Complicated Terrains Research Articles

Self-Adaptive Obstacle Crossing of an AntiBot From Reconfiguration Control and Mechanical Adaptation

AbstractOne drawback of wheeled robots is their inferiority to conquer large obstacles and perform well on complicated terrains, which limits their application in rescue missions. To provide a solution to this issue, an ant-like six-wheeled reconfigurable robot, called AntiBot, is proposed in this paper. The AntiBot has a Sarrus reconfiguration body, a three-rocker-leg passive suspension, and mechanical adaptable obstacle-climbing wheeled legs. In this paper, we demonstrate through simulations and experiments that this robot can change the position of its center of mass actively to improve its obstacle-crossing capability. The geometric and static stability conditions for obstacle crossing of the robot are derived and formulated, and numerical simulations are conducted to find the feasible region of the robot’s configuration in obstacle crossing. In addition, a self-adaptive obstacle-crossing algorithm is proposed to improve the robot’s obstacle-crossing performance. A physical prototype is developed, and using it, a series of experiments are carried out to verify the effectiveness of the proposed self-adaptive obstacle-crossing algorithm.

A new integral method for directly partitioning flow fields in limited domains over complex underlying surfaces

A new integral method is developed for directly partitioning a horizontal velocity field into its rotational and divergent components in a limited domain without actually computing stream-function and velocity potential. In this method, the previous integral method is reformulated to skip the intermediate steps that solve for stream-function and velocity potential first and then compute the rotational and divergent velocities via finite-differencing from stream-function and velocity potential, respectively. This reformulation takes the advantage that the previous integral formulations for computing stream-function and velocity potential are spatially differentiable and thus can be used to derive new integral formulations for directly computing rotational and divergent velocities. By skipping the intermediate steps, the new method eliminates the finite-difference discretization errors that cause the previous integral method fail to retain adequate accuracies when applied to complicate flow fields induced by severe weather and complex underlying surfaces over limited domains. The superior performances and improved accuracies of the new integral method over the previous integral method as well as another widely used previous method are demonstrated by numerical experiments with both idealized complex flow and real severe weather events in limited domains over complicated terrains. Thus, unless stream-function and velocity potential must be computed and actually used for some applications, the new integral method is recommended.

Stable Locomotion of Humanoid Robots on Uneven Terrain Employing Enhanced DAYANI Arc Contour Intelligent Algorithm

Abstract Humanoid robots must be capable of walking on complicated terrains and tackling a variety of obstacles leading to their wide range of possible implementations. To that aim, in this article, the issue of humanoid robots walking on uneven terrain and tackling static and dynamic obstacles is examined. It is inspected by implementing a novel Enhanced DAYANI Arc Contour Intelligent (EDACI) Algorithm that designs trajectory by searching feasible points in the environment. It provides an optimum steering angle, and step optimization is performed by Broyden–Fletcher–Goldfarb–Shanno (BFGS) Quasi-Newton method that leads to guide the humanoid robot stably to the target. The leg length policy has been presented, and a reward-based system has been implemented in the walking pattern generator that provides the optimum gait parameters. One humanoid robot act as a dynamic obstacle to others if they are navigating on a single terrain. It may generate a situation of deadlock, which needs to be solved. In this article, a dining philosopher controller (DPC) is employed to deal with and solve this issue. Simulations are used to evaluate the proposed approach in several uneven terrains having two humanoid NAOs. The findings indicate that it can precisely and efficiently produce optimal collision-free paths, demonstrating its efficacy. Experiments in similar terrain are performed that validate the results with a deviation under 6%. The energy efficiency of the developed controller is evaluated in reference to the inbuilt controller of NAO based on energy consumption. In order to check the feasibility and accuracy of the developed controller, a comparison with an established technique is provided.

Comparative analysis of two flow decomposition approaches and their applications in diagnosing water vapor in extreme precipitation events over Xinjiang province, China

Water vapor flux divergence under the terrain-following coordinate system is decomposed into slow and fast manifolds with the adoption of the Barnes filter method and the synoptic approach based on the Helmholtz theorem in this study. The performances and applications of both methods are evaluated in precipitating events over the Xinjiang province in China when traditional analysis fails to capture the evolutions of extreme precipitations caused by multi-scale systems and complicated terrains. A blizzard with a short duration under weak moisture environments and a persistent torrential rainfall event with abundant water vapor in the summer are selected as test examples for comparative analysis of the relationships between water vapor divergence and precipitation characteristics with the adoptions of both traditional synoptic diagnosis and two decomposition methods. It is found that divergent areas of the total water vapor flux divergence at the middle and high levels are blocked by false convergence at the low levels as the precipitation weakens in both cases, which leads to the failure of traditional synoptic diagnoses. Meanwhile, the two decomposition methods can provide superior indicators for extreme precipitation, especially before rainfall decreases or terminates. The synoptic approach performs better than the Barnes filter method as the latter sharply decreases in accuracy as the complexity of the flow fields and moisture conditions increase. Remedies for relieving this problem are proposed before being used for further applications.

