Effect of 450 MHz Microwave Modulated with 217 Hz on Human EEG in Rest

Summary This study focuses on discrimination of changes, produced by low-level microwave exposure in intensity and time variability of the human EEG at rest. The power spectral density (PSD) method and nonlinear scaling analysis of the length distribution of low variability periods (LDLVP) were selected for analysis of the EEG signal. During the study, 19 healthy volunteers were exposed to a microwave (450 MHz) of 217 Hz frequency on-off modulation. The field power density at the scalp was 0.16 mW/cm². The experimental protocol consisted of ten cycles of repetitive microwave exposure. Signals from frontal, temporal, parietal and occipital EEG channels on EEG theta, alpha and beta rhythms were analysed. Exposure to microwave causes average increase of EEG activity. LDLVP analysis discriminated significant effect in time variability for 2 subjects (11%). PSD method detected significant changes in intensity for 4 subjects (21%). The effect of low-level microwave exposure is stronger on EEG beta rhythm in temporal and parietal regions of the human brain.     

机械式模拟运输台仿真研究

模拟运输振动试验台作为一种机械式随机振动模拟器,能够较好地再现汽车运输振动环境。针对模拟运输台在调试、使用时具有一定盲目性的问题,进行了运动学仿真。仿真结果与实测数据吻合良好,验证了模型建立的正确性,调整模拟运输台上可变参数进行一系列的仿真,总结这些参数对于最终结果影响的规律。仿真结果表明,模拟运输台的台面振动由系统自激振动和凸轮带动台面强迫振动复合而成;台面上功率谱密度的第一主峰主要和系统的自激振动有关,第二主峰主要和凸轮带动台面的强迫振动有关。     

含信号控制人行横道的街道峡谷污染物扩散三维数值模拟

耦合微观交通仿真和机动车尾气排放模型,分别对含信号控制人行横道和不含信号控制人行横道的街道峡谷污染物排放进行计算,并以此为排放源,采用k-ε两方程模型与组分输运方程对风向与街道垂直时的污染扩散情况进行了三维数值模拟.结果表明,k-ε两方程模型与组分输运方程可以较好地模拟风向与街道垂直时三维街道峡谷内的污染物扩散情况.峡...     

氯气泄漏扩散半径估算与应急处置

氯气泄漏是常见的化学事故之一.通过对氯气的理化性质、危险特性和泄漏原因分析,估算氯气泄漏的扩散半径,同时以扩散半径作参考,提出氯气泄漏的应急处置措施,为氯气泄漏事故应急处理提供技术支持.     

Pool evaporation: Experimental tests at medium-scale with gasoline

Pool evaporation is a major source of flammable vapour clouds. Predicting the evaporation rate of a liquid hydrocarbon pool is therefore a key issue of dispersion modelling for safety concerns. This paper presents small- and medium-scale experiments of pool evaporation carried out with liquid hydrocarbons (pentane, heptane), hydrocarbon “gasoline-like” mixtures and gasoline. Liquid mass loss was measured and the evaporation rate deduced with its evolution in time. Other observations are highlighted, regarding the evolution of liquid temperatures, mixture compositions, and scale effects like the influence of pool length on surface evaporation rate. Comparisons with well-known correlations are then shown. The authors finally suggest a new semi-empirical correlation with a set of parameters fitted on the performed experiments.     

CFD simulations of dust dispersion in the 1 m3 explosion vessel

According to standard procedures, flammability and explosion parameters for dusts and dust mixtures are evaluated in 20 L and/or 1 m³ vessels, with equivalent results provided a correct ignition delay time (60 ms in the 20 L vessel; 600 ms in the 1 m³ vessel). In this work, CFD simulations of flow field and dust concentration distribution in the 1 m³ spherical vessel are performed, and the results compared to the data previously obtained for the 20 L. It has been found that in the 1 m³ vessel, the spatial distribution of the turbulent kinetic energy is lower and much more uniform. Concerning the dust distribution, as in the case of the 20 L, dust is mainly concentrated at the outer zones of the vortices generated inside the vessel. Furthermore, an incomplete feeding is attained, with most of the dust trapped in the perforated annular nozzle. Starting from the maps of dust concentration and turbulent kinetic energy, the deflagration index K_St is calculated in both vessels. In the conditions of the present work, the K_St is found to be 2.4 times higher in the 20 L than in the 1 m³ vessel.     

