Optical Fiber Based Sensors for Harsh Environments

The primary objective of this study is to develop optical fiber-based sensors that are capable of operating in extreme conditions. Silica-based optical fibers are well known for their resilience to harsh environments. Whether they are integrated into distributed sensing schemes or as point sensors, optical fibers offer low-costs, highly accurate sensing platforms for various physical quantities. In this dissertation, state-of–the-art Al-doped radiation sensitive optical fibers for distributed ionizing radiation measurements are presented for the first time. This optical fiber sensor, coupled with a Rayleigh scattering-based optical frequency domain reflectometry (OFDR) scheme, was used to monitor and quantitate ionizing gamma radiation from a 60Co radioactive isotope. An alternative multi-core optical fiber was deployed to simultaneously monitor two different parameters. The dual-core fiber has been fabricated with two distinct optical cores to allow for differences between the cores’ temperature and strain coefficients. With such differences, temperature and strain changes were discriminated using a Brillouin scattering time domain analyzer (B-OTDA). Ultrafast lasers are commonly used to inscribe thermally stable nanostructures on optical fibers’ cores. IR laser-induced structures inscribed on low-loss, radiation-hard silica fibers were used to develop point and distributed sensors for in-pile nuclear reactor measurements. The sensors were subjected to, arguably the most challenging of artificial environments, with temperatures above 600°C, and high neutron fluxes at levels above 1.2×1014 n/s/cm2. The sensors were also used to monitor the temperature distribution inside of a solid oxide fuel cell (SOFC). The information obtained from the operational SOFC can be used to prolong its lifetime and increase its efficiency. Lastly, additive manufacturing embedding of optical fibers into metallic parts were attempted. A nickel-iron alloy, Invar-36, was investigated as a coating material for silica. The coefficient of thermal expansion (CTE) of Invar-36 can be carefully engineered to be close to that of silica. With a reduced CTE mismatch at the glass-metal interface, problems of adhesion and delamination can be deterred to extreme conditions. The proposed sensor designs and implementations would allow monitoring complex structures, and harsh environments like in SOFCs, gas turbines, robotics, or in high performance machinery, with minimal invasiveness

Host plant mediates foraging behavior and mutual interference among adult Stethorus gilvifrons (Coleoptera: Coccinellidae) preying on Tetranychus urticae (Acari: Tetranychidae)

Citation: Bayoumy, M. H., Osman, M. A., & Michaud, J. P. (2014). Host plant mediates foraging behavior and mutual interference among adult Stethorus gilvifrons (Coleoptera: Coccinellidae) preying on Tetranychus urticae. Retrieved from http://krex.ksu.eduPhysical plant characteristics can influence predator foraging and their behavioral responses to each other. This study examined the searching efficiency and functional response of adult female Stethorus gilvifrons Mulsant foraging for Tetranychus urticae Koch (Acari: Tetranychidae) on castor bean, common bean, and cucumber leaves. Experiments conducted on leaf discs in arenas for 12 h revealed a type II functional response for S. gilvifrons on all host plants. Per capita searching efficiency and killing power decreased with increasing predator density on all plants, but most notably on common bean, the plant with the highest prey consumption rates, due to greater mutual interference. Attack rates were highest on common bean and lowest on castor bean, whereas handling times were shortest on common bean and longest on cucumber, such that the daily predation rate was maximal on common bean. Host plant interacted with predator and prey densities to affect searching efficiency and functional response, the differences in mite consumption among host plants increasing with predator and prey densities. The waxy layers of castor bean leaves and high trichome counts of cucumber leaves appeared to reduce predator foraging efficiency. Thus, the efficacy of S. gilvifrons against T. urticae is likely to be greatest on plants such as Phaeseolus vulgaris L. that have relatively smooth leaves

Extreme marine heatwaves and cold-spells events in the Southern North Sea: classifications, patterns, and trends

