Effect of crosspath resistance between adjacent rotor bars onperformance of inverter-fed high-speed induction motor

The effects of crosspath resistance between adjacent rotor bars on steady state performance of inverter-fed high-speed cage induction motors are discussed. It is shown that the equivalent rotor resistance and leakage reactance change with crosspath resistance between adjacent rotor bars for various values of the fundamental supply frequency and the slip. The steady state characteristics of the high-speed induction motor drives for various crosspath resistance are discussed on the basis of theoretical and experimental results. The results of this research are applied in the design of a high-speed induction motor with uninsulated rotor bars     

Analysis of inverter-fed high-speed induction motor consideringcrosspath resistance between adjacent rotor bars

The purpose of this work is to analyze the steady state performance of an inverter-fed high-speed induction motor with trapezoidal rotor bars taking into account crosspath resistance between adjacent rotor bars. The performance of the induction motor drives for various crosspath resistances of two kinds of rotor slot shapes, a rectangular bar and a trapezoidal bar, is discussed on the basis of theoretical and experimental results of a 2.2 kW 500 Hz 15000 rev/min three-phase induction motor. It is also shown that the equivalent rotor resistance and leakage reactance change with crosspath resistance between adjacent rotor bars for various values of the fundamental supply frequency, the rotor slip, and the harmonics. The results of this research will be applied for design consideration of a high-speed induction motor with uninsulated rotor bars     

Rotor resistance adaptation for sensorless vector-controlled induction machines

The vector control method is widely used for induction motor drives. In these applications, a rotational transducer such as a shaft encoder is used. A rotational transducer, however, cannot be mounted in some cases, such as motor drives in a hostile environment or high-speed motor drives. Several sensorless vector-controlled induction machine drive methods have been proposed. These methods have the disadvantage that rotor resistance variation causes errors in the estimation of the motor speed. It is difficult to estimate the motor speed and the rotor resistance simultaneously, because the equivalent rotor resistance is the ratio of the rotor resistance to the slip at steady state. Therefore, we have proposed a method of simultaneously estimating the motor speed and the rotor resistance of an induction motor by superimposing ac components on the field current command. This paper presents a modified method of the rotor resistance adaptation. The validity of the proposed method is verified by experiments. © 1998 Scripta Technica, Electr Eng Jpn, 125(2): 65–72, 1998     

Electrochemical and structural study of Ce0.8Sm0.2−xLaxO1.9 electrolyte materials for SOFC

Ce_0.8Sm_0.2−xLa_xO_1.9 powders, denoted as La_xSDC (for x=0, 0.01, 0.03, 0.05, 0.07 and 0.1), were synthesized via the mechanical milling reaction method. The La³⁺ doping content has a remarkable influence on structural and electrical properties. The phase identification and morphology were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Lattice parameters were calculated by the Rietveld method. It was observed that the lattice parameter values in Ce_0.8Sm_0.2−xLa_xO_1.9 systems obey Vegard's law. The pellets were then sintered at 1500 °C in air for 7 h. The relative densities of these pellets were over 93.7%.The electrical conductivity was studied using two-probe impedance spectroscopy and results showed that the conductivity of Ce_0.8Sm_0.2−xLa_xO_1.9 first increased and then decreased with La dopant content x. Results also showed that Ce_0.8Sm_0.17La_0.03O_1.9 had the highest electrical conductivity, σ₇₀₀ °C equal to 3.8×10⁻² Scm⁻¹ and an activation energy equal to 0.77 eV. It was therefore concluded that co-doping with the appropriate amount of La can further improve the electrical properties of ceria electrolytes.     

Effects of Silica and Titanium Oxide Particles on a Human Neural Stem Cell Line: Morphology,Mitochondrial Activity,and Gene Expression of Differentiation Markers

