Multi-layer quasi-zero-stiffness meta-structure for high-efficiency vibration isolation at low frequency

An easily stackable multi-layer quasi-zero-stiffness(ML-QZS)meta-structure is proposed to achieve highly efficient vibration isolation performance at low frequency.First,the distributed shape optimization method is used to design the unit cel,i.e.,the single-layer QZS(SL-QZS)meta-structure.Second,the stiffness feature of the unit cell is investigated and verified through static experiments.Third,the unit cells are stacked one by one along the direction of vibration isolation,and thus the ML-QZS meta-structure is constructed.Fourth,the dynamic modeling of the ML-QZS vibration isolation metastructure is conducted,and the dynamic responses are obtained from the equations of motion,and verified by finite element(FE)simulations.Finally,a prototype of the ML-QZS vibration isolation meta-structure is fabricated by additive manufacturing,and the vibration isolation performance is evaluated experimentally.The results show that the vibration isolation performance substantially enhances when the number of unit cells increases.More importantly,the ML-QZS meta-structure can be easily extended in the direction of vibration isolation when the unit cells are properly stacked.Hence,the ML-FQZS vibration isolation meta-structure should be a fascinating solution for highly efficient vibration isolation performance at low frequency.

Establishment of a Highly Efficient Regeneration System for the Mature Embryo Culture of Wheat

Establishment of a highly efficient regeneration system for the mature embryo of wheat will provide a convenient tool for wheat tissue culture and transformation, thereby facilitating the transformation of foreign genes into wheat. By using the mature embryos derived from 20 different wheat lines including Shi 4185, Yumai 66, Lunxuan 987, CB037, Yangmai 6, Xinchun 9, Bobwhite, Han 6172, Zheng 9023, Jimai 20, Ningchun 4, and Jing 411, the effects of some factors including inoculation methods, initiating culture media, organic additives, antioxidants, and auxins on the regeneration from the explants were evaluated. The results indicated that the scraping embryo culture was better than the whole embryo culture, the Aa medium was better than the SD2 medium and dicamba was better than 2,4-D in increasing the regeneration frequency. An Adi medium was established in this study by adding silver nitrate, cysteine, ascorbic acid, dicamba, glutamine into the Aa medium at the concentration of 4,40, 100, 2, and 5 mg L^-1, respectively. By using the Adi medium and the scraping technique, the regeneration frequencies of the mature embryos of CB037, Lunxuan 987, Hart 6172, Yangmai 6, Bobwhite, Zheng 9023, Shi 4 185, and Jimai 20 became 85.6, 60,1, 46.0, 42.1,42.0, 34.0, 33.0, and 32.0%, respectively, which were about 5-8 times higher than that obtained from the conventional culture mediums and techniques. This novel regeneration system could be helpful in wheat transformation.

Separation efficiency of alumina particles in Al melt under high frequency magnetic field

The effects of separation time and magnetic induction intensity on the separation efficiency of alumina particles with diameters varying from 30 to 200 μm in aluminum melt were investigated. The experimental results show that the particle-accumulated layer is formed in the periphery of the solidified specimen when the diameter of the separated molten metal, the magnetic induction intensity and the separation time are 10 mm, 0.04 T and 1 s, respectively. When the separation time is 2 s, the particle-accumulated layer can be observed obviously and the separation efficiency is about 80%. There are few alumina particles in the inner of the solidified specimen when the separation time is 3 s. The separation efficiency higher than 85% can be achieved when the separation time is longer than 3 s. When the magnetic induction intensity is 0.06 T, the visible particle-accumulated layer can be formed in 1 s and the separation efficiency is higher than 95%. The experimental results were compared with the calculated results at last.

Using irrigation intervals to optimize water-use efficiency and maize yield in Xinjiang,northwest China

Worldwide, scarce water resources and substantial food demands require efficient water use and high yield.This study investigated whether irrigation frequency can be used to adjust soil moisture to increase grain yield and water use efficiency(WUE) of high-yield maize under conditions of mulching and drip irrigation.A field experiment was conducted using three irrigation intervals in 2016: 6, 9, and 12 days(labeled D6, D9, and D12) and five irrigation intervals in 2017: 3, 6, 9, 12, and 15 days(D3, D6, D9, D12, and D15).In Xinjiang, an optimal irrigation quota is 540 mm for high-yield maize.The D3, D6, D9, D12, and D15 irrigation intervals gave grain yields of 19.7, 19.1–21.0, 18.8–20.0, 18.2–19.2, and 17.2 Mg ha^-1 and a WUE of 2.48, 2.53–2.80, 2.47–2.63, 2.34–2.45, and 2.08 kg m-3, respectively.Treatment D6 led to the highest soil water storage, but evapotranspiration and soil-water evaporation were lower than other treatments.These results show that irrigation interval D6 can help maintain a favorable soil-moisture environment in the upper-60-cm soil layer, reduce soilwater evaporation and evapotranspiration, and produce the highest yield and WUE.In this arid region and in other regions with similar soil and climate conditions, a similar irrigation interval would thus be beneficial for adjusting soil moisture to increase maize yield and WUE under conditions of mulching and drip irrigation.

