• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1997.10a
• /
• pp.129-133
• /
• 1997

본 연구에서는 LiNbO$_3$ 단결정 소재의 광손상에 대한 저항성을 향상시키는 첨가물로 잘 알려져 이쓴 MgO 및 ZnO를 첨가하여 육성한 조화용융조성(congruent melting composition)의 LiNbO$_3$ 단결정의 domain 구조는 이들 dopants를 첨가함에 따라 single domain에서 ring 형태의 주기적인 domains으로 변화함을 확인하였고, 첨가된 이온이 domain 형성에 미치는 영향을 전자현미경(SEM-WDS)으로 관찰하였다. 또한, 육성한 [Li1-5xNb5(x-y)Mg(or Zn)5y]Nb1-4x+3yO3 단결정들의 유전율(전이온도) 변화 및 광학적 특성[광투과율, 굴절률]을 측정하여 undoped LiNbO$_3$단결정과 비교하였다. 첨가물을 첨가함에 따라 전이온도는 약 20~3$0^{\circ}C$정도 증가하였으며, 10-3 order의 굴절률 변동치를 나타내었다. 또한, 육성된 결정들의 투과율은 대체로 70~80%를 나타내었고, 첨가물을 첨가함에 따라 흡수단과 OH- 흡수 band는 단파장쪽으로 각각 약 5~10nm, 40nm이동됨을 확인하였다. 이는 LiNbO$_3$단결정의 광손상 저항성이 향상되었음을 간접적으로 보여주는 결과이다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.17 no.6
• /
• pp.272-276
• /
• 2007

The various colored cubic zirconia single crystals for jewelry were grown by skull melting method of excellent productivity. The cubic zirconia is similar to the character of diamond, which has high refractive index, large dispersion and high hardness. It is possible that the development of new colored cubic zirconia by doping 3d-transition elements or 4f-rare earth elements. The colored cubic zirconia is representative of synthetic gemstone which was grown up by mixing one or over two materials among $Pr_6O_{11},\;TiO_2,\;MnO_2\;and\;Er_2O_3$ as coloring agent. Subsequent heat treatment improves the quality of color and uniformity. This study is aimed the color reappearance of cubic zirconia such as natural peridot, smoky-quartz and red-tourmaline.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.22 no.4
• /
• pp.170-177
• /
• 2012

Amethyst gems represents thermal effects of far-infrared emission, promotes the body's metabolism, and attracts attention as an eco-friendly interior material. In this paper, amethyst increase the value of jeweling by applying the characteristic purple motif, furthermore, I will intend to develop of design model. Metal crafting of brooch & necklace in the works performed based on the organic three-dimensional shape of the Rhino CAD Data. It was made possible through the precise laminated wax processing and then combining the amethyst. I researched the ornament modeling by applying the 'Golden Ratio', and suggesting utilizing method for interior jewel modeling, and also, is expected that this paper on the amethyst modeling design can contribute to the manufacturers' productivity.

• Aerospace Engineering and Technology
• /
• v.2 no.2
• /
• pp.1-10
• /
• 2003

An airship is statically unstable, because it has no wing, comparatively small tail and large hull. Hence, an accurate prediction of dynamic stability is critical. In this study, dynamic stability data of the Mid-Size Airship is acquired through forced oscillation wind tests. The test was done in BAR LAMP which is Birhle Applied Research Inc's facility located in Germany. The test was composed with 16 static runs and 26 dynamic runs. As a result, dynamic characteristics of the airship depends on sideslip angle, angular rate and its direction as well as angle of attack. Generally, it is obtained that 3 directional moments have damping, but normal force, side force, and cross-derivatives are unstable. The dynamic derivatives are not sensitive to control surfaces, but have nonlinear dependency on sideslip angle.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.11
• /
• pp.6838-6844
• /
• 2014

3GPP LTE-Advanced systems adopt multiple antennas for high speed data transmission. In general, the receiver complexity of a spatially mutiplexed (SM) multiple-input multiple-output (MIMO) system grows in proportion to the number of candidate vectors. A large number of candidate vectors increases the reliability of the soft output values. The maximum likelihood (ML) signal detection with a large number of candidate vectors achieves high performance. On the other hand, low complexity receiver techniques with a small number of candidate vectors provide soft output values, such as low reliability. This paper addresses the improving reliability of the soft output obtained from a small number of candidate vectors. The improved performance of the proposed technique with the aid of computer simulations is reported.

• Korean Journal of Optics and Photonics
• /
• v.9 no.3
• /
• pp.175-180
• /
• 1998

Nd:YAG single crystal widely used as solid state laser was grown by Czochralski method. <111> single crystal with 0.9at% of $Nd^{3+}$ was grown from the Czochralski furnace with a automatic diameter control system. The vertical temperature gradient in the liquid was the major factor that influence the crystal quality, and the crystal diameter was controlled by the home made computer program. The crystal boule with $\phi$50mm$\times$ι100mm effective size was cut, polished, and antireflection coated. The optical evaluation such as absorption spectrum, fluorescence spectrum coincide with typical features of Nd:YAG single crystal. The laser rod was assembled into the CW laser generator with a Kr lamp. The maximum CW laser output was 70 W and the threshold power and efficiency was 1.3kW and 1.64% respectively.

• Journal of the Korean Magnetics Society
• /
• v.21 no.3
• /
• pp.108-115
• /
• 2011

Principles in the synthesis of small-sized high-quality crystals for the experimental condensed matter physics will be discussed in this paper. Synthesis process and cautions will be introduced especially for the synthesis methods which can be easily accessible to researchers. Starting from the solid state reaction which is the most common synthesis method, I will explain the quartz tube sealing that is crucial for making polycrystalline materials as well as single crystals in various conditions. Finally, basics of single crystal growth and various techniques will be introduced on the whole for the researchers who are not familiar with the material synthesis.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.13 no.6
• /
• pp.279-283
• /
• 2003

In this study, ZnTe : S single crystal thin films substituted by sulfur were grown on GaAs (100) substrates by hot-wall epitaxy. The photoluminescence (PL) characteristics of ZnTe : S single crystal thin films was measured to investigate the effects due to sulfur atoms in the ZnTe layer. The Peak of 2.339 eV identified as the isoelectronic center was observed in low temperature PL spectrum, but PL spectra which the origin had not been well-explained were not observed. Temperature dependence of PL intensities of the light hole free exciton was explained by extrinsic self-trapping. Besides it is reported that the emission lines near absorption edge at room temperature were observed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.6A
• /
• pp.905-912
• /
• 1999

In this paper we explain a trellis representation of block codes and derive their MAP decoding algorithm based on it. We also analyze the performance of block codes and concatenated codes with block codes as components by computer simulations, which were performed by changing the structures and constituent codes of concatenated codes. Computer simulations show that soft decision decoding of block codes get an extra coding gain than their hard decision decoding and that concatenated codes using block codes have good performance in the case of high code rate.

• The Journal of Information Technology
• /
• v.3 no.1
• /
• pp.9-28
• /
• 2000

This study aims determinants of tax professional's aggressiveness which perform duplicated role in tax decision-making. Especially, I would explain correlation between cognitive trait of tax practitioner and tax professional's aggressiveness. Final results of this study is following; First, positive correlation between tax practitioner size and tax professional's aggresiveness is significant. Second, correlation among tax substitution fee, friendship between practitioner and professional, knowledge about tax of practitioner, tax professional's aggressiveness is positively significant. Third, influence of tax practitioner's aggresiveness on tax professional's aggressive is positively significant.