Short-range Systems Research Articles

Antenna Design Considerations for Ground Penetrating Radar Landmine Detection

The performance of very short-range radar systems, such as ground penetrating radar for antipersonnel landmine detection, is critically dependent on the impulse characteristics of the antennas that are used. Typically, a pair of individual antennas is used in the radar, one for transmit and one for receive. These antennas are usually closely spaced for reasons of both portability and close in detectability. A variety of design techniques are used to achieve their wideband performance in terms of return loss, isolation, radiation patterns, polarization, and impulse formation. Not only the antenna elements but also their surrounds form the overall antenna structure and this ensemble becomes integral to the antenna performance and design process. Both the antenna and the surrounding structure can create late time signals or time sidelobes, which are in effect a form of self-generated clutter. Minimizing the duration of the antenna impulse response assists in reducing self-generated clutter and achieving optimum radar performance. This article considers the impact of the antenna on the system performance of the radar and shows that the clutter performance of the antenna can be the prime metric of system detection rather than the noise figure, given that the self-clutter often exceeds the latter.

Land–Snow Data Assimilation Including a Moderately Coupled Initialization Method Applied to NWP

Abstract Initialization methods are needed for geophysical components of Earth system prediction models. These methods are needed from medium-range to decadal predictions and also for short-range Earth system forecasts in support of safety (e.g., severe weather), economic (e.g., energy), and other applications. Strongly coupled land–atmosphere data assimilation (SCDA), producing balanced initial conditions across the land–atmosphere components, has not yet been introduced to operational numerical weather prediction (NWP) systems. Most NWP systems have evolved separate data assimilation (DA) procedures for the atmosphere versus land/snow system components. This separated method has been classified as a weakly coupled DA system (WCDA). In the NOAA operational short-range weather models, a moderately coupled land–snow–atmosphere assimilation method (MCLDA) has been implemented, a step forward from WCDA toward SCDA. The atmosphere and land (including snow) variables are both updated within the DA using the same set of observations (aircraft, radiosonde, satellite radiances, surface, etc.). Using this assimilation method, land surface state variables have cycled continuously for 6 years since 2015 for the 3-km NOAA HRRR model and with CONUS cycling since 1997. Month-long experiments were conducted with and without MCLDA for both winter and summer seasons using the 13-km Rapid Refresh model with atmosphere (50 levels), soil (9 levels), and snow (up to 2 layers if present) on the same horizontal grid. Improvements were evident for 2-m temperature for all times of day out to 6–12 h for both seasons but stronger in winter. Better temperature forecasts were also shown in the 1000–900-hPa layer corresponding roughly to the boundary layer. Significance Statement Accuracy of weather models depends on accurate initial conditions for soil temperature and moisture as well as for the atmosphere itself. This paper describes a moderately coupled data assimilation method that modifies soil conditions based on forecast error corrections indicated by atmospheric observations. This method has been tested for a month-long period in summer and winter and shown to consistently improve short-range forecasts of 2-m temperature and moisture. This coupled data assimilation method is used already in NOAA operational short-range models to improve its prediction skill for clouds, convective storms, and general weather conditions.

Explaining the cuspy dark matter halos by the Landau–Ginzburg theory

AbstractThe equilibrium cold dark matter halos show the almost universal innerr−1{r}^{-1}cusps, whose physical origin is still not completely clear. This work tries to further clarify this problem by the Landau–Ginzburg (LG) theory, which is often used to study the long-range correlation of the fluctuations in the critical phenomenon, and we will first introduce it in detail. The order parameter in this work is the density fluctuation, and the external perturbation is denoted by its gravitational effects on the particles. Then we discuss the availability of the aforementioned method for the cold dark matter halos and show that the universalr−1{r}^{-1}cusp may even form at the early age of the halo formation and can be expected for the dark matter halos with all the scales, which is also consistent with recent works. This article suggests that ther−1{r}^{-1}cusp may originate from the long-range correlations of the gravitating system. This correlation also exists in the short-range system near the critical point, and the difference is that the correlation length in the gravitating system is much longer than that of the short-range system.

