Development of a fiber-optic system for testing instruments for monitoring nuclear power plants

The necessity of testing the equipment for monitoring the operation of nuclear power plants is justified. It is proposed to use optical fiber and pulsed laser radiation for these purposes. It is established that optical fiber is more resistant to radiation than other communication systems. The design of a fiber-optic emergency simulator is developed. The calculation of its characteristics is carried out. Their experimental research was carried out. It was found that with an optical signal delay of 98.6 microseconds, the loss is – 26 dB with an uneven frequency response of ± 2 dB. This makes it possible to test the entire set of equipment that uses optical signals used to control a nuclear power plant.

Determination of adjusted range corrections measured by electro-optical systems

Electromagnetic radiation used to determine ranges passes through media with different characteristics that affect the electromagnetic waves propagation speed and, accordingly, the accuracy of distance determination. The problem of the radio signal delay due to the influence of the atmosphere is an urgent problem, the solution of which is currently limited mainly to the calculation of range corrections using various atmospheric models. Depending on the required accuracy, the length of the measured line, the range of zenith distances, the availability of information about the state of the atmosphere, a flat, spherical, ellipsoidal model of atmospheres is used to determine the range corrections. In view of the fact that the parameters of the atmosphere characterizing its state along the electromagnetic wave path at the time of measurement, as a rule, are unknown, it becomes necessary to apply one or another hypothesis about the distribution of atmospheric parameters with height. In this paper, we propose a solution to the problem of determining corrections to the measured ranges from the known parameters of the atmosphere only at the initial and final points of the electromagnetic waves’ trajectory.

Performance Monitoring of the Barrel Time-of-Flight Supermodule for the PANDA Experiment at FAIR

The PANDA experiment at FAIR in Darmstadt will use proton-antiproton collisions, with momenta ranging from 1.5 GeV/c to 15 GeV/c, on a fixed target to study open questions in hadron physics. The Barrel Time-of-Flight detector for this experiment is a scintillating tile hodoscope based on 16 identical and independent subdetectors called Super-Modules arranged in a cylindrical configuration. We have conducted performance studies on one such Super-Module to prove the feasibility of the Barrel Time-of-Flight detector design. Time resolution, signal delay and amplitude drop along the length of the detector were measured and analyzed as a function of the position on the individual scintillator tiles. A time resolution of about 50 ps has been achieved, which is very important for event timing and particle identification.

Method of description for the dynamics of the signal delay change in discrete time with changing aircraft position in space

The article presents an innovative approach to the description of the aircraft range parameter in discrete time when simulating the process of its repositioning in space. A method of describing the dynamics of changes in signal delay in discrete time when the aircraft is changing its spatial position is proposed. Such a model adequately describes the change in signal delay in discrete time. The direction of estimation for the adequacy of radio signal delay change simulation in algorithms of optimum filtration is defined in accordance with the aerodynamic properties of the aircraft. Simulation of the signal delay dynamic change is carried out (it is completely described by the dynamics of change in the distance to the aircraft). The transformation stages of simulation data for the initial model in continuous time with realization of the standard Gaussian random numbers are justified. Information on the simulation data transformation taking into account the correlation matrix of discrete white noise is provided. A method of calculating the transition matrix through the Laplace transform is proposed. The scientific-applied direction of research is determined – it lies in the development of a method for the legitimate representation for the mathematical model of aircraft’s changing range in discrete time within one-dimensional space: the longitudinal and the transverse dimensions. This approach takes into account the continuous description for a system of stochastic differential equations. A comprehensive algorithm for modeling the values of discrete white noise on modern computer equipment and calculating the dynamics of the aircraft range parameter changes is proposed. This algorithm allows to correctly form the a priori information about the change of the vector parameters of the aircraft spatial position at discrete moments of time. As a result, it was shown that the use of the obtained information in the optimal filtering algorithms minimizes the error when determining distance to the aircraft and, accordingly, allows to increase the accuracy and adequacy of the signal delay simulation in discrete time. The results of this research can be used in modernization of the existing models and development of promising on-board radar stations, integrated rangefinders, systems of radio technical reconnaissance and electronic warfare systems, as well as in technical implementation of aircraft flight simulation systems.

