New Observations of Balmer Continuum Flux in Solar Flares, Instrument Description and First Results

Increase in the Balmer continuum radiation during solar flares was predicted by various authors but never firmly confirmed observationally using ground-based slit spectrographs. Here we describe a new post-focal instrument - Image Selector - enabling to measure the Balmer continuum flux from the whole flare area, in analogy of successful detections of flaring dMe stars. The system was developed and put into operation at the horizontal solar telescope HSFA-2 of the Ond\v{r}ejov Observatory. We measure the total flux by a fast spectrometer from a limited but well defined region on the solar disk. Using a system of diaphragms, the disturbing contribution of a bright solar disk can be eliminated as much as possible. Light curves of the measured flux in the spectral range 350 - 440 nm are processed, together with the H{\alpha} images of the flaring area delimited by the appropriate diaphragm. The spectral flux data are flat-fielded, calibrated and processed to be compared with model predictions. Our analysis of the data proves that the described device is sufficiently sensitive to detect variations in the Balmer continuum during solar flares. Assuming that the Balmer-continuum kernels have at least a similar size as those visible in H\alpha, we find the flux increase in the Balmer continuum to reach 230 % - 550 % of the quiet continuum during the observed X-class flare. We also found temporal changes in the Balmer continuum flux starting well before the onset of the flare in H{\alpha}.Comment: 12 pages, 4 figure

Micromechanics Based Inelastic and Damage Modeling of Composites

Micromechanics based models are considered for application to viscoelasticity and damage in metal matrix composites. The method proposes a continuation and development of Dvooák’s transformation field analysis, considering the piecewise uniform eigenstrains in each material phase. Standard applications of the method to a two-phase are considered in this study model, i.e., only one sub-volume per phase is considered. A continuous model is used, employing transformation field analysis with softening in order to prevent the tensile stress overstepping the tensile strength. At the same time shear cracking occurs in the tangential direction of the possible crack. This is considered in the principal shear stresses and they make disconnections in displacements. In this case, discontinuous models are more promising. Because discrete models, that can describe the situation more realistically have not been worked out in detail, we retain a continuous model and substitute the slip caused by overstepping the damage law by introducing eigenparameters from TFA. The various aspects of the proposed methods are systematically checked by comparing with finite element unit cell analyses, made through periodic homogenization assumptions, for SiC/Ti unidirectional lay-ups.

An Algorithm for Investigating the Structure of Material Surfaces

The aim of this paper is to summarize the algorithm and the experience that have been achieved in the investigation of grain structure of surfaces of certain materials, particularly from samples of gold. The main parts of the algorithm to be discussed are:1. acquisition of input data,2. localization of grain region,3. representation of grain size,4. representation of outputs (postprocessing)

Application of Discrete Element Methods to the Problem of Rock Bumps

This paper is a continuation of a previous paper by the authors. Applications of two discrete element methods (DEM) to several fields of geotechnics are discussed. The free hexagon element method is considered a powerful discrete element method, and is widely used in mechanics of granular media. It substitutes the methods for solving continuum problems. In order to complete the study, other discrete element methods are discussed. The second method starts with the classical particle flow code (PFC, which uses dynamic equilibrium), but we apply static equilibrium in our case. The second method is called the static particle flow code (SPFC). The numerical experiences and comparison with experimental results from scaled models are discussed

