• Geomechanics and Engineering
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• 제30권5호
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• pp.449-460
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• 2022

Safe underground construction in a rock mass requires adequate ground investigation and effective determination of rock conditions. The estimation of rock mass behavior is difficult, because rock masses are innately anisotropic and heterogeneous at different scales and are affected by various environmental factors. Quantitative rock mass classification systems, such as the Q-system and rock mass rating, are widely used for characterization and engineering design. The measurement of rock classification parameters is subjective and can vary among observers, resulting in questionable accuracy. Geophysical investigation methods, such as seismic surveys, have also been used for ground characterization. Torsional shear wave propagation characteristics in cylindrical rods are equal to that in an infinite media. A probabilistic quantitative relationship between the Q-value and shear wave velocity is thus investigated considering long-wavelength wave propagation in equivalent continuum jointed rock masses. Individual Q-system parameters are correlated with stress-dependent shear wave velocities in jointed rocks using experimental and numerical methods. The relationship between the Q-value and the shear wave velocity is normalized using a defined reference condition. This relationship is further improved using probabilistic analysis to remove unrealistic data and to suggest a range of Q-values for a given wave velocity. The proposed probabilistic Q-value estimation is then compared with field measurements and cross-hole seismic test data to verify its applicability.

• 한국자원식물학회지
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• 제15권3호
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• pp.221-226
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• 2002

새우난초의 대량 증식 시스템을 확립하기 위하여 새우난초 종자 무균파종 및 순화 방법에 따른 생육특성 을 조사하였다. 발아율은 MS배지 에서 65% 이상이었고 유묘의 대량증식이 가능하였다. 계대배양한 유묘의 증식은 고체배지 보다는 액체배지에서 생육상태 가 더 양호한 경향을 보였다. 순화실험 결과, 70%차광조건에서 플라스틱 멀칭으로 습도를 80% 이상 유지하였을 때 100% 순화 생존하였다. 기내 육성된 배양묘는 백태로 뿌리를 감싸 심었을 때 발근이 가장 잘 이루어졌으나 순화과정 중에서 백태 대신에 질석과 펄라이트를 1:1 부피비로 이용한 경우에도 88%의 비교적 높은 생존율을 보였다.

• 대한기계학회논문집B
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• 제24권11호
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• pp.1486-1496
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• 2000

The initial flame kernel development and flame propagation in a constant volume combustion chamber is analyzed by the heat release rate and the mass fraction burnt. The combustion pressure is measured with a piezoelectric type pressure sensor. In order to evaluate the effects of ignition system and ignition energy on the flame propagation, four different ignition systems are designed and tested, and the ignition energy is varied by the dwell time. Several different spark plugs are also tested and examined to analysis the effects of electrodes on flame kernel development. The results show that the when the dwell time is increased, and when the spark plug gap is extended, heat release rate and the mass burnt fraction are increased. The materials and shapes of electrodes affect the flame development, because they change the energy transfer efficiency from electrical energy to chemical energy. The diameter of electrodes influences not only the heat release rate but also the mass burnt fraction as well.

• 융합보안논문지
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• 제8권4호
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• pp.173-181
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• 2008

최근 웜에 의한 사이버 위협이 증가함에 따라 웜의 확산 특성을 분석하기 위한 전파 모델이 연구되고 있다. 대표적인 예로 수학적 모델링 기법인 Epidemic(SI), KM(Kermack-MeKendrick), Two-Factor, AAWP(Analytical Active Worm Propagation)등의 모델 기법들이 제시되었다. 하지만, 기존 모델 방법들은 대부분 코드레드와 같은 네트워크를 대상으로 하는 랜덤 스캐닝 기법에 대해서만 모델링이 가능하다. 또한 거시적인 분석만 가능하고 특정 위협에 대해 예측하는데 한계점을 가지고 있다. 따라서 본 논문에서는 과거의 위협 발생 데이터를 근거로 하여 Mass SQL Injection 같은 사이버위협에 적용 가능한 마코브 체인(markov chain) 기반 예측 방법을 제시한다. 이를 통하여 각 위협별 발생 확률 및 발생빈도를 예측할 수 있다.

• The Journal of the Acoustical Society of Korea
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• 제26권2E호
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• pp.50-55
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• 2007

SBN (Structure-Borne Noise) reduction in resiliently mounted machineries are predicted by using mass-spring model and wave model. In mass-spring model, mount is modeled as a spring, while in wave model, mount is considered as an equivalent elastic rod for taking account into longitudinal wave propagation. The predictions for SBN reduction through mounts are compared to the measurements for four different pumps. It is found that the mass-spring model is valid only in low frequency range below few hundred Hz, while for high frequency ranges longitudinal wave propagation in the mount must be considered to explain the measurements. It is also shown that impedance of the floor slightly affects low frequency behaviour in mass-spring and wave model below 50 Hz - 80 Hz, so that in engineering practice the effect of floor impedance may be neglected in computing mount performance.

• Journal of Forest and Environmental Science
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• 제34권1호
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• pp.77-81
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• 2018

Mass production of forest medicinal plants is related to quality control of raw medicinal materials. Plant tissue culture is an important technology to produce high-quality plant materials. Numerous factors are reported to influence the success of in vitro regeneration of medicinal plants. Embryogenesis is known to be the most effective techniques and it has developed in some medicinal plant species. Various in vitro cultural condition for direct and/or indirect somatic embryogenesis systems have developed in Epimedium koreaum, Bupleurum falcatum, Paeonia lactiflora, Chrysanthemum zawadskii, Houttuynia cordata etc. In this study, we provide the present statue and information of in vitro propagation techniques that is able to apply as an efficient system for rootstock propagation system of forest medicinal plants.

