• The Journal of Korea Robotics Society
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• v.14 no.4
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• pp.293-300
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• 2019

In this paper, an Embedded solution for fast navigation and precise positioning of mobile robots by floor features is introduced. Most of navigation systems tend to require high-performance computing unit and high quality sensor data. They can produce high accuracy navigation systems but have limited application due to their high cost. The introduced navigation system is designed to be a low cost solution for a wide range of applications such as toys, mobile service robots and education. The key design idea of the system is a simple localization approach using line features of the floor and delayed localization strategy using topological map. It differs from typical navigation approaches which usually use Simultaneous Localization and Mapping (SLAM) technique with high latency localization. This navigation system is implemented on single board Raspberry Pi B+ computer which has 1.4 GHz processor and Redone mobile robot which has maximum speed of 1.1 m/s.

• IEMEK Journal of Embedded Systems and Applications
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• v.16 no.6
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• pp.285-292
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• 2021

Autonomous vehicles are divided into an upper controller that calculates control value through cognitive judgment and a lower controller that appropriately transmits its control value to an actuator. Here, the longitudinal control in a lower controller has a problem as the road slopes due to the property of the Acceleration sensor to output the acceleration as the slope of the device. Therefore, in this paper, a sigmoid function is proposed to determine the slope to compensate for this problem. Through the experiment, Checked performance by comparing the existing table model with the proposed model.

• Bulletin of the Korean Chemical Society
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• v.21 no.3
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• pp.300-304
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• 2000

The B3LYP method based on the density functional theory(DFT) is shown to be much better than the ab initio MP2 method for structural determination of diphosphadithiatetrazocine systems having transannular S--S bonding. The presence of bonding between the two sulfur atoms across the cyclic ring is theoretically confirmed in the case of the neutral diphosphadithiatetrazocine. The S--S dobding disappears in the ionized species. The planarity of the dicationic heterocyclic ring system turns out to be closely associated with the $\pi-electron$ delocalization over the entire ring as well as the N-S-N bonds, which become stiffened upon ionizaiton. In the case of dianionic species, the chair-boat and chair conformers are nearly degenerate and far more stable than the crown conformer.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.168.2-168.2
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• 2003

Akt/Ptotein Kinase B (PKB) is a serine/threonine kinase and activated by PI3K pathway. Akt/PKB regulates a variety of cellular responses including proliferations, differentiations and insulin signaling pathway. Recent evidence also indicates that the abnormal activities or expression of Akt/PKB is closely associated with cancer, diabetes and neuro-degenerative diseases. These findings mean that Akt/PKB is likely to be a new therapeutic target for the treatment of disease. (omitted)

• International journal of advanced smart convergence
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• v.10 no.1
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• pp.56-61
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• 2021

Neighbor path selection is to pre-select alternate routes in case geographically correlated failures occur simultaneously on the communication network. Conventional heuristic-based algorithms no longer improve solutions because they cannot sufficiently utilize historical failure information. We present a novel solution model for neighbor path selection by using machine learning technique. Our proposed machine learning neighbor path selection (ML-NPS) model is composed of five modules- random graph generation, data set creation, machine learning modeling, neighbor path prediction, and path information acquisition. It is implemented by Python with Keras on Tensorflow and executed on the tiny computer, Raspberry PI 4B. Performance evaluations via numerical simulation show that the neighbor path communication success probability of our model is better than that of the conventional heuristic by 26% on the average.

• Electronics and Telecommunications Trends
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• v.38 no.1
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• pp.36-45
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• 2023

The increasing demand for ultra-high efficiency of compact power conversion systems for electric vehicle applications has brought GaN power semiconductors to the fore due to their low conduction losses and fast switching speed. In particular, the development of materials and core device processes contributed to remarkable results regarding the publication of vertical GaN power devices with high breakdown voltage. This paper reviews recent advances on GaN material technology and vertical GaN power device technology. The GaN material technology covers the latest technological trends and GaN epitaxial growth technology, while the vertical GaN power device technology examines diodes, Trench FETs, JFETs, and FinFETs and reviews the vertical GaN PiN diode technology developed by ETRI.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.57.4-58
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• 2020

The B-fields in Star-forming Region Observations (BISTRO) is a large program of the James Clerk Maxwell Telescope (JCMT) to study the roles of magnetic fields in molecular clouds on intermediate scales (a few thousands au or larger scales), in which a large number of researchers over the world are involved. This project was initiated in 2016 with polarimetric observations of nearby star-forming regions and has been extended toward massive and farther regions (BISTRO-2) and various evolutionary stages and environmental conditions (BISTRO-3). The current status of the BISTRO projects is reported. In addition, we discuss magnetic fields in the Serpens Main molecular cloud, which is one of the BISTRO star-forming regions. Utilizing the Histogram of Relative Orientations method, which compares polarization directions with density gradients, we show that magnetic fields are parallel to filaments in less dense filamentary structures but perpendicular to dense ones. Furthermore, the magnetic field directions with respect to density gradients vary again with density in denser core regions, which is understood by core formation and pinched fields. Note: (PI) D. Ward-Thompson, (co-PIs) P. Bastien, T. Hasegawa, W. Kwon, S. Lai, and K. Qiu

