• 터널과지하공간
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• 제21권6호
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• pp.471-479
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• 2011

최근 한반도 및 주변해역에서 발생한 규모 4.8 이상의 5개 중규모 지진으로부터 관측된 속도 지반운동 파형을 이용하여 수평 응답스펙트럼을 분석하고 결과를 우선 가속도 지반운동을 이용하여 얻어진 수평 응답스펙트럼, 국내 원자력 관련 구조물의 내진설계 기준, 마지막으로 국내 일반 구조물 및 건축물 내진설계기준과 각각 비교하였다. 연구에 이용된 지반운동은 수평성분 102개(NS 및 EW 성분 포함)이며 고유진동수에 따른 응답을 구하고 각각의 최대 지반 속도 값을 이용하여 정규화 분석을 수행하였다. 첫째, 가속도 응답스펙트럼과 비교한 결과 속도 응답스펙트럼 값은 특히 중간주기에서 높은 응답을 보여 주었고 이에 비해 가속도 응답스펙트럼은 특히 단주기 즉 높은 고유진동수 영역에서 높은 응답을 보여 주었다. 둘째, 국내 원자력시설물의 내진기준으로 이용되고 있는 Reg. Guide 1.60과 비교한 결과 속도 응답스펙트럼 값은 약 6-7Hz를 시작점으로 보다 낮은 장주기 영역에서 기준값을 초과하는 현상을 보여 주었다. 셋째, 500년 재래주기에 해당하는 국내 일반 구조물 및 건축물 내진설계기준인 표준 설계응답스펙트럼을 SC, SD 및 SE지반 조건과 같은 3개 지반조건과 동시에 비교한 결과 차례로 약 1.5초, 2초 및 3초에서 시작하여 보다 장주기 영역에서 국내 일반 구조물 표준 설계 응답스펙트럼값을 초과하였다. 동일한 부지에서 일반적으로 가속도 응답스펙트럼은 단주기에서 가장 큰 값을 나타내며, 속도 응답 스펙트럼은 중간주기에서 가장 크며, 마지막으로 변위 응답스펙트럼은 장주기에서 가장 큰 값을 가진다는 국외 연구결과가 국내 지반운동을 이용한 결과에서 역시 적용가능하다는 점을 확인시켜 주었다. 최근 국내에서도 건축물의 초고층화 등으로 구조물의 디자인이 기존의 단주기에 비해 중간주기 및 장주기 영역이 상대적으로 강조되고 있어 이러한 중간주기영역에서 수평 응답스펙트럼의 정보는 향후 대단히 중요하다고 할 수 있다.

• Smart Structures and Systems
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• 제9권1호
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• pp.1-20
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• 2012

In bridge engineering, maintenance strategies and thus budgetary demands are highly influenced by construction type and quality of design. Nowadays bridge owners and planners tend to include life-cycle cost analyses in their decision processes regarding the overall design trying to optimize structural reliability and durability within financial constraints. Smart permanent and short term monitoring can reduce the associated risk of new design concepts by observing the performance of structural components during prescribed time periods. The objectives of this paper are the discussion and analysis of influence line or influence field approaches in terms of (a) an efficient incorporation of monitoring information in the structural performance assessment, (b) an efficient characterization of performance indicators for the assessment of structures, (c) the ability of optimizing the positions of sensors of a monitoring system, and (d) the ability of checking the robustness of the monitoring systems applied to a structure. The proposed influence line- model correction approach has been applied to an integrative monitoring system that has been installed for the performance assessment of an existing three-span jointless bridge.

• 한국제4기학회지
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• 제19권2호
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• pp.13-17
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• 2005

The Khogno Khan mountain special protected area belongs to Khogno Khan subdistrict of Gurvanbulag district of Bulgan Province and is 46.9 sq.km. with its main feature being mountain forest zone. In this paper we present some results of research of the Anthropological and archaeological team of Mongolian Korean Joint research expeditions carryied out in Khogno Khan mountain special protected area from 27 July to 1 August, 2000. During archaeological reconnaissance we discovered around 27 localities of archaeological monuments belonging to different historical periods (from the Neolithic up to the Mongolian period, $13^{th}-17^{th}$ Century) in the territory of the Khogno Khan special protected area. Based on the results, we especially want to point out 1). The archaeological and historic monuments (from the Neolithic up to modern era) found in the Khogno Khan mountain and its surrounding area show that since the Neolithic period (around 8000 years ago) this area was occupied by the ancestors of Mongolians and it was used during subsequent historic periods on the one hand. 2). On the other hand the Khogno Khan mountain region was one area where there occurred intensive admixture between populations of Kurgan culture, Deerstone culture from the West Mongolia and the population of slab graves culture from Central and East Mongolia during Bronze and Early Iron Age. 3). Today the mountain is one of the area with a unique assemblage of archaeological monuments from different historic periods, what naturally seems like an open-air natural museum of Mongolian Prehistory.

• 천문학회보
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• 제41권1호
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• pp.46.2-46.2
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• 2016

We explore the similarity and difference of the quasi-periodic pulsations (QPPs) observed during the solar and stellar X-ray flares. For this, we identified 59 solar QPPs in the X-ray observed by the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and 52 stellar QPPs from X-ray Multi Mirror Newton observatory (XMM-Newton). The Empirical Mode Decomposition (EMD) method and least-square-fit with the damped sine function are applied to obtain the periods and damping times of the QPPs. We found that (1) the periods and damping times of the stellar QPPs are 7.80 and 13.80 min, which are comparable with those of the solar QPPs 0.55 and 0.97 min. (2) The ratio of the damping times to the periods observed in the stellar QPPs are found to be statistically identical to the solar QPPs, (3) The damping times are well describe by the power law. The power indices of the solar and stellar QPPs are $0.891{\pm}0.172$ and $0.953{\pm}0.198$, which are consistent with the previous results. Thus, we conclude that the underlying mechanism responsible for the stellar QPPs are the natural oscillations of the flaring or adjacent coronal loops as in the Sun.

