In this paper we estimate the degree of approximation of wavelet expansions. Our result shows that the degree has the exponential decay for function f(x)∈L2 continuous in a finite interval (a, b) which is much superi...In this paper we estimate the degree of approximation of wavelet expansions. Our result shows that the degree has the exponential decay for function f(x)∈L2 continuous in a finite interval (a, b) which is much superior to those of approximation by polynomial operators and by expansions of classical orthogonal series.展开更多
The effect of the degree of milling(DM)on the distribution of the residual bran layer on the surface of rice grains and subsequent rice quality is essential for rice milling technology.This study used scanning electro...The effect of the degree of milling(DM)on the distribution of the residual bran layer on the surface of rice grains and subsequent rice quality is essential for rice milling technology.This study used scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)to examine the microstructure of japonica rice grains,the microstructural changes in different bran portions after milling,and the content and distribution changes of the elements and nutrients in rice after milling to identify the components that can quantify bran residue according to DM.The SEM results revealed that the thickness of the bran layer and the depth of the grooves in different parts of a rice grain varied,while the depth of the grooves differed between varieties.When DM was 12%,aleurone layer(Al)cells embedded in endosperm(En)remained in the dorsal area.It was speculated that this was the reason why there was no significant difference in bran degree when the DM estimated via grain weight loss increased from 10%to 14%(P>0.05).The EDS elemental mapping image showed the qualitative distribution of the elements,which was condensed in the bran and uniform in the En.The compositional changes revealed that milling caused the loss of rice nutrients,and the loss rate of DM at 0–10%was more serious than that of DM at 10%–14%.Higher DM(>10%)could remove marginal bran from the dorsal groove.Therefore,the crude protein,ash,crude fat,dietary fiber,vitamin B1(VB1),and vitamin B2(VB2)content did not change significantly(P>0.05),while the magnesium(Mg),kalium(K),and phosphorus(P)levels decreased substantially(P<0.05).The microstructural and compositional changes indicated that the DM estimated via the grain weight loss increased from 2%to 10%,with the bran decreasing progressively.The DM estimated via the grain weight loss increased from 10%to 14%,with minimal changes in the residual bran in the dorsal grooves of the rice grains,while the Mg,P,and K levels presented precise DM indices during the rice milling process.This result will provide a theoretical reference for the accurate evaluations of DM.展开更多
Improving the primary steam parameters is one of the most direct ways to improve the cycle efficiency of a powergeneration system. In the present study, the typical problem connected to the excessively high superheat ...Improving the primary steam parameters is one of the most direct ways to improve the cycle efficiency of a powergeneration system. In the present study, the typical problem connected to the excessively high superheat degree ofextraction steam in an ultra-supercritical (USC) double-reheat unit is considered. Using a 1000 MW power plantas an example, two systems (case 1 and case 2) are proposed, both working in combination with a regenerativesteam turbine. The thermal performances of these two systems are compared with that of the original systemthrough a heat balance method and an exergy balance strategy. The results reveal that the two coupled systemscan significantly reduce the superheat degree of extraction steam, turbine heat rate, and coal consumption of theunit and improve the energy utilization efficiency. These results will provide useful theoretical guidance to futureinvestigators wishing to address the general problem relating to energy conservation and modelling of the coupledextraction steam regenerative system of USC double-reheat units.展开更多
Theoretical derivation of local resistance coefficient of sudden expansion tube is presented. Several assumptions are analyzed in the theoretical derivation. That the head loss shall be neglected is affirmed. Experime...Theoretical derivation of local resistance coefficient of sudden expansion tube is presented. Several assumptions are analyzed in the theoretical derivation. That the head loss shall be neglected is affirmed. Experimental data proves that the pressure before and after sudden expansion section is basically the same. That the friction force on the side face of control body is neglected is denied and it is pointed out that such neglect is the main cause for error between theoretical calculation and actual measurement. Experimental device for measuring local resistance coefficient is designed in combination with theoretical derivation process. Optimal gradually varied flow section is selected after sudden expansion pipe in Bernoulli equation based on variation of piezometer tube head. It is pointed out in accordance with experimental data analysis that the value of local resistance coefficient of sudden expansion tube determined through experimental data is closer to the actual situation during pipeline design.展开更多
