Structural properties of lead vanadate glasses containing La3+ or Fe3+ ions

Structural properties of lead vanadate glasses containing La³⁺ or Fe³⁺ ions were investigated using X-ray diffraction, Fourier transform infrared spectroscopy and laser Raman spectroscopy. Crystalline Pb₂V₂O₇ was formed for the molar composition 66.7PbO-33.3V₂O₅. Incorporation of greater quantities of La³⁺ into lead metavanadate glass caused the crystallization of Pb₂V₂O₇. Fourier transform infrared and laser Raman spectra also suggested the presence of LaVO₄. Incorporation of Fe³⁺ ions into lead metavanadate glass, up to 20 wt% Fe₂O₃, did not cause crystallization inside the glass matrix. Changes in the vibrational spectra are discussed.     

Spectroscopic characterization of alkali borosilicate glasses containing iron ions

Structural properties of alkali borosilicate glasses containing iron ions were investigated using infrared, laser Raman and Mössbauer spectroscopy. Two types of glasses were prepared: SRL-type with the composition 18.5 wt% Na₂O, 10.0 wt% B₂O₃, 52.5 wt% SiO₂, 4.0 wt% Li₂O, 10 wt% TiO₂ and 5.0 wt% CaO, and sodium borosilicate glass with the composition 16.7 wt% Na₂O, 18.7 wt% B₂O₃ and 64.6 wt% SiO₂. Raman spectroscopy showed that orthosilicates are the dominant amorphous phase in the SRL-type of glass. Incorporation of iron in the SRL-type of glass induced polymerization of silicate units and -Si-O-Fe- copolymerization. It was concluded that different amorphous phases are simultaneously present in the SRL-type of glass containing iron ions. Interpretation of the Raman spectra is given. Incorporation of iron ions into the sodium borosilicate glass also affected the corresponding IR spectra. The valence state of iron and its coordination were determined by⁵⁷Fe Mössbauer spectroscopy.     

Pilot Contamination Suppression Based Coordination in Multi-cell Massive MIMO Systems

The conventional millimeter wave systems are mostly designed to operate only for the Gaussian noise model. In many physical channels, such as urban and indoor radio channels, the ambient noise is known through experimental measurements to be non-Gaussian. Hence, recent research findings state that a mixture noise model with additive impulsive noise is a more realistic approximation for millimeter wave channels. In this paper, we propose a novel approach to suppress the impulsive noise effects on single-user millimeter wave massive multiple-input-multiple-output system using an adaptive fuzzy logic filter. Hence, a fuzzy median filter is applied to the system and it is aimed to minimize the effects of the impulsive noise by ordering samples based on fuzzy rank. Simulation results show that the proposed filter successfully suppresses the impulsive noise effects and achieves a better bit error rate and spectral efficiency performance than the competing methods in the literature while also working efficiently in Gaussian noise.

     

A Pentagonal Shaped Microstrip Planar Antenna with Defected Ground Structure for Ultrawideband Applications

A new compact pentagonal microstrip patch antenna with slotted ground plane structure, developed for use in ultrawideband applications, is studied in this article. The proposed antenna is mainly constituted by a pentagonal shaped patch antenna, a defected ground plane structure, two stubs, and four slots to improve the bandwidth. The designed antenna has an overall dimension of 30?×?17.59?×?1.6 mm³, for WIMAX/WLAN/WiFi/HIPERLAN-2 /Bluetooth/LTE/5G applications with a very large bandwidth starting from 2.66 to 10.82 GHz (S₁₁?<???6 dB). A parametric study of the ground plane structure was carried out to find the final and the optimal UWB antenna, and to confirm that the antenna has good performance and broader bandwidth. The proposed antenna prototype has been fabricated. The measured results indicate that the antenna has a good impedance matching. The antenna has an electrically small dimension with a good gain, a notable efficiency, and a wide impedance bandwidth, which makes this antenna an excellent candidate for ultrawideband wireless communication, microwave imaging, radar applications, and the major part of the mobile phone frequencies as well.

     

ac impedance, X-ray photoelectron spectroscopy and density functional theory studies of 3,5-bis(n-pyridyl)-1,2,4-oxadiazoles as efficient corrosion inhibitors for carbon steel surface in hydrochloric acid solution

