• Journal of Biomedical Engineering Research
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• v.30 no.6
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• pp.503-509
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• 2009

The development of technology has led to ubiquitous health care service, which enables many patients to receive medical services anytime and anywhere. For the ubiquitous health care environment, real-time measurement of biomedical signals is very important, and the medical instruments must be small and portable or wearable. So, such devices have been developed to measure biomedical signals. In this study, we develop the biomedical monitoring device which is sensing the PPG signal, one of the useful signal in the field of ubiquitous healthcare. We design a watch-like biomedical signal monitoring system without a finger probe to prevent the user's inconvenience. This system obtains the PPG from the radial artery using a sensor in the wrist band. But, new device developed in this paper is easy to get the motion artifacts. So, we proposed new algorithm removing the motion artifacts from the PPG signal. The method detects motion artifacts by changing the degree of brightness of the light source. If the brightness of the light source is reduced, the PPG pulses will disappear. When the PPG pulses have disappeared completely, the remaining signal is not the signal that results from the changing blood flow. We believe that this signal is the motion artifact and call it the noise reference signal. The motion artifacts are removed by subtracting the noise reference signal from the input signal. We apply this algorithm to the system, so we can stabilize the biomedical monitoring system we designed.

• Journal of Digital Convergence
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• v.16 no.7
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• pp.259-265
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• 2018

Compartment models, a type of mathematical model, have been widely applied to characterize the changes in a dynamic system with sequential events or processes, such as the spread of an epidemic disease. A compartment model comprises compartments, and the relations between compartments are depicted as boxes and arrows. This principle is similar to that of the system dynamics (SD) approach to constructing a simulation model with stocks and flows. In addition, both models are structured using differential equations. With this mutual and translatable principle, this study, in terms of SD, translates a reference SEIR model, which was developed in a recent study to characterize the transmission of the Middle East respiratory syndrome (MERS) in South Korea. Compared to the replicated result of the reference SEIR model (Model 1), the translated SEIR model (Model 2) demonstrates the same simulation result (error=0). The results of this study provide insight into the application of SD relative to constructing an epidemic compartment model using schematization and differential equations. The translated SD artifact can be used as a reference model for other epidemic diseases.

• Journal of Chest Surgery
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• v.32 no.8
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• pp.693-701
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• 1999

Recently non-invasive diagnostic imaging replaced the invasive catheter angiography in the diagnosis of vascular disease. Catheter methods are now almost confined to the purpose of intervention. Coronary artery or coronary artery bypass graft still needs catheter technique because of small diameter and the cardiac motion. The last challenge for radiologists in this domain is to obtain a non-invasive imaging. Electron beam tomography(EBT) for high temporal resolution is able to obtain a coronary arteriogram or coronary artery bypass graft (CABG), of which CABG imaging is quite useful for the evaluation of patency. In our experience as well as others, the accuracy of EBT angiogram in evaluating CABG patency revealed that the accuracy of patency of saphenous vein grafts(SVG) is high due to relatively wide lumen, short and straight course and less influence from cardiac motion. The sensitivity and specificity of patency of SVGs were 92%, 97% respectively in the prospective evaluat on and 100% each in the retrospective evaluation. A false positive and a false negative case are rudimentary errors in the initial learing period. In contrast the analysis of left internal mammary artery(LIMA) graft was difficult due to the inherent small size and the adjacent surgical clips provoking beam-hardening artifact; therefore, the method of combining 3 dimensional reconstruction and flow mode study was important in improving the accuracy of LIMA patency. The sensitivity and specificity of LIMA patency were 100% and 80% in both prospective and retrospective evaluation. Therefore, EBT angiography is an accurate non-invasive diagnostic modality for evaluating the patency of CABG, particularly in SVGs. The accuracy can be improved with the improvement of the EBT and the development of the image reconstruction software.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6284-6289
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• 2013

