YI CHENG - Academia.edu (original) (raw)

Papers by YI CHENG

Eur. Phys. J. …, 2006

The photoionization cross-section and number density of the P 1/2,3/2 excited levels of sodium ha... more The photoionization cross-section and number density of the P 1/2,3/2 excited levels of sodium have been measured as a function of the laser energy using two-step laser excitation in conjunction with a thermionic diode working in the space charge limited mode. ...

We evaluated the adequacy of computational algorithms as models of human face p r ocessing by loo... more We evaluated the adequacy of computational algorithms as models of human face p r ocessing by looking at how the algorithms and humans process individual faces. By comparing model-and human-generated m e asures of the similarity between pairs of faces, we were able to assess the accord b etween several automatic face recognition algorithms and human perceivers. Multidimensional scaling MDS was used t o c r ea t e a s p atial representation of the subject response patterns. Next, the model response patterns were p r ojected into this space. The results revealed a c ommon bimodal structure for both the subjects and for most of the models. The bimodal subject structure r e ected strategy di erences in making similarity decisions. For the models, the bimodal structure was related t o c ombined aspects of the representations and the distance metrics used i n the implementations.

Physics Letters A, 1991

By constraining the potential of the Kadomtsev-Petviashvili (KP) equation to its co-invariants ex... more By constraining the potential of the Kadomtsev-Petviashvili (KP) equation to its co-invariants expressed in terms of the squared eigenfunctions, the KP equation is reduced to a (1 + 1)-dimensional system consisting of the generalized multicomponent nonlinear Schrödinger and ...

We present a systematic approach to the construction of soliton solutions for the 5reduction of t... more We present a systematic approach to the construction of soliton solutions for the 5reduction of the C-type sub-hierarchy for the Kadomtsev-Petviashvili(CKP) hierarchies starting from the general τ-function τ (n+k) of the Kadomtsev-Petviashvili (KP) hierarchy. We obtain the one-soliton and two-soliton solutions for the bi-directional Kaup-Kupershmidt (bKK) equation, i.e. the 5-reduction of CKP hierarchy.

Journal of molecular …, 2002

The bacterial toxin ColE7 contains an H–N–H endonuclease domain (nuclease ColE7) that digests cel... more The bacterial toxin ColE7 contains an H–N–H endonuclease domain (nuclease ColE7) that digests cellular DNA or RNA non-specifically in target cells, leading to cell death. In the host cell, protein Im7 forms a complex with ColE7 to inhibit its nuclease activity. Here, we present the ...

Engineering in Medicine and …, 2005

This study uses an FPGA to perform high-speed DNA sequence matching as an alternative to using ge... more This study uses an FPGA to perform high-speed DNA sequence matching as an alternative to using general purpose computer CPUs. The FPGA is programmed using the Verilog HDL and interfaced using a graphical user interface programmed in JAVA. Design overviews and details for a small scale design are given as well as plans for larger scale expansion. Encouraging results of the small scale model currently in production are also provided. Results of a successful match and no match are shown.

Numerical simulation of fully developed hydrodynamics of a riser and a downer was carried out usi... more Numerical simulation of fully developed hydrodynamics of a riser and a downer was carried out using an Eulerian-Lagrangian model, where the particles are modeled by the discrete element method (DEM) and the gas by the Navier-Stokes equations. Periodic flow domain with two side walls was adopted to simulate the fully developed dynamics in a 2D channel of 10 cm in width. All the simulations were carried out under the same superficial gas velocity and solids holdup in the domain, starting with a homogenous state for both gas and solids, and followed by the evolution of the dynamics to the heterogeneous state with distinct clustering in the riser and the downer. In the riser, particle clusters move slowly, tending to suspend along the wall or to flow downwards, which causes wide residence time distribution of the particles. In the downer, clusters still exist, but they have faster velocities than the discrete particles. Loosely collected particles in the clusters move in the same direction as the bulk flow, resulting in plug flow in the downer. The residence time distribution (RTD) of solids was computed by tracking the displacements of all particles in the flow direction. The results show a rather wide RTD for the solids in the riser but a sharp peak RTD in the downer, much in agreement with the experimental findings in the literature. The ensemble average of transient dynamics also shows reasonable profiles of solids volume fraction and solids velocity, and their dependence on particle density.

