载荷影响下的机电阻抗协整结构损伤识别方法

高频机电阻抗(electromechanical impedance, 简称EMI)方法利用粘贴在结构表面的压电传感器(piezoelectric transducer, 简称PZT)进行主动激励，通过连续监测和分析PZT机电导纳信号的变化评估结构的健康状态；然而EMI方法容易受到环境工况变化的影响，导致结构损伤的误报。针对此问题，采用时间序列协整方法处理及消除结构工作载荷对阻抗谱特征信号的影响。该方法是基于结构动荷载作用下PZT阻抗谱导纳信号的非平稳特征，将动荷载影响下的阻抗谱非平稳时间序列经线性组合变换成平稳时间序列，根据得到的协整余量序列有效判断结构的健康状态。为验证该方法的有效性，开展了动应力影响下铝梁结构的螺栓松动损伤识别实验。结果表明，协整消除了动态应力对EMI方法的影响，当铝梁内存在持续变化的应力时，仍可以准确识别螺栓松动。机电阻抗协整方法能够消除结构健康监测中荷载作用的影响，及时准确地进行结构损伤识别。     

Cell Death Mechanisms Induced by CLytA-DAAO Chimeric Enzyme in Human Tumor Cell Lines

The combination of the choline binding domain of the amidase N-acetylmuramoyl-L-alanine (CLytA)-D-amino acid oxidase (DAAO) (CLytA-DAAO) and D-Alanine induces cell death in several pancreatic and colorectal carcinoma and glioblastoma cell lines. In glioblastoma cell lines, CLytA-DAAO-induced cell death was inhibited by a pan-caspase inhibitor, suggesting a classical apoptotic cell death. Meanwhile, the cell death induced in pancreatic and colon carcinoma cell lines is some type of programmed necrosis. In this article, we studied the mechanisms that trigger CLytA-DAAO-induced cell death in pancreatic and colorectal carcinoma and glioblastoma cell lines and we acquire a further insight into the necrotic cell death induced in pancreatic and colorectal carcinoma cell lines. We have analyzed the intracellular calcium mobilization, mitochondrial membrane potential, PARP-1 participation and AIF translocation. Although the mitochondrial membrane depolarization plays a crucial role, our results suggest that CLytA-DAAO-induced cell death is context dependent. We have previously detected pancreatic and colorectal carcinoma cell lines (Hs766T and HT-29, respectively) that were resistant to CLytA-DAAO-induced cell death. In this study, we have examined the putative mechanism underlying the resistance in these cell lines, evaluating both detoxification mechanisms and the inflammatory and survival responses. Overall, our results provide a better understanding on the cell death mechanism induced by CLytA-DAAO, a promising therapy against cancer.     

External validity and factor structure of individual and group workload ratings

Work teams experience workload from the group dynamics in addition to the usual sources of individual workload. This study had three objectives: to assess the responsiveness of new rating scales for group workload (GWL), investigate their component structure, and determine if changes in workload occur as the team matures. Participants (360 individuals, 44 groups) engaged in an emergency response (ER) simulation in the form of a board game; team size, game difficulty (one versus two opponents), and time constraints were varied. ER teams rated workload after each of two sessions using the NASA Task Load Index (TLX) and GWL. GWL was most responsive to larger task demands and reflected changes in coordination demand over time. Components reflected mixtures of TLX and GWL scales and suggested that self-organising processes were operating.     

Towards standardisation of proof load testing: pilot test on viaduct Zijlweg

Proof load tests of bridges can be very useful for structures with a lack of information, or for structures of which the effect of material degradation is difficult to assess. Contrary to diagnostic load testing, proof load testing is not well-defined in current standards in terms of required load and analysis of measurements. The risk related to the high loads used in proof load testing requires standardisation for these tests. The paper highlights important considerations for proof load testing that may lead to the development of guidelines in the Netherlands, by illustrating a pilot study on the viaduct Zijlweg in the Netherlands. This reinforced concrete bridge rates too low in shear. Topics of interest are the required load that the bridge has to withstand to be approved by the load test and the interpretation of the measurements during the test to avoid permanent damage to the structure. These measurements were compared to the stop criteria from existing codes for buildings, to examine if recommendations for the use with bridges can be formulated. The final result of the test on this case study is that the capacity of the viaduct is proven to be sufficient for shear and bending moment.     

船体结构冰载荷反演方法及试验验证

冰载荷是影响船舶冰区航行期间结构安全的重要环境载荷。船舶的冰压监测通常采用应变传感器，合理地布放传感器是识别冰载荷的基础。通过对比船体外板结构试验中的冲击载荷和不同测试方案下的应变信号，确定了最佳应变传感器布放方案；采用Green核函数方法建立了船体外板结构应变冲击载荷间的响应关系，并对采集信号在噪声影响下反演的不适定性进行了分析；采用Tikhonov正则化方法克服了载荷反演过程中出现的数值不稳定问题；最后将试验中的响应用到载荷识别分析中，反演的载荷可以较为准确地反映冲击载荷的时域特征并且载荷识别精度良好。     

Predicting Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) populations and associated grain damage in smallholder farmers’ maize stores: A machine learning approach

