Structural and microwave absorption properties of CoFe_(2)O_(4)/residual carbon composites

Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_(4)/residual carbon from coal gasification fine slag(CFO/RC)composites were created using a novel hydrothermal method.Various mechanisms for microwave absorption,including conductive loss,natural resonance,interfacial dipole polarization,and magnetic flux loss,are involved in these composites.Consequently,compared with pure residual carbon materials,this composite offers superior capabilities in microwave absorption.At 7.76GHz,the CFO/RC-2 composite achieves an impressive minimum reflection loss(RL_(min))of-43.99 dB with a thickness of 2.44 mm.Moreover,CFO/RC-3 demonstrates an effective absorption bandwidth(EAB)of up to 4.16 GHz,accompanied by a thickness of 1.18mm.This study revealed the remarkable capability of the composite to diminish electromagnetic waves,providing a new generation method for microwave absorbing materials of superior quality.

HPM视角下构建符合学生认知规律的概念教学——以“数系的扩充和复数的概念”为例

在HPM视角下的教学中,教师应基于“大观念、大主题、大单元”的教学理念,准确把握数学史料的“深度”,构建符合学生认知规律、适合学生认知结构的教学活动,让学生体会和感悟数系扩充的原则,实现数集的再一次扩充.同时,设置合适的问题串,使学生在新概念生成的过程中,提高自己的理性思维能力,实现对概念的自主探究.

HPM视角下高职数学课程思政教学的探索与实践

在高等职业教育中,高职数学在公共基础课程中占据着举足轻重的地位,承载着立德树人的使命,而课程思政是实现这一使命的有效途径。本文在简要概述HPM与课程思政的基础上,从扩充教师数学史知识,教学设计,运用信息技术和社团活动等角度阐述了HPM视角下高职数学课程思政的教学策略,融入HPM中的数学史典故、杰出数学家的事迹等具体案例,对高职数学课程思政的教学改革进行了积极探索尝试。

UWB HPM对雷达方舱内电子设备的影响仿真分析

针对高功率微波辐照下雷达方舱内电子设备的响应和毁伤效应等实际问题,通过建立雷达方舱和舱内电缆模型进行了辐照仿真分析。结果表明,高功率微波信号在进入方舱时,方舱起到一定的滤波作用,类似带通滤波器;雷达方舱和舱内设备的反射会影响方舱内场强分布和极化,造成方舱内电场分布不均匀,各向异性降低,但尚未达到混响室程度;通过仿真概略计算了方舱内信号分布和传输特性;方舱内电缆耦合信号电压基本在同一个数量级,超宽谱信号辐照影响主要以扰乱为主。针对上述影响,提出了相应加固措施,可为雷达在高功率微波武器攻击下进行后门防护加固提供理论支撑。

MXene Hollow Spheres Supported by a C–Co Exoskeleton Grow MWCNTs for Efficient Microwave Absorption

High-performance microwave absorption(MA) materials must be studied immediately since electromagnetic pollution has become a problem that cannot be disregarded. A straightforward composite material, comprising hollow MXene spheres loaded with C–Co frameworks, was prepared to develop multiwalled carbon nanotubes(MWCNTs). A high impedance and suitable morphology were guaranteed by the C–Co exoskeleton, the attenuation ability was provided by the MWCNTs endoskeleton, and the material performance was greatly enhanced by the layered core–shell structure. When the thickness was only 2.04 mm, the effective absorption bandwidth was 5.67 GHz, and the minimum reflection loss(RLmin) was-70.70 d B. At a thickness of 1.861 mm, the sample calcined at 700 ℃ had a RLmin of-63.25 d B. All samples performed well with a reduced filler ratio of 15 wt%. This paper provides a method for making lightweight core–shell composite MA materials with magnetoelectric synergy.

