Static Trajectories Research Articles

Charger and receiver deployment for trajectory coverage with delay constraint in mobile wireless rechargeable sensor networks

Wireless Rechargeable Sensor Networks (WRSNs) powered by radio-frequency radiation attract a lot of attention for their sustainability and convenience, etc. One focus is how to rationally deploy the key devices, such as receiver and charger, to improve the network performance and deployment budget. This paper considers a novel deployment problem for WRSNs in a two-dimensional space with static trajectories, deploying the minimum number of wireless chargers and receivers for mobile nodes, subject to the non-overtime updating probability requirement for mobile node at any location of the trajectories. This timeliness communication problem is tricky and NP-hard when involving the influence of three practical delays (retransmission delay, charging delay and competition delay). Therefore, a performance controllable discretization strategy is proposed, based on which the Greedy Heuristic (GH) and Particle Swarm Optimization (PSO) based approximate solutions are introduced. The execution process and time complexity of these two solutions are analyzed, and then the numerical results of extensive simulations are introduced to verified the scalability, accuracy and efficiency of the two solutions. As a result, the GH solution has better deployment success rate and efficiency, and is the recommended solution for the novel problem. Finally, two real-life scenarios (indoor exhibition hall and hospital interior road) are introduced to further verify the robustness of the two solutions under the practical challenges of uneven density of mobile nodes, restricted deployment locations and occlusion of wireless links.

Representation of seasonal land use dynamics in SWAT+ for improved assessment of blue and green water consumption

Abstract. In most (sub)-tropical African cultivated regions, more than one cropping season exists following the (one or two) rainy seasons. An additional cropping season is possible when irrigation is applied during the dry season, which could result in three cropping seasons. However, most studies using agro-hydrological models such as the Soil and Water Assessment Tool (SWAT) to map blue and green evapotranspiration (ET) do not account for these cropping seasons. Blue ET is a portion of crop evapotranspiration after irrigation application, while green ET is the evapotranspiration resulting from rainfall. In this paper, we derived dynamic and static trajectories from seasonal land use maps to represent the land use dynamics following the major growing seasons to improve simulated blue and green water consumption from simulated evapotranspiration in SWAT+. A comparison between the default SWAT+ set-up (with static land use representation) and a dynamic SWAT+ model set-up (with seasonal land use representation) is made by a spatial mapping of the ET results. Additionally, the SWAT+ blue and green ET were compared with the results from the four remote sensing data-based methods, namely SN (Senay), EK (van Eekelen), the Budyko method, and soil water balance method (SWB). The results show that ET with seasonal representation is closer to remote sensing estimates, giving higher performance than ET with static land use representation. The root mean squared error decreased from 181 to 69 mm yr−1, the percent bias decreased from 20 % to 13 %, and the Nash–Sutcliffe efficiency increased from −0.46 to 0.4. Furthermore, the blue and green ET results from the dynamic SWAT+ model were compared to the four remote sensing methods. The results show that the SWAT+ blue and green ET are similar to the van Eekelen method and performed better than the other three remote sensing methods. It is concluded that representation of seasonal land use dynamics produces better ET results, which provide better estimations of blue and green agricultural water consumption.

Comparison of non-coplanar optimization of static beams and arc trajectories for intensity-modulated treatments of meningioma cases

Two methods for non-coplanar beam direction optimization, one for static beams and another for arc trajectories, were proposed for intracranial tumours. The results of the beam angle optimizations were compared with the beam directions used in the clinical plans. Ten meningioma cases already treated were selected for this retrospective planning study. Algorithms for non-coplanar beam angle optimization (BAO) and arc trajectory optimization (ATO) were used to generate the corresponding plans. A plan quality score, calculated by a graphical method for plan assessment and comparison, was used to guide the beam angle optimization process. For each patient, the clinical plans (CLIN), created with the static beam orientations used for treatment, and coplanar VMAT approximated plans (VMAT) were also generated. To make fair plan comparisons, all plan optimizations were performed in an automated multicriteria calculation engine and the dosimetric plan quality was assessed. BAO and ATO plans presented, on average, moderate global plan score improvements over VMAT and CLIN plans. Nevertheless, while BAO and CLIN plans assured a more efficient OARs sparing, the ATO and VMAT plans presented a higher coverage and conformity of the PTV. Globally, all plans presented high-quality dose distributions. No statistically significant quality differences were found, on average, between BAO, ATO and CLIN plans. However, automated plan solution optimizations (BAO or ATO) may improve plan generation efficiency and standardization. In some individual patients, plan quality improvements were achieved with ATO plans, demonstrating the possible benefits of this automated optimized delivery technique.

