• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2008년도 Techno-Fair 및 합동춘계학술대회 논문집 전기물성,응용부문
• /
• pp.143-144
• /
• 2008

this paper describes the electric field distribution interpretation along a shield form inner vacuum interrupter(VI). The equipotential line and electric field in a VI are analysed by a finite element method at various shield form. in result, The electric potentials of end shield form was increased or decreased because it was various the length of shield and between external insulation and source area or fix._end shield. finally shield is how to electric field affect, and advance, and will achieve the optimum design of VI inside shield.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1998년도 추계학술대회 논문집
• /
• pp.113-116
• /
• 1998

This study should investigate to what extent the electric field of a vacuum interrupter might be influenced by the electric potential of floating arc shield. The electric potentials of floating shield and electric fields of a vacuum interrupter are analysed by a finite element method against variation of gap distances from 1mm to 12mm. The electric potentials of floating shield was increased with the gap distance, which is because the relative position of shield is closer to fixed contact so that the capacitance distribution inside interrupter is varied. The calculated results show that the maximum value of electric field of a vacuum interrupter with floating shield is nearly same to that without shield at shorter gap distance(below 5mm), however at larger gaps a significant increment of electric field is achieved in interrupter with shield companying with model without shield, which is due to the influence of charged floating shield.

• Structural Engineering and Mechanics
• /
• 제84권5호
• /
• pp.699-706
• /
• 2022

Settlement control techniques are critical for the safety of shield tunnel constructions, especially for facing complex situations. In this study, the shield tunnel structure from Huaita east road station to Heping Road station in Xuzhou metro No.3 line (China) is taken as engineering background, which has various complex problems of the upper-soft and lower-hard composite stratum conditions, twin curve shield tunnels, and underpass the foundation of the piled raft. The deformation characteristics of shield tunnelling passing through buildings are explored. Subsequently, comprehensive research methods of numerical simulation and field measurement are adopted to analyzing the effectiveness of settlement control by using the top grouting technique. The results show that the settlement of the buildings has obvious spatial characteristics, and the hysteresis effect can be obviously observed in soil deformation caused by shield construction. Meanwhile, the two shield constructions can cause repeated disturbances, reducing the soil deformation's hysteresis effect. Moreover, the shield tunnel's differential settlement is too large when a single line passes through, and the shield construction of the outer curve can cause more significant disturbance in the tunnel than the inside curve. Notably, the proposed process control parameters and secondary topgrouting method can effectively control the deformation of the shield tunnel, especially for the long-term deformation.

• 대한방사선기술학회지:방사선기술과학
• /
• 제46권6호
• /
• pp.519-526
• /
• 2023

This study was intended to evaluate the shielding rate of radiation shields manufactured using 3D printers that have recently been used in various fields by comparing them with existing shields made of lead, and to find out their applicability through experiments. A 3D printer shield made of tungsten filament 1 mm, 2 mm, 4 mm shield, RNS-TX (nanotungsten) 1.1 mm, lead 0.2 mmPb, and 1mmPb were exposed to ^99mTc, ¹⁸F, and ²⁰¹TI for 15, 30, 45 minutes, and 60 minutes after measuring cumulative dose three times. Based on this, the shielding rate of each shield was calculated based on the dose in the absence of the shield. In addition, ^99mTc, ¹⁸F, and ²⁰¹TI were located 100 cm away from the phantom in which the OSLD nano Dot device was inserted, and if there was no shield for 60 minutes, the dose of thyroid was measured using 1.0 mm of lead shield, 1.1 mm of RNS-TX shield, and 2 mm of tungsten shield made by 3D printer. The use of shields during radiation shielding emitted from open radiation sources all resulted in a reduction in dose. The radiation dose emitted from the radionuclides under the experiment was all reduced when the shield was used. This study has been confirmed that tungsten is a material that can replace lead due to its excellent performance and efficiency as shield, and that it even shows the possibility of manufacturing a customized shield using 3D printer.

• 한국터널지하공간학회 논문집
• /
• 제15권5호
• /
• pp.483-496
• /
• 2013

본 논문에서는 연약지반에 건설되는 Shield TBM 터널의 시공기술을 제시하였다. 이 연구를 수행하기 위하여 Shield TBM 장비를 축소 제작하여 축소모형 시험을 수행하였으며, 쉴드터널 굴착을 모사하기 위하여 다양한 장비들이 적용되었다. 또한 축소모형시험 중 Shield TBM 장비로 인해 발생되는 지반의 거동을 계측하였으며, 지반의 안정성은 시뮬레이션 결과를 토대로 평가하였다. 이를 바탕으로 쉴드터널의 안전한 시공을 위한 기초자료로 활용하고자 한다. 결론적으로 Shield-TBM 구간에 대한 실내축소모형시험을 통하여 설계의 신뢰성을 확보하고, 시공 시 안전을 위한 개선사항 등과 특히, Shield TBM 추진시 쉴드터널이 통과하는 공항 활주로의 안정성을 확보하기 위한 시공방안을 제시하고자 한다.

