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Autonomous driving systems (ADSs) need to be able to respond quickly to changes in the dynamic traffic scenario. However, regardless of the changes occurring in traffic scenes, the current local path planning frameworks of ADSs are based on the fixed frequency re-planning path (i.e., running their planning algorithms repeatedly). This planning method makes it difficult to provide a reasonable traveling path, agility, and comfort for driverless vehicles in changing traffic scenarios. Therefore, this article performs an in-depth analysis of the problems of traditional planning frameworks which use a fixed frequency to replan the path and proposes a novel path planning framework that is universal based on multiple-models. The proposed framework divides the planning process into several layers, each of which has different functions. With this framework, the ADS can adaptively adjust the planning process according to the changes in traffic scenes and then provide different path planning algorithms to ensure its safety and flexibility in the process of driving. Moreover, the problems caused by the traditional planning framework can be solved. This framework has been applied to the autonomous vehicle ``Pioneer'', which won first place in the 2019 China Intelligent Vehicle Future Challenge (IVFC). The effectiveness and rationality of the integrated framework of local path planning proposed in this article were verified by a large number of tests in real-world traffic scenarios.

A method for determining the dynamic parameters of the operator of a mobile fire engine based on a segway, which fully characterize its dynamic properties – delay time and inertia was developed. The development of the method includes four stages. At the first stage, the problem of obtaining analytical relationships for determining the dynamic parameters of the operator is solved. These relationships include the frequency characteristics of the operator at a fixed frequency and its static parameter. At the second stage, the choice of a fixed frequency is substantiated using a criterion that minimizes errors in determining the dynamic parameters. It is shown that the fixed frequency for the characteristic parameters of the operator does not exceed 0.5Hz. The third stage includes substantiation of the procedure for determining the frequency characteristics of the operator and its static parameter. The frequency characteristics of the operator at a fixed frequency and its static parameter are determined numerically. This procedure is based on using the data obtained by measuring the values of the operator’s transfer function at fixed time intervals. To obtain data, an interactive analog engine is used, which can also perform the functions of a simulator. The time intervals are chosen according to the Kotelnikov-Nyquist-Shannon theorem. At the last stage, the procedure for determining the dynamic parameters of the operator of a segway-based mobile fire engine is described. It is shown that the error in determining the dynamic parameters of the operator of a mobile fire engine does not exceed 9.0%, if the error in determining its frequency characteristics at a frequency of 2.5s–1does not exceed 2.0%

Background Water content variation during plant growth is one of the most important monitoring parameters in plant studies. Conventional parameters (such as dry weight) are unreliable; thus, the development of rapid, accurate methods that will allow the monitoring of water content variation in live plants is necessary. In this study, we aimed to develop a non-invasive, radiofrequency-based monitoring system to rapidly and accurately detect water content variation in live plants. The changes in standing wave ratio (SWR) caused by the presence of stem water and magnetic particles in the stem water flow were used as the basis of plant monitoring systems. Results The SWR of a coil probe was used to develop a non-invasive monitoring system to detect water content variation in live plants. When water was added to the live experimental plants with or without illumination under drought conditions, noticeable SWR changes at various frequencies were observed. When a fixed frequency (1.611 GHz) was applied to a single experimental plant (Radermachera sinica), a more comprehensive monitoring, such as water content variation within the plant and the effect of illumination on water content, was achieved. Conclusions Our study demonstrated that the SWR of a coil probe could be used as a real-time, non-invasive, non-destructive parameter for detecting water content variation and practical vital activity in live plants. Our non-invasive monitoring method based on SWR may also be applied to various plant studies.

In this paper, we have analyzed TEC data obtained at Indian stations such as Agra, Lucknow, Hyderabad, Bangalore, and Port Blair and VLF amplitude data of NWC fixed frequency (f = 19.8 KHz) transmitter signals recorded at Agra for ±15 days from the day of occurrence of a strong earthquake of magnitude M = 8.5 on 11 April, 2012 in Indonesian region. The analysis is performed using well established statistical methods. We have found simultaneous seismogenic anomalies in TEC and VLF data prior and after the occurrence of the earthquake. Some of the anomalies occurring after the earthquake are identified as due to high solar activity. These anomalies are excluded from our analysis. Some on the VLF anomalies are simultaneous with TEC anomalies indicating that the effect of the earthquake from ground reaches to lower ionosphere and also penetrates up to upper ionosphere in a mechanism possibly involving atmospheric gravity waves (AGWs). These results are also supported by the ground based ULF measurements at Agra using a search coil magnetometer in which we found amplitude bursts in all the three components of the sensor on the day of earthquake after its occurrence. Finally, this multi-instruments and multi-stations data study has confirmed that the strong earthquake affects not only the epicenter area but also the adjoining region and the effect is larger away from the epicenter than that close to the epicenter. This is explained in terms of generation of AGWs from the epicenter.

