ZnO(110)衬底上单层黑磷烯的外延生长

二维黑磷烯作为新一代半导体材料,具有可调带隙和高载流子迁移率等优点,具有广阔的应用前景.但二维黑磷烯目前还不能直接大规模制备,限制了其进一步的研究和应用.分子束外延是一种广泛使用的具有较高外延质量的单晶薄膜生长方法,在制备二维黑磷烯方面具有广阔的应用前景.本文基于密度泛函理论计算筛选了ZnO(110)、GaN(110)、BP(110)和SiC(110)四种潜在的衬底,研究了二维黑磷烯在这些衬底上的生长情况.研究表明,ZnO(110)上的黑磷单层及团簇结构是稳定的,且磷在该表面扩散特性也有助于磷团簇的成核生长.本研究为高效制备二维黑磷烯及其他二维材料提供了有益的指导.

pH响应型BTA@DME/Cu^(2+)-BTA微胶囊的制备及涂层的防腐性能

文中以天然硅藻土(DME)为微容器,采用真空浸渍法负载苯并三氮唑(BTA)缓蚀剂,同时将具有pH响应性的Cu^(2+)-BTA络合物包覆在BTA@DME外表面,制备了pH响应型BTA@DME/Cu^(2+)-BTA微胶囊。扫描电镜、能谱仪及解络合宏观实验证明了BTA的成功负载以及Cu^(2+)-BTA层的成功包覆,微胶囊中BTA的负载率为44.6%。制备的微胶囊具有pH缓释性,pH为7,Cu^(2+)浓度为60 mmol/L时,形成的Cu^(2+)-BTA络合物结构致密,微胶囊中BTA的释放率低于10%;pH为5和2时,微胶囊中BTA的释放率分别为50%和80%。添加5%BTA@DME/Cu^(2+)-BTA微胶囊的环氧树脂划痕涂层具有最佳防腐效果,在浸泡周期内,阻抗模量越来越高,从浸泡1 d后的2.8×10^(5)Ω·cm^(2)增加到浸泡30 d后的1.36×106Ω·cm^(2)。

Material Removal Characteristics of Single-Crystal 4H-SiC Based on Varied-Load Nanoscratch Tests

Single-crystal silicon carbide(SiC)has been widely applied in the military and civil fields because of its excellent physical and chemical properties.However,as is typical in hard-to-machine materials,the good mechanical properties result in surface defects and subsurface damage during precision or ultraprecision machining.In this study,single-and double-varied-load nanoscratch tests were systematically performed on single-crystal 4H-SiC using a nanoindenter system with a Berkovich indenter.The material removal characteristics and cracks under different planes,indenter directions,normal loading rates,and scratch intervals were analyzed using SEM,FIB,and a 3D profilometer,and the mechanisms of material removal and crack propagation were studied.The results showed that the Si-plane of the single-crystal 4H-SiC and edge forward indenter direction are most suitable for material removal and machining.The normal loading rate had little effect on the scratch depth,but a lower loading rate increased the ductile region and critical depth of transition.Additionally,the crack interaction and fluctuation of the depth-distance curves of the second scratch weakened with an increase in the scratch interval,the status of scratches and chips changed,and the comprehensive effects of the propagation and interaction of the three cracks resulted in material fractures and chip accumulation.The calculated and experimental values of the median crack depth also showed good consistency and relativity.Therefore,this study provides an important reference for the high-efficiency and precision machining of single-crystal SiC to ensure high accuracy and a long service life.

Prediction of Grinding Force by an Electroplated Grinding Wheel with Orderly-Micro-Grooves

The ability to predict a grinding force is important to control,monitor,and optimize the grinding process.Few theoretical models were developed to predict grinding forces when a structured wheel was used in a grinding process.This paper aimed to establish a single-grit cutting force model to predict the ploughing,friction and cutting forces in a grinding process.It took into the consideration of actual topography of the grinding wheel,and a theoretical grinding force model for grinding hardened AISI 52100 by the wheel with orderly-micro-grooves was proposed.The model was innovative in the sense that it represented the random thickness of undeformed chips by a probabilistic expression,and it reflected the microstructure characteristics of the structured wheel explicitly.Note that the microstructure depended on the randomness of the protruding heights and distribution density of the grits over the wheel.The proposed force prediction model was validated by surface grinding experiments,and the results showed(1)a good agreement of the predicted and measured forces and(2)a good agreement of the changes of the grinding forces along with the changes of grinding parameters in the prediction model and experiments.This research proposed a theoretical grinding force model of an electroplated grinding wheel with orderly-micro-grooves which is accurate,reliable and effective in predicting grinding forces.

