A 2-V, 1-10 GHz BiCMOS transceiver chip for multimode wirelesscommunications networks

This paper concerns the design consideration, fabrication process, and performance results for an ultra-broadband, low-voltage, low-power, BiCMOS-based transceiver chip for cellular-satellite-LAN wireless communication networks. The transceiver chip incorporates an RF amplifier, a Gilbert down-mixer, and an IF amplifier in the receive path, and an IF amplifier, a Gilbert up-mixer, and an RF amplifier in the transmit path. For an RF frequency in the 1-10 GHz band and an IF frequency in the 100-1000 MHz band, the developed transceiver chip consumes less than 60 mW at 2 V, to yield a downconversion gain of 40 dB at 1 GHz and 10 dB at 10 GHz and an upconversion gain of 42 dB at 1 GHz and 11 dB at 10 GHz. To avoid possible start-up problems caused during “stand-by” to “enable” mode transition, a simple switching technique is employed for enabling either the receive or the transmit path, by changing the value of a reference voltage applied to both the down- and the up-mixers. While the developed transceiver chip exhibits the best performance for a dc supply voltage of 2 V, it shows a graceful degradation for a ±0.15 V voltage deviation. The transceiver's chip size is 1.04 mm×1.04 mm     

A Novel Approach to Detect Faults Occurring During Power Swings by Abrupt Change of Impedance Trajectory

The main purpose of power swing blocking is to distinguish faults from power swings. However, faults occurred during a power swing should still be detected and cleared promptly. This paper proposes an index based on detecting abrupt jump of impedance trajectory by utilization of the predicting capability of the Kalman Filter. The proposed index is calculated by assessing the difference between predicted and actual samples of impedance. The predicted impedance samples are obtained using the Kalman filter and Taylor expansion, which are used in this paper to track the phasor precisely. Second order of Taylor expansion is used to decrease the corrugation effect of impedance estimation and increase the reliability of the proposed method. Furthermore, in order to increase the selectivity of the proposed method, the proposed index is armed with phase comparison logic to detect internal faults. The instantaneous estimation and prediction capability of the Kalman filter are two reasons for proposing the use of Kalman filter. Intensive studies have been performed and the merit of the method is demonstrated by test simulations.     

基于无谐波检测和选择性谐波补偿原理的组合式同相供电系统控制策略

针对组合式同相供电系统同相补偿装置(CCD)的常规控制方法受负载电流检测精度影响严重,且不能良好跟踪高速铁路负载高次谐波电流的缺陷,提出一种选择性谐波电流控制策略。该控制策略仅需要保留CCD的两单相变流器输出电压、电流的检测部分,不需要检测负载电流;并通过矢量比例积分控制器对连接负载的单相变流器输出电流误差中的各次谐波单独跟踪。该设计方法不受负载电流检测精度的影响,对牵引负荷各个频段谐波都具有良好的跟踪性能。利用MATLAB/Simulink搭建组合式同相供电的常规控制模型、改进控制模型和基于改进控制策略的半桥四臂模块化多电平电路模型,对交-直型、交-直-交型、混跑3种负载分别进行控制,仿真验证了改进电流控制方法的正确性以及在实际工程实现中的有效性。     

Control system of a linear induction accelerator of an X-ray complex: Structure,hardware, and test performance

The structure, operation logic, and hardware tools of the control system of a linear induction accelerator for an X-ray complex are considered. The hardware developed in the CompactPCI standard for the control system is described. The possibility of embedding of smart microelectronic equipment into high-voltage elements of the facility is analyzed.     

A prospective study of unplanned endotracheal extubation in intensive care unit patients

OBJECTIVE: To evaluate incidence, factors associated with unplanned endotracheal extubation (UEE), and prognostic factors for reintubation. DESIGN: A prospective study over a 32-mo period. SETTING: A 16-bed general intensive care unit of a tertiary university hospital. PATIENTS: Adult subjects undergoing endotracheal intubation for >48 hrs. INTERVENTIONS: Observation of patients who presented unplanned extubation. MEASUREMENTS AND MAIN RESULTS: Over the 32-mo period, there were 59 episodes of UEE in 55 patients (frequency 7.3%). Deliberate self-extubation occurred in 46 episodes (77.9%), while there were 13 episodes (22.1%) of accidental extubation. Twenty-seven (45.8%) episodes occurred in patients who were receiving full mechanical ventilatory support and 32 (54.2%) episodes occurred during the weaning period from mechanical ventilation. Reintubation was required in 27 (45.8%) episodes of UEE. The need for reintubation after UEE was 36.9% in deliberate self-extubation patients and 76.9% in accidental extubation patients (p = .01). Only 15.6% (5/32) of patients who presented UEE during weaning required reintubation, while reintubation was mandatory in 81.5% (22/27) of patients who presented UEE during full mechanical ventilatory support (p < .001). A multiple logistic regression analysis was performed to determine the variables independently associated with the need for reintubation: days of mechanical ventilation were significantly associated with the need for reintubation, and weaning was associated with no need for reintubation. The model correctly classified the need for reintubation in 84.7% (50/59) of cases. CONCLUSIONS: Reintubation in UEE patients strongly depends on the type of mechanical ventilatory support. The probability of requiring reintubation if UEE occurs during full ventilatory support is higher than if UEE occurs during weaning. These data suggest that some patients are under mechanical ventilation longer than necessary.     

Tip loss corrections for wind turbine computations

As an essential ingredient in the blade element momentum theory, the tip loss effect of rotors plays an important role in the prediction of wind turbine performance. Various tip loss corrections based on the Prandtl tip loss function are analysed in the article. Comparisons with measurements and theoretical analyses show that existing tip loss correction models are inconsistent and fail to predict correctly the physical behaviour in the proximity of the tip. A new tip loss correction model is proposed that remedies the inconsistency. Comparisons between numerical and experimental data show that the new model results in much better predictions of the loading in the tip region. Copyright © 2005 John Wiley & Sons, Ltd.     

Why are most drowning victims men? Sex differences in aquatic skills and behaviors

Two biopsy cases of elastofibroma--one unilateral and one bilateral--are described. A study of 100 autopsies revealed 13 elderly patients with elastofibroma. Males (n = 10; 16.9%) were more affected than females (n = 3; 7.3%). Pre-elastofibroma-like morphological changes (e.g. few or many degenerated elastic fibres) were observed in 81% of the autopsies. Minor pre-elastofibroma-like changes were seen in males and major changes predominantly in females. In addition to physiological ageing as yet unknown factors, rather than abnormal elastogenesis or degeneration, seem to be involved in this pseudotumour.     

Work Function of PbZrO3

This paper reports the results of work function (WF) changes of undoped PbZrO₃ during subsequent isothermal oxidation and reduction experiments at 500°C in the p(O₂) range between 10 and 2.1 × 10⁴ Pa. The results, obtained during three consecutive runs, indicate that heating at 500°C leads to continuous changes of surface properties resulting in a complex WF vs. time characteristic. The WF changes during the first oxidation are determined by a p(O₂)-induced structural transition. The second oxidation results in two competitive processes, such as rapid increase of oxygen non-stoichiometry followed by a structural transition. Finally, the third oxidation is determined by changes of oxygen nonstoichiometry.