scholarly journals Sequential Processing of Cold Gas Sprayed Alloys by Milling and Deep Rolling

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3699
Author(s):  
Daniel Meyer ◽  
Lars Schönemann ◽  
Nicole Mensching ◽  
Volker Uhlenwinkel ◽  
Bernhard Karpuschewski
Keyword(s):  
Deposition Process ◽  
Material Behavior ◽  
Material Composition ◽  
Deep Rolling ◽  
Forming Process ◽  
Material Deposition ◽  
Particle Bonding ◽  
Future Work ◽  
The Impact ◽  
Cold Gas

Cold gas spraying (CS) is a solid-state material deposition process which, in addition to the flexible repair of individual component areas, also enables the build-up of larger samples. The layers are created on a substrate by the impact-induced bonding of highly accelerated micrometer particles. Since melting does not occur, the material composition can be varied flexibly and independently of material-specific melting points. In this work, the influence of the described forming process on subsequent machining by milling and deep rolling is investigated. The process forces measured during milling and the surface topography after milling and deep rolling were influenced by the material composition and the CS-related properties, e.g., high material hardness or particle bonding. In contrast to prior assumptions, deep rolling was shown to have no influence on the determined hardness depth profile for the investigated materials. Future work will focus on additional analyses, such as the determination of half-widths, to obtain further insight on the material behavior.

Molecular Dynamics Simulation of Au Cluster Depositing on Au Surface in Cold Gas Spray

2007 ◽  
Author(s):  
Hong Gao ◽  
Liangju Zhao ◽  
Danling Zeng ◽  
Lijuan Gao
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Crystalline Structure ◽  
Influence Factors ◽  
Cold Spraying ◽  
Deposition Process ◽  
Local Area ◽  
Dynamics Simulation ◽  
The Impact ◽  
Cold Gas

Cold gas spray is a relatively new coating technique by which coatings can be formed without significant heating of the sprayed powder. In contrast to the conventional thermal spray processes, such as flame, arc, and plasma spraying, in cold spraying there is no melting of particles prior to impact on the substrate. In cold spray, particles are accelerated to a very high velocity by a flowing gas with supersonic speed and the temperature of spray particles is much lower than its melting point. However, being accomplished in so short an interval, the impact and deposition processes are difficult to be observed by experimental ways. Using molecular dynamics simulation, the deposition of nano-scale Au clusters on Au (001) surface was studied. The many-body potential is used to simulate the interatomic force between the atoms. By taking “snapshot”, the impact, deposition process and the final appearances of the cluster and the substrate were observed directly. It is found that both the substrate and the cluster deform and lose the crystalline structure. But after reconstruction and relaxation, both of them recover the crystalline structure. By calculating the temperatures of the substrate and the local area influenced by impinging, it is found that the melt phenomenon occurs during impact and deposition, whereas the temperature of the rest region of the substrate is still below the melt point. In addition, the influence factors on deposition, such as incident velocity and the size of the cluster, are discussed in the paper. Simulation results show that the higher incident velocity or the larger size of the cluster could result in stronger interaction between the substrate and the cluster owing to the higher kinetic energy of the cluster.

Characteristics of Thick Film Deposition in Powder Jet Machining

2013 ◽  
Vol 7 (6) ◽  
pp. 630-637
Author(s):  
Chihiro Nishikawa ◽  
◽  
Naohide Mizukuchi ◽  
Akihiko Tomie ◽  
Keita Shimada ◽  
...  
Keyword(s):  
Deposition Process ◽  
Film Deposition ◽  
Abrasive Jet Machining ◽  
Material Deposition ◽  
Transmission Electron ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Impact Phenomena ◽  
Deposition Processes ◽  
The Impact

