Perturbation methods for the estimation of parameter variability in stochastic model updating

The problem of model updating in the presence of test-structure variability is addressed. Model updating equations are developed using the sensitivity method and presented in a stochastic form with terms that each consist of a deterministic part and a random variable. Two perturbation methods are then developed for the estimation of the first and second statistical moments of randomised updating parameters from measured variability in modal responses (e.g. natural frequencies and mode shapes). A particular aspect of the stochastic model updating problem is the requirement for large amounts of computing time, which may be reduced by making various assumptions and simplifications. It is shown that when the correlation between the updating parameters and the measurements is omitted, then the requirement to calculate the second-order sensitivities is no longer necessary, yet there is no significant deterioration in the estimated parameter distributions. Numerical simulations and a physical experiment are used to illustrate the stochastic model updating procedure.     

辽西义县盆地下白垩统义县组大康堡层纹泥地球化学特征及其古气候意义

辽西义县盆地义县组大康堡层剖面(辅助标准地层剖面)纹泥发育,占沉积层的60%~70%,为沉积期古环境研究提供了良好素材。通过对湖相纹泥进行岩石学及地球化学研究,探讨了大康堡层沉积期古气候、物源及湖水盐度变化。结果表明:纹泥化学蚀变指数多在65~67之间,变化幅度较小,对气候变化不敏感;w(Rb)/w(Sr)值较低,由下至上逐渐增大,大康堡层沉积期气候较温暖、湿润,存在寒冷、干燥向温暖、湿润变化的趋势;纹泥层偶厚度由下至上逐渐减小,降水量逐渐减少;成分变异指数在1.3~11.6之间,均大于1,代表了初始沉积产物及活动的构造环境;大康堡层物源以偏酸性火山岩为主,如义县组主期火山岩;稀土元素w(La)_n/w(Yb)_n值大于1,稀土元素在湖水滞留时间较长,沉降速率较慢;稀土元素w(La)_n/w(Yb)_n值由下至上逐渐减小,在垂向序列上沉积物沉降速率有逐渐增加的趋势,湖水盐度逐渐升高。     

基于情绪体验的ASD儿童干预机器人造型研究

目的 为提升ASD儿童干预机器人的训练效果,为教辅人员、设计师等提供参考,提出以ASD儿童情绪体验特点为基础的干预机器人拟人化造型特征评价方法。方法 对市场上的机器人造型样本进行拟人度评分,并从中选取代表性样本;从20余项HRV指标中筛选出8项代表性指标,通过HRV实验收集数据;使用改进的PAD情绪量表获取ASD儿童情绪体验主观得分;通过逐步回归法筛选出对情绪体验得分影响较大的HRV指标;以HRV指标为自变量、情绪体验得分为因变量,建立回归关系,为ASD儿童干预机器人造型的设计和方案评价提供理论依据。结果 研究表明,几何型机器人往往带来“放松的”情绪体验,类人型机器人会带来“高兴的”情绪体验,而真人型机器人则可能带来“焦虑的”情绪体验。同时,ASD儿童的愉悦度、唤醒度、优势度与HRV指标之间存在一定的相关性。结论 将改进的PAD情绪量表应用于ASD儿童干预机器人的造型评价中,建立情绪体验和HRV指标之间的回归模型,为设计和评估适合ASD儿童的机器人提供了理论依据,更好地促进了ASD儿童干预机器人的发展。     

冷却猪肉中气单胞菌暴露评估的不确定性和变异性

探讨冷却猪肉中气单胞菌暴露评估是否区分不确定性和变异性对结果的影响,并基于前期评估结果,对冷却猪肉中气单胞菌从销售到食用前阶段的增殖情况通过点估计和概率分布估计两种方法来实现。结果表明：点估计可能低估食用风险,概率分布考虑了输入量的各种可能性,推测结果更符合实际情况;同时,以符合正态分布的家庭贮藏温度为例修正参数设置,考虑全为不确定性,部分不确定性、部分变异性,全为变异性3 种可能情况,得到区分不确定性和变异性后的风险概率由不区分前的22.1%降为20.2%,全为变异性的概率仅为11.0%,从方法论角度探讨不同方法获得的风险差异,为后续定量风险评估提高精确性和可靠性提供理论参考。     

