• Proceedings of the KOR-BRONCHOESO Conference
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• 1981.05a
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• pp.4.3-5
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• 1981

The Silicone tracheal T-tube was designed to maintain an adequate tracheal airway as well as to provide support in the stenotic reconstituted or reconstructed trachea. This report is our experiences with using silicone T-tube which were successfully used to two cases with extensive laryngotracheal trauma, and one case with decannulation difficulty for 9 months. Authors strongly believe that silicone T-tube is an excellent device out of consideration for our experienced cases, though many techniques have been applied for the treatments of tracheal problems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2B
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• pp.133-142
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• 2007

WPANs are formed in relatively small area and a PNC that serves as a central control device plays an important role in the operation and organization of a piconet. Typical applications of WPANs are security system and health monitoring system. In these type of systems, guaranteeing realtime service is very important, and communications cannot take place when the PNC malfunctions. Thus, in this situation, it is necessary to elect a new PNC as soon as possible. For this reason, we propose distributed PNC election scheme that considers not only QoS support but also network connectivity to avoid possible network partition. Simulation results show proposed mechanism can select PNC with guaranteeing QoS and connectivity for a limited period.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1732-1739
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• 2018

With the explosion of digital devices, interaction technologies between human and devices are required more than ever. Especially, hand gesture recognition is advantageous in that it can be easily used. It is divided into the two groups: the contact sensor and the non-contact sensor. Compared with non-contact gesture recognition, the advantage of contact gesture recognition is that it is able to classify gestures that disappear from the sensor's sight. Also, since there is direct contacted with the user, relatively accurate information can be acquired. Electromyography (EMG) and force-sensitive resistors (FSRs) are the typical methods used for contact gesture recognition based on muscle activities. The sensors, however, are generally too sensitive to environmental disturbances such as electrical noises, electromagnetic signals and so on. In this paper, we propose a novel contact gesture recognition method based on Flexible Epidermal Tactile Sensor Array (FETSA) that is used to measure electrical signals according to movements of the wrist. To recognize gestures using FETSA, we extracted feature sets, and the gestures were subsequently classified using the support vector machine. The performance of the proposed gesture recognition method is very promising in comparison with two previous non-contact and contact gesture recognition studies.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.16 no.3
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• pp.23-32
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• 2012

Objectives: The objective of this study is to investigate and valuate currently provided database management systems (DBMS) of traditional Korean medical knowledge. Methods: We searched DBMS on the web and smart device application markets (Apple App Store and Google Play Store). Key words for searching were 'traditional medicine', 'acupuncture', 'moxibustion', 'herbal medicine', and '한의학'. We looked into each DBMS to find out its scopes and limits, and each was valuated according to its functionality, accessibility, and utility. Results: 186 DBMS of traditional Korean medical knowledge were investigated and 91% of them were applications for smart devices. Almost all DBMS provided acupuncture and herb information, and a small amount of DMBS provided prescription and research paper information. Functionality, accessibility, and utility valuation were performed by using scoring system from 0 to 2. Mean values of functionality, accessibility, and utility were 0.86, 1.29, and 1.09. Conclusions: On the whole, high accessibility and low functionality were found, and various data-calculating functions were not implemented. Further researches and developments about traditional Korean medical knowledge DBMS are necessary to provide correct traditional Korean medical information and to support the studies about Korean medicine.

• International Journal of Contents
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• v.16 no.1
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• pp.57-64
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• 2020

We sought to compare upper extremity muscle activity between handwriting on paper and touchscreen with dominant and non-dominant hands in younger adults (age 23.90±1.12) and the elderly (age 75.55±5.76). Muscle activity (percent of maximum voluntary contraction) in the biceps brachii muscle, triceps brachii muscle, flexor carpi ulnaris muscle, and extensor carpi ulnaris muscle was measured using an electromyography device. As a result, our data indicate that muscle activity is lower in younger adults than the elderly. Besides, muscle activity is lower in the dominant versus non-dominant hand, and lower when writing using a touchscreen than on paper. These results can be used to support recommending touchscreens in the elderly. Also, they can be used as baseline data for comparing the performance of non-paretic side and paretic side in patients relative to the central nervous system.

