基于无线网络的拖拉机遥操作系统设计与试验

为降低驾驶员的劳动强度以及改善其工作条件,设计了一套基于无线网络的拖拉机遥操作系统。首先提出了拖拉机遥操作系统总体设计方案,然后针对茂源MY250型拖拉机进行了执行机构改造,包括离合、制动、转向、油门、熄火执行机构以及启动控制,并设计了遥操作控制系统,包括用户界面与车载控制系统。最后进行了通信性能测试、执行功能测试与驾驶试验。结果表明,遥操作系统平均指令通信时延为0.074 ms,视频时延最大不超过373 ms,拖拉机各执行机构控制误差最大不超过2.21%,行驶速度为2.08 km/h时,直线行驶最大误差绝对值不超过208.5 mm,RMS误差最大不超过85.5 mm。

Ordered Macroporous MoS_(2)-Carbon Composite with Fast and Robust Sodium Storage Properties to Solve the Issue of Kinetics Mismatch of Sodium-Ion Capacitors

Metal-ion capacitors(including Li^(+),Na^(+),and K^(+))effectively combine a battery negative electrode capable of reversibly intercalating metal cations,together with an electrical double-layer positive electrode.However,such novel cell design has a birth defect,namely kinetics mismatch between sluggish negative electrode and fast positive electrode,thus limiting the energy-power performance.Herein,we design a MoS_(2)-carbon composite anode with the ordered macroporous architecture and interlayer-expanded feature,exhibiting the fast and reversible Na^(+)redox processes.This kinetically favored anode is coupled with a homemade activated carbon cathode that allows for the excellent electrochemical performance of sodiumion capacitor with respect to large specific capacity,high-rate capability,and robust cycling.Through quantification of the potential swings of anode and cathode via a three-electrode Swagelok cell,we for the first time observe the abnormal variation law of potential swings and thus directly providing the evidence that the kinetics gap has been filled up by this kinetically favored anode.Our results represent a crucial step toward understanding the key issues of kinetics mismatch for hybrid cell,thus propelling the development of design of kinetically favored anode materials for high-performance metalion capacitors.

Dynamic Testing of an IEC 61850 Based 110 kV Smart Substation Solution

This paper presents the dynamic simulation and testing to verify the smart substation solutions designed for a brown field 110 kV retrofitting project. An IEC 61850 based aotomation design, transitioning the conventional substation into a smart substation, where existing current/voltage transformers remain in service, and smart Field Apparatus Interface Units (FAIUs) are utilised to bridge the conventional primary system to the IEC 61850 based secondary system. While outdoor switchgears and field instrument transformers are equipped with FAIUs, MV indoor switchgears are installed with IEDs mounted on the top. Direct point-to-point connections serve as process buses, and a single PRP/RSTP LAN is employed at station bus level. Extensive dynamic simulation and testing were conducted in the Smart Substation Technologies Lab, and test results show the smart substation performance meets and exceeds the substation reliability requirement.

Developmental toxicity assessment of neonicotinoids and organophosphate esters with a human embryonic stem cell-and metabolism-based fast-screening model

In recent years,neonicotinoids(NEOs)and organophosphate esters(OPEs)have been widely used as substitutes for traditional pesticides and brominated fame-retardants,respectively.Previous studies have shown that those compounds can be frequently detected in environmental and human samples,are able to penetrate the placental barrier,and are toxic to animals.Thus,it is reasonable to speculate that NEOs and OPEs may have potential adverse effects in humans,especially during development.We employed a human embryonic stem cell differentiation-and liver S9 fraction metabolism-based fast screening model to assess the potential embryonic toxicity of those two types of chemicals.We show that four NEO and five OPE prototypes targeted mostly ectoderm specification,as neural ectoderm and neural crest genes were down-regulated,and surface ectoderm and placode markers up-regulated.Human liver S9 fraction's treatment could generally reduce the effects of the chemicals,except in a few specific instances,indicating the liver may detoxify NEOs and OPEs.Our findings suggest that NEOs and OPEs interfere with human early embryonic development.

Temperature regulates negative supercoils to modulate meiotic crossovers and chromosome organization

Crossover recombination is a hallmark of meiosis that holds the paternal and maternal chromosomes(homologs)together for their faithful segregation,while promoting genetic diversity of the progeny.The pattern of crossover is mainly controlled by the architecture of the meiotic chromosomes.Environmental factors,especially temperature,also play an important role in modulating crossovers.However,it is unclear how temperature affects crossovers.Here,we examined the distribution of budding yeast axis components(Red1,Hop1,and Rec8)and the crossover-associated Zip3 foci in detail at different temperatures,and found that both increased and decreased temperatures result in shorter meiotic chromosome axes and more crossovers.Further investigations showed that temperature changes coordinately enhanced the hyperabundant accumulation of Hop1 and Red1 on chromosomes and the number of Zip3 foci.Most importantly,temperature-induced changes in the distribution of axis proteins and Zip3 foci depend on changes in DNA negative supercoils.These results suggest that yeast meiosis senses temperature changes by increasing the level of negative supercoils to increase crossovers and modulate chromosome organization.These findings provide a new perspective on understanding the effect and mechanism of temperature on meiotic recombination and chromosome organization,with important implications for evolution and breeding.

