• Korean Journal of Materials Research
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• v.20 no.5
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• pp.241-245
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• 2010

One of the weak points of the Cr-doped SZO is that until now, it has only been fabricated on perovskite substrates, whereas NiO-ReRAM devices have already been deposited on Si substrates. The fabrication of RAM devices on Si substrates is important for commercialization because conventional electronics are based mainly on silicon materials. Cr-doped ReRAM will find a wide range of applications in embedded systems or conventional memory device manufacturing processes if it can be fabricated on Si substrates. For application of the commercial memory device, Cr-doped $SrZrO_3$ perovskite thin films were deposited on a $SrRuO_3$ bottom electrode/Si(100)substrate using pulsed laser deposition. XRD peaks corresponding to the (112), (004) and (132) planes of both the SZO and SRO were observed with the highest intensity along the (112) direction. The positions of the SZO grains matched those of the SRO grains. A well-controlled interface between the $SrZrO_3$:Cr perovskite and the $SrRuO_3$ bottom electrode were fabricated, so that good resistive switching behavior was observed with an on/off ratio higher than $10^2$. A pulse test showed the switching behavior of the Pt/$SrZrO_3:Cr/SrRuO^3$ device under a pulse of 10 kHz for $10^4$ cycles. The resistive switching memory devices made of the Cr-doped $SrZrO_3$ thin films deposited on Si substrates are expected to be more compatible with conventional Si-based electronics.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.4
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• pp.57-66
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• 2009

수학적 모델은 수량과 수질의 예측을 위해 현장 조사의 대안으로 사용되어지며 이러한 모델의 사용과 실측에 불확실성이 존재하게 된다. 불확실성에 대한 많은 연구들이 진행되어 왔으나 시나리오에 의한 모델링 과정에서 발생하는 불확실성에 대한 연구는 미흡한 실정이다. 본 연구에서는 산림이 농경지와 목초지로의 변화에 따른 시나리오를 설계한 후 시나리오 적용에 따른 SWAT (Soil and Water Assessment Tool) 매개변수의 불확실성을 분석하고자 하였다. 몬테카를로 기법 (Monte Carlo simulation)을 이용하여 각 매개변수별 1,000개의 난수를 발생하였으며 앙상블 유량모의 기법을 이용하여 미국 Alabama주 카하바강 상류 (50,967ha)를 대상으로 각 난수별 100개의 유량을 통해 불확실성을 분석하였다. 분석 결과 산림지역이 농경지와 목초지로 변화 되었을 때 유출량이 증가하는 것으로 분석되었으며, 임야가 목초지 보다 농경지로 변화되었을 때 유출량은 더욱 증가하는 것으로 나타났다. 각 시나리오별 SWAT 매개변수의 불확실성은 AWC (Available water capacity), CN (Curve number), GWREVAP (groundwater re-evaporation coeffeicient), REVAPMN (minimum depth of water in shallow aquifer for re-evaporation to occur)순으로 크게 나타났으며, Ksat (Saturated hydraulic conductivity)와 ESCO(Soil evaporation compensation factor)는 유출량의 변화에 큰 영향을 미치지 못하는 것으로 분석되었다. 토지피복별 산림 면적이 클 경우 불확실성이 크게 나타나 산림이 목초지와 농경지로 변함에 따라 불확실성은 감소하는 것으로 나타났다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.16 no.1
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• pp.1-15
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• 1980

An underwater recording system was designed to measure the sound spectra of the underwater noises produced by fishing gears in operation. Recorded were noi~es from three types of fishing gears: an anchovy set net, three anchovy boat seine net and a stern trawlnet. Acoustic analysis were made using a heterodyne analyzer, a digital frequency analyzer and a level recorder. The no;'e produced by the anchovy set net was found in the high frequency region of the onset of ambient noise spectrum with a slope of - 6 dB/octave. Here the ambient noise spectrum is higher, though similar in shape, than Knudsen spectrum, and is attributed to the breaking action of the coastal wave. Measured noise spectra during the fishing operations of the anchovy boat seine nets are attributed to the background noise of the sea in the presence of the fishing vessels. The frequency distribution of the noise was 20~5, 000 Hz in the case of two steel anchovy boat seiners, and 20-3,000 Hz in the case of the wooden anchovy boat seiner. The predominant frequency range was 250~350 Hz and maximum sound pressure level was 122 dB (re $1\muPa$) in the case of the steel boat and ] 17 dB in the case of the wooden boat. The noises produced by the trawl fishing gears are remarkably higher than the background noi~e in the presence of the fishing vessel. The frequency distribution of the noi~e was 20-6,300 Hz. The predominant frequency range was 100~200 Hz and maximum sound pressure level was 137 dB ( re $1\muPa$) . The noise spectra were not so much different from that caused by vibrations of the towing cable and the structure of the ground rope of the trawl net towed in an experimental tank.

