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BackgroundOpioid use disorder presents a public health issue afflicting millions across the globe. There is a pressing need to understand the opioid supply chain to gain new insights into the mitigation of opioid use and effectively combat the opioid crisis. The role of anonymous online marketplaces and forums that resemble eBay or Amazon, where anyone can post, browse, and purchase opioid commodities, has become increasingly important in opioid trading. Therefore, a greater understanding of anonymous markets and forums may enable public health officials and other stakeholders to comprehend the scope of the crisis. However, to the best of our knowledge, no large-scale study, which may cross multiple anonymous marketplaces and is cross-sectional, has been conducted to profile the opioid supply chain and unveil characteristics of opioid suppliers, commodities, and transactions. ObjectiveWe aimed to profile the opioid supply chain in anonymous markets and forums via a large-scale, longitudinal measurement study on anonymous market listings and posts. Toward this, we propose a series of techniques to collect data; identify opioid jargon terms used in the anonymous marketplaces and forums; and profile the opioid commodities, suppliers, and transactions. MethodsWe first conducted a whole-site crawl of anonymous online marketplaces and forums to solicit data. We then developed a suite of opioid domain–specific text mining techniques (eg, opioid jargon detection and opioid trading information retrieval) to recognize information relevant to opioid trading activities (eg, commodities, price, shipping information, and suppliers). Subsequently, we conducted a comprehensive, large-scale, longitudinal study to demystify opioid trading activities in anonymous markets and forums. ResultsA total of 248,359 listings from 10 anonymous online marketplaces and 1,138,961 traces (ie, threads of posts) from 6 underground forums were collected. Among them, we identified 28,106 opioid product listings and 13,508 opioid-related promotional and review forum traces from 5147 unique opioid suppliers’ IDs and 2778 unique opioid buyers’ IDs. Our study characterized opioid suppliers (eg, activeness and cross-market activities), commodities (eg, popular items and their evolution), and transactions (eg, origins and shipping destination) in anonymous marketplaces and forums, which enabled a greater understanding of the underground trading activities involved in international opioid supply and demand. ConclusionsThe results provide insight into opioid trading in the anonymous markets and forums and may prove an effective mitigation data point for illuminating the opioid supply chain.

Frictional wear between the armature and the rails directly affects the armature-rails contact condition, thereby affecting the service life and launch efficiency of the electromagnetic rail launcher. In order to explore the influence of temperature on the frictional wear of electromagnetic rail launcher, the source of heat load on the launcher is analyzed, a frictional wear model under the effect of temperature is established and the effect of temperature on the wear between armature and rail is analyzed. Using the finite element method, the pulse forming network is used to power the launcher, the contact resistance variation curve with time is found out, the 3D finite element calculation model is established considering the electromagnetic field-temperature field-stress field, etc., and the data related to the armature wear amount in the two states considering the temperature field and not considering the temperature field are compared and analyzed. The results show that with the armature movement, the temperature of the contact surface of the armature-rails gradually increases, the elastic modulus and hardness of the material in the contact area decrease, and the change trends of the wear volume and wear rate of the armature in the two states are the same. The maximum wear rate of the armature when considering the temperature field is 1.15 mm3/ms, which is 1.2 times of the maximum wear rate of the armature without considering the temperature field.

[Objective]The purpose of this paper is to investigate the effect of drip irrigation amount on dry matter accumulation and distribution, as well as the yield formation of the grain machine harvest maize .[Method]The study was based on the drip irrigation experiment established in 2018 in the Experimental Field of Inner Mongolia Academy of Agricultural and Animal Husbandry Sciences. The experiment consisted of five irrigation treatments by irrigating 415 m³/hm² (W1), 645 m³/hm² (W2), 945 m³/hm² (W3), 1 275 m³/hm² (W4) and 1 605 m³/hm² (W5), respectively. A rain-fed plot was taken as the control (CK). In each treatment, we measured the accumulation and distribution of above-ground dry matter in 2020 and 2021. Logistic model was used to describe the temporal change in dry matter accumulation, from which we further analyze the characteristics of dry matter accumulation and distribution, as well as the relationship of drip irrigation amount and yield under different treatments. [Result] Irrigation significantly increased the dry matter accumulation in the upper part of the plant; temporal change in the dry matter accumulation is well described by the logistic model, with R² >0.888. In 2020 and 2021, the maximum growth rate of the dry matter accumulation increased as the irrigation amount increased, with the increase in the CK being the least and the increase in W5 being the highest. The biological yield in W5 was the highest in both 2020 and 2021; the harvest index in W4 and W3 was the highest, being 0.51 and 0.50 respectively. Compared with CK, irrigation reduced dry matter distribution in the vegetative organs at maturity stage but increased dry matter accumulation in the grains. With the increase in irrigation amount, the economic yield in 2020 first increased, followed by a decline, maximizing in W4, reaching 14 282.42 kg/hm² in 2021. The yield in W4 (15 480.33 kg/hm²) and W5 (15 892.52 kg/hm²) was significantly higher than that in other treatments. [Conclusion]Optimizing irrigation amount can significantly increase dry matter accumulation in the aboveground part, and promote distribution of dry matter in the grain. In drought years with average annual natural precipitation between 364.2 and 390.7 mm, the optimum drip irrigation amount is 1 275 m³/hm² for grain machine harvest maize (planting density is 7.5x104 plants/hm²) in the arid and semi-arid areas in central and western Inner Mongolia. [ABSTRACT FROM AUTHOR]