Visual analysis of geospatial multivariate data for investigating radioactive deposition processes

The Fukushima nuclear accident of 2011 raised awareness of the importance of radioactive deposition processes, especially for proposing aerosol measures against possible air pollution. However, identifying these types of processes is often difficult due to complicated terrains. This paper presents an application study for identifying radioactive deposition processes by taking advantage of visual interaction with topographic data. The idea is to visually investigate the correspondence of the spatial positions to the air dose rate along with relevant attributes. This is accomplished by composing scatterplots of pairwise attributes, onto which we project terrain areas to interactively find specific patterns of such attributes. We applied our approach to the analysis of air dose rate distribution data around the Fukushima nuclear plant after the accident. Our visualization technique clearly distinguished contamination areas derived from different deposition processes and thus is useful for elucidation of the deposition process.

Humanoid navigation: A firefly based approach

AbstractHumanoid navigation has been the center of attraction among robotic researchers since many years by virtue of their increasing use in industrial automation and smart manufacturing. In the current research, a firefly based computer vision integrated navigational analysis has been performed on humanoid robots for smooth movement by negotiation with obstacles present in complicated terrains. Here, the logic of the firefly algorithm has been used to design the controller by careful consideration of the navigational parameters. A computer vision based method is integrated along with the developed controller to resolve some conflicting situations that may arise by encountering large sized obstacle or detection of an obstacle exactly in front of the robot where the robot becomes confused regarding the direction of turn. The developed navigational model has been tested in simulation environments by considering NAO robot as the humanoid platform. The simulation results are also verified through an experimental platform developed under research laboratory conditions. The data obtained from both the platforms are compared in terms of navigational parameters and are found to be in close proximity to each other. Finally, the developed navigational model is also authenticated against other existing models for validating better efficiency.

Multilayer, locality aware, telecommunication network deployment algorithm

Purpose – In this paper we propose an iterative approach for the deployment of rural telecommunication networks.
 Methodology/approach/design – This approach relies heavily on the concept of locality, prioritizing small ‘cells’ with a considerable population density, and exploits the natural nesting of the distribution of rural communities, focusing in communities which are populous enough to justify the investment required to provide them with connectivity, and whose sheer size promotes the formation of ‘satellite’ communities that could be benefited from the initial investment at a marginal expense. For this approach, the concept of ‘cells’ is paramount, which are constructed iteratively based on the contour of a Voronoi tessellation centered on the community of interest. Once the focal community has been ‘connected’ with network of the previous layer, the process is repeated with less populous communities at each stage until a coverage threshold has been reached. One of the main contributions of this methodology is that it makes every calculation based on ‘street distance’ instead of Euclidean, giving a more realistic approximate of the length of the network and hence the amount of the investment. To test our results, we ran our experiments on two segregated communities in one of the most complicated terrains, due to the mountain chains, in the state of Chiapas, Mexico.
 Findings – The results suggest that the use of ‘street distance’ and a local approach leads to the deployment of a remarkably different network than the standard methodology would imply.
 Practical implications – The results of this paper might lead to a significant reduction in the costs associated with these kinds of projects and therefore make the democratization of connectivity a reality. In order to make our results reproducible, we make all our code open and publicly available on GitHub.

Spatial correlation-based WRF observation-nudging approach in simulating regional wind field

Accurately simulating the wind field of large-scale region, for instant urban areas, the locations of large span bridges, wind farms and so on, is very difficult, due to the complicated terrains or land surfaces. Currently, the regional wind field can be simulated through the combination of observation data and numerical model using observation-nudging in the Weather Research and Forecasting model (WRF). However, the main drawback of original observation-nudging method in WRF is the effects of observation on the surrounding field is fully mathematical express in terms of temporal and spatial, and it ignores the effects of terrain, wind direction and atmospheric circulation, while these are physically unreasonable for the turbulence. For these reasons, a spatial correlation-based observation-nudging method, which can take account the influence of complicated terrain, is proposed in the paper. The validation and comparation results show that proposed method can obtain more reasonable and accurate result than original observation-nudging method. Finally, the discussion of wind field along bridge span obtained from the simulation with spatial correlation-based observation-nudging method was carried out.

