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THE NUMERICAL SIMULATION OF ASTRO-CLIMATE CONDITIONS OVER THE TIBETAN PLATEAU
QIAN, XUAN,YAO, YONGQIANG,WANG, HONGSHUAI,LIU, LIYONG The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
The wind field and precipitable water vapor over the Tibetan Plateau are analyzed using the numerical model WRF. The spatial and vertical distributions of the relevant meteorological factors are summarized, providing evidence for selecting and further evaluating an astronomical site. This study serves as a further demonstration towards astro-climate regionalization, and provides us with an essential database for an astronomical site survey over the Tibetan Plateau.
Modeling and Analysis of an Avionic Battery Discharge Regulator
Qian Chen,Haihong Yu,Xiaoming Huang,Yi Lu,Peng Qiu,Kai Tong,Jiazhuo Xuan,Feng Xu,Xiaohua Xuan,Weibo Huang,Yajing Zhang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3
The avionic battery discharge regulator (BDR) plays an important role in a power-conditioning unit. With its merits of high efficiency, stable transfer function, and continuous input and output currents, the non-isolated Weinberg converter (NIWC) is suitable for avionic BDR. An improved peak current control strategy is proposed to achieve high current-sharing accuracy. Current and voltage regulators are designed based on a small signal model of a three-module NIWC system. The system with the designed regulators operates stably under any condition and achieves excellent transient response and current-sharing accuracy.
Modeling and Analysis of an Avionic Battery Discharge Regulator
Chen, Qian,Yu, Haihong,Huang, Xiaoming,Lu, Yi,Qiu, Peng,Tong, Kai,Xuan, Jiazhuo,Xu, Feng,Xuan, Xiaohua,Huang, Weibo,Zhang, Yajing The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3
The avionic battery discharge regulator (BDR) plays an important role in a power-conditioning unit. With its merits of high efficiency, stable transfer function, and continuous input and output currents, the non-isolated Weinberg converter (NIWC) is suitable for avionic BDR. An improved peak current control strategy is proposed to achieve high current-sharing accuracy. Current and voltage regulators are designed based on a small signal model of a three-module NIWC system. The system with the designed regulators operates stably under any condition and achieves excellent transient response and current-sharing accuracy.
Qian, Jingui,Wu, Xuan,Kim, Dong-Su,Lee, Dong-Weon Elsevier Sequoia 2017 Sensors and actuators. A Physical Vol.263 No.-
<P><B>Abstract</B></P> <P>This study reports a seesaw-structured triboelectric nanogenerator (S-TENG) for efficiently harvesting electrical energy from rotational motion of mechanical systems. The designed S-TENG with two arms is comprised four contact-pair units with distinctly different triboelectric polarity materials. The generated electric power from the unique structure based on the seesaw system was double at every machine rotation cycle. A magnetically coupled contact mechanism was also utilized to reduce the wear of the polymer material. It was experimentally confirmed that the proposed design significantly improved the reliability and long-term stability in comparison with currently available TENG systems based on the sliding mechanism. In addition, micro-pyramid patterns were formed on the polymer surface to enhance the surface charge density. Through systematic experiments with a variety of operational conditions, an instantaneous maximum output power density of 13.86W/m<SUP>2</SUP> was achieved at a rotation speed of 200rpm under a constant magnetic field strength of 0.2T. The S-TENG has been demonstrated as a direct power source to drive small electronic devices such as commercial LED arrays and to charge an energy storage unit. This study further expanded the potential applications of the S-TENG to realize the self-powered wireless sensor nodes such as structural health and condition monitoring system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A seesaw-structured triboelectric nanogenerator for wireless sensor node is proposed. </LI> <LI> The theory analysis of nonparallel contact-mechanism of TENG are presented. </LI> <LI> High output performance are achieved with various rotation speed and magnetic force. </LI> <LI> Long-term stability and reliability of rotating TENG are significantly improved. </LI> <LI> As power source to drive small electronics and wireless sensor node are demonstrated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Xuan Zhang,ZhiPing Mao,Qian Wu,LinPing Zhang 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.3
In this report, hexakis (4-nitrophenoxy) cyclotriphosphazene (HNCP) and ethylene–octene copolymer grafted-maleic anhydride (POE-g-MA) were blended with pure PET together. The fire retardant ability and thermal stability of PET/HNCP/POE-g-MA were investigated respectively. The results indicated that HNCP and POE-g-MA had a synergic effect on the dripping resistance of PET besides the enhancement in flame retardancy to a certain degree. LOI values of the polymers with both POE-g-MA and 10 wt%HNCP were higher than that of pure PET and no drips just containing 1 wt%POE-g-MA. The reason was that HNCP could be well dispersed in PET when POE-g-MA was added, forming a more effective char layer and preventing dripping of polymers. Indeed, the morphology of charred residue of PET/HNCP/POE-g-MA showed that a porous protective layer with a dense surface was formed. The thermogravimetric analysis revealed that addition of HNCP improved the thermal stability and the yield of char residue of the PET/POE-g-MA systems. Based on a series of experiment results, the synergistic effect of HNCP and POE-g-MA on the anti-dripping of PET was also discussed. In the PET/HNCP/POE-g-MA system, POE-g-MA played a role of compatibilizer. The improved compatibility and dispersion provided the composite with the ideal flame retardancy, thermal stability and anti-dripping property.
Self-dispersed crumpled graphene balls in oil for friction and wear reduction
Dou, Xuan,Koltonow, Andrew R.,He, Xingliang,Jang, Hee Dong,Wang, Qian,Chung, Yip-Wah,Huang, Jiaxing National Academy of Sciences 2016 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.113 No.6
<P>Ultrafine particles are often used as lubricant additives because they are capable of entering tribological contacts to reduce friction and protect surfaces from wear. They tend to be more stable than molecular additives under high thermal and mechanical stresses during rubbing. It is highly desirable for these particles to remain well dispersed in oil without relying on molecular ligands. Borrowing from the analogy that pieces of paper that are crumpled do not readily stick to each other (unlike flat sheets), we expect that ultrafine particles resembling miniaturized crumpled paper balls should self-disperse in oil and could act like nanoscale ball bearings to reduce friction and wear. Here we report the use of crumpled graphene balls as a high-performance additive that can significantly improve the lubrication properties of polyalphaolefin base oil. The tribological performance of crumpled graphene balls is only weakly dependent on their concentration in oil and readily exceeds that of other carbon additives such as graphite, reduced graphene oxide, and carbon black. Notably, polyalphaolefin base oil with only 0.01-0.1 wt % of crumpled graphene balls outperforms a fully formulated commercial lubricant in terms of friction and wear reduction.</P>
고분자전해질형 연료전지의 동적모델링 및 최적화에 관한 연구
현동길(Xuan Dongji),김진완(Kim Jinwan),남양해(Nan Yanghai),닝천(Ning Qian),김영배(Kim Youngbae) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The output power efficiency of the fuel cell system depends on the anode pressure, cathode pressure, temperature, demanded current, air and hydrogen humidity. Thus, it is necessary to determine the optimal operation condition. In this paper, we developed a dynamic model of fuel cell system which contains mass flow model, membrane hydration model and electro-chemistry model. Experiments have been performed to evaluate the PEMFC stack model. In order to determine the maximum output power and minimum use of hydrogen in a certain condition, Response surface methodology (RSM) optimization based on verified PEMFC stack model is presented. The results provide an effective method to optimize the operation condition in varied situations