Effect of bismuth oxide on the thermal stability and Judd-Ofelt parameters of Er 3(+)/Yb3(+) co-doped aluminophosphate glasses

The Er3+/Yb3+ co-doped glasses with compositions of xBi(2)O(3)-(65-x)P2O5-4Yb(2)O(3)-11Al(2)O(3)-5BaO-15Na(2)O (where x = 0, 2.5, 5, 7.5 and 10 mol%) were prepared using the normal melt quench technique. The optical absorption spectra of the glasses were recorded in the wavelength range 300-1700 nm. The effect of Bi2O3 content on the thermal stability and absorption spectra of glasses was investigated. In addition, the Judd-Ofelt parameters and oscillator strengths were calculated by employing Judd-Ofelt theory. It was observed that the positions of the fundamental absorption edge and cut-off wavelength shifted towards red as the content of Bi2O3 increased. However, there were no red shifts found both in the peak wavelength and in the center of mass wavelength of all absorption bands with Bi2O3 content increasing. The results of Judd-Ofelt theory analysis showed that Judd-Ofelt parameters Omega(t), (t = 2, 4, 6) changed sharply when Bi2O3 concentration exceeded 5 mol%. The variation trends of experimental oscillator strength were similar with those of Judd-Ofelt parameters as function of Bi2O3 concentrations. Moreover, differential scanning calorimetry experiments showed that the increases of Bi2O3 content weakened the network structure and then lowered the thermal stability of the glasses. The spontaneous emission probability A(rad), branching ratio beta and the radiative lifetime tau(rad) were also calculated and analyzed. The stimulated emission cross-section of Er3+ was calculated according to the McCumber theory. It was found that the stimulated emission cross-section of Er3+ was monotonically increases with Bi2O3 content increasing. (C) 2006 Elsevier B.V. All rights reserved.

Effects of desiccation and CO2 concentrations on emersed photosynthesis in Porphyra haitanensis (Bangiales, Rhodophyta), a species farmed in China

The effects on photosynthesis of CO, and desiccation in Porphyra haitanensis were investigated to establish the effects of increased atmospheric CO2 on this alga during emersion at low tides. With enhanced desiccation, net photosynthesis, dark respiration, photosynthetic efficiency, apparent carboxylating efficiency and light saturation point decreased, while the light compensation point and CO2 compensation point increased. Emersed net photosynthesis was not saturated by the present atmospheric CO2 level (about 350 ml m(-3)). and doubling the CO2 concentration (700 ml m(-3)) increased photosynthesis by between 31% and 89% at moderate levels of desiccation. The relative enhancement of emersed net photosynthesis at 700 ml m(-3) CO2 was greater at higher temperatures and higher levels of desiccation. The photosynthetic production of Porphyra haitanensis may benefit from increasing atmospheric CO2 concentration during emersion.

Magnetic characterization of Co1-xNixFe2O4 (0 <= x <= 1) nanoparticles prepared by co-precipitation route

Magnetic nanoparticles of Ni-doped cobalt ferrite [Co1-xNixFe2O4(0 <= x <= 1)] synthesized by coprecipitation route have been studied as a function of doping concentration (x) and particle size. The size of the particles as determined by X-ray diffractometer (XRD) and transmission electron microscope (TEM) analyses was found in the range 12-48 nm. The coercivity (H-C) and saturation magnetization (M-S) showed a decreasing behavior with increasing Ni concentration. M-S of all the samples annealed at 600 degrees C lies in the range 65.8-13.7 emu/gm. Field-cooled (FC) studies of the samples showed horizontal shift (exchange bias) and vertical shift in the magnetization loop. Strong decrease in exchange bias (H-b) and vertical shift (delta M) was found for low Ni concentrations while negligible decrease was found at higher concentrations. The presence of exchange bias in the low Ni-concentration region has been explained with reference to the interface spins interaction between a surface region (with structural and spin disorder) and a ferrimagnetic core region. M(T) graphs of the samples showed a decreasing trend of blocking temperature (T-b) with increasing Ni concentration. The decrease of T-b with increasing Ni concentration has been attributed to the lower anisotropy energy of Ni+2 ions as compared to Co+2 that increases the probability of the jump across the anisotropy barrier which in turn decreases the blocking temperature of the system.

