基于J-C本构模型的金属拉伸实验模拟研究

本研究基于J-C本构模型对金属拉伸实验进行了模拟研究。首先,参考国家标准GB/T 228.1-2021《金属材料拉伸实验第1部分:室温试验方法》制作实验检材,并进行拉伸实验。其次,利用线性回归对实验数据进行求解,计算出Abaqus内J-C本构模型所需的参数数值。接着将获得的材质参数输入Abaqus有限元分析软件内进行材质的选择和模拟模型的建立,并施加一端固定约束,一端线性位移的边界条件。最后,将模拟求得的应力与应变输出后绘图,与实验中采集的应力与应变进行比对分析。研究结果表明,基于J-C的本构模拟对于金属材料的单轴拉伸实验具有较好的还原性,其模拟结果与真实数据较为接近,且应力集中和断裂点判断较为准确。

注塑和3D打印聚乳酸/乙烯-醋酸乙烯共聚物共混物形态和韧性

将聚乳酸与韧性聚合物共混是改善聚乳酸韧性的有效途径。文中报道了韧性良好的乙烯-醋酸乙烯共聚物(EVA)与聚乳酸共混,获得增韧聚乳酸。发现EVA对聚乳酸的增韧效果与成型加工方法有关:注塑成型的EVA/聚乳酸共混物中,EVA呈球状分布,可以明显提高冲击强度;3D打印成型的EVA/聚乳酸共混物中,EVA呈独特微纤结构,对增韧有利,可以克服3D打印在制品中引入孔隙的负面影响,提高聚乳酸的冲击强度。

High-resolution structure-from-motion models covering 160 km-long surface ruptures of the 2021 M_(W)7.4 Madoi earthquake in northern Qinghai-Tibetan Plateau

The May 222021 M_(W)7.4 Madoi,Qinghai,China earthquake presented a rare opportunity to apply the modern unmanned aerial vehicle(UAV)photography method in extreme altitude and weather conditions to image surface ruptures and near-field effects of earthquake-related surface deformations in the remote Tibet.High-resolution aerial photographs were acquired in the days immediately following the mainshock.The complex surface rupture patterns associated with this event were covered comprehensively at 3-6 cm resolution.This effort represents the first time that an earthquake rupture in the interior of the Qinghai-Tibetan Plateau has been fully and systematically captured by such high-resolution imagery,with an unprecedented level of detail,over its entire length.The dataset has proven valuable in documenting subtle and transient rupture features,such as the significant mole-tracks and opening fissures,which were ubiquitous coseismically but degraded during the subsequent summer storm season.Such high-quality imagery also helps to document with high fidelity the fractures of the surface rupture zone(supplements of this paper),the pattern related to how the faults ruptured to the ground surface,and the distribution of off-fault damage.In combination with other ground-based mapping efforts,the data will be analyzed in the following months to better understand the mechanics of earthquake rupture related to the fault zone rheology,rupture dynamics,and frictional properties along with the fault interface.

Ni-Al mixed metal oxide with rich oxygen vacancies: CO methanation performance and density functional theory study

Ni-Al mixed metal oxides have been successfully prepared by high shear mixer(HSM)and coprecipitation(CP)methods for low temperature CO methanation.In this work,Ni-Al(HSM-CP)catalyst presented small Ni crystallite size and high surface area,which all contribute to the methanation reaction at low temperature conditions.The obtained Ni-Al(HSM-CP)sample exhibited a mass of defective oxygen,thereby accelerating the dissociation of CO and ultimately increasing the activity of the catalyst.Ni-Al(HSM-CP)catalyst offered the best activity with CO conversion=100%and CH_(4) selectivity=93%at 300℃,and the CH_(4) selectivity can reach 81.8%at 200℃.In situ Fourier transform infrared spectroscopy and density functional theory show that CHO and COH intermediates with lower activation energy barriers are produced during the reaction,and hydrogen-assisted carbon–oxygen bond scission is more favorable.

数据推断:信息物理融合系统数据泄露威胁范式和防御方法

随着计算单元和物理对象的高度集成,信息系统和物理系统正逐渐耦合发展为信息物理融合系统(cyber-physical system,CPS).根据CPS物理系统的客观规律,或业务流程间的复杂关联关系,CPS数据之间存在相互推断的可能;当出现从低安全域数据向高安全域数据的准确推断途径时,将引发推断型数据泄露威胁.本文通过分析数据推断引发的CPS数据泄露事件,从数据窃取和数据推断两个维度,提出数据泄露威胁的范式;将数据推断归纳为3类问题:状态估计问题、参数辨识问题和盲源分离问题,从模型驱动、数据驱动和数据–模型双驱动的角度,总结了数据推断的方法和算法.以电力市场为例,展示了基于公开电价数据推断电力系统关键参数的过程,验证了数据推断可以引发严重CPS数据泄露威胁.同时,分析了现有数据保护方法应对数据推断攻击时面临的挑战,探讨了CPS数据推断防御和数据安全治理的研究方向.