• Animal cells and systems
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• v.16 no.6
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• pp.469-478
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• 2012

Sex hormones have long been considered to play an important role in bone turnover rate, periodontal diseases, and wound healing. We have studied the effect of porcine testis steroid extract (PTSE), an extract of porcine testes, which holds a good ratio of 19-nortestosterone (nandrolone), testosterone, androstenedione, $17{\beta}$-estradiol, and estrone, on the healing rate of a standardized full-thickness linear wound on the back of the rat. Skin punch or carbon dioxide ($CO_2$) laser methods were used to create the deep skin injury in two groups of animals. The animals were treated with the PTSE cream, control cream and Vaseline (control) to find out the effect in re-epithelialization, contraction, and formation of granulation and scar tissues. Histological examination after 21 days showed 100, 87.4, and 80.5% recovery of epidermis, dermis, and hypodermis, respectively in the PTSE-treated animals. Similarly, on the 15th day of treatment, complete healing of intact skin was observed in the PTSE cream-treated animals among the laser radiation group. Even though the beginning of re-epithelialization phase and completion of serum crust formation was also observed in the base cream- and Vaseline-treated animals respectively, the complete healing cycle was observed only in the PTSE-treated group. The white blood cell count in the PTSE-treated group showed that PTSE cream is nontoxic to animals.

• Korean Journal of Materials Research
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• v.20 no.10
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• pp.543-549
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• 2010

The hydrogen energy had recognized clean and high efficiency energy source. The research field of hydrogen energy was production, storage, application and transport. The commercial storage method was using high pressure tanks but it was not safety. However metal hydride was very safety due to high chemical stability. Mg and Mg alloys are attractive as hydrogen storage materials because of their lightweight and high absorption capacity (about 7.6 wt%). Their range of applications could be further extended if their hydrogenation properties and degradation behavior could be improved. The main emphasis of this study was to find an economical manufacturing method for Mg-Ti-Ni-H systems, and to investigate their hydrogenation properties. In order to examine their hydrogenation behavior, a Sievert's type automatic pressure-compositionisotherm (PCI) apparatus was used and experiments were performed at 423, 473, 523, 573, 623 and 673 K. The results of the thermogravimetric analysis (TGA) revealed that the absorbed hydrogen contents were around 2.5wt.% for (Mg8Ti2)-10 wt.%Ni. With an increasing Ni content, the absorbed hydrogen content decreased to 1.7 wt%, whereas the dehydriding starting temperatures were lowered by some 70-100 K. The results of PCI on (Mg8Ti2)-20 wt.%Ni showed that its hydrogen capacity was around 5.5 wt% and its reversible capacity and plateau pressure were also excellent at 623 K and 673 K.

• Publications of The Korean Astronomical Society
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• v.22 no.4
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• pp.201-209
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• 2007

We have preliminarily designed two infrared optical systems of the multi-purpose infrared camera system (MIRIS) which is the main payload of STSAT-3. Each optical system consists of a Cassegrain telescope, a field lens and a 1:1 re-imaging lens system that is essential for providing a cold stop. The Cassegrain telescope is identical for both of two infrared cameras, but the field correction lens and re-imaging lens system are different from each other because of different bands of wavelength. The effective aperture size is 100mm in diameter and the focal ratio is f/5. The total length of the optical system is 300mm and the position of the cold stop is 25mm from the detector focal plane. The RMS spot size is smaller than $40{\mu}m$ over the whole detector plane.

• Journal of Microbiology
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• v.40 no.2
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• pp.91-97
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• 2002

Enteroaggregative E. coil (EAEC) is an important aethiological causal agent of diarrhea in people of developed and undeveloped countries. Different in vitro and in vivo models have been proposed to study the pathdgenic and immune mechanisms of EAEC infaction. The aim of this study was to analyze whether BALB/c mice could be used as an animal model to study EAEC pathogenesis Six-week-old BALB/c mice were inoculated with EAEC strain 042 (044:H88) nalidixic acid resistant, and re-inoc-ulated ten days after. Mice feces were monitored for the presence of the EAEC strain over a period of 20 days . Bacteria were enumerated on MacConkey agar containing 100$\mu$g of nalidixic acid per ml. Results showed that 35% of the animals were colonized for 3 days, 15% for 5 and 10% for more than 7 days . After re-inoculation only 16% of the animals remained colonized for more than 3 days. During the necropsy, the intestinal fluid of same of the infected animals presented mucus and blood. Six of these fluids showed the presence of IgA antibodies againset Pet toxin and IgG natibodies raised against the toxin were also detected in the animal serum. Histopathologic evidence confirms the stimulation of mucus hypersecretion, an increased amount of goblet cells and the presence of bacterial aggregates in the apical surfaces of intestinal epithelial cells. Edema was present in the submucosa. These results suggest that BALB/c mice could be used as an animal model for in vivo study of EAEC infection.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.206-206
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• 2010

