A pre-study of free burning arcs between carbon electrodes for potential use in gasification processes is presented. Free-burning arcs offer the potential to be used without additional gas feed or significant changes to gas flows in established gasification systems as well as with minimal cooling requirements for improved energy efficiency. Direct current (DC) arcs with currents up to 200 A and power levels up to 40 kW have been operated in molecular gas mixtures of H2, CO and CO2. The electrical characteristics and dynamic behaviour of the arcs under various electrode configurations have been analysed, along with an assessment of electrode erosion. Finally, concepts for the power sources have been deduced and tested.

The characteristics of filling gas and its resulting arcing behavior is a major factor influencing the current-limiting and switching performance of gas-filled direct current (DC) switches. The use of hydrogen (H2) or mixtures containing H2 as dielectric gas has shown increased breaking performance in compact DC switches. However, arcs in such gases, especially in pure H2 show a complex fluctuating dynamics, especially at higher filling pressures and by simultaneous use of magnetic blown-off. This paper conducts an electrical and optical study of the rapid and unstable arc behavior in H2 at pressures of 1 and 6 bar using a model switch with arc runners. The results remark the significant impact of filling pressure on the arc voltage and the coupled current limiting performance. Moreover, the arc dynamics become more unstable and faster, and the arc shape becomes strongly distorted. Compared to atmospheric pressure, the rate of increase in arc voltage and arc length are noticeably higher.

This paper deals with double-pulse laser-induced breakdown spectroscopy (LIBS) underwater, which is a promising analytical method for elemental analysis in the deep sea up to a water depth of 6000 m. A double-pulse laser with a wavelength of 1064 nm is used, which provides a pulse energy of up to 266 mJ for each laser pulse (in single pulse mode), a pulse width of 5–7 ns and a pulse delay in the range of 0.5 to 20 µs. In the double-pulse LIBS method, the first laser pulse creates a cavity on the material surface, and then the second laser pulse forms the plasma in this cavity. It is expected that the plasma is affected by the cavity’s size and lifetime. For this reason, the influence of focus position, pulse energy and pulse delay on the cavity and plasma formation at shallow water depth has been investigated.

When designing high-voltage elements, knowing if the corona effect will be present during their life cycle is relevant. Therefore, designers consider several prediction criteria based on physical features related to breakdown discharge principles to predict the corona effect. The introduced practical set-up consists of a concave cone electrode with a hemispheric tip above a plate to evaluate selected corona prediction criteria. The hemisphere has a fixed diameter of 7 mm, and the electrode separation ranges from 2.5 to 39 cm. Information about the corona mode inception under different voltage sources was extracted using an intensified charge-coupled device camera and a partial discharge metre. The prediction criteria were connected to a specific corona mode depending on the main discharge structure behind its development. The average deviation between these criteria and experimental results was around eight percent. Underlying assumptions in criteria are also discussed in light of the experimental results.

Introducción: la osteomielitis crónica no bacteriana (CNO) es una enfermedad autoinflamatoria ósea y se manifiesta con un amplio espectro clínico, presentándose con afectación monofocal o multifocal. Dado que no es siempre multifocal o recurrente, o ambas, fue propuesto que CNO se utilice como un término que comprenda a todas las presentaciones y la osteomielitis multifocal crónica recurrente (CRMO) se utilice para formas recurrentes y multifocales. Objetivo: presentar un caso clínico inédito, de baja prevalencia a nivel mundial, en una adolescente portadora de una enfermedad autoinflamatoria ósea que planteó desafíos diagnósticos y terapéuticos. Descripción: adolescente, mujer, 11 años, previamente sana que se presentó con dorso-lumbalgia invalidante de un mes de evolución, sin otra sintomatología asociada. Tras varias consultas en emergencia, ingresa a planta de internación pediátrica del Hospital Central de las Fuerzas Armadas (HCFFAA) en octubre de 2021. Resonancia nuclear magnética (RNM) de columna evidencia foco de edema óseo en cuerpo de T11, hemograma normal; VES 48 mm/h, ANA, anti-DNA, FR y HLA B27 negativos. Resultados: luego de descartar procesos infecciosos, oncohematológicos y una vez obtenido el resultado de una biopsia por punción ósea que evidenciaba elementos inflamatorios, se llegó al diagnóstico de CNO en el mes de febrero de 2022, tiempo récord comparando este caso con la literatura internacional. El diagnóstico de esta entidad clínica promedio a nivel mundial es de 12 meses.

The electrical characteristic of arcs sensitively depends on many factors like electrode material and shape, working gas and gas pressure. Arc sheath voltages and electrode resistance have to be considered in particular for shorter arcs. The arc voltage behaviour is important to the switching performance. But its knowledge also allows to estimate the power consumption of the arc and the heat transferred to the electrodes. Arc voltage models are easy to integrate in power grid simulations and benefitial for the design of arc power sources. Whereas specific arc voltage models are available meanwhile for many examples, there are still knowledge gaps for arcs in a wide range of parameters. This paper provides a review of recently developed electric arc models for high and low voltage switching as well as for welding with the focus on vacuum arcs, short arcs and arcs at low current.