巩膜接触镜的临床应用及研究进展

巩膜接触镜是一种不与角膜接触,完全由巩膜支撑的大直径、硬性、透气性接触镜。过去巩膜接触镜仅用于治疗严重的眼部疾病且仅少数医生拥有验配处方权。近年来,随着镜片材料、设计的不断更新,巩膜接触镜的安全性在不断提高,其应用范围也日渐广泛。巩膜接触镜可通过中和光学像差为角膜不规则患者提供清晰稳定的视力,还可有效治疗各种眼表疾病,已成为一种新型的眼表疾病治疗手段。尽管巩膜接触镜应用于临床治疗的有效性已得到充分证明,但巩膜接触镜的验配及使用较复杂,且需要长期的随访和护理。现就巩膜接触镜的特性和分类、发展历程、临床应用以及不良反应等方面进行阐述,以全面了解巩膜接触镜的现状,为巩膜接触镜的应用提供参考。

COVID-19 containment: China provides important lessons for global response

The world must act fast to contain wider international spread of the epidemic of COVID-19 now.The unprecedented public health efforts in China have contained the spread of this new virus.Measures taken in China are currently proven to reduce human-to-human transmission successfully.We summarized the effective intervention and prevention measures in the fields of public health response,clinical management,and research development in China,which may provide vital lessons for the global response.It is really important to take collaborative actions now to save more lives from the pandemic of COVID-19.

Estimation of reproduction numbers of COVID-19 in typical countries and epidemic trends under different prevention and control scenarios

The coronavirus disease 2019(COVID-19)has become a life-threatening pandemic.The epidemic trends in different countries vary considerably due to different policy-making and resources mobilization.We calculated basic reproduction number(R0)and the time-varying estimate of the effective reproductive number(Rt)of COVID-19 by using the maximum likelihood method and the sequential Bayesian method,respectively.European and North American countries possessed higher (R0)and unsteady Rt fluctuations,whereas some heavily affected Asian countries showed relatively low (R0)and declining Rt now.The numbers of patients in Africa and Latin America are still low,but the potential risk of huge outbreaks cannot be ignored.Three scenarios were then simulated,generating distinct outcomes by using SEIR(susceptible,exposed,infectious,and removed)model.First,evidence-based prompt responses yield lower transmission rate followed by decreasing Rt.Second,implementation of effective control policies at a relatively late stage,in spite of huge casualties at early phase,can still achieve containment and mitigation.Third,wisely taking advantage of the time-window for developing countries in Africa and Latin America to adopt adequate measures can save more people’s life.Our mathematical modeling provides evidence for international communities to develop sound design of containment and mitigation policies for COVID-19.

Formation processes and source contributions of ground-level ozone in urban and suburban Beijing using the WRF-CMAQ modelling system

Beijing faces the challenge of high levels of ozone(O_(3))pollution.In this study,the Weather Research and Forecasting model and Community Multiscale Air Qualitymodel(CMAQ)were used to simulate atmospheric O_(3) concentrations in Beijing.To investigate the formation mechanisms and source contributions of O_(3) pollution in different regions of Beijing,process analysis and the integrated source apportionmentmethodwithin the CMAQwere applied to O_(3) concentrations in the summer of 2018.The process analysis results showed that vertical diffusion was the major contributor to O_(3) concentrations at all receptor sites in Beijing,at>65.94μg/(m^(3)·hr).Gas-phase chemical reactions consumed a significant amount of O_(3) in urban and inner suburban areas(>−5.57μg/(m^(3)·hr)),while near-surface chemical reactions made positive contributions in outer suburban areas(>4.72μg/(m^(3)·hr)).The O_(3) formation chemical reactions indicated that NO titration,which removes O_(3) at night-time,mainly occurred in urban areas.The weaker chemical reactions occurring near the surface in outer suburbs suggested that suburban-area O_(3) was produced in the upper atmospheric layers and was transported vertically to the lower layers.The O_(3) source apportionment results showed that boundary contributions were the dominant contributor to O_(3) pollution in Beijing(>40%).The contribution of non-local emissions to O_(3) levels was significantly greater in the outer suburbs than in urban and inner suburban areas due to topography.This study increases the understanding of the complex processes of O_(3) formation in different areas of Beijing and informs the implementation of O_(3) control plans.

具梯度项及非线性非齐次项的∞-Laplace方程

本文研究Ω上规范化∞-Laplace方程的Dirichlet问题∆n∞u+a|Du|=f(x,u),u|∂Ω=g,其中ΩC R^n是有界区域,a∈R,f∈C(Ω×R;R),g∈C(∂Ω),给出确保解存在的有关非齐次项f的充分条件.进一步,对一般的f,得到当区域Ω足够小时,解存在;当区域Ω足够大且f不变号时,除了可能的常数解外,不存在其他解.特别地,本文给出梯度项对解的存在与不存在性的本质影响.本文通过一些具体例子阐释上述结论,并且给出关于f(x,u)=-λu^p-δ情形Dirichlet问题正解存在性结果的清晰的完全刻画,其中涉及一个有关梯度项系数的"阈值".

