• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2257-2262
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• 2014

$C_{60}$ is widely investigated because of its unique structure. But its applications in solid propellant seem to be relatively neglected. $C_{60}$ has more outstanding features than carbon black which is widely used as a catalyst ingredient of solid propellant. To combine the advantages of fullerene and lead salts, another good composite in propellant catalysts, we synthesized a kind of fullerene phenylalanine lead salt (FPL) and explored its thermal performances by differential thermal analysis (DTA) and thermogravimetry analysis (TGA). The results show it undergoes four exothermic processes started from 408 K. Combined TGA and X-ray diffractometer (XRD), the decomposition mechanism of FPL was derived by TG-IR and comparing IR spectra of FPL and its residues after burned to $327^{\circ}C$, $376^{\circ}C$ and $424^{\circ}C$, respectively. Effect of FPL on the decomposition characteristic of hexogen (RDX), a type of explosive in propellant, has been investigated using DTA at different heating rate, which shows the decomposition temperatures of the explosive are all reduced by more than 20 K. The corresponding activation energy ($E_a$) is decreased by $30kJ{\cdot}mol^{-1}$. So FPL has potential application as a combustion catalyst in solid propellant.

• 한국물환경학회지
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• 제36권6호
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• pp.489-499
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• 2020

Effective science-based management of the basin water resources requires an understanding of the characteristics of the streams, such as the baseflow discharge. In this study, the base flow was estimated in the two watersheds with the least artificial factors among the Nakdong River watersheds, as determined using the chemical hydrograph separation technique. The 16-year (2004-2019) discontinuous observed stream flow and electrical conductivity data in the Total Maximum Daily Load (TMDL) monitoring network were extended to continuous daily data using the TANK model and the 7-parameter log-linear model combined with the minimum variance unbiased estimator. The annual base flows at the upper Namgang Dam basin and the upper Nakdong River basin were both analyzed to be about 56% of the total annual flow. The monthly base flow ratio showed a high monthly deviation, as it was found to be higher than 0.9 in the dry season and about 0.46 in the rainy season. This is in line with the prevailing common sense notion that in winter, most of the stream flow is base flow, due to the characteristics of the dry season winter in Korea. It is expected that the chemical-based hydrological separation technique involving TANK and the 7-parameter log-linear models used in this study can help quantify the base flow required for systematic watershed water environment management.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2008년도 추계학술대회
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• pp.181-184
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• 2008

The paper describes a Layered Modulation using the SVC signals and studies the properties of the modulation with respect to several parameters by the computer simulation. The SVC signals will include a base layer signal and an enhancement signal, and the base layer signal is the more important one in its channel robustness. The parameters will include a carrier frequency, a bandwidth, power level, modulation type and code rate. We analyze the demodulating and decoding process of the Layered Modulation system through several scatter plots. And then we discuss the affect of the layer signal power difference to the BER performance, which also proves the base layer signal is more important than the enhancement layer signal.

• Journal of electromagnetic engineering and science
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• 제3권1호
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• pp.7-11
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• 2003

CDMA(code division multiple access) has very large peak to average power ratio(PAR) and behave as noise-like wide band digital signals with 1.2288 Mbps transmission rate. For signals with high PAR like CDMA, it is reasonable to prescribe occupied bandwidth(OBW) as average occupied bandwidth. Bandwidth measurements of CDMA signals at remote site are affected by co-channel and adjacent channel interference from adjacent CDMA base station, distortion of signal by fading effect, spurious emission and environment noises. In this study, we have compared OBW measurements in an on-air environment with those measured in a base station using adjacent channel leakage ratio(ACLR) as a reference measurement factor. As results of analysis, the OBW at ACLR$\geq$35 ㏈ shows nearly same statistical characteristics regardless of the measurement locations and environments.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 봄 학술발표회 논문집
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• pp.29-32
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• 1991

This is the study on the performance of workability and engneering properties of flowing concrete using the superplasticizers, which are being used for control of the consistency of fresh concrete without modifying the properties of the hardened concrete and for production of high quality concrete at a low water-cement ratio. It is the aim of this study to analyze and investigate workability and engineering properties of flowing concrete according to the addition rate in poor and rich mix proportions of base concrete. Base on this fundamental investigation for the development of flowing concrete mix design, it could be drawn that the workability and engineering properties of flowing concreteare influenced greatly by mix proportion and dosage of superplasticizers.

