• Title/Summary/Keyword: influence coefficients

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Recognition of Radar Emitter Signals Based on SVD and AF Main Ridge Slice

  • Guo, Qiang;Nan, Pulong;Zhang, Xiaoyu;Zhao, Yuning;Wan, Jian
    • Journal of Communications and Networks
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    • 제17권5호
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    • pp.491-498
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    • 2015
  • Recognition of radar emitter signals is one of core elements in radar reconnaissance systems. A novel method based on singular value decomposition (SVD) and the main ridge slice of ambiguity function (AF) is presented for attaining a higher correct recognition rate of radar emitter signals in case of low signal-to-noise ratio. This method calculates the AF of the sorted signal and ascertains the main ridge slice envelope. To improve the recognition performance, SVD is employed to eliminate the influence of noise on the main ridge slice envelope. The rotation angle and symmetric Holder coefficients of the main ridge slice envelope are extracted as the elements of the feature vector. And kernel fuzzy c-means clustering is adopted to analyze the feature vector and classify different types of radar signals. Simulation results indicate that the feature vector extracted by the proposed method has satisfactory aggregation within class, separability between classes, and stability. Compared to existing methods, the proposed feature recognition method can achieve a higher correct recognition rate.

Thermal analysis on composite girder with hybrid GFRP-concrete deck

  • Xin, Haohui;Liu, Yuqing;Du, Ao
    • Steel and Composite Structures
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    • 제19권5호
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    • pp.1221-1236
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    • 2015
  • Since the coefficients of thermal expansion (CTE) between concrete and GFRP, steel and GFRP are quite different, GFRP laminates with different laminas stacking-sequence present different thermal behavior and currently there is no specification on mechanical properties of GFRP laminates, it is necessary to investigate the thermal influence on composite girder with stay-in-place (SIP) bridge deck at different levels and on different scales. This paper experimentally and theoretically investigated the CTE of GFRP at lamina's and laminate's level on micro-mechanics scales. The theoretical CTE values of laminas and laminates agreed well with test results, indicating that designers could obtain thermal properties of GFRP laminates with different lamina stacking-sequence through micro-mechanics methods. On the basis of the CTE tests and theoretical analysis, the thermal behaviors of composite girder with hybrid GFRP-concrete deck were studied numerically and theoretically on macro-mechanics scales. The theoretical results of concrete and steel components of composite girder agreed well with FE results, but the theoretical results of GFRP profiles were slightly larger than FE and tended to be conservative at a safety level.

장주기 중력외파의 동해안 연안지형변화에 미치는 영향 연구 : 사례연구 - 일산해변 (Effect of Infra-Gravity Waves on Nearshore Morphodynamics in the East Coast : Case Study - Ilsan Beach)

  • 손동휘;유제선;신현화
    • Ocean and Polar Research
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    • 제40권2호
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    • pp.87-98
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    • 2018
  • It is widely known that infragravity waves can exert significant influence on wave run-up over beaches. Large run-ups can lead to overwash, flooding and severe coastal erosion. In spite of the importance of infragravity waves in relation to wave run-up and coastal erosion, few studies have been carried out with regard to the impact of infragravity waves on nearshore morphodynamics with respect to eastern beaches in Korea. The purpose of this study is to investigate the importance of infragravity waves in nearshore numerical modelling. For the study, XBeach model was set up to analyze morphodynamics in December 2016, in Ilsan beach which is located in Ilsan-dong, Ulsan Metropolitan City. After validation of the XBeach model, numerical experiments were conducted by using various directional spreading coefficients. As the directional spreading coefficients are increased, the effect of infragravity waves is also enhanced by narrowband frequency. With the increasing effect of infragravity waves, the amount of sediment transport is also increased and an erosion dominant pattern is found in the south part of Ilsan beach and a deposition pattern in the north part of the beach mainly due to the wave incident direction of NNE.

