Laboratory Tests Study on the Power Dissipation Characteristics of Conductor Self-Damping and Aeolian Vibration Dampers

2010 ◽  
Vol 29-32 ◽  
pp. 2290-2295 ◽  
Author(s):  
Yuan Kun Chen ◽  
Li Li ◽  
Kun Ye ◽  
Peng Yin
Keyword(s):  
Transmission Line ◽  
Natural Frequency ◽  
Vibration Frequency ◽  
Power Dissipation ◽  
Laboratory Tests ◽  
Theoretical Method ◽  
Test Results ◽  
Vibration Effect ◽  
Aeolian Vibration ◽  
Line Engineering

In this paper, laboratory tests on conductor aeolian vibration were designed and carried out, through which the power dissipation characteristics of conductor self-damping and wire dampers(bretelles) were investigated. In addition, the theoretical method was established to estimate the power dissipated by wire damper. The results show that conductor tension and vibration frequency have great influences on its self-damping property; furthermore, the results present that the natural frequency of wire damper is related with its length and the length of wire damper has significant impact on its anti-vibration effect. The theoretical method for calculating the power dissipated by wire damper was verified to be reliable by the test results. These conclusions can provide references for the research and anti-vibration design of transmission line engineering.

In-plane free vibrations of multi-span transmission lines

2019 ◽  
Vol 46 (12) ◽  
pp. 1114-1127
Author(s):  
Liming Qi ◽  
Ameng Xu ◽  
Xiaohui Liu
Keyword(s):  
Transmission Line ◽  
Natural Frequency ◽  
Transmission Lines ◽  
Geometrical Parameter ◽  
Main Idea ◽  
Vertical Motion ◽  
Theoretical Method ◽  
Free Vibrations ◽  
Theoretical Expression ◽  
Theoretical Formulation

A theoretical method of in-plane mode and natural frequency of multi-span transmission lines is presented. The main idea is to establish moment balance equations of each insulator string and in-plane vertical motion equation of each span in multi-span section when the effect of conductor inertia component parallel to the chord on the additional horizontal tension of conductor is considered. The validity of theoretical mode and natural frequency is demonstrated by consistency with the numerical results of a typical five-span transmission line based on ABAQUS. It is shown that the mode of the five-span transmission line with a larger elasto-geometrical parameter exhibits asymmetrical shape that differed from those of single-span conductor. Considering the complexity of the theoretical expression, a simplified theoretical formulation of the modes and natural frequencies of multi-span transmission lines is obtained. Based on the curve of the frequency changing with the elasto-geometrical parameter, the various internal resonance conditions are discussed.

scholarly journals Experimental Investigation and Optimization Design of Multi-Support Pipeline System

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xiantao Zhang ◽  
Wei Liu ◽  
Yamei Zhang ◽  
Yujie Zhao
Keyword(s):  
Natural Frequency ◽  
Vibration Frequency ◽  
Installation Space ◽  
Pipeline System ◽  
Test Results ◽  
Frequency Sweep ◽  
Analysis And Design ◽  
Engine Vibration ◽  
Aero Engine ◽  
Dynamic Frequency

AbstractThe design of aircraft hydraulic pipeline system is limited by many factors, such as the integrity of aviation structure or narrow installation space, so the limited clamp support position should be considered. This paper studied the frequency adjustment and dynamic responses reduction of the multi-support pipeline system through experiment and numerical simulation. To avoid the resonance of pipeline system, we proposed two different optimization programs, one was to avoid aero-engine working range, and another was to avoid aircraft hydraulic pump pulsation range. An optimization method was introduced in this paper to obtain the optimal clamp position. The experiments were introduced to validate the optimization results, and the theoretical optimization results can agree well with the test. With regard to avoiding the aero-engine vibration frequency, the test results revealed that the first natural frequency was far from the aero-engine vibration frequency. And the dynamic frequency sweep results showed that no resonance occurred on the pipeline in the engine vibration frequency range after optimization. Additionally, with regard to avoiding the pump vibration frequency, the test results revealed that natural frequencies have been adjusted and far from the pump vibration frequency. And the dynamic frequency sweep results showed that pipeline under optimal clamp position cannot lead to resonance. The sensitivity analysis results revealed the changing relationships between different clamp position and natural frequency. This study can provide helpful guidance on the analysis and design of practical aircraft pipeline.

scholarly journals Experimental analysis of zero-natural-frequency damper for transmission line large cross project based on NES

2021 ◽  
Vol 2076 (1) ◽  
pp. 012109
Author(s):  
Bin Zhao ◽  
Jiajun Si ◽  
Zhao Zhang ◽  
Jingshan Han
Keyword(s):  
Transmission Line ◽  
Natural Frequency ◽  
Complex Terrain ◽  
Nonlinear Energy Sink ◽  
Design Parameters ◽  
Vibration Effect ◽  
Actual Design ◽  
Practical Engineering ◽  
Application Requirements ◽  
Cross Project

