气相色谱法测定合成气制烯烃水相产物中低碳醇、醛、酮、酸化合物

采用气相色谱法建立了合成气制烯烃(SGTO)水相产物中低碳醇、醛、酮、酸的测定方法,对分离条件进行优化,使用标准试样测定了线性范围和工作曲线,考察了方法的精密度和准确度,并采用该方法对SGTO实际水相产物中低碳醇、醛、酮、酸进行了测定。实验结果表明,在一定质量浓度范围内,低碳醇、醛、酮、酸各组分均呈现良好的线性关系,相关系数大于0.99。标样的回收率在93.4%~109.8%之间,6次重复测定的相对标准偏差小于3.9%。SGTO实际水相产物中低碳(C1~6)醇、醛、酮、酸的分析结果表明,SGTO实际水相产物中低碳(C1~6)醇、醛、酮、酸的总含量(w)在1.5%~3.0%之间;其中,乙醇的含量最高,丙酮其次。     

An effective approach for parameter determination of the digital phase-locked loop in the z-domain

In digital communication systems, typical methodologies in determining loop parameters of the digital phase-locked loop (DPLL) are based on the mapping transformation from the analog domain to the digital domain. However, such transform based algorithms are relatively complicated and not straightforward, and they also cause the problem that loop parameters are affected by the pre-detection integration time greatly. To solve these issues, an effective direct method of determining loop parameters of the second-order DPLL in the z-domain is proposed in this paper. Through ascertaining specific positions of the closed-loop system function's poles inside the right-hand side of the z-plane's unit circle, unknown parameters are calculated directly and flexibly in this method, which enables the DPLL to acquire good low-pass filtering characteristic and system stability. This novel method not only reduces the complexity of solving the parameters, but also eliminates the effect of the pre-detection integration time on loop parameters. Simulation results are provided to confirm the feasibility of the proposed method and to show that the DPLL obtained by this method achieves the similar tracking performance to the discretized PLL.     

Pulsed phase thermography imaging of fatigue-loaded composite adhesively bonded joints

We applied pulsed phase thermography to image and size damage in adhesively bonded joints. Specifically, the initiation and propagation of fatigue-induced damage in single lap joints with carbon fiber epoxy adherends was investigated. Lap joint specimens with various levels of manufacturing defects were fabricated and loaded in low-cycle fatigue. A calibration specimen with artificial defects was used to design a threshold algorithm for sizing of the damaged regions. The dominant failure mode in specimens without manufacturing defects was fiber-failure, whereas joints failing prematurely demonstrated adhesive failure. Imaging of the lap joints after regular number of fatigue cycles revealed that manufacturing defects could be detected and the resulting, imminent adhesive failure could be identified prior to joint failure. Additionally, the extent of this damage could be accurately estimated through the sizing algorithm. Due to the brittle nature of fiber-failure, it could not be detected prior to failure of the joint, however this was not critical, as the goal was to identify premature failure of the adhesively bonded joint.     

Growth morphology and crystallography of precipitate in a new high-temperature structural intermetallic Ti–40Al–10Fe

Based on TiAl alloys bearing high levels of Nb, which are prospective high-temperature intermetallics, a new dual-phase alloy (Ti–40Al–10Fe (at%)) with precipitate growth direction close to the slipping plane normal of the matrix was developed. Transmission electron microscopy revealed that the annealed alloy was composed of equiaxed grains of τ₂-TiAl₂Fe and γ-TiAl phases. Aging treatment at 1000 °C produced polygon-shaped γ-TiAl precipitate from the τ₂-TiAl₂Fe matrix. The precipitation reaction of the face-centered cubic structure of τ₂-TiAl₂Fe into the ordered face-centered tetragonal structure of γ-TiAl phase was systematically investigated in terms of crystallographic features, including mutual orientation relationship, growth direction, habit plane, side facets, and interfacial dislocation structure. The observed growth direction <973> was close to the normal of the slip plane {111}, with a discrepancy angle of ∼20°. Thus, the observed two-phase microstructure might significantly improve strengthening. It could also be quantitatively controlled by selection of precipitate and matrix with phase structures and lattice parameters that meet a certain requirement.     

First-principles derived complexion diagrams for phase boundaries in doped cemented carbides

This article reviews a method for calculating an equilibrium interfacial phase diagram depicting regions of stability for different interface structures as function of temperature and chemical potentials. Density functional theory (DFT) is used for interfacial energies, Monte Carlo simulations together with cluster expansions based on DFT results for obtaining configurational free energies, and CALPHAD-type modeling for describing the thermodynamic properties of the adjoining bulk phases. An explicit case, vanadium doped cemented carbides, is chosen to illustrate the progress in the research field and the interfacial diagram, a complexion diagram, for the phase boundary WC(0 0 0 1)/Co is constructed as function of temperature and chemical potentials.     

