Progress in developments of dry coal beneficiation

Abstract China’s energy supply heavily relies on coal and China’s coal resource and water resource has a reverse distribution. The problem of water shortages restricts the applications of wet coal beneficiation technologies in drought regions. The present situation highlights the significance and urgency of developing dry beneficiation technologies of coal. Besides, other countries that produce large amounts of coal also encounter serious problem of lack of water for coal beneficiation, such as American, Australia, Canada, South Africa, Turkey and India. Thus, dry coal beneficiation becomes the research hot-points in the field of coal cleaning worldwide in recent years. This paper systematically reviewed the promising research efforts on dry coal beneficiation reported in literature in last 5 years and discussed the progress in developments of dry coal beneficiation worldwide. Finally, we also elaborated the prospects and the challenges of the development of dry coal beneficiation

The stability analysis of separated feed ultrasonic milling

The full-discretization method introduced by Ding has high computational efficiency without loss of any numerical precision regardless of low and high radial depth of cut for the stability analysis of ordinary milling operation in time domain. Contrast to ordinary milling, it exists the separation phenomenon between each cutter tooth and the workpiece in feed ultrasonic milling operation. So before analyzing the system stability by the full-discretization method, the contact state between the cutter tooth and the workpiece should be made clear. In this paper, the trajectory method is proposed by the authors to judge the contact state between the cutter tooth and the workpiece. The stability analysis is developed for separated feed ultrasonic and ordinary end milling operations by the above methods and is validated via time domain simulations and experiments for both operations. The analyses show excellent agreement with both the time domain simulations and the experiments. Further, several end milling experiments were conducted that demonstrate the result ultrasonic vibration in feed direction can suppress chatter in machining operations

The stability analysis of separated feed ultrasonic milling

The full-discretization method introduced by Ding has high computational efficiency without loss of any numerical precision regardless of low and high radial depth of cut for the stability analysis of ordinary milling operation in time domain. Contrast to ordinary milling, it exists the separation phenomenon between each cutter tooth and the workpiece in feed ultrasonic milling operation. So before analyzing the system stability by the full-discretization method, the contact state between the cutter tooth and the workpiece should be made clear. In this paper, the trajectory method is proposed by the authors to judge the contact state between the cutter tooth and the workpiece. The stability analysis is developed for separated feed ultrasonic and ordinary end milling operations by the above methods and is validated via time domain simulations and experiments for both operations. The analyses show excellent agreement with both the time domain simulations and the experiments. Further, several end milling experiments were conducted that demonstrate the result ultrasonic vibration in feed direction can suppress chatter in machining operations

A novel high-strength large vibrating screen with duplex statically indeterminate mesh beam structure

Screening is an indispensable unit process for separation of materials. Large vibrating screen is extensively used in coal processing because of its large production capacity. In this study, a novel large vibrating screen with duplex statically indeterminate mesh beam structure (VSDSIMBS) was presented. The dynamic model of VSDSIMBS was proposed, and characteristic parameters were obtained by theoretical calculations. In order to obtain more reliable and believable research results, model of a traditional vibrating screen (TVS) with the same mass was also established for comparisons with VSDSIMBS. The finite element (FE) method was applied to study the performance of VSDSIMBS and FE analysis of VSDSIMBS and TVS was completed by using characteristic parameters. Modal analysis results indicated that VSDSIMBS could avoid the resonance and run more smoothly than TVS. Furthermore, harmonic response analysis results showed that VSDSIMBS could improve the entire stress distribution, reduce high stress areas, and increase the strength of vibrating screen. With DSIMBS, the maximum stress of vibrating screen decreased from 130.53 to 64.54 MPa. The full-scale experimental tests were performed to validate the credibility and accuracy of FE analysis results. The stress and displacements of VSDSIMBS were measured under working conditions. The test results obtained are in good agreement with simulation results, and accord with conclusions made from FE analysis

Heme oxygenase-1 prevents non-alcoholic steatohepatitis through suppressing hepatocyte apoptosis in mice

