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M.A. Malik, K. Majchrzak and K.N. Braszczyńska-Malik

Abstract

AM50/Mg2Si composites containing 5.7 wt. % and 9.9 wt. %. of Mg2Si reinforcing phase were prepared successfully by casting method. The microstructure of the cast AM50/Mg2Si magnesium matrix composites was investigated by light microscopy and X-ray diffractometry (XRD). The microstructure of these composites was characterized by the presence of α-phase (a solid solution of aluminium in magnesium), Mg17Al12 (γ-phase), Al8Mn5 and Mg2Si. It was demonstrated that the Mg2Si phase was formed mainly as primary dendrites and eutectic.

Open access

M.H.M. Rashid

Abstract

In this paper we establish for a bounded linear operator defined on a Banach space several sufficient and necessary conditions for which property (gaw) holds. In this work, we consider commutative perturbations by algebraic operator and quasinilpotent operator for T ∈ B(X ) such that T * satisfies property (gaw). We prove that if A is an algebraic and T ∈ PS(X ) is such that AT = TA, then ƒ(T * + A*) satisfies property (gaw) for every ƒ ∈ Hc(σ(T + A)). Moreover, we show that if Q is a quasi-nilpotent operator and T ∈ PS(X ) is such that TQ = QT, then ƒ(T * + Q*) satisfies the property (gaw) for every ƒ ∈ Hc(σ(T +Q)). At the end of this paper, we apply the obtained results to a number of subclasses of PS(X ).

Open access

P. Zygoń, J. Peszke, M. Gwozdźik, Z. Nitkiewicz and M. Malik

Abstract

The paper presents results of studies on carbon nanotubes - as received, after cleaning and also after modification. Functional groups as well as metal nanoparticles have been attached, originating from cobalt sulphate, copper acetate and a mixture of hydrogen bromide and bromide. The surface studies on an atomic forces microscope (AFM), X-ray studies (phase composition analysis, crystallite sizes determination) as well as Raman spectroscopy studies were carried out on such nanotubes.

The surface topography studies have shown that after the modification the diameter and length of nanotubes change. Also the surface development changes, which has been determined through roughness parameter measurements.

The change of intensity, of crystallite size and of half-value width of main reflections originating from carbon for nanotubes modified in various ways have been determined using the X-ray analysis.

Open access

M.A. Malika, K. Majchrzak and K.N. Braszczyńska-Malik

Abstract

Cast magnesium matrix composites reinforced with silicon carbide particles were investigated by using Raman microscopy. 3C, 4H and 6H polytypes of SiC particles were identified in the investigated composites. Additionally, Mg2Si compound was detected by Raman microscopy in the composites microstructure.

Open access

S. Malik, P. Bordei, A. Rusali and D. M. Iliescu

Abstract

Our study was conducted by consulting angioCT sites made on a CT GE LightSpeed VCT64 Slice CT and a CT GE LightSpeed 16 Slice CT, following the path and relationships of the descending thoracic aorta against the vertebral column, outside diameters thereof at the thoracic vertebrae T4, T7, T12 and posterior intercostal arteries characteristics. The origin of of the descending thoracic aorta we found most commonly on the left flank of the lower edge of the vertebral body T4, but I have encountered cases where it had come above the lower edge of T4 on level of intervertebral disc T4-T5 or even at the upper edge of T5 vertebral body. At thoracic vertebra T4, on a total of 30 cases, the descending thoracic aorta present a diameter of 20.0 to 32.6 mm, values that correspond to male gender and to females diameter ranging from 25.5 to 27, 4 mm. At level of T7 thoracic vertebra, thoracic aorta present a diameter of 19.6 to 29.5 mm, values found in men, in women the diameter being from 21.9 to 25.2 mm. At thoracic vertebra T12, on a total of 27 cases, the descending thoracic aorta present a diameter of 17.6 to 27.7 mm, in males the diameter was from 17.6 to 27.7 mm and females diameter ranging from 21.1 to 25.2. The length of the descending thoracic aorta was from 18.40 to 19.41 cm.

