• Smart Structures and Systems
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• 제7권5호
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• pp.365-378
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• 2011

Piezo-based active structural health monitoring (SHM) requires amplifiers specifically designed for capacitive loads. Moreover, with the increase in number of applications of wireless SHM systems, energy efficiency and cost reduction for this type of amplifiers is becoming a requirement. General lab grade amplifiers are big and costly, and not built for outdoor environments. Although some piezoceramic power amplifiers are available in the market, none of them are specifically targeting the wireless constraints and low power requirements. In this paper, a piezoceramic transducer amplifier for wireless active SHM systems has been designed. Power requirements are met by two digital On/Off switches that set the amplifier in a standby state when not in use. It provides a stable ${\pm}180$ Volts output with a bandwidth of 7k Hz using a single 12 V battery. Additionally, both voltage and current outputs are provided for feedback control, impedance check, or actuator damage verification. Vibration control tests of an aluminum beam were conducted in the University of Houston lab, while wireless active SHM tests of a wind turbine blade were performed in the Harbin Institute of Technology wind tunnel. The results showed that the developed amplifier provided equivalent results to commercial solutions in suppressing structural vibrations, and that it allows researchers to perform active wireless SHM on moving objects with no power wires from the grid.

• 센서학회지
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• 제28권2호
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• pp.76-80
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• 2019

The characteristics of a titanium oxide layer prepared using a plasma electrolytic oxidation (PEO) process were investigated, using an extended gate ion sensitive field effect transistor (EG-ISFET) to confirm the layer's capability to react with hydrogen ions. The surface morphology and element distribution of the PEO-processed titanium oxide were observed and analyzed using field-emission scanning-electron microscopy (FE-SEM) and energy-distribution spectroscopy (EDS). The titanium oxide prepared by the PEO process was utilized as a hydrogen-ion sensing membrane and an extended gate insulator. A commercially available n-channel enhancement MOS-FET (metal-oxide-semiconductor FET) played a role as a transducer. The responses of the PEO-processed titanium oxide to different pH solutions were analyzed. The output drain current was linearly related to the pH solutions in the range of pH 4 to pH 12. It was confirmed that the titanium-oxide layer prepared by the PEO process could feasibly be used as a hydrogen-ion-sensing membrane for EGFET measurements.

• 동의생리병리학회지
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• 제35권5호
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• pp.177-184
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• 2021

The root bark of Morus alba L. (MA) used in traditional oriental medicine for the treatment of pulmonary diseases exerts various pharmacological activities including anticancer effects. In the current study, we investigated the effects of MA on the migration and invasion of colorectal carcinoma cells. Results from a transwell assay showed that the methylene chloride extract of MA (MEMA) suppressed the migration and invasion of HCT116 human colorectal carcinoma cells in a concentration-dependent manner. MEMA reduced both mRNA and protein levels of matrix metalloproteinase (MMP)-9, but did not suppress the expression of MMP-2 in HCT116 cells. As a molecular mechanism, MEMA inhibited the phosphorylation of mitogen-activated protein kinases (MAPKs), including ERK, JNK and p38, in a dose-dependent manner. In addition, MEMA dephosphorylated both Src and signal transducer and activator of transcription 3 (STAT3) in HCT116 cells. Taken together, we demonstrate that MEMA suppressed the migration and invasion capacity of HCT116 human colorectal cancer cells by downregulation of MMP-9 and inactivation of both MAPKs and Src/STAT3 signaling pathway.

• 대한기계학회논문집A
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• 제38권2호
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• pp.227-233
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• 2014

본 논문은 상용화된 와이어 본딩용 초음파 혼 시스템에서 발생하는 와이어 본딩 불량의 원인을 진동해석을 통하여 파악하고자 한다. 먼저 링 형상의 압전 구동기와 초음파 혼 그리고 캐필러리 등 각 부품의 진동 특성과 136kH의 가진 주파수 근처에서 발생하는 전체 초음파 혼 시스템의 주요 진동 모드들을 유한요소해석을 이용하여 구하였다. 136kHz에서 공진되는 전체 트랜스듀서 시스템의 진동 모드가 종진동 모드가 아닌 굽힘 진동 모드임을 조화 가진 해석과 실험으로 확인하였다. 136kHz에서 발생하는 굽힘 진동 모드는 캐필러리 끝단의 움직임이 종방향 뿐만 아니라 좌우 횡방향으로도 큰 변위가 발생하기 때문에 정밀 작업 시 본딩 불량의 원인이 될 수 있다. 가진 주파수 대역 근처인 119kHz에서 발생하는 종진동 모드는 캐필러리의 횡방향 진동이 감소하기 때문에 본딩 성능의 향상을 위해서 이러한 종진동 모드를 이용하도록 설계 변경이 필요함을 제시하였다.

