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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 3. |
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| 4. |
- Sun, C., et al.
(författare)
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Beam division multiple access for massive MIMO downlink transmission
- 2015
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Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781467364324 ; 2015-September, s. 1970-1975
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Konferensbidrag (refereegranskat)abstract
- We study a multiuser multicarrier downlink communication system in which the base station (BS) employs a large number of antennas. By assuming frequency-division duplex operation, we provide a beam domain channel model as the number of BS antennas grows asymptotically large. With this model, we first derive a closed-form upper bound on the achievable ergodic sum-rate before developing necessary conditions to asymptotically maximize the upper bound, with only statistical channel state information at the BS. Inspired by these conditions, we propose a beam division multiple access (BDMA) transmission scheme, where the BS communicates with users via different beams. For BDMA transmission, we design user scheduling to select users within non-overlapping beams, work out an optimal pilot design under a minimum mean square error criterion, and provide optimal pilot sequences by utilizing the Zadoff-Chu sequences. The proposed BDMA scheme reduces significantly the pilot overhead, as well as, the processing complexity at transceivers. Simulations demonstrate the high spectral efficiency of BDMA transmission and the advantages in the bit error rate performance of the proposed pilot sequences.
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| 5. |
- Sun, C., et al.
(författare)
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Beam Division Multiple Access Transmission for Massive MIMO Communications
- 2015
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 63:6, s. 2170-2184
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Tidskriftsartikel (refereegranskat)abstract
- We study multicarrier multiuser multiple-input multiple-output (MU-MIMO) systems, in which the base station employs an asymptotically large number of antennas. We analyze a fully correlated channel matrix and provide a beam domain channel model, where the channel gains are independent of sub-carriers. For this model, we first derive a closed-form upper bound on the achievable ergodic sum-rate, based on which, we develop asymptotically necessary and sufficient conditions for optimal downlink transmission that require only statistical channel state information at the transmitter. Furthermore, we propose a beam division multiple access (BDMA) transmission scheme that simultaneously serves multiple users via different beams. By selecting users within non-overlapping beams, the MU-MIMO channels can be equivalently decomposed into multiple single-user MIMO channels; this scheme significantly reduces the overhead of channel estimation, as well as, the processing complexity at transceivers. For BDMA transmission, we work out an optimal pilot design criterion to minimize the mean square error (MSE) and provide optimal pilot sequences by utilizing the Zadoff-Chu sequences. Simulations demonstrate the near-optimal performance of BDMA transmission and the advantages of the proposed pilot sequences.
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| 6. |
- Xu, Jin-Long, et al.
(författare)
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Formation of a Massive Lenticular Galaxy Under the Tidal Interaction with a Group of Dwarf Galaxies
- 2023
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Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 958:2
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Tidskriftsartikel (refereegranskat)abstract
- Based on the atomic-hydrogen (H i) observations using the Five-hundred-meter Aperture Spherical radio Telescope, we present a detailed study of the gas-rich massive S0 galaxy NGC 1023 in a nearby galaxy group. The presence of a H i extended warped disk in NGC 1023 indicates that this S0 galaxy originated from a spiral galaxy. The data also suggest that NGC 1023 is interacting with four dwarf galaxies. In particular, one of the largest dwarf galaxies has fallen into the gas disk of NGC 1023, forming a rare bright-dark galaxy pair with a large gas clump. This clump shows the signature of a galaxy but has no optical counterpart, implying that it is a newly formed starless galaxy. Our results first suggest that a massive S0 galaxy in a galaxy group can form via the morphological transformation from a spiral under the joint action of multiple tidal interactions.
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| 7. |
- Ye, Xiao, et al.
(författare)
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Modeling and control strategy development of a parallel hybrid electric bus
- 2013
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Ingår i: International Journal of Automotive Technology. - : Springer Science and Business Media LLC. - 1976-3832 .- 1229-9138. ; 14:6, s. 971-985
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the system modeling, control strategy design, and experiment validation of a parallel hybridelectric bus with an automatic manual transmission (AMT) and a dry clutch. The mathematical model representation and thesystem architecture of the powertrain are first described. Next, a complete control scheme including energy managementstrategy and coordinated control of the AMT and the clutch is presented. The controller and powertrain models are thenintegrated in a way that the power management and the hybrid driveline perform in real world. The analysis and validationthrough model simulation and comparison with experiment data are conducted. A good agreement between the model andexperiment demonstrates the efficacy and credibility of the integrated model. The integrated model is employed in bothsimulation and bench-test assessments for the development of a hybrid control unit. The results indicate that the model-baseddesign methodology is beneficial to systematically analyzing and understanding the dynamics of hybrid electric powertrain.
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