Solar Coronal Mass Ejection as a Result of Magnetic Helicity Accumulation in the Corona

Coronal mass ejections（CMEs） are a major form of solar activities.A CME takes away 10^15-16 g of plasma from solar low corona,to disturb the near-Earth space if the CME direction is favorable.Here we summarize our understandings and reasoning that lead us to conclude that CMEs are the unavoidable products of magnetic helicity accumulation in the corona.Our study puts the formation of magnetic flux ropes and CME eruptions as natural and unavoidable results of coronal evolution.     

Giant magnetic field from moiré induced Berry phase in homobilayer semiconductors

When quasiparticles move in condensed matters, the texture of their internal quantum structure as a function of position and momentum can give rise to Berry phases that have profound effects on the material’s properties. Seminal examples include the anomalous Hall and spin Hall effects from the momentum-space Berry phases in homogeneous crystals. Here, we explore a conjugate form of the electron Berry phase arising from the moiré pattern: the texture of atomic configurations in real space. In homobilayer transition metal dichalcogenides, we show that the real-space Berry phase from moiré patterns manifests as a periodic magnetic field with magnitudes of up to hundreds of Tesla. This quantity distinguishes moiré patterns from different origins, which can have an identical potential landscape, but opposite quantized magnetic flux per supercell. For low-energy carriers, the homobilayer moirés realize topological flux lattices for the quantum-spin Hall effect. An interlayer bias can continuously tune the spatial profile of the moiré magnetic field, whereas the flux per supercell is a topological quantity that can only have a quantized jump observable at a moderate bias. We also reveal the important role of the non-Abelian Berry phase in shaping the energy landscape in small moiré patterns. Our work points to new possibilities to access ultra-high magnetic fields that can be tailored to the nanoscale by electrical and mechanical controls.     

Phase locking dynamics in 2D Josephson junction arrays with external load

Phase locking in a basic two-dimensional hybrid Josephson junction array consisting of two rows and four columns shunted by an external load is investigated, exploiting an approximation combining the ideas of harmonic balance with that of the slowly varying phase procedure. Using small ring inductances, the junction voltages within the same row oscillate nearly in-phase unless the external magnetic flux in the loops is near a multiple of a quarter of the flux quantum. Without external load we have found a stable antiphase regime where both rows carry out uniform interferometer oscillations. A stable in-phase regime, favored in an optimized radiation source, can be reached by means of an external inductive shunt for small external fields only.     

The compound cylinder and the strength problem

A general discussion is given of the effects of various strength theories on the design of compound cylinders composed of as many as four tubes. Departing from the usual practice in problems of this type, the more modern theories of strength are included.The problem considered is limited to simultaneous, yielding in all component tubes of the cylinder under the action of bore pressure. In addition, new short design procedures employing graphical means are discussed which will considerably reduce the time ordinarily required in such calculations. The methods used are flexible since component tubes of different materials following different strength theories can be treated as easily as cylinders composed of tubes of one material.     

Magnetic fields in the sun

The observed properties of solar magnetic fields are reviewed, with particular reference to the complexities imposed on the field by motions of the highly conducting gas. Turbulent interactions between gas and field lead to heating or cooling of the gas according as the field energy density is less or greater than the maximum kinetic energy density in the convection zone. The field strength above which cooling sets in is 700 G.A weak solar dipole field may be primeval, but dynamo action is also important in generating new flux. The dynamo is probably not confined to the convection zone, but extends throughout most of the volume of the sun. Planetary tides appear to play a role in driving the dynamo.     

高效节能低噪风扇优化设计

根据扭曲风叶成型原理和叶栅理论,推导出扭曲风叶风扇气动设计计算方法,分析叶轮结构与其气动性能参数的内在关系,编制成风扇优化设计软件。通过该软件得到了用户需要的座舱风扇的扇叶几何图形及气动特性曲线,并与实测的数据相比较,误差在设计范围内。     

Refillable and magnetically actuated drug delivery system using pear-shaped viscoelastic membrane

We report a refillable and valveless drug delivery device actuated by an external magnetic field for on-demand drug release to treat localized diseases. The device features a pear-shaped viscoelastic magnetic membrane inducing asymmetrical deflection and consecutive touchdown motion to the bottom of the dome-shaped drug reservoir in response to a magnetic field, thus achieving controlled discharge of the drug. Maximum drug release with 18 ± 1.5 μg per actuation was achieved under a 500 mT magnetic flux density, and various controlled drug doses were investigated with the combination of the number of accumulated actuations and the strength of the magnetic field.     

