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An Experimental on Filtration and Clogging of Geotextile Filters around Drain Pipes in Fine Tailings
Dong-dong Li,Xuan Cui,Jing-qi Huang,Ya-bing Han 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.5
Needle-punched nonwoven geotextiles have been used as filters for decades in mine drainage systems. But the physical clogging of geotextiles by fine particles has continued to receive increasing attention. In this study, the permeation characteristics of a drain pipe wrapped with geotextiles were investigated based on a new radial flow experiment apparatus, and particle size distribution (PSD), pore water pressure (PWP), and scanning electron microscopy (SEM) analyses were employed to identify the geotextile clogging mechanism. The geotextile cleaning methods after clogging were also discussed. The results showed that an exponential decay of hydraulic conductivity (K) with time under different flow conditions. Particles less than 30 μm migrated to the drainage pipe under the action of seepage forces, and a dense and thick cake layer was formed upstream of the geotextile filter. According to microscopic analysis, the clogging process of geotextiles was divided into three stages: pore blockage and cake formation, filter cake dynamic growth and cake layer filtration. Backwash cleaning is a good way to remove a filter cake layer on the surface of geotextiles, which can recover 60% of the hydraulic conductivity (K0).
Xuan-Dong Nguyen,Ngo Xuan Quang,Thanh Luu Pham,Bijeesh Kozhikkodan Veettil 한국해양과학기술원 2022 Ocean science journal Vol.57 No.1
The Mekong River Delta is a hotspot of aquaculture and fish biodiversity. In this study, fish community structure, migration, threatened status and economic value were investigated in the Co Chien River (COR) from August 2017 to July 2019. A total of 3640 fish specimens were collected from 11 sampling stations in the COR. These belong to 133 species of 107 genera of 58 families of 17 orders. The Perch-like order (Perciformes) is the most diverse group, with 65 species accounting for 48.87% of total species collected. The catfish order (Siluriformes) is the second-most diverse group with 15 species (11.28%) and the carps (Cypriniformes) with 14 species (10.53%) is the third. The remaining major groups in the order of diversity are the Herring (Clupeiformes) consisting of 9 species (6.77%) and the Flounder (Pleuronectiformes) consisting of 7 species (5.26%). The remaining orders have number of species varying from 1 to 3 (0.75–2.26%). Among the 133 species recorded, 6 species were considered as Vulnerable category based on the Vietnam Red Data Book (2007). According to the IUCN Red list (2021), 1 species (Coilia mystus) is Endangered (0.75%), 2 species (Maculabatis gerrardi and Pangasius krempfi) are Vulnerable (1.50%), 4 species are Near Threatened (3.01%), 6 species are Data deficient (4.51%), and 76 species are considered as Least concern (57.14%). The results shown that 79 species were migratory fishes (20 species migrated from the upstream and 59 species migrated from the sea), 41 species are endemic species for the MR (30.83% of the total species collected and 23.70% of total endemic species of the MR) and 36 fish species are considered as of local economic value (27.07%). The diversity of fish species was found to be more diverse in the dry season than the wet season, which indicates the influence of river water salinity changes on fish diversity in the region.
Effects of Electric Filed on Electrospray Process: Experimental and Simulation Study
Xuan Dong,Yuansheng Zheng,Binjie Xin,Huaiyuan Liu,Lantian Lin 한국섬유공학회 2020 Fibers and polymers Vol.21 No.11
At present, there exists a widely-held view that electric field plays an extremely important role in the electrosprayprocess. Aimed at investigating into the effects of electric field distribution and intensity on the electrospray process andresultant microsphere diameter, a variety of necessary and relevant tests were performed in this study by inviting an auxiliaryelectrode ring. The three-dimensional electric fields of the electrospray system were simulated, in addition, high-speedphotography was adopted to recognize the electrospray modes. The results of a series of electrospray experiments demonstratedthat not only electrospray mode but also resultant microsphere diameters are influenced, to a considerable degree, by the electricfield. Such simulation results were verified by above-mentioned experiments that from higher electric field intensity comessmaller microsphere diameter, due to the fission caused by the surface charge, and besides, more uniform electric fielddistribution produces more uniform microsphere diameter.
