CHIRAL CARBON NANOTUBES AND CARBON NANOTUBE CHIRAL COMPOSITES:PREPARATION AND APPLICATIONS

XIAOQING CHEN,XIAO-YUN LIAO,JIN-GANG YU,FEI-PENG JIAO,XINYU JIANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.4

A review of preparation of chiral carbon nanotubes (CNTs) and carbon nanotube chiral composites is presented. Novel chiral separation science and technology based on CNTs is analyzed and discussed, with the emphasis in two topics. The first topic concerns the possibility of application of chiral CNTs in resolution and chiral sensing. The second topic centers on the subject of enantioseparation based on CNT chiral composites. Despite the crucial functionalization of CNTs using chiral selectors, better resolution could also be achieved by using a mixture of CNTs and optical pure substances as chiral selectors. Due to their ability of improving the degree of enantioseparation, CNTs could find their potential applications in the resolution in the future.

A Multiplexing Modulation Strategy Based on Single-phase AC/DC Converter with OptimizedE-Capless Function

Xiaoqing Wang,Lei Jing,Bodong Li,Ning Chen,Maohang Qiu,Min Chen 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Active power decoupling (APD) techniques prove to be efficient in cutting passive component size for single-phase AC/DC converter, usually against bulky electrolytic capacitors (E-Cap) on DC side. Generally, no adding extra switches is expected to realize E-Capless function as well as original power factor correction (PFC). This paper proposes a multiplexing modulation strategy with optimized power-decoupling reference algorithm, employing a small LC branch as power decoupling circuit to replace large electrolytic capacitors, which could further reduce dclink capacitance. Both simulation and experimental results for a 1kW prototype are presented in this paper to validate the performance of proposed method.

Experimental and Modeling Studies on the Sorption Breakthrough Behaviors of Butanol from Aqueous Solution in a Fixed-bed of KA-I Resin

Xiaoqing Lin,Renjie Li,Qingshi Wen,Jinglan Wu,Jiansheng Fan,Xiaohong Jin,Wenbin Qian,Dong Liu,Xiaochun Chen,Yong Chen,Jingjing Xie,Jianxin Bai,Han-Jie Ying 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.2

Removal of biobutanol from acetone-butanolethanol (ABE) fermentation broth can be achieved by fixed-bed sorption by means of KA-I resin, and the relevant breakthrough curves would provide much valuable information to help design a continuous fixed-bed sorption process in field application. In the present study, the effects of several important design parameters, i.e., initial butanol concentration (Cf: 3.0 ~ 30.0 g/L), inlet flow rate (Qf: 0.5~ 5.5 mL/min) and adsorbent bed height (Z: 4.2 ~ 18.0 cm),on the adsorption breakthrough curves of KA-I resin in a fixed-bed column were investigated. It was found that the amount of adsorbed butanol at breakthrough point was increased with an increase in the value of Cf and Z; and with decrease in the value of Qf. However, the maximum sorption capacities of butanol at saturated point were basically unchanged. Three well-established fixed-bed adsorption models, namely Thomas, Yoon-Nelson and Adams-Bohart,were applied to predict the breakthrough curves and to determine the characteristic parameters of fixed-bed column,which are the basis for the process design at a real scale. Good agreement between the theoretical breakthrough curves and the experimental result were observed using Thomas and Yoon-Nelson models.

Effect of Temperature on the Strength Characteristics of Unsaturated Silty Clay in Seasonal Frozen Region

Huie Chen,Haotian Guo,Xiaoqing Yuan,Yating Chen,Chao Sun 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.9

The strength characteristics of unsaturated silty clay after the cooling and single freeze-thawcycle were studied by using Global Digital Systems Ltd. (GDS) triaxial test system aftercontrolling initial matric suction. The results demonstrate that, the initial matrix suction andfreezing process can strengthen the shear strength of the soil, which makes the stress-straincurve of the soil show certain strain hardening characteristics at different temperatures. whenthe temperature is negative (including 0°C), the curve has a flat transition section whosestrength does not change with deformation, and the flat transition section becomes shorter asthe temperature and confining pressure decrease. The strength of the soil at negativetemperature and the speed at which it reaches its peak value are much greater than those ofthe soil after positive temperature and single freeze-thaw cycle, and the contribution ofconfining pressure to the strength decreases with the decrease of temperature. The effect oftemperature change (15oC to -15oC) on soil strength is mainly reflected in the total cohesion,and the effect of freeze-thaw on the effective internal friction angle is more significant. Thestrength and deformation characteristics of soil under the freezing process and freeze-thawcycle are determined by the initial matric suction, the form of connection between soilparticles, the migration of unfrozen water, and the degree of water-ice phase transformation.

