| 1. |
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| 2. |
- Liu, Wanlei, et al.
(författare)
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Rapid Acceleration of Arctic Near-Surface Wind Speed in a Warming Climate
- 2024
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Ingår i: GEOPHYSICAL RESEARCH LETTERS. - 0094-8276 .- 1944-8007. ; 51:8
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Tidskriftsartikel (refereegranskat)abstract
- Arctic near-surface wind speed (NWS) plays an increasingly crucial role in influencing the local air-sea interactions and the safety of trans-Arctic shipping, but its potential changes in a warming climate and underlying causes remain unclear. Using reanalysis and model simulation data sets, we reveal that the Arctic NWS has increased remarkably since the 1960s, with the strongest increase in the Arctic Ocean surface. We propose that the acceleration of Arctic NWS is primarily driven by reduced stability in the lower troposphere due to increased upward heat fluxes and decreased surface roughness owing to the losses of Arctic glaciers and sea ice in a warming climate. In addition, the coupled climate models project a robust increase in the Arctic NWS under various warming scenarios during the 21st century, especially in the vicinity of the Kara Sea and the Beaufort Sea. The speed at which wind blows near the surface in the Arctic is important for understanding local air-sea interactions and ensuring the safety of ships traveling across the region. However, how and why Arctic wind speeds are changing in a warming climate remains unclear. Using a combination of data analysis and model simulations, we found that the wind speed in the Arctic overall had been markedly increasing since the 1960s, especially over the sea. This increase in wind speed seems to have mainly been caused by human-induced warming, whereby more heat is transferred into the air making the lower part of the atmosphere less stable. In addition, the melting of glaciers and sea ice in the Arctic has made the surface smoother, helping wind to blow faster. Models used to project future climate change reveal that the wind in the Arctic is simulated to increase further, especially in certain areas such as the Kara Sea and the Beaufort Sea. Reanalyzes and CMIP6 model simulations show increasing near-surface wind speed (NWS) in the Arctic region since 1960s Decreases in surface roughness and atmospheric stability could contribute to the increasing Arctic NWS CMIP6 models project a continued increase in the Arctic NWS in various future warming scenarios
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| 3. |
- Sun, Xiaoming, et al.
(författare)
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Adjustable hardness of hydrogel for promoting vascularization and maintaining sternness of stem cells in skin flap regeneration
- 2018
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Ingår i: Applied Materials Today. - : Elsevier. - 2352-9407. ; 13, s. 54-63
-
Tidskriftsartikel (refereegranskat)abstract
- The matrix mechanical stiffness of biomaterials plays an important role in the pluripotency and biological function of stem cells in the microenvironment. It is a key step to adjust the stiffness of biomaterials for inducing stem cells to promote vascularization in order to promote damaged tissue repair. In this study, we transplant adipose derived stem cells (ADSCs) within an in situ forming dextran hydrogel with controllable mechanical strength formed by cross-linking glycidyl methacrylate derivatized dextran and dithiothreitol, which can regulate the stemness and biological functions of stem cells. We show that softer dextran hydrogel can better maintain stemness markers expression of ADSCs, and significantly stimulate ADSCs to secrete angiogenic factors. The ADSCs-encapsulated hydrogel distinctly promote the skin flap survival compared to direct cell injection. Bioluminescence imaging analysis shows that in situ forming dextran hydrogel can improve cells retention, and postmortem analysis reveals that the transplanted ADSCs with hydrogel can promote vascularization. These results support the use of injectable dextran hydrogel for skin ischemia tissue regeneration. (C) 2018 Elsevier Ltd. All rights reserved.
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| 4. |
- Abelev, Betty, et al.
(författare)
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Long-range angular correlations on the near and away side in p-Pb collisions at root S-NN=5.02 TeV
- 2013
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < P-T,P-assoc < P-T,P-trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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| 5. |
- Abelev, Betty, et al.
(författare)
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Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :11
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.
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| 6. |
- Gao, Tanguang, et al.
(författare)
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Accelerating permafrost collapse on the eastern Tibetan Plateau
- 2021
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 16:5
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Tidskriftsartikel (refereegranskat)abstract
- Permafrost collapse can rapidly change regional soil-thermal and hydrological conditions, potentially stimulating production of climate-warming gases. Here, we report on rate and extent of permafrost collapse on the extensive Tibetan Plateau, also known as the Asian Water Tower and the Third Pole. Combined data from in situ measurements, unmanned aerial vehicles (UAV), manned aerial photographs, and satellite images suggest that permafrost collapse was accelerating across the Eastern Tibetan Plateau. From 1969 to 2017, the area of collapsed permafrost has increased by approximately a factor of 40, with 70% of the collapsed area forming since 2004. These widespread perturbations to the Tibetan Plateau permafrost could trigger changes in local ecosystem state and amplify large-scale permafrost climate feedbacks.
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| 7. |
- Ji, Fuxiang, 1991-, et al.
(författare)
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Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl6
- 2023
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Ingår i: Advanced Optical Materials. - : Wiley-Blackwell. - 2162-7568 .- 2195-1071.
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron–phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK−1 based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III–V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.
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| 8. |
- Ji, Fuxiang, 1991-, et al.
(författare)
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Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl6
- 2024
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Ingår i: Advanced Optical Materials. - : John Wiley & Sons. - 2162-7568 .- 2195-1071. ; 12:8
-
Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron-phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK(-1) based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III-V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.
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| 9. |
- Li, Ruihuan, et al.
(författare)
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Vacancy trapping mechanism for multiple helium in monovacancy and small void of vanadium solid
- 2013
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 440:1-3, s. 557-561
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Tidskriftsartikel (refereegranskat)abstract
- Using first-principles methods, we have investigated the microscopic mechanism for He trapping in two kinds of vacancy defects (monovacancy and 9-atom void) inside vanadium host lattice. In the monovacancy, single He prefers to occupy the octahedral site near vacancy rather than vacancy center. Inside vacancy defects, the He-He equilibrium distances range in 1.6-2.2 angstrom. After more He atoms are incorporated, the magnitude of trapping energy decreases and the host lattice expand dramatically. A monovacancy and 9-atom void can host up to 18 and 66 He atoms, respectively, with internal pressure up to 7.5 and 19.3 GPa. The atomic structures of selected He clusters trapped in vacancies are compared with the gas-phase clusters. The strong tendency of He trapping at vacancies and 9-atom voids provides an explanation for experimentally observed He bubble formation at vacancy defects in metals.
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| 10. |
- Lu, Rui, et al.
