• 한국산업보건학회지
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• 제32권1호
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• pp.21-30
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• 2022

Objectives: The purpose of this study is to suggest an optimal method by comparing the analysis methods of work environment measurement datasets including left-censored data where one or more measurements are below the limit of detection (LOD). Methods: A computer program was used to generate left-censored datasets for various combinations of censoring rate (1% to 90%) and sample size (30 to 300). For the analysis of the censored data, the simple substitution method (LOD/2), β-substitution method, maximum likelihood estimation (MLE) method, Bayesian method, and regression on order statistics (ROS)were all compared. Each method was used to estimate four parameters of the log-normal distribution: (1) geometric mean (GM), (2) geometric standard deviation (GSD), (3) 95th percentile (X95), and (4) arithmetic mean (AM) for the censored dataset. The performance of each method was evaluated using relative bias and relative root mean squared error (rMSE). Results: In the case of the largest sample size (n=300), when the censoring rate was less than 40%, the relative bias and rMSE were small for all five methods. When the censoring rate was large (70%, 90%), the simple substitution method was inappropriate because the relative bias was the largest, regardless of the sample size. When the sample size was small and the censoring rate was large, the Bayesian method, the β-substitution method, and the MLE method showed the smallest relative bias. Conclusions: The accuracy and precision of all methods tended to increase as the sample size was larger and the censoring rate was smaller. The simple substitution method was inappropriate when the censoring rate was high, and the β-substitution method, MLE method, and Bayesian method can be widely applied.

• 한국표면공학회지
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• 제23권2호
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• pp.24-29
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• 1990

The TiN filmms were deposited on the stainless steel substrates by BARE techinique in order to investigate the effects of process parameters such as source-to-substate distance (15-35cm), N2 pressure(4$\times$10-10 -1$\times$10-3mb)and bias voltage(O-2000V), on the deposition rate, the concentration ratio [N/Ti] and the surface color of the films. The deposition rate was deduced from the weight measurement, the [N/ti] ratio by ESCA. The deposition rate decreased with a relationship of=40.2/D2 where D was source-to-substrate distance. The effect of the bias voltage and the N2pressure on the deposition rate, however, appeared negligble. The [N/Ti] ratio was in the narrow range of 0.7 tp 0.8 It increased slightly with the N2 partial pressure and deceased with the source-to-substrate distance. It was confired by ESCA that a significant amount of oxygen and carbon was contaminated after deposition in the top surface of TiN films. The surface color of TiN film was changed from light gold yellow to reddish gold yellow with increasing [N/Ti] ratio.

• Smart Structures and Systems
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• 제17권4호
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• pp.647-667
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• 2016

In this paper, dynamic displacement is estimated with high accuracy by blending high-sampling rate acceleration data with low-sampling rate displacement measurement using a two-stage Kalman estimator. In Stage 1, the two-stage Kalman estimator first approximates dynamic displacement. Then, the estimator in Stage 2 estimates a bias with high accuracy and refines the displacement estimate from Stage 1. In the previous Kalman filter based displacement techniques, the estimation accuracy can deteriorate due to (1) the discontinuities produced when the estimate is adjusted by displacement measurement and (2) slow convergence at the beginning of estimation. To resolve these drawbacks, the previous techniques adopt smoothing techniques, which involve additional future measurements in the estimation. However, the smoothing techniques require more computational time and resources and hamper real-time estimation. The proposed technique addresses the drawbacks of the previous techniques without smoothing. The performance of the proposed technique is verified under various dynamic loading, sampling rate and noise level conditions via a series of numerical simulations and experiments. Its performance is also compared with those of the existing Kalman filter based techniques.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.323-325
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• 1995

An Inductively Coupled Plasma(ICP) was employed to prepare the Diamond-Like Carbon film with $CH_4$ gas. We observed the changes of mechanical, optical properties and internal stress of the films according to the variation of discharge power and negative-self bias. When weak magnetic field is applied, the properties of film are observed to change drastically. In magnetized case, the micro-hardness and the internal stress increase up to critical point and droped down in marked contrast to unmagnetized case. It suggests that large amount of ion flux exists due to high dissociation rate of the reactive radicals in plasma with magnetic field as reported elsewhere. As a result of FT-IR absorption measurement it could be confirmed that the $CH_x$ bonding and the micro-hardness and the internal stress decreased with the increase of negative-self bias.

• 대한전기학회논문지:전력기술부문A
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• 제48권10호
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• pp.1279-1286
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• 1999

In conventional GPS/DR integration schemes, the GPS position (or pseudo-range) information is used in calibrating DR sensors. In those schemes, however, an inaccurate calibration may degrade the position accuracy when the GPS measurement is not available. This paper presents a new integration scheme where the GPS velocity information is used in calibrating DR sensors. Also proposed is a new error model of DR sensors for calibrating the bias error and the tilt error in dynamic environments. The proposed model makes it possible that the errors of both the DR sensor parameters and the velocity are calibrated using the GPS carrier-based velocity(or the pseudo-range rate) measurement while the DR position error is calibrated using the GPS position measurement. Since the DR sensors are calibrated accurately, the positioning accuracy is drastically improved when the GPS measurements are unavailable.

