Improved room-temperature hydrogen storage performance of lithium-doped MIL-100(Fe)/graphene oxide (GO) composite

Li⁺ doping is regarded as an effective strategy to enhance the room-temperature hydrogen storage of metal-organic frameworks (MOFs). In this work, Li⁺ is doped into both MIL-100(Fe) and MIL-100(Fe)/graphene oxide (GO) composite, and it is demonstrated that the hydrogen uptake of Li⁺ doped MIL-100(Fe)/GO (2.02 wt%) is improved by 135% compared with Li⁺ doped MIL-100(Fe) (0.86 wt%) at 298 K and 50 bar, which is ascribed to its higher isosteric heat of adsorption (7.33 kJ/mol) resulting from its more accessible adsorption sites provided by doped Li⁺ ions and ultramicropores. Grand canonical Monte Carlo (GCMC) simulation reveals that Li⁺ ions distributing in the interface between MIL-100(Fe) and GO within MIL-100(Fe)/GO composite is favorable for hydrogen adsorption owing to the increased number of adsorption sites, thus contributing to the enhanced hydrogen storage capacity. These findings demonstrate that MIL-100(Fe)/GO is a more promising Li⁺ doping substrate than MIL-100(Fe).     

基于卷积神经网络的5G蜂窝网络无线定位方法

5G蜂窝网络发展迅猛，其覆盖面积将逐渐增大，因此使用5G蜂窝网络进行定位是有研究潜力的研究方向。本文提出一种新的深度学习技术来实现高效、高精度和低占用的定位，以代替传统指纹定位过程中繁重的指纹库生成以及距离计算。该方法建立了一个特殊的卷积神经网络，并根据5G天线信号的接收信号强度指示、相位和到达角等特征量，选择合适的输入数据格式构造样本组建训练集，对该卷积神经网络进行训练。训练得到的卷积神经网络可以替代指纹定位中的庞大指纹库，非常有利于直接在5G移动设备端实现定位。虽然卷积神经网络在训练过程中需要大量时间，但在训练完毕后直接进行分类定位的速度非常快，可以保障定位实现的实时性。本文所实现的卷积神经网络权重与偏置所占内存不到0.5 MB，且能够在实际应用环境中以95%的定位准确率以及0.1 m的平均定位精度实现高精度定位。     

Field-Effect Chiral Anomaly Devices with Dirac Semimetal

Charge-based field-effect transistors (FETs) greatly suffer from unavoidable carrier scattering and heat dissipation. Analogous to valley degree of freedom in semiconductors, chiral anomaly current in Weyl/Dirac semimetals is theoretically predicted to be nearly nondissipative over long distances, but still lacks experimental ways to efficiently control its transport. Here, field-effect chirality devices are demonstrated with Dirac semimetal PtSe₂, in which its Fermi level is close to the Dirac point in the conduction band owing to intrinsic defects. The chiral anomaly is further corroborated by the planar Hall effect and nonlocal valley transport measurement, which can also be effectively modulated by external fields, showing robust nonlocal valley transport with micrometer diffusion length. Similar to charge-based FETs, the chiral conductivity in PtSe₂ devices can be modulated by electrostatic gating with an ON/OFF ratio of more than 10³. Basic logic functions in the devices are also demonstrated with electric and magnetic fields as input signals.     

小微数据包高效无线传输技术的发展和趋势

5G-NR和B5G系统都需能高效地支持小微数据包(块)的传输,且在不同的无线传输技术(如宽带或超低时延)之间快速灵活地切换。系统梳理和比较和小微数据包(块)相关的多种无线传输技术,如两步RACH、预配置授权和公共资源竞争等,分析它们对3GPP各个系统和各个RAN协议的影响和复杂度优劣等,并进一步展望其未来发展和应用趋势。     

The effect of rare-earth oxides on the energy storage performances in BaTiO3 based ceramics

In this work, 0.7BaTiO₃-0.3Sr_0.2Bi_0.7TiO₃ (0.7BT-0.3SBT) ceramics with 0.15 mol% various rare-earth oxides doped are designed and synthesized by the conventional solid-state route. All prepared samples exhibited a single perovskite phase and dense microstructure with fine grain size (0.2–0.5 μm) after sintering at 1180 °C. Especially, the Gd-doped 0.7BT-0.3SBT ceramics exhibited excellent energy storage performances; the corresponding recoverable energy density and efficiency were 3.2 J/cm³ and 91.5% under an electric field of 330 kV/cm, respectively. Meanwhile, doping with Gd caused the BT-based ceramics to possess excellent temperature (30–150 °C) and outstanding frequency stabilities (10–1000 Hz). Moreover, the pulsed charge-discharge experiments revealed that a high power density of 59 MW/cm³ and a fast discharge speed of 110 ns with outstanding temperature stability could be synchronously obtained in the Gd-doped composition. All these features are attractive for pulsed power applications.     

