Relative Losses Research Articles

ECONOMIC DAMAGE ASSESSMENT METHODOLOGY IN CASE OF TRANSFORMER LOAD RATIO DEVIATION

The aim of the study is to develop a methodology for assessing economic damage when the transformer load factor deviates. In the process of research, a method was used to determine the optimal load of a power transformer. A method for assessing economic damage in case of a deviation of its load factor has been developed. The optimal load factor of a power transformer has been determined according to the criterion of the minimum cost of money for the transformation of electrical energy. The load level of power transformers can be assessed by two criteria: by the maximum integral value of the effi ciency and by the minimum loss of money during the transformation of electricity. According to the proposed methodology, the assessment of damage is carried out when the load factor of the transformer deviates from the optimal values, for which the relative losses of electrical energy are calculated. The results obtained when evaluating energy and fi nancial and economic effi ciency show that when the load factor is overestimated relative to the optimal values, it is much more preferable to overestimate than underestimate. The reliability of the results is confi rmed by the satisfactory agreement of the calculated results with the experimental data obtained at the operating power plant.

Sucrose, salicylic acid and citric acid solutions to extent vase life of Vriesea incurvata Gaudich. (Bromeliaceae) floral scapes

Vriesea incurvata is a native bromeliad from Brazilian Atlantic Rainforest and commercialized as an ornamental pot plant. The morphological characteristics of its floral scape may also indicate it as a new product to use as a cut flower. However, its postharvest behavior was unknown. This study was conducted to determine its vase life by applying distilled water (control) and solutions containing sucrose (50 g L-1), salicylic acid (50 μM), and citric acid (50 g L-1) for periods of 8 and 24 h. Floral scapes maintained in solutions showed vase life greater than 16 days when compared to the control (distilled water). However, solutions with sucrose evidenced the best behaviors related to the maintenance of physiological and aesthetic features during the vase life of the floral scapes. It is concluded that solutions with sucrose, salicylic acid, and citric acid applied for 8 and 24 h extend the vase life of the V. incurvata floral scapes. Sucrose applied for 8 h promotes the maintenance of color, brightness, and turgidity; improves water balance, and reduces the relative fresh weight losses of floral scapes throughout the vase life, extending their longevity up to 24 days.

Experimental setup for studying two-phase flows in micro-and minichannels at ultra-high heat fluxes: methodology and first experimental results

The study of phase-change phenomena under high and ultra-high heat fluxes is urgent because of fast development of electronics and microelectronics. We have developed a test section with power of 3.5 kW with a heater of 1x1 cm2 and adjustable geometry of the channel for achieving ultra-high heat fluxes in flow boiling and shear-driven liquid film experiments. The methodology of calculating heat losses in the test section is proposed and verified by flow boiling experiment versus another well studied test section. Observed trend of decrease of relative heat losses with increase in the heat flux makes it possible to assume that the heat flux as high as 2.5 kW/cm2 can be reached by this test section.

Colored optic filters on c‐Si IBC solar cells for building integrated photovoltaic applications

