Blackbox macro-modeling of the nonlinearity based on Volterra series representation of X-parameters

Volterra series representation is a powerful mathematical model for nonlinear devices. However, the difficulties in determining higher-order Volterra kernels limited its broader applications. This paper proposed a systematic approach that enables a convenient extraction of Volterra kernels from X-parameters for the first time. Then the Vandermonde method is employed to separate different orders of Volterra kernels at the same frequency, which leads to a highly efficient extraction process. The proposed Volterra series representation based on X-parameters is further benchmarked for verification. The proposed new algorithm is very useful for the blackbox macro-modeling of nonlinear devices and systems. © 2014 IEEE.postprin

Volterra Series-Based Time-Domain Macromodeling of Nonlinear Circuits

Volterra series (VS) representation is a powerful mathematical model for nonlinear circuits. However, the difficulties in determining higher order Volterra kernels limited its broader applications. In this paper, a systematic approach that enables a convenient extraction of Volterra kernels from X-parameters is presented. A concise and general representation of the output response due to arbitrary number of input tones is given. The relationship between Volterra kernels and X-parameters is explicitly formulated. An efficient frequency sweep scheme and an output frequency indexing scheme are provided. The least square linear regression method is employed to separate different orders of Volterra kernels at the same frequency, which leads to the obtained Volterra kernels complete. The proposed VS representation based on X-parameters is further validated for time-domain verification. The proposed method is systematic and general-purpose. It paves the way for time-domain simulation with X-parameters and constitutes a powerful supplement to the existing blackbox macromodeling methods for nonlinear circuits.postprin

A numerical study of the impact of climate and emission changes on surface ozone over South China in Autumn time in 2000-2050

2012-2013 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

A novel polyphase multipole square-wave permanent magnet motor drive for electric vehicles

A novel high-power-density permanent magnet (PM) motor drive for electric vehicles (EVs) is proposed. The motor is a polyphase multipole square-wave PM motor, which can be classified as a kind of PM brushless DC motor. The distinct features of the proposed motor as compared to those of the conventional PM brushless DC motor are as follows. First, the multipole magnetic circuit arrangement enables the minimization of the magnetic yoke, resulting in the reduction of motor volume and weight. Second, the coil span is purposely designed to be equal to one slot pitch, thus saving the amount of copper used. Third, by using a fractional number of slots per pole per phase, the arrangement of the numbers of poles and slots is so unique that the magnetic force between the stator and the rotor at any rotating position is uniform, hence eliminating the cogging torque that usually occurs in PM motors. Finally, the motor can be controlled to operate at a constant torque region and a constant power region with field weakening, thus both high starting torque and high cruising speed can be achieved. Therefore, as the proposed motor drive possesses the distinct advantages of high power density, high efficiency, and superior dynamic performance, it is very suitable for EV applications. A prototype of a five-phase 22-pole 5 kW motor drive has been designed for an experimental EV.published_or_final_versio

Compact Nonlinear Yagi-Uda Nanoantennas

Nanoantennas have demonstrated unprecedented capabilities for manipulating the intensity and direction of light emission over a broad frequency range. The directional beam steering offered by nanoantennas has important applications in areas including microscopy, spectroscopy, quantum computing, and on-chip optical communication. Although both the physical principles and experimental realizations of directional linear nanoantennas has become increasingly mature, angular control of nonlinear radiation using nanoantennas has not been explored yet. Here we propose a novel concept of nonlinear Yagi-Uda nanoantenna to direct second harmonic radiation from a metallic nanosphere. By carefully tuning the spacing and dimensions of two lossless dielectric elements, which function respectively as a compact director and reflector, the second harmonic radiation is deflected 90 degrees with reference to the incident light (pump) direction. This abnormal light-bending phenomenon is due to the constructive and destructive interference between the second harmonic radiation governed by a special selection rule and the induced electric dipolar and magnetic quadrupolar radiation from the two dielectric antenna elements. Simultaneous spectral and spatial isolation of scattered second harmonic waves from incident fundamental waves pave a new way towards nonlinear signal detection and sensing.published_or_final_versio

Phytochemical Constituents and Pharmacological Activities of Plants from the Genus Adiantum: A Review

Adiantum is a genus of ca. 200 species in the family Adiantaceae, distributed extensively across the world from cool temperate zones to hot tropical regions. A lot of Adiantum species have been used in traditional Chinese medicine to cure human and animal diseases including relief of internal heat or fever, enhancement of urination, removal of urinary calculus, and sundry other curative claims. Chemical studies have shown the presence of various classes of compounds, the main ones being triterpenoids, flavonoids, phenyl propanoids, steroids, alicyclic acids, lipids and long-chain compounds. The extract of this genus as well as pure compounds isolated from it have been demonstrated to possess multiple pharmacological activities such as analgesic, antinociceptive, anti-implantation, and antimicrobial activities. In this review, we have addressed the phytochemistry and pharmacological activities of the Adiantum species in order to collate existing information on this plant as well as highlight its multi-activity properties as a medicinal agent.Keywords: Adiantum species, Adiantaceae, Phytochemical constituents, Pharmacological activities

