A direct decarbonation route without obvious morphology damage was developed for large micrometer-scale layered double hydroxides（LDHs）.First,we synthesized pure,hexagonal-shaped LDHs with lateral dimension of micro...A direct decarbonation route without obvious morphology damage was developed for large micrometer-scale layered double hydroxides（LDHs）.First,we synthesized pure,hexagonal-shaped LDHs with lateral dimension of micrometer-size by the recently reported urea hydrolysis method.Then,using HNO_3-NaNO_3 mixed solution,the obtained LDH with carbonate anions in the interlayer（LDH_CO_3） was directly decarbonated to its nitrate form,LDH_NO_3,its morphology and particle size were still unchanged.Compared with the recently published two-step decarbonation method,the direct decarbonation reported herein is very convenient.展开更多
The Regional Atmospheric Modeling System （RAMS） and the computational fluid dynamics （CFD） codes known as FLUENT are combinatorially applied in a multi-scale numerical simulation of the urban surface layer （USL）...The Regional Atmospheric Modeling System （RAMS） and the computational fluid dynamics （CFD） codes known as FLUENT are combinatorially applied in a multi-scale numerical simulation of the urban surface layer （USL）. RAMS and FLUENT are combined as a multi-scale numerical modeling system, in which the RAMS simulated data are delivered to the computational model for FLUENT simulation in an offline way. Numerical simulations are performed to present and preliminarily validate the capability of the multi-scale modeling system, and the results show that the modeling system can reasonably provide information on the meteorological elements in an urban area from the urban scale to the city-block scale, especially the details of the turbulent flows within the USL.展开更多
The velocity ratio of a free shear layer has an important influence on the spatial development of the large scale coherent structures in the layer. In this study, numerical simulations are performed to get an insight ...The velocity ratio of a free shear layer has an important influence on the spatial development of the large scale coherent structures in the layer. In this study, numerical simulations are performed to get an insight into this problem. The obtained numerical results agree quite well with those of a linear inviscid stability theory and the available experimental data.展开更多
The purpose of this paper is to study the energy efficiency of a local living space exposed to solar radiation in the subtropical climate of Casablanca. The study was mainly focused on the contribution of a phase chan...The purpose of this paper is to study the energy efficiency of a local living space exposed to solar radiation in the subtropical climate of Casablanca. The study was mainly focused on the contribution of a phase change material (PCM), inserted into a 7-cm thick air layer of a double brick wall, in two different locations. We note that the experimental study was conducted using two real-scale test cavities, located in the Faculty of Science Ain Chock-Casablanca. Two PCM mounting methods were used for the south and west walls, in order to test its energy efficiency as a storage and retrieval means of the solar flux coming from the outside. In the case of the southern wall, the PCM is put directly on the internal side of the outside part of the double wall (Case 1). For the west wall, the PCM is placed 1.2 cm away from the internal side of the outer part of the double wall (Case 2). The first result shows that the PCM placed to the wall allows storing the solar heat during the day and releasing it to the outside of the building at night. While in the second case, the PCM keeps the heat stored day and night.展开更多
Many real communication networks, such as oceanic monitoring network and land environment observation network,can be described as space stereo multi-layer structure, and the traffic in these networks is concurrent. Un...Many real communication networks, such as oceanic monitoring network and land environment observation network,can be described as space stereo multi-layer structure, and the traffic in these networks is concurrent. Understanding how traffic dynamics depend on these real communication networks and finding an effective routing strategy that can fit the circumstance of traffic concurrency and enhance the network performance are necessary. In this light, we propose a traffic model for space stereo multi-layer complex network and introduce two kinds of global forward-predicting dynamic routing strategies, global forward-predicting hybrid minimum queue（HMQ） routing strategy and global forward-predicting hybrid minimum degree and queue（HMDQ） routing strategy, for traffic concurrency space stereo multi-layer scale-free networks. By applying forward-predicting strategy, the proposed routing strategies achieve better performances in traffic concurrency space stereo multi-layer scale-free networks. Compared with the efficient routing strategy and global dynamic routing strategy, HMDQ and HMQ routing strategies can optimize the traffic distribution, alleviate the number of congested packets effectively and reach much higher network capacity.展开更多
