George Arghir

Technical University of Cluj-Napoca

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Ioan Petean

Babeș-Bolyai University

Liviu Brânduşan

Technical University of Cluj-Napoca

Maria Tomoaia-Cotişel

Babeș-Bolyai University

Dan Anastasiu Pop

Technical University of Cluj-Napoca

Cristian Suciu

Technical University of Cluj-Napoca

Gertrud Alexandra Paltinean

Babeș-Bolyai University

Aurora Mocanu

Babeș-Bolyai University

Marius Bărăian

Technical University of Cluj-Napoca

V. Candea

Technical University of Cluj-Napoca

Gabriel Batin

Technical University of Cluj-Napoca

Cooperative Institutions

Technical University of Cluj-Napoca

Babeș-Bolyai University

Academy of Romanian Scientists

Spitalul Clinic Județean de Urgență Cluj-Napoca

Romanian Academy

University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca

Iuliu Hațieganu University of Medicine and Pharmacy

Universitatea Națională de Știință și Tehnologie Politehnica București

University of Auckland

University of Southern California

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ON THE MATHEMATICAL ALGORITHM OF SOME ANCIENT DRACHMAS MINTING TIME

ACTA TECHNICA NAPOCENSIS - Series: APPLIED MATHEMATICS, MECHANICS, and ENGINEERING (2014)

George Arghir Ioan Petean Emanoil Pripon Petru Păşcuţă

It was selected three Dyrrachium drachmas issued between 229-30 BC of the Treasure of Cehei to establish minting time. There were measured dimensions, weights, and hardness. Finally they were subjected to X-ray diffraction determining the crystallographic parameter, grain size, and material relative deformation that existed at the measurements time. It was established the amount of silver as 96 – 98 weight %. Relative deformation was considered conclusive of all the results that led to the determination years of minting drachmas and those that were magister monetarius who supervised for, under whose authority coins were issued. They are, in order of age, Phereneikos in 164.5 BC, then Meniskos in 115 BC, and the last Xenon 103 BC. Key words: ancient drachmas, XRD patterns, relative deformation

Treasure

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CORROSION TESTS OF AlMn1 / Ni201 BRAZED JOINT BY SALINE AND ACIDIC SPRAYING

ACTA TECHNICA NAPOCENSIS - Series: APPLIED MATHEMATICS, MECHANICS, and ENGINEERING (2019)

Nicu-Marian Trandafir George Arghir Liviu Brânduşan Gabriel Batin

Heat exchangers of hybrid vehicles contain brazed joints composed by aluminum alloy AlMn1 and nickel Ni201. Depending on the environment in which they are located, these joints can corrode and, consequently, endanger the functionality of the heat exchanger. As the AlMn1 / Ni201 brazed joint is a metallic joint, it must be tested for corrosion, especially if the hybrid car circulates in areas with high salinity of air or water (sea breeze, saline mines etc.). At the same time, acid corrosion testing is required because hybrid vehicles contain more batteries and in case of battery failure, leakage or loss of sulfuric acid may corrode the AlMn1 / Ni201 brazed joint. In this work, it is demonstrated that the acid corrosion rate is higher than the saline corrosion rate due to the higher aggressiveness of acetic acid compared to that of sodium chloride. Key words: brazing, aluminum-nickel brazing

Brazing

Mist

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The Study of Fatigue Behaviour at the Contact of some Sintered Materials from Powder Based on Iron

Advanced materials research (2007)

Liviu Brânduşan George Arghir

Iron powder

10.4028/0-87849-460-x.115

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On the algorithmic behaviour of complex physical systems

arXiv (Cornell University) (2012)

Dan Anastasiu Pop G. M. Mocanu George Arghir

Starting from the idea that the underlying mechanisms driving the observable processes in nature are algorithmic, we exemplify this in two ways: nature works as a computing machine and thus the processes running on it optimize themselves in an intrinsic manner so as to save time. As a first example we will place the empirical analysis of oxidation in the context of algorithm complexity analysis. Second, we will show that deformations suffered by a shape-memory alloy may be produced by nature showing a LIFO (Last In First Out) behaviour.

