The processes involved in the solid-to-liquid phase transition

The detailed study of crystals and the dynamics of the melting process in two and three dimensions is a fundamental and interesting research topic, which is important for increasing our knowledge of solid state physics. In natural crystals, structure information can be obtained principally by Bragg-scattering of neutrons, electrons or photons on the crystal, followed by an analysis in Fourier space. Dynamical aspects cannot be investigated in these systems. Recently, a new crystalline system was discovered whose properties are such that the melting transition can be investigated in great detail — the ‘plasma crystal’. This article presents the results of such an investigation and shows evidence for the existence of intermediate phases between the solid, liquid and gaseous phases. The observed ‘structured’ phase transition may be specific for plasma crystals but, alternatively, it may indicate the existence of intermediate stages in the melting transition more generally.     

Room-temperature multiferroicity and diversified magnetoelectric couplings in 2D materials

Multiferroics are rare in nature due to the mutual exclusive origins of magnetism and ferroelectricity. The simultaneous coexistence of robust magnetism/ferroelectricity and strong magnetoelectric coupling in single multiferroics is hitherto unreported, which may also be attributed to their potential conflictions. In this paper, we show the first-principles evidence of such desired coexistence in ultrathin-layer CuCrS₂ and CuCrSe₂. The vertical ferroelectricity is neither induced by an empty d shell nor spin-driven, giving rise to an alternative possibility of resolving those intrinsic exclusions and contradictions. Compared with their bulk phases, the ferromagnetism in the thin-layer structures (two–six layers) can be greatly stabilized due to the enhanced carrier density and orbital shifting by vertical polarization, and the Curie temperatures of both ferromagnetism and ferroelectricity can be above room temperature. Moreover, a considerable net magnetization can be reversed upon ferroelectric switching, where the change in spin-resolved band structure also renders efficient ‘magnetic reading + electrical writing’. The thickness-different layers may even exhibit diversified types of magnetoelectric coupling, which both enriches the physics of multiferroics and facilitates their practical applications.     

Production rate and diameter analysis of spherical monodisperse microbubbles from two-dimensional,expanding-nozzle flow-focusing microfluidic devices

Flow-focusing microfluidic devices (FFMDs) can produce microbubbles (MBs) with precisely controlled diameters and a narrow size distribution. In this paper, poly-dimethyl-siloxane based, rectangular-nozzle, two-dimensional (2-D) planar, expanding-nozzle FFMDs were characterized using a high speed camera to determine the production rate and diameter of Tween 20 (2% v/v) stabilized MBs. The effect of gas pressure and liquid flow rate on MB production rate and diameter was analyzed in order to develop a relationship between FFMD input parameters and MB production. MB generation was observed to transition through five regimes at a constant gas pressure and increasing liquid flow rate. Each MB generation event (i.e., break-off to break-off) was further separated into two characteristic phases: bubbling and waiting. The duration of the bubbling phase was linearly related to the liquid flow rate, while the duration of the waiting phase was related to both liquid flow rate and gas pressure. The MB production rate was found to be inversely proportional to the sum of the bubbling and waiting times, while the diameter was found to be proportional to the product of the gas pressure and bubbling time.     

低维结构铁电材料光电性能和铁电薄膜红外焦平面列阵器件物理研究

系统研究了晶粒尺寸对铁电性、相结构、晶格动力学和光致发光等性质的影响。研究了择优取向钛锆酸铅铁电薄膜异质结构的取向机理、光学常数以及电学性质,并采用建模的方法分析了影响铁电薄膜红外探测器的因素     

科学思想扩散的阶段性 ——以绿色会计思想在我国的扩散为例

 本文利用维普数据库资料的实证调查核算，研究了绿色会计思想在我国的扩散问题。文章发现，绿色会计思想在我国的扩散经历了3个阶段，目前处于一种稳步发展阶段。这种阶段性反映了知识创新包括三个阶段：发现－初步接受阶段，学术界热点阶段和社会应用阶段。     

Liquid crystals: the race is on

The expression ‘liquid crystal’ raises questions in that it is a contradiction in terms. In this paper we explain precisely what is meant by this expression, concentrating mainly on the physical properties of liquid crystals and the functioning of liquid crystal displays (LCDs for short) — currently so familiar from watches, calculators, small computers, and electronic games.     

Sliding mode optimal control for linear systems

This paper addresses the optimal control problem for a linear system with respect to a Bolza–Meyer criterion with a non-quadratic non-integral term. The optimal solution is obtained as a sliding mode control, whereas the conventional linear feedback control fails to provide a causal solution. Performance of the obtained optimal controller is verified in the illustrative example against the conventional LQ regulator that is optimal for the quadratic Bolza–Meyer criterion. The simulation results confirm an advantage in favor of the designed sliding mode control.     

