• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.253-256
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• 2006

The HPFRCCs show the multiple crack and damage tolerance capacity due to the interfacial bonding of the fibers to the cement matrix. For practical application, it is needed to investigate the fractural behavior and of HPFRCCs and understand the micro-mechanism of cement matrix with reinforcing fiber. The objectives of this paper are to examine the compressive behavior, fracture and damage process of HPFRCC by acoustic emission technique. Total four series were tested, and the main variables were the hybrid type, polyethylene (PE) and steel cord (SC), and fiber volume fraction. The damage progress by compressive behavior of the HPFRCCs is characteristic for the hybrid fiber type and volume fraction. And from acoustic emission (AE) parameter value, it is found that the second and third compressive load cycles resulted in successive decrease of the ring-down count rate as compared with the first compressive load cycle.

• 대한임베디드공학회논문지
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• 제17권4호
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• pp.239-247
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• 2022

The existing studies on the localization in the GNSS (Global Navigation Satellite System) denied environment usually exploit low-cost MEMS IMU (Micro Electro Mechanical Systems Inertial Measurement Unit) sensors to replace the GNSS signals. However, the navigation system still requires GNSS signals for the normal environment. This paper presents an integrated GNSS/INS (Inertial Navigation System) navigation system which combines GNSS and multiple IMU sensors using extended Kalman filter in partially GNSS-denied environments. The position and velocity of the INS and GNSS are used as the inputs to the integrated navigation system. The Mahalanobis distance is used for novelty detection to detect the outlier of GNSS measurements. When the abnormality is detected in GNSS signals, GNSS data is excluded from the fusion process. The performance of the proposed method is evaluated using MATLAB/Simulink. The simulation results show that the proposed algorithm can achieve a higher degree of positioning accuracy in the partially GNSS-denied environment.

• 한국융합학회논문지
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• 제9권3호
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• pp.217-222
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• 2018

본 논문에서는 정확한 수의 희귀 세포 포집 및 이송을 위한 마이크로 폴리머 칩 플랫폼의 디자인과 제작, 그리고 프로토콜을 소개하고 있다. 본 플랫폼과 프로토콜은 기존의 통계학적인 샘플 준비 방법인 희석(Dilution)의 한계와 고가이며 형광염색이 요구되는 유세포분석기(Fluorescence activated cell sorter)의 단점을 극복하였다. 타켓 세포를 선택적으로 쉽고 간단하게 채집할 수 있으며 채집되는 세포의 수는 시각적으로 검증되므로 매우 정확한 방법이다. 또한, 채집된 세포들은 마이크로 챔버 등의 원하는 곳으로 세포의 손실 없이 이송 또는 주입 시킬 수 있다. 본 연구는 암진단 등을 목적으로 하는 칩 속의 실험실(Lab on a chip) 등에 필요한 희귀 세포 샘플 준비를 위해 활용 될 수 있을 뿐만 아니라 세포분석을 위한 싱글/더블/다수 세포 샘플의 준비에도 활용 가능하다. 본 논문에서 제시하는 세포 채집 플랫폼과 프로토콜을 검증하기 위해 5개의 인간 암세포(MCF-7)를 채집한 뒤 세포계수기(Hemocytometer) 안으로 주입시켜 세포의 수를 확인하였다.

• Transactions on Electrical and Electronic Materials
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• 제3권1호
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• pp.30-37
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• 2002

A focusing grating coupler (FGC) was not fabricated by the 'Continuous Path Control'writing strategy but by an electron-beam lithography system of more general exposure mode, which matches not only the address grid with the grating period but also an integer multiple of the address grid resolution (5 nm). To more simplify the fabrication, we are able to reduce a process step without large decrease of pattern quality by excluding a conducting material or layer such as metal (Al, Cr, Au), which are deposited on top or bottom of an e-beam resist to prevent charge build-up during e-beam exposure. A grating pitch period and an aperture feature size of the FGC designed and fabricated by e-beam lithography and reactive ion etching were ranged over 384.3 nm to 448.2 nm, and 0.5 $\times$ 0.5 mm$^2$area, respectively. This fabrication method presented will reduce processing time and improve the grating quality by means of a consideration of the address grid resolution, grating direction, pitch size and shapes when exposing. Here our investigations concentrate on the design and efficient fabrication results of the FGC for coupling from slab waveguide to a spot in free space.

