회원작품 - 구산동도서관마을

최재원,Choi, Jaewon 대한건축사협회 2017 建築士 Vol.574 No.-

Microstrip Square Open Loop와 Tunable Negative Resistance를 이용한 저위상 잡음 전압 제어 발진기

최재원,이종민,서철헌,Choi, Jae-Won,Lee, Chong-Min,Seo, Chul-Hun 한국전자파학회 2006 한국전자파학회논문지 Vol.17 No.12

마이크로스트립 개방형 루프 공진기는 발진기의 위상 잡음을 줄이기 위해서 적용되었다. 마이크로스트립 스퀘어 개방형 루프 공진기는 큰 결합 계수 값을 가지고, 이로 인해 높은 Q 값을 가지며 전압 제어 발진기의 위상잡음을 감소시킨다. 전압 제어 발진기의 주파수 조절 범위를 증가시키기 위하여 버랙터 다이오드가 전압 제어발진기의 조절 가능한 부성 저항에 연결되어졌다. 전압 제어 발진기의 출력 파워와 하모닉 특성은 각각 4.83dBm과 -28.83 dBc이다. 위상 잡음 특성은 주파수 조절 범위 $5.735{\sim}5.845GHz$에서 $-112.33{\sim}-116.16dBc/Hz$ @ 100 kHz이다. The microstrip square open loop resonator has been employed to reduce the phase noise in VCO. The microstrip square open loop resonator has the large coupling coefficient value, which makes a high Q value, and has reduced the phase noise of VCO. To increase the tuning range of VCO, varactor diode has been connected at the tunable negative resistance in VCO. The output power and harmonic characteristics of VCO has been obtained 4.83 dBm and -28.83 dBc, respectively. The phase noise of VCO has been $-112.33{\sim}-116.16dBc/Hz$ @ 100 kHz in the tuning range, $5.735{\sim}5.845GHz$.

결함내성을 가진 도메인네임 서버의 구축 및 연동시험

최재원,Choi, Jae-Won 한국정보통신학회 2011 한국정보통신학회논문지 Vol.15 No.1

DNS(Domain Name System)는 인터넷상의 호스트의 도메인주소를 IP주소로 변환하거나 IP주소를 도메인주소로 변환하는 이름해결 메카니즘을 총칭한다. 본 논문에서는 1차 DNS 서버가 오류로 인해 정지하더라도 2차 DNS 서버가 대신하여 서비스를 지속할 수 있도록 하는 결함내성을 갖는 DNS 시스템 구축에 관해 연구하였다. DNS(Domain Name System) is the Name Resolution Mechanism that makes conversion from a Domain Name of a computer on the Internet to an IP Address or the reverse conversion. In this paper we researched on the Foundation techniques of Fault-tolerant DNS Servers that the secondary DNS can take over and provide continuous services even though primary DNS stops due to some critical errors.

다양한 입자크기 및 표면개질 버텀애쉬를 이용한 폴리에틸렌/버텀애쉬 복합소재의 특성

최재원,김하연,정용찬,전병철,Choi, Jae Won,Kim, Ha Youn,Chung, Yong-Chan,Chun, Byoung Chul 한국섬유공학회 2013 한국섬유공학회지 Vol.50 No.1

Surface treated bottom ash was utilized as a filler to prepare plastic composites. Bottom ash surface was modified with octyltriethylammonium bromide (OTAB) or hexyltriethylammonium bromide (HTAB) by ion exchange procedure in methanol solution. Surface-modified bottom ash was then melt-compounded with HDPE to investigate its compatibility with the matrix material. The mechanical properties such as tensile, compressive, and impact strength, in addition to morphologies, were analyzed to determine the advantage of surface treatment compared to using bottom ash without treatment. Tensile strength and compressive strength increased with increasing bottom ash content.

Fabrication of Sub-Micron Size $Al-AlO_x-Al$ Tunnel Junction using Electron-Beam Lithography and Double-Angle Shadow Evaporation Technique

최재원,류시정,박정환,류상완,김정구,송운,정연욱,Rehmana, M.,Choi, J.W.,Ryu, S.J.,Park, J.H.,Ryu, S.W.,Khim, Z.G.,Song, W.,Chong, Y. 한국초전도학회 2009 Progress in superconductivity Vol.10 No.2

We report our development of the fabrication process of sub-micron scale $Al-AlO_x-Al$ tunnel junction by using electron-beam lithography and double-angle shadow evaporation technique. We used double-layer resist to construct a suspended bridge structure, and double-angle electron-beam evaporation to form a sub-micron scale overlapped junction. We adopted an e-beam insensitive resist as a bottom sacrificing layer. Tunnel barrier was formed by oxidation of the bottom aluminum layer between the bottom and top electrode deposition, which was done in a separate load-lock chamber. The junction resistance is designed and controlled to be 50 $\Omega$ to match the impedance of the transmission line. The junctions will be used in the broadband shot noise thermometry experiment, which will serve as a link between the electrical unit and the thermodynamic unit.