• 한국해양공학회지
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• 제10권3호
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• pp.14-23
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• 1996

The corrosion fatigue test were carried out to evaluate the fatigue characteristics of accelerated cooled (ACC) TMCP high tensile strength steels and weld joint with high heat input by one side one run submerged are welding. In this paper, the fatigue crack growth behaviors were investigated with the center crack tension specimen of base metal and heat affected zone in substitute sea water and air, respectively Main results obtained are sunnarized as follows: 1. The fatigue crack growth rates in sea water faster than those in air environment for the different heat input values, crack growth rate of base metal is very fast and effect of heat input is not remarkable. 2. In HAZ (82kJ/cm, 116kJ/cm), the crack branching phenomena were observed in both air and sea water environment, 3. In SEM observation, the corrosion effect on base metal was larger than that on HAZ in corrosion environment.

• 한국환경과학회지
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• 제1권2호
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• pp.105.1-113
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• 1992

The present study was performed to develop the removal system of the offensive gases, including hydrogen sulfide of acid gas, ammonia or amice of base gas, from the nightsoil treatment plant. In order to remove the offensive gases, the Fe-EDTA system liquid phase catalytic oxidation method with the bubble lift column reactor was employed. From the results obtained, it was confirmed that the offensive gases can be deodorized simultaneously and also hydrogen sulfide of acid gas, ammonia of base gas completely removed at pH 6.45. In addition, as input gases feed rate the efficiency of acid gas did not change but the efficiency of base gases decreased to approximately 90 % at pH 6, 0. From the result of particle size analyzer, it was found that the particle sizes including sulfur and other impurites grew up to $21{\mu}m$ over 72hour reaction time.

• 한국컴퓨터산업학회논문지
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• 제4권10호
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• pp.587-598
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• 2003

본 연구에서는 학술논문을 대상으로 하여 표제와 초록에 대한 2단계 색인어 유사관계행렬을 구축하였다. 동시출현빈도 기반으로 구축된 색인어 유사관계행렬은 호환관계에 따른 질의 확장으로 재현률을 유지하면서 2단계 내용기반 검색으로 정확률을 향상시키기 위한 색인구조이다. 따라서, 주제 분석을 통해 영역지식을 추출하고 이용자의 정보 요구와 영역지식을 퍼지논리 기반으로 추론하였다. 본 연구는 질의에 본질적으로 가지고 있는 용어 불일치 및 정보표현을 향상시키기 위한 연구이다.

• 대한기계학회논문집
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• 제18권11호
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• pp.3091-3097
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• 1994

An expert system for NC part programming of NC lathe (ESPP-1) is developed as a part of Computer-Adied Manufacturing system. Conventional computer-assisted part programming system essentially requires an NC part programmer who is an expert in NC part programming. But the developed ESSP-1 can allow an inexperienced person to make an excellent NC data for the NC Lathe without any problem, since the system has a knowledge base composed of EIA and ISO NC code, feed rate, spindle speed, machining coordinates selection, and tool selection etc., which were directly evoked from some skilled NC part programmers, and referenced some machining handbooks. This paper discusses the algorithm of the expert system for NC part programming of the NC lathe (ESPP-1) and the performance comparisons between the developed expert system and the conventional system.

• Journal of Welding and Joining
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• 제19권5호
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• pp.540-547
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• 2001

This study has evaluated the wear behavior of PTA (Plasma Transferred Arc) Inconel 625 and Stellite 6 overlays on Nimonic 80A substrate. Nimonic 80A alloy was also included for comparison. In order to evaluate the wear performance, three-body abrasive wear test and pin-on-disk dry sliding wear test were performed. Microstructural development during the solidification of deposits is also discussed. Wear test results show that the wear rate of Stellite 6 deposit is lower than that of Inconel 625 deposit and Nimonic 80A. The sliding wear resistance of overlay deposits follows a similar trend to the abrasive wear resistance, but for Nimonic 80A. The main wear mechanisms were abrasive wear for Inconel 625 deposit, adhesive wear and delamination for Stellite 6 deposit in pin-on-disk dry sliding wear test and ploughing in three-body abrasive wear test. Cross sectional examinations of the worn surface of pin specimens after pin-on-disk dry sliding wear test implies that the plastic deformation near worn surface has occurred during the wear testing.