| 1. |
- Gazzotti, Stefano, et al.
(författare)
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Cellulose nanofibrils as reinforcing agents for PLA-based nanocomposites : An in situ approach
- 2019
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 171, s. 94-102
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Tidskriftsartikel (refereegranskat)abstract
- One-pot in situ polymerization approach was explored for the preparation of polylactide (PLA)-cellulose nano-fibril (CNF) bio-nanocomposites. CNF were first prepared through enzymatic and mechanical treatment of bleached hardwood kraft pulp. The bio-nanocomposites- were then fabricated through ring opening polymerization (ROP) of L-lactide, in the presence of various amounts of fibrils. Molecular weight, thermal properties, surface morphology, mechanical and wettability properties of the PLA-CNF nanocomposites were evaluated. DSC analysis demonstrated the effect of CNF on crystallization and crystalline morphology of PLA. Improved modulus for the nanocomposites with respect to standard PLA was demonstrated, however, the differences in tensile stress were small probably due to the counteracting effects of reinforcement from CNF and the decreasing molecular weight as a function of CNF concentration. The absence of pulled-out fibers was assessed, highlighting the strong interface and covalent attachment of PLA chains on CNF surface. Finally, the covalent bonding of PLA chains on CNF surface was demonstrated by isolating the non-soluble part, consisting of PLA-grafted CNF, and characterization of this residue.
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| 2. |
- Lionello, Michele, et al.
(författare)
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Energy‐efficient operation of indirect adiabatic data center cooling systems via Newton‐like phasor extremum seeking control
- 2021
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Ingår i: International journal of adaptive control and signal processing (Print). - : John Wiley & Sons. - 0890-6327 .- 1099-1115. ; 35:7, s. 1298-1315
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers the problem of optimizing the operation of Indirect Adiabatic Cooling (IAC) systems with application to data centers. Optimal operation is achieved when the required cooling demand is satisfied at the minimum energy cost. For this purpose, we design a supervisory control system, where the higher layer determines the optimal set‐points for the local controllers by employing an Extremum Seeking Control (ESC) scheme. In particular, we consider a Newton‐like phasor ESC, which augments the derivative estimator underlying the phasor approach to capture also the Hessian of the plant index and then it uses these estimates to steer the system along a Newton‐like direction. The effectiveness of the considered approach is tested in simulation by exploiting a Matlab‐based simulation environment including an IAC system and a computer room.
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| 3. |
- Lucchese, Riccardo, et al.
(författare)
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Gradient-free optimization of data center cooling using Extremum Seeking
- 2019
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Ingår i: Proceedings of the 22nd Nordic Process Control Workshop. - : Technical University of Denmark. ; , s. 35-37
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We consider the thermal management problem of provisioning the cooling airflow to data center rooms. Building on a virtual plant capturing the thermal behaviour of both the cooling equipment and the room-side heat load, we evaluate a 2D phasor-based Extremum Seeking Control (ESC) strategy that strives to satisfy the cooling demand while minimizing the cooling provisioning cost.
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| 4. |
- Lucchese, Riccardo, et al.
(författare)
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Newton-like phasor extremum seeking control with application to cooling data centers
- 2019
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Ingår i: IFAC-PapersOnLine. - : IFAC Papers Online. - 2405-8963.
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Konferensbidrag (refereegranskat)abstract
- We design a Newton-like phasor-based Extremum Seeking Control (ESC) aimed at multi-variable nonlinear control systems. We first augment the derivative estimator underlying the phasor approach to capture the Hessian of the plant index. Then we use these estimates to steer the system along a Newton-like direction. We assess the closed-loop stability of the proposed scheme and demonstrate its effectiveness in a data center cooling scenario.
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| 5. |
- Lucchese, Riccardo, et al.
(författare)
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On Economic Cooling of Contained Server Racks using an Indirect Adiabatic Air Handler
- 2020
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Ingår i: Thirty Sixth Annual Semiconductor Thermal Measurment, Modeling and Management Symposium. - : IEEE. ; , s. 24-31
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Konferensbidrag (refereegranskat)abstract
- We study the economic operation of a free-cooling setup in which an Indirect Adiabatic Air Handler (IAAH) recovers heat from an array of server racks placed in a contained aisle. For this setting we propose two different control policies: in the first approach, the airflow supply rate to the racks is maintained constant while only the process- side operations of the IAAH are optimized. In the second approach, also the room-side rate is updated adaptively. Building on calibrated models of the IAAH and the servers, we design experimental trials considering different outdoor temperatures and humidity conditions as well as varying computational workloads. The in silico analysis contributes actionable insights on the optimal thermal and cost operations of the system.
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| 6. |
- Rampazzo, Roberto, et al.
(författare)
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Extragalactic Astronomy : From Pioneers to Big Science
- 2016
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Ingår i: From the Realm of the Nebulae to Populations of Galaxies. - Cham : Springer. - 9783319310046 - 9783319310060 ; , s. 1-92
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Bokkapitel (refereegranskat)abstract
- At the beginning of the nineteenth century one of the scientific issues driving the research of astronomers, like the Herschels, was to test if all the nebulæ can be resolved into stars.
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