• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6B
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• pp.561-569
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• 2010

In this study, the impact of climate change on extreme drought events is investigated by comparing drought severity-area-duration curves under present and future climate. The depth-area-duration analysis for characterizing an extreme precipitation event provides a basis for analysing drought events when storm depth is replaced by an appropriate measure of drought severity. In our climate-change impact experiments, the future monthly precipitation time series is based on a KMA regional climate model which has a $27km{\times}27km$ spatial resolution, and the drought severity is computed using the standardized precipitation index. As a result, agricultural drought risk is likely to increase especially in short duration, while hydrologic drought risk will greatly increase in all durations. Such results indicate that a climate change vulnerability assessment for present water resources supply system is urgent.

• International Journal of Ocean System Engineering
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• v.2 no.3
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• pp.151-159
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• 2012

The characteristics of an impact load and pressure were experimentally investigated. Drop tests were carried out using a modified Wigley with CB = 0.56. The vertical force, pressures, and vertical accelerations were measured. A 6-component load cell was used to measure the forces, piezo-electric sensors were used to capture the impact pressure, and strain-gauge type accelerometers were used to measure the vertical accelerations. A 50-kHz sampling rate was applied to capture the peak values. The repeatability of the measured data was confirmed and the basic characteristics of the impact load and pressure such as the linearity to the falling height were observed for all of the measurements. A simple formula was derived to extract the physical impact load from the measured force based on a simple mass-sensor-mass diagram, which was validated by comparing impact forces with existing data using the mathematical model of Faltinsen and Chezhian (2005). The effects of the elasticity of the model and change in acceleration during the water entry were investigated. It is interesting to observe that the impact loads occurred and reached peak values at the same time duration after water entry for all drop heights.

• Earthquakes and Structures
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• v.14 no.6
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• pp.577-587
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• 2018

The quantitative assessment of the seismic collapse risk of a structure requires the usage of an optimal intensity measure (IM) which can adequately characterise the severity of the ground motion. Research suggests that the average spectral acceleration ($Sa_{avg}$) may be an efficient and sufficient alternate IM as compared to the more traditional first mode spectral acceleration, $Sa(T_1)$, particularly during seismic collapse risk estimation. This study primarily presents a comparative evaluation of the sufficiency of the average spectral acceleration with respect to ground motion duration, and secondarily assesses the impact of ground motion duration on collapse risk estimation. By assembling a suite of 100 historical ground motions, incremental dynamic analysis of 60 different inelastic single-degree-of-freedom (SDF) oscillators with varying periods and ductility capacities were analysed, and collapse risk estimates obtained. Linear regression models are used to comparatively quantify the sufficiency of $Sa_{avg}$ and $Sa(T_1)$ using four significant duration metrics. Results suggests that an improved sufficiency may exist for $Sa_{avg}$ when the period of the SDF system increases, particularly beyond 0.5, as compare to $Sa(T_1)$. In reference to the ground motion duration measures, results indicated that the sufficiency of $Sa_{avg}$ is more sensitive to significant duration definitions that consider almost the full wave train of an accelerogram ($SD_{a5-95}$ and $SD_{v5-95}$). In order to obtain a reduced variability of the collapse risk estimate, the 5-95% significant duration metric defined using the Arias integral ($SD_{a5-95}$) should be used for seismic collapse risk estimation in conjunction with $Sa_{avg}$.

• Tuberculosis and Respiratory Diseases
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• v.83 no.4
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• pp.303-311
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• 2020

Background: If the duration of mechanical ventilation (MV) is related with the intensive care unit (ICU) readmission must be clarified. The purpose of this study was to elucidate if prolonged MV duration increases ICU readmission rate. Methods: The present observational cohort study analyzed national healthcare claims data from 2006 to 2015. Critically ill patients who received MV in the ICU were classified into five groups according to the MV duration: MV for <7 days, 7-13 days, 14-20 days, 21-27 days, and ≥28 days. The rate and risk of the ICU readmission were estimated according to the MV duration using the unadjusted and adjusted analyses. Results: We found that 12,929 patients had at least one episode of MV in the ICU. There was a significant linear relationship between the MV duration and the ICU readmission (R²=0.85, p=0.025). The total readmission rate was significantly higher as the MV duration is prolonged (MV for <7 days, 13.9%; for 7-13 days, 16.7%; for 14-20 days, 19.4%; for 21-27 days, 20.4%; for ≥28 days, 35.7%; p<0.001). The analyses adjusted by covariables and weighted with the multinomial propensity scores showed similar results. In the adjusted regression analysis with a Cox proportional hazards model, the MV duration was significantly related to the ICU readmission (hazard ratio, 1.058 [95% confidence interval, 1.047-1.069], p<0.001). Conclusion: The rate of readmission to the ICU was significantly higher in patients who received longer durations of the MV in the ICU. In the clinical setting, closer observation of patients discharged from the ICU after prolonged periods of MV is required.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.158-159
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• 2016