Protection of Polish critical infrastructure (CI) against air threats

The goal of this paper is to analyse challenges related to protecting Polish critical infrastructure (CI) against air threats, such as UAVs, as a case study in a wider discussion on protection of critical infrastructure worldwide. The Polish legal definition of critical infrastructure and laws regarding the protection of such facilities are explained in the article in order to provide context. A review of scientific literature and open-source analysis of known air attacks on CI and the capabilities of air platforms are also included, with special attention being paid to unmanned systems. The threats themselves have been divided into two groups of scenarios: peacetime threats and crisis situations that have hybrid wartime scenarios. Depending on the scenario, the different capabilities of actors must be taken into account. Peacetime air threats include the use of commercially available drones. Those devices have limited capabilities, in terms of weaponisation, due to the limited weight of their cargo and the flight range. More advanced devices, including custom–built drones and military systems, can be supplied and used by state actors. Therefore, there are different requirements regarding protection systems. In peacetime, anti-drone systems are certainly recommended due to their capabilities and safety of use for bystanders. In more dangerous scenarios, typical military systems, including Very Short-Range Air Defence, Short-Range Air Defence and Medium Range Air Defence systems have to be employed or dedicated kinetic counter-drone systems deployed.

Low Complexity Neural Network Equalization Based on Multi-Symbol Output Technique for 200+ Gbps IM/DD Short Reach Optical System

Nowadays, Neural network (NN) has been proved to be an effective solution for nonlinear equalization in short reach optical systems. However, recent research has mainly focused on implementing more powerful NNs for equalization, while ignoring their adaptability to equalization tasks. In this paper, we propose Multi-Symbol Output (MSO)-Neural Networks (NN) for nonlinear equalization in high-speed short reach optical interconnects. The results show that the proposed MSO design works well on Deep Neural Networks (DNN), Long Short-Term Memory neural networks (LSTM) and Gate Recurrent Unit (GRU), which are the recent NN-based equalization structures. By increasing output symbols of the NNs, the number of slide windows in equalization can be sharply reduced, and so the complexity is reduced. By the same time, more information is brought to the MSO-NNs in back-propagations, therefore performance gain achieved. A 212-Gb/s 1-km Pulse Amplitude Modulation (PAM)-4 optical link is experimentally demonstrated as the target system, and the proposed MSO-NN equalizers are used to compare with traditional equalization algorithms including Volterra Nonlinear Equalizer (VNE) and single-symbol output NNs. Experimental results show that MSO design could help reduce the complexity of NN required for nonlinear equalization in the target system by around 2/3, and the proposed MSO-LSTM performs much better than VNE and 1 dB better than SSO-LSTM at the same time. Based on the proposed MSO-LSTM, transmission with BER under HD-FEC over 1 km NZDSF is achieved with a ROP at -2 dBm. Our work is well expandable and the proposed MSO design can be extended to other NN-based equalizers, which can help reduce complexity and learn more info from the training data and gain performance. The proposed MSO-NNs further enhance the performance and reduces the complexity of NN equalizers, provides assurance for future real-time high-speed short-range optical systems, and brings new ideas to NN-based equalizer design.

Lieb–Robinson bound in one-dimensional inhomogeneous quantum systems

Lieb–Robinson bound (LRB) in one-dimensional noninteracting many-electron systems with the disordered and quasiperiodic on-site potentials is studied numerically. For the short-range hopping system, a logarithmic light cone (i.e. |x|=βlogt+x0) is found in the system with the disordered on-site potential for small time. The coefficient β decreases with the increasing strength of disordered. When time is large, the bound does not change with time (i.e. |x|=C). For the generalized Fibonacci quasiperiodic (GFQ) system, the on-site potential is taken as V or −V according to two kinds of GFQ sequences. It is found that the system has a power-law light cone (i.e. |x|∝tγ, with 0<γ<1). The exponent γ decreases with the increasing V. We also find that γ for the first class of GFQ system is larger than that for the second class of GFQ system with the same V. Finally, the effects of the long-range hopping which decays like r−α with the distance r on LRB are discussed.

