• Physical Therapy Korea
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• v.20 no.3
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• pp.19-26
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• 2013

The smart-phone has become a necessity for most people. In this study, we determined that using a smart-phone for 20 minutes can cause increased neck and shoulder muscle activities and fatigue. Seventeen healthy male smart-phone users who attended Yonsei University played a smart-phone game for 20 minutes and changes in their bilateral cervical erector spinae and upper trapezius muscle activities and fatigue were measured. To assess muscle activities and fatigue, we used the following variables: the median frequency, the 50th percentile Amplitude probability distribution function (APDF) value (median load), and the discrepancy in the 90th percentile APDF value and the 10th percentile APDF value (APDF range). A paired t-test was used to compare pre-smart-phone-use status with post-smart-phone-use-status. The median frequency of the bilateral cervical erector spinae and the upper trapezius decreased significantly after 20 minutes of smart-phone use (p<.05). In addition, the 50th percentile APDF value of the bilateral cervical erector spinae and the right upper trapezius increased significantly (p<.05). The APDF range of the bilateral cervical erector spinae and the upper trapezius also increased significantly (p<.05). However, the 50th percentile APDF range of the left upper trapezius was not significantly different (p>.05). These findings suggest that using smart-phones for 20 minutes can induce muscle fatigue and increased neck and shoulder muscle activities.

• Clinical and Experimental Pediatrics
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• v.61 no.3
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• pp.71-77
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• 2018

Purpose: Small for gestational age (SGA) is confusingly defined as birth weight (BW) either below 3rd percentile or 10th percentile for infants. This study aimed to compare postnatal catch-up growth between SGA groups according to different definitions. Methods: Data of 129 infants born with BW below the 10th percentile and admitted to Korea University Anam Hospital and Ansan Hospital were retrospectively reviewed. Height and weight were measured at 6, 12, and 24 months. Results were compared between group A (BW: <3rd percentile) and group B (BW: 3rd-10th percentile). Results: Group A included 66 infants and group B included 63. At age 6 months (n=122), 62.9% of group A and 71.7% (P=0.303) of group B showed catch-up growth in weight. At 6 months (n=69), 55.9% of group A and 80.0% of group B (P<0.05) showed catch-up growth in height. At 12 months (n=106), 58.5% of group A, and 75.5% (P=0.062) of group B showed catch-up growth in weight. At 12 months (n=75), 52.8% of group A and 64.1% of group B (P=0.320) showed catch-up growth in height. Up to age 24 months, 66.7%/80.0% in group A and 63.6%/80.0% in group B showed catch-up growth in weight/height. Conclusion: Despite different definitions, there were no significant differences between the two SGA groups in postnatal catch-up growth up to age 24 months, except for height at 6 months. Compared to infants with appropriate catch-up growth, low gestational age and BW were risk factors for failed catch-up growth at 6 months.

• Journal of Community Nutrition
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• v.1 no.2
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• pp.81-87
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• 1999

Body mass index(BMI) is recognized as one of the most useful indexes for adiposity in children and adults. This study was conducted to provide information on BMI distribution by age and sex in Korean children, and to identify sociodemographic factors that affected BMI among children. The study was conducted on 2376 children(boys 1184, girls 1192) living in a middle-size city in Korea. Subjects were selected from the primary schoolchildren in grades 1-6 using the two-stage sampling method. Their mean age was 9.4 years. The percentile of BMI tended to increase as age increased in both sexes. The 85th percentile for boys, aged 6-12 years, was 19.8kg/㎡, and the 95th percentile was 22.5kg/㎡. The 85th percentile for girls, aged 6-12 years, was 18.9kg/㎡, and the 95th percentile was 21.5kg/㎡. Multiple regression analysis was carried out to predict BMI from percent ideal body weight (PIBW), age and sex. After adjusting PIBW and age, BMI for boys was 0.062kg/㎡ lower than that for girls. One year of age increased BIM by 0.55kg/㎡. The prevalence rate of overweight and obesity based on PIBW was 15.8% and 15.0% for boys, and 14.0% and 11.0% for girls, respectively. Demographic factors such as sex, age, and parents' obesity influenced children's BMI. After adjusting for sex, age and parents' BMI, the presence of another children in family, and mother's employment status showed a strong effect on children's BMI. The results suggest an age-sex specific BMI distribution of Korean children. The present study also provides direct evidence of a correlation between early life environmental factors, such as presence of siblings or mother's employment, and BMI level in Korean children.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.4
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• pp.11-20
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• 2022

Currently, the operation rule of agricultural reservoirs in case of drought events follows the drought forecast warning standard of agricultural water supply. However, it is difficult to preemptively manage drought in individual reservoirs because drought forecasting standards are set according to average reservoir storage ratio such as 70%, 60%, 50%, and 40%. The equal standards based on average water level across the country could not reflect the actual drought situation in the region. In this study, we proposed the improvement of drought operation rule for agricultural reservoirs based on the percentile approach using past water level of each reservoir. The percentile approach is applied to monitor drought conditions and determine drought criteria in the U.S. Drought Monitoring (USDM). We applied the drought operation rule to reservoir storage rate in extreme 2017 spring drought year, the one of the most climatologically driest spring seasons over the 1961-2021 period of record. We counted frequency of each drought criteria which are existing and developed operation rules to compare drought operation rule determining the actual drought conditions during 2016-2017. As a result of comparing the current standard and the percentile standard with SPI6, the percentile standard showed severe-level when SPI6 showed severe drought condition, but the current standard fell short of the results. Results can be used to improve the drought operation criteria of drought events that better reflects the actual drought conditions in agricultural reservoirs.

