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Characteristic Analysis of Transient Electromagnetic Disturbance Data in Substation  [PDF]
Xin Wu, Shu Li
Journal of Computer and Communications (JCC) , 2015, DOI: 10.4236/jcc.2015.35013
Abstract:

Characteristic analysis of transient electromagnetic disturbance data is very important. In this paper, the time-domain and frequency-domain characteristics of transient electromagnetic disturbance caused by switching operations in substations are analyzed. Two methods are adopted in time-domain analysis. One method is histogram and the other one is normality test. An appropriate procedure for the normality test is proposed. Furthermore, the method used in frequency- domain analysis is to obtain overall envelope. These statistical characteristic analysis methods are showed to be of great value in analyses of the measured samples. The simulation results showed that these methods are effective.

On the use, by Einstein, of the principle of dimensional homogeneity, in three problems of the physics of solids
CARNEIRO, FERNANDO L. LOBO B.;
Anais da Academia Brasileira de Ciências , 2000, DOI: 10.1590/S0001-37652000000400009
Abstract: einstein, in 1911, published an article on the application of the principle of dimensional homogeneity to three problems of the physics of solids: the characteristic frequency of the atomic nets of crystalline solids as a function of their moduli of compressibility or of their melting points, and the thermal conductivity of crystalline insulators. recognizing that the physical dimensions of temperature are not the same as those of energy and heat, einstein had recourse to the artifice of replace that physical parameter by its product by the boltzmann constant, so obtaining correct results. but nowadays, with the new basic quantities "thermodynamic temperature q (unit- kelvin)'', "electric current i (unit ampère)'' and "amount of substance mol (unit-mole)'', incorporated to the si international system of units, in 1960 and 1971, the same results are obtained in a more direct and coherent way. at the time of einstein's article only three basic physical quantities were considered - length l, mass m, and time t. he ignored the p theorem of dimensional analysis diffused by buckingham three years later, and obtained the "p numbers'' by trial and error. in the present paper is presented a revisitation of the article of einstein, conducted by the modern methodology of dimensional analysis and theory of physical similitude.
Effect of power frequency excitation character on ferroresonance in neutral-grounded system

Hui Meng,Liu Chong-Xin,

中国物理 B , 2010,
Abstract: In most earlier ferroresonance studies the traditional excitation characteristic of iron core, in which the traditional excitation characteristic contains harmonic voltages or currents, has been used as if it were made up of pure fundamental voltage or current. However, this is not always true. In comparison with traditional excitation characteristics, this paper introduces the power frequency excitation characteristic of the iron core, which contains no harmonics. The power frequency excitation characteristic of iron core has been obtained by Elector Magnetic Transient Program, resulting in discrete voltage and current pairs. Extensive simulations are carried out to analyse the effect of power frequency excitation characteristic on potential transformer ferroresonance. A detailed analysis of simulation results demonstrates that with power frequency excitation characteristic of iron core inclusion at certain excitation voltage the ferroresonance may happen, conversely it may not happen with traditional excitation characteristic inclusion.
Pemodelan Ciri Getaran Teoritik dan Eksperimental Berbasis Kerja Gaya pada Mesin Reciprocating
Fransiskus Louhenapessy,Achmad Zubaydi,Suhardjono .,I Made Ariana
Jurnal Teknik Mesin , 2010,
Abstract: This study aims to model vibration response characteristics of theoretical and experimental work based force of dynamic components in reciprocating mesins. The method used was to analyze force that accumulates on main bearing area of theoretical, experimental vibration signal reconstruction and validation. Modeling involves process compression force that causes compression force and inertia force. The analysis uses a mathematical formulation of Newton are mesinered to produce a dynamic force. Results indicate that maximum total force accumulated in main bearing is 194.4 N and 29.7 N vertical direction and horizontal direction. Results of analysis theoretical and experimental vibration signals are validated by first reconstructing experimental vibration signal, in time domain and frequency to eliminate noise signals using Matlab software. Results of the validation process obtained clearance to bearing C1 = 60 μm, this value is accordance with measurement of bearing clearance dimensions manually. Modelling vibration characteristics can be used for treatment of mesin vibration signal monitoring based on scheduled.
On the use, by Einstein, of the principle of dimensional homogeneity, in three problems of the physics of solids
CARNEIRO FERNANDO L. LOBO B.
Anais da Academia Brasileira de Ciências , 2000,
Abstract: Einstein, in 1911, published an article on the application of the principle of dimensional homogeneity to three problems of the physics of solids: the characteristic frequency of the atomic nets of crystalline solids as a function of their moduli of compressibility or of their melting points, and the thermal conductivity of crystalline insulators. Recognizing that the physical dimensions of temperature are not the same as those of energy and heat, Einstein had recourse to the artifice of replace that physical parameter by its product by the Boltzmann constant, so obtaining correct results. But nowadays, with the new basic quantities "Thermodynamic Temperature theta (unit- Kelvin)'', "Electric Current I (unit Ampère)'' and "Amount of Substance MOL (unit-mole)'', incorporated to the SI International System of Units, in 1960 and 1971, the same results are obtained in a more direct and coherent way. At the time of Einstein's article only three basic physical quantities were considered - length L, mass M, and time T. He ignored the pi theorem of dimensional analysis diffused by Buckingham three years later, and obtained the "pi numbers'' by trial and error. In the present paper is presented a revisitation of the article of Einstein, conducted by the modern methodology of dimensional analysis and theory of physical similitude.
Time-Series Characteristics of Wind Power and Its Impact on Jilin Power Grid  [PDF]
Yanping Xu, Yong Sun, Taiyi Zheng, Hongyi Cai, Peng Li, Shuo Ma
Journal of Power and Energy Engineering (JPEE) , 2014, DOI: 10.4236/jpee.2014.24029
Abstract: With the rapid development of wind power, the large-scale wind power integration brings a new range of issues in dispatching operation. In order to gain a better grasp of the influence caused by wind power combined to the grid, the paper first establishes the impact characteristic indexes, and then analyzes the regularity of wind power time series in different spatial and temporal scales. At last, according to the analysis results, this paper assesses the impact of time-series characteristics of wind power on power grid, such as the frequency regulation, peak load regulation, which can provide the reference for wind power optimal dispatching of Jilin Power Grid.
Wavelet-Based Response Computation for Base-Isolated Structure under Seismic Excitation  [PDF]
Wensheng Ding, Zhi Sun
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.25020
Abstract: This paper presents a wavelet-based approach for estimating the response of the base-isolated structure under seismic ground motions. The seismic ground motion record is expressed as the multi-scale wavelet coefficients which presents the time frequency characteristics of the seismic excitation. The wavelet domain governing differential equation between the wavelet coefficients of the excitation and response is derived. Numerical study on a one-storey base isolated structure is performed. The result shows that the wavelet based response computation method is of high precision.
Disk Bimorph-Type Piezoelectric Energy Harvester  [PDF]
V. Tsaplev, R. Konovalov, K. Abbakumov
Journal of Power and Energy Engineering (JPEE) , 2015, DOI: 10.4236/jpee.2015.34010
Abstract:

