Tourism patterns and determinants in the Great Lakes Region: populations,resources, roads,and perceptions

The Great Lakes Region of North America is attractive to tourists because of its vast areas of water, thousands of kilometers of shorelines, huge public forests, numerous parks, extensive commercial tourist facilities, interesting cities, and good highways. Most of the region's 65 million residents live in the southern industrial and agricultural portion so summer recreational travel is largely in a northerly direction to the lakes, shorelines, forests, and privately owned seasonal homes known as cottages. This travel involves international border crossings as Americans travel to rural and urban tourism destinations in Ontario, Canadians visit cities in the United States, and residents of both nations take circular tours around the Great Lakes. Each year, Ontario and neighboring American states spend a total of more than 20 million on tourism publicity trying to capture a larger share of the 40 billion spent in the region annually by tourists. However, the amount, nature, and patterns of tourist travel across the border are not well documented because of the lack of exit surveys.     

An assessment of fuzzy logic vessel path control

A fuzzy logic controller for ship path control in restricted waters is developed and evaluated. The controller uses inputs of heading, yaw rate, and lateral offset from the nominal track to produce a commanded rudder angle. Input variable fuzzification, fuzzy associative memory rules, and output set defuzzification are described. Two maneuvering situations are evaluated: track keeping along a specified path where linearized regulator control is valid; and larger maneuvers onto a specified path where nonlinear modeling and control are required. For the track keeping assessment, the controller is benchmarked against a conventional linear quadratic Gaussian (LQG) optimal controller and Kalman filter control system. The Kalman filter is used to produce the input state variable estimates for the fuzzy controller as well. An initial startup transient and regulator control performance with an external hydrodynamic disturbance are evaluated using linear model simulations of a crude oil tanker. A fully nonlinear maneuvering model for a smaller product tanker is used to assess the larger maneuvers     

Solar soft X-ray flare spectra from OSO-4

Solar flare spectral data, covering the wavelength range 0.7–8.5 Å, are derived from the NRL Bragg crystal spectrometers aboard OSO-4. A detailed analysis of the soft X-ray spectra for the 3b flare of 16 November 1967 (2140 UT) is presented, and it is found that electron temperatures derived from continua and emission lines are compatible with a two or more component plasma, differing in temperature by 6–10 × 10⁶K.     

On the use of horizontal acoustic Doppler profilers for continuous bed shear stress monitoring

Continuous monitoring of bed shear stress in large river systems may serve to better estimate alluvial sediment transport to the coastal ocean.Here we explore the possibility of using a horizontally deployed acoustic Doppler current profiler(ADCP) to monitor bed shear stress,applying a prescribed boundary layer model,previously used for discharge estimation.The model parameters include the local roughness length and a dip correction factor to account for sidewall effects.Both these parameters depend on river stage and on the position in the cross-section, and were estimated from shipborne ADCP data.We applied the calibrated boundary layer model to obtain bed shear stress estimates over the measuring range of the HADCP.To validate the results,co-located coupled ADCPs were used to infer bed shear stress,both from Reynolds stress profiles and from mean velocity profiles. From HADCP data collected over a period of 1.5 years,a time series of width profiles of bed shear stress was obtained for a tidal reach of the Mahakam River,East Kalimantan,Indonesia.A smaller dataset covering 25 hours was used for comparison with results from the coupled ADCPs.The bed shear stress estimates derived from Reynolds stress profiles appeared to be strongly affected by local effects causing upflow and downflow,which are not included in the boundary layer model used to derive bed shear stress with the horizontal ADCP.Bed shear stresses from the coupled ADCP are representative of a much more localized flow,while those derived with the horizontal ADCP resemble the net effect of the flow over larger scales.Bed shear stresses obtained from mean velocity profiles from the coupled ADCPs show a good agreement between the two methods,and highlight the robustness of the method to uncertainty in the estimates of the roughness length.     

