Experimental study on preparation of nanoparticle-surfactant nanofluids and their effects on coal surface wettability

To improve the efficiency of coal seam water injection,the influence of nanofluids on coal surface wettability was studied based on the nano drag reduction and injection enhancement technology in the field of tertiary oil recovery.The composition optimization and performance evaluation of nanofluids with nano-silica and sodium lauryl sulfate as the main components were carried out,and the effects of the nanofluid with the optimal ratio on coal wettability were studied through spontaneous upward imbibition experiments.The results show that the composite nanofluid has a lower surface tension,and the lowest value of the interfacial tension is 15.79 m N/m.Therefore,the composite nanofluid can enhance the wettability of coal.However,its effects on coal samples with different metamorphic degrees is different,that is,low rank coal is the largest,middle rank coal is the second,and high rank coal is the least.In addition,a functional relationship between time and imbibition height is found for pulverized coal with different particle sizes.When the particle size of pulverized coal is 60–80 mesh,the wettability of nanofluid to coal is best.The findings in this paper provide a new perspective for improving the water injection efficiency for coal seams with low permeability.

Dissolution and recrystallization of perovskite induced by N-methyl-2-pyrrolidone in a closed steam annealing method

High quality perovskite films with large columnar grains are greatly desired for efficient perovskite solar cells. Here, low volatility N-methyl-2-pyrrolidone(NMP) was added in MAI/IPA solution in a two-step spin-coating method, which promoted the conversion of lead iodide to perovskite. The perovskite films were annealed by a closed-steam annealing method to prolong the recrystallization process of perovskite films assisted by the residual NMP. It leaded to high quality CH_3NH_3PbI_3 perovskite films with large columnar grains due to its enhancement of the Oswald ripening. The large grain perovskite film leaded to efficient carrier transformation and injection, and low recombination. The photovoltaic performance of the perovskite solar cells was improved significantly.

保加利亚一例散养户发生非洲猪瘟案例报告

非洲猪瘟进入国内一年多来,尽管采取了各项措施,但仍给养猪业造成巨大经济损失,进而影响到猪肉的供应。"猪粮安天下",猪肉价格的上涨也带动了其他肉食品的价格,甚至推动了CPI升高。目前生猪"稳生产、保供给"已经成为当务之急,散养户作为中国养殖业的主力军,在未来很长一段时间内仍将存在,发挥好这个群体的作用,将会显著加快中国养猪业的复养之路,分散发病风险。在非洲猪瘟将长期共存背景下,要想让散养户敢养猪、养好猪,必须配套足够的技术支持措施。一年多与非洲猪瘟斗争的经验让我们认识到面对非洲猪瘟我们并非无计可施,规模化猪场如此、散养户亦如此,只不过我们总结的更多经验是针对规模化猪场,很少有能让散养户采取的方案。希望这个针对散养户案例的总结,能给散养户的复养之路提供一些感悟与参考。

空气加速器结构对熔喷气流场的影响

为降低熔喷纤维的直径,设计了带有空气加速器的新型模头,考察了空气加速器结构对其下方流场的影响。借助Fluent软件对新型模头的气流场进行了数值计算,分析了流场中空气速度和空气温度的分布规律。研究结果表明,空气加速器结构对流场性能有很大的影响。当空气加速器间距减小、空气加速器高度增加、空气加速器倾角减小、空气加速器侧面为内圆弧状时,纺丝线上的空气速度峰值增大、空气温度提高。综合对比,在空气加速器半间距为10mm、空气加速器高度为30 mm、空气加速器倾角为60°、空气加速器侧面为内圆弧状的条件下,新型模头下方流场中的气流速度极值最大、气流温度更高。

Interfacial engineering of transition-metal sulfides heterostructures with built-in electric-field effects for enhanced oxygen evolution reaction

