Deployment Energy Consumption Research Articles

Underwater Real-time Video Transmission via Wireless Optical Channels with Swarms of AUVs

Underwater wireless optical communication (UWOC) has received widespread attention recently due to its distinct advantages in terms of high bandwidth, low power consumption, low delay and confidentiality. However, unlike underwater acoustic communication systems, it suffers from constraints, such as limited communication range and misalignment in oceanic extreme environments. To perform long-distance high bandwidth transmission such as real-time video streaming, it requires relaying technology to perform reliable and robust transmission. Although pre-deploying a large number of sensor nodes is one of the possible solutions, this is impractical in response to emergency events, such as oil pipeline leakage and maritime search and rescue. To this end, in this paper, we propose to leverage a swarm of autonomous underwater vehicles (AUVs) to establish reliable underwater optical communication links in a rapidly changing marine environment for real-time video transmission. We first model the optical transmission channel, and then calculate both the optical angle and the reliable communicating range that satisfy a pre-defined bit error rate (BER). We then formulate the optimization problem based on two aligned solutions while targeting on minimizing both deployment energy consumption and time latency, in which the AUV's uncertainty issue caused by localization error and hovering instability is considered. Finally, we design an adaptive optical beam and power adjustment algorithm to enhance the robustness of the optical link further. Through extensive simulations, the results demonstrate that the proposed scheme is efficient and achieves reliable and robust communication.

Node Self-Deployment Algorithm Based on Pigeon Swarm Optimization for Underwater Wireless Sensor Networks.

At present, free-to-move node self-deployment algorithms aim at event coverage and cannot improve network coverage under the premise of considering network connectivity, network reliability and network deployment energy consumption. Thus, this study proposes pigeon-based self-deployment algorithm (PSA) for underwater wireless sensor networks to overcome the limitations of these existing algorithms. In PSA, the sink node first finds its one-hop nodes and maximizes the network coverage in its one-hop region. The one-hop nodes subsequently divide the network into layers and cluster in each layer. Each cluster head node constructs a connected path to the sink node to guarantee network connectivity. Finally, the cluster head node regards the ratio of the movement distance of the node to the change in the coverage redundancy ratio as the target function and employs pigeon swarm optimization to determine the positions of the nodes. Simulation results show that PSA improves both network connectivity and network reliability, decreases network deployment energy consumption, and increases network coverage.

Combined Constructive Solutions for Increasing Cast C-Frame Stiffness of Mechanical Presses

With responsibility as its central element, sustainable development is a concept that calls for permanently increasing information usage while minimising material and energy consumption. Waste – particularly of energy – cannot last, and is evidently not a long-term solution. In the field of machine-tools structures deemed sustainable fulfil their functions for a sufficiently long period of time, while consuming as small as possible amounts of energy and including a small as possible volume of material. In a machine-tool, as in numerous other industrial products, energy consumption in deployment significantly exceeds that of their manufacturing. A conclusive example is that of mechanical presses, machine-tools with long service lives and considerable deployment energy consumption. With increasing stiffness of presses, deployment energy consumption is smaller. Detailed research conducted by the authors has yielded a series of innovative constructive solutions for mechanical press cast C-frames – frames with ribbed lateral walls, frames with pre-stressed front columns and shortened frames – with increased stiffness and minimum additional metal consumption as their main relevant characteristics. The finite element based study of these novel constructive solutions has revealed stiffness increases of 1 to 12 %, significantly depending on the type of constructive solution. The novel solutions can be combined in view of cumulating the obtained positive effects. The paper presents relevant examples of such combined constructive solutions and the results related to stiffness increase obtained by means of the conducted FEA study.