Output feedback tracking control for rigid body attitude via immersion and invariance angular velocity observers

A novel immersion and invariance (I&I) angular velocity observer is presented for the attitude tracking control of a rigid body with the lack of angular rate. Global exponential convergence of angular velocity estimate errors are guaranteed by an innovative filter design for the estimates' Euclidean norm. The proposed method requires fewer filter states compared with existing I&I angular velocity observer designs, which achieves a simpler closed-loop structure (dynamic reduction). The observer synthesis and convergence are independent of the control torque, which leads to much convenience in establishing “separation property” when combining a proportional-derivative attitude tracking controller driven by angular velocity estimates. A rigorous stability analysis is provided to ensure the (almost) global asymptotic convergence of the overall closed-loop tracking errors, and several numerical simulations are carried out to demonstrate the effectiveness of the combined implementation of proposed angular velocity observer and full-state feedback attitude tracking controller.     

哌嗪基单丁酰胺酸钙/锌的合成及对PVC热稳定性研究

以丁二酸酐、哌嗪、氯化钙、氯化锌为原料，通过两步反应制备了哌嗪基单丁酰胺酸钙/锌（PSACa/Zn）热稳定剂。采用元素分析、电感耦合等离子体原子发射光谱仪（ICP?OES）和傅里叶变换红外光谱仪（FTIR）对产品结构进行表征，通过刚果红试纸法、转矩流变仪法、热失重法考察了PSACa/Zn对PVC的热稳定性能，并筛选了PSACa和PSAZn的最佳配比。结果表明，PSACa和PSAZn对PVC的静态热稳定时间分别可达74.5、41.5 min，优于硬脂酸钙（CaSt₂）、硬脂酸锌（ZnSt₂）热稳定剂；PSACa和PSAZn复配使用时，以m_PSACa∶m_PSAZn=1∶1时性能最佳，对PVC静态热稳定时间可达92 min，动态热稳定时间可达905 s；发现PSACa/Zn对PVC的长期热稳定性良好。     

Synthesis of hexacelsian barium aluminosilicate by film boiling chemical vapour process

An original oxide/oxide ceramic-matrix composite containing mullite-based fibers and a barium aluminosilicate matrix has been synthesized by the film boiling chemical vapour infiltration process. Alkoxides were used as liquid precursors for aluminum, silicon and barium oxides. The structure and microstructure of the oxide matrix were characterized by Scanning Electron Microscopy, Energy Dispersive Spectroscopy and X-ray diffraction. Apart from small residual mullite and amorphous phase amounts, the oxide matrix is composed of the hexacelsian phase, conferring to the material interesting perspectives for high-temperature electromagnetic and structural applications.     

地面-巷道瞬变电磁法探测采空区积水的应用

为探测呈祥煤矿副斜井在3#煤层下方是否充水,进行了地面-巷道瞬变电磁探测技术的应用。结合一矿81402工作面上方存在不明采空积水区、距离较远、井下正常超前物探难以覆盖的现状,制定了地面-巷道瞬变电磁探测方案。应用过程中发现,相对传统瞬变电磁法,地面-巷道瞬变电磁法受地形影响较小,对浅部数据地质信息反应较好,所观测的数据质量比较高。此外,3条巷道对采空区积水的位置有反映,与调查的采空区积水位置基本一致。实践表明,探测结果为采空区积水的防治提供了参考依据,可以运用到类似工程问题的实践中。     

Birthweight and Lipids in Adult Life: Population-Based Cross Sectional Study

The purpose of this study was to examine the association of birthweight with lipid profile in the general adult population. Participants in the second-wave of a nationally representative cross sectional AusDiab-study were asked to complete a birthweight questionnaire. Fasting total cholesterol (TC), LDL-C, HDL-C, and triacylglycerol levels were modeled against birthweight. Four thousand five hundred and two people reported their birthweights, mean (SD) of 3.4(0.7) kg. Females with low birthweight-LBW had higher levels of TC, LDL-C, and triacylglycerols, but no difference in HDL-C, than those with normal-birthweight-NBW;≥2.5 kg. People with LBW showed a trend toward increased risk for high TC (≥5.5 mmol/L) compared to NBW. Among females with LBW, the risk for high LDL-C (≥3.5 mmol/L) was increased compared to those of NBW. The risk for low HDL-C (<0.9 mmol/L) was increased among males with LBW compared to those with NBW. Examination of the relationship on the continuum showed no differences except for high triacylglycerol levels among females with the lowest birthweight quintile compared to the higher birthweight quintile. However, the risk for various abnormalities by birthweight quintiles was similar to that when we used the traditional definition of LBW vs. NBW. Females and males with low birthweight differ in their risk for lipids abnormalities. Females had higher risk for high LDL-C, whereas males had high risk for low HDL-C (<0.9 mmol/L). In addition, females with low birthweight had the highest triacylglycerol levels. High LDL-C, low HDL-C, and high triacylglycerols are well-recognized risk factors for cardiovascular disease.     

