• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.91-99
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• 2017

In order to meet the thermal performance analysis accuracy requirements of high density permanent magnet synchronous motor (PMSM), a method of multi physical domain coupling thermal analysis based on control circuit, electromagnetic and thermal is presented. The circuit, electromagnetic, fluid, temperature and other physical domain are integrated and the temperature rise calculation method that considers the harmonic loss on the frequency conversion control as well as the loss non-uniformly distributed and directly mapped to the temperature field is closer to the actual situation. The key is to obtain the motor parameters, the realization of the vector control circuit and the accurate calculation and mapping of the loss. Taking a 48 slots 8 poles high density PMSM as an example, the temperature rise distribution of the key components is simulated, and the experimental platform is built. The temperature of the key components of the prototype machine is tested, which is in agreement with the simulation results. The validity and accuracy of the multi physical domain coupling thermal analysis method are verified.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.176-187
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• 2015

DC bias will cause abnormal vibration of transformers. Aiming at such a problem, transformer vibration affected by DC bias has been studied combined with transformer core and winding vibration mechanism use multi-physical field simulation software COMSOL in this paper. Furthermore the coupling model of electromagnetic-structural force field has been established, and the variation pattern of inner flux density, distribution of mechanical stress, tension and displacement were analyzed based on the coupling model. Finally, an experiment platform has been built up which was employed to verify the correctness of model.

• Coupled systems mechanics
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• 제1권4호
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• pp.297-309
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• 2012

As a result of the medium coupling, propagation characteristics of ultrasonic waves guided by a multi-phase medium can be different from those in a homogeneous system. This phenomenon becomes prominent for a medium consisting of phases with considerably distinct material and physical properties (e.g., submerged structures or human bones covered with soft tissues). In this study, the coupling effect arising from both fluid and soft tissues on wave propagation in engineering structures and human bone phantoms, respectively, was explored and calibrated quantitatively, with a purpose of enhancing the precision of ultrasonic-wave-based non-destructive evaluation (NDE) and clinical quantitative ultrasound (QUS). Calibration results were used to rectify conventional NDE during evaluation of corrosion in a submerged aluminium plate, and QUS during prediction of simulated healing status of a mimicked bone fracture. The results demonstrated that with the coupling effect being appropriately taken into account, the precision of NDE and QUS could be improved.

• Journal of the Korean Physical Society
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• 제80권
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• pp.30-36
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• 2022

Holographic model of massive scalar field with its self-interaction λϕⁿ in AdS space is able to give a logarithmic scale dependence to marginal multi-trace deformation couplings on its dual conformal field theory, where λ is the self-interaction coupling of the scalar field, ϕ, and n is an integral number. In arXiv:1501.06664, the authors realize this feature by looking at bulk scalar solutions near AdS boundary imposing a specific boundary condition between the coefficients of non-normalizable and normalizable modes of the scalar field excitations. We study the same holographic model to see scale dependence of marginal deformations on the dual conformal field theory by employing completely different method: holographic Wilsonian renormalization group. We solve Hamilton-Jacobi equation derived from the holographic model of massive scalar with λϕⁿ interaction and obtain the solution of marginal multi-trace deformations up to the leading order in λ. It turns out that the solution of marginal multi-trace deformation also presents logarithmic behavior in energy scale near UV region.

• 한국측량학회지
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• 제25권1호
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• pp.69-75
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• 2007

The information in physical planning field shows the socio-economic potentials of land resources while cadastral data does the physical and legal realities of the land. The two domains commonly deal with land information but have different views. Cadastre has to evolved to the multi-purpose ones which provide value-added information and support a wide spectrum of decision makers by mixing their own information with other spatial/non-spatial databases. In this context, the demands of data exchange between the two domains is growing up but this cannot be done without resolving the heterogeneity between the two information applications. Both of either discipline sees the reality within its own scope, which means each has a unique way to abstract real world phenomena to the database. The heterogeneity problem emerges when an GIS is autonomously and independently established. It causes considerable communication difficulties since heterogeneity of representations forms unique data semantics for each database. The semantic heterogeneity obviously creates an obstacle to data exchange but, at the same time, it can be a key to solve the problems too. Therefore, the study focuses on facilitating data sharing between the fields of cadastre and physical planning by resolving the semantic heterogeneity. The core job is developing a conversion mechanism of cadastral data into the information for the physical planning by DB coupling techniques.

• Structural Engineering and Mechanics
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• 제66권4호
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• pp.505-513
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• 2018

Steam flooding is widely used in heavy oil reservoir with coupling effects among the formation temperature change, fluid flow and solid deformation. The effective stress, porosity and permeability in this process can be affected by the multi-physical coupling of thermal, hydraulic and mechanical processes (THM), resulting in a complex interaction of geomechanical effects and multiphase flow in the porous media. Quantification of the state of deformation and stress in the reservoir is therefore essential for the correct prediction of reservoir efficiency and productivity. This paper presents a coupled fluid flow, thermal and geomechanical model employing a program (MATLAB interface code), which was developed to couple conventional reservoir (ECLIPSE) and geomechanical (ABAQUS) simulators for coupled THM processes in multiphase reservoir modeling. In each simulation cycle, time dependent reservoir pressure and temperature fields obtained from three dimensional compositional reservoir models were transferred into finite element reservoir geomechanical models in ABAQUS as multi-phase flow in deforming reservoirs cannot be performed within ABAQUS and new porosity and permeability are obtained using volumetric strains for the next analysis step. Finally, the proposed approach is illustrated on a complex coupled problem related to steam flooding in an oil reservoir. The reservoir coupled study showed that permeability and porosity increase during the injection scenario and increasing rate around injection wells exceed those of other similar comparable cases. Also, during injection, the uplift occurred very fast just above the injection wells resulting in plastic deformation.

