Semiconductor-film grafting-a new approach to OEICs

The use of semiconductor-film grafting for the hybrid integration of optoelectronic devices and its advantages in post-transfer fabrication are described. It is shown that grafted films are optically coupled to the substrate, making it possible to mix the semiconductor properties with some properties in the substrate, not commonly found in semiconductors, to yield new devices with no counterpart in other technologies. The semiconductor-film grafting, device fabrication, optical interaction between the semiconductor film and host substrate, and the integration of lasers with glass and LiNbO₃ waveguides are discussed     

Cytogenetic abnormalities in pediatric myelodysplastic syndrome: a report of three cases

Three consecutive cases of pediatric myelodysplastic syndrome (MDS) diagnosed over a three-year period in Queen Mary Hospital, Hong Kong, were described. Depending on the classification system used, they comprised two cases of chronic myelomonocytic leukemia (CMMoL) of which one can be reclassified as juvenile chronic myeloid leukemia (JCML) and one cases of refractory anemia with excess of blasts (RAEB) or an alternative diagnosis of atypical CML. Cytogenetic abnormalities were detected in all of them on examination of bone marrow cells. Of the two CMMoL, one had monosomy 21, whereas the other had hypodiploidy. The patient with RAEB had a complex karyotype of 46,X,del(X)(q24),t(1;7) (p22;q32),add(15)(q26)(8). The balanced translocation (1;7) seen in this patient was exceedingly rare and, to the best of our knowledge, was reported only twice in the literature. The karyotypic abnormalities that we saw in our patients were not well recognized in pediatric MDS. This report emphasizes the importance of cytogenetic study in children suspected of suffering from MDS, which remains a rare disorder of childhood, and a need to rationalize current classification schemes.     

A look-ahead Levinson algorithm for general Toeplitz systems

The authors present an extension of Levinson's algorithm that is guaranteed to be weakly stable for a large class of general Toeplitz matrices, namely, those that do not have many consecutive ill-conditioned leading principal submatrices. The new algorithm adapts itself to the given Toeplitz matrix by skipping over all the ill-conditioned leading principal submatrices encountered during the solution process. This is done by a look-ahead strategy that monitors the condition of the leading principal submatrices and, if necessary, switches to a block step of suitable size. The overhead of the look-ahead algorithm is typically small compared to the classical Levinson algorithm, and in addition a reliable condition number estimate is produced     

Threshold voltage and C-V characteristics of SOIMOSFET's related to Si film thickness variation on SIMOX wafers

C-V characteristics of fully depleted SOI MOSFETs have been studied using a technique for measuring silicon-film thickness using a MOSFET. The technique is based on C-V measurements between the gate and source/drain at two different back-gate voltages, and only a large-area transistor is required. Using this technique, SOI film thickness mapping was made on a finished SIMOX wafer and a thickness variation of ±150 Å was found. This thickness variation causes as much as a 100-mV variation in the device threshold voltage. The silicon-film thickness variation and threshold-voltage variation across a wafer shows a linear correlation dependence for a fully depleted device. C-V measurements of the back-gate device yield the buried-oxide thickness and parasitic capacitances. The effects of GIDL (gate-induced drain leakage) current on C-V characteristics are also discussed     

A software system for anticipating the size and shape of submerged arc welds

A software system for computing the size and shape of bead-on-plate submerged arc (SA) welds is described in this presentation. The system is based on algorithms originated by McGlone et al., Chandel et al. and Yang et al. Essentially the system consists of a specially designed interface for welding/materials/design/fabrication engineers, automated plotting for parametric studies, a simplified data base for storing/editing/retrieving frequently used welding parameters and pictorial graphics for displaying weld size and shape. The use of the system in engineering practice is discussed at some length.     

The performance of reference-based M-ary PSK with trelliscoded modulation in Rayleigh fading

The performance of trellis-coded M-ary phase shift keying (MPSK) is analyzed for three types of phase detection system; differential detection, pilot-symbol-aided detection and pilot-tone-aided detection. A near-exact solution to the probability of event error in Rayleigh fading is derived, and two extremely tight upper bounds generated. They improve the Chernoff upper bound by at least a factor of four at medium and high signal-to-noise ratios (SNR)     

Discovering useful concept prototypes for classification based on filtering and abstraction

The nearest-neighbor algorithm and its derivatives have been shown to perform well for pattern classification. Despite their high classification accuracy, they suffer from high storage requirement, computational cost, and sensitivity to noise. We develop anew framework, called ICPL (Integrated Concept Prototype Learner), which integrates instance-filtering and instance-abstraction techniques by maintaining a balance of different kinds of concept prototypes according to instance locality. The abstraction component, based on typicality, employed in our ICPL framework is specially designed for concept integration. We have conducted experiments on a total of 50 real-world benchmark data sets. We find that our ICPL framework maintains or achieves better classification accuracy and gains a significant improvement in data reduction compared with existing filtering and abstraction techniques as well as some existing techniques.     

Relationships of fracture toughness and dislocation mobility in intermetallics

An analytical method has been developed and used to compute the Peierls-Nabarro (P-N) barrier energy, U _P-N, for relevant slip systems in several intermetallics, including NiAl, FeAl, Nb-Ti-Al (B2), Ni₃Al (L1₂), TiAl (L1₀), TiCr₂, NbCr₂ (C14, C15), Nb₅Si₃ (D8 _l ), Mo₅SiB₂ (D8 _l ), and Mo₅Si₃ (D8 _m ). The P-N barrier energy and a generalized fault energy, γ _F, are combined and used as a measure of dislocation mobility. Furthermore, a fracture model has been developed to describe the process of thermally activated dislocations moving away from the crack tip and to predict the corresponding fracture resistance. A ductility index defined in terms of the ratio of γ _s/(U _P-N+γ _F), where γ _s is the surface energy, is used to correlate with the fracture toughness, K _C, of individual intermetallics. The correlation indicates that fracture toughness increases with increasing values of γ _s/(U _P-N+γ _F), in accordance with the fracture model formulated based on thermally activated slip. The use of the fracture model for predicting the effects of slip behavior, temperature, and alloy additions on fracture resistance is demonstrated for selected intermetallics including NiAl, TiAl, Laves phase, and Nb₅Si₃.