(författare)
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Direction-of-Arrival Estimation in the Presence of Phase Noise
- 2020
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Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 24:8, s. 1710-1714
-
Tidskriftsartikel (refereegranskat)abstract
- This letter proposes a robust direction-of-arrival (DoA) estimator in the presence of phase noise (PN). For a multi-antenna system with independent oscillators, the received signals will be corrupted by multiple independent PN sources, resulting in severe performance degradation of the DoA estimator, especially for millimeter-wave systems. However, due to the time-varying nature of PN, the number of associated unknowns grows with the size of the snapshots, making the calibration challenging. To tackle this problem, we use a piece-wise linear model to approximate PN so that the number of associated unknowns can be reduced. Then we estimate the DoA and the PN parameters iteratively via a nonlinear least squares estimator. To evaluate the effectiveness of the proposed scheme, the Cramer-Rao lower bound (CRLB) of the DoA estimation in the presence of PN is derived. Numerical results show a significant performance improvement of the proposed DoA estimator compared to the results without calibration.
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| 11. |
- Wan, Yan, et al.
(författare)
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The orbital effect on the anomalous magnetism and evolution in LaxY1-xVO3 (0 <= x <= 0.2) single crystals
- 2023
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 932, s. 167526-
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Tidskriftsartikel (refereegranskat)abstract
- The orbital effect on the anomalous magnetism and evolution of single crystals with low La doping, LaxY1-xVO3 (x = 0, 0.1, and 0.2), has been studied using single-crystal X-ray diffraction, specific heat, mag-netization, and Raman-scattering techniques. It is found that substituting Y3+ by La3+ increases the de-generacy of the yz/zx orbitals and decreases the Jahn-Teller distortion. These weakens the G-type (antiphase ordering along the c axis) orbital ordering phase. Meanwhile, the substituting decreases the magnetism entropy, indicating the shrinking of the t2g and eg orbital hybridization, eventually destabilizing the C-type (in-phase ordering along the c axis) antiferromagnetic ordering phase. In addition, the mechanism for the shrinking of the diamagnetism with increasing x is analyzed. It may attribute to the competition between the antisymmetric Dzyaloshinsky-Moriya interaction and the single-ion anisotropy.
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| 12. |
- Ye, Lian, et al.
(författare)
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Feasibility analysis of plastic and biomass hydrochar for blast furnace injection
- 2023
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- Hydrothermal carbonization (HTC) technology upgrades combustible waste (CW) to high-quality fuel known as hydrochar. However, there is a research gap regarding the application limit of hydrochar instead of fossil fuels in blast furnaces. In this study, the physical, chemical, and metallurgical properties of hydrochar were thoroughly analyzed. The results showed that gross calorific value, grindability, ignition temperature, explosivity, combustion and gasification all improved by HTC process compared with the waste feedstocks. Moreover, the HTC process can effectively remove harmful elements (K, Na, Cl, and S) from feedstocks into liquid and gas phase without adding other reagents, reducing harmful effects in the blast furnace. Removal rates by HTC were >80% for alkali metals and >73.9% for Cl (reaching 98.18% for polyvinyl chloride hydrochar). The environmental benefit calculation shows that the CO2 emission reduction of replacing bituminous coal with 40% HTC-treated maize straw can reach 94.7 kg/tHM. The annual CO2 reduction can reach 1.7 x 107 kg and the annual coal reduction is 1.5 x 107 kg of a blast furnace. The results showed that hydrochar is a clean energy source compared with fossil fuel alternatives and meets the blast furnace injection requirements.
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| 13. |
- Zhang, Hanzhi, et al.
(författare)
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Quantitative estimation of the contribution of dustsources to Chinese loess using detrital zircon U-Pbage patterns
- 2016
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Ingår i: Journal of Geophysical Research - Earth Surface. - 2169-9003 .- 2169-9011. ; 121:11, s. 2085-2099
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Tidskriftsartikel (refereegranskat)abstract
- The origin and provenance of the loess deposits of the Chinese Loess Plateau (CLP) are stilldebated. In order to pinpoint the dust sources, surface samples from the piedmont of the NortheasternTibetan Plateau, the Gobi Altai Mountains, and modern eolian dunes from the Tengger desert and Mu Ussand field were analyzed by using the detrital zircon dating technique. In order to quantitatively discriminatethe content of different potential sources, zircon grains of different ages were grouped according to theirtectonic origin. Zircon grains aged from 1300 to 550 Ma were assigned to the Northeastern Tibetan Plateau,and grains aged from 550 to 0 Ma to the Northeastern Tibetan Plateau or the Gobi Altai Mountains, or to acombination of the two. Zircon ages of around 2.8 Ga to 1.3 Ga may be a mixture of sources from theNortheastern Tibetan Plateau, Gobi Altai Mountains, or North China Craton. Sediments from the Tenggerdesert and Mu Us sand field consist of a mixture of the three sources and exhibit a high degree of spatialvariability in terms of their source. In the northern part of the two deserts, 43–83% of the sediments arederived from the Gobi Altai Mountains, while in the south, material from the Northeastern Tibetan Plateaucomprises 51–98% of the sediments. Loess deposits from the CLP also comprise a mixture of the threedifferent sources, with material from the Northeastern Tibetan Plateau making the dominant contribution(65–100%), with material from the North China Craton and the Gobi Altai Mountains comprising 0–35% and0–40% of the loess deposits, respectively. The contributions from the three sources to the loess deposits onCLP vary spatially. Application of the novel statistical method of provenance group analysis demonstratesthat the loess deposits comprise a mixture of material from a broad region of northern China and that theNortheastern Tibetan Plateau material makes the dominant contribution.
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| 14. |
- Zhang, Jinbao, et al.
(författare)
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Chemical Dopant Engineering in Hole Transport Layers for Efficient Perovskite Solar Cells : Insight into the Interfacial Recombination
- 2018
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 12:10, s. 10452-10462
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Tidskriftsartikel (refereegranskat)abstract
- Chemical doping of organic semiconductors has been recognized as an effective way to enhance the electrical conductivity. In perovskite solar cells (PSCs), various types of dopants have been developed for organic hole transport materials (HTMs); however, the knowledge of the basic requirements for being efficient dopants as well as the comprehensive roles of the dopants in PSCs has not been clearly revealed. Here, three copper-based complexes with controlled redox activities are applied as dopants in PSCs, and it is found that the oxidative reactivity of dopants presents substantial impacts on conductivity, charge dynamics, and solar cell performance. A significant improvement of open- circuit voltage (V-oc) by more than 100 mV and an increase of power conversion efficiency from 13.2 to 19.3% have been achieved by tuning the doping level of the HTM. The observed large variation of V-oc for three dopants reveals their different recombination kinetics at the perovskite/HTM interfaces and suggests a model of an interfacial recombination mechanism. We also suggest that the dopants in HTMs can also affect the charge recombination kinetics as well as the solar cell performance. Based on these findings, a strategy is proposed to physically passivate the electron- hole recombination by inserting an ultrathin Al2O3 insulating layer between the perovskite and the HTM. This strategy contributes a significant enhancement of the power conversion efficiency and environmental stability, indicating that dopant engineering is one crucial way to further improve the performance of PSCs.
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| 15. |
- Abelev, Betty, et al.
