펨토초 레이저에 의한 SUS 가공 특성 및 리플 생성

손익부,고명진,김영섭,노영철 한국레이저가공학회 2009 한국레이저가공학회지 Vol.12 No.1

Ripple formation of femtosecond laser in stainless steel is investigated using 184 fs pulses with a center wavelength of 785 nm. The effect of the laser polarization relative to the translation direction is observed. For drilling with a certain aspect ratio, reflections at the hole walls take place, leading to a non-uniform intensity distribution deep inside the formed hole. Finally, it is shown that a circular polarization during the drilling process significantly improves the quality of the produced holes.

γ-Benzene Hexachloride 투여로 인한 췌장의 외분비 및 내분비 세포의 변화에 관한 초미세형태학적 연구

박성대,김익동,손태중 慶北大學校 醫科大學 1980 慶北醫大誌 Vol.21 No.2

저자는 γ-BHC 투여로 인한 췌장의 외분비 및 내분비 세포의 변화를 미세 형태학적 측면에서 알아 보고자 생쥐에 0.15%의 γ-BHC를 0.15㎎및 0.3㎎을 1일 1회 7일간 단독투여한 군과 γ-BHC와 glutathione을 병용 투여한 군과를 각각 경시적으로 관찰하고 그 성적을 요약하면 다음과 같다. 광학현미경적으로는 충혈, 간질의 부종, 그리고 지방공포등이 경하게 외분비 조직내에 일어나고 내분비 세포에서는 아무런 변화를 관찰할 수 없었다. 전자현미경적으로는 핵에 있어서는 핵 변연의 불규칙, perinuclear space의 확장 및 heterochromatin의 증가 등이, RER에 있어서는 공포화, 수포화, 단열, intracisternal granule의 증가 및 ribosome의 탈락 등이, Golgi장치에서는 확장이, 효소원 과립에 있어서는 수의 감소 및 내용물의 전자밀도의 저하를 나타내는 incomplete zymogen granule의 출현이, lysosome에 있어서는 각종 형태의 것의 증가를 그리고 mitochondria에 있어서는 종창, cristae의 감소 및 그 안에 lysosome양 물질의 출현등이 관찰되었다. 이들 현상은 γ-BHC와 glutathione을 병용한 군에서보다 γ-BHC 단독으로 투여한 군에서 더 현저하고 투여 후 1일째와 3일째 사이에는 뚜렷한 차이가 없었다. Langerhans섬에서는 alpha 및 beta세포의 핵변연의 불규칙과 heterochromatin의 증가, mitochondria 종창 및 cristae의 감소 그리고 Golgi 장치의 확장 등이 경하게 나타났다. 이상의 연구 성적을 종합하여 볼 때 혈류를 따라 췌장에 들어간 γ-BHC는 외분비 세포에 있어서는 먼저 핵을 침해하고 이로 인하여 세포질 내의 소기관 특히 단백합성기구 및 energy 생산기구에 변성 내지 파괴성 변화를 가져오고 이들 변성 물질 내지 파괴산물을 처리하기 위하여 lysosome이 증가 되었다고 믿어진다. Langerhans섬에 있어서는 주로 alpha 및 beta세포에 경한 변성성 변화를 야기하는 것으로 생각된다. 또 이상의 변화들은 glutathione 을 병용투여함으로써 다소 경감된다. The author had administered 0.15㎎ and 0.3㎎ of 0.15%, γ-BHC per day for a week with or without 20㎎ of glutathione to the mice. Observation was made periodically to investigate the ultrastructural changes of pancreatlc exocrine and endocrine cells brought by γ-BHC. The results were summarized as follows. On light microscopic examination, congestion, intersititial edema, and fatty vacuolization were observed exocrine cells slightly but none found in islets. On electron microscopic examination, in the nuclei, irregularity of margin, widening of peinuclear spaces, and increase in amount of heterochromatin occurred. In the RER, shedding of ribosomes, increase in intracisternal granules, fragmentation, vesiculation and vacuolization; dilatation of Golgi complexes; appearance of incomplete zymogen granules suggesting decrease in number and electron density of zymogen granules; increase lysosomes in variable stages; swelling, loss of cristae, and appearance of lysosome-like structures in mitochondria. These changes were more pronounced in groups administered γ-BHC only than in combined. However there is no significant differences in structural changes between the frist and the third day observation of the above animals. In the alpha and beta cells of Langerhans islets, irregularity of nuclear margin, increase in amount of heterochromatin, loss of cristae and swelling of mitochondria and dilatation of Golgi complexes observed in slight degree. From the above results, it is specufated that the γ-BHC in pancreatic exocrine cells absorbed through blood circulation had injured the nuclei and, as a result, degenerative and destructive changes of cell organelles particularly in the organelles participating protein synthesis and energy production about, with resultant increase of lysosomes to eliminate degenerative and destructive materials. In Langerhans islets, slight degenerative changes were occurred mainly in the alpha and beta cells. All changes descrbed above appears to be mitigated by adding glutathione to γ-BHC.

