Broadband optical gain via interference in the free electron laser: principles and proposed realizations

We propose experimentally simplified schemes of an optically dispersive interface region between two coupled free electron lasers (FELs), aimed at achieving a much broader gain bandwidth than in a conventional FEL or a conventional optical klystron composed of two separated FELs. The proposed schemes can {\it universally} enhance the gain of FELs, regardless of their design when operated in the short pulsed regime

Models of Outdoor Recreational Travel

The purpose of this investigation was to evaluate models of travel flow from population centers throughout the United States to outdoor recreational areas in Kentucky. Data were obtained by means of a license-plate, origin-destination survey at 160 sites within 42 recreational areas and by means of a continuous vehicle counting program at eight of these sites. Attempts to simulate distributed travel flows concentrated on various single-equation models, a cross-classification model, and gravity and intervening opportunities models. The cross-classification model was found to be an acceptable means for simulating and predicting outdoor recreational travel flows and was decidedly superior to the other models. From the cross-classification model, per capita distributed flows were found to (1) decrease at a decreasing rate with increasing population of the origin zone, (2) increase at a variable rate with increasing attraction of tbe recreational area, and (3) decrease at a decreasing rate with increasing distance. The intervening opportunities model was found to be unacceptable as a distribution model since it could not effectively accommodate the widely differing sizes of the 42 recreational areas. The gravity model, on the other hand, was quite effective in distributing actual productions and attractions. Problems associated with tbe gravity model were limited to difficulties in accurately estimating trip productions and attractions in the trip generation phase of analysis

Impacts of the Extended-Weight Coal Haul Road System (Interim Report)

The Extended-Weight Coal Haul Road System, created by Kentucky\u27s Legislature in 1986, consists of all roads which carry over 50,000 tons of coal in a calendar year. Trucks hauling coal on this system are authorized to exceed normal weight limits through the payment of an annual decal fee. A research study was initiated in July of 1992 to analyze the impacts of the extended-weight system. This interim report, prepared after one year of a three-year study, describes the analyses performed thus far and presents preliminary findings, recommendations, and a discussion of future work. Analyses in this report are based on: historical data on coal production and transportation: data from coal decal applications; interviews of legislators, transportation official, coal company representatives, and coal trucking representatives: newspaper articles; vehicle classification data; a pavement cost analysis; and accident data. Preliminary conclusions include: 1) The extended-weight system has apparently been somewhat successful in accomplishing its primary objectives: to enhance the competitiveness and economic viability of Kentucky\u27s coal industry and to eliminate the perceived need for coal haulers to violate the law in order to be competitive; 2) Overall accident rates are no higher on the extended-weight system than on other comparable routes, but the fatal accident data is significantly higher on the extended- weight system; 3) The coal-decal fee structure results in a net annual loss in Road Fund revenue of approximately $2 trillion; 4) Forty percent of the revenue from data sales is allocated to the counties, although less than ten percent of the extended-weight system is county-maintained; 5) The heavier weights of coal-decal trucks add approximately$9 million annually to pavement overlay costs and increase other highway costs to an (as yet) undetermined extant; 6) Road users throughout the state are subsidizing the movement of Kentucky coal by underwriting the increased costs of maintaining and improving the infrastructure. The following preliminary recommendations ware developed: 1) Route geometry and cross section should be considered when deciding which routes will be included in the extended-weight system; 2) The selection of routes for the extended-weight system should include consideration of system connectivity; 3) Countermeasures should be evaluated and implemented to alleviate the braking problem for heavy trucks approaching signalized intersections; 4) A revision to the allocation of Energy Recovery Road Fund dollars should be considered to more accurately reflect the composition of the extended-weight system

