Recovery of High Purity Calcium Sulfate from Phosphogypsum I: Thermodynamic Study of SO42- Purification

Chemical agents SO42- and Ca2+ in phosphogypsum could be recycled to make high-purity calcium sulfate whisker. A key step in this process is to decompose phosphogypsum using NaOH solution to obtain Na2SO4 solution and Ca(OH)2 residue. In this decomposition process, thermodynamic analysis indicates that the majority of impurities reports to the residue phase Ca(OH)2，with minor amounts of Si and Al impurities end up in Na2SO4 solution in forms of Na2SiO3 and KAlO2. Based on phase diagram at 25oC for the Na2SO4-SiO32--AlO2- system, Si and Al impurities may be removed via precipitation by adjusting pH value of the Na2SO4 solution. In verification tests on a sodium phosphate solution of pH 13.2 with 17.7mg/L of Al and 3.41mg/L of Si, when pH was adjusted to 12 no Al was detected in the solution with 8.48% Si removal. After solution pH was further lowered to 7, Al was still negligible in the liquid phase, but Si removal was increased to 75.89%.

Variable Neighborhood Search for Parallel Machines Scheduling Problem with Step Deteriorating Jobs

In many real scheduling environments, a job processed later needs longer time than the same job when it starts earlier. This phenomenon is known as scheduling with deteriorating jobs to many industrial applications. In this paper, we study a scheduling problem of minimizing the total completion time on identical parallel machines where the processing time of a job is a step function of its starting time and a deteriorating date that is individual to all jobs. Firstly, a mixed integer programming model is presented for the problem. And then, a modified weight-combination search algorithm and a variable neighborhood search are employed to yield optimal or near-optimal schedule. To evaluate the performance of the proposed algorithms, computational experiments are performed on randomly generated test instances. Finally, computational results show that the proposed approaches obtain near-optimal solutions in a reasonable computational time even for large-sized problems

Regression models for near-infrared measurement of subcutaneous adipose tissue thickness

Obesity is often associated with the risks of diabetes and cardiovascular disease, and there is a need to measure subcutaneous adipose tissue (SAT) thickness for acquiring the distribution of body fat. The present study aimed to develop and evaluate different model-based methods for SAT thickness measurement using an SATmeter developed in our laboratory. Near-infrared signals backscattered from the body surfaces from 40 subjects at 20 body sites each were recorded. Linear regression (LR) and support vector regression (SVR) models were established to predict SAT thickness on different body sites. The measurement accuracy was evaluated by ultrasound, and compared with results from a mechanical skinfold caliper (MSC) and a body composition balance monitor (BCBM). The results showed that both LR- and SVR-based measurement produced better accuracy than MSC and BCBM. It was also concluded that by using regression models specifically designed for certain parts of human body, higher measurement accuracy could be achieved than using a general model for the whole body. Our results demonstrated that the SATmeter is a feasible method, which can be applied at home and in the community due to its portability and convenience

International Spread of Tet(X4)-Producing Escherichia coli Isolates

Tigecycline resistance in bacteria has become a significant threat to food safety and public health, where the development of which is attributed to plasmid-mediated tet(X4) genes. In this study, the genomes of 613 tet(X4)-producing Escherichia coli (E. coli) isolates, available from public databases, are evaluated to determine their international prevalence and molecular characterization. These E. coli isolates have been disseminated in 12 countries across Asia and Europe. It was found that pigs and their products (n = 162) were the most common vehicle, followed by humans (n = 122), chickens (n = 60), and the environment (n = 49). Carbapenems-resistant genes blaNDM-5 (1.3%) and blaNDM-1 (0.2%) were identified, as well as colistin-resistant genes mcr-1.1 (12.6%) and mcr-3.1 (0.5%). It was noted that the tigecycline-resistant gene cluster tmexC-tmexD-toprJ1 was identified in seven (1.1%) isolates. Phylogenomic results indicated that tet(X4)-producing E. coli isolates fell into seven lineages (lineages I, II, III, IV, V, VI, and VII), and international spread mainly occurred in Asian countries, especially China, Pakistan, Singapore, and Malaysia. Four forms of tet(X4) transposon units were found, including the I-type (IS26-tet(X4)-ISCR2), II-type (ΔIS1R-tet(X4)-ISCR2), III-type (ISCR2-tet(X4)-ISCR2), and IV-type (ISCR2-tet(X4)-ΔISCR2). These findings underline further challenges for the spread of E. coli bearing tet(X4) gene

