scholarly journals An Accurate GEO SAR Range Model for Ultralong Integration Time Based on mth-Order Taylor Expansion

2021 ◽  
Vol 13 (2) ◽  
pp. 255
Author(s):  
Binbin Zhou ◽  
Xiangyang Qi ◽  
Heng Zhang
Keyword(s):  
Taylor Expansion ◽  
Propagation Distance ◽  
Integration Time ◽  
Fast Time ◽  
Simulation Experiments ◽  
Stop And Go ◽  
Geo Satellite ◽  
Order Expansion ◽  
Disaster Monitoring ◽  
Orbital Height

As the Geosynchronous Earth Orbital Synthetic Aperture Radar (GEO SAR) allows a wide area viewing combined with a short revisit cycle, it is suitable for many applications that require high timeliness, such as natural disaster monitoring, weather supervision, and military reconnaissance. However, the ultralong integration time and the invalidation of “stop-and-go” assumption caused by the raise of orbital height also greatly increase the difficulty of signal processing. In this paper, a generalized method for calculating the accurate propagation distance between a GEO satellite and a target with ultralong integration time is proposed. This range model is mainly composed of an accurate pulse transmitting distance and an error compensation term for “stop-and-go” assumption failure. The transmitting distance is obtained by Taylor expansion, and the specific derivation process of the general formula of the mth-order expansion is given, in this paper. As for the compensation term, this is achieved by approximately calculating the pulse receiving distance based on twice Taylor expansion, the first expansion is for fast-time and the other is for slow-time. Finally, a series of simulation experiments were conducted to verify the effectiveness and superiority of this new range model for an ultralong integration time.

The Lord of the Ring Road: A Review and Evaluation of Autonomous Control Policies for Traffic in a Ring Road

2022 ◽  
Vol 6 (1) ◽  
pp. 1-25
Author(s):  
Fang-Chieh Chou ◽  
Alben Rome Bagabaldo ◽  
Alexandre M. Bayen
Keyword(s):  
Reinforcement Learning ◽  
Traffic Control ◽  
Road Traffic ◽  
Control Algorithms ◽  
Dynamical Models ◽  
Vehicle Miles Traveled ◽  
Simulation Experiments ◽  
Traffic Condition ◽  
Ring Road ◽  
Stop And Go

This study focuses on the comprehensive investigation of stop-and-go waves appearing in closed-circuit ring road traffic wherein we evaluate various longitudinal dynamical models for vehicles. It is known that the behavior of human-driven vehicles, with other traffic elements such as density held constant, could stimulate stop-and-go waves, which do not dissipate on the circuit ring road. Stop-and-go waves can be dissipated by adding automated vehicles (AVs) to the ring. Thorough investigations of the performance of AV longitudinal control algorithms were carried out in Flow, which is an integrated platform for reinforcement learning on traffic control. Ten AV algorithms presented in the literature are evaluated. For each AV algorithm, experiments are carried out by varying distributions and penetration rates of AVs. Two different distributions of AVs are studied. For the first distribution scenario, AVs are placed consecutively. Penetration rates are varied from 1 AV (5%) to all AVs (100%). For the second distribution scenario, AVs are placed with even distribution of human-driven vehicles in between any two AVs. In this scenario, penetration rates are varied from 2 AVs (10%) to 11 AVs (50%). Multiple runs (10 runs) are simulated to average out the randomness in the results. From more than 3,000 simulation experiments, we investigated how AV algorithms perform differently with varying distributions and penetration rates while all AV algorithms remained fixed under all distributions and penetration rates. Time to stabilize, maximum headway, vehicle miles traveled, and fuel economy are used to evaluate their performance. Using these metrics, we find that the traffic condition improvement is not necessarily dependent on the distribution for most of the AV controllers, particularly when no cooperation among AVs is considered. Traffic condition is generally improved with a higher AV penetration rate with only one of the AV algorithms showing a contrary trend. Among all AV algorithms in this study, the reinforcement learning controller shows the most consistent improvement under all distributions and penetration rates.

scholarly journals A cavity-enhanced ultraviolet absorption instrument for high-precision, fast-time-response ozone measurements