LD Pumped High Efficient Intracavity Frequency-Doubled Green Laser

A laser diode (LD) pumped Q switched high efficient intracavity frequency doubled Nd ∶YAG laser is reported here. The authors have designed an optical coupler and pointed out that the key to increasing harmonic conversion efficiency is to decrease the loss of fundamental wave. In the experiments, a fundamental mode output laser was acquired. When the pumping power was 12 W, 2.6 W average output power at 1 064 nm with AO Q switch was obtained. 2.1 W average output power at 532 nm was obtained with intracavity frequency doubling, and the highest second harmonic conversion efficiency was 82 0 0.

Transmission Characteristic Simulation of High Frequency Acousto-Optic Modulators

The way by which one can make sure the operating mode of the modulation is by observing the Comsol results of the designed model of proposed acousto-optic modulator (AOM). These results include the pressure distribution, sound pressure distribution, stress distribution at piezoelectric, far-field analysis that describes the diffracted light orders, and electric potential versus light frequency. Throughout the simulating process of modulator operating using Comsol, it begins when the RF is power by a voltage of 100 V, the light is then split into first ordered diffraction, which implies that the modulator is in the operating mode. The use of semiconductor materials is due to its smaller gap that easily transfers the energy that leads to generating first order diffraction when they provided a voltage power. It mentioned that zero order diffraction indicates the modulator does not run;other orders are appearing with increasing the frequency of light leading to decrease of the efficiency of the modulator performance.

面向环境射频能量收集的宽频整流电路

整流电路是射频能量回收系统的核心,能够将射频能量转换为直流。但由于整流电路中使用的二极管具有非线性特性,导致整流效率会随频率变化而降低。为解决这一问题,本文提出一种具有宽频带的整流电路,它通过采用与二极管串联的短路线、与二极管并联的开路线以及多级微带线结构来调整阻抗匹配,实现了在宽频带范围内的高转换效率。设计的整流电路在0 dBm的输入功率下,从1.7~2.7 GHz,均达到50%的整流转换效率,最高整流转换效率为63.3%。该宽带整流电路可以运用在无线能量收集系统中。

高频双频Buck变换器平面集成磁件优化设计

针对目前开关器件和磁性元件性能不足导致双频Buck变换器的效率和功率密度低的问题,研究了一种高效高功率密度的双频Buck变换器。变换器将工作在连续导通(CCM)模式,采用解耦合的平面集成电感器完成系统磁元件的集成,结合磁件的集成方法、有限的PCB层数和变换器的特性给出双频Buck变换器的参数,然后,提出了一种双频Buck变换器平面磁件的设计方法,并完成系统磁元件的优化设计。最后,基于第3代半导体SiC器件以及平面集成磁件,设计了额定功率200 W、开关频率400 kHz的双频Buck变换器。结果表明:该变换器峰值效率将达到96.1%,功率密度为46.1 W/in^(3)(1 in=25.4 mm),验证了双频Buck变换器设计方法的正确性和有效性。

S Zorb装置反应器接收器脱气线和再生器取热盘管改造

某公司对S Zorb装置首个运行周期内出现的反应器接收器脱气线泄漏、再生器取热盘管泄漏等运行问题开展了技术攻关,提出了工艺优化调整、工程技术改造建议。2019年大检修时对反应器脱气线进行扩径,由DN100扩径为DN150,控制气提量小于670 m^(3)/h,对再生系统取热蒸汽和再生风流控阀等进行了工程技术改造。第二运行周期未出现脱气线减薄泄漏和再生器取热盘管泄漏问题。2023年6月大检修时对上次大检修改造部位进行检查以验证工程改造的有效性,经全面检查,确认脱气线内部未发现冲刷痕迹,再生器取热盘管打压合格,外观正常,证明改造措施有效,可以满足“四年一修”目标要求。

