On the performance of the CREL system

This paper presents the performance results of a comprehensive approach to the parallel execution of rule systems. It describes the semantics of a Concurrent Rule Execution Language, CREL, and the architecture of the system that compiles and executes CREL programs. The system has been designed to avoid run-time overhead by performing extensive compile-time analysis and by parallelizing compilation. Static dependency analysis, based on serializability, coupled with a set of optimizing transforms, partitions the program into subsets, called clusters. Clusters execute independently of each other and communicate though asynchronous message passing. At run time two additional sources of parallelism are exploited—run-time consistency checking allowing multiple rules to fire, and match-level parallelism. The CREL system is implemented on a Sequent Symmetry shared-memory computer. This paper presents the results of a factorial experiment that isolates and evaluates each source of parallelism in the CREL system and each possible combination of those methods. The results suggest that multiple-rule firing is the single most important source of parallelism in CREL programs and that the use of static dependency analysis based on serializability is instrumental to effectively exploit parallelism.     

Bayesian Availability Using Gamma Distributed Priors

Classical statistical estimation techniques have limited usage in predicting system availability when a system, e.g., a computer or telecommunications system, is highly reliable. A Bayesian solution is suggested in this paper. Gamma priors, which are rich in shapes, are assigned to the scale parameters of a gamma distributed component on-time and off-time. Estimation of the gamma priors follows engineer's past experiences for reliability modeling. Both steady-state and instantaneous availabilities are derived using Bayes Theorem. An illustration highlights the assessment and evaluation of the proposed availability measure.     

Fabrication and properties of PLZT ceramics from spray-dried aqueous solution

PLZT ceramics with the composition of 9/62/38 (La/Zr/Ti) were fabricated from spraydried aqueous solution. Complete crystallization of the spray-dried powder is achieved after 1 hr calcination at 650‡ C as compared to 800‡ C, 1 hr for conventional mixedoxide method. Sintering environment plays an important role in the densification of PLZT ceramics. Densities of the atmosphere sintered samples are much higher than those of normal sintered ones. PLZT ceramics derived from spray-dried powders have properties comparable to those derived from sol-gel ones. The spray-dried method presents a less expensive and more effective approach in the synthesis of PLZT ceramics.     

Design of quasi-elliptic function filters with a dual-passband response

Compact miniaturized hairpin resonators are used to design cross-coupled filters with a dual-passband response of elliptic function type. The hairpin resonators are treated as a stepped impedance resonator (SIR) in analysis. In a filter, two different hairpin resonators are used to establish proper couplings required for the two design frequencies. Two filters are fabricated and measured. The results show a good agreement with the simulation.     

Phase composition and properties of solid solutions of GdFeO3–GdInO3 bulks

Solid solutions of the GdFeO₃–GdInO₃ system were prepared at 1550 °C by ceramic powder processing. The formulated composition was Gd(Fe_1−xIn_x)O₃ (GFI) with the indium contents at x = 0, 0.25, 0.5, 0.75, and 1.0. A stable phase of Gd(Fe_1/3In_2/3)O₃ in our system was identified by X-ray diffraction and phase composition analysis. Multi-phase morphologies were observed for GFI bulks with x = 0.5 and 0.75. Dielectric and electrical properties of the GFI bulks were investigated. The addition of 25% In³⁺ in GdFeO₃ had an obvious enhancement in polarization and led to an elevated resonance frequency. Dielectric properties of GFI bulks except GdInO₃ were strongly dependent upon the test frequency, which corresponded to the response of polarization mechanism. GdInO₃ displayed as a stable dielectric, which was frequency- and temperature-insensitive. GdInO₃ was thermally activated and became leaky until above 600 °C.     

Scaling laws and internal structure for characterizing electrospun poly[(R)-3-hydroxybutyrate] fibers

