Factors affecting forensic electric network frequency matching-A comprehensive study

The power system frequency fluctuations could be captured by digital recordings and extracted to compare with a reference database for forensic timestamp verification.It is known as the Electric Network Frequency(ENF)criterion,enabled by the properties of random fluctuations and intra-grid consistency.In essence,this is a task of matching a short random sequence within a long reference,whose accuracy is mainly concerned with whether this match could be uniquely correct.In this paper,we comprehensively analyze the factors affecting the reliability of ENF matching,including the length of test recording,length of reference,temporal resolution,and Signal-to-Noise Ratio(SNR).For synthetic analysis,we incorporate the first-order AutoRegressive(AR)ENF model and propose an efficient Time-Frequency Domain noisy ENF synthesis method.Then,the reliability analysis schemes for both synthetic and real-world data are respectively proposed.Through a comprehensive study,we quantitatively reveal that while the SNR is an important external factor to determine whether timestamp verification is viable,the length of test recording is the most important inherent factor,followed by the length of reference.However,the temporal resolution has little impact on performance.Finally,a practical workflow of the ENF-based audio timestamp verification system is proposed,incorporating the discovered results.

Paraelectric Doping Simultaneously Improves the Field Frequency Adaptability and Dielectric Properties of Ferroelectric Materials:A Phase-Field Study

Recent years,the polarization response of ferroelectrics has been entirely studied.However,it is found that the polarization may disappear gradually with the continually applied of electric field.In this paper,taking K0.48Na0.52NbO3(KNN)as an example,it was demonstrated that the residual polarization began to decrease when the electric field frequency increased to a certain extent using a phase-field methods.The results showed that the content of out-of-plane domains increased first and then decreased with the increase of applied electric field frequency,the maximum polarization disappeared at high frequencies,and the hysteresis loop became elliptical.In order to further study the abnormal changes of hysteresis loops of ferroelectrics under high electric field frequency,we analyzed the hysteresis loop and dielectric response of solid solution 0.1SrTiO_(3)-0.9K_(0.48)Na_(0.52)NbO_(3).It was found that the doped hysteresis loop maintained its shape at higher frequency and the dielectric constant increased.This kind of doping has a higher field frequency adaptability,which has a key guiding role in improving the dielectric properties of ferroelectric thin films and expanding the frequency application range of ferroelectric nano memory。

Distributed Model Predictive Load Frequency Control of Multi-area Power System with DFIGs

Reliable load frequency control LFC is crucial to the operation and design of modern electric power systems. Considering the LFC problem of a four-Area interconnected power system with wind turbines, this paper presents a distributed model predictive control DMPC based on coordination scheme. The proposed algorithm solves a series of local optimization problems to minimize a performance objective for each control area. The generation rate constraints GRCs, load disturbance changes, and the wind speed constraints are considered. Furthermore, the DMPC algorithm may reduce the impact of the randomness and intermittence of wind turbine effectively. A performance comparison between the proposed controller with and without the participation of the wind turbines is carried out. Analysis and simulation results show possible improvements on closed-loop performance, and computational burden with the physical constraints. © 2014 Chinese Association of Automation.

A Parametric Autoregressive Model for the Extraction of Electric Network Frequency Fluctuations in Audio Forensic Authentication

This paper proposes a new method for extracting ENF （electric network frequency） fluctuations from digital audio recordings for the purpose of forensic authentication. It is shown that the extraction of ENF components from audio recordings is realizable by applying a parametric approach based on an AR （autoregressive） model. The proposed method is compared to the existing STFT （short-time Fourier transform） based ENF extraction method. Experimental results from recorded electrical grid signals and recorded audio signals show that the proposed approach can improve the time resolution in the extracted ENF fluctuations and improve the detection of tampering with short alterations in longer audio recordings.

Electrical stimulation upregulates angiopoietin-1/Tie-2 mRNA expression in a rat model of focal cerebral ischemia

Angiopoietin-1/tyrosine kinase with immunoglobulin and epidermal growth factor homology domains 2 （Tie-2） is a newly discovered signaling pathway of angiogenesis. Angiogenesis benefits recovery of neurological functions such as swallowing. In the present study, a rat model of dysphagia following stroke was induced by middle cerebral artery occlusion to investigate the influence of low frequency electrical stimulus with bidirectional square waves and triangular waves on angiopoietin-1/-13e-2 mRNA expression. Reverse transcription-polymerase chain reaction results showed that low frequency electrical stimulus significantly improved the neurological scores of the model rats, and increased angiopoietin-1/＇13e-2 mRNA expression. This demonstrates that low frequency electrical stimulation can ameliorate neurological function in rats with focal brain ischemia, potentially through regulation of angiopoietin-1/-13e-2 expression in the angiogenesis pathway.

Electromagnetic Environmental Impact of 500-kV Double -Circuit Transmission Lines

The strength of the power frequency electric intensity and magnetic field of the 500-kV double circuit transmission lines was calculated by using the equivalent charge method and the Ampere's Law, and the environmental impact factors of the fields were evaluated. By optimizing the phase sequence, the frequency electric intensity and magnetic field strength can be reduced. Within a distance of 25 m from the center of the transmission line, the power frequency electric intensity and magnetic field strength fall off sharply with the distance increase. Finally, the best phase sequence and the minimum ground clearance of the transmission lines were obtained to meet the requirements of the least impact on envionment.

