• 한국전기전자재료학회논문지
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• 제20권11호
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• pp.925-931
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• 2007

We successively fabricated the Ni metal mask by additive method and evaluated the effects of wetting agents addition on the microstructure, hardness, and friction coefficient. In the process, the additive patterns with fine hole and pitch were made by photolithography technique and subsequently Ni plate was electroformed on the patterns. We found that the microstructure and mechanical properties were significantly varied when the different combinations of the wetting agents were used. When the wetting agents of both SF-1 and SF-2 were added, the microstructure consisted of crystal and amorphous phases, the grain size reduced to 5-40 nm, the RMS value decreased to 11.4 nm and the wear resistance improved. In addition, the hardness was as high as 638 Hv which is higher than that of commercial stainless steel mask and this improvement is probably due to the presence of amorphous Phase and fine grain size. The improvement of the wear resistance can provide a higher reliability and a longer service life.

• 한국정밀공학회지
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• 제19권2호
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• pp.106-113
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• 2002

Stencil is used normally as a mask for seeder pasting on pad of PCB. The objective of this study is to develop stencil cutting system and determine optimal conditions which make good-quality stencil by using a Nd:YAG laser. The effects of process parameters such as laser power, type of mask, gas pressure, cutting speed and pulse width old the cut edge quality were investigated. In order to analyse fille cut surface characteristics(roughness, kerf width, dross) optical microscopy, SEM photography and roughness test were used. As a result, the optimal conditions of process parameters were determined, and the practical feasibility of the proposed system is also examined by using a commercial Gerber file for PCB stencil manufacturing.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.809-809
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• 2013

We report a new method for highly controllable local patterning of a hydrogel on microfabricated cantilevers and fabrication of all hydrogel microcantilevers. We constructed a dynamic mask based photolithography setup using a commercial beam projector, a 3-axis microstage and other optical components. Dynamic masks generated from the beam projector controlled the shape, size, and position of hydrogel patterns while the 3-axis microstage mainly controlled the thickness of hydrogel patterns and hydrogel microcantilevers. Using the constructed setup, polyethyleneglycol diacrylate (PEGDA) was patterned on microfabricated cantilevers in a highly controlled manner. Currently, the smallest PEGDA patternable is a 5-${\mu}m$-diameter circle with a thickness of ~$10{\mu}m$. To confirm thicknesses of patterned PEGDAs on silicon microcantilevers, resonance frequencies of microcantilevers were measured before and after each PEGDA patterning. Thicknesses extracted from resonance measurements showed good agreement with measurements using an optical microscope. In addition, PEGDA microcantilevers with various dimensions and thicknesses were fabricated on glass and silicon substrates. Surfaces of fabricated all hydrogel microcantilevers were flat enough to facilitate other post processing and to be used for various sensing applications.

• Transactions on Electrical and Electronic Materials
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• 제7권4호
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• pp.173-179
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• 2006

Due to the limitations of the channel length, the lateral spread for two-dimensional impurity distributions is critical for the analysis of devices including the integrated complementary metal oxide semiconductor (CMOS) circuits and high frequency semiconductor devices. The developed codes were then compared with the two-dimensional implanted profiles measured by transmission electron microscope (TEM) as well as simulated by a commercial TSUPREM4 for verification purposes. The measured two-dimensional TEM data obtained by chemical etching-method was consistent with the results of the developed analytical model, and it seemed to be more accurate than the results attained by a commercial TSUPREM4. The developed codes can be applied on a wider energy range $(1KeV{\sim}30MeV)$ than a commercial TSUPREM4 of which the maximum energy range cannot exceed 1MeV for the limited doping elements. Moreover, it is not only limited to diffusion process but also can be applied to implantation due to the sloped and nano scale structure of the mask.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.989-992
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• 1997

The objective of this study is to develop stencil cutting process and determine optimal conditions which make good-quality stencil by using a Nd:YAG laser. The effects of process parameters such as laser power, type of mask, gas pressure, cutting speed and pulse width on the cut edge quality were investigated. In order to analyze the cut surface characteristics(roughness, kerf width, dross) optical microscopy, SEM photography and roughness test were used. A a results, the optimal conditions of process parameters were determined, and the practical feasibility of the proposed system is also examined by using a commercial gerber file for PCB stencil manufacturing.