• 한국작물학회지
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• 제52권2호
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• pp.220-227
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• 2007

Sweetpotato fields in Korea are highly infected with virus and virus like diseases that greatly diminish both yield and quality as indicated by field observations and laboratory tests. In order to solve this problem, there is an urgent need to produce and mass propagate virus-free planting materials for distribution to the farmers. These experiments were conducted, firstly, to determine the most appropriate culture media, nutrient solution, and cutting intervals to maintain growth and vigor of tissue cultured plantleta as mother plants for propagation in insect-proof greenhouse. And as a labor saving method, the production efficiency of plug trays for rapid propagation of stem cuttings as a source of planting materials was likewise evaluated. Results showed that plants grown in medium B supplied with 0.5 and 1.0 strength of MS nutrients had high growth rate, and 20-day cutting interval was the best. 72-plug tray was better than 128-plug. Secondly, it was to develop a technique for the production of first-generation seed roots using hydroponics cultivation system. The yield of virus-free plants propagated in the non-insect proof and open-field cultivation was 2,402 kg/10a, 6% higher than those in the insect-proof cultivation, and the rate of virus re-infection was 18% higher compared to 3.3% with insect-proof cultivation. Lastly, it was to investigate the growth performance of virus free plants in farmers' field. Differences were existed in the yield depending on the variety used, but virus free plants showed an increase of $6{\sim}24%$ over virus infected plants.

• Geomechanics and Engineering
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• 제21권3호
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• pp.227-236
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• 2020

Non-destructive exploration using elastic waves has been widely used to characterize rock mass properties. Wave propagation in jointed rock masses is significantly governed by the characteristics and orientation of discontinuities. The relationship between spatial heterogeneity (i.e., joint spacing) and wavelength for elastic waves propagating through jointed rock masses have been investigated previously. Discontinuous rock masses can be considered as an equivalent continuum material when the wavelength of the propagating elastic wave exceeds the spatial heterogeneity. However, it is unclear how stress-dependent long-wavelength elastic waves propagate through a repetitive rock-joint system with multiple joints. A preliminary numerical simulation was performed in in this study to investigate long-wavelength elastic wave propagation in regularly jointed rock masses using the three-dimensional distinct element code program. First, experimental studies using the quasi-static resonant column (QSRC) testing device are performed on regularly jointed disc column specimens for three different materials (acetal, aluminum, and gneiss). The P- and S-wave velocities of the specimens are obtained under various normal stress levels. The normal and shear joint stiffness are calculated from the experimental results using an equivalent continuum model and used as input parameters for numerical analysis. The spatial and temporal sizes are carefully selected to guarantee a stable numerical simulation. Based on the calibrated jointed rock model, the numerical and experimental results are compared.

• 대한기계학회논문집B
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• 제24권12호
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• pp.1608-1614
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• 2000

For the purpose of obtaining fundamental data which is needed to develope combustion system of LPG engine, we made constant volume chamber and analyzed flame propagation characteristics under different intial temperature, initial pressure and equivalence ratio which affect combustion of LPG. We investigated flame propagation speed of each fuel using laser deflection method and compared with the investigated flame propagation speed of each fuel using laser deflection method and compared with the results of image processing of flame. As a result, the maximum flame propagation speed was found at equivalence ratio 1.0 and 1.1 for LPG and gasoline, respectively. In the lean region, we can see that flame propagation speed of LPG surpasses that of gasoline. On the contrary, flame propagation speed of gasoline surpasses LPG in the rich region. As initial temperature and initial pressure were higher, flame propagation speed was faster. And, as equivalence ratio was larger and initial temperature was higher, combustion duration was shorter and maximum combustion pressure was higher.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2000년도 The 7th International Symposium
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• pp.114-115
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• 2000

Aralia elata is found in mountain areas all over Korean peninsula. Aralia elata is the scientific name for Japanese angelica tree. The tree belongs to the family Araliaceae, commonly known as ginseng family. Bud sprouts from apical shoot tip of the plants are rich in flavor and thus mainly used for both folk medicine and vegetable. The stalks with apical buds are gathered in the early spring and planted in sandy soil or water in the greenhouse. The sprouting buds are then collected and sold as fresh vegetable. Although the plants have been used for food, they have been cultivated in a very small scale. In spring, local farmers just go around mountain areas to search the trees and gather the stalks as much as they get and sell them to the market. No conservation efforts have been made to stop the exploitation or to save the dwindling population. We tried to provide local farmers with the plants that may be used as an alternative to stalks from wild populations. This will bel! p conserve the wild populations. However, it is hard to propagate them either by conventional cuttings or by seed germination in a short period of time. Mass propagation using tissue culture systems have shown a great promise with several woody plants. Recently we developed a mass propagation technique via somatic embryogenesis system using mature and/or juvenile explants for Aralia elata. Several factors affecting somatic embryogenesis system including SE(somatic embryo) induction, embryogenic callus proliferation, SE germination, plant regeneration and transplanting to field frill be presented. And some problems arising for the somatic embryogenesis system will be also discussed.