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A new equation for dielectric permittivity of saturated soils based on polarization mechanics
Ren-peng CHEN, Yun-min CHEN, Wei XU, Zhi-gang LIANG, Wei FENG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(3): 293-302.
https://doi.org/10.1631/jzus.A071620
Based on polarization mechanisms, such as electronic, ionic and orientational polarizations, a new equation for dielectric permittivity of soil is proposed to interpret the dielectric behavior of a mixture like soil, in terms of polarization process of its components and the interactions between its components. The dielectric permittivity is expressed in terms of a frequency-dependent part and a frequency-independent part. These two parts correspond to polarizations occurred at different frequency range. It is a new volumetric mixing model with theoretical background. Based on time domain reflectometry (TDR) measurements of saturated soil samples and test data from literature, comparisons of this model with some well established mixing models show that the curves for saturated sand soils and slurries resulted from the new equation, which agree well with TDR measurements, are close to those calculated from Birchak’s model.
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Effect of pile-cap connection on behavior of torsionally loaded pile groups
Ling-gang KONG, Li-min ZHANG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(3): 303-312.
https://doi.org/10.1631/jzus.A0720022
To evaluate the responses of fixed and pinned pile groups under torsion, a method is presented to analyze the nonlinear behavior of free-standing pile groups with rigid pile caps. The method is capable of simulating the nonlinear soil response in the near field using p-y and τ-θ curves, the far-field interactions through Mindlin’s and Randolph’s elastic solutions, and the coupling effect of lateral resistance on torsional resistance of the individual piles using an empirical factor. Based on comparisons of the solutions for fixed- and pinned-head, 1×2, 2×2, and 3×3 pile groups subjected to torsion, it was found that pile-cap connection significantly influences the torsional capacity of pile groups and the assignment of applied torques in the pile groups. In this study, the applied torques for the pinned-head pile groups are only 44%~64% of those for the corresponding fixed-head pile groups at a twist angle of 2°. Such a difference is mainly due to the change of the lateral resistances of individual piles in the groups.
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Nonlinear stochastic optimal bounded control of hysteretic systems with actuator saturation
Rong-hua HUAN, Wei-qiu ZHU, Yong-jun WU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(3): 351-357.
https://doi.org/10.1631/jzus.A071275
A modified nonlinear stochastic optimal bounded control strategy for random excited hysteretic systems with actuator saturation is proposed. First, a controlled hysteretic system is converted into an equivalent nonlinear nonhysteretic stochastic system. Then, the partially averaged Itô stochastic differential equation and dynamical programming equation are established, respectively, by using the stochastic averaging method for quasi non-integrable Hamiltonian systems and stochastic dynamical programming principle, from which the optimal control law consisting of optimal unbounded control and bang-bang control is derived. Finally, the response of optimally controlled system is predicted by solving the Fokker-Planck-Kolmogorov (FPK) equation associated with the fully averaged Itô equation. Numerical results show that the proposed control strategy has high control effectiveness and efficiency.
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Research on cubic polynomial acceleration and deceleration control model for high speed NC machining
Hong-bin LENG, Yi-jie WU, Xiao-hong PAN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(3): 358-365.
https://doi.org/10.1631/jzus.A071351
To satisfy the need of high speed NC (numerical control) machining, an acceleration and deceleration (acc/dec) control model is proposed, and the speed curve is also constructed by the cubic polynomial. The proposed control model provides continuity of acceleration, which avoids the intense vibration in high speed NC machining. Based on the discrete characteristic of the data sampling interpolation, the acc/dec control discrete mathematical model is also set up and the discrete expression of the theoretical deceleration length is obtained furthermore. Aiming at the question of hardly predetermining the deceleration point in acc/dec control before interpolation, the adaptive acc/dec control algorithm is deduced from the expressions of the theoretical deceleration length. The experimental result proves that the acc/dec control model has the characteristic of easy implementation, stable movement and low impact. The model has been applied in multi-axes high speed micro fabrication machining successfully.
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Application of the ISCST3 model for predicting PCDD/F concentrations in agricultural soil in the vicinity of a MSWI plant in China
Meng-xia XU, Jian-hua YAN, Sheng-yong LU, Xiao-dong LI, Tong CHEN, Ming-jiang NI, Hui-fen DAI, Ke-fa CEN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(3): 373-380.
https://doi.org/10.1631/jzus.A071420
Based on the Industrial Source Complex Short-Term Version 3 (ISCST3) model, a simplified modeling approach was developed to predict concentrations of congeners of polychlorinated-p-dioxins and dibenzofurans (PCDD/Fs) of agricultural soil, within a radius of 3 km from a municipal solid waste incinerator (MSWI) plant after its 4-year operation in Hangzhou, China. Comparisons were made between the measured and estimated congener-specific concentrations and the international-toxic equivalent (I-TEQ) values of soil samples with respect to distance from the stack. The results indicate that the predictions of soil PCDD/F concentrations and I-TEQ values were generally lower than their observations, and that the higher the degree of underestimation seems, the greater the further downwind one gets. Nevertheless, most of the predictions were in good agreement with the trend of measured ones and were within a factor of ten for samples located within 1 km of the plant. Besides, analysis of contributions of various deposition pathways confirms that in addition to wet particle deposition, the dry gaseous deposition is essential for realistic prediction of PCDD/F depositions to soil, especially for tetra- and penta-chlorinated dioxins.
