University of Architecture, Civil Engineering and Geodesy

About: University of Architecture, Civil Engineering and Geodesy is a education organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Finite element method & Beam (structure). The organization has 3808 authors who have published 3822 publications receiving 30736 citations. The organization is also known as: Sofia Polytechnic.

Estimation of land surface evapotranspiration over complex terrain based on multi‐spectral remote sensing data

Abstract: Land surface evapotranspiration (ET) plays an important role in energy and water balances. ET can significantly affect the runoff yield of a basin and the available water resources in mountainous areas. The existing models to estimate ET are typically applicable to plains, and excessive data are required to calculate the surface fluxes accurately. This study established a simple and practical model capable of depicting the surface fluxes while using relatively less parameters. Considering the complex terrain, solar radiation was corrected by importing a series of topographic factors. The water deficit index (WDI), a measure of land surface wetness, was calculated by applying the fc (vegetation fractional cover)-Trad (land surface temperature) framework in the TTME (two-source trapezoid model for evapotranspiration) model to mountainous areas after corrections of temperature based on altitude variations. The model was successfully applied to the Kaidu River Basin, a basin with few gauges located in the east Tien Shan Mountains of China. Based on the time scale extensions, ET was analyzed at different time scales from 2000 to 2013. The results demonstrated that the corrected solar radiation and WDI were reasonably distributed in space and that this model is applicable to ungauged catchments, such as the Kaidu River Basin.

Water-resistant fiber-reinforced gypsum cement-pozzolanic composites

Abstract: Gypsum and gypsum-cement-pozzolanic composites are of significant interest as materials and products for building decoration. The current tendency to reduce the consumption of gypsum-based materials and products in the context of growth and development of the finishing materials market depends on the decrease in their competitiveness compared to peers. This leads to significant interest in improving the quality of products based on gypsum and gypsum-cement-pozzolanic binder. Dispersed reinforcement is one of the ways of improving performance characteristics. The role of the type of reinforcing fibers in the formation of the gypsum-cement-pozzolanic composites structure and properties is studied in article. The influence relations of the cellulose fibers content with varying grinding degrees on the relative flexural and compressive strength of a gypsum-cement-pozzolanic matrix are obtained. It was found that the optimal content of cellulose fibers in the modified gypsum-cement-pozzolanic matrix is 0.5-1% by weight of the binder, the best indicators of flexural and compressive strength are achieved by grinding cellulose fibers to 30°SR. Using scanning electron microscopy, it was found that the microstructure of a disperse-reinforced gypsum-cementpozzolanic matrix is characterized by a uniform cellulose fibers distribution, the predominance of directionally frame reinforcement with a fibers linear orientation in the sheet plane. In this way the right choice of the type, crushing degree and cellulose fibers content can improve the quality and expand the application area of the produced gypsum-cementpozzolanic composites.

Failure behavior of composite sandwich structures under local loading

Abstract: Usually when analyzing the mechanical response of foam-cored fiber-reinforced composite sandwich structures to localized static loading, the face sheets are treated as a linear-elastic material and no damage initiation and growth is considered. However, practice shows that at higher indentation magnitudes damage develops in the face sheet in the area of contact with the indentor, which could lead to local failure of the face laminate due to the loss of bending stiffness and strength. Therefore, the main objective of the present study is to develop a damage model for predicting the local failure in the composite face sheet and its influence on the load–displacement behavior of sandwich structures under local loading. For this purpose, the Hoffman failure criterion is incorporated into a finite element modeling procedure using the ABAQUS program system. Results deducted from the modeling procedure are compared with experimental data obtained in the case of static indentation tests performed on sandwich beam specimens using steel cylindrical indentors. It is shown that taking into account the damage in the face sheet leads to a substantial improvement in the performance of the model when simulating the mechanical behavior of the sandwich structures at higher indentation values.

Curve lane detection based on the binary particle swarm optimization

Abstract: The method of B-spline curve fitting linebased on the binary particle swarm optimization is presented in this paper. First, according to the characteristics of the vertical and transverse width of the line must be straight, to extract the lane line feature points, and sorting out the feature points. Then, we select the cubic B-spline curve to fit the curve lane, first the discrete bunary particle swarm algorithm to optimize the number n of the control points, then by the least square method to calculate the control points of B-spline curve, according to the B-spline crrve fitting out the corresponding curve line. In order todetect corners recognition performance in a variety of road conditions has carried on the experimental study and the results show that the method has great adaptability.