双生物识别图象的光学加密方法研究

本文提出了一种将两幅生物识别图象通过一套光学系统进行同时加密的方法。该方法先将一幅图象转换为纯相位和进行纯相位编码,再对另一幅图象编码,然后经过4f光学系统作频率域纯相位编码,并利用与编码过程类似的方法进行解码。可以证明该方法的编码图象为恒定的白噪声。解码过程具有鲁棒性,相位部分图象加密的安全性要高于振幅部分图象的加密。并分析了加性高斯噪声对解码图象的影响     

Throughput and delay analysis of free access tree algorithm withminislots

An analysis is made of the throughput and delay performance of two classes of free-access tree algorithms with minislots. In one class, binary feedback information is available in minislots, and in the other, ternary feedback information is available. It is shown that the highest maximum throughput 0.56714 is achieved in the limiting case where the number of minislots in a (large) slot is infinity and minislot overhead is zero. A lower bound of the average transmission delays in these algorithms is analytically derived. The obtained lower bound is also a lower bound of the average delay of the whole class of the free-access algorithms     

加权的基于多播节点的多播路由算法

在许多多播应用中,降低多播树网络费用非常重要.本文提出了加权的基于多播节点的多播路由算法（WDDMC算法）.由于改变了DDMC（Destination-Driven routing for low-cost Multicast ）算法中的指示函数,适当降低了多播节点作为中间节点的优先级,提高非多播节点作为中间节点的优先级,从而使得多播树更接近最小Steiner树.在随机网络上的仿真结果表明,WDDMC算法的多播树网络费用优于DDMC算法.该算法的复杂度与DDMC算法完全相同.     

A rigorous derivation of the relation between the effective areaand the directive gain and its extension to lossy antennas

It is well known that the effective area of a receiving antenna is linearly related to the directive gain of the same antenna in the transmitting mode. Conventionally, this relation is derived by constructing a two-port network involving the transfer impedance between a pair of antennas. Next, by use of the Thevenin theorem, the received power is related with the open-circuit voltage, which in turn is proportional to the transfer impedance. Alternatively, from field analysis, the received power is related to the effective area and the directive gain. Then, the reciprocity theorem is used to equate the transfer impedances between a pair of antennas. Based on these, the area-directivity relation is derived. However, it is indicated that the circuit model with the open-circuit voltage is not rigorous. In this investigation, the reciprocity theorem is used in a different way to directly derive the power absorbed at the load in terms of the radiated electric field in the transmitting mode. Thereby, the area-directivity relation is derived in a straightforward and rigorous manner. In the derivation of the relation, it is seen that the current in the terminal gap should be uniform. Thus, one limitation of this well-known relation is found. The effect of ohmic loss due to finite conductivity of the antenna material can be taken into consideration in the derivation. Thus, the area-directivity relation is extended such that it is applicable to lossy antennas     

A simple model for fatigue life

A simple model to handle fatigue-life length problems is discussed. The characteristic property of the model is that it combines the Palmgren-Miner rule with time invariance. The model is applied to situations with both random strength and random load. The randomness in the life is generated by the random strength and not by the random load. The only property of the random load that affects the life is its damage intensity, which is independent of the particular realization in the ergodic-load case. The damage intensity is even independent of the distribution of the random function, provided its level-crossing intensity is known. Particular attention is given to simple random strength models. In general, the exhaustion density is a random function, but in the simple models the only randomness that appears in the strength is either randomness in the time scale or randomness in the amplitude scale. The model is well-suited for comparative calculations under different load conditions, since it connects fatigue life for random loads to fatigue life for periodically oscillating loads, which is usually measured in experiments     

低云中短波红外表观辐射模型研究

在对空红外系统的多光谱探测和红外仿真中，云的干扰不可忽略，所以，对云的辐射特性的研究至关重要。在不同的波段，云的辐射特性会有很大的差异，为了研究各个不同波段云的表现辐射特性．需要计算云的光谱辐射量。在典型观测模式下建立了低云的表观光谱辐射模型，研究了对云背景辐射有贡献的各个辐射分量的计算方法。基于传统的二流近似模型获取各个参数，引入云的光谱光学厚度的经验公式。进而获得了低云在中短波段的光谱辐射特性，有效地计算出了云背景在1-5μm的中短波段内的表现光谱辐亮度数据，并且节省了计算时间。经过比较发现，该模型的计算结果与实测结果有较好的一致性。可以为云背景多光谱分析、探测及仿真提供背景数据。     