Enhancing Low-Frequency Microwave Absorption Through Structural Polarization Modulation of MXenes

Two-dimensional carbon-based materials have shown promising electromagnetic wave absorption capabilities in mid-and high-frequency ranges,but face challenges in low-frequency absorption due to limited control over polarization response mecha-nisms and ambiguous resonance behavior.In this study,we pro-pose a novel approach to enhance absorption efficiency in aligned three-dimensional(3D)MXene/CNF(cellulose nanofibers)cavities by modifying polarization properties and manipulating resonance response in the 3D MXene architecture.This controlled polarization mechanism results in a significant shift of the main absorption region from the X-band to the S-band,leading to a remarkable reflection loss value of-47.9 dB in the low-frequency range.Furthermore,our findings revealed the importance of the oriented electromagnetic coupling in influencing electromagnetic response and microwave absorption properties.The present study inspired us to develop a generic strategy for low-frequency tuned absorption in the absence of magnetic element participation,while orientation-induced polarization and the derived magnetic resonance coupling are the key controlling factors of the method.

Achieving Ultra-Broad Microwave Absorption Bandwidth Around Millimeter-Wave Atmospheric Window Through an Intentional Manipulation on Multi-Magnetic Resonance Behavior

The utilization of electromagnetic waves is rapidly advancing into the millimeter-wave frequency range,posing increasingly severe challenges in terms of electromagnetic pollution prevention and radar stealth.However,existing millimeter-wave absorbers are still inadequate in addressing these issues due to their monotonous magnetic resonance pattern.In this work,rare-earth La^(3+)and non-magnetic Zr^(4+)ions are simultaneously incorporated into M-type barium ferrite(BaM)to intentionally manipulate the multi-magnetic resonance behavior.By leveraging the contrary impact of La^(3+)and Zr^(4+)ions on magnetocrystalline anisotropy field,the restrictive relationship between intensity and frequency of the multi-magnetic resonance is successfully eliminated.The magnetic resonance peak-differentiating and imitating results confirm that significant multi-magnetic resonance phenomenon emerges around 35 GHz due to the reinforced exchange coupling effect between Fe^(3+)and Fe^(2+)ions.Additionally,Mosbauer spectra analysis,first-principle calculations,and least square fitting collectively identify that additional La^(3+)doping leads to a profound rearrangement of Zr^(4+)occupation and thus makes the portion of polarization/conduction loss increase gradually.As a consequence,the La^(3+)-Zr^(4+)co-doped BaM achieves an ultra-broad bandwidth of 12.5+GHz covering from 27.5 to 40+GHz,which holds remarkable potential for millimeter-wave absorbers around the atmospheric window of 35 GHz.

Compositional and Hollow Engineering of Silicon Carbide/Carbon Microspheres as High-Performance Microwave Absorbing Materials with Good Environmental Tolerance

Microwave absorbing materials(MAMs)characterized by high absorption efficiency and good environmental tolerance are highly desirable in practical applications.Both silicon carbide and carbon are considered as stable MAMs under some rigorous conditions,while their composites still fail to produce satisfactory microwave absorption performance regardless of the improvements as compared with the individuals.Herein,we have successfully implemented compositional and structural engineering to fabricate hollow Si C/C microspheres with controllable composition.The simultaneous modulation on dielectric properties and impedance matching can be easily achieved as the change in the composition of these composites.The formation of hollow structure not only favors lightweight feature,but also generates considerable contribution to microwave attenuation capacity.With the synergistic effect of composition and structure,the optimized SiC/C composite exhibits excellent performance,whose the strongest reflection loss intensity and broadest effective absorption reach-60.8 dB and 5.1 GHz,respectively,and its microwave absorption properties are actually superior to those of most SiC/C composites in previous studies.In addition,the stability tests of microwave absorption capacity after exposure to harsh conditions and Radar Cross Section simulation data demonstrate that hollow SiC/C microspheres from compositional and structural optimization have a bright prospect in practical applications.

Microwave shock motivating the Sr substitution of 2D porous GdFeO_(3) perovskite for highly active oxygen evolution