Photonic approach to microwave frequency measurement with extended range based on phase modulation

We propose and demonstrate a photonic approach to instantaneous frequency measurement with an extended range based on phase modulation. In the measurement system, two optical wavelengths and two dispersion fiber segments are used to construct the frequency-dependent amplitude comparison functions （ACFs）. Several ACFs can be utilized jointly to determine the microwave frequency without ambiguities beyond a monotonic region of the lone conventional ACF. The measurable range of microwave frequency can be extended and the accuracy can be improved by selecting an ACF with a large slope. The experimental results show that the errors are limited within ±140 MHz of a frequency measuremental range from 8 to 20 GHz.

Instantaneous frequency measurement based on transversal microwave filters with high resolution

We propose a novel photonic technique for microwave frequency measurement based on transversal microwave filters with high resolution. Two parallel microwave filters with sine and cosine frequency responses are obtained by cross gain modulation in a single semiconductor optical amplifier, which introduces two different frequency responses to achieve an amplitude comparison function. We also demonstrate a proof-of-concept experiment. The measurement error is less than ±0.04 GHz for the first band range of 0–3.45 GHz and less than ±0.03 GHz for the second band range of 3.45–5.8 GHz. Our scheme is found to be capable of being extended for larger frequency range measurements using a shorter fiber length.

Non-Invasive Treatment to Grade 1 Essential Hypertension by Percutaneous Laser and Electric Pulse to Acupoint with Music:A Randomized Controlled Trial

Objective： To study a non-drug therapy for hypertension disease by combining percutaneous laser and electric pulse stimulation to acupoint with music, and to test the efficiency of the combining treatment to grade 1 essential hypertension. Methods： A total of 174 patients with grade 1 essential hypertension were randomly assigned to 3 groups with a random number table after Chinese medicine（CM） syndrome differentiation： the photoelectric and musical treatment group（Group 1, with a self-developed multi-mode audio frequency pulse photoelectric therapeutic apparatus）, acupuncture group（Group 2）, and oral placebo group（Group 3）, 58 cases per group. The curative effect of each group was evaluated by the changes of blood pressure and CM syndrome integral before and after treatment. Results： Compared with Group 3, there were significant decrease of blood pressure and CM syndrome integral in Group 1 and Group 2（P〈0.01）. Compared with Group 2, Group 1 showed the highest decrease in systolic pressure（P〈0.017）. The total effective rate of anti-hypertension in Group 1（91.38%, 53/58） was significantly higher than that in Group 2（74.13%, 43/58） and Group 3（18.97%, 11/58, P〈0.05 or P〈0.01）; and that in Group 2 was also significantly higher than that in Group 3（P〈0.01）. There were significant difference in the total effective rate of CM syndrome integral in both Group 1（93.10%, 54/58） and Group 2（84.48%, 49/58） as compared with Group 3（17.24%, 10/58, P〈0.01）, while there was no significant difference between Group 1 and Group 2（P〉0.05）. Conclusions： The multi-mode audio frequency pulse photoelectric therapeutic apparatus, combining music, laser and electric pulse stimulation, is clinically useful for grade 1 essential hypertension. This ＂three in one＂ therapy method is non-invasive, easy and simple to handle. It is expected to be popularized as a new alternative treatment.

Optical,UV-Vis spectroscopy studies,electrical and dielectric properties of transition metal-based of the novel organic–inorganic hybrid(C_(6)H_(10)N_(2))(Hg_(2)Cl_(5))_(2)·3H_(2)O

In this work,we are interested in the synthesis of new hybrid material(C_(6)H_(10)N_(2))(Hg_(2)Cl_(5))_(2)·3H_(2)O grown by hydrothermal methods.X-ray diffraction indicates that this compound crystallizes at 150(2)K in the monoclinic system with C2/c space group,with the following unit cell parameters:a=19:6830(15)Å,b=18:1870(15)Å,c=6:8567(6)Å,β=93:224ð3Þ○and Z=4.On the other hand,the optical properties of this compound were studied using ultraviolet-visible(UV-Vis)spectroscopy in the range 200-800 nm.Furthermore,the optical absorbances are used to determine the absorption coefficientαand the optical band gap E g,so the Tauc model was used to determine the optical gap energy of the compound(C_(6)H_(10)N_(2))(Hg_(2)Cl_(5))_(2)·3H_(2)O.The analysis of the results revealed the existence of optical allowed indirect transition mechanisms with the band gap energy equal to(2.37 eV)for liquid and(4.33 eV)for solid.Impedance measurements indicate that the electrical and dielectric properties are strongly dependent on both temperature and frequency.Nyquist plots(Z'' versus Z ')show that the conductivity behavior is accurately represented by an equivalent circuit model which consists of a series combination of bulk and grain boundary.Furthermore,the angular frequency dependence plots of the real and imaginary parts,ε' andε'',of complex dielectric permittivityε*and tanδlosses at several temperatures between 303 and 453 K were studied for the title compound.Finally,the modulus plots can be characterized by the presence of two relaxation peaks.