一种基于顺序统计量的距离扩展目标检测器

该文提出一种高斯白噪声中的距离扩展目标检测器。实际目标的宽带雷达回波能量往往集中于若干距离单元中,基于这一事实,对检测窗内的回波数据按能量降序进行排列,然后顺序进行能量积累和检测,直到做出判决为止。文中详细推导了检测器的虚警概率,给出了设置检测门限的方法。最后通过Monte Carlo实验,利用两类特殊能量分布方式的距离像和一个实际目标的实测距离像,对比分析了该文提出的基于顺序统计量的距离扩展目标检测器相对于能量积累检测器的性能。对于回波能量集中于少数距离单元的距离像,该文提出的检测器比能量检测器具有更好的检测性能。     

Sequential decoding for multiple access channels

The use of sequential decoding in multiple access channels is considered. The Fano metric, which achieves all achievable rates in the one-user case, fails to do so in the multiuser case. A new metric is introduced and an inner bound is given to it achievable rate region. This inner bound region is large enough to encourage the use of sequential decoding in practice. The new metric is optimal, in the sense of achieving all achievable rates, in the case of one-user and pairwise-reversible channels. Whether the metric is optimal for all multiple access channels remains an open problem. It is noted that even in the one-user case, the new metric differs from the Fano metric in a nontrivial way, showing that the Fano metric is not uniquely optimal for such channels. A new and stricter criterion of achievability in sequential decoding is also introduced and examined     

一种高速捷变并行调制矢量信号源的FPGA实现

在信号调制过程中,为了缩短载波生成的捷变时间,分析了影响捷变时间的因素。提出了单频信号的并行合成结构,解决了载波频率受现场可编程逻辑门阵列( FPGA)时钟限制的问题。为了解决调制过程中采样频率受时钟约束的问题,给出了矢量信号的正交并行调制结构。通过在FPGA上编写Verilog代码实现了时钟频率为160 MHz、采样率为1.92 Gsample/s的并行矢量信号调制,载波频率为200~300 MHz可变,捷变时间小于35 ns。结果表明,并行载波生成和并行调制的方法在克服系统时钟约束方面有较强的实用性。     

An example of a hybrid system: coherent optical system with Costasloop in receiver-system for transmission in baseband

The possibility of hybrid system construction is considered in this paper. The coherent optical system is the constituent part of this system. The first part of the system is constructed in passband (optical cable is transmission medium), and the second part of the system is constructed in baseband. The heterodyne optical receiver is used as optical receiver. Estimation is not done just after demodulation, but it is done at the end of the section in baseband. Taking into account shot noise of photodetectors, laser phase noise (transmitter laser and local laser) and noise which is generated during transmission by means of the section in baseband, we determine the performances of the proposed system     

埋磁芯PCB产品研究开发

随着PCB行业发展步入系统封装(SOP)阶段,PCB无源器件隐埋技术也成当今研究的热点。我司的埋铜技术的研究已经较成熟,但是对于磁芯的埋入还没涉及过,而目前电源部分电感大都需要手工贴装,工作效率低,存在焊接焊点不良等风险,不利于产品设计小型、高密化,所以对在PCB中埋入磁芯的研究很有必要。在文章中,我们得出磁芯埋入的控制方法,使产品能够满足客户对电感的要求。     

小波变换结合子带编码的Internet图像传输的计算机模拟

尽管Internet带宽巨大，但网络的信息量、用户数量更是庞大的，其拥塞情况是随机的。图像信号在Internet上根据网络拥塞情况进行分层传输与接收是一件有意义的研究工作。当网络处于正常状态时，实时传输高清晰度图像，当网络拥塞情况较严重时，主动丢弃增强层信号仅恢复基本层图像信号。本文从三个方面探讨了小波变换结合子带编码的Internet图像传输的计算机模拟，首先分别介绍小波变换、子带编码的各自特点，接着介绍Internet图像传输的特点，最后给出计算机模拟的实验。     

