• Journal of Radiation Protection and Research
• /
• v.26 no.3
• /
• pp.167-175
• /
• 2001

Semiconductor diode detectors coated with neutron reactive material are presently under investigation for various uses, such as remote sensing of thermal neutrons, fast neutron counting, and thermal neutron radiography. Theory indicates that single-coated devices can yield thermal neutron efficiencies from 4% to 11 %, which is supported by experimental evidence. Radiation endurance measurements indicate that the devices function well up to a limiting thermal neutron fluence of $10^{13}/cm^2$, beyond which noticeable degradation occurs. Thermal neutron contrast images of step wedges and simple phantoms, taken with dual in-line pixel devices, show promise for thermal neutron imaging detectors.

• Journal of the Korean Society of Safety
• /
• v.32 no.5
• /
• pp.69-75
• /
• 2017

Structural safety evaluation for static strength of thin plate RC member with high strength concrete is conducted in this study. Static strengths were predicted and compared with the experimental values. Predicted values were calculated by the evaluation formula based on the punching shear behavior and the yield line theory which can appear in the plate members. Static load tests were carried out for the specimens with high strength concrete and the test results were compared with the required performance in design. The comparison results show that the specimens with high strength concrete have sufficient structural safety for flexural and punching shear performance required in design. High strength concrete specimens exhibited excellent strength despite their small thickness. The range of concrete strengths applied in this study was about 60 MPa to 100 MPa.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.12 no.1
• /
• pp.1-14
• /
• 1999

선형탄성이론을 기초로 한 구조해석의 경우 사용하중상태에서의 변형과 응력은 만족할 만한 결과를 나타내지만, 항복후의 처짐과 파괴시의 극한하중 산정의 정확한 해석이 불가능하다. 평판의 극한해석시, 상한계 이론을 바탕으로 한 항복선 이론이 널리 사용되고 있으나 이론적으로 평판의 강도를 과대평가하게 된다. 그러므로, 임의의 하중조건과 경계조건에 대한 비선형 거동과 극한내하력을 산정할 수 있는 해석기법이 필요하다. 평판의 정확한 극한하중을 위해 p-Version 유한요소법을 제안하며, p-Version의 해석치를 범용 구조해석 프로그램인 ADINA의 결과와 문헌의 이론치와 비교하였다.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.33-36
• /
• 2004

The current Korea bridge design specifications have no provisions about concrete Barrier. And there are no test results of registence strength of the concrete barrier at the vehicle collision sites. This paper reports experimental results of concrete barrier on bridge deck conctructed by standard drawing of SB5 grade. Eight specimens were tested under static test. The specimens are divided by two groups (D-series and B-series). D-series is to show failure pattern of bridge deck. B-series is to show failure pattern of concrete Barrier. The test results compared with calculation results using Yield-Line theory of AASHTO LRFD Bridge Design Specifications.

• 전기의세계
• /
• v.27 no.5
• /
• pp.69-75
• /
• 1978

3 phase induction motor applied in the method of connecting it directly across the line needs large current when it starts. At that time, leakage magnetic pathes of interior of the motor are severely saturated and leakage reactances are decreased because of saturation. Consequently, increased current and raised powerfactor yield increase of starting torque. The author, noticing those phenomena, derived experimentally the raion of decreasing leakage reactance from the fact that when voltage applied to motor is increased under locked condition the magnitude of current and phase angle are varied, and determined tha equations of starting current and starting torque, considering the decrease of leakage reactance by the large starting current. The author calculated the characteristics of Current-Time and Speed-Time with the determined equation at specific load conditions, and compared the values obtained from above calculations with those from circle diagram's method and the practically recorded values at same load conditions. Therefore, the authos got a confidience that the results of the derived theory coincide with the practically measured values more well than circle diagram's results and circle diagram's equation should be modified in order to analize the starting status of a induction motor.

• Journal of the Society of Naval Architects of Korea
• /
• v.60 no.4
• /
• pp.213-221
• /
• 2023

