Flash Energy Research Articles

Lightning NOx in the 29–30 May 2012 Deep Convective Clouds and Chemistry (DC3) Severe Storm and Its Downwind Chemical Consequences

AbstractA cloud‐resolved storm and chemistry simulation of a severe convective system in Oklahoma constrained by anvil aircraft observations of NOx was used to estimate the mean production of NOx per flash in this storm. An upward ice flux scheme was used to parameterize flash rates in the model. Model lightning was also constrained by observed lightning flash types and the altitude distribution of flash channel segments. The best estimate of mean NOx production by lightning in this storm was 80–110 mol per flash, which is smaller than many other literature estimates. This result is likely due to the storm having been a high flash rate event in which flash extents were relatively small. Over the evolution of this storm a moderate negative correlation was found between the total flash rate and flash extent and energy per flash. A longer‐term simulation at 36‐km horizontal resolution with parameterized convection was used to simulate the downwind transport and chemistry of the anvil outflow from the same storm. Convective transport of low‐ozone air from the boundary layer decreased ozone in the anvil outflow by up to 20–40 ppbv compared with the initial conditions, which contained stratospheric influence. Photochemical ozone production in the lightning‐NOx enhanced convective plume proceeded at a rate of 10–11 ppbv per day in the 9–11 km outflow layer over the 24‐hr period of downwind transport to the Southern Appalachians. Photochemical production plays a large role in the restoration of upper tropospheric ozone following deep convection.

Secondary neutron dosimetry for conformal FLASH proton therapy.

Cyclotron-based proton therapy systems utilize the highest proton energies to achieve an ultra-high dose rate (UHDR) for FLASH radiotherapy. The deep-penetrating range associated with this high energy can be modulated by inserting a uniform plate of proton-stopping material, known as a range shifter, in the beam path at the nozzle to bring the Bragg peak within the target while ensuring high proton transport efficiency for UHDR. Aluminum has been recently proposed as a range shifter material mainly due to its high compactness and its mechanical properties. A possible drawback lies in the fact that aluminum has a larger cross-sectionof producing secondary neutrons compared to conventional plastic range shifters. Accordingly, an increase in secondary neutron contamination was expected during the delivery of range-modulated FLASH proton therapy, potentially heightening neutron-induced carcinogenic risks to thepatient. We conducted neutron dosimetry using simulations and measurements to evaluate excess dose due to neutron exposure during UHDR proton irradiation with aluminum range shifters compared to plastic rangeshifters. Monte Carlo simulations in TOPAS were performed to investigate the secondary neutron production characteristics with aluminum range shifter during 225MeV single-spot proton irradiation. The computational results were validated against measurements with a pair of ionization chambers in an out-of-field region ( 30cm) and with a Proton Recoil Scintillator-Los Alamos rem meter in a far-out-of-field region (0.5-2.5m). The assessments were repeated with solid water slabs as a surrogate for the conventional range shifter material to evaluate the impact of aluminum on neutron yield. The results were compared with the International Electrotechnical Commission (IEC) standards to evaluate the clinical acceptance of the secondary neutronyield. For a range modulation up to 26cm in water, the maximum simulated and measured values of out-of-field secondary neutron dose equivalent per therapeutic dose with aluminum range shifter were found to be and , respectively, overall higher than the solid water cases (simulation: ; measurement: ). The maximum far out-of-field secondary neutron dose equivalent was found to be ( ) and ( ) for the simulations and rem meter measurements, respectively, also higher than the solid water counterparts (simulation: ( ) ; measurement: ( ) ). We conducted simulations and measurements of secondary neutron production under proton irradiation at FLASH energy with range shifters. We found that the secondary neutron yield increased when using aluminum range shifters compared to conventional materials while remaining well below the non-primary radiation limit constrained by the IECregulations.