简析传统音乐文化资源的保护及传承

随着全球化时代的到来,各国的文化也在逐渐地融合,各种文化带来的冲击使得我国传统音乐的发展一波三折。19世纪时人们对于西方文化有了新的认识,也导致了国民与本国文化的严重脱节,崇洋的现象随处可见,我国的传统音乐正遭受着严重的考验。因此本文通过分析传统音乐的概念以及意义,提出了保护与传承传统音乐文化资源的措施。     

A “twisted” microfluidic mixer suitable for a wide range of flow rate applications

This paper proposes a new “twisted” 3D microfluidic mixer fabricated by a laser writing/microfabrication technique. Effective and efficient mixing using the twisted micromixers can be obtained by combining two general chaotic mixing mechanisms: splitting/recombining and chaotic advection. The lamination of mixer units provides the splitting and recombination mechanism when the quadrant of circles is arranged in a two-layered serial arrangement of mixing units. The overall 3D path of the microchannel introduces the advection. An experimental investigation using chemical solutions revealed that these novel 3D passive microfluidic mixers were stable and could be operated at a wide range of flow rates. This micromixer finds application in the manipulation of tiny volumes of liquids that are crucial in diagnostics. The mixing performance was evaluated by dye visualization, and using a pH test that determined the chemical reaction of the solutions. A comparison of the tornado-mixer with this twisted micromixer was made to evaluate the efficiency of mixing. The efficiency of mixing was calculated within the channel by acquiring intensities using ImageJ software. Results suggested that efficient mixing can be obtained when more than 3 units were consecutively placed. The geometry of the device, which has a length of 30 mm, enables the device to be integrated with micro total analysis systems and other lab-on-chip devices.     

A new twist on graphene: an interview with Pablo Jarillo-Herrero and Allan MacDonald

Graphene is the building block of graphite, made of carbon atoms bonded into sheets of hexagonal rings just a single atom thick. Although such isolated sheets had been predicted for many decades to exist, and had been grown on other surfaces, interest in this material exploded after the discovery in 2004 that single sheets could be made easily and cheaply by separating them mechanically from graphite flakes (a process called exfoliation). Although graphene is often advertised as a ‘wonder material’—electronically conducting, transparent and extremely strong and flexible—much of the interest in it is more fundamental. As a 2D conductor, graphene shows unusual electronic and magnetic properties that enable the study of quantum-mechanical effects of confinement and of correlations between electron motions—some of which might find applications in electronic devices. The excitement of this discovery was reflected in the award of the 2010 Nobel Prize in Physics to two pioneers in the field: Andre Geim and Konstantin Novoselov of the University of Manchester in the UK.This rich behavior is broadened still further when two graphene sheets are brought close enough to interact with one another. In particular, the electronic properties may then depend on the relative orientation of the sheets: how aligned the two ‘honeycomb’ lattices are. Two grids superimposed on one another may create ‘superlattices’: regularities at larger scales than the grid spacing, due to registry (commensurability) between the two at certain angles. This so-called moiré effect is sometimes evident for two closely spaced grid-like fences seen from afar. Experimentally exploring the electronic properties of such ‘twisted bilayer graphene’ requires an ability to precisely control the position and orientation of the two sheets. These phenomena are now recognized as generic to other 2D materials, such as hexagonal sheets of boron nitride. They have revealed a fertile playground for condensed-matter physics. In particular, striking electronic properties appear at certain ‘magic-angle’ twists of the layers.NSR spoke to two of the leading experts in the study of magic-angle twisted bilayer graphene (MATBG): experimentalist Pablo Jarillo-Herrero of the Massachusetts Institute of Technology and theorist Allan MacDonald of the University of Texas at Austin.     

Optimal control of a flywheel energy storage system with a radial flux hybrid magnetic bearing

This paper describes the design and implementation of digital controllers for a flywheel energy storage device that incorporates a radial flux hybrid permanent magnetic bearing. Although the uncontrolled device is asymptotically stable, active control is required to: (i) ensure that a finite radial air gap is maintained at all times, and (ii) attenuate the oscillations of the flywheel which reduce the efficiency of the motor generator. The paper presents the design of gain scheduled discrete time linear quadratic regulator (LQR) and linear quadratic Gaussian (LQG) controllers for this rotordynamic system. Real time experiments are conducted to investigate the performance of the controllers. The result indicates that the LQR controller with approximate system velocities is easier to implement than the LQG controller, and also provides superior performance.     

构建我国开放式科技中介信息服务体系

我国科技中介业发展的主要现状及问题是:区域结构不平衡,区域之间的开放与合作刚刚起步;主体结构不平衡,功能定位模糊;行业结构层次偏低,缺少有竞争实力的旗舰;科技中介服务业发展的软环境薄弱等。为了加快构建我国开放式科技中介信息服务体系,应从三个层次入手:一是构建联系我国区域之间的科技中介信息服务网络;二是构建联系我国各类创新主体在境内、外之间的科技中介信息服务网络;三是构建联系我国本土企业与跨国公司之间科技中介信息服务网络。     

甚低频信号数字化传输及处理技术

为避免甚低频信号在传输中受到其他设备带来的噪声干扰,采用一种新的解决方案,对甚低频信号数字化后,利用双绞线进行传输,双绞线传输接口采用ADSL方案,其传输距离远、抗干扰能力强。此方案可有效解决甚低频信号传输中的干扰问题,并为下一步的甚低频信号数字处理提供了基础。     

Efficient dielectrophoretic cell enrichment using a dielectrophoresis-well based system

Whilst laboratory-on-chip cell separation systems using dielectrophoresis are increasingly reported in the literature, many systems are afflicted by factors which impede “real world” performance, chief among these being cell loss (in dead spaces, attached to glass and tubing surfaces, or sedimentation from flow), and designs with large channel height-to-width ratios (large channel widths, small channel heights) that make the systems difficult to interface with other microfluidic systems. In this paper, we present a scalable structure based on 3D wells with approximately unity height-to-width ratios (based on tubes with electrodes on the sides), which is capable of enriching yeast cell populations whilst ensuring that up to 94.3% of cells processed through the device can be collected in tubes beyond the output.     

