• 한국토양비료학회지
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• 제24권2호
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• pp.86-94
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• 1991

Soil Taxonomy에서는 화산회토(火山灰土)를 Inceptisols의 아목(亞目)인 Andepts로 분류(分類)하였는데, 1990년부터는 Andisols이라는 새로운 목(目)으로 분류(分類)하고 있다. Andisols의 중심개념(中心槪念)은 교질부분(膠質部分)이 Allophane과 같은 short-range-order 광물(鑛物)이거나 Al-유기복합체(有機複合體)가 주(主)가 되는 토양(土壤)이다. 따라서 Andisols 분류(分類)의 기준이 되는 Andic 특성(特性)을 규정(規定)하는데 선택적(選擇的) 추출방법(抽出方法)이 이용(利用)된다. 본(本) 연구(硏究)는 제주도(濟州道)의 한라산(漢拏山) 남사면(南斜面)에 Toposequence를 이루고 있는 10개 토양통(土壤統)과 제주도(濟州島)의 주요 토양군(土壤群)인 암갈색토(暗褐色土), 농암갈색토(濃暗褐色土), 흑색토(黑色土), 갈색삼림토(褐色森林土)를 대상으로 하여 Pyrophosphate, Dithionite-Citrate 및 Oxalate로 침출(浸出)되는 Al, Fe, Si 등을 분석하고 주요 토양(土壤)의 Allophane과 Ferrihydrite, Al-, Fe-유기복합체(有機複合體)등의 함량(含量)을 조사하여 Andic 특성(特性)을 고찰(考察)하였다. 1. Allophane과 Ferrihydrite와 같은 Short-range-order 광물(鑛物)이나 Al(Fe)-유기복합체(有機複合體)는 저지대(低地帶)에 분포(分布)한 암갈색토(暗褐色土)인 월평(月坪) 및 용흥통(龍興統)에서는 낮으나 그외 토양(土壤)에서는 높았다. 2. 저지대(低地帶)에 분포(分布)한 토양(土壤)을 제외하면 지대(地帶)가 높아질수록 Allophane 함량(含量)이 감소(減少)하고 Al-유기복합체(有機複合體) 함량(含量)이 증가(增加)하는 경향(傾向)이며, 토심(土深)이 깊어질수록 Allophane 함량(含量)이 증가(增加)하고 Al-유기복합체(有機複合體) 함량(含量)이 낮아졌다. 3. 중산간지대(中山間地帶)에 분포(分布)한 오라(吾羅) 및 아라통(我羅統)과 분석구(噴石口)에 분포(分布)한 토양(土壤)인 노로(老路) 및 적악통(赤岳統)에서는 존토층(全土層)을 통하여 Allophane과 Ferrihydrite 함량(含量)이 높았다. 4. 지대(地帶)가 높아질수록 pH가 낮고 유기물(有機物) 함량(含量)이 높아짐에 따라 고지대(高地帶)에 분포(分布)한 흑색토(黑色土) 평대통(坪垈統)과 갈색산림토(褐色森林土)인 토산(兎山) 및 흑악통(黑岳統)의 A층(層)에서는 활성(活性) Al이 주(主)로 Al-유기복합체(有機複合體)의 구성분(構成分)으로 존재(存在)하기 때문에 Allophaned의 함량(含量)이 낮으나 토심(土深)이 Al-유기복합체(有機複合體)보다는 Allophane의 구성분(構成分)으로 존재(存在)하고 따라서 Allophane 함량(含量)이 높았다.

• 전자공학회논문지
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• 제53권5호
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• pp.47-54
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• 2016

수중 환경에서는 특정한 대역이나 형태의 신호를 송수신함으로써 거리(range) 관점에서 높은 해상도를 얻는 것이 필요하다. 본 논문의 탐지 거리인 1 km 이내 근거리에서 미확인 원통형 물체를 탐지 및 식별하기 위해서는 능동소나에 사용되는 송신신호의 설계가 매우 중요하다. 최적의 소나 송신신호를 설계하기 위해서는 탐지 거리를 최대로 갖는 최적 주파수와 신호의 대역폭을 고려하여 개별 파라미터의 적절한 trade-off 값을 찾는 것이 필수 요건이다. 본 논문에서는 EE (Echo Excess) 최대화와 SNR 최대화의 관점으로 여러 파라미터들의 변화에 따라 다양한 조건에서 최적 주파수를 분석하였다. 또한 거리 해상도(range resolution)와 방위각 해상도(azimuth resolution)의 목표 성능을 만족시키는 관점에서 송신신호 파라미터 결정 연구를 수행하였다.

• 한국유체기계학회 논문집
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• 제7권1호
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• pp.17-23
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• 2004

Aeroacoustic characteristics of sirocco fan used in Over-The-Range (OTR) has been analyzed in this paper. A microwave hood combination over the gas range is short for the OTR. The flow phenomena of the double-sided sirocco fan was analyzed numerically and experimentally by using commercial code and three dimensional PIV for flow visualization. Also, microphone array is used in order to understand acoustic characteristics of OTR. Two dimensional unsteady flow and acoustic simulation is tried to qualitatively estimate the effects of tonal noise and broadband noise on the overall sound pressure level. It is found that tonal sound is generated from the strong interaction between the impeller and cutoff while broadband sound is generated from the strong secondary flows along the scroll surface. To reduce the noise level, the V-shape cut-off was applied to improve the sound quality by reducing tonal noise. So the peak noise at BPF (Blade Passing Frequency) was almost reduced. The shape of flow-guide to suppress the secondary flow over the scroll surface was carefully checked. It is found that this affects flow pattern at the fan exit and reduces the broad band noise. Through this numerical and experimental study, the sound pressure level was lowered by 4dBA compared to that of the previous fan at the operating point.

