Input-Dependence in Function-Learning

In the standard model of inductive inference, a learner gets as input the graph of a function, and has to discover (in the limit) a program for the function. In this paper, we consider besides the graph also other modes of input such as the complement of the graph, the undergraph and the overgraph of the function. The relationships between these models are studied and a complete picture is obtained. Furthermore, these notions are also explored for learning with oracles, learning in teams and learning in the presence of additional information. S. Jain and F. Stephan were supported in part by NUS grant numbers R252-000-212-112 and R252-000-308-112. E. Martin is jointly appointed at the UNSW and National ICT Australia which is funded by the Australian Government’s Department of Communications, Information Technology and the Arts and the Australian Research Council through Backing Australia’s Ability and the ICT Centre of Excellence Program.     

Ultrahigh efficiency obtained with GaAs-on-insulator MESFETtechnology

Significant results of measurement and calculation of power-added efficiency (PAE) and drain efficiency are presented for MESFET's that use GaAs-on-insulator. Ultrahigh PAE of 89% was obtained at 8 GHz with a gain of 9.6 dB using a 3-V supply. When the voltage was increased to 4 V, the peak PAE was 93% at 210 mW/mm with 9.2-dB gain. The ideal current-voltage characteristics with practically zero leakage current and large transconductance near pinchoff yielded PAE values approaching the theoretical limits of overdriven operation. The application of conventional assumptions concerning drain efficiency is discussed relative to devices that approach these theoretical limits. Also discussed are the pitfalls of various figures of merit of efficiency when applied to these devices. Hence, there are two types of technical barriers associated with very-high-efficiency devices: the physical realization and their characterization     

Attainable regions of reactive distillation. Part II: Single reactant azeotropic systems

In reactive distillation (RD) one can conveniently manipulate the concentration profiles on the reactive stages by exploiting the difference in volatility of the various components. This property of RD can be advantageously used to improve the selectivity toward the desired product in case of series or series parallel reactions, and obtain a performance superior to the network of conventional reactors. In the previous work [Agarwal, V., et al., 2008. Attainable regions of reactive distillation—Part I. Single reactant non-azeotropic systems. Chemical Engineering Science, submitted for publication], we introduced representative unit models of RD to obtain the attainable regions of RD for non-azeotropic systems. In this work, we extend the approach to a system involving single binary azeotrope. Design guidelines have been formulated based on the residue curve maps, to obtain the improved attainable region with the help of these representative RD models either alone or in the form of their network.     

Multi-centimeter length vapor grown carbon fibers for industrial applications

Vapor grown carbon fiber (VGCF) has been grown since long using the method of chemical vapor deposition. VGCF of tens of centimeter length were produced here using a thermal chemical vapor deposition system. A 6″ electric furnace and a 40 cm long ceramic substrate were used for the purpose. VGCFs were found to grow over 30 cm along the length of the substrate. The ceramic substrate was seeded with iron catalyst and kept almost at the center of the horizontal furnace during the VGCF growth. Before starting the furnace, evacuation of the tube was done with the help of a rotary pump and Ar was used to displace air from the tube. For the growth of VGCFs, mixtures of methane and hydrogen gases were used for a period of 1 to 2 h at 1100 °C. Effect of pre-heating was carried out to study the growth enhancement of VGCFs. Three pre-set temperatures were used for this purpose and preliminary results indicate that 300 °C and 400 °C of pre-heating increased the average diameter of fibers as well as the weight per unit area.     

Characterization of Non-Alloyed Ohmic Contacts to Si-Implanted AlGaN/GaN Heterostructures for High-Electron Mobility Transistors

This paper reports results of a study of non-alloyed ohmic contacts on Si-implanted AlGaN/GaN heterostructures, obtained from current–voltage characteristics of transfer-length method (TLM) test structures. It is shown that the measured contact resistance from the Ti/Au/Ni metal contacts, deposited on Si-implanted regions, to the two-dimensional electron gas channel at the AlGaN/GaN heterointerface of the non-implanted region, is formed by three different components: (i) contact resistance between the metal␣and the semiconductor (0.60 ± 0.16 Ω mm), (ii) resistance of the implanted region (0.62 ± 0.03 Ω mm) and (iii) an additional resistance (0.72 ± 0.24 Ω mm) giving a total value of 1.9 ± 0.3 Ω mm. The specific ohmic contact resistance was determined to be (2.4 ± 0.5) × 10⁻⁵ Ω cm².     