Optical engineering of infrared PbS CQD photovoltaic cells for wireless optical power transfer systems

Infrared photovoltaic cells(IRPCs)have attracted considerable attention for potential applications in wireless optical power transfer(WOPT)systems.As an efcient fber-integrated WOPT system typically uses a 1550 nm laser beam,it is essential to tune the peak conversion efciency of IRPCs to this wavelength.However,IRPCs based on lead sulfde(PbS)colloidal quantum dots(CQDs)with an excitonic peak of 1550 nm exhibit low short circuit current(Jsc)due to insufcient absorption under monochromatic light illumination.Here,we propose comprehensive optical engineering to optimize the device structure of IRPCs based on PbS CQDs,for 1550 nm WOPT systems.The absorption by the device is enhanced by improving the transmittance of tin-doped indium oxide(ITO)in the infrared region and by utilizing the optical resonance efect in the device.Therefore,the optimized device exhibited a high short circuit current density of 37.65 mA/cm^(2)under 1 sun(AM 1.5G)solar illumination and 11.91 mA/cm^(2)under 1550 nm illumination 17.3 mW/cm^(2).Furthermore,the champion device achieved a record high power conversion efciency(PCE)of 7.17%under 1 sun illumination and 10.29%under 1550 nm illumination.The PbS CQDs IRPCs under 1550 nm illumination can even light up a liquid crystal display(LCD),demonstrating application prospects in the future.

Methodological and reporting quality of comprehensive hypertension guidelines published between 2017 and 2022

Hypertension,also known as high blood pressure,is a serious medical condition that may cause severe health problems,such as heart attack and stroke.According to the World Health Organization(WHO),^([1])an estimated 1.28 billion adults worldwide aged 30–79 years had hypertension in 2021,two-third of whom were living in low-and middle-income countries.Many national and international clinical practice guidelines(CPGs)on the diagnosis,evaluation,and treatment of hypertension have been published to promote its control.Among these,comprehensive hypertension guidelines provide broader direction to more target users,especially primary healthcare practitioners,than“narrow”types of guidelines.

电力系统安全仿真技术:工程安全、网络安全与信息物理综合安全

电力系统安全仿真是面向电力系统自身故障或外部攻击等安全威胁,通过仿真实验或借助数值计算研究系统行为的技术.随着自动控制、网络通信、人工智能等信息技术的广泛应用,电力系统已发展成为物理系统与信息系统深度耦合的信息物理融合系统.物理破坏或网络攻击产生的故障在电力系统中相互关联,可跨域传播,产生新的安全威胁形态.电力系统安全仿真正在面临新的挑战.本文回顾了历史上影响广泛的电力系统安全事件;从工程安全、网络安全、信息物理综合安全3个维度,分析电力系统安全仿真的需求和技术发展,对代表性的安全仿真平台进行分类和总结;探讨电力系统安全仿真技术面临的挑战和发展趋势.

Towards suppressing dielectric loss of GO/PVDF nanocomposites with TA-Fe coordination complexes as an interface layer

In this work, graphene oxide(GO) nanosheets with surface modification by Tannic and Fe coordination complexes(TA-Fe) were incorporated into poly(vinylidene fluoride)(PVDF) to prepare high constant but low loss polymer nanocomposites, and the effect of TA-Fe interlayer on dielectric properties of the GO@TA-Fe/PVDF nanocomposites was investigated. The results indicate that the dosage, mixing ratio, and reaction time of TA-Fe complexes have obvious influences on the dielectric properties of the nanocomposites. Furthermore, the TA-Fe interlayer significantly influences the electrical properties of GO@TA-Fe nanoparticles and their PVDF composites, and the GO@TA-Fe/PVDF composites exhibit superior dielectric properties compared with raw GO/PVDF. Dielectric losses of the GO@TA-Fe/PVDF are significantly suppressed to a rather low level owing to the presence of TA-Fe layer, which serves as an interlayer between the GO sheets, thus preventing them from direct contacting with each other. Additionally, the dynamic dielectric relaxation of the GO/PVDF and GO@TA-Fe/PVDF nanocomposites was investigated in terms of temperature.

