Femtosecond laser based high-performance micro-hole drilling on metal with vibration assistance and AgNW/CNT hybrid film patterning

윤지욱 과학기술연합대학원 대학교 2015 국내박사

In this dissertation, development of laser micromachining process for industrial applications and those experimental results are described. First, based on interaction mechanism between femtosecond pulse and material, theoretical background of femtosecond laser micromachining process is introduced. Second, two different researches using femtosecond laser are described in the paper as title of femtosecond laser micro hole drilling integrated with vibration module, patterning technique for silver nanowire (AgNW) / carbon nanotube (CNT) hybrid conductive film. First, femtosecond laser micromachining integrated with vibration module for micro hole drilling has been studied. Thickness of 30 ㎛ Invar alloy is drilled to investigate on angle control of hole taper by changing parameters including amplitude of vibration module and laser pulse energy. Wavelength of 795 nm, pulse width of 90 fs femtosecond laser system integrated with vibration module, so called the hybrid laser system, is used for the experiment. Displacement of focusing position is generated by moving the objective lens vertically by vibration module. The displacement value is range from 0 to 16 ㎛ by following the amplitude parameter, and the test is conducted without changing parameters except displacement of the focused beam. Comparison between shape of the ablated hole with vibration module and without is reported and discussed about possible mechanisms. Various micro machined holes with different taper angle results are observed, and holes with different taper angle are resulted. Second, femtosecond laser micromachining for patterning silver nanowire (AgNW) / carbon nanotube (CNT) hybrid conductive film have studied. A femtosecond laser which specifications of 1027nm wavelength and 380fs pulse width is used for the experiment. Ablation test for the AgNW/CNT film is performed at laser fluence values ranging from 9.7 mJ/cm2 to 70.8 mJ/cm2, and the threshold of the film is found at 13.6 mJ/cm2. By increasing laser flunce, diameter of crater is sharply increased until fluence reaches at 65.2 mJ/cm2, and damage to the glass substrate is observed when fluence is over than 67.9 mJ/cm2. Fluence value for line pattering is determined as fluence value of 67.9 mJ/cm2 which is not influenced value to glass substrate. From the measurement result of the patterned line, the irregularly ablated area is easily observed near the completely ablated region. To pattern line without residual at the irradiated area, quasi flat-top beam profile is employed instead of the conventional Gaussian’s. The measurement result of the patterned line shows dramatically decreased uneven area when the quasi flat-top energy distribution is used.

생애주기에 따른 교육목회 커리큘럼 연구: 성인초기(20~45세)를 중심으로

윤지욱 장로회신학대학교 일반대학원 2024 국내석사

파장가변형 광섬유 간섭필터의 제작 연구

윤지욱 경희대학교 대학원 1999 국내석사

광섬유 브래그 격자를 이용한 광 전달망에서의 광 신호대 잡음비 측정

윤지욱 충남대학교 대학원 2007 국내박사

A simple optical signal-to-noise ratio (OSNR) monitoring method is proposed and experimentally demonstrated. The proposed OSNR monitoring method has a simple configuration which is composed of optical circulator, fiber Bragg gratings (FBGs). OSNR can be measured by anaalyzing the transmitted optical signal power and the reflected optical signal power from FBG. The channel signal power can be monitored by measuring reflected signal power from FBG. The amplified spontaneous emission (ASE) noise of each channel signal can be obtained by subtracting crosstalk and residual channel signal power from the transmitted signal power from FBG. The monitoring error for OSNR is less than 0.8 dB in the channel power range of -19.2 dBm to -32.1 dBm and in the OSNR range from 14 dB to 27 dB compared with commercial optical spectrum analyzer with an optical resolution of 0.1 nm. The proposed method can be used to signal regeneration and regulation of multi-channel signals in the optical transport networks using optical cross connects or reconfigurable optical add-drop multiplexers.

