Number Of Test Points Research Articles

Strain response prediction of offshore wind turbine tower under free vibration

Strain monitoring of critical locations in offshore wind turbine tower is essential for fatigue life prediction and safe operation of wind turbine. This paper theoretically analyses the feasibility of predicting tower strain under free vibration using the modal superposition method. A finite element numerical model of the tower is established, and the displacement mode and strain mode parameters of the tower are extracted. The initial displacement and strain of the tower at cut-out wind speed are analyzed, and the first three modal coordinate of the tower are calculated using test points of displacement or strain separately. Subsequently, the full field strain of the tower is predicted using the modal superposition method. Comparative results demonstrate higher accuracy in modal coordinate values calculated using test points of displacement, and the accuracy and errors of strain prediction using different numbers of test points are compared, emphasizing the crucial role of selecting optimal positions and numbers of test points in improving prediction accuracy.

Prediction error analysis for intelligent management and predictive diagnostics systems

Random signal prediction is efficient for intelligent management and predictive diagnostics systems. Aim. The paper aims to analyse the error of random signal prediction. To develop recommendations for the selection of random signal extrapolator parameters. Methods. The paper uses the mathematics of the theory of random functions, formalization adopted in the theory of pulse systems, mathematical description of extrapolators with Chebyshev polynomials orthogonal over a set of equally spaced points. The coefficients of the predicting polynomial are selected according to the minimal least squares. Results. The paper describes the mathematical model of the extrapolator. Design ratios were obtained for prediction error assessments. The maximum and prediction interval-averaged relative mean square error of extrapolation were defined. The authors analyse the error of extrapolation of random processes defined by the sum of a centred stationary random process and a deterministic time function. Based on diverse calculations, recommendations were defined that allow selecting the parameters of the extrapolator (degree of the extrapolating polynomial, number of test points that precede the prediction interval, discretisation interval of the predicting function) under the specified input signal models. Conclusion. The use of extrapolators based on Chebyshev polynomials orthogonal on a set of equally spaced points and the least square method allows implementing a procedure for calculating predicted values of a random process with the required accuracy. Under the specified models of the predicting signal, a method was developed that allows selecting the extrapolator’s parameters (order, number of points involved in the generation of the prediction, sample spacing) for the purpose of ensuring the required accuracy.

Commentary: Rethinking 10-2 visual fields in early diagnosis of glaucoma for a glided glaucoma practice: The right choice to pick up a feeble noise?

Commentary: Rethinking 10-2 visual fields in early diagnosis of glaucoma for a glided glaucoma practice: The right choice to pick up a feeble noise?

Application of the singular value and pivoted QR decompositions to reduce experimental efforts in compressor characterization

Compressor characterization, either by running experiments in a turbocharger test rig or by detailed CFD modelling, can be expensive and time-consuming. In this work, a novel method is proposed which can be used to build a complete compressor map from a reduced number of measured operating points combined with a previously collected database. The methodology is based on the application of the Singular Value Decomposition (SVD) method to acquire the orthonormal bases of a matrix which contains the information of previous compressor observations. These bases are used along with pivoted QR decomposition to obtain the minimum number of measurement points which are required to implement this technique as well as its optimal placement within the map. The reconstruction of two different compressor maps was made to validate the method. The results show a substantially better trade-off between number of testing points and accuracy compared to standard equidistributed sampling.

The Assessment of Visual Fields in Infants Using Saccadic Vector Optokinetic Perimetry (SVOP): A Feasibility Study.

