Cell-free massive multiple-input multipleoutput(MIMO)is a promising technology for future wireless communications,where a large number of distributed access points(APs)simultaneously serve all users over the same time...Cell-free massive multiple-input multipleoutput(MIMO)is a promising technology for future wireless communications,where a large number of distributed access points(APs)simultaneously serve all users over the same time-frequency resources.Since users and APs may locate close to each other,the line-of-sight(Lo S)transmission occurs more frequently in cell-free massive MIMO systems.Hence,in this paper,we investigate the cell-free massive MIMO system with Lo S and non-line-of-sight(NLo S)transmissions,where APs and users are both distributed according to Poisson point process.Using tools from stochastic geometry,we derive a tight lower bound for the user downlink achievable rate and we further obtain the energy efficiency(EE)by considering the power consumption on downlink payload transmissions and circuitry dissipation.Based on the analysis,the optimal AP density and AP antenna number that maximize the EE are obtained.It is found that compared with the previous work that only considers NLo S transmissions,the actual optimal AP density should be much smaller,and the maximized EE is actually much higher.展开更多
A metropolitan city such as Los Angeles (LA) is an ideal study site with a very high population density, and it houses at least 3 treatment plants where sewage is treated preliminarily and then progressing to tertiary...A metropolitan city such as Los Angeles (LA) is an ideal study site with a very high population density, and it houses at least 3 treatment plants where sewage is treated preliminarily and then progressing to tertiary treatment before discharging into the LA River. We will gain a better understanding of the water quality in the LA River and the nitrate load in the watershed system by examining the influence of waste water treatment plants (WWTPs). The goal of this study is to pinpoint the exact source of nitrate in the LA River using the isotope signatures. We have selected sampling locations both upstream and downstream of the WWTP. This serves to monitor nitrate levels, aiding in the assessment of treatment plant effectiveness, pinpointing nitrate pollution sources, and ensuring compliance with environmental regulations. The research explores the isotopic composition of NO3 in relation to atmospheric nitrogen and Vienna Standard Mean Ocean Water, shedding light on the contributions from various sources such as manure, sewage, soil organic nitrogen, and nitrogen fertilizers. Specifically, there is a change in the δ15NAir value between the dry and wet seasons. The isotope values in the Tillman WWTP sample changed between dry and wet seasons. Notably, the presence of nitrate originating from manure and sewage is consistent across seasons, emphasizing the significant impact of anthropogenic and agricultural activities on water quality. This investigation contributes to the broader understanding of nitrogen cycling in urban water bodies, particularly in the context of wastewater effluent discharge. The findings hold implications for water quality management and highlight the need for targeted interventions to mitigate the impact of nitrogen-containing compounds on aquatic ecosystems. Overall, the study provides a valuable framework for future research and environmental stewardship efforts aimed at preserving the health and sustainability of urban water resources. This data informs decisions regarding additional treatment or mitigation actions to safeguard downstream water quality and ecosystem health.展开更多
Visibility conditions between antennas,i.e.Line-of-Sight(LOS)and Non-Line-of-Sight(NLOS)can be crucial in the context of indoor localization,for which detecting the NLOS condition and further correcting constant posit...Visibility conditions between antennas,i.e.Line-of-Sight(LOS)and Non-Line-of-Sight(NLOS)can be crucial in the context of indoor localization,for which detecting the NLOS condition and further correcting constant position estimation errors or allocating resources can reduce the negative influence of multipath propagation on wireless communication and positioning.In this paper a Deep Learning(DL)model to classify LOS/NLOS condition while analyzing two Channel Impulse Response(CIR)parameters:Total Power(TP)[dBm]and First Path Power(FP)[dBm]is proposed.The experiments were conducted using DWM1000 DecaWave radio module based on measurements collected in a real indoor environment and the proposed architecture provides LOS/NLOS identification with an accuracy of more than 100%and 95%in static and dynamic senarios,respectively.The proposed model improves the classification rate by 2-5%compared to other Machine Learning(ML)methods proposed in the literature.展开更多
为解决船舶导航系统跟踪精度受限、艏向控制稳定性差等问题,提出船舶导航系统智能控制与优化方法。以船舶动力学模型为控制设计基础,运用视线(Line of Sight,LOS)导航算法,通过轨迹偏差计算期望艏向角,简化航迹控制为艏向角控制;引入坐...为解决船舶导航系统跟踪精度受限、艏向控制稳定性差等问题,提出船舶导航系统智能控制与优化方法。以船舶动力学模型为控制设计基础,运用视线(Line of Sight,LOS)导航算法,通过轨迹偏差计算期望艏向角,简化航迹控制为艏向角控制;引入坐标补偿策略,依据航段方位角差修正转向偏差,优化期望艏向角,减少航迹切换误差;以优化后的期望艏向角为线性自抗扰控制器(Linear Active Disturbance Rejection Controller,LADRC)输入,经扩张状态观测器(Extended State Observer,ESO)估计干扰并补偿后,结合比例-微分(Proportional-Derivative,PD)控制律输出信号控制舵机转向,实现船舶导航智能优化控制。实验结果显示,该方法的应用可以降低期望艏向角波动,避免航迹切换时艏向突变;使舵角输出更平稳,增强航向控制稳定性;获取贴近规划路径的导航路径,缩小航迹偏差。展开更多
Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,redu...Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,reducing the system's adaptability to high-speed reversal scanning and decreasing scanning efficiency.This study proposes a novel sinusoidal variable-speed roll scanning strategy,which reduces abrupt changes in speed and acceleration,minimizing time loss during reversals.Based on the forward image motion compensation strategy in the pitch direction,we establish a line-of-sight(LOS)position calculation model with vertical flight path correction(VFPC),ensuring that the central LOS of the scanned image remains stable on the same horizontal line,facilitating accurate image stitching in whisk-broom imaging.Through theoretical analysis and simulation experiments,the proposed method improves the scanning efficiency by approximately 18.6%at a 90o whiskbroom imaging angle under the same speed height ratio conditions.The new VFPC method enables wide-field,high-resolution imaging,achieving single-line LOS horizontal stability with an accuracy of better than O.4 mrad.The research is of great significance to promote the further development of airborne area-array whisk-broom imaging technology toward wider fields of view,higher speed height ratios,and greater scanning efficiency.展开更多
The article explores the pivotal moments,significant encounters,and lasting influences in the life of Austrian modernist composer Arnold Schoenberg,who spent his final 17 years in Los Angeles after fleeing Hitler’s E...The article explores the pivotal moments,significant encounters,and lasting influences in the life of Austrian modernist composer Arnold Schoenberg,who spent his final 17 years in Los Angeles after fleeing Hitler’s Europe with his family in 1933.As the United States’film capital and a city featured by the technological advancements of sound in cinema at that period,Los Angeles attracted numerous musicians,includingémigrés like Schoenberg.However,it also set limits on their professional aspirations.The article delves into Schoenberg’s legacy in the city and the efforts to preserve his memory within this cultural landscape.Through uncovering little-known,forgotten,or newly discovered facts about Schoenberg’s life,it reconstructs the vibrant cultural scene of early 20th-century Vienna and,more importantly,Los Angeles during the 1930s.The article also highlights the pedagogical aspect of Schoenberg’s activities,offering a holistic view of his multifaceted personality as a composer,artist,and teacher.展开更多
基金supported in part by the National Natural Science Foundation of China under Grant 62171231in part by the Jiangsu Provincial Key Research and Development Program(No.BE2020084-1)。
文摘Cell-free massive multiple-input multipleoutput(MIMO)is a promising technology for future wireless communications,where a large number of distributed access points(APs)simultaneously serve all users over the same time-frequency resources.Since users and APs may locate close to each other,the line-of-sight(Lo S)transmission occurs more frequently in cell-free massive MIMO systems.Hence,in this paper,we investigate the cell-free massive MIMO system with Lo S and non-line-of-sight(NLo S)transmissions,where APs and users are both distributed according to Poisson point process.Using tools from stochastic geometry,we derive a tight lower bound for the user downlink achievable rate and we further obtain the energy efficiency(EE)by considering the power consumption on downlink payload transmissions and circuitry dissipation.Based on the analysis,the optimal AP density and AP antenna number that maximize the EE are obtained.It is found that compared with the previous work that only considers NLo S transmissions,the actual optimal AP density should be much smaller,and the maximized EE is actually much higher.
文摘A metropolitan city such as Los Angeles (LA) is an ideal study site with a very high population density, and it houses at least 3 treatment plants where sewage is treated preliminarily and then progressing to tertiary treatment before discharging into the LA River. We will gain a better understanding of the water quality in the LA River and the nitrate load in the watershed system by examining the influence of waste water treatment plants (WWTPs). The goal of this study is to pinpoint the exact source of nitrate in the LA River using the isotope signatures. We have selected sampling locations both upstream and downstream of the WWTP. This serves to monitor nitrate levels, aiding in the assessment of treatment plant effectiveness, pinpointing nitrate pollution sources, and ensuring compliance with environmental regulations. The research explores the isotopic composition of NO3 in relation to atmospheric nitrogen and Vienna Standard Mean Ocean Water, shedding light on the contributions from various sources such as manure, sewage, soil organic nitrogen, and nitrogen fertilizers. Specifically, there is a change in the δ15NAir value between the dry and wet seasons. The isotope values in the Tillman WWTP sample changed between dry and wet seasons. Notably, the presence of nitrate originating from manure and sewage is consistent across seasons, emphasizing the significant impact of anthropogenic and agricultural activities on water quality. This investigation contributes to the broader understanding of nitrogen cycling in urban water bodies, particularly in the context of wastewater effluent discharge. The findings hold implications for water quality management and highlight the need for targeted interventions to mitigate the impact of nitrogen-containing compounds on aquatic ecosystems. Overall, the study provides a valuable framework for future research and environmental stewardship efforts aimed at preserving the health and sustainability of urban water resources. This data informs decisions regarding additional treatment or mitigation actions to safeguard downstream water quality and ecosystem health.
