液体粘滞系数精确测量系统设计

采用沉降法测量液体粘滞系数受手工按秒表、视差及小球下落偏离中心等因素影响,测量结果准确度不高.采用激光光电传感器结合单片机计时,克服人工秒表计时的视差和反应误差,测量小球下落速度的准确度高,引导学生掌握一种新型计时、测速、计数的方法.本研究既保留原实验装置的操作和实验内容,又增加了激光光电计时器的原理及使用方法,扩大了知识面,提高了测量精确度,体现了实验教学的现代化.研究结果表明:该系统测量的蓖麻油的粘滞系数(14℃)的相对误差只有3.5%,大大提高了粘滞系数测量精度,为粘滞系数测量和计时器的设计提供了研究思路和方法.     

基于粘滞流体B样条模型的快速非刚体配准方法

基于粘滞流体模型的非刚体配准算法是一种适合个体差异较大配准场合的方法。其关键步骤为求解偏微分运动方程组,但原始算法中采用直接离散结合同步超松弛(SOR)的方法相当耗时。为了缩短求解时间,提出一种基于粘滞流体B样条模型的快速方法。首先利用B样条对速度场进行建模,将方程组未知量转为B样条系数,减小计算负担;接着利用B样条的一些重要性质,推导出基于快速傅里叶变换(FFT)的B样条系数求解方法,进一步加快求解速度。实验结果表明,新算法在保持原始算法相同配准精度的同时,具有很快的计算速度。     

成都市PM2.5、PM10变化特征及其与气象因素的关系

为研究气象因素对成都市大气细颗粒物 (PM2.5)、可吸入颗粒物 (PM10) 的影响, 收集了2015―2018 年成都市 PM2.5、PM10的月平均浓度, 采用Pearson 相关分析法, 分析了成都市PM2.5、PM10与气象条件的关系。结果表明： (1) 2015 ―2018 年, 成都市PM2.5、PM10年平均浓度虽然年际间差别较小, 但整体呈现逐年缓慢下降趋势, 2015 年以来成都市的 一系列大气污染控制措施是PM2.5、PM10逐年缓慢下降的原因; 2015―2018 年成都市PM2.5、PM10浓度季节变化特征整体 表现为冬季 > 春季 > 秋季> 夏季。(2) 不同气象因素对成都市PM2.5、PM10月平均浓度的影响程度不同, 降水量与气温 是影响成都市PM2.5、PM10月平均浓度的主要因素, 两者与PM2.5、PM10呈较高的负线性相关, 其中PM2.5、PM10与降水量 的相关系数均为 −0.612, 与月平均气温的相关系数分别为 −0.822、−0.776, 降水会通过捕获大气中的颗粒物来去除 PM2.5、PM10, 而温度的升高会加强PM2.5、PM10等污染物在垂直方向上的对流运动, 从而对成都市污染物浓度的降低起 到重要作用; 日照时数、月平均风速、相对湿度等与PM2.5、PM10月平均浓度整体也呈现负相关, 但与降水量和气温相 比, 日照时数、月平均风速与PM2.5、PM10月平均浓度的相关性较低, 而相对湿度与PM2.5、PM10月平均浓度的相关性则 更加微弱, 表明相对湿度的变化对成都市PM2.5、PM10的积累和扩散影响很小。     

基于G1-CRITIC-云物元法的风电集群有功控制策略综合评价

为全面衡量风电集群有功控制效果、合理筛选控制方法使其综合性能最优,提出基于G1-CRITIC-云物元法的风电集群有功控制策略综合评价方法。首先,从安全稳定性、经济性、利用水平3个方面构建评价指标体系;其次,基于G1-CRITIC法对指标进行权重分配;最后,引入云物元理论实现评价等级边界的模糊化并计算控制策略的综合等级隶属度,有效提升评价结果的合理性与准确性。案例分析验证了所提方法的有效性。     

Energy coupled to matter for magnetic alignment of rare earth–doped alumina

Energy coupled to matter (ECM) concepts such as magnetic field–assisted processing were used to align rare earth–doped alumina ceramics in the presence of applied fields. The addition of gadolinium and ytterbium dopants to alumina increased the magnetic susceptibility anisotropies, and induced magnetic torques that led to significant alignment of ceramic particles under the application of magnetic fields as low as 1.8?T. In comparison, undoped alumina materials showed minimal alignment under applied field strengths as high as 9?T. Density function theory modeling indicated that the specific dopant type dictated changes in the magnetic properties of different rare earth–doped alumina systems by directly affecting the magnetic moment localization and magnetocrystalline anisotropy.     