A Duplexing Hybrid Slot Antenna Design With High Isolation for Short-Range Radar Detection and Identification Applications at 24 GHz Band

This paper presents a duplexing hybrid antenna architecture for short-range radar systems with high isolation and low loss between the two transmitting (TX) and receiving (RX) ports. The antenna utilizes a single slot for common resonance shared by the two TX and RX port excitations. These two ports were constructed through two parallel microstrip lines crossing over the specified shaped slot. The feeding structures of these two microstrip feedings and the separation are optimally designed to ensure the mutual coupling signals out-of-phase, and therefore the signal cancellation can be achieved, leading to a high isolation between these two ports. In this design, the slot length is 0.92λ at 24.125 GHz, forming an equivalent short circuit at the other port. Given the initial design criteria, the design with the optimal isolation could readily be found by minimal full-wave simulations. Meanwhile, the equivalent circuit model was used to investigate the working principles and to improve the isolation bandwidth and impedance matching at the central frequency. The measured maximum isolation is 70 dB at 24.125 GHz. The RF front-end modules with TX and RX amplifiers are also integrated to validate its feasibility for the radar system application. The mechanisms to widen the isolation bandwidth are also addressed.

Effects of Chronological Age, Relative Age, and Maturation Status on Accumulated Training Load and Perceived Exertion in Young Sub-Elite Football Players.

The aims of this study were 1) to analyze the influence of chronological age, relative age, and biological maturation on accumulated training load and perceived exertion in young sub-elite football players and 2) to understand the interaction effects amongst age grouping, maturation status, and birth quartiles on accumulated training load and perceived exertion in this target population. A 6-week period (18 training sessions and 324 observation cases) concerning 60 young male sub-elite football players grouped into relative age (Q1 to Q4), age group (U15, U17, and U19), and maturation status (Pre-peak height velocity (PHV), Mid-PHV, and Post-PHV) was established. External training load data were collected using 18 Hz global positioning system technology (GPS), heart-rate measures by a 1 Hz short-range telemetry system, and perceived exertion with total quality recovery (TQR) and rating of perceived exertion (RPE). U17 players and U15 players were 2.35 (95% CI: 1.25–4.51) and 1.60 (95% CI: 0.19–4.33) times more likely to pertain to Q1 and Q3, respectively. A negative magnitude for odds ratio was found in all four quartile comparisons within maturation status (95% CI: 6.72–0.64), except for Mid-PHV on Q2 (95% CI: 0.19–4.33). Between- and within-subject analysis reported significant differences in all variables on age group comparison measures (F = 0.439 to 26.636, p = 0.000 to 0.019, η2 = 0.003–0.037), except for dynamic stress load (DSL). Between-subject analysis on maturity status comparison demonstrated significant differences for all training load measures (F = 6.593 to 14.424, p = 0.000 to 0.037, η2 = 0.020–0.092). Interaction effects were found for age group x maturity band x relative age (Λ Pillai’s = 0.391, Λ Wilk’s = 0.609, F = 11.385, p = 0.000, η2 = 0.391) and maturity band x relative age (Λ Pillai’s = 0.252, Λ Wilk’s = 0.769, F = 0.955, p = 0.004, η2 = 0.112). Current research has confirmed the effects of chronological age, relative age, and biological maturation on accumulated training load. Perceived exertion does not seem to show any differences concerning age group or maturity status. Evidence should be helpful for professionals to optimize the training process and young football players’ performance.

Clusters in colloidal dispersions with a short-range depletion attraction: Thermodynamic identification and morphology

HypothesisParticle aggregation is ubiquitous for many colloidal systems, and drives the phase separation or the formation of materials with a highly heterogeneous large-scale structure, such as gels, porous media and attractive glasses. While the macroscopic properties of such materials strongly depend on the shape and size of these particle aggregates, the morphology and underlining aggregation physical mechanisms are far from being fully understood. Recently, it has been proposed that for reversible colloidal aggregation, the cluster morphology in the case of colloids interacting with short-range attractive forces is determined by a single variable, namely, the reduced second virial coefficient, B2∗. ExperimentsWe examined this proposal by performing confocal microscopy experiments and computer simulations on a large collection of short-ranged attractive colloidal systems with different values of the attraction strength and range. FindingsWe show that in all cases a connection between the colloidal cluster morphology and B2∗ can be established both in experiments and simulations. This physical scenario holds at all investigated thermodynamic conditions, namely, in the fluid state, in the metastable region and in non-equilibrium conditions. Our findings support the connection between reversible colloidal aggregation and the so-called extended law of corresponding states.