• 한국군사과학기술학회지
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• 제12권1호
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• pp.123-132
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• 2009

Civil petitions and law suits against the military rifle shooting noise have been increased because many military shooting ranges are located near civilian residential area. In order to solve the noise problems, military have devised various methods. In this study, propagation properties of rifle shot through atmosphere were investigated. The military rifle shooting noise level at 5m from muzzle was between $l14{\sim}120dB$ in all directions. The noise level loom both backward and sideward away from system firing range consisting lines of 8 shooting locations were 90dB, when shots were all fired within 10 seconds. At present some of military bases established sound barriers, muzzle enclosures, silencers, and indoor shooting ranges to reduce noises and these prevention methods can reduce noise by $5{\sim}20dB,\;5{\sim}9dB,\;5{\sim}13dB,\;40{\sim}50dB$, respectively. Even though indoor shooting range has the best performance, it requires very expensive construction cost and has short length between target and shooter. In comparison, muzzle enclosure is cheap, but because it is installed in fixed position it can only be used in one shooting position. Therefore a commander should select appropriate methods to reduce military rifle shooting noise considering distance from residential area to the range, mission of military training, budget, etc.

• Journal of Communications and Networks
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• 제5권4호
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• pp.309-318
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• 2003

This paper presents an in-depth study of a UWB indoor radio channel between 1 and 9 GHz, which was used for the subsequent development of a new statistical UWB multipath channel model, focusing on short range indoor scenarios. The channel sounding process was carried out covering different indoor environments, such as laboratories, halls or corridors. A combination of new and traditional parameters has been used to accurately model the channel impulse response in order to perform a precise temporal estimation of the received pulse shape. This model is designed specifically for UWB digital systems, where the received pulse is correlated with an estimated replica of itself. The precision of the model has been verified through the comparison with measured data from equivalent scenarios and cases, and highly satisfactory results were obtained.

• 센서학회지
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• 제22권1호
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• pp.44-48
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• 2013

For a successful commercialization of microbolometer, it is required to develop a robust package including thermal stabilizing mechanism. In order to regulate the temperature within some operating range, thermoelectric cooler is generally used but it's not easy to model the whole package due to the coupled physics nature of thermoelectric cooler. In this paper, SPICE-compatible modeling methodology of a microbolometer package is presented, whose steady-state results matched well with FEM results at the maximum difference of 5.95%. Although the time constant difference was considerable as 15.7%, it can be offset by the quite short simulation time compared to FEM simulation. The developed model was also proven to be useful for designing the thermal stabilizer through parametric and transient analyses under the various working conditions.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(4)
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• pp.13-16
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• 2001

In the Dedicated Short Range Communication (DSRC) system channel, a large number of bit errors occur because of Additive White Gaussian Noise (AWGN) and fading. When an image data is transmitted under the condition, reconstructed image quality is significantly degraded. In this paper, as an alternative to the error correcting code and/or automatic repeat request scheme, we propose an error recovery scheme for image data transmission. We first analyze how transmission errors in the DSRC system channel degrade image quality. Then, in order to improve image quality, we propose error resilient and concealment schemes for still image transmission using DCT-based fixed length coding, hamming code, cyclic redundancy check, and interleaver. Finally, we show its performance by an experiment.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2006년도 High Temperature Superconductivity Vol.XVI
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• pp.14-14
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• 2006

• 한국광물학회지
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• 제12권1호
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• pp.23-31
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• 1999

The dehydroxylation of kaolinite was investigated in detail by means of energy-filtering transmission electron microscope with both orientations parallel and perpendicular to c. The dehydroxylation could be characterized by the broad background including (0.211) band (20~24$^{\circ}$ 2$\theta$) on X-ray diffraction and by the three halo rings (d-spacing : 3.28~4.40$\AA$ (near (02,11) band), 2.41~245$\AA$ (near (20,13) band), 1.16~1.23$\AA$ (near (0.8,44) band)), and (02,11) and (20,13) spots on electron diffraction. These indicate existence of a short-range order along the a and b axes. Interplanar spacing of (001) is reduced to about 6.86$\AA$ and the sharp additional intensity maximum of about 14.2$\AA$ reveals that metakaolinite has a modulated structure along c axis. It is proposed that the modulated structure is attributed to the domains consisting of more than two-layers due to the changes of positions of the vacant octahedral sites in successive layers.

• Carbon letters
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• 제4권3호
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• pp.126-132
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• 2003

Granular Activated Carbon (GAC) has been proven to be an excellent material for many industrial applications. A systematic study has been carried out of the kinetics of physical as well as chemical activation of phenolic resin chars. Physical activation was carried out using $CO_2$ and chemical activation using KOH as activating agent. There are number of factors which influence the rate of activation. The activation temperature and residence time at HTT varied in the range $550{\sim}1000^{\circ}C$ and $\frac{1}{2}{\sim}8$ hrs respectively. Kinetic studies show that the rate of chemical activation is 10 times faster than physical activation even at much lower temperature. Above study show that the chemical activation process is suitable to prepare granular activated carbon with very high surface area i.e.$ 2895\;m^2/g$ in short duration of time i.e. 1 to 2 hrs at lower temperature i.e. $750^{\circ}C$ from phenolic resins.