Wenjun Zhang - Academia.edu (original) (raw)

Papers by Wenjun Zhang

Research paper thumbnail of Using JPEG and JPEG2000 compressions for fast image quality metrics based on free energy theory

2014 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Bayesian Error Concealment With DCT Pyramid for Images

ABSTRACT In this paper, the problem of concealing missing image blocks is casted into a framework... more ABSTRACT In this paper, the problem of concealing missing image blocks is casted into a framework of Bayesian estimation. The conditional expectation of the missing block vector is taken over a pilot vector of correctly decoded pixels near the missing block. Multiple observations of the missing vector and pilot vectors obtained in a neighborhood are used to approximate the expectation. We design a multiscale estimation approach with discrete cosine transform pyramid to improve estimation efficiency. The DC image of the missing block is recovered first, and then more details related to high-frequency AC coefficients are recovered successively. Moreover, the algorithm operates in an iterative mode through using estimated block to refine the searching process for the next estimation. The algorithm is found to perform very well for a wide range of block loss rates. Substantial improvement over 14 existing error concealment (inclusive of inpainting) algorithms on various images is demonstrated in our extensive experiments, under different test conditions inclusive of high-loss rates and large block sizes.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A cooperative multicast strategy based on spatial diversity with power constraint

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Identification of the Polyketide Biosynthetic Machinery for the Indolizidine Alkaloid Cyclizidine

Organic letters, Jan 16, 2015

The cyclizidine biosynthetic gene cluster was identified from Streptomyces NCIB 11649, which reve... more The cyclizidine biosynthetic gene cluster was identified from Streptomyces NCIB 11649, which revealed the polyketide biosynthetic machinery for cyclizidine alkaloid biosynthesis. Both in vivo mutagenesis study and in vitro biochemical analysis provided insight into the timing and mechanism of the biosynthetic enzymes that produce cyclizidine-type indolizidine alkaloids.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of An improved contrast-tone mapping algorithm for image contrast enhancement

2011 8th International Conference on Information, Communications & Signal Processing, 2011

In this paper, an improved image contrast enhancement algorithm extending the existing contrast-t... more In this paper, an improved image contrast enhancement algorithm extending the existing contrast-tone mapping framework is proposed. The proposed method improves the existing algorithm with new definition of image contrast and novel constraints to the optimization. Experimental results demonstrate that the proposed Improved Optimal Contrast-tone Mapping (IOCTM) algorithm outperforms existing histogram equalization based method as well as existing OCTM method.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Bacterial genome mining of enzymatic tools for alkyne biosynthesis

ACS chemical biology, Jan 6, 2015

The alkyne is an important functionality widely used in material science, pharmaceutical science,... more The alkyne is an important functionality widely used in material science, pharmaceutical science, and chemical biology, but the importance of this functionality is contrasted by the very limited number of enzymes known to be involved in alkyne biosynthesis. We recently reported the first known carrier protein-dependent pathway for terminal alkyne formation, and in silico analysis suggested that this mechanism could be widespread in bacteria. In this paper, we screened additional homologous gene cassettes presumed to be involved in alkyne biosynthesis using both in vitro biochemical study and an E. coli-polyketide synthase (PKS) reporting system for in vivo analysis. We discovered and characterized a new terminal alkyne biosynthetic pathway comprised of TtuA, B, and C from Teredinibacter turnerae T7901. While the acyl-CoA ligase homolog (TtuA) demonstrated promiscuity in the activation and loading of medium-chain fatty acids onto the carrier protein (TtuC), the desaturase homolog (Tt...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Image denoising using local tangent space alignment

Proceedings of SPIE - The International Society for Optical Engineering

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Preparation and performance of a novel graphene oxide sheets modified rare-earth luminescence material

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Reduced Graphene Oxide/ZnO Composites and Its High Photocatalytic Activity for Degradation of Methylene Blue

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Ammonia stimulates growth and nitrite-oxidizing activity of Nitrobacter winogradskyi