Couple-based particle swarm optimization for short-term hydrothermal scheduling

A novel couple-based particle swarm optimization (CPSO) is presented in this paper, and applied to solve the short-term hydrothermal scheduling (STHS) problem. In CPSO, three improvements are proposed compared to the canonical particle swarm optimization, aimed at overcoming the premature convergence problem. Dynamic particle couples, a unique sub-group structure in maintaining population diversity, is adopted as the population topology, in which every two particles compose a particle couple randomly in each iteration. Based on this topology, an intersectional learning strategy using the partner learning information of last iteration is employed in every particle couple, which can automatically reveal useful history information and reduce the overly rapid evolution speed. Meanwhile, the coefficients of each particle in a particle couple are set as distinct so that the particle movement patterns can be described and controlled more precisely. In order to demonstrate the effectiveness of our proposed CPSO, the algorithm is firstly tested with four multimodal benchmark functions, and then applied to solve an engineering multimodal problem known as STHS, in which two typical test systems with four different cases are tested, and the results are compared with those of other evolutionary methods published in the literature.     

P-IoT自组网模式研究

为降低专网物联网(P-IoT)的建网成本,实现灵活部署和增强抗毁性以满足行业用户的应用要求,需对P-IoT自组网模式进行研究。首先,阐述了P-IoT自组网模式的重要性;在此基础上,从系统架构、支持的拓扑类型、协议栈设计以及技术优势对P-IoT自组网模式加以分析;最后,分析了P-IoT自组网模式在智能抄表与智能林防领域的创新应用。P-IoT自组网模式在多种应用环境下都能很好地满足行业用户的需求,在未来专网市场P-IoT自组网模式必将具备极强的竞争力。     

Laboratory tests on the engineering properties of sensor-enabled geobelts (SEGB)

To measure geosynthetic reinforcement strains, sensor-enabled geobelts (SEGB) that perform the reinforcement and self-measurement functions were developed in this paper. The SEGB of high-density polyethylene (HDPE) filled with carbon black (CB) were fabricated by both the industry and the laboratory. To study the mechanical properties and tensoresistivity performance of the SEGB, in-isolation tests and in-soil tests were performed. Hot pyrocondensation pipes (HPP) were used to protect the SEGB against the influence of water. For the SEGB specimens developed in the laboratory, the optimal CB filler content was 47.5%. For the SEGB fabricated by the industry, the optimal CB content was slightly decreased compared to the SEGB fabricated in the laboratory. For the modified SEGB sealed with HPP, the strain at the fracture was improved, while its tensile stress and the frictional property of the geobelt-soil interfaces both decreased slightly. In the pull-out tests, the self-measurement function of the SEGB was proved to be effective for evaluating the deformation behavior of geosynthetic reinforcement. The results are helpful for further application of SEGB technology in engineering.     

Improved stability of nano-sized La0.6Sr0.4Co0.2Fe0.8O3-δ-Ce0.8Sm0.2O1.9 composite cathodes by substituting Sr2+ with Ca2+

The nano-sized composite cathodes prepared by infiltrating La_0.6Sr_{0. 4}Co_0.2Fe_0.8O_3-δ (LSCF) or La_0.6Ca_0.4Co_0.2Fe_0.8O_3-δ (LCCF) into the Ce_0.8Sm_0.2O_1.9 (SDC) scaffolds exhibit different electro-catalytic activity and microstructure evolution. Compared with LSCF-SDC nano-sized composite cathode, the LCCF-SDC composite cathode shows the higher microstructure stability. There is no observable coarsening or sintering and no diffraction peaks of other impurity phase are detected for both LSCF and LCCF after being aged at 600 °C for 500 h, but the lattice distortion is less if La³⁺ ions are substituted by Ca²⁺ ions instead of by Sr²⁺ in LaCo_0.2Fe_0.8O_3-δ (LCFO) lattice. The oxygen vacancy concentration is also less in LCCF than in LSCF. The less lattice distortion and oxygen vacancy concentration prohibit the Ca²⁺ ions segregation on the LCCF cathode surface because of less strain in the LCCF lattice and less electrostatic interactions between the negatively charge A-site dopants (Ca′_La) and the positively charged oxygen vacancies (V_o^··) on LCCF surface. The greater binding energy of Ca–O maybe also hinder the enrichment of Ca²⁺ ions on the cathode surface. After being aged in air at 600 °C for 500 h, more Sr²⁺ ions gather on the LSCF cathode surface to form a Sr-rich inert phase, which is detrimental to the oxygen reduction reaction on the cathode surface.