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In this paper, we propose and numerically demonstrate a chaotic watermarking encryption and secure transmission scheme based on two synchronized response lasers (RLs) subject to identical injection from a driving laser (DL). In this proposed system, the chaos signals from DL can be optimized after passing through a phase modulator and a dispersion component, then the chaotic signal with large bandwidth and low TDS is obtained. Simultaneously injecting this chaotic signal into two identical RLs, high-quality chaos synchronization between two RLs can be realized. Both synchronized chaotic signals are respectively divided into two parts. One is used to generate shared keys required by the watermarking encryption, and the other is used as chaotic carrier to realize the secure message transmission. After introducing the synchronized optical chaos into the watermarking encryption algorithm, the normalized correlation of the extracted watermark without long-distance transmission is 0.9554 and can still maintain above 0.9 over 200km transmission fiber. The message transmission and watermark extraction have good robustness to the fiber parameter mismatches, and excellent performances can be maintained even within 20% mismatches range. Moreover, the security of the watermarking encryption algorithm and the message transmission can be guaranteed simultaneously.

Based on chaos synchronization of two response lasers (RLs) injected by the common chaos signals from a driving laser (DL) with double optical feedback (DOF) and an additional neural network (NN), a bidirectional chaotic secure communication system with machine learning capability is proposed and the long-distance digital image transmission and recognition performances are numerically investigated. The simulated results show that the time delay signature (TDS) of the driving chaotic signals from DL with DOF is greatly weakened under suitable operation conditions. Two RLs can generate chaos signals with low TDS and broad bandwidth, and the high-quality chaos synchronization between two RLs can be achieved while the synchronization quality between DL and any one of RLs is extremely bad, which is helpful to realize the secure communication. Using the synchronized chaos output signals from two RLs as chaos carriers and chaos masking (CM) encoding method, the bidirectional 10 Gb/s secure communication over 140 km fiber channel can be realized and the effects of the fiber parameters on the communication performances are discussed. After adopting an additional NN, a long-distance digital image transmission and recognition based on this proposed secure communication system can be realized and the communication distance can be extended to 220 km.

As data volumes grow rapidly, distributed computations are widely employed in data-centers to provide cheap and efficient methods to process large-scale parallel datasets. Various computation models have been proposed to improve the abstraction of distributed datasets and hide the details of parallelism. However, most of them follow the single-layer partitioning method, which limits developers to express a multi-level partitioning operation succinctly. To overcome the problem, we present the NDD (Nested Distributed Dataset) data model. It is a more compact and expressive extension of Spark RDD (Resilient Distributed Dataset), in order to remove the burden on developers to manually write the logic for multi-level partitioning cases. Base on the NDD model, we develop an open-source framework called Bigflow, which serves as an optimization layer over computation engines from most widely used processing frameworks. With the help of Bigflow, some advanced optimization techniques, which may only be applied by experienced programmers manually, are enabled automatically in a distributed data processing job. Currently, Bigflow is processing about 3 PB data volumes daily in the data-centers of Baidu. According to customer experience, it can significantly save code length and improve performance over the intuitive programming style.

This work aims to investigate high-frequency ultrasound findings in epididymal malformations and their clinical significance. Eighty-five of 9,849 patients who had been examined using high-frequency ultrasound for infertility, varicocele, scrotal swelling, and so on had epididymal malformations. A retrospective analysis was conducted on the ultrasound findings of epididymal malformations in these 85 patients. There were a total of 117 malformed epididymides in 85 patients with epididymal malformations. The detection rate of epididymal malformations using high-frequency ultrasound was 0.86 % (85/9,849). High-frequency ultrasound can be used to diagnose epididymal malformation and seminiferous duct blockage.

The modulation response characteristics of a Fabry-Perot semiconductor laser (slave FP-LD) subjected to light injection from another Fabry-Perot semiconductor laser (master FP-LD) have been investigated theoretically. The results show that the modulation response performances of the slave FP-LD depend on the light injection strength, the central mode frequency detuning Δf and the mode spacing difference Δλ between the slave FP-LD and the master FP-LD. With the increase of the light injection strength from the master FP-LD, the 3 dB modulation bandwidth of the slave FP-LD will be enhanced; however, if the injection strength is increased to certain degree, the front side of the relaxation oscillation peak will be reduced to below 3 dB, which results in the rapid decrease of the 3 dB modulation bandwidth. With the increase of Δf, for a relatively small injection strength level, the 3 dB modulation bandwidth will behave a monotonous enlargement until the slave FP-LD operates in a period-one state (P1). For a relatively strong optical injection level, the slave FP-LD has a broad injection-locked frequency detuning area. Within the injection-locked area, with the increase of frequency detuning Δf, the 3dB modulation bandwidth increases at first and then decreases after experiencing a maximum value. For given light injection strength and frequency detuning, the 3 dB modulation bandwidth of the slave FP-LD has two maximums and behaves a symmetrical distribution with the change of Δλ. By choosing reasonable parameters, the 3 dB modulation bandwidth can be significantly improved. For the parameter values selected in this paper, the 3 dB modulation bandwidth can increase 5.5 times compared with the case of free running.