• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권8호
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• pp.392-398
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• 2006

The properties of tunable dielectric materials on RF frequency band are important high tunability and low loss for RF variable devices, variable capacitor, phased array antenna and other components application. Various composite of BST(barium strontium titanate) ratio combined with other non-electrical active oxide ceramics have been formulated for such uses. We present the tunable properties and Curie temperature on BST thick films. The grain growth of the weight ratio of $BaTiO_3$ increased. This can be explained by the substitute $Sr^{2+}$ ion for $Ba^{2+}$ ion in the $BaTiO_3$ system. The Curie temperature was shifted to lower temperature with increasing $SrTiO_3$in the $BaTiO_3-SrTiO_3$ system, because of decreasing the lattice constant. Also, the dielectric constant, tunability and K-factor of $(Ba_xSr_{1-x})TiO_3$ at over the Curie temperature decreased, at over the $60^{\circ}C$ fixation, maximum dielectric constant at Curie temperature and hence sharper phase transformation occurred at Curie temperature. The result were interpreted as a process of internal stress relaxation resulting form the increase of $90^{\circ}$ domains induced the BST. As a result, It is concluded that over the Curie temperature, frequency response and DC field effect for the tunable properties of BST thick film are suppressed by the transition broadening. For the application of tunable devices, that the curie temperature was investigated to be increased.

• 한국자동차공학회논문집
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• 제5권4호
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• pp.130-141
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• 1997

Work on the reduction of particulate matter(PM) from a diesel vehicl has led to a new trp system and a control method to control the combustion rate of the PM filtrated in the trap, which was named as 'Active Exhaust Feeding Regeneration(AEFR) System' by its operation mechanism. Ceramic cordierite filter is a major component of the trap and susceptible to thermal shock. Therefore the system should be designed to reduce the peak temperature and temperature gradients in the trap ; these have been considered to be the main factors causing thermal shock of the filter during the regeneration. It uses the engine's exhaust gas partially for the regeneration of the ceramic filter. It controlled bypass flow rate of the engine's exhaust gas precisely to control the temperature of the gas entrained into the filter. Gas temperatures were measured inside filter, and the oxygen concentration at the outlet of the filter was also monitored during the regeneration to analyze the combustion process of the PM. The temperature distributions and temperature gradients in the filter during the regeneration varied widely according to the regeneration control schemes. Finally, this system shows relatively low peak temperature and temperature gradients in the filter during its regeneration. It is considered that this system uses a mew method to control the combustion rate of the PM, which is different from the methods used in the previous studies.

• 대한금속재료학회지
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• 제46권11호
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• pp.762-769
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• 2008

Hydrogenated amorphous silicon(a-Si : H) layers, 120 nm and 50 nm in thickness, were deposited on 200 $nm-SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by E-beam evaporation. Finally, 30 nm-Ni/120 nm a-Si : H/200 $nm-SiO_2$/single-Si and 30 nm-Ni/50 nm a-Si:H/200 $nm-SiO_2$/single-Si were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 30 minute. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide on the 120 nm a-Si:H substrate showed high sheet resistance($470{\Omega}/{\Box}$) at T(temperature) < $450^{\circ}C$ and low sheet resistance ($70{\Omega}/{\Box}$) at T > $450^{\circ}C$. The high and low resistive regions contained ${\zeta}-Ni_2Si$ and NiSi, respectively. In case of microstructure showed mixed phase of nickel silicide and a-Si:H on the residual a-Si:H layer at T < $450^{\circ}C$ but no mixed phase and a residual a-Si:H layer at T > $450^{\circ}C$. The surface roughness matched the phase transformation according to the silicidation temperature. The nickel silicide on the 50 nm a-Si:H substrate had high sheet resistance(${\sim}1k{\Omega}/{\Box}$) at T < $400^{\circ}C$ and low sheet resistance ($100{\Omega}/{\Box}$) at T > $400^{\circ}C$. This was attributed to the formation of ${\delta}-Ni_2Si$ at T > $400^{\circ}C$ regardless of the siliciation temperature. An examination of the microstructure showed a region of nickel silicide at T < $400^{\circ}C$ that consisted of a mixed phase of nickel silicide and a-Si:H without a residual a-Si:H layer. The region at T > $400^{\circ}C$ showed crystalline nickel silicide without a mixed phase. The surface roughness remained constant regardless of the silicidation temperature. Our results suggest that a 50 nm a-Si:H nickel silicide layer is advantageous of the active layer of a thin film transistor(TFT) when applying a nano-thick layer with a constant sheet resistance, surface roughness, and ${\delta}-Ni_2Si$ temperatures > $400^{\circ}C$.