<p>Abstract</p> <p>Objective</p> <p>Heme oxygenase-1 (HO-1), the rate-limiting enzyme in heme catabolism, has been reported to have potential antioxidant properties. However, the role of HO-1 on hepatocyte apoptosis remains unclear. We aim to elucidate the effects of HO-1 on oxidative stress related hepatocellular apoptosis in nutritional steatohepatitis in mice.</p> <p>Methods</p> <p>C57BL/6J mice were fed with methionine-choline deficient (MCD) diet for four weeks to induce hepatic steatohepatitis. HO-1 chemical inducer (hemin), HO-1 chemical inhibitor zinc protoporphyrin IX (ZnPP-IX) and/or adenovirus carrying HO-1 gene (Ad-HO-1) were administered to mice, respectively. Hepatocyte apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay, the mRNA and protein expression of apoptosis related genes were assayed by quantitative real-time PCR and Western blot.</p> <p>Results</p> <p>Hepatocyte signs of oxidative related apoptotic injury were presented in mice fed with MCD diet for 4 weeks. Induction of HO-1 by hemin or Ad-HO-1 significantly attenuated the severity of liver histology, which was associated with decreased hepatic lipid peroxidation content, reduced number of apoptotic cells by TUNEL staining, down-regulated expression of pro-apoptosis related genes including Fas/FasL, Bax, caspase-3 and caspase-9, reduced expression of cytochrome p4502E1 (CYP2E1), inhibited cytochrome c (Cyt-c) release, and up-regulated expression of anti-apoptosis gene Bcl-2. Whereas, inhibition of HO-1 by ZnPP-IX caused oxidative stress related hepatic injury, which concomitant with increased number of TUNEL positive cells and up-regulated expression of pro-apoptosis related genes.</p> <p>Conclusions</p> <p>The present study provided evidences for the protective role of HO-1 in preventing nutritional steatohepatitis through suppressing hepatocyte apoptosis in mice.</p

Multi-scale pressure analysis and fluidization quality characterization of dry dense medium fluidized bed

Coal beneficiation is the source technology of clean processing and utilization of coal. Dry coal beneficiation is an important way for efficient separation and upgrading of easily sliming coal in arid area. Dry dense medium fluidized bed forms a certain density of gas-solid fluidized bed by updraft-driven heavy medium particles fluidization, thus achieving coal separation according to bed density. The uniformity and stability of bed density, namely the bed fluidization quality, is the key to determine the separation accuracy. Due to the disturbance of airflow, bubbles, moving internals, feeding and other factors, the fluidization behavior of the bed is complex and changeable, and the pressure signal shows non-uniformity, non-linearity and multi-scale characteristics. Based on the characteristics of axial differential transmission and lateral equivalent diffusion of pressure signal in dry dense medium fluidized bed, the fluctuation characteristics of axial differential pressure were studied emphatically, and a quantitative characterization method of fluidization quality was proposed. The results show that: Based on time domain analysis, the probability density distribution of total pressure drop in Geldart A type separation fluidized bed is close to normal distribution. When the bed is in the particulate expansion, due to the uneven distribution of contact force between particles, the probability density shows the right deviation and the peak, deviating from the normal distribution. Through frequency domain analysis, it is found that the dominant frequency of bubbles dominates the whole axial interval of fluidized bed at the later stage of bed expansion. After complete fluidization, the dominant frequency of bubbles only controls the central region of the bed. The dominant frequency of bed concentration signal changes obviously along the bed axial distribution. Combined with the results of time-domain and frequency-domain signal analysis, a fluidization quality characterization model was proposed, where the standard deviation of axial fluctuation is weighted and averaged, and the dominant frequency of sub-bed concentration is taken as the weight value. This model can comprehensively evaluate the uniformity and stability of density distribution of dry dense medium fluidized bed, and provide strong support for the steady-state control and accurate separation of dry dense medium fluidized bed

