抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

System Identification I

This chapter contains sections titled: Historical Review Supervised Multilayer Networks Unsupervised Neural Networks: Kohonen Network Unsupervised Networks: Adaptive Resonance Theory Network Model Validation Summary References Recommended Exercises

Nonlinear System Identification

https://www.tandfonline.com/doi/pdf/10.1080/14686996.2018.1530938

Thermoelectric materials and applications for energy harvesting power generation

Representation of ac power systems by frequency-dependent impedance equivalents is an emerging technique in the dynamic analysis of power systems including power electronic converters. The technique has been applied for decades in dc-power systems, and it was recently adopted to map the impedances in ac systems. Most of the work on ac systems can be categorized into two approaches. One is the analysis of the system in the dq domain, whereas the other applies harmonic linearization in the phase domain through symmetric components. Impedance models based on analytical calculations, numerical simulation, and experimental studies have been previously developed and verified in both domains independently. The authors of previous studies discuss the advantages and disadvantages of each domain separately, but neither a rigorous comparison nor an attempt to bridge them has been conducted. This paper attempts to close this gap by deriving the mathematical formulation that shows the equivalence between the dq -domain and the sequence-domain impedances. A modified form of the sequence-domain impedance matrix is proposed, and with this definition the stability estimates obtained with the generalized Nyquist criterion become equivalent in both domains. The second contribution of this paper is the definition of a mirror frequency decoupled (MFD) system. The analysis of MFD systems is less complex than that of non-MFD systems because the positive and negative sequences are decoupled. This paper shows that if a system is incorrectly assumed to be MFD, this will lead to an erroneous or ambiguous estimation of the equivalent impedance.

/pdf/a-modified-sequence-domain-impedance-definition-and-its-5r7590os6t.pdf

A Modified Sequence-Domain Impedance Definition and Its Equivalence to the dq-Domain Impedance Definition for the Stability Analysis of AC Power Electronic Systems

Grid impedance affects the stability and control performance of grid-connected power electronic devices, such as inverters used to integrate wind and solar energy. Adaptive control of such inverters, to guarantee stability under different grid conditions, requires online measurement of the grid impedance performed in real time. Such online measurement can be performed by injecting a current perturbation from the inverter into the grid and by reading the grid voltage responses. To minimize the impact on the inverter operation, the injection must be kept as small as possible while producing enough voltage perturbation that can be reliably measured and processed to extract its various frequency components. This paper proposes the use of a discrete-interval binary sequence (DIBS) for this application to minimize the injection. The DIBS is a computer-optimized binary sequence, where the energy is maximized at specified harmonic frequencies based on the expected grid-impedance characteristics. Experimental results based on a three-phase grid-connected inverter are presented to demonstrate the effectiveness of the proposed methods.

Online Grid Impedance Measurement Using Discrete-Interval Binary Sequence Injection

Grid impedance and the output impedance of grid-connected inverter are important parameters for the operation of grid-connected systems, such as solar, wind, and other distributed-generation resource systems. The impedance mismatch between the grid and the interfacing circuit often generates harmonic resonances that lead to reduced power quality and even instability. Since the impedances usually vary over time as a function of many parameters, online measurements are required for stability assessment and adaptive control of the inverters. Several methods have been proposed for quick, accurate measurements of impedances, but the use of multiple-input multiple-output (MIMO) identification techniques have not been considered. Applying the MIMO techniques, different components of the inverter output impedance or grid impedance can be simultaneously measured during a single measurement cycle. Therefore, the operating conditions of the system can be kept constant during the measurements, and the overall measurement time is significantly reduced. This paper shows the use of orthogonal binary sequences to simultaneously measure the “d” and “q” components of grid-connected inverter output impedance and/or grid impedance. Experimental results based on a three-phase grid-connected inverter are presented and used to demonstrate the effectiveness of the proposed methods.

MIMO-Identification Techniques for Rapid Impedance-Based Stability Assessment of Three-Phase Systems in DQ Domain

Grid impedance is an important parameter for the operation and control of grid-connected inverters used for the integration of solar, wind, and other distributed generation resources. Since the grid impedance usually varies over time and with grid operation conditions, online measurement is required for adaptive control of grid-connected inverters. Existing online measurement methods based on impulse perturbation and Fourier analysis require large current or voltage injection that may interfere with normal operation of the inverter. This paper proposes the use of maximum-length binary sequence (MLBS) injection and averaging Fourier techniques to overcome the drawbacks of impulse injection. Experimental results based on a three-phase grid-connected inverter are presented and used to demonstrate the effectiveness of the proposed methods.

Broadband methods for online grid impedance measurement

Grid impedance affects the stability and control performance of grid-connected power electronic devices such as inverters used to integrate wind and solar energy. Adaptive control of such inverters to guarantee stability under different grid conditions requires real-time measurement of the grid impedance performed online by the inverters themselves. Existing online measurement methods based on broadband excitations such as maximum-length binary sequence (MLBS) require relatively high injection that may interfere with normal grid control functions, or degrade inverter output current quality, especially when the grid impedance is low and a high current needs to be injected in order to produce sufficient voltage perturbation. This paper proposes the use of a discrete-interval binary sequence (DIBS) for such cases. The DIBS is a computer-optimized binary sequence where the energy is maximized at specified harmonic frequencies to minimize the required level of signal injection. Experimental results based on a three-phase grid-connected inverter are presented to demonstrate the effectiveness of the proposed methods.

Online grid impedance measurement using discrete-interval binary sequence injection

Many modern commercial ships are electric ships, i.e., they utilize integrated electric propulsion (IEP ), where electric motors with variable speed drives are used for ship propulsion. This provides a number of advantages, such as reduced size and weight, electric power availability aboard the ship, reduced vibration, and more flexibility in generation engine placement by eliminating the mechanical connection between engines and propulsion. Most cruise ships, many yachts, and even cargo ships utilize IEP. There is also significant interest in IEP for military ships.

Tomi Roinila

Papers

Online Grid Impedance Measurement Using Discrete-Interval Binary Sequence Injection

MIMO-Identification Techniques for Rapid Impedance-Based Stability Assessment of Three-Phase Systems in DQ Domain

Broadband methods for online grid impedance measurement

Online grid impedance measurement using discrete-interval binary sequence injection

Stability of Shipboard DC Power Distribution: Online Impedance-Based Systems Methods