Strongly enhanced and directionally tunable second-harmonic radiation from a plasmonic particle-in-cavity nanoantenna

© 2016 American Physical Society.Second-harmonic (SH) generation is tremendously important for nonlinear sensing, microscopy, and communication systems. One of the great challenges of current designs is to enhance the SH signal and simultaneously tune its radiation direction with a high directivity. In contrast to the linear plasmonic scattering dominated by a bulk dipolar mode, a complex surface-induced multipolar source at the doubled frequency sets a fundamental limit to control the SH radiation from metallic nanostructures. In this work, we harness a plasmonic hybridization mechanism together with a special selection rule governing the SH radiation to achieve the high-intensity and tunable-direction emission by a metallic particle-in-cavity nanoantenna (PIC-NA). The nanoantenna is modelled with a first-principle, self-consistent boundary element method, which considers the depletion of pump waves. The giant SH enhancement arises from a hybridized gap plasmon resonance between the small particle and the large cavity that functions as a concentrator and reflector. Centrosymmetry breaking of the PIC-NA not only modifies the gap plasmon mode boosting the SH signal, but also redirects the SH wave with a unidirectional emission. The PIC-NA has a significantly larger SH conversion efficiency compared to existing literature. The main beam of the radiation pattern can be steered over a wide angle by tuning the particle's position.published_or_final_versio

A framework for automatic semantic video annotation

The rapidly increasing quantity of publicly available videos has driven research into developing automatic tools for indexing, rating, searching and retrieval. Textual semantic representations, such as tagging, labelling and annotation, are often important factors in the process of indexing any video, because of their user-friendly way of representing the semantics appropriate for search and retrieval. Ideally, this annotation should be inspired by the human cognitive way of perceiving and of describing videos. The difference between the low-level visual contents and the corresponding human perception is referred to as the ‘semantic gap’. Tackling this gap is even harder in the case of unconstrained videos, mainly due to the lack of any previous information about the analyzed video on the one hand, and the huge amount of generic knowledge required on the other. This paper introduces a framework for the Automatic Semantic Annotation of unconstrained videos. The proposed framework utilizes two non-domain-specific layers: low-level visual similarity matching, and an annotation analysis that employs commonsense knowledgebases. Commonsense ontology is created by incorporating multiple-structured semantic relationships. Experiments and black-box tests are carried out on standard video databases for action recognition and video information retrieval. White-box tests examine the performance of the individual intermediate layers of the framework, and the evaluation of the results and the statistical analysis show that integrating visual similarity matching with commonsense semantic relationships provides an effective approach to automated video annotation

Dual fluorescence from aqueous 1-naphthylamine solutions of high pH - Excited-state acidic dissociation of naphthylamine

Dual fluorescence at ca. 447 nm and 545 nm was observed from the aqueous 1-naphthylamine (NA) solutions at pH higher than 13.6. Similar dual fluorescence was also found with sodium 1-naphthylaminoacetate(NAA), but not with N, N-disubstituted 1-aminonaphthalenes such as sodium 1-naphthylaminodiacetate (NADA) and 1-dimethylaminonaphthalene (DMAN). No change in absorption spectra of NA and NAA was observed in this pH region. It was proposed that the dual fluorescence observed with NA and NAA was due to the excited state dissociation of the primary and secondary amines at high pH. From the dual fluorescence intensity ratio pH titration curve, the pK(a)(.)'s of NA and NAA were estimated to be between 14 and 15 which are much lower than the ground state pK(a). The novel approach is such a simple, convenient and frequent analysis technique that it can be widely used in detecting the substitutional derivatives of aminonaphthalene

Hepatitis B Virus Core Promoter Double Mutations (A1762T, G1764A) Are Associated with Lower Levels of Serum Dihydrolipoyl Dehydrogenase

Published by S. Karger AG, BaselObjectives: The aim of this study was to identify serum proteins with differential concentrations between hepatocellular carcinoma (HCC) patients and HBsAg asymptomatic carriers among individuals infected with hepatitis B virus (HBV) with basal core promoter (BCP) double mutations (A1762T, G1764A). Methods: iTRAQ and liquid chromatography-tandem mass spectrometry were used to identify differentially expressed protein, and an ELISA test was used for the validation test. Results: The total number of proteins identified was 1,125, of which 239 showed statistically significant differences in their expression. The relative concentrations of serum dihydrolipoyl dehydrogenase (DLD), which showed the most significant correlation with liver diseases and infection, were significantly lower in HCC patients than asymptomatic HBsAg carriers and individuals negative for HBsAg. However, only the difference between HCC patients with BCP double mutations and HBsAg-negative individuals could be confirmed by ELISA. Meanwhile, we found that the concentrations of serum DLD in those infected with HBV with BCP double mutations were significantly lower than in individuals with the wild-type BCP. However, the difference in the concentrations of serum DLD between individuals with wild-type BCP and those negative for HBsAg was not significant. Conclusions: HBV with BCP double mutations are associated with lower concentrations of serum DLD