The paper deals with the rotor vibration in journal bearings to prepare a model for verifying the rotor vibration active control. The rotor is maintained in equilibrium position by forces generated in oil film. Bearing forces can be modelled as a spring and damper system. The main goal of the simulation study is to verify the model principle and to estimate parameters by comparing simulation results with experimental data, namely the instability of motion. Test stand with rotor supported in two journal bearings was designed for these purposes. The stand will be equipped with four piezoactuators enabling excitation of bearings by practically arbitrary dynamic force. Theoretical analysis of the influence of external excitation on rotor behaviour was carried out. Up to now the study shows that simple kinematic excitation is effective for reducing rotor excursion while passing critical speeds. To suppress self-exciting vibration of the rotor it is necessary to look for more sophisticated solution. and Obsahuje seznam literatury
Over the past 40 years, much has been published on the ultrastructure and cellular development of embryonic structures in a wide range of cestodes. However, the literature contains many discrepancies in both terminology and interpretations because of the facts that these organisms are phylogenetically diverse within their respective orders and families, the habitats that affect embryonic envelope structure are diverse, and the work has been done in various laboratories around the world. This review and synthesis was initiated by a working group of biologists from around the world convened at the Fifth International Workshop on Cestode Systematics and Phylogeny in České Budĕjovice, at the Institute of Parasitology of the Biology Centre, Academy of Sciences of the Czech Republic. It brings together the data from published work and establishes a uniform terminology and interpretation based on the data as they are presented. A consensus was reached for standardised definitions of the oncosphere, hexacanth, coracidium, embryonic envelopes, outer envelope, inner envelope, embryophore, vitelline capsule, shell, and outer coat. All of these are defined as components of the embryo or its vitellocyte-derived or uterine-derived coatings.
The contribution focuses on the design of a control algorithm aimed at the operative control of runoff water from a reservoir during flood situations. Management is based on the stochastically specified forecast of water inflow into the reservoir. From a mathematical perspective, the solved task presents the control of a dynamic system whose predicted hydrological input (water inflow) is characterised by significant uncertainty. The algorithm uses a combination of simulation model data, in which the position of the bottom outlets is sought via nonlinear optimisation methods, and artificial intelligence methods (adaptation and fuzzy model). The task is written in the technical computing language MATLAB using the Fuzzy Logic Toolbox.
In this paper, we consider a distributed stochastic computation of AXB=C with local set constraints over an multi-agent system, where each agent over the network only knows a few rows or columns of matrixes. Through formulating an equivalent distributed optimization problem for seeking least-squares solutions of AXB=C, we propose a distributed stochastic mirror-descent algorithm for solving the equivalent distributed problem. Then, we provide the sublinear convergence of the proposed algorithm. Moreover, a numerical example is also given to illustrate the effectiveness of the proposed algorithm.
Oxidative stress is an imbalance between free radicals and antioxidants, and is an important etiological factor in the development of hypertension. Recent experimental evidence suggests that subpressor doses of angiotensin II elevate oxidative stress and blood pressure. We aimed to investigate the oxidative stress related mechanism by which a subpressor dose of angiotensin II induces hypertension in a normotensive rat model. Normotensive male Wistar rats were infused with a subpressor dose of angiotensin II for 28 days. The control group was sham operated and infused with saline only. Plasma angiotensin II and H2O2 levels, whole-blood glutathione peroxidase, and AT-1a, Cu/Zn SOD, and p22phox mRNA expression in the aorta was assessed. Systolic and diastolic blood pressures were elevated in the experimental group. There was no change in angiotensin II levels, but a significant increase in AT-1a mRNA expression was found in the experimental group. mRNA expression of p22phox was increased significantly and Cu/Zn SOD decreased significantly in the experimental group. There was no significant change to the H2O2 and GPx levels. Angiotensin II manipulates the free radical-antioxidant balance in the vasculature by selectively increasing O2 - production and decreasing SOD activity and causes an oxidative stress induced elevation in blood pressure in the Wistar rat., M. M. Govender, A. Nadar., and Obsahuje bibliografii
Light is critical in determining plant structure and functioning in dune ecosystems, which are characterised by high incident and reflected radiation. Light variations demand great plasticity of the photosynthetic apparatus. This study assessed the phenotypic plasticity of foredune species by analysing their light response and dark recovery curves measured under field conditions. We also addressed the question how coexisting species, structurally distinct, differed in their photochemical efficiency in response to short-term changes in light. Finally, we examined how the varying intensity of stressors operating along a dune gradient affected responses to light. The species differed in light use strategies but showed similar patterns of the dark recovery. Species differences in photochemistry varied seasonally, with species being winter specialists, summer specialist or generalists. Some aspects of their photochemistry varied significantly along the gradient. Unexpectedly, other traits did not vary as predicted. For example, changes in light efficiency of plants along the gradient were not consistent with assumed directional changes in the severity of stressors. The different light use strategies observed in coexisting species did not conform to the prediction that stressors constrain the range of possible functional designs in harsh environments. However, the species followed very similar patterns of post-illumination recovery, which suggests that evolutionary pressures might be acting to maintain similar recovery mechanisms. Our results indicated that dune gradients might be nondirectional, which determines unpredictable patterns of variation in leaf traits along the dune gradient. Seasonal differences in the relative performance may allow species to coexist where otherwise one species would exclude the other., R. Bermúdez, R. Retuerto., and Obsahuje bibliografii
