Performance analysis of dual-frequency range estimation methods in the presence of ionospheric and multipath propagation effects

2012 ◽  
Author(s):  
Jie Zhang ◽  
Danai Skournetou ◽  
Elena-Simona Lohan ◽  
Wei Wang ◽  
Stephan Sand
Keyword(s):  
Performance Analysis ◽  
Multipath Propagation ◽  
Estimation Methods ◽  
Dual Frequency ◽  
Frequency Range ◽  
Range Estimation ◽  
Propagation Effects

scholarly journals A Pilot Study on Home Range and Habitat Use of Chinese Goral (Naemorhedus Griseus): Exploring GPS Tracking Data in Cliff Landscape by Three Estimation Methods

2021 ◽  
Author(s):  
yang teng ◽  
Shupei TANG ◽  
lai heda meng ◽  
Liji Wu ◽  
Zhiqing HAN ◽  
...  
Keyword(s):  
Home Range ◽  
Habitat Use ◽  
Estimation Methods ◽  
Conservation Strategies ◽  
Gps Tracking ◽  
Tracking Data ◽  
Size Estimation ◽  
Range Estimation ◽  
Lower Altitude ◽  
Effective Conservation

Abstract Home range size estimation is a crucial basis for developing effective conservation strategies and provides important insights into animal behavior and ecology. This study aimed at analyzing the home range variations, the influence of altitude in habitat selection, and comparing three methods in home range estimation of Chinese gorals (Naemorhedus griseus) living at a cliff landscape. The results indicated that there were significant differences between the annual home range sizes of individual animals but there was no difference in their seasonal home range sizes based on GPS tracking data of five female Chinese gorals from February 2015 to September 2018. The monthly home ranges decreased dramatically in May, June and July due to birth-giving. Notable seasonal variations were found in the micro-habitats of the Chinese gorals, as reflected by the altitude they inhabit, with higher altitude habitats used in spring and lower altitude habitats used in winter. Additionally, the altitude of monthly habitats was lowest in January, which may indicate an adaptation to low air temperature. We also found differences between estimation methods, namely minimum convex polygon (MCP), kernel density estimation (KDE) and α-local convex hull (α-LoCoH), with seasonal home range sizes derived from α-LoCoH being substantially smaller than those derived from MCP and KDE. In conclusion, our findings filled the gaps in home range study for this endangered species and contributed to effective conservation strategies. Considerations shall have to be given to the variations in home range estimation caused by different methods when dealing with rugged habitats, so as to make sure that any interpretation concerning the habitat use of the targeted species made on basis of such results would be meaningful and valid.

scholarly journals A Pilot Study on Home Range and Habitat Use of Chinese Goral (Naemorhedus Griseus): Exploring GPS Tracking Data in Cliff Landscape by Three Estimation Methods

2021 ◽  
Author(s):  
Yang Teng ◽  
Shupei TANG ◽  
Dalai Menghe ◽  
Liji Wu ◽  
Zhiqing HAN ◽  
...  
Keyword(s):  
Home Range ◽  
Habitat Use ◽  
Estimation Methods ◽  
Conservation Strategies ◽  
Gps Tracking ◽  
Tracking Data ◽  
Size Estimation ◽  
Range Estimation ◽  
Lower Altitude ◽  
Effective Conservation

Abstract Home range size estimation is a crucial basis for developing effective conservation strategies and provides important insights into animal behavior and ecology. This study aimed at analyzing the home range variations, the influence of altitude in habitat selection, and comparing three methods in home range estimation of Chinese gorals (Naemorhedus griseus) living at a cliff landscape. The results indicated that there were significant differences between the annual home range sizes of individual animals but there was no difference in their seasonal home range sizes based on GPS tracking data of five female Chinese gorals from February 2015 to September 2018. The monthly home ranges decreased dramatically in May, June and July due to birth-giving. Notable seasonal variations were found in the micro-habitats of the Chinese gorals, as reflected by the altitude they inhabit, with higher altitude habitats used in spring and lower altitude habitats used in winter. Additionally, the altitude of monthly habitats was lowest in January, which may indicate an adaptation to low air temperature. We also found differences between estimation methods, namely minimum convex polygon (MCP), kernel density estimation (KDE) and α-local convex hull (α-LoCoH), with seasonal home range sizes derived from α-LoCoH being substantially smaller than those derived from MCP and KDE. In conclusion, our findings filled the gaps in home range study for this endangered species and contributed to effective conservation strategies. Considerations shall have to be given to the variations in home range estimation caused by different methods when dealing with rugged habitats, so as to make sure that any interpretation concerning the habitat use of the targeted species made on basis of such results would be meaningful and valid.

