• 항공우주시스템공학회지
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• 제15권4호
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• pp.1-6
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• 2021

The non-explosive holding and release mechanism is used to prevent damage to the mission component caused by explosives when the deployment structure for Cube Satellites is separated. However, among the several types available, the non-explosive holding and release mechanism system using nylon wires depend on the nylon wire knot method and tightening power of the worker. Therefore, in this study, we conducted experiments with the operation of a new holding and release mechanism system by conceptualizing the Boa System Dial, which can provide a constant tightening force regardless of worker proficiency and deploying a imitational solar panel. In this study, the process of binding and unbinding with constant tension was recorded while applying the novel non-explosive holding and release mechanism using the Boa System Dial proposed. In addition, required advances are indicated for the application of the proposed system to actual Cube Satellites.

• 한국터널지하공간학회 논문집
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• 제9권3호
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• pp.251-261
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• 2007

본 연구는 터널굴착 공사에 의한 지반거동을 평가하여, 구조물의 형상, 위치, 굴착공정 변화등의 다양한 조건과 지반/구조물의 상호작용이 고려된 모형실험을 기본으로 수행하였다. 굴착진행 단계에 따른 구조물의 손상 거동 평가시 인접 구조물이 밀집된 도심지 굴착에서는 보다 안전하고 보수적인 평가가 나타나는 각변위와 수평변형율에 의한 손상도표를 활용하는 것이 보다 안전할 것으로 판단된다. 모형실험시 구조물에 발생된 균열의 손상수준을 손상도표에서 평가해 본 결과, 균열손상 수준이 적용된 평가가 각변위와 수평변형율만 적용된 손상수준보다 안전측으로 평가되는 것을 확인할 수 있었다. 그러므로, 각변위와 수평변형율 뿐만 아니라 균열이 고려된 손상평가를 수행하는 것이 보다 바람직할 것으로 판단된다.

• Corrosion Science and Technology
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• 제12권4호
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• pp.179-184
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• 2013

Pipe wall thinning caused by erosion and corrosion can adversely affect the operation of aged nuclear power plants. Some injured workers owing to pipe rupture has been reported and power reduction caused by unexpected pipe damage has been occurred consistently. Therefore, it is important to develop erosion-corrosion damage prediction model and investigate its mechanisms. Especially, liquid droplet impingement erosion(LDIE) is regarded as the main issue of pipe wall thinning management. To investigate LDIE mechanism with corrosion environment, we developed erosion-corrosion damage simulation apparatus and its capability has been verified through the preliminary damage experiment of 6061-Al alloy. The apparatus design has been based on ASTM standard test method, G73-10, that use high-speed rotator and enable to simulate water hammering and droplet impingement. The preliminary test results showed mass loss of 3.2% in conditions of peripheral speed of 110m/s, droplet size of 1mm-diameter, and accumulated time of 3 hours. In this study, the apparatus design revealed feasibility of LDIE damage simulation and provided possibility of accelerated erosion-corrosion damage test by controlling water chemistry.

• BMB Reports
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• 제53권2호
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• pp.112-117
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• 2020

A recent study suggested that methylation of ubiquitin-like with PHD and RING finger domain 1 (UHRF1) is regulated by SET7 and lysine-specific histone demethylase 1A (LSD1) and is essential for homologous recombination (HR). The study demonstrated that SET7-mediated methylation of UHRF1 promotes polyubiquitination of proliferating cell nuclear antigen (PCNA), inducing HR. However, studies on mediators that interact with and recruit UHRF1 to damaged lesions are needed to elucidate the mechanism of UHRF1 methylation-induced HR. Here, we identified that poly [ADP-ribose] polymerase 1 (PARP1) interacts with damage-induced methylated UHRF1 specifically and mediates UHRF1 to induce HR progression. Furthermore, cooperation of UHRF1-PARP1 is essential for cell viability, suggesting the importance of the interaction of UHRF1-PARP1 for damage tolerance in response to damage. Our data revealed that PARP1 mediates the HR mechanism, which is regulated by UHRF1 methylation. The data also indicated the significant role of PARP1 as a mediator of UHRF1 methylation-correlated HR pathway.

• Asian Pacific Journal of Cancer Prevention
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• 제13권10호
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• pp.4879-4881
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• 2012

Epidermal growth factor receptor (EGFR) overexpression is associated with resistance to chemotherapy and radiotherapy. The EGFR modulates DNA repair after radiation-induced damage through an association with the catalytic subunit of DNA protein kinase. DNA double-strand breaks (DSBs) are the most lethal type of DNA damage induced by ionizing radiation, and non-homologous end joining is the predominant pathway for repair of radiation-induced DSBs. Some cell signaling pathways that respond to normal growth factors are abnormally activated in human cancer. These pathways also invoke the cell survival mechanisms that lead to resistance to radiation. The molecular connection between the EGFR and its control over DNA repair capacity appears to be mediated by one or more signaling pathways downstream of this receptor. The purpose of this mini-review was not only to highlight the relation of the EGFR signal as a regulatory mechanism to DNA repair and radiation resistance, but also to provide clues to improving existing radiation resistance through novel therapies based on the above-mentioned mechanism.

