Experimental study on vacuum preloading with flocculation for solid-liquid separation in waste slurry

Wu, Yajun,Kong, Gangqiang,Lu, Yitian,Sun, De'an Techno-Press 2017 Geomechanics & engineering Vol.13 No.2

This vacuum preloading combined with polyacrylamide (PAM) flocculation was proposed to separating solid-liquid in waste slurry and to improving bearing capacity of soft soil ground. By using waste slurry taken from drilled shaft construction site in Shanghai, China, a series of settling column tests with four typical flocculants and one normal for waste slurry were carried out for comparative analysis. The optimal amounts for each flocculant were obtained from the column tests. Then, model tests on vacuum preloading with anionic polyacrylamide (APAM) flocculation and without flocculants were carried out. The out of water and the settlement of slurry surface ground were monitored during the model tests, and the changes in water content, particle-size and pore-size distributions in different positions after the model tests were measured and discussed. It is found that water content of the waste slurry without APAM flocculation changed from 204 to 195% by 24 hours standing and 15 hours vacuum preloading, while the water content of the waste slurry with APAM flocculation was declined from 163 to 96% by 24 hours standing, and was further reduced into 37% by 136 hours vacuum preloading, which shows that the combined method is feasible and effective.

Phosphorus Release from Lake Sediments: Effects of pH,Temperature and Dissolved Oxygen

YunHai Wu,Yajun Wen,Jianxin Zhou,Yunying Wu 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.1

Sediments can release Phosphorus (P) into overlying water under certain environmental conditions, which may have a significant impact on water quality and result in continuous eutrophication. We used laboratory experiments to evaluate effects of pH,temperature, and Dissolved Oxygen (DO) on P release from Lake Xuanwu, China. The results demonstrate that effects of pH on P release from sediments were distinct; more P was released under alkaline conditions than acidic conditions, but the least amount of P was released under neutral pH. Increasing temperature resulted in more release of P and a longer time to achieve equilibrium between sediment P release and P in overlying water. Influences of DO supply levels on P release were also quite significant; anaerobic conditions were more conducive to the release of P than aerobic conditions. Orthogonal experiments show that the 3 significant factors on P release from sediments were, in descending order, DO, temperature, and pH. These findings have important management implications for Lake Xuanwu.

Performance Analysis of Energy-Efficient Secure Transmission for Wireless Powered Cooperative Networks with Imperfect CSI

Yajun Zhang,Jun Wu,Bing Wang,Hongkai Wang,Xiaohui Shang 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.9

The paper focuses on investigating secure transmission in wireless powered communication networks (WPCN) that involve multiple energy-constrained relays and one energy-constrained source. The energy is harvested from a power beacon (PB) while operating in the presence of a passive eavesdropper. The study primarily aims to achieve energy-efficient secure communications by examining the impact of channel estimation on the secrecy performance of WPCN under both perfect and imperfect CSI scenarios. To obtain practical insights on improving security and energy efficiency, we propose closed-form expressions for secrecy outage probability (SOP) under the linear energy harvesting (LEH) model of WPCN. Furthermore, we suggest a search method to optimize the secure energy efficiency (SEE) with limited power from PB. The research emphasizes the significance of channel estimation in maintaining the desired performance levels in WPCN in real-world applications. The theoretical results are validated through simulations to ensure their accuracy and reliability.

CO2 Capture on a Novel Porous Silicate Material from Coal Gangue: Equilibrium, Kinetic, and Thermodynamic Studies

Yajun Gao,Hong Du,Yu Wu,Kai Liu,Jianbin Zhang 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.2

The adsorption of CO2 on a novel porous silicate material (PSM) from coal gangue at T = (288.15, 303.15, and 318.15) K was thoroughly characterized, and the experimental results showed that the adsorption capacity increased with the increasing pressures. Furthermore, the isotherm data were well fitted to Double–Langmuir model, and the adsorption process was found to be exothermic in nature with a decrease in entropy. Meanwhile, thermodynamic results also showed that the adsorption occurred via a spontaneous and enthalpy driven process and controlled by physisorption. In addition, the adsorption performance was still stable after 10 times adsorption—desorption cycles, which indicated that the PSM had a positive regeneration performance.

