• Nuclear Engineering and Technology
• /
• 제35권5호
• /
• pp.497-505
• /
• 2003

This paper describes a computational approach to the quantification of primary damage under irradiation and demonstrates the effect of neutron energy spectra on the formation of the displacement cascade. The development of displacement cascades in ${\alpha}-Iron$ has been simulated using the MOLDY code - a molecular dynamics code for simulating radiation damage. The primary knock-on atom energy, key input to the MOLDY code, was determined from the SPECTER code calculation on two neutron spectra. The two neutron spectra include; (i) neutron spectrum in the instrumented irradiation capsule of the high-flux advanced neutron application reactor (HANARO), and (ii) neutron spectrum at the inner surface of the reactor pressure vessel steel for the Younggwang nuclear power plant No.5 (YG 5). Minor differences in the normalized neutron spectra between the two spectra produce similar values of PKA energy, which are 4.7 keV for HANARO and 5.3 keV for YG 5. This similarity implies that primary damage to the components of the commercial nuclear reactors should be well simulated by irradiation in the HANARO. Moreover, the application of the MD calculations corroborates this statement by comparing cascades simulation results.

• 한국안전학회지
• /
• 제38권2호
• /
• pp.36-43
• /
• 2023

In this study, a four-point bending test was conducted to assess and detect the damage to reinforced concrete structures using the acoustic emission (AE) technique. Based on the crack investigation results, flexural failure was classified into four stages and compared with the characteristic analysis results of AE parameters. The parametric characterization indicated that the activity of the primary AE signal was high in the early stage, and that of the second signal increased after the flexural cracks stabilized. Because the secondary AE signal included noise generated by friction, parameter-based analysis for damage assessment was performed using the primary signal; the secondary signal was used as complement. The activity analyses of the primary and secondary signals effectively classified crack propagation; however, determining the macrocracks and yielding of reinforcing bars had certain limitations. Nevertheless, applying the damage index with cumulative AE energy is a complementary technique for detecting and assessing structure damage that well detects the occurrence of macrocracks.

• 시큐리티연구
• /
• 제14호
• /
• pp.261-283
• /
• 2007

범죄두려움의 원인을 설명하기 위한 최근의 연구들에서는 성, 연령, 경제수준, 범죄 피해경험 등의 미시적인 개인수준과 거시적인 지역수준과의 연계를 시도하는 연구에 관심과 노력을 보이고 있다. 하지만 이 연구에서는 이러한 지역수준의 특성에 대한 개인의 관심과 해석은 개인의 특성으로서 과거의 범죄피해경험, 범죄피해의 취약성 정도, 범죄관련 정보에 대한 관심에 따라 다를 수 있다고 보며, 미시적인 수준과 거시적인 수준의 연계를 시도하기에 앞서 개인적인 수준에서 개인의 특성과 범죄두려움의 관계에 대해서 실증적인 분석을 실시하였다. 따라서 이 연구의 목적은 범죄두려움이 과연 개인의 특성에 따라서 어떻게 느끼게 되며 또한 얼마나 많은 영향을 받게 되는지를 실증적으로 검증하는 데에 그 목적이 있다. 이 연구의 조사결과 우선 범죄피해경험이 집단간의 차이가 통계적으로 유의미한 인구통계학적 특성은 연령, 결혼상태, 최종학력, 거주하는 장소였으며, 범죄피해의 취약성 정도는 성별과 결혼상태, 범죄관련 정보에 대한 관심은 성별, 연령, 최종학력, 가족 수입, 거주장소 위치에 따라서 집단 간의 통계적으로 유의미한 차이가 있는 것으로 나타났다. 둘째, 개인적 특성 요인과 범죄두려움의 상관관계 분석을 실시한 결과 독립변수 세요인 모두 범죄두려움과 통계적으로 유의미한 상관관계를 나타내고 있었으며, 특히 범죄피해에 대한 취약성 요인이 범죄두려움과 가장 상관관계가 높게 나타났다. 마지막으로 개인의 특성으로서 범죄피해의 취약성, 범죄정보에 대한 관심, 범죄피해경험은 범죄두려움에 영향을 미쳤으며, 특히 이러한 개인적 특성 요인 중 자신이 범죄피해에 대해 취약하다고 생각 하는 범죄피해의 취약성이 범죄두려움에 가장 많은 영향을 미치는 요인으로 나타났다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
• /
• pp.200-204
• /
• 1994

