Towards on the MOOCs Knowledge Discovery Based on Concept Lattice

Junfeng Gao,Jingye Qu,Zhong Xin 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.5

This paper puts forward the methods on MOOCs knowledge organization and discovery, adopts the method of Formal Concept Analysis, uses concept lattice as the support tool, and selects the data from “Coursera” to cluster the courses and mine the inner knowledge association among courses, so as to discover the connotative knowledge correlation among MOOCs on the same topic and the structure characteristics among courses. Finally, based on the supergraph of the MOOCs concept lattice, the paper puts forward the visualization navigation method of the courses and provides flexible guiding principles for the learners whose knowledge structure is unusual in various fields when choosing the courses, so as to promote the development and improvement of the MOOCs websites by the knowledge organization and knowledge discovery technology.

Research Progress of Hydrostatic Bearing and Hydrostatic-Hydrodynamic Hybrid Bearing in High-End Computer Numerical Control Machine Equipment

Xiaodong Yu,Weicheng Gao,Yanan Feng,Guangqiang Shi,Shihao Li,Minmin Chen,Ruiming Zhang,Junfeng Wang,Wentao Jia,Jianhua Jiao,Ruichun Dai 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.6

Hydrostatic bearing has the advantages of wide speed range, large bearing capacity, high precision and stability. Hydrostatic-hydrodynamic hybrid bearing can make up for the lack of stiffness of hydrostatic bearing and prevent tribological failure under the condition of high speed and heavy load. Therefore, hydrostatic bearing and hydrostatic-hydrodynamic hybrid bearing have become important bearing parts of high-end computer numerical control (CNC) machine equipment. The research on hydrostatic and hydrostatic-hydrodynamic open a new way for precision improvement of high-end CNC machine equipment. This paper reviews research progress of hydrostatic linear guideway, hydrostatic rest and ram, hydrostatic thrust bearing, hydrostatic-hydrodynamic thrust bearing and hydrostatic-hydrodynamic spindle of high-end CNC machine equipment, and discusses the influence of structure and working parameters on lubrication performance, accuracy and stability of bearing parts. Finally, the future research direction in hydrostatic bearing and hydrostatic-hydrodynamic hybrid bearing are suggested. This review provides a theoretical basis for design and development of high-end CNC machine equipment in the future.

Platelet Nitrogen and Sulfur Co-doped Ordered Mesoporous Carbon with Inexpensive Methylene Blue as a Single Precursor for Electrochemical Detection of Herbicide Amitrole

Shenghai Zhou,Hongbo Xu,Yanjun Wei,Jing Gao,Yue Feng,Ning Wang,Junfeng Gao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.8

Heteroatom-doped ordered mesoporous carbons (OMCs) have currently been considered as promising electrode materials for electrochemical sensors due to the combined advantages of ordered mesoporous materials and heteroatom-doped carbon materials. Herein, a novel nitrogen and sulfur co-doped OMCs (N,S-OMC) has been prepared via a nanocasting strategy with an inexpensive methylene blue as single precursor. The obtained mesoporous carbon has platelet morphology, short mesoporous channel together with a large surface area (549 m2/g) as well as rich N- and S-containing functional groups (6.8 at.% N and 2.3 at.% S). Compared with the graphene (GR) and carbon nanotube (CNT) electrode material, the N,S-OMC exhibited a higher electrochemical activity towards the oxidation of herbicide amitrole, ascribable to N,S-OMC's open mesoporous structures and abundant electroactive defect sites on the carbon skeleton. And, an amitrole electrochemical sensor with N,S-OMC modified electrode as working electrode was fabricated, exhibiting a good selectivity, stability, reproducibility and wide linear range of 3–750 μM. Moreover, the N,S-OMC-based electrochemical sensor was proved feasible in river water sample analyses, showing a satisfied recovery ranging from 97.03% to 105.42%. The results not only demonstrate cheap methylene blue can be used as single precursor for the N,S-OMC preparation, but also confirm the N,S-OMC is promising in amitrole sensor fabrication.