The pulsing of argon in a temporal analysis of products (TAP) reactor and reactor modeling of the... more The pulsing of argon in a temporal analysis of products (TAP) reactor and reactor modeling of the response curves were used to measure the effective intraparticle diffusivities in porous materials. The diffusivity that can be measured is limited: (1) at the low end by intraparticle diffusion being too slow such that just a small fraction of the pulse gets into

A series of Ag-doped manganese oxide octahedral molecular sieves (OMS-2) were synthesized by the ... more A series of Ag-doped manganese oxide octahedral molecular sieves (OMS-2) were synthesized by the reflux method in an acid medium. The structure of the catalysts was characterized by X-ray diffraction, N 2 adsorption, transmission electron microscopy, and temperature-programmed desorption (TPD). The effect of the promoter Ag was deduced. The results showed that the catalysts have the typical cryptomelane structure with a one-dimensional channel. The doping with Ag resulted in Ag/OMS-2 catalysts with a higher specific surface area and narrower pore size distribution than OMS-2. The catalysts showed excellent catalytic activity for CO oxidation and the catalytic activity was increased after Ag introduction. O 2-TPD and CO-TPD results showed that this was because the doping with Ag increased the rate of CO adsorption and the diffusion of lattice oxygen ions.

ABSTRACT Industrial trials detailed in a riser−downer coupling reactor proposed for the fluid cat... more ABSTRACT Industrial trials detailed in a riser−downer coupling reactor proposed for the fluid catalytic cracking (FCC) process are presented in this paper. The trials are based on the fundamental research of hydrodynamics, mixing behaviors, and laboratory-scale hot experiments described in our previous investigations. Compared with the riser reactor with the same feeds and catalyst, the LPG and propylene yield increased by 8.15 and 4.30 wt %, respectively. The gasoline octane number likewise reached 94.8 with 28 wt % olefin content. However, dry gas is significantly suppressed, and the coke has little change in yield even with the increased catalyst to oil ratio. With some gasoline recycling, the LPG and propylene yield increased by 11.45 and 5.06 wt %, respectively, and the olefin content in gasoline significantly decreased to 22 wt %; the high octane number (95.4) is maintained. The computational fluid dynamics (CFD) coupled with a 6-lump kinetic model is also applied to simulate the FCC process for the industrial trials. The yield of propylene and butylene and the temperature profile along the axis direction demonstrated consistency between the simulation results and the experimental data.

ABSTRACT Coal pyrolysis to acetylene in thermal plasma provides a direct route to make chemicals ... more ABSTRACT Coal pyrolysis to acetylene in thermal plasma provides a direct route to make chemicals from coal resources, where the rapid heating and release of volatile matters in coal particles play the dominant role in the overall reactor performance. A mechanism model incorporating the heat conduction in solid materials, diffusion of released volatile gases, and reactions was proposed for a deep understanding of the heat transport inside a coal particle under extreme environmental conditions such as high temperatures greater than 2000 K and milliseconds of reaction time. The two competing rates model, known as the Kobayashi model, was applied to describe the devolatilization kinetics, which was verified by comparing the predicted yield of volatiles with the experimental data in the literature. Thermal balance between coal particles and the hot carrier gas was established, and the four influencing factors including the heating rate, particle size, reactants flow ratio, and heat of devolatilization were paid attention when analyzing the heating profile inside the particles and the yield of volatiles. The results showed that the inherent resistance due to the volatiles released from coal particles seriously impeded the thermal energy transportation from heating gas to the particle. This led to a weakened heating rate, i.e., a long heating up time, and thereafter a low yield of volatiles, especially when the particle size was large (e.g., >40 μm). Meanwhile, the heat conduction inside the coal particle also imposed additional resistance to reduce the heat transportation rate from heating gas to the particle, especially when the particle size was larger than 80 μm. The predicted yield of volatiles considering the mechanism of the two resistances agreed reasonably with the reported experimental data under different operating conditions but was smaller than that which could be obtained when neither resistance is considered. It can be concluded that the proposed heat transport mechanism inside coal particles works well in understanding the coal pyrolysis process at ultrahigh temperatures.

