Applying Z-Curve Technique to Compute Skyline Set in Multi Criteria Decision Making System

T. Vijaya Saradhi,Kodukula Subrahmanyam,P. Venkateswara Rao,Hye-jin Kim 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.12

The skyline queries are the best tools to be used in distributed multi criteria decision making of web based applications for user commendations. However, as the Data dimensions are increasing size of dominance set and skyline set is also increasing. Increasing dimensionality becomes the major problem with real word databases. In skyline computation major cost depends on finding dominance tests between high dimensional objects and the order in which they are accessing. Space filling Z-curve is the best suitable way to address the challenges in skyline computation. In this proposed work, we incorporated Z-curve with optimized skyline boundary detection algorithm to effective access and early pruning. In this paper efficient hybrid index structure was proposed which takes the advantage of sorting and partition approaches to improve the storage and search efficiency. Experimental results show that our propose approach is better than the previous static skyline computation techniques in terms of searching and finding skyline set.

Delamination strength of composite curved beams reinforced by grooved stainless-steel Z-pins

Ju, Hyunwoo,Nguyen, Khanh-Hung,Chae, Song-Su,Kweon, Jin-Hwe Elsevier 2017 Composite structures Vol.180 No.-

<P><B>Abstract</B></P> <P>When a laminated composite structure with curvature is subjected to a bending load, the most important failure mode is due to delamination in curved regions. In this study, the reinforcement effect of grooved Z-pins is investigated for preventing delamination of curved beams. Through a four-point bending test, the effect of stainless-steel pin diameter and areal density on bending failure of curved beams is studied. For areal pin densities of 0.5, 1.0, and 2.0%, pin diameters of 0.3 and 0.5mm result in average pin strength increases of 21, 27, and 42% and 8.7, 12, and 32%, respectively. When the pin size is small, the pin is inserted closer to 90° from the mid-plane, a smaller resin-rich zone is generated, and there is less laminate damage.</P>

Analysis of Transient Ground Impedances Based on Soil Ionization under Impulse Voltage

Kim, Hoe-Gu,Lee, Bok-Hee The Korean Institute of IIIuminating and Electrica 2016 조명·전기설비학회논문지 Vol.30 No.8

In this paper, the behavior of transient ground impedances in a coaxial cylindrical electrode system stressed by impulse voltages were experimentally investigated. The ground impedance-time characteristics and the voltage-current behavior for 4 types of soils were analyzed and discussed. Also, this paper modeled the electrode system into two-dimensional axial symmetry and analyzed the soil ionization growth and electric field distribution in the vicinity of the surface of the ground electrode. As a result, the ground impedance-time (Z-t) curves are dependent on the types of soils. The voltage-current (V-I) curves for all sample soils show a 'cross-closed loop' of ${\infty}$-shape under ionization. When an impulse voltage is applied to the ground electrode buried in the ground, the electric field intensity around the ground electrode changes over time. It is known that transient ground impedance is dependent on the time-varying soil ionization in the vicinity of the surface of a ground electrode.

Analysis of Transient Ground Impedances Based on Soil Ionization under Impulse Voltage

Hoe-Gu Kim,Bok-Hee Lee 한국조명·전기설비학회 2016 조명·전기설비학회논문지 Vol.30 No.8

In this paper, the behavior of transient ground impedances in a coaxial cylindrical electrode system stressed by impulse voltages were experimentally investigated. The ground impedance-time characteristics and the voltage-current behavior for 4 types of soils were analyzed and discussed. Also, this paper modeled the electrode system into two-dimensional axial symmetry and analyzed the soil ionization growth and electric field distribution in the vicinity of the surface of the ground electrode. As a result, the ground impedance-time (Z-t) curves are dependent on the types of soils. The voltage-current (V-I ) curves for all sample soils show a ‘cross-closed loop’ of ∞-shape under ionization. When an impulse voltage is applied to the ground electrode buried in the ground, the electric field intensity around the ground electrode changes over time. It is known that transient ground impedance is dependent on the time-varying soil ionization in the vicinity of the surface of a ground electrode.

