• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.214-214
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• 2003

During a model test of Hutton TLP, a "ringing" response was first observed about 20 years ago. This phenomenon is a resonant build up over the time of wave period and this burst-like motion can cause the extreme load on the TLP tether. It is often detected in the large and steep irregular waves but the generation mechanism leading to the "ringing" is not yet well understood. According to the research since then, the higher order harmonic components may account for the "ringing" on the floating offshore structures. The main purpose of the present research is, thus, to measure the higher harmonic forces exerted on a vertical truncated circular column and to compare them with available data. A vertical truncated cylinder with a diameter of 3.5inch and a draft of 10.5inch is used as a test structure, which is a scaled model of ISSC TLP column. The cylinder is installed at a distance of 45ft from the wave maker in order to avoid parasitic waves created in the wave flap. Attached to the upper part of the cylinder are two force gages to measure the horizontal (surge) and vertical (heave) forces on the cylinder. The incoming waves are Stokes waves with a slope ranging from 0.06 to 0.24. The forces and waves are measured for 60 seconds with a sampling rate of 50 Hz. Among the recorded data, the first 10 waves are excluded because of transient behavior of the waves and the next The horizontal and vertical forces are analyzed up to 5th order harmonics. The horizontal forces are then compared to the values from the theoretical model called "FNV model". In addition, force transfer functions are also investigated. Major findings in this research are below. 1) The first order forces measured are slightly larger than the theoretical values of "FNV model" 2) The "FNV model" considerably overpredicts the second order forces. 3) The larger the amplitude and more extreme the wave slope, the smaller the predictions are compared to the experimental. 4) The higher harmonic forces are significantly smaller than the first harmonic force for all wave parameters. 5) The normalized forces vs. waves slopes are almost constant in the lower harmonics but vary a lot in the higher harmonics. 6) The trend of forces is more nonlinear in the horizontal forces than in the vertical forces as the wave slope increases. 7) The part of the results above is also observed by other researchers and confirmed again through the present work.

• Journal of the Korea Computer Industry Society
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• v.2 no.4
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• pp.565-572
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• 2001

At the most recent years, laser medical instruments, laser applications and laser nuclear fusion need strong visible light and ultraviolet rays. Nonlinear optical devices, such as harmonic generators and parametric oscillators, provide a means of extending the frequency range of available laser sources. Frequency conversion is a useful technique for extending the utility of high-power lasers. It utilizes the nonlinear optical response of an optical medium in intense radiation fields to generate new frequencies. These progresses have been used to generate high-power radiation in all spectral regions, from the ultraviolet to the far infrared. Optical parametric oscillators and amplifiers generate two waves of lower frequency They are capable of generating a range of wavelengths from a single frequency source, in some cases spanning the entire visible and near infrared regions. Consequently, in order to obtain the green light, the pulsed Nd:YAG laser using multiple-mesh PFN(Pulsed Forming Network) method with Nonlinear optical device was adopted. We compared the current pulseshapes with the laser output energy, and conversion efficiency.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.214-217
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• 2011

A fresnoite glass-ceramics has been investigating considerably because of the second order nonlinearity as well as its permanent optical nonlinearity. However, the chemical compositions of transparent glass-ceramics examined in the previous studies have been limited to adjust the composition close to fresnoite stoichiometrically. In this study, to investigate the effect of strontium ions in glass-ceramics on second order nonlinearity, $K_2O-TiO_2-SiO_2$ (KTS) glasses soaked in molten $Sr(NO_3)_2$ were prepared. Crystalline phases of the soaked glasses were measured by X-ray diffraction (XRD) as soaking times and additional heat treatment. The exchange of strontium ions into the glass was verified by Field Emission Scanning Electron Microscope (FE-SEM). And the phenomena of second order harmonic generation (SHG) was observed using Nd-YAG laser.

• Polymer(Korea)
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• v.25 no.6
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• pp.803-810
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• 2001

A nonlinear optical hyperbranched polyester (PE-Azo/Hyper) was synthesized from 4-[N,N-bis(hydroxyethyl)amino-4'-formyl] azobenzene and cyanoacetic acid by a Knoevenagel polycondensation using 4-(dimethylamino) pyridine as a base. The resulting polymer was soluble in polar aprotic solvents such as N,N-dimethylformamide and 1-methyl-2-pyrrolidinone and could be processed into optical quality films by spin coating. The molecular weight was determined to be $M_w$=61,800 ($M_W/M_n{=1.86}$) by gel permeation chromatography using polystyrene as a standard. No melting point was detected by differential scanning Calorimeter, indicating that this polymer presents an amorphous state. It shows a glass transition temperature of $121^{\circ}C$. The second-order nonlinear optical coefficient $d_{33}$ of the poled polymer determined by the second harmonic generation at 1064 nm was 25.4 pm/V.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.618-622
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• 2008

