MC-DS-CDMA 시스템에서 비선형 전력증폭기와 반송파 주파수 편차의 영향

최승국,조경아,Choi Seung-Kuk,Cho Kyoung-Ah 한국정보통신학회 2005 한국정보통신학회논문지 Vol.9 No.3

This paper evaluates the BER performance of MC-DS-CDMA systems in frequency selective Rayleigh fading channel, considering the carrier frequency offset and the nonlinear high power amplifier. In the uplink MC-DS-CDMA, the BER performance is better than in the downlink. This paper presents the required output back-off of the nonlinear amplifier and value of frequency offset for good BER performance. MC-DS-CDMA 시스템의 상$\cdot$하향링크에서 비선형 전력 증폭기와 반송파 주파수 편차의 영향을 고려하여 데이터가 주파수 선택적 Rayleigh 페이딩 채널을 통하여 전송될 때 비트 오류율을 분석한다. 분석 결과, 여러 명 사용자 경우에 상향링크가 하향링크 경우에 비하여 비트 오류율 특성이 우수하다. 본 논문에서는 우수한 비트 오류율 특성을 위하여 상$\cdot$하향링크에서 사용자 수에 따라 요구되는 비선형 증폭기의 최대 출력 전력 대 평균 출력 전력 비(OBO)와 반송파 주파수 편차의 크기를 구한다.

상온에서 RF 스퍼터링 방법으로 증착한 Hafnium Oxide 박막의 저항 변화 특성

한용,조경아,윤정권,김상식,Han, Yong,Cho, Kyoung-Ah,Yun, Jung-Gwon,Kim, Sang-Sig 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.9

In this study, we fabricate resistive switching random access memory (ReRAM) devices constructed with a Al/$HfO_2$/ITO structure on glass substrates and investigate their memory characteristics. The hafnium oxide thin film used as a resistive switching layer is sputtered at room temperature in a sputtering system with a cooling unit. The Al/$HfO_2$/ITO device exhibits bipolar resistive switching characteristics, and the ratio of the high resistance (HRS) to low resistance states (LRS) is more than 60. In addition, the resistance ratio maintains even after $10^4$ seconds.

전기방사법으로 제조된 Cu₂O-PVP 나노사의 전기적 특성

곽기열,조경아,윤정권,김상식,Kwak, Ki-Yeol,Cho, Kyoung-Ah,Yun, Jungg-Won,Kim, Sang-Sig 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.8

Hybrid nanofibers made of $Cu_2O$ and polyvinyl pyrrolidone were fabricated by electrospinning on glass substrates. The current magnitude of the $Cu_2O$-PVP hybrid nanofibers is 10 times larger than that of pure PVP nanofibers. In addition, $Cu_2O$-PVP nanofibers possess high sensitivity to air at room temperature than pure PVP nanifibers.

ZnO 나노선 트랜지스터를 기반으로 하는 Al 나노입자플로팅 게이트 메모리 소자의 특성

김성수,조경아,김상식,Kim, Sung-Su,Cho, Kyoung-Ah,Kim, Sang-Sig 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.4

In this paper, nonvolatile nano-floating gate memory devices are fabricated with ZnO nanowires and Al nanoparticles on a $SiO_2/Si$ substrate. Al nanoparticles used as floating gate nodes are formed by the sputtering method. The fabricated device exhibits a threshold voltage shift of -1.5 V. In addition, we investigate the endurance and retention characteristics of the nano-floating gate memory device.

치과 치료 시 진정법 시행에 대한 실태 조사 연구

배치훈,김혁,조경아,김미선,서광석,김현정,Bae, Chi-Hoon,Kim, Hyuk,Cho, Kyoung-Ah,Kim, Mi-Seon,Seo, Kwang-Suk,Kim, Hyun-Jeong 대한치과마취과학회 2014 Journal of Dental Anesthesia and Pain Medicine Vol.14 No.1

Background: Dental phobia or anxiety of patients is the serious impediment to appropriate and effective dental treatment. Sedative technique helps to mitigate patients' fear and anxiety thus make them more cooperative and familiar to dental practices. With increasing attention to sedative dentistry in dentists, educational requirements and technical qualification also become stricter but actual survey on recent sedative dentistry has not been reported yet. Especially there is insufficient study reporting the survey of sedative dentistry subjected to Korean adults. In this paper, we conducted a survey study on the actual condition and practice related to sedation with a questionnaire to dentists in South Korea. Methods: The survey was done for members of The Korean Dental Society of Anesthesiology (KDSA), who had great interest in sedation and for whom survey-by-mail was convenient. 472 members of The KDSA having dental license and solid address and contact information were subjected to the survey by sending them survey questions about their sedative techniques and knowledge. In order to increase the response rate, small gifts were presented to those who accurately responded to the survey questions and text messages and phone calls were made to encourage their participation. We collected their responses over two months and examined the returned surveys. Statistical analysis was performed using IBM SPSS Statistics 21 for each question. Results: Out of 472 dentists, 181 responded (38.4% response rate). 63.0% (114 dentists; 77 male and 37 female) of respondents had experience on sedative technique and their average age was $39.8{\pm}7.6$ year. 74 of them were private practitioners, 17 of them were professors (14.9%), 11 of them were dentists-in-service (9.6%), 11 of them were residents (specialist training) (9.6%) and 1 of them was military doctors (0.9%). There were 89 dentists (78.1%) who were specialists or receiving trainings to be specialist, most of whom were pediatric dentists (55, 48.2%) and oral surgeon (31, 27.2%). The most popular route for drug medications was orderly oral, inhalational, intravenous medication. Combination of oral and inhalational medications or single use of intravenous medication was the most common. The most preferred sedative drug was pocral in oral sedation and midazolam in intravenous sedation. 48.2% of practitioners responded that they experienced side effects and emergency situations. Airway obstruction was the most frequent. Conclusions: Results from the survey show that the protocol and system for sedative dentistry have been improved compared to the past. Nevertheless, quality of emergency protocol, monitoring devices and preparation of sedative drugs was still insufficient to achieve safe sedative procedure. This study acquires novelty since actual survey on recent sedative dentistry for adult patients has not been reported yet.

