125,592 research outputs found
Mechanisms for surface potential decay on fluorinated epoxy in high voltage DC applications
No full textEpoxy resin has been extensively used for decades as an insulation material in high voltage transmission systems. However, this insulation material does suffer from bulk and surface charging when used as insulating spacer, mainly in high voltage DC applications. By applying fluorination treatment, the surface of polymeric insulation is chemically treated and so modifies charge transport characteristics of the material. In doing so, excellent surface properties can be obtained without compromising the bulk characteristics of the polymeric insulation. In this paper, the authors investigate the surface potential decay performance of non-fluorinated and fluorinated epoxy resin samples. The surface decay performance of insulating material is a crucial parameter in dissipating accumulation of surface and bulk charge that can lead to premature breakdown of the insulating material. The epoxy samples were characterised by Energy Dispersive X-Ray (EDX) analysis to determine the changes in chemical composition of the samples before and after fluorination treatment. Surface potential decay measurement using positive corona discharging was then performed, followed by bulk DC conductivity measurement to further explain the mechanisms which govern the surface potential decay. The existence of surface-fluorinated layer on the treated samples had been found to play a major role in dictating the movement of charges away from the surface during the decay process. The influence of fluorination treatment on the decay mechanisms was discussed
Pholcus linzhou Zhang & Zhang 2000
No full text<i>Pholcus linzhou</i> Zhang & Zhang, 2000 <p>(Fig. 25)</p> <p> <i>Pholcus linzhou</i> Zhang & Zhang 2000: 152, f. 2A–I.</p> <p> <b>Diagnosis.</b> This species, one of seven similar species (see remark <i>P</i>. <i>henanensis</i>), is very similar to <i>P. mianshanensis</i> <b>sp. nov.</b> in the shape of the epigynum, both with long whip-shaped apophysis (Figs. 25A and 16A). It differs from the latter by the shape of the tip of the procursus (Figs. 25G–H), and by the mountain range-shaped uncus (Fig. 25G).</p> <p> <b>Redescription.</b> Male (holotype) total length 5.0: cephalothorax 1.5 long, 1.8 wide; abdomen 3.5 long, 1.5 wide. Leg I: 36.1 (9.1+0.8+8.7+15.1+2.4), tibia II: 6.0, tibia III: 4.2, tibia IV: 6.1; tibia I L/D: 62. Prosoma shape as in Fig. 25C. Carapace short, broad and almost circular, ochre, with pair of brown marks broadly connecting to ocular area. Cephalic region raised, with brown central stripe, ocular area dark yellow. Clypeus 0.50, slightly ochre, without marks. Distance AME–AME 0.04. Diameter AME 0.09, ALE 0.14, PME 0.14, PLE 0.16. Chelicerae as in Fig. 25E, with pair of black apophyses distally and pair of unsclerotized thumbshaped apophyses proximolaterally. Labium and endites yellow. Sternum slightly ochre, with four pairs of yellow marginal marks and a central mark on it as in Fig. 25F. Femora, patellae and tibiae ochre, with dark rings, metatarsi and tarsi brown. Abdomen cylindrical, pale ochre, dorsum with many of brown spots on it as in Fig. 25C. Venter pale brown, without marks. Palps as in Figs. 25G and 25H, bulb with a mountain rangeshaped uncus and short appendix.</p> <p> <b>Variation.</b> Tibia I in 14 male paratypes (two males missing tibia I): 7.9–9.0 (mean 8.6). Body length in 16 males paratypes: 4.1–5.2.</p> <p>Female: in general very similar to male. Total length of paratype bodies 4.6–5.5. A paratype measured, total length 5.3: cephalothorax 1.6 long, 1.5 wide; abdomen 3.7 long, 1.8 wide. Tibia I: 7.8. Clypeus 0.58 high. Epigynum roughly semicircular as in Fig. 25A, with a long whip-shaped apophysis on the top and a semicircular dark shadow centrally. Dorsal view as in Fig. 25B, with a mounded sclerotized arch anteriorly and a pair of oval pore plates.</p> <p> <b>Distribution.</b> Henan, Hebei.</p> <p> <b>Material examined.</b> CHINA: <b>Henan</b>, Linzhou City, Hongqi Canal, May 11, 1999, leg. F. Zhang, male holotype, 5♂, 3♀ paratypes (MHBU); Shibanyan, July 24, 2006, leg. B. S. Zhang, 5♀ (MHBU); Dengfeng County, Sanhuangzhai Scenic Spot, August 6, 2002, leg. J. Y. Yang, 3♂, 2♀ (MHBU). <b>Hebei</b>, Wu’an County, Liejiang Town, June 28, 1999, leg. F. Zhang, 11♂, 5♀ paratypes (MHBU).</p>Published as part of <i>Zhang, Feng & Zhu, Ming-Sheng, 2009, A review of the genus Pholcus (Araneae: Pholcidae) from China, pp. 1-114 in Zootaxa 2037 (1)</i> on pages 50-52, DOI: 10.11646/zootaxa.2235.1.2, <a href="http://zenodo.org/record/5317608">http://zenodo.org/record/5317608</a>
