Relative edge energy in the stability of transition metal nanoclusters of different motifs

When a structure is reduced to a nanometer scale, the proportion of the lowly-coordinated edge atoms increases significantly, which can play a crucial role in determining both their geometric and electronic properties, as demonstrated by the recently established generalized Wulff construction principle [S. F. Li, et al., Phys. Rev. Lett., 2013, 111, 115501]. Consequently, it is of great interest to clarify quantitatively the role of the edge atoms that dominate the motifs of these nanostructures. In principle, establishing an effective method valid for determining the absolute value of the surface energy and particularly the edge energy for a given nanostructure is expected to resolve such a problem. However, hitherto, it is difficult to obtain the absolute edge energy of transition metal clusters, particularly when their sizes approach the nanometer regime. In this paper, taking Ru nanoclusters as a prototypical example, our first-principles calculations introduce the concept of relative edge energy (REE), reflecting the net edge atom effect over the surface (facet) atom effect, which is fairly powerful to quasi-quantitatively estimate the critical size at which the crossover occurs between different configurations of a given motif, such as from an icosahedron to an fcc nanocrystal. By contrast, the bulk effect should be re-considered to rationalize the power of the REE in predicting the relative stability of larger nanostructures between different motifs, such as fcc-like and hcp-like nanocrystals

Low-loss narrowband filtering switch based on coaxial resonators

© 2013 IEEE. In this paper, a narrowband filtering switch with low loss and high selectivity is presented based on coaxial resonators for the first time. PIN diodes mounted on the printed circuit boards are embedded into a coaxial filter to enable ON and OFF states. In the ON-state, the PIN diodes are turned OFF, which do not introduce the loss and affect the linearity. Two transmission zeros are generated by a novel feeding structure, which improves the skirt selectivity. In the OFF-state, the PIN diodes are turned on. Then, lumped capacitors are loaded to the coaxial resonators so that the resonant frequencies of the resonators are changed. The passband at the operating frequency cannot be formed, resulting in high isolation. For demonstration, the coaxial-resonator-based filtering switch is designed and fabricated. Good agreement between simulated and measured results verifies the proposed ideas. Comparison with other reported filtering switches is given. The proposed filtering switch shows the advantages of high Q-factor, relatively compact size, and wide stopband responses, which is attractive in wireless systems

On the discovery of continuous truth: a semi-supervised approach with partial ground truths

In many applications, the information regarding to the same object can be collected from multiple sources. However, these multi-source data are not reported consistently. In the light of this challenge, truth discovery is emerged to identify truth for each object from multi-source data. Most existing truth discovery methods assume that ground truths are completely unknown, and they focus on the exploration of unsupervised approaches to jointly estimate object truths and source reliabilities. However, in many real world applications, a set of ground truths could be partially available. In this paper, we propose a semi-supervised truth discovery framework to estimate continuous object truths. With the help of ground truths, even a small amount, the accuracy of truth discovery can be improved. We formulate the semi-supervised truth discovery problem as an optimization task where object truths and source reliabilities are modeled as variables. The ground truths are modeled as a regularization term and its contribution to the source weight estimation can be controlled by a parameter. The experiments show that the proposed method is more accurate and efficient than the existing truth discovery methods

Thermally induced conduction type conversion in n-type InP

n-type semiconducting InP is changed into p-type semiconducting by short time annealing at 700 °C. Further annealing for a longer time leads to a second conduction-type conversion changing the material back to n type again but with a much higher resistivity. These conduction conversions indicate the formation of both acceptor and donor defects and the progressive variation of their relative concentrations during annealing. © 1999 American Institute of Physics.published_or_final_versio

Substrate co-doping modulates electronic metal-support interactions and significantly enhances single-atom catalysis

Transitional metal nanoparticles or atoms deposited on appropriate substrates can lead to highly economical, efficient, and selective catalysis. One of the greatest challenges is to control the electronic metal–support interactions (EMSI) between the supported metal atoms and the substrate so as to optimize their catalytic performance. Here, from first-principles calculations, we show that an otherwise inactive Pd single adatom on TiO2(110) can be tuned into a highly effective catalyst, e.g. for O2 adsorption and CO oxidation, by purposefully selected metal–nonmetal co-dopant pairs in the substrate. Such an effect is proved here to result unambiguously from a significantly enhanced EMSI. A nearly linear correlation is noted between the strength of the EMSI and the activation of the adsorbed O2 molecule, as well as the energy barrier for CO oxidation. Particularly, the enhanced EMSI shifts the frontier orbital of the deposited Pd atom upward and largely enhances the hybridization and charge transfer between the O2 molecule and the Pd atom. Upon co-doping, the activation barrier for CO oxidation on the Pd monomer is also reduced to a level comparable to that on the Pd dimer which was experimentally reported to be highly efficient for CO oxidation. The present findings provide new insights into the understanding of the EMSI in heterogeneous catalysis and can open new avenues to design and fabricate cost-effective single-atom-sized and/or nanometer-sized catalysts