Scalable synthesis of macroscopic porous carbon sheet anode for potassium-ion capacitor

Carbon materials hold the great promise for application in energy storage devices owing to their low cost, high thermal/chemical stability, and high electrical conductivity. However, it remains challenging to synthesize high-performance carbon electrodes in a simple, scalable and sustainable way. Here, we report a facile method for scalable synthesis of porous carbon anode by using cheap and easily accessible zeolitic imidazolate framework-8 as a template and polyvinylpyrrolidone as an additional carbon source. The obtained porous carbon shows the macroscopic sheet-like morphology, which has the highly disordered structure, expanded interlayer spacing, abundant pore structure, and nitrogen doping properties. This porous carbon anode is demonstrated to have the excellent K^(+) charge storage properties in specific capacity, rate capability, and cycling stability. A potassium-ion capacitor assembled by using this porous carbon as the anode, delivers a maximum energy density of 85.12 Wh/kg and power density of 11860 W/kg as well as long cycle life exceeding 3000 cycles. This represents a critical advance in the design of low cost and scalable carbon material for applications in energy storage devices.

Phase-and epidemic region-adjusted estimation of the number of coronavirus disease 2019 cases in China

The outbreak of the coronavirus disease 2019 in China was first reported in Wuhan in December 2019 and gradually spread to other areas in China.After implementation of prevention and control measures,the estimation of the epidemic trend is needed.A phase-and region-adjusted SEIR model was applied for modeling and predicting the number of cases in Wuhan,Hubei Province and regions outside Hubei Province in China.The estimated number of infections could reach its peak in late February 2020 in Wuhan and Hubei Province,which is 55303–84520 and 83944–129312,respectively,while the epidemic peaks in regions outside Hubei Province in China could appear on February 13,2020 with the estimated 13035–19108 cases.According to the estimation,the outbreak would abate in March and April all over China.Current estimation provided evidence for planned work resumption under stringent prevention and control in China to further support the fight against the epidemic.Nevertheless,there is still possibility of the second outbreak brought by the work resumption and population migration,especially from Hubei Province and high intensity cities outside Hubei Province.Strict prevention and control measures still need to be considered in the regions with high intensity of epidemic and densely-populated cities.

Progress and perspectives on two-dimensional silicon anodes for lithium-ion batteries

Silicon(Si)anodes with extremely high theoretical capacities are considered indispensable for next-generation high-energy lithium-ion batteries(LIBs).However,several intractable problems,including pulverization,poor electrical contact,and continuous side reactions caused by the large volume change of Si during lithia-tion/delithiation,lead to a short cycle life and poor rate capability,thus hindering the commercial use of Si anodes in LIBs.Two-dimensional(2D)Si with a unique graphene-like structure has a short ion diffusion path-way,small volume change during lithiation,and efficient redox site utilization,making it more promising than bulk Si or Si with other versatile structures for use in LIBs.Theoretical analysis demonstrated that the low energy barrier on the surface of 2D Si accelerates the transport of Li+.However,the issues surrounding 2D Si,includ-ing the tedious and user-unfriendly synthesis,ease of restacking,and atmospheric sensitivity,limit its practical applications,which are discussed in this review.Furthermore,possible solutions to these remaining challenges and new directions are provided,with the aim of designing practical and high-performance 2D Si anodes for next-generation LIBs.

Advanced all-solid-state lithium-selenium batteries enabled by selenium-nitrogen doped hierarchic meso-microporous carbon nanospheres composite cathode

Selenium,an element belonging to the same group in the periodic table as sulfur,has a high electronic conductivity(1×10^(-5)S/cm)and a high volumetric energy density(3253 mA h/cm^(3)),which is a prospective cathode material for high-energy all-solid-state rechargeable batteries.However,its wide use is hindered by large volume expansion and low utilization rate.In this work,Se-infused nitrogen-doped hierarchical meso-microporous carbon composites(Se/NHPC)are prepared by a melt-diffusion process.Amorphous Se is uniformly dispersed in meso-micropores of NHPC with a high mass loading of 81%.All-solid-state Li-Se batteries fabricated by using Se/NHPC as the cathode,a Li-In alloy as the anode,and Li_(6)PS_(5)Cl as the solid-state electrolyte,deliver a highly reversible capacity of 621 m Ah/g(92%of theoretical capacity),a good rate capability and a high capacity retention value of 80.9%after 100 cycles.It is found that the capacity decay of Se cathode is mainly related to the interfacial degradation and the separation of Se from the carbon substrate,as suggested by the continuous increase of interfacial resistance and the structural transformation from amorphous Senchains to Se8rings initial discharge/charge cycle and then to the trigonally crystalline Se chains structure after the long-term cycles.