Vehicle Routing Problem with Time Windows and Simultaneous Delivery and Pick-Up Service Based on MCPSO

This paper considers two additional factors of the widely researched vehicle routing problem with time windows (VRPTW). The two factors, which are very common characteristics in realworld, are uncertain number of vehicles and simultaneous delivery and pick-up service. Using minimization of the total transport costs as the objective of the extension VRPTW, a mathematic model is constructed. To solve the problem, an efficient multiswarm cooperative particle swarm optimization (MCPSO) algorithm is applied. And a new encoding method is proposed for the extension VRPTW. Finally, comparing with genetic algorithm (GA) and particle swarm optimization (PSO) algorithm, the MCPSO algorithm performs best for solving this problem

Risk Chain Mining of Hazard Sources in Metro Operation System Safety: A New Method to Mine and Control Risk for Safety Management

Abstract With the promotion of the major strategy of national transportation power, the super-large-scale metro operation network has become an inevitable trend, and operation safety has become increasingly prominent. Metro operation dispatch logs and accident reports were taken as the research object, the hazard sources were efficiently and accurately identified, the risk chains of hazard sources were mined, and the risk evolution mechanism was revealed. Firstly, the transportation lexicon was constructed to improve the accuracy of word segmentation, the text features were extracted based on the term frequency-inverse document frequency (TF-IDF) algorithm, and the key eigenvalues were mined to identify the key hazard sources. Secondly, pattern matching was used to extract explicit causality, and the Self-Attention BiLSTM extracted implicit causality and integrated event trigger word position identification to enhance the effectiveness of implicit causality extraction. Finally, an example was given to verify the efficiency and accuracy of the model, the experiments showed that the F value of extraction effect was increased by nearly 10%, the extraction accuracy was 87.53%, the identification of operational hazard sources was more accurate, and the visualization of risk evolution law was realized

Determination of Iridium and Rhodium in Copper Anode Slime by Inductively Coupled Plasma-Mass Spectrometry with Nickel Sulphide Fire Assay

BACKGROUND With the wide application of iridium and rhodium in aerospace, electronics, energy and other fields, it has become a very attractive metal in the world. In China, iridium and rhodium ore resources are relatively scarce with low grade, so it is essential to recover iridium and rhodium from secondary mineral resources. Copper anode slime enriches most of the precious metals such as iridium and rhodium in ores, which has high comprehensive recovery value. At present, there is no detection standard for iridium and rhodium in copper anode slime. The migration behavior of iridium and rhodium was not clear, so it was difficult to achieve directional enrichment and efficient extraction of iridium and rhodium metals. Therefore, the development of detection methods for iridium and rhodium in copper anode slime is an important prerequisite for the recovery and extraction of iridium and rhodium. OBJECTIVES An analytical method for accurate determination of iridium and rhodium in copper anode slime was established to maximize the utilization of mineral resources and the recycling rate of iridium, rhodium and other precious metals. At the same time, it could provide data support for the purification of iridium and rhodium in copper anode slime. METHODS In this paper, a method for determination of iridium and rhodium in copper anode slime by inductively coupled plasma-mass spectrometry (ICP-MS) with nickel sulphide fire assay was established. In the experiment, the precious metals iridium and rhodium in the sample were captured by nickel sulphide fire assay. The NiS beads were dissolved with 50% hydrochloric acid so that the precipitation of rhodium and iridium was separated from silver and other impurity elements through filtration when it was hot. The precipitates containing iridium and rhodium were effectively separated from silver and other impurity elements. The precipitate of iridium and rhodium with filter film were transferred into a closed digestion tank and dissolved in 50% aqua regia. The contents of iridium and rhodium in the solution were directly determined by ICP-MS. RESULTS The conditions such as the ingredient of nickel sulphide fire assay, the concentration of hydrochloric acid, tellurium coprecipitation, the sealing digestion time and temperature were studied. The experimental results showed that the molten slag was acidic when the ratio of nickel to sulfur was 4∶1, and it could effectively capture the iridium and rhodium in the sample with good fluidity of molten slag and the separation effect of slag buckle. When the NiS beads were dissolved by 50% hydrochloric acid, the dissolution reaction of NiS beads was suitable and complete. The precipitation containing rhodium and iridium was separated from impurity elements and filtered when hot. The precipitation was sealed and digested by dilute aqua regia (1∶1) at 160℃ for 2-3h. The possible MS interference was eliminated by selecting a suitable determination isotope. The 185Re was selected as the internal standard of 103Rh and 203Tl as the internal standard of 193Ir to eliminate the effect of signal drift, the results of iridium and rhodium had high precision and accuracy. The standard solution series of iridium and rhodium were determined under the optimized experimental conditions. The results indicated that the mass concentration of iridium and rhodium in the range of 10-100μg/L were linear to the ratio of the intensity of iridium and rhodium to the internal standard mass spectrometry. The calibration curves of iridium and rhodium were y=36674.6x+8264.7 and y=45686.7x+288.6, respectively, and the linear correlation coefficient (r) of calibration curves of iridium and rhodium were more than 0.999. The detection limits for iridium and rhodium were 0.007μg/L and 0.011μg/L, respectively, and the lower limits of detection were 0.024μg/L and 0.038μg/L, respectively. The content results of rhodium and iridium in 8 actual samples with the method showed that, the relative standard deviation (RSD, n=7) was between 1.40% and 4.57%, and the recovery was in the range of 95.00% to 103.65%. CONCLUSIONS The method has high efficiency and accuracy and can meet the detection requirements of copper anode slime samples