The incorporation of partial A-site substitution in perovskite oxides represents a promising strategy for precisely controlling the electronic configuration and enhancing its intrinsic catalytic activity.Conventional methods for A-site substitution typically involve prolonged high-temperature processes.While these processes promote the development of unique nanostructures with highly exposed active sites,they often result in the uncontrolled configuration of introduced elements.Herein,we present a novel approach for synthesizing two-dimensional(2D)porous GdFeO_(3) perovskite with A-site strontium(Sr)substitution utilizing microwave shock method.This technique enables precise control of the Sr content and simultaneous construction of 2D porous structures in one step,capitalizing on the advantages of rapid heating and cooling(temperature~1100 K,rate~70 K s^(-1)).The active sites of this oxygen-rich defect structure can be clearly revealed through the simulation of the electronic configuration and the comprehensive analysis of the crystal structure.For electrocatalytic oxygen evolution reaction application,the synthesized 2D porous Gd_(0.8)Sr_(0.2)FeO_(3) electrocatalyst exhibits an exceptional overpotential of 294 mV at a current density of 10 mA cm^(-2)and a small Tafel slope of 55.85 mV dec^(-1)in alkaline electrolytes.This study offers a fresh perspective on designing crystal configurations and the construction of nanostructures in perovskite.

Microwave-assisted exploration of the electron configuration-dependent electrocatalytic urea oxidation activity of 2D porous NiCo_(2)O_(4) spinel

Urea holds promise as an alternative water-oxidation substrate in electrolytic cells.High-valence nickelbased spinel,especially after heteroatom doping,excels in urea oxidation reactions(UOR).However,traditional spinel synthesis methods with prolonged high-temperature reactions lack kinetic precision,hindering the balance between controlled doping and highly active two-dimensional(2D)porous structures design.This significantly impedes the identification of electron configuration-dependent active sites in doped 2D nickel-based spinels.Herein,we present a microwave shock method for the preparation of 2D porous NiCo_(2)O_(4)spinel.Utilizing the transient on-off property of microwave pulses for precise heteroatom doping and 2D porous structural design,non-metal doping(boron,phosphorus,and sulfur)with distinct extranuclear electron disparities serves as straightforward examples for investigation.Precise tuning of lattice parameter reveals the impact of covalent bond strength on NiCo_(2)O_(4)structural stability.The introduced defect levels induce unpaired d-electrons in transition metals,enhancing the adsorption of electron-donating amino groups in urea molecules.Simultaneously,Bode plots confirm the impact mechanism of rapid electron migration caused by reduced band gaps on UOR activity.The prepared phosphorus-doped 2D porous NiCo_(2)O_(4),with optimal electron configuration control,outperforms most reported spinels.This controlled modification strategy advances understanding theoretical structure-activity mechanisms of high-performance 2D spinels in UOR.

Field test of high-power microwave-assisted mechanical excavation for deep hard iron ore

Microwave-assisted mechanical excavation has great application prospects in mines and tunnels,but there are few field experiments on microwave-assisted rock breaking.This paper takes the Sishanling iron mine as the research object and adopts the self-developed high-power microwave-induced fracturing test system for hard rock to conduct field experiments of microwave-induced fracturing of iron ore.The heating and reflection evolution characteristics of ore under different microwave parameters(antenna type,power,and working distance)were studied,and the optimal microwave parameters were obtained.Subsequently,the ore was irradiated with the optimal microwave parameters,and the cracking effect of the ore under the action of the high-power open microwave was analyzed.The results show that the reflection coefficient(standing wave ratio)can be rapidly(<5 s)and automatically adjusted below the preset threshold value(1.6)as microwave irradiation is performed.When using a right-angle horn antenna with a working distance of 5 cm,the effect of automatic reflection adjustment reaches the best among other antenna types and working distances.When the working distance is the same,the average temperature of the irradiation surface and the area of the high-temperature area under the action of the two antennas(right-angled and equal-angled horn antenna)are basically the same and decrease with the increase of working distance.The optimal microwave parameters are:a right-angle horn antenna with a working distance of 5 cm.Subsequently,in further experiments,the optimal parameters were used to irradiate for 20 s and 40 s at a microwave power of 60 kW,respectively.The surface damage extended 38 cm×30 cm and 53 cm×30 cm,respectively,and the damage extended to a depth of about 50 cm.The drilling speed was increased by 56.2%and 66.5%,respectively,compared to the case when microwaves were not used.