(författare)
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Underlying Event measurements in pp collisions at root s=0.9 and 7 TeV with the ALICE experiment at the LHC
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :7
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.
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| 16. |
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| 17. |
- Barrat, Jean-Louis, et al.
(författare)
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Soft matter roadmap
- 2024
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 2515-7639. ; 7:1
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Forskningsöversikt (refereegranskat)abstract
- Soft materials are usually defined as materials made of mesoscopic entities, often self-organised, sensitive to thermal fluctuations and to weak perturbations. Archetypal examples are colloids, polymers, amphiphiles, liquid crystals, foams. The importance of soft materials in everyday commodity products, as well as in technological applications, is enormous, and controlling or improving their properties is the focus of many efforts. From a fundamental perspective, the possibility of manipulating soft material properties, by tuning interactions between constituents and by applying external perturbations, gives rise to an almost unlimited variety in physical properties. Together with the relative ease to observe and characterise them, this renders soft matter systems powerful model systems to investigate statistical physics phenomena, many of them relevant as well to hard condensed matter systems. Understanding the emerging properties from mesoscale constituents still poses enormous challenges, which have stimulated a wealth of new experimental approaches, including the synthesis of new systems with, e.g. tailored self-assembling properties, or novel experimental techniques in imaging, scattering or rheology. Theoretical and numerical methods, and coarse-grained models, have become central to predict physical properties of soft materials, while computational approaches that also use machine learning tools are playing a progressively major role in many investigations. This Roadmap intends to give a broad overview of recent and possible future activities in the field of soft materials, with experts covering various developments and challenges in material synthesis and characterisation, instrumental, simulation and theoretical methods as well as general concepts.
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| 18. |
- Cheng, Wenhao, et al.
(författare)
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A Low-Cost Laser Welding Monitoring Framework Based on Depth-Wise Separable Convolution with Photoelectric Signals
- 2024
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Ingår i: International Journal of Precision Engineering and Manufacturing (IJPEM). - : Springer. - 2234-7593 .- 2005-4602.
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, the process monitoring based on optical radiation detection widely applied in laser welding monitoring process, such as visual cameras, spectrometers and photoelectric sensors. This study proposes a low-cost monitoring model based on a CNN module with the combination of convolution and depth-wise separable convolution (DSC) applying the industrial photoelectric sensors. This model aims to generate more effective features from the primitive signals captured by the visible light photoelectric sensor and the reflective laser photoelectric sensor, without pre-processing in advance. The DSC is applied to generate features to reveal the inherent features of welding statuses, and especially reduce the computing costs during monitoring process. The proposed model in this study acquired high accuracy with low space complexity and time complexity compared with the traditional model. The model also performs well under the limited and unbalanced welding data, indicating its good robustness. This study provides a low-cost method for real-time monitoring of laser welding process.
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| 19. |
- Gao, Shigen, et al.
(författare)
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Fuzzy adaptive automatic train operation control with protection constraints : A residual nonlinearity approximation-based approach
- 2020
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Ingår i: Engineering applications of artificial intelligence. - : Elsevier BV. - 0952-1976 .- 1873-6769. ; 96
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we present fuzzy adaptive control based on residual nonlinearity approximation in the presence of protection constraints for the target trajectory tracking problem observed in automatic train operation. Herein, protection constraints refer to a condition wherein the speed and position of a controlled train are not allowed to surpass the boundaries imposed by automatic train protection and moving authority. By defining proper coordinate transformation, the protection constraints are converted to an error-prescribed performance control problem that facilitates operational efficiency by reducing the margin with respect to target trajectories. Based on the prescribed performance control methodology, we present an improved scheme using fuzzy residual nonlinearity approximation and establish the uniformly ultimately boundedness (UUB) property. A novel feature therein is that the ultimate boundary of the proposed scheme is simultaneously characterized by the prescribed performance functions and control parameters, with rigorous and analytically mathematical expressions; while pioneering the prescribed performance control methodology, the ultimate boundary is characterized solely by the prescribed performance functions. To verify the effectiveness and advantages of the proposed scheme, the controllers are applied to the automatic train operation on the Beijing Yizhuang line, which contains 13 operational intervals. Finally, comparative and simulation results are presented to validate the proposed method.
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| 20. |
- Hu, J., et al.
(författare)
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Adaptive bipartite tracking control for coopetition networks
- 2015
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Ingår i: 2015 34th Chinese Control Conference (CCC). - : IEEE Computer Society. - 9789881563897 ; , s. 7067-7072
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Konferensbidrag (refereegranskat)abstract
- Cooperation and competition are two typical interactional relationships in natural and engineering networked systems. Some interesting collective behaviors can emerge through local interactions within the networked systems. This paper considers a bipartite consensus for a group of agents interacting both cooperatively and competitively. Meanwhile, the intrinsic nonlinear dynamics of all the agents are unknown for the neighboring agents. Thus, the interaction network, which we call a coopetition network, is firstly represented by a signed graph. Then, some adaptive estimate laws are proposed for the unknown dynamics. Finally, an adaptive tracking control is designed for each agent to reach a bipartite consensus on the state of the leader. Some sufficient conditions are derived for bipartite consensus of multi-agent systems with the help of a structural balance theory. Simulation results are provided to demonstrate the bipartite consensus formation.
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| 21. |
- Hu, J., et al.
(författare)
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Bipartite consensus strategies for coopetition networks
- 2014
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Ingår i: 2014 33rd Chinese Control Conference (CCC). - : IEEE Computer Society. - 9789881563842 ; , s. 1505-1510
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Konferensbidrag (refereegranskat)abstract
- Cooperation and competition are two typical interactional relationships in natural and engineering networked systems. Some interesting collective behaviors can emerge through local interactions within the networked systems. This paper focuses on the coexistence of competition and cooperation (i.e., coopetition) at the network level and, simultaneously, the collective dynamics on such coopetition networks. The coopetition network is represented by a directed signed graph. The interaction relationship between the agents on the coopetition network is described by a multi-agent system. We investigate two bipartite consensus strategies for the agents such that all the agents converge to a final state characterized by identical modulus but opposite sign. Under a weak connectivity assumption that the signed network has a spanning tree, some sufficient conditions are derived for bipartite consensus of multi-agent systems with the help of a structural balance theory. Finally, simulation results are provided to demonstrate the bipartite consensus formation.
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| 22. |
- Jiang, Huanxiang, et al.