Research on key risk chain mining method for urban rail transit operations: A new approach to risk management

To ensure the safety of urban rail transit operations and uncover the transmission dynamics of risk sources, a key risk chain mining method for urban rail transit operation is proposed. Firstly, the H-Apriori association rule algorithm is proposed for the characteristics of low frequency but high riskiness of high hazard degree risk sources in urban rail transit operation, which adds a new hazard degree evaluation index to the traditional Apriori algorithm and couples with support degree two-dimensionally to mine the strong association rules among risk sources. Secondly, we construct a weighted risk network with risk sources as network nodes and strong association rules as network edges, and propose a key risk chain mining method for urban rail transit operation based on path search theory to mine key risk chains from the weighted risk network. Finally, using the actual urban rail transit operation data of a city in China as an example, a total of 17 key risk chains are mined, and then 5 key risk sources and 8 key chain break locations are obtained by riskiness and frequency analysis of key risk chains, and control plans are proposed. The research outcomes introduce a novel approach to mining risk chains in urban rail transit operations, shedding light on the propagation mechanisms, triggering probabilities, and degrees of unsafety associated with risk sources. The results not only provide theoretical support but also offer methodological guidance for pinpointing locations of risk chain breaks and refining the control of risk sources

Development of dual-drug-loaded stealth nanocarriers for targeted and synergistic anti-lung cancer efficacy

Combination chemotherapy is widely exploited for suppressing drug resistance and achieving synergistic anticancer efficacy in the clinic. In this paper, the nanostructured targeting methotrexate (MTX) plus pemetrexed (PMX) chitosan nanoparticles (CNPs) were developed by modifying methoxy polye (thylene glycol) (mPEG), in which PEGylation CNPs was used as stealth nanocarriers (PCNPs) and MTX was employed as a targeting ligand and chemotherapeutic agent as well. Studies were undertaken on human lung adenocarcinoma epithelial (A549) and Lewis lung carcinoma (LLC) cell lines, revealing the anti-tumor efficacy of nanoparticle drug delivery system. The co-delivery nanoparticles (MTX-PMX-PCNPs) had well-dispersed with sustained release behavior. Cell counting kit-8 (CCK8) has been used to measure A549 cell viability and the research showed that MTX-PMX-PCNPs were much more effective than free drugs when it came to the inhibition of growth and proliferation. Cell cycle assay by flow cytometry manifested that the MTX-PMX-PCNPs exhibited stronger intracellular taken up ability than free drugs at the same concentration. In vivo anticancer effect results indicated that MTX-PMX-PCNPs exhibited a significantly prolong blood circulation, more tumoral location accumulation, and resulted in a robust synergistic anticancer efficacy in lung cancer in mice. The results clearly demonstrated that such unique synergistic anticancer efficacy of co-delivery of MTX and PMX via stealth nanocarriers, providing a prospective strategy for lung cancer treatment

Aqueous-phase biphasic dehydroaromatization of bio-derived limonene into p-cymene by soluble Pd nanocluster catalysts

A biphasic approach to the dehydroaromatization of bioderived limonene into water-insol. p-cymene using sol. Pd nanoparticle catalysts in an aq. phase (³150 °C, 2 bar H2) was successfully achieved with a conversion of 93% and a selectivity of 82%. The Pd nanoparticles, operating under forcing conditions (180 °C, 2 bar H2), can be recycled at least four times without noticeable degrdn. The effects of temp., pressure, reaction time, pH, catalyst concn., metal type, the type and amt. of polymer stabilizer, and the prepn. method were systematically investigated to optimize the process and provide insight into the mechanisms involved