http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : Yunji Wang (검색결과 28 건)
- 무료
- 기관 내 무료
- 유료
-
Wind pressure characteristics of a low-rise building with various openings on a roof corner
Wang, Yunjie,Li, Q.S. Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.21 No.1
Wind tunnel testing of a low-rise building with openings (holes) of different sizes and shapes on a roof corner is conducted to measure the internal and external pressures from the building model. Detailed analysis of the testing data is carried out to investigate the characteristics of the internal and external pressures of the building with different openings' configurations. Superimposition of the internal and external pressures makes the emergence of positive net pressures on the roof. The internal pressures demonstrate an overall uniform distribution. The probability density function (PDF) of the internal pressures is close to the Gaussian distribution. Compared with the PDF of the external pressures, the non-Gaussian characteristics of the net pressures weakened. The internal pressures exhibit strong correlation in frequency domain. There appear two humps in the spectra of the internal pressures, which correspond to the Helmholtz frequency and vortex shedding frequency, respectively. But, the peak for the vortex shedding frequency is offset for the net pressures. Furthermore, the internal pressure characteristics indirectly reflect that the length of the front edge enhances the development of the conical vortices.The objective of this study aims to further understanding of the characteristics of internal, external and net pressures for low-rise buildings in an effort to reduce wind damages to residential buildings.
-
Brain MRI Segmentation and Bias Estimation Via An Improved Non-Local Fuzzy Method
Yunjie Chen,Zhengkai Wang,Jin Wang,Yuhui Zheng 보안공학연구지원센터 2015 International Journal of Grid and Distributed Comp Vol.8 No.4
Intensity in homogeneities cause considerable difficulties in the quantitative analysis of Magnetic Resonance (MR) images. Thus intensity in homogeneities estimation is a necessary step before quantitative analysis of MR data can be undertaken. This paper proposes a new energy minimization framework for simultaneous estimation of the intensity in homogeneities and segmentation. The intensity in homogeneities is modeled as a linear combination of a set of basis functions, and parameterized by the coefficients of the basis functions. The energy function depends on the coefficients of the basis functions, the membership ratios and the centroids of the tissues in the image. Intensity in homogeneities estimation and image segmentation are simultaneously achieved by calculating the result of minimizing this energy. Furthermore, in order to improve its robustness to noise, the membership ratios are adapted by using nonlocal information. Experimental results on both real MR images and simulated MR data show that our method can obtain more accurate results when segmenting images with bias field and noise.
-
Wind pressure characteristics of a low-rise building with various openings on a roof corner
Yunjie Wang,Q.S Li 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.1
Wind tunnel testing of a low-rise building with openings (holes) of different sizes and shapes on a roof corner is conducted to measure the internal and external pressures from the building model. Detailed analysis of the testing data is carried out to investigate the characteristics of the internal and external pressures of the building with different openings\' configurations. Superimposition of the internal and external pressures makes the emergence of positive net pressures on the roof. The internal pressures demonstrate an overall uniform distribution. The probability density function (PDF) of the internal pressures is close to the Gaussian distribution. Compared with the PDF of the external pressures, the non-Gaussian characteristics of the net pressures weakened. The internal pressures exhibit strong correlation in frequency domain. There appear two humps in the spectra of the internal pressures, which correspond to the Helmholtz frequency and vortex shedding frequency, respectively. But, the peak for the vortex shedding frequency is offset for the net pressures. Furthermore, the internal pressure characteristics indirectly reflect that the length of the front edge enhances the development of the conical vortices.The objective of this study aims to further understanding of the characteristics of internal, external and net pressures for low-rise buildings in an effort to reduce wind damages to residential buildings
-
-
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.
-
A New Bias Field Estimation Method based on Adapted PSO Method
Yunjie Chen,Yingying Chu,Jin Wang,Yuhui Zheng 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.8
It is hard to segmentation brain MR images for the bias fields. In this paper, a new fuzzy anisotropic diffusion function is presented to reduce the effect of the noise. We use Legendre polynomial functions to reconstruct the bias field, which make the entropy of the recovered image be smallest. But it needs to compute a lot of parameters to reconstruct the bias. The traditional method uses the gradient descending method to compute the parameters. The method plunges into local best easily. In order to deal with this problem, Particle swarm optimization (PSO) method is analyzed. A new particle swarm technique is proposed that incorporates initial location information and use mutate operation make the particles away from local maxima. The experiments show that the new method can get accurate result robustly.
-
Yunjie Chen,Qin Xu,Yuhui Zheng,Jin Wang,Jeong-Uk Kim 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.5
Accurate segmentation for magnetic resonance (MR) images is an essential step in quantitative brain image analysis, and hence has attracted extensive research attention. However, due to the existence of noise and intensity inhomogeneity, also named as bias field, many segmentation methods suffer from limited accuracy. This paper presents a novel variational framework for the registration, segmentation and bias estimation simultaneously. We first presented an improved segmentation model by using the intensity statistic distributions with different means and variances in local regions. The model can estimate the bias field meanwhile segmenting images. We also proposed an anisotropic non-rigid registration method by using the structure tensor information and nonlocal information to contain the information of the image details. Finally, we defined a coupled term to combine the segmentation and registration. The registration term can provide shape information as a prior to guide the segmentation and the segmentation term can provide the edge information to guide the registration. The segmentation and registration can obtain benefit from each other. Our statistical results on both synthetic and clinical images show that the proposed method can overcome the difficulties caused by noise and bias fields and obtain more accurate results.
-
-
An image thresholding method based on the target extraction
Yunjie Zhang,Yi Li,Zhijun Gao,Weina Wang 한국전산응용수학회 2008 Journal of applied mathematics & informatics Vol.26 No.3-4
In this paper an algorithm, based on extracting a certain target of an image, is proposed that is capable of performing bilevel threshold- ing of image with multimodal distribution. Each pixel in the image has a membership value which is used to denote the characteristic relationship between the pixel and its belonging region (i.e. the object or background). Using the membership values of image set, a new measurement, which simultaneously measures the measure of fuzziness and the conditional en- tropy of the image, is calculated. Then, thresholds are found by optimally minimizing calculated measurement. In addition, a fuzzy range is defined to improve the threshold values. The experimental results demonstrate that the proposed approach can select the thresholds automatically and ef- fectively extract the meaningful target from the input image. The resulting image can preserve the object region we target very well. In this paper an algorithm, based on extracting a certain target of an image, is proposed that is capable of performing bilevel threshold- ing of image with multimodal distribution. Each pixel in the image has a membership value which is used to denote the characteristic relationship between the pixel and its belonging region (i.e. the object or background). Using the membership values of image set, a new measurement, which simultaneously measures the measure of fuzziness and the conditional en- tropy of the image, is calculated. Then, thresholds are found by optimally minimizing calculated measurement. In addition, a fuzzy range is defined to improve the threshold values. The experimental results demonstrate that the proposed approach can select the thresholds automatically and ef- fectively extract the meaningful target from the input image. The resulting image can preserve the object region we target very well.
-
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
