• Journal of the Korean Society of Industry Convergence
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• v.23 no.3
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• pp.433-444
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• 2020

This study proposes a method to improve the sleep stage and efficiency estimation of sleep apnea patients using a UWB (Ultra-Wideband) radar. Motion and respiration extracted from the radar signal were used. Respiratory signal disturbances by motion artifacts and irregular respiration patterns of sleep apnea patients are compensated for in the preprocessing stage. Preprocessing calculates the standard deviation of the respiration signal for a shift window of 15 seconds to estimate thresholds for compensation and applies it to the breathing signal. The method for estimating the sleep stage is based on the difference in amplitude of two kinds of smoothed respirations signals. In smoothing, the window size is set to 10 seconds and 34 seconds, respectively. The estimated feature was processed by the k-nearest neighbor classifier and the feature filtering model to discriminate between the sleep periods of the rapid eye movement (REM) and non-rapid eye movement (NREM). The feature filtering model reflects the characteristics of the REM sleep that occur continuously and the characteristics that mainly occur in the latter part of this stage. The sleep efficiency is estimated by using the sleep onset time and motion events. Sleep onset time uses estimated features from the gradient changes of the breathing signal. A motion event was applied based on the estimated energy change in the UWB signal. Sleep efficiency and sleep stage accuracy were assessed with polysomnography. The average sleep efficiency and sleep stage accuracy were estimated respectively to be about 96.3% and 88.8% in 18 sleep apnea subjects.

• The Journal of the Acoustical Society of Korea
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• v.22 no.2
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• pp.145-152
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• 2003

In this paper, assuming that the score of speech utterance is the product of HMM log likelihood and HMM weight, we propose a new method that HMM weights are adapted iteratively like the general MCE training. The proposed method adjusts HMM weights for better performance using delta coefficient defined in terms of misclassification measure. Therefore, the parameter estimation and the Viterbi algorithms of conventional 1:.um can be easily applied to the proposed model by constraining the sum of HMM weights to the number of HMMs in an HMM set. Comparing with the general segmental MCE training approach, computing time decreases by reducing the number of parameters to estimate and avoiding gradient calculation through the optimal state sequence. To evaluate the performance of HMM-based speech recognizer by weighting HMM likelihood, we perform Korean isolated digit recognition experiments. The experimental results show better performance than the MCE algorithm with state weighting.

• Journal of Environmental Science International
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• v.23 no.6
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• pp.1049-1060
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• 2014

We investigated the spatiotemporal variations of dissolved inorganic nutrients along a saline gradient to estimate nutrient fluxes in the Seomjin River estuary during dry (March 2005, March 2006, March 2007, and March 2008) and rainy seasons (August 2005, July 2006, July 2007, and July 2008). Dissolved inorganic nitrogen concentrations were similar in the endmembers of freshwater for the rainy and dry seasons. In contrast, the concentrations of dissolved inorganic phosphate and silicate in the rainy season were approximately 2-3 times higher than those in the dry season. River discharge was approximately 10 times higher in the rainy season ($212m^3sec^{-1}$) than in the dry season ($21m^3sec^{-1}$). The fluxes of dissolved inorganic nitrogen, phosphate, and silicate were 2.91, 0.004, and 2.51 tons $day^{-1}$ in the dry season and 7.45, 0.421, and 30.5 tons $day^{-1}$ in the rainy season, respectively. Although the range of nutrient concentrations were similar to previous results from investigations in the Seomjin River estuary, the nutrient fluxes were differed according to river discharge for different survey periods.

• Journal of the Korean Geographical Society
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• v.49 no.3
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• pp.339-356
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• 2014

Easy access to DEMs and the development of technology treating DEMs make it easier to extract stream longitudinal profiles from DEMs than previously done. Since such profiles possess many problems such as artificial flats and steps, it should be required for them to be smoothed like natural profiles to estimate gradient values along those sections. However smoothing itself comes with much distortion of raw profile from original DEMs. There has been no research evaluating quantitatively the effects due to smoothing process. Here we attempt to quantify the effects of major smoothing methods on raw and real profiles, suggest a new method to overcome the limitations of them, and evaluate it. This study not only suggests a new smoothing method, but also provides a guideline for choosing a proper smoothing method.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.3
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• pp.139-148
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• 2000

A mass balance/photochemical modeling approach was used to evaluate the sea-to-air dimethyl sulfide (DMS) fluxes in tropical regions and part of the Southern Ocean. The flux determinations were based on 10 airborne observations by ACE 1 transit flights (i.e., Flights 4-9 and 29-32). The DMS flux values for the tropical regions ranged from 1.0 to 7.4 $\mu$mole/$m^2$/day with an average estimate of 4.2$\pm$2.3 $\mu$mole/$m^2$/day. The seasonal variations in the DMS flux predicted for the equatorial Pacific Ocean based on atmospheric DMS measurements were not entirely consistent with those derived from seawater DMS measurements were not entirely consistent with those derived from seawater DMS measurements reported in previous literature. Inhomogeneities in the DMS flux field were found to cause significant shifts in the atmospheric DMS levels even in the same sampling location. Accordingly, no definitive statement can be made at this stage regarding systematic differences or agreements in the DMS flux estimates from the two approaches. Moreover, this study strongly suggests that DMS oxidation is the most likely dominant source of SO$_2$in tropical regions, which is also supported by another set of compiled observations. Finally, these SO$_2$observations indicate that, when significant data was available for both the boundary and buffer layers, the vertical SO$_2$gradient between these two zones was primarily negative.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.1
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• pp.37-46
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• 2017

