Mechanical spectroscopy of quasicrystals

Quasicrystals are solids with long-range quasiperiodic order and orientational order with disallowed crystallographic symmetry (e.g. 5-fold). In addition to the point defects known from crystals (vacancies, interstitials, or antistructure atoms) quasicrystals contain phasonic defects (phasons), which represent violations of the matching rules. Phasons allow displacement of atoms without contribution of vacancies. In icosahedral AlPdMn single quasicrystals two internal friction peaks are observed. Peak A at 370 K (f=3 Hz) has an activation enthalpy of 0.98 eV and a frequency factor close to the Debye frequency (2×10¹⁵ s⁻¹) and is therefore attributed to point defects, i.e. atomic jumps enabled by phason flips or vacancies. Peak B at 870 K (f=3 Hz) is determined by an activation enthalpy of 4 eV and an abnormal high frequency factor (3×10²⁴ s⁻¹), is much broader than a simple Debye-peak, and highly asymmetric. The temperature variation of the relaxation time exhibits significant deviation from ideal Arrhenius behaviour for higher temperatures (T>920 K) indicating a sort of phase transition. Peak B can be attributed to a relaxation process in which dislocation movement is controlled by creation and movement of phason defects.     

Three-dimensional compositional gradients in water-borne urethanes and latexes: spectroscopic approaches

Stratification of individual components in thermosetting coatings plays an important role during film formation and affects a number of macroscopic properties. This behavior is particularly pronounced for water-borne coatings, and therefore molecular level understanding of interactions in latexes and responsiveness of individual components during coalescence of water-borne polyurethanes are of particular interest. The presence of macromolecular arrangements and interactions among various components near the film–air (F–A) and the film–substrate (F–S) interfaces can be effectively monitored using attenuated total reflectance (ATR) and step-scan photoacoustic (SSPA) Fourier transform infrared (FT-IR) spectroscopy. Both approaches are capable of obtaining information from various surface depths and complement each other if one seeks molecular level information from 0 to 150 μm into the film. In this presentation combined ATR and PA information along with IR and/or Raman surface imaging will be presented to establish three-dimensional representation of polyurethane film formation and the effect of copolymer/polymer blend latexes on coalescence processes in Sty/n-BA.     

All-Optical Label Extractor/Eraser for In-Band Labels and 160-Gb/s Payload Based on Microring Resonators

Photonic integration of an all-optical packet switch (AOPS) is a crucial issue since it leads to a great reduction of volume, power consumption, and costs. Recently, a 1 times 4 AOPS was successfully demonstrated by using an all-optical label extractor/eraser. The label extractor/eraser was implemented by means of fiber Bragg gratings and optical circulators that prevent the photonic integration of the AOPS. Here, we demonstrate a passive and asynchronous photonic integrated all-optical label extractor/eraser by using narrowband silicon-nitride add-drop ring-resonators. By exploiting the narrow bandwidth of the drop port and pass-through port error-free simultaneous separation/erasing of the in-band labels from the 160-Gb/s packet payload was demonstrated without noticeable pulse-shape distortions.     

Quantitative pressure and strain field analysis of helium precipitates in silicon

The structural properties of overpressurised helium precipitates formed by low dose ion implantation and subsequent annealing of silicon are investigated by quantitative transmission electron microscopy techniques. These precipitates, which show pronounced platelet geometry, are analysed with respect to their geometry, crystallographic orientation and their particular gas pressure values. The dependence of the measured platelet pressure versus the radius is discussed in terms of a Griffith crack. Experimental results on the shape and the crystallographic orientation of the platelets are discussed in the framework of anisotropic elastic properties and surface energies of silicon. The ability of the precipitates to punch-out dislocation loops is discussed in terms of associated threshold shear stress values and evaluated with regard to the defect size dependency.     

上海市规划系统干部教育培训体系初探

通过对上海市规划系统干部教育培训的现状与问题分析,从系统、整体的角度研究干部教育培训体系,提出较为完善的干部教育培训体系框架,科学有序地开展干部教育培训。既是一次对上海市规划系统干部教育培训体系的初步探索,也是一次对上海市规划系统干部教育培训工作规律的深入思考与有益探索。     

Assessment of polybrominated diphenyl ether exposures and health risks associated with consumption of southern Mississippi catfish

Despite the growing public interest in polybrominated diphenyl ethers (PBDEs), there are relatively few studies in the published literature which characterize and quantify human intake of these compounds. In this study, PBDE concentrations were measured in southern Mississippi catfish to determine background levels, daily intake, and risk associated with the consumption of these chemicals from a primary food source for residents in this region of the United States. A total of 33 wild catfish samples were collected from five sites, and 28 farm-raised catfish samples were purchased, all of which were from locations in southern Mississippi. All samples were analyzed for 43 PBDEs (mono- through deca-congeners) using high-resolution gas chromatography-mass spectrometry. Both PBDE concentrations (sigmaPBDE ranged from 0.3 to 23.3 ng/g wet weight) and congener profiles varied by fish type and location; however, BDE congeners 47, 99, 100, 153, and 154 were the dominant contributors in all samples. The estimated daily intake of PBDEs associated with consumption of the catfish ranged from 0.03 to 1.80 ng/kg-day. Evaluation of the cancer risk for BDE 209 and the noncancer hazard for BDE congeners 47, 99, 153, and 209 indicated that health risks/hazards due to fish consumption in adults are substantially lower than risk levels generally considered to be at the U.S. EPA minimum concern level.     

嵌入式系统网络互连的挑战

由于越来越多的设备需要通过Internet进行通信或者控制,因此互连和安全功能成为除操作系统之外,设计者们所面临的主要设计需求     

Water-processable polymer-nanocrystal hybrids for thermoelectrics

We report the synthesis and thermoelectric characterization of composite nanocrystals composed of a tellurium core functionalized with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Solution processed nanocrystal films electronically out perform both PEDOT:PSS and unfunctionalized Te nanorods while retaining a polymeric thermal conductivity, resulting in a room temperature ZT ～ 0.1. This combination of electronic and thermal transport indicates the potential for tailored transport in nanoscale organic/inorganic heterostructures.     

A wavelet Galerkin method for the stokes equations

The purpose of this paper is to investigate Galerkin schemes for the Stokes equations based on a suitably adapted multiresolution analysis. In particular, it will be shown that techniques developed in connection with shift-invariant refinable spaces give rise to trial spaces of any desired degree of accuracy satisfying the Lady?enskaja-Babu?ka-Brezzi condition for any spatial dimension. Moreover, in the time dependent case efficient preconditioners for the Schur complements of the discrete systems of equations can be based on corresponding stable multiscale decompositions. The results are illustrated by some concrete examples of adapted wavelets and corresponding numerical experiments.