Vibration of circular plate with multiple eccentric circular perforations by the Rayleigh-Ritz method

The free vibration of a circular plate with multiple perforations is analyzed by using the Rayleigh-Ritz method. Admissible functions are assumed to be separable functions of radial and tangential coordinates. Trigonometric functions are assumed in the circumferential direction. The radial shape functions are the boundary characteristic orthogonal polynomials generated following the Gram-Schmidt recurrence scheme. The assumed functions are used to estimate the kinetic and the potential energies of the plate depending on the number and the position of the perforations. The eigenvalues, representing the dimensionless natural frequencies, are compared with the results obtained using Bessel functions, where the exact solution is available. Moreover, the eigenvectors, which are the unknown coefficients of the Rayleigh-Ritz method, are used to present the mode shapes of the plate. To validate the analytical results of the plates with multiple perforations, experimental investigations are also performed. Two unique case studies that are not addressed in the existing literature are considered. The results of the Rayleigh-Ritz method are found to be in good agreement with those from the experiments. Although the method presented can be employed in the vibration analysis of plates with different boundary conditions and shapes of the perforations, circular perforations that are free on the edges are studied in this paper. The results are presented in terms of dimensionless frequencies and mode shapes.     

Thermogravimetric Determination of Carbon, Nitrogen, and Oxygen in Aluminum Nitride

A thermogravimetric method for the measurement of carbon, nitrogen, and oxygen in aluminum nitride is described. Since carbon oxidation occurs at lower temperatures than the oxidation of the aluminum compounds, thermogravimetric analyses in the respective temperature regimes can yield measurement of the oxygen, nitrogen, and carbon content. Thermogravimetric analyses were performed on mixtures of aluminum nitride and carbon with various concentrations in order to evaluate the accuracy of this method. The results were compared with those obtained by the hot gas extraction method. Errors produced by overlapping of the temperature ranges of the reactions were evaluated and experimental conditions were optimized to minimize error. This method can produce reliable results at elemental concentrations higher than a few percent. The absolute errors of the C/AI, N/Al, and O/Al atomic ratios were less then 0.02. The detection limit was evaluated to 0.2 wt% of each element. The applicability of the method to the study of the kinetics of the nitridation reaction was demonstrated.     

Assessment of cleaning effectiveness for new ecological systems on ancient tempera icon by complementary microscopy techniques

The study presents an old icon painted in egg tempera on lime wood, with a poor conservation condition and clogged dirt deposits. The icon is attributed to an anonymous painter of XIXth century and to the neo‐classical style of painting. The painting layer was done with only a hand full of pigments, earth colors that were often used in painting the icons from XVIIth to XIXth century in Eastern Europe, that have Byzantine influences. Taking into consideration the nature and the structure of the materials from the upper layers of the painting, affected by deposits of dirt over time, a series of cleaning recipes were studied, using the so called cleaning tests with compatible mixtures of different juices and infusion from indigenes plants, that were freshly done and odorless. A low alkaline 95% ethyl alcohol solution, combined with a few drops of ammoniac 25%, was used as a reference system, due to its compatibility with the greasy deposits found on the polychrome layer and on the wood. The cleaning capacity of the new systems used, in comparison with the standard solution, was analyzed through modern analytical methods of evaluating the degree of cleaning, more exactly by means of visible and UV reflectography, CIE L*a*b* colorimetry by reflection assisted by SEM‐EDX and IR spectroscopy. Microsc. Res. Tech. 77:1060–1070, 2014. © 2014 Wiley Periodicals, Inc.     

