도서관정책과 도서관문화의 발전

이경구,Lee, Gyeong-Gu 대한출판문화협회 1990 출판저널 Vol.74 No.-

DVD-ROM 시스템에 적용한 신경망 등화기에 관한 성능

이경구,최수용,옹성환,유철우,홍대식,Lee, Kyung-Goo,Choi, Soo-Yong,Ong, Sung-Hwan,You, Cheol-Woo,Hong, Dae-Sik 대한전자공학회 1998 電子工學會論文誌, S Vol.s35 No.10

차세대 저장매체로서 이미 그 규격이 확정된 재생 전용 디지털 다기능 디스크 시스템에 등화기를 적용하여 그 성능을 분석한다. 재생 전용 디지털 다기능 디스크 시스템에서는 정보 기록 시에 비선형 왜곡현상을 유발할 수 있으므로 이의 보상을 위해 비선형 입출력 사상능력이 뛰어나다고 알려져 있는 신경망 등화기를 적용한다. 또한, 결정궤환 구조의 등화기는 변조부호와 결합하여 사용하면 성능 개선을 보장할 수 없다는 것을 확인하기 위한 실험을 한다. 두 종류의 시스템에 대한 등화 실험으로 신경망을 이용한 등화기가 기존의 등화기에 비해 더 좋은 등화성능을 보이며 이는 채널의 비선형성이 증가할수록 확연해지는 결과를 얻었다. 또한, 랜덤한 데이터열의 간섭 보상에는 결정궤환 구조의 등화기가 우수한 성능을 보이지만 변조 부호화된 데이터열의 간섭 보상에는 결정궤환이 없는 구조와 비교하여 성능 개선이 없다는 결과를 얻었다. Several equalizers are applied to the DVD-ROM(Digital Versatile Disc-Read Only Memory) system. Because imperfect writing process may cause nonlinear distortion in the reply signal, neural equalizers which have strong nonlinear mapping capability are applied to the system to compensate the nonlinear distortion. Experimental results to verify that the combination of decision-feedback type equalizers and modulation code is formidable are also given. The experimental results shwo that the SNR gain of the neural equalizers over the conventional equalizers becomes much as the nonlinearity in the channel increases. Furthermore, the decision-feedback type equalizers outperform the equalizers which have no decision-feedback in eliminating ISI(Intersymbol Interference) of random data sequence but there is no performance gain of the decision-feedback type equalizers over the equalizers without decision-feedback when these are applied to compensate the ISI of modulation-encoded data sequence.

독서새물결운동과 도서관의 연계방안

이경구,Lee, Gyeong-Gu 한국도서관협회 1994 圖協會報 Vol.35 No.6

변화에의 대응을 위한 현실인식의 중요성

이경구,Lee, Gyeong-Gu 한국도서관협회 1997 圖協會報 Vol.38 No.3

가압주조법에 의해 제조된 AC4C Al / coated SiC 복합재료의 마모특성에 관한 연구

이경구,이도재 ( Kyung Ku Lee,Doh Jae Lee ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.4

N/A Effects of SiC particle on wear resistance of AC4C Al/SiC composite were studied. Experimental variables included were types of metallic coatings such as Cu and Ni-P, and volume fraction of SiC particle in composite. The results of wear test showed that the wear resistance of AC4C Al/SiC composite is increased linearly with volume fraction of SiC particles. In the range of our experimental conditions, there is no significant difference in wear resistance between the type of pretreatment for coating on SiC particles used for composite specimens the as-received SiC reinforced and coated SiC reinforced composite. Wear debries generated during wear test are identified as Al from matrix alloy of specimen, and iron oxide from steel block which is counter part of abrasion test. Severe subsurface plastic deformation is observed at the regions close to the wear surface, and the surface region were work hardened.

PFC 법에 있어서의 Al-Cu 다결정리본의 응고특성

이경구,이상목,홍준표 ( Kyung Ku Lee,Sang Mok Lee,Chun Pyo Hong ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.4

N/A Polycrystalline Al-Cu ribbons were produced by planar flow casting(PFC). Solidification behavior and microstructual changes of the ribbons have been investigated as a function of ribbon thickness and processing parameters. The solidification front velocity, V varies within the ribbon, decreasing with increasing the distance, S from the wheel-contact surface, as V=17.6S^(-1). In Al-4.5wt%Cu alloy, rapid decrease in solidification velocity toward the free surface causes a change in solidification morphology from planar to cellular, and finally, to dendritic. The length and inclination of columnar grains solidified with planar front were related to the wheel velocity. The transition from particulate degenerate eutectic structure to regular lamellar eutectic structure was observed to be caused by a difference of the relative growth velocites of α-Al and θ during solidification in the Al-Cu eutectic alloy.