• 한방재활의학과학회지
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• 제24권4호
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• pp.49-60
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• 2014

Objectives The purpose of this study is to research current trends of acupuncture treatment of lumbar herniated intervertebral disc using the PubMed database. Methods We set up the search strategy and investigated clinical trials on acupuncture treatment of lumbar herniated intervertebral disc through PubMed search. This study analyzed previous researched papers published from January 1st, 2000 to April 30th, 2014, and classified them by publication year, journal names, types of literature, treatment methods and evaluation scales. To assess the quality of the reviewed literature, randomized controlled trial (RCT) studies were assessed by Cochrane's risk of bias (ROB) tool and non-RCT studies were assessed by risk of bias for non-randomized studies (RoBANS). Results We found 35 studies on the acupuncture treatment of lumbar herniated intervertebral disc. Papers on this topic have been published, on average, three to four times annually in 9 journals since the mid-2000's. The journal with the largest number of publications was Chinese Acupuncture & Moxibustion, and most of articles were classified as RCT. Acupuncture treatment was performed individually or together with other treatments. The most frequently used pain evaluation index was visual analogue scale (VAS). The index of effective rate was used frequently but there was a lack of objectivity. In regards to the quality of the studies, outcome assessment in RCT showed that random sequence generation, allocation concealment, and the blinding of participants and personnel increase potential of risk of bias. For non-RCT assessment, outcome showed that confounding variable, measurement of intervention were at high risk of bias. Conclusions In order to obtain objective clinical evidence of acupuncture treatment of lumbar herniated intervertebral disc, further clinical studies should be designed to minimize the risk of bias, using STRICTA with larger sample sizes.

• 전기의세계
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• 제28권9호
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• pp.43-50
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• 1979

Silicon nitride films were chemically deposited on silicon substrates by reacting SiCl$_{4}$ and NH$_{3}$ in a nitrogen atmosphere at 700~1100 .deg.C. The deposition rate increased rapidly with deposition temperature upto about 1000 .deg.C, and became less temperature dependent above this temperature. The etch rate of films in buffered HF solution decreased, with an increase of deposition temperature, and a heat treatment at a temperature higher than that of the deposition considerably reduced the etch rate. It indicates that the heat treatment resulted in a densification of the films. Surface charge density of 3~4 * 10$^{11}$ /cm$^{2}$ was determined from the C-V characteristics of MNS diode, and it was also found that surface charge density depended on deposition temperature, but not film thickness. The current-voltage characteristics displayed a logI-V$^{1}$2/ dependence in the temperature range of 300~500.deg.K. Measurement of the slope of this characteristics and its dependence on temperature and bias polarity suggest that conduction in sili con nitride films arises from the Poole-Frenkel mechanism.

• Nutrition Research and Practice
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• 제12권4호
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• pp.283-290
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• 2018

BACKGROUND/OBJECTIVES: Indirect calorimetry is the gold-standard method for the measurement of resting energy expenditure. However, this method is time consuming, expensive, and requires highly trained personnel. To overcome these limitations, various predictive equations have been developed. The objective of this study was to assess the validity of predictive equations for resting energy expenditure (REE) in Korean non-obese adults. SUBJECTS/METHODS: The present study involved 109 participants (54 men and 55 women) aged between 20 and 64 years. The REE was measured by indirect calorimetry. Nineteen REE equations were evaluated for validity, by comparing predicted and measured REE results. Predictive equation accuracy was assessed by determining percent bias, root mean squared prediction error (RMSE), and percentage of accurate predictions. RESULTS: The measured REE was significantly higher in men than in women (P < 0.001), but the difference was not significant after adjusting for body weight (P > 0.05). The equation developed in this study had an accuracy rate of 71%, a bias of 0%, and an RMSE of 155 kcal/day. Among published equations, the $FAO_{weight}$ equation gave the highest accuracy rate (70%), along with a bias of -4.4% and an RMSE of 184 kcal/day. CONCLUSIONS: The newly developed equation provided the best accuracy in predicting REE for Korean non-obese adults. Among the previously published equations, the $FAO_{weight}$ equation showed the highest overall accuracy. Regardless, at an individual level, the equations could lead to inaccuracies in a considerable number of subjects.

• 대한한방부인과학회지
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• 제35권4호
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• pp.37-56
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• 2022

Objectives: The purpose of this study is to assess the effect of electroacupuncture for treating postpartum hypogalactia. Methods: We searched 9 databases on May, 2022, which contained four English, two Chinese, one Japanese, and two Korean databases. Randomized controlled trials (RCTs) were eligible. Measurement of outcome included total effective rate, lactation amount, serum prolactin level, and degree of breast fullness. The risk of bias was assessed by two independent authors using the Cochrane risk of bias tool. Results: 101 trials were screened, 5 RCTs were finally selected. Number of participants per study ranged from 56 to 273. The treatment group was effective of improving total effective rate, lactation amount, serum prolactin level compared with control group, and the result was stastically significant. The quality of the evidence for specific comparisons ranged from low to high. Conclusions: Included studies showed that electroacupuncture on acupoints related to lactation would be effective way to increase milk supply among mothers who are suffering from postpartum hypogalactia. In the future, further high-quality RCTs are needed to prove effectiveness of electroacupuncture for relieving hypogalactia with low risk of bias.

• Transactions on Electrical and Electronic Materials
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• 제7권5호
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• pp.235-239
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• 2006

Charge dynamics in polymeric materials after aged under ac electric field using the pulsed electroacoustic (PEA) technique is reported. The emphasis is placed on charge decay. The charge dynamics of the ac aged additive free low density polyethylene (LDPE) samples under dc bias differ from the sample without ac ageing, indicating changes brought in by ac ageing. It is believed that a slow decay rate of charge in the ac aged sample is related to the formation of deep traps in the material. However, chemical analysis by infrared spectroscope (FTIR) and Raman microscope reveals no significant chemical changes taken place in the bulk of the material after ac ageing. Further experiments on irradiated LDPE have revealed a similar behaviour, i.e. the charge decay is slower in irradiated samples than that of fresh sample. The findings presented clearly indicate that space charge measurement can be used as a diagnostic tool to monitor ageing in polymeric materials.