The growth plate(GP)is a crucial tissue involved in skeleton development via endochondral ossification(EO).The bone organoid is a potential research model capable of simulating the physiological function,spatial struc...The growth plate(GP)is a crucial tissue involved in skeleton development via endochondral ossification(EO).The bone organoid is a potential research model capable of simulating the physiological function,spatial structure,and intercellular communication of native GPs.However,mimicking the EO process remains a key challenge for bone organoid research.To simulate this orderly mineralization process,we designed an in vitro sh Ca_(v)3.3 ATDC5-loaded gelatin methacryloyl(Gel MA)hydrogel model and evaluated its bioprintability for future organoid construction.In this paper,we report the first demonstration that the T-type voltage-dependent calcium channel(T-VDCC)subtype Ca_(v)3.3 is dominantly expressed in chondrocytes and is negatively correlated with the hypertrophic differentiation of chondrocytes during the EO process.Furthermore,Ca_(v)3.3 knockdown chondrocytes loaded with the Gel MA hydrogel successfully captured the EO process and provide a bioink capable of constructing layered and orderly mineralized GP organoids in the future.The results of this study could therefore provide a potential target for regulating the EO process and a novel strategy for simulating it in bone organoids.展开更多
We present radial velocity(RV)curve templates of RR Lyrae first-overtone(RRc)stars constructed with the Mg I b triplet and Hαlines using time-domain Medium-Resolution Survey spectra of seven RRc stars from Large Sky ...We present radial velocity(RV)curve templates of RR Lyrae first-overtone(RRc)stars constructed with the Mg I b triplet and Hαlines using time-domain Medium-Resolution Survey spectra of seven RRc stars from Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)Data Release 9.Additionally,we derive the relation between the stellar RV curve amplitudes and g-band light curve amplitudes from Zwicky Transient Facility(ZTF)public survey.For those RRc stars without ZTF g-band light curves,we provide the conversions from the light curve amplitudes in ZTF r-and i-bands,Gaia G-band,and V-band from the All-Sky Automated Survey for Supernovae to those in ZTF g-band.We validate our RV curve templates using the RRc star SV Scl and find the uncertainties of systemic RV are less than 2.11 km s~(-1)and 6.08 km s~(-1)based on the Mg I b triplet and Hαlines,respectively.We calculate the systemic RVs of 30 RRc stars using the RV curve templates constructed with the Mg I b triplet and Hαlines and find the systemic RVs are comparable with each other.This RV curve template will be particularly useful for obtaining the systemic RV of RRc using the LAMOST spectroscopy.展开更多
During the long term evolution of globular clusters(GCs), some member stars are lost to the field. The recently found nitrogen-rich(N-rich) metal-poor field stars are promising candidates of these GC escapees, since N...During the long term evolution of globular clusters(GCs), some member stars are lost to the field. The recently found nitrogen-rich(N-rich) metal-poor field stars are promising candidates of these GC escapees, since N enhancement is the fingerprint of chemically enhanced populations in GCs. In this work, we discuss the possibility of identifying N-rich metal-poor field stars with the upcoming Chinese Space Station Telescope(CSST). We focus on the main survey camera with NUV, u, g, r, i, z, y filters and slitless spectrograph with a resolution about 200.The combination of UV sensitive equipment and prominent N-related molecular lines in the UV band bodes well for the identification: the color–color diagram of(u-g) versus(g-r) is capable of separating N-rich field stars from normal halo stars, if metallicity can be estimated without using the information on u-band photometry.Besides, the synthetic spectra show that a signal-to-noise ratio of 10 is sufficient to identify N-rich field stars. In the near future, a large sample of N-rich field stars found by CSST, combined with state-of-the-art N-body simulations will be crucial to deciphering GC-Galaxy co-evolution.展开更多
