• Investigative Magnetic Resonance Imaging
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• 제21권3호
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• pp.171-176
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• 2017

Purpose: To compare different MR sequences for quantification of gadolinium concentration. Materials and Methods: Gadolinium contrast agents were diluted into 36 different concentrations. They were scanned using gradient echo (GRE) and ultrashort echo time (UTE) and R1, $R2^*$ and phase values were estimated from collected data. For analysis, ROI masks were made for each concentration and then ROI value was measured by mean and standard deviation from the estimated quantitative maps. Correlation analysis was performed and correlation coefficient was calculated. Results: Using GRE sequence, R1 showed a strong linear correlation at concentrations of 10 mM or less, and $R2^*$ showed a strong linear correlation between 10 to 100 mM. The phase of GRE generally exhibited a negative linear relationship for concentrations of 100 mM or less. In the case of UTE, the phase had a strong negative linear relationship at concentrations 100 mM or above. Conclusion: R1, which was calculated by conventional GRE, showed a high performance of quantification for lower concentrations, with a correlation coefficient of 0.966 (10 mM or less). $R2^*$ showed stronger potential for higher concentrations with a correlation coefficient of 0.984 (10 to 100 mM), and UTE phase showed potential for even higher concentrations with a correlation coefficient of 0.992 (100 mM or above).

• 한국생산제조학회지
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• 제19권2호
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• pp.241-250
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• 2010

A recurrent adaptive model-free intelligent control with a friction estimation law is proposed to enhance the positioning performance of the mover in PMLSM system. For the PMLSM with nonlinear friction and uncertainty, an adaptive recurrent fuzzy neural network(ARFNN) and compensated control law in $H_{\infty}$ performance criterion are designed to mimic a perfect control law and compensate the approximated error between ideal controller and ARFNN. Combined with friction observer to estimate nonlinear friction parameters of the LuGre model, on-line adaptive laws of the controller and observer are derived based on the Lyapunov stability criterion. To analyze the effectiveness our control scheme, some simulations for the PMLSM with nonlinear friction and uncertainty were executed.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.243-246
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• 2006

본 논문은 골밀도 진단시스템의 원격 진료를 위한 시스템구축에 관한 논문이다. GRE VPN을 이용하여 프로세싱 자원 소모를 줄였으며, 귀중한 IP 주소를 효율적으로 이용할 수 있도록 구성하였다. GRE 터널링을 사용함으로써 네트워크의 기밀성을 유지하였고 Source 자체가 공개된 LINUX를 낮은 사양의 H/W에 포팅 하여 저가격을 실현함으로써 원격의료망을 작은 예산으로 구축할 수 있는 시스템을 제시하였다.

• International Journal of Advanced Culture Technology
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• 제9권1호
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• pp.218-223
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• 2021

Pervasive enhancement and required enforcement of the Internet of Things (IoTs) in a distributed massively multiplayer online architecture have effected in massive growth of Big-Data in terms of server over-load. There have been some previous works to overcome the overloading of server works. However, there are lack of considered methods, which is commonly applicable. Therefore, we propose a combing Sparse Auto-Encoder and Load-Balancing, which is ProGReGA for Big-Data of server loads. In the process of Sparse Auto-Encoder, when it comes to selection of the feature-pattern, the less relevant feature-pattern could be eliminated from Big-Data. In relation to Load-Balancing, the alleviated degradation of ProGReGA can take advantage of the less redundant feature-pattern. That means the most relevant of Big-Data representation can work. In the performance evaluation, we can find that the proposed method have become more approachable and stable.

• 한국방사선학회논문지
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• 제12권4호
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• pp.475-480
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• 2018

하복부 MRI 검사에서 환자는 body array coil과 물리적으로 접촉하여 검사를 받는다. 이 연구에서는 아크릴 보조장치(ACR)를 설계하여 코일과 환자의 비접촉식 스캔을 가능하게하고, ACR을 이용해서 획득 한 영상을 ACR 없이 얻은 영상와 비교하여 실현 가능성을 평가하였다. Ingenia 3.0TTM MR 시스템과 dStreamTM torso coil (Philips Healthcare, Netherlands)을 사용하여 10건(F : 5, m : 5)을 테스트하였다. 대표적인 두가지 pulse sequence(T1 AXE TSE, eTHRIVE (GRE))를 사용하여, 스캔 한 영상을 정량적, 정성적으로 비교 분석 하였다. 정성적으로 보면, TSE는 ACR의 유무에 관계없이 4.44와 4.56의 평균값을, GRE에서는 각각 4.34와 4.28을 보여준다. 정량적으로, TSE는 ACR 유무에 관계없이 12.15 CNR, 17.95 SNR 및 12.71 CNR, 18.96 SNR을 보였으며, GRE는 ACR이 있는 경우와 없는 경우 각각 17.72 CNR, 22.59 SNR 및 18.26 CNR, 24.47 SNR을 보여주었다. 즉, ACR의 사용이 환자를 편안하게 하지만, 화질에는 큰 영향이 없음을 확인하였다. 우리는 하복부 환자의 MRI 검사용 아크릴 보조 장치를 설계하고 적용해보았다. 우리의 결과는 환자와의 물리적 접촉없이 현재의 복부 MRI 스캔과 유사한 이미지 품질을 얻을 수 있음을 보여주었다.

