非平衡磁控溅射类金刚石碳膜的性能

用非平衡磁控溅射的方法在室温下制备了光滑、均匀、致密的类金刚石(DLC)薄膜,分析和研究了DLC膜的形貌、结构和摩擦特性.结果表明,靶工作电流对DLC膜的沉积有重要的影响.随着工作电流的增大,薄膜的沉积速率增大,薄膜中sp3键的含量增加.薄膜的摩擦系数随着工作电流的增加略有增大,在摩擦的初始阶段,摩擦系数较高,随着摩擦循环次数的增加,摩擦系数逐渐减小,并逐渐趋于稳定.     

磁控溅射Al-Mg-B薄膜成分优化

采用多靶磁控共溅射技术,利用高纯度Al,Mg和B单质靶材为溅射源,室温下在单晶Si(100)表面上成功制备了低摩擦系数的非晶态Al-Mg-B硬质薄膜.通过改变Al/Mg混合靶体积配比及靶材溅射功率来调控薄膜成分,最终制备的Al-Mg-B薄膜成分接近AlMgB_(14)相的元素成分比,其Vickers硬度约为32 GPa.XRD及HR-TEM分析表明.制备的薄膜均为非晶态XPS测试表明薄膜内部存在B-B及Al-B单键;FTIR进一步测试表明,在波数1100 cm~(-1)处出现较为明显的振动吸收峰,证明制备的薄膜中含有B_(12)二十面体结构,这也是薄膜具有超硬性的主要原因.薄膜摩擦磨损测试表明薄膜摩擦系数在0.07左右.     

Intuitionistic fuzzy similarity measures based on min–max operators

Pattern Analysis and Applications - Intuitionistic fuzzy sets, introduced by Atanassov, offer a new possibility to describe in a more adequate way many real problems. An important tool for...     

The Romanian wordnet in a nutshell

The project on the Romanian wordnet has been under continuous development for more than 10 years now. It has been in constant use in many projects and applications which determined, to a large extent, the content and coverage of various lexical domains. The article presents the most recent developments of the Romanian wordnet and offers quantitative data for its current version.     

SPECTRAL METHODS FOR HISTORICAL PAPER ANALYSIS: COMPOSITION AND AGE APPROXIMATION

The research has been focusing on some connection between the chemical composition of the papers obtained by Fourier transform infrared (FTIR) spectroscopy and the nature of the fillers, determined by energy dispersion X-ray fluorescence (EDXRF) spectroscopy. The present paper corroborates the FTIR and EDXRF results obtained for some historical papers from books of the XIX-th and XX-th centuries, from private collections. These analytical results allowed a first approximation of technological paper composition and of the age determination of the samples. This analytical method can elaborate some properly methods for paper documents preservation, taking into account the aging and degradation processes of the historical paper.     

Analysis on background magnetic field to generate eddy current by pulsed gradient of permanent-magnet MRI

In this paper the analytical expressions for the magnetic field H and induction B in iron-pole plates generated by MRI gradient coil are given using line-current and the multilayer dielectric plate model with the mirror-image method.Eddy current emanates from the magnetic flux in the iron-pole plates.In order to fully suppress the eddy current,this magnetic flux should be fully eliminated.The research results indicate the magnetic permeability of the resist-eddy plate must be bigger than that of magnetic po...     

Chemical‐looping combustion process: Kinetics and mathematical modeling

Chemical Looping Combustion technology involves circulating a metal oxide between a fuel zone where methane reacts under anaerobic conditions to produce a concentrated stream of CO₂ and water and an oxygen rich environment where the metal is reoxidized. Although the needs for electrical power generation drive the process to high temperatures, lower temperatures (600–800°C) are sufficient for industrial processes such as refineries. In this paper, we investigate the transient kinetics of NiO carriers in the temperature range of 600 to 900°C in both a fixed bed microreactor (WHSV = 2‐4 g CH₄/h/g oxygen carrier) and a fluid bed reactor (WHSV = 0.014‐0.14 g CH₄/h per g oxygen carrier). Complete methane conversion is achieved in the fluid bed for several minutes. In the microreactor, the methane conversion reaches a maximum after an initial induction period of less than 10 s. Both CO₂ and H₂O yields are highest during this induction period. As the oxygen is consumed, methane conversion drops and both CO and H₂ yields increase, whereas the CO₂ and H₂O concentrations decrease. The kinetics parameter of the gas–solids reactions (reduction of NiO with CH₄, H₂, and CO) together with catalytic reactions (methane reforming, methanation, shift, and gasification) were estimated using experimental data obtained on the fixed bed microreactor. Then, the kinetic expressions were combined with a detailed hydrodynamic model to successfully simulate the comportment of the fluidized bed reactor. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Thermal stability of gelatin gels: Effect of preparation conditions on the activation energy barrier to melting

10, 20, and 40 wt.% aqueous gelatin gels were prepared under isothermal (annealing at 15, 20, and 25 °C for 15 to 120 min) and nonisothermal (cooling at 1 °C min⁻¹) conditions. Isoconversional kinetic analysis of DSC data on gel melting (gel-sol transition) of all types of gels revealed significant variations in the activation energy throughout the process. Activation energy barrier to melting of isothermally prepared gels was in the range 160-190 kJ mol⁻¹ and found to increase with increasing the annealing temperature that was the major effect discovered. Activation energy barrier to melting of nonisothermally prepared gels was determined to be around 120-140 kJ mol⁻¹ and increase with increasing the concentration. Local reversibility of the gel melting was demonstrated by using temperature modulated DSC.     

Photochromic properties of polyimide and polysiloxane azopolymers

BACKROUND: One of the most important properties of the azobenzene chromophores is the photochemical trans–cis isomerization induced by UV or visible light. In azopolymers, the photoisomerization induces conformational changes in the polymer chains, which in turn lead to macroscopic variations in the chemical and physical properties of the surroundings and media. RESULTS: This work reports the photochromic behaviour and surface structuring capacity of azopolymers having rigid polyimide and flexible polysiloxane structures, respectively. These polymers have good thermostabilities, with the degradation process starting above 315 °C. The glass transition temperature of the azopolyimide is 228 °C, while that of the azopolysiloxane modified with thymine is 34 °C. CONCLUSION: The experiments show that the azobenzene groups can isomerize even in the case of the rigid polyimide, but the maximum degree of conversion to the cis isomer is less than in the case of the flexible polysiloxane. This behaviour is reversed in solution, probably due to both the thymine and azo group interactions and for conformational reasons. The azopolymers show a good surface structuring capacity. The polysiloxane is more sensitive in the case of low irradiation energy and irradiation time. By increasing the irradiation time for both polymers, the modulation depth increases and has comparable values. Copyright © 2008 Society of Chemical Industry