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Measuring Chandler Wobble amplitude variations using IERS EOP C04 data
Get PDFWe analyzed the Earth's long-term polar motion using the time series IERS EOP C04 (from 1984 to 2023) to determine the variation of amplitude of the Chandler wobble. To compare the results based on the C04 with the Belgrade latitude data (BLZ series 1949-1985) results, we calculated the variations of latitude at BLZ point using the C04 coordinates (x, y). The secular part of these latitude variations was determined by use of the least-squares method (LSM) and removed from the data to get residuals. We used the Fourier transforms (DFT) to obtain annual and semiannual oscillations and to remove them from the residuals (to get a new set of residuals). These new residuals were divided into 33 independent 1.2 years subintervals. For each subinterval, we calculated the amplitude, period and phase of the Chandler nutation using the LSM. The quasi-periodic instability of 33 values of the amplitude of the Chandler wobble is detected with a period of 54.5 years using LSM (it was 38.5 years from BLZ data 1949-1985); the amplitude of that quasi-periodic variation is 0.″087 (0.″06 from BLZ data). The amplitude of the Chandler nutation varies with a minimum of 0.″012 (at 2019.3) and a maximum of 0.″230 (at 1994.1); the period is stable, but the phase is not stable. We applied the Abbe criterion to explain the variability in 33 values of the Chandler wobble amplitude, and the hypothesis that there is no trend in these 33 values is rejected. The obtained amplitude modulation is in accordance with other published papers about similar subject (and with our results based on BLZ data). Probably, the cause is lying in the hydro-atmospheric circulation that could influence calculated quasi-periodic variation. A possible explanation can be found in changes of core-mantle electromagnetic coupling (in line with the last few years investigations). In recent papers, it has been noticed that the effects of geomagnetic jerks are more important for exciting free nutation than the atmosphere and oceans.Editors: Luka Popović, Ana Vudragović and Milena Jovanovi
Short-term forecasting of PM10and PM2.5 concentrations with Facebook's Prophet Model at the Belgrade-Zeleno brdo
Get PDFWe demonstrate the use of Facebook's Prophet (usually just called Prophet) model for short-term air quality forecasting at Belgrade-Zeleno brdo monitoring station. To address missing data, we applied minimally-altering data distribution imputation techniques. Linear interpolation proved effective for short-term gaps (1–3 hours), hourly mean method for mid-term gaps (24–26 hours), and Hermite interpolation polynomial for long-term gaps (132–148 hours). The most significant data change was a 3.4% shift in skewness. Partitioning the time series enabled a detailed quality assessment of the Prophet model, with PM2.5predictions being more precise than PM10. Using the longest time series for forecasting yielded absolute errors of 6.5μg/m3forPM10and 2.7μg/m3for PM2.5. Based on 173 forecasts, we anticipate Prophet model root-mean-square values under 6.26μg/m3and 9.99μg/m3for PM2.5 and PM10in 50% of cases. The Prophet model demonstrates several advantages and yields satisfactory results. In future research, the results obtained from the Prophet model will serve as benchmark values for other models. Additionally, the Prophet model is capable of providing satisfactory air quality forecasting results and will be utilized in future resear
Augmented state estimation of urban settings using on-the-fly sequential Data Assimilation
Get PDFA data-driven investigation of the flow around a high-rise building is per- formed by combining heterogeneous experimental samples and numerical models based on the Reynolds-Averaged Navier–Stokes (RANS) equations. The experimental data, which include velocity and pressure measurements obtained by local and sparse sensors, replicate realistic conditions of future automated urban settings. The coupling between experiments and the nu- merical model is performed using techniques based on the Ensemble Kalman Filter (EnKF), including advanced manipulations such as localization and inflation. The augmented state estimation obtained via EnKF has also been employed to improve the predictive features of the RANS model via opti- mization of the free global model constants of two turbulence models used to close the equations, namely the K − ε and the K − ω SST turbulence models. The optimized inferred values are far from the classical values prescribed as general recommendations and implemented in codes, but also different from other data-driven analyses reported in the literature. The results obtained with this new optimized parametric description show a global improvement for both the velocity and pressure fields. In addition, some topological im- provements for the flow organization are observed downstream, far from the location of the sensors
