• 한국전기전자재료학회논문지
• /
• 제25권9호
• /
• pp.723-726
• /
• 2012

A current intensity convertible CLD chip was fabricated using small and large FET cell configuration. Pinch-off current of 8.82 mA and 11.56 mA were obtained for small and large cell in the CLD chip, respectively. Constant current was fairly maintained until the breakdown voltage of 60 V. Measured knee voltage, $V_k$ were 3.8 V and 4.5 V for small and large cell, respectively. We configured current amplifying chip with parallel connection of each cells, by connecting 8 individual large cells in parallel network, 92.0 mA of current was obtained. The pinch-off constant current of CLD chip was varied very linearly with respect to the number of parallel connected cell.

• Journal of Microbiology and Biotechnology
• /
• 제21권10호
• /
• pp.1081-1087
• /
• 2011

An internally radiating photobioreactor was applied for the production of astaxanthin using the unicellular green alga Haematococcus pluvialis. The cellular morphology of H. pluvialis was significantly affected by the intensity of irradiance of the photobioreactor. Small green cells were widespread under lower light intensity, whereas big reddish cells were predominant under high light intensity. For these reasons, growth reflected by cell number or dry weight varied markedly with light conditions. Even under internal illumination of the photobioreactor, light penetration was significantly decreased as algal cells grew. Therefore, we employed a multistage process by gradually increasing the internal illuminations for astaxanthin production. Our results revealed that a multistage process might be essential to the successful operation of a photobioreactor for astaxnthin production using H. pluvialis.

• Journal of the Optical Society of Korea
• /
• 제11권1호
• /
• pp.1-5
• /
• 2007

We investigate the efficiency of an optical intensity modulator based on an electrically tunable $LiNbO_3$ reflection grating. Assuming a grating coupling coefficient and the waveguide propagation loss, waveguide length is varied to find its effect on the modulator slope efficiency and the device capacitance. With the low propagation loss of the $LiNbO_3$ waveguide, a very efficient optical intensity modulator can be achieved for a low frequency (${\sim}1GHz$) as long as the requirement for the grating coupling coefficient is satisfied.

• Journal of Korean Vacuum Science & Technology
• /
• 제2권1호
• /
• pp.49-54
• /
• 1998

The effect of deposition paratmeters on the solid-phase crystallization of amorphous silicon films deposited by plasma-enhanced chemical vapor deposition has been investigated by x-ray diffraction. The amorphous silicon films were prepared on Si(100) wafers using SiH4 gas with and without H2 dilution at the substrate temperatures between 12$^{\circ}C$ and 38$0^{\circ}C$. The R. F. powers and the deposition pressures were also varied. After crystallizing at $600^{\circ}C$ for 24h, the films exhibited (111), (220), and (311) x-ray diffraction peaks. The (111) peak intensity increased as the substrate temperature decreased, and the H dilution suppressed the crystallization. Increasing R.F. powers within the limits of etching level and increasing deposition pressures also have enhanced the peak intensity. The peak intensity was closely related to the deposition rate, which may be an indirect indicator of structural disorder in amorphous silicon films. Our results are consistent with the fact that an increase of the structural disorder I amorphous silicon films enhances the grain size in the crystallized films.

• 한국해양공학회지
• /
• 제8권2호
• /
• pp.115-123
• /
• 1994

Under variable amplitude loading conditions, retardation or accelerated condition of fatigue crack growth occurs with every cycle, Because fatigue crack growth behavior varied depend on load time history. The modeling of stress amplitude with storm loading acted to ships and offshore structures applied this paper. The crack closure behavior examine by recording the variation in load-strain relationship. By taking process mentioned above, fatigue crack growth rate, crack length, stress intensity factor, and crack closure stress intensity factor were obtained from the stress cycles of each type of storm ; A(6m), B(7m), C(8m), D(9m), E(11m) and F(15m) which was wave height. It showed that the good agreement with between the experiment results and simulation of storm loads. So this estimated method of crack propagtion rate gives a good criterion for the safe design of vessels and marine structure.

• Korean Chemical Engineering Research
• /
• 제48권3호
• /
• pp.337-341
• /
• 2010

직경 1 m, 높이 1 m의 교반탱크 내 유체흐름 패턴을 상용 전산유체역학 프로그램의 하나인 CFX를 사용하여 해석함으로써 교반속도, 임펠러 회전날개의 경사각, 방해판의 존재 유무, 탱크바닥 형태가 흐름패턴에 미치는 영향을 알아보았다. 방해판이 없을 경우 탱크 중심에서 와류가 관찰되었으며 교반속도가 증가함에 따라 탱크 중심의 와류 현상이 증가하였으나, 방해판 설치에 의해 와류가 감소하였다. 임펠러 날개의 경사각을 증가시킴으로써 교반탱크 상하로의 유체흐름이 증가하였고 와류도 감소하였다. 탱크바닥을 수평으로 하는 것 보다 둥글게 함으로써 탱크 바닥 구석에서 유체흐름이 원활하게 변화하였다.