정신분열병에 대한 리스페리돈의 효과 및 안정성

이민수,김용구,김영훈,연병길,오병훈,윤도준,윤진상,이철,정희연,강병조,김광수,김동언,김명정,김상훈,김희철,나철,노승호,민경준,박기창,박두병,백기청,백인호,손봉기,손진욱,양병환,양창국,우행원,이정호,이종범,이홍식,임기영,전태연,정영조,정영철,정인과,정인원,지익성,채정호,한상익,한선호,한진희,서광윤 大韓神經精神醫學會 1998 신경정신의학 Vol.37 No.1

연구목적 : 본 시험의 목적은 임상시험 시작전에 연구자들을 대상으로 PANSS Workshop을 통하여 PANSS, ESRS에 대한 국내에서의 표준화 작업을 구축하고 새로운 정신병 치료제인 리스페리돈의 효과와 안정성을 재확인하여 리스페리돈 사용에 대한 적정화를 이루는데 있다. 연구방법 : 1996년 4월부터 1996년 9월까지 국내 39개 대학병원 정신과에 입원중인 혹은 증상이 악화되어 입원하는 정신분열병 환자 377명을 대상으로 다시설 개방 연구를 시행하였다. 1주일간의 약물 배설기간을 가진후, 리스페리돈을 8주간 투여하였고, 기준점, 1주, 2주, 4주, 그리고 8주후에 평가되었다. 용량은 제1일에는 리스페리돈 1mg씩 1일 2회, 제2일에는 2mg씩 1일 2회, 제3∼7일에는 3mg씩 1일 2회 투여하였다. 이후 환자의 임상상태에 따라 임의로 증량할 수 있으며, 최대 일일 16mg을 초과하지 않도록 하였다. 추체외로 증상을 조절하기 위한 투약을 허용하였다. 임상증상 및 부작용의 평가는 PANSS(Positive and Negative Syndrome Scale), CGI(Clinical Global Impression) 그리고 ESRS(Extrapyramidal Symptom Rating Scale)을 사용하였다. 연구결과 : 377명중 343명(91%)이 8주간의 연구를 완결하였다. 치료 종결시점인 8주후 PANSS 총점수가 20% 이상 호전된 경우를 약물 반응군으로 정의할때, 약물반응군은 81.3%였다. 리스페리돈에 반응하는 예측인자로는 발병연령, 이전의 입원 횟수, 유병기간이 관련 있었다. 리스페리돈은 1주후부터 PANSS양성, 음성, 및 일반정신병리 점수상에 유의한 호전을 보여 효과가 빨랐다. CGI의 경우도 기준점에 비해 1주후부터 유의한 감소를 나타내었다. ESRS의 경우, 파킨슨 평가점수는 기준점과 비교해 투여 1주, 2주, 4주후 유의하게 증가되었다가 8주후 기준점과 차이가 없었다. Dystonia 평가점수는 1주후만 유의한 증가를 보였으며, dyskinesia 평가점수는 유의한 차이가 없었다. 혈압, 맥박수의 생명징후 및 일반 혈액학 검사, 생화학적 검사, 심전도 검사에서 유의한 변화는 없었다. 결 론 : 이상의 다시설 개방 임상 연구를 통해 리스페리돈은 정신분열병 환자에서 양성증상뿐만 아니라 음성증상 및 전반적인 증상에도 효과적인 것으로 사료된다. 보다 명확한 평가를 위해서는 다른 항정신병약물과의 이중맹검 연구가 필요할 것으로 생각되며, 또한 장기적 치료에 대한 평가도 함께 이루어져야 하겠다. Objective : The purpose of this study was to investigate the efficacy and safety of risperidone in the treatment of Korean schizophrenic patients. Method : This multicenter open study included 377 schizophrenic patients drawn from 39 university hospitals. After a wash-out period of 1 week, the schizophrenic patients were treated with risperidone for 8 weeks and evaluated at 5 points ; at baseline, and 1, 2, 4 and 8 weeks of treatment. The dose was increased from 2mg/day(1mg twice daily) to 6mg/day(3mg twice daily) during the first week and adjusted to a maximum of 16mg/day over the next 7 weeks according to the patient's clinical response. Medication to control extrapyramidal symptoms was permitted. The psychiatric and neurological status of the patients was assessed by PANSS, CGI, and ESRS scales. Results : 343(91%) of 377 patients completed the 8-week trial period. Clinical improvement, as defined by a 20% or more reduction in total PANSS score at end point, was shown by 81.3% of patients. The predictors of response to risperidone were associated older age, shorter duration of illness, fewer previous hospitalization. Risperidone had rapid onset of action ; a significant decrease of the total PANSS and three PANSS factor(positive, negative, general), and CGI was already noticed at the end of first week. For the ESRS, parkinsonism rating scores were significantly increased until week 4 comparing with baseline. Dystonia rating scores were significantly increased until week 1, and dyskinesia rating scores were not significantly changed during the study. Laboratory parameters including vital sign, EKG, hematological, and biochemical values showed no significant changes during the trial. Conclusions : This study suggests that risperidone is generally safe and effective against both the positive and negative symptoms in our group of patients.