The demand for Liquefied Natural Gas (LNG) carriers and LNG-fueled ships has significantly increased in recent years due to the sulfur-oxide emission regulations by the International Maritime Organization (IMO). The main goal of this paper is to introduce the process for the Engineering Critical Assessment (ECA) of IMO independent type-B cargo tanks made from 9% nickel alloy. A methodology proposed by the British Standard was used to conduct ECA for any structure with initial flaws. Based on this standard, a Matlab code was developed to perform ECA. Coarse mesh Finite Element Analysis (FEA) was performed on an independent type-B LNG cargo tank with a capacity of 15,000 m³. The location with the highest development of maximum principal stress was identified at the bottom of the cargo tank. Fine mesh FEA was performed to obtain the stress range required for ECA. The dynamic cargo tank loads used for FEA were determined using some ship rules presented by Det Norske Veritas. As a result of performing a 20-year long-term crack propagation analysis with a semi-elliptical surface crack, the fracture-to-yield ratio exceeded the Fracture Assessment Line (FAL) and some structural reinforcement was necessary. Performing a 15-day short-term crack propagation analysis, the fracture-to-yield ratio remained within the FAL, and no significant LNG leaks were expected. This paper is believed to provide a guide for performing ECA of LNG cargo tanks in the future by providing the basic theory and application sample necessary to perform ECA.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.3
• /
• pp.237-247
• /
• 2017

This paper investigates structural characteristics of internal vertical diaphragm and its influence on the connection strength between concrete filled tubular(CFT) column and beam. CFT columns are hybrids that combine two materials in one member. They have the benefits of steel for high tensile strength and ductility and of concrete for high compressive strength and stiffness. Analytical method of the flexural strength of vertical diaphragm to account moment transfer between panel zones is presented using yield line theory. Connection design is verified by a set of monotonic tests and numerical analysis with different diaphragm thicknesses. Plastic zones of CFT flange was found and matched closely to FEM results. Both analytical and experimental results showed good agreement that vertical diaphragm effectively alleviates the stress and transfer the force.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1991.10a
• /
• pp.133-138
• /
• 1991

The aim of the present paper is to develop a computer program predicting ultimate fracture strength of initially cracked structure under monotonically increasing external loads. For this purpose, two kinds of 3-D isoparametric solid elements, one 6-node wedge element and another 8-node brick element are formulated along the small deformation theory. Plasticity in the element is checked using von Mises' yield criterion. Elasto-plastic stiffness matrix of the element is calculated taking account of strain hardening effect. If the principal strain at crack tip which is one nodal point exceeds the critical strain dependin on the material property, crack tip is supposed to be opened and the crack tip node which was previously constrained in the direction perpendicular to the crack line is released. After that, the crack lay be propagated to the adjacent node. Once a crack tip node is fractured, the energy of the newly fractured node should be released which is to be absorbed by the remaining part. The accumulated reaction force which was carried by the newly fractured node so far is then applied in the opposite direction. During the action of crack tip relief force, since unloading may be occured in the plastic element, unloading check should be made. If a plastic element unloads, elastic stress-strain equation is used in the calculation of the stiffness matrix of the element, while for a loading element, elasto-plastic stress-strain equation is continuously used. Verification of the computer program is made comparing with the experimental results for center cracked panel subjected to uniform tensile load. Also some factors affecting ultimate fracture strength of initially cracked plate are investigated. It is concluded that the computer program developed here gives an accurate solution and becomes useful tool for predicting ultimate fracture load of initially cracked structural system under monotonically increasing external loads.

• Journal of Korean Society of Steel Construction
• /
• v.25 no.3
• /
• pp.279-287
• /
• 2013

The steel members are applied to high rise building since they have high strength compare to the concrete member. On the other hand, the elastic buckling is likely to occur in steel member because of their small section. When the elastic buckling occur, the steel structure lose a load carrying capacity. The steel frame would be unstable due to a rapid decline in strength by buckling. The purpose of this study is the development of FLD(Force Limiting Device) to prevent a elastic buckling for a slender member. Further, the behavior of steel structures with FLD would be stable by high energy absorption capacity. The proposed type of FLD is the type of out-of-plane resistance. In this study, member test and FEM analysis for proposed type were performed. The test parameters are thickness and gradient angle of out-of-plane plate. The proposed type may be effective method for FLD.

• Journal of Astronomy and Space Sciences
• /
• v.15 no.2
• /
• pp.359-371
• /
• 1998

We present the design specifications and the performance estimation of the FUVS (Far Ultraviolet Spectrograph) proposed for the observations of aurora, day/night airglow and astronomical objects on small satelltes in the spectral range of $900~1750AA$. The design of FUVS is carried out with the full consideration of optical characteristics of the grating and the aspheric substrate. Two independent methods, ray-tracing and the wave front aberration theory, are employed to estimate the performance of the optical design and it is verified that both procedures yield the resolution of $2~5AA$ in the entire spectral range. MDF (Minimum Detectable Flux) is also estimated using the known characteristics of the reflecting material and MCP, to study the feasibility of detection for faint emission lines from the hot interstellar plasmas. The results give that the observations from 1 day to 1 week, depending on the line intensity, can detect such faint emission lines from diffuse interstellar plasmas.