New atomic scale simulation models for hydroxides and oxyhydroxides

This work has three aims. First to review the significance of hydroxide containing systems to materials science. Second to report two consistent and transferable sets of interatomic potentials that facilitate the atomic scale modelling of such systems. The first set of potentials is based on the assumption that ions adopt their full formal charge states, the second model assumes that partial charges are more realistic. The third aim is use the models to predict the structures of an extensive set of oxides, hydroxides, and oxyhydroxides. The predictions are compared with experimental results and previous computational studies. Both potential sets yield excellent agreement with the experimental data. A feature of the interatomic potential sets is the use of a screened Coulombic potential to describe the oxygen-hydrogen interaction at short distances rather than the more widely used Coulomb-subtracted Morse potential. The potential sets are discussed in the context of the new structures and processes that they can be employed to model.     

基于应变监测数据预测值的藏式古建筑木结构健康状态评估

为增加藏式古建筑木结构的安全冗余度,该文提出了短期应变监测数据预测方法,以此对藏式古建筑木结构健康状态进行预判性评估。以回廊结构为对象,利用Sobel算子与卷积神经网络方法处理传感器带来的多种数据异常。通过多项式回归和功率谱密度的方法确定应变监测数据组分。引入变分模态分解法对数据进行解耦,以Prophet算法预测短期温度监测应变,以Gumbel极值理论预测不同重现期下的人群监测应变。以不同重现期下的应变监测数据预测值的叠加结果确定需重点关注的结构位置和需立即修缮的结构位置,以满足藏式古建木构的预防性保护要求和最小扰动原则。     

化学吸收法脱除尾气中硒化氢的模拟计算

应用Aspen Plus软件模拟计算了以氢氧化钠水溶液为吸收剂脱除尾气中硒化氢组分的化学吸收过程。分析讨论了吸收剂流量、浓度、温度等参数对脱除效果的影响,得出适用于模拟工况吸收过程的设计操作条件。模拟结果可以为实际工业设计及操作过程提供参考依据。     

Prediction of viscoelastic material functions from constant stress- or strain-rate experiments

To predict durability of polymeric structures an information on polymer’s long-term properties in the form of relaxation modulus and/or creep compliance is required. It is well known that determination of relaxation or creep properties from experimental data is an inverse problem, which, due to presence of experimental errors in input data, becomes ill-posed. To find a stable solution using standard integration schemes is practically impossible. In this paper we propose a “hands-on” methodology which bypasses the solution of ill-posed integral equation and allows finding long-term relaxation or creep properties from simple constant strain rate or constant stress-rate experiments performed at different temperatures. The proposed approach can be applied not only for characterization of viscoelastic materials in solid state but can also be used for prediction of time-dependent properties of polymer melts. The paper presents the detailed steps of the proposed method as well as its validation on several simulated and real experimental data. It has been shown that the proposed approach can accurately reconstruct the desired long-term time-dependent properties obtained in traditional way (i.e., from step loading).     

A review of data on spreading and vaporisation of cryogenic liquid spills

This review summarises the availability and utility of experimental data on the rates of spread and vaporisation of spillages of pressure liquefied and cryogenic liquids on a variety of surfaces including: soil; sand; concrete; and water. It is intended that the paper acts as a review of those sources of information that can be used to allow the validation of current and future computer software which is to be used to predict the likely effects of such spillages, and also to extend the range of materials to which it may be applied.The majority of investigations found cover LNG or LPG, due to their widespread bulk usage, with others studying liquid nitrogen, oxygen, hydrogen, or ammonia.     

Metastable structures and isotope exchange reactions in polyoxometalate ions provide a molecular view of oxide dissolution

Reactions involving minerals and glasses in water are slow and difficult to probe spectroscopically but are fundamental to the performance of oxide materials in green technologies such as automotive thermoelectric power generation, CO2 capture and storage and water-oxidation catalysis; these must be made from geochemically common elements and operate in hydrous environments. Polyoxometalate ions (POMs) have structures similar to condensed oxide phases and can be used as molecular models of the oxide/water interface. Oxygen atoms in POM exchange isotopes at different rates, but, at present, there is no basis for predicting how the coordination environment and metal substitution influences rates and mechanisms. Here we identify low-energy metastable configurations that form from the breaking of weak bonds between metals and underlying highly coordinated oxygen atoms, followed by facile hydroxide, hydronium or water addition. The mediation of oxygen exchange by these stuffed structures suggests a new view of the relationship between structure and reactivity at the oxide/solution interface.     

