Unsteady flow field numerical calculations of a ship’s rotating Weis-Fogh-type propulsion mechanism with the advanced vortex method

The Weis-Fogh mechanism, found in the hovering flight of a small bee, is a unique and efficient lift generation. In this study, we proposed a rotating type propulsion model that applies the principle of the Weis-Fogh mechanism and calculated the unsteady flow field of the propulsion model with the advanced vortex method. The wing (NACA0010 airfoil) and channel are approximated by source and vortex panels, and free vortices are introduced away from the body surfaces. The viscous diffusion of fluid is represented using the core-spreading model to the discrete vortices. We investigated the thrust and drag coefficients, pressure field, vorticity field, velocity vector field, and average propulsive efficiency of the propulsion model by changing the rotating angle velocity. The force acting on the wing depended heavily on the directions of the thrust and drag and the thrust and drag coefficients largely fluctuated with the change in the rotating angles. The average thrust increased as the rotating angle velocity increased. The maximum propulsive efficiency was 27.9% at a calculated angle velocity. The flow field of this rotating type propulsion mechanism is unsteady and very complex because the wing rotates and moves unsteadily in the channel. However, using the advanced vortex method, it could be calculated accurately.     

油田三维构造应力场、裂缝与油气运移

叙述了地应力与裂缝和油气运移的关系。用有限元法对辽河滩海油田进行了三维构造应力场的模拟计算．给出了地应力场的分布特征及其对裂缝发育和油气运移积聚的控制作用，并对油气积聚的有利地区进行了预测。     

浅谈桥梁深基坑挡土墙防护施工方案

本文根据该项工程实际情况和相关技术标准、水文地质特征,对施工准备、测量放线、基坑开挖、挡土墙施工、基坑监测等关键部分进行深入研究。     

护坡植物根系与岩体相互作用的力学特性

通过野外原位拉拔试验，选取灌木铁仔、黄荆、羊蹄甲和禾本科金发草等4种植物，按着生点基岩风化程度不同，测定植株的抗拔力、单根的力学特性和生物指标，研究护坡植物根系与岩体相互作用的力学特性。试验结果表明：受根系构型、受力单根的极限抗拉力及作用根系数量的影响，其单根极限抗拉力随根径的增加而增大，之间有很好的幂函数关系；随植物类型不同，单根的拉力-伸长率关系不同，且极限伸长率随着根径的不同而变化，羊蹄甲与黄荆的拉力-伸长率为线性关系，遵从胡克定律，而灌木铁仔的拉力-伸长率为对数函数关系，羊蹄甲与黄荆根系的极限伸长率表现为随根径增大而降低，铁仔根系的极限伸长率与根径的关系表现出单峰形曲线；在地茎或株高相近的情况下，灌木的抗拔力随基岩风化程度的加剧而增大，在基岩风化程度相近的情况下，抗拔力随地茎、株高及地下生物量的增加而增大，之间具有很好的指数关系；草本植物金发草生物指标与抗拔力之间无明显的数学关系，与基岩问的力学作用不明显。探明根系力学作用特性随植被与基岩类型改变而改变的特征，可为岩石边坡植被护坡工程构造设计及植被类型选择提供必要的参考。     

Analytical modeling and experimental study of tensile strength of asphalt concrete composite at low temperatures

In this study, analytical modeling of the tensile strength of hot-mix asphalt (HMA) mixtures at low temperatures was developed. To do this, HMA mixtures were treated as a two-phase composite material with aggregates (coarse and fine) dispersed in an asphalt mastic matrix. A two-phase composite model, which was similar to Papanicolaou and Bakos's [J. Reinforced Plast. Compos. 11 (1992) 104] model with a particle embedded in an infinite matrix, was proposed. Unlike Papanicolaou and Bakos's model, an axial stress was introduced to the fiber end to consider the load transferred from the asphalt mastic the aggregate. Efforts were also made to consider the effect of aggregate gradation, asphalt mastic degradation, and interfacial damage between the aggregates and asphalt mastic matrix on the tensile strength of the HMA mixtures. Experimental investigations were conducted to validate the developed theoretical relations. A reasonable agreement was found between the predicted tensile strength and the experimental results at low temperatures. Parameters affecting the tensile strength of asphalt mixtures were discussed based on the calculated results.     

