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951.
仿冒(Phishing)危害愈演愈烈,本文针对其攻击行为进行了详细的分析与介绍,其中使用了建立攻击森林和对攻击进行分类等方法,进而建立了Phishing攻击模型.提出了相应的Phishing攻击的防范理论体系和具体措施.同时高起点地分析了IPv6环境下的Phishing攻击及其防御. 相似文献
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954.
从SF6电气设备水分的来源,分析了湿度超标的原因,并提出了解决问题方法,以及工作中应该注意的问题. 相似文献
955.
《Ceramics International》2020,46(5):5876-5886
Additive Manufacturing (AM) technologies applied to the titanium alloys have attracted attention from industries in recent years. Despite one of the main goals of AM is the reduction of manufacturing steps, semi-finish/finish machining operations are still required so as to obtain the desired geometrical tolerance and surface features. In this study, the solid end mill was manufactured by Al2O3/Si3N4 (Sialon) ceramic materials and employed in high-speed slot milling of Ti6Al4V alloy fabricated by the Direct Metal Laser Sintering (DMLS) AM technology to study the tool wear characteristics during processing. The Raman spectroscopic method was employed to characterize the molecular structures of Sialon ceramics for the manufacturing of the cutting tool. The morphologies and elemental maps of wear region of the ceramic tool were examined by scanning electron microscope and energy dispersive spectroscopy techniques. The results show that the adhesion wear and diffusion wear are the dominant wear mechanisms, and the chemical stability of Al2O3/Si3N4 (Sialon) ceramics fabricated as the solid ceramic tool to the attack of the atoms from additive manufactured Ti6Al4V is relatively weak under the atmosphere. The difference of thermal expansion coefficients of diffusion layer and tool substrate accelerates the initiation and propagation of thermal cracks formed on the diffusion interface. Moreover, fracturing and crater-like groves near the tool edge were finally formed due to the removal of adhered workpiece material. 相似文献
956.
Tarun Sai Ghanta Sridhar Aparna Namrata Verma Doddipatla Purnima 《Polymer Engineering and Science》2020,60(8):1717-1759
Polyamide 6 (PA6)-based composites are of evolving interest due to its high strength, wear resistance, and barrier properties. The use of binary composites mostly with nanomaterial and glass fibers has been reviewed and presented in literature. However to obtain a balance of properties like stiffness, toughness, and strength along with cost reduction, ternary composites of PA6 have been designed. To achieve the balance, PA6 blend-based composites, with combination of microfiller/nanofiller or PA6 with combination micro-microfiller, PA6 with microfiller/nanofiller and fiber have been designed. The properties of PA6-based ternary hybrid composites depend on type of dispersed phase used, presence of compatibilizer, type of filler used (nanofiller or microfiller or fiber or hybrid) and combination of fillers used. However, a review in this direction is not available in literature. Here, in this study, an overall understanding of various fillers, dispersed phase, and their combinations can be understood along with the discussion on effect of these on tensile properties and morphology of hybrid composite. In this study, an attempt has been made to review the various fillers and dispersed phase and their combinations which have been used in designing the PA6 hybrid composite with good balance of stiffness, toughness, and strength. 相似文献
957.
《Ceramics International》2020,46(9):13114-13124
In this study, plasma electrolyte oxidation (PEO) method was employed to modify the surface of Ti–6Al–4V. Effects of different concentrations of ZrO2 nanoparticles (0, 1, 3 and 5 g/l) into a phosphate-based electrolyte on the morphology, wettability, antibacterial and corrosion behaviors of coatings were investigated. Microstructural analyses of coatings were evaluated using scanning electron microscopy with an energy dispersive spectrometer. Also, X-ray diffraction, contact angle instrument and profilometry were respectively used to perform phase analysis, wettability, and surface roughness of the coatings. The antibacterial test was conducted with spot inoculation method on four pathogenic bacteria. Polarization and impedance spectroscopy measurements were performed in Hank's solution to investigate the corrosion behavior of coatings. The results revealed that PEO coatings without nanoparticles and by increasing the concentration of the ZrO2 nanoparticles up to 3 g/l in the electrolyte led to a significant improvement in the antibacterial activities of gram-negative bacteria (P. aeruginosa and E. Coli). In the case of gram-positive bacteria, the PEO coated samples demonstrated improved antibacterial effects but addition of ZrO2 nanoparticles in the PEO coatings resulted in deterioration of antibacterial effect. The sample coated with 3 g/l ZrO2 nanoparticles showed the peak corrosion resistance compared to its counterparts. 相似文献
958.
