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1
He, Junping, Yujin Liu, Cong Wang, and Lingling Cao. "Magnetic Coupling Common Mode Conducted EMI Analysis and Improvement in a Boost Converter." World Electric Vehicle Journal 12, no. 4 (November 9, 2021): 225. http://dx.doi.org/10.3390/wevj12040225.
Повний текст джерелаАнотація:
Common mode (CM) electromagnetic interference (EMI) has been a difficult subject in electromagnetic compatibility (EMC) analysis and design of power converters for electric vehicles (EV) because of its complex formation mechanism and hidden propagation path. This paper studies a new mechanism of CM conducted emission caused by the leakage flux of a toroidal inductor in the main circuit of a boost DC/DC converter. The stray magnetic source and the CM inducted loops are firstly identified out by simulation analysis and experiments. Then a comprehensive conducted emission circuit model including magnetic coupling parameters is built to explain this CM EMI formation mechanism. Finally, several effective magnetic coupling suppression methods are proposed and verified, such as changing the installation angle of the inductor and the shape of the magnetic core. The research results are helpful to the EMC understanding and design of power electronic converters.
2
Zarei, Seyed Fariborz, and Saeed Khankalantary. "A Simplified Frequency Model for Industrial Common-Mode Chocks Used in High-Power Converters." Journal of Electromagnetic Engineering and Science 21, no. 1 (January 31, 2021): 15–22. http://dx.doi.org/10.26866/jees.2021.21.1.15.
Повний текст джерелаАнотація:
This paper proposes a simplified analytical model for electromagnetic interference (EMI) filters used in high-power converters. Highpower converters produce radio frequency conducted noise because they use high-frequency switching in the range of a few kHz to tens of kHz. The noise propagates into the power grid, which disturbs the functionality of the radio frequency apparatuses. Well-known standards, such as CISPR, provide the measurement and assessment methodologies for these devices. Moreover, the emission level of the noise is restricted at the source side. Using EMI filters is the most effective approach for dealing with this issue. However, due to the nonlinear nature of the common-mode (CM) cores, the modeling of the cores is a complicated task, which makes the selection and design of the filters less than optimal. In this paper, an analytical modeling of the CM filters is provided to suit the nonlinear frequency-dependent behavior of the CM cores. The simplicity of the proposed model makes it a very suitable choice for inclusion in the design procedures, which results in a more accurate and optimum filter selection among the many available commercial industrial filters. To validate the proposed model, the frequency-dependent model obtained is verified by experimental tests with a commercial CM choke. According to the results, the proposed model accurately describes the actual EMI filter behavior.
3
An, Zong Yu, Quan Di Wang, and Ya Li Zheng. "Conducted EMI Noise Prediction in DC Converter System for Electric Vehicle Application." Applied Mechanics and Materials 325-326 (June 2013): 486–89. http://dx.doi.org/10.4028/www.scientific.net/amm.325-326.486.
Повний текст джерелаАнотація:
In this paper, common mode (CM) conducted perturbations are predicted and compared with experiments in a full-bridge transformer-isolated buck converter system, thanks to a complex approach based on experimental measurements and on the modeling of the complete equivalent circuit. Its different part are considered and represented by a circuit of lumped parameters. Simulation and experiment of CM emission in the conducted frequency range (150 kHz-30 MHz) are compared. It is shown that the CM emission in the system can be calculated by the proposed model, and experiment has successfully confirmed this approach.
4
Kołodziejski, Wojciech, Stanisław Kuta, and Jacek Jasielski. "Open-Loop Class-BD Audio Amplifiers with Balanced Common-Mode Output." Electronics 10, no. 12 (June 9, 2021): 1381. http://dx.doi.org/10.3390/electronics10121381.
Повний текст джерелаАнотація:
This paper presents new architectures and implementations of original open-loop Class-BD audio amplifiers with balanced Common-Mode output. The output stage of each proposed amplifier includes the typical H-bridge with four MOSFETs and four additional MOSFET switches that balance and keep the Common-Mode output constant. The presented amplifiers employ the extended NBDD PWM or PSC PWM modulation scheme. When the output stage is built only on NMOSFET transistors, gate drivers require a floating power supply, using a self-boost charge pump with capacitive isolation of the control signal. The use of complementary MOSFETs in the output stage greatly simplifies gate control systems. The proposed amplifiers were compared to the typical Class-BD configuration, using the optimal NBDD modulation with respect to audio performance of the Differential-Mode (DM) and Common-Mode (CM) outputs. Basic SPICE simulations and experimental studies have shown that the proposed Class-BD amplifiers have similar audio performance to the prototype with the optimal NBDD modulation scheme, while at the same time having a balanced constant voltage CM output, thus eliminating the main contributor to radiation emission. As a result, the filtering of the DM output signals can be greatly simplified, while the filtering of the CM output signals can be theoretically eliminated. Practically, due to the timing errors added by the gate drivers, spikes are generated at the CM output, which are very easy to filter out by the reduced LC output filter, even at very low L.
5
Jia, Xiaoyu. "Influence of System Layout on CM EMI Noise of SiC Electric Vehicle Powertrains." CPSS Transactions on Power Electronics and Applications 6, no. 4 (December 2021): 298–309. http://dx.doi.org/10.24295/cpsstpea.2021.00028.
Повний текст джерелаАнотація:
This paper investigates the influences of system layout on common mode (CM) EMI noise of an electric vehicle (EV) powertrain with a traction inverter using silicon carbide (SiC) MOSFETs. First, a system level conducted EMI model for the whole SiC EV powertrain is presented, which includes a battery pack, DC cables, a SiC inverter, AC cables, and a PMSM. Then, the impacts of system layout, such as the AC cable length, the AC cable type, and the DC cable type (shielded cable and unshielded cable) on CM EMI noise are analyzed through time domain simulations of the system level conducted EMI model. Next, a conducted EMI emission test-bed for a SiC EV powertrain is built. Finally, experiments on the test-bed are carried out to verify the influences of system layout on CM EMI noise in the SiC EV powertrain.
6
Tramonte, Denis, Yin-Zhe Ma, Yi-Chao Li, and Lister Staveley-Smith. "Searching for H i imprints in cosmic web filaments with 21-cm intensity mapping." Monthly Notices of the Royal Astronomical Society 489, no. 1 (August 5, 2019): 385–400. http://dx.doi.org/10.1093/mnras/stz2146.
Повний текст джерелаАнотація:
ABSTRACT We investigate the possible presence of neutral hydrogen (H i) in intergalactic filaments at very low redshift (z ∼ 0.08), by stacking a set of 274 712 2dFGRS galaxy pairs over 21-cm maps obtained with dedicated observations conducted with the Parkes radio telescope, over a total sky area of approximately 1300 deg2 covering two patches in the northern and in the southern Galactic hemispheres. The stacking is performed by combining local maps in which each pair is brought to a common reference frame; the resulting signal from the edge galaxies is then removed to extract the filament residual emission. We repeat the analysis on maps cleaned removing either 10 or 20 foreground modes in a principal component analysis. Our study does not reveal any clear H i excess in the considered filaments in either case; we determine upper limits on the total filament H i brightness temperature at $T_{\rm b} \lesssim 10.3 \, \mu \text{K}$ for the 10-mode and at $T_{\rm b} \lesssim 4.8 \, \mu \text{K}$ for the 20-mode removed maps at the 95 per cent confidence level. These estimates translate into upper limits for the local filament H i density parameter, $\Omega _{\rm HI}^{\rm (f)} \lesssim 7.0\times 10^{-5}$ and $\Omega _{\rm HI}^{\rm (f)} \lesssim 3.2\times 10^{-5}$, respectively, and for the H i column density, $N_{\rm HI} \lesssim 4.6\times 10^{15}\, \text{cm}^{-2}$ and $N_{\rm HI} \lesssim 2.1\times 10^{15}\, \text{cm}^{-2}$, respectively. These column density constraints are consistent with previous detections of H i in the warm-hot intergalactic medium obtained observing broad Ly α absorption systems. This work shows for the first time how such constraints can be achieved using the stacking of galaxy pairs on 21-cm maps.
7
Zhao, Yuanhong, Marielle Saunois, Philippe Bousquet, Xin Lin, Antoine Berchet, Michaela I. Hegglin, Josep G. Canadell, et al. "Inter-model comparison of global hydroxyl radical (OH) distributions and their impact on atmospheric methane over the 2000–2016 period." Atmospheric Chemistry and Physics 19, no. 21 (November 13, 2019): 13701–23. http://dx.doi.org/10.5194/acp-19-13701-2019.
Повний текст джерелаАнотація:
Abstract. The modeling study presented here aims to estimate how uncertainties in global hydroxyl radical (OH) distributions, variability, and trends may contribute to resolving discrepancies between simulated and observed methane (CH4) changes since 2000. A multi-model ensemble of 14 OH fields was analyzed and aggregated into 64 scenarios to force the offline atmospheric chemistry transport model LMDz (Laboratoire de Meteorologie Dynamique) with a standard CH4 emission scenario over the period 2000–2016. The multi-model simulated global volume-weighted tropospheric mean OH concentration ([OH]) averaged over 2000–2010 ranges between 8.7×105 and 12.8×105 molec cm−3. The inter-model differences in tropospheric OH burden and vertical distributions are mainly determined by the differences in the nitrogen oxide (NO) distributions, while the spatial discrepancies between OH fields are mostly due to differences in natural emissions and volatile organic compound (VOC) chemistry. From 2000 to 2010, most simulated OH fields show an increase of 0.1–0.3×105 molec cm−3 in the tropospheric mean [OH], with year-to-year variations much smaller than during the historical period 1960–2000. Once ingested into the LMDz model, these OH changes translated into a 5 to 15 ppbv reduction in the CH4 mixing ratio in 2010, which represents 7 %–20 % of the model-simulated CH4 increase due to surface emissions. Between 2010 and 2016, the ensemble of simulations showed that OH changes could lead to a CH4 mixing ratio uncertainty of >±30 ppbv. Over the full 2000–2016 time period, using a common state-of-the-art but nonoptimized emission scenario, the impact of [OH] changes tested here can explain up to 54 % of the gap between model simulations and observations. This result emphasizes the importance of better representing OH abundance and variations in CH4 forward simulations and emission optimizations performed by atmospheric inversions.
8
Pringle, K. J., K. S. Carslaw, T. Fan, G. W. Mann, A. Hill, P. Stier, K. Zhang, and H. Tost. "A multi-model assessment of the efficacy of sea spray geoengineering." Atmospheric Chemistry and Physics Discussions 12, no. 3 (March 9, 2012): 7125–66. http://dx.doi.org/10.5194/acpd-12-7125-2012.