위아전절제술 환자에서 흉부 경막외 자가진통요법의 비교 연구

윤지욱 부산대학교 대학원 2004 국내석사

술 후 통증치료를 위해 경막외공간에 투여하는 각각의 약제들의 효능과 부작용을 알아보기 위해 위아전절제술을 시행 받는 환자에서 세 군으로 나누어 경막외 자가통증조절을 위해 M군은 0.2 % ropivacaine과 morphine 40 μg/mL, F군은 0.2 % ropivacaine과 fentanyl 4 μg/mL, E군은 0.2 % ropivacaine과 epinephrine 2 μg/mL 150 mL를 만들어 각 군별 혼합용액을 투여하여 다음과 같은 결과를 얻었다. 1. 술 후 6 시간에서 M군과 F군이 E군 보다 유의하게 낮은 VAS 점수를 나타내었다. 술 후 24 시간에서는 F군이 E군보다 유의하게 낮은 VAS 점수를 나타내었다. 2. 세 군의 부작용에 대한 연구에서 소양증의 정도는 F군과 E군이 M군보다 6, 24 시간에서 유의하게 낮았다. 3. 24 시간에 투여한 약물의 총량은 M군이 F군과 E군보다 유의하게 적었다 이상의 결과로 위아전절제술 시 통증의 완화를 위한 흉추 경막외차단 시 epinephrine과 ropivacaine의 병용 투여 시 부작용은 거의 나타나지 않았으며, 진통작용은 낮았으나 환자가 만족하지 못할 정도는 아니었다. 따라서 아편유사제에 의한 부작용이 우려되는 환자에서는 epinephrine과 국소마취제의 병용 투여를 고려해 볼 수 있을 것으로 생각한다. Background: Local anesthetics and opioids have been widely used for epidural patient controlled analgesia (PCEA). Epinephrine also have been known to potentiate the analgesic effect of epidurally administered local anesthetics or opioids. The aim of this study was to compare analgesic effects and side effects of PCEA with ropivacaine mixed with either morphine, fentanyl, or epinephrine. Materials and Methods: Sixty-seven subtotal gastrectomy patients with postoperative analgesia by PCEA were randomly allocated into Group M; 0.2% ropivacaine and 40 ug/ml morphine, Group F; 0.2% ropivacaine and 4 ug/ml fentanyl, or Group E; 0.2% ropivacaine and 2 ug/ml epinephrine. The visual analogue scale (VAS) for pain and side effects at 6 and 24 hours postoperatively were measured. Results: The VAS scores were significantly higher in group E compared to group M and F at 6 hours postoperatively and to group F at 24 hours postoperatively. The total doses of PCEA in M group were lower than those of F and E groups. The incidence and severity of postoperative nausea were higher in group M compared to group F, E at 6 and 24 hours postoperatively. Conclusion: Epinephrine provided lesser side effects and higher VAS score compared to fentanyl or morphine mixed with ropivacaine PCEA . Epinephrine instead of opioids may be used for PECA without significant side effects, however the dose adjustment of PCEA may be needed for adequate analgesia.

Effect of propofol preconditioning on hypoxic-cultured human osteoblast

윤지욱 부산대학교 2012 국내박사

골 손상 환자는 저산소성 환경이 발생하면 골 형성 감소가 일어날 수 있으며 여러 임상 상황에서 진정제 및 마취제를 투여 받을 수 있다. 중환자실 및 수술실에서 널리 사용되는 propofol 은 골 손상 시 재형성 과정에 영향을 미칠 수 있다. 이 연구에서는 골아세포의 혈관생성과 세포 분화 및 증식을 나타내는 인자들을 이용해서 저산소성 환경에서 배양된 골아세포의 성장과 기능에 대한 propofol 전 처치의 효과를 연구하였다. 인간 골아세포에 propofol 3, 30, 300 μM 을 각각 전 처치 후 1% 산소농도 하에서 48 시간 동안 배양한 후 각 군들을 세포의 생존능력은 MTT 분석방식으로, 분화와 증식에 관련된 인자들은 PCR 과 Western blot analysis 방법으로 서로 비교하였다. 저산소성 환경에서 배양된 골아세포에 대한 propofol 전 처치는 BMP-2, TGF-β1, type I collagen, osteocalcin, Akt 와 같은 분화와 증식에 관련된 인자들의 활성을 촉진하였고 저산소성 환경에서 적응에 관련된 인자인 HIF-1 활성도 유도하였다. Propofol 은 농도가 300 μM 일 때 세포의 생존능력을 억제하였다. 저산소성 환경으로 배양된 골아세포에서 propofol 은 임상과 관련된 농도로는 세포독작용이 없었고 분화와 성장에 도움을 주었으며 저산소성 환경에서 혈관형성과 골 형성을 촉진시킨다고 추측할 수 있었다.

Design of high performance oxide semiconductor gas sensors using multi-modal porosity, micro-reactors, and regenerative sensing surface

