555,853 research outputs found
Jingyi-Chen/cloud_parcel_mode: cloud parcel model
No full textThis is the first release of the cloud parcel model developed by Jingyi Chen. The development of this model was supported by Stony Brook University and Brookhaven National Laboratory in 2012-2014 (adiabatic version) and 2015-2017 (entrainment-mixing with entrained aerosols).
The publications associated with this code is below:
Chen, J., Y. Liu, M. Zhang, and Y. Peng (2016), New understanding and quantification of the regime dependence of aerosol-cloud interaction for studying aerosol indirect effects, Geophysical Research Letter, 43, 1780–1787, doi:10.1002/2016GL067683.
Chen, J., Y. Liu, M. Zhang, and Y. Peng (2018), Height dependency of aerosol-cloud interaction regimes, Journal of Geophysical Research: Atmospheres, doi: 10.1002/2017JD027431.
Chen, J., Y. Liu and M. Zhang (2020), Effects of Lateral Entrainment-Mixing with Entrained Aerosols on Cloud Microphysics, Geophysical Research Letter, doi: 10.1029/2020GL087667
Enhanced pump absorption of active fiber components with skew rays
No full textWe propose a model and then demonstrate a technique that can be used to optimize pump absorption in active multimode fibers with different cladding geometries, by varying the angle of pump light excitation. The analysis of the contribution of different ray groups at different wavelengths enables the design optimization of active and passive fiber components in fiber lasers.George Y. Chen, Christophe A. Codemard, Michalis N. Zervas, Tanya M. Monro, and David G. Lancaste
Calibration of the Pulsed Electroacoustic Technique in the Presence of Trapped Charge
No full textThe influence of pulse voltage on the accuracy of charge density distribution in the pulsed electroacoustic technique (PEA) is discussed. It is shown that significant error can be introduced if a low dc voltage and high pulse voltage are used to calibrate charge density. However, our main focus in the present paper is to deal with one of the practical situations where space charge exists in the material prior to any measurements. The conventional calibration method can no longer be used to calibrate charge density due to the interference by the charge on the electrode induced by space charge. A method has been proposed which is based on two measurements. Firstly, the sample containing charge is measured without any applied voltage. The second measurement is carried out with a small external applied voltage. The applied voltage should be small enough so there is no disturbance of the existing charge in the sample. The difference of the two measurements can be used for calibration. An additional advantage of the proposed method avoids the influence of the pulse voltage on calibration and therefore gives a more accurate representation of space charge. The proposed method has been validated
The effect of degassing on morphology and space charge
No full textIt is believed that space charge buildup in cross-linked polyethylene (XLPE) insulation is the main cause for premature failure of underground power cables. The space charge activities in XLPE depend on many factors such as additives, material treatment, ambient temperature, insulator/electrode interface, etc. Degassing is one of the material treatment process commonly employ in cable manufacturing to improve insulation performance. In this paper, investigation on the effect of degassing period has on the morphology and space charge was carried out. Planar XLPE samples of the same composite were subjected to different degassing time. It is discovered that apart from removing volatile by-products, degassing also anneal XLPE material; changing the morphology as a result
Effect of polyethylene interface on space charge formation
No full textThis paper reports the results of an investigation into the space charge formation and decay at different material interfaces. In particular, the influence of the interface between electrode and polymer or polymer and polymer on the space charge dynamics has been studied. Planar samples were subjected to high dc electric stresses for extended periods of time and space charge measurements taken using the pulsed electroacoustic (PEA) technique. It has been found that the types of interface between electrode and polymer play a significant role in determining the charge distribution in the insulation and that the interface between polymer and polymer acts as a potential barrier to electrons whilst allowing positive charge carriers through easily
A novel calibration method for PD measurement in power cables and joints using capacitive couplers
No full textPartial discharge (PD) measurements are universally accepted as a technique giving some indication of the state of the insulation in high voltage apparatus. Cable end users are keen to adopt an on-line PD monitoring during commissioning of systems. However, because of noisy environments and the problems of interference the conventional methods are difficult to implement. As a consequence, ultra-high frequency (UHF) / very high frequency (VHF) techniques of on-site detection of partial discharges have been developed. A technique based on the capacitive coupling has received much attention. It has been demonstrated that it is possible to using the technique to monitor the partial discharge in cables, particularly in joints/terminations. However, in order to obtain quantitative information about PD, calibration is required for this technique. Existing calibration methods are difficulty to implement on-site. In this paper a novel method is proposed and compared with the conventional method on a short piece of cable. It has been shown that individual capacitive coupler can also be accurately calibrated on-site and online using the new method, therefore it provides quantitative information about the amount of apparent discharge. In practice this is important for electricity utilities as the quantitative information about PD can be used to determine the quality of cable system and to decide whether the system needs to be repaired or replaced
Replication Data for: Large-scale all-atom simulations for water permeability of human aquaglyceroporin AQP10 (authors: Roberto A Rodriguez and Liao Y Chen)
No full textSimply untar the file in a linux workstation, you can ran the scripts for pmemd.cuda and namd2.13 to produce the results reported in "Large-scale all-atom simulations for water permeability of human aquaglyceroporin AQP10 (authors: Roberto A Rodriguez and Liao Y Chen)
Space charge and charge trapping characteristics of cross-linked polyethylene subjected to ac electric stresses
No full textThis paper reports on the result of space charge evolution in cross-linked polyethylene (XLPE) planar samples of approximately 220 ?m thick. The space charge measurement technique used in this study is the PEA method. There are two phases to this experiment. In the first phase, the samples were subjected to dc 30 kVdc/mm and ac (sinusoidal) electric stress level of 30 kVpk/mm at frequencies of 1 Hz, 10 Hz and 50 Hz ac. In addition, ac space charge under 30 kVrms/mm and 60 kVpk/mm electric stress at 50 Hz was also investigated. The volts off results showed that the amount of charge trapped in XLPE sample under dc electric stress is significantly bigger than samples under ac stress even when the applied ac stresses are substantially higher. The second phase of the experiment involves studying the dc space charge evolution in samples that were tested under ac stress during the first phase of the experiment. Ac ageing causes positive charge to become more dominant over negative charge. It was also discovered that ac ageing creates deeper traps, particularly for negative charge. This paper also gave a brief overview of the data processing methods used to analyse space charge under ac electric stress
Mechanisms for surface potential decay on fluorinated epoxy in high voltage DC applications
Full text linkEpoxy 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
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