Longitudinal airflow can sharply suppress the drifting and ablation of the electrical arc formed between a train’s pantograph and overhead contact wire, according to a modeling and experimental study of pantograph–catenary systems under low-pressure conditions. The researchers built a magnetohydrodynamic model that coupled electric, magnetic, thermal, fluid and arc-motion dynamics, then tested the method in a vacuum chamber with copper and carbon electrodes. In experiments conducted at atmospheric pressure, increasing the airflow to 45 metres per second reduced the measured arc drift height from 27.6 millimetres to zero and shortened the arc-root distance from 51.3 to 3.9 millimetres. The same airflow setting also produced progressively less carbon-electrode damage, supporting the proposal as a possible current-collection control method for railways operating at high altitude.

The need for such control arises because the pantograph–catenary system carries the electrical energy used by electric trains, while the stability of its contact strongly affects operating safety and efficiency. Lower atmospheric pressure presents a particularly difficult environment. The study notes that reduced air density and breakdown-field strength can lower the ignition threshold for pantograph–catenary arcs, increase their frequency and duration, and enlarge the region affected by arcing. Repeated arcing can cause irreversible high-temperature ablation and electrical wear on contact wires and pantograph strips. It can also generate broad-band electromagnetic interference that may affect onboard signalling and traction-control systems, with potential consequences including insulator flashover and disruption of the traction network. These background risks motivate efforts to understand and restrain the spatial movement of arcs in plateau environments.

Existing arc models include the Cassie and Mayr black-box approaches, which support analysis of interactions between arcs and traction-network circuits but do not represent an arc’s changing spatial shape. Magnetohydrodynamic models offer a more physical alternative by coupling electromagnetic, flow and thermal fields. Previous work represented crosswind effects on pantograph–catenary arcs and examined how decreasing pressure affects arc-root jumping, in which the root forms at a new location after the elongated column reaches a critical length. Other studies have shown that magnetic fields can stabilize welding and switching arcs. Airflow regulation, however, has been investigated more extensively in welding than in pantograph–catenary systems, whose dissimilar electrodes, high operating speed, open environment, changing electrode gap and constrained vehicle installation space make their arc dynamics more complicated.

The new model represents an arc initially 6 millimetres long and 2 millimetres in diameter between a copper anode and a carbon cathode. It includes the surrounding air, both electrodes and a central longitudinal-airflow channel beneath the copper electrode, including a 1.5-millimetre control-airflow inlet. A separate inlet represents train-induced airflow and was set to 40 metres per second. Calculations covered pressures of 101, 80 and 60 kilopascals, longitudinal airflow from zero to 80 metres per second and a total simulation time of 25 milliseconds. Air properties were adjusted with pressure, while the electrodes were assigned distinct densities, resistivities, thermal conductivities and heat capacities. The governing equations represented electrical potential and current, magnetic-vector potential, mass and momentum conservation, energy conservation, viscous dissipation, Joule heating and net volumetric radiation.

The calculations use several explicit simplifications. Arc ignition is omitted, and the plasma is treated as being in local thermodynamic equilibrium. Flow in the air and arc domains is assumed laminar and incompressible, while metal vapour generated by electrode evaporation and phase change is excluded. These assumptions make it possible to examine large-scale arc motion and temperature distribution but prevent the simulation from directly calculating electrode mass loss, crack width or crater area. Copper was assigned the anode and carbon the cathode; a Gaussian distribution represented current entering through the copper electrode, and the bottom of the carbon electrode was grounded. The air boundary was treated as magnetically insulated, and the initial temperatures were set to 300 kelvin for the air and electrodes and 5,000 kelvin for the arc domain. The experimental apparatus was separate from the numerical model and provided direct physical measurements of damage.

Without longitudinal airflow, the simulated arc passed through two stages. During the first 10 milliseconds, its column elongated continuously, bent under airflow influence, and developed greater drift height and arc-root distance. From 10 to 25 milliseconds, the column and root distance fluctuated through repeated shortening and elongation. The authors associate this behaviour with the electrical and mechanical limits of the arc: once a column reaches a critical length, the voltage and energy available between the electrodes may no longer sustain continuous burning, and a shorter path of lower resistance may form on the electrode surface. The resulting root “jump” shortened the column before airflow stretched it again. Arc development became faster and both drift height and root distance increased as pressure fell. Temperature briefly exceeded 10,000 kelvin and reached a maximum within roughly two to three milliseconds before fluctuating, while arc voltage rose as the column lengthened and resistance increased.

Longitudinal airflow changed these trajectories in the simulations. As speed increased, drift height, root distance and temperature all declined, with the greatest reductions occurring at lower airflow speeds before the curves began to level off. At 101 kilopascals, the calculated drift height fell from 37.5 millimetres without control airflow to zero at 45 metres per second, while root distance decreased from 57.3 to 3.7 millimetres and temperature dropped from 12,900 to 8,650 kelvin. The airflow needed to eliminate drift was 45, 40 and 35 metres per second at pressures of 101, 80 and 60 kilopascals, respectively; speeds required to bring root distance below 5 millimetres were 45, 40 and 30 metres per second. The authors attribute the stronger response at lower pressure to reduced plasma density, which weakens the arc’s inherent rigidity, Lorentz force and thermal buoyancy, allowing airflow load to become a more dominant influence on its motion.