Compensation ratio-dependent concentration of a V InH 4 complex in n-type liquid encapsulated Czochralski InP

The concentration of hydrogen-indium vacancy complex V InH 4 in liquid encapsulated Czochralski undoped and Fe-doped n-type InP has been studied by low-temperature infrared absorption spectroscopy. The V InH 4 complex is found to be a dominant intrinsic shallow donor defect with concentrations up to ∼10 16 cm -3 in as-grown liquid encapsulated Czochralski InP. The concentration of the V InH 4 complex is found to increase with the compensation ratio in good agreement with the proposed defect formation model of Walukiewicz [W. Walukiewicz, Phys. Rev. B 37, 4760 (1998); Appl. Phys. Lett. 54, 2094 (1989)], which predicts a Fermi-level-dependent concentration of amphoteric defects. © 1998 American Institute of Physics.published_or_final_versio

Genetic relationships among alfalfa gemplasms resistant to common leaf spot and selected Chinese cultivars assessed by sequence-related amplified polymorphism (SARP) markers

Genetic relationships among 26 alfalfa cultivars, of which, 12 were of high resistance to common leaf spot (CLS), were assessed using sequence-related amplified polymorphism (SRAP) markers. 34 SRAP primer combinations were selected for fingerprinting of these cultivars and a total of 281 bands were observed, among which 115 were polymorphic (40.93%). Based on molecular data, 26 cultivars were classified into 5 groups. Group I included 12 Chinese cultivars, most of which had a low CLS resistance and were planted in cold and/or drought region in China, while 10 of 11 cultivars with a high CLS resistance were put in group II or group IV respectively. Furthermore, the clustering pattern was, on the whole, consistent with their CLS resistance or geographic origins. In addition, there was a low genetic diversity among alfalfa cultivars from China. In conclusion, SRAP markers may serve as a quick tool to analyze the genetic relationships and genetic diversity among alfalfa cultivars in conjunction with DNAbulking method. The information produced by this study on the genetic relationships and genetic diversity among 26 cultivars could be useful to select parents in a CLS resistance breeding program of alfalfa.Key words: Lucerne, SRAP, Medicago sativa, common leaf spot, genetic relationship

A computational cognition model of perception, memory, and judgment

The mechanism of human cognition and its computability provide an important theoretical foundation to intelligent computation of visual media. This paper focuses on the intelligent processing of massive data of visual media and its corresponding processes of perception, memory, and judgment in cognition. In particular, both the human cognitive mechanism and cognitive computability of visual media are investigated in this paper at the following three levels: neurophysiology, cognitive psychology, and computational modeling. A computational cognition model of Perception, Memory, and Judgment (PMJ model for short) is proposed, which consists of three stages and three pathways by integrating the cognitive mechanism and computability aspects in a unified framework. Finally, this paper illustrates the applications of the proposed PMJ model in five visual media research areas. As demonstrated by these applications, the PMJ model sheds some light on the intelligent processing of visual media, and it would be innovative for researchers to apply human cognitive mechanism to computer science.</p

Electrical and FT-IR measurements of undoped N-type INP materials grown from various stoichiometric melts

P-rich, In-rich and Stoichiometric undoped InP melts have been synthesed by phosphorus in-situ injection method. InP crystal ingots have been grown from these melts by Liquid Encapsulated Czochralski (LEC). Samples from these ingots grown from various Stoichiometric melts have been characterized by Hall Effect and Fourier Transform Infrared (FT-IR) spectroscopy measurements respectively. The Hall Effect measurement results indicate that the net carrier concentration of P-inch undoped InP is higher than that of In-rich and Stoichiometric undoped InP materials. FT-IR spectroscopy measurements reveal that there are intensive absorption peaks which have been proved to be hydrogen related indium vacancy complex V InH 4. By comparing FT-IR spectra, it is found that P-rich InP material has the most intensive absorption peak of V InH 4, while In-rich InP material has the weakest absorption peak.published_or_final_versio

Quantitative Analysis of Curing Mechanisms of Epoxy Resin by Mid- and Near- Fourier Transform Infra Red Spectroscopy

This article informs the essence of major work done by a number of researchers on the analysis of two-step curing mechanism of diglycidyl ether of bisphenol A (DGEBA) epoxy resin in presence of amine curing agents using near- and mid-IR technology. Various peaks used as a marker for resin formation are discussed and their implementation is comprehensively studied. In addition to this, a wide range of information about the importance of reference peaks in both near-IR (NIR) and mid-IR (MIR) regions are congregated and their accuracy is audited. Also discrepancies observed by researchers in epoxy conversion (α) in NIR and MIR regions are reviewed to highlight the comparative advantages of both regions, one over the other.Defence Science Journal, Vol. 64, No. 3, May 2014, pp. 314-321, DOI:http://dx.doi.org/10.14429/dsj.64.732