Stationary Measures of Three-State Quantum Walks with Defect on the One-Dimension Lattice

In this paper, we focus on the space-inhomogeneous three-state on the one-dimension lattice, a one-phase model and a two-phase model include. By using the transfer matrices method by Endo et al., we calculate the stationary measure for initial state concrete eigenvalue. Finally we found the transfer matrices method is more effective for the three-state quantum walks than the method obtained by Kawai et al.

自修复超疏水涂层研究进展

介绍了近年来自修复超疏水涂层的研究进展,总结了自修复超疏水涂层的多种制备方法。重点介绍了本征型和外援型2种自修复超疏水涂层,其中外援型主要有由pH引发、温度引发和光引发的自修复超疏水涂层;本征型重点介绍了基于超分子聚合物的自修复超疏水涂层。同时介绍了自修复超疏水涂层在金属防腐、自清洁、防污、防冰、油水分离等诸多领域的应用,最后展望了自修复超疏水涂层的发展前景。

亚麻油微胶囊的制备及环氧涂层的自修复性能

以亚麻油(LO)为芯材、聚氨酯(PU)为壁材通过界面聚合法,在水包油(O/W)乳液体系中制备了包覆率高、热化学稳定的LO@PU微胶囊,讨论了乳化剂种类及浓度、搅拌速度、芯壁比等对微胶囊成囊性能的影响。所制备的微胶囊分散效果好、形貌规则、成球性好,粒径为(60±21)μm;微胶囊具有较好的热稳定性,热分解温度为235~480℃;微胶囊芯材LO的质量分数为55.6%。同时,制备了含微胶囊的自修复环氧涂层,盐水浸泡实验和电化学阻抗实验表明,含有10%微胶囊的环氧树脂涂层的自修复及防腐蚀性能最好,划痕涂层浸泡30 d后的阻抗模量仍为1.0×10^(4)Ω·cm^(2)。

Analysis of molecular variation in porcine reproductive and respiratory syndrome virus in China between 2007 and 2012

In the present study, 89 porcine reproductive and respiratory syndrome virus(PRRSV) isolates in China during 2007 to 2012 were randomly selected from the GenBank genetic sequence database. Evolutionary characteristics of these isolates were analyzed based on the sequences of non-struc-tural protein 2(Nsp2) and glycoprotein 5(GP5). The genetic variations of the isolates were also compared with six representative strains. The results showed that a high degree of genetic diversity exists among the PRRSV population in China. Highly pathogenic PRRSV isolates, with a discon-tinuous deletion of a 30 amino acid residue in the Nsp2 region, remained the most dominant virus throughout 2007–2012 in China. Owing to the extensive use of representative vaccine strains, natu-ral recombination events occurred between strains. Three isolates – HH08, DY, and YN-2011 – were more closely related to vaccine strains than the other isolates. Both YN-2011 and DY were the evolu-tionary products of recombination events between strains SP and CH-1R. The results of the present study provide useful information for the epidemiology of PRRSV as well as for vaccine development.

Identification and analysis of AP2/ERF gene family in tomato underabiotic stress

AP2/ERE-type transcription factors,as a type of plant-specific transcription factors,play a key role in plant biotic and abiotic stress.Meanwhile,they have been studied in many plants,but rarely in tomatoes.In this study,we performed a genome-wide analysis of the SlAP2/ERF gene family of tomato,and finally identified 29 SlAP2/ERF genes and divided them into different subfamilies.At the same time,its basic physical and chemical properties were analyzed.We also constructed phylogenetic trees with 30 Arabidopsis AP2/ERF proteins and 28 potatoes AP2/ERF proteins to ensure conservative homology between them.In addition,we mapped 29 SlAP2/ERF transcription factors on 10 different chromosomes,and identified 43 responsive plant hormones,responsive light signals,tissue-specific expression and stress response elements from 2000bp upstream of the promoter region,and we analyzed conserved motifs and gene structures of SlAP2/ERF.The tertiary structure of SlAP2/ERF protein was constructed by homology modeling,and the protein-protein interaction network was constructed based on Arabidopsis Thaliana.Finally,the expression pattern of tomato in different tissues was studied by using gene expression database,and the expression level of tomato under abiotic stress was detected by q-RT-PCR.These results provide comprehensive information for further study of the function of the SlAP2/ERF gene family.

