在对DGA(Domain Generate Algorithm)域名僵尸主机的检测中,传统的DGA域名检测方法具有误报率较高、预测准确性较低的不足.为了改善该问题,本文提出一种基于深度学习神经网络的方法来检测伪随机域名,它结合了信息熵和长短期记忆神经网络...在对DGA(Domain Generate Algorithm)域名僵尸主机的检测中,传统的DGA域名检测方法具有误报率较高、预测准确性较低的不足.为了改善该问题,本文提出一种基于深度学习神经网络的方法来检测伪随机域名,它结合了信息熵和长短期记忆神经网络(Long Short Term Memory, LSTM).该方法先通过基于信息熵的检测,对域名是否合法进行初步检测,然后通过基于优化的LSTM网络模型对非法的域名进行第二次检测.本文基于长短期记忆神经网络模型,分析了在不同优化函数、超参数、网络结构和阈值衰减联合下检测效果的差异,并从中选择最优组合.实验结果表明,该方法在降低检测耗时的同时,能够获得较高的准确率和较低的误报率,整体检测效果得到了显著提升.展开更多
Magnetite nanoparticles with different sizes and different assemblies were synthesized via hydrothermal method.Micromagnetic simulation shows the magnetite nanocubes with different sizes have different energy states,w...Magnetite nanoparticles with different sizes and different assemblies were synthesized via hydrothermal method.Micromagnetic simulation shows the magnetite nanocubes with different sizes have different energy states,which determines the assembly mode.Magnetite nanocubes with the side length of 30-60 nm tended to be dispersed while both nanochains and dispersed nanoparticles were found to grow for the nanocubes with the side length less than 30 nm,which can be explained in the fact that the above two assembly modes have very close energies.The assembly mode of nanocubes with the size bigger than 60 nm is generally nanorings consisting of connected inter-grown nanocubes and the nanocubes are no longer single domain.The simulations are consistent with the experimental results.展开更多
A novel asymmetrical Pi-shaped defected ground structure （DGS） with 3-interations Koch fractal curves is proposed to design a microstrip low-pass filter （LPF） with uhra-wide stop-band （SB）. The proposed LPFs wit...A novel asymmetrical Pi-shaped defected ground structure （DGS） with 3-interations Koch fractal curves is proposed to design a microstrip low-pass filter （LPF） with uhra-wide stop-band （SB）. The proposed LPFs with a single resonator and two cascaded resonators are both designed, simulated, manufactured and measured. Simulation and experiment results demonstrate that the designed LPF has a very sharp transition band （TB） and an ultra-wide SB performance compared with the existed similar symmetrical and asymmetrical DGS. The proposed LPF with two cascaded resonators is with a compact size of 36. 8 mm x 24.0 mm, a very low insertion loss of less than 0.7 dB under 1.9 GHz, and a wide SB from 2.2 GHz to 8 GHz with rejection of larger than 30 dB.展开更多
The magnetic domain structures of the 100 oriented Fe 81 Ga 19 polycrystalline alloys with rapid quenching(RQ) and post-annealing(PA) thermal treatments are investigated by using magnetic force microscopy(MFM).The sur...The magnetic domain structures of the 100 oriented Fe 81 Ga 19 polycrystalline alloys with rapid quenching(RQ) and post-annealing(PA) thermal treatments are investigated by using magnetic force microscopy(MFM).The surfaces of the RQ alloy rods take on the dendritic domains after undergoing a standard mechanical polishing.While after PA processing,the distinct domain structures are observed at different temperatures.The wide stripe-like domain patterns appear in the surface of those PA rods at 550°C while the ramous domains remain at 400°C annealing.X-ray diffraction patterns indicate that a thin iron layer is formed on the surface of the specimens annealed at higher temperature.The soft magnetic iron layer,actually acting as a shield for the stray fields emerging from the internal magnetic structures underneath,brings about the presentation of the wide internal domains.展开更多
Compact dual-band bandpass filter(BPF)for the 5 th generation mobile communication technology(5 G)radio frequency(RF)front-end applications was presented based on multilayer stepped impedance resonators(SIRs).The mult...Compact dual-band bandpass filter(BPF)for the 5 th generation mobile communication technology(5 G)radio frequency(RF)front-end applications was presented based on multilayer stepped impedance resonators(SIRs).The multilayer dual-band SIR BPF can achieve high selectivity and four transmission zeros(TZs)near the passband edges by the quarter-wavelength tri-section SIRs.The multilayer dual-band SIR BPF is fabricated on a 3-layer FR-4 substrate with a compact dimension of 5.5 mm×5.0 mm×1.2 mm.The measured two passbands of the multilayer dual-band SIR BPF are 3.3 GHz-3.5 GHz and 4.8 GHz-5.0 GHz with insertion loss(IL)less than 2 dB respectively.Both measured and simulated results suggest that it is a possible candidate for the application of 5 G RF front-end at sub-6 GHz frequency band.展开更多
文摘在对DGA(Domain Generate Algorithm)域名僵尸主机的检测中,传统的DGA域名检测方法具有误报率较高、预测准确性较低的不足.为了改善该问题,本文提出一种基于深度学习神经网络的方法来检测伪随机域名,它结合了信息熵和长短期记忆神经网络(Long Short Term Memory, LSTM).该方法先通过基于信息熵的检测,对域名是否合法进行初步检测,然后通过基于优化的LSTM网络模型对非法的域名进行第二次检测.本文基于长短期记忆神经网络模型,分析了在不同优化函数、超参数、网络结构和阈值衰减联合下检测效果的差异,并从中选择最优组合.实验结果表明,该方法在降低检测耗时的同时,能够获得较高的准确率和较低的误报率,整体检测效果得到了显著提升.