Повний текст джерелаАнотація:
Abstract. Artificially increasing the albedo of marine clouds by the mechanical emission of sea spray aerosol has been proposed as a geoengineering technique to slow the warming caused by anthropogenic greenhouse gases. A previous global model study found that only modest increases and sometimes even decreases in cloud drop number (CDN) concentrations would result from plausible emission scenarios. Here we extend that work to examine the conditions under which decreases in CDN can occur, and use three independent global models to quantify maximum achievable CDN changes. We find that decreases in CDN can occur when at least three of the following conditions are met: the injected particle number is <100 cm−3, the injected diameter is >250–300 nm, the background aerosol loading is large (≥150 cm−3) and the in-cloud updraught velocity is low (<0.2 ms−1). With lower background loadings and/or increased updraught velocity, significant increases in CDN can be achieved. None of the global models predict a decrease in CDN as a result of geoengineering, although there is considerable diversity in the calculated efficiency of geoengineering, which arises from the diversity in the simulated background aerosol distributions. All three models show a small dependence of geoengineering efficiency on the injected particle size and the geometric standard deviation of the injected mode. However, the achievability of significant cloud drop enhancements is strongly dependent on the cloud updraught speed. With an updraught speed of 0.1 ms−1 a global mean CDN of 375 cm−3 (previously estimated to cancel the forcing caused by CO2 doubling) is achievable in only about 50 % of cloudy grid boxes irrespective of the amount of aerosol injected. But at 0.2 ms−1 a CDN of 375−3 becomes achievable everywhere. Updraught speeds of less than 0.2 ms−1 are common in low-level clouds. Thus, a cloud drop concentration of 375 cm−3 cannot be attained uniformly, regardless of the number of injected particles.
9
Hussein, Tareq, Omar Al-Jaghbeer, Nizar Bqour, Bilal Zidan, and Bashar Lahlouh. "Exposure to Aerosols Emitted from Common Heating Combustion Sources Indoors—The Jordanian Case as an Example for Eastern Mediterranean Conditions." Atmosphere 13, no. 6 (May 25, 2022): 870. http://dx.doi.org/10.3390/atmos13060870.
Повний текст джерелаАнотація:
In Jordan, ~61% of total residential energy consumption is consumed by heating spaces using portable kerosene (K) and liquified petroleum gas (LPG) heaters. Here, we evaluated the indoor air quality (IAQ) versus the use of K and LPG heaters inside a test room reflecting the typical conditions of Jordanian dwellings during the winter season. The experimental setup included particle size distribution (diameter 0.01–25 µm) measurements, and we utilized a simple sectional indoor aerosol model (SIAM) to estimate the emission rate and lifetime of the combustion products in the test room. The particle number (PN) concentration during the LPG operation was 6 × 104–5.9 × 105 cm−3, depending on the setting at minimum, medium, or maximum. The K heater operation increased with the PN concentrations to a range of 4 × 105–8 × 105 cm−3. On average, the particle losses were 0.7–1.6 h−1 for micron particles (1–10 µm) and 0.8–0.9 h−1 for ultrafine particles (<0.1 µm). The emission rate from the LPG heater was 1.2 × 1010–2.8 × 1010 particles/s (6.6 × 106–8.0 × 106 particles/J), and that for the K heater was about 4.4 × 1010 particles/s (1.9 × 107 particles/J). The results call for the immediate need to apply interventions to improve the IAQ by turning to cleaner heating processes indoors.
10
Ptak, A., P. Serlemitsos, T. Yaqoob, R. Mushotzky, Y. Terashima, and H. Kunieda. "3.10. X-ray constraints on accretion and starburst processes in galactic nuclei." Symposium - International Astronomical Union 184 (1998): 109–10. http://dx.doi.org/10.1017/s0074180900084230.
Повний текст джерелаАнотація:
Although the galaxies in our sample are heterogenous in their optical classifications (LLAGN: M51, NGC 3147, NGC 4258; LINER: NGC 3079, NGC 3310, NGC 3998, NGC 4579, NGC 4594; starburst: M82, NGC 253, NGC 3628, NGC 6946), they are fit well by a “canonical” spectrum with a hot, optically-thin thermal component with T ~ 8 × 106 K and an absorbed (NH ~ 1022 cm−2) power-law with an energy index α ~ 0.7–0.8. Both the “soft” component, most likely due to SN or superwind-heated ISM, and the “hard” power-law, most likely due to a micro-AGN and/or blackhole candidates, appear to be common in low-activity galaxies. If the soft component is associated with a superwind outflow, than ~ 10% of the X-ray emission is due to “swept-up” ISM rather than superwind emission. The abundance of Fe relative to α-process elements tends to be sub-solar, possibly due to dust-depletion and/or type-II SN enrichment. The lack of short-term variability in the hard component suggests that if it is due to an AGN, then the mode of accretion is probably fundamentally different from “normal” Seyfert galaxies.
11
Guyon, P., G. P. Frank, M. Welling, D. Chand, P. Artaxo, L. Rizzo, G. Nishioka, et al. "Airborne measurements of trace gas and aerosol particle emissions from biomass burning in Amazonia." Atmospheric Chemistry and Physics 5, no. 11 (November 8, 2005): 2989–3002. http://dx.doi.org/10.5194/acp-5-2989-2005.
Повний текст джерелаАнотація:
Abstract. As part of the LBA-SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke, Aerosols, Clouds, Rainfall, and Climate) 2002 campaign, we studied the emission of carbon monoxide (CO), carbon dioxide (CO2), and aerosol particles from Amazonian deforestation fires using an instrumented aircraft. Emission ratios for aerosol number (CN) relative to CO (ERCN/CO) fell in the range 14-32 cm-3 ppb-1 in most of the investigated smoke plumes. Particle number emission ratios have to our knowledge not been previously measured in tropical deforestation fires, but our results are in agreement with values usually found from tropical savanna fires. The number of particles emitted per amount biomass burned was found to be dependent on the fire conditions (combustion efficiency). Variability in ERCN/CO between fires was similar to the variability caused by variations in combustion behavior within each individual fire. This was confirmed by observations of CO-to-CO2 emission ratios (ERCO/CO2), which stretched across the same wide range of values for individual fires as for all the fires observed during the sampling campaign, reflecting the fact that flaming and smoldering phases are present simultaneously in deforestation fires. Emission factors (EF) for CO and aerosol particles were computed and a correction was applied for the residual smoldering combustion (RSC) fraction of emissions that are not sampled by the aircraft, which increased the EF by a factor of 1.5-2.1. Vertical transport of smoke from the boundary layer (BL) to the cloud detrainment layer (CDL) and the free troposphere (FT) was found to be a very common phenomenon. We observed a 20% loss in particle number as a result of this vertical transport and subsequent cloud processing, attributable to in-cloud coagulation. This small loss fraction suggests that this mode of transport is very efficient in terms of particle numbers and occurs mostly via non-precipitating clouds. The detrained aerosol particles released in the CDL and FT were larger than in the unprocessed smoke, mostly due to coagulation and secondary growth, and therefore more efficient at scattering radiation and nucleating cloud droplets. This process may have significant atmospheric implications on a regional and larger scale.
12
Antivachis, Michael. "Input/Output EMI Filter Design for Three-Phase Ultra-High Speed Motor Drive GaN Inverter Stage." CPSS Transactions on Power Electronics and Applications 6, no. 1 (March 2021): 74–92. http://dx.doi.org/10.24295/cpsstpea.2021.00007.
Повний текст джерелаАнотація:
Pairing wide-bandgap (WBG) inverters with high-speed motors results in compact and effi cient motor drives, but requires special attention on electromagnetic interference (EMI) aspects. This paper focuses on electromagnetic compatibility (EMC) of high-speed motor drives, supplied by a DC source. In order to protect the nearby equipment from the EMI noise of the WBG inverter, a fi lter that complies with conducted EMI regulations is placed at the inverter DC input-side. However, there is no clear mandate requiring from inverters to comply with conducted EMI regulations at the AC output-side, where only the motor is placed. For this reason, there is no full consensus whether it is necessary to use an output fi lter, and if so, what type of output fi lter would be suitable, i.e., if differential-mode (DM), common-mode (CM) or both DM/CM output fi lter would fi t best. A full sine-wave output fi lter (FSF) is proposed in this paper, that features both DM and CM attenuation, and capacitors connected to the DC link. Besides the several well established benefi ts of a FSF, such as purely sinusoidal motor currents and the protection of the motor against high du/dt originating from the fast switching of the semiconductor devices, a FSF at the inverter output-side, also reduces the CM EMI emissions at the inverter input-side. Namely, since the inverter housing, the motor housing and the interconnecting shielded cable are all grounded, CM emissions generated at the inverter output-side are directly mapped to the inverter input-side, i.e., there is an input-to-output CM noise interrelation. A FSF reduces the output-side CM EMI emissions and thus mitigates the input-to-output CM noise mutual influence. Two types of FSF (c-FSF and d-FSF) are comparatively evaluated, in terms of volume, losses and EMI performance. The theoretical consideration are tested within the context of a high-speed 280 krpm, 1 kW motor drive, with 80 V DC supply. The experimental results validate the good performance of the proposed filter concept.
13
Guyon, P., G. Frank, M. Welling, D. Chand, P. Artaxo, L. Rizzo, G. Nishioka, et al. "Airborne measurements of trace gas and aerosol particle emissions from biomass burning in Amazonia." Atmospheric Chemistry and Physics Discussions 5, no. 3 (May 9, 2005): 2791–831. http://dx.doi.org/10.5194/acpd-5-2791-2005.
Повний текст джерелаАнотація:
Abstract. As part of the LBA-SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia – Smoke, Aerosols, Clouds, Rainfall, and Climate) 2002 campaign, we studied the emission of carbon monoxide (CO), carbon dioxide (CO2), and aerosol particles from Amazonian deforestation fires using an instrumented aircraft. Emission ratios for aerosol number (CN) relative to CO (ERCN/CO) fell in the range 14–32 cm-3 ppb-1 for most of the time, in agreement with values usually found from tropical savanna fires. The number of particles emitted per amount biomass burned was found to be dependant on the fire condition (combustion efficiency). Variability in the ERCN/CO between fires was similar to the variability caused by variations in combustion behavior within each individual fire. This was confirmed by observations of CO-to-CO2 emission ratios (ERCO/CO2), which stretched across the same wide range of values for individual fires as for all the fires observed during the sampling campaign, indicating that flaming and smoldering phases are present simultaneously in deforestation fires. Emission factors (EF) for CO and aerosol particles were computed and a correction was applied for the residual smoldering combustion (RSC) fraction of emissions that are not sampled by the aircraft. The correction, previously unpublished for tropical deforestation fires, suggested an EF about one and a half to twice as large for these species. Vertical transport of biomass-burning plumes from the boundary layer (BL) to the cloud detrainment layer (CDL) and the free troposphere (FT) was found to be a very common phenomenon. We observed a 20% loss in particle number as a result of this vertical transport and subsequent cloud processing, attributable to in-cloud coagulation. This small loss fraction suggests that this mode of transport is very efficient in terms of particle numbers and occurs mostly via non-precipitating clouds. The detrained aerosol particles released in the CDL and FT were larger due to coagulation and secondary growth, and therefore more efficient at scattering radiation and nucleating cloud droplets than the fresh particles. This process may have significant atmospheric implications on a regional and larger scale.
