| 1. |
- Hong, Yuanyuan, et al.
(författare)
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A Multi-Floor Arrayed Waveguide Grating Based Architecture with Grid Topology for Datacenter Networks
- 2020
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Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 8, s. 107134-107145
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a grid topology based passive optical interconnect (POI) architecture that is composed of multiple floors of arrayed waveguide grating routers (AWGRs) to offer high connectivity and scalability for datacenter networks. In the proposed POI signal only needs to pass one AWGR, and thus can avoid the crosstalk accumulation and cascaded filtering effects, which exist in many existing POI architectures based on cascaded AWGRs. Meanwhile, due to high connectivity, the proposed grid topology based POI also has the potential advantage of high reliability. Simulation results validate the network performance. With a proper node degree, the proposed grid topology can achieve acceptable blocking probability. Besides, steady performance is kept when the number of floors increases, indicating good scalability of the proposed POI.
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| 2. |
- Chen, Jiajia, et al.
(författare)
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Characterization of Longitudinal Thermal Conductivity of Graphene Film
- 2021
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Ingår i: 2021 22nd International Conference on Electronic Packaging Technology, ICEPT 2021.
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Konferensbidrag (refereegranskat)abstract
- The chase of high performance by chip manufacturers has greatly increased the power consumption of integrated circuits, which brings great challenges to the heat dissipation of electronics systems. It has also slowed down following up of the Moore's Law, and it is expected to hit the wall soon [1]. Graphene film with high in-plane thermal conductivity is one of the key materials to make it possible for electronics industry to continue to follow the Moore's Law. However, there are few studies focusing on the longitudinal thermal conductivity of graphene films. The purpose of this study is to investigate the longitudinal thermal conductivity of graphene films according to ASTM D5470 [2]. The results show that the longitudinal thermal conductivity of the pressed graphene film is greater than that of the unpressurized graphene film. The longitudinal thermal conductivity is 10.6 W/m· K for the unpressurized graphene film and 20.6 W/m· K for the pressed graphene film.
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| 3. |
- Guo, Sihua, et al.
(författare)
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Characterization of a Novel Cost-efficient and Environmentally Friendly Graphene-enhanced Thermal Interface Material
- 2023
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Ingår i: 24th European Microelectronics and Packaging Conference, EMPC 2023.
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Konferensbidrag (refereegranskat)abstract
- With the continuous development of electronic devices, effective heat dissipation has become a major factor affecting service life. Thermal interface materials (TIM) play a key role in controlling heat dissipation of electronic devices and have thus attracted widespread attention. In this study, we used graphene flakes (GF) derived from graphene film that is wasted during the preparation of commercial large-scale graphene-enhanced TIMs as thermally conductive fillers to formulate a new TIM. The thermal conductivity of the developed TIM is 50% higher with GFs than without. Furthermore, the TIM has a tensile strength of 0.46 MPa with an elongation at break of 1225%, a maximum compression strength of 0.64 MPa at 50% compression, and high mechanical cycle stability. This report provides a cost-efficient and environmentally friendly approach to producing high-performance TIMs for electronic cooling applications.
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| 4. |
- Li, Jun, 1988, et al.
(författare)
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Bandwidth Slicing to Boost Federated Learning over Passive Optical Networks
- 2020
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Ingår i: IEEE Communications Letters. - : Institute of Electrical and Electronics Engineers Inc.. - 1089-7798 .- 1558-2558. ; 24:7, s. 1492-1495
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Tidskriftsartikel (refereegranskat)abstract
- During federated learning (FL) process, each client needs to periodically upload local model parameters and download global model parameters to/from the central server, thus requires efficient communications. Meanwhile, passive optical network (PON) is promising to support fog computing where FL tasks can be executed and the traffic generated by FL needs to be transmitted together with other types of traffic for broadband access. In this letter, a bandwidth slicing algorithm in PONs is introduced for efficient FL, in which bandwidth is reserved for the involved ONUs collaboratively and mapped into each polling cycle. Results reveal that the proposed bandwidth slicing significantly improves training efficiency while achieving good learning accuracy for the FL task running over the PON.
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| 5. |
- Li, Jun, 1988, et al.
