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李明賢,崔閏和 弘益大學校 科學技術硏究所 2005 科學技術硏究論文集 Vol.16 No.-
This paper presents a coverage-aware, energy-efficient node scheduling scheme for wireless sensor networks. It identifies redundant nodes using a coverage-aware scheme to reduce redundant data transmissions and to use their energy for communication to the base station. Simulation results show that the proposed scheme can noticeably improve system lifetime while maintaining sensing coverage.
( Myeong Su Chu ),( Hyeon Jeong Yun ),( Myeong Jun Song ),( Seung Won Jung ),( Young Seok Kim ),( Si Hyun Bae ),( Jong Young Choi ),( Sang Wook Choi ),( Seung Kew Yoon ) 대한간학회 2016 춘·추계 학술대회 (KASL) Vol.2016 No.1
Aims: Biopsy is still the gold standard for the diagnosis of nonalcoholic steatohepatitis (NASH) but the definition may vary in evaluation of biopsies for clinical trials. Recently, a scoring system (steatosis, activity, fibrosis[SAF]) allowing the use of an algorithm (fatty liver inhibition of progression [FLIP]) reported for the classification of liver injury in morbid obesity. We evaluated the application of SAF score and FLIP algorithm in Korean patients with nonalcoholic fatty liver disease (NAFLD). Methods: We analyzed the 126 patients with biopsy-proven NAFLD in 5 centers in Korea from Aug, 2008 to April, 2016. Results: In total study populations, 56 patients (44.4 %) were diagnosed to NASH, 70 (55.6%) as NAFLD including 60 patients of a gray zone (NAS 3-4) according to NAS scoring system. Based FLIP algorithms, 72 patients (57.1 %) were categorized as NASH, 54 (42.9 %) as NAFLD. 21 patients (35%) in gray zone (NAS 3-4) and 5 patients (NAS ≥5) were categorized as NASH and steatosis, respectively. The activity score (ballooning+ lobular inflammation) enabled discriminating NASH. All patients with NASH had A ≥3, whereas 3 patients (5.2%) with A2 had NASH. Especially, the presence of ballooning in activity score was the significant factor to discriminate NASH and steatosis. This activity score was also closely correlated with both alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and Fragmented cytokeratin-18, respectively (P=0.000, 0.023, 0.006 respectively). Fibrosis grade by SAF score was significantly correlated with NAFLD fibrosis score and fibroscan (P=0.026, 0.000, respectively). Conclusions: The FLIP algorithm and SAF score system in the NAFLD may provide the favorable tools in Korean patients. Among the SAF score, the ballooning of hepatocyte may be an important factor to discriminate NASH and NAFLD, although it is one of the major limitations of liver biopsy.
무선 센서 네트워크에서 동시다발적으로 발생하는 허위 보고서 주입 공격과 웜홀 공격에 대한 보안 기법
최현명(Hyeon-Myeong Choi),조대호(Tae-Ho Cho) 한국지능시스템학회 2010 한국지능시스템학회 학술발표 논문집 Vol.20 No.2
본 논문은 무선 센서 네트워크에서 센서 노드의 특징과 취약점을 이용하여 발생 가능한 다양한 공격 기법 중허위 보고서 주입 공격과 웜홀 공격이 동시다발적으로 발생하는 경우에 이를 효율적으로 탐지하고 방어하기 위한 기법을 제안한다. 기존의 제안된 기법들은 각각의 공격에 대한 방어만을 고려하여 실제 네트워크에서 동시다발적으로 발생하는 공격에 대한 방어는 불가능 하였다. 제안 기법은 메시지 확인 응답을 통하여 허위보고서의 여과 단계와 웜홀 노드의 검출 단계를 수행 한다. 또한 검출된 허위 보고서는 즉시 제거되고 웜홀 노드가 검출이 되면 메시지의 전달 경로를 효율적으로 수정하여 에너지 효율성을 유지하는 동시에 높은 수준의 보안성을 제공한다.
이종명(Jong-Myeong Lee),유현탁(Hyeon-Tak Yu),박규진(Gyu-Jin Park),최현철(Hyeon-Cheol Choi),최병근(Byeong-Keun Choi) 한국소음진동공학회 2015 한국소음진동공학회 논문집 Vol.25 No.7
This paper provides how to solve the problems analytically and experimentally that occur for testing the water injection pump under development. First of all, water injection pump, based on shaft system dynamic analysis, is verified by measuring the behavior of the shaft system. After the water injection pump is measured, the structural resonances which can cause excessive noise, degradation the equipment life and malfunction are found. Therefore, by changing the structural design, the resonance should be avoided. Application of the design variables to the experimentally resonance avoidance is difficult. So analytically, with application of the design variables, the design will be changed with mode analysis using FEM.
