• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.381-385
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• 2016

Recently, white LEDs, especially, warm white LEDs have been intensively investigated due to outstanding optical properties, long term stability and low power consumption. In this study, mixed type and patterned type of remote phosphors were prepared by screen printing process employing green and red phosphor. Each type of remote phosphor exhibited distinctive photoluminescence spectrum. For example, the mixed type of remote phosphor exhibited unique spectrum, while the patterned type showed expectable spectrum depending on the concentration of phosphors. This indicates that a small amount of red phosphor dramatically reduced the green photoluminescence in the case of mixed-type remote phosphor, whereas the effect was negligible in the patterned-type remote phosphor. The possibility of undesirable chemical reaction was further investigated by using scanning electron microscopy and X-ray diffraction.

• Journal of Sensor Science and Technology
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• v.28 no.6
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• pp.366-370
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• 2019

In this study, we have successfully fabricated a highly conductive transparent electrode using Ag nanowires, based on piezoelectric polyvinylidene difluoride (PVDF) film, that can be applied as transparent and flexible speakers. The structural morphology of the Ag nanowires was confirmed by a detailed scanning electron microscopy. Ultraviolet-visible spectroscopy demonstrated that the transparent electrode fabricated by the Ag nanowires exhibited a transmittance of above 70%. The transparent electrode also showed very low sheet resistance with high flexibility. We have further developed an anti-oxidation coating layer by using a tetraethyl orthosilicate-poly trimethyloxyphenylsilane (TEOS-PTMS) slurry technique. It was confirmed that the transmittance and sheet resistance of the antioxidant film depends critically on the humidity of the film surface. We believe such Ag nanowire electrodes are a very promising next-generation transparent electrode technology that can be used in future flexible and transparent devices.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.154-157
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• 2005

The use of electron-beam(E-Beam) manufacture systems provides a means to alleviate optic exposure equipment's problems. We designed an E-beam manufacture system with SEM function. Optimal beam scanning is one of the most important conditions in the performance of E-beam and SEM. The performance of E-beam manufacture system and images of SEM are a close affinity with each other. Developed E-beam manufacture system consist of the controllers of high voltage, scanning, optic and high voltage generator. In this paper, we analyze the condition of steady beam scanning and describe the development of controller fer optimal beam scanning.

• Korean Journal of Optics and Photonics
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• v.17 no.4
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• pp.312-316
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• 2006

In this study, a miniature fiber-optic radiation sensor has been developed using a water-equivalent organic scintillator for electron beam therapy dosimetry. The intensity of Cerenkov light is measured and characterized as a function of the incident angle of the electron beam from a LINAC. Also, a subtraction method using a background optical fiber without a scintillator and an optical discrimination method using optical filters are investigated to remove Cerenkov light, which could cause problems or limit the accuracy for detecting a fluorescent light signal in a fiber-optic radiation sensor.

• Macromolecular Research
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• v.12 no.5
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• pp.484-489
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• 2004

We have prepared a phenothiazine-based nonlinear optical (NLO) chromophore that displays a fairly high microscopic nonlinearity through intramolecular charge transfer. The phenothiazine unit plays important roles of contributing its high electron donating ability and connecting the resonance pathway through a conjugative effect in the cyclized ring adjacent to the aromatic ring. Theoretical calculations and an absorption spectroscopic study provided useful information concerning the microscopic nonlinearity of the chromophores. We investigated the electro-optic (EO) properties of the guest-host systems in amorphous polycarbonate containing the synthesized chromophores at different concentrations under different poling temperatures. A real-time pole and probe method provided a much greater amount of information regarding how the EO properties can arise and how they can be optimized.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.24-29
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• 2006

The use electron-beam(E-beam) manufacturing system provides a means to alleviate optic exposure equipment's problems. We are developing an E-beam manufacturing system with scanning electron microscope(SEM) function. The E-beam manufacturing system consist of high voltage generator, beam blanker, condenser lenses, object lenses, stigmator and stage. The development of E-beam manufacturing system is used on the method of remaking SEM's structure. The functions of SEM are developed. It is important for the test of E-beam performance. In E-beam manufacturing system and SEM, beam focus is important function. In this paper, we propose intelligent remote control function for beam focus in E-beam manufacturing system. The function extends the user's function and gives convenience.