Biotechnology, biotechnological equipment, Jan 2, 2014

The aim of this study was to obtain a nitrite-oxidizing bacterium with high nitrite oxidation act... more The aim of this study was to obtain a nitrite-oxidizing bacterium with high nitrite oxidation activity for controlling nitrite levels. A nitrite-oxidizing bacterium, ZS-1, was isolated from the water of a coastal Pseudosciaena crocea-rearing pond. The strain was identified as Nitrobacter winogradskyi based on the phylogenetic analyses of the 16S ribosomal ribonucleic acid gene and nxrA sequence of ZS-1. Under aerobic condition, the nitrite-oxidizing activity of ZS-1 did not change considerably in the range of pH 7-9, but was strongly inhibited by lower (pH = 6) and higher (pH = 10) pH values. The optimum temperature range is 25-32 °C. Lower temperature made the adaptive phase of ZS-1 longer but did not affect its maximum nitrite oxidization rate. The nitrite-oxidizing activity of ZS-1 started to be inhibited by ammonia and nitrate when the concentrations of ammonia and nitrate reached 25 mg L(-1) and 100 mg L(-1), respectively. The inhibition was stronger with higher concentration o...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The Performance Analysis of Coded Cache in Wireless Fading Channel

The rapid growth of data volume and the accompanying congestion problems over the wireless networ... more The rapid growth of data volume and the accompanying congestion problems over the wireless networks have been critical issues to content providers. A novel technique, termed as coded cache, is proposed to relieve the burden. Through creating coded-multicasting opportunities, the coded-cache scheme can provide extra performance gain over the conventional push technique that simply pre-stores contents at local caches during the network idle period. But existing works on the coded caching scheme assumed the availability of an error-free shared channel accessible by each user. This paper considers the more realistic scenario where each user may experience different link quality. In this case, the system performance would be restricted by the user with the worst channel condition. And the corresponding resource allocation schemes aimed at breaking this obstacles are developed. Specifically, we employ the coded caching scheme in time division and frequency division transmission mode and f...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of An Interpolation Based Channel Estimation Method for MIMO OFDM Systems

2008 IEEE 68th Vehicular Technology Conference, 2008

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Rapid production of a bulk of porous mesh reduced graphene oxide films using a naked flame

J. Mater. Chem. C, 2015

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Robust Region-of-Interest Scalable Coding with Leaky Prediction in H.264/AVC

2007 IEEE Workshop on Signal Processing Systems, 2007

Bookmarks Related papers MentionsView impact

Research paper thumbnail of 318620 Characterization of the Biosynthetic Pathway of Physostigmine

Physostigmine is a tryptophan-derived natural product with a rare pyrroloindole skeleton. Because... more Physostigmine is a tryptophan-derived natural product with a rare pyrroloindole skeleton. Because of its ability to reversibly inhibit acetylcholinesterase, physostigmine has been used to treat a variety of neurological disorders, including glaucoma and Alzheimer’s disease. However, despite its medicinal uses, little is known about the biosynthesis of physostigmine and pyrroloindole alkaloids in general. In this work, we identified the biosynthetic gene cluster for physostigmine in the producer, Streptomyces griseofuscus, and confirmed its function by heterologous expression. Gene deletion mutants and in vitro assays with purified enzymes further enabled us to identify the set of enzymes essential for physostigmine biosynthesis and propose an enzymatic pathway for the transformation of tryptophan into physostigmine. We find that the formation of the pyrroloindole skeleton proceeds by an unexpected N-acetylated intermediate that is necessary for methylation of C-3 of the indole ring ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Incorporating TCP Acknowledgements in MAC Layer in IEEE 802.11 Multihop Ad Hoc Networks

GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Modeling TCP Throughput in IEEE 802.11 Based Wireless Ad Hoc Networks

6th Annual Communication Networks and Services Research Conference (cnsr 2008), 2008

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of CyberC10 code

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Characterization of Heronamides Biosynthesis Reveals a Tailoring Hydroxylase and Indicates Migrated Double Bonds

Chembiochem : a European journal of chemical biology, Jan 21, 2015

Heronamides belong to a growing family of β-amino acid component containing polyketide macrolacta... more Heronamides belong to a growing family of β-amino acid component containing polyketide macrolactams (βPMs) with an unsaturated side chain. The biosynthetic gene cluster of heronamide F was identified from a deep-sea derived Streptomyces sp. SCSIO 03032. The involvement of the identified gene cluster in heronamide biosynthesis was confirmed by the functional characterization of the P450 enzyme HerO as an 8-hydroxylase tailoring heronamide biosynthesis. The presence of migrated double bonds in the conjugated diene containing side chain of heronamides were confirmed by feeding experiments with labelled small carboxylic acid molecules. This study represents the first demonstration of migrated double bonds in βPMs with an unsaturated side chain.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Brightness preserving video contrast enhancement using S-shaped Transfer function

