In this paper, we present an analytical model to determine the network connectivity probability of a linear vehicular ad hoc network (VANET) formed by communication equipped vehicles on a two-way street scenario. We c...In this paper, we present an analytical model to determine the network connectivity probability of a linear vehicular ad hoc network (VANET) formed by communication equipped vehicles on a two-way street scenario. We consider the highway to be consisting of two lanes with vehicles moving in both directions on these lanes and focus on the probability of being able to convey messages from a source vehicle to a destination vehicle, which may be multiple hops away. Closed form analytical expression is obtained for the network connectivity probability in the presence of Nakagami fading channel. In our model, the transmission range of each vehicle is modeled as a random variable due to channel fading. The analytical results are validated by extensive simulations.展开更多
Objective： To investigate functional connectivity within default mode network （DMN） and ex-ecutive control network （ECN） in vascular cognitive im-pairment, no dementia （VCIND）. Methods： Twenty-eight VCIND pati...Objective： To investigate functional connectivity within default mode network （DMN） and ex-ecutive control network （ECN） in vascular cognitive im-pairment, no dementia （VCIND）. Methods： Twenty-eight VCIND patients and sixteen healthy controls were recruit-ed. A seed-based connectivity analysis was performed us-ing data from resting-state functional magnetic resonance imaging （fMRI）. Based on previous fndings, posteriorcingulate cortex （PCC） and dorsolateral prefrontal cortex （DLPFC） were chosen as regions of interest to study these networks.One-sample t-test and two-sample t-test were used for statistical analysis. Results： Compared with thecontrols, the VCIND group exhibited increased functional activity in such DMN regions as the left inferior temporal gyrus, parahippocampal gyrus, and medial frontal gyrus. The VCIND group had decreased functional connectivity of DMN at right superior frontal gyrus, left mid-cingu-late area, the medial part of left superior frontal gyrus, and bilateral medial frontal gyrus. The VCIND group also showed decreased functional connectivity of ECN pri-marilyat left inferior parietal gyrus, right angular gyrus, right middle occipital gyrus, and right middle frontal cor-tex. Conclusions： Increased functional connectivity with-in DMN and decreased functional connectivity within ECN suggested dysfunction of these two networks, which mightbe associated with the cognitive defcitsin patients with VCIND. These fndingsmay help usunderstandthe pathogenesis and clinical characteristics of VCIND.展开更多
针对数据库查询优化中多表连接优化问题,任务是找到一个合适的连接顺序使查询执行计划最优,为此提出一种查询语句的嵌入表示方法SmartEncoder。通过优化查询语句中多表连接的嵌入表示信息,得到更丰富的关于连接的信息,将多表连接顺序选...针对数据库查询优化中多表连接优化问题,任务是找到一个合适的连接顺序使查询执行计划最优,为此提出一种查询语句的嵌入表示方法SmartEncoder。通过优化查询语句中多表连接的嵌入表示信息,得到更丰富的关于连接的信息,将多表连接顺序选择优化建模为深度强化学习问题,根据动作的概率分布选择连接,从过去的经验中学习,生成更好的查询执行计划。在Join Order Benchmark数据集上的实验结果表明,SmartEncoder能够有效提高查询的效率。展开更多
文摘In this paper, we present an analytical model to determine the network connectivity probability of a linear vehicular ad hoc network (VANET) formed by communication equipped vehicles on a two-way street scenario. We consider the highway to be consisting of two lanes with vehicles moving in both directions on these lanes and focus on the probability of being able to convey messages from a source vehicle to a destination vehicle, which may be multiple hops away. Closed form analytical expression is obtained for the network connectivity probability in the presence of Nakagami fading channel. In our model, the transmission range of each vehicle is modeled as a random variable due to channel fading. The analytical results are validated by extensive simulations.
文摘Objective： To investigate functional connectivity within default mode network （DMN） and ex-ecutive control network （ECN） in vascular cognitive im-pairment, no dementia （VCIND）. Methods： Twenty-eight VCIND patients and sixteen healthy controls were recruit-ed. A seed-based connectivity analysis was performed us-ing data from resting-state functional magnetic resonance imaging （fMRI）. Based on previous fndings, posteriorcingulate cortex （PCC） and dorsolateral prefrontal cortex （DLPFC） were chosen as regions of interest to study these networks.One-sample t-test and two-sample t-test were used for statistical analysis. Results： Compared with thecontrols, the VCIND group exhibited increased functional activity in such DMN regions as the left inferior temporal gyrus, parahippocampal gyrus, and medial frontal gyrus. The VCIND group had decreased functional connectivity of DMN at right superior frontal gyrus, left mid-cingu-late area, the medial part of left superior frontal gyrus, and bilateral medial frontal gyrus. The VCIND group also showed decreased functional connectivity of ECN pri-marilyat left inferior parietal gyrus, right angular gyrus, right middle occipital gyrus, and right middle frontal cor-tex. Conclusions： Increased functional connectivity with-in DMN and decreased functional connectivity within ECN suggested dysfunction of these two networks, which mightbe associated with the cognitive defcitsin patients with VCIND. These fndingsmay help usunderstandthe pathogenesis and clinical characteristics of VCIND.
文摘针对数据库查询优化中多表连接优化问题,任务是找到一个合适的连接顺序使查询执行计划最优,为此提出一种查询语句的嵌入表示方法SmartEncoder。通过优化查询语句中多表连接的嵌入表示信息,得到更丰富的关于连接的信息,将多表连接顺序选择优化建模为深度强化学习问题,根据动作的概率分布选择连接,从过去的经验中学习,生成更好的查询执行计划。在Join Order Benchmark数据集上的实验结果表明,SmartEncoder能够有效提高查询的效率。
