Journal of Central South University 

About: Journal of Central South University is an academic journal published by Springer Science+Business Media. The journal publishes majorly in the area(s): Microstructure & Heat transfer. It has an ISSN identifier of 2095-2899. Over the lifetime, 3845 publications have been published receiving 34250 citations. The journal is also known as: Zhongnan Daxue xuebao. Yingwen ban.

AE waveform characteristics of rock mass under uniaxial loading based on Hilbert-Huang transform

Abstract: Acoustic Emission (AE) waveforms contain information on microscopic structural features that can be related with damage of coal rock masses. In this paper, the Hilbert-Huang transform (HHT) method is used to obtain detailed structural characteristics of coal rock masses associated with damage, at different loading stages, from the analyses of the characteristics of AE waveforms. The results show that the HHT method can be used to decompose the target waveform into multiple intrinsic mode function (IMF) components, with the energy mainly concentrated in the C1–C4 IMF components, where the C1 component has the highest frequency and the largest amount of energy. As the loading continues, the proportion of energy occupied by the low-frequency IMF component shows an increasing trend. In the initial compaction stage, the Hilbert marginal spectrum is mainly concentrated in the low frequency range of 0–40 kHz. The plastic deformation stage is associated to energy accumulation in the frequency range of 0–25 kHz and 200–350 kHz, while the instability damage stage is mainly concentrated in the frequency range of 0–25 kHz. At 20 kHz, the instability damage reaches its maximum value. There is a relatively clear instantaneous energy peak at each stage, albeit being more distinct at the beginning and at the end of the compaction phase. Since the effective duration of the waveform is short, its resulting energy is small, and so there is a relatively high value from the instantaneous energy peak. The waveform lasts a relatively long time after the peak that coincides with failure, which is the period where the waveform reaches its maximum energy level. The Hilbert three-dimensional energy spectrum is generally zero in the region where the real energy is zero. In addition, its energy spectrum is intermittent rather than continuous. It is therefore consistent with the characteristics of the several dynamic ranges mentioned above, and it indicates more clearly the low-frequency energy concentration in the critical stage of instability failure. This study well reflects the response law of geophysical signals in the process of coal rock instability and failure, providing a basis for monitoring coal rock dynamic disasters.

Industrial wastes applications for alkalinity regulation in bauxite residue: A comprehensive review

Abstract: Bauxite residue is a highly alkaline material generated from the production of alumina in which bauxite is dissolved in caustic soda. Approximately 4.4 billion tons of bauxite residues are either stockpiled or landfilled, creating environmental risks either from the generation of dust or migration of filtrates. High alkalinity is the critical factor restricting complete utilization of bauxite residues, whilst the application of alkaline regulation agents is costly and difficult to apply widely. For now, current industrial wastes, such as waste acid, ammonia nitrogen wastewater, waste gypsum and biomass, have become major problems restricting the development of the social economy. Regulation of bauxite residues alkalinity by industrial waste was proposed to achieve ‘waste control by waste’ with good economic and ecological benefits. This review will focus on the origin and transformation of alkalinity in bauxite residues using typical industrial waste. It will propose key research directions with an emphasis on alkaline regulation by industrial waste, whilst also providing a scientific reference point for their potential use as amendments to enhance soil formation and establish vegetation on bauxite residue disposal areas (BRDAs) following large-scale disposal.

Heat transfer study on solid and porous convective fins with temperature-dependent heat generation using efficient analytical method

Abstract: A simple and highly accurate semi-analytical method, called the differential transformation method (DTM), was used for solving the nonlinear temperature distribution equation in solid and porous longitudinal fin with temperature dependent internal heat generation. The problem was solved for two main cases. In the first case, heat generation was assumed variable by fin temperature for a solid fin and in second heat generation varied with temperature for a porous fin. Results are presented for the temperature distribution for a range of values of parameters appearing in the mathematical formulation (e.g. N, ɛ G , and G). Results reveal that DTM is very effective and convenient. Also, it is found that this method can achieve more suitable results in comparison to numerical methods.

Flow of Casson nanofluid with viscous dissipation and convective conditions: A mathematical model

Abstract: The magnetohydrodynamic (MHD) boundary layer flow of Casson fluid in the presence of nanoparticles is investigated. Convective conditions of temperature and nanoparticle concentration are employed in the formulation. The flow is generated due to exponentially stretching surface. The governing boundary layer equations are reduced into the ordinary differential equations. Series solutions are presented to analyze the velocity, temperature and nanoparticle concentration fields. Temperature and nanoparticle concentration fields decrease when the values of Casson parameter enhance. It is found that the Biot numbers arising due to thermal and concentration convective conditions yield an enhancement in the temperature and concentration fields. Further, we observed that both the thermal and nanoparticle concentration boundary layer thicknesses are higher for the larger values of thermophoresis parameter. The effects of Brownian motion parameter on the temperature and nanoparticle concentration are reverse.

Heat transfer and nanofluid flow over a porous plate with radiation and slip boundary conditions

Abstract: Presence of different terms with various values can alter the thermal behavior of the nanofluids flow over porous surfaces. The aim of this research is to study the influence of nanoparticles volume fraction, nanoparticles type, suction or injection, the heat generation or absorption, the Eckert number, thermal and velocity slip parameters, and radiation on the velocity and temperature fields on the flow and heat transfer over a porous flat plate. Four different types of nanoparticles including metal nanoparticles (Cu), metal oxide nanoparticles (Al2O3) and carbon-based nanomaterials (MWCNTs and SWCNTs) which were dispersed in the water (as based fluid) are studied. The governing equations are converted into the ordinary differential equations using similarity solution and solved numerically by the RKF45 algorithm. The results of the simulations showed a contradiction with the results of other researchers who expressed that using nanoparticles with higher thermal conductivity and volume fraction led to increasing heat transfer rate in nanofluids; this study proves that, in some cases, boosting the volume fraction of nanoparticles has a potential to decrease the heat transfer rate due to significant changes in values of some parameters including radiation, heat generation, and viscous dissipation.