Energy Hole Research Articles

Multi‐hoped cooperative communication‐based wireless underground sensor network design

SummaryDeepwater utilization and underwater sound communication with inadequate bandwidth, elongated propagation interruption, signal failure issues, and sensor node malfunction due to ecological circumstances are the limitations of the underwater wireless sensor network. Further, the challenges in underground wireless sensor network (WSN) include superior bandwidth, high power expenses, information handling, and cross‐layer design. On the other hand, cooperative communications facilitate competent employment of communication resources, by permitting nodes in a network to work together in information communication. As wireless sensor networks adapt to multi‐hop transmission in high data traffic, there is a high demand for achieving energy efficiency. Moreover, in the course of proximity nodes to the sink, an energy hole is started for the extended network lifetime. This paper proposes the design of multi‐hoped cooperative communication‐based wireless underground sensor networks that guarantees energy efficiency in a hostile environment. In addition, network coverage and connectivity improvement are also improved by this proposed design.

A Traffic-Load-Based Algorithm for Wireless Sensor Networks’ Lifetime Extension

It has been shown in the literature that the lifetime of a wireless sensor network is heavily connected to the number of transmissions that network nodes have to undertake. Considering this finding, along with the effects of the energy hole problem where nodes closer to the sink node transmit more than the more distant ones, a node close to the sink node will be the one that transmits the most, while it will also be the node that will deplete its battery first. Taking into consideration that the failure of a single network node to operate, due to its battery being discharged, can lead to a network stopping its operation, the most energy-consuming node in the network will also be the one that will be responsible for the network’s termination. In this sense, the most energy-consuming node’s energy consumption optimization is the main case in this paper. More specifically, in this work, it is firstly shown that the energy consumption of a wireless sensor network is closely related to each network node’s traffic load, that is the transmissions of the packets that are created or forwarded by a node. The minimization of the most energy-consuming node’s energy consumption was studied here, while the implementation of a traffic-load-based algorithm is also proposed. Under the proposed algorithm, given a simple shortest path approach that assigns a parent (i.e., the next hop towards the sink node) in each network node and the knowledge it provides regarding the distance (in hops in this paper’s case) of network nodes from the sink node, the proposed algorithm exploits the shortest path’s results in order to discover, for all network nodes, neighbors that are of the same distance (from the sink node) with the initially assigned parent. Then, if such neighbors exist, all these neighbors are equally burdened with the parenting role. As a result, the traffic load is shared by all of them. To evaluate the proposed algorithm, simulation results are provided, showing that the goals set were achieved; thus, the network lifetime was prolonged. In addition, it is shown that under the algorithm, a fairer distribution of the traffic load takes place.

Numerical Simulation of n‐MoSe2/p‐Si Solar Cells by AFORS‐HET

AbstractFor a thorough understanding of n‐MoSe2/p‐Si heterojunction solar cells, the effect of the MoSe2 band gap, the back electrode work function, the density of interface states, as well as the introduction of the interface layer on the performance of MoSe2/Si heterojunction solar cells is systematically investigated via AFORS‐HET simulation software. It is shown that a higher MoSe2 band gap, a higher back electrode work function, a lower density of interface states, and an introduction of a thin intrinsic hydrogenated amorphous silicon as an interface layer, are favorable for the achievement of high‐performance MoSe2/Si heterojunction solar cells. Through the simulation optimization, a photovoltaic conversion efficiency of 12.31% with an open‐circuit voltage of 0.61 V, a short‐circuit current density of 26.47 mA cm−2, as well as a fill factor of 75.4%, can be obtained for the n‐MoSe2/p‐Si heterojunction solar cells. To interpret the obtained simulation results, the authors have carefully analyzed the current–voltage curves, energy band diagrams, electron and hole concentration distributions, electron and hole recombination rates, etc. This study indicates that silicon‐based heterojunction solar cells with MoSe2 as an active layer are of great significance in the development of high‐efficiency photovoltaic devices.