• International Journal of Oral Biology
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• 제33권4호
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• pp.137-141
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• 2008

The present study reports the protective properties of a total methanol extract of B. platyphylla var. japonica against ultraviolet (UV)-C irradiation. Pretreatment of Chinese hamster fibroblast (V79-4) cells with a total methanol extract significantly increased cell survival following $300\;J/m^2$ of UV-C irradiation. The total methanol extract was further fractionated into 5 fractions: n-hexane, dichloromethane, ethylacetate, n-butanol and water fractions. Among these fractions, B. platyphylla var. japonica ethylacetate, butanol and water fractions showed significant protective effects against the cellular damage induced by UV-C irradiation. In order to elucidate the mechanism underlying this protective effect, DPPH (Editor note: abbreviations should be spelled out at first use.) radical scavenging and lipid peroxidation inhibitory activity were measured. Significant radical scavenging and lipid peroxidation inhibitory activities were observed for the ethylacetate fraction. In summary, the present data demonstrate that an extract of B. platyphylla var. japonica has a significant protective effect against UV-C irradiation. The underlying mechanism of this protective effect may involve radical scavenging and inhibition of lipid peroxidation by the B. platyphylla var. japonica extract.

• 동력기계공학회지
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• 제15권5호
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• pp.22-29
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• 2011

In this study, the damage mechanism of large scale steam turbine due to water induction was analyzed and recovery characteristics were reviewed. A turbine consists of the rotating rotor and the stationary casing, and the clearance between them is very small for the efficiency enhancement. If water induction, while relatively cold steam or water is introduced into turbine, occurs, the considerable humping is caused at the casing near the initial water induction point and that induces the rubbing between rotor and casing. Finally, it leads to the catastrophic failure. Bowed rotor has the different characteristics in the recovery depending on damage degree. The elastic deformation due to light rubbing is recovered by turning the rotor with 3 rpm under normal operation condition, but most plastic deformation due to rubbing deforms the local microstructure and that results in permanent deformation which could not be recovered under normal operation condition. Bowed rotor has diverse characteristics depending on the recovery method, and the method is empirical and needs the cutting edge technology. Careful recovery treatment of the rotor will eliminate the risks and secure the high quality rotor similar to new rotor. If any critical error is made during the recovery, the rotor would not be recovered permanently and it should be scrapped.

• Advances in Computational Design
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• 제6권1호
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• pp.1-13
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• 2021

Failure of a Multi-storeyed reinforced concrete framed structure occurs when a primary vertical structural component is isolated or made fragile, due to artificial or natural hazards. Load carried by vertical component (column) is transferred to neighbouring columns in the structure, if the neighbouring column is incompetent of holding the extra load, this leads to the progressive failure of neighbouring members and finally to the failure of partial or whole structure. The collapsing system frequently seeks alternative load path in order to stay alive. One of the imperative features of collapse is that the final damage is not relative to the initial damage. In this paper, the effect on the column and beam adjacent to statically removed vertical element in terms of axial force, shear force and bending moment is investigated. Using Alternate load path method, numerical modelling of two dimensional one bay, two bay with variation in storey heights are analysed with FE model in order to obtain better understanding of failure mechanism of multi-storeyed reinforced concrete framed structure. The results indicate that the corner column is more susceptible to progressive collapse when compared to middle column, using this simplified methodology one can easily predict how the structure can be made to stay alive in case of sudden failure of any horizontal or vertical structural element before designing.

• 대한기계학회논문집
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• 제18권3호
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• pp.600-611
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• 1994

The purpose of this research is to propose a model for the prediction of residual strength. For this purpose, two-paremeter model based on Caprino's is developed and formulated by the ratio of indentation due to impact and normalized residual strength. The damage zone is considered only as an indentation. Impact tests are carried out on laminated composites by steel balls. Test material is carbon/epoxy laminate. The specimens are composed of $[{\pm}45^{\circ}/0^{\circ}/90^{\circ}]_2$ and $[\pm}45^{\circ}]_4$ stacking sequence and have $0.75^T{\times}0.26^W{\times}100^L(mm) dimension. A proposed model shows a good correlation with the experimental results And failure mechanism due to high impact velocity is discussed on CFRP laminates to examine the initiation and development of damage by fractography and ultrasonic image ststem. The effect of the unidirectional ply position on the residual strength is considered here.

• Journal of Radiation Protection and Research
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• 제45권1호
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• pp.11-15
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• 2020

Background: There have been various studies to investigate the mechanisms of DNA damage from low-energy electrons. To understand the mechanism of these strand breaks, it is necessary to investigate the dissociation mechanism of the DNA constituents, that is, bases, sugars, and phosphates. Materials and Methods: We studied the dissociation of thymine base upon interaction with low-energy electrons. For this experiment, thymine powder was pressed onto the indium base and irradiated by 5 eV electrons. Results and Discussion: Non-irradiated and irradiated thymine samples were compared and analyzed using the X-ray photoelectron spectroscopic technique to analyze the dissociation patterns of the molecular bonds after low-energy electron irradiation of thymine. Conclusion: With 5 eV electron irradiation, C-C and N-C = O bonds are the primary dissociations that occur in thymine molecules.