Organic matter(OM) is an important component of sediment. Bioturbation/bioirrigation can remobilize OM and heavy metals that were previously buried in the sediment. The remobilization of buried organic matter, thalliu...Organic matter(OM) is an important component of sediment. Bioturbation/bioirrigation can remobilize OM and heavy metals that were previously buried in the sediment. The remobilization of buried organic matter, thallium(Tl), cadmium(Cd), copper(Cu) and zinc(Zn) from sediment was studied in a laboratory experiment with three organisms: tubificid,chironomid larvae and loach. Results showed that bioturbation/bioirrigation promoted the release of dissolved organic matter(DOM) and dissolved Tl, Cd, Cu and Zn, but only dissolved Zn concentrations decreased with exposure time in overlying water. The presence of organisms altered the compositions of DOM released from sediment,considerably increasing the percentage of fulvic acid-like materials(FA) and humic acidlike materials(HA). In addition, bioturbation/bioirrigation accelerated the growth and reproduction of bacteria to enhance the proportion of soluble microbial byproduct-like materials(SMP). The DOM was divided into five regions in the three-dimensional excitation emission matrix(3 D-EEM), and each part had different correlation with the dissolved heavy metal concentrations. Dissolved Cu had the best correlation with each of the DOM compositions, indicating that Cu in the sediment was in the organic-bound form.Furthermore, the organism type and heavy metal characteristics both played a role in influencing the remobilization of heavy metal.展开更多
Aimed at studying normali zed radial basis function network (NRBFN), this paper introduces the subtractiv e clustering based on a mountain function to construct the initial structure of NR BFN, adopts singular value ...Aimed at studying normali zed radial basis function network (NRBFN), this paper introduces the subtractiv e clustering based on a mountain function to construct the initial structure of NR BFN, adopts singular value decomposition (SVD) to analyze the relationship betwe en neural nodes of the hidden layer and singular values, cumulative contribution ratio, index vector, and optimizes the structure of NRBFN. Finally, simulation and performance comparison show that the algorithm is feasible and effective.展开更多
The preparation of ultra fine Y A G( Y3 Al5 O12) po w der through co precipitation techniquew as investigated . The for m ation tem perature of Y A G w as lo wered belo w 800 ℃ by carefullycontrolling process...The preparation of ultra fine Y A G( Y3 Al5 O12) po w der through co precipitation techniquew as investigated . The for m ation tem perature of Y A G w as lo wered belo w 800 ℃ by carefullycontrolling process para m eters . Ultra fine Y A G po w der w ith even size distribution , spheri cal shapes , and 40 n m particle size has been produced . It is found that for m ation of Y A Gisnot through the Y A M an d Y A Pinter mediate phases that are often observed during the synthe sis of Y A G by m ixed oxide m ethod . The sm all particle size of the precursor po w der , them olecular scale mixing of the constituents , and the poly m orphic transfor m ation of Al2 O3during heating accou nt m ainly for the reduction of for m ation tem perature of Y A Gan d the e lim ination of inter m ediate Y A M and Y A Pphases .展开更多
受到单一或频域的特征提取限制,导致在复杂工况下机床工作数据存在微弱故障特征淹没现象,直接降低特征提取质量,间接影响机床的故障定位和诊断性能,为此提出基于双域深度学习与特征提取的机床故障定位与诊断方法。利用传感器设备同步采...受到单一或频域的特征提取限制,导致在复杂工况下机床工作数据存在微弱故障特征淹没现象,直接降低特征提取质量,间接影响机床的故障定位和诊断性能,为此提出基于双域深度学习与特征提取的机床故障定位与诊断方法。利用传感器设备同步采集振动、温度、电流等机床多源工作数据。构建双域深度学习网络,输入初始采集数据,分别提取机床的时域和频域工作特征,通过双域特征融合,得出机床工作特征提取结果。根据机床故障机理与表现,设定机床故障诊断标准。计算提取特征与故障诊断标准之间的特征匹配度,根据特征匹配度与阈值之间的关系,得出机床故障诊断结果,进而确定机床故障点位置。通过性能测试实验得出结论:与传统方法相比,优化设计方法的机床故障定位精度大幅提升,误诊率明显降低,同时受试者工作特征(receiver operating characteristic,ROC)曲线下面积(area under the curve,AUC)指标明显增大,由此证明优化设计方法在定位和诊断方面具有明显优势。展开更多
The paper gives two estimates of the distance between adjacent zeros of solutions of the first\|order delay differential equation x′(t)+p(t)x(t-τ) =0 in the case when p(t)≥0 and ∫ t t-τ p(s)d s-1e ...The paper gives two estimates of the distance between adjacent zeros of solutions of the first\|order delay differential equation x′(t)+p(t)x(t-τ) =0 in the case when p(t)≥0 and ∫ t t-τ p(s)d s-1e oscillates or p(t) itself oscillates.展开更多
From the constitutive model with generalized force fields for a viscoelastic body with damage, the differential equations of motion for thin and thick plates with damage are derived under arbitrary boundary conditions...From the constitutive model with generalized force fields for a viscoelastic body with damage, the differential equations of motion for thin and thick plates with damage are derived under arbitrary boundary conditions. The convolution-type functionals for the bending of viscoelastic thin and thick plates with damage are presented, and the corresponding generalized variational principles are given. From these generalized principles, all the basic equations of the displacement and damage variables and initial and boundary conditions can be deduced. As an example, we compare the difference between the dynamical properties of plates with and without damage and consider the effect of damage on the dynamical properties of plates.展开更多
