基于无人机可见光谱遥感的玉米长势监测

玉米是我国重要的粮食作物之一,在我国种植规模最大、发展最快。玉米的长势会直接影响到其产量和品质,因此通过对玉米的长势进行有效监测,可以为田间管理、早期产量估算提供宏观的参考信息,为国家和相关部门决策提供重要的参考依据。以无人机为遥感平台,搭载影像传感器构建遥感系统,获取玉米可见光谱遥感影像。利用ENVI软件对获取的玉米冠层可见光谱彩色图像进行几何校正和辐射校正,然后对图像进行彩色图像灰度化和增强处理。利用对农田复杂背景适应能力较好以及具有较强光照适应性的AP-HI算法完成作物分割来提取玉米覆盖度信息。在计算玉米覆盖度时,首先利用AP-HI算法将图像进行分割,并转换为二值图,来去除图像中的土地、水管、道路、作物残渣等背景,以保留玉米的二值图像。图像中的农田存在道路区域,计算实际作物覆盖度时需将其排除。道路区域出现在图像的四个边界以及相对正中的位置处,对这些位置分别进行处理,统计其中黑色像素点的个数,根据像素点个数确定道路宽度,并将道路部分从二值图中去除。去除后的二值图中,白色像素为无作物区域,黑色像素为玉米种植区域,统计黑色像素占总像素的比例,以此确定作物的多少。选取80×80像素值作为单位面积,对处理图像进行分块标记,得到区块数为720,对单位面积的分块进行全区域扫描,每当扫描到一个黑色像素值就将总的统计面积加1,直至扫描到6 400个像素点,计算其中含有的总的黑色像素值数目与6 400的比值,直至将720个区块黑色像素点占总像素比例统计完全,即可计算图像中黑色像素数与总像素数之比,即为玉米覆盖度。在此基础上,根据实际情况计算玉米冠层孔隙率,并建立覆盖度与叶面积指数模型,完成玉米叶面积指数反演,为玉米长势监测提供理论依据。     

Cleaning of artificially soiled paper with 532-nm nanosecond laser radiation

Cleaning of paper is a challenging task due to the fact that a contamination should be removed and a fragile organic original material has to be preserved. Pulsed laser cleaning of artificially soiled Whatman© filter paper samples serving as models for historical paper was performed. Different cleaning strategies employing 8-ns laser pulses at 532 nm wavelength were applied to clean paper avoiding undesired effects like discoloration (yellowing) and mechanical deterioration of the substrate. Multi shot experiments with low-energy pulses were compared with single pulse investigations utilizing high pulse energies achieving a constant energy load incident on the samples in both cases. The cleaning efficiency and possible yellowing effects were evaluated by means of a multi spectral imaging system. An extensive microscopic analysis of the cleaned parts of the samples provided insight into the remaining soiling on the surface and in the bulk of the paper material after laser treatment. As a reference, a hard and a soft eraser were used to clean the samples.     

Detergency of stainless steel surface soiled with human brain homogenate: an XPS study

In the detergency field of re-usable medical devices, a special attention is focused on the non conventional transmissible agent called prions which is a proteinaceous infectious agent. Few cleaning procedures are effective against prions and few techniques are available to study cleaning effectiveness with respect to proteins in general. In our study, X-ray photoelectron spectroscopy (XPS) has been used to evaluate the effectiveness of detergent formulations to remove proteins from stainless steel surface soiled with a brain homogenate (BH) from human origin. Our results showed that XPS is a reliable surface analysis technique to study chemical species remaining on surface and substrate properties after cleaning procedures. A semi-quantitative evaluation of the detergency effectiveness could also be performed.     

Multifocus image fusion and denoising scheme based on homogeneity similarity

A novel image fusion algorithm based on homogeneity similarity is proposed in this paper, aiming at solving the fusion problem of clean and noisy multifocus images. Firstly, the initial fused image is acquired with one multiresolution image fusion method. The pixels of the source images, which are similar to the corresponding initial fused image pixels, are considered to be located in the sharply focused regions. By this method, the initial focused regions are determined. In order to improve the fusion performance, morphological opening and closing are employed for post-processing. Secondly, the homogeneity similarity is introduced and used to fuse the clean and noisy multifocus images. Finally, the fused image is obtained by weighting the neighborhood pixels of the point of source images which are located at the focused region. Experimental results demonstrate that, for the clean multifocus image fusion, the proposed method performs better than some popular image fusion methods in both subjective and objective qualities. Furthermore, it can simultaneously resolve the image restoration and fusion problem when the source multifocus images are corrupted by the Gaussian white noise, and can also provide better performance than the conventional methods.     

