http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
A Novel Breast mass segmentation method based on patch merging and GHFCM
Shenghua Gu,Yunjie Chen,Jin Wang,Jeong-Uk Kim 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.10
Breast cancer is regarded as one of the most frequent mortality causes among women. It is very important to create a system to diagnose suspicious masses in mammograms for early breast cancer detection. In this paper, we propose an automatic breast mass segmentation method based on patch merging method and generalized hierarchical Fuzzy C Means (GHFCM). The patch merging method is used to obtain the adaptive region of interest (ROI), while the GHFCM method which is able to overcome the drawbacks of effect of image noise and Euclidean distance FCM which is sensitive to outliers is used to obtain the precisely mass segmentation results. The new method is evaluated over MiniMIAS dataset. The segmentation performance from experimentations demonstrates that our method outperforms the other compared methods.
Yuxiang Wang,Yunjie Gu,Wuhua Li,Xiangning He 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
In virtual vector control schemes for singlephase current-regulated voltage source inverters, a transient disturbance may be induced due to the time-delay in the virtual orthogonal signal. This disturbance deteriorates the dynamic current-tracking capability and power quality. A unified scalar model is developed to analyze the phenomenon. Based on this model, an improved control scheme with a pre-compensator is proposed to solve the problem. The pre-compensator reshapes the current commands so that the transient disturbance signal is eliminated while the desired response is unaffected. Experimental results of the proposed strategy are compared with the conventional solution to substantiate enhanced dynamic performance.
Yifan Zhang,Yitong Li,Yunjie Gu,Timothy C. Green 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
Grid-following inverters have been widely adopted as a grid interface for renewable energy resources, but ensuring their transient stability has been a growing challenge in part because of a lack of clarity on how interactions between the inverter’s various outer control loops impact transient response. In this paper, the nonlinear dynamics and transient stability of grid-following inverters are investigated, where not only the phase-locked loop (PLL) but also the DC-link voltage control (DVC) and the AC terminal voltage control (TVC) are taken into account. The use of bandwidth separation method is proposed, though which the original differential equations can be simplified, and their order can be reduced, providing that the separation between their bandwidths is sufficiently large. Analysis of the interaction between the DVC and the PLL is developed, proving that this interaction negatively impacts stability. Furthermore, optimal combinations of bandwidth of PLL and DVC are identified under various types of grid faults. The impact of TVC on transient stability is analyzed. All of the results and the conclusions drawn from them are verified by simulation.
Synchronous Frequency Resonance of Virtual Synchronous Generators and Damping Control
Jinhua Wang,Yuxiang Wang,Yunjie Gu,Wuhua Li,Xiangning He 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
The Virtual Synchronous Generator (VSG) is an effective solution for high-penetration renewable energy sources integrated into the power system. Although the VSG has a similar behavior as the conventional synchronous generator, the fast and flexible control capability of converters may give rise to some specific characteristics. In this paper, it is explained that flux dynamics may induce synchronous frequency resonance in VSGs, which possibly leads to power-angle oscillations. A precise small-signal model is established to investigate the synchronous frequency resonance phenomenon. Based on this model, two damping control methods are proposed, which suppress the resonance through increasing the virtual mechanical inertia or adding virtual electrical resistance. The effectiveness of the theoretical conclusions is verified by simulation and experimental results.