In this study, we examined the long-term spatiotemporal trend of marine heatwaves (MHW) and marine cold spells (MCS) characteristics in the southern North Sea over the last four decades (1982-2021). We then estimated the difference between their annual mean values and the possible relationship with the large-scale climate modes of natural sea surface temperature (SST) and atmospheric variability using satellite SST data. The SST warming rate was 0.33 ± 0.06°C/decade and was associated with an increase in MHW frequency (0.85 ± 0.39 events/decade) and a decrease in MCS frequency (-0.92 ± 0.40 events/decade) over the entire period. We found a distinct difference between the annual mean values of MHW and MCS characteristics, with a rapid increase in total MHW days (14.36 ± 8.16 days/decade), whereas MCS showed an opposite trend (-16.54 ± 9.06 days/decade). The highest MHW frequency was observed in the last two decades, especially in 2014 (8 events), 2020 (5 events), and 2007 (4 events), which were also the warmest years during the study period. Only two years (2010 and 2013) in the last two decades had higher MCS frequency, which was attributed to the strong negative phase of the North Atlantic Oscillation (NAO). Our results also show that on the annual scale, both the East Atlantic Pattern (EAP) and the Atlantic Multidecadal Oscillation (AMO) play a more important role in the formation of the MHW in the southern North Sea than the other teleconnections (e.g., the NAO). However, the NAO made the largest contribution only in the winter. Strong significant (p < 0.05) positive/negative correlations were found between oceanic and atmospheric temperatures and the frequency of MHW/MCS. This suggests that with global warming, we can expect an increase/decrease in MHW/MCS occurrences in the future

Shear Strength Characteristics of Cemented Clayey Sand Soil

Several techniques of soil stabilization are available to improve the behavior of many types of soil. The addition of cement to soils have proved a significant effect on the geotechnical properties of treated soils. In this study, an artificial clayey sand soil samples were prepared by mixing 20% kaolin clay of fine sand. Initially, compaction tests were conducted on soil mixture to study the effect of kaolin addition on maximum dry density, optimum moisture content of mixed soil at a relative density of 55%. The mixed soils were improved by cement. Then ,a series of unconfined compression tests were performed to clarify the performance of improved soil with different cement contents at the optimum water content of each cement content ,and the samples examined after two hours from preparation, and curing period of 7 days and 14 day. Results of compaction test indicate that adding kaolin increasing maximum dry density and moisture content. Tests results show that addition of cement to soil mixture increased stiffness and unconfined compression strength (UCS), and leading to a brittle behavior

Comparison between P&O and SSO techniques based MPPT algorithm for photovoltaic systems

Solar photovoltaic (SPV) systems are a renewable source of energy that are environmentally friendly and recyclable nature. When the solar panel is connected directly to the load, the power delivered to the load is not the optimal power. It is therefore important to obtain maximum power from SPV systems for enhancing efficiency. Various maximum power point tracking (MPPT) techniques of SPV systems were proposed. Traditional MPPT techniques are commonly limited to uniform weather conditions. This paper presents a study of MPPT for photovoltaic (PV) systems. The study includes a discussion of different MPPT techniques and performs comparison for the performance of the two MPPT techniques, the P&O algorithm, and salp swarm optimization (SSO) algorithm. MATLAB simulations are performed under step changes in irradiation. The results of SSO show that the search time of maximum power point (MPP) is significantly decreased and the MPP is obtained in the shortest time with high accuracy and minimum oscillations in the generated power when compared with P&O

Effect of maternal dexamethasone administration on daily fetal movement count and its correlation with Doppler studies and cardiotocography

Background: Decreased fetal movements is a frequent reason for unplanned consultations through the third trimester ranging between 4% and 16% in various populations it is often a sign of fetal compromise and associated with severe outcomes such as fetal growth restriction, preterm birth and fetal death therefore it is important to question the effect of maternal dexamethasone administration for fetal well-being and its relation on decreased fetal movement which is detected by Doppler studies and cardiotocography. Methods: The current study was performed on 220 pregnant women with gestational age between 28-34 weeks who received antenatal dexamethasone at Ain Shams university hospitals.Results: Regarding fetal movements, there was significant decrease in fetal movement at the 24th hour (Day 2) after 1st and 2nd doses of dexamethasone then re-increased at 48th hour and 72nd hour but still significantly lower than baseline.Conclusions: Administration of dexamethasone had no harmful effects on the fetuses or the mothers, except for a transient decrease of fetal movements in only after 24 hours of the first dose.

NDM-559: EXPERIMENTAL INVESTIGATION OF TWO-WAY CONCRETE PANELS EXPOSED TO IMPACT LOAD

Protecting existing and new structures from potential terrorist attacks and accidents is becoming an essential consideration in the design of most structures. Building façade is the first layer exposed to external loading, thus it acts as the first line of defence against external loads. Precast concrete panels are mostly used in external building\u27s façade for modern construction, and therefore their resistance to other dynamic loads such as impact load needs further evaluation. This paper presents the results of an experimental research on two-way reinforced concrete panels as well as thin ferrocement concrete panels under impact loading. The impact test apparatus used is versatile enough to test large variety of specimens modeling façade units. The performance of the panels under impact load is evaluated in terms of: the failure mode; the maximum impact loads sustained by the panels; the number of impact loads up to failure; the maximum load transmitted to the supporting frame; and the strain induced in the panels. The effect of the different design parameters including the reinforcement amount, spacing and location across the panel thickness on the dynamic response of the panel to impact load are considered. Results clearly showed the significant effect of reinforcement on the overall resistance to impact loading. This research outcomes provide a better understanding of the performance of concrete panels under impact loading that can help enhancing structural design under such loads