Deriving atmospheric parameters of a large sample of stars is of vital importance to understand the formation and evolution of the Milky Way.Photometric surveys,especially those with near-ultraviolet filters,can offer...Deriving atmospheric parameters of a large sample of stars is of vital importance to understand the formation and evolution of the Milky Way.Photometric surveys,especially those with near-ultraviolet filters,can offer accurate measurements of stellar parameters,with the precision comparable to that from low/medium resolution spectroscopy.In this study,we explore the capability of measuring stellar atmospheric parameters from Chinese Space Station Telescope(CSST)broad-band photometry(particularly in the near-ultraviolet bands),based on synthetic colors derived from model spectra.We find that colors from the optical and near-ultraviolet filter systems adopted by CSST show significant sensitivities to the stellar atmospheric parameters,especially the metallicity.According to our mock data tests,the precision of the photometric metallicity is quite high,with typical values of0.17 and 0.20 dex for dwarf and giant stars,respectively.The precision of the effective temperature estimated from broad-band colors are within 50 K.展开更多
Objective:To investigate the economic burden of patients with acute kidney injury(AKI)by analyzing the distribution of hospitalization expenses and its influencing factors in the Affiliated Hospital of Hebei Universit...Objective:To investigate the economic burden of patients with acute kidney injury(AKI)by analyzing the distribution of hospitalization expenses and its influencing factors in the Affiliated Hospital of Hebei University.Methods:The hospitalization information of patients with AKI from January 2020 to January 2023 was collected and sorted through the hospital charging system and the factors affecting the total hospitalization cost were analyzed by multiple linear regression.Results:Univariate analysis showed that age,occupation,marriage,length of hospitalization,recovery of renal function,and stage of AKI had significant effects on hospitalization cost(P<0.05).The result of the multiple linear regression analysis model showed that age(t=4.11,P<0.0001),length of hospitalization(t=16.10,P<0.0001),recovery of renal function(t=3.26,P<0.0001),AKI stage(t=5.23,P=0.002)are factors affecting the economic burden of patients with AKI.Conclusion:AKI patients should be managed according to age stratification to effectively control the progression of the disease and improve the quality of the medical services provided.This will reduce the economic burden of patients.展开更多
AIM To develop a contrast-enhanced ultrasound(CEUS)predictive model for distinguishing intrahepatic cholangiocarcinoma(ICC) from hepatocellular carcinoma(HCC) in high-risk patients.METHODS This retrospective study con...AIM To develop a contrast-enhanced ultrasound(CEUS)predictive model for distinguishing intrahepatic cholangiocarcinoma(ICC) from hepatocellular carcinoma(HCC) in high-risk patients.METHODS This retrospective study consisted of 88 consecutive high-risk patients with ICC and 88 high-risk patients with HCC selected by propensity score matching between May 2004 and July 2016. Patients were assigned to two groups, namely, a training set and validation set, at a 1:1 ratio. A CEUS score for diagnosing ICC was generated based on significant CEUS features. Then, a nomogram based on the CEUS score was developed, integrating the clinical data. The performance of the nomogram was then validated and compared with that of the LR-M of the CEUS Liver Imaging Reporting and Data System(LI-RADS).RESULTS The most useful CEUS features for ICC were as follows: rim enhancement(64.5%), early washout(91.9%), intratumoral vein(58.1%), obscure boundary of intratumoral non-enhanced area(64.5%), and marked washout(61.3%, all P < 0.05). In the validation set, the area under the curve(AUC) of the CEUS score(AUC = 0.953) for differentiation between ICC and HCC was improved compared to the LI-RADS(AUC = 0.742)(P < 0.001). When clinical data were added, the CEUS score nomogram was superior to the LI-RADS nomogram(AUC: 0.973 vs 0.916, P = 0.036, Net Reclassification Improvement: 0.077, Integrated Discrimination Index: 0.152). Subgroup analysis demonstrated that the CEUS score model was notably improved compared to the LIRADS in tumors smaller than 5.0 cm(P < 0.05) but not improved in tumors smaller than 3.0 cm(P > 0.05).CONCLUSION The CEUS predictive model for differentiation between ICC and HCC in high-risk patients had improved discrimination and clinical usefulness compared to the CEUS LIRADS.展开更多
