Real-Time Color Image Processing Using Order Statistics Filters

The Vector Rank M-type K-Nearest Neighbour (VRMKNN) filter to remove impulsive noise from color images and video color sequences is presented. This filter utilizes multichannel image processing by using the vector approach and the Rank M-Type K-Nearest Neighbour (RMKNN) algorithm. Simulation results indicate that the proposed filter consistently outperforms other color image filters by balancing the tradeoff between noise suppression and detail preservation. The implementation of the filter was realized on the DSP TMS320C6711 to demonstrate that the proposed filter potentially could provide a real-time solution to quality video transmission.     

超音速激光沉积Ti-6Al-4V合金结合界面特征数值模拟及试验验证

目的探究超音速激光沉积(SLD)过程中激光辐照温度和颗粒撞击速度对Ti-6Al-4V合金结合界面特征的影响规律,并通过试验对数值模拟结果进行验证。方法基于Johnson-cook材料模型,利用ABAQUS2017软件并采用欧拉-拉格朗日耦合CEL(CoupledEuler-Lagrange)计算模型和Lagrange计算模型,进行Ti-6Al-4V单颗粒和多颗粒的撞击行为数值模拟,并结合超音速激光沉积试验验证模拟结果。采用扫描电镜(SEM)和光镜(OM)对涂层的界面结合特征进行观察和分析。结果单颗粒撞击温度场模拟结果表明,当激光辐照温度为1073K时,随着撞击速度的增加,颗粒界面结合温度不断升高。当撞击速度为800m/s和900 m/s时,颗粒与基体局部最高温度分别为1876.7 K和1874.8 K,界面发生微熔。800 m/s时,颗粒压缩率为34.3%,扁平率为1.27,有效塑性应变为2.6,基体的凹坑深度为7.88μm,该参数下的超音速激光沉积涂层界面结合良好。多颗粒撞击温度场模拟结果表明,当撞击速度为800 m/s时,随着激光辐照温度的升高,孔隙逐渐减少。激光辐照温度为1073 K时,颗粒撞击界面的温度高达3463.7 K,但颗粒内部的温度还未达到熔点并保留在1073～1676.8 K。随着激光功率的升高,钛合金涂层的孔隙率降低为0.67%(SLD 700W),约为同条件下CS涂层孔隙率(8.31%)的1/12。结论激光辐照的热能使颗粒与基体以及颗粒间界面处的温度达到了材料熔点,实现颗粒表面微熔形成冶金结合。冷喷涂Ti-6Al-4V涂层中,颗粒与基体以及颗粒间均存在明显的孔隙,超音速激光沉积Ti-6Al-4V涂层颗粒与基体以及颗粒间的界面结合良好,试验结果与数值模拟结果大致吻合。     

Wood density and annual growth variability of <Emphasis Type="Italic">Picea abies</Emphasis> (L.) Karst. growing in the Ukrainian Carpathians

The purpose of this study was to increase knowledge of the variability of wood density and annual growth of Norway spruce growing in the Ukrainian Carpathians. The material consisted of 21 trees which were cut between 600 m and 1200 m asl from south-west and north-east expositions of the mountain Dovshka. The ovendry and relative wood density increased from the bottom (630 m asl) to the top (1190 m asl) of the mountain and was related to increasing number of tree rings in 1 cm, whereas the width of annual rings decreased expressively. Three significant categories of altitude (forest types) of Norway spruce timbers were estimated for the mountain forest stands. The highest average ovendry wood density (413 kg m^?3) and number of tree rings in 1 cm (17.1) were characterized by spruce trees growing at the wet rocky bilberry spruce forest (above 1000 m asl). Wood density and annual growth are two variables which were significantly correlated with each other and the altitude (R = 0.5–0.6).     

Fluorescence detection with high time resolution: from optical microscopy to simultaneous force and fluorescence spectroscopy

Picosecond time-resolution fluorescence signal detection over many hours is possible using the time-correlated single photon counting (TCSPC) technique. Advanced TCSPC with clock oscillator set by the pulsed laser and data analysis provides a tool to investigate processes in single molecules on time scale from picoseconds to seconds. Optical imaging techniques combined with TCSPC allow one to study the spatial distribution of fluorescence properties in solution and on a surface. Mechanical manipulation of a single macromolecule by means of an atomic-force microscope makes it possible to detect fluorescence signal changes as a function of mechanical conformations of a fluorescent dye attached to a single DNA molecule.     

Evaluating student response to WeBWorK, a web-based homework delivery and grading system

As the use of web-based homework delivery and checking systems expands, we have greater need to evaluate how students engage with these systems and how changes in the systems influence student behavior. Reported here is the assessment of WeBWorK, an open-source web-based homework program used largely in postsecondary math and science courses, with recent extension to high school courses. WeBWorK draws from a large library of problems to generate individual assignments and provides immediate feedback about correctness of students’ answers. WeBWorK allows entries in multiple choice, formula and numerical formats. The entries recorded by the system create an extensive database of student interactions with the system.In our two-part study, we (1) review 2387 student surveys about WeBWorK in three semesters across a range of mathematics courses and (2) test a model designed to classify student responses to system feedback, permitting a fine-grained analysis of the system’s records at the keystroke level for a cohort of 96 Calculus I students.Based on this data, our goals are, first, to understand how students use the system and respond to its feedback; second, to analyze the impact of upgrades to the system interface on student users, and third, to evaluate the efficiency of training raters to classify student records.We find that the introduction of new features to the WeBWorK interface (improvements generated by our initial assessment) were welcomed by most students and reduced the overall number of submitted errors by half by the third year of the study. Importantly, the interface improvements reduced the number of errors that were not pedagogically useful. We also find that our error classification model, called here the Student Response Model, was a good fit for our student sample, as reflected by inter-rater reliability of three raters who coded the student records. In sum, our error classification model appears to be useful for analyzing formula entries. To make this assessment model widely available, we designed a system of exercises to train raters to classify student response files for WeBWorK and similar web-based systems.     

