• Korean Parent-Child Health Journal
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• v.3 no.2
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• pp.18-24
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• 2000

The purpose of this research is to investigate Sleep/Activity pattern of normal neonate in Kangwon area. The subjects of this research were 23 normal neonate who visited pediatric clinic of kangneung general hospital from Jun 15, 1999 to August 10, 2000. The instrument of this research was the NCASA. The results of this research were as follows: 1. The mean time of daytime sleep was 8.21 hours. The mean time of nighttime sleep was 5.70 hours. The mean time of total daily sleep was 13.92 hours. The mean time of longest sleep period was 5.02 hours. The mean time of regularity of sleep were daytime 46.59%, nighttime 74.43%, total daily sleep 55.88%. The mean frequency of nighttime wakening was 2.03 times. 2. The each mean time of activity were daytime 7.72 hours, nighttime 2.28 hours, daily total activity 9.99 hours. The mean time of the longest activity period was 6.16 hours. The mean times of feeding frequency were daytime feeding 4.53, nighttime feeding 1.92, total daily feeding 6.45. The mean of regularity of feeding frequency was 65.71%.

• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.1
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• pp.87-98
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• 2016

A single machine scheduling problem for jobs with stochastic processing time is considered in this study. Shortest processing time (SPT) sequencing according to the expected processing times of jobs is optimal for schedules with minimal expected mean flow time when all the jobs arrive to be scheduled and their expected processing times are known. However, SPT sequencing according to the expected processing time may not be optimal for the minimization of the mean flow time when the actual processing times of jobs are known. This study evaluates the complexity of SPT sequencing through a comparison of the mean flow times of schedules based on the expected processing times and actual processing times of randomly generated jobs. Evaluation results show that SPT sequencing according to the expected flow time exhibits chaotic variation to the optimal mean flow time. The relative deviation from the optimal mean flow time increases as the number of jobs, processing time, or coefficient of variation increases.

• Wind and Structures
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• v.26 no.5
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• pp.293-304
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• 2018

A numerical study is conducted on the flow characteristics of a rectangular cylinder (chord-to-width ratio C/W = 2 - 10) mounted close to a rigid wall at gap-to-width ratios G/W = 0.25 - 6.25. The effects of G/W and C/W on the Strouhal number, vortex structure, and time-mean drag and lift forces are examined. The results reveal that both G/W and C/W have strong influences on vortex structure, which significantly affects the forces on the cylinder. An increase in G/W leads to four different flow regimes, namely no vortex street flow (G/W < 0.75), single-row vortex street flow ($0.75{\leq}G/W{\leq}1.25$), inverted two-row vortex street flow ($1.25<G/W{\leq}2.5$), and two-row vortex street flow (G/W > 2.5). Both Strouhal number and time-mean drag are more sensitive to C/W than to G/W. For a given G/W, Strouhal number grows with C/W while time-mean drag decays with C/W, the growth and decay being large between C/W = 2 and 4. The time-mean drag is largest in the single-row vortex street regime, contributed by a large pressure on the front surface, regardless of C/W. A higher C/W, in general, leads to a higher time-mean lift. The maximum time-mean lift occurs for C/W = 10 at G/W = 0.75, while the minimum time-mean lift appears for C/W = 2 at the same G/W. The impact of C/W on the time-mean lift is more substantial in single-row vortex regime. The effect of G/W on the time-mean lift is larger at a larger C/W.

• International Journal of Reliability and Applications
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• v.7 no.2
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• pp.127-140
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• 2006

AIn this paper we introduce and study a multivariate notions of mean inactivity time (MIT) functions. Basic properties of these functions are derived and their relationship to the multivariate conditional reversed hazard rate functions is studied. A partial ordering, called MIT ordering, of non-negative random vectors is introduced and its basic properties are presented. Its relationship to reversed hazard rate ordering is pointed out. Finally, using the MIT ordering, a bivariate and multivariate notions of IMIT (increasing mean inactivity time) class is introduced and studied.

• Journal of Ocean Engineering and Technology
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• v.16 no.3
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• pp.8-18
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• 2002

Formulation of the far-field method for the prediction of time-mean hydrodynamic force and moment acting on a 3-D surface-piercing body in waves is reviewed. It is found that the inequality between the weight of the floating body and its buoyancy force permits the replacement of the fluid particles inside the control surface by the fluid particles outside the control surface. Under such circumstances, momentum exchanges across the control surface make the time-mean value of the time rate of the momentum of the fluid inside the control surface non-vanishing. It is a second-order quantity which is hard to calculate by the far-field method. The drift forces and moments on half-immersed ellipsoids are calculated by both the far-field method and the near-field method. The discrepancy between two numerical results is presented and discussed.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.3
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• pp.220-228
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• 1996

This paper presents a extended stochastic Petri net (ESPN) model for CTN(Circulated Token with No duration) service in the data link layer of IEC/ISA fieldbus. It is assumed that a station on the fieldbus has a specified minimum token holding time, a finite capacity buffer, and one transmitter queue with the highest priority. The mean transmission (or service) time at a station and the mean token rotation time for the symmetric fieldbus system atr derived using the presented SPN model and the moment generating function. These performance measures are represented in terms of the minimum token holding time, the number of stations, the arrival rate of messages, and the mean length of messages. The presented performance measure are validated by computer simulations.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1439-1442
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• 2010

Time-lag recurrent neural networks model (Time-Lag RNNM) is used to estimate daily pan evaporation (PE) using limited climatic variables such as max temperature ($T_{max}$), min temperature ($T_{min}$), mean wind speed ($W_{mean}$) and mean relative humidity ($RH_{mean}$). And, for the performances of Time-Lag RNNM, it is composed of training and test performances, respectively. The training and test performances are carried out using daily time series data, respectively. From this research, we evaluate the impact of Time-Lag RNNM for the modeling of the nonlinear time series data. We should, thus, construct the credible data of the daily PE using Time-Lag RNNM, and can suggest the methodology for the irrigation and drainage networks system. Furthermore, this research represents that the strong nonlinear relationship such as pan evaporation modeling can be generalized using Time-Lag RNNM.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1111-1115
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• 2006

We present heuristic interpretations of the mean waiting time of $Geo^X/G/1$ vacation queues with set-up time. The heuristic interpretation of the mean waiting time is originally proposed for the continuous-time queues. We demonstrate that the heuristic approach is useful for the discrete-time queues as well.

• The Korean Journal of Applied Statistics
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• v.34 no.2
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• pp.255-266
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• 2021

The purpose of this study is to compare the effects of treatment on stage III stomach cancer data obtained from the SEER program of the National Cancer Institute and to identify the significant risk factors for the survival rates of stage III stomach cancer. Since the proportional hazards assumption was violated for treatment, we used the restricted mean survival time as an alternative to the proportional hazards model. The restricted mean survival time was estimated using pseudo-observations, and the effects of treatment were compared using a test statistic based on the estimated restricted mean survival times. We conducted the regression analysis using a generalized linear model to investigate the significant predictors for the restricted mean survival time of patients with stage III stomach cancer. We found that there was a significant difference between the restricted mean survival times of treatment groups. Age at diagnosis, race, substage, grade, tumor size, surgery, and treatment were significant predictors for the restricted mean survival time of patients with stage III stomach cancer. Surgery was the most significant predictor for increasing the restricted mean survival time of patients with stage III stomach cancer.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.1137-1140
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• 2005

We present the discrete-time version of the heuristic interpretation of the mean waiting time known well about the continuous-time version. The heuristic approach is mainly based on an arriving customer's viewpoint. We obtain the mean waiting time of $Geo^X/G/1$ queueing systems, including vacation queues.