Dynamics and synchronization in a memristor-coupled discrete heterogeneous neuron network considering noise

Research on discrete memristor-based neural networks has received much attention.However,current research mainly focuses on memristor–based discrete homogeneous neuron networks,while memristor-coupled discrete heterogeneous neuron networks are rarely reported.In this study,a new four-stable discrete locally active memristor is proposed and its nonvolatile and locally active properties are verified by its power-off plot and DC V–I diagram.Based on two-dimensional(2D)discrete Izhikevich neuron and 2D discrete Chialvo neuron,a heterogeneous discrete neuron network is constructed by using the proposed discrete memristor as a coupling synapse connecting the two heterogeneous neurons.Considering the coupling strength as the control parameter,chaotic firing,periodic firing,and hyperchaotic firing patterns are revealed.In particular,multiple coexisting firing patterns are observed,which are induced by different initial values of the memristor.Phase synchronization between the two heterogeneous neurons is discussed and it is found that they can achieve perfect synchronous at large coupling strength.Furthermore,the effect of Gaussian white noise on synchronization behaviors is also explored.We demonstrate that the presence of noise not only leads to the transition of firing patterns,but also achieves the phase synchronization between two heterogeneous neurons under low coupling strength.

Dynamical behavior of memristor-coupled heterogeneous discrete neural networks with synaptic crosstalk

Synaptic crosstalk is a prevalent phenomenon among neuronal synapses,playing a crucial role in the transmission of neural signals.Therefore,considering synaptic crosstalk behavior and investigating the dynamical behavior of discrete neural networks are highly necessary.In this paper,we propose a heterogeneous discrete neural network(HDNN)consisting of a three-dimensional KTz discrete neuron and a Chialvo discrete neuron.These two neurons are coupled mutually by two discrete memristors and the synaptic crosstalk is considered.The impact of crosstalk strength on the firing behavior of the HDNN is explored through bifurcation diagrams and Lyapunov exponents.It is observed that the HDNN exhibits different coexisting attractors under varying crosstalk strengths.Furthermore,the influence of different crosstalk strengths on the synchronized firing of the HDNN is investigated,revealing a gradual attainment of phase synchronization between the two discrete neurons as the crosstalk strength decreases.

Study of the spatial growth of stimulated Brillouin scattering in a gas-filled hohlraum via detecting the driven ion acoustic wave

In an experiment performed on the Shenguang-III prototype laser facility, collective Thomson scattering (TS) is used to study the spatialgrowth of stimulated Brillouin scattering (SBS) in a gas-filled hohlraum by detecting the SBS-driven ion acoustic wave. High-quality timeresolved SBS and TS spectra are obtained simultaneously in the experiment, and these are analyzed by a steady-state code based on theray-tracing model. The analysis indicates that ion–ion collisions may play an important role in suppressing SBS growth in the Au plasma;as aresult, the SBS excited in the filled gas region is dominant. In the early phase of the laser pulse, SBS originates primarily from the high-densityplasma at the edges of the interaction beam channel, which is piled up by the heating of the interaction beam. Throughout the duration of thelaser pulse, the presence of the TS probe beam might mitigate SBS by perturbing the density distribution around the region overlapping withthe interaction beam.

Construction of 2D Zn‐MOF/BiVO_(4)S‐scheme heterojunction for efficient photocatalytic CO_(2) conversion under visible light irradiation

The construction of S‐scheme heterojunction photocatalysts has been regarded as an effective avenue to facilitate the conversion of solar energy to fuel.However,there are still considerable challenges with regard to efficient charge transfer,the abundance of catalytic sites,and extended light absorption.Herein,an S‐scheme heterojunction of 2D/2D zinc porphyrin‐based metal‐organic frameworks/BiVO_(4)nanosheets(Zn‐MOF/BVON)was fabricated for efficient photocatalytic CO_(2)conversion.The optimal one shows a 22‐fold photoactivity enhancement when compared to the previously reported BiVO4 nanoflake(ca.15 nm),and even exhibits~2‐time improvement than the traditional g‐C3N4/BiVO4 heterojunction.The excellent photoactivities are ascribed to the strengthened S‐scheme charge transfer and separation,promoted CO_(2)activation by the well‐dispersed metal nodes Zn_(2)(COO)_(4)in the Zn‐MOF,and extended visible light response range based on the results of the electrochemical reduction,electron paramagnetic resonance,and in‐situ diffuse reflectance infrared Fourier transform spectroscopy.The dimension‐matched Zn‐MOF/BVON S‐scheme heterojunction endowed with highly efficient charge separation and abundant catalytic active sites contributed to the superior CO2 conversion.This study offers a facile strategy for constructing S‐scheme heterojunctions involving porphyrin‐based MOFs for solar fuel production.