Developing highly efficient,durable,and non-noble electrocatalysts for the sluggish anodic oxygen evolution reaction(OER)is the pivotal for meeting the practical demand in water splitting.However,the current transition-metal electrocatalysts still suffer from low activity and durability on account of poor interfacial reaction kinetics.In this work,a facile solid-state synthesis strategy is developed to construct transition-metal sulfides heterostructures(denoted as MS_(2)/NiS_(2),M=Mo or W)for boosting OER electrocatalysis.As a result,MoS2/NiS2 and WS2/NiS2 show lower overpotentials of 300 mV and 320 mV to achieve the current density of 10 mA·cm^(-2),and smaller Tafel slopes of 60 mV.dec^(-1) and 83 mV.dec^(-1)in 1 mol·L^(-1) KOH,respectively,in comparison with the single MoS2,WS2,NiS2,as well as even the benchmark RuO2.The experiments reveal that the designed heterostructures have strong electronic interactions and spontaneously develop a built-in electric field at the heterointerface with uneven charge distribution based on the difference of band structures,which promote interfacial charge transfer,improve absorptivity of OH-,and modulate the energy level more comparable to the OER.Thus,the designed transition-metal sulfides heterostructures exhibit a remarkably high electrocatalytic activity for OER.This study provides a simple strategy to manipulate the heterostructure interface via an energy level engineering method for OER and can be extended to fabricate other heterostructures for various energy-related applications.

Design of Real-time Electricity Prices and Wireless Communication Smart Meter

Under the background of smart grid’s real-time electricity prices theory, a real-time electricity prices and wireless communication smart meter was designed. The metering chip collects power consumption information. The real-time clock chip records current time. The communication between smart meter and system master station is achieved by the wireless communication module. The “freescale” micro controller unit displays power consumption information on screen. And the meter feedbacks the power consumption information to the system master station with time-scale and real-time electricity prices. It results that the information exchange between users and suppers can be realized by the smart meter. It fully reflects the demanding for communication of smart grid.

Study on Voltage Sag Detection of Wind Power System Based on HHT

For the output of wind power system has the characteristics of randomness, volatility and intermittence, the voltage of wind power system fluctuates frequently and voltage sag is one of the most common voltage fluctuations in wind power system. For the problem of voltage sag of wind power system, the limitations of the detection methods such as the square detection method, the half-wave RMS detection method and wavelet transform are summed up, and a new detecting method named Hilbert-huang Transform(HHT) is put forward in this paper, which can detect the voltage sag accurately and timely. In order to solve the problem of end effect in the process of empirical mode decompostion (EMD), a self-adaptive method named improved waveform matching is applied in dealing with the end issue. Voltage fluctuations are reflected by two parameters named voltage amplitude and frequency of each intrinsic mode function (IMF) in HHT. The practicality of the method is verified by Matlab simulation.

Effects of intermittent loading time and stress ratio on dwell fatigue behavior of titanium alloy Ti-6Al-4V ELI used in deep-sea submersibles

Different components of deep-sea submersibles,such as the pressure hull,are usually subjected to intermittent loading,dwell loading,and unloading during service.Therefore,for the design and reliability assessment of structural parts under dwell fatigue loading,understanding the effects of intermittent loading time on dwell fatigue behavior of the alloys is essential.In this study,the effects of the intermittent loading time and stress ratio on dwell fatigue behavior of the titanium alloy Ti-6 Al-4 V ELI were investigated.Results suggest that the dwell fatigue failure modes of Ti-6 Al-4 V ELI can be classified into three types,i.e.,fatigue failure mode,ductile failure mode,and mixed failure mode.The intermittent loading time does not affect the dwell fatigue behavior,whereas the stress ratio significantly affects the dwell fatigue life and dwell fatigue mechanism.The dwell fatigue life increases with an increase in the stress ratio for the same maximum stress,and specimens with a negative stress ratio tend to undergo ductile failure.The mechanism of dwell fatigue of titanium alloys is attribute to an increase in the plastic strain caused by the part of the dwell loading,thereby resulting in an increase in the actual stress of the specimens during the subsequent loading cycles and aiding the growth of the formed crack or damage,along with the local plastic strain or damage induced by the part of the fatigue load promoting the cumulative plastic strain during the dwell fatigue process.The interaction between dwell loading and fatigue loading accelerates specimen failure,in contrast to the case for individual creep or fatigue loading alone.The dwell fatigue life and cumulative maximum strain during the first loading cycle could be correlated by a linear relationship on the log–log scale.This relationship can be used to evaluate the dwell fatigue life of Ti alloys with the maximum stress dwell.

