镜面对称法绝对测量中的误差补偿方法

提出了一种对镜面对称法绝对测量中的原理性误差进行补偿的方法。镜面对称法绝对测量中,需要旋转其中一块平板,由于旋转次数的有限性,重构的三板波前均存在缺失cNθ项的原理性误差。通过增加一次不同角度的旋转,根据Zernike多项式在极坐标系中形式的旋转不变性,对旋转前后的波前差值求解多项式系数方程,获得了cNθ项的多项式系数,进而对原理性误差进行了补偿。由于cNθ项包含无穷多项,根据精度的需要和计算开销决定补偿的项数。模拟实验证明了该补偿方法的有效性。     

医用加速器二极磁铁的非单一工作模式电源控制器设计

近年来,离子治疗技术在国内外发展迅速.为满足加速器调试和不同治疗方案对医用回旋加速器装置的不同束流能量要求,二极磁铁电源要求工作在可相互切换的直流、有序触发和周期脉冲三种模式.使用中国科学院近代物理研究所自主研发的集成盒装式控制器,实现了对电源的控制和保护功能.为了适应调试和治疗两种不同场合的需求,控制器还支持本地和远...     

An Improved Encoder-Decoder Network Based on Strip Pool Method Applied to Segmentation of Farmland Vacancy Field

In the research of green vegetation coverage in the field of remote sensing image segmentation, crop planting area is often obtained by semantic segmentation of images taken from high altitude. This method can be used to obtain the rate of cultivated land in a region (such as a country), but it does not reflect the real situation of a particular farmland. Therefore, this paper takes low-altitude images of farmland to build a dataset. After comparing several mainstream semantic segmentation algorithms, a new method that is more suitable for farmland vacancy segmentation is proposed. Additionally, the Strip Pooling module (SPM) and the Mixed Pooling module (MPM), with strip pooling as their core, are designed and fused into the semantic segmentation network structure to better extract the vacancy features. Considering the high cost of manual data annotation, this paper uses an improved ResNet network as the backbone of signal transmission, and meanwhile uses data augmentation to improve the performance and robustness of the model. As a result, the accuracy of the proposed method in the test set is 95.6%, mIoU is 77.6%, and the error rate is 7%. Compared to the existing model, the mIoU value is improved by nearly 4%, reaching the level of practical application.     

激光沉积修复BT20合金的显微组织和力学性能

针对BT20钛合金锻件当量孔损伤进行激光沉积修复试验,考察了修复试样的组织和力学特点。修复区与基材之间形成了致密冶金结合,Al,Zr,Mo,V合金元素由锻件基体到激光修复区均匀分布,无宏观偏析,硬度分布从基材到修复区依次提高。热影响区组织是由基材的双态组织过渡到网篮组织;修复区组织为粗大的原始柱状β晶,晶粒内为α/β网篮组织,晶内α片层取向随机,宽0.4~0.5μm。修复过程中发现,激光加工工艺参数选择不当、坡度过大等原因会造成修复区组织形成气孔和熔合不良等缺陷,但是通过优化工艺参数可以获得无缺陷修复试样。修复试样的室温静拉伸结果表明,试样的抗拉强度接近锻件基体强度,但修复件的韧性比锻件稍有提高。     

重离子加速器示范装置被动式束流配送系统次级中子特征的蒙特卡罗研究

在碳离子放射治疗中,碳离子束在剂量配送过程中会与束流输运线相互作用,形成以中子辐射为主的外辐射场.由于中子是高LET射线,具有较高的相对生物学效应,减少碳离子放疗中产生的次级中子有助于降低放疗后正常组织并发症几率及二次肿瘤风险.利用蒙特卡罗方法对保守情况(能量为400 MeV/u,多叶光栅完全闭合)下碳离子治疗被动式束...     

Mach-Zehnder interferometers assembled with optical microfibers or nanofibers

We demonstrate Mach-Zehnder interferometers (MZI) assembled using optical microfibers or nanofibers (MNFs) drawn from silica fibers and tellurite glasses. As-assembled MZIs, with dimensions of tens to hundreds of micrometers, show good interference fringes with extinction ratios of approximately 10 dB. The path-length difference of the MZI can be tuned by micromanipulation under an optical microscope. The MNF-assembled MZIs demonstrated here show advantages of easy fabrication, in situ tunability, and compact size.     