Rapid detection of coal ash based on machine learning and X-ray fluorescence

Real-time testing of coal ash plays a vital role in the chemical, power generation, metallurgical, and coal separation sectors. The rapid online testing of coal ash using radiation measurement as the mainstream technology has problems such as strict coal sample requirements, poor radiation safety, low accuracy, and complicated equipment replacement. In this study, an intelligent detection technique based on feed-forward neural networks and improved particle swarm optimization (IPSO-FNN) is proposed to predict coal quality ash content in a fast, accurate, safe，and convenient manner. The data set was obtained by testing the elemental content of 198 coal samples with X-ray fluorescence (XRF). The types of input elements for machine learning (Si, Al, Fe, K, Ca, Mg, Ti, Zn, Na, P) were determined by combining the X-ray photoelectron spectroscopy (XPS) data with the change in the physical phase of each element in the coal samples during combustion. The mean squared error and coefficient of determination were chosen as the performance measures for the model. The results show that the IPSO algorithm is useful in adjusting the optimal number of nodes in the hidden layer. The IPSO-FNN model has strong prediction ability and good accuracy in coal ash prediction. The effect of the input element content of the IPSO-FNN model on the ash content was investigated, and it was found that the potassium content was the most significant factor affecting the ash content. This study is essential for real-time online, accurate, and fast prediction of coal ash

A Systematic Stakeholder Selection Model in Requirements Elicitation for Software Projects: A Systematic Mapping Study

Context. The appropriate stakeholder selection for software engineering is an essential stage and the precondition of software requirements elicitation. However, the stakeholder analysis hasn’t get enough attention in the requirement elicitation field as it was commonly recognized as a self-evidence process in practice. Objectives. In this study, we investigated the current status of this area. Collated the affecting factors which influence the appropriate stakeholder selection on Software Engineering (SE) with respect to the requirement elicitation purpose. On the basic of this objective, we investigated a systematic conceptual model which aims to guide the appropriate stakeholder selection of software projects. Finally, we evaluate the meaning to practice of our model. Methods. We conducted the systematic mapping study for the first objective. The objective of selecting affecting factors is on the basic of the first objective. The objective to evaluate the meaning to practice is realized by interviewing 10 experienced software product managers. Results. The recent studies on this area have been classified according to their different focuses. We described the methods of each included papers on systematic mapping study. We collected 12 factors used by previous studies and select 6 factors for our model. And we generated our model by six steps. The interview to ten practitioners is used to evaluate our model. Conclusions. We extracted six factors according to previous studies, then proposed a systematic stakeholder selection model for software projects on the basic of analysis to those factors. Generally, our model’s meaning to practice has been confirmed by interviews with experienced practitioners

A Systematic Stakeholder Selection Model in Requirements Elicitation for Software Projects: A Systematic Mapping Study

Context. The appropriate stakeholder selection for software engineering is an essential stage and the precondition of software requirements elicitation. However, the stakeholder analysis hasn’t get enough attention in the requirement elicitation field as it was commonly recognized as a self-evidence process in practice. Objectives. In this study, we investigated the current status of this area. Collated the affecting factors which influence the appropriate stakeholder selection on Software Engineering (SE) with respect to the requirement elicitation purpose. On the basic of this objective, we investigated a systematic conceptual model which aims to guide the appropriate stakeholder selection of software projects. Finally, we evaluate the meaning to practice of our model. Methods. We conducted the systematic mapping study for the first objective. The objective of selecting affecting factors is on the basic of the first objective. The objective to evaluate the meaning to practice is realized by interviewing 10 experienced software product managers. Results. The recent studies on this area have been classified according to their different focuses. We described the methods of each included papers on systematic mapping study. We collected 12 factors used by previous studies and select 6 factors for our model. And we generated our model by six steps. The interview to ten practitioners is used to evaluate our model. Conclusions. We extracted six factors according to previous studies, then proposed a systematic stakeholder selection model for software projects on the basic of analysis to those factors. Generally, our model’s meaning to practice has been confirmed by interviews with experienced practitioners