Search

With the development of building materials, construction technology, and design concepts, suspended arched roofs (SARs) are becoming increasingly popular. The wind loads of arched roofs springing from ground level (ARSGL) and vaulted roofs on side walls (VRSW) have already been studied; however, the wind loads of SARs, which are very different from those of ARSGL or VRSW, have not received adequate attention. Based on the wind tunnel tests of a rigid model of an actual SAR design scheme, the mean value, root mean square (RMS) value, and most unfavorable value of the wind pressure coefficient and overall lift coefficient of this type of roof are analyzed. Furthermore, the influence of the buildings below or surrounding it is investigated and discussed. The test results indicate that the net wind pressure of the SAR is affected by the upper- and lower-surface wind pressures. Both the most unfavorable wind pressure (positive pressure) and suction (negative pressure) coefficients of the SAR are larger near the edge (arch foot) and smaller in the internal area. The maximum values of the most unfavorable pressure and suction coefficients of the tested SAR are 4.5 and 8.0, respectively, and these values are larger than those of ARSGL and VRSW. The buildings below cause airflow congestion under the SAR and eventually increase the net pressure coefficients near the windward edge of the SAR. The shielding effects of the surrounding buildings of the tested SAR reduce the wind pressure coefficient; however, the wind pressure in some areas of the tested SAR increases because of the narrow tube effects between surrounding buildings. The lift coefficient of the tested SAR significantly increases because of the presence of buildings below in some cases. [ABSTRACT FROM AUTHOR]

Slender structures are sensitive to wind loads, and aeroelastic effects during vortex-induced resonance have considerable influences on their survivability, serviceability, and habitability. However, the vortex-induced aeroelastic effects and the effects of turbulence intensity on unsteady aerodynamic forces of an aeroelastic prism remain far from been fully understood. In this study, a series of wind tunnel tests, including the pressure measurements of a rigid model and simultaneous measurements of the pressure and response of an aeroelastic model, were conducted in three different wind flows. The characteristics of unsteady aerodynamic forces and the effects of turbulence intensity on the unsteady aerodynamic forces were systematically investigated. The mechanism of aeroelastic effects and the variations of aerodynamic damping ratios were also discussed. Wind-induced responses were predicted by the unsteady aerodynamic forces and compared with the measured values. The experimental results show that vortex-induced aeroelastic effects on the wind-induced responses and the unsteady aerodynamic forces are significant. An increase in the turbulence intensity may result in a weak correlation of the unsteady aerodynamic forces and thus suppress the vortex-induced aeroelastic effects. Moreover, the amplitudes of the positive and negative peaks of the aerodynamic damping ratios decrease with the increase of the turbulence intensity. In addition, the wind-induced responses predicted by the unsteady aerodynamic forces measured from the aeroelastic model are the closest to the measured responses. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method for estimating the evolutionary power spectral density (EPSD) of a nonstationary process based on a single sample. In the proposed method, a sample of a nonstationary process is decomposed into several components with a new binomial fitting decomposition (BFD). The EPSD of each component can be estimated using a newly proposed time-varying standard deviation estimation method and short-time Thomson multiple-window spectrum estimation method. The EPSD of the analyzed nonstationary sample is obtained by combining the EPSDs of all components. Via a comprehensive numerical study, the applicability of the proposed EPSD estimation method (for estimating the EPSD of a nonstationary process) is analyzed and compared with those by the Priestley method and wavelet-based method. The numerical results indicate that the estimated EPSD by the proposed method is more consistent with the corresponding theoretical one than those by the other two methods. Finally, the EPSDs of Storm Ampil, measured atop the Shanghai World Financial Center, are analyzed by the proposed method. [ABSTRACT FROM AUTHOR]

Libraries offer reusable functionality through Application Programming Interfaces (APIs) with usage constraints such as call conditions or orders. Constraint violations, i.e. API misuses, commonly lead to bugs and security issues. Although researchers have developed various API misuse detectors in the past few decades, recent studies show that API misuse is prevalent in real-world projects, especially for secure socket layer (SSL) certificate validation, which is completely broken in many security-critical applications and libraries. In this paper, we introduce SSLDoc to effectively detect API misuse bugs, specifically for SSL API libraries. The key insight behind SSLDoc is a constraint-directed static analysis technique powered by a domain-specific language (DSL) for specifying API usage constraints. Through studying real-world API misuse bugs, we propose ISpec DSL, which covers majority types of API usage constraints and enables simple but precise specification. Furthermore, we design and implement SSLDoc to automatically parse ISpec into checking targets and employ a static analysis engine to identify potential API misuses and prune false positives with rich semantics. We have instantiated SSLDoc for OpenSSL APIs and applied it to large-scale open-source programs. SSLDoc found 45 previously unknown security-sensitive bugs in OpenSSL implementation and applications in Ubuntu. Up to now, 35 have been confirmed by the corresponding development communities and 27 have been fixed in master branch. [ABSTRACT FROM AUTHOR]

