Due to potential energy and cost savings benefits, adhesive joining has been recently considered for heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems. HVAC adhesive bonding requires cost-effective and adequate surface preparations of adherents. This article investigates the use of abrasion, traditional single-beam laser, and a laser-interference technique as surface preparations of copper surfaces. Surface morphology is characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Effective submicrometer peak-to-valley structuring with a periodicity of similar to 2.7 mu m was demonstrated for laser-interference processing. Single-lap shear tests were conducted for 89 joints made with bondline thicknesses of 0.15 and 0.3 mm. Data on process variables and measured variables included open-time, bond length, maximum load, displacement at failure, shear lap strength, and failure mode. A statistical analysis was conducted on each lot to determine the lower limit with 95% confidence intervals for displacements at failure and shear lap strengths. A comparison is presented between the properties of laser-structured joints with respect to those prepared by abrasion, which is considered the baseline surface preparation technique. Based on this comparison, one single-beam laser technique and two laser-interference techniques were shown to exhibit vastly superior performance over the joints made with abraded specimens.

Convective instabilities in the semi-solid mushy zone can trigger channel formation that leads to defects known as freckles, channel segregates and A-type segregates. In the present work, Flemings’ model is used to determine conditions for the onset of local remelting when buoyancy-driven flow is suddenly triggered in an initially stagnant mushy zone. An expression in the form of a Rayleigh number, and its associated critical value Racrit, above which the local remelting condition is satisfied, are derived. Using thermophysical data from CALPHAD, these expressions are evaluated using results from benchmark experimental and numerical studies for the nickel-based superalloy SX-1 and Pb–Sn alloys. The correlation of this local-remelting criterion with previously reported empirical criteria is also tested for various steel compositions. It is found that Racrit varies with the local average solid fraction and several thermophysical properties. Since these properties can vary substantially within a relatively narrow composition range, it is suggested that Racrit is a strongly composition dependent parameter.

In the present study, the physico-chemical quality of the water in the Midia coastal area, the Tasaul Lake and the Siutghiol Lake water bodies were analyzed, as integrated sites in the territory of the North Dobrogea FLAG. This study allows establishing the state of favourability of the aquatic ecosystem, focusing on the chlorophyll content as the basis of the trophic level. The premise of a stable ecosystem induces the possibility of developing natural fish resources. An essential attribute in the context of preserving natural heritage and increasing the attractiveness for fishing activities, is the need to evaluate the qualitative and quantitative profile of the phytoplankton and, respectively, the eutrophication indicators. If aquaculture activities will be developed in the analyzed areas in the future, they could increase the economic value of the Romanian sector of the Black Sea. The biological analyzes of the water quality are the basis of the substantiation of some methods of its determination and evaluation. Thus, testing the concentration of chlorophyll, the classes of algae and the photosynthetic activity, are useful for the evaluation of eutrophication in the aquatic environment, but also for the evaluation of productivity in the surface waters studied. At the same time, the determination and evaluation of the physical and chemical parameters of water quality allowed the realization of some correlations with the structure of the biota. In this sense, the analysis methods are based on the use of modern equipment based on real time (in situ) determinations.

Metal additive manufacturing, characterized by rapid solidification, yields refined grains with a distinctive cellular subgrain microstructure that plays a pivotal role in determining material properties. Due to the significant computational expense demanded to simulate the required physics with submicron spatial resolution, their numerical simulations have been limited to proof-of-concept studies to either 2D or small subregions of a melt pool. In this study, an open-source, scalable, solidification code, muMatScale, based on the cellular automaton method, has been developed to predict the grain and the underlying subgrain microstructure over an entire melt pool. The model incorporates flexible parallelization schemes, utilizing MPI and OpenMP GPU Offloading, in addition to appropriate multi-physics specific to non-equilibrium rapid solidification in AM. The impact of nucleation parameters on grain microstructures was investigated with a focus on grain size variations and morphology transitions. With selected nucleation parameters, the simulation predicted the grain size, subgrain morphology, crystallographic orientation, and microsegregation aligned with experimental measurements. The model demonstrates that epitaxial grain growth is a dominant factor at the melt pool boundary, influencing grain size variation under different grain sizes in the build plate while maintaining consistent primary dendrite arm spacing under identical thermal conditions. The highly efficient numerical model enables large-scale simulations with a spatial resolution of 100nm or less, unveiling unprecedented insights into thermal and solutal diffusion driven grain growth, and the subgrains with microsegregation within grains in 3D across scales. muMatScale will enable the linking of submicron length-scale microstructure to part-level material behavior by investigating fundamental solidification problems at the intercellular scale in many-track and many-layer builds.

