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Experimental determination of distributions of soot particle diameter and number density by emission and scattering techniques
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作者 柳华蔚 郑树 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第1期400-405,共6页
A diagnostics method was presented that uses emission and scattering techniques to simultaneously determine the distributions of soot particle diameter and number density in hydrocarbon flames. Two manta G-504 C camer... A diagnostics method was presented that uses emission and scattering techniques to simultaneously determine the distributions of soot particle diameter and number density in hydrocarbon flames. Two manta G-504 C cameras were utilized for the scattering measurement, with consideration of the attenuation effect in the flames according to corresponding absorption coefficients. Distributions of soot particle diameter and number density were simultaneously determined using the measured scattering coefficients and absorption coefficients under multiple wavelengths already measured with a SOC701 V hyper-spectral imaging device, according to the Mie scattering theory. A flame was produced using an axisymmetric laminar diffusion flame burner with 194 mL/min ethylene and 284 L/min air, and distributions of particle diameter and number density for the flame were presented. Consequently, the distributions of soot volume fraction were calculated using these two parameters as well, which were in good agreement with the results calculated according to the Rayleigh approximation,demonstrating that the proposed diagnostic method is capable of simultaneous determination of the distributions of soot particle diameter and number density. 展开更多
关键词 SOOT PARTICLE DIAMETER SOOT PARTICLE NUMBER density SOOT volume FRACTION SCATTERING measurement
基于新兴编码微载体的多元生物检测
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作者 徐月霜 王欢 +2 位作者 陈宝安 刘宏 赵远锦 《中国科学:材料科学(英文版)》 CSCD 2019年第3期289-324,共36页
随着对大量生物分子的高通量分析的需求不断增长,多元分析成为用于进行大规模生物分析的前景技术.在目前的技术中,基于编码微载体的液相芯片已被广泛用于如临床、医学、营养和环境等诸多研究领域的多元生物检测中.这些编码微载体除了具... 随着对大量生物分子的高通量分析的需求不断增长,多元分析成为用于进行大规模生物分析的前景技术.在目前的技术中,基于编码微载体的液相芯片已被广泛用于如临床、医学、营养和环境等诸多研究领域的多元生物检测中.这些编码微载体除了具有独特的编码形式,还具有更高的灵活性,更好的灵敏度及更快的反应动力学.在本综述中,我们根据编码方法描述了一些常见的编码微载体,并且介绍了它们在不同靶标(如蛋白质,核酸及细胞)的多元生物分析中的应用,以及在不同领域(如监测食品安全,药物研究和临床诊断)中的应用. 展开更多
关键词 BARCODE SUSPENSION ARRAY BIOASSAY multiplex particle
Determination of the particle load based on detailed suspended sediment measurements at a hydropower plant 预览
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作者 Anant Kumar Rai Arun Kumar 《国际泥沙研究:英文版》 SCIE 2019年第5期409-421,共13页
Suspended sediment particles contained in inflows of water systems of hydropower plants (HPPs) cause hydro-abrasive erosion of the hydraulic turbines and structures leading to significant maintenance costs, efficiency... Suspended sediment particles contained in inflows of water systems of hydropower plants (HPPs) cause hydro-abrasive erosion of the hydraulic turbines and structures leading to significant maintenance costs, efficiency reductions, and downtime. Relevant parameters such as suspended sediment concentration (SSC), particle size distribution (PSD), shape, and mineralogical composition were measured with an online multi-frequency acoustic instrument and based on manually taken samples from the end of the sand trap of the Toss HPP in the Himalayan region, India. In the laboratory, the samples were analyzed using the gravimetric method, laser diffraction, turbidity, dynamic digital image processing, scanning electron microscope, petrography analysis, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The online instrument and the samples provided measurement results at a single point. To investigate vertical gradients in concentration and particle sizes, additional samples were collected 9 times at 7 relative water depths. The SSC, most particle sizes, and particle shape were found to be evenly distributed over depth except d90, i.e. the diameter which is not exceeded by 90% of the particle mass. d90 measured at 76% of the water depth was in the range of fine sand and was multiplied by 1.05 to obtain an average value representative for the entire depth. Improved methodologies to quantify both particle shape and size in an analytical model for hydro-abrasive erosion are proposed. Also, the PSD measuring performance of laser diffraction and dynamic imaging was studied and similar values of the median particle sizes were obtained from both instruments. Further, multi-frequency acoustic, turbidity and laser diffraction techniques were found suitable for SSC measurement at the test case HPP. 展开更多
