Drag reduction of turbulent channel flows over an anisotropic porous wall with reduced spanwise permeability

The direct numerical simulation (DNS) is carried out for the incompressible viscous turbulent flows over an anisotropic porous wall. Effects of the anisotropic porous wall on turbulence modifications as well as on the turbulent drag reduction are investigated. The simulation is carried out at a friction Reynolds number of 180, which is based on the averaged friction velocity at the interface between the porous medium and the clear fluid domain. The depth of the porous layer ranges from 0.9 to 54 viscous units. The permeability in the spanwise direction is set to be lower than the other directions in the present simulation. The maximum drag reduction obtained is about 15.3% which occurs for a depth of 9 viscous units. The increasing of drag is addressed when the depth of the porous layer is more than 25 wall units. The thinner porous layer restricts the spanwise extension of the streamwise vortices which suppresses the bursting events near the wall. However, for the thicker porous layer, the wall-normal fluctuations are enhanced due to the weakening of the wall-blocking effect which can trigger strong turbulent structures near the wall.

Oral administration of Bifidobacterium breve improves anti-angiogenic drugs-derived oral mucosal wound healing impairment via upregulation of interleukin-10

Recent studies have suggested that long-term application of anti-angiogenic drugs may impair oral mucosal wound healing.This study investigated the effect of sunitinib on oral mucosal healing impairment in mice and the therapeutic potential of Bifidobacterium breve(B.breve).A mouse hard palate mucosal defect model was used to investigate the influence of sunitinib and/or zoledronate on wound healing.The volume and density of the bone under the mucosal defect were assessed by micro-computed tomography(micro-CT).Inflammatory factors were detected by protein microarray analysis and enzyme-linked immunosorbent assay(ELISA).The senescence and biological functions were tested in oral mucosal stem cells(OMSCs)treated with sunitinib.Ligated loop experiments were used to investigate the effect of oral B.breve.Neutralizing antibody for interleukin-10(IL-10)was used to prove the critical role of IL-10 in the pro-healing process derived from B.breve.Results showed that sunitinib caused oral mucosal wound healing impairment in mice.In vitro,sunitinib induced cellular senescence in OMSCs and affected biological functions such as proliferation,migration,and differentiation.Oral administration of B.breve reduced oral mucosal inflammation and promoted wound healing via intestinal dendritic cells(DCs)-derived IL-10.IL-10 reversed cellular senescence caused by sunitinib in OMSCs,and IL-10 neutralizing antibody blocked the ameliorative effect of B.breve on oral mucosal wound healing under sunitinib treatment conditions.In conclusion,sunitinib induces cellular senescence in OMSCs and causes oral mucosal wound healing impairment and oral administration of B.breve could improve wound healing impairment via intestinal DCs-derived IL-10.

Experimental Study on Electrostatically Actuated Micro-Gripper Based on Silica Process

The characteristics of a kind of comb-drive electrostatic actuated micro-gripper are tested. The test platform using a microscope-CCD-computer, the state information of the micro-gripper obtained by data acquisition and image processing, voltage-displacement characteristic curve is obtained and the mathematical equation is established. The analysis of the characteristic equation has shown the consistency and rationality of the theoretical design and the experimental results. The main factors that cause the difference between the theoretical design and the actual test performance are analyzed, and the design method and experimental results is obtained for the micro-gripper in the field of micro-assembly.

Record-breaking High-temperature Outlook for 2023: An Assessment Based on the China Global Merged Temperature(CMST) Dataset

According to the latest version(version 2.0) of the China global Merged Surface Temperature(CMST2.0) dataset, the global mean surface temperature(GMST) in the first half of 2023 reached its third warmest value since the period of instrumental observation began, being only slightly lower than the values recorded in 2016 and 2020, and historically record-breaking GMST emerged from May to July 2023. Further analysis also indicates that if the surface temperature in the last five months of 2023 approaches the average level of the past five years, the annual average surface temperature anomaly in 2023 of approximately 1.26°C will break the previous highest surface temperature, which was recorded in 2016of approximately 1.25°C(both values relative to the global pre-industrialization period, i.e., the average value from 1850 to1900). With El Ni?o triggering a record-breaking hottest July, record-breaking average annual temperatures will most likely become a reality in 2023.

