Tuning strategies and structure effects of electrocatalysts for carbon dioxide reduction reaction

Carbon dioxide emissions have increased due to the consumption of fossil fuels,making the neutralization and utilization of CO_(2) a pressing issue.As a clean and efficient energy conversion process,electrocatalytic reduction can reduce carbon dioxide into a series of alcohols and acidic organic molecules,which can effectively realize the utilization and transformation of carbon dioxide.This review focuses on the tuning strategies and structure effects of catalysts for the electrocatalytic CO_(2) reduction reaction(CO_(2)RR).The tuning strategies for the active sites of catalysts have been reviewed from intrinsic and external perspectives.The structure effects for the CO_(2)RR catalysts have also been discussed,such as tandem catalysis,synergistic effects and confinement catalysis.We expect that this review about tuning strategies and structure effects can provide guidance for designing highly efficient CO_(2)RR electrocatalysts.

Tuning Martensitic Phase Transition by Non-Magnetic Atom Vacancy in MnCoGe Alloys and Related Giant Magnetocaloric Effect

The effects of non-magnetic atom vacancy on structural, martensitic phase transitions and the corresponding magnetocMoric effect in MnCoGel-x alloys are investigated using x-ray diffraction and magnetic measurements. The introduction of non-magnetic atom vacancy leads to the decrease of the martensitic transition temperature and realizes a temperature window where magnetic and martensitic phase transitions can be tuned together. Moreover, the giant magnetocaloric effect accompanied with the coupled magnetic-structural transition is ob- tained. It is observed that the peak values of magnetic entropy change of MnCoGeo.97 are about -13.9, -35.1 and -47.4J.kg-1K-1 for △H = 2, 5, 7T, respectively.

双阻尼模型调谐质量阻尼器在随机激励下的减震性能研究

该文提出黏滞阻尼与滞变阻尼共同作用的双阻尼模型调谐质量阻尼器(Dual Damping Tuned Mass Damper,DD-TMD),并对白噪声作用下DD-TMD进行减震优化研究。讨论了DD-TMD的构成、优势和应用范围,并总结了DD-TMD的力学机理。提出适用于DD-TMD的H_(2)优化方法,并通过数值寻优得到了最优参数和基于稳定区域的DD-TMD参数优化方法。此外,通过DD-TMD的H_(2)优化方法进一步得到了DD-TMD的等效附加黏滞阻尼比,为工程设计奠定应用基础。以变摩擦摆式调谐质量阻尼器(Variable Friction Pendulum Tuned Mass Damper,VFP-TMD)为DD-TMD的实际应用算例,通过20条地震波检验所提出的优化方法对地震激励的减震性能影响。结果表明:H_(2)优化下的DD-TMD可以提供与常规黏滞阻尼TMD相当的控制效果。采用DD-TMD可以通过随机理论成功模拟与常摩擦阻尼等效的黏滞阻尼,并为带有初始摩擦的VFP-TMD提供有效可靠的优化设计方法。相较于前人所做的数值寻优方法,按照DD-TMD模型优化的VFP-TMD可以提供更加优异的减震控制效果且阻尼耗能能力提高了16.6%。

Silicon carbide resonant tuning fork for microsensing applications in high-temperature and high G-shock environments

We present the fabrication and testing of a silicon carbide （SiC） balanced mass doublended tuning fork that survives harsh environments without compromising the device strain sensitivity and resolution bandwidth. The device features a material stack that survives corrosive environments and enables high-temperature operation. To perform hightemperature testing, a specialized setup was constructed that allows the tuning fork to be characterized using traditional silicon electronics. The tuning fork has been operated at 600°C in the presence of dry steam for short durations. This tuning fork has also been tested to 64 000 G using a hard-launch, soft-catch shock implemented with a light gas gun. However, the device still has a strain sensitivity of 66 Hz/μe and strain resolution of 0. 045 μe in a 10 kHz bandwidth. As such, this balanced-mass double-ended tuning fork can be used to create a variety of different sensors including strain gauges, accelerometers, gyroscopes, and pressure transducers. Given the adaptable fabrication process flow, this device could be useful to micro-electro-mechanical systems （MEMS） designers creating sensors for a variety of different applications.

