Combustion kinetics of the hydrochar was investigated using a multi-Gaussian-distributed activation energy model(DAEM)to ex-pand the knowledge on the combustion mechanisms.The results demonstrated that the kinetic par...Combustion kinetics of the hydrochar was investigated using a multi-Gaussian-distributed activation energy model(DAEM)to ex-pand the knowledge on the combustion mechanisms.The results demonstrated that the kinetic parameters calculated by the multi-Gaussian-DAEM accurately represented the experimental conversion rate curves.Overall,the feedstock combustion could be divided into four stages:the decomposition of hemicellulose,cellulose,lignin,and char combustion.The hydrochar combustion could in turn be divided into three stages:the combustion of cellulose,lignin,and char.The mean activation energy ranges obtained for the cellulose,lignin,and char were 273.7-292.8,315.1-334.5,and 354.4-370 kJ/mol,respectively,with the standard deviations of 2.1-23.1,9.5-27.4,and 12.1-22.9 kJ/mol,re-spectively.The cellulose and lignin contents first increased and then decreased with increasing hydrothermal carbonization(HTC)temperature,while the mass fraction of char gradually increased.展开更多
In many practical applications of image segmentation problems,employing prior information can greatly improve segmentation results.This paper continues to study one kind of prior information,called prior distribution....In many practical applications of image segmentation problems,employing prior information can greatly improve segmentation results.This paper continues to study one kind of prior information,called prior distribution.Within this research,there is no exact template of the object;instead only several samples are given.The proposed method,called the parametric distribution prior model,extends our previous model by adding the training procedure to learn the prior distribution of the objects.Then this paper establishes the energy function of the active contour model(ACM)with consideration of this parametric form of prior distribution.Therefore,during the process of segmenting,the template can update itself while the contour evolves.Experiments are performed on the airplane data set.Experimental results demonstrate the potential of the proposed method that with the information of prior distribution,the segmentation effect and speed can be both improved efficaciously.展开更多
为实现能源多梯度利用并减少环境污染,气-电耦合的综合能源系统(integrated energy system,IES)逐渐占据全球能源结构的重要部分。为明晰系统运行特性并充分挖掘能源子网调度潜力,综合能源系统动态仿真研究逐渐深入。天然气网中,管道传...为实现能源多梯度利用并减少环境污染,气-电耦合的综合能源系统(integrated energy system,IES)逐渐占据全球能源结构的重要部分。为明晰系统运行特性并充分挖掘能源子网调度潜力,综合能源系统动态仿真研究逐渐深入。天然气网中,管道传输过程深刻影响着其动态过程。然而现有管道传输过程时域仿真算法存在着精度与效率的两难。为解决上述问题,提出一种基于时域二端口模型的综合能源系统气网动态仿真算法。首先基于特征线法,构建气网源荷节点关系矩阵,进一步给出时域二端口模型;随后参考特征线法数值格式,构建状态量空间分布矩阵,用于获取气网状态量分布,并提出基于时域二端口模型和分布矩阵的气网动态仿真算法。算例结果表明,所提出的方法具有高效率和高精度两大优势,适合于气-电耦合的综合能源系统的较长时间仿真。展开更多
通过热重红外联用研究煤与污泥不同掺混比例样品的燃烧特性以及气体排放特性,分别利用Coats-Redfern模型和分布式活化能模型(distributed activation energy model,DAEM)对污泥与煤的掺烧过程进行动力学分析,研究2种模型的适用性。结果...通过热重红外联用研究煤与污泥不同掺混比例样品的燃烧特性以及气体排放特性,分别利用Coats-Redfern模型和分布式活化能模型(distributed activation energy model,DAEM)对污泥与煤的掺烧过程进行动力学分析,研究2种模型的适用性。结果表明,与单一煤样相比,10%掺混比例样品的着火点降低了11℃,可燃性能改善,稳燃性能提高,综合燃烧特性指数提高。此外,10%掺混比例样品燃烧过程中NO和SO 2的吸收峰比单一煤样的吸收峰低,说明一定比例掺混煤和污泥可以降低污染物的排放浓度。另外DAEM的拟合相关性系数比Coats-Redfern模型更高,表明DAEM更加适用于污泥与煤混合燃烧过程动力学分析。展开更多
The nonlinear dynamics of cantilevered piezoelectric beams is investigated under simultaneous parametric and external excitations. The beam is composed of a substrate and two piezoelectric layers and assumed as an Eul...The nonlinear dynamics of cantilevered piezoelectric beams is investigated under simultaneous parametric and external excitations. The beam is composed of a substrate and two piezoelectric layers and assumed as an Euler-Bernoulli model with inextensible deformation. A nonlinear distributed parameter model of cantilevered piezoelectric energy harvesters is proposed using the generalized Hamilton＇s principle. The proposed model includes geometric and inertia nonlinearity, but neglects the material nonlinearity. Using the Galerkin decomposition method and harmonic balance method, analytical expressions of the frequency-response curves are presented when the first bending mode of the beam plays a dominant role. Using these expressions, we investigate the effects of the damping, load resistance, electromechanical coupling, and excitation amplitude on the frequency-response curves. We also study the difference between the nonlinear lumped-parameter and distributed- parameter model for predicting the performance of the energy harvesting system. Only in the case of parametric excitation, we demonstrate that the energy harvesting system has an initiation excitation threshold below which no energy can be harvested. We also illustrate that the damping and load resistance affect the initiation excitation threshold.展开更多
基金the National Nat-ural Science Foundation of China(Nos.52074029,51804026)the USTB-NTUT Joint Research Program(No.06310063)Chuan Wang would like to acknowledge the funding support from Vinnova(dnr:2017-01327).
