Kinds Of Terrains Research Articles

Methods of Calculating Wind Loads on Long-Span Girder Bridges with Tall Piers and Comparison of Values

Calculating wind resistance is an important process in the design of highway bridges. The current codes of many countries include different rules and formulas regarding the calculation of wind resistance. In this paper, the transverse-direction wind loads on long-span girder bridges with tall piers were calculated using six codes from different countries under various terrain, pier height, and girder length conditions. The pier-bottom shear force and moment results of transverse wind loads calculated using these six codes were compared with those obtained using the buffeting frequency domain method. Results showed that, in Class B terrain, wind load results predicated on China’s 2004 general codes for the design of highway bridges and culverts, China’s 2004 wind-resistant design specifications for highway bridges, Japan’s 2007 wind-resistant design manual for highway bridges, and Part 2 of Britain’s 2006 steel, concrete, and composite bridge specifications for loads resembled each other closely. Some difference was found to exist among Classes A, C, and D terrain. The 2007 AASHTO LRFD bridge design specifications and China’s 2001 load codes for the design of building structures showed significant differences from the other four codes on all kinds of terrain. The applicability of the wind load rules in the AASHTO LRFD bridge design specifications to long-span girder bridges with tall piers merits further discussion. China’s wind load calculations of load code for the design of building structures mainly depended on the empirical parameters of architectural structures with large dimensions, and had limited applicability to bridge structures. For long-span girder bridges with tall piers, such as bridges with span length-to-width or -depth ratios exceeding 30, or pier height-to-transverse-width ratio exceeding 10.7, the wind load calculated using these codes was generally underestimated due to the neglect of the effects of aeroelastic forces, which must be taken into account in the design of these kinds of bridges.

Using the ellipse propagation model for mobile location estimation

Mobile location estimation or mobile positioning is becoming an important service for a mobile phone network. Among different kinds of mobile location estimation technologies, only the class of the signal strength based algorithm which estimates the location of Mobile Stations (MSs) by the Received Signal Strength (RSS) can be applied to different kinds of radio cellular networks, and therefore, is more general. We have designed a directional propagation model – the Ellipse Propagation Model (EPM), which makes use of a common signal propagation model to perform a location estimation. EPM enhanced the traditional propagation model by resembling the contour line of the signal strength as an ellipse rather than a circle and hence becoming more realistic. We have tested EPM with real data taken in Hong Kong and it is proven that EPM outperforms other existing location estimation algorithms among different kinds of terrains.

A Mobile Robot Platform with Double Angle-Changeable Tracks

This paper presents a different structured mobile robot platform (MRP) with double tracks, which consists of two segments connected with a swing joint. As the angle between the two segments of the robot platform can be changed, the robot can travel over steep obstacles and climb up stairs. Two track-adjusting devices with passive track-adapting function are designed especially, which ensure that the tracks are always tight to keep the robot platform running reliably. In addition, a design idea for the track wheels is presented. The wheel could be favorable for the robot running smoothly in many kinds of terrains without the tracks coming apart from their wheels. Furthermore, the robot platform has other characteristics such as compact architecture and large useful inner space for arranging the control system and vibration absorption system. Experiments proved that the MRP can run flexibly and reliably in indoor and outdoor environments, and be suitable as a mobile carrier for executing search, rescue, detection and scout missions.

Comparing real-time and incremental heuristic search for real-time situated agents

Real-time situated agents, such as characters in real-time computer games, often do not know the terrain in advance but automatically observe it within a certain range around themselves. They have to interleave searches with action executions to make the searches tractable when moving autonomously to user-specified coordinates. The searches face real-time requirements since it is important that the agents be responsive to the commands of the users and move smoothly. In this article, we compare two classes of fast heuristic search methods for these navigation tasks that speed up A* searches in different ways, namely real-time heuristic search and incremental heuristic search, to understand their advantages and disadvantages and make recommendations about when each one should be used. We first develop a competitive real-time heuristic search method. LSS-LRTA* is a version of Learning Real-Time A* that uses A* to determine its local search spaces and learns quickly. We analyze the properties of LSS-LRTA* and then compare it experimentally against the state-of-the-art incremental heuristic search method D* Lite on our navigation tasks, for which D* Lite was specifically developed, resulting in the first comparison of real-time and incremental heuristic search in the literature. We characterize when to choose each one of the two heuristic search methods, depending on the search objective and the kind of terrain. Our experimental results show that LSS-LRTA* can outperform D* Lite under the right conditions, namely when there is time pressure or the user-supplied h-values are generally not misleading.