PurposeTo examine the feasibility of saccadic vector optokinetic perimetry (SVOP), an automated eye tracking perimeter, as a tool for visual field (VF) assessment in infants.MethodsThirteen healthy infants aged between 3.5 and 12.0 months were tested binocularly using an adapted SVOP protocol. SVOP uses eye tracking technology to measure gaze responses to stimuli presented on a computer screen. Modifications of SVOP for testing infants included adjusting the fixation target to display a short animation, increasing the stimulus size to equivalent to Goldmann V, and introducing a tiered test pattern strategy. Binocular, single-quadrant confrontation VF testing and Keeler preferential looking cards visual acuity testing was also performed.ResultsUsing multiple test attempts when required, all but the youngest infant (12 of 13 [92.3%]) successfully completed a 4-point screening test. Seven infants (53.8%) successfully completed the 12-point test, four (30.8%) successfully completed the 20-point test, and three (23.1%) successfully completed the 40-point test. The effect of multiple test attempts and the complexity of the test pattern (number of test points) on performance was investigated, including test completion rate, percentage of correctly seen stimuli, and average time per tested stimulus.ConclusionsThe modified SVOP test strategy allowed successful assessment of binocular VFs in healthy infants. Future data collection from larger cohorts of infants is needed to derive normative limits of detection and assess accuracy in detecting and monitoring infant VF abnormalities.Translational RelevanceEye tracking perimetry may provide a useful method of automated VF assessment in infants.

YOUNG’S MODULUS AND DEFLECTION ASSESSMENT ON PAVEMENT USING A LIGHTWEIGHT DEFLECTOMETER

This research implemented direct assessment in the field on road structures using the LightWeight Deflectometer (LWD) method. This method is similar to the Falling Weight Deflectometer (FWD)method. The LWD method uses a lower loads compared to the FWD method. LWD method was chosenbecause the equipment is quite portable and straightforward allowing it to be used directly in the field, makinginspection easier. The LWD method is more suitable for assessing the pavement conditions in which thevolume of road use is not too high. This study aims to determine the value of the road structure conditionsbased on material properties. The location of the survey was Kupang City, East Nusa Tenggara, and Indonesia.The number of test points is 77 main points, with each point consisting of several tests. The test results obtainedin this study are the value of deflection and modulus of elasticity at each test point. In addition, a radius ofcurvature analysis was carried out to determine the base of the pavement structure conditions. LWD testing bygiving a load on the surface of the pavement was found to predict the base conditions of the road structure.This study also analyzes the EFWD conversion value from the ELWD test results and the correlation betweenthese methods is presented.

ANALYZING THE PERFORMANCE OF PURE LATERATION IN INDOOR ENVIRONMENTS WITH VARIOUS PERFORMANCE METRICS

Nowadays, determining the location of the users and devices in indoor buildings is promising research topic. Accurate position determination of the users for indoor environments is used for numerous applications such as public safety, supermarkets, health care applications, travelling, social networks and tourism. However, global positioning systems created for outdoor localizations cannot be used for indoor positioning systems (IPS) because detecting the exact position of a target is an issue for IPS. For indoor environments, there are several positioning algorithms such as lateration, fingerprinting, dead reckoning etc. Lateration is low cost and easy to deploy when compared to other existing algorithms. Therefore, in this study, received signal strength based pure lateration that uses synthetic data generated from MATLAB is proposed. The performance of pure lateration is investigated in terms of several performance metrics such as effect of varying number of the access points (AP), varying dimensions of the measurement area, varying Gaussian Noise power and varying number of test points in the field. The simulation of the pure lateration algorithm is conducted in MATLAB. The effect of the performance metrics are investigated and discussed in details. According to the results, accuracy performance of lateration is increased when the number of APs increase in the area, however this will bring some hardware costs. In addition, when the number of test points increases in the field, in other words the step size between two test points decreases in the field the error performance of lateration is also enhanced however, this will also cause to computational costs. Finally, enlarging the measurement area causes to decrease the accuracy performance of lateration as expected. The main purpose of this study is to obtain the optimum conditions for lateration to provide a solution for real time applications. For future work, the real time implementations of this study are performed and to improve the accuracy performance, it is aimed to use a curve fitting idea to the measured values.

