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Mitigation of Load Frequency Fluctuation Using a Centralized Pitch Angle Control of Wind Turbines
Junqiao, Liu,Rosyadi, Marwan,Takahashi, Rion,Tamura, Junji,Fukushima, Tomoyuki,Sakahara, Atsushi,Shinya, Koji,Yosioka, Kazuki Journal of International Conference on Electrical 2013 Journal of international Conference on Electrical Vol.2 No.1
In this paper an application of centralized pitch angle controller for fixed speed wind turbines based wind farm to mitigate load frequency fluctuation is presented. Reference signal for the pitch angle of each wind turbine is calculated by using proposed centralized control system based on wind speed information. The wind farm in the model system is connected to a multi machine power system which is composed of 4 synchronous generators and a load. Simulation analyses have been carried out to investigate the performance of the controller using real wind speed data. It is concluded that the load frequency of the system can be controlled smoothly.
Junqiao Wang,Shaoping Nie,Lijiao Kan,Haihong Chen,Steve W. Cui,Aled O. Phillips,Glyn O. Phillips,Mingyong Xie 한국식품과학회 2017 Food Science and Biotechnology Vol.26 No.1
Four polysaccharides (named as P1, P2, and P3 from three natural Cordyceps sinensis and P4 from cultured C. sinensis) were obtained by hot-water extraction and ethanol precipitation and their structural characteristics as well as antioxidant potentials were compared. Results revealed that the backbone of P1, P2, and P3 comprised α-1,4-glucose, with a branching point mainly at position 6 and terminating at glucose. On the other hand, the structure of P4 was highly complex, mainly comprising glucose, galactose, and mannose, with 1,4-glucose and 1,4-galactose as the main chain. For in vitro antioxidant assays, all the four polysaccharides showed similar scavenging capacity against DPPH and hydroxyl radicals, whereas P1 had a relatively low ferric reducing ability, possibly related to a combination of factors such as the phenolic compounds and amino acids that conjugated in polysaccharides.
Nanoscale Friction on Confined Water Layers Intercalated between MoS<sub>2</sub> Flakes and Silica
Lee, Hyunsoo,Jeong, Hochan,Suh, Joonki,Doh, Won Hui,Baik, Jaeyoon,Shin, Hyun-Joon,Ko, Jae-Hyeon,Wu, Junqiao,Kim, Yong-Hyun,Park, Jeong Young American Chemical Society 2019 The Journal of Physical Chemistry Part C Vol. No.
<P>Frictional energy dissipation at the interfaces of two-dimensional (2D) materials through the excitation and transfer processes of kinetic energy into the bulk can be easily influenced by an intercalated water film. An enhancement of friction on water-intercalated graphene has been observed. Is this frictional enhancement by confined water a general phenomenon? We address this issue by investigating the frictional behavior of confined water layers intercalated between single-layer molybdenum disulfide (MoS<SUB>2</SUB>), synthesized using chemical vapor deposition, and a silica substrate. The icelike water was intercalated by exposure to high-humidity air. We found that the intercalated water molecules morphologically deform the 2D MoS<SUB>2</SUB> sheet, forming distinct subdomains after the exposure to high humidity. We found that the adsorption of the icelike water layer between the MoS<SUB>2</SUB> and the silica leads to friction enhancement, compared with a pristine MoS<SUB>2</SUB>/silica sample, which is associated with additional phononic friction energy dissipation at the solid-liquid interface, as indicated by the phonon distribution analysis from the empirical force-field calculations. Moreover, the atomic stick-slip behavior shows that the lattice orientation of the hydrophilic MoS<SUB>2</SUB> affects water molecule diffusion at the interface of the MoS<SUB>2</SUB>/silica substrate. Chemical mapping of the water-intercalated MoS<SUB>2</SUB> on silica using scanning photoelectron microscopy and vacuum annealing processes shows water intercalation without changing the intrinsic composition of the MoS<SUB>2</SUB> on silica.</P> [FIG OMISSION]</BR>
Suh, Joonki,Park, Tae-Eon,Lin, Der-Yuh,Fu, Deyi,Park, Joonsuk,Jung, Hee Joon,Chen, Yabin,Ko, Changhyun,Jang, Chaun,Sun, Yinghui,Sinclair, Robert,Chang, Joonyeon,Tongay, Sefaattin,Wu, Junqiao American Chemical Society 2014 NANO LETTERS Vol.14 No.12
<P>Layered transition metal dichalcogenides (TMDs) draw much attention as the key semiconducting material for two-dimensional electrical, optoelectronic, and spintronic devices. For most of these applications, both <I>n</I>- and <I>p</I>-type materials are needed to form junctions and support bipolar carrier conduction. However, typically only one type of doping is stable for a particular TMD. For example, molybdenum disulfide (MoS<SUB>2</SUB>) is natively an <I>n</I>-type presumably due to omnipresent electron-donating sulfur vacancies, and stable/controllable <I>p</I>-type doping has not been achieved. The lack of <I>p</I>-type doping hampers the development of charge-splitting <I>p</I>–<I>n</I> junctions of MoS<SUB>2</SUB>, as well as limits carrier conduction to spin-degenerate conduction bands instead of the more interesting, spin-polarized valence bands. Traditionally, extrinsic <I>p</I>-type doping in TMDs has been approached with surface adsorption or intercalation of electron-accepting molecules. However, practically stable doping requires substitution of host atoms with dopants where the doping is secured by covalent bonding. In this work, we demonstrate stable <I>p</I>-type conduction in MoS<SUB>2</SUB> by substitutional niobium (Nb) doping, leading to a degenerate hole density of ∼3 × 10<SUP>19</SUP> cm<SUP>–3</SUP>. Structural and X-ray techniques reveal that the Nb atoms are indeed substitutionally incorporated into MoS<SUB>2</SUB> by replacing the Mo cations in the host lattice. van der Waals <I>p</I>–<I>n</I> homojunctions based on vertically stacked MoS<SUB>2</SUB> layers are fabricated, which enable gate-tunable current rectification. A wide range of microelectronic, optoelectronic, and spintronic devices can be envisioned from the demonstrated substitutional bipolar doping of MoS<SUB>2</SUB>. From the miscibility of dopants with the host, it is also expected that the synthesis technique demonstrated here can be generally extended to other TMDs for doping against their native unipolar propensity.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-12/nl503251h/production/images/medium/nl-2014-03251h_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl503251h'>ACS Electronic Supporting Info</A></P>
Tuning the optical and electrical properties of MoS<sub>2</sub> by selective Ag photo-reduction
Kim, Eunpa,Lee, Yoonkyung,Ko, Changhyun,Park, Yunjeong,Yeo, Junyeob,Chen, Yabin,Choe, Hwan Sung,Allen, Frances I.,Rho, Junsuk,Tongay, Sefaattin,Wu, Junqiao,Kim, Kyunghoon,Grigoropoulos, Costas P. American Institute of Physics 2018 APPLIED PHYSICS LETTERS Vol.113 No.1