ABSTRACT The gas–solid flows in a two-dimensional downer of 10 m in height and 0.10 m in width we... more ABSTRACT The gas–solid flows in a two-dimensional downer of 10 m in height and 0.10 m in width were simulated using a CFD–DEM method, where the motion of particles was modeled by discrete element method (DEM) and the gas flow was described by Navier–Stokes equations. The simulations revealed a rich variety of developing flow structures in the downer under different operating conditions. The two-phase flow development can be clearly characterized by the micro-scale particle distributions in the downer. Near the inlet, the particle distribution is dominated by the distributor design. Then, the particles disperse in the column, forming a homogeneous transit region. After that clusters start to form and modulate the gas–solid flow field till the fully-developed state. The particle-scale simulation disclosed that the clusters are composed of loosely collected particles, and these particles have the same flow direction as the bulk flow so that no particle backmixing can be observed. As the particles in the downer have the tendency to maintain the inertia, the capability of lateral transfer of particles is relatively weak, which was illustrated by tracking the movement of the single particles and clusters. The simulations of the inlet effect on the hydrodynamics in the downer showed that the gas–solid flow structure and the mixing behavior are sensitive to the inlet design. An inappropriate design or operation would probably cause the undesired flow phenomena such as the wide distribution of residence times. The time-averaged hydrodynamics based on the transient simulations showed good agreement with the experimental findings in the literature. The simulation based on the CFD–DEM coupled approach provides a theoretical way to comprehensively understand the physics at micro- to macro-scales in the co-currently downward gas–solid flows.

A series of Ag-doped manganese oxide catalyst were synthesized by the reflux method in an acid me... more A series of Ag-doped manganese oxide catalyst were synthesized by the reflux method in an acid medium. The surface structure of the catalysts was characterized by N 2 adsorption, XRD and TEM experiments. The catalysts showed excellent catalytic activity for CO oxidation. The adsorption and oxidation of CO on a 1.0% Ag/MnO x catalyst between 393 and 493 K were studied by means of single pulse experiments in a TAP reactor. The adsorption of CO was reversible at these temperatures and CO 2 was formed in an oxidation reaction of CO and lattice oxygen. Curve fitting to the experimental TAP response curves of the reactant and product was used to determine the kinetic parameters for the elementary steps. The activation energies were 83 kJ/mol for CO desorption, 31 kJ/mol for CO 2 desorption, and 116 kJ/mol for the surface CO oxidation by lattice oxygen. In addition, the effect of coadsorbed O 2 on CO adsorption was studied by the TAP technique. Below 353 K, there was a sharp increase, by about one order of magnitude, in the rate constant of CO adsorption promoted by the presence of coadsorbed O 2 .

Many different configurations of the inlet and outlet in the risers have been studied. According ... more Many different configurations of the inlet and outlet in the risers have been studied. According to their effects on the structure of gas-solids two-phase llow, the inlet and outlet effects can be classified as the restriction on the solids circulation flow and the arrangement of open area. Both of them inltuence the axial and radial distributions of bed voidage seriously. Since hydrodynamics at the bottom and top sections in risers depend strongly on the inlet and outlet configurations, the effects of inlet and outlet must be considered carefully when modeling riser flows. It is important to design the riser conligurations at the inlet and outlet to meet overall processes design requirements.

Downer reactor, in which gas and solids move downward co-currently, has unique features such as t... more Downer reactor, in which gas and solids move downward co-currently, has unique features such as the plug-flow reactor performance and relatively uniform flow structure compared to other gas-solids fluidized bed reactors, e.g., bubbling bed, turbulent bed and riser. Downer is therefore acknowledged as a novel multiphase flow reactor with great potential in high-severity operated processes, such as the high temperature, ultra-short contact time reactions with the intermediates as the desired products. Typical process developments in industry have directed to (1) the new-generation refinery process for cracking of heavier feedstock to gasoline and light olefins (e.g., propylene) as by-products; and (2) coal pyrolysis in hydrogen plasma which opens up a direct means for producing acetylene, i.e., a new route to synthesize chemicals from a clean coal utilization process. This paper is to give a comprehensive review on the development of fundamental researches on downer reactors as well as the particular industrial demonstrations for the fluid catalytic cracking (FCC) of heavy oils and coal pyrolysis in thermal plasma.

... Strategies for enzyme/prodrug cancer therapy. Clin Cancer Res, 2001, 7: 3314–3324. 6. Denny W... more ... Strategies for enzyme/prodrug cancer therapy. Clin Cancer Res, 2001, 7: 3314–3324. 6. Denny WA. Prodrug strategies in cancer therapy. ... Gene Ther, 2002, 9: 291–296. 8. Nuyts S, Van Mellaert L, Theys J, et al. Clostridium spores for tumor-specific drug delivery. ...

