Orbit Response Recognition During Touchdowns by Instantaneous Frequency in Active Magnetic Bearings

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Mindong Lyu ◽  
Tao Liu ◽  
Zixi Wang ◽  
Shaoze Yan ◽  
Xiaohong Jia ◽  
...  
Keyword(s):  
Instantaneous Frequency ◽  
Sampling Period ◽  
Threshold Value ◽  
Mean Value ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Local Variance ◽  
Displacement Signal ◽  
Novel Method ◽  
The Mean

During touchdowns of active magnetic bearings (AMB), the violent collision between rotors and touchdown bearings (TDB) can cause damages to both parts. Orbit response recognition provides a way for the AMB controller to automatically switch the control algorithm to actively suppress the rotor–TDB vibration and promptly relevitate the rotor during touchdowns. A novel method based on Hilbert transform (HT) is proposed to recognize the orbit responses (pendulum vibration, combined rub and bouncing, and full rub) in touchdowns. In this method, the rotor suspension status is monitored by the AMB controller in real-time. When touchdown is detected, the rotor displacement signal during the sampling period is intercepted, and the instantaneous frequency (IF) is calculated by HT. Then, the local variance of IF during the sampling period is calculated, and it is compared with the threshold value. Combined rub and bouncing can be identified for it has the largest local variance. Finally, the mean value of IF during the sampling period is calculated and is compared with the other threshold value. Pendulum vibration can be identified for it has a lower and fixed mean value, while full rub has a larger value. The principle of the recognition method is demonstrated by the simulated results of a thermo-dynamic model. The results reveal that the method is feasible in recognizing the orbit responses and can be implemented in the AMB controller to help switch the control algorithms automatically in case of touchdowns.

Algorithm for Automatic Pattern Classification Designed for Real Metallographic Images

2014 ◽  
pp. 165-179
Keyword(s):  
Pattern Classification ◽  
Threshold Value ◽  
Mean Value ◽  
Process Quality ◽  
Steel Plant ◽  
Central Axis ◽  
Grey Scale ◽  
The Mean ◽  
Metallographic Images

The problem of automatic pattern classification in real metallographic images from the steel plant ArcelorMittal Ostrava is addressed. The goal is to monitor the process quality in the steel plant. In the images of metal, there are dark dots that are produced by imperfections along the central axis of each plate. It is necessary to determine automatically the number and sizes of these dots. The number and sizes of the dots is a measure of how imperfect each plate is. The process is presented that segments the area of plates that contains segregation, identifies those rows of pixels along which the dots lie, and counts the pixels that are marked as dots by evaluating all the vertical columns of pixels that intersect the rows that contain the dots. The threshold value is set to be 95% of the mean value of grey scale for each column of pixels and makes the dots white. White dots that are most likely noise are removed to identify dots that are smaller than 4 connected pixels across. The explanations related to the obtained results are firmly related to the information provided by human experts.

Significant Features Selection Resistant to Temporal Distortions

2013 ◽  
Vol 284-287 ◽  
pp. 3154-3158
Author(s):  
Ta Te Lu
Keyword(s):  
Mean Value ◽  
Video Sequences ◽  
Detection Accuracy ◽  
Features Selection ◽  
Maximum Eigenvalue ◽  
Block Partition ◽  
Local Variance ◽  
Video Frames ◽  
The Mean ◽  
Video Reconstruction

Most patterns in continuous video sequences are similar. Temporal distortion, e.g. frames dropping, insertions, transposition, is a challenging issue for video reconstruction to find the actual missing positions in video sequences. The aim of this paper is to raise the detection accuracy and synchronize video frames back to original positions following temporal synchronization distortions. The successive video frames have similar statistics but the statistics in some local regions may differ from one another. Therefore, the block partition is partitioned into non-overlapping blocks by each frame, and then the local variance is calculated and taken as the block feature in each block. For most of the video frames, the pixels within the frame blocks are correlated and the maximum eigenvalue will be far from other eigenvalues. In this case, the maximum eigenvalue is set as the dominated block feature. For less correlated blocks, the values of the eigenvalues will be a little closer. In this case, the mean value of the eigenvalues represents the dominated block feature. Then, the sum of variance is regarded as the frame feature to calculate from these selective dominated blocks. Simulation results show the proposed methods are robust in evaluating the missing positions against temporal distortions.