Obstacle Handling Mechanism for Mobile Anchor Assisted Localization in Wireless Sensor Networks

Localization is necessary for applications such as warning systems, where the sensed data along with the location of occurrence is essential for decision making in Wireless Sensor Networks (WSNs). Equipping each sensor node with a global positioning system (GPS) unit is infeasible, as it increases both the power consumption and cost of the deployed network. A more practical approach is to employ a single or a few GPS-equipped mobile anchor nodes (MANs). These MANs localize the unknown sensor nodes by broadcasting their current locations periodically while moving in the area of interest. In a realistic environment, obstacles may be present in the deployment area that obstruct the radio connectivity between unknown sensors and the MANs. In this paper, we propose a mechanism to handle irregular obstacles in the path of various existing static trajectories. Also, we have considered an accurate and reliable channel model to provide a realistic evaluation of the proposed method. The results are compared on the basis of four different localization techniques, namely, accuracy priority trilateration (APT), time priority trilateration (TPT), weighted centroid localization (WCL) and weight-compensated weighted centroid localization (WCWCL). Experimental and simulation results show that the proposed method effectively handles regular and irregular obstacles in the deployed environment.

Localization in Wireless Sensor Networks with Mobile Anchor Node Path Planning Mechanism

Determining the accurate locations of randomly deployed sensors in a given geographical region is a critical problem in the field of Wireless Sensor Networks. Various approaches have been proposed in the past to tackle this problem. Most of the existing techniques rely on the use of a beacon node which traverses throughout the region with limited power sources. Sensors use the beacon node positions for self localization. The trajectory of the beacon node has an influence on the accuracy, time and efficiency of the localization algorithm. In this paper, we propose Cosine Rule based Localization (CRL) algorithm for static trajectories of the mobile beacon node. Existing schemes use trilateration for position estimation of sensor nodes. The proposed method uses the Cosine rule on received beacon positions and distances obtained from RSSI in such a way that lines representing distances intersect at one point for the application of the Cosine rule. Simulation results reveal that CRL enables the unknown sensors to locate themselves with better accuracy in comparison with the existing trilateration technique for all the trajectories.

Harvesting entanglement with detectors freely falling into a black hole

We carry out the first investigation of the entanglement and mutual information harvesting protocols for detectors freely falling into a black hole. Working in $(1+1)$-dimensional Schwarzschild black hole spacetime, we consider two pointlike Unruh-DeWitt (UDW) detectors in different combinations of free-falling and static trajectories. Employing a generalization of relative velocity suitable for curved spacetimes, we find that the amount of correlations extracted from the black hole vacuum, at least outside the near-horizon regime, is largely kinematic in origin (i.e. it is mostly due to the relative velocities of the detectors). Second, correlations can be harvested purely from the black hole vacuum even when the detectors are causally disconnected by the event horizon. Finally, we show that the previously known `entanglement shadow' near the horizon is indeed absent for the case of two free-falling-detectors, since their relative gravitational redshift remains finite as the horizon is crossed, in accordance with the equivalence principle.

Entanglement amplification between superposed detectors in flat and curved spacetimes

We consider an entanglement harvesting protocol between two Unruh-deWitt detectors in quantum superpositions of static trajectories in the static de Sitter and thermal Minkowski spacetimes. We demonstrate for the first time that the spatial superposition of each detector's path allows entanglement to be harvested from the quantum field in regimes where it would be otherwise impossible for detectors on classical trajectories. Surprisingly, for detectors on sufficiently delocalized trajectories in a thermal bath, the amount of harvested entanglement grows with the temperature of the field, violating a no-go theorem derived by Simidzija et al. [Phys. Rev. D 98, 085007]. We also discover interesting effects for mutual information harvesting, which depends sensitively on the nonlocal correlations between the superposed trajectories between the paths of the respective detectors.

Ground and thermal states for the Klein-Gordon field on a massless hyperbolic black hole with applications to the anti-Hawking effect

On an $n$-dimensional, massless, topological black hole with hyperbolic sections, we construct the two-point function both of a ground state and of a thermal state for a real, massive, free scalar field arbitrarily coupled to scalar curvature and endowed with Robin boundary conditions at conformal infinity. These states are used to compute the response of an Unruh-DeWitt detector coupled to them for an infinite proper time interval along static trajectories. As an application, we focus on the massless conformally coupled case and we show, numerically, that the anti-Hawking effect, which is manifest on the three-dimensional case, does not occur if we consider a four-dimensional massless hyperbolic black hole. On the one hand, we argue that this result is compatible with what happens in the three- and four dimensional Minkowski spacetime, while, on the other hand, we stress that it generalizes existing results concerning the anti-Hawking effect on black hole spacetimes.