Lightweight encryption for short-range wireless biometric authentication systems in Industry 4.0

Most recent solutions for users’ authentication in Industry 4.0 scenarios are based on unique biological characteristics that are captured from users and recognized using artificial intelligence and machine learning technologies. These biometric applications tend to be computationally heavy, so to monitor users in an unobtrusive manner, sensing and processing modules are physically separated and connected through point-to-point wireless communication technologies. However, in this approach, sensors are very resource constrained, and common cryptographic techniques to protect private users’ information while traveling in the radio channel cannot be implemented because their computational cost. Thus, new security solutions for those biometric authentication systems in their short-range wireless communications are needed. Therefore, in this paper, we propose a new cryptographic approach addressing this scenario. The proposed solution employs lightweight operations to create a secure symmetric encryption solution. This cipher includes a pseudo-random number generator based, also, on simple computationally low-cost operations in order to create the secret key. In order to preserve and provide good security properties, the key generation and the encryption processes are fed with a chaotic number sequence obtained through the numerical integration of a new four-order hyperchaotic dynamic. An experimental analysis and a performance evaluation are provided in the experimental section, showing the good behavior of the described solution.

Modeling of the Missile Launch Dynamic Processes in Short-Range Air Defense System

Armament systems such as guns, launchers simulators are effective tools for training armed forces personnel. A firearm is a complex biomechanical system, so the best quality of training is achieved when training in a simulator, repeating the dynamic processes of the weapon by simulating the perception of real weapon use (feeling). The paper investigates the dynamic and stability properties of the short-range air defense system RBS-70. The RBS-70 short-range air defense system is designed to combat low-flying air targets. The purpose of this paper is to present the physical and mathematical models with com numerical dynamic simulation of the launcher in the first phase of missile flight. The theoretical model was formulated in the vertical plane and verified by the numerical modeling simulation.

The principle of operation of an autodyne optoelectronic transceiver of short-range radar systems

The description of the device and the principle of operation of a new type of autodyne transceiver of short-range radar systems (SRRS), made on the basis of an optoelectronic oscillator (OEO), is presented. The antenna is connected to the OEO through a dividing-decoupling device (DDD), which provides, on the one hand, conditions for generating self-oscillations in the system and, on the other hand, transmitting and receiving radio signals with minimal losses. The scheme of the DDD and the method of calculating their parameters are considered. A mathematical model of the autodyne system based on the OEO has been developed, and the basic relations for determining its parameters and characteristics have been obtained. It is demonstrated that the use of OEO provides a significant increase in the equivalent Q-factor of the oscillator system and the reduction in its own noise. The improvement of these parameters of the autodyne SRRS will significantly increase the range of operation, expand the range of operating frequencies and the scope of their application. The prospects of using autodynes based on OEO in the creation of detection systems of objects with a small effective scattering area, such as unmanned aerial vehicles, for protection against which the use of conventional (distant) radars is ineffective, are noted.

Attitude sensors relative angular misalignment estimation in integrated navigation systems

When using modern navigation systems as part of an on-board system, the navigation task can be solved in several ways: using positional, velocity and angular corrections, and systems using measurements of various physical nature—radio, such as short-range and long-range navigation radio systems, GLONASS/GPS satellite global navigation systems, optical—celestial navigation systems—can operate as correctors. The best performance of INS and its sensors (gyroscopes and accelerometers) errors estimation can be obtained when all types of correction are implemented simultaneously. At the same time, it is particularly difficult to implement correction according to attitude parameters due to the fact that the measuring axes of the INS and correctors may not match on board of moving objects. Such a mismatch is commonly called relative angular misalignment. The paper considers a possible approach to the attitude sensors relative angular misalignment estimation in integrated navigation systems (NS), carried out in motion when the NS is in operating mode.