With the application of k-space trajectory in a different manner and analyzing the influence of noise and its direction, this study was conducted to obtain high-quality images with minimal influence of noise during an MRI examination for cerebrovascular disease, which has a low signal for imaging. To evaluate influence of the noise of different k-space trajectories, a linear Cartesian coordination trajectory and non-Cartesian coordination trajectory were applied to 38 people who had received a high-resolution MRI examination for the early detection of cerebrovascular disease. As a result, the non-Cartesian coordination trajectory showed a 43.32% lower signal of lumens in the internal carotid artery than a linear Cartesian coordination trajectory, and the noise level was also 50.19% lower in a non-Cartesian coordination trajectory. This result shows that noise occurs less in a non-Cartesian coordination trajectory than a linear Cartesian coordination trajectory, and a non-Cartesian coordination trajectory is more effective in low-signal and low-resolution MRI examination. Therefore, when performing high-resolution MRI examination with a low-signal cerebrovascular system, the use of non-Cartesian coordination k-space trajectory will minimize the influence of noise and provide good images.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.2
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• pp.70-80
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• 2003

We report the first direct measurement of $CO_2$ flux over Kwangneung broadleaf deciduous forest, one of the tower flux sites in KoFlux network. Eddy covariance system was installed on a 30 m tower along with other meteorological instruments from June to August in 2002. Although the study site was non-ideal (with valley-like terrain), turbulence characteristics from limited wind directions (i.e., 90$\pm$45$^{\circ}$) was not significantly different from those obtained at simple, homogeneous terrains with an ideal fetch. Despite very low rate of data retrieval, preliminary results from our analysis are encouraging and worthy of further investigation. Ignoring the role of advection terms, the averaged net ecosystem exchange (NEE) of $CO_2$ ranged from -1.2 to 0.7 mg m$^{-2}$ s$^{-1}$ from June to August in 2002. The effect of weak turbulence on nocturnal NEE was examined in terms of friction velocity (u*) along with the estimation of storage term. The effect of low uf u* NEE was obvious with a threshold value of about 0.2 m s$^{-1}$ . The contribution of storage term to nocturnal NEE was insignificant; suggesting that the $CO_2$ stored within the forest canopy at night was probably removed by the drainage flow along the hilly terrain. This could be also an artifact of uncertainty in calculations of storage term based on a single-level concentration. The hyperbolic light response curves explained ＞80% of variation in the observed NEE, indicating that $CO_2$ exchange at the site was notably light-dependent. Such a relationship can be used effectively in filling up the missing gaps in NEE data through the season. Finally, a simple scaling analysis based on a linear flow model suggested that advection might play a significant role in NEE evaluation at this site.

• Journal of the Korean Society of Radiology
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• v.13 no.6
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• pp.879-887
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• 2019

The purpose of this study is to establish a physiological injection protocol according to body weight, in order to minimize amount of contrast medium and optimize contrast enhancement in pediatric patients performing thoracic CT examinations. The 80 pediatric patients under the age of 10 were studied. Intravenous contrast material containing 300 mgI/ml was used. The group A injected with a capacity of 1.5 times its weight, and groups B, C and D added 5 to 15 ml of normal saline with a 10% decrease in each. The physiologic model which can be calculated by weight about amount of injection of contrast medium and normal saline, flow rate and delay time were applied. To assess image quality, measured average HU value and SNR of superior vena cava, pulmonary artery, ascending and descending aorta, right and left atrium, right and left ventricle. CT numbers of subclavian vein and superior vena cava were compared to identify the effects of reducing artifacts due to normal saline. Comparing SNR according to the contrast medium injection protocol, significant differences were found in superior vena cava and pulmonary artery, descending aorta, right and left ventricle, and CT numbers showed significant differences in all organs. In particular, B group with a 10% decrease in contrast medium and an additional injection of saline showed a low degree of contrast enhancement in groups with a decrease of more than 20%. In addition, the group injected with normal saline greatly reduced contrast enhancement of subclavian vein and superior vena cava, and the beam hardening artifact by contrast medium was significantly attenuated. In conclusion, the application of physiological protocol for injection of contrast medium in pediatric thoracic CT examinations was able to reduce artifacts by contrast medium, prevent unnecessary use of contrast medium and improve the effect of contrast enhancement.