Optimizing adsorption of arsenic(III) by NH2-MCM-41 using response surface methodology

YunHai Wu,Yanping Jin,Julin Cao,Palizhati Yilihan,Yajun Wen,Jianxin Zhou 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5

Response surface methodology (RSM) was used to optimize process parameters for arsenic (As(III)) removal from aqueous solution using amine-functionalized MCM-41 (NH2-MCM-41). Four independent variables such as pH, initial metal concentration, temperature and adsorbent dosage were investigated. The optimal conditions to remove As(III) by NH2-MCM-41 was found to be pH 5.62, initial As(III) concentration 5.00 mg/L, temperature 20 8C and NH2-MCM-41 dosage 5.00 g/L. XRD, FTIR and SEM analyses testified to the obvious change of the surface morphology and the presence of metal on the sorbent after adsorption. 2013 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Genetic Variation and Evolution of the Pi9 Blast Resistance Locus in the AA Genome Oryza Species

Jinling Liu,Yajun Hu,Yuese Ning,Nan Jiang,Jun Wu,전종성,Yinghui Xiao,Xionglun Liu,Liangying Dai,Guo-Liang Wang 한국식물학회 2011 Journal of Plant Biology Vol.54 No.5

The rice nucleotide-binding site–leucine-rich repeat (NBS-LRR)-encoding resistance (R) gene Pi9 confers broad-spectrum resistance to the fungal pathogen Magnaporthe oryzae. The Pi9 locus comprises many NBS-LRR-like genes and is an ancient locus that is highly conserved in cultivated and wild rice species. To understand the genetic variation and molecular evolutionary mechanism of the Pi9 alleles in different rice species, we studied five AA genome Oryza species including two cultivated rice species (Oryza sativa and Oryza glaberrima) and three wild rice species (Oryza nivara, Oryza rufipogon, and Oryza barthii). A 2.9-kb fragment spanning the NBS-LRR core region of the Pi9 gene was amplified and sequenced from 40 accessions. Sequence comparison revealed that the Pi9 alleles had an intermediate-diversified nucleotide polymorphism among the AA genome Oryza species. Sequence variations were more abundant in the LRR region than in the NBS region, indicating that the LRR region has played a more important role for the evolution of the Pi9alleles. Furthermore, positive selection was found to be the main force promoting the divergence of the Pi9 alleles,especially in the LRR region. Our results reveal the characteristics and evolutionary dynamics of the Pi9 alleles among the two cultivated and three wild rice species.

Association between Plasma Osmolality and Case Fatality within 1 Year after Severe Acute Ischemic Stroke

Meng Liu,Yilun Deng,Yajun Cheng,Zilong Hao,Simiao Wu,Ming Liu 연세대학교의과대학 2021 Yonsei medical journal Vol.62 No.7

Purpose: Plasma osmolality, a marker of dehydration, is associated with cardiovascular mortality. We aimed to investigatewhether elevated plasma osmolality is associated with case fatality within 1 year after severe acute ischemic stroke. Materials and Methods: We included severe ischemic stroke patients (defined as National Institutes of Health Stroke Scale ≥15score) within 24 hours from symptom onset admitted to the Department of Neurology, West China Hospital between January 2017and June 2019. Admission plasma osmolality was calculated using the equation 1.86*(sodium+potassium)+1.15*glucose+urea+14. Elevated plasma osmolality was defined as plasma osmolality >296 mOsm/kg, indicating a state of dehydration. Study outcomesincluded 3-month and 1-year case fatalities. Multivariable logistic regression was performed to determine independent associationsbetween plasma osmolality and case fatalities at different time points. Results: A total of 265 patients with severe acute ischemic stroke were included. The mean age was 71.2±13.1 years, with 51.3%being males. Among the included patients, case fatalities were recorded for 31.7% (84/265) at 3 months and 39.6% (105/265) at1 year. Elevated plasma osmolality (dehydration) was associated with 3-month case fatality [odds ratio (OR) 1.98, 95% confidenceinterval (CI) 1.07–3.66, p=0.029], but not 1-year case fatality (OR 1.51, 95% CI 0.84–2.72, p=0.165), after full adjustment for confoundingfactors. Conclusion: Elevated plasma osmolality was independently associated with 3-month case fatality, but not 1-year case fatality, forsevere acute ischemic stroke.

