• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.264-264
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• 2016

최근에 charge trap flash (CTF) 기술은 절연막에 전하를 트랩과 디트랩 시킬 때 인접한 셀 간의 간섭현상을 최소화하여 오동작을 줄일 수 있으며 낸드 플래시 메모리 소자에 적용되고 있다. 낸드 플래시 메모리는 고집적화, 대용량화와 비휘발성 등의 장점으로 인해 핸드폰, USB, MP3와 컴퓨터 등에 이용되고 있다. 기존의 실리콘 기반의 플래시 메모리 소자는 좁은 밴드갭으로 인해 투명하지 않고 고온에서의 공정이 요구되는 문제점이 있다. 따라서, 이러한 문제점을 개선하기 위해 실리콘의 대체 물질로 산화물 반도체 기반의 플래시 메모리 소자들이 연구되고 있다. 산화물 반도체 기반의 플래시 메모리 소자는 넓은 밴드갭으로 인한 투명성을 가지고 있으며 저온에서 공정이 가능하여 투명하고 유연한 기판에 적용이 가능하다. 다양한 산화물 반도체 중에서 비정질 In-Ga-Zn-O (a-IGZO)는 비정질임에도 불구하고 우수한 전기적인 특성과 화학적 안정성을 갖기 때문에 많은 관심을 받고 있다. 플래시 메모리의 고집적화가 요구되면서 절연막에 high-k 물질을 atomic layer deposition (ALD) 방법으로 적용하고 있다. ALD 방법을 이용하면 우수한 계면 흡착력과 균일도를 가지는 박막을 정확한 두께로 형성할 수 있는 장점이 있다. 또한, high-k 물질을 절연막에 적용하면 높은 유전율로 인해 equivalent oxide thickness (EOT)를 줄일 수 있다. 특히, HfOx와 AlOx가 각각 trap layer와 blocking layer로 적용되면 program/erase 동작 속도를 증가시킬 수 있으며 넓은 밴드갭으로 인해 전하손실을 크게 줄일 수 있다. 따라서 본 연구에서는 ALD 방법으로 AlOx와 HfOx를 게이트 절연막으로 적용한 a-IGZO 기반의 thin-film transistor (TFT) 플래시 메모리 소자를 제작하여 메모리 특성을 평가하였다. 제작 방법으로는, p-Si 기판 위에 열성장을 통한 100 nm 두께의 SiO2를 형성한 뒤, 채널 형성을 위해 RF sputter를 이용하여 70 nm 두께의 a-IGZO를 증착하였다. 이후에 소스와 드레인 전극에는 150 nm 두께의 In-Sn-O (ITO)를 RF sputter를 이용하여 증착하였고, ALD 방법을 이용하여 tunnel layer에 AlOx 5 nm, trap layer에 HfOx 20 nm, blocking layer에 AlOx 30 nm를 증착하였다. 최종적으로, 상부 게이트 전극을 형성하기 위해 electron beam evaporator를 이용하여 platinum (Pt) 150 nm를 증착하였고, 계면 결함을 최소화하기 위해 퍼니스에서 질소 가스 분위기, $400^{\circ}C$, 30 분의 조건으로 열처리를 했다. 측정 결과, 103 번의 program/erase를 반복한 endurance와 104 초 동안의 retention 측정으로부터 큰 열화 없이 메모리 특성이 유지되는 것을 확인하였다. 결과적으로, high-k 물질과 산화물 반도체는 고성능과 고집적화가 요구되는 향후 플래시 메모리의 핵심적인 물질이 될 것으로 기대된다.

