Study of structural,electrical and optical properties of vanadium oxide condensed films deposited by spray pyrolysis technique

Vanadium oxides condensed films are prepared on glass substrates, using spray pyrolysis (SP) technique.The effects of substrate temperature, vanadium concentration in initial solution and the solution spray rate on the nano-structural, electrical, and optical properties of deposited films were investigated. Characterizations of the samples were performed using X-ray diffraction (XRD),scanning electron microscopy (SEM), and UV-Vis spectroscopy methods. The type and concentration of the charge carriers were determined and measured by Hall effect experiment. XRD patterns showed that the prepared films had polycrystalline structure, mostly tetragonal β-V₂O₅ and V₄O₉ phases with the preferred orientation along (200) direction. The Hall effect experiment revealed that all samples were n-type, except the ones deposited at substrate temperatures Tsub = 300 ℃ and Tsub = 450 ℃, vanadium concentration 0.1 mol/L and solution spray rate 10 mL/min.The charge carrier concentrations obtained were in the range 10¹⁶–10¹⁸ cm^-3. The lowest sheet resistance (R_s) was obtained for the samples prepared at T_sub = 450 ℃, vanadium concentration 0.05 mol/L and solution spray rate 10 mL/min. It was also found that the optical transparency of the samples changed from 20% to 75% and the optical band gap of the samples was from 2.22 eV to 2.58 eV, depending on the deposition conditions.     

考虑骨料尺寸的混凝土岩石边界效应断裂模型

该文比较了边界效应模型（BEM）和尺寸效应模型（SEM）在研究材料断裂性能方面的不同。提出了由处于准脆性断裂状态的三点弯曲试件的峰值荷载P_max,同时确定材料参数--断裂韧度K_IC与拉伸强度f_t的理论与方法。由于实验室条件下混凝土试件高度W与骨料最大粒径d_max的比例W/d_max约为5~20,试件的非均质性明显,破坏为准脆性断裂控制。因此,区别于以连续介质力学为基础的应用于准脆性断裂研究的力学模型,该文研究将骨料最大粒径d_max引入相应的断裂模型解析表达式中,由参数组合β d_max来计算结构峰值状态对应的裂缝扩展量,通过离散参数β的不同取值,实现了对材料参数--断裂韧度与拉伸强度的准确预测。基于不同学者的相同尺寸W而不同初始裂缝长度a₀,以及相同初始缝高比a₀/W而不同尺寸W的几何相似的砂浆、混凝土及岩石类材料试件的试验成果（骨料最大粒径d_max从1.2 mm~40 mm变化）,验证了所提理论与方法的合理性。     

Microwave-assisted rapid synthesis of alumina nanoparticles using tea,coffee and triphala extracts

Alumina nanoparticles (AlNP) were synthesized from aluminium nitrate using extracts of tea, coffee and triphala—a well known herbal plant as well as a nontoxic and eco—friendly green material. The synthesis was carried out taking 1:4 ratio of metal salt and these extracts under microwave irradiations at 540 W, which gave better yield of nanoparticles. Water was taken as solvent medium. The formations of AlNP were initially monitored by the colour changes occurring in the reaction mixture during the incubation period. As synthesized nanoparticles were characterized by scanning electron microscope (SEM),
UV–Visible (UV–Vis) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The AlNP were found to be spherical in shape in case of tea and coffee extracts with a size of 50–200 nm and to be oval shaped in case of triphala extract with an average size of 200–400 nm. The formation of AlNP with the microwave-assistance using these plant extracts has proved to be very faster than any other methods. In addition, excellent reproducibility of these nanoparticles, without the use of any additional capping agent or stabilizer will have great advantages in comparison with microbial synthesis, avoiding all the tedious and hygienic complications.     

膨胀蛭石/石膏复合保温材料的制备与表征

分别以微波法和微波化学法制备的膨胀蛭石为骨料, 采用模压成型工艺制备了膨胀蛭石/石膏复合保温材料, 研究了膨胀蛭石的片径、膨胀方法和熟石膏/膨胀蛭石的质量比(膏石比)与膨胀蛭石/石膏复合保温材料的含水率、导热系数和抗压强度的关系。结果表明: 膨胀蛭石/石膏保温材料的导热系数和抗压强度随膨胀蛭石的片径的增大而减小, 与膏石比呈二次函数关系, 并随膏石比的增大而增大; 在相同的实验条件下, 采用微波化学法制备的膨胀蛭石制作的保温材料(导热系数为0.082 W(m·K)-1)与以微波法制备的膨胀蛭石制作的保温材料(导热系数为0.097 W(m·K)-1)相比, 具有更好的保温性能。制备的复合保温材料可以用作隔热、吸声和湿度调节材料。      

