scholarly journals Highway Reliability Management Model Based on Depth Recursion for Transportation Demand

CONVERTER ◽  
2021 ◽  
pp. 470-481
Author(s):  
Guozhen Sang
Keyword(s):  
Transition Probability ◽  
Estimation Method ◽  
Sampling Technique ◽  
Reliability Estimation ◽  
Estimation Accuracy ◽  
Optimal Test ◽  
Transportation Demand ◽  
Reliability Management ◽  
Model Based ◽  
The Difference

An effective estimation method for the highway reliability management according to the Zhukov usage model based on the recursive test is put forward. This method makes use of the important sampling technique to ensure that under the conditions of the unbiased reliability estimation, the depth recursion is used to measure the difference between the operation profile and the distribution of the zero variance sampling, to correct the test profile by adjusting the transition probability between all the states through the heuristic iterative process. It has proved theoretically that the reliability of the estimation using the modified test profile test is unbiased estimate with the variance of 0. Finally, the heuristic iterative algorithm for the generation of the optimal test profile of the highway reliability estimation is given. The simulation results show that the method put forward in this paper can significantly reduce the variance of the estimate compared with the Newton algorithm, and can increase the speed of the recursive test while improving the estimation accuracy at the same time. The research done in this paper can effectively meet the requirements of the transportation industry in the tertiary industry.

scholarly journals Estimation accuracy of covariance matrices when their eigenvalues are almost duplicated

2018 ◽  
Vol 7 ◽  
Author(s):  
Kantaro Shimomura ◽  
Kazushi Ikeda
Keyword(s):  
Covariance Matrix ◽  
Estimation Method ◽  
Estimation Accuracy ◽  
Essential Information ◽  
The Matrix ◽  
The Difference ◽  
Processing Techniques ◽  
Monotonic Property ◽  
Signal Processing Techniques ◽  
Special Case

The covariance matrix of signals is one of the most essential information in multivariate analysis and other signal processing techniques. The estimation accuracy of a covariance matrix is degraded when some eigenvalues of the matrix are almost duplicated. Although the degradation is theoretically analyzed in the asymptotic case of infinite variables and observations, the degradation in finite cases are still open. This paper tackles the problem using the Bayesian approach, where the learning coefficient represents the generalization error. The learning coefficient is derived in a special case, i.e., the covariance matrix is spiked (all eigenvalues take the same value except one) and a shrinkage estimation method is employed. Our theoretical analysis shows a non-monotonic property that the learning coefficient increases as the difference of eigenvalues increases until a critical point and then decreases from the point and converged to the distinct case. The result is validated by numerical experiments.

scholarly journals A Novel ULA-Difference-Coarray-Based DOA Estimation Method for General Coherent Signals

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zhang Chen ◽  
Hao Wu ◽  
Yongxiang Liu
Keyword(s):  
Good Accuracy ◽  
Linear Array ◽  
Estimation Method ◽  
Doa Estimation ◽  
Estimation Accuracy ◽  
Coherent Signals ◽  
Low Snr ◽  
Sample Covariance ◽  
Lower Complexity ◽  
The Difference

In this article, a difference-coarray-based direction of arrival (DOA) method is introduced, which utilizes the uniform linear array (ULA) in a novel fashion to address the problem of DOA estimation for coherent signals. Inspired by the coarray-based estimators employed in cases of sparse arrays, we convert the sample covariance matrix of the observed signals into the difference coarray domain and process the signals using a spatial smoothing technique. The proposed method exhibits good accuracy and robustness in both the uncorrelated and coherent cases. Numerical simulations verify that the ULA difference coarray- (UDC-) based method can achieve good DOA estimation accuracy even when the SNR is very low. In addition, the UDC-based method is insensitive to the number of snapshots. Under extremely challenging conditions, the proposed UDC-ES-DOA method is preferred because of its outstanding robustness, while the UDC-MUSIC method is suitable for most moderate cases of lower complexity. Due to its demonstrated advantages, the proposed method is a promising and competitive solution for practical DOA estimation, especially for low-SNR or snapshot-limited applications.

scholarly journals A Time-Efficient and Accurate Open Circuit Voltage Estimation Method for Lithium-Ion Batteries

