Design of reinforcement learning for perimeter control using network transmission model based macroscopic traffic simulation.

Perimeter control is an emerging alternative for traffic signal control, which regulates the traffic flows on the periphery of a road network. Some model-based approaches have been suggested earlier for the optimization of perimeter control based on macroscopic fundamental diagrams (MFDs). However, there are several limitations when considering their application to a large-scale urban area because the model-based approaches may not be scalable to multiple regions and inappropriate for handling various effects caused by the shape change of MFDs. Therefore, we propose a model-free and data-driven approach that combines reinforcement learning (RL) with the macroscopic traffic simulation based on the recently developed network transmission model. First, we design four perimeter control models with different macroscopic traffic variables and parametrizations. Then, we validate the proposed models by evaluating their performances with the test demand scenarios at different levels. The validation results show that the model containing travel demand information adapts to a new demand scenario better than the model containing only density-related factors.

A Study on the Characteristics of Infrequent and Frequent Outpatients Visiting Korean Traditional Medical Facilities.

OBJECTIVES: This study was intended to analyze the characteristics of infrequent and frequent outpatients visiting Korean medical facilities, and find the related variables of frequent users. METHODS: The data source was the Report on the Usage and Consumption of Korean Medicine (2011) published by the Ministry of Health and Welfare and Korea Institute for Health and Social Affairs. We analyzed outpatient data using SAS 9.2. RESULTS: As much as 46.6% of the patients used Korean medical services over 11 times in 3 months. The proportion of frequent users increased depending on age, and their proportion was high in the low-income and low-education group. People with musculoskeletal disease, stroke, hypertension, and obesity were more likely to use Korean medical services. In general, patients were satisfied with their treatment, with frequent outpatients being more satisfied than infrequent outpatients. In logistic regression analysis, age and musculoskeletal disease were significant determinants of frequency of use of Korean medical services. CONCLUSION: Age, musculoskeletal disease, and specific diseases were highly associated with frequent Korean medical utilization.

A case of infected left atrial myxoma with concomitant mitral valve endocarditis.

Myxoma is the most common primary tumor in the heart. Cardiac myxomas can present in various manners including embolization and fever, sometimes simulating endocarditis. However, they are rarely infected. We report here a case of an infected left atrial myxoma that seeded a normal mitral valve and atypically presented with multiple embolic events in the lower extremities along with multiple splenic and a cerebellar infarction.