분할 병합 방식을 이용한 가변 블록 변환 부호화 ( Variable Block Size Transform Coding Using Split and Merge Method )

김광택,김승종,김태우,김재훈,민병식,김한우,최병욱 대한전자공학회 1994 대한전자공학회 학술대회 Vol.1994 No.1

측쇄결합 폴리머 필름의 전기광학 특성 측정

김광택,이소영,이남권,송재원,박이순,금창대 한국광학회 1998 한국광학회지 Vol.9 No.4

전기광학 폴리머(electro-optic polymer)의 다양한 전기광학 특성을 동시에 측정하기 위한 실험장치와 기법을 제안하였다. 제안된 실험장치를 이용하여 폴링(poling)전 측쇄(side-chain)결합형 전기광학 폴리머 필름에 강한 de 및 ac 전기장을 인가시 발생하는 전기광학 효과와 복굴절을 관측하였다. 다양한 폴링조건에 따른 전기광학 계수의 의존성을 실시간으로 측정하였다. 폴링후의 폴리머 필름의 열적 안정성을 평가하기 위하여 전기광학 효과의 이완현상을 측정하여 잘 알려진 전기광학 폴리머와 특성을 비교하였다. 이 실험장치는 실험과정과 시간을 줄일 수 있다. We proposed an in situ measurement set-up and technique to measure the various electro-optic(E-O) properties of the E-O polymer. Using the proposed measurement set-up, the electro-optic effect and birefringence of unpoled side-chain E-O polymer induced by the strong dc and ac electric field were observed. The dependence of the E-O coefficients on the various poling conditions were measured with real time. To evaluate the thermal stability of the poled polymer the relaxation of the E-O effect was measured and the result was compared with well known polymer materials. The proposed measurement reduces the number of experimental steps and saves measurement time.

생체 적합 소재 응용을 위한 비대칭 마그네트론 스퍼터링으로 제작된 Ni 도핑된 탄소 박막의 제조 및 특성

김광택,박용섭 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.1

Various Ni-doped carbon (C:Ni) thin films were fabricated using different Ni target power densities byunbalanced magnetron sputtering (UBM). The effects of target power density on the structural, physical, surface, andelectrical properties of C:Ni films were investigated. The UBM C:Ni thin films exhibited uniformly smooth surfaces. The rms surface roughness and friction coefficient values of the C:Ni films decreased with the increase in target powerdensity. The physical properties of the films such as hardness and elastic moduli increased while their electricalproperties such as resistivity decreased with the increase in the target power density. These results show that an increaseof the power density leads to an increase in the proportion of Ni and nanocrystallization of the amorphous carbon film;this contributes to the changes observed in the physical and electrical characteristics. 본 논문에서는 비대칭 마그네트론 스퍼터링법으로 Ni 타겟 전력 밀도에 따라 증착시킨 Ni 도핑 탄소(C:Ni) 박막의 표면, 구조, 전기적 특성등을 고찰하였다. 비대칭 스퍼터링 장치로 증착한 C:Ni 박막은 균일하고 결함이 없이 증착되었으며, Ni 타겟 전력 밀도 증가에 따라 표면거칠기와 마찰계수 값은 감소하였다. C:Ni 박막의 경도와 탄성계수 값은 전력밀도에 따라 증가하였고 박막의 비저항 값은 타겟 전력 밀도 증가에 따라 감소하였다. 이러한 결과는 전력밀도 증가는 비정질 탄소 박막에 금속인 Ni의 비율이 증가시키고, 박막의 나노결정화를 향상시켜 박막의 구조적, 물리적, 전기적 특성 변화에 기여했다.