基于GIMMS、VGT和MODIS的中国东部植被指数对比分析

GIMMS NDVI、VGT NDVI和MODIS NDVI/EVI是目前在植被变化有关研究中经常使用的植被遥感数据,它们之间的差异也得到了广泛关注。然而,在分析这些数据之间的差异时,较少有研究注意到植被本身固有的季节循环可能夸大了各数据间的相关关系。应用2000~2006年GIMMS NDVI、VGT NDVI、MODIS NDVI/EVI等不同植被遥感数据,对比了基于这些数据集的中国东部植被年际变化的差异,探讨了植被季节循环对不同遥感数据之间相关性的影响。结果表明:由不同遥感数据提取的植被年际变化特征具有明显的一致性,然而,植被本身固有的季节循环特征掩盖了不同数据集的差异。季节循环去除前,各数据集之间具有显著的相关性;季节循环去除后,各数据集的相关性明显降低,但不同数据集在北部区域依然具有较好的一致性,其差异主要出现在南部区域,差异最明显的是GIMMS与MODIS数据,二者在淮河以南的区域几乎不存在显著相关。     

Spatial variability of soil resistivity and rational sampling for corrosion assessment of carbon steel in Daqing area

Soil resistivity is one of the key indicators of the corrosive classification assessment on metal materials in soil environment. This paper presents variance characters of various quantity of soil resistivity samples data based on the semi-variance function methods of Geo-statistical Analysis by analyzing the regional soil resistivity sampling data in Daqing area. Furthermore, the variance of the soil resistivity as well as entire soil circumstance due to different sampling amounts are also analyzed and compared by means of using the characteristic parameters of the semi-variance function. In addition, this work also studied the rational sampling quantities according to various measurement errors required and evaluated the local soil corrosivity on carbon steel based on the actual measuring data in this area.     

Acute Glucose Shift Induces the Activation of the NLRP3 Inflammasome in THP-1 Cells

We aimed to investigate the effect of acute glucose shift on the activation of the NLRP3 inflammasome, IL-1β secretion, and underlying signaling pathways in THP-1 cells. THP-1 cells were divided into four groups and exposed to the following glucose concentrations for 24 h: constant normal glucose (NG, 5.5 mM), constant high glucose (HG, 25 mM), normal to high glucose shift (NG-to-HG, 5.5 to 25 mM), and high to normal glucose shift (HG-to-NG, 25 to 5.5 mM). Cell viability, oxidative stress, and the levels of NLRP3 inflammasome components were assessed. Both directions of the acute glucose shift increased the activation of the NLRP3 inflammasome, generation of reactive oxygen species (ROS), and expression of phosphorylated p38 MAPK, JNK, and NF-κB compared with either constant NG or HG. Treatment with N-acetylcysteine, a pharmacological antioxidant, inhibited the acute glucose shift-induced generation of ROS, activation of NLRP3 inflammasome, and upregulation of MAPK-NF-κB. Further analysis using inhibitors of p38 MAPK, JNK, and NF-κB indicated that acute glucose shifts promoted IL-1β secretion by activating the signaling pathway in a ROS-MAPK-NF-κB-NLRP3 inflammasome in THP-1 cells. These findings suggested that acute changes in glucose concentration might cause monocyte inflammation, which is associated with diabetic complications.     

Integrating generations with advanced reference counting garbage collectors

We propose the use of generations with modern reference counting. A reference counting collector is well suited to collect the old generation, containing a large fraction of live objects that are modified infrequently. Such a collector can be combined with a tracing collector to collect the young generation, typically containing a small fraction of live objects. We have designed such a collector appropriate for running on a multiprocessor. As our building blocks, we used the sliding‐views on‐the‐fly collectors. We have implemented the new collector on the Jikes Research Java Virtual Machine (Jikes RVM) and compared it with the concurrent reference counting collector supplied with the Jikes RVM package. Our measurements demonstrate short pause times, retaining those of the original on‐the‐fly collectors and a gain in application throughput time. It turns out that a modern reference counting collector may benefit from the use of generations. Copyright © 2006 John Wiley & Sons, Ltd.     

随机场理论在桩基承载力可靠度分析中应用

根据Vanmarcke提出的土层概率模型、土性相关距离的定义及方差折减函数的基本性质,描述土性参数的空间变异性.并运用空间递推平均法及其改进方法分别求出相关距离.通过实例采用JC法计算单桩竖向承载力可靠度指标.论文目的在于提供合理的解决问题的思路和统计计算方法,这些方法同样适用于其他地基承载力可靠度分析应用.     

洛惠渠灌区地下水盐动态规律研究

根据洛惠渠灌区地质地貌,将整个灌区划分为三层阶地,通过对三层阶地上的地下水盐动态进行实时监测,运用双因子方差分析方法,详细论述了地下水电导率随地下水位在不同时期及不同分布条件下的变化情况。结果表明,地下水电导率变化与水位变化有很大关系,且表现出很强的区域特征：各阶地EC值均随水位的上升而增加,高EC值出现在高水位区,第一阶地高水位电导率存在显著变异。另外微地域环境、气候、生物、人类活动等外界因素也会影响地下水盐的动态过程。因此,有效降低该灌区地下水位是控制土壤盐化的重要措施,是实现农业可持续发展的关键所在。