• 한국산학기술학회논문지
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• 제17권6호
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• pp.715-720
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• 2016

본 논문에서는, 휴대기기를 위한 PWM(Pulse Width Modulation), 전압모드 DC-DC 승압형 컨버터를 제안한다. 제안하는 컨버터는 현재 소형화 되어가고 있는 휴대기기 시장에 적합하도록 1 MHz의 스위칭 주파수를 사용하여 칩 면적을 줄였다. 제안하는 DC-DC 컨버터는 전력단과 제어단으로 이루어지며 전력단은 인덕터, 출력 커패시터, MOS 트랜지스터 등으로 구성되며 제어단은 연산증폭기, 밴드갭 회로, 소프트 스타트 블록, 히스테리시스 비교기와 비겹침 드라이버로 구성된다. 설계된 회로는 히스테리시스 비교기와 논오버랩 드라이버를 사용하여 낮은 전압에서 구동되는 휴대기기의 잡음의 영향을 줄이고 출력전압 리플을 감소시켰다. 제안하는 회로는 1-poly 6-metal CMOS 매그나칩/하이닉스 $0.18{\mu}m$ 공정을 사용하여 레이아웃을 진행하였다. 설계된 컨버터는 입력 전압 3.3 V, 출력전압 5 V, 출력전류 100 mA 출력전압 대비 1%의 출력 전압 리플과 1 MHz의 스위칭 주파수의 특성을 갖는다. 본 논문에서 제안하는 승압형 DC-DC 컨버터는 PDA, 휴대폰, 노트북 등 휴대용 전자기기 시장에 맞는 고효율, 소형화 컨버터로서 유용하게 사용 될 것으로 사료된다.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1485-1490
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• 2014

We have designed and developed a new ladder type tetrafused ${\pi}$-conjugated building block such as dihydroindolo[3,2-b]indole (DINI) and investigated its role as an electron rich unit. The photovoltaic properties of a new semiconducting ${\pi}$-conjugated polymer, poly[[5,10-bisoctyl-5,10-dihydroindolo[3,2-b]indole-[5,6- bis(octyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole]], represented by PDINI-OBTC8 are described. The new polymer PDINI-OBTC8 was synthesized in donor-acceptor (D-A) fashion, where fused ${\pi}$-conjugated tetracyclic DINI, and 5,6-bis(octyloxy)-4,7-di(thiophen-2-yl) benzo[c][1,2,5]thiadiazole (OBTC8) were employed as electron rich (donor) and electron deficient (acceptor) moieties, respectively. The conventional bulk heterojunction (BHJ) device structure ITO/PEDOT:PSS/PDINI-OBTC8:PCB71M/LiF/Al was utilized to fabricate polymer solar cells (PSCs), which comprises the blend of PDINI-OBTC8 and [6,6]-phenyl-$C_{71}$-butyric acid methyl ester ($PC_{71}BM$) in BHJ network. A BHJ PSC that contain PDINI-OBTC8 delivered power conversion efficiency (PCE) value of 1.68% with 1 vol% of 1,8-diidooctane (DIO) under the illumination of A.M 1.5G 100 $mW/cm^2$.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제38권
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• pp.39.1-39.6
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• 2016

Background: Temporomandibular joint (TMJ) ankylosis in children often leads to facial deformity, functional deficit, and negative influence of the psychosocial development, which worsens with growth. The treatment of TMJ ankylosis in the pediatric patient is much more challenging than in adults because of a high incidence of recurrence and unfavorable growth of the mandible. Case report: This is a case report describing sequential management of the left TMJ ankylosis resulted from trauma in early childhood. The multiple surgeries including a costochondral graft and gap arthroplasty using interpositional silicone block were performed, but re-ankylosis of the TMJ occurred after surgery. Alloplastic TMJ prosthesis was conducted to prevent another ankylosis, and signs or symptoms of re-ankylosis were not found. Additional reconstruction surgery was performed to compensate mandibular growth after confirming growth completion. During the first 3 years of long-term follow-up, satisfactory functional and esthetic results were observed. Conclusions: This is to review the sequential management for the recurrent TMJ ankylosis in a growing child. Even though proper healing was expected after reconstruction of the left TMJ with costal cartilage graft, additional surgical interventions, including interpositional arthroplasty, were performed due to re-ankylosis of the affected site. In this case, alloplastic prosthesis could be an option to prevent TMJ re-ankylosis for growing pediatric patients with TMJ ankylosis in the beginning.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.330-336
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• 2002