로드 밸런싱 Active-Active 방식의 웹 서버 이중화 구축 및 결함내성 시험

최재원,Choi, Jae-Won 한국정보통신학회 2014 한국정보통신학회논문지 Vol.18 No.1

본 논문에서는 Active-Active 방식의 웹서버 이중화 방법에 관해 연구하였다. Rsync과 crontab을 이용하여 웹서버간에 주기적인 복사가 이루어지도록 하여 동일한 상태를 유지시켰다. 로드밸런싱서버가 웹서버를 교대로 실행하여 부하를 분산하고, 빠른 서비스가 제공되도록 하였다. 또한 임의의 웹서버에 장애가 발생하더라도 또 다른 웹서버에 의해 서비스가 계속 유지되도록 하였다. In this paper we researched on the Duplication Techniques for Active-Active Web Servers. Rsync and crontab utilities make copy periodically between web servers and maintain the same status. Load Balancing Server makes web servers load balanced and fast servicing by executing web servers alternatively. Even though one web server stops due to some critical errors, the remaining web server can take over and provide services continuously.

마이크로스트립 사각 개방 루프 공진기와 가변 부성 저항을 이용한 저위상 잡음 Push-Push 전압 제어 발진기

최재원,서철헌,Choi, Jae-Won,Seo, Chul-Hun 한국전자파학회 2007 한국전자파학회논문지 Vol.18 No.8

본 논문에서는 마이크로스트립 사각 개방 루프 공진기와 가변 부성 저항을 이용한 향상된 push-push 전압제어 발진기를 제시하였다. 마이크로스트립 사각 개방 루프 공진기는 큰 결합 계수 값을 갖는데, 이는 Q값을 크게 만들고, 전압 제어 발진기의 위상 잡음을 줄인다. 1.8V의 공급 전압을 사용한 전압 제어 발진기는 $5.744{\sim}5.859GHz$의 주파수 조절 범위에서 $-124.67{\sim}-122.67dBc/Hz\;@\;100 kHz$의 위상 잡음 특성을 갖는다. 이 전압 제어 발진기의 FOM은 같은 주파수 조절 범위에서 $-202.83{\sim}-201dBc/Hz\;@\;100 kHz$의 값을 갖는다. 마이크로 스트립 사각 개방 루프 공진기를 이용한 단일 종단 전압 제어 발진기와 마이크로스트립 공진기를 이용한 push-push 발진기와 비교했을 때 개선된 위상 잡음 특성은 각각 -8.51 dB와 -33.67 dB이다. In this paper, a novel push-push voltage-controlled oscillator(VCO) using microstrip square open loop resonator and tunable negative resistance is presented. The microstrip square open loop resonator has the large coupling coefficient value, which makes a high Q value, and has reduced phase noise of VCO. The VCO with 1.8V power supply has phase noise of $-124.67{\sim}-122.67dBc/Hz\;@\;100 kHz$ in the tuning range, $5.744{\sim}5.859 GHz$. The FOM of this VCO is $-202.83{\sim}-201dBc/Hz\;@\;100 kHz$ in the same tuning range. When it has been compared with single-ended VCO using microstrip square open loop resonator, and push-push oscillator using microstrip line resonator, the reduced phase noise has been -8.51dB, and -33.67dB, respectively.

재활용(再活用) 굴 껍질 분말(粉末)을 이용(利用)한 고밀도 폴리에틸렌계 난연 소재(素材)의 제조(製造)와 물성(物性)

최재원,조태근,안준형,이성호,정용찬,전호석,전병철,Choi, Jae-Won,Cho, Tae-Keun,Ahn, Jun-Hyung,Lee, Sung-Ho,Chung, Yong-Chan,Jeon, Ho-Seok,Chun, Byoung-Chul 한국자원리싸이클링학회 2008 資源 리싸이클링 Vol.17 No.4

