一种高效安全的EPS AKA协议

针对4G认证与密钥协商协议(EPS AKA)中存在的安全问题,提出了一种高效安全的改进协议(ES-AKA).该协议不仅能够抵抗重定向攻击和重放攻击,同时消除了密钥K泄露的安全隐患.安全性和协议性能分析表明:在更高的安全性能下,该协议降低了服务网络的存储空间和归属网络的计算量,有效减少了认证过程的比特通信量.     

A high sensitivity localized surface plasmon resonance sensor based on D-shaped photonic crystal fiber for low refractive index detection

In this paper, a localized surface plasmon resonance (LSPR) refractive index sensor based on photonic crystal fiber (PCF) is proposed to solve the problem of low refractive index analyte detection. 31 silver nanowires are placed on the surface of the D-shaped PCF, which increases the contact area between the plasma material and the analyte. The simulation results indicate that the maximum sensitivity of the sensor reaches 16 400 nm/RIU, and the refractive index detection range is 1.26—1.33. It is proved that the sensor has a good prospect in low refractive index detection.     

Influence of CuO addition to BaSm2Ti4O12 microwave ceramics on sintering behavior and dielectric properties

Microwave dielectric ceramics of tungsten–bronze-type BaSm₂Ti₄O₁₂ were prepared by doping CuO (up to 2 wt.%) as the liquid-phase sintering aid. The effects of CuO additive on the densification, micro structure and dielectric properties were investigated. Due to the liquid-phase effect, the sintering temperature of BaSm₂Ti₄O₁₂ ceramics with 1 wt.% CuO addition can be effectively reduced to 1160 °C, about 200 °C lower than that of pure BaSm₂Ti₄O₁₂ ceramics, while good microwave dielectric properties of ɛ_r = 75.8, Q*f = 4914.6 GHz and τ_f = −7.65 ppm/°C were still achieved.     

Epitaxial growth of nonpolar GaN films on r-plane sapphire substrates by pulsed laser deposition

Single-crystalline nonpolar GaN epitaxial films have been successfully grown on r-plane sapphire (Al₂O₃) substrates by pulsed laser deposition (PLD) with an in-plane epitaxial relationship of GaN[1-100]//Al₂O₃[11-20]. The properties of the ~500 nm-thick nonpolar GaN epitaxial films grown at temperatures ranging from 450 to 880 °C are studied in detail. It is revealed that the surface morphology, the crystalline quality, and the interfacial property of as-grown ~500 nm-thick nonpolar GaN epitaxial films are firstly improved and then decreased with the growth temperature changing from 450 to 880 °C. It shows an optimized result at the growth temperature of 850 °C, and the ~500 nm-thick nonpolar GaN epitaxial films grown at 850 °C show very smooth surface with a root-mean-square surface roughness of 5.5 nm and the best crystalline quality with the full-width at half-maximum values of X-ray rocking curves for GaN(11-20) and GaN(10-11) of 0.8° and 0.9°, respectively. Additionally, there is a 1.7 nm-thick interfacial layer existing between GaN epitaxial films and r-plane sapphire substrates. This work offers an effective approach for achieving single-crystalline nonpolar GaN epitaxial films for the fabrication of nonpolar GaN-based devices.     

Synthesis and characterization of castor oil and ricinoleic acid capped CdS nanoparticles using single source precursors

We report the synthesis of castor oil and ricinoleic acid capped CdS nanoparticles by the thermolysis of piperidine (1) and tetrahydroquinoline (2) dithiocarbamate complexes of cadmium(II) at temperatures varying from 190 °C to 300 °C. Reaction parameters such as time and temperature were varied to study their effect on the properties and morphology. The optical properties of CdS were typical of particles that displayed quantum confinement effects. X-ray diffraction studies revealed the existence of both cubic and hexagonal phases depending on the reaction conditions. Ricinoleic acid capped CdS gave cubic phase particles whereas castor oil capped CdS gave both cubic and hexagonal phases dependent on the reaction temperature and the type of complex used. The morphology of the particles varied from oval-short rods to spherical shaped particles with sizes ranging from 10 to 22 nm. Rhodamine B (RhB) dye photodegradation studies of a representative CdS nanoparticles’ sample have been carried out in the presence of halogen light and studied using UV–visible spectroscopy.     

Blood smear analyzer for white blood cell counting: A hybrid microscopic image analyzing technique

Total count and differential count of leukocytes or white blood cells (WBC) in blood samples are very important pathological factors for diagnosing a disease. There are not enough pathological infrastructures in the remote places of India and other developing countries. The objective of this work is to design a system, compatible with telemedicine, for automatic calculation of the total count and differential count of WBC from the blood smear slides. Hemocytometer based WBC counting provides more accurate result than manual counting, but hemocytometer preparation process needs expertise. As this device is targeted for remote places, blood smear technique is adopted to reduce the overhead of the operator. In the proposed system, microscopic images of blood smear sample are processed to highlight the WBC for segmentation. Region segmentation procedure involves background scaling and redundant region elimination from the region set. After segmentation, the more accurate region boundary is restored by using gradient based region growing with neighbourhood influence. Individual regions are separately classified on the basis of shape, size, color and texture features independently using different fuzzy and non-fuzzy techniques. A final decision is taken by combining these classification results, which is a kind of hybridization. A set of rules has been generated for making final classification decision based on outputs from various classifiers. The sensitivity and specificity of the system are found to be 96.4% and 79.6%, respectively on a database of 150 blood smear slides collected from different health centres of Kolkata Municipal Corporation, Kolkata, India.     