Integrating airborne SAR, Landsat TM and airborne geophysics data for improving geological mapping in the Amazon region: the Cigano Granite, Carajás Province, Brazil

This study examines the value of integrating airborne C‐band Synthetic Aperture Radar (SAR), Landsat Thematic Mapper (TM) and airborne gamma spectroradiometric data with field, petrographic and geochemical data for geological mapping of the Cigano batholith, an important representative of the Paleoproterozoic granitic magmatism in the Carajás Mineral Province (CMP), Amazon region. Distinct schemes for the integration of radar/optical and radar/optical/gamma data were evaluated and the geological information derived from the integrated products was verified in the field. The investigation allowed the re‐evaluation of previous geological information and the definition of distinct domains within the Cigano pluton and country rocks. The importance of brittle structures related to the tectonic evolution of the area and the location of intensely altered zones in the pluton was emphasized, favouring new insights into current geological and exploratory models of the area. The application of a similar approach as operational routine in exploration programmes in the Amazon region is justified considering the limited geological information, the availability of aerogeophysical data and airborne/spaceborne remote sensing data (radar, optical) and the high costs of field mapping in this kind of terrain.

Study of Hydrological Simulation on the Basis of Digitized Basin

On the basis of geographic information systems, indices of basin terrains and some other characteristics were extracted. Drainage networks were created by different mesh sizes of digital elevation model (DEM) in the basin with different kinds of terrain. These drainage networks were analyzed and the indices of the length and slope of the flow routine were derived. According to the basic principle and the mechanism of rainfall-runoff production, the definition and physical meaning of the parameters of the Xinanjiang hydrological model, relevant relationships between several sensitive parameters, and the indices were studied. The relationships were adopted to determine the parameters and the influence was studied with different kinds of mesh sizes of DEM in the basins with different terrains. In this way, the model parameters studied derived from the relationships can be used in an ungauged basin. The results extracted in this paper can then be adopted as the theoretical foundation for the study of the digital hydrological model.

Halfway to Mars [next generation planetary rover

A team of engineers from the Carnegie Mellon University's Robotics Institute in Pittsburgh has traveled to the Atacama Desert in Chile to test its new concepts and designs for the next generation of planetary rovers to be used in Mars. Using a prototype called Zoe, the team came to Atacama to see how well the rover copes with the kind of terrain its successors will find in Mars. Zoe can roam autonomously and can make some rudimentary decisions about what terrain to explore. Its main task is to hunt for evidence that some kind of microbial life flourished in the planet's warmer, watery past, as well as signs that some of it might have held on to the present day. It uses a fluorescence imager to inspect rocks and dirt for the presence of chlorophyll, lipids, carbohydrates, proteins and DNA. The data collected by Zoe are then compared with those recorded by the scientists using a process known as ground truthing.

Using LDA Method to Provide Mobile Location Estimation Services within a Cellular Radio Network

Mobile location estimation is becoming an important value-added service for a mobile phone operator. It is well-known that GPS can provide an accurate location estimation. But it is also a known fact that GPS does not perform well in urban areas like downtown New York and cities like Hong Kong. Then many mobile location estimation approaches based on the cellular radio networks have been proposed to compensate the problem of the lost of GPS signals for providing location services to mobile users in metropolitan areas, but there exists no general solution since each algorithm has its own advantage depending on specific terrain and environmental factors. In this paper, we propose a selector method with LDA among different kinds of mobile location estimation algorithms we had proposed in previous work to combine their merits, then provide a more accurate estimation for location services. And we build up a three-level binary decision tree to classify these four algorithms. These three levels are named as Stat-Geo level, CG-nonCG level and CT-EPM level. And the success ratios of these three levels are 85.22%, 88.45% and 88.89% respectively. We have tested our selector method with real data taken in Hong Kong and the experiment results have shown that our selector method outperforms other existing location estimation algorithms among different kinds of terrains.

