| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Zhirnov, Ivan, et al.
(författare)
-
Process quality assessment with imaging and acoustic monitoring during Laser Powder Bed Fusion
- 2022
-
Ingår i: Procedia CIRP. - : Elsevier. - 2212-8271. ; 111, s. 363-367
-
Tidskriftsartikel (refereegranskat)abstract
- Acoustic monitoring of laser powder bed fusion (LPBF) has shown a high sensitivity to stochastic defects, e.g., cracks, pores and lack of fusion (LOF), and melting instability. The advantage of this method is the possibility to filter raw data and extract acoustic signal features for the data analysis, thus minimizing data and computing time. In this research during the build of components from hot work tool steel powder, acoustic signals and powder bed images were acquired for post-process data analysis and search for correlations with LOF. Different densities caused by LOF were obtained by changing the shielding gas velocity. In the analysis, selected combinations of features with the relationship between the build phases and the final properties such as density and surface roughness, were investigated. For the current dataset prediction of the optimal state showed an accuracy of 98%. This investigation suggests the applicability of the smart data-centric machine learning method to predict the relationship of process parameters, monitoring signals, and material properties. © 2022 The Authors. Published by Elsevier B.V.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Bensow, Rickard, 1972
(författare)
-
Simulation of Unsteady Propeller Blade Loads Using OpenFOAM
- 2013
-
Ingår i: Numerical Towing Tank Symposium.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Unsteady propeller blade loads are important to consider in the design of the propulsion system in order to avoid problems with noise and vibrations. This is normally done through an analysis of the average wake field flowing into the propulsor in order to correctly match the different components of the propulsion system. As computational resources increase, it now starts to become possible to better study the impact on the natural wake flow unsteadiness and how this influences the behaviour of the propeller. This work is a feasibility study to investigate different computational aspects regarding the flow around a propeller operating in a ship wake. The simulations are performed in OpenFOAM 2.2.x using LES, Large Eddy Simulation.The interest concerns both how the sliding mesh implementation in OpenFOAM performs and how large variation in the propeller flow that the resolved transient wake field incurs.
|
|
| 8. |
- Zhirnov, Ivan, et al.
(författare)
-
Measurement of Basic Geometric Characteristics of Particle Flow Between Surfacing Head and Substrate
- 2017
-
Ingår i: Measurement techniques. - : Springer Science and Business Media LLC. - 0543-1972 .- 1573-8906. ; 59:11, s. 1187-1190
-
Tidskriftsartikel (refereegranskat)abstract
- We present a method of determining the geometric characteristics of gas-powder flow during laser cladding with coaxial injection. We evaluate the effect of the operating parameters (feed rate and channel width of powder injection) on the geometry of particle flow. Optical diagnostics of the laser cladding is carried out by an infrared camera.
|
|
| 9. |
- Di Baldassarre, Giuliano, et al.
(författare)
-
Sociohydrology : Scientific Challenges in Addressing the Sustainable Development Goals
- 2019
-
Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 55:8, s. 6327-6355
-
Tidskriftsartikel (refereegranskat)abstract
- The Sustainable Development Goals (SDGs) of the United Nations Agenda 2030 represent an ambitious blueprint to reduce inequalities globally and achieve a sustainable future for all mankind. Meeting the SDGs for water requires an integrated approach to managing and allocating water resources, by involving all actors and stakeholders, and considering how water resources link different sectors of society. To date, water management practice is dominated by technocratic, scenario-based approaches that may work well in the short term but can result in unintended consequences in the long term due to limited accounting of dynamic feedbacks between the natural, technical, and social dimensions of human-water systems. The discipline of sociohydrology has an important role to play in informing policy by developing a generalizable understanding of phenomena that arise from interactions between water and human systems. To explain these phenomena, sociohydrology must address several scientific challenges to strengthen the field and broaden its scope. These include engagement with social scientists to accommodate social heterogeneity, power relations, trust, cultural beliefs, and cognitive biases, which strongly influence the way in which people alter, and adapt to, changing hydrological regimes. It also requires development of new methods to formulate and test alternative hypotheses for the explanation of emergent phenomena generated by feedbacks between water and society. Advancing sociohydrology in these ways therefore represents a major contribution toward meeting the targets set by the SDGs, the societal grand challenge of our time. Plain Language Summary Water crises that humanity faces are increasingly connected and are growing in complexity. As such, they require a more integrated approach in managing water resources, which involves all actors and stakeholders and considers how water resources link different sectors of society. Yet, water management practice is still dominated by technocratic approaches, which emphasize technical solutions. While these approaches may work in the short-term, they often result in unintended consequences in the long-term. Sociohydrology is developing a generalizable understanding of the interactions and feedbacks between natural,technical and social processes, which can improve water management practice. As such, advancing sociohydrology can contribute to address the global water crises and meet the water-related targets defined by the United Nations' Sustainable Development Goals.
|
|
| 10. |
- Ehrenborg, Casimir, et al.
(författare)
-
Capacity Bounds and Degrees of Freedom for MIMO Antennas
- 2021
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 69:9, s. 5388-5400
-
Tidskriftsartikel (refereegranskat)abstract
- The optimal spectral efficiency and number of independent channels for MIMO antennas in isotropic multipath channels are investigated when bandwidth requirements are placed on the antenna. By posing the problem as a convex optimization problem restricted by the port Q-factor a semi-analytical expression is formed for its solution. The antennas are simulated by method of moments and the solution is formulated both for structures fed by discrete ports, as well as for design regions characterized by an equivalent current. It is shown that the solution is solely dependent on the eigenvalues of the so-called energy modes of the antenna. The magnitude of these eigenvalues is analyzed for a linear dipole array as well as a plate with embedded antenna regions. The energy modes are also compared to the characteristic modes to validate characteristic modes as a design strategy for MIMO antennas. The antenna performance is illustrated through spectral efficiency over the Q-factor, a quantity that is connected to the capacity. It is proposed that the number of energy modes below a given Q-factor can be used to estimate the degrees of freedom for that Q-factor.
|
|