基金supported under ministry subsidy for research for Gdansk University of Technology。
文摘Visibility conditions between antennas,i.e.Line-of-Sight(LOS)and Non-Line-of-Sight(NLOS)can be crucial in the context of indoor localization,for which detecting the NLOS condition and further correcting constant position estimation errors or allocating resources can reduce the negative influence of multipath propagation on wireless communication and positioning.In this paper a Deep Learning(DL)model to classify LOS/NLOS condition while analyzing two Channel Impulse Response(CIR)parameters:Total Power(TP)[dBm]and First Path Power(FP)[dBm]is proposed.The experiments were conducted using DWM1000 DecaWave radio module based on measurements collected in a real indoor environment and the proposed architecture provides LOS/NLOS identification with an accuracy of more than 100%and 95%in static and dynamic senarios,respectively.The proposed model improves the classification rate by 2-5%compared to other Machine Learning(ML)methods proposed in the literature.
文摘为解决船舶导航系统跟踪精度受限、艏向控制稳定性差等问题,提出船舶导航系统智能控制与优化方法。以船舶动力学模型为控制设计基础,运用视线(Line of Sight,LOS)导航算法,通过轨迹偏差计算期望艏向角,简化航迹控制为艏向角控制;引入坐标补偿策略,依据航段方位角差修正转向偏差,优化期望艏向角,减少航迹切换误差;以优化后的期望艏向角为线性自抗扰控制器(Linear Active Disturbance Rejection Controller,LADRC)输入,经扩张状态观测器(Extended State Observer,ESO)估计干扰并补偿后,结合比例-微分(Proportional-Derivative,PD)控制律输出信号控制舵机转向,实现船舶导航智能优化控制。实验结果显示,该方法的应用可以降低期望艏向角波动,避免航迹切换时艏向突变;使舵角输出更平稳,增强航向控制稳定性;获取贴近规划路径的导航路径,缩小航迹偏差。
基金Supported by the National Key Research and Development Program(2023YFC3107602)。
文摘Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,reducing the system's adaptability to high-speed reversal scanning and decreasing scanning efficiency.This study proposes a novel sinusoidal variable-speed roll scanning strategy,which reduces abrupt changes in speed and acceleration,minimizing time loss during reversals.Based on the forward image motion compensation strategy in the pitch direction,we establish a line-of-sight(LOS)position calculation model with vertical flight path correction(VFPC),ensuring that the central LOS of the scanned image remains stable on the same horizontal line,facilitating accurate image stitching in whisk-broom imaging.Through theoretical analysis and simulation experiments,the proposed method improves the scanning efficiency by approximately 18.6%at a 90o whiskbroom imaging angle under the same speed height ratio conditions.The new VFPC method enables wide-field,high-resolution imaging,achieving single-line LOS horizontal stability with an accuracy of better than O.4 mrad.The research is of great significance to promote the further development of airborne area-array whisk-broom imaging technology toward wider fields of view,higher speed height ratios,and greater scanning efficiency.
文摘The article explores the pivotal moments,significant encounters,and lasting influences in the life of Austrian modernist composer Arnold Schoenberg,who spent his final 17 years in Los Angeles after fleeing Hitler’s Europe with his family in 1933.As the United States’film capital and a city featured by the technological advancements of sound in cinema at that period,Los Angeles attracted numerous musicians,includingémigrés like Schoenberg.However,it also set limits on their professional aspirations.The article delves into Schoenberg’s legacy in the city and the efforts to preserve his memory within this cultural landscape.Through uncovering little-known,forgotten,or newly discovered facts about Schoenberg’s life,it reconstructs the vibrant cultural scene of early 20th-century Vienna and,more importantly,Los Angeles during the 1930s.The article also highlights the pedagogical aspect of Schoenberg’s activities,offering a holistic view of his multifaceted personality as a composer,artist,and teacher.