Modeling Water Pollution of Soil

The government of the Czech Republic decided that in the location to the west of Prague, capital city of the Czech Republic, some deep mines should be closed because of their low efficiency of coal mined i.e. small amounts and low quality of the coal extracted in the final stage of mining. The locations near Prague influenced the decision to do maintenance on the abandoned mines, as the thread of soil pollution was unacceptably high in the neighborhood of the capital city. Before the mines were closed it was necessary to separate existed extensive horizontal location of salt water below a clay layer in order not to deteriorate the upper fresh water. The salt water could not be allowed to pollute the upper layer with the fresh water, as many wells in villages in the neighborhood of the former mines would be contaminated. Two horizontal clay layers (an insulator and a semi-insulator) separated the two horizons containing salt water and fresh water. Before starting deep mining, vertical shafts had to be constructed with concrete linings to enable the miners to access the depths. The salt water was draining away throughout the existence of the mine. The drainage was designed very carefully to avoid possible infiltration of salt water into the upper horizon. Before the mines were abandoned it was necessary to prevent contact between the two kinds of waters in the shafts. Several options were put forward, the most efficient of which appeared to be one that proposed filling the shafts with spoil soil and creating a joint seal made of disparate material at the interface between the salt water and fresh water to create a reliable stopper. The material for the spoil soil was delivered from deposits located not far from the shafts. This material consisted of a variety of grains of sand, big boulders of slate, slaty clay, sandstone, etc.. Chemical admixtures were considered to improve the flocculation of the filling material. The stopper was positioned at a depth of 220–300 m below the terrain. As an alternative, thinner stoppers were considered, but this option was discarded.The aim of this paper is to describe the design of the stoppers applied to separate the two types of water along the contact horizon using Desai’s DSC theory (Distinct State Concept), and generalized plane strain in the multiphase problem of water flow in a porous medium. In addition, a comparison of some results from scale experimental models with numerical solutions was carried out. The intrinsic material properties of stoppers for numerical computations were obtained from physical and chemical laboratory tests. The models were evaluated for the complete underground work, particularly in its final stage of construction.

Dimethyl ether as a renewable fuel for diesel engines

ArticleThe area of automotive fuel, or fuel components, which can be produced from biomass also includes dimethyl ether, otherwise known as DME. The issue of the use of DME as a fuel is one which has been monitored until recently. Biomass can also be used as the raw material for the production of DME. DME has therefore replaced the previously-used CFCs (chlorofluorocarbons), which are now banned for their role in dangerous levels of ozone depletion. With regard to its physical properties and combustion characteristics, it is currently expected that DME will soon apply significantly as a fuel in the municipal sector and in households, and as an alternative fuel for motor vehicles with diesel engines. DME is a suitable fuel for diesel engines and can be considered as one of the most promising diesel fuel replacements. DME is a suitable fuel for diesel engines mainly due to its low self-ignition temperature and good cetane figures. It is well miscible with most organic solvents and because the polar solvent is water-immiscible. The advantage is its high levels of purity, and its being free of sulphur, nitrogen, or metals. The physical properties of DME are very similar to the physical properties of LPG. DME requires relatively complex and costly fuel accessories, but the original compression ratio of the diesel engine is maintained. A diagram of the fuel system is illustrated in the paper. The paper analyses the dependence of vapour pressure on temperature, the dependence of the density on temperature, kinematic viscosity, the flash point, the boiling point, and the solubility of water. The objective is to evaluate this interesting energy source for applications in diesel engines

Energy analysis of hydrogen as a fuel in the Czech Republic

ArticleThe concept of ‘hydrogen economy’ dates back to the 1970s. It was first introduced as s response to the first oil crisis. In the context of the hydrogen economy, it is important to calculate how much hydrogen would be needed to power all motor vehicles in the Czech Republic. This is main topics of this paper. To calculate the amount of hydrogen, we used two different methods. One is based on thermodynamic laws and the other on normal operating conditions. Both approaches yielded comparable results. It was found out that even with the use of all the electricity produced in the Czech Republic in 2016, we would not be able to cover the amount of energy that is required for production. It would cover only 75% resp. 76% depending on the calculation method used. Eventually, the Czech Republic could buy necessary amount of hydrogen and it would cost between 11 and 29 billion euros which is between 6% and 16% of GDP of the Czech Republic. In the calculations, authors found out that most fuel is burnt in the passenger cars. Therefore, we made a sensitivity analysis to find out how much our results would differ if fuel consumption changed. It turns out that with an increase in consumption of 1l per 100 km, hydrogen production coverage will decrease by about 4% (again with the use of all electricity produced in the Czech Republic)

