Design and Fabrication of a Three Dimensional Spiral Micromixer

In this work, we present a three dimensional micromixer which consists of two layers of spiral channels overlapped together in the vertical direction. This micromixer is designed by using a smooth channel twisted into double‐layer spiral geometry with simple topological structure. Based on the principle of Dean effects, this kind of structure is beneficial to produce, enhance and sustain the Dean vortices, which can perturb the laminar fluid effectively. In order to improve the mixing performance, the detailed parameters have been optimized by using the computational fluid dynamics software. The results indicate that the erect channel which is connected with the two layers of spiral channels plays a critical role for well mixing. Meanwhile, the effect of mixing has been identified in a fabricated glass‐micromixer. The mixing ef?ciency of 90% has been achieved by optimizing the flow rate and the structure of the erect channel. Thus, this micromixer has manifested high mixing efficiency and presents good practicability in the versatile microfluidic systems.     

Synchronizing spiral waves in a coupled Rssler system

The synchronisation of spiral patterns in a drive-response Rssler system is studied.The existence of three types of synchronisation is revealed by inspecting the coupling parameter space.Two transient stages of phase synchronisation and partial synchronisation are observed in a comparatively weak feedback coupling parameter regime,whilst complete synchronisation of spirals is found with strong negative couplings.Detailed observations of the synchronous process,such as oscillatory frequencies,parameters mismatches and amplitude variations,etc,are investigated via numerical simulations.     

多层螺旋CT多平面重建在胃肠道淋巴瘤诊断中的应用及与临床分期的相关性研究

为研究多层螺旋CT多平面重建在胃肠道淋巴瘤诊断中的应用价值及检测结果与临床分期的相关性,本次研究筛选我院2016年1月~2019年6月收治的50例经病理学检查证实的胃肠道淋巴瘤患者为观察组,另选同期50例非胃肠道淋巴瘤患者为对照组,均实施多层螺旋CT多平面重建,对比两组及观察组内不同组织类型、不同临床分期患者CT重建参数(图像客观噪声、信噪比)的差异,利用Pearson相关性分析法对CT重建参数与胃肠道淋巴瘤临床分期的相关性进行检验。病理学检查证实,50例胃肠道淋巴瘤患者中有弥漫性大B细胞淋巴瘤25例、黏膜相关淋巴瘤19例、小B细胞淋巴瘤4例、套细胞淋巴瘤2例,与多层螺旋CT多平面重建符合率差异无统计学意义(P>0.05)。观察组图像客观噪声低于对照组,信噪比高于对照组,差异有统计学意义(P<0.05)。观察组内不同组织类型患者、不同临床分期患者CT重建参数差异有统计学意义(P<0.05)。Pearson相关性分析结果提示,多层螺旋CT多平面重建参数中图像客观噪声与胃肠道淋巴瘤临床分期呈负向相关性(r=-0.74,P<0.05),信噪比与胃肠道淋巴瘤临床分期呈正相关性(r=0.71,P<0.05)。据此可得,在胃肠道淋巴瘤诊断中多层螺旋CT多平面重建取得的效果更佳且CT重建参数与临床分期密切相关,对于辨别组织类型和判断临床分期具有重要参照价值,值得推广。     

Influence of Spiral Framework on Nonlinear Optical Materials

A series of spiral donor–π–acceptor frameworks (i.e. 2 – 2 , 3 – 3 , 4 – 4 , and 5 – 5 ) based on 4‐nitrophenyldiphenylamine with π‐conjugated linear acenes (naphthalenes, anthracenes, tetracenes, and pentacenes) serving as the electron donor and nitro (NO₂) groups serving as the electron acceptor were designed to investigate the relationships between the nonlinear optical (NLO) responses and the spirality in the frameworks. A parameter denoted as D was defined to describe the extent of the spiral framework. The D value reached its maximum if the number of NO₂ groups was equal to the number of fused benzene rings contained in the linear acene. A longer 4‐nitrophenyldiphenylamine chain led to a larger D value and, further, to a larger first hyperpolarizability. Different from traditional NLO materials with charge transfer occurring in the one‐dimensional direction, charge transfer in 2 – 2 , 3 – 3 , 4 – 4 , and 5 – 5 occur in three‐dimensional directions due to the attractive spiral frameworks, and this is of great importance in the design of NLO materials. The origin of such an enhancement in the NLO properties of these spiral frameworks was explained with the aid of molecular orbital analysis.     

