分类: 计算机科学 >> 计算机科学的集成理论 提交时间: 2022-05-10 合作期刊: 《计算机应用研究》
摘要: 随着电子信息技术的快速发展,数据的安全性问题日益严峻,传统单一制密码算法在安全性与运算速率上已不能满足要求。为了解决大数据时代下所提出的加密需求,提出了一种基于国密算法SM2、SM3、SM4的高速混合加密系统的硬件设计方案,并针对SM2和SM4算法的底层硬件结构进行优化:对SM2算法采用Karatsuba-Ofman模乘器与点运算并行方案进行优化;对SM4算法提出了一种基于复合域S盒的二次流水全展开硬件架构。实验结果表明,该系统所实现的各算法电路均具有较高性能:SM2的点乘时间缩短至68.37 (s;SM3的杂凑值生成仅需0.71 (s;SM4吞吐率最高达53.76 Gbit/s。相比同等安全性的SM2算法,该混合系统在加密时间上减小了26.67%,具有实用价值。与相关工作进行对比分析,可证明该方案在安全性和加解密性能上均有一定优势。
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: A series of Sm-doped LDPE-Na2SO4 composites were successfully achieved by melt mixing and hot pressing methods. Their morphology, structure and luminescent properties were characterized by scanning electron microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and photoexcitation (PE), photoluminescence (PL) spectra, respectively. The sizes and concentrations of free volume cavities in composites were studied by positron annihilation lifetime spectroscopy (PALS). SEM micrographs showed that Na2SO4:Sm3+ particles were well-distributed in the polymer matrix. XRD analyses revealed that the addition of Na2SO4:Sm3+ had no effect on the original crystal structure of LDPE. The dominant photoexcitation peak was observed at about 402 nm. The photoluminescence spectra consisted of four main peaks at 563, 598, 644 and 706 nm which could be associated to the transitions 4G5/2→6HJ (J=5/2, 7/2, 9/2 and 11/2, respectively) within the 4f5 electronic configuration of Sm3+. The effect of different doping concentration of Na2SO4:Sm3+ on the luminescent properties of the composites was investigated. The luminescent intensity of the composites increased with phosphor concentration.
分类: 材料科学 >> 材料科学(综合) 提交时间: 2023-03-31 合作期刊: 《腐蚀科学与防护技术》
摘要: 利用扫描电镜(SEM)结合能谱分析(EDS)、X射线衍射(XRD)、腐蚀失重实验、电化学极化曲线等方法,研究了0.1%,0.4%,0.7%和1.0%的Sm对AZ91D合金的微观组织和腐蚀性能的影响,并对其腐蚀机理进行分析。结果表明:随着Sm含量的增加,合金中粗大的枝状第二相(β-Mg17Al12)逐渐断裂变小,其体积分数下降,因为Sm会结合Al形成颗粒状的Al2Sm和杆状的Al3Sm,从而减少晶界处第二相的数量,使第二相呈不连续分布;AZ91D的耐腐蚀性随着Sm加入量的增多,先增加后降低;当Sm加入量为1.0%时,合金的耐腐蚀性与不添加Sm的AZ91D接近;Sm的最佳添加量为0.4%。
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: The comprehensive structural and luminescence study of Sm-doped SiO2-Na2SO4 composite materials are reported. The samples were synthesized by melt-mixing mixture of Na2SO4 and SmF3 into the SiO2 matrix at 1050 C for 30 min. X-ray di raction (XRD) pattern shows the characteristic structure of the SiO2 and addition of 20% Na2SO4:Sm has no e ect on the basic crystal structure of the SiO2. Scanning electron microscopy (SEM) shows the clear di erence in morphological structure between the composite and host SiO2. From photoexcitation (PE) spectra of the as-synthesized composite, the highest excitation e ciency was observed at 402 nm. The photoluminescence (PL) spectra of as-synthesized composite phosphors obtained under 402 nm excitation consist of five narrow emission bands with peaks at 563, 598, 644, 704 and 784 nm. These are assigned to the 4G5=2 ! 6HJ (J=5/2, 7/2, 9/2, 11/2 and 13/2, respectively) transitions within 4f5 electronic configuration of Sm3+. Highest luminescence intensity was observed with SiO2-10%Na2SO4:Sm.