Direct Writing of a 1-to-4 Optical Splitter and Packaging Technology Using a Femtosecond Laser

Ik-Bu Sohn Sohn,Hyoung-Jong Lee,Hyoung-Ju Park,이만섭 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.4

A 1-to-N optical splitter was fabricated using a focused 785-nm femtosecond laser to directly write a series of 1-to-2 Y-junction splitters in fused silica. The femtosecond laser direct writing technique has the potential to generate not only channel waveguide, but also three-dimensional optical devices. In this paper, a 1-to-4 optical splitter and U-grooves, which are used for fiber alignment, are simultaneously fabricated in fused silica glass by using near-IR femtosecond laser pulses. The obtained splitter was characterized in terms of its optical properties at a wavelength of 1550 nm. The fiber-aligned optical splitter has a low insertion loss, less than 9 dB, including an intrinsic splitting loss of 6 dB and an excess loss due to passive alignment of a single-mode fiber. A 1-to-N optical splitter was fabricated using a focused 785-nm femtosecond laser to directly write a series of 1-to-2 Y-junction splitters in fused silica. The femtosecond laser direct writing technique has the potential to generate not only channel waveguide, but also three-dimensional optical devices. In this paper, a 1-to-4 optical splitter and U-grooves, which are used for fiber alignment, are simultaneously fabricated in fused silica glass by using near-IR femtosecond laser pulses. The obtained splitter was characterized in terms of its optical properties at a wavelength of 1550 nm. The fiber-aligned optical splitter has a low insertion loss, less than 9 dB, including an intrinsic splitting loss of 6 dB and an excess loss due to passive alignment of a single-mode fiber.

Performance analysis of CO₂ laser polished angled ribbon fiber

Sohn, Ik-Bu,Choi, Hun-Kook,Noh, Young-Chul,Lee, Man-Seop,Oh, Jin-Kyoung,Kim, Seong-min,Ahsan, Md. Shamim Elsevier 2017 Optical fiber technology Vol.33 No.-

<P><B>Abstract</B></P> <P>This paper demonstrates CO<SUB>2</SUB> laser assisted simultaneous polishing of angled ribbon fibers consisting eight set of optical fibers. The ribbon fibers were rotated vertically at an angle of 12° and polished by repetitive irradiation of CO<SUB>2</SUB> laser beam at the end faces of the fibers. Compared to mechanically polished sharp edged angled fibers, CO<SUB>2</SUB> laser polishing forms curve edged angled fibers. Increase in the curvature of the end faces of the ribbon fibers causes the increase of the fibers’ strength, which in turn represents great robustness against fiber connections with other devices. The CO<SUB>2</SUB> laser polished angled fibers have great smoothness throughout the polished area. The smoothness of the fiber end faces have been controlled by varying the number of laser irradiation. After CO<SUB>2</SUB> laser polishing, the average value of the fiber angle of the ribbon fibers is ∼8.28°. The laser polished ribbon fibers show low insertion and return losses when connecting with commercial optical communication devices. The proposed technique of polishing the angled ribbon fibers is highly replicable and reliable and thus suitable for commercial applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Achieved CO<SUB>2</SUB> laser assisted polishing of angled ribbon fibers. </LI> <LI> CO<SUB>2</SUB> laser polished angled ribbon fibers show smooth end faces, which can reduce mechanical damage. </LI> <LI> CO<SUB>2</SUB> laser polished ribbon fibers show low insertion & return losses when connecting with optical devices. </LI> <LI> The proposed technique of polishing the angled ribbon fibers is highly replicable and reliable. </LI> </UL> </P>

