Electron emission: From the Fowler–Nordheim relation to the Child–Langmuir law

Universal voltage‐current characteristics are presented for a planar diode, showing the general transition from the Fowler–Nordheim relation to the Child–Langmuir law. These curves are normalized to the intrinsic scales that are constructed from the Fowler–Nordheim coefficients A, B. They provide an immediate assessment of the importance of the space charge effects, once the gap voltage, gap spacing, and the Fowler–Nordheim coefficients are specified. An example in the parameter regime of vacuum microelectronics is presented.  Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69957/2/PHPAEN-1-6-2082-1.pd

Efficacy and safety of repeated transcranial magnetic stimulation combined with escitalopram in the treatment of major depressive disorder: a meta-analysis

ObjectiveThis study was designed to systematically review the efficacy and safety of repeated transcranial magnetic stimulation (rTMS) combined with escitalopram in treating major depressive disorder (MDD).MethodsDatabases including PubMed, Embase, Cochrane, Web of Science, CNKI, Wanfang, VIP Journal, and China Biomedical Literature databases were electronically searched for randomized controlled trials of rTMS combined with escitalopram intervention for MDD treatment from the inception of these databases to 27 May 2023. Two reviewers independently screened the studies, extracted the data, and assessed the quality of the included studies. R 4.2.2 was then used for a meta-analysis.ResultsIn total, 19 articles involving 1,032 patients were included. The results of the meta-analysis showed that Hamilton Depression Rating Scale (HAMD) scores were significantly lower in the group receiving rTMS combined with escitalopram (experimental group) than that in the control group [weighted mean difference (WMD) = −5.30, 95% confidence interval (95% CI): −6.44 to −4.17, p < 0.01]. The response rate of the experimental group was significantly higher than that of the control group [odds ratio (OR): 5.48; 95% CI: 3.72 to 8.07; p < 0.01]. No significant difference in the adverse reaction rate was observed between the two groups (OR: 1.04, 95% CI: 0.71 to 1.52, p = 0.82).ConclusionOur findings suggest that rTMS combined with escitalopram can benefit patients with MDD in a safe manner, which may help in guiding clinical practice.Systematic review registrationDOI number: 10.37766/inplasy2023.11.0114, INPLASY2023110114

An analysis of emission characteristics and intrinsic beam quality of field emitter.

The subject of vacuum microelectronics has grown dramatically in recent years since field emitter arrays (FEAs) promise a variety of applications such as flat panel displays, miniaturized rf amplifiers and bright electron sources. FEAs can now be built with microfabrication technologies used for integrated circuits. In this study, the effects of space charge, of emitter materials and of the geometric structure on the electron emission processes in field emitter arrays have been theoretically investigated. Universal current-voltage characteristics are constructed by using a one dimensional model, showing the transition from the non space charge limited flow to Child-Langmuir space charge limited flow. These curves are normalized to the intrinsic scales that are constructed from the Fowler-Nordheim (F-N) coefficients A, B and the field enhancement factor. They provide an immediate assessment of the importance of space charge effects, once the applied voltage, effective electrode gap spacing, F-N coefficients, and the field enhancement factor are specified. The result predicted by this analysis is found to be consistent with the experimental observation for a specific field emitter. The general condition of space charge limited flow for both thermionic and field emission has been formulated. For the first time, we explicitly identify two types of space charge limited flow: (1) the non-zero-surface-field space charge limited flow which may be found in field emission as well as in thermionic emission, and (2) the conventional zero-surface-field space charge limited flow restricted only to thermionic emission. These two types are confirmed through the constructed current-voltage (J-V) characteristics and surface electric field-voltage (E\rm\sb{s}-V) relationships for the field and thermionic emission in the different regimes. The field distributions derived in second type are rather different from the well-known Child-Langmuir field distributions, especially in the near-cathode region. The intrinsic beam quality of an idealized two-dimensional field emitter is evaluated. Under the assumption that the space charge effects are negligible, we construct a scaling law for the intrinsic emittance of an isolated emitter. This scaling law takes into account the F-N emission law and the effects of local field enhancement. It is given in terms of the height and width of the emitter, anode-cathode separation and voltage drop, as well as the F-N coefficients. Typical value of the normalized emittance of the tip is 0.012 mm-mrad.Ph.D.Nuclear EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104822/1/9610185.pdfDescription of 9610185.pdf : Restricted to UM users only

A Tubular Flexible Triboelectric Nanogenerator with a Superhydrophobic Surface for Human Motion Detecting

