Communication-Aware Mobile Relaying via an AUV for Minimal Wait Time:A Broad Learning-Based Solution

Dear Editor,This letter studies the communication-aware mobile relaying via an autonomous underwater vehicle(AUV)for minimal wait time.Compared with the analysis-based channel prediction solution,the proposed discrete Kirchhoff approximation solution has a higher estimation accuracy.

Communication-Aware Formation Control of AUVs With Model Uncertainty and Fading Channel via Integral Reinforcement Learning

Most formation approaches of autonomous underwater vehicles(AUVs)focus on the control techniques,ignoring the influence of underwater channel.This paper is concerned with a communication-aware formation issue for AUVs,subject to model uncertainty and fading channel.An integral reinforcement learning(IRL)based estimator is designed to calculate the probabilistic channel parameters,wherein the multivariate probabilistic collocation method with orthogonal fractional factorial design(M-PCM-OFFD)is employed to evaluate the uncertain channel measurements.With the estimated signal-to-noise ratio(SNR),we employ the IRL and M-PCM-OFFD to develop a saturated formation controller for AUVs,dealing with uncertain dynamics and current parameters.For the proposed formation approach,an integrated optimization solution is presented to make a balance between formation stability and communication efficiency.Main innovations lie in three aspects:1)Construct an integrated communication and control optimization framework;2)Design an IRL-based channel prediction estimator;3)Develop an IRL-based formation controller with M-PCM-OFFD.Finally,simulation results show that the formation approach can avoid local optimum estimation,improve the channel efficiency,and relax the dependence of AUV model parameters.

Model-Free Formation Control of Autonomous Underwater Vehicles:A Broad Learning-Based Solution

Dear Editor,We develop a broad learning-based algorithm to enforce the formation control of AUVs.Compared with the deep learning(DL)based formation solutions,our solution employs the broad learning system(BLS)to remodel the learning framework without a retraining process.

武夷山平须舞虻属Platypalpus五新种(双翅目:舞虻科)

平须舞虻属Platypalpus Macquart是舞虻科中最大的属之一,已知560余种分布世界各地,我国已知66种。武夷山仅报道1种:弯刺平须舞虻Platypalpus curvispinus Yang&Yang,2003。本文记述武夷山平须舞虻属5新种:叉平须舞虻Platypalpus bifurcates sp.nov.,宽端平须舞虻Platypalpus latiapicatus sp.nov.,宽斑平须舞虻Platypalpus latimaculatus sp.nov.,武夷山平须舞虻Platypalpus wuyishanus sp.nov.,先锋岭平须舞虻Platypalpus xianfenglinganus sp.nov.;并编制了武夷山平须舞虻属的分种检索表。

Five new species of Hilara(Diptera:Empididae)from Shalulishan,China

The genus Hilara Meigen, 1822 is one of the largest genera in Empididae and is distributed worldwide with over 400 known species. Six species are newly reported from Shalulishan, with five of the species described as new to science: Hilara brevispina sp. nov., Hilara cirencuoana sp. nov., Hilara dorsiprocessa sp. nov., Hilara dorsispina sp. nov., and Hilara tenuispina sp. nov. A key to these species in the genus Hilara is presented.

Intermolecular coupling enhanced thermopower in single-molecule diketopyrrolopyrrole junctions

Sorting out organic molecules with high thermopower is essential for understanding molecular thermoelectrics.The intermolecular coupling offers a unique chance to enhance the thermopower by tuning the bandgap structure of molecular devices,but the investigation of intermolecular coupling in bulk materials remains challenging.Herein,we investigated the thermopower of diketopyrrolopyrrole(DPP)cored single-molecule junctions with different coupling strengths by varying the packing density of the self-assembled monolayers(SAM)using a customized scanning tunneling microscope break junction(STM-BJ)technique.We found that the thermopower of DPP molecules could be enhanced up to one order of magnitude with increasing packing density,suggesting that the thermopower increases with larger neighboring intermolecular interactions.The combined density functional theory(DFT)calculations revealed that the closely-packed configuration brings stronger intermolecular coupling and then reduces the highest occupied molecular orbital(HOMO)-lowest unoccupied molecular orbital(LUMO)gap,leading to an enhanced thermopower.Our findings offer a new strategy for developing organic thermoelectric devices with high thermopower.