Two A356 aluminum alloys (Al–Si–Mg), one with 0.09 wt.

The Material Plasma Exposure eXperiment (MPEX) project seeks to design a steady-state linear plasma facility at Oak Ridge National Laboratory that will be used to study plasma-material interactions (PMIs) at fusion prototypic levels, supporting the evaluation and development of materials for the next generation of fusion devices. This study is focused on PMI exposure of small-size neutron-irradiated specimens, which are clamped onto an actively cooled component. A thermohydraulic evaluation of a new MPEX target assembly design to assess the appropriate operation during MPEX operation is presented. To further guide the design and assess the structural integrity of the components under expected loads, preliminary thermomechanical stress analyses were also conducted. To ensure good thermal contact between the components, thermal interface materials, such as silver flexible graphite, were used in the assembly.It was found that the maximum target temperatures of 1572, 1463, and 1315 K were obtained for Grafoil thicknesses of 0.61, 0.38, and 0.25 mm, respectively. The distribution of the axial deformation at high heat fluxes showed that there are no gaps between components, indicating good contact at material interfaces. Moreover, the contact pressure between the target and other components indicated that very good contact was established at these interfaces. The stress-strain conditions for the target will be further used to assess the appropriate operation during MPEX experiments and gain insight into materials science phenomena during PMI experiments.

Modern heat recovery steam generators (HRSGs) operate at elevated temperatures, leading to the formation of oxides inside the tubes of heat exchangers (HXs). This oxide growth reduces the heat recovery efficiency. Moreover, after reaching a certain critical thickness, some oxide scales detach from the tube surface (exfoliation), causing erosion damage to the components downstream. Predicting the metal temperature distribution and associated oxide thickness in the HXs of an HRSG can aid in mitigating these problems. A computational fluid dynamics (CFD) model was developed within the commercial code STAR-CCM+ for the prediction of fluid flow, conjugate heat transfer, and associated oxidation in HRSGs. Moreover, a new Porous Media Model (PMM) method was developed to model the fin effect on the heat transfer in HX, which can substantially reduce the prohibitive computational costs of fin meshes. The developed CFD model was used to conduct a high-fidelity simulation of a real-scale HRSG to investigate flow, heat transfer, and oxide growth. The calculated oxide thickness on different tubes can be used to identify HX regions that require oxide-resistant coatings to prevent exfoliation and ensuing damages. Furthermore, this CFD framework can serve as a reference for future studies that intend to model and investigate high-temperature oxidation in HXs used for any applications.

The present paper introduces a brief history of high density infrared (HDI) lamp systems and their use in advanced materials development and fabrication. Two types of lamp systems have been developed and are in use at Oak Ridge National Laboratory (ORNL) Infrared Processing Center (IPC), namely, plasma arc lamps and tungsten halogen lamps. The plasma arc lamp is used for processes that require high heating rates or high temperatures. Such applications include sheet fabrication and coatings using refractory metals, traditionally difficult-to-process materials, such as intermetallics and ceramics, thermal forming, and selective heat treating. There are significant cost savings for thin sheet fabrication when compared with standard warm/hot deformation processes. Tungsten halogen systems are used for lower temperature materials. Applications include coatings and claddings, debindering operations, braze joining, tooling preheating, and billet heating. A mathematical model has also been developed for the simulation of infrared heating.

The development of sensors and control and command modules capable of extracting environmental data has made it possible to build an underwater drone for monitoring and collecting water samples from hard-to-reach areas. In this paper we present the project that focuses on the fundamental challenges related to communication, control but also the analysis of water parameters in real time.

