Papers by Keyword: Dispersion

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Authors: Hui Lan Ren, Ping Li
Abstract: The dynamic response of polycrystalline alumina were investigated in the pressure range of 0-13Gpa by planar impact experiments. Manganin gauges were employed to obtain the stress-time histories. From the free surface particle velocity profiles indicate the dispersion of the “plastic” wave for alumina. Using path line principle of Lagrange Analysis the dynamic mechanical behaviors for alumina under impact loading are analyzed, such as nonlinear, strain rate dependence, dispersion and declination of shock wave in the material. A damage model applicable to ceramics subjected to dynamic compressive loading is developed. The model is based on the damage micromechanics and established on wing crack nucleation and growth. The results of the dynamic damage evolution model are compared to the experimental results and a good correlation is obtained.
Authors: H.W. Jun, Hyun Kwang Seok, Joo Sun Kim, Hai Won Lee
Abstract: A feasibility study was conducted, in order to fabricate WC-Co powder granule as high-performance feedstock for thermal spraying process, by spray drying weakly flocculated nano-particulate slurries under various conditions. The defects were evaluated with respect to the amount of additives to prepare spherical WC-Co feedstock powders with few morphological defects and homogeneous microstructures. The characteristics of feedstock powders heat-treated at 850~ 1200ı were analyzed using SEM, EPMA, and Hg-porosimetry. The microstructure investigation revealed that the relative portion of larger pores around 10 µm increased with increasing heattreatment temperature. On the other hand, the relative portion of smaller pores of 1 µm decreased due to the coalescence of WC particles, leading to dense feedstock powders with less defects such as hollow or craters. The hardness of thermal-sprayed coat developed with the feedstock in this study, which had exceptionally high feedstock strength, was superior to that of any other sprayed coat obtained with commercial feedstock powders.
Authors: Chun Ping Liu, Yun Shi, Yan Dong Tang, Xin Liao
Abstract: A graphing method is presented in this paper for estimating the parameters of solute transport in soils based on the convection-dispersion equation (CDE). The ratio of flux concentration change with time (dc/dt) is obtained on data of breakthrough curve (BTC) of solute transport in a semi-infinite soil column. Using graphing software, for example, the Microsoft Excel, can draw two curves of t1.5dc/dt and dc/dt respect to time. Each curve has single peak. The two curves are used to estimate the retardation factor and dispersion coefficient in the CDE. Hypothetical examples and displacement experimental data of two soils were used to validate the new graphing method for its accuracy and stability for estimating the two parameters. The stability of parameter estimation is evaluated by the standard deviations of estimation parameters to their average value. The accuracy of the new method is assessed by comparing it with other two most used methods that are the CXTFIT and the slope methods. The results show that the method has both high accuracy and good stability. The new method is particularly good for the estimation of parameter R. The method is a deterministic method and it is simple in terms of calculations. It also has the advantages of uniqueness and no initial guess of the parameters over the CXTFIT method. The new method provides an alternative approach for estimating parameters of solute transport in soils. It is simple, accurate, stable, and saves time.
Authors: Yu Wei Sun, Yu Kun Bai
Abstract: A dual-core photonic crystal fiber (PCF) with high birefringence, short coupling length and broadband flat dispersion is proposed in the paper. The symmetry of the original symmetric structure composed of hexagonally distributed air holes is distorted by replacing the innermost 12 air holes with 6 elliptical air holes. The characteristics of the dual-core PCF such as birefringence, coupling length and chromatic dispersion are analyzed by tuning its structural parameters. The results demonstrated that the dual-core PCF exhibits simultaneously a birefringence of up to 10-2, a coupling length of 68.178 for the x-polarization and 74.825 for the y-polarization, and a broadband flat dispersion ranging from 1.1 to 1.6. The novel dual-core PCF may find applications in polarization-maintaining fibers and fiber-based polarization beam splitters/couplers with broadband flat dispersion.
Authors: Xiao Bo Wang, Chuan Sheng Wang
Abstract: Quantitative evaluation of carton black’s dispersion is useful for researching the influence of every kind of mixing procedure on carton black’s dispersion and the relationship between carton black’s dispersion and rubber’s property. Though analyzing standard images, the rule was found that the total number of carton black in rubber image changed smaller with the improvement of dispersion level. Combined with divided feature regions, the evaluation model of carton black’s dispersion was built on the basis of the total number of carton black in rubber image. The result of the evaluation describes the tendency of carton black’s size in the process of mixing and shows the distribution of carton black’s size.