Hierarchical three-dimensional flower-like Co3O4 archi- tectures with a mesocrystal structure as high capacity anode materials for long-lived lithium-ion batteries

In this work, we rationally design a high-capacity electrode based on three- dimensional （3D） hierarchical Co3O4 flower-like architectures with a mesocrystal nanostructure. The specific combination of the micro-sized 3D hierarchical architecture and the mesocrystal structure with a high porosity and single crystal-like nature can address the capacity fading and cycling stability as presented in many conversion electrodes for lithium-ion batteries. The hierarchical 3D flower-like Co3O4 architecture accommodates the volume change and mitigates mechanical stress during the lithiation-delithiation processes, and the mesocrystal structure provides extra lithium-ion storage and electron/ion transport paths. The achieved hierarchical 3D Co3O4 flower-like architectures with a mesocrystal nanostructure exhibit a high reversible capacity of 920 mA.h.g-1 after 800 cycles at 1.12 C （1 C = 890 mA.h.gq）, improved rate performance, and cycling stability. The finding in this work offers a new perspective for designing advanced and long-lived lithium-ion batteries.

Regulating bifunctional flower-like NiFe_(2)O_(4)/graphene for green EMI shielding and lithium ion storage

Environment and energy are the eternal hot topics in the world,multiloculated microscale materials have attracted great attention in the field of electromagnetic interference(EMI)shielding and lithium ions storage.Herein,a novel flower-like NiFe_(2)O_(4)/graphene composite with adjustable structure was fabricated as EMI shielding material and anode material of lithium-ion batteries.NiFe_(2)O_(4)/graphene composite is a potential green EMI shielding material.The EMI shielding effectiveness(SE)increases with the increase of graphene content in NiFe_(2)O_(4)/graphene composite,and the total EMI SE of NiFe_(2)O_(4)/graphene with 73.6 wt.%graphene increases from 26.5 to 40.6 d B with the increase of frequency in 2–18 GHz.Furthermore,it exhibits long-life and large capacity lithium storage performance at high current density.The capacity reaches 732.79 m Ah g^(-1)after 100 cycles at 0.1 A g^(-1),recovering to more than 139%from the minimum capacity value.After 300 cycles at 0.5 A g^(-1),the capacity increases to 688.5 mAh g^(-1).The initial capacities at 2 and 5 A g^(-1)are 704.9 and 717.8 mAh g^(-1),and remain 297.9 and 203.2 m Ah g^(-1)after 1000 cycles.The distinguished EMI shielding performance and electrochemical performance are mainly ascribed to the structure regulation of NiFe_(2)O_(4)/graphene composite,as well as the synergistic effect of graphene and NiFe_(2)O_(4).This research opens up infinite opportunities for the application of multifunctional and interdisciplinary materials.

Highly insulating alkane rings with destructive σ-interference

Destructive quantum interference(DQI)provides a unique approach to controlling the leakage current in the OFF state of molecular devices.However,the DQI in π-conjugated molecular building blocks cannot exhibit ultralow conductance due to the existence of covalently bonded σ-transport channels.Thus,suppressing the σ-contribution via σ-DQI is essential for the fabrication of molecular junctions with high insulation and effective modulation of conductance in single-molecule junctions.Here,we demonstrate the existence of σ-DQI even in a simple series of C_(m)C_(n) ring molecules,with parallel chains of m and n alkyl units(where m,n=6,8 or 10),by measuring their electrical conductance and Seebeck coefficients.Counterintuitively,the conductance of the symmetric C_(n)C_(n) rings is lower than that of the corresponding single chains(C_(n)),which is in contrast to the conductance superposition law in multi-channeled systems.Combined theoretical calculations reveal that the gauche conformation in a shorter chain fixed by another chain leads to the decreased conductance in alkyl rings,which originates from the phase-coherent tunneling and DQI in σ-conjugated systems.Our finding suggests that through appropriate conformation locking by cyclization,the covalent alkane system can exhibit DQI,which offers strategies for future designs of molecular electronic devices and materials.

Quantum interference enhanced thermopower in single-molecule thiophene junctions

Quantum interference(QI)effects,which offer unique opportunities to widely manipulate the charge transport properties in the molecular junctions,will have the potential for achieving high thermopower.Here we developed a scanning tunneling microscope break junction technique to investigate the thermopower through single-molecule thiophene junctions.We observed that the thermopower of 2,4-TPSAc with destructive quantum interference(DQI)was nearly twice of 2,5-TP-SAc without DQI,while the conductance of the 2,4-TP-SAc was two orders of magnitude lower than that of 2,5-TP-SAc.Furthermore,we found the thermopower was almost the same by altering the anchoring group or thiophene core in the control experiments,suggesting that the QI effect is responsible for the increase of thermopower.The density functional theory(DFT)calculations are in quantitative agreement with the experimental data.Our results reveal that QI effects can provide a promising platform to enhance the thermopower of molecular junctions.