Analysis of acoustic Doppler current profiler mean velocity measurements in shallow flows

Acoustic Doppler current profilers (ADCPs) are commonly used instruments for measurement of natural streamflow and flow in manmade channels. Velocities measured in a profile by the instrument are used to estimate the discharge in a channel. A Teledyne RD Instruments StreamPro ADCP was used to measure the mean velocity simultaneously with a laser Doppler anemometer (LDA) in a laboratory flume. An average of 3.9% under-prediction of the mean velocity measured by the ADCP occurred when compared to the measurements of the LDA. Moreover, this study shows that the sampling duration of the measurements significantly impacts the mean point velocities measured by up to 50%.     

考虑煤层倾角和钻孔倾角的钻屑量理论研究

为准确预测与预防深部开采煤与瓦斯突出,建立了考虑煤层倾角与钻孔倾角的新钻屑量理论计算公式,并分析了煤层倾角和钻孔倾角对钻屑量的影响。以平煤股份有限公司八矿为研究对象,将钻屑量理论计算值与该矿己15-21030风巷现场钻屑量实测值进行对比验证,得出在煤层倾角一定时,钻屑量随钻孔倾角增大呈幂指数递减关系,减小的比率呈“V”形变化趋势,原钻屑量理论值与实测值平均误差为5.5%,在考虑煤层倾角与钻孔倾角情况下的新钻屑量理论值与实测值平均误差为3.9%。     

The Crosstalk of Adipose-Derived Stem Cells (ADSC), Oxidative Stress,and Inflammation in Protective and Adaptive Responses

The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs is a major goal in repair medicine. Stem cells are classified by their potential to differentiate into functional cells. Compared with other sources, adipose-derived stem cells (ADSCs) have the advantage of being abundant and easy to obtain. ADSCs are considered to be tools for replacing, repairing, and regenerating dead or damaged cells. The capacity of ADSCs to maintain their properties depends on the balance of complex signals in their microenvironment. Their properties and the associated outcomes are in part regulated by reactive oxygen species, which mediate the oxidation-reduction state of cells as a secondary messenger. ADSC therapy has demonstrated beneficial effects, suggesting that secreted factors may provide protection. There is evidence that ADSCs secrete a number of cytokines, growth factors, and antioxidant factors into their microenvironment, thus regulating intracellular signaling pathways in neighboring cells. In this review, we introduce the roles of ADSCs in the protection of cells by modulating inflammation and immunity, and we develop their potential therapeutic properties.     

基于ABAQUS的发动机缸盖工装强度分析

分析计算某型号发动机缸盖及工装的应力与局部位移,基于HyperMesh软件建立缸盖及工装的仿真模型,使用ABAQUS软件进行静力学计算,对处于夹紧状态下的发动机缸盖进行4个典型工位的加工工况分析计算,得出工件加工位置最大位移与工装所受最大应力。通过强度和位移校核,最终结果满足缸盖的加工需求,为工艺制定提供了有效的数据支持。     

Novel hybrid serpentine-interdigitated flow field with multi-inlets and outlets of gas flow channels for PEFC applications

In our previous study, a novel flow field design for a polymer electrolyte fuel cell (PEFC) called “Hybrid Serpentine-Interdigitated (HSI)” had been proposed. Although it was very promising in terms of performance and pressure drop, it still had a major drawback of the low oxygen concentration area. To improve its design and performance, three HSI configurations with different numbers of gas inlet and outlet, namely one inlet and one outlet HSI (1-IO HSI), one inlet and two outlets HSI (1I-2O HSI) and two inlets and two outlets HSI (2-IO HSI) were numerically investigated and compared with the conventional single channel serpentine (1S). The investigation on the cell performance and other transport behaviors has been carried out using CFD techniques via ANSYS FLUENT software. At a practical operating potential of about 0.6 V of 50 cm² PEFCs, the 2-IO HSI offered the best distributions of oxygen, current density and water due to the shorter channel length. More importantly, the 2-IO HSI could contribute to a reduction in cathode pressure drop by 90%, as compared with the 1S, resulting in the enhancement in the net power output by 6%, approximately.     