기도-기관지 질환의 냉동치료

김광택,Kim, Kwang-Taik 대한기관식도과학회 2009 大韓氣管食道科學會誌 Vol.15 No.2

측면 연마된 단일모드 광섬유와 열 광학 다중모드 평면도파로를 이용한 능동형 광 결합기

김광택,유호종,김성국,이소영,송재원,이상재,김시홍,강신원 한국광학회 1999 한국광학회지 Vol.10 No.3

본 논문에서는 측면이 연마된 단일모드 광섬유와 폴리머 다중 평면도파로가 결합했을 때 발생하는 모드 결합현상을 이용한 능동형 광결합기를 연구하였다. 제안된 소자는 파장가변 광필터나 광변조기로 이용할 수 있을 뿐만 아니라, 광도파로 물질의 굴절률, 복굴절, 전기광학 계수, 열광학 계수 등을 측정하는 도구로 응용할 수 있다. BPM으로 최적화된 결합기를 설계하였고, 열광학 폴리머를 능동 평면 도파로층으로 이용하여 결합기를 제작하였다. 제작된 소자는 -0.5dB 이하 손실, 공진파장 -13dB 소멸비. 그리고 열광학 효과에 의해 -1.5nm/$^{\circ}C$ 정도의 파장 가변성을 보였다. 본 연구의 결과로 볼 때 열광학 능동형 광결합기는 광변조기, 파장가변 광필터, 광센서 등으로 이용될 가능성이 높다. In this paper, we have investigated a fiber type active coupler which utilizes the mode coupling between the side polished single mode optical fiber and the active multimode planar waveguide. The proposed device can be used for not only tunable wavelength filter or optical intensity modulator but also a tool for measuring optical properties of guiding material such as refractive index, birefringence, electro-optic coefficient, and thermo-optic coefficient. We gave designed and optimized a coupler structure using the BPM and fabricated the device using thermo-optic polymer as active planar waveguide overlay. The device showed that insertion loss was less then 0.5 dB, extinction ratio was -13 dB at the resonance wavelength, and the wavelength tunablity due to thermo-optic effect was -1.5 nm/$^{\circ}C$. The active coupler using thermo-optic effect can be used as a wavelength tunable filer, an optical intensity modulator and an optical sensor. pulses that are subsequently compressed by a dispersive optical fiber. Experimental results show that $sech^2$ shape pulses with a pulse width of ~14 ps and a time bandwidth product of ~0.34 are successfully generated at 10 GHz repetition rate. In contrast to other methods, such as higher order soliton compression, this approach does not depend on the optical power and thus shows promise for application to low-power lasers.

In-line Variable Optical Attenuator Based on the Bending of the Tapered Single Mode Fiber

김광택,강지훈,황보승,임기건 한국광학회 2009 Current Optics and Photonics Vol.13 No.3

We propose a simple in-line variable optical attenuator (VOA) based on the bending effect of tapered single mode fibers. The influence of the taper structure and the reflective index of the external medium surrounding the taper region on the bending loss of the tapered fiber have been investigated experimentally. An attenuation range exceeding 35 dB and a very low excess loss of < 0.2 dB at 1550 nm were achieved. The measured polarization dependent loss of the present VOA at the attenuation level of 10 dB, 20 dB, and 30 dB were 0.1 dB, 0.2 dB, and 0.5 dB, respectively.

