Guava Disease Detection Using Deep Convolutional Neural Networks: A Case Study of Guava Plants

Food production is a growing challenge with the increasing global population. To increase the yield of food production, we need to adopt new biotechnology-based fertilization techniques. Furthermore, we need to improve early prevention steps against plant disease. Guava is an essential fruit in Asian countries such as Pakistan, which is fourth in its production. Several pathological and fungal diseases attack guava plants. Furthermore, postharvest infections might result in significant output losses. A professional opinion is essential for disease analysis due to minor variances in various guava disease symptoms. Farmers’ poor usage of pesticides may result in financial losses due to incorrect diagnosis. Computer-vision-based monitoring is required with developing field guava plants. This research uses a deep convolutional neural network (DCNN)-based data enhancement using color-histogram equalization and the unsharp masking technique to identify different guava plant species. Nine angles from 360∘ were applied to increase the number of transformed plant images. These augmented data were then fed as input into state-of-the-art classification networks. The proposed method was first normalized and preprocessed. A locally collected guava disease dataset from Pakistan was used for the experimental evaluation. The proposed study uses five neural network structures, AlexNet, SqueezeNet, GoogLeNet, ResNet-50, and ResNet-101, to identify different guava plant species. The experimental results proved that ResNet-101 obtained the highest classification results, with 97.74% accuracy.

Wind turbine icing characteristics and icing-induced power losses to utility-scale wind turbines

A field campaign was carried out to investigate ice accretion features on large turbine blades (50 m in length) and to assess power output losses of utility-scale wind turbines induced by ice accretion. After a 30-h icing incident, a high-resolution digital camera carried by an unmanned aircraft system was used to capture photographs of iced turbine blades. Based on the obtained pictures of the frozen blades, the ice layer thickness accreted along the blades’ leading edges was determined quantitatively. While ice was found to accumulate over whole blade spans, outboard blades had more ice structures, with ice layers reaching up to 0.3 m thick toward the blade tips. With the turbine operating data provided by the turbines’ supervisory control and data acquisition systems, icing-induced power output losses were investigated systematically. Despite the high wind, frozen turbines were discovered to rotate substantially slower and even shut down from time to time, resulting in up to 80% of icing-induced turbine power losses during the icing event. The research presented here is a comprehensive field campaign to characterize ice accretion features on full-scaled turbine blades and systematically analyze detrimental impacts of ice accumulation on the power generation of utility-scale wind turbines. The research findings are very useful in bridging the gaps between fundamental icing physics research carried out in highly idealized laboratory settings and the realistic icing phenomena observed on utility-scale wind turbines operating in harsh natural icing conditions.

A novel approach for measurement and decomposition of the economywide costs of shutting down tourism and related service sectors against COVID-19

The trade-off between desirable public health outcomes and undesirable economic outcomes of anti-pandemic measures forces policy makers everywhere to seek the right combination of measures to balance the public health concerns against employment and income considerations. This article describes a novel input–output approach to assessing economywide costs of shutting down tourism and related sectors to curb the spread of COVID-19. Our framework allows for a decomposition of the total effects of shutdowns into sectoral output losses resulting from (i) suspension of the delivery of inputs to other sectors, (ii) termination of the demand for inputs produced by these sectors, and (iii) the interruption of payments to the owners of factors of production employed in the sectors ordered to shut down. We illustrate the use of this methodological framework to measure and decompose the effects of recent shutdown orders issued in Turkey, a country of major tourism activity.

Performance evaluation of GaN and Si based driver circuits for a SiC MOSFET power switch

<p>Silicon Carbide (SiC), new power switches (PSW) require new driver circuits which can take advantage of their new capabilities. In this paper a novel Gallium Nitride (GaN) based gate driver is proposed as a solution to control SiC power switches. The proposed driver is implemented and is performance compared with its silicon (Si) counterparts on a hard switching environment. A thorough evaluation of the energy involved in the switching process is presented showing that the GaN based circuit exhibits similar output losses but reduces the control power needed to operate at a specified frequency.</p>

Output Losses from Currency Crises and the Role of Central Bank

Generally, one of the important issues related to currency crises is the output losses caused by these phenomena. In this study, determinants of output losses and particularly the role of the central bank will be evaluated during currency crises. Moreover, the paper tries to investigate the roles of macroeconomic variables and also monetary, fiscal and exchange rate policies on the output losses during currency crises. In this regard, an econometric model with panel data has been used for emerging market countries during 1980-2016. The results show that currency crises accruing have a positive and significant effect on output losses. While the successful defence of central bank has had the negative effects on the output losses, but it is positive for the unsuccessful defence and the non-intervention or immediate depreciation. However, the role of the macroeconomic condition is important where total foreign reserves can be considered as a buffer against the output losses, while inflation and deviation of the real exchange rate from its trend have had positive effects on the output losses. Finally, the output losses can be reduced by an active monetary, fiscal and exchange rate policies.

Future heat stress to reduce people’s purchasing power

With increasing carbon emissions rising temperatures are likely to impact our economies and societies profoundly. In particular, it has been shown that heat stress can strongly reduce labor productivity. The resulting economic perturbations can propagate along the global supply network. Here we show, using numerical simulations, that output losses due to heat stress alone are expected to increase by about 24% within the next 20 years, if no additional adaptation measures are taken. The subsequent market response with rising prices and supply shortages strongly reduces the consumers’ purchasing power in almost all countries including the US and Europe with particularly strong effects in India, Brazil, and Indonesia. As a consequence, the producing sectors in many regions temporarily benefit from higher selling prices while decreasing their production in quantity, whereas other countries suffer losses within their entire national economy. Our results stress that, even though climate shocks may stimulate economic activity in some regions and some sectors, their unpredictability exerts increasing pressure on people’s livelihood.

Precaution, Social Distancing and Tests in a Model of Epidemic Disease

I develop an extension of a canonical epidemiology model in which the policy in place determines the probability of transmission of an epidemic disease during economic and social interaction. I use the model to evaluate the effects of isolating symptomatic individuals, of increasing social distancing and of tests such as polymerase chain reaction – PCR – or Rapid Diagnostic Test that discriminate between currently infected agents, and its combination with a serology test like Neutralization Assay that is able to discriminate between immune and vulnerable healthy individuals, together with the role of enforcement to prevent interactions involving infected but asymptomatic agents. I find that isolating symptomatic individuals has a large effect at delaying and reducing the pick of infections. The combination of this policy with a PCR test is likely to represents only a negligible improvement in the absence of enforcement, whereas with full enforcement there is an additional delaying and reduction in the pick of infections. Social distancing alone cannot achieve similar effects without incurring in enormous output losses. I explore the combined effect of social distancing at early stages of the epidemic with a following period of tests and find that the best outcome is obtained with a light reduction of human interaction for about three months together with a subsequent test of the population over 40 days.