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Abstract

The efficiency of the most modern photovoltaic cells currently reaches 40–45%, which is achieved by concentrator systems. However, despite better device efficiencies concentrator photovoltaic cells have major drawback, namely the high amount of waste heat, which requires new cooling solutions.

This paper gives a short overview of the current cooling techniques and proposes a novel microchannel cooling solution for concentrator photovoltaic cells. In the concept, the microscale channels are integrated into the backside metallization of the PV device. The paper gives a description of the technological process that can be used to produce microchannels on the back of solar cells and shows the optimization of the channels to achieve optimal cooling performance.

Open access
Pollack Periodica
Authors: Marek Šutúš, Jaroslav Hrudka, Gergély Rózsa, Ivona Škultétyová, and Štefan Stanko

Abstract

This research deals with creating a hydrodynamic combined sewerage overflow chamber model an ANSYS Workbench 19.2, Fluid Flow (Fluent). The 3D graphics model was created in the SpaceClaim modeling software, which serves as the basis for hydrodynamic modeling. The model was created according to a real combined sewerage overflow chamber in Banská Bystrica. The cores of the work are simulations that should correspond to the estimated flow in the combined sewerage overflow chamber. The aim of this paper is to compare the impact of inflow speed and flow rakes.

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Abstract

Nowadays, digital technology and measurement are improving to measure some systems in accurate conditions without errors. From these improvements and developments, it is necessary to analyse performances and condition of bicycle and biker before high level computations. In this experimental investigation, a high quality and very light bicycle and a well-equipped trained biker were trained to test the system with different road and region conditions. The purpose of this investigation is to predict unwanted conditions of bicycle before computations and activity. Otherwise, this kind of experimental trained testing will give some information from unwanted bicycle accidents. Moreover, in this experimental work, a power meter and measurement instrument with sensors are used to measure real time parameters. As can be concluded from experimental results and the analysis, the proposed work has a good design and analysis for good material bicycles. The displacement analysis is also outlined with load of a 63 kg biker.

Open access

Abstract

Presence of pathogenic strains of Escherichia coli in foodstuffs may pose a health risk for a consumer. Therefore, knowledge on the effect of environmental factors on the growth ability of E. coli is of great importance. In this work, the effect of incubation temperature (6–46 °C) and the combined effect of temperature and water activity (0.991–0.930) on the growth dynamic of E. coli PSII were analysed. Based on the growth curves obtained, growth parameters were calculated by using the Baranyi D-model. Growth parameters were further analysed in secondary phase of predictive modelling. Using the CM model that describes the effect of combined factors, cardinal values (T min = 4.8 ± 0.4 °C, T opt = 41.1 ± 0.8 °C, T max = 48.3 ± 0.9 °C, a wmin = 0.932 ± 0.001, and a wopt = 0.997 ± 0.003) for the isolate were calculated. Under optimal conditions, the specific growth rate is µ opt = 2.84 ± 0.08 h−1. The results obtained may contribute to the assessment of the risk associated with the possible E. coli presence in raw materials and to the search for preventive measures with defined degree of accuracy and reliability.

Open access

Abstract

A numerical simulation procedure is presented to predict residual stress states in multi-pass welds in oil transportation pipes. In this paper, a two-dimensional thermo-mechanical finite element model is used to calculate the temperature distribution, hardness, and the distribution of residual stresses during multi-pass welding of pipes of dissimilar metals and varying thicknesses. In this model, the temperature dependence of the thermal and mechanical properties of the material was considered. The present model was validated using the hardness measurement. Good agreement was found between the measurement and the numerical simulation results. The simulated result shows that the two-dimensional model can be effectively used to simulate the hardness test and predict the residual stress in the pipe weld. The simulation results and measurements suggest that the model with moving heat source can obtain a good prediction of residual welding stress. Both the two-dimensional and the three-dimensional modeling can be used to estimate the residual stresses in different weld regions and help saving time.

