• Computational Structural Engineering
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• v.7 no.4
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• pp.145-150
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• 1994

Seismic isolation in ordinary buildings has been successively adapted to provide flexibility for the reduction of base shear forces and its concept is accepting wide agreement in lengthening the natural, period to lessen the spectral acceleration transmitted into the structure. However, one of difficulties in implementing the innovative concept to nuclear structures is due to more severe requirements in both understanding and predicting the characteristics of isolators and the behavior of cushioned structures, Stochastic analysis has been carried out to investigate the response of base isolated nuclear containers to the random earthquake ground motion.

• Magazine of the Korea Concrete Institute
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• v.5 no.1
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• pp.115-127
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• 1993

본 연구의 목적은 프리캐스트 콘크리트(P.C) 대형판 아파트 구조물에 대한 우리나라 내진설계기준안 및 지침을 수립하기 위해 필요로 하는 정보를 취득하는데 있다. 이것은 실제 지진과 유사한 진동을 발생시키는 진동대를 사용하여 P.C대형판 구조물의 거동을 분석관찰함으로써 달성되었다. 여기에 사용된 시험체중의 하나는 습식접합 1/3 축소 3층 입체 P.C모델이었다. 지진파를 일으키기 위해 4mx4m 크기의 진동대가 사용되었다. 또한 선택한 입력지진가속도파는 Taft N21E 성분기록지진파로서 최대지진가속도(PGA)는 원하는 지진세기수준에 따라 조정되었고 시간축으로는 동적상사성법칙에 따라 축소되었다. 이 P.C모델의 진동대 실험을 통해 얻은 결과를 근거로 하여, 근거로 하여 다음과 같은 결론을 도출하였다. (1)이 시험체에 관한한, 지진안전계수는 7-8정도로 나타났으며, (2)이 P.C모델이 감쇠계수는 대체로, 철근콘크리트구조물 감쇠계수의 두배에 해당하는 값인 8%정도이며, (3) 이 모델은 접합부의 벌어짐과 미끄러짐에 의한 에너지소산을 통해서 2-3정도의 전체적인 변위연성비를 보여주었다.

• Geomechanics and Engineering
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• v.25 no.2
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• pp.143-157
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• 2021

Expansive soil is the most predominant geologic hazard which shows a large amount of shrinkage and swelling with changes in their moisture content. This study investigates the macro-mechanical and micro-structural behaviours of dredged natural expansive clay from coal mining treated with ordinary Portland cement or hydrated lime addition. The stabilised expansive soil aims for possible reuse as pavement materials. Mechanical testing determined geotechnical engineering properties, including free swelling potential, California bearing ratio, unconfined compressive strength, resilient modulus, and shear wave velocity. The microstructures of treated soils are observed by scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy to understand the behaviour of the expansive clay blended with cement and lime. Test results confirmed that cement and lime are effective agents for improving the swelling behaviour and other engineering properties of natural expansive clay. In general, chemical treatments reduce the swelling and increase the strength and modulus of expansive clay, subjected to chemical content and curing time. Scanning electron microscopy analysis can observe the increase in formation of particle clusters with curing period, and x-ray diffraction patterns display hydration and pozzolanic products from chemical particles. The correlations of mechanical properties and microstructures for chemical stabilised expansive clay are recommended.

• Journal of Ecology and Environment
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• v.35 no.1
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• pp.41-50
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• 2012

To determine the movement patterns, home range, and use of structural features of captive-bred one- or two-year-old Amur ratsnake (Elaphe schrenckii) juveniles in the natural habitat, we radio-tracked a total of 11 juvenile snakes in a mountain valley in Chiaksan National Park, South Korea, between August 21 and September 20, 2010 and between June 13 and July 13, 2011. During the first week of the release, most juveniles moved short distances, daily, but they increased their distances after the first week. The body weight of the juveniles was negatively related with the movement rate (dividing the number of movements by the number of relocations), which was positively related with the mean daily distances moved and the size of both a kernel 50% and 95% home range. During the study period, the juveniles moved daily, approximately 17 m, and the size of the minimum convex polygon and the 50% and 95% kernel home ranges were 1.8 ha, 0.4 ha, and 3.0 ha, respectively. The released captive-bred juveniles were more frequently confirmed underground or on the ground rather than on rocks or on trees. Our results suggest that the body condition of released individuals, the seasonal time of the release, and the existence of available prey and shelters in the habitat should be carefully considered when releasing captive-bred Amur ratsnake juveniles for the rehabilitation of field populations.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1148-1158
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• 2005

