• 핵의학기술
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• 제27권2호
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• pp.95-98
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• 2023

Purpose: The precision error of a bone density meter reflects the equipment and reproducibility of results by an examiner. Precision error values can be expressed as coefficient of variation (CV), CV%, and root mean square-SD (RMS-SD). The International Society for Clinical Densitometry (ISCD) currently recommends using RMS-SD as the precision error value. When a 95% confidence interval is applied, the least significant change (LSC) value is calculated by multiplying the precision error value by 2.77. Exceeding the LSC value reflects a significant difference in measured bone density. Therefore, the LSC value of a bone density equipment is an essential factor for accurately determining a patient's bone density. Accordingly, we aimed to calculate the LSC value of a bone density meter (Lunar iDXA, GE) and compare it with the value recommended by the ISCD. We also assessed whether the value measured by the iDXA equipment was below the LSC value recommended by ISCD. Material and Methods: The bone densities of the lumbar spine and thighs of 30 participants were measured twice, and the LSC values were calculated using the precision calculation tool provided by the ISCD (http://www.iscd.org). To check the reproducibility of the measurement, patients were asked to completely dismount from the equipment after the first measurement; the patient was then repositioned before proceeding with the second measurement. Results: The LSC values derived using the CV% values recommended by the ISCD were 5.3% for the lumbar spine and 5.0% for the thigh. The LSC values measured using our bone density equipment were 2.47% for the lumbar spine and 1.61% for the thigh. The LSC value using RMS-SD was 0.031 g/cm² for the lumbar spine and 0.017 g/cm² for the thigh. Conclusion: that the findings confirm that the CV% value measured using our bone density meter and the LSC value using RMS-SD were maintained very stably. This can be helpful for obtaining accurate measurements during bone density follow-up examinations.

• 한국해양공학회지
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• 제34권3호
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• pp.167-179
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• 2020

Recently, the increasing importance of artificial intelligence (AI) technology has led to its increased use in various fields in the shipbuilding and marine industries. For example, typical scenarios for AI include production management, analyses of ships on a voyage, and motion prediction. Therefore, this study was conducted to predict a response amplitude operator (RAO) through AI technology. It used a neural network based on one of the types of AI methods. The data used in the neural network consisted of the properties of the vessel and RAO values, based on simulating the in-house code. The learning model consisted of an input layer, hidden layer, and output layer. The input layer comprised eight neurons, the hidden layer comprised the variables, and the output layer comprised 20 neurons. The RAO predicted with the neural network and an RAO created with the in-house code were compared. The accuracy was assessed and reviewed based on the root mean square error (RMSE), standard deviation (SD), random number change, correlation coefficient, and scatter plot. Finally, the optimal model was selected, and the conclusion was drawn. The ultimate goals of this study were to reduce the difficulty in the modeling work required to obtain the RAO, to reduce the difficulty in using commercial tools, and to enable an assessment of the stability of medium/small vessels in waves.

• Asian Pacific Journal of Cancer Prevention
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• 제17권3호
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• pp.1405-1410
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• 2016

Background: The European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Bone Metastases Module (EORTC QLQ-BM22) is a recently designed supplement to EORTC Quality of Life Questionnaire-C30 (EORTC QLQ-C30). Additional psychometric properties, especially using confirmatory factor analysis (CFA) and the Rasch model, are warranted. Materials and Methods: A total of 573 patients with bone metastases were enrolled from eight countries with a mean${\pm}$SD age of $55.8{\pm}13.7years$. Slightly more than two thirds of them were female (n=383; 66.8%). CFA was used to examine the BM22 framework; Rasch models were applied to understand misfit items and differential item functioning (DIF). Results: The fit indices were satisfactory in CFA (comparative fit index=0.972, Tucker-Lewis index=0.964, root mean square error of approximation=0.076, and standardized root mean square residual=0.045). All items fit well in the Rasch models (mean square values were between 0.5 and 1.5), and only one item (number 17) displayed DIF across gender. However, there were six DIF items across Canada and Taiwan, ten across Canada and Iran, and six across Taiwan and Iran. Conclusions: The BM22 has satisfactory psychometric properties, and could assess the QoL of patients with bone metastases specifically focusing on their symptoms. Clinicians may want to use it to capture the underlying QoL for patients with bone metastases. However, the score of item 17 should be interpreted with caution when comparing male and female patients. In addition, researchers should note that variation in DIF items may occur when conducting an international study.