(författare)
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Enabling technologies for low-latency service migration in 5G transport networks [Invited]
- 2021
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Ingår i: Journal of Optical Communications and Networking. - : Institute of Electrical and Electronics Engineers Inc.. - 1943-0620 .- 1943-0639. ; 13:2, s. A200-A210
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Tidskriftsartikel (refereegranskat)abstract
- The fifth generation (5G) mobile communications system is envisioned to serve various mission-critical services such as industrial automation, cloud robotics, and safety-critical vehicular communications. To satisfy the stringent end-to-end latency requirement of these services, fog computing has been regarded as a promising technology to be integrated into 5G networks, in which computing, storage, and network functions are provisioned close to end users, thus significantly reducing the latency caused in transport networks. However, in the context of fog-computing-enabled 5G networks, the high mobility feature of users brings critical challenges to satisfy the stringent quality of service requirements. To address this issue, service migration, which transmits the associated services from the current fog server to the target one to follow the users' travel trace and keep the service continuity, has been considered. However, service migration cannot always be completed immediately and may lead to a situation where users experience a loss of service access. In this regard, low-latency service migration plays a key role to reduce the negative effects on services being migrated. In this paper, the factors that affect the performance of service migration are analyzed. To enable low-latency service migration, three main enabling technologies are reviewed, including migration strategies, low-latency, and high-capacity mobile backhaul network design, and adaptive resource allocation. Based on a summary of the reviewed technologies, we conclude that dynamic resource allocation is the worthiest one to research. Therefore, we carry out a use case, where reinforcement learning (RL) is adopted for autonomous bandwidth allocation in support of low-latency service migration in a dynamic traffic environment and evaluate its performance compared to two benchmarks. The simulation demonstrates that the RL-based algorithm is able to self-adapt to a dynamic traffic environment and gets converged performance, which has an obviously smaller impact on non-migration traffic than the two benchmarks while keeping the migration success probability high. Meanwhile, unlike the benchmarks, the RL-based method shows performance fluctuations before getting converged, which may cause unstable system performance. It calls for future research on advanced smart policies that can get convergence quickly, particularly for handling the migration of latency-sensitive services in 5G transport networks.
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| 6. |
- Li, Jun, 1988, et al.
(författare)
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Scalable Federated Learning over Passive Optical Networks
- 2021
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Ingår i: 2021 Optical Fiber Communications Conference and Exhibition, OFC 2021 - Proceedings. - : Institute of Electrical and Electronics Engineers Inc.. - 9781943580866
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Konferensbidrag (refereegranskat)abstract
- Two-step aggregation is introduced to facilitate scalable federated learning (SFL) over passive optical networks (PONs). Results reveal that the SFL keeps the required PON upstream bandwidth constant regardless of the number of involved clients, while bringing 10% learning accuracy improvement. © 2021 OSA.
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| 7. |
- Shen, Zhiyang, et al.
(författare)
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A Critical Assessment of graphene based heat pipes for electronics and power module cooling applications
- 2023
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Ingår i: 2023 24th International Conference on Electronic Packaging Technology, ICEPT 2023.
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Konferensbidrag (refereegranskat)abstract
- As the most effective heat transfer device, heat pipes have received widespread attention, but traditional heat pipes may be difficult to meet heat dissipation requirements in the near future. Since graphene was discovered, its ultra-high thermal conductivity has been the focus of people's research and application. Therefore, the combination of graphene and heat pipes is a method to improve the performance of existing heat pipes. This paper is a critical assessment of recent advances in graphene-based heat pipes. In the paper, we conducted a simple theoretical analysis of the operation of the heat pipe, and also summarized the research status, enhancement mechanism, and enhancement method of graphene-enhanced heat pipes, and predicted the future development direction. The results show that depositing graphene-based materials on wicks, using graphene-based nanofluids, and application of graphene composites are effective ways to enhance the performance of heat pipes.
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| 8. |
- Yuan, Mingzhi, et al.
(författare)
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Fragmentation and structural transitions of few-layer graphene under high shear stress
- 2021
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 118:21
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Tidskriftsartikel (refereegranskat)abstract
- A key factor that determines the mechanical and electrical performance of graphene-based materials and devices is how graphene behaves under extreme conditions, yet the response of few-layer graphene to high shear stress has not been investigated experimentally. Here we applied high pressure and shear to graphene powder using a rotational diamond anvil cell and studied the recovered sample with multiple means of characterization. Sustaining high pressure and shear, graphene breaks into nanometer-long clusters with generation of large number of defects. At a certain stress level, it transforms to amorphous state and carbon onions. The reduction of infrared reflectivity in the severely sheared phase indicates the decrease in conductivity. Our results unveil the shear sensitive nature of graphene, point out the effects of shear on its physical properties, and provide a potential method to manipulate this promising material.
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| 9. |
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| 10. |
- Zhang, Lin, et al.
(författare)
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Cr-promoted formation of B2+L21 composite nanoprecipitates and enhanced mechanical properties in ferritic alloy
- 2023
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Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 243
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Tidskriftsartikel (refereegranskat)abstract
- The critical role of Cr on nanoprecipitates and the mechanical property of Fe-Ni-Al-Mn ferritic steel were systematically studied in this research. The two types of nanoprecipitates in the Cr added alloy were characterized through a combination of aberration-corrected scanning transmission electron microscopy and atom probe tomography techniques. The atomic-scale structure and chemistry analysis reveal that fine globular-shaped precipitates have a B2-structure, while coarse elongated precipitates have B2+L21 composite structures. The first-principles calculations reveal that the segregation of Cr at the L21/bcc interface reduces the interface and strain energy for the nucleation of the L21-type phase. With the increasing precipitate size, the B2 structure is gradually transformed to L21 to reduce elastic strain, thereby promoting the formation of B2+L21 composite nanoprecipitate. The addition of 10 wt% Cr results in an increase of ∼275 MPa in yield strength without obvious loss of ductility. The effect of Cr on the strength mechanisms were quantitatively analyzed, revealing that the strength of the ferritic alloy mainly improved by the formation of B2+L21 composite nanoprecipitate, which is more effective than solid solution strengthening.
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