一类(1,t,n)门限群签名方案的设计

该文针对现有门限群签名的主要弱点———难以抵御部分成员的合谋攻击以及事后无法追查签名者,结合了将签名成员分等级的思想,提出了一种(1,t,n)门限群签名方案,并对该方案进行了证明和安全性讨论。     

一个基于ECC的ElGamal型(t,n)门限数字签名方案

This paper comprehensively introduces and analyzes Shamir Secret Sharing, Pedersen's Verifiable SecretSharing based on ECC, verifiable secret sharing without a trusted center based on ECC and an ElGamal digital signa-ture scheme based on ECC. Based on the theoretical introduction, an ElGamal_type(t, n) threshold digital signaturescheme Based on ECC is designed. The performance of the scheme is analyzed. And an application based on thescheme is described. In the scheme, a trusted center to deal with the sharing secret is eliminated. No secret communi-cation is required in the signature issuing phase. The scheme is characterized by excellent security as well as high effi-ciency.     

基于ElGamal的前向安全性数字签名方案

前向安全思想是保护数字签名系统密钥安全的重要方法。利用可信中心和z次多项式，提出了一种具有前向安全性的新型ElGamal数字签名方案，其密钥更新算法简单，系统的计算量少。攻击者即使获得某个时期的密钥，也无法对其他时期的密钥构成威胁。     

Study on the instability of organic field-effect transistors based on fluorinated copper phthalocyanine

The effects of positive and negative gate-bias stress on organic field-effect transistors (OFET) based on tantalum (Ta)/tantalum pentoxide (Ta₂O₅)/fluorinated copper phthalocyanine (F₁₆CuPc) structure are investigated as a function of stress time and stress temperature. It is shown that gate-bias stress induces a parallel threshold voltage shift (ΔV_T) of OFETs without changes of field-effect mobility μ_EF and sub-threshold slope (ΔS). The ΔV_T is observed to be logarithmically dependent on time at high gate-bias appropriate to OFET operation. More importantly, the shift is directional, namely, be large shift under positive stress and almost do not move under negative stress. The threshold voltage shift is temperature dependent with activation energy of 0.51 eV. We concluded that threshold voltage shift of the OFET with F₁₆CuPc as active layer is due to charge trapping in the insulator in which trapped carriers have redistribution.     

Design of a Tree Ring Structure Analysis System to Estimate the Accurate Age of Tree Species in Sri Lanka

Determination of an age in a particular tree species can be considered as a vital factor in forest management. In this research we have introduced a novel scheme to determine the accurate age of the tree species in Sri Lanka. This is initially developed for the tree species called‘Hora’ (Dipterocarpus zeylanicus ) in wet zone of Sri Lanka. Here the core samples are extracted and further analyzed by means of the different image processing techniques such as Gaussian kernel blurring, use of Sobel filters, double threshold analysis ,Hough line transformation and etc. The operations such as rescaling, slicing and measuring are also used in line with image processing techniques to achieve the desired results. Ultimately a Graphical user interface (GUI) is developed to cater for the user requirements in a user friendly envi-ronment. It has been found that the average growth ring identification accuracy of the proposed system is 93% and the overall average accuracy of detecting the age is 81%. Ultimately the proposed system will provide an insight and contributes to the forestry related activities and researches in Sri Lanka.     

PMOS剂量计的长期室温退火

为掌握ＰＭＯＳ剂量计的应用方式并提高其应用精度,研究了ＰＭＯＳ剂量计的辐照剂量记录－阈电压在室温下的长期退火表现。结果表明：氧化物电荷的隧道退火与界面态的后生长效应是造成退火的原因,ＰＭＯＳ剂量计辐照及贮藏偏置是决定其退火方向和程度大小的重要因素。负偏置条件能较好地保持其辐照记录,在正偏置贮存下的退火较大。     

图像增强技术在DSA减影中的应用

从DSA(Digital Subtraction Angiography,数字减影血管造影)医学图像的特点出发,提出了在实现DSA减影时,减影前先进行对数变换,减影后再进行单阈值分割的解决方案来增强血管信息.该方案已用Delphi具体软件实现,图像效果符合医学诊断的要求,得到了医学专家的充分肯定.     

指针式仪表示值识别系统研究

指针式仪表识别系统采用机器视觉技术和数字图像处理算法,实现了对指针式仪表示值的自动识别.使用图像差影法、自适应阈值分割算法和最小二乘法进行圆心拟合;提出区域分割方法及中心投影法,对表盘图像进行分块处理,提取表盘刻度,快速识别出表盘指针所处位置.实验表明,采用该系统的识别值与目测值的最大偏差为0.16μm,最小偏差为0.10 μm,检定时间缩短为原来的1/1000,提高了检定效率、检定精度和检定结果的准确性.     

小水电站生态流量对电能损失率的影响分析

小水电站多以追求最大发电效益为目的,电站下游河道生态流量往往处于"无"或"少"的不良状况,对生态环境影响日益凸显.为研究电站下泄生态流量对电站电能损失的影响及影响因子的作用,本文选取江西省遂川县为研究区域,采用主成分分析法分析小水电站生态流量对电站电能损失率的影响.结果表明:(1)河道生态流量对小水电站目前运行实际发电量的损失率的影响阈值一般控制在[10％,20％].(2)电站效能属性第一主成分包括年利用小时数(M4)、设计流量与多年平均流量比(M5)和水量利用率(M6);电站出力属性第二主成分包括设计水头(M2)和设计流量(M3);装机规模(M1)为第三主成分装机属性单一主要指标;其中,M2和M4对电能损失率呈负作用,表明参数越大,相应电能损率失越大;M1、M3、M5和M6对电能损失率起积极正向作用,参数越大,相应电能损失越小.建议在小水电整改评估工作过程中,以考证M4、M5和M6的真实性和可靠性为先,后以电站铭牌特征值M2、M3和M1收集为辅,便于整改评估工作的顺利开展.本研究可为小水电站的评价认定和电能损失补偿提供一定的技术支撑和参考.     

基于变精度粗糙集阈值的选取

针对变精度粗糙集阚值选取缺乏可预见性的问题,提出了基于集合可辨性的阚值选取方法．在变精度粗糙集模型研究的基础上．首先在满足集合可辨性条件下,选定可分辨类相关的阈值的上界;然后在近似分类质量保持不变的前提下．选定阈值区间,最后依据变精度粗糙集近似约简标准．确定阈值范围．实例计算验证了该方法的有效性．