Algorithm for adaptive correction of the ship's movement along the trajectory in the presence of a sea current

В статье предложен алгоритм адаптивной коррекции движения судна по траектории при наличии морского течения. В основе предлагаемого подхода лежит алгоритм градиента вспомогательных функций. Показаны преимущества предложенного алгоритма адаптивной коррекции движения судна по траектории. Сущность предлагаемого подхода заключается в замене прямолинейного участка маршрута судна, новой виртуальной траекторией и использовании ее во вспомогательной функции и при вычислении соответствующего вектора градиента. Компьютерное моделирование подтвердило эффективность предложенного алгоритма адаптивной коррекции. Адаптивные свойства разработанного алгоритма выражаются в том, что он обеспечивает асимптотически точное движение по участкам запланированной траектории, не используя информации о скорости и направлении морского течения. Предполагается использование предложенного адаптивного алгоритма при разработке систем автоматического управления движением судна по маршруту. The article proposes an algorithm for adaptive correction of the ship's movement along the trajectory in the presence of a sea current. The proposed approach is based on the gradient algorithm of auxiliary functions. The advantages of the proposed algorithm for adaptive correction of the ship's motion along the trajectory are shown. The essence of the proposed approach is to replace the straight-line section of the ship's route with a new virtual trajectory and use it in an auxiliary function and in calculating the corresponding gradient vector. Computer simulation has confirmed the effectiveness of the proposed adaptive correction algorithm. The adaptive properties of the developed algorithm are expressed in the fact that it provides asymptotically accurate movement along sections of the planned trajectory, without using information about the speed and direction of the sea current. It is supposed to use the proposed adaptive algorithm in the development of systems for automatic control of the ship's movement along the route.

Numerical Modeling of A New Virtual Trajectory Password Architecture

With the development of digital technology, Computer technology, communication technology and multimedia technology gradually infiltrate into each other and become the main core of information technology. In information technology, digital, text, graphics, images, sound, video, animation and other information carriers are spread through computers and the Internet. Due to the openness, sharing, dynamic and other characteristics of the Internet, information security is threatened and interfered. Information security has become a strategic issue that people must pay attention to, which is related to social stability, economic development and national security. This paper studies a new kind of virtual track cryptography, which breaks through the traditional character memory method and transforms it into memory graphics by using mathematical modeling, and changes the surface memory method from memorizing numbers and characters to memorizing trajectory graphics, so as to make the traditional process of people memorizing passwords easier.

Uncertainty Relations in Hydrodynamics

The qualitative behaviors of uncertainty relations in hydrodynamics are numerically studied for fluids with low Reynolds numbers in 1+1 dimensional system. We first give a review for the formulation of the generalized uncertainty relations in the stochastic variational method (SVM), following the work by two of the present authors [Phys. Lett. A 382, 1472 (2018)]. In this approach, the origin of the finite minimum value of uncertainty is attributed to the non-differentiable (virtual) trajectory of a quantum particle and then both of the Kennard and Robertson-Schrödinger inequalities in quantum mechanics are reproduced. The same non-differentiable trajectory is applied to the motion of fluid elements in the Navier-Stokes-Fourier equation or the Navier-Stokes-Korteweg equation. By introducing the standard deviations of position and momentum for fluid elements, the uncertainty relations in hydrodynamics are derived. These are applicable even to the Gross-Pitaevskii equation and then the field-theoretical uncertainty relation is reproduced. We further investigate numerically the derived relations and find that the behaviors of the uncertainty relations for liquid and gas are qualitatively different. This suggests that the uncertainty relations in hydrodynamics are used as a criterion to classify liquid and gas in fluid.

Repetitive Control for Multi-Joint Arm Movements Based on Virtual Trajectories

According to the neuromuscular model of virtual trajectory control, the postures and movements of limbs are performed by shifting the equilibrium positions determined by agonist and antagonist muscle activities. In this study, we develop virtual trajectory control for the reaching movements of a multi-joint arm, introducing a proportional-derivative feedback control scheme. In virtual trajectory control, it is crucial to design a suitable virtual trajectory such that the desired trajectory can be realized. To this end, we propose an algorithm for updating virtual trajectories in repetitive control, which can be regarded as a Newton-like method in a function space. In our repetitive control, the virtual trajectory is corrected without explicit calculation of the arm dynamics, and the actual trajectory converges to the desired trajectory. Using computer simulations, we assessed the proposed repetitive control for the trajectory tracking of a two-link arm. Our results confirmed that when the feedback gains were reasonably high and the sampling time was sufficiently small, the virtual trajectory was adequately updated, and the desired trajectory was almost achieved within approximately 10 iterative trials. We also propose a method for modifying the virtual trajectory to ensure that the formation of the actual trajectory is identical even when the feedback gains are changed. This modification method makes it possible to execute flexible control, in which the feedback gains are effectively altered according to motion tasks.

