Existing methods for tracking mobile sinks in Wireless Sensor Networks (WSNs) often incur considerable energy consumption and overhead. To address this issue, we propose a Detour-Aware Mobile Sink ...Tracking (DAMST) method via analysis of movement angle changes of mobile sinks, for collecting data in a low-overhead and energy efficient way. In the proposed method, while a mobile sink passes through a region, it appoints a specific node as a region agent to collect information of the whole region, and records nodes near or on its trajectory as footprints. If it needs information from the region agent in a future time it will construct an energy efficient path from the region agent to itself by calculating its own movement angles according to the footprints, as well as getting rid of detours by analyzing these movement angles. Finally, the performance of the tracking method is evaluated systematically under different trajectory patterns and footprint appointment intervals. The simulation results consolidate that DAMST has advantages in reducing energy consumption and data overhead.
To solve the problem of large training samples requirement of space time adaptive processing (STAP), a jointly sparse matrices recovery-based method is proposed for clutter plus noise covariance ...matrix estimation by exploiting the transmitting waveform orthogonality of multiple-in multiple-out (MIMO) radar. The clutter spatio-temporal spectrum estimation problem is modeled as a sparse matrix reconstruction problem. Multiple training samples are generated based on the received signal of MIMO radar from a single training range cell. In order to recover the spatio-temporal spectrum matrices corresponding to different training samples, a jointly 2-D iterative adaptive approach is formulated to provide high accuracy and efficiency. Compared with the existing sparse recovery (SR)-based STAP method with single training range cell, due to the application of matricization process and MIMO radar, the proposed method can not only improve the clutter covariance matrix estimation accuracy but also reduce the computational complexity. In the heterogeneous and non-stationary environment, the proposed method can achieve better clutter suppression performance than conventional SR-based STAP methods using multiple training range cells. Simulation results are given to demonstrate the advantages of the proposed method over existing methods.
Mobile Crowd Sensing (MCS) is an emerging sensing paradigm which employs mobile devices, carried by participants, to sense real-time information. Most previous studies on task allocation in practical ...applications lack a way of calculating real participant density and making a detailed analysis of it. In this work, first, a fuzzy logic control method is employed to obtain the participant density in different time and space based on participants’ travel time and space. Further, according to the participant density, we can calculate the effective quantity of samples a task requires in a specific time and space. Then, the utility of all tasks can be obtained by considering both the attributes of tasks and the participant-side factors. Last, a hybrid greedy algorithm is proposed to allocate both urgent and non-urgent tasks to ensure the urgent tasks can be allocated as soon as possible and to maximize the utility of all tasks. The simulation results show that the proposed hybrid greedy algorithm is superior to other baselines in terms of the utility of all tasks.
It is unclear whether the health equity of autism spectrum disorders (ASDs) has changed in different years, regions, and gender. The aims of this study were to provide a comprehensive description of ...the ASDs burden and provide evidence for improvement in health policies regarding ASDs inequality. This study is a population-based cross-sectional study based on the Global Burden of Disease datasets 1990-2019. We collected detailed information on ASDs between 1990 and 2019 in 204 countries worldwide, derived from the Global Burden of Disease study in 2019. Burden was calculated in terms of the incidence, prevalence and years lived with disability (YLDs). Concentration curves and concentration indices were used to summarize the degree of income-related inequality in the burden of ASDs. The overall age-standardized incidence rate (ASIR), age-standardized prevalence rate (ASPR) and age-standardized YLDs rate (ASYR) of ASDs was 9.3 (95 %UI 7.7-11.1), 369.4 (95 %UI 305.9-441.2), 56.3 (95 %UI 36.8-81.5) per 100,000 people, respectively. The ASIR, ASPR and ASYR of ASDs affected three times as many males as females. The changing trends of age-standardized rates of ASDs showed that the ASIR of ASDs a slow growing trend globally. However, the ASPR and ASYR of ASDs showed a slow decreasing trend globally. All the concentration curves were below the line of equality and statistically significant. There was no significant difference in the age-standardized rate for different years in socio-demographic index-related inequality happened over 29 years (p > 0.05). The global burden of ASDs has remained higher in males and pro-rich, the income-related inequality tended not to change between 1990 and 2019.
It remains a challenge to develop efficient electrocatalysts in neutral media for hydrogen evolution reaction (HER) due to the sluggish kinetics and switch of the rate determining step. Although ...metal phosphides are widely used HER catalysts, their structural stability is an issue due to oxidization, and the HER performance in neutral media requires improvement. Herein, a new material, i.e., grapevine‐shaped N‐doped iron phosphide on carbon nanotubes, as an efficient HER catalyst in neutral media is developed. The optimized catalyst shows an overpotential of 256 mV at a large current density of 65 mA cm−2, which is even 10 mV lower than that of the commercial 20% Pt/C catalyst. The excellent performance of the catalyst is further studied by combined computational and experimental techniques, which proves that the interaction between nitrogen and iron phosphides can provide more efficient active structures and stabilize the metal phosphide electrocatalysts for HER.
N‐doped FeP/carbon nanotube (CNT) grapevine‐shaped catalysts are successfully synthesized by a facile hydrothermal‐annealing method. The introduction of N can enhance the hydrogen evolution performance by optimizing electronic structure and stabilizing the structure of the material simultaneously under working condition. This work provides a facile method to stabilize metal phosphides for electrocatalysis process.