Highly bright and low turn-on voltage CsPbBr3 quantum dot LEDs via conjugation molecular ligand exchange

All-inorganic CsPbBr3 perovskite quantum dots (QDs) hold great promise as candidate materials for next-generation electroluminescent displays owing to their excellent optoelectronic properties.However,the long insulating ligands on the surface of CsPbBr3 QDs originating from the synthesis process hinder the fabrication of high-performance optoelectronic devices.Herein,an efficient ligand-exchange route is proposed with the use of perovskite-precursor-based halide ligands,including a series of phenalkylammonium bromides with a π-conjugation benzene ring and different branch lengths.Based on the ligand-exchange method,the conductivity of the CsPbBr3 QD layer is significantly improved owing to ligand shortening and the insertion of the π-conjugation benzene ring.As a result,high brightness (up to 12,650 cd/m2)and low tum-on voltage (as low as 2.66 V) can be realized in CsPbBr3 QD light-emitting diodes (QLEDs),leading to dramatic improvements in device performance with a current efficiency of 13.43 cd/A,power efficiency of 12.05 lm/W,and external quantum efficiency of 4.33%.

基于智能手机的实时远程快速现场评估在超声内镜引导细针穿刺抽吸中的价值

目的探讨联合智能手机实时图片交流进行远程快速现场评估(rapid on-site evaluation,ROSE)的可行性,以及远程ROSE在提高超声内镜医师诊断效率中的作用。方法回顾性分析2020年4月—2021年5月于山东大学齐鲁医院接受超声内镜引导细针穿刺抽吸术(endoscopic ultrasound-guided fine needle aspiration,EUS-FNA)诊断的188例患者资料。其中2020年4—10月未行ROSE的为非ROSE组(91例),2020年11月—2021年5月引入了ROSE的为ROSE组(97例),ROSE组中2020年11月—2021年3月为手机组(52例),即内镜医师通过智能手机微信发送ROSE图像给细胞病理医师;2021年4—5月为self-ROSE组(45例),由经过细胞病理培训的超声内镜医师独立判断ROSE结果。比较患者基本信息、ROSE结果、术后病理及术后随访情况,分析远程ROSE的诊断效能。结果188例患者中179例(95.2%)为胰腺实性病变,9例(4.8%)为腹腔病变。非ROSE组、手机组、self-ROSE组穿刺次数差异无统计学意义[3(3,4)比3(3,4)比3(2,4),H=1.320,P=0.517]。以最终诊断为金标准,非ROSE组诊断的敏感度、特异度、准确率、阳性预测值、阴性预测值、Kappa值分别为80.6%(58/72)、89.5%(17/19)、82.4%(75/91)、96.7%(58/60)、54.8%(17/31)、0.6,ROSE组相应指标为97.4%(74/76)、100.0%(21/21)、97.9%(95/97)、100.0%(74/74)、91.3%(21/23)、0.9,手机组为95.2%(40/42)、100.0%(10/10)、96.2%(50/52)、100.0%(40/40)、83.3%(10/12)、0.9,self-ROSE组为100.0%(34/34)、100.0%(11/11)、100.0%(45/45)、100.0%(34/34)、100.0%(11/11)、1.0。ROSE组的敏感度(P=0.002)、准确率(P=0.001)和阴性预测值(P=0.009)高于非ROSE组,其余诊断效能指标差异无统计学意义(P>0.05)。手机组和self-ROSE组上述诊断效能指标差异无统计学意义(P>0.05)。结论智能手机微信辅助下实时远程ROSE能很好地适应病理科及超声内镜医师需求,远程ROSE应用后内镜医师诊断准确率与细胞病理医师相当,有助于内镜下获得更充分的标本,提高EUS-FNA诊断准确性。