An Accurate Identification of Extended XML Tree Pattern for XQuery Language

Husheng Liao,Xiaoqing Li,Junpeng Chen 보안공학연구지원센터 2014 International Journal of Database Theory and Appli Vol.7 No.5

In order to utilize high-performance XML tree pattern query (TPQ) for implementing of XQuery language effectively, it is necessary to analysis the query plan and identify tree pattern from it. In this paper, we extend the functional intermediate language FXQL, which is used to implement XQuery language, with an extended XML generalized tree pattern representation (GTP++). Then, we propose an XML tree pattern identification approach, which is composed of a suit of query expression rewriting rules for extracting tree pattern and a GTP++ construction algorithm. Based on this approach, both explicit and implied propositional logic, various structural constraints and predicates can be extracted across nested query blocks in XQuery FLWOR expressions. The tree pattern identified by this approach is more holistic and precisely than previous methods. The approach expands the application of XML tree pattern query technology in the implementation of XQuery language. Experiments show its effectiveness and practicability.

In Situ Growth of MOF-Derived NaCoPO4@Carbon for Asymmetric Supercapacitive and Water Oxidation Electrocatalytic Performance

Peng Guo,Zhaojie Wang,Hongyu Chen,Shaohui Ge,Chen Chen,Haowei Wang,Jinbao Zhang,Minglei Hua,Shuxian Wei,Xiaoqing Lu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.15 No.01

The increasing energy crisis promotes the study on novel electrode materials with high performance for supercapacitive storage and energy conversion. Transition metal phosphates have been reported as a potential candidate due to the unique coordination and corresponding electronic structure. Herein, we adopted a facile method for preparing NaCoPO4@C derived from a metal organic framework (MOF) as a bifunctional electrode. ZIF-67 was synthesized before a refluxing process with Na2HPO4 to form a precursor, which is transformed into the final product via calcination in different atmospheres. Specifically, the resultant NaCoPO4@C exhibits a high specific capacitance of 1178.7 F g -1 at a current density of 1 A g -1 for a supercapacitor. An asymmetric supercapacitor (ASC) assembled with active carbon displays a high capacitance of 163.7 F g -1 at 1 A g -1. In addition, as an oxygen evolution reaction (OER) catalyst, the NaCoPO4@C electrode requires only 299 mV to drive a current density of 10 mA cm -2. These results suggest that the rational design of MOF-derived NaCoPO4@C provides a variety of practical applications in electrochemical energy conversion and storage.

Modeling and Design of Zero-Voltage-Switching Controller for Wireless Power Transfer Systems Based on Closed-Loop Dominant Pole

Chen, Cheng,Zhou, Hong,Deng, Qijun,Hu, Wenshan,Yu, Yanjuan,Lu, Xiaoqing,Lai, Jingang The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

Zero-Voltage-Switching (ZVS) operation for a Wireless Power Transfer (WPT) system can be achieved by designing a ZVS controller. However, the performance of the controller in some industrial applications needs to be designed tightly. This paper introduces a ZVS controller design method for WPT systems. The parameters of the controller are designed according to the desired performance based on the closed loop dominant pole placement method. To describe the dynamic characteristics of the system ZVS angle, a nonlinear dynamic model is deduced and linearized using the small signal linearization method. By analyzing the zero-pole distribution, a low-order equivalent model that facilitates the controller design is obtained. The parameters of the controller are designed by calculating the time constant of the closed-loop dominant poles. A prototype of a WPT system with the designed controller and a five-stage multistage series variable capacitor (MSVC) is built and tested to verify the performance of the controller. The recorded response curves and waveforms show that the designed controller can maintain the ZVS angle at the reference angle with satisfactory control performance.