광섬유-평면도파로 광 결합기를 이용한 광 필터 제작과 특성 측정

김광택,이소영,손경락,이종훈,송재원,이상재,김시홍,강신원 한국광학회 1999 한국광학회지 Vol.10 No.5

측면 연마된 단일모드 광섬유와 다중모드 폴리머 평면도파로 사이의 소산장 결합을 이용한 광필터를 제작하고 그 특성을 측정하였다. 소자의 편광의존성을 줄일 수 있는 방법 제안하였으며 실험으로 검증하였다. 그리고 광필터의 공진파장과 여과 깊이는 평면도파로의 두께와 연마깊이로서 적절히 선택할 수 있음을 실험으로 보였다. 광섬유 연마과정, 폴리머 평면도파로 제작 등을 포함한 소자제작 공정을 소개하였다. 제작된 광필터의 3㏈대역폭은 15nm, 삽입손실은 0.2㏈, 편광에 따른 공진 파장의 차이는 2nm 이하였다. 그리고 주위온도에 의한 공진파장의 이동거리는 -0.35nm/$^{\circ}C$로 측정되었다. Optical filters utilizing the evanescent filed coupling between the side polished fiber and polymer planar waveguide were fabricated and optical properties of the devices were measured. A scheme for reducing polarization dependent properties of the device was proposed and demonstrated experimentally. Our measurement results showed that resonance wavelengths and filtering depth of the optical filters can be determined by adjusting thickness of planar waveguide and polishing depth of the fiber. The device fabrication procedure including fiber polishing steps and formation of polymer planar waveguide were described. The optical characteristics of fabricated optical filers were that 3 dB bandwidth was 15 nm, the resonance wavelength difference between the TE and TM polarized response was less then 2 nm, and insertion loss was less then 0.2 dB. The measured resonance wavelength drift dut to the variation of ambient temperature was -0.35 nm/$^{\circ}C$.

심장판막치환수술후 항혈소판제의 혈전방지 효과에 관한 임상관찰 및 실험적 연구

김광택 고려대학교 의과대학 1987 고려대 의대 잡지 Vol.24 No.1

Thromboembolism is one of the main complications in the course of patients having prosthetic cardiac valve replacement. Prevention of thromboembolism after prosthetic cardiac valve replacement is mandatory for patient. The thromboembolic events of 54 patients who were treated with ticlopidine and aspirin after cardiac valve replacement were evaluated and compared with that of patients who were treated with warfarin and aspirin after same type operation. The follow-up period ranged from 4 to 110 months (mean of 48 months). There were 11 major thromboembolic episodes including three deaths in the warfarin group during mean follow-up period of 56 months. Two cases of cerebrovascular accident and one hemarthrosis were noted due to overdose of warfarin. In ticlopidine + aspirin group, there was only one fatal thromboembolic episode three months after mitral valve replacement during mean follow-up period of 18 months. Although the exact mechanism of the thromboembolic events is incompletely understood, it is clear that interaction of platelets with prosthetic surface results in adhesion and aggregation. We measured the parameters of platelet function in aggregation curve of platelet with platelet aggregometer (Chrono-log aggregometer, model No.430). Aggregation test was performed with three final concentrations of epinephrine in 10 μM/L, adenosine diphosphate in 5 μM/L and 10 μM/L. Twenty eight patients with prosthetic cardiac valves and 35 healthy volunteers were subgrouped as follows to evaluate the effect of antithrombotic drugs used. GroupⅠ; Eleven patients treated with 250-500㎎ of ticlopidine and 0.5gm of aspirin as a daily single dose after cardiac valve replacement (14 St. Jude Medical and 1 Carpentier-Edwards, 9 patients with atrial fibrillation among them). Group Ⅱ; Ten patients treated with 3-5㎎ of warfarin and 0.75gm of aspirin 6 months and single aspirin dose was matained afterwards as a life long regimen (3 St. Jude Medical, 1 Hall-Kaster and 7 Carpentier-Edwards valve, 9 patients in atrial fibrillation). Group Ⅲ; Seven patients who abandoned anticoagulant treatment (warfarin + aspirin) 6-12 months after the regimen as group Ⅱ(3 St. Jude Medical, 1 Bjo¨rk-Shiley, 1 Hall-Kaster, 3 Carpentier-Edwards valve, 2 of them are with atrial fibrillation). Normal control group; 35 healthy volunteers (28 males and 7 females) The following results were obtained. 1. The mean maximal platelet aggregability in groupⅠinduced by 10 μM/L epinephrine was 15.6% and 17.5 and 18.7% in B.M. in proportion to the induction by 5 and 10 μM/L ADP. 2. The mean maximal platelet aggregability in group Ⅱ induced by 10 μM/L epinephrine was 16.5% and 27.4 and 44.7% in B.M. in proportion to the induction by 5 and 10 μM/L ADP. 3. The mean maximal platelet aggregability in group Ⅲ induced by 10 μM/L epinephrine was 65% and 56.5 and 51.8% in B.M. in proportion to the induction by 5 and 10 μM/L ADP. 4. The mean maximal platelet aggregability in the normal subjects induced by 10 μM/L epinephrine was 64% and 65 and 69% in B.M. in proportion to the induction by 5 and 10 μM/L ADP. 5. Reversible change of platelet aggregation curve induced by 5 and 10 μM/L was noted all of the patients in group Ⅰ. Ticlopidine and aspirin produced a significant inhibition of platelet aggregation in the presence of ADP and epinephrine in this study. To evaluate the effectiveness of aspirin and ticlopidine as a antithromboembolic agents after cardiac valve replacement, an animal experiment was performed in 5 dogs. In 5 dogs,18mm polytetrafluoroethylene conduits containg home-made prosthetic cardiac valve were implanted between right ventricle and pulmonary artery. As antiplatelet agent, ticlopidine 200 ㎎/day was used in the post operation period during which time monthly laboratory parameters were obtained including hemoglobin, hematocrit, white cell count, lactic acid dehydrogenase, platelet count. Among the survived 4 dogs after conduit graft implantation two dogs died of the thromboermbolic complication. The two remaining dogs were investigated post operative 3 months period. Died dogs were autopsied at 4 and 6th week postoperatively and the heart and lungs were excised and examined grossly. Both valves had thrombus formation on the valve ring and disc. In conclusion, according to our clinical data and animal experimental data maintenance with combined therapy of aspirin and ticlopidine was effective in prevention of thromboembolism after cardiac valve replacement and hemorrhagic complication was negligible compared to the anticoagulant therapy with warfarin.