Prostephanus truncatus is a notorious pest of stored-maize grain and its spread throughout sub-Saharan Africa has led to increased levels of grain storage losses. The current study developed models to predict the level of P. truncatus infestation and associated damage of maize grain in smallholder farmer stores. Data were gathered from grain storage trials conducted in Hwedza and Mbire districts of Zimbabwe and correlated with weather data for each site. Insect counts of P. truncatus and other common stored grain insect pests had a strong correlation with time of year with highest recorded numbers from January to May. Correlation analysis showed insect-generated grain dust from boring and feeding activity to be the best indicator of P. truncatus presence in stores (r = 0.70), while a moderate correlation (r = 0.48) was found between P. truncatus numbers and storage insect parasitic wasps, and grain damage levels significantly correlated with the presence of Tribolium castaneum (r = 0.60). Models were developed for predicting P. truncatus infestation and grain damage using parameter selection algorithms and decision-tree machine learning algorithms with 10-fold cross-validation. The P. truncatus population size prediction model performance was weak (r = 0.43) due to the complicated sampling and detection of the pest and eight-week long period between sampling events. The grain damage prediction model had a stronger correlation coefficient (r = 0.93) and is a good estimator for in situ stored grain insect damage. The models were developed for use under southern African climatic conditions and can be improved with more input data to create more precise models for building decision-support tools for smallholder maize-based production systems.     

Full-chip wire-oriented back-end-of-line TDDB hotspot detection and lifetime analysis

Time-dependent dielectric breakdown (TDDB) has become an important cause of failure for inter-metal dielectrics (IMD) in integrated circuits as feature sizes continue to shrink and novel materials are introduced. Although many studies have been conducted to understand the underlying physics of this issue, not enough work has been focused on evaluating TDDB lifetime of practical chip designs in the physical design stage. This paper proposes a full-chip TDDB failure analysis methodology to evaluate lifetime and identify TDDB hotspots in VLSI layouts, which are essentially interconnect wires that have high failure risk due to TDDB. The proposed method features three new techniques compared to existing methods. First, we have developed a partitioning-based scheme to deal with scaling of full-chip analysis by partitioning the full chip layout into small tiles. Second, for each tile, the new method calculates a newly-introduced TDDB failure metric called TDDB Damage for vulnerable wires. Such a wire-oriented TDDB analysis is the first of its kind and is very amenable for physical design as the wires can be easily adjusted or re-routed for TDDB-aware optimization. Third, the new method considers the impact of the non-uniform electric field calculated using the finite element method (FEM), which significantly improves the accuracy of TDDB risk evaluation. Experimental results show that the proposed new TDDB analysis method is more accurate than a recently proposed full-chip TDDB analysis method in which electrical field is treated as a constant value. Additionally, the proposed method can analyze a practical VLSI layout in a few hours.     

纵轴式掘进机截割头载荷影响因素的仿真分析

针对现有掘进机截割头载荷特性研究方法采用单一影响因素不能全面反映截割头载荷及其波动变化规律的问题,通过分析截割头瞬时载荷,确定了纵轴式掘进机在水平截割工况下截割头载荷的主要影响因素有截割岩石特性、截割头掏槽深度、截割头吃刀深度、截割头转速和截割臂摆速。针对某纵轴式掘进机水平截割工况,采用Matlab对影响截割头载荷的多种因素进行仿真分析,得到了各向载荷及其波动随各因素的变化规律:截割头载荷随着岩壁普氏系数的增大而增加,其中横向阻力增加尤为明显,横向阻力波动程度高于其他方向载荷,且随着岩壁普氏系数的增大呈减小趋势;随着截割头掏槽深度的增加,截割头各向载荷近似呈线性增加,其中升力增加幅度最大,各向载荷波动则随着截割头掏槽深度的增大而减小;随着吃刀深度的增加,截割头载荷总体呈增大趋势,载荷波动程度则随之减小;在截割头转速一定的情况下,截割头载荷均随着截割臂摆速的增加而增大,在同一摆速下,截割头载荷随着截割头转速的减小而增大,横向阻力波动明显高于升力和推进阻力波动,横向阻力和推进阻力波动按截割头载荷规律变化,升力波动则与之相反。截割头载荷波动变化规律与截割头载荷变化规律不尽一致,有时甚至相互冲突。因此,掘进机作业过程中应合理选择截割头掏槽深度、吃刀深度等操作参数和截割头转速、截割臂摆速等运动参数,使各参数相互匹配,以减小掘进机振动,延长使用寿命。     

生物滴滤床法降解二氯甲烷废气的因素影响特征

二氯甲烷作为溶剂广泛应用于制药行业，其挥发性废气对人类健康和大气环境的危害极大。本文采用生物滴滤床对某制药厂浓度范围在0.02~2g/m³的二氯甲烷废气进行了为期132天的中试规模实验。在适宜的停留时间、温度、喷淋量和pH等实验条件下，控制适当的进气浓度可得到高效去除效率并且废气出口浓度达标。实验揭示了生物膜内生物降解是过程的限制因素，结果表明，在喷淋量为1200L/h、进气浓度范围为0.45~0.65g/m³时该生物系统去除效率最高可达98.9%，最大去除负荷可达EC_max=155.25g/(m³·h)。随着进气浓度的增加，去除负荷随之增大，而去除效率下降，废气出口浓度超标，表明生物滴滤系统已处于反应控制。此外，间歇实验表明，该生物系统具有良好的稳定性。指出生物滴滤床的设计、运行取决于当地的二氯甲烷废气排放标准。