Novel DDoS Feature Representation Model Combining Deep Belief Network and Canonical Correlation Analysis

Distributed denial of service (DDoS) attacks launch more and more frequently and are more destructive. Feature representation as an important part of DDoS defense technology directly affects the efficiency of defense. Most DDoS feature extraction methods cannot fully utilize the information of the original data, resulting in the extracted features losing useful features. In this paper, a DDoS feature representation method based on deep belief network (DBN) is proposed. We quantify the original data by the size of the network flows, the distribution of IP addresses and ports, and the diversity of packet sizes of different protocols and train the DBN in an unsupervised manner by these quantified values. Two feedforward neural networks (FFNN) are initialized by the trained deep belief network, and one of the feedforward neural networks continues to be trained in a supervised manner. The canonical correlation analysis (CCA) method is used to fuse the features extracted by two feedforward neural networks per layer. Experiments show that compared with other methods, the proposed method can extract better features.     

屈服强度1100 MPa级超高强钢热处理组织及性能

摘要：随着工程机械向大型化轻量化方向发展，超高强钢的市场需求越来越大且综合性能要求越来越严格。结合5000mm宽厚板生产线及热处理装备，研究淬火过程中淬火温度对屈服强度1100MPa级超高强度钢组织及力学性能的影响。结果表明，淬火温度决定了合金元素的溶解和分布状态、原始奥氏体晶粒尺寸，影响试验钢的综合力学性能。不同淬火温度下，基本微观组织为板条马氏体。随着淬火温度的升高，原奥氏体晶粒尺寸增大；当淬火温度由840℃升高至990℃时，原奥氏体晶粒平均尺寸由9.0μm增加到22.5μm。采用900～930℃淬火及350℃回火的热处理工艺，试验钢可获得最佳的强韧性匹配，此时屈服强度为1125～1155MPa、抗拉强度为1306～1335MPa、断后伸长率为12.5%～14.0%，布氏硬度为415～419，－40℃冲击功为80～100J，抗拉强度与布氏硬度比值范围在3.10～3.20之间，满足标准GB/T 28909—2012对Q1100E的要求。     

Evolutions of the Micro- and Macrostructure and Tensile Property of Cu-15Ni-8Sn Alloy During Electromagnetic Stirring-Assisted Horizontal Continuous Casting

Metallurgical and Materials Transactions B - The present study investigates the evolution of the micro- and macrostructure and tensile property of the Cu-15Ni-8Sn (weight percent) alloy prepared by...     

Non‐planar projection performance evaluation and projector pose optimization

In projector applications, the actual display effect is primarily dependent on two aspects: projector performance parameters (intrinsic properties), and projector placement (extrinsic properties). Many studies have been conducted on the impact of the original resolution, illumination, and contrast ratio on projection performance. However, few studies have focused on the influence of extrinsic properties, including the position and orientation of the projector on the projection effect. In this paper, three projection performance evaluation criteria—projection resolution, resolution difference, and projection distance difference—are proposed in terms of extrinsic properties. Based on these evaluation criteria, a projection performance evaluation function was constructed. Through this function, as well as optimization employing the multi‐start and Monte Carlo methods, projector pose parameters corresponding to optimal projection effects can be obtained. Evaluations demonstrated that the proposed projection performance evaluation criteria could correctly describe the impacts of projector placement on projection effects. Projection systems arranged according to the projector pose optimization methods achieved good performance on screens in difference shapes with different numbers of projectors, where the resolution and display improved with no change of projector hardware parameters. The optimal projector poses calculated using these optimization methods can provide theoretical guidance for practical projector placement.     

Cross-sectional investigation of radiation damage of 2 MeV proton-irradiated silicon carbide

Cross-sectional investigation is an important method to study ion irradiation effects in the depth direction. In this study, 2 Me V H~+was implanted in 6 H-SiC single crystals to investigate the effects of light ion irradiation on SiC. Raman spectroscopy and scanning electronic microscopy(SEM) were carried out on crosssectional samples to reveal the in-depth damage states and dopant behavior. The most damaged region is a little shallower than that predicted by the SRIM procedure,owing to the uncertainty in SRIM simulations. Layered structures representing zones of varying damage after2 MeV H ion irradiation are clearly observed. Two bands are observed in SEM images, of which on band corresponds to the damage peak, while the other band at the end of the H ion-affected area is probably a result of H diffusion propelled by a hydrogen-rich layer during irradiation.A charge accumulation effect related with conductivity on the sample surfaces during SEM tests is observed in theH-implanted area. A model is proposed to explain these phenomena.     

SplitPass: A Mutually Distrusting Two-Party Password Manager

Using a password manager is known to be more convenient and secure than not using one, on the assumption that the password manager itself is safe. However recent studies show that most popular password managers have security vulnerabilities that may be fooled to leak passwords without users’ awareness. In this paper, we propose a new password manager, SplitPass, which vertically separates both the storage and access of passwords into two mutually distrusting parties. During login, all the parties will collaborate to send their password shares to the web server, but none of these parties will ever have the complete password, which significantly raises the bar of a successful attack to compromise all of the parties. To retain transparency to existing applications and web servers, SplitPass seamlessly splits the secure sockets layer (SSL) and transport layer security (TCP) sessions to process on all parties, and makes the joining of two password shares transparent to the web servers. We have implemented SplitPass using an Android phone and a cloud assistant and evaluated it using 100 apps from top free apps in the Android official market. The evaluation shows that SplitPass securely protects users’ passwords, while incurring little performance overhead and power consumption.     

聚丙烯酰胺-咪唑类聚离子液体凝胶的辐射合成及其对铀和碘的吸附

采用γ射线辐射引发技术制备了一类聚丙烯酰胺-咪唑类聚离子液体凝胶(PAm-C_nvim_2Br_2)。当吸收剂量为5kGy时,得到了凝胶分数超过95%的聚离子液体凝胶,其溶胀度可由吸收剂量控制。合成的PAmC_nvim_2Br_2可以从碳酸盐溶液中吸附铀最大吸附量约130mg/g,或从碘化钠溶液中吸附碘离子最大吸附量约160mg/g,吸附过程符合Langmuir模型。红外与XPS分析表明,吸附过程遵循离子交换的反应机理。PAmC_nvim_2Br_2凝胶对铀及碘有很好的吸附、解吸性能,有望用于含有铀和碘的放射性废水处理。