Multilevel carbon architecture of subnanoscopic silicon for fast‐charging high‐energy‐density lithium‐ion batteries

Silicon(Si)is widely used as a lithium‐ion‐battery anode owing to its high capacity and abundant crustal reserves.However,large volume change upon cycling and poor conductivity of Si cause rapid capacity decay and poor fast‐charging capability limiting its commercial applications.Here,we propose a multilevel carbon architecture with vertical graphene sheets(VGSs)grown on surfaces of subnanoscopically and homogeneously dispersed Si–C composite nanospheres,which are subsequently embedded into a carbon matrix(C/VGSs@Si–C).Subnanoscopic C in the Si–C nanospheres,VGSs,and carbon matrix form a three‐dimensional conductive and robust network,which significantly improves the conductivity and suppresses the volume expansion of Si,thereby boosting charge transport and improving electrode stability.The VGSs with vast exposed edges considerably increase the contact area with the carbon matrix and supply directional transport channels through the entire material,which boosts charge transport.The carbon matrix encapsulates VGSs@Si–C to decrease the specific surface area and increase tap density,thus yielding high first Coulombic efficiency and electrode compaction density.Consequently,C/VGSs@Si–C delivers excellent Li‐ion storage performances under industrial electrode conditions.In particular,the full cells show high energy densities of 603.5 Wh kg^(−1)and 1685.5 Wh L^(−1)at 0.1 C and maintain 80.7%of the energy density at 3 C.

FAST周边喀斯特峰丛洼地不同演替阶段土壤微生物群落变化

为探索FAST周边喀斯特峰丛洼地不同植被演替阶段土壤微生物群落结构变化规律及其影响因素,该文以FAST周边草本、灌木、乔木3个演替阶段表层土壤为研究对象,采用高通量测序技术,研究不同演替阶段土壤微生物多样性、群落组成及与土壤化学性状之间的关系。研究发现:随着演替进行,土壤细菌和真菌的Shannon指数和Chao1指数呈显著下降趋势。不同演替阶段变形菌、放线菌和酸杆菌均为优势细菌门,分别占细菌群落的34.83%、19.22%、18.56%;子囊菌和担子菌为优势真菌门,分别占真菌群落的40.72%、40.11%。Pearson相关性分析发现,土壤pH、有机质、全氮、碱解氮和有机质显著影响细菌和真菌多样性;Spearman相关性分析发现,全磷、全钾、速效钾、氧化铝和交换性镁与变形菌门呈显著负相关关系(P<0.05),土壤pH、交换性钙与放线菌门呈显著正相关关系(P<0.01),铁铝氧化物与子囊菌门呈显著负相关关系(P<0.01),有效磷与担子菌门呈显著负相关关系(P<0.01)。冗余分析和Mantel分析表明,土壤pH是影响细菌和真菌群落组成的共有关键化学因子。研究结果对深入理解峰丛洼地喀斯特森林土壤微生物的变化特征与规律、科学保护和发展FAST周边喀斯特森林生态环境具有重要参考价值。

质粒DNA Fast NGS测序方法的开发和应用

质粒DNA是最常用的基因运载工具,在基因合成技术中扮演着至关重要的角色。如何实现合成质粒DNA的准确且快速检测,是确保基因组完整性和提高基因合成效率的关键。尽管基于一代DNA的测序方法,其准确性已成为行业标准,但在检测通量、检测速度和检测成本等方面仍然存在局限性,这促使科学家们不断寻求新的解决方案。基于生物酶库,开发了DNA建库酶TN5,建立了高通量质粒DNA检测方案——Fast NGS。利用不同长度、不同质量的质粒DNA样本评估了Fast NGS的可行性,并对质粒DNA样本进行了高通量测序,最后对比了Fast NGS与Sanger测序的效率。结果表明,DNA建库酶TN5蛋白的纯度和质量符合二代测序要求。Fast NGS适用于3~8 kb基因合成质粒的测序检测,其检测通量高达2500个·12 h-1,测序成功率超过95%,测序准确性与一代测序相当,并且无明显序列偏好性。Fast NGS实现了质粒DNA的高通量、快速且低成本检测,为基因合成技术的发展提供了新的方向。