2020 ◽  
Vol 13 (12) ◽  
pp. 6877-6887
Author(s):  
Reem A. Hannun ◽  
Andrew K. Swanson ◽  
Steven A. Bailey ◽  
Thomas F. Hanisco ◽  
T. Paul Bui ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Light Emitting Diode ◽  
Optical Cavity ◽  
Deposition Velocity ◽  
Flux Measurement ◽  
Ultraviolet Absorption ◽  
Time Response ◽  
Integration Time ◽  
Fast Time ◽  
Optical Cell

Abstract. The NASA Rapid Ozone Experiment (ROZE) is a broadband cavity-enhanced UV (ultraviolet) absorption instrument for the detection of in situ ozone (O3). ROZE uses an incoherent LED (light-emitting diode) light source coupled to a high-finesse optical cavity to achieve an effective pathlength of ∼ 104 m. Due to its high sensitivity and small optical cell volume, ROZE demonstrates a 1σ precision of 80 pptv (parts per trillion by volume) in 0.1 s and 31 pptv in a 1 s integration time, as well as an e-fold time response of 50 ms. ROZE can be operated in a range of field environments, including low- and high-altitude research aircraft, and is particularly suited to O3 vertical-flux measurements using the eddy covariance technique. ROZE was successfully integrated aboard the NASA DC-8 aircraft during July–September 2019 and validated against a well-established chemiluminescence measurement of O3. A flight within the marine boundary layer also demonstrated flux measurement capabilities, and we observed a mean O3 deposition velocity of 0.029 ± 0.005 cm s−1 to the ocean surface. The performance characteristics detailed below make ROZE a robust, versatile instrument for field measurements of O3.

scholarly journals A Trajectory Optimization Strategy for Connected and Automated Vehicles at Junction of Freeway and Urban Road

2021 ◽  
Vol 13 (17) ◽  
pp. 9933
Author(s):  
Zhongtai Jiang ◽  
Dexin Yu ◽  
Huxing Zhou ◽  
Siliang Luan ◽  
Xue Xing
Keyword(s):  
Trajectory Optimization ◽  
Minimum Principle ◽  
Optimization Strategy ◽  
Automated Vehicles ◽  
Simulation Experiments ◽  
Urban Road ◽  
Second Stage ◽  
Stop And Go ◽  
Vehicle Trajectory ◽  
Junction Structure

The phenomenon of stop-and-go traffic and its environmental impact has become a crucial issue that needs to be tackled, in terms of the junctions between freeway and urban road networks, which consist of freeway off-ramps, downstream intersections, and the junction section. The development of Connected and Automated Vehicles (CAVs) has provided promising solutions to tackle the difficulties that arise along intersections and freeway off-ramps separately. However, several problems still exist that need to be handled in terms of junction structure, including vehicle merging trajectory optimization, vehicle crossing trajectory optimization, and heterogeneous decision-making. In this paper, a two-stage CAV trajectory optimization strategy is presented to improve fuel economy and to reduce delays through a joint framework. The first stage considers an approach to determine travel time considering the different topological structures of each subarea to ensure maximum capacity. In the second stage, Pontryagin’s Minimum Principle (PMP) is employed to construct Hamiltonian equations to smooth vehicle trajectory under the requirements of vehicle dynamics and safety. Targeted methods are devised to avoid driving backwards and to ensure an optimal vehicle gap, which make up for the shortcomings of the PMP theory. Finally, simulation experiments are designed to verify the effectiveness of the proposed strategy. The evaluation results show that our strategy could effectively militate travel delays and fuel consumption.

Chemical ionisation mass spectrometry for the measurement of atmospheric amines

2012 ◽  
Vol 9 (3) ◽  
pp. 190 ◽  
Author(s):  
Huan Yu ◽  
Shan-Hu Lee
Keyword(s):  
Real Time ◽  
Gas Phase ◽  
Mass Spectrometer ◽  
Detection Limits ◽  
Integration Time ◽  
Fast Time ◽  
Aerosol Formation ◽  
Secondary Aerosol ◽  
Chemical Ionisation ◽  
Ionisation Mass