Surface layer turbulence parameters over a complex terrain

Abstract The structure of the surface boundary layer over homogeneous conditions is nowadays well understood. However, there is no sufficient knowledge of the corresponding structure over complex topography. Another major issue in micrometeorological studies is the description of the turbulence with low wind speeds. Considering that almost all concentration of population and industry occurs in regions of complex terrain and that low wind speeds are the most critical ones to the dispersion of pollutants, additional studies are still essential in helping the understanding of the structure of PBL over such kind of terrain and such type of stability. This is the purpose of this paper in which a data set collected in a valley, using a sonic anemometer, is presented and discussed. Results reveal that the turbulence parameters in the convective and stable surface layer follow similarity relationships only if special conditions regarding wind direction and wind speed exist in relation to the surrounding terrain. In other words when the air masses travel for longer distances over a flat terrain.

Energy-Optimal Design of Walking Machines

In a general definition of robot components given by Wolfram Stadler, communications and power supply are included showing the close relation between robots and walking machines. Both of them are based on mechatronics allowing variable programmable operations. Biped walking represents a complex motion of sophisticated systems in nature as well as in engineering. A young human requires more than 1 year to learn walking while old humans need additional devices for save walking. While passive machines walk only on inclined planes, active machines may walk in all kinds of terrains. However, the active devices known from literature consume so much energy that their operation time is very restricted. In this paper the modeling of walking systems using the method of multibody dynamics is presented including the contact and impact problem inherent to biped walking. The limit cycle of passive motions is investigated as well as the related stability using shooting approaches with optimization techniques. The active machines proposed are controlled using the principles of inverse dynamics and advanced linear control strategies. In particular, the energy consumption between passive and active walking machines is compared by a coefficient of efficiency. At the time being human walking is still the most efficient and it is considered as a benchmark for the mechatronic design of walking machines.

Induction effects of 2-D structures on buried pipelines

The implementation of cathodic protection systems is very complicated since many factors can contribute for current flowing off the pipe. The design requires the characterization of the parameters impacting the corrosion process, such as soil resistivity, size of the pipe and quality of the coating. The authors study the effect of geomagnetic fields on the pipe-induced currents considering it as an additional cause of corrosion. A theoretical method previously implemented to model the currents induced on pipes embedded in homogeneous soils indicated a dependence between the intensity of the currents and the electrical resistivity of the soil, and predicted that a drainage of current through the pipe would occur at zones of shallow electrical discontinuities. They present another method for the calculation of the induced currents that allows the authors to consider also multilayered structures and lateral discontinuities in the Earth resistivity. Applying this method, they quantify the currents induced in pipelines embedded in different bidimensional structures in order to obtain an estimation of the effects produced by the presence of such kinds of terrains. They then applied this method to model measured data. Field work was performed along a 200 km-route of a pipeline system. In this zone, the pipe-to-soil potential was measured at different sites and a geophysical study was made to determine the discontinuities in soil resistivities. They obtained a correlation of the measured currents and soil resistivity consistent with the theoretical predictions.

Some Turbulence Characteristics in Stable Atmospheric Boundary Layer Flow

Abstract Atmospheric boundary layer measurements during stable and near neutral condition from seven sites in different kinds of terrain have been analyzed in order to find relationships among turbulence parameters. The shape of the spectral and cospectral distributions turned out to be well represented by the universal expressions found for ideal sites. For near neutral conditions in the surface layer σw/u* increases and σu/u* decreases with height. These results agree with previous result found in the literature for both atmospheric and some wind tunnel data. The ratio σw/σu first increases and then decreases as stability increases in the surface layer. This can be interpreted as a combined effect of stability and the presence of the ground. In a stable layer well above the ground σw/σu decreases monotonically with stability, in accordance with laboratory measurements and numerical simulations of free shear flow. The ratio wθ/uθ was also investigated. For near neutral conditions the ratio scatters aroun...

On the consistency of stability classification schemes when applied to non-homogeneous terrain

In order to ascertain the degree of confidence one should place on stability classification schemes when applied to a site in non-homogeneous terrain, the differences of stability classes, calculated by various methods, for two adjacent sites (8 km apart) in a coastal urban region are examined and are found to be considerable. The cause of this difference appears to be changes in surface characteristics such as roughness, albedo, etc. and local topographically induced flow patterns (but not sea-breeze), which suggests that popular classification schemes, such as the Pasquill-Turner one, should be modified to include at least the effect of surface roughness and albedo, and thus to differentiate between various kinds of terrain.

