• Water Engineering Research
• /
• 제5권2호
• /
• pp.81-99
• /
• 2004

Long term streamflow regime under virtual climate change scenario was examined. Rainfall forecast simulation of the Canadian Global Coupled Model (CGCM2) of the Canadian Climate Center for modeling and analysis for the IPCC SRES B2 scenario was used for analysis. The B2 scenario envisions slower population growth (10.4 billion by 2010) with a more rapidly evolving economy and more emphasis on environmental protection. The relatively large scale of GCM hinders the accurate computation of the important streamflow characteristics such as the peak flow rate and lag time, etc. The GCM rainfall with more than 100km scale was downscaled to 2km-scale using the space-time stochastic random cascade model. The HEC-HMS was used for distributed hydrologic model which can take the grid rainfall as input data. The result illustrates that the annual variation of the total runoff and the peak flow can be much greater than rainfall variation, which means actual impact of rainfall variation for the available water resources can be much greater than the extent of the rainfall variation.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2003년도 학술발표회논문집(1)
• /
• pp.151-158
• /
• 2003

Recently, there has been considerable interest in the influence of El Nino/Southern Oscillation (ENSO) on a global scale. ENSO has been measured by a simple index called Southern Oscillation Index (SOI). The statistical characteristics of SOI have been also focused to reveal the influence of ENSO. The SOI trend shows that El Nino events are generally getting stronger and more frequently occurring than La Nina events. However, the variation of SOI has varied significantly in a long-term. The SOI values are computed using the mean value and its standard deviation of the base period from 1951 to 1980. In the present study, the different base periods are applied to compute the SOI values and the influence of the different base periods is investigated in detail to reveal the long-term variation of SOI From the results, we could conclude that the present SOI should be carefully considered as a criterion to judge whether the El Nino and La Nina events are occurring.

• 한국지역사회생활과학회지
• /
• 제21권4호
• /
• pp.469-479
• /
• 2010

Using data from the 2001 National Long-Term Care Survey database, this study analyzed gender differences in factors affecting caregiver burdens of spouse caregivers in Korea. Multiple regression was used to estimate factors influencing caregiver burdens of caregiving wives and caregiving husbands respectively. The results showed that there was a significant variability in predictors of caregiver burdens of spouses who take care of the impaired elderly. ADL functional status of care recipients and social support were significant for both the caregiving wives model and caregiving husbands model in influencing caregiving burdens. It was noticeable to report that a caregiver's self-rated health status, monthly caregiving expenses, a care recipient's self-rated health status were unique predictors for the caregiving wives model. These findings suggest that it is vital for planners and providers to take gender differences in spousal caregiving into account when designing and formulating community-based long-term care service programs.

• 한국대기환경학회지
• /
• 제19권5호
• /
• pp.561-568
• /
• 2003

Surface ozone concentrations are highly sensitive to meteorological variability. Therefore, in order to reveal the long-term changes in ozone due to the changes in precursor emissions, we need to remove the effects of meteorological fluctuations on the annual distribution of surface ozone. In this paper, the meteorologically adjusted trends of daily maximum surface ozone concentrations in two major Korean cities (Seoul and Busan) are investigated based on ozone data from 11 (Seoul) and 6 (Busan) sites over the period 1992 ∼ 2000. The original time series consisting of the logarithm of daily maximum ozone concentrations are splitted into long-term, seasonal and short-term component using Kolmogorov-Zurbenko (KZ) filter. Meteorological effects are removed from filtered ozone series using multiple linear regression based on meteorologcial variables. The long-term evolution of ozone forming capability due to changes in precursor emission can be obtained applying the KZ filter to the residuals of the regression. The results indicated that meteorologically adjusted long-term daily maximum ozone concentrations had a significant upward trend (Seoul: ＋ 3.02% yr$^{-1}$ , Busan: ＋ 3.45% yr$^{-1}$ ). These changes of meteorologically adjusted ozone concentrations represent the effects of changing background ozone concentrations as well as the more localized changes in emissions.