Advection, diffusion and delivery over a network

Many biological, geophysical and technological systems involve the transport of resource over a network. In this paper we present an algorithm for calculating the exact concentration of resource at any point in space or time, given that the resource in the network is lost or delivered out of the network at a given rate, while being subject to advection and diffusion. We consider the implications of advection, diffusion and delivery for simple models of glucose delivery through a vascular network, and conclude that in certain circumstances, increasing the volume of blood and the number of glucose transporters can actually decrease the total rate of glucose delivery. We also consider the case of empirically determined fungal networks, and analyze the distribution of resource that emerges as such networks grow over time. Fungal growth involves the expansion of fluid filled vessels, which necessarily involves the movement of fluid. In three empirically determined fungal networks we found that the minimum currents consistent with the observed growth would effectively transport resource throughout the network over the time-scale of growth. This suggests that in foraging fungi, the active transport mechanisms observed in the growing tips may not be required for long range transport.Comment: 54 pages including appendix, 10 figure

Impacts of the Extended-Weight Coal Haul Road System

The Extended-Weight Coal Haul Road System, created by the Kentucky Legislature in 1986, consists of all roads which carry over 50,000 tons of coal in a calendar year. Trucks hauling coal on this system are authorized to exceed normal weight limits through the payment of an annual decal fee. A research study was initiated in July of 1992 to analyze the impacts of the extended-weight system. Analyses in this report are based on the following: historical data on coal production and transportation: data from coal decal applications; interviews of legislators. transportation officials. coal company representatives. and coal trucking representatives: newspaper articles; vehicle classification data: analyses of pavement costs: pavement rideability data; and accident data. Primary conclusions include: I) The extended-weight 5)\u27Stem has apparently been somewhat successful in accomplishing the objective of enhancing the competitiveness and economic viability of the Kentucky coal industry; 2) Overall accident rates did not increase as a result of implementation of the extended-weight system. but the fatal accident injury rates were significantly higher on the extended-weight system and for trucks operating with the coal decal; 3) Advance-warning flashers have been evaluated and recommended as a means of reducing intersection accidents involving heavy/coal trucks; 4) The coal-decal fee structure results in a net annual loss in Road Fund revenue of approximately S2 million; 5) Forty percent of revenue from decal fees are allocated to counties even though county-maintained roads comprise only eight percent of the extended-weight system; 6) Heavier weights of coal-decal trucks add approximately $9 million annually to the pavement overlay costs; 7) Road users throughout the state are subsidizing the movement of Kentucky coal by participating in the cost of maintaining and improving tile highway system; and 8) Possibly reflecting the increased funding of extended-weight roads., the rideability index. has risen to a level above the statewide average. The primary recommendation was that the extended-weight system should evolve into a comprehensive trucking network. A Resource and Commodity Highway System was evaluated as a separate study and found to be a feasible and desirable means of providing a trucking highway network that is fully compatible with the dimensions and characteristics of large trucks

Communities, families and migration: some evidence from Cornwall

© Maney Publishing 2007Taking its cue from Pooley and Turnbull’s (1998) claim that there is no evidence of any difference in the propensity to migrate by region or settlement size, this article investigates the appropriate scale for migration research. It presents some preliminary findings from a micro-level study of three occupationally contrasting communities in Cornwall in the second half of the 19th century. Reconstructing the migration histories of a cohort of children from the 1851 census enumerators’ books and making use of local and online census and civil registration index databases, the study identifies some clear differences in migration patterns and propensity at the community level. Moving from patterns to processes it argues that labour markets and occupational structures remain the most important explanatory variables structuring migration, but that these were mediated at the individual level by the influence of the family which played a key role in facilitating or deterring movement

