 RCTs. We collected data including gender and age of patients, intervention, treatment frequency and type of adverse events in clinical trials from their case report forms. Results : Among the 949 patients, 83 patients(8.7%) suffered at least one adverse event throughout the clinical trials. Types of adverse event in acupuncture & moxibustion clinical trials are common cold, skin changes, pain, dizziness, bruise, gastrointestinal diseases, changes of blood chemistry, burn. Adverse events were significantly correlated to patients' age, intervention, body mass index and treatment group. Conclusions : A Guide-line for collecting and managing adverse events of acupuncture & moxibustion clinical trials are needed.

• Geomechanics and Engineering
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• 제25권2호
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• pp.135-142
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• 2021

This study provided a new research perspective for processing and analyzing AE data to evaluate rock failure. Cluster method and information entropy theory were introduced to investigate temporal and spatial correlation of acoustic emission (AE) events during the rock failure process. Laboratory experiments of granite subjected to compression were carried out, accompanied by real-time acoustic emission monitoring. The cumulative length and dip angle curves of single links were fitted by different distribution models and distribution functions of link length and directionality were determined. Spatial scale and directionality of AE event distribution, which are characterized by two parameters, i.e., spatial correlation length and spatial correlation directionality, were studied with the normalized applied stress. The entropies of link length and link directionality were also discussed. The results show that the distribution of accumulative link length and directionality obeys Weibull distribution. Spatial correlation length shows an upward trend preceding rock failure, while there are no remarkable upward or downward trends in spatial correlation directionality. There are obvious downward trends in entropies of link length and directionality. This research could enrich mathematical methods for processing AE data and facilitate the early-warning of rock failure-related geological disasters.

• 천문학논총
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• 제7권1호
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• pp.97-105
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• 1992

The most favourable possibilities to observe the phenomena of gravitational lensing are the high amplification events and the time delay between the images. These effects provide us the information to determine the Hubble parameter and the matter distribution in the universe. The image properties due to micro-lensing also is of an importance to find out the size and the structure of the source.

• 천문학회지
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• 제25권2호
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• pp.79-90
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• 1992

The physical properties of the flux factor K and its application are discussed in connection to the high amplification events. The effects due to random motions of stars in a foreground galaxy are examined in the frame work of moving caustics of gravitational microlenses.

• 한국세라믹학회지
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• 제35권12호
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• pp.1266-1273
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• 1998

Al2O3/(5~20vol%)LaAl11O18 composites in which the second phase was dispersed with a elongated grain shape were fabricated using Al2O3 and La2O3 composition by hot-pressing. In order investigate the in-fluence of LaAl11O18 on the toughening of LaAl11O18 on the toughening of Al2O3 matrix composites AE(acoustic emission) analysis was con-ducted together with an evaluation of fracture toughness using of SEPB technique. The degree of AE events occurred in composites were more than those in monolithic alumina. The occurrences of AE event increased with increasing the amount of LaAl11O18 phase in the Al2O3/LaAl11O18 composite is two times higher compared to monolithic alu-mina. The main toughening mechanism was attributed to the bridging of LaAl11O18 grains at tip of pro-pagating crack.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제28권1호
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• pp.16-23
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• 2002

To understand the micro-mechanical changes and the effects of the fluoride on rat's femur after administration of sodium fluoride, the three-point bending test, acoustic emission analysis during the three-point bending test and scanning electron microscopy were performed. The obtained results were as follows: 1. Bone strength increased in the rats given 1, 5, 10 and 20 ppm of fluoride but, there were no statistical significances (p>0.05). 2. With increasing the concentration of fluoride, most AE events released rapidly just before the maximum load and smaller events were recorded than the control group's. The average of cumulative AE event counts until maximum load of the femur in 20 ppm group were significantly small with respect to the control group's (p<0.05). 3. Fracture surfaces were well coincide with the results of acoustic emission behavior. Analyses of fracture surfaces indicated that, consistent with its the highest load, rat femur in 20 ppm fluoride group displays the roughest surface.

• 콘크리트학회논문집
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• 제11권4호
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• pp.107-116
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• 1999

The damage in concrete structures generally starts with microcracking and thus it is important to find and explore these microcracks in concrete in order to ensure appropriate safety and serviceability. The purpose of the present study is to identify the damage characteristics of concrete structures due to cracking by employing the acoustic emission techniques. A comprehensive experimental study has been done. The cracking damage under tensile and flexural loadings have been identified and the bond damage between steel and concrete have been also characterized. It is seen that the amplitudes and energy level of Acoustic Emission(AE) events are found to be relatively small for bond cracking damages and large for tensile cracking damages. The characteristic equations of the AE events for various cracking damages have been proposed based on the present test data. The internal microcracks are progressively developed ahead of a visible actual crack and the present study clearly exhibits these damage mechanism for various types of cracking in concrete. The present study provides useful data which can be used to identify the various types of cracking damages in concrete structures. This will allow efficient maintenance of concrete structures through monitoring of internal cracking based on acoustic emission.