2013 Visual Communications and Image Processing (VCIP), 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Using JPEG and JPEG2000 compressions for fast image quality metrics based on free energy theory

2014 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Bayesian Error Concealment With DCT Pyramid for Images

ABSTRACT In this paper, the problem of concealing missing image blocks is casted into a framework... more ABSTRACT In this paper, the problem of concealing missing image blocks is casted into a framework of Bayesian estimation. The conditional expectation of the missing block vector is taken over a pilot vector of correctly decoded pixels near the missing block. Multiple observations of the missing vector and pilot vectors obtained in a neighborhood are used to approximate the expectation. We design a multiscale estimation approach with discrete cosine transform pyramid to improve estimation efficiency. The DC image of the missing block is recovered first, and then more details related to high-frequency AC coefficients are recovered successively. Moreover, the algorithm operates in an iterative mode through using estimated block to refine the searching process for the next estimation. The algorithm is found to perform very well for a wide range of block loss rates. Substantial improvement over 14 existing error concealment (inclusive of inpainting) algorithms on various images is demonstrated in our extensive experiments, under different test conditions inclusive of high-loss rates and large block sizes.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A cooperative multicast strategy based on spatial diversity with power constraint

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Identification of the Polyketide Biosynthetic Machinery for the Indolizidine Alkaloid Cyclizidine

Organic letters, Jan 16, 2015

The cyclizidine biosynthetic gene cluster was identified from Streptomyces NCIB 11649, which reve... more The cyclizidine biosynthetic gene cluster was identified from Streptomyces NCIB 11649, which revealed the polyketide biosynthetic machinery for cyclizidine alkaloid biosynthesis. Both in vivo mutagenesis study and in vitro biochemical analysis provided insight into the timing and mechanism of the biosynthetic enzymes that produce cyclizidine-type indolizidine alkaloids.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of An improved contrast-tone mapping algorithm for image contrast enhancement

2011 8th International Conference on Information, Communications & Signal Processing, 2011

In this paper, an improved image contrast enhancement algorithm extending the existing contrast-t... more In this paper, an improved image contrast enhancement algorithm extending the existing contrast-tone mapping framework is proposed. The proposed method improves the existing algorithm with new definition of image contrast and novel constraints to the optimization. Experimental results demonstrate that the proposed Improved Optimal Contrast-tone Mapping (IOCTM) algorithm outperforms existing histogram equalization based method as well as existing OCTM method.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Bacterial genome mining of enzymatic tools for alkyne biosynthesis

ACS chemical biology, Jan 6, 2015

The alkyne is an important functionality widely used in material science, pharmaceutical science,... more The alkyne is an important functionality widely used in material science, pharmaceutical science, and chemical biology, but the importance of this functionality is contrasted by the very limited number of enzymes known to be involved in alkyne biosynthesis. We recently reported the first known carrier protein-dependent pathway for terminal alkyne formation, and in silico analysis suggested that this mechanism could be widespread in bacteria. In this paper, we screened additional homologous gene cassettes presumed to be involved in alkyne biosynthesis using both in vitro biochemical study and an E. coli-polyketide synthase (PKS) reporting system for in vivo analysis. We discovered and characterized a new terminal alkyne biosynthetic pathway comprised of TtuA, B, and C from Teredinibacter turnerae T7901. While the acyl-CoA ligase homolog (TtuA) demonstrated promiscuity in the activation and loading of medium-chain fatty acids onto the carrier protein (TtuC), the desaturase homolog (Tt...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Image denoising using local tangent space alignment

Proceedings of SPIE - The International Society for Optical Engineering

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Preparation and performance of a novel graphene oxide sheets modified rare-earth luminescence material

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Reduced Graphene Oxide/ZnO Composites and Its High Photocatalytic Activity for Degradation of Methylene Blue

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Ammonia stimulates growth and nitrite-oxidizing activity of Nitrobacter winogradskyi