Comparison of Back-Scattering and Forward-Scattering Methods in Short Range Microwave Imaging Systems

Microwave imaging technique allows obtaining images of hidden objects in structures and media using microwaves. Usually in short-range microwave imaging systems, the back-scattered signal is used, when a combined transmit-receive antenna scans over a plane, forming a two-dimensional synthesized aperture, while the signal reflected from the object of observation is recorded, as a result of which a microwave hologram of the object is formed. The second option involves registering the forward-scattered signal, when the transmitting and receiving antennas are located on opposite sides of the object and scan synchronously. The purpose of this work is a theoretical and experimental comparison of these two sounding options, identifying the advantages and disadvantages of each option, taking into account the features that arise when solving various problems of microwave imaging. Keywords: microwave holography, mivrowave image, back-scattered signal, forward-scattered signal, range resolution.

Сравнение вариантов зондирования "на отражение" и "на просвет" в системах радиовидения малой дальности

Microwave imaging technique allows obtaining images of hidden objects in structures and media using microwaves. Usually in short-range microwave imaging systems, the back-scattered signal is used, when a combined transmit-receive antenna scans over a plane, forming a two-dimensional synthesized aperture, while the signal reflected from the object of observation is recorded, as a result of which a microwave hologram of the object is formed. The second option involves registering the forward-scattered signal, when the transmitting and receiving antennas are located on opposite sides of the object and scan synchronously. The purpose of this work is a theoretical and experimental comparison of these two sounding options, identifying the advantages and disadvantages of each option, taking into account the features that arise when solving various problems of microwave imaging.

Unified Reciprocal Space Processing for Short-Range Active and Passive Imaging Systems

Large scale sensing systems increasingly operate in short-range geometries, providing three-dimensional imaging capabilities that leverage the large number of degrees of freedom of distributed arrays. The two most powerful modes of operation include active, multiple-input multiple-output arrays, in which an image is processed from signals measured using different pairs of transmitting and receiving antennas; and passive, synthetic aperture interferometric radiometer arrays, which can image using ambient, non-cooperative radiation by processing signals measured at different receiving antenna pairs. In this paper, we explore the analogy between these two imaging modes, and outline a generalized framework for analyzing these systems in the array near field. Focusing on the similarities between the formalisms describing the operation of generic active and passive systems, it is proposed, to our knowledge for the first time in the scientific literature, to adapt a Fourier-based imaging technique optimized for short-range active MIMO systems to passive technologies, interrogating the emissivity of a spatially distributed target. The systematic method presented in this paper provides a framework for characterizing and optimizing short range coherent or incoherent systems used in threat detection and non-destructive testing applications.

Features of Signals from Distributed Targets of an Autodyne Pulse Radar with Linear Frequency Modulation

A mathematical model has been developed to describe the signals of an autodyne short-range radar system (SRRS) with simultaneous pulse modulation (PM) of amplitude and linear frequency modulation (LFM). The features of the formation of signals received from a distributed target in the form of an ensemble of an arbitrary number of point reflectors are considered. Calculations of signals by the proposed step method are performed for the case of two point reflectors on a location object situated at different distances from the SRRS. The distinctive properties of the signals generated when receiving the first and subsequent radiation reflected from the target are established. After sending the probing radiation, the reception of the first reflected radiation from a set of brilliant points is accompanied by the formation of a linear superposition of signals from individual reflectors. The reception of subsequent reflections causes the appearance of a combinational interaction of the signals of individual reflectors. The nature and magnitude of such interaction is determined by the magnitude of the feedback parameter of the autodyne SRRS, which depends on the values of the frequency deviation and the delay time of the reflected radiation. The results of experimental studies of the autodyne SRRS with simultaneous amplitude and LPM have been obtained using the oscillator module made on the 8-millimeter Gann diode.

