Grain orientation evolution and multi-scale interfaces enhanced thermoelectric properties of textured Sr0.9La0.1TiO3 based ceramics

Sr_0.9La_0.1TiO₃ based textured ceramics (SLTT-S3T) with a texture fraction of 0.81 are successfully fabricated by the reactive template grain growth method, in which Sr_0.9La_0.1TiO₃/20 wt%Ti was used as matrix and 10 wt% plate-like Sr₃Ti₂O₇ template seeds were used as templates. The phase transition, microstructure evolution, and the anisotropic thermoelectric properties of SLTT-S3T ceramics were investigated. The results show that the ceramics are mainly composed of Sr_0.9La_0.1TiO₃ and rutile TiO₂ phases. Grains grow with a preferred orientation along (h00). A maximum ZT of 0.26 at 1073 K was achieved in the direction perpendicular to the tape casting direction. The low lattice thermal conductivity of 1.9 W/(m K) at 1073 K was obtained decreased by 34%, 40%, and 38% compared with non-textured, SrTiO₃ and Sr_0.9La_0.1TiO₃ ceramics prepared by the same process, can be attributed to the enhanced phonon scattering by the complex multi-scale boundaries and interfaces. This work provides a strategy of microstructural design for thermoelectric oxides to decrease intrinsic lattice thermal conductivity and further regulate thermoelectric properties via texture engineering.     

Two-dimensional complete neighborhood preserving embedding

Complete neighborhood preserving embedding (CNPE) is an improvement to the neighborhood preserving embedding (NPE) algorithm, which can address the singularity and stability problems of NPE and at the same time preserve useful discriminative information. However, CNPE works with vectorized representations of data, and thus, the original 2D face image matrices should be previously transformed into the same dimensional vectors. Such a matrix-to-vector transform usually leads to a high-dimensional image vector space, which makes the eigenanalysis quite difficult and time-consuming. Beyond computational issues, some spatial structural information between nearby pixels may be lost after vectorization. In this paper, we develop a new scheme for image feature extraction, namely, two-dimensional complete neighborhood preserving embedding (2D-CNPE). 2D-CNPE builds the eigenmatrix and the weight matrix which characterize local neighborhood properties of data directly based on the original face images, and then, the optimal embedding axes are obtained by performing an eigen-decomposition. Experimental results on three face databases show that the proposed 2D-CNPE achieves better performance than other feature extraction methods, such as Eigenfaces, Fisherfaces, and 2D-PCA.     

Numerical Investigation of Integrated Design on Uniform Fluid Distribution for Radial Flow Adsorber

Theoretical Foundations of Chemical Engineering - Non-uniform distribution of air in radial flow adsorber restricts the development of large-scale air separation units (ASUs). The cross-sectional...     

六分量大阻力复合式结构天平研制与应用

着陆巡视器和探月返回舱等短钝体风洞试验模型具有更大的阻力测量范围和更短的长度尺寸,为了提高该类模型在风 洞试验中的测量精准度,研制了一种新型复合式结构大阻力六分量应变天平。 与传统串联式结构天平相比,复合式结构天平结 构紧凑而阻力承载能力更强,能够完全安装于模型内部从而减少温度对天平测量精准度的影响;数值模拟结果表明,复合式结 构天平的平均应变、灵敏度、强度等能够满足风洞试验要求;复合式结构天平静态校准综合校准准度优于 0. 21%,满足国军标相 关技术指标。     

The hydrogen flow characteristics of the multistage hydrogen Knudsen compressor based on the thermal transpiration effect

Multistage hydrogen Knudsen compressor based on the thermal transpiration effect has very exciting prospect for the hydrogen transmission in the micro devices. Understanding of the hydrogen flow characteristic is the key issue for the designs and applications of the hydrogen energy systems. Firstly, the numerical models of the multistage hydrogen Knudsen compressor are established. The distributions of the rarefaction, velocity and temperature at different stages of the hydrogen flow are calculated and presented. Moreover, the dimensional pressure increases of the hydrogen gas flow are analyzed, and the flow behaviors in the microchannel and the connection channel are discussed. Secondly, the numerical simulation at different connection channel height is implemented, and the hydrogen gas flow characteristics in the connection are analyzed. Especially, the performances of the pressure drop in the connection channel under different channel heights are studied, and the hydrogen gas compression characteristics of different cases are compared and discussed. Also, the effect of the connection channel height on the hydrogen gas pressure increase in the microchannel is investigated. The studies presented in this paper could be greatly beneficial for the hydrogen detection and transmission.     

