Novel wide range speed control of permanent magnet brushless motor drives

This paper presents a novel approach for wide range speed control of permanent magnet (PM) brushless motor drive, including both sinewave and squarewave versions. As compared with conventional flux-weakening control, the approach takes definite advantages that it can be applied to the squarewave PM brushless motor drive directly, and even to the motor drive with negligible mutual inductances between phase windings. Moreover, it is easier to implement than flux-weakening control because no coordinate transformation is needed. The key of this approach is to make use of the transformer EMF in such a way that it weakens the rotational EMF when the motor operate above the base speed, leading to achieve constant-power operation. Computer simulation and experimental results show that the proposed approach works well.published_or_final_versio

Permanent magnet brushless drives

The purpose of this paper is to present an optimal efficiency control scheme for constant power operation of phase decoupling (PD) PM brushless DC motor drives. The key is to adaptively adjust the advanced conduction angle to minimize the system losses for a given operation point in the constant power region. The strategy for constant power operation of PD PM brushless DC motor drives is exemplified using a 5-phase 22-pole PD PM brushless DC motor. In the sections that follow, the newly-developed optimal efficiency control technique is then illustrated. Then, after describing the corresponding implementation, both computer simulation and experimental results are presented, and some conclusions are offered.published_or_final_versio

Optimal-efficiency control for constant-power operation of phase-decoupling permanent-magnet brushless motor drives

In this paper, a control approach to optimize the system efficiency of phase-decoupling (PD) permanent-magnet (PM) brushless motor drives during constant-power operation is presented. The approach is to adaptively adjust the advanced conduction angle to minimize the total system losses for a given operation point in the constant-power region. The corresponding minimum total losses are determined by minimizing the input current for a fixed voltage source. Both computer simulation and experimental results are given for illustration.published_or_final_versio

Novel permanent magnet motor drives for electric vehicles

Novel permanent magnet (PM) motor drives have been successfully developed to fulfil the special requirements for electric vehicles such as high power density, high efficiency, high starting torque, and high cruising speed. These PM motors are all brushless and consist of various types, namely rectangular-fed, sinusoidal-fed, surface-magnet, buried-magnet, and hybrid. The advent of novel motor configurations lies on the unique electro-magnetic topology, including the concept of multipole magnetic circuit and full slot-pitch coil span arrangements, leading to a reduction in both magnetic yoke and copper, decoupling of each phase flux path, and hence an increase in both power density and efficiency. Moreover, with the use of fractional number of slots per pole per phase, the cogging torque can be eliminated. On the other hand, by employing the claw-type rotor structure and fixing an additional field winding as the inner stator, these PM hybrid motors can further provide excellent controllability and improve efficiency map. In the PM motors, by purposely making use of the transformer EMF to prevent the current regulator from saturation, a novel control approach is developed to allow for attaining high-speed constant-power operation which is particularly essential for electric vehicles during cruising. Their design philosophy, control strategy, theoretical analysis, computer simulation, experimental tests and application to electric vehicles are described. © 1996 IEEE.published_or_final_versio

Ultralow Thermal Conductivity, Multiband Electronic Structure and High Thermoelectric Figure of Merit in TlCuSe

The entanglement of lattice thermal conductivity, electrical conductivity, and Seebeck coefficient complicates the process of optimizing thermoelectric performance in most thermoelectric materials. Semiconductors with ultralow lattice thermal conductivities and high power factors at the same time are scarce but fundamentally interesting and practically important for energy conversion. Herein, an intrinsic p-type semiconductor TlCuSe that has an intrinsically ultralow thermal conductivity (0.25 W m−1 K−1), a high power factor (11.6 µW cm−1 K−2), and a high figure of merit, ZT (1.9) at 643 K is described. The weak chemical bonds, originating from the filled antibonding orbitals p-d* within the edge-sharing CuSe4 tetrahedra and long TlSe bonds in the PbClF-type structure, in conjunction with the large atomic mass of Tl lead to an ultralow sound velocity. Strong anharmonicity, coming from Tl+ lone-pair electrons, boosts phonon–phonon scattering rates and further suppresses lattice thermal conductivity. The multiband character of the valence band structure contributing to power factor enhancement benefits from the lone-pair electrons of Tl+ as well, which modify the orbital character of the valence bands, and pushes the valence band maximum off the Γ-point, increasing the band degeneracy. The results provide new insight on the rational design of thermoelectric materials

