• Current Optics and Photonics
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• v.8 no.2
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• pp.162-169
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• 2024

This study investigates the temperature sensitivities of fiber Bragg grating (FBG) across a broad temperature spectrum ranging from -196 ℃ to 900 ℃. We developed the FBG temperature measurement system using a high-temperature tubular furnace and liquid nitrogen to supply consistent high and low temperatures, respectively. Our research showed that the FBG temperature sensitivity changed from 1.55 to 10.61 pm/℃ in the range from -196 ℃ to 25 ℃ when the FBG was packaged with a quartz capillary. In the 25-900 ℃ range, the sensitivity varied from 11.26 to 16.62 pm/℃. Contrary to traditional knowledge, the FBG temperature sensitivity was not constant. This inconsistency primarily stems from the nonlinear shifts in the thermo-optic coefficient and thermal expansion coefficient across this temperature spectrum. The theoretically predicted and experimentally determined temperature sensitivities of FBGs encased in quartz capillary were remarkably consistent. The greatest discrepancy, observed at 25 ℃, was approximately 1.3 pm/℃. Furthermore, it was observed that at 900 ℃, the FBG was rapidly thermally erased, exhibiting variable reflected intensity over time. This study focuses on the advancement of precise temperature measurement techniques in environments that experience wide temperature fluctuations, and has considerable potential application value.

• Current Optics and Photonics
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• v.8 no.4
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• pp.355-365
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• 2024

Wavefront coding (WFC) imaging systems can redistribute the energy of an interference laser spot on an image plane sensor by wavefront phase modulation and reduce the peak intensity, realizing laser protection while maintaining imaging functionality by leveraging algorithmic post-processing. In this paper, a spiral axicon WFC imaging system is proposed, and the performance for laser protection is investigated by constructing a laser transmission model. An Airy disk on an image plane sensor is refactored into a symmetrical hollow ring by a spiral axicon phase mask, and the maximum intensity can be reduced to lower than 1% and single-pixel power to 1.2%. The spiral axicon phase mask exhibits strong robustness to the position of the interference laser source and can effectively reduce the risk of sensor damage for an almost arbitrary lase propagation distance. Moreover, we revealed that there is a sensor hazard distance for both conventional and WFC imaging systems where the maximum single-pixel power reaches a peak value under irradiation of a power-fixed laser source. Our findings can offer guidance for the anti-laser reinforcement design of photoelectric imaging systems, thereby enhancing the adaptability of imaging systems in a complex laser environment. The laser blinding-resistant imaging system has potential applications in security monitoring, autonomous driving, and intense-laser-pulse experiments.

• Korean Journal of Food Science and Technology
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• v.37 no.3
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• pp.405-411
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• 2005

Chitosan, second largest biomass after cellulose on earth, has potential for use as functional food package due to its antibacterial activity. However, due to high melting temperature of chitosan, chitosan films have been made by casting method. Because gelatin has relatively low molting temperature depending upon amount of plasticizer added, it was added to chitosan to produce commercially feasible film. The objective of the current study was to determine optimum blend ratio and amount of chitosan/gelatin blend solutions against antibacterial activities for extruder resin. Gram-positive bacteria (Bacillus cereus ATCC 14579 and Listeria monocytogenes ATCC 15313) and -negative bacteria (Escherichia coli ATCC 25922 and Salmonella enteritidis IFO 3313) were used. Paper (8 mm) diffusion and optical density methods were used to evaluate effect of different blending ratio solutions on the inhibition of bacterial growth. Measured clear none size ranged from 8 mm to 18.07 mm in paper diffusion test. For B. cereus, E. coli, and S. enteritidis, addition of $50\;{\mu}L$ blend solution (chitosan/gelatin = 2/8: 0.3 mg) resulted in clear zone on paper disc. In L. monocytogenes, inhibition effect was observed with 0.6 mg chitosan (chitosan/gelatin=4/6). Minimum inhibitory concentration (MIC) values of B. cerues, L. monocytogenes, E. coli, and S. enteritidis with addition of chitosan were 0.1461, 0.2419, 0.0980, and 0.0490 mg/mL, respectively, These results indicate possibility of producing commercially feasible film with addition of optimum chitosan/gelatin amount.