Hyeon-Jae Shin,Jang-Young Choi,Hyung-Il Park,Seok-Myeong Jang IEEE 2012 IEEE transactions on magnetics Vol.48 No.11
<P>This study is devoted to the analysis of the vibration characteristics of a permanent magnet synchronous motor (PMSM) through investigation into its electromagnetic vibration sources. For this purposed, we derive analytical solutions for the magnetic fields generated by permanent magnets (PMs) in terms of a magnetic vector potential and a two-dimensional (2-D) polar coordinate system. A 2-D permeance function is also introduced in order to consider slotting effects. The electromagnetic vibration sources such as torque ripple, cogging torque, and radial force density are analyzed using these solutions. The analytical results are validated extensively with finite element (FE) analyses. The fast Fourier transformation (FFT) analysis is employed for investigating the specific harmonic orders of the electromagnetic vibration sources that affect the vibration of the PMSM. Finally, mechanical modal analysis results and test results such as vibration measurements are obtained to confirm the validity of the analysis methods presented in this paper.</P>
All-carbon fiber-based chemical sensor: Improved reversible NO<sub>2</sub> reaction kinetics
Choi, Seon-Jin,Lee, Dong-Myeong,Yu, Hayoung,Jang, Ji-Soo,Kim, Min-Hyeok,Kang, Joon-Young,Jeong, Hyeon Su,Kim, Il-Doo Elsevier 2019 Sensors and actuators. B Chemical Vol.290 No.-
<P><B>Abstract</B></P> <P>All-carbon fiber-based chemiresistor is fabricated by assembling reduced graphene oxide (RGO) fiber and carbon nanotube (CNT) fiber as reversible NO<SUB>2</SUB> sensing layer and flexible heater, respectively. Both graphene oxide (GO) and CNT fibers were synthesized by wet-spinning technique facilitating lyotropic nematic liquid crystal (LC) property. Randomly entangled CNT fiber-based heater, which is embedded in one surface of colorless polyimide (cPI) film with thickness of ˜200 μm, exhibits high bending stability and heating property up to 100 °C. Single reduced graphene oxide (RGO) fiber obtained after heat treatment at 900 °C in H<SUB>2</SUB>/N<SUB>2</SUB> ambient was integrated on the CNT fiber-embedded cPI heater, thereby establishing a new type of all-carbon fiber sensing platform. As a result, accelerated NO<SUB>2</SUB> adsorption and desorption kinetics were achieved with RGO fiber at an elevated temperature. In particular, a 9.22-fold enhancement in desorption kinetic (<I>k</I> <SUB>des</SUB> = 8.85 × 10<SUP>–3</SUP> s<SUP>–1</SUP>) was observed at 100 °C compared with the desorption kinetic (<I>k</I> <SUB>des</SUB> = 0.96 × 10<SUP>–3</SUP> s<SUP>–1</SUP>) at 50 °C, which was attributed to the effective heating by CNT fiber networks. This work pioneered a research on the use of emerging carbonaceous fibers for potential application in wearable chemical detectors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel all-carbon fiber-based NO<SUB>2</SUB> sensor was fabricated for reliable environmental monitoring. Both RGO fiber and CNT fiber were synthesized by wet-spinning process, which is facile and compatible with large-scale production. </LI> <LI> Unique sensing architectures of 1D graphene fiber were achieved with nitrogen doping for NO<SUB>2</SUB> sensors. Highly conductive nitrogen-doped reduced graphene oxide (RGO) fiber was achieved with wrinkled surface morphology. </LI> <LI> CNT fibers were firstly demonstrated as heating networks for reversible NO<SUB>2</SUB> reaction. The CNT fibers with high electrical conductivity and mechanical stability are suitable for heating element to control the operating temperature of sensor. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Hyeon-Jae Shin,Jang-Young Choi,Yu-Seop Park,Min-Mo Koo,Seok-Myeong Jang,Hyungsuk Han IEEE 2014 IEEE transactions on magnetics Vol.50 No.11
<P>This paper examines the effects of the electromagnetic source on the vibration of a double-sided axial permanent magnet generator with a slotless stator depending on the ac and dc-load conditions. The slotless machine has no cogging torque. Most of the vibration originates from the torque ripple and axial force distributions, which result from the current load conditions. The 3-D finite element analysis results are compared with voltage, current, and torque measurements. The order tracking analysis of the vibration test data clearly demonstrates the dependence of the critical harmonics on the load conditions.</P>