In this paper, we suggest new music composition algorithm based on fractal theory. User can define and control fractal shape by setting an initial state and production rules in L-System. We generate an asymmetric fractal tree based on L-System and probability. Then a music is generated by the fractal tree image using sonification techniques. We introduce two composition algorithm using the fractal tree. First, monophonic music can be generated by mapping x and y axis to velocity and pitch, respectively Second, harmonic music also can be generated by mapping x and y axis to time and pitch, respectively Using our composition algorithm, user can easily generate a music which has repeated pattern created by recursive feature of fractal, and a music which has structure similar to fractal tree image.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.167-185
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• 1999

In the present paper, KLN crystals have been grown along <001>, <100> and <110> directions by the top seeded solution growth (TSSG) method from Li-richer melts with different compositions. The morphologies of KLN crystals grown along different directions have been studied, and the well-developed facets have been unambiguously indexed using X-ray goniometer and stereographic projection analysis. The growth mechanism and defects such as cracks and inclusions were discussed on the basis of observations of facets on the crystal-melt interfaces. The crystal compositions were determined by chemical analysis method. The structure and lattice constants of KLN crystals were determined and calculated on the basis of XRD data by using TREOR90 and PIRUM programs. The Curie temperature and optical absorption were determined by dielectric constant peak and spectrum measurements, respectively. The blue SHG characteristics of a KLN sample were also investigated using a pulsed dye laser. PACS: 42.70.M;81.10;81.10A;42.65.K.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.284-285
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• 2000

광굴절률 현상은 optical signal processing과 홀로그램 기억소자로 널리 응용 될 수 있기 때문에 지금까지 광범위하게 연구되어져 왔다. 광굴절률 현상에서 중요한 변수는 빛이 있는 동안 drift, diffusion 과 photovoltaic current와 같은 전하 운반 메카니즘을 통해서 local charge의 재분포에 따른 공간전하장(Space-charge field, $E_{sc}$ )이다. 지금까지 single beam에 의한 공간전하장을 측정하는 방법으로 birefringenc $e^{1.2}$ 와 interference metho $d^{3}$을 이용하여 굴절률 변화를 측정함으로써 얻을 수 있었다. 그러나 이런 방법들은 공간전하장의 변화를 측정하기위해서 전기광학계수를 측정하여 얻는 간접적인 방법이고 또한 실험방법도 다소 복잡하다. 따라서 본 투고에서는 이미 발표된 광굴절률 현상시 제 2 고조파 세기(SHG)의 변화로부터 공간전하장을 간단하게 측정하는 방법을 이용하여 congruent, MgO가 4mole%, F $e_2$O가 0.1mole% 첨가된 LiNb $O_3$ 단결정의 공간전하장에 대해서 연구를 하였다. 이 방법은 전기광학물질인 LiNb $O_3$에서 SHG 위상정합조건이 dc 전기장에 의존하는 성질을 이용한 것이다. 그리고 온도가 일정할 경우 전기장의 변화에 따라 SHG의 크기가 변함을 이용하였다. (중략)

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.4
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• pp.396-401
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• 1999

In the present paper, potassium lithium niobate(KLN) crystals have been grown along <001>, <100> and <110> directions by the top seeded solution growth (TSSG) method from Li-richer melts with different compositions. The morphologies of KLN crystals grown along different directions have been studied, and the well-developed facets have been unambiguously indexed using X-ray goniometer and stereographic projection analysis. The growth mechanism and defects such as cracks and inclusions were discussed on the basis of observations of facets on the crystal-solution interfaces. The crystal compositions were determined by a chemical analysis method. The structure and lattice constants of KLN crystals were determined and calculated on the basis of XRD data by using TREOR90 and PIRUM programs. The Curie temperature and optical absorption were determined by dielectric constant peak and spectrum measurements. respectively. The blue second harmonic generation (SHG) characteristics of KLN sample were also investigated using a pulsed dye laser.

• Journal of the Korean Ceramic Society
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• v.43 no.9 s.292
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• pp.569-574
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• 2006

Transparent glass-ceramics containing fresnoite crystals have been prepared by controlled heat treatment in $K_2O-BaO-TiO_2-SiO_2$ and their nonlinear optical and luminescent properties were investigated using Maker fringe method and Spectrofluorometer. The second harmonic generation was observed in all samples and the values decreased with increasing $K_2O$ content. The luminescence of blue light at ${\sim}482nm$ could be observed and it was shown that the luminescent property was controlled by the $K_2O$ content.

• Journal of Information Display
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• v.4 no.2
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• pp.29-34
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• 2003

We have studied liquid crystal (LC) molecular alignment on rubbed and photoaligned surfaces. Particular attention was paid to the intermolecular liquid crystalline interaction. We will first show that uniform molecular orientation on a rubbed surface does not mean spatially uniform interaction between the surface and LC molecules. Rather LCs tend to align themselves through LC interaction. The existence of nonuniformity of rubbing was successfully visualized by double surface treatment. The importance of intermolecular LC interaction was also found in the orientation formation process in 5CB evaporated on rubbed and photoaligned surfaces. By simultaneously analyzing polarized UVNIS absorption and second-harmonic generation (SHG) using the maximum entropy method, we succeeded in obtaining the temporal variation of the orientational distribution functions in the film forming process. The distribution anisotropy and pretilt are found to be generated under the influence of intermolecular LC interaction.