Powder jet machining can be used for both material removal (abrasive jet machining) and material deposition processes (powder jet deposition) by changing the powder spray conditions. The transition from the removal to the deposition is investigated. The transition between these two phenomena, removal and deposition, is studied through simulating the impact phenomena of two alumina particles with a glass substrate using the Smoothed Particle Hydrodynamics (SPH) method in this study. Crystalline structures of an alumina film created were observed with a Transmission Electron Microscope (TEM). Observation indicates that a thick multicrystalline film is created when the blasted particles are monocrystalline alumina. It is also concluded that fractures within the particle material are necessary for the deposition process, and that fragments less than 100 nm in size contribute to the deposition of the thick films.

scholarly journals IMPACT OF STRAIN RATE ON MICROALLOYED STEEL SHEET BREAKING

2014 ◽  
Vol 54 (4) ◽  
pp. 281-284 ◽  
Author(s):  
Mária Mihaliková ◽  
Miroslav Német ◽  
Marek Vojtko
Keyword(s):  
Strain Rate ◽  
Steel Sheet ◽  
Loading Rate ◽  
External Factor ◽  
Strength Properties ◽  
Material Behavior ◽  
Material Strength ◽  
Forming Process ◽  
Surface Character ◽  
The Impact

<p>Strain rate is a significant external factor and its influence on material behavior in forming process is a function of its internal structure. The contribution is analysis of the impact of loading rate from 1.6 x 10<sup>-4 </sup>ms<sup>-1</sup> to 24 ms<sup>-1</sup> to changes in the fracture of steel sheet used for bodywork components in cars. Experiments were performed on samples taken from HC420LA grade strips produced by cold rolling and hot dip galvanizing. Material strength properties were compared based on measured values, and changes to fracture surface character were observed.</p>

Computer simulation study about the dependence of amorphous silicon photonic waveguides efficiency on the material quality

2020 ◽  
Vol 90 (3) ◽  
pp. 30502
Author(s):  
Alessandro Fantoni ◽  
João Costa ◽  
Paulo Lourenço ◽  
Manuela Vieira
Keyword(s):  
Amorphous Silicon ◽  
High Throughput Screening ◽  
Simulation Analysis ◽  
Low Cost ◽  
Deposition Process ◽  
Large Area ◽  
Sidewall Roughness ◽  
Sensing Applications ◽  
Fabrication Defects ◽  
The Impact

Amorphous silicon PECVD photonic integrated devices are promising candidates for low cost sensing applications. This manuscript reports a simulation analysis about the impact on the overall efficiency caused by the lithography imperfections in the deposition process. The tolerance to the fabrication defects of a photonic sensor based on surface plasmonic resonance is analysed. The simulations are performed with FDTD and BPM algorithms. The device is a plasmonic interferometer composed by an a-Si:H waveguide covered by a thin gold layer. The sensing analysis is performed by equally splitting the input light into two arms, allowing the sensor to be calibrated by its reference arm. Two different 1 × 2 power splitter configurations are presented: a directional coupler and a multimode interference splitter. The waveguide sidewall roughness is considered as the major negative effect caused by deposition imperfections. The simulation results show that plasmonic effects can be excited in the interferometric waveguide structure, allowing a sensing device with enough sensitivity to support the functioning of a bio sensor for high throughput screening. In addition, the good tolerance to the waveguide wall roughness, points out the PECVD deposition technique as reliable method for the overall sensor system to be produced in a low-cost system. The large area deposition of photonics structures, allowed by the PECVD method, can be explored to design a multiplexed system for analysis of multiple biomarkers to further increase the tolerance to fabrication defects.

