Advanced Materials Research Vols. 383-390

Abstract: The binary eutectic of lauric acid-stearic acid / expanded perlite composite phase change materials (PCM) was prepared using the method of vacuum impregnation. The structures and properties of this composite PCM were characterized by FT-IR, SEM, DSC and TG analysis. The results showed that the binary eutectic of fatty acid had been composed with porous skeleton expanded perlite completely in a physical method, the phase transition temperature of composite PCM was about 33.0 °C and latent heat was 131.3 J/g. it had a good thermal stability after 100 times of recycling and gave the phase transition temperature 33.5 °C and the latent heat of 128.1 J/g respectively.

Abstract: This paper presents the methane coupling with a new developed rotary multidentate helix electrode under plasmas at atmospheric pressure and in the presence of hydrogen to investigate the effects of peak voltage input the electric fields and feed flow rate on CH₄ conversion and C₂ yield and selectivity. The best result without remarkable amount of coke is 69.85% of single pass yield of C₂ hydrocarbons with 70.46% of CH₄ conversion and 99.14% of selectivity of C₂ hydrocarbons. The emission of excited species such as excited radicals and atoms (C,CH,C₂,H and H₂) were detected in the spectra range of 300 nm～700 nm.

Abstract: The gas monitor with optical fiber is developed in this paper based on the principle that the absorption light changes with gas intensity under absorptive peak wavelength. The LED of driving light source is selected by the absorptive peak wavelength of measured gas. The light source driving circuit with the different frequency is used to detect the varied gas in real time. The techniques of phase-sensitive detected and ratio between measured signal and reference signal is used to ensure measurement accuracy. The examination system chooses low loss 50cm-long quartz optical fiber as long distance transmitting channel. The light source adopts low power pulse modulation semiconductor LED. 50cm-long absorption gas room is used to ensure measurement sensitivity. The system adopts the technique to carry out scheme combining optical fiber sensing technique with computer data handling technique. Uniting sensing light signal and stimulating light power transfer and measured parameter sensing, the advantages of optical fiber system, micro-electron electric circuit and computer compatibility can be sufficiently realized. The entire measurement system can attain light, the engine and electricity integration, and realize multi-parameter and multi-function. The experiment result of methane and acetylene intensity indicates that the system has higher detected sensitivity and detected accuracy. The system is not only used to detect the methane and acetylene intensity, but also to detect other gas intensity under a little structure parameter change.

Abstract: Methane is an easily burning and exploding gas. It is the primary component of many gas fuels such as mine gas and natural gas and so on. In the coal mine accidences of our country, the casualties caused by gas explosion covers over 50% in all great casualties, and it becomes the largest obstruction of safe production. Incident online detecting methane gas density has important significance for mine and plant safe production and personal safety. Based on the near infrared spectral absorption of methane, a system using absorption type optical fiber for high sensitivity methane detection is demonstrated in this paper. DFB LD is adopted as light source in this paper. Modulating the light source, methane gas is detected by second harmonic. The ratio of the fundamental and second harmonic signal can be used for eliminating the interference owing to light power changing. The mathematical model of gas concentration harmonic measurement is built up. The result of methane concentration is also shown. The system overcomes the defect of great interference of available instruments by light route. It has advantages such as high sensitivity, quick response speed, large dynamic range, preventing electromagnetic interference, preventing burning and explosion, not easily being poisoned and so on. The probe can be put in condition of easily burning and exploding, being poisonous being high temperature and so on that man and instrument can not easily enter. It can realize online continuous telecontrol and telemeter.

Abstract: A great deal of energy can be absorbed when the inner diameter of a steel tube is inflated by inserting a rigid rod. This procedure has some advantages: high energy absorbed per length, constant compress force and robust to the direction of insertion force. Therefore, this is very fit for energy-absorber for some light vehicles. The effect of energy-absorbing is investigated by impact test and simulation in this paper. Applications for full frontal impact and offset frontal impact of a minibus are discussed.

Abstract: The TLM model of 3 - phase pow er t ran sm ission line is developed. Appling the transmission line modeling (TLM) method to analysis 1000kV ultrahigh voltage( UHV) AC transmission line, the obtained results prove that it is economical and reasonable to transmit the natural power by power transmission, and the transmission lines is a long-distance transmission power ; but both the super power and the power transmission, the transmission power reduce with the increase of transmission distance.

Abstract: Coal char combustion under the O₂/CO₂ atmosphere is one of the prospect cleaner coal technologies, its combustion characteristics and dynamics research are the foundations of project application. In this paper, the results of a study on the combustion characteristics of three coal chars ( Liupanshui lignite, Zhungeer bituminous ,Qinhuangdao anthracite) under different oxygen volume content （21%、25%、30%、35%）are presented by TGA, the effect of oxygen volume content to coal-char reaction were analyzed. Simultaneously classical dynamics and time effect fractal dynamics had carried on the analysis separately to the coal char combustion. The results showed that, with higher the oxygen content, the lower the ignition、burnout temperatures are, the char combustion time shorten, activation energy reduces slightly whether use classical dynamics or time effect dynamics analysis, and the activation energy obtained by the former is smaller than the latter.

Abstract: Rotor flux observation is a key step in implementation of a field-oriented vector control system. Aiming at eliminating the influence of the actual speed fluctuation and rotor resistance variety, an adaptive rotor flux observer was proposed to accurately estimate the flux of induction motors in modern high performance drivers, based on the conception of close-loop flux estimation and the extended state observer theory. The performance of the proposed scheme is verified through simulation and experiment.

Abstract: The idea of this paper roots in the electromagnetic compatibility design of the whole aircraft system, in which out of band characteristics of airborne antennas are of equal importance as their characteristics in band. The definition of antenna characteristics for out of band is interpreted. Horn antennas are the main research objects in this paper. In order to make characteristic of this type antenna for out of band have a general, this paper is special to select pyramidal horn antenna and conical horn antenna. The characterization framework of horn antennas radiation characteristics for out of band is established, and the theoretical expressions of their radiation characteristics for out of band are given. In ensuring better antenna characteristics in band, four horn antennas that are different types of sizes, different frequency band width are simulated and analyzed by using electromagnetic simulation software HFSS. It is meaningful to analyze radiation characteristics and summarize different features for various performance parameters of these horn antennas for in band and out of band. Focus on characteristics of the changes for the maximum gain, 3dB beam width parameters of horn antennas within the working frequency band and out of working band. The results show that: radiation characteristics of horn antenna are the law within the working frequency band and out of working band.

Abstract: The crane reel is generally manufactured by section welding method when the diameter is over 380mm. With the cumulative fatigue damage principle which is based on stress S-N curve, the fatigue damage of one crane reel is analyzed by finite element method, the reel weld fatigue strength and fatigue life are calculated, and the simulation results are proved to be reliable. This method provides an efficient reference for crane reel design and residual life estimation.