Reduction of experimental effort in conventional engine calibration process by using reduced order model

The calibration process of the internal combustion engine becomes more costly and time-consuming than ever due to complexity of the engines and stringent emission regulations. The accurate and fast calibration of the engine requires a lot of performance tests which demands time, cost, and expert manpower as well as test facilities that must be taken into considerations. This process needs a large number of test points which should be examined to get an optimum map of the engine. Although some works have been done on reducing test time for the engine calibration, still the process timing remains one of the challenges for the automotive industry. The present study aims to decrease the calibration cost and time by employing the proper orthogonal decomposition (POD) method. The POD-based reduced order model is applied to reduce the number of experimental engine tests to regenerate the entire calibration table by using only a few operating points accurately. The low, mid-range and high RPM test points of a small single-cylinder, two-stroke engine are chosen as the input to the mathematical model to regenerate the missing calibration data. The comparison between the generated and the corresponding experimental data indicates that they are in good agreement (<10% difference) which implies the POD model is capable to decrease the number of test points and consequently the run time of dynamometer. Furthermore, although this approach is implemented for a conventional calibration process, however, the methodology can be extended to complex calibration procedures.

Construction of Two-Dimensional Regression Models of the Current-voltage Characteristics of the Output Current of Field-Effect Transistors Using the PLExp Information System

A problem was formulated and a methodology proposed for constructing the two-dimensional current-voltage characteristic of an output current of a field transistor in the form of its dependence on the input and output voltages. With the aid of the PLExp information system, the design of the computational test was fulfilled and the results of field studies were processed in studying the characteristics of the output current of field transistors with a controlling p–n transition. A two-dimensional regression analysis of the dispersion of the experimental data was conducted, the quality of the regression models that were constructed was evaluated, and the effect on the quality of the regression model from the number of input test points was studied. A regression model using the orthogonal central second-order composition plot was developed. The results of computational test on field studies are provided in the form of the table of coefficients of the polynomials for the two-dimensional regression models and in the form of graphs. In order to construct the current-voltage characteristics, polynomial two-dimensional regression models constructed on nine observational points were used. The ranges of factor variation within which the regression model is significant were established. The significance of the regression equation as a whole was evaluated using two criteria: the Fisher criterion and the criterion of the mean error of approximation. It was discovered that decreasing the number of test points by a factor of three does not result in significant quality degradation of the regression model. The proposed experimental method based on the regression model makes it possible to construct the two-dimensional characteristics also of other types of insulated-gate field effect transistors.

РOSSIBILITY OF USE AND ADAPTATION OF GENETIC ALGORITHMS FOR RATIONAL DESIGN OF TOOTHED HELICAL REDUCERS AND GEARBOXES

The article is devoted to the possibility of using and adapting genetic algorithms (GA) for rational design of cylindrical reducers gearboxes. The main theory of the LP-search method are considered, which allow to evaluate the possibilities of this method and analyze the prospects of its expansion using the ideology of GA. The basic theory concerning GA are considered. The main differences between GA and classical optimization methods are given. The algorithmic scheme of classical GA is described. An analysis of the main genetic selection of parents, cross-breeding and mutations is given. An estimation of the basic genetic operators is made on their productivity and convenience of use, and determined by their choice for further work. Possible variants of modifications of GA sequences are considered considering the features of the problem of rational design of geared cylindrical gearboxes. The first one provides an algorithm that allows a significant increase in the number of viable individuals, that is, test points satisfying the numerical and functional limitations of the data, thereby offsetting the lack of limitation on the maximum possible number of test points in the LP-search. The following describes an algorithm that focuses primarily on the selection of more qualitative test points and the creation of an appropriate population that is inherent in genetic-evolutionary algorithms (GEAs). It is based on the operator - the withdrawal of less quality points, as well as the mandatory use of the operator mutation. Thus, a theoretical basis for further testing of proposed modifications of GA algorithms was created.

Experimental Investigations on Subsequent Yield Surface of Pure Copper by Single-Sample and Multi-Sample Methods under Various Pre-Deformation.