Contamination and Radionuclides Concentration in Imported Canned Foodstuffs in Baghdad Markets

2015 ◽  
Vol 61 ◽  
pp. 49-57
Author(s):  
Abdul Jabbar Abbas Oudah ◽  
Asia H. Al-Mashhadani
Keyword(s):  
Sweet Corn ◽  
Milk Powder ◽  
Threshold Value ◽  
Mean Value ◽  
Dose Equivalent ◽  
Radium Equivalent Activity ◽  
High Purity Germanium ◽  
Radium Equivalent ◽  
The Mean ◽  
Indoor And Outdoor

This work was concerned with study the contamination and concentration of natural and man-made radioactivity 40K, 137Cs, 214Bi (238U series) and 228Ac (232Th series) in 19 different imported foodstuffs canned samples (Mushrooms, Black Olives, Broad Beans, Peaches, Sweet Corn, Tomato Past, Green Peas, Chick Peas, Baby milk 1,2,3 and Full milk powder) , were collected from locally markets in different regions in Baghdad city. Samples were analyzed by high-purity germanium (HPGe) detector gamma spectrometer systems from Canberra, with high resolution (2.0 keV at 1332 keV) and relative efficiency of ~30% for 137Cs (661.7 keV) and provide (Software Genie 2000 from Canberra). From the data obtained, the activity concentrations (Bq/kg or Bq/l) for 40K, 137Cs, 214Bi and 228Ac in above foodstuff samples were measured. It was found that these values lie within the worldwide range for radioactivity in food. The mean value of radium equivalent activity (Raeq) in all samples it was below the threshold value of 370 Bq/kg. The all value of indoor and outdoor annual effective dose equivalent in samples it was lower than the world average values (0.45 mSv/y for indoor and 0.07 mSv/y for outdoor).

Frequency Analysis of the Orbit Responses of Active Magnetic Bearings in Touchdown Using Hilbert Transform

2017 ◽  
Vol 17 (08) ◽  
pp. 1750086 ◽  
Author(s):  
Mindong Lyu ◽  
Zixi Wang ◽  
Tao Liu ◽  
Xiaohong Jia ◽  
Yuming Wang
Keyword(s):  
Working Conditions ◽  
Hilbert Transform ◽  
Instantaneous Frequency ◽  
Magnetic Bearing ◽  
Contact Forces ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Analysis Model ◽  
Rotor Vibration ◽  
Significant Difference

Touchdown bearing (TDB) is one of the key elements in active magnetic bearings (AMBs). When the magnetic bearing fails or is exposed to an overload, touchdown events will occur. According to ISO 14839, three typical orbit responses (pendulum vibration, combined rub and bouncing, and full rub) can be detected in touchdown events. The magnitude of the dynamic forces between the rotor and TDBs has been considered as an indicator to identify these orbit responses. However, the contact forces may not be easy to measure with precision. The instantaneous frequency of the rotor vibration is another significant difference between them. In this paper, a performance analysis model has been established that considers the dynamic and thermal effects in touchdown events. Simulations under different working conditions have been conducted and a recommendation for safety working conditions of the AMB system has been developed. The instantaneous frequency of the rotor vibration has been computed using Hilbert transform and the frequency characteristics of the three orbit responses have been analyzed and discussed. The results reveal that the instantaneous frequency of the pendulum vibration is almost fixed. The instantaneous frequency of the combined rub and bouncing fluctuates vehemently in most cases. The instantaneous frequency of the backward whirl shows periodic regularity.

scholarly journals A New Method for Defuzzification and Ranking of Fuzzy Numbers Based on the Statistical Beta Distribution

