Curvature-dimension inequalities and Li-Yau inequalities in sub-Riemannian spaces

In this paper we present a survey of the joint program with Fabrice Baudoin originated with the paper \cite{BG1}, and continued with the works \cite{BG2}, \cite{BBG}, \cite{BG3} and \cite{BBGM}, joint with Baudoin, Michel Bonnefont and Isidro Munive.Comment: arXiv admin note: substantial text overlap with arXiv:1101.359

In vitro genotoxicity of piperacillin impurity-A

The manufacturing and storage of the piperacillin produce different impurities of various concentrations, which may influence the efficacy and safety of the drug. Since no report of genotoxicity data is available on the impurities of piperacillin, further studies were designed and conducted to provide information for establishing the safety profile and qualification of the piperacillin impurity-A. Salmonella typhimurium strains were exposed to Piperacillin impurity-A for Ames tests. Neither increase in number of revertants indicative of mutagenic activity nor inhibition of bacterial growth, indicative of cytotoxicity were observed up to 5 mg/plate both in the presence and absence of metabolic activation. Similarly, chromosomal aberration assay did not reveal any significant alterations up to 5 mg/culture as compared to the negative control both in the presence and absence of metabolic activation (S9 mix). The results of these studies indicate that Piperacillin impurity-A is non-mutagenic in Ames test and non-clastogenic in chromosomal aberration study

Subwavelength atom localization via amplitude and phase control of the absorption spectrum. II

Journals published by the American Physical Society can be found at http://publish.aps.org/Interaction of the internal states of an atom with spatially dependent standing-wave cavity field can impart position information of the atom passing through it leading to subwavelength atom localization. We recently demonstrated a different regime of atom localization [Phys. Rev. A 72, 013820 (2005)], namely sub-half-wavelength localization through phase control of electromagnetically induced transparency. This regime corresponds to extreme localization of atoms within a chosen half-wavelength region of the standing-wave cavity field. Here we present further investigation of the simplified model considered earlier and show interesting features of the proposal. We show how the model can be used to simulate a variety of energy-level schemes. Furthermore, the dressed-state analysis is employed to explain the emergence and suppression of the localization peaks, and the peak positions and widths. The range of parameters for obtaining clean sub-half-wavelength localization is identified

Control and operation of a new 8/6-pole split-winding doubly salient permanent magnet motor drive

This paper proposes a new 8/6-pole split-winding doubly salient permanent magnet (DSPM) motor drive. The analysis, control, implementation and experiments of the motor drive are presented. The magnetic field analysis is carried out using a finite element method. The split-winding topology is proposed to extend the constant power operation range. The control strategy for the DSPM motor drive is developed. Two operation modes, namely 4-phase and 2-phase operation modes, are proposed for the 8/6-pole DSPM motor drive. In 4-phase operation mode, a half-bridge power converter but without split capacitors is used to reduce the number of power devices and to eliminate the problem of voltage unbalance in the capacitors. The drive system is implemented and tested. The experimental results show that the developed control scheme can operate the DSPM motor properly, and the DSPM motor drive offers high efficiency over a wide power range and good dynamic performance. Furthermore, the 2-phase operation mode of the 8/6-pole DSPM motor offers the potential of eliminating the torque ripple of the motor drive.published_or_final_versio

A new 3-phase brushless doubly-fed doubly salient machines

A new 3-phase 12/8-pole brushless doubly-fed doubly-salient (BDFDS) machine is presented in this paper. The core is to design, modeling, analyze and control the proposed BDFDS machine. The output power equation is analytically derived, and the initial calculation of machine dimensions and parameters are also discussed. By using finite element analysis, the field distributions of the BDFDS machine at different field current and load are obtained, in which the magnetic saturation and the coupling between field current flux and armature current flux are considered; furthermore, the static characteristics of the proposed machine are given. Based on the static characteristics, the system mathematical model has been established. Hence, the evaluation of system performances is conducted by computer simulations in which the simulation model combines the machine with a 3-phase half-bridge converter. A 12/8-pole BDFDS machine is designed and built for exemplification, and a drive system employing this new machine has been developed and investigated experimentally. Experimental results are also given to verify the validity of the theoretical analyses.published_or_final_versio

A new doubly salient permanent magnet motor

In this paper, a new 8/6-pole doubly salient permanent magnet (DSPM) motor is proposed and analyzed. The key is to analytically derive the output power density of the DSPM motor in terms of the rotor-to-stator pole ratio. Hence, the analytical design, finite element analysis and computer simulation of the proposed 8/6-pole DSPM motor are presented. The results show that this DSPM motor has following major features: it can achieve higher power density than an induction motor; its power density is proportional to the ratio of rotor pole and stator pole numbers; there is a maximum speed limitation which is proportional to the voltage but inversely proportional to the phase winding turns and the rate of change of PM flux; at high speed, the distribution of phase current is asymmetric and current regulation is needed in the negative stroke. Compared with the well known 6/4-pole DSPM motor, the proposed 8/6-pole one offers higher power density, wider speed range and less phase current magnitude.published_or_final_versio

Development of doubly salient permanent magnet motor flywheelenergy storage for building integrated photovoltaic system

With ever-increasing concerns on environmental protection, the full utilization of inexhaustible solar energy is highly desirable. In this paper, a new energy storage system is proposed which consists of a building integrated photovoltaic (BIPV) array, a DC-DC converter, a doubly salient permanent magnet (DSPM) motor drive incorporated with a high-speed flywheel, and an inverter. It has the advantages that the BIPV array is practically feasible in modern cities, while the DSPM motor flywheel offers high efficiency, long cycle life and environmental friendliness.published_or_final_versio

Design of a new non-rare-earth magnetic variable gear for hybrid vehicular propulsion system

This study presents the design of a new non-rare-earth magnetic variable gear (MVG) with 16 electrically controlled gear ratios, which incorporates both the concept of the magnetic gear and the concept of the memory machine. The high-remanence low-coercivity permanent magnet material: namely, the aluminium–nickel–cobalt is adopted to realise the controllable gear ratios. The key is to design the stationary ring newly integrated with magnetising windings in such a way that 16 sets of gear ratios can be achieved so as to fulfil different driving requirements and road conditions. First, the original MVG, the improved MVG and the proposed MVG are discussed. Then, a comprehensive analysis of the proposed MVG is conducted. Consequently, the proposed MVG is extended to electronic-continuously variable transmission for hybrid vehicular propulsion. By using finite element analysis, the electromagnetic performances of three MVGs at various gear ratios are evaluated, hence validating the theoretical design. Moreover, the process of gear-ratio-changing is simulated and analysed. A quantitative comparison among these MVGs is also carried out. Hence, the corresponding validity can be further verified.postprin

Static characteristics of a new doubly salient permanent magnet motor

In this paper, magnetic field analysis of a new doubly salient permanent magnet (DSPM) motor is carried out based on finite element method (FEM). Hence, the corresponding static characteristics, including PM flux linkage, self-inductance, mutual inductance, and static torque are deduced (the interaction between the PM field and armature field are taken into account). New methods for measuring the motor inductance are also proposed. The theoretical analysis is verified by experimental results.published_or_final_versio

Static characteristics of a new doubly salient permanent magnet motor

In this paper, magnetic field analysis of a new doubly salient permanent magnet (DSPM) motor is carried out based on the finite element method (FEM). Hence, the corresponding static characteristics, including PM flux-linkage, self-inductance and mutual-inductance, are deduced (the interaction between PM field and armature field are taken into account). A method for measuring the motor inductance is newly proposed. The theoretical analysis is verified by experimental results.published_or_final_versio