Abstract The operation experience of transmission line large cross project shows that the traditional anti-aeolian-vibration devices had poor adaptability to complex terrain and micro meteorological conditions, and they were difficult to meet the application requirements of super large cross project at this stage. A zero-natural-frequency damper was designed by introducing nonlinear energy sink in this paper, and the solid prototypes were processed. According to the actual design parameters of conductor using in a large cross project, the anti-vibration effect was tested by using the indoor simulation test span. The test results showed that the anti-vibration effect of the scheme based on the zero-natural-frequency damper could meet the needs of practical engineering. The installation of this damper could improve conductors’ and fittings’ adaptability to complex terrain and enhance the wind and anti-vibration ability of transmission line.

scholarly journals A Vibration-Based Structural Health Monitoring System for Transmission Line Towers

Electronics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 515 ◽  
Author(s):  
Long Zhao ◽  
Xinbo Huang ◽  
Ye Zhang ◽  
Yi Tian ◽  
Yu Zhao
Keyword(s):  
Structural Health Monitoring ◽  
Transmission Line ◽  
Natural Frequency ◽  
Health Monitoring ◽  
Structural Changes ◽  
Natural Frequencies ◽  
Transmission Tower ◽  
Health Monitoring System ◽  
Wind Speeds ◽  
Before And After

In this paper, we present a vibration-based transmission tower structural health monitoring system consisting of two parts that identifies structural changes in towers. An accelerometer group realizes vibration response acquisition at different positions and reduces the risk of data loss by data compression technology. A solar cell provides the power supply. An analyser receives the data from the acceleration sensor group and calculates the transmission tower natural frequencies, and the change in the structure is determined based on natural frequencies. Then, the data are sent to the monitoring center. Furthermore, analysis of the vibration signal and the calculation method of natural frequencies are proposed. The response and natural frequencies of vibration at different wind speeds are analysed by time-domain signal, power spectral density (PSD), root mean square (RMS) and short-time Fouier transform (STFT). The natural frequency identification of the overall structure by the stochastic subspace identification (SSI) method reveals that the number of natural frequencies that can be calculated at different wind speeds is different, but the 2nd, 3rd and 4th natural frequencies can be excited. Finally, the system was tested on a 110 kV experimental transmission line. After 18 h of experimentation, the natural frequency of the overall structure of the transmission tower was determined before and after the tower leg was lifted. The results show that before and after the tower leg is lifted, the natural frequencies of each order exhibit obvious changes, and the differences in the average values can be used as the basis for judging the structural changes of the tower.

Investigating the vibrational behaviour of a rotating two-blade propeller by using a self-tracking method

2018 ◽  
Vol 233 (3) ◽  
pp. 835-847 ◽  
Author(s):  
Mohammad-Reza Ashory ◽  
Farhad Talebi ◽  
Heydar R Ghadikolaei ◽  
Morad Karimpour
Keyword(s):  
Natural Frequency ◽  
Measurement Errors ◽  
Mode Shapes ◽  
Model Parameters ◽  
Test Results ◽  
Modal Assurance Criterion ◽  
Tracking Method ◽  
Strong Resemblance ◽  
Test Scenarios ◽  
Good Agreement

This study investigated the vibrational behaviour of a rotating two-blade propeller at different rotational speeds by using self-tracking laser Doppler vibrometry. Given that a self-tracking method necessitates the accurate adjustment of test setups to reduce measurement errors, a test table with sufficient rigidity was designed and built to enable the adjustment and repair of test components. The results of the self-tracking test on the rotating propeller indicated an increase in natural frequency and a decrease in the amplitude of normalized mode shapes as rotational speed increases. To assess the test results, a numerical model created in ABAQUS was used. The model parameters were tuned in such a way that the natural frequency and associated mode shapes were in good agreement with those derived using a hammer test on a stationary propeller. The mode shapes obtained from the hammer test and the numerical (ABAQUS) modelling were compared using the modal assurance criterion. The examination indicated a strong resemblance between the hammer test results and the numerical findings. Hence, the model can be employed to determine the other mechanical properties of two-blade propellers in test scenarios.

Predicting abnormal laboratory blood test results in the intensive care unit using novel features based on information theory and historical conditional probability (Preprint)

2021 ◽  
Author(s):  
Camilo E. Valderrama ◽  
Daniel J. Niven ◽  
Henry T. Stelfox ◽  
Joon Lee
Keyword(s):  
Machine Learning ◽  
Intensive Care ◽  
Conditional Probability ◽  
Blood Test ◽  
Laboratory Tests ◽  
Conditional Entropy ◽  
Admission Diagnosis ◽  
Test Results ◽  
Abnormal Laboratory ◽  
Blood Tests