Application of ultrasound to textiles washing in aqueous solutions

The ultrasound was applied to textile washing as a mechanical action for soil removal. The polyester fabric was soiled with carbon black or oleic acid as a model contaminant, and washed with the original fabric in aqueous solutions without and with alkali or surfactant by applying ultrasound, shaking or stirring action. The detergency and soil redeposition were evaluated from the change in the surface reflectance of artificially soiled fabrics and the original fabric due to washing. In comparison with shaking and stirring actions, ultrasound was found to remove the particulate and oily soils efficiently in a short time and at low bath ratio. With increasing ultrasound power, the detergency of both soils increased and exceeded that obtained with Wascator, a horizontal axis drum type washer. Using three standard fabrics for determining mechanical action during washing, it was shown that ultrasound washing caused little mechanical damage to the fabric. However, the soil redeposition was frequently observed for ultrasonic washing, especially at low bath ratio.     

Anti-graffiti nanocomposite materials for surface protection of a very porous stone

The preservation of stone substrates from defacement induced by graffiti represents a very challenging task, which can be faced by applying suitable protective agents on the surface. Although different anti-graffiti materials have been developed, it is often found that their effectiveness is unsatisfactory, most of all when applied on very porous stones, e.g. Lecce stone. The aim of this work was to study the anti-graffiti behaviour of new nanocomposite materials obtained by dispersing montmorillonite nanoparticles (layered aluminosilicates with a high-aspect ratio) into a fluorinated polymer matrix (a fluorinated polyurethane based on perfluoropolyether blocks). Polymeric structure was modified by inducing a cross-linking process, in order to produce a durable anti-graffiti coating with enhanced barrier properties. Several composites were prepared using a naturally occurring and an organically modified montmorillonite clay (1, 3, and 5 % w/w concentrations). Materials were applied on Lecce stone specimens, and then their treated surfaces were soiled by a black ink permanent marker or by a black acrylic spray paint. Several repeated staining/cleaning cycles were performed in order to evaluate anti-graffiti effectiveness. Colorimetric measurements were selected to assess the anti-graffiti performance. It was found that the presence of 3 % w/w organically modified montmorillonite in the polymer coating is enough to induce a durable anti-graffiti effect when the stone surface is stained by acrylic paint. Less promising results are obtained when staining by permanent marker is considered as all the investigated treatments afford a reasonable protection from ink only for the first staining/cleaning cycle.     

Cleaning of artificially soiled paper using nanosecond, picosecond and femtosecond laser pulses

Cleaning of cultural assets, especially fragile organic materials like paper, is a part of the conservation process. Laser radiation as a non-contact tool offers prospects for that purpose. For the studies presented here, paper model samples were prepared using three different paper types (pure cellulose, rag paper, and wood-pulp paper). Pure cellulose serves as reference material. Rag and wood-pulp paper represent essential characteristics of the basic materials of real-world artworks. The papers were mechanically soiled employing pulverized charcoal. Pure and artificially soiled paper samples were treated with laser pulses of 28 fs (800 nm wavelength) and 8–12 ns (532 nm) duration in a multi pulse approach. Additionally, the cellulose reference material was processed with 30 ps (532 nm) laser pulses. Damage and cleaning thresholds of pure and soiled paper were determined for the different laser regimes. Laser working ranges allowing for removal of contamination and avoiding permanent modification to the substrate were found. The specimens prior and after laser illumination were characterized by light-optical microscopy (OM) and scanning electron microscopy (SEM) as well as multi spectral imaging analysis. The work extends previous nanosecond laser cleaning investigations on paper into the ultra-short pulse duration domain.     

Ultra-smooth platinum surfaces for nanoscale devices fabricated using chemical mechanical polishing

A technique involving two steps of chemical mechanical polishing (CMP) has been developed to produce ultra-smooth metal surfaces with an RMS roughness better than 0.1 nm. A figure of merit termed degree of smoothness (DOS) is proposed for the purpose of quantifying the extent of smoothness of a polished metal surface. A post CMP metal slurry cleaning solution was used for cleaning Pt slurry for the first time and by applying special techniques, a very high quality clean surface was attained. Applications of the polished Pt electrodes in interfacing molecular switching devices with self-assembled monolayers of molecules have been found to dramatically improve the packing and orientation of the molecular monolayer with a huge improvement in the molecular electronics device yields. These smooth metal surfaces may open doors for new opportunities in future nanoscale devices. PACS 81.05.Bx; 81.16.Rf; 81.65.Ps     

神光-Ⅲ主机激光装置片状放大器洁净控制进展

针对神光-Ⅲ主机激光装置片状放大器的洁净控制采取了一系列有效措施。除了设计上更有利于洁净控制外,机械结构件表面残留不挥发性有机污染物也达到了低于1 mg/m2的水平。为了进一步提高放大器洁净度,进行了光照清洗。实验结果表明:神光-Ⅲ主机装置的洁净水平与美国国家点火装置接近,光照清洗时内部气溶胶等级维持在5 000~10 000之间,且绝大部分表面有机残留物在最初几发光照清洗中已被释放,从而得到一个干净的放大器腔体,减少了放大器运行时光学元件受污染和损伤的几率。     

