定向凝固宏微观热质传递及双扩散流作用

针对氯化铵水溶液定向凝固实验,从枝晶微尺度到宏观尺度耦合模拟了相变热质传递过程,并考察了双扩散流的影响.研究结果表明,NH4CI-H2O溶液的枝晶微界面浓度变化与非平衡态的谢尔方程趋于一致.两相区内液相率较高,易于流动的产生;热浮升力形成逆时针回流,溶质浮升力形成顺时针回流;热浮升力作用大于溶质浮升力.但双扩散流几乎不影响凝固沿着结晶室高度方向进行的一维定向特性.数值模拟中低估了两相区的渗透率,是造成两相区厚度模拟结果小于实验值的原因.     

Application of EDXRF and Thin Window EPMA for the Investigation of the Influence of Hot Air Heating on the Generation and Deposition of Particulate Matter

This paper presents a systematic micro-analytical study for the assessment of the influence of a typical hot-air blow-in heating system on the generation, transport and deposition of suspended particulate matter (SPM) in the church of Rocca Pietore (Italian Alps). This kind of heating system is very popular in cold regions due to its fast response and economic properties. The size, chemical composition and abundance of individual particles responsible for the negative impact on the displayed artworks are determined by ultra-thin window EPMA. EDXRF is used to determine the bulk chemical composition of SPM. Some gaseous pollutants (SO₂, NO₂ and O₃) are sampled with the application of passive diffusion tubes and quantified with ion-chromatography and spectrophotometry. It is pointed out that several deterioration processes, such as the abrasion of the plastered walls, the re-suspension of the particulate pollution and the generation of NO₂ gas, arise mainly from using the heating system. Each of these observations is a concern for the preservation of the displayed works of art.     

温盐双扩散均衡场中的振荡现象

在一种简单的边界加密的坐标变换下,用高精度的差分法研究了温盐双扩散系统.为了保证求解的稳定性和精确性,对流项采用了四阶精度的迎风格式,扩散项和涡量方程的浮力项则采用四阶精度的中心差.首先针对温度占优(Rρ=032)和盐度占优(Rρ=168)的情形进行了计算,得到了与文献[2]和[12]一致的结果,从而验证方法的正确性.其次系统地给出了不同Lewis数下的流动形态,包括稳定的对称结构、周期性振荡结构和非周期非对称的随机运动形态 关键词： 温盐双扩散 高精度格式 周期性振荡结构     

Two-Point Correlations and Critical Line of the Driven Ising Lattice Gas in a High-Temperature Expansion

Based on a high-temperature expansion, we compute the two-point correlation function and the critical line of an Ising lattice gas driven into a nonequilibrium steady state by a uniform bias E. The lowest nontrivial order already reproduces the key features, i.e., the discontinuity singularity of the structure factor and the (qualitative) E dependence of the critical line. Our approach is easily generalized to other nonequilibrium lattice models and provides a simple analytic tool for the study of the high-temperature phase and its boundaries.     

On Diffusive Equilibria in Generalized Kinetic Theory

We investigate the solvability of equations Q(f,f)+ ² f=0 in term of nonnegative integrable densities fL ¹ ₊(R ³). Here, Q(f, f) is a generalized collision operator. If Q is the Boltzmann operator, the only solution is 0. In contrast, we show that if Q is the pseudo-Maxwellian collision operator for granular flow, then there are non -trivial weak solutions of ().     

方腔内双扩散混合对流非线性格子Boltzmann研究

采用格子Boltzmann方法对方腔内双扩散混合对流的非线性特性进行数值模拟.发热圆位于方腔中心,流体从方腔左侧底部流进,流出位置分别为顶部右侧、中间和左侧三种情况.结果表明,不同参数下的双扩散混合对流存在稳态定常解、周期性振荡解和非周期性振荡解,监测点速度相图分别表现为最终到达一个点、一个封闭环和没有规律的曲线.     

新型门控光子计数法测量高散射介质的光学参量

讨论了一种新型而且简单的门控光子计数法，用来测量高散射介质的光学参量。当一束光脉冲入射到高散射介质后，该方法可以恢复出光脉冲经过散射后从介质表面逸出的波形。与传统的门控光子计数法相比，该方法利用计数器控制门可以移动的特点，通过滑动宽度为60ns的控制门实现较高的时间分辨力200ps。在此波形的基础上，Patterson—Chance方法可以快速而且准确计算出被测介质的光学参量。在模型介质上的实验，验证了该方法的可行性，实验结果与复杂的时间相关的单光子计数加曲线拟合方法相比较，误差小于10％。     

Application of passive sampling technique in monitoring research on quality of atmospheric air in the area of Tczew,Poland

This paper presents the results of atmospheric air quality research in Tczew (adjacent to the Vistula River) on the content of BTEX compounds. procedure applied during the sampling of the analytes from the air used the passive sampling technique (diffusive passive sampler, Radiello^®). For determination of BTEX compounds in atmospheric air, two-stage thermal desorption technique combined with gas chromatography (TD-GC-FID) was applied.

Research was conducted from March to December 2011. The annual average concentration of benzene, toluene, ethylbenzene and total xylenes determined in atmospheric air for the monitoring period were: 0.87 μg m^–3, 2.9 μg m^–3, 1.3 μg m^–3 and 5.9 μg m^–3, respectively. In order to pre-identify potential sources of emissions of BTEX compounds, statistical analysis was carried out. This determined interactions between specified concentration levels of BTEX compounds in atmospheric air for the monitored area.     

An analytical study of linear and nonlinear double diffusive convection in a fluid saturated anisotropic porous layer with Soret effect

The double diffusive convection in a horizontal anisotropic porous layer saturated with a Boussinesq fluid, which is heated and salted from below in the presence of Soret coefficient is studied analytically using both linear and nonlinear stability analyses. The normal mode technique is used in the linear stability analysis while a weak nonlinear analysis based on a minimal representation of double Fourier series method is used in the nonlinear analysis. The generalized Darcy model including the time derivative term is employed for the momentum equation. The critical Rayleigh number, wavenumber for stationary and oscillatory modes and frequency of oscillations are obtained analytically using linear theory. The effect of anisotropy parameters, solute Rayleigh number, Soret parameter and Lewis number on the stationary, oscillatory, finite amplitude convection and heat and mass transfer are shown graphically.     

Robust DNA‐Bridged Memristor for Textile Chips

Electronic textiles may revolutionize many fields, such as communication, health care and artificial intelligence. To date, unfortunately, computing with them is not yet possible. Memristors are compatible with the interwoven structure and manufacturing process in textiles because of its two‐terminal crossbar configuration. However, it remains a challenge to realize textile memristors owing to the difficulties in designing advanced memristive materials and achieving high‐quality active layers on fiber electrodes. Herein we report a robust textile memristor based on an electrophoretic‐deposited active layer of deoxyribonucleic acid (DNA) on fiber electrodes. The unique architecture and orientation of DNA molecules with the incorporation of Ag nanoparticles offer the best‐in‐class performances, e.g., both ultra‐low operation voltage of 0.3 V and power consumption of 100 pW and high switching speed of 20 ns. Fundamental logic calculations such as implication and NAND are demonstrated as functions of textile chips, and it has been thus integrated with power‐supplying and light emitting modules to demonstrate an all‐fabric information processing system.