Measuring optical vortices by means of dual shearing-type Sagnac interferometers

Measuring the positions of optical vortices is an essential part in the researches of speckles and adaptive optics. The measurement accuracy is restricted by the performance of optical devices and the properties of optical vortices, such as density and size. In order to achieve high accuracy and wide range of application, the dual shearing-type Sagnac interferometers is proposed using two shearing plates to adjust the precision of optical vortices measurement. The shearing displacements are able to balance the measuring precision and the value of the intensity ratio point to provide optimum measurement performance. This method is useful for the observation of optical vortices with different sizes and densities, especially for the high density condition

Coordinated control strategy of reactive power compensation based on a flexible distribution network transformer

In order to solve the problem of the power quality caused by distributed power access to the distribution network, this paper proposes a coordinated control strategy of reactive power compensation based on a flexible distribution transformer. First, the working principle of the flexible distribution transformer is analyzed, and the mathematical model of energy acquisition and the regulation converter of the flexible distribution transformer are studied as well. The device-level control strategies of energy acquisition and regulation converters are proposed, respectively. Then, in order to maintain the stability of the bus voltage and quickly respond to the reactive power changes of the system, a coordinated control strategy for the reactive power compensation of flexible distribution transformers is proposed. The priority herein is to maximize the reactive power compensation capacity of the energy harvesting converter. When the energy harvesting converter reaches the compensation upper limit, the control converter is used for reactive power compensation to further suppress the grid voltage fluctuation. Finally, it is verified through simulations that the flexible distribution transformer can realize the reactive power compensation of the distribution network and effectively improve the power quality of the distribution network

Extraordinary Thermoelectric Properties of Topological Surface States in Quantum-Confined Cd3As2 Thin Films

Topological insulators and semimetals have been shown to possess intriguing thermoelectric properties promising for energy harvesting and cooling applications. However, thermoelectric transport associated with the Fermi arc topological surface states on topological Dirac semimetals remains less explored. In this work, we systematically examine thermoelectric transport in a series of topological Dirac semimetal Cd3As2 thin films grown by molecular beam epitaxy. Surprisingly, we find significantly enhanced Seebeck effect and anomalous Nernst effect at cryogenic temperatures when the Cd3As2 layer is thin. Combining angle-dependent quantum oscillation analysis, magnetothermoelectric measurement, transport modelling and first-principles simulation, we isolate the contributions from bulk and surface conducting channels and attribute the unusual thermoeletric properties to the topological surface states. Our analysis showcases the rich thermoelectric transport physics in quantum-confined topological Dirac semimetal thin films and suggests new routes to achieving high thermoelectric performance at cryogenic temperatures

Assessment of Ecological Cumulative Effect due to Mining Disturbance Using Google Earth Engine

Open-pit mining and reclamation damage the land, resulting in unknown and significant changes to the regional ecology and ecosystem services. Surface mining restoration procedures necessitate a significant amount of money, typically at an unclear cost. Due to temporal and regional variability, few studies have focused on the cumulative impacts of mining activities. To investigate the ecological cumulative effects (ECE) of past mining and reclamation activities, this study continuously tracked land cover changes spatially and temporally based on phenological indices and focuses on the spatial and temporal evolution of past mining and reclamation areas using the LandTrendr algorithm. The cumulative trends of ecosystem services in the Pingshuo mining area from 1986 to 2021 were revealed using a uniform standard value equivalent coefficient. Meanwhile, the cumulative ecological effects due to essential ecosystem service functions were analyzed, including soil formation and protection, water containment, biodiversity maintenance, climate regulation, and food production. The synergistic effects and trade-offs among the functions were also explored using Spearman’s correlation coefficient. The results showed that (1) open-pit mining resulted in 93.51 km2 of natural land, 39.60 km2 of disturbed land, and 44.58 km2 of reclaimed land in the Pingshuo mine; (2) open-pit mining in the mine mainly resulted in the loss of 122.18 km2 (80.91%) of native grassland, but, through reclamation into grassland (31.30 km2), cropland (72.95 km2), and forest land (10.62 km2), the damaged area caused by mining only slightly increased; (3) the cumulative ecological value of the mining area declined by 128.78 million RMB; however, the real cumulative value per unit area was lower in the disturbance area (1483.47 million RMB) and the reclamation area (1297.00 million RMB) than in the natural area (2120.98 million RMB); (4) the cumulative value of the food production function in the study area increased, although the values of all individual functions in the study area decreased. Most of the cumulative values of services had a strong synergistic relationship. However, in the natural area, food production (FP) showed a trade-off relationship with the cumulative value of biodiversity maintenance (BM), soil formation and protection (SP), and water conservation (WC) service functions, respectively. This study constructed a methodology for analyzing mining-impacted ecosystem services using time-series processes, reproducing historically complete information for policymakers and environmental regulators

