Some Stability Results for Markovian Economic Semigroups

The paper studies existence, uniqueness and stability of stationary equilibrium distributions in a class of stochastic dynamic models common to economic analysis. The stability conditions provided are suitable for treating multi-sector models and nonlinear time series models with unbounded state.Markov processes, asymptotic stability, semigroups

Routing in a many-to-one communication scenario in a realistic VDTN

In this paper, we evaluate and compare the performance of different routing protocols in a many-to-one communication within a Vehicular Delay Tolerant Network (VDTN). Seven groups with three stationary sensor nodes sense the temperature, humidity and wind speed and send these data to a stationary destination node that collect them for statistical and data analysis purposes. Vehicles moving in Tirana city roads in Albania during the opportunistic contacts will exchange the sensed data to destination node. The simulations are conducted with the Opportunistic Network Environment (ONE) simulator. For the simulations we considered two different scenarios where the distance of the source nodes from the destination is short and long. For both scenarios the effect of node density, ttl and node movement model is evaluated. The performance is analyzed using delivery probability, overhead ratio, average latency, average number of hops and average buffer time metrics. The simulation results show that the increase of node density increases the delivery probability for all protocols and both scenarios, and better results are achieved when shortest-path map-based movement model is used. The increase of ttl slightly affects the performance of all protocols. By increasing the distance between source nodes and destination node, delivery probability is decreased almost 10% for all protocols, the overhead for sprayandwait protocol does not change, but for other protocols is slightly increased and the average number of hops and average latency is increased.Peer ReviewedPostprint (author's final draft

Can climate models capture the structure of extratropical cyclones?

Composites of wind speeds, equivalent potential temperature, mean sea level pressure, vertical velocity, and relative humidity have been produced for the 100 most intense extratropical cyclones in the Northern Hemisphere winter for the 40-yr ECMWF Re-Analysis (ERA-40) and the high resolution global environment model (HiGEM). Features of conceptual models of cyclone structure—the warm conveyor belt, cold conveyor belt, and dry intrusion—have been identified in the composites from ERA-40 and compared to HiGEM. Such features can be identified in the composite fields despite the smoothing that occurs in the compositing process. The surface features and the three-dimensional structure of the cyclones in HiGEM compare very well with those from ERA-40. The warm conveyor belt is identified in the temperature and wind fields as a mass of warm air undergoing moist isentropic uplift and is very similar in ERA-40 and HiGEM. The rate of ascent is lower in HiGEM, associated with a shallower slope of the moist isentropes in the warm sector. There are also differences in the relative humidity fields in the warm conveyor belt. In ERA-40, the high values of relative humidity are strongly associated with the moist isentropic uplift, whereas in HiGEM these are not so strongly associated. The cold conveyor belt is identified as rearward flowing air that undercuts the warm conveyor belt and produces a low-level jet, and is very similar in HiGEM and ERA-40. The dry intrusion is identified in the 500-hPa vertical velocity and relative humidity. The structure of the dry intrusion compares well between HiGEM and ERA-40 but the descent is weaker in HiGEM because of weaker along-isentrope flow behind the composite cyclone. HiGEM’s ability to represent the key features of extratropical cyclone structure can give confidence in future predictions from this model

The Bellingham Centennial, Local History, and the University

Local and academic historians seemingly stand on two sides of a ravine. The former focus on local pioneers and old buildings. Practitioners of local history often have little formal training in the academic discipline of history. Some are not interested in the work of academic historians, because they believe too little of it relates directly to places they know and about which they care deeply. On the other side of the ravine, many academic historians look down upon local historians, usually because local historians’ interests seem provincial; they rarely seem to be able to relate the landmark church or school building or the actions of a local pioneer or family member to the larger questions that preoccupy members of college and university history departments

Review of: Street Meeting: Multiethnic Neighborhoods in Early Twentieth-Century Los Angeles

A number of geographers and historians have observed that an unusually diverse mix of people populated many Los Angeles neighborhoods prior to World War II. Few scholars, however, have explored how the diversity of these neighborhoods affected the history of Los Angeles and the experiences of its residents. Mark Wild’s Street Meeting departs from earlier studies that have focused on a single ethnic group. Wild explores how African American, immigrant, and working-class Anglo residents negotiated the multiethnic environments in which they lived. He also explains how local elected officials and middle-class social reformers responded to the growing diversity of these neighborhoods