基于偏振特性的液晶光开关原理研究

根据液晶响应速度快,对光的吸收少的特性,研究了液晶光开关的工作原理,并与其它光开关相比较,分析了液晶光开关在光纤通讯方面的应用前景,建立了三种液晶光开关的物理模型。     

BaTiO3-CoFe2O4复合多铁纳米陶瓷的制备及性能研究

采用化学共沉淀法和溶胶凝胶法制备BaTiO3-CoFe2O4两相复合陶瓷粉体,并通过成型1200℃烧结制备BaTiO3-CoFe2O4两相复合陶瓷,测试XRD和TEM,并对其介电,漏电,铁电进行了研究。XRD分析制备的BTO陶瓷为四方结构,铁电性较好,具有较大的介电常数和较低的介电损耗,CFO陶瓷为尖晶石结构,复合陶瓷具有两相结构,同时具有铁电性和磁性。     

浙江省近500年来干湿状况变化的若干特征

利用杭州、宁波、金华、温州4站近500余年(1470～1990)来的旱涝等级序列及实测降水资料,分析了浙江省近500年来干湿状况变化的若干特征.浙江省干湿状况的长期变化是以干湿期交替出现为特征的,有明显的阶段性和准周期性,没有趋于某一极端的趋势.近500年来,干湿变化与冷暖变化之间的联系以冷干、暖湿形式为主.此外,还指出浙江省干湿状况的变化与太阳黑子磁周期活动有较密切的关系.     

On metastable states of equilibrium in thermodynamics

In this paper the concept of reversibility is considered, and it is found that the question of reversibility of a process depends upon the number of independent variables of a system. For a single homogeneous closed phase subject only to mechanical and thermal changes, just two independent variables have been considered in classic thermodynamics. This practice requires that some states be characterized as metastable. Justification is offered for a change in this accepted view. Instead of classifying systems in phases, it is proposed to consider systems on the basis of number of types of transformation.A single gaseous phase subject to dissociation is found to be analogous to a liquid vapor system; each system has three independent variables, such as p, v, T, and equations of state will be of the form ? = F(p, v, T) = G(p, T, x) and v = (Θ(p, T, x) where e is the internal energy and x the degree of transformation. These equations include all metastable states.     

重油催化裂化沉降器油气相态计算

为了确定重油催化裂化沉降器中液相组分的数量及其对结焦的贡献，以工业重油催化裂化装置的沉降器为研究对象，按照正构烷烃模型分子法确定基团组成的方法，利用已编写的气化率计算程序，求取了沉降器内反应油气的重组分——油浆馏分的气化率，确定反应油气的气、液相比例。计算结果表明，在实际工业操作条件下，重油催化裂化沉降器内的油浆馏分以气、液两相状态存在，其露点温度为488.8℃，露点温度直接取决于油浆终馏分的沸程，而且油浆分压对其泡点和露点温度也有较大影响。     

创新漏斗视角下开放性和独占性机制对企业创新绩效的影响研究

开放性有利于企业获取更多的创新机会,但开放式创新过程中也需要考虑独占性损失的风险,因为独占性对企业创新新颖性和效率等绩效存在重要的影响。本研究旨在剖析独占性机制和开放性对创新漏斗不同阶段的创新绩效的影响。整合企业跨界搜索理论与知识保护理论,基于332家广东省制造业企业的问卷调查数据,探讨开放性与独占性机制对创新漏斗不同阶段的创新绩效影响。研究发现：正式独占性机制的使用负向影响创新漏斗创意形成阶段的创新效率,半正式独占性机制的使用有利于提升创新漏斗创意形成阶段的创新效率,而非正式独占性机制则有助于创新漏斗创意形成和新产品开发与商业化阶段的创新新颖性的提升;另外,创新新颖性通过创新漏斗整个阶段的横向合作开放性来解释,尤其是与高校科研院所的合作,与竞争对手合作开放性对新产品开发与商业化阶段的创新新颖性积极正相关,而垂直合作开放性则对新产品开发与商业化阶段的创新效率具有正相关关系。     

高层领导风格在企业系统生命周期各个阶段的权变性研究

企业信息系统生命周期的各个阶段面临着不同的关键任务,需要高层管理者表现出不同的领导风格,通过领导风格和企业信息系统生命周期各个阶段的匹配,以有效地促进企业信息系统在各个阶段的成功。通过对威海一家具有较长信息化经历的企业进行案例研究发现,在系统采纳阶段,变革型的领导风格更有助于企业关注于未来的发展并及时做出战略性决策;在系统实施阶段,交易型的领导风格更有助于管理和控制具体的实施任务;在消化吸收和扩展阶段,变革和交易混合型的领导风格更有利于系统和企业内部业务流程的融合,以及系统向外部供应链的扩展。本文的研究成果能够为企业在信息系统生命周期的不同阶段选择合适的信息化领导人提供指导。     

Sliding mode controller design for linear systems with unmeasured states

This paper addresses the optimal controller problem for a linear system over linear observations with respect to different Bolza–Meyer criteria, where (1) the integral control and state energy terms are quadratic and the non-integral term is of the first degree or (2) the control energy term is quadratic and the state energy terms are of the first degree. The optimal solutions are obtained as sliding mode controllers, each consisting of a sliding mode filter and a sliding mode regulator, whereas the conventional feedback LQG controller fails to provide a causal solution. Performance of the obtained optimal controllers is verified in the illustrative example against the conventional LQG controller that is optimal for the quadratic Bolza–Meyer criterion. The simulation results confirm an advantage in favor of the designed sliding mode controllers.     