Uncertainty Relations in Hydrodynamics

Uncertainty relations in hydrodynamics are numerically studied. We first give a review for the formulation of the generalized uncertainty relations in the stochastic variational method (SVM), following the work by two of the present authors [Phys.\ Lett.\ A\textbf{382}, 1472 (2018)]. In this approach, the origin of the finite minimum value of uncertainty is attributed to the non-differentiable (virtual) trajectory of a quantum particle and then both of the Kennard and Robertson-Schr\"{o}dinger inequalities in quantum mechanics are reproduced. The same non-differentiable trajectory is applied to the motion of fluid elements in the Navier-Stokes-Fourier equation or the Navier-Stokes-Korteweg equation. By introducing the standard deviations of position and momentum for fluid elements, the uncertainty relations in hydrodynamics are derived. These are applicable even to the Gross-Pitaevskii equation and then the field-theoretical uncertainty relation is reproduced. We further investigate numerically the derived relations and find that the behaviors of the uncertainty relations for liquid and gas are qualitatively different. This suggests that the uncertainty relations in hydrodynamics are used as a criterion to classify liquid and gas in fluid.

Quantitative 3D Trajectory Measurement for Percutaneous Endoscopic Lumbar Discectomy

Background: Percutaneous endoscopic lumbar discectomy (PELD) has become an increasingly popular minimally invasive spinal surgery. Due to the technical evolution of PELD, the focus of decompression has shifted from the central nucleus to the subannular-protruded disc herniation, which allows direct neural decompression. Surgical entry into the spinal canal leads to the greater possibility of bony structure obstruction, thus the location and direction of the working channel are crucial. The existing preoperative measuring methods mainly rely on 2-dimensional (2D) x-ray images or MRI cross-sections. Because the bony structure and the trajectory are 3-dimensional (3D), the relationship between the anatomical lumbar structure and the working channel cannot be precisely evaluated. Objectives: To investigate a 3D method and quantitatively evaluate the trajectory for percutaneous endoscopic lumbar discectomy (PELD). Study Design: Technical note. Setting: Pain medicine center of a university hospital. Methods: Twenty patients suffering from L4/5 disc herniation were enrolled in this study. After reconstructing the preoperative CT images, the virtual trajectory was placed into the intervertebral foramen through gradient-changing angulations in relation to the coronal and transverse planes. The overlapping portion of the virtual trajectory and the lumbar vertebrae was evaluated. In addition, the probability of atypical structure involvement was calculated. Results: As cephalad angulation (CA) increased, the intersection volume of the L4 inferior articular process increased, while the total intersection volume, the intersection volume of the L5 superior articular process, the intersection volume of the facet joint, and the volume proportion of L5 superior articular process intersection in the facet joint all decreased. As coronal plane angulation (CPA) increased, the total intersection volume, the intersection volume of the L4 inferior articular process, and the intersection volume of the facet joint all increased, while the volume proportion of the L5 superior articular process intersection in the facet joint decreased. When CA increased to 15°-20°, there was a high probability of atypical structure involvement, whereas such a probability in the groups of CA 0° (CPA 15°, 20°, and 25°), CA 5° and CA 10° was low. Limitations: Only patients with L4/5 herniation were evaluated in this study. Conclusions: In terms of the regularity, the ideal angulation for L4/L5 PELD is CPA 5°-10° and CA 5°-10°, which can lead to a relatively low level of total damage to the bony structure, minimal damage to the facet joint, and negligible involvement of atypical structures. Key words: Lumbar disc herniation, percutaneous endoscopic lumbar discectomy (PELD), transforaminal, trajectory, 3D method, quantitative measurement, angulation, bony structure obstruction

Ground Target Tracking Guidance Law for Fixed-Wing Unmanned Aerial Vehicle: A Search and Capture Approach

One important problem for unmanned aerial vehicles (UAVs) in mission applications is to track ground targets automatically. A major concern is how to keep the tracking process stable and efficient while the motion of the ground targets changes rapidly. In this brief, a new guidance strategy for the ground target “Search and Capture” based on a virtual target is proposed. First, a virtual trajectory, which is composed of straight lines and arcs, is generated based on the motion of the target. The straight lines are used to capture, while the arcs are used to search, and switch between straight line and arc when some condition is met; second, we design a new guidance law based on line-of-sight (LOS) which makes a UAV to track the virtual target automatically. This new method solves the following three problems simultaneously: (1) The UAV always keeps a constant speed to track the target with changing velocity, (2) the generated trajectory meets the flight constraints of the UAV, and (3) the speed range of the ground target can be from the stationary to almost the maximum cruising speed of the UAV. Simulation results show that the proposed guidance strategy can achieve stable tracking for various motions of the ground target.

La escuela secundaria en los recorridos biográficos de jóvenes urbanos escolarizados: evaluaciones, referencias ideales, soportes y proyecciones al porvenir. / The secondary school in youth urban scholar’s biographical paths: evaluations, ideal ...

Presentamos un recorte de una tesis doctoral finalizada sobre los sentidos que adquiere la secundaria para jóvenes de Córdoba (Argentina) en desiguales condiciones de vida y escolaridad. En clave biográfica, analizamos cómo dichos sentidos se inscriben en particulares trayectorias familiares y en una trayectoria virtual de cara al porvenir que los jóvenes anticipan. Mostraremos cómo la permanencia y continuidad en la secundaria se nutre de referencias ideales y de prácticas relacionales afectivas que operan como sostenes de las escolaridades juveniles. In this article we present part of a finished doctoral thesis above the meanings that secondary school has for young people in Cordoba (Argentina) who inhabit unequal living conditions andeducational access. In a biographical approach, we analyze how these meanings are inscribed in particular family trajectories and in a virtual trajectory toward the future that they anticipate. Likewise, we will show how permanence and continuity in the secondary school is nourished by ideal references and affective relational practices that operate supporting youth’s schooling.