The Misdirection and Return of Graduate Course Teaching

Graduate course teaching plays an irreplaceable role in knowledge mastery,skill enhancement,and quality cultivation of graduate students.This paper addresses current issues in graduate course teaching,such as ambiguous objectives,formulaic content,formalistic operation,and oversimplified evaluation.It proposes corresponding solutions with the hope of steering graduate course teaching back to its original purpose and realizing its true significance.

Fabricating Na/In/C Composite Anode with Natrophilic Na-In Alloy Enables Superior Na Ion Deposition in the EC/PC Electrolyte

In conventional ethylene carbonate(EC)/propylene carbonate(PC)electrolyte,sodium metal reacts spontaneously and deleteriously with solvent molecules.This significantly limits the practical feasibility of high-voltage sodium metal batteries based on Na metal chemistry.Herein,we present a sodium metal alloy strategy via introducing NaIn and Na_(2)In phases in a Na/In/C composite,aiming at boosting Na ion deposition stability in the common EC/PC electrolyte.Symmetric cells with Na/In/C electrodes achieve an impressive long-term cycling capability at 1 mA cm^(-2)(>870 h)and 5 mA cm^(-2)(>560 h),respectively,with a capacity of 1 mAh cm^(-2).In situ optical microscopy clearly unravels a stable Na ion dynamic deposition process on the Na/In/C composite electrode surface,attributing to a dendrite-free and smooth morphology.Furthermore,theoretical simulations reveal intrinsic mechanism for the reversible Na ion deposition behavior with the composite Na/In/C electrode.Upon pairing with a highvoltage NaVPOF cathode,Na/In/C anode illustrates a better suitability in SMB s.This work promises an alternative alloying strategy for enhancing Na metal interfacial stability in the common EC/PC electrolyte for their future applications.

A Survivability Routing Mechanism in SDN Enabled Wireless Mesh Networks:Design and Evaluation

In software-defined networking,the separation of control plane from forwarding plane introduces new challenges to network reliability.This paper proposes a fault-tolerant routing mechanism to improve survivability by converting the survivability problem into two sub-problems:constructing an elastic-aware routing tree and controller selection.Based on the shortest path tree,this scheme continuously attempts to prune the routing tree to enhance network survivability.After a certain number of iterations,elastic-aware routing continues to improve network resiliency by increasing the number of edges in this tree.Simulation results demonstrate this fault-tolerant mechanism performs better than the traditional method in terms of the number of protected nodes and network fragility indicator.

In-situ fabrication of vertical heterogeneous nickel diselenide-molybdenum diselenide architectures as bifunctional overall water-splitting electrocatalyst

Despite the rapid advances in electrocatalysts based on two-dimensional(2D)transition metal dichalco-genides(TMDs)materials,they are subject to serious aggregation,poor conductivity and the presence of inactive basal planes.Herein,we have successfully demonstrated the in-situ construction of NiSe_(2)-MoSe_(2) heterostructure arrays on carbon cloth(NiSe_(2)-MoSe_(2)/CC)by a facile two-step hydrothermal process.The presence of the synergistic effect in the heterostructures effectively optimizes the poor conductivity and hydrophilicity,and thus enables fast electron transfer,leading to enhanced electrochemical reaction.Fur-thermore,density functional theory calculations reveal that the electrons redistribution at the heterojunc-tion interface and the reduced Gibbs free energy of hydrogen adsorption for hydrogen evolution reaction(HER)/the Gibbs free energy change value of rate-determining step for oxygen evolution reaction(OER),thus enhancing the HER/OER catalytic activity.Importantly,the device displays a good performance with a low overpotential of 98 and 310 mV for HER and OER,respectively,and a low cell voltage of 1.59 V for its corresponding electrolyzer(10 mA cm^(-2)).This work presents the high-performance water splitting of bifunctional electrocatalysts based on 2D TMDs materials and offers a novel design concept of interface engineering.

Three-dimensional Ag/carbon nanotube-graphene foam for high performance dendrite free lithium/sodium metal anodes