14
Gezari, D. Y., M. D. Thornley, S. R. Heap, S. N. Shore, F. Varosi, S. J. Meatheringham та S. P. Maran. "NGC 7027: New 7.8–20.0 μm Array Camera and Hα/Hβ CCD Image Analysis of Dust, PAH and Ionized Gas Distribution". Symposium - International Astronomical Union 155 (1993): 230. http://dx.doi.org/10.1017/s0074180900170925.
Повний текст джерелаАнотація:
Infrared array camera images of the planetary nebula NGC7027 at seven wavelenghts between 7.8 and 20μm taken at the IRTF telescope are compared to Hα and Hβ images obtained at the CFHT, and published 2-, 6-, and 20-cm VLA maps, all made with better than ∼ 1 arcsec resolution. The mid-infrared images have also been deconvolved using the Maximum Residual Likelihood algorithm to show structural details on the ∼ 0.3 arcsec scale. The visible, infrared and radio images are aligned with ±0.2 arcsec astrometric precision using common features and visible stars. Image algebra can then be readily performed. The images are analysed to determine the spatial distribution of poly cyclic aromatic hydrocarbon (PAH) grains and ionized gas relative to the continuum dust emission. The results show the extent of the mid-infrared dust continuum, the PAH emission features at 8.65 and 11.25μm, and would reveal any contribution from 9.8 μm “silicate” emission. The optically thicker 20-cm emission more closely resembles the extinction-corrected Hα distribution. The large grains giving rise to the visible extinction (derived from the Hα/Hβ ratio) are distribued differently from the mid-infrared and ionized gaz, indicating the location of the outer cold dust. The 11.6μm image could contain both PAH and continuum grain emission, and we have attempted to separate the two components. It appears that the overall emission distributions are quite similar for all the infrared wavelengths, so the various dust constituents are generally uniformly mixed. However there are indications that the 11.6μm PAH emission distribution is patchy and not identical to the continuum dust, although not distinctly different in radial distance from the center. The ionized gas distribution peaks inside that of the dust continuum. The visible/infrared/radio spatial analysis, and color indices calculated from the infrared images, are used to develop a detailed new morphological model of NGC7027 based on this comprehensive multi-wavelength data set.
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Pseftogkas, Andreas, Maria-Elissavet Koukouli, Ioanna Skoulidou, Dimitrios Balis, Charikleia Meleti, Trissevgeni Stavrakou, Luigi Falco, et al. "A New Separation Methodology for the Maritime Sector Emissions over the Mediterranean and Black Sea Regions." Atmosphere 12, no. 11 (November 8, 2021): 1478. http://dx.doi.org/10.3390/atmos12111478.
Повний текст джерелаАнотація:
The aim of this paper is to apply a new lane separation methodology for the maritime sector emissions attributed to the different vessel types and marine traffic loads in the Mediterranean and the Black Sea defined via the European Marine and Observation Data network (EMODnet), developed in 2016. This methodology is implemented for the first time on the Copernicus Atmospheric Monitoring Service Global Shipping (CAMS-GLOB-SHIP v2.1) nitrogen oxides (NOX) emissions inventory, on the Sentinel-5 Precursor Tropospheric Monitoring Instrument (TROPOMI) nitrogen dioxide (NO2) tropospheric vertical column densities, and on the LOTOS-EUROS (Long Term Ozone Simulation—European Operational Smog) CTM (chemical transport model) simulations. By applying this new EMODnet-based lane separation method to the CAMS-GLOB-SHIP v2.1 emission inventory, we find that cargo and tanker vessels account for approximately 80% of the total emissions in the Mediterranean, followed by fishing, passenger, and other vessel emissions with contributions of 8%, 7%, and 5%, respectively. Tropospheric NO2 vertical column densities sensed by TROPOMI for 2019 and simulated by the LOTOS-EUROS CTM have been successfully attributed to the major vessel activities in the Mediterranean; the mean annual NO2 load of the observations and the simulations reported for the entire maritime EMODnet-reported fleet of the Mediterranean is in satisfactory agreement, 1.26 ± 0.56 × 1015 molecules cm−2 and 0.98 ± 0.41 × 1015 molecules cm−2, respectively. The spatial correlation of the annual maritime NO2 loads of all vessel types between observation and simulation ranges between 0.93 and 0.98. On a seasonal basis, both observations and simulations show a common variability. The wintertime comparisons are in excellent agreement for the highest emitting sector, cargo vessels, with the observations reporting a mean load of 0.98 ± 0.54 and the simulations of 0.81 ± 0.45 × 1015 molecules cm−2 and correlation of 0.88. Similarly, the passenger sector reports 0.45 ± 0.49 and 0.39 ± 0.45 × 1015 molecules cm−2 respectively, with correlation of 0.95. In summertime, the simulations report a higher decrease in modelled tropospheric columns than the observations, however, still resulting in a high correlation between 0.85 and 0.94 for all sectors. These encouraging findings will permit us to proceed with creating a top-down inventory for NOx shipping emissions using S5P/TROPOMI satellite observations and a data assimilation technique based on the LOTOS-EUROS chemical transport model.
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Zhang, J., A. D. Liu, C. Zhou, G. Zhuang, W. X. Ding, G. H. Hu, G. S. Xu, et al. "Determination of the radial position of zero density for profile reflectometry on experimental advanced superconducting tokamak." Journal of Instrumentation 18, no. 01 (January 1, 2023): T01001. http://dx.doi.org/10.1088/1748-0221/18/01/t01001.
Повний текст джерелаАнотація:
Abstract The Experimental Advanced Superconducting Tokamak (EAST) reflectometry is a Frequency-Modulated Continuous-Wave monostatic system with the transmission lines similar to the ITER reflectometer design. One of the most significant and common problems for reflectometry to reconstruct the density profile is the determination of initialization, i.e. zero density position (R start), which could be determined by the extraordinary mode (X-mode) reflectometry. The main source of noise still comes from the wave scattering of plasmas despite the sweeping period of around 10 microseconds. It is found that to reduce the random noise of R start, averaging on 25 periods is the optimal solution. During the L-mode discharges with only lower hybrid wave (LHW) heating, R start would move outwards and its fluctuation and the high frequency components of turbulence around R start would be obviously increased when the 2.45 GHz system is switched on, while no obvious change is observed in the 4.6 GHz case. These phenomena are consistent with that 2.45 GHz LHW has less current drive ability than 4.6 GHz LHW on EAST. During ELMy H-mode, the peak of R start is consistent with Deuterium signal and the maximum displacement is about 3 cm. The comparison of density profiles from reflectometry and Lithium beam emission spectroscopy (Li-BES) suggests that setting the density at R start to (4 ± 2)× 1017 m-3 is much better than zero, while this value is somewhat empirical and closely related to the amplitude threshold for determining the first probing frequency corresponding to R start.
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Vollmer, B., M. Soida, R. Beck, and M. Powalka. "Deciphering the radio star formation correlation on kpc scales." Astronomy & Astrophysics 633 (January 2020): A144. http://dx.doi.org/10.1051/0004-6361/201935923.
Повний текст джерелаАнотація:
One of the tightest correlations in astronomy is the relation between the integrated radio continuum and the far-infrared (FIR) emission. Within nearby galaxies, variations in the radio–FIR correlation have been observed, mainly because the cosmic ray electrons migrate before they lose their energy via synchrotron emission or escape. The major cosmic-ray electron transport mechanisms within the plane of galactic disks are diffusion, and streaming. A predicted radio continuum map can be obtained by convolving the map of cosmic-ray electron sources, represented by that of the star formation, with adaptive Gaussian and exponential kernels. The ratio between the smoothing lengthscales at 6 cm and 20 cm can be used to determine, between diffusion and streaming, which is the dominant transport mechanism. The dependence of the smoothing lengthscale on the star formation rate bears information on the dependence of the magnetic field strength, or the ratio between the ordered and turbulent magnetic field strengths on star formation. Star formation maps of eight rather face-on local and Virgo cluster spiral galaxies were constructed from Spitzer and Herschel infrared and GALEX UV observations. These maps were convolved with adaptive Gaussian and exponential smoothing kernels to obtain model radio continuum emission maps. It was found that in asymmetric ridges of polarized radio continuum emission, the total power emission is enhanced with respect to the star formation rate. At a characteristic star formation rate of $ \dot{\Sigma}_*=8 \times 10^{-3}\,M_{\odot} $ yr−1 kpc−2, the typical lengthscale for the transport of cosmic-ray electrons is l = 0.9 ± 0.3 kpc at 6 cm, and l = 1.8 ± 0.5 kpc at 20 cm. Perturbed spiral galaxies tend to have smaller lengthscales. This is a natural consequence of the enhancement of the magnetic field caused by the interaction. The discrimination between the two cosmic-ray electron transport mechanisms, diffusion, and streaming is based on (i) the convolution kernel (Gaussian or exponential); (ii) the dependence of the smoothing kernel on the local magnetic field, and thus on the local star formation rate; (iii) the ratio between the two smoothing lengthscales via the frequency dependence of the smoothing kernel, and (iv) the dependence of the smoothing kernel on the ratio between the ordered and the turbulent magnetic field. Based on our empirical results, methods (i) and (ii) cannot be used to determine the cosmic ray transport mechanism. Important asymmetric large-scale residuals and a local dependence of the smoothing length on Bord/Bturb are most probably responsible for the failure of methods (i) and (ii), respectively. On the other hand, the classifications based on l6 cm/l20 cm (method iii) and Bord/Bturb (method iv), are well consistent and complementary. We argue that in the six Virgo spiral galaxies, the turbulent magnetic field is globally enhanced in the disk. Therefore, the regions where the magnetic field is independent of the star formation rate are more common. In addition, Bord/Bturb decreases, leading to a diffusion lengthscale that is smaller than the streaming lengthscale. Therefore, cosmic ray electron streaming dominates in most of the Virgo spiral galaxies.
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Varajão, Diogo, Rui Esteves Araújo, Luís Miranda, and João Peças Lopes. "EMI Filter Design for a Single-stage Bidirectional and Isolated AC–DC Matrix Converter." Electronics 7, no. 11 (November 12, 2018): 318. http://dx.doi.org/10.3390/electronics7110318.
Повний текст джерелаАнотація:
This paper describes the design of an electromagnetic interference (EMI) filter for the high-frequency link matrix converter (HFLMC). The proposed method aims to systematize the design process for pre-compliance with CISPR 11 Class B standard in the frequency range 150 kHz to 30 MHz. This approach can be extended to other current source converters which allows time-savings during the project of the filter. Conducted emissions are estimated through extended simulation and take into account the effect of the measurement apparatus. Differential-mode (DM) and common-mode (CM) filtering stages are projected separately and then integrated in a synergistic way in a single PCB to reduce volume and weight. A prototype of the filter was constructed and tested in the laboratory. Experimental results with the characterization of the insertion losses following the CISPR 17 standard are provided. The attenuation capability of the filter was demonstrated in the final part of the paper.
