改进海鸥算法的多阈值图像分割算法北大核心CSCD

为进一步提高图像分割精度,改善传统多阈值图像分割方法计算量大、分割慢的问题,提出了改进海鸥算法(improved seagull optimization algorithm,ISOA)的多阈值图像分割方案。针对原始海鸥算法(seagull optimization algorithm,SOA)存在早熟、寻优精度不足的问题,首先,采用cubic混沌映射优化初始解,提高搜索效率;其次,引入鹰栖息优化算法(eagle perching optmizer,EPO)的缩放因子和疯狂算子进行扰动,并与麻雀搜索算法(sparow search algorithm,SSA)警戒者的位置更新相结合,优化寻优精度和收敛速度,避免陷入局部最优。利用6种基准测试函数对ISOA进行寻优性能测试。最后,将ISOA与图像分割的最优阈值选取相结合,进行基于Otsu的多阈值图像分割,并与现有分割算法进行对比。仿真结果表明,ISOA在基于Otsu的图像分割中,100%取得了最优值,且80.9%的结果优于其余算法,使图像的分割精度和质量均得到了优化。     

城市大面积停电事件影响及特征分析

为全面准确了解和把握大面积停电事件的诱发因素和基本特征,对国内外近十余年来发生的典型大面积停电事件进行梳理,从中归纳和总结出事态演化的基本规律.以大面积停电事件的诱发、发展和灾情蔓延过程作为逻辑主线,梳理出事件应对处置的各项主要任务;以有效完成这些任务为目标,全面梳理相关主体所需匹配的应急能力和应急资源,做好应对城市大面积停电事件应急准备工作,提升应急处置及救援能力.     

Sound Absorption Performance and Mechanism of Aluminum Foams with Double Main Pore-Porous Cell Wall Structure

To enhance the sound absorption performance of open-cell aluminum foam, the double main pores-porous cell walls (DMP-PCW) aluminum foams via infiltration casting of preforms mixed with two sizes of NaCl particles are prepared. The pore structure, sound absorption performance, and mechanism of DMP-PCW aluminum foam are investigated. The pore structure consists of double-sized main pores similar to the NaCl particles and the cell wall pores formed by the connections between NaCl particles. It is found that the static flow resistivity of DMP-PCW aluminum foam reaches an optimum value of 28105 Pa.s m⁻² when the volume proportion of small main pores increases, the size of cell wall pores decreases, and the number of cell wall pores per unit main pore surface area (NPPA) increases. At 800–6300 Hz, the average absorption coefficient is 0.89. In addition, the Wilson model predicts the sound absorption properties of DMP-PCW aluminum foam. The predicted values agree well with the measured values. The finite-element acoustic simulations and dynamic viscous-thermal permeability calculations reveal that the improved sound absorption performance of DMP-PCW aluminum foam is correlated to the enhanced sound transmission caused by increased NPPA and increased viscous-thermal loss due to the double main pore structure.     

An efficient secure proxy verifiably encrypted signature scheme

Verifiably encrypted signature is an important cryptographic primitive, it can convince a verifier that a given ciphertext is an encryption of signature on a given message. It is often used as a building block to construct an optimistic fair exchange. In this paper, we propose a new concept: a proxy verifiably encrypted signature scheme, by combining proxy signature with a verifiably encrypted signature. And we formalize security model of proxy verifiably encrypted signature. After a detail construction is given, we show that the proposed scheme is provably secure in the random oracle model. The security of the scheme is related to the computational Diffie–Hellman problem.     

Geometric Hermite interpolation for space curves

This paper considers the geometric Hermite interpolation for spacial curves by parametric quartic Bézier curve. In additon to position and tangent direction, the curvature vector is prescribed at each knot. We prove that under appropriate assumptions the interpolant exists locally with one degree of freedom. Moreover, we prove the interpolant is 6th order accurate.     

论鄱阳湖生态经济区农业产业化经营背景下农村职业教育的发展

《鄱阳湖生态经济区规划》是2009年12月国务院批准的国家区域性战略规划。《规划》中特别指出,要积极推进农业产业化经营以及大力发展职业技术教育。本文从教育功能的角度,阐述＂农村职业教育发展＂与＂推进鄱阳湖生态经济区农业产业化经营＂二者的相互关系。鄱阳湖生态经济区建设离不开农村职业教育的可持续发展。     

最短路径算法效率研究

从经典的最短路径算法—Dijkstra算法入手,针对同一算法,分别采用三种不同的存储结构存储临时标号节点,通过对无序结构、桶结构、堆结构存储的分析与比较,提出基于堆结构的Dijkstra算法的效率高于其他两种算法,特别适合于大规模网络。     

一种新的公平电子货币系统

基于一次离散对数证明和Schnorr盲签名方案给出了一种新的公平电子货币来实现电子货币匿名的可控性。该方案不仅能够实现多重花费和多重存款的追踪，并且还能有效地实现货币追踪和用户追踪。