Хидроелектране као део интегралних речних система складно уклопљених у еколошко, социјално и урбано окружење
Get PDFУ оквиру Просторног плана Србије, све планиране хидроелектране налазе
се у класи тзв. интегралних речних система, и као такве део су и мера за
еколошко уређење простора. Адекватним пројектовањем и управљањем
хидроенергетских система поред њиховог складног уклапања у окружење,
могуће је и побољшавати еколошке услове, посебно у кризним хидролошким
ситуацијама. То постаје посебно значајно у условима климатских
промена, чија је једна од неповољних последица погоршавање екстремних
хидролошких феномена – повећавање великих вода и продужавање
трајања малих вода. Акумулационе ХЕ се могу реализовати у оквиру
вишенаменских система, и њима се могу остваривати и мере активне
одбране од поплава (ублажавање врхова поплавних таласа). Адекватним
диспозицијама могуће је постићи и побољшавање режима малих вода
у кризним периодима, као и управљање температурним и кисеоничним
режимима, према потребама водених екосистема. Каскаде ХЕ на Дрини,
Великој Морави, Ибру – највећим делом су планиране у коритима за
велику воду, тако да се изградња тих ХЕ може синхронизовати са мерама
које се свакако морају реализовати (ојачање и надвишење насипа, ојачање
заптитних касета) за потребе достизања захтеваних степена заштите од
великих вода. Сви ти каскадни системи, са доста стабилизованим нивоима,
омогућавају да се на складан начин уклопе у урбане матрице градова у
приобаљу, како би се та насеља на најбољи начин заиста ,,спустила“ на
водотоке са стабилним акваторијама.
Може се закључити да ХЕ не само да нису ,,реметилачки“ фактор у
еколошком, социјалном и урбаном простору, већ ће, тратиране као део
интегралних речних система и мера уређања простора, бити све важнији
део мера уређења и унапређења животне средине
A Novel Semi-Analytical (Inertial) Solution for Determining Permeability of Highly Pervious Porous Materials Using the Two-Reservoir Laboratory Setup
Get PDFTwo conventional experimental procedures for determination of the water permeability of saturated porous medium are the constant and the falling head permeability tests. The first one is more applicable on more permeable materials where the outflow from the sample is measured at variety of constant water heads, while the second one is more convenient for low permeable materials, utilizing the continuous measurements of the water head falling due to filtration through the saturated sample. However, neither of the two is useful for materials of high permeability and large cross-sectional area. The constant head permeability test faces technical issues since a significant and continuous water discharge is required, while the falling head permeability test has limitations due to neglection of the Forchheimer's high-velocity flow through the sample, but also the influence of inertia on the fluid mass. Here we proposed an approach for determination of the water permeability of saturated porous medium based on the agreement between the measured water level change in two connected reservoirs containing a porous sample and the new semi-analytical expression describing that change by accounting for the mentioned theoretical deficiencies. This efficient approach has been tested on four pervious paver samples, and results showed satisfactory agreement with the constant head permeability data. It has been also confirmed the proposed semi-analytical solution is more accurate than the falling head permeability approach in case of highly pervious materials, while for low permeable materials it reduces to the conventional approach
Nature-based Solutions (NBS) at work and monitoring their performance – the innovative research case of the EU-funded project euPOLIS
Get PDFClimate change impacts are affecting and will continue to widely affect particularly urban areas and their dwellers. These impacts not only come with economic losses, but also directly threaten the health of urban dwellers, as well as the functionality of urban ecosystems in terms of providing ecosystem services (EES) and ensuring habitats for threatened biodiversity. Nature-based Solutions (NBS) are approaches that can tackle many of these impacts by mimicking natural processes.