关键词 Suspended sediment concentration Hydro-abrasive EROSION HYDROPOWER PARTICLE size distribution PARTICLE shape MINERALOGICAL composition
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Exploration of particle technology in fine bubble characterization
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作者 Renliang Xu Yaru Wang Zhaojun Li 《颗粒学报:英文版》 SCIE EI CAS CSCD 2019年第5期109-115,共7页
Fine bubble technology has been applied in many fields, including semiconductor processing, waste water treatment, and agricultural development. Fine bubble technology has the advantages of being environ-mentally beni... Fine bubble technology has been applied in many fields, including semiconductor processing, waste water treatment, and agricultural development. Fine bubble technology has the advantages of being environ-mentally benign, and ease of production and use when compared with other processes that involve chemicals or biological agents. However, the mechanisms of fine bubble applications in many aspects still require exploration. The characterization of fine bubbles is one of the essential issues for better understanding the technology. This article reviews modern particle characterization technologies, espe-cially those that can be used to characterize fine bubbles, and briefly reports on some applications of fine bubbles. 展开更多
关键词 FINE BUBBLES BUBBLE CHARACTERIZATION PARTICLE technology PARTICLE size
Dynamic hydraulic jump and retrograde sedimentation in an open channel induced by sediment supply: experimental study and SPH simulation
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作者 ZHENG Xiao-gang CHEN Ri-dong +2 位作者 LUO Min KAZEMI Ehsan LIU Xing-nian 《山地科学学报:英文版》 SCIE CSCD 2019年第8期1913-1927,共15页
Mountainous torrents often carry large amounts of loose materials into the rivers, thus causing strong sediment transport. Experimentally it was found for the first time that when the intensive sediment motion occurs ... Mountainous torrents often carry large amounts of loose materials into the rivers, thus causing strong sediment transport. Experimentally it was found for the first time that when the intensive sediment motion occurs downstream over a gentle slope, the siltation of the riverbed is induced and the sediment particles can move upstream rapidly in the form of a retrograde sand wave, resulting in a higher water level along the river. To further study the complex mechanisms of this problem, a sediment mass model in the framework of the Smoothed Particle Hydrodynamics(SPH) method was presented to simulate the riverbed evolution, sediment particle motion, and the generation and development of dynamic hydraulic jump under the condition of sufficient sediment supply over a steep slope with varying angles. Because the sediment is not a continuous medium, the marker particle tracking approach was proposed to represent a piece of sediment with a marked sediment particle. The twophase SPH model realizes the interaction between the sediment and fluid by moving the bed boundary particles up and down, so it can reasonably treat the fluid-sediment interfaces with high CPU efficiency. The critical triggering condition of sediment motion, the propagation of the hydraulic jump and the initial siltation position were all systematically studied. The experimental and numerical results revealed the extra disastrous sediment effect in a mountainous flood. The findings will be useful references to the disaster prevention and mitigation in mountainous rivers. 展开更多
关键词 DYNAMIC hydraulic jump RETROGRADE SEDIMENTATION SEDIMENT supply Mountainous river Smoothed PARTICLE Hydrodynamics MARKED SEDIMENT PARTICLE
Statistical characteristics and mechanism analysis of adhered particle on surface under strong electric field
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作者 Yunpeng Jiang Lee Li +4 位作者 Ming Lu Rumeng Wang Yiwen Jiang Shanfeng Liu Chao Su 《中国颗粒学报:英文版》 SCIE EI CAS CSCD 2019年第2期110-122,共13页