Design, Development, and Biopharmaceutical Properties of Buccoadhesive Compacts of Pentazocine

Buccoadhesive compacts (BCs) of pentazocine (PZ) were prepared by the direct compression method using polymers like carbopol 974P (CP 974P) and hydroxypropyl methylcellulose (HPMC K4M) in ratios of 1:0 (batch B₁), 1:1 (B₂), 1:2 (B₃), 1:4 (B₄), and 0:1 (B₅). The compacts were evaluated for thickness uniformity, weight variation, drug content uniformity, and swelling index. Swelling was increased with an increase in HMPC K4M content in the compacts. An in vitro assembly was developed to measure and compare the bioadhesive strength of compacts. The maximum bioadhesive strength was observed in compacts formulated with a combination of CP 974P and HPMC K4M. The compacts were evaluated in vitro for 24 hr in pH 6.6 phosphate buffer using a standardized dissolution apparatus. The data were evaluated by a simple power equation (M_t/M_∞ = Ktⁿ); it was observed that all the compacts followed non-Fickian release kinetics. Some of the buccoadhesive compacts were evaluated in vivo in rabbits. The compacts gave controlled blood level profiles with a twofold to threefold increase in area-under-the-curve (AUC) values in comparison to oral administration of aqueous drug solution.     

Diversity sustains an evolving network

We study an evolutionary model of a complex system that evolves under catalytic dynamics and Darwinian selection and exhibits spontaneous growth, stasis and then a collapse of its structure. We find that the typical lifetime of the system increases sharply with the diversity of its components or species. We also find that the prime reason for crashes is a naturally occurring internal fragility of the system. This fragility is captured in the network organizational character and is related to a reduced multiplicity of pathways or feedback loops between its components. These results apply to several generalizations of the model as well. This work suggests new parameters for understanding the robustness of evolving molecular networks, ecosystems, societies and markets.     

攻克超低成本手机的设计挑战

超低成本(ULC)手机是最近三年来的热点话题.目前ULC手机一般指低于20美元的手机,它们形成了一个独特的细分市场,需要采用特殊市场策略才能确保成功.     

Microstructure–Thermal Conductivity Relationships for Plasma-Sprayed Yttria-Stabilized Zirconia Coatings

The microstructures of plasma-sprayed yttria-stabilized zirconia (YSZ) coatings are complex, contributing to challenges in establishing microstructure–thermal conductivity relationships. Furthermore, the dynamic evolution of microstructure and properties during service offers a significant challenge in defining design strategies and extended coating performance. In this paper, the relationship between microstructure and thermal conductivity is investigated for three sets of plasma-sprayed YSZ coating systems prepared using different morphology powders, different particle size distributions, and controlled modification of particle states through plasma torch parameters. Both ambient and temperature-dependent thermal conductivity were conducted in the as-sprayed and thermally aged states. The results suggest that a range of thermal conductivities can be achieved from the coatings, offering potential for microstructural tailoring for desired performance. The results also demonstrate that different as-deposited microstructures display varying propensity for sintering and these attributes need to be considered in the design and manufacturing cycle. This expansive study of a range of coatings has also allowed synthesis of the results through thermal conductivity–porosity maps and has allowed elucidation of the contributing microstructural components for both the ambient and high-temperature thermal conductivity. Considering that the operating thermal transport mechanisms are different at these two temperature extremes, such mapping strategies are of value to both science and technology.     

Performance enhancement in latent heat thermal storage system: A review

Phase change material (PCM) based latent heat thermal storage (LHTS) systems offer a challenging option to be employed as an effective energy storage and retrieval device. The performance of LHTS systems is limited by the poor thermal conductivity of PCMs employed. Successful large-scale utilization of LHTS systems thus depends on the extent to which the performance can be improved. A great deal of work both experimental and theoretical on different performance enhancement techniques has been reported in the literature. This paper reviews the implementation of those techniques in different configurations of LHTS systems. The influence of enhancement techniques on the thermal response of the PCM in terms of phase change rate and amount of latent heat stored/retrieved has been addressed as a main aspect. Issues related to mathematical modeling of LHTS systems employing enhancement techniques are also discussed.