• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.12
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• pp.53-60
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• 2005

This work proposes a 10b 100 MS/s $1.4\;mm^2$ CMOS ADC for low-power multimedia applications. The proposed two-step pipeline ADC minimizes chip area and power dissipation at the target resolution and sampling rate. The wide-band SHA employs a gate-bootstrapping circuit to handle both single-ended and differential inputs with 1.2 Vp-p at 10b accuracy while the second-stage flash ADC employs open-loop offset sampling techniques to achieve 6b resolution. A 3-D fully symmetrical layout reduces the capacitor and device mismatch of the first-stage MDAC. The low-noise references are integrated on chip with optional off-chip voltage references. The prototype 10b ADC implemented in a 0.18 um CMOS shows the maximum measured DNL and INL of 0.59 LSB and 0.77 LSB, respectively. The ADC demonstrates the SNDR of 54 dB, the SFDR of 62 dB, and the power dissipation of 56 mW at 100 MS/s.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.12 s.354
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• pp.65-73
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• 2006

This work presents a 14b 200KS/s $0.87mm^2$ 1.2mW 0.18um CMOS algorithmic A/D converter (ADC) for intelligent sensors control systems, battery-powered system applications simultaneously requiring high resolution, low power, and small area. The proposed algorithmic ADC not using a conventional sample-and-hold amplifier employs efficient switched-bias power-reduction techniques in analog circuits, a clock selective sampling-capacitor switching in the multiplying D/A converter, and ultra low-power on-chip current and voltage references to optimize sampling rate, resolution, power consumption, and chip area. The prototype ADC implemented in a 0.18um 1P6M CMOS process shows a measured DNL and INL of maximum 0.98LSB and 15.72LSB, respectively. The ADC demonstrates a maximum SNDR and SFDR of 54dB and 69dB, respectively, and a power consumption of 1.2mW at 200KS/s and 1.8V. The occupied active die area is $0.87mm^2$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.294-294
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• 2010

CdS는 $CuInSe_2$계, CdTe계 이종접합 태양전지의 junction partner로 많이 이용되어 왔다. CdS는 전극으로 쓰일 뿐만 아니라 빛을 투과시키는 창문층으로 사용되어 높은 변환 효율을 나타낸다. 이종접합 태양전지에서 창문층은 가시광 영역에서 광투과율이 높고, 전기적으로 비저항이 낮아야 에너지 손실 없이 태양광을 광흡수층까지 투과시킬 수 있다. CdS 박막은 CBD법(solution growth technique), 진공증착법(vacuum evaporation), 스퍼터법(sputtering), 스프레이 열분해법(spray pyrolysis), 전착법(electrodeposition)에 의해 제조되고, 그 중 용액성장법(solution growth technique)이라고도 불리는 CBD법(chemical bath deposition)을 이용하여 CdS 박막을 제조하였다. CBD법은 다른 방법에 비해 제조 과정이 비교적 간단할 뿐만 아니라 제조 단가가 저렴하고, 넓은 면적의 박막 제조가 가능하며 재현성도 우수하다는 장점이 있다. CdS 박막을 제조하기 위한 cadmuim 이온공급원으로는 $CdSO_4$를 사용하였고 sulfur 이온공급원으로는 $SC(NH_2)_2$를 사용하였다. CBD법에서 박막의 물성에 영향을 미칠 수 있는 요인인 sulfur 이온공급원과 cadmium 이온공급원의 비, 용액의 온도, pH를 변화시켜 CdS 박막을 제조하였다. 각각의 조건에 의해 제조된 CdS의 박막의 두께는 Tencor P-1을 이용하여 측정되었고, UV-Visible spectrometer를 이용하여 파장에 따른 광투과율을 측정하였다. CdS 박막의 결정 구조를 조사하기 위해 X선 회절분석(XRD ; X-ray diffraction)을 하였고, AFM(Atomic Force Microscope)으로 표면 특성을 관찰하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.3
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• pp.258-264
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• 2004

In this paper, MMIC double balanced star mixer for 40 ㎓ was implemented on GaAs substrate with backside vias. In the design of the MMIC mixer, the design of balun and diode was required. A novel balun structure using microstrip to CPS was presented. The 40 ㎓ balun was designed based on the design experience of the scale-down balun by 2 ㎓. The balun may be suitable for fabrication in MMIC process with backside via and can easily be applied for DBM(Double Balanced Mixer). A Schottky diode was designed and implemented using p-HEMT process considering the compatability with other high frequency MMIC's fabricated on p-HEMT base process. Finally, the double balanced star mixer was fabricated using the balun and the p=HEMP Schottky diode. The measured performance of mixer shows 30 ㏈ conversion loss at 18 ㏈m LO power. This insufficient performance is caused by the unwanted diode at AlGaAs junction in vertical structure of p-HEMT. If the p-HEMT's gate is recessed to AlGaAs layer, and so the diode is eliminated, the mixer's performances will be improved.