정보화 기술이 급속히 발전함에 따라서 보다 많은 양의 data를 전송, 처리, 저장 하게 되면서 이를 처리 할 수 있는 대용량, 고속, 비휘발성의 차세대 메모리의 개발이 요구 되고 있다. 이 중 저항 변화 메모리(ReRAM)는 일반적으로 전이금속산화물을 이용한 MIM 구조로서 적당한 전기 신호를 가하면 저항이 높아서 전도되지 않는 상태(Off state)에서 저항이 낮아져 전도가 가능한 상태(On state)로 바뀌는 메모리 특성을 가진다. ReRAM은 비휘발성 메모리이며 종래의 비휘발성 기억소자인 Flash memory 보다 access time이 $10^5$배 이상 빠르며, 2~5V 이하의 낮은 전압에서 동작이 가능하다. 또한 구조가 간단하여 공정상의 결함을 현저히 줄일 수 있다는 점 등 많은 장점들이 있어서 Flash memory를 대체할 수 있는 유력한 후보로 여겨지고 있다. 저항 변화의 특징을 잘 나타내는 물질에는 $TiO_2$, $Al_2O_3$, $NiO_2$, $HfO_2$, $ZrO_2$등의 많은 전이금속산화물들이 있다. 본 연구에서는 Reactive DC-magnetron Sputtering 방법과 DC-magnetron sputter를 이용하여 Ti를 증착한 후 Oxidation 방법으로 각각 증착한 $TiO_2$박막을 사용하여 저항변화특성을 관찰하였다. $TiO_2$상부에 Atomic Layer Deposition (ALD)를 이용하여 $HfO_2$ 박막을 증착하여 표면처리를 하고, 또한 $TiO_2$에 다른 전이 금속박막 층을 추가 증착하여 저항변화 특성에 접합한 조건을 찾는 연구를 진행하였다. 하부 전극과 상부 전극 물질로는 Si 100 wafer 위에 Pt 또는 TiN을 사용하였다. 저항변화 특성을 평가하기 위해 Agilent E5270B를 이용하여 current-voltage (I-V)를 측정하였다. X-ray Diffraction (XRD)를 이용하여 증착 된 전기금속 박막 물질의 결정성을 관찰했으며, Atomic Force Microscopy (AFM)을 이용하여 증착 된 샘플의 표면을 관찰했다. SEM과 TEM을 통해서는 sample의 미세구조를 확인 하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.615-627
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• 1997

An experiment was performed to local heat transfer coefficient and Nusselt number in the circular duct of 180.deg. bend for Re=6*10$^{4}$, 8*10$^{4}$ and 1*10$^{5}$ at swirling flow and non-swirling flow conditions. The test tube with circular section was made by stainless which has curvature ratio 9.4. The wall of test tube was heated directly by electrical power to 3.51 kw and swirling motion of air was produced by a tangential inlet to the pipe axis at the 180 degree. Measurements of local wall temperatures and bulk mean temperature of air are made at four circumferential positions in the 16 stations. The wall temperatures show particularly reduced distribution curve at bend for non-swirling flow but this effect does not appear for swirling flow. Nusselt number distributions for swirling flow which was calculated from the measured wall and bulk temperatures were higher than that of non-swirling flow. Average Nusselt number of swirling flow increased about 90 ~ 100% than that of non-swirling flow whole through the test tube. The Nu/N $u_{DB}$ values at the station of 90.deg. for non-swirling flow and swirling flow are respectively about 2.5 and 4.8 at Re=6*10$^{4}$. Also that is good agreement with Said's result for non-swirling flow. flow.

• Restorative Dentistry and Endodontics
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• v.21 no.2
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• pp.585-601
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• 1996

The purpose of this study was to elucidate the effect of blood-and saliva-contamination during dentin pretreatment procedure on tensile bond strength, and to investigate the effect of contaminant-removing treatments on the recovery of bond strength of dentin bonding agents. Dentin specimens prepared from freshly extracted bovine mandibular anterior teeth were divided into non-contaminated control and contaminated experimental groups. The specimens of the contaminated group were contaminated with saliva or blood after etching or priming procedure, followed by contaminant-removing treatments. All the specimens were bonded with All Bond$^{(R)}$ 2 dentin bonding agent and Bisfil$^{TM}$ composite resin or Scotchbond$^{TM}$ Multipurpose and Z100. After all the bonded specimens were stored in $37^{\circ}C$ distilled water for 24 hours, tensile bond strengths were measured. The contaminated dentin and fractured dentin surfaces were examined under the scanning electron microscope. The results were as follows : Contaminated specimens showed lower bond strength than non-contaminated ones regardless of the kind of contaminant, contamination time and contaminant-removing treatments, except specimens which were acid-etched following saliva contamination after etching in All Bond$^{(R)}$ 2 groups (p<0.05). Blood contaminant resulted in much bond strength decrease than saliva ones (p<0.01), and contamination after priming resulted in much decrease in bond strength than after etching (p<0.01). Re-etching resulted in increase of bond strength in the specimens contaminated with saliva after etching but not in blood contaminated ones. Re-priming resulted in increase of bond strength in the specimens contaminated after priming regardless of the kind of contaminant.