Designing a Program using Augmented Reality Technologies and some Interactive Educational Aids to Simplify Science of Remote sensing for Elementary School Students

The present research aims to develop innovative methods that simplify science. The author adopts the descriptive analytical approach by designing an electronic educational system that involve some electronic games that contribute to spreading awareness and culture of sensing and space in the Egyptian society. Teaching methods have been devised to motivate children and develop their skills, mix science with imagination and use interactive education based on Augmented Reality (AR) to search for minerals and rocks with satellite images. Thus, there is an interactive educational method based on augmented reality with cartoons and interaction to simplify sensor and space sciences. Augmented reality (AR) has gained increased recognition in various fields; learning via augmented reality technology will help learners comprehend learning content in a more creative frame of mind than ever before. It is substantial to understand the dynamics of augmented reality adoption to encourage students to employ this highly innovative and impactful type of technology in learning process

Responses of Satellite Chlorophyll-a to the Extreme Sea Surface Temperatures over the Arabian and Omani Gulf

peer reviewedExtreme events such as Marine Heat Waves (MHWs) and Low Chlorophyll-a (LChl-a) in the ocean have devastating impacts on the marine environment, particularly when they occur simultaneously (i.e., the compound of MHWs and LChl-a events). In this study, we investigate the spatiotemporal variability of MHWs and LChl-a events in the Arabian and Omani Gulf. For this purpose, we used satellite-based high-resolution observations of SST (0.05° × 0.05°; from 1982 to 2020) and chlorophyll-a concentration data (0.04° × 0.04°; from 1998 to 2020). Hourly air temperature, wind, and heat flux components from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) were used to explain the link between these extreme events and atmospheric forcings. Moreover, our results revealed that the annual frequency of MHW and LChl-a is related to the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). The results revealed an average SST warming trend of about 0.44 ± 0.06 °C/decade and 0.32 ± 0.04 °C/decade for the Arabian Gulf (AG) and the Gulf of Oman (OG), respectively. This warming rate was accompanied by MHW frequency and duration trends of 0.97 events/decade and 2.3 days/decade, respectively, for the entire study region from 1982 to 2020. The highest annual MHW frequencies were recorded in 2010 (6 events) and 2020 (5 events) associated with LChl-a frequency values of 4 and 2, respectively. La Niña events in 1999, 2010, 2011, and 2020 were associated with higher frequencies of MHW and LChl-a. The positive phase of IOD coincides with high MHW frequency in 2018 and 2019. The longest compound MHW and LChl-a event with a duration of 42 days was recorded in 2020 at OG. This extreme compound event was associated with wind stress reduction. Our results provide initial insights into the spatiotemporal variability of the compound MHW and LChl-a events that occurred in the AG and OG

Inter-Annual Variability and Trends of Sea Level and Sea Surface Temperature in the Mediterranean Sea over the Last 25 Years

peer reviewedSea level and sea surface temperature inter-annual variability and trends in the Mediterranean Sea were investigated during the period 1993–2017. These were carried out using gridded absolute dynamic topography from satellite altimetry, tide gauge (TG) time series from 25 stations and gridded sea surface temperature (SST) from advanced very-high-resolution radiometer (AVHRR) data. The coastal TG data were used to verify the satellite derived sea level. Moreover, the contributions of atmospheric pressure and North Atlantic Oscillation (NAO) to sea level changes were also examined. The results revealed that the Mediterranean Sea exhibits inter-annual spatiotemporal coherent variability in both sea level and SST. The spatial variability in sea level is more significant over the Adriatic and Aegean Seas, most of the Levantine basin, and along the Tunisian shelf. Marked spatial variability in SST occurs over the central part of the Mediterranean Sea with maximum amplitude in the Tyrrhenian Sea. The highest temporal variability of sea level and SST was found in 2010 and 2003, respectively. The inter-annual variability of sea level and SST accounts for about 32% and 3% of the total variance of sea level and SST, respectively. An analysis of sea level anomaly reveled large negative values during the extended winter of 2011–2012, which may be attributed to the strong positive phase of NAO index. Satellite altimetry indicated a significant positive sea level trend of 2.7 ± 0.41 mm/year together with a significant warming of 0.036 ± 0.003 °C/year over the whole Mediterranean Sea for the period 1993–2017