Ultra Fast Shutter Driven by Pulsed High Current

Radiation simulation utilizing plasma radiation sources (PRS) generates a large number of undesirable debris, which may damage the expensive diagnosing detectors. An ultra fast shutter (UFS) driven by pulsed high current can erect a physical barrier to the slowly moving debris after allowing the passage of X-ray photons. The UFS consists of a pair of thin metal foils twisting the parallel axes in a Nylon cassette, compressed with an outer magnetic field, generated from a fast capacitor bank, discharging into a single turn loop. A typical capacitor bank is of 7.5μF charging voltages varying from 30 kV to 45 kV, with corresponding currents of approximately 90 kA to140 kA and discharging current periods of approximately 13.1μs. A shutter closing time as fast as 38 microseconds has been obtained with an aluminium foil thickness of 100 micrometers and a cross-sectional area of 15 mm by 20 mm. The design, construction and the expressions of the valve-closing time of the UFS are presented along with the measured results of valve-closing velocities.

Design of fast crystallization of nanosized zeolite omega crystals at higher temperatures

Fast crystallization of nanosized zeolite crystals is a very popular process used for practical zeolite catalyst applications. Herein, we report a designer crystallization process for nanosized zeolite omega crystals based on the relationship between the crystallization time and temperature in the Arrhenius equation. Compared to the conventional hydrothermal synthesis of zeolite omega(72 h at room temperature and 240 h at 100℃, MAZ-100), the crystallization of zeolite omega presented in this work only requires a very short time interval(5 h at 180℃, MAZ-180). Physicochemical characterizations, including XRD, SEM, N2 sorption isotherms, and 27 Al MAS NMR show that the product of zeolite omega(MAZ-180) has good crystallinity and uniform nanocrystals. More importantly, after the loading of Pt nanoparticles(0.5 wt%), the Pt/H-MAZ-180 catalyst exhibits higher isomer selectivity and lower cracking selectivity than those of the Pt/H-MAZ-100 catalyst in the hydroisomerization of n-dodecane. These results suggest the potential applications of these omega nanocrystals as supporting catalyst compounds in industrial processes.

Fast-transient techniques for high-frequency DC–DC converters

A 30 MHz voltage-mode controlled buck converter with fast transient responses is presented.An improved differential difference amplifier(DDA)-based Type-III compensator is proposed to reduce the settling times of the converter during load transients,and to achieve near-optimal transient responses with simple PWM control only.Moreover,a hybrid scheme using a digital linear regulator with automatic transient detection and seamless loop transition is proposed to further improve the transient responses.By monitoring the output voltage of the compensator instead of the output voltage of the converter,the proposed hybrid scheme can reduce undershoot and overshoot effectively with good noise immunity and without interrupting the PWM loop.The converter was fabricated in a 0.13μm standard CMOS process using 3.3 V devices.With an input voltage of 3.3 V,the measured peak efficiencies at the output voltages of 2.4,1.8,and 1.2 V are 90.7%,88%,and 83.6%,respectively.With a load step of 1.25 A and rise and fall times of 2 ns,the measured 1%settling times were 220 and 230 ns,with undershoot and overshoot with PWM control of 72 and 76 mV,respectively.They were further reduced to 36 and 38 mV by using the proposed hybrid scheme,and 1%settling times were also reduced to 125 ns.

