多算法融合的眼底图像渗出液分割

利用眼底图像中渗出液的亮度与边缘特征,文中采用一种多算法融合的渗出液自动检测分割方法来解决目前传统算法灵敏度低以及检测中存在视盘和其它微血管瘤等暗病灶的干扰等问题。为了提高分割效率和准确率,文中对原始图像进行顶帽底帽变换来增强图像对比度,采用GA与KSW熵法相结合的双阈值分割法对眼底图像进行渗出液分割。实验在Kaggle数据库上进行测试,结果显示该算法在像素层统计的SE和阳性预测值PPV分别为83.6%和93.2%,在图像层统计的SE、SP与AC分别为95.2%、86.2%和90.8%。在另一个独立的DIARETDB1数据库上进行测试,获得的结果分别为82.4%、93.3%、93.6%、96.2%和89.9%。与其它算法对比,文中方法可以很好地区分开渗出液与暗病灶,且检测时间短,具有准确性和高效性。     

随机保费下扰动风险模型总索赔盈余的大偏差

考虑随机保费下带干扰的风险模型,其中保费额和索赔额各自形成了END的随机变量序列,保费次数是由一个拟更新过程描绘,干扰项是由一个布朗运动过程来刻画.在索赔额分布属于一致变化类的条件下,给出了总索赔盈余过程的精致大偏差.     

Determination of Minimum Miscibility Pressure of CO2–Oil System: A Molecular Dynamics Study

CO₂ enhanced oil recovery (CO₂-EOR) has become significantly crucial to the petroleum industry, in particular, CO₂ miscible flooding can greatly improve the efficiency of EOR. Minimum miscibility pressure (MMP) is a vital factor affecting CO₂ flooding, which determines the yield and economic benefit of oil recovery. Therefore, it is important to predict this property for a successful field development plan. In this study, a novel model based on molecular dynamics to determine MMP was developed. The model characterized a miscible state by calculating the ratio of CO₂ and crude oil atoms that pass through the initial interface. The whole process was not affected by other external objective factors. We compared our model with several famous empirical correlations, and obtained satisfactory results—the relative errors were 8.53% and 13.71% for the two equations derived from our model. Furthermore, we found the MMPs predicted by different reference materials (i.e., CO₂/crude oil) were approximately linear (R² = 0.955). We also confirmed the linear relationship between MMP and reservoir temperature (T_R). The correlation coefficient was about 0.15 MPa/K in the present study.     

Dissociation of Cyclotrimethylenetrinitramine Under 1064-nm Laser Irradiation Investigated by Time-of-Flight Mass Spectrometer

Laser-induced dissociation pathways of cyclotrimethylenetrinitramine have been investigated with a focused laser of 1064 nm by use of a time-of-flight mass spectrometer. The ions produced from the cyclotrimethylenetrinitramine surface were detected and the mass spectra of both positive and negative ions were obtained. According to the possible distribution of the decomposition products, possible dissociation paths of cyclotrimethylenetrinitramine were proposed. The influence of the intensity and the delay time of the laser beam to the decomposition have also been studied. The results may possibly throw some light on our understanding of the reactions taking place in laser ignition.     

A Dynamic Optimal Pilot Design Method for OFDM Systems

Wireless communication systems are increasingly adopting orthogonal frequency division multiplexing to enable high data rate transmission. Such systems employ pilot symbols to estimate wireless channels. While pilot symbols facilitate channel acquisition, they consume part of bandwidth, which in turn reduces spectral efficiency. In this paper, a new pilot design method with virtual subcarriers is proposed. The pilots can be dynamic designed with the previous bit error rate (BER) and signal-to-noise ratio (SNR). The BER sectioned is utilized as the performance metric for the optimization of the total number of pilots. And then the proposed scheme maximizes a simple function relevant to SNR strategy based on the allocation of pilot locations. So the dynamic pilot design will optimize the total number and locations jointly and offer the potential of enhancing data rate while maintaining the quality of service in time-varying wireless channels. Comparing with the conventional pilot design which is commonly used in many protocols, the proposed scheme is more robust to the channel state, which could make good trade-off between data transmission efficiency and channel estimate accuracy.     

基于n粒子GHZ态和单光子混合的量子安全直接通信

为了提高量子安全传输效率,采用n粒子Greenberger-Horne-Zeilinger(GHZ)态的特性,对其与单光子混合的量子安全直接通信进行了研究,设计了通信的执行过程,讨论了通信的传输效率、量子比特利用率和编码容量,并对其安全性进行了理论分析。结果表明,该方案可以将信息的编码容量提升至(n+1)bit,将传输效率提升至200%。该协议能够抵御截获重发和测量重发攻击、特洛伊木马攻击和拒绝服务攻击以及辅助粒子攻击和纠缠攻击。     

Proteus仿真软件在集成电路应用课程教学中的实践

集成电路应用课程是高职院校电子类专业的一门专业课。Proteus软件下的虚拟开发环境,具有不受实训场地限制,有利于促进课程的实践教学的特点。本文介绍了使用Proteus软件进行课堂教学、实训和课程设计等各实践教学环节中的应用实例及体会。     

A Fast Decoupled Nominal 2-D Direction-of-Arrival Estimation for Coherently Distributed Source

In this paper, we consider the problem of the nominal 2-D (azimuth and elevation) direction-of-arrival (DOA) estimation for coherently distributed source. This new approach is based on the rotation matrices of three parallel uniform linear arrays as deduced, which has decoupled the nominal 2-D DOA from those of angular spreads. The estimator makes use of the eigenvalue decomposition to beamspace data to estimate the nominal elevation DOA. And then using a new cross-correlation matrix, the nominal azimuth DOA estimates are decoupled from the elevation estimates and can be obtained with no searching. The proposed algorithm has lower computational complexity particularly when the radio of array size to the number of source is large, at the expense of negligible performance loss. Simulation results verify the effectiveness of the proposed method.     

μC/OS-Ⅱ中最高优先级查找算法分析

μC/OS-Ⅱ内核是采用占先式调度方式的实时内核,保证最高优先级任务一旦进入就绪态,就能立刻得到CPU的使用权,减少系统响应时间,从而保证系统实时性。文中阐述μC/OS-Ⅱ内核如何通过查表法快速找出就绪态中优先级最高的任务,并详细分析了就绪态中最高优先级任务调度方法和查找算法,最后给出了相应的例子。