Finite-Time Sideslip Differentiator-Based LOS Guidance for Robust Path Following of Snake Robots

This paper presents a finite-time sideslip differentiator-based line-of-sight(LOS)guidance method for robust path following of snake robots.Firstly,finite-time stable sideslip differentiator and adaptive LOS guidance method are proposed to counteract sideslip drift caused by cross-track velocity.The proposed differentiator can accurately observe the cross-track error and sideslip angle for snake robots to avoid errors caused by calculating sideslip angle approximately.In our method,the designed piecewise auxiliary function guarantees the finite-time stability of position errors.Secondly,for the case of external disturbances and state constraints,a Barrier Lyapunov functionbased backstepping adaptive path following controller is presented to improve the robot’s robustness.The uniform ultimate boundedness of the closed-loop system is proved by analyzing stability.Additionally,a gait frequency adjustment-based virtual velocity control input is derived to achieve the exponential convergence of the tangential velocity.At last,the availability and superiority of this work are shown through simulation and experiment results.

Oxygen vacancies enriched Ni-Co/SiO_(2)@CeO_(2) redox catalyst for cycling methane partial oxidation and CO_(2) splitting

Redox catalysts play a vital role in the interconversion of two significant greenhouse gases,CO_(2)and CH_(4),via chemical looping methane dry reforming technology.Herein,a series of transition metals-alloyed and core-shell structured Ni-M/SiO_(2)@CeO_(2)(M=Fe,Co,Cu,Mn,Zr)redox catalyst were fabricated and evaluated in a gas-solid fixed-bed reactor for cycling CH_(4)partial oxidation(PO_(x))and CO_(2)splitting.The catalysts are composed of spherical SiO_(2)core and CeO_(2)shell,and the highly dispersed Ni alloy nanoparticles are the interlayer between core and shell.The oxygen vacancy concentration of Ni-M/SiO_(2)@CeO_(2)followed the order of Co>Cu>Fe>Mn>Zr,and Ni alloying with transition metals significantly enhanced oxygen storage capacity(OSC).Ni-Co/SiO_(2)@CeO_(2)catalyst with abundant oxygen vacancies and a high OSC showed the lowest temperatures of CH_(4)activation(610℃)and CO_(2)decomposition(590℃),thus demonstrating excellent redox reactivity.The catalyst exhibited superior activity and structural stability in the continuous CH_(4)/CO_(2)redox cycles at 615℃,achieving 87%CH_(4)conversion and 83%CO selectivity.The proposed catalyst shows great potential for the utilization of CH_(4)and CO_(2)in a redox mode,providing a new sight for design redox catalyst in chemical looping or related fields.

Enhancing the Efficiency of Multi-Electrolyzer Clusters with Lye Mixer:Topology Design and Control Strategy

The rise in hydrogen production powered by renewable energy is driving the field toward the adoption of systems comprising multiple alkaline water electrolyzers.These setups present various operational modes:independent operation and multi-electrolyzer parallelization,each with distinct advantages and challenges.This study introduces an innovative configuration that incorporates a mutual lye mixer among electrolyzers,establishing a weakly coupled system that combines the advantages of two modes.This approach enables efficient heat utilization for faster hot-startup and maintains heat conservation post-lye interconnection,while preserving the option for independent operation after decoupling.A specialized thermal exchange model is developed for this topology,according to the dynamics of the lye mixer.The study further details startup procedures and proposes optimized control strategies tailored to this structural design.Waste heat from the caustic fully heats up the multiple electrolyzers connected to the lye mixing system,enabling a rapid hot start to enhance the system’s ability to track renewable energy.A control strategy is established to reduce heat loss and increase startup speed,and the optimal valve openings of the diverter valve and the manifold valve are determined.Simulation results indicate a considerable enhancement in operational efficiency,marked by an 18.28%improvement in startup speed and a 6.11%reduction in startup energy consumption inmulti-electrolyzer cluster systems,particularlywhen the systems are synchronized with photovoltaic energy sources.The findings represent a significant stride toward efficient and sustainable hydrogen production,offering a promising path for large-scale integration of renewable energy.

c-Fos expression within the L_5 spinal cord dorsal horn after spinal nerve ligation in rats Is intraplantar administration of glutamate different from intrathecal administration?