Biotechnology, biotechnological equipment, Jan 2, 2014

The aim of this study was to obtain a nitrite-oxidizing bacterium with high nitrite oxidation act... more The aim of this study was to obtain a nitrite-oxidizing bacterium with high nitrite oxidation activity for controlling nitrite levels. A nitrite-oxidizing bacterium, ZS-1, was isolated from the water of a coastal Pseudosciaena crocea-rearing pond. The strain was identified as Nitrobacter winogradskyi based on the phylogenetic analyses of the 16S ribosomal ribonucleic acid gene and nxrA sequence of ZS-1. Under aerobic condition, the nitrite-oxidizing activity of ZS-1 did not change considerably in the range of pH 7-9, but was strongly inhibited by lower (pH = 6) and higher (pH = 10) pH values. The optimum temperature range is 25-32 °C. Lower temperature made the adaptive phase of ZS-1 longer but did not affect its maximum nitrite oxidization rate. The nitrite-oxidizing activity of ZS-1 started to be inhibited by ammonia and nitrate when the concentrations of ammonia and nitrate reached 25 mg L(-1) and 100 mg L(-1), respectively. The inhibition was stronger with higher concentration o...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The Performance Analysis of Coded Cache in Wireless Fading Channel

The rapid growth of data volume and the accompanying congestion problems over the wireless networ... more The rapid growth of data volume and the accompanying congestion problems over the wireless networks have been critical issues to content providers. A novel technique, termed as coded cache, is proposed to relieve the burden. Through creating coded-multicasting opportunities, the coded-cache scheme can provide extra performance gain over the conventional push technique that simply pre-stores contents at local caches during the network idle period. But existing works on the coded caching scheme assumed the availability of an error-free shared channel accessible by each user. This paper considers the more realistic scenario where each user may experience different link quality. In this case, the system performance would be restricted by the user with the worst channel condition. And the corresponding resource allocation schemes aimed at breaking this obstacles are developed. Specifically, we employ the coded caching scheme in time division and frequency division transmission mode and f...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of An Interpolation Based Channel Estimation Method for MIMO OFDM Systems

2008 IEEE 68th Vehicular Technology Conference, 2008

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Rapid production of a bulk of porous mesh reduced graphene oxide films using a naked flame

J. Mater. Chem. C, 2015

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Robust Region-of-Interest Scalable Coding with Leaky Prediction in H.264/AVC

2007 IEEE Workshop on Signal Processing Systems, 2007

Bookmarks Related papers MentionsView impact

Research paper thumbnail of 318620 Characterization of the Biosynthetic Pathway of Physostigmine

Physostigmine is a tryptophan-derived natural product with a rare pyrroloindole skeleton. Because... more Physostigmine is a tryptophan-derived natural product with a rare pyrroloindole skeleton. Because of its ability to reversibly inhibit acetylcholinesterase, physostigmine has been used to treat a variety of neurological disorders, including glaucoma and Alzheimer’s disease. However, despite its medicinal uses, little is known about the biosynthesis of physostigmine and pyrroloindole alkaloids in general. In this work, we identified the biosynthetic gene cluster for physostigmine in the producer, Streptomyces griseofuscus, and confirmed its function by heterologous expression. Gene deletion mutants and in vitro assays with purified enzymes further enabled us to identify the set of enzymes essential for physostigmine biosynthesis and propose an enzymatic pathway for the transformation of tryptophan into physostigmine. We find that the formation of the pyrroloindole skeleton proceeds by an unexpected N-acetylated intermediate that is necessary for methylation of C-3 of the indole ring ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Incorporating TCP Acknowledgements in MAC Layer in IEEE 802.11 Multihop Ad Hoc Networks

GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Modeling TCP Throughput in IEEE 802.11 Based Wireless Ad Hoc Networks

6th Annual Communication Networks and Services Research Conference (cnsr 2008), 2008

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of CyberC10 code

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Characterization of Heronamides Biosynthesis Reveals a Tailoring Hydroxylase and Indicates Migrated Double Bonds

Chembiochem : a European journal of chemical biology, Jan 21, 2015

Heronamides belong to a growing family of β-amino acid component containing polyketide macrolacta... more Heronamides belong to a growing family of β-amino acid component containing polyketide macrolactams (βPMs) with an unsaturated side chain. The biosynthetic gene cluster of heronamide F was identified from a deep-sea derived Streptomyces sp. SCSIO 03032. The involvement of the identified gene cluster in heronamide biosynthesis was confirmed by the functional characterization of the P450 enzyme HerO as an 8-hydroxylase tailoring heronamide biosynthesis. The presence of migrated double bonds in the conjugated diene containing side chain of heronamides were confirmed by feeding experiments with labelled small carboxylic acid molecules. This study represents the first demonstration of migrated double bonds in βPMs with an unsaturated side chain.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Brightness preserving video contrast enhancement using S-shaped Transfer function

2013 Visual Communications and Image Processing (VCIP), 2013

Bookmarks Related papers MentionsView impact