Dispersion behavior and thermal conductivity characteristics of Al2O3–H2O nanofluids

Dongsheng Zhu,Xinfang Li,Nan Wang,Xianju Wang,Jinwei Gao,Hua Li 한국물리학회 2009 Current Applied Physics Vol.9 No.1

Nanofluid is a kind of new engineering material consisting of solid nanoparticles with sizes typically of 1–100 nm suspended in base fluids. In this study, Al2O3–H2O nanofluids were synthesized, their dispersion behaviors and thermal conductivity in water were investigated under different pH values and different sodium dodecylbenzenesulfonate (SDBS) concentration. The sedimentation kinetics was determined by examining the absorbency of particle in solution. The zeta potential and particle size of the particles were measured and the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to calculate attractive and repulsive potentials. The thermal conductivity was measured by a hot disk thermal constants analyser. The results showed that the stability and thermal conductivity enhancements of Al2O3–H2O nanofluids are highly dependent on pH values and different SDBS dispersant concentration of nano-suspensions, with an optimal pH value and SDBS concentration for the best dispersion behavior and the highest thermal conductivity. The absolute value of zeta potential and the absorbency of nano-Al2O3 suspensions with SDBS dispersant are higher at pH 8.0. The calculated DLVO interparticle interaction potentials verified the experimental results of the pH effect on the stability behavior. The Al2O3–H2O nanofluids with an ounce of Al2O3 have noticeably higher thermal conductivity than the base fluid without nanoparticles, for Al2O3 nanoparticles at a weight fraction of 0.0015 (0.15 wt%), thermal conductivity was enhanced by up to 10.1%. Nanofluid is a kind of new engineering material consisting of solid nanoparticles with sizes typically of 1–100 nm suspended in base fluids. In this study, Al2O3–H2O nanofluids were synthesized, their dispersion behaviors and thermal conductivity in water were investigated under different pH values and different sodium dodecylbenzenesulfonate (SDBS) concentration. The sedimentation kinetics was determined by examining the absorbency of particle in solution. The zeta potential and particle size of the particles were measured and the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to calculate attractive and repulsive potentials. The thermal conductivity was measured by a hot disk thermal constants analyser. The results showed that the stability and thermal conductivity enhancements of Al2O3–H2O nanofluids are highly dependent on pH values and different SDBS dispersant concentration of nano-suspensions, with an optimal pH value and SDBS concentration for the best dispersion behavior and the highest thermal conductivity. The absolute value of zeta potential and the absorbency of nano-Al2O3 suspensions with SDBS dispersant are higher at pH 8.0. The calculated DLVO interparticle interaction potentials verified the experimental results of the pH effect on the stability behavior. The Al2O3–H2O nanofluids with an ounce of Al2O3 have noticeably higher thermal conductivity than the base fluid without nanoparticles, for Al2O3 nanoparticles at a weight fraction of 0.0015 (0.15 wt%), thermal conductivity was enhanced by up to 10.1%.

Adsorption properties of Friedel’s salt for the nitrate in the landfill

Dongsheng Shen,Jun Yao,Qingna Kong,Huayue Zhu,Zhen Zhang 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.2

Adsorption characteristics of nitrate on Friedel’s salt under the landfill circumstance were investigated to explore the effect of Friedel’s salt on the migration of nitrate in the landfill. Friedel’s salt was synthesized by a coprecipitation method and characterized by XRD and FTIR spectroscopy. The kinetics and isotherm of the adsorption were studied. The effect of the variation of landfill circumstance on the adsorption was also discussed. The result showed that the adsorption capacity of Friedel’s salt for nitrate was 2.494mg g−1. The adsorption process was exothermic and could be well described by pseudo-second-order kinetics and Langmuir-Freundlich equation. Cl− could enhance the adsorption, while SO4 2−, PO4 3− and organic matter could restrict the adsorption. The results suggested that the migration of nitrate in the landfill could be altered by Friedel’s salt, which was related to the variation of the landfill circumstance.