BACKGROUND： Injection of glutamate （Glu） in normal animals can cause neuronal c-Fos expression; however, whether Glu can induce spinal neuronal c-Fos expression in pain models is unclear. OBJECTIVE： To examine the effects of intraplantar and intrathecal injection of Glu on c-Fos expression in the L5 spinal cord dorsal horn Ⅰ/Ⅱ and Ⅲ/Ⅳ layers after spinal nerve ligation, and to study the effects of the N-methyI-D-aspartic acid （NMDA） receptor antagonist, D-2-amino-5-phosphonopentanoate （D-AP5）, and a selective group I mGluR antagonist, 7-hydroyiminocyclo propan[a]chromen-lacarboxylic acid ethyl ester （cpccoEt）. DESIGN, TIME AND SETTING： A randomized, controlled animal study was performed at the Department of Pharmacology, Oral Anatomy, and Neurobiology, Osaka University Graduate School of Dentistry, from December 2005 to December 2006. MATERIALS： Glu （5 μmol）, D-AP5 （50 nmot） and cpccoEt （250 nmol） were provided by Wako Pure Chemical Industries, Osaka, Japan, and diluted in saline （50 μL）. The pH of all solutions was adjusted to 7.4. METHODS： Twelve rats were randomly divided into sham operation （n = 6） and spinal nerve ligation （SNL; n = 6） groups for behavioral assessments of neuropathic pain after ligation surgery of the left L5-6 nerve segment. Another 60 rats were randomly divided into sham operation, SNL, saline-intraplantar, saline-intrathecal, Glu-intraplantar, Glu-intrathecal, D-AP5-intrathecal, Glu-D-AP5-intrathecal, cpccoEt-intrathecal, and Glu-cpccoEt-intrathecal groups, with 6 rats in each group. All groups except sham operation group received a similar SNL. On day 14, rats received a 50-μL injection of saline, Glu, D-AP5, and/or cpccoEt into the left intraplantar or intrathecal L5-4 segments. MAIN OUTCOME MEASURES： The number of c-Fos positive neurons in both Ⅰ/Ⅱ and Ⅲ/Ⅳ spinal layers at L6 was observed using immunohistochemistry 2 hours after administration. RESULTS： （1） SNL increased the level of c-Fos expression in two sides of the spinal cord, particularly on Ⅲ/Ⅳ spinal layers of the ligated side. （2） Intraplantar or intrathecal administration of saline significantly increased the c-Fos labeled neurons in Ⅰ/Ⅱ spinal layers of the ligated side, compared with SNL alone （P 〈 0.01）. （3） Intraplantar Glu （5 μmol） increased the number of c-Fos positive neurons in Ⅰ/Ⅱ spinal layers compared with intraplantar saline （P〈 0.01）. （4） The number of c-Fos neurons in Ⅰ/Ⅱ spinal layers on both the ipsilateral and contralateral side after intraplantar Glu was lower than intrathecal Glu （P〈 0.01）, with a 3-fold higher induction by intrathecal Glu. （5） Co-administration of D-AP5 or cpccoEt reduced the effects of intrathecal Glu （P 〈 0.01）. CONCLUSION： Intrathecal Glu increases c-Fos expression more than intraplantar Glu. Antagonists of NMDA and group I mGluRs block this effect.

Genetic analysis and gene mapping of a dwarf and liguleless mutation in barley

Leaf development underlies crop growth and productivity and has been a major target of crop domestication and improvement.However,most genes controlling leaf development in barley remain unknown.We identified a dwarf and liguleless(dl)mutant derived by ethylmethane sulfonate mutagenesis.The dl mutant showed dramatic changes in shoot architecture compared with wild-type(Yangnongpi 5)plants.Besides lacking ligules,the dl mutant showed much shorter plant height(28 cm)than Yangnongpi 5(78 cm).By map-based cloning,the dl gene was localized to a 56.58-kb genomic interval on the long arm of chromosome 7.A C-to-T single-nucleotide substitution was identified at exon position 790,and is a functional mutation resulting in a proline-to-serine substitution at the 264th amino acid residue of HORVU7Hr1G106960.Consequently,HORVU7Hr1G106960 was identified as the DL gene,encoding 269 amino acids and containing the Arabidopsis LSH1 and Oryza G1(ALOG)domain.DL is highly similar to rice OsG1-LIKE 1/2(OsG1L1/2)and sorghum AWN1/AWN1-10 at the amino acid level.Although the dl mutant allele showed no expression changes in selected tissues by real-time PCR,we propose HORVU7Hr1G106960 as a candidate gene conferring the dwarf and liguleless phenotype in barley.