SCI citation analysis and impact factor prediction of JZUS-B in 2008
No full textWe analysis the SCI citation of Journal of Zhejiang University-SCIENCE B, predict its 2008 Impact Factor in the range of 0.737~0.915, and list the top-10 SCI cited articles
An iterative method for integrated hump sequencing, train makeup, and classification track assignment in railway shunting yard
No full textIn a railway shunting yard, the transformation of inbound trains into properly composed outbound trains is a complex task because it involves decisions of multiple operations processes. This study addresses the integrated optimization of hump sequencing, train makeup, and classification track assignment problem in a railway shunting yard. Several key practical yard operation constraints are considered, including train formulation constraints, hump sequencing constraints, and limitations of the maximum number and capacity of classification tracks. By introducing a new representation of block flow, the integrated problem, which adopts the extended single-stage strategy and the train-to-track policy, is formulated as a unified 0-1 integer linear programming model. The objective of the proposed model is to minimize the weighted-sum of the total dwell time of all railcars and the formulation deviation penalties of all outbound trains. Then, an iterative two-phase decomposition approach is developed to reduce the complexity of solving the integrated problem. The first phase aims to explore all feasible humping sequences using a Branch-and-Bound (B&B) algorithm. Each time a new humping sequence is generated in the first phase, the second phase containing a Branch-and-Price (B&P) algorithm is applied to solve the integrated train makeup and classification track assignment problem with the known humping sequence found in the first phase. In addition, greedy heuristics and lower bounding techniques are designed in both phases to improve computational efficiency. Comprehensive experiments are investigated based on a set of real-life instances. The results show that exact approaches provide optimal solutions, whereas heuristic approaches yield satisfactory solutions within a shorter computation time. Moreover, sensitivity analyses on the number of classification tracks and the effects of different deviation penalties are also performed to gain more managerial insights
Chemical composition and κ data_urban Beijing_summer 2017
No full textThis is the data used in the paper of “Liu, J., Zhang, F.,Xu, W., Sun, Y., Chen, L., Zhang, R., Li, S., Ren, J., Hu, B., Zhang, R., et al. Hygroscopicity of organic aerosols linked to formation mechanisms. Geophysical Research Letters
Physics-Based Channel Modeling for IRS-Assisted mmWave Communication Systems
No full textDue to the large path loss in millimeter wave (mmWave) band, the transmission path between transmitter (Tx) and intelligent reflecting surface (IRS) is considered as a Rayleigh fading channel, and a physics-based channel model is proposed for IRS-assisted mmWave communication system in urban scenario. Also, the horizontal and vertical rotation angles of IRS and the relationship between the scattering gain of IRS reflecting unit and its effective aperture in the incident direction and the desired reflection direction are considered in the proposed model. For the considered communication scenario, the existing reflection phases, which are designed to align the virtual line-of-sight (VLoS) components among Tx, IRS, and receiver (Rx) with the LoS components between Tx and Rx, are not the appropriate reflection phases. Based on the proposed model, we first obtain the statistical phases of the virtual scattering components within a cluster by minimizing phase differences between different IRS reflection