With the deployment of ultra-dense low earth orbit(LEO)satellite constellations,LEO satellite access network(LEO-SAN)is envisioned to achieve global Internet coverage.Meanwhile,the civil aviation communications have i...With the deployment of ultra-dense low earth orbit(LEO)satellite constellations,LEO satellite access network(LEO-SAN)is envisioned to achieve global Internet coverage.Meanwhile,the civil aviation communications have increased dramatically,especially for providing airborne Internet services.However,due to dynamic service demands and onboard LEO resources over time and space,it poses huge challenges in satellite-aircraft access and service management in ultra-dense LEO satellite networks(UDLSN).In this paper,we propose a deep reinforcement learning-based approach for ultra-dense LEO satellite-aircraft access and service management.Firstly,we develop an airborne Internet architecture based on UDLSN and design a management mechanism including medium earth orbit satellites to guarantee lightweight management.Secondly,considering latency-sensitive and latency-tolerant services,we formulate the problem of satellite-aircraft access and service management for civil aviation to ensure service continuity.Finally,we propose a proximal policy optimization-based access and service management algorithm to solve the formulated problem.Simulation results demonstrate the convergence and effectiveness of the proposed algorithm with satisfying the service continuity when applying to the UDLSN.展开更多
There is still a dearth of systematic study on picture stitching techniques for the natural tubular structures of intestines,and traditional stitching techniques have a poor application to endoscopic images with deep ...There is still a dearth of systematic study on picture stitching techniques for the natural tubular structures of intestines,and traditional stitching techniques have a poor application to endoscopic images with deep scenes.In order to recreate the intestinal wall in two dimensions,a method is developed.The normalized Laplacian algorithm is used to enhance the image and transform it into polar coordinates according to the characteristics that intestinal images are not obvious and usually arranged in a circle,in order to extract the new image segments of the current image relative to the previous image.The improved weighted fusion algorithm is then used to sequentially splice the segment images.The experimental results demonstrate that the suggested approach can improve image clarity and minimize noise while maintaining the information content of intestinal images.In addition,the method's seamless transition between the final portions of a panoramic image also demonstrates that the stitching trace has been removed.展开更多
Achieving conservation goals in natural habitats requires a balanced approach that integrates both sustainable community development and nature conservation,rather than completely excluding human activities from wilde...Achieving conservation goals in natural habitats requires a balanced approach that integrates both sustainable community development and nature conservation,rather than completely excluding human activities from wilderness areas.However,limited understanding exists regarding locals'willingness to participate(WTP)in the construction and stewardship of national parks as well as their driving factors behind this willingness.To identify the key drivers that promote locals'WTP in national parks,we investigated local residents'participation willingness and embedded an additional structure perceived value(PV)into the Theory of Planned Behavior(TPB)model,analyzing the data by using structural equation modeling.Local communities were slightly willing to participate in Changtang National Park and conservation in general;interestingly,nomads'willingness was stronger than settlers'.Perceived behavioral control(PBC)exhibited the most significant impact on WTP,with particular emphasis on the livelihood risks associated with grasslands.PV indirectly influenced WTP by affecting attitude(ATT),personal/social norms(PSN),and PBC,while it did not have a direct impact on WTP.For settlers and nomads,different variables influence their varying levels of willingness to engage in park participation.These results deepen our understanding of community willingness to participate and differences in drivers of WTP between settlers and nomads,contributing to relevant knowledge to inform seeking a balance between sustainable community development and nature conservation.展开更多
