Table of Content

23 December 2014, Volume 20 Issue 6

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Friction-Induced Nanofabrication of Small Line-Width Structure on Silicon Surface Based on Si3N4 Probe

YAO Yiang-Yiang, CHEN Lei, GUO Jian, JIAN Lin-Mao

2014, 20(6):  669-679.  doi:10.3969/j.issn.1007-2861.2014.04.006

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Talking into account limitations of traditional nanofabrication approaches such as complicated manipulation and high cost, a new friction-induced fabrication method is proposed. With the native oxidation layer as etching “mask”, nanofabrication of silicon can be achieved by scanning with a Si₃N₄ probe and subsequent selective etching in KOH solution. By optimization of the tip radius, the groove structure with small line-width can be realized on monocrystalline silicon surface. Then, etching time dependence of groove depth is investigated to determine the best etching time for fabricating nanostructure.Finally, the effect of applied load and number of sliding cycles on nanostructure fabrication is studied. As a maskless and simple method, the proposed nanofabrication approach makes possible to fabricate surface texture with special functions, micromechanical valves for fluidic manipulation, single-electron devices, etc. With these advantages and potential applications, the direct fabrication method provides opportunities for nanofabrication

Effect of AIBI as Free Radical Initiator on Abrasive-Free Polishing of Hard Disk Substrate

REN Xiao-yan, LEI Hong, CHEN Ru-ling, CHEN Yi

2014, 20(6):  680-688.  doi:10.3969/j.issn.1007-2861.2014.04.007

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To optimize the existing slurry for abrasive-free polishing (AFP) of hard disk substrate, a water-soluble free radical initiator, 2, 20-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (AIBI) is introduced to the H₂O₂-based slurry. The polishing results show that, the material removal rate (MRR) of hard disk substrate polished with H₂O₂-based slurry containing AIBI is obviously higher than that without AIBI. The acting mechanism of the improved MRR is investigated. Electron paramagnetic resonances tests show that, by comparison with H₂O₂ slurry, H₂O₂-AIBI slurry provides higher concentration of hydroxyl radicals. Auger electron spectrometer analyses further demonstrate that the oxidation ability of H₂O₂-AIBI slurry is much greater than H₂O₂ slurry. In addition, potentiodynamic polarization tests show that the corrosion dissolution rate of hard disk substrate in H₂O₂-AIBI slurry is increased. Therefore that stronger oxidation ability and a higher corrosion dissolution rate of H₂O₂-AIBI slurry lead to higher MRR can be concluded.

Maskless Selective Fabrication and Photoluminescence
of Patterned Si Nanowire Arrays

ZHANG Shuai-1, 2 , LV Wen-Hui-2, SHI Wei-Min-1, HUANG Lu-1, YANG Wei-Guang-1, LIU Jin-1

2014, 20(6):  689-693.  doi:10.3969/j.issn.1007-2861.2014.01.002

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A reasonable selective maskless etching process is developed to fabricate patterned Si nanowire arrays on the basis of metal-assisted silicon chemical etching. The patterned Si nanowire arrays are successfully fabricated in a selective maskless etching process. The surface morphology and photoluminescence of the patterned Si nanowire arrays are characterized by a scanning electron microscope (SEM) and a Raman spectrometer. It is indicated that patterned Si nanowire arrays are high quality porous micro- and nanostructured arrays. The photoluminescence of patterned Si nanowire arrays reveals that a strong light emission peak at 663 nm is obtained. Results show that a simple and efficient process to fabricate patterned Si nanowire arrays for Si-based optoelectronic integrated devices can be obtained.

Effect of Pre-roasting on Mineral Phase Transformations and Gas Reduction of Nickel Laterite Ores

XU Yu-Ling, GUO Shu-Jiang, BIAN Yu-Xiang, CHEN Song, DING Wei-Zhong, TAN Ding-Sheng

2014, 20(6):  697-700.  doi:10.3969/j.issn.1007-2861.2014.01.025

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This paper studies mineralogical phase transformations of Indonesia nickel laterite ores during roasting. The influence of pre-roasting temperature on the degree of gas(V (CO) : V (O₂)=50 : 50)reduction is also investigated. Different factors affecting reduction of the laterite ores are tested and analyzed with various means such as differential scanning calorimeter thermal gravimetric (DSC/TG), Brunauer Emmett Teller (BET) specific surface area analysis, X-ray diffraction (XRD) and scanning electron microscope (SEM).The results show that, during the roasting process, goethite is dehydrolyzed at about 300°C. It is then transformed to hematite and serpentine decomposes around 600~700°C leading to formulation of olivine if agglomerating is at higher temperature. Nickel and iron metallization rate increases with the increasing pre-roasting temperature by using gas mixture (V (CO) : V (O₂)=50 : 50). The highest reduction rate can reach 86.81% with the sample being roasted at 700°C. If the calcination temperature exceeds the olivine formation temperature, the nickel metallization rate declines to 66.73%.