10.48550/arxiv.1207.5398

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UTILISATION OF COMPOSITE MATERIALS IN THE MODEL AIRCRAFT CONSTRUCTION

ACTA TECHNICA NAPOCENSIS - Series: APPLIED MATHEMATICS, MECHANICS, and ENGINEERING (2017)

George Arghir Paul Béré

Constructing dihedral U optimum wing Super Climber glider, having 30 % horizontal part of the wingspan, using composite materials for wing and for horizontal stabilizer is better. It has a slight increase of lift and speed, better cruise stability, safety determalization, never broke at the dihedral start, never fallen on a wing and climb on the air (after 50 test flights). It is more resistant to shocks. Super Climber (SC) has the same size as Climber (C) and uses the same airfoil profile for wing – B 7406f, for horizontal stabilizer – C is using CRD 921 and SC – Clark Y 70 %. Both are F1E class gliders – gliders with automatic steering – slope soaring gliders. The composite material construction is more favorable aerodynamically and in use (training and in contests). Key words : Model airplane, glider, U optimum wing, composite materials

Wingspan

Climb

Airplane

Wing loading

Chord (peer-to-peer)

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INFLUENCE OF WING TIP SHAPE ON LONGITUDINAL

ACTA TECHNICA NAPOCENSIS - Series: APPLIED MATHEMATICS, MECHANICS, and ENGINEERING (2016)

George Arghir

Abstract : There were analyzed four different wing tip shapes. The coefficient of restoration, CR, is given by the ratio of the largest half wing to the smaller half wing in horizontal projection. Flight is stable for CR = 1.00. The influence of wing thickness profile is high. Increasing in the thickness from 5 mm to 15 mm (3 times), CR increases by 48% (5 mm) and 34% (15 mm). Increasing tilt angle, γ, CR increases from 1.00 to ∞ for γ = 0o, respectively, 80o (α = 10 °) (α - angle of the wing tip to the horizontal), then jump to -∞ and grow with negative values. CR increase from 1.00 to ∞ jumping to -∞ for γ = 60°, with α = 30°. Sideslip occurs when model aircraft has horizontally the longitudinal axes and wing is verticals. Airplane model is in an unstable area, for γ = 80o, respectively, 60o for α = 10o, respectively, 30o. The wing tip should be made of straight lines not rounded. Key words : Glider airplane model, wing end shape, longitudinal stability.

Airplane

Washout

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Calcium and magnesium content in brier (Rosa canina L.) fruits at the

Andreea Brașovan Vasilica Mândroc Ramona Flavia Câmpean Ioan Petean Vlad Codrea

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MICROSTRUCTURE OF THE Fe-FeMn TRANSITION ZONE

Cristian Suciu George Arghir Liviu Brânduşan Ioan Petean

The transition zone microstructure between pressed and sintered iron powder and ferromanganese powder was studied. Cylindrical specimens of iron base powder and ferromanganese powder (to give 5-15 mass% Mn) at the top for analysis of manganese diffusion zone in steel was made. Specimens were pressed at 600 MPa and sintered in H2 and endogas at temperatures of 1120oC and 1230oC for 30 minutes. Sintered specimens were analyzed by optical microscopy and micro-hardness test. The addition of manganese leads to a linear increase of hardness, influencing strongly the microstructure of ferrite, pearlite, and bainite, and increasing porosity.

Ferromanganese

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The Study of Fatigue Behaviour at the Contact of some Sintered Materials from Powder Based on Iron

Advanced materials research (2007)

Liviu Brânduşan George Arghir

The analysis of a large range of sintered parts shows the fact, they are strained at contact fatigue, in most of the cases. The Hertzian pressure, at which materials in contact are subjected, establishes the appearance of variable stress, which records a maximum at some depth under the contact surface. In the case of sintered materials this stress variation conducts to a faster degradation of strained surface than in the case of compact materials. This is because the stress variation establishes a critical state at the level of stress concentrators, generated by pores, standing in material structure, leading to formation of some cracks which may propagate at the level intergranular necks, producing removal for some particles of material. The accomplished research on sintered materials, having different chemical compositions, revealed the fact, at the beginning, that the materials undergo a cold hardening, indicated by a hardness increasing, followed by some cracks generating, accompanied by their extension and material removal. This process develops in the same mode for all investigated materials, but with different intensity.

Hardening (computing)

10.4028/www.scientific.net/amr.23.115

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GREEN DENSITY MODELLING OF IRON AND FERROMANGANESE MIXED POWDERS

ACTA TECHNICA NAPOCENSIS - Series: APPLIED MATHEMATICS, MECHANICS, and ENGINEERING (2012)

Cristian Suciu George Arghir Ioan Petean Dan Frunză Liviu Brânduşan

An experimental study on green density of iron and ferromanganese mixed powders was done. The influence of added Mn up to 15 wt. % to Fe powder on the compressibility has been investigated. Cylindrical specimens of mixed iron powder (DWP400) and ferromanganese powder (FeMn80C20) were made . The samples were bilaterally pressed at 100 to 600 MPa. Pressed samples were analyzed by density measurements and also by numerical method. The density of mixed powders decreases as the manganese content increases, and have the maximum value for a content of 5 wt. % Mn. Key words: density, manganese, iron, simulation

Ferromanganese

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