The paper presents linearized coefficients for finite-length journal bearings based on the HD forces with multiplicative correction polynomials applied to the infinitely short and the infinitely long ...solutions under the assumption of π-film boundary condition. Based on the linear theory, stability thresholds and their dependence on the length-to-diameter ratio are investigated. Moreover, using the numerical continuation method the change of the generalized Hopf bifurcation which separates regions with subcritical and supercritical Hopf is documented. All results are compared with those of the solution obtained using the finite differences method.
•Stiffness and damping coefficients for the finite-length journal bearings.•Analysis of the influence of length-to-diameter ratio on the dynamic coefficients.•Stability analysis of a single finite-length bearing using Routh-Hurwitz criterion.•Determination of stability curve properties using numerical continuation.•Comparison with FDM-based solution.
This paper introduces a method for identifying internal resonance regimes in free-vibrating systems with multiple nonlinear couplings, illustrated using a chain of two Rott’s pendula. The method ...based on decomposing Hamiltonian and subsequent treatment of the coupling energies allows for a comprehensive understanding of autoparametric system behaviour. A novel signal-processing-based coupling energy evaluation significantly enhances the effectiveness of the method, revealing internal resonances with slow energy exchange. In the theoretical part, a general step-by-step procedure applicable to any conservative coupled oscillators is introduced. We demonstrate that concerning such free-vibrating systems, the proposed method effectively uncovers internal resonances influenced by system parameters, initial conditions, and the initial energy of the system. Through an illustrative example of the system with multiple quadratic couplings, we also show that slow energy exchange occurs for sum and difference internal resonances.
•Identifying internal resonances using decomposition of Hamiltonian.•General procedure applicable to any conservative oscillator.•Novel signal-processing boosts efficiency, revealing slow energy exchange modes.•Illustrative demonstration via chain of two Rott’s pendula.
This article presents an energy-based method for examining the dynamics of an autoparametric double pendulum with quadratic coupling. The method is based on decomposing the total energy (Hamiltonian) ...into partial terms and studying these terms in the time domain. The article then demonstrates using this method to analyse internal resonances in various regimes, including regular periodic, quasiperiodic, and chaotic motion. This study also explores higher-order resonances linked to the geometric tuning parameter and initial energy, which enrich the complexity of the system. The work focuses on identifying conditions that lead to the development of internal resonances and analysing energy exchange mechanisms at various initial energy levels. This analysis uses Fast Lyapunov Indicators and Poincaré maps for these higher energy levels to identify chaotic regimes. Within these regimes, the assessment of coupling energy contributes to a deeper understanding of the studied system. Moreover, the research demonstrates how energy-based methods can be used to investigate auto-parametric systems.
•Energy-based approach for autoparametric pendulum with quadratic coupling.•In-depth exploration of internal resonances across motion types.•Chaos detection using Fast Lyapunov Indicators.•Higher-order resonances linked to system parameters revealed.•Method applicable for various autoparametric systems.
•Various approaches to the linearization of floating ring bearings.•Estimation of instability regions using enhanced Campbell diagrams.•Comparison of the linear analysis results with fully nonlinear ...run-up simulations.
A floating-ring bearing (FRB) is composed of a journal, a floating ring and a housing which are separated by two thin oil films. This system is inherently nonlinear and if it is lightly loaded or operated at high speeds, it is prone to the fluid-induced instability. The threshold speed for the instability of a journal bearing with one oil film can be estimated using linearized forces acting in the film. However, the linear analysis of FRB might be problematic because results of such an analysis are usually difficult to interpret. Nevertheless, the linear analysis can provide some fundamental insights into system behaviour. This work aims to evaluate in detail the use of linear theory in the stability analysis of rotating systems supported on FRBs. Several approaches for the linearization of the forces acting in FRB are proposed and analysed. The results are visualized in the form of a holistic Campbell diagram which together depicts natural frequencies, whirl frequencies, modal damping and precession of mode shapes. Moreover, it is demonstrated that the holistic Campbell diagram can be used to interpret – and to some extent, also to predict – results of nonlinear analysis.