원형강관 X-이음 트러스접합부의 압축 주강관소성화 평가

이경구,신용섭,손은지,Lee, Kyungkoo,Sin, Yong Sup,Son, Eun Ji 한국강구조학회 2015 韓國鋼構造學會 論文集 Vol.27 No.5

원형강관구조 접합부는 재료의 발전과 접합부의 복잡한 국부 거동 때문에 지속적인 연구되고 있다. 이 연구는 지강관에 압축력이 작용하는 원형강관 X-이음 트러스접합부의 주강관 소성화변형과 접합부 강도에 재료강도와 주강관벽세장비가 미치는 영향을 파악하는 것을 목적으로 한다. 이를 위하여 재료강도와 주강관벽세장비를 변수로 하여 다양한 원형강관 X-이음 트러스접합부에 대하여 범용 유한요소해석 프로그램인 ANSYS Mechanical APDL을 사용하여 정밀유한요소해석을 수행하였다. 해석결과를 토대로 현행 건축구조기준에서 제시하는 주강관소성화 한계상태의 접합부 설계강도를 검토하였다. 결론적으로 원형강관 X-이음 트러스접합부 설계에서 고려해야 할 사항을 제시하였다. The researches on circular hollow section(CHS) connections have been conducted continuously because of development of material properties and complex local behavior of the connections. The purpose of this study is that the effects of material strength and chord wall slenderness on chord plastification and strength of CHS X-joint truss connection under compression on branch member were evaluated. To this end, finite element analyses were performed for various connections, using ANSYS Mechanical APDL program. Based on the analysis results, the design strength of the connections according to chord plastification limit state in KBC were examined. Finally, special considerations for CHS X-joint connection design were suggested.

비탄성 국부좌굴을 고려한 철골 모멘트 접합부의 회전능력에 대한 변수 연구

이경구,Lee, Kyung Koo 한국강구조학회 2008 韓國鋼構造學會 論文集 Vol.20 No.5

동반논문(모델개발)에서는 특별철골모멘트골조의 강접합 보-기둥 접합부의 회전능력을 예측하기 위한 해석모델을 제안하였다. 본 논문에서는 접합부 회전능력 기준으로 두 개의 극한상태를 고려하였다. 첫째, 보 단면의 국부좌굴로 인해 공칭소성강도까지 강도저하가 발생하였을 때를 회전능력으로 보는 강도저하 극한상태를 고려하였다. 둘째, 큰 진폭의 변형이 몇 번 반복 후에 좌굴된 플랜지에서 소성변형률 축적으로 야기 되는 저주기 피로 파단을 극한상태로 고려하였다. 두 극한상태까지 제안한 모델을 이용하여 단조증가하중 및 반복하중하에 일련의 해석을 수행하였다. 실무설계에서 사용되는 범위안의 다양한 H-형강 보를 모델링한 후, 플랜지 및 웨브 폭-두께비와 같은 보 단면의 기하학적 변수가 WUF-W 접합부의 회전능력과 저주기 피로수명에 미치는 영향을 관찰하였다. In the companion paper (Model Development), an analytical model estimating the available rotation capacity of fully restrained beam-column connections in special steel moment-resisting frames was proposed. In this paper, two limit states were considered as the connection rotation capacity criteria: (i) strength degradation failure when the strength falls below the nominal plastic strength due to the local buckling of the beam's cross-section and (ii) low-cycle fatigue fracture caused by plastic strain accumulation at the buckled flange after only a few cycles of high-amplitude deformation. A series of analyses are conducted using the proposed model with two limit states under monotonic and cyclic loadings. Beam section geometric parameters, such as flange and web slenderness ratios, varied over the practical ranges of H-shapedbeams to observe their effect on the rotation capacity and low-cycle fatigue life of pre-qualified WUF-W connections.

Al / SiCp 복합재료에서 보강재 표면의 금속 피복층이 젖음성과 계면 강도에 미치는 영향

이경구,이도재 ( Kyung Ku Lee,Doh Jae Lee ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.4

N/A Effects of metal coating treatment on SiC particle on wetting behavior and interfacial strength were studied. Experimental variables are included types of coated metallic films such as Cu and Ni-P, and temperatures of heat-treatment under vacuum. The experimental results concerning wetting phenomena of liquid Al on SiC, showed that coating treatment of metallic film on SiC particles remarkably improves the wetting behavior of liquid Al on SiC, especially in the case of Ni-P coating. The interfacial strength of Al/SiC composites made of coated SiC plate was higher than that of the composite with non-coated SiC plate although the coating treatment was not perfect.

Squeeze Casting 법에 의해 제조된 A356 / coated SiC 복합재료의 미세조직과 기계적 특성에 관한 연구

이경구,이도재 ( Kyung Ku Lee,Doh Jae Lee ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.5

N/A Influence of interfacial structure between matrix and particle in A356/coated SiC composite fabricated by squeeze casting method was studied. Experimental variables are types of coated metallic film on SiC particles such as Cu, Ni-P, and applied pressure for squeeze casting. It was found that coating treatment on SiC particles improves the wetting of liquid A356 alloy on SiC particles. SiC particle distribution is very homogeneous in A356 matrix alloy which is fabricated by squeeze casting. Analysing the surface morphology of fractured A356/coated SiC, it was concluded that metallic thin film by coating treatment on SiC particle improves the interfacial bonding between particle and matrix, and so does on mechanical properties such as tensile strength. However, there was on significant difference in hardness between those composite made of as-received SiC particle and coated SiC particle.