• 청정기술
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• 제26권4호
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• pp.286-292
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• 2020

본 연구는 Cu/CeO2-X 촉매의 저온 CO 산화 활성에 미치는 영향을 촉매의 구조적 특성, 반응 특성을 통해 확인하였다. 사용된 촉매는 습윤 함침법으로 제조되었으며, 각기 다른 소성온도(300~600 ℃)에서 형성된 CeO2 (지지체)를 이용하여 Cu (활성금속)를 담지함으로써 Cu/CeO2-X 촉매를 제조하였다. 제조된 Cu/CeO2-X 촉매는 저온 CO 산화 활성을 평가하였다. 125 ℃에서 Cu/CeO2_300 촉매는 90% 이상의 활성을 나타냈으며, CeO2의 소성온도가 증가됨에 따라 활성이 점차 감소하여, Cu/CeO2_600 촉매는 65%를 나타냈다. 다음으로 촉매의 물리/화학적 특성을 Raman, BET, XRD, H2-TPR, XPS 분석으로 확인하였다. XPS 분석 결과, CeO2-X의 소성온도가 낮을 수록 불안정한 Ce3+ 종(비 화학양론 종) 비율이 증가하였다. 증가된 Ce3+종은 Cu와 결합함으로 써 치환결합을 형성하였으며 Raman 분석의 CeO2 peak 변화와 H2-TPR 분석의 치환결합 구조의 환원 peak를 통해 확인하였다. 결과적으로 Cu와 CeO2의 치환 결합 형성은 촉매의 redox 특성 및 저온 CO 산화 활성을 증진시켰다고 판단된다.

• 한국전기전자재료학회논문지
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• 제14권10호
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• pp.861-867
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• 2001

In this paper, in order to investigate the catalytic effect of the sludge exhausted from waterworks on NO$_{x}$ removal, we measure NO removal characteristics with and without sludge pellets in BaTiO$_3$-sludge packed-bed reactor of plate-plate geometry. NO initial concentration is 50 ppm balanced with air and a gas flow rate is 5ι/min. Gas temperature is changed from 25 to 10$0^{\circ}C$ to investigate the role of sludge pellet on removing active oxygen species and NO$_2$. BaTiO$_3$pellets is filled for coronal discharge at upstream of reactor and sludge pellets is filled for catalytic effect at downstream of reactor. The volume percent of sludge pellets to BaTiO$_3$pellets is changed from 0% to 100% and AC voltage is supplied to the reactor for discharging simulated gases. In the results, when sludge pellets is put at the downstream of plasma reactor, NO removal rate is slightly increased. However, NO$_2$and $O_3$ as by-products during NO removal is significantly decreased from 51ppm without sludge pellets to 5 ppm with sludge pellets and from 50 ppm without sludge pellets to 0.004ppm with sludge pellets, respectively. Therefore, NO$_{x}$(NO+NO$_2$) removal rate is increased up to 93%. It is thought that sludge pellet maybe react with active oxygen species and NO$_2$ generated by corona discharge in surface of BaTiO$_3$pellets, the then NO$_2$O$_3$as by-products are considerably decreased. When we increase gas temperature from room temperature to 10$0^{\circ}C$, NO removal rate is decreased, while NO$_2$ concentration is independent on gas temperature. These result suggest that the removal mechanism of active oxygen species and NO$_2$in sludge pellet is not absorption, but chemical reaction. Therefore we expect that sludge pellets exhausted for waterworks could be used as catalyst for NO$_{x}$ removal with high removal rate and low by-product.oduct.

• 대한지역사회영양학회지
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• 제5권1호
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• pp.100-108
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• 2000

Seven constructs of sanitary management :time temperature, storage, cross-contamination, personal hygiene, equipment facility and documentation management were evaluated to investigate the perceived performance of sanitary management for school food service managers, Using a four-part questionnaire containing the seven constructs of sanitary management HACCP program, demographic information and characteristics of food service facilities participants rated their self-perceptions regarding sanitary management. Of the 550 possible respondents, 248(45.1%) completed the study. For the perceived sanitary manage-ment variables, the participants rated them between 2.66 and 4.16(5-point Likert scale). Temperature management presented the lowest performances while storage management showed the highest. The number of years of work experience of the food service managers and the serving location correlated significantly to sanitary management variables. Documentation management was also highly correlated to the other sanitary management constructs. The respondents ranked the managers leadership and professional knowledge regrading HACCP as most important, followed by the facilitys supporting equipment and human resources second, to successfully implement the HACCP system at the school food service facilites, Awareness of this study indicating low performance on temperature management suggests an active training program is needed for sanitary management of school food service.