• 패션비즈니스
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• 제26권6호
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• pp.105-115
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• 2022

Wearing a mask is still advised since COVID-19 continues to spread. However, masks may also irritate the skin and cause mask acne, often known as "maskne", which is a type of acne mechanica caused by friction between the skin and clothing. Therefore, there is a need to develop an effective maskne cosmetic. In this study, we made the maskne cosmetics containing humulus lupulus extract and copper tripeptide-1 and investigated its stability and safety. To measure stability, a centrifugation test and heat-cool cycling were done, and changes in viscosity and pH were measured for 8 weeks. The Cumulative Irritation Test (CIT, WKIRB-202111-HR-096) was performed and positive reactions were determined by the ICDRG criteria. The results indicated that the samples were stable after centrifugation, temperature cycling, viscosity, and pH tests. In addition, cosmetic safety test results revealed that maskne cosmetics containing humulus lupulus extract and copper tripeptide-1 did not cause any skin responses. These findings indicate that prepared maskne cosmetics' stability and safety were comparable to those of currently available commercial cosmetics.

• 한국의학물리학회지:의학물리
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• 제13권3호
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• pp.135-138
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• 2002

치료대상 병소에 분할 방사선수술을 시술할 경우 회전중심(isocenter)은 정확하고 재현성 이 있어야 한다. 본 연구는 노발리스 방사선 수술장비와 정위 마스크 시스템을 사용한 분할방사선 수술에서 회전중심의 재현성을 측정하고 평가 하였다. 마스크는 열가소성 재질의 상용을 사용하였고 회전중심의 재현성을 측정하기 위해 고안된 머리 모양의 아크릴 팬텀에 맞도록 제작하였다. 팬텀의 내부에는 직경 5 mm의 아크릴봉을 수직으로 세우고 그 끝단을 회전중심으로 선택하였으며 예상되는 회전중심점에 pin hole을 낸 monochromic 필름을 설치하여 방사선 조사 후 회전중심의 재현성을 측정할 수 있도록 하였다. 측정 결과 회전중심은 공간오차가 평균 1 mm 이내이고 표준편차 또한 2 mm 이내여서 이미 보고된 타 문헌에서의 측정값과 비교해 볼 때 모든 측정값이 제시된 오차범위 내에 있었다. 결론적으로 분할방사선수술에 사용하는 정위 마스크 시스템은 매우 정확하고 재현성이 우수하였으며, 실제로 방사선 수술대상의 병소의 직경이 10 mm 정도 이상이라면 일반적인 한번의 고선량 방사선 수술에 정위 마스크 시스템의 사용이 가능할 것으로 사료된다.

• Journal of Positioning, Navigation, and Timing
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• 제12권2호
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• pp.101-111
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• 2023

Many spoofing detection studies have been conducted to cope with the most difficult types of deception among various disturbances of GPS, such as jamming, spoofing, and meaconing. In this paper, we propose a spoofing detection scheme based on elevation masked-relative received power between GPS L1 and L2 signals in a system using a multi-band array antenna. The proposed scheme focuses on enabling spoofing to be normally detected and minimizes the possibility of false detection in an environment where false alarms may occur due to pattern distortion among elements of an array antenna. The pattern distortion weakens the GPS signal strength at low elevation. It becomes confusing to detect a spoofing signal based on the relative power difference between GPS L1 and L2, especially when GPS L2 has weak signal strength. We propose design parameters for the relative power threshold including beamforming gain, the minimum received power difference between L1 and L2, and the patch antenna gain difference between L1 and L2. In addition, in order to eliminate the weak signal strength of GPS L2 in the spoofing detection process, we propose a rotation matrix that sets the elevation mask based on platform coordinates. Array antennas generally do not have high usefulness in commercial areas where receivers are operated alone, but are considered essential in military areas where GPS receivers are used together with signal processing for beamforming in the direction of GPS satellites. Through laboratory and live sky tests using the device under test, the proposed scheme with an elevation mask detects spoofing signals well and reduces the probability of false detection relative to that without the elevation mask.

