Characterization and methanol adsorption of walnut-shell activated carbon prepared by KOH activation

Walnut-shellactivated carbons(WSACs)were prepared by the KOH chemicalactivation.The effects of carbonization temperature,activation temperature,and ratio of KOH to chars on the pore development of WSACs were investigated.Fourier transform infrared spectroscopy(FTIR),X-ray powder diffraction(XRD),and scanning electron microscopy(SEM)were employed to characterize the microstructure and morphology of WSACs.Methanoladsorption performance onto the optimalWSAC and the coal-based AC were also investigated.The results show that the optimalpreparation conditions are a carbonization temperature of 700 ℃,an activation temperature of 700 ℃,and a mass ratio of 3.The BET surface area,the micropore volume,and the micropore volume percentage of the optimalWASC are 1636 m~2/g,0.641 cm~3/g and 81.97%,respectively.There are a lot of micropores and a certain amount of meso-and macropores.The characteristics of the amorphous state are identified.The results show that the optimalWSAC is favorable for methanoladsorption.The equilibrium adsorption capacity of the optimalWSAC is 248.02mg/g.It is shown that the equilibrium adsorption capacity of the optimalWSAC is almost equivalent to that of the common activated carbon.Therefore the optimalWSAC could be a potentialadsorbent for the solar energy adsorption refrigeration cycle.     

用于频率综合的电荷泵锁相环电路设计

在阐述了锁相环频率综合的工作原理、分析和设计方法的基础上,结合环路稳定性和相位噪声两方面因素对锁相环电路进行了建模及分析。采用安捷伦公司的ADS软件对锁相环进行了系统设计及仿真,并采用Cadence公司的Spectre-RF系列软件进行了锁相环具体电路设计和仿真。采用该方案设计的锁相环输出频率范围18.15 23 GHz,相位噪声-90 dBc/Hz,锁定时间小于5μs。     

A (4-fluorophenyl)(phenyl)phosphine oxide-modified epoxy resin with improved flame-retardancy,hydrophobicity, and dielectric properties

The compound (4-fluorophenyl)(phenyl) phosphine oxide (4-FPO) was designed, synthesized, and used in the modification of epoxy resin (EP). The 4-FPO-modified EP was prepared by curing the reaction mixture of diglycidyl ether of bisphenol A (DGEBA) and 4-FPO in the presence of 4,4′-diaminodiphenylsulfone (DDS). Compared with the unmodified EP, the limiting oxygen index value of the EP/4-FPO-0.6 (4-FPO-modified EP with 0.6 wt% of phosphorus) increased to 31.6%, and the sample achieved UL-94 V-0 rating. The peak of the heat release rate, average of the heat release rate, and total heat release of EP/4-FPO-0.6 were reduced by 39, 24, and 19%, respectively. Mechanism study showed that the quenching effect in the gas and barrier effect in the condensed phase were responsible for the enhanced flame-retardant properties of the 4-FPO-modified EP. The results showed that hydrophobicity and dielectric properties of the modified EP were clearly improved.     

Flow profile measurement in microchannel using the optical feedback interferometry sensing technique

The need to accurately measure flow profiles in microfluidic channels is well recognised. In this work, we present a new optical feedback interferometry (OFI) flow sensor that accurately measures local velocity in fluids and enables reconstruction of a velocity profile inside a microchannel. OFI is a self-aligned interferometric technique that uses the laser as both the transmitter and the receiver thus offering high sensitivity, fast response, and a simple and compact optical design. The system described here is based on a commercial semiconductor laser and has been designed to achieve a micrometer-range spatial resolution. The sensor performance was validated by reconstructing the velocity profile inside a circular cross-section flow-channel with 320  $\upmu $ m internal diameter, with a relative error smaller than 1.8 %. The local flow velocity is directly measured, thus avoiding the need for model based profile calculation and uncertainties inherent to this approach. The system was validated by successfully extracting the flow profiles in both Newtonian and shear-thinning liquids.     

从设计软件中获取明细表信息技术研究

机械机电行业中大量使用设计软件制作的工程图纸,如何从这些图纸中有效和快速的获取其中的明细表信息是一个关键环节.本文针对目前明细表信息提取过程繁琐、效率不高的问题,通过对明细表信息提取方法的阐述,实现了从设计软件图纸中简洁、快速的读取信息的目标.在此基础上还可以把这些信息集成到一个软件中,以便实现和其他软件系统的集成.     