A Survey of Human-centered Intelligent Robots:Issues and Challenges

Intelligent techniques foster the dissemination of new discoveries and novel technologies that advance the ability of robots to assist and support humans. The human-centered intelligent robot has become an important research field that spans all of the robot capabilities including navigation, intelligent control, pattern recognition and human-robot interaction. This paper focuses on the recent achievements and presents a survey of existing works on human-centered robots. Furthermore, we provide a comprehensive survey of the recent development of the human-centered intelligent robot and discuss the issues and challenges in the field.

NeuroBiometric:An Eye Blink Based Biometric Authentication System Using an Event-Based Neuromorphic Vision Sensor

The rise of the Internet and identity authentication systems has brought convenience to people's lives but has also introduced the potential risk of privacy leaks.Existing biometric authentication systems based on explicit and static features bear the risk of being attacked by mimicked data.This work proposes a highly efficient biometric authentication system based on transient eye blink signals that are precisely captured by a neuromorphic vision sensor with microsecond-level temporal resolution.The neuromorphic vision sensor only transmits the local pixel-level changes induced by the eye blinks when they occur,which leads to advantageous characteristics such as an ultra-low latency response.We first propose a set of effective biometric features describing the motion,speed,energy and frequency signal of eye blinks based on the microsecond temporal resolution of event densities.We then train the ensemble model and non-ensemble model with our Neuro Biometric dataset for biometrics authentication.The experiments show that our system is able to identify and verify the subjects with the ensemble model at an accuracy of 0.948 and with the non-ensemble model at an accuracy of 0.925.The low false positive rates(about 0.002)and the highly dynamic features are not only hard to reproduce but also avoid recording visible characteristics of a user's appearance.The proposed system sheds light on a new path towards safer authentication using neuromorphic vision sensors.

The impact of academic stress on medical students attending college in the Inner Mongolia Area of China

The aim of this study was to examine whether student characteristics affect the risk of health conditions, and explore whether the degree of academic stress affects the level of distress. We surveyed medical students in the Inner Mongolia Medical College China using a questionnaire. A logistic regression analysis was used to ascertain factors associated with distress. The Wilcoxon Mann-Whitney test was used to determine the relationship between distress and different academic stress levels. Of the 6044 students completing questionnaires, 47.5% self-reported distressing body symptoms induced by academic stress. Chi square tests showed statistically significant associations between distress and gender, academic stress, and residence;feeling academic stress caused a more than 1.5 times risk of distress. Gender and academic stress were significantly associated with distress in non-conditional binary logistic regression models. Compared with male students, female students was more likely to feel distress. The Wilcoxon Mann-Whitney test also showed that the distress rate increased with academic stress and a dose-response relationship between the distress rate and stress level was found. The present study indicates that it is important to reduce academic stress and manage it in order that better outcomes be achieved in regard to distress, especially in females.

Guest Editorial for Special Issue on Human-centered Intelligent Robots:Issues and Challenges

The special issue aims to address a broad spectrum of topics ranging from human-centered intelligent robots acting as a servant,secretary,or companion to intelligent robotic functions.The special issue publishes original papers of innovative ideas and concepts,new discoveries,and novel applications and business models relevant to the field of human-centered intelligent robots.In this special issue,modeling,intelligent control,

