| 1. |
- You, Xiaohu, et al.
(författare)
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Towards 6G wireless communication networks: vision, enabling technologies, and new paradigm shifts
- 2021
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Ingår i: Science China Information Sciences. - : Science Press. - 1674-733X .- 1869-1919. ; 64:1
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Forskningsöversikt (refereegranskat)abstract
- The fifth generation (5G) wireless communication networks are being deployed worldwide from 2020 and more capabilities are in the process of being standardized, such as mass connectivity, ultra-reliability, and guaranteed low latency. However, 5G will not meet all requirements of the future in 2030 and beyond, and sixth generation (6G) wireless communication networks are expected to provide global coverage, enhanced spectral/energy/cost efficiency, better intelligence level and security, etc. To meet these requirements, 6G networks will rely on new enabling technologies, i.e., air interface and transmission technologies and novel network architecture, such as waveform design, multiple access, channel coding schemes, multi-antenna technologies, network slicing, cell-free architecture, and cloud/fog/edge computing. Our vision on 6G is that it will have four new paradigm shifts. First, to satisfy the requirement of global coverage, 6G will not be limited to terrestrial communication networks, which will need to be complemented with non-terrestrial networks such as satellite and unmanned aerial vehicle (UAV) communication networks, thus achieving a space-air-ground-sea integrated communication network. Second, all spectra will be fully explored to further increase data rates and connection density, including the sub-6 GHz, millimeter wave (mmWave), terahertz (THz), and optical frequency bands. Third, facing the big datasets generated by the use of extremely heterogeneous networks, diverse communication scenarios, large numbers of antennas, wide bandwidths, and new service requirements, 6G networks will enable a new range of smart applications with the aid of artificial intelligence (AI) and big data technologies. Fourth, network security will have to be strengthened when developing 6G networks. This article provides a comprehensive survey of recent advances and future trends in these four aspects. Clearly, 6G with additional technical requirements beyond those of 5G will enable faster and further communications to the extent that the boundary between physical and cyber worlds disappears.
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| 2. |
- Zhao, Yaofeng, et al.
(författare)
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Ornithorhynchus anatinus (Platypus) Links the Evolution of Immunoglobulin Genes in Eutherian Mammals and Nonmammalian Tetrapods
- 2009
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 183:5, s. 3285-3293
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Tidskriftsartikel (refereegranskat)abstract
- The evolutionary origins of mammalian immunoglobulin H chain isotypes (IgM, IgD, IgG, IgE, and IgA) are still incompletely understood as these isotypes differ considerably in structure and number from their counterparts in nonmammalian tetrapods. We report in this study that the platypus (Ornithorhynchus anatinus) Ig H chain constant region gene locus contains eight Ig encoding genes, which are arranged in an mu-delta-o-gamma 2-gamma 1-alpha 1-epsilon-alpha 2 order, spanning a total of similar to 200 kb DNA, encoding six distinct isotypes. The o (o for Ornithorhynchus) gene encodes a novel Ig H chain isotype that consists of four constant region domains and a hinge, and is structurally different from any of the five known mammalian Ig classes. This gene is phylogenetically related to nu (epsilon) and gamma, and thus appears to be a structural intermediate between these two genes. The platypus delta gene encodes ten heavy chain constant region domains, lacks a hinge region and is similar to IgD in amphibians and fish, but strikingly different from that in eutherian mammals. The platypus Ig H chain isotype repertoire thus shows a unique combination of genes that share similarity both to those of nonmammallian tetrapods and eutherian animals and demonstrates how phylogenetically informative species can be used to reconstruct the evolutionary history of functionally important genes.
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| 3. |
- Chen, Youchun, et al.
(författare)
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Insights into the working mechanism of cathode interlayers in polymer solar cells via [(C8H17)(4)N](4)[SiW12O40]
- 2016
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Ingår i: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 4:48, s. 19189-19196
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Tidskriftsartikel (refereegranskat)abstract
- A low-cost (amp;lt;$1 per g), high-yield (amp;gt;90%), alcohol soluble surfactant-encapsulated polyoxometalate complex [(C8H17)(4)N](4)[SiW12O40] has been synthesized and utilized as a cathode interlayer (CIL) in polymer solar cells (PSCs). A power conversion efficiency of 10.1% can be obtained for PSCs based on PTB7-Th (poly[[2,6-4,8-di(5-ethylhexylthienyl) benzo[1,2-b;3,3-b]-dithiophene][3-fluoro-2[(2-ethylhexyl) carbonyl] thieno [3,4-b]-thiophenediyl]]):PC71BM ([6,6]-phenyl C71-butyric acidmethyl ester) due to the incorporation of [(C8H17)(4)N](4)[SiW12O40]. Combined measurements of current density-voltage characteristics, transient photocurrent, charge carrier mobility and capacitance-voltage characteristics demonstrate that [(C8H17)(4)N](4)[SiW12O40] can effectively increase the built-in potential, charge carrier density and mobility and accelerate the charge carrier extraction in PSCs. Most importantly, the mechanism of using [(C8H17)(4)N](4)[SiW12O40] as the CIL is further brought to light by X-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS) of the metal/ [(C8H17)(4)N](4)[SiW12O40] interface. The findings suggest that [(C8H17)(4)N](4)[SiW12O40] not only decreased the work function of the metal cathodes but also was n-doped upon contact with the metals, which provide insights into the working mechanism of the CILs simultaneously improving the open circuit voltage, short circuit current and fill factor in the PSCs.
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| 4. |
- Fan, Qunping, 1989, et al.
(författare)
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A Non-Conjugated Polymer Acceptor for Efficient and Thermally Stable All-Polymer Solar Cells
- 2020
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 59:45, s. 19835-19840
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Tidskriftsartikel (refereegranskat)abstract
- A non-conjugated polymer acceptor PF1-TS4 was firstly synthesized by embedding a thioalkyl segment in the mainchain, which shows excellent photophysical properties on par with a fully conjugated polymer, with a low optical band gap of 1.58 eV and a high absorption coefficient >105 cm−1, a high LUMO level of −3.89 eV, and suitable crystallinity. Matched with the polymer donor PM6, the PF1-TS4-based all-PSC achieved a power conversion efficiency (PCE) of 8.63 %, which is ≈45 % higher than that of a device based on the small molecule acceptor counterpart IDIC16. Moreover, the PF1-TS4-based all-PSC has good thermal stability with ≈70 % of its initial PCE retained after being stored at 85 °C for 180 h, while the IDIC16-based device only retained ≈50 % of its initial PCE when stored at 85 °C for only 18 h. Our work provides a new strategy to develop efficient polymer acceptor materials by linkage of conjugated units with non-conjugated thioalkyl segments.
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| 5. |
- Meng, Yuan, et al.