中国石松类和蕨类植物多样性研究进展

石松类和蕨类植物是维管植物的第二大类群,其起源可追溯到4亿年前。在被子植物出现之前,石松类和蕨类植物在古地球生态系统中占主导地位,其重要性一直延续到现在。自20世纪40年代开始,中国石松类和蕨类植物研究就令世界瞩目,尤其是2017年第19届国际植物学大会在中国深圳召开后的5年时间里,中国石松类和蕨类植物研究更是面向世界、走向国际,研究更为广泛的科学问题,在物种多样性、保护、系统演化和生态适应性等方面取得了一系列重要研究进展。2017–2022年,多个中国研究团队利用多组学数据构建了世界石松类和蕨类植物科级水平的生命之树并提出了关键性状孢子囊环带演化的新模式;解决了石松类和蕨类植物中目级、科级、属级和种级众多关键的系统分类学等问题,发表了106个新分类群;开展了大量的植物区系调查和研究,出版了6部中国石松类和蕨类植物多样性专著和1部世界性专著;对65种国家重点保护的石松类和蕨类植物进行了迁地保护,同时实现了桫椤科、水蕨属(Ceratopteris)、观音座莲属(Angiopteris)和鹿角蕨(Platycerium wallichii)等重点保护类群的孢子繁殖;在系统发育框架下,研究了石松类和蕨类植物的生态修复功能和生态适应性演化。通过对2017–2022年研究成果的总结和思考,本文对未来石松类和蕨类植物的发展提出以下建议:(1)提高中国寡型科属以及世界性大科大属的关注力度;(2)加强西藏、四川等薄弱地区石松类和蕨类植物的调查研究,并结合新技术,如DNA条形码等以提高区系调查中物种鉴别的效率和准确性;(3)运用多学科交叉的研究方法厘清各科、属、种间系统关系的同时,还应加强系统和生态适应性演化之间的协同研究;(4)关注石松类和蕨类植物系统位置作为陆生维管植物演化起点的共性科学问题;(5)加强石松类和蕨类植物系统分类学与生态学、植物化学、保护生物学等学科间交叉合作研究。

Wind farm polymerization influences on security and economic operation in power system based on Copula function

Wind speed dependences on different areas in a wind farm have influences on security and economic operation in power system.In order to simulate the correlation of wind speed series between different positions,this paper applies Copula function and rank correlation matrix methods to measure the coherence of wind speed in a wind farm.The correlated wind sample space is established.According to active power output characteristics of wind turbines,the polymerization model in a wind farm can be achieved.Monte Carlo optimal power flow is applied to IEEE-30 and IEEE-300 bus systems based on the principle of energy saving dispatching.The study shows that the accuracy of outputs is improved,thus reducing the fluctuation ranges in unit generating costs and power flow in branches while considering wind speed polymerization.This approach provides a new method to improve the effectiveness of energy saving dispatching and system operation arrangement.Results have been tested to be effective.

Recent advances in flexible and wearable organic optoelectronic devices

Flexible and wearable optoelectronic devices have been developing to a new stage due to their unique capacity for the possibility of a variety of wearable intelligent electronics, including bendable smartphones, foldable touch screens and antennas, paper-like displays, and curved and flexible solid-state lighting devices. Before extensive commercial applications, some issues still have to be solved for flexible and wearable optoelectronic devices. In this regard, this review concludes the newly emerging flexible substrate materials, transparent conductive electrodes, device architectures and light manipulation methods. Examples of these components applied for various kinds of devices are also summarized. Finally, perspectives about the bright future of flexible and wearable electronic devices are proposed.

Diagnostic assays for COVID-19:a narrative review

Coronavirus disease 2019(COVID-19)is a newly emerged infectious disease caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).The number of COVID-19 cases is continuously increasing and no effective drugs or vaccines are currently available.Accurate and efficient diagnostic testing methods are desperately needed for the detection of SARS-CoV-2 and antiviral antibodies in infected individuals.Various assay techniques,including nucleic acid tests[eg,polymerase chain reaction(PCR),reverse transcription-PCR,real-time loop-mediated isothermal amplification,and CRISPR-Cas-based detection],serological tests[eg,immunoglobulin(Ig)A,IgM/G],imaging tests(eg,computed tomography and positron-emission tomography),and nanoparticle-based detections have been reported for COVID-19 diagnosis.This review aims to present the current diagnostic tools for SARS-CoV-2 and their performance characteristics to inform the appropriate selection of diagnostic and surveillance technologies at optimal testing times.We also describe the advantages of detection using combined nucleic acid and imaging tests,or serological testing and point-of-care diagnostics.Developing reliable protein biomarkers targeting the conserved proteins of SARS-CoV-2 rather than IgA,IgM,or IgG would be useful to manage SARS-CoV-2.