• Journal of Ginseng Research
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• 제41권4호
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• pp.602-607
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• 2017

Background: Panax ginseng is a traditional herb used for medicinal purposes in eastern Asia. P. ginseng contains various ginsenosides with pharmacological effects. In this study, floralginsenoside A (FGA), ginsenoside Rd (GRD), and ginsenoside Re (GRE) were purified from P. ginseng berry. Methods: Chemical structures of FGA, GRD, and GRE were determined based on spectroscopic methods, including fast atom bombardment mass spectroscopy, ID-nuclear magnetic resonance, and infrared spectroscopy. Inhibitory activities of these compounds on melanogenesis were studied by measuring the expression of protein and melanin content in the melan-a cell line. This inhibitory activity was confirmed by observing pigmentation and tyrosinase activities of zebrafish. Results: GRD, GRE, and FGA were not cytotoxic at concentrations less than $20{\mu}M$, $80{\mu}M$, and $160{\mu}M$ in melan-a cells, respectively. GRD, GRE, and FGA inhibited melanin biosynthesis in melan-a cells by 15.2%, 22.9%, and 23.9% at $20{\mu}M$, $80{\mu}M$, and $160{\mu}M$, respectively. FGA was observed to display the most potent inhibitory effect. In addition, FGA decreased microphthalmia-associated transcription factor protein expression in a dose-dependent manner. Moreover, FGA induced extracellular signal-regulated kinase phosphorylation level in melan-a cells. In addition, melanin pigment content and tyrosinase activity in zebrafish treated with FGA at $160{\mu}M$ were reduced. Conclusion: FGA showed the most potent inhibition of melanogenesis in both in vitro and in vivo studies. This study suggests that FGA purified from P. ginseng may be an effective melanogenesis inhibitor.

• 한국해양학회지:바다
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• 제24권1호
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• pp.106-127
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• 2019

국가해양생태계종합조사의 일환으로 우리나라의 주요 하천인 한강, 금강, 낙동강 하구역에 서식하는 저서동물 군집 특성을 파악하였다. 현장조사는 2015년부터 2017년에 걸쳐 매 계절별(겨울: 2월, 봄: 5-6월, 여름: 7-9월, 가을: 11월)로 수행하였다. 시료채집은 한강 하구역에 7개, 금강 하구역에 6개, 낙동강 하구역에 7개의 정점을 설정하여 총 20개의 정점에서 수행되었다. 대형저서동물 채집은 van Veen grab(채집면적 $0.1m^2$)을 사용하여 각 정점 당 3회씩 반복채집 후 1 mm 망목의 표준체를 이용하여 펄을 제거하였다. 조사결과 총 1,008종의 저서동물이 출현하였으며 한강 하구역에서 602종, 금강 하구역에서 612종, 낙동강 하구역에서 619종이 출현하여 유사한 양상을 보였다. 평균 밀도는 $1,357ind./m^2$로서 한강 하구역에서 $1,127ind./m^2$, 금강 하구역에서 $1,357ind./m^2$ 및 낙동강 하구역에서 $1,587ind./m^2$으로 한강 하구역이 가장 낮고 낙동강 하구역이 가장 높았다. 평균 생체량은 $116.8g/m^2$으로 한강 하구역에서 $49.0g/m^2$, 금강 하구역에서 $129.0g/m^2$ 및 낙동강 하구역에서 $174.2g/m^2$이 출현하여 밀도와 유사한 양상을 보였다. 한강과 금강, 낙동강 하구역 모두 환형동물이 출현종수와 밀도에서 우점 분류군이었다. 한강과 금강 하구역에서는 연체동물이, 낙동강 하구역에서는 극피동물이 생체량 우점 분류군이었다. 각 하구역에서 4% 이상의 밀도 점유율을 보이는 우점종은 모두 다모류로서 한강 하구역의 경우 Dispio oculata와 Heteromastus filiformis, Aonides oxycephala였으며, 금강 하구역에서는 Heteromastus filiformis와 Scoletoma longifolia, 낙동강 하구역에서는 Pseudopolydora sp.와 Aphelochaeta sp.였다. 이러한 우점종들은 하구역에 따라 출현밀도의 차이가 있었다. 본 연구 결과 한강 하구역에서는 평균 입도, 금강 하구역에서는 염분 및 실트함량, 낙동강 하구역에서는 염분, 용존산소, 강열감량, 실트 함량이 군집 조성에 영향을 미치고 있었다. 따라서 한강 하구역의 경우 퇴적환경 변화를 초래하는 요인들(골재채취, 제방축조, 매립 등)에 대한 관리가 우선되어야 할 것으로 판단되며, 금강 하구역에서는 금강으로부터의 담수유입 및 주변 퇴적 환경에 변화를 줄 수 있는 요인들에 대한 관리가 우선시 되어야 할 것으로 보인다. 또한 낙동강 하구역의 경우 마산만 내측의 빈산소수괴 발달 양상과 주요 우점종의 공간분포에 대한 모니터링을 중점적으로 해야 할 것으로 판단된다.