(författare)
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Appropriate Molecular Interaction Enabling Perfect Balance Between Induced Crystallinity and Phase Separation for Efficient Photovoltaic Blends
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society. - 1944-8244 .- 1944-8252. ; 12:23, s. 26286-26292
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Tidskriftsartikel (refereegranskat)abstract
- Fluorination is a promising modification method to adjust the photophysical profiles of organic semiconductors. Notably, the fluorine modification on donor or acceptor materials could impact the molecular interaction, which is strongly related to the morphology of bulk heterojunction (BHJ) blends and the resultant device performance. Therefore, it is essential to investigate how the molecular interaction affects the morphology of BHJ films. In this study, a new fluorinated polymer PBDB-PSF is synthesized to investigate the molecular interaction in both nonfluorinated (ITIC) and fluorinated (IT-4F) systems. The results reveal that the F-F interaction in the PBDB-PSF:IT-4F system could effectively induce the crystallization of IT-4F while retaining the ideal phase separation scale, resulting in outstanding charge transport. On the contrary, poor morphology can be observed in the PBDB-PSF:ITIC system because of the unbalanced molecular interaction. As a consequence, the PBDB-PSF:IT-4F device delivers an excellent power conversion efficiency of 13.63%, which greatly exceeds that of the PBDB-PSF:ITIC device (9.84%). These results highlight manipulating the micromorphology with regard to molecular interaction.
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| 23. |
- Li, Changle, et al.
(författare)
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MC-MAC : a multi-channel based MAC scheme for interference mitigation in WBANs
- 2018
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Ingår i: Wireless networks. - : Springer. - 1022-0038 .- 1572-8196. ; 24:3, s. 719-733
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Tidskriftsartikel (refereegranskat)abstract
- Wireless body area networks (WBANs) support the inter-operability of biomedical sensors and medical institutions with convenience and high-efficiency, which makes it an appropriate solution for the pervasive healthcare. Typically, WBANs comprise in-body or around-body sensor nodes for collecting data of physiological feature. Therefore, the efficient medium access control (MAC) protocol is a crucial paramount to coordinate these devices and forward data to the medical center in an efficient and reliable way. However, the extensive use of wireless channel and coexistence of WBANs may result in inevitable interference which will cause performance degradation. Besides, contention-based access in single channel in WBANs is less efficient for dense medical traffic on account of large packet delay, energy consumption and low priority starvation. To address these issues above, we propose a multi-channel MAC (MC-MAC) scheme to obtain better network performance. Considering the characteristic and emergency degree of medical traffic, we introduce a novel channel mapping and selection mechanism, cooperating with conflict avoidance strategy, to organize nodes to access available channels without collisions. In addition, we have evaluated the performance of MC-MAC and the standard IEEE 802.15.6 via simulation and hardware test. The test is conducted by hardware platform based on prototype system of WBANs. Both of the analysis and simulation results show that MC-MAC outperforms the IEEE 802.15.6 in terms of packet delay, throughput, packet error rate and frame error rate
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| 24. |
- Li, Tianhao, et al.
(författare)
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Controllability of networked multiagent systems based on linearized Turing's model
- 2024
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 162
-
Tidskriftsartikel (refereegranskat)abstract
- Turing's model has been widely used to explain how simple, uniform structures can give rise to complex, patterned structures during the development of organisms. However, it is very hard to establish rigorous theoretical results for the dynamic evolution behavior of Turing's model since it is described by nonlinear partial differential equations. We focus on controllability of Turing's model by linearization and spatial discretization. This linearized model is a networked system whose agents are second order linear systems and these agents interact with each other by Laplacian dynamics on a graph. A control signal can be added to agents of choice. Under mild conditions on the parameters of the linearized Turing's model, we prove the equivalence between controllability of the linearized Turing's model and controllability of a Laplace dynamic system with agents of first order dynamics. When the graph is a grid graph or a cylinder grid graph, we then give precisely the minimal number of control nodes and a corresponding control node set such that the Laplace dynamic systems on these graphs with agents of first order dynamics are controllable.
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| 25. |
- Li, Yibei, 1993-, et al.
(författare)
-
A Convex Optimization Approach to Inverse Optimal Control
- 2018
-
Ingår i: 2018 37Th Chinese Control Conference, CCC (CCC). - : IEEE. - 9789881563958 ; , s. 257-262
-
Konferensbidrag (refereegranskat)abstract
- In this paper, the problem of inverse optimal control (IOC) is investigated, where the quadratic cost function of a dynamic process is required to be recovered based on the observation of optimal control sequences. In order to guarantee the feasibility of the problem, the IOC is reformulated as an infinite-dimensional convex optimization problem, which is then solved in the primal-dual framework. In addition, the feasibility of the original IOC could be determined from the optimal value of reformulated problem, which also gives out an approximate solution when the original problem is not feasible. In addition, several simplification methods are proposed to facilitate the computation, by which the problem is reduced to a boundary value problem of ordinary differential equations. Finally, numerical simulations are used to demonstrate the effectiveness and feasibility of the proposed methods.
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| 26. |
- Liu, Caifeng, et al.
(författare)
-
A Zebrafish Model Discovers a Novel Mechanism of Stromal Fibroblast-Mediated Cancer Metastasis
- 2017
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Ingår i: Clinical Cancer Research. - : AMER ASSOC CANCER RESEARCH. - 1078-0432 .- 1557-3265. ; 23:16, s. 4769-4779
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: Cancer metastasis can occur at the early stage of tumor development when a primary tumor is at the microscopic size. In particular, the interaction of malignant cells with other cell types including cancer-associated fibroblasts (CAF) in promoting metastasis at the early stage of tumor development remains largely unknown. Here, we investigated the role of CAFs in facilitating the initial events of cancer metastasis when primary tumors were at microscopic sizes. Experimental Design: Multicolor-coded cancer cells and CAFs were coimplanted into the transparent zebrafish body and metastasis at a single-cell level was monitored in living animals. Healthy fibroblasts, tumor factor-educated fibroblasts, and CAFs isolated from various tumors were tested for their ability to facilitate metastasis. Results: We showed that CAFs promoted cancer cell metastasis at the very early stage during primary tumor development. When a primary tumor was at the microscopic size consisting of a few hundred cells, CAFs were able to hijack cancer cells for dissemination from the primary site. Surprisingly, a majority of metastatic cancer cells remained in tight association with CAFs in the circulation. Furthermore, stimulation of non-metastasis-promoting normal fibroblasts with TGF-B, FGF-2, HGF, and PDGF-BB led to acquisition of their metastatic capacity. Conclusions: Cancer metastasis occurs at the very early stage of tumor formation consisting of only a few hundred cells. CAFs are the key cellular determinant for metastasis. Our findings provide novel mechanistic insights on CAFs in promoting cancer metastasis and targeting CAFs for cancer therapy should be aimed at the early stage during cancer development. (C) 2017 AACR.
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| 27. |
- Lu, Junjing, et al.
