• Title/Summary/Keyword: change point analysis

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Analysis on Fitting Characteristics of a Metal-Sealing Pipe of the Hydrogen Fuel Tank for FCEV (FCEV용 고압연료탱크 메탈씰링 파이프의 체결특성 해석)

  • Lee, J.M.;Jeong, J.H.;Chon, M.S.;Lee, H.W.
    • Transactions of Materials Processing
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    • v.27 no.1
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    • pp.54-59
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    • 2018
  • In connecting parts of a hydrogen fuel cell vehicle, since the rubber ring is permeable to hydrogen, it is necessary to use a metal sealing structure which ensures leakage stability. Finite element analysis was performed to verify the fitting characteristics of the metal sealing structure, which is used to connect the pipe to a high pressure hydrogen FCEV tank. Deformation shape, contact distance and axial load were compared experimentally and these values were in agreement with each other. In the contact surface, between the pipe and the fitting body, the stress at the edge of the contact surface was higher than the center point, which was considered to be a good characteristic in view point of the leakage. The location of the contact points has almost no change in the upper part of the fitting, but that of the lower parts move downward as the fastening amount increases. The contact pressure at the lower part is maintained at the same constant level.

A Study on the Nozzle Flow in the Sub-scale High-Altitude Test (축소형 고공환경모사 시험에서의 노즐 유동에 관한 연구)

  • Choi, Jiseon;Lee, Seongmin;Lee, Heejune;Ko, Youngsung;Kim, Seonjin;Lee, Jungmin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.1011-1015
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    • 2017
  • In this study, numerical and experimental studies on the nozzle flow in a sub-scale cold flow test were conducted to simulate high altitude condition. In the theoretical calculation, the temperature of the nozzle outlet is calculated to be lower than the liquefaction point, and the fluid exists at the phase change point. Also, numerical analysis result is higher than theory calculation but lower than liquefaction temperature. As a result of cold flow test, it was confirmed that the temperature was much higher than theory and analysis. This is because it assumed that it is adiabatic in the theoretical calculation, but the experiment in the actual environment is not the adiabatic but the heat exchange with the outside exists.

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Review for time-dependent ROC analysis under diverse survival models (생존 분석 자료에서 적용되는 시간 가변 ROC 분석에 대한 리뷰)

  • Kim, Yang-Jin
    • The Korean Journal of Applied Statistics
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    • v.35 no.1
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    • pp.35-47
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    • 2022
  • The receiver operating characteristic (ROC) curve was developed to quantify the classification ability of marker values (covariates) on the response variable and has been extended to survival data with diverse missing data structure. When survival data is understood as binary data (status of being alive or dead) at each time point, the ROC curve expressed at every time point results in time-dependent ROC curve and time-dependent area under curve (AUC). In particular, a follow-up study brings the change of cohort and incomplete data structures such as censoring and competing risk. In this paper, we review time-dependent ROC estimators under several contexts and perform simulation to check the performance of each estimators. We analyzed a dementia dataset to compare the prognostic power of markers.

Experience and Vision of Nutrition Education by Nutrition Teacher Candidate in School (예비영양교사의 학교에서의 영양교육 경험 및 방향 설정에 대한 인식 조사)

  • Lee, Eun-Ju;Lee, Hae-Young
    • Journal of the Korean Society of Food Culture
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    • v.24 no.4
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    • pp.440-450
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    • 2009
  • The purposes of study were to survey the status of nutrition education in school and investigate the perception of nutrition teacher candidates concerning the direction and ideal method for nutrition education. A questionnaire was distributed to 554 nutrition teacher candidates from August to October, 2006. A total of 468 usable data were collected (84.5% response rate). The statistical data analysis was completed by using SPSS for Windows (ver. 10.0) for descriptive analysis, ANOVA and $X^2$-test. About 52% of respondents had nutrition education teaching experience. Half of the respondents indicated that the necessity for nutrition education stemmed from their own need for such education. The main problem in students' dietary life was 'the increasing intake of processed foods, instant foods and fast foods (4.23 out of Likert 5 point scale)' and the major nutritional problem was 'high calorie intake with low essential nutrients (3.96 out of Likert 5 point scale)'. Over half the respondents (53.4%) recommended that nutrition education be oriented towards behavioral change rather than knowledge delivery. Social learning theory was preferred mostly as an theory apt to nutrition education (60.3%) and the most effective means of education was referred to organizing the regular class for nutrition education (50.5%). The 'playing such as songs or game' was reported as both effective and realizable method in nutrition education.