Open access

I. Vasková, M. Hrubovčáková, J. Malik and Š. Eperješi

Abstract

Ductile cast iron (GS) has noticed great development in last decades and its boom has no analogue in history humankind. Ductile iron has broaden the use of castings from cast iron into areas, which where exclusively domains for steel castings. Mainly by castings, which weight is very high, is the propensity to shrinkage creation even higher. Shrinkage creation influences mainly material, construction of casting, gating system and mould. Therefore, the main realized experiment was to ascertain the influence of technological parameters of furane mixture on shrinkage creation in castings from ductile iron. Together was poured 12 testing items in 3 moulds forto determine and compare the impact of various technological parameters forms the propensity for shrinkage in the casting of LGG.

Open access

M.H.M. Rashid and T. Prasad

Abstract

A Banach space operator T satisfies property (Bgw) if the complement in the approximate point spectrum σa(T) of the semi-B-essential approximate point spectrum σSHF+-(T) coincides with the set of isolated eigenvalues of T of Unite multiplicity E°(T). We find conditions for Banach Space operator tosatfafy the property (Bgw). We also study the stability of property (Bgw) under perturbations by nilpotent operators, by finite rank operators, by quasi-nilpotent operators and by Riesz operators commuting with T.

Open access

Vaibhav Koutu, Lokesh Shastri and M. M. Malik

Abstract

In the present work, powder zinc oxide samples were prepared by varying NaOH concentration (0.1 M – 0.4 M) using wet-chemical co-precipitation method. As-synthesized ZnO was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL) and Raman spectroscopy. Formation of hexagonal wurtzite structure of the ZnO samples has been revealed from XRD studies. This study further suggests reduction in crystallite size from 40 nm to 23 nm with an increase in NaOH concentration which is confirmed by FESEM. PL and Raman spectroscopy studies of these samples show significant peak shift towards the higher and lower energy respectively, with maximum PL emission between 400 nm and 470 nm region of the visible spectrum. Noticeable inverse relationship between optical properties of ZnO nanoparticles and NaOH concentration may be attributed to the rapid nucleation during the synthesis process. With these remarkable properties, ZnO nanoparticles may find applications in nanoelectronic devices, sensors, nanomedicine, GATE dielectrics, photovoltaic devices, etc.

Open access

Stankovičová M., Miháliková V., Mezovský Ľ., Lašáková A., Medlenová V. and Malík I.

Abstract

In present work, we have studied kinetics of alkaline hydrolysis of 14 compounds, which are phenylcarbamic acid derivatives with integrated N-phenylpiperazine moiety in the structure. The compounds possessed moderate antiarrhythmic and antimycobacterial activity. Their hydrolysis was carried out in an aqueous medium ethanol sodium hydroxide solution. The course of the hydrolysis was observed spectrophotometrically in visible as well as in ultraviolet regions. The pseudo-first order rate constants were calculated at several temperatures. The values of the activation energy EA were determined by the Arrhenius equation. The rate of hydrolysis of the compounds under the study increase with the increase in temperature and it has been differentiated according to the substitution of N-phenylpiperazine as well as to the alkoxy substitution on phenyl ring.

Open access

S. Malik, R. Baz, C. Dina, P. Bordei, A. Rusali and D. M. Iliescu

Abstract

Our study was conducted by the examination of angioCT’s, performing external measurements of aortic arch and the exo and endoaortic measurements of its three. The diameter of the thoracic aorta prior to the origin of the brachiocephalic arterial trunk was found with an average of 31.65 mm and below the left subclavian artery origin we found an average diameter of 24.3 mm. The brachiocephalic arterial trunk had an average diameter of 11.575 mm, 6.05 at carotid artery level and 9.05 mm at the level of the left subclavian artery. The endoaortic average diameter of the brachiocephalic arterial trunk: horizontally, 13.0 mm and vertically 11.7 mm; left common carotid artery horizontal diameter was 10.5 mm and 9.7 mm vertically and the left subclavian artery have 14.1 mm horizontally and 10.8 mm vertically.