• 터널과지하공간
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• 제19권6호
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• pp.567-582
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• 2009

일본의 기후현의 카미오카광산은 지하 약 1,000 m의 대심도에, 우주에서 도래하는 소립자의 관측과 양자의 붕괴현상 등을 연구하기 위한 실험시설 SUPER-KAMIOKANDE가 건설되었다. 이 시설 설계를 위한 기초 자료의 하나로, 초기지압 측정을 실시하여 건설 예정지의 암반 응력 상태를 파악했다. 측정 방법은, 일본 전력중앙연구소(Central Research Institute of the Electric Power Industry)에서 개발한 ８성분 변형률 게이지를 이용한 공경변화법, Sugahara와 Obara가 개발한 16성분 구면 게이지를 이용한 구면 공저변형법, 오스트레일리아의 CSIRO에 의해 개발된 Hollow Inclusion Cell을 이용한 공벽변형률법이다. ３종류의 방법에 의해 얻어진 결과가 일치하지는 않았지만, ６응력성분의 평균치를 이용하여 주응력 방향 및 크기를 결정하였다.

• 터널과지하공간
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• 제18권6호
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• pp.457-464
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• 2008

암반 굴착기술의 고속화 및 정밀한 암반손상평가를 위해서는 암석의 동적파괴 메커니즘에 관한 연구가 중요하다. 본 연구에서는 충격파형 제어 Split Hopkinson Pressure Bar (SHPB) 시스템을 이용하여 모의 암석시료에 단계별 충격하중을 가하여 취성재료의 동적파괴 특성 및 동적손상메커니즘을 분석하였다. 실험시료의 손상도 평가를 위하여 충격실험 전후에 모든 시료에 대하여 P파 및 S파 속도를 측정하였으며, 탄성파 속도 감쇠정도에 따른 손상도를 평가하였다. 모의 연암 시료와 경암 시료의 탄성파 속도 감쇠비는 충격하중이 증가함에 따라 비슷한 수준으로 증가하는 경향을 보였으나, 최종 변형률의 경우 모의 연암 시료에서 현저히 높은 값을 나타내었다.

• 패션비즈니스
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• 제7권4호
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• pp.121-128
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• 2003

A new textile material, poly(trimethylene terephthalate) polymer, has been introduced to the textile industry. The structure of PTT is similar to the PET, while the tensile deformation and subsequent recovery property is better than that of PET. In this study, the physical and mechanical properties of textile woven fabrics made of PTT, PET, and nylon 6 yarns as the filling yarn were determined using the Kawabata Evaluation System (KES), including tensile, bending, shearing, compression, and surface related parameters. On top of these measurements, the subjective ratings by evaluators were performed on the fabric samples. From the examination of the stress-strain behavior of the yarn specimens focused on the recovery mode, it was evident that the PTT specimen developed lower stress at 3% elongation. The subsequent recovery curve showed that the PTT has less stress-decay rate than the other specimens, implying that the recovery behavior of the PTT is recommendable for the end-uses including stretchable textile materials, sports wears, etc. The KES bending rigidity(B) value of the PTT sample fabric was lower than that of the PET sample fabric. Subjective evaluation of the fabric samples by the evaluators on the descriptive word pair "soft - not soft" showed similar tendency with the KES B determination of the fabric samples.

• Nuclear Engineering and Technology
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• 제50권2호
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• pp.313-317
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• 2018

Licenses for the storage of spent nuclear fuel (SNF) and vitrified highly active waste in casks under dry conditions are limited to 40 years and have to be renewed for prolonged storage periods. If such a license renewal has to be expected since as in accordance with the new site selection procedure a final repository for spent fuel in Germany will not be available before the year 2050. For transport and possible unloading and loading in new casks for final storage, the integrity and the maintenance of the geometry of the cask's inventory is essential because the SNF rod cladding and the cladding of the vitrified highly active waste are stipulated as a barrier in the storage concept. For SNF, the cladding integrity is ensured currently by limiting the hoop stress and hoop strain as well as the maximum temperature to certain values for a 40-year storage period. For a prolonged storage period, other cladding degradation mechanisms such as inner and outer oxide layer formation, hydrogen pick up, irradiation damages in cladding material crystal structure, helium production from alpha decay, and long-term fission gas release may become leading effects driving degradation mechanisms that have to be discussed.

• Nuclear Engineering and Technology
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• 제45권4호
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• pp.469-476
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• 2013

In a postulated severe core damage accident in a PHWR, multiple failures of core cooling systems may lead to the collapse of pressure tubes and calandria tubes, which may ultimately relocate inside the calandria vessel forming a terminal debris bed. The debris bed, which may reach high temperatures due to the decay heat, is cooled by the moderator in the calandria. With time, the moderator is evaporated and after some time, a hot dry debris bed is formed. The debris bed transfers heat to the calandria vault water which acts as the ultimate heat sink. However, the questions remain: how long would the vault water be an ultimate heat sink, and what would be the failure mode of the calandria vessel if the heat sink capability of the reactor vault water is lost? In the present study, a numerical analysis is performed to evaluate the thermal loads and the stresses in the calandria vessel following the above accident scenario. The heat transfer from the molten corium pool to the surrounding is assumed to be by a combination of radiation, conduction, and convection from the calandria vessel wall to the vault water. From the temperature distribution in the vessel wall, the transient thermal loads have been evaluated. The strain rate and the vessel failure have been evaluated for the above scenario.

