Non-isothermal Kinetics of Pyrolysis of Three Kinds of Fresh Biomass

The pyrolysis kinetics of three different kinds of fresh biomass （grass： triple A, wheat straw, corn straw） in nitrogen flow were studied by thermogravimetric analysis at five different heating rates. The kinetic parameters of the pyrolysis process were calculated using the method of Ozawa-Flynn-Wall and the mechanism of reactions were investigated using the method of Popescu. It was found that the values of activation energy varied in different temperature ranges. The pyrolysis processes are well described by the models of Zhuravlev （Zh） and valid for diffusion-controlled between 200 ℃ and 280 ℃, by Ginstling-Brounshtein （G-B）, valid for diffusion-control between 280 ℃ and 310 ℃, for first-order chemical reaction between 310℃ and 350 ℃. by Zhuravlev （Zh） valid for diffusion-control between 350 ℃ and 430 ℃ and by the one-way transport model when temperatures are over 430 ℃.     

Influence of Lithological Characters of Coal Bearing Formation on Stability of Roof of Coal Seams

Lithology is one of the important factors influencing the stability of roof of coal seams. In order to investigate this, the phenomenon of underground pressure and distribution of pressure were studied by using the local observation and simulation test with similar materials. The observation results show that the distance of initial weighting and periodic weighting of the mudstone roof is shorter than that of sandstone roofs. The sandstone roof with a high strength has a longer distance of initial weighting and periodic weighting, the abutment stress on the working face is big and the height of caving and fracture zone is high. The peak point of abutment stress in the sandstone roof is near to the working face and the pressure bump is inclined to occur. The result is contrary to that in case of the mudstone roof with a low strength. While in the transition zone of nipped sandstone, roof rock-mass is broken and is poor in stability, therefore, it is difficult to hold the roof.     

Analysis of Road Base Uniformity via the Deviation of Modulus of Asphalt Mixtures

The modulus deviation of base material calculated from the data of falling weight deflectometer （FWD） was used to evaluate the uniformity of road base so as to reflect the construction quality. Four parameters,the repeatability standard deviation of the data in the same driveway, the reproducibility standard deviation of the data in the different driveway, the consistency statistics value of the data in the different driveway, and the consistency statistics value of the data in the same driveway, were introduced for the construction uniformity analysis. The experimental result shows that the materials modulus calculated from FWD has a highly correlative relationship with the uniformity of road base.     

Electrochemical determination of Gibbs free energy of formation of magnesium ferrite

The standard Gibbs free energy of formation of magnesium ferrite was determined by means of two types of solid state electrochemical cells: one using MgZr4(PO4)6 (MZP) as the solid electrolyte and the other using CaF2 as the solid electrolyte. The first cell was operated in the range of 950 to 1100 K. The second cell was operated in the range of 1125 to 1200 K. The reversibility of the cell EMFs was confirmed by microcoulometric titration. The Gibbs energy changes of magnesium ferrite relative to component oxides were calculated based on EMF measurements and are given by following expressions, respectively: △G(o)Ⅰ = -3579-15 T (J/mol) and △G(o)Ⅱ =6258-24.3 T (J/mol). The results obtained from two different cells are consistent with each other. The results also are in agreement with Rao's and Tretjakov's data in the measured temperature range. When the Gibbs free energies of formation of MgO and Fe2O3 were substituted in the reaction, the Gibbs free energies of formation of MgFe2O4 was obtained in two temperature ranges and the formations are shown as follows: △G(o)Ⅰ Formation = -1427394 360.5 T (J/mol) and △G(o)Ⅱ Formation = -1417557 351.2 T (J/mol).     

Investigation of the Thermal Decomposition Properties of Polyoxymethylene

By testing the melt index （MI）, tensile strength and breaking extension ratio, the thermal ageing rate of polyoxymethylene （POM） was analyzed and compared. The surface morphology and type of function group of POM surface were observed and analyzed by SEM and XPS. The results show that the MI value increases gradually with the ageing time at 120℃, indicating that the thermal oxidation decomposition occurrs slowly. The effect of 20-day thermal ageing on the tensile strength and breaking extension ratio of POM is not obvious, showing that the ageing of POM is quite a long process. After 105-day, thermal ageing cracking and powdering occurr on the POM surface. XPS determination shows the Cls spectra of samples before and after ageing include two peaks of C-C and C-O, while after ageing the content of C-C decreases and the content of C-O increases, indicating that the thermal ageing of POM is mainly the breaking and decomposing of C-C bond. The Ols/Cls ratio of original samples is 56.98% and after 105-day thermal ageing the ratio is 72.92%.     

Influence of Particle Size on Piezoelectricity of Piezo-composites

Serial material model （Dilute model）and Limited Units （LU）method were employed to analyze the performance of binary piezo-composite system.The reckoned electric potential deployments illustrated difference while the particles were different.Their piezoelectricities were also calculated according to the model,and furthermore comparation suggested that small particles living in the tolerance improve the piezoelectricity of piezo-composite.Experiments coinciding with analyses were processed simultaneously. Ceramics were milled for different time in order to control the concentration of particle size.The results showed that the filled particles enhanced the piezoelectricity of binary piezo-composite system efficiently whereas too many chips deteriorated the performance of piezo-composites.     