• 한국해양학회지:바다
• /
• 제26권1호
• /
• pp.49-61
• /
• 2021

국립수산과학원(NIFS)의 정선 관측은 높은 시공간 해상도를 가지며 장기간 동안 같은 정점에서 관측을 수행해오고 있어, 전 세계적으로 유례를 찾아볼 수 없을 만큼 귀중한 자료를 생산하고 있으나, 자료의 신뢰성 문제로 해양 기후 변화 연구에 실제적으로 활용되는 경우가 드물었다. 본 연구에서는 동해 심층 물성이 갖는 작은 자연적 변동성의 특성을 활용함으로써 반세기 이상 축적된 정선 관측 자료에서 나타나는 오차를 정량적으로 평가하여, 해양의 장기 변동성 연구에 기여하는 것을 목적으로 한다. 1℃ 등수온면에서 산출한 NIFS 염분 표준 오차는 평균적으로 1961~1980년 자료의 경우 약 0.160 g/kg, 1981년~1994년은 약 0.060 g/kg, 1995~2002년에는 약 0.020 g/kg, 2003년~2014년이 약 0.010 g/kg으로 시기에 따라 크게 달라져온 것으로 분석되었다. 특히 2011년~2014년 사이에 비정상적으로 오차가 증가된 해가 있었으며, 이것은 센서 관리의 미흡으로 염분 편향이 발생하였기 때문으로 파악되었다. 반면, 2012년도에는 안정적인 관측이 수행되어 거의 0.001 g/kg 의 오차를 갖는 매우 정확한 염분 자료가 얻어졌음이 확인되었다. 이 결과를 통해 품질 관리 과정의 체계화와 센서 관리 전문화 시스템을 확충한다면 국립수산과학원 정선 관측이 기후 변화로 인한 해양 변동성 연구에 크게 기여할 수 있을 만큼 충분히 고품질의 자료를 생산할 수 있을 것으로 기대한다. 마지막으로 현 정선 관측의 개선 방향에 대해 몇 가지 제언을 첨부하였다.

• 한국습지학회지
• /
• 제21권spc호
• /
• pp.61-68
• /
• 2019

최근 장기적인 기후 변동성을 고려하기 위하여 대기-해양 순환 패턴을 수치화한 기상인자가 수문 변수 예측에 널리 사용되고 있다. 또한 정확하고 안정적인 예측을 위해 인공신경망 기반의 예측 모형이 꾸준히 발전하고 있다. 기상인자를 활용하여 기후 변동성을 고려한 수문량 예측은 수자원 및 환경 보존의 장기적인 관리에 효율적으로 활용될 수 있으므로 수문 변수에 유의한 인자의 파악과 이를 활용한 예측 모형의 적용은 꾸준한 도전이 될 것이다. 본 연구에서는 우리나라 한강 유역 댐 유입량에 통계적으로 유의한 상관성이 있는 대표 기상인자를 선정하고, 이를 인공신경망 앙상블 모형에 적용하여 댐 유입량 예측을 수행하였다. 이를 위해 앙상블 경험적 모드분해법을 활용하여 댐 유입량과 기상인자간의 통계적 상관성을 확인하였으며, 기존 단일 인공신경망 모형의 한계를 보완한 인공신경망 앙상블 모형을 구축하였다. 예측 수행 결과, 5개 댐 상관계수 평균이 훈련 기간에서 0.88, 검증 기간에서 0.68의 예측력을 보이는 것을 확인하였으며, 본 연구에서의 절차를 토대로 우리나라의 다양한 수문 변수와 기후 변동성간의 관계를 활용한 다양한 적용 사례가 나오길 기대한다.

• KIEAE Journal
• /
• 제10권3호
• /
• pp.63-74
• /
• 2010

The general housing causes various environmental problems on the squandering of the resources and the production of the construction wastes, as it was removed and rebuilt because of the short-life in 20-30 years after constructing. The short-life of the general housing makes the rebuilt-term short and takes a negative attitude in maintenance. In the other hand, the long-life housing is constantly dwelling house that considers the carbon reduction among the world issues, Support and Infill. The long-life housing promotes the durability of Support and maximize the variability of Infill through separation of Support & Infill. It's useful dwelling house in maintenance as well as various life-cycle and life style. As the maintenance guideline of dwelling house is used for long-life housing, there is not distinction considering who controls maintenance and there is not conception considering alteration, variability and convenience. Consequently, it is required to develop the proper maintenance guideline applied maintenance process for long-life housing. Therefore this study shows efficient maintenance guideline for manager in long-life housing.

