Analytical RS-GBSM-Based Nonstationary Low-Altitude Air-to-Air Channel Modeling over Open Area

Aerial communication is very flexible due to almost no restrictions on geographical conditions. In recent years, with the development and application of the unmanned aerial vehicle, the air-to-air communication attracts dense interests from the researchers. More accurate and precise channel modeling for air-to-air communication is a new hot topic because of its essential role in the performance evaluation of the systems. This paper presents an analytical nonstationary regular-shaped geometry-based statistical model for low-altitude air-to-air communication over an open area with considerations on ground scattering. Analytical expressions of the channel impulse response and the autocorrelation functions based on the three-ray model are derived. Based on the assumption of uniform distribution of the ground scatterers, the distributions of the channel coefficients such as time delay and path attenuation are derived, simulated, compared, and fitted. The nonstationary characteristics of the channel are observed through the time-variant distributions of the channel coefficients as well as the time-variant autocorrelated functions and time-variant Doppler power spectrum density.

Influence of highest dominant frequency area on fibrillation dynamics and frequency spectrum on electrograms

Introduction Highest Dominant Frequency (HDF) has been extensively described as one of the descriptors for Atrial Fibrillation (AF) and some studies also describe the total area activating at this frequency. However, the influence of this area on the registered power spectrum of the electrogram is usually not explained. Objective To describe the role of the highest Dominant Frequency Area (DFA) on the electrogram signal. Methods HL1 cell line monolayers were used as AF in vitro model and cultured on p35 plates (N=15) until confluence was reached. Optical mapping was performed to evaluate the electrophysiological activity of the samples employing Ca2+ transient quantification and activation frequency (Hz). Pseudo electrograms were calculated from the recorded signals and their frequency spectrum was evaluated. Results Two different groups were identified during the study: a group in which the DFA was higher than 0.2% of the total area (hDFA) and a group in which it was lower (lDFA). For hDFA cultures, the ratio between the DF of the catheter and the culture was significantly higher in the hDFA group (0.90±0.18; 0.47±0.13; p-value <0.0001), indicating that more complex scenarios lead to dissociation between the HDF of the tissue and HDF registered on the electrogram. This relation is identified in Figure 1, where the R2 values for both cases are 0.99 and 0.62 respectively. Figure 2 shows two examples with different DFA and the respective Ca2+ signals, electrograms, and power spectrum density of both signals, exemplifying how lDFA cases can lead to a mismatch between the power spectrum density of the optical mapping signal and the electrogram. Conclusions Complex arrhythmic scenarios identified as lDFA present a low correlation between the power spectrum registered on the culture and the electrogram, whereas samples in which the DFA is large, the DF from the catheter presents high correlation ratios among both signals, suggesting that clinical scenarios with high variability on the electrophysiological substrate may be difficult to interpret. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III and Ministerio de Ciencia Innovaciόn y Universidades Figure 1. HDF from tissue vs EGM-HDF Figure 2. Example of two cultures

Determination of isolator damages in electric power transmission lines with continuous wavelet transform and multitape power spectrum density

PurposeDetection of deformation of devices in high voltage electricity transmission line systems is an important issue in terms of economy and reuse. This study is aimed to detect devices that are deformed or thought to have suffered due to environmental and electrical reasons.Design/methodology/approachIn this experimental study, it was ensured that the sound and deformed insulators used in energy transmission lines were determined by the analysis of the sounds obtained by using the impact method. Equal intensity impact was applied to the isolator using the pendulum and the resulting sound noise signal analyses were made using power spectral density (PSD), magnitude scalogram (MS), multitape power spectrum density (MPSD) and continuous wavelet transform (CWT) methods in the study. In the analysis results, the isolators that are not visible to the eye and have certain damage were successfully separated from the intact insulators. Especially, MPSD and CWT analysis results are quite satisfactory.FindingsDamage analysis of insulators used in electricity transmission lines has been made. A total of 40 insulators were examined in two categories in their group, both damaged and not damaged. Data collection system was established. The data obtained from the data collection system were analysed and compared using four analysis methods. PSD, MS, MPSD and CWT analyses were made in the study. All the analyses carried out generally contain features that distinguish damaged and undamaged insulators from each other, the most successful results are MS and CWT results. CWT results are very successful in terms of time and amplitude, and it has been proposed as a method that can be used to separate damaged and undamaged insulators.Originality/valueIt can be suggested as a result of experimental tests that the results of CWT analysis can be used in the pulse noise method in isolators to be tested for reuse in electrical power transmission lines.