• Journal of radiological science and technology
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• v.37 no.4
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• pp.253-259
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• 2014

Large volume of $6{\times}6{\times}12mm^3$ CdZnTe ${\gamma}$-ray detector was fabricated with CdZnTe single crystals grown by Traveling Heater Method (THM) to evaluate the energy resolution of 662 keV in $^{137}Cs$. Hole tailing effect which originated from the large mobility difference in electron and hole degrade energy resolution of radiation detector and its effects become more severe for a large volume detectors. Generally, single carrier collection technique is very useful method to remove/minimize hole tailing effect and thereby improvement in energy resolution. Virtual Frisch-grid technique is also one of single charge collection method through weighting potential engineering and it is very simple and easily applicable one. In this paper, we characterized CZT detector grown by THM and evaluated the effectiveness of virtual Frisch-grid technique for a high energy gamma-ray detector. The proper position and width of virtual Frisch-grid was determined from electric field simulation using ANSYS Maxwell ver. 14.0. Energy resolution of 2.2% was achieved for the 662 keV ${\gamma}$-peak of $^{137}Cs$ with virtual Frisch-grid CdZnTe detector.

• Journal of the Korean Chemical Society
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• v.50 no.5
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• pp.362-368
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• 2006

SH group modifying chemicals were used to characterize the eight cysteine residues of cabbage PLD. 5,5-dithiobis(2-nitrobenzoate)(DTNB) was used to titrate the SH group of cysteine residues . Based on the optical density at 412nm due to the reduced DTNB, 4 SH groups are found to be present in a native PLD while 8 SH groups in the denatured PLD whose tertiary structure was perturbed by 8M urea. The results imply that among the 8 cysteine residues of PLD, the half(4) are exposed on the surface whereas the other half are present at the interior of the enzyme tertiary structure. The PLD was inactivated by SH modifying reagents such as p-chloromercuribenzoate(PCMB), iodoacetate, iodoacetamide, and N-ethylmaleimide. At the addition of dithiothreitol(DTT) only the PCMB inhibited PLD activity was recovered reversibly. The micro-environment of the exposed SH group of cysteine residues was examined with various disulfide compounds with different functional groups and we found that anionic or neutral disulfides appear to be more effective than the positively charged cystamine for inactivating the PLD activity. The effect of redox state of cysteine residues on the PLD activity was further explored with H2O2. The oxidation of SH groups by H2O2 inhibited the PLD activity more than 70%, which was mostly recovered by DTT. From these results, we could confirm chemically that all the cysteine residues of PLD are present as in their reduced SH forms and the 4 SH groups exposed on the surface of the enzyme may play important roles in the regulation of PLD activity.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.11a
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• pp.57-58
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• 2001

용수 다소비 산업으로 분류되는 제지공업의 특성 상, 용수사용의 억제 및 용수의 무방류화에 대한 압력이 증가되고 있는 반면, 초지환경은 날로 열악해지고 있는 실정이다. 한 예로써, 용지의 재활용율 및 재사용 비율이 증가함에 따라 원료의 저급화가 심 각한 수준에 이르고 있으며, 이러한 초지환경의 변화는 각질화되고 극도로 미세화된 다량의 미세섬유 발생 및 잡고지로부터 유입되는 점착성 이물질과 무기 충진제의 도입 등을 유발함으로서 제품의 물리적 성질 저하, 탈수부하 증가로 인한 생산성 저하, 약품사용량 증가 등을 초래하여, 결과적으로는 폐수처리장의 부하를 증대시킴과 동시에 청수사용량 및 폐수방류량을 증가시키는 악순환을 되풀이하게 된다. 국내 제지산업이 국제적 경쟁력을 갖추기 위해서는 제품의 증대가 필수적이나, 원료와 설비의존도를 감안할 때, 제품특성과 공정 분을 결정하는 습부공정을 정확히 파악하여 최적 운전조건을 확립하는 것이 가장 경제적이고 용이한 방법일 뿐만 아니라 전체 제지공정의 정정화에도 기여할 수 있을 것으로 판단된다. 일정규모이상의 종이를 생산하는 제지공장은 거의 대부분 컴퓨터로 처리되는 온라인 공정조절 시스템(On-line process control system)을 구비하고 료의 도입에서부터 설비운전 및 제품의 기본적인 품질관리까지 실시간의 자동화되고 안정적인 운전과 관리시스템을 유지하고 있다. 그러나 전체 제지공정 중, 제품 물성과 운전조건의 대부분을 결정하는 습부공정만큼은 아직도 주기적인 분석이 행해지고 있지 않을 뿐만 아니라, 슬러리의 농도나 보류도 정도를 제이하면 분석항목 조차도 변변히 확립되어 있지 않을 실정이다. 이는 다량의 물 속에 존재하게 되는 용전물질(Dissolved solids, DS), 부유물질(Suspended solids, SS), 섬 유(Fibers), 무기 미 세분(Inorganic f fines), 그리고 투입되는 약품간에 발생하는 계면동전현상 및 이러한 현상과 최종 지제 품의 물성간의 상관관계에 대한 이해 정도나 경험 부족에서 기인하는 것으로 생각된다. 1 1983년 미국제지기술연합회(T APpI)의 제지용 첨가제 분과위원회(Papermaking A Additive Committee)에서는 습부공정의 적절한 조절을 위해 어떤 항목들이 필요하며 그 중요도는 어떠한가를 조사하였으며, 그 결과로 전하밀도, 제타전위, 보류도 및 여수 도, 무기 미세분 함량 등이 중요하다고 보고하였다. 그러나 지료의 전기적 특성을 실시 간으로 측정하는 기자재류가 최근에 이르러서야 도입되고 있는 실정이기 때문에 충분 한 현장적용 사례가 보고되지 못하고 있으며, 결과적으로 얻어진 정보와 최종 지제품의 물성 및 초지기 운전조건과의 상관관계를 확립하는 작업결과는 더욱 찾아보기 어렵다. 따라서, 본 연구에서는, 라이너지 제조공장의 습부공정에 투입되는 약품이 지료 의 전기적 성질, 즉 전하밀도와 제타전위에 미치는 영향을 모니터링함으로서 지료의 전기적 성질들과 습부 공정상태와의 상관관계를 살펴보고자 하였다. 본 연구는 다음과 같은 순서로 진행하였다.