Although lithium metal and sodium metal are promised as ideal anodes for lithium ion batteries(LIBs)and sodium ion batteries(SIBs),they still suffer from inevitable dendrite growth.In light of this,silver nanoparticles(Ag NPs)are sputtered onto three-dimensional carbon nanotube decorated graphene foam(3D CNT-GF)to construct superior 3D Ag/CNT-GF composite matrix for lithium metal anodes(LMAs)and sodium metal anodes(SMAs).With this design,lithiophilic/sodiophilic Ag NPs could provide favorable sites to guide Li/Na metal nucleation and growth,thus leading to low nucleation overpotentials,high Coulombic efficiency and long cycle performance.Accordingly,3D Ag/CNT-GF electrodes can stably cy-cle for 1000 and 750 cycles at 3 mA cm^(−2)with 1 mAh cm^(−2)for SMAs and LMAs,respectively.More attractively,it can also stably sustain 300 cycles(SMAs)and 500 cycles(LMAs)at a large current den-sity of 5 mA cm^(−2)with 1 mAh cm^(−2).The excellent electrochemical performance can be attributed to the lithiophilic/sodiophilic electrode surface,3D porous electrode structure and the dendrite-free mor-phology as demonstrated by ex-situ scanning electron microscopy(SEM)and in-situ optical microscopy analyses.Furthermore,full cells based on Na@3D Ag/CNT-GF||Na 3 V 2(PO 4)3@carbon(NVP@C)and Li@3D Ag/CNT-GF||LiFePO 4(LFP)could deliver highly reversible capacities of 90.1 and 106.4 mAh g^(−1),respec-tively,at 100 mA g^(−1)after 200 cycles for SIBs and LIBs,respectively.This work demonstrates a novel 3D Ag/CNT-GF matrix for boosting Li/Na deposition stability for their future applications.

SnFe_(2)O_(4)/ZnIn_(2)S_(4)/PVDF piezophotocatalyst with improved photocatalytic hydrogen production by synergetic effects of heterojunction and piezoelectricity

The polarized electric field inside piezoelectric materials has been proven to be a promising technique to boost photogenerated charge separation.Herein,a novel flexible SnFe_(2)O_(4)/ZnIn_(2)S_(4)/polyvinylidene fluoride((CH2CF2)_(n),PVDF)(P-SZ)film piezophotocatalyst was successfully synthesized by combining PVDF,an organic piezoelectric material,with a SnFe_(2)O_(4)/ZnIn_(2)S_(4)(SFO/ZIS)type II heterojunction photocatalyst.The hydrogen evolution rate of SFO/ZIS heterojunction with a SFO content of 5%is about 846.79μmol·h^(−1)·g^(−1),which is 3.6 times that of pristine ZIS.Furthermore,after being combined with PVDF,the optimum hydrogen evolution rate of P-SZ is about 1652.7μmol·h^(−1)·g^(−1)in the presence of ultrasound,which exceeds that of 5%SFO/ZIS by an approximate factor of 2.0.Based on experimental results,the mechanism of the improved photocatalytic performance of P-SZ was proposed on the basis of the piezoelectric field in PVDF and the formed heterojunction between SFO and ZIS,which effectively boosted the separation of photoinduced charges.This work provides an efficient strategy for multi-path collection and utilization of natural solar and vibrational energy to enhance photoactivity.

Three-dimensional Au/carbon nanotube-graphene foam hybrid nanostructure for dendrite free sodium metal anode with long cycle stability

Sodium metal anode has been attracting widely research attention due to its large capacity and low electrode potential as the anode of sodium-ion batteries.However,the uncontrollable growth of Na dendrite is one of the critical issues for its real applications.Herein,a three-dimensional(3 D) nanostructure composed of gold nanoparticles(Au NPs) supported on 3 D carbon nanotube-graphene foam(3 D CNT-GF)was designed and fabricated as the host of sodium metal anode.Na@3 D Au/CNT-GF anode can deliver a Coulombic efficiency of 99.14% and stably cycle for 2600 h at 1 mA cm^(-2) with 1 mAh cm^(-2).It can cycle for 300 h at 5 mA cm^(-2) with 1 mAh cm^(-2).Detailed results indicate that its excellent electrochemical performance can be attributed to the unique macroporous structure and sodiophilic surface formed by Au NPs guiding the uniform sodium metal deposition enabled a dendrite-free morphology investigated by the ex-situ SEM and in-situ optical microscopy.At last,a full cell was assembled with Na@3 D Au/CNT-GF as the anode and Na_(3) V_(2)(PO_(4))_(3)@C as the cathode.It can deliver a capacity of 84.6 mAh g^(-1) at 100 mA g^(-1)after 200 cycles.Our results demonstrate that 3 D Au/CNT-GF is a promising sodium metal anode host.

Spiking-free HGO-based DSC for flexible joint manipulator

The tracking control problem for Flexible Joint Manipulator Control System(FJMCS)with unmeasurable states is addressed in this paper.Firstly,a High-Gain Observer(HGO)is constructed to estimate the unmeasurable states and the uncertainties.Then,a Dynamic Surface Control(DSC)scheme is developed by using the estimation of HGO.The newly proposed controller has two advantages over the existing methods:(A)a novel Spike Suppression Function(SSF)is developed to avoid the estimation spike problem in the existing HGO-based controllers.(B)Unlike the existing observer-based partial feedback control scheme that can only estimate the unmeasurable states,the proposed HGO can estimate both the unmeasurable states and uncertainties.The closed-loop system stability is proved by the Lyapunov theory.Simulation results demonstrate the effectiveness of the proposed controller.