The triboelectric nanogenerator (TENG) is a newly arisen technology for mechanical energy harvesting from the environment, such as raindrops, wind, tides, and so on. It has attracted widespread attention in flexible electronics to serve as self-powered sensors and energy-harvesting devices because of its flexibility, durability, adaptability, and multi-functionalities. In this work, we fabricated a tubular flexible triboelectric nanogenerator (TF-TENG) with energy harvesting and human motion monitoring capabilities by employing polydimethylsiloxane (PDMS) as construction material, and fluorinated ethylene propylene (FEP) films coated with Cu as the triboelectric layer and electrode, serving in a free-standing mode. The tube structure has excellent stretchability that can be stretched up to 400%. Modifying the FEP films to obtain a superhydrophobic surface, the output performance of TF-TENG was increased by at least 100% compared to an untreated one. Finally, as the output of TF-TENG is sensitive to swing angle and frequency, demonstration of real-time monitoring of human motion state was realized when a TF-TENG was worn on the wrist

A Flexible Wireless sEMG System for Wearable Muscle Strength and Fatigue Monitoring in Real Time

Abstract The detection of surface electromyography (sEMG) signals on the skin has attracted increasing attention because of its ability to monitor muscle conditions in a noninvasive manner and thus possesses great application potential to assess athletic status and training efficiency in real time or to evaluate postoperative muscle rehabilitation conveniently. Here, a flexible wireless sEMG monitoring system that consists of a stretchable sEMG epidermal patch and a flexible printed circuit board to provide real‐time evaluation of muscle strength and fatigue is reported. The epidermal patch is designed to have good stretchability and permeability and optimized to ensure a low contact impedance with the skin and minimized background noise for sEMG signal acquisition with high fidelity. Six commonly used time‐domain and two frequency‐domain features extracted from sEMG signals are systematically analyzed, and a strategy for feature selection and pattern identification is proposed that eventually enables the real‐time assessment of muscle strength and fatigue by using an integrated system in a wearable form

High-Resolution Ammonia Emissions from Nitrogen Fertilizer Application in China during 2005–2020

The accurate estimation of ammonia emission is essential for quantifying secondary inorganic aerosol formation and reactive nitrogen deposition. During the last decades, both fertilizer type and the total amount of nitrogen fertilizer in China have changed, while the resulting changes in ammonia emissions and their spatio-temporal variations are unclear. In this study, we compile a long-term (2005–2020) high-resolution ammonia emission inventory for synthetic fertilizer in China with bottom-up method. We parameterized emissions factors (EFs) considering the impacts of soil properties, method of fertilizer application, fertilizer type, crop type, ambient temperature and wind speed. Meanwhile, the monthly nitrogen fertilizer application is calculated by detailed information on crop-specific fertilizer application practices. For the spatial distribution, the ammonia emissions from fertilizer mostly concentrate in eastern and southwestern China, coincident with the high density of agriculture activity and population in these regions. For the seasonal variation, the ammonia emissions from fertilizer application peak in spring and summer because of dense fertilizer application and high ambient temperature. For the long-term trend, we estimate that the emissions from synthetic fertilizer increased from 5.38 Tg in 2005 to 5.53 Tg in 2008 and remained nearly unchanged during 2008–2012, then decreased to 3.96 Tg in 2020. Urea, ammonium bicarbonate (ABC) and nitrogenous compound fertilizer are major fertilizer types used in China. Despite the increased use of nitrogen fertilizer, ammonia emissions remained stable throughout 2008–2012 with the declined use of ABC. This stable period also reflects ammonia emission increases in western China, offsetting the decreases in eastern China. Furthermore, our emission inventory provides a monthly estimation at a spatial resolution of 0.1 degrees, which can be applied to global and regional atmospheric chemistry model simulations

High-Resolution Ammonia Emissions from Nitrogen Fertilizer Application in China during 2005–2020

The accurate estimation of ammonia emission is essential for quantifying secondary inorganic aerosol formation and reactive nitrogen deposition. During the last decades, both fertilizer type and the total amount of nitrogen fertilizer in China have changed, while the resulting changes in ammonia emissions and their spatio-temporal variations are unclear. In this study, we compile a long-term (2005–2020) high-resolution ammonia emission inventory for synthetic fertilizer in China with bottom-up method. We parameterized emissions factors (EFs) considering the impacts of soil properties, method of fertilizer application, fertilizer type, crop type, ambient temperature and wind speed. Meanwhile, the monthly nitrogen fertilizer application is calculated by detailed information on crop-specific fertilizer application practices. For the spatial distribution, the ammonia emissions from fertilizer mostly concentrate in eastern and southwestern China, coincident with the high density of agriculture activity and population in these regions. For the seasonal variation, the ammonia emissions from fertilizer application peak in spring and summer because of dense fertilizer application and high ambient temperature. For the long-term trend, we estimate that the emissions from synthetic fertilizer increased from 5.38 Tg in 2005 to 5.53 Tg in 2008 and remained nearly unchanged during 2008–2012, then decreased to 3.96 Tg in 2020. Urea, ammonium bicarbonate (ABC) and nitrogenous compound fertilizer are major fertilizer types used in China. Despite the increased use of nitrogen fertilizer, ammonia emissions remained stable throughout 2008–2012 with the declined use of ABC. This stable period also reflects ammonia emission increases in western China, offsetting the decreases in eastern China. Furthermore, our emission inventory provides a monthly estimation at a spatial resolution of 0.1 degrees, which can be applied to global and regional atmospheric chemistry model simulations

