A Novel Sparse Array for Localization of Mixed Near-Field and Far-Field Sources

As we all know, nested array can obtain a larger array aperture and more degrees of freedom using fewer sensors. In this study, we not only designed an enhanced symmetric nested array (ESNA), which achieved more consecutive lags and more unique lags compared with a generalized nested array but also developed a special cumulant matrix, in the case of a given number of sensors, which can automatically generate the largest consecutive lags of the array. First, the direction-of-arrivals (DOAs) of mixed sources are estimated using the special cumulant matrix. Then, we can estimate the range of the near-field source in the mixed source using a one-dimensional spectral search through estimated DOAs, and in the mixed sources, the near-field and far-field sources are classified by bringing in the range parameter. The largest consecutive lags and composition method of ESNA are also given, under a given number of sensors.Our algorithm has moderate computation complexity, which provides a higher resolution and improves the parameters’ estimation accuracy. Numerical simulation results demonstrate that the proposed array showed an outstanding performance under estimation accuracy and resolution ability for both DOA and range estimation compared with existing arrays of the same physical array sensors.

DUAL SPHERICAL ELECTRIC FIELD VOLTAGE SENSOR

Мы живем в мире высоких энергетических технологий, способных передавать электрическую энергию на большие расстояния. Эту энергию невозможно сосредоточить только внутри передающих энергетических систем. Она выплескивается наружу в виде электрических полей. Эти электрические поля неблагоприятно воздействуют на окружающую среду, технические и биологические объекты. В связи с этим необходимо контролировать уровни электрических полей, важной характеристикой которых является напряженность электрического поля. Для восприятия электрического поля необходимы датчики напряженности электрического поля. Существующие датчики неудобны в эксплуатации и имеют высокую погрешность восприятия напряженности электрического поля, достигающую ± 20%. Bыдвигается идея создания универсального датчика нового вида, относящeгося к виду сдвоенных датчиков. Его универсальность заключается в том, что он воплощает в себе все виды известных датчиков - одинарные, сдвоенные и теперь еще двойные. Погрешность восприятия напряженности неоднородного электрического поля сдвоенных датчиков не превышает +5 % во всем пространственном диапазоне измерения 0£ a £1. При этом расстояние d до источника поля ограничено только радиусом сферического основания датчика, т.е. d » R , в то время как для датчиков, входящих в состав сдвоенного датчика, в том же пространственном диапазоне измерение погрешности составляет ± 35 %. Используя сдвоенный датчик, можно добиться значительного повышения точности измерения напряженности неоднородных электрических полей в широком пространственном диапазоне измерений по сравнению с известными датчиками We live in a world of high energy technologies capable of transmitting electrical energy over long distances. This energy cannot be concentrated only within the transmitting energy systems. It spills out in the form of electric fields. These electric fields adversely affect the environment, technical and biological objects. In this regard, it is necessary to control the levels of electric fields, an important characteristic of which is the strength of the electric field. Sensors of the electric field strength are required to sense the electric field. The existing sensors are inconvenient in operation and have a high error in the perception of the electric field strength, reaching ± 20%. In the work under consideration, the idea of creating a universal sensor of a new type, related to the type of dual sensors, is put forward. Its versatility lies in the fact that it embodies all types of known sensors - single, twin, and now dual. The error in the perception of the intensity of the inhomogeneous electric field of the dual sensors does not exceed + 5% in the entire spatial measurement range 0£ a £1. In this case, the distance d to the field source is limited only by the radius of the spherical base of the sensor, i.e. d » R . At the same time, for sensors that are part of a dual sensor in the same spatial measurement range, the error is ± 35%. Using a dual sensor, it is possible to achieve a significant increase in the accuracy of measuring the strength of inhomogeneous electric fields in a wide spatial measurement range in comparison with known sensors.

Magnetic position sensors

Magnetic position sensors are popular in industrial and automotive applications since they are robust, resistant to dust and oil and they can be cheap. However, precise magnetic position sensors can achieve 0.015 % accuracy and 10 nm resolution. The maximum achievable range is about 20 m. DC magnetic position sensors are using a permanent magnet as a field source. As a field sensor, magnetoresistors are often used instead of traditional Hall sensors. Eddy current sensors work also with non-magnetic conduction targets. Magnetostrictive sensors are based on the time-of-flight of the elastic wave excited in the magnetostrictive material. The sensors can be several meters long and their applications range from level meters to hydraulics. Magnetic trackers and long-range position sensors utilize AC field sources, which are detectable from distances up to 20 m. Compared to optical instruments magnetic trackers do not need direct view. Their applications include surgery, mixed reality, and underground and underwater navigation.

