The balancing of robotic systems is an important issue because it allows significant reduction of torques. However the literature review shows that the gravity balancing of robotic systems is carried ...out by weightless springs. For many balancing schemes it is the source of errors.
This paper deals with an analytically tractable solution for the gravity balancing considering the spring mass. For this purpose, the relationship between the stiffness coefficient of the spring and its mass is provided. Then this relationship is introduced into the balancing equation and spring elastic force is determined taking into account its mass. For zero length springs, the stiffness coefficient of the springs is determined from a quadratic equation and for non-zero length springs from a cubic equation. In this way, an exact balancing of gravitational forces is achieved, which allows improving the balancing accuracy of robotic systems.
The efficiency of the suggested approach is illustrated by numerical examples. An application to the balancing of the leg orthosis for robotic rehabilitation is also presented.
In this paper we present a high repetition rate experimental platform for examining the spatial structure and evolution of Biermann-generated magnetic fields in laser-produced plasmas. We have ...extended the work of prior experiments, which spanned over millimeter scales, by spatially measuring magnetic fields in multiple planes on centimeter scales over thousands of laser shots. Measurements with magnetic flux probes show azimuthally symmetric magnetic fields that range from 60 G at 0.7 cm from the target to 7 G at 4.2 cm from the target. The expansion rate of the magnetic fields and evolution of current density structures are also mapped and examined. Electron temperature and density of the laser-produced plasma are measured with optical Thomson scattering and used to directly calculate a magnetic Reynolds number of
$1.4\times {10}^4$
, confirming that magnetic advection is dominant at
$\ge 1.5$
cm from the target surface. The results are compared to FLASH simulations, which show qualitative agreement with the data.
Novel 3-amino-1-(3,5-dimethyl-1
H
-pyrazol-1-yl)-2,7-naphthyridines were synthesized on the basis of monohydrazides derived from 2,7-naphthyridines. The cyclization of 3-chloro-1-(3,5-dimethyl-1
H
...-pyrazol-1-yl)-2,7-naphthyridine with hydrazine hydrate gave the tricyclic pyrazolo3,4-
c
-2,7-naphthyridine, which was used to prepare the novel heterocyclic system pyrimido1',2':1,5pyrazolo3,4-
c
-2,7-naphthyridine.
The existence of pulsations in HgMn stars is still being debated. To provide the first unambiguous observational detection of pulsations in this class of chemically peculiar objects, the bright star ...HD 45975 was monitored for nearly two months by the CoRoT satellite. Independent analyses of the light curve provide evidence of monoperiodic variations with a frequency of 0.7572 d-1 and a peak-to-peak amplitude of ~2800 ppm. Multisite, ground-based spectroscopic observations overlapping the CoRoT observations show the star to be a long-period, single-lined binary. Furthermore, with the notable exception of mercury, they reveal the same periodicity as in photometry in the line moments of chemical species exhibiting strong overabundances (e.g., Mn and Y). In contrast, lines of other elements do not show significant variations. As found in otherHgMn stars, the pattern of variability consists in an absorption bump moving redwards across the line profiles. We argue that the photometric and spectroscopic changes are more consistent with an interpretation in terms of rotational modulation of spots at the stellar surface. In this framework, the existence of pulsations producing photometric variations above the ~50 ppm level is unlikely in HD 45975. This provides strong constraints on the excitation/damping of pulsation modes in this HgMn star.
The territory of Armenia, although relatively small, is geologically and tectonically complex. Its complexity is not only due to a dense network of faults. It results from a complicated history of ...tectonic development including several phases of mountain formation and planation, and the extensive development of fold-block, tectonic and magmatic processes. An important scientific task is identification of earthquake-prone structural blocks by analysing seismotectonic data on geotectonic zones in Armenia. This article describes the seismotectonic analysis of geological and geophysical data on the Viraayots-Karabakh zone.
We used a wide spectrum of modern tectonic-geomorphological indices and GIS technologies in order to assess the neotectonic (Neogene – Quaternary) activity of the main block units of the study area and to classify the block units by their tectonic activity levels. Tectonics of the study area is contrasting, and many tectonically active blocks are in the immediate neighbourhood with passive blocks.
Based on the records of seismic events of various magnitudes and historic earthquake data, we analysed modern seismicity of the block units. For each block, a quantitative analysis of its total seismic energy release was performed, and relationships between the released seismic energy values and the number of recorded earthquakes were analyzed. Based on such analysis, we identify a group of blocks wherein the total released seismic energy values are high, but the numbers of seismic events recorded in these blocks are rather limited. In the context of block tectonic activity, analysing these data makes it possible to detect the blocks with the highest probability of the occurrence of strong earthquakes.