磁电雷管结构及生产工艺的优化设计

为解决当前磁电雷管生产工艺复杂、成本较高的问题,设计了一种新型磁电雷管。首先,阐述了磁电雷管的设计原理。在此基础上,分析了感应电流I₂与次级绕组匝数n₂、次级端脚线及桥丝电阻R₂、磁导率μ、电流频率f的关系,确定了n₂、R₂、μ和f等的取值。生产中,采用了磁环、脚线定位注塑措施;确定了磁电雷管的磁环材料,初、次级绕组匝数和电线材质;优化了点火药配方和桥丝的直径,点火药选择m(苦味酸钾)∶m(高氯酸钾)＝47.30∶44.65的零氧配方,桥丝直径为0.03 mm,解决了规模生产的一致性问题。结果表明:本产品生产工艺简单,能够实现大批量生产,同时具有很强的可靠性,满足了行业的需求。     

Effect of reducing agents on the structure of zinc oxideunder microwave irradiation

Zinc oxide was synthesized from zinc sulphate using different reducing agents under microwave irradiation.The influence of sodium borohydride, hydrazine
hydrate and urea on the shape and size of the products were investigated by scanning electron microscopy (SEM) and  X- ray diffraction (XRD). SEM showed the nano-sized spherical and rectangular shaped structures in case of sodium borohydride and hydrazine hydrate, whereas micro-sized hexagonal structures were formed in case of urea under the same irradiation power. The reducing agents played an important role in forming the various structures.
Thus different shapes and size of structures were produced by only varying the reducing agent, which had wide applications in various fields.     

Approaching lean product development using system dynamics:investigating front-load effects

Competing with successful products has become perplexing with several uncertainties and transmutes from time to time as customers’ expectations are
dynamic. That is why manufacturing firms exhaustively strive to look for a better competitive frontier using wellestablished and innovative product development (PD) processes. In this paper, we would like to answer three research questions: (i) What would be the effects of frontloading
in PD? (ii) Can we improve our PD process endlessly? (iii) When is the critical time that the firm should take remedial action for improvements? As a contribution to the vast numbers of improvement methods in new product development (NPD), this paper investigates the effects of front-loading using set-based concurrent engineering (SBCE) on cost and lead time. Models are developed and treated using a system dynamics (SD) approach. We assign a hypothetical upfront investment for SBCE and compare its effects on  total cost and lead time of the development process. From the research, it is found that the total cost of PD is reduced almost by half-although the front loading is higher in order to encompass multiple design alternatives. The total product lead time is reduced by almost 20 %. The model reveals the critical time for improvement of the PD process. We use SD tool (e.g., STELLA) for simulation and visualization of the complex PD model, using SBCE as one of several strategies to frontload activities in the NPD process.     

Synthesis of Fullerenols from Halofullerenes

Halogenated fullerenes were used as reagents to prepare fullerenols. Depending on reaction conditions two types of substances (complex mixtures of products with average compositions C₆₀O_nH_m, n=10-26, m=14-30 and C₆₀O_nH_mM_k, M=K, Na; n=17-24, m=16-28, k=3-8) possessing essentially different water solubility were obtained. Highly soluble metal-containing species are most likely ionic compounds similar to metal derivatives of alcohols-alcoholates. An electron withdrawing effect of the carbon cage could make alkali metal fullerenolates (C₆₀(OH)_x(OM)_y) inert towards hydrolysis. Halogens were selectively substituted when fullerene bromides and chlorides were treated with silver trifluoroacetate. Fullerenol esters C₆₀(OOCCF₃)_n formed were then hydrolyzed to form C₆₀(OOCCF₃)_x(OH)_y. Attempts to cleave all ester groups in C₆₀(OOCCF₃)_x(OH)_y failed in acidic media, while alkaline hydrolysis was accompanied by unselective polyhydroxylation of the fullerene cage.     