Highly Reversible Zinc Metal Anode in a Dilute Aqueous Electrolyte Enabled by a pH Buffer Additive

Aqueous zinc-ion batteries have drawn increasing attention due to the intrinsic safety, cost-effectiveness and high energy density. However, parasitic reactions and non-uniform dendrite growth on the Zn anode side impede their application. Herein, a multifunctional additive, ammonium dihydrogen phosphate (NHP), is introduced to regulate uniform zinc deposition and to suppress side reactions. The results show that the NH₄⁺ tends to be preferably absorbed on the Zn surface to form a “shielding effect” and blocks the direct contact of water with Zn. Moreover, NH₄⁺ and (H₂PO₄)⁻ jointly maintain pH values of the electrode-electrolyte interface. Consequently, the NHP additive enables highly reversible Zn plating/stripping behaviors in Zn//Zn and Zn//Cu cells. Furthermore, the electrochemical performances of Zn//MnO₂ full cells and Zn//active carbon (AC) capacitors are improved. This work provides an efficient and general strategy for modifying Zn plating/stripping behaviors and suppressing side reactions in mild aqueous electrolyte.     

Ammonium Ion Batteries: Material,Electrochemistry and Strategy

Ammonium-ion batteries (AIBs) have recently attracted increasing attention in the field of aqueous batteries owing to their high safety and fast diffusion kinetics. The NH₄⁺ storage mechanism is quite different from that of spherical metal ions (e.g. Li⁺, Na⁺, K⁺, Mg²⁺, and Zn²⁺) because of the formation of hydrogen bonds between NH₄⁺ and host materials. Although many materials have been proposed as electrode materials for AIBs, their performances hardly meet the requirement of future electrochemical energy storage devices. It is thus urgent to design and exploit advanced materials for AIBs. This review highlights the state-of-the-art research on AIBs. The insights into the basic configuration, operating mechanism and recent progress of electrode materials and corresponding electrolytes for AIBs have been comprehensively outlined. The electrode materials are classified and compared according to different NH₄⁺ storage behaviour in the structure. The challenges, design strategies and perspectives are also discussed for the future development of AIBs.     

Halogen-Incorporated Sn Catalysts for Selective Electrochemical CO2 Reduction to Formate

Electrochemically reducing CO₂ to valuable fuels or feedstocks is recognized as a promising strategy to simultaneously tackle the crises of fossil fuel shortage and carbon emission. Sn-based catalysts have been widely studied for electrochemical CO₂ reduction reaction (CO₂RR) to make formic acid/formate, which unfortunately still suffer from low activity, selectivity and stability. In this work, halogen (F, Cl, Br or I) was introduced into the Sn catalyst by a facile hydrolysis method. The presence of halogen was confirmed by a collection of ex situ and in situ characterizations, which rendered a more positive valence state of Sn in halogen-incorporated Sn catalyst as compared to unmodified Sn under cathodic potentials in CO₂RR and therefore tuned the adsorption strength of the key intermediate (*OCHO) toward formate formation. As a result, the halogen-incorporated Sn catalyst exhibited greatly enhanced catalytic performance in electrochemical CO₂RR to produce formate.     

Manganese/Cobalt Bimetallic Relay Catalysis for Divergent Dehydrogenative Difluoroalkylation of Alkenes

The involvement of manganese radical for halogen atom transfer (XAT) reactions has been esteemed as one reliable method but encountered with limited catalytic models. In this paper, a novel bimetallic relay catalysis of Mn₂(CO)₁₀ and cobaloxime has been developed for divergent dehydrogenative difluoroalkylation of alkenes using commercially available difluoroalkyl bromides. A wide range of structurally diverse terminal, cyclic and internal alkenes as well as tetrasubstituted alkenes are found to be good coupling partners to deliver difluoroalkylated allylic products and difluoromethylated cyclic products, accompanied with the production of H₂ as the by-product. This bimetallic relay strategy features broad substrate scope, mild reaction conditions and excellent functional group compatibility. Its success represents an important step-forward to expedite the construction of a rich library of difluoroalkylated products.