윤지욱 Korea University 2016 국내박사

Metal oxide semiconductor gas sensors exhibit irreplaceable advantages such as simple structure, cost-effectiveness, and facile integration, which have been widely used to detect toxic, explosive, and inflammable gases. Recently, the applications of metal oxide semiconductor gas sensors are rapidly expanding to medical, environmental and mobile communication technologies by the combination with Internet of Things (IoTs). However, three of the greatest obstacles for the real and future applications still remain, which include 1) low sensitivity, 2) poor selectivity, and 3) humidity dependent gas sensing behaviors. In present thesis, I propose the novel strategies for designing highly sensitive, selective, and humidity independent metal oxide semiconductor gas sensors based on highly functionalized nano/micro-architected spheres including trimodal porous SnO2 nanospheres, Pd-loaded SnO2 and Co3O4 yolk-shell micro-reactors, and CeO2 uniformly coated In2O3 hollow spheres. The rapid and effective transfer of analytic gases to sensor surfaces through porous structure is essential for enhancing the gas response of metal oxide semiconductor gas sensors. For this, highly gas accessible and porous SnO2 spheres, which have three-dimensionally interconnected and size-tunable trimodal pores (micro-, meso-, and macro-pores), were prepared by a facile one-pot spray pyrolysis of an aqueous solution containing sacrificial templates of both macroscale polystyrene spheres (diameter: ~ 100 nm) and mesoscale-diameter (~ 20 nm), long carbon nanotubes and subsequent heat-treatment. The prepared SnO2 nanospheres with trimodal pores (size: ~ 3, ~ 20, and ~ 100 nm) showed unprecedentedly high response to several ppb levels of ethanol. Such an ultrahigh gas response is explained with respect to the hierarchical porosity and pore-size-dependent gas diffusion mechanism. Considering the recent rapid increasing of the necessity to detect numerous biomarkers and environmental gases, a new strategy to achieve gas selectivity should be addressed. The selective detection of representative indoor air pollutants such as xylene and toluene (methylbenzenes) was successfully demonstrated by a new micro-reactor concept using Pd-loaded SnO2 yolk-shell spheres, which was hardly accomplished by using other oxide nanostructures. The Pd-loaded SnO2 yolk-shell micro-reactors were prepared by a facile one-pot spray pyrolysis method, showed high response (S: resistance ratio) to 5 ppm of o-xylene and toluene with negligible cross-responses to 5 ppm of other interfering gases. In addition, the validity of micro-reactor concept was further confirmed by the selective gas sensor using Pd-loaded Co3O4 micro-reactors. The unusually high gas selectivity to chemically stable methylbenzenes is attributed to the highly controlled gas reforming reaction within both Pd-loaded SnO2 and Co3O4 micro-reactors with semipermeable shells. Finally, dynamic self-refreshing of the sensing surface was suggested as a new strategy to eliminate the humidity dependence of the gas sensing characteristics in metal oxide semiconductor gas sensors. The CeO2 nanoclusters were uniformly coated on the surface of In2O3 hollow spheres via layer-by-layer (LBL) assembly. In2O3 sensors LBL-coated with CeO2 nanoclusters showed humidity independent gas sensing characteristics such as gas response (S), sensor resistance in air (Ra), gas selectivity, and 90% response/recovery times (res and recov) even under continuously changing atmospheres (from dry to relative humidity of 80%), while pure In2O3 sensors showed significant humidity dependent gas sensing behaviors. The mechanism underlying the dynamic refreshing of the In2O3 sensing surface regardless of humidity variation is investigated in relation to the role of CeO2 and the chemical interaction among CeO2, In2O3, and water vapor (H2O). Three new and novel strategies suggested in the present thesis are 1) the design of multi-modal porous nanospheres with high pore interconnectivity, 2) the promotion of gas reforming reaction using catalyst-loaded yolk-shell micro-reactors, and 3) the realization of dynamic regenerative sensing surface via loading CeO2 nanoclusters on gas sensing materials. These can be generally used to design high performance gas sensors and pave a new way to develop highly sensitive, selective, and humidity independent gas sensor for real and future applications.

Femto-second 레이저를 이용한 금형재료 미세가공

윤 지욱 경북대학교 대학원 2009 국내석사

Nevertheless laser machining have several problems, such as heat transfer, it become popular for many fields of research and industry in the world. Especially femtosecond laser is widely using for many laser applications because of its characteristic of minimizing the heat transfer to the near area which can be a problem for machining process. In order to examine the potentiality of laser micromachining on mold material, we tested by femtosecond laser on the STAVAX which is well known for mold material for plastic injection process. We tested on the STAVAX using different pulse energy and different pulse numbers(single, 1, 5, 10, 25, 50, 100 pulses). The damage threshold and morphological change on the surface were examined using the SEM. The single pulse induced-damage threshold was measured 3.97TW/cm². In case of the multiple pulse-induced ablation, the damage threshold decreased with the number of pulses. We were able to observe the multiple pulse-induced ripple structure on the surface. The ripple structure is characterized as the repetitive lines with a 400nm pitch and the orientation is governed by the polarization of incident laser beam. We were also able to micromachine the grating lines with different pitch and different polarization angle. The ripple pattern angle which depends on the polarization angle was observed, as we expected. We observed the gap of undamaged area was not stable which polarization angle was 45, 0 degree. With this test result, we decided the grating fabrication with 90 degree polarization angle which is stable about the gap of unprocessed area. We fabricated diffraction grating which we designed alphabet letter "N". Fabricated area was 2mm x 2mm and we analyzed the diffraction grating using He-Ne laser.