Rapid crystallization of poly(ethylene 2,6-naphthalate) via aryl amide derivatives

ABSTRACT

A very small amount of aryl amide derivative (TMB-5) was used for nucleating Poly(ethylene 2,6-naphathalate) (PEN) by melt blending. The crystalline temperature, crystallinity, and nucleation efficiency of the composites were increased as a result of the addition of TMB-5. The half-time of crystallization decreased upon the addition of TMB-5 and the work required in folding polymer chains were reduced simultaneously in the polymer mixtures. The crystal size of the PEN/TMB-5 blends became smaller due to the increase of nucleation sites. The TMB-5 had no effect on the PEN crystal type. TMB-5 slightly increased the impact strength of PEN.     

Composite fibers of La0.5Sr0.5CoO3-δ-LaSrCoO4±δ with high catalytic activity toward oxygen reduction reaction

To promote catalytic activity toward oxygen-reduction reaction in the intermediate temperature solid-oxide fuel cells, we prepared a dual-phase composite cathode material 75 mol%La0.5Sr0.5CoO_3-δ-LaSrCoO_4±δ with a fibrous structure via one-pot electrospinning of a polymer containing solution. We then investigated the micro-structure and electrochemical performance of this fibrous composite. The results confirm that the fibrous composite is composed of intimately mixed nano-crystalline grains and that the compositional phases are compatible with each other. Compared with the corresponding single-phase fibers, the nano-crystalline size of the composite is more stable, and the fine nano-crystalline grains are more resistant to growth and coarsening, indicating the mutual dispersion and suppression between the constituent phases. Furthermore, compared with the corresponding single-phase fibers, the electrochemical performance of this fibrous composite cathode is more favorable. At 800 °C, its area specific resistance (ASR) is as low as 0.03 Ω cm², and maximum output power density is as high as 960 mW cm⁻², which is achieved from an electrolyte-supported single cell that was developed using this cathode. After aging this cathode for a long time, ASR is less worsened and the output power density decreases only slightly, indicating that the prolonged electrochemical performance in the running cells is more stable.     

UV/TiO_2光催化氧化工艺脱汞的试验研究

UV/TiO_2光催化技术在TiO_2催化剂的作用下可将烟气中Hg~0氧化脱除。利用自制的UV/TiO_2氧化试验台研究了影响Hg~0去除率的相关因素,结果表明,在无催化剂和有紫外灯情况下可脱除少量Hg~0;Hg~0去除率随催化剂活性组分含量的增加而上升,但上升速率逐渐下降;在温度(50～200)℃范围内,Hg~0去除率无明显变化;Hg~0去除率随着Hg~0初始浓度的升高逐渐下降;Hg~0去除率随着烟气中氧含量先上升后趋于不变。UV/TiO_2氧化工艺脱汞可为燃煤电厂烟气脱汞提供理论指导。     

Acoustic emission analysis using Bayesian model selection for damage characterization in ceramic matrix composites

Acoustic emission (AE) during tensile testing of three-dimensional woven SiC/SiC composites was analyzed by a statistical modeling method based on a Bayesian approach to quantitatively evaluate the fracture process. Gaussian mixture models and Weibull mixture models were utilized as candidate models describing the AE time-series data. After fitting AE time-series data to these models with Markov Chain Monte Carlo (MCMC) methods, the model selection was conducted by stochastic complexity. Among the candidate models, the two-component Weibull mixture model was automatically selected. It was confirmed that the component distributions in the two-component Weibull mixture model were corresponding to the evolution of matrix cracking and fiber breakage, respectively. Since the proposed AE analysis method can determine the number of component distributions without the decision of researchers and inspectors, it is expected to be useful for an understanding of the fracture process in newly developed materials and the reliability assessment in service.     

Synergistic effects of modified TiO2/multifunctionalized graphene oxide nanosheets as functional hybrid nanofiller in enhancing the interface compatibility of PLA/starch nanocomposites

The aim of this study is to investigate the synergistic effects of modified TiO₂/multifunctionalized graphene oxide nanosheets at different ratios on the interface compatibility between starch and poly(lactic acid) (PLA). To this end, silanylated nano-TiO₂ (MTiO₂, 1 and 2%) and alkylated maleic anhydride grafted graphene oxide (f-GO, 0.1, 0.2, and 0.4%) at different combinations are blended with the PLA-starch composites using solution blending technique. Then, the synergistic effects of MTiO₂ and f-GO on PLA/starch matrix are investigated in terms of the morphology, crystallinity, structural characterization, thermal stability, dynamic mechanical, and antiaging properties, and the related mechanisms. The Raman and Fourier transform infrared spectroscopy spectra verify the successful synthesis of the two modified nanofillers (f-GO and MTiO₂) and the formation of strong hydrogen bond within the PLA-starch nanocomposites. Due to the strong interfacial interaction and the synergistic effect from the combination of 1% MTiO₂ and 0.2% f-GO, obvious improvement was observed in PLA-starch versus other nanocomposites in terms of morphology, thermal stability, surface hydrophobicity, storage modulus, ultraviolet-shielding capacity, and aging-resistance. Furthermore, differential scanning calorimeter (DSC), isothermal crystallization kinetic, and X-ray diffraction analysis demonstrate that f-GO and the M-TiO₂ significantly synergize in enhancing the crystallization rate and crystallinity of PLA/starch matrix. These results provide novel insights for constructing high-performance nanocomposites and facilitate their applications in food packaging.