Low temperature associated damage mechanism is not well known for asphalt concrete. Many studies have related the thermal cracking of pavement in the roadway in cold region with overall shrinkage of the pavement surface under assumption of homogeneous material. This study, however, was intiated based on the assumption that thermal incompatibility of materials (heterogeneous) in asphalt concrete mixture would be the primary cause of the damages. Acoustic emission technique and microscopic obsevation were employed to evaluate damage mechanism of asphalt concrete due to low temperature. The first method showed the sufficient evidence that asphalt concrete could be damaged by lowered temperature only. The second method showed that the damage by temperature resulted in micro-cracks at the interface between asphalt matrix and aggregate particle. It was concluded that these damage mechanisms were the primary cause of major thermal cracking of asphalt pavement in cold region.

• Nuclear Engineering and Technology
• /
• 제52권7호
• /
• pp.1537-1544
• /
• 2020

Molecular dynamics (MD) simulations were conducted to investigate the temperature effects on the primary damage in gallium nitride (GaN) material. Five temperatures ranging from 300 K to 900 K were studied for 10 keV Ga primary knock-on atom (PKA) with inject direction of [0001]. The results of MD simulations showed that threshold displacement energy (E_d) was affected by temperatures and at higher temperature, it was larger. The evolutions of defects under various temperatures were similar. However, the higher temperature was found to increase the peak number, peak time, final time and recombination efficiency while decreasing the final number. With regard to clusters, isolated point defects and little clusters were common clusters and the fraction of point defects increased with temperature for vacancy clusters, whereas it did not appear in the interstitial clusters. Finally, at each temperature, the number of Ga interstitial atoms was larger than that of N and besides that, there were other different results of specific types of split interstitial atoms.

• 약학회지
• /
• 제47권6호
• /
• pp.369-375
• /
• 2003

Xiaoshuan Zaizao Wan (XZW) has been used in China to improve hemiplegia, deviation of eye and mouth, and dysphasia due to cerebral thrombosis. To characterize pharmacological actions of XZW, we evaluated its effects on neuronal cell damage induced in primary cultured rat cortical cells by various oxidative insults, glutamate or N-methyl-D-aspartate (NMDA), and $\beta$-amyloid fragment ($A_{\beta(25-35)}$). XZW was found to inhibit the oxidative neuronal damage induced by $H_2O_2$, xanthine/xanthine oxidase, or $Fe^{2+}$/ascorbic acid. It also attenuated the excitotoxic damage induced by glutamate or NMDA. The NMDA-induced neurotoxicity was more effectively inhibited than the glutamate-induced toxicity. In addition, we found that XZW protected neurons against the $A_{\beta(25-35)}$-induced toxicity. Moreover; XZW exhibited dramatic inhibition of lipid peroxidation in rat brain homogenates and mild 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. Taken together; these results demonstrate that XZW exerts neuroprotective effects against oxidative, excitotoxic, or $A_{\beta(25-35)}$-induced neuronal damage. These findings may provide pharmacological basis for its clinical usage treating the sequelae caused by cerebral thrombosis. Furthermore, XZW may exert beneficial effects on Alzheimer's disease and other oxidative stress-related neurodegenerative disorders.

• Journal of Chest Surgery
• /
• 제26권9호
• /
• pp.667-676
• /
• 1993

Boprosthetic cardiac valves fail from biological and metabolic as well as mechanical reasons, and the limited durability is the main factor of marked withdrawal in their clinical use. Starting the use of bioprosthetic valves in 1976, up to the end of 1992, the consecutive 178 patients have undergone re-replacement of glutaraldehyde-treated xenograft valves for primary tissue failure [PTF]among the patients who had initial valve replacement at Seoul national University Hospital. The explanted valves were 69 porcine aortic [51 Hancock, 12 Angell-Shiley and 6 Carentier-Edwards] and 141 bovine pericardial [129 standard-profile and 12 low-profile ionescu-Shiley] valwes, with an overall incidence of PTF of 15.2%. The operative mortality rate of re-replacement was 5.1%. Calcific degeneration and tissue damage in relation to calcification were the most frequent modes of PTF on gross examinatin of the explanted valves resulting hemodynamically in valvular regurgitation. The number of Hancocg porcine and the standard-profile Ionescu-Shiley valves in valves in mitral position failed more often from tissue damage [tears, holes, and loss or destruction of cuspal tissue] than calcification [68.3% vs. 39.0%, p<0.01] with resultant regurgitation in 61%, the Ionescu-Shiley valves in the same position in 53%. The tendency of more calcification than tissue damage[71.3% vs. 33.3%, p<0.001]with stenosis in 53%. The tendency of more calcification and immobility of cusps in the latter group was partly explainable by the inclusion of patients of pediatric age. Observation made in this study suggest : many of bioprosthetic valves would fail from calcification and tissue damage : some fail prematurely because of mechanical stress probably owing to the valve design in construction ; andeven those valves escaped early damage would be subject to calcify in the prolonged follow-up period. In conclusion, at the present time, the clinical use of bioprostheticxenograft valves seems to be quite limited until further improvement in biocompatibility and refinement in valve design in manufacture are achieved.

