• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 춘계학술대회
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• pp.179-183
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• 1996

Most of the conventional electrocardiogaphies fail to detect signals other than P-QRS-T due to the limited SNR and bandwidth. High-resolution electrocardiography (HRECG) provides better SNR and wider bandwidth for the detection of micro-potentials with higher frequency components such as ventricual late potentials(LP). In this paper, we developed a HRECG using uncorrected XYZ lead. The overall gain of the amplifier is 4000 and the bandwidth is $0.5{\sim}300Hz$ without using 60Hz notch filter. Three 16-bit AH converters sample X, Y, and Z signals simultaneously with a sampling frequency of 2000Hz. Sampled data are transmitted to PC via a DMA-controlled serial communication channel using RS-485 and HDLC protocol. The noise level of the developed HRECG is less than $5{\mu}V_{rms,\;RTI}$. In order to further reduce the noise level, signal averaging technique is implemented utilizing template matching method. The SNR of the developed HRECG is high enough for the detection of LP.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.146-147
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• 2007

We present full 3-D simulation of dielectrophoretic (DEP) deflection of particle trajectory in micro channel and compare the simulation results with experimental results. In simulation, the particle 3-D movements along x, y and z-axis are simulated precisely, and the streamlines of particles movements and the change of particle height are investigated experimentally. Therefore, the deflection performance is investigated on the designed and fabricated deflection microchip.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.228-228
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• 2002

The DLS(Data Link System) is located in the PDTS(Payload Data Transmission Subsystem) of KOMPSAT-II, and its main function is to provide communication link with Ground Segment as a space segment. DLS receive the data of MSC, OBC from DCSU(Data Compression Storage Unit) and transmit to the Ground Station by X-Band RF link. DLS is consist of CCU(Channel Coding Unit), QTX(QPSK Transmitter, ASU(Antenna Switch Unit) CCU makes a packet for communication after several kind of data processing such like Ciphering, RS Coding. QTX transmit PDTS data by OQPSK. Modulation. ASU is the unit for reliability of antenna switching. So, DLS's function is consists of ciphering, RS coding, CCSDS packetizing, randomizing, modulation and switching to antenna. These DLS's functions are controlled by PMU(Payload Management Unit). All commands to DLS are sent by PMU and all telemetries of DLS are sent to the PMU. The PMU receives commands from OBC and sends telemetries to the OBC. The OBC communicates with Ground Station by S-Band RF link. This paper presents the on-orbit DLS operation concept through the ground segment.

• 대한기계학회논문집B
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• 제26권2호
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• pp.345-352
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• 2002

A suboptimal control law in turbulent pipe flow is derived and tested. Two sensing variables ∂p/∂$\theta$│$\_$w/ and ∂v$\_$$\theta$/∂γ│$\_$w/ are applied with two actuations ø$\_$$\theta$/ and ø$\_$γ/. To test the suboptimal control law, direct numerical simulations of turbulent pipe flow at Re$\_$$\tau$/=150 are performed. When the control law is applied, a 13∼23% drag reduction is achieved. The most effective drag reduction is made at the pair of ∂v$\_$$\theta$/∂γ│$\_$w/ and ø$\_$γ/. An impenetrable virtual wall concept is useful for analyzing the near-wall suction and blowing. The virtual wall concept is useful for analyzing the near-wall behavior of the controlled flow. Comparison of the present suboptimal control with that of turbulent channel flow reveals that the curvature effect is insignificant.

• Geomechanics and Engineering
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• 제13권6호
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• pp.947-961
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• 2017

An innovative spiral variable-section capillary model is established for piping critical hydraulic gradient of cohesion-less soils causing water/mud inrush in tunnels. The relationship between the actual winding seepage channel and grain-size distribution, porosity, and permeability is established in the model. Soils are classified into coarse particles and fine particles according to the grain-size distribution. The piping critical hydraulic gradient is obtained by analyzing starting modes of fine particles and solving corresponding moment equilibrium equations. Gravities, drag forces, uplift forces and frictions are analyzed in moment equilibrium equations. The influence of drag force and uplift force on incipient motion is generally expounded based on the mechanical analysis. Two cases are studied with the innovative capillary model. The critical hydraulic gradient of each kind of sandy gravels with a bimodal grain-size-distribution is obtained in case one, and results have a good agreement with previous experimental observations. The relationships between the content of fine particles and the critical hydraulic gradient of seepage failure are analyzed in case two, and the changing tendency of the critical hydraulic gradient is accordant with results of experiments.