Energy sink-holes avoidance method based on fuzzy system in wireless sensor networks

The existence of a mobile sink for gathering data significantly extends wireless sensor networks (WSNs) lifetime. In recent years, a variety of efficient rendezvous points-based sink mobility approaches has been proposed for avoiding the energy sink-holes problem nearby the sink, diminishing buffer overflow of sensors, and reducing the data latency. Nevertheless, lots of research has been carried out to sort out the energy holes problem using controllable-based sink mobility methods. However, further developments can be demonstrated and achieved on such type of mobility management system. In this paper, a well-rounded strategy involving an energy-efficient routing protocol along with a controllable-based sink mobility method is proposed to extirpate the energy sink-holes problem. This paper fused the fuzzy A-star as a routing protocol for mitigating the energy consumption during data forwarding along with a novel sink mobility method which adopted a grid partitioning system and fuzzy system that takes account of the average residual energy, sensors density, average traffic load, and sources angles to detect the optimal next location of the mobile sink. By utilizing diverse performance metrics, the empirical analysis of our proposed work showed an outstanding result as compared with fuzzy A-star protocol in the case of a static sink.

A Survey on Cluster Head Selection and Cluster Formation Methods in Wireless Sensor Networks

In recent years, wireless sensor networks (WSNs) have been growing rapidly because of their ability to sense data, communicate wirelessly, and compute data efficiently. These networks contain small and low-powered sensor nodes that organize and configure themselves to carry out their functions. Even though WSNs are cheap, easy to deploy, flexible, and efficient, there are some challenges in terms of energy efficiency and network lifetime. Clustering in WSNs is the most reliable solution for the challenges, in which nodes are grouped into few clusters, and a cluster head (CH) is selected for data aggregation and data transfer to the base station (BS). However, there are still many challenges such as energy hole and isolated node problems that exist because of inefficient CH selection and cluster formation methods. In this work, we comprehensively reviewed various nonmetaheuristic and metaheuristic methods for CH selection and cluster formation that are used in networks from various environmental settings, for a better understanding of how the aforementioned problems are tackled by some authors. Moreover, the methods’ parameter settings, advantages, limitations, and future directions are presented with a brief performance summary of the approaches.

An Enhanced Heterogeneous Gateway-Based Energy-Aware Multi-Hop Routing Protocol for Wireless Sensor Networks

Wireless Sensor Networks (WSNs) continue to provide essential services for various applications such as surveillance, data gathering, and data transmission from hazardous environments to safer destinations. This has been enhanced by the energy-efficient routing protocols that are mostly designed for such purposes. Gateway-based Energy-Aware Multi-hop Routing protocol (MGEAR) is one of the homogenous routing schemes that was recently designed to more efficiently reduce the energy consumption of distant nodes. However, it has been found that the protocol has a high energy consumption rate, lower stability period, and poorer data transmission to the Base station (BS) when it was deployed for a longer period of time. In this paper, an enhanced Heterogeneous Gateway-based Energy-Aware multi-hop routing protocol (HMGEAR) is proposed. The proposed routing scheme is based on the introduction of heterogeneous nodes in the existing scheme, selection of the head based on the residual energy, introduction of multi-hop communication strategy in all the regions of the network, and implementation of energy hole elimination technique. All these strategies are aiming at reducing energy consumption and extend the life of the network. Results show that the proposed routing scheme outperforms two existing ones in terms of stability period, throughputs, residual energy, and the lifetime of the network.

A New Function for Frequency Analysis in the Risk Assessment of Offshore Oil-Related Platforms

_ Risk assessment of offshore oil-related platforms such as the floating production storage and offloading system (FPSO) is extremely important. In earthquakes prone to target sea areas, earthquakes should be considered as one of the important external forces that cause severe damage. In such risk assessments, for estimating the appearance frequency of seismic energy, the complementary cumulative distribution function (CCDF) of seismic energy of a considered area is usually based on the Gutenberg–Richter law. Furthermore, it is important to estimate the CCDF of the leak hole diameter when estimating the damage caused by an oil spill accident in an offshore oil-related platform. Some ship classification societies recommend using a formula based on the power law distribution as used in those processes. However, the power law distribution has a drawback in that, i.e., it is essentially impossible to accurately estimate the CCDF over the entire domain of the random variables. The authors have developed an enhanced power law distribution function that eliminates such defects in the power law distribution function and some practical methods for estimating its parameters. In this study, the developed function is applied to the CCDFs of the seismic energy and leak hole diameter. The results demonstrate that the function fits the existing data with sufficient accuracy. Therefore, the new function introduced here can be well used in the frequency analysis of the risk assessment of offshore oil-related platforms. Introduction In the risk assessment of offshore oil-related platforms like floating production storage and offloading system (FPSO), it is necessary to estimate probabilistic characteristics of external forces against them. Earthquakes are a major external force. Furthermore, it is necessary to estimate the damage when an external force is applied. The frequency of external forces, such as earthquakes, is low, but the damage is extensive. However, damage to offshore oil-related platforms is caused by not only these external forces, but also oil leaks resulting from some factors, such as operation errors and corrosion, that may cause accidents such as fire and explosion. Therefore, it is also essential to estimate the probabilistic characteristics of such damage for the risk assessment of offshore oil-related platforms.