Using copper thin-walled tubular specimens, the subsequent yield surfaces under pre-tension, pre-torsion and pre-combined tension-torsion are measured, where the single-sample and multi-sample methods are applied respectively to determine the yield stresses at specified offset strain. The rule and characteristics of the evolution of the subsequent yield surface are investigated. Under the conditions of different pre-strains, the influence of test point number, test sequence and specified offset strain on the measurement of subsequent yield surface and the concave phenomenon for measured yield surface are studied. Moreover, the feasibility and validity of the two methods are compared. The main conclusions are drawn as follows: (1) For the single or multi-sample method, the measured subsequent yield surfaces are remarkably different from cylindrical yield surfaces proposed by the classical plasticity theory; (2) there are apparent differences between the test results from the two kinds of methods: the multi-sample method is not influenced by the number of test points, test order and the cumulative effect of residual plastic strain resulting from the other test point, while those are very influential in the single-sample method; and (3) the measured subsequent yield surface may appear concave, which can be transformed to convex for single-sample method by changing the test sequence. However, for the multiple-sample method, the concave phenomenon will disappear when a larger offset strain is specified.

Compressive light beam induced current sensing for fast defect detection in photovoltaic cells

In this paper, a fast and efficient defect location system utilizing compressive sensing is proposed for detecting defects in solar cells. It measures the total output of the sample solar cell under excitation of patterns displayed by a liquid crystal display. Then the defects are located compressively by solving a convex problem using a small number of photo-electric current measurements — far fewer than the total possible number of testing points. The feasibility of proposed method and its detection performance were evaluated. The experimental results indicate that a sparse distribution of defects can be compressively located using measurements whose number is about 30–60% of all possible testing points and that the detection speed can be increased by a factor of 10–15 while retaining a reasonable accuracy. An additional advantage of the proposed detection system is that no mechanical moving components or optical lens are used and thus no mechanical instabilities or optical distortions are introduced. This advantage in particular means that there is significant potential to further improve the detection speed since electrical measurements can be very fast. Overall, the proposed method has significant potential for improving the efficiency and speed of inspection and classification of industrial photovoltaic devices.

Piece-wise moving least squares approximation

The standard moving least squares (MLS) method might have an expensive computational cost when the number of test points and the dimension of the approximation space are large. To reduce the computational cost, this paper proposes a piece-wise moving least squares approximation method (PMLS) for scattered data approximation. We further apply the PMLS method to solve time-dependent partial differential equations (PDE) numerically. It is proven that the PMLS method is an optimal design with certain localized information. Numerical experiments are presented to demonstrate the efficiency and accuracy of the PMLS method in comparison with the standard MLS method in terms of accuracy and efficiency.

Analog Circuit Test Point Selection Incorporating Discretization-Based Fuzzification and Extended Fault Dictionary to Handle Component Tolerances

Analog circuit test point selection aims to find the least number of test points that can isolate all the fault modes (including the fault-free case). The fault dictionary, which uses the integer-valued codes to represent the diagnosability of a specific test point, is very popular and saves computation efforts. However, the classical fault dictionary has a limited ability to handle the component tolerances and continuous-valued monitoring variables. To solve the problem, the approach of clustering-based discretization (CBD) is used to abstract the information of data samples distribution. We also develop a new fault dictionary construction technique called extended fault dictionary (EFD). An element of EFD is a set containing either a single integer code or multiple integer codes. The fault isolation rules are redefined, and a novel entropy measure is created in line with CBD of the continuous values. The practical test point selection procedures are presented, which avoids the likelihood to include a redundant test point. Finally, two application studies of circuit test point election are presented, showing that the proposed method provides an effective implementation option for the engineering practice of circuit diagnosis.

