• Title, Summary, Keyword: Sensitivity

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Conceptual Study of Brain Dedicated PET Improving Sensitivity

  • Shin, Han-Back;Choi, Yong;Huh, Yoonsuk;Jung, Jin Ho;Suh, Tae Suk
    • Progress in Medical Physics
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    • v.27 no.4
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    • pp.236-240
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    • 2016
  • The purpose of this study is to propose a novel high sensitivity neuro-PET design. The improvement of sensitivity in neuro-PET is important because it can reduce scan time and/or radiation dose. In this study, we proposed a novel PET detector design that combined conical shape detector with cylindrical one to obtain high sensitivity. The sensitivity as a function of the oblique angle and the ratio of the conical to cylindrical portion was estimated to optimize the design of brain PET using Monte Carlo simulation tool, GATE. An axial sensitivity and misplacement rate by penetration of ${\gamma}$ rays were also estimated to evaluate the performance of the proposed PET. The sensitivity was improved by 36% at the center of axial FOV. This value was similar to the calculated value. The misplacement rate of conical shaped PET was about 5% higher than the conventional PET. The results of this study demonstrated the conical detector proposed in this study could provide subsequent improvement in sensitivity which could allow to design high sensitivity PET for brain imaging.

Moral Sensitivity, Empathy and Perceived Ethical Climate of Psychiatric Nurses Working in the National Mental Hospitals (국립정신의료기관 간호사의 도덕적 민감성과 공감능력 및 지각된 윤리풍토의 관계)

  • Jo, Hyekyung;Kim, Sunah
    • Journal of Korean Academy of Psychiatric and Mental Health Nursing
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    • v.26 no.2
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    • pp.204-215
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    • 2017
  • Purpose: The purpose of this study was to identify the relationships between Moral Sensitivity, Empathy and Perceived Ethical Climate for nurses working in national mental hospitals and to provide basic data for the development of interventions that enhance Moral Sensitivity and help psychiatric hospital nurses in Ethical Decision-making. Methods: This descriptive cross-sectional study was conducted with 182 psychiatric nurses working in the national mental hospitals. Data were collected through self-report questionnaires which included the Moral Sensitivity Questionnaire (MSQ), Interpersonal Reactivity Index (IRI), and Hospital Ethical Climate Survey (HECS). Results: The mean score for MSQ was 5.19, for IRI, 2.49, and for HECS, 3.73. There was a significant positive correlation between moral sensitivity and empathy (r=.24, p=.001), between moral sensitivity and perceived ethical climate (r=.17, p=.025) and between empathy and perceived ethical climate (r=.17, p=.025). Conclusion: Findings indicate that moral sensitivity can be enhanced by improving empathy, a personal factor, and ethical climate, an organization factor. Further identification of the relationship between moral sensitivity and personal and organizational factors will be useful in the development of interventions to enhance moral sensitivity of nurses working in psychiatric wards.

Single and High-Lift Airfoil Design Optimization Using Aerodynamic Sensitivity Analysis

  • Kim, Chang Sung;Lee, Byoungjoon;Kim, Chongam;Rho, Oh-Hyun
    • International Journal of Aeronautical and Space Sciences
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    • v.2 no.1
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    • pp.20-27
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    • 2001
  • Aerodynamic sensitivity analysis is performed for the Navier-Stokes equations coupled with two-equation turbulence models using a discrete adjoint method and a direct differentiation method respectively. Like the mean flow equations, the turbulence model equations are also hand-differentiated to accurately calculate the sensitivity derivatives of flow quantities with respect to design variables in turbulent viscous flows. The sensitivity codes are then compared with the flow solver in terms of solution accuracy, computing time and computer memory requirements. The sensitivity derivatives obtained from the sensitivity codes with different turbulence models are compared with each other. The capability of the present sensitivity codes to treat complex geometry is successfully demonstrated by analyzing the flows over multi-element airfoils on Chimera overlaid grid systems.

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Sensitivity analysis of weights in multi-layer perceptron realizing continuous mappings

  • Choi, Chong-Ho;Choi, Jin-Young
    • 제어로봇시스템학회:학술대회논문집
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    • pp.1377-1382
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    • 1990
  • In Multi-Layer Perceptron (MLP) which realizes continuous mappings, the output errors is directly affected by the weight errors which may be caused by the limited precision of digital or analog hardware in implementations. So, it is important to study the sensitivity due to the perturbation of connection weights between neurons. In this paper, we derive a sensitivity function to the statistical weight perturbations in MLP with differentiable activation functions. This sensitivity function can be regarded as an ensemble average of deterministic sensitivity measures due to the perturbations of weights. Hence, this sensitivity function can be used as the criteria for selecting weights with the minimum sensitivity among possible sets of connection weights in MLP. For the verification of the validity of the proposed sensitivity function, computer simulations have been performed and through the simulations we find good agreement between the theoretical and simulation results.

