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The Behavior of Rectangular and Circular Reinforced Concrete Columns Under Biaxial Multiple Excitation
Full text linkThe aim of this study is to investigate the dynamic performance of rectangular and circular reinforced concrete (RC) columns considering biaxial multiple excitations. For this purpose, an advanced nonlinear finite element model which can simulate various features of cyclic degradation in material and structural components is used. The implemented nonlinear fiber beam-column model accounts for inelastic buckling and low-cycle fatigue degradation of longitudinal reinforcement and can simulate multiple failure modes of RC columns under dynamic loading. Hypothetical rectangular and circular columns are used to investigate the failure modes of RC columns. A detailed ground motion selection is implemented to generate real mainshock and aftershocks. It was found that multiple excitations due to aftershock has the potential of increasing the damage of the RC columns and longitudinal reinforcements are significantly affected low-cycle fatigue. Also, it was found that rectangular column is more sensitive to accumulative damage due to cyclic fatigue. This study increases the accuracy of structural analysis of RC columns and consequently improves understanding the failure modes of RC columns with different cross-sectional shapes
Determination of Working Pressure for Airport Runway Rubber Mark Cleaning Vehicle Based on Numeric Simulation
Full text linkIn this paper, numeric simulations are performed for three dimension models built according to actual surface cleaner in airport runway rubber mark cleaning vehicle using ANSYS FLUENT software on the basis of previous research finished by the authors. After analyzing the simulated flow fields under different standoff distances between nozzle outlet and runway surface and different discharge pressures at nozzle outlet, the relationships of normal stress and shear stress at striking point to outlet pressure and standoff distance are obtained. Finally, the most appropriate discharge pressure at nozzle outlet for the studied surface cleaner model is found, and this will provide theoretical basis for future rubber mark cleaning process in airports and equipment model selection in subsequent design of airport runway rubber mark cleaning vehicles
An Algorithm for Mining Gradual Moving Object Clusters Pattern From Trajectory Streams
Full text linkThe discovery of gradual moving object clusters pattern from trajectory streams allows characterizing movement behavior in real time environment, which leverages new applications and services. Since the trajectory streams is rapidly evolving, continuously created and cannot be stored indefinitely in memory, the existing approaches designed on static trajectory datasets are not suitable for discovering gradual moving object clusters pattern from trajectory streams. This paper proposes a novel algorithm of gradual moving object clusters pattern discovery from trajectory streams using sliding window models. By processing the trajectory data in current window, the mining algorithm can capture the trend and evolution of moving object clusters pattern. Firstly, the density peaks clustering algorithm is exploited to identify clusters of different snapshots. The stable relationship between relatively few moving objects is used to improve the clustering efficiency. Then, by intersecting clusters from different snapshots, the gradual moving object clusters pattern is updated. The relationship of clusters between adjacent snapshots and the gradual property are utilized to accelerate updating process. Finally, experiment results on two real datasets demonstrate that our algorithm is effective and efficient
EIAS: An Efficient Identity-Based Aggregate Signature Scheme for WSNs Against Coalition Attack
Full text linkWireless sensor networks (WSNs) are the major contributors to big data acquisition. The authenticity and integrity of the data are two most important basic requirements for various services based on big data. Data aggregation is a promising method to decrease operation cost for resource-constrained WSNs. However, the process of data acquisitions in WSNs are in open environments, data aggregation is vulnerable to more special security attacks with hiding feature and subjective fraudulence, such as coalition attack. Aimed to provide data authenticity and integrity protection for WSNs, an efficient and secure identity-based aggregate signature scheme (EIAS) is proposed in this paper. Rigorous security proof shows that our proposed scheme can be secure against all kinds of attacks. The performance comparisons shows EIAS has clear advantages in term of computation cost and communication cost when compared with similar data aggregation scheme for WSNs
Dynamics Modeling and Stability Analysis of Tilt Wing Unmanned Aerial Vehicle During Transition
Full text linkIn the transition mode of quad tilt wing-unmanned aerial vehicle (QTW-UAV), the system stability of UAV will change with the tilt angle changes, which will cause serious head drop down. Meanwhile, with the complex air flow and other disturbances, the system is prone to side bias, frying, stall and other kinetic stability problems, hence the system stability analysis has become an urgent problem to be solved. To solve the stability problem, we need the quantitative criteria of system stability and effective tool of stability analysis, and can improve the stability of the motion control by optimizing the structural parameters of the aircraft. Therefore, based on the design of the mechanical structure, the quantitative relationship between the structure parameters of the aerial vehicle and kinetic stability of the system transition mode is established by the Lyapunov exponent method. In this paper, the dynamic modeling of the position and attitude angle is carried out and the stability of the system is analyzed by Lyapunov exponent, the results show that changing the mechanical structure of the system can improve the flight stability for the system transition mode and lay a theoretical foundation for the system stability analysis. Compared with the Lyapunov direct method, this method can be construct easily, has a simple calculation process and so on. We improve the flight stability by optimizing the structure and the experiment confirms that expanding area can enhance flight stability within limits