• 감성과학
• /
• 제2권2호
• /
• pp.37-42
• /
• 1999

Long-term exposure to loud noise affects performance since it changes arousal level, distracts attention, and also is able to evoke subjective stress accompanied by negative emotional states. The purpose of the study was to analyze dynamics of subjective and physiological variables during a relatively long-lasting (30 min) exposure to white noise (85 dB[A]). Physiological signals were recorded on 15 college students during 30 min of intense auditory stimulation. Autonomic variables, namely skin conductance level , non-specific SCR number, inter-best intervals in ECG, heart rate variability index (HF/LF ratio of HRV), skin temperature, as well as respiration rate were analyzed on 5 min epoch basis. Psychological assessment (subjective rating of stress level) was also repeated every 5 min. Statistical analysis was employed to trace the time course of the dynamics of subjective and autonomic physiological variables and their relationships. Results showed that the intense noise evoked subjective stress as well as associated autonomic nervous system responses. However it was shown that physiological variables endured specific changes in the process of exposure to the loud white noise. Discussed were probable psychophysiological mechanisms mediating reactivity to long-term auditory stimulation of high intensity, namely short-term activation, followed by transient adaptation (with relatively stable autonomic balance) and then a subsequent wave of arousal due to tonic sympathetic dominance.

• Journal of Korea Trade
• /
• 제27권1호
• /
• pp.60-78
• /
• 2023

Purpose - The study analyzed 90 online firms worldwise and observed them for ten years to investigate their investments and firm performance variabilities. This study attemped to verify the existence of agency problems in online firms. Through this, the paper intends to expand the scope of research in the fields of investment and firm value both empirically and in theory. This study also attempted to supplement the insufficient logic of previous studies by analyzing the relationship between investment and profitability. Design/methodology - In this study, the investment is subdivided into over-, under-, and neutral investments, and an empirical analysis of the firm performance was conducted. As investment generally has long-term effects, the impact of a firm's investment on future firm performance and variabilities in firm performance was considered over the short-and medium-term period. Findings - It was found that there was a negative relationship between firms with an overinvestment and future firm performance. Underinvestment has no clear statistically significant results on firm performance. This implies that overinvestment causes more reduction in future firm performance than underinvestment. It was also found that underinvestment and overinvestment significantly increased the variability of firm performance. A positive significance was found between under- and over- investment with a variability of 3 years and overinvestment with a variability of 4 years in the future. A negative relationship was found between neutral investment propensity and future performance variabilities. Neutral investment has less effect on the future performance variability of a firm than a firm's overinvestment and underinvestment. For online firms, underinvestment and overinvestment have a greater effect on the firm's future performance variability than neutral investment. Originality/value - The agency theory predicts that information asymmetry and adverse selection problems exacerbate conflicts of interest among stakeholders, thus firm performance. The study contributed to accumulating research on online firms that are currently underexplored by analyzing the investment behavior of major firms in the online industry.

• Steel and Composite Structures
• /
• 제4권5호
• /
• pp.385-402
• /
• 2004

Nearly 400 composite railway bridge decks of a new kind belonging to the trough type with U-shaped cross section have been constructed in Belgium over the last fifteen years. The construction of these bridge decks is rather complex with the preflexion of precambered steel girders, the prestressing of a concrete slab and the addition of a 2nd phase concrete. Until now, they have been designed with a classical computation method using a pseudo-elastic analysis with modular ratios. Globally, they perform according to the expectations but variability has been observed between the measured and the computed camber of these bridge decks just after the transfer of prestressing and also at long-term. A statistical analysis of the variability of the relative difference between the measured camber and the computed camber is made for a sample of 36 bridge decks using no less than 10 variables. The most significant variables to explain this variability at prestressing are the ratio between the maximum tensile stress reached in the steel girders during the preflexion and the yield strength and the type of steel girder. For the same sample, the long-term camber under permanent loading is computed by two methods and compared with measurements taken one or two years after the construction. The camber computed by the step-by-step method shows a better agreement with the measured camber than the camber computed by the classical method. The purpose of the paper is to report on the statistical analysis which was used to determine the most significant parameters to consider in the modeling in order to improve the prediction of the behaviour of these composite railway bridge decks.