• 생태와환경
• /
• 제42권4호
• /
• pp.487-494
• /
• 2009

We compared spatial and temporal variations of water chemistry between high-flow year ($HF_y$) and low-flow year ($LF_y$) in an artificial lentic ecosystem of Daechung Reservoir. The differences in the rainfall distributions explained the variation of the annual inflow and determined flow characteristics and water residence time and modified chemical and biological conditions, based on TP, suspended solids, and chlorophylla, resulting in changes of ecological functions. The intense rainfall and inflow from the watershed resulted in partial disruption of thermal structure in the metalimnion depth, ionic dilution, high TP, and high suspended solids. This condition produced a reduced chlorophyll-a in the headwaters due to low light availability and rapid flushing. In contrast, reduced inflow and low rainfall by drought resulted in strong thermal difference between the epilimnion and hypolimnion, low inorganic solids, high total dissolved solids, and low phosphorus in the ambient water. The riverine conditions dominated the hydrology in the monsoon of $HF_y$ and lacustrine conditions dominated in the $HF_y$. Overall data suggest that effective managements of the flow from the watershed may have an important role in the eutrophication processes.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
• /
• pp.27-30
• /
• 2002

Boron Phosphide films were deposited on the glass substrate at the low temperature, $550^{\circ}C$, $480^{\circ}C$, by the reaction of $B_{2}H_{6}$, with $PH_{3}$ using CVD. The reactant gas rates were 50 cc/min and 20 cc/min for $B_{2}H_{6}$, 50 cc/min and 40 cc/min for $PH_{3}$ and $1.5\ell$/min for $N_{2}$ carrier gas. The films were annealed for 1hour, 3hours in $N_{2}$ ambient at $550^{\circ}C$ and $400^{\circ}C$. The deposition rate was $1000{\AA}$/min and the refractive index of film was 2.6. From results of XRD measurement the films have the preferred orientation of (1 0 1). For as deposited the film, the data of VIS spectrophotometer show 75.49%, 76.71% for 1hr-annealed and 86.4% for 3hrs-annealed. From AFM datas the surface condition of obtained films are was shown $73{\AA}$, $88.9{\AA}$ and $220{\AA}$ for as-deposited, for 1hr-annealed and for 3hr annealed, respectively.

• 대한전자공학회논문지
• /
• 제22권5호
• /
• pp.75-82
• /
• 1985

Weighted Least Square(W.L.S.)알고리즘을 통한 계수식별 이론과 출력 증차를 최소로 하기위해 한단계 앞서서 제어입력을 결정하는 제어이론을 결수한 기준 모델 통용제어를 응용한 연료펌프 시스템을 설계하였다. 시스템의 성능에 관계되는 샘플링 이기 7, 비중계수 공및 State Yarlable Filter(5. Y. F.)의 릴터계수의 값은 컴퓨터 시뮬레이션을 통해 결정했으며, 특히 주독온도의 변화로 인해 연료의 점성도가 변하므로서 공정의 동특성을 나타내는 공량계수가 변하는 것에 대한 제어시스템의 적응도를 레팔레이션(regu lation)과 추종(tracking)관점에서 고찰하였다.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2008년도 하계학술발표대회 논문집
• /
• pp.663-668
• /
• 2008

This study was carried out solar heating system design for district heating and it's the performance analysis by experiment. This experimental system was installed in Bundang district heating area in the end of 2006. The flat plate and vacuum tube solar collector are combined in one system. So district heating water is heated first by flat plate solar collector and than by vacuum tube solar collector. This solar heating system has not a solar buffer tank and is operating with variable flow rate to obtain a setting temperature of $90{\sim}95^{\circ}C$. As a result, the daily solar thermal collection efficiency is about 30 to 40% for the plate type and 50 to 55% for the vacuum tube solar collector. It varied especially depend on the weather condition like as solar radiation and ambient temperature. This variable flow rate system can be also reduced much pumping power more than 50%.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 춘계학술대회논문집
• /
• pp.1010-1013
• /
• 2003

It is said that the goal of the design of good acoustical environment is at first the reduction of undesirable sounds, and in addition the introduction of desirable sounds by which our minds are soothed. The task of creating the desirable sounds leads to the realization of a comfortable acoustic environment and the design of soundscape. It may be an important starting point of soundscape design to select suitable sounds for the target spaces, because each space has a different surrounding condition and requires a special ambient sound. This paper aims to survey preference of the environmental sounds suitable for the public spaces in urban areas such as parks, bus terminals. 35 kinds of natural sounds are rated by 26 pairs of adjectives. The results of psycho-acoustic experiments are as follows. 1. The proper adjectives for expressing the environmental sounds are classified into 6 groups of comfort, pleasure, fullness, variety, distinctness, naturalness. 2. Bird singing, murmuring of a stream, artificial sounds, singing of insects and animals are the affirmative order of preference. 3. Green musics consisted of music and natural sounds are preferred to the pure natural sounds. 4. Sound level relative to background noise causes various preferences to natural sounds in public spaces.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
• /
• pp.343-347
• /
• 2004

