Adaptive image enhancement based on clustering of wavelet coefficients for infrared sea surveillance systems

Most of the techniques developed for infrared (IR) image enhancement (IE) depend heavily on the scene, environmental conditions, and the properties of the imaging system. So, with a set of predefined scenario properties, a content-based IR-IE technique can be developed for better situational awareness. This study proposes an adaptive IR-IE technique based on clustering of wavelet coefficients of an image for sea surveillance systems. Discrete wavelet transform (DWT) of an image is computed and feature vectors are constructed from subband images. Clustering operation is applied to group similar feature vectors that belong to different scene components such as target or background. Depending on the feature vectors, a weight is assigned to each cluster and these weights are used to compute gain matrices which are used to multiply wavelet coefficients for the enhancement of the original image. Enhancement results are presented and a comparison of the performance of the proposed algorithm is given through subjective tests with other well known frequency and histogram based enhancement techniques. The proposed algorithm outperforms previous ones in the truthfulness, detail visibility of the target, artificiality, and total quality criteria, while providing an acceptable computational load.     

密度泛函理论研究碳链长度对氯化三烷基铵萃取氯化汞的影响

运用密度泛函理论方法研究了烷基碳链长度对氯化三烷基铵络合氯化汞的影响,计算结果表明,氯化三烷基铵与氯化汞的络合作用随着氯化三烷基铵中烷基碳链的增长而增强.通过对络合物的键长、Mayer键级和Mulliken电荷分析可知,电子富集在氯化三烷基铵的Cl原子上,并和Hg原子之间形成静电吸引作用.当烷基长度小于3时,烷基的电子效应影响较为明显,增强了原子之间的电子转移,使得络合物更稳定;当氯化三烷基铵烷基碳链长度大于3后,烷基链长对络合物中的电子转移不再有影响,络合物的稳定性受到烷基的几何效应影响更为明显.     

Sulfur speciation in two typical soil samples using X-ray absorption near-edge structure spectroscopy and chemical fractionation

Sulfur K-edge X-ray absorption near-edge structure spectroscopy and chemical sequential extraction was respectively used to study the speciation of sulfur in two sulfur-rich soils samples. Sulfur K-edge X-ray absorption near-edge structure spectroscopy analysis obtained a variety of spectra. Spectral fitting of the X-ray absorption near-edge structure spectra utilizing a large set of model compounds showed great differences between these two sulfur-rich soil samples. It was found that both of the soil samples had high sulfur content (8.40 and 11.57?g?kg^?1, respectively). Chemical extraction results suggested that sulfur mainly existed as organic in the ancient paddy soil (7.37?g?kg^?1) and more reduced sulfur was identified in it. X-ray absorption near-edge structure spectroscopy also got similar results. These organic forms of sulfur existed in organic matter across a range of oxidation states. There was high proportion of oxidized sulfur in the sulfuric acid plant that mainly existed as sulfate.     

孔洞和孪晶界对银纳米线形变行为联合影响的分子动力学模拟

Based on molecular dynamics simulations, the plastic deformation of silver nanowires under uniaxial tension has been studied systematically. In this paper, the mechanical properties of [111]-oriented twin nanowires with different hole sizes have been studied. The existence of holes has no effect on the elastic deformation stage. The hole on the twin boundary has two main roles in the plastic deformation stage. During the initial stages of plastic deformation, the main function of the hole is to produce new dislocations as dislocation sources at small hole sizes.Upon increasing the hole size, the main effect changes to stop dislocation slip. During the late stages of plastic deformation, the two functions of the hole complement each other, upon increasing the hole size, the function of the hole as dislocation sources becomes obvious, leading to weakening of the plasticity of the nanowires.     

Liquid–liquid equilibrium and interfacial tension of the ternary system heptane + thiophene + 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide

The liquid–liquid equilibrium (LLE) of the ternary system comprising heptane, thiophene and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C₂mim][NTf₂]) was determined at 25 °C and atmospheric pressure, for preliminary evaluation of the potential of this ionic liquid as solvent for the desulfurisation of transportation fuels. Classical parameters such as solute distribution ratio and selectivity were calculated from the LLE data and subsequently analysed. The LLE data were also correlated by means of the ‘Non-Random Two-Liquid’ (NRTL) equation. Besides the LLE, another critical property for the design of extraction processes, namely the interfacial tension, was determined in parallel, throughout the immiscibility domain of the ternary system. For the first time, the LLE and the interfacial tension of a ternary system involving an ionic liquid are jointly reported.     

