Accommodation of lattice mismatch in Ge_(x)Si_(1−x)/Si superlattices

We present evidence that the critical thickness for the appearance of misfit defects in a given material and heteroepitaxial structure is not simply a function of lattice mismatch. We report substantial differences in the relaxation of mismatch stress in Ge_(0.5)Si_(0.5)/Si superlattices grown at different temperatures on (100) Si substrates. Samples have been analyzed by x‐ray diffraction, channeled Rutherford backscattering, and transmission electron microscopy. While a superlattice grown at 365 °C demonstrates a high degree of elastic strain, with a dislocation density <10^5 cm^(−2) , structures grown at higher temperatures show increasing numbers of structural defects, with densities reaching 2×10^(10) cm^(−2) at a growth temperature of 530 °C. Our results suggest that it is possible to freeze a lattice‐mismatched structure in a highly strained metastable state. Thus it is not surprising that experimentally observed critical thicknesses are rarely in agreement with those predicted by equilibrium theories

Route Segment Level Analysis of Bus Safety Incidents

This paper analyzes collision and non-collision incidents that occurred on TriMet’s bus system over a near two-year period. The bus route network was decomposed into stop and line haul segments, and a typology of models was estimated from segment level incident, risk exposure, and roadway feature data. The frequency of non-collision incidents – mainly slips, trips and falls – was estimated to be primarily related to associated risk exposure variables. The frequency of collision incidents was also estimated to be related to risk exposure variables, as well as a number of roadway design variables. The findings serve as an initial step in informing the safety planning process

Review essay: Anthony Howe. Byron and the Forms of Thought (Liverpool: Liverpool UP, 2013) and Carla Pomare. Byron and the Discourse of History (Farnham and Burlington: Ashgate, 2013).

This essay is a comparative review of two recently published books in Byron studies: Anthony Howe's Byron and the Forms of Thought (Liverpool: Liverpool UP, 2013) and Carla Pomare's Byron and the Discourse of History (Farnham and Burlington: Ashgate, 2013)

The Oregon DOT Slow-Speed Weigh-In--Motion (SWIM) Project: Final Report

Weigh-in-motion (WIM) systems have provided an effective means of data collection for pavement research and facility design, traffic monitoring, and weight enforcement for over 40 years. In weight enforcement, WIM systems have been increasingly used to screen potentially overweight vehicles. Vehicles that exceed weight limits as measured on a WIM scale are then weighed on a static scale, which is subject to accuracy standards specified by the National Institute of Standards and Technology (1998). The use of WIM for screening purposes reduces queuing at weigh stations, resulting in considerable savings for both truckers and enforcement agencies. To date, however, WIM systems have not been certified for direct applications to weight enforcement

An Evaluation of Automatic Passenger Counters: Validation, Sampling, and Statistical Inference

While automatic passenger counters (APC\u27s) offer the potential for cait effective data recovery and management, they also introduce new complications in the data recovery process. This report addresses three issues associated with the implementation of APC\u27s, based on an evaluation of the recent experiences of the Tri-County Metropolitan Transportation District of Oregon (Tri-Met). First is the issue of validation, which is concerned with both the recovery and accuracy of APC passenger data. The second issue concerns the development of a sampling methodology for APC\u27s compatible with UMTA\u27s Section 15 reporting requirements. Third is the issue of inferring system-level ridership from sample data in the presence of selective APC failures. We find that the APC\u27s are providing systematically accurate passenger counts. Analysis of the data recovered from September to November 1988 also shows that sampling was representative, based on the set of trains from which ridership data were successfully recovered. The initial selection/assignment of trains, however, was not representative. Given that APC\u27s record operating data for all bus trips comprising a train assignment, a cluster sampling method is formulated that ensures an overall random selection of bus trips via a random first stage selection of trains. Selective data recovery failures can hamper the process of inferring system-level ridership from the sample estimates. For example, when failure rates vary by bus type or time of day, inferences drawn from the sample of recovered data may over or under-represent total system ridership. In such circumstances, post hoc stratification of the sample data may be required. We outline several alternative corrections based on a-priori knowledge of the mix of bus types and schedule characteristics in the system

A Ranking of U.S. Graduate Programs in Urban Studies and Urban Affairs

A ranking of 33 Urban Studies and Urban Affairs graduate programs in the U.S. is developed from peer ratings obtained in a program survey and from citation activity reported in the Social Sciences Citation Index over the 1986-89 period. In addition, a breakdown of citations by broadly defined subject areas is presented. The survey revealed a difference between Ph.D. and MUS/MA programs in the perceived relative importance of peer evaluation and citations as rating criteria. The survey results also indicate that the degree of familiarity with other programs is lower than what has been observed in most social science disciplines

Analysis of Transit Fare Evasion in the Rose Quarter

Tri-Met collected fare evasion data for buses and MAX trains passing outbound through the Rose Quarter Monday, June 11 through Saturday, July 7. Beginning September 2001, Tri-Met’s “Fareless Square’s” free zone was extended towards the Lloyd District, with an eastern boundary of NE 14th. Prior to this, all trips between the Central Business District and Lloyd Center required a full Zone 1 fare

Talking in the present, caring for the future: Language and environment

This paper identifies a new source that explains environmental behaviour: the presence of future tense marking in language. We predict that languages that grammatically mark the future affect speakers' intertemporal preferences and thereby reduce their willingness to address environmental problems. We first show that speakers of languages with future tense marking are less likely to adopt environmentally responsible behaviours and to support policies to prevent environmental damage. We then document that this effect holds across countries: future tense marking is an important determinant of climate change policies and global environmental cooperation. The results suggest that there may be deep and surprising obstacles for attempts to address climate change