Y形偏心支撑钢框架的地震反应折减系数和超强系数

该文采用静力推覆和能力谱方法分析了基于我国抗震规范设计的12 个Y 形偏心支撑钢框架的地震反应折减系数R和超强系数Ω及赘余度超强系数Ω₃, 分析了结构层数、楼层高跨比对各系数的影响。研究结果表明:Y 形偏心支撑钢框架的设计地震作用可在我国现行抗震规范的基础上降低20%左右。     

拉-压循环加载下铝合金疲劳裂纹扩展的压载荷效应研究

应用弹塑性有限元方法与增量塑性损伤理论指出疲劳裂纹扩展的压载荷效应是裂纹尖端塑性损伤的结果, 建立了在拉-压循环加载下铝合金疲劳裂纹扩展速率的双参数预报模型, 对LY12-M 高强铝合金MT 试件在应力比R=0、-0.5、-1、-2 进行了疲劳裂纹扩展实验。结果表明:当最大应力强度因子K_max相同时, 恒幅拉压加载(应力比R<0)的疲劳裂纹扩展速率明显高于恒幅拉拉加载(应力比R=0)的情况, 拉-压循环载荷的压载荷部分对疲劳裂纹扩展速率具有促进作用。该文得出的LY12-M 铝合金在拉-压循环加载下的疲劳裂纹扩展速率预报模型与实验结果符合较好。     

Site symmetry of Yb in In0.5Ga0.5P

The site symmetry of Yb³⁺ in In_0.5Ga_0.5P grown by liquid phase epitaxy has been investigated using a polarized luminescence spectroscopic technique. The site symmetry of indium in In_0.5Ga_0.5P was lowered from T_d to C_2v resulting from substitution of indium by ytterbium. The lowering symmetry was confirmed by the spectroscopic observation of the splits of Γ₈ levels of T_d in C_2v symmetry. The substitutional site symmetry of Yb³⁺ in In_0.5Ga_0.5P, i.e. Yb_ln³⁺, was revealed as C_2v.     

泡沫金属弹性变形尺度效应的理论与数值研究

泡沫金属的力学性能强烈依赖于内部结构。当构件特征尺寸与胞孔特征尺寸d处于相同数量级时,表现出明显的尺度效应。为了揭示这种尺度效应的力学机理,研究了泡沫金属试件的剪切和纯弯曲试验。一方面,利用应变梯度弹性理论给出解析解,其中包含了材料内禀尺寸l_c这一关键模型参数。另一方面,把每段胞壁视为铁木辛柯梁,从而建立梁链网作为泡沫金属的微观力学模型。通过应变能等效原理建立应变梯度连续体和基体金属材料弹性参数之间的关系。发现,边界层的约束条件对泡沫金属的力学响应有重要影响。弯曲问题中,只有对离散模型上下表面施加恰当的附加转角约束后,应变梯度理论解与链网模型数值解才能够吻合。这为理解应变梯度理论中的非传统边界条件提供了一个直观的实例。通过数据拟合,得到了内禀尺寸l_c与胞孔特征尺寸d之间的关系,与文献结论相符。     

电磁轨道发射过程中电枢运动特性参量的一种简捷算法

在介绍了电磁轨道发射装置发射过程模拟方法的基础上, 将电枢位移x(t) 、电枢速度v(t)等变量视为独立函数, 给出了发射过程中回路电流#em/em#(t) 的解析表达式。基于回路电流#em/em#(t) 、电枢位移x(t) 、电枢速度v(t)和电枢加速度a(t) 的基本方程, 提出了电磁轨道发射过程中电枢运动特性参量的一种简捷算法, 给出了该算法的流程图, 并指出了时间步长和收敛准则的确定方法。该算法可以移植到任何具备二次开发平台的有限元软件之中。通过电磁轨道发射装置的计算实例, 表明了该算法的有效性和可靠性。     

塑钢纤维轻骨料混凝土与钢筋粘结锚固试验研究

通过对内贴应变片钢筋的直接拔出试验,分析钢筋直径、相对锚固长度（l_a/d）及混凝土相对保护层厚度（c/d）对塑钢纤维轻骨料混凝土与钢筋间粘结性能的影响,得出不同钢筋直径、锚固长度及相对保护层厚度对试件粘结锚固性能的影响规律,并提出塑钢纤维轻骨料混凝土钢筋锚固长度计算公式。试验结果表明:随钢筋直径的增大,试件粘结刚度增强,极限粘结强度先提高后降低;增加钢筋锚固长度会降低试件极限平均粘结强度,同时极限粘结强度对应钢筋自由端滑移量减小,试件粘结韧性则随锚固长度的增加而减小;混凝土相对保护层厚度增加会使试件极限粘结强度先提高然后趋于平稳。根据试验结果得到的钢筋锚固长度计算公式与规范给出的计算公式进行比较,从极限粘结强度的角度看,规范中的钢筋锚固长度计算公式偏于保守。     

