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Sökning: WFRF:(Zhu Kun)

  • Resultat 41-50 av 65
  • Föregående 1234[5]67Nästa
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41.
  • Zhang, Shuai, et al. (författare)
  • MIMO Reference Antennas with Controllable Correlations and Total Efficiencies
  • 2014
  • Ingår i: Progress In Electromagnetics Research. - 1070-4698 .- 1559-8985. ; 145, s. 115-121
  • Tidskriftsartikel (refereegranskat)abstract
    • MIMO reference antennas are proposed for over the air (OTA) measurement applications. The reference antennas could get rid of feeding cable interference and control envelope correlation coefficients (ECC) continuously by only changing the length of an etched slot on a dual-feed PIFA. If only the ECC is investigated, the MIMO reference antenna is optimized to have a small variation of total efficiency from 70% to 50% when the ECC increases from 0.1 to 0.88. The prototypes are fabricated and measured in a scattered field chamber (SFC). Measurements agree well with the simulations. If the MIMO performance is studied, the MIMO reference antenna is proposed to own a large variation of total efficiencies from 90% to 47% while the ECC increases from 0 to 0.98. The bandwidth of the proposed reference antennas depend on the size of the antennas. This method is valid for all the frequencies.
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42.
  • Zhang, S. W., et al. (författare)
  • Synthesis of narrowly distributed polystyrene-encapsulated silica nanoparticles via emulsion polymerization
  • 2017
  • Ingår i: Journal of Dispersion Science and Technology. - 0193-2691 .- 1532-2351. ; 38:3, s. 451-456
  • Tidskriftsartikel (refereegranskat)abstract
    • Polystyrene (PS)-encapsulated silica nanoparticles were successfully synthesized by conventional emulsion polymerization for solving the aggregation matter of nanoscaled silica. The grafting coupling agents and PS on the silica surface were detected by Fourier Transform Infrared (FTIR) spectroscopy. The influence of silica and monomer to water ratios and initiator concentration on particle size distribution of the nanocomposite latex was investigated. The particle size distribution firstly narrowed and then broadened with the increase of silica and monomer to water ratios and initiator concentration. The narrow distribution could be controlled in an appropriate silica and monomer to water ratio and an initiator concentration of 1/15 and 2wt%, respectively. From the evaluation of transmission electron microscopy (TEM) micrographs and dynamic light scattering (DLS) measurement, it was proved that the nanocomposite latex did not have all sphere-like shape, but contained tiny amounts of irregular bodies. The formation mechanism of PS-encapsulated silica nanoparticles was also discussed.
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43.
  • Zhou, Yongqiang, et al. (författare)
  • Inflow rate-driven changes in the composition and dynamics of chromophoric dissolved organic matter in a large drinking water lake
  • 2016
  • Ingår i: Water Research. - 0043-1354. ; 100, s. 211-221
  • Tidskriftsartikel (refereegranskat)abstract
    • Drinking water lakes are threatened globally and therefore in need of protection. To date, few studies have been carried out to investigate how the composition and dynamics of chromophoric dissolved organic matter (CDOM) in drinking water lakes are influenced by inflow rate. Such CDOM can lead to unpleasant taste and odor of the water and produce undesirable disinfection byproducts during drinking water treatment. We studied the drinking water Lake Qiandao, China, and found that the concentrations of suspended particulate matter (SPM) in the lake increased significantly with inflow rate (p
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44.