Effect of Ge Incorporation on Bandgap and Photosensitivity of Amorphous SiGe Thin Films

We investigated the structural and optical properties of amorphous-SiGe thin films synthesized via a low-cost, high-growth rate deposition method. Films were formed by e-beam evaporation of mixed pellets of Si and Ge. Film composition was varied by changing the weight ratio of Si and Ge pellets mixture. Films were amorphous with a composition uniform. Ge-rich films are in tensile stress, while Si-rich films are in compressive stress. As the Ge fraction increases (from 22 at.% to 94 at.%), the optical bandgap decreases (from 1.7 eV to 0.9 eV) and the photosensitivity of the films extends into IR band of solar spectrum. By changing the weighted ratio of the evaporation source mixture, the bandgap and optical sensitivity of a-SiGe films can be easily tuned. Our studies prove that a-SiGe films are a tunable absorber. This can be used for photo-detector, photovoltaic and microelectronic applications to extend the spectral response.

Beam-beam effects and mitigation in a future proton-proton collider

The beam-beam effects in a hadron collider with an unprecedented energy scale were studied.These effects are strongly related to the attainable luminosity of the collider.Long-range interactions were identified as the major factor limiting the dynamic aperture,which is strongly dependent on the crossing angle,β*,and bunch population.Different mitigation methods of the beam-beam effects were addressed,with a focus on the compensation of long-range interactions by electric curren wires.The CEPC-SPPC project is a two-stage large circular collider,with a first-stage circular electron-positron collider(CEPC)and a second-stage super proton-proton collider(SPPC).The design of the SPPC aims to achieve a center-of-mass energy of 75 TeV and peak luminosity of approximately 1×10^(35) cm^(-2)s^(-1).We studied the beam-beam effects in the SPPC and tested the effectiveness of the mitigation methods.We found that with compensation using electric current wires,the dynamic aperture is at an acceptable level.Moreover,considering the significant emittance damping in this future proton-proton collider the beam-beam effects and compensation are more complicated and are studied using long-term tracking.It was found that with a smaller emittance,the head-on interactions with a crossing angle become more prominent in reducing the beam stability,and combined head-on and long-range compensation is needed to improve the beam quality.When the reduction in population owing to burnoff was included,it was found that the coupling between the transverse and longitudinal planes at smaller emittance is the main driving source of the instabilities.Thus,crab cavities and emittance control are also necessary than just the compensation of the long-range interactions to improve the beam stability.This study serves as an example for studying the beam-beam effects in future proton-proton colliders.

薄储层厚度对地震反射波的影响规律研究

薄储层的衰减机制主要包含固有衰减和散射衰减,在地震频带范围内,散射衰减主要表现为薄层调谐效应,固有衰减主要由介质的黏弹性导致。为了厘清储层厚度对地震波的影响规律,应用广义传播矩阵正演算法对比分析了各向同性楔状模型和各向异性楔状模型地震波振幅随偏移距的变化特征,然后利用改进的反演谱分解技术和频变AVO反演方法提取模型正演数据的频散属性,最后分析储层厚度对地震波频散特征的影响规律。研究结果表明,固有衰减会明显减小储层的反射振幅,而散射衰减使储层反射振幅随着厚度先增加后减小;地震波频散随着地层厚度的增加呈“M”型变化,其两个极大值分别出现在λ/20和λ/2附近(λ为波长),极小值对应厚度为λ/4;当储层厚度小于λ/4时,散射衰减对反射振幅和频散的影响明显强于固有衰减。

地震作用下调谐黏滞质量阻尼器阻尼比增效效应与优化设计研究

调谐黏滞质量阻尼器(Tuned Viscous Mass Damper,TVMD)是一种有效的被动惯容减震装置,本文针对地震作用下建筑结构TVMD阻尼比增效效应与优化设计展开研究。将TVMD对结构自身阻尼耗能功率的控制效果归纳为TVMD等效附加阻尼比,并基于随机振动理论推导了等效附加阻尼比的理论表达式。为了使TVMD更具实际应用价值,TVMD理论上应取得比同阻尼系数的黏滞阻尼器(VD)更大的等效附加阻尼比,这一现象定义为TVMD阻尼比增效效应,并定义了阻尼比增效系数来量化评估阻尼比增效效应。将等效附加阻尼比和阻尼比增效系数均作为优化目标,提出了TVMD最优设计参数理论解。参数分析结果表明,本文解具有良好的稳定性和适用性,为了更高效地发挥阻尼比增效效应,推荐TVMD质量比不超过0.3或阻尼比不超过0.1。以某七层标准钢框架结构作为工程算例展示了TVMD设计流程,并验证了本文解的有效性和优越性。算例分析结果表明,使用本文解设计TVMD能显著放大其阻尼元件变形,表现出了理想的阻尼比增效效应。与传统解相比,本文解还具有另一个明显优势,即保证TVMD的减震效果优于同阻尼系数的VD,不存在减震效率问题。