Position Errors and Interference Prediction-Based Trajectory Tracking for Snake Robots

This work presents a trajectory tracking control method for snake robots.This method eliminates the influence of time-varying interferences on the body and reduces the offset error of a robot with a predetermined trajectory.The optimized line-of-sight(LOS)guidance strategy drives the robot’s steering angle to maintain its anti-sideslip ability by predicting position errors and interferences.Then,the predictions of system parameters and viscous friction coefficients can compensate for the joint torque control input.The compensation is adopted to enhance the compatibility of a robot within ever-changing environments.Simulation and experimental outcomes show that our work can decrease the fluctuation peak of the tracking errors,reduce adjustment time,and improve accuracy.

Rapid identification of full-length genome and tracing variations of monkeypox virus in clinical specimens based on mNGS and amplicon sequencing

The monkeypox virus(MPXV)has triggered a current outbreak globally.Genome sequencing of MPXV and rapid tracing of genetic variants will benefit disease diagnosis and control.It is a significant challenge but necessary to optimize the strategy and application of rapid full-length genome identification and to track variations of MPXV in clinical specimens with low viral loads,as it is one of the DNA viruses with the largest genome and the most AT-biased,and has a significant number of tandem repeats.Here we evaluated the performance of metagenomic and amplicon sequencing techniques,and three sequencing platforms in MPXV genome sequencing based on multiple clinical specimens of five mpox cases in Chinese mainland.We rapidly identified the full-length genome of MPXV with the assembly of accurate tandem repeats in multiple clinical specimens.Amplicon sequencing enables cost-effective and rapid sequencing of clinical specimens to obtain high-quality MPXV genomes.Third-generation sequencing facilitates the assembly of the terminal tandem repeat regions in the monkeypox virus genome and corrects a common misassembly in published sequences.Besides,several intra-host single nucleotide variations were identified in the first imported mpox case.This study offers an evaluation of various strategies aimed at identifying the complete genome of MPXV in clinical specimens.The findings of this study will significantly enhance the surveillance of MPXV.

SHARP POINTWISE-IN-TIME ERROR ESTIMATE OF L1 SCHEME FOR NONLINEAR SUBDIFFUSION EQUATIONS

An essential feature of the subdiffusion equations with theα-order time fractional derivative is the weak singularity at the initial time.The weak regularity of the solution is usually characterized by a regularity parameterσ∈(0,1)∪(1,2).Under this general regularity assumption,we present a rigorous analysis for the truncation errors and develop a new tool to obtain the stability results,i.e.,a refined discrete fractional-type Grönwall inequality(DFGI).After that,we obtain the pointwise-in-time error estimate of the widely used L1 scheme for nonlinear subdiffusion equations.The present results fill the gap on some interesting convergence results of L1 scheme onσ∈(0,α)∪(α,1)∪(1,2].Numerical experiments are provided to demonstrate the effectiveness of our theoretical analysis.

Linearized Transformed L1 Galerkin FEMs with Unconditional Convergence for Nonlinear Time Fractional Schr¨odinger Equations

A linearized transformed L1 Galerkin finite element method(FEM)is presented for numerically solving the multi-dimensional time fractional Schr¨odinger equations.Unconditionally optimal error estimates of the fully-discrete scheme are proved.Such error estimates are obtained by combining a new discrete fractional Gr¨onwall inequality,the corresponding Sobolev embedding theorems and some inverse inequalities.While the previous unconditional convergence results are usually obtained by using the temporal-spatial error spitting approaches.Numerical examples are presented to confirm the theoretical results.

Analysis of L1-Galerkin FEMs for Time-Fractional Nonlinear Parabolic Problems

This paper is concerned with numerical solutions of time-fractional nonlinear parabolic problems by a class of L1-Galerkin finite element methods.The analysis of L1 methods for time-fractional nonlinear problems is limited mainly due to the lack of a fundamental Gronwall type inequality.In this paper,we establish such a fundamental inequality for the L1 approximation to the Caputo fractional derivative.In terms of the Gronwall type inequality,we provide optimal error estimates of several fully discrete linearized Galerkin finite element methods for nonlinear problems.The theoretical results are illustrated by applying our proposed methods to the time fractional nonlinear Huxley equation and time fractional Fisher equation.

Snake robots play an important role in social services and military needs

Intelligent robotic systems have gradually penetrated into the fields of social services and military reconnaissance with the rapid economic development.Snake robots,as multi-redundant bionic robots,play an indispensable and important role in public life and military needs.1 These robots have been widely favored and highly regarded by the academia and industry because of 1)their small size and flexibility,thereby easily entering small spaces for work,2)their ability to carry a variety of equipment for disaster rescue and military reconnaissance,and 3)their variety of movement modes,which can adapt to various complex terrain environments.

