Chemical Vapor Deposition Growth of Graphene Domains Across the Cu Grain Boundaries

Yang Wang,Yu Cheng,Yunlu Wang,Shuai Zhang,Chen Xu,Xuewei Zhang,Miao Wang,Yang Xia,Qunyang Li,Pei Zhao,Hongtao Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.08

Many aspects in the chemical vapor deposition (CVD) growth of graphene remain unclear such as its behavior near the catalyst grain boundaries. Here we investigate the CVD growth mechanism of graphene across the Cu grain boundaries using unidirectional aligned graphene domains, which simplifies the analysis of both graphene and Cu to a large extent. We found that for a graphene domain grown across the Cu grain boundary, the domain orientation is determined by the Cu grain where the domain nucleation center is located, and the Cu grain boundary will not change the growth behavior for this graphene domain. This growth mechanism is consistent with the Custep-attached nucleation and edge-attachment-limited growth mechanism for H-terminated graphene domains and will provide more guidance for the synthesis of high-quality graphene with less domain boundaries.

Hemicastration induced spermatogenesis-related DNA methylation and gene expression changes in mice testis

Yixin Wang,Long Jin,Jideng Ma,Li Chen,Yuhua Fu,Keren Long,Silu Hu,Yang Song,Dazhi Shang,Qianzi Tang,Xun Wang,Xuewei Li,Mingzhou Li 아세아·태평양축산학회 2018 Animal Bioscience Vol.31 No.2

Objective: Hemicastration is a unilateral orchiectomy to remove an injured testis, which can induce hormonal changes and compensatory hypertrophy of the remaining testis, and may influence spermatogenesis. However, the underlying molecular mechanisms are poorly understood. Here, we investigated the impact of hemicastration on remaining testicular function. Methods: Prepubertal mice (age 24 days) were hemicastrated, and their growth was monitored until they reached physical maturity (age 72 days). Subsequently, we determined testis DNA methylation patterns using reduced representation bisulfite sequencing of normal and hemicastrated mice. Moreover, we profiled the testicular gene expression patterns by RNA sequencing (RNA-seq) to examine whether methylation changes affected gene expression in hemicastrated mice. Results: Hemicastration did not significantly affect growth or testosterone (p>0.05) compared with control. The genome-wide DNA methylation pattern of remaining testis suggested that substantial genes harbored differentially methylated regions (1,139) in gene bodies, which were enriched in process of protein binding and cell adhesion. Moreover, RNA-seq results indicated that 46 differentially expressed genes (DEGs) involved in meiotic cell cycle, synaptonemal complex assembly and spermatogenesis were upregulated in the hemicastration group, while 197 DEGs were downregulated, which were related to arachidonic acid metabolism. Integrative analysis revealed that proteasome 26S subunit ATPase 3 interacting protein gene, which encodes a protein crucial for homologous recombination in spermatocytes, exhibited promoter hypomethylation and higher expression level in hemicastrated mice. Conclusion: Global profiling of DNA methylation and gene expression demonstrated that hemicastration-induced compensatory response maintained normal growth and testicular morphological structure in mice.

Model-free Optimal Tracking Control for an Aircraft Skin Inspection Robot with Constrained-input and Input Time-delay via Integral Reinforcement Learning

Xuewei Wu,Congqing Wang 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.1

This paper presents a model-free optimal tracking control algorithm for an aircraft skin inspection robot with constrained-input and input time-delay. To tackle the input time-delay problem, the original system is transformed into a delay-free system with constrained-input and unknown input coupling term. In order to overcome the optimal control problem subject to constrained-input,a discounted value function is employed. In general, it is known that the HJB equation does not admit a classical smooth solution. Moreover, since the input coupling term of the delay-free system is unknown, a model-free integral reinforcement learning(IRL) algorithm which only requires the system sampling data generated by arbitrary different control inputs and external disturbances is proposed. The model-free IRL method is implemented on an actor-critic neural network (NN) structure. A system sampling data set is utilized to learn the value function and control policy. Finally, the simulation verifies the effectiveness of the proposed algorithm.