Na／Ca比对粉煤灰微晶玻璃显微硬度的影响

以粉煤灰为主要原材料,采用熔融一烧结法制备了不同Na／Ca比的微晶玻璃材料。用差示扫描量热分析方法分析了基础玻璃的热性质并制定了微晶玻璃的烧结制度。用X射线衍射分析了微晶玻璃样品的晶相组成,用光学显微镜分析了样品的组织形貌,测试了微晶玻璃的显微硬度,并讨论了不同Na／Ca比对粉煤灰微晶玻璃的晶相组成、形貌及性能的影响。结果表明随着Na／Ca比的减小,样品显微硬度值呈上升趋势。     

马氏体相变形核机制的研究

应用JEM-2100电镜、QUANTA-400环扫电镜对钢中马氏体相变的形核进行了观察,发现马氏体不仅可在奥氏体晶内形核,而且可在晶界、相界面等处形核。认为马氏体是在缺陷处依靠结构涨落、能量涨落形核,是晶格重构的过程,不是切变过程。研究计算了马氏体晶核的临界尺寸和形核功。     

一维光子晶体传输矩阵法的分析改进

为了更准确地分析一维光子晶体的光子禁带特性和研究改善光子晶体性能的方法,通过在传输矩阵法的推导过程中加入了多重反射的概念和修正了传输矩阵的相位项,改进了用传输矩阵分析一维光子晶体禁带特性的方法,提高了计算精确度,结合理论仿真数据与实验测量值的对比证明了该改进算法的有效性,尤其是在非垂直入射的情况下,改进算法与实验数据符合良好。另外还探讨了组成光子晶体膜层的高低折射率介质的折射率比值,光学厚度,周期数等参数对光子禁带特性的影响,并提出了通过选用合适的光学厚度和周期数,采用新型材料,引入多缺陷态结构等改进一维光子晶体禁带特性的初步设想。     

Crystal face dependent intrinsic wettability of metal oxide surfaces

Knowledge of intrinsic wettability at solid/liquid interfaces at the molecular level perspective is significant in understanding crucial progress in some fields, such as electrochemistry, molecular biology and earth science. It is generally believed that surface wettability is determined by the surface chemical component and surface topography. However, when taking molecular structures and interactions into consideration, many intriguing phenomena would enrich or even redress our understanding of surface wettability. From the perspective of interfacial water molecule structures, here, we discovered that the intrinsic wettability of crystal metal oxide is not only dependent on the chemical components but also critically dependent on the crystal faces. For example, the crystal face of α-Al₂O₃ is intrinsically hydrophobic with a water contact angle near 90°, while another three crystal faces are intrinsically hydrophilic with water contact angles <65°. Based on surface energy analysis, it is found that the total surface energy, polar component and Lewis base portion of the hydrophobic crystal face are all smaller than the other three hydrophilic crystal faces indicating that they have different surface states. DFT simulation further revealed that the adsorbed interfacial water molecules on each crystal face hold various orientations. Herein, the third crucial factor for surface wettability from the perspective of the molecular level is presented, that is the orientations of adsorbed interfacial water molecules apart from the macro-level chemical component and surface topography. This study may serve as a source of inspiration for improving wetting theoretical models and designing controllable wettability at the molecular/atomic level.     

A two phase investment game for competitive opinion dynamics in social networks

We propose a setting for two-phase opinion dynamics in social networks, where a node’s final opinion in the first phase acts as its initial biased opinion in the second phase. In this setting, we study the problem of two camps aiming to maximize adoption of their respective opinions, by strategically investing on nodes in the two phases. A node’s initial opinion in the second phase naturally plays a key role in determining the final opinion of that node, and hence also of other nodes in the network due to its influence on them. However, more importantly, this bias also determines the effectiveness of a camp’s investment on that node in the second phase. In order to formalize this two-phase investment setting, we propose an extension of Friedkin–Johnsen model, and hence formulate the utility functions of the camps. We arrive at a decision parameter which can be interpreted as two-phase Katz centrality. There is a natural tradeoff while splitting the available budget between the two phases. A lower investment in the first phase results in worse initial biases in the network for the second phase. On the other hand, a higher investment in the first phase spares a lower available budget for the second phase, resulting in an inability to fully harness the influenced biases. We first analyze the non-competitive case where only one camp invests, for which we present a polynomial time algorithm for determining an optimal way to split the camp’s budget between the two phases. We then analyze the case of competing camps, where we show the existence of Nash equilibrium and that it can be computed in polynomial time under reasonable assumptions. We conclude our study with simulations on real-world network datasets, in order to quantify the effects of the initial biases and the weightage attributed by nodes to their initial biases, as well as that of a camp deviating from its equilibrium strategy. Our main conclusion is that, if nodes attribute high weightage to their initial biases, it is advantageous to have a high investment in the first phase, so as to effectively influence the biases to be harnessed in the second phase.