The wavelet-based theory of spatial naturally curved and twisted linear beams

The paper presents the wavelet-based discretization of the linearized finite-strain beam theory which assumes small displacements, rotations and strains but is capable of considering an arbitrary initial geometry and material behaviour. In the numerical solution algorithm, we base our derivations on the vector of strain measures as the only unknown functions in a finite element. In such a way the determination of the beam quantities does not require the differentiation. This is an important advantage which allows a wider range of shape functions. In the present paper, the classical polynomial interpolation is compared to scaling and wavelet function interpolations. The computational efficiency of the method is demonstrated by analyzing initially curved and twisted beams

The quaternion-based three-dimensional beam theory

This paper presents the equations for the implementation of rotational quaternions in the geometrically exact three-dimensional beam theory. A new finite-element formulation is proposed in which the rotational quaternions are used for parametrization of rotations along the length of the beam. The formulation also satisfies the consistency condition that the equilibrium and the constitutive internal force and moment vectors are equal in its weak form. A strict use of the quaternion algebra in the derivation of governing equations and for the numerical solution is presented. Several numerical examples demonstrate the validity, performance and accuracy of the proposed approach. (C) 2009 Elsevier B.V. All rights reserved

Dynamics of spatial beam structures using quaternion parametrization of ro- tations

In the present thesis a new formulation of the three dimensional geometrically exact Reissner beam theory based on quaternion algebra is presented. Rotations are fully replaced by rotational quaterni- ons. The same approach is used for both linearization and the numerical implementation. The finite element method for solving nonlinear differential equations is presented where the kinematic quantities displacements and rotational quaternions are choosen as the primary unknown functions. Equations are discretizied by collocation mehod and primary unknowns are interpolated. The interpolation and the collocation points coincide. At internal nodes the formulation satisfies the weak equality of equilibrium and constitutive internal forces, while the equilibrium equations are satisfied at the edges of the beam. The present family of finite elements for static and dynamic analysis allows arbitrary initial geometry and a general form of the constitutive law describing the material of the beam. The static equations are solved using the Newton iteration procedure for solving nonlinear equations. For the update procedure of the rotational quaternion and other non-aditive quantities special formulae are derived. Proposed nume- rical method does not suffer from shear locking phenomenon and the choosen interpolation of rotational quaternions is objective with respect to conservation of strains with rigid body motion. For time inte- gration two different approaches are presented: the classic Runge-Kutta method and the combination of the extension of the Newmark discretization algoritm to the quaternion parametrization of rotation and the Newton iteration method. For both approaches the algebraic boundary condition are modified to the differential form with respect to time. The first integration method does not require the linearized equations however it has been developed for the sistem of first-order differential equations and the beam equations must be written this way while the second approach properly considers the nonlinearity of the rotations and related quantities and is directly applicable for solving second-order differential equations. Finally the moving mass problem is studied. Mass moves along the centroid line of a beam according to the motion equation of the moving mass which is coupled with the system for governing equations of spatial beams under dynamic loading. The geometry of the beam as well as the boudary and initial conditions of the beam and the mass are arbitrary

Integrating rotation from angular velocity

Abstract\ud The integration of the rotation from a given angular velocity is often required in practice. The present paper explores how the choice of the parametrization of rotation, when employed in conjuction with different numerical time-integration schemes, effects the accuracy and the computational efficiency. Three rotation parametrizations – the rotational vector, the Argyris tangential vector and the rotational quaternion – are combined with three different numerical time-integration schemes, including classical explicit Runge–Kutta method and the novel midpoint rule proposed here. The key result of the study is the assessment of the integration errors of various parametrization–integration method combinations. In order to assess the errors, we choose a time-dependent function corresponding to a rotational vector, and derive the related exact time-dependent angular velocity. This is then employed in the numerical solution as the data. The resulting numerically integrated approximate rotations are compared with the analytical solution. A novel global solution error norm for discrete solutions given by a set of values at chosen time-points is employed. Several characteristic angular velocity functions, resulting in small, finite and fast oscillating rotations are studied

Determination of strain correction factors for bridge weigh-in-motion systems

The paper presents an automatic procedure for the correction of bridge weigh–in‐motion (B‐WIM) measurements, which are used to determine the axle loads of heavy vehicles using instrumented bridges. According to the European Specifications for Weigh‐in‐Motion criteria, using this procedure the weighing results could be improved by up to one accuracy class. Whereas measurements performed on steel structures provide reliable information about the global behaviour of individual bridges, which is accounted for in the\ud B‐WIM algorithms, cracks that are present in concrete structures can, depending on their locations with respect to installed strain transducers, amplify or reduce the response. In the present work special care was taken to detect and calibrate any strain transducer which showed a disproportional response. The accuracy of the method was investigated numerically in relation to the extensive data which were available in the case of a reinforced concrete bridge (motorway underpass), located near Ljubljana, Slovenia, and then validated by a one‐to‐one comparison of the B‐WIM weighing results and the\ud statically weighed test vehicles