This work reports results of our study on the dynamic responses of the buried pipelines both along the axial and the transverse directions under various boundary end conditions. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends. We have studied the seismic responses of the buried pipelines with the various boundary end conditions both along the axial and the transverse direction. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends for the axial direction, and three more cases including the guided ends, the simply supported ends, and the supported-guided ends for the transverse direction. The buried pipelines are modeled as beams on elastic foundation while the seismic waves as a ground displacement in the form of a sinusoidal wave. The natural frequency and its mode, and the effect of parameters have been interpreted in terms of free vibration. The natural frequency varies most significantly by the soil stiffness and the length of the buried pipelines in the case of free vibration, which increases with increasing soil stiffness and decreases with increasing length of the buried pipeline. Such a behavior appears most prominently along the axial rather than the transverse direction of the buried pipelines. The resulting frequencies and the mode shapes obtained from the free vibration for the various boundary end conditions of the pipelines have been utilized to derive the mathematical formulae for the displacements and the strains along the axial direction, and the displacements and the bending strains along the transverse direction in case of the forced vibration. The negligibly small difference of 6.2% between our result and that of Ogawa et. al. (2001) for the axial strain with a one second period confirms the accuracy of our approach in this study.

• Structural Monitoring and Maintenance
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• v.2 no.1
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• pp.35-48
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• 2015

The main objective of this study is to evaluate the long-term performance of various concrete composites in natural marine environment prevailing in the Gulf region. Durability assessment studies of such nature are usually carried out under aggressive environments that constitute seawater, chloride and sulfate laden soils and wind, and groundwater conditions. These studies are very vital for sustainable development of marine and off shore reinforced concrete structures of industrial design such as petroleum installations. First round of testing and evaluation, which is presented in this paper, were performed by standard tests under laboratory conditions. Laboratory results presented in this paper will be corroborated with test outcome of ongoing three years field exposure conditions. The field study will include different parameters of investigation for high performance concrete including corrosion inhibitors, type of reinforcement, natural and industrial pozzolanic additives, water to cement ratio, water type, cover thickness, curing conditions, and concrete coatings. Like the laboratory specimens, samples in the field will be monitored for corrosion induced deterioration signs and for any signs of failureover initial period ofthree years. In this paper, laboratory results pertaining to microsilica (SF), ground granulated blast furnace slag (GGBS), epoxy coated rebars and calcium nitrite corrosion inhibitor are very conclusive. Results affirmed that the supplementary cementing materials such as GGBS and SF significantly impacted and enhanced concrete resistivity to chloride ions penetration and hence decrease the corrosion activities on steel bars protected by such concretes. As for epoxy coated rebars applications under high chloride laden conditions, results showed great concern to integrity of the epoxy coating layer on the bar and its stability. On the other hand corrosion inhibiting admixtures such as calcium nitrite proved to be more effective when used in combination with the pozzolanic additives such as GGBS and microsilica.

• Journal of the Korean GEO-environmental Society
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• v.14 no.6
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• pp.31-38
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• 2013

This study carried out fundamental study on the forest road pavement method of cementing the ground using the compaction equipment after laying by mixing with eco-friendly stabilizer, natural soil and water. Target strength of pavement was set to 2.0MPa and the specimen was produced per mixing ratio of cement, kinds of natural soil and curing period to evaluate the durability and unconfined compressive strength. Unconfined compressive strength test was conducted to compare strength by producing the test specimen mixing environment-friendly cement as well as the test specimen mixing cement with the same mixing ratio. To evaluate the durability, surface abrasion test and water flow resistance test were conducted. In addition, SB and GB tests were conducted using iron marble and golf ball to evaluate the walking satisfaction since it can be used by visitors due to the feature of forest road.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.61.1-61.1
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• 2015

We performed a monitoring campaign of a Jupiter-Family comet 17P/Holmes, which underwent the dramatic outburst on 23.3 October 2007 at $r_h=2.44AU$, to investigate the secular change in activity and subsequent physical properties of the inner dust coma before and after the 2014 perihelion passage. The monitoring observation was carried out over two years: from May to July 2013, from July to November 2014, and January 2015 with ~weekly cadence. We conducted photometry monitoring in Rc band using four ground-based telescopes, which are the Ishigakijima Astronomical Observatory 105cm telescope, the Okayama Astrophysical Observatory 50cm telescope, the Nishi-Harima Astronomical Observatory 2m telescope, and the T30 51cm i-telescope, respectively. In order to examine the dust production rate, we put a constraint upon the physical distance from the center of the nucleus as rho=2500km and conducted aperture photometry. We found that the average absolute Rc magnitude over the period between July to November 2014 was mR(1,1,0)~12.29, which was approximately 1.5 magnitudes fainter than those of 2013 data. Accordingly, comet 17P/Holmes seemed to become dormant, although a minor eruption was detected on January 26, 2015. In this presentation, we will introduce our ongoing project for 17P/Holmes and discuss why the nucleus becomes dormant within one orbital period.