Construction of an Innovative Development Model of Intelligent Media under the Coverage of a Wireless Sensor Network

A distributed network composed of sensor nodes with limited computing and communication capabilities is a wireless sensor network, which is a system that can autonomously and intelligently complete target tasks according to the surrounding environment. With its wide application in the fields of smart medical care, smart home, networks of vehicles, and smart media, its communication performance requirements are also increasing. According to the needs of different application scenarios, the first key problem to be solved in wireless sensor networks is what optimization coverage strategy to adopt, which will have a direct impact on the optimal allocation of very limited resources such as node energy, communication bandwidth, computing power, and other network services’ quality. Nodes adopt a probability-based joint perception model, and its algorithm is a node scheduling mechanism based on the connected dominating set to construct a tree. Each node sets the waiting time and becomes a candidate node priority according to the remaining energy and the distance from the parent node. In this paper, the issue of energy fairness is considered in heterogeneous wireless sensor networks. In order to prevent the occurrence of “energy holes,” this paper proposes a node deployment model similar to cellular networks. By deploying heterogeneous sensor nodes in this way, energy saving can be achieved. Based on this model, game theory is used to simulate the data packet transmission process between sensor nodes, an energy consumption mechanism suitable for each stage of data transmission is proposed, and Nash equilibrium is finally obtained by rationally designing the measurement function. The node deployment scheme proposed in this paper not only balances the energy consumption of the network but also prolongs the life cycle of the network. Aiming at the three-dimensional (3D) space environment, this paper studies a node deployment mechanism that guarantees connectivity and has a perceptual coverage degree of k with the help of the Reuleaux tetrahedron model. In this paper, a node deployment strategy is proposed and compared with the node deployment algorithm for 3D sensor network based on truncated octahedron. The simulation experiment results show that the wireless sensor network with artificial intelligence can not only optimize the production process of intelligent media but also improve each link of the media industry chain and further catalyze the development of new formats in the media industry. The experimental results also show that the algorithm can effectively meet the requirements of sensing coverage and connectivity coverage, the number of working nodes is small, the network life cycle is significantly prolonged, and the overall energy consumption of the network is reduced. The study results of this paper provide a reference for follow-up research on the construction of innovative development model of intelligent media under the coverage of wireless sensor network.

Interfacial engineering induced highly efficient CoNiP@NiFe layered double hydroxides bifunctional electrocatalyst for water splitting

Reasonably constructing heterostructure is an efficient strategy to improve the intrinsic activity of catalyst for both hydrogen and oxygen evolution reactions. Herein, a heterostructure of CoNiP and NiFe layered double hydroxides (CoNiP@NiFe LDHs) is successfully prepared via a quick two-step electrodeposition method. The electrons rearrangement at the interface composed of CoNiP and NiFe LDHs promoted by the disparity of their unique work functions can increase the electron density of CoNiP, further optimizing the Gibbs free energy for the adsorption of hydrogen. Thus, CoNiP@NiFe LDHs need a low overpotential of 68 mV to reach 10 mA cm−2. Meanwhile, the modulated valence band energy level (EVB) and holes collection at the space charge region of NiFe LDHs layer significantly enhance the oxygen evolution reaction performance of CoNiP@NiFe LDHs, which presents a low overpotential of 255 mV at 50 mA cm−2. The assembled electrolyzer using CoNiP@NiFe LDHs as electrodes also exhibits a low cell voltage of 1.59 V at 50 mA cm−2.

