Application of the state deterioration evolution based on bi-spectrum in wind turbine

2013 ◽  
Vol 228 (11) ◽  
pp. 1958-1967 ◽  
Author(s):  
Xu Xiaoli ◽  
Jiang Zhanglei ◽  
Wang Hongjun ◽  
Wu Guoxin ◽  
Zuo Yunbo ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Graphical Representation ◽  
Vibration Signal ◽  
Mean Value ◽  
The State ◽  
Low Speed ◽  
Feature Parameters ◽  
Normal Distribution Curve ◽  
Actual Equipment ◽  
The Mean

Concerning the problem of large rotating machinery like wind turbine which runs in low speed and non-stationary state, this research mainly focuses on separating fault trend feature from non-fault feature and the method of state deterioration evolution based on bi-spectrum. Firstly, the experimental signal such as low-speed startup vibration signal of rotor test rig in the normal state and a plurality of unbalanced state have been collected. Bi-spectrum method is applied to extract fault feature which submerged in complex background noise. On the basis of bi-spectrum analysis, the fault feature evolutionary matrix is defined to represent the state of equipment deterioration. The eigenvalues of fault feature evolutionary matrix are computed and fitted to a normal distribution curve, from which the mean value and variance are taken as fault feature parameters. Fault feature parameters are verified effectively by experiments. Finally, depending on fault feature parameters, graphical representation of state deterioration evolution is established. It is beneficial to provide guidelines for equipment deterioration trend. This method is applied to analyze the real vibration signal of wind turbine with the type of WD646/600 KW, and actual equipment condition verified the effectiveness of the proposed method.

scholarly journals A Truncated Matrix Completion Algorithm Using Prior Information for Wind Turbine Clutter Suppression

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Minghe Mao ◽  
Tianhe Li ◽  
Mingwei Shen ◽  
Ning Cao ◽  
Rui Shi ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Prior Information ◽  
Matrix Completion ◽  
Diagonal Element ◽  
Mean Value ◽  
Singular Value ◽  
Clutter Suppression ◽  
Shrinking Process ◽  
The Mean ◽  
Recovery Result

The conventional matrix completion (MC) regularizes each singular value equally, and thus the rank cannot be well approximated, which greatly limits the flexibility and accuracy of MC usage. In this paper, a truncated MC algorithm using prior information to determine the threshold while generating the target rank is proposed for the wind turbine clutter suppression of weather radar. During the singular value shrinking process, an appropriate threshold is selected to obtain the optimal approximation of the sampling matrix. Specifically, the mean value of the diagonal element in the recovered weather matrix is calculated to improve the robustness of the recovery result effectively. Simulation results demonstrate that the proposed algorithm reduces the computational complexity as well as further improves the MC accuracy and realizes the effective suppression of the wind turbine clutter.

Grain Orientation Spread Values in if Steels after Plastic Deformation and Recrystallization

2011 ◽  
Vol 702-703 ◽  
pp. 269-272 ◽  
Author(s):  
Abdelhak Ayad ◽  
Nathalie Allain-Bonasso ◽  
Nadjet Rouag ◽  
Francis Wagner
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Detection Limit ◽  
Grain Orientation ◽  
Mean Value ◽  
The State ◽  
If Steel ◽  
Deformation Degree ◽  
The Mean ◽  
Grain Orientation Spread

From an EBSD map made on a polycrystal one can define a set of grains using a criterion of misorientation between the adjacent pixels. Once such a list of grains is obtained, various quantities can be associated to each grain such as its size, (mean) orientation, GOS (Grain Orientation Spread) etc... The GOS associated to one grain is the mean value of the misorientations between all the pixels of the grain and the mean orientation of the grain. This value is quite sensitive to the state of the material (degree of plastic deformation, degree of recrystallization for example). Therefore it can help in interpreting the evolution of a microstructure during thermomechanical treatments. It is the purpose of this presentation to provide GOS values for an IF steel after several degrees of plastic deformation as well as after several annealing treatments which lead to partially or totally recrystallized states. The sources of influence on GOS values (as grain detection limit or grain size) are analyzed. The link between the values and the state of the material will be discussed at a global stage for a given population of grains.