• The Korean Journal of Pain
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• 제22권1호
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• pp.39-46
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• 2009

Background: Ketamine has an indirect sympathetic stimulation effect. We investigated heart rate variability (HRV) as a marker of cardiac autonomic function after a target controlled infusion (TCI) of ketamine with a plasma concentration of 30 or 60 ng/ml. Methods: In 20 adult volunteers, the mean of the R wave to the adjacent R wave interval (RRI), the range of RRI, the root mean square successive difference of intervals (RMSSD), the total power, the low frequency (LF, 0.04-0.15 Hz) power, the high frequency (HF, 0.15-0.4 Hz) power, the normal unit HF (nuHF), the normal unit LF (nuLF), the LF/HF ratio and the SD1 and the SD2 in the Poincare plot were measured before and after a TCI of ketamine. We observed for any psychedelic symptoms or sedation. Results: There were no differences in the mean and range of the RRI, RMSSD, total power, LF power, HF power, nuHF, nuLF, LF/HF ratio, SD1 and SD2 between before and after ketamine administration. The OAA/S score was higher and there were more psychedelic symptoms with a 60 ng/ml plasma concentration than with a 30 ng/ml plasma concentration. Conclusions: This study did not show any effect of a low plasma concentration of ketamine on the autonomic nervous system.

• 한국태양에너지학회 논문집
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• 제40권2호
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• pp.37-48
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• 2020

This study compares cloud radiation model (CRM) and sunshine fraction radiation model (SFRM) according to the solar altitude using hourly sunshine duration (SD) and cloud cover (CC) data. Solar irradiance measurements are not easy for the expensive measuring equipment and precise measuring technology. The two models with the site fitting and South Korea coefficients have been analyzed for fourteen cities of South Korea during the period (1986-2015) and evaluated using the root mean square error (RMSE) and the mean bias error (MBE). From the comparison of the results, it is found that the SFRM with the site fitting coefficients could be the best method for fourteen locations. It may be concluded that the SFRM models of South Korea coefficients generated in this study may be used reasonably well for calculating the hourly horizontal global irradiance (HGI) at any other location of South Korea.

• 한국HCI학회논문지
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• 제10권2호
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• pp.13-19
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• 2015

디스플레이 기술은 비약적으로 발전되었다. 특히 플렉서블 디스플레이에 대한 연구를 관련 기업들이 앞다투어 진행하고 있다. 현재 시장에는 플렉서블 디스플레이의 초기 단계인 커브드 디스플레이를 사용한 스마트폰, TV 등이 출시되어 있고, 데스크탑용 커브드 모니터 역시 최근에 출시되어 사무용 또는 엔터테인먼트용으로 이용되고 있다. 본 연구의 목적은 엔터테인먼트용으로 50" 멀티 모니터를 사용시 모니터의 곡률이 사용 자세 제어에 미치는 영향에 관한 것이다. 실험에는 두 종류의 곡률 (평면, 곡률반경 600mm)이 사용되었다. 총 10명의 근골격계질환이 없고, 양안 시력이 모두 0.8이상이고, 색맹 또는 색약이 아닌 평균 (SD) 20.9 (1.5)세의 대학생들이 실험에 참여하였다. 피험자들은 일반적인 VDT 환경의 실험실에서 각 곡률당 30분씩 핸들과 페달을 사용해 운전 게임을 하였다. 각 피험자가 운전 게임을 하는 동안 의자 위에 놓여진 압력 매트를 통해 이들의 COP (Center of Pressure)가 측정되었다. 자세 제어 분석을 위하여, 총 4개의 COP 측정치, Mean Velocity, Median Power Frequency, Root-Mean-Square (RMS) Distance, 그리고 95% Confidence Ellipse Area를 사용하였다. 실험 결과, 곡면대비 평면 디스플레이에서 전후 방향 (Anterior-Posterior; AP)의 RMS distance값이 더 큰 경향을 보였다. 이 결과를 통해 평면 디스플레이를 사용하여 운전 게임을 하는 동안 피험자의 전후 방향으로 몸을 더 많이 움직였다고 할 수 있다. 이는 평면 디스플레이가 곡면 디스플레이보다 화면의 가로방향으로 시거리 차이가 더 크기 때문에, 초점의 이동시간이 더 길어지는 것과 관련이 있을 수 있다. 또한, 평면 디스플레이 대비 곡면 디스플레이에서 더 높은 몰입감을 느끼거나, 더 집중할 수 있는 것과 관련이 있을 수 있다. 디스플레이 곡률에 따른 이런 행동상의 차이가 근골격계 질환에 미치는 영향에 대한 추가 연구가 필요하다.

• Safety and Health at Work
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• 제14권3호
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• pp.332-339
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• 2023

Background: The aim of the study was to test the validity and reliability of the Perceived Future Decent Work Securement Scale for Turkish nursing students. Methods: A cross-sectional, methodological study design was used. The study was carried out at three nursing undergraduate programs in Turkey during the academic year of 2020-2021 with 336 senior nursing students. Language validity and content validity analyses were performed for the scale adaptation, followed by confirmatory factor analysis (CFA) for construct validity. The reliability of the scale was determined using the test-retest and Cronbach's alpha internal consistency coefficient. Results: The scale-content validity index score was 0.988. In CFA, all goodness-of-fit indices verified the acceptable fit of the model; its root mean square error of approximation was 0.076; the normed fit index was 0.909; the standardized mean square residual was 0.097; the relative fit index was 0.881; the goodness-of-fit index was 0.915; the adjusted goodness-of-fit index was 0.872 and χ²/df = 2.932. The overall reliability was α = 0.86. The item-total correlations of the scale were above the acceptable level, and the test-retest analysis had a high correlation. The access to healthcare (14.68, SD 3.53) obtained the highest average score, and the adequate compensation (8.52, SD 3.76) was the lowest rated by the senior nursing students. Conclusion: The Perceived Future Decent Work Securement Scale is a valid and reliable scale to assess nursing students' future decent work securement.