AbstractBuilding Integrated Photovoltaic systems can produce a significant portion of the energy demand of urban areas. Despite their potential, they remain a niche technology that architects and project engineers still find esthetically limited. The dark blue or black color of standard photovoltaic panels is considered inappropriate for restoration projects of historic buildings and represents a major constraint on the development of new projects. This work will provide insight into how the use of optic filters can offer new pathways for architectural acceptance of photovoltaic panels. Optic filters selectively reflect or transmit light by interference and can be designed and fabricated using cost‐effective and industrially compatible processes. By using in‐house developed ray tracing software coupled with TCAD Sentaurus, more than 400 colors were obtained, and their impact on the opto‐electrical performance of interdigitated back‐contacted solar cells was studied. Results show a maximum efficiency loss of 1.6% absolute at the perpendicular incidence of light on the range of obtained colors when compared with a standard dark blue solar cell. Simulations for different angles of incidence showed that the current reduction on the standard device could be modeled using a cosine relationship. The colored cells, however, deviated significantly from this relationship. We propose that the angular behavior of any cell (colored or standard) could be simulated by modifying the effective irradiance with scaling factors equal to the ratios of the photogenerated current at any angle with respect to the value at normal incidence. We demonstrate that this approach accurately models the effect of the color filter and allows for an easy transition from a bare cell to an encapsulated one. Due to the spectral effect of the filter, we developed both a spectrally resolved optical model and a two‐dimensional finite volume transient thermal model. In case of the optical model, we demonstrate an accuracy in the prediction of the reflectance produced by the color with values of mean bias error (MBE) between 2.0% and 3.9%. As for the thermal model, it was validated by first analyzing a standard model under conditions of nominal operating cell temperature and then comparing its results with published scientific literature. Later, we compare its prediction against 2 weeks of measurements. In both cases the thermal model proves an adequate accuracy, yielding differences below 1.5°C with respect to other scientific works and an MBE value of 0.89°C as well as a root‐mean‐square error value of 2.10°C for the entire measurement period. With the validated models, we studied the effect of the encapsulation on the color perception. We present two options of color filters. The first one produces relatively low reflectance losses and presents relative annual direct current (DC) energy losses of up to 6.4% for Delft, in the Netherlands, and up to 5.9% for Alice Springs in Australia. However, this first option has very poor color brightness. The second studied filter produces highly saturated bright colors. Improving brightness can increase the annual DC relative losses up to 13.7% and 13.5% for Delft and Alice Springs, respectively. Overall, we demonstrate that colored filters based on multilayer optical stacks are a versatile option for coloring cells that allow a good compromise between esthetics and performance.

Paddy soils have a much higher microbial biomass content than upland soils: A review of the origin, mechanisms, and drivers

Many studies have shown that the microbial biomass content in paddy soils is much higher than that in upland soils, but a comprehensive review of the underlying mechanisms and processes is lacking. We conducted a meta-analysis of published literature on the microbial biomass content in continuous paddy soils (>1700 data pairs) and paddy-upland rotation soils (>1100 data pairs) as compared to that in adjacent upland soils (>360 data pairs), measured by the fumigation extraction or fumigation incubation method. The microbial biomass carbon (MBC) content in paddy soils was double that in upland soils. This MBC surplus in paddy soils compared to upland soils was explained by (1) higher input of root C and rhizodeposits by rice plants compared with upland crops; (2) lower oxygen availability and consequently slower microbial turnover; (3) higher microbial C assimilation efficiency in paddy soils; and (4) additional C stabilization on iron (oxyhydr)oxides in paddy soils. The proportion of MBC in total soil organic C in paddy-upland rotation, paddy, and upland soils was 3.5%, 2.5%, and 2.1%, respectively. The higher microbial biomass C/N ratio in paddy soils (12.4 ± 0.11) compared to upland soils (9.9 ± 0.21) reflects greater N losses (through nitrate leaching and denitrification) in relation to slower C losses under anoxic conditions. Despite higher temperature and better water availability, microbial biomass turnover was 1.1–1.6 times slower in paddy soils than in upland soils because of oxygen limitation. Multiple stepwise regression and redundancy analyses showed that microbial biomass in continuous paddy and paddy-upland rotation soils was affected by similar soil factors (such as total N and organic C), whereas microbial biomass in upland soils was mainly affected by pH and the organic C content. Paddy-upland rotation soils undergo oxic–anoxic cycles and consequently can absorb and coprecipitate organic compounds with iron (oxyhydr)oxides as an additional advantage for C stabilization. We conclude that the reduced microbial activity and slower microbial turnover under oxygen-limited conditions lead to nearly two times higher microbial biomass content in paddy than in upland soils.

