International visibility of Armenian domestic journals:the role of scientific diaspora

Purpose:Nearly 122 scientific journals are currently being published in Armenia-of which only six are indexed by WoS and/or Scopus databases.The majority of the national journals are published in the Armenian language,solely possessing abstracts written in English,although there are also English-language and multi-language journals with articles not only in Armenian but also in other foreign languages.The aim of this article is to study the visibility of the(non-indexed)national Armenian journals in the WoS database through citation analysis.In consideration of the existence of a relevant Armenian“diaspora”in the world,this article also attempts to estimate its impact in terms of citation statistics.Design/methodology/approach:For this end,we have identified citations to the national/domestic Armenian journals in the WoS database in comparison with the share of citations received from“diaspora”researchers(researchers of Armenian origin born in foreign countries and those originally from Armenia who have emigrated to foreign countries).Findings:Among the 116 Armenian domestic journals analyzed(not indexed by WoS),only 47 were found to be cited in WoS.Of these journals,almost 12%are citations by“diaspora”researchers,most of which concern Social Science and Humanities journals.Research limitations:Although the surnames of Armenians end with-i(y)an,sometimes,the Diaspora Armenians,surnames are changed or modified or they are not ending with-i(y)an,in this case we may fail to identify them.Practical implications:This study can help to build new,more deep and comprehensive relations with scientific diasporas.Originality/value:This study offers a new understanding of multifaced research collaboration with scientific diasporas and their role in internationalization of domestic journals.

Analyzing the Interplay of Sintering Conditions on Microstructure and Hardness in Indirect Additive Manufacturing of 17-4PH Stainless Steel

Indirect additive manufacturing(AM)methods have recently attracted attention from researchers thanks to their great potential for cheap,straightforward,and small-scale production of metallic components.Atomic diffusion additive manufacturing(ADAM),a variant of indirect AM methods,is a layer-wise indirect AM process recently developed based on fused deposition modeling and metal injection molding.However,there is still limited knowledge of the process conditions and material properties fabricated through this process,where sintering plays a crucial role in the final consolidation of parts.Therefore,this research,for the first time,systematically investigates the impact of various sintering conditions on the shrinkage,relative density,microstructure,and hardness of the 17-4PH ADAM samples.For this reason,as-washed samples were sintered under different time-temperature combinations.The sample density was evaluated using Archimedes,computed tomography,and image analysis methods.The outcomes revealed that sintering variables significantly impacted the density of brown 17-4PH Stainless Steel samples.The results indicated more than 99% relative densities,higher than the value reported by Markforged Inc.(~96%).Based on parallel porosities observed in the computed tomography results,it can be suggested that by modifying the infill pattern during printing,it would be possible to increase the final relative density.The microhardness of the sintered samples in this study was higher than that of the standard sample provided by Markforged Inc.Sintering at 1330℃ for 4 h increased the density of the printed sample without compromising its mechanical properties.According to X-ray diffraction analysis,the standard sample provided by Markforged Inc.and“1330℃—4 h”one had similar stable phases,although copper-rich intermetallics were more abundant in the microstructure of reference samples.This study is expected to facilitate the adoption of indirect metal AM methods by different sectors,thanks to the high achievable relative densities reported here.

Improvement of Surface Mechanical and Tribological Characteristics of L-PBF Processed Commercially Pure Titanium through Ultrasonic Impact Treatment

Multi-pass ultrasonic impact treatment(UIT)was applied to modify the microstructure and improve the mechanical and tribological characteristics at the near-surface region of commercially pure Ti(CP-Ti)specimens produced by the laser powder bed fusion(L-PBF)method.UIT considerably refined the L-PBF process-related acicular martensites(α′-M)and produced a well-homogenized and dense surface microstructure,where the porosity content of 1-,3-,and 5-pass UITed samples was reduced by 43,60,and 67%,respectively.The UITed samples showed an enhancement in their near-surface mechanical properties up to a depth of about 300μm.The nanoindentation results for the 3-pass UITed sample revealed an increase of about 53,45,and 220%in its nanohardness,H/E_(r),and H_(3)/E_(r)^(2)indices,respectively.The stylus profilometry results showed that performing the UIT removed the L-PBF-related features/defects and offered a smooth surface.The roughness average(R_(a))and the skewness(R_(sk))of the 3-pass UITed sample were found to be lower than those of the L-PBFed sample by 95 and 223%,respectively.Applying the UIT also enhanced the material ratio,where the maximum load-bearing capacity(~100%)in as-L-PBFed(as-built)and 3-pass UITed samples was obtained at 60-and 10-µm depths,respectively.The tribological investigations showed that applying the UIT resulted in a significant reduction of wear rate and average coefficient of friction(COF)of CP-Ti.For instance,under the normal pressures of 0.05 and 0.2 MPa,the wear rate and COF of the 3-pass UITed sample were lower than those of the L-PBFed sample by 65 and 58%,and 20 and 17%,respectively.