• The korean journal of orthodontics
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• v.28 no.4 s.69
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• pp.499-515
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• 1998

The purpose of this study was to examine the associations of head posture the position of the tongue or the hyoid bone to craniofacial structure. Cephalograms taken in Natural head position(NHP) of 90 dental students (50 in male, 40 in female, 20 to 30 years in age) were traced and measured using the extracranial true horizontal and vertical lines. The obtained results were as follows; 1. There was no sex difference in head posture, but the hyoid bone was placed anteroinferiorly in male more than in female and anteroinferior inclination of the hyoid bone showed greatly in male. 2. The more inclined was the cervical column, the less prognathic was the face in natural head posture, and the larger cervical curvature, the more vertical pattern of the face. 3. The less small showed craniocervical angulation, the more anteriorly placed was the hyoid bone to the cranial base, and there was no significantly association between craniocervical angulation and the vertical position of the hyoid bone. 4. The more prognathic was the mandible, the more anteriorly placed was the hyoid bone, and there was slightly association between the craniofacial morphology and the vertical position of the hyoid bone.

• Journal of the Korean Magnetics Society
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• v.20 no.5
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• pp.173-177
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• 2010

The electronic structure of charge-density-wave (CDW) system $CeTe_2$ has been investigated by using angle-resolved photoemission spectroscopy (ARPES). The clearly dispersive band structures are observed in the measured ARPES spectra, indicating the good quality of the single-crystalline sample employed in this study. The four-fold symmetric patterns are observed in the constant energy (CE) mappings, indicating the $2{\times}2$ lattice deformation in the Te(1) sheets. The observed CE images are similar to those of $LaTe_2$, suggesting that Ce 4f states have the minor contribution to the CDW formation in $CeTe_2$. This study reveals that the carriers near the Fermi level should have mainly the Te(1) 5p and Ce 5d character, that the Te(1) 5p bands contribute to the CDW formation, and that the Ce 5d bands cross the Fermi level even in the CDW state.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.135-139
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• 2015