Microwave-assisted exploration of the electron configuration-dependent electrocatalytic urea oxidation activity of 2D porous NiCo_(2)O_(4) spinel

Urea holds promise as an alternative water-oxidation substrate in electrolytic cells.High-valence nickelbased spinel,especially after heteroatom doping,excels in urea oxidation reactions(UOR).However,traditional spinel synthesis methods with prolonged high-temperature reactions lack kinetic precision,hindering the balance between controlled doping and highly active two-dimensional(2D)porous structures design.This significantly impedes the identification of electron configuration-dependent active sites in doped 2D nickel-based spinels.Herein,we present a microwave shock method for the preparation of 2D porous NiCo_(2)O_(4)spinel.Utilizing the transient on-off property of microwave pulses for precise heteroatom doping and 2D porous structural design,non-metal doping(boron,phosphorus,and sulfur)with distinct extranuclear electron disparities serves as straightforward examples for investigation.Precise tuning of lattice parameter reveals the impact of covalent bond strength on NiCo_(2)O_(4)structural stability.The introduced defect levels induce unpaired d-electrons in transition metals,enhancing the adsorption of electron-donating amino groups in urea molecules.Simultaneously,Bode plots confirm the impact mechanism of rapid electron migration caused by reduced band gaps on UOR activity.The prepared phosphorus-doped 2D porous NiCo_(2)O_(4),with optimal electron configuration control,outperforms most reported spinels.This controlled modification strategy advances understanding theoretical structure-activity mechanisms of high-performance 2D spinels in UOR.

The Assessment of Global Surface Temperature Change from 1850s:The C-LSAT2.0 Ensemble and the CMST-Interim Datasets

Based on C-LSAT2.0,using high-and low-frequency components reconstruction methods,combined with observation constraint masking,a reconstructed C-LSAT2.0 with 756 ensemble members from the 1850s to 2018 has been developed.These ensemble versions have been merged with the ERSSTv5 ensemble dataset,and an upgraded version of the CMSTInterim dataset with 5°×5°resolution has been developed.The CMST-Interim dataset has significantly improved the coverage rate of global surface temperature data.After reconstruction,the data coverage before 1950 increased from 78%−81%of the original CMST to 81%−89%.The total coverage after 1955 reached about 93%,including more than 98%in the Northern Hemisphere and 81%−89%in the Southern Hemisphere.Through the reconstruction ensemble experiments with different parameters,a good basis is provided for more systematic uncertainty assessment of C-LSAT2.0 and CMSTInterim.In comparison with the original CMST,the global mean surface temperatures are estimated to be cooler in the second half of 19th century and warmer during the 21st century,which shows that the global warming trend is further amplified.The global warming trends are updated from 0.085±0.004℃(10 yr)^(–1)and 0.128±0.006℃(10 yr)^(–1)to 0.089±0.004℃(10 yr)^(–1)and 0.137±0.007℃(10 yr)^(–1),respectively,since the start and the second half of 20th century.

微波热冲快速制备二维多孔La_(0.2)Sr_(0.8)CoO_(3)钙钛矿用于高效电催化析氧反应

析氧反应(OER)被认为是电解水的关键限制步骤,已被广泛作为清洁能源方式用于解决能源和环境问题。钙钛矿氧化物(ABO_(3))具有可调的电子结构、高灵活性的元素组成,能在OER中表现出良好的催化活性。然而,钙钛矿氧化物的合成通常需要经历长时间的高温,极易导致金属的聚集和影响材料的本征活性。气相微波技术可以显著缩短热处理时间,从而减少相关的碳排放。这项技术不仅解决了对碳中性过程日益增长的需求,而且还增加了对合成的控制,以避免产品的不良团聚。本文采用微波热冲法快速制备了二维(2D)多孔La_(0.2)Sr_(0.8)CoO_(3)钙钛矿。伴随微波过程的快速熵增可以有效地暴露La_(0.2)Sr_(0.8)CoO_(3)结构中丰富的活性位点。此外,高能微波冲击过程可以精准地将Sr2+引入到LaCoO_(3)的晶格中,通过增加Co的氧化态来增加氧空位量。这种锶元素取代镧引入的氧空位能极大提高催化剂的本征催化活性。对于碱性电解液中的OER应用,制备的La_(0.2)Sr_(0.8)CoO_(3)在10 m A·cm^(-2)下展现出了360 m V的过电位,Tafel斜率为76.6 mV·dec^(-1)。且在经历30000秒的长时间循环测试后仍能维持初始电流密度的97%。这项研究为高活性二维钙钛矿的合成提供了一种简便、快速的策略。