Effects of a magnetic field on the free convective flow through a porous medium bounded by an infinite vertical porous plate with constant heat flux

This paper investigates the effects of a magnetic field on the free convective flow of a viscous, incompressible, dissipative fluid through a porous medium, occupying a semi-infinite region of the space bounded by an infinite vertical and porous plate. The plate is subjected to a normal suction velocity and the heat flux at the plate is constant. The magnetic field is of uniform strength and is applied perpendicular to the plate. An analytical solution to the problem is obtained. The influence of the magnetic parameter (M) and permeability parameter (K) is discussed for the case of air (P = 0.71) when the plate is subjected to a constant suction velocity and is being cooled by free convection currents.     

Methods for estimating the number of relevant documents in a collection

Several statistical sampling methods are evaluated for estimating the total number of relevant documents in a collection for a given query. The total number of relevant documents is needed in order to compute recall values for use in evaluating document retrieval systems. The simplest method considered uses simple random sampling to estimate the number of relevant documents. Another type of random sampling, which assigns unequal selection probabilities to the individual documents in the collection, is also investigated. An alternative approach considered uses curve fitting and extrapolation, where a smooth curve is developed which relates precision to document rank. Another curve relates a function of precision to the query-document score. In either case, the curve is extrapolated to the total number of documents in order to estimate the number of relevant documents. Empirical comparisons are made of all three methods.     

碳纳米管的生长机理

目前,对于碳纳米管成核及生长机理依然理解不充分,文章描述了碳纳米管在电弧蒸发法及激光蒸发法的生长过程。许多早期的模型都是假设在生长过程中有气相现象,但是有一个实验证据表明多壁碳纳米管和单壁碳纳米管两者的形成都包含有一个固态的转换。而在促进纳米管生长的过程中,升温速率好像也是一个重要的因素。     

具有定子电压误差补偿的MRAS磁链观测器

在电压型逆变器供电的交流异步电机驱动系统中,应用模型参考自适应(MRAS)磁链观测器进行磁链观测时,常用定子电压给定值代替实际值,从而带来幅值误差和直流偏值,造成磁链观测误差,影响电机低速运行的稳定性.为了提高交流异步电机无速度传感器矢量控制的低速性能,提出了一种定子电压幅值和直流偏置补偿办法,仿真实验验证了所提出方法的有效性     

Comparison of digoxin concentration in plastic serum tubes with clot activator and heparinized plasma tubes

Introduction:

Sample type recommended by the manufacturer for the digoxin Abbott assay is either serum collected in glass tubes or plasma (sodium heparin, lithium heparin, citrate, EDTA or oxalate as anticoagulant) collected in plastic tubes. In our hospital samples are collected in plastic tubes. Our hypothesis was that the serum sample collected in plastic serum tube can be used interchangeably with plasma sample for measurement of digoxin concentration. Our aim was verification of plastic serum tubes for determination of digoxin concentration.

Materials and methods:

Concentration of digoxin was determined simultaneously in 26 venous blood plasma (plastic Vacuette, LH Lithium heparin) and serum (plastic Vacuette, Z Serum Clot activator; both Greiner Bio-One GmbH, Kremsmünster, Austria) samples, on Abbott AxSYM analyzer using the original Abbott Digoxin III assay (Abbott, Wiesbaden, Germany). Tube comparability was assessed using the Passing Bablok regression and Bland-Altman plot.

Results:

Serum and plasma digoxin concentrations are comparable. Passing Bablok intercept (0.08 [95% CI = −0.10 to 0.20]) and slope (0.99 [95% CI = 0.92 to 1.11]) showed there is no constant or proportional error.

Conclusion:

Blood samples drawn in plastic serum tubes and plastic plasma tubes can be interchangeably used for determination of digoxin concentration.     

基于双层委托代理关系的村镇银行治理机制分析

从中央政府、地方政府与村镇银行的双重委托-代理关系出发,通过逻辑分析与数理求解的方法,对村镇银行的治理模式与治理机制进行分析,研究结果表明：地方政府对于村镇银行激励强度与村镇银行“支农”努力的成效系数正相关,与村镇银行的支农成本、村镇银行的风险规避系数以及村镇银行所处的外部风险程度负相关;中央政府对于地方政府的向下分成比例与村镇银行“支农”努力的成效系数负相关,与村镇银行的支农成本、村镇银行的风险规避系数以及村镇银行所处的外部风险程度正相关。