电流模式控制Boost变换器中的呼吸现象

本文揭示了在电流模式控制Boost变换器中,由于存在内部或外部耦合电路引起的传导和辐射干扰,使得有可能产生呼吸现象,这是一种以较长的周期按顺序交替历经规则、分谐波和混沌状态的时间分叉现象,在功率变换电路中是一种非正常的工作状态.可以通过建立具有固定初相位的模拟干扰信号,并使其频率与变换器的开关频率相同,以便将呼吸现象(时间分叉)转换为参数分叉,并从分叉控制的角度来对这种呼吸现象进行合理解释和理论分析,从而给出变换器稳定设计的理论依据.理论分析结果与数值仿真是完全一致的,另外,在电路实验中也得到了印证.     

Cusp磁场中CZ硅氧浓度分布的数值模拟

利用FEAMG-CZ软件,模拟研究了cusp磁场对称面(定义为0高斯面)与熔体自由表面距离对直拉硅固液界面氧浓度分布的影响。结果表明:随着0高斯面的下移,熔体中的最小氧浓度降低,而固液界面的氧浓度升高,且径向均匀性变差。分析表明,这与熔体自由表面处的Marangoni流有关,抑制该流动有利于熔体中氧的蒸发,从而在自由表面下获得更低氧浓度的熔体,但会阻碍自由表面下方低氧熔体往固液界面的输运。因此,推断当0高斯面位于熔体自由表面下某一位置时,固液界面氧浓度将达到最低。模拟中,该位置位于Hm=0～-0.01m之间。     

基于相位解卷绕的膛内弹丸运动信号处理

国内外常规靶场主要使用微波干涉仪测量膛内弹丸纵向运动多普勒信号,根据膛内弹丸位移与其相位存在的线性关系,精确计算位移参数。针对一般Hilbert变换相位线性化存在的计算复杂度高、运算量大等不足,提出采用数字信号相位解卷绕算法对Hilbert变换得到的相位进行处理,使相位曲线连续化的方法。试验表明,该方法程序实现简洁、易调试、效率高,成功应用于某型号火炮实弹射击内弹道运动参数测量中。     

A Fractional-N CMOS DPLL with Self-Calibration

A digital phase-locked loop (DPLL) based on a new digital phase-frequency detector is presented.The self-calibration technique is employed to acquire wide lock range,low jitter,and fast acquisition.The DPLL works from 60 to 600MHz at a supply voltage of 1.8V.It also features a fractional-N synthesizer with digital 2nd-order sigma-delta noise shaping,which can achieve a short lock time,a high frequency resolution,and an improved phase-noise spectrum.The DPLL has been implemented in SMIC 0.18μm 1.8V 1P6M CMOS technology.The peak-to-peak jitter is less than 0.8% of the output clock period and the lock time is less than 150 times of the reference clock period after the pre-divider.     

Retraction: 3D Printing of Bilineage Constructive Biomaterials for Bone and Cartilage Regeneration

Adv. Funct. Mater. 2017 , 27, 1703117 DOI: 10.1002/adfm.201703117 The above article, first published online on 31 July 2017 in Wiley Online Library ( https://doi.org/10.1002/adfm.201703117 ) and corrected on 19 March 2019 ( https://doi.org/10.1002/adfm.201900376 ) has been retracted by agreement with the authors, the journal Editor‐in‐Chief, and Wiley‐VCH Verlag GmbH & Co. KGaA. The retraction has been agreed upon due to several flawed figures as published in the article, containing duplicate images, which calls the validity of these data into question. Reference C. Deng, Q. Yao, C. Feng, J. Li, L. Wang, G. Cheng, M. Shi, L. Chen, J. Chang, C. Wu, Adv. Funct. Mater. 2017 , 27, 1703117.     