An empirical study of the relationships among employee’s perceptions of HR practice,human capital,and department performance: A case of AT & T Subordinate telecoms company in Taiwan

The telecom industry in Taiwan began to enter a vigorous development stage after Taiwan’s Legislative Yuan enacted the three major telecommunications laws in 1996. After 2003, the number of mobile phone subscribers began to shrink after reaching a climax penetration rate of 111%. The problems which were ignored during the high growth period began to appear. This research discusses which human practices are effective in developing human capital and whether they will influence the performance of the telecom industry. Human capital is used as a mediate variable between human resources and department performance. Through a questionnaire survey, an analysis by mean, standard deviation, and Pearson correlation is performed. A causal multivariable analysis by structural equation modeling (SEM) is used to test the causal relationship among these factors.     

基于长周期光纤光栅液位传感器的实验研究

利用长周期光纤光栅(LPFG)的基模和包层模间的耦合特性,设计制作了一种基于LPFG的液位传感器。LPFG包层模对环境折射率的响应不同,随着液位的变化,其透射功率发生变化。用该传感器对蒸馏水和乙醇的液位变化进行测量,当液位在0.0～17.5mm范围内变化时,LPFG透射功率分别变化了6.8719dB和13.4360dB,其灵敏度为0.389 6dB/mm和0.7678dB/mm。结果表明,液体的折射率越大,传感器的灵敏度越高,并且具有良好的线性关系。     

Simultaneous tuning of the phase transition temperature and infrared optical properties of Mo-doped VO2 powders for intelligent infrared stealth materials

The development of an intelligent infrared camouflage material whose infrared emissivity can actively adapt to environmental changes is a key frontier in the field of infrared stealth. In this study, Mo-doped VO₂ powder was prepared via a hydrothermal method, which led to an intelligent infrared camouflage material whose infrared radiation characteristic can adaptively change with the environmental temperature. The samples were characterized by XRD, SEM, DSC, FTIR and infrared thermal imaging. Combined with the results of the first-principles calculation, the coupling effect mechanism of Mo⁶⁺ doping concentration on the phase transition temperature and infrared photoelectric properties of VO₂ material was systematically analyzed. The results showed that Mo⁶⁺ impurities had significant effects on the structure, morphology, composition, phase transition temperature and infrared reflectivity of VO₂ powder. The doping process effectively reduced the phase transition temperature of VO₂ and expanded the change range of infrared emissivity (△ε) before and after the metal-to-insulator (MIT) transition. With the increasing amount of Mo⁶⁺ doping, the infrared reflectance of VO₂(M) gradually decreased at low temperatures, while the infrared reflectance of VO₂(R) increased at high temperatures. The MIT transition temperature of Mo-doped VO₂ versus undoped VO₂ reduced to 31.5 °C, and the △ε increased by 153%, this is expected to meet the performance requirements of intelligent infrared stealth materials.     

Enhanced magnetodielectric properties of Co2Z ferrite ceramics for ultrahigh frequency applications achieved via Cr3+ ion doping

Phase formation, microstructure, magnetic properties, and dielectric properties of Ba_1.5Sr_1.5Co₂Fe₍₂₃−_x)Cr_xO₄₁ (0.0 ≤ x ≤ 1.0) ceramics, in which Fe³⁺ ions were substituted by Cr³⁺ ions, were systematically investigated. X-ray diffraction results reveal that Z-type hexagonal ferrite was formed by sintering at 1250 °C, and Cr³⁺ ions successfully enter lattice without destroying crystal structure. Analysis of the microstructure reveals that Cr³⁺ ion doping has significant effect on crystal micromorphology. Samples with x = 0.4 have the most homogeneous micromorphology and the highest sintering density of 5.12 g/cm³. In addition, under the influence of external magnetic field, all samples exhibit typical soft magnetic character and hysteresis characteristics, with saturation magnetization up to 63.86 emu/g (x = 0.6). Particularly, compared with undoped sample, Cr-doped samples have outstanding magnetic–dielectric properties. Firstly, with increasing Cr³⁺ amount, real part of the permeability (μ′) reaches the maximum value of 10.70 at x = 0.4, while cutoff frequency exceeds 2 GHz, and Snoek constant reaches ∼19.50 GHz. Furthermore, due to more homogeneous microstructure, samples with x = 0.4 have low magnetic loss and can maintain high quality factor (Q) over a broad frequency range. Moreover, real part of the permittivity (ε′) reaches the maximum value of 16.90 at x = 0.6, and dielectric loss remains lower than 0.013 for frequencies below 0.7 GHz. Consequently, magnetic–dielectric materials prepared in this work are expected to have extensive application prospects for ultrahigh-frequency devices.