3,382 research outputs found

    Numerical simulation and irreversibility analysis of nanofluid flow within a solar absorber duct equipped with a novel turbulator

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    This research presents an innovative alteration to the solar collector's design by integrating a 4-lobed tube with helical tape. The choice of a working fluid, a combination of water and alumina nanoparticles, is purposeful, aiming to reduce irreversibility. Extensive numerical simulations, along with thorough benchmark verification, meticulously assess the system's performance, demonstrating strong alignment with established benchmarks.This study delves into the interaction among pivotal parameters—D* (diameter ratio), Re (Reynolds number), and N (revolution number)—and their impact on essential performance metrics, encompassing ηII (second law performance), Xd (exergy drop), and Φx (exergy drop ratio). With the elevation of all three parameters, the intensified swirl flow facilitates improved heat absorption by the nanofluid, resulting in reduced entropy generation and subsequently, a decrease in exergy drop. More precisely, the increments in Re, N, and D* lead to significant reductions in the value of Xd, with approximately 52.1 %, 4.02 %, and 5.03 %, respectively. When N = 4, D*=0.02, the amount of ηII for Re = 2e4 is 8.38 times greater than that of Re = 4e3. Increasing D* and N leads to substantial improvements in ηII, with approximately 50.02 % and 30.15 % enhancements, respectively. The highest ηII, reaching 0.582, is attained when D*=0.048, N = 7, and Re = 2e4

    Nanoliposomal Auraptene: A Comprehensive Study on Preparation, Characterization, Cytotoxicity, and Anti-Angiogenic Potential

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    Aims: To suppress angiogenesis, auraptene is used in the form of liposome to enhance solubility and effectiveness. Background: Nanoliposomes are spherical nano-sized capsules enclosed by lipid membranes, serving as a biocompatible vehicle to enhance the delivery of therapeutic agents. Objective: The objective of this research is to prepare and characterize nanoliposome-encapsulated auraptene and compare its cytotoxic and anti-angiogenic effects to non-liposomal auraptene. Methods: Liposomal auraptene was formulated using DSPC/DSPG/Cholesterol (molar ratio of 4:1:2) in combination with two different molar ratios of auraptene (0.1 and 0.05). The entrapment efficiency was evaluated using High-Performance Liquid Chromatography (HPLC). Various parameters, including Dynamic Light Scattering (DLS), zeta potential, stability, and release kinetics, were investigated. Subsequently, both liposomal and non-liposomal auraptene, along with bare liposomes, were applied to the MDA-MB-231 cell line for a duration of 72 hours at 37°C at varying concentrations. Cytotoxicity was assessed using the MTT assay. Additionally, the study examined the anti-angiogenic effects on the vessels in the chorioallantoic membrane of chick embryos. Results: The entrapment efficiency of auraptene was found to be satisfactory at 50%. The liposome size ranged from 85 to 241 nm, with a Z-Average of 190.9 nm. The zeta potentials for all formulations were consistently around -55.7, and the Polydispersity Index (PDI) was less than 0.3 for all formulations. The release profile demonstrated approximately 80% drug release over a period of 130 hours. Notably, liposomal auraptene exhibited a significantly lower IC50 value (38.61 [95% Confidence Interval: 30.56 to 48.78]) compared to non-liposomal auraptene (50.36 [95% Confidence Interval: 43.58 to 58.19]) (p = 0.0240). Conclusion: Moreover, the administration of 2.5 and 5 µM of liposomal auraptene led to a reduction in the vessels within the chorioallantoic membrane at the injection site when compared to the control group. In summary, the use of biodegradable nanoliposomal carriers improved the solubility, release profile, and stability of auraptene while demonstrating anticancer and anti-angiogenic properties

    Towards optimization of beam mode for high efficiency laser thermal forming within metallurgical constraints

