2D numerical study on the deflection of thin steel plate subjected to gaseous detonation wave interaction

An elaborate numerical study with a validated LS-DYNA® immersed boundary method fluid-solid interaction code is used to characterize the influence of pre-detonation pressure, ignition point location and time duration on plastic deformation of thin steel plates subjected to hydrogen-oxygen gaseous detonation. Simulation relies on the modeling of detonation by chemical reaction kinetic and its propagation by conservative element solution element solver. Immersed boundary method is used to simulate the interface motion between the detonating gas and the deforming plate to facilitate the assessment of fluid pressure distribution on the plate surface. The numerical tool relates the pressure distribution and gaseous detonation parameters to the plate macroscopic deformation by employing multi-species reactive Euler's equations for the gas and assuming a Johnson-Cook material model for the plate. The numerical model simulated the experimental tests and a good agreement between them was obtained where specific features of gas detonation-driven forming were considered. With the confidence of the validation, the numerical model investigated the effects of different parameters such as the gaseous mixture initial temperature and combustion cylinder longitudinal capacity on overpressure-time history and strain-time history. It is demonstrated that the larger longitudinal capacity of combustion cylinder and more distant ignition point location have a great influence on increasing the detonation wave intensity. Eventually, the rate-dependent Johnson-Cook failure criterion was used to assess the failure state of plate under high-intensity detonations.     

Multi-period wind integrated optimal dispatch using series PSO-DE with time-varying Gaussian membership function based fuzzy selection

Wind power has emerged as the most promising option for providing sustainable eco-friendly power supply to the modern world. Due to its unpredictable nature, integration of wind power into the conventional power grid is a very challenging task having dynamic characteristics. Due to the inherent uncertainty associated with wind availability, additional spinning reserve needs to be scheduled in order to maintain security and supply reliability. Multi-period multi-objective optimal dispatch (MPMOOD) is presented for wind integrated power system with reserve constraints. The complex relationship between wind power availability, spinning reserve allocation and their impact on economic/environmental cost are analysed using an elaborate model.A new multi-objective Series PSO-DE (SPSO-DE) hybrid algorithm is proposed where the two paradigms, differential evolution (DE) and particle swarm optimization (PSO) share domain information and maintain a synergistic cooperation to overcome their individual weaknesses. For multi-objective (MO) problems, the selection operation in SPSO-DE is replaced by a 5-class time-varying fuzzy selection mechanism (TVFSM) to avoid saturation and to increase Pareto diversity. To promote convergence towards the central part of the Pareto front and to quickly isolate the boundary solutions, Guassian membership function is employed. Elitism is applied to preserve good solutions and momentum operation is used to stop premature convergence. The proposed method expedites the search for the best solution, i.e. the solution which satisfies all the objectives of the MO problems. To test the performance and computational efficiency, the proposed method is applied on two standard test power systems.     

Power system state estimation using a direct non-iterative method

This paper describes a new method for state estimation of a non-linear AC power system in a non-iterative manner. This method is based on the Kipnis–Shamir relinearization technique that is used to solve over-defined sets of polynomial equations. The technique transforms the equations to a higher dimensional linear space which allows the states to be solved in a non-iterative manner. Given accurate measurements, this new state estimation method provides the same results as traditional iterative state estimation methods, and the proposed method does not require an initial guess of system states nor does it have issues with convergence.     

Extraction of Mn(II) from NaCl solution by NaCl/sodium oleate/n-pentanol/n-heptane microemulsion system

A microemulsion (ME) consisting of sodium oleate, n-pentanol, n-heptane and sodium chloride (NaCl) solution was used for Mn(II) extraction. The cation exchange mechanism of Mn(II) extraction by sodium oleate (NaOL) was confirmed by the analysis of continuous variation of the NaOL concentration and the infrared spectrum. The effect of the extraction time, the cosurfactant type and volume fraction, the volume ratio of aqueous to ME (R), the initial concentration of Mn(II), temperature, pH and the NaCl concentration in aqueous phase on the extraction yield of Mn(II) were investigated. The extraction percentage of Mn(II) was up to 99% when R = 1. Both the extraction and re-extraction had good extraction efficiency. Therefore, the extraction of Mn(II) by NaCl/sodium oleate/n-pentanol/n-heptane ME is an effective approach.     

Enhanced mechanical properties of W-doped Nb4AlC3 ceramics

The W-doped Nb₄AlC₃ ceramics [(Nb_1-xW_x)₄AlC₃, x?=?0–0.0375] were successfully fabricated by in-situ reactive hot-press-aided method using elemental niobium, aluminum, graphite and tungsten powders. The XRD results suggest that the matrix phase (Nb_1-xW_x)₄AlC₃ and the second phase (Nb_1-xW_x)C were simultaneously formed when W was added. The SEM images show that (Nb_1-xW_x)C is dispersed in the W-doped Nb₄AlC₃ ceramics matrix. The mechanical properties of Nb₄AlC₃ were greatly enhanced by W doping. Typically, the (Nb_0.975W_0.025)₄AlC₃ exhibits the highest flexural strength (483?±?21?MPa), fracture toughness (8.5?±?0.3?MPa?m^1/2) and Young′s modulus (382?±?18?GPa) at room temperature (RT), which are increased by 59%, 15% and 30%, respectively, compared with the present Nb₄AlC₃. The Vickers hardness of (Nb_0.9625W_0.0375)₄AlC₃ (4.8?±?0.2?GPa) is 92% higher than that of Nb₄AlC₃. The (Nb_0.975W_0.025)₄AlC₃ also retains a high flexural strength of 344?±?4?MPa at 1400?°C (71% of RT value), which is much higher than the RT flexural strength (303?±?22?MPa) of the present Nb₄AlC₃. The strengthening effect is attributed to the solid solution of W and the incorporation of the second phase (Nb_1-xW_x)C. The excellent mechanical properties endow the W-doped Nb₄AlC₃ ceramics as promising high-temperature structural materials.     

