Influences of flexible defect on the interplay of supercoiling and knotting of circular DNA

Knots are discovered in biophysical systems, such as DNA and proteins. Knotted portions in knotted DNA are significantly bent and their corresponding bending angles are comparable with or larger than the sharp bending angle resulting in flexible defects. The role of flexible defects in the interplay of supercoiling and knotting of circular DNA were predicted by a Monte Carlo simulation. In knotted DNA with a particular knot type, a flexible defect noticeably enhances the supercoiling of the knotted DNA and the decreasing excitation energy makes the knotted portion more compact. A reduction in twist rigidity and unwinding of flexible defects are incorporated into the numerical simulations, so that interplay of supercoiling and knotting of circular DNA is studied under torsional conditions. Increasing unwinding not only results in a wider linking number distribution, but also leads to a drift of the distribution to lower values. A flexible defect has obvious effects on knotting probability. The summation of equilibrium distribution probability for nontrivial knotted DNA with different contour length does not change with excitation energy monotonically and has a maximum at an intermediate value of excitation energy around 5 kBT. In the phase space of knot length and gyration radius of knotted DNA, knot length does not anticorrelate with its gyration radius, which is attributed to the flexible defect in the knotted portion, which leads to the release of bending energy and inhibited the competition between entropy and bending energy.     

A mathematical model for identifying an optimal waste management policy under uncertainty

In the municipal solid waste (MSW) management system, there are many uncertainties associated with the coefficients and their impact factors. Uncertainties can be normally presented as both membership functions and probabilistic distributions. This study develops a scenario-based fuzzy-stochastic quadratic programming (SFQP) model for identifying an optimal MSW management policy and for allowing dual uncertainties presented as probability distributions and fuzzy sets being communicated into the optimization process. It can also reflect the dynamics of uncertainties and decision processes under a complete set of scenarios. The developed method is applied to a case study of long-term MSW management and planning. The results indicate that reasonable solutions have been generated. They are useful for identifying desired waste-flow-allocation plans and making compromises among system cost, satisfaction degree, and constraint-violation risk.     

降雪对地表附近自由空间量子信道的影响及参数仿真

量子通信具有覆盖面广、安全保密的优势,是当前通信领域国内外的研究热点.在自由空间量子通信过程中,光量子信号需要在地表上空一定高度进行传输,因此各种环境因素,例如降雪、沙尘暴、降雨、雾霾、浮尘等,不可避免地会影响量子通信性能.然而,迄今为止,降雪对地表附近自由空间量子信道影响的研究尚未展开.为此,根据降雪的强度,将降雪分...     

A Distributed Architecture for Secure Delegated Quantum Computation

In this paper, we propose a distributed secure delegated quantum computation protocol, by which an almost classical client can delegate a (dk)-qubit quantum circuit to d quantum servers, where each server is equipped with a 2k-qubit register that is used to process only k qubits of the delegated quantum circuit. None of servers can learn any information about the input and output of the computation. The only requirement for the client is that he or she has ability to prepare four possible qubits in the state of (|0〉+eiθ|1〉)/2, where θ∈{0,π/2,π,3π/2}. The only requirement for servers is that each pair of them share some entangled states (|0〉|+〉+|1〉|−〉)/2 as ancillary qubits. Instead of assuming that all servers are interconnected directly by quantum channels, we introduce a third party in our protocol that is designed to distribute the entangled states between those servers. This would simplify the quantum network because the servers do not need to share a quantum channel. In the end, we show that our protocol can guarantee unconditional security of the computation under the situation where all servers, including the third party, are honest-but-curious and allowed to cooperate with each other.     

A Multinomial Approximation Approach for the Finite Time Survival Probability Under the Markov-modulated Risk Model

In this paper, we consider the problem of computing different types of finite time survival probabilities for a Markov-Modulated risk model and a Markov-Modulated risk model with reinsurance, both with varying premium rates. We use the multinomial approximation scheme to derive an efficient recursive algorithm to compute finite time survival probabilities and finite time draw-down survival probabilities. Numerical results show that by comparing with MCMC approximation, discretize approximation and diffusion approximation methods, the proposed scheme performs accurate results in all the considered cases and with better computation efficiency.

     

量子纠缠信令网Poisson生存模型及保真度分析

量子信令态在传输过程中,由于环境影响产生退相干,造成信令损伤,从而会对构建高生存性的量子纠缠信令网产生影响. 为分析所造成的影响,建立了自然灾害下的量子信令网Poisson损伤模型. 首先,根据信令保真度定义了灾害级数;其次,提出信令态平均损伤量子比特数,并给出信令网生存函数;最后,研究了信令损伤的修复策略并进行仿真. 仿真结果表明,灾害级数的增加会大大降低信令网生存性,而增加信令转接点数和控制信令损伤上限可改善生存性,且该修复策略循环次数少,并可将信令态的保真度由0.6快速提高到0.9,信令网的生存函数由0.4提高到0.9. 关键词： 量子通信 量子信令网 保真度 生存函数     

用自适应MG法,FMG法求解Helmholtz方程

本文针对Ｖ循环、Ｗ循环和多重网格法中最优光滑次数及循环体个数难以确定的缺点，以Ｈｅｌｍｈｏｌｔｚ方程为例给出自适应的多重网格算法和自适应的完全多重网格算法。     

用概率断裂力学方法预测管状接头的疲劳寿命

本文研究了Ｔ型管状接头在面内和面外弯曲循环载荷作用下的疲劳强度问题，通过将材料常数和初始裂纹尺寸作为随机变量，采用ＭｏｎＣａｒｌｏ模拟方法对疲劳寿命进行了统计分析．同时，对计算结果进行了线性回归，并与实验结果作了比较。     

激光冲击强化“残余应力洞”的形成机制

利用ABAQUS有限元软件进行了单个圆形高斯光斑的激光冲击强化数值模拟,分析材料表面光斑中心区域形成的"残余应力洞"现象,并通过分析材料的动态力学响应特征揭示了"残余应力洞"的形成机制。结果表明:在冲击波加载时,光斑边界处会产生很强的剪切应力,形成向四周传播的表面稀疏波和向材料内部传播的剪切波。当稀疏波同时传播到光斑中心,发生相遇、汇聚,使材料产生急剧的上下位移过程,造成冲击波加载塑性变形后的二次塑性变形。二次塑性变形中形成了较大的剪切塑性应变,并降低了冲击波加载阶段产生的轴向和径向塑性应变,使残余压应力降低,从而形成"残余应力洞"。     

Fabrication and characterization of Ge20Sb15S65 chalcogenide glass for photonic crystal fibers

Chalcogenide glasses are known for their high transparency in the mid-infrared (IR) range, which includes two atmospheric windows that lie from 3 to 5 μm and 8 to 12 μm, respectively. Chalcogenide photonic crystal fibers have numerous potential applications in the field of IR, such as spectroscopy, microscopy, astronomy, biology, and sensing. In this paper, Ge₂₀Sb₁₅S₆₅ chalcogenide glass was fabricated and systematically studied. Chalcogenide glass has high transmission property (>70 %), good thermal stability, and good mechanical stability. The glass transition temperature T _g is 296 °C, and no exothermic peak was associated with crystallization up to 500 °C, which indicates its suitability for fiber drawing. As a result of its excellent mechanical properties, preforms with a variety of geometrical patterns were fabricated by using mechanical drilling. The near-field intensity distribution image of the drawn fiber shows a strong light propagation confinement.