• 한국미생물·생명공학회지
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• 제19권4호
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• pp.383-389
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• 1991

저온에서 높은 활성을 나타내는 알칼리성 protease를 생산하기 위하여 여러가지 시료로부터 집적배양에 의해 저온성 세균을 분리하였다. 분리된 세균은 저온.알칼리성 Pseudomonas sp.인 것으로 판명되었으며, 효소생산을 위한 균생육의 최적 pH는 10.0, 온도 $20^{\circ}C$에서 4일간 배양하였을 때였다. 이 효소 활성의 최적 pH 및 온도는 각각 pH 10.5 및 $40^{\circ}C$였으며, pH 및 열안정성은 각각 pH 7.0~13.0, 온도 $50^{\circ}C$이하의 범위에서 비교적 안정하였다.

• Plant Resources
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• 제5권2호
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• pp.141-154
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• 2002

In this experiment, three kinds of mutations(ge, re, and eml )relating to the size of embryos were used to study their generation, genetic mechanism and developmental characteristics, and the interactions between embryo and endosperm were also examined. Giant embryo mutation comprises 7 kinds including the already isolated ge, and ge-2, which share an identical gene site. The SAM and the size of radicule for the ge showed little difference compared to a normal type. The number of embryo cells did not increased as much as it would affect the size of embryo. Therefore, the enlargement of embryo was due to the enlargement of scutellum that originated from the corpulence of each cell. Both F$_1$' s of re ]and odm 49 formed reduce embryos, and other combinations of hybridization showed all wild type of embryo sizes. Accordingly, the odm 49 must have an identical gene site of re 1, while odm 48 and odm 62 have different gene sites. Their shoots and radicules also shrank by the same ratio, however no sign of physical change was noticed. The size of embryo cell showed no change, while the number of cells was the half of that of wild types. The three gene sites of re represent all of them control the size of the entire embryo forming organs. The eml 1 was defined to have temperature sensibilities that the generation of endosperms was active at a high temperature while that was hampered at a low temperature.

• 한국기계가공학회지
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• 제19권1호
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• pp.56-62
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• 2020

The purpose of this study is to observe the visualization of the flow field for air flow distributed in the car from the ventilation fan installed in the ceiling of the passenger elevator car through the numerical analysis using computational fluid dynamics. STAR-CCM+, which is a code used for the numerical analysis, was used to predict the airflow distribution inside the elevator car. The numerical analysis of the distribution of the air current in the elevator was carried out. As a result, the analysis results for each point and the visualization of the air current distribution and the temperature distribution in the elevator car and were obtained. It was found that heat transfer was actively occurring inside the car due to the influence of the flow field discharged from the ventilation vent installed in the ceiling in the elevator car, and especially the convection heat transfer of Model-2 was more active than that of Model-1. As a result, the temperature distribution inside the car was found to be relatively low. In addition, the temperature distribution at a cross-section of 1700mm height in the elevator car shows that Model-2 is the location of the ventilation vent which makes people feel more comfortable.

• 한국표면공학회지
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• 제30권6호
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• pp.406-411
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• 1997

Transparent conductive thin films have found many applications in active and passive electronic and opto-electronic devices such as flat panel display electrode, solar cell electrode and window heat mirror, etc. Low resistivity and high transmittance of these films can beotained by controlling deposition parameters which are oxygen partial pressure, substrate temperature and dopant concentration. In this study, non-stoichiometric and Sb-doped thin electrical properties of undoped films have been degraded with increase of substrate temperature and optical properties have been improved in Sb-doped films. The resistivity of $2.5\times10^{-3}\Omega\textrm{cm}$,/TEX>, average transmittance of 80% and sheet resistance of 130$\Omega$/$\square$ at thickess of 2000 $\AA$ could be obrained at optmal condimal conditions which were at $400^{\circ}C$ of substrate temperature, 58% of oxygen partial pressure and 5% of Sb doping concentration.