Pulse-modulation eddy current probes for imaging of external corrosion in nonmagnetic pipes

Since the nonmagnetic pipe is normally utilized in corrosive and hostile environment, it is prone to the external corrosion which occurs on the outer surface of the pipe and severely undermines the structural integrity and safety. Although Pulsed Eddy Current technique (PEC) is currently preferred for detection and evaluation of subsurface defects in tubular conductors, it is subject to technical drawbacks. In light of this, Pulse-modulation Eddy Current technique (PMEC) is intensively investigated in the paper for enhancement of the evaluation sensitivity to external corrosion and accuracy of corrosion imaging. Closed-form expressions of the PMEC response and its sensitivity to external corrosion in tubular conductors are formulated via the Extended Truncated Region Eigenfunction Expansion (ETREE) modeling. Following simulations for analysis and comparison of field signals and evaluation sensitivities of PMEC and PEC, experiments of PMEC for evaluation and imaging of external corrosion are carried out. Through theoretical and experimental investigation, it has been found that regarding the evaluation and imaging of external corrosion in nonmagnetic pipes, the PMEC-based probe have higher sensitivity and imaging accuracy than that based on PEC. The superiority of PMEC to PEC in inspection of tubular conductors is further identified.     

3D ECT reconstruction by an improved Landweber iteration algorithm

Electrical capacitance tomography (ECT) is a relatively mature non-invasive imaging technique that attempts to map dielectric permittivity of materials. Recently, 3D ECT has gained interest because of its potential to generate volumetric images. The study of a fast and accurate image reconstruction algorithm is a challenge task, especially for 3D reconstruction. In this paper, we propose an improved Landweber iteration algorithm. We incorporate an additional acceleration term into the cost function and apply an adaptive threshold operation to the image obtained in each iteration for reducing artefacts. The algorithm proposed is tested by the noise-free and noise-contaminated capacitance data. Sensitivity matrixes and capacitance data of a 3D ECT sensor are obtained by using the finite element (FE) method. Extensive simulations in 3D reconstruction are carried out. The results verify the effectiveness of these improvements. Both the reconstruction time and the artefacts in the reconstructed image are reduced obviously. The experimental results of 3D reconstruction of objects in the shape of letters U and L confirm the effectiveness of the proposed algorithm further.     

Development of microsatellite markers and a preliminary assessment of population structuring in the rice weevil,Sitophilus oryzae (L.)

The rice weevil, Sitophilus oryzae is one of the primary pests of stored grains worldwide. To develop and implement an effective integrated pest management strategy, an understanding of the population structuring of this destructive pest is vital. In this study we used Illumina paired-end sequencing to develop S. oryzae species-specific microsatellite markers, and used these markers to conduct a preliminary assessment of population structuring in four populations of S. oryzae from three countries (Australia, China, and USA). 7,635,996 raw sequencing reads were produced, with 11,794 microsatellites detected and 214,257 primer options designed. 48 microsatellite markers were selected for further validation, with 10 markers amplifying consistently across the four S. oryzae populations. These markers displayed a high level of polymorphism overall (6.67 alleles/locus), though this was slightly lower within populations (3.10–4.88 alleles/locus). We used the markers to conduct a preliminary assessment of genetic structuring among the four S. oryzae populations: three laboratory cultures (New South Wales, Queensland, and Santai) and a field collected population from Kansas. Analyses suggest high levels of genetic differentiation between the sample locations, with a global F_ST of 0.239, and pairwise F_ST values ranging from 0.100 to 0.395. Bayesian clustering analyses suggest these four populations formed four distinct clusters, with a similar pattern identified by Principal Coordinate Analysis. These microsatellite markers, together with our preliminary population genetic analyses, will provide a valuable resource for population genetic research, and contribute to effective integrated pest management strategies in the future.     

Effect of YSZ-incorporated glass-based composite coating on oxidation behavior of K438G superalloy at 1000 °C

A glass-based composite coating incorporating YSZ particles was prepared by sintering on K438G superalloy substrates. The YSZ additions increased the cyclic oxidation resistance at 1000 °C, while the formation of zircon resulting from interfacial reactions between YSZ and the glass matrix worked reversely. Besides, the YSZ inclusions changed the crystallization behavior of the glass matrix, and only anorthite precipitated during cyclic oxidation. Due to the synergy of sand-blasting and sealing effect of the glass-based coating, the oxidation behavior of K438G was changed and a layer of alumina instead of chromia formed at the substrate/coating interface. Furthermore, a gahnite layer formed at the alumina/gahnite interface because of interfacial reactions between alumina and the glass matrix, leading to the formation of a bi-layered thermally grown oxide. Thus, the alumina layer was protected from the attack of the active glass matrix. Accordingly, the coated K438G superalloy exhibited satisfactory oxidation resistance at 1000 °C.     

Capacitance-based liquid holdup measurement of cryogenic two-phase flow in a nearly-horizontal tube

Liquid holdup measurement of cryogenic fluids is an area of considerable significance because of its inevitable occurrence in LNG transportation, rocket propellant delivery and superconducting equipment cooling, etc. To measure the liquid holdup of cryogenic two-phase flow, a capacitance sensor was carefully designed, which consists of a pair of optimized concave-electrode form with the electric circuit for the small capacitance detection. Four flow patterns were realized to evaluate the performance of the sensor in visualization experiments with liquid nitrogen and vaporous nitrogen. An image method was employed to calibrate the capacitance sensor, which led to a mathematical relationship between the capacitance and the liquid holdup. The results indicated that the obtained correlation between liquid holdup and capacitance satisfactorily coincided with the measured data.