Hedonic Value of Transit Accessibility: An Empirical Analysis in a Small Urban Area

Many programs of the SAFETEA-LU have pointed to improving transit services and individuals' accessibility in small urban areas. Urban economic theory suggests that improving accessibility by investing in transportation has the potential to drive up bids for land. However, will the improved transit accessibility in small urban areas increase property values? A number of studies have investigated the impact of rail transit on home sales but produced mixed results. Further, few studies have explored how transit influences the lease rate of apartments. This question is more relevant because transit accessibility tends to have a greater impact on apartment dwellers than home owners. Using about 400 apartment dwellers in Fargo, North Dakota, this study developed a hedonic price model to determine implicit price of proximity to bus routes. We found a negative impact of bus transit on apartment rent after controlling for other factors, however. We speculated that in a small urban area, this negative relationship could be mainly attributable to spurious relationships from other causal factors, as well as nuisance effects of bus transit itself

Antifouling Properties of Smooth and Structured Polyelectrolyte Thin Films

The goal of this thesis is the development of smooth and structured polyelectrolyte surfaces and to correlate the surface properties with their antifouling performance. Strategies in antifouling are focused on two aspects: surface chemistry and surface topography. Therefore, two types of surfaces, polysaccharide coatings with different chemistries and poly(acrylic acid)/polyethylenimine multilayers with different topographies, have been studied in this thesis. Three polysaccharides, hyaluronic acid (HA), alginic acid (AA) and pectic acid (PA), were covalently coupled on glass or silicon surfaces. The results of protein adsorption tests on these coatings indicate that surface charge, molecular conformation and reaction with calcium play important roles in the interactions between polysaccharides and proteins. The settlements of bacteria (Pseudomonas fluorescens, Vibrioalginolyticus, Cobetia marina and Marinobacter hydrocarbonoclasticus ), algae (Navicula perminuta and Ulva linza) and invertebrate cyprids (Balanus amphitrite) on polysaccharide coatings reveal that surface properties such as wettability, swelling in water and interactions with ions have great influence on biofouling. Polyelectrolyte multilayers were applied to study the effect of topography on marine biofouling. These multilayers were constructed by the deposition of the oppositely charged polyelectrolytes, poly(acrylic acid) (PAA) and polyethylenimine (PEI) through a layer-by-layer spray coating method. Hierarchical surface structures with different texture sizes and roughnesses were obtained by adjusting the pH of the polyelectrolyte solutions. Settlement of Ulva spores and barnacle cyprids was remarkably reduced by the multilayers with large texture size and high roughness. The effect of topography on biofouling is related to the attachment points between the surface and the fouling organisms. Surface modifications on polyelectrolyte multilayers with fluorinated silane and poly(ethylene glycol) (PEG) combined topography and chemistry. The antifouling performance of modified multilayers was determined by both the topography of the multilayer film and the chemistry of the surface. Several techniques were applied to analyze the surface properties of the coatings, including contact angle measurement, spectral ellipsometry, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM)

"Preference in IRL" - What Does It Mean?

Many studies these days attempt to find a solution to this problem, however, the true definition of “preference” still remains ambiguous. Almost all of the works out there lack a clear explanation of what “preference” actually means in a real world context. At the high level, our study aims to define human preference as the cause of the difference in understanding of the environment between human and the agent. We also prove that, under some environmental settings, preference cannot exist, thus cannot be learned.In this work, we propose a method which serves the purpose of evaluating whether that preference is compatible with the environment, and whether it is safe to be applied. We start with defining threshold values that each serves a different purpose. These values will be used later on as the metrics to evaluate preference, in which the human demonstration can be suboptimal with respect to the current environment