利用微弧氧化技术在Ti6Al4V钛合金表面制备出蓝色微弧氧化膜。对微弧氧化膜的微观形貌和元素组成进行了分析,并对微弧氧化膜的显微硬度进行了测试。结果表明:微弧氧化膜表面光整,呈均匀深蓝色,其主要由Ti、Mn、O和C四种元素组成,还含有少量的V、Al和Si元素;微弧氧化膜的表面粗糙度约为0.159μm,与钛合金的表面粗糙度相近;微弧氧化膜的显微硬度为5 437.4 MPa,显著高于钛合金的显微硬度。 相似文献
959.
目前1-烷氧基-2,2,6,6-四甲基哌啶基化合物的合成主要是以醛酮法为主。醇法合成虽然醇价格便宜,但合成效率很低。为解决这一问题,本文对醇法合成工艺进行了深入探讨,并以乙醇和4-羟基-2,2,6,6-四甲基哌啶氮氧自由基(ZJ-701)为原料,30%过氧化氢为氧化剂,氯化铜和吡啶配合物为催化剂,通过氧化和自由基偶合合成了1-甲氧基-2,2,6,6-四甲基哌啶-4-醇,通过红外光谱、核磁共振谱和质谱表征了其结构。通过实验进一步优化了反应时间、温度等一系列合成条件。研究结果表明:当反应时间为12h,反应温度为78℃,n(ZJ-701)∶n(乙醇)∶n(H2O2)∶n(CuCl2)∶n(吡啶)=1∶39.25∶17.01∶0.034∶0.36时,产品产率最高,为60.6%,质量分数为98.8%,熔点为87~90℃。该方法具有原料乙醇便宜易得、反应条件温和、产品提纯容易等优点。 相似文献
960.
Xian Yang Yu Zhang Xuejie Zhang Jian Chen Haisen Huang Dongsheng Wang Xirong Chai Gening Xie Maxim S. Molokeev Haoran Zhang Yingliang Liu Bingfu Lei 《Journal of the American Ceramic Society》2020,103(3):1773-1781
The red emission with suitable peak wavelength and narrow band is acutely required for high color rendering index (CRI) white LEDs without at the cost of the luminous efficacy. Herein, the Li2Ca2Mg2Si2N6:Eu2+ red phosphor was prepared with facile solid-state method using Ca3N2, Mg3N2, Si3N4, Li3N, and Eu2O3 as the safety raw materials under atmospheric pressure for the first time, which shows red emission peaking at 638 nm with full width at half maximum (FWHM) of 62 nm under blue light irradiation and becomes the desired red phosphor to realize the balance between luminous efficacy and high CRI in white LEDs. The morphology, structure, luminescence properties, thermal quenching behavior, and chromaticity stability of the Li2Ca2Mg2Si2N6:Eu2+ phosphor are investigated in detail. Concentration quenching occurs when the Eu2+ content exceeds 1.0 mol%, whereas high-temperature photoluminescent measurements show a 32% drop from the room-temperature efficiency at 423 K. In view of the excellent luminescence performances of Li2Ca2Mg2Si2N6:Eu2+ phosphor, a white LEDs with CRI of 91 as a proof-of-concept experiment was fabricated by coating the title phosphor with Y3Al5O12:Ce3+ on a blue LED chip. In addition, the potential application of the title phosphor in plant growth LED device was also demonstrated. All the results indicate that Li2Ca2Mg2Si2N6:Eu2+ is a promising red-emitting phosphor for blue LED-based high CRI white LEDs and plant growth lighting sources. 相似文献