• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.3
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• pp.183-195
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• 2007

MEMS technology is proven to be an enabling technology to realize many components for optical networking applications. Due to its widespread applications, VOA has been one of the most attractive MEMS based key devices in optical communication market. Micromachined shutters and refractive mirrors on top of silicon substrate or on the device layer of SOI (Silicon-on-insulator) substrate are the approaches trapped tremendous research activities, because such approaches enable easier alignment and assembly works. These groups of devices are known as the planar VOAs, or two-dimensional (2-D) VOAs. In this review article, we conduct the comprehensively literature survey with respect to MEMS based planar VOA devices. Apparently MEMS VOA technology is still evolving into a mature technology. MEMS VOA technology is not only the cornerstone to support the future optical communication technology, but the best example for understanding the evolution of optical MEMS technology.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.12a
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• pp.130-135
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• 2003

Low dielectric constant SiOC(-H) films have been prepared by inductively coupled plasma chemical vapor deposition using bis-trymethylsilyl-methane (BTMSM) and $O_2$ precursors. The annealing effects on the structural and electrical properties were studied. The results indicate post-annealing could efficiently remove the hydroxyl (-OH) related groups from the as-deposited films and cause the chemical structure re-arrangement, resulting in the more nano-pores being formed in the annealed SiOC(-H) films. The dielectric constant decreased from 2.7 to 2.1, and the refractive index decreased from 1.427 to 1.32.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.120-124
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• 2002

Considerable progress has been made in organic photorefractive materials, since the first observation of photorefractive phenomena from organic materials. Within recent years, a large number of organic photorefractive materials, especially amorphous materials. have been developed based on polymeric composites, fully functional polymers and the multifunctional chromophore approach. Among these organic photorefractive materials, some of them containing carbazole components as a charge transporting function have been demonstrated to exhibit high performance photorefractive effects. The carbazole building blocks with charge transporting functionality or multifunctions play a very important role in photorefraction and have been widely used in the molecular design approach to new organic photo- refractive materials.

• Food Science and Preservation
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• v.8 no.3
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• pp.331-337
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• 2001

The oxidative stability of tallow heated was studied by different frying condition (temperature 130, 150, and 180$^{\circ}C$;heating time, each 10hours per day, total 240hrs). Changes of physicochemical parameters such as acid value, peroxide value, iodine value, dielectric constant, content of polar components and polymer, refractive index, smoke point, viscosity and color changes in tallow heated were also measured. Acid value, dielectric constant, refractive index, viscosity, and content of polar component and polymer increased as the tallow was heated longer, whereas iodine value and smoke point decreased and peroxide value was increased and decreased repeatedly. These parameters changed to a greater extent as the heating temperature went up. The color became darkened with the increase of red and yellow values during heating. The decree of coloration was proportional to heating temperature.

• Korean Journal of Optics and Photonics
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• v.22 no.6
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• pp.247-255
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• 2011

The optical performance of LLF(Lenticular Lens Film)-based backlight was studied by using optical simulation as functions of the aspect ratio and the refractive index of lenticular lenses. In order to perform reliable simulation, the BSDF(bi-directional scattering distribution function) of the scattering dots on the bottom surface of the light guide plate was obtained as a superposition of the Lambertian and the elliptic Gaussian distribution components by comparing the experimental results and the simulation for the luminance distribution on the light guide. Based on this approach, an appropriate BSDF of the scattering dots of the light guide was constructed. The resultant values of the optimized aspect ratio and the refractive were found to be 1.25 and 1.65, respectively. In spite of the hybrid aspects of LLF incorporating both diffusing and collimating functions, the optical performance, in particular the on-axis luminance of LLF-based backlight was inferior by about 20% compared to that of conventional backlights adopting one prism film. However, the combination of two lenticular lens films resulted in comparable luminance gain as well as smooth decrease in the luminance with the viewing angle without exhibiting any side lobes.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1049-1056
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• 2023

The height of the atmospheric boundary layer indicates the peak developed when turbulence is generated by mixing heat and water vapor, and is generally determined through thermodynamic methods. Wind profilers produce atmospheric information from the scattering of signals sent into the atmosphere. A method for making the spectrum of turbulent components, turbulent kinetic energy dissipation rate, and refractive index structure coefficient was presented to determine the atmospheric boundary layer depth. Compared with the vertical distribution characteristics of potential temperature and specific humidity based on radiosonde data, the determination method of the atmospheric boundary layer height from wind profiler output was evaluated as very useful.