The study of the experimental investigation of a disk-type piezoelectric energy harvester presented. The harvester contains disk bimorph piezoceramic element of the umbrella form and contains two disk PZT plates. The element is excited at the base point at its center. The element is supplied by a loading ring mass to decrease its resonance frequency. The dependences of the vibration displacement along the radii of the bimorph and the ring mass from the frequency of excitation are presented and the output voltage frequency response is also presented as well. The idle mode and the load duty are investigated. The value of the internal resistance of the harvester is obtained using the load characteristic. The piezoelectric specific power is estimated experimentally.

Complexity and characteristic frequency studies in ECG signals of mice based on multiple scale factors
XiaoDong Yang,AiJun He,Peng Liu,TongFeng Sun,XinBao Ning
Science China Life Sciences , 2011, DOI: 10.1007/s11427-011-4173-y
Abstract: Existing methods of physiological signal analysis based on nonlinear dynamic theories only examine the complexity difference of the signals under a single sampling frequency. We developed a technique to measure the multifractal characteristic parameter intimately associated with physiological activities through a frequency scale factor. This parameter is highly sensitive to physiological and pathological status. Mice received various drugs to imitate different physiological and pathological conditions, and the distributions of mass exponent spectrum curvature with scale factors from the electrocardiogram (ECG) signals of healthy and drug injected mice were determined. Next, we determined the characteristic frequency scope in which the signal was of the highest complexity and most sensitive to impaired cardiac function, and examined the relationships between heart rate, heartbeat dynamic complexity, and sensitive frequency scope of the ECG signal. We found that all animals exhibited a scale factor range in which the absolute magnitudes of ECG mass exponent spectrum curvature achieve the maximum, and this range (or frequency scope) is not changed with calculated data points or maximal coarse-grained scale factor. Further, the heart rate of mice was not necessarily associated with the nonlinear complexity of cardiac dynamics, but closely related to the most sensitive ECG frequency scope determined by characterization of this complex dynamic features for certain heartbeat conditions. Finally, we found that the health status of the hearts of mice was directly related to the heartbeat dynamic complexity, both of which were positively correlated within the scale factor around the extremum region of the multifractal parameter. With increasing heart rate, the sensitive frequency scope increased to a relatively high location. In conclusion, these data provide important theoretical and practical data for the early diagnosis of cardiac disorders.
地铁与地面车辆引发振动的时频特征比较研究
Comparative Study on Time-Frequency Characteristic of the Vibration Induced by Underground Subway and Road Vehicle
 [PDF]

李广振, 宗刚, 张斌, 任晓崧
Hans Journal of Civil Engineering (HJCE) , 2015, DOI: 10.12677/HJCE.2015.41002
Abstract:
在同一场地同时测得地铁和地面卡车两类振源引发场地振动的加速度响应,从时频角度统计信号有效频段、有效持时,其次分别以有效值、时频能量为参考量就振动沿距离衰减规律对两种振动进行比较分析。从分析结果来看,地铁与地面车辆引发振动在有效频段和有效持时方面差别显著;在衰减规律方面,地面交通引发振动在传播过程中放大现象不明显,而地铁引发振动在传播过程中放大现象则相对明显,且以时频能量为评价指标时,最大放大倍数为6.5倍,从这一方面也说明时频能量改善了有效值计算中对信号能量平均化处理的不足。
A field test is carried out at a site where the vibration signal of both metro and road vehicles can be detected. Analyzing the vibration response in the respect of time-frequency of effective frequency band and effective duration, studying the attenuation law in the reference of RMS and time-frequency energy, this article highlights the differences between the two references in vibra-tion signal analysis. Out of the results, the time-frequency characteristic of the vibration induced by metro and road vehicle differs sharply; in the respect of attenuation law, the amplification of vibration induced by road vehicle during propagating is not so obvious but that of vibration induced by metro is clear, which reaches 6.5 in the reference of time-frequency energy; further more,this also demonstrates time-frequency energy method improves the deficiencies of RMS (root- mean-value) which is an average of the total energy on the whole history.
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