• Journal of the Korean Institute of Gas
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• v.21 no.3
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• pp.61-69
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• 2017

The commercial development of unconventional gas is pursued in North America because it is more feasible owing to the technology required to improve productivity. Shale reservoir have low permeability and gas production can be carried out through cracks generated by hydraulic fracturing. The decline rate during the initial production period is high, but very low latter on, there are significant variations from the initial production behavior. Therefore, in the prediction of the production rate using deterministic decline curve analysis(DCA), it is not possible to consider the uncertainty in the production behavior. In this study, production rate of the Eagle Ford shale is predicted by Arps Hyperbolic and Modified SEPD. To minimize the uncertainty in predicting the Estimated Ultimate Recovery(EUR), Monte Carlo simulation is used to multi-wells analysis. Also, kernel density function is applied to determine probability distribution of decline curve factors without any assumption.

• Journal of the Korean Institute of Gas
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• v.22 no.1
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• pp.64-77
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• 2018

This paper presents the prediction of the original gas in place(OGIP) by using the material balance method and decline curve analysis method with production history and pressure transient test data for four coalbed methane wells in the Horseshoe Canyon field. In this study, the conventional gas equation and the Jensen and Smith(J&S) equation were used to material balance analysis, and the Arps' empirical correlation and Khaled method were applied to decline curve analysis. From the results, the OGIP estimated from the conventional gas and the J&S method was small in difference as under 12%. Also, in case of decline curve analysis, it was found that the Khaled method has appropriated to calculate the OGIP, because the OGIP was estimated as unlimited value by the Arps' equation from the decline exponent of 1 - 3.5. The OGIP difference between conventional gas method and Khaled method was calculated as 8.67% ~ 31.04%, and those between J&S method and Khaled method was 13.67% ~ 26.49%.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.10
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• pp.5891-5893
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• 2013

Incidence/mortality of liver cancer follow logistic curves because there is a limit reflecting the prevalence of hepatitis virus carriers in the cohort. The author fitted logistic curves to incidence/mortality data covering the nine five-year cohorts born in 1911-1955 of both sexes. Goodness-of-fit of logistic curves was sufficiently precise to be used for future predictions. Younger cohorts born in 1936 or later were predicted to show constant decline in incidence/mortality in the future. The male cohort born in 1931-35 showed an elevated incidence/mortality of liver cancer early in their lives supporting the previous claim that this particular cohort had suffered massive HCV infection due to nation-wide drug abuse in the 1950s. Declining case-fatality observed in younger cohorts suggested improved treatment of liver cancer. This study demonstrated that incidence/mortality of liver cancer follow logistic curves and fitted logistic formulae can be used for future prediction. Given the predicted decline of incidence/mortality in younger cohorts, liver cancer is likely to be lost to history in the not-so-distant future.

• Journal of Environmental Science International
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• v.17 no.2
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• pp.257-267
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• 2008

Groundwater recharge characteristics in a fractured granite area, Mt. Geumjeong, Korea. was interpreted using bedrock groundwater and wet-land water data. Time series analysis using autocorreclation, cross-correlation and spectral density was conducted for characterizing water level variation and recharge rate in low water and high water seasons. Autocorrelation analysis using water levels resulted in short delay time with weak linearity and memory. Cross-correlation function from cross-correlation analysis was lower in the low water season than the high water season for the bedrock groundwater. The result of water level decline analysis identified groundwater recharge rate of about 11% in the study area.

• Journal of the Korean Society of Radiology
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• v.85 no.1
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• pp.184-196
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• 2024

Purpose We investigated potentially promising imaging findings and their combinations in the evaluation of cognitive decline. Materials and Methods This retrospective study included 138 patients with subjective cognitive impairments, who underwent brain MRI. We classified the same group of patients into Alzheimer's disease (AD) and non-AD groups, based on the neuropsychiatric evaluation. We analyzed imaging findings, including white matter hyperintensity (WMH) and cerebral microbleeds (CMBs), using the Kruskal-Wallis test for group comparison, and receiver operating characteristic (ROC) curve analysis for assessing the diagnostic performance of imaging findings. Results CMBs in the lobar or deep locations demonstrated higher prevalence in the patients with AD compared to those in the non-AD group. The presence of lobar CMBs combined with periventricular WMH (area under the ROC curve [AUC] = 0.702 [95% confidence interval: 0.599-0.806], p < 0.001) showed the highest performance in differentiation of AD from non-AD group. Conclusion Combinations of imaging findings can serve as useful additive diagnostic tools in the assessment of cognitive decline.