A quantum-chemical investigation on the conformations and electronic properties of bis[2-{2-methoxy-4,6-di(t-butyl)phenyl}ethenyl]benzenes (MBPBs) as building block for ${\pi}$-conjugate polymer are performed in order to display the effects of t-butyl and methoxy group substitution and of kink(ortho and meta) linkage. The conjugation length of the polymers can be controlled by substituents and kink linkages of backbone. Structures for the molecules, o-, m-, and p-MBPBs as well as unsubstituted o-, m-, and p-DSBs were fully optimized by using semiempirical AM1, PM3 methods, and ab initio HF method with 3-21G(d) basis set. The potential energy curves with respect to the change of single torsion angle are obtained by using semiempirical methods and ab initio HF/3-21G(d) basis set. The curves are similar shape in the molecules with respect to the position of vinylene groups. It is shown that the conformations of the molecules are compromised between the steric repulsion interaction and the degree of the conjugation. Electronic properties of the molecules were obtained by applying the optimized structures and geometries to the ZINDO/S method. ZINDO/S analysis performed on the geometries obtained by AM1 method and HF/3-21G(d) level is reported. The absorption wavelength on the geometries obtained by AM1 method is much longer than that by HF/3-21G(d) level. The absorption wavelength of MBPBs are red shifted with comparison to that of corresponding DSBs in the same torsion angle because of electron donating substituents. The absorption wavelength of isomers with kink(orth and meta) linkage is shorter than that of para linkage.

• 한국멀티미디어학회논문지
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• 제15권4호
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• pp.472-484
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• 2012

보행자의 안전한 보행을 위해 점자형 또는 일반 보도블록이 널리 쓰이고 있다. 불량한 시공 및 유지상태와 장애물은 보행자의 사고를 유발한다. 본 연구는 안전한 보행을 위해 영상에서 가시거리에 위치한 블록의 형태 패턴과 텍스처 특징을 분석하여 보도블록을 검출하는 방법을 제안한다. 보도는 특정모양의 블록이 일정 간격에 반복 배치되어 규칙성을 띄며, 주변 환경 또는 용도에 따라 그 형태는 다양하다. 높은 빈도를 띄는 단일 모양의 다각형을 분석하여 형태 패턴을 추출한다. 일부영역은 이물질 또는 조각난 블록이 원래의 형태를 왜곡시켜 검출되지 않는다. 이 문제는 텍스처 특징벡터 값을 분석하여 해결한다. 앞서 검출된 모든 영역에 대해 분석된 텍스처 특징벡터는 가우시안 분포를 나타내고, 미검출 영역에 대해 분석한 텍스처 특징벡터가 가우시안 분포를 만족하는지 판단한다. 만족된 영역은 보도블록으로 검출한다. 본 실험은 다양한 형태의 보도블록을 인식하였고 95.9%의 정확성을 보였다.

• 한국콘텐츠학회논문지
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• 제9권8호
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• pp.91-98
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• 2009

본 논문은 암호화된 영상 데이터가 유비쿼터스 환경 하에서 무선 간섭에 의한 랜덤 오류를 가질 때 복호화 과정의 오류 산사태에 대한 해결책을 제시하였다. 영상 획득 장치는 영상 압축과 암호화 기능을 가지고서 데이터 트래픽 양을 줄이고 개인 정보를 보호하도록 구성한다. 블록 암호 알고리즘은 암호문의 단일 비트 오류가 여러 개의 픽셀 결함을 유발하는 산사태 효과를 겪을 수 있다. 새로운 고장 극복 방식은 오류의 산사태 효과를 다루는데 3 차원 데이터 셔플을 활용하여 에러 비트를 여러 프레임으로 분산시켜서 고립된 영상 결함으로 나타나도록 한다. 인접 화소 값에 대한 평균화 또는 다수결 회로는 에러정정을 위한 데이터 증가 없이 두드러져 보이는 화소 결함을 극복하도록 한다. 이 방식은 기존 Hamming code 방식보다 33% 적은 데이터 트래픽 부하를 가진다.

• Journal of information and communication convergence engineering
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• 제10권1호
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• pp.85-90
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• 2012

A 40-MS/sec 10-bit pipelined analog to digital converter (ADC) with a 1.2 Vpp differential input signal is proposed. The implemented pipelined ADC consists of eight stages of 1.5 bit/stage, one stage of 2 bit/stage, a digital error correction block, band-gap reference circuit & reference driver, and clock generator. The 1.5 bit/stage consists of a sub-ADC, digital to analog (DAC), and gain stage, and the 2.0 bit/stage consists of only a 2-bit sub-ADC. A bootstrapped switch with a constant resistance is proposed to improve the linearity of the input switch. It reduces the maximum VGS variation of the conventional bootstrapped switch by 67%. The proposed bootstrapped switch is used in the first 1.5 bit/stage instead of a sample-hold amplifier (SHA). This results in the reduction of the hardware and power consumption. It also increases the input bandwidth and dynamic performance. A reference voltage for the ADC is driven by using an on-chip reference driver without an external reference. A digital error correction with a redundancy is also used to compensate for analog noise such as an input offset voltage of a comparator and a gain error of a gain stage. The proposed pipelined ADC is implemented by using a 0.18-${\mu}m$ 1- poly 5-metal CMOS process with a 1.8 V supply. The total area including a power decoupling capacitor and the power consumption are 0.95 $mm^2$ and 51.5 mW, respectively. The signal-to-noise and distortion ratio (SNDR) is 56.15 dB at the Nyquist frequency, resulting in an effective number of bits (ENOB) of 9.03 bits.