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Design Sensitivity Analysis for the Vibration Characteristic of Vehicle Structure (수송체 구조물의 진동특성에 관한 설계민감도 해석)

  • 이재환
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.19-24
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    • 1992
  • Design sensitivity analysis method for the vibration of vehicle structure is developed using adjoint variable method. A variational approach with complex response method is used to derive sensitivity expression. To evaluate sensitivity, FEM analysis of ship deck and vehicle structure are performed using MSC/NASTRAN on the super computer CRAY2S, and sensitivity computation is carried on PC. The accuracy of sensitivity is verified by the results of finite difference method. When compared to structural analysis time on CRAY2S, sensitivity computation is remarkably economical. The sensitivity of vehicle frame can be used to reduce the vibration responses such as displacement and acceleration of vehicle.

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Design Sensitivity Analysis of Eigen Problem Using NASTRAN (NASTRAN을 이용한 고유치 문제의 설계 민감도 해석)

  • 윤광수;이태희
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.508-512
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    • 1997
  • Design sensitivity analysis of Eigen Problem give systematic design improvement information for noise and vibration of a system. Based on reliable results form commercial FE code(UAI/NASTRAN), three computational procedures for design sensitivity analysis of eigen problem are suggested. Those methods are finite difference,design sensitivity analysis using external module and design sensitivity analysis running with NASTRAN. To verify the suggested methods, a numerical example is given and these results are compared with the results from UAI/NASTRAN eigen sensitivity option. We can conclude that design sensitivity coefficient of eigen proplems can be computed outside of the FE code as easy as inside of the FE code.

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The Parametric Sensitivity Analyses of linear System Relative to the Characteristic Ratios of Coefficient(II) : K-Polynomial Case (계수의 특성비에 대한 선형계의 파라미터적 감도해석(II) : K-다항식의 경우)

  • 김영철;김근식
    • Journal of Institute of Control, Robotics and Systems
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    • v.10 no.4
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    • pp.295-303
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    • 2004
  • Previously it has been shown that the all pole systems resulting good time responses can be characterized by so called K-polynomial. The polynomial is defined in terms of the principal characteristic ratio $\alpha_1$ and the generalized time constant $\tau$ . In this paper, Part II presents several sensitivity analyses of such systems with respect to $\alpha_1$ and $\tau$ changes. We first deal with the root sensitivity to the perturbation of $\alpha_1$ . By way of determining the unnormalized function sensitivity, both time response sensitivity and frequency response sensitivity are derived. Finally, the root sensitivity relative to $\tau$ change is also analyzed. These results provide some useful insight and background theory when we select of and l to compose a reference model of which denominator is a K-polynomial, which is illustrated by examples.

Optimum Sensitivity of Objective Function using Equality Constraint (등제한조건을 이용한 목적함수에 대한 최적민감도)

  • Yi S.I.;Shin J.K.;Park G.J.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.464-469
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    • 2005
  • Optimum sensitivity analysis (OSA) is the process to find the sensitivity of optimum solution with respect to the parameter in the optimization problem. The prevalent OSA methods calculate the optimum sensitivity as a post-processing. In this research, a simple technique is proposed to obtain optimum sensitivity as a result of the original optimization problem, provided that the optimum sensitivity of objective function is required. The parameters are considered as additional design variables in the original optimization problem. And then, it is endowed with equality constraints to penalize the additional variables. When the optimization problem is solved, the optimum sensitivity of objective function is simultaneously obtained as Lagrange multiplier. Several mathematical and engineering examples are solved to show the applicability and efficiency of the method compared to other OSA ones.

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Optimum Sensitivity of Objective Function Using Equality Constraint (등제한조건을 이용한 목적함수에 대한 최적민감도)

  • Shin Jung-Kyu;Lee Sang-Il;Park Gyung-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.12
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    • pp.1629-1637
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    • 2005
  • Optimum sensitivity analysis (OSA) is the process to find the sensitivity of optimum solution with respect to the parameter in the optimization problem. The prevalent OSA methods calculate the optimum sensitivity as a post-processing. In this research, a simple technique is proposed to obtain optimum sensitivity as a result of the original optimization problem, provided that the optimum sensitivity of objective function is required. The parameters are considered as additional design variables in the original optimization problem. And then, it is endowed with equality constraints to penalize the additional variables. When the optimization problem is solved, the optimum sensitivity of objective function is simultaneously obtained as Lagrange multiplier. Several mathematical and engineering examples are solved to show the applicability and efficiency of the method compared to other OSA ones.

Initial-phase Sensitivity Analysis of Harmonic Measurements via Windowed DFT

  • Song, Shuping;Wang, Fuzong;Cheng, Guozhu
    • Transactions on Electrical and Electronic Materials
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    • v.15 no.4
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    • pp.182-188
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    • 2014
  • When the windowed DFT algorithm is applied in harmonic measurements, the problem of initial-phase sensitivity will be encountered, this has an effect on harmonic amplitude accuracy. In this paper, the origin of initial-phase sensitivity is analyzed and the main factors that influence the level of initial-phase sensitivity are demonstrated. A method of reducing initial-phase sensitivity is proposed to increase the stability of harmonic measurements. We found that initial-phase sensitivity is determined by the side lobe peak level of the window functions when synchronous deviation is fixed. In addition, increasing the length of the time recorded can be used to remove initial-phase sensitivity. The correctness and validity of our conclusions have been confirmed through numerical results and field tests.