ELEVATION ANGLE MEASUREMENT ABOVE THE SEA SURFACE USING THE ROOT-MUSIC METHOD. SELECTION OF SOLUTIONS

Sea surface height can be measured with the delay between reflected and direct global navigation satellite system (GNSS) signals. The arrival time of a feature point, such as the waveform peak, the peak of the derivative waveform, and the fraction of the peak waveform is not the true arrival time of the specular signal; there is a bias between them. This paper aims to analyze and calibrate the bias to improve the accuracy of sea surface height measured by using the reflected signals of GPS CA, Galileo E1b and BeiDou B1I. First, the influencing factors of the delay bias, including the elevation angle, receiver height, wind speed, pseudorandom noise (PRN) code of GPS CA, Galileo E1b and BeiDou B1I, and the down-looking antenna pattern are explored based on the Z-V model. The results show that (1) with increasing elevation angle, receiver height, and wind speed, the delay bias tends to decrease; (2) the impact of the PRN code is uncoupled from the elevation angle, receiver height, and wind speed, so the delay biases of Galileo E1b and BeiDou B1I can be derived from that of GPS CA by multiplication by the constants 0.32 and 0.54, respectively; and (3) the influence of the down-looking antenna pattern on the delay bias is lower than 1 m, which is less than that of other factors; hence, the effect of the down-looking antenna pattern is ignored in this paper. Second, an analytical model and a neural network are proposed based on the assumption that the influence of all factors on the delay bias are uncoupled and coupled, respectively, to calibrate the delay bias. The results of the simulation and experiment show that compared to the meter-level bias before the calibration, the calibrated bias decreases the decimeter level. Based on the fact that the specular points of several satellites are visible to the down-looking antenna, the multi-observation method is proposed to calibrate the bias for the case of unknown wind speed, and the same calibration results can be obtained when the proper combination of satellites is selected.

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UUX Method Selection

i-com ◽

10.1515/icom-2016-0011 ◽

2016 ◽

Vol 15 (1) ◽

Author(s):

Holger Fischer ◽

Michaela Kauer-Franz ◽

Dominique Winter ◽

Stefan Latt

Keyword(s):

Software Development ◽

Present Article ◽

User Experience ◽

Interactive System ◽

Human Centered Design ◽

Method Selection ◽

Development Processes ◽

Context Of Use ◽

Selection Of

AbstractThe establishment of human-centered design within software development processes is still a challenge. Numerous methods exist that aim to increase the usability and user experience of an interactive system. Nevertheless, the selection of appropriate methods remains to be challenging, as there are multiple different factors that have a significant impact on the appropriateness of the methods in their context of use. The present article investigates current strategies of method selection based on a conference workshop with practitioners. The results show that usability and user experience professionals concentrate on five to seven well-known methods and will need more support to select and use further ones.

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Construction and Method Selection of Comprehensive Evaluation Index System for Foreign Oil Cooperation Programs

DEVELOPMENT ECONOMICS OF CHINA ◽

10.47297/wspdecwsp2515-797301.20180201 ◽

2018 ◽

Vol 2 (1) ◽

pp. 3-18

Author(s):

XU Hailong

Keyword(s):

Index System ◽

Comprehensive Evaluation ◽

Evaluation Index System ◽

Evaluation Index ◽

Method Selection ◽

Selection Of

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Model-Based Design and Optimization of Passive Shoulder Exoskeletons

10.1115/detc2021-69437 ◽

2021 ◽

Author(s):

Ali Nasr ◽

Spencer Ferguson ◽

John McPhee

Keyword(s):

Elevation Angle ◽

Differential Algebraic Equations ◽

Joint Torque ◽

Algebraic Equations ◽

Joint Torques ◽

Design And Optimization ◽

Passive Mechanism ◽

Wide Range ◽

Passive Exoskeleton ◽

Selection Of

Abstract To physically assist workers in reducing musculoskeletal strain or to develop motor skills for patients with neuromuscular disabilities, recent research has focused on Exoskeletons (Exos). Designing active Exos is challenging due to the complex human geometric structure, the human-Exoskeleton wrench interaction, the kinematic constraints, and the selection of power source characteristics. Because of the portable advantages of passive Exos, designing a passive shoulder mechanism has been studied here. The study concentrates on modeling a 3D multibody upper-limb human-Exoskeleton, developing a procedure of analyzing optimal assistive torque profiles, and optimizing the passive mechanism features for desired tasks. The optimization objective is minimizing the human joint torques. For simulating the complex closed-loop multibody dynamics, differential-algebraic equations (DAE)s of motion have been generated and solved. Three different tasks have been considered, which are common in industrial environments: object manipulation, over-head work, and static pointing. The resulting assistive Exoskeleton’s elevation joint torque profile could decrease the specific task’s human shoulder torque. Since the passive mechanism produces a specific torque for a given elevation angle, the Exoskeleton is not versatile or optimal for different dynamic tasks. We concluded that designing a passive Exoskeleton for a wide range of dynamic applications is impossible. We hypothesize that augmenting an actuator to the mechanism can provide the necessary adjustment torque and versatility for multiple tasks.

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Characteristics and Applications of the Ground-Based X Band Low Elevation Angle Brightness Temperatures under Low Sea State Based on Measured Data

Remote Sensing ◽

10.3390/rs12111736 ◽

2020 ◽

Vol 12 (11) ◽

pp. 1736

Author(s):

Zhongqing Cao ◽

Lixin Guo ◽

Shifeng Kang ◽

Xianhai Cheng ◽

Qingliang Li ◽

...

Keyword(s):

Wind Speed ◽

Meteorological Data ◽

Surface Wind ◽

Elevation Angle ◽

Surface Wind Speed ◽

Sea Surface ◽

Sea State ◽

Sea Surface Wind Speed ◽

Sea Surface Wind ◽

X Band

In ground-based microwave radiometer remote sensing, low-elevation-angle (−3°~3°) radiation data are often discarded because they are considered to be of little value and are often difficult to model due to the complicated mechanism. Based on the observed X-band horizontal polarization low elevation angle microwave radiation data and the meteorological data at the same time, this study investigated the generation mechanism of low elevation angle brightness temperature (LEATB) and its relationship with meteorological data, i.e., temperature, humidity, and wind speed, under low sea state. As a result, one could find that the LEATB was sensitive to the atmosphere at the elevation angle between 1° to 3°, and a diurnal variation of the LEATB reached up to 10 K. This study also found a linear relationship between the LEATB and sea surface wind speed under low sea state at an elevation range from −3° to 0°, i.e., the brightness temperature decreased as the wind speed increased, which was inconsistent with the observations at the elevation angle from −10° to −5°. The variation of the LEATB difference according to the change in the over-the-horizon detection capability (OTHDC) of the shipborne microwave radar was examined to identify the reason for this phenomenon theoretically. The results showed that the LEATB difference was significantly influenced by a change in the OTHDC. Further, this study examined a remote sensing method to extract the sea surface wind speed data from experimental LEATB data under low sea state. The results demonstrated that the X-band horizontal polarization LEATBs were useful to retrieve the sea surface wind speed data at a reasonable accuracy—the root mean square error of 0.02408 m/s. Overall, this study proved the promising potential of the LEATB data for retrieving temperature profiles, humidity profiles, sea surface winds, and the OTHDC.

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