Tribological behaviour of AZ31 magnesium alloy reinforced by bimodal size B_(4)C after precipitation hardening

This study investigated dry sliding wear properties of AZ31 magnesium alloy and B_(4)C-reinforced AZ31 composites containing 5, 10, and 20 wt.% B_(4)C with bimodal sizes under different loadings(10-80 N) at various sliding speeds(0.1-1 m/s) via the pin-on-disc configuration.Microhardness evaluations showed that when the distribution of B_(4)C particles was uniform the hardness of the composites increased by enhancing the reinforcement content. The unreinforced alloy and the composite samples were examined to determine the wear mechanism maps and identify the dominant wear mechanisms in each wear condition and reinforcement content. For this purpose, wear rates and friction coefficients were recorded during the wear tests and worn surfaces were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry analyses. The determined wear mechanisms were abrasion, oxidation, delamination, adhesion, and plastic deformation as a result of thermal softening and melting. The wear evaluations revealed that the composites containing 5 and 10 wt.% B_(4)C had a significantly higher wear resistance in all the conditions. However, 20 wt.% B_(4)C/AZ31 composite had a lower resistance at high sliding speeds(0.5-1 m/s) and high loadings(40-80 N) in comparison with the unreinforced alloy. The highest wear resistance was obtained at high sliding speeds and low loadings with the domination of oxidative wear.

Microstructure and Mechanical Performance of Ti-6Al-4V Lattice Structures Manufactured via Electron Beam Melting(EBM):A Review

Electron beam melting(EBM) process is an additive manufacturing process largely used to produce complex metallic components made of high-performance materials for aerospace and medical applications.Especially,lattice structures made by Ti-6A1-4V have represented a hot topic for the industrial sectors because of having a great potential to combine lower weights and higher performances that can also be tailored by subsequent heat treatments.However,the little knowledge about the mechanical behaviour of the lattice structures is limiting their applications.The present work aims to provide a comprehensive review of the studies on the mechanical behaviour of the lattice structures made of Ti-6A1-4V.The main steps to produce an EBM part were considered as guidelines to review the literature on the lattice performance:(1) design,(2) process and(3) post-heat treatment.Thereafter,the correlation between the geometrical features of the lattice structure and their mechanical behaviour is discussed.In addition,the correlation among the mechanical performance of the lattice structures and the process precision,surface roughness and working temperature are also reviewed.An investigation on the studies about the properties of heat-treated lattice structure is also conducted.

A Comprehensive Overview on the Latest Progress in the Additive Manufacturing of Metal Matrix Composites: Potential, Challenges, and Feasible Solutions

Nowadays, as an emerging technology, additive manufacturing(AM) has received numerous attentions from researchers around the world. The method comprises layer-by-layer manufacturing of products according to the 3D CAD models of the objects. Among other things, AM is capable of producing metal matrix composites(MMCs). Hence, plenty of works in the literature are dedicated to developing different types of MMCs through AM processes. Hence, this paper provides a comprehensive overview on the latest research that has been carried out on the development of the powder-based AM manufactured MMCs from a scientific and technological viewpoint, aimed at highlighting the opportunities and challenges of this innovative manufacturing process. For instance, it is documented that AM is not only able to resolve the reinforcement/matrix bonding issues usually faced with during conventional manufacturing of MMCs, but also it is capable of producing functionally graded composites and geometrically complex objects. Furthermore, it provides the opportunity for a uniform distribution of the reinforcing phase in the metallic matrix and is able to produce composites using refractory metals thanks to the local heat source employed in the method. Despite the aforementioned advantages, there are still some challenges needing more attention from the researchers. Rapid cooling nature of the process, significantly different coe fficient of expansion of the matrix and reinforcement, processability, and the lack of suitable parameters and standards for the production of defect-free AM MMCs seem to be among the most important issues to deal with in future works.

