Numerous investigations have indicated that structural modal parameters are significantly impacted by varying environmental and operational conditions. This phenomenon will cause confusion when conducting modal-based damage detection and model updating. This paper investigates the dependency of modal frequencies, modal shapes and the associated damping ratios on temperature and wind velocity. The nonlinear principal component analysis (NLPCA) is first employed as a signal pre-processing tool to distinguish temperature and wind effects on structural modal parameters from other environmental factors. The pre-processed dataset by NLPCA implies the relationship between modal parameters and temperature as well as wind velocity. Consequently, the artificial neural network (ANN) technique is employed to model the relationship between the pre-processed modal parameters and environmental factors. Numerical results indicate that pre-processed modal parameters by NLPCA can retain the most features of original signals. Furthermore, the pre-processed modal frequency and damping ratios are dramatically affected by temperature and wind velocity. The ANN regression models have good capacities for mapping relationship of environmental factors and modal frequency, damping ratios. However, environmental effects on the entire modal shapes are insignificant. damping ratio are the accurate reflection of the structural properties such as stiffness and damage. However, the application vibration-based damage detection method for civil engineering structures is complicated, because modal parameters of a real structure are strongly affected by factors other than structural damages. These factors include (i) variations in material properties; (ii) environmental variability (such as temperature, wind velocity and humidity, etc.) and variability in operational conditions (such as traffic flow) during measurement; and (iii) errors associated with measured datasets and processing techniques. If the effect of these uncertainties on modal parameters is larger than or comparable to effect of structural damage on its modal parameters, the structural damage cannot be reliably identified. As a matter of fact, it has been observed from some field tests that the variation of modal parameters due to changes of environmental factors is very significant, and can be even larger than those due to rather severe structural damage. For example, Alampalli [3] presented that the relative modal frequency differences (df ) of a bridge due to freezing of the supports (df 5 40-50%) were an order of magnitude larger than changes due to damage (df 5 3-8%), which was in that case an artificial saw cut across the bottom flanges of both girders. Therefore, studying the environmental effects on modal parameters is important for reliable performance of damage detection algorithm. Considerable research efforts have been devoted to investigating the influence of environmental factors on dynamical characteristics via field measurements and dynamic tests, including Roberts and...

A simply prepared gold nanoparticle-based sensor, 5,5'-dithiobis (2-nitrobenzoic acid) (DTNBA)-modified gold nanoparticles, was prepared to explore the sensitive and selective detection of metal ions using a colorimetric technique. The selective detection of trace levels (93.6 ppb) Cr3+ in aqueous solution was achieved over 15 other metal ions. The functionalized gold nanoparticles became aggregated in solution in the presence of Cr3+ by an ion-templated chelation process, which caused an easily measurable change in the extinction spectrum of the particles and provided an inherently sensitive method for Cr3+ detection in aqueous solution.

Variation in the type of tissue that larvae feed on can produce marked differences in developmental rate and body size, which can compromise predictions of minimum postmortem interval. A series of experiments were conducted to investigate the effect of fat content in the diet on larval growth in Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae), an important forensic blowfly species in China. Bionomical parameters such as body size, development time, mortality, and sex ratio were observed. The results indicated that fat content in the diet has a dramatic effect on the body size and larval development. More dietary fat content was beneficial for development of larvae in first and early second instar. But it was adverse in the later third instar. Significantly, a high-fat diet resulted in increased development rates and the production of undersized larvae and adults. Overall mortality of larvae and pupa was higher when more fat was added to the diet, but sex ratio of adults was not negatively affected. This study highlights that the fat content in the diet should be considered in the entomological research and forensic application when estimating minimum postmortem interval on the basis of larval body size and developmental stage.

The dynamic interaction between a bridge and a moving train has been widely studied. However, there is a significant gap in our understanding of how the presence of isolation bearings influences the dynamic response, especially when an earthquake occurs. Here, we formulate a coupled model of a train-bridge-bearing system to examine the bearings’ dynamic effects on the system responses. In the analysis, the train is modeled as a moving oscillator, the bridge is a one span simply supported beam and one isolation bearing is installed under each support of the bridge. A mathematical model using fractional derivatives is used to capture the viscoelastic properties of the bearings. The vertical response is the focus of this investigation. Dynamic substructuring is used in modeling to efficiently capture the coupled dynamics of the entire system. Illustrative numerical simulations are carried out to examine the effects of the bearings. The results demonstrate that although the presence of bearings typically decreases the bridge seismic responses, there is a potential to increase the bridge response induced by the moving train.

By proposing device-independent protocols, S. Pironio et al. [Nature 464, 1021[Nature 464, -1024[Nature 464, (2010] and R. Colbeck et al. [Nature Physics 8, 450-453 (2012)] proved that new randomness can be generated by using perfectly free random sources or partially free ones as seed. Subsequently, Li et al. [Phys. Rev. A 84, 034301 (2011)] studied this topic in the framework of semi-device-independent and proved that new randomness can be obtained from perfectly free random sources. Here we discuss whether and how partially free random sources bring us new randomness in semi-device-independent scenario. We propose a semi-device-independent randomness expansion protocol with partially free random sources, and obtain the condition that the partially free random sources should satisfy to generate new randomness. In the process of analysis, we acquire a new 2-dimensional quantum witness. Furthermore, we get the analytic relationship between the generated randomness and the 2-dimensional quantum witness violation.