치의학대학원생의 심폐소생술 지식 및 심폐소생술 수행능력에 대한 조사연구

서광석,이정만,조경아,김현정,신터전,현홍근,김영재,김정욱,장기택,이상훈,김종철,Seo, Kwang-Suk,Lee, Jung-Man,Cho, Kyoung Ah,Kim, Hyun-Jeong,Shin, Teo Jeon,Hyun, Hong-Keun,Kim, Young-Jae,Kim, Jung-Wook,Jang, Ki-Taeg,Lee, Sang-Hoon,Kim, C 대한치과마취과학회 2012 Journal of Dental Anesthesia and Pain Medicine Vol.12 No.4

Background: This study evaluates the existing cardiopulmonary resuscitation (CPR) knowledge and skills of 1 st year dental students and also compares their CPR performance skill with those of 4 th year students. Methods: Incoming 1 st year and 4 th year dental students were surveyed about the level of their CPR knowledge before conventional CPR instruction. After we trained them for CPR performance, we tested CPR performance skill to randomly selected 10 1st year and 4 th year dental students and compared their CPR performance. Results: Overall CPR knowledge was low for both 1 st and 4 th year dental students. Especially, only 1 among 89 fourth year dental students answered the right sequence of CPR revised in 2010. Overall CPR performance was relatively low for both 1 st and 4 th year dental students. Irrespective of previous experiences of CPR education, their CPR performance was not statistically different. Conclusions: Retraining of CPR is a necessity. Information about the existing CPR knowledge for dental students will aid in establishing the goal of future CPR training and improve the current deficiency.

혈관 생성 억제 제를 투여한 신생마우스 폐 조직에서 Retinoic acid의 세포자멸사의 억제

주선영 ( Sun Young Ju ),조경아 ( Kyoung Ah Cho ),유경하 ( Kyung Ha Ryu ),우소연 ( So Youn Woo ),박은애 ( Eun Ae Park ),조수진 ( Su Jin Cho ) 대한주산의학회 2008 Perinatology Vol.19 No.1

목적: Retinoic acid는 폐포 재생에 중요한 역할을 하는 것으로 알려져 있어서 미숙아의 기관지폐이형성중의 예방에 사용되고 있다. 기관지폐이형성중의 병태생리는 미숙한 폐의 내피세포와 외피세포의 세포자멸사를 일으킴과 관련이 있다. 이에 본 연구에서 VEGFR2 억제가 신생 폐에서 세포자멸사를 증가시키는지, 또 retinoic acid의 투여가 본 폐 발달 억제 동물모형에서 세포자멸사를 억제하는지 알아보고자 하였다. 방법: VEGFR2 억제제인 SU1498을 생후3일된 마우스에 주사하고, 폐포발달이 이루어지는 그 후 10일간 retinoic acid나 위약을 주사하였다. 형태학적인 분석을 하였고, 세표자멸사를 비교분석하기 위해서 TUNEL 염색과 Annexin V을 표지자로 FACS출 시행하였다. 자멸사한 세포를 확인하기 위해서 동일초점 현미경으로 분석하였다. 결과: SU1498를 주사한 마우스에서 폐포면적과 평균폐포용적이 의미 있게 감소하였다. 세포자멸사도 약 3배 의미 있게 증가하였다. 자멸사한 세포는 내피세포와 상피세포에 분포하였다. Retinoic acid를 주사한 약 50%의 세포자멸사가 감소하였고, 형태학적으로 정상에 가까운 폐포 발달이 유지되었다. 결론: VEGFR2 억제를 하면 내피세포와 상피세포의 세포자멸사가 증가되면서 폐 발달이 저해되었다. 이어서 retinoic acid를 주사하면 세포자멸사가 억제되어 폐 발달유지에 도움이 되었다. 이러한 retinoic acid에 의한 세포자멸사의 억제가 기관지폐이형성증 예방에 기여할 것으로 추정된다. Background: Retinoic acid is known to play a role in alveolar regeneration and is used in the prevention of bronchopulmonary dysplasia (BPD) in premature infants. Many factors involved in the pathogenesis of BPD induce apoptosis of the endothelium and epithelium of the premature lung. We hypothesized that VEGFR2 inhibition would increase apoptosis in the newborn lung and retinoic acid would decrease apoptosis in our model of inhibited lung growth. Material and Methods: SU1498, a VEGFR2 inhibitor or vehicle was given to three-day-old mice. Subsequent retinoic acid or vehicle injection was given for ten days for the duration of alveolarization. Morphometric analyses were performed. Apoptosis was assessed with TUNEL staining and Annexin V staining. Co-localization of apoptotic cells with endothelial and epithelial cells was performed. Results: SUI498 injection reduced alveolar surface area and mean alveolar volume in newborn mice. Apoptosis was increased by three-fold in SU1498 injected mice. Apoptotic cells co-localized to endothelial and epithelial cells. Retinoic acid significantly reduced the degree of apoptosis by 50% in SU1498 injected mice and maintained lung development. Conclusion: VEGFR2 inhibition caused an arrest in lung development accompanied by an increase in apoptosis of endothelial and epithelial cells of the neonatal lung in mice. Subsequent retinoic acid treatment reduced apoptosis and we speculate that retinoic acid may preserve lung growth in bronchopulmonary dysplasia by inhibiting apoptosis in the neonatal lung.