分类: 物理学 >> 核物理学 提交时间: 2016-08-30
摘要: We explore a dark matter model extending the standard model particle content by one fermionic SU(2)L triplet and two fermionic SU(2)L quadruplets, leading to a minimal realistic UV-complete model of electroweakly interacting dark matter which interacts with the Higgs doublet at tree level via two kinds of Yukawa couplings. After electroweak symmetry-breaking, the physical spectrum of the dark sector consists of three Majorana fermions, three singly charged fermions, and one doubly charged fermion, with the lightest neutral fermion χ01 serving as a dark matter candidate. A typical spectrum exhibits a large degree of degeneracy in mass between the neutral and charged fermions, and we examine the one-loop corrections to the mass differences to ensure that the lightest particle is neutral. We identify regions of parameter space for which the dark matter abundance is saturated for a standard cosmology, including coannihilation channels, and find that this is typically achieved for mχ01∼2.4 TeV. Constraints from precision electroweak measurements, searches for dark matter scattering with nuclei, and dark matter annihilation are important, but leave open a viable range for a thermal relic.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-23
摘要: A comparative study on the morphology, structure and luminescence modifications of LDPE–Na2SO4:Sm3+ composite induced by gamma irradiation was reported for the first time. The composites were irradiated with irradiation doses of 10, 30, and 50 kGy in air at room temperature. Modifications on structural and luminescence properties of LDPE–Na2SO4:Sm3+ composites were investigated by using several analytical methods. The X-ray diffraction (XRD) patterns revealed that the cross-linking improved the crystallinity of the composites. Scanning electron microscope (SEM) images illustrated the surface modifications of composites induced by irradiation. Results of positron annihilation lifetime spectroscopy (PALS) suggested that gamma irradiation affected the free volumes concentrations in the samples. The photoluminescence (PL) spectra of non-irradiated and irradiated composites consisted of four main peaks at 563, 598, 644 and 706 nm which could be assigned to the 4G5/2 6HJ (J =5/2, 7/2, 9/2 and 11/2, respectively) transitions within the electronic configuration of Sm3+. Meanwhile, we observed an additional peak at about 686 nm in the irradiated composites, owing to the conversion of Sm3+ Sm2+. Concentrations of the Sm2+ centers linearly increased with gamma irradiation doses, which partly accounted for the degradation of PL intensity of Sm3+ peaks.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-06-27
摘要: With the assistance of two extra groups, i.e., an extra hidden gauge group SU(2)(D) and a global U(1) group, we propose a two component dark matter (DM) model. After the symmetry SU(2)(D) x U(1) being broken, we obtain both the vector and scalar DM candidates. The two DM candidates communicate with the standard model (SM) via three Higgs as multi-Higgs portals. The three Higgs are mixing states of the SM Higgs, the Higgs of the hidden sector and real part of a supplement complex scalar singlet. We study relic density and direct detection of DM in three scenarios. The resonance behaviors and interplay between the two component DM candidates are represented through investigating of the relic density in the parameter spaces of the two DMs masses. The electroweak precision parameters constrains the two Higgs portals couplings (lambda(m) and delta(2)). The relevant vacuum stability and naturalness problem in the parameter space of lambda(m) and delta(2) are studied as well. The model could alleviate these two problems in some parameter spaces under the constraints of electroweak precision observables and Higgs indirect search.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: 稀土三价钐离子掺杂不同基质发光材料由于在照明、显示器件、激光等许多领域都具有广泛的应用前景而受到广泛关注并得到深入研究.本文介绍了三价钐离子的能级结构、荧光物质发光性能的影响因素及三价钐离子掺杂不同基质发光材料的发光机理和发光性能,提出了稀土荧光物质在户外领域应用时存在的问题及解决问题的途径,对荧光物质/聚合物复合材料的发展方向进行了展望.认为制备工艺简单、成本低、化学性能稳定、转光效率高的荧光物质/聚合物复合材料兼备聚合物和荧光物质二者的优点,作为一种新型的功能复合材料具有较大的市场前景.
