HLA配型、交叉反应组(CREGs)误配率与肾移植术后早期排斥反应的关系

目的:探讨人类白细胞抗原(HLA)配型、交叉反应组(CREGs)误配率与尸体肾移植术后早期急性排斥反应的关系。方法:应用泰萨奇单克隆抗体干板进行供受者HLA-Ⅰ类抗原分型;微量序列特异性引物法进行HLA-Ⅱ类基因分型;泰萨奇混合抗原板检测群体反应性抗体(PRA)。结果:PRA阴性131例肾移植患者HLA配型,误配率为6MM、5MM、4MM、3MM、2MM、1MM、0MM的移植例数分别为0、4、26、49、33、15、4,术后早期急性排斥反应发生率分别为0、25%、23.1%、14.3%、12.1%、6.7%、0。CREGs误配率为6MM、5MM时无移植病例。CREGs误配率为4MM、3MM、2MM、1MM、0MM时,排斥反应发生率分别为28.6%、22.9%、9.5%、6.9%、5.5%。结论:HLA配型、交叉组配型可显著提高供受者的HLA相配率,对选择最佳的供者,降低早期急性排斥反应的发生,提高肾移植效果具有重要的意义。

时序特征图像配准算法的抗噪性分析

提出了一种基于时序特征变化的图像配准算法,通过时序灰度特征的分析和提取,实现了可见光与红外非固形动态目标图像的有效配准。重点分析了该算法的抗噪能力,当噪声对配准精度产生明显影响时,设计了一种预处理滤波方法,通过减小噪声项在时序特征提取中的影响,从而降低了算法的误配率。利用蜡烛火焰作为探测目标,通过实验表明,在图像信噪比为10 dB的情况下该算法的抗噪性较好,能够实现非固形目标的可见光与红外图像配准。当目标图像信噪比等于6 dB时,该算法就无法完成图像配准,此时采用预处理滤波方法,算法的误配率得以降低,能成功实现非固形目标的可见光与红外图像配准。实验中计算得到预处理方法的关键参数m取0.25时效果最好。

机器学习算法的激光主动图像与被动红外图像配准研究

激光图像受到多种因素影响,有时会模糊不清,不够清晰,信噪比低,针对当前方法的激光主动图像与被动红外图像配准误差大等难题,为了获得理想的激光主动图像与被动红外图像配准结果,提出了基于机器学习算法的激光主动图像与被动红外图像配准方法。首先分析激光主动图像与被动红外图像配准的研究现状,找到激光主动图像与被动红外图像配准效果差的原因,然后采集激光主动图像和被动红外图像,并对它们进行一定预处理,最后采用机器学习算法建立激光主动图像与被动红外图像配准模型,并与传统方法进行了激光主动图像与被动红外图像配准对比实验,结果表明,本方法的激光主动图像与被动红外图像配准正确率超过91%,误配率控制9%以内,图像配准时间大约为8 s,图像配准效率要高于传统方法,具有十分广泛的前景。

Performance of an Improved One-Way Error Reconciliation Protocol Based on Key Redistribution

In data post-processing for quantum key distribution, it is essential to have a highly efficient error reconciliation protocol. Based on the key redistribution scheme, we analyze a one-way error reconciliation protocol by data simulation. The relationship between the error correction capability and the key generation efficiency of three kinds of Hamming code are demonstrated. The simulation results indicate that when the initial error rates are （0,1.5%], （1.5,4%], and （4,11%], using the Hamming （31,26）, （15,11）, and （7,4） codes to correct the error, respectively, the key generation rate will be maximized. Based on this, we propose a modified one-way error reconciliation protocol which employs a mixed Hamming code concatenation scheme. The error correction capability and key generation rate are verified through data simulation. Using the parameters of the posterior distribution based on the tested data, a simple method for estimating the bit error rate （BER） with a given confidence interval is estimated. The simulation results show that when the initial bit error rate is 10.00%, after 7 rounds of error correction, the error bits are eliminated completely, and the key generation rate is 10.36%; the BER expectation is 2.96×10^-10, and when the confidence is 95% the corresponding BER upper limit is 2.17×10^-9. By comparison, for the single （7,4） Hamming code error reconciliation scheme at a confidence of 95%,the key generation rate is only 6.09%, while the BER expectation is 5.92x 10＂9, with a BER upper limit of 4.34×10^-8. Hence, our improved protocol is much better than the original one.

Memory Safety Based on Probabilistic Memory Allocation

Some unsafe languages,like C and C++,let programmers maximize performance but are vulnerable to memory errors which can lead to program crashes and unpredictable behavior.Aiming to solve the problem,traditional memory allocating strategy is improved and a new probabilistic memory allocation technology is presented.By combining random memory allocating algorithm and virtual memory,memory errors are avoided in all probability during software executing.By replacing default memory allocator to manage allocation of heap memory,buffer overflows and dangling pointers are prevented.Experiments show it is better than Diehard of the following aspects:memory errors prevention,performance in memory allocation set and ability of controlling working set.So probabilistic memory allocation is a valid memory errors prevention technology and it can tolerate memory errors and provide probabilistic memory safety effectively.

Investigation of a Design Modification for Double Helical Gears Reducing Vibration and Noise

To reduce vibration and noise and increase transmission efficiency, a three segment method for modifying the pinion profile was proposed. Cutter surface equations were deduced by changing the shape of the cutter-edge, substituting three segment parabolas for the line. The influence of longitudinal tooth modifications on tooth surface load distributions was discussed. Transmission error minimization and uniformity of tooth surface load distribution were chosen as optimization goals and the modified parameters were obtained by applying the complex method. Finally, an experiment comparing the loaded transmission error, vibration, and noise both before and after modifications was carried out. The results indicate that the modified design is reliable.

Energy Efficient Power Allocation Scheme for Distributed Antenna Systems with Target BER Constraint

The energy efficiency(EE) of distributed antenna system with quality of service(Qo S) requirement is investigated over composite Rayleigh fading channel,where the shadow fading,path loss and Rayleigh fading are all considered. Our aim is to maximize the EE which is defined as the ratio of the transmission rate to the total consumed power subject to the maximum transmit power of each remote antenna constraint and Qo S(target BER) requirement. According to the definition of EE and using the upper bound of average EE,the optimized objective function is provided. Based on this,utilizing Karush-KuhnTucker conditions and numerical calculation,a suboptimal energy efficient power allocation(PA) scheme is developed,and the closedform expression of PA coefficients is derived. The scheme may obtain the EE performance close to the existing optimal scheme. Moreover,it has relatively lower complexity than the existing scheme because only the statistic channel information and less iteration are required. Simulation results show the presented scheme is valid and can meet the target BER requirement,and the EE can be increased as target BER requirement decreases.

Performance analysis of quantum key distribution based on air-water channel

Considering the air-water interface and ocean water’s optical attenuation,the performance of quantum key distribution(QKD)based on air-water channel is studied.The effects of photons’various incident angles to air-water interface on quantum bit error rate(QBER)and the maximum secure transmission distance are analyzed.Taking the optical attenuation of ocean water into account,the performance bounds of QKD in different types of ocean water are discussed.The simulation results show that the maximum secure transmission distance of QKD gradually reduces as the incident angle from air to ocean water increases.In the clearest ocean water with the lowest attenuation,the maximum secure transmission distance of photons far exceeds the the working depth of underwater vehicles.In intermediate and murky ocean waters with higher attenuation,the secure transmission distance shortens,but the underwater vehicle can deploy other accessorial methods for QKD with perfect security.So the implementation of OKD between the satellite and the underwater vehicle is feasible.