红外系统小目标成像自动调光方法

提出了一种实时调整红外相机积分时间的方法。针对成像为点目标且灰度值变化剧烈的情况,为保证红外辐射特性测量的精度,标定了相机在不同积分时间下亮度与成像灰度值的对应关系,确定了红外相机响应关系线性度较好的区域;提出了点目标弥散范围的计算方法,并对红外系统的模拟图像和真实图像进行匹配获得最优化估计的目标位置、尺寸以获取目标的所有灰度值,而后根据亮度与灰度的关系对积分时间进行调整。实验结果证明,可同时调整两个不同红外相机的积分时间以保证灰度值处于理想区间内,调整频率可达25Hz,满足高速飞行器试验的实时性要求。     

A quantitative analysis of SNR in the short-time Fourier transformdomain for multicomponent signals

A quantitative analysis is given for the signal-to-noise ratio (SNR) in the short-time Fourier transform domain for multicomponent signals in additive white noise. It is shown that the SNR is increased on the order of O(N/K), where K is the number of components of a signal, N/T is the sampling rate, and T is the window size. The SNR increase rate is optimal for given K. For this result, the SNR definition is generalized, which is suitable for signals not only in the time domain but also in other domains. This theory is illustrated by one numerical example     

DDR3芯片基于XR8238A全地址全功能老炼过程测试

集成电路老炼的主要目的是模拟芯片的工作寿命,加偏压、加高温模拟产品最坏的工作条件,作为可靠性监控和从批次产品中剔除早期失效产品。取决于老炼时间的长短,早衰期或者损耗期的缺陷均可导致芯片的失效。第三代双倍数据率同步动态随机存储器目前还没有一套完整的老炼试验方法。基于设备XR8238A设计一套印制板,区别于传统的老炼试验模式,给芯片写入完整的数据,输出符合预期的波形,有效地完成了老炼过程测试,提供了第三代双倍数据率同步动态随机存储器产品出货平均故障间隔时间试验的一种方法,提升了集成电路老炼的效果。     

创新铸就高质量

该文回顾了质量管理发展的历史,探索了现代企业质量管理中提高产品质量的一种新实践模式,即将6sigma的分析方法与TRIZ的创新理论相结合,彻底地解决矛盾,而不是优化参数,最终达到满意的质量水平。并且通过企业的一个实际案例,来讲解具体的操作办法。     

单脉冲接收组件

介绍的接收组件为单脉冲接收系统的重要部件。本组件包含三个接收通道。微波部分采用了管芯器件 ,小型化工艺 ,电路设计采用了 CAD技术。主要性能 :功率增益为3 0～ 3 5 d B;噪声系数为 4d B;开关时间不大于 5 0 ns;开关隔离度大于 40 d B;镜频抑制度大于 2 5 d B;在 -5 0～ + 60℃的温度范围内通道间的幅度变化不一致性不大于 1 .8d B;相位变化不一致性不大于 2 5°。外形尺寸为 67.5 mm× 47mm× 2 1 mm。     

On the scalar approximation in fiber optics

It is widely accepted that the scalar approximation is valid when the gradient of the permittivity distribution Δε/ε is small. Such a condition is demanding since it precludes a rapidly varying permittivity distribution, which is usually the case in a practical optical fiber due to some kind of fluctuation in a fabrication process. Here, the scalar approximation is derived from the electric field integral equation. From the result it is seen that the applicability of the scalar approximation does not depend on the roughness in the permittivity distribution as long as the permittivity in the core is close to that in the cladding     

一种多传感器融合的多维数据互联算法

多传感器融合的数据关联问题一直是目标跟踪领域的核心与难点之一.文中提出了一种多传感器融合的多维数据互联算法.首先进行多目标跟踪模式的判断,根据跟踪模式选取不同维数的数据互联算法,对现有的多维数据互联算法存在问题进行了分析和改进,给出了算法实现的伪代码.仿真与实验结果表明,该算法对弹道目标跟踪具有较好的效果,对复杂环境下的多目标也能进行稳定地跟踪.