Current network infrastructures exhibit poor power efficiency, running network devices at full ca... more Current network infrastructures exhibit poor power efficiency, running network devices at full capacity all the time regardless of the traffic demand and distribution over the network. Most research on router power management are at component level or link level, treating routers as isolated devices. A complementary approach is to facilitate power management at network level by routing traffic through different paths to adjust the workload on individual routers or links. Given the high path redundancy and low link utilization in today's large networks, this approach can potentially allow more network devices or components to go into power saving mode. This paper proposes an intra-domain traffic engineering mechanism, GreenTE, which maximizes the number of links that can be put into sleep under given performance constraints such as link utilization and packet delay. Using network topologies and traffic data from several widearea networks, our evaluation shows that GreenTE can reduce line-cards' power consumption by 27% to 42% under constraints that the maximum link utilization is below 50% and the network diameter remains the same as in shortest path routing.

We report the first in situ quantitative visualization and characterization of electro-induced ch... more We report the first in situ quantitative visualization and characterization of electro-induced chitosan hydrogel growth in an aqueous environment. This was enabled with a pair of sidewall electrodes within a transparent fluidic system, which allowed us to resolve the electrogelling mechanism and interpret the dominant causes responsible for the formation and density distribution of the deposited hydrogel. The pH and the time-dependent growth profiles of the chitosan hydrogel were directly visualized, analyzed, and characterized. The results indicate that the gelation and immobilization of chitosan onto the cathode at a pH above its pK a value ($6.3) are due to the electrochemically generated concentration gradient of reactant OH À ions, and their subsequent neutralization of the NH 3 + groups of chitosan chains in solution near the cathode. The increased gel density around the fringes of the electrodes was demonstrated and correlated with the electrophoretic migration of chitosan cations during deposition. Simulation of the electric potential/field distribution, together with the corresponding dry film topography confirmed the non-uniform, electric field-dependent density distribution of deposited hydrogel. This report provides fundamental understanding towards the mechanism and the kinetics of the electro-induced chitosan gel formation. It also provides important guidelines for pursuing its application in bio-components integrated microsystems. The method in use exemplifies a simple, effective and non-destructive approach for in situ characterization of electro-responsive biopolymers in an aqueous environment.

Eur. Phys. J. …, 2006

The photoionization cross-section and number density of the P 1/2,3/2 excited levels of sodium ha... more The photoionization cross-section and number density of the P 1/2,3/2 excited levels of sodium have been measured as a function of the laser energy using two-step laser excitation in conjunction with a thermionic diode working in the space charge limited mode. ...

We evaluated the adequacy of computational algorithms as models of human face p r ocessing by loo... more We evaluated the adequacy of computational algorithms as models of human face p r ocessing by looking at how the algorithms and humans process individual faces. By comparing model-and human-generated m e asures of the similarity between pairs of faces, we were able to assess the accord b etween several automatic face recognition algorithms and human perceivers. Multidimensional scaling MDS was used t o c r ea t e a s p atial representation of the subject response patterns. Next, the model response patterns were p r ojected into this space. The results revealed a c ommon bimodal structure for both the subjects and for most of the models. The bimodal subject structure r e ected strategy di erences in making similarity decisions. For the models, the bimodal structure was related t o c ombined aspects of the representations and the distance metrics used i n the implementations.

Physics Letters A, 1991

By constraining the potential of the Kadomtsev-Petviashvili (KP) equation to its co-invariants ex... more By constraining the potential of the Kadomtsev-Petviashvili (KP) equation to its co-invariants expressed in terms of the squared eigenfunctions, the KP equation is reduced to a (1 + 1)-dimensional system consisting of the generalized multicomponent nonlinear Schrödinger and ...

We present a systematic approach to the construction of soliton solutions for the 5reduction of t... more We present a systematic approach to the construction of soliton solutions for the 5reduction of the C-type sub-hierarchy for the Kadomtsev-Petviashvili(CKP) hierarchies starting from the general τ-function τ (n+k) of the Kadomtsev-Petviashvili (KP) hierarchy. We obtain the one-soliton and two-soliton solutions for the bi-directional Kaup-Kupershmidt (bKK) equation, i.e. the 5-reduction of CKP hierarchy.