Preparation of a blocked isocyanate compound and its grafting onto styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer

The epsilon-caprolactam was used to block the isocyanate group to enhance the storage stability of allyl (3-isocyanate-4-tolyl) carbamate. The spectra of FTIR and NMR showed that blocked allyl (3-isocyanate-4-tolyl) carbamate (BTAI) possesses two chemical functions, an 1-olefin double bond and a blocked isocyanate group. The FTIR spectrum showed BTAI could regenerate isocyanate group at elevated temperature. DSC and TG/DTA indicated the minimal dissociation temperature was about 135 degrees C and the maximal dissociation rate appeared at 226 degrees C. Then the styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer (SEBS) was functionalized by BTAI via melt free radical grafting. The effect of temperature, monomer and initiator concentrations on the grafting degree and grafting efficiency was evaluated. The highest grafting degree was obtained at 200 degrees C. The grafting degree and grafting efficiency increased with the enhanced concentration of BTAI or initiator.

Determination of ultra-trace concentrations of elements in high purity tellurium by inductively coupled plasma mass spectrometry after Fe(OH)(3) coprecipitation

In this work, a method was established for the determination of impurities in high purity tellurium by inductively coupled plasma mass spectrometry (ICP-MS) after Fe(OH)(3) coprecipitation. After comparison of coprecipitation ability and separation efficiency between Fe(OH), and Al(OH)(3), Fe(OH)(3) was chosen as the precipitate. A separation factor of 160 for 200 mg tellurium was obtained under conditions of pH 9 and 2 mg of Fe3(+). The 13 elements, such as Bi, Sn, Pb, In, Tl, Cd, Cu, Co, Ni, Zn, Ti, Be and Zr, could be almost completely coprecipitated under these conditions. In addition, Te memory effect imposed on the ICP-MS instrument was assessed, as well as Te matrix effect that caused the low recovery of Ga, As, Sb and V in real sample was discussed. Finally, the method was evaluated through recovery test and was applied to practical sample analysis, with detection limits of most of the elements being below 0.15 mug g(-1) and R.S.D. below or at approximately 10%, which indicated that this method could fully satisfy the requirements for analysis of 99.999% similar to 99.9999% high purity Te.

Anomalous Thermal Stability of Nd-Fe-Co-Al Bulk Metallic Glass

The thermal stability of Nd60Fe20Co10Al10 bulk metallic glass (BMG) has been studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), isochronal dilatation and compression tests. The results show that the glass transition of the BMG takes place quite gradually between about 460 and 650 K at a heating rate of 0.17 K/s. Several transformation processes are observed during continuous heating with the first crystallization process beginning at about 460 K, while massive crystallization takes place near the solidus temperature of the alloy. The positive heat of mixing between the two major constituents, Nd and Fe, and, consequently, a highly inhomogeneous composition of the attained amorphous phase are responsible for the anomalous thermal stability in this system. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

Interactions of CO, HCl, and Sox in Pulverised Coal Flames

The effect of HCl and SO_2 on CO oxidation in pulverised coal flames was investigated experimentally and kinetically in an entrained flow combustion reactor. Two bituminous coals (German 'Goettelborn' and a Polish coal) were used as fuels with a feeding rate of 1 or 1.5 kg/h. HCl or SO_2 is introduced into the reactor premixed with the primary air. Experimental results indicate that HCl addition may inhibit CO oxidation in coal flames and increases CO emission. Reducing temperature in the reactor will enhance the inhibitory effect of HCl on CO oxidation. The measured CO profiles along the reactor height clearly show that the addition of HCl may inhibit CO oxidation. In the experimental range of SO_2 addition. The inhibiting effect of SO_2 on CO oxidation is less significant than HCl. A detailed kinetic mechanism is used to model the reactions. And the controlling reactions are analysed.