Precisely introducing defects into periodic structures by using a double-step laser scanning technique

We demonstrate a promising method to precisely introduce desired defects into large-area periodic structures by using a double-step laser scanning technique. A multiexposure two-beam interference technique is first used to create 2D periodic structures. A low power femtosecond laser combined with a high numerical aperture objective lens is then used to map the periodic structures to determine the positions and orientations of air holes or material cylinders without intermediate development. Based on the mapping results, the desired defects are written precisely into these structures by increasing the power of the femtosecond laser to induce a multiphoton polymerization effect. The experimental results show that defects are patterned with accurate positions and orientations. This proposed technique should be useful for fabrication of photonic crystals with well-defined defects.     

Prediction of fatigue life of metallic structures with welded joints using automatic learning systems

Welded metallic joints are prone to fatigue damage, which may lead to sudden and catastrophic structural failure. In this research, fatigue failures of metallic structures with welded joints are analyzed using an approach based on automatic learning technology. A database of physics-based parameters, including material properties, loading histories, and stresses around potential cracking sites, is constructed based on experimental results and numerical analyses. Various automatic learning tools are used to search for the mathematical formulas and data patterns embedded in the database. The obtained rules and formulas can be used to support design of welded metallic structures. This approach provides a new way to locate fatigue-prone areas, predict fatigue lives, and may lead to designs of more fatigue resistant structures. It complements the classical deterministic and statistical fatigue failure predictions.     

A model predicting carbonation depth of concrete containing silica fume

Silica fume (SF) has been used since long as a mineral admixture to improve durability and produce high strength and high performance concrete. Due to the pozzolanic reaction between calcium hydroxide and silica fume, compared with ordinary Portland cement, the carbonation of concrete containing silica fume is much more complex. In this paper, based on a multi-component concept, a numerical model is built which can predict the carbonation of concrete containing silica fume. The proposed model starts with the mix proportions of concrete and considers both Portland cement hydration reaction and pozzolanic reaction. The amount of hydration products which are susceptible to carbonate, such as calcium hydroxide (CH) and calcium silicate hydrate (CSH), as well as porosity can be obtained as associated results of the proposed model during the hydration period. The influence of water-binder ratio and silica fume content on carbonation is considered. The predicted results agree well with experimental results.     

男式无缝内衣压力舒适预测模型构建

以相同款式与材料,不同筒径、组织结构和编织方法的12件男式无缝内衣作为研究对象,通过中号体型青年男子在静态下穿着,测试不同部位的压力大小及进行主观舒适感评价。运用主客观评价、灰色关联和多元线性回归方法将所得数据进行分析,确定了衡量男式无缝内衣上体和下体的舒适压力部位,分别为上体的肘部、肩部、胸部,下体的腰部、臀部和小腿部,并建立了预测压力感受数学模型。经验证该模型具有较好的准确性,可为企业在批量生产前预测无缝内衣压力是否达到舒适要求。     

Finite element simulation and experimental study on mechanical behavior of 3D woven glass fiber composite sandwich panels

The results of finite element simulation followed by an experimental study are presented in order to investigate the mechanical behavior of three-dimensional woven glass-fiber sandwich composites using FE method. Experimental load–displacement curves were obtained for flatwise compressive, edgewise compressive, shear, three-point bending and four-point bending loads on the specimens with three different core thicknesses in two principal directions of the sandwich panels, called warp and weft. A 3D finite element model is employed consisting of glass fabric and surrounding epoxy resin matrix in order to predict the mechanical behavior of such complex structures. Comparison between the finite element predictions and experimental data showed good agreement which implies that the FE simulation can be used instead of time-consuming experimental procedures to study the effect of different parameters on mechanical properties of the 3D woven sandwich composites.     

