Multi-terminal transport measurements of MoS2 using a van der Waals heterostructure device platform.

Cui, Xu,Lee, Gwan-Hyoung,Kim, Young Duck,Arefe, Ghidewon,Huang, Pinshane Y,Lee, Chul-Ho,Chenet, Daniel A,Zhang, Xian,Wang, Lei,Ye, Fan,Pizzocchero, Filippo,Jessen, Bjarke S,Watanabe, Kenji,Taniguchi, Nature Pub. Group 2015 Nature nanotechnology Vol.10 No.6

<P>Atomically thin two-dimensional semiconductors such as MoS2 hold great promise for electrical, optical and mechanical devices and display novel physical phenomena. However, the electron mobility of mono- and few-layer MoS2 has so far been substantially below theoretically predicted limits, which has hampered efforts to observe its intrinsic quantum transport behaviours. Potential sources of disorder and scattering include defects such as sulphur vacancies in the MoS2 itself as well as extrinsic sources such as charged impurities and remote optical phonons from oxide dielectrics. To reduce extrinsic scattering, we have developed here a van der Waals heterostructure device platform where MoS2 layers are fully encapsulated within hexagonal boron nitride and electrically contacted in a multi-terminal geometry using gate-tunable graphene electrodes. Magneto-transport measurements show dramatic improvements in performance, including a record-high Hall mobility reaching 34,000???cm(2)???V(-1)???s(-1) for six-layer MoS2 at low temperature, confirming that low-temperature performance in previous studies was limited by extrinsic interfacial impurities rather than bulk defects in the MoS2. We also observed Shubnikov-de Haas oscillations in high-mobility monolayer and few-layer MoS2. Modelling of potential scattering sources and quantum lifetime analysis indicate that a combination of short-range and long-range interfacial scattering limits the low-temperature mobility of MoS2.</P>

Low-Temperature Ohmic Contact to Monolayer MoS₂ by van der Waals Bonded Co/<i>h</i>-BN Electrodes

Cui, Xu,Shih, En-Min,Jauregui, Luis A.,Chae, Sang Hoon,Kim, Young Duck,Li, Baichang,Seo, Dongjea,Pistunova, Kateryna,Yin, Jun,Park, Ji-Hoon,Choi, Heon-Jin,Lee, Young Hee,Watanabe, Kenji,Taniguchi, Tak American Chemical Society 2017 NANO LETTERS Vol.17 No.8

<P>Monolayer MoS2, among many other transition metal dichalcogenides, holds great promise for future applications in nanoelectronics and optoelectronics due to its ultrathin nature, flexibility, sizable band gap, and unique spin valley coupled physics. However, careful study of these properties at low temperature has been hindered by an inability to achieve low-temperature Ohmic contacts to monolayer MoS2, particularly at low carrier densities. In this work, we report a new contact scheme that utilizes cobalt (Co) with a monolayer of hexagonal boron nitride (h-BN) that has the following two functions: modifies the work function of Co and acts as a tunneling barrier. We measure a flat-band Schottky barrier of 16 meV, which makes thin tunnel barriers upon doping the channels, and thus achieve low-T contact resistance of 3 k Omega.mu m at a carrier density of 5.3 x 10(12)/cm(2). This further allows us to observe Shubnikov-de Haas oscillations in monolayer MoS2 at much lower carrier densities compared to previous work.</P>

Multifunctional, flexible and mechanically resilient porous polyurea/graphene composite film

Xu Cui,Chunyan Zhang,Sherif Araby,Rui Cai,Gulnur Kalimuldina,Zhaokun Yang,Qingshi Meng 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.105 No.-

In this study, a porous polyurea/graphene platelet (GnP) composite film with high flexibility and multifunctionalitywas developed and investigated for strain sensing and energy storage applications. Morphology and mechanical properties were studied; tensile strength and Young’s modulus wereenhanced by 132% and 900%, respectively at 5 wt% GnPs. The polyurea/GnP film exhibited high sensitivityto various strains– namely, tension, compression, bending and twisting. In tensile strain, gauge factor was1.86 and 6.26 within strain ranges of 0–30% and 30–60%, respectively. Interestingly, the film showedpiezoresistive and capacitive-type strain sensor under compression load; a 33% increase in relative resistancewith response time of 108 millisecond; and 22% increase in relative capacitance with response timeof 92 millisecond when load of 5 kPa was applied. Furthermore, the strain sensor showed high durabilityand reliability over 20,000 cycles. The developed polyurea/GnP film showed a stable capacitive performanceover 20,000 charge–discharge cycles. This work provides important insights for the potential ofpolyurea/graphene films in multifunctional sensors and flexible energy storage applications.