3D thermo-electro-chemo-mechanical coupled modeling of solid oxide fuel cell with double-sided cathodes

A solid oxide fuel cell based on double-sided cathodes is developed in our group, showing special properties and many advantages under some harsh conditions. To optimize the cell further, a thermo-electro-chemo-mechanical coupled 3D model is developed to simulate the distributions of temperature, current density, fuel gas and thermal stress under different voltages. The numerical results indicate that the temperature distribution, current, fuel gases and thermal stress is non-uniform in the cell at different voltages. The distribution of thermal stress in the electrolyte is also non-uniform because of the un-even electrochemical reaction and convective heat transfer. Furthermore, the result shows that about 47%~54% of maximum 1st principal stress in SOFC is caused by the mismatch of coefficients of thermal expansion (CTEs) among materials, while the other part of the maximum 1st principal stress is mainly caused by temperature gradient.     

基于流固耦合的柱面气膜密封支撑结构性能研究

利用流固耦合分析方法,研究一种波箔结构柔性支撑柱面气膜密封,探讨气膜厚度、浮环与转子的偏心率以及柔性支撑结构的泊松比、弹性模量、波箔数量等参数对支撑结构等效应力及变形量的影响。结果表明:柔性支承结构满足柱面气膜密封的正常运作,不会造成因为气膜刚度过大而使得浮环与波箔发生破坏性变形,并且变形量远小于波箔高度;柔性支撑的等效应力和变形量随平均气膜厚度的增大而减小,随偏心率的增加而增大,随支撑材料泊松比的增大而增大;弹性模量的增加并不影响柔性支撑结构的等效应力,但是会使变形量减小;增加波箔数量,柔性支撑的等效应力略有减小,变形量显著减小。     

Moisture transfer and stress development during high-temperature drying of Chinese fir

Abstract

The knowledge of moisture content (MC) and drying stress are crucial parameters to control the drying process and maintain the quality of dried wood. Herein, we investigated the pattern of moisture transfer and stress development in Chinese fir during the high-temperature drying process. The MC in each layer of lumber was separated into bound water and free water via nuclear magnetic resonance (NMR), and the drying and residual stress were measured using prong test method. There was different MC in each layer along the thickness, resulting in an MC gradient that initially increased and then decreased, which is consistent with the trend of drying stress. The T₂₁ peak indicating bound water shifted to the left especially when MC was below the fiber saturation point, signifying that the discharge of moisture became difficult with prolonged drying time. The ratio of bound water to free water was different in each layer, indicating that the moisture transfer was different along the thickness. Furthermore, the residual stress was greater than the corresponding drying stress though the disparity reduced gradually, which suggests that the MC gradient was the largest affecting factor for drying stress at high MC stages but decreased to some extent as the drying process continued.     

Investigation of the residual stress in UO2-Mo composites via a neutron diffraction method

UO₂-Mo composites with a core-shell structure have been considered candidates for the thermal conductivity (TC)-enhanced UO₂ pellets and have demonstrated commercial potential for use in novel high-level safety reactors. Nevertheless, UO₂-Mo composites tend to form micro-cracks that are caused by the presence of residual stress (RS) during manufacturing. In this work, neutron diffraction measurements were employed to analyse the RS in UO₂-Mo core-shell structured composites fabricated by spark plasma sintering (SPS) for the first time. It was found that in the UO₂-Mo composites, the RS state present in the UO₂ matrix was tensile in nature. The RS in the UO₂ matrix increased with increaseing Mo content. There was a maximum value of 148 ± 15 MPa in the UO₂-10 vol% Mo composite. The micro-cracks produced in the high-Mo content composites were explained by the results of the neutron diffraction measurements. These results could provide significant guidance for the manufacturing and improvement of the operational performance of UO₂-Mo composites as next-generation fuels.