Prediction of nitrogen oxide emission concentration in cement production process: a method of deep belief network with clustering and time series.

The concentration of nitrogen oxide (NOx) emissions is an important environmental index in the cement production process. The purpose of predicting NOx emission concentration during cement production is to optimize the denitration process to reduce NOx emission. However, due to the problems of time delay, nonlinearity, uncertainty, and data continuity in the cement production process, it is difficult to establish an accurate NOx concentration prediction model. In order to solve the above problems, a NOx emission concentration prediction model using a deep belief network with clustering and time series features (CT-DBN) is proposed in this paper. Particularly, to improve data sparsity and enhance data characteristics, a clustering algorithm is introduced into the model to process the original data of each variable; the time series containing delay information are introduced into the input layer, which combines previous and current variable data into time series data to eliminate the influence of the time delay on the prediction of NOx emission concentration. In addition, restricted Boltzmann machine (RBM) is used to extract data features, and a gradient descent algorithm is used to reversely adjust network parameters to establish a deep belief network model (DBN). Experiments prove that the method in this paper has higher accuracy, stronger stability, and better generalization ability in predicting NOx emission concentration in cement production. The CT-DBN model realizes the accurate prediction of NOx emission concentration, provides guidance for denitration control, and reduces NOx emissions.

[Research on mental fatigue information transmission integration mechanism based on theta-gamma phase amplitude coupling].

Mental fatigue is a subjective fatigue state caused by long-term brain activity, which is the core of health problems among brainworkers. However, its influence on the process of brain information transmission integration is not clear. In this paper, phase amplitude coupling (PAC) between theta and gamma rhythm was used to study the electroencephalogram (EEG) data recorded before and after mental fatigue, so as to explain the effect of mental fatigue on brain information transmission mechanism. The experiment used a 4-hour professional English reading to induce brain fatigue. EEG signals of 14 male undergraduate volunteers before and after mental fatigue were recorded by Neuroscan EEG system. Phase amplitude coupling value was calculated and analyzed. t test was used to compare the results between two states. The results showed that theta phase of more than 90% of the electrodes in the whole brain area jointly modulated gamma amplitude of the right central area and the right parietal area, and the coupling effect among different brain regions significantly decreased ( P < 0.05) when participants had felt mental fatigue. This paper shows that phase amplitude coupling can explain the influence of mental fatigue on information transmission mechanism. It could be an important indicator for mental fatigue detection. On the other hand, the results also provide a new measure to evaluate the effect of neuromodulation in relieving mental fatigue.

Comparison of nanofluoridated hydroxyapatite of varying fluoride content for dentin tubule occlusion.

PURPOSE: To evaluate the viability of a series of nano-fluoridated hydroxyapatite (nano-FHA) formulations of varying fluoride content for the occlusion of exposed dentin tubules, in comparison to nano-hydroxyapatite (nano-HA). METHODS: Nano-FHA powders with varying levels of fluoride ion were synthesized to substitute hydroxyl ions (⁻OH) present in hydroxyapatite (HA). Nano-FHA were defined as 2nFHA,4nFHA,6nFHA, 8nFHA and 10nFHA, with the molar ratio of F(⁻ to Ca243; of 0.002,0.004,0.006,0.008 and 0.01, respectively. The powders were synthesized using a wet chemistry route, and characterized by transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The methylthiazol tetrazolium (MTT) assay was used to assess cell viability toward nano-FHA. According to the content of F⁻, the nano-nFHA and nano-HA powders were divided into six groups, with the artificial saliva as control. They were spread over the dentin surface for 1 minute and repeated three times per day for 7 consecutive days. After washing and brushing with distilled water for an additional 7 days, scanning electron microscopy was used to evaluate the in vitro plugging rate of the tubules and penetrating depth. RESULTS: The 2nFHA, 4nFHA, 6nFHA, 8nFHA and 10nFHA powders were prepared and characterized. The 8nFHA had less crystallinity compared to 2nFHA,4nFHA, and 6nFHA.The MTT assay (from 12 to 120 hours) showed that the cell viability of the L-929 fibroblasts in the 2nFHA, 4nFHA, 6nFHA, 8nFHA, 10nFHA, and nano-HA groups ranged from 80.54± 3.35% to 112.9± 4.8%. Most of the nano-FHA powders successfully occluded dentin tubules. The plugging rate of 8nFHA was significantly higher than that of the 2nFHA, 4nFHA, 6nFHA and nano-HA groups. The penetrating depth of the 8nFHA group into the tubules was also significantly higher than that of the other nano-FHA and nano-HA group. CLINICAL SIGNIFICANCE: The nano-FHA formulation 8nFHA showed higher plugging rate and penetrating depth into the tubules. It has the potential to be used as a desensitizing agent in treating dentin hypersensitivity with better long-term durability and efficacy of dentin tubule occlusion.

[Spatial distribution of dead and vital bacteria in the native dental biofilm].

OBJECTIVE: To examine the spatial distribution of dead and vital bacteria in the early formation of native dental biofilm. METHODS: An experimental dental biofilm model in the oral cavity was established by enamel slabs and the spatial distribution of dead and vital bacteria in the early colonization of native dental biofilm on the enamel surface was observed by in situ real-time and dynamic observations and optical sections utilizing confocal laser scanning microscope (CLSM) and live and dead bacterial fluorescence staining technique. RESULTS: At the initial stage of dental biofilm formation, the structure was sparse and the percentage of dead cells reached 70% - 80% at the inner layers. In the middle layers the structure became denser than in the inner layers, which was mainly composed of vital cells (40% - 70%), and void-like structures were surrounded by vital bacteria. In the outer layers, the structure was sparse and vital cells occupied 20% - 40%. CONCLUSIONS: Native dental biofilms showed an uneven spatial distribution of vital and dead microorganisms. The percentage of vital microorganisms was lower adjacent to the enamel surface, increased in the z-axis towards the central parts, and decreased again towards the outer layers. The dead bacteria is an integral component in the early formation of native dental biofilm. Bacteria in the biofilms increased with time forming abundant channels.