Spin-Rotation Symmetry Breaking in the Superconducting State of CuxBi2Se3

Spontaneous symmetry breaking is an important concept for understanding physics ranging from the elementary particles to states of matter. For example, the superconducting state breaks global gauge symmetry, and unconventional superconductors can break additional symmetries. In particular, spin rotational symmetry is expected to be broken in spin-triplet superconductors. However, experimental evidence for such symmetry breaking has not been conclusively obtained so far in any candidate compounds. Here, by 77Se nuclear magnetic resonance measurements, we show that spin rotation symmetry is spontaneously broken in the hexagonal plane of the electron-doped topological insulator Cu0.3Bi2Se3 below the superconducting transition temperature Tc=3.4 K. Our results not only establish spin-triplet superconductivity in this compound, but may also serve to lay a foundation for the research of topological superconductivity

Pan-cancer analysis of the extent and consequences of intratumor heterogeneity

Intratumor heterogeneity (ITH) drives neoplastic progression and therapeutic resistance. We used the bioinformatics tools ‘expanding ploidy and allele frequency on nested subpopulations’ (EXPANDS) and PyClone to detect clones that are present at a >= 10% frequency in 1,165 exome sequences from tumors in The Cancer Genome Atlas. 86% of tumors across 12 cancer types had at least two clones. ITH in the morphology of nuclei was associated with genetic ITH (Spearman’s correlation coefficient, rho = 0.24-0.41; P 2 clones coexisted in the same tumor sample (HR = 1.49, 95% CI: 1.20-1.87). In two independent data sets, copy-number alterations affecting either 75% of a tumor’s genome predicted reduced risk (HR = 0.15, 95% CI: 0.08-0.29). Mortality risk also declined when > 4 clones coexisted in the sample, suggesting a trade-off between the costs and benefits of genomic instability. ITH and genomic instability thus have the potential to be useful measures that can universally be applied to all cancers

A Fuzzy System for Concept-Level Sentiment Analysis

Winner for Task 1 and Most Innovative ApproachInternational audienceAn emerging field within Sentiment Analysis concerns the investiga-tion about how sentiment concepts have to be adapted with respect to the different domains in which they are used. In the context of the Concept-Level Sentiment Analysis Challenge, we presented a system whose aims are twofold: (i) the implementation of a learning approach able to model fuzzy functions used for building the relationships graph representing the appropriateness between sentiment concepts and different domains (Task 1); and (ii) the development of a semantic resource based on the connection between an extended version of WordNet, SenticNet, and ConceptNet, that has been used both for extracting concepts (Task 2) and for classifying sentences within specific domains (Task 3)

Mitochondrial DNA Copy Number Is Associated with Breast Cancer Risk

Mitochondrial DNA (mtDNA) copy number in peripheral blood is associated with increased risk of several cancers. However, data from prospective studies on mtDNA copy number and breast cancer risk are lacking. We evaluated the association between mtDNA copy number in peripheral blood and breast cancer risk in a nested case-control study of 183 breast cancer cases with pre-diagnostic blood samples and 529 individually matched controls among participants of the Singapore Chinese Health Study. The mtDNA copy number was measured using real time PCR. Conditional logistic regression analyses showed that there was an overall positive association between mtDNA copy number and breast cancer risk (Ptrend = 0.01). The elevated risk for higher mtDNA copy numbers was primarily seen for women with <3 years between blood draw and cancer diagnosis; ORs (95% CIs) for 2nd, 3rd, 4th, and 5th quintile of mtDNA copy number were 1.52 (0.61, 3.82), 2.52 (1.03, 6.12), 3.12 (1.31, 7.43), and 3.06 (1.25, 7.47), respectively, compared with the 1st quintile (Ptrend = 0.004). There was no association between mtDNA copy number and breast cancer risk among women who donated a blood sample ≥3 years before breast cancer diagnosis (Ptrend = 0.41). This study supports a prospective association between increased mtDNA copy number and breast cancer risk that is dependent on the time interval between blood collection and breast cancer diagnosis. Future studies are warranted to confirm these findings and to elucidate the biological role of mtDNA copy number in breast cancer risk. © 2013 Thyagarajan et al

Study on Resistance Switching Properties of Na0.5Bi0.5TiO3Thin Films Using Impedance Spectroscopy

The Na0.5Bi0.5TiO3(NBT) thin films sandwiched between Au electrodes and fluorine-doped tin oxide (FTO) conducting glass were deposited using a sol–gel method. Based on electrochemical workstation measurements, reproducible resistance switching characteristics and negative differential resistances were obtained at room temperature. A local impedance spectroscopy measurement of Au/NBT was performed to reveal the interface-related electrical characteristics. The DC-bias-dependent impedance spectra suggested the occurrence of charge and mass transfer at the interface of the Au/NBT/FTO device. It was proposed that the first and the second ionization of oxygen vacancies are responsible for the conduction in the low- and high-resistance states, respectively. The experimental results showed high potential for nonvolatile memory applications in NBT thin films