Field rapid determination of soil accessible Cr(Ⅵ) is of great significance for on-site assessment and decision-making about the health risks of contaminated sites. When the thickness of solutions ...with various concentrations of Cr(Ⅵ) is constant, there would be a quantitative relationship between the chromogenic difference of Cr(Ⅵ) solutions and the concentration of Cr(Ⅵ). The chromogenic difference could be described by Red (R), Green (G), Blue (B) values. Based on the chromogenic reaction between 1,5-diphenylcarbazide and Cr(Ⅵ), this study first established the calibration curve between the chromogenic difference and the concentration of Cr(Ⅵ) in standard solution with or without 0.01 M CaCl2, using an RGB color sensor. This is the subsequent determination basis of the method for rapidly assessing accessible Cr(Ⅵ) in the field (M-RGB). Then, the concentration of accessible Cr(Ⅵ) of contaminated soil with “hand-shaking + standing” field extraction method was compared with “end-over-end shaking” laboratory extraction method. Finally, the accessible Cr(Ⅵ) of contaminated soil extractants was determined via M-RGB integrating the field extraction method. Results indicated there was a highly significant linear relationship between colorimetric difference value (∆E) and Cr(Ⅵ) concentration in the range of 0.1–3 mg/L (R2 > 0.99, P < 0.01), based on the Euclidean formula for calculating ∆E. The “hand-shaking + standing” field extraction method was effective in obtaining accessible Cr(Ⅵ) extractants with or without 0.01 M CaCl2, with the high extraction efficiency within 100±1%. The concentrations of accessible Cr(Ⅵ) in various polluted soils determined by M-RGB were consistent with that determined by the ultraviolet-visible spectrophotometry, with the relative error within ±5%, and the relative standard deviation ≤ 20%. The spiked recovery experiments showed that the recovery of M-RGB was between 95% and 105%, which means M-RGB could realize the trace analysis for accessible Cr(Ⅵ) in the field.
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•Color difference of Cr(Ⅵ) solutions was linearly correlated with its concentration logarithmic value.•1,5-diphenylcarbazide was used as colorimetric reactant for Cr(Ⅵ).•Hand shaking + standing method can be used to extract accessible Cr(Ⅵ) in the field.•RGB color sensor can be used for rapidly assessing soil accessible Cr(Ⅵ) in the field.
A model prediction controller (MPC) based on radial basis function (RBF) neural network is designed to counter the model uncertainty and multiple constraints of the autonomous underwater vehicle ...(AUV). On this basis of path following control with MPC, the RBF neural network is trained online with real-time measurement data to compensate for the AUV's model uncertainty, thus suppressing the interference of model uncertainty on the MPC and reducing its overshoot and tracking error. Simulation results show that the path following algorithm based on RBF-MPC has better transient and steady-state performance compared with the classical MPC algorithm.
针对自主水下航行器(AUV)的模型不确定性和多约束的特点, 设计了基于径向基(RBF)神经网络的模型预测控制器。在使用模型预测控制(MPC)进行路径跟踪控制的基础上, 利用实时测量数据在线训练RBF神经网络, 对AUV模型不确定性进行补偿, 抑制了模型不确定性对模型预测控制器的干扰, 减小了系统的超调量和跟踪误差。仿真结果表明, 基于RBF-MPC路径跟踪控制算法与经典的MPC算法相比, 具有更好的暂态和稳态性能。
Molecular distillation (MD) was used to increase the purity of octacosanol extracts from transesterified rice bran wax (RBW), and the effects of MD parameters on the purification process and ...efficiency were studied. The octacosanol content, triacontanol content and the ratio of octacosanol content (
C
o) to triacontanol content (
C
t) in distillates and residues, the yields of distillates and residues, and split ratio (yield of distillates to the yield of residues) were investigated in the circumstance of temperature and pressure changes.