Synthesis and properties of (Hf1-xTax)C solid solution carbides

Thermodynamically stable (Hf_1–xTa_x)C (x?=?0.1–0.3) compositions were selected by First Principle Calculation and synthesized in nanopowders via high-energy ball milling and carbothermal reduction of commercial oxides at 1450?°C. The formation of a solid solution during powder synthesis was investigated. The solid solution carbide powders were sintered at 1900?°C by spark plasma sintering without a sintering aid. As a result, the (Hf_1–xTa_x)C solid solution carbides exhibited high densities, excellent hardness and fracture toughness (ρ: 98.7–100.0%, HVN: 19.69–19.98?GPa, K_IC: 5.09–5.15?MPa?m^1/2) compared with previously reported HfC and HfC–TaC solid solution carbides.     

Preparation of biaxially textured Ce1-x(Y0.2Zr0.8)xOδ buffer layers on RABiTS NiW tapes by chemical solution deposition

Highly (100)-oriented Ce_1-x(Y_0.2Zr_0.8)_xO_δ (CYZO) films were prepared on biaxially textured NiW substrates by a chemical solution deposition approach using metal inorganic salts as starting materials. It has been found that both the preferential orientation and surface roughness of CYZO films decrease gradually with increasing of the doping percentage of Y³⁺ and Zr⁴⁺ ions. The epitaxial growth relationship of (220)_CYZO//(200)_NiW and [00?l]_CYZO//[001]_NiW was demonstrated by XRD texture measurement as well as atomic resolution STEM observation. XRD, Raman and XPS spectra results indicate that Y³⁺ and Zr⁴⁺ ions were indeed introduced into CeO₂ lattice to substitute Ce⁴⁺ ions and form cubic fluorite CYZO solid solution. Moreover, CeO₂ buffer layer can be endowed a strong enough capability to prevent element diffusion through co-doping of yttrium and zirconium, provided that an optimal doping ratio of them is adopted. This will provide a new approach to fabricating strong-barrier single buffer layer for coated conductor.     

Thermal stability of nanometric TiC-carbon composites: effects of carbon allotropes and Zr milling impurities

In the ISOL (Isotope Separator OnLine) method a target at high temperatures (up to 2300?°C), is bombarded with high energy protons in order to produce isotopes through nuclear reactions which are simultaneously extracted from the target, ionized and delivered to physics experiments. Due to the enhanced isotope release properties of nanosized porous materials, titanium carbide-carbon porous nanocomposites have been developed at CERN and tested up to 1500?°C. In the interest of the ISOL application, in this study we extended the range of temperatures up to 1800?°C, to test the sintering hindering capabilities of different carbon allotropes. Carbon black was the most effective with the smallest TiC crystallite size: <80?nm at 1800?°C. Additionally, using thermodynamic modelling, ex-situ X-ray powder diffraction and in-situ gas phase analysis, we show that there are interesting additional phase and lattice parameter changes due to the ZrO₂ impurities from the attrition milling.     

Microwave-assisted solution synthesis,microwave sintering and magnetic properties of cobalt ferrite

A simple, soft, and fast microwave-assisted hydrothermal method was used for the preparation of nanocrystalline cobalt ferrite powders from commercially-available Fe(NO₃)₃?9H₂O, Co(NO₃)₂?6H₂O, ammonium hydroxide, and tetrapropylammonium hydroxide (TPAH). The synthesis was conducted in a sealed-vessel microwave reactor specifically designed for synthetic applications, and the resulting products were characterized by XRD, FE-SEM, TEM, and HR-TEM. After a systematic study of the influence of the microwave variables (temperature, reaction time and nature of the bases), highly crystalline CoFe₂O₄ nanoparticles with a high uniformity in morphology and size, were directly obtained by heating at 130?°C for 20?min using the base TPAH. Dense ceramics of cobalt ferrite were prepared by non-conventional, microwave sintering of synthesized nanopowders at temperatures of 850–900?°C. The magnetic properties of both the nanopowders and the sintered specimens were determined in order to establish their feasibility as a permanent magnet.     

组合赋权的TOPSIS在冲击地压危险性评价中的应用

为了合理准确地评价煤矿冲击地压危险性,在现有评价冲击地压危险性实例的基础上,从煤矿地质因素和开采因素2个方面,选取10个主要的影响指标,利用熵权法和指标相关性权重法分别计算影响冲击地压危险性的各评价指标权重,再根据组合赋权的方法得出各指标的综合权重,构建基于逼近理想解理论的冲击地压危险性评价模型。以重庆砚石台煤矿为例,选取20组评价冲击地压危险性样本数据进行分析,确定评价冲击地压危险性的最优和最劣状况,然后计算出各个评价方案与最优和最劣状况的距离,最后综合最优与最劣距离,确定评价对象的相对贴近度。应用结果表明:评价结果与实际情况一致,且该模型相较其他模型的评价结果更加科学准确,表明该方法有良好的实用价值。