| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Chen, Ling, et al.
(författare)
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Reliable and efficient RAR-based distributed model training in computing power network
- 2024
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Ingår i: Journal of Optical Communications and Networking. - 1943-0620 .- 1943-0639. ; 16:5, s. 527-540
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Tidskriftsartikel (refereegranskat)abstract
- The computing power network (CPN) is a novel network technology that integrates computing power from the cloud, edge, and terminals using IP/optical cross-layer networks for distributed computing. CPNs can provide an effective solution for distributed model training (DMT). As a bandwidth optimization architecture based on data parallelism, ring all-reduce (RAR) is widely used in DMT. However, any node or link failure on the ring can interrupt or block the requests deployed on the ring. Meanwhile, due to the resource competition of batch RAR-based DMT requests, inappropriate scheduling strategies will also lead to low training efficiency or congestion. As far as we know, there is currently no research that considers the survivability of rings in scheduling strategies for RAR-based DMT. To fill this gap, we propose a scheduling scheme for RAR-based DMT requests in CPNs to optimize the allocation of computing and wavelength resources considering the time dimension while ensuring reliability. In practical scenarios, service providers may focus on different performance metrics. We formulate an integer linear programming (ILP) model and a RAR-based DMT deployment algorithm (RDDA) to solve this problem considering four optimization objectives under the premise of the minimum blocking rate: minimum computing resource consumption, minimum wavelength resource consumption, minimum training time, and maximum reliability. Simulation results demonstrate that our model satisfies the reliability requirements while achieving corresponding optimal performance for DMT requests under four optimization objectives.
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| 3. |
- Wang, Jiabin, et al.
(författare)
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A numerical investigation on the improvement of anti-snow performance of the bogies of a high-speed train
- 2020
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 234:10, s. 1319-1334
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, numerical simulations combining unsteady Reynolds-averaged Navier-Stokes (URANS) simulation and the discrete phase model are used to study the application of countermeasure for snow accumulation in the regions of bogie cavities of a high-speed train. The influence of the cowcatcher heights and guide structure configurations on the flow features and snow accumulation was studied. The results of the study show that the cowcatcher with a downward elongation of 4% of the distance between the two axles decreases the snow accumulation in the first and the second bogie regions by about 56.6% and 13.6%, respectively. Furthermore, the guide structures have been found to significantly alter the velocity and pressure distribution in the second bogie region, resulting in a relatively large snow-accumulation reduction. The deflector is found to perform better in reducing snow accumulation when compared to the diversion slots. The cowcatcher, elongated in the downward direction, and the deflector proved to be a good countermeasure for snow accumulation around the bogies of high-speed trains operating in snowy weather conditions. © IMechE 2019.
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| 4. |
- Wang, Jiabin, et al.
(författare)
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An improved delayed detached eddy simulation study of the bogie cavity length effects on the aerodynamic performance of a high-speed train
- 2020
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science. - : SAGE Publications. - 2041-2983 .- 0954-4062. ; 234:12, s. 2386-2401
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Tidskriftsartikel (refereegranskat)abstract
- This paper uses an improved delayed detached eddy simulation method to investigate the unsteady flow features of the high-speed trains with various cavity lengths at Re = 1.85x10(6). The improved delayed detached eddy simulation results are validated against the experimental data obtained during previous wind tunnel tests. The effects of cavity length on the resistance force, flow structures beneath the high-speed train and in the wake are analyzed. The results show that a longer cavity significantly increases the streamwise velocity level near the rear plates and forms a stronger impinging flow on the rear plates, and thus contributes to a higher value of resistance. Furthermore, a longer cavity decreases the pressure coefficients around the near wake region from the top of the ballast to the tail nose in the vertical direction and thereby increases the pressure drag of the high-speed train. Additionally, a longer bogie cavity is found to increase the longitudinal vortex scales in the near wake region. All these changes on the flow field bring to 5.8% and 11.5% drag increase when the bogie cavities are elongated by 20% and 40%, respectively, of the wheelbase.
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| 5. |
- Wang, Jiabin, et al.
(författare)
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Impact of bogie cavity shapes and operational environment on snow accumulating on the bogies of high-speed trains
- 2018
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 176, s. 211-224
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the snow accumulation on the bogies of high-speed trains has been investigated using a numerical simulation method based on the unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) coupled with the Discrete Phase Model (DPM). The effects of bogie cut outs’ shape, running speed of high-speed trains and snow particle density and diameter on the snow accumulation and particle movement characteristics are discussed. The results show that the bogie installation region with inclined plates shows better anti-snow performance than the configuration with straight plates, which greatly affects the flow structure and snow concentration distribution in the upper space of bogie regions. The running speed of high-speed trains has dominant effect on the snow accumulation on the bogies, and the snow accumulation issue of bogie becomes more serious with increasing running speed. Furthermore, the snow particle density and diameter also have large influence on the snow accumulation on the bogies. With the increase of snow particle density and diameter, the flow range at height direction around bogie region of snow particles become lower and the quality of snow accumulation decrease significantly.
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| 6. |
- Wang, Jiabin, et al.
(författare)
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Impact of rotation of wheels and bogie cavity shapes on snow accumulating on the bogies of high-speed trains
- 2019
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Ingår i: Cold Regions Science and Technology. - : Elsevier BV. - 0165-232X. ; 159, s. 58-70
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Tidskriftsartikel (refereegranskat)abstract
- The snow accumulation on the bogies of a high-speed train was studied using the unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) coupled with the Discrete Phase Model (DPM). The effects of the rotation of wheels, shape of bogie fairings and length of bogie cavities on the flow characteristics and snow accumulation around bogie regions are discussed. The results show that the rotation of wheels significantly affects the flow characteristic and snow distribution around rear plates and the snow accumulation on the top surface of bogies. The shape of bogie fairings has been found to have large influence on the velocity profiles at the inlet and the outlet of bogie cavity, and thereby on the snow accumulation. The bogies without fairing have been found to be less influenced by the snow in the flows without crosswinds. The length of the bogie's cavity was found to have dominant role on the distribution of particle concentration and snow accumulation on the bogie surface. The total mass of snow accumulation on the bogie surface was shown to decrease with the shorter bogie cavity. Finally, the shorter bogie cavity is recommended for the design of the high-speed trains running under the circumstances permitted by the vehicle gauge.