In this case, the euPOLIS project, aims at creating cities-for-healthy-people by introducing NBS as a common practice in the urban planning methodologies, to locally improve thermal comfort, enhance biodiversity, mitigate pollution, improve climate resilience, provide open areas that stimulate social exchange and inclusivity, and much more, all contributing to enhancing public health and wellbeing (PH&WB) of citizens. By selecting 4 front-runner cities acting as demo-cases in different biogeographical and climatic regions, NBS are designed and tailored to each urban environment characteristics and problems. An innovative urban planning methodology that actively engage citizens is firstly developed, then tested and finally put into practice in all FR cities and resulting into a set of NBS interventions which aim to enhance the outdoor environmental conditions of the sites, supporting and promoting increased physical activity of citizens (as a precursor for health and well-being enhancements) and providing ground for socio-cultural and business improvements. These NBSs are then, implemented and constructed on each site, and carefully monitored before, under and after construction in order to measure their expected impacts.
The monitoring phase is based on an exhaustive data collection approach of different variables (environmental, social, public health and well-being, urban), which together with the posterior data analysis are expected to be important research tools and methodologies allowing to withdraw evidence-based conclusions of the NBS impacts. Different approaches to monitor NBS will be used, such as biodiversity surveys and environmental modelling, that in combination with in-situ sensors and satellite imagery and will provide insights about the environmental status of the site. In addition, the use of wearables together with health apps will help to determine the effects on PH & WB of citizens. Finally, questionaries on-site along with other qualitative methods will help to shed light on the enhanced social and economic conditions. NBS implemented in the project sites will therefore cover a multi-disciplinary consortium, actively engage citizens for consultation in all phases of the project and have a strong focus on PH & WB with the assessment of multiple co-benefits the solutions can provide. The enhanced EES by the newly introduced NBS, are expected to revitalize the urban ecosystems, protect local biodiversity and by doing so, regenerate the economic, social, cultural aspects of the site. Finally, this process is expected to directly/indirectly improve PH & WB in the demonstration sites.
The euPOLIS Project is on-going and expected to finish by August 2024, when the results and conclusions of the developed urban planning methodologies and NBS impacts on PH&WB will be shared, discussed and potentially scaled-up in other urban environments impacted by climate change
Upscaling and downscaling landslide susceptibility maps
Get PDFAlthough without official standardization, landslide susceptibility models (LSM) have entered preliminary stages of design and planning practice worldwide. As design and planning itself undergoes from lower to higher level of detail, different scales of LSM apply. Nevertheless, the LSMs are mainly produced in regional scales, whereas national and local are rarely available. Limitations of downscaling and upscaling LSMs are considered herein, by comparing LSMs coming from continental scale on one hand, and regional scale on the other, while the validation was performed using national scale model (Figure 1) at 30 m pixel resolution. Pan- European model (Wilde et al. 2018) is downscaled from 200 to 30 m pixel resolution using re-gridding method based on various interpolation techniques (linear, spline, Kriging) over the area of the City of Doboj in Republic of Srpska (Bosnia and Herzegovina). The LSM for the City of Doboj (Sandić et al. 2023) was upscaled from 5 to 30 m resolution using various resampling techniques (nearest neighbor, bilinear interpolation and cubic convolution). All maps were made using heuristic or combined heuristic approaches with standard landslide conditioning factors as raster inputs (geological, geomorphological, environmental, etc.). The best performing downscaling option was spline interpolation, while cubic convolution gave the best match against the referent LSM for the upscaling. Other downscaling variants tend to pixelate the map at 30 m resolution, whereas upscaling was not that considerably affected by technique choice. For large scale urban planning and preliminary design it is important to avoid pixilation as much as possible and smoothen the susceptibility classes so they can be compared against various elements, such as road and railway network features (higher-order curves, bridges, tunnels) and urban fabric footprints (housing, industrial, infrastructure). Results indicate that downscaling can be misleading and should be avoided if there is time and resource to perform appropriate local or regional scale LSM
Hankel determinant of second order for inverse functions of certain classes of univalent functions
Get PDFIn this paper we determine mainly sharp upper bounds for the Hankel
determinant of second order for the inverse functions of functions from some
classes of univalent functions