pH-Based immunoassay: explosive generation of hydrogen ions through an immuno-triggered nucleic acid exponential amplification reaction

Mao, Dongsheng,Chen, Tianshu,Chen, Huinan,Zhou, Mengru,Zhai, Xingwei,Chen, Guifang,Zhu, Xiaoli The Royal Society of Chemistry 2019 The Analyst Vol.144 No.13

<P>In this work, we propose a novel concept and a proof-of-concept strategy for the fabrication of a pH-based immunoassay platform with a certain degree of universality and scalability to make it adaptable for different application scenarios. The immunoreactions for the target detection are converted to pH changes through an engineered and optimized isothermal nucleic acid amplification, named exponential amplification reaction (EXPAR). Thus, a variety of well-developed methods for pH analysis, <I>e.g.</I> pH indicators, pH-strips and pH meters, can be applied for immunoassay directly. Here, we show that this proof-of-concept strategy is applicable for both macromolecular and micromolecular antigens by adopting human platelet-derived growth factor-BB (PDGF-BB) and chloramphenicol (CAP) as the model targets, respectively. The detection can be achieved using a colorimetric pH indicator after a 15 min reaction of the immuno-triggered isothermal nucleic acid amplification. In addition, compared with the traditional enzyme-linked immunosorbent assay (ELISA), the performance of our strategy, especially the detection limits, is improved to varying degrees for different targets, making the strategy a promising alternative for diverse application scenarios of immunoassay.</P>

UIO-based Fault Estimation and Accommodation for Nonlinear Switched Systems

Haoshuang Chen,Dongsheng Du,Dewen Zhu,Yan Yang 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.2

This paper investigates the problems of fault estimation and fault accommodation for a class of nonlinearswitched systems. First, an augmented switched system is constructed by forming an augmented state vectorcomposed of the state vector and the fault vectors. Then, an unknown input observer (UIO) is designed for theaugmented switched system to estimate the augmented state vector. With the assist of the average dwell-time(ADT) method and the switched Lyapunov function technique, sufficient conditions are obtained to guarantee thatthe error system is globally uniformly asymptotically stable (GUAS) with a prescribed H∞ performance index. Analgorithm is provided to show the procedures on how to design the UIO. Moreover, the results are extended to themeasurement disturbances case. Based on signal compensation principle, a dynamic output feedback controller isdesigned to ensure the asymptotical stability of the closed-loop system. Finally, simulation results are presented todemonstrate the proposed technique.

Dual-Coupled Inductor High Gain DC/DC Converter with Ripple Absorption Circuit

Jie Yang,Dongsheng Yu,Mohammed Alkahtani,Ligen Yuan,Zhi Zhou,Hong Zhu,Maxwell Chiemeka 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.6

High-gain DC/DC converters have become one of the key technologies for the grid-connected operation of new energy power generation, and its research provides a significant impetus for the rapid development of new energy power generation. Inspired by the transformer effect and the ripple-suppressed ability of a coupled inductor, a double-coupled inductor high gain DC/DC converter with a ripple absorption circuit is proposed in this paper. By integrating the diode-capacitor voltage multiplying unit into the quadratic Boost converter and assembling the independent inductor into the magnetic core of structure coupled inductors, the adjustable range of the voltage gain can be effectively extended and the limit on duty ratio can be avoided. In addition, the volume of the magnetic element can be reduced. Very small ripples of input current can be obtained by the ripple absorption circuit, which is composed of an auxiliary inductor and a capacitor. The leakage inductance loss can be recovered to the load in a switching period, and the switching-off voltage spikes caused by leakage inductance can be suppressed by absorption in the diode-capacitor voltage multiplying unit. On the basis of the theoretical analysis, the feasibility of the proposed converter is verified by test results obtained by simulations and an experimental prototype.