폴리이미드가 코팅된 측면 연마 광섬유를 이용한 습도 센서

김광택,양재창 한국센서학회 2023 센서학회지 Vol.32 No.1

We investigated a humidity sensor based on a polyimide-coated side-polished optical fiber. The polyimide film absorbed moisture, causing the resonant wavelength of the sensor to shift to a longer wavelength owing to the changes in the optical properties of the film. The experimental results showed that the resonant wavelength of the device shifted by 17–18 nm when relative humidity changed from 30% to 90%.

얇은 중간 금속층을 포함한 측면 연마 광섬유 결합기를 이용한 편광 분리기

김광택,이준옥 대한전자공학회 2003 電子工學會論文誌-SD (Semiconductor and devices) Vol.40 No.9

얇은 중간 금속층을 가지는 측면 연마 광섬유 결합기를 이용한 편광분리기를 구현하였다. 실험 결과는 적절한 두께론 가지는 중간 금속층은 두 측면 연마된 광섬유 사이에서 TE 편광 성분의 광결합은 차단시키는 반면 TM 편광성분의 광결합은 허용함을 보여주었다. 측면 연마 광섬유를 이용한 편광분리기 설계 및 제작 기법을 기술하였다. 제작된 편광분리기는 TE와 TM 편광에 대하여 18dB와 23dB의 분리비를 보였다. 삽입손실은 TE 편광의 경우 0.7dB, TM 편광의 경우 1.3dB로 측정되었다. We have demonstrated an in-line polarization splitter based on a side-polished fiber coupler including a thin metal intermediate layer. The experimental results revealed that the metal layer with proper thickness prevents TE polarization component from optical coupling between two contacted side-polished fibers, whereas it allows TM polarization component to the coupling. The design and fabrication techniques about the polarization splitter exploiting the side-polished fibers have been presented. The fabricated polarization splitter exhibited 18dB and 23dB of isolation ratio for TE polarization and TM polarization, respectively. The measured insertion loss for TE and TM polarization was 0.7dB and 1.3dB, respectively.