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61.
With the application of an energy rebound circuit for the pulsewidth modulation (PWM)-controlled rectifier, an improved current source gate turn-off thyristor (GTO) inverter system capable of producing sinusoidal inputs and outputs is presented. The energy rebound circuit in the inverter is used to turn off the thyristors in the rectifier for applying PWM control techniques and also to clamp the spike voltage produced in the inverter circuit. The principles and circuit operations of this system are described in detail, and requirements for PWM control of the rectifier are investigated. The conditions for satisfying the requirements of the energy rebound circuit are analyzed by experimental and theoretical methods. The PWM-controlled current source GTO inverter system is used to drive an eight-pole 400 Hz 5.5 kW induction motor. Analytical and experimental results, as well as the characteristics of the motor drives, are given 相似文献
62.
Dissipation and superfluid density of a thin helium film (superfluid transition at temperature Tc=0.88 K), placed in 10 m porous glass are studied as a function of oscillation amplitude or AC amplitude at fixed temperatures near superfluid transition. The measurements are performed using a high-Q torsional oscillator in the free decay mode as well as constant drive mode. Results show decreasing superfluid density with increasing velocity and non-monotonic behavior of the dissipation in the film. 相似文献
63.
Naoyuki Kubota Yusuke Nojima Fumio Kojima Toshio Fukuda 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2006,10(10):891-901
The purpose of this study is to develop partner robots that can obtain and accumulate human-friendly behaviors. To achieve this purpose, the entire architecture of the robot is designed, based on a concept of structured learning which emphasizes the importance of interactive learning of several modules through interaction with its environment. This paper deals with a trajectory planning method for generating hand-to-hand behaviors of a partner robot by using multiple fuzzy state-value functions, a self-organizing map, and an interactive genetic algorithm. A trajectory for the behavior is generated by an interactive genetic algorithm using human evaluation. In order to reduce human load, human evaluation is estimated by using the fuzzy state-value function. Furthermore, to cope with various situations, a self-organizing map is used for clustering a given task dependent on a human hand position. And then, a fuzzy state-value function is assigned to each output unit of the self-organizing map. The robot can easily obtain and accumulate human-friendly trajectories using a fuzzy state-value function and a knowledge database corresponding to the unit selected in the self-organizing map. Finally, multiple fuzzy state-value functions can estimate a human evaluation model for the hand-to-hand behaviors. Several experimental results show the effectiveness of the proposed method. 相似文献
64.
A PWM inverter with an induction motor often has a problem with a leakage current that flows through the distributed electrostatic capacitance from the motor windings to the ground. The authors present an analytical model of the system with leakage current and the strategy to suppress it. Two types of suppression circuit are discussed. The current-type circuit, although compact in size, not only acts as an excellent suppressor but also becomes a high-performance filter of the output voltage 相似文献
65.
Rodrigo Scherer Paula Rossini Augusti Vivian Caetano Bochi Camila Steffens Leadir Lucy Martins Fries Ana Paula Daniel Ernesto Hashime Kubota João Radünz Neto Tatiana Emanuelli 《Food chemistry》2006,99(1):136-142
The effect of two slaughter methods (immersion in ice-water slurry and electrical stunning followed by ice slurry asphyxiation) on chemical and microbiological parameters of grass carp (Ctenopharyngodon idella) stored in ice for 20 days was evaluated. No differences in total volatile basic nitrogen (TVB-N), pH, carbohydrate or protein content of mucus were observed between the slaughter methods. Ice-slaughtered fish had lower bacteria counts at the beginning of storage, but higher counts than fish slaughtered by electricity at the end of storage (p < 0.05). However, no significant differences in the shelf life were observed between the slaughter methods evaluated (limit of acceptability – counts > 3 × 106 CFU g−1 – attained after 13–16 days). Results indicated that the chemical parameters evaluated have a limited applicability to assess the shelf life of grass carp stored in ice, since pH limit (6.8) was exceeded after 4 days, while TVB-N limit (30 mg%) was not attained after 20 days of storage. 相似文献
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68.
The usefulness of INR as an index for assessing anticoagulation was studied using 85 outpatients, all suffering cardiovascular diseases and receiving warfain as subjects. The thrombotest, prothrombin time and INR were measured at follow-up, monthly intervals. The correlation between the thrombotest value and the INR value were assessed retrospectively. We found a stronged correlation between them. The 10 approximately 25% range of the thrombotest value, the therapeutic range, corresponded to 2.29 approximately 3.60 of the INR value. The INR value was more accurate than the thrombotest valve in the situation of prolonged coagulation time. It is recommended to use INR as an objective index for the anticoagulation due to increase accuracy and objectivity when comparing the data among the various institutions. 相似文献
69.
M Narita Y Matsuzono Y Takekoshi S Yamada O Itakura M Kubota H Kikuta T Togashi 《Canadian Metallurgical Quarterly》1998,5(6):799-803
Rapid ventricular pacing (RVP) in dogs creates a well characterized model of dilated cardiomyopathy. Standard pacing protocols use RVP at 240-260 beats/min for 2-4 weeks, and result in high mortality rates if continued longer. The authors describe a modification of RVP that results in significant heart failure by 4 weeks, but can be continued for up to 10 weeks with low mortality. Nineteen mongrels underwent RVP at 215 beats/min for 10 weeks. Serial pressure-volume analysis and echocardiography were performed in this model to assess longitudinally changes in left ventricular (LV) function and volumes. The mortality rate was 10%. Significant progressive LV dysfunction with concomitant LV enlargement was observed throughout the pacing period. Finally, norepinephrine levels were elevated at the end of pacing, consistent with an activated sympathetic system. This modified RVP protocol permits long-term pacing with a low mortality rate and results in progressive heart failure throughout the pacing period. This model would be useful in the long-term evaluation of newer surgical and medical therapies of the failing heart. 相似文献
70.
A small, low-noise 0.78 μm-band laser diode unit, containing a Faraday rotator which suppresses optical feedback, was developed. Stable low-noise characteristics were realised within the 3 mW to 10 mW output power. Greater than 40 dB signal/noise ratio was obtained in an optical video disc with this unit 相似文献