Construction of a Quadratic Model for Predicted and Measured Global Solar Radiation in Chile

Global solar radiation data for sites in Chile are analysed and presented in a form suitable for their use in engineering. A new model for monthly average data is developed to predict monthly average global radiation with acceptable accuracy by using actinographic data due to scarcing of pyranometer data. Use of the new quadratic model is proposed because of its relatively wider spectrum of values for Angstrom coefficients ao, al, and a2.     

Numerical Analysis of Nano-Aperture Light Source for High-Density Optical Data Storage

Two unconventional nano-aperture light sources, an L-shaped nano-aperture source and a 3D nano-aperture source for high-density optical data storage, are numerically investigated. With incidence of a Gaussian beam, the spot size of the Poynting vector coupled into the recording medium is 130 × 175 nm^2 for the L-aperture and 120 × 135 nm^2 for the 3D nano-aperture. The quantitative analyses indicate that the unconventional nanoaperture sources can provide enough power density to record marks in the commercial recording medium. It is feasible to use a laser diode with a nano-aperture as an active nanometer light source for high-density optical data storage.     

Three-dimensional analysis of silver nano-particles doping effects on super resolution near-field structure

The super resolution near-field structure which incorporates a AgOx thin film was studied through the calculation using three-dimensional (3D) finite-difference time-domain method. The influences of the optical field distribution generate by some factors, e.g., the polarization direction, the wavelength of incident light and the size of silver nano-particles, which are sensitive to the surface plasmon resonance are discussed in detail. The goal of this study is to explain the physical mechanisms responsible for the super-resolution near-field structure phenomena in 3D model and give a better understanding of the optical properties between AgOx layer and incident light.     

Mechanical spectroscopy of laser deposited polymers

Pulsed laser deposition (PLD) at 248 nm in ultra high vacuum was used to produce thin poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) films. The ablation and deposition mechanisms were found to be similar in both systems. Having the same backbone, these polymers differ in the size of their polar side groups leading to changes in their dynamics. Studies of the relaxation processes were performed using mechanical torsion and bending spectroscopy by means of a double-paddle oscillator (DPO) and an in-situ plasma plume excited reed (PPXR), respectively. A strong increase of the mechanical damping was observed during annealing of the polymer films well above the glass transition temperature T _g, while in-situ X-ray measurements did not reveal any structural changes. For PEMA, the glass transition temperature T _g=335 K and the main absorption maximum appear at lower temperatures compared to PMMA (T _g=380 K), allowing one to measure the mechanical properties in a much wider range above T _g.     

Theoretical and experimental aspects of optical storage of information via refreshing by inverse seeding in a photorefractive Ba0.77Ca0.23TiO3 crystal (BCT)

We present a new experimental setup for the optical storage of information via refreshing by inverse seeding (OSIRIS), which allows a sixfold increase of the storage time of holograms in a Ba_0.77Ca_0.23TiO₃ crystal (BCT). The setup consists of two four-wave mixing processes with common amplified signal waves and phase-conjugated (pc) waves. Temporal behaviours of the amplified and pc signal waves for the OSIRIS experiment as well as for the common four-wave mixing experiment are compared and discussed. The solutions of coupled equations under the depleted-pump approximation are obtained in order to estimate the pc reflectivities and coupling gains of gratings inside the crystal. Received: 13 December 2000 / Revised version: 26 January 2001 / Published online: 27 April 2001     

Dynamics of BF 4 - anion reorientation in the spin-crossover compound [Fe(1-n-propyl-1H-tetrazole) 6 ](BF 4 ) 2 and in its Zn II analogue

¹⁹ F and ¹¹ B spin-lattice relaxation times were measured in [ Zn ( ptz ) ₆ ] ( BF ₄ ) ₂ and in the spin-crossover compound [ Fe ( ptz ) ₆ ] ( BF ₄ ) ₂ . For both compounds BF ₄ ^- anion reorientation is active above 50 K. For [ Zn ( ptz ) ₆ ] ( BF ₄ ) ₂ , the anion-reorientation dynamics is different in the temperature regions of 50-90 K, 90-120 K, and above 150 K; between 120 and 150 K it changes rapidly reflecting a structural change. In [ Fe ( ptz ) ₆ ] ( BF ₄ ) ₂ the mechanism for the paramagnetic relaxation involving the ¹⁹ F nuclei is found to be of the diffusion-limited type according to the theory of Lowe and Tse. The present results prove that the spin-crossover takes place in a dynamic surrounding and not in a static crystal lattice. Received 09 February 1999 and Received in final form 14 June 1999     

Growth mechanism of scales of SiC nanowires with/without ZnS powders at varying temperatures

The growth mechanism of scales of crystalline SiC nanowires (SiC-NWs) obtained by directly evaporating solid carbon on silicon wafer with/without ZnS powders at varying temperatures is being discussed. More aligned SiC-NWs of small size and good crystalline structure were formed when ZnS was used. Random SiC-NWs of big size and poor crystalline structure were obtained at conditions free of ZnS. Furthermore, the improved crystalline structure and increased diameter of SiC-NWs were observed when the higher temperature was employed.     

Experiments of Multi-Level Read-Only Recording Using Readout Signal Wave-Shape Modulation

An innovative multilevel read-only recording method is proposed. In this method, a short pit/land is deliberately inserted to the original land/pit. This modifies the wave-shape of readout signM. Taking the wave-shape as the symbol of level detection, a signal wave-shape modulation （SWSM） multilevel method is realized. This method is carried out and validated on the DVD read-only manufacture and readout system. A capacity of 15 GB can be expected, and a bit error rate of 10-4 is achieved. The capacity can meet the demand of high definition movie publication. This method also provides a potential multi-level solution for other storage formats and systems.     

Line parameter validation using ground-based solar occultation measurements: Water vapor—A case study

Water vapor spectroscopy data for the 720 nm absorption band (4ν polyad) are validated in the context of atmospheric radiative transfer calculations. We validate line parameters from the HITRAN-2000 database and from the ULB-UFR-BIRA database which have been used for the 2004 release of HITRAN. For this purpose, ground-based high resolution observations of the direct solar radiation are compared with simulated spectra. Line parameters are selected for validation based on a full error characterization including instrument noise and uncertainties in the atmospheric profile data. For a subset of the line parameters validated in the present study independent high-accuracy data are available. The comparison with these independent reference data confirms the capability of our approach to improve water vapor spectroscopic data.