In this paper, performance strategies on GPU-based HPC platforms of a cellular automata (CA) simulation code for non-equilibrium solidification, including nucleation, grain growth, solute partitioning and transport for the metal additive manufacturing (AM) process are investigated using OpenMP 4.5. To accurately report the speed-up for multicore CPUs and GPUs, a rigorous performance analysis employed optimizations appropriate for both CPU-only code (baseline) and GPU offload codes for an isothermal test problem. The performance results on Summit at the Oak Ridge Leadership Computing Facility indicate that using a precomputed list of interface cells significantly decreased the wall-clock time on GPUs. The speedup due to GPU acceleration was evaluated for a full Summit node and measured to be 1.8X when comparing a 6 MPI tasks run with 6 GPUs versus 36 MPI tasks on the CPU only. That speed-up was found to be 7.9X when comparing 6 MPI tasks with 6 GPUs versus the 6 MPI tasks running on the CPU only. Performance measurements showed that system total time is almost constant for runs with more than 96 MPI tasks (or GPUs), indicating that the GPU-accelerated code showed an excellent weak scaling performance. Finally, a rapid directional solidification problem was considered to demonstrate the CA code capability on Summit. It was found that a mesh size of at least 0.05 mu m is recommended for the AM-like simulations in order to obtain accurate elongated grain microstructure and elongated subgrain features, which are in qualitative good agreement with experimental data. The results presented in this study indicate that the performance strategies on GPU-based HPC platforms for the CA code are appropriate for novel HPC exascale platforms.(c) 2022 Elsevier B.V. All rights reserved.

In the present study, the main physical-chemical parameters (temperature, conductivity, turbidity, pH, dissolved oxygen, biochemical oxygen consumption, ammonium, nitrate and phosphate ions) and the representative groups of phytoplankton (green algae, cyanobacteria, diatoms and cryptophytics) are analysed with direct influence on the quality of aquatic life. The average values obtained by analysing the samples collected in July 2023 in the bordering area of fishing activities (marine site –Midia-Navodari area and Lake sites – Tasaul Lake and Siutghiol Lake) are presented and discussed. The modern techniques of in situ analysis of the physical-chemical and biological parameters of the water allowed an evaluation of the quality of the surface waters regarding the trophic potential. The optimal values of the indicators of the eutrophication regime and of the oxygen regime, as well as the presence of the main groups of primary producers, suggest the existence of favourable conditions for the development of fishing and aquaculture activities. The study contributes to the achievement of the general objective of the Dobrogea North FLAG strategy for the development of fishing activities based on the knowledge of environmental aspects, in order to maintain economic and ecological sustainability.

When it comes to designing a mini-submarine, the most important questions are what it should look like to achieve the purpose for which it was built and what propulsion force is required to operate it at expected parameters. This paper aims to answer some of these questions using a numerical analysis designed to optimize the body shape using the Ansys CFX software package. The mini-submarine understudy is research one and it is equipped with eight thrusters. The optimization aims to choose an optimal body shape between the frame type which is the simplest, cheapest, easiest to execute and offers easy access to all components, and the closed hull type which is more compact has lower hydrodynamic resistance, but is difficult to execute, is expensive and difficult to access inside for interventions and inspection. The cases of study are incompressible turbulent flow for a complete submerged body, distinguished by the complexity of the form and the conditions under which the computation must be performed. The simulation will be done at several speeds, according to the known power of the thrusters in steady-state conditions. The results will be compared whit measuring data, analyzed, and presented comparatively base on hydrodynamic resistance and speed, but will be discussed the other criteria as well.

Additive manufacturing (AM), or 3D printing, of metals is transforming the fabrication of components, in part by dramatically expanding the design space, allowing optimization of shape and topology. However, although the physical processes involved in AM are similar to those of welding, a field with decades of experimental, modeling, simulation, and characterization experience, qualification of AM parts remains a challenge. The availability of exascale computational systems, particularly when combined with data-driven approaches such as machine learning, enables topology and shape optimization as well as accelerated qualification by providing process-aware, locally accurate microstructure and mechanical property models. We describe the physics components comprising the Exascale Additive Manufacturing simulation environment and report progress using highly resolved melt pool simulations to inform part-scale finite element thermomechanics simulations, drive microstructure evolution, and determine constitutive mechanical property relationships based on those microstructures using polycrystal plasticity. We report on implementation of these components for exascale computing architectures, as well as the multi-stage simulation workflow that provides a unique high-fidelity model of process–structure–property relationships for AM parts. In addition, we discuss verification and validation through collaboration with efforts such as AM-Bench, a set of benchmark test problems under development by a team led by the National Institute of Standards and Technology.