The corrosion inhibition properties of a new class of oxadiazole derivatives, namely 3,5-bis(n-pyridyl)-1,2,4-oxadiazoles (n-DPOX) for C38 carbon steel corrosion in 1 M HCl medium were analysed by electrochemical impedance spectroscopy (EIS). An adequate structural model of the interface was used and the values of the corresponding parameters were calculated and discussed. The experimental results showed that these compounds are excellent inhibitors for the C38 steel corrosion in acid solution and that the protection efficiency increased with increasing the inhibitors concentration. Electrochemical impedance data demonstrate that the addition of the n-DPOX derivatives in the corrosive solution decreases the charge capacitance and simultaneously increases the function of the charge/discharge of the interface, facilitating the formation of an adsorbed layer over the steel surface. Adsorption of these inhibitors on the steel surface obeys to the Langmuir adsorption isotherm. X-ray photoelectron spectroscopy (XPS) and the thermodynamic data of adsorption showed that inhibition of steel corrosion in normal hydrochloric solution by n-DPOX is due to the formation of a chemisorbed film on the steel surface. Quantum chemical calculations using the Density Functional Theory (DFT) and the Quantitative Structure Activity Relationship (QSAR) approach were performed on n-DPOX derivatives to determine the relationship between molecular structure and their inhibition efficiencies. The results of the quantum chemical calculations and experimental inhibition efficiency were subjected to correlation analysis and indicate that their inhibition effect is closely related to E_HOMO, E_LUMO, and dipole moment (μ).     

From a domain analysis to the specification and detection of code and design smells

Code and design smells are recurring design problems in software systems that must be identified to avoid their possible negative consequences on development and maintenance. Consequently, several smell detection approaches and tools have been proposed in the literature. However, so far, they allow the detection of predefined smells but the detection of new smells or smells adapted to the context of the analysed systems is possible only by implementing new detection algorithms manually. Moreover, previous approaches do not explain the transition from specifications of smells to their detection. Finally, the validation of the existing approaches and tools has been limited on few proprietary systems and on a reduced number of smells. In this paper, we introduce an approach to automate the generation of detection algorithms from specifications written using a domain-specific language. This language is defined from a thorough domain analysis. It allows the specification of smells using high-level domain-related abstractions. It allows the adaptation of the specifications of smells to the context of the analysed systems. We specify 10 smells, generate automatically their detection algorithms using templates, and validate the algorithms in terms of precision and recall on Xerces v2.7.0 and GanttProject v1.10.2, two open-source object-oriented systems. We also compare the detection results with those of a previous approach, iPlasma.     

Reusable model transformations

Model transformations written for an input metamodel may often apply to other metamodels that share similar concepts. For example, a transformation written to refactor Java models can be applicable to refactoring UML class diagrams as both languages share concepts such as classes, methods, attributes, and inheritance. Deriving motivation from this example, we present an approach to make model transformations reusable such that they function correctly across several similar metamodels. Our approach relies on these principal steps: (1) We analyze a transformation to obtain an effective subset of used concepts. We prune the input metamodel of the transformation to obtain an effective input metamodel containing the effective subset. The effective input metamodel represents the true input domain of transformation. (2) We adapt a target input metamodel by weaving it with aspects such as properties derived from the effective input metamodel. This adaptation makes the target metamodel a subtype of the effective input metamodel. The subtype property ensures that the transformation can process models conforming to the target input metamodel without any change in the transformation itself. We validate our approach by adapting well known refactoring transformations (Encapsulate Field, Move Method, and Pull Up Method) written for an in-house domain-specific modeling language (DSML) to three different industry standard metamodels (Java, MOF, and UML).     

氟化处理对植入材料Mg-Ca二元合金腐蚀行为的影响(英文)

在室温下,将Mg-0.5Ca合金在不同浓度的氢氧化钠和HF溶液浸渍不同的时间,研究HF处理对合金腐蚀行为的影响。采用原子力显微镜、X射线衍射、场发射扫描电子显微镜表征样品的微观组织变化。通过动电位极化和Kokubo溶液浸泡试验测试样品的耐腐蚀性。结果表明,与35%HF处理的样品相比,经40%HF溶液处理的Mg-0.5Ca合金具有更均匀、更致密、更薄的涂层(12.6μm)。电化学测试表明,在Kokubo溶液中,经氟化物处理的Mg-0.5Ca合金样品的耐腐蚀性比未处理样品的高35倍;前者的体外降解速率远远低于后者的。在40%HF溶液处理过的样品表面只出现了一些腐蚀点,而未经处理的样品完全被腐蚀产物覆盖且出现了分层现象。40%HF处理的Mg-0.5Ca合金,具有低的降解速率和良好的生物相容性,是一种有潜力的植入材料。     

DECOR: A Method for the Specification and Detection of Code and Design Smells

Code and design smells are poor solutions to recurring implementation and design problems. They may hinder the evolution of a system by making it hard for software engineers to carry out changes. We propose three contributions to the research field related to code and design smells: 1) Decor, a method that embodies and defines all the steps necessary for the specification and detection of code and design smells, 2) Detex, a detection technique that instantiates this method, and 3) an empirical validation in terms of precision and recall of Detex. The originality of Detex stems from the ability for software engineers to specify smells at a high level of abstraction using a consistent vocabulary and domain-specific language for automatically generating detection algorithms. Using Detex, we specify four well-known design smells: the antipatterns Blob, Functional Decomposition, Spaghetti Code, and Swiss Army Knife, and their 15 underlying code smells, and we automatically generate their detection algorithms. We apply and validate the detection algorithms in terms of precision and recall on Xerces v2.7.0, and discuss the precision of these algorithms on 11 open-source systems.