Testing tyres of mobile forest machines in the soil testing canal

The article focuses on the research of tyre rolling resistances in the soil test channel environment. The specific monitored tyre was a Mitas TS05 10.0/75-15.3 10PR diagonal tyre with an arrow tread. The measurement itself was divided into two stages. In the first stage, measurements of rolling resistance were performed on a solid concrete base of the laboratory in order to determine the internal component of rolling resistance of the tyre. In the second stage, rolling resistances were monitored on forest soil deposited in the main body of the soil channel. The mentioned measurements of rolling resistance can be considered key for further evaluation of traction and energy properties of tyres. Despite some complications which occurred during the measurement, the results obtained indicate the conclusions reached by other researchers in the field. The main conclusion of this research is to confirm the justification of using the correct or optimal level of inflation pressures of tyres of mobile energy means depending on the properties of the surfaces on which they move in order to reduce not only their energy intensity but also greater environmental acceptability.

A new scheme to enhance the performance of permutation index–differential chaos shift keying communications system

In this paper, a new scheme based on permutation index–differential chaos shift keying is proposed, modeled, and evaluated in AWGN channel environment. Data is sent by frames, and each frame is headed by a single reference signal and followed by some information-bearing signals. Modulation is performed through permutations of a reference signal according to the mapped data. At the receiver, each incoming information-bearing signal undergoes all inverse permutation possibilities to perform a correlation with the delayed and stored version of the received reference signal. To decode the information bits, the detector selects the highest correlator outputs. The proposed scheme named single reference–permutation index–differential chaos shift keying is an enhanced version of PI-DCSK, and uses a single reference signal for multiple information-bearing ones. Hence, the energy requirement is saved by almost a half. The bit error performance is studied using the baseband system model and analytically tested using Gaussian approximation method. Results show the BER performance outperforms other standard and recently developed differentially coherent chaos systems, including Permutation Index–DCSK by an average of 2.25 dB. Moreover, the analytical form which is developed to predict the bit error rate (BER) is validated by simulation. Results demonstrate the performance in AWGN is closely matching with the simulation results, particularly at high SNR.

Optimisation of the Two-Tier Distribution System in Omni-Channel Environment

This paper deals with the problem of the design and configuration of a distribution system that supports the delivery of goods to customers using various commercial channels. In this sense, a modelled distribution system, called an omni-channel distribution system, should ensure the delivery of the same products in different ways while guaranteeing its highest efficiency. The authors propose a single-criterion mixed-integer programming model for the configuration of a complex distribution system of goods in an omni-channel environment. A minimized cost function, composed of key logistics elements including transport, warehouse location, and manipulation processes, is the objective function. The model was experimentally verified, and as a result, potential savings of around 5–8% of the omni-channel design distribution system costs versus the multi-channel distribution system costs were identified. In the paper, an extended sensitivity analysis is also performed to show how specific parameters of the model can change the final recommendation.

Two-Stage Channel Adaptive Algorithm for Unmanned Aerial Vehicles Localization with Cellular Networks

Unmanned aerial vehicle (UAV) is regarded as a powerful tool to expand the existing ground wireless network into aerial space. Since high mobility is an essential characteristic for UAV, it is important to carry out an accurate, real-time, and high-precision localization in terms of safe operation and communication link maintenance. The cellular network-based localization technology has provided UAV a solution with both high coverage and seamless connection. However, the complex channel environment between the UAV and terrestrial base station (BS) would have weakened the localization performance. To solve this problem, a two-stage channel adaptive algorithm for cellular-connected UAV has been proposed. The first stage of the algorithm is to revise the observation error introduced by the complex channel environment using the model of DDPG. The second stage is to locate the UAV position with TDOA algorithm using the revised observation values. Simulation results have demonstrated that the proposed algorithm can achieve the channel adaptive effect by revising the observation errors and improve location performance greatly, especially for UAVs at a relative lower altitude.

