A tractable large-signal dynamic model-application to stronglycoupled distributed feedback lasers

The modulation characteristics of DFB semiconductor lasers have been studied using a transfer matrix method combined with an appropriate rate equation analysis. The model takes into account longitudinal mode spatial hole burning, as well as the nonuniform current injection resulting from the axially varying Fermi voltage, and can be used for the efficient simulation of static, small-signal, and large-signal dynamic properties. The program is applied to the interpretation of experimental data from a strongly coupled InGaAsP/InP DFB laser. The experimental high-frequency properties of this device are well described by the simulations     

The geographic variation of cancer incidence in Ontario

OBJECTIVES: Our objectives were (1) to describe an analysis of the spatial pattern of cancer incidence in Ontario and (2) to discuss the quality of data in the Ontario Cancer Registry with respect to the accuracy of local cancer rates. METHODS: Cancer incidence rates were calculated for 22 cancer sites in 49 counties of Ontario during 1976 to 1986. Capture-recapture methods were used to estimate completeness of case registration, and completeness of residence information was also assessed. Spatial autocorrelation was used in measuring the geographic pattern of incidence rates. Comparisons were also made between sexes and with earlier data from 1966 to 1975. RESULTS: The quality of the geographic data in the registry appeared good, and corrections for incomplete or inaccurate registration had little impact. About one third of the sex-site combinations showed some evidence of spatial patterning in the cancer rate. Particularly strong regional variation was noted for cancers of the stomach, lung, uterus, and prostate. CONCLUSIONS: The analysis revealed a number of cancers with significant spatial patterning of risk. Further work is needed to relate the cancer data to other information on potential life-style and environmental factors.     

The influence of packaging materials on RF performance

At frequencies beyond 1 GHz, every component of the IC package contributes to the RF performance, whether required or not. In this work, we study the effects of packaging materials namely, the substrate and the globtop/underfill material on RF performance. We have measured interconnects on two area-array CSPs, the ball grid array and the polymer stud grid array using IMEC’s MCM-D technology. The measurements on the package interconnect show that the losses in the package substrate material account for about 50% of the total losses at 1.8 GHz and this drops to less than 20% at 5.2 GHz. The losses due to impedance mismatch dominate the losses especially below 10 GHz and considerable improvement in performance cannot be obtained by using an improved/expensive substrate. The other study is about the influence of globtop/underfill materials on wirebonds (through 3D EM simulations) as well as on standard 50 Ω MCM-D transmission lines (through experiments). While a higher value of dielectric constant of the globtop/underfill material is better on wirebonds, the influence of loss tangent is felt only above values of 0.1. The influence of seven different globtop/undefill materials on 50 Ω transmission lines has been used to extract their dielectric constant and loss tangent values at 30 GHz. These results are very valuable since one can hardly find the properties of globtop/underfill materials beyond 1 GHz.     

Environmental degradation using functionally graded material approach

Attempts to model the degradation of polymer composites have been restricted to modelling the effects of selected degradation mechanisms. No comprehensive model has yet been accepted to predict the effect of the natural environment on the strength of polymer composites. From a review of available literature, it appears that the matrix of a polymer composite is most affected by exposure to the natural environment. Further, the damage appears to progress from the surface into the interior of the laminate. An approach has been developed to determine the properties of the damaged layer and combine the properties of the damaged and undamaged layer to obtain bulk material properties of the laminate.     

Promise is Debt, Threat Another Matter: The Effect of Credibility on the Interpretation of Conditional Promises and Threats.

Evidence from reasoning tasks shows that promises and threats both tend to receive biconditional interpretations. They also both display high speaker control. On the face of it, the only difference seems to be the positive or negative signing of the consequent. In a promise, the speaker tries to persuade the hearer to do something by holding out the prospect of a particular reward; in a threat, the speaker tries to refrain the hearer from doing something by holding out the prospect of a particular punishment. This paper investigates the respects in which conditional promises and threats differ further by means of an inference task. The credibility of the consequent was manipulated in order to examine whether the acceptability ratings of inferences based on promises and on threats would be equally affected. The results of the inference task and an analysis of the reasons people give for their answers suggest that the credibility of promises is less affected by the use of excessive consequents than the credibility of threats. In other words, promise remains debt, whereas threat is another matter. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

High quality LTCC resonator for voltage-controlled oscillator

Design and technology of microwave conductor lines embedded in low-temperature cofired ceramic (LTCC) multilayer substrates are summarized with a focus on achieving the highest possible quality (Q) factor for a given line inductance. The work was initiated to test the integrability of base station voltage-controlled oscillators (VCOs) in ceramic multilayer substrates. This approach leads to a miniaturization of current versions by a factor of 2 to 4. However, base station specifications for phase noise and hence resonator Q are extremely demanding. Therefore, both the design and the processing technology were optimized. By choosing a twin-line design with two parallel lines vertically separated by a single LTCC layer, Q factors of 90 and 180 have been achieved for integrated 5.5 nH inductors at frequencies of 640 MHz and 1650 MHz, respectively. Application of this result to VCO modules in standard LTCC technology already yields low phase noise levels, e.g., -136 dBc/Hz at 100 kHz offset, which is suitable for base station applications. However, further noise reduction is expected from a dedicated high Q fabrication process that uses conventional via punching and filling steps to replace the ceramic material between the two lines by conductive silver paste. This raises the Q to 120 and 200, respectively, at the two frequencies and adds extra degrees of freedom to LTCC design for low-loss wireless solutions.     

Aqueous Processing and Stabilization of Manganese Zinc Ferrite Powders via a Passivation–Dispersion Approach

A dispersion scheme for aqueous processing of manganese zinc ferrite suspensions is presented. The addition of oxalic acid leads to the formation of a uniform negative charge on the surface such that a cationic polyelectrolyte, polyethyleneimine (PEI), adsorbs and provides electrosteric dispersion. At 0.5 w/w (weight percent with respect to the dry powder) oxalic acid addition, there is a relatively uniform negative surface charge (approximately −30 mV) within the suspension pH range investigated (3–10), eliminating the isoelectric point (pH ∼7.6) present for the as-received metal oxide powder. At the addition of 0.5 w/w PEI on an oxalate-treated surface, the surface charge is constant and positive (∼20 mV) through a wide pH range, ∼5–10. The resulting rheological data for passivation–dispersion of relatively high-solids manganese zinc ferrite suspensions (∼80 wt%) demonstrate improved colloid stability with improved rheological properties. The resulting apparent viscosity and Bingham yield point is 0.01 Pa·s (12.0 cP) and 0.24 Pa (2.4 dynes/cm²), respectively. A sulfonated napthalene-based dispersant, typically used in industry, gives an apparent viscosity and Bingham yield point of 0.03 Pa·s (32 cP) and 3.1 Pa (31 dynes/cm²), respectively.