On the constraints violation in forward dynamics of multibody systems

It is known that the dynamic equations of motion for constrained mechanical multibody systems are frequently formulated using the Newton-Euler’s approach, which is augmented with the acceleration constraint equations. This formulation results in the establishment of a mixed set of partial differential and algebraic equations, which are solved in order to predict the dynamic behavior of general multibody systems. The classical resolution of the equations of motion is highly prone to constraints violation because the position and velocity constraint equations are not fulfilled. In this work, a general and comprehensive methodology to eliminate the constraints violation at the position and velocity levels is offered. The basic idea of the described approach is to add corrective terms to the position and velocity vectors with the intent to satisfy the corresponding kinematic constraint equations. These corrective terms are evaluated as function of the Moore-Penrose generalized inverse of the Jacobian matrix and of the kinematic constraint equations. The described methodology is embedded in the standard method to solve the equations of motion based on the technique of Lagrange multipliers. Finally, the effectiveness of the described methodology is demonstrated through the dynamic modeling and simulation of different planar and spatial multibody systems. The outcomes in terms of constraints violation at the position and velocity levels, conservation of the total energy and computational efficiency are analyzed and compared with those obtained with the standard Lagrange multipliers method, the Baumgarte stabilization method, the augmented Lagrangian formulation, the index-1 augmented Lagrangian and the coordinate partitioning method.The first author expresses his gratitude to the Portuguese Foundation for Science and Technology through the PhD grant (PD/BD/114154/2016). This work has been supported by the Portuguese Foundation for Science and Technology with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941.info:eu-repo/semantics/publishedVersio

Nitrogen mineralization and denitrification in Lake Michigan sediment

Organic nitrogen mineralization mechanisms, fluxes, and fates in Lake Michigan sediments were examined by measuring accumulation rates of inorganic nitrogen in laboratory microcosms. Neither ammonium nor nitrate increased substantially in flow-cell or slurry microcosms of offshore, silty sediments. In experiments with gastight chambers containing intact offshore, silty sediment cores (sampled at 45- and 100-m water depths), the total fluxes of nitrogen (NH4+, N03-, and N2) across the sediment-water interface ranged from 14 to 51 µg-atoms N m-2 h-1. Nitrogen gas accounted for 93-98% of the total inorganic nitrogen flux from the sediment to the water. Inputs of inorganic nitrogen via mineralization processes (mediated by microbial decomposition and invertebrate excretion) appeared to be the major factors controlling the rates of both nitrification and denitrification in these sediments. The overlying water did not serve as a significant net source of nitrate driving the denitrification reaction. These results thus indicate that denitrification is a dominant sink for mineralized nitrogen in these silty Lake Michigan sediments and that this process is closely coupled with the initial mineralization of organic nitrogen in the sediments

Zmieność przestrzenna całkowitej zawartości rtęci w poziomie powierzchniowym gleb obszaru Pojezierza Gnieźnieńskiego

The paper presents the results of total mercury content in terms of pollution of agricultural soils of Gniezno Lakeland by this element, as well as spatial characteristics of this metal. Statistical relationship between content of mercury in arable-humous horizon and active, exchangeable and hydrolytic acidity, organic carbon and total nitrogen was also demonstrated. For the analysis 213 bulk samples from surface horizons were collected. The total mercury content in selected soil samples were determined by mercury analyzer AMA 254. The precision of the method and obtained results was confirmed with reference material TILL-3 (Certificate of Analysis 1995) and S-VM (Certificate Czechoslovak Reference Material) for Hg determination. Physical and chemical properties of soil samples were determined following standard procedures. Statistical analysis of results was evaluated on the basis of computer programme “STATISTICA” 6.0 PL. Studies of the total mercury content showed relatively small differences in the concentrations of the element in analyzed area. The total mercury content ranged from 0.0081 to 0.1620 mg kg–1, and only in the one case exceeded the average natural concentration of this element. On the basis of statistical analysis between the total mercury content and selected physicochemical properties of soil such as pH in H2O, pH in KCl, hydrolytic acidity, organic carbon and total nitrogen was found that there are average correlations by Pearson (0.3 rxy < 0.5).W pracy przedstawiono wyniki badań całkowitej zawartości rtęci w aspekcie zanieczyszczenia gleb uprawnych Pojezierza Gnieźnieńskiego tym pierwiastkiem, a także specyfiki rozmieszczenia przestrzennego tego metalu. Oceniono również statystyczne zależności pomiędzy zawartością rtęci a kwasowością czynną, wymienną i hydrolityczną, zawartością węgla organicznego oraz ogólną zawartością azotu. Do analiz pobrano 213 zbiorczych próbek z powierzchniowych poziomów ornopróchnicznych. Całkowitą zawartość rtęci w wybranych do analiz próbkach glebowych oznaczono w analizatorze rtęci AMA 254. Dokładność zastosowanej procedury analitycznej oznaczania Hg potwierdzono na podstawie analizy certyfikowanego materiału odniesienia TILL-3 oraz S-VM. Właściwości fizykochemiczne próbek glebowych oznaczono metodami analitycznymi ogólnie przyjętymi w gleboznawstwie. Analizę statystyczną wyników badań przeprowadzono za pomocą programu komputerowego "STATISTICA" 6.0 PL. Badania całkowitej zawartości rtęci wykazały stosunkowo niewielkie zróżnicowanie stężenia tego pierwiastka na analizowanym obszarze. Całkowita zawartość rtęci wahała się w zakresie od 0,0081 do 0,1620 mg kg-1, i tylko w jednym przypadku przekroczyła naturalne średnie stężenie tego pierwiastka. Na podstawie przeprowadzonych obliczeń zależności statystycznych pomiędzy całkowitą zawartością rtęci i wybranymi właściwościami fizykochemicznymi ornopróchniczych poziomów gleb uprawnych, tj. kwasowością czynną, wymienną i hydrolityczną, zawartością węgla organicznego oraz ogólną zawartością azotu stwierdzono, że pomiędzy badanymi zmiennymi występują przeciętne statystycznie korelacje wg Pearsona (0,3 rxy < 0,5)

