多机电力系统变结构励磁控制器的设计研究

基于多机电力系统的非线性模型,利用状态反馈精确线性化方法和变结构控制理论,提出了一种新的电力系统变结构励磁控制器设计方法。在设计中取消了参考机,并实现了多机系统的分散控制。3机系统的仿真结果表明,提出的变结构励磁控制器可以有效地改善系统在大干扰下的暂态稳定性。     

提高暂态稳定性的HVDC与发电机励磁的非线性最优协调控制

针对大扰动情形,为进一步提高交直流混合电力系统的暂态稳定性,提出了一种高压直流输电(HVDC)与发电机励磁协调的控制方法。通过建立HVDC系统与发电机的综合模型,将现代控制理论中直接反馈线性化方法与线性系统最优控制理论相结合,设计出一种HVDC与发电机励磁协调的非线性最优控制规律。仿真结果表明,该协调控制器能明显提高交直流互联系统的功角稳定性和频率稳定性,改善直流系统的性能。     

励磁装置的电磁兼容设计

励磁装置是发电机的主要辅机,其性能好坏直接关系到电力生产的可靠性。良好的电磁兼容设计是励磁装置品质的可靠保证,结合励磁装置的特点,主要从设备自身防护的角度重点论述励磁装置的交、直流侧过电压及过电压抑制,高次谐波及谐波抑制,可控硅同步及触发脉冲的噪声抑制,量测回路的噪声抑制等措施,测试试验及现场应用验证了其实用性。     

进口 15 000 m3/h空分装置同步电机励磁系统国产化技术改造

对邯钢动力厂引进前苏联的15000m^3／h制氧空气压缩机同步电动机软启动装置的控制以及励磁系统进行探讨研究。重点对国产化改造后的励磁系统与软启动装置相配合的有关技术理论问题进行了全面分析，并介绍了应用的效果。     

Simulating the Intensifying Effect of Phosphors on Imaging Plate with UV photons

It is assumed from the energy level that ultraviolet (UV) photons may have intensifying effect on BaFBr: Eu^2 .In this paper, effect of UV photons (220-290 nm) on the PSL intensity of X-ray irradiated BaFBr:Eu^2 was measured and compared to that on the PSL intensity of 220 nm photons irradiated BaFBr: Eu^2 . It was found that after the excitation of UV photons the PSL intensity of X-ray irradiated samples decreases least at 250 nm and that of 220 nm photons irradiated samples increases most at 250 nm. When the irradiation sources are X-rays and 220 nm photons the excited electrons are photoelectron and thermal-electrons, respectively, and they have different possibility of being captured by electron traps or combined with luminescent centers. And the peak at 250 nm can be explained with the model of electrons tunneling. It is assumed that the electrons excited by 250 nm have the most possibility of tunneling.     

Correlated fluorescence lifetime and spectral measurements in living cells

Studies of proteins' interaction in cells by FRET can take benefit from two important photo-physical properties describing fluorescent proteins: fluorescence emission spectrum and fluorescence lifetime. These properties provide specific and complementary information about the tagged proteins and their environment. However, none of them taken individually can completely quantify the involved fluorophore characteristics due to their multiparametric dependency with molecular environment, experimental conditions, and interpretation complexity. A solution to get a better understanding of the biological process implied at the cellular level is to combine the spectral and temporal fluorescence data acquired simultaneously at every cell region under investigation. We present the SLiM-SPRC160, an original temporal/spectral acquisition system for simultaneous lifetime measurements in 16 spectral channels directly attached to the descanned port of a confocal microscope with two-photon excitation. It features improved light throughput, enabling low-level excitation and minimum invasivity in living cells studies. To guarantee a fairly good level of accuracy and reproducibility in the measurements of fluorescence lifetime and spectra on living cells, we propose a rigorous protocol for running experiments with this new equipment that preserves cell viability. The usefulness of SLiM approach for the precise determination of overlapping fluorophores is illustrated with the study of known solutions of rhodamine. Then, we describe reliable FRET experiments in imaging mode realized in living cells using this protocol. We also demonstrate the benefit of localized fluorescence spectrum-lifetime acquisitions for the dynamic study of fluorescent proteins. proteins.     

The effects of refractive index heterogeneity within kidney tissue on multiphoton fluorescence excitation microscopy

Although multiphoton fluorescence excitation microscopy has improved the depth at which useful fluorescence images can be collected in biological tissues, the reach of multiphoton fluorescence excitation microscopy is nonetheless limited by tissue scattering and spherical aberration. Scattering can be reduced in fixed samples by mounting in a medium whose refractive index closely matches that of the fixed material. Using optical 'clearing', the effects of refractive index heterogeneity on signal attenuation with depth are investigated. Quantitative measurements show that by mounting kidney tissue in a high refractive index medium, less than 50% of signal attenuates in 100 μm of depth.     

Frequency characteristics of stiffness and damping effect of ferro fluid bearing

Damping characteristics and frequency characteristics of ferro fluid bearing (FFB) spindles were measured using a high-frequency vibration base driven by a piezo actuator. Using the high-frequency vibration base, high-frequency excitation was added to ferro fluid bearing spindles mounted on the vibration base, and it was proved that ferro fluid bearing spindles have effective damping. And the damping effect became larger with higher spindle rotational speed. Also we have measured spindle runout of a ferro fluid bearing spindle using a lock-in amplifier to increase S/N ratio and succeeded to measure nano meter order displacements.     

4Pi-confocal images with axial superresolution

We present two-photon excitation 4Pi-confocal images of clustered fluorescence beads demonstrating three-dimensional far-field light microscopy with unprecedented resolution. For an excitation wavelength of 760 nm, the lateral and axial resolution amounts to 200 and 145 nm, respectively. The four-fold improved axial resolution is achieved by engineering the point-spread function through a suitable combination of aperture enlargement, two-photon excitation, confocalization and three-point deconvolution. In contrast to their confocal counterparts, 4Pi-confocal images do not exhibit the typical axial elongation. The axial resolution in the 4Pi-confocal images corresponds to about one-fifth of the wavelength and surpasses the lateral resolution by 25%.     

考虑动作误差的低励限制与失磁保护定值配合方法研究

关于低励限制与失磁保护定值匹配的研究多聚焦于将其转换到同一功率平面或阻抗平面进行校核的方法,鲜有文献考虑实际装置动作特性对定值匹配结果的影响。该文从理论上详细分析各参数变化对失磁保护和低励限制的影响,提出基于装置动作误差的低励限制与失磁保护定值匹配校核原则,并论述定值失配时的定值调整方法,为当前各发电厂开展低励限制与失磁保护定值校核及整定提供了有效指导原则。