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Kawamuro, Taiki, Claudio Ricci, Masatoshi Imanishi, Richard F. Mushotzky, Takuma Izumi, Federica Ricci, Franz E. Bauer, et al. "BASS XXXII: Studying the Nuclear Millimeter-wave Continuum Emission of AGNs with ALMA at Scales ≲100–200 pc." Astrophysical Journal 938, no. 1 (October 1, 2022): 87. http://dx.doi.org/10.3847/1538-4357/ac8794.
Повний текст джерелаАнотація:
Abstract To understand the origin of nuclear (≲100 pc) millimeter-wave (mm-wave) continuum emission in active galactic nuclei (AGNs), we systematically analyzed subarcsecond resolution Band-6 (211–275 GHz) Atacama Large Millimeter/submillimeter Array data of 98 nearby AGNs (z < 0.05) from the 70 month Swift/BAT catalog. The sample, almost unbiased for obscured systems, provides the largest number of AGNs to date with high mm-wave spatial resolution sampling (∼1–200 pc), and spans broad ranges of 14–150 keV luminosity { 40 < log [ L 14 − 150 / ( erg s − 1 ) ] < 45 }, black hole mass [ 5 < log ( M BH / M ⊙ ) < 10 ], and Eddington ratio ( − 4 < log λ Edd < 2 ). We find a significant correlation between 1.3 mm (230 GHz) and 14–150 keV luminosities. Its scatter is ≈0.36 dex, and the mm-wave emission may serve as a good proxy of the AGN luminosity, free of dust extinction up to N H ∼ 1026 cm−2. While the mm-wave emission could be self-absorbed synchrotron radiation around the X-ray corona according to past works, we also discuss different possible origins of the mm-wave emission: AGN-related dust emission, outflow-driven shocks, and a small-scale (<200 pc) jet. The dust emission is unlikely to be dominant, as the mm-wave slope is generally flatter than expected. Also, due to no increase in the mm-wave luminosity with the Eddington ratio, a radiation-driven outflow model is possibly not the common mechanism. Furthermore, we find independence of the mm-wave luminosity on indicators of the inclination angle from the polar axis of the nuclear structure, which is inconsistent with a jet model whose luminosity depends only on the angle.
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Martone, R., C. Guidorzi, R. Margutti, L. Nicastro, L. Amati, F. Frontera, M. Marongiu, M. Orlandini та E. Virgilli. "A cumulative search for hard X/γ-ray emission associated with fast radio bursts in Fermi/GBM data". Astronomy & Astrophysics 631 (22 жовтня 2019): A62. http://dx.doi.org/10.1051/0004-6361/201936284.
Повний текст джерелаАнотація:
Context. Fast radio bursts (FRBs) are millisecond-long bursts uniquely detected at radio frequencies. FRB 131104 is the only case for which a γ-ray transient positionally and temporally consistent was claimed. This high-energy transient had a duration of ∼400 s and a 15–150 keV fluence Sγ ∼ 4 × 10−6 erg cm−2. However, the association with the FRB is still debated. Aims. We aim at testing the systematic presence of an associated transient high-energy counterpart throughout a sample of the FRB population. Methods. We used an approach like that used in machine learning methodologies to accurately model the highly-variable Fermi/GBM instrumental background on a time interval comparable to the duration of the proposed γ-ray counterpart of FRB 131104. A possible γ-ray signal is then constrained considering sample average lightcurves. Results. We constrain the fluence of the possible γ-ray signal in the 8–1000 keV band down to 6.4 × 10−7 (7.1 × 10−8) erg cm−2 for a 200-s (1-s) integration time. Furthermore, we found the radio-to-gamma fluence ratio to be η > 108 Jy ms erg−1 cm2. Conclusions. Our fluence limits exclude ∼94% of Fermi/GBM detected long gamma-ray bursts and ∼96% of Fermi/GBM detected short gamma-ray bursts. In addition, our limits on the radio-to-gamma fluence ratio point to a different emission mechanism from that of magnetar giant flares. Finally, we exclude a γ-ray counterpart as fluent as the one possibly associated with FRB 131104 to be a common feature of FRBs.
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Olofsson, H., J. H. Black, T. Khouri, W. H. T. Vlemmings, E. M. L. Humphreys, M. Lindqvist, M. Maercker, L. Nyman, S. Ramstedt, and D. Tafoya. "Heavy-element Rydberg transition line emission from the post-giant-evolution star HD 101584." Astronomy & Astrophysics 651 (July 2021): A35. http://dx.doi.org/10.1051/0004-6361/202140537.
Повний текст джерелаАнотація:
Context. We report the detection of two lines at millimetre wavelengths towards the immediate surroundings of the post-giant and most likely post-common-envelope star HD 101584 using high-angular-resolution ALMA observations. The circumstellar environment of this object is rich in different molecular species, but we find no viable identifications in terms of molecular lines. Aims. We aim to determine whether or not these lines can be attributed to the Rydberg transitions – X30α and X26α – of neutral atoms of elements heavier than carbon. Methods. A simple model in strict local thermodynamic equilibrium for a warm-gas environment of the moderate-temperature star (Teff ≈ 8500 K) was constructed to corroborate our findings. A geometrically thin, disc-like geometry seen face-on was chosen and a distance of 1 kpc. Results. The observed flux densities of the lines and the continuum at 232 and 354 GHz can be reproduced using ≈10−3 M⊙ of gas at a temperature of ≈2800 K and a hydrogen density of ≈1012 cm−3, assuming solar abundances for the elements. The gas lies within a distance of about 5 au from the star (assuming a distance of 1 kpc). The ionisation fraction is low, ≈3 × 10−5. The origin of such a region is not clear, but it may be related to a common-envelope-evolution phase. With these conditions, the line emissions are dominated by Rydberg transitions within the stable isotopes of Mg. A turbulent velocity field in the range 5.5–7.5 km s−1 is required to fit the Gaussian line shapes. An upper limit to the average magnetic field in the line-emitting region of 1 G is set using the Zeeman effect in these lines. Conclusions. We speculate that Rydberg transitions of heavy elements may be an interesting probe for the close-in environments of other moderate-temperature objects like AGB stars, red supergiants, yellow hypergiants, and binaries of various types.
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Asmi, E., V. Kondratyev, D. Brus, T. Laurila, H. Lihavainen, J. Backman, V. Vakkari, et al. "Aerosol size distribution seasonal characteristics measured in Tiksi, Russian Arctic." Atmospheric Chemistry and Physics 16, no. 3 (February 3, 2016): 1271–87. http://dx.doi.org/10.5194/acp-16-1271-2016.
Повний текст джерелаАнотація:
Abstract. Four years of continuous aerosol number size distribution measurements from the Arctic Climate Observatory in Tiksi, Russia, are analyzed. Tiksi is located in a region where in situ information on aerosol particle properties has not been previously available. Particle size distributions were measured with a differential mobility particle sizer (in the diameter range of 7–500 nm) and with an aerodynamic particle sizer (in the diameter range of 0.5–10 μm). Source region effects on particle modal features and number, and mass concentrations are presented for different seasons. The monthly median total aerosol number concentration in Tiksi ranges from 184 cm−3 in November to 724 cm−3 in July, with a local maximum in March of 481 cm−3. The total mass concentration has a distinct maximum in February–March of 1.72–2.38 μg m−3 and two minimums in June (0.42 μg m−3) and in September–October (0.36–0.57 μg m−3). These seasonal cycles in number and mass concentrations are related to isolated processes and phenomena such as Arctic haze in early spring, which increases accumulation and coarse-mode numbers, and secondary particle formation in spring and summer, which affects the nucleation and Aitken mode particle concentrations. Secondary particle formation was frequently observed in Tiksi and was shown to be slightly more common in marine, in comparison to continental, air flows. Particle formation rates were the highest in spring, while the particle growth rates peaked in summer. These results suggest two different origins for secondary particles, anthropogenic pollution being the important source in spring and biogenic emissions being significant in summer. The impact of temperature-dependent natural emissions on aerosol and cloud condensation nuclei numbers was significant: the increase in both the particle mass and the CCN (cloud condensation nuclei) number with temperature was found to be higher than in any previous study done over the boreal forest region. In addition to the precursor emissions of biogenic volatile organic compounds, the frequent Siberian forest fires, although far away, are suggested to play a role in Arctic aerosol composition during the warmest months. Five fire events were isolated based on clustering analysis, and the particle mass and cloud condensation nuclei number were shown to be somewhat affected by these events. In addition, during calm and cold months, aerosol concentrations were occasionally increased by local aerosol sources in trapping inversions. These results provide valuable information on interannual cycles and sources of Arctic aerosols.
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Oganesyan, G., L. Nava, G. Ghirlanda, A. Melandri, and A. Celotti. "Prompt optical emission as a signature of synchrotron radiation in gamma-ray bursts." Astronomy & Astrophysics 628 (August 2019): A59. http://dx.doi.org/10.1051/0004-6361/201935766.
Повний текст джерелаАнотація:
Information on the spectral shape of prompt emission in gamma-ray bursts (GRB) is mostly available only at energies ≳10 keV, where the main instruments for GRB detection are sensitive. The origin of this emission is still very uncertain because of the apparent inconsistency with synchrotron radiation, which is the most obvious candidate, and the resulting need for considering less straightforward scenarios. The inclusion of data down to soft X-rays (∼0.5 keV), which are available only in a small fraction of GRBs, has firmly established the common presence of a spectral break in the low-energy part of prompt spectra, and even more importantly, the consistency of the overall spectral shape with synchrotron radiation in the moderately fast-cooling regime, the low-energy break being identified with the cooling frequency. In this work we further extend the range of investigation down to the optical band. In particular, we test the synchrotron interpretation by directly fitting a theoretically derived synchrotron spectrum and making use of optical to gamma-ray data. Secondly, we test an alternative model that considers the presence of a black-body component at ∼keV energies, in addition to a non-thermal component that is responsible for the emission at the spectral peak (100 keV–1 MeV). We find that synchrotron radiation provides a good description of the broadband data, while models composed of a thermal and a non-thermal component require the introduction of a low-energy break in the non-thermal component in order to be consistent with optical observations. Motivated by the good quality of the synchrotron fits, we explore the physical parameter space of the emitting region. In a basic prompt emission scenario we find quite contrived solutions for the magnetic field strength (5 G < B′< 40 G) and for the location of the region where the radiation is produced (Rγ > 1016 cm). We discuss which assumptions of the basic model would need to be relaxed in order to achieve a more natural parameter space.
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Soma, Venugopal Rao, and Abdul Kalam Shaik. "Femtosecond Filaments for Standoff Detection of Explosives." Defence Science Journal 70, no. 4 (July 13, 2020): 359–65. http://dx.doi.org/10.14429/dsj.70.14962.