• 조명전기설비학회논문지
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• 제20권4호
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• pp.43-48
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• 2006

풍력 발전 시스템과 태양광 발전 시스템을 상호 보완함으로써 안정적인 전력 공급과 에너지 이용 효율의 향상을 꾀할 수 있는 풍력-태양광 복합발전 시스템에 대한 관심이 고조되고 있다. 본 연구에서는 이러한 복합 발전 시스템을 효율적이고 안정적으로 운용하기 위하여 시스템의 각종 데이터들을 수집, 분석하고 파일로 저장하며 이를 인터넷을 이용하여 원격지에서도 모니터링 할 수 있는 시스템을 구축한다. 교류와 직류의 각종 전압, 전류들을 비롯한 풍속, 조도, 온도 등의 물리량을 측정하기 위하여 여러 형태의 변환기를 사용하였고 신호 조절 회로를 구성하였다. 데이터 수집 보드를 이용하여 컴퓨터로 데이터들을 저어 들였으며, 시스템 운용을 위한 서버 프로그램과 이를 원격지에서 실시간 모니터링 및 저장된 데이터들을 다운로드 할 수 있는 클라이언트 프로그램을 개발하였다. 측정된 데이터를 시간, 기상 등의 여러 조건과 연관하여 분석하였다.

• 한국의류산업학회지
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• 제21권6호
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• pp.697-707
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• 2019

This review paper deals with materials, classification, and a current article investigation on smart textile sensors for wearable vital signs monitoring (WVSM). Smart textile sensors can lose electrical conductivity during vital signs monitoring when applying them to clothing. Because they should have to endure severe conditions (bending, folding, and distortion) when wearing. Imparting electrical conductivity for application is a critical consideration when manufacturing smart textile sensors. Smart textile sensors fabricate by utilizing electro-conductive materials such as metals, allotrope of carbon, and intrinsically conductive polymers (ICPs). It classifies as performance level, fabric structure, intrinsic/extrinsic modification, and sensing mechanism. The classification of smart textile sensors by sensing mechanism includes pressure/force sensors, strain sensors, electrodes, optical sensors, biosensors, and temperature/humidity sensors. In the previous study, pressure/force sensors perform well despite the small capacitance changes of 1-2 pF. Strain sensors work reliably at 1 ㏀/cm or lower. Electrodes require an electrical resistance of less than 10 Ω/cm. Optical sensors using plastic optical fibers (POF) coupled with light sources need light in-coupling efficiency values that are over 40%. Biosensors can quantify by wicking rate and/or colorimetry as the reactivity between the bioreceptor and transducer. Temperature/humidity sensors require actuating triggers that show the flap opening of shape memory polymer or with a color-changing time of thermochromic pigment lower than 17 seconds.

• 한국항공우주학회지
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• 제38권10호
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• pp.992-997
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• 2010

과학기술위성3호(STSAT-3)용 홀추력시스템(HPS)의 추력제어모듈(PCM)은 압력정밀도 5%이하와 유량정밀도 3%이하를 목표로 한다. 압력제어기는 비례유량제어밸브(PFCV)와 저압압력센서를 사용하여 목표압력을 제어하도록 하고, 유량제어기는 PFCV와 홀추력기의 에노우드(anode) 전류를 이용하여 유량을 조절한다. 제어형태로는 비례,적분(PI) 제어기를 선택하고, PI 이득은 Matlab 시뮬레이션을 통하여 정한다. 시험결과 압력정밀도 <${\pm}$5%와 유량정밀도 <${\pm}$1.87%를 얻었다. 본 논문은 홀추력 제어모듈의 설계, 구현, 그리고 성능시험 결과를 기술한다.