(författare)
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Influence of land use type and urbanization level on the distribution of pharmaceuticals and personal care products and risk assessment in Beiyun River, China
- 2021
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Ingår i: Chemosphere. - : Pergamon Press. - 0045-6535 .- 1879-1298. ; 287:Pt 1
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Tidskriftsartikel (refereegranskat)abstract
- Influence of land use type and urbanization level on the distribution of pharmaceuticals and personal care products (PPCPs) from the developed regions of Beijing-Tianjin-Hebei in the northern China was evaluated. The seasonal and spatial variations of the 22 target PPCPs were analyzed in the 63 sampling sites along the whole Beiyun River Basin. Results showed that the total PPCPs concentration had a wide variation range, from 132 ng L-1 to 25474 ng L-1. Spatial interpolation analysis showed that agricultural land presented higher PPCPs contamination level than build-up land (p < 0.05) and the concentration was negatively correlated with urbanization level. Source apportionment showed the untreated sewage source contributed to 34%-53% of the PPCPs burden in the Beiyun River. Risk assessment indicated that diethyltoluamide, carbamazepine, octocrylene, gemfibrozil and triclocarban had high risks (RQ > 1), and small tributaries had the highest mixed risk (MRQ = 34). Species sensitivity distribution combined with the safety threshold method showed that PPCPs would have potential risk on aquatic organisms even at very low concentrations and triclocarban posed the highest risk in the Beiyun River.
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| 6. |
- Wu, Chuanyan, et al.
(författare)
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PEPRF : Identification of Essential Proteins by Integrating Topological Features of PPI Network and Sequence-based Features via Random Forest
- 2021
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Ingår i: Current Bioinformatics. - : Bentham Science Publishers Ltd.. - 1574-8936. ; 16:9, s. 1161-1168
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Tidskriftsartikel (refereegranskat)abstract
- Background: Essential proteins play an important role in the process of life, which can be identified by experimental methods and computational approaches. Experimental approaches to identify essential proteins are of high accuracy but with the limitation of time and resource-consuming. Objective: Herein, we present a computational model (PEPRF) to identify essential proteins based on machine learning. Methods: Different features of proteins were extracted. Topological features of Protein-Protein Interaction (PPI) network-based are extracted. Based on the protein sequence, graph theory-based features, in-formation-based features, composition and physichemical features, etc., were extracted. Finally, 282 features are constructed. In order to select the features that contributed most to the identification, Re-liefF-based feature selection method was adopted to measure the weights of these features. Results: As a result, 212 features were curated to train random forest classifiers. Finally, PEPRF get the AUC of 0.71 and an accuracy of 0.742. Conclusion: Our results show that PEPRF may be applied as an efficient tool to identify essential pro-teins.
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| 7. |
- Xu, Feng, et al.
(författare)
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Broadband spectroscopic sensor for real-time monitoring of industrial SO2 emissions
- 2007
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Ingår i: Applied Optics. - 2155-3165. ; 46:13, s. 2503-2506
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Tidskriftsartikel (refereegranskat)abstract
- A spectroscopic system for continuous real-time monitoring of SO2, concentrations in industrial emissions was developed. The sensor is well suited for field applications due to simple and compact instrumental design, and robust data evaluation based on ultraviolet broadband absorption without the use of any calibration cell. The sensor has a detection limit of 1 ppm, and was employed both for gas-flow simulations with and without suspended particles, and for in situ measurement of SO2 concentrations in the flue gas emitted from an industrial coal-fired boiler. The price/performance ratio of the instrument is expected to be superior to other comparable real-time monitoring systems.
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| 8. |
- Yu, Chuanhe, et al.
(författare)
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A mechanism for preventing asymmetric histone segregation onto replicating DNA strands
- 2018
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Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 361:6409, s. 1386-+-
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Tidskriftsartikel (refereegranskat)abstract
- How parental histone (H3-H4)2 tetramers, the primary carriers of epigenetic modifications, are transferred onto leading and lagging strands of DNA replication forks for epigenetic inheritance remains elusive. Here we show that parental (H3-H4)2 tetramers are assembled into nucleosomes onto both leading and lagging strands, with a slight preference for lagging strands. The lagging strand preference increases markedly in cells lacking Dpb3 and Dpb4, two subunits of the leading strand DNA polymerase, Pol ε, due to the impairment of parental (H3-H4)2 transfer to leading strands. Dpb3-Dpb4 binds H3-H4 in vitro and participates in the inheritance of heterochromatin. These results indicate that different proteins facilitate the transfer of parental (H3-H4)2 onto leading vs lagging strands, and that Dbp3-Dpb4 plays a significant role in this poorly understood process.
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| 9. |
- Biemont, E, et al.
(författare)
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Doubly ionized thorium: Laser lifetime measurements and transition probability determination of interest in cosmochronology
- 2002
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 567:2, s. 1276-1283
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Tidskriftsartikel (refereegranskat)abstract
- The first lifetime measurements have been performed for six levels of doubly ionized thorium, an important cosmochronometer in astrophysics for estimating the age of the Galaxy. The levels, belonging to the 5f(2), 5f7p, 7s7p, and 6d7p configurations of Th III, have been measured by the time-resolved laser-induced fluorescence method and compared with relativistic Hartree-Fock calculations including configuration interaction and core-polarization effects. Taking advantage of the excellent agreement between theory and experiment, a first set of transition probabilities of astrophysical interest has been deduced for this ion from a combination of the experimental lifetimes and of the theoretical branching fractions.
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| 10. |
- Biemont, E, et al.
(författare)
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Lifetime measurements and calculations in singly ionized ytterbium
- 2002
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075. ; 35:22, s. 4743-4749
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Tidskriftsartikel (refereegranskat)abstract
- New radiative lifetimes, measured by time-resolved laser-induced fluorescence spectroscopy, are reported for five Rydberg states of singly ionized ytterbium. Free Yb+ ions were produced in a laser-induced plasma. The experimental results have been compared with HFR calculations, taking core-polarization effects into account, and a good agreement (within 25%) between theory and experiment is observed for four levels. HFR results are also proposed for np (n less than or equal to 7) and nf (n less than or equal to 8) Rydberg states and compared with available data.
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| 11. |
- Biemont, E, et al.
(författare)
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Lifetime measurements for doubly ionized uranium
- 2002
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 35:7, s. 1701-1705
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Tidskriftsartikel (refereegranskat)abstract
- The first lifetime measurements for doubly ionized uranium are reported in the present work. They relate to five levels belonging to the configurations 5f(2)6d(2), 5f(2)6d7s and 5f(3)7p and have been obtained with a time-resolved laser-induced-fluorescence technique, the ions being produced by laser ablation of a uranium oxide target.
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| 12. |
- Biémont, E, et al.
(författare)
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Radiative lifetime and oscillator strength determinations in Sm III
- 2003
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 399:1, s. 343-349
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 6 levels belonging to the4f5(6Hdeg,6Fdeg)5d configuration of Sm III have beenmeasured for the first time using a time-resolved laser-inducedfluorescence technique. Experimental data have been compared withsemi-empirical calculations. The agreement is excellent for 4 levelswith 6Fdeg as a parent term. Larger discrepancies(53 and 37) are observed for 2 levels with 6Hdegand 6Fdeg, respectively, as a parent term and areexplainable by strong mixing and cancellation effects occurring in theline strength calculations which are responsible of instabilitiesoccurring in the lifetimes considered as a function of J value withinthe term. Branching ratios for the lines depopulating the levels ofinterest have been measured by Fourier transform spectroscopy. A firstset of oscillator strengths has been deduced for this ion.
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| 13. |
- Biemont, E, et al.
