高铁场景下有源智能超表面辅助的能效优化研究

针对高铁场景中无源智能超表面(reconfigurable intelligent surface,RIS)引入的“乘性衰落”效应问题,一种有效解决办法是部署有源RIS。然而,传统的有源RIS全连接架构中大量有源元件会导致过高的硬件成本和功耗,因此提出一种有源RIS子连接架构,旨在满足车地通信中传输速率要求的同时兼顾系统的能量效率。首先,基于高铁场景的特殊性建立有源RIS辅助多用户的系统模型;其次,考虑基站最大发射功率约束、有源RIS发射功率约束和有源RIS相移矩阵约束,提出系统能量效率最大化问题,并通过使用分式规划理论中的拉格朗日对偶变换和二次变换,将上述非凸问题转化为凸优化问题;最后,提出一种联合发射波束成形和有源RIS相移矩阵的交替优化算法。仿真结果表明,相比传统无源RIS和有源RIS全连接架构方案,所提方案能有效解决“乘性衰落”问题,并且在满足用户传输速率的同时实现更高的能量效率。

The ultrastructure of the spermatozoon of Octopus ocellatus Gray, 1849 (Cephalopoda: Octopoda)

Morphology of the spermatozoon of Octopus ocellatus was studied by light, scanning electron, and transmission electron microscopes. Sperm are 600-700 um long, with a large number of granules in diameter about 130 um. Each spermatozoon is composed of a head, neck, and tail. The head is made up of an acrosomal complex anterior to the nucleus. The spiral acrosomal complex consists of an electron-lucent vesicle, lacuna, and an electron-dense acrosomal vesicle. Additionally, the spiral acrosomal vesicle has numerous equidistant striations, and is surrounded by many small granules （20 nm diameter）. A long straight nucleus, which is electron-densed, has a deep posterior concavity, the nuclear vacuole. At the terminal end of the nucleus is a sleeve-like structure with a concave posterior nuclear fossa （PNF）. The neck is short connecting the PNF. The basal body is located in the PNF and gives rise to the axoneme. This structure connects the head, neck, and tail. The tail is divided into a middle piece and a principal piece. The middle piece, having a 9＋9＋2 arrangement, is surrounded by a mitochondrial sheath and terminates by an electron-dense fibrous sheath. The principal piece is the longest part of the sperm with coarse fibers tapering posteriorly. The results of this study shall provide some useful information for artificial breeding of this species.

Dynamic analysis of elastic screen surface with multiple attached substructures and experimental validation

A feasible method to improve the reliability and processing efficiency of large vibrating screen via the application of an elastic screen surface with multiple attached substructures （ESSMAS） was proposed. In the ESSMAS, every screen rod, with ends embedded into elastomer, is coupled to the main screen structure in a relatively flexible manner. The theoretical analysis was conducted, which consists of establishing dynamic model promoted from the fuzzy structure theory as well as calculating for the equivalent stiffness of each attached structure. According to the numerical simulation using the NEWMARK-fl integration method, this assembling pattern significantly leads to the screen surface/rod having larger vibration intensity than that of the corresponding position on screen structure, which specifically, with an averaged acceleration amplitude increasing ratio of 11.37% in theoretical analysis and 20.27% in experimental test. The experimental results, within a tolerant error, also confirm the established model and demonstrate the feasibility of ESSMAS.

Interface enhanced superconductivity in monolayer FeSe films on MgO(001):charge transfer with atomic substitution

Interface enhanced superconductivity over 50 K has been discovered in monolayer Fe Se films grown on several TiO_2-terminated oxide substrates.Whether such phenomenon exists in other oxide substrates remains an extremely interesting topic.Here we report enhanced superconductivity with an onset transition temperature of 18 K in monolayer Fe Se on Mg O(001) substrate by transport measurement.Scanning transmission electron microscopy investigation on the interface structure indicates that Fe Se films grow epitaxially on Mg O(001) and that overlayer Fe atoms diffuse into the top two layers of Mg O and substitute Mg atoms.Our density functional theory calculations reveal that this substitution promotes the charge transfer from the Mg O substrate to the Fe Se films,an essential process that also occurs in monolayer Fe Se on TiO_2-terminated oxides and contributes to the enhanced superconductivity therein.Our finding suggests that superconductivity enhancement in monolayer Fe Se films on oxides substrates is rather general as long as charge transfer is allowed at the interface,thus pointing out an explicit direction for searching for new high temperature superconductivity by interface engineering.

Cluster of solar active regions and onset of coronal mass ejections

round-the-clock solar observations with full-disk coverage of vector magnetograms and multi-wavelength images demonstrate that solar active regions(ARs) are ultimately connected with magnetic field. Often two or more ARs are clustered, creating a favorable magnetic environment for the onset of coronal mass ejections(CMEs). In this work, we describe a new type of magnetic complex: cluster of solar ARs. An AR cluster is referred to as the close connection of two or more ARs which are located in nearly the same latitude and a narrow span of longitude. We illustrate three examples of AR clusters, each of which has two ARs connected and formed a common dome of magnetic flux system. They are clusters of NOAA(i.e., National Oceanic and Atmospheric Administration) ARs 11226 & 11227, 11429 & 11430, and 11525 & 11524. In these AR clusters, CME initiations were often tied to the instability of the magnetic structures connecting two partner ARs, in the form of inter-connecting loops and/or channeling filaments between the two ARs. We show the evidence that, at least, some of the flare/CMEs in an AR cluster are not a phenomenon of a single AR, but the result of magnetic interaction in the whole AR cluster. The observations shed new light on understanding the mechanism(s) of solar activity. Instead of the simple bipolar topology as suggested by the so-called standard flare model, a multi-bipolar magnetic topology is more common to host the violent solar activity in solar atmosphere.

The approximate Jordan forms of operators on Σ_e^1 type Banach spaces

This paper studies the structure of operators on Σ1e type Banach spaces.It solves the problem of the small compact perturbations of operators with connected spectra.Namely,it shows that every operator with a connected spectrum on separable Σ1e type Banach spaces is a small compact perturbation of a strongly irreducible operator.Based on this result,this paper establishes the approximate Jordan forms of operators on Σ1e type Banach spaces with Schauder bases.