Xiangjun Zhang

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The challenge of image interpolation is to preserve spatial details. We propose a soft-decision interpolation technique that estimates missing pixels in groups rather than one at a time. The new technique learns and adapts to varying scene structures using a 2-D piecewise autoregressive model. The model parameters are estimated in a moving window in the(More)
Specific risk behaviors related to different sexually transmitted infections have not been widely evaluated among men who have sex with men in China. In the present study, a total of 302 MSM were recruited from Beijing with a prevalence of HIV, syphilis, and anal HPV infection as 9.9, 19.2 and 71.4%, respectively. Lower education level was observed to be(More)
In compressive sensing (CS), a challenge is to find a space in which the signal is sparse and, hence, faithfully recoverable. Since many natural signals such as images have locally varying statistics, the sparse space varies in time/spatial domain. As such, CS recovery should be conducted in locally adaptive signal-dependent spaces to counter the fact that(More)
For the new signal acquisition methodology of compressive sensing (CS) a challenge is to find a space in which the signal is sparse and hence recoverable faithfully. Given the nonstationarity of many natural signals such as images, the sparse space is varying in time or spatial domain. As such, CS recovery should be conducted in locally adaptive,(More)
We propose a new non-linear approach of high order context to image interpolation. A global texture orientation map is generated by directional Gabor filters to estimate the edge directions in subpixel precision. The interpolation direction is further refined by a kernel Fisher discriminant that exploits prior knowledge gained from a training set.(More)
Depression and anxiety are common among persons recently diagnosed with HIV infection. We examined whether depression or anxiety was associated with delayed initiation of antiretroviral therapy (ART) among a prospective cohort of Chinese men who have sex with men (MSM) who were newly diagnosed with HIV. The Hospital Anxiety and Depression Scale (HADS) was(More)
H.264 SVC extension, as the state of art scalable video coding standard, can offer a single code stream to serve diverse communication bandwidths and display resolutions. However, the rate-distortion performance of H.264 SVC is still inferior to the non-scalable H.264 AVC. To reduce the performance gap between H.264 SVC and H.264 AVC, we propose a(More)
Linking and engaging HIV-positive patients in care is the key bridging step to glean the documented health and prevention advantages of antiretroviral therapy (ART). In China, HIV transmission among men who have sex with men (MSM) is surging, yet many HIV-positive MSM do not use HIV care services. We conducted a qualitative study in order to help positive(More)
Considering that quincunx lattice is a more efficient spatial sampling scheme than square lattice, we investigate a new approach of image coding for quincunx sample arrangement. The key findings are: 1) adaptive directional lifting is particularly suited to decorrelate samples on quincunx lattice, and 2) quincunx samples can be processed by a 2D piecewise(More)
Recently, many researchers started to question a long-standing paradox in the engineering practice of digital photography: oversampling followed by compression, and pursue more intelligent sparse sampling techniques. In this research we take a practical approach of uniform down sampling in image space, and the sampling is made adaptive by a spatially(More)