Sea State Characterization Using Experimental One-Dimensional Radar Signatures and Fractal Techniques

This paper presents a novel method of sea state characterization by using four criteria, which are applied to normalized experimental Synthetic Aperture Radar (SAR) one–dimensional signatures (range profiles), provided to our research group by SET 215 Working Group on “SAR radar techniques”. These criteria are the “Fractal Dimension”, “Fractal Length”, “Variance σ2”, and “Power Spectrum Density - Least Squares”. The “Fractal Dimension” and “Fractal Length” criteria, which appear to be the most important out of the four criteria, use the “blanket” technique to provide sea state characterization from SAR radar range profiles. It is based on the calculation of the area of a “blanket”, corresponding to the range profile under examination, and then on the calculation of the corresponding “Fractal Dimension” and “Fractal Length” of the range profile. The main idea concerning this proposed technique is the fact that normalized SAR radar range profiles, corresponding to different sea states, produce different values of “Fractal Dimension” and “Fractal Length” for all angles of incidence examined here. As a result, a sea state characterization technique for two different sea states (turbulent and calm sea) is presented in this paper.

Research on Embedded Controller of Hydraulic Vibrating Table Based on DSP

Background: Vibration control loop is the key technology adopt to improve the control performance of vibration table, which is set outside of the hydraulic vibration table servo control loop. However, the huge number of signal processing work prompts high demands on the calculation ability of the vibration controller. One kind of multi-CPU embedded vibration controller constructed by Digital Signal Processor (DSP) is proposed considering the working principle of the hydraulic vibration table and the Power Spectrum Density (PSD) reproduction process. The embedded controller consists of an acquisition unit, a calculation unit, and a monitoring unit distributes vibration control tasks to different processing unit to realize distributed algorithm calculations. Every processing unit uses dual-port memory to accomplish data interaction between each other. The development of the embedded controller provides a benchmark engineering case for the design of the hydraulic vibration table vibration controller. Objective: This article focuses on the development of the multi-CPU embedded vibration controller and the distributed calculations. Meanwhile, the power spectrum density experiment is carried out to verify the performance of hydraulic vibration embedded controller. Methods: 1) The structure of the hydraulic vibration table control system is given, that is, two closed-loop controls. The bandwidth of the system is further broadened by the vibration control of the outer loop. Besides, the accuracy of vibration control is also improved. Then, the development needs of the vibration controller is put forward according to the detail process of the power spectrum density replication. 2) An arithmetic processing unit is formed by using TI C2000 series DSP to calculate a large number of signal processing and a signal acquisition unit at a high speed. In order to improve signal processing efficiency, the signal acquisition unit is used to perform preprocessing calculations (data acquisition and filtering) and vibration control calculations in a distributed manner. 3) Processing speed is further improved by taking a full advantage of DSP software sources include lots of library functions and optimized assembly library functions. 4) The friendly operation of the controller and the safety monitoring of the experiment process are realized by the industrial computer served as the human-computer interaction unit. 5) Multi-CPU data sharing is achieved through using dual-port RAM to realize. Results: Through experiments, the developed embedded controller is fully estimated. The experiment shows that the developed hydraulic vibration table can realize real-time vibration control. Concerning the acceleration power spectrum density reproduction experiment, 256 acceleration response samples are calculated, and the update time is 4ms. The tracking accuracy of the time-domain waveform is controlled within 0.3%. Conclusion: The use of the developed embedded controller with a signal conditioning equipment can achieve real-time control of the hydraulic vibration table, but the performance of the embedded controller can be promoted in advance, and the performance improvement of the hydraulic vibration table embedded controller can be studied from the following aspects: 1)The Fourier calculation is executed by the acquisition unit to share the calculation workload of the calculation unit; 2) The computing unit uses a signal processor chip with better performance, although this will bring development difficulties; 3) The monitoring computer can use an embedded controller with superior performance instead of an industrial computer to reduce the size, improve the performance; 4) The DSP real-time operating system should be used and the task scheduling of vibration control experiments should be optimized.

