A significant advance toward achieving practical applications of graphene as a two-dimensional material in nanoelectronics would be provided by successful synthesis of both n-type and p-type doped graphene. However, reliable doping and a thorough understanding of carrier transport in the presence of charged impurities governed by ionized donors or acceptors in the graphene lattice are still lacking. Here we report experimental realization of few-layer nitrogen-doped (N-doped) graphene sheets by chemical vapor deposition of organic molecule 1,3,5-triazine on Cu metal catalyst. When reducing the growth temperature, the atomic percentage of nitrogen doping is raised from 2.1% to 5.6%. With increasing doping concentration, N-doped graphene sheet exhibits a crossover from p-type to n-type behavior accompanied by a strong enhancement of electron-hole transport asymmetry, manifesting the influence of incorporated nitrogen impurities. In addition, by analyzing the data of X-ray photoelectron spectroscopy, Raman spectroscopy, and electrical measurements, we show that pyridinic and pyrrolic N impurities play an important role in determining the transport behavior of carriers in our N-doped graphene sheets.

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This study analyses empirically how built environment affects school travel with a focus on independence from adults and travel mode. Students in three elementary schools—Chinan, Jingmei and Xinhwa—in Taipei’s Wenshan District are analysed after questionnaire surveys. The survey data are analysed using nested logit models at two decision levels. Analytical results indicate that high shade-tree density and high sidewalk coverage encourage children to walk to school independently, while large block sizes and increased intersection numbers discourage children from walking to school independently. Furthermore, although high building density, high vehicle density and diversified mode option encourage children to travel home after school by walking, bus or vanpool, block size and road width discourage children from so doing. These results are mostly similar to the findings of previous studies, although they also have some differences. Based on the empirical evidence presented in this study, three strategies are recommended for reshaping the built environment in Taipei: compact structure, pedestrian-friendly design and frequent bus services.

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Since the development of Taipei subway system, which represented a new type of infrastructure in Taiwan, various studies have conducted with-and-without comparisons before the opening of the subway systems. However, this study compared property prices before and after the opening of the Taipei subway system. Samples along the subway red line were selected and investigated for two periods: 1993–1995 AC. (before subway opening) and 1997–1999AC. (after subway opening ). The samples were analyzed using multiple regression, Chow test, and fuzzy regression. Based on the empirical analysis, the following conclusions can be reached: First, subway opening significantly influences hedonic prices of floor space, building age, and distance from public facilities (schools or parks). Second, the influences of subway system opening on hedonic price varies significantly according to different submarkets such as subway construction , location in city, position of property relative to subway stations, land use zoning, and building type. Third, both traditional regression and Tanaka et al. (1980) fuzzy regression are useful, but generally, traditional regression is more persuasive than the other regression in analyzing hedonic prices. The analysis abilities of other fuzzy regression methods still need to be explored. Copyright Springer-Verlag 2004

The compact-city paradigm has received increased attention worldwide for its ability to achieve sustainable development. However, the claim that the compact-city paradigm contributes to sustainability has not been sufficiently verified. In this study we evaluate how major concepts in the compact-city paradigm affect urban sustainability. Correspondingly, the complementary strategies for facilitating compact-city progress are recommended. Structural equation modeling was applied to ninety-two samples of medium-sized or small-sized cities in Taiwan. Latent variables and observed variables were analyzed in the model's structure. According to the results a high-density pattern and intensification negatively affect the environmental and social sustainability, but positively affect economic sustainability. Furthermore, mixture of land use is beneficial to economic sustainability, and does not significantly affect environmental or social sustainability. On the basis of the empirical results, strategies that guide the compact-city paradigm toward the goals of sustainability are also proposed.

This study empirically examines the connections between urban form and travel demand at the aggregate level using traffic analysis zone data from Taipei, Taiwan, for the year 2000. Nine latent variables and 26 observed variables were analysed using structural equation modelling. By clarifying the direct and indirect effects, the empirical evidence indicates that density is positively related to trip generation and negatively associated with private mode split; mixed land use reduces trip generation and indirectly increases private mode split and a pedestrian-friendly built environment significantly reduces private mode split. Empirical evidence indicates that land use density, diversity and design affect travel demand in urban areas both directly and indirectly.