Full treatment of the proton radiography technique for laser-driven capacitor-coil targets

Ultrafast proton radiography has been frequently used for direct measurement of the electromagnetic fields around laser-driven capacitor-coil targets. The goal is to accurately infer the coil currents and their magnetic field generation for a robust magnetic field source that can lead to many applications. The technique often involves numerical calculations for synthetic proton images to reproduce experimental measurements. While electromagnetic fields are the primary source for proton deflections around the capacitor coils, stopping power and small angle deflection can also contribute to the observed experimental features. Here we present a comprehensive study of the proton radiography technique including all sources of proton deflections as a function of coil shapes, current magnitudes, and proton energies. Good agreements were achieved between experimental data and numerical calculations that include both the stopping power and small angle deflections, particularly when the induced coil currents were small.

HYBRID MODELUNG FOR ELECTRODYNAMIC ANALYSIS OF LARGE-SIZED OBJECTS

Рассматриваются методы моделирования сложных электродинамических структур, которые состоят из антенны и объекта-носителя, размеры которого превышают 100 длин волн. При выполнении моделирования предлагается рассчитывать характеристики антенны с использованием метода конечного интегрирования, а при установке на платформу-носитель - с использованием метода геометрической дифракции и физической оптики. Развитие современных вычислительных сред позволилo реализовать систему гибридного моделирования, которая позволяет достичь высокой производительности, автоматизации и точности результатов полученного моделирования. При выполнении исследования изучалась ситуация с установкой антенны спутникового позиционирования на подводной лодке, причем размеры носителя антенны превышали 800 длин волн, что делало невозможным применение метода конечного интегрирования для решения задачи. Pассматривается три способа решения поставленной задачи: с использованием диаграммы направленности и ее ручным переносом на место планируемой установки антенны, однонаправленного метода гибридного моделирования с применением источника ближнего поля, гибридного моделирования с обратной связью между проектами. Получено, что наибольшую точность обеспечивает метод гибридного моделирования с обратной связью, однако его применение требует высокой скорости накопителя данных, а также занимает длительное время. Самым скоростным методом является метод гибридного моделирования с однонаправленной связью, так как обеспечиваются автоматизированный расчет и решение поставленной задачи The article discusses methods for modeling complex electrodynamic structures, which consist of an antenna and a carrier object whose dimensions exceed 100 wavelengths. When performing the simulation, we propose to calculate the characteristics of the antenna using the finite integration method and installed on the carrier platform using the method of geometric diffraction and physical optics. The development of modern computing environments has made it possible to implement a hybrid simulation system, which allows achieving high performance, automation, and accuracy of the results of the simulation. When performing the study, we studied the situation with the installation of a satellite positioning antenna on a submarine, and the dimensions of the antenna carrier exceeded 800 wavelengths, which made it impossible to use the finite integration method to solve the problem. The paper considers three ways to solve the problem posed: using the radiation pattern and its manual transfer to the site of the planned antenna installation, unidirectional hybrid modeling method using a near-field source, hybrid modeling with feedback between projects. We found that the highest accuracy is provided by the method of hybrid simulation with feedback, but its application requires a high speed of the data accumulator, and also takes a long time. The fastest method is the method of hybrid modeling with unidirectional communication, as it provides an automated calculation and solution of the problem