• Korean Journal of Chemical Engineering
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• 제35권12호
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• pp.2487-2495
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• 2018

Inspired by the specific amino acid sequence Asn-Pro-Ala (NPA) of water channel aquaporins (AQPs), we fabricated polyamide (PA) nanofiltration (NF) membranes by introducing reduced glutathione (GSH) in interfacial polymerization (IP) method. Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectrometry (XPS), scanning electron microscope (SEM), atomic force microscopy (AFM), zeta potential and static water contact angle measurement were employed to characterize the chemical composition, morphology, electronegativity and hydrophilicity of the NF membranes. The water flux of GSH/PIP-TMC NF membrane reached $32.00L\;m^{-2}h^{-1}$ at 0.2 MPa, which was approximately twice than that of pristine PIP-TMC NF membrane when the ratio of GHS to piperazidine (PIP) was 40% during IP process. More water channels were built as GSH was embedded into PA layer. The fabricated NF membranes also took on potent rejection for dyes and $Na_2SO_4$. This study presents a simple and facile method to simulate water channels-based biological materials which may find potential application in water treatment.

• 대한원격탐사학회지
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• 제18권4호
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• pp.201-207
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• 2002

복사전달모델과 KOMPSAT-1/OSMI 자료를 이용하여 황사함지 가능성을 조사하였다. 그리고 황사탐지를 위한 OSMI의 특성을 파악하기 위하여 OSMI와 SeaWiFS의 자료를 이용하여 공간 분광분석과 채널별 스펙트럼 분석을 실시하고, 또한 에어로솔 광학두께를 상호 비교하였다. OSMI와 SeaWiFS 자료를 이용한 x축 방향의 분광분석 결과, 865nm에서 분광특성이 비슷함을 알 수 있었고, 채널별 스펙트럼 분석에서는 765nm과 865nm에서 SeaWiFS의 결과와 비슷하여 이 밴드에서의 OSMI 자료의 활용 가능성을 확인할 수 있었다. 이들 밴드를 이용하여 산출한 OSMI의 황사탐지 화상은 MODIS에서 얻어진 화상과 비슷함을 알 수 있었다. 황사 때의 광학두께는 약 0.8~l.0으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제17권10호
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• pp.919-924
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• 1996

Crystal structure of two inclusion compounds Cd(pn)Ni(CN)4·0.25G (G=toluene and p-xylene, pn=1,2-diaminopropane) have been determined from single-crystal X-ray diffraction data; toluene clathrate: monoclinic P21/n, a=13.838(6), b=26.893(5), c= 7.543(5) Å, γ=90.92(3)°, Z=4, R=0.0616; p-xylene clathrate: monoclinic P21/n, a=13.895(2), b=26.900(3), c=7.613(1) Å, γ=91.06(1)°, Z=4, R=0.0486. The host structures determined for toluene- and pxylene-guest clathrates are substantially identical to the U-type structures observed for the straight chain aliphatic-guest clathrates. However, the alternating arrangement of occupied channels with the guest molecules and vacant channels appears in the host structure. The non-centrosymmetric toluene molecules are distributed about the inversion center to give an image like p-xylene molecule. The guests, toluene and p-xylene, prefer the U-type channel, favoring the interaction between the π-electrons of the aromatic ring and the pn-amino groups to hold the aromatic ring vertical to the cyanometallate meshes.

• Advances in Energy Research
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• 제3권2호
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• pp.81-95
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• 2015

Microgrid, which can be considered as an integration of various dispersed resources (DRs), is characterized by number of DRs interfaced through the power electronics converters. The microgrid comprising these DRs is often operated in an islanded mode. To minimize the cost, reduce complexity and increase reliability, it is preferred to avoid any communication channel between them. Consequently, the droop control method is traditionally adopted to distribute active and reactive power among the DRs operating in parallel. However, the accuracy of distribution of active and reactive power among the DRs controlled by the conventional droop control approach is highly dependent on the value of line impedance, R/X i.e., resistance to reactance ratio of the line, voltage setting of inverters etc. The limitations of the conventional droop control approach are demonstrated and a modified droop control approach to reduce the effect of impedance mis-match and improve the time response is proposed. The error in reactive power sharing is minimized by inserting virtual impedance in line with the inverters to remove the mis-match in impedance. The improved time response is achieved by modifying the real-power frequency droop using arctan function. Simulations results are presented to validate the effectiveness of the control approach.

• 대한조선학회논문집
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• 제42권5호
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• pp.427-434
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• 2005

The free surface influenced the wake behind a rotating propeller and its effects were investigated experimentally in a circulating water channel with the variation of water depth. Instantaneous velocity fields were measured using two-frame PIV technique and ensemble-averaged to study the phase-averaged flow structure in the wake region. For an isolated propeller, the flow behind the propeller is affected only by the propeller rotation speed, the leading on the blades and the proximity of the propeller to the free surface. The phase-averaged mean velocity fields show that the potential wake and the viscous wake developed on the blade surfaces. The interaction between the tip vortices and the slipstream causes the oscillating trajectory of tip vortices. The presence of the free surface greatly affected the wake structure, especially for propeller immersion depth of 0.6D. At small immersion depths, the free surface modified the tip and trailing vortices and the slipstream flow structure downstream of X/D = 0.3 in the propeller wake.