Direct imaging of hydrogen-atom columns in a crystal by annular bright-field electron microscopy

Enhancing the imaging power of microscopy to identify all chemical types of atom, from low- to high-atomic-number elements,would significantly contribute for a direct determination of material structures. Electron microscopes have successfully provided images of heavy-atom positions, particularly by the annular dark-field method, but detection of light atoms was difficult owing to their weak scattering power. Recent developments of aberration-correction electron optics have significantly advanced the microscope performance, enabling identification of individual light atoms such as oxygen, nitrogen, carbon, boron and lithium. However, the lightest hydrogen atom has not yet been observed directly, except in the specific condition of hydrogen adatoms on a graphene membrane. Here we show the first direct imaging of the hydrogen atom in a crystalline solid YH(2), based on a classic 'hollow-cone' illumination theory combined with state-of-the-art scanning transmission electronmicroscopy. The optimized hollow-cone condition derived from the aberration-corrected microscope parameters confirms that the information transfer can be extended to 22.5 nm(-1), which corresponds to a spatial resolution of about 44.4 pm. These experimental conditions can be readily realized with the annular bright-field imaging in scanning transmission electron microscopy according to reciprocity, revealing successfully the hydrogen-atom columns as dark dots, as anticipated from phase contrast of a weak-phase object.     

Adsorption equilibrium of hydrogen on graphene sheets and activated carbon

For obtaining the technical data to evaluate the performance of hydrogen storage by adsorption on graphene sheets (GS), analysis of adsorption equilibrium of hydrogen on the GS and the activated carbon were carried out based on the hydrogen adsorption data covering a wide temperature range. The GS and SAC-02 activated carbon, which respectively had a specific surface area about 300 m²/g and 2074 m²/g, were selected as adsorbents. Six adsorption isotherms of excess amounts of high purity hydrogen were measured at temperature from 77.15 K to 293.15 K and pressure up to 6 MPa. Parameters of Langmuir, Langmuir–Freundlich and Toth equations were set by non-linear fit against adsorption data, predicting accuracy of the equations was then evaluated by the accumulated relative errors between experimental data and those from the equations under different pressure regions. Absolute adsorption amounts determined by the modified equation were used to calculate the isosteric heat of adsorption.It shows that both adsorption isotherms of hydrogen on the GS and the activated carbon have the features of Type I, but the trend of isotherms varying over the pressure is different within the lower temperature region. Results from Langmuir equation have the largest error. Toth equation can much accurately predict the adsorption data with an overall accumulated relative error less than 4%. The value of the isosteric heat of hydrogen adsorption on the GS is about 5.06–6.37 kJ/mol, which is much higher than 4.05–5.52 kJ/mol for hydrogen on the SAC-02 activated carbon under the whole experimental condition. It reveals that interaction between hydrogen molecules and the graphene layer is stronger than that of hydrogen and carbon surface, and Toth equation could be appropriate to analyzing adsorption equilibrium for hydrogen on carbon based adsorbents.     

A novel fabrication method of silicon nano-needles using MEMS TMAH etching techniques

Nano-needles play important roles in nanoscale operations. However, current nano-needle fabrication is usually expensive and controling the sizes and angles is complicated. We have developed a simple and low cost silicon nano-needle fabrication method using traditional microelectromechanical system (MEMS) tetramethyl ammonium hydroxide (TMAH) etching techniques. We take advantage of the fact that the decrease of the silicon etch rate in TMAH solutions exhibits an inverse fourth power dependence on the boron doping concentration in our nano-needle fabrication. Silicon nano-needles, with high aspect ratio and sharp angles θ as small as 2.9°, are obtained, which could be used for bio-sensors and nano-handling procedures, such as penetrating living cells. An analytic model is proposed to explain the etching evolution of the experimental results, which is used to predict the needle angle, length, and etching time. Based on our method, nano-needles with small acute angle θ can be obtained.     