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
A. Rahmani ◽  
F. Hosseinzadeh Lotfi ◽  
M. Rostamy-Malkhalifeh ◽  
T. Allahviranloo
Keyword(s):  
Beta Distribution ◽  
Granular Computing ◽  
Fuzzy Numbers ◽  
Mean Value ◽  
Human Reasoning ◽  
Fuzzy Information ◽  
Numerical Examples ◽  
Novel Method ◽  
The Mean ◽  
Ranking Of Fuzzy Numbers

Granular computing is an emerging computing theory and paradigm that deals with the processing of information granules, which are defined as a number of information entities grouped together due to their similarity, physical adjacency, or indistinguishability. In most aspects of human reasoning, these granules have an uncertain formation, so the concept of granularity of fuzzy information could be of special interest for the applications where fuzzy sets must be converted to crisp sets to avoid uncertainty. This paper proposes a novel method of defuzzification based on the mean value of statistical Beta distribution and an algorithm for ranking fuzzy numbers based on the crisp number ranking system on R. The proposed method is quite easy to use, but the main reason for following this approach is the equality of left spread, right spread, and mode of Beta distribution with their corresponding values in fuzzy numbers within(0,1)interval, in addition to the fact that the resulting method can satisfy all reasonable properties of fuzzy quantity ordering defined by Wang et al. The algorithm is illustrated through several numerical examples and it is then compared with some of the other methods provided by literature.

Order Decision by Difference Method for Least Square in Trend Fitting

2012 ◽  
Vol 160 ◽  
pp. 373-376
Author(s):  
Yu Hua Dong ◽  
Xin Ming Zhou
Keyword(s):  
Difference Method ◽  
Threshold Value ◽  
High Accuracy ◽  
Mean Value ◽  
Least Square ◽  
Decision Criteria ◽  
Trend Extraction ◽  
Proper Order ◽  
The Mean ◽  
Fitting Accuracy

A difference method to order decision for least square in trend fitting is proposed in this paper. When the least square is used for fitting trend, choosing the proper order is important for trend fitting accuracy. We can use difference n times to obtain difference result data, and the mean value can be taken as decision criteria. Comparing with the threshold value, when the mth difference result mean is smaller, the trend fitting order for least square can be set to m. Simulation processing results show that this method resolve the problem of order decision for least square in trend fitting, and the method has high accuracy for trend extraction.

scholarly journals Evaluation of Radiation Hazard Indices in Mining Sites of Nasarawa State, Nigeria

2020 ◽  
pp. 8-16
Author(s):  
U. Rilwan ◽  
I. Umar ◽  
G. C. Onuchukwu ◽  
H. A. Abdullahi ◽  
M. Umar
Keyword(s):  
Gamma Spectrometry ◽  
Sodium Iodide ◽  
Threshold Value ◽  
Mean Value ◽  
Radiation Hazard ◽  
Hazard Indices ◽  
Mean Values ◽  
Mining Sites ◽  
The Mean ◽  
Radiation Hazard Indices

This work evaluates the radiation hazard indices from some selected mining sites in Nasarawa West, using Sodium Iodide Thallium Gamma Spectrometry. Raeq ranged from 100.39-197.40 Bq/Kg with a mean 161.44 Bq/Kg, which is lower than the average of 370 Bq/Kg. The GADR ranged from 44.85 nGy/hr-90.71 nGy/hr with the mean 73.68 nGy/hr. which is also below the average of 89 nGy/hr for soil. The AGED ranged from 315.77 mSv/yr-640.91 mSv/yr with the mean 519.19. Which is above the threshold value of 300 mSv/yr. ACI ranged from 0.73-1.45 with the mean value 1.18 which is above the standard of unity. The AEDE (outdoor) ranges from 0.055 mSv/yr-0.111 mSv/yr with the mean 0.090 mSv/yr which is above the 0.07 mSv/yr standard permissible limit. The AEDE (indoor) ranged from 0.220 mSv/yr-0.445 mSv/yr, with the mean value 0.361mSv/yr. This is below the 0.45 mSv/yr threshold. The ELCR ranged from 00.770-1.558 with the mean value 1.265 and from 0.193-0.389 with the mean value 0.317 for outdoor and indoor respectively, which exceed the 0.29 X 10-3 threshold limit. The External  and  Internal  Hazard  indices ranges from 0.271-0.533 and 0.289-0.675 as well as mean values 0.435 and 0.512 respectively, which are  below the threshold. Therefore, there may be serious radiological effects to the populace.