• The Journal of Korean Physical Therapy
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• 제26권5호
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• pp.324-330
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• 2014

Purpose: The aim of the current study was to compare the muscle architecture of lower extremity using rehabilitative ultrasound imaging (RUSI) in young adults in Seoul and Hanoi. Methods: The study design was a comparative study of muscle cross-sectional area of lower extremity. Sixty healthy young subjects (Seoul group: 30, Hanoi group: 30) participated in this study. Real-time B-mode RUSI with a 7.5MHz linear transducer was used for measurement of cross-sectional area, pennation angle, and muscle thickness of the rectus femoris, tibialis anterior, and medial gastrocnemius muscles. Independent t-test was used for statistical analysis. Results: Significant difference in cross sectional area of rectus femoris was observed between Korean young adults and Hanoi young adults (p<0.01). Muscle thickness and pennation angle of tibialis anterior in Korean young adults were greater than in Hanoi young adults (p<0.01). In addition, the muscle thickness and pennation angle of the medial part of gastrocnemius muscle were greater in Korean young adults than in Hanoi young adults (p<0.01). In addition, in the results for gender, men had larger muscle architectures than women in both groups (p<0.01). Conclusion: This study, using RUSI, showed significant difference in muscle architectures of lower extremity in a diverse group of young adults RUSI.

• 대한본초학회지
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• 제27권4호
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• pp.9-16
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• 2012

Objective : Canavalia gladiata DC semen (CGS) have been used to improve hematopoietic activity. In the current study, we investigated whether CGS regulate hemato-potentiating function using hematopoietic stem cells (HSCs) as a testing system. Methods : HSCs isolated from femur in mice with leukopenia and thrombocytopenia induced induced by CTX. Then, Real-time PCR was performed to measure the mRNA expression and hematopoietic related gene (EPO, IL-3, SCF, c-kit, GM-CSF), the phoaphorylation of GATA-1 and STAT-5a/b were observed by ELISA method, and the number of granulocyte erythrocyte monocyte macrophage colony-forming units (CFU-GEMM) and erythroid burst forming units (BFU-E), semisolid clonogenic assay was performed. Result : When HSCs were treated with CGS, the expression of hematopoietic related genes (EPO, IL-3, SCF, c-kit, and GM-CSF) were significantly increased at the levels of mRNA as well as production in HSCs. Additionally, CGS enhanced phosphorylation of STAT-1 and signal transducer and activator of transcription-5a/b (STAT-5a/b) in HSCs. Furthermore, CGS significantly enhanced the growth rate of granulocyte erythrocyte monocyte macrophage colony-forming units (CFU-GEMM) and erythroid burst forming units (BFU-E) in vitro. Conclusion : These result suggest that CGS has hematopoietic enhancement via hematopoietic cytokine-mediated GATA-1/STAT-5a/b pathway.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.195-195
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• 2012

Recently, graphene based solution-gated field-effect transistors (SGFETs) have been received a great attention in biochemical sensing applications. Graphene and reduced graphene oxide (RGO) possess various advantages such as high sensitivity, low detection limit, label-free electrical detection, and ease of fabrication due to their 2D nature and large sensing area compared to 1D nanomaterials- based nanobiosensors. Therefore, graphene or RGO -based SGFET is a good potential candidate for sensitive detection of protons (H+ ions) which can be applied as the transducer in various enzymatic or cell-based biosensing applications. However, reports on detection of H+ ions using graphene or RGO based SGFETs have been still limited. According to recent reports, clean graphene grown by CVD or exfoliation is electrochemically insensitive to changes of H+ concentration in solution because its surface does not have terminal functional groups that can sense the chemical potential change induced by varying surface charges of H+ on CVD graphene surface. In this work, we used RGO -SGFETs having oxygen-containing functional groups such as hydroxyl (OH) groups that effectively interact with H+ ions for expectation of increasing pH sensitivity. Additionally, we also investigate RGO based SGFETs for bio-sensing applications. Hydroloytic enzymes were introduced for sensing of biomolecular interaction on the surface of RGO -SGFET in which enzyme and substrate are acetylcholinesterase (AchE) and acetylcholine (Ach), respectively. The increase in H+ generated through enzymatic reaction of hydrolysis of Ach by AchE immobilized on RGO channel in SGFET could be monitored by the change in the drain-source current (Ids).