Tea is a widely consumed beverage and has many important physiological properties and potential health benefits. In this study, a novel method based on supercritical fluid chromatography coupled with mass spectrometry...Tea is a widely consumed beverage and has many important physiological properties and potential health benefits. In this study, a novel method based on supercritical fluid chromatography coupled with mass spectrometry (SFC-MS) was developed to simultaneously determine 11 amino acids in different types of tea (green teas, Oolong tea, black tea and Pu-erh tea). The separation conditions for the analysis of the selected amino acids including the column type, temperature and backpressure as well as the type of additive, were carefully optimized. The best separation of the 11 amino acids was obtained by adding water (5%, v/v) and trifluoroacetic acid (0.4%, v/v) to the organic modifier (methanol). Finally, the developed SFC-MS method was fully validated and successfully applied to the determination of these amino acids in six different tea samples. Good linearity (r ≥ 0.993), precision (RSDs≤ 2.99%), accuracy (91.95%-107.09%) as well as good sample stability were observed. The limits of detection ranged from 1.42 to 14.69 ng/mL, while the limits of quantification were between 4.53 and 47.0 ng/mL. The results indicate that the contents of the 11 amino acids in the six different tea samples are greatly influenced by the degree of fermentation. The proposed SFC-MS method shows a great potential for further investigation of tea varieties.展开更多
The exploration for renewable and clean energies has become crucial due to environmental issues such as global warming and the energy crisis. In recent years,floating offshore wind turbines(FOWTs) have attracted a con...The exploration for renewable and clean energies has become crucial due to environmental issues such as global warming and the energy crisis. In recent years,floating offshore wind turbines(FOWTs) have attracted a considerable amount of attention as a means to exploit steady and strong wind sources available in deep-sea areas. In this study, the coupled aero-hydrodynamic characteristics of a spar-type 5-MW wind turbine are analyzed. An unsteady actuator line model(UALM) coupled with a twophase computational fluid dynamics solver naoe-FOAM-SJTU is applied to solve three-dimensional Reynolds-averaged NavierStokes equations. Simulations with different complexities are performed. First, the wind turbine is parked. Second, the impact of the wind turbine is simplified into equivalent forces and moments. Third, fully coupled dynamic analysis with wind and wave excitation is conducted by utilizing the UALM. From the simulation, aerodynamic forces, including the unsteady aerodynamic power and thrust, can be obtained, and hydrodynamic responses such as the six-degrees-of-freedom motions of the floating platform and the mooring tensions are also available. The coupled responses of the FOWT for cases of different complexities are analyzed based on the simulation results. Findings indicate that the coupling effects between the aerodynamics of the wind turbine and the hydrodynamics of the floating platform are obvious. The aerodynamic loads have a significant effect on the dynamic responses of the floating platform, and the aerodynamic performance of the wind turbine has highly unsteady characteristics due to the motions of the floating platform. A spar-type FOWT consisting of NREL-5-MW baseline wind turbine and OC3-Hywind platform system is investigated. The aerodynamic forces can be obtained by the UALM. The 6 DoF motions and mooring tensions are predicted by the naoe-FOAM-SJTU. To research the coupling effects between the aerodynamics of the wind turbine and the hydrodynamics of the floating platform, simulations with different complexities are performed. Fully coupled aero-hydrodynamic characteristics of FOWTs, including aerodynamic loads, wake vortex, motion responses, and mooring tensions, are compared and analyzed.展开更多
This paper investigates subcarrier and power allocation in a multi-UAV OFDM system.The study considers a practical scenario,where certain subcarriers are unavailable for dynamic subcarrier allocation,on account of pre...This paper investigates subcarrier and power allocation in a multi-UAV OFDM system.The study considers a practical scenario,where certain subcarriers are unavailable for dynamic subcarrier allocation,on account of pre-allocation for burst transmissions.We first propose a novel iterative algorithm to jointly optimize subcarrier and power allocation,so as to maximize the sum rate of the uplink transmission in the multiUAV OFDM system.The key idea behind our solution is converting the nontrivial allocation problem into a weighted mean square error(MSE) problem.By this means,the allocation problem can be solved by the alternating optimization method.Besides,aiming at a lower-complexity solution,we propose a heuristic allocation scheme,where subcarrier allocation and transmit power allocation are separately optimized.In the heuristic scheme,closedform solution can be obtained for power allocation.Simulation results demonstrate that in the presence of stretched subcarrier resource,the proposed iterative joint optimization algorithm can significantly outperform the heuristic scheme,offering a higher sum rate.展开更多