Efficacy of the Amsler Grid Test in Evaluating Glaucomatous Central Visual Field Defects

To investigate the efficacy of the Amsler grid test in detecting central visual field (VF) defects in glaucoma. Prospective, cross-sectional study. Patients with glaucoma with reliable Humphrey 10-2 Swedish Interactive Threshold Algorithm standard VF on the date of enrollment or within the previous 3 months. Amsler grid tests were performed for each eye and were considered "abnormal" if there was any perceived scotoma with missing or blurry grid lines within the central 10 degrees ("Amsler grid scotoma"). An abnormal 10-2 VF was defined as ≥3 adjacent points at P < 0.01 with at least 1 point at P < 0.005 in the same hemifield on the pattern deviation plot. Sensitivity, specificity, and positive and negative predictive values of the Amsler grid scotoma area were calculated with the 10-2 VF as the clinical reference standard. Among eyes with an abnormal 10-2 VF, regression analyses were performed between the Amsler grid scotoma area and the 10-2 VF parameters (mean deviation [MD], scotoma extent [number of test points with P < 0.01 in total deviation map] and scotoma mean depth [mean sensitivity of test points with P < 0.01 in total deviation map]). Sensitivity, specificity, and positive and negative predictive values of the Amsler grid scotoma area. A total of 106 eyes (53 patients) were included (mean ± standard deviation age, 24-2 MD and 10-2 MD = 66±12 years, -9.61±8.64 decibels [dB] and -9.75±9.00 dB, respectively). Sensitivity, specificity, and positive and negative predictive values of the Amsler grid test were 68%, 92%, 97%, and 46%, respectively. Sensitivity was 40% in eyes with 10-2 MD better than -6 dB, 58% in eyes with 10-2 MD between -12 and -6 dB, and 92% in eyes with 10-2 MD worse than -12 dB. The area under the receiver operating characteristic curve of the Amsler grid scotoma area was 0.810 (95% confidence interval, 0.723-0.880, P < 0.001). The Amsler grid scotoma area had the strongest relationship with 10-2 MD (quadratic R(2)=0.681), followed by 10-2 scotoma extent (quadratic R(2)=0.611) and 10-2 scotoma mean depth (quadratic R(2)=0.299) (all P < 0.001). The Amsler grid can be used to screen for moderate to severe central vision loss from glaucoma.

Performance Modeling of Multi-tiered Web Applications with Varying Service Demands

Multi-tiered transactional web applications are frequently used in IT enterprise based systems. Due to their inherent distributed nature, pre-deployment testing for high-availability and varying concurrency are important for post-deployment performance. Accurate performance modeling of such applications can help estimate values for future deployment variations as well as validate experimental results. In order to theoretically model performance of multi-tiered applications, we use queuing networks and Mean Value Analysis (MVA) models. While MVA has been shown to work well with closed queuing networks, there are particular limitations in cases where the service demands vary with concurrency. This variation of service demands for various resources (CPU, Disk, Network) is demonstrated through multiple experiments. This is further contrived by the use of multi-server queues in multi-core CPUs, that are not traditionally captured in MVA. We compare performance of a multi-server MVA model alongside actual performance testing measurements and demonstrate this deviation. Using spline interpolation of collected service demands, we show that a modified version of the MVA algorithm (called MVASD ) that accepts an array of service demands, can provide superior estimates of maximum throughput and response time. Results are demonstrated over multi-tier vehicle insurance registration and e-commerce web applications. The mean deviations of predicted throughput and response time are shown to be less the 3% and 9% , respectively. Additionally, we analyze the effect of spline interpolation of service demands as a function of throughput on the prediction results. Using Chebyshev Nodes , the tradeoff between the number of test points and the spline interpolation/prediction accuracy is also studied.Â

Progression of Vision Loss in Macular Telangiectasia Type 2.