(författare)
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Time-resolved laser-induced fluorescence lifetime measurements and theoretical transition probabilities in Tb III
- 2002
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 65:5
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Tidskriftsartikel (refereegranskat)abstract
- Lifetimes of four short-lived levels belonging to the 4f(8)(F-7)6p configuration of Tb III have been measured using a two-step excitation time-resolved laser-induced fluorescence technique. They agree quite well with multiconfigurational relativistic Hartree-Fock calculations performed with inclusion of core-polarization effects. Using the experimental lifetimes and the theoretical branching fractions, a set of transition probabilities has been deduced for this ion.
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| 14. |
- Blagoev, K, et al.
(författare)
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Radiative lifetimes of 6sns S-3(1) and 6snd D-3(1) excited states of HgI
- 2002
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 66:3
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Tidskriftsartikel (refereegranskat)abstract
- Natural radiative lifetimes have been measured along the 6sns S-3(1) (n=7-10) and 6snd D-3(1) (n=6-11) Rydberg series of neutral mercury using time-resolved laser-induced fluorescence spectroscopy in a laser-produced mercury plasma. The states of Hg I investigated in the present work were populated from the ground state by a stepwise excitation process. Relativistic Hartree-Fock calculations, including intravalence interactions and core-polarization effects, have been performed and the theoretical lifetimes have been compared with the measurements.
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| 15. |
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| 16. |
- Cao, Zhiguo, et al.
(författare)
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Economic status as a determinant of national PCDD/PCDF releases and implications for PCDD/PCDF reduction
- 2013
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 91:3, s. 328-335
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Tidskriftsartikel (refereegranskat)abstract
- The annual releases of polychlorinated dibenzo-para-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) from 68 countries/regions were investigated by correlating quantitative emissions with economic status of the nations. The national dioxin/furan inventories were developed using the PCDD/PCDF Standardized Toolldt, which presents the quantitative releases from ten major source groups to five release vectors. The correlation between intensity of PCDDIPCDF release and economic status was discussed and the influence of economic status on composition of five release vectors and ten source groups was studied. As PCDD/PCDF are mainly released from human activities to environmental matrices, release per person (RpP) and release per unit area (RpA) are defined to reflect release burden (Donor) and contamination burden (Receptor), respectively. Based on these two concepts, International PCDD/PCDF Reduction Burden is characterized by burden quotient (BQ) and a calculation model is established. The numbers of countries/regions with high, moderate and low International PCDD/PCDF Reduction Burden were 19,31 and 18, respectively. The information in this paper can be used for politicians to develop legislations to improve International PCDD/PCDF Reduction.
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| 17. |
- Chen, Guanying, et al.
(författare)
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Near vacuum ultraviolet luminescence of Gd3+ and Er3+ ions generated by super saturation upconversion processes
- 2009
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Ingår i: Optics Express. - 1094-4087. ; 17:19, s. 16366-16371
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Tidskriftsartikel (refereegranskat)abstract
- Near vacuum ultraviolet (UV) upconversion (UC) emissions with a spectral resolution of 1 nm, from the (6)G(J), D-6(J), I-6(J), P-6(J) levels of Gd3+ and the L-2(17/2), D-4(7/2), H-2(2)(9/2), D-2(5/2), (4)G(7/2), K-2(13/2), P-2(3/2) levels of Er3+, were observed under 974 nm laser excitation. Mechanism analyses illustrate that successive energy transfers (ETs) from Yb3+ to Er3+ generate UV UC radiations in Er3+, while two resonant ETs from Er3+ to Gd3+ lead to UV UC radiations in Gd3+. Power dependence analyses indicate that the expected inefficient four- and five-photon processes have been switched into efficient two-photon processes due to a super saturation UC phenomenon that employs consecutive saturations at the intermediate states. (C) 2009 Optical Society of America
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| 18. |
- Dai, Zhenwen, et al.
(författare)
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Time-resolved laser-induced fluorescence measurements of Rydberg states in LuI and comparison with theory
- 2003
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075. ; 36:3, s. 479-487
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved laser-induced fluorescence measurements have been performed for ten odd Rydberg states of neutral lutetium, belonging to the 6s(2)(S-1)np(n = 8-9) and 6 s(2)(S-1)nf (n = 5-8) series. For 6S(2)(S-1)8p and 6s(2)(S-1)7f, the experimental lifetimes corresponding to the two J values within the doublet differ substantially. Comparison with theoretical values, calculated with extensive configuration interaction and core-polarization effects included, shows that the experimental trends are adequately reproduced both for np (n = 8-9) and nf (n = 5-8) states.
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| 19. |
- Gan, Haiyun, et al.
(författare)
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Checkpoint Kinase Rad53 Couples Leading- and Lagging-Strand DNA Synthesis under Replication Stress
- 2017
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Ingår i: Molecular Cell. - : Elsevier. - 1097-2765 .- 1097-4164. ; 68:2, s. 446-455
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Tidskriftsartikel (refereegranskat)abstract
- The checkpoint kinase Rad53 is activated during replication stress to prevent fork collapse, an essential but poorly understood process. Here we show that Rad53 couples leading- and lagging-strand synthesis under replication stress. In rad53-1 cells stressed by dNTP depletion, the replicative DNA helicase, MCM, and the leading-strand DNA polymerase, Pol ε, move beyond the site of DNA synthesis, likely unwinding template DNA. Remarkably, DNA synthesis progresses further along the lagging strand than the leading strand, resulting in the exposure of long stretches of single-stranded leading-strand template. The asymmetric DNA synthesis in rad53-1 cells is suppressed by elevated levels of dNTPs in vivo, and the activity of Pol ε is compromised more than lagging-strand polymerase Pol δ at low dNTP concentrations in vitro. Therefore, we propose that Rad53 prevents the generation of excessive ssDNA under replication stress by coordinating DNA unwinding with synthesis of both strands.
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| 20. |
- Liu, Zhidan, et al.
(författare)
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A novel configuration of microbial fuel cell stack bridged internally through an extra cation exchange membrane.
- 2008
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Ingår i: Biotechnology Letters. - : Springer Science and Business Media LLC. - 1573-6776 .- 0141-5492. ; 30, s. 1017-1023
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports a novel configuration of stacked microbial fuel cells (MFCs) bridged internally through an extra cation exchange membrane (CEM). The MFC stack (MFC(stack)), assembled from two single MFCs (MFC(single)), resulted in double voltage output and half optimal external resistance. COD removal rate was increased from 32.4% to 54.5%. The performance improvement could be attributed to the smaller internal resistance and enhanced cations transfer. A result from a half cell study further confirmed the important role of the extra CEM. This study also demonstrated MFCs where the anode and cathode were sandwiched between two CEMs possessed significantly high power outputs.
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| 21. |
- Liu, Zhidan, et al.
(författare)
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Microbial fuel cell based biosensor for in situ monitoring of anaerobic digestion process.
- 2011
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Ingår i: Bioresource Technology. - : Elsevier BV. - 1873-2976 .- 0960-8524. ; 102, s. 10221-10229
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Tidskriftsartikel (refereegranskat)abstract
- A wall-jet microbial fuel cell (MFC) was developed for the monitoring of anaerobic digestion (AD). This biofilm based MFC biosensor had a character of being portable, short hydraulic retention time (HRT) for sample flow through and convenient for continuous operation. The MFC was installed in the recirculation loop of an upflow anaerobic fixed-bed (UAFB) reactor in bench-scale where pH of the fermentation broth and biogas flow were monitored in real time. External disturbances to the AD were added on purpose by changing feedstock concentration, as well as process configuration. MFC signals had good correlations with online measurements (i.e. pH, gas flow rate) and offline analysis (i.e. COD) over 6-month operation. These results suggest that the MFC signal can reflect the dynamic variation of AD and can potentially be a valuable tool for monitoring and control of bioprocess.