Experimental and mechanism research on volatilization characteristics of HCl in desulfurization wastewater evaporation process using high temperature flue gas

Ma Shuangchen,Chai Jin,Wu Kai,Wan Zhongcheng,Xiang Yajun,Zhang Jingrui,Fan Zixuan 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.66 No.-

Due to the promulgation of “water pollution control action plan” in China, zero liquid discharge of desulfurization wastewater has become a new trend for water pollution control in power plants. The HCl volatilization in desulfurization wastewater evaporation process is the key problem that may influence the application of evaporation technology, so experiment was carried out in self-made experimental system. The effects of temperature, pH, Cl− concentration, total dissolved solids and main metal ions on HCl volatilization were explored. Results have shown that HCl volatilization increases respectively from 5.42% to 20.43% and 2.22% to 9.18% with the increasing temperature from 180 °C to 380 °C in two kinds of actual desulfurization wastewater evaporation process. When pH < 7, Cl− concentration is the main influencing factor on HCl volatilization; the higher Cl− concentration is, the higher HCl volatilization will be observed. While pH > 7, pH becomes the dominant factor, increasing pH will inhibit HCl volatilization; Mechanism of HCl volatilization was studied simultaneously by XRD and TGA. Gaseous HCl mainly comes from the combination of free H+ and Cl−, hydrolysis of Ca2+ and Mg2+ in liquid phase and hydrolysis of hydrate in high temperature solid phase; Ways to inhibit HCl volatilization in process were put forward according to the experimental results. The use of Ca(OH)2 to adjust the pH of desulfurization wastewater to 9.0–10.0 can inhibit HCl volatilization economically and efficiently. This study provides the key data for the application of flue gas evaporation technology under high temperature. The research results have important theoretical and practical values for the engineering practice of this technology.

Microstructure and phase constitution near the interface of Cu/3003 torch brazing using Al-Si-La-Sr filler

Fei Yan,Daorong Xu,S.C. Wu,Qinde Sun,Chunming Wang,Yajun Wang 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.12

It has been mainly studied in this paper on brazing of Cu to Al using Al–Si filler metal. The optimized scanning rate of 2.5 mm/s is first obtained through simulating the temperature field of Cu-Al brazing process based on ANSYS software. Then the brazing of Cu-C11000 to Al-3003 using Al–Si–La–Sr filler is carried out by torch brazing technology. It is found that the brazing seam region is mainly consisted of α-Al solid solution and CuAl2 IMC. Further experimental results also show that the rare earth element La in filler metal can not only refine the grain, but also promote the dispersion of intermetallic compounds into the brazing seam, which significantly improves the brazing seam microstructure and mechanical properties of the joints.

Influence of pump start-up mode on the stability of mixed-flow pumps

Zhenbo Tang,Guojun Zhu,Jianjun Feng,Yajun Wu,Kai Liu,Qiang Lu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

To analyse the influence of the start-up mode on the stability of the mixed-flow pump, start-up experiments are performed. And the external characteristic parameters, pressure fluctuation and shaft vibration data are collected by a multi-channel synchronous signal acquisition system during start-up. These data are analyzed by the time-frequency analysis method and wavelet partial coherence analysis method. Results reveal a positive correlation between the impeller angular acceleration and the time change rate of external characteristic parameters. During the start-up process, the variation law of the external characteristic parameters similar with the law of impeller rotating speed rise. The amplitude of the shaft vibration has a positive correlation with the start-up acceleration of the impeller. The influence of guide vane pressure fluctuations on the shaft vibrations is greater within 0~2 s after the start of the mixedflow pump. With the strart-up time extension, the partial coherence between the shaft vibration and the pressure fluctuations in guide vane is enhanced in low frequency band, which increases the risk of flow-induced vibration of the pump shaft.