三氧化二铝PLOT柱气相色谱法分离氢同位素自旋异构体

氢同位素核自旋异构体正-仲态比例影响氢同位素的低温物性,有必要对其比例进行测定。本文利用活性三氧化二铝多孔层开管(Porous Layer Open Tubular,PLOT)柱实现了正-仲氢同位素(氕、氘)的基线分离,发展了一种可在液氮温度下测定同核分子正-仲态比例的色谱分析技术。研究结果表明,与传统三氧化二铝填充柱相比,高效PLOT柱实现了正、仲氕(o-H_2、p-H_2)以及正、仲氘(o-D2、p-D2)的基线分离(分离度R_s大于1.5),当流量为5 m L·min-1时,分离度R_s(p-H_2,o-H_2)=6.9,R_s(o-D2,p-D2)=1.8。正仲态分离度与进样量、流量均有关系。根据峰面积的积分结果,常温(298 K)下正、仲氕比例为2.77:1,正、仲氘比例为1.78:1,与理论测算值基本符合。HD与o-H_2实现了部分分离,R_s(o-H_2,HD)=0.5,根据理论预测,实现HD与o-H_2的基线分离(R_s达到1.5),理论塔板数需要达到3.9×105。     

Measurement of unsaturated shear strength parameters of silty sand and its correlation with unconfined compressive strength

Compressive strength and direct shear testing parameters on unsaturated soil are often used in analysis and design of several geotechnical infrastructures. Rarely, any attempt has been made to quantify shear strength of unsaturated soil under different net normal stress conditions. The objectives of this study are to quantify shear strength parameters of unsaturated silty sand and to establish a simple correlation of it with unconfined compressive strength. Consolidated drained direct shear tests and unconfined compressive strength tests were performed to determine shear strength of unsaturated completely decomposed granite (CDG) soil. To interpret this, a series of typical soil water characteristic curves (SWCC) of CDG soil under different net normal stresses were also measured. Experimental results show that the unsaturated shear strength significantly increases with increase in net normal stress and matric suction. A new model for prediction of unconfined compression strength of unsaturated soil from shear strength and initial suction was proposed. The predictions from newly proposed model were found to be consistent with the measured unconfined compressive strength. This correlation can be useful in economical and rapid design/analysis of geotechnical infrastructure.     

高效液相色谱法分析环己基苯液相氧化体系的组成

采用高效液相色谱法建立了常温下环己基苯(CHB)液相氧化体系中各组分含量的测定方法,利用间接碘量法测定环己基苯氢过氧化物(CHBHP)浓度并以此标定高效液相色谱法,绘制了CHB、CHBHP和1-苯基环己醇(PCHO)3种组分的标准曲线,并用于实际试样的测定。实验结果表明,CHB,PCHO,CHBHP的线性相关系数分别为0.995 5,0.998 2,0.990 7;CHB和PCHO的加标回收率均大于99%,CHBHP的加标回收率接近100%;对实际试样进行了5次平行实验,3种组分的相对标准偏差均不超过0.35%,精密度和准确度高,重复性良好,解决了难以获得CHBHP标准物质的问题。     

Preparation of Mo(Si,Al)2 feedstock used for air plasma spraying

In order to prepare high quality Mo(Si,Al)₂ feedstock characterized with C40 phase, higher Al doping amount and excellent flowability, Mo(Si_1–x,Al_x)₂ with different Al contents (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by self-propagating high-temperature synthesis first and Mo(Si_0.6,Al_0.4)₂ was confirmed as the suitable material through X-ray diffraction analysis. A series of tests with different parameters of induction plasma spheroidization were applied to improving the flowability of feedstock. Mo(Si,Al)₂ feedstock with excellent flowability (26.2 s/50 g) was prepared through adding hydrogen into sheath gas and decreasing the powder feeding rate. The composition segregation occurred in the spheroidized powder after Al consumption and oxidation. The inhomogeneous structure of the same particle was caused by the asymmetric heating and cooling when particle passed through the plasma jet.     

37%丙炔氟·丙草悬乳剂的气相色谱分析

采用气相色谱法对37%丙炔氟·丙草悬乳剂中的丙炔氟草胺、丙草胺进行同柱分析和定量。结果表明,该方法中丙炔氟草胺、丙草胺的线性相关系数分别为0.999 4和0.999 6,标准偏差分别为0.06、0.21,变异系数分别为2.84%、0.59%,平均回收率分别为99.35%、99.03%。