• 한국응용곤충학회지
• /
• 제31권2호
• /
• pp.174-181
• /
• 1992

씨고자리파리(Delia platura) 유충의 피해가 차후 대두 생육과 생산성에 미치는 영향을 기상생태형별로 조사하고 또 해충종합관리의 방안으로서 토양내 유기물함량, 토양의 종류, 피복등과 피해정도와의 관계를 분석한 결과를 종합해 보면 다음과 같다. 콩 초생단엽의 피해로 영양생장이 지연되었는데 일장에 의해 유도되는 개화기에는 큰 변화가 없었다. 인위적으로 적엽한 구 보다는 충접종에 의한 피해구에서 생육지연 현상이 두드러졌는데 이는 초생단엽 피해 외에 지하 경.근부가 함께 피해를 받은 때문이었다. 생산량은 초생단엽이 25% 피해를 받은 구부터 크게 감소하였다. 콩의 출현속도는 무피복구에 비해 피복구에서 빨랐는데 투명비닐의 촉진 효과가 가장컸다. 식양토와 식토구에서 재배한 콩의 피해가 적었으며 토양내 부엽토 함량이 증가하면 출현속도가 빨라져 초생단엽의 피해가 감소하는 것으로 나타났다.

• 대한소아치과학회지
• /
• 제31권2호
• /
• pp.153-158
• /
• 2004

소아치과 임상에서 기성금관 수복은 광범위한 우식병소를 가졌거나 치수치료를 받은 치아에 필수적인 술식으로 간주된다. 그러나 기성금관 장착을 위한 치아삭제 과정 중 인접 치면에 의원성 손상이 생길 경우 우식이환율이 높아질 수 있다. 특히 제 2유구치에 기성금관을 위한 지대치를 형성할 때 인접한 제 1대구치 근심면에 발생될 수 있는 의원성 손상은 치아 우식으로 진행될 잠재성을 가지게 된다. 따라서 본 연구는 제 2유구치의 기성금관을 위한 지대치 형성과정에서 생길 수 있는 제 1대구치의 의원성 손상의 유형과 정도를 알아보고자 하였다. 부산대학교병원에 내원한 소아들을 대상으로 기성금관으로 수복한 제 2유구치의 원심면을 치간이개용 고무링으로 치간이개를 한 후 러버인상재로 인접면의 인상을 채득하고 주사 전자현미경상에서 관찰하여 의원성 손상의 정도를 확인하였다. 제 1대구치의 근심면이 인기된 시편을 주사 전자현미경으로 관찰한 결과, 약 66.7%에서 다양한 유형과 정도의 의원성 손상을 확인할 수 있었다. 따라서 유구치의 기성금관 장착을 위한 지대치 형성과정에서는, 치간이개용 고무링이나 wedge를 이용한 치간이개, matrix band를 이용한 인접 치면의 보호, 인접면 삭제방법의 수정 등과 같은 의원성 손상을 예방하기 위한 술자의 노력이 필요할 것으로 사료되었다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
• /
• pp.28.1-28.1
• /
• 2011

Radiation-induced displacement damage which has caused the increase of the dark current in the focal plane adopted in the Ozone Monitoring Instrument (OMI) was studied in regards of the primary protons and the secondaries generated by the protons in the orbit. By using the Monte Carlo N-Particle Transport Code System (MCNPX) version 2.4.0 along with the Stopping and Range of Ions in Matter version 2010 (SRIM2010), effects of the primary protons as well as secondary particles including neutron, electron, and photon were investigated. After their doses and fluxes that reached onto the charge-coupled device (CCD) were examined, displacement damage induced by major sources was presented.