金属及合金中射程参数的研究SCIEI

本文应用金属中Wigner-Sietz(W-S)半径数据和引入等效电荷概念,结合Ziegler的质子注入数据,导出了计算重离子注入各种金属中的电子阻止本领S_c(E)的公式,计算结果与文献中的实测值结果甚为一致。同样,应用合金中的W-S半径,导出了适用于合金硼化物和CsCl型合金的S_c(E)计算公式。计算结果表明,公式对单硼或二硼化合物符合得较好,而对一些复杂结构的合金以及Cr_5B_3和W_2B_5是不适合的。对CsCl型合金,S_c(E)对Bragg定律的偏离系数γ和合金中电荷转移量成正比,后者越大表明金属键越强,则合金对离子的阻止本领越大,这与实验结果是吻合的。合金中两元素在同一周期中位置相差越远,这种趋势越明显。不同周期元素组成的合金更加强了这种趋势。     

SEM‐EDX and microftir studies on evaluation of protection capacity of some thin phosphate layers

This article presents the SEM‐EDX and microFTIR study and the corrosion behavior of new five types of phosphated coatings obtained by coprecipitation in acid aqueous medium of some metal cations, pursuing the influence of the addition of other cations and a moderator of precipitation, on the uniformity and compactness of the layers and on the morphology of dendritic structure of Zn(II) and Fe(II) phosphates. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Mg的晶界偏聚效应及其对Ni_3Al(0.1B)抗腐蚀性能的影响

在金属间化合物Ni_3Al(0.1B)中注入能量为120keV,剂量为1×10~(16)ion/cm~2的Mg~+离子用多次扫描循环极化曲线测量和光学显微镜观察研究其腐蚀行为.发现经Mg~(+)离子注入后的样品在0.5mol/L H_2SO_4溶液中的抗蚀性能有很大的改善对Mg原子的偏聚现象进行实验测试和计算机模拟,增进了对Mg~(+)离子注入提高金属间化合物抗蚀性能机制的了解     

Calculation of optimal thermal load of intermittently heated buildings

A building is permanently in thermodynamic non-equilibrium due to changing weather, free gains and indoor temperature set-point. Load calculation in dynamic conditions is an essential goal of building energy simulation. This paper demonstrates that the load calculation is a control problem. Supposing that the thermal model of the building is linear and that the model of the building, the weather conditions and occupational program are known in the design stage, the paper proposes an unconstrained optimal control algorithm which uses feed-forward to compensate the weather conditions and model predictive programming (MPP) for set-point tracking. MPP is obtained by modifying the dynamic matrix control (DMC), a variant of model predictive control (MPC).The peak load depends on the set-back time of the indoor temperature: smaller the set-back time, larger the peak load, but smaller energy consumption. Then, the choice of the weighting coefficients in the model predictive programming may be done on economical considerations.     

Digital image correlation techniques to investigate strain fields and cracking phenomena in asphalt materials

This paper is the outcome of a specific task group of the RILEM Technical Committee 241-MCD “Mechanisms of Cracking and Debonding in Asphalt and Composite Pavements”. The group on “Advanced Measurement Techniques” was established in 2011 to investigate DIC applications for non-destructive and non-contact measurements of strain fields during laboratory testing. The paper illustrates different DIC/optical flow applications in measuring strain distribution during laboratory testing. Specific applications of DIC for evaluating crack initiation and crack propagation in asphalt materials are presented.     

Acetylcholinesterase voltammetric biosensors based on carbon nanostructure-chitosan composite material for organophosphate pesticides

A sensitive biosensor for chloropyrifos (CPF), an organophosphorus pesticide, was developed by immobilizing acetylcholinesterase (AChE) through covalent bonding to an oxidized exfoliated graphite nanoplatelet (xGnPs)–chitosan cross-linked composite. Because of the increased surface area and the conductive properties of the nanomaterial, AChE developed a high affinity for acetylthiocholine (ATCI) and formed thiocholine with a fast response. The response of the sensor was a linear function of ATCI concentration in two segments, one from 0.005 to 0.039 mM and the second from 0.064 mM to 0.258 mM. The corresponding equation for the first range was i_p(A) = 2.26 × 10^? 5c + 4.39 × 10^? 7 (R² = 0.992) and the equation for the second was i_p(A) = 6.80 × 10^? 6c + 1.30 × 10^? 6 (R² = 1.000), with a detection limit of 1.58 × 10^? 10 M. The fabrication of the sensor was simple, the response was fast and the stability acceptable. This sensor has many potential applications, the foremost being in organophosphorus pesticides.