Association of size‐fractionated indoor particulate matter and black carbon with heart rate variability in healthy elderly women in Beijing

Associations between size‐fractionated indoor particulate matter (PM) and black carbon (BC) and heart rate variability (HRV) and heart rate (HR) in elderly women remain unclear. Twenty‐nine healthy elderly women were measured for 24‐hour HRV/HR indices. Real‐time size‐fractionated indoor PM and BC were monitored on the same day and on the preceding day. Mixed‐effects models were applied to investigate the associations between pollutants and HRV/HR indices. Increases in size‐fractionated indoor PM were significantly associated with declines in power in the high‐frequency band (HF), power in the low‐frequency band (LF), and standard deviation of all NN intervals (SDNN). The largest decline in HF was 19% at 5‐minute moving average for an interquartile range (IQR) increase (24 μg/m³) in PM_0.5. The results showed that smaller particles could lead to greater reductions in HRV indices. The reported associations were modified by body mass index (BMI): Declines in HF at 5‐minute average for an IQR increase in PM_0.5 were 34.5% and 1.0% for overweight (BMI ≥25 kg/m²) and normal‐weight (BMI <25 kg/m²) participants, respectively. Moreover, negative associations between BC and HRV indices were found to be significant in overweight participants. Increases in size‐fractionated indoor PM and BC were associated with compromised cardiac autonomic function in healthy elderly women, especially overweight ones.     

High-Speed Trains Automatic Operation with Protection Constraints: A Resilient Nonlinear Gain-based Feedback Control Approach

This paper addresses the control design for automatic train operation of high-speed trains with protection constraints. A new resilient nonlinear gain-based feedback control approach is proposed, which is capable of guaranteeing, under some proper non-restrictive initial conditions, the protection constraints control raised by the distance-to-go (moving authority) curve and automatic train protection in practice. A new hyperbolic tangent function-based model is presented to mimic the whole operation process of high-speed trains. The proposed feedback control methods are easily implementable and computationally inexpensive because the presence of only two feedback gains guarantee satisfactory tracking performance and closed-loop stability, no adaptations of unknown parameters, function approximation of unknown nonlinearities, and attenuation of external disturbances in the proposed control strategies. Finally, rigorous proofs and comparative simulation results are given to demonstrate the effectiveness of the proposed approaches.      

基于敏感度分析的机床关键几何误差元素辨识与评定

为了正确识别和判定机床关键几何误差元素对机床精度设计的影响,以PCV-620立式加工中心为研究对象,采用多体系统理论建立机床空间误差模型,从而得到机床几何误差元素与机床精度之间的关联函数。对空间误差模型进行灵敏度分析,获得机床各运动方向的局部灵敏度系数,完成机床关键几何误差元素的初步辨识。以局部灵敏度系数为基础,提出一种与局部灵敏度系数和工作空间中任意位置处的几何误差元素值相关的全局灵敏度系数计算方法,将其作为机床关键几何误差元素的辨识和评定标准,分析得到PCV-620立式加工中心的关键几何误差元素包含3项定位误差、3项垂直度误差和5项直线度误差。     

基于DSP技术的配电房关键位置温度测量系统

目前配电房关键位置温度测量系统未设计温度智能标定程序,导致系统温度测量精度和正确率较低,为此提出设计基于DSP技术的配电房关键位置温度测量系统。硬件方面,考虑系统核心模块和测量性能,优化系统硬件结构和显示模块。软件方面,设计系统温度采集模块,采集配电房关键位置温度,设计温度测算程序和温度智能标定程序,智能测量配电房关键位置温度。实验结果表明:该系统受到外界温度因素影响较小,拟合曲线拟合度较高,具有较高的温度测量精度和正确率。     

Taste matters most: Effects of package design on the dynamics of implicit and explicit product evaluations over repeated in-home consumption