Polarimetric analysis and modeling of multifrequency SAR signaturesfrom Gulf Stream fronts

Using airborne synthetic aperture radar data from the 1990 Gulf Stream Experiment, this paper investigates the polarization and wavelength dependence of radar signatures for narrow fronts with converging flows occurring within the Gulf Stream. The signal-to-background ratios of the cross-polarization backscatter return from a convergent front were found much higher than those of copolarization returns, when the flight path is crossing the front. However, a second convergent front, imaged at 45°, showed that the signal-to-background ratios are nearly equal for co- and cross-polarizations. A polarimetric procedure, which has been successfully used to measure terrain slopes and to generate elevation maps, is applied to the convergent front to explain the polarization and imaging geometry dependence of these radar responses. A theoretical modeling of radar modulation using an ocean wave model and a composite-Bragg scattering model, which incorporates the effect of breaking waves, was developed. Calculations with the model agree reasonably well with the radar measurements at various polarizations for three radar frequencies: P-band (68 cm in wavelength), L-band (24 cm), and C-band (5.7 cm)     

华北北部古生代大陆地壳增生过程中的岩浆作用与成矿效应

包括前寒武纪克拉通与显生宙造山带两大构造单元的华北北部,古生代时期板块构造体制下古亚洲洋的裂解-扩展-消亡与汇聚大陆边缘的俯冲-碰撞-伸展循环构成了其大陆地壳增生与再造演化的基本图景,并形成了一系列记录这些因果演变连续过程的岩浆侵入与喷发事件。这些物质记录无疑是研究汇聚大陆边缘壳-幔作用和物质交换、大陆地壳演化与大规模成矿作用耦合关系的绝佳窗口。本文在系统总结最近几年积累的年代学和岩石地球化学资料的基础上,以一些带有特定过程印记的标志性岩浆事件为纲领,表征这些古生代岩浆作用形成过程中的地球动力学演变,揭示其所记录的华北北部大陆地壳的多阶段增生与再造演化机制,并初步探讨了有利地球动力学过程制约下的岩浆行为引起的成矿物质聚集效应。     

内蒙古白云鄂博地区基底岩石锆石年代学及对构造背景的指示

白云鄂博地区的克拉通基底岩石主要由糜棱岩化花岗片麻岩(2588±15Ma),正长岩、花岗闪长岩(2018±15Ma)和黑云母花岗片麻岩、含石榴石蓝晶石花岗片麻岩(～1890Ma)等组成,白云鄂博超大型稀土矿床就位于华北克拉通太古代基底之上。太古代克拉通基底在早元古代中晚期(2.0Ga)又经历了一次强烈的碰撞造山运动,造成了闪长质与花岗质岩浆侵位,以及1.9Ga片麻岩相变质事件。     

Sun-induced variations in time in the global positioning system

Sun-induced effects on the measurement and transfer of time information reported by orbiting satellites are reexamined. The problem of transforming the frequency of coherent radio signals to the Geocentric Inertial Coordinate frame (as required during the transfer of time information) involves an implicit, dependence on earth-sun-clock orientation that has been omitted, except in Very-Long-Baseline Interferometry (VLBI) studies. This known VLBI effect leads to an important second order Doppler effect. The effect explains systematic deviations between the time reported by satellites in the Global Positioning System (GPS) relative to Universal Time (UT) and can be used to improve existing bounds for the validity of the equivalence principle.     

Data model for system conceptualization in groundwater studies

Development of a conceptualization of a hydrogeologic system serves as the basis of groundwater modeling. While existing groundwater data models are designed to store groundwater system information, none is designed to capture its conceptual view. This study addresses this need by presenting a new object-oriented Conceptualization Groundwater Data Model that represents a groundwater system as a series of aquifer layers with defined aquifer properties and water boundary conditions. A case study is presented that develops the conceptual view of the groundwater system beneath Konza Prairie. This single conceptualization is used to support groundwater models across existing technologies of finite difference, finite element, and analytical element methods. While the models each employ different mathematics, data input files, and formats, all models are founded on the same conceptualization process that is represented using this new data model. The case study illustrates the data model's promise as an effective mechanism for groundwater system conceptualization and data storage, and utility for various groundwater computational models. This conceptualization of a groundwater data model suggests a new focus on incorporating system conceptualization into data model design.