Members of the Philometridae represent the most important group of dracunculoid nematodes parasitizing fishes. In his monograph treating the Dracunculoidea, Moravec (2006) reported a total of 11 genera and 105 species of philometrids parasitizing freshwater, brackish-water and marine fishes. However, during the last six years (2007-2012), an additional 42 new species of Philometridae have been described, representing a 40% increase of the number of nominal species. Most of these species (30) belong to Philometra Costa, 1845, mainly represented by parasites of marine fishes, a few others (8) to Philometroides Yamaguti, 1935, and a single one to each of the following genera: Caranginema Moravec, Montoya-Mendoza et Salgado-Maldonado, 2008, Dentiphilometra Moravec et Wang, 2002, Dentirumai Quiazon et Moravec, 2013* and Spirophilometra Parukhin, 1971. Moreover, three new genera, Afrophilometra Moravec, Charo-Karisa et Jirků, 2009, Caranginema and Dentirumai, were erected. Representatives of seven genera, Afrophilometra, Buckleyella Rasheed, 1963, Caranginema, Dentiphilometra, Dentirumai, Paraphilometroides Moravec et Shaharom-Harrison, 1989 and Rumai Travassos, 1960, were studied using scanning electron microscopy (SEM) for the first time. Thirteen known but poorly described philometrid species were redescribed and, in some species of Caranginema and Philometra, previously unknown conspecific males were discovered and described. The male surface ultrastructure studied by SEM provided new taxonomically important features for species distinction. Gene sequencing was used in several recent studies and advanced our understanding of phylogenetic interrelationships among representatives of seven genera (Afrophilometra, Alinema Rasheed, 1963, Caranginema, Nilonema Khalil, 1960, Philometra, Philometroides and Rumai) and of the extent of the biodiversity of philometrids. New data were obtained on the biology and pathogenicity of several species of Nilonema, Philometra, Philometroides and Rumai. The need to carry out surveys in order to find males and to use SEM and gene sequencing to identify philometrids is emphasized. Appropriate quantitative methods to determine the impact of philometrids in ovarian tissue on host fecundity are recommended. Further detailed studies on philometrids would be significant not only from the theoretical viewpoint, but also because of their practical implications. A list of philometrid nematode species by continents is provided.
River runoff is not only a crucial part of the global water cycle, but it is also an important source for hydropower and an essential element of water balance. This study presents a system-theory-based model for river runoff forecasting taking the Hailiutu River as a case study. The forecasting model, designed for the Hailiutu watershed, was calibrated and verified by long-term precipitation observation data and groundwater exploitation data from the study area. Additionally, frequency analysis, taken as an optimization technique, was applied to improve prediction accuracy. Following model optimization, the overall relative prediction errors are below 10%. The system-theory-based prediction model is applicable to river runoff forecasting, and following optimization by frequency analysis, the prediction error is acceptable.
We studied gas exchange of leaves on branches that had been cut and then re-cut under water to assess the utility of measuring gas exchange on leaves of excised canopy branches. There was large variation between species in their ability to photosynthesize following excision. Some species maintained up to 86.5% of intact photosynthetic rate 60 min after excision, whereas other species dropped below 40% of intact photosynthetic rates within 3 min. Three species showed significant reductions in maximum rates of gross photosynthetic rate (PG) on leaves of excised branches relative to intact branches. Excision significantly reduced carboxylation rates (Vcmax) in four species and electron transport (Jmax) in two species. There were also significant increases in compensation irradiance and reductions of day rates of respiration relative to intact measurements. While gas exchange on excised branches can provide useful measures for canopy species, responses of individual species to branch excision need to be taken into account. Measurements on pre-screened species allow a greater understanding of canopy photosynthesis of large trees when canopy access is not an option. and L. S. Santiago, S. S. Mulkey.
A one-dimensional two-zone mathematical model, comprising a pair of advection-dispersion equations coupled by a mass exchange term, is proposed to study longitudinal dispersion in channels with sequences of pools and riffles. An implicit finite-difference numerical scheme is employed, and its effectiveness is assessed with reference to known analytical solutions. Moreover, sets of longitudinal dispersion experiments were performed on various simple geometries of sequences of pools and riffles developed in a laboratory flume. The results were compared with corresponding numerical solutions to calibrate the two-zone model. and Pro studium podélné disperze v korytech s opakující se soustavou tůní a prahů byl navržen jednorozměrný dvouzónový matematický model. Model zahrnuje dvojici rovnic pro advektivní disperzi doplněných výrazem pro přenos hmoty. Byl použit implicitní model konečných diferencí a jeho vhodnost ověřena porovnáním se známým analytickým řešením. Navíc, v laboratorním žlabu byla provedena série měření podélné disperze pro různé jednoduché geometrie koryta se střídajícími se tůněmi a prahy. Pro kalibraci dvouzónového modelu byly výsledky měření porovnány s odpovídajícími matematickými řešeními.