This paper proposed an approach to combining the recently developed FACTS and WAMS technologies to damp inter-area low-frequency oscillations and enhance transfer capability of interconnected power systems. The approach includes three steps: Firstly we use PRBS probing technique and N4SID to obtain a reduced-order model of the studied system. Then wide-area measurements are employed as feedback signals and an optimal damping control loop is designed via LQR approach for the FACTS controller in a multi-machine environment. Finally with communication delays of WAMS considered, a least square prediction algorithm is developed to derive instant feedback quantities, and thus make the proposed control practicable in real systems. To verify the effectiveness of the proposed approach, case study is fulfilled using a two-area four-machine power system with STATCOM, one of the most promising FACTS controllers, connected to the inter-area transmission. Extensive digital simulation results demonstrate its validity in damping inter-area power oscillation and enhancing transfer capability along long-distance tie lines.
Star trackers measure the attitude of a spacecraft by matching the stars captured by the camera and those stored in the onboard database, whose directions are already known. The information (i.e., location and brightness) on the stars in the captured image must be correctly and timely provided for star recognition. This process is called star centroid extraction. The hardware implementation of the star centroid extraction algorithm using parallel and pipelined architecture is a proper solution to ensuring higher accuracy as well as lower time cost. However, some limits restrict the performance of these kinds of algorithms. For example, faint stars, disturbing objects (e.g., the moon, bright planets, and so on), and noise pixels are not valid stars but resume a large amount of resource. Some irregularly shaped star spots may cause the algorithms to obtain inaccurate results. To solve these problems, this paper proposes a star centroid extraction method implemented on field programmable gate arrays (FPGAs) with a dynamic rooted tree architecture. In contrast to the traditional connected domain segmentation method, this method merges the equivalence table in the process of scanning, such that only one scan of the image is needed. Moreover, this method profits from a strict equivalence merging logic and can deal with various irregularly shaped star spots. Experiments are performed both on PC simulations and FPGA platforms, and results show that this method achieves good performance at a very low resource cost.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
With the launch of HD/SD multicast channel,we have entered a transitional period from SD to HD.This paper specifically discusses how to solve the problem of signal up and down conversion: the concrete realization of the hardware or software approach based on signal and file.Related to board structure,operational mode,as well as the analysis of the problems encountered in the practical application.
Correction for 'On-demand quantum spin Hall insulators controlled by two-dimensional ferroelectricity' by Jiawei Huang et al., Mater. Horiz., 2022, DOI: https://doi.org/10.1039/d2mh00334a.
We propose a setup that integrates a quantum point contact (QPC) and a Josephson junction on a quantum spin Hall sample, experimentally realizable in InAs/GaSb quantum wells. The confinement due to both the QPC and the superconductor results in a Kramers pair of Majorana zero-energy bound states when the superconducting phases in the two arms differ by an odd multiple of π across the Josephson junction. We investigate the detection of these Majorana pairs with the integrated QPC, and find a robust switching from normal to Andreev scattering across the edges due to the presence of Majorana Kramers pairs. Such a switching of the current represents a qualitative signature where multiterminal differential conductances oscillate with alternating signs when the external magnetic field is tuned. We show that this qualitative signature is also present in current cross-correlations. Thus, the change of the backscattering current nature affects both conductance and shot noise, the measurement of which offers a significant advantage over quantitative signatures such as conductance quantization in realistic measurements.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Here we report calculation of the differential interference angles (including b≤ρ and b≥ρ) for singlet-triplet mixed states of Na2(A1∑u+, v=8～b3П0u, v=14) system in collision with Na, in order to study the collision induced quantum interference on rotational energy transfer in an atom-diatom system. The calculation is based on the first-order Born approximation of time-dependent perturbation theory, and the anisotropic Lennard-Jones interaction potentials are also employed. The relationships between differential interference angle and impact parameter, including collision diameter and velocity, are obtained.
An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
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