Small Signal Modeling, Analysis and Control of Naturally Clamped Soft-switching Current-fed Three-Phase Bidirectional DC/DC Converter

Xuewei Pan,Peng Wang,Quoc Nam Trinh,Akshay Kumar Rathore 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

A small signal analysis and a closed loop control design of naturally commutated current-fed threephase isolated dc/dc converter are presented in this paper. State-space averaging technique is used to derive the small signal model. Based on the derived small signal model, a closed two-loop controller is designed and implemented on mixed signal (analog and digital) processor Cypress PSoC 5. A complete design procedure is presented. Simulation results using PSIM 9.0.4 and experimental waveforms from a 750W prototype with the designed controller are illustrated to verify the stability of the control system. Experimental results for step changes in load clearly show satisfactory transient performance of the converter and validate closed two-loop design.

Long-chain alcohols derived from the microalga Monoraphidium

Yang, Xuewei,Dai, Xin,Zhang, Rui,Shao, Cong,Geng, Shu,Chen, Guangyi,Liu, Xianhua,Wang, Guangyi Techno-Press 2013 Advances in energy research Vol.1 No.2

This study was to investigate the composition and characteristics of long-chained alcohols extracted from the algal strain Monoraphidium 3s35. The production of biomass was optimized using different cultivation methods. Under the aerated growth condition, this strain yielded up to 37.26% extracts of dry weight and $576mgL^{-1}$ biomass. The major compounds of the extracts are mainly long-chained alcohols (89.24%), with carbon chain length ranging from 12 to 20. Interestingly, or the long-chained alcohols, 3-(2-Methoxyethyl)-1-nonanol, 3,7,11,15-Tetramethyl-2-hexadecen-1-ol and oleyl alcohol accounted for 53.68%, 23.45%, and 12.11%, respectively. Because of their amphipathic nature, these long-chained alcohols have been widely used in bioenergy production and cosmetics industry. Furthermore, Monoraphidium 3s35 produced 9.73% of $C_{17}$ and $C_{20}$ alkanes, which can be used as an important supplement for the petrodiesel-like fuel.

Switching Motion Control of Aircraft Skin Inspection Robot Using Backstepping Scheme and Nussbaum Disturbance Observer

Congqing Wang,Junjun Jiang,Xuewei Wu,Linfeng Wu 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.6

In this paper, a backstepping control using switching strategy is proposed for the motion control of the aircraft skin inspection robot with double frame in the presence of external disturbances. The inspection robot equipped with a CCD camera and an ultrasonic sensor can alternately adsorb and move on the aircraft surface. The influence of the external disturbances is obvious in the switching motion. The disturbances are efficiently estimated using a Nussbaum disturbance observer (NDO), and the disturbance observer errors are uniformly ultimately bounded. Then, the backstepping control method is used to design the motion controller. The stability of the closed-loop robot system is proved by Lyapunov analysis through the average dwell time method .The tracking errors and the disturbance observer errors are semi-globally uniformly bounded using the proposed control schemewith NDO,and NDO is compared with Super-twisting disturbance observer. Finally, simulation results illustrate that the proposed control scheme with NDO can achieve satisfactory tracking performance under the external disturbance.

Anaerobic Ammonium-Oxidizing Bacteria in Cow Manure Composting

( Tingting Wang ),( Lijun Cheng ),( Wenhao Zhang ),( Xiuhong Xu ),( Qingxin Meng ),( Xuewei Sun ),( Huajing Liu ),( Hongtao Li ),( Yu Sun ) 한국미생물생명공학회(구 한국산업미생물학회) 2017 Journal of microbiology and biotechnology Vol.27 No.7

Composting is widely used to transform waste into valuable agricultural organic fertilizer. Anaerobic ammonium-oxidizing (anammox) bacteria play an important role in the global nitrogen cycle, but their role in composting remains poorly understood. In the present study, the community structure, diversity, and abundance of anammox bacteria were analyzed using cloning and sequencing methods by targeting the 16S rRNA gene and the hydrazine oxidase gene (hzo) in samples isolated from compost produced from cow manure and rice straw. A total of 25 operational taxonomic units were classified based on 16S rRNA gene clone libraries, and 14 operational taxonomic units were classified based on hzo gene clone libraries. The phylogenetic tree analysis of the 16S rRNA gene and deduced HZO protein sequences from the corresponding encoding genes indicated that the majority of the obtained clones were related to the known anammox bacteria Candidatus “Brocadia,” Candidatus “Kuenenia,” and Candidatus “Scalindua.” The abundances of anammox bacteria were determined by quantitative PCR, and between 2.13 × 10⁵ and 1.15 × 10⁶ 16S rRNA gene copies per gram of compost were found. This study provides the first demonstration of the existence of anammox bacteria with limited diversity in cow manure composting.