BACKGROUND Redundancy in laboratory blood tests is common in intensive care units (ICU), affecting patients' health and increasing healthcare expenses. Medical communities have made recommendations to order laboratory tests more judiciously. Wise selection can rely on modern data-driven approaches that have been shown to help identify redundant laboratory blood tests in ICUs. However, most of these works have been developed for highly selected clinical conditions such as gastrointestinal bleeding. Moreover, features based on conditional entropy and conditional probability distribution have not been used to inform the need for performing a new test. OBJECTIVE We aimed to address the limitations of previous works by adapting conditional entropy and conditional probability to extract features to predict abnormal laboratory blood test results. METHODS We used an ICU dataset collected across Alberta, Canada which included 55,689 ICU admissions from 48,672 patients with different diagnoses. We investigated conditional entropy and conditional probability-based features by comparing the performances of two machine learning approaches to predict normal and abnormal results for 18 blood laboratory tests. Approach 1 used patients' vitals, age, sex, admission diagnosis, and other laboratory blood test results as features. Approach 2 used the same features plus the new conditional entropy and conditional probability-based features. RESULTS Across the 18 blood laboratory tests, both Approach 1 and Approach 2 achieved a median F1-score, AUC, precision-recall AUC, and Gmean above 80%. We found that the inclusion of the new features statistically significantly improved the capacity to predict abnormal laboratory blood test results in between ten and fifteen laboratory blood tests depending on the machine learning model. CONCLUSIONS Our novel approach with promising prediction results can help reduce over-testing in ICUs, as well as risks for patients and healthcare systems. CLINICALTRIAL N/A

scholarly journals Utilisation of laboratory test results for patient management by clinicians at two large referral hospitals in Zambia

2020 ◽  
Author(s):  
Sabe Mwape ◽  
Victor Daka ◽  
Scott Matafwali ◽  
Kapambwe Mwape ◽  
Jay Sikalima ◽  
...  
Keyword(s):  
Teaching Hospital ◽  
Laboratory Tests ◽  
Patient Management ◽  
Medical Laboratory ◽  
Test Results ◽  
Cross Sectional ◽  
Childrens Hospital ◽  
Laboratory Test Results ◽  
Laboratory Results ◽  
Referral Hospitals

Background Medical laboratory diagnosis is a critical component of patient management in the healthcare setup. Despite the availability of laboratory tests, clinicians may not utilise them to make clinical decisions. We investigated utilsation of laboratory tests for patient management among clinicians at Ndola Teaching Hospital (NTH) and Arthur Davison Childrens Hospital (ADCH), two large referral hospitals in the Copperbelt Province, Ndola, Zambia. Method We conducted a descriptive cross-sectional study among clinicians. The study deployed self-administered questionnaires to evaluate clinician utilisation, querying and confidence in laboratory results. Additional data on demographics and possible laboratory improvements were also obtained. Data were entered in Microsoft excel and exported to SPSS version 16 for statistical analysis. Results Of the 80 clinicians interviewed, 96.2% (77) reported using laboratory tests and their results in patient management. 77.5% (62) of the clinicians indicated they always used laboratory results to influence their patient management decisions. Of the selected laboratory tests, clinicians were more confident in using haemoglobin test results (91.2%). There was no statistically significant association between the clinicians gender or qualification and use of test results in patient management. Conclusion Our findings show that despite the majority querying laboratory results, most of the clinicians use laboratory results for patient management. There is need for interactions between the laboratory and clinical area to assure clinician confidence in laboratory results. Key words: utilisation, clinicians, laboratory tests, Ndola Teaching Hospital, Arthur Davison Childrens Hospital

Study of the effect of test parameters on the assessment of steel resistance to carbon dioxide corrosion

2021 ◽  
Vol 87 (12) ◽  
pp. 36-41
Author(s):  
A. S. Fedorov ◽  
E. L. Alekseeva ◽  
A. A. Alkhimenko ◽  
N. O. Shaposhnikov ◽  
M. A. Kovalev
Keyword(s):  
Carbon Dioxide ◽  
Laboratory Tests ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Sample Surface ◽  
Test Results ◽  
Carbon Dioxide Corrosion ◽  
Gas Industry ◽  
Test Parameters ◽  
Repeatability And Reproducibility

Carbon dioxide (CO2) corrosion is one of the most dangerous types of destruction of metal products in the oil and gas industry. The field steel pipelines and tubing run the highest risk. Laboratory tests are carried out to assess the resistance of steels to carbon dioxide corrosion. However, unified requirements for certain test parameters are currently absent in the regulatory documentation. We present the results of studying the effect of the parameters of laboratory tests on the assessment of the resistance of steels to CO2 corrosion. It is shown that change in the parameters of CO2 concentration, chemical composition of the water/brine system, the buffer properties and pH, the roughness of the sample surface, etc., even in the framework of the same laboratory technique, can lead in different test results. The main contribution to the repeatability and reproducibility of test results is made by the concentration of CO2, pH of the water/brine system, and surface roughness of the samples. The results obtained can be used in developing recommendations for the choice of test parameters to ensure a satisfactory convergence of the results gained in different laboratories, as well as in elaborating of a unified method for assessing the resistance of steels to carbon dioxide corrosion.

scholarly journals Research on Single Tower Cost Prediction Technology of Transmission Line Engineering Based on 3D Design

2020 ◽  
Vol 1601 ◽  
pp. 022035
Author(s):  
Wenhan Chen ◽  
Xuecheng Qi ◽  
Jingyu Fang ◽  
Jian Shao ◽  
Chao Chen
Keyword(s):  
Transmission Line ◽  
Cost Prediction ◽  
3D Design ◽  
Line Engineering
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