Właściwości gleb w otoczeniu Zakładów Przemysłu Wapienniczego Trzuskawica S.A., Zakład Kujawy

Effect of pollutants emitted by plants Trzuskawica Lime Industry S.A., Department of Kujawy and Lafarge “Cement” on the physicochemical properties of soils in this region, mainly pH and the state of exchangeable complex was studied. Soil samples were collected in late August and September 2007, during post-harvest. There were 16 soil samples selected from arable-humus horizon, from the area of about 4000 m2. In the samples taken for analysis active and exchangeable acidity, hydrolytic acidity, calcium carbonate, total exchangeable cations, and organic C content were determined. Statistical analysis was performed using STATISTICA 8.0 PL programme. As a result of the studies there were found a high degree of soils alkalization, due to high accumulation of lime pollutants emitted in the past, and high natural content of calcium carbonate in soils in the vincinity of plants. The highest share of Ca2+ ions in the cation exchangeable capacity of soil complex there was found. The degree of cation saturation of analyzed soils and their cation exchange capacity was significantly related to the content of alkaline cations. Comparison of results from the years 1992–2007 indicates a continuing high pH values and the nature of saturation of soil exchangeable complex due to the presence of exchangeable calcium in the soils surrounding Trzuskawica Lime Plant Industry S.A., Department of Kujawy and Lafarge “Cement”. Based on the studies can not be determine the impact of each individual, the two largest plants, emitting limestone pollutants, on the environment in their surroundings.Przedmiotem badań był wpływ zanieczyszczeń emitowanych przez Zakłady Przemysłu Wapienniczego Trzuskawica S.A., Zakład Kujawy i Lafarge "Cement", na fizykochemiczne właściwości gleb uprawnych w tym rejonie, przede wszystkim odczyn i stan kompleksu sorpcyjnego. Próbki gleb do badań zostały pobrane na przełomie sierpnia i września 2007 r., w okresie pożniwnym. Do badań wytypowano 16 próbek glebowych z poziomu ornopróchnicznego, z obszaru o powierzchni około 4000 m2. W pobranych do analizy próbkach oznaczono kwasowość czynną i wymienną, kwasowość hydrolityczną oraz zawartość węglanu wapnia, zasadowych kationów wymiennych i C-organicznego. Obliczenia statystyczne wykonano z wykorzystaniem programu komputerowego STATISTICA 8.0 PL. Na podstawie przeprowadzonych badań stwierdzono wysoki stopień alkalizacji gleb, wynikający z dużej akumulacji zanieczyszczeń wapiennych emitowanych w przeszłości oraz dużej naturalnej zawartości węglanu wapnia w glebach w otoczeniu zakładów. Największy udział w kationowej pojemności wymiennej kompleksu sorpcyjnego miały jony Ca2+. Stopień wysycenia analizowanych gleb zasadami oraz ich pojemność sorpcyjna były istotnie związane z zawartością kationów o charakterze zasadowym. Porównanie wyników badań z lat 1992-2007 wskazuje na utrzymujące się duże wartości pH i stopnia wysycenia zasadami glebowego kompleksu sorpcyjnego, spowodowany obecnością wymiennych form wapnia w glebach w otoczeniu Zakładów Przemysłu Wapienniczego Trzuskawica S.A., Zakład Kujawy i Lafarge "Cement". Na podstawie przeprowadzonych badań nie można określić wpływu każdego z osobna, dwóch największych zakładów, emitujących zanieczyszczenia wapienne, na stan gleby w ich otoczeniu

Mercury in the soils of the hunting plots and the surrounding forests

Some trace elements, because of their high capacity for bioaccumulation, can pose a threat to the adequate development and growth of plants, animals and humans, which concerns mostly mercury (Hg) and its compounds that characterize by strong toxic properties. The aim of the research was to compare the Hg content in the Arenosols of arable fields (food plots), referred to as hunting plots, as well as in the soils of neighbouring forests. Research was performed in the Szubin Forest District (northern Poland). To assess the effect of mercury on the environment, we used dandelion (Taraxacum officinale) as a bioindicator. The samples were collected from the soil profiles from 8 hunting plots and 8 woodland areas in close vicinity of these plots. Mercury was assayed with the atomic absorption spectrometry applying the AMA 254 analyser. The mercury contamination factor (CF) and the potential ecological risk index (Er) values were determined with the local Hg value of the geochemical background (5.7 µg/kg). Assuming such very low Hg concentration as the reference value for the parent material of the soils, the mean CF value points to a considerable anthropogenic mercury accumulation in the surface horizons. The soils of hunting plots as well as forest soils are not contaminated with mercury. The total Hg content falls within the natural content level and reaches in the mineral horizons – from 3.5 to 20.7 µg/kg, while in the litter layer – from 60.3 to 166.7 µg/kg. The mercury bioconcentration factor (BCF) and translocation factor (TF) values point to a clear accumulation in the aboveground parts of dandelion. We found a significantly positive correlation between the content of mercury and organic carbon as well as the clay fraction. The mercury content in the soils under study varies and it depends on the soil origin and the effect of anthropogenic factors. In the forest soils of the Pomorze and Kujawy Province the mercury content of the geochemical background is relatively low. The areas of the Szubin Forest District do not undergo an excessive anthropopressure and sources of Hg depositions in soil surfaces can be the deposition of mercury from air