基于改进LMD的泵站摆度信号分析

局部均值分解(local mean decomposition, LMD)在分析非线性、非平稳信号时具有特有的分析能力,特别适合泵站机组摆度信号的分析.但是在信号分解为固有旋转分量的过程中,由于局域均值和包络估计函数在数据端点存在误差,会产生端点效应,严重时导致信号分解结果失真.针对这一问题,从全面考虑曲线幅值和几何形状相似性出发,提出基于灰色B型关联度和欧氏距离的端点效应抑制方法.为评价该端点效应抑制方法的抑制效果,提出分解前后的信号能量变化的评价标准.通过与原始局域均值分解算法、镜像映射法和波形匹配法等传统方法相比,验证该方法的有效性和优越性.仿真信号和泵站主轴摆度实测信号的应用表明,该方法能够有效地抑制端点效应,提高LMD分解过程中重构信号精度,更好地提取泵站机组摆度信号故障特征.     

分数次Hardy算子的交换子在Lipschitz空间上的端点估计

主要研究分数次Hardy算子和Lipschitz函数生成的交换子在Lipschitz空间上的端点估计.分数次积分算子的方法不适用于分数次Hardy算子,将给出新的方法,同时也将考虑分数次极大算子的交换子的结果.     

From research measurements to application: Bridging the gap; Overview of practical and scientific measurements in nutrition

Research that advances the practice of poultry nutrition covers a wide range, including fundamental studies that explore mechanisms in cells or a small number of birds and applied research that determines product yield in authentic production facilities. Ultimately, the applied research informs the economic analysis necessary for implementation of novel nutritional strategies or products. Nutritional controversies arise from applied research experiments that were not designed and interpreted based on the realities learned from mechanistic work. The experimental design and measurements selected for comparing nutrient sources or setting nutrient recommendations should be informed by underlying mechanistic information, such as the relative priorities of cells and tissues for the nutrient and the shape of the dose response relationship across a wide range of added dietary levels of the nutrient. Integrating mechanistic and applied research provides more robust results that can be used across wider ranges of diets and husbandry conditions.     

HHT方法在结构模态参数识别中的改进

在Hilbert-Huang变换(HHT)的基础上,采用ChebyshevⅠ类带通滤波器对测量响应进行滤波,使得经EMD分解得到的固有模态函数(IMF)包含所有需要的模态,解决了模态混淆问题;采用去端点法预处理模态响应的相位和幅值,进行线性最小二乘法拟合,解决了端点效应问题;并推导了如何利用HHT识别比例阻尼结构体系的振型,获得了结构的各阶模态参数.分别通过4自由度数值试验和4自由度实验室框架结构试验说明了本文算法的有效性.     

Life in the fast lane: Revisiting the fast growth—High survival paradigm during the early life stages of fishes

Early life survival is critical to successful replenishment of fish populations, and hypotheses developed under the Growth-Survival Paradigm (GSP) have guided investigations of controlling processes. The GSP postulates that recruitment depends on growth and mortality rates during early life stages, as well as their duration, after which the mortality declines substantially. The GSP predicts a shift in the frequency distribution of growth histories with age towards faster growth rates relative to the initial population because slow-growing individuals are subject to high mortality (via starvation and predation). However, mortality data compiled from 387 cases published in 153 studies (1971–2022) showed that the GSP was only supported in 56% of cases. Selection against slow growth occurred in two-thirds of field studies, leaving a non-negligible fraction of cases showing either an absence of or inverse growth-selective survival, suggesting the growth-survival relationship is more complex than currently considered within the GSP framework. Stochastic simulations allowed us to assess the influence of key intrinsic and extrinsic factors on the characteristics of surviving larvae and identify knowledge gaps on the drivers of variability in growth-selective survival. We suggest caution when interpreting patterns of growth selection because changes in variance and autocorrelation of individual growth rates among cohorts can invalidate fundamental GSP assumptions. We argue that breakthroughs in recruitment research require a comprehensive, population-specific characterization of the role of predation and intrinsic factors in driving variability in the distribution and autocorrelation of larval growth rates, and of the life stage corresponding to the endpoint of pre-recruited life.     

Limitations of soil microbial biomass carbon as an indicator of soil pollution in the field

The size of the soil microbial biomass carbon (SMBC) has been proposed as a sensitive indicator for measuring the adverse effects of contaminants on the soil microbial community. In this study of Australian agricultural systems, we demonstrated that field variability of SMBC measured using the fumigation-extraction procedure limited its use as a robust ecotoxicological endpoint. The SMBC varied up to 4-fold across control samples collected from a single field site, due to small-scale spatial heterogeneity in the soil physicochemical environment. Power analysis revealed that large numbers of replicates (3-93) were required to identify 20% or 50% decreases in the size of the SMBC of contaminated soil samples relative to their uncontaminated control samples at the 0.05% level of statistical significance. We question the value of the routine measurement of SMBC as an ecotoxicological endpoint at the field scale, and suggest more robust and predictive microbiological indicators.     