Characteristics of the Lateral Resistance of Pile according to the Lateral Loading Rate in Dense Sand (조밀한 모래지반에서 수평재하속도에 따른 말뚝의 수평저항 특성)

  • Gichun Kang;Hyejeong Park;Seong-kyu Yun;Jiseong Kim
    • Journal of the Korean Geosynthetics Society
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    • v.22 no.3
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    • pp.97-103
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    • 2023
  • Recently, research on the lateral resistance of pile foundations has been actively conducted. In experimental studies on the lateral resistance of pile foundations, displacement control or load control methods are used. However, in the case of the displacement control method, the lateral resistance of the pile varies depending on the rate of the load applied to the pile. Therefore, this study seeks to determine the change in lateral resistance of pile foundations according to lateral loading rate through model experiments. The experimental results showed that the lateral resistance of the pile tended to decrease as the lateral loading rate applied to the pile head increased. In order to confirm this, a model experiment of the side change of the ground and pile according to the loading rate was additionally conducted. Through inverse analysis, the change in the depth of the rotation point according to the lateral loading rate was identified. Through the change in the lateral resistance of the pile foundation and the depth of the rotating point according to the lateral loading rate, it was proposed to test the loading rate within 1.5 mm/min during the lateral loading test of the pile.

A Study on the Effect of Acupuncture on Anesthesia and the Mode of Action (The Second Report) (자침(刺鍼)이 마취(痲醉)에 미치는 작용기전(作用機轉) 연구(硏究) (제(第) 2 보(報)))

  • Park, Hee-soo;Park, Kyoung-sik
    • Journal of Acupuncture Research
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    • v.19 no.4
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    • pp.140-151
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    • 2002
  • This study was carried to identify whether acupuncture at several meridian points can affect the human anesthesia or not through the analysis of serum intermediates, such as, melatonin, serotonin, TSH, cortisol in human serum. We investigated the effect of accupuncture on the change of serum intermediates which have frequently been made a subject of discussion owing to its hyponic and sedative properties in practice. The result obtained were as follow ; 1. Serum melatonin levels was hardly affected at 40 minutes after general acupuncture on Hab-Gog, Nae-Gwan, and the other meridian points as compared with that($5.64{\pm}1.02pg/ml$) of resting control group. But on day 1 after acupuncture, these tend to increase significantly ($7.95{\pm}2.05pg/ml$ to $8.21{\pm}1.57pg/ml$, p <0.05). On the other hand, control group under sleep showed the serum level of $7.39{\pm}1.03pg/ml$. Additional acupuncture at In-Dang induced the increased melatonin level, especially at 40minutes after acupuncture(p <0.05). 2. Serotonin level in resting control serum recorded $51.14{\pm}8.17{\mu}g/ml$. Acupuncture at determined meridian point intend to increase average level of serotonin, but not significant. However observation on day 1 after acupuncture at Hab-Gwan meridian point and under sleeping showed the significantly increased serotonin level, $74.05{\pm}35.83{\mu}g/ml$, $70.44{\pm}13.08{\mu}g/ml$, respectively. 3. TSH level in intact human serum recorded $0.85{\pm}0.24{\mu}IU/ml$. and the serum exposed to acupuncture showed the irregular pattern of TSH level in a mean range of $0.76{\pm}0.44{\mu}IU/ml$ to $1.06{\pm}0.38{\mu}IU/ml$, regardless of meridian point or time after acupuncture. 4. The values of serum cortisol in control group were $11.76{\pm}2.06{\mu}g/dl$ in resting, $7.51{\pm}2.85{\mu}/dl$ under sleep, respectively. The level of serum cortisol in 40minutes after acupuncture was markedly (p <0.05) reduced to the serum levels of $5.65{\pm}2.58{\mu}g/dl$ (Hab-Gog, Nae-Gwan), $7.58{\pm}3.21{\mu}g/dl$ (Gyo-Gam, Sin-Mun besides Hab-Gog, Nae-Gwan), $6.43{\pm}3.54{\mu}g/dl$ (In-Dang besides to Hab-Gog, Nae-Gwan), respectively, as compared with control, intending to increase a little on day 1 after acupuncture. From the above results, the analysis of serum intermediates suggest that acupunctuation at meridian points applied to at this study act upon the phase of light anaesthesia or hypnosis, at the same time affect pituitary-adrenal axis rather than hypothalamus-pituitary axis in the secretary system of hormone and also don't affect dorsal-raphe nucleus according to the observation of change transition in serum intermediates, such as TSH, serotonin, and cortisol.