High oxidation temperature of SiC shows a tendency of carbide formation at the interface which results in poor MOSFET transfer characteristics. Thus we developed oxidation processes in order to get low interface charge densities. N-type 6H-SiC MOS capacitors were fabricated by different oxidation processes: dry, wet, and dry­reoxidation. Gate oxidation and Ar anneal temperature was $1150^{\circ}C.$ Ar annealing was performed after gate oxidation for 30 minutes. Dry-reoxidation condition was $950^{\circ}C,$ H2O ambient for 2 hours. Gate oxide thickness of dry, wet and dry-reoxidation samples were 38.0 nm, 38.7 nm, 38.5 nm, respectively. Mo was adopted for gate electrode. To investigate quality of these gate oxide films, high frequency C- V measurement, gate oxide leakage current, and interface trapped charge densities (Dit) were measured. The interface trapped charge densities (Dit) measured by conductance method was about $4\times10^{10}[cm^{-1}eV^{-1}]$ for dry and wet oxidation, the lowest ever reported, and $1\times10^{11}[cm^{-1}eV^{-1}]$ for dry-reoxidation

• Bulletin of the Korean Chemical Society
• /
• 제32권3호
• /
• pp.1067-1070
• /
• 2011

We have demonstrated that solution-based fabrication of NiO films as HTL can be used for the construction of IOSCs. Type of solvent of NiO-solution, and annealing procedure of the active layers were optimized for obtaining a PCE of 3% of IOSC. The photovoltaic performance of NiO-based device is comparable to that of the same type of solar cell using PEDT:PSS instead of NiO. These solution-based processes can be a promising method for a mass production OSCs under ambient condition.

• 한국환경과학회지
• /
• 제15권10호
• /
• pp.929-933
• /
• 2006

Indoor air quality is the dominant contributor to total personal exposure because most people spend a majority of their time Indoors. Especially when indoor environments have sources of contaminants, exposure to in-door air can potentially pose a greater threat than exposure to ambient air. In this study, estimations of volatile organic compounds and formaldehyde omission rate in indoor environments of new apartments were carried out using mass balance model in indoor environment, because indoor air quality can be affected by source generation, outdoor air level, ventilation, decay by reaction, temperature, humidity, mixing condition and so on. Considering the estimated emission rate of volatile organic compounds and formaldehyde, it Is suggested that new apartment should be designed and constructed in the aspect of using construction materials to emit low hazardous air pollutants.

• 한국세라믹학회지
• /
• 제35권1호
• /
• pp.88-96
• /
• 1998

The structural and electrical properties of titanium dioxide(TiO2) thin films deposited on p-type (100) si and 4$^{\circ}$off(100) Si substartes by metalorganic chemical vapor deposition (MOCVD) have been studied with post rapid thermal annealing. TiO2 thin films of anatase phase were grown at 300-500$^{\circ}C$ using titanium post rapid thermal annealing at a temperature of 800$^{\circ}C$ for 30sec. rutile phase was observed in the condition of the deposition temperature over 350$^{\circ}C$ in the ambient air atmosphere and at 500$^{\circ}C$ in cacuu,. SEM and AFM study show-ed surface roughness were increased slightly from 40${\AA}$to 55${\AA}$ after annealing due to grain growth and phase transformation. From capacitane-voltage measurement of Al/TiO2./p-Si structure after annealing we obtained ideal capacitance-voltage characteristics of MOS structure with dielectric constant of 16-22 in case of (100) Si and about 30- in case of 4$^{\circ}$off(100) Si but showed the higher leakage current.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
• /
• pp.614-615
• /
• 2009

For the high reflectance under the ambient light condition, a highly efficient diffractive reflector has been proposed, based on a micro grating structure.[1] This reflector was designed to show highly concentrated distribution of the reflected light to the normal direction of the reflector under specific incident conditions of the light. In order to apply a diffractive reflector to a reflective liquid crystal display, the coupling between the viewing angle characteristics of a liquid crystal (LC) cell and the reflective distribution of the reflector should be considered. Under the optimum configuration confirmed through the analysis of the coupling between a LC cell and a reflector, a reflective vertical alignment (VA) cell with a diffractive reflector shows contrast ratio and brightness much higher than that with a conventional bumpy reflector.