A crowdsourcing approach to building a legal ontology from text

This article focuses on the problems of application of artificial intelligence to represent legal knowledge. The volume of legal knowledge used in practice is unusually large, and therefore the ontological knowledge representation is proposed to be used for semantic analysis, presentation and use of common vocabulary, and knowledge integration of problem domain. At the same time some features of legal knowledge representation in Ukraine have been taken into account. The software package has been developed to work with the ontology. The main features of the program complex, which has a Web-based interface and supports multi-user filling of the knowledge base, have been described. The crowdsourcing method is due to be used for filling the knowledge base of legal information. The success of this method is explained by the self-organization principle of information. However, as a result of such collective work a number of errors are identified, which are distributed throughout the structure of the ontology. The results of application of this program complex are discussed in the end of the article and the ways of improvement of the considered technique are planned.     

Deep Semisupervised Learning-Based Network Anomaly Detection in Heterogeneous Information Systems

The extensive proliferation of modern information services and ubiquitous digitization of society have raised cybersecurity challenges to new levels. With the massive number of connected devices, opportunities for potential network attacks are nearly unlimited. An additional problem is that many low-cost devices are not equipped with effective security protection so that they are easily hacked and applied within a network of bots (botnet) to perform distributed denial of service (DDoS) attacks. In this paper, we propose a novel intrusion detection system (IDS) based on deep learning that aims to identify suspicious behavior in modern heterogeneous information systems. The proposed approach is based on a deep recurrent autoencoder that learns time series of normal network behavior and detects notable network anomalies. An additional feature of the proposed IDS is that it is trained with an optimized dataset, where the number of features is reduced by 94% without classification accuracy loss. Thus, the proposed IDS remains stable in response to slight system perturbations, which do not represent network anomalies. The proposed approach is evaluated under different simulation scenarios and provides a 99% detection accuracy over known datasets while reducing the training time by an order of magnitude.     

Determining the Optimized Interlayer Separation Distance in Vertical Stacked 2D WS2:hBN:MoS2 Heterostructures for Exciton Energy Transfer

The 2D semiconductor monolayer transition metal dichalcogenides, WS₂ and MoS₂, are grown by chemical vapor deposition (CVD) and assembled by sequential transfer into vertical layered heterostructures (VLHs). Insulating hBN, also produced by CVD, is utilized to control the separation between WS₂ and MoS₂ by adjusting the layer number, leading to fine‐scale tuning of the interlayer interactions within the VLHs. The interlayer interactions are studied by photoluminescence (PL) spectroscopy and are demonstrated to be highly sensitive to the input excitation power. For thin hBN separators (one to two layers), the total PL emission switches from quenching to enhancement by increasing the laser power. Femtosecond broadband transient absorption measurements demonstrate that the increase in PL quantum yield results from Förster energy transfer from MoS₂ to WS₂. The PL signal is further enhanced at cryogenic temperatures due to the suppressed nonradiative decay channels. It is shown that (4 ± 1) layers of hBN are optimum for obtaining PL enhancement in the VLHs. Increasing thickness beyond this causes the enhancement factor to diminish, with the WS₂ and MoS₂ then behaving as isolated noninteracting monolayers. These results indicate how controlling the exciton generation rate influences energy transfer and plays an important role in the properties of VLHs.     

3-D dynamic interaction between a penny-shaped crack and a thin interlayer joining two elastic half-spaces

Three-dimensional (3-D) elastodynamic interaction between a penny-shaped crack and a thin elastic interlayer joining two elastic half-spaces is investigated by an improved boundary integral equation method or boundary element method. The penny-shaped crack is embedded in one of the half-spaces, perpendicular to the interlayer and subjected to a time-harmonic tensile loading on its surfaces. Effective “spring-like” boundary conditions are applied to approximate the effects of the thin layer in the mathematical model. Integral representations for the displacement and the stress components are derived by using modified Green’s functions, which satisfy the “spring-like” boundary conditions identically. Then, application of the dynamic loading condition on the crack-surfaces results in a boundary integral equation (BIE) for the crack-opening-displacement over the crack-surfaces only. A solution procedure is developed for solving the BIE numerically. Numerical results for the mode-I dynamic stress intensity factor (SIF) are presented and discussed to show the variations of the mode-I dynamic SIF with the angular coordinate of the crack-front points, the dimensionless wave number, the material mismatch and the crack-layer distance.     

Formation of coatings with tailored properties on polyperoxide-modified polymeric surfaces

Modification (peroxidation) of polymer surfaces, polypropylene, polyethylene, polyethylene terephthalate, nylon 6-6, poly(phenylene oxide), and ethylene–propylene copolymer were affected by the surface grafting of functional polyperoxides (FPPs) such as poly(5-tert-butylperoxy-5-methyl-1-hexene-3-yne-co-octylmethacrylate) (VEP-co-OMA), poly{N-[(tert-butylperoxy)-methyl]acrylamide-co-octyl methacrylate} (PO-co-OMA), and poly(tert-butylperoxy-methacrylate-co-octyl methacrylate) (PEst-co-OMA). The degree of surface modification was shown to be determined primarily by the structure of the polymer substrate. Using a peroxidized surface as an initiator of grafted copolymerization enabled the grafting of functional monomers (acrylic acid, acrylamide, 4-vinylpyridine, and hydroxyethyl methacrylate) and polysaccharides (heparin, dextran, etc.) and thereby imparted adhesive, antibacterial, haemocompatible properties to the polymer surface.