A preservative is a mandatory component of the eye drops designed to prevent microbial contamination in an opened bottle. Most of the preservative agents are either detergents, or oxidants; the most ...widely used and well-studied preservative - benzalkonium chloride - is a detergent. Due to regular usage of glaucoma eye drops, cytotoxic impact of the preservatives on anterior eye surface is considered the principal cause of its pathology, which leads to a decrease in quality of life. The high cost of preservative-free pharmacological forms and the complicated process of developing new preservatives make the usage of eye drops with minimal required concentration of preservative agent and a moistening component a good compromise. The most commonly utilized moistening component is polyvinyl alcohol - synthetic polymeric hydrogel, which is also used in artificial tears and bioengineering.
Nematode fauna of fish in Armenia Hakobyan, A. R.; Abrahamyan, V. V.; Shcherbakov, O. V. ...
Rossijskij parazitologičeskij žurnal,
03/2024, Letnik:
18, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The purpose of the research is to study the species composition of nematodes dwelling in fish in natural reservoirs and on artificial pond fish farms in Armenia. Materials and methods. The studies ...were performed at the Research Center for Veterinary Medicine and Veterinary and Sanitary Expertise of the Armenian National Agrarian University and at the Laboratory of Molecular Parasitology of the Scientific Center of Zoology and Hydroecology from March 2020 to December 2022. Traditional ichthyo-parasitological methods were used to study 246 fish of 10 species from fish farms in the Ararat and Armavir Regions, from Lake Sevan and the Sevjur, Hrazdan, Marmarik, Akhuryan and Debed Rivers, as well as the Yerevan, Aparan and Akhuryan reservoirs. The study results were statistically processed (descriptive statistics) using the BioStat software. Results and discussion. The fish were found to have four types of nematodes: Contracaecum microcephalum Rudolphi, 1819, Philometroides sanguineus Rudolphi, 1819, Rhabdochona fortunatowi Dinnik, 1933 and Cystidicola farionis Fischer, 1798. Parasites were found in the body, on the serosa, in the air bladder walls, the intestinal lumen and the caudal fin thickness. The total nematode infection rate in fish was 9.76%. The nematode infection rate in fish was characterized by low values of prevalence and intensity other than the infection by the species Rh. fortunatowi (up to 24 specimens per fish). Among the found nematodes, the species C. microcephalum posed a potential threat to human health.
The study is focused on searching for spatial regularities in the occurrence of earthquake hypocenters in different geological settings in Northern Armenia. Tectonic-geomorphological indices are ...applied to define the tectonic activity of blocks composing the study area, which was manifested within a long period of time, starting from the neotectonic development period. The blocks are classified accordingly. The regional seismic activity is analysed considering the block structure of the study area. Earthquake focal mechanisms are determined, and dominant displacement trends are identified. Based on the comparative analysis of the blocks’ tectonic activity indicators and the locations of seismic events differing in strength, regular patterns of spatial distribution of seismic events are identified. It is established that the earthquake hypocenters of different strength occur in certain block structures; and the predominant types of movements in the earthquake hypocenters are largely determined by types of fault structures. It is emphasized that investigating the blocks’ neotectonic activity is important for discovering the general patterns of spatial distribution of seismic events.
The Aragats Space-Environmental Center provides monitoring of different species of secondary cosmic rays at two altitudes and with different energy thresholds. One-minute data is available on-line ...from
http://crdlx5.yerphi.am/DVIN/index2.php. We present description of the main monitors along with data acquisition electronics. Also we demonstrate the sensitivity of the different species of secondary cosmic ray flux to geophysical conditions, taking as examples the extremely violent events of October–November 2003. We introduce correlation analysis of the different components of registered time-series as a new tool for the classification of the geoeffective (events on earth affected by solar activity) events and for the forecasting of the severity of the upcoming geomagnetic storm.
The densities of a water-salt solution without and a water-salt solution with DNA were studied depending on the concentration of NaCl in the solution when they were irradiated with millimeter ...electromagnetic waves of non-thermal intensity, which are resonant for vibrations of hexagonal water molecular structures with a frequency of 50.3 GHz. Studies have shown that the density of solutions increases with irradiation. Density change due to irradiation is minimal for 0.9% NaCl solution (saline). Viscometric measurements have shown that irradiation (which leads to dehydration of DNA) does not lead to a noticeable change in the secondary and tertiary structure of DNA for a physiological solution of DNA.
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