units, and then obtain the reflection phases by minimizing the phase differences of the derived statistical phases for all clusters. By comparing with the existing reflection phases, the designed reflection phases can significantly enhance the system performance gains of mmWave communications. Using the designed reflection phases, the expressions of received signal power and upper bound of ergodic sum capacity are derived in this paper, which are validated by using Monte-Carlo simulation results. Numerical results show that the proposed mmWave channel model could accurately simulate the propagation characteristics of IRS. Also, numerical results show that the performance gains of IRS-assisted systems are equivalent to that of large-scale communication systems without using IRS
Compressible Rayleigh-Taylor turbulent mixing under different acceleration histories
No full textCompressible Rayleigh-Taylor turbulent mixing (CRTM) induced by Rayleigh-Taylor instability occurs when a compressible fluid of heavy density is accelerated or supported against gravity by a compressible fluid of light density, and is of fundamental importance in applications from combustion, to inertial confinement fusion, and to astrophysics. Traditionally, CRTFs are studied under constant acceleration histories. Due to the nature of the processes, however, it is necessary to study CRTF under general acceleration histories g(t). In this aspect, the evolution of Rayleigh-Taylor turbulent mixing under complex acceleration histories, including changes in signs, have been studied numerically[1] and experimentally[2] for incompressible flows, leaving an open question on that of compressible flows. In fact, most engineering problems are compressible. In addition, the available engineering turbulence models cannot capture the variation of mixing width for CRTM with complex acceleration histories, such as the gravity reversal. In order to better understanding the dynamic of CRTM under different variation histories, several DNS cases with different acceleration histories have been conducted and analyzed
A non-steady model for the transport of iron(III) across n-decanol supported liquid membrane facilitated by D2EHPA
No full textAre Chinese loess deposits essentially continuous?
No full textWe conducted a paleomagnetic examination of the last glacial loess of three representative profiles along an east-west transect in the central Loess Plateau in order to assess the continuity of Chinese loess. The results show that the Xifeng and Luochuan profiles record the Laschamp geomagnetic excursion but with different morphologies. Together with the published results from Weinan, southern plateau, our results suggest that sedimentation of the last glacial loess in the central-southern plateau was continuous at the time scale equivalent to the duration of the Laschamp excursion (~2 kyr), but probably episodic at finer time scales (<2 kyr). No geomagnetic excursion was found at the Yichuan profile near the Yellow River valley, where loess accumulation may be strongly affected by local environmental changes and thus may have been discontinuous. Both site location and time scale therefore need to be considered when considering continuity of Chinese loess.<br/
Branching fraction and CP asymmetry of the decays B+→K0Sπ+ and B+→K0SK+
No full textAn analysis of B+ → K0
Sπ+ and B+ → K0
S K+ decays is performed with the LHCb experiment. The pp
collision data used correspond to integrated luminosities of 1 fb−1 and 2 fb−1 collected at centre-ofmass
energies of
√
s = 7 TeV and
√
s = 8 TeV, respectively. The ratio of branching fractions and the
direct CP asymmetries are measured to be B(B+ → K0
S K+
)/B(B+ → K0
Sπ+
) = 0.064 ± 0.009 (stat.) ±
0.004 (syst.), ACP(B+ → K0
Sπ+
) = −0.022 ± 0.025 (stat.) ± 0.010 (syst.) and ACP(B+ → K0
S K+
) =
−0.21 ± 0.14 (stat.) ± 0.01 (syst.). The data sample taken at
√
s = 7 TeV is used to search for
B+
c
→ K0
S K+ decays and results in the upper limit ( fc · B(B+
c
→ K0
S K+
))/( fu · B(B+ → K0
Sπ+
)) <
5.8 × 10−2 at 90% confidence level, where fc and fu denote the hadronisation fractions of a ¯b
quark
into a B+
c or a B+ meson, respectively
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