A novel ceramic matrix composite based on YNbO4–TiO2 for microwave applications

This work presents the dielectric properties of YNbO₄ (YNO)–TiO₂ composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO₂ to YNO results in the formation of a Y(Nb_0.5Ti_0.5)₂O₆ phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of TiO₂. Moreover, the addition of TiO₂ results in an improvement in the thermal stability of YNO, with YNO63 demonstrating a resonant frequency of ?8.96 ppm.°C^?1. We utilised numerical simulations to evaluate the behaviour of these materials as dielectric resonator antennae and it is found that they exhibit a reflection coefficient below ?10 dB at the resonant frequency, with a realised gain of 4.94 – 5.76 dBi, a bandwidth of 665–1050 MHz and a radiation efficiency above 84%. Our results indicate that YNO–TiO₂ composites are interesting candidates for microwave operating devices.     

Quality enhancement of the abundant under‐valued crustacean,lobster krill (Munida spp.), during its chilled storage

Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product.     

Activity-Directed Synthesis: A Flexible Approach for Lead Generation

Activity-directed synthesis (ADS) is a structure-blind, functional-driven molecular discovery approach. In this Concept, four case studies highlight the general applicability of ADS and showcase its flexibility to support different medicinal chemistry strategies. ADS deliberately harnesses reactions with multiple possible outcomes, and allows many chemotypes to be evaluated in parallel. Resources are focused on bioactive molecules, which emerge in tandem with associated synthetic routes. Some of the future challenges for ADS are highlighted, including the realisation of an autonomous molecular discovery platform. The prospects for ADS to become a mainstream lead generation approach are discussed.     

Improving narrow bandgap a-SiGe:H alloys grown by hot-wire chemical vapor deposition

We have improved the electronic properties of narrow-bandgap (Tauc gap below 1.5 eV) amorphous-silicon germanium alloys (a-SiGe:H) grown by hot-wire chemical vapor deposition (HWCVD) by lowering the substrate temperature and deposition rate. Prior to this work, we were unable to grow a-SiGe:H alloys with bandgaps below 1.5 eV that had photo-to-dark conductivity ratios comparable with our plasma-enhanced CVD (PECVD) grown materials [B.P. Nelson et al., Mater. Res. Soc. Symp. 507 (1998) 447]. Decreasing the filament diameter from our standard configuration of 0.5 mm to 0.38 or 0.25 mm provides first big improvements in the photoresponse of these alloys. Lowering the substrate temperature from our previous optimal temperatures (T_sub starting at 435 °C) to at 250 °C provides additional photo-to-dark conductivity ratio increasing by two orders of magnitude for growth conditions containing 20–30% GeH₄ in the gas phase (relative to the total GeH₄+SiH₄ flow).     

Predicting Forest Age Classes from High Spatial Resolution Remotely Sensed Imagery Using Voronoi Polygon Aggregation

Efficient identification of forest age is useful for forest management and ecological applications. Here we propose a user-assisted method for determining forest age using high spatial resolution remotely sensed imagery. This method requires individual trees to be extracted from imagery and represented as points. We use a local maximum filter to generate points that are converted to Voronoi polygons. Properties of the Voronoi polygons are correlated with forest age and used to aggregate points (trees) into areas (stands) based on three forest age classes. Accuracy of the aggregation ranges from approximately 68% to 78% and identification of the mature class is more consistent and accurate than the younger classes.     

High dynamic range InP HBT delta-sigma analog-to-digital converters

To date, the development of multifunction multicarrier digital receivers for cellular base station and military communications applications has been limited by the demanding dynamic range requirements for the analog-to-digital converter (ADC). The use of oversampling delta-sigma modulators provides a promising approach to overcoming the dynamic range barriers Nyquist-rate converters face in the same applications. This paper discusses issues involved in the design of high-speed high dynamic range wide-band delta-sigma ADCs for such communications applications. Test results of prototype designs are also presented. The delta-sigma modulators described in this paper operate at sampling frequencies ranging from 1 to 2.5 GHz with center frequencies ranging from dc to 100 MHz, providing between 74 and 84.2 dB signal-to-noise ratio (12 and 13.7 bits) for bandwidths of 25 and 12.5 MHz, respectively. The loop filters are continuous-time low-pass and bandpass implementations of order 6 and 10, and were fabricated in an InP heterojunction bipolar (HBT) technology. A typical tenth-order design consumes 6 W of power and occupies a die area of 23.5 mm/sup 2/.     

Improved RNS FIR filter architectures

A new architecture for implementing finite-impulse response (FIR) filters using the residue number system (RNS) is detailed. The design is based on using a restricted modulus set, with moduli of the form 2/sup n/,2/sup n/-1, and 2/sup n/+1. This does not restrict the modulus set to the common 3 modulus set {2/sup n/-1,2/sup n/,2/sup n/+1}, but any number of pairwise relatively prime moduli of this form, for example, {5,7,17,31,32,33}. Based on a comparison with a 2's complement design, the new RNS design can offer a significant speed improvement. The gain is obtained by using a set of small moduli, selected so as to minimize critical path delay and area. An algorithmic approach is used to obtain full adder based architectures that are optimized for area and delay. The modulus set is optimum based on cost parameters for each modulus. This new architecture presents a practical approach to implementing a fast RNS FIR filter.     

以太网供电技术的发展

面向以太网供电（PoE）的IEEE802．3af标准将以太网网络连接引向了一个全新的方向，即以10／100／1000Mbps数据速率一并输送DC功率。伴随PoE而出现的一组独特的问题和崭新的思维方式是许多拥有以太网设备设计经验的工程师过去所并不熟悉的。目前，PoE一般用于VoIP电话、无线接入点和安全摄像机。而随着PoE技术的进步，改进标准的呼声渐起，旨在造就新兴的应用。     

A Revised Methodology for Research on Metamemory: Pre-judgment Recall And Monitoring (PRAM).

A revised methodology is described for research on metacognitive monitoring, especially judgments of learning (JOLs), to investigate psychological processing that previously has been only hypothetical and unobservable. During data collection a new stage of recall occurs just prior to the JOL, so that during data analysis the items can be partitioned into subcategories to measure the degree of JOL accuracy in ways that are more analytic than was previously possible. A weighted-average combinatorial rule allows the component measures of JOL accuracy to be combined into the usual overall measure of metacognitive accuracy. An example using the revised methodology offers a new explanation for the delayed-JOL effect, in which delayed JOLs are more accurate than immediate JOLs for predicting recall. (PsycINFO Database Record (c) 2010 APA, all rights reserved)