Search

Even though soil temperature in urban environment influences a range of processes, it has been studied rather sparsely in comparison with surface temperature or air temperature. Our research extends the soil temperature observation in Olomouc (Czechia) and uses semi-stationary measurement to describe detailed spatial variability of soil temperature in the area of a medium-sized Central European city. Differences in soil temperature 20 cm below grass-covered surface may exceed 3°C due to soil type, shadow cast by buildings and grass characteristics, which means that the representativeness of the data on soil temperature from a meteorological station within a city may be limited. Further research and a conceptual approach towards the study of soil temperature in urban landscape is needed.

The concept of topophobia has been known in Geography for decades. Places which evoke fear in people’s minds can be found in almost every city. The perception of fear within an urban environment shows a certain spatio-temporal concentration and is often represented by fear of crime. The meaning of topophobic places, however, derived from the experience of fear of crime changes over time, and thus can alter the usual patterns of population behaviours in relation to time (in the time of the day and over longer periods) and space. A spatiotemporal understanding of these changes is therefore crucial for local decision-makers. Using data from the Czech Republic, this paper deals with the analysis of topophobic places, and is based on an empirical survey of the inhabitants of four cities, using the concept of mental mapping. In contrast to most similar geographical studies, the paper emphasises the temporal dimension of the fear of crime. The results have shown that over time there are significant differences in the meanings of topophobic places, and they have demonstrated the necessity of taking local specifics into account. The paper shows how the intensity of and the reasons for fears vary, depending on time and place. In general, the results provide support for the idea of place as a process and contain useful information for spatial planning and policy in urban areas.

A comprehensive understanding of the assessment of an urban space by its residents is viewed as one of the most in demand approaches within the endogenous strategies of urban space planning. As a rule, this process only leads to the identification of topophilic or topophobic places. What is lacking is the identification and interpretation of places that may contain both topophobic and topophilic meanings. Thus, the main objective of this paper is to explore, analyse, and compare ambivalently perceived places within an urban environment. Methodologically, the paper stems from the perception of space. More specifically, the phenomenon of mental maps is elaborated on. The analysis proves the ambivalent perception of selected places in the town under study (Šternberk, the Czech Republic), which points, to the complexity of human perception that characterises each community. Two synthetic maps based on four follow-up methodical procedures are provided, accompanied by two analytical maps.

Landscape has always been the focus of artistic interest. Landscape is also the object of research interest of geographers, and it offers a field for cooperation between art and geography. Our study focuses on landscape painting as an important source in identifying landscape changes. We focused on discovering the location where the painter placed his canvas. We used Czech landscape paintings from the end of the nineteenth century in the Iron Mountains. We have combined information about paintings and their authors with terrain analysis in GIS. We have carried out field research and consulted a painter to localise the locations where the landscapes were painted. Main map depicts the sites of selected landscape paintings from where the painters captured the image of the landscape. Our proposed combination of terrain analysis with the information about the paintings and the painters is a convenient way to identify the sites of the paintings.

The aim of this paper was to assess the impact of heat-waves on mortality in ten Czech cities, using data recorded during the summers of 2015 and 2016. Temperature-related mortality during heat-waves was investigated by comparing mortality figures on heat-wave days and those on other days by means of the Mann-Whitney U test. Results for all-cause mortality, cardiovascular and respiratory diseases (CVD+R) mortality, as well as for mortality in the over-65 age group, show statistically significant differences (p

This study describes the co-hydrotreating of mixtures of rapeseed oil (0–20 wt%) with a petroleum feedstock consisting of 90 wt% of straight run gas oil and 10 wt% of light cycle oil. The hydrotreating was carried out in a laboratory flow reactor using a sulfided NiMo/Al2O3 catalyst at a temperature of 345 °C, the pressure of 4.0 and 8.0 MPa, a weight hourly space velocity of 1.0 h−1 and hydrogen to feedstock ratio of 230 m3∙m−3. All the liquid products met the EU diesel fuel specifications for the sulfur content (−1). The content of aromatics in the products was very low due to the high hydrogenation activity of the catalyst and the total conversion of the rapeseed oil into saturated hydrocarbons. The addition of a depressant did not affect the cold filter plugging point of the products. The larger content of n-C17 than n-C18 alkanes suggested that the hydrodecarboxylation and hydrodecarbonylation reactions were preferred over the hydrodeoxygenation of the rapeseed oil. The hydrogen consumption increased with increasing pressure and the hydrogen consumption for the rapeseed oil conversion was higher when compared to the hydrotreating of the petroleum feedstock.

