• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.431-437
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• 1997

A gradient-index (GRIN) substrate is proposed as a novel signal propagation medium of planar optics. The GRIN substrate provides planar-optics designers not only a 3-dimensional signal propagation space, but also an additional smart optical functioning component like as a diffraction-limited imaging lens. The novel and smart functioning of the GRIN substrate was confirmed by experiment on imaging of an input signal to multiple destinations.

• Korean Journal of Optics and Photonics
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• v.28 no.2
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• pp.68-74
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• 2017

To minimize chromatic variations across a wavelength band, we suggest a new design that corrects the first- and second-order wavelength derivatives of the refractive power. Based on this method, a diffraction-limited collimator is designed. The design is very stable against wavelength change, as expected. The chromatic change of the effective focal length is less than 0.002% in the wavelength range from 360 to 410 nm.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.365.2-365.2
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• 2014

Nickel sulfide (NiS) has been utilized in optoelectronic applications, such as transformation-toughening agent for materials used in semiconductor applications, catalysts, and cathodic materials in rechargeable lithium batteries. Recently, high quality nickel sulfide thin films have been explored using ALD/CVD technique. Suitable precursors are needed to deposit thin films of inorganic materials. However, nickel sulfide precursors available for ALD/CVD process are very limited to nickel complexes with dithiocarbamate and alkanethiolate ligands. Therefore, it is essential to prepare novel nickel sulfide suitable for ALD/CVD precesses. Herein we report on the synthesis and characterization of new nickel sulfide complex with designed aminothiolate ligand. Furthermore thin films of NiS have been prepared on silicon oxide substrates by spin coating nickel precursor 10 wt% in THF. The novel complex has been characterized by means of 1H-NMR, elemental analysis, thermogravimetric analysis (TGA), X-ray Diffraction (XRD) and scanning electron microscope (SEM).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.164-168
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• 1996

The relation between crystallinity and thermal history in low density polyethylene thin films and their effect on electric conduction phenomena and dielectric breakdown was studied. The low density polythylene thin films obtained by the solution growth method heat-treated at 140[$^{\circ}C$] for 2 h and subsequently cooling to various ways. The degree of crystallinity was estimated by the X-ray diffraction measurement for the specimen of slowly cooling, ICE quenching and liquid nitrogen quenching. The result shows that the crystallinity decreases become faster as the cooling speed increased, and that conduction phenomenon is governed by the space charge limited current in high field. It was found that the dielectric breakdown field increases with an increase in cooling speed and test number in self-healing breakdown method.

• Korean Journal of Crystallography
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• v.14 no.1
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• pp.7-12
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• 2003

The compound SrA1₂(BO₃)₂O is a good host lattice for negative thermal expansion. We have measured thermal expansion over the limited temperature range by X-ray diffraction and ceramic dilatometry. In the aluminum borate compound, a thermal contraction is observed with a coefficient -1.64×10/sup -4/ Å/℃ on the c axis in the temperature range 23∼215℃ and with a maximum change -1.75㎛ in length of a ceramic bar of 20㎜ in the temperature range 110∼170℃, respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.104-107
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• 2007

An aspheric microlens array to improve the properties of multi optical probes was designed and fabricated. To generate multi optical probes with good qualities, a microlens array with the minimum spherical aberration was designed by ray tracing. Using the reflow process, a master pattern of aspheric microlens array was made and finally with the ultraviolet-imprinting (UV-imprinting) method, the aspheric microlens array was replicated. The reflow condition was optimized to realize the master pattern of the microlens array with the designed aspheric shape. The intensity distribution of the optical probes at the focal plane showed a diffraction-limited shape.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.545-550
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• 2005

A parametric loudspeaker is a device to generate highly directional sound using ultrasounds. The parametric loudspeaker could be used to focus sound in a limited space, so it is important to study the characteristics of the parametric loudspeaker in near-field. Mechanism of the audible sound generation in the parametric loudspeaker is explained by nonlinear interaction of the ultrasounds and is modeled as KZK equation, the nonlinear wave equation which contains attenuation, nonlinearity and diffraction. To measure the directional characteristics of the parametric loudspeaker precisely, a method to reduce the spurious signal which taints the measured signal was invented. With the method, directivity patterns of the parametric loudspeaker were measured and compared to the approximated solution and piston sources.

• Korean Journal of Optics and Photonics
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• v.2 no.4
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• pp.186-192
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• 1991

For the micro-lithography using a excimer laser beam $(\lambda\leq0.248$\mu\textrm{m})$. a mirror system consisting of four spherical surfaces with reductlon magnification 5X is designed. Initially the aplanat, flat field and the distortion free condition of the system are analytically investigated within Seidel 3rd order aberrations. And the computer-aided optimization technique has been employed for the further improved performance of the system. The final system has N.A. of 0.15 and image field diameter 3.3 mm, and has the diffraction-limited performance for KrF eximer laser beam.

• ETRI Journal
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• v.41 no.1
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• pp.61-72
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• 2019

In this paper, we demonstrate the current concepts in holographic tomography (HT) realized within limited angular range with illumination scanning. The presented solutions are based on the work performed at Warsaw University of Technology in Poland and put in context with the state of the art in HT. Along with the theoretical framework for HT, the optimum reconstruction process and data visualization are described in detail. The paper is concluded with the description of hardware configuration and the visualization of tomographic reconstruction, which is calculated using a provided processing path.

• Journal of Korean Port Research
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• v.4 no.1
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• pp.21-31
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• 1990

The application of computer model to the port and harbor development is categorized in the field of port development policy, economic analysis and evaluation, civil engineering analysis, hydrodynamic analysis, evaluation of social and natural environment effect, etc. The study in this paper, however, is limited to hydrodynamic analysis, especially the analysis of water wave propagation and response to the shore structure due to the construction and implementation of shore boundary, the mathematical formulation of the numerical model is established systematically based on the hybrid Element Method and applied to solving the wave refraction, diffraction and radiation problems for a circular basin, the artificial beach or lagoon in terms of coastal zone development.