Ultra-broadband microwave absorber and high-performance pressure sensor based on aramid nanofiber,polypyrrole and nickel porous aerogel

Electronic devices have become ubiquitous in our daily lives,leading to a surge in the use of microwave absorbers and wearable sensor devices across various sectors.A prime example of this trend is the aramid nanofibers/polypyrrole/nickel(APN)aerogels,which serve dual roles as both microwave absorbers and pressure sensors.In this work,we focused on the preparation of aramid nanofibers/polypyrrole(AP15)aerogels,where the mass ratio of aramid nanofibers to pyrrole was 1:5.We employed the oxidative polymerization method for the preparation process.Following this,nickel was thermally evaporated onto the surface of the AP15 aerogels,resulting in the creation of an ultralight(9.35 mg·cm^(-3)).This aerogel exhibited a porous structure.The introduction of nickel into the aerogel aimed to enhance magnetic loss and adjust impedance matching,thereby improving electromagnetic wave absorption performance.The minimum reflection loss value achieved was-48.7 dB,and the maximum effective absorption bandwidth spanned 8.42 GHz with a thickness of 2.9 mm.These impressive metrics can be attributed to the three-dimensional network porous structure of the aerogel and perfect impedance matching.Moreover,the use of aramid nanofibers and a three-dimensional hole structure endowed the APN aerogels with good insulation,flame-retardant properties,and compression resilience.Even under a compression strain of 50%,the aerogel maintained its resilience over 500 cycles.The incorporation of polypyrrole and nickel particles further enhanced the conductivity of the aerogel.Consequently,the final APN aerogel sensor demonstrated high sensitivity(10.78 kPa-1)and thermal stability.In conclusion,the APN aerogels hold significant promise as ultra-broadband microwave absorbers and pressure sensors.

Fusion SST from Infrared and Microwave Measurement of FY-3D Meteorological Satellite

Sea surface temperature(SST)is one of the important parameters of global ocean and climate research,which can be retrieved by satellite infrared and passive microwave remote sensing instruments.While satellite infrared SST offers high spatial resolution,it is limited by cloud cover.On the other hand,passive microwave SST provides all-weather observation but suffers from poor spatial resolution and susceptibility to environmental factors such as rainfall,coastal effects,and high wind speeds.To achieve high-precision,comprehensive,and high-resolution SST data,it is essential to fuse infrared and microwave SST measurements.In this study,data from the Fengyun-3D(FY-3D)medium resolution spectral imager II(MERSI-II)SST and microwave imager(MWRI)SST were fused.Firstly,the accuracy of both MERSIII SST and MWRI SST was verified,and the latter was bilinearly interpolated to match the 5km resolution grid of MERSI SST.After pretreatment and quality control of MERSI SST and MWRI SST,a Piece-Wise Regression method was employed to correct biases in MWRI SST.Subsequently,SST data were selected based on spatial resolution and accuracy within a 3-day window of the analysis date.Finally,an optimal interpolation method was applied to fuse the FY-3D MERSI-II SST and MWRI SST.The results demonstrated a significant improvement in spatial coverage compared to MERSI-II SST and MWRI SST.Furthermore,the fusion SST retained true spatial distribution details and exhibited an accuracy of–0.12±0.74℃compared to OSTIA SST.This study has improved the accuracy of FY satellite fusion SST products in China.

基于HPM视角下的等差数列前n项和教学研究

数学史与数学教育之间的关系(HPM)是数学课堂上实现立德树人的重要途径之一,也是课程思政在教学中的重要体现。本论文将从HPM的角度出发,对等差数列的教学设计进行探讨,并将数学史与课堂教学相结合,以期对高中数学教学的科研与教学起到一定的借鉴作用。The relationship between the history of mathematics and mathematics education (HPM) is one of the important ways to achieve moral education in mathematics classrooms, and it is also an important manifestation of ideological and political education in teaching. In this paper, we will explore the teaching design of arithmetic sequences from an HPM point of view, and integrate the history of mathematics into classroom teaching, aiming to provide reference and assistance for high school teachers’ research and teaching.