The temperature response also revealed a practical plateau. The researchers defined the optimal airflow speed as the point after which increasing speed by 5 metres per second changes arc temperature by less than 3 per cent. At atmospheric pressure this occurred at 40 metres per second, compared with 30 metres per second at 60 kilopascals. The reported temperature reduction was 33.8 per cent at 101 kilopascals and 38.1 per cent at 60 kilopascals. Airflow strengthened convective heat removal, which lowered plasma temperature and, in turn, increased deionization and reduced Joule heating. Once thermal exchange approached saturation and the minimum temperature required for self-sustaining arc combustion was approached, further increases in speed produced little additional cooling. The model therefore indicates that the airflow speeds required for control decline as ambient pressure falls.

Laboratory testing used a vacuum chamber capable of controlling pressure with an accuracy of plus or minus 100 pascals, a constant-current supply rated from zero to 150 amperes, an arc igniter, a fan with continuously adjustable airflow from zero to 60 metres per second, a high-speed camera and an oscilloscope. Airflow at the electrode outlet was measured with an anemometer accurate to plus or minus 0.5 metres per second. The camera operated at 6,400 frames per second with an exposure of five microseconds, while each two-second arc test was repeated five times and the mean was reported. Tests at 101 kilopascals used airflow speeds of zero, 20, 30 and 45 metres per second. Without control airflow, high-speed images showed increasing arc drift. At 45 metres per second, drift was virtually absent during the final development phase and root distance was substantially shortened, with observed morphologies broadly consistent with the numerical results.

The experiments also found reductions in carbon-electrode ablation that increased with airflow speed. Microscopy showed shorter ablation areas, smaller craters and narrower crack propagation as the controlled airflow rose. The maximum crack width was 66.7 micrometres without airflow and decreased at higher speeds, while analytical weighing showed progressively less mass loss from the carbon electrode. The proposed mechanism is that stronger airflow promotes arc-root slippage, shortening the time the root remains at one point, while convective cooling lowers temperature and local energy density. These are experimental observations rather than direct outputs of the simulation: because the model omits electrode evaporation and metal-vapour transport, it cannot quantitatively predict ablation rates or near-electrode energy balances. The study therefore demonstrates reduced damage under its controlled laboratory conditions, not a complete first-principles calculation of all processes responsible for electrode wear or a proven field performance level in operating plateau railways.

Subject of Research: Experimental and numerical evaluation of airflow control of pantograph–catenary arcs at low pressure.

Article Title: Research on regulation method for suppression of pantograph-catenary arc by airflow in low-pressure environment

Article References: Xu, Z., Wang, S., Dong, K., & Gao, G. (2026). Research on regulation method for suppression of pantograph-catenary arc by airflow in low-pressure environment. iScience, 29(11), Article 117951. https://doi.org/10.1016/j.isci.2026.117951

Image Credits: AI Generated

DOI: 10.1016/j.isci.2026.117951

Keywords: pantograph–catenary systems, railway electrification, electric arcs, low-pressure environments, longitudinal airflow, magnetohydrodynamic modelling, electrode ablation, high-speed rail, plateau railways, arc suppression, Research, regulation

Gov. Tony Evers and state environmental regulators announced the launch of new grant programs Tuesday to help communities and private well owners address PFAS contamination.

Apple’s warning about AI agents misusing Full Disk Access sparks a debate over Mac security, privacy, and the potential consequences for developers and users. The MacVoices Live! panel examines Apple’s permission system, the need for more granular controls, and concerns about restricting legitimate applications and developer options. The discussion also questions Mark Zuckerberg’s involvement in drafting the White House’s voluntary AI regulatory accord and whether self-regulation is the best solution to potentially dangerous advances in AI. 

💾

A whistleblower lawsuit in California is alleging millions of pounds of Driscoll's fruit containing non-compliant levels of pesticides and chemicals crossed the border into Canada, and the company tried to cover it up.

Paper raises questions about safety of food and other products as early onset breast cancer rates surge worldwide.

For children growing up in South Africa’s farming communities, exposure to pesticides may not end when the tractors leave the fields.

According to the Center for Biological Diversity, a Pennsylvania power plant has been leaching toxic chemicals into surrounding waters for years.

The Trump Administration has rolled back a major climate rule, falsely claiming greenhouse gas emissions from power plants do not impact the climate or human health.

European Commission (EC) President Ursula von der Leyen (pictured) outlined plans to restrict children’s access to social media under the watchdog’s proposed EU Kids Act, as concerns mount over the impact of addictive online services and increasingly capable AI systems.

In her annual State of the Union address, von der Leyen told the European Parliament: “What we are witnessing is a great capture of our children. A capture of their attention, their focus, their minds.” She explained the proposed EU Kids Act would ban children under 13 from social media and bar under 15 users from having personal accounts.

