scholarly journals A Controllable Success Fix Rate Threshold Determination Method for GNSS Ambiguity Acceptance Tests

2019 ◽  
Vol 11 (7) ◽  
pp. 804 ◽  
Author(s):  
Lei Wang ◽  
Ruizhi Chen ◽  
Lili Shen ◽  
Fu Zheng ◽  
Yanming Feng ◽  
...  
Keyword(s):  
Likelihood Ratio ◽  
Failure Rate ◽  
Test Theory ◽  
Acceptance Test ◽  
Determination Method ◽  
Ratio Requirement ◽  
Threshold Determination ◽  
Gnss Data ◽  
The Impact ◽  
Acceptance Tests

GNSS integer ambiguity acceptance test is one of the open problems in GNSS data processing. A number of ambiguity acceptance tests have been proposed from different perspectives and then unified into the integer aperture estimation framework. The existing comparative studies indicate that the impact of test statistics form on the test performance is less critical, while how to construct an efficient, practical test threshold is still challenging. Based on the likelihood ratio test theory, a new computationally efficient ambiguity acceptance test with controllable success fix rate, namely the fixed likelihood ratio (FL-) approach is proposed, which does not require Monte Carlo simulation. The study indicates that the fixed failure rate (FF-) approach can only control the overall failure rate of the acceptance region, but the local failure rate is not controllable. The proposed FL-approach only accepts the fixed solution meeting the likelihood ratio requirement. With properly chosen likelihood ratio threshold, the FL-approach achieves comparable success rate as the FF-approach and even lower failure rate than the FF-approach for the strong underlying model cases. The fixed success fix rate of the FL-approach is verified with both simulation data and real GNSS data. The numerical results indicate that the success fix rate of the FL-approach achieves >98% while the failure rate is <1.5%. The RTK positioning with ambiguities tested by the FL-approach achieved 1–2cm horizontal precision and 2–4 cm vertical precision for all tested baselines, which confirms that the FL-approach can serve as a reliable and efficient threshold determination method for the GNSS ambiguity acceptance test problem.

scholarly journals Improving GNSS Ambiguity Acceptance Test Performance with the Generalized Difference Test Approach

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 3018 ◽  
Author(s):  
Lei Wang ◽  
Ruizhi Chen ◽  
Lili Shen ◽  
Yanming Feng ◽  
Yuanjin Pan ◽  
...  
Keyword(s):  
Success Rate ◽  
Failure Rate ◽  
Rapid Determination ◽  
Integer Ambiguity ◽  
Threshold Function ◽  
Acceptance Test ◽  
Data Set ◽  
Fixed Failure Rate ◽  
Gnss Data ◽  
Difference Test

In Global navigation satellite system (GNSS) data processing, integer ambiguity acceptance test is considered as a challenging problem. A number of ambiguity acceptance tests have been proposed from different perspective and then unified into the integer aperture estimation (IA) framework. Among all the IA estimators, the optimal integer aperture (OIA) achieves the highest success rate with the fixed failure rate tolerance. However, the OIA is of less practical appealing due to its high computation complexity. On the other hand, the popular discrimination tests employ only two integer candidates, which are the essential reason for their sub-optimality. In this study, a generalized difference test (GDT) is proposed to exploit the benefit of including three or more integer candidates to improve their performance from theoretical perspective. The simulation results indicate that the third best integer candidates contribute to more than 70% success rate improvement for integer bootstrapping success rate higher than 0.8 case. Therefore, the GDT with three integer candidates (GDT3) achieves a good trade-off between the performance and computation burden. The threshold function is also applied for rapid determination of the fixed failure rate (FF)-threshold for GDT3. The performance improvement of GDT3 is validated with real GNSS data set. The numerical results indicate that GDT3 achieves higher empirical success rate while the empirical failure rate remains comparable. In a 20 km baseline test, the success rate GDT3 increase 7% with almost the same empirical failure rate.

scholarly journals Evaluation of Energy Absorption Capabilities of Polyethylene Foam under Impact Deformation

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3613
Author(s):  
Baohui Yang ◽  
Yangjie Zuo ◽  
Zhengping Chang
Keyword(s):  
Energy Absorption ◽  
Failure Modes ◽  
High Strain ◽  
Early Stage ◽  
High Energy ◽  
Test Method ◽  
Test Theory ◽  
Strain Rates ◽  
Impact Properties ◽  
The Impact

Foams are widely used in protective applications requiring high energy absorption under impact, and evaluating impact properties of foams is vital. Therefore, a novel test method based on a shock tube was developed to investigate the impact properties of closed-cell polyethylene (PE) foams at strain rates over 6000 s−1, and the test theory is presented. Based on the test method, the failure progress and final failure modes of PE foams are discussed. Moreover, energy absorption capabilities of PE foams were assessed under both quasi-static and high strain rate loading conditions. The results showed that the foam exhibited a nonuniform deformation along the specimen length under high strain rates. The energy absorption rate of PE foam increased with the increasing of strain rates. The specimen energy absorption varied linearly in the early stage and then increased rapidly, corresponding to a uniform compression process. However, in the shock wave deformation process, the energy absorption capacity of the foam maintained a good stability and exhibited the best energy absorption state when the speed was higher than 26 m/s. This stable energy absorption state disappeared until the speed was lower than 1.3 m/s. The loading speed exhibited an obvious influence on energy density.

scholarly journals Threshold determination method of Duffing chaotic system based on multi-scale entropy