HPM视域下小学数学教师专业发展的路径设计

HPM即数学史及数学教育,它适应了小学阶段学生的学习特征和数学教学规律,为小学数学教师的专业发展提供了有效载体。在教师探索和使用HPM模式的过程中,教师应以行动研究为基础,探索HPM模式的个体化实践经验,教师组织则需要以协同探索为基础,构建基于HPM的有效教学体系。只有个体和组织相互支持,建立起有机的学习和实验共同体,教师才能以HPM为载体实现专业发展。为此,学校需要为HPM教学模式的探索和实践提供保障,包括物质资源投入、规章制度和文化建设等。

Abnormal uterine bleeding successfully treated via ultrasoundguided microwave ablation of uterine myoma lesions: Three case reports

BACKGROUND Microwave endometrial ablation(MEA)is a minimally invasive treatment method for heavy menstrual bleeding.However,additional treatment is often required after recurrence of uterine myomas treated with MEA.Additionally,because this treatment ablates the endometrium,it is not indicated for patients planning to become pregnant.To overcome these issues,we devised a method for ultrasound-guided microwave ablation of uterine myoma feeder vessels.We report three patients successfully treated for heavy menstrual bleeding,secondary to uterine myoma,using our novel method.CASE SUMMARY All patients had a favorable postoperative course,were discharged within 4 h,and experienced no complications.Further,no postoperative recurrence of heavy menstrual bleeding was noted.Our method also reduced the myoma’s maximum diameter.CONCLUSION This method does not ablate the endometrium,suggesting its potential appli-cation in patients planning to become pregnant.

基于HPM视角下的数学课例分析——以“对数函数的概念”为例

对数是数学中一个非常重要的概念,它在各种科学和工程领域都有着广泛的应用。在教学中如何有效地教授对数的概念成为了一个重要的挑战。本文基于HPM视角进行教学设计,以对数函数的概念为例,深入探讨了教学设计的过程。通过分析学生对对数的理解过程,帮助学生更好地理解对数的概念,利用HPM来引导学生重构历史,构建概念,引导学生掌握对数的基本概念、加强数学推理能力和与实际问题结合等。本研究可以有效提升学生对对数的理解和运用能力,提高教学效果和激发学生的学习兴趣,也可为今后教学实践提供了有益的借鉴。

HPM视角下的数列教学研究

以高中数学课题数列为例,运用附加式、复制式和重构式三种模式将数学史融入高中数列教学,旨在优化课堂教学,增强课堂的趣味性,拓宽学生的视野,激发学生的思维。

HPM视角下基于认知结构学习理论的教学设计——以“数系的扩充与复数的概念”为例

数系的扩充与人类历史进程紧密相连,每次突破都是原有认知的颠覆。本文以“数系的扩充与复数的概念”为例,从HPM视角出发,结合认知结构学习理论进行教学设计。通过融入数学历史发展脉络,揭示数系扩充的逻辑必然性,引导学生主动构建复数概念的认知框架。教学采用情境模拟、合作探究等方法,激发学生兴趣,促进知识内化。结果显示,学生在理解复数概念的同时,深化了对数学发展进程的认识,有效提升了数学思维能力。在此基础上,提出三点建议:注重学生认知发展,完善知识网络结构;数学史要抛弃表面化,深入融合教学内容;立足数学教育实际,加强案例实证研究。The expansion of the number system is closely related to the process of human history, and every breakthrough is a subversion of existing cognition. This article takes the expansion of number systems and the concept of complex numbers as an example, starting from the HPM perspective and combining cognitive structure learning theory for instructional design. By integrating the historical development of mathematics, revealing the logical inevitability of the expansion of the number system, and guiding students to actively construct a cognitive framework for the concept of complex numbers. Teaching adopts methods such as situational simulation and collaborative exploration to stimulate students’ interest and promote knowledge internalization. The results showed that while students understood the concept of complex numbers, they deepened their understanding of the development process of mathematics and effectively improved their mathematical thinking ability. On this basis, three suggestions are proposed: focus on students’ cognitive development and improve the knowledge network structure;The history of mathematics should abandon superficiality and deeply integrate teaching content;Based on the reality of mathematics education, strengthen case empirical research.

HPM微课在高中数学教学中的应用探究

HPM微课具有即时性、统一性的优点,是一种优良的现代教学工具,将它应用在高中数学教学中,有助于生动呈现知识,降低教学难度。教学实践中要注意应用的方法策略,一是指导学生课前预习,二是形成完整知识框架,三是开展微课测试活动,四是鼓励学生相互学习交流,五是呈现学习易错点,六是优化考前辅导,七是模块化讲解知识,这对高中数学教学具有较强的参考和指导意义。