Insulators on high-voltage Uansmission lines are almost the only man-made structures on the Earth's surface intended for long-term operation under strong electric fields. After samples of natural contaminant parti... Insulators on high-voltage Uansmission lines are almost the only man-made structures on the Earth's surface intended for long-term operation under strong electric fields. After samples of natural contaminant particles were collected from insulator surfaces in China, it was found that the particle diameter distribution (PDD) was mainly concentrated in the 5-50 μm range. To analyze the statistical characteristics of these particles, this work studies the physical processes of particle collision and adhesion using the theories of hydrodynamics and collision dynamics. The physical model considers coupling of the fluid field and the electric field, introduces an adhesion criterion, and establishes a particle and surface collision model. The effects of relative humidity, wind speed, aerodynamic shape, electric field type, and electric field strength on particle adhesion were analyzed. The results show that the relative humidity and wind speed have very significant effects and the influences of the electric field type and the electric field strength are obvious, but the in fluence of the aerodynamic shape is relatively weak. The simulation results support the statistical characteristics determined in this work. The physical model established here provides reference values for study of the adhesion characteristics of particles on surfaces under electric fields. 展开更多
关键词 CONTAMINANT PARTICLE COLLISION ADHESION PARTICLE DIAMETER Simulation analysis
Effect of Particle Size Distribution on Radiative Heat Transfer in High-Temperature Homogeneous Gas-Particle Mixtures 预览
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作者 LIANG Dong HE Zhenzong +1 位作者 XU Liang MAO Junkui 《南京航空航天大学学报:英文版》 EI CSCD 2019年第5期733-746,共14页
The weighted-sum-of-gray-gas(WSGG)model and Mie theory are applied to study the influents of particle size on the radiative transfer in high temperature homogeneous gas-particle mixtures,such as the flame in aero-engi... The weighted-sum-of-gray-gas(WSGG)model and Mie theory are applied to study the influents of particle size on the radiative transfer in high temperature homogeneous gas-particle mixtures,such as the flame in aero-engine combustor.The radiative transfer equation is solved by the finite volume method.The particle size is assumed to obey uniform distribution and logarithmic normal(L-N)distribution,respectively.Results reveal that when particle size obeys uniform distribution,increasing particle size with total particle volume fraction fvunchanged will result in the decreasing of the absolute value of radiative heat transfer properties,and the effect of ignoring particle scattering will also be weakened.Opposite conclusions can be obtained when total particle number concentration N0 is unchanged.Moreover,if particle size obeys L-N distribution,increasing the narrowness indexσor decreasing the characteristic diameter Dˉwith the total particle volume fraction fvunchanged will increase the absolute value of radiative heat transfer properties.With total particle number concentration N0 unchanged,opposite conclusions for radiative heat source and incident radiation terms can be obtained except for radiative heat flux term.As a whole,the effects of particle size on the radiative heat transfer in the high-temperature homogeneous gas-particle mixtures are complicated,and the particle scattering cannot be ignoring just according to the particle size. 展开更多
关键词 particle size distribution WSGG radiative heat transfer gas-particle mixtures
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Inflows/outflows driven particle dynamics in an idealised lake 预览
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作者 Cheng-hua Dang Jingchun Wang Qiuhua Liang 《水动力学研究与进展:英文版》 SCIE EI CSCD 2019年第5期873-886,共14页
