• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.7
• /
• pp.669-676
• /
• 2015

In this paper, we described the simulation results of the phase offset performance of a clock in holdover mode which was normally operated in GPS Disciplined Oscillator (GPSDO). In the TIE model, we included the time error term caused by environmental temperature variation because one of the most important parameters of clock phase error is the frequency offset and drift caused by the variation of temperature. For the simulation, we employed Maximum Time Interval Error (MTIE) for the performance evaluation when the frequency offset and drift are estimated by using an Unbiased Finite Impulse Response (UFIR) filter with ladder algorithm. We assumed that the noise in the GPS measurement is white Gaussian with zero mean and 1 ns standard deviation, and temperature linearly varies with a slope of $1{^{\circ}C}$ per hour. From the simulation results, the followings were observed. First, with the estimation error of temperature of less than 3 % and the temperature compensation period of less than 900 seconds, the requirement of CDMA2000 phase synchronization under 10 us could be achieved for more than 40,000 seconds holdover time if we employ an OCXO (Oven Controlled Crystal Oscillator) clock. Second, in order to achieve the requirement of LTE-TDD under 1.5 us for more than 10,000 seconds holdover time, below 3 % estimation error and 500 seconds should be retained if a Rubidium clock is adopted.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.16 no.6
• /
• pp.112-123
• /
• 2017

The accurate forecasting of the public transportation's transit and arrival time has become increasingly important as more people use buses and subways instead of personal vehicles under the government's public transportation promotion policy. Using bus management system (BMS) data, which provide information on the real-time bus location, operation interval, and operation history, it is now possible to analyze the bus schedule reliability. However, the punctuality should always be considered together with the operation safety. Therefore, this study suggests a new methodology to secure both reliability and safety using the BMS data. Unlike other studies, we calculated the bus travel time between two bus stops by dividing the total travel length into 6 sections using 5 different measuring points. In addition, the optimal travel time for each bus route was proposed by analyzing the mean, standard deviation and coefficient of variation of the each section's measurement. This will ensure the reliability, safety and mobility of the bus operation.

• Journal of Biomedical Engineering Research
• /
• v.38 no.6
• /
• pp.277-284
• /
• 2017

This paper presents an implantable pH measurement electrode for wireless gastroesophageal reflux measurement. Usually, gastroesophageal reflux is diagnosed by a catheter-type wire connection between the esophagus and the diagnostic device which brings many side effects such as restriction of daily living, pain, and discomfort in the nasal cavity and pharynx of patients. In order to solve these issues, researchers have been studied a wireless measurement method and a micro-sized pH electrode for human body insertion is necessary. Commercial glass packaged pH meter is formed by a sensing and a reference electrodes in a KCl solution. However, if the glass meter is inserted into the human body, there are risks of leakage of the solution, breakage of the glass package, injury of the body elements. Therefore, the solution should be solidified on the micro-sized noble metal wire which has a characteristic of biocompatible. After solidified wire fabrication, the designed meter was tested for feasibility of measurement and the result was well agreed with pH values of commercial pH meter. Potentials in pH 1 to 12 solution was measured to obtain the sensitivity of the sensor with linearity. And we have designed a simulation of gastroesophageal reflux with symptom frequency, interval, and duration time in pH 2 solution. The proposed sensor has capable to get the same potential for 24 measurements in 3 days, and it has sensed same pH values of 2 for one hour with every 10 minutes. Furthermore, the sensor was survived for 48 hours with reasonable potentials in the acid solution.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.221-221
• /
• 2015

Sustainable use of water resource and conservation of water quality are essential problems in the world. Especially, problems of water quality are serious one for human health as well as ecological system of all creatures on the earth. Recently, the importance of total effluent load as well as the concentrations of pollutant materials has been recognized not only for the conservation of water quality but also for sustainable water use in watersheds. However, the measurement or estimation of total effluent load from non-point source area such as farm lands or forests may be more difficult because both of concentration and discharge of the water are greatly changed depending on various factors especially metrological conditions such as rainfall, while the measurement from a point source area may be easy because the concentration of pollutant materials and amount of discharge water are relatively steady. Therefore, the total effluent load from a non-point source is often estimated by statistical relationships between concentration and discharge, which is called as L-Q equation. However, a lot of work and time are required to collect and analyze water samples and to get the accurate relationship or regressive equation. So, we proposed a new system for direct measurement of total effluent load of water quality from non-point source areas to solve the problem. In this system, the overflow depth at a hydraulic weir is measured with a pressure gage every hourly interval to calculate the amount of hourly discharge at first. Then, the operating time of a small electric pump to collect an amount of water which is proportional to the discharge is calculated to intake the water into a storage tank. The stored water is taken out a few days later in a case of storm event or several weeks later in a case of non-rainfall event and the concentrations of water quality such as total nitrogen and phosphorous are analyzed in a laboratory. Finally, total load of the water quality can be calculated by multiplying the concentration by the total volume of discharge. The system was installed in a small experimental forestry watershed to check the performance and know the total load of water quality from the forest. It was found that the system to collect a proportional amount of water to actual discharge operated perfectly and a total load of water quality was analyzed accurately. As the result, it was expected that the system will be very available to know the total load from a non-point source area.