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| 7. |
- Krajnovic, Sinisa, 1970, et al.
(författare)
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PARTIALLY-AVERAGED NAVIER- STOKES SIMULATIONS IN ENGINEERING FLOWS
- 2018
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Ingår i: Proceedings of the Thermal and Fluids Engineering Summer Conference. - 2379-1748. - 9781567004724 ; 2018-March, s. 543-546
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Konferensbidrag (refereegranskat)abstract
- This paper presents the most recent applications of the Partially-Averaged Navier-Stokes equations for engineering flows together with the review of the previous work in the field. Partially-Averaged Navier Stokes (PANS) simulation has been successfully used for several different applications of flows around ground vehicles. Examples of flows studied using PANS are that of the flow around square-back Ahmed body, flow around simplified passenger vehicle influenced by crosswinds, flow around simplified intercity trains, to the influence of passive and active flow control on the reduction of the aerodynamic drag on simplified vehicles. The idea of the application of hybrid methods such as PANS is to decrease the resolution requirements that are needed in turbulence resolving simulations such as LES. The resolution requirements of LES are normally very high in the near-wall regions, and this is where the PANS method is expected to activate more turbulence modelling, and thereby decrease the computational effort. The PANS method used by the authors is based on the variable switching coefficient that regulates the amount of the turbulence modelling in the simulation. Previous studies have shown that such implementation of PANS is in line with the requirements that PANS should adapt to the computational grid. The most recent predictions range from simplified ground vehicle flow, flow around a freight train locomotive to the investigation of active flow control for trucks and ships. The new predictions show good agreement with the experimental observations.
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| 8. |
- Liu, Tanghong, 1976, et al.
(författare)
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Wave effects in a realistic tunnel induced by the passage of high-speed trains
- 2019
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798. ; 86, s. 224-235
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Tidskriftsartikel (refereegranskat)abstract
- As a high-speed train passes through a tunnel, aerodynamic pressure waves propagate backwards and forward in the tunnel, and they persist for a long time after the train is gone. Understanding the aerodynamic characteristics influenced by various factors on a tunnel is essential for ensuring the safety of tunnel structures. Field measurements were conducted in a 2812 m-long tunnel to systematically investigate the pressure characteristics during the passage of CRH2-150C and CRH380AL high-speed trains through the tunnel, both in single-train and intersecting cases. The results reveal that as the train speed increases, the location of the maximum peak-to-peak pressure variation shifts toward the tunnel entrance, mainly driven by the change in the negative pressure peak. The train length induces significant differences in peak pressures on the tunnel wall in the middle of the tunnel, and a long train brings more massive subsequent pressure waves than a short train in the post-train stage, but they decay faster. The intersection of two trains in the tunnel not only causes a significant change in the peak pressure and its location, but also has a significant effect on damage factor (the damage level on a structure subjected to a specific load) after train leaving the tunnel, with a 65.3% of this factor during trains operating in the tunnel.
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| 9. |
- Meng, Fanda, 1987, et al.
(författare)
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A tandem giant magnetoresistance assay for one-shot quantification of clinically relevant concentrations of N-terminal pro-B-type natriuretic peptide in human blood
- 2021
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 413:11, s. 2943-2949
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Tidskriftsartikel (refereegranskat)abstract
- We report a microfluidic sandwich immunoassay constructed around a dual-giant magnetoresistance (GMR) sensor array to quantify the heart failure biomarker NT-proBNP in human plasma at the clinically relevant concentration levels between 15 pg/mL and 40 ng/mL. The broad dynamic range was achieved by differential coating of two identical GMR sensors operated in tandem, and combining two standard curves. The detection limit was determined as 5 pg/mL. The assay, involving 53 plasma samples from patients with different cardiovascular diseases, was validated against the Roche Cobas e411 analyzer. The salient features of this system are its wide concentration range, low detection limit, small sample volume requirement (50 μL), and the need for a short measurement time of 15 min, making it a prospective candidate for practical use in point of care analysis.
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| 10. |
- Meng, Fanda, 1987, et al.
(författare)
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Dynamic Range Expansion of the C-Reactive Protein Quantification with a Tandem Giant Magnetoresistance Biosensor
- 2021
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 6:19, s. 12923-12930
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we report a convenient analytical method for a full-range quantification of the C-reactive protein (CRP), a blood biomarker of infection and cardiovascular events. We determine CRP over the entire diagnostically relevant concentration range in undiluted human blood serum in a single test, using a tandem giant magnetoresistance (GMR) sensor. The tandem principle combines a sandwich assay and a competitive assay, which allows for the discrimination of the concentration values resulting from the multivalued dose-response curve ("Hook"effect), which characterizes the one-step sandwich assay at high CRP concentrations. The sensor covers a linear detection range for CRP concentration from 3 ng/mL to 350 μg/mL, the detection limit (s/n = 3) is 1 ng/mL. The prominent features of the chip-based method are its expanded dynamic range and low sample volume (50 μL), and the need for a short measurement time of 15 min. These figures of merit, in addition to the low detection limit equal to the established assay instrumentation, make it a viable candidate for use in point-of-care diagnostics.
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