This paper considers fluid mixing driven by inflows connected to a circular shallow lake using a numerical framework consisting of a shallow water hydrodynamic model and a passive particle-tracking model.With the flow... This paper considers fluid mixing driven by inflows connected to a circular shallow lake using a numerical framework consisting of a shallow water hydrodynamic model and a passive particle-tracking model.With the flow field driven by alternate inflows predicted by a shallow water model,particle trajectories are traced out using a particle tracking model.The horizontal fluid mixing dynamics are then interpreted using dynamics system analysis approaches including finite-time Lyapunov exponent(FTLE)and Lagrangian coherent structure(LCS).From the simulation results,it is confirmed that periodic inflows are able to create a weak dynamic system in an idealised circular lake,with the particle dynamics controlled by a single dimensionless parameter associated with the inflow duration.The mixing and transport property of the lake changes from regular to chaotic as the value of the dimensionless parameter increases until global chaotic particle dynamics is achieved.By further analysing the advection of particles injected continuously to the inflows(freshwater),the fate of“freshwater”particles in a“polluted”lake is tracked and revealed.The results provide useful guidance for engineering applications,i.e.,transferring freshwater from rivers to improve the water quality in polluted water bodies such as lakes.The presented approach will be able to facilitate the design of‘optimised’schemes for such engineering implementation. 展开更多
关键词 Shallow environmental flow Lagrangian particle dynamics particle tracking inflows and outflows finite-time Lyapunov exponent Lagrangian coherent structure
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Generalized algorithms for particle motion and collision with streambeds 预览
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作者 Patricio A.Moreno-Casas Fabian A. Bombardelli Juan Pablo Toro 《国际泥沙研究:英文版》 SCIE 2019年第4期295-306,共12页
Recent theoretical and numerical models for the motion of saltating particles close to stream beds are constituted of three sub-models: a) a set of equations describing the particle “free flight”, b) a sub-model to ... Recent theoretical and numerical models for the motion of saltating particles close to stream beds are constituted of three sub-models: a) a set of equations describing the particle “free flight”, b) a sub-model to calculate the post-collision particle velocity, and c) a mathematical representation of the bed roughness. In this paper, a comprehensive three-dimensional (3-D), theoretical/numerical model for bedload motion at large Reynolds numbers is presented. By using geometric considerations and stochastic parameters to characterize collisions with the wall, five new sub-models for representation of bed roughness are, for the first time to the best of our knowledge, proposed and implemented. The emphasis of this paper is on the particle model, for which Basset, Magnus, drag, submerged weight, virtual mass, and lift forces are included. For the range of particle sizes (sands) analyzed herein, it is found that the stream-wise contribution of the Basset force, compared to other forces, may be as large as 60%. Whereas in the wall-normal direction, the Basset force is equally important as the drag force, and it is exceeded only by the submerged weight. It is also found that the best agreement between numerical and experimental results in terms of jump length, jump height, and stream-wise particle velocity is achieved for restitution and friction coefficients of 0.65 and 0.1, respectively. Important conclusions are obtained regarding the lack of realistic prediction with available “roughness” models with small ranges of angles. 展开更多
关键词 Particlesaltation PARTICLE COLLISION PARTICLE ROTATION Bed-load TRANSPORT Basset FORCE
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Settling behavior of non-spherical particles in power-law fluids:Experimental study and model development
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作者 Zhengming Xu Xianzhi Song +2 位作者 Gensheng Li Zhaoyu Pang Zhaopeng Zhu 《颗粒学报:英文版》 SCIE EI CAS CSCD 2019年第5期30-39,共10页