Enhanced Hybrid Ant Colony Optimization for Machining Line Balancing Problem with Compound and Complex Constraints

Targeted at the machining production line balancing problem, based on the precedence constraint relation of the present machining task, this article suggests adding practical constraints such as advanced station preparations, post-auxiliary tasks, and tool changing. The study introduced ‘tight’ and ’or’ constraints to bring the problem definition closer to the actual situation. For this problem, a mixed-integer programming model was constructed in this study. The model redefines the machining and auxiliary processing tasks and adds new time constraints to the station. The model considers two optimisation objectives: the number of stations and the machining line balancing rate. In view of the complexity of the problem, heuristic task set filtering mechanisms were designed and added to the ant colony optimisation, to satisfy the above compound and complex constraints. The processing task chain was constructed using the rules of ant colony pheromone accumulation and a random search mechanism. The study designed a Gantt chart generation module to improve the usability and visibility of the program. Ultimately, through an actual case study of a complex box part including 73 processing elements and realising the design and planning of machining production lines that meet complex constraints by substituting algorithms, the balance rates of several groups of optimisation schemes were higher than 90%, which showed that the algorithm is effective and has a good economy and practicability

Adjustable Structure for Feedback Active Headrest System Using the Virtual Microphone Method

Active headrest is an essential application for active noise control, capable of reducing low-frequency disturbance around an error microphone. However, in most cases, attaching microphones to ears is not feasible and noise attenuation performance is vulnerable to plant response variations. This paper presents a multichannel feedback active headrest system combined with the virtual microphone method and a manually adjustable headrest structure for users. Applying the virtual microphone method can transfer the attenuation target from the distant microphone to the ear. The proposed adjustable headrest structure allows for secondary loudspeakers and the corresponding microphone to be moved as a single unit while maintaining the relative distances between the secondary loudspeakers and microphones constant to ensure that the related plant responses are consistent. Experiments were conducted to validate the performance against multi-sinusoidal machine noise. The results demonstrate the benefits of the proposed structure over conventional structures. Additionally, the applicability of the three commonly used virtual sensing methods (the auxiliary filter method, remote microphone method, and virtual microphone method) in various practical conditions was verified when using the proposed adjustable headrest structure. Furthermore, 10 volunteers were involved in the evaluation, and the robustness of the proposed system for various users was confirmed

A Narrow Dual-Band Monolayer Unpatterned Graphene-Based Perfect Absorber with Critical Coupling in the Near Infrared

The combination of critical coupling and coupled mode theory in this study elevated the absorption performance of a graphene-based absorber in the near-infrared band, achieving perfect absorption in the double bands (98.96% and 98.22%), owing to the guided mode resonance (the coupling of the leak mode and guided mode under the condition of phase matching, which revealed 100% transmission or reflection efficiency in the wavelet band), and a third high-efficiency absorption (91.34%) emerged. During the evaluation of the single-structure, cross-circle-shaped absorber via simulation and theoretical analysis, the cross-circle shaped absorber assumed a conspicuous preponderance through exploring the correlation between absorption and tunable parameters (period, geometric measure, and incident angle of the cross-circle absorber), and by briefly analyzing the quality factors and universal applicability. Hence, the cross-circle resonance structure provides novel potential for the design of a dual-band unpatterned graphene perfect absorber in the near-infrared band, and possesses practical application significance in photoelectric detectors, modulators, optical switching, and numerous other photoelectric devices