Inter-Comparison of Lightning Measurements in Quasi-Linear Convective Systems

Data from four lightning networks collected during three quasi-linear convective systems (QLCS) are used to understand the differences in detection for optimizing their combined use. Additionally, using unique aspects from each network provides a more complete picture of lightning in a thunderstorm. The four lightning networks examined include a Lightning Mapping Array (LMA), the Earth Networks Total Lightning Network (ENTLN), the Geostationary Lightning Mapper (GLM), and the National Lightning Detection Network (NLDN). The data from each network are inter-matched and locations where each network uniquely detected a flash versus all are analyzed in reference to three QLCSs, including two QLCSs that occurred in the Southeast (22 March 2022 and 30 March 2022) during the Propagation, Evolution, and Rotation in Linear Systems (PERiLS) field campaign, and one case from Oklahoma (26 February 2023). Unique aspects of the lightning provided by each network are examined, including flash initiation altitude, size, type, and energy. Lightning flash trends and characteristics for each QLCS are similar between networks in general, but deviate in certain conditions and locations. Times of decreased matching between networks were associated with localized increases in lightning rates, smaller flash sizes, and lower-energy flashes. The differences in each network’s performance across the QLCSs demonstrates the importance of understanding the limitations in each and the advantage of using multiple networks.

Performance Evaluation of the Lightning Imaging Sensor on the International Space Station

Abstract Optical lightning observations from low-Earth orbit play an important role in our understanding of long-term global lightning trends. Lightning Imaging Sensors (LIS) on the Tropical Rainfall Measuring Mission (TRMM) satellite (1997–2015) and International Space Station (2017–present) capture optical emissions produced by lightning. This study uses the well-documented TRMM LIS performance to determine if the ISS LIS performs well enough to bridge the gap between TRMM LIS and the new generation of Geostationary Lightning Mappers (GLMs). The average events per group and groups per flash for ISS LIS are 3.6 and 9.9, which are 18% and 10% lower than TRMM LIS, respectively. ISS LIS has 30% lower mean group energy density and 30%–50% lower mean flash energy density than TRMM LIS in their common (±38°) latitude range. These differences are likely the result of larger pixel areas for ISS LIS over most of the field of view due to off-nadir pointing, combined with viewing obstructions and possible engineering differences. For both instruments, radiometric sensitivity decreases radially from the center of the array to the edges. ISS LIS sensitivity falls off faster and more variably, contributed to by the off-nadir pointing. Event energy density analysis indicate some anomalous hotspot pixels in the ISS LIS pixel array that were not present with the TRMM LIS. Despite these differences, ISS LIS provides similar parameter values to TRMM LIS with the expectation of somewhat lower lightning detection capability. In addition, recalculation of the event, group, and flash areas for both LIS datasets are strongly recommended since the archived values in the current release versions have significant errors.

Millisecond flash lamp curing for porosity generation in thin films

Flash lamp annealing (FLA) with millisecond pulse durations is reported as a novel curing method for pore precursor's degradation in thin films. A case study on the curing of dielectric thin films is presented. FLA-cured films are being investigated by means of positron annihilation spectroscopy (PAS) and Fourier-transform infrared (FTIR) spectroscopy in order to quantify the nm-scale porosity and post-treatment chemistry, respectively. Results from positron annihilation reveal the onset of the formation of porous voids inside the samples at 6 ms flash treatment time. Moreover, parameter's adjustment (flash duration and energy density) allows for identifying the optimum conditions of effective curing. Within such a systematic investigation, positron results indicate that FLA is able to decompose the porogen (pore precursors) and to generate interconnected (open porosity) or isolated pore networks with self-sealed pores in a controllable way. Furthermore, FTIR results demonstrate the structural evolution after FLA, that help for setting the optimal annealing conditions whereby only a residual amount of porogen remains and at the same time a well-densified matrix, and a hydrophobic porous structures are created. Raman spectroscopy suggests that the curing-induced self-sealing layer developed at the film surface is a graphene oxide-like layer, which could serve as the outside sealing of the pore network from intrusions.

전력량계 작업 시 아크플래시 재해 경감방안 연구

About 23 million electronic Watt-hour meters are installed in Korea, and more than 2 million meters are newly installed or replaced every year. Usually, the work is performed on live line and sometimes injuries are occurred due to arc flash by improper behavior or misconnection. In Korea, Watt-hour meter workers are advised to wear personal protective equipment(PPE) level 1, but it is not reviewed well whether they can sufficiently prevent injury caused by arc flash under the guideline. In this paper, we calculate the arc flash energy according to the IEEE 1584 standard that may occur in an actual Watt-hour meter working environment and review the required PPE level by the NFPA 70E for injury prevention. In addition, an economical arc energy reduction solution is proposed instead of wearing a higher PPE level equipment. The effectiveness of the solution is verified through field experiments.