Construction project consists of several stages such as planning, design, construction, operation/maintain, etc. Decisions made in the planning and design stage have a significant impact on the construction and operation/maintain stages. Identifying key resources contributing to duration and cost of design alternatives is an important measure to achieve effective coordination between design and construction. This study proposes a method which finds an optimal design alternative by taking into account of resource planning, expected duration, and cost in construction stage. Base on literature review relative to the assessment of design alternatives, a method which predicts required resources, duration, and cost of the design alternative is established. Then, a method that identifies an optimal design alternative based on the preference of a certain project criteria is developed. Finally, a case study is presented.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1803-1806
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• 2007

The General roles of a spacer grid(SG) are providing a lateral and vertical support for fuel rods, promoting a mixing of coolant and keeping guide tubes straight so as not to impede a control rod insertion under any normal or accidental conditions. To evaluate the impact characteristics of a SG such as impact velocity, critical buckling strength and duration time, a few types of impact tests for SGs have been conducted. In a previous study, a new welding method, a through-welding method, was proposed to increase critical buckling strength of a SG without any design change or material change and was verified by impact tests with $7{\times}7$ partial SG specimens.In this paper, the effect of through-welding method in case of a $16{\times}16$ full-size SG is investigated by pendulum impact tests with $16{\times}16$ SG specimens. And the increase of critical buckling strength for full-size SGs is measured by comparison with impact results of spot-welded and through-welded SGs.

• The Journal of the Korea Contents Association
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• v.15 no.12
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• pp.314-325
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• 2015

This study examines the impact of sleep duration on Korean adolescents' suicidal impulse. A gender-based analysis was conducted using binary logistic regression method. The major findings are as follows. First, weekday sleep duration had a significant effect only on male adolescents. Male adolescents who sleep less than seven hours on a weekday are likely to experience suicidal impulse by 1.9 times higher than the others. This effect remained significant even when other relevant variables were controlled. On the other hand, female adolescents who have less than seven hours of sleep on a weekday have about 1.3 times higher chances to experience suicidal impulse. However, this effect became insignificant when other variables such as stress were controlled. Meanwhile, weekend sleep duration did not have any significant effect on both male and female adolescents. By demonstrating the different effects between weekday/weekend sleep duration and male/female adolescents, this study supports the claim that it is necessary to take a social approach in studying sleep duration.

• Journal of the Korean Geotechnical Society
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• v.32 no.8
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• pp.5-14
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• 2016

The leakage of water under sewer pipelines is one of main sources of sinkholes in urban areas. We performed laboratory model tests to investigate the presence of cavities using impact-echo method, which is a nondestructive test method. To simulate a concrete sewer pipe, a thin concrete plate was built and placed over container filled with sand. The cavity was modeled as an extruded polystyrene foam box. Two sets of tests were performed, one over sand and the other on cavity. A new impact device was developed to apply a consistent high frequency impact load on the concrete plate, thereby increasing the reliability of the test procedure. The frequency and transient characteristics of the measured reflected waveforms were analyzed via fast Fourier transform and short time Fourier spectrum. It was shown that the shapes of Fourier spectra are very similar to one another, and therefore cannot be used to predict the presence of cavity. A new index, termed resonance duration, is defined to record the time of vibration exceeding a prescribed intensity. The results showed that the resonance duration is a more effective parameter for predicting the presence of a cavity. A value of the resonance period was proposed to estimate the presence of cavity. Further studies using various soil types and field tests are warranted to validate the proposed approach.

• International journal of advanced smart convergence
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• v.8 no.1
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• pp.196-203
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• 2019

We have reviewed the potential impact of blockchain technology on the music industry by analyzing the views of academia and the industry experts. The music industry had rapid changes from the physical market to the digital market in the past decades. The consumers download and stream music online and mobile during the digital dominant market. While streaming music has been recently growing at a fast rate, fair distribution of revenue to the artists continues to be an issue. Some industry experts believe that the issue of fair distribution of revenue to the artist may be resolved using blockchain technology, while some are skeptical about the application or the duration of impact. The blockchain may enhance speedier payment using smart contracts, provide additional revenue and promote the music if excellent fan support is achieved. The positive impact on the music industry may only be possible if there are detailed consideration of the industry and careful understanding of the customers.

• The Journal of Asian Finance, Economics and Business
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• v.9 no.6
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• pp.245-252
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• 2022

This study examines the strength of the impact of fiscal policy tools on economic wellbeing as measured by per capita income in Malaysia from 1996 to 2020. The impact of fiscal policy instruments on economic wellness, represented by real income per capita, is measured using the autoregressive distributed lags model. The speed of adjustment from short-run disequilibrium to long-run equilibrium is also measured to assess the strength of the fiscal instruments' impact on per capita income. Empirical results exhibit the existence of co-integration relationships between per capita income, tax revenue, and government spending. The findings provide strong support for the presence of a long-run positive impact on government spending and a long-run negative impact of tax revenue on per capita income. The coefficient of ECT_t-1 indicates that deviations from a short-run disequilibrium to a long-run equilibrium from the current to the future period are corrected with a speed of 76% (equivalent to a duration of 1.5-2 years to return to equilibrium). The practical and policy implication of the results is fiscal instruments play a significant role, mainly in alleviating the economic impact of the COVID-19 pandemic in the long run.