Type Synthesis of Walking Robot Legs

Walking robots use leg structures to overcome obstacles or move on complicated terrains. Most robots of current researches are equipped with legs of simple structure. The specific design method of walking robot legs is seldom studied. Based on the generalized-function (GF) set theory, a systematic type synthesis process of designing robot legs is introduced. The specific mobility of robot legs is analyzed to obtain two main leg types as the goal of design. Number synthesis problem is decomposed into two stages, actuation and constraint synthesis by name, corresponding to the combinatorics results of linear Diophantine equations. Additional restrictions are discussed to narrow the search range to propose practical limb expressions and kinematic-pair designs. Finally, all the fifty-one leg structures of four subtypes are carried out, some of which are chosen to make up robot prototypes, demonstrating the validity of the method. This paper proposed a novel type synthesis methodology, which could be used to systematically design various practical robot legs and the derived robots.

Digital image stabilization in mountain areas using complete ensemble empirical mode decomposition with adaptive noise and structural similarity

Cameras mounted on scouting vehicles frequently suffer from image shake because of unintentional motions. Image shake is a main source of inaccuracies that lead to bad scouting results, particularly in mountain areas with complicated terrains. To overcome this disadvantage, this study proposes a digital image stabilization method based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and structural similarity (SSIM) to generate a stable scouting video sequence. The proposed method first calculates the global motion vector (GMV) from a scouting video sequence using the bit-plane matching algorithm. To separate jitter motion from intentional motion, we decompose GMV into several modes using CEEMDAN. Then according to different structural characteristics, SSIM is used to draw a boundary among modes to separate jitter motion from intentional motion. To evaluate stabilization performance in complicated situations, several known methods and the proposed stabilization method are compared. Experimental results show that CEEMDAN outperforms the other stabilization methods under mountain area conditions.

Quaternion Neural-Network-Based PolSAR Land Classification in Poincare-Sphere-Parameter Space

We propose a quaternion neural-network-based land classification in Poincare-sphere-parameter space. By representing the Stokes vector on/in the Poincare sphere geometrically, we construct two analysis parameters, namely, the position vector and the variation vector, to describe the feature of a pixel in test area. Then, by employing a quaternion feedforward neural network, we generate successful classification results for detecting lake, grass, forest, and town areas. In comparison with the conventional C-matrix-based methods, the proposed method has higher classification performance, especially in detecting forest and town areas. Moreover, the classification result of the proposed method is not influenced by height information. This fact suggests that the proposed classification method can be used for complicated terrains.

Validation study of TMPA 3B42V6 in a typical alpine and gorge region: Jinsha River basin, China

Abstract. Because of density and distribution flaws inherent with in situ rainfall measurements, satellite-based rainfall products, especially the Tropical Rainfall Measuring Mission (TRMM), were expected to offer an alternative or complement for modeling of hydrological processes and water balance analysis. This study aims at evaluating the validity of a standard product, the TRMM Multi-satellite Precipitation Analysis (TMPA) 3B42V6, by comparing it with in situ ground gauge datasets on a typical alpine and gorge region in China, the Jinsha River basin. The validation study involved the performance of the 3B42V6 product on 3 h, daily and monthly temporal scales. Statistical analysis methods were used for rainfall and rain event estimation. The results affirmed that the 3B42V6 product demonstrated increasing accuracy when the temporal scales were increased from 3 h to daily to monthly. The mean correlation coefficient of rainfall time series between the 3B42V6 product and the gauge over the Jinsha River basin reached 0.34 on the 3 h scale, 0.59 on the daily scale, and 0.90 on the monthly scale. The mean probability of detection (POD) of the 3B42V6 product reached 0.34 on the 3 h scale and 0.63 on the daily scale. The 3B42V6 product of 80.4% of stations obtained an acceptable bias (± 25%) over the investigation area. A threshold of nearly 5.0 mm d−1 in daily rainfall intensity split the 3B42V6 product into overestimates (< 5.0 mm d−1) and underestimates (> 5.0 mm d−1). The terrain elements of altitude, longitude, and latitude were the major influencing factors for 3B42V6 performance. In brief, the 3B42V6 dataset has great potential for research on hydrologic processes, especially daily or large temporal scale. As for fine temporal scale applications, such as flood predictions based on a 3 h scale dataset, it is necessary to conduct adjustments or to combine the 3B42V6 product with gauges to be more accurate regarding the issues in the study area or in analogous regions with complicated terrains.