• 한국정밀공학회지
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• 제24권8호통권197호
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• pp.81-88
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• 2007

This paper presents the development of a new inchworm actuation system using the shearing deformation of the piezoelectric actuators. In this new actuation system, piezoelectric shearing/expanding actuators, an inertial mass and an advanced preload system are configured innovatively to generate the motion of an inertial mass. There are two modes in the new actuation system: (1) stick mode, and (2) clamp mode. In stick mode, the deformation of the piezoelectric shearing actuators drives an inertial mass by means of the friction force at their contact interface. On the other hand, in clamp mode, the piezoelectric expanding actuators provide the gripping force to an inertial mass and, as a result, eliminate its backward motion following the rapid backward deformation of the piezoelectric shearing actuators. To investigate the feasibility of the proposed new actuation system, the experimental system is built up, and the static performance evaluation and dynamic analysis are conducted. The open-loop performance of the linear motion of the proposed new actuation system is evaluated. In dynamic analysis, the mathematical model for the contact interface is established based on the LuGre friction model and the equivalent parameters are identified.

• 한국정밀공학회지
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• 제25권12호
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• pp.89-99
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• 2008

In this paper, the position tracking control problem of the servo system with nonlinear dynamic friction is issued. The nonlinear dynamic friction contains a directly immeasurable friction state variable and the uncertainty caused by incomplete parameter modeling and its variations. In order to provide the efficient solution to these control problems, we propose the composite control scheme, which consists of the robust friction state observer, the FNN approximator and the approximation error estimator with sliding mode control. In first, the sliding mode controller and the robust friction state observer is designed to estimate the unknown internal state of the LuGre friction model. Next, the FNN estimator is adopted to approximate the unknown lumped friction uncertainty. Finally, the adaptive approximation error estimator is designed to compensate the approximation error of the FNN estimator. Some simulations and experiments on the servo system assembled with ball-screw and DC servo motor are presented. Results show the remarkable performance of the proposed control scheme. The robust friction state observer can successfully identify immeasurable friction state and the FNN estimator and adaptive approximation error estimator give the robustness to the proposed control scheme against the uncertainty of the friction parameters.

• 한국공작기계학회논문집
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• 제18권1호
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• pp.90-102
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• 2009

In this paper, a tracking control problem for a mechanical servo system with nonlinear dynamic friction is treated. The nonlinear friction model contains directly immeasurable friction state and the uncertainty caused by incomplete modeling and variations of its parameter. In order to provide the efficient solution to these control problems, we propose a hybrid control scheme, which consists of a robust friction state observer, a RFNN estimator and an approximation error estimator with sliding mode control. A sliding mode controller and a robust friction state observer is firstly designed to estimate the unknown infernal state of the LuGre friction model. Next, a RFNN estimator is introduced to approximate the unknown lumped friction uncertainty. Finally, an adaptive approximation error estimator is designed to compensate the approximation error of the RFNN estimator. Some simulations and experiments on the mechanical servo system composed of ball-screw and DC servo motor are presented. Results demonstrate the remarkable performance of the proposed control scheme.