To address the frequency fluctuation problem caused by the power dynamic imbalance between the power system and the loadwhen a large number of newenergy sources are connected to the grid,a two-layer fuzzy control stra...To address the frequency fluctuation problem caused by the power dynamic imbalance between the power system and the loadwhen a large number of newenergy sources are connected to the grid,a two-layer fuzzy control strategy is proposed for the participation of the energy storage battery system in FM.Firstly,considering the coordination of FM units responding to automatic power generation control commands,a comprehensive allocation strategy of two signals under automatic power generation control commands is proposed to give full play to the advantages of two FM signals while enabling better coordination of two FM units responding to FM commands;secondly,based on the grid FM demand and battery FM capability,a double-layer fuzzy control strategy is proposed for FM units responding to automatic power generation control commands in a coordinated manner under dual-signal allocation mode to precisely allocate the power output depth of FM units,which can control the fluctuation of frequency deviation within a smaller range at a faster speed while maintaining the battery charge state;finally,the proposed Finally,the proposed control strategy is simulated and verified inMatlab/Simulink.The results show that the proposed control strategy can control the frequency deviation within a smaller range in a shorter time,better stabilize the fluctuation of the battery charge level,and improve the utilization of the FM unit.展开更多
Gently dipping fractures subjected to river incision are widely distributed on rock slopes.In this paper,a rock slope on the Nujiang River(China)is investigated to study the role of gently dipping fractures in the roc...Gently dipping fractures subjected to river incision are widely distributed on rock slopes.In this paper,a rock slope on the Nujiang River(China)is investigated to study the role of gently dipping fractures in the rock slopes evolution.Detailed field surveys indicate that gentle fractures are concentrated in four main zones.Moreover,the kinematics of the fracture system suggest that the genesis of these fractures can be synthesized into a progressive evolution model.This model indicates that the joints begin with the formation of an array of en echelon cracks that are subjected to continued crack elongation and shearing before ultimately approaching one another and interacting to form a complex joint system.Geomechanical analysis is performed to reveal the mechanisms of this genesis,and three main fracture patterns are identified based on the slope stress and are classified with respect to the slope evolution.Based on the detail field investigations and the evolutionary history of the river valley,we propose that intermittent incision by the river was the main factor contributing to the concentrated distribution of gently dipping joints.展开更多
According to this paper, the dragon-shape strategy is the optimized option of China＇s future strategy with respect to the geographic distribution of regional economy.
Laterally-coupled ridge-waveguide distributed feedback lasers fabricated without epitaxial regrowth steps have the advantages of process simplification and low cost.We present a laterally coupled grating with slots.Th...Laterally-coupled ridge-waveguide distributed feedback lasers fabricated without epitaxial regrowth steps have the advantages of process simplification and low cost.We present a laterally coupled grating with slots.The slots etched between the ridge and grating area are designed to suppress the lateral diffusion of carriers and to reduce the influence of the aspect-ratio-dependent-etching effect on the grating morphology in the etching process.Moreover,the grating height in this structure can be decreased to lower the aspect ratio significantly,which is advantageous over the conventional laterally coupled ridge waveguide gratings.The effects of five main structural parameters on the coupling characteristics of gratings are studied by MODE Solutions.It is found that varying the lateral width of the grating can be used as an effective way to tune the coupling strength;narrow slots(100 nm and 300 nm)and wide ridge(2μm–4μm)promote the stability of grating coupling coefficient and device performance.It is important to note that the grating bottom should be fabricated precisely.The comparative study of carrier distribution and mode field distribution shows that the introduction of narrow slots can strengthen the competitive advantage and stability of the fundamental mode.展开更多
Solid particle heat storage technology offers a potential solution to the challenges posed by the significant growth of renewable energy sources,particularly in terms of grid security and stability.Consequently,it has...Solid particle heat storage technology offers a potential solution to the challenges posed by the significant growth of renewable energy sources,particularly in terms of grid security and stability.Consequently,it has the capability to optimize the energy utilization efficiency of the power system.In order to investigate the transport regulation characteristics of solid particles in the thermal storage and release system of a circulating fluidized bed(CFB),a test rig with a capacity of 0.1 MW(th)was established.This rig was utilized to systematically study the transport regulation characteristics of solid particles under the double U-type valve feed structure and U-type valve discharge structure.The experimental findings indicate that the system's design enables efficient and rapid storage and release of solid particles in the CFB.The air distribution mode,specifically the double U-type valve feed structure and the U-type valve discharge structure,significantly influence the feed and discharge characteristics of the ash storage bin.It was observed that the impact of loose air on these characteristics is more substantial than that of the return air,irrespective of the feed structure or the return structure.When adjusting the feed and discharge rate,it is recommended to adopt a scheme that involves coarse adjustment through loose air and fine adjustment through return air.展开更多
Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too ...Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too challenging to achieve automatic closed-loop control. Previous work has focused on controlling the crystal size distribution, where the size of a crystal is often defined as the diameter of a sphere that has the same volume as the crystal. This paper reviews the new advances in morphological population balance models for modelling and simulating the crystal shape distribution （CShD）, measuring and estimating crystal facet growth kinetics, and two- and three-dimensional imaging for on-line characterisation of the crystal morphology and CShD. A framework is presented that integrates the various components to achieve the ultimate objective of model-based closed-loop control of the CShD. The knowledge gaps and challenges that require further research are also identified.展开更多
The probability distribution of the differential group delay for arbitrary mode coupling is simulated with Monte-Carlo method. Fitting the simulation results, we obtain probability distribution function for arbitrary ...The probability distribution of the differential group delay for arbitrary mode coupling is simulated with Monte-Carlo method. Fitting the simulation results, we obtain probability distribution function for arbitrary mode coupling.展开更多
The residence time distribution （RTD） of solids and the fluidized structure of a bubbling fluidized bed were investigated numerically using computational fluid dynamics simulations coupled with the modified structur...The residence time distribution （RTD） of solids and the fluidized structure of a bubbling fluidized bed were investigated numerically using computational fluid dynamics simulations coupled with the modified structure-based drag model. A general comparison of the simulated results with theoretical values shows reasonable agreement. As the mean residence time is increased, the RTD initial peak intensity decreases and the RTD curve tail extends farther. Numerous small peaks on the RTD curve are induced by the back- mixing and aggregation of particles, which attests to the non-uniform flow structure of the bubbling fluidized bed. The low value of t50 results in poor contact between phases, and the complete exit age of the overflow particles is much longer for back-mixed solids and those caught in dead regions. The formation of a gulf-stream flow and back-mixing for solids induces an even wider spread of RTD.展开更多
The velocity distribution of sinter and gas in vertical cooling furnace(VCF)has an important influence on gas-solid heat transfer.Based on the slot model of single hopper in the VCF of Meishan Iron and Steel Co.,Ltd.,...The velocity distribution of sinter and gas in vertical cooling furnace(VCF)has an important influence on gas-solid heat transfer.Based on the slot model of single hopper in the VCF of Meishan Iron and Steel Co.,Ltd.,the velocity and particle size distribution of sinter and the velocity and pressure distribution of gas were studied using a computational fluid dynamics-discrete element method model to obtain the gas-solid flow rule in the VCF.The results showed that the velocity of sinter near the wall and the edge of vent cowl was lower than that in the rest of the same plane.Therefore,the rectangular section of the vertical cooling furnace can be divided into a quasi-static zone,a plug flow zone and a convergent flow zone according to the flow velocity of the sinter.The average particle size and the void fraction of sinter bed were distributed in"W"and"V"shape along the width direction,respectively.The distribution of gas velocity in the furnace cavity was uneven,and the high-velocity area gradually changed from the center to the edge of the furnace cavity with the rise of gas.Reducing the ratio of edge to center gas flow from 2.7∶1 to 0.7∶1 could improve the gas velocity,but could not change the gas velocity distribution.The gas velocity distribution was more affected by the average particle size distribution of the sinter bed.It was suggested that measures need be taken to adjust it to improve the gas velocity distribution in the VCF.展开更多
In radar target detection, an optimum processor needs to automatically adapt its weights to the environment change. Conventionally, the optimum weights are obtained by substantial independently and identically distrib...In radar target detection, an optimum processor needs to automatically adapt its weights to the environment change. Conventionally, the optimum weights are obtained by substantial independently and identically distributed (i.i.d.) interference samplings, which is not always realistic in an inhomogeneous clutter background of airborne radar. The lack of i.i.d. samplings will inevitably lead to performance deterioration for optimum processing. In this paper, a novel parametric adaptive processing method is proposed for airborne radar target detection based on the modified Doppler distributed clutter (DDC) model with contribution of clutter's internal motion. It is different from the conventional methods in that the adaptive weights are determined by two parameters of DDC model, i.e., angular center and spread. A low-complexity nonlinear operators approach is also proposed to estimate these parameters. Simulation and performance analysis are also provided to show that the proposed method can remarkably reduce the dependence of i.i.d. samplings and it is computationally efficient for practical use.展开更多
基金funded by the Gansu Provincial Science and Technology Information Disclosure System Project(21ZD8JA001)Tianyou Innovation Team of Lanzhou Jiaotong University(TY202009).