• Structural Engineering and Mechanics
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• 제72권4호
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• pp.479-489
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• 2019

The corrosion of reinforcement leads to a gradual decay of structural strength and durability. Several models for crack occurrence prediction and crack width propagation are investigated in this paper. Analytical and experimental models were used to predict the bond strength in the period of corrosion propagation. The manner of flexural strength loss is calculated by application of these models for different scenarios. As a new approach, the variation of the concrete beam neutral axis height has been evaluated, which shows a reduction in the neutral axis height for the scenarios without loss of bond. Alternatively, an increase of the neutral axis height was observed for the scenarios including bond and concrete section loss. The statistical properties of the parameters influencing the strength have been deliberated associated with obtaining the time-dependent bending strength during corrosion propagation, using Monte Carlo (MC) random sampling method. Results showed that the ultimate strain in concrete decreases significantly as a consequence of the bond strength reduction during the corrosion process, when the section reaches to its final limit. Therefore, such sections are likely to show brittle behavior.

• 한국압력기기공학회 논문집
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• 제19권2호
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• pp.163-170
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• 2023

Since spent nuclear fuel assemblies (SFA) are transported to interim storage or final disposal facility after cooling the decay heat, finite element analysis (FEA) with simplification is widely used to show their integrity against cladding failure to cause dispersal of radioactive material. However, there is a lack of research addressing the comprehensive impact of shape and element simplification on analysis results. In this study, for the optimization of a typical pressurized water reactor SFA, different types of finite element models were generated by changing number of fuel rods, fuel rod element type and assembly length. A series of FEA in use of these different models were conducted under a shock load data obtained from surrogate fuel assembly transportation test. Effects of number of fuel rods, element type and length of assembly were also analyzed, which shows that the element type of fuel rod mainly affected on cladding strain. Finally, an optimal finite element model was determined for other practical application in the future.

• 대한조선학회논문집
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• 제55권1호
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• pp.37-44
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• 2018

To understand the dynamic characteristics of the vessel with hydroelastic response, it is very important to estimate the dynamic modal parameters such as mode shapes, natural frequency, and damping ratio. These dynamic modal parameters of full scale ship are a priori unknowns, hence to be estimated directly based upon the full scale measurement data. In this paper, dynamic modal parameters were extracted by signal processing of acceleration and strain data measured from a large container ship whose loading capacity is 9400TEU. The mode shapes of the vibrating hull were identified using the proper orthogonal decomposition and the vibration response of hull was decomposed into its modal magnitudes. Natural frequencies of specific modes were derived via Fourier transform of these modal magnitude. Also, the free decay signal of the vibrating hull was obtained through the random decrement technique and the damping ratio was estimated with accuracy.

• 한국동물위생학회지
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• 제15권1호
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• pp.32-45
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• 1992

In order to establish and enzyme-linked immunosorbent assay to ILTV, field virus strain of ILTV was propagated in chorioallantoic membrane of the embryonated eggs. purified and used as antigen. The antisera selected from the field samples and immunized chickens based on serum neutralization test were used as the standard positive and negative sera in all tests. It was found that optimal antigen concentration was $2{\mu}g$ of protein per well and a 1 : 100 dilution of standard serum showed low background optical density with negative serum and high P/N values of positive sera. A 1 : 500 dilution of the rabbit anti-chicken IgG peroxidase conjugate produced a high P/N values and thirty minutes was chosen as suitable time to read the optical density of the enzyme substrate reaction and optical density was consistent during the 16 hours after stopper was treated. When coated antigen was kept on microplate for varying time up to 16 hours at $4^{\circ}C$ or $37^{\circ}C,$ no significant difference was observed between the treatment. The coated antigen could be kept without change of antigenicity for at least one month at $-70^{\circ}C,\; -20^{\circ}C,\; 4^{\circ}C$ and room temperature. When blocking buffer contanining bovine serum albumin was mixed directly with conjugate and serum at 10% level induced higher P/N values compared to blocking antigen coated microplate with the same blocking buffer. The coefficience of correlation between ELISA and SN test was 0.577. When antibody response of chickens, vaccinated with ILTV, was examined by ELISA and SN test, antibody rising and decay pattern between the two test was similar until 11 weeks of age. However 12 weeks onward antibody titer checked on by SN test was slightly lower than that tested by ELISA.

• The Plant Pathology Journal
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• 제26권4호
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• pp.353-359
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• 2010

In order to control postharvest spoilage of satsuma mandarin fruits, rhizobacteria were isolated from soil samples. The Pantoea agglomerans strain 59-4 (Pa 59-4) which suppresses the decay of mandarin fruit by green and blue mold, was tested for the control efficacy and its mode of action was investigated. Pa 59-4 inhibited infection by green and blue mold on wounded mandarins, which were artificially inoculated with a spore suspension of Penicillium digitatum and P. italicum with control efficacies of 85-90% and 75-80%, respectively. The biocontrol efficacy was increased by raising the concentration of cells to between $10^8$ and $10^9\;cfu/ml$, and pretreatment with the antagonist prevented subsequent infection by green mold. The population of Pa 59-4 was increased more than 10 fold during the 24 hr incubation at $20^{\circ}C$, indicating that colonization of the wound site might prevent the infection by green mold. Despite poor antifungal activity, the Pa 59-4 isolate completely inhibited the germination and growth of P. digitatum spores at $1{\times}10^8\;cfu/ml$. We argue that the control efficacy was mediated by nutrient competition. Overall, the effective rhizobacterium, Pa 59-4, was shown to be a promising biocontrol agent for the postharvest spoilage of mandarin fruits by green and blue mold.