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With the large-scale development of offshore wind power, the suitable access point to power grid for offshore wind farm is more beneficial for voltage source converter high voltage direct current (VSC-HVDC) power transmission. Aiming at large scale offshore wind farm integrated by the VSC-HVDC, the evaluation indexes of wind power accommodation capability, grid voltage stability, grid-connected point vulnerability and construction cost were proposed by analyzing the main influencing factors of grid-connected. Based on the theory of information entropy and fuzzy analytic hierarchy process, a combination weighting model was established to determine the index weights, , and a comprehensive optimization method of access point selection was proposed. Simulation results of eastern Shandong power grid of China integrated with offshore wind farm demonstrate that the proposed method enhances the capability of wind power accommodation and improves the security and stability of power grid.

New energy power sources can be categorized into grid-following and grid-forming types based on their synchronization characteristics with the grid. Due to the different basic control operation principles of these two types of new energy power sources, they can lead to the instability of the grid-connected system through different paths. A mathematical model is established to describe the dynamic characteristics of the grid-following and the grid-forming new energy power resources, and the control block diagram of the nonlinear dynamic characteristic equation is compared and analyzed. The similarity between grid-following and grid-forming new energy power supply is revealed, and we preliminarily discuss the influencing factors of the stability of new energy sources. Using a single-machine infinite system model, the influence of key control parameters on transient stability is separately investigated for grid-following and grid-forming types. The influence of the converter synchronous loop control parameters on the system is verified, and the factors affecting the stability are discussed in combination with current limiting and frequency limiting. The research will provide reference for the design of a new energy power grid connection system. [ABSTRACT FROM AUTHOR]

Bundled networks, obtained by attaching a copy of a fiber structure to each node on the base structure, serve as important realistic models for the geometry and dynamics of nontranslationally invariant systems in condensed matter physics. Here, we analyze the first-passage properties, including the mean first-passage time, the mean-trapping time, the global-mean first-passage time (GFPT), and the stationary distribution, of a biased random walk within such networks, in which a random walker moves to a neighbor on base with probability γ and to a neighbor on fiber with probability 1 − γ when the walker at a node on base. We reveal the primary properties of both the base and fiber structure, which govern the first-passage characteristics of the bundled network. Explicit expressions between these quantities in the bundled networks and the related quantities in the component structures are presented. GFPT serves as a crucial indicator for evaluating network transport efficiency. Unexpectedly, bases and fibers with similar scaling of GFPT can construct bundled networks exhibiting different scaling behaviors of GFPT. Therefore, bundled networks can be tailored to accommodate specific dynamic property requirements by choosing a suitable base and fiber structure. These findings contribute to advancing the design and optimization of network structures. [ABSTRACT FROM AUTHOR]

The Eccentric Connectivity Index (ECI) and Eccentric Distance Sum (EDS) are two important topological indices with wide applications in biology and chemistry. The Vicsek Fractal (VF) is a notable structure in both polymer physics and network science, and is also known as a regular hyperbranched polymer in the academic realm. In this study, the ECI and EDS of the VF are evaluated analytically by exploring the self-similarity of the structure. First, we derive the recurrence formulas for the ECI and EDS with respect to the generation t of the VF. Then, exact results for the ECI and EDS of the VF are obtained by solving the recurrence relations. The results indicate that the ECI and EDS of the VF scale with a network size of N t are ECI ∼ N t 1 + log p + 1 3 and EDS ∼ N t 2 + 2 log p + 1 3 , respectively. The results obtained not only reveal the biological activity and physical properties of the VF but also shed light on the control of the beamwidth in the azimuth plane and the design of the maglev centrifugal blood pump. [ABSTRACT FROM AUTHOR]

A class of self-similar networks, obtained by recursively replacing each edge of the current network with a well-designed structure (generator) and known as edge-iteration networks, has garnered considerable attention owing to its role in presenting rich network models to mimic real objects with self-similar structures. The generator dominates the structural and dynamic properties of edge-iteration networks. However, the general relationships between these networks' structural and dynamic properties and their generators remain unclear. We study the fractal and first-passage properties, such as the fractal dimension, walk dimension, resistance exponent, spectral dimension, and global mean first-passage time, which is the mean time for a walker, starting from a randomly selected node and reaching the fixed target node for the first time. We disclose the properties of the generators that dominate the fractal and first-passage properties of general edge-iteration networks. A clear relationship between the fractal and first-passage properties of the edge-iteration networks and the related properties of the generators are presented. The upper and lower bounds of these quantities are also discussed. Thus, networks can be customized to meet the requirements of fractal and dynamic properties by selecting an appropriate generator and tuning their structural parameters. The results obtained here shed light on the design and optimization of network structures. [ABSTRACT FROM AUTHOR]