This study compares the hydrotreating of the mixture of petroleum middle distillates and the same mixture containing 20 wt % of rapeseed oil. We also study the effect of the temperature and the weight hourly space velocity (WHSV) on the co-hydrotreating of gas oil and rapeseed oil mixture. The hydrotreating is performed over a commercial hydrotreating Ni-Mo/Al2O3 catalyst at temperatures of ca. 320, 330, 340, and 350 °C with a WHSV of 0.5, 1.0, 1.5, and 2.0 h−1 under a pressure of 4 MPa and at a constant hydrogen flow of 28 dm3·h−1. The total conversion of the rapeseed oil is achieved under all the tested reaction conditions. The content of the aromatic hydrocarbons in the products reached a minimum at the lowest reaction temperature and WHSV. The content of sulphur in the products did not exceed 10 mg∙kg−1 at the reaction temperature of 350 °C and a WHSV of 1.0 h−1 and WHSV of 0.5 h−1 regardless of the reaction temperature. Our results show that in the hydrotreating of the feedstock containing rapeseed oil, a large amount of hydrogen is consumed for the dearomatisation of the fossil part and the saturation of the double bonds in the rapeseed oil and its hydrodeoxygenation.

Catalytic hydrocracking represents an optimal process for both heavy petroleum fractions and Fischer–Tropsch (FT) wax upgrading because it offers high flexibility regarding the feedstock, reaction conditions and products’ quality. The hydrocracking of a heavy vacuum gas oil with FT wax was carried out in a continuous-flow catalytic unit with a fixed-bed reactor and a co-current flow of the feedstock and hydrogen at the reaction temperatures of 390, 400 and 410 °C and a pressure of 8 MPa. The increasing reaction temperature and content of the FT wax in the feedstock caused an increasing yield in the gaseous products and a decreasing yield in the liquid products. The utilisation of the higher reaction temperatures and feedstocks containing the FT wax showed a positive influence on the conversion of the fraction boiling above 400 °C to lighter fractions. Although the naphtha and middle distillate fractions obtained via atmospheric and vacuum distillations of the liquid products of hydrocracking did not comply with the particular quality standards of automotive gasolines and diesel fuels, the obtained products still present valuable materials which could be utilised within an oil refinery and in the petrochemical industry.

Kerosene from the hydrocracking is commonly used to produce JET fuel. Depending on the deactivation of the catalyst, the aromatic content of such kerosene increases to a level where it can no longer be used for JET fuel production. The objective of this study was to determine whether the aromatic content of kerosene from hydrocracking can be reduced under the conditions used for hydrotreating straight-run middle distillates. The kerosene obtained from a real hydrocracker unit was investigated in a laboratory fixed-bed unit packed with a Ni-Mo/Al2O3 catalyst. Aromatics content was analyzed utilizing ASTM D6379 (HPLC). As a result of the hydrogenation, the aromatic content was reduced from 22.6 to 14.5 wt.% (3 MPa) and 3.0 wt.% (6 MPa). The product contained 60–70 wt.% cycloalkanes. The smoke point was improved by 3.3 mm (3 MPa) up to 9.7 mm (6 MPa), and the cetane index by 1.1 or 3.9 units, respectively. The (H/C)at ratio in kerosene increased from 1.89 to 1.98. Furthermore, no significant cracking occurred during the hydrogenation. Overall, we demonstrate that the aromatic content of such kerosene can be very well controlled by downstream hydrogenation under conditions common in oil refineries for the desulfurization of middle distillates. [ABSTRACT FROM AUTHOR]