• Journal of Magnetics
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• v.18 no.2
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• pp.173-177
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• 2013

Cantilever-detected high-frequency electron spin resonance (ESR) is a powerful method of sub-terahertz and terahertz ESR spectroscopy for a tiny magnetic sample at low temperature. In this technique, a small magnetization change associated with ESR transition is detected as deflection of a sample-mounted cantilever. So far, we have succeeded in ESR detection at 370 GHz using a commercial piezoresistive microcantilever. The spin sensitivity was estimated to ${\sim}10^{12}$ spins/gauss. In order to further increase the sensitivity, we adopt a fiber-optic-based detection system using a Fabry-Perot interferometer in place of piezoresistive system. Fabry-Perot cavity is formed between an optical-fiber end and microcantilever surface, and a change in the interference signal, corresponding to the cantilever deflection, is sensitively detected. This system is suitable for low-temperature and high-magnetic-field experiments because of its compact setup and less heat dissipation. In this study, performance of Fabry-Perot interferometer is evaluated, and its application to cantilever-detected ESR measurement is described.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.2
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• pp.135-141
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• 2012

Purpose: Polymerization of HEMA(2-hydroxyethyl methacrylate) which can be used in the soft contact lens has been performed by using electron beam(EB) irradiation, and examined the best condition for the polymerization. Comparing the physical properties of the contact lenses to the one fabricated by thermal polymerization method, we check the use possibility of the EB irradiation to the fabrication of the soft contact lens. Methods: We investigated the degree of polymerization of the HEMA according to the composition of the monomer, the additive ratio and the dose of electron beam (0~120 kGy). The degree of polymerization was measured depending on the EB dose to research the best synthetic condition under the EB irradiation. The physical properties of the contact lens such as water content(%), oxygen transmissibility(Dk/t) and optical transmittance were analysed by using the FT-IR results with comparing the two different polymerization method (thermal and electron beam polymerization) with same additive ratio. Results: When the dose of electron beam was above 100 kGy, the degree of polymerization of HEMA was above 99% with regardless using cross-linker and initiator. The water content of the lens fabricated by EB method showed 10% higher than the one by the thermal method which was 40%. The lens fabricated by EB method also showed higher oxygen transmissibility(Dk/t) as same with the water content, and showed twice higher value in the lens fabricated by pure HEMA. According to the FT-IR results, hydrophilic property of the lens fabricated by EB method was increased due to increasing the intermolecular hydrogen bonding. It showed above 90% optical transmittance in the visible range of wavelength on the contact lenses fabricated by the both of two different polymerization method. Conclusions: The polymerization of HEMA without cross-linker and initiator was successful above 100 kGy of EB irradiation. Moreover the lens fabricated from the polymer synthesized by pure HEMA with 100 kGy of EB showed the highest water content and oxygen transmissibility. Therefore EB irradiation is another possible method to synthesize the polymer which can be used for the soft contact lens.

• Applied Microscopy
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• v.32 no.2
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• pp.131-147
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• 2002

Optic lobes of Todarodes pacificus and Octopus minor are largely divided into cortex and medulla, the cortex being composed of three layers (an outer granule cell layer, a plexiform layer, and an inner granule cell layer). The cortex of Todarodes pacificus is about $420{\sim}450{\mu}m$ thick, being $170{\sim}200{\mu}m$ thicker than that of Octopus minor of which thickness is about $250{\sim}290{\mu}m$. In the outer granule cell layer of Todarodes pacificus, three types of nerve cells (type-A, type-B and type-C) and neuroglial cells that surround or contact with the neurons are observed, while in the outer granule cell layer of Octopus minor, two types of nerve cells (type-A and type-B) and a single type of neuroglial cells are observed. In a plexiform layer, a presynaptic bag and nerve endings are connected to each other, consequently forming various types of synaptosomes. The synaptosomes of Todarodes pacificus contain electron dense vesicles, electron dense-core vesicles and electron lucent vesicles, either individually or in a mixture. On the other hand, three types of synaptosomes a mixture of electron dense-core vesicles and electron lucent vesicles, electron lucent vesicles only, and electron dense-core vesicles only are observed in Octopus minor. The structures of the inner granule cell layer are almost similar in the two species. It is composed of two types of nerve cells (type-A, type-B) and a single type of neuroglial cells. In the medulla of Todarodes pacificus, the cells of $7{\times}5{\mu}m$ are arranged to a line and form the palisade cell layer, but these are not observed in Octopus minor.

• Journal of Sensor Science and Technology
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• v.17 no.2
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• pp.100-105
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• 2008

The objectives of this study are to measure and to remove Cerenkov lights generated in a fiber-optic radiation sensor by a charge-coupled device. we have fabricated a fiber-optic radiation sensor which comprises an organic scintillator, a plastic optical fiber and a charge-coupled device. Charge-coupled device as a light measuring tool has many advantages which are easy in multi-dimensional measurements, high spatial resolution and relatively low cost.