Efforts to Recover State Financial Losses through Asset Blocking as a Corruption Law Enforcement Strategy

One of the elements in the criminal act of corruption is the loss of state finances. Against this state financial loss, the good old Corruption Law, namely Law no. 3 of 1971 and the newer Law no. 31 of 1999 in conjunction with Law no. 20 of 2001, stipulates a policy that state financial losses must be returned or replaced by perpetrators of corruption (Asset Recovery). The application of the law on state financial losses in relation to criminal acts of corruption that must be proven is the existence of state financial losses that have a causal relationship with the actions of the perpetrators of corruption. In this paper, the author uses a descriptive qualitative methodology to describe the conditions as they are, without giving treatment or manipulation to the variables studied.

Soil freezing-thawing induces immediate shifts in microbial and resource stoichiometry in Luvisol soils along a postmining agricultural chronosequence in Western Germany

Freeze-thaw (FT) events exert a great physiological stress on soil microorganisms and hence impact biogeochemical processes in soils. As numerous environmental factors affect microbial and chemical responses to FT, a better understanding of the leverage factors that regulate the responses to FT events is required. To date, FT-induced shifts and transformations in microbial and resource stoichiometry have received particularly little attention. We exposed fifteen Luvisol soils with different time after restoration and corresponding differences in soil organic C contents from a postmining agricultural chronosequence to a single FT event and analysed changes in soil chemistry and microbial stoichiometry one hour and eighteen hours after thawing. FT considerably altered soil biochemical attributes within the first hours of thawing. Microbial biomass C declined substantially after FT, and its relative losses were positively correlated with enhanced dissolved organic C contents. Thus, microbial cell lysis likely led to the significant increase of dissolved organic C. Moreover, microbial biomass C losses were disproportionally higher in C-rich soils, suggesting that soil microorganisms in high-C soils might be particularly prone to FT stress. Microbial biomass N marginally decreased one hour after thawing, yet returned to initial levels eighteen hours after thawing. The alternating responses of microbial biomass C and N caused a strong stoichiometric reduction of the microbial C:N ratio. The resulting microbial oversaturation with N relative to C is likely the first step in the chain of processes that generally lead to the high N losses commonly recorded in agricultural soils in the aftermath of FT events. Metabolic activity of the soil microbial community increased with the relative decline of the microbial biomass C:N ratio eighteen hours after thawing, suggesting increased levels of microbial metabolic expenditure due to stoichiometric shifts. The strength of the FT-driven biochemical responses was strongly dependent on soil organic C content, indicating that high-C soils might be especially vulnerable to initial C and N losses due to shifts in microbial stoichiometry.

The Effects of Filter Capacitors on Cable Ripple at Different Sections of the Wind Farm Based Multi-Terminal DC System

In most DC power systems, power electronic devices can introduce ripple content into the DC grid, where large input ripple currents on the DC link can have a negative influence. Under these circumstances, DC side filters play an important role in the reduction of ripple content. In this paper, based on a full detailed closed loop model of the entire offshore wind farm multi-terminal DC network, the effect of filter capacitors connected at different sections of the system on the limitation of the AC ripple content, particularly in the DC cables, is studied. In contrast to other work on HVDC for offshore wind, where simplified or equivalent circuits are mainly used while concentrating on the power and control system, this study can be regarded as the specific study of filter capacitors operating within a detailed system model. Utilising the advantages of PLECS, which is a highly effective tool in the simulation of power electronic circuits, no small-signal or simplified equivalent models are used in the system, and the entire study is based on detailed and accurate models of the semiconductor elements and transformers, which help to provide more realistic simulation results and a better understanding of the system. Another novel point in this paper is a new concept, relative losses, which is proposed to simplify extensively the calculation of losses in this research. Finally, the size of the filter capacitors at different sections of the system under different situations is suggested.