Optimal Control of Aeroelastic StochasticVibration of Aerocraft

ＯｐｔｉｍａｌＣｏｎｔｒｏｌｏｆａｅｒｏｅｌａｓｔｉｃＳｔｏｃｈａｓｔｉｃＶｉｂｒａｔｉｏｎｏｆＡｅｒｏｃｒａｆｔＷＡＮＧＳＨＩＺＨＯＮＧＳＨＥＮＹＩＺＨＡＮＧＹＯＮＧＺＨＵＹＩＮＦＡ王世忠，沈毅，张涌，朱银法（Ｄｅｐｔ．ｏｆＡｓｔｒｏｎａｕｔｉｃｓ...     

Journal of Central South University of Technology

1 Aims and scope Central South University (CSU) is one of Chinese key universities, which is affiliated with the Ministry of Education. "Journal of Central South University of Technology" (ISSN 1005-9784, CODEN JCSTFT) is sponsored by CSU.     

Effects of synthetic conditions of pulse galvanostatic method on electroactivity of polyaniline

1　INTRODUCTIONConducting polymers, due to their potentialapplication prospects, have been investigated ex tensively during the past decade[1 10]. Conductingpolyaniline (PANI), on account of its excellent op tical and electronic properties, is promising inmany fields, such as electronic devices, electro chromic devices, and ion switching devices[11 16].The morphology of conductive PANI can varygreatly with the preparation methods and condi tions. Gene…     

Journal of Huaihai Institute of Technology General Table of Contents,2002

Vol.1 1　No.1　 ( Sum No.36)The Generalized Degree for Multi- valued Compact Perturbations of m- accretive Operators　　 L I Yu- qiang,L IU L i- wei(1)……………………………………………………………………………………………………A Hybrid Algorithm for the Optimization of Multi- peak Continuous Function XU Shi- gang,ZHAO Shu- yu(5 )……………A Study on the Design of L ong and Thin Metal's Bending Machine YOU Zhuan(8)…………………………………………Design Methods of Fast Ethernet…     

Cu—Zr—Al大块非晶合金的制备及性能研究

采用铜模铸造的方法制备了Cu48Zr52-x Alx（x=6,7,8,9,10,at％）几种合金奠射线衍射（XRD）实验检验Cu48Zr44Al8,Cu48Zr43Al两种合金样品为完全非晶态．对样品进行差示扫描量热分析（DSC）考查三种大块非晶合金的非晶形成能力,以及灿的添加对非晶形成能力的影响．结果表明：当铝含量X=9时,合金的非晶形成能力及热稳定性最好．     

Microstructure, crystalline phase and electrical properties of Li0.06（Na0.5K0.5）0.94Nb（1-2x/5）MgxO3 lead-free piezoelectric ceramics

MgO-modified Li0.06(Na0.5K0.5)0.94NbO3(L6NKN) lead-free piezoelectric ceramics were synthesized by normal sintering at a relatively low temperature of 1000°C.The crystalline phase,microstructure,and electrical properties of the ceramics were investigated with a special emphasis on the influence of MgO content.The addition of MgO effectively improves the sinterability of the L6NKN ceramics.X-ray diffraction analysis indicates that the morphotropic phase boundary(MPB) separating orthorhombic and tetragonal ph...     

Effect of Li content on the microstructure and properties of lead-free piezoelectric （K0.5Na0.5）1-xLixNbO3 ceramics prepared by SPS

Lead-free piezoelectric （K0.5sNa0.5）1-xLixNbO3 （x = 0at%-20at%） ceramics were synthesized by spark plasma sintering （SPS） at low temperature and the effects of LiNbO3 addition on its crystal structure and properties were also studied. When the Li content was less than 6at%, a single proveskite phase with the similar structure of （K0.5Na0.5）NbO3 was formed; and a secondary phase with K3Li2Nb5O15 structure was observed in the 6at% 〈 x 〈 20at% compositional range. Furthermore, LiNbO3 existed as the third phase when the Li content was higher than 8at%. The grain sizes increased from 200-500 nm to 5-8 μm when the K3Li2Nb5O15 and LiNbO3 like phases were formed. With increasing Li content, the relative density of the ceramics first decreased from 97% to 93% and then kept constant. The piezoelectric coefficient d33, dielectric constant, and planner electromechanical coupling factor exhibited a decreasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K3Li2Nb5O15 and LiNbO3. The formation of dense microstructure with a single phase is necessary in improving the properties of the （K0.5Na0.5）1-xLixNbO3 ceramics.     