Unmanned aerial vehicles(UAVs)can be employed as aerial base stations(BSs)due to their high mobility and flexible deployment.This paper focuses on a UAV-assisted wireless network,where users can be scheduled to get ac...Unmanned aerial vehicles(UAVs)can be employed as aerial base stations(BSs)due to their high mobility and flexible deployment.This paper focuses on a UAV-assisted wireless network,where users can be scheduled to get access to either an aerial BS or a terrestrial BS for uplink transmission.In contrast to state-of-the-art designs focusing on the instantaneous cost of the network,this paper aims at minimizing the long-term average transmit power consumed by the users by dynamically optimizing user association and power allocation in each time slot.Such a joint user association scheduling and power allocation problem can be formulated as a Markov decision process(MDP).Unfortunately,solving such an MDP problem with the conventional relative value iteration(RVI)can suffer from the curses of dimensionality,in the presence of a large number of users.As a countermeasure,we propose a distributed RVI algorithm to reduce the dimension of the MDP problem,such that the original problem can be decoupled into multiple solvable small-scale MDP problems.Simulation results reveal that the proposed algorithm can yield lower longterm average transmit power consumption than both the conventional RVI algorithm and a baseline algorithm with myopic policies.展开更多
基金supported by the National Natural Science Foundation of China(No.31800784)the Chongqing Key Laboratory of Precision Medicine in Joint Surgery(No.425Z2138)+2 种基金the Chongqing Excellent Scientist Project(No.425Z2W21)the Chongqing Natural Science Foundation General Project(No.cstc2021jcyjmsxm X0135)the Chongqing Postdoctoral Research Project Special Fund(No.2021XM3033)。
文摘The growth plate(GP)is a crucial tissue involved in skeleton development via endochondral ossification(EO).The bone organoid is a potential research model capable of simulating the physiological function,spatial structure,and intercellular communication of native GPs.However,mimicking the EO process remains a key challenge for bone organoid research.To simulate this orderly mineralization process,we designed an in vitro sh Ca_(v)3.3 ATDC5-loaded gelatin methacryloyl(Gel MA)hydrogel model and evaluated its bioprintability for future organoid construction.In this paper,we report the first demonstration that the T-type voltage-dependent calcium channel(T-VDCC)subtype Ca_(v)3.3 is dominantly expressed in chondrocytes and is negatively correlated with the hypertrophic differentiation of chondrocytes during the EO process.Furthermore,Ca_(v)3.3 knockdown chondrocytes loaded with the Gel MA hydrogel successfully captured the EO process and provide a bioink capable of constructing layered and orderly mineralized GP organoids in the future.The results of this study could therefore provide a potential target for regulating the EO process and a novel strategy for simulating it in bone organoids.
基金supported by the National Key Research and Development Program of China(2023YFA1608100)the National Natural Science Foundation of China(NSFC,grant Nos.12090044,11833006 and 12303023)+3 种基金the science research grants from the China Manned Space Project including the CSST Milky Way and Nearby Galaxies Survey on Dust and Extinction Project CMS-CSST-2021-A09 and No.CMS-CSST-2021-A08.G.C.LHubei Provincial Natural Science Foundation with grant No.2023AFB577the Key Laboratory Fund of Ministry of Education under grant No.QLPL2022P01National Natural Science Foundation of China(NSFC,Grant No.U1731108)。
文摘We present radial velocity(RV)curve templates of RR Lyrae first-overtone(RRc)stars constructed with the Mg I b triplet and Hαlines using time-domain Medium-Resolution Survey spectra of seven RRc stars from Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)Data Release 9.Additionally,we derive the relation between the stellar RV curve amplitudes and g-band light curve amplitudes from Zwicky Transient Facility(ZTF)public survey.For those RRc stars without ZTF g-band light curves,we provide the conversions from the light curve amplitudes in ZTF r-and i-bands,Gaia G-band,and V-band from the All-Sky Automated Survey for Supernovae to those in ZTF g-band.We validate our RV curve templates using the RRc star SV Scl and find the uncertainties of systemic RV are less than 2.11 km s~(-1)and 6.08 km s~(-1)based on the Mg I b triplet and Hαlines,respectively.We calculate the systemic RVs of 30 RRc stars using the RV curve templates constructed with the Mg I b triplet and Hαlines and find the systemic RVs are comparable with each other.This RV curve template will be particularly useful for obtaining the systemic RV of RRc using the LAMOST spectroscopy.