Classic droop control ensures the synchronization of distributed generation (DG) units inside a microgrid without requiring any deployment of communication links, however it causes unwanted frequency fluctuations and degrades system dynamics. Angle droop control and V−I control have been developed as two major global positioning system (GPS)‐based control methods, both of which realize a fixed‐frequency operation of the microgrid through synchronizing DG units with GPS timing technology and brings improvement to the dynamic response of the overall system. This paper reveals the similarities and the correlations between these two methods that they can both be regarded as different forms of virtual impedance control. A novel adaptive virtual impedance control method is proposed accordingly to generalize GPS‐based control strategies into a unified control frame. An impedance and inner controller design approach considering both stability constraints and power quality requirements based on the small‐signal model of GPS‐based microgrids is presented for practical implementation. An adaptive transient resistance concept is adopted to enhance the system stability during large disturbances and grid faults. Case studies are presented to validate the system performance and fault ride‐through abilities of the proposed control scheme.

The present study aimed to propose and assess the physiological responses of a novel graded karate test. Ten male national-level karate athletes (age 26 ± 5 yrs; body mass 69.5 ± 11.6 kg; height 1.70 ± 0.09 m) performed two exercise tests (separated by 2-7 days): 1) a running-based cardiopulmonary exercise test; 2) a graded karate test. The cardiopulmonary exercise test was comprised of an individualized ramp protocol for treadmill running, and the graded karate test was comprised of a sequence of ‘kisami-gyaku-zuki” punching at a fixed frequency of a stationary target that becomes progressively distant. Cardiorespiratory responses, blood lactate concentration, and perceived exertion were measured. A verification phase was also performed in both tests to confirm the maximal physiological outcomes. The graded karate test evoked similar maximal responses to the running protocol: V̇O2 (57.4 ± 5.1 vs 58.3 ± 3.5 mL·kg-1·min-1; p = 0.53), heart rate (192 ± 6 vs 193 ± 10]beats.min-1; p = 0.62) and blood lactate (14.6 ± 3.4 vs 13.1 ± 3.0 mmol·L-1; p = 0.14) with a shorter duration (351 ± 71 vs 640 ± 9 s; p < 0.001). Additionally, the graded karate test evoked higher V̇O2 (72.6 ± 6.5 vs 64.4 ± 4.3 %V̇O2MAX; p = 0.005) and heart rate (89.4 ± 4.6 vs 77.3 ± 7.2 %HRMAX p < 0.001) at the ventilatory threshold and a higher heart rate (97.0 ± 2.4 vs 92.9 ± 2.2 %HRMAX; p = 0.02) at the respiratory compensation point. Incremental and verification phases evoked similar responses in V̇O2 and minute-ventilation during both tests. This novel displacement-based sport-specific test evoked similar maximal and higher submaximal responses, indicating a superior pathway to assess karate athletes.

This paper is concerned with the elastic near cloaking for the Lame system in three-dimensions using the notion of elastic scattering coefficients (ESC). Accordingly, the ESC of arbitrary three-dimensional objects are designed and some of their properties are discussed using elements of the elastic layer potential theory. Then, near-cloaking structures, coined as ESC-vanishing-structures, are constructed for the elastic cloaking at a fixed frequency or a band of frequencies. These multi-layered structures are designed so that their first few significant ESC vanish ahead of transformation-elastodynamics. The invisibility effect is achieved as the arbitrary elastic object inside the cloak has near-zero scattering cross-section for a band of frequencies. The cloaking effect for the Lame system is significantly enhanced by the proposed near-cloaking structures.

This paper is concerned with the inverse scattering problem for the three-dimensional Maxwell equations in bi-anisotropic periodic structures. The inverse scattering problem aims to determine the shape of bi-anisotropic periodic scatterers from electromagnetic near-field data at a fixed frequency. The factorization method is studied as an analytical and numerical tool for solving the inverse problem. We provide a rigorous justification of the factorization method which results in the unique determination and a fast imaging algorithm for the periodic scatterer. Numerical examples for imaging three-dimensional periodic structures are presented to examine the efficiency of the method.

There are some studies in the literature in order to make the interpretation of human tissues having different characteristics. Some of these studies focused on the evaluation of human face tissues. Vibration signals generated from vocal cords have been used in these studies about human face tissues. However, any study using the vibration signals recorded by applying the external vibration source having fixed frequency value is not available in the literature. In this study, it is aimed to investigate the frequency characteristics of the vibration signals recorded from the human face. These signals obtained from nine different regions on the faces of subjects are analysed using frequency characteristics. In the analysis stage, median and maximum frequency values are calculated and evaluated. So, the softness and hardness interpretation about these regions on the face can be made and the frequency ranges of these regions can be determined. As a result, it is observed that low-frequency signals are dominant in hard regions and high-frequency signals are dominant in soft regions.