Impact of box section coverage on the hydraulic parameters of open channels

Abstract The effects of box coverage blockage on the hydraulic characteristics of open channels within the case of sub-critical flow in the open channel were explored experimentally in research. Fifty-two test runs were utilized to attain the research's objectives, with four water discharges of 2, 5, 8, and 11 L/sec, three-box coverage side dimensions of 8.8, 10.4, and 12.90 cm, and four coverage blockage ratios of 0, 10, 20, and 30%. The water depth and velocity were measured in each run. The results revealed that increasing the blockage ratios, water discharge, and a diminishing within the area passing water through the coverage led to an increment of the heading up, head losses, and water surface level. The worst-case situation was a little coverage dimension (8.80 cm side) with 30% blockage and discharge of 11 L/s. Within blockage ratios, of 0, 10, 20, and 30% and discharge 11 L/s, the relative heading up ratio (hRu%) values were 85, 97, 111, and 125 percent respectively, and for the relative head losses ratio values downstream the coverages (hRloss%) were 88, 99, 113, and 131 percent respectively related to the depth of a non-coverage case. The flow velocities and the relative area passing water through the coverage were the most effective variables on heading up and head losses. The relative heading up and the relative head loss increased with the increment of the Froude number (Frd). Within a constant relative wetted area of coverage (Ar), and increasing the Froude number (Frd) by 0.01 percent, the relative heading up and relative head loss approximately increased by 5.5% and 6.2% respectively. It is recommended to implement the periodic maintenance of the coverage to improve the discharge capacity of the open channel.

Simulation modelling of yield losses caused by wheat stem rust

AbstractStem rust, or black rust, of wheat, caused by Puccinia graminis f. sp. tritici, has recently re‐emerged in several parts of the world, with epidemics occurring in eastern Africa, as well as northern and southern Europe. Damage mechanisms from disease dynamically affect the physiology of the crop as it grows and develops, and as the epidemic progresses, leading to yield losses in the stem rust‐diseased wheat stand. Process‐based agrophysiological models that include disease‐induced damage mechanisms can help to better understand the physiological processes leading to yield losses, and to inform strategic decisions such as breeding strategies. Such models have not been developed for wheat stem rust so far. Two damage mechanisms for stem rust, light stealing and assimilate diversion, were incorporated in the agrophysiological simulation model WHEATPEST. The model, tested from experimental field data retrieved from the literature, provides a satisfactory representation of the system, although consistently underestimates relative yield losses by about 6.9%, resulting in relative yield losses between 17% and 56%. Analyses highlight the importance of the diversion of assimilates toward the pathogen in the magnitude of yield loss. Considering only the reduction of green leaf area would underestimate damage from stem rust by at least threefold. The analysis also shows the importance of the dynamic interplay between disease and crop growth, especially the dynamics of leaf area, on yield loss. Directions to consider additional damage mechanisms are proposed, and perspectives for future research, especially in relation to plant breeding strategies under climate change, are offered.

Energy efficiency of a 3-level shunt active power filter powered by a fuel-cell / battery DC bus with regulated duty cycles

Introduction. Nowadays, electrical energy is indispensable in industrial, tertiary and domestic appliances. However, its efficiency is becoming affected by the presence of the disturbances that appear in the electrical networks such as harmonics, unbalance, sags/swells, flickers …etc. Indeed, the disturbances cause a decrease in the power factor and an increase in the power losses. In this paper, the harmonic disturbance is considered and a 3-level shunt active power filter powered by a hybrid fuel-cell/battery DC is applied to mitigate current harmonic components from the electrical feeder. Aim. Studying the energy efficiency of a system based on a 3-level shunt active filter powered by a hybrid fuel-cell / battery DC bus. Methodology. It is a matter of finding the suitable formulas that express the efficiency and the relative power losses according to the load factor (which is the ratio between the short-circuit active power and the load active power) and the load power factor. The DC bus energy is controlled using an energy management algorithm that contributes in generating the required reference input currents and output voltages of the fuel-cell and the battery. The DC/DC converters control circuits are performed in a closed loop by means of regulated duty cycles. Results. The simulation results carried-out under MATLAB/Simulink environment show better filtering quality if compared with the case of open loop control of the DC/DC converters and lesser differences between the fuel-cell power, the battery power and their respective reference powers. Which concerns the energy efficiency, the results demonstrate that higher efficiency and lower relative power losses can be achieved only when higher load factor and load power factor are attained. Therefore, the compensating system of the power factor is very important to improve the energy efficiency.