Role of adsorption on surface composition of Pd–Cu nanoparticles

Monte-Carlo (MC) simulation is used to study the role of adsorption of hydrogen, oxygen and carbon monoxide (CO) on the surface composition and surface bond geometry of Pd–Cu nanoparticles. For clean particles the surface is found to be enriched in Cu. But in the presence of adsorbed hydrogen and CO there is a segregation reversal from Cu segregation at low coverage to Pd segregation at high coverage. In the presence of adsorbed oxygen, on the contrary, the extent of Cu segregation increases with coverage. For a 586-atom nanoparticle with 50% Pd in the bulk the corner sites are found to be occupied by Cu atoms up to one monolayer adsorption. But, while the occupancy of 7, 8 and 9-coordinated sites by Cu atoms decreases with increase of H and CO coverage, for oxygen adsorption this occupancy increases with coverage. The relevance of such results in catalysis studies is discussed.     

Application of ultrasonics to enhance the efficiency of cleaning Thelephora ganbajun

The Thelephora ganbajun is a rare edible mushroom which is distributed only in Yunnan area of China. It grows generally in the red soil under Burma pine. Therefore, there is a lot of dirt on the mushroom. The dirt adheres and embeds on the root firmly and deeply, thus to clean them is very difficult. The paper reports an efficient method to clean T. ganbajun using ultrasonic cleaner. The optimum parameters for ultrasonic clean are: detergent: 0.67%, sample:water=1:100, T=21.5-25.0 degrees C, and cleaning time: 20 min. Under the optimum condition, the cleaning efficiency can be increased 55.5% than that without sonication. Higher cleaning efficiency and more edible parts of the rare mushroom was got.     

Observational effects in black and white holes (dynamical wormholes)

The models of wormholes with a topology based on a Reissner-Nordström black and white hole are considered. In these models, there are one entrance in one universe (a black hole) and one exit into another universe (a white hole) corresponding to this entrance. The passage of matter through the wormhole in these models is possible only in one direction (from past to future). All models are considered under the assumption of spherical symmetry. It is shown that all models without a throat do not violate the null energy condition. The model of a Reissner-Nordström black hole containing no singularities inside the horizon has been constructed. The trajectories of particles and light rays passing from one universe into another have been constructed for the simplest Reissner-Nordström black and white hole. Distinctive features have been found for the images of objects from another universe observed through such objects. The characteristics of these images are compared with those for ordinary wormholes.     

Observation of oxygen contamination at ZnSe/GaAs interfaces using SIMS

ZnSe epilayers were grown on GaAs (1 0 0) substrates using MBE. The native contamination (oxide and carbon) was removed in situ from the substrate surfaces by conventional thermal cleaning and by exposure to atomic hydrogen. A maximum substrate temperature of 600 °C was required for the thermal cleaning process, while a substrate temperature of 450 °C was sufficient to clean the substrate using hydrogen. ZnSe epilayers were also grown on As capped GaAs epilayers, which were decapped at a maximum temperature of 350 °C. SIMS profiles showed the existence of oxygen at the interface for all of the substrate preparation methods. The oxygen surface coverage at the interface was found to be 0.03% for the atomic hydrogen cleaned substrate and 0.7% for the thermally cleaned substrate.     

Optical Diffractive Memories: Angular Selectivity and Diffraction Efficiency in Dichromated Gelatin

Two thousand images of resolution 512×512 pixels as a regular matrix pattern of 10×10 elements are stored, where each element is angularly multiplexed 20 times in a 25 μm thickness of dichromated gelatin emulsion without cross-talk effect. The surface area of the matrix is 1 cm². We show good concordance of the angular selectivity between the experimental result and theory. The diffraction efficiency of each 20 multiplexed images is measured and has nearly the same value. Examples of reconstructed images for multiple applications are given, for example, storage of 160,000 images on a 3′1/2 floppy disc format, which is about 100 min of black and white film. Application can be made to automobile cartography and storage of X-ray images as well as weather forecast images. Colored diffractive images are also possible and are illustrated.     

