• Journal of the Optical Society of Korea
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• v.12 no.3
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• pp.126-130
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• 2008

We propose and experimentally demonstrate an effective method to reduce near-field speckle noise at the output of a 50 ${\mu}m$ graded index multimode fiber using a short cylindrical piezoelectric transducer(PZT) vibrating in the radial direction. The fiber was coiled as tightly as possible around the mandrel of the PZT and a periodic stretching effect was caused by the radial oscillations of the actuator. The output of the optical fiber using the He-Ne laser source was intensively observed by a CCD camera. By counting all the pixels corresponding to relative intensity graded into 256 levels in the selected area and by calculating standard deviation and mean value of the intensity, we could measure the speckle contrast and vibration effect quantitatively with reduction ratio of pixels and line profile of the illuminated region. It was clearly observed that the characteristics of the speckle pattern in the vibration-on state were significantly improved over that of the vibration-off state due to time-averaged smoothing.

• Journal of Oral Medicine and Pain
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• v.26 no.2
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• pp.161-171
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• 2001

In order to determine how oral mucosal change relates to inducing factors of burning mouth syndrome, the difference in pain perception scale and keratinization rate between burning mouth syndrome patients and normal subjects were investigated. Twenty patients (13 female, 7 male, mean age: 59 years), presenting in the Department of Oral Medicine, Chonnam National University Hospital were participated in this study. All subjects had been complaining of constant oral burning pain for more than a year, none took any strong analgesics, and none had oral mucosal lesions. Twenty volunteers (11 females, 9 males, mean age: 25 years) were also participated in this study as a control group. The control subjects had never had any symptoms of oral burning pain. A thermal stimulation using a Nd-YAG laser and cytological smear were carried out to anterodorsal part of tongue, tip of tongue, the left buccal mucosa, the lower lip mucosa and the chief complaint site. Stimulation of the dorsum of left hand was also carried out to contrast the mucosal area of burning mouth syndrome subjects and the control subjects. The laser output power could be adjusted from 0.75W to 4W. The pain perception scale of the burning mouth syndrome subjects were lower than in control subjects in the chief complaint area, the anterodorsal part of tongue and the buccal mucosa(p<0.01). The keratinization rate of burning mouth syndrome subjects, however, was higher keratinization rate than in normal subjects in the same area and lower lip mucosa(p<0.001). From above results, the anterodorsal part of tongue is the most appropriate site to use diagnostic laser stimulation. The higher level of keratinization and the lower level of thermal pain perception of the burning mouth syndrome subjects are explained as a protective mechanism against xerostomia and burning sensations. The application of Nd-YAG laser stimuli and cytological smear to oral mucosal surface could therefore be usefully employed as appropriate and standardized diagnostic tools for chronic orofacial pain subjects.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.12
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• pp.1626-1632
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• 2018

In this paper, we describe the fabrication and characterization of a hydrogen peroxide ($H_2O_2$) sensor based on palladium and copper (PdCu) electroplated laser induced graphene (LIG) electrodes. $CO_2$ laser was used to form LIG electrodes on a PI film. This fabrication method allows simple control of the LIG electrode size and shape. The PdCu was electrochemically deposited on the LIG electrodes to improve the electrocatalytic reaction with $H_2O_2$. The electrochemical performance of this sensor was evaluated in terms of selectivity, sensitivity, and linearity. The physical characterization of this sensor was conducted using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), which confirmed that PdCu was formed on the laser induced graphene electrode. In order to increase the sensor sensitivity, the Pd:Cu ratio of the electroplated PdCu was varied to five different values and the condition of highest amperometric current at an identical of $H_2O_2$ concentration was chosen among them. The resulting amperometric current was highest when the ratio of Pd:Cu was 7:3 and this Pd;Cu ratio was employed in the sensor fabrication. The fabricated PdCu/LIG electrode based $H_2O_2$ sensor exhibited a sensitivity of $139.4{\mu}A/mM{\cdot}cm^2$, a broad linear range between 0 mM and 16 mM of $H_2O_2$ concentrations at applied potential of -0.15 V, and high reproducibility (RSD = 2.6%). The selectivity of the fabricated sensors was also evaluated by applying ascorbic acid, glucose, and lactose separately onto the sensor in order to see if the sensor ourput is affected by one of them and the sensor output was not affected. In conclusion, the proposed PdCu/LIG electrode based $H_2O_2$ sensor seems to be suitable $H_2O_2$ sensor in various applications.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.7
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• pp.31-36
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• 2004

In comparison with in-plane lasers, predicting the output power and differential quantum efficiency of Vertical-Cavity Surface-Emitting Lasers(VCSELs) is very difficult due to the distributed Bragg reflector(DBR) layers. Therefore, effective cavity model and transfer matrix method have been adapted in order to calculate the output power and differential quantum efficiency The effective cavity model is inappropriate to calculate output power and differential quantum efficiency while it is practically adequate to calculate the threshold gain and threshold current density The reason is that the effective cavity model can not take account of the absorption in GaAs stack layer right below the metal aperture. In this paper, we have compared the threshold current and differential quantum efficiency calculated by using transfer matrix method with effective cavity model and we have made a study of the validity of the effective cavity model. Finally, we have confirmed the versatility of the transfer matrix method with these studies.