Costs and benefits of trade shocks: Evidence from Chilean local labor markets

We study Chile’s labor market responses to trade shocks during 1996–2006, exploiting spatial and time variations in trade exposure arising from initial differences in industry specialization across local labor markets and the evolution of shocks across industries. We take advantage of China’s supply and demand’s worldwide shocks to instrument for Chinese import competition and demand for Chilean exports. Our main finding is that increasing manufacturing import competition implied a significant rise in labor informality in more exposed local markets, especially among young and unskilled workers. These groups also suffered significant relative wage losses. Meanwhile, locations that benefited most from the increased demand for primary products experienced a relative increase in employment, particularly among young individuals, and reallocation from self-employment towards salaried jobs in the formal sector, along with relative wage gains among old-age workers. Interestingly, these areas experienced a smaller increase in tertiary education enrollment rates than less exposed areas.

Bias-dependent displacement damage effects in a silicon avalanche photodiode

Radiation effects studies on a commercial beveled-edge avalanche photodiode (APD) showed that applying reverse bias to the device during irradiation enhanced the severity of apparent damage. Proton microbeam irradiations were made using a proton beam energy of 2 MeV and fluence ranging from 2.0×1010 to 5.1×1012 cm−2. Charge collection measurements using the ion beam induced charge (IBIC) technique showed that relative losses increased by up to an order of magnitude when the reverse bias applied during irradiation increased from 50 to 1500 V. The presence of reverse bias also led to equivalent losses in charge collection that would only be seen in irradiations with an order of magnitude higher fluence in unbiased APDs. The results demonstrate that bias-enhanced irradiation damage is insufficiently understood and must be accounted for in characterizations of radiation effects.

Primary energy efficiency potentials of district heat driven refrigeration systems

District heat driven absorption chillers (AChs) contribute to a higher utilisation of the district heating network in summer and thus to a reduction of the relative heat losses. Due to higher investment but lower operating costs, AChs usually cover the base load, but compression chillers (CChs) are installed for peak load as well. For ACh and CCh, heat rejection is often realised via cooling towers (CTs). In addition, many systems provide the option of free cooling in winter by using the cooling towers to cover the cooling demand directly. Thus, absorption cooling (AC), compression cooling (CC) and free cooling (FC) represent three operating modes for cold generation in one overall refrigeration system. The concept of allocating base load and peak load is usually realised by activating CC when AC exceeds the capacity limit. FC is activated when the ambient temperature falls below a certain switchover value.In this study, extensive monitoring data from a large-scale field test (“Field test absorption chillers for CCHP systems”) are used to show that refrigeration systems controlled in such or similar ways have considerable potential to increase primary energy efficiency, even if the individual chillers are operated efficiently. Therefore, models are applied to the individual primary components (ACh, CCh, CT and auxiliary pumps). By using these models, thermal and/or electrical part-load efficiencies of AC, CC and FC and their specific dependencies on the ambient temperature and chilled water set temperature are calculated. Taking into account district heating and electricity primary energy factors allows to determine the operating mode with the lowest primary energy demand for each load condition measured in the field test within one year. The savings potential of 14% resulting from this example shows how promising the application of a model-based system control is compared to conventional strategies.