High‐Temperature Particulate Matter Filtration with Resilient Yttria‐Stabilized ZrO2 Nanofiber Sponge

Particulate matter (PM) is a major air pollutant in many regions, jeopardizing ecosystems and public health. Filtration at pollutant source is one of the most important ways to protect the environment, however, considering the high‐temperature exhaust gas emissions, effective removal of PM and related pollutants from their sources remains a major challenge. In this study, a resilient, heat‐resisting, and high‐efficiency PM filter based on yttria‐stabilized ZrO₂ (YSZ) nanofiber sponge produced with a scalable solution blow spinning process is reported. The porous 3D sponge composed of YSZ nanofibers is lightweight (density of 20 mg cm^?3) and resilient at both room temperature and high temperatures. At room‐temperature conditions, the YSZ nanofiber sponge exhibits 99.4% filtration efficiency for aerosol particles with size in the range of 20–600 nm, associated with a low pressure drop of only 57 Pa under an airflow velocity of 4.8 cm s^?1. At a high temperature of 750 °C, the ceramic sponge maintains a high filtration efficiency of 99.97% for PM_0.3–2.5 under a high airflow velocity of 10 cm s^?1. A practical vehicle exhaust filter to capture particles with filtration efficiency of >98.3% is also assembled. Hence, the YSZ nanofiber sponge has enormous potential to be applied in industry.     

Light‐Activated,Multi‐Semiconductor Hybrid Microswimmers

Using a dynamic fabrication process, hybrid, photoactivated microswimmers made from two different semiconductors, titanium dioxide (TiO₂) and cuprous oxide (Cu₂O) are developed, where each material occupies a distinct portion of the multiconstituent particles. Structured light‐activated microswimmers made from only TiO₂ or Cu₂O are observed to be driven in hydrogen peroxide and water most vigorously under UV or blue light, respectively, whereas hybrid structures made from both of these materials exhibit wavelength‐dependent modes of motion due to the disparate responses of each photocatalyst. It is also found that the hybrid particles are activated in water alone, a behavior which is not observed in those made from a single semiconductor, and thus, the system may open up a new class of fuel‐free photoactive colloids that take advantage of semiconductor heterojunctions. The TiO₂/Cu₂O hybrid microswimmer presented here is but an example of a broader method for inducing different modes of motion in a single light‐activated particle, which is not limited to the specific geometries and materials presented in this study.     

Viscosity and Density at High Pressures in an Associative Ternary

The dynamic viscosity and the density of the associative ternary mixture water+diacetone alcohol+2-propanol have been measured as a function of temperature T (303.15, 323.15, and 343.15 K) and pressure P (100 MPa). The experimental results correspond to 698 values of and . With reference to the 54 values previously published on pure substances and 486 values for three corresponding binaries, the system is globally described by 1188 experimental values for various values of P, T and composition. The results for are discussed in terms of excess activation energy of viscous flow.     

PM10 remote sensing from geostationary SEVIRI and polar-orbiting MODIS sensors over the complex terrain of the European Alpine region

The subject of this study is to investigate the capability of spaceborne remote sensing data to predict ground concentrations of PM₁₀ over the European Alpine region using satellite derived Aerosol Optical Depth (AOD) from the geostationary Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and the polar-orbiting MODerate resolution Imaging Spectroradiometer (MODIS). The spatial and temporal resolutions of these aerosol products (10 km and 2 measurements per day for MODIS, ∼ 25 km and observation intervals of 15 min for SEVIRI) permit an evaluation of PM estimation from space at different spatial and temporal scales. Different empirical linear relationships between coincident AOD and PM₁₀ observations are evaluated at 13 ground-based PM measurement sites, with the assumption that aerosols are vertically homogeneously distributed below the planetary Boundary Layer Height (BLH). The BLH and Relative Humidity (RH) variability are assessed, as well as their impact on the parameterization. The BLH has a strong influence on the correlation of daily and hourly time series, whilst RH effects are less clear and smaller in magnitude. Despite its lower spatial resolution and AOD accuracy, SEVIRI shows higher correlations than MODIS (r_SEV∼ 0.7, r_MOD∼ 0.6) with regard to daily averaged PM₁₀. Advantages from MODIS arise only at hourly time scales in mountainous locations but lower correlations were found for both sensors at this time scale (r∼ 0.45). Moreover, the fraction of days in 2008 with at least one satellite observation was 27% for SEVIRI and 17% for MODIS. These results suggest that the frequency of observations plays an important role in PM monitoring, while higher spatial resolution does not generally improve the PM estimation. Ground-based Sun Photometer (SP) measurements are used to validate the satellite-based AOD in the study region and to discuss the impact of aerosols' micro-physical properties in the empirical models. A lower error limit of 30 to 60% in the PM₁₀ assessment from space is estimated in the study area as a result of AOD uncertainties, variability of aerosols properties and the heterogeneity of ground measurement sites. It is concluded that SEVIRI has a similar capacity to map PM as sensors on board polar-orbiting platforms, with the advantage of a higher number of observations. However, the accuracy represents a serious limitation to the applicability of satellites for ground PM mapping, especially in mountainous areas.