Review of: Popular Culture in the Age of White Flight: Fear and Fantasy in Suburban Los Angeles, by Eric Avila

Eric Avila\u27s ambitious and engaging Popular Culture in the Age of White Flight argues that a new \u27new mass culture\u27 emerged in the United States in the years following the Second World War. The new mass culture of the nineteenth century reflected the development of modern, industrial cities; this new \u27new mass culture \u27 mirrored the development of a new, post-industrial, suburban society. In this new culture, cities represented sites of decay and danger occupied by dark-skinned criminals. Suburbs, on the other hand, represented sites of order and safety inhabited by homogeneous groups of white people. As this new culture replaced an older culture, new theme parks such as Disneyland replaced old amusement parks such as those at Coney Island, new baseball parks such as Los Angeles\u27s Dodger Stadium replaced old parks such as Brooklyn\u27s Ebbets Field, and freeways replaced streetcars. The dramatic suburban­ization of the Los Angeles region after World War II makes it the ideal venue in which to explore the contours of this new culture. Avila analyzes a number of Hollywood films, Disneyland, Dodger Stadium, and Southern California\u27s freeways to reveal how a suburban white identity formed in the region

Review of: Politics in Black and White: Race and Power in Los Angeles, by Raphael J. Sonenshein

The automobile-inspired sprawl of Los Angeles has fascinated historians and other social scientists. Few scholars outside Southern California, however, have realized that patterns of race relations in Los Angeles are of national significance. This book, along with Mike Davis\u27s City of Quartz (1990), should cause historians to reexamine some of their assumptions about racial politics in U.S. cities. Politics in Black and White is a valuable and important study of race and politics in Los Angeles during the last three decades. It argues that several groups of citizens were largely excluded from city politics because Los Angeles was a western city without a strong political machine

Ultrasonic guided wave tomography of pipes: A development of new techniques for the nondestructive evaluation of cylindrical geometries and guided wave multi-mode analysis

This dissertation concentrates on the development of two new tomographic techniques that enable wide-area inspection of pipe-like structures. By envisioning a pipe as a plate wrapped around upon itself, the previous Lamb Wave Tomography (LWT) techniques are adapted to cylindrical structures. Helical Ultrasound Tomography (HUT) uses Lamb-like guided wave modes transmitted and received by two circumferential arrays in a single crosshole geometry. Meridional Ultrasound Tomography (MUT) creates the same crosshole geometry with a linear array of transducers along the axis of the cylinder. However, even though these new scanning geometries are similar to plates, additional complexities arise because they are cylindrical structures. First, because it is a single crosshole geometry, the wave vector coverage is poorer than in the full LWT system. Second, since waves can travel in both directions around the circumference of the pipe, modes can also constructively and destructively interfere with each other. These complexities necessitate improved signal processing algorithms to produce accurate and unambiguous tomographic reconstructions. Consequently, this work also describes a new algorithm for improving the extraction of multi-mode arrivals from guided wave signals. Previous work has relied solely on the first arriving mode for the time-of-flight measurements. In order to improve the LWT, HUT and MUT systems reconstructions, improved signal processing methods are needed to extract information about the arrival times of the later arriving modes. Because each mode has different through-thickness displacement values, they are sensitive to different types of flaws, and the information gained from the multi-mode analysis improves understanding of the structural integrity of the inspected material. Both tomographic frequency compounding and mode sorting algorithms are introduced. It is also shown that each of these methods improve the reconstructed images both qualitatively and quantitatively

Review of: Bodies in Doubt: An American History of Intersex

People whose bodies are not unambiguously either male or female have lived in America since at least the early years of European colonization. Until now, however, these people and the legal and medical debates that surrounded them have remained invisible to most historians. Elizabeth Reis has carefully examined legal and medical literature from the colonial era to the present to explain how perceptions and treatment of intersex people have changed over time

Review of: LA City Limits: African American Los Angeles From the Great Depression to the Present

Over the past twenty years a number of historians have attempted to explain why an African American “underclass” emerged in many U.S. cities after World War II. Most historians agree that racial discrimination in housing and employment and employers’ decisions to relocate factories to suburbs, other regions, and other countries left large numbers of African Americans trapped in increasingly impoverished and dangerous neighborhoods near the centers of these cities. The studies of “the urban crisis,” however, have focused primarily on northeastern cities. Josh Sides argues that an examination of the experiences of African Americans in Los Angeles will change historians’ understanding of this crisis