Dezhi Chen - Academia.edu (original) (raw)

Papers by Dezhi Chen

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

Novel RGO–hematite nanocomposites have been successfully fabricated using a surfactant-governed a... more Novel RGO–hematite nanocomposites have been successfully fabricated using a surfactant-governed approach in the presence of polyvinylpyrrolidone (PVP) under mild wet chemical conditions (105 °C). A series of characterization methods including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the as-prepared single-crystal hematite particles with relatively uniform size are embedded in RGO layers to form unique quasi shell–core nanostructures. The microwave absorption properties of the RGO–hematite composites were studied in detail; as an absorber, the RGO–hematite nanocomposites possess excellent microwave absorbing properties. The enhanced microwave absorbing properties were also explained based on the structures of the nanocomposites.

Aerial Remote Sensing (Aerial RS) image compression & transmission on-board system, not only is t... more Aerial Remote Sensing (Aerial RS) image compression & transmission on-board system, not only is the core of Aerial RS supervising, but also the key technology about the security of data obtainment. The requirement of Aerial RS is stricter on the data quality and security. If we transmit the images through some special channels while the images are obtained during the task of Aerial RS, the control center on the ground could acquire the status of the whole Aerial RS system. Besides, it could also backup the images immediately. Image compression & transmission system is the important bridge between the Aerial RS system on-board and the control center. The research group of Aerial RS data processing in Peking University, integrates all the necessary technologies including compression algorithm & hardware, integration of function modules, protocol of data packing & unpacking. The research group has developed an efficient compression method that has been optimized both in software struct...

Lecture Notes in Computer Science, 2007

Neural network approaches for time series forecasting, which have the property of simpleness, non... more Neural network approaches for time series forecasting, which have the property of simpleness, nonlinearity and effectiveness, have been broadly utilized in many domains. In this paper, an improved training algorithm of back-propagation neural network for time series forecasting by using dynamic learning rate in the training process is proposed. The results of some studied cases demonstrate this algorithm can increase the efficiency of neural network training and the precision of forecasts.

Proceedings. 2005 IEEE International Geoscience and Remote Sensing Symposium, 2005. IGARSS '05., 2005

In this paper, we propose strategies for road extraction from high-resolution satellite images, w... more In this paper, we propose strategies for road extraction from high-resolution satellite images, which combine automatic and semi-automatic methods. It performs road extraction according to following steps: firstly, extracting road automatically in Region Defined by User (RDU); secondly, if the result of automatic extraction is acceptable, repeating the first step in another RDU, if not, performing semi-automatic road extraction; thirdly,

Proceedings. 2005 IEEE International Geoscience and Remote Sensing Symposium, 2005. IGARSS '05., 2005

Proceedings. 2005 IEEE International Geoscience and Remote Sensing Symposium, 2005. IGARSS '05., 2005

Arable land protection has been a global hotspot, because how can we exploit arable-land resource... more Arable land protection has been a global hotspot, because how can we exploit arable-land resources is an important topic for the regional future socio-economic stability and sustainable development in China. Managing and monitoring the change of arable-land on quantity and quality can provide the background and foundation information. The paper starts with the introduction of the necessity to monitor the

2006 12th Biennial IEEE Conference on Electromagnetic Field Computation, 2006

A new semi-analytical method, subregion expansion method (SEM), is presented for computational el... more A new semi-analytical method, subregion expansion method (SEM), is presented for computational electromagnetics. In this scheme, the entire field domain is divided into subregions; in each subregion, a semi-analytical expansion is constructed to approximate the solution. Then all these subregions are jointed together at the fictitious boundaries, and all the boundary conditions are satisfied to determine the coefficients of the

2009 International Conference on Energy and Environment Technology, 2009

This paper analyses the stator teeth geometry effects on cogging force of permanent magnet linear... more This paper analyses the stator teeth geometry effects on cogging force of permanent magnet linear generators. The method making translator adjacent sides' permanent magnet allotropic is proposed to minimize the cogging force of four sided permanent magnet linear generators. The dynamic modeling of the generator's performance is based on finite element method. The generator is coupled to a particular mechanical system for sea wave energy extraction applications. The methodology involves minimization of cogging force through analysis the relationship between cogging force and relative position of permanent magnet on adjacent sides.