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| 22. |
- Liu, Zhidan, et al.
(författare)
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Study of operational performance and electrical response on mediator-less microbial fuel cells fed with carbon- and protein-rich substrates
- 2009
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Ingår i: Biochemical Engineering Journal. - : Elsevier BV. - 1369-703X. ; 45:3, s. 185-191
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Tidskriftsartikel (refereegranskat)abstract
- The inducement of electroactive consortia was carried Out in dual-chamber MFCS using acetate-based substrate- and a protein-rich synthetic wastewater in fed-batch mode. The characteristics of these MFCs were then compared. MFCs based on acetate-induced consortia (MFCAce) achieved more than twice higher maximum power, and one half of optimal external resistance in comparison to MFCs based on consortia (MFCPro) induced by a protein-rich wastewater. Furthermore, these MFCs exhibited various electrical responses even identical Substrate being applied. MFCAce preferred carbon-neutral substrates. whereas MFCPro exhibited better performance on nitrogen rich feedstock. In particular, for glucose-glutamic acid solution with gradually decreased glucose/glutamic acid ratio, MFCPro exhibited increasing electrical responses than MFCAce. These results suggest that it is possible to optimize the behavior and characteristics of MFC through proper selection of feeding substrate. (C) 2009 Elsevier B.V. All rights reserved.
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| 23. |
- Lou, Xiutao, et al.
(författare)
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Detection of elemental mercury by multimode diode laser correlation spectroscopy
- 2012
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Ingår i: Optics Express. - 1094-4087. ; 20:5, s. 4927-4938
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a method for elemental mercury detection based on correlation spectroscopy employing UV laser radiation generated by sum-frequency mixing of two visible multimode diode lasers. Resonance matching of the multimode UV laser is achieved in a wide wavelength range and with good tolerance for various operating conditions. Large mode-hops provide an off-resonance baseline, eliminating interferences from other gas species with broadband absorption. A sensitivity of 1 mu g/m(3) is obtained for a 1-m path length and 30-s integration time. The performance of the system shows promise for mercury monitoring in industrial applications.
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| 24. |
- Lou, Xiutao, et al.
(författare)
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Gas detection by correlation spectroscopy employing a multimode diode laser
- 2008
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Ingår i: Applied Optics. - 2155-3165. ; 47:13, s. 2392-2398
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Tidskriftsartikel (refereegranskat)abstract
- A gas sensor based on the gas-correlation technique has been developed using a multimode diode laser (MDL) in a dual-beam detection scheme. Measurement of CO2 mixed with CO as an interfering gas is successfully demonstrated using a 1570 run tunable MDL. Despite overlapping absorption spectra and occasional mode hops, the interfering signals can be effectively excluded by a statistical procedure including correlation analysis and outlier identification. The gas concentration is retrieved from several pair-correlated signals by a linear-regression scheme, yielding a reliable and accurate measurement. This demonstrates the utility of the unsophisticated MDLs as novel light sources for gas detection applications.
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| 25. |
- Lou, Xiutao, et al.
(författare)
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Oxygen measurement by multimode diode lasers employing gas correlation spectroscopy
- 2009
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Ingår i: Applied Optics. - 2155-3165. ; 48:5, s. 990-997
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Tidskriftsartikel (refereegranskat)abstract
- Multimode diode laser (MDL)-based correlation spectroscopy (COSPEC) was used to measure oxygen in ambient air, thereby employing a diode laser (DL) having an emission spectrum that overlaps the oxygen absorption lines of the A band. A sensitivity of 700 ppm m was achieved with good accuracy (2%) and linearity (R-2 = 0.999). For comparison, measurements of ambient oxygen were also performed by tunable DL absorption spectroscopy (TDLAS) technique employing a vertical cavity surface emitting laser. We demonstrate that, despite slightly degraded sensitivity, the MDL-based COSPEC-based oxygen sensor has the advantages of high stability, low cost, ease-of-use, and relaxed requirements in component selection and instrument buildup compared with the TDLAS-based instrument. (C) 2009 Optical Society of America
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| 26. |
- Lou, Xiutao, et al.
(författare)
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Temperature-Corrected Oxygen Detection Based on Multi-Mode Diode Laser Correlation Spectroscopy
- 2013
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Ingår i: Journal of Spectroscopy. - : Hindawi Limited. - 2314-4920 .- 2314-4939. ; 2013, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Temperature-corrected oxygen measurements were performed by using multi-mode diode laser correlation spectroscopy at temperatures ranging between 300 and 473 K. The experiments simulate in situ monitoring of oxygen in coal-combustion exhaust gases at the tail of the flue. A linear relationship with a correlation coefficient of -0.999 was found between the evaluated concentration and the gas temperature. Temperature effects were either auto-corrected by keeping the reference gas at the same conditions as the sample gas, or rectified by using a predetermined effective temperature-correction coefficient calibrated for a range of absorption wavelengths. Relative standard deviations of the temperature-correction coefficient calibrated for a range of absorption wavelengths. Relative standard deviations of the temperature-corrected oxygen concentrations obtained by different schemes and at various temperatures were estimated, yielding a measurement precision of 0.6%.
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| 27. |
- Muhammed, Alemu Jorgi, et al.
(författare)
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Resource Allocation for Energy-Efficient NOMA System in Coordinated Multi-Point Networks
- 2021
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Ingår i: IEEE Transactions on Vehicular Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9545 .- 1939-9359. ; 70:2, s. 1577-1591
-
Tidskriftsartikel (refereegranskat)abstract
- This paper studies user scheduling and power allocation problem to maximize the energy efficiency (EE) for non-orthogonal multiple access (NOMA) in downlink Coordinated Multi-Point networks. In the proposed framework, a more practical scenario the imperfect channel state information, imperfect successive interference cancellation and data outage are investigated. To address the considered problem, the optimization problem is formulated constrained by the total power and the outage probability requirements. However, the EE objective function is with a non-convex structure. Accordingly, we first convert the optimization problem to make the objective function concave and analytically tractable. Furthermore, we split the joint optimization problem to find a suboptimal solutions to the original problem. As a result, we first propose a suboptimal user-scheduling algorithm to improve the system's EE. Due to the non-convex function of the transmit power, we invoke a sequential successive convex approach to address the non-convex problem by its lower bound concave function. Besides, the fractional objective function is converted to its equivalent subtractive form. Finally, we derive a power control scheme to address the proposed framework. Simulation results endorse the effectiveness of the proposed algorithm and their performance gains in terms of EE compared to both NOMA and OFDMA variants.
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| 28. |
- Qu, Zhiguo, et al.