• Journal of Korea Trade
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• v.25 no.1
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• pp.1-17
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• 2021

Purpose - The global trend of protectionism has expanded since the onset of US President Donald Trump's administration in 2017. This global phenomenon has led to a significant reduction in world trade volume and a negative impact on economic development in some countries where the external sector accounts for a large proportion of GDP. Although Korea is a country vulnerable to this deteriorating trade environment, few studies have examined the relationship between protectionism and its business cycles based on Korean data. Thus, this paper investigates the impact of protectionism on Korea's business cycle. Design/methodology - To identify future implications, we conduct a structural vector autoregression (VAR) analysis using monthly Korean data from 1994 to 2015. Macroeconomic variables in the model include the industrial production index, inflation rates, exports (or net exports), interest rates, and exchange rates. For the identification of the shock reflecting the expansion of protectionism, we use an antidumping investigation (ADI) data. Since ADIs are followed generally by the imposition of antidumping tariffs, they have no contemporaneous impact on tariffs and are also contemporaneously exogenous to other endogenous variables in the VAR model. We examine two kinds of ADI shocks i) shocks on Korean exports imposed by Korea's trading partners (ADI-imposed shocks) and ii) shocks on imports imposed by the Korean government (ADI-imposing shocks). Findings - We find that Korea's exports decline sharply due to ADI-imposed shocks; the lowest point at the third month after the initial shock; and do not recover until 24 months later. Simultaneously, the inflation rate decreases. Therefore, the ADI-imposed shock can be regarded as a negative shock on the demand curve where both production and price decrease. In contrast, the ADI-imposing shock generates a different response. The net exports decline, but the inflation rate increases. These can be seen as standard responses with respect to the negative shock on the supply curve. Originality/value - We shed light on the relationship between protectionism and Korea's economic fluctuations, which is rarely addressed in previous studies. We also consider the effects of both protective policy measures on imports to Korea imposed by the Korean government and on policy measures imposed by Korea's trading partner countries on its exports.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.177-184
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• 2017

Understanding trends and drivers of technology diffusion is imperative to forecast new technology adoption and understand the process of technological innovation. Our research utilizes a quantitative trend analysis considering both technological and economic indicators for trends and drivers of technology diffusion for 32nm, 22nm, and 14nm logic semiconductor technology. In terms of technological performance, the technology diffusion curve showed an S-curve pattern during the stages of maturity and decline, and the diffusion curve showed evidence supporting the learning curve. The diffusion curve showed the life cycle duration of 2 years, and the rate of technological performance and obsolescence are observed quantitatively between generations. Architectural innovation is affected by technological drivers more significantly than economic drivers. This research has implications as empirical research on the trends and drivers of technology diffusion in the high-tech semiconductor industry, and is meaningful in forecasting new technology adoption or build technology strategy.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.297-299
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• 2021

Predicting future productivity of tight oil is an important task for analyzing residual oil recovery and reservoir behavior. In general, productivity prediction is made using the decline curve analysis(DCA). In this study, we intend to propose an effective model for predicting future production using deep learning-based recurrent neural networks(RNN), LSTM, and GRU algorithms. As input variables, the main parameters are oil, gas, water, which are calculated during the production of tight oil, and the type curve calculated through various cluster analyzes. the output variable is the monthly oil production. Existing empirical models, the DCA and RNN models, were compared, and an optimal model was derived through hyperparameter tuning to improve the predictive performance of the model.

• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.6
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• pp.25-40
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• 2015

Korean tourist areas are designated/managed in accordance with the Tourism Promotion Act. Since Taejongdae was designated as a tourist area in 1969, a total of 230 tourist areas have been designated/built/operated. It has been 46 years since the first tourist area was designated. According to the Tourism Area Life Cycle by Butler, it is estimated that the flow of the life cycle will be reflected in ups and downs over time. Thus, this study aimed to provide basic data for suggesting the direction of changes and development of the future tourist areas after analyzing the life cycle stage of domestic tourist areas, by applying the Tourism Area Life Cycle by Butler. The research method was based on the tourist areas by year, the number of visitors, and data of the target to derive the change transition curve, obtained by dividing the life cycle stages of the tourist areas based on the visitor rate of change. In the analysis results, more than 1/3 of domestic tourist areas are reaching the stagnation/decline stage, and tourist areas such as hot springs and seaside/beach resources show a particularly high ratio of stagnation/decline. The tourist areas that already have reached the stagnation/decline stage will need to analyze the causes for the decline, seek for resolution measures, and introduce new innovative elements. Even though the results of this study are not sufficient to be used as an absolute standard to decide the life cycle stage of domestic tourist areas, it is considered to be adequate for phenomenologically understanding the life cycle stage of Korean tourist areas. Based on this study, the causes for the stagnation/decline of tourist areas can be revealed while it can be also used as basic research to establish revitalization measures for tourist areas by introducing new innovation.

• Journal of the Korean Institute of Gas
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• v.20 no.3
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• pp.1-11
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• 2016

Production data from hydraulically fractured well in coalbed methane (CBM) reservoirs was analyzed using decl ine curve analysis (DCA), flow regime analysis, and flowing material balance to forecast the production performance and to determine estimated ultimate recovery (EUR) and timing for applying the DCA. To generate synthetic production data, reservoir models were built based on the CBM propertie of the Appalachian Basin, USA. Production data analysis shows that the transient flow (TF) occurs for 6~16 years and then the boundary dominated flow (BDF) was reached. In the TF period, it is impossible to forecast the production performance due to the significant errors between predicted data and synthetic data. The prediction can be conducted using the production data of more than a year after reached BDF with EUR error of approximately 5%.