Exploring the origin of a large cavity in Abell 1795 using deep Chandra observations

We examine deep stacked Chandra observations of the galaxy cluster Abell 1795 (over 700ks) to study in depth a large (34 kpc radius) cavity in the X-ray emission. Curiously, despite the large energy required to form this cavity (4PV=4x10^60 erg), there is no obvious counterpart to the cavity on the opposite side of the cluster, which would be expected if it has formed due to jets from the central AGN inflating bubbles. There is also no radio emission associated with the cavity, and no metal enhancement or filaments between it and the BCG, which are normally found for bubbles inflated by AGN which have risen from the core. One possibility is that this is an old ghost cavity, and that gas sloshing has dominated the distribution of metals around the core. Projection effects, particularly the long X-ray bright filament to the south east, may prevent us from seeing the companion bubble on the opposite side of the cluster core. We calculate that such a companion bubble would easily have been able to uplift the gas in the southern filament from the core. Interestingly, it has recently been found that inside the cavity is a highly variable X-ray point source coincident with a small dwarf galaxy. Given the remarkable spatial correlation of this point source and the X-ray cavity, we explore the possibility that an outburst from this dwarf galaxy in the past could have led to the formation of the cavity, but find this to be an unlikely scenario.Comment: 10 pages, 6 figures. Accepted for publication in MNRA

Detection of a variable ultra-fast outflow in the Narrow Line Seyfert 1 galaxy PG 1448+273

Relativistically blueshifted absorption features of highly ionised ions, the so-called ultra-fast outflows (UFOs), have been detected in the X-ray spectra of a number of accreting supermassive black holes. If these features truly originate from accretion disc winds accelerated to more than 10 per cent of the speed of light, their energy budget is very significant and they can contribute to or even drive galaxy-scale feedback from active galactic nuclei (AGN). However, the UFO spectral features are often weak due to high ionisation of the outflowing material, and the inference of the wind physical properties can be complicated by other spectral features in AGN such as relativistic reflection. Here we study a highly accreting Narrow Line Seyfert 1 galaxy PG 1448+273. We apply an automated, systematic routine for detecting outflows in accreting systems and achieve an unambiguous detection of a UFO in this AGN. The UFO absorption is observed in both soft and hard X-ray bands with the XMM-Newton observatory. The velocity of the outflow is (26900 +- 600) km/s (~0.09c), with an ionisation parameter of log ({\xi} / erg cm s^-1)=4.03_{-0.08}^{+0.10} and a column density above 10^23 cm^-2. At the same time, we detect weak warm absorption features in the spectrum of the object. Our systematic outflow search suggests the presence of further multi-phase wind structure, but we cannot claim a significant detection considering the present data quality. The UFO is not detected in a second, shorter observation with XMM-Newton, indicating variability in time, observed also in other similar AGN.Comment: Accepted for publication in MNRAS. 14 pages, 11 figures, 1 tabl

Učinkovitost i kvaliteta indukcijskog zagrijavanja i kaljenja osovina startera dizel motora

Presented work discusses a complex process of inductive heating and quenching of carbon steel planetary shafts for diesel engine starters. On the measurements base of temperature fields on the surface of the planetary shafts by thermographic camera and theoretical knowledge, a mathematical model for temperature conditions determination in the shaft during the entire process of heating and quenching was carried out. On the basis of developed mathematical model a computer program was developed, and used for analyses and induction hardening process optimization of planetary shafts.U ovom se radu raspravlja o složenom procesu indukcijskog zagrijavanja i kaljenja osovina iz ugljičnog čelika za pokretanje dizelskih motora. Na temelju rezultata mjerenja temperaturnih polja na površini osovina termografskom kamerom i teorijskih spoznaja, razvijen je matematički model temperaturnih uvjeta tijekom procesa zagrijavanja i kaljenja osovina. Na temelju postavljenog matematičkog modela razvijen je računalni program koji je korišten za analizu i optimizaciju procesa zagrijavanja osovina

Nanošenje električnom iskrom za popravak alata

The electrospark deposition is a process for surfacing of hard metal alloys, e.g. carbides and stellites, on the surfaces of new or old machine elements. In this process, a high current is conducted through an oscillating electrode and a substrate for a very short period of time. In the paper, the process is described and the thickness of deposited layer, chemical composition, dilution rate and the layer roughness are determined.Nanošenje električnom iskrom postupak je za navarivanje tvrdih metalnih slitina, npr. karbida i stelita, na površinu novih ili starih elemenata strojeva. U tom postupku visoka struja provodi se kroz oscilirajuću elektrodu i supstrat na vrlo kratko vrijeme. U članku opisan je postupak i određeni su debljina nanesenog sloja, kemijski sastav, stupanj miješanja i hrapavost sloja