The Impact of BRICS in Reconstructing the International Order

2020 ◽  
pp. 87
Author(s):  
Tareq Mohammed Dhannoon AL Taie
Keyword(s):  
International System ◽  
Political Influence ◽  
Active Role ◽  
International Order ◽  
First Century ◽  
International Affairs ◽  
Strategic Action ◽  
Brics Countries ◽  
Future Work ◽  
The Impact

The BRICS countries have a historical aspiration for global leadership, especially Russia and China, and other countries trying to have a position in the pyramid of international powers in the twenty-first century, especially Brazil, India and South Africa, they worked to unify their efforts, in order to achieve integration in the strategic action, activate its role in International affairs, ending American domination , and restructuring an international system that have an active role in its interactions.       The research hypothesis is based on the idea that the BRICS group, despite the nature of its economic composition and its long-term goals, but its political influence as a bloc, is greater than the proportion of its economic influence in restructuring the new international order. The BRICS group has the capabilities to reshape the international order, but disputes among some of its members represent a challenge to its future work. Its goals will not be achieved without teamwork. Third world countries, especially those that reject unipolarism, have regarded one of the pillars supporting multi-polarity, aiming of giving them freedom of movement in international relations. The ultimate goal of the BRICS is a political nature, as economic mechanisms are used to achieve political goals.

Relay Selection-aware Non-orthogonal Multiple Access Networks: Direct and Relaying Mode

2020 ◽  
Vol 13 (3) ◽  
pp. 348-354
Author(s):  
Dinh-Thuan Do ◽  
Minh-Sang V. Nguyen
Keyword(s):  
Relay Selection ◽  
Multiple Access ◽  
Decode And Forward ◽  
Selection Scheme ◽  
Fixed Power ◽  
Transmission Quality ◽  
Improved Performance ◽  
Outage Probabilities ◽  
Future Work ◽  
The Impact

Objective: In this paper, Decode-and-Forward (DF) mode is deployed in the Relay Selection (RS) scheme to provide better performance in cooperative downlink Non-orthogonal Multiple Access (NOMA) networks. In particular, evaluation regarding the impact of the number of multiple relays on outage performance is presented. Methods: As main parameter affecting cooperative NOMA performance, we consider the scenario of the fixed power allocations and the varying number of relays. In addition, the expressions of outage probabilities are the main metric to examine separated NOMA users. By matching related results between simulation and analytical methods, the exactness of derived formula can be verified. Results: The intuitive main results show that in such cooperative NOMA networks, the higher the number of relays equipped, the better the system performance can be achieved. Conclusion: DF mode is confirmed as a reasonable selection scheme to improve the transmission quality in NOMA. In future work, we will introduce new relay selections to achieve improved performance.

Modeling and Experiments of Laser Cladding With Droplet Injection

2005 ◽  
Vol 127 (9) ◽  
pp. 978-986 ◽  
Author(s):  
J. Choi ◽  
L. Han ◽  
Y. Hua
Keyword(s):  
Fluid Flow ◽  
Laser Cladding ◽  
Dynamic Motion ◽  
Cladding Layer ◽  
Melt Pool ◽  
Material Deposition ◽  
Modeling And Experiments ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
The Impact

Laser aided Directed Material Deposition (DMD) is an additive manufacturing process based on laser cladding. A full understanding of laser cladding is essential in order to achieve a steady state and robust DMD process. A two dimensional mathematical model of laser cladding with droplet injection was developed to understand the influence of fluid flow on the mixing, dilution depth, and deposition dimension, while incorporating melting, solidification, and evaporation phenomena. The fluid flow in the melt pool that is driven by thermal capillary convection and an energy balance at the liquid–vapor and the solid–liquid interface was investigated and the impact of the droplets on the melt pool shape and ripple was also studied. Dynamic motion, development of melt pool and the formation of cladding layer were simulated. The simulated results for average surface roughness were compared with the experimental data and showed a comparable trend.

scholarly journals A Qualitative Study of COVID-19 Distress in University Students

2021 ◽  
pp. 216769682110251
Author(s):  
Samantha G. Farris ◽  
Mindy M. Kibbey ◽  
Erick J. Fedorenko ◽  
Angelo M. DiBello
Keyword(s):  
University Students ◽  
Undergraduate Students ◽  
Mental Health Problems ◽  
Financial Strain ◽  
Public Response ◽  
Viral Spread ◽  
Future Work ◽  
The Impact ◽  
Viral Outbreak ◽  
Selection Of