(författare)
-
An improved sectional model to simulate multi-component aerosol dynamics in a containment of pressurized water reactor
- 2021
-
Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502 .- 1879-1964. ; 157
-
Tidskriftsartikel (refereegranskat)abstract
- Simulating an evolving aerosol population in a reactor containment is essential for estimating the radioactivity that is possible to leak to the environment. In this study, a sectional model is developed to simulate multi-component aerosol dynamics in the containment during severe ac-cidents of a pressurized water reactor by improving the widely used MAEROS (Multicomponent AEROSol) model. An important advantage of the improved model is its simplified calculation method by introducing a series of correction factors to the equation coefficients when the thermal boundary conditions and the aerosol particle density in the containment change continuously. In addition, the restriction of the maximum section number in the MAEROS model is removed. The reliability of the model is validated against four analytical solutions and three sets of test data. Moreover, the improvements in the model are also proven to be necessary to effectively capture the influences of thermal boundary conditions and aerosol particle density on aerosol dynamics.
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| 28. |
- Lu, Y., et al.
(författare)
-
Fuzzy hegselmann-krause opinion dynamics with opinion leaders
- 2019
-
Ingår i: 2019 Chinese Control Conference (CCC). ; , s. 6019-6024
-
Konferensbidrag (refereegranskat)abstract
- In this paper, from the perspective of opinion dynamics theory, we investigate the intrinsic interaction principles of a group of autonomous agents and develop a fuzzy opinion dynamics model with leaders. First, this paper divides group agents into three subgroups: opinion followers, positive opinion leaders, and negative opinion leaders according to the opinion's update manner and influence. Then, we consider the uncertainty of the agents' opinion gaps and apply the Fuzzy Inference Machine to the effects of the leaders' opinions on a certain follower's opinion. The innovation of this paper is that the weight is distributed from 0 to 1 in accordance with the closeness among the opinion leaders and followers, which is closer to real life. Finally, the simulation results show that the proposed model can effectively explain the opinion interaction and evolution and conforms with the existing theoretical results in the field of opinion dynamics.
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| 29. |
- Pei, Huiling, et al.
(författare)
-
Impact of Probe Coupling on Emulation Accuracy in Massive MIMO OTA Testing
- 2020
-
Ingår i: 14th European Conference on Antennas and Propagation, EuCAP 2020.
-
Konferensbidrag (refereegranskat)abstract
- The sectored multi-probe anechoic chamber (MPAC) setup has been proposed in the literature for OTA testing of massive MIMO base stations (BSs). However, the previous studies assume ideal isotropic probes, i.e., the radiation patterns and mutual coupling among the probe antennas have not been considered. In this paper, the impact of the mutual coupling of realistic probes on the simulation accuracy of two popular channel emulation methods, i.e. the pre-faded signal synthesis (PFS) method and the plane wave synthesis (PWS) method in the sectored MPAC system is investigated. Our results show that the PFS method is more robust to mutual coupling than the PWS method.
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| 30. |
- Sheng, Weili, et al.
(författare)
-
Design matters: New insights on optimizing energy consumption for residential buildings
- 2021
-
Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788. ; 242
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we construct a unique database for 1228 residential buildings in Hong Kong to investigate how the spatial features of these residential buildings affect the electricity consumption in the communal area. We choose Hong Kong for this analysis as the city owns a large number of standard-type residential buildings managed by the public institution, which could be affected strongly by environmental policies. Both the machine learning method, based on the Least Absolute Shrinkage and Selection Operator (LASSO), and econometric regressions are adopted to analyse the data. We first utilize the machine learning LASSO technique to identify the most relevant factors for the subsequent econometric analysis. Our results show that the electricity demand for relatively low consumption building types, such as Twin Tower, is 6% lower than that of the high consumption building types. Newly constructed buildings usually belong to the medium consumption types, with the estimated monthly electricity consumption per apartment in communal areas to be around 50.2 kWh on average in 2020. These findings shed light on the nexus between spatial features and energy use for complex buildings, potentially contributing to the better crafting of energy-saving policy and the improvement of residential building programmes.
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| 31. |
- Song, Wenjun, et al.
(författare)
-
Intrinsic reduced attitude formation with ring inter-agent graph
- 2017
-
Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 85, s. 193-201
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the reduced attitude formation control problem for a group of rigid-body agents using feedback based on relative attitude information. Under both undirected and directed cycle graph topologies, it is shown that reversing the sign of a classic consensus protocol yields asymptotical convergence to formations whose shape depends on the parity of the group size. Specifically, in the case of even parity the reduced attitudes converge asymptotically to a pair of antipodal points and distribute equidistantly on a great circle in the case of odd parity. Moreover, when the inter-agent graph is an undirected ring, the desired formation is shown to be achieved from almost all initial states.
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| 32. |
- Tian, Chen, et al.
(författare)
-
Functional Failure Behavior of Submerged Entry Nozzle during the Continuous Casting Process of the Bearing Steel GCr15
- 2024
-
Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 95:8
-
Tidskriftsartikel (refereegranskat)abstract
- The submerged entry nozzle (SEN) is an indispensable functional structural ceramic in the current continuous casting production. The stability and safety of the SEN is very important during the casting process. In this article, the functional failure of the SEN during the continuous casting process of the bearing steel GCr15 is studied. The results show that the functional failure of the SEN during the bearing steel GCr15 casting process is caused by the clogging inside the SEN which is led by the low cleanliness and the high impurities n the molten steel. The clogging in the SEN can be divided into solidified steel area, loose area, dense area, and surface area. To improve the castability of bearing steel or other high-cleanliness steel, it is necessary to strengthen the refining process and treatment effect, strengthen the sealing and the effect of the protective casting of the molten steel, and moderate optimization of nozzle materials or the application of external fields on the SEN.
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| 33. |
- Waikar, Sushrut S, et al.
(författare)
-
Relationship of proximal tubular injury to chronic kidney disease as assessed by urinary kidney injury molecule-1 in five cohort studies
- 2016
-
Ingår i: Nephrology, Dialysis and Transplantation. - : Oxford University Press (OUP). - 0931-0509 .- 1460-2385. ; 31:9, s. 1460-1470
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The primary biomarkers used to define CKD are serum creatinine and albuminuria. These biomarkers have directed focus on the filtration and barrier functions of the kidney glomerulus even though albuminuria results from tubule dysfunction as well. Given that proximal tubules make up ∼90% of kidney cortical mass, we evaluated whether a sensitive and specific marker of proximal tubule injury, urinary kidney injury molecule-1 (KIM-1), is elevated in individuals with CKD or with risk factors for CKD.METHODS: We measured urinary KIM-1 in participants of five cohort studies from the USA and Sweden. Participants had a wide range of kidney function and were racially and ethnically diverse. Multivariable linear regression models were used to test the association of urinary KIM-1 with demographic, clinical and laboratory values.RESULTS: In pooled, multivariable-adjusted analyses, log-transformed, creatinine-normalized urinary KIM-1 levels were higher in those with lower eGFR {β = -0.03 per 10 mL/min/1.73 m(2) [95% confidence interval (CI) -0.05 to -0.02]} and greater albuminuria [β = 0.16 per unit of log albumin:creatinine ratio (95% CI 0.15-0.17)]. Urinary KIM-1 levels were higher in current smokers, lower in blacks than nonblacks and lower in users versus nonusers of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers.CONCLUSION: Proximal tubule injury appears to be an integral and measurable element of multiple stages of CKD.