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.15 no.2
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• pp.182-187
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• 1986

Experimental measurements of the heat transfer and heat flux to a jet impinging on a heated surface were obtained in the nucleate boiling regimes. Tes-variables were jet at velocity and aspect ratio ($b/\ell$) of the heated surface. A slope of nucleate boiling curve increased with increasing the aspect ratio of the heated surface, namely approaching a rectangular square, and it is shown that surface tension has an important role for the onset of nucleate boiling heat transfer. A generalized correlation of the jet nucleate boiling heat transfer. A generalized correlation of the jet nucleate boiling heat transfer was found using a pi theorem.

• Proceedings of the Korea Information Processing Society Conference
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• 2024.05a
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• pp.229-230
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• 2024

최근 드론으로 극한 환경에서 범죄 수배자 및 실종자를 탐색하는 시도가 활발하다. 이때 생체 인증 기술인 얼굴 인증 기술을 사용하면 탐색 효율이 높아지지만, 암호화되지 않은 인증 프로토콜 적용 시 생체 정보 유출의 위험이 있다. 본 논문에서는 드론이 수집한 얼굴 이미지 템플릿을 암호화하여 안전하게 인증할 수 있는 효율적인 생체 인증 프레임워크인 DF-PPHDM(Privacy-Preserving Hamming Distance biometric Matching for Drone-collected Facial images)을 제안한다. 수집된 얼굴 이미지는 암호문 형태로 서버에 전달되며 서버는 기존 등록된 암호화된 템플릿과의 Hamming distance 분석을 통해 검증한다. 제안한 DF-PPHDM을 RaspberryPI 4B 환경에서 직접 실험하여 분석한 결과, 한정된 리소스를 소유한 드론에서 효율적인 구현이 가능하며, 인증 단계에서 7.83~155.03 ㎲ (microseconds)가 소요된다는 것을 입증하였다. 더불어 서버는 드론이 전송한 암호문으로부터 생체 정보를 복구할 수 없으므로 프라이버시 침해 문제를 예방할 수 있다. 향후 DF-PPHDM에 AI(Artificial Intelligence)를 결합하여 자동화 기능을 추가하고 코드 최적화를 통해 성능을 향상시킬 예정이다.

• Journal of Chest Surgery
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• v.32 no.5
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• pp.442-447
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• 1999

Introduction: Understanding the normal distribution of the tracheal diameter and crross- sectional area is one of the key elements in the management of various tracheal pathologies or tracheal reconstruction for the patients in growing age. However, data for Korean standard has been lacking. This study was designed to analyze retrospectively the distribution of tracheal diameter and cross-sectional area in young Koreans, which can afford fundamental data for the management of tracheal diseases. Material and Method: Of the patients who underwent computerized tomogram of the chest between May 1996 and August 1998, one hundred six young patients(age range: 0-20 years) were included. Patients with any conditions which might affect the tracheal cross-sectional area or diameter, such as tracheal disease, previous operation, mediastinal tumor, or obstructive lung disease were excluded from the study. Gender distribution was 69 males and 37 females. Tracheal diameters, anterior-posterior and transverse, were measured at the level of the thoracic inlet(level I) and the aortic arch(level II). Types of the trachea were divided into round, oval, or horseshoe shaped on cross-sectional view, and the dimension was calculated by using the equation of A=1/4$\pi$ab(A; area, $\pi$; 3.14, a; anterior-posterior diameter, b; transverse diameter). We analyzed the distribution of the diameter at each level and compared the cross-sectional area with respect to age and gender. A p-value lower than 0.05 wa considered significant. Result: The trachea of patients less than 5 years old were round in shape at both of level I and II, and no differences in cross-sectional area was observed between the levels(p=NS). As the age increased, the trachea become oval in shape at level I while it remained round in shape at level II(p=0.020). The tracheal diameter and cross-sectional area increased as the age increased with a linear correlation(r>0.9). In patients less than 5 years of age, female patients showed larger cross-sectional area than male patients (p=0.020), and it was reversed in patients older than 15 years of age(p=0.002). Conclusion: From the above results, we suggest chest computerized tomogram as a safe and reliable tool in measuring the tracheal diameter and cross-sectional area. We also provide the data as a standard for distribution of the tracheal diameter and cross-sectional area in young Korean population.