Three-dimensional microfluidic structure embedded in photostructurable glass by femtosecond laser for lab-on-chip applications

A new technology for rapid prototyping of lab-on-chip devices is described. Direct write of a near-infrared femtosecond laser forms three-dimensional (3D) latent images inside photostructurable glass. Modified regions are developed by a post-annealing and then preferentially etched away in dilute hydrofluoric acid solution with an etching selectivity of 40–50 times, resulting in the formation of true 3D hollow microstructures inside the glass. Microfluidic structures with microcells and microchannels embedded in the glass are fabricated by this technique. PACS 42.62.-b; 47.85.Np; 81.05.Kf     

60keV质子辐照对TiNi记忆合金薄膜马氏体相变的影响

利用磁控溅射的方法在氧化后的单晶Si基片上制备了TiNi形状记忆合金薄膜，利用示差扫描量热法和原位X射线衍射研究了薄膜的马氏体相变特征。通过60keV质子注入（辐照）薄膜样品研究了H+离子对合金薄膜马氏体相变特征的影响，结果表明氢离子注入后引起了马氏体相变开始Ms和结束点Mf以及逆马氏体相变开始As和结束温度Af的下降，而对R相变开始Rs和结束温度Rf影响不大。掠入射X射线衍射表明H+离子注入后有氢化物形成。H+离子注入形成的氢化物是引起相变点的变化的主要因素。     

Role of cleaning methods on bond quality of Ti coated glass/imidex system

Thin film materials are widely used in the fabrication of semiconductor microelectronic devices. In thin film deposition, cleanliness of substrate surface have become critically important as over 50% of yield losses in integrated circuit fabrication are caused by microcontamination [1]. There are many wafer cleaning techniques. The most successful approach for silicon wafer cleaning technique is RCA clean [2]. But for glass substrate it is still not known which procedure of cleaning is the best. This paper provides an understanding of the right way of glass wafer cleaning method, with a focus towards identifying good bond strength. Two wafer cleaning techniques have been used for cleaning glass substrates in the context of laser micro-joining of dissimilar substrates. First cleaning procedure involves two steps, first cleaning in acetone solution and then in DI water solution. After each step dried with N₂. Second cleaning procedure involves four steps, first cleaning with 1% Alconox solution, second in DI water, third in acetone solution and finally in a methanol solution and dried with N₂ after each step. Deposition of Ti thin film on top of these two types of substrate using DC magnetron sputtering method also showed better adhesion of Ti film on glass for the second type of cleaning method. Scanning electron microscopy (SEM) analyses of the lap shear tested failed surfaces for these two kinds of samples revealed strong bond for samples prepared by second cleaning method compared to first cleaning method. Characterization of these two sets of samples using X-ray photoelectron spectroscopy (XPS) has shown excellent contamination removal for the second cleaning method. This modification is believed to be due to reduction of carbon contamination.     

The asymptotic form of three-particle wavefunctions and the cross sections

The asymptotic behavior of three-particle wavefunctions in the coordinate representation is examined as all three particles move towards infinity. We investigate both the wave-function for a particle incident on a bound state, and that for three free incident particles. The results are expressed in terms of cross sections, and they lead to a clean separation of the double-scattering terms from the “true” three-particle scattering amplitude. We also derive the relevant reciprocity theorems from time-reversal invariance.     

Surface cleaning of metals by pulsed-laser irradiation in air

The surface-cleaning effect of metals was investigated using KrF-excimer-laser irradiation of metal surfaces in air. The laser-induced cleaning of copper, stainless steel and aluminum surfaces was studied. It is found that laser cleaning is an effective cleaning process for metals even if the metal surfaces are heavily contaminated. It is also found that short wavelength and pulse duration are necessary for laser surface-cleaning. The energy density of the laser pulse is an important parameter in the cleaning process. Low energy density results in a cleaner surface but a larger pulse number is required, whereas high energy density can achieve higher cleaning efficiency but the temperature rise can cause surface oxidation and secondary contamination. In contrast to the KrF-excimer-laser, the pulsed CO₂ laser is not effective in surface-cleaning. The mechanisms of laser cleaning may include laser photodecomposition, laser ablation and surface vibration due to the impact of the laser pulse. Laser cleaning provides a new dry process to clean different substrate surfaces and can replace the conventional wet cleaning processes such as ultrasonic cleaning with CFC and other organic solvents.     

Removal of 10-nm contaminant particles from Si wafers using argon bullet particles

Removal of nanometer-sized contaminant particles (CPs) from substrates is essential to successful fabrication of nano scale devices. But the cleaning limit of various current technologies stay around 50 nm. Cryogenic aerosol beam has long been successfully employed to remove CPs down to 50 nm, and supersonic particle beam using particles smaller than 100 nm lowered the limit of cleaning down to 20 nm size. In this study, the particle beam technique that uses nanometer-sized bullet particles moving at supersonic velocity was improved, and successfully employed to remove contaminant particles as small as 10 nm. Ar nano-bullets of about 20–50 nm were generated by gas-phase nucleation, and growth in a supersonic nozzle: appropriate size and velocity of the nano-bullets were obtained by optimizing the Ar/He mixture fraction and nozzle contours. Cleaning efficiency >95% was attained. Nano-bullet velocity was found to be the most important parameter affecting removal of contaminant particles in the 10-nm size range.