Journal of molecular …, 2002

The bacterial toxin ColE7 contains an H–N–H endonuclease domain (nuclease ColE7) that digests cel... more The bacterial toxin ColE7 contains an H–N–H endonuclease domain (nuclease ColE7) that digests cellular DNA or RNA non-specifically in target cells, leading to cell death. In the host cell, protein Im7 forms a complex with ColE7 to inhibit its nuclease activity. Here, we present the ...

Engineering in Medicine and …, 2005

This study uses an FPGA to perform high-speed DNA sequence matching as an alternative to using ge... more This study uses an FPGA to perform high-speed DNA sequence matching as an alternative to using general purpose computer CPUs. The FPGA is programmed using the Verilog HDL and interfaced using a graphical user interface programmed in JAVA. Design overviews and details for a small scale design are given as well as plans for larger scale expansion. Encouraging results of the small scale model currently in production are also provided. Results of a successful match and no match are shown.

Numerical simulation of fully developed hydrodynamics of a riser and a downer was carried out usi... more Numerical simulation of fully developed hydrodynamics of a riser and a downer was carried out using an Eulerian-Lagrangian model, where the particles are modeled by the discrete element method (DEM) and the gas by the Navier-Stokes equations. Periodic flow domain with two side walls was adopted to simulate the fully developed dynamics in a 2D channel of 10 cm in width. All the simulations were carried out under the same superficial gas velocity and solids holdup in the domain, starting with a homogenous state for both gas and solids, and followed by the evolution of the dynamics to the heterogeneous state with distinct clustering in the riser and the downer. In the riser, particle clusters move slowly, tending to suspend along the wall or to flow downwards, which causes wide residence time distribution of the particles. In the downer, clusters still exist, but they have faster velocities than the discrete particles. Loosely collected particles in the clusters move in the same direction as the bulk flow, resulting in plug flow in the downer. The residence time distribution (RTD) of solids was computed by tracking the displacements of all particles in the flow direction. The results show a rather wide RTD for the solids in the riser but a sharp peak RTD in the downer, much in agreement with the experimental findings in the literature. The ensemble average of transient dynamics also shows reasonable profiles of solids volume fraction and solids velocity, and their dependence on particle density.

The pulsing of argon in a temporal analysis of products (TAP) reactor and reactor modeling of the... more The pulsing of argon in a temporal analysis of products (TAP) reactor and reactor modeling of the response curves were used to measure the effective intraparticle diffusivities in porous materials. The diffusivity that can be measured is limited: (1) at the low end by intraparticle diffusion being too slow such that just a small fraction of the pulse gets into

A series of Ag-doped manganese oxide octahedral molecular sieves (OMS-2) were synthesized by the ... more A series of Ag-doped manganese oxide octahedral molecular sieves (OMS-2) were synthesized by the reflux method in an acid medium. The structure of the catalysts was characterized by X-ray diffraction, N 2 adsorption, transmission electron microscopy, and temperature-programmed desorption (TPD). The effect of the promoter Ag was deduced. The results showed that the catalysts have the typical cryptomelane structure with a one-dimensional channel. The doping with Ag resulted in Ag/OMS-2 catalysts with a higher specific surface area and narrower pore size distribution than OMS-2. The catalysts showed excellent catalytic activity for CO oxidation and the catalytic activity was increased after Ag introduction. O 2-TPD and CO-TPD results showed that this was because the doping with Ag increased the rate of CO adsorption and the diffusion of lattice oxygen ions.

ABSTRACT Industrial trials detailed in a riser−downer coupling reactor proposed for the fluid cat... more ABSTRACT Industrial trials detailed in a riser−downer coupling reactor proposed for the fluid catalytic cracking (FCC) process are presented in this paper. The trials are based on the fundamental research of hydrodynamics, mixing behaviors, and laboratory-scale hot experiments described in our previous investigations. Compared with the riser reactor with the same feeds and catalyst, the LPG and propylene yield increased by 8.15 and 4.30 wt %, respectively. The gasoline octane number likewise reached 94.8 with 28 wt % olefin content. However, dry gas is significantly suppressed, and the coke has little change in yield even with the increased catalyst to oil ratio. With some gasoline recycling, the LPG and propylene yield increased by 11.45 and 5.06 wt %, respectively, and the olefin content in gasoline significantly decreased to 22 wt %; the high octane number (95.4) is maintained. The computational fluid dynamics (CFD) coupled with a 6-lump kinetic model is also applied to simulate the FCC process for the industrial trials. The yield of propylene and butylene and the temperature profile along the axis direction demonstrated consistency between the simulation results and the experimental data.