Hyperspectral Characteristics of Canopy Components and Structure for Phenological Assessment of an Invasive Weed

Spectral reflectance values of four canopy components (stems, buds, opening flowers, and postflowers of yellow starthistle (Centaurea solstitialis)) were measured to describe their spectral characteristics. We then physically combined these canopy components to simulate the flowering stage indicated by accumulated flower ratios (AFR) 10%, 40%, 70%, and 90%, respectively. Spectral dissimilarity and spectral angles were calculated to quantitatively identify spectral differences among canopy components and characteristic patterns of these flowering stages. This study demonstrated the ability of hyperspectral data to characterize canopy components, and identify different flowering stages. Stems had a typical spectral profile of green vegetation, which produced a spectral dissimilarity with three reproduction organs (buds, opening flowers, and postflowers). Quantitative differences between simulated flower stages depended on spectral regions and phenological stages examined. Using full-range canopy spectra, the initial flowering stage could be separated from the early peak, peak, and late flowering stages by three spectral regions, i.e. the blue absorption (around 480 nm) and red absorption (around 650 nm) regions and NIR plateau from 730 nm to 950 nm. For airborne CASI data, only the red absorption region and NIR plateau could be used to identify the flowering stages in the field. This study also revealed that the peak flowering stage was more easily recognized than any of the other three stages.     

卫星光学反射膜光谱反射率空间综合环境退化研究

对玻璃基底和金属基底的铝反射膜在紫外、低能电子、低能质子的综合环境作用下的光谱反射率退化进行了实验研究。试验结果表明两种铝反射膜的光谱反射率均发生了退化,且光谱反射率的退化主要集中在可见光波段,在近红外波段退化很小;玻璃基底铝反射膜退化在420 nm左右出现峰值点,2种金属基底铝反射膜的退化的峰值点在450 nm左右。由于电荷沉积在玻璃中后会抑制带电粒子入射,因此玻璃基底铝反射膜的退化要小于金属基底铝反射膜。     

预氧化聚丙烯腈/g-C3N4光催化降解罗丹明B

以聚丙烯腈(PAN)和g-C_3N_4为原料,采用超声波辅助分散的溶液浸渍法及煅烧法制备了具有共轭结构的预氧化聚丙烯腈/g-C_3N_4复合光催化剂(CPAN/g-C_3N_4),采用XRD、SEM、FTIR、UV-Vis DRS、EIS等技术对光催化剂进行了表征,考察了CPAN/g-C_3N_4对罗丹明B(Rh B)的可见光催化降解性能。结果表明:CPAN与g-C_3N_4具有良好的协同作用,使g-C_3N_4片状结构堆叠体颗粒显著减小,明显增强了光催化剂在全部光谱范围内的光吸收,有效提高了光生电子-空穴分离效率;在PAN与g-C_3N_4质量比为1∶200、煅烧温度250 ℃、煅烧时间1 h条件下所制备的CPAN/g-C_3N_4光催化活性最高,且具有良好的光催化活性稳定性。超氧自由基和光生空穴为CPAN/g-C_3N_4复合光催化剂光降解罗丹明B的主要活性物种。     

面源模式的通用算法探讨

提出了矩形面源扩散模拟计算的数值积分法和中心虚点源法,以及二者结合的综合法,并用算例进行了计算精度、计算速度和结果连续性的对比.结果表明:与传统的后置虚点源法及其改进算法——谷清经验法相比,该算法与理论真值的相对误差可从20%以上降低到3%以下,并且可以准确地反映风向和面源的形状,但在计算量上要增大十几倍到上百倍.对于任意不规则面源,提出了正方形分割算法,并对分割正方形的取舍采用简便的重心判断法,以准确方便地模拟其形状.综合运用笔者提出的适于机算的通用面源算法,对不同的计算任务权衡速度和精度采用合适的算法,可以处理各种气象条件下任意形状面源的扩散计算,并可取得理想的计算精度.