Viscosity evaluation of Fe–Ni–Co ternary alloy from the measured binary systems

Yanhui Liu,Xuewei Lv,Chenguang Bai,Pingsheng Lai,JinSheng Wang 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.30 No.-

The iso-viscosity curves of liquid Fe–Ni–Co ternary alloys at 1600 8C were investigated with consideringthe excess viscosity of ternary alloy by the means of three models (Kohler, Toop and Chou) from themeasured sub-binary data in this work. Excess viscosities were used instead of excess thermodynamicproperties in geometrical models, and the excess viscosities of the sub-binary systems were fit by usingthe 3rd degree (n = 3) Redlich–Kister polynomial. The increase of Ni content results in the decrease of theviscosity of the ternary alloy, while Fe has opposite effect. When the molar content of Ni within the alloydoes not exceed 50%, the increase of Co lowers the viscosity. Once its content is above 50%, Co canpromote the increase of the viscosity of the ternary alloy. Similarity coefficients of the Fe–Ni, Fe–Co andNi–Co three binary systems mentioned in the Chou model have been calculated and their values are 0.82,0.20 and 0.47, respectively, showing that the Fe–Ni–Co ternary system is not exactly the ‘‘Kohler model’’or ‘‘Toop model’’, so both Kohler model and Toop model cannot obtain the accurate predicted values. Thepredicted iso-viscosity curves calculated by the Chou model should be recommended. Some activationenergies of the ternary alloy were calculated by the three models and compared with three sub-binarysystems, and the evaluated activation energies calculated by the Chou model should be recommended. Except the sample AE3 and AE6, other activation energy values predicted by three different models aresimilar by a narrow margin. The activation energies for AE3 and AE6 are the lowest and highest,respectively, because of the mix effect of the ternary alloy.

Hybrid Energy Supply based Energy Efficiency and Spectral Efficiency Tradeoff for Green Cellular System

Baogang Li,Xuewei Wang 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.3

The tradeoff between energy efficiency (EE) and spectral efficiency (SE) under the smart grid with joint energy harvesting and grid power supply is considered. The price factor in economics is used to propose the economic EE and SE. Then a new EE-SE tradeoff metric called the EE-SE adaptive tradeoff (ESAT) is built under the fluctuating harvesting energy. Furthermore, the offline optimization problem is put forward and the solution is discussed. The offline solutions based on the branch-and-bound algorithm and the Lagrange dual decomposition method are discussed to analyze the influence of renewable energy quantity on the proposed structure. Numerical results indicate that the proposed ESAT framework is efficient to the tradeoff between EE and SE.

Raman Spectral Band Oscillations in Large Graphene Bubbles

Huang, Yuan,Wang, Xiao,Zhang, Xu,Chen, Xianjue,Li, Baowen,Wang, Bin,Huang, Ming,Zhu, Chongyang,Zhang, Xuewei,Bacsa, Wolfgang S.,Ding, Feng,Ruoff, Rodney S. American Physical Society 2018 Physical Review Letters Vol.120 No.18

<P>Raman spectra of large graphene bubbles showed size-dependent oscillations in spectral intensity and frequency, which originate from optical standing waves formed in the vicinity of the graphene surface. At a high laser power, local heating can lead to oscillations in the Raman frequency and also create a temperature gradient in the bubble. Based on Raman data, the temperature distribution within the graphene bubble was calculated, and it is shown that the heating effect of the laser is reduced when moving from the center of a bubble to its edge. By studying graphene bubbles, both the thermal conductivity and chemical reactivity of graphene were assessed. When exposed to hydrogen plasma, areas with bubbles are found to be more reactive than flat graphene.</P>