• 산경연구논집
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• 제12권8호
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• pp.33-39
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• 2021

Purpose: The influence of age on time preference is not identified in the usual cross-sectional analysis. This study aims to test whether age affects time preference after controlling for the effects of individual heterogeneity including cohort effects. Research design, data and methodology: Drawing on a nationally representative panel dataset of Indonesians, we estimate the effects of age on time preference after controlling for unobserved individual heterogeneity as well as potential cohort effects. We measure time preference exploiting information on two sets of multiple price lists: one for a one-year delay, and the other for a five-year delay. Results: When we controlled for time-invariant individual characteristics, including birth cohort effects in a fixed effects model, the older men and women were more patient in a linear fashion, particularly when the delay was longer. To highlight the importance of controlling for individual fixed effects, we repeated the specification without controlling for individual fixed effects in OLS or censored maximum likelihood regression; we found no relation between age and impatience in men or women and for a one or five-year delay. Conclusions: The older men and women are more patient, and time preferences are correlated with unobserved individual heterogeneity.

• 대한기계학회논문집B
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• 제27권3호
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• pp.326-333
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• 2003

In the measurement using DMA and CPC in series, there is some time delay for particles classified in DMA to detect in CPC. During this time, the DMA time-response changes due to the velocity profile of sampling tube and the diffusion of particles in the volume that exists between the DMA exit and the detector of ultra-fine CPC. This is called mixing effect. In the accelerated measurement methods like the TSI -SMPS, the size distribution is obtained from the correlation between the time-varying electrical potential of the DMA and the corresponding particle concentrations sampled in DMA. If the DMA time -response changes during this delay time, this can cause the error of a size distribution measured by this accelerated technique. The kernel function considering this mixing effect using the residence time distribution is proposed by Russell et al. In this study, we obtained a size distribution using this kernel to compare to the result obtained by the commercial accelerated measurement system, TSI -SMPS for verification and considered the errors that result from the mixing effect with the geometric mean diameters of originally sampled particles, using virtually calculated responses obtained with this kernel as input data.

• 한국산업융합학회 논문집
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• 제20권3호
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• pp.205-212
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• 2017

This paper focuses on worst-case delay analysis of the time-triggered IEEE 802.15.4 protocol to satisfy the industrial quality-of-service (QoS) performance. The IEEE 802.15.4 protocol is considered to be unsuitable for industrial networks because its medium access control method is contention-based CSMA/CA, which exhibits unstable performance with an unbounded delay distribution under heavy traffic. To avoid these limitations, this paper presents a time-triggered version of the nonbeacon-enabled network of IEEE 802.15.4 that relies on a time division multiplexing access (TDMA) method implemented in the application layer without any modification of specification. The timing analysis of this time-triggered IEEE 802.15.4 was executed, and the worst-case transmission delay was calculated. Based on this analysis, the time-triggered IEEE 802.15.4 is a promising alternative for wireless industrial networking.

• 품질경영학회지
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• 제40권3호
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• pp.270-277
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• 2012

Purpose: In this paper, storage lifetime of delay system in the fuse of 81MM illuminating projectile is estimated. Methods: Accelerated degradation testings of tungsten delay system using both temperature and humidity stresses were performed, and then delay time increase of the systems were analyzed as degradation data based on distribution-based degradation processes. Results: The estimated storage lifetime of detonator is between 11.8 years and 17.6 years with each stress-life relationship. Conclusion: Comparing with field data, storage lifetime of 90% reliability is about 12 years.

• Journal of Preventive Medicine and Public Health
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• 제26권4호
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• pp.650-660
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• 1993