Condition Diagnostic of Two-stroke Low-speed Diesel Engine using Acoustic Emission Sensor
Dong Xuan Thin(동수안 틴),Myeongho Song(송명호),Don Chool Lee(이돈출) 한국소음진동공학회 2019 한국소음진동공학회 논문집 Vol.29 No.5
Currently, condition diagnostic technologies of general machinery and their structures based on an acoustic emission sensor (AES) are widely used and applied to a variety of fields. An AES is an efficacious and powerful tool for measuring the high-frequency vibrations of reciprocating or rotating devices. Data acquisition (DAQ) and analysis software (S/W) for AES operating at high frequencies from 50 kHz to 1 MHz is necessary. In this regard, an S/W has been developed to facilitate the simultaneous monitoring of 12 channels using National Instrument’s (NI) NI6366 DAQ device and C# programming language to achieve a sampling rate of 2 MS/s for each channel. In a case study involving a two-stroke low-speed diesel engine during sea trial, the firing conditions of all the cylinders and the working conditions of the top bracing (TB) were detected. Based on the results, it was demonstrated that the recorded vibrations under normal firing conditions have a larger amplitude than the vibrations that occur under the misfiring conditions, in all investigated operation ranges. In addition, the TB on-off condition was detected by a 1/80 octave analysis of the AES signal via wave transmission. When the mechanical components participate in the moving process, there is the possibility of the generation of friction and wear including deformation and micro-fraction, as well as slipping between moving parts. These results can serve as useful information for the detection of mechanical working conditions in the future.
Minimum Wages and Firm Productivity: Evidence from Vietnamese Manufacturing Firms
Dong Xuan Nguyen 한국국제경제학회 2019 International Economic Journal Vol.33 No.3
This paper empirically examines the minimum-wage impact on firm productivity. Using a detailed Vietnamese firm-level dataset from 2010 through 2015, the regression results suggest that firms raise their labor productivity, total factor productivity, capital intensity and revenue in response to increased minimum wage standards. Firms that pay their workers below the minimum wage react more positively in raising their labor productivity than high-wage firms. Minimum wages has had a more pronounced impact on firms’ labor productivity, total factor productivity and capital intensity since the uniform wage rate was introduced for both domestic private and foreign-invested enterprises in 2012.
The treatment effect of novel hGHRH homodimer to male infertility hamster
Xu-Dong Zhang,Xiao-Yuan Guo,Jing-Xuan Tang,Lin-Na Yue,Juan-Hui Zhang,Tao Liu,Yu-Xia Dong,Song-Shan Tang 대한생리학회-대한약리학회 2018 The Korean Journal of Physiology & Pharmacology Vol.22 No.6
Extra-hypothalamic growth hormone-releasing hormone (GHRH) plays an important role in reproduction. To study the treatment effect of Grin (a novel hGHRH homodimer), the infertility models of 85 male Chinese hamsters were established by intraperitoneally injecting 20 mg/kg of cyclophosphamide once in a week for 5 weeks and the treatment with Grin or human menopausal gonadotropin (hMG) as positive control was evaluated by performing a 3-week mating experiment. 2-8 mg/kg of Grin and 200 U/kg of hMG showed similar effect and different pathological characteristics. Compared to the single cyclophosphamide group (0%), the pregnancy rates (H-, M-, L-Grin 26.7, 30.8, 31.3%, and hMG 31.3%) showed significant difference, but there was no difference between the hMG and Grin groups. The single cyclophosphamide group presented loose tubules with pathologic vacuoles and significant TUNEL positive cells. Grin induced less weight of body or testis, compactly aligned tubules with little intra-lumens, whereas hMG caused more weight of body or testis, enlarging tubules with annular clearance. Grin presented a dose-dependent manner or cell differentiation-dependentincrease in testicular GHRH receptor, and did not impact the levels of blood and testicular GH, testosterone. Grin promotes fertility by proliferating and differentiating primitive cells through up-regulating testicular GHRH receptor without triggering GH secretion, which might solve the etiology of oligoasthenozoospermia.