ABSTRACT Coal pyrolysis to acetylene in thermal plasma provides a direct route to make chemicals ... more ABSTRACT Coal pyrolysis to acetylene in thermal plasma provides a direct route to make chemicals from coal resources, where the rapid heating and release of volatile matters in coal particles play the dominant role in the overall reactor performance. A mechanism model incorporating the heat conduction in solid materials, diffusion of released volatile gases, and reactions was proposed for a deep understanding of the heat transport inside a coal particle under extreme environmental conditions such as high temperatures greater than 2000 K and milliseconds of reaction time. The two competing rates model, known as the Kobayashi model, was applied to describe the devolatilization kinetics, which was verified by comparing the predicted yield of volatiles with the experimental data in the literature. Thermal balance between coal particles and the hot carrier gas was established, and the four influencing factors including the heating rate, particle size, reactants flow ratio, and heat of devolatilization were paid attention when analyzing the heating profile inside the particles and the yield of volatiles. The results showed that the inherent resistance due to the volatiles released from coal particles seriously impeded the thermal energy transportation from heating gas to the particle. This led to a weakened heating rate, i.e., a long heating up time, and thereafter a low yield of volatiles, especially when the particle size was large (e.g., >40 μm). Meanwhile, the heat conduction inside the coal particle also imposed additional resistance to reduce the heat transportation rate from heating gas to the particle, especially when the particle size was larger than 80 μm. The predicted yield of volatiles considering the mechanism of the two resistances agreed reasonably with the reported experimental data under different operating conditions but was smaller than that which could be obtained when neither resistance is considered. It can be concluded that the proposed heat transport mechanism inside coal particles works well in understanding the coal pyrolysis process at ultrahigh temperatures.

ABSTRACT The gas–solid flows in a two-dimensional downer of 10 m in height and 0.10 m in width we... more ABSTRACT The gas–solid flows in a two-dimensional downer of 10 m in height and 0.10 m in width were simulated using a CFD–DEM method, where the motion of particles was modeled by discrete element method (DEM) and the gas flow was described by Navier–Stokes equations. The simulations revealed a rich variety of developing flow structures in the downer under different operating conditions. The two-phase flow development can be clearly characterized by the micro-scale particle distributions in the downer. Near the inlet, the particle distribution is dominated by the distributor design. Then, the particles disperse in the column, forming a homogeneous transit region. After that clusters start to form and modulate the gas–solid flow field till the fully-developed state. The particle-scale simulation disclosed that the clusters are composed of loosely collected particles, and these particles have the same flow direction as the bulk flow so that no particle backmixing can be observed. As the particles in the downer have the tendency to maintain the inertia, the capability of lateral transfer of particles is relatively weak, which was illustrated by tracking the movement of the single particles and clusters. The simulations of the inlet effect on the hydrodynamics in the downer showed that the gas–solid flow structure and the mixing behavior are sensitive to the inlet design. An inappropriate design or operation would probably cause the undesired flow phenomena such as the wide distribution of residence times. The time-averaged hydrodynamics based on the transient simulations showed good agreement with the experimental findings in the literature. The simulation based on the CFD–DEM coupled approach provides a theoretical way to comprehensively understand the physics at micro- to macro-scales in the co-currently downward gas–solid flows.

A series of Ag-doped manganese oxide catalyst were synthesized by the reflux method in an acid me... more A series of Ag-doped manganese oxide catalyst were synthesized by the reflux method in an acid medium. The surface structure of the catalysts was characterized by N 2 adsorption, XRD and TEM experiments. The catalysts showed excellent catalytic activity for CO oxidation. The adsorption and oxidation of CO on a 1.0% Ag/MnO x catalyst between 393 and 493 K were studied by means of single pulse experiments in a TAP reactor. The adsorption of CO was reversible at these temperatures and CO 2 was formed in an oxidation reaction of CO and lattice oxygen. Curve fitting to the experimental TAP response curves of the reactant and product was used to determine the kinetic parameters for the elementary steps. The activation energies were 83 kJ/mol for CO desorption, 31 kJ/mol for CO 2 desorption, and 116 kJ/mol for the surface CO oxidation by lattice oxygen. In addition, the effect of coadsorbed O 2 on CO adsorption was studied by the TAP technique. Below 353 K, there was a sharp increase, by about one order of magnitude, in the rate constant of CO adsorption promoted by the presence of coadsorbed O 2 .