A fast approach to optimize dye loading of photoanode via ultrasonic technique for highly efficient dye-sensitized solar cells

A distinctive method is proposed by simply utilizing ultrasonic technique in Ti02 electrode fabrication in order to improve the optoelectronic performance of dye-sensitized solar cells （DSSCs）. Dye molecules are at random and single molecular state in the ultrasonic field and the ultrasonic wave favors the diffusion and adsorption processes of dye molecules. As a result, the introduction of ultrasonic technique at room temperature leads to faster and more well-distributed dye adsorption on TiO2 as well as higher cell efficiency than regular deposition, thus the fabrication time is markedly reduced. It is found that the device based on 40 kHz ultrasonic （within 1 h） with N719 exhibits a Voc of 789 mV, Jsc of 14.94 mA]cm2 and fill factor （FF） of 69.3, yielding power conversion efficiency （PCE） of 8.16%, which is higher than device regularly dyed for 12 h （PCE = 8.06%）. In addition, the DSSC devices obtain the best efficiency （PCE = 8.68%） when the ultrasonic deposition time increases to 2.5 h. The DSSCs fabricated via ultrasonic technique presents more dye loading, larger photocurrent, less charge recombination and higher photovoltage. The charge extraction and electron impedance spectroscopy （EIS） were performed to understand the influence of ultrasonic technique on the electron recombination and performance of DSSCs.

MONITORING ELECTROLYTIC REACTION OF NUCLEAR FAST RED BY HIGH PERFORMANCE CAPILLARY ELECTROPHORESIS

A specific example is given to show that high performance capillary electrophoresis can serve as a simple and effective menthod for the moniforing of an dectrochedemical oxidation reaction of nuclear fast red.

Running slow or running fast;that is the question:The merits of high-intensity interval training

In a recent issue of the Journal of Sport and Health Science,García-Pinillos et al.~1 reviewed evidence on the effects of highintensity intermittent training(interval training)(HIIT)on muscular and performance adaptations in recreational runners.

Fast Electrical Detection of Carcinoembryonic Antigen Based on AlGaN/GaN High Electron Mobility Transistor Aptasensor

As one of the most important tumor-associated antigens of colorectal adenocarcinoma, the carcinoembryonic antigen （CEA） threatens human health seriously ali over the globe. Fast electrical and highly sensitive detection of the CEA with A1GaN/GaN high electron mobility transistor is demonstrated experimentally. To achieve a low detection limit, the Au-gated sensing area of the sensor is functionalized with a CEA aptamer instead of the corresponding antibody. The proposed aptasensor has successfully detected different concentrations （ranging from 50picogram/milliliter （pg/ml） to 50 nanogram/milliliter （ng/ml）） of CEA and achieved a detection limit as low as 50pg/ml at Vas = 0.5 V. The drain-source current shows a c/ear increase of 11.5μA under this bias.

NEW TECHNOLOGY OF ROADSIDE ENTRY SUPPORT IN ADVANCING-MINING BY PUMPING HIGHWATER-CONTENT FAST SETTING-SOLIDIFYING MATERIALS

Roadside entry supporting technology by pumping high water-content fast setting-solidifying materials in advancing-mining was industrially tested in Yangzhuang Coal Mine, Huaibei Coal Mining Administration. Roadside packing parameters were determined according to the properties of high water-content fast setting-solidifying materials, as well as geological and mining conditions. A new roadside packing technological system was designed to use pumping-delivery method to transport the materials. With respect to the special conditions in the advancing mining system, effective temporary support systems were designed and tried. The technical and economic benefits from this new industrial experiment were carefully analyzed and evaluated.

Impairment of extra-high frequency auditory thresholds in subjects with elevated levels of fasting blood glucose

This study was performed to assess whether there is an association between elevated Fasting Blood Glucose(FBG) and hearing impairment in Bangladeshi population. A total of 142 subjects(72 with elevated FBG; 70 control) were included in the study. The mean auditory thresholds of the control subjects at 1,4,8 and 12 kHz frequencies were 6.35 ± 0.35,10.07 ± 0.91,27.57 ± 1.82, 51.28 ± 3.01 dB SPL(decibel sound pressure level), respectively and that of the subjects with elevated FBG were 8.33 ± 0.66,14.37 ± 1.14, 38.96 土 2.23, and 71.11 ± 2.96 dB.respectively. The auditory thresholds of the subjects with elevated FBG were significantly(p < 0.05) higher than the control subjects at all the above frequencies, although hearing impairment was most evidently observed at an extra-high(12 kHz) frequency. Subjects with a long duration of diabetes(>10 years) showed significantly(p < 0.05) higher level of auditory thresholds at 8 and 12 kHz, but not at 1 and 4 kHz frequencies,compared to subjects with shorter duration of diabetes(≤10 years). In addition, based on the data of odds ratio, more acute impairment of hearing at the extra-high frequency was observed in diabetic subjects of both older(>40 years) and younger(<40 years) age groups compared to the respective controls. The binary logistic regression analysis showed a 5.79-fold increase in the odds of extra-high frequency hearing impairment in diabetic subjects after adjustment for age, gender and BMI. This study provides conclusive evidence that auditory threshold at an extra-high frequency could be a sensitive marker for hearing impairment in diabetic subjects.

直流快速开断技术研究进展和展望

由于直流电流无自然过零点且短路电流上升率高,直流电流快速开断与系统故障切除成为制约直流电力系统发展的一大瓶颈。该综述首先介绍了直流快速开断技术要求与难点。其次,详细分析了直流快速开断过程涉及的关键技术,包括电流转移技术、固态式直流开断技术、介质恢复技术和高速机械开关技术等,综述了各种技术的当前发展现状及其应用情况,对比了不同技术方案的特点及适应性。最后,对直流快速开断技术未来发展方向进行了讨论和总结,为小型化、高性能、低成本、高可靠快速直流断路器的研发及推广应用提供了新的技术思路。

低延迟低抖动的FAST解码器设计与实现

为了解决金融FAST(financial information exchange adapted for streaming)协议面临的纯软件解码延迟高,FPGA(field programmable gate array)硬件解码开发周期长、更新困难的问题,提出了基于OpenCL和HLS的硬件解码模式。通过对FAST数据解码的标记、切分、合并、解码模块进行流水优化,对切分和字段解码进行并行操作,将数据的输入输出改为流式接口减少I/O口的延时以及对切分数组进行分割映射等优化方式实现了解码过程低延迟、低抖动。实验结果表明,相比纯软件解码,本文提出的解码器处理速度提升了11倍,解码延迟缩短至1/6,抖动幅度控制在10 ns之内。相比传统HDL方式的FPGA定制硬件开发,开发效率可提升3~4倍,从而更好地满足产品更新换代的需求。

池式钠冷快堆堆内自然循环余热排出设计研究

基于装量功率比约为1 t/MW的较典型池式钠冷大功率快堆的堆内自然循环设计,采用ERAC程序,对两组4种不同事故余热排出系统(DHRS)输入条件下,反应堆在紧急停堆后堆内的自然循环余热排出特性进行分析。结果表明,从DHRS启用到其对堆芯产生显著冷却效应,需要较长时间,在千秒量级。在该段时间内,堆芯余热的排出依靠反应堆固有的热工流体安全特性。随后,在堆内关键温度上升到限值之前启用DHRS带出池内热量,使堆内关键温度处于下降趋势即可满足安全要求;相比将独立热交换器(DHX)布置在冷池,将其布置在热池时,热池温度及主容器壁温相对要低,这有利于主容器的温度控制,其效果要优于布置于冷池。另外,不同布置会对堆芯盒内、盒间流流量产生影响,但总体上对堆芯的冷却效应影响不大;池式钠冷快堆余热排出设计中,要充分利用固有热工流体安全特性,降低对DHRS的时效性要求。可以考虑将全部的DHX都布置在热池,并缩小设备体积、降低散热功率设计值,或在不降低安全性的前提下选用其他更经济便捷的有效方式等,以此大幅降低余热排出设备投入成本,降低反应堆运行成本,提高经济性。本文研究结果可为我国后续的商用快堆、一体化快堆等池式液态金属堆的堆内自然循环设计提供重要参考。