To investigate progressive vision loss in patients with macular telangiectasia (MacTel) type 2 and to compare the ability to detect functional decline between microperimetry and visual acuity testing. Change of cumulative defect size (number of test points with absolute scotoma) on microperimetry testing and change in distance best-corrected visual acuity (BCVA) were evaluated in a prospective longitudinal observational study. The mean review period was 55.3 months (SD 17.3 months). In 58% of 71 eyes (40 patients) included for analysis, microperimetry revealed spread (n = 31) or new development (n = 10) of an absolute scotoma. At the same time, BCVA decreased more than two lines in only 17% (n = 12). Twenty-five (35%) eyes showed no change in visual function. Presence of an absolute scotoma at baseline, but not baseline BCVA, was predictive for functional decline on longitudinal microperimetry testing. Eyes with an absolute scotoma at baseline (n = 33) showed further growth of the scotoma in 94% (n = 31). In contrast, only 26% (n = 10) of eyes without an absolute scotoma at baseline (n = 38) developed an absolute scotoma de novo. Scotoma growth rate (new test points with an absolute scotoma per year) was 0.62 ± 0.10 for all eyes and 1.30 ± 0.12 for the subgroup of eyes with scotoma at baseline. Scotomata always first occurred in the quadrant temporal to the foveal center. A characteristic feature in patients with MacTel type 2 is progressive focal loss of macular sensitivity, preceding loss of visual acuity. Microperimetry is sensitive to detect such functional decline and thus may provide considerable power when being used as a functional outcome measure in future clinical trials.

A general method for analog test point selection using multi-frequency analysis

An important problem that arises in analog testing for fault dictionary approach is the test point selection. It consists of selecting a minimum set of test points to achieve the highest percentage of isolation. By using the concepts of ambiguity set and integer-coded dictionary, it can be formulated as a combinatorial optimization problem. On the basis of the formulation, this paper develops a general and accurate method for test point selection. This is achieved by presenting a new ambiguity set partition method based on hierarchical clustering and an improved entropy index method. Besides, multi-frequency analysis is also incorporated in the described method. The proposed method is tested and compared with exhaustive search through its application to two benchmark circuits. The results indicate that, compared with the extant methods, our method search for a test point set that not only includes a minimum number of test points but also has a good performance in terms of diagnostic accuracy and fault isolation rate. Meanwhile, the proposed method can be extended to deal with the problem of test point selection for some specific fault model.

Vibrational Properties of Sundatang Soundboard

Abstract This paper presents the measurement of vibrational properties of sundatang soundboard. Sundatang is a plucked stringed traditional musical instrument that is popular among the Kadazandusun communities in Sabah, Malaysia. The vibrational properties of the soundboard are measured using CADA-X impact hammering system in a condition where the instrument is without any string. There are two types of sundatang used in this study; one made from acacia and the other from vitex wood. In this measurement, frequency response functions (FRFs) and modal parameters of the top plate and back plate of this instrument are obtained. It is found that in free edge, fundamental frequency of both plates of acacia sundatang is greater than the vitex sundatang in a range of 112 Hz to 230 Hz. However, in clamped edge (attached to its ribs), it was modified to a lower frequency and closer to each other in the range of 55 Hz to 59 Hz. Another finding is the detection of the excitation of similar mode shape at different resonance frequencies. This phenomenon is termed as Different State of Mode (DSM) which is observed may be because the number of testing points is not enough. Findings of this study provide important information to the study of quality development of this instrument

Environment for the analysis of functional self-test quality in digital systems

Dependability of computer architectures has become one of the most important engineering concerns. One of the possibilities to increase the dependability is to develop architectures with dedicated self-test capabilities which allow achieving high quality of testing in terms of fault coverage. We propose a new methodology for Built-in Self-Test (BIST), which combines the inherent functionality of the architecture with a small amount of pre-generated test data stored in the memory, and uses for monitoring of the test process a restricted number of test points, configured as a set of signature analysers. Contrary to the traditional scan-path based logic BIST, the proposed solution does not need additional hardware for test pattern generation, and will not have any impact on the working performance of the system. On the other hand, testing at normal working conditions allows exercising the system on-line and at-speed, facilitating the detection of dynamic faults like delays and crosstalks to achieve high test quality. The new self-test method is free from the negative aspect of over-testing, compared to the traditional logic BIST approaches. A method is presented to generate optimized test data for selected test routines, and to choose minimum set of test- points for response analysis. A tool framework is proposed to emulate self-testing architectures, and to carry out fault simulation for evaluating the test quality in terms of fault coverage.