The address discharge time lags are investigated in each subfield time in AC plasma display panel and a modified driving waveform is proposed to reduce the address discharge time lag by applying different additional scan voltage under no misfiring discharge production. The weak plasma discharge in AC PDP is generated by applying high positive-going ramp waveform to the scan electrode during the first reset period and that induce the production of the priming particle and wall charge. Because the wall charge becomes the wall voltage in a cell, the wall plus external address voltage produce the address discharge. However, as the wall charge in a cell is gradually disappeared as time passed, the address discharge time in the subfield time for 1 TV frame is lagged. In the first subfield time, the address discharge is faster produced than the other subfield time because the wall charge are much remained by the high positive-going ramp voltage during the reset period in the first subfield time. Meanwhile, from the second to last subfield, the address discharge production time is gradually delayed due to the dissipation of the wall charge in a cell. In this study, the address discharge time lags are measured in each subfield time and the total address discharge time lags are shortened by applying the different additional scan voltage during the address period in each the subfield time.

• Journal of IKEEE
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• v.22 no.2
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• pp.495-498
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• 2018

In this paper, we propose an DAP system for dose evaluation of medical and industrial X-ray generator. Based on the DAP measurement technique using the Ion-Chamber, the proposed system can clearly measure the exposure radiation dose generated by the diagnostic X-ray apparatus. The hardware part of the DAP measures the amount of charge in the air that is captured by an X-ray. The high-speed processing algorithm part for cumulative radiation dose measurement through microcurrent measures the amount of charge captured by X-ray at a low implementation cost (power) with no input loss. The wired/wireless transmission/reception protocol part synchronized with the operation of the X-ray generator improves communication speed. The PC-based control program part for interlocking and aging measures the amount of X-ray generated in real time and enables measurement graphs and numerical value monitoring through PC GUI. As a result of evaluating the performance of the proposed system in an accredited testing laboratory, the measured values using DAP increased linearly in each energy band (30, 60, 100, 150 kV). In addition, since the standard deviation of the measured value at the point of 4 division was ${\pm}1.25%$, it was confirmed that the DAP showed uniform measurements regardless of location. It was confirmed that the normal operation was not less than ${\pm}4.2%$ of the international standard.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.2
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• pp.103-109
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• 2020

Purpose: The purpose of this study was to evaluate the preload maintenance of the retaining screw when using anaerobic sealing agents in implant fixture and abutment components. Specifically, the study examines the effects of anaerobic sealing agents on different types of screws. Materials and methods: External hexagon implants made of titanium and anti-rotational abutments were used. Titanium abutment screws and ebony abutment screws from the same manufacturer were used. The experiment was divided into four groups (n = 10 in each group). In the control group, no sealing agent was used at the implant fixture and abutment screw interface. All abutment screws were tightened according to the manufacturer's recommended torque (30 N.cm). After 24 hours, the removal torque (detorque) of each screw was measured using a digital torque gauge device. The data were analyzed by two-way ANOVA test according to normality distribution satisfaction. Results: Looking at the results for each group, titanium screws and no treatment showed detorque values of 20.3 ± 1.6 N.cm. titanium screws and applied anaerobic sealing agent showed detorque values of 32.4 ± 6.7 N.cm. Ebony screws and no treatment showed detorque values of 20.2 ± 1.5 N.cm. ebony screws and applied anaerobic sealing agent showed detorque values of 30.4 ± 4.5 N.cm. Conclusion: The detorque value was higher in the case of using anaerobic sealing agents in both the titanium screw and ebony screw groups. But there was no difference between the two screws.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.4
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• pp.419-432
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• 2010

Various torque generating devices have been developed and employed to apply a proper torque. These devices are usually calibrated by the manufacturer to apply appropriate torque levels for their specific implants and attachments. The purpose of this investigation was to determine and compare the accuracy of the torque controllers. In this study, 4 types of torque controllers were used; torque limiting device(TLD), torque indicating device(TID) and contra angle torque driver(CA), electronic torque controller(ETC). Digital torque gauge was employed to measure the de-torque value. Thirty cycles of tightening and loosening were repeated with each torque controller. All implant torque controllers have shown slight errors and deviations. The contra angle torque driver exhibited the most accurate data. In the limitation of this study, it would be recommended that the implant torque controllers should be checked whether uniformed and precise torque can be generated and a measuring error should be corrected.