Efficient Numerical Computation of Time-Fractional Nonlinear Schrodinger Equations in Unbounded Domain

The aim of this paper is to derive a stable and efficient scheme for solving the one-dimensional time-fractional nonlinear Schrodinger equation set in an unbounded domain.We first derive absorbing boundary conditions for the fractional system by using the unified approach introduced in[47,48]and a linearization procedure.Then,the initial boundary-value problem for the fractional system with ABCs is discretized,a stability analysis is developed and the error estimate O(h^(2)+τ)is stated.To accel-erate the L1-scheme in time,a sum-of-exponentials approximation is introduced to speed-up the evaluation of the Caputo fractional derivative.The resulting algorithm is highly efficient for long time simulations.Finally,we end the paper by reporting some numerical simulations to validate the properties(accuracy and efficiency)of the derived scheme.

De Novo Biosynthesis of Vindoline and Catharanthine in Saccharomyces cerevisiae

Vinblastine has been used clinically as one of the most potent therapeutics for the treatment of several types of cancer.However,the traditional plant extraction method suffers from unreliable supply,low abundance,and extremely high cost.Here,we use synthetic biology approach to engineer Saccharomyces cerevisiae for de novo biosynthesis of vindoline and catharanthine,which can be coupled chemically or biologically to vinblastine.On the basis of a platform strain with sufficient supply of precursors and cofactors for biosynthesis,we reconstituted,debottlenecked,and optimized the biosynthetic pathways for the production of vindoline and catharanthine.The vindoline biosynthetic pathway represents one of the most complicated pathways ever reconstituted in microbial cell factories.Using shake flask fermentation,our engineered yeast strains were able to produce catharanthine and vindoline at a titer of 527.1 and 305.1μg·liter^(−1),respectively,without accumulating detectable amount of pathway intermediates.This study establishes a representative example for the production of valuable plant natural products in yeast.

Unconditionally optimal convergence of an energy-conserving and linearly implicit scheme for nonlinear wave equations

In this paper,we present and analyze an energy-conserving and linearly implicit scheme for solving the nonlinear wave equations.Optimal error estimates in time and superconvergent error estimates in space are established without certain time-step restrictions.The key is to estimate directly the solution bounds in the H-norm for both the nonlinear wave equation and the corresponding fully discrete scheme,while the previous investigations rely on the temporal-spatial error splitting approach.Numerical examples are presented to confirm energy-conserving properties,unconditional convergence and optimal error estimates,respectively,of the proposed fully discrete schemes.

Stability Analysis of Runge-Kutta Methods for Nonlinear Neutral Volterra Delay-Integro-Differential Equations

This paper is concerned with the numerical stability of implicit Runge-Kutta methods for nonlinear neutral Volterra delay-integro-differential equations with constant delay.Using a Halanay inequality generalized by Liz and Trofimchuk,we give two sufficient conditions for the stability of the true solution to this class of equations.Runge-Kutta methods with compound quadrature rule are considered.Nonlinear stability conditions for the proposed methods are derived.As an illustration of the application of these investigations,the asymptotic stability of the presented methods for Volterra delay-integro-differential equations are proved under some weaker conditions than those in the literature.An extension of the stability results to such equations with weakly singular kernel is also discussed.

REQUIRED NUMBER OF ITERATIONS FOR SPARSE SIGNAL RECOVERY VIA ORTHOGONAL LEAST SQUARES

In countless applications,we need to reconstruct a K-sparse signal x∈R n from noisy measurements y=Φx+v,whereΦ∈R^(m×n)is a sensing matrix and v∈R m is a noise vector.Orthogonal least squares(OLS),which selects at each step the column that results in the most significant decrease in the residual power,is one of the most popular sparse recovery algorithms.In this paper,we investigate the number of iterations required for recovering x with the OLS algorithm.We show that OLS provides a stable reconstruction of all K-sparse signals x in[2.8K]iterations provided thatΦsatisfies the restricted isometry property(RIP).Our result provides a better recovery bound and fewer number of required iterations than those proposed by Foucart in 2013.