脑和肌肉组织芳香烃受体核转运蛋白的类似蛋白1(brain and muscle Arnt-like protein 1,Bmal1)是生物钟的核心元件之一,常呈现出昼夜节律性表达。Bmal1在肿瘤中的作用及其调控机制复杂多样,目前研究显示Bmal1可以受多种信号通路的正负...脑和肌肉组织芳香烃受体核转运蛋白的类似蛋白1(brain and muscle Arnt-like protein 1,Bmal1)是生物钟的核心元件之一,常呈现出昼夜节律性表达。Bmal1在肿瘤中的作用及其调控机制复杂多样,目前研究显示Bmal1可以受多种信号通路的正负反馈性调控,通过调控原癌基因和抑癌基因与某些信号通路发生相互作用,从而在肿瘤的发生发展过程中发挥抑癌或促癌的作用。此外,Bmal1也可以被表观遗传调控因子调控进而影响其表达。Bmal1的表达会影响化疗药物的敏感性,因此,针对个性化治疗,Bmal1可以作为直接分子目标确定最佳药物管理时间,从而提高抗癌药物的疗效。本文主要综述Bmal1在不同肿瘤中发挥的作用及其调控机制。展开更多
A novel quantitative cellular automata (CA) model that simulates and predicts hillslope runoff and soil erosion caused by rainfall events was developed by integrating the local interaction rules and the hillslope surf...A novel quantitative cellular automata (CA) model that simulates and predicts hillslope runoff and soil erosion caused by rainfall events was developed by integrating the local interaction rules and the hillslope surface hydraulic processes. In this CA model, the hillslope surface was subdivided into a series of discrete spatial cells with the same geometric features. At each time step, water and sediment were transported between two adjacent spatial cells. The flow direction was determined by a combination of water surface slope and stochastic assignment. The amounts of interchanged water and sediment were computed using the Chezy-Manning formula and the empirical sediment transport equation. The water and sediment discharged from the open boundary cells were considered as the runoff and the sediment yields over the entire hillslope surface. Two hillslope soil erosion experiments under simulated rainfall events were carried out. Cumulative runoff and sediment yields were measured, respectively. Then, the CA model was applied to simulate the water and soil erosion for these two experiments. Analysis of simulation results indicated that the size of the spatial cell, hydraulic parameters, and the setting of time step and iteration times had a large impact on the model accuracy. The comparison of the simulated and measured data suggested that the CA model was an applicable alternate for simulating the hillslope water flow and soil erosion.展开更多
基金supported in part by the National Key R&D Program of China under Grant 2020YFB1806104in part by Innovation and Entrepreneurship of Jiangsu Province High-level Talent Program+1 种基金in part by Natural Sciences and Engineering Research Council of Canada (NSERC)the support from Huawei
文摘With the deployment of ultra-dense low earth orbit(LEO)satellite constellations,LEO satellite access network(LEO-SAN)is envisioned to achieve global Internet coverage.Meanwhile,the civil aviation communications have increased dramatically,especially for providing airborne Internet services.However,due to dynamic service demands and onboard LEO resources over time and space,it poses huge challenges in satellite-aircraft access and service management in ultra-dense LEO satellite networks(UDLSN).In this paper,we propose a deep reinforcement learning-based approach for ultra-dense LEO satellite-aircraft access and service management.Firstly,we develop an airborne Internet architecture based on UDLSN and design a management mechanism including medium earth orbit satellites to guarantee lightweight management.Secondly,considering latency-sensitive and latency-tolerant services,we formulate the problem of satellite-aircraft access and service management for civil aviation to ensure service continuity.Finally,we propose a proximal policy optimization-based access and service management algorithm to solve the formulated problem.Simulation results demonstrate the convergence and effectiveness of the proposed algorithm with satisfying the service continuity when applying to the UDLSN.
基金the Special Research Fund for the Natural Science Foundation of Chongqing(No.cstc2019jcyjmsxm1351)the Science and Technology Research Project of Chongqing Education Commission(No.KJQN2020006300)。
文摘There is still a dearth of systematic study on picture stitching techniques for the natural tubular structures of intestines,and traditional stitching techniques have a poor application to endoscopic images with deep scenes.In order to recreate the intestinal wall in two dimensions,a method is developed.The normalized Laplacian algorithm is used to enhance the image and transform it into polar coordinates according to the characteristics that intestinal images are not obvious and usually arranged in a circle,in order to extract the new image segments of the current image relative to the previous image.The improved weighted fusion algorithm is then used to sequentially splice the segment images.The experimental results demonstrate that the suggested approach can improve image clarity and minimize noise while maintaining the information content of intestinal images.In addition,the method's seamless transition between the final portions of a panoramic image also demonstrates that the stitching trace has been removed.