• Journal of Information Processing Systems
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• v.10 no.4
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• pp.618-627
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• 2014

Nowadays mobile users are using a popular service called Location-Based Services (LBS). LBS is very helpful for a mobile user in finding various Point of Interests (POIs) in their vicinity. To get these services, users must provide their personal information, such as user identity or current location, which severely risks the location privacy of the user. Many researchers are developing schemes that enable a user to use these LBS services anonymously, but these approaches have some limitations (i.e., either the privacy prevention mechanism is weak or the cost of the solution is too much). As such, we are presenting a robust scheme for mobile users that allows them to use LBS anonymously. Our scheme involves a client side application that interacts with an untrusted LBS server to find the nearest POI for a service required by a user. The scheme is not only efficient in its approach, but is also very practical with respect to the computations that are done on a client's resource constrained device. With our scheme, not only can a client anonymously use LBS without any use of a trusted third party, but also a server's database is completely secure from the client. We performed experiments by developing and testing an Android-based client side smartphone application to support our argument.

• Journal of Power Electronics
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• v.17 no.3
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• pp.601-609
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• 2017

Gallium nitride (GaN) power switching devices are promising candidates for high switching frequency and high efficiency power conversion due to their fast switching, low on-state resistance, and high-temperature operation capability. In order to facilitate the use of these new devices better, it is required to investigate the device characteristics and performance in detail preferably by comparing with various conventional silicon (Si) devices. This paper presents a comprehensive study of GaN high electron mobility transistor (HEMT) based non-isolated point-of-load (POL) synchronous buck converter operating at 2.7 MHz with a high step-down ratio (24 V to 3.3 V). The characteristics and performance of GaN HEMT and three different Si devices are analytically investigated and the optimal operating point for GaN HEMT is discussed. Zero-voltage switching (ZVS) is implemented to minimize switching loss in high switching frequency operation. The prototype circuit and experimental data support the validity of analytical and simulation results.

• Electrical & Electronic Materials
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• v.9 no.7
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• pp.719-726
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• 1996

DLTS measurements were performed to study the annealing induced changes of the trap centers in MOV and to shed more light on the stability mechanism of the MOV. Two electron traps, Ec-0.26[eV] and Ec-(O.2-0.3)[eV], were observed in the unannealed samples in large quantities(7-9 X 1014[CM 3]), whereas the three electron traps Ec-0.17 [eV], Ec-0.26[eV] and Ec-(O.2-0.3)[eV] were observed far less in the annealed samples. The minima in the Ec-0.26[eV] trap density, coupled with the presented results that unannealed devices are unstable whereas 600.deg. C annealed devices are most stable, suggests that the instability of the MOV under long term electrical stressing is related to the Ec-0.26[eV] trap. This results support that the ion migration model for the device instability where the Ec-0.26[eV] defects may be the interstitial zinc or the migrating ions. The interstitial zinc originated as a result of the nonstoichiometric nature of ZnO might cause the degradation of the I-V characteristics of the MOV with long term electrical stressing.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.71-79
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• 2008

In the manufacture of flat panel display devices, there is a strong demand for contactless glass panel handling devices that can manipulate a glass panel without contaminating or damaging it. To fulfill this requirement, an electrostatic suspension device far glass panels where the glass panel is supported by electrostatic forces without any mechanical contact is proposed. To implement the system with low cost and compactness, switched-voltage control scheme that is based on the relay feedback control is utilized. Relay feedback control method deploys only a single high-voltage power supply that can deliver a DC voltage of positive and/or negative polarity and thus high voltage amplifiers that are costly and bulky are not needed any more. It is shown that despite the inherent limit cycle property of the relay feedback based control, an excellent performance in vibration suppression is attained due to the presence of a relatively large squeeze film damping originating from the electrodes and levitated object. Using this scheme, a $100{\times}100mm^2$ glass panel was levitated stably with airgap variation decreasing down to $1\;{\mu}m$ at an airgap of $100\;{\mu}m$.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.6_spc
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• pp.714-720
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• 2016

Rubbing and misalignment are the most usual faults that occurs in rotating machinery and with them severe effect on power plant availability. Especially blade rubbing is hard to detect on FFT spectrum using the vibration signal. In this paper, the possibility of feature analysis of vibration signal is confirmed under blade rubbing and misalignment condition. And the lab-scale rotor test device provides the blade rubbing and shaft misalignment modes. Feature selection based on GA (genetic algorithm) is processed by the extracted feature of the time domain. Then, classification of the features is analyzed by using SVM (support vector machine) which is one of the machine learning algorithm. The results of features selection based on GA compared with those based on PCA (principal component analysis). According to the results, the possibility of feature analysis is confirmed. Therefore, blade rubbing and shaft misalignment can be diagnosed by feature of vibration signal.