Ring inversion process for a series of 3,5‐dialkyl‐1‐oxa‐3,5‐diazacyclohexanes: 1H DNMR study and semiempirical calculations

The ring inversion process for a series of 3,5‐dialkyl‐1‐oxa‐3,5‐diazacyclohexanes was studied using proton dynamic nuclear magnetic resonance (¹H DNMR) spectroscopy in conjunction with semiempirical calculations. At low temperature, the ring methylene protons decoalesced into two AB spin systems in a 2:1 ratio. Lineshape simulations of the DNMR spectra provided first‐order rate constants for magnetic exchange. The energy barrier for each inversion reaction was calculated from the respective rate constants. In general, as the size of the N‐alkyl group increased, the barrier to ring inversion decreased. A similar trend was seen in semiempirical calculations that modeled the ring inversion process. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of Interaction upon Translocation of Confined Polymer Chain Through Nanopore

运用二维的键长涨落模型和蒙特卡洛方法研究高分子链从一个受限空间到自由空间穿孔过程中,链单体与纳米孔之间的相互作用.结果表明,在不同的链长和纳米孔交互作用下,高分子链成功穿越自由能能垒取决于链长和纳米孔长度,并且由于交互作用降低了自由能能垒,导致高分子链在纳米管的平均捕获时间缩短.     

Behaviour of the current in a two-dimensional Bttiker Landauer motor with entropic barriers

The behaviour of the current in a two-dimensional Büttiker--Landauer motor, which is a position-dependent temperature-driven Brownian motor, is investigated in the presence of entropic and energy barriers. It is found that the motion of the Brownian particles is influenced by the shape of the channel. The existence of an entropic barrier can cause an asymmetric current as the flatness ratio of the shape varies. There exists an optimized flatness ratio (nonzero) at which the current reaches its maximum value.     

The influence of the structures and compounds of DLC coatings on the barrier properties of PET bottles

To reduce the oxygen transmission rate through a polyethylene terephthalate (PET) bottle (an organic plastic) diamond-like carbon (DLC) coatings on the inner surface of the PET bottle were deposited by radio frequency plasma-enhanced chemical vapour deposition (RF-PECVD) technology with C₂H₂ as the source of carbon and Ar as the diluted gas. As the barrier layer to humidity and gas permeation, this paper analyses the DLC film structure, composition, morphology and barrier properties by Fourier transform infrared, atomic force microscopy, scanning electron microscopy and oxygen transmission rate in detail. From the spectrum, it is found that the DLC film mainly consists of sp³ bonds. The barrier property of the films is significantly relevant to the sp³ bond concentration in the coating, the film thickness and morphology. Additionally, it is found that DLC film deposited in an inductively coupled plasma enhanced capacitively coupled plasma source shows a compact, homogeneous and crack-free surface, which is beneficial for a good gas barrier property in PET bottles.     

Concentric-ring structures in an atmospheric pressure helium dielectric barrier discharge

This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a two-dimensional diffusion--drift model at atmospheric pressure between two parallel circular electrodes covered with thin dielectric layers. With a relative high frequency the discharge structures present different appearances of ring structures within different radii in time due to the evolvement of the filaments. The spontaneous electron density distributions help understanding the formation and development of self-organized discharge structures. During a cycle the electron avalanches are triggered by the electric field strengthened by the feeding voltage and the residual charged particles on the barrier surface deposited in the previous discharges. The accumulation of charges is shown to play a dominant role in the generation and annihilation of the discharge structures. Besides, the rings split and unify to bring and annihilate rings which form a new discharge structure.     

Erratum to "Quantum compact model for thin-body double-gate Schottky barrier MOSFETs"

<正>The statement for the third paragraph of the right column of page 3079 (Chinese Physics B, 2008, Vol. 17,No. 8, pp. 3077-3082 )[1]is inappropriate. This paragraph should be restated as follows.     

磁通量子比特qubit信号强度随势垒偏置电压的变化

在20mK极低温下,测量了超导磁通量子比特的环流方向,并测到量子比特(qubit)信号.通过改变磁通量子比特的势垒高度,得到qubit信号强度随势垒高度的变化的实验数据并建立理论模型解释了实验现象.     

一维势垒散射中粒子的概率分布

利用数值计算方法研究了E>U0、0相似文献   

介质阻挡放电跃变升压模式下靶波斑图研究

在大气压氩气介质阻挡放电中,首次通过跃变外加电压得到了稳定的靶波斑图.实验分别研究了跃变再缓变和直接跃变升压模式下靶波斑图的稳定性和波长选择.研究发现,跃变再缓变升压之后得到的靶波斑图不稳定,其与螺旋波相互转换.在这种转换中,靶波每次出现的时间为几十毫秒.直接跃变升压得到的靶波斑图稳定性明显增强,其稳定时间通常为5 min以上.比较不同升压模式下靶波斑图的波长,发现直接跃变升压模式下波长随电压升高减小较快.综上表明,升压模式对靶波斑图的稳定性和波长都有影响. 关键词： 介质阻挡放电 靶波斑图 跃变升压 缓变升压