文摘To address the frequency fluctuation problem caused by the power dynamic imbalance between the power system and the loadwhen a large number of newenergy sources are connected to the grid,a two-layer fuzzy control strategy is proposed for the participation of the energy storage battery system in FM.Firstly,considering the coordination of FM units responding to automatic power generation control commands,a comprehensive allocation strategy of two signals under automatic power generation control commands is proposed to give full play to the advantages of two FM signals while enabling better coordination of two FM units responding to FM commands;secondly,based on the grid FM demand and battery FM capability,a double-layer fuzzy control strategy is proposed for FM units responding to automatic power generation control commands in a coordinated manner under dual-signal allocation mode to precisely allocate the power output depth of FM units,which can control the fluctuation of frequency deviation within a smaller range at a faster speed while maintaining the battery charge state;finally,the proposed Finally,the proposed control strategy is simulated and verified inMatlab/Simulink.The results show that the proposed control strategy can control the frequency deviation within a smaller range in a shorter time,better stabilize the fluctuation of the battery charge level,and improve the utilization of the FM unit.
基金financially supported by the National Natural Science Foundation of China (Grant No. 41521002 41130745+2 种基金 41272330)State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project (Grant No. SKLGP2016Z015)supported by the Funding of Science and Technology Office of Sichuan Province (Grant Nos. 2015JQ0020)
文摘Gently dipping fractures subjected to river incision are widely distributed on rock slopes.In this paper,a rock slope on the Nujiang River(China)is investigated to study the role of gently dipping fractures in the rock slopes evolution.Detailed field surveys indicate that gentle fractures are concentrated in four main zones.Moreover,the kinematics of the fracture system suggest that the genesis of these fractures can be synthesized into a progressive evolution model.This model indicates that the joints begin with the formation of an array of en echelon cracks that are subjected to continued crack elongation and shearing before ultimately approaching one another and interacting to form a complex joint system.Geomechanical analysis is performed to reveal the mechanisms of this genesis,and three main fracture patterns are identified based on the slope stress and are classified with respect to the slope evolution.Based on the detail field investigations and the evolutionary history of the river valley,we propose that intermittent incision by the river was the main factor contributing to the concentrated distribution of gently dipping joints.
文摘According to this paper, the dragon-shape strategy is the optimized option of China＇s future strategy with respect to the geographic distribution of regional economy.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61804013,61804014,and 61805023)Department of Science and Technology of Jilin Province,China(Grant Nos.20190302052GX and 20210201030GX)。
文摘Laterally-coupled ridge-waveguide distributed feedback lasers fabricated without epitaxial regrowth steps have the advantages of process simplification and low cost.We present a laterally coupled grating with slots.The slots etched between the ridge and grating area are designed to suppress the lateral diffusion of carriers and to reduce the influence of the aspect-ratio-dependent-etching effect on the grating morphology in the etching process.Moreover,the grating height in this structure can be decreased to lower the aspect ratio significantly,which is advantageous over the conventional laterally coupled ridge waveguide gratings.The effects of five main structural parameters on the coupling characteristics of gratings are studied by MODE Solutions.It is found that varying the lateral width of the grating can be used as an effective way to tune the coupling strength;narrow slots(100 nm and 300 nm)and wide ridge(2μm–4μm)promote the stability of grating coupling coefficient and device performance.It is important to note that the grating bottom should be fabricated precisely.The comparative study of carrier distribution and mode field distribution shows that the introduction of narrow slots can strengthen the competitive advantage and stability of the fundamental mode.
基金financially supported by the"High efficiency and low nitrogen combustion technology and demonstration of coal-fired industrial boiler",Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.Y82C0532G1)。
文摘Solid particle heat storage technology offers a potential solution to the challenges posed by the significant growth of renewable energy sources,particularly in terms of grid security and stability.Consequently,it has the capability to optimize the energy utilization efficiency of the power system.In order to investigate the transport regulation characteristics of solid particles in the thermal storage and release system of a circulating fluidized bed(CFB),a test rig with a capacity of 0.1 MW(th)was established.This rig was utilized to systematically study the transport regulation characteristics of solid particles under the double U-type valve feed structure and U-type valve discharge structure.The experimental findings indicate that the system's design enables efficient and rapid storage and release of solid particles in the CFB.The air distribution mode,specifically the double U-type valve feed structure and the U-type valve discharge structure,significantly influence the feed and discharge characteristics of the ash storage bin.It was observed that the impact of loose air on these characteristics is more substantial than that of the return air,irrespective of the feed structure or the return structure.When adjusting the feed and discharge rate,it is recommended to adopt a scheme that involves coarse adjustment through loose air and fine adjustment through return air.