基金support from the China Manned Space Project Nos. CMS-CSST-2021-B03,CMS-CSST-2021-A08, and________the National Natural Science Foundation of China under grant No. 12233013,12073090+8 种基金the Natural Science Foundation of Guangdong Province under grant No. 2022A1515010732grant support provided by Proyecto Fondecyt Iniciación No. 11220340ANID Concurso de Fomento a la Vinculación Internacional para Instituciones de Investigación Regionales (Modalidad corta duración) Proyecto No. FOVI210020Joint Committee ESO-Government of Chile 2021 (ORP 023/2021)Becas Santander Movilidad Internacional Profesores 2022, Banco Santander Chilesupport from the National Natural Science Foundation of China through grant 21BAA00619the one-hundred-talent project of Sun Yat-sen Universitythe Fundamental Research Funds for the Central UniversitiesSun Yat-sen University (22hytd09)。
文摘During the long term evolution of globular clusters(GCs), some member stars are lost to the field. The recently found nitrogen-rich(N-rich) metal-poor field stars are promising candidates of these GC escapees, since N enhancement is the fingerprint of chemically enhanced populations in GCs. In this work, we discuss the possibility of identifying N-rich metal-poor field stars with the upcoming Chinese Space Station Telescope(CSST). We focus on the main survey camera with NUV, u, g, r, i, z, y filters and slitless spectrograph with a resolution about 200.The combination of UV sensitive equipment and prominent N-related molecular lines in the UV band bodes well for the identification: the color–color diagram of(u-g) versus(g-r) is capable of separating N-rich field stars from normal halo stars, if metallicity can be estimated without using the information on u-band photometry.Besides, the synthetic spectra show that a signal-to-noise ratio of 10 is sufficient to identify N-rich field stars. In the near future, a large sample of N-rich field stars found by CSST, combined with state-of-the-art N-body simulations will be crucial to deciphering GC-Galaxy co-evolution.
基金the science research grants from the China Manned Space Project with No.CMS-CSST-2021-A08.Y.Hthe science research grants from the China Manned Space Project with No.CMS-CSST-2021-B05+3 种基金the NSFC for grant Nos.11903027 and11833006the NSFC for grant Nos.11973001,12090040,and 12090044the National Key R&D Program of China for grant No.2019YFA0405503.H.W.Zthe National Key R&D Program of China for grant No.2019YFA0405504。
文摘Deriving atmospheric parameters of a large sample of stars is of vital importance to understand the formation and evolution of the Milky Way.Photometric surveys,especially those with near-ultraviolet filters,can offer accurate measurements of stellar parameters,with the precision comparable to that from low/medium resolution spectroscopy.In this study,we explore the capability of measuring stellar atmospheric parameters from Chinese Space Station Telescope(CSST)broad-band photometry(particularly in the near-ultraviolet bands),based on synthetic colors derived from model spectra.We find that colors from the optical and near-ultraviolet filter systems adopted by CSST show significant sensitivities to the stellar atmospheric parameters,especially the metallicity.According to our mock data tests,the precision of the photometric metallicity is quite high,with typical values of0.17 and 0.20 dex for dwarf and giant stars,respectively.The precision of the effective temperature estimated from broad-band colors are within 50 K.