On the clinotron effect in a backward-wave tube

The results of a theoretical study of the clinotron effect in a clinotron model, which takes into account static electron trajectories in the focusing magnetic field and the initial spacing between the lower beam boundary and the surface of the slow-wave structure, are presented. Physical processes of interaction between a thick electron beam with transverse dimensions comparable with the length of the slow wave and the RF field at its oblique incidence onto the structure are considered. It is demonstrated that, as the current is increased from the starting to the working value, a beam tilt is necessary to reduce the nonlinear effects of interaction between the beam and the RF field and prevent the complex self-oscillation dynamics in the clinotron; in the small amplitude mode (start), the beam tilt is related to optimization of the beam supply into the interaction space, which ensures the minimum starting current. In addition, it is shown that, in the presence of the initial spacing between the beam and structure, the reduced clinotron efficiency η/С increases and, at the optimum tilt angle, is no less than the normalized efficiency of classical backward-wave tubes with a thin electron beam.

Clinotron in the amplification mode

A self-consistent nonlinear theory for a clinotron model that takes into account static electron trajectories in the focusing magnetic field and the loss in the slow-wave structure, the clinotron amplification mode is analyzed for different ratios of the operating and starting currents, input signal levels, and the inclination angle of the electron beam relative to the surface of the slow-wave structure. The gain and the amplification band are calculated. It is demonstrated that the main theoretical data are qualitatively consistent with the experimental results obtained using a clinotron model operating in the five millimeter wave band.

Impact of static trajectories on localization in wireless sensor networks

A Wireless Sensor Network (WSN) consists of many sensors that communicate wirelessly to monitor a physical region. Location information is critical essential and indispensable for many applications of WSNs. A promising solution for localizing statically deployed sensors is to benefit from mobile location-aware nodes called beacons. However, the essential problem is to find the optimum path that the mobile beacon should travel in order to improve localization accuracy, time and success as well as energy efficiency. In this paper, we evaluate the performance of five mobile beacon trajectories; Random Way Point, Scan, Hilbert, Circles and Localization algorithm with a Mobile Anchor node based on Trilateration (LMAT) based on three different localization techniques such as Weighted Centroid Localization and trilateration with time priority and accuracy priority. This evaluation aims to find effective and essential properties that the trajectory should have. Our simulations show that a random movement cannot guarantee the performance of localization. The results also show the efficiency of LMAT regarding accuracy, success and collinearity while the Hilbert space filling curve has lower energy consumption. Circles path planning can help to localize unknown sensors faster than others at the expense of lower localization precision.

Internal representation of movement sequences built upon either static line drawings or trajectories of moving object

In this paper, we explore the issue of the nature (perceptual, abstract, or motor) of neural codes used by CNS in order to store the internal representation of elements of a sequence of movements. Reported are the results of two experiments in which two independent groups of 16 right handed adults repeated, after a given delay, the piecewise trajectories (open polygonal chains) using the graphical tablet. A trajectory was shown either as a static line-drawing (static mode) or a small moving pointer (dynamic mode). The results show that: 1) for the delay varying from 0 to 1 s, the latent time of the trajectory production is greater in the dynamic than in the static mode, with the latent time is no different under to presentation conditions when the production delay reaches 3 s; 2) the latent time is exponentially decaying as the trajectory production delay increases from 0 to 3000 ms, with the characteristic decay time being different in the static (377 ms) and the dynamic (656 ms) presentation modes. The results of the present study are in line with the view that the internal representation of the sequence of movements is perceptual and it is converted into the motor codes at the later stages prior to movement execution. It is suggested in the paper that the observed exponential decay of the latent time might be related to the transformation of the early sensory (iconic) representation into the perceptual trajectory representation.

Image guidance can support scaphoid K-wire insertion: an experimental study and initial clinical experience

In the treatment of small bone fractures, such as the scaphoid bone, conventional navigation is limited by its dependence on fixed reference arrays. We introduce a new technique based on reference markers in surgical instruments. If visible on a standard fluoroscopic image, static trajectories are overlaid in this image to guide implant insertions. Fixed markers are not required. The purpose of this study was to identify the possible advantages of the new guidance technique. For this study, 20 artificial hand specimens were randomized into two groups and blinded with polyurethane foam: 10 were treated conventionally and 10 were image guided. We used a clip containing radiopaque markers, which was detected by the system's workstation. A static trajectory was displayed consecutively in the fluoroscopic image to serve as an aiming device. Secondly, we included 3 patients with fractures of the scaphoid bone to test the integrability of this novel method in a clinical setting. In the experimental setup, trajectory guidance reduced the duration of surgery and radiation exposure. Furthermore, it reduced the perforation rate. Accuracy was not improved by the new technique. For clinical cases, the system was integrated into the accommodated surgical workflow and rated as very helpful by users. The system helped reduce the misplacement rate and the emission of radiation. The main limitations were that trajectories were not displayed in real time and could only be shown in a single fluoroscopic image. However, the system is simple and can be easily integrated into the surgical workflow.

