电子设计发展趋势——开源PCB设计

正电子设计领域的一大趋势是开源硬件及其配套的开源原理图和PCB布局图的使用。使用开源硬件及其配套资源意味着工程师可以方便地使用现有设计方案,从而提高效率并缩短产品上市时间。随着工程师更加深入地了解传统PCB与开源PCB设计之间的区别,该趋势将极有可能获得进一步增长。开源PCB设计较传统PCB设计具有几大优势,其中包括电源和数字部分以及高速数据部分的重复可用性,这使得工程师更加青睐于开源PCB设计。在以往的设计过     

Towards trustworthy collaboration in spectrum sensing for ad hoc cognitive radio networks

Cognitive radio networks (CRN) make use of dynamic spectrum access to communicate opportunistically in frequency bands otherwise licensed to incumbent primary users such as TV broadcast. To prevent interference to primary users it is vital for secondary users in CRNs to conduct accurate spectrum sensing, which is especially challenging when the transmission range of primary users is shorter compared to the size of the CRN. This task becomes even more challenging in the presence of malicious secondary users that launch spectrum sensing data falsification (SSDF) attacks by providing false spectrum reports. Existing solutions to detect such malicious behaviors cannot be utilized in scenarios where the transmission range of primary users is limited within a small sub-region of the CRN. In this paper, we present a framework for trustworthy collaboration in spectrum sensing for ad hoc CRNs. This framework incorporates a semi-supervised spatio-spectral anomaly/outlier detection system and a reputation system, both designed to detect byzantine attacks in the form of SSDF from malicious nodes within the CRN. The framework guarantees protection of incumbent primary users’ communication rights while at the same time making optimal use of the spectrum when it is not used by primary users. Simulation carried out under typical network conditions and attack scenarios shows that our proposed framework can achieve spectrum decision accuracy up to 99.3 % and detect malicious nodes up to 98 % of the time.     

AVS Intellectual Property Rights (IPR) Policy

The AVS Workgroup has developed an IPR Policy to facilitate the adoption of standards in the marketplace The policy is based on consideration of IPR issues in parallel with the technical work for drafting the standard. The paper describes the relationship between IPR and the standard, and how the goals for the standard must be complemented by goals for the IPR. The existing IPR policies of the ITU and ISO are outlined, and then the AVS IPR policy is described, organized by its three main components： commitment to license on declared basic terms, disclosure of intellectual property, and protection of IPR.     

Development and evaluation of multiple regression models for prediction of sweet cherry liking

In two experiments, multiple regression models were developed and evaluated to identify the relevant sensory attributes for cherry liking. In Experiment 1, 16 judges evaluated 18 cherry varieties for seven visual characteristics (colour intensity, uniformity-of-colour, speckles, size, stem length, external firmness and ‘visual’ liking) and seven flavour/texture characteristics (flesh firmness, flesh colour intensity, juiciness, sweetness, sourness, flavour intensity and ‘flavour/ texture’ liking). Stepwise multiple regression was used to develop the most appropriate statistical models for prediction of visual and flavour/texture liking based on visual and flavour/texture characteristics, respectively. Both models were simple and easily understandable with two sensory variables. The best model for visual liking required only size and uniformity-of-colour variables; whereas, the best model for flavour/texture liking required sweetness and flavour intensity variables. In Experiment 2, 18 judges evaluated 30 sweet cherry cultivars, using the same methodology, to create a validation data set. Correlation coefficients (R) and prediction standard errors (PSEs) between the observed (Experiment 2) and predicted (Experiment 1) liking scores were used to evaluate the prediction equations. The prediction equation for flavour/texture liking was most satisfactory (R = 0.85, PSE = 0.61). A new equation developed from the validation data confirmed the importance of sweetness and flavour intensity. In contrast, the prediction equation for visual liking was less satisfactory (R = 0.56) and a new equation developed from the validation data set confirmed only size as an important variable.     

Multiple-antenna techniques for wireless communications - a comprehensive literature survey

The use of multiple antennas for wireless communication systems has gained overwhelming interest during the last decade - both in academia and industry. Multiple antennas can be utilized in order to accomplish a multiplexing gain, a diversity gain, or an antenna gain, thus enhancing the bit rate, the error performance, or the signal-to-noise-plus-interference ratio of wireless systems, respectively. With an enormous amount of yearly publications, the field of multiple-antenna systems, often called multiple-input multiple-output (MIMO) systems, has evolved rapidly. To date, there are numerous papers on the performance limits of MIMO systems, and an abundance of transmitter and receiver concepts has been proposed. The objective of this literature survey is to provide non-specialists working in the general area of digital communications with a comprehensive overview of this exciting research field. To this end, the last ten years of research efforts are recapitulated, with focus on spatial multiplexing and spatial diversity techniques. In particular, topics such as transmitter and receiver structures, channel coding, MIMO techniques for frequency-selective fading channels, diversity reception and space-time coding techniques, differential and non-coherent schemes, beamforming techniques and closedloop MIMO techniques, cooperative diversity schemes, as well as practical aspects influencing the performance of multiple-antenna systems are addressed. Although the list of references is certainly not intended to be exhaustive, the publications cited will serve as a good starting point for further reading.     