Thermal Marangoni flow has been observed inside droplets on heated surfaces, finally resulting in a coffee stain effect. This study aims to visualize and control the thermal Marangoni flow by employing periodic vertical vibration. The variations in the contact angle and internal volume of the droplet as it evaporates is observed by using a combination of continuous light and a still camera. With regard to the internal velocity, the particle image velocimetry system is applied to visualize the internal thermal Marangoni flow. In order to estimate the internal temperature gradient and surface tension on the surface of a droplet, the theoretical model based on the conduction and convection theory of heat transfer is applied. Thus, the internal velocity increases with an increase in plate temperature. The flow directions of the Marangoni and gravitational flows are opposite, and hence, it may be possible to control the coffee stain effect.

• Journal of the Korea Society of Computer and Information
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• v.8 no.4
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• pp.13-20
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• 2003

Based on the studies on the motion vector distributions estimated on the image sequences, we proposed constrained diamond search (DS) algorithm for fast block-matching motion estimation. By considering the fact that motion vectors are searched within the 2 pixels distance in vertically and horizontally on average, we confirmed that DS algorithm achieves close performance on error ratio and requires less computation compared with new three-step search (NTSS) algorithm. Also, by applying displaced frame difference (DFD) to DS algorithm, we reduced the computational loads needed to estimate the motion vectors within the stable block that do not have motions. And we reduced the possibilities falling into the local minima in the course of estimation of motion vectors by applying DFD to DS algorithm. So, we knew that proposed constrained DS algorithm achieved enhanced results as aspects of error ratio and the number of search points to be necessary compared with conventional DS algorithm, four step search (FSS) algorithm, and block-based gradient-descent search algorithm

• Journal of the Korean Geotechnical Society
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• v.21 no.9
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• pp.77-86
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• 2005

Since slope sliding and loss of railway triggered by a rainfall produce instability in the operation of trains, a proper method to estimate the slope stability considering rainfall Is required. from the field study, sliding induced by rainfall depends on the engineering properties of soils, three dimensional aspect of the slope, rainfall intensity and geological conditions of the soil layers. In this study, among various types of sliding, slope Instability caused by the surface runoff water at the concave zones in a slope is investigated. The depth of runoff water is calculated by using the Rational method and Manning equation. The occurrence of runoff water is evaluated by a comparison between the calculated infiltration rate and rainfall intensity. Pressure heads which can be calculated from the modified Iverson model are used to calculate the factor of safety along the vertical depth of the slope. The modified Iverson model considers the depth of runoff water, thus the maximum hydraulic gradient along the depth of slope is greater than one.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.7
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• pp.3253-3260
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• 2014

Background: A case-control study was conducted to evaluate the effect of household exposure, dietary habits, smoking and Glutathione S-Transferases M1, T1 polymorphisms on lung cancer among women in Mizoram, India. Materials and Methods: We selected 230 newly diagnosed primary lung cases and 460 controls from women in Mizoram. Multivariate logistic regression analysis was performed to estimate adjusted odds ratio (OR). Results: Exposure of cooking oil fumes (p<0.003), wood as heating source for cooking (p=0.004), kitchen inside living room (p=0.001), improper ventilated house (p=0.003), roasting of soda in kitchen (p=0.001), current smokers of tobacco (p=0.043), intake of smoked fish (p=0.006), smoked meat (p=0.001), Soda (p<0.001) and GSTM1 null genotype (p=0.003) were significantly associated with increased risk of lung cancer among women in Mizoram. Significantly protective effect was observed for intake of bamboo shoots (p=<0.001) and egg (p<0.001). A clear increase in dose response gradient was observed for total cooking dish years. Risk for lung cancer tends to increase with collegial effect of indoor environmental sources (p=0.022). Significant correlation was also observed for interaction of GST polymorphisms with some of dietary habits. Conclusions: We confirmed the important role of exposure of cooking oil emission and wood smoke, intake of smoked meat, smoked fish and soda (an alkali preparation used as food additives in Mizoram) and tobacco consumption for increase risk of lung cancer among Women in Mizoram.

• The Journal of the Korea Contents Association
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• v.16 no.4
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• pp.614-623
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• 2016

Grid(pipe network) design is an important element of Smart Water Grid, which essential to estimate hydraulic parameters such as the pressure, friction factor, friction velocity, head loss and energy slope. Especially, friction velocity in a grid is an important factor in conjunction with energy gradient, friction coefficient, pressure and head loss. However, accurate estimation friction head loss, friction velocity and friction factor are very difficult. The empirical friction factor is still estimated by using theory and equation which were developed one hundred years ago. Therefore, in this paper, new equation from maximum velocity and friction velocity is developed by using integration relationship between Darcy-Weisbach's friction head loss equation and Schlichting equation and regression analysis. To prove the developed equation, smooth pipe data areis used. Proposed equation shows high accuracy compared to observed data. Study results are expected to be used in stability improvements and design in a grid.