2020 ◽  
Vol 69 (16) ◽  
pp. 160501
Author(s):  
Ze-Hui Huang ◽  
Ya-An Li ◽  
Zhe Chen ◽  
Lian Liu
Keyword(s):  
Chaotic System ◽  
Determination Method ◽  
Multi Scale ◽  
Threshold Determination

scholarly journals Sensitivity Of Differential Item Functioning Detection Methods On National Mathematics Examination In North Sumatera Province, Indonesia

2019 ◽  
Vol 8 (5C) ◽  
pp. 1538-1549
Keyword(s):  
Differential Item Functioning ◽  
Likelihood Ratio ◽  
Classical Test Theory ◽  
Test Theory ◽  
Detection Methods ◽  
Ratio Method ◽  
Suitable Model ◽  
Data Set ◽  
Item Functioning ◽  
Mathematics Examination

The purpose of this study was to examine the differences in sensitivity of three methods: IRT-Likelihood Ratio (IRT-LR), Mantel-Haenszel (MH) and Logistics Regression (LR), in detecting gender differential item functioning (DIF) on National Mathematics Examination (Ujian Nasional: UN) for 2014/2015 academic year in North Sumatera Province of Indonesia. DIF item shows the unfairness. It advantages the test takers of certain groups and disadvantages other group test takers, in the case they have the same ability. The presence of DIF was reviewed in grouping by gender: men as reference groups (R) and women as focus groups (F). This study used the experimental method, 3x1 design, with one factor (i.e. method) with three treatments, in the form of 3 different DIF detection methods. There are 5 types of UN Mathematics Year 2015 packages (codes: 1107, 2207, 3307, 4407 and 5507). The 2207 package code was taken as the sample data, consisting of 5000 participants (3067 women, 1933 men; for 40 UN items). Item selection was carried out based on the classical test theory (CTT) on 40 UN items, producing 32 items that fulfilled, and item response theory selection (IRT) produced 18 items that fulfilled. With program R 3.333 and IRTLRDIF 2.0, it was found 5 items were detected as DIF by the IRT-Likelihood Ratio-method (IRTLR), 4 items were detected as DIF by the Logistic Regression method (LR), and 3 items were detected as DIF by the MantelHaenszel method (MH). To test the sensitivity of the three methods, it is not enough with just one time DIF detection, but formed six groups of data analysis: (4400,40),(4400,32), (4400,18), (3000,40), (3000,32), (3000,18), and generate 40 random data sets (without repetitions) in each group, and conduct detecting DIF on the items in each data set. Although the data lacks model fit, the 3 parameter logistic model (3PL) is chosen as the most suitable model. With the Tukey's HSD post hoc test, the IRT-LR method is known to be more sensitive than the MH and LR methods in the group (4400,40) and (3000,40). The IRT-LR method is not longer more sensitive than LR in the group (4400,32) and (3000,32), but still more sensitive than MH. In the groups (4400,18) and (3000,18) the IRT-LR method is more sensitive than LR, but not significantly more sensitive than MH. The LR method is consistently tested to be more sensitive than the MH method in the entire analysis groups.

scholarly journals A New Wavelet Threshold Determination Method Considering Interscale Correlation in Signal Denoising

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Can He ◽  
Jianchun Xing ◽  
Juelong Li ◽  
Qiliang Yang ◽  
Ronghao Wang
Keyword(s):  
Simulation Experiment ◽  
Simple Calculation ◽  
Signal Denoising ◽  
Determination Method ◽  
Propagation Characteristics ◽  
Correlation Index ◽  
Denoising Method ◽  
Threshold Determination ◽  
New Correlation ◽  
Simulation Results

Due to simple calculation and good denoising effect, wavelet threshold denoising method has been widely used in signal denoising. In this method, the threshold is an important parameter that affects the denoising effect. In order to improve the denoising effect of the existing methods, a new threshold considering interscale correlation is presented. Firstly, a new correlation index is proposed based on the propagation characteristics of the wavelet coefficients. Then, a threshold determination strategy is obtained using the new index. At the end of the paper, a simulation experiment is given to verify the effectiveness of the proposed method. In the experiment, four benchmark signals are used as test signals. Simulation results show that the proposed method can achieve a good denoising effect under various signal types, noise intensities, and thresholding functions.

Differentiating Among High-Achieving Learners: A Comparison of Classical Test Theory and Item Response Theory on Above-Level Testing

2020 ◽  
Vol 64 (3) ◽  
pp. 219-237
Author(s):  
Brandon LeBeau ◽  
Susan G. Assouline ◽  
Duhita Mahatmya ◽  
Ann Lupkowski-Shoplik
Keyword(s):  
Item Response Theory ◽  
Item Response ◽  
Classical Test Theory ◽  
Reliability And Validity ◽  
Test Theory ◽  
Response Theory ◽  
Classical Test ◽  
High Achieving Students ◽  
High Achieving ◽  
The Impact

This study investigated the application of item response theory (IRT) to expand the range of ability estimates for gifted (hereinafter referred to as high-achieving) students’ performance on an above-level test. Using a sample of fourth- to sixth-grade high-achieving students ( N = 1,893), we conducted a study to compare estimates from two measurement theories, classical test theory (CTT) and IRT. CTT and IRT make different assumptions about the analysis that impact the reliability and validity of the scores obtained from the test. IRT can also differentiate students based on the student’s grade or within a grade by using the unique string of correct and incorrect answers the student makes while taking the test. This differentiation may have implications for identifying or classifying students who are ready for advanced coursework. An exploration of the differentiation for Math, Reading, and Science tests and the impact the different measurement frameworks can have on classification of students are explored. Implications for academic talent identification with the talent search model and development of academic talent are discussed.

Sign in / Sign up

Export Citation Format

Share Document