Solid-particle settling occurs in many natural and industrial processes, such as in the transportation of drilling cuttings and fracturing proppant. Knowledge of the drag coefficient and settling velocity of cuttings ... Solid-particle settling occurs in many natural and industrial processes, such as in the transportation of drilling cuttings and fracturing proppant. Knowledge of the drag coefficient and settling velocity of cuttings and proppant is of significance to hydraulics design, wellbore cleanout, and fracture optimization. We conducted 553 tests to investigate the settling characteristics of spherical and non-spherical particles in power-law fluids. Three major particle shapes (spherical, cubic, and cylindrical) and eight different particle sphericities were used to simulate cuttings and proppant, and power-law fluids were applied to simulate drilling and fracturing fluids. Based on the data analysis, a new drag coefficient-particle Reynolds number correlation was developed to determine the drag coefficient in a power-law fluid for spherical and non-spherical particles. The drag coefficient increases as the sphericity decreases for the same particle Reynolds number. For a specific particle shape, the drag coefficient decreases as the particle Reynolds number increases, but the decreasing trend is reduced at high particle Reynolds number conditions. An explicit settling-velocity equation was proposed to calculate the settling velocity of spherical and non-spherical particles in power-law fluids by considering the effect of sphericity. A suitable range for the proposed model is 0.0001 < Re <200, 0.471 <φ< 1, and 0.505 < n < 1. An illustrative example is presented to show how to calculate the drag coefficient and settling velocity in power-law fluids with given particle and fluid properties. 展开更多
关键词 SETTLING velocity Drag coefficient NON-SPHERICAL PARTICLE SPHERICAL PARTICLE POWER-LAW FLUIDS
Discrete element simulation of cylindrical particles using super-ellipsoids
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作者 Yongzhi Zhao Lei Xu +1 位作者 Paul B. Umbanhowar Richard M. Lueptow 《颗粒学报:英文版》 SCIE EI CAS CSCD 2019年第5期55-66,共12页
A discrete element model based on super-ellipsoids was used to simulate cylindrical particle flow. The model can describe a cylindrical particle accurately provided the shape indices of the super-ellipsoids are set to... A discrete element model based on super-ellipsoids was used to simulate cylindrical particle flow. The model can describe a cylindrical particle accurately provided the shape indices of the super-ellipsoids are set to appropriate values. To achieve more rapid calculations, we implemented an "oriented bounding box algorithm"(OBBA) for the initial contact detection of cylindrical particles. Several types of Simulations were performed to validate the super-ellipsoid model and the contact-detection algorithm. First, the effect of shape index of the super-ellipsoids on model accuracy was investigated through three simulations: impact of a cylindrical particle on a flat wall, flow of cylindrical particles in a rotating tumbler, and segregation of cylindrical particles of different length flowing down a bounded heap. The simulation results show that the super-ellipsoids describe cylindrical particles accurately when the shape index that specifies the sharpness of the cylinder edges is sufficiently large. The efficiency of the OBBA is measured by simulations in which a box is filled with cylindrical particles and a tumbler that contains cylindrical particles is rotated. The simulation results show that the OBBA can accelerate the calculations significantly. The effect of particle shape (such as aspect ratio and shape index) on the calculation speed was obtained. The simulation of rod-like particles tended to take more calculation time than that of disk-like particles, and the simulation time increased with an increasing particle-shape index. 展开更多
关键词 Discrete element method Super-ellipsoid Super-quadric Cylindrical PARTICLE NON-SPHERICAL PARTICLE GRANULAR material
On the breakage function for constructing the fragment replacement modes
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作者 Wei Zhou Kun Xu +1 位作者 Gang Ma Xiaolin Chang 《颗粒学报:英文版》 SCIE EI CAS CSCD 2019年第3期207-217,共11页