Roll-to-Roll Gravure Printed Electrochemical Sensors for Wearable and Medical Devices

Bariya, Mallika,Shahpar, Ziba,Park, Hyejin,Sun, Junfeng,Jung, Younsu,Gao, Wei,Nyein, Hnin Yin Yin,Liaw, Tiffany Sun,Tai, Li-Chia,Ngo, Quynh P.,Chao, Minghan,Zhao, Yingbo,Hettick, Mark,Cho, Gyoujin,Jav American Chemical Society 2018 ACS NANO Vol.12 No.7

<P>As recent developments in noninvasive biosensors spearhead the thrust toward personalized health and fitness monitoring, there is a need for high throughput, cost-effective fabrication of flexible sensing components. Toward this goal, we present roll-to-roll (R2R) gravure printed electrodes that are robust under a range of electrochemical sensing applications. We use inks and electrode morphologies designed for electrochemical and mechanical stability, achieving devices with uniform redox kinetics printed on 150 m flexible substrate rolls. We show that these electrodes can be functionalized into consistently high performing sensors for detecting ions, metabolites, heavy metals, and other small molecules in noninvasively accessed biofluids, including sensors for real-time, <I>in situ</I> perspiration monitoring during exercise. This development of robust and versatile R2R gravure printed electrodes represents a key translational step in enabling large-scale, low-cost fabrication of disposable wearable sensors for personalized health monitoring applications.</P> [FIG OMISSION]</BR>

Roles of RpoS in Yersinia pseudotuberculosis stress survival, motility, biofilm formation and type VI secretion system expression

Jingyuan Guan,Xiao Xiao,Shengjuan Xu,Fen Gao,Jianbo Wang,Tietao Wang,Yunhong Song,Junfeng Pan,Xihui Shen,Yao Wang 한국미생물학회 2015 The journal of microbiology Vol.53 No.9

RpoS (σS), the stationary phase/stress σ factor, controls the expression of a large number of genes involved in cellular responses to a variety of stresses. However, the role of RpoS appears to differ in different bacteria. While RpoS is an important regulator of flagellum biosynthesis, it is associated with biofilm development in Edwardsiella tarda. Biofilms are dense communities formed by bacteria and are important for microbe survival under unfavorable conditions. The type VI secretion system (T6SS) discovered recently is reportedly associated with several phenotypes, ranging from biofilm formation to stress sensing. For example, Vibrio anguillarum T6SS was proposed to serve as a sensor for extracytoplasmic signals and modulates RpoS expression and stress response. In this study, we investigated the physiological roles of RpoS in Yersinia pseudotuberculosis, including bacterial survival under stress conditions, flagella formation, biofilm development and T6SS expression. We found that RpoS is important in resistance to multiple stressors–including H2O2, acid, osmotic and heat shock–in Y. pseudotuberculosis. In addition, our study showed that RpoS not only modulates the expression of T6SS but also regulates flagellum formation by positively controlling the flagellar master regulatory gene flhDC, and affects the formation of biofilm on Caenorhabditis elegans by regulating the synthesis of exopolysaccharides. Taken together, these results show that RpoS plays a central role in cell fitness under several adverse conditions in Y. pseudotuberculosis.

Hardware Implementation of Two-level Scheduling Algorithm in μC/OS-II

Guangwu Zhang,Yan Li,Yidong Chen,Huaiguo Dong,Huanhuan Chi,Min Shi,Junfeng Gao 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.4

Aiming at the problem that μC/OS-II does not support round-robin scheduling of the same priority task, a two-level hybrid task scheduling strategy was proposed. In the first level, by putting the task priority as criterion for task scheduling, a preemptive scheduling of different priority task was implemented. And in the second level, adopting time slice circulars scheduling strategy, round-robin scheduling of same priority task was implemented. The waiting list of tasks was designed by on-chip registers of FPGA and the ready list of tasks was designed by RAM of FPGA, and to implement time slice circulars scheduling, hardware circuit for finding successor of task was designed. The system adopted VHDL, and simulated by the software ISE10.1. The simulation results show that the hardware implementation of the system is well-worked.

