双主电源并联运行的微电网小信号稳定性分析与控制参数优化北大核心

在基于多主从电源控制的微电网系统中,主电源逆变器的控制参数对系统的稳定性和动态性能有着至关重要的影响。文中以含有两个主电源的双主电源为电网系统为例,首先介绍了系统的控制方式,然后对系统建立了详细的小信号模型,通过计算系统状态矩阵的特征值和参与因子,分析了系统的稳定性和动态性能。在此基础上提出了含有根轨迹法与粒子群算法的控制参数综合优化方案,对逆变器的控制参数进行了协调优化,仿真和实验结果验证了参数优化方案的有效性。     

Single-element ultrasound transducer for combined vessel localization and ablation

This report describes a system that utilizes a single high-intensity focused ultrasound (HIFU) transducer for both the localization and ablation of arteries with internal diameters of 0.5 and 1.3 mm. In vitro and in vivo tests were performed to demonstrate both the imaging and ablation functionalities of this system. For imaging mode, pulsed acoustic waves (3 cycles for in vitro and 10 cycles for in vivo tests, 2 MPa peak pressure) were emitted from the 2-MHz HIFU transducer, and the backscattered ultrasonic signal was collected by the same transducer to calculate Doppler shifts in the target region. The maximum signal amplitude of the Doppler shift was used to determine the location of the target vessel. The operation mode was then switched to the therapeutic mode and vessel occlusion was successfully produced by high-intensity continuous HIFU waves (12 MPa) for 60 s. The system was then switched back to imaging mode for residual flow to determine the need for a second ablation treatment. The new system might be used to target and occlude unwanted vessels such as vasculature around tumors, and to help with tumor destruction.     

Diisopropylammonium chloride: a ferroelectric organic salt with a high phase transition temperature and practical utilization level of spontaneous polarization

A simple organic salt, diisopropylammonium chloride, shows the highest ferroelectric phase transition temperature among molecule-based ferroelectrics with a large spontaneous polarization, making it a candidate for practical technological applications.     

基于小波变换的硬拷贝全息水印

提出一种基于离散小波变换的硬拷贝数字全息水印方法。首先利用共轭对称延拓傅里叶计算全息生成水印全息图;然后对其进行小波分解,将包含全部水印信息的高频分量嵌入到载体图像小波分解的中频区域以实现信息隐藏。由于全息图的频谱可控性和不可撕毁性,本文全息水印方法具有很好的不可见性,可以实现水印盲提取,不仅能够抵抗剪切、噪声、滤波和...     

Purification, cloning, expression and immunological analysis of Scylla serrata arginine kinase, the crab allergen

BACKGROUND: Although crustaceans have been reported to be one of the most common causes of IgE‐mediated allergic reactions, there are no reports about the characterization and identification of arginine kinase (AK) from the mud crab (Scylla serrata) as allergen. In the present study, the purification, molecular cloning, expression and immunological analyses of the IgE allergen AK from the mud crab were investigated. RESULTS: The results showed that cloned DNA fragments of AK from the mud crab had open reading frames of 1021 bp, predicted to encode proteins with 356 amino acid residues. Sequence alignment revealed that mud crab AK shares high homology with other crustacean species. Mud crab AK gene was further recombined with the vector of pGEX‐4T‐3 and expressed in Escherichia coli BL 21. 2‐D electrophoresis suggested that native AK (nAK) and recombinant AK (rAK) shared the same molecular weight of 40 kDa, and the pI is 6.5 and 6.3, respectively. The nAK and rAK were further confirmed by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry. Immunoblotting analysis and colloidal gold immunochromatographic assay (GICA) using sera from subjects with crustacean allergy confirmed that the nAK and rAK reacted positively with these sera, indicating AK is a specific allergen of mud crab. CONCLUSION: Both of purified nAK and rAK reacted positively with sera from subjects with crustacean allergy in immunoblotting and GICA analysis, indicating AK is a common allergen of mud crab. In vitro expressed AK is proposed as a source of the protein for immunological or clinical studies. Copyright © 2011 Society of Chemical Industry     

Implementation of vibrational phase contrast coherent anti-Stokes Raman scattering microscopy

Detection of molecules using vibrational resonances in the fingerprint region for narrowband coherent anti-Stokes Raman scattering (CARS) is challenging. The spectrum is highly congested resulting in a large background and a reduced specificity. Recently we introduced vibrational phase contrast CARS (VPC-CARS) microscopy as a technique capable of detecting both the amplitude and phase of the CARS signal, providing background-free images and high specificity. In this paper we present a new implementation of VPC-CARS based on a third-order cascaded phase-preserving chain, where the CARS signal is generated at a single (constant) wavelength independent of the vibrational frequency that is addressed. This implementation will simplify the detection side considerably.     

棕榈油精炼的改进措施

棕榈油和它的分提物的物理精炼,是目前马来西亚广泛采用的精炼方法。在同时进行水蒸汽脱酸和脱臭过程之前,通常先有一个预处理工段,包括酸的调节,活性白土的吸附和过滤。在预处理工段除去胶质和微量金属杂质的效率,对于水蒸汽精炼后的油的质量有重大的影响。本文将讨论一些可采用的预处理方法,着重评价它们在改进物理精炼棕榈油产品质量方面的效果和提高物理精炼过程的效率。这些方法包括用酸和用水脱胶,分步白土脱色,用活性炭吸附和湿法脱色。也将谈及在水蒸汽蒸馏方面已经达到工厂实际应用规模的其他改进方法,包括增添筛板塔或填料塔做为脱酸的预蒸馏塔。