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Additive manufacturing (AM) has gained increasing popularity in various quality critical applications such as aerospace and healthcare due to its high flexibility in fabricating complex geometries with novel materials. However, the relatively poor layer-wise surface quality may lead to compromised property and functionality of AM products. The experimental studies have demonstrated that the AM machine parameters could have significant effects on the resulting surface morphology. Therefore, it is critically needed to analyze the surface morphology in AM and further correlate the morphology features with machine parameters. In practice, there are two major challenges: (1) the surface profiles are usually highly nonlinear; and (2) a large fraction of outliers and missing regions may commonly exist in the measured surface profile. To address these challenges, this paper applies a convolutional autoencoder-based approach to extract informative features from surface profile. With the application of regularization, the autoencoder model is capable of discovering effective low dimensional representations from the high dimensional surface profile data with a large fraction of corruptions. Through supervised machine learning, the correlation between surface morphology and machine parameters can be further quantified. To validate the effectiveness of the proposed method, a case study in laser engineered net shaping (LENS) is conducted to identify the variation of the surfaces fabricated under similar settings of machine parameters. The result shows that the classification accuracy based on the proposed method could achieve 70%, which outperforms benchmark methods. Therefore, the developed convolutional autoencoder-based surface morphology analysis approach has promising potential for surface morphology feature extraction in AM.

In this study, the variations of spray characteristics are tested with air-assisted siphon type different size liquid atomizers. The spray characteristics are analyzed considering three atomizers having the same inlet diameter, with different constricted areas and exit diameters for the flow rates of 42, 57, and 71l pm. Three different mixtures of Oleic Acid with Ethanol, and three different mixtures of Di-Octyl Phthalate (DOP) with Ethanol are employed as working fluids along with the six different suction heights. Experimental outcomes show that, for the same flow rates, solution, and suction height, the droplet size changes by varying the diameter of the constricted area and exit area. The change of any area in atomizer changes the level of turbulence in flow that results in the variation of droplet size and its distribution. The increasing flow rate also assists in increasing the droplet size. Since the droplet size distribution decreases with the increasing viscosity, the use of DOP and Ethanol mixture increases the droplet size as it is more viscous than the Oleic Acid and Ethanol mixture. It is also noticed that at a constant airflow rate, Number Median Aerodynamic Diameter (NMAD), and liquid consumption rate are inversely proportional, whereas the Geometrical Standard Deviation (GSD) and Mass Median Aerodynamic Diameter (MMAD) is directly proportional to the suction height.

A new concept of double pass solar water heater using reflector has been introduced in this paper to improve its thermal efficiency. Here the design, construction, and performance scrutiny of double pass solar water have been discussed. The consequence of the mass flow rate on the outlet temperature, thermal performance, and overall performance has been analyzed. Moreover, the performance result has been compared with the single-pass solar water heater. The data are taken for a different mass flow rate of 0.0022 kg/s, 0.0028 kg/s, 0.0033 kg/s, 0.0039 kg/s and 0.0044 kg/s from 9 a.m. to 4 p.m. at an interval of 30 min. The maximum efficiency obtained for a higher mass flow rate of 0.0044 kg/s is 50.26%. The maximum efficiency for other mass flow rates is 47.61%, 47.98%, 48.82%, and 48.89%, respectively. All these efficiencies are found in the middle of the day around 12.00 p.m.–1.00 p.m. as the maximum solar radiation is observed in that period. Though the sunlight radiation is not much higher in this month for the same mass flow rate, the efficiency of double pass solar water heater using reflector is much greater than a conventional single-pass solar water heater.