재활용한 고밀도 폴리에틸렌(HDPE)에 무기계 폐기물인 패각을 도입하여 함량 변화에 따른 기계적 물성 및 난연성을 조사하였다. 상기 복합소재의 기계적 물성 향상을 위하여 상용화제(PE-g-MA)를 첨가하였고, 난연성 향상을 위하여 다양한 종류의 난연제($Al_2O_3$, $Sb_2O_3$)를 첨가하여 이에 따른 기계적 물성 및 난연성을 종합적으로 평가하였다. 측정 결과 HDPE에 패각만 혼합하는 것보다는 추가적으로 상용화제를 혼합하는 것이 매트릭스인 HDPE와 패각과의 계면 결합력이 증대되어 패각만을 혼합하였을때 보다 물성 저하가 보완되었고, 충격강도의 경우 순수 HDPE와 유사한 값을 나타내었다. 한편, 난연제 첨가에 따른 기계적 물성의 저하는 관찰되지 않았다. 제조된 HDPE 복합소재의 UL-94 규격에 의한 난연성 측정 결과 패각만을 혼합한 경우 패각 40wt% 함유된 경우가 순수 HDPE보다 불이 붙을 때까지 걸리는 시간과 타는 시간이 지연됨을 확인할 수 있었다. 또한 패각을 난연제와 함께 복합화하여 제조한 소재에서는 뚜렷한 난연 효과를 관찰할 수 있었으며, 난연 효과는 $Al_2O_3$보다 $Sb_2O_3$가 효과적이었다. 난연성 측정 결과 UL-94 V-0 등급은 $Al_2O_3$를 첨가한 그레이드 중 상용화제를 넣은 그레이드와 패각 40wt%가 함유된 그레이드에서, 그리고 $Sb_2O_3$를 첨가한 그레이드 중 상용화제를 첨가한 모든 그레이드에서 관찰되었다. Waste shell powder was added to the high density polyethylene(HDPE), and resultant mechanical properties and flame retardancy were analyzed in terms of shell content. Compatibilizer(PE-g-MA) was used to enhance the mechanical properties of the prepared HDPE/shell composites, and several flame retardant agents($Al_2O_3$, $Sb_2O_3$) were utilized to improve flame retardancy. Addition of the compatibilizer resulted in an improved mechanical properties due to the increased interfacial bonding between HDPE matrix and shell powder. In the case of impact strength, it even reached to the impact strength of pure HDPE. Also the addition of the flame retardant agents did not exhibit mechanical property decrease. UL-94 flammability test on the prepared HDPE/shell composites indicated that at 40wt% of shell only inclusion, time to ignite the flame and the total time of flame duration increased. When flame retardant agents mixed with shell powder were added to the HDPE matrix, improved flame retardancy was observed. Generally, flame retardancy effect of $Al_2O_3$ was better than $Sb_2O_3$. UL-94 V-0 classification was observed for the specimens with $Al_2O_3$ and compatibilizer at more than 40wt% shell, and also for specimens with $Sb_2O_3$ and compatibilizer at all shell content.

편광현미경을 이용한 PTT/PTN 블렌드의 등온결정화 거동 분석

최재원,차희철,김영호,Choi, Jae-Won,Cha, Hee-Cheol,Kim, Young-Ho 한국섬유공학회 2005 한국섬유공학회지 Vol.42 No.6

Isothermal crystallization behaviors of poly(trimethylene terephthalate) (PTT), poly(trimethylene naphthalate) (PTN), and PTT/PTN blends were analyzed using a polarizing microscope equipped with a hot-stage. As the melting time at $260^{\circ}C$ of PTT/PTN blends increased, the crystallization proceeded slowly due to the copolymer formation which resulted from the ester interchange reaction at the elevated temperature. PTT and m-rich blends formed spherulites over the temperature range of experiment, but PTN formed spherulites only at lower crystallization temperatures such as $150^{\circ}C$. PTN and PTN-rich blends formed distorted spherulites at high temperatures such as $180^{\circ}C$, which seemed to result from the $\beta-crystal$ formation of PTN at that temperature. The radial growth rate of the spherulite formed during the crystallization was obtained by the measurement of radii of the spherulites. The radial growth rate decreased as PTN content in the blends increased.

$^1H-NMR$과 WAXS를 이용한 폴리(트리메틸렌 테레프탈레이트)/폴리(트리메틸렌 나프탈레이트) (50/50) 블렌드의 에스터 교 환반응 연구

최재원,오태환,김영호,Choi, Jae-Won,Oh, Tae-Hwan,Kim, Young-Ho 한국섬유공학회 2005 한국섬유공학회지 Vol.42 No.5

Poly(trimethylene terephthalate) (PIT) and poly(trimethylene naphthalate) (PTN) blends of 50/50 weight ratio, T5N5, were prepared by solution blending-precipitation method, and the effect of melting time on the degree of randomness, sequence length, and crystalline structure of melt-pressed blends obtained by melting T5N5 on a hot stage at $260^{\circ}C$ for different times and quenching into liquid nitrogen was studied using DSC, $^1H-NMR$ and WAXS. The T5N5 blend showed two $T_gs$ corresponding to that of PTT and PTN, which indicated that PTT and PTN were immiscible. But the melt-pressed blends melted at $260^{\circ}C$ for 2 minutes or more showed single $T_g$ indicating that the system became miscible. $^1H-NMR$ analysis confirmed that the blends became block copolymers and that the degree of randomness increased as melting time increased. The sequence length of PTT component was larger than that of PTN in the resultant copolymer. Although PTT and PTN were present in the same amount in the blend, PTT component crystallized more easily than the PTN component due to the larger block length of PTT. The crystalline structure of the component polymers was the same as that of homopolymers. The WAXS patterns showed that the crystalline structure of PTN in the melt-pressed blends was $\beta-form$ when they were annealed at $180^{\circ}C$ but it was a-form when annealed at $140^{\circ}C$, exhibiting the same behavior as homo PTN.