手性分子结构对嵌段共聚物自组装螺旋的影响

手性小分子诱导嵌段共聚物手性组装是构筑手性可控螺旋结构的一种有效方法,但是目前对手性小分子引导螺旋结构形成的机制还没有明确认识。文中利用具有不同化学结构的手性掺杂剂与聚1,4-丁二烯-b-聚环氧乙烷(PBd-b-PEO)共组装,研究了手性小分子化学结构的差异对螺旋结构形成的影响。通过小角散射、透射电镜和圆二色光谱证明了苹果酸和扁桃酸诱导嵌段共聚物中PEO形成螺旋相结构,而酒石酸二苄酯和二乙酰基酒石酸由于氢键位点和取代基效应无法诱导形成螺旋相结构。组装体由于聚合物结构变化和手性分子聚集态变化而呈现不同的手性信号变化规律。通过分子模拟分析了共组装体系中氢键缔合体的稳定性,从能量角度解释了手性分子结构对聚合物形成螺旋结构的影响。

Transport of dissolved oxygen at the sediment-water interface in the spanwise oscillating flow

The distribution and concentration of dissolved oxygen(DO)play important roles in aerobic heterotroph activities and some slow chemical reactions,and can affect the water quality,biological communities,and ecosystem functions of rivers and lakes.In this work,the transport of high Schmidt number DO at the sediment-water interface of spanwise oscillating flow is investigated.The volume-averaged Navier-Stokes(VANS)equations and Monod equation are used to describe the flow in the sediment layer and the sediment oxygen demand of microorganisms.The phase-averaged velocities and concentrations of different amplitudes and periods are studied.The dependence of DO transfer on the amplitude and period is analyzed by means of phase-average statistical quantities.It is shown that the concentration in the sediment layer is positively correlated with the turbulence intensity,and the DO concentration and penetration depth in the sediment layer increases when the period and amplitude of the oscillating flow increase.Moreover,in the presence of oscillating flow,a specific scaling relationship exists between the Sherwood number/oxygen consumption of aerobic heterotrophs and the Reynolds number.

Impact of spray droplets on momentum and heat transport in a turbulent marine atmospheric boundary layer

Droplet-laden turbulent airflow(i.e. the mixture of dry air and water vapor) in the marine atmospheric boundary layer is described by an open channel flow configuration in direct numerical simulation(DNS). The dispersed phase, the spray droplets are tracked in a Lagrangian framework, and their impact on the carrier airflow is modeled with the two-way coupling between the two phases. A wide-range droplet size is typically found near the air–sea interface according to the sea spray concentration function(SSCF). The interactions of the droplets with turbulent airflow including mass, momentum, and energy exchange are investigated here. We found a balancing mechanism exists in the droplet effects on the turbulent drag coefficient, since spray droplets lead to a decreased vertical turbulent momentum transport, but also lead to an increased droplet contribution to total drag coefficient. For the heat transfer, as droplet mass loading increasing, the total Nusselt number decreases due to the depression of turbulent heat flux and enhanced negative droplet convective flux.

双层蒸汽套管磁-温综合泄漏检测应用

本文针对双层蒸汽套管在运行过程中出现的泄漏问题,综合运用了弱磁检测技术和温度检测技术检测泄漏点,该方法有非开挖、在役检测、快速定位等特点。为了使弱磁检测信号显现地更加的明显,采用了磁梯度测量方法,剔除了背景地磁场的干扰,比单测分量的精度更高。根据双层蒸汽套管泄漏形式,利用磁-温综合检测技术确定了双层蒸汽套管走向以及泄漏点的位置。本文主要以双层蒸汽套管泄漏为案列,阐述了磁-温综合检测技术的应用过程以及工程应用经验。

Global land-surface air temperature change based on the new CMA GLSAT data set

The China Meteorological Administration(CMA)has recently developed a new global monthly homogenized land-surface air temperature data set.Based on this data set,we reanalyzed the change in global annual mean land-surface air temperature(LSAT)during three time periods(1901–2014,1979–2014 and 1998–2014).The results show that the linear trends of global annual mean LSAT were 0.104°C/decade,0.247°C/decade and 0.098°C/decade for the three periods,respectively.The trends were statistically significant except for the period 1998–2014,the period that