Robust Design Optimization of Gear Parameters for a Wind Turbine Using Interval Analysis

2010 ◽  
Vol 224 (10) ◽  
pp. 2235-2245 ◽  
Author(s):  
R Dong ◽  
W Sun ◽  
H Xu
Keyword(s):  
Wind Turbine ◽  
Design Optimization ◽  
Robust Design ◽  
Optimization Method ◽  
Mean Value ◽  
Robust Design Optimization ◽  
Upper And Lower Bounds ◽  
Interval Numbers ◽  
Minimum Sensitivity ◽  
The Mean

A robust design optimization method is suggested to optimize the system parameters of a gear transmission for a wind turbine with minimum sensitivity of fatigue strength to variations in uncertain application factor, dynamic load coefficient, material property parameters, and other coefficients representing unknown working condition. Interval numbers are employed to model the uncertainties by which only the upper and lower bounds are needed. Based on interval mathematics, the original real-valued objective and constraint functions are replaced by the interval-valued functions, which directly represent the variation bounds of the new functions under uncertainty. The single-objective function is converted into two-objective functions for minimizing the mean value and the variation, and the constraint functions are reformulated with the acceptable robustness level, resulting in a bi-level mathematical model. The optimization results of gear parameter demonstrate the validity and feasibility of the presented method.

Preparedness of Nigerian University Libraries for the Acquisition and Management of Digital Records

Libri ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Brendan Asogwa ◽  
Adizetu Ali ◽  
Chioma Onoh ◽  
Martha Asogwa ◽  
Margaret Ngwuchukwu ◽  
...  
Keyword(s):  
Mean Value ◽  
The State ◽  
Management Policy ◽  
Records Management ◽  
Electronic Format ◽  
University Libraries ◽  
The Mean ◽  
Nigerian University ◽  
Major Factors ◽  
Practical Implications

Abstract This paper assessed the extent to which federal university libraries in Nigeria have prepared for management of their records in electronic format. Specifically it investigated the extent to which university libraries have provided ICT infrastructures for digital records, made institutional plans for e-records management, and enacted policies that guide e-records management, among other areas. Survey research design was used. The instruments for data collection were questionnaire, observation checklist, and oral interviews. The population of the study was 84 librarians drawn randomly from 18 federal university libraries in Nigeria. Data was analyzed using mean scores and simple percentages. The criterion of judgment was that if the mean value of any item of the research instruments scored 2.50+ and above, it was rated high; if otherwise, it was considered low. The study found that ICT facilities were available in all the libraries, but the state of preparedness for their utilization for e-records management was low. Inadequate funding, intermittent electricity supply, absence of e-records management policy, etc. were the major factors hindering preparedness for e-records management. Adequate budgetary provision, increasing power supply, and enactment of digital records management policy were among the recommendations made. With regards to practical implications, federal university libraries may not steadily use their e-records in a networked/connected environment. These records may become inaccessible over time. This study was the first to investigate extensively on the state of preparedness of Nigerian university libraries for digital records management.

scholarly journals Using A Two Treatment Factorial Design To Analyze The First Day Percent Change In Price For Initial Public Offerings

2011 ◽  
Vol 7 (7) ◽  
Author(s):  
Barry Thornton ◽  
Michael Adams ◽  
Russell Baker
Keyword(s):  
Factorial Design ◽  
Initial Public Offerings ◽  
Stock Prices ◽  
Mean Value ◽  
The State ◽  
Public Offerings ◽  
Percent Change ◽  
Final Offer ◽  
The Mean ◽  
The Relationship

<p class="MsoNormal" style="text-align: justify; margin: 0in 0.5in 0pt;"><span style="font-size: 10pt;"><span style="font-family: Times New Roman;">An area of considerable interest in finance is the behavior of IPO stock prices on the first day of issue.<span style="mso-spacerun: yes;">&nbsp; </span>This paper uses a sample of 282 IPOs from 2002 through 2007 to investigate the performance of the first day percent change in price (FDPCP) of these stocks.<span style="mso-spacerun: yes;">&nbsp; </span>A two treatment factorial design is utilized to determine if two factors impact the mean value of this variable.<span style="mso-spacerun: yes;">&nbsp; </span>The first factor, or treatment, is the relationship between the final offer price and the price range found in the prospectus associated with SEC Form S-1, also known as the "red herring."<span style="mso-spacerun: yes;">&nbsp; </span>The second treatment is the state of the market at the time of issue, bull or bear.<span style="mso-spacerun: yes;">&nbsp; </span>This experimental design allows for the testing of three hypotheses.<span style="mso-spacerun: yes;">&nbsp; </span>The first hypothesis looks at the relationship between the mean value of the FDPCP and the value of the final offer price relative to the filing range found in the initial prospectus.<span style="mso-spacerun: yes;">&nbsp; </span>The second hypothesis looks at the relationship between the mean value of the FDPCP and the state of the market at the time of issue, while the third hypothesis seeks to determine if there is an interaction between the two treatments.</span></span></p>