Deep-sea mining and deep-sea exploration require methods for material analysis that can be used directly in the deep sea. A promising method is double-pulse laser-induced breakdown spectroscopy (LIBS), which was already used to measure zinc emission lines up to 600 bar. In this paper, the detection limits for zinc and copper in brass alloys were investigated using double-pulse LIBS at up to 600 bar to show up to which water pressure zinc and copper can be detected for the respective alloy. A double-pulse laser with a wavelength of 1064 nm, a pulse duration of 5-7 ns and a pulse energy of up to 266 mJ (in single-pulse mode) for each pulse was used. To optimize the emission spectrum for the respective water pressure, the delay between the laser pulses was varied. It was found that the detection limit for zinc and copper in brass alloys decreases with increasing water pressure. (c) 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0)

A spark gap with fixed contacts was applied as a model setup for low voltage surge protection of DC currents. Therefore, the spark gap was combined with a parallel IGBT, resulting in a hybrid switching operation. The recovery behavior was investigated by spectroscopic methods. In earlier studies, we used optical emission spectroscopy in the visible spectral range to obtain plasma temperatures from atomic copper lines. Now, these results were extended by experiments considering the UV range. On the one hand, emission spectra of resonant atomic copper were taken. On the other hand, optical absorption spectroscopy of these lines revealed knowledge on the densities of atomic ground levels and hence, on the partition composition. It was found that the copper densities are too low to take significant influence on the conductivity of the remaining gas. Hence, the conductance could be determined based on air plasma composition and the temperatures obtained from OES.

Double-pulse LIBS is a promising technique for deep-sea applications. LIBS measurements in shallow water with up to 400 mJ each pulse were done to select laser parameters which promote optimized spectral line emission from plasma even at elevated pressures, where line broadening until loss of most of the spectral information can occur. Optical emission spectroscopy, using a Czerny-Turner spectrometer, has been applied to investigate the dependence of the emitted radiation on laser parameters and hydrostatic pressure. It has been found, that higher laser pulse energies, especially with short pulse delay as required in high water pressure, can also have an adverse effect on the measured spectrum.

The applied experimental setup consists of a pair of fixed electrodes forming a short gap in air. The electrodes are connected with a thyristor forming a parallel current path. Once the thought flashover ignited arc has burnt a given time in the range of several hundreds of microseconds, the thyristor will be fired causing a commutation of the current in the semiconductor path. Hence, the current through the electrode gap will be reduced. The extinguishment of the arc permits the creation of a current zero in the gap. The focus of the experimental work is set to the analysis of the arc plasma during the DC phase and its distinction in the current extinction phase (current zero). High speed camera observation and optical emission spectroscopy are carried out and combined with the electrical measurements.

Digital prototyping enables cost-effective production and modular optimization of surge protection devices (SPD). Numerical model of SPD prototypes involves complex multiphysics phenomena. However, the processes related to impulse current arcs in spark gaps are not well understood so far. Limited knowledge exists regarding hydrodynamic effects, plasma states, and radiation properties. This work studies an impulse current 8/20 µs with an amplitude of about 5 kA in experiment and simulation.

In support of the Climate Action Teams initiative, we evaluate Chile's potential for greenhouse gas (GHG) mitigation beyond its Nationally Determined Contributions (NDCs) through implementing ambitious actions. An open multisector model is used to project GHG emissions. The results indicate that additional efforts are required to meet Chile's NDC commitments. However, ambitious actions could yield a significant mitigation surplus at a reasonable cost, with a maximum potential of 75 (65–82) MtCO2e beyond the committed carbon budget. About one-third of this potential can be achieved at a mean abatement cost of less than 20 USD/tCO2e, and an additional 65% can be obtained with a mean abatement cost ranging between 20 and 50 USD/tCO2e. The estimated capital cost required for implementing these actions is 5.3 (4.9–5.3) billion USD from 2020 to 2030. In addition to mitigating GHG emissions, these actions also have significant health co-benefits, with an estimated avoidance of up to 2,250 (2,180–2,320) premature PM2.5-induced deaths between 2020 and 2030. The health co-benefit between 2020 and 2030 is estimated to be around 1.5 billion USD. The study also suggests that an early coal-power phase-out is not the most efficient mitigation action in the power sector. We estimate that a carbon tax between 40–45 USD/tCO2e could achieve the same level of emissions reduction as closing coal-fired power by 2025 but at a significantly lower cost.

Optical diagnostic methods, which can be used for determination of arc plasma temperature, anode surface temperature, densities of plasma species during the arcing and in the post-arc phase are presented. Those methods have been applied for determination of the properties of high-current vacuum arcs in dependency on the anode activity (various highcurrent anode modes). A model vacuum circuit breaker was used to grant the optical access to the arc plasma and to the electrodes. Typical switching conditions, i.e. arc initialization by separation of CuCr contacts during the AC operation in the range 1-28kA magnitude have been used. The methods are exemplarily illustrated with corresponding results.