• 대한의생명과학회지
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• 제12권3호
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• pp.177-183
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• 2006

To demonstrate the effect of formulation conditions and evaluations of structural integrity from ovalbumin containing poly lactide glycolide copolymer (PLGA) microspheres for Vaccine delivery, OVA microspheres were prepared by a W/O/W multiple emulsion solvent extraction technique. Dichloromethan (DCM) and Ethyl acetate (EA) were applied as an organic phase and poly vinyl alcohol (PVA) as a secondary emulsion stabilizer. Microspheres were characterized for particle size, morphology (optical microscopy and Scanning Electron Microscope (SEM)). Protein denaturation was evaluated by size exclusion chromatography (SEC), SDS-PAGE and isoelectric focusing (IEF). Residual organic solvent was estimated by gas chromatography (GC) and differential scanning calorimetry (DSC). Optical photomicrograph and SEM revealed that micro spheres were typically spherical but various morphologies were observed. Mean particle size $(d_{vs})$ of microspheres were in the range of $3{\sim}50{\mu}m$. Also, The protein stability was not affected by the fonnulation process and residual organic solvent was beyond the detection below 0.1ppm. These results demonstrated that micro spheres might be a good candidate for the parenteral vaccine delivery system.

• 센서학회지
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• 제30권3호
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• pp.170-174
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• 2021

As the rising attention to the medical and healthcare issue, Bio-MEMS (Micro electro mechanical systems) platform such as bio sensor, cell culture system, and microfluidics device has been studied extensively. Bio-MEMS platform mostly has high resolution structure made by biocompatible material such as polydimethylsiloxane (PDMS). In addition, three dimension structure has been applied to the bio-MEMS. Lithography can be used to fabricate complex structure by multiple process, however, non-rectangular cross section can be implemented by introducing optical apparatus to lithography technic. X-ray lithography can be used even for sub-micron scale. Here in, we demonstrated lines with round shape cross section using the tilted gold absorber which was deposited on the oblique structure as the X-ray mask. This structure was used as a mold for PDMS. Molded PDMS was applied to the cell culture platform. Moreover, molded PDMS was bonded to flat PDMS to utilize to the sub-micro channel. This work has potential to the large area bio-MEMS.

• 디지털콘텐츠학회 논문지
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• 제7권3호
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• pp.161-168
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• 2006

와이브로(Wibro - Wireless Broadband Internet)는 OFDMA/TDD (Orthogonal Frequency Division Multiple Access/Time Division Duplex)방식의 광대역 무선전송기술을 사용하여 상/하향 비대칭 전송 특성을 갖는 IP기반 무선데이터 트래픽을 효과적으로 수용할수 있는 시스템이다. 와이브로 서비스는 기존 셀률러망과 다르게 IP망을 기반으로 서비스되기 때문에 단말기의 이동과 관계없이 끊임없는 연결을 유지하기 위해서는 핸드오버가 지원되어야 한다. 기존의 Micro Mobility 방식과 일반적인 Mobile IP 방식은 핸드오프시 지연속도와 패킷손실의 문제점을 가지고 있다. 이러한 문제점을 최소화 하기위해서 IETF라는 프로토콜이 제안되었고, IETF의 Mip4, Mip6, Mipshop WG을 중심으로 표준화가 진행되었다. 본 논문에서는 와이브로 망에서의 문제점을 개선하여 단말기의 효율적인 핸드오버 지연을 최대한 줄이기 위한 기법들과 보안요구사항 및 지원방향 대해 연구 분석 함.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 금형가공,미세가공,플라스틱가공 공동 심포지엄
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• pp.193-197
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• 2005

