• Title/Summary/Keyword: Integrated Gradient

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In Vivo High Resolution NMR Imaging by Using Surface Gradient Coil (평면 경사자계 코일을 사용한 고분해능 NMR 생체 영상법에 관한 연구)

  • Yi, Jeong-Han;Oh, Woo-Jin;Cho, Zang-Hee
    • Proceedings of the KOSOMBE Conference
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    • v.1990 no.11
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    • pp.48-51
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    • 1990
  • A new in vivo high resolution imaging method which is performed with a newly developed three channel surface gradient coil (SGC) is described. The surface gradient coil can produce more than an order of magnitude stronger gradient fields with good linearity within a limited imaging region. To increase the signal to noise ratio (SNR), we have developed an RF coil integrated surface gradient coil set. In this paper, the geometrical structures and characteristics of the proposed surface gradient coil are discussed and experimentally obtained high resolution images ($50\;{\mu}m$ to $100\;{\mu}m$) of a water filled phantom and a human volunteer's knee using the new surface RF coil integrated SGC set are presented for the demonstration of the in vivo high resolution imaging capability of the new imaging method.

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Nonlocal strain gradient model for thermal stability of FG nanoplates integrated with piezoelectric layers

  • Karami, Behrouz;Shahsavari, Davood
    • Smart Structures and Systems
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    • v.23 no.3
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    • pp.215-225
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    • 2019
  • In the present paper, the nonlocal strain gradient refined model is used to study the thermal stability of sandwich nanoplates integrated with piezoelectric layers for the first time. The influence of Kerr elastic foundation is also studied. The present model incorporates two small-scale coefficients to examine the size-dependent thermal stability response. Elastic properties of nanoplate made of functionally graded materials (FGMs) are supposed to vary through the thickness direction and are estimated employing a modified power-law rule in which the porosity with even type of distribution is approximated. The governing differential equations of embedded sandwich piezoelectric porous nanoplates under hygrothermal loading are derived through Hamilton's principle where the Galerkin method is applied to solve the stability problem of the nanoplates with simply-supported edges. It is indicated that the thermal stability characteristics of the porous nanoplates are obviously influenced by the porosity volume fraction and material variation, nonlocal parameter, strain gradient parameter, geometry of the nanoplate, external voltage, temperature and humidity variations, and elastic foundation parameters.

RADIAL ABUNDANCE GRADIENT IN GLOBULAR CLUSTERS

  • Chun, M.S.
    • Journal of The Korean Astronomical Society
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    • v.14 no.1
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    • pp.13-17
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    • 1981
  • The observed radial UBV colour variations (both B-V and U-B) of some globular clusters are examined for correlations with radial variations in the integrated spectra. The results show that the presence of a radial colour gradient is correlated with the presence of a gradient of the CN (and possibly the G-band) line strength, in the sense that the CN (and possibly the G-band) is stronger in the centre (where the cluster is redder) and becomes weaker in the outer region of the cluster (where the cluster is bluer). This may suggest that a primordial abundance, possibly nitrogen and carbon gradient was set up in the early stage of cluster formation.

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RADIAL COLOR GRADIENT IN A GLOBULAR CLUSTER 1. M68

  • Yi, Su-Kyoung;Chun, Mun-Suk
    • Journal of Astronomy and Space Sciences
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    • v.7 no.2
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    • pp.105-111
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    • 1990
  • Stars in M 68 from the observed-magnitude diagrams with CCD were integrated to find any radial gradient. The result shows that M 68 has a slightly bluer core. The main cause of these calculated radial color variations seems to come from the random distribution of ginants.

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Simulation analysis on the separation characteristics and motion behavior of particles in a hydrocyclone

  • Xu, Yanxia;Tang, Bo;Song, Xingfu;Sun, Ze;Yu, Jianguo
    • Korean Journal of Chemical Engineering
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    • v.35 no.12
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    • pp.2355-2364
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    • 2018
  • We evaluated the effect of particle size and associated dynamics on a hydrocyclone separation process in order to understand the movement of the particle trajectories inside the hydrocyclone via numerical analysis, with particles of acid hydrolysis residues discharged in $TiO_2$ production via the sulfate method as a case study. The values obtained from the numerical simulation were successfully compared with those from experimental tests in the literature, allowing a description of the dynamics of the particles, their acting forces, and their relevant properties together with separation efficiency. The results showed that particle motion is jointly controlled by the drag force, the pressure gradient force and the centrifugal force. With increasing particle size, the influence of the drag force is weakened, whereas that of the centrifugal force and pressure gradient is strengthened. Factors including particle density, slurry viscosity, and inlet slurry flow rate also contribute to a clear and useful understanding of particle motion behavior in the hydrocyclone as a method for improving the separation efficiency.