Meanwhile, 13 to 15-year-olds would only be able to use “mini accounts” set up and supervised by parents, with limited features and time restrictions. Platforms would also be required to implement additional safety features for users aged 15 to 18.

“We are reversing the burden of proof,” she said, adding, “platforms will have to prove that they are safe”.

Von der Leyen noted young Europeans now spend four to six hours a day on screens, pointing to concerns around addictive features, harmful content, online bullying and growing rates of sleep issues, anxiety and suicide.

“We do not have to accept addictive features. We do not have to accept children being drawn into ever more extreme content. We do not have to accept that girls have their photos used for AI-generated sexualised images,” she argued.

The measures form part of the EU Kids Act, which the EC is due to propose tomorrow (17 September). The proposal would introduce age checks across social media, video sharing platforms, app stores, online games and AI services.

The EC is also preparing a broader Digital Fairness Act aimed at addressing addictive design features beyond services used by children.

AI tipping point
AI was also a focus of the address, with von der Leyen describing it as “the second tipping point of our times”.

She warned that increasingly capable models could create new security risks, including more powerful hacking capabilities and the potential for self-improving systems to cause mass harm.

She revealed the EC plans to work with partners including the UK and Canada on “model evaluation, verification, early warning, AI security and much more”, while also seeking greater European computing capacity and investment in local AI companies.

Von der Leyen called on the region to use AI to support sectors including healthcare, manufacturing, transport and agriculture, while retaining human oversight. “Our approach is clear. We want AI… But above all, we want AI with human agency.”

Global concerns have been mounting over the pace of AI development this week, as Anthropic and OpenAI chiefs called for a slowdown in frontier AI development after researchers warned of existential risks from increasingly capable systems.

The post EU sets out social media limits for children   appeared first on Mobile World Live.

More than 50 years after oil drilling was carried out, Kenya's Kargi community is suing BP, alleging contaminated water contributed to cancers and livestock deaths.

The Diamond Alkali Superfund site covers a sprawling swath of North Jersey, including parts of Newark Bay and the lower Passaic River.

Accenture agreed to pay the US government $25 million to settle allegations it used race and sex as factors in hiring and promotion decisions at its federal services business.

The US Department of Justice (DoJ) alleged Accenture Federal Services (AFS) falsely certified it was complying with anti-discrimination requirements attached to federal contracts while using race and sex in employment decisions from 2017 onwards.

The government claim AFS “took race or sex into account when making hiring decisions to achieve progress toward non-public workforce composition goals”. According to the DoJ, AFS provided business leaders with monthly reports summarising the percentage of each race and sex within the unit to show how closely the workforce matched representation targets.

“These demographic goals were designed to, and did, drive changes in hiring practices based on race and sex,” the DoJ argued, adding the targets prompted a round of entry-level recruitment at the company in late 2020 and early 2021.

It also stated candidates who advanced AFS’ demographic goals received additional visibility during managing director promotion discussions and that the company reserved access to some training, mentoring, leadership development and education programmes based on race or sex.

The agreement added the settlement was not an admission of liability.

An Accenture spokesperson told Reuters: “We have cooperated with the government’s review, and we are pleased to put ⁠this ​matter behind us to avoid the costs ​and resource demands of prolonged litigation.”

The Donald Trump administration has taken aim at DEI practices across the federal government and its contractors. Deloitte agreed to pay $21.5 million in August, while IBM agreed to a $17 million settlement in April over allegations concerning illegal DEI practices.

Last year, US operators T-Mobile US, Verizon and AT&T ended or scaled back diversity initiatives.

The post Accenture agrees $25M DEI settlement appeared first on Mobile World Live.

A new bipartisan effort in Congress to rein in automated license plate readers takes a page from the national drinking age: Comply, or risk losing federal highway funding.

The proposal ceases to be an inference from observations and known physics and becomes an appeal to the absurd.

Source

For years, Perdue Agribusiness has been embroiled lawsuits over claims it polluted local groundwater with PFAS, the cancer-causing "forever chemical." So neighbors were skeptical when Perdue asked to increase the treated wastewater it pours in a local stream.

The US Environmental Protection Agency (EPA) worked directly with pesticide maker Bayer in approving the controversial herbicide dicamba earlier this year, presenting the company with different options for how to reduce drift and runoff and then aligning on those options in the final decision, according to internal agency records.  

The chemical, found in dozens of popular sunscreens, can potentially act as an endocrine disruptor.

An ambitious bill to keep toxic “forever chemicals” off California produce lost its teeth after the chemical and agricultural industries spent hundreds of thousands of dollars lobbying against it.

We tested 21 popular kids' snacks and discovered some options parents may want to limit, and some options that are lower in harmful chemicals than others.

Fridges are piling up in laybys across the country as recycling centres refuse to take anymore. It's the backfiring result, in part, of pettifogging green waste disposal regulation, says Ben Pile.

The post Green Rules Mean Britain Can’t Even Recycle a Fridge appeared first on The Daily Sceptic.