Effect of In-situ Annealing on Properties of CdZnTe Crystals

ZHANG Thao, MIN Jia-Hua, LIANG Xiao-Yan, TENG Jia-Qi, SHI Bin-Bin, WANG Lin-Jun

2014, 20(6):  701-706.  doi:10.3969/j.issn.1007-2861.2014.01.027

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CdZnTe (CZT) single crystals were grown by a modified vertical Bridgman method. After the growth was completed, the crystals were annealed at a constant temperature for a long time. Infrared microscope, I-V characteristic curves, and multi-channel spectrometer were employed to analyze Te inclusions distribution in the crystal, electrical resistivity and spectroscopy response of CZT wafers. The results show that in-situ annealing can greatly decrease concentration of Te inclusions, and most of the Te inclusion sizes are less than 5 μm. In addition, electrical resistivity of CZT is increased from 4.54×10⁸ to 3.73×10¹⁰  after annealing. The ²⁴¹Am@59.5 keV   keV keV-ray pulse height spectra of CZT crystal after in-situ annealing reaches 7.29%.

Unique Absorption Spectrum and Microstructure Characteristics of Golden Seawater Cultured Pearl

YAN Jun-1, LIU Pei-Jun-2, ZHANG Xu-2, SHU Dan-Yan-2, HU Xian-Chao-3, WANG Xiao-Xiang-1

2014, 20(6):  707-714.  doi:10.3969/j.issn.1007-2861.2014.01.024

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A systematic study on the golden seawater cultured pearl (gold CP) were carried out using ultraviolet-visible (UV-VIS) absorption spectrum, field emission scanning electron microscope (FE-SEM) and Fourier transform infrared (FTIR) spectra. The following results were obtained. Density of imbricate structure on the surface of gold CP is different, maybe a result of the slight varied UV-VIS absorption spectrum. From inside to outside of nacreous layer in the cross-section, aragonite sheet or prism structure has not been found in the region near the nucleus. In contrast, aragonite crystal exists in a form of sheet structure in the middle and the outer part of the nacreous layer. The surface of nacreous layer displays the characteristic of multistage structural units, and a micro-sheet existing in the surface of nacreous layer is composed of many aragonite nano-particles.

Symmetry Detection in Natural Images via Edge Feature Learning

SHEN Wei-1, 2 , CHENG Xiao-Jing-1, 2 , ZENG Dan-1, 2

2014, 20(6):  715-725.  doi:10.3969/j.issn.1007-2861.2014.03.012

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This paper studies symmetry detection in natural images, which is a challenging problem in computer vision. To differentiate symmetry and non-symmetry in natural images is intractable due to the large variation in objects and the cluttered scene. To address this problem, two types of edge features motivated by the fact that symmetries are complementary to edges are proposed. These two types of features are both defined on pairs of edges to search pairs of edges with consistent high strength and equal distances to symmetries, respectively. The proposed edge features at multiple scales and orientations
and integrate them with low level cues (color, brightness and texture) under a multiple instance learning framework to detect symmetries are extracted. The experimental results on SYMMAX300 dataset demonstrate that both proposed edge features can improve performance of symmetry detection.

Half-Discrete Hilbert-Type Inequality Containing Logarithmic Kernel

YANG Bi-Cheng-1, CHEN Qiang-2

2014, 20(6):  726-732.  doi:10.3969/j.issn.1007-2861.2014.02.006

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Using a method of weight coefficients, complex analysis and parameterization,a half-discrete Hilbert-type inequality containing a logarithmic kernel and an optimal constant factor is given. Optimal extension with multi-parameters, equivalent forms and homogeneous forms for a particular parameter are deduced.

Growth of Solutions of a Class of Higher Order Non-homogeneous Linear Differential Equations with Meromorphic Coefficients

JIN Jin, FAN Yi, ZUO Jian-Jun, WU Ling-Ling

2014, 20(6):  733-740.  doi:10.3969/j.issn.1007-2861.2014.01.008

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Using the Nevanlinna theory of value distribution of meromorphic functions,and the methods of differential equations, relationship is investigated between the higher order linear differential equations with meromorphic coefficients and functions with smaller growth, and precise estimation is obtained between meromorphic solutions of nonhomogeneous linear differential equations and functions with smaller growth.

Existence of Solutions for an Initial Control Problem with Dynamic Boundary Conditions

TONG Chun-1, 2 , WANG Yuan-Di-1

2014, 20(6):  741-748. 

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An initial control problem with dynamic boundary conditions is investigated by using a method of maximal principle. The comparison principle and existence of solutions for the control problem under some assumptions are proved. Some examples with multiple solutions and unique solution are gived.

Birth-Death Branching Tree with Nodes Being Multiparous

WANG Jia-Yuan-1, FU Yun-Bin-1, 2

2014, 20(6):  749-756.  doi:10.3969/j.issn.1007-2861.2014.01.010

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It is assumed that only one son-node is born in each delivery in the model of Markov birth-death branching tree. This paper assumed that the number of son-nodes born in each delivery is a random variable, and develop a model of birth-death branching tree with nodes being multiparous. Existence of this model is shown. We study the numbers of living nodes, dead nodes, connected components, son-nodes of any node at any age, and son-nodes at dying moment.