A simplified method is presented for evaluating the dynamic properties of structures considering the effects of soil–pile–structure interaction (SPSI). A substructure method is used to establish the model of the soil–pile–structure system which is characterized by several dimensionless parameters. The shear-type structure is modeled as a generalized single-degree-of-freedom system using the virtual displacement principle, and the impedance functions of the floating pile-foundation are formulated by the thin-layer method. A number of coupled systems are analyzed and the results are used as the statistical base to obtain the mathematical relations between the dimensionless parameters and the dynamic properties. The dynamic properties solved by the equations are compared with those of the field experiment, shaking-table test and other analytical methods. The results indicated that the proposed equations are of high accuracy and can be used to obtain the dynamic properties of piles directly without performing complex analysis. [ABSTRACT FROM AUTHOR]

The infrared traffic image acquired by the intelligent traffic surveillance equipment has low contrast, little hierarchical differences in perceptions of image and the blurred vision effect. Therefore, infrared traffic image enhancement, being an indispensable key step, is applied to nearly all infrared imaging based traffic engineering applications. In this paper, we propose an infrared traffic image enhancement algorithm that is based on dark channel prior and gamma correction. In existing research dark channel prior, known as a famous image dehazing method, here is used to do infrared image enhancement for the first time. Initially, in the proposed algorithm, the original degraded infrared traffic image is transformed with dark channel prior as the initial enhanced result. A further adjustment based on the gamma curve is needed because initial enhanced result has lower brightness. Comprehensive validation experiments reveal that the proposed algorithm outperforms the current state-of-the-art algorithms. [ABSTRACT FROM AUTHOR]

Optimal sensor placement (OSP) method plays a key role in setting up a health monitoring system for large-scale structures. This paper describes the implementation of monkey algorithm (MA) as a strategy for the optimal placement of a predefined number of sensors. To effectively maintain the population diversity while enhancing the exploitation capacities during the optimization process, a novel niching monkey algorithm (NMA) by combining the MA with the niching techniques is developed in this paper. In the NMA, the dual-structure coding method is adopted to code the design variables and a chaos-based approach instead of a pure random initialization is employed to initialize the monkey population. Meanwhile, the niche generation operation and fitness sharing mechanism are modified and incorporated to alleviate the premature convergence problem while enhancing the exploration of new search domain. In addition, to promote interactions and share the available resources, the replacement scheme is proposed and adopted among the niches. Finally, numerical experiments are conducted on a high-rise structure to evaluate the performance of the proposed NMA. It is found that the innovations in the proposed NMA can effectively improve the convergence of algorithm and generate superior sensor configurations when compared to the original MA. [ABSTRACT FROM AUTHOR]

The differential equation for inclined cables under axial narrow-band stochastic excitations is established with consideration of the cable sag and variations of cable tension along the cable. Gaussian and first-order non-Gaussian closed-form solutions are derived by employing the statistical moment truncation method to solve the moment equation. A long cable (Cable A20 of No. 2 Nanjing Bridge over the Yangtze River) is taken as an example to demonstrate the application of the theoretical model presented. The Monte Carlo method is also adopted to simulate the responses of the cable numerically under investigation. The general response characteristics of the cable are analyzed, particularly, the variation characteristics of the response of the cable depending on the excitation bandwidth when the ratio of the central frequency of excitation to the first frequency of cable is equal to one or two. Parametric vibrations of the real Cable A20 excited by the buffeting vibration of the bridge deck of No. 2 Nanjing Bridge over the Yangtze River are also calculated. [ABSTRACT FROM AUTHOR]

Due to their sensitivity to wind, the design of large-span roofs is generally governed by wind loads. For some flexible large-span roofs with low damping and concentrated modes, the effect of multi-mode coupling should be taken into account in computing the resonant buffeting response and equivalent static wind loads. Such an effect is considered by the modified SRSS method in this paper via the modal coupling factor. Based on the same SRSS method, the equivalent static wind loads combining the mean, background, and resonant components, are computed. Particularly, the background and resonant components are computed by the LRC method and the equivalent inertia force method considering the modal coupling effects by the modified SRSS method, respectively. The method is then applied to the computation of wind-induced vibration responses and equivalent static wind load distributions of a real large-span roof. The results show that the modal coupling effect on the resonant component can be identified by the present method with high accuracy. [ABSTRACT FROM AUTHOR]

Polysaccharide coated PLA nanoparticles bearing aldehyde groups were prepared by dialysis of DMSO solution of cholesterol hydrophobic-modified dextran polyaldehyde and PLA against water. The average diameter of the nanoparticles was about 160 nm, and the size distribution was nearly homogenous. The nanoparticles were functionalized simultaneously with CD71 and EGFR antibody through the Schiff's base reaction, and then radiolabeled with 99mTc. After perfused the radiolabeled nanoparticles into tumor-bearing rats through left common carotid artery, the radioactivity in liver, spleen, kidney and brain was measured by scintillation counter. The results showed that less than 2% of nanoparticles were uptaken by the brain due to the uptake of the nanoparticles by the RES system. However, the coupling of transferrin antibody on the nanoparticles facilitated the penetration of nanoparticles across the blood brain barrier, and more specially, compared with monofuctionalized and native nanoparticles, the multifunctionalization enhanced the tumor accumulation of the nanoparticles in vivo. [ABSTRACT FROM AUTHOR]