In this paper, several mathematical models for the large scale structures in some special kinds of mixing layers, which might be practically useful for enhancing the mixing, are proposed. First, the linear growth rate...In this paper, several mathematical models for the large scale structures in some special kinds of mixing layers, which might be practically useful for enhancing the mixing, are proposed. First, the linear growth rate of the large scale structures in the mixing layers was calculated. Then, using the much improved weakly non-linear theory, combined with the energy method, the non-linear evolution of large scale structures in two special mixing layer configurations is calculated. One of the mixing lavers has equal magnitudes of the upstream velocity vectors, while the angles between the velocity vectors and the trailing edge were pi /2 - phi and pi /2 + phi, respectively. The other mixing layer was generated by a splitter-plate with a 45-degree-sweep trailing edge.展开更多
Electrical characteristics of a nozzle-attached meso-scale premixed methane-air flame under low-frequency AC （0-4300 V, 0-500 Hz） and DC （0-3300 V） electric fields were studied. I-V curves were measured under diff...Electrical characteristics of a nozzle-attached meso-scale premixed methane-air flame under low-frequency AC （0-4300 V, 0-500 Hz） and DC （0-3300 V） electric fields were studied. I-V curves were measured under different experimental conditions to estimate the magnitude of the total current 10^0-10^2μA, the electron density 10^15-10^16 m^-3 and further the power dissipation 〈 0.7 W in the reaction zone. At the same time, the meso-scale premixed flame conductivity 10^-4-10^-3 Ω^-1. m^-1 as a function of voltage and frequency was experimentally obtained and was believed to represent a useful order-of magnitude estimate. Moreover, the influence of the collision sheath relating to Debye length （31-98 μm） and the contamination layer of an active electrode on measurements was discussed, based on the combination of simulation and theoretical analysis. As a result, the electrode sheath dimension was evaluated to less than 0.5 mm, which indicated a complex effect of the collision sheath on the current measurements. The surface contamination effect of an active electrode was further analyzed using the SEM imaging method, which showed elements immigration during the contamination layer formation process.展开更多
In this study, the development of a convective boundary layer （CBL） in the Badaujilin region was investigated by comparing the observation data of two cases. A deep neutral layer capped a CBL that occurred on 30 Aug...In this study, the development of a convective boundary layer （CBL） in the Badaujilin region was investigated by comparing the observation data of two cases. A deep neutral layer capped a CBL that occurred on 30 August 2009. This case was divided into five sublayers from the surface to higher atmospheric elevations： surface layer, mixed layer, inversion layer, neutral layer, and sub-inversion layer. The development process of the CBL was divided into three stages： S1, S2, and S3. This case was quite different from the development of the three-layer CBL observed on 31 August 2009 because the mixed layer of the five-layer CBL （CBL5） eroded the neutral layer during S2. The specific initial structure of the CBL5 was correlated to the synoptic background of atmosphere during nighttime. The three-stage development process of the CBL5 was confirmed by six simulations using National Center for Atmospheric Research （USA） large-eddy simulation （NCAR-LES）, and some of its characteristics are presented in detail.展开更多
基金the National Natural Science Foundation of China(No.5 1073 162)for financial supportK.C. Wong Education Foundation,Hong Kong
文摘A direct decarbonation route without obvious morphology damage was developed for large micrometer-scale layered double hydroxides（LDHs）.First,we synthesized pure,hexagonal-shaped LDHs with lateral dimension of micrometer-size by the recently reported urea hydrolysis method.Then,using HNO_3-NaNO_3 mixed solution,the obtained LDH with carbonate anions in the interlayer（LDH_CO_3） was directly decarbonated to its nitrate form,LDH_NO_3,its morphology and particle size were still unchanged.Compared with the recently published two-step decarbonation method,the direct decarbonation reported herein is very convenient.
基金This study was supported by the National Natural Science Foundation of China （Grant Nos. 40233030, 40405004, 40405014）.
文摘The Regional Atmospheric Modeling System （RAMS） and the computational fluid dynamics （CFD） codes known as FLUENT are combinatorially applied in a multi-scale numerical simulation of the urban surface layer （USL）. RAMS and FLUENT are combined as a multi-scale numerical modeling system, in which the RAMS simulated data are delivered to the computational model for FLUENT simulation in an offline way. Numerical simulations are performed to present and preliminarily validate the capability of the multi-scale modeling system, and the results show that the modeling system can reasonably provide information on the meteorological elements in an urban area from the urban scale to the city-block scale, especially the details of the turbulent flows within the USL.
基金Project supported by the National Natural Science Foundation of china
文摘The velocity ratio of a free shear layer has an important influence on the spatial development of the large scale coherent structures in the layer. In this study, numerical simulations are performed to get an insight into this problem. The obtained numerical results agree quite well with those of a linear inviscid stability theory and the available experimental data.
