POLSAR Image Analysis of Wetlands Using a Modified Four-Component Scattering Power Decomposition

It is important to monitor environmental changes of the Earth's cover by remotely sensed data. This paper analyzes seasonal changes of a wetland by a modified polarimetric four-component scattering power decomposition method. The data sets analyzed here are L- and X-band fully polarimetric synthetic aperture radar (POLSAR) data, which have been acquired by the NICT/JAXA airborne polarimetric and interferometric synthetic aperture radar system in 2004. Since there existed a deficiency in the currently adopted decomposition schemes in that negative powers appear in a few pixels in the image analysis, we modified the approach taking into account physical conditions. It is shown by the modified scheme that the seasonal changes and features of the vegetation near Sakata Lagoon in Niigata, Japan, are observed clearly, demonstrating the utility of POLSAR image analysis for wetland assessments in general.     

基于状态连续变化的Hopfield神经网络的图像复原

针对图像复原提出了神经元状态连续变化的Hopfield神经网络模型,详细讨论了两种连续函数串行、全并 行复原算法的收敛性和参数选择,仿真实验表明,该模型能够精确达到能量极小点,并对复原图像的信噪比有一定的提高。     

Using SERS Tags to Image the Three‐Dimensional Structure of Complex Cell Models

Methods to image complex 3D cell cultures are limited by issues such as fluorophore photobleaching and decomposition, poor excitation light penetration, and lack of complementary techniques to verify the 3D structure. Although it remains insufficiently demonstrated, surface‐enhanced Raman scattering (SERS) imaging is a promising tool for the characterization of biological complex systems. To this aim, a controllable 3D cell culture model which spans nearly 1 cm² in surface footprint is designed. This structure is composed of fibroblasts containing SERS‐encoded nanoparticles (i.e., SERS tags), arranged in an alternating layered structure. This “sandwich” type structure allows monitoring of the SERS signals in the z‐axis and with mm dimensions in the xy‐axis. Taking advantage of correlative microscopy techniques such as electron microscopy, it is possible to corroborate nanoparticle positioning and distances in z‐depths of up to 150 µm. This study reveals a proof‐of‐concept method for detailed 3D SERS imaging of a complex, dense 3D cell culture model.     

基于H-α和改进C-均值的全极化SAR图像非监督分类

该文提出一种基于H-α和改进C-均值的全极化SAR图像非监督分类方法.该方法先按H-α对全极化SAR图像进行基于散射机理的分类,再将分类结果作为改进C-均值算法的初始类别划分,从而实现地物分类.迭代次数确定是C-均值动态聚类算法的关键,文中利用图像熵给出了一种新的迭代终止准则.与H-α方法相比,该文方法能在保留分类结果物理散射机理的同时,实现有效的地物分类.NASA/JPL实验室AIRSAR系统获取的L波段旧金山全极化SAR数据的实验结果验证了该文方法的有效性.     

Patterned Growth of P‐Type MoS2 Atomic Layers Using Sol–Gel as Precursor

2D layered MoS₂ has drawn intense attention for its applications in flexible electronic, optoelectronic, and spintronic devices. Most of the MoS₂ atomic layers grown by conventional chemical vapor deposition techniques are n‐type due to the abundant sulfur vacancies. Facile production of MoS₂ atomic layers with p‐type behavior, however, remains challenging. Here, a novel one‐step growth has been developed to attain p‐type MoS₂ layers in large scale by using Mo‐containing sol–gel, including 1% tungsten (W). Atomic‐resolution electron microscopy characterization reveals that small tungsten oxide clusters are commonly present on the as‐grown MoS₂ film due to the incomplete reduction of W precursor at the reaction temperature. These omnipresent small tungsten oxide clusters contribute to the p‐type behavior, as verified by density functional theory calculations, while preserving the crystallinity of the MoS₂ atomic layers. The Mo containing sol–gel precursor is compatible with the soft‐lithography techniques, which enables patterned growth of p‐type MoS₂ atomic layers into regular arrays with different shapes, holding great promise for highly integrated device applications. Furthermore, an atomically thin p–n junction is fabricated by the as‐prepared MoS₂, which shows strong rectifying behavior.     

Determination of the Complex Permittivity of Materials by a Modified Resonator Method Based on the Theory of Small Perturbations Using a Resonator of the Reflective Type

Journal of Communications Technology and Electronics - A modified resonator method for determining the complex permittivity of materials based on the theory of small perturbations where a resonator...     

Formation of Low-Resistance Ohmic Contact by Damage-Proof Selective-Area Growth of Single-Crystal <Emphasis Type="Italic">n</Emphasis><Superscript>+</Superscript>-GaN Using Plasma-Assisted Molecular Beam Epitaxy

To achieve very low ohmic contact resistance, an n ⁺-GaN layer was selectively deposited using plasma-assisted molecular beam epitaxy (PAMBE). During this process polycrystalline GaN grew on the patterned SiO₂ region, which was subsequently removed by a heated KOH solution, resulting in damage to the n ⁺-GaN surface. To prevent this damage, an additional SiO₂ layer was selectively deposited only on the n ⁺-GaN region. To optimize the fabrication process the KOH etching time and n ⁺-GaN layer thickness were adjusted. This damage-proof scheme resulted in a specific contact resistance of 4.6 × 10⁻⁷ Ω cm². In comparison, the resistance with the KOH etching damage was 4.9 × 10⁻⁶ Ω cm² to 24 × 10⁻⁶ Ω cm². The KOH etching produced a large number of pits (4.1 × 10⁸ cm⁻²) and degraded the current transport. X-ray photoelectron spectroscopy (XPS) and secondary-ion mass spectrometry (SIMS) analysis indicated that KOH etching was very effective in removing the oxide from the GaN surface and that the O-H bonding at the GaN surface was likely responsible for the degraded contact performance. The optimum n ⁺-GaN thickness was found to be 54 nm.