Повний текст джерелаАнотація:
In this report, we present our results from various studies to qualitatively discriminate the common military explosives viz. RDX, TNT and HMX in their pure form at a distance of ~6.5 m in standoff mode using femtosecond (fs) filament induced breakdown spectroscopy technique (fs FIBS) together with principal component analysis. A ~30 cm length fs filament obtained by a two-lens configuration was used to interrogate those energetic molecules in the form of pressed pellets (150 mg each). The plasma emissions were collected by a Schmidt-Cassegrain telescope (SCT) from a distance of ~8 m away from the investigation zone. Additionally, a few significant results obtained from the LIBS-based investigations of nitroimidazoles with respect to the standoff distance (~2 m) are discussed. Furthermore, we have also summarised a few important results from our recent investigations of bulk energetic materials in various configurations (including those with fs filaments). The results obtained from various fs FIBS configurations corroborate that the filament generation and its properties, the size and f-number of collection optics influence signal strength in the FIBS technique. These results project the fs FIBS technique as a potential technique for investigations aimed at hazardous materials and harsh environments in the standoff mode.
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Wang, Xue, Xiao-Qiong Wen, Li-Ru Wang, Yuan-Tian Yang, and Xiao-Dong Xue. "Re-illumination and pause behavior of streamer filament of streamer discharge in water." Acta Physica Sinica 71, no. 1 (2022): 015203. http://dx.doi.org/10.7498/aps.71.20211162.
Повний текст джерелаАнотація:
The streamer discharge in water is a main object for studying the basic physical and chemical processes of an electric discharge in water. In this paper, the re-illuminations and the pause behaviors of a streamer filament of the microsecond pulsed streamer discharge in water with different conductivities (20 to 800 µS/cm) are studied by adopting a needle-plate electrode system and an ultra-high-speed camera system. The cause why the re-illumination of the streamer filament is difficult to detect by using the camera system as the water conductivity gets higher is discussed. It is found that the re-illumination alternately occurs among different streamer filaments, and two modes of the re-illumination are identified: one is that the whole filament quenches and then illuminates again; the other is that only the tip part of the filament quenches and then resumes the illumination. The appearance rate of the re-illumination of the streamer filament decreases rapidly as the water conductivity increases, and then drops to zero as the water conductivity exceeds 540 µS/cm. Within a water conductivity range of 20–800 µS/cm, the appearance rate of segmentation in shockwave pattern of the streamer filament is larger than 65%, indicating that the pause is a common behavior of the streamer filament. By measuring the difference in radius between two adjacent shockwave segments, the average pause period of the streamer filament is estimated at 157 ns, which is almost not affected by the water conductivity. As the water conductivity increases, the light intensity of the streamer filament increases rapidly. The light intensity of the streamer filament cannot decay to the noise level of the camera system during the pause period of the streamer filament as the water conductivity exceeds 350 µS/cm. The streamer filament produces glow on the light emission image, which makes it difficult to distinguish the “extinction and illumination” process by the camera system.
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Herrmann, Maximilian, Moritz Schöne, Christian Borger, Simon Warnach, Thomas Wagner, Ulrich Platt, and Eva Gutheil. "Ozone depletion events in the Arctic spring of 2019: a new modeling approach to bromine emissions." Atmospheric Chemistry and Physics 22, no. 20 (October 19, 2022): 13495–526. http://dx.doi.org/10.5194/acp-22-13495-2022.
Повний текст джерелаАнотація:
Abstract. Ozone depletion events (ODEs) are a common occurrence in the boundary layer during Arctic spring. Ozone is depleted by bromine species, which are most likely emitted from snow, sea ice, or aerosols in an autocatalytic reaction cycle. Previous three-dimensional modeling studies of ODEs assumed an infinite bromine source at the ground. In the present study, an alternative emission scheme is presented in which a finite amount of bromide in the snow is tracked over time. For this purpose, a modified version of the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) is used to study ODEs in the Arctic from February to May 2019. The model data are compared to in situ measurements, ozone sonde flights, and satellite data. A simulation of the ODEs in the Arctic spring of 2009 using the infinite-bromide assumption on first-year (FY) ice is transferred to the spring of 2019, which achieves good agreement with the observations; however, there is some disagreement in April 2009 and 2019 with respect to an overestimation concerning both the magnitude and the number of ODEs. New simulations using the finite-bromide assumption greatly improve agreement with in situ observations at Utqiaġvik, Alaska, Zeppelin Mountain, Svalbard, and Pallas, Finland, in April 2019, suggesting that bromide on the sea ice is depleted to an extent that reduces the bromine release. The new simulations also slightly improve the agreement with observations at these sites in February and March. A comparison to measurements near Eureka, Canada, and Station Nord, Greenland, shows that multi-year ice and possibly snow-covered land may be significant bromine sources. However, assuming higher releasable bromide near Eureka does not remove all disagreement with the observations. The numerical results are also compared to tropospheric-BrO vertical column densities generated with a new retrieval method from TROPOspheric Monitoring Instrument (TROPOMI) observations. BrO vertical column densities (VCDs) above 5×1013 molec. cm−2 observed by the satellite agree well with the model results. However, the model also predicts BrO VCDs of around 3×1013 molec. cm−2 throughout the Arctic and patches of BrO VCDs of around 1014 molec. cm−2 not observed by the satellite, especially near Hudson Bay. This suggests that snow at Hudson Bay may be a weaker bromine source in late spring compared to snow in the north.
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Benscoter, B. W., D. K. Thompson, J. M. Waddington, M. D. Flannigan, B. M. Wotton, W. J. de Groot, and M. R. Turetsky. "Interactive effects of vegetation, soil moisture and bulk density on depth of burning of thick organic soils." International Journal of Wildland Fire 20, no. 3 (2011): 418. http://dx.doi.org/10.1071/wf08183.
Повний текст джерелаАнотація:
The boreal biome is characterised by extensive wildfires that frequently burn into the thick organic soils found in many forests and wetlands. Previous studies investigating surface fuel consumption generally have not accounted for variation in the properties of organic soils or how this affects the severity of fuel consumption. We experimentally altered soil moisture profiles of peat monoliths collected from several vegetation types common in boreal bogs and used laboratory burn tests to examine the effects of depth-dependent variation in bulk density and moisture on depth of fuel consumption. Depth of burning ranged from 1 to 17 cm, comparable with observations following natural wildfires. Individually, fuel bulk density and moisture were unreliable predictors of depth of burning. However, they demonstrated a cumulative influence on the thermodynamics of downward combustion propagation. By modifying Van Wagner’s surface fuel consumption model to account for stratigraphic changes in fuel conditions, we were able to accurately predict the maximum depth of fuel consumption for most of the laboratory burn tests. This modified model for predicting the depth of surface fuel consumption in boreal ecosystems may provide a useful framework for informing wildland fire management activities and guiding future development of operational fire behaviour and carbon emission models.
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Neubauer, David, Sylvaine Ferrachat, Colombe Siegenthaler-Le Drian, Philip Stier, Daniel G. Partridge, Ina Tegen, Isabelle Bey, Tanja Stanelle, Harri Kokkola, and Ulrike Lohmann. "The global aerosol–climate model ECHAM6.3–HAM2.3 – Part 2: Cloud evaluation, aerosol radiative forcing, and climate sensitivity." Geoscientific Model Development 12, no. 8 (August 21, 2019): 3609–39. http://dx.doi.org/10.5194/gmd-12-3609-2019.
Повний текст джерелаАнотація:
Abstract. The global aerosol–climate model ECHAM6.3–HAM2.3 (E63H23) as well as the previous model versions ECHAM5.5–HAM2.0 (E55H20) and ECHAM6.1–HAM2.2 (E61H22) are evaluated using global observational datasets for clouds and precipitation. In E63H23, the amount of low clouds, the liquid and ice water path, and cloud radiative effects are more realistic than in previous model versions. E63H23 has a more physically based aerosol activation scheme, improvements in the cloud cover scheme, changes in the detrainment of convective clouds, changes in the sticking efficiency for the accretion of ice crystals by snow, consistent ice crystal shapes throughout the model, and changes in mixed-phase freezing; an inconsistency in ice crystal number concentration (ICNC) in cirrus clouds was also removed. Common biases in ECHAM and in E63H23 (and in previous ECHAM–HAM versions) are a cloud amount in stratocumulus regions that is too low and deep convective clouds over the Atlantic and Pacific oceans that form too close to the continents (while tropical land precipitation is underestimated). There are indications that ICNCs are overestimated in E63H23. Since clouds are important for effective radiative forcing due to aerosol–radiation and aerosol–cloud interactions (ERFari+aci) and equilibrium climate sensitivity (ECS), differences in ERFari+aci and ECS between the model versions were also analyzed. ERFari+aci is weaker in E63H23 (−1.0 W m−2) than in E61H22 (−1.2 W m−2) (or E55H20; −1.1 W m−2). This is caused by the weaker shortwave ERFari+aci (a new aerosol activation scheme and sea salt emission parameterization in E63H23, more realistic simulation of cloud water) overcompensating for the weaker longwave ERFari+aci (removal of an inconsistency in ICNC in cirrus clouds in E61H22). The decrease in ECS in E63H23 (2.5 K) compared to E61H22 (2.8 K) is due to changes in the entrainment rate for shallow convection (affecting the cloud amount feedback) and a stronger cloud phase feedback. Experiments with minimum cloud droplet number concentrations (CDNCmin) of 40 cm−3 or 10 cm−3 show that a higher value of CDNCmin reduces ERFari+aci as well as ECS in E63H23.
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Hakala, Simo, Mansour A. Alghamdi, Pauli Paasonen, Ville Vakkari, Mamdouh I. Khoder, Kimmo Neitola, Lubna Dada, et al. "New particle formation, growth and apparent shrinkage at a rural background site in western Saudi Arabia." Atmospheric Chemistry and Physics 19, no. 16 (August 21, 2019): 10537–55. http://dx.doi.org/10.5194/acp-19-10537-2019.
Повний текст джерелаАнотація:
Abstract. Atmospheric aerosols have significant effects on human health and the climate. A large fraction of these aerosols originates from secondary new particle formation (NPF), where atmospheric vapors form small particles that subsequently grow into larger sizes. In this study, we characterize NPF events observed at a rural background site of Hada Al Sham (21.802∘ N, 39.729∘ E), located in western Saudi Arabia, during the years 2013–2015. Our analysis shows that NPF events occur very frequently at the site, as 73 % of all the 454 classified days were NPF days. The high NPF frequency is likely explained by the typically prevailing conditions of clear skies and high solar radiation, in combination with sufficient amounts of precursor vapors for particle formation and growth. Several factors suggest that in Hada Al Sham these precursor vapors are related to the transport of anthropogenic emissions from the coastal urban and industrial areas. The median particle formation and growth rates for the NPF days were 8.7 cm−3 s−1 (J7 nm) and 7.4 nm h−1 (GR7−12 nm), respectively, both showing highest values during late summer. Interestingly, the formation and growth rates increase as a function of the condensation sink, likely reflecting the common anthropogenic sources of NPF precursor vapors and primary particles affecting the condensation sink. A total of 76 % of the NPF days showed an unusual progression, where the observed diameter of the newly formed particle mode started to decrease after the growth phase. In comparison to most long-term measurements, the NPF events in Hada Al Sham are exceptionally frequent and strong both in terms of formation and growth rates. In addition, the frequency of the decreasing mode diameter events is higher than anywhere else in the world.