An Alkaline pH Control Strategy for Methionine Adenosyltransferase Production in Pichia pastoris Fermentation

Xiaoqing Hu,Ju Chu,Si-Liang Zhang,Ying-ping Zhuang,Xin Wu,Huaxin Chen,Zhongyuan Lv,Zhongyi Yuan 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.5

Pichia pastoris is a successful system forexpressing heterologous proteins and its fermentation pH isalways maintained below 7.0. However, particular proteinsare unstable under acidic conditions, such as methionineadenosyltransferase (MAT), and thus fermentation underacidic pH conditions is unsuitable because protein activityis lost owing to denaturation. Here, a strategy employingalkaline pH in the late fermentation period was developedto improve MAT production. Initially, P. pastoris KM71was transformed with the mat gene to overexpress MAT. After 72 h of in vitro incubation at different pH values, theexpressed MAT displayed highest stability at pH 8.0;however, pH 8.0 inhibited cell growth and induced cellrupture, thus affecting protein production. To balance MATstability and Pichia cell viability, different pH controlstrategies were compared. In strategy A (reference), theinduction pH was maintained at 6.0, whereas in strategy B,it was gradually elevated to 8.0 through a 25 h transitionperiod (80 ~ 105 h). MAT activity was 0.86 U/mg (twofoldhigher than the control). However, MAT content wasreduced by 50% when compared with strategy A, becauseof proteases released upon cell lysis. To improve cellviability under alkaline conditions, glycerol was added inaddition to methanol (strategy C). When compared withstrategy B, the MAT-specific activity remained nearlyconstant, whereas the expression level increased to 1.27 g/L. The alkaline pH control strategy presented herein for MATproduction represents an excellent alternative for expressingproteins that are stable only under alkaline conditions.

Experimental study on wake-induced vibrations of two circular cylinders with two degrees of freedom

Xiaoqing Du,Benjian Jiang,Chin Dai,Guoyan Wang,Suren Chen 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.26 No.2

Wind tunnel tests are conducted to investigate wake-induced vibrations of two circular cylinders with a center-to-center spacing of 4 diameters and attack angle varying from 0 to 20 for Reynolds numbers between 18,000 and 168,800. Effects of structural damping, Reynolds number, attack angle and reduced velocity on dynamic responses are examined. Results show that wake-induced vortex vibrations of the downstream cylinder occur in a wider range of the reduced velocity and have higher amplitudes in comparison to the vortex-induced vibration of a single circular cylinder. Two types of wake-induced instability phenomena with distinct dynamic characteristics are observed, which may be due to different generation mechanisms. For small attack angles like 5 and 10, the instability of the downstream cylinder characterizes a one-degree-of-freedom (1-DOF) oscillation moving in the across-wind direction. For a large attack angle like 20, the instability characterizes a two-degree-of-freedom (2-DOF) oscillation with elliptical trajectories. For an attack angle of 15, the instability can transform from the 1-DOF pattern to the 2-DOF one with the increase of the Reynolds number. Furthermore, the two instabilities show different sensitivity to the structural damping. The 1-DOF instability can be either completely suppressed or reduced to an unsteady oscillation, while the 2-DOF one is relatively less sensitive to the damping level. Reynolds number has important effects on the wake-induced instabilities.

Characterization and Application to Fiber Reinforced Composite of Catechol/polyethyleneimine Modified Polyester Fabrics by Musselinspiration

Yuan Chen,Xiaoqing Wu,Junfu Wei,Hailiang Wu 한국섬유공학회 2020 Fibers and polymers Vol.21 No.11

In order to nondestructively prepare polyamine modified polyethylene glycol terephthalate (PET) fabric, codepositionof catechol and polyethyleneimine onto PET fiber was conducted by the means of mussel-inspired method. Thesurface morphology, composition of woven fabric were investigated by FESEM and ATR-FTIR, XPS, respectively, whoseresults demonstrated successful modification has taken place on PET fiber surface. The TG-DSC data proved that the meltingtemperature and decomposition temperature increased from 253.78 oC and 394.08 oC to 255.01 oC and 398.21 oC,respectively. The surface polarity was characterized through the dynamic contact angle. The results indicated that the fabricdisplayed optimal surface properties at the PEI-CA mass ratio of 1:1. The modified PET fabric was utilized to prepare thefiber reinforced epoxy composite and its mechanical performances including tensile, flexural and short beam shear strengthwere evaluated. The obtained results indicated that the interlaminar shear strength (ILSS) has been significantly improved by57.02 %. The novel way to modify fabrics has great potential in recycling waste fabric for preparing fiber reinforcedcomposite.