• Journal of Korean Society of Forest Science
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• v.83 no.3
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• pp.311-321
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• 1994

Experiments were conducted to evaluate the efficacy of ground and foliar sprinkling of natural water for control of the pine needle gall midge, Thecodiplosis japonensis, by disturbing the reproductive behavior of adults such as copulation and oviposition. Diurnal ground spray for whole area application and foliar spray for single tree treatment were tested at day time during the period of adult emergence. The results obtained are as follows : 1. The population density of overwintering larvae in soil was not affected by the water spray during the adult emergence period. 2. Spraying the water showed no effect on the whole period and number of adult emergence, but retarded early emergence and facilitated Late emergence. The difference in the emerging time by 50% emergence day was approximately 7 days. 3. Ground spray was significantly different from control in gall formation rates but was not sufficient for effective control. As a single-tree treatment, the foliar spray was found to be highly effective for control of the pine needle gall midge, Average gall formation of spray plots and untreated ones were 2.6% and 38%, respectively ; control value exceeded 90%. 4. Ground spray of water was not effective in reducing larvae in gall of needle. Foliar spray, however, reduced 45% of larval numbers. 5. Foliar spray accelerated shoot growth by 15%-18%. 6. Foliar spray was highly effective for the control of sucking insects, such as mites and aphids on pine trees.

• Journal of the Korean Society of Costume
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• v.37
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• pp.253-273
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• 1998

The culture reflects the ideology of a particular period in time and such values change according to the needs and requests of that time which eventually becomes an important factorin forming the exterior. The clothing is part of a way that composes and expresses the inherent substance of society and culture. Also, the clothing itself manifests the artistic values and behavior of mankind as an external structure maintaining its place as a big part in culture. The purpose of this study are to elucidat the concept of naturalism, which is discussed in many facets in the modern era; I studied the concept as well as the history of naturalism in order to manifest the meaning of clothing in the context of culture and I explained the concept in terms of the modern era. On such ground, I explained the naturalism expressed through clothing and characterized the exter-nal form of clothing. Also, in order to know the stream of naturalism in the modern context, I referred to the Vogue magazine of the 90s, using Delong's ABC method. Naturalism, in the context of modern fashion is a way to express the nostalgia of nature's vi-ability and purity of ecology apart from the artificial and structural appearance that resulted form scientific enhancement and hence, the ecological crisis. Naturalism pursues the soft- ness and comfort of the natural silhouette, color and material of the human body and it can be said that naturalism emphasizes the mix-ture of three substances : human, nature and clothing. The naturalism can be characterized by the factors expressed in clothing as follows. First, the naturalism shown in the form it-self draws the beauty of the bodyline without any reduction nor exaggeration. Without any distorttion of the human bodyline it shown the curve as one moves along, using the soft material. Second, the naturalism shown in color most-ly uses the natural tone with added white color and other color low in intensity and value like the receded colors of the earth that could be compared to the beauty of ecru. Third, the naturalism shown in the material is thin, light and soft in texture. In order to bring out the most natural curve of the human body, the natural fiber becomes the main material, sometimes, using crude materials. Due to the lindustrial improvement, softness and elasticity is added to the natural fibers giving them an important role as materials. Fourth, the naturalism shown in textile depicts the real natural objects in life. According to my study, the personality of naturalism in modern clothing was shown to be most strong in material and then in the order of form, texture and textile. The material com-posed of the natural silhouette and natural fibers were used to make soft color. In form, Paul Poiret made appearance expressing the natural beauty of the human body without the corset ; it continued with the inner lining making the clothing hard but in the 90s, lining-less, extremely exposed clothes and knit wear is used to emphasize the natural beauty of the body. In color and textile, the tendency spok-en above is not as strong but in color, instead of high intensity or value, the usage of neutral colors with added white color or ecru color, ear-th tone is increasing. In textile, the usage of flowers as natural material is seen frequently. As a whole, naturalistic trend in the 90s is increasing and the modern fashion is breaking out from the artificial and architectural form and conforming to a form that can realize the natural beauty of the human body. And the natural color and textile that conforms to such ideas are being used to pursue the human oriented trend that has appeared due to the increase in usage of soft natural fiber. Nowadays, the idea of returning to nature, defying the artificiality, desiring the leisure and psychological abundance that can be explained as naturalistic way of thinking is necessitated in this modern era as long as humans coexist with nature, this tendency will continue in clothing.