Computer Simulation and Verification of Adiabatic Temperature and Apparent Activity Energy of the NiO/Al Aluminothermic System

Song, Yuepeng,Zhu, Yanmin,Gao, Dongsheng,Guo, Jing,Kim, Hyoung Seop The Korean Powder Metallurgy Institute 2013 한국분말재료학회지 (KPMI) Vol.20 No.5

Recently, self-propagating high-temperature synthesis (SHS), related to metallic and ceramic powder interactions, has attracted huge interest from more and more researchers, because it can provide an attractive, energy-efficient approach to the synthesis of simple and complex materials. The adiabatic temperature $T_{ad}$ and apparent activation energy analysis of different thermit systems plays an important role in thermodynamic studies on combustion synthesis. After establishing and verifying a mathematic calculation program for predicting adiabatic temperatures, based on the thermodynamic theory of combustion synthesis systems, the adiabatic temperatures of the NiO/Al aluminothermic system during self-propagating high-temperature synthesis were investigated. The effect of a diluting agent additive fraction on combustion velocity was studied. According to the simulation and experimental results, the apparent activation energy was estimated using the Arrhenius diagram of $ln(v/T_{ad}){\sim}/T_{ad}$ based on the combustion equation given by Merzhanov et al. When the temperature exceeds the boiling point of aluminum (2,790 K), the apparent activation energy of the NiO/Al aluminothermic system is $64{\pm}14$ kJ/mol. In contrast, below 2,790 K, the apparent activation energy is $189{\pm}15$ kJ/mol. The process of combustion contributed to the mass-transference of aluminum reactant of the burning compacts. The reliability of the simulation results was experimentally verified.

Will a Wiener Filter Decrease the Accuracy of HRTEM Displacement Measurements of Aperiodic Structures?

Gen Li,Dongsheng Song,Zhenyu Liao,Jing Zhu 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.12

Modern Cs-corrected high-resolution transmission electron microscopy (HRTEM) has pushed the resolution limit to sub-angstrom scale and has made possible the quantitative analyses of local aperiodic atomic structures. After images have been obtained, a Wiener filter is often used to improve the signal-to-noise ratio, especially for those samples containing both crystal and large amorphous components. However, a Wiener filter may introduce distortions in the original experimental images. From this point of view, having a fundamental understanding of the effect of a Wiener filter on the accuracy of atomic displacement measurements in aperiodic structures is important. In this work, we first review the principle of the Wiener filter and theoretically discuss the origin of the distortions induced in aperiodic structures by using a Wiener filter. Then, using hypothetical experimental systems that contains both aperiodic crystal structures and amorphous layers, we carried out synthetic experiments to quantitatively estimate the effect of the Wiener filter on the measurements of aperiodic displacements. Compared with the values for a non-filtered image, the signal-to-noise ratio was significantly improved, and the accuracy of the displacement measurement was not decreased when proper Wiener filter parameters were used. Such results are of great importance for the processing of HRTEM images.

Dual-Coupled Inductor High Gain DC/DC Converter with Ripple Absorption Circuit

Yang, Jie,Yu, Dongsheng,Alkahtani, Mohammed,Yuan, Ligen,Zhou, Zhi,Zhu, Hong,Chiemeka, Maxwell The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.6

High-gain DC/DC converters have become one of the key technologies for the grid-connected operation of new energy power generation, and its research provides a significant impetus for the rapid development of new energy power generation. Inspired by the transformer effect and the ripple-suppressed ability of a coupled inductor, a double-coupled inductor high gain DC/DC converter with a ripple absorption circuit is proposed in this paper. By integrating the diode-capacitor voltage multiplying unit into the quadratic Boost converter and assembling the independent inductor into the magnetic core of structure coupled inductors, the adjustable range of the voltage gain can be effectively extended and the limit on duty ratio can be avoided. In addition, the volume of the magnetic element can be reduced. Very small ripples of input current can be obtained by the ripple absorption circuit, which is composed of an auxiliary inductor and a capacitor. The leakage inductance loss can be recovered to the load in a switching period, and the switching-off voltage spikes caused by leakage inductance can be suppressed by absorption in the diode-capacitor voltage multiplying unit. On the basis of the theoretical analysis, the feasibility of the proposed converter is verified by test results obtained by simulations and an experimental prototype.