Factors Influencing Spotlighting Counts of Deer

Experimental spotlighting of deer (Odocoileus virginianus and 0. hemionus) in meadows along a 68-mile route in the Black Hills, South Dakota, during the summer of 1958 indicated that the technique can be a means of studying population trends. Herd composition, availability of preferred foods in meadows, type and size of meadow, hour of observation, and several meteorological factors influencd nightly counts. Time can be standardized if counts are made only during a 4-hour period beginning 1 hour after sunset; nearly 79 percent of the 25,808 deer appearances were observed within this period. Over 82 percent were noted within 5 hours after sunset. Correlation of the combined effects of temperature, cloud cover, precipitation, dew, and relative humidity with deer counts was high. Temperature exerted the strongest influence on deer behavior. Statistical analysis of data from a selected portion of the route revealed a curvilinear relationship between temperature, day of season, and deer counts. The derived equation can be used for predicting counts for a given date at a given temperature. The technique of spotlighting open areas to count deer where they congregate at night has limited use on most deer ranges; however, the method could be a useful means for detecting changes in deer-population densities on some ranges if the relationship of factors affecting deer behavior, and therefore affecting nightly counts, are understood. This report evaluates several such factors studied during summer spotlighting of meadows in the Black Hills of South Dakota in 1958. Biologists in South Dakota have found that spotlight counts of deer are indicative of area deer population (Berner, L. M. 1953. Deer management in the Black Hills of South Dakota. Annual Meeting, Soc. Am. Foresters, Colorado Springs. Mimeo. 23pp). Previous to this study, spotlighting was tried in spring and fall, but counts of deer were erratic, primarily because of seasonal movements of local herds. Other states have attempted to census deer by spotlighting, but their programs have generally failed to yield reliable data (Personal communication from R. J. Boyd 1958, R. S. Cook 1958, R. L. Dawning 1958, L. L. Eberhardt 1958, J. L. Egan 1958). The 68-mile spotlighting route, divided into seven convenient segments (Fig. 1), transected various kinds of terrain, vegetative cover, and land-use patterns. It extended upward in elevation from 5,000 feet near Hill City to 6,800 feet northwest of Deerfield. Over 56 miles of the route ran through meadows which averaged about 200 yards in width on either side of the road. One portion of the route ran through 30 miles of continuous meadow. Most of the bottomlands along the route are privately owned and are cultivated for oats (Avena sativa), alfalfa (Medicago sativa), and other hays (Fig. 2). Sheep and cattle are pastured on some of them as well as on public lands along the route. The latter are predominantly upland prairies and forests (Fig. 3). Uncultivated meadows generally support dense growths of mixed grasses, mainly bluegrass (Poa pratensis), western wheatgrass (Agropyron Smithii), and crested wheatgrass (Agropyron sp.), along the creeks, especially in beaver flows. The ecotone between the dense ponderosa pine (Pinus ponderosa )-Black Hill spruce (Picea glauca) forest and the meadows is dominated by aspen (Populus tremuloides) and paper birch (Betula papyrifera). The

Commonplace viewing and depth discrimination.

Measures of commonplace depth discrimination were obtained at observation distances of 200, 750, and 1500 feet in an Arctic area over flat terrain. Comparisons were made with similar measures taken over four different kinds of terrain (including an airstrip) in a desert area and with similar data reported by other investigators.The results indicate that within a range of 100 to 3000 feet the standard deviation (precision) of depth discrimination is related to observation distance (D) approximately as the function, D1.35. Within the same range the associated binocular image disparity decreases approximately as D−0.65. It is suggested that for commonplace viewing the angle of disparity is better conceived of as a measure of relative depth acuity rather than of stereoscopic acuity.The results also suggest that under the conditions studied commonplace depth acuity is 95–100% finer than stereoscopic acuity alone, binocular acuity is only slightly, if at all, superior to monocular acuity, and that the qualities of the terrain such as its texture have little or no effect. It was concluded that stereoscopic vision makes only a slight contribution to the precision of depth discrimination although it may be very important in producing a feeling or effect of depth. The hypothesis was put forth that vernier acuity is the major basis for commonplace depth discrimination.