Robust adaptive fuzzy control scheme for nonlinear system with uncertainty

In this paper, a robust adaptive fuzzy control scheme for a class of nonlinear system with uncertainty is proposed. First, using prior knowledge about the plant we obtain a fuzzy model, which is called the generalized fuzzy hyperbolic model （GFHM）. Secondly, for the case that the states of the system are not available an observer is designed and a robust adaptive fuzzy output feedback control scheme is developed. The overall control system guarantees that the tracking error converges to a small neighborhood of origin and that all signals involved are uniformly bounded. The main advantages of the proposed control scheme are that the human knowledge about the plant under control can be used to design the controller and only one parameter in the adaptive mechanism needs to be on-line adjusted.

A critical review on nickel-based cathodes in rechargeable batteries

The 3d transition-metal nickel(Ni)-based cathodes have long been widely used in rechargeable batteries for over 100 years,from Ni-based alkaline rechargeable batteries,such as nickel-cadmium(Ni-Cd)and nickel-metal hydride(Ni-MH)batteries,to the Ni-rich cathode featured in lithium-ion batteries(LIBs).Ni-based alkaline batteries were first invented in the 1900s,and the well-developed Ni-MH batteries were used on a large scale in Toyota Prius vehicles in the mid-1990s.Around the same time,however,Sony Corporation commercialized the first LIBs in camcorders.After temporally fading as LiCoO_(2) dominated the cathode in LIBs,nickel oxide-based cathodes eventually found their way back to the mainstreaming battery industry.The uniqueness of Ni in batteries is that it helps to deliver high energy density and great storage capacity at a low cost.This review mainly provides a comprehensive overview of the key role of Ni-based cathodes in rechargeable batteries.After presenting the physical and chemical properties of the 3d transition-metal Ni,which make it an optimal cationic redox center in the cathode of batteries,we introduce the structure,reaction mechanism,and modification of nickel hydroxide electrode in Ni-Cd and Ni-MH rechargeable batteries.We then move on to the Ni-based layered oxide cathode in LIBs,with a focus on the structure,issues,and challenges of layered oxides,LiNiO_(2),and LiNi_(1−x−y)Co_(x)Mn_(y)O_(2).The role of Ni in the electrochemical performance and thermal stability of the Ni-rich cathode is highlighted.By bridging the“old”Ni-based batteries and the“modern”Ni-rich cathode in the LIBs,this review is committed to providing insights into the Ni-based electrochemistry and material design,which have been under research and development for over 100 years.This overview would shed new light on the development of advanced Ni-containing batteries with high energy density and long cycle life.

Stable isotope in precipitation in China:A review

The isotope ratios in precipitation are associated with various meteorological processes and display obvious spatial and temporal distributions, and thus can be used as impo~_nt techniques in inversing atmospheric processes, tracing vapor sources, and reflect- ing the local weather and climate conditions. The composition and distribution of stable isotopes in precipitation in China are summarized and the factors that influence isotope ratios are elucidated. An overview of related research progress in China during the past several decades is presented and the prospects for future work in this subject area are described.

Satellite-measured water vapor isotopologues across the Tianshan Mountains,central Asia

The satellite-based water vapor stable isotope measurements have been widely used in modern hydrological and atmospheric studies.Their use is important for arid areas where the precipitation events are limited,and below-cloud evaporation is strong.This study presents the spatial and temporal characteristics of water vapor isotopologue across the Tianshan Mountains in arid central Asia using the NASAAura Tropospheric Emission Spectrometer(TES).The near-surface water vapor stable isotopes are enriched in summer and depleted in winter,consistent with the seasonality of precipitation isotopes.From the surface to 200 hPa,the isotope values in water vapor show a decreasing trend as the atmospheric pressure decreases and elevation rises.The vapor isotope values in the lower atmosphere in the southern basin of the Tianshan Mountains are usually higher than that in the northern basin,and the seasonal difference in vapor isotopes is slightly more significant in the southern basin.In addition,bottom vapor isotopologue in summer shows a depletion trend from west to east,consistent with the rainout effect of the westerly moisture path in central Asia.The isotopic signature provided by the TES is helpful to understand the moisture transport and below-cloud processes influencing stable water isotopes in meteoric water.

