• Steel and Composite Structures
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• 제39권1호
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• pp.1-20
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• 2021

An exact solution based on refined third-order theory (TOT) has been presented for functionally graded porous curved beams having deep curvature. The displacement field of the refined TOT is derived by imposing the shear free conditions at the outer and inner surfaces of curved beams. The properties of the two phase composite are tailored according the power law rule and the effective properties are computed using Mori-Tanaka homogenization scheme. The equations of motion as well as consistent boundary conditions are derived using the Hamilton's principle. The curved beam stiffness coefficients (A, B, D) are obtained numerically using six-point Gauss integration scheme without compromising the accuracy due to deepness (1 + z/R) terms. The porosity has been modeled assuming symmetric (even) as well as asymmetric (uneven) distributions across the cross section of curved beam. The programming has been performed in MATLAB and is validated with the results available in the literature as well as 2D finite element model developed in ABAQUS. The effect of inclusion of 1 + z/R terms is studied for deflection, stresses and natural frequencies for FG curved beams of different radii of curvature. Results presented in this work will be useful for comparison of future studies.

• 산업기술연구
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• 제16권
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• pp.247-256
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• 1996

The multilevel grid file(MLGF) is a dynamic multidimensional file organization supporting multi-attribute accesses efficiently. The paper proposes new method for batch-constructing MLGFs. Our method consists of two phases. The first phase begins by relocating all the objects in order that logically adjacent objects in multidimensional domain space are clustered in one dimensional physical space. For this, our method employs the Z-ordering scheme, which effectively maps multidimensional space into one dimensional space preserving proximity. The second phase paginates the relocated objects and creates leaf level directory entries, each of which corresponds to a object page. Simultaneously, it performs same actions on the directory entries recursively in a bottom-up fashion until the root directory fits in a page. For performance evaluation, we analyze our method in terms of the number of page accesses. The result shows the optimality of our method.

• The Korean Journal of Ecology
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• 제9권4호
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• pp.209-223
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• 1986

The forest stands of Seonusan area, South-western Korea, were classified into three alliances and nine communities by the Z-M school scheme. Of these one alliance and four association were recognized in this study, that is, an alliance, Carpinion laxiflorae and four associations, Casrpinetum tschonoskii, Quercetum variabilis, Carpinetum laxiflorae and Rhododendro mucronulati-Pinetum densiflorae. Hierachy of Seonunsan area forest vegetation by Z-M scheme was as fallows: Pinion densiflorae Suz.-Tok. 1966. 1. Rhododendro mucronlati-Pinetum densiflorae ass.l nov., 2. Pinus thunbergii community. Carpinion laxiflorae all. nov., 1. Quercus serrata-Carpinus tschonoskii community, 2. Quercus aliena-Carpinus tschonoskii community, 3, Carp inetum tschonoskii ass. nov., a. Typical subass., b. Sasa borealis subass. 4. Quercetum variabilis ass. nov., a Sasa borealis subass. b. Typical subass, 5. Carpinetum laxiflorae ass. nov., Zelkovion serratae Miyawaki et al., 1977., 1. Orixo-Zelk ovetum serratae Miyawaki et H. Tohma 1975., a Typical subass., b. Thea sinensis facies, 2. Thea sinensis-Camellia japonica community.

• 한국태양에너지학회 논문집
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• 제23권4호
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• pp.29-35
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• 2003

We studied the water splitting into $H_2$ and $O_2$ using two different semiconductor photo catalysts and redox mediator, mimicking the Z-scheme mechanism of the photosynthesis, $H_2$ evolution took place on a Pt-$SrTiO_2$ (Cr-Ta doped) photocatalyst using $I^-$ electron donor under the visible light irradiation. The Pt-$WO_3$ photocatalyst showed an excellent activity of the $O_2$ evolution using $IO_3^-$ electron acceptor under visible light. $H_2$ and $O_2$ gases evolved in the stoichiometric ratio($H_2/O_2$=2) under visible light using a mixture of the Pt-$WO_3$ and Pt-$SrTiO_3$ (Cr-Ta doped) suspended in NaI aqueous solution. We proposed a two-step photo-excitation mechanism using redox mediator under the visible irradiation.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제29권1호
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• pp.59-68
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• 2022

For a finite group G ⊂ GL(n, ℂ), the G-Hilbert scheme is a fine moduli space of G-clusters, which are 0-dimensional G-invariant subschemes Z with H⁰(𝒪_Z ) isomorphic to ℂ[G]. In many cases, the G-Hilbert scheme provides a good resolution of the quotient singularity ℂⁿ/G, but in general it can be very singular. In this note, we prove that for a cyclic group A ⊂ GL(n, ℂ) of type ${\frac{1}{r}}$(1, …, 1, a) with r coprime to a, A-Hilbert Scheme is smooth and irreducible.