In delay tolerant networks, the success rate and the transmission speed are restricted by limited social interaction and complex node mobility pattern analysis. To increase the success rate and ...reduce the transmission delay in delay tolerant networks, we propose Daily Routine Analysis for Node Searching in delay tolerant networks. In Daily Routine Analysis for Node Searching, each node is required to generate a Staying Probability Table and a Transiting Probability Table by analyzing its own daily routine, then to distribute its Staying Probability Table and Transiting Probability Table to the whole network with the help of other nodes having different mobility patterns. On the basis of the Staying Probability Table and Transiting Probability Table, Daily Routine Analysis for Node Searching further provides a node tracking strategy and an opportunistic routing strategy for delivering data from the source node to the destination node. Trace-driven experiments are performed to compare Daily Routine Analysis for Node Searching with previous node searching methods. The experimental results demonstrate that Daily Routine Analysis for Node Searching is able to promote the success rate and reduce the transmission delay effectively.
Considering the social properties of mobile sinks, we propose a biased trajectory dissemination of uncontrolled mobile sinks for event collection in wireless sensor networks. In biased trajectory ...dissemination of uncontrolled mobile sink, we first divide the whole network into clusters which can be managed by cluster heads that are elected in turn for intra-cluster event collection and inter-cluster communication. Second, for a mobile sink, we further divide the clusters it visits into biased clusters and non-biased clusters according to its staying probability. The mobile sink will send its mobility message which shows its location as it moves into a new cluster. We then construct a biased loop which is composed of all biased clusters and some non-biased clusters to disseminate a mobile sink’s mobility message only to clusters on it when the mobile sink moves into a biased cluster. We also construct query path that connects any cluster head that is not on the biased loop to a cluster head on it. An event could be transmitted to the biased loop along the query path for further forwarding to the mobile sink. Numerous simulations show the superior performance of biased trajectory dissemination of uncontrolled mobile sink compared to the representative schemes in terms of average path length, delay, and network energy consumption.
Earlier, various attempts to develop graphene structures using chemical and nonchemical routes were reported. Being efficient, scalable, and repeatable, 3D printing of graphene-based polymer inks and ...aerogels seems attractive; however, the produced structures highly rely on a binder or an ice support to stay intact. The presence of a binder or graphene oxide hinders the translation of the excellent graphene properties to the 3D structure. In this communication, we report our efforts to synthesize a 3D-shaped 3D graphene (3D2G) with good quality, desirable shape, and structure control by combining 3D printing with the atmospheric pressure chemical vapor deposition (CVD) process. Direct ink writing has been used in this work as a 3D-printing technique to print nickel powder–PLGA slurry into various shapes. The latter has been employed as a catalyst for graphene growth via CVD. Porous 3D2G with high purity was obtained after etching out the nickel substrate. The conducted micro CT and 2D Raman study of pristine 3D2G revealed important features of this new material. The interconnected porous nature of the obtained 3D2G combined with its good electrical conductivity (about 17 S/cm) and promising electrochemical properties invites applications for energy storage electrodes, where fast electron transfer and intimate contact with the active material and with the electrolyte are critically important. By changing the printing design, one can manipulate the electrical, electrochemical, and mechanical properties, including the structural porosity, without any requirement for additional doping or chemical postprocessing. The obtained binder-free 3D2G showed a very good thermal stability, tested by thermo-gravimetric analysis in air up to 500 °C. This work brings together two advanced manufacturing approaches, CVD and 3D printing, thus enabling the synthesis of high-quality, binder-free 3D2G structures with a tailored design that appeared to be suitable for multiple applications.
In delay tolerant networks (DTNs), the delivery rate and delivery speed are restricted by node selfishness. To promote the delivery rate and reduce the delivery delay in DTNs, we propose a hybrid ...incentive trade model (HITM), which uses reputation compensation to stimulate nodes to give up their temporary benefits and transfer their forwarding missions to other more qualified nodes. Furthermore, HITM gives credit payment and reputation promotion to nodes whose mission transferring behaviors are capable of reducing delivery delay or promoting delivery reliability, and conversely punishes nodes whose mission transferring behaviors could prolong the delivery delay or impair the delivery reliability. Trace-driven experiments are performed to compare HITM with previous representative incentive schemes. The experiment results demonstrate that the HITM can effectively limit node selfishness, thereby promoting the delivery rate as well as reducing the delivery delay.
The adsorption performance of the amino modification of zirconium metal–organic framework (UiO-66(NH2)) for the removal of antimony (Sb) from aqueous solution has been investigated. The influence of ...equilibrium concentration, solution pH, temperature, and contact time on the Sb adsorption were investigated by the batch method. Compared with original UiO-66, the UiO-66(NH2) adsorption capacity for Sb(III) and Sb(V) increased to 61.8 mg/g and 105.4 mg/g for Sb(III) and Sb(V), although the surface area of UiO-66(NH2) decreased from 486.31 m2/g to 113.46 m2/g. The adsorption equilibrium data of Sb on UiO-66(NH2) fitted well with the Langmuir adsorption model, and the kinetics data fitted well with the second-order adsorption model. Thermodynamic parameters indicated that adsorption processes of Sb were feasible, endothermic, and spontaneous. The adsorption isotherm parameters indicated that the Sb adsorption data fitted well with the Langmuir model. The mean adsorption energy obtained from the Dubinin–Radushkevich (D–R) isotherm model further revealed that the Sb adsorption process was chemisorption. Additionally, FTIR analysis and X-ray photoelectron spectroscopy (XPS) study revealed that the Zr–O bond and amino group played a significant role in the Sb removal. Thus, UiO-66(NH2) is a promising candidate for Sb contaminated water remediation on the basis of low-cost, easy availability, high Sb adsorption capacity, nontoxicity, and high stability.
PDF