Analysis of COVID-19 Guideline Quality and Change of Recommendations:A Systematic Review

Background.Hundreds of coronavirus disease 2019(COVID-19)clinical practice guidelines(CPGs)and expert consensus statements have been developed and published since the outbreak of the epidemic.However,these CPGs are of widely variable quality.So,this review is aimed at systematically evaluating the methodological and reporting qualities of COVID-19 CPGs,exploring factors that may influence their quality,and analyzing the change of recommendations in CPGs with evidence published.Methods.We searched five electronic databases and five websites from 1 January to 31 December 2020 to retrieve all COVID-19 CPGs.The assessment of the methodological and reporting qualities of CPGs was performed using the AGREE II instrument and RIGHT checklist.Recommendations and evidence used to make recommendations in the CPGs regarding some treatments for COVID-19(remdesivir,glucocorticoids,hydroxychloroquine/chloroquine,interferon,and lopinavir-ritonavir)were also systematically assessed.And the statistical inference was performed to identify factors associated with the quality of CPGs.Results.We included a total of 92 COVID-19 CPGs developed by 19 countries.Overall,the RIGHT checklist reporting rate of COVID-19 CPGs was 33.0%,and the AGREE II domain score was 30.4%.The overall methodological and reporting qualities of COVID-19 CPGs gradually improved during the year 2020.Factors associated with high methodological and reporting qualities included the evidence-based development process,management of conflicts of interest,and use of established rating systems to assess the quality of evidence and strength of recommendations.The recommendations of only seven(7.6%)CPGs were informed by a systematic review of evidence,and these seven CPGs have relatively high methodological and reporting qualities,in which six of them fully meet the Institute of Medicine(IOM)criteria of guidelines.Besides,a rapid advice CPG developed by the World Health Organization(WHO)of the seven CPGs got the highest overall scores in methodological(72.8%)and reporting qualities(83.8%).Many CPGs covered the same clinical questions(it refers to the clinical questions on the effectiveness of treatments of remdesivir,glucocorticoids,hydroxychloroquine/chloroquine,interferon,and lopinavirritonavir in COVID-19 patients)and were published by different countries or organizations.Although randomized controlled trials and systematic reviews on the effectiveness of treatments of remdesivir,glucocorticoids,hydroxychloroquine/chloroquine,interferon,and lopinavir-ritonavir for patients with COVID-19 have been published,the recommendations on those treatments still varied greatly across COVID-19 CPGs published in different countries or regions,which may suggest that the CPGs do not make sufficient use of the latest evidence.Conclusions.Both the methodological and reporting qualities of COVID-19 CPGs increased over time,but there is still room for further improvement.The lack of effective use of available evidence and management of conflicts of interest were the main reasons for the low quality of the CPGs.The use of formal rating systems for the quality of evidence and strength of recommendations may help to improve the quality of CPGs in the context of the COVID-19 pandemic.During the pandemic,we suggest developing a living guideline of which recommendations are supported by a systematic review for it can facilitate the timely translation of the latest research findings to clinical practice.We also suggest that CPG developers should register the guidelines in a registration platform at the beginning for it can reduce duplication development of guidelines on the same clinical question,increase the transparency of the development process,and promote cooperation among guideline developers all over the world.Since the International Practice Guideline Registry Platform has been created,developers could register guidelines prospectively and internationally on this platform.

Evaluation of the Integrated Information System for Brucellosis Case Diagnosis and Management-Inner Mongolia Autonomous Region,China,2019

What is already known about this topic?Wulanchabu City Center for Endemic Disease Prevention and Control had established and used a Brucellosis Integrated Information System(BIIS)since 2013.However,it had not been systematically evaluated and promoted so far.What is added by this report?The BIIS had significantly improved the efficiency of brucellosis reporting and provided convenience for follow-up management of cases,which was valuable for finishing completely routine therapy.However,the stability of the system needs to be improved.What are the implications for public health practice?The results of the BIIS assessment demonstrated its advantages and disadvantages,which could provide some evidence for its implementation in other areas of China.

Does More Trading Lead to Better Market Linkage?Evidence from the Commodity Futures Markets

In this study,we use eight pairs of commodity futures data to investigate the impact of the recently launched nighttime trading session by Chinese futures exchanges.We conduct a thorough empirical analysis on the cross-market information transmission mechanisms between China and the U.S.We apply various econometric analyses including the co-integration analysis,the forecast error variance decomposition analysis,and the volatility spillover analysis with a bivariate GARCH model.Findings in this study indicate that,after the launching of nighttime-trading hours in China,the price discovery function of the Chinese futures market is noticeably improved,and that the Chinese market began to dominate the U.S.market in the bidirectional volatility spillover process.Thus,the introduction of the nighttime-trading hours appears to be an effective step toward China’s long-term goal of establishing pricing power in key commodities on the global financial market.