(författare)
-
Quantum detectable Byzantine agreement for distributed data trust management in blockchain
- 2023
-
Ingår i: Information Sciences. - Philadelphia, PA : Elsevier. - 0020-0255 .- 1872-6291. ; 637
-
Tidskriftsartikel (refereegranskat)abstract
- No system entity within a contemporary distributed cyber system can be entirely trusted. Hence, the classic centralized trust management method cannot be directly applied to it. Blockchain technology is essential to achieving decentralized trust management, its consensus mechanism is useful in addressing large-scale data sharing and data consensus challenges. Herein, an n-party quantum detectable Byzantine agreement (DBA) based on the GHZ state to realize the data consensus in a quantum blockchain is proposed, considering the threat posed by the growth of quantum information technology on the traditional blockchain. Relying on the nonlocality of the GHZ state, the proposed protocol detects the honesty of nodes by allocating the entanglement resources between different nodes. The GHZ state is notably simpler to prepare than other multi-particle entangled states, thus reducing preparation consumption and increasing practicality. When the number of network nodes increases, the proposed protocol provides better scalability and stronger practicability than the current quantum DBA. In addition, the proposed protocol has the optimal fault-tolerant found and does not rely on any other presumptions. A consensus can be reached even when there are n−2 traitors. The performance analysis confirms viability and effectiveness through exemplification. The security analysis also demonstrates that the quantum DBA protocol is unconditionally secure, effectively ensuring the security of data and realizing data consistency in the quantum blockchain. © 2023 The Authors
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| 29. |
- Quinet, P, et al.
(författare)
-
Radiative lifetime measurements and transition probability calculations in lanthanide ions
- 2002
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Ingår i: Journal of Alloys and Compounds. - 0925-8388. ; 344:1-2, s. 255-259
-
Tidskriftsartikel (refereegranskat)abstract
- We have undertaken a systematic investigation of spectroscopic properties of lanthanide ions (Z=57-71). Using time-resolved laser-induced fluorescence following one- or two-photon excitations, a large number of radiative lifetimes have been measured at the Lund Laser Centre for singly, doubly and trebly ionized atoms. These new measurements have been used for testing theoretical calculations performed within the framework of a relativistic Hartree-Fock approach taking core-polarization effects into account. Using the experimental lifetimes (when available) and the theoretical branching fractions, a large number of transition probabilities, most of them of astrophysical interest, have been deduced and are stored in a new database (DREAM). Up to now, the results obtained concern the following ions: La2+, Ce2+, Ce2+, Pr2+, Ho2+, Er2+, Tm2+, Tm2+, Yb2+, Yb2+, Yb2+, Lu2+ and Lu2+. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 30. |
- Tiwari, Prayag, 1991-, et al.
(författare)
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Quantum Fuzzy Neural Network for multimodal sentiment and sarcasm detection
- 2024
-
Ingår i: Information Fusion. - Amsterdam : Elsevier. - 1566-2535 .- 1872-6305. ; 103, s. 1-14
-
Tidskriftsartikel (refereegranskat)abstract
- Sentiment and sarcasm detection in social media contribute to assessing social opinion trends. Over the years, most artificial intelligence (AI) methods have relied on real values to characterize the sentimental and sarcastic features in language. These methods often overlook the complexity and uncertainty of sentimental and sarcastic elements in human language. Therefore, this paper proposes the Quantum Fuzzy Neural Network (QFNN), a multimodal fusion and multitask learning algorithm with a Seq2Seq structure that combines Classical and Quantum Neural Networks (QNN), and fuzzy logic. Complex numbers are used in the Fuzzifier to capture sentiment and sarcasm features, and QNN are used in the Defuzzifier to obtain the prediction. The experiments are conducted on classical computers by constructing quantum circuits in a simulated noisy environment. The results show that QFNN can outperform several recent methods in sarcasm and sentiment detection task on two datasets (Mustard and Memotion). Moreover, by assessing the fidelity of quantum circuits in a noisy environment, QFNN was found to have excellent robustness. The QFNN circuit also possesses expressible and entanglement capabilities, proving effective in various settings. Our code is available at https://github.com/prayagtiwari/QFNN. © 2023 Elsevier B.V.
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| 31. |
- Xu, Can, et al.
(författare)
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Autofluorescence insensitive imaging using upconverting nanocrystals in scattering media
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 93:17
-
Tidskriftsartikel (refereegranskat)abstract
- Autofluorescence is a nuisance in the field of fluorescence imaging and tomography of exogenous molecular markers in tissue, degrading the quality of the collected data. In this letter, we report autofluorescence insensitive imaging using highly efficient upconverting nanocrystals (NaYF4: Yb3+ /Tm3+) in a tissue phantom illuminated with near- infrared radiation of 85 mW/cm(2). It was found that imaging with such nanocrystals leads to an exceptionally high contrast compared to traditional downconverting fluorophores due to the absence of autofluorescence. Upconverting nanocrystals may be envisaged as important biological markers for tissue imaging purposes. c 2008 American Institute of Physics. [DOI: 10.1063/1.3005588]
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| 32. |
- Xu, Huailiang, et al.
(författare)
-
Radiative lifetime measurements in ErII by time-resolved laser spectroscopy
- 2003
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36:9, s. 1771-1781
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 30 excited states of Er 11, ranging in energy from 25 592 to 36 148 cm(-1), have been measured by means of a time-resolved laser-induced fluorescence (LIF) technique. Free, singly ionized erbium ions were produced in a laser-induced plasma. A tunable laser, with 1 ns duration pulse, was employed to selectively excite the Er+ ions. The lifetime values were evaluated from the transient LIF signals recorded by a fast detection system. A comparison of the new results with previously published values is given. HFR calculations, including core-polarization contributions, are found to be in reasonable agreement with experiment, but the present calculations clearly indicate that further laboratory and theoretical work is urgently needed, particularly for the low lying odd configurations of this complex ion.
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| 33. |
- Yu, Chuanhe, et al.
(författare)
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Strand-specific analysis shows protein binding at replication forks and PCNA unloading from lagging strands when forks stall
- 2014
-
Ingår i: Molecular Cell. - : Elsevier BV. - 1097-2765 .- 1097-4164. ; 56:4, s. 551-563
-
Tidskriftsartikel (refereegranskat)abstract
- In eukaryotic cells, DNA replication proceeds with continuous synthesis of leading-strand DNA and discontinuous synthesis of lagging-strand DNA. Here we describe a method, eSPAN (enrichment and sequencing of protein-associated nascent DNA), which reveals the genome-wide association of proteins with leading and lagging strands of DNA replication forks. Using this approach in budding yeast, we confirm the strand specificities of DNA polymerases delta and epsilon and show that the PCNA clamp is enriched at lagging strands compared with leading-strand replication. Surprisingly, at stalled forks, PCNA is unloaded specifically from lagging strands. PCNA unloading depends on the Elg1-containing alternative RFC complex, ubiquitination of PCNA, and the checkpoint kinases Mec1 and Rad53. Cells deficient in PCNA unloading exhibit increased chromosome breaks. Our studies provide a tool for studying replication-related processes and reveal a mechanism whereby checkpoint kinases regulate strand-specific unloading of PCNA from stalled replication forks to maintain genome stability.
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| 34. |
- Zhan, Qiuqiang, et al.