Absolute oral bioavailability of fenofibric acid and choline fenofibrate in rats determined by ultra‐performance liquid chromatography tandem mass spectrometry

Choline fenofibrate is the choline salt of fenofibric acid, which releases free fenofibric acid in the gastrointestinal tract. To estimate the absolute oral bioavailability of fenofibric acid and choline fenofibrate, a novel and sensitive UPLC–MS/MS method with liquid–liquid extraction procedure was developed for the determination of fenofibric acid in rat plasma. The separation was achieved on a Phenomenex Kinetex C₁₈ column (50 × 2.1 mm, 2.6 μm) containing 2 mm ammonium acetate–methanol with a gradient elution program. Validations of this method including specificity, sensitivity (limit of quantification, 5 ng/mL), linearity (0.005–10 μg/mL), accuracy (within ±4.3%), precision (intra‐ and inter‐day coefficient of variation <11.3%), recovery (94.9–105.2% for fenofibric acid), matrix effect, stability and dilution, were all within acceptable limits. This method successfully supported the determination of fenofibric acid and choline fenofibrate. The absolute oral bioavailability was 93.4% for choline fenofibrate and 40.0% for fenofibric acid. These results suggested that choline fenofibrate and fenofibric acid had a better in vivo pharmacokinetic behavior than that of fenofibrate. The two new orally administrated pharmaceuticals, fenofibric acid and choline fenofibrate, can be developed as alternatives to fenofibrate.     

Characterization of the carrot defect in 4H-SiC epitaxial layers

Characterization of the epitaxial defect known as the carrot defect was performed in thick 4H-SiC epilayers. A large number of carrot defects have been studied using different experimental techniques such as Nomarski optical microscopy, KOH etching, cathodoluminescence and synchrotron white beam X-ray topography. This has revealed that carrot defects appear in many different shapes and structures in the epilayers. Our results support the previous assignment of the carrot defect as related to a prismatic stacking fault. However, we have observed carrot defects with and without a visible threading dislocation related etch pit in the head region, after KOH etching. Polishing of epilayers in a few μm steps in combination with etching in molten KOH and imaging using Nomarski optical microscope has been used to find the geometry and origin of the carrot defects in different epilayers. The defects were found to originate both at the epi-substrate interface and during the epitaxial growth. Different sources of the carrot defect have been observed at the epi-substrate interface, which result in different structures and surfaces appearance of the defect in the epilayer. Furthermore, termination of the carrot defect inside the epilayer and the influence of substrate surface damage and growth conditions on the density of carrot defects are studied.     

Layer-stacking irregularities in C36-type Nb–Cr and Ti–Cr Laves phases and their relation with polytypic phase transformations

Specific layer-stacking irregularities have been identified in C36 (4H) Nb–Cr and Ti–Cr Laves phases on the basis of X-ray diffraction line-profile analysis and high-resolution transmission electron microscopy. Domain boundaries and transformation errors within domains could be distinguished. The layer-stacking irregularities in both C36-NbCr₂ and C36-TiCr₂ can be associated with a preceding C14 (2H) → C36 (4H) phase transformation carried out by glide of mobile synchro-Shockley partial dislocation dipoles in an ordered fashion. The stacking irregularities observed can be interpreted as deviations from such perfect “ordered glide”. The interpretation is supported by the observation that, in the case of C36-NbCo₂, where no preceding C14 → C36 transformation occurs, different layer-stacking irregularities are observed.     

Target extraction from blurred trace infrared images with a superstring galaxy template algorithm

Accurate and efficient targets extraction from blurred trace infrared images has very important meaning for latent trace evidence collection in crime scene. Based on the superstring theory, a superstring galaxy template extraction algorithm for infrared trace target is presented. First, all of the pixels are divided into three classes: target pixels, background pixels and blurred pixels. Next, the superstring template characteristics for every pixel in a blurred infrared image are calculated as the features of each pixel. Finally, a galaxy covering algorithm is proposed, target pixels and background pixels are used for training the galaxy covering domain of every galaxy classifiers, and these classifiers will divide each blurred pixel into two classes: a target pixel or a background pixel. Experimental results indicate that the superstring galaxy template algorithm can improve the target extraction rate and reduce the extraction error rate.     

Determination of Cadmium and Lead in Sea Water after Extraction Using Electrothermal Atomisation. Minimisation of Interferences from Co-Extracted Sea Salts

Abstract

Interferences from small amounts of sea salt in the determination of cadmium and lead were investigated. Test samples were made to mimic solutions obtained after extraction of sea water for trace metal analysis. Sea salt concentrations in the range 0–400 mg/l were investigated. Background absorption from this salt was high but easily minimised through the addition of nitric acid (2 % v/v). Sensitivity reductions due to the salt were considerable and varied from one graphite tube to the other. This problem was overcome by the addition of 1000 mg lanthanum per litre of sample. The positive effect of the lanthanum matrix modification is thought to be due to a change of the graphite tube surface.