Diagnostics of hydraulic fluids used in aviation

ArticleDiagnostics is a maintenance industry that monitors performance, parameters, and follow – up. Diagnosing hydraulic fluids means comparing the parameters of the used hydr aulic fluid sample to the parameters of the clean fluid. It is also essentia l to monitor the limit values either by the aircraft manufacturer or by the manufacturer of the hydraulic fluid. This means that the manufacturer recommends the limitations of the liquid parameters. The measurements of the fluid samples give an overview of the liquid quality. Most businesses focus on so – called proactive maintenance. The main senses and objectives of proactive maintenance are: lubricant sample analysis, lubricant sta tus, machine status, next step recommendation, database saving and trend analysis. This article focuses on the quality of hydraulic fluid focused in aviation. The aim of the article was to determine the properties of the hydraulic fluid used in the A320 ai rcraft family, determine the interval of its exchange. Monitoring the state of the hydraulic fluid could contribute to the timely detection of the problem, thus avoiding a failure of the device or the system as a whole. The tracking proposal is an integral part of this article

Effects of blood parasite infections on spatiotemporal migration patterns and activity budgets in a long-distance migratory passerine

How blood parasite infections influence the migration of hosts remains a lively debated issue as past studies found negative, positive or no response to infections. This particularly applies to small birds, for which monitoring of detailed migration behaviour ovea whole annual cycle has been technically unachievable so far. Here, we investigate how bird migration is influenced by parasite infections. To this end, we tracked great reed warblers (Acrocephalus arundinaceus) with multi-sensor loggers, characterized general migration patterns as well as detailed flight bout durations, resting times and flight heights and related these to the genus and intensity of their avian haemosporidian infections. We found migration distances to be shorter and the onset of autumn migration to be delayed with increasing intensity of blood parasite infection, in particular for birds with Plasmodium and mixed-genus infections. Additionally, the durations of migratory flight bout were prolonged for infected compared to uninfected birds. But since severely infected birds and particularly birds with mixed genus infections had shorter resting times, initial delays seemed to be compensated for and the timing in other periods of the annual cycle was not compromised by infection. Overall, our multi-sensor logger approach revealed that avian blood parasites have mostly subtle effects on migratory performance and that effects can occur in specific periods of the year only

Rufous Common Cuckoo chicks are not always female

This is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this recordThe Common Cuckoo (hereafter Cuckoo) shows two adult plumage morphs—adult male plumage is grey and adult females are either grey or, less frequently, rufous. The situation is less clear in juveniles, as both sexes exhibit variable proportions of grey and rufous colour. We thus describe the patterns related to sex-specific plumage colour variation in a central European Cuckoo population. We genetically determined the sex of 91 Cuckoo chicks and using visual classification of photographs we scored juvenile plumage colouration of individual chicks into five classes based upon the increasing proportion of rufous colour on feathers. To verify these scores, we sampled chick feathers and quantified the proportion of rufous colour of individual feathers by digital image analysis. We found that juvenile females had a higher proportion of rufous colour of feathers than juvenile males. However, the difference was marginally non-significant based on visual inspection alone, and some male chicks even showed intensively rufous plumage like those of juvenile females. In contrast, we captured only grey adult males (n = 37), while five out of 20 adult females were rufous. The rufous colour of Cuckoo feathers considerably differed from the grey colour and the difference seemed to be larger in adults than in juveniles. We show that chicks, unlike adult females, cannot be visually assigned to either of the adult morphs. Therefore, we encourage further investigation of Cuckoo plumage colouration across the species’ range to examine the process of plumage maturation. A detailed genetic analysis is necessary to understand the origin of Cuckoo feather colouration.This study was supported by the Czech Science Foundation (project 17-12262S) and by the Institutional Research Plan (RVO: 68081766)