桥梁高性能钢HPS485W疲劳裂纹扩展速率试验研究

以国产桥梁用高性能钢HPS485W为研究对象,对7.5mm、12.5mm和19.5mm的HPS485W紧凑拉伸试样分别在应力比R=0.1、R=0.5和R=0.8的疲劳荷载下进行疲劳裂纹扩展速率(da/dN)试验,采用七点递增多项式的方法进行局部拟合求得试样的疲劳裂纹扩展速率。与传统桥梁用钢14MnNb相比,该文试验测得高性能钢HPS485W具有更优越的忍受疲劳裂纹扩展能力。试验结果表明:试样厚度是影响疲劳裂纹扩展速率的关键因素;对同一厚度的试样,疲劳裂纹扩展速率随着应力比R的增大而增大。此外,对19.5mm试样在荷载比R=0.1的情况下,进行工程门槛值的试验测定和理论门槛值的数值求解,分析求得19.5mm的HPS485W的理论门槛值为7.22MPa·m1/2。该文试验得到的HPS485W疲劳裂纹扩展曲线,可用于高性能钢桥的抗疲劳、防断裂设计与寿命预测。     

A new low-field determination of the proton gyromagnetic ratio inwater

The proton gyromagnetic ratio in water has been measured by the low field method using atomic magnetic resonance in ⁴He, a multicurrent solenoid and an induction method for the dimensional measurement of the solenoid. The result for air and vacuum environment is γ'_p (low, air)=2.67515451×10⁸ s^-1 T^-1 (0.18×10^-6), γ'_p (low, vacuum)=2.67515418×10⁸ s^-1 T^-1 (0.18×10^-6), based on the adopted values K_J-90=483597.9 GHz/V, R_K-90=25812.807 Ω, and measured values γ(⁴ He)/γ'_p=658.200556, γ(⁴He) (air)=1760.78819×10⁸ s^-1 T^-1 (0.18×10^-6), K_J-90, R_K-90     

Experimental determination of the gyromagnetic ratio of thehelium-4 atom in terms of that of the helium-3 nucleus

The ratio R=γ_4He(2³S₁)/γ_3He (1¹S₀) has been measured using gaseous samples in low magnetic field. The result, R=864.02276±3×10 ^-8, leads to a value of γ_4He=1760.78798(3×10^-7)×10⁸ ×rad×s^-1×T^-1     

High-accuracy time transfer via geostationary satellites:preliminary results

Signal-delay phase measurements have been performed with Ku-band Earth station and VSAT (very-small-aperture terminal) facilities in various loop-around schemes using both a satellite simulator and geostationary satellites. Stability plots show that the standard deviation of pair differences (σ_y) is 4×10^-10 _τ^-1 for a C/No (carrier-to-noise density) ratio of 65 dB-Hz. This white-noise behavior continues for several days, when satellite simulator data shows σ _y to be 3×10^-15. Absolute phase-delay measurements show reproducibility to better than 1 ns over a 16-day sample time. This suggests the potential for accuracy to this level, given an appropriate calibration. A measurement method is described which determines the principal time-delay constant affecting the accuracy of time synchronization using a two-way satellite communications technique     

v-PrBO3的晶体结构、相变和光学性质

采用高温固相合成法分别在1200和1500℃合成了λ-PrBO₃和ν-PrBO₃样品, 并通过单晶X射线衍射确定了ν-PrBO3的晶体结构。结果表明该结构为三斜晶系, 空间群为P1, 晶胞参数为a = 0.6302 (4) nm, b = 0.6521 (4) nm, c = 0.6525 (4) nm,α = 94.312(7)°,β = 107.335(7)°,γ = 106.455(7)°, V = 0.2417(2) nm³, Z = 4。同时研究了从λ-PrBO₃到ν-PrBO₃的相变过程, 并从漫反射光谱得出λ-PrBO3和?-PrBO3的光学带隙均为4.96 eV。在X射线和紫外激发下,均未观测到λ-PrBO3和?-PrBO3样品在紫外可见波长范围内的Pr³⁺特征发光。     

Experimental investigation on the effects of process parameters of GMAW and transient thermal analysis of AISI321 steel

Gas metal arc welding (GMAW) develops an arc by controlling the metal from the wire rod and the input process parameters. The deposited metal forms a weld bead and themechanical properties depend upon the quality of the weld bead. Proper control of the process parameters which affect the bead geometry, the microstructures of the weldments and the mechanical properties like hardness, is necessary. This experimental study aims at developing mathematical models for bead height (HB), bead width (WB) and bead penetration (PB) and investigating the effects of four process parameters
viz: welding voltage, welding speed, wire feed rate and gas flow rate on bead geometry, hardness and microstructure of AISI321 steel with 10 mm thickness. The transient thermal analysis shows temperature and residual stress distributions at different conduction and convection conditions.