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1803 ◽  
Author(s):  
Yingjie Chen ◽  
Geng Yang ◽  
Xu Liu ◽  
Zhichao He
Keyword(s):  
Lithium Ion Batteries ◽  
Open Circuit Voltage ◽  
Estimation Method ◽  
Nonlinear Function ◽  
Lithium Ion ◽  
Open Circuit ◽  
Constant Current ◽  
Estimation Accuracy ◽  
Battery Modeling ◽  
The Difference

The open circuit voltage (OCV) of lithium-ion batteries is widely used in battery modeling, state estimation, and management. However, OCV is a function of state of charge (SOC) and battery temperature (Tbat) and is very hard to estimate in terms of time efficiency and accuracy. This is because two problems arise in normal operations: (1) Tbat changes with the current (I), which makes it very hard to obtain the data required to estimate OCV—terminal voltage (U) data of different I under the same Tbat; (2) the difference between U and OCV is a complex nonlinear function of I and is very difficult to accurately calculate. Therefore, existing methods have to design special experiments to avoid these problems, which are very time consuming. The proposed method consists of a designed test and a data processing algorithm. The test is mainly constant current tests (CCTs) of large I, which is time-efficient in obtaining data. The algorithm solves the two problems and estimates OCV accurately using the test data. Experimental results and analyses showed that experimental time was reduced and estimation accuracy was adequate.

scholarly journals A Hybrid Method for SOC Estimation of Power Battery

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Jiliang Yi ◽  
Xuechun Zhou ◽  
Jin Zhang ◽  
Zhongqi Li
Keyword(s):  
Hybrid Method ◽  
Estimation Method ◽  
Threshold Value ◽  
Least Square ◽  
Convergence Time ◽  
Equivalent Model ◽  
Estimation Accuracy ◽  
Soc Estimation ◽  
Power Battery ◽  
The Difference

The accuracy of battery state of charge (SOC) is crucial for solving the problems such as overcharge, overdischarge, and mileage anxiety of electric vehicle power battery. In this study, an SOC estimation method using a hybrid method (HM) based on threshold switching is proposed, which combines the advantages of the extended Kalman filter (EKF) and the ampere hour integration (AHI) to improve the estimation accuracy and convergence speed. First, the parameters of the second-order RC equivalent model are identified using the least square. Then, the equation of EKF for updating the state variable is reconstructed by using the identified parameters to solve the problem of multiple iterations caused by the uncertainty of the initial value. Finally, the difference between the estimated voltage and the sampling voltage is used as the threshold value for switching between the AHI and the EKF to estimate the SOC of the battery. Simulation results show that the estimated SOC error of the proposed algorithm is less than 1.6% and the convergence time is within 70 s. Experiments under different SOC initial values are carried out to prove the advantages of the proposed method.

On Estimating the Reliability of Multiple Failure Region Problems Using Approximate Metamodels

2009 ◽  
Vol 131 (12) ◽  
Author(s):  
Ramon C. Kuczera ◽  
Zissimos P. Mourelatos
Keyword(s):  
Limit State ◽  
Estimation Method ◽  
Sampling Technique ◽  
Computational Effort ◽  
Reliability Estimation ◽  
Accurate Estimation ◽  
Limit States ◽  
Failure Region ◽  
Sample Points ◽  
Global And Local

In a complex system it is desirable to reduce the number of expensive function evaluations required for an accurate estimation of the probability of failure. An efficient reliability estimation method is presented for engineering systems with multiple failure regions and potentially multiple most probable points. The method can handle implicit nonlinear limit state functions with correlated or noncorrelated random variables, which can be described by any probabilistic distribution. It uses a combination of approximate or “accurate-on-demand,” global and local metamodels, which serve as indicators to determine the failure and safe regions. Sample points close to limit states define transition regions between safe and failure domains. A clustering technique identifies all transition regions, which can be, in general, disjoint, and local metamodels of the actual limit states are generated for each transition region. Importance sampling generates sample points only in the identified transition and failure regions, thus, allowing the method to focus on the areas near the failure region and not expend computational effort on the sample points in the safe domain. A robust maximin “space-filling” sampling technique is used to construct the metamodels. Two numerical examples highlight the accuracy and efficiency of the method.

