The availability of power for use in space is a key requirement for many future space activities. The use of microwave/millimeter-wave power transmission in space provides an alternative energy generation and delivery system. Three - phase experiments on board the space shuttle are proposed to demonstrate the feasibility of microwave power transmission in space.
Two main objectives of transportation planning are to simulate the current traffic volume and to forecast the future traffic volume on a transportation network. Traffic demand modeling typically consists of the following tasks: (1) defining traffic analysis zones (TAZs) based on land-use characteristics; (2) building the transportation network; (3) collecting traffic data for calibration; and (4) performing the four-step traffic demand modeling process of trip generation, trip distribution, mode choice and trip assignment. The first two tasks used to be time-consuming because paper maps and aerial photographs were the primary tools for constructing TAZs and the transportation network. In recent years, transportation planners have used geographic information systems (GIS) to perform the tasks. A GIS is a tool capturing, storing, and analyzing spatial or geo-referenced data. It also has the additional capability in data integration, such as integration of socioeconomic and traffic data for traffic demand modeling. This paper describes the authors' experience of using a GIS to prepare TAZs and the transportation network for an Idaho statewide traffic demand model. ARC/INFO is the GIS software package for the pilot study, Latah County. The authors have used ARC/INFO to construct TAZs from different data sources. Using AML programs, they have run experiments to automatically assign TAZ centroids and centroid connectors, and to measure the effect of centroids and centroid connectors on traffic demand forecast. Overall, GIS has proven to be an efficient and effective tool for the study. It should be noted, however, that GIS cannot by itself improve the quality of input data, a critical factor in transportation planning.
A series solution for TM scattering from a dielectric biconvex cylinder, which is formed by a semicircle and a portion of circular arc, buried in a shallow circular gap of a perfectly conducting plane is derived in this paper. The electric fields of biconvex cylinder region and its outer semi-unbounded region are represented in terms of an infinite series of cylindrical waves with unknown coefficients respectively. By employing Graf's addition theorem and matching the boundary conditions, the unknown coefficients are determined. The comparisons with available data in the literature point out a good agreement for the circular cylinder case. Some plotted results for the backscattering width and far-field radiation pattern reveal how the scattering properties have influenced by varying the depth-to-half-width ratio of the dielectric biconvex cylinder.
The flow characteristics around a pipeline partially buried in a rigid porous seabed of infinite depth are numerically examined using the classical boundary-element method. A simplified model, comprising an impermeable circular pipe with/without a permeable protective coating, is applied to analyze the oscillating-flow case. Darcy’s law and the potential-flow theory form the basis of this study. Taking advantage of the regular perturbation method prohibits the occurrence of the highly ill-conditioned linear systems because of substantial a difference in the order of magnitude among the flux and pressure continuity conditions across the soil- and coating-water interfaces. The computed results of uncoated cases reveal that the pore-fluid velocity rapidly increases in seabed areas close to the pipe. A remedy for this is to utilize a precoated permeable layer, which effectively eliminates the localized regions of the flow-induced pressure concentration. Numerical experiments show helpful results so far, which might lead to the development of cheap novel approaches to prevention of the piping effect.
This study revisits the freely vibrating problem of asymmetric L-shaped membranes using a three-segmented domain decomposition (3-SDD) strategy. Motivated by the need for more accurate and flexible methods, the 3-SDD strategy is compared with the previously proposed two-segmented domain decomposition (2-SDD) strategy. The region-matching technique is used to derive an alternative series solution, and the eigenvalues obtained are compared with those in existing research. The convergence behavior and sensitivity analyses reveal that the 3-SDD strategy offers improved accuracy and stability, particularly for higher truncation terms. Detailed comparisons of the first four eigenvalue squares show strong agreement between the 3-SDD and 2-SDD strategies, confirming the reliability of both methods. This research establishes a foundation for the vibration analysis of complex membrane structures, emphasizing the benefits of the 3-SDD approach for upcoming engineering applications and showcasing its potential for broader applicability in practical scenarios. The findings underscore the importance of utilizing multi-segmented decomposition strategies to enhance the accuracy and flexibility of free vibration analysis.
The scattering of plane SH waves incident on a circular sectorial canyon is considered. An accurate region-matching technique is applied to derive a rigorous series solution. Appropriate wavefunctions are employed to describe antiplane motions. Judicious basis functions, involving Gegenbauer polynomials, are well utilized to correctly capture the singular behaviour in stress fields near the canyon bottom. The enforcement of matching conditions on the auxiliary boundary leads to the determination of unknown coefficients. Plotted results demonstrate the influence of pertinent parameters on surface and subsurface motions. Both steady-state and transient results are included. The solution technique proposed achieves a considerable reduction in the computational effort, facilitating benchmark computations. The derived series solution enriches the limited list of series solutions presently known for canyon problems related to SH-wave scattering.
We have searched for long-lived (\ensuremath{\gtrsim}${10}^{\mathrm{\ensuremath{-}}5}$ s) doubly charged negative atomic ions produced in a high-current cesium sputter source with a tandem-accelerator-based charge spectrometer. The results of these ultrasensitive searches for doubly charged negative atomic ions of group VI B and VIII B elements, and hydrogen that can survive the acceleration to the tandem terminal, are reported. No evidence of doubly charged negative atomic ions was observed, and upper limits for the ratio of production (and survival) of doubly charged to singly charged negative atomic ions were obtained for the cesium sputter source.
The scattering problem of transverse electric wave from a dielectric biconvex cylinder buried in a shallow circular trough of a ground plane is investigated and a rigorous series solution is also derived. Based on the region-matching method, the analysed region is decomposed into two subregions by introducing a semi-circular auxiliary boundary. The magnetic field of each subregion is expressed in terms of cylindrical wave functions with unknown expansion coefficients. After imposing the matching conditions and the boundary condition on the trough surface with the aid of Graf's addition theorem, the unknown coefficients are determined. Comparisons with published data for a dielectric circular cylinder case show very good agreement. Visible effects of depth-to-half-width ratios of a dielectric biconvex cylinder on echo width, far-field pattern and near-field distribution are illustrated in graphical form.
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