Search results for " element"
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Augsnes piesārņojuma ar smagajiem metāliskajiem elementiem izvērtējums dzelzceļa apkārtnē
2018
Augsnes piesārņojuma ar smagajiem metāliskajiem elementiem izvērtējums dzelzceļa apkārtnē. Jansons Ā., zinātniskais vadītājs Dr. chem., doc. Osīte A. Bakalaura darbs, 52 lappuses, 21 attēls, 7 tabulas, 25 literatūras avoti, 5 pielikumi. Latviešu valodā. Darba ietvaros ir veikta smago metālisko elementu – dzelzs, mangāna, vara, cinka, niķeļa un svina jonu kvantitatīvā analīze augsnes paraugos, kas ievākti Torņakalna, Jāņavārtu, Dārziņu un Kūdras dzelzceļa staciju apkārtnē – blakus stacijai (vilcienu bremzēšanas ceļa sākumā) un atstatus no tās. Vispirms tika veikta ievākto augsnes paraugu sagatavošana mineralizācijai (žāvēšana, homogenizēšana, sijāšana). Augsnes paraugu matricas sagraušana ti…
Lauksaimniecības augsnes ķīmiskā sastāva izvērtējums pēc dažādu mēslošanas līdzekļu iestrādes
2015
Darbā analizēti augsnes un zālaugu paraugi uz vieglo stabilo izotopu attiecību masspektrometriju, sadarbojoties ar Latvijas Valsts mežzinātnes institūtu „Silava”. Paraugi iegūti no Viduslatvijas, Skrīveriem. Augsnes paraugiem noteikts augsnes pH, cinks, mangāns, varš, svins, niķelis, kadmijs un kobalta saturs. Iegūtie rezultāti tika izvērtēti.
Metālisko elementu saturs augsnē Liepājas Ziemeļu Fortu teritorijā
2019
Metālisko elementu saturs augsnē Liepājas Ziemeļu fortu teritorijā. Butkus D., darba vadītāja Mg. chem., lektore Balcerbule Z. Bakalaura darbs, 45 lappuses, 21 attēls, 18 tabulas, 32 literatūras avoti, 4 pielikumi. Latviešu valodā. Darbā ir veikta metālisko elementu analīze Ziemeļu fortu teritorijā ņemtajos augsnes paraugos. Augsnes izvilkumi gatavoti HNO3 šķīdumos, veikta arī mineralizācija ar mikroviļņu enerģiju. Elementu koncentrācijas tika noteiktas ar liesmas atomabsorbciometrijas un ICP – MS metodēm. Iegūtie rezultāti tika salīdzināti ar LR MK augsnes un grunts kvalitātes normatīviem un literatūrā pieejamiem datiem.
Energy analysis of a non-linear dynamic impact using FEM
2014
In the car industry, the Finite Element Method (FEM) is being more and more used to analyze the crashworthiness performance of vehicles. In order to validate the results, these impact simulations are normally compared with real crash footage and acceleration data. This paper studies the deformation- and energy output of a simple dummy model during a non-linear dynamic impact. The dummy model is crashed into an obstacle at three different velocities to observe the energy dissipated through different damping mechanisms. Furthermore, in impact simulations, material damping plays an important role in energy dissipation. However, it can be difficult to determine realistic damping parameter value…
Modelling Aspects in Accumulative Roll Bonding process by Explicit Finite Element Analysis
2013
Accumulative Roll-Bonding (ARB) process is a severe plastic deformation (SPD) process, capable of developing grains below 1 μm in diameter and improving mechanical properties of the material. In this study, the authors compared two different FE-codes with respect of its applicability for numerical analysis of the ARB process. Modelling this process was achieved using the explicit code for Abaqus/CAE both in 2D and 3D. The proposed model was used to assess the impact of ARB cycles on the final material properties. The numerical results in 2D and 3D were compared and contrasted. The research work presented in this paper is focused on the simulation optimization based on CPU time minimization.…
Geochemistry of REE, Zr and HF in a wide range of pH and water composition: The Nevado del Ruiz volcano hydrothermal system (Colombia)
2015
International audience; The geochemical behaviour of Rare Earth Elements, Zr and Hf was investigated in the thermal waters of Nevado del Ruiz volcano system. A wide range of pH, between 1.0 and 8.8, characterizes these fluids. The acidic waters are sulphate dominated with different Cl/SO4 ratios. The important role of the pH and the ionic complexes for the distribution of REE, Zr and Hf in the aqueous phase was evidenced. The pH rules the precipitation of authigenic Fe and Al oxyhydroxides producing changes in REE, Zr, Hf amounts and strong anomalies of Cerium. The precipitation of alunite and jarosite removes LREE from the solution, changing the REE distribution in acidic waters.Y–Ho and Z…
Dissemination of a Carbapenem-Resistant Acinetobacter baumannii Strain Belonging to International Clone II/Sequence Type 2 and Harboring a Novel AbaR…
2013
ABSTRACT An outbreak of hospital-acquired Acinetobacter baumannii infections, caused by a bla OXA-23 -positive carbapenem-resistant strain belonging to international clone II/ST2, was detected in Latvia. The strain was partially equipped with the armA gene and the intI1-aacA4-catB8-aadA1-qacE Δ 1 class 1 integron. In addition, the strain carried AbaR25, a novel AbaR4-like resistance island of ∼46,500 bp containing structures similar to the previously described AbaR22 and Tn 6167 islands. AbaR25 was characterized by the occurrence of a second copy of Tn 6022a interrupted by Tn 2006 carrying the bla OXA-23 gene.
Technical Note: Prediction Models of Airborne Sound Insulation of Multilayer Materials with Viscoelastic Thin Sheets
2008
The growing introduction of new insulation materials in building acoustics has caused an increase of the importance of the prediction tools. Appropriate simulations allow strictly necessary laboratory measurements to be identified. In this way, costs are reduced. The demands of new legislation has resulted in the appearance of various software designed to facilitate prediction. The prediction models are based on different hypotheses: adaptation of impedances, spatial behaviour of spectral components, statistical energy distribution, the Finite Element Method (FEM), etc. Each of these models and methods offer advantages and contain limitations. In this paper, different models for prediction…
A SYMMETRIC AND POSITIVE DEFINITE BEM FOR 2-D FORCED VIBRATIONS
1997
A BEM formulation for 2D elastodynamics in the time domain has been presented. The formulation gives a resolving system that involves boundary displacements only. The stiffness and mass matrices of the boundary discretized body are frequency independent, symmetric and positive definite
Complex power distribution analysis in plates covered with passive constrained layer damping patches
2012
International audience; The vibration of a plate partially covered with a passive constrained layer damping (PCLD) patch is studied from an energetic point of view. The damped plate is excited by an acoustic plane wave. The study is done with a numerical two-dimensional multilayer plate model. Results of the present model are compared to those obtained with three-dimensional finite element models. It is shown that the present model gives accurate results, even for the layer's inner behavior. It is less expansive in terms of computational cost; hence, it can simulate efficiently the structure for higher frequencies. Mathematical formulas for complex mechanical power are presented, and the li…