Obravnava bolnikov z neklonsko eritrocitozo

Eritrocitoza je stanje povečane skupne mase eritrocitov, ki se pojavi zaradi zelo heterogenih vzrokov. Bolniki so lahko brez simptomov ali pa imajo simptome in znake povečane viskoznosti krvi. Pri obravnavi bolnika z eritrocitozo uporabljamo diagnostični algoritem, ki omogoča opredelitev vzroka eritrocitoze in ustreznega zdravljenja. V prvem koraku potrjujemo absolutno eritrocitozo s koncentracijo hemoglobina (Hb) > 185 g/L in/ali hematokritom (Ht) > 0,52 za moške ter s Hb > 165 g/L in/ali Ht > 0,48 za ženske. V drugem koraku hkrati izključujemo pravo policitemijo in iščemo sekundarne pridobljene vzroke eritrocitoze, kot so bolezni pljuč, srca, ledvic, tumorji z neustreznim izločanjem eritropoetina. Omeniti velja, da je po smernicah Svetovne zdravstvene organizacije (SZO) diagnosticiranje prave policitemije ob ustrezni klinični sliki določeno že pri nižjih vrednostih, natančneje ob Hb > 165 g/L ali Ht > 0,49 za moške ter Hb > 160 g/L ali Ht > 0,48 za ženske. V tretjem koraku bolnike, ki nam jih ni uspelo opredeliti kljub natančnim diagnostičnim preiskavam, napotimo na genetsko testiranje za opredelitev prirojene eritrocitoze. Ko izključimo pravo policitemijo, sekundarno pridobljeno in prirojeno eritrocitozo, ostane skupina oseb s t. i. idiopatsko eritrocitozo. Priporočeno zdravljenje je odvisno od vzroka eritrocitoze, najpogosteje pa vključuje jemanje acetilsalicilne kisline in ustrezno zniževanje hematokrita z venepunkcijami ob rednih kontrolah krvne slike

Welfare and meat quality of lambs

Recently, in many parts of the world, greater importance has been given to lamb meat as well as to the intensive production of lamb and sheep, due to demand for this type of meat at affordable prices. In Serbia, similar to most European countries, the structure of total sheep meat production comprises about 70% lamb meat and 30% sheep meat. This study assessed resource-based measures on 11 dairy sheep farms and investigated, in a total of 30 lambs, the effects of sex, the presence of bruises and pneumonia in carcasses, and carcass and meat quality. Carcass (carcass length, thigh length, croup width, subcutaneous fat thickness, presence of bruises) and meat quality (pH, temperature, drip, thawing and cooking losses, color, and meat quality classes) traits were measured post mortem. The most common deficiencies on farms were high stocking density, poor hygienic conditions, dirty drinkers, and lack of outdoor access. Regarding sex differences, higher prevalences of carcass bruises and severe pneumonia were recorded in male lambs. Meat pH (pH45min), sensory color score, and prevalence of dark, firm and dry (DFD) meat were higher in lambs with carcass bruises. The occurrence of quality defects (DFD meat) was higher in lambs with severe pneumonia. It can be concluded that it is necessary to improve the welfare conditions on the lamb farms and pre-slaughter conditions in order to achieve better lamb meat quality.U mnogim delovima sveta, sve više se daje na značaju jagnjećem mesu kao i intenzivnom načinu gajenja jagnjadi i ovaca, usled velike potražnje za jagnjadima po povoljnim cenama. U Srbiji, kao i u najvećem broju zemalja Evrope, akcenat je stavljan na jagnjeće meso, pri čemu u strukturi ukupne proizvodnje ovčijeg mesa oko 70% čini zaklana jagnjad, a ostatak ovce i ovnovi. U ovom istraživanju, ispitani su uslovi dobrobiti na 11 farmi ovaca na osnovu indirektnih pokazatelja, kao i uticaj pola, prisustva modrica i pneumonije na kvalitet trupa i mesa 30 jagnjadi. Postmortem su određivani pokazatelji kvaliteta trupa (dužina trupa, dužina buta, širina sapi, prekrivenost trupa masnim tkivom, prisustvo pneumonija, konformacija i prisustvo modrica) i mesa tovnih jagnjadi (pH, temperatura, sposobnost vezivanja vode mesa, boja mesa, klase kvaliteta mesa). Najčešći nedostaci na ispitivanim farmama su velika gustina naseljenosti, loši higijenski uslovi, prljave pojilice, kao i nedostatak ispusta. Kod muške jagnjadi utvrđen je veći procenat modrica na trupu i patoloških promena na plućima, u odnosu na žensku jagnjad. Kod jagnjadi sa modricama na trupu utvrđena je viša pH (pH45min) vrednost mesa i senzorna ocena za boju mesa, kao i veća učestalost tamnog, suvog i čvrstog (TČS) mesa. Učestalost TČS mesa bila je veća kod jagnjadi sa teškom pneumonijom. Na osnovu rezultata može se zaključiti da je neophodno poboljšati uslove dobrobiti jagnjadi na farmi i tokom postupanja sa jagnjadima pre klanja, kako bi se dobilo meso boljeg kvaliteta