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Study on the change in the Satisfaction Degree on the Residential Environment and the change in the Selection Tendency of the Residential Property - Targeting Seoul Residences - (주거환경 만족도와 주거선택요소 중요도 변화에 관한 연구 - 서울지역 거주자를 중심으로 -)

  • Kim, Joon-Hwan;Choi, Young-Moon
    • Journal of the Korean housing association
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    • v.19 no.3
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    • pp.31-38
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    • 2008
  • Recently, Seoul residential real estate market showed a big change, especially in 2007. The residential property price in Seoul had been mainly affected by 5 provideces: Kangnam-gu, Seocho-gu, Songpa-gu, Gangdong-gu and Yangchun-gu, but these providences started to show the decrease in price while the other providences ironically showed the opposite direction. Therefore, this project was derived from this phenomenon recognition and the necessity as the new market trend requires. The pre-research was carried out with the point of social-population academic view, but this project provides the analysis on the new market trend by simplifying the complex valuation indexes, originated from the pre-research. In result, the aspects of the change could be categorized into time-manner classification and territorial-manner classification, in cope with the change in the satisfaction degree on the residential environment and the selection tendency of the residential property. Based on the the moving-preferred area criteria, the territorial classification was categorized into 3 areas: 5 providences, which showed the initial decrease in real estate price (area 1), the other Kangnam area (area 2), and Kangbuk area (area 3). The result illustrated the reasonable change in the satisfaction degree on the residential environment and the selection tendency of the residential property. This project was able to reach the following conclusion : Firstly, the housing development planning should be devised by the residential environment, including the view and the natural environment, not by the area. Secondly, the housing development planning in the other Kangnam area (area 2) and Kangbuk area (area 3) should embrace the business function, not the housing development only. Last, the housing development planning in Kangbuk area (area 3) should be able to enhance education and culture function and be connected by various transportation system. This project analyzes the change in the satisfaction degree on the residential environment and the selection tendency of the residential property. Thereafter, this project has the purpose of providing the aid in understanding of the basis of housing development information.