This study aims to describe the causes of medically unnecessary hospital stay at a teaching tertiary hospital, using modified version of Delay Tool in which the causes of delay are divided into slx major categories : delay related to test scheduling, test results, surgery, medical staff, patient/family, and administration. For the analysis of hospital stay, 6,479 inpatient-days were reviewed in two medical and four surgical departments for one month. Initially inappropriate hospital stays were identified using Appropriateness Evaluation Protocol (AEP), and causes of delay listed in Delay Tool were assigned to each of them. In both medical and surgical services, the most important cause of delay was related to medical staffs, ranging from 3.6% to 51.6% of total inpatient days. Next important category was delay related to test scheduling in medical services ($4.7{\sim}9.2%$), and delay related to surgery in surgical services ($7.3{\sim}15.0%$). Among subcategories of delay related to medical staffs, delay due to conservative care was the most important cause of inappropriate hospital stay ($2.9{\sim}6.4%$). Each clinical departments had different distribution among delay categories, which could not be fully justified by their clinical charateristics. The Delay Tool would be helpful in exploring factors related to the inefficient use of hospital beds. As a measurement tool of inappropriate hospital stay, however, the Delay Tool should be refined in the definitions of categories and its contents.

• 제어로봇시스템학회논문지
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• 제21권4호
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• pp.315-320
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• 2015

This paper describes the implemenation of localization and visualization scheme to find out an ultrasonic source caused by defects of a power distribution line equipment. To increase the fault detection performance, $2{\times}4$ sensor array is configured with MEMS ultrasonic sensors, and from the sensor signals aquired, the azimuth and elevation angles of the ultrasonic source is estimated based on the delay-sum beam forming method. Also, to visualize the estimated location, it is marked on the background image. Experimental results show applicability of the present technique.

• 소성∙가공
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• 제20권3호
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• pp.250-256
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• 2011

Vacuum-assisted thermoforming is one of the critical steps for the successful application of film insert molding(FIM) to parts of complex shapes. If the thickness distribution of the formed film is non-uniform, cracking, deformation, warping, and wrinkling can easily occur at the injection molding stage. In this study, the effects of processing parameters, which include the film heating time, plug depth, plug speed and vacuum delay time, on film thickness distribution were investigated. It was found that the film thickness at the part sidewall decreases with increasing the film heating time and plug depth, but the thickness at the bottom was found to exhibit the opposite behavior. The film thickness of the sidewall was observed to increase at higher plug speed and vacuum delay time of 0 ~ 0.3sec.

• 공학논문집
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• 제2권1호
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• pp.95-102
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• 1997

본 논문은 랜덤 억세스 LAN 프로토콜인 DMSA 시스템에서 스테이션 분포형태의 효과에 대하여 분석한다. 몬테카를로 시뮬레이션기법을 이용하여 몇가지 스테이션 분포 형태에 대하여 각 스테이션의 utilization을 평가한다. 또한, 스테이션의 숫자가 시스템의 utilization-delay 성능에 미치는 효과를 분석한다.

• Journal of the Korean Data and Information Science Society
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• 제17권3호
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• pp.687-705
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• 2006

In this paper we consider GPH distribution that is defined as a distribution for sum of random number of random variables following exponential distribution. We establish approximation process of general distributions to GPH distributions and offer numerical results for various cases to show the accuracy of the approximation. We also propose analysis method of delay distribution of queueing systems using approximation to GPH distributions and offer numerical results for various queueing systems to show applicability of GPH approximation.

• 한국안전학회지
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• 제25권1호
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• pp.17-21
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• 2010

The chemistry and ignition delay of hydrogen/air/HFP premixed mixtures was investigated numerically with unsteady perfectly stirred reactor(PSR). The detailed chemistry of 93 species and 817 reaction mechanism was introduced for hydrogen/air/HFP mixtures. The results shows the temporal concentration variations of major or reactants such as hydrogen and oxygen during autoignition were similar to the spatial distribution of premixed flame while water vapor produced at the ignition temperature was decomposed later, which can be clarified with the relate species production rates that the the re-growth (or shoulder) of OH concentration is a result of F radicals attacking $H_20$ forming OH and HF. For the stoichiometric $H_2$/air mixture inhibited by 20% HFP, HFP thermal decomposition reaction prevails over the radical attack such as H at initial stage. Even though relatively large HFP addition contributes to delay the ignition, chemical effect on the ignition delay is not effective because of late thermal decomposition of HFP. The most small ignition delay was observed at a slightly fuel lean condition ($\phi$ = 0.9), and temperature dependency of ignition delay was clearly shown near 900 K.