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21.
Brasselet E 《Physical review letters》2012,108(8):087801
We report on the generation of tunable structured light fields endowed with various sets of phase singularities from a single topological defect in a nematic liquid crystal mesophase. The experimental demonstration relies on the use of electric field-induced nonsingular topological defects called "umbilics." 相似文献
22.
Melting in two spatial dimensions, as realized in thin films or at interfaces, represents one of the most fascinating phase transitions in nature, but it remains poorly understood. Even for the fundamental hard-disk model, the melting mechanism has not been agreed upon after 50 years of studies. A recent Monte?Carlo algorithm allows us to thermalize systems large enough to access the thermodynamic regime. We show that melting in hard disks proceeds in two steps with a liquid phase, a hexatic phase, and a solid. The hexatic-solid transition is continuous while, surprisingly, the liquid-hexatic transition is of first order. This melting scenario solves one of the fundamental statistical-physics models, which is at the root of a large body of theoretical, computational, and experimental research. 相似文献
23.
A. Yu. Panarin V. S. Chirvony K. I. Kholostov P.-Y. Turpin S. N. Terekhov 《Journal of Applied Spectroscopy》2009,76(2):280-287
We have optimized the procedure for preparation of nanostructured silver films on the surface of mesoporous silicon (PSi)
to use them as active substrates in surface-enhanced Raman scattering (SERS) spectroscopy. The greatest enhancement of the
SERS signal was observed for samples obtained when the silver was deposited on PSi from an aqueous AgNO3 solution with concentration 1⋅10–2 M over a 10–15 minute period. The detection limit for rhodamine 6G on SERS-active substrates prepared by the optimized procedure
was 1⋅10–10 M. The enhancement factor for the SERS signal on these surfaces was estimated as ≈2⋅108. We have shown that SERS-active substrates based on mesoporous silicon are promising for detection and study of complex organic
compounds, in particular tetrapyrrole molecules.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 298–306, March–April, 2009. 相似文献
24.
Hawthorn DG Hill RW Proust C Ronning F Sutherland M Boaknin E Lupien C Tanatar MA Paglione J Wakimoto S Zhang H Taillefer L Kimura T Nohara M Takagi H Hussey NE 《Physical review letters》2003,90(19):197004
The transport of heat and charge in cuprates was measured in single crystals of La(2-x)Sr(x)CuO(4+delta) (LSCO) across the doping phase diagram at low temperatures. In underdoped LSCO, the thermal conductivity is found to decrease with increasing magnetic field in the T-->0 limit, in striking contrast to the increase observed in all superconductors, including cuprates at higher doping. In heavily underdoped LSCO, where superconductivity can be entirely suppressed with an applied magnetic field, we show that a novel thermal metal-to-insulator transition takes place upon going from the superconducting state to the field-induced normal state. 相似文献
25.
26.
Ali Alaeldine Nicolas Lacrampe Richard Perdriau Fabrice Caignet Etienne Sicard 《Microelectronics Journal》2008,39(12):1728-1735
This paper presents a comparative study of susceptibility reduction techniques for electromagnetic interference (EMI) in digital integrated circuits (ICs). Both direct power injection (DPI) and very-fast transmission-line pulsing (VF-TLP) methods are used to inject interference into the substrate of a single test chip. This IC is built around six functionally identical cores, differing only by their EMI protection strategies (RC protection, isolated substrate, meshed power supply network) which were initially designed for low emission design rules. The ranking of three of these cores in terms of electromagnetic immunity is then compared with the one of their radiated emission, thanks to near-field scanning (NFS) measurements. This leads to the establishing of design guidelines for low EMI in digital ICs. 相似文献
27.
Etienne Nowak Luca PerniolaGérard Ghibaudo Gabriel MolasGilles Reimbold Barbara De SalvoFabien Boulanger 《Solid-state electronics》2011,58(1):75-82
This paper describes the effect of geometry in charge-trap (CT) memory devices. We first theoretically analyze the impact of the curvature radius on the behavior of the gate current in Gate-All-Around devices, and then describe the change to make to planar model in order to fit the cylindrical devices characteristics. This model is used to simulate Nanocrystal and SONOS program, erase and retention behaviors. The dynamics enhancement during program/erase due to the bending of the active region in such cylindrical devices is explained. The scaling perspectives conclude this paper. 相似文献
28.
This paper reports insights about energy savings in buildings dedicated to tertiary activity. The goal is to employ as much as possible natural light flows to minimize the artificial light source consumption. Although the solar energy is power-efficient to light and heat a room, this natural source remains complex to manage and can generate inconveniences related to occupants visual comfort. The authors propose a global solution to deal with visual comfort by controlling the daylight contribution to the indoor light atmosphere. This control structure is based on the use of an innovative sensor of light conditions and it was implemented within an experimental room equipped with classic Venetian blinds. This paper focuses on the control laws to apply in order to meet visual needs for current tasks performed in offices. 相似文献
29.
The network interconnection and its regulation consist in solving the following dilemma: increase competition and preserve the universal service through access charges, which symbolizes today institutional organization within the telecommunication industry. This paper presents some of the economic and social factors that drive the interconnection policies namely ona (open network architecture) in the United States, or onp (open network provision) in Europe. In the first section, we list some social and economical issues related to open network policies. In the second section, we study the different answers brought up by the regulator through alternative interconnection price formulas. In conclusion, we discuss the stakes and risks of interconnection, while the technological evolution of network introduces intelligent software in switching équipement and implements the tremendous abilities of the digital broadband networks. 相似文献
30.
Charrière F Marian A Montfort F Kuehn J Colomb T Cuche E Marquet P Depeursinge C 《Optics letters》2006,31(2):178-180
For what we believe to be the first time, digital holographic microscopy is applied to perform optical diffraction tomography of a pollen grain. Transmission phase images with nanometric axial accuracy are numerically reconstructed from holograms acquired for different orientations of the rotating sample; then the three-dimensional refractive index spatial distribution is computed by inverse radon transform. A precision of 0.01 for the refractive index estimation and a spatial resolution in the micrometer range are demonstrated. 相似文献