基于模糊控制策略的快速反射镜伺服控制

伺服性能是保证精确跟踪的前提条件,为了探索出提高快速反射镜伺服性能的控制方法,提出一种将模糊控制策略与PID结构相结合的模糊控制器用于快速反射镜伺服回路。该模糊控制器既继承了PID便于工程实现的优点,又拥有可自适应整定控制参数的特点,从而可提高现有快速反射镜的伺服性能,更好地适应各类运行工况。以基于高频摇摆电机的快速反射镜为应用对象设计了模糊控制器,进行仿真实验,并与基于传统PID控制的现有方案进行了对比。对实际工况下快速反射镜伺服性能的仿真实验结果表明:基于模糊控制策略的快速反射镜将抑制带宽从50 Hz提高到120 Hz、随机输入信号下稳态误差均方根从12. 996″压缩到1. 620″,验证了所提出的模糊控制器对提升快速反射镜伺服性能的可行性及有效性;基于模糊控制的快速反射镜可作为高精度复合轴系统中的子轴部分,应用于战术激光武器等要求跟瞄精度达到微弧度量级的光束定向场合。     

基于DSP技术的RFID读写器设计

文中介绍了RFID系统及RFID读写器,论述了基于DSP技术的RFID读写器设计方法.在描述RFID系统组成的基础上,给出了读写器的软硬件设计流程.重点阐述了RFID读写器的防冲突设计.该读写器已应用于门禁系统中,实际应用结果表明其性能良好.     

柠檬醛对阿糖胞苷抗白血病细胞HL-60强效增敏作用研究

通过对柠檬醛与临床首选药物之一阿糖胞苷联用抗白血病细胞株HL-60的研究,探索二者联用的生物效应及其作用机制。采用MTT和DAPI核染色等方法观察柠檬醛同阿糖胞苷的不等浓度组合HL-60的增殖抑制和诱导凋亡作用,相分析电泳激光散射技术检测联用对细胞表面电荷的影响。柠檬醛显示一定的抑制HL-60增殖,促进其凋亡的效应,并与阿糖胞苷有较显著的协同性,增加柠檬醛浓度与药物阿糖胞苷联合作用可使膜表面电位下降的幅度增大。柠檬醛有联合阿糖胞苷临床治疗潜力。     

Efficient and photostable CsPbl2Br solar cells realized by adding PMMA

Organic-inorganic hybrid perovskite materials demonstrate promising applications in high-efficiency perovskite solar cells (PSCs) with a certified power conversion efficiency (PCE) of 25.5％ (https://www.nrel.gov/pv/cell-efficiency.html).However, intrinsically volatile and thermally unstable nature of the organic cations result in poor thermal stability of organic-inorganic hybrid perovskite materials, hampering the commercialization of organic-inorganic hybrid PSCs[1].All-inorganic CsPbl3-xBrx (x =0-3) perovskites have been attracting great attention in recent years because of their higher thermal stability[2].Among the reported CsPbl3-xBrx perovskites, CsPbl2Br bears a reasonable balance between bandgap and phase stability, thus becomes the most extensively studied material[3-15].Though there are many works aiming at achieving high-efficiency CsPbl2Br PSCs, improving the photostability of CsPbl2Br PSCs is another key for commercialization of all-inorganic PSCs.Intriguingly, it has been reported that CsPbl2Br is susceptible to make light-induced phase segregation, i.e.severe segregation of CsPbl2Br to low-bandgap I-rich and wide-bandgap Br-rich domains via ion diffusion, leading to obvious current-voltage hysteresis and decrease of stabilized power output (SPO)[16-20].Such a light-induced phase segregation can be suppressed by optimizing the interface between perovskite layer and charge-transport layer[18, 19].     

Using fluorinated and crosslinkable fullerene derivatives to improve the stability of perovskite solar cells

Organic-inorganic hybrid perovskite solar cell (PSC) is a third-generation photovoltaic technology[1,2],and the certi-fied power conversion efficiency (PCE) has reached 25.5％(https://www.nrel.gov/pv/cell-efficiency.html),which can rival solar cells based on crystalline-Si and other inorganic semi-conductors.The intrinsic instability of perovskite materials could impede PSC commercialization[3].To date,a variety of strategies such as composition engineering,additive engi-neering,interface engineering and encapsulation technique are employed to improve the long-term stability of PSCs[4-9].In particular,fullerene materials with high electron mobility,high electron affinity,small reorganization energy and ad-justable energy level have been widely utilized as interfacial layers or additives in PSCs for efficiency and stability improve-ment[10].Among them,fluorinated and crosslinkable fullerene derivatives can improve the stability of PSCs effectively.The fluorinated fullerene derivatives could improve the mois-ture stability because of the hydrophobicity of fluorine atom.The crosslinked fullerene derivatives can protect the electron-transport layers (ETLs) against solvent erosion during per-ovskite solution deposition,and the as-formed organic net-works can improve mechanical stability of PSCs.