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关键词： Tube hydro-mechanical forming   Thin-walled hollow component   Large deformation   Hydroforming   FE modeling  

摘要： The automobile exhaust manifold regularly has a multi-valved shape that used to be formed by the combination of stamping and welding. The current study intended to investigate and develop a tube hydro-mechanical forming (THMF) process to form an integral automobile exhaust manifold that has the characters of large deformation and small corner. It included three stages such as pre-forming stage, die-forming stage, and calibration stage. In addition, the non-feasibility of one-step hydroforming process was proved by FE modeling and experimental for the target component. An optimal loading path was obtained through the principle of dichotomy for pre-forming stage and die-forming stage, corresponding to the maximum thinning ratio of 19.7% and 13.27% respectively. The variation of stress and strain states were analyzed for the whole process. As a consequent, the thickness distribution exhibited a V-shaped along axial direction at each stage, while a fluctuated distribution after die-forming was presented along radial direction in the multi-valved area. For the final component, a maximum thinning ratio of 28.53% and the large deformation above 60% obtained from FE modeling kept a reasonable agreement with that achieved from experiments. It showed that THMF has advantages of not only decreasing the internal pressure but also improving the formability of tube.

关键词： hydrokinetic turbine   vertical axis turbine   open channel flow  

摘要： Preliminary design of a new installation concept of a drag-driven vertical axis hydrokinetic turbine is presented. The device consists of a three-bladed, wheel-shaped, turbine partially embedded in relatively shallow channel streambanks. It is envisioned to be installed along the outer banks of meandering rivers, where the flow velocity is increased, to maximize energy extraction. To test its applicability in natural streams, flume experiments were conducted to measure velocity around the turbine and power performance using Acoustic Doppler Velocimetry and a controlled motor drive coupled with a torque transducer. The experiment results comprise the power coefficient, the spatial evolution of the mean velocity deficit, and a description of the flow structures generated by the turbine and responsible for the unsteadiness of the wake flow. Applying a triple decomposition on the Reynolds stresses, we identify the dominant contribution to such unsteadiness to be strongly associated with the blade passing frequency.

关键词： Ceramic microfiltration   Industrial dye wastewater   Adsorption   Membrane fouling   Organic dye  

摘要： In this study, combined effect of types of anionic dye compounds and solution pHs on organic removal efficiency and membrane fouling on the alumina-based microfiltration (MF) flat-tubular membrane was investigated using a laboratory-scaled, fluidized bed membrane reactor at constant permeate flux operation. For the Congo-Red dye solution at the solution pH of 6, there was no increase in suction pressure with only 10% of organic removal efficiency measured by ultraviolet-visible (UV-Vis) spectrometer during operational period. However, lowering the solution pH to 4.5 accelerated suction pressure increase while higher than 90% organic removal efficiency was achieved. At the solution pH of 4.5, a zwitterion nature characterized by Congo-Red dye compound resulted in more deposit of cake layer on membrane than that formed at higher pH. In the case of Tartrazine and Acid Orange 7 which are categorized as anionic dye compound, the increase in suction pressure with time was much slower than that observed with Congo Red at same solution pH (4.5) and permeate flux (40 L m(-2)h(-1)). Our results suggested that higher fouling rate should be associated closely with higher organic removal efficiency in ceramic MF membrane filtration. Regardless of types of dye compounds tested, granular activated carbon (GAC) fluidized in submerged ceramic membrane reactor was found to be propitious tool to reduce membrane fouling with excellent organic removal due to adsorption functionality and scouring action provided by GAC fluidization on membrane. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Semi-classical Theory   Superfluid density   Anisotropic gap function  

摘要： In this research, we investigated the superfluid density of anisotropic S-wave superconductors by Semi-classical Theory in 3D spherical Fermi surface. The anisotropic gap function was studied by ellipse spherical and pancake spherical model. The superfluid density was derived analytically and applied to MgB2 and CaAlSi superconductors. We found that CaAlSi superconductors show the properties of anisotropic one band S-wave superconductors but the MgB2 superconductors cannot fit well with our model.

关键词： Quartz  

摘要： The Huzhagaitu molybdenum deposit is a newly discovered porphyry deposit in the middle segment of the Derbugan metallogenic belt in Inner Mongolia. The molybdenum orebodies are mainly hosted within the Early Yanshan granodiorite, and its contact zone with rhyolite. The deposit is dominated by molybdenum mineralization and pyrite mineralization, accompanied by lead-zinc mineralization and a small amount of copper mineralization. The ore-forming process can be divided into four stages: silicification stage, quartz-molybdenum stage, quartz-polymetallic sulphide stage, and quartz-calcite stage. There are four types of fluid inclusions: liquid-rich phase inclusions, vapor-rich phase inclusions, multiphase inclusions including daughter minerals and CO2-bearing three-phase inclusions. With the main mineralization stage as the focus of our research, this study carried out microscopic temperature measurement and laser Raman microprobe analysis for the inclusions in quartz or calcite in different mineralization stages (stage II to IV). The results show that the homogenization temperatures of the inclusions in the quartz-molybdenum-pyrite stage are mainly concentrated between 280℃ and 400℃, and the salinities vary from 2.57% to 51.68%. In this stage, vapor-rich phase inclusions and multiphase inclusions including daughter minerals coexist with CO2-bearing three-phase inclusions. The liquid phase composition of L-type inclusions is mainly H2O-NaCl. The gas phase composition of V-type inclusions is mainly H2O, and some of them also contain CO2. Characteristic peak of laser Raman shift of daughter mineral chalcopyrite was detected in halite-bearing three phase inclusions. In the quartz-pyrite stage with lead-zinc mineralization and chalcopyrite mineralization, the homogenization temperatures of the inclusions are concentrated between 180℃ and 280℃, and the salinities vary from 0.18% to 9.73%. In late stage, only L-type inclusions occur in quartz-calcite veins, with the homogeniza