scholarly journals Esthetic Assessment Succeeding Anterior Atrophic Maxilla Augmentation with Cancellous Bone-Block Allograft and Late Restoration Loading

2021 ◽  
Vol 10 (20) ◽  
pp. 4635
Author(s):  
Sarit Naishlos ◽  
Eran Zenziper ◽  
Helena Zelikman ◽  
Joseph Nissan ◽  
Shaked Mizrahi ◽  
...  
Keyword(s):  
Cancellous Bone ◽  
Threshold Value ◽  
Mean Value ◽  
Bone Block ◽  
Anterior Maxilla ◽  
Long Term Stability ◽  
Implant Placement ◽  
Atrophic Maxilla ◽  
The Mean ◽  
Loading Methods

Background: Various conditions may lead to bony deficiency in the anterior maxilla. The present study evaluated esthetic (PES—pink esthetic score and WES—white esthetic score) results after augmentation of the anterior atrophic maxilla using cancellous bone-block allograft followed by implant placement and late (conventional) loading. Methods: Cohort study that included 33 patients with missing teeth in the upper anterior region characterized by extensive bone loss. Allogeneic cancellous bone-blocks were used for augmentation. Six months later, a dental implant was inserted. After a waiting time of an additional six-months, implant exposure and reconstruction were performed. The mean follow-up period was 62.93 ± 17.37 months (range 19–82 months). Results: The mean value of PES/WES was 17.8 ± 2.78. All patients had a PES/WES value above 12 (threshold value defined as clinically acceptable esthetics). The mean value of PES was 9.0 ± 1.79 and the mean value of WES was 8.8 ±1.84. Conclusions: Bone augmentation of the anterior atrophic maxilla using cancellous block-allograft and late loading supports achievement of a predictable esthetic result with long-term stability of soft and hard tissues around implant-supported reconstructions.

scholarly journals Relationship between urinary zearalenone concentration and embryo production in superovulated cattle

2013 ◽  
Vol 56 (1) ◽  
pp. 360-366 ◽  
Author(s):  
M. Takagi ◽  
T. Hirai ◽  
S. Shiga ◽  
S. Uno ◽  
E. Kokushi ◽  
...  
Keyword(s):  
Field Study ◽  
Threshold Value ◽  
Mean Value ◽  
Urine Samples ◽  
Holstein Cows ◽  
Embryo Production ◽  
The Mean ◽  
Group 2 ◽  
Urine Levels ◽  
Group 1

Abstract. This field study aimed to investigate the relationships between the urinary zearalenone (ZEN) concentration, which reflects dietary ZEN intake, and the numbers of total and transferable embryos in superovulated cattle. A total of 38 cows (Japanese Black, n=16; Holstein, n=22) were superovulated for commercial embryo production. Urine samples were collected from all cows at the time of embryo flushing and the urinary ZEN concentration was measured. The ZEN concentration was corrected for the creatinine (Crea) concentration as follows: ZEN (pg/mL)/Crea (mg/dL); the corrected ZEN concentration was expressed in pg/mg Crea. The cows were divided into two groups according to whether the urinary ZEN level was less than (group 1) or more than (group 2) the mean value for each breed (Japanese Black: 97.4 pg/mg Crea; range 44.5–91.3 pg/mg Crea; Holstein: 155.5 pg/mg Crea; range 32.7–146.9 pg/mg Crea). The embryo flushing results were compared between the two groups within each breed. Overall, the total number of embryos collected and the number of transferable embryos did not differ significantly between the groups. These results suggest that natural ZEN contamination resulting in urine levels below the threshold value (i.e. below the maximal permissible urinary ZEN concentration) does not affect embryo production in Japanese Black and Holstein cows undergoing superovulation.

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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