Remediation of petroleum contaminated soils through composting and rhizosphere degradation

Composting along with rhizodegradation was used to remediate petroleum-contaminated soils in the Yellow River Delta, China. The average concentration of total petroleum hydrocarbons (TPH) in these soils was reduced from 7900-17,900 mg kg(-1) to 1400-3700 mg kg(-1) after field composting. The best volume ratio of amendment to contaminated soil was 2/1 and the best C/N ratio was 15/1. After composting, four local dominant plant species, Seepweed, Sealavander, Central Asia Saltbush and Reed, were selected and planted in composted soils for rhizodegradation in the field. After 90 days of cultivation, the highest net TPH degradation rate was over 40% for Seepweed, probably because of strong root system and active microbial community. In addition, Seepweed roots significantly reduced the surface and volume of soil micropores (which are able to sequestrate organic compounds inside), thus increasing the bioavailability of TPH. In sum, composting followed with planting Seepweed was most effective in remediating the contaminated soil in the Yellow River Delta.     

战斗机汉语合成话音告警用语设计参数的测定

以机座舱宽带澡声为背景．在视听高负荷条件下，用4种不同语声(男高音、男巾音、女高音，女中音)的战斗机汉语合成话音告警用语．通过工效学实验．实测200名飞行员，得出战斗机汉语合成语音告警用语的设计参数。此研究结果为飞机设计部门提供客观依据，同时也为使用部门提供定量评价标准。     

A new soft template-oriented method for the preparation of hollow analcime microspheres with nanosheets-assembled shells

This paper highlights a controlled synthesis of two-dimensional analcime nanosheets templated by organic additives and an impressive strategy that hollow hierarchical analcime microspheres with layered shells can be assembled by taking advantage of the intrinsic growth law of material. Specifically, ultrathin analcime nanosheets were initially obtained by precisely manipulating the amounts of cetyltrimethylammonium cation (CTA⁺) and ethylenediaminetetraacetate (EDTA^4?) in the synthesis system. As building blocks, these nanosheets then self-assembled layer by layer from outside to inside driven by the reversed crystal growth mechanism of analcime, resulting in a hollow structure with lamellar shells and enhanced specific surface area of 722.3 m² g^?1. Series of experiments were carried out in order to explore the influence of CTA⁺ and EDTA^4? on the formation of analcime nanosheets. The results indicated that CTA⁺ was the micro-mesoporogen of hierarchical analcime and synergistically collaborated with EDTA^4? in directing analcime nanosheets. The effect of hydrothermal temperature was discussed and a surfactant packing parameter (g = V/a ₀ l) was cited to explain the behavior of organics. In addition, the investigation of hydrothermal process clearly revealed the crystallization and self-assembly process of hollow structure. And the UV Raman results unraveled that four-membered rings (4MRs) as the active building units for analcime framework were firstly formed in the synthesis gel, followed by reconstruction and self-assembly which lead to the formation of 6MRs and 8MRs.     

Corrosion Inhibition Mechanism with Spilt Cell Technique of Rare Earth Metal on LC4 Al Alloy

A new method of studying the corrosion inhibition mechanism of rare earth metal(REM) on LC4 Al alloy with the spilt cell technique was studied. The principle and experimental method of the spilt cell technique were analyzed. By measuring the change of net-electric current between the two electrodes caused by the change of the amount of oxygen in the solution and the addition of CeCl₃, the influence of corrosive performance of CeCl₃ on LC4 super-power aluminum alloy in the 0.1 mol·L⁻¹ NaCl solution was investigated. Meanwhile, the conditional changes of pH values, CeCl₃ solution, additire and time of performance were also studied. Finally, the features of electrode surface were revealed by using SEM and X-ray energy-dispersive spectrometry (EDS). By combining these with other electric chemical techniques, such as potential-time curve, polarization curve et al.     

Microstructure and micro-hardness of the Inconel 718 superalloy coating prepared by cold gas dynamic spraying

Inconel 718 superalloy coating was prepared on a martensitic steel substrate by cold gas dynamic spraying (CGDS).Microstructure and micro-hardness of the coating were characterized by means of scanning electronic microscope (SEM),energy dispersive spectrometer (EDS),and micro-hardness and nano-indentation tests.The results have indicated that the coating’s thickness can reach more than 300 μm,and there exists a good interfacial cohesion between the coating and the substrate.The quantity and size of the defects at the bottom,middle and top areas increase gradually.There is no significant change to the original microstructure of the Inconel 718 superalloy particle after the process of CGDS;and an obvious torsional deformation on the particle’s profile is produced while little deformation at the center part occurs.The micro-hardness of the coating at the bottom,middle and top areas decreases in turn.Compared with the bottom area,the micro-hardness of the middle and top areas decreases by about 10% and 21%,respectively.The nano-hardness of the coating is much lower than the original particle,which decreases by about 13.5% at the bottom area and 28% at the top area,respectively.The distribution of micro-defects is an important factor to the micro-hardness of the coating.