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Fu, Kaining, Wei Chen, and Subin Lin. "A General Transformer Evaluation Method for Common-Mode Noise Behavior." Energies 12, no. 10 (May 23, 2019): 1984. http://dx.doi.org/10.3390/en12101984.
Повний текст джерелаАнотація:
In isolated power converters, the transformer is a key part of voltage transformation and isolation. Since common-mode (CM) noise is rather difficult to suppress compared with different-mode (DM) noise, more and more scholars are paying attention to the characteristics of CM noise, especially in high-frequency CM noise behaviors. CM noise can be further divided into conducted CM noise and radiated CM noise, and the main focus of this paper is on conducted CM noise. The CM coupling capacitance of the transformer is one of the main contributors of CM noise, which has been verified in many previous studies. Hence, eliminating the CM noise in a transformer coupling path can significantly lower the whole CM noise level of the converter. Professional conducted electromagnetic interference (EMI) testing instruments are quite expensive. In this paper, a general transformer evaluation technique for CM noise behavior is proposed. Only a signal generator and oscilloscope can achieve transformer CM noise behavior evaluation. PCB planar flyback transformers are designed, and a series of noise spectrums and voltage waveforms can verify the effectiveness of the proposed transformer evaluation method. The flyback adapter porotype can pass the EMI standard limited line EN55022 class B by the proposed evaluation method.
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Dib, Willian Hoffmann, Janaína De Fátima Gonzalez Munster Cicarello, Larissa Kummer, and Maurici Luzia Charnevski Del Monego. "Geostatistical assessment of trace metals in urban soils, Paraná, Brazil." Revista Ibero-Americana de Ciências Ambientais 11, no. 6 (May 19, 2020): 358–70. http://dx.doi.org/10.6008/cbpc2179-6858.2020.006.0029.
Повний текст джерелаАнотація:
Trace metals are common pollutants in urban soils thus making important the assessment of these pollutants. The main purpose of this study was investigated the concentrations of trace metals in urban soils in the industrial region of Curitiba, in the State of Paraná, Brazil and to examine the applicability of geostatistical modeling for assessing the environmental impact generated. For the analyses of trace elements, soil samples were collected at a depth of 0-20 cm and subjected to an acid digestion, in accordance with the 3050B method. The identification of trace elements was through the technique Spectroscopy of Optical Emission. The soil texture was also analyzed and the data were determined by the compositional analysis method. For the geostatistical mapping, it was used the software R, with the geoR package. The spatial variability of the sampled data was analyzed previously calculating the classic statistical indicators. The results indicated an approximated normal distribution of the data samples which is desirable. Then, the Matheron's classical estimator was used to compute the experimental semivariogram for several directions. No effect of anisotropy was shown. The semivariogram was fitted to three theoretical models: spherical, exponential and Gaussian. The results of cross-validation of spherical model suggested that it is the best model among the others. Finally, the predictions of metals at unknown locations were obtained by ordinary kriging. In relation to the values obtained of metals and the standard values of the Brazilian referee legislation of management of contaminated sites, only one site had Ni levels higher than is allowed and other metals were ok. The generated map shows clearly the spatial variation of trace metals in the studied area. The results are suitable and suggest that the use of this methodology provides significant contributions to management of contaminated areas by different trace metals.
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Mei, A., and F. Tombesi. "XMM-Newton spectrum of the radio-loud quasar 3C 215: Slim accretion disk or SMBH binary." Astronomy & Astrophysics 653 (September 2021): A100. http://dx.doi.org/10.1051/0004-6361/202140473.
Повний текст джерелаАнотація:
Context. Radio-loud active galactic nuclei (RL AGN) exhibit very powerful jet emission in the radio band, while the radio-quiet (RQ) AGN do not. This RL-RQ dichotomy would imply a sharp difference existing among these two classes, however, modern theoretical models and observations suggest a common nuclear environment that is possibly characterized by different working regimes. Aims. We explore the geometrical structure and mutual interactions of the innermost components of the broad line radio galaxy 3C 215, with a particular focus on the accretion and ejection mechanisms involving the central supermassive black hole (SMBH). We compare these observational features with those of the RQ Seyfert 1 galaxies. Investigating their differences is aimed at improving our understanding of the jet launching mechanisms and devising an explanation for why this phenomenon is efficient only in a small fraction of all the AGNs. Methods. Using high-quality data from a ∼60 ks observation with XMM-Newton, we carried out a detailed X-ray spectral analysis of 3C 215 in the broad energy range of 0.5−10 keV. We modeled the spectrum with an absorbed double power-law model for the primary continuum, reprocessed by reflection from ionized and cold neutral material and modified by relativistic blurring. We also compared our results with those of earlier multi-wavelength observations. Results. We obtained a primary continuum photon index from the corona, namely, Γ1 = 1.97 ± 0.06, along with evidence of a jet contribution, modeled as a power law with photon index of Γ2 ≃ 1.29. The reflector, which is possibly attributed to the accretion disk and portions of the broad-line region (BLR), is ionized (logξ = 2.31−0.27+0.37 erg s−1 cm) and relatively distant from the SMBH (Rin > 38 Rg), where Rg = GMBH/c2 is the gravitational radius. The obscuring torus seems patchy, dust-poor, and inefficient, while the jet emission shows a twisted and knotted geometry. We propose three scenarios to describe the following characteristics: 1. An ADAF state in the inner disk; 2. A slim accretion disk; and 3. A sub-pc SMBH binary system (SMBHB). Conclusions. While the first scenario is not in agreement with the SMBH accretion regime, the slim disk scenario is consistent with the observational features of this radio galaxy, showing that 3C 215 is similar to non-jetted AGNs, accreting at a high rate. Nonetheless, the first two scenarios are unable to account for the particular shape of 3C 215 jet emission. The SMBHB scenario seems to be in agreement with almost all 3C 215 observational features, but we are not able to unequivocally determine this source as a strong SMBHB candidate. A final determination will require further analysis.
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Kojima, Kazunobu, Shuhei Ichikawa, Osamu Maida, Kohei Shima, and Shigefusa Chichibu. "(Invited) Characterization of Semiconductor Crystals Based on Omnidirectional Photoluminescence (ODPL) Spectroscopy." ECS Meeting Abstracts MA2022-01, no. 31 (July 7, 2022): 1301. http://dx.doi.org/10.1149/ma2022-01311301mtgabs.
Повний текст джерелаАнотація:
The performance of optical devices based on nitride semiconductors operating in the ultraviolet and visible wavelength regimes has been remarkably improved. For example, high-efficiency blue InGaN light-emitting diodes (LEDs) with an external quantum efficiency (EQE) of over 80% was achieved [Y. Narukawa, M. Ichikawa1, D. Sanga, M. Sano, and T. Mukai, J. Phys. D: Appl. Phys. 43, 354002 (2010)], and green laser diodes (LDs) was realized [Y. Enya, Y. Yoshizumi, T. Kyono, K. Akita, M. Ueno, M. Adachi, T. Sumitomo, S. Tokuyama, T. Ikegami, K. Katayama and T. Nakamura, Appl. Phys. Express 2, 082101 (2009)]. Recently, deep-ultraviolet AlGaN LEDs and LDs have also become hot topics. The nitride semiconductors have been actively applied not only to optical applications but also to electronic devices such as high-voltage transistors and high-electron mobility transistors based on their high breakdown voltage and saturation electron velocity. The performance of these optical and electronic devices relies on the crystal growth technology, where quality of GaN freestanding substrate is one of the most important issues. In recent years, it has become common for the "high-quality" GaN freestanding crystals to have a threading dislocation (TD) density of 106 cm-2 or less. TD density of 106 cm-2 corresponds to an average distance between TDs of 10 μm, which means that the TDs are sparser than 1 μm, the order of the carrier diffusion length. In other words, the TDs are no longer dominant in recombination processes of minority carriers (although this is a rather broad argument). In this case, the recombination processes, especially nonradiative recombination process, are likely to be dominated by point defects and impurities rather than by the sparse TDs. In fact, a negative correlation between room-temperature (RT) photoluminescence (PL) lifetime for the near-band-edge (NBE) emission and the concentration of VGaVN (a divacancy consisting of Ga and N vacancies) has been pointed out by a combined study of time-resolved PL measurements, positron annihilation spectroscopy, and theoretical calculations [S. F. Chichibu, A. Uedono, K. Kojima, H. Ikeda, K. Fujito, S. Takashima, M. Edo, K. Ueno, and S. Ishibashi, J. Appl. Phys. 123, 161413 (2018)]. Since PL lifetime measured at RT indicates nonradiative recombination lifetime when the internal quantum efficiency (IQE) of the crystal is low, this negative correlation means that the lower concentration of VGaVN induces larger intensity of the NBE emission. Actually, we have observed PL lifetime exceeding 2 ns at RT in a GaN crystal grown by halide vapor phase epitaxy (HVPE) on m-plane GaN grown by the acidic ammonothermal method as a seed crystal [K. Kojima, Y. Tsukada, E. Furukawa, M. Saito, Y. Mikawa, S. Kubo, H. Ikeda, K. Fujito, A. Uedono, and S. F. Chichibu, Appl. Phys. Express 8, 095501 (2015)]. This is an extremely long value for a GaN crystal, which means that the nonradiative recombination lifetime is long, i.e., the IQE of the NBE emission is large. In this case, the validity of the approximation where the PL lifetime at RT is directly read into the nonradiative recombination lifetime becomes an issue. Therefore, in order to compare the quality of GaN freestanding crystals, it is important to measure the IQE as well as the PL lifetime. The IQE value for the NBE emission in semiconductor crystals is a quantity that represents the balance between radiative and nonradiative recombination processes and is directly related to the concentration of point defects and impurities that form deep levels. Therefore, the IQE can be used as an indicator of not only the energy-saving performance of optical devices but also the performance of GaN crystals as a substrate material in electronic devices. In this presentation, the characterization of semiconductors with direct bandgap by using omnidirectional photoluminescence (ODPL) spectroscopy, a technique that can determine the IQE from the EQE without the need for model calculations, will be reviewed. Using GaN, ZnO, and metal halide perovskites as examples, specific procedures and applications of IQE determination will be discussed. In particular, the ability to measure large sample crystals or wafers is one of the major features of the ODPL spectroscopy, and it is expected to be combined with mapping measurements of the entire surface of semiconductor wafers and various types of nonlinear and microscopic spectroscopy.