Authors: Zheng Xu, Shou Ci Lu
Abstract: A new electrostatic dispersion device was designed to reduce the agglomeration of fine powder in the air. This device is using the repulse force between particles which charged the same charge to prevent the particles from reuniting. The effects of charge voltage, particle size, the distant between electrode, and moisture content on the dispersion degree of the powder are discussed. The invalidation time of the electrostatic dispersion is also highlighted in the paper. The results show that the electrostatic dispersion is an effective method for the fine powders in the air. The charge voltage is the most important parameter for the dispersion. Middle size particle got best dispersion. When the distance between the electrodes is 24cm, the dispersion degree reaches the maximum. The humidity of the powder not only affects the charge of the powder, but also affects the dispersion degree of the powder.
Authors: Xiang Ying Hao, Cui Zhang, Shuang Xi Liu, Hai Fu Guo
Abstract: Zeolites mordenite (MOR) and β decorated with high dispersion degree and loading content of CuO composite (symbolized as CuO/zeolite) were prepared via a novel method-the stepped hydrothermal synthesis. The resultant composite were characterized with details by powder XRD, ICP-AES, H2-TPR and TEM techniques. Shown by experiment, the stepped hydrothermal synthetic method adopted in the present research using urea as alkali source as well as benefiting from the ultrasonic wash treatment hardly damages the zeolitic framework structure. Compared with ammonia, high dispersion degree and loading level of CuO are yielded as a consequence of the employment of urea as alkali source. Besides, the ultrasonic wash treatment not only removes some CuO precursors that deposit on the external surface of the porous support but also produces a uniform distribution of CuO particles with smaller dimension on the surface of zeolites: CuO are dispersed in nanoscale of about 4-8 nm on mordenite and 2-5 nm on zeolite β. The present synthetic strategy could be therefore applied as a novel general method for the manufacture of functional materials in a wide spectrum.
Authors: Dong Ming Qi, Rui Zhang, Jie Xu, Xing Cong Shen, Koh Hei Nitta
Abstract: A novel phenolic rigid organic filler (named K3) was dispersed in isotactic polypropylene matrix (iPP) by melt-mixing process, and a series of K3/iPP blends was prepared with or without maleic anhydride-grafted polypropylene (MAPP) as compatibilizer. The influences of K3 and MAPP on the filler dispersion were studied using Polarized Optical Microscope (POM) and Fourier Transform Infrared Spectroscopy (FTIR). The influences on the modulus of blends were studied by tensile test and Dynamic Mechanical Analysis (DMA). It was found that K3 can be dispersed in iPP matrix in a spherical form and its particles size can be adjusted by MAPP content. The incorporation of K3 and MAPP can obviously improve the Youngs modulus and storage modulus of blends.
Authors: Shu Ping Yi, Hai Yi Ma, Hua An Wang
Abstract: Near surface disposal of low and intermediate level radioactive waste (LILW) requires a detailed site investigation of the potential sites, in which the transport behavior of solutes in the groundwater system is one of the key processes that needed to be addressed. An investigation is undertaking for the disposal of LILW at a potential site in Southern China. In-situ test have been conducted to study the hydrogeologic characteristics of the site. Firstly, tests including pit permeability tests, injecting tests, water pressure tests, pumping tests and laboratory permeability tests have been performed according to the specific field conditions. Hydraulic conductivities for different layers of rock and soils have been calculated and their recommended values have been presented. And then in-situ dispersion tests have been performed at an area adjacent to the disposal site with non-sorbed tracers. A numerical model has been developed for the site based on data obtained during the site investigation, and has been calibrated with available measured groundwater level and measured tracer concentrations in the dispersion tests. Calibrated results indicate that the longitudinal dispersion coefficient is equal to 5.0×10-3 m2/d. Preliminary predictions have been performed for the groundwater flow and solute advection-dispersion behavior according to the design of the site, in which the center valley will be backfilled with low permeable materials. Predicted results indicate that the groundwater exhibits a lower water table and a smaller hydraulic gradient under designed site condition than under natural condition. All the tracers remain underground in the site and transport slowly mainly through advection and dispersion. Finally, conclusions for the study have been presented and the key tasks for future work have been discussed. This study provides an insight understanding of the hydrogeology characteristics of the disposal site and is useful for the assessment of environment impacts of the site under disposal of LILW.
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