单瓣长寿花‘萨姆巴’高效快速繁殖体系的构建

选取单瓣长寿花‘萨姆巴’的叶片为外植体,设计正交试验,研究不同种类植物生长激素及其浓度配比的培养基对长寿花叶片愈伤组织的诱导、不定芽的分化和不定芽生根的影响,并研究试管苗炼苗及移栽的成活情况。试验结果表明,诱导长寿花叶片产生愈伤组织的最适培养基是MS+6-BA 1.0 mg/L+NAA 0.2 mg/L+2,4-D 0.2 mg/L,诱导率是83.33%。诱导愈伤组织不定芽分化的最适培养基是MS+6-BA 2.0 mg/L+NAA 0.3 mg/L,增殖系数是21.4。最适的不定芽生根培养基为1/2MS+IBA 0.2 mg/L+NAA 0.2 mg/L,生根系数为7.03。试管苗移栽到蛭石∶营养土=1∶1的基质中培养,移栽的成活率可达100%。

太赫兹频段高速移动场景参考信号方案研究

针对太赫兹频段高速移动场景,提出了一种参考信号方案——增强型离散傅里叶变换扩展正交频分复用(E DFT-s-OFDM)DMRS:将具有循环前缀(CP)和循环后缀(CS)的参考信号序列分割为首部和尾部参考信号序列,然后分别嵌入每个OFDM符号的尾部和首部。这种方案的优点在于,前一个OFDM符号的尾部和后一个OFDM符号的首部构成一个完整的参考信号序列,从而允许接收端在每个OFDM符号间隔内都能进行信道估计,提高了信道估计的精度和实时性。此外,相邻OFDM符号的首部和尾部参考信号序列相同,从而省去了每个OFDM符号的传统循环前缀(CP),提高了频谱效率。仿真结果表明,在太赫兹频段高速移动场景下,与5G NR DFT-s-OFDM波形的DMRS方案相比,该方案的信道估计更精确,通信系统的频谱效率更高。

空间高温区自由活塞斯特林发电机工作特性试验研究

测试了不同冷端温度下,外负载、运行压力和加热功率对高温区自由活塞斯特林发电机的热端温度、电电效率、输出功率、频率的影响。研究结果表明,在同一冷端温度时,加热功率的增加使发电机的电电效率、输出功率、热端温度上升,而外负载、运行压力的增加则起相反作用;发电机的频率与外负载呈负相关变化,与运行压力、加热功率呈正相关变化。提升冷端温度使发电机的输出功率、电电效率和频率下降,热端温度上升。在三种不同冷端温度下,外负载、加热功率和运行压力对发电机输出特性的影响规律不变。经过测试,发电机在运行温区为495~1058 K时,最大输出功率103.681 W,电电效率20.5%。

废旧磷酸铁锂电池集流体分离与正极材料再生

通过优化NaOH碱溶条件高效去除集流体黏结剂,保留完整铝箔;利用固相法再生LiFePO 4。当NaOH为0.8 mol/L、固液比20 mL/g、40℃反应10 min,正极材料的分离率达到99.78%,超声1 min后铝箔回收率为76%,解决了碱溶条件下铝箔回收的繁琐问题。球磨转速500 r、球磨5 h,补充10%高纯LiFePO 4的方式固相再生,再生LiFePO 4的最高放电比容量为新材料的94.75%,60次循环测试后为初始放电比容量的88.62%。

甚高频超声特征对皮肤混合瘤的诊断价值

目的分析皮肤混合瘤(mixed tumor of the skin,MTS)的甚高频超声特征,探讨甚高频超声特征对MTS的诊断价值。方法选取2019年1月至2024年3月于杭州市第三人民医院皮肤科手术并经病理证实为MTS的63例患者为观察组,与同期其他皮肤良性肿瘤63例患者作为对照组,回顾性分析并总结MTS的甚高频超声特征,评价甚高频超声特征对MTS的诊断效能。结果两组患者的肿瘤长径、横径、纵横比,是否伴钙化,有无囊性,血流分级,阻力指数比较,差异无统计学意义(P>0.05)。MTS有更明显的假包膜,且大部分内部回声欠均匀,后方伴增强效应,血流以边缘血流为主,两组比较,差异有统计学意义(P<0.05),受试者操作特征曲线结果显示绘制假包膜、内部回声欠均匀、边缘血流为主及后方增强效应4者联合的诊断效能最高,曲线下面积为0.772,敏感度为77.8%,特异性为71.4%。结论MTS具有特定的甚高频超声特征,甚高频超声可对MTS临床诊断提供帮助。

基于频率控制的封闭腔体微波无线输能技术

随着航空航天技术的快速发展,封闭腔体内的无线能量传输(Wireless Power Transmission,WPT)技术开始受到广泛关注.基于频率控制的WPT技术,可实现对电大封闭腔体(103×λ3)内的多方位传感器进行可控和高效的无线充电.电大腔体内的电场分布对频率的变化敏感,利用频率变化实现对封闭腔体场分布控制.实验结果表明,在S波段的1 m3腔体最高WPT传输效率为96.6%.设计的宽带整流电路实测整流效率最高为80%,整流效率高于50%的带宽为1.65 GHz.在2.401~2.495 GHz频段实现控制双接收机的不同工作状态,展现其在航空航天器等封闭空间中为传感器无线供电的应用前景.