• 정신신체의학
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• 제3권1호
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• pp.3-10
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• 1995

A comparison was made between the effect of subjective stress and that of objective stress on immune function in male medical college students. Interaction between perceived stress, psychopathology and natural killer-cell(NK) activity was assessed during an exam period, non-exam period, and vacation. No significant difference was found in NK activity among these three periods, but scores of perceived stress related to unusual happenings during an exam period and related to interpersonal relationship during vacation were found to have significantly positive correlation with NK activity, respectively. In psychopathology, only scores of anxiety during an exam period had significantly positive correlation with NK activity. These results suggest that immune function is more likely to be affected by subjective stress than objective stress and that subjective stress such as some perceived stress and subclinical level of anxiety may positively affect immune function.

• Journal of Magnetics
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• 제20권3호
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• pp.207-210
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• 2015

Modifications in the structural and magnetic properties of co-precipitated cobalt ferrite nanoparticles can be accomplished by varying the annealing time periods during the synthetic process. Experimental results show that high-purity cobalt ferrite nanoparticles are obtained using a co-precipitation process. The dependence of the crystallite sizes on the annealing time was successfully demonstrated using XRD and SEM. Finally, vibrating sample magnetometer analyses show that the magnetic properties of the cobalt ferrite nanoparticles depend on their relative particle sizes.

• Journal of the Korean Wood Science and Technology
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• 제24권2호
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• pp.1-6
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• 1996

This study was performed to investigate the feasibility of using sonic stress-wave technique in the longitudinal direction for the assessment of incipient decay of radiata pine wood. Decayed bending specimens by Tyromyces palustris and Gloeophyllum trabeum for varoious periods were tested nondestructively using stress-wave technique in the longitudinal direction and destructively. Decay detection, quantitative assessment of decay, and the prediction of residual strength of decayed wood with less than five percent weight loss can be feasible using stress-wave parameters (wave velocity, wave impedance, stress-wave elasticity) measured by stress-wave technique in the longitudinal direction and their percent reduction due to decay.

• 한국대기환경학회지
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• 제14권5호
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• pp.479-490
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• 1998

The concentrations of ten inorganic (sodium, chloride, sulfate, ammonia, etc.) and three organic (acetate, formate, and MSA) ions associated with airborne particulate matter were measured from Cheju Island, Korea during the three field intensive campaigns conducted in (1) Sept./oct. 1997 (fall), (2) Dec. 1997 (winter), and (3) April 1998 (spring). The results of our measurements indicated that the concentration levels of most ionic species were decreasing significantly across the three experimental periods. The patterns of concentration reduction were clear as the sum of all cation and anion species changed dramatically across those periods such as 294> 144 > 65 and 193 >96>74 nequiv/m3, respectively. The changes were best explained in terms of the wind rose patterns of the study site. Since our sampling spot is located on the western-end point of Cheju Island, it is likely to reflect the effects of diverse sources such as natural, marine processes during NW and local non-maritime ones during SE winds. .Hence, the periodical changes in ionic concentrations may be accounted for by the comparable changes in wind direction. To further investigate environmental characteristics of these ionic components, correlation analysis was conducted not only between meteorological and ion data but between different ion-pairs. The results of these analyses confirm that the concentration levels of ionic species are strongly affected by wind speed and temperature and that there are certain patterns between ion species to which such effects apply. In light of the significance of the wind rose patterns in the area, we further extended these analyses into four data groups that were divided on the basis of wind direction. The results of these analyses showed that the strength of correlations between important pairs (e.g.:. between windspeed and most of major inorganic species including sodium and chloride) can be ranked on the distribution of major ions are very diverse, depending on data grouping scheme for such analysis. The results of this study thus suggest that environmental behavior of chemical components be analyzed in various respects, rather than simple standard, especially if measurements are made in complex environmental condition under which both natural and anthropogenic effects are competing each other.

• Korean Journal of Hydrosciences
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• 제4권
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• pp.51-63
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• 1993

This study is to verify the applicability of statistical models in predicting flood frequency at the stage gaging stations of which the flow is under natural condition in the Han River basin. The results of the study show that the statistical flood frequency models were proven to be fairly reasonable to apply in practice, and also were compared with sampling variance to calibrate the statistical efficiency of the estimators of the T year floods Q(T) by two different flood frequency models. As a result, it was showed that for return periods greater than about T = 10 years the annual exceedance series estimators of Q(T) has smaller sampling variance than the annual maximum series estimators. It was showed that for the range of return periods the partial duration series estimators of !(T) has smaller sampling variance than the annual maximum series estimate only if the POT model contains at least 2N(N : record length) items or more in order to estimate Q(T) more efficiently than the ANNMAX model.

• 한국농공학회지
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• 제43권2호
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• pp.122-131
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• 2001

When mixed with lime, sand-bentonite mixture is characterized by considerable hydraulic properties similar to natural pozzolans and may therefore be increased in the strength of sand-bentonite mixture. The present study reports that results obtained in a series of laboratory tests carried out using particular mixing ratio of lime-sand-bentonite with the aim of investigating physical characteristics, permeability and strength. The results were compared and analyzed according to hydration time and lime content. Test results showed that increasing of strength and decreasing of permeability by proper lime content. Curing for longer periods increased unconfined compressive strength of mixture. Based on results of the falling head permeability test, mixtures of lime content 3%, 6% and 9% were satisfied in using as liner after 8-day curing periods.