基金National Natural Science Foundation of China,No.42142022。
文摘Achieving conservation goals in natural habitats requires a balanced approach that integrates both sustainable community development and nature conservation,rather than completely excluding human activities from wilderness areas.However,limited understanding exists regarding locals'willingness to participate(WTP)in the construction and stewardship of national parks as well as their driving factors behind this willingness.To identify the key drivers that promote locals'WTP in national parks,we investigated local residents'participation willingness and embedded an additional structure perceived value(PV)into the Theory of Planned Behavior(TPB)model,analyzing the data by using structural equation modeling.Local communities were slightly willing to participate in Changtang National Park and conservation in general;interestingly,nomads'willingness was stronger than settlers'.Perceived behavioral control(PBC)exhibited the most significant impact on WTP,with particular emphasis on the livelihood risks associated with grasslands.PV indirectly influenced WTP by affecting attitude(ATT),personal/social norms(PSN),and PBC,while it did not have a direct impact on WTP.For settlers and nomads,different variables influence their varying levels of willingness to engage in park participation.These results deepen our understanding of community willingness to participate and differences in drivers of WTP between settlers and nomads,contributing to relevant knowledge to inform seeking a balance between sustainable community development and nature conservation.
文摘近年来,抑郁症(major depressive disorder,MDD)与注意缺陷多动障碍(attention deficit hyperactivity disorder,ADHD)共病的现象愈发受到关注。在成人患者中,MDD共病ADHD通常意味着治疗费用高昂、药物反应欠佳以及疾病预后不良,且现有药物治疗存在一定局限性。考虑到执行功能障碍作为MDD和ADHD的关键共同特征,从执行功能层面出发,探讨共病在脑影像学方面的潜在机制,并寻求更为有效的治疗方法,显得尤为重要。近年来的研究表明,经颅直流电刺激(transcranial direct current stimulation,tDCS)作为一种能够调节特定脑区活动的非侵入性物理治疗方法,可有效改善MDD及成人ADHD的相关症状。该文回顾成人MDD共病ADHD所面临的治疗困境,从与执行功能相关的脑结构、脑功能网络等多个维度,综述成人MDD共病ADHD的可能机制,同时探讨了tDCS在治疗成人MDD共病ADHD的应用前景。
文摘脑和肌肉组织芳香烃受体核转运蛋白的类似蛋白1(brain and muscle Arnt-like protein 1,Bmal1)是生物钟的核心元件之一,常呈现出昼夜节律性表达。Bmal1在肿瘤中的作用及其调控机制复杂多样,目前研究显示Bmal1可以受多种信号通路的正负反馈性调控,通过调控原癌基因和抑癌基因与某些信号通路发生相互作用,从而在肿瘤的发生发展过程中发挥抑癌或促癌的作用。此外,Bmal1也可以被表观遗传调控因子调控进而影响其表达。Bmal1的表达会影响化疗药物的敏感性,因此,针对个性化治疗,Bmal1可以作为直接分子目标确定最佳药物管理时间,从而提高抗癌药物的疗效。本文主要综述Bmal1在不同肿瘤中发挥的作用及其调控机制。
基金Project supported by the National Science Fund for Distinguished Young Scholars of China (No. 40225004)the National Natural Science Foundation of China (No. 40471048)
文摘A novel quantitative cellular automata (CA) model that simulates and predicts hillslope runoff and soil erosion caused by rainfall events was developed by integrating the local interaction rules and the hillslope surface hydraulic processes. In this CA model, the hillslope surface was subdivided into a series of discrete spatial cells with the same geometric features. At each time step, water and sediment were transported between two adjacent spatial cells. The flow direction was determined by a combination of water surface slope and stochastic assignment. The amounts of interchanged water and sediment were computed using the Chezy-Manning formula and the empirical sediment transport equation. The water and sediment discharged from the open boundary cells were considered as the runoff and the sediment yields over the entire hillslope surface. Two hillslope soil erosion experiments under simulated rainfall events were carried out. Cumulative runoff and sediment yields were measured, respectively. Then, the CA model was applied to simulate the water and soil erosion for these two experiments. Analysis of simulation results indicated that the size of the spatial cell, hydraulic parameters, and the setting of time step and iteration times had a large impact on the model accuracy. The comparison of the simulated and measured data suggested that the CA model was an applicable alternate for simulating the hillslope water flow and soil erosion.