Investigation of One-dimensional Consolidation of Fractional Derivative Model for Viscoelastic Saturated Soils Caused by the Groundwater Level Change

Xu-Bing Xu,Zhen-Dong Cui 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.12

The Fractional calculus theory is introduced into the Merchant model to study the mechanical characteristics of saturated soils. Laplace transform is applied to the 1D consolidation and the fractional derivative Merchant model constitutive equations of saturated soils. In the transform domain, the analytical solutions of effective stress and settlement are obtained by solving the simultaneous equation. The Crump’s method is used to the numerical inversion of Laplace transform, and the semi-analytical solution of the one-dimensional consolidation is obtained. A series of parameters, such as the fractional order, compression modulus, coefficient of viscosity, permeability coefficient and the variation models of groundwater level, are studied. Considering the continuity conditions, the 1D consolidation equation of single-layer saturated soil is generalized to multi-layer soils, and then the influence of different boundaries on several kinds of consolidation behavior was analyzed.

Enhancing the Anaerobic Digestion of Corn Stalks Using Composite Microbial Pretreatment

( Xu Feng Yuan ),( Pei Pei Li ),( Hui Wang ),( Xiao Fen Wang ),( Xu Cheng ),( Zong Jun Cui ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.7

A composite microbial system (XDC-2) was used to pretreat and hydrolyze corn stalk to enhance anaerobic digestion. The results of pretreatment indicated that sCOD concentrations of hydrolysate were highest (8,233 mg/l) at the fifth day. XDC-2 efficiently degraded the corn stalk by nearly 45%, decreasing the cellulose content by 22.7% and the hemicellulose content by 74.1%. Total levels of volatile products peaked on the fifth day. The six major compounds present were ethanol (0.29 g/l), acetic acid (0.55 g/l), 1,2-ethanediol (0.49 g/l), propionic acid (0.15 g/l), butyric acid (0.22 g/l), and glycerine (2.48 g/l). The results of anaerobic digestion showed that corn stalks treated by XDC-2 produced 68.3% more total biogas and 87.9% more total methane than untreated controls. The technical digestion time for the treated corn stalks was 35.7% shorter than without treatment. The composite microbial system pretreatment could be a cost-effective and environmentally friendly microbial method for efficient biological conversion of corn stalk into bioenergy.

Role of Transcutaneous Electrical Nerve Stimulation in Treating Children With Overactive Bladder From Pooled Analysis of 8 Randomized Controlled Trials

Huanqin Cui,Yi Yao,Zhunan Xu,Zhenli Gao,Jitao Wu,Zhongbao Zhou,Yuanshan Cui 대한배뇨장애요실금학회 2020 International Neurourology Journal Vol.24 No.1

Purpose: Transcutaneous electrical neural stimulation (TENS), as a non-invasive modality, has been clinically used as an alternative treatment for children with overactive bladder (OAB). We conducted a pooled analysis to explore the effect of TENS on OAB. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-analysis guideline was followed in this study. The MEDLINE, Embase, and Cochrane Central Register of Controlled Trials databases, as well as the reference lists of the retrieved studies, were used to find trials relevant for assessing the use of TENS to treat OAB. Results: Of the 246 records identified, 8 publications were analyzed in our study. Our analysis found that TENS resulted in a greater decrease of wet days/wk, daily voiding frequency, daily incontinence episodes, and daily number of voids than was observed in the control group. Furthermore, TENS-treated patients showed similar visual analogue scale (VAS) scores to patients in the control group, demonstrating that the application of TENS did not increase patients’ discomfort and pain. TENS had a relative advantage in the number of partial responses, but no clear differences were found in frequency of no response or a full response compared to the control group. In urodynamic testing, TENS led to obvious improvements in average voided volume and maximum voided volume in children with OAB. Conclusions: TENS had a remarkable effect on the improvement of urodynamic indexes and objective OAB symptoms without a significant increase in VAS scores for children with OAB.

Torrential Rainfall Responses to Radiation and Ice Clouds over Jiang-Huai Valley, China in July 2007

Fengwen Xu,Xiaofeng Xu,Xiaopeng Cui,Guoping Zhang 한국기상학회 2013 Asia-Pacific Journal of Atmospheric Sciences Vol.49 No.4

The effects of radiation and ice clouds on a torrential rainfall event of Jiang-Huai Valley over China are investigated through a series of two-dimensional sensitivity cloud-resolving model experiments. The model is integrated with an imposed large-scale vertical velocity and zonal wind constructed from the National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS) from 2 to 9 July 2007, while the control experiment is compared with two sensitivity experiments that exclude radiation and ice clouds, respectively. The exclusion of ice clouds decreases model domain mean surface rain rate through the weakened mean net condensation and the mean hydrometeor change from loss to gain during the life span of the rainfall event. The sensitivity of the mean rain rate to radiation occurs only in the later period of the rainfall event and is less than that to ice clouds. The reduction in the mean rain rate caused by the elimination of radiation is associated with the decreases in the mean net condensation and latent heat, which corresponds to the strengthened mean local atmospheric cooling.