Wearable Robots for Human Underwater Movement Ability Enhancement:A Survey

Underwater robot technology has shown impressive results in applications such as underwater resource detection.For underwater applications that require extremely high flexibility,robots cannot replace skills that require human dexterity yet,and thus humans are often required to directly perform most underwater operations.Wearable robots(exoskeletons)have shown outstanding results in enhancing human movement on land.They are expected to have great potential to enhance human underwater movement.The purpose of this survey is to analyze the state-of-the-art of underwater exoskeletons for human enhancement,and the applications focused on movement assistance while excluding underwater robotic devices that help to keep the temperature and pressure in the range that people can withstand.This work discusses the challenges of existing exoskeletons for human underwater movement assistance,which mainly includes human underwater motion intention perception,underwater exoskeleton modeling and human-cooperative control.Future research should focus on developing novel wearable robotic structures for underwater motion assistance,exploiting advanced sensors and fusion algorithms for human underwater motion intention perception,building up a dynamic model of underwater exoskeletons and exploring human-in-theloop control for them.

Influence of Modifier in Supercritical CO₂on Qualitative and Quantitative Extraction Results of <i>Eucalyptus</i>Ecential Oil

A supercritical CO2 extraction behavior of Eucalyptus oil was investigated under different conditions of pressure, temperature and time with or without cosolvent. The pressure range was from 8 to 25 MPa, temperature from 35 to 55&deg;C and CO2 flow rate from 10 to 26 g/min. For 1,8-cineole the appropriate extracting pressure was 15 MPa and temperature was 45&deg;C. When CO2 flow rate was 18 g/min, it was benefit to extract the other three substances (limonene, p-cymene and γ-terpinene, respectively) except 1,8-cineole. Prolonging extraction time could not obviously increase the extract concentration, but the extract yield would increase. The results also indicated that ethanol as a modifier could improve extraction velocity and extraction concentration.

Cancer mortality in Inner Mongolia of China, 2008-2010

Objective: The aim of our study was to determine the status of the common cancer in Inner Mongolia of China. Methods: We obtained data from the Centers for Disease Control in the Inner Mongolia from five monitoring points of DRS in Inner Mongolia from 2008 to 2010. We calculated the crude mortality, the proportion of all cause of death during the three years, further calculated cancer mortality, the proportion of cancer death and PYLL by genders. Results: During the period 2008-2010, the crude mortality of all cause of death is 518.02 per million in Inner Mongolia. As the second most common cause of death, the mortality dying from cancer is 127.11 per million, accounting for over one fifth of all deaths. Among all deaths from cancer, the lung cancer had the highest mortality rates (46.25 per million in males and 17.95 per million in females) and PYLL (0.72 in males and 0.41 in females), followed by the liver cancer (23.76 per million) and the gastric cancer (16.15 per million). The female breast cancer is the fourth leading cancer from mortality and PYLL for 7.65 per million and 0.17. Conclusion: Our analysis determined the severity of cancer death in Inner Mongolia of China from 2008 to 2010.Our study found that the cancer mortality in Inner Mongolia is lower than Chinese average level and most west countries, higher than some Africa countries. Our results will guide future cancer control strategies in Inner Mongolia of China.

INVARIANTS-PRESERVING DU FORT-FRANKEL SCHEMES AND THEIR ANALYSES FOR NONLINEAR SCHRÖDINGER EQUATIONS WITH WAVE OPERATOR

Du Fort-Frankel finite difference method(FDM)was firstly proposed for linear diffusion equations with periodic boundary conditions by Du Fort and Frankel in 1953.It is an explicit and unconditionally von Neumann stable scheme.However,there has been no research work on numerical solutions of nonlinear Schrödinger equations with wave operator by using Du Fort-Frankel-type finite difference methods(FDMs).In this study,a class of invariants-preserving Du Fort-Frankel-type FDMs are firstly proposed for one-dimensional(1D)and two-dimensional(2D)nonlinear Schrödinger equations with wave operator.By using the discrete energy method,it is shown that their solutions possess the discrete energy and mass conservative laws,and conditionally converge to exact solutions with an order of for ofο(T^(2)+h_(x)^(2)+(T/h_(x))^(2))1D problem and an order ofο(T^(2)+h_(x)^(2)+h_(Y)^(2)+(T/h_(X))^(2)+(T/h_(y))^(2))for 2D problem in H1-norm.Here,τdenotes time-step size,while,hx and hy represent spatial meshsizes in x-and y-directions,respectively.Then,by introducing a stabilized term,a type of stabilized invariants-preserving Du Fort-Frankel-type FDMs are devised.They not only preserve the discrete energies and masses,but also own much better stability than original schemes.Finally,numerical results demonstrate the theoretical analyses.