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Zhang, Gang, Yang Zhao, and Wei Yan. "A Compact Differential-Mode Wide Stopband Bandpass Filter with Good and Wideband Common-Mode Suppression." Wireless Communications and Mobile Computing 2018 (2018): 1–4. http://dx.doi.org/10.1155/2018/4032183.
Повний текст джерелаАнотація:
This letter presents a microstrip differential-mode (DM) bandpass filter (BPF) with high and wide stopband suppression under both DM and common-mode (CM) operations. A new coupling topology is formed up to realize the DM BPF by integrating a pair of λ/2 microstrip transmission lines and two multimode resonators. The DM and CM equivalent half-circuits are established to explain the operating principal. For validation, a DM BPF operating at 2.2 GHz is implemented. Experimental results indicate that the presented DM BPF exhibits not only sharp DM passband selectivity but also deep and ultrawide stopband suppression of more than 30 dB for both DM and CM.
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AKSAMIT, Witold. "Detailed analysis of common mode and differential mode conducted emission generation in switch mode power supplies." PRZEGLĄD ELEKTROTECHNICZNY 1, no. 8 (August 5, 2016): 230–35. http://dx.doi.org/10.15199/48.2016.08.60.
Повний текст джерела
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Liu, Dongliang, Haoqi Zhu, and Ruiguang Zhao. "Novel Common-Mode Current Suppression Method in Transformerless PV Grid-Connected System." Applied Sciences 8, no. 11 (October 26, 2018): 2072. http://dx.doi.org/10.3390/app8112072.
Повний текст джерелаАнотація:
The existence of high-frequency components in common-mode (CM) current would reduce the stability of a non-isolated PV grid-connected system. It has great impacts on the output power quality when the generated power from PV is low. The method of single CM inner loop in suppressing the high-frequency components has poor effect. Based on the CM equivalent circuit model and the cause analysis of the CM current, a novel dual CM inner loops method is proposed to restrain the high-frequency components in CM current. This method not only meets the grid connection demand of CM current, but also overcomes the high frequency resonant problem. Furthermore, the high-frequency components in CM current from the outer parasitic circuit are substantially reduced. Finally, the proposed method is verified by simulation and experimental results.
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Zhang, Wei, Jin Shi, Gangxiong Wu, Longlong Lin, and Kai Xu. "A Balanced Substrate Integrated Waveguide Phase Shifter with Wideband Common-Mode Suppression." Micromachines 14, no. 2 (January 22, 2023): 285. http://dx.doi.org/10.3390/mi14020285.
Повний текст джерелаАнотація:
In this paper, a slotted substrate integrated waveguide (SIW) is used to create a balanced phase shifter with wideband common-mode (CM) suppression. Differential-mode (DM) impedance matching and CM suppression are achieved by utilizing the fact that TE20 mode and TE10 (TE30) mode can only transmit DM signals and CM signals, respectively, and by increasing the bandwidth for CM suppression via slots. Furthermore, a wideband phase shift with low phase deviation can be obtained due to the phase slop counteract between the slot and the delay line. Compared with the state-of-the-art, the proposed one has the advantages of wideband CM suppression, wide phase shift range, and a simple and easy-to-make structure. Five prototypes covering the frequency of 3.5 GHz are designed with the relative operating bandwidth for 45° ± 2° (90° ± 4.5°, 135° ± 6°, and 180° ± 8°) phase shifter of 20% (20%, 20%, and 20%), with the minimum insertion loss of 0.41 dB (0.5 dB, 0.58 dB, and 0.59 dB), with the minimum return loss greater than 15 dB, and with the relative bandwidth for 15-dB CM suppression of 59% (59%, 58%, and 57%).
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Li, Mengzi, Shishan Wang, and Jian Guo. "Suppression Approaches of Far-Field Radiated Emission Using Common-Mode Inductor." Journal of Electronics and Advanced Electrical Engineering 1, no. 2 (May 3, 2021): 1–5. http://dx.doi.org/10.47890/jeaee/2020/mengzili/11120006.
Повний текст джерелаАнотація:
The miniaturization and integration of Switching Mode Power Supply (SMPS) is increasing, making it more complicated to analyze and predict its far-field radiated emission, and, consequently, studying the suppression method of far-field radiated emission of SMPS is of practical significance and engineering value. In this paper, a high-frequency SMPS is selected as the research object, whose far-field radiated emission is measured under the condition of three typical suppression methods. The experimental results verified the effectiveness of common-mode inductor and are of reference value for EMC design of power converter. Keywords: SMPS; EMC; Far-field Radiated Emission;
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Pierściński, Kamil, Dorota Pierścińska, Aleksandr Kuźmicz, Grzegorz Sobczak, Maciej Bugajski, Piotr Gutowski, and Krzysztof Chmielewski. "Coupled Cavity Mid-IR Quantum Cascade Lasers Fabricated by Dry Etching." Photonics 7, no. 3 (July 3, 2020): 45. http://dx.doi.org/10.3390/photonics7030045.
Повний текст джерелаАнотація:
In this work, two-section, coupled cavity, mid-IR quantum cascade lasers (QCLs) were characterized in terms of their tuning range and emission stability under operation towards potential application in detection systems. Devices were processed by inductively coupled plasma reactive ion etching (ICP-RIE) from InP-based heterostructure, designed for emission in the 9.x micrometer range. Single mode devices were demonstrated with a better than 20 dB side mode suppression ratio (SMRS). The fabrication method resulted in improved yield, as well as high repeatability of individual devices. Continuous, mode-hop-free tuning of emission wavelength was observed across ~4.5 cm−1 for the range of temperatures of the heat sink from 15 °C to 70 °C. Using the thermal perturbation in the lasing cavity, in conjunction with controlled hopping between coupled-cavity (CC) modes, we were able to accomplish tuning over the range of up to ~20 cm−1.
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Szymański, Jerzy Ryszard, and Marta Żurek-Mortka. "Ground Leakage Current Caused by Common-Mode Voltage of PWM inverter." Journal of Civil Engineering and Transport 1, no. 1 (January 31, 2020): 15–25. http://dx.doi.org/10.24136/tren.2019.002.
Повний текст джерелаАнотація:
In railway tractive vehicles, three-phase PWM (Pulse Width Modulation) inverters generate parasitic Differential-Mode Voltages (DMV) and Common-Mode Voltages (CMV). Parasitic voltages are a side effect of using the width modulation to shape the phase-to-phase inverter’s voltage. In this article, the authors present a mathematical description of the DM and CM voltages and carry out their spectral analysis. Based on the spectral harmonics analysis, the authors present a method for filtration of harmonics of DM and CM voltages aimed at limiting the capacitance parasitic currents: due to DM voltage – phase-to-phase parasitic current and CM voltage – ground parasitic currents. As the final result of the tests, almost complete elimination of leakage parasitic current form PE shock protection system was achieved.
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BRAUN, DIETER, BRUNO C. TITECA, and ARNOUT CEULEMANS. "The vibronic fine structure of the emission spectrum of silicon phthalocyanine." Journal of Porphyrins and Phthalocyanines 05, no. 01 (January 2001): 33–43. http://dx.doi.org/10.1002/1099-1409(200101)5:1<33::aid-jpp303>3.0.co;2-9.
Повний текст джерелаАнотація:
Sharp line emission spectra of the silicon phthalocyanine complex ((n- C 6 H 13)3 SiO )2 SiPc at low temperatures are resolved in multiple sites, and the vibronic fine structure of single-site emissions is identified. DFT methods are used to calculate the complete set of normal modes of the Cl 2 SiPc analogue. Geometry optimization of the excited state further yields the Franck–Condon and Jahn–Teller distortions in the emitting state. These results are combined to obtain theoretical Huang–Rhys factors for the active modes, which compare favourably with the experimental spectrum. The dominant satellites are a 675 cm−1 mode, which is identified as a totally symmetric bending of the four pyrrole rings, and a 1552 cm−1 mode, which is assigned to an antisymmetric stretching of the aza-nitrogens with tetragonal b 1 g symmetry.
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Mardiono, Djoko Anwar, Gunawan Toto Hadiyanto, and Intan Kumala Sari. "Penggunaan Common-Mode Filter dan Differential-Mode Filter Pada EMI Driver Lampu LED." Zona Teknik: Jurnal Ilmiah 15, no. 2 (December 29, 2021): 1. http://dx.doi.org/10.37776/zt.v15i2.811.
Повний текст джерелаАнотація:
Power Energy efficiency for public application commonly used driver IC that operate by (Pulse Width Modulation) PWM, The effect of this implementation will generate EMI (Electromagnetic Interference) that can make radio signal distortion or other electronic distortion in the around device area. The action to reduce the signal distortions shall use Filter implementation in the electronic device circuit. The filter to reduce signal distortion are power line filter or ferrite beads filter. Power line filter used for reduce and to filtering noise signal from Power line source from PLN power line or from power line distribution Conduction emission., The ferrite beads filter implementation for noise reduction or filtering from Source power supply to load. Implement of both filters at the circuit diagram will impact to reduce noise signal that make distortion to the signal source.
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Tan, Ruoxi, Shangbin Ye, Cheng Yu, Chenghao Deng, and Anjian Zhou. "Research on Electromagnetic-Radiated Emission of Multi-in-One Electric Drive System." World Electric Vehicle Journal 12, no. 3 (August 21, 2021): 127. http://dx.doi.org/10.3390/wevj12030127.
Повний текст джерелаАнотація:
The strong electromagnetic interference produced by the electric drive system is the main factor that leads to the strong radiated emission of electric vehicles. It is very important to study the influence of the electric drive system on vehicle-radiated emission by taking the common-mode current of the electric drive system as the interference source. In this paper, the conducted emission model of the electric drive system is proposed, and the common-mode current is calculated by this model. The influence of filter on the common-mode interference current of HVDC cables is calculated and analyzed, and then the radiating antenna effect model of HVDC cables is established. Based on this, a vehicle-level radiated emission simulation model including an electric drive system and DC cables was established. The effectiveness of the conducted emission model was verified by experiments. The effects of different shielding structures on the shielding efficiency of HVDC cables were compared. Quantitative guidance for EMI suppression design of multi-in-one electric drive system design can be provided by the model in this paper.
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Pierściński, Kamil, Dorota Pierścińska, Grzegorz Sobczak, Aleksandr Kuźmicz, Krzysztof Chmielewski, Katarzyna Krajewska, and Piotr Gutowski. "Monolithic, Optically Coupled, Multi-Section Mid-IR Quantum Cascade Lasers." Photonics 8, no. 12 (December 16, 2021): 583. http://dx.doi.org/10.3390/photonics8120583.