Proposal for Development of a Resource and Commodity Highway System

In 1986, the Kentucky General Assembly established the Extended Weight Coal and Coal By-Products Haul Road System. This system includes approximately 3,200 miles of the most significant coal-haul roads in the state and permits coal trucks to carry much larger payloads than trucks with other commodities. In many ways, the extended-weight system has been very successful. Coal-transportation productivity has been substantially increased, and Kentucky coal continues to remain competitive in the marketplace. At the same time, infrastructure costs have risen substantially--to considerably greater levels than the increase in revenue produced by the requisite coal decal fees--and the extended-weight system has proven to be difficult to manage. Moreover, there is a fundamental inequity in the preferential treatment that has been extended to coal haulers and to the specific regions in which they travel. In pursuit of its goal of providing the best possible transportation system to all citizens of the Commonwealth and its recognition of the key influence of transportation productivity on the national and international competitiveness of Kentucky industry, the Kentucky Transportation Cabinet recently initiated an evaluation of the extended-weight system and an identification of ways in which the extended-weight system might evolve into a comprehensive trucking network that would effectively serve the entire Commonwealth. Key considerations in forming future alternatives included the necessity for 1) limited mileage in order to contain costs; 2) permanency to promote efficient management; 3) more lenient weight limits for commodities other than coal; 4) statewide service; and 5) a connected, continuous trucking network

The Antarctic Slope Current in a Changing Climate

The Antarctic Slope Current (ASC) is a coherent circulation feature that rings the Antarctic continental shelf and regulates the flow of water towards the Antarctic coastline. The structure and variability of the ASC influences key processes near the Antarctic coastline that have global implications, such as the melting of Antarctic ice shelves and water mass formation that determines the strength of the global overturning circulation. Recent theoretical, modeling, and observational advances have revealed new dynamical properties of the ASC, making it timely to review. Earlier reviews of the ASC focused largely on local classifications of water properties of the ASC's primary front. Here, we instead provide a classification of the current's frontal structure based on the dynamical mechanisms that govern both the along‐slope and cross‐slope circulation; these two modes of circulation are strongly coupled, similar to the Antarctic Circumpolar Current. Highly variable motions, such as dense overflows, tides, and eddies are shown to be critical components of cross‐slope and cross‐shelf exchange, but understanding of how the distribution and intensity of these processes will evolve in a changing climate remains poor due to observational and modeling limitations. Results linking the ASC to larger modes of climate variability, such as El Niño, show that the ASC is an integral part of global climate. An improved dynamical understanding of the ASC is still needed to accurately model and predict future Antarctic sea ice extent, the stability of the Antarctic ice sheets, and the Southern Ocean's contribution to the global carbon cycle

The role of the g9/2 orbital in the development of collectivity in the A = 60 region: The case of 61Co

An extensive study of the level structure of 61Co has been performed following the complex 26Mg(48Ca, 2a4npg)61Co reaction at beam energies of 275, 290 and 320 MeV using Gammasphere and the Fragment Mass Analyzer (FMA). The low-spin structure is discussed within the framework of shell-model calculations using the GXPF1A effective interaction. Two quasi-rotational bands consisting of stretched-E2 transitions have been established up to spins I = 41/2 and (43/2), and excitation energies of 17 and 20 MeV, respectively. These are interpreted as signature partners built on a neutron {\nu}(g9/2)2 configuration coupled to a proton {\pi}p3/2 state, based on Cranked Shell Model (CSM) calculations and comparisons with observations in neighboring nuclei. In addition, four I = 1 bands were populated to high spin, with the yrast dipole band interpreted as a possible candidate for the shears mechanism, a process seldom observed thus far in this mass region

Cross-shell excitation in two-proton knockout: Structure of 52^{52}Ca

The two-proton knockout reaction $^9$Be($^{54}$Ti,$^{52}$Ca$+ \gamma$) has been studied at 72 MeV/nucleon. Besides the strong feeding of the $^{52}$Ca ground state, the only other sizeable cross section proceeds to a 3$^-$ level at 3.9 MeV. There is no measurable direct yield to the first excited 2$^+$ state at 2.6 MeV. The results illustrate the potential of such direct reactions for exploring cross-shell proton excitations in neutron-rich nuclei and confirms the doubly-magic nature of $^{52}$Ca