Clara Ng: A Brief Journey of A Remarkable Female for Our Time

2019 ◽  
Author(s):  
Adib Rifqi Setiawan
Keyword(s):  
Qualitative Methods ◽  
Publishing Industry ◽  
Sampling Technique ◽  
Data Sources ◽  
Validity And Reliability ◽  
External Audit ◽  
Narrative Approaches ◽  
Career Opportunities ◽  
The Difference ◽  
Interviewing Techniques

This work examines what it has been and continues to be like for Clara Ng to be a home mother and an author in the publishing industry. Our exploration uses qualitative methods of narrative approaches in the form of biographical studies. Participants as data sources were selected using a purposive sampling technique which was collected based on retrospective interviewing techniques and then checked for validity and reliability using external audit. It gained that Clara Ng is a remarkable female whose synthesizes the difference between home mother and author’s career in the publishing industry. She did not seek fame nor did she seek self aggrandizement, her whole life was one of service to humanity, an indefatigable work ethic, and humility. Clara Ng’s journey offers insights offers examples of many ways in which home mothers can, and should, work to improve the career opportunities available to those who follow in their footsteps.

scholarly journals Low-complexity beam-domain channel estimation and power allocation in hybrid architecture massive MIMO systems

2019 ◽  
Vol 2019 (1) ◽  
Author(s):  
Xiao Chen ◽  
Zaichen Zhang ◽  
Liang Wu ◽  
Jian Dang
Keyword(s):  
Channel Estimation ◽  
Power Allocation ◽  
Spectral Efficiency ◽  
Communication Systems ◽  
Mimo Systems ◽  
Beam Steering ◽  
Estimation Method ◽  
Low Complexity ◽  
Estimation Accuracy ◽  
Hybrid Architecture

Abstract In this journal, we investigate the beam-domain channel estimation and power allocation in hybrid architecture massive multiple-input and multiple-output (MIMO) communication systems. First, we propose a low-complexity channel estimation method, which utilizes the beam steering vectors achieved from the direction-of-arrival (DOA) estimation and beam gains estimated by low-overhead pilots. Based on the estimated beam information, a purely analog precoding strategy is also designed. Then, the optimal power allocation among multiple beams is derived to maximize spectral efficiency. Finally, simulation results show that the proposed schemes can achieve high channel estimation accuracy and spectral efficiency.

scholarly journals Educational Video Improves Knowledge about Outpatients’ Usage of Antibiotics in Two Public Hospitals in Indonesia

Antibiotics ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 606
Author(s):  
Fauna Herawati ◽  
Rika Yulia ◽  
Bustanul Arifin ◽  
Ikhwan Frasetyo ◽  
Setiasih ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
General Hospital ◽  
Sampling Technique ◽  
Knowledge Score ◽  
Antibiotic Use ◽  
Public Hospitals ◽  
Educational Video ◽  
Inappropriate Use ◽  
Quasi Experimental ◽  
The Difference

The inappropriate use or misuse of antibiotics, particularly by outpatients, increases antibiotic resistance. A lack of public knowledge about “Responsible use of antibiotics” and “How to obtain antibiotics” is a major cause of this. This study aimed to assess the effectiveness of an educational video about antibiotics and antibiotic use to increase outpatients’ knowledge shown in two public hospitals in East Java, Indonesia. A quasi-experimental research setting was used with a one-group pre-test—post-test design, carried out from November 2018 to January 2019. The study population consisted of outpatients to whom antibiotics were prescribed. Participants were selected using a purposive sampling technique; 98 outpatients at MZ General Hospital in the S regency and 96 at SG General Hospital in the L regency were included. A questionnaire was used to measure the respondents’ knowledge, and consisted of five domains, i.e., the definition of infections and antibiotics, obtaining the antibiotics, directions for use, storage instructions, and antibiotic resistance. The knowledge test score was the total score of the Guttman scale (a dichotomous “yes” or “no” answer). To determine the significance of the difference in knowledge before and after providing the educational video and in the knowledge score between hospitals, the (paired) Student’s t-test was applied. The educational videos significantly improved outpatients’ knowledge, which increased by 41% in MZ General Hospital, and by 42% in SG General Hospital. It was concluded that an educational video provides a useful method to improve the knowledge of the outpatients regarding antibiotics.

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