金属屋面铝板抗风性能数值模拟研究

连续焊接不锈钢金属屋面系统是一种新型金属屋面围护体系,因其易于加工、轻质高强的特点,近年来被广泛应用于体育馆、航站楼、车站等各类大型公共建筑中。连续焊接不锈钢金属屋面系统涉及的问题具有综合性、复杂性,这也导致我国至今还未有金属屋面围护系统的相关施工和管理规范,不利于这类屋面的推广应用。基于上述问题,对连续焊接不锈钢金属屋面系统展开相关研究。首先介绍了金属屋面构造,通过分析连续焊接不锈钢金属屋面系统的构造,总结出其优点:整体性和密封性良好、耐久性优良、维护成本低。基于有限元分析软件MIDAS Fea建立金属屋面铝板数值模拟分析模型,模拟屋面系统在风载作用下的破坏过程,对连续焊接不锈钢金属屋面系统的抗风性能进行研究分析。对金属屋面铝板施加沿z轴正方向的均布荷载8.0 kN/m^2,分析铝板的变形及受力情况。分析结果表明:三角形板的中间位置位移最大,方向主要沿z轴正向;相较于中间位置的板,处在边缘的板由于约束差,位移较大;对于边缘位置板和中间位置板,当荷载达到6.4 kN/m^2时,增加相同的荷载,位移增量变大,即荷载-位移曲线呈非线性增长,铝板产生非线性变形;在8.0 kN/m^2的均布荷载作用下,相邻三角形铝板连接部位的凹槽处应力较大,将率先进入塑性阶段;在三角形铝板中,角点处应力最为集中,故应力增长较快,且应力最大;凹槽处的连接板通过螺栓与下部结构相连,在荷载传递的过程中,屋面三角形板所承受的竖向荷载均通过连接板传给螺栓,由于螺栓连接较弱,容易产生应力集中现象,进而导致结构破坏,必要时应采取相应加强措施。通过对结构的模态分析,得到其前5阶振型和周期。对屋面板进行风压时程分析,得到各测点对应的最大位移、应力响应。在此基础上,结合金属屋面铝板在风吸作用下的破坏模式,提出了提高屋面抗风极限承载力的若干建议。

浙江佛学院二期工程(弥勒圣坛)须弥山结构设计

浙江佛学院二期是用现代建筑语言进行建设的大型宗教建筑。须弥山及兜率天宫为本工程的核心部分,须弥山为混凝土剪力墙结构,外形为圆筒形状,高度为56.85 m,须弥山顶部设置大平台,由24榀平面悬挑桁架组成,桁架最大悬挑尺寸为22.5 m,悬挑桁架根部支撑于环向布置的24根钢骨混凝土柱上。兜率天宫为钢框架结构,高度为33 m,其最外侧钢柱通过混凝土环梁竖向转换,中间钢柱通过混凝土牛腿与须弥山混凝土筒体连接,最内侧钢柱落在大跨度钢梁上。本工程下部须弥山采用混凝土剪力墙结构,上部兜率天宫采用钢框架结构,上下部刚度差异大,是一种复杂的混合结构形式,且存在悬挑、转换、楼板开洞等特点。本项目分析中地震加速度按7度(0.1g)参数取值,阻尼比按混凝土0.05、钢结构0.03计算,场地特征周期0.20 s,水平地震影响系数最大值0.08,竖向地震按水平地震影响系数的0.65选取,混凝土剪力墙抗震等级三级,钢结构抗震等级三级。对须弥山与兜率天宫整体模型和仅考虑须弥山的分模型进行计算分析。结果表明:分模型计算结果与整体模型有较大出入,且分模型计算难于考虑钢结构与混凝土结构的相互影响。为确保设计安全可靠,应采用整体建模和分模型两种模型进行计算并按包络受力进行设计。须弥山大平台采用24榀平面悬挑钢桁架组成。计算结果表明,悬挑桁架刚度大,舒适度高,悬挑钢桁架一阶面外弹性屈曲荷载系数可达19.1,且根据幕墙安装要求,又增加了3道刚性系杆,悬挑钢桁架整体稳定性满足要求。为确保罕遇地震下受力安全可靠,在悬挑钢桁架根部采用增加混凝土环梁的方式进行构造加强。对结构进行了多遇地震时程分析和设防烈度地震、罕遇地震分析,结果表明:结构抗震性能满足设防烈度地震弹性要求;罕遇地震下层间位移角均满足GB 50011—2010《建筑抗震设计规范》要求,但罕遇地震下有部分构件屈服。对部分屈服构件进行加大截面处理,对转换部位承托兜率天宫的混凝土梁采用增大截面和配筋的方式进行加强。