• 전력전자학회논문지
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• 제23권1호
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• pp.9-15
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• 2018

This study investigates a bidirectional quasi-Z-source inverter (Bq-ZSI) system with bidirectional power transfer capability and a modified space vector modulation scheme for reducing the ripple of the inductor current. By replacing the diode in the impedance network with an active switch, the power flow can be bidirectional. The average inductor current of the Bq-ZSI network is negative in the regenerative braking mode, thereby regenerating the power. In addition, modified space vector modulation scheme is applied to the Bq-ZSI to control shoot-through time effectively. A 5 kW prototype is built and tested to implement the proposed system. Experimental results show that the Bq-ZSI system is capable of regenerative braking of the induction motor and that the modified space vector modulation method is efficient.

• 전기학회논문지
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• 제62권6호
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• pp.767-781
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• 2013

In this paper, we proposes the AC input voltage and current sensorless control scheme to control the input power factor and DC output voltage of the three-phase Z-source PWM rectifier. For DC-link voltage control which is sensitive to the system parameters of the PWM rectifier, fuzzy-PI controller is used. Because the AC input voltage and current are estimated using only the DC-link voltage and current, AC input voltage and current sensors are not required. In addition, the unity input power factor and DC output voltage can be controlled. The phase-angle of the detected AC input voltage and estimated voltage, the response characteristics of the DC output voltage according to the DC voltage references, the FFT results of the estimated voltage and current, efficiency, and the response characteristics of the conventional PI controller and fuzzy-PI controller are verified by PSIM simulation.

• 농약과학회지
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• 제16권4호
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• pp.350-356
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• 2012

숙련도시험 수행 및 분석법확립은 분석기관의 지속적인 시험결과에 대한 신뢰성 확보 및 시험기관의 분석능력 관리를 위한 정도관리 체계에 포함되는 항목이다. Emamectin benzoate 및 lufenuron 유제 시료에 대한 분석법 검증, 안정성 및 균질성을 확인한 후, 농약 이화학시험 분석기관(33개 기관)을 대상으로 두 약제에 대한 시료를 배포하여 숙련도시험을 수행하였으며, 분석기관의 수행능력을 z값으로 평가하였다. Emamectin benzoate는 참여기관 총 33개 중 이상값은 2개 기관(6.0%), z값이 |Z| > 3.0 및 |Z| < -3.0 범위을 나타내는 부적합은 2개 기관(6.0%) 및 z값이 -2.0 < |Z| -3.0 및 2.0 < |Z| < 3.0 범위인 검토대상은 3기관(9.0%)이었고, lufenuron에 대한 z값의 범위가 검토대상인 기관은 3개(9.0%)였다. 본 연구는 국내 농약 이화학시험 분석기관에 적합한 정도관리 체계 마련을 위하여 숙련도 시험의 적용가능성을 확인하였으며, 추가적으로 다양한 농약제품에 대한 숙련도시험을 수행하여 보완이 필요하다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.39.2-39
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• 2002

This paper presents adaptive add-on control algorithms for theconventional mode of operation of MEMS z-axis gyroscopes. This scheme is realized by adding an outer loop to a conventional force-balancing scheme that includes a parameter estimation algorithm. The parameter adaptation algorithm estimates the angular rate, identifies and compensates the quadrature error, and may permit on-line automatic mode tuning. The convergence and resolution analysis show that the proposed adaptive add-on control scheme prevents the angular rate estimate from being contaminated by the quadrature error, while keeping ideal resolution performance of a conventional force-balancing scheme.

• 한국통신학회논문지
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• 제42권2호
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• pp.291-298
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• 2017

본 논문에서는 송신단 채널 정보가 없는 다중안테나 Z-간섭 채널에서 수신단의 재구성 안테나를 통해 얻을 수 있는 자유도(DoF: degrees of freedom) 이득을 구한다. 수신단이 가지는 재구성 안테나의 안테나 모드 스위칭 패턴 디자인을 통해 간섭 신호는 정렬하고 원하는 신호를 위해 충분한 신호부공간(signal subspace)을 남겨두는 새로운 선형 기법을 제안한다. 제안하는 기법의 핵심은 송신단에서 일정 구간동안 신호를 보내지 않음으로써 수신단에서 그 동안 받은 간섭신호를 부가 정보(side information)로 간섭 제거에 활용하는 것이다. 결론적으로, 수신단이 가지는 재구성 안테나를 활용해 재구성 안테나 모드의 개수가 RF 체인의 수 보다 클 때 더 큰 자유도 이득을 얻을 수 있음을 밝힌다.