Effect of Technological Mismatch on Photovoltaic Array: Analysis of Relative Power Loss

This study conducts a comparative evaluation of the performance of modules and the arrays under standard test conditions. An equivalent circuit model was developed alongside a computational scheme. The model input data were obtained from the manufacturer’s specification datasheets. They were used to analyse the maximum Fill Factor (FF) and Relative Power Losses (RPL) for Parallel (P), Series (S) and Series-Parallel (SP) configurations. For matching modules, the RPL was insignificant, but for mismatched modules, the parallel configuration (P) and series-parallel (SP) yielded RPL of 1.3 %, while the series configuration (S) produced RPL of 2.6 %. Thus, short circuit defects associated with the P and SP configuration were well below the open circuit defects associated with the series configuration (S). These results clearly show that the large photovoltaic plant needs to be configured with multiple blocks or strings of SP configuration in order to suppress RPL. In addition, the designer and installers of large solar power plants should adopt modules with uniform electrical and thermal properties in the construction of large solar power plants. The trivial RPL associated with the matched modules should be taken into consideration, as well.

Composite salt corrosion deterioration characteristics and damage calculation models of concrete incorporated with corrosion inhibiting admixtures

This research investigation was an experimental study which was intended to verify the corrosion deterioration characteristics of C30 concrete incorporated with different dosage amounts of corrosion inhibiting admixtures (abbreviated as CIA in this study) under the environmental conditions of composite salt corrosion. Damage calculation models were proposed for the purpose of evaluating the influencing effects of the different dosage amounts. The experimentation results showed that when the content of CIA was 5%, the compressive strength of the concrete could be effectively improved. In addition, the average penetration depth and migration coefficient of the chloride ions, along with the macrocell current of the rebars, could be decreased. At the same time, the mass loss rates, relative dynamic elastic modulus losses, accumulative damage, and internal pore quantities of the examined concrete specimens incorporated with 5% CIA were observed to be significantly lower than those of ordinary concrete samples during every freezing-thawing cycle. Furthermore, the degree of anti-corrosion deterioration of the concrete was significantly promoted. This study's established chloride ions permeability models, rebars corrosion model, and concrete freezing-thawing damage models, were found to have the ability to more accurately reflect the variations of various performance indexes of the concrete in composite salt erosion environments. Therefore, it was considered that the established damage models could potentially provide valuable guidance for forecasting the life expectancy of concrete in the future.

Strategies to mitigate ammonia and nitrous oxide losses across the manure management chain for intensive laying hen farms

Circular economy principle aims to achieve sustainable production systems, focusing on the waste valorisation and the reduction of gaseous losses to the atmosphere. Nitrogen (N) compounds in terms of ammonia (NH3) and nitrous oxide (N2O) represent the major losses to the atmosphere of laying hen manure management chain. We present a study aimed to evaluate NH3 and N2O emission and mitigation strategies at housing, storage and land spreading stages. The whole manure management chain was evaluated under different scenarios which combined mitigation strategies of each stage. Two intensive laying hen facilities were involved in the study. Evaluated mitigation strategies were: (i) frequency of manure removal from housing facility, (ii) dried manure storage after passing throughout a manure drying tunnel (MDT) compared to fresh manure storage and (iii) fresh or dried manure incorporation versus surface land application. Increasing the frequency of manure removal from 4 days to 1/3 daily, reduced N losses around 68%. Dried manure storage achieved around 75% reduction in N losses compared to fresh manure storage. Spreading dried manure on grassland surface reduced ≈77% NH3 losses in relation to the emission level reached by fresh manure. The reduction was similar when dried manure was incorporated compared to surface application of fresh manure (≈79%). A 40% reduction in N losses was achieved using the MDT compared to no drying strategy. In the whole manure management chain, the combination of strategies that most reduced N losses was: removal frequency of 1/3 daily, dry storage after passing through the MDT and incorporated land application. These strategies reduced N losses between 40 and 60% compared to the 4 days of removal frequency, fresh storage and surface application of fresh manure.