(författare)
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Using 915 nm Laser Excited Tm3+/Er3+/Ho3+-Doped NaYbF4 Upconversion Nanoparticles for in Vitro and Deeper in Vivo Bioimaging without Overheating Irradiation
- 2011
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 5:5, s. 3744-3757
-
Tidskriftsartikel (refereegranskat)abstract
- Successful further development of superhigh-constrast upconversion (UC) bioimaging requires addressing the existing paradox: 980 nm laser light is used to excite upconversion nanoparticles (UCNPs), while 980 nm light has strong optical absorption of water and biological specimens. The overheating caused by 980 nm excitation laser light in UC bioimaging is computationally and experimentally investigated for the first time. A new promising excitation approach for better near-infrared to near-infrared (NIR-to-NIR) UC photoluminescence in vitro or in vivo imaging is proposed employing a cost-effective 915 nm laser. This novel laser excitation method provides drastically less heating of the biological specimen and larger imaging depth In the animals or tissues due to quite low water absorption. Experimentally obtained thermal-graphic maps of the mouse in response to the laser heating are investigated to demonstrate the less heating advantage of the 915 nm laser. Our tissue phantom experiments and simulations verified that the 915 nm laser is superior to the 980 nm laser for deep tissue imaging. A novel and facile strategy for surface functionalization is utilized to render UCNPs hydrophilic, stable, and cell targeting. These as-prepared UCNPs were characterized by TEM, emission spectroscopy, XRD, FTIR, and zeta potential. Specifically targeting UCNPs excited with a 915 nm laser have shown very high contrast UC bioimaging. Highly stable DSPE-mPEG-5000-encapsulated UCNPs were injected into mice to perform in vivo imaging. Imaging and spectroscopy analysis of UC photoluminescence demonstrated that a 915 nm laser can serve as a new promising excitation light for UC animal imaging.
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| 35. |
- Zhang, Xiaoou, et al.
(författare)
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Investigation of the adsorption behavior of glycine peptides on 12% cross-linked agarose gel media
- 2010
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1217:12, s. 1916-1925
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Tidskriftsartikel (refereegranskat)abstract
- The highly cross-linked 12% agarose gel Superose 12 10/300 GL Causes retardation of glycine peptides when mobile phases containing varying concentrations of acetonitrile in water are used An investigation has been made into the retention mechanism behind this retardation using the glycine dipeptide (GG) and tripeptide (GGG) as models The dependence of retention times of analytical-size peaks Under different experimental conditions was interpreted such that the adsorption most probably was caused by the formation of hydrogen bonds but that electrostatic interactions cannot be ruled Out Thereafter, a nonlinear adsorption study Was undertaken at different acetonitrile content in the eluent, using the elution by characteristic points (ECPs) method on strongly overloaded GG and GGG peaks With a new evaluation tool, the adsorption energy distribution (AED) Could be calculated prior to the model selection These calculations revealed that when the acetonitrile content in the eluent was varied from 0% to 20% the interactions turned from (i) being homogenous (GG) or mildly heterogeneous (GGG), (ii) via a more or less stronger degree of heterogeneity around one site to (iii) finally a typical bimodal energy interaction comprising of two sites (GG at 20% and GGG at 10% and 20%) The Langmuir, Toth and bi-Langmuir models described these interesting adsorption trends excellently Thus, the retardation observed for these glycine peptides is interpreted as being of mixed-mode character composed of electrostatic bonds and hydrogen bonds.
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| 36. |
- Zhang, Zhengquan, et al.
(författare)
-
6G WIRELESS NETWORKS Vision, Requirements, Architecture, and Key Technologies
- 2019
-
Ingår i: IEEE Vehicular Technology Magazine. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1556-6072 .- 1556-6080. ; 14:3, s. 28-41
-
Tidskriftsartikel (refereegranskat)abstract
- A key enabler for the intelligent information society of 2030, 6G networks are expected to provide performance superior to 5G and satisfy emerging services and applications. In this article, we present our vision of what 6G will be and describe usage scenarios and requirements for multi-terabyte per second (Tb/s) and intelligent 6G networks. We present a large-dimensional and autonomous network architecture that integrates space, air, ground, and underwater networks to provide ubiquitous and unlimited wireless connectivity. We also discuss artificial intelligence (AI) and machine learning [1], [2] for autonomous networks and innovative air-interface design. Finally, we identify several promising technologies for the 6G ecosystem, including terahertz (THz) communications, very-large-scale antenna arrays [i.e., supermassive (SM) multiple-input, multiple-output (MIMO)], large intelligent surfaces (LISs) and holographic beamforming (HBF), orbital angular momentum (OAM) multiplexing, laser and visible-light communications (VLC), blockchain-based spectrum sharing, quantum communications and computing, molecular communications, and the Internet of Nano-Things.
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| 37. |
- Zhang, Zhiguo, et al.
(författare)
-
A Meta-Graph Deep Learning Framework for Forecasting Air Pollutants in Stockholm
- 2023
-
Ingår i: 2023 IEEE World Forum on Internet of Things: The Blue Planet: A Marriage of Sea and Space, WF-IoT 2023. - : Institute of Electrical and Electronics Engineers Inc..
-
Konferensbidrag (refereegranskat)abstract
- Forecasting air pollution is an important activity for developing sustainable and smart cities. Generated by various sources, air pollutants distribute in the atmospheric environment due to the complex dispersion processes. The emerging sensor and data technologies have promoted the development of data-driven approaches to replace conventional physical models in urban air pollution forecasting. Nevertheless, it is still challenging to capture the intricate spatial and temporal patterns of air pollutant concentrations measured by heterogeneous sensors, especially for long-term prediction of the multi-variate time series data. This paper proposes a deep learning framework for longer-term forecast of air pollutants concentrations using air pollution sensing data, based on a conceptual framework of meta-graph deep learning. The key modules in the framework include meta-graph units and fusion layers, which are designed to learn temporal and spatial correlations respectively. A detailed case was formulated for forecasting air pollutants in Stockholm using air quality sensing data, meteorological data and so on. Experiments were conducted to evaluate the performance of the proposed modelling framework. The computational results show that it outperforms the baseline models and conventional deterministic dispersion models, demonstrating the potential of the framework to be deployed for the real air quality information systems in Stockholm.
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| 38. |
- Zhang, Zhiguo, et al.
(författare)
-
Experimental and theoretical studies of DyIII: radiative lifetimes and oscillator strengths of astrophysical interest
- 2002
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - 1365-2966. ; 334:1, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- The lifetimes of three short-lived levels belonging to the 4f(9) 6p configuration and of two long-lived levels of the 4f(9) 5d configuration of Dy iii have been measured for the first time using time-resolved laser-induced fluorescence techniques. They are in good agreement with theoretical values calculated within the framework of a pseudo-relativistic configuration interaction approximation. Using the experimental lifetimes and the theoretical branching fractions, a first set of transition probabilities of astrophysical interest has been obtained for Dy III.
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| 39. |
- Zhang, Zhengquan, et al.
(författare)
-
Full-Duplex Device-to-Device-Aided Cooperative Nonorthogonal Multiple Access
- 2017
-
Ingår i: IEEE Transactions on Vehicular Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9545 .- 1939-9359. ; 66:5, s. 4467-4471
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a full-duplex device-to-device (D2D)-aided cooperative nonorthogonal multiple access (NOMA) scheme to improve the outage performance of the NOMA-weak user in a NOMA user pair, where the NOMA-weak user is helped by the NOMA-strong user with the capability of full-duplex D2D communications. The expressions for the outage probability are derived to characterize the performance of the proposed scheme. The results show that the proposed cooperative NOMA scheme can achieve superior outage performance compared to the conventional NOMA and orthogonal multiple access (OMA). In order to further improve the outage performance, an adaptive multiple access (AMA) scheme is also studied, which dynamically switches between the proposed cooperative NOMA, conventional NOMA, and OMA schemes, according to the level of residual self-interference and the quality of links. The results show that the AMAscheme outperforms the above multiple access schemes in terms of outage performance.