Several in vivo studies suggest that nanoparticles (smaller than 100 nm) have the ability to reach the brain tissue. Moreover, some nanoparticles can penetrate into the brains of murine fetuses through the placenta by intravenous administration to pregnant mice. However, it is not clear whether the penetrated nanoparticles affect neurogenesis or brain function. To evaluate its effects on neural stem cells, we assayed a human neural stem cell (hNSCs) line exposed in vitro to three types of silica particles (30 nm, 70 nm, and <44 μm) and two types of titanium oxide particles (80 nm and < 44 μm). Our results show that hNSCs aggregated and exhibited abnormal morphology when exposed to the particles at concentrations ≥ 0.1 mg/mL for 7 days. Moreover, all the particles affected the gene expression of Nestin (stem cell marker) and neurofilament heavy polypeptide (NF-H, neuron marker) at 0.1 mg/mL. In contrast, only 30-nm silica particles at 1.0 mg/mL significantly reduced mitochondrial activity. Notably, 30-nm silica particles exhibited acute membrane permeability at concentrations ≥62.5 μg/mL in 24 h. Although these concentrations are higher than the expected concentrations of nanoparticles in the brain from in vivo experiments in a short period, these thresholds may indicate the potential toxicity of accumulated particles for long-term usage or continuous exposure.     

Frequency- and time-domain analyses of nonuniform lossy coupledtransmission lines with linear and nonlinear terminations

A new technique for the frequency- and time-domain characterization of nonuniform coupled transmission lines is presented in this paper. In the frequency domain, a method-of-moments-based approach is used to compute the 2N×2N scattering parameter matrix of the N-coupled lines using special frequency-dependent basis functions that give good accuracy over very large bandwidths. In the time domain, the structure's S-parameters are used as its Green's function and are combined with source and terminating load conditions to obtain its transient response. The proposed method can account for loss and is particularly suitable for wideband microwave component designs and ultrahigh-speed/large-bandwidth digital interconnects, including nonlinear terminating loads. A detailed formulation of both the frequency- and time-domain approaches is presented. Several examples of two- and three-line structures are analyzed and the results are compared to published results and other computer-aided-design simulations     

Design of dome-shaped non-imaging Fresnel lenses taking chromatic aberration into account

Concentration PV system is a technology for providing solar-based electricity at very high conversion efficiency of 40%. It needs solar concentration of 500 suns or more, for which the authors developed dome-shaped non-imaging Fresnel lenses with a certain acceptance half angle. As conventional design method uses only one wave length, the performance suffers from chromatic aberration. In this paper, a new design method is proposed. One of the points is that it uses two kinds of design wave length which covers a given range of solar spectrum for the concentration. The other is that new design points are located on the corners of prisms while the conventional point is at the center of prisms. Numerical examples with the concentration ratio of 500 were designed and optical efficiency was examined by ray tracing simulation. The results indicate that the lens based on the conventional way has dish-like shape and the lenses designed by the proposed method have relatively deep dome shape in contrast. The optical efficiency of the new design is better than that of the conventional one at the incident angle equal to the acceptance half angle. It was concluded that the proposed method could produce more effective solar concentrator with a certain tolerance of solar incident angle.     

High-throughput formulation screening system for self-microemulsifying drug delivery

Purpose: To develop a high-throughput formulation screening (HTFS) system for self-microemulsifying drug delivery system (SMEDDS) formulations. Methods: Formulations were prepared by dispensing surfactants and a model compound (Nilvadipine) dissolved in ethanol and oil with a robotic liquid dispenser. Screenings of emulsion particle size and phase stability were conducted for selecting SMEDDS formulations by a turbidity assay. Results: Formulations were prepared at 40 minute/96-formulation. Both the screenings were conducted at 1 minute/96-formulation. SMEDDS formulations and the most suitable hydrophilic surfactant (HS)/lipophilic surfactant (LS) combination, which formed the largest SMEDDS area on its corresponding phase diagram, were selected by SMEDDS–HTFS system with minimal manpower (one person) and compound consumption (0.2 mg/formulation). Conclusions: SMEDDS–HTFS system enabled rapid and efficient selections of SMEDDS formulations and the most suitable HS/LS combination for SMEDDS.     

Denaturation of egg antigens by cooking

Changes in egg protein contents by cooking were measured with an ELISA kit using Tris-HCl buffer in model foods including cake, meatballs, pasta and pudding made with whole egg, egg-white and egg-yolk. The egg protein contents were lowest in the deep-fried model foods of cakes and meatballs. Ovalbumin (OVA) was undetectable (<1 μg/g) and ovomucoid (OVM) was lowest in pouched meatballs, suggesting that processing temperature and uniform heat-treatment affect the detection of egg protein. Furthermore, egg protein contents were below 6 μg/g in the pouched meatballs and pasta made with egg-yolk, and OVA and OVM were not detected by Western blotting analysis with human IgE from patients' serum. On the other hand, processed egg proteins were detected with an ELISA kit using a surfactant and reductant in the extract buffer.