The Expressions of Vector Gravity and Gravity Gradient Tensor due to an Elliptical Cylinder (타원 기둥에 의한 벡터 중력 및 중력 변화율 텐서 반응식)

  • Hyoungrea Rim
    • Geophysics and Geophysical Exploration
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    • v.26 no.1
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    • pp.1-7
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    • 2023
  • This study derives the expressions of vector gravity and gravity gradient tensor due to an elliptical cylinder. The vector gravity for an arbitrary three-dimensional (3D) body is obtained by differentiating the gravitational potential, including the triple integral, according to the shape of the body in each axis direction. The vector gravity of the 3D body with axial symmetry is integrated along the axial direction and reduced to a double integral. The complex Green's theorem using complex conjugates subsequently converts the double integral into a one-dimensional (1D) closed-line integral. Finally, the vector gravity due to the elliptical cylinder is derived using 1D numerical integration by parameterizing a boundary of the elliptical cross-section as a closed line. Similarly, the gravity gradient tensor due to the elliptical cylinder is second-order differentiated from the gravitational potential, including the triple integral, and integrated along the vertical axis direction reducing it to a double integral. Consequently, all the components of the gravity gradient tensor due to an elliptical cylinder are derived using complex Green's theorem as used in the case of vector gravity.

Integrated Path Planning and Collision Avoidance for an Omni-directional Mobile Robot

  • Kim, Dong-Hun
    • International Journal of Fuzzy Logic and Intelligent Systems
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    • v.10 no.3
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    • pp.210-217
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    • 2010
  • This paper presents integrated path planning and collision avoidance for an omni-directional mobile robot. In this scheme, the autonomous mobile robot finds the shortest path by the descendent gradient of a navigation function to reach a goal. In doing so, the robot based on the proposed approach attempts to overcome some of the typical problems that may pose to the conventional robot navigation. In particular, this paper presents a set of analysis for an omni-directional mobile robot to avoid trapped situations for two representative scenarios: 1) Ushaped deep narrow obstacle and 2) narrow passage problem between two obstacles. The proposed navigation scheme eliminates the nonfeasible area for the two cases by the help of the descendent gradient of the navigation function and the characteristics of an omni-directional mobile robot. The simulation results show that the proposed navigation scheme can effectively construct a path-planning system in the capability of reaching a goal and avoiding obstacles despite possible trapped situations under uncertain world knowledge.

A Development of a Path-Based Traffic Assignment Algorithm using Conjugate Gradient Method (Conjugate Gradient 법을 이용한 경로기반 통행배정 알고리즘의 구축)

  • 강승모;권용석;박창호
    • Journal of Korean Society of Transportation
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    • v.18 no.5
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    • pp.99-107
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    • 2000
  • Path-based assignment(PBA) is valuable to dynamic traffic control and routing in integrated ITS framework. As one of widely studied PBA a1gorithms, Gradient Projection(GP) a1gorithm typically fields rapid convergence to a neighborhood of an optimal solution. But once it comes near a solution, it tends to slow down. To overcome this problem, we develop more efficient path-based assignment algorithm by combining Conjugate Gradient method with GP algorithm. It determines more accurate moving direction near a solution in order to gain a significant advantage in speed of convergence. Also this algorithm is applied to the Sioux-Falls network and verified its efficiency. Then we demonstrate that this type of method is very useful in improving speed of convergence in the case of user equilibrium problem.

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Multi-Robot Path Planning for Environmental Exploration/Monitoring (미지 환경 탐색 및 감시를 위한 다개체 로봇의 경로계획)

  • Lee, Soo-Yong
    • Journal of Institute of Control, Robotics and Systems
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    • v.18 no.5
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    • pp.413-418
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    • 2012
  • This paper presents a multi-robot path planner for environment exploration and monitoring. Robotics systems are being widely used as data measurement tools, especially in dangerous environment. For large scale environment monitoring, multiple robots are required in order to save time. The path planner should not only consider the collision avoidance but efficient coordination of robots for optimal measurements. Nonlinear spring force based planning algorithm is integrated with the spatial gradient following path planner. Perturbation/Correlation based estimation of spatial gradient is applied. An algorithm of tuning the stiffness for robot coordination is presented. The performance of the proposed algorithm is discussed with simulation results.

Performance Analysis of Explainers for Sentiment Classifiers of Movie Reviews (영화평 감성 분석기를 대상으로 한 설명자의 성능 분석)

  • Park, Cheon-Young;Lee, Kong Joo
    • Annual Conference on Human and Language Technology
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    • 2020.10a
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    • pp.563-568
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    • 2020
  • 본 연구에서는 블랙박스로 알려진 딥러닝 모델에 설명 근거를 제공할 수 있는 설명자 모델을 적용해 보았다. 영화평 감성 분석을 위해 MLP, CNN으로 구성된 딥러닝 모델과 결정트리의 앙상블인 Gradient Boosting 모델을 이용하여 감성 분류기를 구축하였다. 설명자 모델로는 기울기(gradient)을 기반으로 하는 IG와 레이어 사이의 가중치(weight)을 기반으로 하는 CAM, 그리고 설명가능한 대리 모델을 이용하는 LIME과 입력 속성에 대한 선형모델을 추정하는 SHAP을 사용하였다. 설명자 모델의 특성을 보기 위하여 히트맵과 관련성 높은 N개의 속성을 추출해 보았다. 설명자가 제공하는 기여도에 따라 입력 속성을 제거해 가며 분류기 성능 변화를 측정하는 정량적 평가도 수행하였다. 또한, 사람의 판단 근거와의 일치도를 살펴볼 수 있는 '설명 근거 정확도'라는 새로운 평가 방법을 제안하여 적용해 보았다.

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