Quantitative study on the effect of surface treatments on the electric characteristics of ZnO nanowires

Treatment of ZnO nanowires (NWs) using hydrogen peroxide with increasing concentration results in a continuous increase in the amount of -OH group at the surfaces of the NWs, which demonstrates different characteristics in the transport behaviors of the NWs. Combined with results from theoretical simulation and microphotoluminescence, the variation in the nanowire transport property is explained by the change of carrier density and mobility as induced by the surface treatment. © 2008 American Chemical Society

Environmental Benefits of Ultra-Low Emission (ULE) Technology Applied in China

Seven scenarios were designed to study the national environmental benefits of ULE in coal-fired power plants (CPPs), ULE in industrial coal burning (ICB) and NH3 emission reduction by using the GEOS-Chem model. The results showed that although the CPPs have achieved the ULE transformation target, the PM2.5 concentration across the country has decreased by 4.8% (1.4 μg/m3). Due to the complex non-linear chemical competition mechanism among nitrate and sulfate, the average concentration of nitrate in the country has increased by 1.5% (0.1 μg/m3), which has reduced the environmental benefits of the power plant emission reduction. If the ULE technology is applied to the ICB to further reduce NOx and SO2, although the PM2.5 concentration can be reduced by 10.1% (2.9 μg/m3), the concentration of nitrate will increase by 2.7% (0.2 μg/m3). Based on the CPPs-ULE, NH3 emissions reduced by 30% and 50% can significantly reduce the concentration of ammonium and nitrate, so that the PM2.5 concentration is decreased by 11.5% (3.3 μg/m3) and 16.5% (4.7 μg/m3). Similarly, based on the CPPs-ICB-ULE, NH3 emissions can be reduced by 30% and 50% and the PM2.5 concentration reduced by 15.6% (4.4 μg/m3) and 20.3% (5.8 μg/m3). The CPPs and ICB use the ULE technology to reduce NOx and SO2, thereby reducing the concentration of ammonium and sulfate, causing the PM2.5 concentration to decline, and NH3 reduction is mainly achieved through reducing the concentration of ammonium and nitrate to reduce the concentration of PM2.5. In order to better reduce the concentration of PM2.5, NOx, SO2 and NH3 emission reduction control measures should be comprehensively considered in different regions of China. By comprehensively considering the economic cost and environmental benefits of ULE in ICB and NH3 emission reduction, an optimal haze control scheme can be determined

Environmental Benefits of Ultra-Low Emission (ULE) Technology Applied in China

Seven scenarios were designed to study the national environmental benefits of ULE in coal-fired power plants (CPPs), ULE in industrial coal burning (ICB) and NH3 emission reduction by using the GEOS-Chem model. The results showed that although the CPPs have achieved the ULE transformation target, the PM2.5 concentration across the country has decreased by 4.8% (1.4 μg/m3). Due to the complex non-linear chemical competition mechanism among nitrate and sulfate, the average concentration of nitrate in the country has increased by 1.5% (0.1 μg/m3), which has reduced the environmental benefits of the power plant emission reduction. If the ULE technology is applied to the ICB to further reduce NOx and SO2, although the PM2.5 concentration can be reduced by 10.1% (2.9 μg/m3), the concentration of nitrate will increase by 2.7% (0.2 μg/m3). Based on the CPPs-ULE, NH3 emissions reduced by 30% and 50% can significantly reduce the concentration of ammonium and nitrate, so that the PM2.5 concentration is decreased by 11.5% (3.3 μg/m3) and 16.5% (4.7 μg/m3). Similarly, based on the CPPs-ICB-ULE, NH3 emissions can be reduced by 30% and 50% and the PM2.5 concentration reduced by 15.6% (4.4 μg/m3) and 20.3% (5.8 μg/m3). The CPPs and ICB use the ULE technology to reduce NOx and SO2, thereby reducing the concentration of ammonium and sulfate, causing the PM2.5 concentration to decline, and NH3 reduction is mainly achieved through reducing the concentration of ammonium and nitrate to reduce the concentration of PM2.5. In order to better reduce the concentration of PM2.5, NOx, SO2 and NH3 emission reduction control measures should be comprehensively considered in different regions of China. By comprehensively considering the economic cost and environmental benefits of ULE in ICB and NH3 emission reduction, an optimal haze control scheme can be determined