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이현구,오치성,김무석,이정한 한국소음진동공학회 2024 한국소음진동공학회 논문집 Vol.34 No.1
온실가스 배출과 이산화탄소로 인한 지구 온난화를 극복하기 위해 자동차 산업은 전기차 개발에 대응하여 시장 변화에 대응하고 있다. 다양한 종류의 전기차 중에서 In-Wheel Motor (IWM)은 간단한 구조, 높은 효율성 및 좋은 공간 활용성으로 인해 미래의 주행 기술 구조로 적합한 솔루션으로 간주된다. IWM의 다양한 소음 원인을 분석한 결과, 250 Hz 미만인 8차와 16차가 ANC (액티브 노이즈 캔슬링) 응용 기술을 사용하여 감소시키기에 적합하다고 판단되었다. 다중 상관관계, 최적 필터 및 2차 노이즈 경로 분석이 수행되었고 시간 주파수 필터링된 최소 제곱 알고리즘이 적용되었다. ANC 기술을 적용함으로써, 8차와 16차 소음이 각각 20 dBA로 감소되었고, 전체적인 소음은 6~8 dBA로 성공적으로 감소되었다. To overcome global warming caused by air pollution and carbon dioxide, the automotive industry is responding to changes in the market by developing electric vehicles. Among the various types of electric vehicles, an in-wheel motor (IWM) is regarded as a suitable solution for future drive train architecture owing to its simple structure, high efficiency, and good space availability. Through the analysis of various IWM noise sources, the 8th and 16th orders, which are less than 250Hz are selected as the subjects to reduce using the ANC application technology. A multi-correlation, optimal filter, and secondary noise path analysis are conducted. Moreover, a time frequency-filtered least mean square algorithm is adapted. Four accelerometers and six speaker positions are chosen through the optimization of ANC. With ANC technology, the 8th and 16th noise are reduced by 20dBA and the overall noise is successfully reduced by 6 to 8dBA, respectively.
이현구,조용범,이강열 대한전자공학회 1996 CAD 및 VLSI 설계연구회지 Vol.5 No.1
ASIC(Application Specific Integrated Circuit) implementation of a parallel switching optimization algorithm to assign an optimal path for the three-stage Clos's packet switch(r×n×r) is presented in this paper. The paper described to VLSI implementation procedure of Hopfield neural network algorithm and ASIC process of the top-down design flow. The neural network switching optimization controller chip was designed to a chip of 20.00×14.00 ㎟ size by 0.8㎛ CMOS SOG process and operated as a switching optimization controller in 25MHz speed.
네스티드로짓모형을 이용한 쇼핑통행의 형태분석에 관한 연구
이현구,조동래 대한교통학회 1989 大韓交通學會誌 Vol.7 No.1
In general, Shopping centers are located in the center of transportation, which induce more traffic concentration than other facilities. As a result, it becomes to one of the aggravating factors of urban & transportation problem such as traffic conjestion, parking problems. Thus, in planning shopping-center, it is desirable that consumer\`s trip pattern is should lie more carefully analyzed in order to alleviate the above problems. This study is aimed at finding the characteristics of shopping tripes and analyzing the choice behavior of shopping center and mode-to-shop. This study has developed a nested logit model in which consumers choose shopping center and mode-to-shop with a sequential structure. The model was estimated using household data from the 1989 May, Seoul metropolitan area and the 18 alternatives of shopping center and 5 mode alternatives. The estimated model have been evaluated and it may be concluded that this model for shopping trips is effective and fesible. The conclusion of this study are as fellows. 1. Out-of-vehicle travel time is more important factor affecting behavior of mode choice than in-vehicle travel time. 2. All of direct-elasticities for mode with respect to the travel time is more elastic than travel cost. 3. Accessibility to shop is more important factor affecting the choice of shopping center than parking space. 4. The value of out-of-vehicle travel time exceeds the value of in-vesicle travel time by 1.64 times.
의성분지(義城盆地)에 분포(分布)하는 백악기(白堊紀) 경상누층군(慶尙累層群)의 셰일에 관(關)한 암석지구화학(岩石地球化學)
이현구,이찬희,김상중,Lee, Hyun Koo,Lee, Chan Hee,Kim, Sang Jung 대한자원환경지질학회 1997 자원환경지질 Vol.30 No.1
The shales from the Euiseong area are interbedded along the bedding in Cretaceous Gyeongsang Supergroup, which are composed mainly of quartz, plagioclase, K-feldspar and associated with trace amount of biotite, muscovite, chlorite, pyrite, hematite, carbonate and clay minerals. The ratio of $Al_2O_3/Na_2O$ and $K_2O/Na_2O$ in shales from the Shindong Group are ranged from 9.16 to 24.32 and from 1.70 to 5.97, and the Hayang Group ranged from 2.76 to 8.89 and from 0.42 to 2.74, which are negative correlated between $K_2O/Na_2O$ and $Al_2O_3/Na_2O$ against $SiO_2/Al_2O_3$ respectively. Those are suggested that controlled of mineral compositions in shales due to substitution and migration of elements by sedimentation and diagenesis. These shale formation were deposited in basin of terrestrial environments originated from the igneous rocks, and the REE of these rocks are not influenced with diagenesis and hydrothermal alterations on the basis of $Al_2O_3$ versus La, La against Ce, Zr versus Yb, the ratios of La/Ce (0.43 to 0.62) and Th/U (1.11 to 10.71). The narrow range in trace and REE element characteristics as Co/Th (0.63 to 1.92), La/Sc (1.98 to 5.90), Sc/Th (0.58 to 1.30), V/Ni (0.90 to 3.25), Cr/V (0.45 to 1.78), Ni/Co (1.88 to 6.67) and Zr/Hf (30.04~60.87) of these shales argues for inefficient mixing of the simple source lithologies during sedimentation. These rocks also show much variation in $La_N/Yb_N$ (6.90 to 17.02), Th/Yb (4.17 to 13.68) and La/Th (1.98 to 5.90), and their origin is explained by derivation from a mixture of intermediate to acidic igneous rocks.
Phosphorescent white organic light-emitting diodes with stable white color depending on luminance
이현구 한국물리학회 2021 Current Applied Physics Vol.21 No.-
We fabricated simple and color-stable phosphorescent white organic light-emitting diodes (OLEDs) without an interlayer using a single host of 1,3-bis(9-carbazolyl)benzene with iridium(III) bis[(4,6-difluorophenyl) pyridinato- N,C2’]picolinate and bis(1-phenylisoquinoline)(acetylacetonate) iridium(III) as blue and red phosphorescent emitters, respectively. The CIE 1931 color coordinate difference of the white OLEDs is (0.008, 0.007) when the luminance of the device is increased from approximately 265 cd/m2 to 9156 cd/m2, which is regarded as visually indistinguishable in practice. In addition, we also measured the decay time of excitons to investigate the emission mechanism in this device using transient photoluminescence and electroluminescence techniques.