• The Journal of Pediatrics of Korean Medicine
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• v.26 no.4
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• pp.24-31
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• 2012

Objectives: The purpose of this study was to estimate differences in physical growth according to sleep during preschool period. Methods: Difference of height and BMI percentile according to quality and quantity of sleep obtained through survey from 377 preschool children was measured using statistical method. Results: There was no significant difference in height and BMI percentile according to bedtime, rising hour, sleeping hours and sleeping environment. Children who had woken up more from scare during sleep showed smaller height percentile. Conclusions: Children who woke up more from scare during sleep could have smaller height.

• Journal of the Korean Society of Safety
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• v.12 no.1
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• pp.113-121
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• 1997

Human reliability attempts to make precise quantitative analyses and predictions of the performance of human-machine(or product) systems. In order to yield more precise human error analysis, precise human error probabilities(HEPs) must be used in the analysis. However, because human behavior is influenced by factors that are called performance shaping factors(PSFs), the effects of PSFs must be considered to obtain precise HEPs, These are called basic HEPs or situation-specific HEPs. This paper presents a theoretical method for obtaining basic HEPs (i.e. , considering PSFs) in quantitative human error analysis. In this method, the weight which characterizes the degree of importance of several PSFs is obtained by the analytic hierarchy process. The quality scores of PSFs in the task situation are obtained by percentile concept. These scores are used in conjunction with the relative Importance weights of PSFs to compute the composite quality percentile score of PSFs in the task situation. Then, a new mapping method of the composite quality percentile score of PSFs into a situation-specific basic HEP is proposed with a numerical example.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.25 no.6
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• pp.17-22
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• 2002

In this paper, We consider some generalization of these five basic indices to cover non-normal distribution. The proposed generalizations are compared with the five basic indices. The results show that the proposed generalizations are more accurate than those basic indices and other generalization in measuring process capability. We compared an estimation methods by Clements with based on sample percentiles WVM to calculate the proposed generalization as an example The results indicated that Clements method is more accurate than percentile method, WVM in measuring process capability But the calculations of percentile method are easy to understand, straightforward to apply, and show be valuable used for applications.

• Proceedings of the ESK Conference
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• 1997.10a
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• pp.443-450
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• 1997

본 연구에서는 safework 소프트웨어를 이용하여 쾌적한 운전좌석에 대한 3차원 모델링을 하였다. 자동차 시트와 운전대의 조절 범위 및 레이아웃(layout), 그리고 운전자의 눈의 위치 등을 결정하기 위하여, 한국인과 미국인 체형의 95th percentile의 성인 남자와 5th percentile의 성인 여자, 그리고 50th percentile의 성인 남자에 대한 최적 운전상태에서의 엉덩이 점(hip point), 운전대 중심(steering wheel center), 눈의 위치(eye point) 등의 3차원상의 위치를 측정하였다. 인간의 모든 치수와 형태학적 윤곽 뿐만 아니라. 신체의 유동성, 기능적 제한 등이 충실히 반영된 safework 마네킹(mannequin)을 이용하 였으며, 여러 신체 부위의 복합적 움직임을 결정하는 역기구학(inverse kinematics)에 근거하여운전좌석을 모델링 하였다. Safework을 이용함으로써 기존의 마네킹이나 실물모형(mockup)의 제작에필요한 시간과 비용을 절약할 수 있을 뿐만 아니라, 인간의 신체 특성과 유사한 마네킹을 이용하여 인간과 환경사이의 인터페이스를 보다 효율적으로 모델링 할 수 있을 것이다.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.52
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• pp.347-354
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• 1999

Statistical Process Control(SPC) which uses control charts is widely used to inspect and improve manufacturing process as a effective method. A parametric method is the most common in statistical process control. Shewhart chart was made under the assumption that measurements are independent and normal distribution. In practice, this assumption is often excluded, for example, in case of (equation omitted) chart, when the subgroup sample is small or correlation, it happens that measured data have bias or rejection of the normality test. A bootstrap method can be used in such a situation, which is calculated by resampling procedure without pre-distribution assumption. In this study, applying bootstrap percentile method to (equation omitted) chart, it is compared and evaluated standard process control limit with bootstrap percentile control limit. Also, under the normal and non-normal distributions, where parameter is 0.5, using computer simulation, it is compared standard parametric with bootstrap method which is used to decide process control limits in process quality.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06b
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• pp.279-283
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• 2007

IT와 네트워크의 발전에 힘입어 많은 서비스를 인터넷을 통해서 제공하고 있다. 인터넷 사용자가 급증하면서 수많은 서비스 요청에 대한 효과적인 처리 방법에 많은 관심이 집중되고 있다. 본 논문에서는 라우터에서 패킷을 대상으로 사용된 Percentile 스케줄 기법을 리눅스 커널 스케줄러에 적용하여, 다양한 서비스 요청에 대해서 적절한 기준에 따라 다른 등급으로 분류하고 차등적인 서비스를 제공하고자 하는 연구를 진행하였다. 논문에서는 리눅스의 기본 스케줄러에 nice()시스템 콜을 이용하여 차등화 스케줄을 적용한 것과 Percentile 스케줄 기법을 리눅스 커널 스케줄러에 적용한 것을 비교 실험하였다. Percentile 스케줄 기법을 적용한 경우 기존의 리눅스 커널에 비해서 등급에 따른 응답시간의 차이가 명확한 것을 관찰할 수 있었다.