Effect of position and force tool control in friction stir welding of dissimilar aluminum-steel lap joints for automotive applications

Widespread use of aluminum alloys for the fabrication of car body parts is conditional to the use of appropriate welding methods,especially if dissimilar welding must be performed with automotive steel grades.Friction stir welding(FSW)is considered to be a reasonable solution to obtain sound aluminum-steel joints.In this context,this work studies the effects of tool position and force control in dissimilar friction stir welding of AA6061 aluminum alloy on DC05 low carbon steel in lap joint configuration,also assessing proper welding parameter settings.Naked eye and scanning electron microscopy(SEM)have been used to detect macroscopic and microscopic defects in joints,as well as to determine the type of intermixture between aluminum and steel.The joint strength of sound joints has been assessed by shear tension test.Results point out that tool force control allows for obtaining joints with better quality and strength in a wider range of process parameters.A process window has been determined for tool force conditions to have joints with adequate strength for automotive purposes.

Comparative analysis of permissioned blockchain frameworks for industrial applications

Blockchain is a technology that creates trust among non-trusting parties without relying on any intermediaries.Consequently,it has attracted the interest of companies operating in a multitude of sectors.However,due to the number of different blockchain solutions that have emerged in the last few years and their rapid changes,it is challenging for such companies to orient their technological decisions.This paper presents a comparative analysis of the key dimensions—namely,governance,maturity,support,latency,privacy,interoperability,flexibility,efficiency,resiliency,and scalability—of some of the most-used permissioned blockchain platforms.Moreover,we present the results of a performance evaluation considering the following frameworks:Hyperledger Fabric 2.2,Hyperledger Sawtooth 1.2,and ConsenSys Quorum 21.1(with both the GoQuorum client and the Hyperledger Besu client).The platforms were tested under similar conditions,and official releases were used,such that our findings provide a reference for companies establishing their technological orientation.

Microstructure and Corrosion Properties of CP-Ti Processed by Laser Powder Bed Fusion under Similar Energy Densities

In this work, two types of CP Ti cubes with similar volumetric energy densities(VED) but diff erent process parameters were produced using laser powder bed fusion(LPBF) method. The corrosion behavior of the fabricated specimens was investigated by conducting electrochemical impedance spectroscopy(EIS) and polarization experiments in simulated body fl uid(SBF) solution at 37 °C. The results indicated that the microstructure and porosities, which are of great importance for biomedical applications, can be controlled by changing the process parameters even under constant energy densities. The sample produced with a lower laser power(E1) was featured with a higher level of porosity and thinner alpha laths, as compared with the sample fabricated with a higher laser power(E2). Moreover, results obtained from the bioactivity tests revealed that the sample produced with a higher laser power conferred a slight improvement in the bioactivity due to the higher amount of porosity. Lower laser power and hence higher porosity level promoted the formation of bone-like apatite on the surface of the printed specimens. The potentiodynamic polarization tests revealed inferior corrosion resistance for the fabricated sample with higher porosity. Moreover, the EIS results after diff erent immersion times indicated that a stable oxide film was formed on the surface of samples for all immersion times. After 1 and 3 days of immersion, superior passivation behavior was observed for the sample fabricated with lower laser power. However, very similar impedance and phase values were observed for all the samples after 14 days of immersion.

Digital Dashboards for Smart City Governance: A Case Project to Develop an Urban Safety Indicator Model

This paper illustrates a case project to design a digital dashboard for governing the urban safety of an Italian city and proposes a methodology for the definition of a set of safety measurement indicators. Results show that the method is easy to be used to identify the most crucial areas of the city, in several domains of application that have been identified. The study can substantially support policy makers in the development of their strategies and in the measurement of the effectiveness of their decisions.