Discontinuous Galerkin Spectral Element Methods for Nonlinear Reaction-Diffusion Equations

WU Hua, HAN Xiao-Fei

2014, 20(6):  757-768.  doi:10.3969/j.issn.1007-2861.2013.07.029

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Discontinuous Galerkin spectral element methods for nonlinear reaction-diffusion equations are considered. The schemes are basically in the Legendre-Galerkin form. The nonlinear term is interpolated through the Chebyshev-Gauss-Lobatto points. The jump term tackled by the central numerical flux in space variation. The fourth-order low-storage Runge-Kutta scheme is applied for time discrete inside each subinterval. The methods can be used to solve discontinuous initial value problems and implemented in a parallel way. Stability and the optimal rate of convergence in L2-norm for the semi-discrete scheme are shown using the approximate results of the Chebyshev-Gauss-Lobatto interpolation operator without a weight function. Numerical results for the continuous and discontinuous problems are given.

Volume of Legendre Ellipsoid of Convex Bodies

HE Shan-Sen

2014, 20(6):  769-777.  doi:10.3969/j.issn.1007-2861.2013.07.030

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A volume formula of the Legendre ellipsoid of convex body is obtained by using two different methods. Also, the volume formula of the Minkowski sum of finite segments is established by using mathematical induction. As applications, the Legendre ellipsoids of several specific convex bodies are calculated and depicted with Matlab.

Terahertz Time-Domain Spectroscopy of Barium Ferrites

YUE Zhong-Yue, JIN Zuan-Ming, LI Gao-Fang, MA Guo-Hong

2014, 20(6):  778-783.  doi:10.3969/j.issn.1007-2861.2013.07.026

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Al-doped and barium ferrite powders were synthesized using the sol-gel autocombustion method. The optical property and spectroscopy of Al-doped and barium ferrite were studied based on terahertz time-domain spectroscopy (THz-TDS). The power absorption and refractive index of the Al-doped and barium ferrite were measured. The result shows that Al-doped decreases the refractive indices of barium ferrites, while the refractive indices of barium ferrites samples decreases with increasing frequency, and Al-doped leads to decrease of the refractive indices.

Impacts of Inclusion on the Domain Structure and Properties of Ferroelectric Particles

SONG Yi-Cheng-1, ZHANG Ying-2, LI Zong-Zan-1

2014, 20(6):  784-790. 

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This work studied the impacts of non-ferroelectric inclusion on the domain structure and properties of a ferroelectric particle by simulating the domain evolution
using phase field method. It is found that the accumulation of polarization charge at the surface of inclusion may lead to local rising or descending of electric potential, which further alters the depolarization electric field, impacts the switching and nucleation of polarization near the inclusion, and finally results in more disordered domain structure. This impact is particularly significant for large inclusions and multiple inclusions. Finally, it is found that the ferroelectricity of the particle decreases significantly with respect to increasing ratio of inclusion by simulating the hysteresis loop, indicating that inclusion in ferroelectric particle
should be avoided as possible as we can in the application of microelectronics.

Application of High Viscosity Grout on Water-Control in Tunnel

CHENG Peng-Da-1, FU Gang-2, LIU Bao-Lin-2, FEI Min-Rui-1, WANG Dao-Zeng-3

2014, 20(6):  791-801.  doi:10.3969/j.issn.1007-2861.2013.07.050

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Gushing water causes many geological disasters in tunnel. High viscosity grout plays a positive role in water controlling under complex geological conditions. In this paper, time-varying viscosity of common cement grout and high viscosity grout are measured and analyzed with experiments. The principle of effective stress for porous medium is applied to analysis the fluid-structure coupling in grouting. Considering coupling physical variables, dynamic models of porosity and permeability are contained. The diffusion radius of grout thus can be defined by porosity and pressure gradient. By filling the shallow rock and compacting deep rock, holes are designed in the grout experiment to reduce static water pressure. The distance between grout holes is arranged referring to the calculation results. Then, rationality of the mathematical model and grout scheme is verified by water monitoring and strength testing. According to the results, gushing water reduces by 97%, and strength of rock increases by 200% to 400%, indicating that gushing water is stopped and the tunnel foundation enhanced.

Modification of Shear Box in a Large Pullout Direct-Shear Instrument

GAO Jun-Li, LI Jing

2014, 20(6):  802-812.  doi:10.3969/j.issn.1007-2861.2014.04.005

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The existing shear boxes of large pullout direct instruments cannot meet the experimental requirements of the geosynthetics-geosynthetics interface and the interface between geosynthetics and the granular material. To solve the problem, both upper and lower shear boxes are modified based on existing large instruments, test requirements, and factors affecting experiments. A grillage of type II is put into the lower shear box to fasten the geosynthetics. The upper shear box can realize a flexible bearing load by fixing the geotextiles to the bottom of inner plate, and a rigid bearing load with a rigid plate. After the modification, direct shear tests of smooth geomembrane and sand interface, smooth geomembrane and geotextile interface are carried out. The results agree with those obtained by other researchers, showing that the equipment modification is reasonable and feasible. A series of direct shear tests of the reinforced geomembrane and sand interface, and there inforced geomembrane and geotextile interface have been performed, verifying stability of the instrument after modification.