Optimization of transmitter and receiver filters for digitalcommunication systems using mean field annealing

A technique for finding transmitter and receiver filters for a wide class of digital communication systems which minimize the bit-error rate (BER) is presented. The technique uses Monte Carlo simulation to estimate the BER and mean field annealing (MFA) to optimize the pulse shapes. Modeling of the link can be as complex as simulation will allow, while MFA is resistant to the statistical variation in the BER estimate from the simulation. Initially, the MFA technique was applied to a binary symmetric channel in a nonsimulation environment, and an approximate analysis of the behavior of MFA for this problem was performed. In a more complex example, MFA was coupled with Monte Carlo simulation techniques to find near-optimal transmit and receive filters for a satellite communications link, taking 6 CPU hours on a DECstation 3100. The BER of the link was found to be as much as three orders of magnitude lower when using the MFA-constructed optimal filters than when using filters from other comparison results. For this example, the pulse shapes obtained using MFA exhibit a low BER even as the parameter controlling the nonlinearity of the satellite-link model is varied over a wide range, thus showing the solution is robust     

Copper contamination of high purity germanium (HP-Ge) through Li-diffusion

It will be shown in this paper that the Li diffusion in HP-Ge, used for γ-ray detectors, always introduces extra Cu. This Cu has a negative influence on the detector resolution. It originates from the Li suspension used. We suggest that the actual diffusion temperature should be kept below 300°C.     

In vitro dissolution of two oral controlled release preparations of diclofenac sodium.

The development of controlled release formulations has brought about the need for appropriate quality control methods such as in vitro dissolution testing. Such tests are principally designed to obtain correlation with the in vivo performance of the formulation (1,2,3). If an in vitro test can be defined offering a good correlation the test may serve for routine quality control or may be useful in screening new drug formulations.     

Cooking DNA: the effect of ‘domestic’ cooking methods on detection of GM potato

The ability to detect GM material in otherwise unprocessed foods cooked using domestic methods is important should ‘ready‐to‐eat’ foods require labelling. This study addresses the issue of DNA degradation in foods as a result of cooking. A number of ‘domestic’ cooking methods were shown to affect the length of DNA sequences able to be PCR amplified from potato samples and the degree of degradation was treatment‐specific. However, a. real‐time PCR assay was developed and. GM material was positively identified in all cooked GM potato samples. This confirms that GM material should be able to be detected in otherwise unprocessed food samples cooked using domestic methods, even if the cooking process has partially degraded the DNA. Results indicate, however, that there may be implications of the cooking process on the ability to accurately quantify GM content in some cooked samples.     

Design and Optimization of Electrically Injected InP-Based Microdisk Lasers Integrated on and Coupled to a SOI Waveguide Circuit

We have performed a numerical study involving the design and optimization of InP-based microdisk lasers integrated on and coupled to a nanophotonic silicon-on-insulator (SOI) waveguide circuit, fabricated through bonding technology. The theoretical model was tested by fitting it to the lasing characteristics obtained for fabricated devices, which we presented previously. A good fit was obtained using parameter values that are consistent with numerical simulation. To obtain optimized laser performance, the composition of the InP-based epitaxial layer structure was optimized to minimize internal optical loss for a structure compatible with efficient current injection. Specific attention was paid to a tunnel-junction based approach. Bending loss was quantified to estimate the minimum microdisk diameter. The coupling between the InP microdisk and Si waveguide was calculated as function of the bonding layer thickness, waveguide offset and waveguide width. To study the lateral injection efficiency, an equivalent electrical network was solved and the voltage-current characteristic was calculated. Based on these results, the dominant device parameters were identified, including microdisk thickness and radius, coupling loss and tunnel-junction p-type doping. These parameters were optimized to obtain maximum wall-plug efficiency, for output powers in the range 1-100 W. The results of this optimization illustrate the potential for substantial improvement in laser performance.     

Analysis of the dynamics of a pendulum vibration absorber

The nonlinear dynamics of an autoparametric vibration absorber of pendulum type is considered. The conditions of existence of periodic motions in the case of monoharmonic excitation are considered. A comparison of the vibration quenching qualities of the autoparametric absorber and a “classical” (linear) dynamic vibration absorber is presented.