Energy-Efficient Computation Offloading for UAV-Assisted MEC: A Two-Stage Optimization Scheme

In addition to the stationary mobile edge computing (MEC) servers, a few MEC surrogates that possess a certain mobility and computation capacity, e.g., flying unmanned aerial vehicles (UAVs) and private vehicles, have risen as powerful counterparts for service provision. In this article, we design a two-stage online scheduling scheme, targeting computation offloading in a UAV-assisted MEC system. On our stage-one formulation, an online scheduling framework is proposed for dynamic adjustment of mobile users' CPU frequency and their transmission power, aiming at producing a socially beneficial solution to users. But the major impediment during our investigation lies in that users might not unconditionally follow the scheduling decision released by servers as a result of their individual rationality. In this regard, we formulate each step of online scheduling on stage one into a non-cooperative game with potential competition over the limited radio resource. As a solution, a centralized online scheduling algorithm, called ONCCO, is proposed, which significantly promotes social benefit on the basis of the users' individual rationality. On our stage-two formulation, we are working towards the optimization of UAV computation resource provision, aiming at minimizing the energy consumption of UAVs during such a process, and correspondingly, another algorithm, called WS-UAV, is given as a solution. Finally, extensive experiments via numerical simulation are conducted for an evaluation purpose, by which we show that our proposed algorithms achieve satisfying performance enhancement in terms of energy conservation and sustainable service provision.

EXPLORING STUDENTS’ STEM IMAGINATION PROCESS THROUGH AN ENGINEERING DESIGN PROCESS

This research was conducted to explore the STEM imagination of Grade 10 students from one Malaysian rural secondary school that adopted the integration of the imagination process in an Engineering Design Process (EDP) through an outreach program in STEM. Four stages of the STEM imagination process were examined: initiation, dynamic adjustment, virtual implementation and implementation. A total of 50 students aged 16 participated in a 10-hour program which engaged them in designing and building two different prototypes. Data on students’ STEM imagination were captured through teachers’ field notes based on focus group interviews and observations. The findings reveal that students needed to draw from their lived experiences to brainstorm problems and solutions around a given scenario, and to arrive at a workable solution in order to move from the initiation to the implementation stage. The findings also suggested that the EDP approach is able to create a supportive environment for nurturing STEM imagination among rural secondary school students.

Динамическая коррекция чувствительности дефектоскопических каналов при высокоскоростном контроле рельсов

The article is aimed at increasing the reliability of high-speed ultrasonic monitoring of long-dimensional objects, in particular, railway rails. The technical documentation for the control does not take into account the features of high-speed rail monitoring, is focused on compliance with the initially set parameters and cannot provide the required reliability of defect detection. The factors that manifest themselves at high scanning speeds and negatively affect the quality of control are considered. Most of these factors cannot be quantified and accounted for in order to adjust the control parameters. An estimate of the number of undetected defects was made when working according to current documents. To ensure reliable control at high speeds, it is proposed to evaluate the current sensitivity of the control using signals from standard design reflectors of the controlled object. As such reflectors, when monitoring rails, it is proposed to use standard holes in the area of bolted joints that are regularly encountered along the scanning path. An expression is obtained for determining the value of the correction of the control sensitivity depending on the scanning speed and the measured size of the signals from the holes. An algorithm for dynamic adjustment of the parameters (sensitivity) of the control is proposed, which increases the reliability of detecting defects in high-speed scanning conditions.

The Relative Contribution of Large-Scale Circulation and Land Surface to Summer Precipitation Over Asian Mid-Low Latitudes

Understanding the contributions of large-scale atmospheric circulation and local land surface processes to precipitation is essentially important for the climate prediction. This study adopts a dynamic adjustment (DA) approach based on constructed circulation analogs to quantitatively isolate the contribution of atmospheric circulation to summer land precipitation (Pr) over Asian mid-low latitudes during 1980-2019. The atmospheric circulation factor is represented by the 500 hPa geopotential height (Z500) from the fifth generation ECMWF reanalysis (ERA5), and the land surface factors, including soil moisture (SM) and net radiation and heat fluxes are from the products of the Global Land Data Assimilation System (GLDAS). The residual component after DA is regarded as the contribution from land surface processes via evaporation mainly resulting from SM. The results indicate that the key SM-Pr feedback areas are mainly located in northeast China and the northern Indian Peninsula. The key influencing area of Z500 on the land Pr anomaly shows a “-+-” tripole pattern in the mid-latitude region. Atmospheric circulation determines the magnitude of summer land Pr, while the residual components reflect the land-atmosphere coupling effect and dominate Pr trend. This conclusion is helpful for better understanding the evolution mechanism of summer climate over Asia mid-low latitudes and may also have application value for climate prediction.

Evaluation of service pressure regulation strategy on the performance of a rural water network based on pulse demand; using the method of characteristics

Reducing the occurrence of pipe bursts, reducing leakage, and reducing energy consumption are the three main goals in implementing pressure control programs in water distribution networks. Service Pressure Regulation Strategy is an evolved approach that encompasses all goals of pressure management. This paper has investigated this approach in a rural network with hydraulic complexities as a case study so that some parts of the network have excess pressure and other low pressure. A computer code based on the Method of Characteristics (MOC) has been developed for network hydraulic analysis. The generated code analyzes unsteady flow, pressure-driven demand analysis, and dynamic adjustment of pressure control valves based on the target node. Also, the experimental results of a laboratory network have been applied to validate and calibrate the numerical simulation. In addition, by measuring the flow rate and pressure of the network and the results of the MNF method, three consumption patterns were used to generate pulsed nodal demands. Studies show that creating Pressure-Management Areas by hydraulic analysis by MOC will determine the best control strategies. The mean pressure has decreased 54% by applying this strategy. Furthermore, the average fluctuations of pressure have reduced from 9.7 meters to 3.5 meters.

Twinning-assisted dynamic adjustment of grain boundary mobility

Grain boundary (GB) plasticity dominates the mechanical behaviours of nanocrystalline materials. Under mechanical loading, GB configuration and its local deformation geometry change dynamically with the deformation; the dynamic variation of GB deformability, however, remains largely elusive, especially regarding its relation with the frequently-observed GB-associated deformation twins in nanocrystalline materials. Attention here is focused on the GB dynamics in metallic nanocrystals, by means of well-designed in situ nanomechanical testing integrated with molecular dynamics simulations. GBs with low mobility are found to dynamically adjust their configurations and local deformation geometries via crystallographic twinning, which instantly changes the GB dynamics and enhances the GB mobility. This self-adjust twin-assisted GB dynamics is found common in a wide range of face-centred cubic nanocrystalline metals under different deformation conditions. These findings enrich our understanding of GB-mediated plasticity, especially the dynamic behaviour of GBs, and bear practical implication for developing high performance nanocrystalline materials through interface engineering.

Visual positioning control of fuze detection manipulator

This paper designs a fuze automatic detection manipulator. Aiming at the problem of autonomous alignment and docking between operation manipulator and detection device, a visual positioning control algorithm for autonomous alignment between fuze and detection device based on fuzzy logic is proposed. Taking the relative position and deviation angle of fuze and detection device as control variables, a two-dimensional fuzzy controller is designed. Through the dynamic adjustment of the controller, the optimal motion parameters can be output. Compared with the traditional fuze detection method, the algorithm further improves the efficiency and positioning accuracy of fuze detection.