• 한국환경보건학회지
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• 제41권3호
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• pp.203-215
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• 2015

Objectives: This study was designed to evaluate the filtration efficiencies and pressure drops of five commercial cloth masks (4 plate type, 1 cup type) in comparison to the performance of a class 1 disposable respirator (reference respirator). A further objective was to evaluate the effects of the number of layers and wash treatment independently on filtration efficiencies and pressure drops. Methods: Polydisperse NaCl aerosols were generated in an aerosol chamber and their concentrations were measured by an optical particle counter (OPC) in the size range of $0.3{\sim}10{\mu}m$ (five channels). Results: The filtration efficiencies of the five cloth masks and the reference respirator were D: 9.5%, C: 18.5%, E: 23.6%, A: 28.5%, B: 29.7% and R: 91.1%, respectively, and the pressure drops through them were C, D: 0.8 Pa, E: 1.7 Pa, B: 6.4 Pa, A: 42.7 Pa and R: 19.3 Pa, respectively. The filtration efficiencies of the cloth masks and reference respirator were below the class 1 respirator criterion (${\geq}94.0%$) of the Ministry of Employment and Labor (MOEL) and Ministry of Food and Drug Safety (MFDS). The pressure drops satisfied the class 1 respirator criterion (${\leq}70Pa$) of MOEL and MFDS. When the cloth masks were folded into two and four layers, the filtration efficiencies of cloth masks A, B, C, D (plate type) increased 1.7-4.6 times, and 2.3-6.8 times, respectively, compared to the efficiencies of the same products in a single layer. Pressure drops increased as the number of layers was increased. The filtration efficiency of cloth mask E with a liner was 1.3 times higher than that of the same mask without a liner, and the pressure drop was lower in the no-liner configuration. After a single washing, the filtration efficiencies of all the cloth mask products decreased 1.04-4.0 times compared to those of the same products intact. For the cloth masks C and E, their filtration efficiencies were significantly decreased after washing (p<0.05). The pressure drops of all cloth masks were 1.2-2.0 times lower after washing. Conclusions: The filtration efficiencies of the five cloth masks were below 30% and did not improve greatly by increasing the number of layers. After a single washing, their performances decreased. Considering the above and other issues identified with cloth masks, such as poor fit and stretched fibers through use, people should not expect protection against particulate matters from the cloth masks on the market.

• Korean Chemical Engineering Research
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• 제61권1호
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• pp.68-73
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• 2023

화재로 인한 인명 피해를 줄이기 위해, 화재 대피용 방연마스크에 대한 관심과 보급이 증가하고 있다. 하지만 시중에 유통되는 방연마스크의 성능 인증 여부와 일반인들이 방연마스크를 적절하게 착용할 수 있는지에 관한 조사가 충분하지 않기 때문에, 방연마스크가 화재 현장에서 피난안전성을 실제로 높일 수 있는지 판단하기가 쉽지 않다. 본 연구는 방연마스크에 대한 일반 사용자의 인식 현황 및 사용 경험을 조사하고, 교육 필요성을 분석하였다. 또한 국내에서 유통 중인 방연마스크 제품들이 국내외 성능 기준에 따라 인증되고 있는지 조사하였다. 아울러 실험을 통해 방연마스크의 착용 신속성 및 활동 편의성을 평가하였다. 235명의 응답자 중 방연마스크를 실제 사용해 본 응답자는 22%에 그치고, 23%는 방연마스크를 모름에도 불구하고, 93%의 응답자는 방연마스크가 화재 피해를 줄일 수 있다고 기대했다. 국내에서 유통 중인 54개의 방연마스크 중 약 41%의 제품이 성능 인증을 받지 않은 것으로 조사 되었다. 국내외 다양한 성능 기준들 중에서 ASTM E 2952 및 KFIS 024만 방연마스크의 착용 신속성을 30초 이내로 규정하고 있다. 그런데 4가지 형태의 방연마스크를 대상으로 착용 신속성을 실험한 결과, 후드형 방연마스크와 자급식 방연마스크는 30초 이내로 착용하기 어려운 것으로 나타났다. 정화식 방연마스크에 비해 자급식 방연마스크를 착용하면, 의사소통의 어려움과 심리적/물리적 불편감을 더 많이 느끼는 것으로 나타났다. 한편, 방연마스크의 착용 교육을 받은 경우, 착용 시간은 약 19%, 오착용 횟수는 약 89% 감소하여, 적절한 착용 교육과 훈련이 매우 중요하다는 것을 확인할 수 있었다.