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    In the laser forming (LF) process, laser induced temperature distribution within the work-piece is of paramount importance. Through control of process parameters and depending on work-piece geometry, the temperature distribution can be altered to achieve either localized plastic compressive strains or elastic-plastic buckling. Conventionally, three process parameters are manipulated in order to control the temperature distribution within the work-piece; traverse speed, average power and spot size. Additionally, the intensity distribution and geometrical shape of the beam incident on the work-piece surface can be manipulated. The latter has the potential to be useful in maintaining bend angle per pass whilst working within strict metallurgical constraints. In this paper, the effect of beam intensity distribution and geometrical shape on the LF of automotive grade high strength DP 1000 steel sheet is investigated numerically and experimentally, with particular emphasis on optimization for minimal micro-structural transformation.</p

    Restrained {2}\{2\}-domination in graphs

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    A restrained {2}\{2\}-dominating function (R{2}\{2\}-DF) on a graph G=(V,E)G=(V,E) is a function f:V{0,1,2}f:V\rightarrow\{0,1,2\} such that : \textrm{(i)} f(N[v])2f(N[v])\geq2 for all vV,v\in V, where N[v]N[v] is the set containing vv and all vertices adjacent to v;v; \textrm{(ii)} the subgraph induced by the vertices assigned 0 under ff has no isolated vertices. The weight of an R{2}\{2\}-DF is the sum of its function values over all vertices, and the restrained {2}\{2\}-domination number γr{2}(G)\gamma_{r\{2\}}(G) is the minimum weight of an R{2}\{2\}-DF on G.G. In this paper, we initiate the study of the restrained {2}\{2\}-domination number. We first prove that the problem of computing this parameter is NP-complete, even when restricted to bipartite graphs. Then we give various bounds on this parameter. In particular, we establish upper and lower bound on the restrained {2}\{2\}-domination number of a tree TT in terms of the order, the numbers of leaves and support vertices

    Synthesis, structure analysis and catalytic activity of two Ln-coordination polymers containing benzophenone-4,4'-dicarboxylate linker

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    Two lanthanide-coordination polymers (Ln-CPs) containing benzophenone-4,4'-dicarboxylate (bpndc(2-)) linker, namely [Er-2(bpndc)(3)(DMF)(2)] (1) and [Yb-2(bpndc)(3)(DMF)(2)] (2) were synthesized and characterized using X-ray crystallography and spectroscopic methods. The topological analysis revealed that both compounds are chiral three-dimensional uninodal 5-connected net of type yfh. These Ln-CPs showed good stability and thus were used as heterogeneous catalysts for the acetalization of glycerol. This study provides some further evidence supporting the effectiveness of Ln-CPs as potential Lewis acid catalysts for chemical transformations

    Hop total Roman domination in graphs

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    AbstractIn this article, we initiate a study of hop total Roman domination defined as follows: a hop total Roman dominating function (HTRDF) on a graph [Formula: see text] is a function [Formula: see text] such that for every vertex u with f(u) = 0 there exists a vertex v at distance 2 from u with f(v) = 2 and the subgraph induced by the vertices assigned non-zero values under f has no isolated vertices. The weight of an HTRDF is the sum of its function values over all vertices, and the hop total Roman domination number [Formula: see text] equals the minimum weight of an HTRDF on G. We provide several properties on the hop total Roman domination number. More precisely, we show that the decision problem corresponding to the hop total Roman domination problem is NP-complete for bipartite graphs, and we determine the exact value of [Formula: see text] for paths and cycles. Moreover, we characterize all connected graphs G of order n with [Formula: see text] Finally, we show that for every tree T of diameter at least 3, [Formula: see text] where [Formula: see text] is the hop total domination number