Повний текст джерелаАнотація:
Mid-infrared (mid-IR λ ≈ 3–12 μm), single-mode-emission Quantum Cascade Lasers (QCLs) are of significant interest for a wide range of applications, especially as the laser sources are chosen for laser absorption spectroscopy. In this work, we present the design, fabrication and characterization of multi-section, coupled-cavity, mid-IR quantum cascade lasers. The purpose of this work is to propose a design modification for a coupled-cavity device, yielding a single-mode emission with a longer range of continuous tuning during the pulse, in contrast to a 2-section device. This effect was obtained and demonstrated in the work. The proposed design of a 3-section coupled-cavity QCL allows for a single-mode emission with 35 dB side-mode suppression ratio. Additionally, the time-resolved spectra of the wavelength shift during pulse operation, show a continuous tuning of ~3 cm−1 during the 2 μs pulse. The devices were fabricated in a slightly modified, standard laser process using dry etching.
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Huang, S., Peijun Liu, Quanzhen Duan, Yuemin Ding, and Zhen Meng. "A −4–4 V Input Common-Mode Range Bidirectional Current Shunt Monitor." Journal of Circuits, Systems and Computers 29, no. 14 (March 25, 2020): 2050221. http://dx.doi.org/10.1142/s0218126620502217.
Повний текст джерелаАнотація:
This study describes a novel bidirectional current shunt monitor (CSM) circuit operating at both positive and negative common-mode (CM) voltages. The proposed CSM circuit mainly consists of two comparators, three error amplifiers, several current-mirror transistors and a few resistors. One comparator is used to detect current flowing direction, and the other one is utilized to ensure good operation of CSM circuit with both positive and negative CM voltages. The proposed CSM circuit has been implemented in SMIC 0.18[Formula: see text][Formula: see text]m standard CMOS process and its performances have been verified by simulations. The simulated results show that the proposed CSM circuit, at a supply voltage of 5[Formula: see text]V and with an input CM voltage range from [Formula: see text] to 4[Formula: see text]V, can sense a voltage difference of 4–40[Formula: see text]mV and keep a constant scaled gain of 100[Formula: see text]V/V. The gain error is less than 0.65% and the common-mode rejection ratio (CMRR) is higher than 130[Formula: see text]dB at 1[Formula: see text]kHz. Simulation results show that the output voltage of CSM circuit varies linearly with the CSM input sense voltage.
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MOHD YUSOFF, M. Z., Z. HASSAN, C. W. CHIN, H. ABU HASSAN, M. J. ABDULLAH, N. N. MOHAMMAD, M. A. AHMAD, and Y. YUSOF. "THE STUDY OF Al0.29Ga0.71N-BASED SCHOTTKY PHOTODIODES GROWN ON SILICON BY PLASMA-ASSISTED MOLECULAR BEAM EPITAXY." Modern Physics Letters B 27, no. 12 (April 22, 2013): 1350085. http://dx.doi.org/10.1142/s0217984913500851.
Повний текст джерелаАнотація:
In this paper, the growth and characterization of epitaxial Al 0.29 Ga 0.71 N grown on Si (111) by RF-plasma assisted molecular beam epitaxy (MBE) are described. The Al mole fraction was derived from the HR-XRD symmetric rocking curve (RC) ω/2θ scans of (0002) plane as x = 0.29. PL spectrum of sample has shown sharp and intense band edge emission of GaN without the existence of yellow emission band, showing that it is comparable in crystal quality of the sample when compared with previous reports. From the Raman measurement of as-grown Al 0.29 Ga 0.71 N layer on GaN / AlN / Si sample. We found that the dominant E 2 (high) phonon mode of GaN appears at 572.7 cm-1. The E 2 (high) mode of AlN appears at 656.7 cm-1 and deviates from the standard value of 655 cm-1 for unstrained AlN . Finally, AlGaN Schottky photodiode have been fabricated and analyzed by mean of electrical characterization, using current–voltage (I–V) measurement to evaluate the performance of this device.
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Kinyaevskiy, I. O., L. V. Seleznev, A. V. Koribut, E. E. Dunaeva, Yu M. Andreev, and A. A. Ionin. "Stimulated Raman scattering of chirped Ti:Sapphire laser pulses in BaWO4 crystal." Izvestiya vysshikh uchebnykh zavedenii. Fizika, no. 11 (2021): 67–70. http://dx.doi.org/10.17223/00213411/64/11/67.
Повний текст джерелаАнотація:
Stimulated Raman scattering of chirped Ti:Sapphire laser pulses in BaWO4 crystal A spectrum transformation of a chirped Ti:sapphire laser pulse stretched to 0.2 ns (with initial transform limited pulse duration of 90 fs) was experimentally studied in a tandem of BaWO4 crystals. To increase stimulated Raman scattering efficiency, broadband laser emission was used as a seed of this process. Efficiency of the Stokes component generation corresponding to the BaWO4 crystal phonon mode ν1(Ag)≈925 cm-1 reached ~ 10%. Generation of the Stokes component corresponding to the weaker phonon mode ν3(Eg)≈795 cm-1, and second Stokes components of ν1(Ag) and ν3(Eg) modes were also observed. Mechanisms reducing the stimulated Raman scattering efficiency for the ν1(Ag) mode are discussed.
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Kuta, Stanisław, Witold Machowski, Wojciech Kołodziejski, and Łukasz Chlastawa. "Filterless, Digital Class-BD Audio Amplifiers with Constant Common Mode Output Voltage." Energies 14, no. 21 (October 26, 2021): 7014. http://dx.doi.org/10.3390/en14217014.
Повний текст джерелаАнотація:
This paper presents new and original architectures and implementations of two filterless, open-loop digital Class-BD audio amplifiers with constant common mode (CM) output voltage. The first, low-power amplifier consists of four ultrahigh-current EL7158 pin drivers, the OUT pins of which form the H bridge. The drivers are controlled from the extended LBDD PWM modulator and have appropriately set voltage levels on the VL and VH pins. The second proposed amplifier consists of two cooperating H-bridge power stages (HBS) implemented on complementary MOSFET pairs and powered by two different voltages. Both HBSs are driven by four EL7158 pin drivers having appropriately adjusted voltage levels on the VL and VH pins and controlled by an extended LBDD PWM modulator. The hybrid 9 bit DPWM modulator uses a linearized Class-BD double-sided modulation scheme with pre-compensation, enabling the most faithful emulation of natural NBDD PWM and, thus, providing attractive spectral characteristics at the DM output. Basic SPICE simulations and experimental results of the proposed digital Class-BD amplifiers were compared with the conventional digital Class-BD amplifiers. The elimination of CM signals significantly contributes to the reduction in electromagnetic interference (EMI), particularly those produced on the cables connecting the loudspeaker to the HBS terminal. Proposed Class-BD amplifiers with original and new topologies, due to their simple design and easy control (no galvanic isolation of control signals and no floating bias power supplies), which generate no CM voltage and feature excellent DM performance, similar to conventional Class-BD amplifiers, are very attractive solutions for filterless Class-BD amplifiers.
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Li, Qiyu, Hongwei Zhou, Jiansong Zhang, Shengdun Zhao, and Jingfeng Lu. "A Virtual Negative Resistor Based Common Mode Current Resonance Suppression Method for Three-Level Grid-Tied Inverter with Discontinuous PWM." Energies 13, no. 7 (April 1, 2020): 1595. http://dx.doi.org/10.3390/en13071595.
Повний текст джерелаАнотація:
The output LC filter of a photovoltaic (PV) string three-level grid-tied inverter that connects the filter capacitor neutral point to dc-link capacitor neutral point can reduce the common-mode (CM) current injected to the grid by letting the CM current circulate within the inverter. However, the internal CM current may resonate because of the existence of the resonant frequency of the internal CM LC circuit. Compared with the traditional continuous pulse-width modulation (CPWM), the resonance can be worse if discontinuous pulse-width modulation (DPWM) is applied, for the zero sequence quantity of DPWM contains more harmonics than that of CPWM. In this paper, a virtual negative resistor based common mode current resonance suppression method for a three-level grid-tied inverter is proposed to overcome the CM current resonance problem in DPWM application. Different positions of the virtual negative resistor in the equivalent CM circuit with different feedback variables are analyzed theoretically. The virtual negative resistor connected in series with the inductor in the equivalent CM circuit is selected to damp the CM current resonance for simplification and damping performance. Different from the implementation in CPWM where a pair of small voltage vectors exist and are used to adjust the CM voltage directly, the proposed method for DPWM application is implemented indirectly by adding the CM adjustment quantity to differential-mode (DM) control quantity with appropriate coefficients. Depending on the sector of DM control quantity in the α β reference frame, the coefficients are calculated using one of three specific voltage vectors. Experimental results are given to demonstrate the effectiveness of theoretical analyses and the proposed method.
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Woiwode, Wolfgang, Michael Höpfner, Lei Bi, Michael C. Pitts, Lamont R. Poole, Hermann Oelhaf, Sergej Molleker та ін. "Spectroscopic evidence of large aspherical <i>β</i>-NAT particles involved in denitrification in the December 2011 Arctic stratosphere". Atmospheric Chemistry and Physics 16, № 14 (29 липня 2016): 9505–32. http://dx.doi.org/10.5194/acp-16-9505-2016.
Повний текст джерелаАнотація:
Abstract. We analyze polar stratospheric cloud (PSC) signatures in airborne MIPAS-STR (Michelson Interferometer for Passive Atmospheric Sounding – STRatospheric aircraft) observations in the spectral regions from 725 to 990 and 1150 to 1350 cm−1 under conditions suitable for the existence of nitric acid trihydrate (NAT) above northern Scandinavia on 11 December 2011. The high-resolution infrared limb emission spectra of MIPAS-STR show a characteristic “shoulder-like” signature in the spectral region around 820 cm−1, which is attributed to the ν2 symmetric deformation mode of NO3− in β-NAT. Using radiative transfer calculations involving Mie and T-Matrix methods, the spectral signatures of spherical and aspherical particles are simulated. The simulations are constrained using collocated in situ particle measurements. Simulations assuming highly aspherical spheroids with aspect ratios (AR) of 0.1 or 10.0 and a lognormal particle mode with a mode radius of 4.8 µm reproduce the observed spectra to a high degree. A smaller lognormal mode with a mode radius of 2.0 µm, which is also taken into account, plays only a minor role. Within the scenarios analyzed, the best overall agreement is found for elongated spheroids with AR = 0.1. Simulations of spherical particles and spheroids with AR = 0.5 and 2.0 return results very similar to each other and do not allow us to reproduce the signature around 820 cm−1. The observed “shoulder-like” signature is explained by the combination of the absorption/emission and scattering characteristics of large highly aspherical β-NAT particles. The size distribution supported by our results corresponds to ∼ 9 ppbv of gas-phase equivalent HNO3 at the flight altitude of ∼ 18.5 km. The results are compared with the size distributions derived from the in situ observations, a corresponding Chemical Lagrangian Model of the Stratosphere (CLaMS) simulation, and excess gas-phase HNO3 observed in a nitrification layer directly below the observed PSC. The presented results suggest that large highly aspherical β-NAT particles involved in denitrification of the polar stratosphere can be identified by means of passive infrared limb emission measurements.