  • Zhou, Yongqiang, et al. (författare)
  • Rainstorm events shift the molecular composition and export of dissolved organic matter in a large drinking water reservoir in China : High frequency buoys and field observations
  • 2020
  • Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 187
  • Tidskriftsartikel (refereegranskat)abstract
    • Rainstorm events can flush large amounts of terrestrial organic-rich material into lakes that are used for drinking water. To date, few studies have been carried out to investigate how rainstorm events change the molecular composition, bio-lability, and flux of upstream-imported dissolved organic matter (DOM), which can impact the odor and taste of drinking water as well as the efficiency of wastewater treatment. We undertook high-frequency buoy monitoring and point sample collection (n = 495), during high, moderate, and low inflow discharge, in Lake Qiandao, a key drinking water source for about 10 million people. Data from two online fluorescent DOM sensors deployed and field samples collected at the river site, Jiekou, and the lake site, Xiaojinshan, showed that rainstorm events increased the specific UV absorbance (SUVA254), humification index (HIX), humic-like components (C1-C2), and FT-ICR MS derived condensed aromatic and polyphenolic compounds (p < 0.001) and decreased the spectral slope of DOM (S275–295), spectral slope ratio (SR), biological index (BIX), and highly bio-degradable peptide-like and aliphatic substances (p < 0.001). Our results suggest that rainstorm events enhanced the export to the lake of colored, hydrophobic, and aromatic DOM. Upstream-derived dissolved organic carbon (DOC) concentrations decreased (p < 0.001), while DOC bio-availability (BDOC) increased only slightly (p < 0.05) during rainstorm events. The loss rate of DOC in Lake Qiandao is 0.82 × 104 t C yr−1, of which 0.30 × 104 t C yr−1 is highly bio-labile, and higher occurrences of both ≥ 25 mm d − 1 and ≥ 50 mm d − 1 rainfall events are anticipated by linear fittings for this region in the future. The application of in situ fluorescence sensors provides an early warning of DOC surge incidents caused by rainstorm events and may be useful in advising drinking water treatment plant managers of changes in raw water DOM quality and treatability.
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45.
  • Zhu, Jie, et al. (författare)
  • Highly secretory expression of recombinant cowpea chlorotic mottle virus capsid proteins in Pichia pastoris and in-vitro encapsulation of ruthenium nanoparticles for catalysis
  • 2020
  • Ingår i: Protein Expression and Purification. - 1046-5928 .- 1096-0279. ; 174
  • Tidskriftsartikel (refereegranskat)abstract
    • The applications of viral protein cages have expanded rapidly into the fields of bionanotechnology and materials science. However, the low-cost production of viral capsid proteins (CPs) on a large scale is always a challenge. Herein, we develop a highly efficient expression system by constructing recombinant Pichia pastoris cells as a “factory” for the secretion of soluble cowpea chlorotic mottle virus (CCMV) CPs. Under optimal induction conditions (0.9 mg/mL of methanol concentration at 30 °C for 96 h), a high yield of approximately 95 mg/L of CCMV CPs was harvested from the fermentation supernatant with CPs purity >90%, which has significantly simplified the rest of the purification process. The resultant CPs are employed to encapsulate Ruthenium (Ru) nanoparticles (NPs) via in-vitro self-assembly to prepare hybrid nanocatalyst, i.e. Ru@virus-like particles (VLPs). The catalytic activity over Ru@VLPs was evaluated by reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The results indicate that, with the protection of protein cages, Ru NPs were highly stabilized during the catalytic reaction. This results in enhanced catalytic activity (reaction rate constant k = 0.14 min−1) in comparison with unsupported citrate-stabilized Ru NPs (Ru-CA) (k = 0.08 min−1). Additionally, comparatively lower activation energy over Ru@VLPs (approximately 32 kJ/mol) than that over Ru-CA (approximately 39 kJ/mol) could be attributed to the synergistic effect between Ru NPs and some functional groups such as amino groups (–NH2) on CPs that weakened the activation barrier of 4-NP reduction. Therefore, enhanced activity and decreased activation energy over Ru@VLPs demonstrated the superiority of Ru@VLPs to unsupported Ru-CA.
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46.
  • Zhu, Kun, et al. (författare)
  • A Simple and Tunable Single-Bandpass Microwave Photonic Filter of Adjustable Shape
  • 2008
  • Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 20:21-24, s. 1917-1919
  • Tidskriftsartikel (refereegranskat)abstract
    • A simple and tunable single-hand pass microwave photonic filter of adjustable shape is proposed and experimentally demonstrated. The filter is based on multiple sources (spectrum-sliced by a Mach-Zehnder interferometer) and two cascaded incoherent optical structures, namely, a dispersion medium of 50-km single-mode fiber and a fiber ring delay line. In the experimental range from 1.0 to 3.8 GHz, a discretely tunable single-hand pass filter with a high Q-factor or a flat-top response is achieved by carefully matching the transfer functions of the two individual optical structures.
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47.