A DFT investigation of the effects of doped Pb atoms on Pd-n clusters (13 <= n <= 116)

Basic properties of cuboctahedral Pd-Pb clusters ranging from 13 to 116 atoms were studied by computational analysis, and the effects of doped Pb atoms on Pd clusters were investigated. The average bond length of Pd-Pb clusters was found to be similar to 0.1 A longer than pure ones, but doped Pb atoms did not constantly expand the Pd-Pd bond lengths in Pd-Pb clusters owing to size effect. In addition, doped Pb atom changed the thickness of surface phase and surface morphology of Pd cluster. The chemical activity of Pd clusters could be enhanced by the doped Pd atoms, although an enough size was required. Lead atoms essentially changed the surface charge population of Pd clusters. The Pd atoms in Pd-Pb clusters were seen to become more electrophilic than in pure Pd clusters, and the probability of being attacked by nucleophilic reagent could be comparable with that of being attacked by electrophilic reagent. Total electron density and deformation electron density revealed that the nature of interaction between metal atoms was metal bond. Weak covalent bond might exist when clusters were in small size. (C) 2011 Elsevier B.V. All rights reserved

Iron regulates chondrocyte phenotype in haemophilic cartilage through the PTEN/PI3 K/AKT/FOXO1 pathway

ABSTRACTObjective Our previous study demonstrated that iron overload could lead to haemophilic cartilage destruction by changing chondrocyte phenotype. This change was caused by iron’s effect on chondrocyte expression of FGF23 and SOX9, in addition to iron-induced chondrocyte apoptosis and cartilage extracellular matrix degradation. However, the underlying mechanisms remain unclear. This study aimed to determine the mechanism by which iron influences chondrocyte phenotype in the pathogenesis of haemophilic cartilage destruction.Methods The expression of the PTEN/PI3K/AKT/FOXO1 signal pathway in the articular cartilage of patients with haemophilic arthritis (HA) or osteoarthritis (OA) was determined using western blot (WB). Additionally, we quantified the expression of iron-induced PTEN, PI3K, p-PI3K, AKT, p-AKT, FOXO1, and p-FOXO1 in primary human normal chondrocyte cells (HUM-iCell-s018) using WB.Results We found that compared to that in patients with OA, the expression of PTEN, PI3K, AKT, and FOXO1 in the articular cartilage of patients with HA was up-regulated, while the expression of p-PI3K, p-AKT, and p-FOXO1 was down-regulated. Additionally, iron increased the expression of PTEN, PI3K, AKT, and FOXO1 and suppressed that of p-PI3K, p-AKT, and p-FOXO1 in chondrocytes in a dose-dependent manner.Conclusions Our findings demonstrated that iron was involved in the pathogenesis of haemophilic cartilage destruction by affecting chondrocyte phenotype through the inhibition of the PTEN/PI3K/AKT/FOXO1 pathway

Investigation of thermal stability of Si0.7Ge0.3Si stacked multilayer with As ion-implantation

The effect of As ion implantation on the stability of SiGe/Si multilayer was systematically studied. The atomic percentage of Ge in as-grown SiGe layer was 30% in this work. A thermally stable Si _0.7 Ge _0.3 /Si multilayer with As ion implantation was attained when the rapid thermal annealing (RTA) treatment temperature did not exceed 850 ^o C. Significant Ge diffusion was observed for the SiGe/Si multilayer with As ion implantation when the RTA temperature was 900 °C or above. However, minor Ge diffusion was attained for the SiGe/Si multilayer without As ion implantation when the RTA treatment temperature was 900 °C. Therefore, , compared with samples without As ion implantation, the stability window of the SiGe/Si multilayer with As ion implantation should be further reduced to 850 °C. As ion implantation plays a critical role in the stability of SiGe/Si multilayer, as it promotes the diffusion of Ge. Consequently, based on the stability of the SiGe/Si multilayer, the highest RTA treatment temperature of 850 °C is proposed for the gate-all-around (GAA) device fabrication process