2010 International Conference on Power System Technology, 2010

The voltage and reactive power is controlled by both double-fed induction generator of constant v... more The voltage and reactive power is controlled by both double-fed induction generator of constant voltage-control and SVC in wind farms. Firstly in this paper, the voltage and reactive power control principles of constant voltage-control double-fed induction generator and SVC are analyzed; secondly, mechanism analysis of coordination control was studied; finally, optimal control model of two devices was obtained through differential

ChemPlusChem, 2013

ABSTRACT Novel α-MnS hollow spheres (MHSs) have been fabricated successfully by a one-pot templat... more ABSTRACT Novel α-MnS hollow spheres (MHSs) have been fabricated successfully by a one-pot template-free solvothermal method. The as-synthesized α-MnS spheres have diameters of about 3–5 μm and porous shells of thickness about 0.5 μm composed of numerous nanocrystals. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption. Time-dependent morphology evolution suggested that transformation of chemical components and Ostwald ripening play vital roles for these hollow structures with a porous shell. The possible formation mechanism for the fabrication of MHSs is proposed. Meanwhile, MHS–reduced graphene oxide (RGO) hybrids have been prepared in the presence of graphene oxide (GO) by using the same procedure. The amount of GO can affect the morphology of α-MnS crystals in hybrids. The microwave absorption and lithium storage properties of the pure MHSs and MHS–RGO hybrids were studied in detail. Compared with pristine MHSs, the MHS–RGO hybrids possess remarkably enhanced microwave absorption and lithium storage properties. The enhanced microwave absorbing and electrochemical properties are also explained.

IEEE International IEEE International IEEE International Geoscience and Remote Sensing Symposium, 2004. IGARSS '04. Proceedings. 2004, 2004

In this paper, we present a novel semi-fragile watermarking scheme based on wavelet packet. The m... more In this paper, we present a novel semi-fragile watermarking scheme based on wavelet packet. The method in the paper includes four parts: first, to produce watermark; second, to scramble watermarking image; third, to embed watermark; last, to inspect and locate tampered marked image. To inspect whether including watermark in an image with the key attained from process of embedding watermarking.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

ACS applied materials & interfaces, Jan 10, 2014

Although numerous kinds of waterborne, nacre-mimetic films with excellent properties have been fa... more Although numerous kinds of waterborne, nacre-mimetic films with excellent properties have been fabricated via different assembly methods, it remains difficult to put those kinds of lightweight materials into practical applications because they are sensitive to water in the environment. Herein, a simple superhydrophobic modification method was used to enhance the repellency of film to water and/or corrosive liquids in the environment. Furthermore, it lowered the gas transmission rate of the films dramatically and improved the heat and flame shield capabilities. This approach could also be applied to other kinds of nacre-mimetic films, proving to be a versatile, low-cost, fast, and facile method to produce large-area and thick, waterborne, multifunctional films with excellent repellency to water and some corrosive liquids in the environment, which will pave the road for the practical applications of nacre-mimetic films.

Dalton transactions (Cambridge, England : 2003), Jan 7, 2012

Olivine-structured LiMnPO(4) with 3D foldaway-lantern-like hierarchical structures have been prep... more Olivine-structured LiMnPO(4) with 3D foldaway-lantern-like hierarchical structures have been prepared via a one-step, template-free, solvothermal approach in ethylene glycol. The foldaway-lantern-like LiMnPO(4) microstructures are composed of numerous nanoplates with thickness of about 20 nm. A series of electron microscopy characterization results indicate that the obtained primary LiMnPO(4) nanoplates are single crystalline in nature, growing along the [010] direction in the (100) plane. Time-dependent morphology evolution suggests that ethylene glycol plays dual roles in oriented growth and self-assembly of such unique structures. After carbon coating, the as-prepared LiMnPO(4) cathode demonstrated a flat potential at 4.1 V versus Li/Li(+) with a specific capacity close to 130 mA h g(-1) at 0.1 C, along with excellent cycling stability.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

… and Systems, 2008. …, 2008

... And some key geometrical feature such as the pole edge is parameterized. After the simulation... more ... And some key geometrical feature such as the pole edge is parameterized. After the simulation by TOSCA solver, the ... The TOSCA simulated average magnetic field during iterations and the required isochronous field is shown in fig. ...