基金Financial support from the following projects and organisa- tions are acknowledged： the China One Thousand Talent Scheme, the National Natural Science Foundation of China （NNSFC） under its Major Research Scheme of Meso-scale Mechanism and Control in Multi-phase Reaction Processes （project reference： 91434126）, the Natural Science Foundation of Guangdong Province （project reference： 2014A030313228）, the UK Engineering and Physical Sciences Research Council （EPSRC） for the projects of Shape （EP/C009541） and StereoVision （EP/E045707）, and the Technology Strategy Board （TSB） for the project of High Value Manufacturing CGM （TP/BD059E）.
文摘Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too challenging to achieve automatic closed-loop control. Previous work has focused on controlling the crystal size distribution, where the size of a crystal is often defined as the diameter of a sphere that has the same volume as the crystal. This paper reviews the new advances in morphological population balance models for modelling and simulating the crystal shape distribution （CShD）, measuring and estimating crystal facet growth kinetics, and two- and three-dimensional imaging for on-line characterisation of the crystal morphology and CShD. A framework is presented that integrates the various components to achieve the ultimate objective of model-based closed-loop control of the CShD. The knowledge gaps and challenges that require further research are also identified.
文摘The probability distribution of the differential group delay for arbitrary mode coupling is simulated with Monte-Carlo method. Fitting the simulation results, we obtain probability distribution function for arbitrary mode coupling.
文摘The residence time distribution （RTD） of solids and the fluidized structure of a bubbling fluidized bed were investigated numerically using computational fluid dynamics simulations coupled with the modified structure-based drag model. A general comparison of the simulated results with theoretical values shows reasonable agreement. As the mean residence time is increased, the RTD initial peak intensity decreases and the RTD curve tail extends farther. Numerous small peaks on the RTD curve are induced by the back- mixing and aggregation of particles, which attests to the non-uniform flow structure of the bubbling fluidized bed. The low value of t50 results in poor contact between phases, and the complete exit age of the overflow particles is much longer for back-mixed solids and those caught in dead regions. The formation of a gulf-stream flow and back-mixing for solids induces an even wider spread of RTD.
基金Financial support provided by the Fundamental Research Funds for the Central Universities of China(N2225022)is gratefully acknowledged.
文摘The velocity distribution of sinter and gas in vertical cooling furnace(VCF)has an important influence on gas-solid heat transfer.Based on the slot model of single hopper in the VCF of Meishan Iron and Steel Co.,Ltd.,the velocity and particle size distribution of sinter and the velocity and pressure distribution of gas were studied using a computational fluid dynamics-discrete element method model to obtain the gas-solid flow rule in the VCF.The results showed that the velocity of sinter near the wall and the edge of vent cowl was lower than that in the rest of the same plane.Therefore,the rectangular section of the vertical cooling furnace can be divided into a quasi-static zone,a plug flow zone and a convergent flow zone according to the flow velocity of the sinter.The average particle size and the void fraction of sinter bed were distributed in"W"and"V"shape along the width direction,respectively.The distribution of gas velocity in the furnace cavity was uneven,and the high-velocity area gradually changed from the center to the edge of the furnace cavity with the rise of gas.Reducing the ratio of edge to center gas flow from 2.7∶1 to 0.7∶1 could improve the gas velocity,but could not change the gas velocity distribution.The gas velocity distribution was more affected by the average particle size distribution of the sinter bed.It was suggested that measures need be taken to adjust it to improve the gas velocity distribution in the VCF.
文摘In radar target detection, an optimum processor needs to automatically adapt its weights to the environment change. Conventionally, the optimum weights are obtained by substantial independently and identically distributed (i.i.d.) interference samplings, which is not always realistic in an inhomogeneous clutter background of airborne radar. The lack of i.i.d. samplings will inevitably lead to performance deterioration for optimum processing. In this paper, a novel parametric adaptive processing method is proposed for airborne radar target detection based on the modified Doppler distributed clutter (DDC) model with contribution of clutter's internal motion. It is different from the conventional methods in that the adaptive weights are determined by two parameters of DDC model, i.e., angular center and spread. A low-complexity nonlinear operators approach is also proposed to estimate these parameters. Simulation and performance analysis are also provided to show that the proposed method can remarkably reduce the dependence of i.i.d. samplings and it is computationally efficient for practical use.
