Oblique Vortex Lattice Implies Unconventional Pairing Symmetry in High Temperature Superconductors

The symmetry of order parameters of YBa₂Cu₃O_{7 –} high temperature superconductor was studied with the Ginzburg–Landau theory. The vortex lattice of a YBa₂Cu₃O₇ superconductor is oblique at a temperature well below the transition temperature T _c, where the mixed s– state is expected to have the lowest energy, whereas very close to T _c, the -wave is slightly lower in energy, and a triangular vortex lattice recovers. The coexistence and the coupling between the s- and d-waves would account for the unusual behaviors such as the upward curvature of the upper critical field curve H _C2(T).     

Probing the Vorticity in a Superconductor Rapidly Quenched from the Normal State

Topological defects such as vortices subsist for some time in a rapidly frozen superconducting film (W. H. Zurek, Phys. Rep. 276, 177, 1996). We propose to use as a probe of the vortex density the finite delay T _d, which, in narrow strips, exists between a current step and the voltage response. Technically, this amounts to driving a bridge into the localized hot-spot regime by means of a pump pulse (laser or electrical). Cooling of such films as epitaxial YBCO-on-MgO, or niobium-on-sapphire, requires only a few nanoseconds at low T. A time t later, a probe pulse is applied to measure T _d. The dependence t T _d is interpreted as a witness of the fossil vorticity, long after quenching into the zero-resistance regime.     

TV Program Recommendation for Multiple Viewers Based on user Profile Merging

Since today’s television can receive more and more programs, and televisions are often viewed by groups of people, such as a family or a student dormitory, this paper proposes a TV program recommendation strategy for multiple viewers based on user profile merging. This paper first introduces three alternative strategies to achieve program recommendation for multiple television viewers, discusses, and analyzes their advantages and disadvantages respectively, and then chooses the strategy based on user profile merging as our solution. The selected strategy first merges all user profiles to construct a common user profile, and then uses a recommendation approach to generate a common program recommendation list for the group according to the merged user profile. This paper then describes in detail the user profile merging scheme, the key technology of the strategy, which is based on total distance minimization. The evaluation results proved that the merging result can appropriately reflect the preferences of the majority of members within the group, and the proposed recommendation strategy is effective for multiple viewers watching TV together.     

知网与同义词词林的信息融合研究

本文主要探讨了将知网(HowNet) 和同义词词林进行信息融合的方法。我们针对知网对词的概念描述和同义词词林对词的语义分类的特点,提出了一种词典信息融合的方法:首先为词林的每个词集确定一个与知网中DEF 类似的概念描述,在此基础上对两部词典中同时收录且均只有一个义项的词语进行双向意义联结,最后根据分类算法对两部词典中同时收录非单一义项的词语进行双向意义联结。实验表明,本文提出的处理策略达到了93 %的信息融合正确率,融合后形成的新词典兼有词林的分类学信息和知网的概念描述信息。     

一种基于GOP的MPEG-2媒体流动切割与合并方法

MPEG-2视频编码技术由于其较高的压缩比和高质量图像，在数字电视及电影等方面具有重要应用。由于编码算法相对较为复杂，迫切需要解决MPEG-2媒体流的切割和合并问题，从而实现有效的节目制作。本文正是针对MPEG-2媒体流，提出了一种基于GOP的压缩域视频分割与合并方法。通过分析媒体流的数据结构，详细蛤出了算法的原理和实现过程。最后，还通过实验证明了该方法的可行性和高效率。     

基于IEEE 1588实现变电站过程总线采样值同步新技术

介绍并分析了网络测量和控制系统的精确时钟同步协议IEEE1588,通过与目前应用广泛的网络时间协议(NTP)相比较,指出其高精度时钟同步实现机制的特殊性。针对IEC61850所定义的过程总线上采样值高精度同步要求,提出了一种基于IEEE1588的合并单元同步实现的新方案。在此方案中,利用现场可编程门阵列(FPGA)对IEEE1588同步报文时标生成点进行精确确定,IEEE1588同步协议的实现利用微控制器完成。     

Reducing Symmetries to Generate Easier SAT Instances

Finding countermodels is an effective way of disproving false conjectures. In first-order predicate logic, model finding is an undecidable problem. But if a finite model exists, it can be found by exhaustive search. The finite model generation problem in the first-order logic can also be translated to the satisfiability problem in the propositional logic. But a direct translation may not be very efficient. This paper discusses how to take the symmetries into account so as to make the resulting problem easier. A static method for adding constraints is presented, which can be thought of as an approximation of the least number heuristic (LNH). Also described is a dynamic method, which asks a model searcher like SEM to generate a set of partial models, and then gives each partial model to a propositional prover. The two methods are analyzed, and compared with each other.     

Symmetry Breaking Constraints for Value Symmetries in Constraint Satisfaction

Constraint satisfaction problems (CSPs) sometimes contain both variable symmetries and value symmetries, causing adverse effects on CSP solvers based on tree search. As a remedy, symmetry breaking constraints are commonly used. While variable symmetry breaking constraints can be expressed easily and propagated efficiently using lexicographic ordering, value symmetry breaking constraints are often difficult to formulate. In this paper, we propose two methods of using symmetry breaking constraints to tackle value symmetries. First, we show theoretically when value symmetries in one CSP correspond to variable symmetries in another CSP of the same problem. We also show when variable symmetry breaking constraints in the two CSPs, combined using channeling constraints, are consistent. Such results allow us to tackle value symmetries efficiently using additional CSP variables and channeling constraints. Second, we introduce value precedence, a notion which can be used to break a common class of value symmetries, namely symmetries of indistinguishable values. While value precedence can be expressed using inefficient if-then constraints in existing CSP solvers, we propose efficient propagation algorithms for implementing global value precedence constraints. We also characterize several theoretical properties of the value precedence constraints. Extensive experiments are conducted to verify the feasibility and efficiency of the two proposals.