聚丙烯/石墨烯纳米复合材料的等温结晶和结晶形态

研究了熔融混合制备的聚丙烯(PP)/热还原氧化石墨烯(TRG)纳米复合材料的等温结晶行为,并探讨TRG对PP等温结晶动力学、结晶的熔融行为以及结晶形态的影响。结果表明,加入TRG可显著提高体系的结晶速率,使PP的平衡熔点升高(TRG为1.5%时提高11℃),结晶度增大(TRG为1.5%时增大6.6%),结晶完善程度提高。用Avrami方程进行等温结晶动力学研究表明,参数n对结晶温度有一定依赖性且加入TRG使n值增大,TRG具有较好的异相成核作用,使PP的半结晶时间缩短60%以上。此外,复合体系中生成的球晶尺寸显著减小。

首发单纯骨转移乳腺癌患者的临床病理特征及预后分析

目的:探讨乳腺癌首发单纯骨转移(bone-only metastasis,BOM)患者的临床病理学特征及预后特点。方法:回顾性分析2009年1月至2016年12月967例于天津医科大学肿瘤医院治疗的转移性乳腺癌患者的临床病理资料。分为180例BOM组与787例非BOM组,对BOM组患者的预后因素行单因素分析和Cox回归模型多因素分析,并根据激素受体(hormone receptor,HR)状态、转移数目及治疗方式行亚组分析。结果:BOM组与非BOM组患者的中位无进展生存(progression-free survival,PFS)时间分别为19.4个月与10.0个月,BOM组中位总生存(overall survival,OS)时间为45.6个月。BOM组与非BOM组HR阳性患者分别占81.7%(147/180)与64.7%(509/787)(P<0.001)。Cox回归模型多因素分析显示HR状态、转移位置、转移数目和治疗方式是BOM患者预后的独立影响因素。BOM组的HR阳性患者内分泌治疗(P=0.004)或联合治疗(P<0.001)较单独化疗的预后更佳。影响BOM组HR阳性患者预后的主要因素为骨转移数目和内分泌治疗。单部位骨转移患者行内分泌治疗(P=0.004)或联合治疗(P=0.002)较单独化疗的预后更佳,多部位骨转移患者行联合治疗较单独化疗(P<0.001)或内分泌治疗(P=0.04)的预后更佳。结论:对于HR阳性BOM尤其是单部位骨转移患者,单纯内分泌治疗可获得较为满意的疗效,而对于多部位BOM则应考虑行联合治疗。

Comparisons of passive microwave remote sensing sea ice concentrations with ship-based visual observations during the CHINARE Arctic summer cruises of 2010–2018

In order to apply satellite data to guiding navigation in the Arctic more effectively,the sea ice concentrations(SIC)derived from passive microwave(PM)products were compared with ship-based visual observations(OBS)collected during the Chinese National Arctic Research Expeditions(CHINARE).A total of 3667 observations were collected in the Arctic summers of 2010,2012,2014,2016,and 2018.PM SIC were derived from the NASA-Team(NT),Bootstrap(BT)and Climate Data Record(CDR)algorithms based on the SSMIS sensor,as well as the BT,enhanced NASA-Team(NT2)and ARTIST Sea Ice(ASI)algorithms based on AMSR-E/AMSR-2 sensors.The daily arithmetic average of PM SIC values and the daily weighted average of OBS SIC values were used for the comparisons.The correlation coefficients(CC),biases and root mean square deviations(RMSD)between PM SIC and OBS SIC were compared in terms of the overall trend,and under mild/normal/severe ice conditions.Using the OBS data,the influences of floe size and ice thickness on the SIC retrieval of different PM products were evaluated by calculating the daily weighted average of floe size code and ice thickness.Our results show that CC values range from 0.89(AMSR-E/AMSR-2 NT2)to 0.95(SSMIS NT),biases range from−3.96%(SSMIS NT)to 12.05%(AMSR-E/AMSR-2 NT2),and RMSD values range from 10.81%(SSMIS NT)to 20.15%(AMSR-E/AMSR-2 NT2).Floe size has a significant influence on the SIC retrievals of the PM products,and most of the PM products tend to underestimate SIC under smaller floe size conditions and overestimate SIC under larger floe size conditions.Ice thickness thicker than 30 cm does not have a significant influence on the SIC retrieval of PM products.Overall,the best(worst)agreement occurs between OBS SIC and SSMIS NT(AMSR-E/AMSR-2 NT2)SIC in the Arctic summer.