• Imaging Science in Dentistry
• /
• v.36 no.2
• /
• pp.89-94
• /
• 2006

Purpose : To evaluate clinical usefulness of facial soft tissue thickness measurement using 3D computed tomographic images. Materials and Methods : One cadaver that had sound facial soft tissues was chosen for the study. The cadaver was scanned with a Helical CT under following scanning protocols about slice thickness and table speed; 3 mm and 3 mm/sec, 5 mm and 5 mm/sec, 7 mm and 7 mm/sec. The acquired data were reconstructed 1.5, 2.5, 3.5 mm reconstruction interval respectively and the images were transferred to a personal computer. Using a program developed to measure facial soft tissue thickness in 3D image, the facial soft tissue thickness was measured. After the ten-time repeation of the measurement for ten times, repeated measure analysis of variance (ANOVA) was adopted to compare and analyze the measurements using the three scanning protocols. Comparison according to the areas was analyzed by Mann-Whitney test. Results : There were no statistically significant intraobserver differences in the measurements of the facial soft tissue thickness using the three scanning protocols (p>0.05). There were no statistically significant differences between measurements in the 3 mm slice thickness and those in the 5 mm, 7 mm slice thickness (p>0.05). There were statistical differences in the 14 of the total 30 measured points in the 5 mm slice thickness and 22 in the 7 mm slice thickness. Conclusion : The facial soft tissue thickness measurement using 3D images of 7 mm slice thickness is acceptable clinically, but those of 5 mm slice thickness is recommended for the more accurate measurement.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.22 no.5
• /
• pp.500-507
• /
• 2002

By this study, on-line real-time radiometric system was developed using a 64 channels linear array of solid state detectors to measure wall thickness of insulated piping system. This system uses an Ir-192 as a gamma ray source and detector is composed of BGO scintillator and photodiode. Ir-192 gamma ray source and linear detector array mounted on a computer controlled robotic crawler. The Ir-192 gamma ray source is located on one side of the piping components and the detector array on the other side. The individual detectors of the detector array measure the intensity of the gamma rays after passing through the walls and the insulation of the piping component under measurement. The output of the detector array is amplified by amplifier and transmitted to the computer through cable. This system collects and analyses the data from the detector array in real-time as the crawler travels over the piping system. The maximum measurable length of pipe is 120cm/min. in the case of 1mm scanning interval.

• Journal of Biomedical Engineering Research
• /
• v.5 no.2
• /
• pp.167-172
• /
• 1984

In the present study, we developed a nuclear stethoscope interfaced with a personal computer (APPLE- II) and evaluated it's performances as compared with the gamma camera. This single-probe, ECG-gated system has been used for displaying the left ventricular time-activity curves, the peak ejection time and its rate, the peak filling time and its rate, and the R-R interval distribution. The radioactivity was measured at every 10msec around the ventricular region, where the activity curves shows the maximal peak to peak variations. The background activity was measured around the lung area showing its counts approximately 50% of the end-diastolic count with minimal variations. The average time-activity curves of 100 beats were used for analysis in the equilibrium study after intravenous injection of 15-20mCi of Tc. The ejection fractions measured by the nuclear stethoscope(Y) were compared with those measured by gamma camera(X) in 47 patients with various heart diseases. The correlation coefficient between two measurements was 0.766 with a relation of Y=1.04 x-8.48. Also, the high reproducibility was obtained for the same patient. Also, the high reproducibility was obtained for the same patient. From this study, we conclude that this device is useful for continuous monitoring in the intensive care unit, as it is portable, compact, and inexpensive.