Soil compression influences the avoidance behavior of Allonychiurus kimi (Collembola) to cadmium and copper

The behavior of soil organisms inhabiting soil pore spaces can be influenced by soil compression, which can affect their avoidance behavior to pollutants. In this study, we aimed to evaluate the effect of soil compression on the avoidance behavior of Allonychiurus kimi (Collembola) to heavy metals cadmium and copper. Initially, to assess the applicability of the avoidance test guideline of the International Organization for Standardization (ISO) developed for Folsomia candida, we investigated the avoidance behavior of A. kimi to cadmium and copper in an artificial soil with a loose structure (bulk density of 0.25 g cm-3), the porous texture of which was sufficiently loose to enable A. kimi to move between pore spaces. The effect of soil compression on the avoidance behavior of A. kimi to both metals was evaluated in compressed soil (bulk density of 0.64 g cm^-3) with a uniformly compressed soil surface, and avoidance behavior was investigated at 24-h intervals over a 120-h period. Given that A. kimi is unable to burrow into compressed soil, the compressed soil test can minimize the effects of differences in soil factors, such as soil porosity and bulk density, on the behavior of this collembolan. In the artificial soil, a statistically significant avoidance behavior of A. kimi was observed at cadmium and copper concentrations greater than 50 and 200 mg kg^-1, respectively, thereby indicating the applicability of the ISO avoidance test guidelines for A. kimi. When compared at the same exposure time point, the avoidance response to both metals in compressed soil was less sensitive than that in uncompressed soil. In addition, we observed differences in the effects of metals on avoidance response in the compressed soil over time, with the effect of cadmium increasing with time and the effect of copper showing the opposite trend. Overall, we found that soil compression can affect the avoidance behavior of A. kimi to cadmium and copper, and we discussed the advantages and limitations of using compressed soil for assessments of pollutant toxicity.     

Behavioural and metabolic responses of Unionida mussels to stress

1. The aim of this study was to assess the extent to which the behavioural traits of freshwater mussels provide suitable indicators of stress in individuals, towards the advancement of non-invasive, remote monitoring techniques to examine population condition.
2. Variation in the expression of particular behavioural metrics was examined in accordance with measurements of oxygen consumption, across environmental stressors (aerial exposure and high concentrations of total suspended solids), and between two freshwater mussel species (Margaritifera margaritifera and Anodonta anatina)
3. Aerobic metabolic rate was quantified using intermittent respirometry, and behaviour was observed using time-lapse footage. Comparisons of metabolic response and the occurrence of behavioural traits, across the two stressors, focused on differences between the 24 h pre-exposure period (pre-exposure), the first 3 h of post-exposure (immediate post-exposure), and the time following the initial 3 h of post-exposure until the end of the experimental run (extended post-exposure).
4. The results of this study demonstrated a relationship between the frequency of occurrence of behavioural responses to stress exposure, associated with valve activity, and significant changes in the metabolic functioning of A. anatina and M. margaritifera mussels. The findings from the study also highlighted substantial intraspecific variation across species and stressors.
5. Data from this research could assist in the development of novel biosensors that track mussel valve activity remotely in their natural environment. When coupled with real-time data examining alterations in environmental metrics, this technology could assist in the monitoring of population condition and aid conservation management.

     

高噪声环境下基于倒谱距离的语音端点检测算法的实现

为了在高噪声环境下得到较清晰的语音信息,对倒谱距离算法进行了改进,利用语音信号的倒谱向量判断语音端点信息。MATLAB仿真实验结果表明,在白噪声和汽车噪声环境下,信噪比分别为10 dB和15 dB时,得到的语音单字清晰度分别达到93%和95%,实现了90~100 dB高噪声环境下可靠的语音通信。     

近红外光谱法检测鸡、鱼肉加热终点温度

【目的】在肉制品生产中,加热终点温度（endpoint temperature,EPT）是控制食源性疾病的关键因素。现有的EPT检测方法诸多,如酶活性测定法,凝血试验和聚丙烯酰胺凝胶电泳（SDS-PAGE电泳）法等,但普遍存在耗时、样品处理繁杂等不足。采用近红外光谱（near-infrared spectroscopy,NIR）结合偏最小二乘法（partial least squares,PLS）检测鸡、鱼肉加热终点温度,为研究近红外光谱法检测肉类EPT的可行性提供参考。【方法】分别将肉样以1℃·min^-1的升温速率进行9个不同温度的加热处理（50、55、60、65、70、75、80、85和90℃）,当达到终点温度时,迅速取出,冰水冷却到4℃。冷却后的肉样和释放的肉汁同时放到均质机中,均质1 min,绞碎成肉糜状。均质后的肉样存放于4℃的冰箱中,共制得144个样品（鸡、鱼肉样品数分别为77和67）。在近红外光谱仪上,采用硫化铅（PbS）检测器和旋转样品池,每个样品连续采集光谱3次,在11 000-4 000 cm^-1波数范围内,以8 cm^-1的分辨率扫描64次。将所采集的鸡、鱼肉的光谱数据分别随机分为校正集（样品总数108,其中鸡肉样58,鱼肉样50）和检验集（样品总数36,其中鸡肉样19,鱼肉样17）,校正集用于校正模型的建立,检验集用于检验模型的预测能力。在建立模型时,采用标准正则变换、一阶微分和Norris Derivative滤波平滑（N-D）3种方法结合对原始光谱进行处理,采用内部交叉验证均方差（cross-validation mean square error,RMSECV）确定主成分数,利用模型对检验集样品的预测均方差（prediction mean square error,RMSEP）、预测值与实测值间的相关系数r及预测标准差σ考察模型的预测性能。【结果】采用校正集的内部交叉验证均方差（RMSECV）确定鸡肉、鱼肉的主成分数分别为9和11,此时校正集的RMSECV值最小,分别为1.59%和0.96%;所得校正模型的预测温度与实际加热温度之间的相关系数分别为0.9844和0.9936;由所建模型对检验集样品的检验结果可看出,实际加热温度与近红外模型预测的加热温度具有很高的相关性,预测值的相关系数r分别为0.9966和0.9832;预测均方差RMSEP分别为3.02%和2.94%;预测标准差σ为0.97和1.63。【结论】本研究所建模型具有很好的预测性能,近红外光谱用于肉制品EPT检测具有很大潜力。