Pedestrian Static Trajectory Analysis of a Hypermarket

In this paper, we propose a combination of pedestrian data collection and analysis and modeling that may yield higher competitive advantage in the business environment. The data collection is only based on simple inventory and questionnaire surveys on a hypermarket to obtain trajectory path of pedestrian movement. Though the data has limitation by using static trajectories, our techniques showed that it is possible to obtain aggregation of flow pattern and alley attractiveness similar to the result of aggregation using dynamic trajectory. A case study of a real hypermarket demonstrates that daily necessity products are closely related to higher flow pattern. Using the proposed method, we are also able to quantify pedestrian behavior that shoppers tend to walk about 7 times higher than the ideal shortest path.

Health-related quality of life trajectories of methamphetamine-dependent individuals as a function of treatment completion and continued care over a 1-year period

This study applies a chronic illness framework to evaluate treatment outcomes among individuals dependent on methamphetamine (MA). Using growth curve modeling, health-related quality of life (HRQOL) trajectories of MA-dependent individuals ( N = 723) were examined over a 1-year period. Results show greater improvements in mental HRQOL trajectories as a function of treatment completion and continued care, although fairly static trajectories in physical health status. Other factors affecting HRQOL trajectories included gender, psychosocial functioning, drug use severity, and health impairment. Results extend research on treatment evaluations for MA dependence, highlighting the importance of continued service utilization for improved quality of life outcomes.

PAIRING PROPERTIES OF SUPERHEAVY NUCLEI

Pairing properties of even-even superheavy N = 184 isotones are studied within the Skyrme-Hartree-Fock+BCS approach. In the particle-hole channel we take the Skyrme energy density functional SLy4, while in the particle-particle channel we employ the seniority pairing force and zero-range δ-interactions with different forms of density dependence. We conclude that the calculated static fission trajectories weakly depend on the specific form of the δ-pairing interaction. We also investigate the impact of triaxiality on the inner fission barrier and find a rather strong Z dependence of the effect.

A quantum weak energy inequality for spin-one fields in curved space–time

Quantum weak energy inequalities (QWEI) provide state-independent lower bounds on averages of the renormalized energy density of a quantum field. We derive QWEIs for the electromagnetic and massive spin-one fields in globally hyperbolic space–times whose Cauchy surfaces are compact and have trivial first homology group. These inequalities provide lower bounds on weighted averages of the renormalized energy density as “measured” along an arbitrary timelike trajectory, and are valid for arbitrary Hadamard states of the spin-one fields. The QWEI bound takes a particularly simple form for averaging along static trajectories in ultrastatic space–times; as specific examples we consider Minkowski space (in which case the topological restrictions may be dispensed with) and the static Einstein universe. A significant part of the paper is devoted to the definition and properties of Hadamard states of spin-one fields in curved space–times, particularly with regard to their microlocal behavior.

A general worldline quantum inequality

Worldline quantum inequalities provide lower bounds on weighted averages of the renormalized energy density of a quantum field along the worldline of an observer. In the context of real, linear scalar field theory on an arbitrary globally hyperbolic spacetime, we establish a worldline quantum inequality on the normal ordered energy density, valid for arbitrary smooth timelike trajectories of the observer, arbitrary smooth compactly supported weight functions and arbitrary Hadamard quantum states. Normal ordering is performed relative to an arbitrary choice of Hadamard reference states. The inequality obtained generalizes a previous result derived for static trajectories in a static spacetime. The underlying argument is straightforward and is made rigorous using the techniques of microlocal analysis. In particular, an important role is played by the characterization of Hadamard states in terms of the microlocal spectral condition. We also give a compact form of our result for stationary trajectories in a stationary spacetime.

Static trajectories of the development of two staggered parallel cracks

The problem of the development of two staggered parallel cracks in a finite plate subjected to uniaxial static tension at infinity is examined on the basis of the method of singular integral equations. The trajectories are calculated by the step-by-step method using the criterion of maximum circumferential stresses. In this case, a segment of the trajectory is approximated by a third-degree polynomial in each step. The results of numeric calculations are presented.