采用局部-全局区域重检测机制的无人机长期跟踪算法

为解决基础跟踪器面对遮挡和移出视野等长期跟踪场景时易出现跟踪失败等问题,提出了一种基于局部-全局区域重检测的无人机长期跟踪算法。设计了基础滤波器,将高置信度样本与其结合,并融入自适应时空正则化,解决了滤波器退化问题,提高了模型鲁棒性以及复杂场景下的性能;优化了滤波器更新策略,通过评价跟踪结果进行自适应更新;设计快速尺度滤波器,解决了跟踪过程中的尺度变化问题;设计了局部-全局区域重检测机制,跟踪失败时启动重检测器恢复跟踪目标,先完成局部区域重检测,若恢复跟踪失败,再利用全局区域重检测器继续恢复目标跟踪状态。实验结果表明:所提算法在UAV20L数据集上的精确度和准确率分别可达0.724和0.621,与基于时空正则化相关滤波器的跟踪算法(STRCF)相比分别提升了25.9%和20.6%,与同类主流算法相比,跟踪效果得到提升,证明了算法的有效性。

轴承转子系统快变过程振动响应的高精度频谱分析

针对高速轴承转子系统的启停过程,研究平稳和非平稳信号的高精度频谱分析方法,利用比例校正法对平稳信号频谱分析后的频率、幅值、相位进行了校正,建立一种将t时空域非平稳信号转变为t~2时空域平稳信号的方法,并基于平稳信号的比例校正法对其进行频谱分析,最后返回到t时空域获得某时刻的频域参数。仿真分析结果表明:该方法可以准确提取平稳信号的谱特征,也能较精确地提取非平稳信号特定时刻的频率、幅值和相位,提取结果精度较好,有效解决轴承转子系统快变过程的谱分析特征提取问题,为动力学特性分析提供了新思路。

基于快速气相色谱电子鼻研究超高压射流处理脱脂乳的感官品质

以新鲜脱脂乳为原料,探究超高压射流(ultra-high pressure jet,UHPJ)处理对脱脂乳感官品质的影响。脱脂乳经100~300 MPa UHPJ处理后,采用电子眼、电子鼻、感官评价分别检测脱脂乳颜色、气味及综合风味变化。结果表明:脱脂乳的主要色号以4095白色为主,占比46.80%~53.83%;电子鼻共检测到酯类、酮类、醛类等42种挥发性风味成分,大部分风味成分呈乳香、果香、烘烤香、青草等气味,主成分分析结果显示,300 MPa处理脱脂乳样品和其他样品风味相差较大;感官评价结果显示,UHPJ处理脱脂乳的乳香和甜味较为突出,不同样品之间在甜味、蛋白胨味、铁锈味、烧焦味和寡淡味方面差异明显,250、300 MPa处理样品生成的二甲基硫等硫化物能够显著增强脱脂乳的烧焦味、蛋白胨味。综上,200 MPa UHPJ处理能较完整地保留脱脂乳中的风味成分,进而实现原料乳风味的保持。

6000t自由锻造水压机改油压机关键技术研究

本文提出了6000t自由锻造水压机升级改造的必要性,介绍了6000t自由锻造水压机升级改造的路径及改造后主要参数,阐述了控制系统升级改造方案及其关键技术。

快速反射镜位移传感器高精度采集电路设计与实现

对位移传感器高精度及低延时的数据采集是实现快速反射镜高精度和高带宽的关键。详细分析了复合轴中快速反射镜位移传感器采集电路的需求,并依此进行了硬件电路和软件设计。经过测试,采集电路有效分辨率可达17bit,数据频率为5kHz,信号采集延时200μs,能够实现对快速反射镜位移传感器信号的高速高精度采集,可有效提升控制带宽和控制精度。