Remediation Characteristics that Appear in the Change of MP3Player I : Re-mediation and Genealogical Change (MP3Player의 변화에서 나타나는 재매개적 특성 I : 계보적 변화와 재매개성)

  • Lee, Jin-Hyuk;Lee, Young-Chun;Koo, Yoon-Hee
    • The Journal of the Korea Contents Association
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    • v.13 no.11
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    • pp.59-68
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    • 2013
  • iPod Touch provided so various application software beyond the early music playback function, and enhanced its UI to the level of UX. Because of these, it was evaluated as innovative. In addition, even though various images were provided through the Internet, some people still classify MP3P as audio device in its product category. As for how audio device became video or image device and which factor contributed to such happening, there may be various factors, such as social, cultural, and technical change, other than fundamental change of medium itself. This study is regarding medium characteristics of MP3Player. In other words, this study classified genealogical changes, which can be categorized into 4 points. This study also analyzed the property of each point according to this classification. The result of analysis showed that there is a relation with technological as well as social context in such genealogical change in MP3player. Even though there are various elements in the change of a device, it can be suggested that the factors of genealogical change in MP3player are influenced by a totality of social needs and contexts and technical changes.

A Study on the Estimation Methods of Nonpoint Pollutant Unit Load - Focus on Nonpoint Pollutant Unit Load in Paddy Field - (비점오염 발생 원단위 산정방법에 대한 고찰 - 논 비점오염 원단위를 중심으로 -)

  • Choi, DongHo;Choi, Soon-Kun;Kim, Min-Kyeong;Hur, Seung-Oh;Hong, Sung Chang;Yeob, So-Jin;Yoon, KwangSik
    • Journal of The Korean Society of Agricultural Engineers
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    • v.61 no.3
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    • pp.15-22
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    • 2019
  • In order to preserve water environment, Total Maximum Daily Load(TMDL) is used to manage the total amount of pollutant from various sources, and the annual average load of source is calculated by the unit load method. Determination of the unit load requires reliable data accumulation and analysis based on a reasonable estimation method. In this study, we propose a revised unit load estimation method by analyzing the unit load calculation procedure of National Institute of Environment Research(NIER) method. Both methods were tested using observed runoff ratio and water quality data of rice paddy fields. The estimated values with the respective NIER and revised NIER methods were highly correlated each other. However, the Event Mean Concentration(EMC) and the runoff ratio considered in the NIER method appeared to be influenced by rainfall classes, and the difference in unit load increases as the runoff and EMC increase. The error can be further increased when the EMC and runoff ratio are changed according to changes in rainfall patterns by climate change and change of agricultural activities. Therefore, it is recommended to calculate unit load by applying the revised NIER method reflecting the non point pollution runoff characteristics for different rainfall classes.

Analysis of Sedimentation and Erosion Environment Change around the Halmi-island, Anmyeondo in West Coast of Korea (안면도 할미섬 주변의 침식·퇴적환경 변화 분석)

  • KIM, Jang-soo;JANG, Dong-Ho
    • Journal of The Geomorphological Association of Korea
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    • v.19 no.2
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    • pp.123-132
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    • 2012
  • In this study, we analyzed sedimentation and erosion environment around Halmiseom on Anmyeon Island using wind direction and wind speed data, gain size analysis data and datum-point measured values. To observe changes in sedimentation and erosion environment around Halmiseon, we installed datum points at 12 locations around Halmiseom and carried out at total of 32 field measurements from May 16th, 2010 to May 8th, 2012. The field measurement results showed that H-3, H-4, H-5 and H-9 points are dominated by sedimentation environment, and H-7, H-8, H-10, H-11 and H-12 points are dominated by erosion environment. Meanwhile, sedimentation and erosion appeared alternately at H-2 and H-6 points. These results indicate that a bank installed in the southwest side of Halmiseom prevented sand of the beach from moving to the northeast side, leaving the sand of the beach being deposited at the sites, and the northeast side, where sand was not provided from beach ridge of Halmiseon was dominated by sedimentation. That is, the southwest side of Halmiseom was dominated by sedimentation, but the northeast side was dominated by erosion in general. However, the opposite trends were observed at H-9 point of the northeast side and H-12 point of the southwest side. According to analysis, since H-9 point is located at the end of sand spit connected to Halmiseom, the supply of sediments by a tidal current is possible. On the other hand, it was difficult to analyze the cause of erosion in case of H-12 point located at the sand dune due to the short measurement period.