High crop yield losses induced by potential HONO sources — A modelling study in the North China Plain

Nitrous acid (HONO) is a major source of hydroxyl radicals in the troposphere through its photolysis, and can significantly influence ozone (O3) levels, thereby causing considerable crop yield losses. Previous studies have assessed relative crop yield losses by using exposure-response equations with observed or simulated O3, however, the contribution of enhanced O3 due to potential HONO sources to the crop yield losses has never been quantified. In this study, for the first time, we evaluated the crop yield losses caused by potential HONO sources in the North China Plain (NCP), which is one of the major grain-producing areas in China suffering from heavy O3 pollution, by using the Weather Research and Forecasting/Chemistry (WRF-Chem) model during the wheat and maize growing seasons of 2016. HONO simulations were significantly improved after including six potential HONO sources in the WRF-Chem model. The potential HONO sources produced a daily maximum 8-h O3 enhancement of 8.1/8.2 ppb during the wheat/maize growing seasons, respectively, and led to ~11.4%/3.3% relative yield losses for wheat/maize, respectively, corresponding to approximately US$3.78/0.66 billion losses, respectively, in NCP in 2016. The above results suggest that potential HONO sources play a significant role in O3 formation and could induce high crop yield losses globally.

FedResilience: A Federated Learning Application to Improve Resilience of Resource-Constrained Critical Infrastructures

Critical infrastructures (e.g., energy and transportation systems) are essential lifelines for most modern sectors and have utmost significance in our daily lives. However, these important domains can fail to operate due to system failures or natural disasters. Though the major disturbances in such critical infrastructures are rare, the severity of such events calls for the development of effective resilience assessment strategies to mitigate relative losses. Traditional critical infrastructure resilience approaches consider that the available critical infrastructure agents are resource-sufficient and agree to exchange local data with the server and other agents. Such assumptions create two issues: (1) uncertainty in reaching convergence while applying learning strategies on resource-constrained critical infrastructure agents, and (2) a huge risk of privacy leakage. By understanding the pressing need to construct an effective resilience model for resource-constrained critical infrastructure, this paper aims at leveraging a distributed machine learning technique called Federated Learning (FL) to tackle an agent’s resource limitations effectively and at the same time keep the agent’s information private. Particularly, this paper is focused on predicting the probable outage and resource status of critical infrastructure agents without sharing any local data and carrying out the learning process even when most of the agents are incapable of accomplishing a given computational task. To that end, an FL algorithm is designed specifically for a resource-constrained critical infrastructure environment that could facilitate the training of each agent in a distributed fashion, restrict them from sharing their raw data with any other external entities (e.g., server, neighbor agents), choose proficient clients by analyzing their resources, and allow a partial amount of computation tasks to be performed by the resource-constrained agents. We considered a different number of agents with various stragglers and checked the performance of FedAvg and our proposed FedResilience algorithm with prediction tasks for a probable outage, as well as checking the agents’ resource-sharing scope. Our simulation results show that if the majority of the FL agents are stragglers and we drop them from the training process, then the agents learn very slowly and the overall model performance is negatively affected. We also demonstrate that the selection of proficient agents and allowing them to complete only parts of their tasks can significantly improve the knowledge of each agent by eliminating the straggler effects, and the global model convergence is accelerated.

Significant Reductions in Crop Yields From Air Pollution and Heat Stress in the United States

AbstractThe joint exposure of plants to surface ozone, atmospheric aerosols, and heat stress can lead to considerable decreases in crop yields. Surface ozone negatively impacts plant photosynthesis while aerosols can have positive or negative effects from its dual impact on light and temperature. Here, using a statistical model, we show that in the United States, as a result of improvements in air quality, the damages caused by ozone and aerosols have decreased since 1980. Historically, relative yield losses due to ozone were 8.7% and 4.8%, and due to aerosols were 11.3% and 23.2% for maize and soybean, respectively. Maize yields are more sensitive to ozone pollution while soybean yields are more sensitive to aerosol pollution. In future RCP 8.5 scenario, absent significant reductions in emissions or improvements in air quality, maize, and soybean would have on average, 58.5% and 36.9% additional yield reductions, respectively, mainly caused by warming. Future climate warming and fossil fuel combustion driven changes to air pollution may have differing impacts on crop yield and should be jointly considered in any assessment of U.S. food security.