Journal of Polymer Science Part A-polymer Chemistry - J POLYM SCI A-POLYM CHEM, 2007

Physica E: Low-dimensional Systems and Nanostructures, 2014

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

Novel RGO–hematite nanocomposites have been successfully fabricated using a surfactant-governed a... more Novel RGO–hematite nanocomposites have been successfully fabricated using a surfactant-governed approach in the presence of polyvinylpyrrolidone (PVP) under mild wet chemical conditions (105 °C). A series of characterization methods including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the as-prepared single-crystal hematite particles with relatively uniform size are embedded in RGO layers to form unique quasi shell–core nanostructures. The microwave absorption properties of the RGO–hematite composites were studied in detail; as an absorber, the RGO–hematite nanocomposites possess excellent microwave absorbing properties. The enhanced microwave absorbing properties were also explained based on the structures of the nanocomposites.

Aerial Remote Sensing (Aerial RS) image compression & transmission on-board system, not only is t... more Aerial Remote Sensing (Aerial RS) image compression & transmission on-board system, not only is the core of Aerial RS supervising, but also the key technology about the security of data obtainment. The requirement of Aerial RS is stricter on the data quality and security. If we transmit the images through some special channels while the images are obtained during the task of Aerial RS, the control center on the ground could acquire the status of the whole Aerial RS system. Besides, it could also backup the images immediately. Image compression & transmission system is the important bridge between the Aerial RS system on-board and the control center. The research group of Aerial RS data processing in Peking University, integrates all the necessary technologies including compression algorithm & hardware, integration of function modules, protocol of data packing & unpacking. The research group has developed an efficient compression method that has been optimized both in software struct...

Lecture Notes in Computer Science, 2007

Neural network approaches for time series forecasting, which have the property of simpleness, non... more Neural network approaches for time series forecasting, which have the property of simpleness, nonlinearity and effectiveness, have been broadly utilized in many domains. In this paper, an improved training algorithm of back-propagation neural network for time series forecasting by using dynamic learning rate in the training process is proposed. The results of some studied cases demonstrate this algorithm can increase the efficiency of neural network training and the precision of forecasts.

Proceedings. 2005 IEEE International Geoscience and Remote Sensing Symposium, 2005. IGARSS '05., 2005

In this paper, we propose strategies for road extraction from high-resolution satellite images, w... more In this paper, we propose strategies for road extraction from high-resolution satellite images, which combine automatic and semi-automatic methods. It performs road extraction according to following steps: firstly, extracting road automatically in Region Defined by User (RDU); secondly, if the result of automatic extraction is acceptable, repeating the first step in another RDU, if not, performing semi-automatic road extraction; thirdly,

Proceedings. 2005 IEEE International Geoscience and Remote Sensing Symposium, 2005. IGARSS '05., 2005

Proceedings. 2005 IEEE International Geoscience and Remote Sensing Symposium, 2005. IGARSS '05., 2005

Arable land protection has been a global hotspot, because how can we exploit arable-land resource... more Arable land protection has been a global hotspot, because how can we exploit arable-land resources is an important topic for the regional future socio-economic stability and sustainable development in China. Managing and monitoring the change of arable-land on quantity and quality can provide the background and foundation information. The paper starts with the introduction of the necessity to monitor the

2006 12th Biennial IEEE Conference on Electromagnetic Field Computation, 2006

A new semi-analytical method, subregion expansion method (SEM), is presented for computational el... more A new semi-analytical method, subregion expansion method (SEM), is presented for computational electromagnetics. In this scheme, the entire field domain is divided into subregions; in each subregion, a semi-analytical expansion is constructed to approximate the solution. Then all these subregions are jointed together at the fictitious boundaries, and all the boundary conditions are satisfied to determine the coefficients of the

2009 International Conference on Energy and Environment Technology, 2009

This paper analyses the stator teeth geometry effects on cogging force of permanent magnet linear... more This paper analyses the stator teeth geometry effects on cogging force of permanent magnet linear generators. The method making translator adjacent sides' permanent magnet allotropic is proposed to minimize the cogging force of four sided permanent magnet linear generators. The dynamic modeling of the generator's performance is based on finite element method. The generator is coupled to a particular mechanical system for sea wave energy extraction applications. The methodology involves minimization of cogging force through analysis the relationship between cogging force and relative position of permanent magnet on adjacent sides.