微调平衡三号方对食管癌调强放疗患者疗效的影响

目的 探讨微调平衡三号方对食管癌调强放疗患者疗效的影响。方法 选择2019年2月至2022年3月江阴市中医院收治的78例食管癌患者,以随机数字表法将其分成研究组与对照组,各39例。2组均接受调强放疗治疗,对照组接受常规肠内营养支持治疗,研究组在对照组的基础上接受微调平衡三号方治疗。2组治疗时间均为3个月。对比2组临床疗效、免疫功能、生存质量(QLQ-C30)量表评分以及不良作用发生率。结果 研究组患者疾病控制率(89.74%)比对照组(71.79%)高(P<0.05)。治疗后,2组患者CD3^(+)、CD8^(+)T淋巴细胞水平均升高(P<0.05),且研究组比对照组高(P<0.05)。治疗后,2组患者CD4^(+)T淋巴细胞、CD4^(+)/CD8^(+)T淋巴细胞水平均降低(P<0.05),且研究组比对照组低(P<0.05)。治疗后,2组QLQ-C30评分均升高(P<0.05),且研究组比对照组高(P<0.05)。2组Ⅰ~Ⅳ级放射性食管炎、消化道反应、骨髓抑制发生率比较差异均无统计学意义(P>0.05)。结论 微调平衡三号方治疗食管癌调强放疗患者疗效确切,可改善患者的免疫功能、生存质量,且安全可靠。

超宽带脉冲作用下抗干扰器件的特性分析

基于高重频超宽带脉冲,研究了高重频超宽带脉冲对自适应调零天线和PIN限幅器的抗干扰性能的影响。基于Matlab和ADS仿真软件搭建模型,并通过实验平台对ADS的仿真结果进行验证。实验结果表明:对于导航接收机中的自适应调零天线,超宽带干扰脉冲会使其射频链路产生饱和效应,从而使功率倒置算法失效,进而无法在干扰方向形成零陷;对于PIN限幅器,超宽带干扰脉冲可以使其产生明显的尖峰泄露效应。相较于ns量级的窄谱高功率微波脉冲,超宽带脉冲对限幅器的干扰能力更强。

大数据在食品生产安全监管中的应用探讨

本文分析了大数据相关技术在食品生产安全监管中的应用,指出了其面临的挑战,提出了一套针对性的食品生产安全大数据监管模型,并探讨了该模型的实施路径和预期效果,以供参考。

悬挑转换结构舒适度分析

通过对楼盖结构竖向振动舒适度的基本理论阐释,明确了舒适度验算的基本方法和提高舒适度的主要措施。结合15 m长悬挑结构的高层建筑工程,采用YJK和MIDAS Gen对不同悬挑部位分别进行竖向自振频率和峰值加速度的多阶多频多工况验算。针对行走激励和有节奏运动的时程荷载分布,分别对楼盖竖向振动响应进行分析比较。对于峰值加速度显著超限的楼盖结构,分别采取提高刚度和增加阻尼的办法,满足振动舒适度的相关要求。在此基础上,对两种解决方案进行了技术判别。通过完整的计算分析,摸清了悬挑转换桁架结构舒适度的内在规律和可靠措施。同时,对《建筑楼盖结构振动舒适度技术标准》(JGJ/T 441—2019)相关章节的设计参数和设计方法进行了探讨,补充了优化建议,以作参考。

石英单晶微机械陀螺仪研究进展

对Z切、ST切、AT切三种切割方式的石英单晶微机械陀螺仪的基本工作原理进行了阐述,梳理了不同类型陀螺仪的发展历程,重点介绍了三种石英单晶微机械陀螺仪的设计结构、性能特点及其应用场景,并从灵敏度、动态范围、稳定性、抗冲击性及工作频率等方面对三种类型石英微机械陀螺仪各自的性能优势与面临的技术挑战进行了评述,总结了当前国内外在石英单晶微机械陀螺仪研究领域的主要进展和创新点。最后,针对不同切割方式的石英单晶微机械陀螺仪的结构及工作特点,分析了其各自的优点与不足,进行了总结和对比,讨论了石英微机械陀螺仪的未来发展方向。