Results indicated that distilling temperature and distilling pressure are very important factors in purification process. The increase of distilling temperature or the decrease of distilling pressure could increase the mean free path (MFP) of molecules; therefore, the components with larger molecular weight could be separated and concentrated onto the condenser, and the yield of distillates increased and the split ratio was higher, but the content of octacosanol in distillates did not increase accordingly.
Purified by MD at 150
°C and 0.5
Torr, the octacosanol content in distillates can be up to 37.6%, increasing by 48.0% over that in the raw octacosanol extracts. The purification processes of octacosanol extracts with MD were further explained by comparing the components of distillates with residues at 0.5
Torr, and the components of distillates at 0.5
Torr with those at 2.0
Torr as well.
Field rapid determination of soil accessible Cu(Ⅱ) was important for environmental safety and human health risk assessment. In this study, an inexpensive red, green, and blue (RGB) color sensor was ...used for quantitative color difference analysis of the colored solution for soil accessible Cu(Ⅱ) with bis-cyclohexanone oxalydihydrazone as color reagent to develop a new method for analyzing soil accessible under field conditions. First, the calibration curve for RGB color sensor method was established in the standard solutions of Cu(II). Then the “hand shaking + standing” field extraction method for accessible Cu(Ⅱ) was developed. Finally, the method was applied in contaminated soils in the laboratory and in the field, and set the values determined by atomic absorption spectroscopy (AAS) as the standard ones. Results indicated that in the range of 0.1–5 mg L−1 Cu(II), the RGB Euclidean chromogenic difference values were directly linear correlated with the concentration of Cu(II) (R2 > 0.999). The interference of Fe(Ⅲ) and Mn(Ⅱ) could be eliminated by adding citric acid. The “hand shaking + standing” field extraction method could effectively extract the accessible Cu(Ⅱ) from soil with the high extraction rates. The concentrations of accessible Cu(II) in various polluted soils determined by RGB color sensor method were consistent with that determined by AAS, with the relative error within ±5%, the relative standard deviation ≤ 20%. The recovery of Cu(II) in RGB color sensor method was between 97% and 105%, which could meet the requirements of trace analysis of accessible Cu(Ⅱ) in the field. The high accuracy and precision of RGB color sensor method was reconfirmed in the rapid field quantitative assessment of soil accessible Cu(Ⅱ). Due to that the RGB color sensor was low cost, rechargeable, portable, mobile, ambient light resistant, the method would have a great potential for the determination of accessible Cu(Ⅱ) in contaminated soils.
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•Bis-cyclohexanone oxalydihydrazone was used as colorimetric reactant for Cu(II).•Color difference of Cu(II) solutions was linear correlated with its concentration.•Citric acid was used to mask interference of Fe(Ⅲ) and Mn(II) for Cu(II) detection.•“Hand shaking + standing” method can be used to extract accessible Cu(II) in field.•RGB color sensor can be used for measurement of soil accessible Cu(Ⅱ) in field.
The purification of crude octacosanol extract from transesterified rice bran wax was carried out by molecular distillation (MD). A central composite rotate design (CCRD) was used in order to optimize ...the experimental parameters: distilling temperature and vacuum degree. Through the response surface methodology (RSM), the optimal MD conditions were determined and the quadratic response surfaces were drawn from the mathematical models. The results suggest that the distillng temperature and vacuum degree significantly affected both octacosanol content and yield of purified products, while the interaction of distilling temperature and vacuum degree was not significant in the two models. The optimum conditions of the purification of crude octacosanol extract were: distilling temperature 176.1
°C and vacuum degree 1.29
Torr. Optimal values predicted by RSM for the octacosanol content and yield of purified product were 25.93% and 51.09%, respectively. Close agreement between experimental and predicted values was obtained.
Purpose
The purpose of this study is to summarize the research progresses in the effects of the interactions between active soil organic carbon (SOC) components and minerals on the sorption, ...immobilization, remobilization, transport, and bioavailability of heavy metals (HMs) in the environment.