Copyright of Croatian Journal Educational / Hrvatski Casopis za Odgoj I Obrazovanje is the property of Uciteljski Fakultet u Zagrebu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, a GC-MS method was developed for the quantification of saccharides in complex mixtures such as bio-oils and bio-oil aqueous phases produced by ablative pyrolysis of lignocellulosic biomass. The samples were first treated using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and the trimethylsilylated (more volatile) derivatives were analyzed by GC-MS. The method offers advantages of great separation capability and simultaneous identification of unknown peaks by comparison of the mass spectra and retention indices with extensive libraries available online. However, even with these tools at hand, the identification of several saccharide-resembling compounds can be challenging especially in such highly complex samples as pyrolysis bio-oils. For this reason, we devised a novel procedure, which eliminates certain saccharides depending on their specific chemical properties before subjecting the samples to the GC-MS analysis. The procedure was based on the combination of aniline treatment (elimination of reducing aldoses), and hydrolysis (elimination of anhydrosugars, glycosides, disaccharides and oligosaccharides). Based on the differences in chromatograms before and after the procedure, the unknown compounds were assigned into groups based on their susceptibility to each treatment. The combination of all methods above has allowed more accurate identification and quantification of saccharides, some of which were not as of today found in bio-oils., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Bio-oils after hydrotreatment can still contain significant amount of phenols and cyclic olefins as the products of an incomplete deoxygenation. The removal of these compounds would be necessary to produce suitable components for automotive fuels. However, no routine method currently exists for the reliable determination of these groups in hydrotreated bio-oils (HBOs). In this paper, we analyzed 140 different pure oxygenates as model compounds using the bromine number method (ASTM D1159) observing that most compounds present in HBOs react with one equivalent of bromine. The determination of phenols using bromine number method in crude bio-oil is complicated especially by the presence of guaiacols and syringols that react with more than one equivalent of bromine and, thus, the obtained result is significantly overestimated. Further we optimized the chromatographic separation of hydrocarbons from HBOs for the selective determination of olefins content. As no other reactive compounds under the conditions of the method, besides phenols and olefins, were observed in HBOs, the difference between HBO bromine number (before hydrocarbons separation) and olefins content correspond to the total amount of phenols. The method was finally applied to 11 HBOs with different content of oxygen, providing a good correlation between phenols and oxygen content., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Liquid transportation fuels in the middle distillate range contain thousands of hydrocarbons making the predictions and calculations of properties from composition a challenging process. We present a new approach of hydrogen content determination by comprehensive two-dimensional gas chromatography with flame ionization detector (GC×GC-FID) using a weighted average method. GC×GC-FID hydrogen determination precision was excellent (0.005 wt% repeatability). The method accuracy was evaluated by high-resolution nuclear magnetic resonance (NMR) technique, which is non-biased, measures the H signal directly and was independently validated by controls in the current study. The hydrogen content (in the range of 12.72-15.54 wt%) in 28 fuel samples were determined using GC×GC-FID. Results were within ± 2% of those obtained via NMR. Owing to the fact that NMR is accepted as an accurate technique for hydrogen content determination, the GC×GC method proposed in this study can be considered precise and accurate., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Quantification models based on the processing of FTIR spectra by partial least squares regression (PLS) were created in order to develop a method for the determination of 2-ethylhexyl nitrate (2-EHN) in diesel fuels. The set of standards was prepared using 2-EHN, biodiesel (FAME) and various mineral diesel fuels (2-EHN free). The standards were prepared in the concentration range of 2-EHN of 0-2436mgkg -1 . The set of the standards was divided into the calibration, validation and test sets. While the calibration set was used to build the model, validation set was used in order to optimize the model parameters. The test set of the standards was used to assess the predictive ability and repeatability of the model. Several hundreds of various models were developed and compared in order to find a suitable combination of the preprocessing methods and number of latent variables. The most promising model was developed using mean centered spectra in the form of their first derivative and smoothed using Gap-Segment derivative. The model showed quite good predictive ability and repeatability., (Copyright © 2017 Elsevier B.V. All rights reserved.)