汽轮机调速系统的自适应L2增益干扰抑制控制

提出一种预置反馈的方法,推导出汽轮机调速控制系统的端口受控哈密顿系统（PCHsystem)模型,进而根据PCH系统的自适应L2增益干扰抑制方法,设计汽轮机调速系统的控制规律,仿真结果表明,这种控制方法能有效抑制干扰,可以在大干扰条件下提高系统暂态稳定性。     

Nonparametric density estimation in presence of bias and censoring

We consider projection estimator methods for the nonparametric estimation of the density of i.i.d. biased observations with a general known bias function w and under right censoring. Adaptive procedures to catch the optimal estimator among a collection by contrast penalization are investigated and proved to give efficient estimators with optimal nonparametric rates of convergence. Monte-Carlo experiments complete the study and illustrate the method.     

汽轮发电机组的非线性分散干扰抑制控制

将非线性鲁棒控制理论应用于多机电力系统的汽轮调速控制系统。在耗散系统理论框架下,用递推设计的方法,构造汽轮发电机组的能量存储函数,以避免求解HJI不等式,从而得到多机系统汽轮调速的非线性L₂增益干扰抑制控制规律。控制策略的所有变量都是可量测的,而且控制量只与本机组的状态量有关,与其他机组的状态量和输电网络的参数无关,因而具有分散性。4机系统仿真结果表明,该控制规律可以提高电力系统的暂态稳定性。     

FACTS的PCH模型与自适应L2增益控制（一）理论篇

采用预置反馈方法,将电力系统中存在的一类仿射非线性系统转换为标准的哈密顿系统,从而导出了单机无穷大电力系统下SVC的PCH（端口受控哈密顿）模型,针对系统的外界干扰和参数不确定性问题,设计了相应的自适应L2增益控制规律,文中直接采用哈密顿函数作为存储函数,不仅保证了数学上的严密性,且具有明确的物理意义,仿真结果表明SVC采用自适应L2控制规律,不但可以确保系统渐近稳定,而且可以有效抑制干扰,对系统的工况具有自适应性。     

Titanium-based solid catalysts for transesterification of methyl-methacrylate by 1-butanol: the homogeneous catalysis contribution

Titanium-based solid catalysts were prepared according to two different procedures. In order to improve the stability of the SiOTi bond in the titanium grafted silica catalysts, the surface remaining hydroxyl groups were passivated to prevent the titanium leaching by SiOTi bond solvolysis. This was performed by grafting trimethoxy-silane groups on isolated silanols of silica, after or before metal grafting. The synthesised materials were characterised by FT-IR spectroscopy, and their catalytic properties evaluated in the reaction of transesterification of methyl-methacrylate (MMA) with 1-butanol (BuOH) in liquid phase to produce butyl-methacrylate (BuMA). An important titanium leaching (18–35%) was always detected with all the solid catalysts.

Investigation of the behaviour of Ti(OBu)₄ as homogeneous catalyst for very small concentrations of titanium was carried out in order to evaluate the catalytic contribution of the active dissolved species. We demonstrate here that the catalytic activity is mainly due to the homogeneous catalysis.     

Asymmetric Russian-doll model for semiconductor lasers

We demonstrate that the asymmetry of a high-power laser diode spectrum with its typical blue tail is related to frequency-dependent diffraction losses. A two-dimensional differential near-field analysis shows that the red longitudinal modes exhibit more self-focusing than the blue ones, reducing their diffraction losses, leading to as much as 20% variation of measured filament sizes in the plane parallel to the junction. The topological analysis of the far-field allows us to isolate the higher losses experienced by the blue modes, in agreement with a wavelength-dependent Kerr-lens model.     

Coherence of pulsed microwave signals carried by two-frequency solid-state lasers

This paper studies the coherence of the radio-frequency (RF) beat note between the two frequencies emitted by a two-eigenstate solid-state laser operating in pulsed regime. Depending on how the pulsed operation regime is obtained-passive Q switching using a saturable absorber or resonant amplitude modulation using pump-power modulation-we show theoretically and experimentally that the RF beat note loses or maintains its coherence from pulse to pulse. Namely, RF coherence is shown to be lost when the laser intensity vanishes between pulses, while it can be maintained if a slight amount of intensity remains inside the cavity between pulses. We give experimental demonstrations of these results for both Nd:YAG and Er-Yb:glass two-frequency pulsed lasers, in connection with applications to lidar-radar systems.     

Iterative space-time soft interference cancellation for UMTS-FDD uplink

Two efficient pilot-aided iterative space-time interference cancellation receivers are studied in order to increase the uplink capacity of the Universal Mobile Telecommunication System (UMTS) in frequency-division duplex (FDD) mode. Both iterative schemes use low-complexity beamforming and path combining techniques associated with soft-input soft-output decoding to mitigate the multiple-access interference in space and time. The difference between the two techniques is in the way they deal with unknown channels: the addition of a space-time channel estimation in each iteration on the one hand and iterative adaptive beamforming and path combining on the other hand. Thanks to the iterative structure, the observation signal used for estimation or adaptation contains less interference from one iteration to the following, and soft estimates of coded bits are available for data-aided estimation or adaptation. A detailed complexity analysis shows that renewing beamforming and path combining in each iteration without a-priori knowledge of the channel has no significant impact on the overall complexity of one iteration. Simulations of true UMTS-FDD uplink communications over a wideband directional channel model reveal that near-single user performance can be obtained for very high system loads, whereas more conventional receivers, such as the interference canceller without beamforming and the two-dimensional RAKE receiver, fail in recovering the transmitted information.     

Comparison between metoprolol orally osmotic once daily and metoprolol two or three times daily in suppressing exercise-induced and daily myocardial ischemia

Metoprolol is a widely used anti-ischemic drug with a relatively short half-life. To improve patient' compliance and to provide 24-hour coverage, its once daily ORally OSmotic (OROS) formulation was developed. In this multicenter double-blind study, the anti-ischemic effects of metoprolol OROS given once daily at doses of 190 and 285 mg were compared to the regular metoprolol formulation of 100 mg 2 or 3 times daily. Sixty-five patients with stable coronary artery disease, positive exercise tests, and ischemic episodes during daily activity as recorded by ambulatory electrocardiographic monitoring (AEM) were included. In the OROS group, 23 patients completed all 3 treatment periods. In these patients, the number of myocardial ischemic episodes decreased from 239 on placebo to 128 during the 190 mg/day dose (p < 0.0001) and to 86 during the 285 mg/day treatment period (p < 0.0001). In the metoprolol group, there were 204 episodes at baseline and 142 and 140 during the 100 mg 2 or 3 times daily treatment periods (p < 0.0001 for both). During exercise testing, time to 1-mm ST depression increased significantly in the OROS group from 6.3 minutes at baseline to 7.1 and 9.6 minutes during 190- and 285-mg treatment periods. In the metoprolol group, it increased from 5.8 to 7.2 and 8.2 minutes, respectively. Both formulations of metoprolol were well tolerated. The OROS formulation was highly effective in suppressing daily and exercise-induced ischemia and exerted its effect throughout the 24-hour period.