Exploring the Difficulties and Challenges of the Local Macao English Language Learners towards the Online Synchronous One-on-one English Learning Class

With the development of technology, the number of English learners who opt for online learning has been increasing. In the past, students had a tendency to download English materials and watch online videos for improving their English skills. Recently, thanks to a shift to online learning, students have been making more use of online synchronous oneon-one English classes to improve their English at leisure. Although this type of learning mode is becoming more and more popular, the study of the difficulties and challenges of English learners in such a field has been under-explored. This study attempts to use a qualitative approach to interview two English learners of different backgrounds to better understand the difficulties and challenges they encountered when using such a learning method. The two interviewees conclude points ranging from the learning aspect, distant feeling, signal delay, instability of the learning software and hardware that lead to technical problems. Certain measures to avoid the problems are also suggested in this paper.

Refractive lengthening of signal trajectories in satellite laser ranging

Aim. The aim of this work is to improve the accuracy of methods for calculating the tropospheric delay caused by the refractive lengthening of the satellite laser rangefinder signal trajectory on the transatmospheric path. Method. One of the main factors that reduce the accuracy of measuring the distance to artificial Earth satellites with satellite laser rangefinders is the influence of the inhomogeneous Earth troposphere on the rangefinder propagation characteristics. This effect leads to an additional signal delay on the measured path, firstly, due to the differences in its propagation speed in a non-uniform environment from the speed of light in vacuum, and secondly, due to the refractive lengthening of the signal trajectory due to the effect of refraction, which is a result of this inhomogeneity. The refractive lengthening is the difference between the real length of a signal trajectory (with the tropospheric part curved by the refraction) and the distance from the observation point to the satellite in a straight line. The calculations are based on use of the integral form of the geometric optics’ ray equation. With the help of well-known quadrature formulas, this integral form is reduced to a system of algebraic equations connecting the elongation due to refraction and the length of the tropospheric part of the trajectory. The main idea of the new method is the refusal of the widespread use of simplified analytical models of the tropospheric profile when calculating the ratio for the signal trajectory lengthening. In the proposed variant, this ratio is given as an integrated function along the trajectory for values that take into account the actual state of the tropospheric profile at the time of measuring the distance to the satellite. Results. Relationships are obtained for the refractive lengthening and the length of the tropospheric part of the trajectory, which depend on the integral values along the path, namely, the angles of the terrestrial and photogrammetric refraction. Scientific novelty and practical importance. The proposed relations make it possible to determine the refractive elongation through the angles of refraction, which take into account the actual state of the inhomogeneous tropospheric layer for the observed satellite of the Earth immediately at the time of measurements.

Diagnosing Obstacles to Speed and Reliability with High-Resolution Automatic Vehicle Locator Data: Bus Time Budgets

Transit riders consistently rate speed and reliability of service as primary drivers of satisfaction, and transit agencies can help retain and grow ridership by improving these components of service. The challenge for transit agency staff is to identify when and where they should focus efforts to improve service quality. Here we propose an approach to data analysis that identifies and isolates specific aspects of service that are limiting speed and reliability. In-vehicle travel time can be decomposed into time spent in motion and time stopped. Time in motion is often dependent on factors common to general traffic, whereas time stopped has some features in common with general traffic (i.e., traffic signals) and some unique to buses (i.e., passenger dwell). Other sources of delay from serving a bus stop include deceleration, acceleration, and signal delay. To improve overall travel time, transit agencies must prioritize interventions that will contribute the most to improving speed and reliability. We used high-resolution automatic vehicle locator data to assign components of speed and reliability within a trip-level “time budget.” We compared typical time budget components across service types, and used the time budget approach to evaluate local service and Rapid bus service operating simultaneously on the same alignment. Results of the delay and variability quantifications suggested particular interventions, as well as the expected size of the resulting effect. With limited resources, the bus time budget approach could aid understanding and prioritization of transit agency efforts to improve speed and reliability.

Sliding Mode Load Frequency Regulator for Different-Area Power Systems with Communication Delays

In this article, a sliding mode control (SMC) is proposed to deal with the frequency deviation problem in interconnected time-delay power systems (ITDPS) with two source power generations. First, the proportional and integral switching surface is used for each area to guarantee the frequency deviation reach zero in normal operating conditions. Then, the stability of the system is ensured with a new Linear Matrix Inequality (LMI) via Lyapunov stability theory. In addition, the SMC law is designed to guarantee the finite time eachability of the system. Finally, impacts of certain physical constraints affecting dynamic performance of the power network such as time-delay is proposed to consider the signal delay in the controller. Effectiveness of the suggested method is validated by simulation studies on the load frequency control under time-delays in the two-area, the step load disturbance and the mismatched uncertainty.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.