编织复合材料弹性性能的细观分析及试验研究

基于细观分析与体积平均法建立了二维编织/RTM复合材料刚度的理论分析方法,该分析方法针对工程应用,具有计算量较小、计算精度高等优点,完成了相应的软件分析工具,并在此基础上对编织复合材料的弹性性能进行分析研究,得到了结构参数对编织复合材料整体力学性能的影响。通过与实验数据的对比表明,分析结果精度高,能够满足工程结构设计和理论分析的需要,为二维编织复合材料的设计、分析和减少试验件提供了理论分析方法。      

Block-by-block approaches for spectrum fatigue crack growth prediction

Two block-by-block approaches for improving spectrum fatigue crack growth prediction were proposed and developed in this paper from the observations and analyses of fatigue crack growth behaviours in either representative specimens or real aircraft structures under flight spectrum loading by using the quantitative fractography method. The first approach is the flight-by-flight approach that can be used to predict crack growth history curves for a tested spectrum crack growth data at different stress level for a critical location. The second approach called the effective block approach can be used to predict crack growth histories for un-tested spectra based on some previously tested spectrum crack growth data. In order to demonstrate the robustness of the block-by-block approaches for aircraft damage tolerance analysis, verification and consistency studies were conducted and presented using fatigue test results for different aircraft structures under several flight spectra. It was found that the block-by-block approaches are able to provide significant advantages over conventional fatigue lifing approaches for aircraft damage tolerance analysis.     

Catalytic wet peroxide oxidation of azo dye (Direct Blue 15) using solvothermally synthesized copper hydroxide nitrate as catalyst

Copper hydroxide nitrate (Cu(2)(OH)(3)NO(3)) was synthesized solvothermally in anhydrous ethanol and characterized by XRD, FTIR, TG-DTA and SEM. The peroxide degradation of an azo dye (Direct Blue 15) on this material was evaluated by examining catalyst loading, initial pH, hydrogen peroxide dosage, initial dye concentration and temperature. The leaching of Cu from the copper hydroxide nitrate during the reaction was also measured. The copper hydroxide nitrate synthesized solvothermally, which was of a novel spherical morphology with complex secondary structures and contained high-dispersed Cu(2)O impurity, showed good performance for oxidation degradation of the azo dye, especially high catalytic activity, high utilization of hydrogen peroxide and a wide pH range, whereas the copper hydroxide nitrate synthesized by the direct reaction of copper nitrate and sodium hydroxide showed low catalytic activity.     

Size-dependent melting point of nanoparticles based on bond number calculation

An integrated model based on bond number and bond strength in a system with a cubo-octahedral structure is developed to predict the size-dependent thermal characteristics of nanoparticles. Without any adjustable parameters, this model can be used to predict the melting point and cohesive energy of low-dimensional materials, suggesting that both depend on the size and on the atomic distance. The good agreement of the theoretical prediction with the experimental and molecular dynamic simulation results confirms the validity of the cubo-octahedron in describing the thermodynamic behaviors of nanoparticles even without considering their crystalline structures.     

钢筋混凝土震塌厚度计算公式对比研究

震塌破坏是钢筋混凝土结构三种局部破坏中的一种,也是影响结构抗局部破坏能力的主要因素。分析对比了目前应用较广泛的钢筋混凝土震塌厚度经验计算公式,并与试验结果进行比较,得到了各经验公式的计算误差和适用范围。在这些经验公式中,Bechtel公式和修正BRL公式的预测值与试验结果吻合得最好,Bechtel公式可用来预测无震塌最小厚度,而修正BRL可用来预测震塌最小厚度,即临界贯穿厚度。     

Supramolecular interaction of modificated nanodiamonds,biomolecules and drugs: molecular modeling

Abstract

Using molecular modeling by the density functional theory B3LYP method with 6-31?G(d) basic set, we analyse the hydrogen bonds formation and their influence on IR-spectra and structure of molecular complexes which is formed due to interaction between nanodiamonds with COOH- surface functionalization and highly toxic drugs on example of doxorubicin and mitoxantrone. Molecular modeling of modificated nanodiamonds and drugs interaction is based on nanodiamond representation by a diamond-like nanoparticle with simpler structure. As a result of calculations the combined IR spectrum is obtained as imposing of IR spectra for molecular complexes of drugs and nanodiamonds in various interaction positions. Combined IR spectra demonstrate a good agreement with experimental data. Received results demonstrate that there can be strong supramolecular interaction between drugs and modificated detonation nanodiamonds. Formed hydrogen bonds can be considered as one of the main mechanisms for targeted drug delivery and for drug retention in cells and, thus, for enhancement of anti-cancer therapeutic efficacy.