The structural and aerodynamic performance of the air inlet volute has an important influence on the performance of the gas turbine. On one hand, it requires the airflow flowing through inlet volute as even as possibl...The structural and aerodynamic performance of the air inlet volute has an important influence on the performance of the gas turbine. On one hand, it requires the airflow flowing through inlet volute as even as possible, in order to reduce the pressure loss, to avoid a decrease in the effective output power and an increase of the fuel consumption rate of the internal combustion engine which indicate the inefficiency of the entire power unit;On the other hand, it requires the size of the inlet volute to be as small as possible in order to save mounting space and production costs. The thesis builds the structure model and develops flow fields numerical simulation of several different sizes of the inlet volutes. Further, the unreasonable aerodynamic structure is improved according to the flow field characteristics and thereby, a better aerodynamic performance of the inlet volute is obtained.展开更多
The finite element method is employed to simulate incompressible viscous unsteady flow in two dimensional channel with a sudden expansion. The streamline patterns and the velocity vector plots are presented at differ...The finite element method is employed to simulate incompressible viscous unsteady flow in two dimensional channel with a sudden expansion. The streamline patterns and the velocity vector plots are presented at different expansion ratios and at different moment. The results obtained have certain significance to analyze the formation of eddies and energy loss in a sudden expansion channel flow and other complex channel flow.展开更多
准确检测变电站中的设备缺陷并及时进行处理是保证电力系统安全运行的重要措施.针对表计缺陷图像背景复杂、目标尺寸不一、外形差别大等问题,提出基于改进YOLOv5(you only look once的第5个版本)的变电站表计缺陷检测算法.为了提高泛化...准确检测变电站中的设备缺陷并及时进行处理是保证电力系统安全运行的重要措施.针对表计缺陷图像背景复杂、目标尺寸不一、外形差别大等问题,提出基于改进YOLOv5(you only look once的第5个版本)的变电站表计缺陷检测算法.为了提高泛化能力、解决训练过程中样本不平衡问题,利用旋转和改变图像亮度的方法进行数据增广.通过引入坐标注意力机制,在聚焦缺陷特征的同时,能突出缺陷特征的差异.为了使边界框回归更快速准确,将EDIOU loss(effective distance intersection over union loss)代替CIOU loos(complete intersection over union loss).实验结果表明:6种算法中,该文算法的准确度、召回率和mAP(mean average preciscion)均最高,分别达85.1%,86.6%,87.3%.因此,该文算法具有优越性.展开更多
部分电离等离子体是惯性约束聚变燃料及天体等离子体中的重要组成部分,该等离子体的输运及流体力学等性质受到束缚电子的显著影响,然而当前基于光谱学的技术手段难以对其进行高精度诊断.本文基于中国科学院近代物理研究所低能离子束与...部分电离等离子体是惯性约束聚变燃料及天体等离子体中的重要组成部分,该等离子体的输运及流体力学等性质受到束缚电子的显著影响,然而当前基于光谱学的技术手段难以对其进行高精度诊断.本文基于中国科学院近代物理研究所低能离子束与等离子体相互作用实验平台,精确测量了100 ke V质子束穿过部分电离氢等离子体靶后的能损,该能损是质子同靶区内自由电子与束缚电子碰撞共同作用的结果.利用已有的能损理论模型,结合激光干涉诊断获得的自由电子密度信息,最终得到了部分电离氢等离子体靶中沿离子路径上的束缚电子密度,并给出了该等离子体的离化度参数.该离子束诊断技术具有在线、原位、分辨率高等优势,为解决部分电离等离子体内部束缚电子密度的诊断问题提供了新的途径.展开更多
基金This work is supported by the Natural Science Foundation of Zhejiang,PR China.
文摘In this paper we estimate the degree of approximation of wavelet expansions. Our result shows that the degree has the exponential decay for function f(x)∈L2 continuous in a finite interval (a, b) which is much superior to those of approximation by polynomial operators and by expansions of classical orthogonal series.
基金the National Key Research and Development Program of China(Grant Number 2017YFD0401101-01)
文摘The effect of the degree of milling(DM)on the distribution of the residual bran layer on the surface of rice grains and subsequent rice quality is essential for rice milling technology.This study used scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)to examine the microstructure of japonica rice grains,the microstructural changes in different bran portions after milling,and the content and distribution changes of the elements and nutrients in rice after milling to identify the components that can quantify bran residue according to DM.The SEM results revealed that the thickness of the bran layer and the depth of the grooves in different parts of a rice grain varied,while the depth of the grooves differed between varieties.When DM was 12%,aleurone layer(Al)cells embedded in endosperm(En)remained in the dorsal area.It was speculated that this was the reason why there was no significant difference in bran degree when the DM estimated via grain weight loss increased from 10%to 14%(P>0.05).The EDS elemental mapping image showed the qualitative distribution of the elements,which was condensed in the bran and uniform in the En.The compositional changes revealed that milling caused the loss of rice nutrients,and the loss rate of DM at 0–10%was more serious than that of DM at 10%–14%.Higher DM(>10%)could remove marginal bran from the dorsal groove.Therefore,the crude protein,ash,crude fat,dietary fiber,vitamin B1(VB1),and vitamin B2(VB2)content did not change significantly(P>0.05),while the magnesium(Mg),kalium(K),and phosphorus(P)levels decreased substantially(P<0.05).The microstructural and compositional changes indicated that the DM estimated via the grain weight loss increased from 2%to 10%,with the bran decreasing progressively.The DM estimated via the grain weight loss increased from 10%to 14%,with minimal changes in the residual bran in the dorsal grooves of the rice grains,while the Mg,P,and K levels presented precise DM indices during the rice milling process.This result will provide a theoretical reference for the accurate evaluations of DM.
基金the Shandong Electric Power Engineering Consulting Institute science and technology project(Grant No.37-K2014-33).
文摘Improving the primary steam parameters is one of the most direct ways to improve the cycle efficiency of a powergeneration system. In the present study, the typical problem connected to the excessively high superheat degree ofextraction steam in an ultra-supercritical (USC) double-reheat unit is considered. Using a 1000 MW power plantas an example, two systems (case 1 and case 2) are proposed, both working in combination with a regenerativesteam turbine. The thermal performances of these two systems are compared with that of the original systemthrough a heat balance method and an exergy balance strategy. The results reveal that the two coupled systemscan significantly reduce the superheat degree of extraction steam, turbine heat rate, and coal consumption of theunit and improve the energy utilization efficiency. These results will provide useful theoretical guidance to futureinvestigators wishing to address the general problem relating to energy conservation and modelling of the coupledextraction steam regenerative system of USC double-reheat units.
文摘Theoretical derivation of local resistance coefficient of sudden expansion tube is presented. Several assumptions are analyzed in the theoretical derivation. That the head loss shall be neglected is affirmed. Experimental data proves that the pressure before and after sudden expansion section is basically the same. That the friction force on the side face of control body is neglected is denied and it is pointed out that such neglect is the main cause for error between theoretical calculation and actual measurement. Experimental device for measuring local resistance coefficient is designed in combination with theoretical derivation process. Optimal gradually varied flow section is selected after sudden expansion pipe in Bernoulli equation based on variation of piezometer tube head. It is pointed out in accordance with experimental data analysis that the value of local resistance coefficient of sudden expansion tube determined through experimental data is closer to the actual situation during pipeline design.
文摘The structural and aerodynamic performance of the air inlet volute has an important influence on the performance of the gas turbine. On one hand, it requires the airflow flowing through inlet volute as even as possible, in order to reduce the pressure loss, to avoid a decrease in the effective output power and an increase of the fuel consumption rate of the internal combustion engine which indicate the inefficiency of the entire power unit;On the other hand, it requires the size of the inlet volute to be as small as possible in order to save mounting space and production costs. The thesis builds the structure model and develops flow fields numerical simulation of several different sizes of the inlet volutes. Further, the unreasonable aerodynamic structure is improved according to the flow field characteristics and thereby, a better aerodynamic performance of the inlet volute is obtained.
文摘The finite element method is employed to simulate incompressible viscous unsteady flow in two dimensional channel with a sudden expansion. The streamline patterns and the velocity vector plots are presented at different expansion ratios and at different moment. The results obtained have certain significance to analyze the formation of eddies and energy loss in a sudden expansion channel flow and other complex channel flow.
文摘准确检测变电站中的设备缺陷并及时进行处理是保证电力系统安全运行的重要措施.针对表计缺陷图像背景复杂、目标尺寸不一、外形差别大等问题,提出基于改进YOLOv5(you only look once的第5个版本)的变电站表计缺陷检测算法.为了提高泛化能力、解决训练过程中样本不平衡问题,利用旋转和改变图像亮度的方法进行数据增广.通过引入坐标注意力机制,在聚焦缺陷特征的同时,能突出缺陷特征的差异.为了使边界框回归更快速准确,将EDIOU loss(effective distance intersection over union loss)代替CIOU loos(complete intersection over union loss).实验结果表明:6种算法中,该文算法的准确度、召回率和mAP(mean average preciscion)均最高,分别达85.1%,86.6%,87.3%.因此,该文算法具有优越性.
文摘部分电离等离子体是惯性约束聚变燃料及天体等离子体中的重要组成部分,该等离子体的输运及流体力学等性质受到束缚电子的显著影响,然而当前基于光谱学的技术手段难以对其进行高精度诊断.本文基于中国科学院近代物理研究所低能离子束与等离子体相互作用实验平台,精确测量了100 ke V质子束穿过部分电离氢等离子体靶后的能损,该能损是质子同靶区内自由电子与束缚电子碰撞共同作用的结果.利用已有的能损理论模型,结合激光干涉诊断获得的自由电子密度信息,最终得到了部分电离氢等离子体靶中沿离子路径上的束缚电子密度,并给出了该等离子体的离化度参数.该离子束诊断技术具有在线、原位、分辨率高等优势,为解决部分电离等离子体内部束缚电子密度的诊断问题提供了新的途径.