The version 2 of the guideline for diagnostic standards of thyroid disorders is an update of the guideline published in 1999 and describes standards of in vitro and in vivo procedures. The following ...statements are modified: In vitro procedures: When measurement of the TSH-receptor antibodies is indicated, the guideline recommends the use of a second generation assay (recombinant human TSH-receptor as antigen). The functional assay sensitivity for the measurement of thyroglobulin should reach a value < or =1 ng/ml. Molecular genetic tests (RET proto-oncogene) are indicated in patients with a newly diagnosed medullary thyroid cancer and in the relatives of patients with hereditary medullary thyroid cancer. In vivo procedures: The sonographic examination should use a probe with a frequency of at least 7.5 MHz. Indications for the thyroid scintigraphy: nodule size > or =1 cm in diameter, autonomous goitre/nodule with clinical or subclinical hyperthyroidism, necessity of a differentiation between Graves' disease and chronic lymphocytic thyroiditis, therapy control after a definitive treatment and - in individual cases - the follow-up of untreated autonomous nodules.
Aerosol samples were collected at Nylsvley Natural Reserve in northeastern South Africa at the beginning of the dry season, when large‐scale fires were absent. Aerosol was collected on quartz fiber ...filters with open face stack filters in an inlet with an upper cutoff mass median diameter of 30 μm;. The samples were analyzed for soluble ions (Cl−, NO3−, SO42−, oxalate, NH4+, Na+, K+, Ca2+, Mg2+), trace metals and crustal elements (Fe, Mn, Ca, Mg, Pb, Cu, Ag, Cd), “black carbon” (BC), total carbon (TC); and in selected samples for aerosol humidity, for mono‐ and dicarboxylic acids and other polar organic components, and for cellulose as a tracer for plant debris. Aerosol mass balances for the individual samples were constructed from the sum of following groups: Humidity (determined as weight loss at 100°C with a microthermobalance), ammonium sulfate, Cl− and NO3−, organic material, BC, and soil dust. On the average, the fit between the sum of the determined groups of components and the gravimetrically determined mass was within 6%, whereas deviations ranged for individual samples from −12 to +27% relative to the gravimetrically determined mass. The main component in aerosol was soil dust (36%), followed by organic material (28%), and ammonium sulfate (27%). Humidity was 6%, BC was 2%, and Cl− and v were 1% of aerosol mass. The low BC/TC ratio of 0.09 indicated little influence from combustion sources. The diurnal trend of the BC/TC ratio of 0.06 during day and 0.14 during night indicated a daytime source for organic components with no BC associated. As there were no industrial or other anthropogenic sources evident, the daytime source of organic components is assumed to be gas‐particle conversion from biogenic emissions. Plant debris and organic acids were the major analytically accessible groups; however, together they form only 7.2% of the carbonaceous material. With 0.4% other polar organics and 5.7% BC in this group, 86.7% of the carbonaceous material remains unidentified.