利用负刚度效应调谐的硅调谐式陀螺仪

为了验证硅调谐式陀螺仪原理的可行性,研究了硅调谐式陀螺仪的调谐机理,硅转子运动模态和加工工艺以及信号检测与再平衡控制回路。提出了一种利用力矩器的负刚度效应来实现硅调谐式陀螺仪调谐的新方法,推导了静电负刚度调谐的理论公式;设计、仿真、加工了硅薄片式转子平衡环部件和电容器极板,给出了电容信号敏感接口电路、升压放大电路、反馈校正电路和再平衡控制回路。在此基础上,实现了硅调谐式陀螺仪原理样机。试验结果证实,利用负刚度效应调谐是可行的,接口电路和再平衡控制回路设计是合理的。初步性能测试表明,硅调谐式陀螺仪可实现标度因数为1.42mV/((°)/s),标度因数非线性为2.47%,量程为±200(°)/s。试验结果验证了该陀螺仪基本原理的可行性。

半波长交流输电线路电容调谐分析

采用半波长交流输电方式时,当线路的自然长度不足半个波长时,需要对电气波长进行人工调谐。基于传输线理论模型的电容调谐网络,要求调谐电容必须均匀分布在整个输电线路上,根据半波长输电条件(即线路的电气长度等于1个工频半波)推导出调谐电容值计算公式,并结合某1 000 k V交流输电线路参数,分别仿真不同调谐电容数时的调谐效果。结果表明,并非补偿点数量越多,调谐效果就越好。当调谐电容数达到8时,调谐效果趋于稳定,即满足了半波长输电要求,同时使得调谐电容数目最少。

基于功率法的TMD系统参数优化与减振性能分析

建立了结构-TMD体系的功率平衡方程,从功率的角度分析了TMD系统在地震激励下减振效果,并考虑结构周期与阻尼比的影响。经HHT变换得到地震激励的时频图,解释了有控体系较无控结构在某些时刻各功率放大的原因。推导了结构基底受简谐荷载作用时,主结构的耗能功率公式,以主结构的耗能功率最小为优化目标得到TMD最优频率比及阻尼比,并与以往的四种优化方法进行了对比。结果表明,基于耗能功率最小的优化方法在随机激励下的位移方差及确定地震波作用下的能量及功率响应的大小均介于上述四种优化方法之间,且较无控结构均有大幅度的减小,因此该优化方法具有一定的适应性与可靠性。

调液阻尼器减振效应研究的综述和展望

调频液体阻尼器(Tuned Liquid Damper,简称TLD)作为一种被动耗能减振装置,近年来在结构减振中得到应用。从减振原理、影响因素、分析方法、设计方法等方面对TLD近年来所取得的成果进行了总结,并探讨了TLD研究的发展趋势,指出TLD数值仿真技术、非线性分析、可控TLD研究和开发、地震下的减振效应以及TLD-结构设计方法将是下一步的研究重点。

分布反馈式光纤激光器的光热调谐方法

针对现有光纤激光器调谐方法通常不能兼顾调谐幅度和调谐速率的问题,提出了一种基于光热效应的调谐方法,有效兼顾了调谐幅度和调谐速率的要求。分析了光纤激光器的输出波长随泵浦功率变化而改变的实验现象,并以980nm泵浦源自身调谐为例,进行了静态和动态实验,结果表明:基于光热效应的分布反馈式光纤激光器静态调谐幅度达392MHz/100mA,动态调谐速率超过2kHz,验证了光纤激光器光热调谐方案的可行性。

TMD对列车作用下大跨钢桁架桥的振动控制研究

南京长江大桥是连接我国南北的重要交通命脉,考虑到列车引起的振动对该桥危害较大,有必要采取有效措施对其进行振动控制。结合车桥动力方程,有限元分析时将列车经过大桥全过程的桥梁结构作为时变系统来考虑,基于ANSYS平台编制了动力时程响应分析程序。据此研究了调谐质量阻尼器(TMD)在该桥减振控制中的参数敏感性和控制效果,并对比分析了列车时速对减振效果的影响。结果表明,TMD在其刚度和阻尼系数取值合理时可达到最优控制效果;设计TMD对该桥列车致振动竖向加速度的控制效果明显,且在列车时速较高时减振效果更加显著。

射频辉光放电等离子体的电探针诊断

本文简要叙述了探针诊断技术的作用，比较了单、双探针测量技术的异同，分析了当前所碰到的主要问题和各种可能的解决办法，着重报导了我们提出和制作的加热调谐单探针装置，不仅抑制了射频干扰，还克服了中毒效应对探针测量的影响。首次成功地测量了射频辉光放电硅烷等离子体的电子能量分布函数、电子平均能量和密度。并对测量结果进行了简要的分析。