基于数字图像处理的控制系统动态性能测量

针对目前位置控制伺服系统动态性能较难准确测量的问题,提出了一种基于激光和数字图像处理的测量思路,实现了对运动轨迹的数字化监测,并以某火炮检修中的位置控制伺服系统为例,详细介绍了系统组成、软件处理系统及相应的试验结果.这是开展位置控制伺服系统动态性能准确测量的有益尝试.     

Review of roll-to-roll fabrication techniques for colloidal quantum dot solar cells

Colloidal quantum dots (CQDs) are of great interest to photovoltaic (PV) technologies as they possess the benefits of solution-processability, size-tunability, and roll-to-roll manufacturability, as well as unique capabilities to harvest near-infrared (NIR) radiation. During the last decade, lab-scale CQD solar cells have achieved rapid improvement in the power conversion efficiency (PCE) from ~1% to 18%, which will potentially exceed 20% in the next few years and approach the performance of other PV technologies, such as perovskite solar cells and organic solar cells. In the meanwhile, CQD solar cells exhibit long lifetimes either under shelf storage or continuous operation, making them highly attractive to industry. However, in order to meet the industrial requirements, mass production techniques are necessary to scale up the fabrication of those lab devices into large-area PV modules, such as roll-to-toll coating. This paper reviews the recent developments of large-area CQD solar cells with a focus on various fabrication methods and their principles. It covers the progress of typical large-area coating techniques, including spray coating, blade coating, dip coating, and slot-die coating. It also discusses next steps and new strategies to accomplish the ultimate goal of the low-cost large-area fabrication of CQD solar cells and emphasizes how artificial intelligence or machine learning could facilitate the developments of CQD solar cell research.     

周期激励下广义离散Duffing系统的多稳态分析

具有硬边界的动基座双自由度动力学系统在受到基座周期性激励与随机冲击扰动时,振子与边界碰撞后的强非线性特性导致系统产生复杂的混沌行为.本文基于Soft Actor-Critic强化学习框架,构建了同时实现振动控制与基座运动跟随的智能算法,研究了宽频域范围内含有硬边界约束的动基座双自由度系统的动力学控制效果.通过构建包含相对位移、控制力的复合奖励函数,实现动力学系统精度较高的轨迹跟踪与振动抑制.结果表明,该算法可以实现频率范围跨2个数量级(0.01Hz到1Hz)的有效振动控制,并通过与PID控制方法的比较,展现了该方法在复杂环境中的稳定性与泛化性.     

Seismic response and stability of underground rock caverns: a case study of Baihetan underground cavern complex

The seismic stability of the underground cavern complex, which houses the Baihetan hydropower plant in Yunnan Province, China, currently the world’s 2nd largest underground rock cavern group, is studied in this article. A preliminary performance-based seismic assessment approach specified for underground rock caverns is firstly proposed. The seismic performance objectives are classified. Reference earthquake motions are specified with the determination of the seismic variables. Detailed dynamic response analyses (Method 2B) are conducted based on the parameters given by the cyclic dynamic loading tests with medium strain rate. The seismic response of acceleration, stress, displacement and failure zones are studied. In addition, the seismic spectrum characteristics are analysed with a newly introduced wavelet packet technique. The mechanism of the support measures for seismic stability is also discussed. The assessment for seismic performance of the underground cavern complex is obtained by integrating these results. Serviceability objective of the underground cavern complex under operating basis earthquake may be satisfied, and the safety objective be feasible but with the presence of the proposed reinforcement system. The seismic isolation design is preferred, yet not necessary. And if any seismic isolation design is to be adopted, the frequency absorption range of the isolation material is expected to be 1–4 Hz.     

横磁处理对1K107纳米晶铁芯磁性能的影响及高频损耗分析

对Fe73.5Cu1Nb3Si13.5B9纳米晶铁芯分别进行普通热处理与横磁处理,并检测铁芯经两种热处理后的各项磁性能。获得了各频率下损耗与幅值磁密的关系。结果表明,横磁处理降低损耗效果较明显,该方法在高频电力电子变压器铁芯领域具有潜在应用前景。损耗分离结果表明,横磁处理后,磁滞损耗、涡流损耗、剩余损耗在总损耗中所占比例分别为不变、升高、降低。横磁处理后,磁畴结构改变,以磁矩旋转磁化为主要磁化方式,降低畴壁共振造成的异常损耗是除降低磁滞损耗外,降低总损耗的另一原因。