2010 International Conference on Power System Technology, 2010

The voltage and reactive power is controlled by both double-fed induction generator of constant v... more The voltage and reactive power is controlled by both double-fed induction generator of constant voltage-control and SVC in wind farms. Firstly in this paper, the voltage and reactive power control principles of constant voltage-control double-fed induction generator and SVC are analyzed; secondly, mechanism analysis of coordination control was studied; finally, optimal control model of two devices was obtained through differential

ChemPlusChem, 2013

ABSTRACT Novel α-MnS hollow spheres (MHSs) have been fabricated successfully by a one-pot templat... more ABSTRACT Novel α-MnS hollow spheres (MHSs) have been fabricated successfully by a one-pot template-free solvothermal method. The as-synthesized α-MnS spheres have diameters of about 3–5 μm and porous shells of thickness about 0.5 μm composed of numerous nanocrystals. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption. Time-dependent morphology evolution suggested that transformation of chemical components and Ostwald ripening play vital roles for these hollow structures with a porous shell. The possible formation mechanism for the fabrication of MHSs is proposed. Meanwhile, MHS–reduced graphene oxide (RGO) hybrids have been prepared in the presence of graphene oxide (GO) by using the same procedure. The amount of GO can affect the morphology of α-MnS crystals in hybrids. The microwave absorption and lithium storage properties of the pure MHSs and MHS–RGO hybrids were studied in detail. Compared with pristine MHSs, the MHS–RGO hybrids possess remarkably enhanced microwave absorption and lithium storage properties. The enhanced microwave absorbing and electrochemical properties are also explained.

IEEE International IEEE International IEEE International Geoscience and Remote Sensing Symposium, 2004. IGARSS '04. Proceedings. 2004, 2004

In this paper, we present a novel semi-fragile watermarking scheme based on wavelet packet. The m... more In this paper, we present a novel semi-fragile watermarking scheme based on wavelet packet. The method in the paper includes four parts: first, to produce watermark; second, to scramble watermarking image; third, to embed watermark; last, to inspect and locate tampered marked image. To inspect whether including watermark in an image with the key attained from process of embedding watermarking.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

ACS applied materials & interfaces, Jan 10, 2014

Although numerous kinds of waterborne, nacre-mimetic films with excellent properties have been fa... more Although numerous kinds of waterborne, nacre-mimetic films with excellent properties have been fabricated via different assembly methods, it remains difficult to put those kinds of lightweight materials into practical applications because they are sensitive to water in the environment. Herein, a simple superhydrophobic modification method was used to enhance the repellency of film to water and/or corrosive liquids in the environment. Furthermore, it lowered the gas transmission rate of the films dramatically and improved the heat and flame shield capabilities. This approach could also be applied to other kinds of nacre-mimetic films, proving to be a versatile, low-cost, fast, and facile method to produce large-area and thick, waterborne, multifunctional films with excellent repellency to water and some corrosive liquids in the environment, which will pave the road for the practical applications of nacre-mimetic films.

Dalton transactions (Cambridge, England : 2003), Jan 7, 2012

Olivine-structured LiMnPO(4) with 3D foldaway-lantern-like hierarchical structures have been prep... more Olivine-structured LiMnPO(4) with 3D foldaway-lantern-like hierarchical structures have been prepared via a one-step, template-free, solvothermal approach in ethylene glycol. The foldaway-lantern-like LiMnPO(4) microstructures are composed of numerous nanoplates with thickness of about 20 nm. A series of electron microscopy characterization results indicate that the obtained primary LiMnPO(4) nanoplates are single crystalline in nature, growing along the [010] direction in the (100) plane. Time-dependent morphology evolution suggests that ethylene glycol plays dual roles in oriented growth and self-assembly of such unique structures. After carbon coating, the as-prepared LiMnPO(4) cathode demonstrated a flat potential at 4.1 V versus Li/Li(+) with a specific capacity close to 130 mA h g(-1) at 0.1 C, along with excellent cycling stability.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

… and Systems, 2008. …, 2008

... And some key geometrical feature such as the pole edge is parameterized. After the simulation... more ... And some key geometrical feature such as the pole edge is parameterized. After the simulation by TOSCA solver, the ... The TOSCA simulated average magnetic field during iterations and the required isochronous field is shown in fig. ...

Journal of Polymer Science Part A-polymer Chemistry - J POLYM SCI A-POLYM CHEM, 2007

Physica E: Low-dimensional Systems and Nanostructures, 2014