• 한국결정성장학회지
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• 제27권4호
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• pp.191-195
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• 2017

본 연구에서는 공기 정화식 마스크의 필터로 사용되는 일반적인 부직포와 전기방사 나노섬유가 코팅된 부직포에 대한 미세 구조를 분석하고 미세먼지 차단 특성을 향상 시킬 수 있는 새로운 마스크 디자인을 제안하였다. 평균적으로 $25{\mu}m$의 직경을 갖는 부직포 섬유와 달리 전기방사 방법으로 형성된 나노섬유는 그 직경이 25 nm~120 nm로 매우 작아 비표면적이 크고, 불규칙적으로 배열된 촘촘한 그물방 구조를 갖고 있었다. 일반적인 부직포 필터는 부직포 섬유 표면의 정전기력에 의해 미세먼지를 흡착할 수 있었지만, 수십 ${\mu}m$ 크기 이상의 기공이 부직포 전반에 걸쳐 존재하기 때문에, 수 ${\mu}m$ 크기를 갖는 미세먼지를 여과하는데 한계가 있었다. 반면 나노섬유가 코팅된 부직포 필터의 경우, 나노섬유의 구조적 특성으로 인해 투과성과 통기성을 유지하면서 수 ${\mu}m$ 크기의 미세먼지를 기계적으로 흡착하여 효과적으로 여과할 수 있었다. 우수한 마스크 필터의 성능과 더불어 올바른 마스크 착용이 미세먼지 차단 특성을 극대화 할 수 있는데, 이를 위해 안면부와 마스크 사이의 틈으로 미세먼지의 유입을 막을 수 있도록 안면부에 밀착이 잘 될 수 있는 새로운 마스크 디자인을 제안하였다.

• Carbon letters
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• 제16권3호
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• pp.192-197
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• 2015

In the present work, we propose a molecule (C₁₄H₁₄) that can be used as a building block of hexagonal diamond-type crystals and nanocrystals, including wurtzite structures. This molecule and its combined blocks are similar to diamondoid molecules that are used as building blocks of cubic diamond crystals and nanocrystals. The hexagonal part of this molecule is included in the C₁₂ central part of this molecule. This part can be repeated to increase the ratio of hexagonal to cubic diamond and other structures. The calculated energy gap of these molecules (called hereafter wurtzoids) shows the expected trend of gaps that are less than that of cubic diamondoid structures. The calculated binding energy per atom shows that wurtzoids are tighter structures than diamondoids. Distribution of angles and bonds manifest the main differences between hexagonal and cubic diamond-type structures. Charge transfer, infrared, nuclear magnetic resonance and ultraviolet-visible spectra are investigated to identify the main spectroscopic differences between hexagonal and cubic structures at the molecular and nanoscale. Natural bond orbital population analysis shows that the bonding of the present wurtzoids and diamondoids differs from ideal sp³ bonding. The bonding for carbon valence orbitals is in the range (2s^0.982p^3.213p^0.02)-(2s^0.942p^3.313p^0.02) for wurtzoid and (2s^0.932p^3.293p^0.01)-(2s^0.992p^3.443p^0.01) for diamantane.

• 농촌의학ㆍ지역보건
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• 제25권2호
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• pp.217-230
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• 2000

For the longest time, our government has played an inconsiderable role in the public health services of Korea, especially as it relates to their investment. Voices have cried out against increases in national health expenditure and for more establishment of public medical facilities. In light of this, the necessity and importance of public medical facilities have come into focus amidst the recent medical crisis. When public medical facilities filled in the gap created by the suspension or closure of private hospitals and clinics as a result of this national crisis and acted as a safety net, the demand for more establishment of such facilities increased. Although patient diagnosis and treatment are the first priority of public medical facilities, they must also deal with scopes that private medical facilities do not deal with, dislike, or have difficulty with. In this respect, the closure or privatization of public hospitals to reduce their number just because of their low profits or financial burdens that must be carried by the government is to ignore their innate importance and social role; therefore, we must do all we can to block such efforts and further empower these public health facilities according to demands of the time. The improvement of public health services can be realized by redefining its goals and roles, increasing government funding, strengthening of existing public health facilities and reorganizing the public health services system. Even if public health facilities were to increase their medical services and be reinforced, they cannot take on all the services related to public health services, Therefore, in a country like ours where public health services come second to private health services in the health care system, the health of citizens can be safeguarded only when private and public facilities cooperate and private medical facilities share the social responsibilities. Only the show of interest and effort by government, politicians, health professionals, professional organizations and public can initiate the improvement that is sought.