Materials and methods
This paper presents a discussion based on a bibliometric analysis of the interactions between SOC components and minerals and their influence on the fate of HMs. An in-depth and comprehensive analysis of publication characteristics of 3351 articles using VOSviewer, Histcite, and Bibliometrix was conducted.
Results and discussion
The analyses revealed that the number of articles in this field varied in four stages and China dominated research in this field. The Chinese Academy of Sciences was the center with the most productive cooperation network and registered the largest number of publications. The analysis of the co-occurrence of keywords showed that the coexistence of SOC components would increase or decrease the adsorption and immobilization of HMs on minerals, and this was influenced by environmental parameters such as pH, redox potential, and solution ionic strength. Anionic HMs have become a research hotspot in recent years, and their environmental behaviors, especially redox reactions at the mineral micro solid-phase interfaces, were significantly influenced by the coexistence of active SOC components. The ternary interaction mechanisms between SOC components, minerals, and HMs were complex and presented no clear reasons why some SOC components would inhibit HM adsorption. Based on the bibliometric analysis and mechanistic insights, we make the following recommendations: Research on the molecular interaction mechanisms at the micro/nanoscale interfaces between SOC components, especially microorganisms and biochar, and minerals with HMs needs to be expanded; the redox transformation of anionic HMs at the organo-mineral interfaces is important for their remediation; the establishment of an accurate model is critical to predict and control the environmental risks of HMs, thus expanding research in this field at the micro/nanoscale could speed up the development of new remediation technologies. There is, therefore, a need to develop more advanced in situ methods for characterizing micro/nanoscale interfaces of ternary systems and the environmental behaviors of HMs at the interfaces.
Conclusions
The environmental behaviors of HMs were affected by the mineral-SOC/soil organic matter (SOM) interaction and environmental conditions. The biochar/microbial-mineral interaction should be of more concern and exploring mineral-SOC/SOM-HM ternary interaction mechanisms by high-resolution characterization technology is necessary.
In this paper, an online Gaussian process(GP)-based model predictive control(MPC) approach is proposed to solve the attitude control of underwater gliders(UGs) in the presence of model uncertainties. ...A GP model is trained online using measurement data to compensate for uncertainties of UGs including external disturbances and inner model errors. In the process of training the GP model, a genetic algorithm is used to optimize hyperparameters to minimize the difference between the model and real system. Meanwhile, a small dictionary of 500 data is designed to reduce computational burden. Simulation results show that compared with standard MPC, the proposed GP-MPC controller has better transient and steady-state performances for a UG's attitude control.
The increasing proportion of distributed power generation in microgrids brings a variety of uncertainties to the dispatch of microgrids. In order to solve this problem, this paper proposes a ...distributed robust optimal scheduling method for microgrid based on discrete scenarios. Firstly, a microgrid model of photovoltaic, energy storage and Demand response loads was proposed. Secondly, the 1-norm and ∞ -norm conditions were combined to constrain the probability distribution of discrete scenes, and the scenario probability constraint model was constructed. Finally, based on the min-max-min two-stage distributed robust optimization model, the Column and Constraint Generation (CCG) algorithm is used for iterative calculation, and the original problem is decomposed into the main problem and the sub-problem for alternating solution, so as to obtain the optimal solution of the original problem. According to the example analysis, the effectiveness of the scheduling method can be verified.
In this paper, a nonparametric system identification algorithm based on a multi-output Gaussian process for underwater gliders is proposed, which can predict the motion of UGs under the conditions of ...few training data, part measurable states, and high coupling degrees. The algorithm combines the nonlinear auto-regressive model with an external input structure and uses the conjugate gradient descent optimization algorithm to develop a nonparametric dynamic system identification scheme. The proposed scheme is implemented over data obtained from the simulated model of a UG ray-like manta of 5° and 10° Z-type steering data. The results show that the root means square errors of the prediction motion are less than 0.01500° compared with the real motion, and the multi-output Gaussian process can be accurately applied to the strong coupling, multi-degree-of-freedom (DOF) of the underwater gliders.