癌症患者维生素D营养状况分析

背景与目的维生素营养状况与癌症患者之间存在一定的关联,已有研究表明缺乏维生素会增加罹患癌症的风险,本研究的目的是了解癌症患者的维生素D营养状况,为进一步实施营养干预提供科学依据。方法本研究回顾性分析了2017年7月-2019年6月在山东省肿瘤医院就诊的癌症患者血清25-羟维生素D的水平,采用SPSS20.0统计软件进行单因素分析和多元线性回归分析。结果本研究共纳入2,487例癌症患者,平均血清25-羟维生素D的浓度为(12.70±6.82)ng/m L,纳入的癌症患者中维生素D缺乏者[25(OH)D<20.00 ng/m L]占比92.20%。单因素分析显示:年龄、身体质量指数(body mass index, BMI)和癌症类型(P<0.05)与维生素D缺乏显著相关。进一步的多因素分析显示,BMI(β=0.71)、年龄(β=-0.56)、季节(与夏季相比,冬季β=-0.99;秋季β=-0.76)和癌症的种类(与其他类型的癌症相比,肺癌β=-1.17;食管-胃癌β=-1.45;结直肠癌β=-1.05)与25-羟维生素D水平显著相关(P<0.05)。结论癌症患者25-羟维生素D水平偏低,存在严重的维生素D缺乏状况,其可能与年龄、BMI、季节和癌症类型有关,这表明应该加强对癌症患者维生素D水平的监测。

Construction of carbon nitride and MoS_2 quantum dot 2D/0D hybrid photocatalyst:Direct Z-scheme mechanism for improved photocatalytic activity

Graphite‐like carbon nitride(g‐C3N4)‐based compounds have attracted considerable attention because of their excellent photocatalytic performance.In this work,a novel direct Z‐scheme system constructed from two‐dimensional(2D)g‐C3N4nanoplates and zero‐dimensional(0D)MoS2quantum dots(QDs)was prepared through the combination of a hydrothermal process and microemulsion preparation.The morphologies,structures,and optical properties of the as‐prepared photocatalysts were characterized by X‐ray diffraction,X‐ray photoelectron spectroscopy,atomic force microscopy,transmission electron microscopy,and UV‐vis diffuse reflectance spectroscopy.In addition,the photocatalytic performances of the prepared2D/0D hybrid composites were evaluated based on the photodegradation of rhodamine B under visible‐light irradiation.The results demonstrated that the introduction of MoS2QDs to g‐C3N4greatly enhanced the photocatalytic efficiency.For the optimum7%MoS2QD/g‐C3N4photocatalyst,the degradation rate constant was8.8times greater than that of pure g‐C3N4under visible‐light irradiation.Photocurrent and electrochemical impedance spectroscopy results further demonstrated that the MoS2QD/g‐C3N4composites exhibited higher photocurrent density and lower chargetransfer resistance than those of the pure g‐C3N4or MoS2QDs.Active species trapping,terephthalic acid photoluminescence,and nitro blue tetrazolium transformation experiments were performed to investigate the evolution of reactive oxygen species,including hydroxyl radicals and superoxide radicals.The possible enhanced photocatalytic mechanism was attributed to a direct Z‐scheme system,which not only can increase the separation efficiency of photogenerated electron‐hole pairs but also possesses excellent oxidation and reduction ability for high photocatalytic performances.This work provides an effective synthesis approach and insight to help develop other C3N4‐based direct Z‐scheme photocatalytic systems for environmental purification and energy conversion.