Introduction: Whether time window affects the intravenous thrombolysis (IVT) effect before endovascular thrombectomy (EVT) is uncertain. We aimed to investigate the effect of different time windows (0–3 h and >3–4.5 h from stroke onset to randomization) on clinical outcomes of EVT with or without IVT in a subgroup analysis of DIRECT-MT. Methods: The primary outcome was the 90-day modified Rankin Scale (mRS) according to time window. Logistic regression models were used to analyze the effect of different treatments (EVT with or without IVT) on outcomes within 0–3 h or >3–4.5 h. Results: Among 656 patients who were included in the analysis, 282 (43.0%) were randomized within >3–4.5 h after stroke onset (125 without IVT and 157 with IVT), and 374 (57.0%) were randomized within 0–3 h (202 without IVT and 172 with IVT). We noted no significant difference in the thrombectomy-alone effect between the time window subgroups according to 90-day ordinal mRS (adjusted common odds ratio [acOR] in patients within 0–3 h: 1.06 [95% CI: 0.73–1.52], acOR in patients within >3–4.5 h: 1.19 [95% CI: 0.78–1.82]) and 90-day functional independence. Thrombectomy alone resulted in an increased proportion of patients with 90-day mRS 0–3 treated within >3–4.5 h (62.90 vs. 48.72%) but not within 0–3 h (65.84 vs. 63.95%). However, there was no interaction effect regarding all outcomes after the Bonferroni correction. Conclusions: Our results did not support thrombectomy-alone administration within 3–4.5 h in patients with acute ischemic stroke from large-vessel occlusion in the subgroup analysis of DIRECT-MT. [ABSTRACT FROM AUTHOR]

Semi-coke is the coproduct of low-rank coal in the preparation of oil and gas, but the current utilization rate of fine-powder semi-coke is low, which limits the development of the low-rank coal pyrolysis industry. This paper uses the numerical simulation method to study the co-combustion characteristics of a large proportion of bituminous coal mixed with semi-coke in a swirl burner. The results show that, in the primary combustion region, with the increase of the blend ratio of semi-coke, the flue gas temperature and NO concentration are lower, and the O2 concentration increase is higher. In the over-fired air (OFA) nozzle area, with the increase of the blend ratio of semi-coke, the flue gas temperature and NO concentration are higher, and O2 concentration is lower. In addition, with the increase of the blend ratio of semi-coke, the main combustion position of the fuel is transferred to the vicinity of the OFA nozzle area, which weakens the degree of air-staging combustion of the furnace. The synergistic effect of co-combustion of semi-coke and bituminous coal helps to reduce the NO concentration at the furnace outlet and improve the combustion efficiency. By comprehensive considering the stable operation of the boiler, burnout rate, and NO emission concentration, the recommended blend ratio of semi-coke should not exceed 60%. [ABSTRACT FROM AUTHOR]

Given an arbitrary connected graph G, the n-polygon graph $ \tau _n(G) $ τ n (G) is obtained by adding a path with length n $ (n\geq ~2) $ (n ≥ 2) to each edge of graph G, and the iterated n-polygon graphs $ \tau _n^g(G) $ τ n g (G) ( $ g\geq ~0 $ g ≥ 0) are obtained from the iteration $ \tau _n^g(G)=\tau _n(\tau _n^{g-1}(G)) $ τ n g (G) = τ n (τ n g − 1 (G)) , with the initial condition $ \tau _n^0(G)=G $ τ n 0 (G) = G. In this paper, a method for calculating the eigenvalues of the normalized Laplacian matrix for graph $ \tau _n(G) $ τ n (G) is presented if the eigenvalues of a normalized Laplacian matrix for graph G is first given. The normalized Laplacian spectra for the graph $ \tau _n(G) $ τ n (G) and graphs $ \tau _n^g(G) $ τ n g (G) ( $ g\geq ~0 $ g ≥ 0) can also then be derived. Finally, as applications, we calculate the multiplicative degree-Kirchhoff index, Kemeny's constant, and the number of spanning trees for the graph $ \tau _n(G) $ τ n (G) and graphs $ \tau _n^g(G) $ τ n g (G) by exploring their connections with the normalized Laplacian spectrum, and obtain exact results for these quantities. [ABSTRACT FROM AUTHOR]

Chronic cough is one of the common diseases in pediatrics, and its occurrence, development and regression are closely related to the theory of xuanfu. Our team believes that the core pathogenesis of this disease is the deficiency of vital qi and the invasion of evil qi, resulting in a loss of control of the xuanfu. Among them, the deficiency of zang-fu organs and the loss of nourishment of the xuanfu are the basis of the disease; the accumulation of phlegm and food and the stagnation of the xuanfu are the root cause of the disease; the wind evil triggers the xuanfu to be the cause of the disease. In children, the lung, spleen and kidney are often deficient, making it easy for the xuanfu to lose its nourishment, which in turn affects the function of the xuanfu in transporting fluids, and when the xuanfu is stagnant due to deficiency, evil qi has an opportunity to take advantage of it;In addition, if the spleen and stomach are not nourished, and the transportation and transformation are not normal, it is easy to accumulate dampness and produce phlegm, or if food stagnates in the middle jiao and stagnates in the xuanfu channel, it will affect the smooth flow of qi and lay the hidden danger for the development of disease;If the cough is triggered by wind pathogen, the internal and external evil qi will interact with each other and the xuanfu will malfunction, resulting in the failure of lung qi to diffuse and purify and coughing, and the condition will linger. In treatment, our team adopted the principle of promoting the situation and removing the stagnation in the xuanfu by dispelling wind evil, resolving phlegm and removing stagnation, and reinforcing vital qi and supplementing deficiency to open up the xuanfu. At the same time, we pay attention to the application of the characteristic medicine to unblock the xuanfu, especially the medicine to regulate qi to unblock the xuanfu, the medicine to dredge the meridians to unblock the xuanfu and the medicine to invigorate the blood to unblock the xuanfu, so as to restore the function of the xuanfu of the lung, then the disease can be cured. [ABSTRACT FROM AUTHOR]