Entropic extensivity and large deviations in the presence of strong correlations

The standard Large Deviation Theory (LDT) mirrors the Boltzmann–Gibbs (BG) factor which describes the thermal equilibrium of short-range Hamiltonian systems, the velocity distribution of which is Maxwellian. It is generically applicable to systems satisfying the Central Limit Theorem (CLT), among others. When we focus instead on stationary states of typical complex systems (e.g., classical long-range Hamiltonian systems), both the CLT and LDT need to be generalized. We focus here on a scale-invariant stochastic process involving strongly-correlated exchangeable random variables which, through the Laplace-de Finetti theorem, is known to yield a long-tailed Q-Gaussian N→∞ attractor in the space of distributions (1<Q<3). We present strong numerical indications that the corresponding LDT probability distribution is given by P(N,z)=P0eq−rq(z)N=P0[1−(1−q)rq(z)N]1/(1−q) with q=2−1/Q∈(1,5/3). The rate function rq(z) seemingly equals the relative nonadditive qr-entropy per particle, with qr≃710+6101Q−1, thus exhibiting a singularity at Q=1 and recovering the BG value qr=1 in the Q→3 limit. Let us emphasize that the extensivity of rq(z)N appears to be verified, consistently with what is expected, from the Legendre structure of thermodynamics, for a total entropy. The present analysis of a relatively simple model somewhat mirroring spin-1/2 long-range-interacting ferromagnets (e.g., with strongly anisotropic XY coupling) might be helpful for a deeper understanding of nonequilibrium systems with global correlations and other complex systems.

N ways to simulate short-range particle systems: Automated algorithm selection with the node-level library AutoPas

AutoPas is an open-source C++ library delivering optimal node-level performance by providing the ideal algorithmic configuration for an arbitrary scenario in a given short-range particle simulation. It acts as a black-box container, internally implementing an extensive set of algorithms, parallelization strategies, and optimizations that are combined dynamically according to the state of the simulation via auto-tuning. This paper gives an overview of the high-level user perspective, as well as the internal view, covering the implemented techniques and features. The library is showcased by incorporating it into the codes LAMMPS and ls1 mardyn, and by investigating various applications. We further outline node-level shared-memory performance and scalability of our auto-tuning software which is comparable to LAMMPS. Program summaryProgram Title: AutoPasCPC Library link to program files:https://doi.org/10.17632/9kdb2p76hv.1Developer's repository link:https://github.com/AutoPas/AutoPasCode Ocean capsule:https://codeocean.com/capsule/0391732Licensing provisions: BSD 2-clauseProgramming language: C++17, CMake 3.14Nature of problem: The evaluation of the short-range pairwise interactions in an N-Body simulation can be achieved using many different algorithms and parallelization techniques. Depending on the nature of the scenario, its current state, and the forces of interest, the optimal algorithm configuration can differ greatly. Choosing this optimum is a non-trivial task even for experts. Furthermore, this optimum can change over the course of a simulation. Typically, a particle simulation software only implements one algorithm for force computation and is thus specialized for a certain type of simulation. It is up to the user to choose the program suitable for his needs.Solution method: The AutoPas library implements a range of state of the art algorithms to find the relevant neighbors for the N-Body pairwise force calculation. It provides multiple shared-memory parallelization strategies using OpenMP and further algorithm optimization parameters that can all be set at run-time. A big burden for users persists in requiring the expert knowledge to pick the optimal solution procedure for a simulation. AutoPas removes this burden by tuning all aforementioned options automatically and dynamically. This way, simulation programs that make use of AutoPas give every domain scientist the possibility to make use of the most suitable algorithm configuration for arbitrary scenarios.

Формирование продукции систем негидростатического моделирования атмосферы COSMO-RuBy (Гидрометцентр России) и WRF-ARW (Белгидромет) для краткосрочного прогноза погоды

The paper considers the results of activities on the development of output products for the non-hydrostatic short-range numerical weather prediction systems: COSMO-RuBy with a grid spacing of 2.2 km at the Hydrometcentre of Russia and WRF-ARW with a grid spacing of 3 km in Belhydromet. The important results of the activities are the organization of the exchange of unified products between the countries and the development at the Hydrometcentre of Russia of two technologies for obtaining the unified products: the multi-model lagged ensemble system and the system for the complex correction based on machine learning of model results. A specialized web-site providing convenient work of forecasters with the COSMO-RuBy results and unified products was created at the Hydrometcentre of Russia based on the feedback from forecasters. The systems of common visualization and verification of COSMO-RuBy and WRF-ARW results are implemented in Belhydromet. Keywords: numerical weather prediction, ensemble forecasting, visualization, machine learning