  • Zhu, Kun, et al. (författare)
  • All-optical coherence-free microwave filter with switchable passbands based on phase and intensity hybrid modulation
  • 2011
  • Ingår i: Optics Communications. - 0030-4018 .- 1873-0310. ; 284:1, s. 140-143
  • Tidskriftsartikel (refereegranskat)abstract
    • A simple all-optical coherence-free microwave notch filter is proposed and experimentally demonstrated. The filter with switchable passbands is based on a single-wavelength optical source and phase-intensity hybrid modulation scheme. The DC bias voltage applied to the Mach-Zehnder intensity modulator can be adjusted to switch signs of the tap coefficients, which affect the baseband response. Both lowpass and bandpass filtering responses are observed in the experiment and agree well with the simulated results.
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48.
  • Zhu, Kun, 1983-, et al. (författare)
  • An Empirical Study of Synchrophasor Communication Delay in a Utility TCP/IP Network
  • 2013
  • Ingår i: International Journal of Emerging Electric Power Systems. - : Walter de Gruyter. - 2194-5756 .- 1553-779X. ; 14:4, s. 341-250
  • Tidskriftsartikel (refereegranskat)abstract
    • Although there is a plethora of literature dealing with Phasor Measurement Unit (PMU) communication delay, there has not been any effort to generalize empirical delay results by identifying the distributions with the best fit. The existing studies typically assume a distribution, or simply build on analogies to communication network routing delay. Specifically, this study provides insight into the characterization of the communication delay of both unprocessed PMU data and synchrophasors sorted by a Phasor Data Concentrator (PDC). The results suggest that a bi-modal distribution containing two normal distributions offers the best fit of the delay of the unprocessed data, whereas the delay profile of the sorted synchrophasors resembles a normal. Based on these results, the possibility of evaluating the reliability of a synchrophasor application with respect to a particular choice of PDC timeout is discussed.
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49.
  • Zhu, Kun, et al. (författare)
  • Analysis of data quality issues in wide area monitoring and control systems
  • 2010
  • Ingår i: 2010 IREP Symposium - Bulk Power System Dynamics and Control - VIII, IREP2010. - Rio de Janeiro. - 9781424474677
  • Konferensbidrag (refereegranskat)abstract
    • Synchronized phasor measurement based Wide Area Monitoring and Control (WAMC) system is becoming a reality with international research and development both in academia and industry. Timely and accurate data with high resolutions holds great promise for more responsible and advanced grid control and operation. Currently, most of the research focuses on the different control schemes and applications. A relatively less addressed aspect is the dependency of the WAMC system on the performance of the Information and Communication Technology (ICT) infrastructure, without whose support the projected functionalities of the WAMC systems will not be achieved. Possible input delay brought by the complex data transfer and processing processes in WAMC systems are presented at the beginning of this paper. Thereafter, simulations where delayed phasor measurements are fed to a typical WAMC application - Static Var Compensation (SVC) are conducted iteratively to detect its maximum tolerated delay. Based on this maximum tolerated delay, the consequences of missing certain data in the phaor packets have been studied. Furthermore, data quality requirements to design a reliable SVC function are analyzed based on simulation results. In conjunction with the requirement discussion, the paper is concluded by proposing a robust ICT architecture to mitigate the aforementioned data quality issues.
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50.
  • Zhu, Kun, et al. (författare)
  • Analysis of phasor data latency in wide area monitoring and control systems
  • 2010
  • Ingår i: 2010 IEEE International Conference on Communications Workshops, ICC 2010. - Capetown. - 9781424468263
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • Synchronized phasor measurement based Wide Area Monitoring and Control (WAMC) system is becoming a reality within international research and development both in academia and industry. Timely and accurate data with high resolutions holds great promise for more responsible and advanced grid control and operation. Currently, most of the research focuses on the different control schemes and applications. A relatively less addressed aspect is the dependency of the WAMC system on the performance of the Information and Communication Technology (ICT) infrastructure, without whose support the projected functionalities of the WAMC systems will be not achieved. Possible delays brought by the complex data transfer and processing processes in WAMC systems are addressed in the first part of this paper. Thereafter, simulations where delayed Phasor measurements are fed to the Static Var Compensator (SVC) are conducted iteratively to detect its maximum tolerated delay. Furthermore, performance requirements for the centralized computation and control actuation are researched and analyzed based on simulation results. It also includes a study on feasibility of compensations using local signal based Power System Stablizers (PSS) in situations with much phasor data delay. The paper is concluded by suggesting ICT architecture for WAMC systems aiming to improve its robustness.
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  • Föregående 1234[5]67Nästa
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