• Journal of Korea Foresty Energy
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• v.22 no.2
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• pp.18-25
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• 2003

Bamboo vinegar was prepared from China-grown bamboo (Phyllostachys pubescens) using simple kiln (400 - 500 $^{\circ}C$), and its physical properties and chemical components were investigated and compared to those of Korea-grown bamboo vinegar. The physical properties of China-grown bamboo vinegar were as follows: Baume specific gravity 4.5, organic acid 9.9%, pH 2.8, tar 3.1% and refractive index 13.1%, respectively. The main components of the bamboo vinegar were acetic acid, 1-hydroxyl-2-propanone, methanol, propionic acid, 1-hydroxyl-2- butanone. There was no significant difference between the components of Korea- and China-grown bamboo vinegars. Total organic materials in China-grown bamboo vinegar were 14.8%, and organic acids (acetic acid, formic acid, propionic acid, and butanoic acid) consisted of 9.0%. These acids corresponded to 61% of total organic materials. Neutral and phenolic compounds consisted of 4.5% and 0.8% of the bamboo vinegar, which were correspond to 6% and 31% of total organic materials, respectively. The physicochemical properties of traditional Chinese bamboo vinegar indicated that it was collected at low temperature and aged for a long time.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.421-421
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• 2006

The light and energy-efficiency of classical liquid crystal displays is notoriously poor due to the use of absorption-based linear polarisers and colour filters. For instance, the light efficiency of PVAL polarisers is typically between 40 and 45 % and the colour filters have a typical efficiency below 35 % which results in a total light and energy-efficiency of the display below 10 %. In the past, a variety of polarizers were developed with an enhanced efficiency in generating linearly polarized light. Typically, these polarizers are based on the polarisationselective reflection, scattering or refraction of light i.e. one polarisation direction of light is directly transmitted to the LCD/viewer and the other polarization direction of light is depolarised and recycled which results in a typical efficiency for generating linearly polarized light of 70-85 %. Also, special colour filters have been proposed based on chiral-nematic reactive mesogens which increase the efficiency of generating colour. Despite the enormous progress in this field, a need persists for improved methods for generating polarized light and colour based on low cost optical components with a high efficiency. Here, the use of holographic phase gratings is reported for the generation of polarized light and colour. The phase grating are recorded in a photopolymer which is coated onto a backor frontlight for LCDs. Typically the recording is performed in the transmisson mode or in the waveguiding mode and slanted phase gratings are generated with their refractive index modulation at an angle between 20o and 45o with the normal of the substrate. It is shown that phase gratings with a high refractive index modulation and a high efficiency can be generated by a proper selection of the photopolymer and illumination conditions. These phase gratings coupleout linearly polarized light with a high contrast (> 100) and the light is directed directly to the LCD/viewer without the need for redirection foils. Dependent on the type of phase grating, the different colours are coupled-out at a slightly different angle which potentially increases the efficiency of classical colour filters. Moreover, the phase gratings are completely transparent in direct view which opens the possibility to use them in frontlights for LCDs. Holographic polarization gratings posses a periodic pattern in the polarization state of light (and not in the intensity of light). A periodic pattern in the polarization direction of linearly polarized light is obtained upon interference of two circularly polarized laser beams. In the second part of the lecture, it is shown that these periodic polarization patterns can be recorded in a linear photo-polymerizable polymer (LPP) and that such an alignment layer induces a period rotation in the director of (reactive and non-reactive) liquid crystals. By a proper design, optical components can be produced with only first order diffraction and with a very high efficiency (>0.98). It is shown that these diffraction gratings are potentially useful in projection displays with a high brightness and energy efficiency

• Korean Journal of Food Science and Technology
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• v.12 no.4
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• pp.324-327
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• 1980

The seeds of Torreya nucifera, which were shown to contain high level of oil, were characterized to evaluate their possible utilization as oil source. Oil was extracted by compression from the seeds and its physico-chemical properties and, total fatty acid composition were determined. The results are summarized as follows: 1. Proximate components of the seeds were shown to be: moisture, 12.3% ; crude protein, 9.46%; crude fat, 54.29 %; fiber, 5.28 %; ash, 2.13%. 2. Physico-chemical characteristics of the seed oil were determined as follows: specific gravity 0.92, refractive index 1.470, iodine value 127, saponification value 182.2, acid value 9.5, ester value 172.7. 3. The major fatty acids of the total lipids were linoleic (46.77%), oleic (31.68%) and palmitic acid (6.92%).

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.334.2-334.2
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• 2016

Silicon nitride (SiNx:H) films are generally used as passivation layer on solar cell and they are usually made by plasma enhanced chemical vapor deposition (PECVD). In this study, we investigated the properties of silicon nitride (SiNx:H) films made by PECVD. Effects of mixture ratio of process gases with silane (SiH4) and ammonia (NH3) on the passivation qualities of silicon nitride film are evaluated. Passivation properties of SiNx:H are focused by making antireflection properties identical with thickness and refractive index controlled. The absorption coefficient of each film was evaluated by spectrometric ellipsometery and the minority carrier lifetimes were evaluated by quasi-steady-state photo-conductance (QSSPC) measurement. The optical properties were obtained by UV-visible spectrophotometer. The interface properties were measured by capacitance-voltage (C-V) measurement and the film components were identified by Fourier transform infrared spectroscopy (FT-IR) and Rutherford backscattering spectroscopy detection (RBS) - elastic recoil detection (ERD).