Optical properties of dye-doped zirconia films by spectroscopic ellipsometry

The optical properties of zirconia films doped with rhodamine 6G and oxazine 725 by the sol-gel process were investigated using spectroscopic ellipsometry (SE). Accurate refractive index n and the extinction coefficient k were determined using a three-oscillator classical Lorentz model in the wavelength range of 300-800 nm. The derived refractive index of dye-doped films exhibited anomalous dispersion in the absorption region. Wavelength tunable output lasing action yellow and near-infrared wavelength region was achieved by DFB configuration using zirconia films doped with R6G and oxazine 725.     

Effect of oxygen exposure on the magnetic properties of ultrathin Co/Ge(1 1 1) films

Influences of oxygen exposure on the magnetic properties of Co/Ge(1 1 1) ultrathin films have been investigated by surface magneto-optic Kerr effect technique. As the oxygen exposure increases on Co/Ge(1 1 1) films, their magnetic properties could be modified. As an example for 15 ML Co/Ge(1 1 1) films, the coercivity increases from 730 to 920 Oe and the remanence Kerr intensity is reduced for 500 Langmuir (L) of oxygen exposure. Corresponding compositions analyzed by Auger electron spectroscopy measurement shows that the amount of oxygen on the surface layers increases with increasing the oxygen exposure time. Oxygen distributes on the topmost layers of the film. The adsorbed oxygen influences the electronic density of states of Co and results in the changes of the magnetic properties. Besides, the appearance of O/Co/Ge interface could modify the stress anisotropy, and as a result the coercivity of ultrathin Co/Ge(1 1 1) film is enhanced.     

SSIMS analysis of organics, polymer blends and interfaces

This paper gives a critical review on the applications of ToF SIMS in the areas of polymer additive characterization and in the study of polymer blends and interfaces. Polymer additives can readily be identified by ToF SIMS using their parent molecular ions or characteristic fragments. This analytical capability has been successfully applied to monitor the migration or segregation of additives during polymer processing. ToF SIMS is an ideal analytical tool for the study of polymer blends and interfaces because it is able to provide information on both surface composition and morphology. In combination with other analytical techniques such as AFM and XPS, ToF SIMS chemical imaging capability has opened up new horizons in the investigation of complex polymer blend systems. Finally the main advantages and limitations of ToF SIMS in these application areas are also discussed.     

Output-sensitive results on convex hulls,extreme points,and related problems

We use known data structures for ray-shooting and linear-programming queries to derive new output-sensitive results on convex hulls, extreme points, and related problems. We show that thef-face convex hull of ann-point setP in a fixed dimensiond≥2 can be constructed in time; this is optimal if for some sufficiently large constantK. We also show that theh extreme points ofP can be computed in time. These results are then applied to produce an algorithm that computes the vertices of all the convex layers ofP inO(n ^2−γ) time for any constant . Finally, we obtain improved time bounds for other problems including levels in arrangements and linear programming with few violated constraints. In all of our algorithms the input is assumed to be in general position. This research was supported by a Killam Predoctoral Fellowship and an NSERC Postgraduate Scholarship.     

Study on the lifetime and attenuation properties of microbubbles coated with carboxylic acid salts

Four kinds of surfactants, sodium laurate, sodium myristate, sodium palmitate and sodium oleate were used to study the effects of surfactant coatings on the lifetime and attenuation of microbubbles. The changes in the size distribution of microbubbles prepared with these surfactants in saline were measured with a Coulter Multisizer (Coulter Electronics Ltd., Luton, UK). Frequency characteristics of ultrasonic attenuation of the microbubble suspensions were measured between 400 kHz and 6 MHz. From the changes in attenuation in the microbubble suspensions over time, it was found that the lifetime of microbubbles in a suspension also depends on the frequency of the irradiating ultrasound. The effect of surfactants on the frequency characteristics of attenuation was also studied, and characteristics of the surfactant coating, including shell elasticity and shell friction parameters were calculated from the measurement results. Microbubbles produced with sodium palmitate had the longest lifetime and the smallest average size. The shell had very little effect on the ultrasonic properties of microbubbles produced with sodium palmitate, suggesting that the sodium palmitate microbubbles behaved ultrasonically as free microbubbles.     

陶瓷/VDF-TrFE 0-3型铁电复合物的三阶非线性介电系数

在自建的非线性介电测试装置上测得了Ｐ笔ＶＤＦ－ＴｒＦＥ共聚物形成的０－３型铁电复合物厚片的三阶非线性介电系数ε３。研究发现,三种复合物的ε３都随陶瓷组分含量的上升而增大,测试场强升高,测得的ε３值减小,但对高陶瓷含量（Φ〉０．０４）的ＢＴ／ＶＤＦ－ＴｒＦＥ和ＰＺ／ＶＤＦ－ＴｒＦＥ复合物则在６ＭＶ／ｍ场强下出现极小值,二相都被预极化的复合物小于仅陶瓷相被预极化的ε３值,ＰＺＴ／ＶＤＦ－ＴｒＦＥ复合物     

Quantitative vibration amplitude measurement with time-averaged digital speckle pattern interferometry

A new method of using time-averaged digital speckle pattern interferometry for the quantitative measurement of vibration amplitude was developed. Signal processing techniques especially the Hilbert transformation for quantitative evaluation of the Bessel fringes obtained in time-averaged digital speckle pattern interferometry were explored. The quadrature signal after Hilbert transformation is equivalent to a 90° phase-shifted interferogram for a monotonically increasing or decreasing phase function. An algorithm was developed for Bessel fringe contrast enhancement and phase extraction. The techniques were tested numerically and experimentally. Sub-fringe quantification of the time-averaged vibration fringes is realised with the proposed method. Compared with the commonly used phase shift method which requires a minimum of two images for image processing, this method requires only one fringe pattern for data extraction.