Dislocations in strained layers: The Ge-Si system

The Ge-Si on Si epilayer system, besides being an interesting technological system in its own right, is a superb model for strained-layer studies. The point defect and symmetry defect structures associated with compound semiconductors can be avoided, allowing a focus on the mechanics of the system. Dislocation sources, glide behavior, and performance effects have been examined for strained-layer systems. Surprises have appeared along the way, but these materials are now becoming characterized well enough for industrial device applications.     

The thermokinetic modeling of substrate rapid solidification

A boundary problem arising from rapid solidification with changing conditions at the moving boundary for the classical Stefan problem was solved by combining the heat transfer with crystallization kinetics using a front-tracking finite-difference scheme. At each time step, the conditions at the moving boundary were determined by an iterative process.     

Constructing candidate word lists using acoustically similar wordgroups

A method for identifying a set of candidate words that matches well with a given utterance is discussed. The method uses precomputed groups of acoustically similar words. Given a vocabulary, for each word a short list of words that are acoustically similar to it is computed. These groups are constructed using training utterances recorded by several speakers and used in an isolated utterance recognition system to construct candidate word lists during recognition. Experiments show that the correct word appears on the short list of candidate words constructed during recognition using this scheme over 98% of the time     

An 8-b 650-MHz folding ADC

An 8-b 650-MHz folding analog-to-digital converter (ADC) with analog error correction in the comparators is presented. With an input frequency of 150 MHz, 7.8 effective bits are obtained. The ADC is implemented in a 1-μm 13-GHz triple-level interconnect bipolar process, requiring 850 mW from a single -4.5 V supply. The die size is 4.2 mm²     

A new eicosapentaenoic acid formed from arachidonic acid in the coralline red algaeBossiella orbigniana

Aqueous extracts of the coralline red algaeBossiella orbigniana have been shown to catalyze the enzymatic oxidation of arachidonic acid to a previously unreported ω6 eicosapentaenoic acid product. This unique fatty acid contains a conjugated tetraene with absorption maxima at 293, 306, and 321 nm, and was identified by spectral methods as 5(Z),8(Z),10(E),12(E),14(Z)-eicosapentaenoic acid. The compound was given the trivial name bosseopentaenoic acid. Under experimental conditions, production of bosseopentaenoic acid was linear up to 2 hr and dioxygen was consumed. Bosseopentaenoic acid, along with several other conjugated tetraenes, was also present in the algae endogenously as revealed by a comparison of the ultraviolet (UV) spectra and the high-performance liquid chromatographic (HPLC) pattern of the purified product and the organic extract ofBossiella.     

Modification of poly(N-vinyl-carbazole) thin films by bromine doping

Poly(N-vinyl-carbazole) (PVK) thin films doped with bromine has been studied by scanning electron microscopy, X-ray diffraction, infrared absorption, X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), optical transmission (visible, near ultra violet) and conductivity measurements. The polymer has been doped at room temperature and at 373 K. It is shown by ESR, XPS and optical measurements that a charge transfer complex (CT-complex) is formed between PVK and Br. However, if some bromine acts as dopant of the polymer there is another bromine contribution, which corresponds to bromine covalently bonded to PVK and some only adsorbed. It is also shown by ESR that there is not only polymer doping by bromine but also some partial polymer degradation. Therefore, it can be said that the optimum doping condition of PVK thin films with bromine has been shown to be room temperature post-doping.     

Solder engineering for optoelectronic packaging

In addition to providing electrical connections, solder is useful in the formation of passive, precision alignments for optoelectronic packaging. Different designs have demonstrated micrometer-level alignment accuracies, and the aligned structures are becoming more and more complex. Solder engineering has been successfully introduced into the field of optoelectronics, and it is expected to be applied to many other areas demanding low-cost, precision alignments.