Novi i značajni podaci o biljkama, algama i gljivama iz JI Evrope i susednih regiona, 10

This paper presents new records and noteworthy data on the following taxa in SE Europe and adjacent regions: red algae Lemanea rigida and Paralemanea torulosa, mycorrhizal fungi Amanita simulans and Terfezia pseudoleptoderma, parasitic fungus Microbotryum vinosum, saprotrophic fungus Sarcoscypha jurana, stonewort Chara tenuispina, mosses Brachytheciastrum collinum and Meesia longiseta, monocots Dactylorhiza romana and Neotinea maculata and dicots Adenophora liliifolia, Ambrosia artemisiifolia and Tanacetum corymbosum subsp. cinereum are given within SE Europe and adjacent regions.U radu su prikazani novi i značajni podaci sa područja JI Evrope i susednih regiona o sledećim taksonima: crvenim algama Lemanea rigida i Paralemanea torulosa, mikorizalnim gljivama Amanita simulans i Terfezia pseudoleptoderma, parazitskoj gljivi Microbotryum vinosum, saprofitnoj gljivi Sarcoscypha jurana, pršljenčici Chara tenuispina, mahovinama Brachytheciastrum collinum i Meesia longiseta, monokotilama Dactylorhiza romana i Neotinea maculata i dikotilama Adenophora liliifolia, Ambrosia artemisiifolia i Tanacetum corymbosum subsp. cinereum

Frequency drift in MR spectroscopy at 3T

Purpose: Heating of gradient coils and passive shim components is a common cause of instability in the B-0 field, especially when gradient intensive sequences are used. The aim of the study was to set a benchmark for typical drift encountered during MR spectroscopy (MRS) to assess the need for real-time field-frequency locking on MRI scanners by comparing field drift data from a large number of sites.Method: A standardized protocol was developed for 80 participating sites using 99 3T MR scanners from 3 major vendors. Phantom water signals were acquired before and after an EPI sequence. The protocol consisted of: minimal preparatory imaging; a short pre-fMRI PRESS; a ten-minute fMRI acquisition; and a long post-fMRI PRESS acquisition. Both pre- and post-fMRI PRESS were non-water suppressed. Real-time frequency stabilization/adjustment was switched off when appropriate. Sixty scanners repeated the protocol for a second dataset. In addition, a three-hour post-fMRI MRS acquisition was performed at one site to observe change of gradient temperature and drift rate. Spectral analysis was performed using MATLAB. Frequency drift in pre-fMRI PRESS data were compared with the first 5:20 minutes and the full 30:00 minutes of data after fMRI. Median (interquartile range) drifts were measured and showed in violin plot. Paired t-tests were performed to compare frequency drift pre- and post-fMRI. A simulated in vivo spectrum was generated using FID-A to visualize the effect of the observed frequency drifts. The simulated spectrum was convolved with the frequency trace for the most extreme cases. Impacts of frequency drifts on NAA and GABA were also simulated as a function of linear drift. Data from the repeated protocol were compared with the corresponding first dataset using Pearson's and intraclass correlation coefficients (ICC).Results: Of the data collected from 99 scanners, 4 were excluded due to various reasons. Thus, data from 95 scanners were ultimately analyzed. For the first 5:20 min (64 transients), median (interquartile range) drift was 0.44 (1.29) Hz before fMRI and 0.83 (1.29) Hz after. This increased to 3.15 (4.02) Hz for the full 30 min (360 transients) run. Average drift rates were 0.29 Hz/min before fMRI and 0.43 Hz/min after. Paired t-tests indicated that drift increased after fMRI, as expected (p &lt; 0.05). Simulated spectra convolved with the frequency drift showed that the intensity of the NAA singlet was reduced by up to 26%, 44 % and 18% for GE, Philips and Siemens scanners after fMRI, respectively. ICCs indicated good agreement between datasets acquired on separate days. The single site long acquisition showed drift rate was reduced to 0.03 Hz/min approximately three hours after fMRI.Discussion: This study analyzed frequency drift data from 95 3T MRI scanners. Median levels of drift were relatively low (5-min average under 1 Hz), but the most extreme cases suffered from higher levels of drift. The extent of drift varied across scanners which both linear and nonlinear drifts were observed.</p

Terrestrial Very-Long-Baseline Atom Interferometry:Workshop Summary

This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more km-scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions