• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.75-80
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• 2011

The main objective of this research is to develop fatigue prediction model for flexible pavements using energy ratio factor and phase angle. The two parameters are considered as fundamental properties of time and temperature dependent viscoelastic asphalt concrete materials. The energy ratio factor is defined as the ratio of the pseudo-total cumulative dissipated energy to the cumulative dissipated energy to failure during the test. The phase angle between the stress and strain ware signals stems from the intrinsic the dependent asphalt mixture behavior. The phase angle was computed and the relationship between the initial mixture stiffness and the initial phase angle is presented. As a result, fatigue prediction model for flexible pavements was proposed using intrinsic properties of viscoelastic asphalt concrete materials.

• Analytical Science and Technology
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• v.6 no.3
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• pp.319-328
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• 1993

Energy transfer process between $Tb^{3+}$ and $Ce^{3+}$ has been studied in LaOCl host. The energy absorbed by $Ce^{3+}$ transfers to $Tb^{3+}$ which has levels emitting strong fluorescence. The probability of energy transfer depends strongly on the concentration or the distance of activator ions. While the energy transferred on $Tb^{3+}$ emits from $^5D_3$ level at low concentration of $Ce^{3+}$, the energy goes back to $Ce^{3+}$(Back Transfer) and then emits from low levels of $Ce^{3+}$ and $Tb^{3+}$ at the high concentration. The Back Transfer process has been identified by the experiment with varying the concentration of the activator, $Ce^{3+}$. The relaxation is more effective if $Ce^{3+}$ intermediates than if not.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.202-202
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• 2000

AC-PDP(Plasma Display Paner)는 기체 방전을 이용한 디스플레이로서 기체에 직접 노출되는 MgO 보호막의 2차전자 방출계수(${\gamma}$는 AC-PDP의 방전특성을 결정짓는 중요한 요소이다. MgO 보호막의 이차전자 방출계수는 AC-PDP에 주입하는 기체의 종류, 결정 방향성과 표면오염상태 등에 영향을 받는다. 본 연구에서는 유리 기판위에 Al 전극을 증착, 에칭후 screen printing으로 유전체를 도포, 소성 한 21inch 규격의 test panel에 MgO 보호막을 E-Beam으로 5000$\AA$ 증착한 후 MgO 보호막을 대기에 노출되는 시간간격을 변수로 하여 대기 열처리 한 MgO보호막의 2차 전자방출계수를 ${\gamma}$-FIB(Focused Ion Beam) 장치를 이용하여 측정하였다. 그리고 대기 노출 간격은 1분, 5분, 20분으로 하여 2차 전자방출계수를 측정하였고, 2차전자방출계수 측정 시 가속전압은 50V에서 200V까지 변화를 주었으며, Ne+을 사용하여 1.2$\times$10-4Torr의 진공도를 유지하며 측정하였다. 또한 각각의 MgO막의 에너지 갭을 광학적 방법을 이용하여 구하였다.

• Electric Engineers Magazine
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• v.253 no.9
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• pp.27-33
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• 2003

기체분자는 보통상태에서는 전기적으로 중성이다. 그러나 기체 분자가 운동에너지를 가지고 있는 다른 원자나 전자 등과 충돌하게 되면 기체 분자내의 전자가 에너지를 흡수하여 여기나 전리하게 된다. 여기나 전리의 상태는 불안정한 상태이므로 순간적으로 안정상태로 복귀하는데 이 때의 에너지차가 빛으로 방출된다. 이와 같이 온도방사와는 달리 냉광으로 발광하는 현상을 루우미네슨스라고 한다

• Journal of Energy Engineering
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• v.7 no.2
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• pp.202-208
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• 1998

As in the other industrial processes, a nuclear power plant involves a steam relieving process through which condensable steam is discharged and condensed in a subcooled pool. An analysis of steam discharge transients was carried out using the method of characteristics to determine the flow characteristics and dynamic loads of piping that are used for structural design of the piping and its supports. The analysis included not only the steam flow rate but also the flow rates of the air and water which originally exist in the pipe. The analytical model was developed for a uniform pipe with friction through which the flow was discharged into a suppression pool. Including the combinations of system elements such as reservoir, valve and branching pipe lines. The piping flow characteristics and dynamic loads were calculated by varying system pressure, pipe length, and submergence depth. It was found that the dynamic load, water clearing time and water clearing velocity at the water/air interface were dependent not only on the system pressure and temperature but also on the pipe length and submergence depth.

• Progress in Medical Physics
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• v.9 no.3
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• pp.185-192
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• 1998

It is necessarily to evaluate the energy of X-ray emitted from linear accelerator in order to determine the accurate absorbed dose. The method of direct measurement for x-ray energy is very difficult and impractical. Therefore the method of using beam quality index is generally used. Several dosimetry protocols recommend the use of quality indices such as depth of dose maximum at radiation central axis, dose gradient, and dose level. The linear accelerator manufactures follow the recommendation as dosimetry protocols. The study was performed for us to select the most suitable parameter among the Quality indices as described above. For photon beams of 4, 6, 10, 15, and 21 MV nominal energies produced by four kinds of accelerators(Mitsubishi, Scanditronix, Siemens, Varian) in eleven institutions, We evaluated the x-ray energies obtained by the Quality indices as recommended by several dosimetry protocols and manufactures. Results showed that there were energy spreads according to the same accelerators and Quality indices even though nominal energies were same. It appeared that the percent depth dose at 10 cm (D$_{10}$(%)) gave the smallest deviation and spread of energies. As energies increased, the energy deviation increased for all the quality indices. It is desirable for the use of unified quality index to compare the evaluation of beam quality at different institutions.

• Tunnel and Underground Space
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• v.20 no.5
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• pp.344-351
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• 2010

Slip along a frictional fracture can be approached as initiation and propagation of a mode II crack along its own plane. Fracture mechanics theories predict that under pure mode II loading initiation will occur when the energy release rate of the fracture attains a critical value ($G_{IIC}$), which is generally taken as a material property. For the past few years the rock mechanics group at Purdue University has investigated experimentally the dependence of $G_{IIC}$ on normal stress and on the frictional characteristics of a fracture. A number of experiments has been conducted first on acrylic, a material that, using photoelastic methods, allows visualization of the stress field ahead of the fracture tip; and later on gypsum, a rock model material with relatively low unconfined compression strength. The experimental investigation has been expanded to include other frictional materials with higher unconfined compression strength. Direct shear tests have been conducted on specimens made with cement paste. New observations together with previous experiments indicate that $G_{IIC}$ can only be considered a material property when the peak friction angle of the discontinuity is similar to the residual friction angle; otherwise the critical energy release rate increases with normal stress.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.2072-2078
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• 2003

In this paper, the boundary element analysis of viscoelastic strain energy release rate G(t) for the cracked linear viscoelastic solids has been attempted. This study proposes the G(t) equation and the calculating method of G(t) by time-domain boundary element analysis for the viscoelastic solids. The G(t) is defined as the derivative of the viscoelastic potential energy II(t) with respect to crack length a. Two example problems are presented to show the applicability of the proposed method to the analysis of the cracked linear viscoelastic solids. Numerical results of example problems show the accuracy and effectiveness of the proposed method.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.157-162
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• 1998

양전자 단층 촬영장치(PET)에 사용되는 주요 양전자 방출 핵종들의 생성 단면적을 평가하였다. 평가한 생성 반응들은 $^{14}$ N(p,$\alpha$)$^{11}$ C,$^{16}$ O(p,$\alpha$)$^{13}$N, $^{14}$ N(d,n)$^{15}$ O,$^{18}$ O(p,n)$^{18}$ F,$^{20}$ Ne(d,$\alpha$)$_{18}$ F 이며, 입사 입자의 에너지 범위는 반응 문턱 에너지부터 약 150 MeV까지이다. 또한 하전입자 범 모니터용 표준 단면적으로서 $^{27}$ Al에 d 및 $^3$He, $\alpha$가 반응하여 $^{22}$ Na가 생성되는 반응의 단면적들을 입사 에너지 약 120 MeV까지 평가하였다. 실험치를 fitting하게나 ALICE95 코드를 이용하여 이론적 계산을 수행하였는데, 평가 단면적의 표준 편차는 10-30%이다 이들 평가 단면적들은 가속기를 이용한 PET용 핵종의 생산율 계산 및 빔 모니터의 표준 단면적으로 사용하기에 적절한 것으로 판단된다.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.343-345
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• 2018

전력 발전사들은 해안을 중심으로 운영되고 있는데, 이는 발전하는 과정에서 회전기기 터빈과 발전기 열을 냉각시키기 위해 해수를 사용한 후, 발생한 온배수는 해안으로 방출되고 있다. 양식장에는 수온 관리를 하는데 큰 비용이 발생하기 때문에 수열에너지를 공급하는데는 경제적으로 매우 중요하다. 따라서 효율적인 스마트 양식장을 운용하기 위해서는 발전소에서 폐수로 방출되는 온배수 에너지원을 재생에너지로 활용하여 이 열을 저장하고 양식수조에 공급하는 온배수 히트펌프의 수온 제어시스템과 양식수조의 최적화 설계를 위하여 새로운 형태의 육상수조 양식구조와 수질과 수온을 제어하는 IoT(Internet of Things)기반의 스마트 양식장이 필요하다.