Analyzing the Structure and Connectivity of Continent-Level Internet Topology
Full text linkThe research and analysis of Internet topology is hot in the field of network measurement, which have important applications in network security, traffic scheduling and many other fields. Most of the existing works are focused on the AS-level and router-level topology, but few works are about the IP-level topology. In fact, obtaining the topology of each continent and knowing how the topologies of the continents are connected to each other can help us understanding the Internet around the world more thoroughly. In this paper, we obtained data sets from RIPE, constructed and analyzed network topologies of all the continents. By analyzing the topological connections between continents, we found out that most of the junctions of inter-continent traces are located in a few countries
A Reliable Stochastic Numerical Analysis for Typhoid Fever Incorporating With Protection Against Infection
Full text linkIn this paper, a reliable stochastic numerical analysis for typhoid fever incorporating with protection against infection has been considered. We have compared the solutions of stochastic and deterministic typhoid fever model. It has been shown that the stochastic typhoid fever model is more realistic as compared to the deterministic typhoid fever model. The effect of threshold number T* hold in stochastic typhoid fever model. The proposed framework of the stochastic non-standard finite difference scheme (SNSFD) preserves all dynamical properties like positivity, bounded-ness and dynamical consistency defined by Mickens, R. E. The stochastic numerical simulation of the model showed that increase in protection leads to low disease prevalence in a population
A Novel Atlas-Based Strategy for Understanding Cardiac Dysfunction in Patients with Congenital Heart Disease
Full text linkTetralogy of Fallot (TOF) is the most common form of cyanotic congenital heart disease. Infants diagnosed with TOF require surgical interventions to survive into adulthood. However, as a result of postoperative structural malformations and long-term ventricular remodeling, further interventions are often required later in life. To help identify those at risk of disease progression, serial cardiac magnetic resonance (CMR) imaging is used to monitor these patients. However, most of the detailed information on cardiac shape and biomechanics contained in these large four-dimensional (4D) data sets goes unused in clinical practice for lack of efficient and comprehensive quantitative analysis tools. While current global metrics of cardiac size and function, such as indexed ventricular mass and volumes, can identify patients at risk of further complications, they are not adequate to explain the underlying mechanisms causing the postoperative malfunctions, and help cardiologists plan optimal personalized treatments. We are proposing a novel approach that uses 4D ventricular shape models derived from CMR imaging exams to generate statistical atlases of ventricular shape and finite-element models of ventricular biomechanics to identify specific features of cardiac shape and biomechanical properties that explain variations in ventricular function. This study has the potential to discover novel biomarkers that precede adverse ventricular remodeling and dysfunction
3-D Temperature Fields in Laminated Shells Subjected to Thermo-Loads
Full text linkThe temperature fields in the laminated shells were studied, including open cylindrical shells and cylindrical shells, according to the thermal theory. Analytical solution of the temperature in the shells with the known temperature on the surfaces was present. The thinning layer approach was introduced to simplify the three-dimensional heat conduction equation. Firstly, the layered shell was divided into N thinner layers. The governing equation was simplified by replacing the variable r by r0 in the center line of every thin layer. The general solutions of temperature satisfying the simplified three-dimensional governing equation in single-layered shell were deduced in the cylindrical coordinate system. Then, the temperature and heat flux relationships between the surfaces could be found by transferring matrixes. According to the continuities of temperature and heat flux in the interface of the laminates, the temperature and heat flux relationships of the surfaces were derived. With the temperature condition on the surfaces, the unknown coefficients in the general solution of temperature were obtained. Finally, the effects from the thinning layer approach were eliminated by analyzing different numbers of thin layers. The validity and accuracy of the proposal method were proved from the convergence and comparison studies. And several numerical examples were studied to investigated the temperature effects from surface temperatures, geometric size of the shells and composition of layers
Alternatives of Small-Scale Biorefineries for the Integrated Production of Xylitol from Sugarcane Bagasse
Full text linkSmall-scale biorefinery from sugarcane bagasse offers new possibilities to the sugar and ethanol industries. The aim of this study was to evaluate the feasibility of a small-scale biorefinery for the production of xylitol from sugarcane bagasse. The liquid fraction from the autohydrolysis treatment was selected as the source of sugars for xylitol and two scenarios were analyzed for the residual solid: ethanol or pellet production. A technical-economic analysis of alternatives was applied. The internal rate of return (IRR) was used to compare the selected proposals. The highest IRR values were obtained when processing 70,000 dry tons per year of bagasse. The results showed promising prospects for a small-scale biorefinery with capacities above 20,000 dry tons per year (xylitol and pellets), and above 50,000 dry tons per year (xylitol and ethanol)