RESEARCH OF AIR IONIZATION OF AIR IN PREMISES ON OPERATION OF COMPUTER EQUIPMENT

All known studies on the effect of computer equipment on the concentration of air ions of both signs have been used for rooms where desktop computers are operated. The expediency of conducting research using a laptop computer is substantiated. Therefore, the urgent task is to study the dynamics of the air ionic composition of the air from the operation of personal computers and identify ways to maintain this indicator at the regulatory level. It is shown that the switched on computer deionizes air, and mainly on one polarity. It is established that this is a consequence of electrification of polymer surfaces. The cause of electrification is triboelectric phenomena, including the directional movement of dry air from the CPU cooling fan. Additional electrification (and consequently - deionization of air) gives the presence of the user. Confirmation of the cause of deionization is the slow recovery of the concentration of air ions after turning on the computer to a certain neutralization of surface charges. The dependences of the change of air ion concentrations on the distance from the electric field source are established. At its intensity of about 5 kV/m with dimensions of 1.0×1.0 m, the critical distance is 1.2-1.3 m. It is recommended to carry out wet absorption for an unambiguous workplace, which provides insignificant electric fields for 1.5 hours. During the operation of many personal computers, it is advisable to neutralize surface charges with an ultrasonic humidifier-ionizer. It is emphasized that the conducted research has a separate character. This is due to the presence of specific synthetic materials It is advisable to conduct research in standard rooms for the operation of computer equipment to obtain information that can be summarized and used to develop sanitary standards for the operation of computer equipment.

Electromagnetic stimulation increases mitochondrial function in osteogenic cells and promotes bone fracture repair

Bone fracture is a growing public health burden and there is a clinical need for non-invasive therapies to aid in the fracture healing process. Previous studies have demonstrated the utility of electromagnetic (EM) fields in promoting bone repair; however, its underlying mechanism of action is unclear. Interestingly, there is a growing body of literature describing positive effects of an EM field on mitochondria. In our own work, we have previously demonstrated that differentiation of osteoprogenitors into osteoblasts involves activation of mitochondrial oxidative phosphorylation (OxPhos). Therefore, it was reasonable to propose that EM field therapy exerts bone anabolic effects via stimulation of mitochondrial OxPhos. In this study, we show that application of a low intensity constant EM field source on osteogenic cells in vitro resulted in increased mitochondrial membrane potential and respiratory complex I activity and induced osteogenic differentiation. In the presence of mitochondrial inhibitor antimycin A, the osteoinductive effect was reversed, confirming that this effect was mediated via increased OxPhos activity. Using a mouse tibial bone fracture model in vivo, we show that application of a low intensity constant EM field source enhanced fracture repair via improved biomechanical properties and increased callus bone mineralization. Overall, this study provides supporting evidence that EM field therapy promotes bone fracture repair through mitochondrial OxPhos activation.

Three-Dimensional Inversion of Borehole-Surface Resistivity Method Based on the Unstructured Finite Element

The electromagnetic wave signal from the electromagnetic field source generates induction signals after reaching the target geological body through the underground medium. The time and spatial distribution rules of the artificial or the natural electromagnetic fields are obtained for the exploration of mineral resources of the subsurface and determining the geological structure of the subsurface to solve the geological problems. The goal of electromagnetic data processing is to suppress the noise and improve the signal-to-noise ratio and the inversion of resistivity data. Inversion has always been the focus of research in the field of electromagnetic methods. In this paper, the three-dimensional borehole-surface resistivity method is explored based on the principle of geometric sounding, and the three-dimensional inversion algorithm of the borehole-surface resistivity method in arbitrary surface topography is proposed. The forward simulation and calculation start from the partial differential equation and the boundary conditions of the total potential of the three-dimensional point current source field are satisfied. Then the unstructured tetrahedral grids are used to discretely subdivide the calculation area that can well fit the complex structure of subsurface and undulating surface topography. The accuracy of the numerical solution is low due to the rapid attenuation of the electric field at the point current source and the nearby positions and sharply varying potential gradients. Therefore, the mesh density is defined at the local area, that is, the vicinity of the source electrode and the measuring electrode. The mesh refinement can effectively reduce the influence of the source point and its vicinity and improve the accuracy of the numerical solution. The stiffness matrix is stored with Compressed Row Storage (CSR) format, and the final large linear equations are solved using the Super Symmetric Over Relaxation Preconditioned Conjugate Gradient (SSOR-PCG) method. The quasi-Newton method with limited memory (L_BFGS) is used to optimize the objective function in the inversion calculation, and a double-loop recursive method is used to solve the normal equation obtained at each iteration in order to avoid computing and storing the sensitivity matrix explicitly and reduce the amount of calculation. The comprehensive application of the above methods makes the 3D inversion algorithm efficient, accurate, and stable. The three-dimensional inversion test is performed on the synthetic data of multiple theoretical geoelectric models with topography (a single anomaly model under valley and a single anomaly model under mountain) to verify the effectiveness of the proposed algorithm.