文摘Objective:To investigate the economic burden of patients with acute kidney injury(AKI)by analyzing the distribution of hospitalization expenses and its influencing factors in the Affiliated Hospital of Hebei University.Methods:The hospitalization information of patients with AKI from January 2020 to January 2023 was collected and sorted through the hospital charging system and the factors affecting the total hospitalization cost were analyzed by multiple linear regression.Results:Univariate analysis showed that age,occupation,marriage,length of hospitalization,recovery of renal function,and stage of AKI had significant effects on hospitalization cost(P<0.05).The result of the multiple linear regression analysis model showed that age(t=4.11,P<0.0001),length of hospitalization(t=16.10,P<0.0001),recovery of renal function(t=3.26,P<0.0001),AKI stage(t=5.23,P=0.002)are factors affecting the economic burden of patients with AKI.Conclusion:AKI patients should be managed according to age stratification to effectively control the progression of the disease and improve the quality of the medical services provided.This will reduce the economic burden of patients.
基金Supported by the National Nature Science Foundation of China,No.81701719the Guangdong Science and Technology Foundation,No.2017A020215195the Guangdong Medical Scientific Research Foundation,No.A2016254
文摘AIM To develop a contrast-enhanced ultrasound(CEUS)predictive model for distinguishing intrahepatic cholangiocarcinoma(ICC) from hepatocellular carcinoma(HCC) in high-risk patients.METHODS This retrospective study consisted of 88 consecutive high-risk patients with ICC and 88 high-risk patients with HCC selected by propensity score matching between May 2004 and July 2016. Patients were assigned to two groups, namely, a training set and validation set, at a 1:1 ratio. A CEUS score for diagnosing ICC was generated based on significant CEUS features. Then, a nomogram based on the CEUS score was developed, integrating the clinical data. The performance of the nomogram was then validated and compared with that of the LR-M of the CEUS Liver Imaging Reporting and Data System(LI-RADS).RESULTS The most useful CEUS features for ICC were as follows: rim enhancement(64.5%), early washout(91.9%), intratumoral vein(58.1%), obscure boundary of intratumoral non-enhanced area(64.5%), and marked washout(61.3%, all P < 0.05). In the validation set, the area under the curve(AUC) of the CEUS score(AUC = 0.953) for differentiation between ICC and HCC was improved compared to the LI-RADS(AUC = 0.742)(P < 0.001). When clinical data were added, the CEUS score nomogram was superior to the LI-RADS nomogram(AUC: 0.973 vs 0.916, P = 0.036, Net Reclassification Improvement: 0.077, Integrated Discrimination Index: 0.152). Subgroup analysis demonstrated that the CEUS score model was notably improved compared to the LIRADS in tumors smaller than 5.0 cm(P < 0.05) but not improved in tumors smaller than 3.0 cm(P > 0.05).CONCLUSION The CEUS predictive model for differentiation between ICC and HCC in high-risk patients had improved discrimination and clinical usefulness compared to the CEUS LIRADS.
基金the financial support from China Postdoctoral Science Foundation(2018M643205)
文摘Tea is a widely consumed beverage and has many important physiological properties and potential health benefits. In this study, a novel method based on supercritical fluid chromatography coupled with mass spectrometry (SFC-MS) was developed to simultaneously determine 11 amino acids in different types of tea (green teas, Oolong tea, black tea and Pu-erh tea). The separation conditions for the analysis of the selected amino acids including the column type, temperature and backpressure as well as the type of additive, were carefully optimized. The best separation of the 11 amino acids was obtained by adding water (5%, v/v) and trifluoroacetic acid (0.4%, v/v) to the organic modifier (methanol). Finally, the developed SFC-MS method was fully validated and successfully applied to the determination of these amino acids in six different tea samples. Good linearity (r ≥ 0.993), precision (RSDs≤ 2.99%), accuracy (91.95%-107.09%) as well as good sample stability were observed. The limits of detection ranged from 1.42 to 14.69 ng/mL, while the limits of quantification were between 4.53 and 47.0 ng/mL. The results indicate that the contents of the 11 amino acids in the six different tea samples are greatly influenced by the degree of fermentation. The proposed SFC-MS method shows a great potential for further investigation of tea varieties.