During the development of the acute phase of ischemic stroke (IS), the cytoplasmic membranes of cells and receptor complex are primarily damaged. Structural changes in brain tissue are accompanied by violations of its electric physical characteristics, which are quite qualitatively possible to record using microwave dielectrometry. The aim of the studywas to learn the features of changes in the dielectric properties of peripheral blood erythrocytes of patients with IS during in vitro exposure to adrenergic drugs depending on the severity of the disease to optimize diagnosis. Material and methods of research.Measurements of complex dielectric constant (CDC) were performed by EHF dielectrometry at a fixed frequency of 39.5 × 109Hz, which is in the region of γ-dispersion. The work was based on the materials of a comprehensive examination of 350 patients with the first in the life of IS on the 1st, 10th and 21st day of the disease. The severity of the condition and the degree of neurological deficit were determined using the stroke scale of the US National Institutes of Health (NIHSS) in the first hours of the disease, in the dynamics of treatment on the 10th and 21st day. There were 2 clinical groups: 1st (n = 183) – patients in a state of moderate severity (mean score on the NIHSS scale 11.74±0.33); 2nd (n = 167) – patients with severe IS (average score on the NIHSS scale 24.06±0.29). Results.In the control group, there was a significant decrease after exposure to adrenaline solution. The reaction to adrenaline in patients with IS was almost absent. It indicates a decreasing of erythrocytes β-adrenoceptors (β-ARs) sensitivity to stimulants due to their desensitisation. In patients with moderate severity, erythrocytes are more reactive than in patients with more severe IS. Conclusions.The deviation of CDC of erythrocytes induced by adrenergic drugs in vitro is a manifestation of a specific response of cells to biologically active substances and depends on the functional state of the sympathoadrenal system

A new topology for 2-D scanning multibeam array antenna (MAA) design is proposed. Different from the traditional 2-D scanning scheme, this new design approach is composed of a 1-D beam-forming network (BFN) and a set of 1-D pattern-reconfigurable antennas, which can together realize 2-D multibeam scanning. Compared with traditional schemes, the proposed topology has advantages of uniplanar configuration and better flexibility in scaling up the array. To demonstrate the validity of the proposed topology, a high-gain 2-D scanning leaky-wave MAA operating at 10 GHz is designed. A horn BFN and a fixed-frequency leaky-wave antenna (LWA) are designed as the feeding part and radiation part, respectively. A number of new techniques are also developed for the design. For the horn BFN, a new phase-compensation method to reduce the gain drop is presented and phase inverters are introduced to provide an extra 180° of phase shift. Meanwhile, some modification of the LWA is conducted for better compatibility between the horn BFN and the LWA. A substrate integrated waveguide (SIW) to half-mode SIW (HMSIW) transition is introduced between the horn BFN and the LWA. The LWAs are terminally shorted to avoid the usage of matched loads. The width of the LWA is investigated to achieve suitable beam coverage and S-parameters. Finally, the antenna is fabricated and experiments are conducted to verify the agreement between simulation and measurement.

In the recent past, multiphase power generation, power transmission, and multiphase drive system are the main focus of research due to their several advantages over existing three phase system. Multiphase drives have better performance over three-phase drives. A multiphase transformer is required at the input of a fixed frequency multiphase drive, rectifier circuit for HVDC applications and multiphase generation and transmission systems. This paper investigates an static three-to seven-phase conversion technique and presents a design of transformer and control strategy to analyze the effect of unbalanced supply on a three-phase to seven-phase transformer. The transformer presented in this paper takes three phase input and a seven-phase output is obtained at the secondary terminals. The paper also discusses input–output unbalancing. A complete design, analysis and simulation of the proposed transformer is presented and experimental validation is also reported in this paper. Experimental and simulation results show that the presented transformer can produce a seven-phase power from three-phase ac power. Input unbalance is reflected at the output of the transformer but is less than the input unbalance. It is also shown that seven-phase output is not produced if one phase of input is open and the transformer has more than three limbs for flux to flow. But a balanced seven-phase output in steady state is produced even in one phase open condition for a three limb core type transformer. A new definition of sequence components of an unbalanced seven-phase system is required for unbalancing study so it is also defined in this paper.