水系合成δ相甲脒铅碘钙钛矿粉末

近年来,甲脒基钙钛矿太阳能电池的光电转换效率取得了显著进展,其商业化前景日益明朗.随着钙钛矿电池商业化的快速发展,对于环境友好、成本低廉的钙钛矿前驱体的需求不断增长.甲脒铅碘钙钛矿材料遇水易分解,因此传统钙钛矿粉末合成方法依赖于有机溶剂和惰性气氛手套箱,不具备成本优势.在此背景下,本文提出了一种经济高效的水系合成高纯度δ相甲脒铅碘(δ-FAPbI_(3))粉末的策略.在水溶液中加入过量氢碘酸,碘离子可使不溶性PbI_(2)转化为可溶性[PbI_(2)+n]n-络合物,将FAPbI_(3)的遇水分解转化为溶解,从而使水系合成成为可能.水系合成的甲脒铅碘粉末具有高纯度、低成本优势,可作为钙钛矿薄膜前驱体材料.与以PbI_(2)和FAI的混合物作为前驱体制备的钙钛矿薄膜相比,以水系合成的δ-FAPbI_(3)粉末为前驱体制备的钙钛矿薄膜具有良好的结晶性,降低了缺陷密度,并有效抑制了有害的离子输运和降解过程,从而增强了载流子传输性能和电池稳定性.在环境空气中以合成粉末为前驱体制备的钙钛矿太阳能电池,最高转化效率可达23.24%.

The methylenetetrahydrofolate reductase genotype 677CT and non-alcoholic fatty liver disease have a synergistic effect on the increasing homocysteine levels in subjects from Chongqing,China

The methylenetetrahydrofolate reductase(MTHFR)genotypes 677CT and 677TT are associated with elevated serum homocysteine(Hcy)levels by means of lowering the activity of MTHFR,and the increase in serum Hcy may be linked to increased susceptibility to nonalcoholic fatty liver disease(NAFLD).However,there are contradictory reports of the relationship among the MTHFR 677CT gene polymorphism,Hcy,and NAFLD.Therefore,the aim of this study was to identify potential associations and interactions of either Hcy levels or the MTHFR 677CT gene polymorphism with the susceptibility to NAFLD in a Chinese population.The association between the MTHFR 677 CT gene polymorphism and Hcy levels was determined in 243 subjects with NAFLD and 388 healthy subjects without NAFLD using polymerase chain reactionrestriction fragment length polymorphism analysis and high-performance liquid chromatography.In subjects with NAFLD,there was no statistical difference in the genotypic and allelic frequencies of the MTHFR 677 CT gene polymorphism,while serum Hcy levels were significantly higher in subjects with NAFLD.Furthermore,these results strongly suggest that the MTHFR 677CT gene polymorphism and NAFLD have a potential synergistic effect on Hcy elevation,although the MTHFR 677CT gene polymorphism was not correlated with NAFLD in a Chinese population.

Characteristics and Possible Formation Mechanisms of Severe Storms in the Outer Rainbands of Typhoon Mujigae(1522)

To better understand how severe storms form and evolve in the outer rainbands of typhoons, in this study, we in- vestigate the evolutionary characteristics and possible formation mechanisms for severe storms in the rainbands of Typhoon Mujigae, which occurred during 2-5 October 2015, based on the NCEP-NCAR reanalysis data, conventional observations, and Doppler radar data. For the rainbands far from the inner core （eye and eyewall） of Mujigae （dis- tance of approximately 70-800 kin）, wind speed first increased with the radius expanding from the inner core, and then decreased as the radius continued to expand. The Rankine Vortex Model was used to explore such variations in wind speed. The areas of strong stormy rainbands were mainly located in the northeast quadrant of Mujigae, and overlapped with the areas of high winds within approximately 300-550 km away from the inner core, where the strong winds were conducive to the development of strong storms. A severe convective cell in the rainbands de- veloped into waterspout at approximately 500 km to the northeast of the inner core, when Mujigae was strengthening before it made landfall. Two severe convective cells in the rainbands developed into two tornadoes at approximately 350 km to the northeast of the inner core after Mujigae made landfall. The radar echo bands enhanced to 60 dBZ when mesocyclones occurred in the rainbands and induced tornadoes. The radar echoes gradually weakened after the mesocyclones weakened. The tops of parent clouds of the mesocyclones elevated at first, and then suddenly dropped about 20 min before the tornadoes appeared. Thereby, the cloud top variation has the potential to be used as an early warning of tornado occurrence.