The study of interfacial Dzyaloshinskii–Moriya interaction (DMI) in perpendicularly magnetized structurally asymmetric heavy metal/ferromagnet multilayer systems is of high importance due to the formation of chiral magnetic textures in the presence of DMI. Here, we report the impact of cobalt oxidation at the Co/AlO x interface in Pt/Co/AlO x trilayer structures on the DMI by varying the post-growth annealing time, Al thickness and substrate. To quantify DMI we employed magneto-optical imaging of the asymmetric domain wall expansion, hysteresis loop shift, and spin-wave spectroscopy techniques. We further correlated the Co oxidation with low-temperature Hall effect measurements and x-ray photoelectron spectroscopy. Our results emphasize the importance of full characterization of the magnetic films that could be used for magnetic random access memory technologies when subjected to the semiconductor temperature processing conditions, as the magnetic interactions are critical for device performance and can be highly sensitive to oxidation and other effects.

Understanding the interfaces in heterostructures at an atomic scale is crucial in enabling the possibility to manipulate underlying functional properties in correlated materials. This work presents a detailed study on the atomic structures of heterogeneous interfaces in La0.7Sr0.3MnO3 (LSMO) film grown epitaxially on c-Al2O3 (0001) with a buffer layer of MgO. Using aberration-corrected scanning transmission electron microscopy, we detected nucleation of periodic misfit dislocations at the interfaces of the large misfit systems of LSMO/MgO and MgO/c-Al2O3 following the domain matching epitaxy paradigm. It was experimentally observed that the dislocations terminate with 4/5 lattice planes at the LSMO/MgO interface and with 12/13 lattice planes at the MgO/c-Al2O3 interface. This is consistent with theoretical predictions. Using the atomic-resolution image data analysis approach to generate atomic bond length maps, we investigated the atomic displacement in the LSMO/MgO and MgO/c-Al2O3 systems. Minimal presence of residual strain was shown at the respective interface due to strain relaxation following misfit dislocation formation. Further, based on electron energy-loss spectroscopy analysis, we confirmed an interfacial interdiffusion within two monolayers at both LSMO/MgO and MgO/c-Al2O3 interfaces. In essence, misfit dislocation configurations of the LSMO/MgO/c-Al2O3 system have been thoroughly investigated to understand atomic-scale insights on atomic structure and interfacial chemistry in these large misfit systems.

In this present study, the effect of heat spreader in a horizontal channel consisting of electronic chips with mixed convection and surface radiation is examined. SIMPLER algorithm with finite volume method is used to solve governing equations using ANSYS 16.2 software. Results show the increase in the performance of heat transfer with an increase in the values of governing parameters like Reynolds number and emissivity of the spreader.

Numerical analysis of mixed convection with surface radiation on a vertical channel is conducted. Five protruding heat sources are mounted on the left wall of the channel, and copper heat spreader is attached upon each heat source. Governing equations are solved using SIMPLER algorithm in ANSYS 16.2 software. Results are presented to depict the effects of parameters like heat spreader width (Ws = W − 2W), emissivity of heat spreader (esp = 0.1–0.9) and Reynolds number (Re 250–750) on the rate of heat transfer by fixing emissivity of heat source and substrate. It is found that with increasing spreader width and emissivity, heat transfer performance increases.

This paper presents a numerical study of a well-established vortex flow receiver and a proposed recirculating flow Solid particle solar receiver (SPSR) capable of achieving high air temperature which is perfectly suitable for the hybrid solar thermal power plant. Solar particle receivers are modeled using discrete particle model (DPM), RNG k- e flow model and discrete ordinate (DO) radiation model. Numerical analysis is done by considering two cases (i) Recirculating flow solar receiver with non-reacting particle and without non-reacting particle as a medium of transferring heat (ii) Vortex flow solar receiver with non-reacting particle and without non-reacting particle as a medium of transferring heat. The examination is carried out to compare the parametric sensitivity of both solar particle receivers with particle and air and without particle as a medium of transferring heat by considering the solar flux that incident on the aperture of the receiver and varying the air flow rate and particle concentration, recirculation rate. The results depict that use of particle enhance the heat transfer for both cases. It is concluded from the thermal behavior of recirculating flow SPSR that about 30% higher cavity thermal efficiency and exhibit higher and uniform heat transfer than a vortex flow SPSR.