Using chloroform/dimethylformamide (CF/DMF) co-solvent, electrospinning of poly[(R)-3-hydroxybutyrate] (PHB) solutions was carried out at ambient temperature. The effects of the applied voltage (V), flow-rate (Q), and solution viscoelastic properties on the Taylor cone, electrified jet, and fiber morphology were investigated. In addition, the electric field developed by the needle-plate electrode configuration was calculated using a finite element analysis to reveal the tip-to-collector (H) effect. Among the processing parameters (V, Q and H), it was found that Q played a key role in determining the jet diameter (d_j) and electrospun fiber diameter (d_f), and scaling laws existed between them, i.e., d_j-Q^0.61 and d_f-Q^0.33. The diameter reduction ratios of D_o/d_j (D_o is the needle diameter) and d_j/d_f were measured as 50-120 and 5-10, respectively; it suggested that major jet stretching took place in the straight electrified jet region, and further chain orientation could be gained by the subsequent process of jet whipping. By changing PHB concentrations from 5 to 15 wt%, the solution viscosity (η_o) was increased from 100 to 4900 cP, whereas the surface tension and solution conductivity remained unchanged; it provided a good model solution to exclusively reveal the η_o effect on the electrospinning process. Our results showed that the η_o-dependence of d_j and d_f also followed simple scaling laws: d_j-η_o^0.06, and d_f-η_o^0.39, with a prefactor depending on the processing variables, mainly the flow-rate. Regardless of the PHB concentrations used, the obtained PHB fibers showed a similar crystallinity fraction of ca. 0.63 and possession of major α-crystals together with a small amount of β-crystals with zigzag chain conformation.     

Water bamboo husk reinforced poly(lactic acid) green composites

The water bamboo husk is one of major agricultural wastes in Taiwan. In this study, the powder obtained from the water bamboo husk was added to poly(lactic acid) (PLA) to form novel reinforced biodegradable composites. Morphologies, mechanical properties, and heat resistance of these water bamboo powder reinforced composites were investigated. The results indicate that the char yields were increased as plant powder was incorporated to PLA. In addition, the mechanical properties were also enhanced due to the addition of powders. The increments of storage moduli of PLA were about 50–200%. Moreover, the increments of loss moduli of PLA were about 70–200%. On the other hand, the T_g of PLA was slightly decreased by the addition of powder, and this may improve the brittle characteristics of PLA. Furthermore, this type of reinforced PLA would be more environmental friendly than the artificial additive‐reinforced one. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Synthesis of polyurethane elastomers hypercross-linked by partially hydrated polyhydroxylated C60

Utilization of polyhydroxylated C₆₀ (fullerenols) in a condensation reaction with diisocyanated oligo(tetramethylene oxide) led to the successful fabrication of elastomeric poly (urethane-ether) networks. These polymer networks exhibit interesting thermal behavior at low temperatures, improved tensile strength and elongation at ambient temperatures, and enhanced thermal mechanical stability at high temperatures, as compared with those of the parent linear polyurethane analogues; or with the conventional oligo (tetramethylene oxide)-derived polyurethane elastomers cross-linked by trihydroxylated reagents (1,I,1-trismethylol propane) or tetrahydroxylated reagents (pentaerythritol). The presence of a limited quantity of water molecules in the condensation reaction of fullerenols with diisocyanated prepolymers modified the physical properties of the resulting elastomeric products with a notable increase in tensile strength, modulus, and Ts over those of elasotmers prepared under anhydrous conditions. These water molecules contributed effectively to the increase of the number of cross-linking centers during the reaction.     

Closed-form physical model for VLSI bipolar devices consideringenergy transport

A closed-form physical model is reported for VLSI bipolar devices considering energy transport. Based on the model, for a base width of 810 Å, the bipolar device, biased at V_cb=2 V, has a peak electron temperature of over 700 K, which results in a 5% reduction in the collector current     

High-speed Modulation of InGaAs: Sb-GaAs-GaAsP quantum-well vertical-cavity surface-emitting lasers with 1.27-/spl mu/m emission wavelength

1.27-/spl mu/m InGaAs: Sb-GaAs-GaAsP vertical-cavity surface-emitting lasers (VCSELs) were grown by metal-organic chemical vapor deposition and exhibited excellent performance and temperature stability. The threshold current changes from 1.8 to 1.1 mA and the slope efficiency falls less than /spl sim/35% as the temperature raised from room temperature to 70/spl deg/C. With a bias current of only 5 mA, the 3-dB modulation frequency response was measured to be 8.36 GHz, which is appropriate for 10-Gb/s operation. The maximal bandwidth is measured to be 10.7 GHz with modulation current efficiency factor (MCEF) of /spl sim/5.25 GHz/(mA)/sup 1/2/. These VCSELs also demonstrate high-speed modulation up to 10 Gb/s from 25/spl deg/C to 70/spl deg/C.