Ferrying Performance Analysis of a New Type All-Terrain Tracked Water Carrier

A new type all-terrain tracked water carrier is customized for water transportation with complicated terrains such as marsh, lake or dessert etc. The vehicle is designed based on combination of all-terrain tracked chassis and water storage tank. The tracked chassis provides the ferrying possibility, while tank structure and the thickness of heat-insulating layer is the key for successful ferrying. To further research the ferrying characteristics, the floatability and initial stability are analyzed. Then to optimize design of the vehicle, mathematic model of buoyancy center, reserve buoyancy and initial stability is established. At last, the field ferrying test is done. The results show the vehicle can ferry successfully in watered areas with a speed of 5.19km/h when fully loaded.

History, Hair, and Reimagining Racial Categories in Junot Díaz's The Brief Wondrous Life of Oscar Wao

In The Brief Wondrous Life of Oscar Wao, Junot Díaz articulates a complex, fluid racial world that defies conventional ideas about racial classification. The novel examines three generations of the Cabral/de León family as they negotiate complicated racial terrains in the Dominican Republic and the United States. This essay explores the historical and cultural factors that have shaped differing conceptions of race in the Dominican Republic and the United States, particularly notions of blackness, whiteness, and Dominican-ness; it then looks to Oscar Wao's engagement with hair as an illustration of the complex, contingent nature of racial categorization.

Spatial and diurnal characteristics of summer rainfall over Beijing Municipality based on a high-density AWS dataset

On basis of quality-control of hourly rainfall dataset of Automatic Weather Stations (AWSs) for the last 4 years (2007–2010), the spatial and diurnal characteristics of summer rainfall in Beijing Municipality (BJM) is analyzed. Results show that the short-duration heavy rainfall events dominate summer rainfall in the study area. Rainfall events with 1–3 h duration make a large contribution to both frequency and amount of summer rainfall, and the total rainfall amount in summer fall almost in the events with duration less than 6 h. Two peaks in diurnal variation of rainfall event frequency are evident, with one in early morning and another in later evening, but only one peak in later evening occurs for diurnal variation of rainfall amount. The exact timing and magnitudes of the peaks vary from one station to another probably due to the influence of the complicated terrains and geographical conditions. Except for the southeast area of the BJM, however, the highest frequency of rainfall events always occurs in evening between 1900 and 2300 (Local Standard Time, or LST), almost consistent to the occurrence time of the maximum rainfall amount. The peak of rainfall event frequency over the southeast area is generally in early morning (0300–0500 LST) which might have been related to the combined influences from land-sea breeze and urbanization.

Vegetation Information Extraction in the South Qinghai Plateau Using Phenology and Supervised Classification

Because of wide ranges,complicated terrains and disparate climates,it is an important problem to increase the classification accuracy for vegetation information extraction in wide ranges.In this paper,it uses division processing and joins vegetation phonological knowledge reflected by NDVI series data and auxiliary information including DEM and GIS data into the supervised classification system to extract vegetation of South Qinghai Plateau.The classification accuracy has reached more than 83.3% by using the method mentioned above and achieved better classification results.It is reliable to help select training areas,using vegetation phonological knowledge,visual interpretation and DEM data and taking land-use data into account.It makes training areas more accurate and improves the accuracy.

Theorizing Resistance in a Global Context Processes, Strategies, and Tactics in Communication Scholarship

In recent years, we have witnessed an increase in scholarship documenting the relevance of theorizing resistance in communication scholarship in globalization contexts. Historically, communication scholars have studied resistance in organizational communication, public relations, health communication, gender, and rhetoric. Our review of this research documents the common threads among distinct yet interdependent lines of scholarship, and we identify additional ways in which communication theorists have explored resistance (and processes for communicating resistance) in the contexts of power, ideology, and hegemony. We conclude our chapter by discussing the need to theorize power, subordination, and resistance as complex and intertwined processes in light of globalization that play out in the complicated terrains of transnational hegemony. In so doing, we suggest an overarching framework for locating studies of resistance in the realm of globalization politics and connecting resistance theories in communication to the possibilities for transformative politics.