Package design influences consumers’ expectations of a product’s sensory properties and expected healthiness and/or tastiness, and potentially also changes actual product perception during consumption. The robustness of these effects is far from clear, however. This study investigated the influence of package cues signalling either hedonic or healthy product properties on expectations and subsequent product evaluation over repeated consumption.In a between-subjects design, 92 participants evaluated product expectations and taste perceptions of a chocolate-sesame flavoured biscuit with a package emphasizing either its healthy (n = 44) or hedonic (n = 48) aspects, both at a central location (CLT) and during six home use tests (HUT), using both explicit (questionnaires) and implicit (IAT) measures.Package design significantly affected (p < 0.05) consumers’ expectations of the product. They expected the biscuit to be tastier, less attractive and less healthy in the hedonic package condition, and less tasty, more attractive and healthier in the healthy package condition. However, these effects did not transfer to actual product evaluations upon tasting, either blind or tasting in combination with viewing the package during the HUTs. Implicit attitudes did change as a result of repeated exposures, depending on the package consumers were provided with, indicating product-package interactions over time (p < 0.05).In conclusion, package design influences product expectations and associations with its healthiness and attractiveness, which is of relevance in product choice and purchase settings. However, at the stage of (repeated) consumption, intrinsic (sensory) properties become the dominant drivers of products’ sensory and hedonic evaluations, and the impact of package cues seems less potent.     

Identification of Wiener systems based on the variable forgetting factor multierror stochastic gradient and the key term separation

The identification of Wiener systems is very difficult because of the output nonlinearity and the parameter product term. To identify the Wiener system, a novel stochastic gradient algorithm based on the multierror and the key term separation is proposed. Firstly, the Wiener system is parameterized as a pseudo-linear model to avoid the products of the parameters. Secondly, a parzen window is used to estimate the probability density function of the error. Thirdly, a stochastic information gradient algorithm with the multierror is adopted to estimate the parameters. The multierror takes the place of the scalar error by the stacked error, which accelerates the algorithm greatly. Fourthly, a variable forgetting factor considering errors is integrated to further speed the algorithm up. Finally, the proposed algorithm is validated by a numerical example and an industrial case. The estimation results indicate that the proposed algorithm can obtain accurate estimates with fast convergence speed.     

Effects of Sr2+ substitution on the crystal structure,Raman spectra,bond valence and microwave dielectric properties of Ba3-xSrx(VO4)2 solid solutions

The effects of Sr²⁺ substitution for Ba²⁺ on microwave dielectric properties and crystal structure of Ba_3-xSr_x(VO₄)₂ (0 ≤ x ≤ 3, BSVO) solid solution were investigated. Such Sr²⁺ substitution contributes to significant reduction in sintering temperature from 1400 °C to 1150 °C. Both permittivity (∑_r) and quality factor (Q × f) values decreased with increasing x value, which was determined to be related with the descending values of average polarizability and packing fraction, whereas the increase in τ_f value was explained by the decreased average VO bond length, A-site bond valence. BSVO ceramics possessed encouraging dielectric performances with ∑_r = 12.2–15.6 ± 0.1, Q × f = 44,340 - 62,000 ± 800 GHz, and τ_f = 24.5–64.5 ± 0.2 ppm/°C. Low-temperature sintering was manipulated by adding B₂O₃ as sintering additive for the representative Sr₃V₂O₈ (SVO) ceramic and only 1 wt.% B₂O₃ addition successfully contributed to a 21.7% decrease in sintering temperature to 900 °C, showing good chemical compatibility with silver electrodes, which render BSVO series and SVO ceramics potential candidates in multilayer electronic devices fabrication.     

Ablation behavior and mechanism of bulk MoAlB ceramic at ∼1670–2550 °C in air plasma flame

In this work, MoAlB samples for plasma exposure test were condensed by spark plasma sintering at 1200 °C for 10 min. Ablation resistance of MoAlB ceramic was investigated in a plasma torch facility for about 30 s at high temperature range of ～1670?2550 °C, which provided a quasi-real hypersonic service environment. The results showed that the linear ablation rate was increased from 0 μm/s at ～1670 °C to 86.4 μm/s at ～2550 °C. At ～1670 °C, the ablated surface of MoAlB ceramic was covered by Al₂O₃ layer, presenting excellent ablation resistance. At ～2220 °C, the macroscopic cracks were induced by thermal stress, which opened up channels for the inward diffusion of oxygen and deteriorated the ablation resistance of the substrate. Above ～2400 °C, the volatile MoO₃ and B₂O₃ and the erosion of viscous oxides by the high shearing force of plasma stream were the main ablation mechanisms.     

建设工程施工企业质量管理实践

建筑工程质量安全是施工企业管理的底线和红线。结合中铁建设集团有限公司近些年在质量管理方面的心得和经验,从施工企业的制度建设、标准化建设、管控手段、人员素质提升、创优创誉等方面,探讨建筑施工企业的质量管理。