The behavior of radial magnetic field (RMF) contacts under the impact of many vacuum arc breaking operations (shots) with high current load have been studied to reveal the contact erosion and its consequences. A model breaker with optical access and a synthetic test circuit have been used. RMF contacts made of Cu-Cr have been studied under AC current pulses with a peak value of about 22.5 kA and frequency of 50 Hz. Each contact pair was loaded with up to 20 shots. Besides the arc current and voltage measurements, various optical diagnostics were used. High-speed cameras were used for analysis of arc behaviour. Near infrared radiation (NIR) spectroscopy was applied for determination of the anode surface temperature after the arc extinguishing. The results show clear changes in arc dynamics, arc voltage and anode surface temperature with progressing number of shots. Contact melting and bridging of the slots of the spiral contacts lead to a decrease of arc rotation. However, the anode surface temperature tends to be lower after a higher number of shot.

Arku elektrikoa etengailuetan gertatzen den efektua da. Etengailuaren kontaktuak bata bestetik aldentzen direnean, etengailutik pasatzen den korronte elektrikoa kontaktuetatik etengailuaren gas isolatzailera pasatzen da, eta hau ionizatuz, bertan arku elektrikoa sortzen da. Arku elektrikoak efektu ez-desiragarriak sor ditzake etengailuetan; beraz, efektu horiek murrizteko asmoz, lan honen helburu nagusia hidrogenoaren baliagarritasuna aztertzea da etengailuaren gas isolatzaile modura. Horretarako, Navier-Stokesen ekuazioak eta Bolumen Finituen Metodoa (ingelesez, Finite Volume Method, FVM) oinarritzat hartuz, simulazio Magnetohidrodinamikoak (ingelesez, Magnetohydrodynamics, MHD) definitu dira ANSYS CFX programaren bitartez. Hala, arku elektrikoaren prozesuan oinarrizkoak diren aldagaiak kalkulatu dira, hala nola, tentsioa, tenperatura eta presioa. Emaitza horiek airea isolatzaile modura darabilten etengailuetan lortutakoekin alderatuz, hidrogenoa simulatutako aplikaziorako gas egokia den ala ez ondorioztatuko da.

Properties of high-current vacuum arcs in dependence on electrode surface status have been studied. The AC current pulses with 16kA (rms) at 50Hz have been applied to spiral contact system made of conventional CuCr material. Each contact pair was loaded with 20 shots. Arc diagnostics comprises arc current and voltage measurements as well as various optical diagnostics. Two high-speed cameras were used for analysis of arc dynamics. Near infrared radiation spectroscopy was applied for determination of the anode surface temperature after the arc extinguishing. The results show clear changes in arc dynamics and anode surface temperature with progressing surface ageing.

Hydrogen or mixtures containing hydrogen represent attractive gases for low-voltage switching devices because of increased arc quenching behaviour. However, fundamental electrical properties of arcs in hydrogen are still not well known. In this paper, first results of a study of a DC switching arc in pure hydrogen at 1 bar between graphite electrodes are presented for low currents of 8 and 16 A. The arc voltage and current are measured during contact separation. High-speed images of the arc are processed to determine the arc length considering the high arc dynamics with erratic elongations and jumps of the electrode attachment. The arc voltage dependence on the length results in a typical sheath voltage of approximately 23 V and mean electric fields in the arc column of 18.7 V/mm at 8 A and 10.8 V/mm at 16A.

The paper deals with further results of the investigation of the plasma of a DC hybrid-switching discharge between metallic contacts combining electrical and optical methods. The setup consists of a model switch using a linear motor as mechanical drive and a semiconductor parallel to the contacts to commutate the current forcing arc extinguishing after a defined arcing-time. Firstly, the current flow remains initially through the contact path due to lower resistance of the closed contacts. During contact opening, the resistance rises due to reduced contact force, finally ending up with a single metal bridge that will be heated until explosion, leading thus to a metal-dominated discharge plasma. High-speed imaging and spatially and time resolved spectroscopy was used to capture the radiation during arcing and during post-arc. Spatially solved spectroscopy delivered the characteristics of radiation during arcing. Intensity lines of the elements of the electrodes indicate a predominately arc in metal vapor. Combining a secondary high voltage DC source it was possible to characterize the behavior of the resistance of the gap during arc and in the post-arc phase also.

Electric arcs generated by transient lightning-type surge currents in protection devices for low voltage appliances are studied by optical emission spectroscopy and spectra simulations. A surge pulse amplitude of 5kA and 8/20µs shape are applied. The arc radiation is recorded by a 3/4m spectrometer and a high-speed camera equipped with metal interference filters for the O I (777nm) and Hα (656nm) lines. Absolute calibration was realized using a tungsten strip lamp. The arc images indicate a non-symmetrical shape. To determine the plasma properties, accompanying simulation solving the equation of radiative transfer for a given pressure and a temperature profile was carried out assuming local thermodynamic equilibrium. Line broadening due to the Stark effect is taken into account. The computed and measured spectra are compared. The conditions are varied until the measured and computed spectra match.

Summary R code and main functions used in the manuscript 'Functional susceptibility of tropical forests to climate change'