• Journal of Intelligence and Information Systems
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• v.29 no.1
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• pp.143-174
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• 2023

With the development of deep learning technologies, Artificial Intelligence powered Optical Character Recognition (AI-OCR) has evolved to read multiple languages from various forms of images accurately. For the financial industry, where a large number of diverse documents are processed through manpower, the potential for using AI-OCR is great. In this study, we present a configuration and a design of an AI-OCR modality for use in the financial industry and discuss the platform construction with application cases. Since the use of financial domain data is prohibited under the Personal Information Protection Act, we developed a deep learning-based data generation approach and used it to train the AI-OCR models. The AI-OCR models are trained for image preprocessing, text recognition, and language processing and are configured as a microservice architected platform to process a broad variety of documents. We have demonstrated the AI-OCR platform by applying it to financial domain tasks of document sorting, document verification, and typing assistance The demonstrations confirm the increasing work efficiency and conveniences.

• Journal of the Korean Professional Engineers Association
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• v.29 no.2
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• pp.15-23
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• 1996

With the ever-increasing importance of high-speed information in society as we move towards the 21 st century, telecommunication laboratories of advanced nations are pressing forward with research and development aimed at implementing its W & P(Visual Intelligent and Personal) services and construction of a new network to support them. In legals to the former, based on a long-term view of technological and market trends, those laboratories are researching and developing services that will make possible an effective progression from the development of services that answer to potential needs towards the full-scale implementation of VI & P services. In regards to the latter, these laboratories are responding in a flexible manner to the increasing diversity and disposal of the communications environment by separating the network into a transmission system and a versatile information control/conversion -ion system and laboratories are working at enhancing the performance of both. Within these board aims, the laboratories are currently focusing our attention in three areas : the technology for a high-speed broadband transmission system featuring optical frequency multiplexing and ATM techniques, network and software technologies for advanced information control and conversion, and technology for constructing a new access network that can provide a comprehensive range of multimedia services. This article describes the laboratories' concept of how VI & P services will develop in the future, and the latest trends in the field of communications. It also describes the ideal configuration of the new network and discusses the important technological aspects of how it is to be constructed. Finally, it presents the results of the laboratories'recent research which include some innovative work, point out the areas requiring future investigation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.113-114
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• 2009

Silicon carbide is one of the most attractive and promising wide band-gap semiconductor material with excellent physical properties and huge potential for electronic applications. Up to now, the most successful method for growth of large SiC crystals with high quality is the physical vapor transport (PVT) method [1, 2]. Since further reduction of defect densities in larger crystal are needed for the true implementation of SiC devices, many researchers are focusing to improve the quality of SiC single crystal through the process modifications for SiC bulk growth or new material implementations [3, 4]. It is well known that for getting high quality SiC crystal, source materials with high purity must be used in PVT method. Among various source materials in PVT method, a SiC powder is considered to take an important role because it would influence on crystal quality of SiC crystal as well as optimum temperature of single crystal growth, the growth rate and doping characteristics. In reality, the effect of powder on SiC crystal could definitely exhibit the complicated correlation. Therefore, the present research was focused to investigate the quality difference of SiC crystal grown by conventional PVT method with using various SiC powders. As shown in Fig. 1, we used three SiC powders with different particles size. The 6H-SiC crystals were grown by conventional PVT process and the SiC seeds and the high purity SiC source materials are placed on opposite side in a sealed graphite crucible which is surrounded by graphite insulation[5, 6]. The bulk SiC crystal was grown at $2300^{\circ}C$ of the growth temperature and 50mbar of an argon pressure. The axial thermal gradient across the SiC crystal during the growth is estimated in the range of $15\sim20^{\circ}C/cm$. The chemical etch in molten KOH maintained at $450^{\circ}C$ for 10 min was used for defect observation with a polarizing microscope in Nomarski mode. Electrical properties of bulk SiC materials were measured by Hall effect using van der Pauw geometry and a UV/VIS spectrophotometer. Fig. 2 shows optical photographs of SiC crystal ingot grown by PVT method and Table 1 shows electrical properties of SiC crystals. The electrical properties as well as crystal quality of SiC crystals were systematically investigated.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.148-153
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• 1999