Environmental contextAmines are of interest to atmospheric chemistry as they may be important gas-phase precursors for secondary aerosol formation. We describe a mass spectrometer for real-time in-situ measurements of gaseous alkyl amines in the atmosphere. This measurement technique will help to evaluate the contribution of amines to the formation of secondary aerosols, including secondary organic aerosol and new particle formation. AbstractWe describe a chemical ionisation mass spectrometer (CIMS) for the ambient measurement of amines, known as important gas-phase precursors for secondary aerosol formation. Protonated ethanol or acetone ions were used as ionisation reagents to selectively detect high proton affinity base compounds (e.g. amines and NH3), thereby minimising interferences from other atmospheric gaseous organic compounds. With ethanol as ionisation reagent (~3 × 105 Hz of ion signals), the CIMS showed similar sensitivities (2.1–8.7 Hz pptv–1) and detection limits (7–41 pptv with a 1-min integration time) for NH3 and several atmospherically relevant key amine compounds containing one to six carbon atoms (C1- to C6-amines and their isomers). The CIMS background signals of the six amines ranged from 9 to 40 pptv, much lower than ~930 pptv for NH3. The CIMS response times were between 13 and 26 s for these amines. The unique combination of the fast time response, high sensitivities and low detection limits allows the use of this CIMS for real time measurements of atmospheric trace amines. During the ambient measurement made in Kent, OH, in November 2011, the measured mixing ratios of C2- and C3-amines were 8 ± 3 (mean ± 1 standard deviation) and 16 ± 7 pptv, whereas those of NH3 were 517 ± 259 pptv.

scholarly journals A Novel Method for Ocean Wind Speed Detection Based on Energy Distribution of Beidou Reflections

Sensors ◽  
2019 ◽  
Vol 19 (12) ◽  
pp. 2779 ◽  
Author(s):  
Qiang Wang ◽  
Yunlong Zhu ◽  
Kittipong Kasantikul
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
High Energy ◽  
Integration Time ◽  
Coherent Integration ◽  
Energy Zone ◽  
Geo Satellite ◽  
Coherent Integration Time ◽  
The Impact ◽  
Correlation Level

The Global Navigation Satellite System Reflectometry (GNSS-R) technique exploits the characteristics of reflected GNSS signals to estimate the geophysical parameters of the earth’s surface. This paper focuses on investigating the wind speed retrieval method using ocean scattered signals from a Beidou Geostationary Earth Orbit (GEO) satellite. Two new observables are proposed by computing the ratio of the low energy zone and the high energy zone of the delay waveform. Coastal experimental raw data from a Beidou GEO satellite are processed to establish the relationship between the energy-related observables and the sea surface wind. When the delay waveform normalized amplitude (this will be referred to as “threshold” in what follows) is 0.3, fitting results show that the coefficient of determination is more than 0.76 in the gentle wind scenario (<10 m/s), with a root mean square error (RMSE) of less than 1.0 m/s. In the Typhoon UTOR scenario (12.7 m/s~37.3 m/s), the correlation level exceeds 0.82 when the threshold is 0.25, with a RMSE of less than 3.10 m/s. Finally, the impact of the threshold and coherent integration time on wind speed retrieval is discussed to obtain an optimal result. When the coherent integration time is 50 milliseconds and the threshold is 0.15, the best wind speed retrieval error of 2.63 m/s and a correlation level of 0.871 are obtained in the UTOR scenario.

scholarly journals EFFICIENT ESTIMATION USING THE CHARACTERISTIC FUNCTION

2016 ◽  
Vol 33 (2) ◽  
pp. 479-526 ◽  
Author(s):  
Marine Carrasco ◽  
Rachidi Kotchoni
Keyword(s):  
Characteristic Function ◽  
Method Of Moments ◽  
Regularization Parameter ◽  
Estimation Procedure ◽  
Efficient Estimation ◽  
Tuning Parameter ◽  
Finite Sample ◽  
Simulation Experiments ◽  
Order Expansion ◽  
Selection Of

The method of moments procedure proposed by Carrasco and Florens (2000) permits full exploitation of the information contained in the characteristic function and yields an estimator which is asymptotically as efficient as the maximum likelihood estimator. However, this estimation procedure depends on a regularization or tuning parameterαthat needs to be selected. The aim of the present paper is to provide a way to optimally chooseαby minimizing the approximate mean square error (AMSE) of the estimator. Following an approach similar to that of Donald and Newey (2001), we derive a higher-order expansion of the estimator from which we characterize the finite sample dependence of the AMSE onα. We propose to select the regularization parameter by minimizing an estimate of the AMSE. We show that this procedure delivers a consistent estimator ofα. Moreover, the data-driven selection of the regularization parameter preserves the consistency, asymptotic normality, and efficiency of the CGMM estimator. Simulation experiments based on a CIR model show the relevance of the proposed approach.