Synthesis of TiO_2/g-C_3N_4 nanocomposites with phosphate–oxygen functional bridges for improved photocatalytic activity

One of the most general methods to enhance the separation of photogenerated carriers for g‐C3N4is to construct a suitable heterojunctional composite,according to the principle of matching energy levels.The interface contact in the fabricated nanocomposite greatly influences the charge transfer and separation so as to determine the final photocatalytic activities.However,the role of interface contact is often neglected,and is rarely reported to date.Hence,it is possible to further enhance the photocatalytic activity of g‐C3N4‐based nanocomposite by improving the interfacial connection.Herein,phosphate-oxygen(P-O)bridged TiO2/g‐C3N4nanocomposites were successfully synthesized using a simple wet chemical method,and the effects of the P-O functional bridges on the photogenerated charge separation and photocatalytic activity for pollutant degradation and CO2reduction were investigated.The photocatalytic activity of g‐C3N4was greatly improved upon coupling with an appropriate amount of nanocrystalline TiO2,especially with P-O bridged TiO2.Atmosphere‐controlled steady‐state surface photovoltage spectroscopy and photoluminescence spectroscopy analyses revealed clearly the enhancement of photogenerated charge separation of g‐C3N4upon coupling with the P-O bridged TiO2,resulting from the built P-O bridges between TiO2and g‐C3N4so as to promote effective transfer of excited electrons from g‐C3N4to TiO2.This enhancement was responsible for the improved photoactivity of the P-O bridged TiO2/g‐C3N4nanocomposite,which exhibited three‐time photocatalytic activity enhancement for2,4‐dichlorophenol degradation and CO2reduction compared with bare g‐C3N4.Furthermore,radical‐trapping experiments revealed that the·OH species formed as hole‐modulated direct intermediates dominated the photocatalytic degradation of2,4‐dichlorophenol.This work provides a feasible strategy for the design and synthesis of high‐performance g‐C3N4‐based nanocomposite photocatalysts for pollutant degradation and CO2reduction.

三阴性乳腺癌辅助化疗预后生物标志物的研究进展

三阴性乳腺癌(triple-negative breast cancer,TNBC)具有组织学分级高、临床分期晚、侵袭性强、易发生转移等特点。由于缺乏有效的治疗靶点,传统化疗仍是TNBC患者主要的治疗选择。作为高度异质性疾病,TNBC需要更为精确的预测生物标志物。组学技术的发展及临床试验的实施为辅助化疗预后生物标志物带来新的探索,涵盖基因、蛋白及微环境成分等不同维度,也包括多分子的联合分析应用。本文将对TNBC辅助化疗预后生物标志物及其潜在分子机制与未来发展方向进行综述。

Physical and optical characteristics of sea ice in the Pacific Arctic Sector during the summer of 2018

The reduction in Arctic sea ice in summer has been reported to have a significant impact on the global climate.In this study,Arctic sea ice/snow at the end of the melting season in 2018 was investigated during CHINARE-2018,in terms of its temperature,salinity,density and textural structure,the snow density,water content and albedo,as well as morphology and albedo of the refreezing melt pond.The interior melting of sea ice caused a strong stratification of temperature,salinity and density.The temperature of sea ice ranged from–0.8℃ to 0℃,and exhibited linear cooling with depth.The average salinity and density of sea ice were approximately 1.3 psu and 825 kg/m3,respectively,and increased slightly with depth.The first-year sea ice was dominated by columnar grained ice.Snow cover over all the investigated floes was in the melt phase,and the average water content and density were 0.74%and 241 kg/m3,respectively.The thickness of the thin ice lid ranged from 2.2 cm to 7.0 cm,and the depth of the pond ranged from 1.8 cm to 26.8 cm.The integrated albedo of the refreezing melt pond was in the range of 0.28–0.57.Because of the thin ice lid,the albedo of the melt pond improved to twice as high as that of the mature melt pond.These results provide a reference for the current state of Arctic sea ice and the mechanism of its reduction.