    Quasi-total Roman reinforcement in graphs

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    AbstractA quasi-total Roman dominating function (QTRD-function) on [Formula: see text] is a function [Formula: see text] such that (i) every vertex x for which f(x) = 0 is adjacent to at least one vertex v for which f(v) = 2, and (ii) if x is an isolated vertex in the subgraph induced by the set of vertices with non-zero values, then f(x) = 1. The weight of a QTRD-function is the sum of its function values over the whole set of vertices, and the quasi-total Roman domination number is the minimum weight of a QTRD-function on G. The quasi-total Roman reinforcement number [Formula: see text] of a graph G is the minimum number of edges that have to be added to G in order to decrease the quasi-total Roman domination number. In this paper, we initiate the study of quasi-total Roman reinforcement in graphs. We first show that the decision problem associated with the quasi-total Roman reinforcement problem is NP-hard even when restricted to bipartite graphs. Then basic properties of the quasi-total Roman reinforcement number are provided. Finally, some sharp bounds for [Formula: see text] are also presented

    Improving Adversarial Robustness via Joint Classification and Multiple Explicit Detection Classes

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    This work concerns the development of deep networks that are certifiably robust to adversarial attacks. Joint robust classification-detection was recently introduced as a certified defense mechanism, where adversarial examples are either correctly classified or assigned to the "abstain" class. In this work, we show that such a provable framework can benefit by extension to networks with multiple explicit abstain classes, where the adversarial examples are adaptively assigned to those. We show that naively adding multiple abstain classes can lead to "model degeneracy", then we propose a regularization approach and a training method to counter this degeneracy by promoting full use of the multiple abstain classes. Our experiments demonstrate that the proposed approach consistently achieves favorable standard vs. robust verified accuracy tradeoffs, outperforming state-of-the-art algorithms for various choices of number of abstain classes.Comment: 20 pages, 6 figure

    Cloud-native RStudio on Kubernetes for Hopsworks

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    In order to fully benefit from cloud computing, services are designed following the "multi-tenant" architectural model, which is aimed at maximizing resource sharing among users. However, multi-tenancy introduces challenges of security, performance isolation, scaling, and customization. RStudio server is an open-source Integrated Development Environment (IDE) accessible over a web browser for the R programming language. We present the design and implementation of a multi-user distributed system on Hopsworks, a data-intensive AI platform, following the multi-tenant model that provides RStudio as Software as a Service (SaaS). We use the most popular cloud-native technologies: Docker and Kubernetes, to solve the problems of performance isolation, security, and scaling that are present in a multi-tenant environment. We further enable secure data sharing in RStudio server instances to provide data privacy and allow collaboration among RStudio users. We integrate our system with Apache Spark, which can scale and handle Big Data processing workloads. Also, we provide a UI where users can provide custom configurations and have full control of their own RStudio server instances. Our system was tested on a Google Cloud Platform cluster with four worker nodes, each with 30GB of RAM allocated to them. The tests on this cluster showed that 44 RStudio servers, each with 2GB of RAM, can be run concurrently. Our system can scale out to potentially support hundreds of concurrently running RStudio servers by adding more resources (CPUs and RAM) to the cluster or system.Comment: 8 pages, 4 figure

    Simulation of melting paraffin with graphene nanoparticles within a solar thermal energy storage system

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    Abstract In this paper, applying new structure and loading Graphene nanoparticles have been considered as promising techniques for enhancing thermal storage systems. The layers within the paraffin zone were made from aluminum and the melting temperature of paraffin is 319.55 K. The paraffin zone located in the middle section of the triplex tube and uniform hot temperatures (335 K) for both walls of annulus have been applied. Three geometries for the container were applied with changing the angle of fins (α = 7.5°, 15° and 30°). The uniform concentration of additives was assumed involving a homogeneous model for predicting properties. Results indicate that loading Graphene nanoparticles causes time of melting to decrease about 4.98% when α = 7.5° and the impact of ϕ improves about 5.2% with reduce of angle from 30° to 7.5°. In addition, as angle declines, the period of melting decreases around 76.47% which is associated with augmentation of driving force (conduction) in geometry with lower α
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