Toward the inter-channel synergy renaissance in emerging markets: evidence from adding clicks to bricks in Serbia

PurposeNewly established intersections between offline and online channels create room for enhancing inter-channel synergies. The nature and structure of emerging markets only further emphasize the need to expand existing knowledge. Consequently, this study investigates inter-channel synergy creation during offline–online retail integration in emerging markets.Design/methodology/approachData collected from 97 companies in Serbia that incorporated online channels into their offline retailing businesses were analyzed using the structural equation modeling method.FindingsThe results show that retailers who have undergone click-to-brick integration in the emerging markets struggle to leverage physical presence for inter-channel synergy creation through digital channels. Essentially, retailers integrating clicks into bricks in emerging markets are less likely to achieve immediate omni-channel synergy, resorting to a multi-iterative transition process.Originality/valueThis research synthesizes knowledge on inter-channel synergy creation in an omni-channel context, as well as existing findings regarding inter-channel integration. This paper presents the first comprehensive study on inter-channel synergy creation during click-to-brick integration in emerging retail markets. Moreover, this study outlines challenges facing retailers seeking channel synergy during click-to-brick integration. The study results have theoretical and practical implications regarding inter-channel synergy creation in the multi-channel environment of emerging markets.

Optimizing Energy Efficiency for Supporting Near-Cloud Access Region of UAV-Based NOMA Networks in IoT Systems

Nonorthogonal multiple access (NOMA) and unmanned aerial vehicle (UAV) are two promising technologies for the wireless fifth generation (5G) networks and beyond. On the one hand, UAVs can be deployed as flying base stations to build line-of-sight (LoS) communication links to two ground users (GUs) and to improve the performance of conventional terrestrial cellular networks. On the other hand, NOMA enables the share of an orthogonal resource to multiple users simultaneously, thus improving the spectral efficiency and supporting massive connectivities. This paper presents two protocols, namely, cloud-based central station- (CCS-) based power-splitting protocol (PSR) and time-switching protocol (TSR), for simultaneous wireless information and power transmission (SWIPT) at UAV employed in power domain NOMA-based multitier heterogeneous cloud radio access network (H-CRAN) of Internet of Things (IoT) system. The system model with k types of UAVs and two users in which the CCS manages the entire H-CRAN and operates as a central unit in the cloud is proposed in our work. Closed-form expressions of throughput and energy efficiency (EE) for UAVs are derived. In particular, the EE is determined for the impacts of power allocation at CCS, various UAV types, and channel environment. The simulation results show that the performance for CCS-based PSR outperforms that for CCS-based TSR for the impacts of power allocation at the CCS. On the contrary, the TSR protocol has a higher EE than the PSR in the cases of the impact of various UAV types and channel environment. The analytic results match Monte Carlo simulations.

Performance Modeling Analysis of D-MSMR-CARQ with Relay Selection in Wireless Sensor Networks

Reliable and efficient real-time transmission is an important and challenging issue for wireless sensor networks (WSNs). Truncated retransmission times and relay selection can effectively reduce transmission delay and improve system throughput. A new direct multisource multirelay cooperative automatic repeat request (D-MSMR-CARQ) protocol based on truncation with two relay selection methods in WSNs is analytically analyzed in this paper. Firstly, based on two different relay selection methods under the maximum ratio combining (MRC), the discrete time Markov chain (DTMC) model of D-MSMR-CARQ protocol and state space is established. Secondly, for each D-MSMR-CARQ protocol based on different relay selection method, we obtain the closed-form expressions of the system average transmission delay and the expressions of the system throughput through state transition probabilities. Finally, numerical results reveal that the first relay selection method outperforms the second relay selection method on the average transmission delay performance for the proposed protocol. More specifically, the delay performance of the proposed protocol can be improved by 13% compared with the nondirect-link protocol when the channel environment is the same; the proposed protocol improves the throughput performance by 47% compared with the nondirect protocol when the channel environment is harsh under the same simulation parameters. Furthermore, the optimal number of source nodes and relay nodes is determined.