Many different configurations of the inlet and outlet in the risers have been studied. According ... more Many different configurations of the inlet and outlet in the risers have been studied. According to their effects on the structure of gas-solids two-phase llow, the inlet and outlet effects can be classified as the restriction on the solids circulation flow and the arrangement of open area. Both of them inltuence the axial and radial distributions of bed voidage seriously. Since hydrodynamics at the bottom and top sections in risers depend strongly on the inlet and outlet configurations, the effects of inlet and outlet must be considered carefully when modeling riser flows. It is important to design the riser conligurations at the inlet and outlet to meet overall processes design requirements.

Downer reactor, in which gas and solids move downward co-currently, has unique features such as t... more Downer reactor, in which gas and solids move downward co-currently, has unique features such as the plug-flow reactor performance and relatively uniform flow structure compared to other gas-solids fluidized bed reactors, e.g., bubbling bed, turbulent bed and riser. Downer is therefore acknowledged as a novel multiphase flow reactor with great potential in high-severity operated processes, such as the high temperature, ultra-short contact time reactions with the intermediates as the desired products. Typical process developments in industry have directed to (1) the new-generation refinery process for cracking of heavier feedstock to gasoline and light olefins (e.g., propylene) as by-products; and (2) coal pyrolysis in hydrogen plasma which opens up a direct means for producing acetylene, i.e., a new route to synthesize chemicals from a clean coal utilization process. This paper is to give a comprehensive review on the development of fundamental researches on downer reactors as well as the particular industrial demonstrations for the fluid catalytic cracking (FCC) of heavy oils and coal pyrolysis in thermal plasma.

... Strategies for enzyme/prodrug cancer therapy. Clin Cancer Res, 2001, 7: 3314–3324. 6. Denny W... more ... Strategies for enzyme/prodrug cancer therapy. Clin Cancer Res, 2001, 7: 3314–3324. 6. Denny WA. Prodrug strategies in cancer therapy. ... Gene Ther, 2002, 9: 291–296. 8. Nuyts S, Van Mellaert L, Theys J, et al. Clostridium spores for tumor-specific drug delivery. ...

Current network infrastructures exhibit poor power efficiency, running network devices at full ca... more Current network infrastructures exhibit poor power efficiency, running network devices at full capacity all the time regardless of the traffic demand and distribution over the network. Most research on router power management are at component level or link level, treating routers as isolated devices. A complementary approach is to facilitate power management at network level by routing traffic through different paths to adjust the workload on individual routers or links. Given the high path redundancy and low link utilization in today's large networks, this approach can potentially allow more network devices or components to go into power saving mode. This paper proposes an intra-domain traffic engineering mechanism, GreenTE, which maximizes the number of links that can be put into sleep under given performance constraints such as link utilization and packet delay. Using network topologies and traffic data from several widearea networks, our evaluation shows that GreenTE can reduce line-cards' power consumption by 27% to 42% under constraints that the maximum link utilization is below 50% and the network diameter remains the same as in shortest path routing.

We report the first in situ quantitative visualization and characterization of electro-induced ch... more We report the first in situ quantitative visualization and characterization of electro-induced chitosan hydrogel growth in an aqueous environment. This was enabled with a pair of sidewall electrodes within a transparent fluidic system, which allowed us to resolve the electrogelling mechanism and interpret the dominant causes responsible for the formation and density distribution of the deposited hydrogel. The pH and the time-dependent growth profiles of the chitosan hydrogel were directly visualized, analyzed, and characterized. The results indicate that the gelation and immobilization of chitosan onto the cathode at a pH above its pK a value ($6.3) are due to the electrochemically generated concentration gradient of reactant OH À ions, and their subsequent neutralization of the NH 3 + groups of chitosan chains in solution near the cathode. The increased gel density around the fringes of the electrodes was demonstrated and correlated with the electrophoretic migration of chitosan cations during deposition. Simulation of the electric potential/field distribution, together with the corresponding dry film topography confirmed the non-uniform, electric field-dependent density distribution of deposited hydrogel. This report provides fundamental understanding towards the mechanism and the kinetics of the electro-induced chitosan gel formation. It also provides important guidelines for pursuing its application in bio-components integrated microsystems. The method in use exemplifies a simple, effective and non-destructive approach for in situ characterization of electro-responsive biopolymers in an aqueous environment.