Thermodynamic Analysis of Intergranular Additives in Sintered Nd-Fe-B Magnet

X. G. Cui,X. H. Wang,C. Y. Cui,G. C. Yin,C. D. Xia,X. N. Cheng,X. J. Xu 한국자기학회 2017 Journal of Magnetics Vol.22 No.2

To get deeper insight into the effect of intergranular additives in sintered Nd-Fe-B magnet and consequently improve the properties better, the interaction between additives (oxide, nitride, and carbide) and Nd-rich phase in the temperature range of 298.15-1400 K was analyzed thermodynamically. It can be found that the oxide additives became less stable than nitrides and carbides. Except for calcium oxide, almost all oxides could react with Nd from Nd-rich phase. To be different from oxide additives, the mechanism of nitrides and carbides was defined with various elements, either reaction with Nd from Nd-rich phase or not. The two different mechanisms would show different effects on the microstructure and hence properties of magnet. The thermodynamic analysis had a better agreement with the experimental information.

Design and Implementation of a Time-frequency Analysis System for Non-stationary Vibration Signals Using Mixed Programming

Miaozhong Sun,Shihai Cui,Yuanli Xu 보안공학연구지원센터 2014 International Journal of Hybrid Information Techno Vol.7 No.6

At present, in the feature extraction of non-stationary vibration signals, many time-frequency analytic methods have emerged to meet the further need of non-stationary signal analysis such as Wavelet Transform (WT), Short Time Fourier Transform (STFT), Wigner-Ville Distribution (WVD), Empirical Mode Decomposition (EMD), Ensemble Empirical Mode Decomposition (EEMD) and so on. However, these time-frequency analysis methods can only be carried out on Matlab platform and the processes are of low efficiency, bringing a lot of inconvenience in signal analysis because they can not run on Windows system independently. According to the defects, a novel method of mixed programming which combines Matlab with Delphi based on COM (component Object Model) module technology is proposed to design a time-frequency analysis system for non-stationary vibration signals assembling fourteen methods. The advantages of two languages are shared with each other. In design of the system, a combined method which combines two or three analytic methods is put forward for relational analytic modules to make the analytic results more perfect and clearer, like WAVELET-FFT, EMD-WVD etc.. This paper uses the EMD-WVD combined method as an example to present the programming thoughts and processes. The effectiveness of the system is validated using a simulation signal and an experimental signal. The system can be executed separated from MATLAB environment.

Rhizospheric fungi of Panax notoginseng: diversity and antagonism to host phytopathogens

Cui-Ping Miao,Qi-Li Mi,Xin-Guo Qiao,You-Kun Zheng,You-Wei Chen,Li-Hua Xu,Hui-Lin Guan,Li-Xing Zhao 고려인삼학회 2016 Journal of Ginseng Research Vol.40 No.2

Background: Rhizospheric fungi play an essential role in the plantesoil ecosystem, affecting plant growth and health. In this study, we evaluated the fungal diversity in the rhizosphere soil of 2-yr-old healthy Panax notoginseng cultivated in Wenshan, China. Methods: Culture-independent Illumina MiSeq and culture-dependent techniques, combining molecular and morphological characteristics, were used to analyze the rhizospheric fungal diversity. A diffusion test was used to challenge the phytopathogens of P. notoginseng. Results: A total of 16,130 paired-end reads of the nuclear ribosomal internal transcribed spacer 2 were generated and clustered into 860 operational taxonomic units at 97% sequence similarity. All the operational taxonomic units were assigned to five phyla and 79 genera. Zygomycota (46.2%) and Ascomycota (37.8%) were the dominant taxa; Mortierella and unclassified Mortierellales accounted for a large proportion (44.9%) at genus level. The relative abundance of Fusarium and Phoma sequenceswas high, accounting for 12.9% and 5.5%, respectively. In total,113 fungal isolates were isolated from rhizosphere soil. They were assigned to five classes, eight orders (except for an Incertae sedis), 26 genera, and 43 species based on morphological characteristics and phylogenetic analysis of the internal transcribed spacer. Fusarium was the most isolated genus with six species (24 isolates, 21.2%). The abundance of Phoma was also relatively high (8.0%). Thirteen isolates displayed antimicrobial activity against at least one test fungus. Conclusion: Our results suggest that diverse fungi including potential pathogenic ones exist in the rhizosphere soil of 2-yr-old P. notoginseng and that antagonistic isolates may be useful for biological control of pathogens.