A Proactive Greedy Routing Protocol Precludes Sink-Hole Formation in Wireless Sensor Networks

A tree topology is a commonly employed topology for wireless sensor networks (WSN) to connect sensors to one or more remote gateways. In many-to-one traffic, routing imposes a heavy burden on downstream nodes, as the same routes are repeatedly used for packet forwarding from one or more sensor chains. The challenge is traffic paths that ensure balanced energy consumption at sink-hole to protect sensors from fast death. This paper proposes an energy consumption pattern-aware greedy routing protocol that proactively protects many-to-one topology from the sink-hole formation. The proposed protocol, Energy Balance-Based Energy Hole Alleviation in Tree Topology (EBEHA-T), precludes energy hole formation rather than retrospectively responding to a hole detection. Updated status of variations in energy consumption patterns at the sink-hole and construction feature of joint nodes in the tree topology aids in routing decision. Performance evaluation of EBEHA-T against benchmark method RaSMaLai shows increased energy-saving across the entire network and a marked improvement in energy consumption balance in energy hole zones. This precludes energy hole formation and the consequent network partitioning, leading to improved network lifetime beyond that of the RasMaLai.

High Thermoelectric Performance SnTe with a Segregated and Percolated Structure.

A nanostructure has a significant role in enhancing the power factor and preventing the heat propagation for thermoelectric materials. Herein, we propose a unique segregated and percolated (SP) microphase-separated structure to enhance the thermoelectric performance of SnTe. The SP structure is composed of insoluble SnTe and AgCuTe, in which AgCuTe with ultralow lattice thermal conductivity undergoes a solid-phase welding during a spark plasma sintering process and forms continuous percolated layers at the interface of isolated SnTe. The SP structure achieved a simultaneous scattering for low energy holes due to the energy offset of the valence band maximum between SnTe and AgCuTe and for phonons due to the noncoherent interfaces between SnTe and AgCuTe, resulting in a high Seebeck coefficient of ∼219.4 μV/K and a low lattice thermal conductivity of ∼1.1 W m-1 K-1 at 800 K for (SnTe)0.55(AgCuTe)0.45. The thermoelectric performance was further enhanced by means of the cosubstitution of In and Mn for Sn in the SnTe lattice, inducing resonance levels and extra phonon scattering. As a result, the SP structure combined with In/Mn codoping enable us to achieve a low lattice thermal conductivity of 0.47 W m-1 K-1, a peak ZT of ∼1.45 at 800 K, and a high average ZT of ∼0.73 (400-800 K) for (Sn0.98In0.01Mn0.01Te)0.75(AgCuTe)0.25.

A rendezvous point‐based data gathering in underwater wireless sensor networks for monitoring applications

SummaryIn underwater wireless sensor networks (UWSNs), most of the mobile sink data gathering scheme assumes that sensor nodes are static. Also, very limited set of works aim to eliminate the data redundancy during data gathering. Moreover, the data collection latency, error rate and load have to be considered in addition to the buffer space and energy level of the nodes. Here, a mobile sink data gathering technique is designed where rendezvous points (RPs) and sojourn times are selected. The RPs, where the mobile sinks stop to gather the data, are selected based on the node density, current traffic load and energy level of nodes. The proposed scheme, that is, adaptive distributed mobile sink data gathering (ADMSDG), eliminates data redundancy even by considering mobility of all the nodes including sink node. Here, multihop data gathering is also considered to address the energy hole problem near the sink based on similarity index. To examine the result, proposed scheme and other state‐of‐the‐art schemes are implemented in NS2.30 having the same environment. Obtained results show that when proposed scheme is experimented with respect to number of nodes, the proposed ADMSDG technique achieves 18% high data collection accuracy with 5% reduced data collection delay and 5% less energy consumption. Similarly, when proposed scheme is experimented with respect to transmission range, the proposed ADMSDG technique achieves 18% high data collection accuracy with 12% reduced data collection delay and 8% less energy consumption.