The fragment replacement method (FRM), a particle breakage simulation method, is often used in discrete element simulations to investigate the particle breakage effect on the mechanical behavior of granular materials.... The fragment replacement method (FRM), a particle breakage simulation method, is often used in discrete element simulations to investigate the particle breakage effect on the mechanical behavior of granular materials. The fragment size distribution of the fragment replacement mode of FRM, which is generally generated based on the fragmentation characteristics of single particles after uniaxial compression, affects the breakage process and the mechanical behavior of the particle assembly. However, existing fragment replacement modes are seldom generated based on experimental data analysis. To capture the fragmentation process and investigate the breakage function for the construction of the fragment replacement mode, 60 numerical single particle compression tests were implemented by DEM. The bonded-particle model was applied to generate the crushable rock particles. The numerical simulations were qualitatively validated by experimental results, and the fragment size of broken single particles was analyzed. The fractal dimension was used to describe the fragmentation degree of single particles after compression. The fragmentation degree was random, and the fractal dimensions of the 60 tests at the same loading displacement fit the Weibull distribution well. The characteristic fractal dimension increased with increasing loading displacement, indicating that the fragmentation of single particles is a gradual process. According to the overall breakage function of the 60 tests at the first bulk breakage, a two-stage distribution model with 4 parameters was proposed and validated by the numerical and experimental results. The various fracture patterns of a single particle at the first bulk breakage under compression tests were well captured by the two-stage distribution model. Finally, an initial application strategy using the two-stage distribution model to construct fragment replacement modes was discussed and presented. 展开更多
关键词 PARTICLE BREAKAGE Single PARTICLE compression test DEM FRAGMENT REPLACEMENT mode BREAKAGE function
风电叶片涂料施工中颗粒问题解决方法探讨
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作者 毛为乙 《现代涂料与涂装》 CAS 2019年第5期57-59,共3页
在风电叶片的涂层施工中,为了提高涂层使用寿命及抗冰冻、自清洁性能,一般在滚涂聚氨酯底漆、弹性聚氨酯中间漆后喷涂一层氟碳涂料。因风电叶片体积大,施工时间长,故漆膜中颗粒难以避免通过改善喷涂环境,改变施工工艺后有效解决了漆膜... 在风电叶片的涂层施工中,为了提高涂层使用寿命及抗冰冻、自清洁性能,一般在滚涂聚氨酯底漆、弹性聚氨酯中间漆后喷涂一层氟碳涂料。因风电叶片体积大,施工时间长,故漆膜中颗粒难以避免通过改善喷涂环境,改变施工工艺后有效解决了漆膜中颗粒问题。 展开更多
关键词 风电叶片 喷涂 施工工艺 施工环境 颗粒
GPU-accelerated scanning path optimization in particle cancer therapy 预览
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作者 Chao Wu Yue-Hu Pu Xiao Zhang 《核技术:英文版》 SCIE CAS CSCD 2019年第4期27-34,共8页
When using the beam scanning method for particle beam therapy, the target volume is divided into many iso-energy slices and is irradiated slice by slice. Each slice may comprise thousands of discrete scanning beam pos... When using the beam scanning method for particle beam therapy, the target volume is divided into many iso-energy slices and is irradiated slice by slice. Each slice may comprise thousands of discrete scanning beam positions. An optimized scanning path can decrease the transit dose and may bypass important organs. The minimization of the scanning path length can be considered as a variation of the traveling salesman problem;the simulated annealing algorithm is adopted to solve this problem. The initial scanning path is assumed as a simple zigzag path;subsequently, random searches for accepted new paths are performed through cost evaluation and criteria-based judging. To reduce the optimization time of a given slice, random searches are parallelized by employing thousands of threads. The simultaneous optimization of multiple slices is realized by using many thread blocks of generalpurpose computing on graphics processing units hardware. Running on a computer with an Intel i7-4790 CPU and NVIDIA K2200 GPU, our new method required only 1.3 s to obtain optimized scanning paths with a total of 40 slices in typically studied cases. The procedure and optimization results of this new method are presented in this work. 展开更多
关键词 PARTICLE BEAM therapy Treatment PLANNING SCANNING PATH optimization
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Kinetic and thermodynamic studies on partitioning of polychlorinated biphenyls (PCBs) between aqueous solution and modeled individual soil particle grain sizes
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作者 Gbadebo Clement Adeyinka Brenda Moodley 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第2期100-110,共11页