This paper is concerned with the inverse acoustic scattering problem with phaseless total-field data at a fixed frequency. An approximate factorization method is developed to numerically reconstruct both the location and shape of the unknown scatterer from the phaseless total-field data generated by incident plane waves at a fixed frequency and measured on the circle $\partial B_R$ with a sufficiently large radius $R$. The theoretical analysis of our method is based on the asymptotic property in the operator norm from $H^{1/2}(\mathbb{S}^1)$ to $H^{-1/2}(\mathbb{S}^1)$ of the phaseless total-field operator defined in terms of the phaseless total-field data measured on $\partial B_R$ with large enough $R$, where $H^s(\mathbb{S}^1)$ is a Sobolev space on the unit circle $\mathbb{S}^1$ for real number $s$, together with the factorization of a modified far-field operator. The asymptotic property of the phaseless total-field operator is also established in this paper with the theory of oscillatory integrals. The unknown scatterer can be either an impenetrable obstacle of sound-soft, sound-hard or impedance type or an inhomogeneous medium with a compact support, and the proposed inversion algorithm does not need to know the boundary condition of the unknown obstacle in advance. Numerical examples are also carried out to demonstrate the effectiveness of our inversion method. To the best of our knowledge, it is the first attempt to develop a factorization type method for inverse scattering problems with phaseless data.

What is the origin of a wave? Why is something waving in the first place? To understand that we need to look at the concept of potential energy and how that gets exchanged with kinetic energy. Just like the pendulum of a classic clock. The pendulum determines the pace of the clock. It does so by swinging from left to right at a fixed frequency. The swinging motion is characterized by a continuous exchange of potential energy and kinetic energy. It has maximum potential energy when it is at its top and has a maximal kinetic energy when it is at the bottom (see Fig. 5.1).

As the competition for marine resources and marine security becomes fierce, the covertness and the security of the underwater acoustic communication (UAC) have drawn more and more attention recently. However, traditional UAC signals with fixed frequency and modulation fashoin are likely to be detected by the eavesdroppers. In order to resolve the problem, abio- inspired covert underwater acoustic communication using cetacean whistle with frequency-shift (BCUAC-FS) is proposed in this paper. In the proposed BCUAC-FSscheme, the frequency- shift is utilized to modulate the information on the time-frequency structure (TFS) of cetacean whistle. The virtual time reversal mirror (VTRM) is adopted to mitigate the multipath interference. The performance of proposed BCUAC scheme, in terms of the covertness and effectiveness, is evaluated by simulations under simulated and experimental channels.

International audience; A new solution for reconfigurable antennas based on the substrate integrated waveguide (SIW) technology is presented in this paper. The structure is designed to operate at 25 GHz for beam-scanning applications. An active coplanar slotted SIW antenna is proposed to cover an area from -32° to +32° with an offset of 9° at the operating frequency without using any phased shifter. The design is based on slots located at the broad face of the SIW structure which are fed by associated SIW holes to excite directly the centered slots via coplanar lines. Each feeder is loaded with a pin diode as binary switch to achieve the electronically beam-scanning function. © 2021 IEEE.

The authors have requested that this preprint be removed from Research Square.

Conventional communications satellites operate with fixed frequency, polarisation and coverage plans that are drawn up years before their launch during the payload definition phase. The satellite will typically be designed for a lifetime of more than fifteen years. During this operating period, changes in bandwidth requirements and the distribution of the service across its geographic coverage are more than likely. A new generation of communication satellites is expected to respond flexibly to these regional and temporal fluctuations in demand. The concept of cellular division of the coverage area and the coverage of these cells with spot beams in connection with the reuse of frequency bands enables this flexibility. The satellite's frequency plan has to be redefined throughout the mission lifetime via commands from the ground. The Flexible Down-Converter DOCON is one of the new components that allow satellite signals to be redistributed between service areas to flexibly reallocate the most critical spectrum resources as needed. DOCON is a flexible Ka-band down-converter from RF = 27.5 ... 30.0 GHz to IF = 17.7 ... 20.2 GHz designed for GEO communication satellites. The device includes the housing, DC-, RF-, and telemetry / tele-command interfaces. An Engineering Model (EM) in form, fit and function was successfully built and tested. The next stage, the Engineering Qualification Model (EQM), is currently in fabrication and will be qualified until end of 2019. The modular concept comprises hermetically sealed LTCC microwave modules as key building blocks. There are three of these LTCC-modules: the Local Oscillator Module (LOM), the Mixer Module (MXM), and the Variable Gain Module (VGM). Their function and realization shall be discussed in this paper.

In this paper, a new pulsewidth modulated gating scheme and a zero-voltage transition (ZVT) auxiliary circuit is proposed for a fixed frequency full-bridge CLL dc–dc resonant converter with a capacitive output filter. An approximate complex ac circuit approach is used for the steady-state analysis of the converter. The optimum design of the converter is described with the help of design curves for a sample converter of 200-W power rating operating at a switching frequency of 100 kHz. The converter with applied gating scheme and ZVT auxiliary circuit provides zero-voltage switching to all the switches for the entire variations in loading and input voltage conditions ensuring higher conversion efficiency. PSIM simulations are carried out to verify theoretical predictions about the performance of the converter for various operating conditions. Finally, experimental results are provided to verify the feasibility of the proposed converter. The theoretical, simulation, and experimental results are given and discussed.