金属间化物（Sm_（1－x）Y_x）_2Fe_（17）N_y磁性能的穆斯堡尔谱

本文主要通过穆斯堡尔谱研究金属间化物（Ｓｍ１－ｘＹｘ）２Ｆｅ１７Ｎｙ（ｘ＝０，０．２，０．４，０．６，０．８和１．０；２＜ｙ＜３）中Ｙ原子对Ｓｍ原子的替代效应以及Ｎ原子的占位问题。研究结果表明，氮原子在以上氮化物中不仅占据９ｅ（６ｈ）晶位，还将占据１８ｇ（３ｂ）晶位。由实验结果我们可以得出以下结论：１）当ｘ＞０．５时，晶体结构发生变化；２）（Ｓｍ１－ｘＹｘ）２Ｆｅ１７Ｎｙ化合物各个铁晶位的平均磁超精细场随Ｙ含量的不同而有变化；３）按照穆斯堡尔谱拟合结果，（Ｓｍ１－ｘＹｘ）２Ｆｅ１７Ｎｙ化合物在Ｙ含量ｘ为０～０．８的范围内都呈现易Ｃ轴各向异性。     

Effects of Si and Ce on the microstructure and hydrogen storage property of Ti_(26.5)Cr_(20)V_(45)Fe_(8.5)Ce_(0.5) alloy

In this paper, the effects of Si and Ce on the microstructure and hydrogen storage property of Ti26.5 Cr20V45Fe8.5Ce0.5 alloy were studied, respectively. First of all, effects of Si on the microstructure and hydrogen storage properties of Ti26.5Cr20(V45Fe8.5)1?xSixCe0.5 (x = 0, 0.5, 1.0, 1.5 and 2.0 at%) alloys were studied by X-ray diffraction, scanning electron microscopy and P-C isotherm measurements. As the Si addition increases, the hydrogen absorption capacities of alloys decrease but the equilibrium pressure increases, due to the formation of Laves phase. Secondly, the effect of Ce on Ti26.5Cr20 (V45Fe8.5)0.98Si2 alloy was studied. It was found that Ce addition is an effective way to eliminate the effect of Si on the hydrogen storage properties of the alloy.     

Preparation and thermal stability of Pd_(40.5)Ni_(40.5)SixP_(19-x) bulk metallic glasses

With the addition of Si to replace some P,Pd_(40.5)Ni_(40.5)Si_xP_(19-x)(x=0,2.5,5,9.5,14,and 19 in atomic number fraction) bulk glassy samples with the diameter of about 5 mm were successfully prepared by use of flux treatment and water quenching technology.With the increase of Si content,the glass forming ability of Pd_(40.5)Ni_(40.5)Si-xP_(19-x) increases first for low Si content and then decreases for high Si content (Si≥9.5at%).The Pd_(40.50Ni_(40.5)Si_5P_(14) glassy alloy possesses the largest supe...     

Formation and corrosion properties of Fe-based bulk metallic glasses

Bulk metallic glass (BMG) formation was explored in the Fe-B-Si-Nb alloy system though combined use of the atomic cluster line approach and the minor alloying strategy. The basic ternary compositions in the Fe-B-Si system were determined by the intersection points of two cluster lines, namely, Fe-B cluster to Si and Fe-Si cluster to B. 3at%-4at% Nb was added to the quaternary Fe-B-Si-Nb alloy. The casting experiments revealed that good glass-forming ability (GFA) occurred at the (Fe73.4Si8.2B18.4)96Nb4 composition, and 3-mm diameter BMG samples were made. The glass transition temperature (Tg), crystallization temperature (Tx, and supercooled liquid region (△Tx=Tx-Tg) of this BMG were measured to be 866, 889, and 23 K, respectively. The BMG shows a high Vickers hardness of about Hv 1164, a Young's modulus of 180 GPa, and a good corrosion resistance in the solutions of 1 mol/L HCl and 3 wt% NaCl.     

两种成分制备态纤维和薄带的巨磁阻抗效应

用熔融抽拉法制备了Co68.25Fe4.5Si12.25B15和Fe72Co8Si5B15两种成分的非晶合金纤维材料。对两种成分制备态纤维和薄带的磁阻抗进行了频谱分析,表明制备态Co68.25Fe4.5Si12.25B15非晶纤维的GMI(Z)=|(Z(H)-Z(20Oe))／Z(20Oe)|高达438.5％,接近国外报导的最大值。分析了磁阻抗中电阻、电感分量随频率的变化,表明电阻的变化对维持高的GMI起主要作用。     

Pressure stress-impedance effect in FeCuNbSiB amorphours ribbons

The stress-impedance effect in Fe73.5Cu1Nb3Si13.5B9 (at%) ribbons is measured to investigate the influences of vacuum annealing and pressure stress. The results can be explained by the influence of induced anisotropy in the magnetization processes at the chosen drive current frequency of 90 MHz. The maximum SI% value of the ribbon annealed at 300 ℃ is 2.52%.     

快淬纳米复合Nd9Fe80Co4Nb1B6永磁合金相结构与磁性能研究

利用X线衍射仪、振动样品磁强计等测试手段研究了纳米复合Nd9Fe80Co4Nb1B6合金的相结构与磁性能,结果表明:淬速为20 m/s的合金,经710℃退火处理后,合金软硬磁性相的晶粒尺寸细小,两相之间具有较强的交换耦合作用,合金具有优良的综合磁性能,即剩磁为0.95 T,矫顽力达到540 kA/m,最大磁能积为112 kJ/m3.选择适当的快淬速度有利于改善退火后合金的相结构,提高合金的综合磁性能.