基金supported by the National Natural Science Foundation of China (Grant No. 50971011)Beijing Natural Science Foundation (Grant No. 1102025)Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20091102110038)
文摘Magnetite nanoparticles with different sizes and different assemblies were synthesized via hydrothermal method.Micromagnetic simulation shows the magnetite nanocubes with different sizes have different energy states,which determines the assembly mode.Magnetite nanocubes with the side length of 30-60 nm tended to be dispersed while both nanochains and dispersed nanoparticles were found to grow for the nanocubes with the side length less than 30 nm,which can be explained in the fact that the above two assembly modes have very close energies.The assembly mode of nanocubes with the size bigger than 60 nm is generally nanorings consisting of connected inter-grown nanocubes and the nanocubes are no longer single domain.The simulations are consistent with the experimental results.
基金supported by the National Natural Science Foundation of China (21656001)
文摘A novel asymmetrical Pi-shaped defected ground structure （DGS） with 3-interations Koch fractal curves is proposed to design a microstrip low-pass filter （LPF） with uhra-wide stop-band （SB）. The proposed LPFs with a single resonator and two cascaded resonators are both designed, simulated, manufactured and measured. Simulation and experiment results demonstrate that the designed LPF has a very sharp transition band （TB） and an ultra-wide SB performance compared with the existed similar symmetrical and asymmetrical DGS. The proposed LPF with two cascaded resonators is with a compact size of 36. 8 mm x 24.0 mm, a very low insertion loss of less than 0.7 dB under 1.9 GHz, and a wide SB from 2.2 GHz to 8 GHz with rejection of larger than 30 dB.
基金supported partially by Hunan Provincial Science and Technology Department of China (Grant No. 2012WK3032)
文摘The magnetic domain structures of the 100 oriented Fe 81 Ga 19 polycrystalline alloys with rapid quenching(RQ) and post-annealing(PA) thermal treatments are investigated by using magnetic force microscopy(MFM).The surfaces of the RQ alloy rods take on the dendritic domains after undergoing a standard mechanical polishing.While after PA processing,the distinct domain structures are observed at different temperatures.The wide stripe-like domain patterns appear in the surface of those PA rods at 550°C while the ramous domains remain at 400°C annealing.X-ray diffraction patterns indicate that a thin iron layer is formed on the surface of the specimens annealed at higher temperature.The soft magnetic iron layer,actually acting as a shield for the stray fields emerging from the internal magnetic structures underneath,brings about the presentation of the wide internal domains.
基金supported by the Beijing Natural Science Foundation(8202036)。
文摘Compact dual-band bandpass filter(BPF)for the 5 th generation mobile communication technology(5 G)radio frequency(RF)front-end applications was presented based on multilayer stepped impedance resonators(SIRs).The multilayer dual-band SIR BPF can achieve high selectivity and four transmission zeros(TZs)near the passband edges by the quarter-wavelength tri-section SIRs.The multilayer dual-band SIR BPF is fabricated on a 3-layer FR-4 substrate with a compact dimension of 5.5 mm×5.0 mm×1.2 mm.The measured two passbands of the multilayer dual-band SIR BPF are 3.3 GHz-3.5 GHz and 4.8 GHz-5.0 GHz with insertion loss(IL)less than 2 dB respectively.Both measured and simulated results suggest that it is a possible candidate for the application of 5 G RF front-end at sub-6 GHz frequency band.