This paper presents a method by which multiple holes of ultra small size can be punched simultaneously. Silicon wafers were used to fabricate punching die. Workpiece used in the present investigation were the rolled pure copper of $3{\mu}m$ in thickness and CP titanium of $1.5{\mu}m$ in thickness. The metal foils were punched with the dies and arrays of circular and rectangular holes were made. The diameter of holes ranges from $2-10{\mu}m$. The process set-up is similar to that of the flexible rubber pad forming or Guerin process. Arrays of holes were punched successfully in one step forming. The punched holes were examined in terms of their dimensions, surface qualities, and potential defect. The effects of the die hole dimension on ultra small size hole formation of the thin foil were discussed. The optimum process condition such as proper die shape and diameter-thickness ratio (d/t) were also discussed. The results in this paper show that the present method can be successfully applied to the fabrication of ultra small size hole array in a one step operation.

• 한국지반공학회논문집
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• 제19권2호
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• pp.171-178
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• 2003

날개크랙과 이차크랙은 암석의 일축압축 및 이축압축 조건에서 관측되는 특정한 형태의 크랙이다. 본 연구에서는 석고로 제작된 실험체내에 발생하는 날개크랙과 이차크랙의 형태적 측면을 미시적 및 거시적 관점에서 관측하였다. 날개크랙의 진행방향을 따라 미소인장크랙이 관측되었으며 미소인장크랙은 공극간의 연결과 분지현상을 통하여 진전되었다. 날개크랙의 개시점에서 다중의 미소인장크랙의 개시가 관측되었으며 미소인장크랙은 굴곡진 진행을 보인다. 또한 이차크랙과는 달리 미소인장크랙은 상대적으로 일정한 크랙의 틈을 보이며 인장에 의한 할렬파괴에 의해 진행되는 것으로 나타났다. 이차크랙의 미시적 관측에서는 미소파쇄대가 관측되었다. 이차크랙의 파괴구간 내에서는 입자 및 집괴의 분리, 경사진 미소파쇄대의 형성 및 불규칙한 크기의 틈을 가진 미소파쇄대가 관측되었다. 이러한 결과는 이차크랙이 전단에 의해 형성됨을 보이고 있다 날개크랙과 이차크랙은 서로 다른 크기의 파괴진행구간을 보이고 있으며 각각의 크랙의 진행 방향에 직각방향으로 측정된 파괴진행구간의 폭은 날개크랙의 경우 10$\mu{m}$에서 20$\mu{m}$ 정도이며 이차크랙은 100$\mu{m}$에서 200$\mu{m}$ 정도이다.

• Journal of Korean Neurosurgical Society
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• 제60권5호
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• pp.550-559
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• 2017

Objective : Subsidence is a frequent complication of anterior cervical discectomy and fusion. Postoperative segmental micromotion, thought to be a causative factor of subsidence, has been speculated to increase with uncinate process resection area (UPR). To evaluate the effect of UPR on micro-motion, we designed a method to measure UPR area based on pre- and postoperative computed tomography images and analyzed the relationship between UPR and subsidence as a proxy of micro-motion. Methods : We retrospectively collected clinical and radiological data from January 2011 to June 2016. A total of 38 patients (53 segments) were included. All procedures included bilateral UPR and anterior plate fixation. UPR area was evaluated with reformatted coronal computer tomography images. To reduce level-related bias, we converted UPR area to the proportion of UPR to the pre-operative UP area (pUPR). Results : Subsidence occurred in 18 segments (34%) and positively correlated with right-side pUPR, left-side pUPR, and the sum of bilateral pUPR (sum pUPR) (R=0.310, 301, 364; p=0.024, 0.029, 0.007, respectively). Multiple linear regression analysis revealed that subsidence could be estimated with the following formula : $subsidence=1.522+2.7{\times}sum\;pUPR$($R^2=0.133$, p=0.007). Receiver-operating characteristic analysis determined that sum $pUPR{\geq}0.38$ could serve as a threshold for significantly increased risk of subsidence (p=0.005, area under curve=0.737, sensitivity=94%, specificity=51%). This threshold was confirmed by logistic regression analysis for subsidence (p=0.009, odds ratio=8.471). Conclusion : The UPR measurement method confirmed that UPR was correlated with subsidence. Particularly when the sum of pUPR is ${\geq}38%$, the possibility of subsidence increased.