Supercritical CO2 (sCO(2)) power cycles are being developed due to their potential for high efficiency and reduced capital cost. It is necessary that these recuperators operate at high pressures and temperatures, up to 30 MPa and 900 K, with effectiveness values > 95% and pressure drops < 1% to achieve high cycle efficiencies. Moreover, it is also necessary to have reasonable cost recuperators to control the capital costs of the sCO(2) power cycles. In this study, a Plate Pin-Fin (PPF) heat exchanger has been proposed as an sCO(2) recuperator. This preliminary recuperator design leverages capabilities enabled by additive manufacturing. Although the PPF design has characteristics similar to those of a plate heat exchanger, small diameter and relatively long fins are used to increase surface area, enhance heat transfer, and provide structural support for the partition plates that separate the fluid streams. Existing correlations for heat transfer and pressure drop were adapted for the PPF heat exchanger. These correlations were implemented in a 1D analytical model and used for the optimization of a 5-kWth high temperature recuperator for an indirect sCO(2) cycle by varying the design parameters to minimize the quantity of material required. A 3D conjugate heat transfer numerical simulations were conducted to validate the heat transfer and pressure loss correlations. A steepest descent method was used to minimize heat exchanger mass for a 5-kW prototype recuperator subject to a maximum specified pressure drop. The design analysis indicated that an optimum PPF recuperator would be attained for the minimum allowable pin transverse spacing, minimum pin width, minimum pin height and near maximum cell aspect ratio. At a low material requirement of 0.216 kg/kW and a pressure drop, which is almost five times lower than the allowable pressure drop design target, the optimized PPF heat exchanger has the high potential to be an alternative to a printed circuit heat exchanger, which is a conservative design basis for the current state-of-the-art sCO(2) recuperators. (c) 2022 Elsevier Ltd. All rights reserved.

Various methods were used, in order to protect the material base; the study subject has been put under various conditions and were thus implemented in an attempt to prolong the operating life and to require less maintenance and replacement of parts. Pulsed laser deposition method was used to cover a S 235 carbon steel sample with a thin nickel film, using laser ablation and thus obtaining a protective layer, offering increased corrosion resistance. S 235 carbon steel samples were covered on a single face with thin films. The material used for laser ablation is nickel. The samples were immersed for 126 days in static seawater at ambient temperature and were individually weighted on the analytic balance at different time intervals, in order to determine the corrosion process speed. The study was performed by employing the gravimetric method. Through the corrosion research process using the gravimetric method, the parallelepiped samples covered with Ni using pulsed laser deposition were immersed 126 days in static sea water at environment temperature. The corroded surfaces, after being submerged in seawater, were investigated using optical microscopy and atomic force microscopy. Atomic force microscopy investigations performed on long-term corrosion-tested samples highlight areas with compact and homogeneous surfaces that did not allow the corrosive agent to interact with the base material, a fact confirmed by optical metallographic analysis. Wave mode images show discontinuities of surface-deposited incipient corrosion points that are possible pathways of the corrosive agent to the sample material. The analysis made on one side thin film covered sample, after a long term corrosion test, using atomic force microscopy investigation and gravimetric test, shows the rate of corrosion, the discontinuities of the surface and the corrosion pitting in the material. Evaluating the method of thin film deposition layer leads to the obtainment of high reliability and low cost material parts using this method. The corrosion rate is established, remains constant and protection of the material base is achieved.

In a 2020 survey of marine professionals, 77% of respondents view cyber-attacks as a high or medium risk to their organizations, yet only 64% said their organization has a business continuity plan in place to follow in the event of a cyber-incident. The study of equipment that manages autonomous ships and in general all equipment that is remotely controlled from the point of view of cyber security, is a necessity nowadays. The autonomous systems represented by remotely operated vessels (ROVs), marine autonomous surface systems (MASS) etc, have as first requirement the safety to be satisfied in their operation. These autonomous systems are composed of connected OT and IT networks, and their endowment with sensors and various cyber physical devices allow real-time data processing to consistently respond to real-world threats. In order to secure the cyber security of autonomous systems, we must consider all the elements that are vulnerable to cyber-attacks, such as the part of the hardware and the operating system used, the configuration of the OT interconnection network, the firmware protection used, all these elements considered across their entire lifecycle. Security in MASS, or USVs and ROVs is nothing new but the consequences of insecurity are critical. Flaws (including security ones) in such systems lead to safety hazards, and can kill. The present article introduces the main vulnerabilities of such remotely operated system and we try to find solution for navigate the ins and outs of cyber security on board remote operated ships, address cybersecurity challenges and compliance considerations, and get you geared up to establish your cyber security action plan. This aspect is important to consider from the design stage when referring to the maritime transport systems that host MASS, USVs and ROVs and its remote control center, e.g., the shore control center.