The psychological effect of the pandemic and measures taken in response to control viral spread are not yet well understood in university students; in-depth qualitative analysis can provide nuanced information about the young adult distress experience. Undergraduate students ( N = 624) in an early US outbreak “hotspot” completed an online narrative writing about the impact and distress experienced due to the COVID-19 pandemic. Data were collected April-May 2020. A random selection of 50 cases were sampled for thematic analysis. Nine themes were identified: viral outbreak distress, fear of virus contraction/transmission, proximity to virus, dissatisfaction with public response, physical distancing distress, social distancing distress, academic and school-related distress, disruptive changes in health behavior and routines, financial strain and unemployment, worsening of pre-existing mental health problems, and social referencing that minimizes distress. Future work is needed to understand the persistence of the distress, in addition to developing methods for assessment, monitoring, and mitigation of the distress.

scholarly journals Impact of a Series of Educational Talks Taught by Health Professionals to Promote Healthy Snack Choices among Children

Children ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 203
Author(s):  
Víctor Arufe Giráldez ◽  
Javier Puñal Abelenda ◽  
Rubén Navarro-Patón ◽  
Alberto Sanmiguel-Rodríguez
Keyword(s):  
Nutritional Quality ◽  
Positive Impact ◽  
Total Sample ◽  
Overweight And Obesity ◽  
Healthy Habits ◽  
Quasi Experimental ◽  
Nutrition And Dietetics ◽  
Future Work ◽  
The Impact

Background: One of the great challenges facing today’s society is the need to combat overweight and obesity in schoolchildren. This study aimed to analyze the impact of a cycle of didactic talks—given to families by a specialist in pediatrics, a specialist in nutrition and dietetics and a specialist in physical exercise—on childrens’ snack choices and nutrition quality. Methods: A longitudinal, quasi-experimental and quantitative investigation was designed, working with a total sample of 50 students divided into control and experimental groups. The nutritional quality of daily snacks was recorded during the month before and the month after the cycle of talks given by health experts. Results: An increase in the nutritional quality of the snacks was observed in the days after the talk—but, after a week, values returned to normal. Conclusions: The giving of educational talks to promote healthy habits may have a positive impact on the nutritional quality of school snacks in the days immediately following the talks. However, some forgetfulness was detected over time, which reduced the nutritional quality of the snacks once more. For future work, it is recommended that researchers measure the impact produced by giving regular talks.

Health, happiness and your future: using a “men’s group” format to work with homeless men in London

2017 ◽  
Vol 13 (4) ◽  
pp. 403-418
Author(s):  
Kate Thompson ◽  
Pippa Brown ◽  
Stephanie Vieira
Keyword(s):  
Mental Health ◽  
Psychosocial Issues ◽  
Horn Of Africa ◽  
Content Type ◽  
Health And Wellbeing ◽  
Care Services ◽  
Homeless Men ◽  
Group Members ◽  
Future Work ◽  
The Impact

Purpose The purpose of this paper is to describe an intervention with a group of homeless men from the Horn of Africa, service users of the Horn of Africa Health and Wellbeing Project in London. The group was conceived by the second author who noted the presence of significant psychosocial issues for her clients, but equally their reluctance to access mainstream mental health or social care services. Design/methodology/approach Designing the group and introducing it to the men involved threw up some challenges which are explored, and the impact of the group on participants is evaluated. Findings Overall both the participants and the facilitators evaluated the group positively and it appeared to have led to lasting change for some of the group members, and this is described. The authors argue that this sort of group may be a more acceptable way to work on psychosocial issues than something more directly focused on mental health intervention. The group protocol is outlined along with suggestions for future work in this area. Originality/value This intervention represents a creative alternative to more mainstream psychological interventions for homeless or exiled men.

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