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Abstract

Many factors determine the efficient operation of a photovoltaic cell. These factors can be the intensity and spectral composition of illumination, the surface temperature, the ambient temperature, and the amount contaminations in the air and on the surface of the cells. The aim of the present study is to describe the effect of temperature gradient on the voltage and amperage changes, as well as the power output of a commercial solar cell through experimental methods and numerical simulations performed in MATLAB. The transient temperature investigations have allowed better understanding the time-dependent behavior of a solar cell under constant intensity illumination. Measurements prove that an increase in the surface temperature of the solar cell significantly reduces its performance. Measurements performed with the solar simulator show good conformity with simulated results.

Open access

Abstract

Thermodynamic efficiency is a crucial factor of a power cycle. Most of the studies indicated that efficiency increases with increasing heat source temperature, regardless of heat source type. Although this assumption generally is right, when the heat source temperature is close to the critical temperature, increasing the heat source temperature can decrease efficiency. Therefore, in some cases, the increase in the source temperature, like using improved or more collectors for a solar heat source can have a double negative effect by decreasing efficiency while increasing the installation costs. In this paper, a comparison of the CO2 subcritical cycle and the Trilateral Flash Cycle will be presented to show the potential negative effect of heat source temperature increase.

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Abstract

The increasing interest in large-panel building apartment renovation has heightened the need for a method-based examination. This research provides support to owners, investors, designers and habitants during decisions taking. The study covers the requirements, renovation trend, and cost evaluation. These criteria were defined by using general findings as the base of optimal renovations, which allows utilizing the results for wider areas. Renovations can be established to maintain or increase the value of apartments and the success of the investments depending on the optimal planning. The comfort needs, material selection, and the way of budget distribution are the main parameters of successful improvements. The analysis covers common quality renovation possibilities.

Open access

Abstract

One of the main problems at the Hričov weir is the scour development in the riverbed just downstream. It is caused of construction the size of the stilling basin was significantly shortened. Flow energy is dissipating just partially. Each flood makes scour close to the foundations of the structure, which potentially endangers its stability. A permanent solution was experimentally investigated in the hydraulic laboratory at the 2D model in a scale of 1:40. Different variants of the secondary stilling basins were designed to minimize creating scours. The investigation and its results are described in this paper.

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Abstract

The development of the social economy has led to the reorganization of the original layout structure and spatial functions of the city. Based on the development background of the Petite Ceinture railway space, this article conceives the attribute transformation and activation method of this industrial heritage. The proposed methodology, applied to the leftover spaces in Paris: integrating the biodiversity; softening the boundary; setting up installations. This paper investigates the relationship between the vitality of leftover space and the texture of the cities. It is proposed to try to reconnect the leftover space with the city through a multi-dimensional system corresponding to the diversified space and make good use of its unique location and internal potential.

Open access
Pollack Periodica
Authors: Ivan Baláž, Yvonna Koleková, Lýdia Moroczová, and Antonio Agüero

Abstract

In the frame of a large parametrical study metal built-up columns made from steel and made of aluminum alloy were investigated. The second order theory is used for the analysis of the battened and laced built-up columns under combined compression and bending. The bottom column ends are fixed and the upper ones are free in the case of in-plane buckling. At the column base the translation and the rotation are fixed, at the column top the translation and the rotation are free in the case of in-plane buckling. Translation is fixed and rotation is free at both column ends in out-of plane buckling. The built-up columns are considered as the columns with effective bending and smeared shear stiffness with a local bow imperfection amplitude e 0 = L/500.

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Abstract

This research work has been conducted to model the uniaxial stress-strain compressive behavior of cement-treated sand and its post-peak softening area. The cylindrical specimens were produced by using limestone powder, sand and high early strength cement. The mixtures were made by using different ratios of water to cement with fixed ratio of limestone powder to cement and cement to sand. The stress-strain behavior in post-peak zone of cement-treated is adjusted with introduction of compression softening factor. Uniaxial compressive stress-strain relationships after amending the Japanese Society of Civil Engineers model are proposed. Finite element analysis shows that the suggested model estimates well the compressive behavior of cement-treated sand.

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Abstract

Sequencing batch reactor systems in wastewater treatment is widely applied activated sludge technology. The system performance is not only dependent on the raw sewage quality and biochemical processes, but the flow pattern within the reactor has a significant impact on the treatment itself. The varying stages of the operation require different fluid flow conditions; biological stage shall be appropriately mixed, whereas low velocity zones favor the phase separation. The aim of this study was to improve sequencing batch reactor operation in order to optimize the treatment efficiency. Numerical fluid dynamic simulations were performed to determine the substrate and biomass homogeneity inside the reactor at the biological phase and the rate of the decantation was estimated at the sedimentation phase. The settling model was calibrated by field measurements. The results revealed that the hydraulic efficiency of the reactor was 87% and the achievable settled solid content was 0.9%.

Open access

Abstract

As part of the research focusing on the safety of vessels during the lockage in navigation locks, two different 1D numerical modeling approaches were tested. These approaches are used to determine the force effects on vessels during the direct filling process of the navigation lock. These numerical models were verified using data measured on a physical model. Using the selected 1D model, a parametric study focusing on the impact of the basic parameters of the navigation lock including the lifting velocity of the gates on the maximum hawser forces was performed. The research has shown that with a suitable design of the upper gate, the direct filling system may also be used for medium-head navigation locks with a normal lift of up to 5 m.

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Abstract

About 800,000 of “Cube houses” which date back to the socialist era are still in use throughout Hungary. These houses are considered to be “outdated” and they bring not only energy but also social issues. This paper presents a refurbishment design solution for the cube house, combining vernacular architecture with modern solutions within the framework of Solar Decathlon Europe 19 competition. The paper investigates the comfort and energy improvement of the refurbished design. Thermal simulation results revealed considerable improvements, which can be considered and implemented to a big proportion of family houses with analogous dimensions, under similar climate conditions.

Open access