Physicochemical properties, multi-elemental composition, and antioxidant activity of five unifloral honeys from Apis cerana cerana

Jiao Wu,Shan Zhao,Xin Chen,Yuanda Jiu,Junfeng Liu,Jinglin Gao,Shijie Wang 한국식품과학회 2023 Food Science and Biotechnology Vol.32 No.13

Honey quality is in relation to botanical origin, and physicochemical properties, elemental composition, and antioxidant activity have been used for assessment and identification of honeys. The goal of this study is to contribute to the general analysis of five unifloral honeys from Cocos nucifera L., Dalbergia benthami Prain, Bombax ceiba L., Castanea mollissima Bl., and mangrove in Hainan province, China. Our results revealed that B. ceiba honey had the highest pH (4.27), color (139.33 mm Pfund), ash content (1.03 g/100 g), and electrical conductivity (1312.00 μS/cm) in five unifloral honeys. Furthermore, B. ceiba honey also contained the highest levels of total phenolic content (75.54 mg GAE/100 g) and total flavonoid content (29.22 mg RE/100 g), as well as the strongest antioxidant activity (DPPH IC50 value, 3.97 mg/mL; FRAP value, 6527.43 µmol TE/kg). Moreover, we revealed a considerable variation in element contents in honeys using ICP-MS, with potassium being the most predominant element. B. ceiba honey had the highest contents of K, Ca, Mg, and P, whereas the highest amount of Na was found in mangrove honey. Overall, our data indicated that B. ceiba honey deserves further research as a potential antioxidant agent.

Quinoxaline-Based Wide Band Gap Polymers for Efficient Nonfullerene Organic Solar Cells with Large Open-Circuit Voltages

Yang, Jie,Uddin, Mohammad Afsar,Tang, Yumin,Wang, Yulun,Wang, Yang,Su, Huimin,Gao, Rutian,Chen, Zhi-Kuan,Dai, Junfeng,Woo, Han Young,Guo, Xugang American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.27

<P>We present here a series of wide-band-gap (<I>E</I><SUB>g</SUB>: >1.8 eV) polymer donors by incorporating thiophene-flanked phenylene as an electron-donating unit and quinoxaline as an electron-accepting co-unit to attain large open-circuit voltages (<I>V</I><SUB>oc</SUB>s) and short-circuit currents (<I>J</I><SUB>sc</SUB>s) in nonfullerene organic solar cells (OSCs). Fluorination was utilized to fine-tailor the energetics of polymer frontier molecular orbitals (FMOs) by replacing a variable number of H atoms on the phenylene moiety with F. It was found that fluorination can effectively modulate the polymer backbone planarity through intramolecular noncovalent S···F and/or H···F interactions. Polymers (P2-P4) show an improved molecular packing with a favorable face-on orientation compared to their nonfluorinated analogue (P1), which is critical to charge carrier transport and collection. When mixed with IDIC, a nonfullerene acceptor, P3 with two F atoms, achieves a remarkable <I>V</I><SUB>oc</SUB> of 1.00 V and a large <I>J</I><SUB>sc</SUB> of 15.99 mA/cm<SUP>2</SUP>, simultaneously, yielding a power-conversion efficiency (PCE) of 9.7%. Notably, the 1.00 V <I>V</I><SUB>oc</SUB> is among the largest values in the IDIC-based OSCs, leading to a small energy loss (<I>E</I><SUB>loss</SUB>: 0.62 eV) while maintaining a large PCE. The P3:IDIC blend shows an efficient exciton dissociation through hole transfer even under a small energy offset of 0.16 eV. Further fluorination leads to the polymer P4 with increased chain-twisting and mismatched FMO levels with IDIC, showing the lowest PCE of 2.93%. The results demonstrate that quinoxaline-based copolymers are promising donors for efficient OSCs and the fluorination needs to be fine-adjusted to optimize the interchain packing and physicochemical properties of polymers. Additionally, the structure-property correlations from this work provide useful insights for developing wide-band-gap polymers with low-lying highest occupied molecular orbitals to minimize <I>E</I><SUB>loss</SUB> and maximize <I>V</I><SUB>oc</SUB> in nonfullerene OSCs for efficient power conversion.</P> [FIG OMISSION]</BR>