文摘The exploration for renewable and clean energies has become crucial due to environmental issues such as global warming and the energy crisis. In recent years,floating offshore wind turbines(FOWTs) have attracted a considerable amount of attention as a means to exploit steady and strong wind sources available in deep-sea areas. In this study, the coupled aero-hydrodynamic characteristics of a spar-type 5-MW wind turbine are analyzed. An unsteady actuator line model(UALM) coupled with a twophase computational fluid dynamics solver naoe-FOAM-SJTU is applied to solve three-dimensional Reynolds-averaged NavierStokes equations. Simulations with different complexities are performed. First, the wind turbine is parked. Second, the impact of the wind turbine is simplified into equivalent forces and moments. Third, fully coupled dynamic analysis with wind and wave excitation is conducted by utilizing the UALM. From the simulation, aerodynamic forces, including the unsteady aerodynamic power and thrust, can be obtained, and hydrodynamic responses such as the six-degrees-of-freedom motions of the floating platform and the mooring tensions are also available. The coupled responses of the FOWT for cases of different complexities are analyzed based on the simulation results. Findings indicate that the coupling effects between the aerodynamics of the wind turbine and the hydrodynamics of the floating platform are obvious. The aerodynamic loads have a significant effect on the dynamic responses of the floating platform, and the aerodynamic performance of the wind turbine has highly unsteady characteristics due to the motions of the floating platform. A spar-type FOWT consisting of NREL-5-MW baseline wind turbine and OC3-Hywind platform system is investigated. The aerodynamic forces can be obtained by the UALM. The 6 DoF motions and mooring tensions are predicted by the naoe-FOAM-SJTU. To research the coupling effects between the aerodynamics of the wind turbine and the hydrodynamics of the floating platform, simulations with different complexities are performed. Fully coupled aero-hydrodynamic characteristics of FOWTs, including aerodynamic loads, wake vortex, motion responses, and mooring tensions, are compared and analyzed.
基金supported by China NSF Grants(61631020)the Fundamental Research Funds for the Central Universities(NP2018103,NE2017103,NC2017003)
文摘This paper investigates subcarrier and power allocation in a multi-UAV OFDM system.The study considers a practical scenario,where certain subcarriers are unavailable for dynamic subcarrier allocation,on account of pre-allocation for burst transmissions.We first propose a novel iterative algorithm to jointly optimize subcarrier and power allocation,so as to maximize the sum rate of the uplink transmission in the multiUAV OFDM system.The key idea behind our solution is converting the nontrivial allocation problem into a weighted mean square error(MSE) problem.By this means,the allocation problem can be solved by the alternating optimization method.Besides,aiming at a lower-complexity solution,we propose a heuristic allocation scheme,where subcarrier allocation and transmit power allocation are separately optimized.In the heuristic scheme,closedform solution can be obtained for power allocation.Simulation results demonstrate that in the presence of stretched subcarrier resource,the proposed iterative joint optimization algorithm can significantly outperform the heuristic scheme,offering a higher sum rate.
基金This work was supported in part by the National Natural Science Foundation of China under Grant 61901216,61631020 and 61827801the Natural Science Foundation of Jiangsu Province under Grant BK20190400+1 种基金the open research fund of National Mobile Communications Research Laboratory,Southeast University(No.2020D08)the Foundation of Graduate Innovation Center in NUAA under Grant No.KFJJ20190408.
文摘Unmanned aerial vehicles(UAVs)can be employed as aerial base stations(BSs)due to their high mobility and flexible deployment.This paper focuses on a UAV-assisted wireless network,where users can be scheduled to get access to either an aerial BS or a terrestrial BS for uplink transmission.In contrast to state-of-the-art designs focusing on the instantaneous cost of the network,this paper aims at minimizing the long-term average transmit power consumed by the users by dynamically optimizing user association and power allocation in each time slot.Such a joint user association scheduling and power allocation problem can be formulated as a Markov decision process(MDP).Unfortunately,solving such an MDP problem with the conventional relative value iteration(RVI)can suffer from the curses of dimensionality,in the presence of a large number of users.As a countermeasure,we propose a distributed RVI algorithm to reduce the dimension of the MDP problem,such that the original problem can be decoupled into multiple solvable small-scale MDP problems.Simulation results reveal that the proposed algorithm can yield lower longterm average transmit power consumption than both the conventional RVI algorithm and a baseline algorithm with myopic policies.