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| 40. |
- Zhang, Zhengquan, et al.
(författare)
-
Full-Duplex Two-Way and One-Way Relaying : Average Rate, Outage Probability, and Tradeoffs
- 2016
-
Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276 .- 1558-2248. ; 15:6, s. 3920-3933
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we systematically study the average rate and outage probability tradeoffs of full-duplex two-way and one-way relaying under residual self-interference. Among various relaying protocols, two common of them are considered: amplify-and-forward (AF) and decode-and-forward (DF). Furthermore, we consider the application of physical-layer network coding (PNC) and analog network coding (ANC) to full-duplex two-way relaying. Novel closed-form expressions for the average rate and outage probability, are presented. The results show that full-duplex two-way relaying can achieve higher rate than one-way relaying in the medium to high signal-to-noise ratio (SNR) region, at the cost of a certain loss in the outage performance. Moreover, DF protocol can achieve better outage performance than the AF one, but it suffers from a certain loss in the rate in the high SNR region. It is also shown that PNC can further improve the rate and outage performance. In addition, the results clearly reveal the effects of time multiplexing, forward protocol, and network coding on relaying systems, which would shed light on designing practical full-duplex relaying schemes.
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| 41. |
- Zhang, Zhengquan, et al.
(författare)
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Heterogeneous Ultradense Networks with NOMA System Architecture, Coordination Framework, and Performance Evaluation
- 2018
-
Ingår i: IEEE Vehicular Technology Magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 1556-6072 .- 1556-6080. ; 13:2, s. 110-120
-
Tidskriftsartikel (refereegranskat)abstract
- Heterogeneous ultradense networks (H-UDNs) are one key enabler for fifth-generation (5G) wireless networks and beyond to satisfy the explosive growth of mobile data traffic, which exploits spatial reuse of scarce spectrum by deploying massive base stations (BSS) to boost network capacity and enhance network coverage. In this article, we present the system architecture for 5G H-UDNs, consisting of virtualized integrated ground-Air-space radio access networks (RANs) and core networks and study network coordination for virtualized H-UDN to efficiently manage computing resources and intercell interference. We look at a cloud-fog-computing coordination framework for efficient computing resource management by achieving reasonable computing task distribution and transfer; computing load balance for computing tasks among virtual computing resources to improve network performance and computing resource efficiency; and a macro-small cell coordination framework for virtualized H-UDN with nonorthogonal multiple access (NOMA) to efficiently manage intercell interference and improve network performance. The joint macro-small enhanced intercell interference coordination (eICIC) and small-small coordinated multipoint joint transmission (CoMP-JT) scheme can efficiently eliminate macro-small intercell interference and utilize small-small intercell interference.
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| 42. |
- Zhang, Zhiguo, et al.
(författare)
-
Improving 3-day deterministic air pollution forecasts using machine learning algorithms
- 2024
-
Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 24:2, s. 807-851
-
Tidskriftsartikel (refereegranskat)abstract
- As air pollution is regarded as the single largest environmental health risk in Europe it is important that communication to the public is up to date and accurate and provides means to avoid exposure to high air pollution levels. Long- and short-term exposure to outdoor air pollution is associated with increased risks of mortality and morbidity. Up-to-date information on present and coming days' air quality helps people avoid exposure during episodes with high levels of air pollution. Air quality forecasts can be based on deterministic dispersion modelling, but to be accurate this requires detailed information on future emissions, meteorological conditions and process-oriented dispersion modelling. In this paper, we apply different machine learning (ML) algorithms - random forest (RF), extreme gradient boosting (XGB), and long short-term memory (LSTM) - to improve 1, 2, and 3d deterministic forecasts of PM10, NOx, and O3 at different sites in Greater Stockholm, Sweden. It is shown that the deterministic forecasts can be significantly improved using the ML models but that the degree of improvement of the deterministic forecasts depends more on pollutant and site than on what ML algorithm is applied. Also, four feature importance methods, namely the mean decrease in impurity (MDI) method, permutation method, gradient-based method, and Shapley additive explanations (SHAP) method, are utilized to identify significant features that are common and robust across all models and methods for a pollutant. Deterministic forecasts of PM10 are improved by the ML models through the input of lagged measurements and Julian day partly reflecting seasonal variations not properly parameterized in the deterministic forecasts. A systematic discrepancy by the deterministic forecasts in the diurnal cycle of NOx is removed by the ML models considering lagged measurements and calendar data like hour and weekday, reflecting the influence of local traffic emissions. For O3 at the urban background site, the local photochemistry is not properly accounted for by the relatively coarse Copernicus Atmosphere Monitoring Service ensemble model (CAMS) used here for forecasting O3 but is compensated for using the ML models by taking lagged measurements into account. Through multiple repetitions of the training process, the resulting ML models achieved improvements for all sites and pollutants. For NOx at street canyon sites, mean squared error (MSE) decreased by up to 60%, and seven metrics, such as R2 and mean absolute percentage error (MAPE), exhibited consistent results. The prediction of PM10 is improved significantly at the urban background site, whereas the ML models at street sites have difficulty capturing more information. The prediction accuracy of O3 also modestly increased, with differences between metrics. Further work is needed to reduce deviations between model results and measurements for short periods with relatively high concentrations (peaks) at the street canyon sites. Such peaks can be due to a combination of non-typical emissions and unfavourable meteorological conditions, which are rather difficult to forecast. Furthermore, we show that general models trained using data from selected street sites can improve the deterministic forecasts of NOx at the station not involved in model training. For PM10 this was only possible using more complex LSTM models. An important aspect to consider when choosing ML algorithms is the computational requirements for training the models in the deployment of the system. Tree-based models (RF and XGB) require fewer computational resources and yield comparable performance in comparison to LSTM. Therefore, tree-based models are now implemented operationally in the forecasts of air pollution and health risks in Stockholm. Nevertheless, there is big potential to develop generic models using advanced ML to take into account not only local temporal variation but also spatial variation at different stations.
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| 43. |
- Zhang, Zhiguo, et al.
(författare)
-
Measurement of lifetimes by laser-induced fluorescence and determination of transition probabilities of astrophysical interest in NdIII
- 2002
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 385:2, s. 724-732
-
Tidskriftsartikel (refereegranskat)abstract
- Selective lifetime measurements by time-resolved laser-induced fluorescence spectroscopy for 5 levels belonging to the 4f(3)5d configuration of doubly ionized neodymium provide a first and useful experimental test of the relativistic Hartree-Fock calculations in this ion of astrophysical interest. As a consequence, the accuracy of the transition probabilities deduced in the present work is well assessed. These new data are expected to help astrophysicists in the future to refine the analysis of the composition of chemically peculiar stars which frequently show large overabundances of lanthanides when compared to the solar system standards.
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| 44. |
- Zhang, Zhiguo, et al.