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| 34. |
- Wang, Jinhuan, et al.
(författare)
-
Modeling and simulating for congestion pedestrian evacuation with panic
- 2015
-
Ingår i: Physica A. - : Elsevier BV. - 0378-4371 .- 1873-2119. ; 428, s. 396-409
-
Tidskriftsartikel (refereegranskat)abstract
- A new multi-agent based congestion evacuation model incorporating panic behavior is proposed in this paper for simulating pedestrian evacuation in public places such as a stadium. Different from the existing results, pedestrians in this model are divided into four classes and each pedestrian's status can be either normal, being overtaken, or casualty. The direction of action for each individual is affected by competitive ability, distance to the exits as well as number and density of occupants within the view field of the agent. Our simulations exhibit that during the evacuation process: (1) The agents gather in front of the exits spontaneously and present arched shapes close to the exits. (2) Under the panic state the agents cohere closely and almost do not change the target exit. So other alternative exits are ignored. (3) For the case without obstacle, the casualties under panic increase greatly. But if there are obstacles (chairs), the congestion can be alleviated. Thus the casualties are reduced. (4) If certain exit is partly clogged, the evacuation becomes more efficient when adding a virtual leader. The overall simulation results show that the proposed model can reproduce the real evacuation process in a stadium quite well.
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| 35. |
- Wang, J., et al.
(författare)
-
Observer-based leader-following tracking control under both fixed and switching topologies
- 2016
-
Ingår i: Control Theory and Technology. - : South China University of Technology. - 2095-6983 .- 2198-0942. ; 14:1, s. 28-38
-
Tidskriftsartikel (refereegranskat)abstract
- This paper studies the tracking problem for a class of leader-follower multi-agent systems moving on the plane using observer-based cooperative control strategies. In our set-up, only a subset of the followers can obtain some relative information on the leader. We assume that the control input of the leader is not known to any of the followers while the system matrix is broadcast to all the followers. To track such a leader, an observer-based decentralized feedback controller is designed for each follower and detailed analysis for the convergence is presented for both fixed and switching interaction topologies between agents with the method of common Lyapunov function. We can also generalize the result to the higher dimension case for fixed topology and some special system matrices of the leader for switching topology.
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| 36. |
- Wang, Sifan, et al.
(författare)
-
Fire carbon emissions over Equatorial Asia reduced by shortened dry seasons
- 2023
-
Ingår i: npj Climate and Atmospheric Science. - 2397-3722. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Fire carbon emissions over Equatorial Asia (EQAS) play a critical role in the global carbon cycle. Most regional fire emissions (89.0%) occur in the dry season, but how changes in the dry-season length affect the fire emissions remains poorly understood. Here we show that, the length of the EQAS dry season has decreased significantly during 1979–2021, and the delayed dry season onset (5.4 ± 1.6 (± one standard error) days decade−1) due to increased precipitation (36.4 ± 9.1 mm decade−1) in the early dry season is the main reason. The dry season length is strongly correlated with the length of the fire season. Increased precipitation during the early dry season led to a significant reduction (May: −0.7 ± 0.4 Tg C decade−1; August: −12.9 ± 6.7 Tg C decade−1) in fire carbon emissions during the early and peak fire season. Climate models from the Coupled Model Intercomparison Project Phase 6 project a continued decline in future dry season length in EQAS under medium and high-emission scenarios, implying further reductions in fire carbon emissions.
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| 37. |
- Wei, Jieqiang, et al.
(författare)
-
Finite-time attitude synchronization with a discontinuous protocol
- 2017
-
Ingår i: 13th IEEE International Conference on Control and Automation, ICCA 2017. - : IEEE Computer Society. - 9781538626795 ; , s. 192-197
-
Konferensbidrag (refereegranskat)abstract
- A finite-time attitude synchronization problem is considered in this paper where the rotation of each rigid body is expressed using the axis-angle representation. One simple discontinuous and distributed controller using the vectorized signum function is proposed. This controller only involves the sign of the state differences of adjacent neighbors. In order to avoid the singularity introduced by the axis-angular representation, an extra constraint is added to the initial condition. It is proved that for some initial conditions, the control law achieves finite-time attitude synchronization. One simulated example is provided to verify the usage of the control protocol designed in this paper.
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| 38. |
- Wei, Jieqiang, et al.
(författare)
-
Finite-time attitude synchronization with distributed discontinuous protocols
- 2018
-
Ingår i: IEEE Transactions on Automatic Control. - Piscataway, New Jersey : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 63:10, s. 3608-3615
-
Tidskriftsartikel (refereegranskat)abstract
- The finite-time attitude synchronization problem is considered in this paper, where the rotation of each rigid body is expressed using the axis-angle representation. Two discontinuous and distributed controllers using the vectorized signum function are proposed, which guarantee almost global and local convergence, respectively. Filippov solutions and non-smooth analysis techniques are adopted to handle the discontinuities. Sufficient conditions are provided to guarantee finite-time convergence and boundedness of the solutions. Simulation examples are provided to verify the performances of the control protocols designed in this paper.
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| 39. |
- Wu, Jingnan, 1994, et al.
(författare)
-
On the Conformation of Dimeric Acceptors and Their Polymer Solar Cells with Efficiency over 18 %
- 2023
-
Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 62:45
-
Tidskriftsartikel (refereegranskat)abstract
- The determination of molecular conformations of oligomeric acceptors (OAs) and their impact on molecular packing are crucial for understanding the photovoltaic performance of their resulting polymer solar cells (PSCs) but have not been well studied yet. Herein, we synthesized two dimeric acceptor materials, DIBP3F-Se and DIBP3F-S, which bridged two segments of Y6-derivatives by selenophene and thiophene, respectively. Theoretical simulation and experimental 1D and 2D NMR spectroscopic studies prove that both dimers exhibit O-shaped conformations other than S- or U-shaped counter-ones. Notably, this O-shaped conformation is likely governed by a distinctive "conformational lock" mechanism, arising from the intensified intramolecular & pi;-& pi; interactions among their two terminal groups within the dimers. PSCs based on DIBP3F-Se deliver a maximum efficiency of 18.09 %, outperforming DIBP3F-S-based cells (16.11 %) and ranking among the highest efficiencies for OA-based PSCs. This work demonstrates a facile method to obtain OA conformations and highlights the potential of dimeric acceptors for high-performance PSCs.
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| 40. |
- Xiaoming, Chen, 1983, et al.