The significance of soil mineral properties and secondary environmental conditions such as pH, temperature, ionic strength and time in the partitioning of eight selected polychlorinated biphenyl (PCB) congeners betwee... The significance of soil mineral properties and secondary environmental conditions such as pH, temperature, ionic strength and time in the partitioning of eight selected polychlorinated biphenyl (PCB) congeners between aqueous solution and soil particles with different grain sizes was studied. The mineral properties of a model soil sample were determined, and Brunauer–Emmett–Teller (BET) adsorption–desorption isotherms were employed to observe the surface characteristics of the individual modeled soil particles. Batch adsorption experiments were conducted to determine the sorption of PCBs onto soil particles of different sizes. The results revealed that the sorption of PCB congeners onto the soil was dependent on the amount of soil organic matter, surface area, and pore size distribution of the various individual soil particles. Low pH favored the sorption of PCBs, with maximum sorption occurring between pH 6.5 and 7.5 with an equilibration period of 8 hr. Changes in the ionic strength were found to be less significant. Low temperature favored the sorption of PCBs onto the soil compared to high temperatures. Thermodynamic studies showed that the partition coefficient (Kd) decreased with increasing temperature, and negative and low values of ΔH° indicated an exothermic physisorption process. The data generated is critical and will help in further understanding remediation and cleanup strategies for polluted water. 展开更多
关键词 Partitioning PCBS Soil particle grain SIZES Kinetics THERMODYNAMIC studies pH
Experimental investigation of crossflow characteristics in multi-jets system at small nozzle-to-plate spacing 预览
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作者 ZHU Keqian SUN Tao +3 位作者 YU Pingping LI Meixiang YUAN Ningyi DING Jianning 《排灌机械工程学报》 CSCD 北大核心 2019年第2期142-147,共6页
To further extend knowledge about the detailed knowledge on the crossflow characteristics in a multi-jets system under a confined space,particle image velocimetry(PIV)was employed to investigate the flow structures to... To further extend knowledge about the detailed knowledge on the crossflow characteristics in a multi-jets system under a confined space,particle image velocimetry(PIV)was employed to investigate the flow structures together with the distributions of the mean velocity components for Reynolds numbers(Re)ranging from 6 213 to 13 418,nozzle-to-plate spacing(H/D)varying from 0.20 to 1.25,respectively.Results show that the crossflow configuration is significantly different from those of large nozzle-to-plate spacing.In addition,a turning point H/D=0.50 is revealed in the profile of the normalized maximum radial velocity which is associated with the heat transfer distribution on the impingement plate. 展开更多
关键词 CROSSFLOW multiple impinging jets SMALL nozzle-to-plate SPACING Reynolds numbers particle image VELOCIMETRY
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Effect of glow discharge on hypersonic flat plate boundary layer 预览
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作者 Chi LI Yunchi ZHANG 《应用数学和力学:英文版》 SCIE EI CSCD 2019年第2期249-260,共12页
Glow discharge is introduced as an artificial disturbance to investigate the evolution of first-and second-mode instabilities in a hypersonic flat plate boundary layer.Experiments are conducted in a Mach 6.5 quiet win... Glow discharge is introduced as an artificial disturbance to investigate the evolution of first-and second-mode instabilities in a hypersonic flat plate boundary layer.Experiments are conducted in a Mach 6.5 quiet wind tunnel using Rayleigh scattering visualization and particle image velocimetry(PIV).Detailed analysis of the experimental observations is provided.It is found that the artificially introduced 17 kHz disturbance,which belongs to the first-mode frequency band,can effectively enhance first-mode waves.Moreover,it can enhance second-mode waves even more intensely.Possible mechanisms to explain this phenomenon are discussed. 展开更多
关键词 GLOW DISCHARGE HYPERSONIC particle image velocimetry(PIV)
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Diurnal Variation of Atmospheric Aerosol Particles in the Phyllostachys heterocycla Forest in Spring 预览
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作者 WANG Qian WANG Cheng +3 位作者 REN Binbin XU Chao GUO Junqi ZHANG Zhongxia 《景观研究:英文版》 2019年第5期116-118,122共4页