The combination of methylenehydrofolate reductase C677T polymorphism screening and gastrointestinal tumor markers detection may be an early screening method for gastrointestinal cancer related to helicobacter pylori infection

Methyltetrahydrofolate reductase(MTHFR)is a key enzyme in folate metabolism,and its single nucleotide polymorphism(SNP)site C677T may be associated with gastrointestinal cancer.However,the relationship between MTHFR C677T polymorphism and gastrointestinal tumor markers carcinoma embryonic antigen(CEA),carbohydrate antigen 199(CA199)and carbohydrate antigen 724(CA724)in Helicobacter pylori(H.pylori)infection is not specified.This study aims to identify the association between MTHFR C677T polymorphism and gastrointestinal tumor markers(CEA,CA199 and CA724)in H.pylori infection.The relationship between MTHFR C677T polymorphism and gastrointestinal tumor markers in 58 patients with H.pylori infection and 94 non-infected patients was studied.We found that TT genotype was a susceptibility factor of H.pylori infection,which was also associated with increased CEA and CA724 levels.Moreover,there was a negative additive interaction between MTHFR gene C677T polymorphism and CEA levels in H.pylori infection.Meanwhile,there were significant differences in CEA levels between MTHFR C677T polymorphism and H.pylori infection.The presence of T allele led to a decrease in CEA levels when ^(13)C urea breath test(^(13)C-UBT)was positive,while the presence of T allele led to an increase in CEA levels when ^(13)C-UBT was negative.Therefore,we suggest that healthy people should take MTHFR C677T polymorphism screening,combined with ^(13)C-UBT and gastrointestinal tumor markers detection,which can screen out the susceptible population of H.pylori,and help to detect gastrointestinal cancer in the early stage.

Trends and Uncertainties in Surface Air Temperature over the Tibetan Plateau,1951–2013

Trends and uncertainties of surface air temperature over the Tibetan Plateau（TP）are evaluated by using observations at 100 meteorological stations during the period 1951–2013.The sampling error variances of gridded monthly data are estimated for every month and every grid box of data.The gridded data and their sampling error variances are used to calculate TP averages,their trends,and associated uncertainties.It is shown that large sampling error variances dominate northern and western TP,while small variances appear over southern and eastern TP.Every month from January to December has a positive linear trend during the study period.February has the largest trend of 0.34±0.18°C（10 yr）^（–1）,and April the smallest at 0.15±0.11°C（10 yr）^（–1）.The uncertainties decrease steadily with time,implying that they are not large enough to alter the TP warming trend.

Effect of laser-discrete-quenching on bonding properties of electroplated grinding wheel with AISI 1045 steel substrate and nickel bond

To improve the bonding strength between the nickel bond and the hub of the electroplated diamond grinding wheel,a hybrid technique was proposed to combine laser prequenching steel substrate and post-electroplating nickel.To validate the effectiveness of the proposed technique,AISI 1045 substrate was nickel-coated.The bonding properties between the electroplated nickel coating and substrate with or without laser-discrete-quenching were discussed comparatively by scratch,indentation,and thermal shock tests.The results show that the prequenching treatment leads to phase transformation of AISI 1045 microstructure from the mixed pearlite and ferrite phases into the martensitic phase.Since the martensitic phase is characterized as a high corrosion resistance,the interface of substrate/coating is smooth and flat in the prequenched zone,and the coating is bonded well with the steel substrate.In contrast to the steel substrate without pre-quenching treatment,the proposed technique significantly enhanced the bonding strengths of the electroplated nickel-coating.On one hand,the average hardness of electroplated nickel-coating on the laser pre-quenched zone is increased by 18.7%,and the scratch depth with the same load become narrower and shallower.On the other hand,the coefficient of friction(CoF)and the vibration amplitude are reduced,and the coating is bonded effectively with the substrate to inhibit the crack initialization at the interface.This prevents effectively the coating from peeling off and improves significantly the thermal shock resistance property.