열처리를 통한 HgSe 나노입자 기반 박막 트랜지스터의 전기적 특성 향상

윤정권(Yun, Jung-Gwon),조경아(Cho, Kyoung-Ah),김상식(Kim, Sang-Sig) 한국전기전자학회 2010 전기전자학회논문지 Vol.14 No.3

본 연구에서는, PVA를 게이트 유전체로 이용하여 백 게이트 (back-gate) 구조의 HgSe 나노입자 박막트랜지스터를 플라스틱 기판위에 제작하였다. 제작된 박막트랜지스터는 에서 5분 동안의 열처리 과정을 통하여 이동도 /Vs, 전류 점멸비 의 우수한 특성을 나타내었다. 열처리에 따른 표면 거칠기의 감소가 소자의 전기적 특성향상의 원인이라는 것을 AFM 이미지를 통하여 확인 할 수 있었다. 0.6%의 strain을 기판에 인가하면서 기판의 휘어짐에 따른 전류변화를 관찰하였다. In this study, we fabricated the HgSe nanoparticle-based thin film transistors (TFTs) of back gate structure with PVA gate dielectric. The fabricated TFTs show the improved electrical characteristics in the mobility of /Vs and the on/off ratio of after annealing process at for 5 min. AFM images demonstrate that the decrease in surface roughness according to annealing process leads to the improvement of electrical characteristics. The change in drain current caused from the conditions of flexible substrate is investigated under 0.6% strain.

Ge 나노입자가 형성된 MOS 캐패시터의 캐패시턴스와 전압 특성

박병준(Park, Byoung-Jun),최삼종(Choi, Sam-Jong),조경아(Cho, Kyoung-Ah),김상식(Kim, Sang-Sig) 한국전기전자학회 2006 전기전자학회논문지 Vol.10 No.2

Al2O3 층의 유무에 따른 Ge 나노입자가 형성된 MOS 구조의 캐패시터의 전압에 대한 캐패시턴스 (C-V)의 특성을 측정하였다. Al20O층이 형성된 MOS 캐패시터의 C-V 곡선은 전압의 변화에 대해 나타나는 반시계 방항의 히스테리시스 특성은 Si 기판과 Ge 나노입자 사이를 전자가 터널링하여 Ge 나노입자에 저장되었기 때문이다. Al2O3 층이 없는 MOS 캐패시터의 경우, 시계 방향의 히스테리시스 특성과 좌측으로 이동한 플랫-밴드 전압 값을 볼 수 있다. 이것은 SiO2 층에 존재하는 산소 결원 (oxygen vacancy) 으로 인한 전하 트랩이 이러한 특성을 나타냈다 할 수 있다. 또, 백색광이 C-V 특성에 미치는 영향에 대하여 논하였다. Capacitance versus voltage (C-V) curves of Ge-nanocrystal (NC)-embedded MOS capacitors with and without a single capping Al2O3 layer are characterized in this work. C-V curves of the Ge-NC-embedded MOS capacitor with the A12O3 layer are counterclockwise in the voltage sweeps, which indicates tile presence of charge storages in the Ge NCs by the tunnelling of charge carriers between the Si substrate and the Ge NCs. In the Ge-NC-embedded MOS capacitor without Al2O3 layer, clockwise hysteresis of the C-V curves and leftward shifts of the flat band voltages are observed for the embedded MOS capacitor without the Al2O3 layer. It is suggested that the characteristics of the C-V curves are due to the charge trapping at oxygen vacancies within a SiO2 layer. In addition, the illumination of the white light enhances the lower capacitance part of the C-V hysteresis. The origin for the enhancement is discussed in this paper.