市内变电站接地系统的设计和分析

为了更好地进行市内变电站的设计和分析,介绍了市内变电站接地系统的基本设计流程,重点讨论了进行市内接地系统设计分析与常规郊区接地系统相比需考虑和出现的新问题。分析结果表明,与常规的接地系统相比,在进行市内接地系统设计时除了要考虑各种常规因素外,还需考虑可能的多块土壤结构、各电压等级电缆在故障电流分布计算中的影响,以及考虑电站入地电流对周边构筑物以及民用设施的安全影响等方面,否则会对电站评估安全计算结果带来显著的误差,遗漏周边安全性评估等,造成安全隐患。     

Crack dynamics in brittle fracture: An atomistic study

It is commonly believed that cracks cannot move faster than the speed of sound on a solid surface known as the Rayleigh wave speed. However, earthquake measurement and, more recently, laboratory experiments give evidence to the contrary for shear dominated crack growth along weak planes in brittle solids. To gain a better understanding of this phenomenon, we have performed molecular dynamics simulations of crack propagation along a weak interface joining two “strong” crystals. The microscopic features describing the nucleation and growth of the transonic crack are elucidated, including the hyperelastic stress field driving the failure mechanism.     

Can crisis management teams mitigate COVID-19's effects? A comparative case study between China and the United States

The COVID-19 pandemic has been the world's greatest challenge since World War II. As an unprecedented global public health crisis, crisis management teams (CMTs) in the infected countries need to rethink to cope with the similar uncertainty and urgency of the ongoing COVID-19 pandemic. The shared context of COVID-19 allows us to explore a cross-nation study of different constructs and CMT to communicate information about crises with the public effectively. Since the pandemic affected all countries, the comparison is warranted. Can CMTs mitigate the effects of COVID-19? Based on the analysis of China and the US cases, our study explores how shared and common knowledge cognition among crisis responders plays a pivotal role in effective CMTs' communication while technological failures and inadequate information disrupt the system, worsening pandemics like COVID-19. Furthermore, organizational dysfunction, such as institutional fragmentation, regulatory hurdles and bureaucratic arrogance, impede effective communication between CMTs. However, effective coordination and decisive leadership could improve coordination effectiveness and reduce crisis costs.     

Impact of Silicon Foliar Application on the Growth and Physiological Traits of Carthamus tinctorius L. Exposed to Salt Stress

Silicon - Althought safflower is a tolerant crop against many environmental stresses, but its yield and performance reduce under stress. The aim of this experiment was to investigate the effect of...     

Epoxy resin/plasticized carbon black composites. Part II. Correlation among network structure and mechanical properties

The network structure, mechanical properties, and thermal gravimetric of epoxy resin filled with plasticized carbon black (CB) have been studied. The effect of CB concentration on composite morphology as well as cross linking density (n), volume fraction of resin (V_r), degree of crystallinity (X_c), mean gap among conductive particles (g), aspect ratio (F), and mechanical property such as modulus of elasticity (Y_m), hardness (H_A), and elongation at break (EB) have been examined and correlated to establish structure–property relationships. According to the thermal gravimetric analysis, the thermal decomposition of the composite took place at a slightly higher temperature than that of green epoxy. It proved that the inclusion of plasticized CB improves the quality of the network structure and enhances the mechanical properties of the composites. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers.     

Double diffusive Buoyancy-driven flow in a fluid-saturated elliptical annulus with a neural network-based prediction of heat and mass transfer

This paper presents a numerical study of buoyancy-driven double-diffusive convection within an elliptical annulus enclosure filled with a saturated porous medium. An in-house built FORTRAN code has been developed, and computations are carried out in a range of values of Darcy–Rayleigh number Ra_m (10 ≤ Ra_m ≤ 500), Lewis number Le (0.1 ≤ Le ≤ 10), and the ratio of buoyancy forces N (−5 ≤ N ≤ 5). In addition, three methods are used, namely the multi-variable polynomial regression, the group method of data handling (GMDH), and the artificial neural network (ANN) for the predictions of heat and mass transfer rates. First, results are successfully validated with existing numerical and experimental data. Then, the results indicated that temperature and concentration distributions are sensitive to the Lewis number and thermal and mass plumes are developing in proportion to the Lewis number. Two particular values of Lewis number Le = 2.735 and Le = 2.75 captured the flow's transition toward an asymmetric structure with a bifurcation of convective cells. The average Nusselt number tends to have an almost asymptotic value for Le » 5. For the case of aiding buoyancies N > 1, the average Nusselt Number $\overline{\mathit{Nu}}$ decreased by 33% when the Lewis number increased to its maximum value. Then, it increased by 10% when the Lewis number increased to Le = 1 for the case of opposing buoyancies N < 1 and then decreased by 33% when the Lewis number increased to its maximum value., contrary to the behavior of the average Sherwood number $\overline{\mathit{Sh}}$ that increased by 700% for both cases N > 1 and N < 1. New correlations of $\overline{\mathit{Nu}}$, and $\overline{\mathit{Sh}}$ as a function of Ra_m, Le, and N are derived and compared with GMDH and ANN methods, and the ANN method showed higher performance for the prediction of $\overline{\mathit{Nu}}$ and $\overline{\mathit{Sh}}$ with R² exceeding 0.99.     

Research on the Effects of Yttrium on Bismuth Titanate Borosilicate Glass System

Silicon - Glasses with the chemical composition of 52B2O3 – 12SiO2–26Bi2O3 – (10 − x)TiO2 - xY2O3, :(0 ≤ x ≤ 10) prepared...     

Ni3V2O8 Nanosheets Grafted on 3D Helical-shaped Carbon Nanocoils as A Binder-free Hierarchical Composite for Efficient Non-enzymatic Glucose Sensing

High fabrication cost, chemical instability, and complex immobilization of enzyme molecules are critical issues of enzyme-based glucose sensors. Designing state-of-the-art, binder-free, and non-enzymatic glucose sensing probes plays an imperative role to cope with the aforementioned issues. 3D carbonaceous nanomaterials coated with transition metal vanadates (TMVs) are a favorable biomimetic platform for glucose quantification. Peculiar hierarchical structure, enhanced conductivity, synergistic interaction, multiple oxidation states, and high catalytic activity would make such composite a potential contender for non-enzymatic glucose sensing. Herein, 3D helical-shaped carbon nanocoils (CNCs) are grown on nickel foam (NF) via chemical vapor deposition method to prepare a robust CNCs/NF scaffold. Then, a hydrothermal route is followed to grow interconnected free-standing Ni₃V₂O₈ nanosheets (NSs) on CNCs/NF scaffold. This novel and binder-free Ni₃V₂O₈ NSs/CNCs/NF hierarchical composite possesses superior electrochemical active area (ECSA) and exceptional electrochemical efficacy. Amperometric analysis exhibits extremely prompt detection time (0.1 s), elevated sensitivity (5214 µA mM⁻¹ cm⁻²), and low detection limit (0.04 µM). Developed sensor demonstrates appreciable recoveries (93.3 to 103.3%) regarding glucose concentration in human serum. The appealing analytical results show that deployment of a 3D helical-shaped hierarchical smart scaffold can be an effective strategy for developing efficient and advanced non-enzymatic glucose sensors.