The influence of Si and V on the kinetics of phase transformation and microstructure of rapidly solidified Al-Fe-Zr alloys

The influence of Si and V on the precipitation kinetics of the rapidly solidified (RS) Al-Fe-Zr alloys is presented. Precipitation kinetics and microstructural development of RS Al-Fe-Zr alloys with Si or V addition have been investigated by the combination of four point electrical resistance measurement, optical microscopy, transmition electron microscopy (TEM) and scanning electron microscopy (SEM). For verification of the electrical resistivity measurement results differential scanning calorimetry (DSC) and differential thermal analysis (DTA) was also applied. Rapidly solidified samples, in the form of thin ribbons, were prepared with the single roll melt spun technique. For determination of the distinctive temperatures at which microstructural transformations occur in-situ electrical resistivity measurement during heating of the ribbons with various constant heating rates has been used. It was found that microstructure decomposition depends on heating rate and shifts to higher temperatures with increasing heating rate. After heating above the distinctive transition temperatures, heating was stopped and microstructure of the samples examined by electron microscopy

Electrospark deposition for die repair

The electrospark deposition is a process for surfacing of hard metal alloys, e.g. carbides and stellites, on the surfaces of new or old machine elements. In this process, a high current is conducted through an oscillating electrode and a substrate for a very short period of time. In the paper, the process is described and the thickness of deposited layer, chemical composition, dilution rate and the layer roughness are determined

Evidence for a Variable Ultrafast Outflow in the Newly Discovered Ultraluminous Pulsar NGC 300 ULX-1

Ultraluminous pulsars are a definite proof that persistent super-Eddington accretion occurs in nature. They support the scenario according to which most Ultraluminous X-ray Sources (ULXs) are super-Eddington accretors of stellar mass rather than sub-Eddington intermediate mass black holes. An important prediction of theories of supercritical accretion is the existence of powerful outflows of moderately ionized gas at mildly relativistic speeds. In practice, the spectral resolution of X-ray gratings such as RGS onboard XMM-Newton is required to resolve their observational signatures in ULXs. Using RGS, outflows have been discovered in the spectra of 3 ULXs (none of which are currently known to be pulsars). Most recently, the fourth ultraluminous pulsar was discovered in NGC 300. Here we report detection of an ultrafast outflow (UFO) in the X-ray spectrum of the object, with a significance of more than 3{\sigma}, during one of the two simultaneous observations of the source by XMM-Newton and NuSTAR in December 2016. The outflow has a projected velocity of 65000 km/s (0.22c) and a high ionisation factor with a log value of 3.9. This is the first direct evidence for a UFO in a neutron star ULX and also the first time that this its evidence in a ULX spectrum is seen in both soft and hard X-ray data simultaneously. We find no evidence of the UFO during the other observation of the object, which could be explained by either clumpy nature of the absorber or a slight change in our viewing angle of the accretion flow.Comment: 10 pages, 4 figures. Accepted to MNRA

Material flow enhancement in production assembly lines under application of zoned order picking systems

Introduced research work relates to the possibility of material flow enhancement in production systems, with the apostrophe on material order picking in production assembly lines. The paper presents basic rules and the results related to formed computer models of zoned order picking systems under the application of developed bound cavities method

Optimalni model metode konačnih elemenata (MKE) konstrukcije strijele plovnog bagera

This paper is presentation of the development of advanced approach for modeling and structural analysis of jib structure which is usually part of waterway bucket dredgers. Object of analysis is a jib structure which will be reconstructed for the excavation of grain material from a river bed. Main goal of paper is to proof benefits of enough sophisticated i.e. “optimal” FEM model for structural analysis of this type of structures in comparison with simple, but not adequate models. Proper stress state is emphasized as primary, but not only condition. It is necessary to reach serviceability and durability state, as well as affordable financial construction circumstances.Rad je kratki prikaz razvitka naprednog pristupa u modeliranju i strukturnoj analizi konstrukcije strijele, koja je uobičajeni dio plovnih bagera. Predmet analize je konstrukcija strijele bagera vedričara rekonstruisanog za iskop šljunka sa dna vodotoka. Cilj rada je da dokaže prednosti dovoljno sofi sticiranog tj. “optimalnog” MKE modela za analizu ovog tipa konstrukcija u odnosu na jednostavne, ali neodgovarajuće modele. Odgovarajuće naponsko stanje je istaknuto kao primarni, ali ne i jedini uvjet za rabljenje bagera. Potrebno je osigurati i odgovarajuće stanje upotrebljivosti i trajnosti, kao i povoljne ekonomske uvjete izrade konstrukcije