Photothermal Desorption of Toluene from Carbonaceous Substrates Using Light Flash.

Millions of workers are occupationally exposed to volatile organic compounds (VOCs) annually. Current exposure assessment techniques primarily utilize sorbent based preconcentrators to collect VOCs, with analysis performed using chemical or thermal desorption. Chemical desorption typically analyzes 1 µL out of a 1 mL (0.1%) extraction volume providing limited sensitivity. Thermal desorption typically analyzes 100% of the sample which provides maximal sensitivity, but does not allow repeat analysis of the sample and often has greater sensitivity than is needed. In this study we describe a novel photothermal desorption (PTD) technique to bridge the sensitivity gap between chemical desorption and thermal desorption. We used PTD to partially desorb toluene from three carbonaceous substrates; activated carbon powder (AC-p), single-walled carbon nanotube (SWNT) powder (SWNT-p) and SWNT felts (SWNT-f). Sorbents were loaded with 435 ug toluene vapour and irradiated at four light energies. Desorption ranged from <0.007% to 0.86% with a single flash depending on substrate and flash energy. PTD was significantly greater and more consistent in SWNT-f substrates compared to AC-p or SWNT-p at all irradiation energies. We attribute the better performance of SWNT-f to greater utilization of its unique nanomaterials properties: high thermal conductivity along the nanotube axis, and greater interconnection within the felt matrix compared to the powdered form.

Open hardware microsecond dispersive transient absorption spectrometer for linear optical response

An open hardware design and implementation for a transient absorption spectrometer are presented that has microsecond time resolution and measures full difference spectra in the visible spectral region from 380 to 750 nm. The instrument has been designed to allow transient absorption spectroscopy measurements of either low or high quantum yield processes by combining intense sub-microsecond excitation flashes using a xenon lamp together with stroboscopic non-actinic white light probing using LED sources driven under high pulsed current from a capacitor bank. The instrument is sensitive to resolve 0.15 mOD flash-induced differences within 1000 measurements at 20 Hz repetition rate using an inexpensive CCD sensor with 200 μm pixel dimension, 40 K electrons full well capacity and a dynamic range of 1800. The excitation flash has 230 ns pulse duration and the 2 mJ flash energy allows spectral filtering while retaining high power density with focussing to generate mOD signals in the 10–4–10–1 ΔOD range. We present the full electronics design and construction of the flash and probe sources, the optics as well as the timing electronics and CCD spectrometer operation and modification for internal signal referencing. The performance characterisation and example measurements are demonstrated using microsecond TAS of Congo red dye, as an example of a low quantum yield photoreaction at 2% with up to 78% of molecules excited. The instrument is fully open hardware and combines inexpensive selection of commercial components, optics and electronics and allows linear response measurements of photoinduced reactions for the purpose of accurate global analysis of chemical dynamics.Graphical abstract

The Evolution of Lightning Flash Density, Flash Size, and Flash Energy During Hurricane Dorian's (2019) Intensification and Weakening

AbstractThe two most distinct inner‐core lightning outbreaks in Hurricane Dorian (2019) are analyzed using the Geostationary Lightning Mapper (GLM). The first outbreak occurred during Dorian's intensification, including a rapid intensification (RI), and the second occurred during weakening. During RI, inner‐core lightning flash density increased as flashes concentrated inside of the radius of maximum wind (RMW). As weakening commenced, numerous flashes still occurred within the RMW, with a flash rate more than three times that during RI–a signal typically associated with strengthening. These flashes, however, were much smaller and less energetic than those during intensification. Evidence is presented that barotropic mixing and secondary eyewall formation increased the number of small, low‐energy lightning flashes in the inner core while simultaneously weakening the storm. The results suggest that flash area and energy from GLM could help distinguish between lightning outbreaks that correspond to intensification and those that correspond to weakening.