• 전자공학회논문지D
• /
• 제34D권2호
• /
• pp.27-37
• /
• 1997

Photoluminescent and cathodoluminescent charcteristics of inorganic luminescent materials were investigated ot develop possible phosphors for thin film electroluminescent (TFEL) device applications. Mg, Zn, and Photoluminescent and cathodoluminescent charcteristics of inorganic luminescent materials were investigated ot develop possible phosphors for thin film electroluminescent (TFEL) device applications. Mg, Zn, and $Si_3N_4$ powders were used to synthesize $(Mg_xZn_{1-x})SiN_2$ host materials. $Tb_4O_7$ and $Eu_2O_3$ powdrs were added as luminescent centers. Very sharp emission spectra of $Tb^{3+}$ ions were observed from $Mg._5Zn._5SiN_2:Tb$ sampels sintered at $1400^{\circ}C$ for an hour and the maximum intensity of emission spectra occured at wavelength of 550nm (green light). Synthetic conditions of $(Mg_xZn_{1-x})SiN_2:Eu$ phosphors were optimized for the hghest luminescence. The Eu concentrations were varied from 0.2% to 1.6%. Before firing, the powders were mixed using ballmills, methanol, acetone, or D.I. water. The Mg/Zn ratio also were varied from x=0.3 to x=0.7. The maximum PL intensity was obtained from a sample with 1.2% Eu concentration and the powder was mixed with methanol and dried before firing. The maximum intensity of the emission spectra occurred t the wavelength of 470nm(blue light). TFEL devices fabricated by using sputter deposition of $(Mg._3Zn._7)SiN_2:Eu$ phosphor layer showed yellowish white emission at the phosphor field of 2MV/cm.

• 음성과학
• /
• 제14권1호
• /
• pp.137-147
• /
• 2007

The purpose of this study was to examine the syllable structures of ten Korean numeric sounds produced by ten students. Each sound was normalized by its maximum intensity value and divided into onset, vowel, and coda sections after finding abrupt or visible changes in energy values or cumulative values of lower spectral energy at each pulse point using four Praat scripts. Then, segmental durations and cumulative intensity values of each syllable were obtained to find a statistical summary of the syllable structure. Intensity values at 100 proportional time points were also collected to compare the ten sounds. Results showed as follows: Firstly, there was not much deviation from the grand average duration and intensity for the majority of the sounds except the two diphthongal sounds on which their boundary points varied among the speakers. Secondly, the onset point for the CV or CVC category sounds and the boundary between the vowel and the nasal or lateral sound were easy to identify, which may be automatically traced later. Thirdly, there seems some tradeoff among the sections maintaining the same total duration per each syllable. Further studies on syllables with various onsets or codas would be desirable to make a general statement on the Korean syllable structure.

• 한국생산제조학회지
• /
• 제6권4호
• /
• pp.80-88
• /
• 1997

An experimental investigation of the fatigue through crack growth behavior under simple stepped variable loading condition has been performed using Al7075-T651. Experiments were carried out by using cantilever bending type specimens, with chevron notches on a small electro-magnetic test machine. Tensile overloads have a retarding effect on the fatigue crack growth rates, therefore tensile overloads were used for the beneficial effect on the fatigue life. While in most cases compressive overloads have only a vanishing effect on crack growth rates, some experiments with single edge crack tension specimens reveal a marked growth retardation. The stress ratios used in this investigations varies from R=0.32 to 0.81, from R=0.04 to 0.76, from R=-0.15 to 0.73, and from R=-0.33 to 0.68 and the peak load for each case was not varied. The crack growth and crack closure were measured by Kikukawa's compliance method with a strain gauge mounted on the backside of each specimens. The results obtained are as follows. When the stepped variable load was applied, the smaller the stress ration was, the larger the delayed retardation of the crack growth rate was. The fatigue crack growh rate data obtained for through cracks were plotted well against the effective stress intensity factor range from 4.0 to 20.0MP{a^{SQRT}m}. It was found that the effective stress intensity factor range ratio was related well to the opening stress intensity factor, the maximum stress intensity factor, and crack length.

• 한국식품과학회지
• /
• 제30권2호
• /
• pp.283-287
• /
• 1998

발아억제 선량범위인 0.15 kGy와 0.30 kGy의 감마선과 전자선이 조사된 감자와 마늘을 대상으로 thermoluminescence (TL) 측정에 의해 방사선 조사유무를 확인하였다. 감자와 마늘로부터mineral을 추출하여 TL 측정을 함으로써 방사선 조사선량과 TL intensity 간의 높은 상관관계를 확인하였다. 방사선 조사되지 않은 시료들은 특이한 TL glowcurve를 나타내지 않았으나 방사선 조사된 시료들은 $200{\sim}260^{\circ}C$부근에서 명확한 TL glowcurve를 나타내었다. 시료의 TL intensity는 조사선량에 따라 증가하였으나 같은 조사선량에서도 방사선 조사선원에 따라 시료의 TL intensity는 일정하지 않았다. 그러나 이상의 결과에서 볼 때 발아억제를 위한 감자와 마늘의 방사선 조사는 TL glowcurve의 측정으로써 조사유무의 확인이 가능하였다.