Abstract:With the increase in urbanization and energy consumption, PM 2.5 has become a major pollutant. This paper investigates the impact of road patterns on PM 2.5 pollution in Beijing, focusing on two questions: Do road patterns significantly affect PM 2.5 concentrations? How do road patterns affect PM 2.5 concentrations? A land-use regression model (LUR model) is used to quantify the associations between PM 2.5 concentrations, and road patterns, land-use patterns, and population density. Then, in the condition of excluding other factors closely correlated to PM 2.5 concentrations, based on the results of the regression model, further research is conducted to explore the relationship between PM 2.5 concentrations and the types, densities, and layouts of road networks, through the controlling variables method. The results are as follows: (1) the regression coefficient of road patterns is significantly higher than the water area, population density, and transport facilities, indicating that road patterns have an obvious influence on PM 2.5 concentrations; (2) under the same traffic carrying capacity, the layout of "a tight network of streets and small blocks" is superior to that of "a sparse network of streets and big blocks"; (3) the grade proportion of urban roads impacts the road patterns' rationality, and a high percentage of branch roads and secondary roads could decrease PM 2.5 concentrations. These findings could provide a reference for the improvement of the traffic structure and air quality of Beijing.

Purpose – Ancient city walls are typical linear space elements of Beijing that represent the transformation of urban form over the past 800 years and have greatly influenced the memory of the entire city. However, recently, most of the walls have been torn down in the process of fast urbanization and old city renewal. The purpose of this paper is to focus on people’s cognition and evaluation of urban memory during this pull-down-and-preserve process. Design/methodology/approach – A sample of 380 participants was investigated on a number of issues using questionnaires, including memory case reminders (stability, variability, temporality), emotional bonding with memory case (identity, dependence, authenticity), and socio-demographic variables (age, education, life experience, length of residence). The urban memory cognition model and attitude evaluation value model which were based on Likert scale were used to process the collected data. Findings – In the three aspects of memory case reminders, stability and temporary elements can be most cognized, whereas variability elements are more difficult due to their change over time. As for emotional bonding with memory case, people show a high level of identification with the walls; the walls’ memory being passed down could enhance people’s memory when mentioning Beijing. Further, higher education groups consider the walls’ authenticity to be most important and are unwilling to accept the outcome of walls-ruins parks; older adults have tolerant attitudes to the ruins parks. Originality/value – This study could not only contribute to the excavation of urban memory, but also strengthen citizens’ sense of identity and cohesiveness, thus shaping the spirit and culture of the city. Some findings could provide applicable guidelines for urban heritage protection and contribute a new perspective on the interrelationship between people and their physical surroundings.