• 정보처리학회논문지D
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• 제10D권2호
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• pp.195-210
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• 2003

이 논문에서는 다차원 색인구조의 동시성을 최대화하는 동시성제어 알고리즘과 이를 위한 회복기법을 제안한다. 다차원 색인구조에서 동시성을 저하는 가장 큰 요인은 MBR 변경연산과 분할 연산이다. 제안하는 알고리즘은 먼저 MBR 변경연산으로 인한 동시성 저하를 최소화하기 위해서 PLC(Partial Lock Coupling) 기법을 제안한다. 이 기법은 기존 방법에 비해 잠금결합을 사용하는 회수를 크게 줄여 동시성을 높인다. 또한, MBR 변경의 수행 중에도 탐색자들이 해당 노드를 접근할 수 있도록 하는 MBR 변경 방법을 제안한다. 분할로 인한 동시성 저하를 해결하기 위해서 노드 분할로 인한 탐색자의 지연 시간을 최소화 할 수 있는 새로운 분할방법을 제안한다. 제안하는 알고리즘을 BADA-4 DBMS의 저장시스템인 MiDAS-3에서 구현하여 성능평가를 수행한다. 다양한 실험을 통해 제안하는 방법이 기존 방법보다 우수함을 보인다. 마지막으로, 이 논문에서는 제안하는 동시성제어 방법에 적절한 회복기법을 제안한다. 회복기법은 동시성을 최대한 보장할 수 있도록 설계되었으며 빠른 회복시간을 보장한다.

• 한국금형공학회:학술대회논문집
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• 한국금형공학회 2008년도 하계 학술대회
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• pp.155-158
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• 2008

Flow imbalance among the cavities was often observed in multi-cavity mold. The flow imbalance affects on the dimensions and physical properties of molded articles. First of all, the origin of flow imbalance is geometrical imbalance of delivery system. However, even the geometry of delivery system is balanced the cavity imbalance is being developed. This comes from the temperature distribution in the cross-section of runner, which is affected by the operational conditions. In this study, experimental study of flow imbalance has been conducted for various injection speeds. This study also suggests new runner design to eliminate flow imbalance in multi-cavity injection mold. Simulation and experimental results showed suggested new designed runner could eliminate or reduce flow imbalance in multi-cavity injection mold.

• 한국정보과학회논문지:데이타베이스
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• 제30권1호
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• pp.80-94
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• 2003

이 논문에서는 질의의 지연을 최소화하는 효율적인 동시성제어 알고리즘을 제안한다. 다차원 색인구조에서 탐색연산을 지연시키고 전체적인 동시성을 떨어뜨리는 주 요인은 노드 분할과 MBR 변경연산이다. 제안하는 알고리즘에서는 분할 연산에 의한 질의의 지연을 최소화하기 위해 분할 노드에서의 배타 잠금 시간을 최소화한다. 분할 전체 기간동안 노드에 배타 래치를 획득하는 것이 아니고 분할 과정중 노드의 물리적인 분할 단계에서만 배타 래치를 획득한다. 또한, MBR 변경 시 발생하는 질의의 지연을 줄이기 위해 부분 잠금 결합(PLC: Partial Lock-Coupling)을 사용한다. PLC 기법은 MBR 증가 연산에 비해 상대적으로 발생 빈도가 적은 MBR 감소 연산에서만 잠금 결합을 수행하여 동시성을 향상시킨다. 성능평가를 위해 제안하는 알고리즘과 링크 기법을 기반으로 하는 기존의 동시성 제어 기법을 바다-III DBMS의 자료저장 시스템인 MIDAS-III상에서 구현한다 다양한 환경에서의 성능평가를 통해 제안하는 알고리즘이 기존의 동시성 제어기법보다 처리율 및 응답시간에서 뛰어난 성능을 나타냄을 보인다.

• 폴리머
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• 제34권2호
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• pp.108-115
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• 2010

본 연구는 MWCNT로 보강된 SBR 나노복합재료를 컴파운딩법(compounding)으로 제조하여 산 처리된 MWCNT와 커플링제 상호간의 물리적 화학적 특성을 조사하였다. 황산과 질산으로 산화된 MWCNT는 FT-IR 분석 결과 -COOH로 기능화됨을 확인하였고, Raman 분석 결과 표면의 defect 존재와 disorder됨을 확인하였다. 또한, 제조된 SBR 복합재료의 가황 특성, 전기적 열적 특성 및 기계적 특성을 비교 평가하였다. 그 결과 산 처리된 MWCNT와 커플링제와의 상호 결합력으로 인해 기계적 물성은 상대적으로 증가하였으나, 전기적 열적 특성은 MWCNT의 defects나 disorder의 형성과 chopping으로 인해 감소됨을 확인할 수 있었다.