(författare)
-
Radiative lifetime measurements and oscillator strengths of astrophysical interest in HoIII
- 2002
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 384:1, s. 364-370
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of three long-lived levels belonging to the 4f(10)5d configuration of Ho III have been measured, for the first time, using the time-resolved laser-induced fluorescence technique. A good agreement between the experimental lifetimes and theoretical results obtained within a multiconfigurational pseudo-relativistic Hartree-Fock (HFR) approach including core-polarization (CP) effects is observed provided an adequate scaling factor is applied to the <4f&VERBAR;r&VERBAR;5d> transition matrix element. From the comparison theory-experiment, it has been possible to assess the reliability of the oscillator strengths of the 4f-5d transitions of astrophysical interest, particularly for the lines depopulating the levels considered in the present work. The present results fill in a gap concerning the f-values of doubly ionized holmium and are needed for a quantitative evaluation of the holmium abundance in some peculiar stars.
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| 45. |
- Zhang, Zhiguo, et al.
(författare)
-
Time-resolved laser spectroscopy of multiply ionized atoms: natural radiative lifetimes in Ce IV.
- 2001
-
Ingår i: Physical Review Letters. - 1079-7114. ; 87:27 Pt 1, s. 273001-273001
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes have been measured for two excited levels of Ce IV using the time-resolved laser-induced fluorescence technique. Ce3+ ions were produced in a laser-induced plasma. In the measurements, a suitable magnetic field was applied to reduce the recombination between electrons and the ions and thus the background light from the recombination, and special care was exercised to avoid flight-out-of-view effects on the lifetime measurements for the high-velocity ions. The experimental lifetime results, tau = 30(2) ns for the level 49 737 cm(-1) and tau = 30(3) ns for the level 52 226 cm(-1), were compared with relativistic Hartree-Fock calculations (tau = 30.5 and 30.0 ns) indicating a particularly excellent agreement.
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| 46. |
- Zhang, Zhengquan, et al.
(författare)
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Two-Timeslot Two-Way Full-Duplex Relaying for 5G Wireless Communication Networks
- 2016
-
Ingår i: IEEE Transactions on Communications. - : IEEE. - 0090-6778 .- 1558-0857. ; 64:7, s. 2873-2887
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a novel two-timeslot two-way full-duplex (FD) relaying scheme, in which the access link and the backhaul link are divided in the time domain, and we study the average end-to-end rate and the outage performance. According to the user equipment capability and services, we investigate two scenarios: three-node I-and four-node Y-relaying channels. Among various relaying protocols, the well-known amplify-and-forward and decode-and-forward are considered. Closed-form expressions for the average end-to-end rate and the outage probability, under the effect of residual self-interference and inter-user interference, are presented. The results show that the proposed two-timeslot two-way FD relaying scheme can achieve higher rate and better outage performance than the half-duplex one, when residual self-interference is below a certain level. Therefore, this relaying scheme presents a reasonable tradeoff between performance and complexity, and so, it could be efficiently used in the fifth-generation wireless networks.
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| 47. |
- Zhiguo, Zhang, et al.
(författare)
-
Experimental and theoretical studies of lifetimes and transition probabilities for Au II
- 2002
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 35:3, s. 483-490
-
Tidskriftsartikel (refereegranskat)abstract
- We report lifetime measurements for three of the 5d(9)6p levels in An II and relativistic multiconfiguration Dirac-Fock (MCDF) calculations of lifetimes and transitions probabilities in this ion. The work was motivated by significant disagreements between previous experimental 5d(9)6p lifetimes, obtained by means of the beam-foil (BF) method and theoretical data based on Hartree-Fock calculations in which relativistic effects were included as perturbations. The new measurements, based on laser-induced fluorescence, support the BF data and are also in excellent agreement with the MCDF results. We confirm that, while computational methods which include perturbative relativistic corrections appear to be adequate for moderately heavy elements such as Ag, fully relativistic calculations are essential for describing systems as heavy as Au.
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| 48. |
- Zhou, Weibin, et al.
(författare)
-
Ion-exchange chromatography of hepatitis B virus surface antigen from a recombinant Chinese hamster ovary cell line
- 2005
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Ingår i: Journal of Chromatography A. ; 1095:1-2, s. 119-125
-
Tidskriftsartikel (refereegranskat)abstract
- About 10% of the Chinese population are chronic carriers of hepatitis B virus (HBV). Thus, the development of a highly efficient process for the preparation of a vaccine based on a recombinant hepatitis B surface antigen (HBsAg) is very important to the Chinese national immunization program. To this end, the ion exchange chromatography recovery of CHO-HBsAg from a recombinant Chinese hamster ovary cell line was shown to increase from about 55 to 80% by the addition of 1% poly(ethylene glycol) (PEG 10,000) to the mobile phase. Furthermore, based on analysis by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE), the intact glycoprotein form of CHO-HBsAg was completely preserved by the addition of PEG. In the absence of PEG the glycoprotein form of CHO-HBsAg was also spread out into the high salt elution fraction. High-performance size-exclusion chromatography with on-line multiangle-laser-light scattering (HPSEC-MALLS) analysis was performed to monitor the status of the CHO-HBsAg aggregate structure assembly, particle size and molecular weight distribution after each purification step, and the results showed further that the presence of PEG facilitated the separation and recovery of intact glycoprotein form of CHO-HBsAg and promoted their assembly to proper virus-like particles, which are both important features and prerequisites of their immunogenicity.
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| 49. |
- Zhou, Weibin, et al.
(författare)
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Molecular characterization of recombinant Hepatitis B surface antigen from Chinese hamster ovary and Hansenula polymorpha cells by high-performance size exclusion chromatography and multi-angle laser light scattering
- 2006
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Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 838:2, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- The molecular weight and size of recombinant Hepatitis B surface antigen (HBsAg) derived from Chinese hamster ovary (CHO) and the Hansenula polymorph have been characterized by high-performance size exclusion chromatography with multi-angle laser light scattering (HPSEC-MALLS). The average molecular weight of CHO-derived HBsAg particle (CHO-rHBsAg) (4921 kDa) was higher than that of H. polymorpha yeast strain (Hans-rHBsAg) (3010 kDa). The size of CHO-rHBsAg (22.1 nm) is nearly the same as that of native HBsAg compared to 18.1 nm for Hans-rHBsAg. The average monomer numbers were found to be 155 for CHO-rHBsAg and 86 for Hans-rHBsAg, respectively. The data obtained support the assumption that the higher immunogenicity of CHO-derived HBsAg is related to its more favorable macromolecular assembly structure.
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- Zhou, Xue, et al.
(författare)
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Sensitive detection of oxygen using a diffused integrating cavity as a gas absorption cell
- 2017
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Ingår i: Sensors and Actuators B: Chemical. - : Elsevier BV. - 0925-4005. ; 241, s. 1076-1081
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Tidskriftsartikel (refereegranskat)abstract
- In this study, an oxygen monitoring system was demonstrated for sensitive oxygen detection. The system is based on tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS). Stable 2nd-harmonic signals of oxygen were detected by measuring the oxygen P9 absorption line at 764.38. nm. In the detection, a cubic diffuse integrating cavity was employed as a gas absorption cell to increase the optical path length and achieve a higher sensitivity. In addition, to perform automatic gas concentration measurements, a data recording and analyzing program based on the National Instruments LabVIEW software platform was developed. An uncertainty of 0.05% and a detection sensitivity of 350 ppmv were obtained using this system.
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