A Body of Circumstantial Evidence for the Irreversible Ectonucleotidase Inhibitory Action of FSCPX,an Agent Known as a Selective Irreversible A1 Adenosine Receptor Antagonist So Far

In previous studies using isolated, paced guinea pig left atria, we observed that FSCPX, known as a selective A₁ adenosine receptor antagonist, paradoxically increased the direct negative inotropic response to A₁ adenosine receptor agonists (determined using concentration/effect (E/c) curves) if NBTI, a nucleoside transport inhibitor, was present. Based on mathematical modeling, we hypothesized that FSCPX blunted the cardiac interstitial adenosine accumulation in response to nucleoside transport blockade, probably by inhibiting CD39 and/or CD73, which are the two main enzymes of the interstitial adenosine production in the heart. The goal of the present study was to test this hypothesis. In vitro CD39 and CD73 inhibitor assays were carried out; furthermore, E/c curves were constructed in isolated, paced rat and guinea pig left atria using adenosine, CHA and CPA (two A₁ adenosine receptor agonists), FSCPX, NBTI and NBMPR (two nucleoside transport inhibitors), and PSB-12379 (a CD73 inhibitor), measuring the contractile force. We found that FSCPX did not show any inhibitory effect during the in vitro enzyme assays. However, we successfully reproduced the paradox effect of FSCPX in the rat model, mimicked the “paradox” effect of FSCPX with PSB-12379, and demonstrated the lipophilia of FSCPX, which could explain the negative outcome of inhibitor assays with CD39 and CD73 dissolved in a water-based solution. Taken together, these three pieces of indirect evidence are strong enough to indicate that FSCPX possesses an additional action besides the A₁ adenosine receptor antagonism, which action may be the inhibition of an ectonucleotidase. Incidentally, we found that POM-1 inhibited CD73, in addition to CD39.     

In vivo transposition of mariner-based elements in enteric bacteria and mycobacteria

mariner family transposons are widespread among eukaryotic organisms. These transposons are apparently horizontally transmitted among diverse eukaryotes and can also transpose in vitro in the absence of added cofactors. Here we show that transposons derived from the mariner element Himar1 can efficiently transpose in bacteria in vivo. We have developed simple transposition systems by using minitransposons, made up of short inverted repeats flanking antibiotic resistance markers. These elements can efficiently transpose after expression of transposase from an appropriate bacterial promoter. We found that transposition of mariner-based elements in Escherichia coli produces diverse insertion mutations in either a targeted plasmid or a chromosomal gene. With Himar1-derived transposons we were able to isolate phage-resistant mutants of both E. coli and Mycobacterium smegmatis. mariner-based transposons will provide valuable tools for mutagenesis and genetic manipulation of bacteria that currently lack well developed genetic systems.     

Optimal discrete filtering for time-delayed systems with respect to mean-square continuous-time error criterion

An optimal linear digital filtering problem for continuous-time dynamic processes is considered. An algorithm for optimal filter design taking into account pure delays in continuous-time networks is presented. The performance of systems, being optimal with respect to discrete-time and continuous-time mean-square errors, is compared. An optimal stochastic model-matching problem is proposed and its solution is presented. © 1998 John Wiley & Sons, Ltd.     

Relating carbon monoxide photoproduction to dissolved organic matter functionality

Aqueous solutions of humic substances (HSs) and pure monomeric aromatics were irradiated to investigate the chemical controls upon carbon monoxide (CO) photoproduction from dissolved organic matter (DOM). HSs were isolated from lakes, rivers, marsh, and ocean. Inclusion of humic, fulvic, hydrophobic organic, and hydrophilic organic acid fractions from these environments provided samples diverse in source and isolation protocol. In spite of these major differences, HS absorption coefficients (a) and photoreactivities (a bleaching and CO production) were strongly dependent upon HS aromaticity (r2 > 0.90; n = 11), implying aromatic moieties are the principal chromophores and photoreactants within HSs, and by extension, DOM. Carbonyl carbon and CO photoproduction were not correlated, implying that carbonyl moieties are not quantitatively important in CO photoproduction. CO photoproduction efficiency of aqueous solutions of monomeric aromatic compounds that are common constituents of organic matter varied with the nature of ring substituents. Specifically, electron donating groups increased, while electron withdrawing groups decreased CO photoproductivity, supporting our conclusion that carbonyl substituents are not quantitatively important in CO photoproduction. Significantly, aromatic CO photoproduction efficiency spanned 3 orders of magnitude, indicating that variations in the CO apparent quantum yields of natural DOM may be related to variations in aromatic DOM substituent group chemistry.