Optimum Design of Dye-Sensitized Solar Module for Building-Integrated Photovoltaic Systems

이규석,강만구 한국전자통신연구원 2017 ETRI Journal Vol.39 No.6

This paper presents a method for determining the optimum active-area width (OAW) of solar cells in a module architecture. The current density–voltage curve of a reference cell with a narrow active-area width is used to reproduce the current density profile in the test cell whose active area width is to be optimized. We obtained self-consistent current density and electric potential profiles from iterative calculations of both properties, considering the distributed resistance of the contact layers. Further, we determined the OAW that yields the maximum efficiency by calculating efficiency as a function of the active-area width. The proposed method can be applied to the design of the active area of a dye-sensitized solar cell in Z-type series connection modules for indoor and building-integrated photovoltaic systems. Our calculations predicted that OAW increases as the sheet resistances of the contact layers and the intensity of light decrease.

암반층에 근입된 낙동강 대심도 퇴적지역 현장타설말뚝의 하중전이 특성

이승배(Seung-Bae Lee),김명학(Myung-Hak Kim) 한국지반환경공학회 2007 한국지반환경공학회 학술발표회논문집 Vol.2007 No.-

습한 토양의 임펄스방전특성

김회구(Hoe-Gu Kim),이복희(Bok-Hee Lee) 대한전기학회 2017 전기학회논문지 Vol.66 No.2

This paper presents the experimental results related to soil ionization and electrical breakdown in a concentric hemispherical electrode system under lightning impulse voltages. Dynamic voltage-current and impedance-time characteristics of soil ionization were measured and analyzed. Also the electrical breakdowns of the soil gap were investigated. The time-lag to the peak current corresponds to the soil ionization propagation. The time of ionization propagation in wet sand is found to decrease with increasing the impulse currents. A drastic decrease in ground resistance was observed during the impulse current spreading in sand. The electrical breakdown appears at the wave tail of impulse voltage and results in a wide scatter in V-t curves. The voltage-current curves have a fan-like shape attributed to ionization processes which result in increasing current and decreasing voltage.

초음파현미경의 고주파 초음파 탐촉자를 이용한 코발트기 초내열합금강의 열화평가

박익근,조동수,김용권,임재생,김정석 한국비파괴검사학회 2004 한국비파괴검사학회지 Vol.24 No.5

V(z)곡선법을 이용한 코발트기 초내열합금강의 열화도 평가 유용성 유무를 고주파 초음파 탐촉자를 이용하여 실험적으로 검증 하였다. 코발트기 초내열 합금이 고온에서 장시간 노출되었을 때 일어나는 미세조직의 변화를 모사하기 위해서 인공열화를 실시하였다. 여로하에 미치는 초음파 음속의 영향을 고찰하고자 10MHz를 이용하여 펄스-에코법으로 종파의 음속을 측정하고 200MHz를 사용하여 V(z)곡선법으로 누설턴성표면파의 음속을 측정하였다. 두 초음파의 음속은 열화시간에 따라서 감소 하였다. 더욱이, 저주파수 종파의 음속변화는 거의 없었지만, 고주파수 누설탄성표면파의 음속변화는 열화시간에 따라서 최대 4.7%의 변화를 나타내었다. 열화에 따른 강도의 변화와 누설탄성표면파의 음속 변화는 양호한 상관관계를 나타내었다. 따라서 열화도 평가에 고주파 탐촉자를 이용한 초음파 현미경의 V(z)곡선법이 유용함을 알 수 있었다. The feasibility of V(z) curve method of scanning acoustic microscope using high frequency transducer was experimentally studied for assessment of the thermal degradation in Co-based superalloy. Thermal degradation was performed to simulate the microstructural changes in Co-based superalloy arising trom long term exposure at high temperature. Longitudinal wave velocity measured by pulse echo method using 10MHz transducer and leaky surface acoustic wave (LSAW) velocity measured by V(z) curve method using 200MHz transducer were measured to investigate the effect on thermal degradation. Ultrasonic velocity decreased as the aging time increased in both ultrasonic waves. Moreover, the low frequency longitudinal wave velocity decreased a little. Otherwise, the high frequency LSAW velocity drastically decreased up to a maximum of 4.7% at the aging time of 4,000hours. A good correlation was found between LSAW and Vickers hardness. Consequently, V(z) curve method of SAM using high frequency transducer could be a potential tool for assessing thermal degradation.