分类: 材料科学 >> 材料科学(综合) 提交时间: 2023-03-31 合作期刊: 《腐蚀科学与防护技术》
摘要: 利用X射线衍射(XRD)、带能谱(EDS)的扫描电镜(SEM)、腐蚀失重实验、极化曲线等方法,研究了1.0%La,0.7%Ce和3.0%Sm对AZ91D合金腐蚀行为的影响,并对其腐蚀机理进行了分析。结果表明:添加La,Ce和Sm后可以细化合金;在AZ91D中添加稀土元素La,Ce和Sm后,合金的自腐蚀电位高,自腐蚀电流低,阴阳极Tafel斜率大,合金耐腐蚀性能明显提高,其腐蚀速率略低于添加单一稀土元素Sm的合金。
分类: 计算机科学 >> 计算机科学的集成理论 提交时间: 2022-05-10 合作期刊: 《计算机应用研究》
摘要: SM9-IBS是中国于2016年公布的一种标识签名算法行业标准。标识签名算法虽然降低了系统管理用户公钥的复杂性,但是却存在密钥撤销的难题。此外,SM9的特殊结构使得已有技术无法完全适用。为此,提出了一种可撤销SM9标识签名算法,可快速实现对用户签名权限的撤销和更新操作。该算法引入一棵完全子树,密钥中心借助该树为每个合法用户生成临时签名密钥,只有使用该密钥生成的签名才可以通过签名验证。在安全性方面,该算法在随机预言机模型中,被证明在适应性选择消息和标识攻击模型下满足存在性不可伪造。在效率方面,该方案在密钥更新阶段当系统用户数量较大、被撤销用户数量较少时,密钥中心更新用户签名密钥的时间开销远小于Boneh等人的更新技术。
提交时间: 2017-05-02
摘要: The 2:17 type Sm-Co sintered magnets were made with strips and ingots, separately. The phase structure and microstructure of the cast alloys and their effects on magnetic properties of the magnets have been comparatively studied. X-ray diffraction analysi
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-05-09
摘要: We investigate the Hamiltonian formulation of f(T) gravity and find that there are five degrees of freedom. The six first class constraints corresponding to the local Lorentz transformation in Teleparallel gravity become second class constraints in f(T) gravity, which leads to the appearance of three extra degrees offreedom and the violation of the local Lorentz invariance in f(T) gravity. In general, there are D-1 extra degrees of freedom for f(T) gravity in D dimensions, and this implies that the extra degrees of freedom correspond to one massive vector field or one massless vector field with one scalar field.
分类: 计算机科学 >> 计算机科学的集成理论 提交时间: 2022-04-07 合作期刊: 《计算机应用研究》
摘要: 车载电子设备的增加使得车载网络面对越来越多的威胁。车载网络中电子控制单元(Electronic Control Unit,ECU)无认证、控制器局域网络(Controller Area Network,CAN)通信数据无加密等缺陷使得车载网络易遭受重放、ECU注入、中间人伪造消息、窃听等恶意攻击,造成严重后果。针对现在的车载网络威胁现提出一种基于SecOC的车载网络安全通信模型,该模型使用SM4的密码算法与基于Bkake2s的改进密钥管理,实现车载ECU的认证和车载网络消息的加密与认证。最后经过分析与测试,该模型可以保护车载网络安全并更高效。
分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Bleomycins (BLMs), as tumor-seeking antibiotics, have been used for over 20 years in treatment of several types of cancers. Several radioisotopes are used in radiolabeling of BLMs for therapeutic and diagnostic purposes. An important points in developing new radiopharmaceuticals, especially therapeutic agents, is the absorbed dose delivered in critical organs. In this work, absorbed dose to organs after injection of 153Sm-, 177Lu- and 166Ho-labeled BLM was investigated by radiation dose assessment resource (RADAR) method based on biodistribution data in wild-type rats. The absorbed dose effect of the radionuclides was evaluated. The maximum absorbed dose for the complexes was observed in the kidneys, liver and lungs. For all the radiolabeled BLMs, bone and red marrow received considerable absorbed dose. Due to the high energy beta particles emitted by 166Ho, higher absorbed dose is observed for 166Ho-BLM in the most organs. The reported data can be useful for the determination of the maximum permissible injected activity of the radiolabeled BLMs in the treatment planning programs.