| 1. |
- Chung, H.S., et al.
(författare)
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Flow characteristics by particle image velocimetry in liquefied natural gas vaporizer model with several baffles
- 2011
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Ingår i: Central South University. Journal. - : Springer Science and Business Media LLC. - 2095-2899. ; 18:5, s. 1719-1725
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Tidskriftsartikel (refereegranskat)abstract
- Shell-and-tube vaporizers are the most commonly used and dominated types of vaporizers in liquefied natural gas (LNG) realm. Due to efficient performance, shell-side flow in this type of vaporizers has received considerable attention and has been investigated extensively. However, the detailed flow structure in the shell needs to be determined for reliable and effective design. Therefore, the objective of this study was to clarify the flow structure in shell by particle image velocimetry (PIV). Experiments were conducted using two types of model; 15% baffle cut having inlet and outlet positions in the direction of 90° to the cut and 30% baffle cut having inlet and outlet positions in the direction of 180° to the cut. Each test section is 169 mm in inner diameter and 344.6 mm in length. The flow features were characterized in different baffle cuts with regards to the velocity vector field and velocity distribution. The results show that the flow characteristics of 15% baffle cut type vaporizer are comparable to those of 30% baffle cut type vaporizer.
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| 2. |
- Jiang, Dong-yi, et al.
(författare)
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Surface water quality and potential health risk assessments in Changsha-Zhuzhou-Xiangtan section of Xiangjiang River, China
- 2019
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Ingår i: journal of central south university. - : Springer Science and Business Media LLC. - 2095-2899 .- 2227-5223. ; 26:12, s. 3252-3260
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Tidskriftsartikel (refereegranskat)abstract
- The Changsha-Xiangtan-Zhuzhou City Group is a heavy industrial district and accepted as the serious pollution area in the Xiangjiang River basin. In this study, 7 metals (Pb, Hg, Cd, As, Zn, Cu and Se) and the river water quality parameters including pH, dissolved oxygen (DO), Escherichia coli (E. coli), potassium permanganate index (CODMn), dichromate oxidizability (CODCr), five-day biochemical oxygen demand (BOD5), ammonia nitrogen (NH4+-N), total nitrogen (TN), total phosphorus (TP) and fluoride (F-) in 18 sampling sites of the Changsha-Xiangtan-Zhuzhou section are monthly monitored in 2016, which is the year to step into the second stage of the Xiangjiang River Heavy Metal Pollution Control Implementation Plan. It is found that E. coli, TN and TP are the main pollutants in the Changsha-Zhuzhou-Xiangtan section, and the pollution of heavy metal is not serious but As with potential risk to local people especially children should be concerned. In addition, Xiangtan city is mainly featured with heavy metal pollution, while Zhuzhou and Changsha city are both featured with other pollutants from municipal domestic sewage.
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| 3. |
- Li-mei, Fang, et al.
(författare)
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Field controllable electronic properties of MnPSe3/WS2 heterojunction for photocatalysis
- 2021
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Ingår i: JOURNAL OF CENTRAL SOUTH UNIVERSITY. - : JOURNAL OF CENTRAL SOUTH UNIV. - 2095-2899 .- 2227-5223. ; 28:12, s. 3728-3736
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal dichalcogenides are interesting candidates as photocatalysts for hydrogen evolution reaction. The MnPSe3/WS2 heterostructure is hence studied here with first principles calculations by exploring its electronic properties under the application of an electric field. It is discovered that the band gap will decrease from the WS2 monolayer to the MnPSe3/WS2 heterostructure with Perdew-Burke-Ernzerhof functional, while increase slightly when electron correlation is involved. The conduction band minimum of the heterostructure is determined by the MnPSe3 layer, while the valence band maximum is contributed by the WS2 layer. The band edges and band gap suggest that the heterostructure will have good photocatalytic properties for water splitting. Moreover, comparing to monolayer WS2, the light absorption in both the ultraviolet and visible regions will be enhanced. When an electric field is present, a linear relation is observed between the electric field and the band gap within specific range, which can thus modulate the photocatalytic performance of this heterostructure.
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| 4. |
- Li-xia, Huang, et al.