• Microbiology and Biotechnology Letters
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• v.26 no.1
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• pp.68-75
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• 1998

The overproduction and high level secretion of Glucose Oxidase (GOD) from A. niger in S. cerevisiae was carried out by cloning GOD gene. For this purpose, using two different strong promoters (ADH1 promoter, GAL10 promoter) and signal sequences (${alpha}$-MF signal sequence of S. cerevisiae and ${alpha}$-amylase signal sequence of A. oryzae) and GAL7- and GOD terminator, four expression vectors were constructed. All the expression vectors were transformed in S. cerevisiae 2805 using auxotroph method. By the flask culture, transformants of pGAL expression vector series containing GAL 10 promotor showed much higher GOD productivity than transformants of pADH expression vector series containing ADH1 promoter Transformants of pGALGO2 containing GAL10 promotor and ${alpha}$-amylase signal sequence has shown the best productivity of GOD ($GOD_{total}$: 10.3 unit/mL, $GOD_{ex}$: 8.7 unit/mL) at 115 hr. This value was three fold higher than that of pGALGO1 containing GAL 10 promotor and ${alpha}$-MF signal sequence, even if the same promotor was involved. Through the ${alpha}$-amylase signal sequence of A. oryzae, GOD was secreted much more than the case of ${alpha}$-MF signal sequence from S. cerevisiae. These results suggest that signal sequence may play a important roles in not only the secretion but also the overproduction of foreign protein. Secretion rate of GOD in pGALGO1 and pGALGO2 was 89% and 84%, respectively, Because of the overglycosylation in S. cerevisiae the molecular weight of recombinant GOD in S. cerevisiae was much larger (250 kDa) than that of nature GOD in A. niger (170 kDa).

• KSBB Journal
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• v.9 no.3
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• pp.306-311
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• 1994

Optical resolution of racemic ${\alpha}$-methylbenzylamine was carried out by using Bacillus licheniformis protease in organic media. Enantioselective amidation of racemic amino with an ester as an acyl donor was successfully employed to resolve the racemate. To enhance reaction rate and enantioselectivity, pH-adjustment by lyophilization of enzyme dissolved in buffer, colyophilization with salts or lyoprotectants, selection of solvents and molecular design of esters were investigated. The optimization of the resolution reaction achieved about 30-fold increase in initial reaction rate and about 12-fold increase in enantioselectivity, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.9
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• pp.944-949
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• 2003

In this paper, the double balance mixer(DBM) for Ku-band LNB using InGaP/GaAs HBT process is suggested for the characteristics of low DC power consumption, low noise figure, low intermodulation distortion and wide dynamic range. The 5 dB conversion gain, 14 dB NF, bandwidth 17.9 GHz and 50.34 dBc IMD are obtained under RF input power of -23 dBm, with bias condition as 3 V and 16 mA. The linearity of InGaP/GaAs HBT, the broad band input matching scheme and the optimization of bias point result in the low IMD, the broad bandwidth and the low power consumption characteristics.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.95-95
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• 2003

Inositol은 세포의증식 및 정보전달과정에 관여하는 phosphatidylinositol (PI)의 구성성분으로서 중요한 세포내 기능을 수행한다. P1는 세포내에서 특이적 인산화효소에 의하여 Pl4-phosphate(PIP), Pl4,5-phosphate($PIP_2$)로 변환되며 PIP$_2$는 phospholipase C(PLC)에 의하여 세포내 second messengers인 1,2-diacylglycerol (DAG)와 inositol 1,4,5-triphosphate ($IP_3$)로 변환된다. 이렇게 생산된 DAG와 IP3는 각각 protein kinase C의 활성과 $Ca^{2++}$의 동원에 관여하여 다양한 세포내 신호전달에 관여하는 것으로 보고되고 있다. 또한 mouse에서 $IP_3$의 작용에 의한 $Ca^{2++}$의 상승은 난모세포의 성숙분열이 촉진되고 돼지 난포세포에 있어서도 PI대사가 일어나고 있는 것으로 보고되고 있다. 본 연구에서는 돼지 미성숙 난모세포의 성숙과 단위발생에 미치는 inositol의 영향을 확인하기 위하여 실시하였다. inositol의 농도가 난포란의 성숙에 미치는 영향을 검토하기 위하여 난포란을 각각 $150 \mu mole$, $250 \mu mole$, $350 \mu mole$, inositol을 포함하는 Whitten's 배양액에서 44시간 성숙시킨 결과 $93.57 \pm 4.21, 93.91 \pm 2.71, 92.96 \pm 3.58%$가 성숙되어 대조구의 $87.10 \pm 4.21$보다 유의적(P<0.05)으로 차이를 나타내었다. 난포란의 등급에 따른 inositol의 영향을 확인하기 위하여 형태적으로 난구세포가 치밀한 난포란과 난구세포가 치밀하지 않은 난포란을 $250 \mu mole$ inositol을 포함하는 Whitten's 배양액에서 성숙을 유도한 결과 난구세포가 치밀한 난포란과 난구세포가 치밀하지 않은 난포란에서 inositol을 첨가하였을 때 성숙율은 각각 $95.35 \pm 2.22와 63.55 \pm 8.12$로 inositol을 첨가하지 않은 대조구보다($89.21 \pm 3.69와 48.56 \pm 8.99$) 유의적인 차이를 보였다. 난구세포가 inositol에 의한 성숙에 미치는 영향을 확인하기 위하여 난구세포를 제거한 난포란을 inositol을 포함하는 배지에서 성숙을 유도한 결과 inositol을 첨가하지 않은 처리구보다 양호한 성숙율을 보였다.

• Electrical & Electronic Materials
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• v.8 no.5
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• pp.572-579
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• 1995

Most of conventional ultrasonic transducers are constructed to generate either longitudinal or shear waves, but not both of them. We investigate the mechanism of dual mode transducers that generate both of the longitudinal and shear waves simultaneously with single PZT element. The study is aimed to find the optimally desired cut by examining the anisotropic piezoelectric properties. Theory predicts that a mixed P/S mode transducer can be constructed using a rotated Z-cut of PZT piezoelectric ceramics. We study the performance of a PZT element as a function of its rotation angle so that its efficiency is optimized to excite the two waves as much as equally strong. The results are verified by the waveform in pulse-echo computer simulation and experiments. When the transducer is subjected to impedance analysis, it shows two thickness mode resonances, each of which being a mixed P/S thickness mode. By examining wave speeds on E transmitter delay line receiver setup, it is confirmed that the transducer can transmit and detect both longitudinal and shear wave simultaneously.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.437-438
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• 2009