Observations of Lightning NOx Production From GOES‐R Post Launch Test Field Campaign Flights

AbstractA primary goal of the Geostationary Operational Environmental Satellite R‐series Post Launch Test (GOES‐R PLT) Field Campaign during spring 2017 was the performance evaluation of the Geostationary Lightning Mapper (GLM) aboard the GOES‐16 satellite. The NASA Goddard Geo‐CAPE Airborne Simulator (GCAS), an ultra‐violet visible spectrometer, piggybacked on the aircraft mission to allow continuous hyper‐spectral measurements at high spectral and spatial resolutions simultaneously with optical lightning detection by the Fly’s Eye GLM Simulator while overflying convective systems. NO2 columns retrieved from GCAS were used to estimate the moles of NOx produced per flash, referred to as lightning NOx production efficiency (LNOx PE) for convective systems over the United States and western Atlantic. The mean PE was determined to be 360 ± 180 mol per flash for optically detected GLM flashes and 230 ± 115 mol per flash for radio‐wave detected Earth Networks Total Lightning Network flashes. These values span the commonly cited range of 100–500 mol per flash for midlatitude flashes. LNOx PE was found to be positively correlated with GLM flash multiplicity and flash optical energy but negatively correlated with flash density. The positive correlations provide encouragement for PE parameterizations in terms of flash energy or multiplicity. Observations during the GOES‐R PLT field campaign provide a preview of the analysis that will be possible when continuous lightning detection is coupled with hourly NO2 columns from a geostationary instrument such as Tropospheric Emissions: Monitoring of Pollution.

An In‐Depth Analysis of Lightning Trends in Hurricane Harvey Using Satellite and Ground‐Based Measurements

AbstractSatellite lightning measurements from the Geostationary Lightning Mapper (GLM) and ground‐based measurements from Earth Networks Total Lightning Network (ENTLN) for Hurricane Harvey (2017) are combined to obtain a better representation of intra‐cloud and cloud‐to‐ground lightning and their relationship to intensification and weakening of the hurricane. Through this combination, detection efficiencies of ENTLN and GLM are calculated for the rainband and eyewall of Harvey. In addition, the combined data set is used to derive the cloud flash fraction (CFF) and cloud pulse fraction (CPF) throughout the study period. The results show that flash and pulse rates increase in both the eyewall and rainband prior to rapid intensification in Harvey. The rainband lightning has the highest correlation to Harvey's intensification, where increases in lightning correspond to the largest periods of wind‐speed intensification. The eyewall CFF is also highly correlated to intensification, with minima in eyewall CFF and CPF coinciding with slower intensification periods in Harvey, while increasing CFF and CPF corresponds to more rapidly intensifying periods. Further, GLM flash characteristics including the events per flash, groups per flash, maximum group area, maximum number of events per group, flash footprint, flash energy, and flash duration are tracked and compared to Harvey's wind‐speeds. Nearly all seven flash characteristics show an increase prior to rapid intensification, with the strongest correlation to intensification found with the rainband lightning spatial characteristics. This research represents a step forward in the application of lightning data that can be used in future studies of tropical cyclone intensification and weakening.

Thermal conductivity enhancement and synergistic heat transfer of z-pin reinforced graphite sheet and carbon fiber hybrid composite

This paper successfully developed a fiber z-pin reinforced graphite sheet (GS) and carbon fiber (CF) hybrid composite laminate. By taking advantages of the superior thermal conductivities of graphite sheet and z-pins, three-dimensional highly conductive paths were constructed to achieve the multifunctions of advanced polymer composites. The effects of ply scheme and z-pin type on the thermal conductivity and heat transfer process of z-pin reinforced GS/CF composites were investigated to reveal the interfacial heat exchange between z-pin and laminas. The results show that both through-thickness and in-plane thermal conductivities are enhanced significantly by implanting through-thickness z-pins in GS/CF composites. This is ascribed to the effective through-thickness conductive paths of z-pins and the synergistic heat transfer of graphite ply and carbon fiber pins. For [GS/CF4/GS]-PAN-pin composite, about 15% laser flash energy transfers through z-pins with a volume fraction of only 2.18%. More obvious heat exchange between z-pins and lamina may be achieved by implanting pitch-based carbon fiber z-pins with higher thermal conductivity and smaller diameter. The resultant through-thickness and in-plane thermal conductivities of [GS/CF4/GS]-pitch-1-pin are measured to be 8.80 W·m−1K−1 and 18.50 W·m−1K−1, which are 13.7 and 8.3 times higher than those of control sample, respectively.