De Novo Design and Synthesis of Polypeptide Immunomodulators for Resetting Macrophage Polarization

Modulating the extracellular matrix microenvironment is critical for achieving the desired macrophage phenotype in immune investigations or tumor therapy.Combining de novo protein design and biosynthesis techniques,herein,we designed a biomimetic polypeptide self-assembled nano-immunomodulator to trigger the activation of a specific macrophage phenotype.It was intended to be made up of(GGSGGPGGGPASAAANSASRATSNSP)n,the RGD motif from collagen,and the IKVAV motif from laminin.The combination of these domains allows the biomimetic polypeptide to assemble into extracellular matrix-like nanofibrils,creating an extracellular matrix-like milieu for macrophages.Furthermore,changing the concentration further provides a facile route to fine-tune macrophage polarization,which enhances antitumor immune responses by precisely resetting tumor-associated macrophage immune responses into an M1-like phenotype,which is generally considered to be tumor-killing macrophages,primarily antitumor,and immune-promoting.Unlike metal or synthetic polymer-based nanoparticles,this polypeptide-based nanomaterial exhibits excellent biocompatibility,high efficacy,and precise tunability in immunomodulatory effectiveness.These encouraging findings motivate us to continue our research into cancer immunotherapy applications in the future.

穿透性角膜移植术与板层角膜移植术治疗圆锥角膜术后客观视觉质量比较

目的:探讨采用双通道视觉质量分析系统(OQAS)评估圆锥角膜患者行穿透性角膜移植术(PKP)和板层角膜移植术(LKP)后的客观视觉质量。方法:前瞻性临床研究。收集2016年1月至2017年12月在青岛眼科医院因圆锥角膜行角膜移植的患者40例进行研究,其中PKP组23例(24眼),LKP组17例(19眼),术前2组患者最佳矫正视力、屈光度和临床分期差异均无统计学意义,术后随访并应用OQAS检查术后的客观视觉质量,检查指标包括客观散射指数(OSI)、调制传递函数(MTF)截止频率、客观对比度视力和泪膜质量OSI变化。分类变量比较采用χ^2检验,组间连续变量比较采用独立样本t检验。结果:术后随访23~25个月,PKP组和LKP组患者角膜植片均保持透明状态,2组间最佳矫正视力、球镜度和柱镜度差异均无统计学意义,但PKP组角膜内皮细胞计数明显低于LKP组(t=3.91,P<0.001)。PKP组的斯特列尔比、20%对比度视力、9%对比度视力以及OSI与LKP组相比,差异均无统计学意义。PKP组的MTF截止频率和100%对比度视力较LKP组高,差异均有统计学意义(t=2.58,P=0.01;t=2.66,P=0.01)。泪膜质量OSI在LKP组明显高于PKP组,差异有统计学意义(t=3.48,P<0.001)。结论:双通道OQAS测量结果表明圆锥角膜患者行PKP术后的客观视觉质量优于行LKP术后,PKP术后的MTF截止频率和对比度视力高于LKP术后。

Optimal Superconvergence of Energy Conserving Local Discontinuous Galerkin Methods for Wave Equations

This paper is concerned with numerical solutions of the LDG method for 1D wave equations.Superconvergence and energy conserving properties have been studied.We first study the superconvergence phenomenon for linear problems when alternating fluxes are used.We prove that,under some proper initial discretization,the numerical trace of the LDG approximation at nodes,as well as the cell average,converge with an order 2k+1.In addition,we establish k+2-th order and k+1-th order superconvergence rates for the function value error and the derivative error at Radau points,respectively.As a byproduct,we prove that the LDG solution is superconvergent with an order k+2 towards the Radau projection of the exact solution.Numerical experiments demonstrate that in most cases,our error estimates are optimal,i.e.,the error bounds are sharp.In the second part,we propose a fully discrete numerical scheme that conserves the discrete energy.Due to the energy conserving property,after long time integration,our method still stays accurate when applied to nonlinear Klein-Gordon and Sine-Gordon equations.

Numerical Investigations of a Class of Biological Models on Unbounded Domain

This paper is concerned with numerical computations of a class of biologi-cal models on unbounded spatial domains.To overcome the unboundedness of spatial domain,we first construct efficient local absorbing boundary conditions(LABCs)to re-formulate the Cauchy problem into an initial-boundary value(IBV)problem.After that,we construct a linearized finite difference scheme for the reduced IVB problem,and provide the corresponding error estimates and stability analysis.The delay-dependent dynamical properties on the Nicholson’s blowflies equation and the Mackey-Glass equa-tion are numerically investigated.Finally,numerical examples are given to demonstrate the efficiency of our LABCs and theoretical results of the numerical scheme.