Monetary Policy Independence and Bond Yield in Developing Countries

  • ANWAR, Cep Jandi;SUHENDRA, Indra
    • The Journal of Asian Finance, Economics and Business
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    • 제7권11호
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    • pp.23-31
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    • 2020
  • This paper investigates the impact of monetary policy independence shock on bond yield by allowing for heterogeneous coefficients in the model based on panel data for 19 developing countries using quarterly data from 1991 to 2016. First, we estimate the model using conventional panel VAR estimation with the assumption of homogeneous coefficients across countries. Second, by performing Chow and Roy-Zellner tests to check the homogeneity assumption, we find that the assumption does not hold in the model. Third, we apply a mean-group estimation for panel VAR as a solution for heterogeneity panel model. The results reveal that central bank independence is effective in reducing bond yield with the maximum at period 6 after the shock. Shock one standard deviation bond yield has a negative effect on consumption and investment. We determine that central bank independence has a contradictory effect on real activity; a negative effect on consumption but a positive influence on investment for the first two years after the shock. Additionally, we split our sample into three groups to make the subgroups pool. Our empirical result shows that monetary policy independence shock reduces bond yield. Meanwhile, the response of economic activity to bond yield varies for all three groups.

An evaluation of iced bridge hanger vibrations through wind tunnel testing and quasi-steady theory

  • Gjelstrup, H.;Georgakis, C.T.;Larsen, A.
    • Wind and Structures
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    • 제15권5호
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    • pp.385-407
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    • 2012
  • Bridge hanger vibrations have been reported under icy conditions. In this paper, the results from a series of static and dynamic wind tunnel tests on a circular cylinder representing a bridge hanger with simulated thin ice accretions are presented. The experiments focus on ice accretions produced for wind perpendicular to the cylinder at velocities below 30 m/s and for temperatures between $-5^{\circ}C$ and $-1^{\circ}C$. Aerodynamic drag, lift and moment coefficients are obtained from the static tests, whilst mean and fluctuating responses are obtained from the dynamic tests. The influence of varying surface roughness is also examined. The static force coefficients are used to predict parameter regions where aerodynamic instability of the iced bridge hanger might be expected to occur, through use of an adapted theoretical 3-DOF quasi-steady galloping instability model, which accounts for sectional axial rotation. A comparison between the 3-DOF model and the instabilities found through two degree-of-freedom (2-DOF) dynamic tests is presented. It is shown that, although there is good agreement between the instabilities found through use of the quasi-steady theory and the dynamic tests, discrepancies exist-indicating the possible inability of quasi-steady theory to fully predict these vibrational instabilities.

화질 개선을 위한 DCT 계수의 동적 제어 (Dynamic Control of DCT Coefficients for Image Quality Improvement)

  • 임용순;이근영
    • 전자공학회논문지S
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    • 제36S권7호
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    • pp.116-123
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    • 1999
  • 일반적으로 비디오 부호화 방법에서는 비트율 제어에 의해 얻은 양자화 파라미터를 사용하면 DCT 계수의 특징을 잃어버리게 되어 화질에 많은 영향을 미치게 되었다. 본 논문에서는 동영상 부호화에서 DCT계수의 동적 제어를 위한 블록의 DCT 특성을 나타내는 블록 계수를 얻었다. 이것을 영상의 각 화소 블록에서 평균(AS) 값을 구하고, 평균값과 영상의 각 화소의 차(DABP)의 평균값을 구하고, DABP와 DCT 계수를 이용하여 블록 계수(BC)를 얻는다. 실험을 통하여 제안한 방법에 의해 동영상의 화질을 개선시킬 수 있었다.

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고분자막을 이용한 $N_2-SO_2$ 혼합기체의 분리에 관한 연구 (A Study on Separation of $N_2-SO_2$ Mixed Gas by Polymer Membranes)

  • 김성준;민병렬;이태희
    • 멤브레인
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    • 제2권2호
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    • pp.135-143
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    • 1992
  • 여러가지 고분자막을 이용하여 $N_2-SO_2$ 혼합기체를 분리하는 데 있어서 압력, 온도 등을 조작변수로 하여 투과계수와 분리인자를 계산하고 이에 따른 기체투과 특성을 규명하고 분리성능을 측정하였다. 실험한 압력의 범위는 0.1~1.0 MPa이었으며, 온도범위는 283~303 K이었다. 압력이 커질수록 투과계수와 분리인자가 증가하였으나, 온도증가에 따라 투과계수와 분리인자는 감소하였다. 본 실험에서 사용된 막 중 Film-Tech사의 FT-30이 $N_2-SO_2$ 혼합기체의 분리능력이 가장 뛰어난 것으로 나타났다.