This study investigates the potential application of hybridized energy system (i.e., PV/Wind/Diesel) with battery storage in the northern region of Bangladesh. A techno-economic feasibility of different system configurations is evaluated and an optimized system is selected using HOMER (Hybrid Optimization Model for Electric Renewable) software. The hybrid system is optimized to meet a remote stand-alone village community’s load demand of 242.56 kWh/day with a 51.52 kW peak load demand. The result of this study indicates that the optimized hybrid system consists of 73 kW PV arrays, a 57 kW Diesel generator, a 387 kWh nominal capacity battery bank, and 28 kW inverters have the minimum Cost of Energy (COE) of 0.37$/kWh and the Net Present Cost (NPC) of $357,284. The outcome also indicates that the optimized system reduces CO2 emission by around 62% in comparison with the kerosene used in a current situation and 67% with the grid connected system. Furthermore, the Life Cycle Emissions-LCE (kg CO2-eq/yr) production is considerably lower in PV/Batt/ICE system than the other system configurations. However, this system has a lower Duty Factor (DF) compared to Wind/Batt/Diesel and Batt/Diesel based system. Although this system is not comparable with the grid tariff, the proposed method is economically feasible than solar micro utility system, Wind/Batt/Diesel system, and Diesel generator only system. Additionally, the article discusses the social and economic benefits of implementing the hybridized system along with their barriers and challenges.

Food is one of the indispensable commodities for human existence. Insufficient production and lack of efficacious preservation system of food are the main causes of deprivation in Bangladesh. Bangl...

A lot of re-usable thermal energy within industrial processes is emitted into the environment every year in the world as energy waste. The aim of this paper was to study the estimating of maximal available heat flow rate using different temperature driving forces by a mathematical surface technique. This technique is based on the usage of pinch analysis principles. The maximal available heat flow rate with different temperature driving forces can be calculated by using a trapezoid surface area within a grand composite curve. This technique can be applied by upgrading large quantities of available heat for steam or electricity generation within industrial processes. The research idea, which is presented using a mathematical surface technique, is founded on increasing the available heat flow rate with different temperature driving forces by using the excess and available heat flow rates regarding waste streams. This technique was tested on an existing formaldehyde process that allows for efficient and additional steam production of 1.2% with a higher outlet temperature for steam generation.

This study presents a numerical modeling of a downdraft gasifier. Wood (biomass) was considered as a feedstock for gasification as it is a cheap biomass and locally available. The numerical study was carried out to predict the flow behavior, the performance of the downdraft gasifier and the syngas composition precisely. The current downdraft gasifier was modeled using standard k–e turbulence model, DPM for discrete phase, nonpremixed combustion model for combustion and DO radiation model for radiation modeling. The flow behavior and the temperature distribution of the downdraft wood gasifier were addressed which helped to understand the internal combustion phenomenon. Results also showed that the predicted syngas compositions were as follows: Nitrogen-54.12%, Hydrogen-8.10%, Carbon Monoxide-16.04%, Carbon Dioxide-13.01%, Methane-2.35%, Water vapor-05.10% by volume. In addition gasifier, thermal efficiency was found about 72%. This gasification process produces syngas which is directly usable as an alterna...

The study presents an analysis and suggests about how renewable sources of energy can be an alternative option to produce electricity in an off-grid area. A case study is done by surveying 235 households in an off-grid area. Techno-economic analysis of the hybrid energy system is employed by using Hybrid Optimization of Multiple Energy Resources (HOMER) software. Four solar-PV modules (each of 1kW), two biogas generators (each of 3kW), three diesel generators (each of 5kW), five batteries (each of 160 Ah) and 5kW converter is found to be the best configuration in terms of Cost of Energy (COE), environmental conditions and Renewable Fraction (RF). The Cost of Energy (COE), Net Present Cost (NPC), capital cost of this configuration is found BDT15.382, BDT10007224, and BDT2582433 respectively. The renewable fraction of this system is found 75% which indicates a lower emission compared with thegrid based system and stand-alone diesel system. Although the COE is higher than grid electricity, this system offers a cheaper option than using kerosene oil and solar home systems (SHSs).