scholarly journals An innovative method to calibrate a spinner anemometer without the use of yaw position sensor

2016 ◽  
Vol 1 (2) ◽  
pp. 143-152 ◽  
Author(s):  
Giorgio Demurtas ◽  
Nick Gerardus Cornelis Janssen
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Calibration Method ◽  
Mean Value ◽  
Position Sensor ◽  
Flow Angle ◽  
Angle Measurements ◽  
Innovative Method ◽  
Calibration Methods ◽  
The Mean

Abstract. A spinner anemometer can be used to measure the yaw misalignment and flow inclination experienced by a wind turbine. Previous calibration methods used to calibrate a spinner anemometer for flow angle measurements were based on measurements of a spinner anemometer with default settings (arbitrary values, generally k1,d  =  1 and k2,d  =  1) and a reference yaw misalignment signal measured with a yaw position sensor. The yaw position sensor is normally present in wind turbines for control purposes; however, such a signal is not always available for a spinner anemometer calibration. Therefore, an additional yaw position sensor was installed prior to the spinner anemometer calibration. An innovative method to calibrate the spinner anemometer without a yaw positions sensor was then developed. It was noted that a non-calibrated spinner anemometer that overestimates (underestimates) the inflow angle will also overestimate (underestimate) the wind speed when there is a yaw misalignment. The new method leverages the non-linearity of the spinner anemometer algorithm to find the calibration factor Fα by an optimization process that minimizes the dependency of the wind speed on the yaw misalignment. The new calibration method was found to be rather robust, with Fα values within ±2.7 % of the mean value for four successive tests at the same rotor position.

scholarly journals CLINICAL ASSESSMENT OF THE CONDITION OF PERIODONTAL TISSUES IN PATIENTS WITH CHRONIC GENERALIZED PERIODONTITIS CLASS II

2021 ◽  
Vol 21 (3) ◽  
pp. 52-57
Author(s):  
M.Yu. Vasko ◽  
I.M. Tkachenko ◽  
V.V. Kovalenko ◽  
O.V. Pavlenkova ◽  
S.A. Pavlenko
Keyword(s):  
Inflammatory Diseases ◽  
Integrated Approach ◽  
Class Ii ◽  
Mean Value ◽  
The State ◽  
Study Group ◽  
Average Value ◽  
Periodontal Tissues ◽  
The Mean ◽  
Periodontal Indices

Introduction. Inflammatory diseases of periodontal tissue are one of the most prevalent worldwide. This pathology has a complex aetiology and ambiguous views on pathogenetic mechanisms; therefore, the approach to the assessment of periodontitis should be integrated. The aim of the study was to assess the state of periodontal tissues in patients with chronic generalized periodontitis class II and absent or compensated somatic pathology. Materials and methods. We examined 20 patients aged 35 to 45 years having a diagnosis of chronic generalized periodontitis class II who had no somatic pathologies or compensated somatic pathology. The patients underwent the assessment of their hygienic, gingival and periodontal indices, measuring the depth of periodontal pockets, the level of the gingival margin, loss of clinical attachment and bleeding during probing. Results. The average value of the Green-Vermillion hygienic index among the study group was 2.16, the papillary-marginal-alveolar index was 56%, and the periodontal Russell index was 3.4scores. The mean value of the depth of periodontal pockets was 3.75, and the loss of clinical attachment was 4.12. The average index of Müllemann's bleeding gums in the surveyed was 4.1. Conclusions. Аn integrated approach to assessing the state of periodontal tissues contributes to a better understanding of the epidemiology, characteristics of the course and predicting the consequences of chronic generalized periodontitis class II.

scholarly journals Low-Speed Bearing Fault Diagnosis Based on Permutation and Spectral Entropy Measures