Taking the Phyllostachys heterocycla forest in Qishan National Forest Park of Fuzhou for example,this study observed the diurnal variation of atmospheric aerosol particles in the forest in the growing season.The resul... Taking the Phyllostachys heterocycla forest in Qishan National Forest Park of Fuzhou for example,this study observed the diurnal variation of atmospheric aerosol particles in the forest in the growing season.The results showed that:① The diurnal variation curves of the particle concentration of the forest and the forest edge had “two peaks and two troughs”,but the peaks and troughs of the forest edge were advanced or delayed.The concentrations of the particles in the forest and at the forest edge had two peaks at 11:00–13:00 and 17:00–19:00 and two troughs at 7:00–9:00 and 15:00–17:00.② For the forest and the forest edge,the diurnal variation trends of the particles of different particle sizes were generally similar,except that the peaks and troughs of fine particles were slightly earlier or lagging than that of coarse particles.③ The concentrations of the particles were positively correlated with temperature,humidity and light,and negatively correlated with wind speed,and the concentrations of the particles at the forest edge were significantly negatively correlated with wind speed. 展开更多
关键词 PHYLLOSTACHYS heterocycla GROWING SEASON ATMOSPHERIC AEROSOL particle DIURNAL variation
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Phase diagrams, mechanisms and unique characteristics of alternating-structured polymer self-assembly via simulations
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作者 Shanlong Li Chunyang Yu Yongfeng Zhou 《中国科学:化学英文版》 SCIE EI CAS CSCD 2019年第2期226-237,共12页
Alternating-structured polymers(ASPs), like alternating copolymers, regular multiblock copolymers and polycondensates, are very important polymer structures with broad applications in photoelectric materials. However,... Alternating-structured polymers(ASPs), like alternating copolymers, regular multiblock copolymers and polycondensates, are very important polymer structures with broad applications in photoelectric materials. However, their self-assembly behaviors,especially the self-assembly of alternating copolymers, have not been clearly studied up to now. Meanwhile, the unique characteristics therein have not been systematically disclosed yet by both experiments and theories. Herein, we have performed a systematic simulation study on the self-assembly of ASPs with two coil alternating segments in solution through dissipative particle dynamics(DPD) simulations. Several morphological phase diagrams were constructed as functions of different impact parameters. Diverse self-assemblies were observed, including spherical micelles, micelle networks, worm-like micelles, disklike micelles, multimicelle aggregates, bicontinuous micelles, vesicles, nanotubes and channelized micelles. Furthermore, a morphological evolutionary roadmap for all these self-assemblies was constructed, along with which the detailed molecular packing models and self-assembly mechanisms for each aggregate were disclosed. The ASPs were found to adopt a folded-chain mechanism in the self-assemblies. Finally, the unique characteristics for the self-assembly of alternating copolymers were revealed especially, including(1) ultra-fine and uniform feature sizes of the aggregates;(2) independence of self-assembled structures from molecular weight and molecular weight distribution;(3) ultra-small unimolecular aggregates. We believe the current work is beneficial for understanding the self-assembly of alternating structured polymers in solution and can serve as a guide for the further experiments. 展开更多
关键词 alternating-structured POLYMER SELF-ASSEMBLY DISSIPATIVE particle dynamics simulations phase diagram
聚氨酯材料液压密封的磨损加速试验方法浅析 预览
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作者 吴用 董旭庆 卫容芳 《液压气动与密封》 2019年第3期77-81,共5页
采用针盘式往复摩擦仪和液压密封测试机对聚氨酯液压密封进行耐磨性能分析,与现场实际磨损情况进行比较,来确定液压密封的磨损加速试验方法;但是采用液压密封测试机有显著压缩量,采用降低磨损的变色和氧化铝颗粒液压油经往复型针盘式摩... 采用针盘式往复摩擦仪和液压密封测试机对聚氨酯液压密封进行耐磨性能分析,与现场实际磨损情况进行比较,来确定液压密封的磨损加速试验方法;但是采用液压密封测试机有显著压缩量,采用降低磨损的变色和氧化铝颗粒液压油经往复型针盘式摩擦仪测试则密封面的磨损加速系数2.1~3.4。此实验有益于液压密封耐磨加速实验损设计和PU密封件设计。 展开更多
关键词 磨损 润滑 颗粒 聚氨酯 液压密封
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