关键词： Fluidized bed drying   vacuum-drying   freezing pretreatment   carrot   shrinkage   rehydration  

摘要： A method for low-temperature drying with high drying rate was developed for heat-sensitive foods and agricultural products. A freezing pretreatment was combined with fluidized bed drying under reduced pressure. Cylindrical carrot samples were frozen and then placed without thawing in a fluidized bed of hygroscopic porous silica gel particles that adsorbed water from the sample during the drying process. The effects of the freezing pretreatment and hygroscopicity of fluidizing particles on the drying characteristics of carrots were examined. A higher drying rate was achieved when carrots samples were subjected to freezing pretreatment than without it. At 12kPa, the volume change was smaller in carrots subjected to freezing pretreatment than in untreated samples. A larger amount of water was absorbed during rehydration by carrots dried at 12kPa than at 101kPa within 120min. The properties of dried carrots were affected not only by freezing pretreatment but also by the pressure applied during the drying process.

关键词： 地质特征   成矿流体特征   板仓萤石矿   湖北  

摘要： 湖北省大悟县板仓大型萤石矿床位于秦岭褶皱系桐柏-大别褶皱带东部,是典型的中低温热液充填型矿床,该矿床至今未开展成矿流体的相关研究。本文在进一步研究矿床地质特征的基础上,系统开展了矿床流体包裹体研究,了解其流体包裹体形态、温度、盐度、密度和成分特征,推断其成矿流体主要为低温低盐度、较低密度的含Na2SO4-NaCl-H2O成矿流体体系的热液流体。本文认为板仓萤石矿床的形成与燕山晚期三大岩体侵入时形成的岩浆热液有密切关系,矿床属于断裂控矿、中低温热液裂隙充填型萤石矿床。

关键词： 二氧化碳   向心透平   进气攻角   流动损失  

摘要： 以实际二氧化碳为工质,通过全三维黏性数值仿真模拟及试验研究的方法,对某闭式布雷顿循环系统的向心透平内部流动特性进行了详细研究。对透平内部10%、50%、90%叶高截面及30%、50%、70%流向截面的流动特性及流动损失进行总结。结果表明,数值仿真结果与试验结果吻和较好。随着叶轮转速不断提高,二氧化碳向心透平的稳定工作范围扩大,流通能力逐步增强。过大的进气攻角会造成动叶吸力面前缘出现流动分离,从而引发主流过膨胀,并沿流向出现逆压梯度。叶顶间隙泄漏流动是造成通道涡旋流动损失及叶片表面径向窜流损失的主要原因。研究成果可为以二氧化碳为工质的向心透平设计及变工况调节提供参考。

关键词： 水上飞机   表面张力   水面   冲击波   撞击  

摘要： 你听说过“水上迫降”吗?它是指飞机遇险时被迫在水面上降落。其实,在水面上降落是非常危险的,因为水的密度是空气的800倍左右,所以水有很强的表面张力。当飞机由于险情失速撞向水面时,在接触水面的一瞬间,水的表面张力会对飞机的撞击点产生冲击,使其结构遭到破坏,由此产生的冲击波还会沿机体传播造成其他部位的损坏。

关键词： 高炉渣   矿渣棉   析晶性能   黏度   表面张力  

摘要： 利用铁尾矿进行高炉渣调质实验,研究了酸度系数( M k )对调质高炉熔渣析晶性能、黏度及表面张力的影响.结果表明:随 M k 的增加,调质熔渣的析晶温度明显降低,当 M k 高于1.4时熔渣温度降至 1 100℃,体系仍为无序玻璃相;随 M k 的增大,调质熔渣黏度对温度变化的敏感性逐渐减弱,适宜成纤黏度范围对应的温度区间逐渐增大,适宜成纤黏度范围内最低成纤温度与析晶温度之差Δ t =( t w- t l)逐渐增大,当 M k为1.2时Δ t 为101.7 ℃;在调质熔渣适宜成纤温度范围内, M k 对熔渣表面张力的影响不大,熔渣表面张力与黏度的比值σ/η(表征熔渣成形难易程度)随 M k 的增大逐渐减小.