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Environmental impact prediction using remote sensing images
Pezhman ROUDGARMI, Masoud MONAVARI, Jahangir FEGHHI, Jafar NOURI, Nematollah KHORASANI
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(3): 381-390.
https://doi.org/10.1631/jzus.A072222
Environmental impact prediction is an important step in many environmental studies. A wide variety of methods have been developed in this concern. During this study, remote sensing images were used for environmental impact prediction in Robatkarim area, Iran, during the years of 2005~2007. It was assumed that environmental impact could be predicted using time series satellite imageries. Natural vegetation cover was chosen as a main environmental element and a case study. Environmental impacts of the regional development on natural vegetation of the area were investigated considering the changes occurred on the extent of natural vegetation cover and the amount of biomass. Vegetation data, land use and land cover classes (as activity factors) within several years were prepared using satellite images. The amount of biomass was measured by Soil-adjusted Vegetation Index (SAVI) and Normalized Difference Vegetation Index (NDVI) based on satellite images. The resulted biomass estimates were tested by the paired samples t-test method. No significant difference was observed between the average biomass of estimated and control samples at the 5% significance level. Finally, regression models were used for the environmental impacts prediction. All obtained regression models for prediction of impacts on natural vegetation cover show values over 0.9 for both correlation coefficient and R-squared. According to the resulted methodology, the prediction models of projects and plans impacts can also be developed for other environmental elements which may be derived using time series remote sensing images.
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In-situ measurement of the dissolved S2− in seafloor diffuse flow system: sensor preparation and calibration
Ying YE, Xia HUANG, Yi-wen PAN, Chen-hua HAN, Wei ZHAO
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(3): 423-428.
https://doi.org/10.1631/jzus.A071360
The preparation approach and calibration result of an improved type of ion selective electrode (ISE), which is used to measure the total dissolved S2−, are introduced in this paper. The improved Ag/Ag2S electrode uses silver wire as the substrate, which is surrounded by electric polymer containing superfine silver powder. After the stabilization of the epoxy-resin, Ag2S layer was formed by chemical reaction with 0.2 mol/L (NH4)2S solution for 5 min. With Ag/AgCl as reference electrode, the Ag/Ag2S electrode can be used to measure dissolved S2−. The correlation between the measured potentials and the logarithm of dissolved S2− is found to be linear, within range of the concentration of dissolved S2− from 10−2~10−7 mol/L. The slope of the regression line between measured potential and logarithm of dissolved S2− is about −27.7, which agrees well with the theoretical Nernst value −29.6. Furthermore, the performance of the improved Ag/Ag2S electrode, such as the response time, sensitivity and stability, greatly outweighs the conventional Ag/Ag2S electrode.
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Study of the behaviour of the dielectric constant in Cu,Fe:BaTiO3
Alioune OUEDRAOGO, Kalifa PALM, Issaka OUEDRAOGO, Guy CHANUSSOT
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(3): 429-434.
https://doi.org/10.1631/jzus.A072218
In this work we study the behaviour of the dielectric constant of BaTiO3 single crystals doped with Cu and Fe for different ion percentages, particularly, the influence of these heterovalent substitutions on the ferroelectric-paraelectric phase transition whose temperature is found at Tc=120 °C for pure samples. The dielectric constant ε in terms of temperature shows that the Curie temperature decreases when the quantity of impurities increases and presents a broadening and flattering of the maximum of ε(T) within higher values, with the transition becoming more and more diffuse. It is interesting to have a material with very high permittivity (high-k) because of its capacity to store an important quantity of electric charges. The ε anisotropy and the Curie-Weiss law are also verified with a good ratio between the slopes of ε−1(T) from both sides of the transition, leading to a Curie constant: C=13×104 K for BaTiO3:1.6%Fe in the polar phase. BaTiO3 is a displacive ferroelectric going through a first-order phase transition. The substitutions have an effect on the dynamics of the perovskite lattice. They induce charges transfer to Ti and a diminution of elastic forces in BaTiO3. Then we discuss the fact that the maximum of permittivity does not depend on the phase transition but on the nature of the material.
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18 articles
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