Competing Superior Electronic Structure and Complex Defect Chemistry in Quasi-One-Dimensional Antimony Chalcogenide Photovoltaic Absorbers

Antimony chalcogenides Sb2Se3 and Sb2S3 are an emerging class of quasi-one-dimensional van der Waals bonded materials with rapid progress and great promise for low-cost, high-efficiency, and scalable thin-film photovoltaics. Here using first-principles theoretical calculations, we show that antimony chalcogenides Sb2Se3 and Sb2S3 possess competing superior electronic structure and complex defect chemistry, limiting their photovoltaic performance. The high optical absorption, large Born effective charge, and high dielectric constant lead to low exciton binding energy and small hole effective mass, which ultimately benefit the photovoltaic performance. In contrast, quasi-1D antimony chalcogenides exhibit complex defect chemistry. The cation–anion antisites are the dominating native defects in the Sb rich condition, while in the Sb poor condition the anion–cation antisites are dominant. In both cases, the anion vacancies are also easy to form. These native defects introduce midgap transition levels which act as electron–hole recombination centers, limit the dopability, and lower the open circuit voltage. As a result, Sb2Se3 is a p-type semiconductor in Se rich condition, while Sb2S3 is an intrinsic semiconductor without significant free carrier density. Additionally, due to the unique quasi-1D structures and strong electron–lattice coupling, antimony chalcogenides are able to accommodate larger lattice relaxation than conventional 3D bulk crystals, resulting in negative-U behavior in their defect structures. Therefore, the competing superior electronic structure and complex defect chemistry suggest that, while antimony chalcogenides are excellent photoabsorbers, effort shall be made to suppress the formation of the detrimental native defects to further improve their open-circuit voltage, electronic transport, and, thus, power conversion efficiency.

Mobile cluster heads on energy conscious predetermined trajectory to minimise the energy hole problem in wireless sensor network

Mobile cluster heads on energy conscious predetermined trajectory to minimise the energy hole problem in wireless sensor network

Mobile cluster heads on energy conscious predetermined trajectory to minimise the energy hole problem in wireless sensor network

Mobile cluster heads on energy conscious predetermined trajectory to minimise the energy hole problem in wireless sensor network

Effect of coupling damage on fatigue behavior of 2198‐T8 aluminum‐lithium alloy thin sheet for fuselage

AbstractBased on fatigue experiment and digital image correlation (DIC) technique, the fatigue damage behavior and the failure mechanism of the 2198 aluminum‐lithium alloy thin sheet used for the fuselage were investigated. Firstly, the influence of hemispherical insert size, impact energy, and rivet hole size Φ on the fatigue performance was explored. Secondly, the axial strain distribution and crack propagation behavior of the coupling damaged specimen under the fatigue cyclic loading were characterized by DIC. The results are as follows: the axial strain along the dent path and the rivet hole section path indicates that there exists a competitive relationship between the discontinuity caused by the rivet hole and the dent damage under the fatigue load. For specimens impacted by the same insert, the critical local plastic strain rate for the transition point of the fatigue fracture is related to the rivet hole size Φ, and it increases with the rise of Φ. After the dent damage being quantified, the final fracture position could be determined by the numerical comparison method.

Bi2WO6 nanosheets assembled BN quantum dots: Enhanced charge separation and photocatalytic antibiotics degradation

Herein, we have exploited their applications in photocatalytic pollution treatment due to the exciting behaviors of the tiny-sized BN quantum dots (BNQDs) co-catalyst in solar energy conversion systems and hole extraction properties. Specifically, Bi2WO6 (BWO) nanosheets were selected as the scattered substrate of fine-sized BNQDs according to their narrow band gap width and stable ultra-thin interface. In addition, the 0D/2D composite made the interface tight and shorten the charge diffusion distance. What’s also interesting was that the designed BNQDs/BWO exhibited a significant separation of photogenerated electron-hole pairs under the promotion of the BNQDs co-catalyst with the ability to attract photoinduced holes. In consequence, an obvious increment in the oxidative degradation efficiency of the best BNQDs/BWO has been achieved than that of individual BWO. The research provided a bottom-up idea for designing composite optoelectronic materials with ultra-fast charge separation by taking 0D co-catalyst as auxiliary.