(författare)
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Adaptive bands filter bank optimized by genetic algorithm for robust speech recognition system
- 2011
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Ingår i: Journal of Central South University of Technology. - : Springer Verlag (Germany). - 1005-9784 .- 1993-0666 .- 2095-2899 .- 2227-5223. ; 18:5, s. 1595-1601
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Tidskriftsartikel (refereegranskat)abstract
- Perceptual auditory filter banks such as Bark-scale filter bank are widely used as front-end processing in speech recognition systems. However, the problem of the design of optimized filter banks that provide higher accuracy in recognition tasks is still open. Owing to spectral analysis in feature extraction, an adaptive bands filter bank (ABFB) is presented. The design adopts flexible bandwidths and center frequencies for the frequency responses of the filters and utilizes genetic algorithm (GA) to optimize the design parameters. The optimization process is realized by combining the front-end filter bank with the back-end recognition network in the performance evaluation loop. The deployment of ABFB together with zero-crossing peak amplitude (ZCPA) feature as a front process for radial basis function (RBF) system shows significant improvement in robustness compared with the Bark-scale filter bank. In ABFB, several sub-bands are still more concentrated toward lower frequency but their exact locations are determined by the performance rather than the perceptual criteria. For the ease of optimization, only symmetrical bands are considered here, which still provide satisfactory results.
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| 5. |
- Liu, Lang, et al.
(författare)
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Quantitative investigation on micro-parameters of cemented paste backfill and its sensitivity analysis
- 2020
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Ingår i: Journal of Central South University. - : Springer. - 2095-2899 .- 2227-5223. ; 27:1, s. 267-276
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical properties of cemented paste backfill (CPB) depend heavily on its pore structural characteristics and micro-structural changes. In order to explore the variation mechanisms of macro-mechanical characteristics and micro-structure of CPB. CPB specimens with different mass concentrations prepared from the full tailings of Xianglushan Tungsten Ore were micro-tests. Moreover, acquired pore digital images were processed by using the pores (particles) and cracks analysis system (PCAS), and a sensitivity analysis was performed. The results show that as the mass concentration of CPB increases from 70% to 78%, the porosity, the average pore area and the number of pores drop overall, leading to a decline in the pores opening degree and enhancing the mechanical characteristics. As the mass concentration of CPB increases, the trend of fractal dimension, probability entropy and roundness is reduced, constant and increased, which can result in an enhancement of the uniformity, an unchanged directionality and more round pores. According to the definition of sensitivity, the sensitivities of various micro-parameters were calculated and can be ranked as porosity > average pore area > number of pores > roundness > fractal dimension > probability entropy.
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| 6. |
- Xiao-ling, Cao, et al.
(författare)
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Dynamic simulation of drum level sloshing of heat recovery steam generator
- 2013
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Ingår i: J CENT SOUTH UNIV. - : Springer Science and Business Media LLC. - 2095-2899. ; 20:2, s. 413-423
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Tidskriftsartikel (refereegranskat)abstract
- Drum level sloshing is the latest discovery in the application of heat recovery steam generator (HRSG) in combined cycle, and shows certain negative influence on drum level controlling. In order to improve drum level controlling, influence factors on the drum level sloshing were investigated. Firstly, drum sub-modules were developed using the method of modularization modeling, and then the model of drum level sloshing was set up as well. Experiments were carried out on the experimental rig, and the model was validated using the obtained experimental results. Dynamic simulation was made based on the model to get a 3-D graph of drum level sloshing, which shows a vivid procedure of drum level sloshing. The effect of feed-water flow rate, main-steam flow rate and heating quantity on the drum level sloshing was analyzed. The simulation results indicate that the signals with frequency higher than 0.05 Hz are that of drum level sloshing, the signals with frequency of 0.0-0.05 Hz are that of drum level trendy and "false water level", and variation of the feed-water flow rates, main-steam flow rates and heating quantities can change the frequency of drum level sloshing, i.e., the frequency of sloshing increases with the increase of feed-water flow rate, or the decrease of the main-steam flow rate and the heating quantity. This research work is fundamental to improve signal-to-noise ratio of drum level signal and precise controlling of drum level.
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