Effect on Wettability of FEP Teflon Surface Morphology

Wettability of FEP Teflon® (a perfluorinated ethylene-propylene copolymer) is vastly improved by heterogeneous nucleation and crystallization in contact with gold, a high surface free energy substrate. The critical surface tension of wetting (γ_e) increases from 18.8 dynes/cm to 40.4 dynes/cm. We compute that this rise in γ_e results from a 20 percent increase in the surface density of gold-nucleated FEP Teflon®. The increase in critical surface tension from 18.8 dynes/cm to 20.6 dynes/cm, for as received FEP Teflon which had been crosslinked by helium in a glow discharge (CASING technique), suggests an increase of the surface density with crosslinking. The critical surface tension of the gold-nucleated FEP Teflon® is sharply decreased from 40.4 dynes/cm to 22.0 dynes/cm by short exposure to the CASING treatment in helium. The results of ATR infrared spectroscopy show that in the surface region of the polymer there are no chemical changes such as the presence of unsaturated groups or the introduction of polar groups by oxidation. We conclude from this study that wettability of the polymer surface is affected by the surface morphology.     

Predicting temporary deal success with social media timing signals

Journal of Intelligent Information Systems - Temporary deals such as flash sales nowadays are popular strategies in retail business for cleaning out excessive inventories. It is known that the...     

Multispectral Photometric Stereo for Spatially-Varying Spectral Reflectances

International Journal of Computer Vision - Multispectral photometric stereo (MPS) aims at recovering the surface normal of a scene measured under multiple light sources with different...     

Modeling of active and passive nonlinear metamaterials

We develop general results for nonlinear metamaterials based on simple circuit models that reflect the elementary nonlinear behavior of the medium. In particular, we consider both active and passive nonlinearities which can lead to gain, harmonic generation and a variety of nonlinear waves depending on circuit parameters and signal amplitude. We show that the medium can exhibit a phase transition to a synchronized state and derive conditions for the transformation based on a widely used multiple time scale approach that leads to the well-known Complex Ginzburg–Landau equation. Further, we examine the variety of nonlinear waves that can exist in such systems, and we present numerical results for both active and passive metamaterial cases.     

Evaluation of 400 low background 10-in. photo-multiplier tubes for the Double Chooz experiment

The Double Chooz is a reactor neutrino experiment which measures the last unknown neutrino mixing angle θ₁₃. The Double Chooz experiment uses two identical detectors placed at sites far and near from Chooz reactor cores. The detector uses 390 low-background and high performance 10-in. Photo-Multiplier Tubes (PMTs) to detect scintillation light from gadolinium loaded liquid scintillator. In order to test and characterize the PMTs and to tune operation parameter, we developed two types of PMT test system and evaluated 400 PMTs before installation. Those PMTs fulfilled our requirements and half of them were installed in the far detector in 2009 and physics data have been successfully taken since 2011.     

A Genetic Algorithm Approach to Multi-Agent Itinerary Planning in Wireless Sensor Networks

It has been shown recently that using Mobile Agents (MAs) in wireless sensor networks (WSNs) can help to achieve the flexibility of over-the-air software deployment on demand. In MA-based WSNs, it is crucial to find out an optimal itinerary for an MA to perform data collection from multiple distributed sensors. However, using a single MA brings up the shortcomings such as large latency, inefficient route, and unbalanced resource (e.g. energy) consumption. Then a novel genetic algorithm based multi-agent itinerary planning (GA-MIP) scheme is proposed to address these drawbacks. The extensive simulation experiments show that GA-MIP performs better than the prior single agent algorithms in terms of the product of delay and energy consumption.     

单向碳/环氧和玻纤/环氧复合材料扭转疲劳性能

提出碳/环氧复合材料作为柔性梁材料的可行性。对相同树脂基体的单向碳纤维复合材料和玻璃纤维/环氧复合材料的扭转疲劳性能进行研究。碳纤维复合材料的初始扭转刚度几乎与玻璃纤维复合材料相同。采用有限元计算的扭转刚度与试验结果吻合:扭转刚度主要受控于材料的剪切刚度。通过控制正弦波扭转的角度,进行了恒定受拉轴向荷载下的扭转疲劳试验。尽管根据循环次数降低了扭矩和扭转刚度振幅,无论是碳纤维还是玻璃纤维复合材料都没出现严重的破坏现象。X-射线CT的检查结果以及有限元计算的结果显示:主要是沿着纤维方向裂缝扩展引起扭转刚度的退化,碳纤维扭转疲劳寿命高于玻璃纤维复合材料。因此,根据扭转刚度和张拉-扭转疲劳性能,证实碳纤维具有很好的性能,可作为柔性梁的抗扭材料。     

Numerical Simulation of Fire Plume-Induced Ceiling Jets Using the Standard k ε Model

The main objective of the present work is an investigation of the accuracy and the reliability of numerical predictions of ceiling jets induced by fire plumes, aiming at practical applications to fire-safety planning. Ceiling jet phenomena are studied numerically using the standard k-ɛ model of turbulence. Computed results are compared with basic experimental data. Of particular interest is the dependence of (a) the computational mesh system, (b) the incompressible or compressible flow assumptions, and (c) initial values of k and ɛ at the inflow on the ceiling jet solutions.