(författare)
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Characterizations of Mutual Coupling Effects on Switch-Based Phased Array Antennas for 5G Millimeter-Wave Mobile Communications
- 2019
-
Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 7, s. 31376-31384
-
Tidskriftsartikel (refereegranskat)abstract
- The fifth generation (5G) millimeter-wave (mmWave) handset demands a cost-effective mmWave array antenna with beam steering capability to overcome the high-pass loss and to ensure seamless connectivity. Unlike sub-6-GHz handsets, emerging mmWave handsets usually employ phased array antennas with a reasonably large number of elements. Unfortunately, due to the legacy of a few antennas in sub-6-GHz handsets, the mutual coupling effect on the mmWave handset has not been thoroughly investigated. In this paper, we study the mutual coupling effect on the mmWave handset performance by comparing array antennas with different inter-element spacing and different configurations. It is found that mutual coupling tends to increase the active reflection (especially at large scanning angles), which in turn reduces the realized gain and maximum scanning angle of the phased array antenna. For a sub-6-GHz multiple-input multiple-output handset with two or four antenna ports and fully digital precoding/decoding, 10-dB isolation is usually regarded as good enough. It is shown in this paper, however, that the outage capacity of the mmWave handset can be clearly improved by reducing the mutual coupling.
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| 41. |
- Xiaoming, Zhang, et al.
(författare)
-
Effects of landuse change on surface runoff and sediment yield at different watershed scales on the Loess Plateau
- 2010
-
Ingår i: INTERNATIONAL JOURNAL OF SEDIMENT RESEARCH. - 1001-6279. ; 25:3, s. 283-293
-
Tidskriftsartikel (refereegranskat)abstract
- Erosion and sediment yield from large and small watersheds exhibit different laws. Variations in surface runoff and sediment yield because of landuse change in four watersheds of different scales from 1 km(2) to 73 km(2) were analyzed. Due to reforestation and farmland terracing, surface runoff and sediment yield reduced by 20-100% and 10-100% respectively. Reductions in surface runoff were differed significantly under different precipitation regimes. For the large watershed (73 km(2)) landuse change had similar effects on surface runoff regardless of changing of precipitation. For the small watershed (1 km(2)) landuse change had fewer effects on surface runoff under high precipitation. The relative changes of sediment yield in the four watersheds under reforestation and farmland terracing decreased as precipitation increased from 350 mm to 650 mm, then increased as precipitation increased from 650 mm to 870 mm. Where initial forest coverage rate was below 45%, sediment yield decreased dramatically as forest coverage rate increased. Watershed management with aiming at reducing both surface runoff and sediment yield should be conducted both on sloping surfaces and in channels in large watersheds.
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| 42. |
- Xu, Yueyue, et al.
(författare)
-
A Game Approach for Defending System Security from an Attacker
- 2023
-
Konferensbidrag (refereegranskat)abstract
- In this paper, a system security problem is studied based on a two-person non-cooperative dynamic game. Security of the system is regarded in the context of observability. Namely a system is secure if it is not observable. Both the defender and attacker are assumed to have means to modify the dimension of unobservable subspace, which is set as the value function. The strategies and algorithms to minimize or maximize the value function are given respectively. Finally, examples are provided to demonstrate the effectiveness of the proposed algorithms and show some interesting game results, including accumulation mode, loop mode and locked mode.
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| 43. |
- Yang, Zhen, et al.
(författare)
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Genetic variation in the GCKR gene is associated with non-alcoholic fatty liver disease in Chinese people
- 2011
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Ingår i: Molecular Biology Reports. - : Springer Science and Business Media LLC. - 0301-4851 .- 1573-4978. ; 38:2, s. 1145-1150
-
Tidskriftsartikel (refereegranskat)abstract
- Recent genome-wide association studies reported that GCKR rs780094 polymorphism is associated with elevated fasting serum triglyceride levels and elevated levels of C-reactive protein (CRP). There are a ample of data on the association between circulating triglyceride, CRP concentrations and risk of non-alcoholic fatty liver (NAFLD). To determine whether the GCKR rs780094 polymorphism contributes to the development of non-alcoholic fatty liver, a case-control study was performed in 903 Chinese subjects. Among study population, 436 patients with B-mode ultrasound-proven NAFLD (318 with steatosis hepatis IA degrees, 90 with steatosis hepatis IIA degrees and 28 with steatosis hepatis IIIA degrees) and 467 controls were genotyped by using TaqMan allelic discrimination assays. We confirmed the association of GCKR rs780094 with NAFLD in Chinese people (OR = 1.607, 95% CI 1.139-2.271, P ([dom]) = 7.2 x 10(-3)). In this study, polymorphism in GCKR rs780094 was not significantly associated with the degree of fatty infiltration of the liver. In addition, the T-allele of GCKR rs780094 was significantly associated with increasing fasting triglyceride (P ([add]) = 3.8 x 10(-4)) and CRP (P ([add]) = 2.9 x 10(-4)) concentrations after adjusting for age, gender, and BMI. The association with NAFLD remained significant after adjustment for triglyceride, while adjustment for CRP abolished the association. Genetic variation in GCKR gene rs780094 polymorphism contributes to the risk of NAFLD in Chinese people. The effect of genotype on NAFLD is probably mediated through chronic low-grade systemic inflammation rather than through dislipidemia.
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| 44. |
- Yang, Zhen, et al.
(författare)
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PPARG gene Pro12Ala variant contributes to the development of non-alcoholic fatty liver in middle-aged and older Chinese population
- 2012
-
Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 1872-8057 .- 0303-7207. ; 348:1, s. 255-259
-
Tidskriftsartikel (refereegranskat)abstract
- Oxidative stress has been suggested to contribute to the development of non-alcoholic fatty liver disease (NAFLD). Peroxisome proliferator-activated receptor gamma (PPAR-gamma) heterozygous mice and Pro12Ala (C/G) polymorphism in PPARG exhibited increased resistance to oxidative stress. Smoking increases the production of reactive oxygen species, which could accelerates oxidative stress under overnutrition. To explore whether the C/G polymorphism, alone or in combination with smoking, may promote the development of non-alcoholic fatty liver, a case-control study was performed in 903 Chinese subjects. Among the study population, 436 patients with B-mode ultrasound-proven NAFLD (318 with steatosis hepatis I degrees, 90 with steatosis hepatis II degrees and 28 with steatosis hepatis III degrees) and 467 controls were genotyped by using TaqMan allelic discrimination assays. After adjusting for confounders, the C/C genotype significantly associated with NAFLD (OR = 1.87, 95%CI 1.13-2.85, p = 0.009); smoking was also an independent risk factor for NAFLD (OR = 1.69, 95%CI 1.18-2.43, p = 0.025). In addition, we found possible synergistic effects, the higher risk group (smokers with the C/C genotype) showed 3.75 times higher risk of NAFLD than the low-risk group (non-smokers with C/G genotype) in a multiple logistic analysis after adjusting for the confounders (p < 0.001), but no departure from additivity was found. Our results indicated that the C/C genotype and smoking were significant independent risk factors for NAFLD. The possible synergistic effects of genotype and smoking may promote the development of NAFLD by aggravating oxidative stress, which supports the hypothesis that oxidative stress contributes to the development of NAFLD. (C) 2011 Elsevier Ireland Ltd. All rights reserved.