文摘The purpose of this paper is to study the energy efficiency of a local living space exposed to solar radiation in the subtropical climate of Casablanca. The study was mainly focused on the contribution of a phase change material (PCM), inserted into a 7-cm thick air layer of a double brick wall, in two different locations. We note that the experimental study was conducted using two real-scale test cavities, located in the Faculty of Science Ain Chock-Casablanca. Two PCM mounting methods were used for the south and west walls, in order to test its energy efficiency as a storage and retrieval means of the solar flux coming from the outside. In the case of the southern wall, the PCM is put directly on the internal side of the outside part of the double wall (Case 1). For the west wall, the PCM is placed 1.2 cm away from the internal side of the outer part of the double wall (Case 2). The first result shows that the PCM placed to the wall allows storing the solar heat during the day and releasing it to the outside of the building at night. While in the second case, the PCM keeps the heat stored day and night.
基金Project supported by the Youth Science Funds of Shandong Academy of Sciences,China(Grant No.2014QN032)
文摘Many real communication networks, such as oceanic monitoring network and land environment observation network,can be described as space stereo multi-layer structure, and the traffic in these networks is concurrent. Understanding how traffic dynamics depend on these real communication networks and finding an effective routing strategy that can fit the circumstance of traffic concurrency and enhance the network performance are necessary. In this light, we propose a traffic model for space stereo multi-layer complex network and introduce two kinds of global forward-predicting dynamic routing strategies, global forward-predicting hybrid minimum queue（HMQ） routing strategy and global forward-predicting hybrid minimum degree and queue（HMDQ） routing strategy, for traffic concurrency space stereo multi-layer scale-free networks. By applying forward-predicting strategy, the proposed routing strategies achieve better performances in traffic concurrency space stereo multi-layer scale-free networks. Compared with the efficient routing strategy and global dynamic routing strategy, HMDQ and HMQ routing strategies can optimize the traffic distribution, alleviate the number of congested packets effectively and reach much higher network capacity.
基金The project supported by the National Natural Science Foundation of China (19642001) and Deutsche Forschungsgemeinschaft (DFG)
文摘In this paper, several mathematical models for the large scale structures in some special kinds of mixing layers, which might be practically useful for enhancing the mixing, are proposed. First, the linear growth rate of the large scale structures in the mixing layers was calculated. Then, using the much improved weakly non-linear theory, combined with the energy method, the non-linear evolution of large scale structures in two special mixing layer configurations is calculated. One of the mixing lavers has equal magnitudes of the upstream velocity vectors, while the angles between the velocity vectors and the trailing edge were pi /2 - phi and pi /2 + phi, respectively. The other mixing layer was generated by a splitter-plate with a 45-degree-sweep trailing edge.
基金supported by National Natural Science Foundation of China(No.51376021)the Fundamental Research Fund for Major Universities(No.2013JBM079)
文摘Electrical characteristics of a nozzle-attached meso-scale premixed methane-air flame under low-frequency AC （0-4300 V, 0-500 Hz） and DC （0-3300 V） electric fields were studied. I-V curves were measured under different experimental conditions to estimate the magnitude of the total current 10^0-10^2μA, the electron density 10^15-10^16 m^-3 and further the power dissipation 〈 0.7 W in the reaction zone. At the same time, the meso-scale premixed flame conductivity 10^-4-10^-3 Ω^-1. m^-1 as a function of voltage and frequency was experimentally obtained and was believed to represent a useful order-of magnitude estimate. Moreover, the influence of the collision sheath relating to Debye length （31-98 μm） and the contamination layer of an active electrode on measurements was discussed, based on the combination of simulation and theoretical analysis. As a result, the electrode sheath dimension was evaluated to less than 0.5 mm, which indicated a complex effect of the collision sheath on the current measurements. The surface contamination effect of an active electrode was further analyzed using the SEM imaging method, which showed elements immigration during the contamination layer formation process.
基金funded by National Basic Research Program of China (Grant Nos. 2009CB421402 and 2010CB950503)National Natural Science Foundation of China (GrantNo. 40975007)
文摘In this study, the development of a convective boundary layer （CBL） in the Badaujilin region was investigated by comparing the observation data of two cases. A deep neutral layer capped a CBL that occurred on 30 August 2009. This case was divided into five sublayers from the surface to higher atmospheric elevations： surface layer, mixed layer, inversion layer, neutral layer, and sub-inversion layer. The development process of the CBL was divided into three stages： S1, S2, and S3. This case was quite different from the development of the three-layer CBL observed on 31 August 2009 because the mixed layer of the five-layer CBL （CBL5） eroded the neutral layer during S2. The specific initial structure of the CBL5 was correlated to the synoptic background of atmosphere during nighttime. The three-stage development process of the CBL5 was confirmed by six simulations using National Center for Atmospheric Research （USA） large-eddy simulation （NCAR-LES）, and some of its characteristics are presented in detail.