• The Korean Journal of Ecology
• /
• 제19권3호
• /
• pp.209-216
• /
• 1996

In order to identify the habitat characteristics of water shield (Brasenia schreberi), water quality and sediment characters were investigated. Water shield had peculial habitats such as old reservoir, developed basin-like reservior, a water depth within 1.5 m, constant water level, and thick sediment layer at the bottom. The species had very dense populations under the favorable growing conditions and occasionally grew together with Utricularia japonica. When water shield decreased, Nelumbo nucifera, Nuphar japonicum and Zizania latifolia increased. Natural populations of water shield need protection because it is endangered by the human activities and their harvest. The optimal conditions for the growth of water shield was near neutral pH. low conductivity and low turbidity. Therefore the input of pollutants should be controlled for its growth. The inorganic ion contents such as K, Mg, and Na were higher in the water shield growing area. Especially iron content of the sediments in the reservoirs with water shield was nearly five times as high as that in the reservoirs without water shield. thus iron might be one of the major limiting factors for the growth. It was considered that molybdenum can be another major factor because water shield is a nitrogen fixing plant.

• Nuclear Engineering and Technology
• /
• 제53권4호
• /
• pp.1318-1322
• /
• 2021

To unveil and delineate the elements applicable to the radiation protection of a femoral entry shield, calculate its mass attenuation coefficient, and demonstrate its dose reduction efficacy for interventional radiologist performing transarterial embolization (TAE) of ruptured hepatocellular carcinoma (rHCC). The lead equivalency of the shield was firstly validated. Electron microscopy was used to confirm the femoral entry shield being lead-free and to analyze the elemental content, with which the mass attenuation coefficient of the shield was calculated. An adult phantom, irradiated at the upper abdomen to simulate the TAE of rHCC, was used together with a dosimeter attached to the palm of a hand phantom. The dose rates at the hand phantom were measured, with the rHCC clinical protocol, without and with the femoral entry shield placed over the right femoral access site of the adult phantom. Without using the shield, the average hand dose rate was measured to be 0.325 µSv/sec. While using the shield, it was determined to be 0.110 µSv/sec. There was significant 66% dose reduction to the hand dose of IRs performing angiographic intervention with the femoral entry shield.

• Geomechanics and Engineering
• /
• 제19권3호
• /
• pp.283-293
• /
• 2019

Evaluating the stability of the excavation face of the cross-river shield tunnel with good accuracy is considered as a nonlinear and multivariable complex issue. Understanding the stability evaluation method of the shield tunnel excavation face is vital to operate and control the shield machine during shield tunneling. Considering the instability mechanism of the excavation face of the cross-river shield and the characteristics of this engineering, seven evaluation indexes of the stability of the excavation face were selected, i.e., the over-span ratio, buried depth of the tunnel, groundwater condition, soil permeability, internal friction angle, soil cohesion and advancing speed. The weight of each evaluation index was obtained by using the analytic hierarchy process and the entropy weight method. The evaluation model of the cross-river shield construction excavation face stability is established based on the idea point method. The feasibility of the evaluation model was verified by the engineering application in a cross-river shield tunnel project in China. Results obtained via the evaluation model are in good agreement with the actual construction situation. The proposed evaluation method is demonstrated as a promising and innovative method for the stability evaluation and safety construction of the cross-river shield tunnel engineerings.

• 한국초전도ㆍ저온공학회논문지
• /
• 제4권1호
• /
• pp.124-128
• /
• 2002

A numerical model to obtain the temperature distribution in a radiation shield of cryogenic systems was proposed. Conformal mapping was used to transform the eccentric physical region of the upper plate to the concentric numerical region. The effects of the thickness of the radiation shield, the emissivities of the vacuum chamber and the radiation shield, and the eccentricity between the centers of the upper plate and the contact area with a cryocooler on the maximum temperature difference in a radiation shield were shown.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2008년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.247-248
• /
• 2008

This paper describes the influence of shield(Arc shield) on the electric fields in a vacuum interrupter(VI). The equipotential line and electric field in a VI are analysed by a finite element method at various shield length. in result, The electric potentials of Arc shield edge was increased because the length too short or long approach the source. it confirmed that equipotential line was influenced that shape and length by end shield. finally this pater proposed to optimal length and shape by arc shield.