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 coefficient 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

Floquet non-equilibrium Green's function and Floquet quantum master equation for electronic transport: The role of electron-electron interactions

Non-equilibrium Green's function (NEGF) and quantum master equation (QME) are two main classes of approaches for electronic transport. We discuss various Floquet variances of these formalisms for transport properties of a quantum dot driven via interaction with an external periodic field. We first derived two versions of the Floquet NEGF. We also explore an ansatz of the Floquet NEGF formalism for the interacting systems. In addition, we derived two versions of Floquet QME in the weak interaction regime. With each method, we elaborate on the evaluation of the expectation values of the number and current operators. We examined these methods for transport through a two-level system that is subject to periodic driving. The results of all four methods show great consistency. We expect these Floquet quantum transport methods to be useful in studying molecular junctions exposed to light.Comment: 11 pages, 5 figure

Floquet driven frictional effects

When the coupled electron-nuclear dynamics are subjected to strong Floquet driving, there is a strong breakdown of the Born-Oppenheimer approximation. In this article, we derive a Fokker-Planck equation to describe non-adiabatic molecular dynamics with electronic friction for Floquet driven systems. We first provide a new derivation of the Floquet quantum-classical Liouville equation (QCLE) for driven electron-nuclear dynamics. We then transform the Floquet QCLE into a Fokker-Planck equation with explicit forms of frictional force and random force. We recast the electronic friction in terms of Floquet Green's functions such that we can evaluate the electronic friction explicitly. We show that the Floquet electronic friction tensor exhibits antisymmetric terms even at equilibrium for real-valued Hamiltonian, suggesting that there is a Lorentz-like force in Floquet driven non-Born Oppenheimer dynamics even without any spin-orbit couplings.Comment: Main: 5 pages, 3 figuers, Supplement: 5 pag

Assessment of anthropometric indices in patients with phenylketonuria

Background: Dietary phenylalanine restriction is the main treatment of phenylketonuria (PKU, OMIM 261600). There are studies which have demonstrated growth retardation in these patients, and some are in contrast. This study is done to assess the growth parameters of treated PKU patients. Method : 105 treated PKU patients were compared to 105 controls matched in age, sex and birth weight. Weight, height, head circumference, weight for height and BMI (weight/height2) were measured and transformed into Z-scores. Correlations between pretreatment plasma Phenylalanine concentrations mean plasma Phenylalanine concentrations, and anthropometric parameters were analyzed in patients. Findings: There was no significant difference between weight Z-scores, weight/height and BMI means, in patients and controls (P: 0.842, p: 0.257, p: 0.622 respectively). There was a significant decrease in height Z-scores of patients more than 2 years old (P: 0.005). Also, there was a significant decrease in patient's Head circumference than controls'(P: 0.03), however this significance got more in patients above 3 years old (P: 0.001). There was not a significant correlation between weight and height Z-scores, and patients' pretreatment plasma phenylalanine (P: 0.054 and 0.15), however this correlation was positively significant in HC Z-scores (r= -0.445, P: 0.01).Moreover,no correlation was found between growth parameters and mean plasma phenylalanine concentrations. Conclusions: Growth parameters are not impaired in early treated PKU patients; however height in patients more than 2 years old and Head circumference in patients more than 3 years old were retarded. Disease severity is a more effective factor in HC growth than dietary adherence

Nonadiabatic dynamics near metal surfaces with periodic drivings: A generalized surface hopping in Floquet representation

With light-matter interaction extending into strong regime, as well as rapid development of laser technology, systems subjecting to a time-periodic perturbation are attracted broad attention. Floquet theorem and Floquet time-independent Hamiltonian are powerful theoretical framework to investigate the systems subjecting to time-periodic drivings. In this study, we extend the previous generalized SH algorithm near metal surface (J. Chem. Theory Comput. 2017, 13, 6, 2430-2439) to the Floquet space, and hence, we develop a generalized Floquet representation based surface hopping (FR-SH) algorithm. Here, we consider open quantum system with fast drivings. We expect that the present algorithm will be useful for understanding the chemical processes of molecules under time-periodic drivings near the metal surface.Comment: 20 pages, 3 fogure

A hierarchical self-healing SLA for cloud computing

The service level agreement (SLA) is a mutual contract between the service provider and consumer which determines the agreed service level objective (SLO). The common SLA is a plain documental agreement without any relation to other dependent SLAs during the different layers of cloud computing. Hence, the cloud computing environment needs the hierarchical and autonomic SLA. This paper proposes the SH-SLA model to generate a hierarchical self-healing SLA in cloud computing. The self-healing ability contains the SLA monitoring, violation detecting and violation reacting processes. In SH-SLA, the related SLAs communicate with each other hierarchically. The SLA would be able to check its QoS and notify the recent status to dependent SLAs. Furthermore, SH-SLA could prevent or propagate the notified violations by an urgent reaction. Consequently, the service providers have a great chance to prevent the violated SLA before sensing by end users. The SH-SLA model is simulated and the experiment results have presented the violation detection and reaction abilities of the proposed model in cloud computing. Besides, the end users meet the lesser violations in SH-SLA than the common SLA

Genetic algorithms-based quality of service service selection in cloud computing using multilayer perceptron

There exist many similar services by different service providers available within the cloud environment. When the service offerings are packaged with similar functionalities, service consumers will be having a difficult time in evaluating the most relevant services that fit to their individual requirement. To address this issue, this paper proposes an effective services classification in cloud environment, which will classify the equivalent services based on their quality of service (QoS). The attribute selection method is based genetic algorithms (GA) and is designed to rank the cloud services before the attributes are being fed into a multi-layer perceptron (MLP) classification system. The results have shown a considerably high performance of 98.5%