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회전속도 의존 매개변수를 가진 회전체-베어링계의 동적 해석 (Dynamic analysis of spin speed dependent parameter rotor-bearing systems)

  • 홍성욱;이종원
    • 대한기계학회논문집
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    • 제12권5호
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    • pp.976-983
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    • 1988
  • 본 연구에서는 회전체 베어링계에 대한 불균형 응답 계산시 회전속도 의존성 을 손쉽게 고려할 수 있는 방법에 대해 논하고자 한다. 그 방법은 람다행렬(lamda matrix)을 도입하여, 회전속도 의존성을 지닌 고유치 문제를 회전속도 의존성이 없는 문제로 변환시킨 후 기존의 모우드 해석기법을 적용하여 불균형 응답특성을 알아내는 방법이다. 이때 베어링의 회전속도 의존성을 다항식(polynomial)으로 근사화할 수 있다는 기본 가정을 두었는데, 이러한 가정은 실제 베어링이 관심있는 회전수 영역에서 고차의 다항식으로 충분히 정확하게 근사화 될 수 있으므로 응용성을 크게 약화시키지 는 않는다. 특별히 회전속도 의존성이 자이로 효과(gyroscopic effect)에 의해서만 기인할 때는 여기서 제시하는 방법은 전혀 오차를 주지 않게 된다.

Online automatic structural health assessment of the Shanghai Tower

  • Zhang, Qilin;Tang, Xiaoxiang;Wu, Jie;Yang, Bin
    • Smart Structures and Systems
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    • 제24권3호
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    • pp.319-332
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    • 2019
  • Structural health monitoring (SHM) is of great importance to super high-rise buildings. The Shanghai Tower is currently the tallest building in China, and a complete SHM system was simultaneously constructed at the beginning of the construction of the tower. Due to the variety of sensor types and the large number of measurement points in the SHM system, an online automatic structural health assessment method with few computations and no manual intervention is needed. This paper introduces a structural health assessment method for the Shanghai Tower that uses the coefficients of an autoregressive (AR) time series model as structural state indicators. An analysis of collected data indicates that the coefficients of the AR model are affected by environmental factors, and the principal component analysis method is used to remove the influence of environmental factors. Finally, the control chart method is used to track the changes in structural state indicators, and a plan for online automatic structure health state evaluation is proposed. This method is applied to long-term acceleration and inclination data from the Shanghai Tower and successfully identifies the changes in the structural state. Overall, the structural state indicators of the Shanghai Tower are stable, and the structure is in a healthy state.

간호·간병통합서비스 병동 간호사의 전문직 자아개념, 간호근무환경 및 팀워크가 직무만족에 미치는 영향 (The Influence of Professional Self-Concept, Nursing Work Environment, and Teamwork on Job Satisfaction of Nurses in Comprehensive Nursing Care Ward)

  • 이정화;정희자
    • 문화기술의 융합
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    • 제8권2호
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    • pp.149-155
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    • 2022
  • 본 연구는 간호·간병통합서비스 병동 간호사의 직무만족의 영향요인을 파악하기 위해 시도한 서술적 조사연구이다. 연구대상자는 간호·간병통합서비스 병동 근무 간호사 114명이였으며, 수집된 자료는 기술통계, t-test, ANOVA, Pearson's correlation coefficients, multiple linear regression analysis을 이용하여 분석하였다. 연구결과 직무만족의 주요 영향요인은 전문직 자아개념 및 팀워크로 나타났으며, 직무만족에 대한 두 변수의 설명력은 66.0%로 나타났다. 따라서 간호·간병통합서비스 병동 간호사의 직무만족을 높이기 위해서는 전문직 자아개념과 간호 조직의 팀워크를 향상시킬 수 있는 교육과 정책적 지원이 필요할 것으로 생각된다.