초음파 현미경을 이용한 나노 박막의 접합 강도 평가

박태성(Tae-Sung Park),곽동열(Dong-Ryul Kwak),박익근(Ik-Keun Park),Chiaki Miyasaka 한국비파괴검사학회 2012 한국비파괴검사학회지 Vol.32 No.4

최근 나노 박막은 MEMS/NEMS, 광학 코팅, 반도체 산업 등 다양한 분야에서 사용이 되고 있다. 박막은 마모, 침식, 부식, 고온 산화를 방지하기 위한 목적으로 사용될 뿐 아니라 특성화된 자기, 유전적 특성을 만들기 위한 목적으로 사용된다. 많은 연구자들이 이러한 박막 구조의 특성(밀도, 입자 크기, 탄성 특성, 필름/기지 계면의 특성)을 평가하기 위하여 많은 연구를 진행하고 있다. 이들 중에 박막과 기지 사이의 접합 특성을 평가하는 것이 많은 연구자들의 주 관심사가 되어 왔다. 본 연구에서는 나노 박막의 접합 특성을 평가하기 위하여 각기 다른 접합 특성을 가지는 폴리머 박막 시험편을 제작하였다. 제작된 시험편의 접합 특성을 측정하기 위하여 초음파현미경의 V(z) 곡선법을 이용하여 표면파의 속도를 측정하였다. 또한 계면을 포함하는 시험편의 표면을 전파하는 표면파의 속도와 접합력의 상관관계를 확인하기 위해 나노 스크래치 시험을 적용하였다. 그 결과 초음파현미경을 이용하여 측정된 표면파의 속도와 나노스크래치 시험을 이용한 임계하중이 일치하는 경향성을 나타내었다. 결론적으로 초음파현미경의 V(z) 곡선법은 나노 스케일 박막 계면에서의 접합 상태를 평가할 수 있는 기법으로 그 가능성을 나타내었다. In recent years, nano-structured thin film systems are often applied in industries such as MEMS/NEMS device, optical coating, semiconductor or like this. Thin films are used for many and varied purpose to provide resistance to abrasion, erosion, corrosion, or high temperature oxidation and also to provide special magnetic or dielectric properties. Quite a number of articles to evaluate the characterization of thin film structure such as film density, film grain size, film elastic properties, and film/substrate interface condition were reported. Among them, the evaluation of film adhesive to substrate has been of great interest. In this study, we fabricated the polymeric thin film system with different adhesive conditions to evaluate the adhesive condition of the thin film. The nano-structured thin film system was fabricated by spin coating method. And then V(z) curve technique was applied to evaluate adhesive condition of the interface by measuring the surface acoustic wave(SAW) velocity by scanning acoustic microscope(SAM). Furthermore, a nano-scratch technique was applied to the systems to obtain correlations between the velocity of the SAW propagating within the system including the interface and the shear adhesive force. The results show a good correlation between the SAW velocities measured by acoustic spectroscope and the critical load measured by the nano-scratch test. Consequently, V(z) curve method showed potentials for characterizing the adhesive conditions at the interface by acoustic microscope.

초음파현미경에서 V(z)곡선의 시뮬레이션

박익근,임재생,윤종학,노승남,서성원 한국공작기계학회 2003 한국공작기계학회 추계학술대회논문집 Vol.2003 No.-

본 연구에서는 초음파현미경의 기하학적 원리와 초음파현미경의 특징중 하나인 V(z)곡선의 간섭파형을 시뮬레이션하였고, 실제 초음파현미경의 V(z)곡선법을 이용하여 미소영역에서의 누설탄성표면파 음속을 측정하였다. 초음파현미경을 이용한 V(z)곡선법의음속측정결과가 시뮬레이션 음속값과 큰차이를 보이지 않으므로 미소영역에 초음파현미경의 V(z)곡선법을 적용하여 초음파의 음속측정이 가능함을 확인하였다. 이는 향후 초음파현미경을 이용하여 미세한 재료의 물성평가에 적용할 수 있을 것으로 기대된다.