Measurements of bottom‐limited ocean impulse responses and comparisons with the time‐domain parabolic equation

1993 ◽  
Vol 93 (5) ◽  
pp. 2599-2616 ◽  
Author(s):  
R. L. Field ◽  
J. H. Leclere
Keyword(s):  
Parabolic Equation ◽  
Time Domain ◽  
Impulse Responses ◽  
The Time Domain

scholarly journals Cardiorespiratory kinetics in exercise physiology: estimates and predictions using randomized changes in work rate

2021 ◽  
Author(s):  
Uwe Hoffmann ◽  
Felix Faber ◽  
Uwe Drescher ◽  
Jessica Koschate
Keyword(s):  
Time Domain ◽  
Ventilatory Threshold ◽  
Exercise Physiology ◽  
Work Rate ◽  
Steady States ◽  
Binary Sequences ◽  
Impulse Responses ◽  
Test Protocol ◽  
Two Phases ◽  
The Time Domain

Abstract Purpose Kinetics of cardiorespiratory parameters (CRP) in response to work rate (WR) changes are evaluated by pseudo-random binary sequences (PRBS testing). In this study, two algorithms were applied to convert responses from PRBS testing into appropriate impulse responses to predict steady states values and responses to incremental increases in exercise intensity. Methods 13 individuals (age: 41 ± 9 years, BMI: 23.8 ± 3.7 kg m−2), completing an exercise test protocol, comprising a section of randomized changes of 30 W and 80 W (PRBS), two phases of constant WR at 30 W and 80 W and incremental WR until subjective fatigue, were included in the analysis. Ventilation ($$\dot{V}_{{\text{E}}}$$ V ˙ E ), O2 uptake ($$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 ), CO2 output ($$\dot{V}{\text{CO}}_{2}$$ V ˙ CO 2 ) and heart rate (HR) were monitored. Impulse responses were calculated in the time domain and in the frequency domain from the cross-correlations of WR and the respective CRP. Results The algorithm in the time domain allows better prediction for $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 and $$\dot{V}{\text{CO}}_{2}$$ V ˙ CO 2 , whereas for $$\dot{V}_{{\text{E}}}$$ V ˙ E and HR the results were similar for both algorithms. Best predictions were found for $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 and HR with higher (3–4%) 30 W steady states and lower (1–4%) values for 80 W. Tendencies were found in the residuals between predicted and measured data. Conclusion The CRP kinetics, resulting from PRBS testing, are qualified to assess steady states within the applied WR range. Below the ventilatory threshold, $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 and HR responses to incrementally increasing exercise intensities can be sufficiently predicted.

Time Domain Replica Signal Based Interference Compensation for SP-MIMO/OFDM with Large Delay Spread Channel

2014 ◽  
Vol 5 (4) ◽  
pp. 1-17
Author(s):  
Taichi Sakaue ◽  
Chang-Jun Ahn ◽  
Tatsuya Omori ◽  
Ken-Ya Hashimoto
Keyword(s):  
Mobile Communications ◽  
Time Domain ◽  
Delay Spread ◽  
Impulse Responses ◽  
Channel State ◽  
Large Delay ◽  
Guard Interval ◽  
Interference Compensation ◽  
Mimo Ofdm ◽  
The Time Domain

In mobile communications, MIMO-OFDM transmission performance suffers severe degradation caused by the large delay spread channel greater than guard interval (GI). This is because the excess delay results in considerable inter-symbol interference (ISI) between adjacent symbols and inter-carrier-interference (ICI) among subcarrier in the same symbol. In case of scattered pilot (SP), the interference of pilot signals causes the deterioration of channel estimation. To mitigate this problem, in this paper, we propose the interference compensation scheme using the time domain replica signals. We make the time domain replica signals from detected signals and the excess channel impulse responses over GI. After compensation of the time domain replica signals and the received signals, we recalculate the channel state information (CSI) and the CSI is updated. Finally, we carry out the channel compensation with updated CSI for obtaining accurate compensated signals.

scholarly journals Time Domain Performance Evaluation of UWB Antennas

2020 ◽  
Author(s):  
Gopikrishna Madanan ◽  
Deepti Das Krishna
Keyword(s):  
Transfer Function ◽  
Impulse Response ◽  
Time Domain ◽  
Performance Comparison ◽  
Radiation Patterns ◽  
Impulse Responses ◽  
Linear Time Invariant ◽  
Uwb Antennas ◽  
Time Domains ◽  
The Time Domain

The performance of printed wideband antennas has to be optimized both in frequency and time domains, to qualify for UWB applications. This is especially true in multi-resonant antenna topologies where the excitation of different modes can change phase centers and radiation patterns with frequency. The study presented in this chapter intends to demonstrate the simulation and experimental design for the time domain characterization of UWB antennas. Modeling the antenna as a linear time-invariant system with transfer function and impulse response, distortion caused to a nanosecond pulse is analyzed. Two planar monopole antenna designs are considered for the comparative study: the SQMA and RMA. SQMA is a traditional CPW-fed monopole design with ground modifications for ultra wide-bandwidth. RMA is a rectangular CPW-fed monopole with an impedance transformer arrangement at the antenna feed. RMA maintains constant impedance over the entire UWB and contributes towards maintaining uniformity in the radiation patterns over the entire frequency band by its design. Transfer function measurements are performed for both the azimuthal and elevation planes and the impulse responses are deduced by performing IFFT. Parameters such as FWHM and ringing are computed from the impulse response for the performance comparison. To evaluate the influence of the antenna geometry on a transmitted/received pulse, the impulse responses are convoluted with a standard UWB pulse. The time-domain distortion for the designs is then compared by computing the Fidelity parameter.

scholarly journals Unidirectional amplification with acoustic non-Hermitian space−time varying metamaterial

2022 ◽  
Vol 5 (1) ◽  
Author(s):  
Xinhua Wen ◽  
Xinghong Zhu ◽  
Alvin Fan ◽  
Wing Yim Tam ◽  
Jie Zhu ◽  
...  
Keyword(s):  
Time Domain ◽  
Frequency Conversion ◽  
Space Time ◽  
Time Varying ◽  
Impulse Responses ◽  
Experimental Realization ◽  
Material Gain ◽  
Time Varying Systems ◽  
Hermitian Space ◽  
The Time Domain

AbstractSpace−time modulated metamaterials support extraordinary rich applications, such as parametric amplification, frequency conversion, and non-reciprocal transmission. The non-Hermitian space−time varying systems combining non-Hermiticity and space−time varying capability, have been proposed to realize wave control like unidirectional amplification, while its experimental realization still remains a challenge. Here, based on metamaterials with software-defined impulse responses, we experimentally demonstrate non-Hermitian space−time varying metamaterials in which the material gain and loss can be dynamically controlled and balanced in the time domain instead of spatial domain, allowing us to suppress scattering at the incident frequency and to increase the efficiency of frequency conversion at the same time. An additional modulation phase delay between different meta-atoms results in unidirectional amplification in frequency conversion. The realization of non-Hermitian space−time varying metamaterials will offer further opportunities in studying non-Hermitian topological physics in dynamic and nonreciprocal systems.

Sign in / Sign up

Export Citation Format

Share Document