• Journal of Korean Neurosurgical Society
• /
• v.62 no.5
• /
• pp.519-525
• /
• 2019

Objective : The circadian pattern of the onset time of aneurysmal subarachnoid hemorrhage (aSAH) has been reported by various authors. However, the effect of the degree of physical exertion on the circadian pattern has not been studied in detail. Therefore, we conducted this study to investigate the effect of physical exertion on the circadian pattern of aSAH. Methods : Of the 335 patients presenting with aSAH from January 2012 to December 2017, 234 patients with identifiable onset time and metabolic equivalent (MET) values were enrolled. The onset time of aSAH was divided into 4-hour intervals. The patient's physical exertion was then assessed on a scale between 1 and 8 METs using generally accepted MET values, and categorized into two groups-light exertion (1 to 4 METs) and moderate to heavy exertion (5 to 8 METs)-to determine the effect of the degree of physical exertion on the onset time distribution of aSAH. Multivariate analysis was used to calculate the odds ratio (OR) between the two groups to determine the effect of the degree of physical exertion on each set of time periods. Results : There was a definite bimodal onset pattern that peaked at 08:00-12:00 hours followed by 16:00-20:00 hours (p<0.001). MET values at all time intervals were found to be significantly higher than the night time (00:00-04:00 hours) values (p<0.031). The MET value distribution showed a unimodal pattern that slightly differed from the bimodal distribution of the onset time of aSAH. There were no significant differences in the ORs of each time interval according to the degree of the MET value. Conclusion : This study reaffirmed that aSAH occurs in a bimodal pattern, especially showing the highest prevalence in the morning. Although aSAH could be related to daily activity, there were no significant changes in diurnal variations affected by the degree of physical exertion.

• Design & Manufacturing
• /
• v.18 no.2
• /
• pp.51-56
• /
• 2024

In this study, a tool was developed for analyzing production lead time in turning operations. It is expected to help to reduce machining time and to identify, for example, tool change intervals. The tool was developed using Visual Basic.Net and features a user-friendly graphical user interface (GUI) that allows users to easily input cutting conditions and calculate the usage time and feeding distance for each cutting tool based on a G-code program. Object-oriented programming techniques were also used to encapsulate and classify complex logic, thereby efficiently organizing and managing the functions and data structures of this analysis tool. The analysis tool provides various outputs. It calculates the use time of each detailed process of the turning operation, the use time of each tool, the use time of each type of feeding, and also generates the data needed for cutting time analysis, which can be visualized in charts. The analysis tool developed in this study is expected to significantly contribute to improving the efficiency of manufacturing processes and increasing productivity, particularly, in the manufacturing of components requiring massive material removal, such as aircraft parts.

• Journal of the Korean Data and Information Science Society
• /
• v.4
• /
• pp.31-44
• /
• 1993

Multivariate exponentially weighted moving average (EWMA) control charts for monitoring the variance-covariance matrix are investigated. A variable sampling interval (VSI) feature is considered in these charts. Multivariate EWMA control charts for monitoring the variance-covariance matrix are compared on the basis of their average time to signal (ATS) performances. The numerical results show that multivariate VSI EWMA control charts are more efficient than corrsponding multivariate fixed sampling interval (FSI) EWMA control charts.

• Journal of Korean Institute of Industrial Engineers
• /
• v.14 no.1
• /
• pp.51-56
• /
• 1988

A spectrum analysis method is presented with an example as an aid to Box and Jerkins' model identification procedure, where the theoretical spectrum of ARMA model and its confidence intervals derived by chi-square distribution are compared. An APL (A Programming Language) program for the method is developed for the 16-bit personal computer.

• 전기의세계
• /
• v.27 no.4
• /
• pp.41-44
• /
• 1978

Intermittent failures exercise their effects only part of the time but constitute a dominant factor for the field failures. We consider the data raliability of the partially self-checking network with which a single intermittent failure will be recovered by a rollback method. Even if the self-testingness of partially self-checking network is guranteed for a set of permanent failures, it sometimes may not be so for intermittent failures. We introduce the notion of error residual and provide the basis for calculating the data reliability. Both the duration of each intermittent failure and the occurrence interval of successive ones are assumed to be negative exponentially distributed; the convolution of the intervals is distributed according to an Erlangen distribution.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.715-722
• /
• 2001

The main purpose of this study is to evaluate early age thermal stresses and to estimate the risk of thermal cracking in the footings of Hyungsan bridge. In this study, stress analyses are performed for several construction stages using the computation of temperature distributions. The stress analysis results show that, not using the embedded pipe cooling, placing the concrete at once for each footings may cause sever thermal cracking. So, the structures should be constructed with one horizontal construction joint. Then the height of each lifts were determined to be 1.50 meters. Using various time intervals between lifts, temperature and stress.

• The Bulletin of The Korean Astronomical Society
• /
• v.33 no.1
• /
• pp.65.1-65.1
• /
• 2008

• Journal of the Korean Statistical Society
• /
• v.28 no.3
• /
• pp.359-370
• /
• 1999

We considered a change-point hazard rate model generalizing constant hazard rate model. This type of model is very popular in the sense that the Weibull and exponential distributions formulating survival time data are the special cases of it. Maximum likelihood estimation and the asymptotic properties such as the consistency and its limiting distribution of the change-point estimator were discussed. A parametric bootstrap method for finding confidence intervals of the unknown change-point was also suggested and the proposed method is explained through a practical example.

• Bulletin of the Korean Mathematical Society
• /
• v.53 no.3
• /
• pp.733-749
• /
• 2016

We aim to compute discretely monitored geometric Asian option prices under the Heston model. This method involves explicit formula for multivariate generalized Fourier transform of volatility process and their integrals over different time intervals using a recursive method. As numerical results, we illustrate efficiency and accuracy of our method. In addition, we simulate scenarios which show evidently practical importance of our work.

• Proceedings of the KOSOMBE Conference
• /
• v.1992 no.05
• /
• pp.79-81
• /
• 1992

This paper describes the design of an adaptive closed circuit anesthesia controller based on a multiplexed mass spectrometer system. The controller deals with measurement deterioration caused by measurement delay and rise time through a tong catheter as well as long sampling times due to the multiplexed measurements. Measurement data is extrapolated between sampling periods to increase the estimation convergence rate. A multiple-step-ahead predictive control algorithm is used to calculate intermediatc control inputs between sampling intervals. Simulations are used to validate the designed controller.