文摘Combustion kinetics of the hydrochar was investigated using a multi-Gaussian-distributed activation energy model(DAEM)to ex-pand the knowledge on the combustion mechanisms.The results demonstrated that the kinetic parameters calculated by the multi-Gaussian-DAEM accurately represented the experimental conversion rate curves.Overall,the feedstock combustion could be divided into four stages:the decomposition of hemicellulose,cellulose,lignin,and char combustion.The hydrochar combustion could in turn be divided into three stages:the combustion of cellulose,lignin,and char.The mean activation energy ranges obtained for the cellulose,lignin,and char were 273.7-292.8,315.1-334.5,and 354.4-370 kJ/mol,respectively,with the standard deviations of 2.1-23.1,9.5-27.4,and 12.1-22.9 kJ/mol,re-spectively.The cellulose and lignin contents first increased and then decreased with increasing hydrothermal carbonization(HTC)temperature,while the mass fraction of char gradually increased.
基金supported by the National Key R&D Program of China(2018YFC0309400)the National Natural Science Foundation of China(61871188)
文摘In many practical applications of image segmentation problems,employing prior information can greatly improve segmentation results.This paper continues to study one kind of prior information,called prior distribution.Within this research,there is no exact template of the object;instead only several samples are given.The proposed method,called the parametric distribution prior model,extends our previous model by adding the training procedure to learn the prior distribution of the objects.Then this paper establishes the energy function of the active contour model(ACM)with consideration of this parametric form of prior distribution.Therefore,during the process of segmenting,the template can update itself while the contour evolves.Experiments are performed on the airplane data set.Experimental results demonstrate the potential of the proposed method that with the information of prior distribution,the segmentation effect and speed can be both improved efficaciously.
文摘为实现能源多梯度利用并减少环境污染,气-电耦合的综合能源系统(integrated energy system,IES)逐渐占据全球能源结构的重要部分。为明晰系统运行特性并充分挖掘能源子网调度潜力,综合能源系统动态仿真研究逐渐深入。天然气网中,管道传输过程深刻影响着其动态过程。然而现有管道传输过程时域仿真算法存在着精度与效率的两难。为解决上述问题,提出一种基于时域二端口模型的综合能源系统气网动态仿真算法。首先基于特征线法,构建气网源荷节点关系矩阵,进一步给出时域二端口模型;随后参考特征线法数值格式,构建状态量空间分布矩阵,用于获取气网状态量分布,并提出基于时域二端口模型和分布矩阵的气网动态仿真算法。算例结果表明,所提出的方法具有高效率和高精度两大优势,适合于气-电耦合的综合能源系统的较长时间仿真。
文摘通过热重红外联用研究煤与污泥不同掺混比例样品的燃烧特性以及气体排放特性,分别利用Coats-Redfern模型和分布式活化能模型(distributed activation energy model,DAEM)对污泥与煤的掺烧过程进行动力学分析,研究2种模型的适用性。结果表明,与单一煤样相比,10%掺混比例样品的着火点降低了11℃,可燃性能改善,稳燃性能提高,综合燃烧特性指数提高。此外,10%掺混比例样品燃烧过程中NO和SO 2的吸收峰比单一煤样的吸收峰低,说明一定比例掺混煤和污泥可以降低污染物的排放浓度。另外DAEM的拟合相关性系数比Coats-Redfern模型更高,表明DAEM更加适用于污泥与煤混合燃烧过程动力学分析。
基金supported by the National Natural Science Foundation of China (Grant 11172087)
文摘The nonlinear dynamics of cantilevered piezoelectric beams is investigated under simultaneous parametric and external excitations. The beam is composed of a substrate and two piezoelectric layers and assumed as an Euler-Bernoulli model with inextensible deformation. A nonlinear distributed parameter model of cantilevered piezoelectric energy harvesters is proposed using the generalized Hamilton＇s principle. The proposed model includes geometric and inertia nonlinearity, but neglects the material nonlinearity. Using the Galerkin decomposition method and harmonic balance method, analytical expressions of the frequency-response curves are presented when the first bending mode of the beam plays a dominant role. Using these expressions, we investigate the effects of the damping, load resistance, electromechanical coupling, and excitation amplitude on the frequency-response curves. We also study the difference between the nonlinear lumped-parameter and distributed- parameter model for predicting the performance of the energy harvesting system. Only in the case of parametric excitation, we demonstrate that the energy harvesting system has an initiation excitation threshold below which no energy can be harvested. We also illustrate that the damping and load resistance affect the initiation excitation threshold.