“Dual-Lock-Dual-Key”Controlled Second Near-Infrared Molecular Probe for Specific Discrimination of Orthotopic Colon Cancer and Imaging-Guided Tumor Excision

Fluorescence imaging in the second infrared window(1000-1700 nm)has emerged as a promising approach to tumor diagnosis.However,the currently available second near-infrared(NIR-II)imaging agents are based on the“always on”modality or single biomarker activation,which are subject to limited imaging contrast,nonspecific response,and even false-positive diagnosis.Here,we developed a H2S/H+dual-stimuli responsive NIR-II fluorescent probe,WH-N3,for precise tumor delimitation and intraoperative fluorescence-guided surgical resection.WH-N3 itself is nonfluorescent,and it can only light up through synergistic activation by H2S and in the tumor acidic environment(TEM).Such a“duallock-dual-key”strategy-based activatable probe exhibited significantly higher tumor-to-normal tissue(T/N)ratios than the“always on”agent(ICG)and single parameter responsive counterpart probes in the imaging of colon tumors,which overexpresses H2S.WH-N3 was also able to visualize the tumor-derived endogenous H2S fluctuation and accurately differentiate tumor types based on H2S content discrepancy.More excitingly,under the guidance of the probe’s highly specific NIR-II fluorescence,a tiny orthotopic colon tumor with diameter down to 0.8 mm was facilely resected.We expect our dual-stimuli responsive strategy will contribute more reliable tools for specific discrimination and imaging-guided excision of tumor.

Asymptomatic and pre-symptomatic infection in Coronavirus Disease 2019 pandemic

With the presence of Coronavirus Disease 2019(COVID-19)asymptomatic infections detected,their proportion,transmission potential,and other aspects such as immunity and related emerging challenges have attracted people’s attention.We have found that based on highquality research,asymptomatic infections account for at least one-third of the total cases,whereas based on systematic review and meta-analysis,the proportion is about one-fifth.Evaluating the true transmission potential of asymptomatic cases is difficult but critical,since it may affect national policies in response to COVID-19.We have summarized the current evidence and found,compared with symptomatic cases,the transmission capacity of asymptomatic individuals is weaker,even though they have similar viral load and relatively short virus shedding duration.As the outbreak progresses,asymptomatic infections have also been found to develop long COVID-19.In addition,the role of asymptomatic infection in COVID-19 remains to be further revealed as the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)variants continue to emerge.Nevertheless,as asymptomatic infections transmit the SARS-CoV-2 virus silently,they still pose a substantial threat to public health.Therefore,it is essential to conduct screening to obtain more knowledge about the asymptomatic infections and to detect them as soon as possible;meanwhile,management of them is also a key point in the fight against COVID-19 community transmission.The different management of asymptomatic infections in various countries are compared and the experience in China is displayed in detail.

The status and development proposal of carbon sources and sinks monitoring satellite system

In order to mitigate global warming,the international communities actively explore low-carbon and green development methods.According to the Paris Agreement that came into effect in 2016,there will be a global stocktaking plan to carry out every 5 years from 2023 onwards.In September 2020,China proposed a"double carbon"target of carbon peaking before 2030 and carbon neutrality before 2060.Achieving carbon peaking and carbon neutrality goals requires accurate carbon emissions and carbon absorptions.China’s existing carbon monitoring methods have insufficient detection accuracy,low spatial resolution,and narrow swath,which are difficult to meet the monitoring requirement of carbon sources and sinks monitoring.In order to meet the needs of carbon stocktaking and support the monitoring and supervision of carbon sources and sinks,it is recommended to make full use of the foundation of the existing satellites,improve the detection technical specifications of carbon sources and sinks monitoring measures,and build a multi-means and comprehensive,LEO-GEO orbit carbon monitoring satellite system to achieve higher precision,higher resolution and multi-dimensional carbon monitoring.On this basis,it is recommended to strengthen international cooperation,improve data sharing policy,actively participate in the development of carbon retrieval algorithm and the setting of international carbon monitoring standards,establish an independent and controllable global carbon monitoring and evaluation system,and contribute China’s strength to the global realization of carbon peaking and carbon neutrality.