A Voronoi-Ant Colony-Based Routing (VoR-Ant-R) Algorithm for WMSNs

Wireless Multimedia Sensor Networks (WMSNs) have been used in many applications and powerful distributed systems. But the performance of WMSNs is suffering from the occurrence of energy holes. To improve the performance of the network and packet delivery ratio, a Voronoi-Ant colony based Routing (VoR-Ant-R) algorithm is proposed for WMSNs to discover the energy holes and finds the shortest path from the source to destination in the WMSNs even though faces some obstacles. The WMSNs are constructed using the Voronoi structure to bypass energy holes. After bypassing the energy hole in the path; an ACO is introduced to select a neighborhood node for data forwarding. This ACO constructs the shortest optimized path to enhance the performance of the WMSNs. The proposed work is experimentally compared with other algorithms such as IEEABR, EEABR, SC, and BEES. The simulation results show that VoR-Ant-R can increase energy efficiency, success rate, reduces energy consumption, and latency.

Artificial Intelligence Based Sensor Network Congestion Fuzzy Control Algorithm

The topology control of sensor sensor network was studied based on fuzzy control algorithm. Aiming at the dynamic changes of the topology of large-scale and heterogeneous artificial intelligence sensor networks and the incomplete information between nodes, a smart network-based congestion control algorithm for sensor networks was proposed and the performance of fuzzy control algorithms was analyzed. Based on this, a fuzzy control algorithm was designed. The algorithm fully considered the residual energy of nodes and the distribution of nodes in the network. Therefore, the reasonable election of the cluster head can be realized through the game between nodes, which effectively avoided energy holes, made the network energy consumption more uniform, prolonged the network life cycle, and optimized the network topology.

Performance Estimation of a Wireless Sensor Network with a Mobile Sink Moving in Different Trajectories at Different Velocities

Background: Throughout the past few years, numerous Medium Access Control (MAC) protocols, routing protocols, node deployment mechanisms and duty cycle variation schemes have been designed for achieving high throughput, low delay and jitter, and long network lifetime in Wireless Sensor Networks (WSNs). In a WSN with static sink, voluminous sensors transmit their sensed data to the sink node. The coordinators mutually present in the range of sensors and sink have to forward a number of packets, which cause rapid depletion of their battery. These coordinators become dead too early resulting in the breakage of the communication channel and formation of energy holes. However, to save energy with a static sink, the duty cycle should be short. A mobile sink is a better option than a static sink if the duty cycle is long, as it balances energy consumption among the sensors. It is well observed that the mobile sink is capable of acquiring homogeneous energy depletion leading to stretched lifetime enhancing network performance. Methods: The vital benefaction of this paper is to present a simulation-based analysis of the network performance with a mobile sink having different trajectories of path traversed at different velocities. The intent is to find out the most appropriate and efficient trajectory and a particular velocity for a specific WSN with 100 nodes. The terrain area of the network is 210×210 m2 with the communication range of 20 m. The routing, network and MAC protocols implemented are Ad hoc On-Demand Distance Vector (AODV), Internet Protocol version 4 (IPv4) and Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 respectively. This paper has evaluated and analyzed the influence of lawn mower, elliptical and circular trajectories of a mobile sink moving at different velocities of 0.5, 1 and 2 m/s. The optimum performance is achieved at the velocity of 2 m/s for a circular trajectory of the mobile sink. It is observed that performance has significantly varied with the variation of trajectories and velocities. The notion of precise utilization of sink mobility improves the performance than a static sink. It is equally important to determine the most effective mechanism to implement mobile sinks and to find out the most appropriate scheme out of them. Results: The attainment parameters just as total messages received, average end to end delay (seconds), jitter (seconds), throughput (bits per second), number of packets dropped, number of packets dropped due to channel access failure, residual battery (mAh) and network lifetime (hours) for different trajectories such as lawn mower, elliptical and circular at different speeds of 0.5, 1 and 2 m/s of the sink node are evaluated and compared. The simulation results present that the circular trajectory and the velocity of 2 m/s have provided optimum performance. Conclusion: The objective was to precisely analyze and evaluate the influence of different trajectories of a mobile sink moving at different velocities in a WSN of 100 nodes to determine the most effective and appropriate trajectory and velocity to optimize the attainments. The intent is to uniform the power exhaustion amidst the sensors. The purpose was to gain the attention of researchers of this field to significantly contribute to novel research.