• Journal of Korea Multimedia Society
• /
• v.24 no.1
• /
• pp.30-39
• /
• 2021

Research in the field of health lighting has continued to advance to reproduce the color temperature of natural light which periodically changes. However, most of this research could only reproduce a uniform circadian color temperature of natural light, therefore failing to realize the characteristics of the circadian cycle of color temperature difference by latitude and longitude. To reproduce the color temperature of natural light on which the characteristics of a region are reflected, the collection technology of real-time characteristics of natural light is needed. If the color temperatures which are not within a periodical pattern due to climate changes, etc., are measured, it will be difficult to judge the occurrence (presence) of the anomalies and to reproduce the circadian cycle of the color temperature of natural light. Therefore, this study proposes an algorithm for judging the anomalies in real time based on the sliding window to reproduce the color temperature of natural light. First, the natural light characteristics DB collected through the on-site measurement were analyzed, the differential values at a one-minute interval were calculated and examined, and then representative color temperature circadian patterns by solar terms were drawn. The anomalies were then detected by the application of the sliding window that calculated the deviation of the color temperature for the measured color temperature data set, which was collected through RGB sensors, while moving along the time sequence. In addition, the presence of anomalies was verified through the comparison study between the detection results and the representative circadian cycle of the color temperature by solar term. The judgment method for the anomalies from the measured color temperature of natural light was proposed for the first time, confirming that the proposed method was capable of detecting the anomalies with an average accuracy of 94.6%.

• The Journal of Korean Physical Therapy
• /
• v.33 no.6
• /
• pp.265-271
• /
• 2021

Purpose: We aimed to analyze the reliability of the test for choice stepping reaction time (CSRT) under an unstable surface and determine whether there were differences in CSRT between support surface conditions (stable vs. unstable conditions) and between age groups (young adults vs. community-dwelling older adults). Methods: Twenty healthy community-dwelling older adults and twenty young adults performed the stepping task under an unstable condition over two visits. The mean of the two trials measured for each visit was used for the analysis. The test-retest reliability was analyzed using intra-class correlation coefficient (ICC) with a 95% confidence interval, standard error of measurement (SEM), and minimal detectable change (MDC). Differences in CSRT between support surface conditions and age groups were analyzed using the independent t-test with Bonferroni correction. Results: Excellent consistency was observed for ICC >0.90 in both groups. Moreover, the SEM and MDC values of the CSRT in older and young adults were 0.03 and 0.09 and 0.01 and 0.04, respectively. There was a significant difference in the CSRT between the age groups under stable (p<0.001) and unstable conditions (p<0.001). Conclusion: The findings demonstrated that the test for CSRT under an unstable condition had reliable results in both groups. Although older adults demonstrated longer reaction times than younger adults in all surface conditions, increasing the balance control demand by implementing a choice stepping task concomitant with a balance task had no influence on the reaction time in both age groups.

• The Journal of Korean Medicine
• /
• v.30 no.1
• /
• pp.120-127
• /
• 2009

Objectives: Sahyangsohapwon (SS) is a herbal medication that has been widely used with circulatory and neural diseases. This study was conducted to assess the effect of SS on the autonomic nervous system by using heart rate variability measurement. Methods: The eligible subjects were enrolled from the healthy male group of ages 20 to 35 years. They were divided into two groups, the SS group (n=26) and the control (n=24). We monitored the ECG of subjects from the time period 14:00 to 18:00. In the SS group, subjects were administered with a dose of SS at the time 15:00, whereas the control group had none. For each hour HRV measurement was monitored every 15 minutes for 512 seconds from the time period 14:00 to 18:00. The mean value, which was calculated using the 4 values during each hour (i.e. 14:00, 14:15, 14:30, 14:45), was used as the representative value for each individual hour. For the measurement values, RR-interval and SDNN (standard deviation of the NN intervals) were used as time domain analysis, and HF (high frequency), LF (low frequency), and LF/HF ratio were used as frequency domain analysis. Results: The LF value showed an increase after one hour of SS administration and showed gradual diminution for each and every hour. The repeated measures of ANOVA for the comparison of the LF value between the SS group and the control group showed significant differences. While, RR interval, SDNN, HF, and LF/HF ratio values showed no significant differences between the two groups. Conclusions: We suggest that the SS might be useful for stabilizing autonomic nervous system by inhibiting sympathetic nerve activation in healthy people.