• 감성과학
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• 제14권4호
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• pp.653-662
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• 2011

최근 3D TV 보급과 확산에 따른 시각 피로문제가 대두되면서 시각 기능과 인지적 관점에서의 연구가 활발하다. 그러나 3D 시각피로가 자율신경계 기능에 미치는 영향에 대한 연구는 미비하다. 따라서 본 연구에서는 3D TV 시청으로 유발되는 3D 시각피로가 자율신경계 기능에 미치는 영향과 이 영향이 교감 및 부교감 신경계와 심혈관계 반응에 미치는 영향을 확인하고자 한다. 피험자는 20 대 남녀 대학생 15 명(남 6 명, 여 9 명, 평균나이 22.53 세 ${\pm}$ 2.55 세)을 대상으로 하였다. 피험자는 편안한 의자에 앉아 3D TV를 1시간 시청하였다. 3D TV 시청 전과 후의 1분간 맥파(PPG, Photo-PlethysmoGram)를 측정하였고 주관설문을 실시하였다. 측정된 신호에서 SDNN (standard deviation of RR intervals), RMS-SD(root mean square successive difference), HF/LF ratio, Ln(LF), Ln(HF)를 추출하여 교감 및 부교감 신경계, 그리고 심혈관계 반응을 확인 하였다. 연구 결과 HF/LF ratio, Ln(LF), Ln(HF)는 시청 후에 유의하게 감소하였고, SDNN, RMS-SD는 통계적 유의차를 확인할 수 없었다. 이 결과는 3D 시각피로가 자율신경계 기능에 영향을 미치고 이로 인해 교감신경계가 항진되는 반응이 나타나며, 심박 변화율이 감소하는 결과를 초래할 가능성을 확인 하였다.

• 터널과지하공간
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• 제12권4호
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• pp.268-276
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• 2002

In this study, a 3D coordinate measurement system equipped with a laser displacement meter for digitizing rock joint surface was established and the digitized data were used to calculate several roughness parameters. The parameters used in this study were micro avenge inclination $angle(i_{ave})$, average slope of joint $asperity(SL_{ ave})$, root mean square of $i-angle(i_{rms})$, standard deviation of height(SDH), standard deviation of $i-angle(SD_i)$, roughness profile $index(R_P)$, and fractal dimension(D). The relationships between the roughness parameters based on the digitzation of the surface profile were analyzed. Since the measured value varied according to the degree of reflection and the variation of colors at the measuring point, rock joint surface was painted in white to minimize the influence of the surface conditions. The comparison of the measured values and roughness parameters before and after painting revealed the better consequence from measurement on the painted surfaces. Also, effect of measuring interval was studied. As measured interval was increased, roughness parameters were exponentially decreased. The incremental sequence of degree of decrease was $SDH\; i_{ave},\; i_{rms},\; SD_i,\;and\; R_ p-1$. As a result of comparison of parameters from pin-type measurement system and laser type measurement system, all value of parameters were higher when laser-type measurement system was used, except SDH.

• 치위생과학회지
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• 제19권4호
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• pp.238-244
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• 2019

Background: Recently, three-dimensional (3D) printing has been hailed as a disruptive technology in dentistry. Among 3D printers, a digital light processing (DLP) 3D printer has certain advantages, such as high precision and relatively low cost. Therefore, the latest trend in resin crown manufacturing is the use of DLP 3D printers. However, studies on the internal fitness of such resin crowns are insufficient. The recently introduced 3D evaluation method makes it possible to visually evaluate the error of the desired area. The purpose of this study is to evaluate the internal fitness of resin crowns fabricated a by DLP 3D printer using the 3D evaluation method. Methods: The working model was chosen as the maxillary molar implant model. A total of 20 resin crowns were manufactured by dividing these into two groups. One group was manufactured by subtractive manufacturing system (PMMA), while the other group was manufactured by additive manufacturing system, which uses a DLP 3D printer. Resin crowns data were measured using a 3D evaluation program. Internal fitness was calculated by root mean square (RMS). The RMS was calculated using the Geomagic Verify software, and the mean and standard deviation (SD) were measured. For statistical analysis, IBM SPSS Statistics for Windows ver. 22.0 (IBM Corp., USA) was used. Then, independent t-test was performed between the two groups. Results: The mean±SD of the RMS were 41.51±1.51 and 43.09±2.32 for PMMA and DLP, respectively. There was no statistically significant difference between PMMA and DLP. Conclusion: Evaluation of internal fitness of the resin crown made using a DLP 3D printer and subtractive manufacturing system showed no statistically significant differences, and clinically acceptable results were obtained.