Baikdu-san was a very active volcano during the Cenozoic era and is believed to be formed in late Cenozoic era. Recently it was also reported that there was a major eruption in or around 1002 A.D. and there are evidences which indicate that it is still an active volcano and a potential volcanic hazard. Remote sensing techniques have been widely used to monitor various natural hazards, including volcanic hazards. However, during an active volcanic eruption, volcanic ash can basically cover the sky and often blocks the solar radiation preventing any use of optical sensors. Synthetic aperture radar(SAR) is an ideal tool to monitor the volcanic activities and lava flows, because the wavelength of the microwave signal is considerably longer that the average volcanic ash particle size. In this study we have utilized several sets of SAR data to evaluate the utility of the space-borne SAR system. The data sets include JERS-1(L-band) SAR, and RADARSAT(C-band) data which included both standard mode and the ScanSAR mode data sets. We also utilized several sets of auxiliary data such as local geological maps and JERS-1 OPS data. The routine preprocessing and image processing steps were applied to these data sets before any attempts of classifying and mapping surface geological features. Although we computed sigma nought ($\sigma$$^{0}$) values far the standard mode RADARSAT data, the utility of sigma nought image was minimal in this study. Application of various types of classification algorithms to identify and map several stages of volcanic flows was not very successful. Although this research is still in progress, the following preliminary conclusions could be made: (1) sigma nought (RADARSAT standard mode data) and DN (JERS-1 SAR and RADARSAT ScanSAR data) have limited usefulness for distinguishing early basalt lava flows from late trachyte flows or later trachyte flows from the old basement granitic rocks around Baikdu-san volcano, (2) surface geological structure features such as several faults and volcanic lava flow channels can easily be identified and mapped, and (3) routine application of unsupervised classification methods cannot be used for mapping any types of surface lava flow patterns.

• Korean Journal of Optics and Photonics
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• v.20 no.3
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• pp.175-181
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• 2009

Holographic lithography is one of the potential technologies for next generation lithography which can print large areas (6") as well as very fine patterns ($0.35{\mu}m$). Usually, photolithography has been developed with two target purposes. One was for LCD applications which require large areas (over 6") and micro pattern (over $1.5{\mu}m$) exposure. The other was for semiconductor applications which require small areas (1.5") and nano pattern (under $0.2{\mu}m$) exposure. However, holographic lithography can print fine patterns from $0.35{\mu}m$ to $1.5{\mu}m$ keeping the exposure area inside 6". This is one of the great advantages in order to realize high speed fine pattern photolithography. How? It is because holographic lithography is taking holographic optics instead of projection optics. A hologram mask is the key component of holographic optics, which can perform the same function as projection optics. In this paper, Surface-Relief TIR Hologram Mask technology is introduced, and enables more robust hologram masks than those previously reported that were formed in photopolymer recording materials. We describe the important parameters in the fabrication process and their optimization, and we evaluate the patterns printed from the surface-relief TIR hologram masks.

• Journal of the Korean Geographical Society
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• v.48 no.4
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• pp.497-508
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• 2013

The objective of this study is to determine the spatiotemporal influences of climatic factors and atmospheric aerosol on phenological cycles of the Korea Peninsular on a regional scale. High temporal-resolution satellite data can overcome limitations of ground-based phenological studies with reasonable spatial resolution. Study results showed that phenological characteristics were similar among evergreen forest, deciduous forest, and grassland, while the inter-annual vegetation index amplitude of mixed forest was differentiated from the other forest types. Forest types with high VI amplitude reached their maximum VI values earlier, but this relationship was not observed within the same forest type. The phase of VI, or the peak time of greenness, was significantly influenced by air temperature. Aerosol optical thickness (AOT) time-series showed strong seasonal and inter-annual variations. Generally, aerosol concentrations were peaked during late spring and early summer. However, inter-annual AOT variations did not have significant relationships with those of VIs. Weak relationships between AOT amplitude and EVI amplitude only indicates that there would be potential impacts of aerosols on vegetation growth in the long run.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.9-14
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• 2008

A Nano particle is a small particle with at least one dimension less than 100 nm Nanoparticle is currently used in an area cf intense scientific research, due to a wide variety cf potential applications in biomedical, optical, and electronic fields. In order to know the biological effect of the nine Nano particles on fertilized egg of Crassostrea gigas experiments were performed Development rates of control (free Nano particles) C. gigas to a particular larval stage (D-shape) was 78%. Development rate of C gigas to a parcicular larval stage (D-shape) after 24 hours exposure to 0.05ppm of AGZ020, Nano silver, P-25 and SnO were 22%, 52%, 58% and 76%, respectively. However, all fertilized eggs were destructed within 8 hours afters exposure to 20ppm of respective particles. On the other hand, All fertilized eggs were not affected after 24 hours respective exposure to 0.05ppm of In, Sb, Sn, Zn, and Ag-$TiO_2$ particles. However, development rates of C. gigas after 24 hours exposure to 20ppm of In, Sb, Sn, Zn, Ag-$TiO_2$ were 57%, 60%, 50%, 65%, and 64% respectively.