2020 ◽  
Vol 10 (13) ◽  
pp. 4666
Author(s):  
Diego Sandoval ◽  
Urko Leturiondo ◽  
Francesc Pozo ◽  
Yolanda Vidal
Keyword(s):  
Damage Detection ◽  
Wind Turbine ◽  
Wind Farms ◽  
Vibration Signal ◽  
General Purpose ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Permutation Entropy ◽  
Offshore Wind Farms ◽  
Low Speed

Despite its influence on wind energy service life, condition-based maintenance is still challenging to perform. For offshore wind farms, which are placed in harsh and remote environments, damage detection is critically important to schedule maintenance tasks and reduce operation and maintenance costs. One critical component to be monitored on a wind turbine is the pitch bearing, which can operate at low speed and high loads. Classical methods and features for general purpose bearings cannot be applied effectively to wind turbine pitch bearings owing to their specific operating conditions (high loads and non-constant very low speed with changing direction). Thus, damage detection of wind turbine pitch bearings is currently a challenge. In this study, entropy indicators are proposed as an alternative to classical bearing analysis. For this purpose, spectral and permutation entropy are combined to analyze a raw vibration signal from a low-speed bearing in several scenarios. The results indicate that entropy values change according to different types of damage on bearings, and the sensitivity of the entropy types differs among them. The study offers some important insights into the use of entropy indicators for feature extraction and it lays the foundation for future bearing prognosis methods.

scholarly journals An innovative method to calibrate a spinner anemometer without use of yaw position sensor

2016 ◽  
Author(s):  
Giorgio Demurtas ◽  
Nick Gerardus Cornelis Janssen
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Calibration Method ◽  
Mean Value ◽  
Position Sensor ◽  
Flow Angle ◽  
Angle Measurements ◽  
Innovative Method ◽  
Calibration Methods ◽  
The Mean

Abstract. A spinner anemometer can be used to measure the yaw misalignment and flow inclination experienced by a wind turbine. Previous calibration methods used to calibrate a spinner anemometer for flow angle measurements were based on measurements of a spinner anemometer with default settings and a reference yaw misalignment signal measured measured with a yaw position sensor. The yaw position sensor is normally present in wind turbines for control purposes, however, such a signal is not always available for a spinner anemometer calibration. Therefore, an additional yaw position sensor has been installed prior to the spinner anemometer calibration. An innovative method to calibrate the spinner anemometer without a yaw positions sensor was then developed. It was noted that a non calibrated spinner anemometer that overestimate (underestimate) the inflow angle will also overestimate (underestimate) the wind speed when there is a yaw misalignment. The new method leverage on the non linearity of the spinner anemometer algorithm to find the calibration factor Fα by an optimization process that minimizes the dependency of the wind speed to the yaw misalignment. The new calibration method was found to be rather robust with Fα values within &amp;pm;2.7 % of the mean value for four successive tests at the same rotor position.

Long-period modulated superstructures in Pd-12.5 at.%Ce and Pd-15 at.%Ce alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 164-165
Author(s):  
Noriyuki Kuwano ◽  
Masaru Itakura ◽  
Kensuke Oki
Keyword(s):  
Electron Microscopy ◽  
Mean Value ◽  
Heavy Elements ◽  
Arc Furnace ◽  
X Ray ◽  
Long Period ◽  
Ultra High Purity ◽  
Heat Treated ◽  
Atomic Scattering ◽  
The Mean

Pd-Ce alloys exhibit various anomalies in physical properties due to mixed valences of Ce, and the anomalies are thought to be strongly related with the crystal structures. Since Pd and Ce are both heavy elements, relative magnitudes of (fcc-fpd) are so small compared with <f> that superlattice reflections, even if any, sometimes cannot be detected in conventional x-ray powder patterns, where fee and fpd are atomic scattering factors of Ce and Pd, and <f> the mean value in the crystal. However, superlattices in Pd-Ce alloys can be analyzed by electron microscopy, thanks to the high detectability of electron diffraction. In this work, we investigated modulated superstructures in alloys with 12.5 and 15.0 at.%Ce.Ingots of Pd-Ce alloys were prepared in an arc furnace under atmosphere of ultra high purity argon. The disc specimens cut out from the ingots were heat-treated in vacuum and electrothinned to electron transparency by a jet method.

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