基于简易实频技术的宽带高效率功率放大器设计

为了满足5G通信系统对功率放大器带宽和效率的要求,基于CGH40010F晶体管,采用简易实频技术,设计了一款工作在n77频段(3.3 GHz~4.2 GHz)的宽带高效率功率放大器。首先采用负载牵引的方法对各频点的基波最佳阻抗值以及二次谐波阻抗空间进行提取,选择简易实频技术设计宽带匹配网络,在其仿真性能良好的前提下,进行了加工测试。测试结果表明,该功率放大器在3.3 GHz~4.2 GHz频段内,漏极效率为58.1%~64.5%,增益为11.1 dB~12.9 dB,饱和输出功率为39.6 dBm~41.3 dBm。该功率放大器的性能良好,且带宽和效率具有一定的优势,可为后续宽带高效率功率放大器的设计提供参考。

高频交易的监管透视——证券市场的结构变革与法律回应

高频交易是当前日益显著的证券交易方式,其各类策略的兴起不仅得益于自动化算法带来的速度优势,还与法律提供的特定市场基础结构密切相关。根据微观市场结构理论的分析,高频交易从根本上影响了市场流动性供给与有效价格形成机制,造成了两方面重大监管挑战:一是高频交易者因市场异常波动而大量撤出可能放大市场的流动性危机,乃至形成系统性的市场崩盘风险;二是其算法模型的内在缺陷及其对专业知情交易者的利益损害,可能削弱长期的市场价格发现能力和资源分配效率。面对高频交易对市场质量的潜在负面影响,证券监管需要超越传统的披露范式,着重在证券市场基础结构层面予以回应。具体而言,监管者应当采取交易减速机制作为事后规制策略,确立高频交易者的做市义务与相应的报偿方案,以及保障投资者对市场数据的公平获取。

双频一体化超宽带探地雷达天线设计

针对目前探地雷达(Ground Penetrating Radar,GPR)产品单一频段工作所导致的耗时费力、效率低等缺点,文中设计实现了一种中心频率分别为400 MHz、1000 MHz且带宽为200~1500 MHz的双频一体化复合阵列天线,并将其应用于超宽带(Ultra-Wide Band,UWB)探地雷达系统中。阵列天线包含3个中心频率为400 MHz和6个中心频率为1000 MHz的蝶形天线,具备双频段同时探测能力,可实现一条测线含两种不同频段的探测结果,克服了传统探地雷达不同频率的重复探测问题,增强了探地雷达系统的实用性。所提出的双频一体化探地雷达天线具有超宽带、高增益、波束窄等特点,其相对带宽为153%,整个带宽内最高实现17.6 dBi峰值增益,半功率波束宽度最窄为7.6°,为高分辨率、高效率探地雷达应用提供了一种新的天线方案。

H-Algorand:基于多块输出的公有链共识机制

面向全网公开且无用户授权机制的公有链目前得到了业界的普遍重视,其中具有良好扩展性、低分叉概率的Algorand机制在公有链中被广泛使用,但Algorand机制存在区块共识效率低、不满足高频交易场景的问题。针对这些问题,首先提出一种多块Algorand(MB-Algorand)机制来提高区块共识效率;其次将Algorand机制与MB-Algorand机制配合使用得到混合Algorand(H-Algorand)机制,该机制兼顾了区块共识效率与安全性两方面的性能。仿真结果表明,在委员会遭受分布式拒绝服务(DDoS)攻击的情况下,H-Algorand机制以一定的安全性能为代价,换取了区块链网络共识效率的显著提升。当一个区块共识失败的概率在1%时,所提机制使区块链网络共识效率在提升了37. 87%的同时,安全性能仅损失4. 9%。

循环水泵节能方式的应用与对比

针对循环水泵能耗高的问题,分析变频调速、定制高效泵、自主选型改造、水泵运行模式优化、高分子涂层技术等不同节能方式在钢铁企业中的应用场景,并对比不同节能方式的优缺点,可为各工序循环水系统节能方式的选择提供参考。