COMPUTATION AND ANALYSIS OF MATHEMATICAL MODEL FOR MOVING FREE BOUNDARY FLOWS

Sohn, Sung-Ik Korean Mathematical Society 2000 대한수학회지 Vol.37 No.5

The nonlinear stage of the evolution of free boundary between a light fluid and a heavy fluid driven by an external force is studied by a potential flow model with a source singlarity. The potential flow model is applied to a bubble and spije evolution for constantly accelerated interface (Rayleigh-Taylor instability) and impulsively accelerated interface (Richtmyer-Meshkow instability). The numerical results of the model show that, in constantly accelerated intergace, bubble grows with constant velocity and the spike falls with gravitational acceleration at later times, while the velocity of the bubble in impulsively accelerated interface decay to zero asymp flow model for the bubble and spike for constantly accelerated interface and impulsively accelerated interface.

Ablation of Polypropylene for Breathable Packaging Films

Ik-Bu Sohn,Young-Chul Noh,Sung-Chul Choi,Do-Kyeong Ko,Jongmin Lee,Young-Jin Choi 한국레이저가공학회 2006 한국레이저가공학회지 Vol.9 No.3

  A Polypropylene (PP) film was ablated using a femtosecond laser with a center wavelength of 785 ㎚, a pulse width of 184 fs and a repetition rate of 1 ㎑. Increments of both pulse energy and the shot number of pulses lead to co-occurrence of photochemical and thermal effect, demonstrated by the spatial expansion of rim on the surface of PP. The shapes of the laser-ablated PP films were imaged by a scanning electron microscope (SEM) and measured a 3D optical measurement system (NanoFocus). And, the oxygen transmission rate (ORT) of periodically laser-ablated PP film were characterized by oxygen permeability tester for modified atmosphere packaging (MAP) of fresh fruit and vegetable. Our results demonstrate that femtosecond pulsed laser is efficient tools for breathable packaging films in modifying the flow of air and gas into and out of a fresh produce container, where the micropatterns are specifically tailored in size, location and number which are easily controlled by laser pulse energy and pulse patterning system.

Formation of a Plano-convex Micro-lens Array in Fused Silica Glass by Using a CO2 Laser-assisted Reshaping Technique

Ik-Bu Sohn,Dongyoon Yoo,Young-Chul Noh,Jae-Hee Sung,Seong-Ku Lee,최훈국,Md. Shamim Ahsan 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.3

We report on fabricating high-fill-factor plano-convex spherical and square micro-lens arrays on fused silica glass surface by using a CO2 laser-assisted reshaping technique. Initially, periodic micro-pillars are encoded on glass surfaces by means of a femtosecond laser beam, afterwards, the micro-pillars are polished several times by irradiating a CO2 laser beam on top of the micro-pillars. Consequently, a spherical micro-lens array with micro-lens size of 50 μm × 50 μm and a square micro-lens array with micro-lens size of 100 μm × 100 μm are formed on the surface of the fused silica glass. We also study the intensity distribution of light passing through the glass sample engraved with a spherical micro-lens array. The simulation result shows that the focal length of the spherical micro-lens array is 35 μm. Furthermore, we investigate the optical properties of glass samples with engraved micro-lens arrays. The proposed CO2-laser-based reshaping technique is simple and fast and shows promises for fabricating arrays of smooth micro-lenses in various transparent materials.

Fabrication of a bi-directional firing multimode fiber using a high repetition rate femtosecond laser and a CO₂laser

Sohn, Ik-Bu,Lee, Ho,Jung, Deok,Noh, Young-Chul,Kim, Changhwan IOP Publishing 2013 Laser physics letters Vol.10 No.10

ANALYTICAL AND NUMERICAL STUDY OF MODE INTERACTIONS IN SHOCK-INDUCED INTERFACIAL INSTABILITY

Sohn, Sung-Ik Korean Mathematical Society 2000 대한수학회논문집 Vol.15 No.1

Mode interactions at Unstable fluid interfaces induced by a shock wave (Richtmyer-Meshkov Instability) are studied both analytically and numerically. The analytical approach is based on a potential flow model with source singularities in incompressible fluids of infinite density ratio. The potential flow model shows that a single bubble has a decaying growth rates at late time and an asymptotic constant radius. Bubble interactions, bubbles of different radii propagates with different velocities and the leading bubbles grow in size at the expense of their neighboring bubbles, are predicted by the potential flow model. This phenomenon is validated by full numerical simulations of the Richtmyer-Meshkov instability in compressible fluids for initial multi-frequency perturbations on the unstable interface.