Symmetric Multistep Methods Revisited: II. Numerical Experiments

1999 ◽  
Vol 173 ◽  
pp. 309-314 ◽  
Author(s):  
T. Fukushima
Keyword(s):  
Multistep Methods ◽  
Computational Time ◽  
Integration Time ◽  
Implicit Methods ◽  
Symmetric Methods ◽  
Celestial Bodies ◽  
The Stability ◽  
Predictor Corrector ◽  
Symmetric Multistep Methods ◽  
Integration Errors

AbstractBy using the stability condition and general formulas developed by Fukushima (1998 = Paper I) we discovered that, just as in the case of the explicit symmetric multistep methods (Quinlan and Tremaine, 1990), when integrating orbital motions of celestial bodies, the implicit symmetric multistep methods used in the predictor-corrector manner lead to integration errors in position which grow linearly with the integration time if the stepsizes adopted are sufficiently small and if the number of corrections is sufficiently large, say two or three. We confirmed also that the symmetric methods (explicit or implicit) would produce the stepsize-dependent instabilities/resonances, which was discovered by A. Toomre in 1991 and confirmed by G.D. Quinlan for some high order explicit methods. Although the implicit methods require twice or more computational time for the same stepsize than the explicit symmetric ones do, they seem to be preferable since they reduce these undesirable features significantly.

Assessing Person Fit With the Information Matrix Test

Methodology ◽  
2015 ◽  
Vol 11 (1) ◽  
pp. 3-12 ◽  
Author(s):  
Jochen Ranger ◽  
Jörg-Tobias Kuhn
Keyword(s):  
Simulation Study ◽  
Type I Error ◽  
Information Matrix ◽  
Small Samples ◽  
Type I ◽  
Person Fit ◽  
Power Of The Test ◽  
Order Expansion ◽  
Trait Stability ◽  
Information Matrix Test

In this manuscript, a new approach to the analysis of person fit is presented that is based on the information matrix test of White (1982) . This test can be interpreted as a test of trait stability during the measurement situation. The test follows approximately a χ2-distribution. In small samples, the approximation can be improved by a higher-order expansion. The performance of the test is explored in a simulation study. This simulation study suggests that the test adheres to the nominal Type-I error rate well, although it tends to be conservative in very short scales. The power of the test is compared to the power of four alternative tests of person fit. This comparison corroborates that the power of the information matrix test is similar to the power of the alternative tests. Advantages and areas of application of the information matrix test are discussed.

PROTOTYPE ALAT PEMANTAU SALURAN AIR BAWAH TANAH DENGAN MENGGUNAKAN WEBCAM C170 BERBASIS RASPBERRY PI

2015 ◽  
Vol 1 (1) ◽  
pp. 37-45
Author(s):  
Irwansyah Irwansyah ◽  
Hendra Kusumah ◽  
Muhammad Syarif
Keyword(s):  
Real Time ◽  
Monitoring System ◽  
Public Awareness ◽  
Underground Water ◽  
Raspberry Pi ◽  
Laptop Computer ◽  
Web Browser ◽  
Disaster Monitoring ◽  
The Times ◽  
Human Desire

Along with the times, recently there have been found tool to facilitate human’s work. Electronics is one of technology to facilitate human’s work. One of human desire is being safe, so that people think to make a tool which can monitor the surrounding condition without being monitored with people’s own eyes. Public awareness of the underground water channels currently felt still very little so frequent floods. To avoid the flood disaster monitoring needs to be done to underground water channels.This tool is controlled via a web browser. for the components used in this monitoring system is the Raspberry Pi technology where the system can take pictures in real time with the help of Logitech C170 webcam camera. web browser and Raspberry Pi make everyone can control the devices around with using smartphone, laptop, computer and ipad. This research is expected to be able to help the users in knowing the blockage on water flow and monitored around in realtime.

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