A planar cubic Bézier spiral

A planar cubic Bézier curve segment that is a spiral, i.e., its curvature varies monotonically with arc-length, is discussed. Since this curve segment does not have cusps, loops, and inflection points (except for a single inflection point at its beginning), it is suitable for applications such as highway design, in which the clothoid has been traditionally used. Since it is polynomial, it can be conveniently incorporated in CAD systems that are based on B-splines, Bézier curves, or NURBS (nonuniform rational B-splines) and is thus suitable for general curve design applications in which fair curves are important.     

Experimental Characterization of On-Chip Single and Double-Coupling Spiral Inductors

Experimental investigations on on-chip single and double-coupling square spiral inductors on silicon substrate are performed. For each pair of double-coupling inductors, they have the same edge distance, but with different turn numbers. Based on the measured S-parameters using de-embedding procedure, the inductance and Q-factor of the single square inductor are examined at first, and good agreement is obtained in the extracted inductance, compared to the predicted values using a closed-form series inductance equation. While for double-coupling spiral inductors, the smaller the product of two turn numbers, the weaker coupling will be, and in particular at low frequencies.     

Selection of Acquisition Scan Methods in Intersatellite Optical Communications

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Rational irreducible plane continua without the fixed-point property

We define rational irreducible continua in the plane that admit fixed-point-free maps with the condition that all of their tranches have the fixed-point property. This answers in the affirmative a question of Hagopian. The construction is based on a special class of spirals that limit on a double Warsaw circle. The closure of each of these spirals has the fixed-point property.

     

一种基于时空变换和压缩感知的磁共振螺旋采样的图像重建算法

螺旋采样磁共振快速成像在功能性成像、并行成像和动态成像等领域发挥着越来越重要的作用.螺旋采样图像重建的传统算法是用核函数将螺旋状分布的k空间数据插值到均匀网格中,再利用傅里叶变换和最小二乘法进行重建.但是基于网格化的算法对核函数过于依赖,在网格化过程中产生难以避免的误差.该文提出了基于时空变换和压缩感知的l1范数的最优化模型和重建算法.时空变换矩阵描述了空间上的磁共振图像与采集到的时域信号间的关系,使得算法直接使用采集到的数据作为保真约束项,避免了网格化过程产生的误差.此外,基于图像处理单元的并行计算被用来提高时空变换矩阵的运算速度,使得算法具有较强的应用价值.     

Spiral wave chimeras in populations of oscillators coupled to a slowly varying diffusive environment

Chimera states are firstly discovered in nonlocally coupled oscillator systems. Such a nonlocal coupling arises typically as oscillators are coupled via an external environment whose characteristic time scale τ is so small (i.e., τ → 0) that it could be eliminated adiabatically. Nevertheless, whether the chimera states still exist in the opposite situation (i.e., τ ≫ 1) is unknown. Here, by coupling large populations of Stuart−Landau oscillators to a diffusive environment, we demonstrate that spiral wave chimeras do exist in this oscillator-environment coupling system even when τ is very large. Various transitions such as from spiral wave chimeras to spiral waves or unstable spiral wave chimeras as functions of the system parameters are explored. A physical picture for explaining the formation of spiral wave chimeras is also provided. The existence of spiral wave chimeras is further confirmed in ensembles of FitzHugh−Nagumo oscillators with the similar oscillator-environment coupling mechanism. Our results provide an affirmative answer to the observation of spiral wave chimeras in populations of oscillators mediated via a slowly changing environment and give important hints to generate chimera patterns in both laboratory and realistic chemical or biological systems.