scholarly journals HIS-Based Semiactive Suspension Dual-Frequency-Range Switching Control to Improve Ride Comfort and Antiroll Performance

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Xiaojian Wu ◽  
Xiang Qiu ◽  
Bing Zhou ◽  
Juhua Huang ◽  
Tingfang Zhang
Keyword(s):  
Ride Comfort ◽  
Control Method ◽  
Excitation Frequency ◽  
Switching Control ◽  
Parameter Sensitivity ◽  
The Body ◽  
Semiactive Control ◽  
Frequency Bandwidth ◽  
Dual Frequency ◽  
Frequency Range

The parameter sensitivity analysis of a hydraulically interconnected suspension (HIS) system shows that the sensitivity of the vibration responses in the bounce and roll modes to the hydraulic parameters are complementary. A novel HIS-based semiactive control method was thereby proposed to improve ride comfort and antiroll performance. In addition, the classic sky-hook max-min damping switched strategy provides significant benefits around the body resonance, but otherwise performs similarly to, or sometimes even worse than, passive suspension. Therefore, a dual-frequency-range switching strategy, which has optimal max-min damping in both frequency ranges, was developed for improving the ride comfort in a wider frequency bandwidth. In this study, a 9-DOF HIS system dynamics model was established, and the hydraulically interconnected subsystem model was validated experimentally. Subsequently, the elastic and damping characteristics of the hydraulically interconnected subsystem, as well as the parameter sensitivity in bounce mode and roll mode, were analyzed. Next, the sensitive parameters were optimized under sinusoidal excitation at various frequencies, and a frequency-range selector used to determine the excitation frequency range and adjust the shock absorber damping was designed. Finally, simulations in the frequency domain and time domain show that the proposed HIS-based semiactive dual-frequency-range switching control suspension improves the ride comfort in a wider frequency bandwidth and enhances the antiroll performance in the transient and steady steering process.

scholarly journals System-Level Model and Simulation of a Frequency-Tunable Vibration Energy Harvester

Micromachines ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 91 ◽  
Author(s):  
Sofiane Bouhedma ◽  
Yongchen Rao ◽  
Arwed Schütz ◽  
Chengdong Yuan ◽  
Siyang Hu ◽  
...  
Keyword(s):  
Energy Harvester ◽  
Element Model ◽  
Industrial Applications ◽  
System Level ◽  
Dual Frequency ◽  
Frequency Range ◽  
Vibration Energy Harvester ◽  
Resonance Frequencies ◽  
Level Model ◽  
System Level Model

In this paper, we present a macroscale multiresonant vibration-based energy harvester. The device features frequency tunability through magnetostatic actuation on the resonator. The magnetic tuning scheme uses external magnets on linear stages. The system-level model demonstrates autonomous adaptation of resonance frequency to the dominant ambient frequencies. The harvester is designed such that its two fundamental modes appear in the range of (50,100) Hz which is a typical frequency range for vibrations found in industrial applications. The dual-frequency characteristics of the proposed design together with the frequency agility result in an increased operative harvesting frequency range. In order to allow a time-efficient simulation of the model, a reduced order model has been derived from a finite element model. A tuning control algorithm based on maximum-voltage tracking has been implemented in the model. The device was characterized experimentally to deliver a power output of 500 µW at an excitation level of 0.5 g at the respected frequencies of 63.3 and 76.4 Hz. In a design optimization effort, an improved geometry has been derived. It yields more close resonance frequencies and optimized performance.

scholarly journals Radio Observations of the Crab Nebula Pulsar

1971 ◽  
Vol 46 ◽  
pp. 73-83
Author(s):  
F. D. Drake
Keyword(s):  
Multipath Propagation ◽  
Crab Nebula ◽  
Crab Pulsar ◽  
Great Intensity ◽  
Radio Observations ◽  
Radiated Power ◽  
Propagation Effects ◽  
The Crab Nebula

The radio properties of the Crab Nebula pulsar are reviewed. The pulsar lies at the centre of the Crab Nebula and has a period of 33 msec. Its increase in period with time releases an amount of energy which is equal in magnitude to the total radiated power. Instabilities in the period of the Crab pulsar have been discovered with timescales ranging from days to months. The length of the pulse increases at longer wavelengths due apparently to multipath propagation effects. A characteristic of the Crab pulsar is the great intensity of the occasional pulse.

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