Оценочное исследование влияния радиоизлучения вышек-ретрансляторов мобильной связи на здоровье людей

Присутствие большого количества вышек-ретрансляторов мобильной связи на крышах зданий в городах поднимает ряд вопросов о возможном влиянии электромагнитного ВЧ-излучения EMF (electromagnetic frequency) и спектральной плотности мощности PSD (power spectrum density) на население даже тогда, когда вышки установлены в городах в соответствии с действующими правилами и стандартами. Цель этой статьи попытаться ответить на эти вопросы путем измерения EMF от локальных вышек-ретрансляторов, построенных в небольшом городе Эль-Кут (Al-Kut) в Ираке. Эта работа исследует влияние электромагнитного излучения от вышек-ретрансляторов мобильной связи на здоровье людей, и на то, как это излучение влияет на иммунитет человека к болезням. Практические измерения получены с помощью измерителя электромагнитного поля и глобальной системы позиционирования GPS и представлены посредством географической информационной системы GIS (geographical information system). В работе выбраны две группы для исследования. Первая группа проживет в районе с тремя вышками, установленными на расстоянии 50–100 м друг от друга. Вторая группа проживает в районе, где вышки установлены за границами этого жилого района на расстоянии более 500 м. Полученные результаты показали, что первая группа страдает от проблем со здоровьем в значительно большей степени, чем вторая группа. Кроме того, высокий процент жилья здесь занимают наиболее образованные и менее осведомленные о влиянии EMF излучения при долгосрочном его воздействии. Этот факт можно объяснить недостатками учебного плана. Таким образом, это исследование рекомендует объединять экологические концепции в правительских учреждениях и организациях для всех взрослых, независимо от их образования, для повышения осведомленности людей в этой области.

Analysis of vehicle ride comfort applying a 2SPS+SR parallel seat mechanism

The violent vibration may cause discomfort to the driver and operation instability in different directions including fore-aft, lateral, and vertical when construction vehicles are driven or operated on off-roads. To improve ride comfort, a novel kind of 2SPS+SR parallel seat mechanism is proposed in this article. First, to verify the motion state of one translation and two rotations, the model of this new seat mechanism was built and analyzed using UG software. Furthermore, the acceleration and power spectrum density between the conventional seat and the 2SPS+SR parallel seat were compared in three directions of vertical, pitching, and rolling when the vehicle was driven on different three-dimensional roads. Then, the comparisons of the weighted vibration level and the root mean square of the total weighted acceleration on different roads were illustrated to denote the ride comfort of the construction vehicle. The results show that this 2SPS+SR parallel seat mechanism could improve the ride comfort of construction vehicles. The results will provide theoretical support for further research on the control of vehicle vibration.

Aging steepens the slope of power spectrum density of 30-minute continuous blood pressure recording in healthy human subjects

Background The increase of blood pressure (BP) variability (BPV) is recognized as an important additional cardiovascular risk factor in both normotensive subjects and hypertensive patients. Aging-induced atherosclerosis and autonomic dysfunction impair the baroreflex and, in turn, augment 24-hour BPV. In small and large animal experiments, impaired baroreflex steepens the slope of the power spectrum density (PSD) of continuous BP in the frequency range of 0.01 to 0.1 Hz. Although the repeated oscillometric BP recording over 24 hours or longer is a prerequisite to quantify BPV in humans, how the very short-term continuous BP recording reflects BPV remains unknown. This study aimed to evaluate the impact of aging on the very short-term (30-min) BPV in healthy human subjects by frequency analysis. Methods We recorded continuous BP tonometrically for 30 min in 56 healthy subjects aged between 28 and 85 years. Considering the frequency-dependence of the baroreflex dynamic function, we estimated the PSD of BP in the frequency range of 0.01 to 0.1 Hz, and compared the characteristics of PSD among four age groups (26–40, 41–55, 56–70 and 71–85 years). Results Aging did not significantly alter mean and standard deviation (SD) of BP among four age groups. PSD was nearly flat around 0.01 Hz and decreased gradually as the frequency increased. The slope of PSD between 0.01 and 0.1 Hz was steeper in older subjects (71 years or older) than in younger subjects (55 years or younger) (p < 0.05). Conclusions Aging steepened the slope of PSD of BP between 0.01 and 0.1 Hz. This phenomenon may partly be related to the deterioration of the baroreflex in older subjects. Our proposed method to evaluate very short-term continuous BP recordings may contribute to the stratification of BPV.