Open access

Abstract

Energy storage on grid level is still a critical issue. Inventions related to development and control of smart buildings, including integrated solar systems can be easily realized by smart control of building management including storage. At buildings, which have high heat capacitance the part of the stored heat can be used for grid stabilization. This means the grid can be balanced with well-set up heating/cooling strategy and well-scheduled timetable via intelligent control of buildings. A possible solution is introduced in this paper, where the surplus production is used for overcooling the building, while the building thermodynamic properties are making it possible to store this amount of energy for days. This paper analyses a cost-effective solution of grid energy storage through a case study.

Open access
Pollack Periodica
Authors: Masy Ari Ulinuha, Eko Mulyanto Yuniarno, I. Ketut Eddy Purnama, and Mochamad Hariadi

Abstract

Facial bones segmentation is an important step to understanding a skull. In this paper, a method for segmenting facial bones from skull point clouds is proposed. The segmentation is based on the deviation angle features. The method consists of three phases: surface normal estimation, feature extraction, and point clouds classification. The method is applied to skull point clouds derived from computed tomography images. For evaluation, the method is compared with manual segmentation. The method has succeeded in segmenting facial bones with Precision = 0.836, Recall = 0.951, and F = 0.890.

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Abstract

Skidmore, Owings & Merrill Limited Liability Partnership as one of the best ‘localized’ overseas design companies in China, has participated in more than ten large-scale urban design projects in Wuhan, which has greatly changed the urban image and architectural style of Wuhan. Its space model of ‘grid road system + high-rise building’ replaces the traditional urban pattern of ‘street + residence’, causing huge cultural conflicts and historical rupture. Based on the planning of Wuhan Hanzheng street as an example, this paper attempts to uncover the cause of formation, the motivation mechanism of ‘grid road system + high-rise buildings’ space model, and to explore how Chinese cities realize the urban modernization with Chinese characteristics.

Open access

Abstract

In this study, the hygienic handling of leafy vegetables was evaluated in ten selected food establishments located in south-eastern Brazil. A 14-question survey was applied in these establishments, addressing the origin of the vegetables, washing procedures, and temperature conditions during storage and exposure. In addition, 30 samples of leafy vegetables were collected and submitted to the enumeration of total coliforms, coliforms at 45 °C and tested for Salmonella. Based on the responses to the survey, the establishments could be clustered into three groups. Group 1 included four establishments, where the vegetables originated from farms exclusively and were displayed to consumers at room temperature, and where most of the food handlers had participated in courses on good handling practices. Group 2 included two establishments that performed a centrifugation step and where vegetables were not available to consumers in a self-service. Finally, group 3 included four establishments, where vegetables originated from suppliers exclusively, were stored under refrigeration, and displayed to consumers on refrigerated tables. The mean count of total coliforms was 2.5 ± 0.7 log MPN/g, while coliforms at 45 °C were detected in only one sample (0.9 log MPN/g). Salmonella was not found in any sample. Microbiological results obtained for leafy vegetables from establishments clustered in the three groups did not differ significantly. These data contribute to a better understanding of the hygienic handling of leafy vegetables in the surveyed Brazilian food establishments.

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Abstract

Fly ash-based geopolymer fine aggregate is a potential replacement material for the natural river sand as it has similar physicochemical properties. This paper reports the experimental investigation of a study conducted using this fine aggregate in concrete with a focus on the properties of fresh and hardened concrete. The geopolymer fine aggregate was developed by air curing process and oven curing method. The oven curing method yielded relatively better mechanical properties in concrete specimens. The oven curing results in better behavior at later age also. Laboratory tests were conducted to ascertain the fresh concrete density, slump value, hardened concrete density, compressive strength, tensile strength, and flexural strength of the concrete specimens. The microstructure of the concrete specimens was analyzed using scanning electron microscope which indicated the agglomeration of the fly ash particles with few voids demonstrating the higher water adsorption capacity of the same. The unreacted particles noted in the microstructure later tend to merge with the lime obtained from the hydration of cement so as to develop improved later age mechanical strength. The results on mechanical properties of the concrete indicate much similar results to that of the concrete developed with the normal river sand, which confirms that the geopolymer sand is an ideal replacement choice for natural river sand.

Open access