Observations of lightning in relation to transitions in volcanic activity during the 3 June 2018 Fuego Eruption

Satellite and ground-based remote sensing are combined to characterize lightning occurrence during the 3 June 2018 Volcán de Fuego eruption in Guatemala. The combination of the space-based Geostationary Lightning Mapper (GLM) and ground-based Earth Networks Total Lightning Network observed two distinct periods of lightning during this eruption totaling 75 unique lightning flash occurrences over five hours (57 in cloud, 18 cloud-to-ground). The first period of lightning coincided with the rapid growth of the ash cloud, while the second maxima occurred near the time of a deadly pyroclastic density current (PDC) and thunderstorm. Ninety-one percent of the lightning during the event was observed by only one of the lightning sensors, thus showing the importance of combining lightning datasets across multiple frequencies to characterize electrical activity in volcanic eruptions. GLM flashes during the event had a median total optical energy and flash length of 16 fJ, and 12 km, respectively. These median GLM flash energies and lengths observed in the volcanic plume are on the lower end of the flash spectrum because flashes observed in surrounding thunderstorms on 3 June had larger median total optical energy values (130 fJ) and longer median flash lengths (20 km). All 18 cloud-to-ground flashes were negative polarity, supportive of net negative charge within the plume. Mechanisms for the generation of the secondary lightning maxima are discussed based on the presence and potential interaction between ash plume, thunderstorm, and PDC transport during this secondary period of observed lightning.

Nondetection of Radio Emissions From Titan Lightning by Cassini RPWS

AbstractThe Saturn‐orbiting Cassini spacecraft completed 126 close Titan flybys from 2004 until 2017. During almost all of them the Cassini Radio and Plasma Wave Science (RPWS) instrument was turned on to search for radio emissions attributed to Titan lightning. Here we report about their nondetection after close inspection of all Titan flybys throughout the Cassini mission. We also infer new and strong constraints on the permissible flash energy and flash rate of potential Titan lightning. The nondetection of lightning flashes by Cassini observations implies that any lightning on Titan must be either very weak, very rare, or does not exist at all, and the latter could be due to cloud electric fields being too low to initiate a discharge. This finding holds important implications for the prebiotic chemistry of Titan and also implies that lightning will not be a significant hazard to the upcoming Dragonfly mission.

Chemical Modification and Tribological Evaluation of Pure Rice Bran Oil as Base Stocks for Biodegradable Lubricants

Vegetable oils act as a potential base stock for biodegradable lubricants. They possess better biodegradability, high flash point, high viscosity index and excellent lubrication properties. They also have some limitations like low thermal and oxidation stability, poor low-temperature properties and narrow range of viscosities. These limitations can be easily altered by chemically modifying vegetable oils or by using additives into these oils. This research work focused on the chemical modification of pure rice bran oil by epoxidation process. The epoxidized product of rice bran oil was then subjected to ring-opening process using different acids such as butanoic acid, benzoic acid and lauric acid. The tribological properties, flash temperature parameter and energy consumption in a four-ball tester for pure rice bran oil (RBO), epoxidized and ring-opened products of RBO were studied. It was noted that the evaluated properties of chemically modified products of RBO were better compared to pure RBO.

Cooling the Arc Flash Hot Spot

Maximum arc flash energy is seen at the secondary of transformers before the first protective device. Reducing transformer primary protection trip times to cool this “hot spot” starts with quicker tripping on the secondary. Zone selective interlocking (ZSI) is a proven means of avoiding the delays of traditional coordination time intervals but interlocking of all devices within a system can raise concerns about construction and testing complications. How much of an arc flash benefit would it be to interlock only main and tie breakers where interlock capable communication exists for automated transfer scheme functions. To determine benefits, arc flash hazards are first reduced to the extent possible with traditional measures. Communication elements are analyzed to determine those having the speed and reliability required for protection quality interlocking. ZSI is then applied between main and tie breakers to demonstrate how the hazards of the arc flash hot spot can be brought under control.

Analysis of parallel connected Fibonacci switched capacitor converter

Switched capacitor converter (SCC) is a power converter without magnetic components. SCCs have been used in various portable electric products such as flash memories and energy harvesting systems. Conservative SCCs separately charge and discharge their output capacitors during one operating cycle. This operation reduces power efficiencies and increases output ripple voltages. To improve this problem, a parallel connected Fibonacci SCC (PFSCC) was suggested. The symmetric structure of the PFSCC can lead to its better output performance. As a preliminary stage to design a hardware and a controller for the PFSCC, this paper performs an analysis of the PFSCC to derive parameters such as its optimized capacitance and power stage transfer function. Also, simulations and comparisons with 4 different SCCs are conducted to verify its performance.