Vehicular particulate emission rates for particle mass (PM), total carbon (TC), black carbon (BC), various trace metals (Zn, Cu, Pb, Ni, V) and elutable ions (SO
4
2−, NH
4
+) were determined in a ...highway tunnel study performed 2002 in Vienna, Austria. For a typical workday fleet with a contribution of 14.8% heavy duty vehicles (HDV) and free cruising conditions averaged emission rates of 45.3±17.5, 39.7±7.3, 27.9±4.0
mg
vehicle
−1
km
−1 were found for PM, TC and BC. Under weekend conditions with 8.1% HDV in the car fleet significantly lower emission rates were observed for TC and BC (35.9±11.9 resp. 24.6±6.9
mg
vehicle
−1
km
−1), whereas the emission rate for PM was nearly unchanged (46.3±17.2
mg
vehicle
−1
km
−1). As the HDV contribution in the car fleet and the emission factors of TC and BC were highly correlated, separate emission factors for HDV and light duty vehicles (LDV) could be derived. The HDV emission rates obtained for TC and BC were 129±36 and 99±34
mg
vehicle
−1
km
−1, the corresponding rates for LDV were 24.3±7.9 and 15.6±7.3
mg
vehicle
−1
km
−1. Totally averaged fleet emission rates for NH
4
+ and SO
4
2− were 1.16±0.41 and 2.13±0.81
mg
vehicle
−1
km
−1. The emission rates for trace metals Zn Cu, Pb, Ni and V were found to be in the range of 1–35
μg
vehicle
−1
km
−1. A good correlation was observed between the individual trace elements except for Ni, indicating a similar dependency on traffic flow and driving patterns.
Several recently published investigations showed a significant improvement in the iodine supply of the German population, but so far Germany is still considered an iodine deficient country. However ...most of the studies presented do not meet the epidemiological criteria established by WHO, UNICEF and ICCIDD and may therefore suffer from a selection bias with respect to goiter prevalence estimates. School children, owing to their easy recruitment, representativeness of different socio-economic classes and high vulnerability of Iodine deficiency disorders (IDD), are one of the best target groups for surveillance of IDD. In this field study a total of 591 children were investigated. The total sample included 268 females and 323 males aged 7-17 years. The following data were collected: thyroid size by ultrasound, urinary iodine concentration in a first-morning spot urine, weight, height, sex and age. The median urinary iodine concentration of the children was 183 microg/L. The proportion of samples with concentrations below 100 microg/L or below 50 microg/L was 15.4% and 4.3% respectively. Urine samples with high iodine concentrations were also found amounting to 17.3%. Almost all families (97%) declared to use iodized kitchen salt and 19.6% of all children are taking regularly iodine tablets. Application of the WHO/ICCIDD thyroid volume references to the German children resulted in a goiter prevalence of 0.2%, using either age/sex-specific or body surface area (BSA)/sex-specific cut-off values. Comparison with the P97 values of the original normative data of Gutekunst and Martin-Teichert however gives a goiter prevalence of 3% as expected. The thyroid volumes of the children in our study appear comparable with those reported recently for iodine sufficient children from Switzerland and for iodine replete Berlin children and for children with sufficient iodine supply in the region of Leipzig, so that Germany probably has no longer to be considered an iodine deficient country. Our own study and the most recently published studies on iodine replete children give rise to the supposition that the WHO/ICCIDD recommended thyroid volume references are too high.
This study was designed to show the effect of a nonionic contrast medium (Iomeprol-300; CM) on the intrathyroidal iodine concentration with and without a concomitant medication with perchlorate (1380 ...mg/d) to block the thyroidal iodine uptake.
Twelve volunteers recieved 100 ml Iomeprol-300 intravenously and the perchlorate prophylaxis mentioned above. Another 12 volunteers got 100 ml Iomeprol-300 only. By means of X-ray-fluorescence-analysis the intrathyroidal iodine concentration was determined in advance as well as 0.2, 1, 3, 5, 7, 24, 48, 72, and 96 hours after the application of the CM.
The intrathyroidal iodine concentration did not change in the group of volunteers on perchlorate medication. Without perchlorate the intrathyroidal iodine concentration decreased after the application of the CM when it was initially high (722 +/- 66 microg/ml before, 670 +/- 65 microg/ml after CM; p = 0.046) and increased in case of a low initial concentration (327 +/- 40 microg/ml before, 381 +/- 25 microg/ml after CM; p = 0.046). The effect is significant but its magnitude is too small to be harmful for a patient with a healthy thyroid. The oral application of 1.4 g/d perchlorate inhibits the thyroidal iodine uptake and the intrathyroidal iodine concentration is unaffected by the application of a CM.
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