The cutting performance of particle reinforced meta ll ic matrix composites (PRMMCs) SiC p/Al in ultrasonic vibration cutting and comm on cutting with carbide tools and PCD tools was experimentally researched in the p...The cutting performance of particle reinforced meta ll ic matrix composites (PRMMCs) SiC p/Al in ultrasonic vibration cutting and comm on cutting with carbide tools and PCD tools was experimentally researched in the paper. The changing rules of chip shape, deformation coefficient, shear angle a nd surface residual stress were presented by ultrasonic vibration cutting. Resul ts show: when adopting common cutting, spiral chip with smaller curl radius will be obtained. The chip with zigzag contour is short and thick. There are lots of sheet cracking both on the face of the chip and on the machined surface. That i s to say, the cutting process of metallic matrix composites(MMCs) is not all lik e the cutting process of plastic material. It is akin to the breaking process of brittle material. By comparison, when adopting ultrasonic cutting, because tool contacts with workpiece intermittently in high frequency, deformation of chip i s small, loose spiral chip with larger curl radius is long and thin. The phenome non is just similar to vibration cutting of plastic material. But the chip still belongs to plastic or semi-plastic segmental chip due to the structure charact eristics of the material itself. Furthermore, the tangential residual compressio n stress of vibration cutting is larger than that of common cutting, axial resid ual stress has a relation to the feed rate and residual stress does not changes obviously with cutting depth and they are in the same order of magnitude on the whole. According to the test result analyzing, the following conclusions are put forward: 1) The extruding deformation is serious in common cutting PRMMCs, defo rmation of it’s chip is larger, and the chip with lesser curl radius is short. Whereas, the deformation of chip in vibration cutting PRMMCs is lesser, the curl radius is bigger, and the loose chips are obtained at every turn. 2) The cuttin g deformation coefficient of chip in vibration cutting is lesser than that in co mmon cutting, however the shear angle is bigger. 3) The tangential residual compression stress of vibration cutting is larger than that of common cutting, a nd residual stress does not change obviously with cutting depth, they are in the same order of magnitude on the whole.展开更多
基金sponsored by the National Natural Science Foundation of China (Nos.21677156,41201498,21107125,51290282,51608515)the National Water Pollution Control and Treatment Science and Technology Major Project (No.2015ZX07205-003)the special fund from the State Key Joint Laboratory of Environment Simulation and Pollution Control (Research Center for Eco-environmental Sciences,Chinese Academy of Sciences) (No.16Z02ESPCR)
文摘Organic matter(OM) is an important component of sediment. Bioturbation/bioirrigation can remobilize OM and heavy metals that were previously buried in the sediment. The remobilization of buried organic matter, thallium(Tl), cadmium(Cd), copper(Cu) and zinc(Zn) from sediment was studied in a laboratory experiment with three organisms: tubificid,chironomid larvae and loach. Results showed that bioturbation/bioirrigation promoted the release of dissolved organic matter(DOM) and dissolved Tl, Cd, Cu and Zn, but only dissolved Zn concentrations decreased with exposure time in overlying water. The presence of organisms altered the compositions of DOM released from sediment,considerably increasing the percentage of fulvic acid-like materials(FA) and humic acidlike materials(HA). In addition, bioturbation/bioirrigation accelerated the growth and reproduction of bacteria to enhance the proportion of soluble microbial byproduct-like materials(SMP). The DOM was divided into five regions in the three-dimensional excitation emission matrix(3 D-EEM), and each part had different correlation with the dissolved heavy metal concentrations. Dissolved Cu had the best correlation with each of the DOM compositions, indicating that Cu in the sediment was in the organic-bound form.Furthermore, the organism type and heavy metal characteristics both played a role in influencing the remobilization of heavy metal.
文摘Aimed at studying normali zed radial basis function network (NRBFN), this paper introduces the subtractiv e clustering based on a mountain function to construct the initial structure of NR BFN, adopts singular value decomposition (SVD) to analyze the relationship betwe en neural nodes of the hidden layer and singular values, cumulative contribution ratio, index vector, and optimizes the structure of NRBFN. Finally, simulation and performance comparison show that the algorithm is feasible and effective.
文摘The preparation of ultra fine Y A G( Y3 Al5 O12) po w der through co precipitation techniquew as investigated . The for m ation tem perature of Y A G w as lo wered belo w 800 ℃ by carefullycontrolling process para m eters . Ultra fine Y A G po w der w ith even size distribution , spheri cal shapes , and 40 n m particle size has been produced . It is found that for m ation of Y A Gisnot through the Y A M an d Y A Pinter mediate phases that are often observed during the synthe sis of Y A G by m ixed oxide m ethod . The sm all particle size of the precursor po w der , them olecular scale mixing of the constituents , and the poly m orphic transfor m ation of Al2 O3during heating accou nt m ainly for the reduction of for m ation tem perature of Y A Gan d the e lim ination of inter m ediate Y A M and Y A Pphases .
文摘受到单一或频域的特征提取限制,导致在复杂工况下机床工作数据存在微弱故障特征淹没现象,直接降低特征提取质量,间接影响机床的故障定位和诊断性能,为此提出基于双域深度学习与特征提取的机床故障定位与诊断方法。利用传感器设备同步采集振动、温度、电流等机床多源工作数据。构建双域深度学习网络,输入初始采集数据,分别提取机床的时域和频域工作特征,通过双域特征融合,得出机床工作特征提取结果。根据机床故障机理与表现,设定机床故障诊断标准。计算提取特征与故障诊断标准之间的特征匹配度,根据特征匹配度与阈值之间的关系,得出机床故障诊断结果,进而确定机床故障点位置。通过性能测试实验得出结论:与传统方法相比,优化设计方法的机床故障定位精度大幅提升,误诊率明显降低,同时受试者工作特征(receiver operating characteristic,ROC)曲线下面积(area under the curve,AUC)指标明显增大,由此证明优化设计方法在定位和诊断方面具有明显优势。
文摘The paper gives two estimates of the distance between adjacent zeros of solutions of the first\|order delay differential equation x′(t)+p(t)x(t-τ) =0 in the case when p(t)≥0 and ∫ t t-τ p(s)d s-1e oscillates or p(t) itself oscillates.
基金Project supported by the National Natural Sciences Foundation of China (No. 10272069) the Shanghai Key Subject Program.
文摘From the constitutive model with generalized force fields for a viscoelastic body with damage, the differential equations of motion for thin and thick plates with damage are derived under arbitrary boundary conditions. The convolution-type functionals for the bending of viscoelastic thin and thick plates with damage are presented, and the corresponding generalized variational principles are given. From these generalized principles, all the basic equations of the displacement and damage variables and initial and boundary conditions can be deduced. As an example, we compare the difference between the dynamical properties of plates with and without damage and consider the effect of damage on the dynamical properties of plates.
文摘The cutting performance of particle reinforced meta ll ic matrix composites (PRMMCs) SiC p/Al in ultrasonic vibration cutting and comm on cutting with carbide tools and PCD tools was experimentally researched in the paper. The changing rules of chip shape, deformation coefficient, shear angle a nd surface residual stress were presented by ultrasonic vibration cutting. Resul ts show: when adopting common cutting, spiral chip with smaller curl radius will be obtained. The chip with zigzag contour is short and thick. There are lots of sheet cracking both on the face of the chip and on the machined surface. That i s to say, the cutting process of metallic matrix composites(MMCs) is not all lik e the cutting process of plastic material. It is akin to the breaking process of brittle material. By comparison, when adopting ultrasonic cutting, because tool contacts with workpiece intermittently in high frequency, deformation of chip i s small, loose spiral chip with larger curl radius is long and thin. The phenome non is just similar to vibration cutting of plastic material. But the chip still belongs to plastic or semi-plastic segmental chip due to the structure charact eristics of the material itself. Furthermore, the tangential residual compressio n stress of vibration cutting is larger than that of common cutting, axial resid ual stress has a relation to the feed rate and residual stress does not changes obviously with cutting depth and they are in the same order of magnitude on the whole. According to the test result analyzing, the following conclusions are put forward: 1) The extruding deformation is serious in common cutting PRMMCs, defo rmation of it’s chip is larger, and the chip with lesser curl radius is short. Whereas, the deformation of chip in vibration cutting PRMMCs is lesser, the curl radius is bigger, and the loose chips are obtained at every turn. 2) The cuttin g deformation coefficient of chip in vibration cutting is lesser than that in co mmon cutting, however the shear angle is bigger. 3) The tangential residual compression stress of vibration cutting is larger than that of common cutting, a nd residual stress does not change obviously with cutting depth, they are in the same order of magnitude on the whole.