Assessment of the Quality of Diesel Fuel from Some Selected Filling Stations in Tarkwa, Ghana

Automobile fuel quality is becoming a subject of concern across the world and particularly in Ghana because of potential problems associated with poor quality fuel. Poor quality fuel leads to health and environmental problems, reduced performance and lifetime of engine and other components of an automobile. This paper presents the assessment of the quality of diesel fuel from selected filling stations in Tarkwa. Fifteen fuel samples were collected from Reseller Outlets (Gao Gao), Local Oil Marketing Companies (LOMCs) and International Oil Marketing Companies (IOMCs). Density, flashpoint and sulphur content of the sampled fuels were examined in the laboratory using hydrometer, Cleveland closed cup flash point tester and energy dispersive x-ray fluorescence spectrometer respectively. All the tests were conducted based on the American Standard for Testing Materials (ASTM) and the results were compared with the requirements of Ghana Standards Authority (GSA). The results from the tests indicated variations in the fuel properties among all the oil marketing companies. All the samples tested were found to be within the required density limit set by GSA. Also, about 81% of the fuels had the flashpoint within the required limit. In general, all the diesel samples had high sulphur content above the GSA limit of 0.005 wt% (50 ppm). It is recommended that; the Government of Ghana should ensure that all oil marketing companies operate within the acceptable sulphur content limit in Ghana and should also consider reducing the acceptable sulphur content to meet international standard in the near future.

Geostationary Lightning Mapper Flash Characteristics of Electrified Snowfall Events

Abstract This study examines characteristics of lightning in snowfall events (i.e., thundersnow, TSSN) from the perspective of the Geostationary Lightning Mapper (GLM) and the National Environmental Satellite Data and Information Service (NESDIS) merged Snowfall Rate (mSFR) product. A thundersnow detection algorithm (TDA) was derived from the GLM and mSFR that resulted in a probability of detection (POD) of 66.7% when compared to the aviation routine weather report (METAR) reports of TSSN. However, using the TDA an additional 2175 lightning flashes within detected snowfall were identified that were not observed by the METAR reports, indicating that TSSN has been under reported in previous literature. TSSN flashes observed by GLM have mean flash areas, durations, and total optical energy outputs of 754 km2, 402 ms, and 1342 fJ, which are between the 50th and 99th percentile values for all flashes within the GLM field of view. A comparison with data from the National Lightning Detection Network (NLDN) indicated that the NLDN had at least one cloud or ground flash detection in 1709 of the 2214 flashes observed by GLM in snowfall. An average of 5.85 NLDN flashes was assigned to a single GLM flash when the NLDN flash data were constrained by the GLM flash duration and spatial footprint. Statistically significant (p &amp;lt; 0.01) differences in flash area and flash energy were found between flashes that were observed by the NLDN and those that were not. Additionally, when GLM was combined with the NLDN, at least 11.1% of flashes involved a tall human-made object like an antenna or wind turbine.

Shock Heating Energy of Umbral Flashes Measured with Integral Field Unit Spectroscopy

Abstract Umbral flashes are periodic brightness increases routinely observed in the core of chromospheric lines within sunspot umbrae and are attributed to propagating shock fronts. In this work we quantify the shock heating energy of these umbral flashes using observations in the near-infrared He i triplet obtained on 2014 December 7 with the SpectroPolarimetric Imager for the Energetic Sun, which is a novel integral field unit spectrograph at the Dunn Solar Telescope. We determine the shock properties (the Mach number and the propagation speed) by fitting the measured He i spectral profiles with a theoretical radiative transfer model consisting of two constant-property atmospheric slabs whose temperatures and macroscopic velocities are constrained by the Rankine–Hugoniot relations. From the Mach number, the shock heating energy per unit mass of plasma is derived to be 2 × 1010 erg g−1, which is insufficient to maintain the umbral chromosphere. In addition, we find that the shocks propagate upward with the sound speed and the Mach number does not depend on the temperature upstream of the shocks. The latter may imply suppression of the amplification of the Mach number due to energy loss of the shocks.