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| 45. |
- Yuan, Xiaoming, et al.
(författare)
-
A new approach to establish both stable and metastable phase equilibria for fcc ordered/disordered phase transition : application to the Al-Ni and Ni-Si systems
- 2012
-
Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 135:1, s. 94-105
-
Tidskriftsartikel (refereegranskat)abstract
- Both two-sublattice (2SL) and four-sublattice (4SL) models in the framework of the compound energy formalism can be used to describe the fcc ordered/disordered transitions. When transferring the parameters of 2SL disregarding the metastable ordered states into those of 4SL, inconsistence in either stable or metastable phase diagrams could appear, as detected in both Al-Ni and Ni-Si systems. To avoid such a kind of drawback, this behavior was analyzed and investigated in the Ni-Si and Al-Ni systems with the aid of first principle calculations. Furthermore, a new approach considering both the stable and metastable fcc ordered phase equilibria deduced from the first principles calculations was proposed to perform a reliable thermodynamic modeling for the fcc ordered/disordered transition. The Ni-Si system was then thermodynamically assessed using the presently proposed approach. The good agreement between the calculation and experiments demonstrates the reliability of the proposed approach. It is expected that the approach is valid for other systems showing complex ordered/disordered transitions.
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| 46. |
- Zhang, Han, et al.
(författare)
-
Consensus control for linear systems with optimal energy cost
- 2018
-
Ingår i: Automatica. - : Elsevier. - 0005-1098 .- 1873-2836. ; 93, s. 83-91
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we design an optimal energy cost controller for linear systems asymptotic consensus given the topology of the graph. The controller depends only on relative information of the agents. Since finding the control gain for such controller is hard, we focus on finding an optimal controller among a classical family of controllers which is based on Algebraic Riccati Equation (ARE) and guarantees asymptotic consensus. Through analysis, we find that the energy cost is bounded by an interval and hence we minimize the upper bound. In order to do that, there are two classes of variables that need to be optimized: the control gain and the edge weights of the graph and are hence designed from two perspectives. A suboptimal control gain is obtained by choosing Q=0 in the ARE. Negative edge weights are allowed, and the problem is formulated as a Semi-definite Programming (SDP) problem. Having negative edge weights means that “competitions” between the agents are allowed. The motivation behind this setting is to have a better system performance. We provide a different proof compared to Thunberg and Hu (2016) from the angle of optimization and show that the lowest control energy cost is reached when the graph is complete and with equal edge weights. Furthermore, two sufficient conditions for the existence of negative optimal edge weights realization are given. In addition, we provide a distributed way of solving the SDP problem when the graph topology is regular.
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| 47. |
- Zhang, Han, 1989-, et al.
(författare)
-
Discrete-Time Inverse Linear Quadratic Optimal Control over Finite Time-Horizon under Noisy Output Measurements
- 2021
-
Ingår i: Control Theory and Technology. - : Springer Nature. - 2095-6983 .- 2198-0942. ; 19:4, s. 563-572
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the problem of inverse quadratic optimal control over finite time-horizon for discrete-time linear systems is considered. Our goal is to recover the corresponding quadratic objective function using noisy observations. First, the identifiability of the model structure for the inverse optimal control problem is analyzed under relative degree assumption and we show the model structure is strictly globally identifiable. Next, we study the inverse optimal control problem whose initial state distribution and the observation noise distribution are unknown, yet the exact observations on the initial states are available. We formulate the problem as a risk minimization problem and approximate the problem using empirical average. It is further shown that the solution to the approximated problem is statistically consistent under the assumption of relative degrees. We then study the case where the exact observations on the initial states are not available, yet the observation noises are known to be white Gaussian distributed and the distribution of the initial state is also Gaussian (with unknown mean and covariance). EM-algorihm is used to estimate the parameters in the objective function. The effectiveness of our results are demonstrated by numerical examples.
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| 48. |
- Zhang, Han, et al.
(författare)
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Inverse optimal control for discrete-time finite-horizon Linear Quadratic Regulators
- 2019
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Ingår i: Automatica. - : Elsevier Ltd. - 0005-1098 .- 1873-2836. ; 110
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider the inverse optimal control problem for discrete-time Linear Quadratic Regulators (LQR), over finite-time horizons. Given observations of the optimal trajectories, or optimal control inputs, to a linear time-invariant system, the goal is to infer the parameters that define the quadratic cost function. The well-posedness of the inverse optimal control problem is first justified. In the noiseless case, when these observations are exact, we analyze the identifiability of the problem and provide sufficient conditions for uniqueness of the solution. In the noisy case, when the observations are corrupted by additive zero-mean noise, we formulate the problem as an optimization problem and prove that the solution to this problem is statistically consistent. The performance of the proposed method is illustrated through numerical examples.
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| 49. |
- Zhang, Han, et al.
(författare)
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Inverse Optimal Control for Finite-Horizon Discrete-time Linear Quadratic Regulator Under Noisy Output
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, the problem of inverse optimal control for finite-horizon discrete-time Linear Quadratic Regulators (LQRs) is considered. The goal of the inverse optimal control problem is to recover the corresponding objective function by the noisy observations. We consider the problem of inverse optimal control in two scenarios: 1) the distributions of the initial state and the observation noise are unknown, yet the exact observations on the initial states and the noisy observations on system output are available; 2) the exact observations on the initial states are not available, yet the observation noises are known white Gaussian and the distribution of the initial state is also Gaussian (with unknown mean and covariance). For the first scenario, we formulate the problem as a risk minimization problem and show that its solution is statistically consistent. For the second scenario, we fit the problem into the framework of maximum-likelihood and Expectation Maximization (EM) algorithm is used to solve this problem. The performance for the estimations are shown by numerical examples.
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| 50. |
- Zhang, Han, 1989-, et al.
(författare)
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Inverse Optimal Control for Finite-Horizon Discrete-time Linear Quadratic Regulator under Noisy Output
- 2019
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728113982 ; , s. 6663-6668
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Konferensbidrag (refereegranskat)abstract
- In this paper, the problem of inverse optimal control for finite-horizon discrete-time Linear Quadratic Regulators (LQRs) is considered. The goal of the inverse optimal control problem is to recover the corresponding objective function by the noisy observations. We consider the problem of inverse optimal control in two scenarios: 1) the distributions of the initial state and the observation noise are unknown, yet the exact observations on the initial states and the noisy observations on system output are available; 2) the exact observations on the initial states are not available, yet the observation noises are known white Gaussian and the distribution of the initial state is also Gaussian (with unknown mean and covariance). For the first scenario, we formulate the problem as a risk minimization problem and show that its solution is statistically consistent. For the second scenario, we fit the problem into the framework of maximum-likelihood and Expectation Maximization (EM) algorithm is used to solve this problem. The performance for the estimations are shown by numerical examples.
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