• Korean Journal of Optics and Photonics
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• v.20 no.5
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• pp.294-300
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• 2009

To improve the output power of a photomixer as a THz source, we propose a four-leaf clover-shaped antenna structure which is composed of a highly resonant radiation element and a stable DC feed element. The resonance characteristics of the proposed structure were investigated on a half-infinite substrate first as a simplified radiation environment in order to save the computation time. Based on the antenna characteristics on a half-infinite substrate, the antenna structure was designed to have a maximum total efficiency and a maximum directivity on an extended hemispherical lens. In comparison with a full-wavelength dipole, an input resistance of this structure increased six fold and this characteristic significantly improved the mismatch efficiency between a photomixer and an antenna. THz output power from this structure is expected to increase by 2.7 times as compared to a full-wavelength dipole case.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.449-453
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• 2021

Interest and investment in renewable energy have increased worldwide, highlighting the need for renewable energy. Solar energy was the most promising energy of all renewable energy sources, and it has the highest investment value. Because photovoltaics require a certain amount of area for installation, high density and high output performance are required. Shingled module is a promising technology in that they are featured by higher density and higher output compared to the conventional modules. Shingled technology uses a laser scribing to divide solar cells that are to be bonded with electrically conductive adhesive (ECA) to produce and connect strings, which has a higher output in the same area than the conventional modules. In the process of producing solar modules, metal ribbons are used to interconnect cells, but they are also needed for string connections in shingled solar cells. Accordingly, in this study, we researched the interconnection that best suits the connector that joins the string to the string. The module outputs produced under the conditions of the string interconnection were compared and analyzed.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2003-2005
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• 2004

본 논문에서는 패러데이 효과(Faraday effect)를 이용하여 초고압 전력설비에서 대전류 측정을 위한 광CT의 온도변화에 따른 특성에 대한 기초 연구를 하였다. 광원으로는 1310[nm] Laser Diode를 사용하고 수신부로는 PIN-Photodiode를 사용하였다. 실험을 위한 온도변환장치는 GIS와 같은 모양으로 재철은 알루미늄으로서 제작하였다. 광의 전송로는 파이버 내에서 편광상태를 유지할 수 있는 30[m]의 싱글모드 언재킷(unjacked) 파이버를 사용하였다. 전류의 측정은 400[A]에서 1300[A] 까지의 범위에서 측정하였으며 온도는 -40[$^{\circ}$]에서 50[$^{\circ}$]까지 10[$^{\circ}$]씩 증가시키면서 측정하였다. 이 때 출력선호는 인가전류의 중가에 따라 비례하여 증가하였으며 주변온도가 높을수록 비례하여 증가하였다.

• Proceedings of the CALSEC Conference
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• 1998.10b
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• pp.335-344
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• 1998

조직의 내외 부에서 추진되고있는 CALS/EC개념이 인터넷의 발전과 함께 우리의 주변에서 생성되는 많은 문서들에 대한 효율적인 관리가 절실히 요구되고 있다. 이러한 다양한 문서들에 대한 체계적인 관리기술로서 기록관리, 양식관리, 보고서관리, 제반규정관리, 저장관리, 검색관리 등을 통하여 최종사용자에게 적기적시에 제공할 수 있는 통합적인 시스템이 필요하다. 이에 관계되는 요소기술로서 EDM(Electronic Document Management), Image Document Management, COLD(Computer Output to Laser Disk), Hypermedia, Workflow, Knowledge Management 및 Groupware등이 개별적으로 또는 일부는 상호 연계되고 있으나, 통합적으로 상호 운용성 측면에서는 많은 문제들이 내포되어있다. 따라서 본 고에서는 이러한 CALS/EC개념에 입각한 문서관리의 효율적인 관리방법을 살펴보고, 다양한 형태의 기능별 문서에 대하여 통합적으로 관리할 수 있는 통합문서관리시스템에 대한 모형을 제시하고자 한다.

• Ceramist
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• v.10 no.3
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• pp.55-66
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• 2007

Infrared Scanning Near-field Optical Microscopy (IR-SNOM) is an extremely powerful analytical instrument since it combines IR spectroscopy's high chemical specificity with SNOM's high spatial resolution. In order to do this in the infrared, specialty chalcogenide glass fibers were fabricated and their ends tapered to generate SNOM probes. The fiber tips were installed in a modified near field microscope and both inorganic and biological samples illuminated with the tunable output from a free-electron laser located at Vanderbilt University. Both topographical and IR spectral images were simultaneously recorded with a resolution of ${\sim}50\;nm$ and ${\sim}100\;nm$, respectively. Unique spectroscopic features were identified in all samples, with spectral images exhibiting resolutions of up to ${\lambda}/60$, or at least 30 times better than the diffraction limited lens-based microscopes. We believe that IR-SNOM can provide a very powerful insight into some of the most important bio-medical research topics.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.3
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• pp.47-55
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• 1996

An optical transmitter, which is a key component of the optical transmission system, converts the electrical signal to optical signal and consists of a high-speed current-pulse driver for laser diode and low-speed feedback loops that stabilize optical power against aging, power supply voltage fluctuations, and ambient temperature changes. In this paper, the power-stabilizing part, which forms the bulk of the optical transmitter circuitry was designed in integrted circuits. Operational amplifiers and reference voltage generation circuits, which were identified as key building blocks for the power-stabilizing feedback loops, were designed and were subsequently verified through HSPICE simulations. The designed operational amplifier consists of a two-stage folded cascode amplifier and class AB output stage, whereas the reference voltage is obtained by bandgap reference circuits. Finally the power-stabilizing circuitry was laid out based on 3\mu$m CMOS design rules for fabrication.