流化床中RDF焚烧时CO、SO_2和HCl的生成

垃圾衍生燃料 (Refuse-Derived Fuels-RDF)具有热值高、易燃烧的优点。RDF的一个潜在应用是与煤进行混烧，替代一部分锅炉燃烧用煤。由于RDF挥发份相当高，因此燃烧时的污染物排放不易控制。本文在非均匀布风流化床中进行了RDF与煤的混烧试验，测量了H_2O、CO、CO_2、NO、N_2O、HCl、SO_2等污染物质的排放特性。结果表明与单纯燃烧RDF相比，混烧时的CO生成量大大下降；SO2生成浓度较低，而HCl的生成量比单纯烧煤时明显增加。

Practical Criterion for Universal Laws and Practical Methods for Construction of Co-variance Sets

给出相对论力学中普遍定律的实用判别法和协变集的实用构造法,还给出实现非普遍定律的“可导出性”的一种实用方法．

Quantum Monte Carlo study of the CO interaction with a dimer model surface for Cr(110)

The chemisorption of CO on a Cr( 110) surface is investigated using the quantum Monte Carlo method in the diffusion Monte Carlo (DMC) variant and a model Cr2CO cluster. The present results are consistent with the earlier ab initio HF study with this model that showed the tilted/ near-parallel orientation as energetically favoured over the perpendicular arrangement. The DMC energy difference between the two orientations is larger (1.9 eV) than that computed in the previous study. The distribution and reorganization of electrons during CO adsorption on the model surface are analysed using the topological electron localization function method that yields electron populations, charge transfer and clear insight on the chemical bonding that occurs with CO adsorption and dissociation on the model surface.

Studies on two-phase co-current air/non-Newtonian shear-thinning fluid flows in inclined smooth pipes

In this work. co-current flow characteristics of air/non-Newtonian liquid systems in inclined smooth pipes are studied experimentally and theoretically using transparent tubes of 20, 40 and 60 turn in diameter. Each tube includes two 10 m lone pipe branches connected by a U-bend that is capable of being inclined to any angle, from a completely horizontal to a fully vertical position. The flow rate of each phase is varied over a wide range. The studied flow phenomena are bubbly, plug flow, slug flow, churn flow and annular flow. These are observed and recorded by a high flow. stratified flow. -speed camera over a wide range of operating conditions. The effects of the liquid phase properties, the inclination angle and the pipe diameter on two-phase flow characteristics are systematically studied. The Heywood-Charles model for horizontal flow was modified to accommodate stratified flow in inclined pipes, taking into account the average void fraction and pressure drop of the mixture flow of a gas/non-Newtonian liquid. The pressure drop gradient model of Taitel and Barnea for a gas/Newtonian liquid slug flow was extended to include liquids possessing shear-thinning flow behaviour in inclined pipes. The comparison of the predicted values with the experimental data shows that the models presented here provide a reasonable estimate of the average void fraction and the corresponding pressure drop for the mixture flow of a gas/ non-Newtonian liquid. (C) 2007 Elsevier Ltd. All rights reserved.

黑体泵浦CO_2-CO,N_2O-CO,CO_2-H_2O和N_2O-H_2O激光的研究

本文对黑体辐射泵浦CO_2激光和N_2O激光由于CO和H_2O的加入所引起的激光功率变化进行了理论和实验研究.CO的加入可使的N_2O激光功率增加28%.

稳态CO激光的解析理论

为了分析CO激光的特性,通常需要对上百个方程进行数值计算,因而解析的分析就成为一个很值得探讨的方面。本文从分布函数方程和辐射强度谱分量传输方程出发,导出稳态CO激光在级联跃迁发射时的增益饱和特性,得到的强度谱分量与增益的关系式适用于均匀和非均匀加宽同时起作用的一般情况。文中所使用的振动分布函数由一个非线性积分方程求得。对两能级特例,本文结果与文献[9]一致。对均匀加宽极限的特例,本文给出的强度和强度谱分量的关系式与文献[4]的结果一致。

半焦在流化床燃烧中Cl元素影响CO氧化的试验

在非均匀布风的流化床燃烧系统中进行了半焦中添加PVC/NaCl的混烧试验,研究了Cl元素对燃烧中CO氧化的影响以及混烧时SO_x等污染物的生成规律.试验结果表明,半焦与PVC/NaCl混烧在技术上可行,添加Cl元素抑制CO氧化,加入PVC增加SO_2排放,而加入NaCl则减少SO_2排放.

卤素对于燃烧中CO氧化和NO生成的影响

卤族元素在燃烧时会影响CO的氧化和NO的生成。本文通过化学平衡方法分析了H2O和HCl对于CO氧化的协同效应,在非均匀布风流化床中进行了PVC塑料与煤或半焦的混烧试验,测量了CO和CH4的排放特性,从而从理论上和实验上证明了HCl对CO氧化的抑制作用。并给出了今后研究的方向和问题。