excessive heat
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2022 ◽  
Author(s):  
Juhi Yadav ◽  
Avinash Kumar ◽  
Rahul Mohan ◽  
Muthulagu Ravichandran

Abstract This study investigates the mechanism of seasonal sea ice variation and recent warming amplification. Seasonal temperature changes in the vertical structure reveal that the autumn and winter seasons are warming more than summer. The thermodynamic processes of sea-ice-air interactions via the heat flux component have been studied. The summer Arctic Sea ice has receded by half (∼52%), producing excessive heat. This sea ice loss plays a significant role in determining the heat exchange between the ocean and atmosphere in the following season. During a warm season, the ocean heats up due to incident solar radiation. As a result, delayed ice growth and atmospheric warming occur. Sea ice and heat flux feedbacks explain a large part of Arctic atmospheric warming. These abrupt changes are closely coupled to accelerated Arctic Sea ice loss and atmospheric warming, which are still uncertain.


2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Hina Gul ◽  
Muhammad Ramzan ◽  
Kottakkaran Sooppy Nisar ◽  
Roshan Noor Mohamed ◽  
Hassan Ali S. Ghazwani

AbstractThe nanofluid flows play a vital role in many engineering processes owing to their notable industrial usage and excessive heat transfer abilities. Lately, an advanced form of nanofluids namely “hybrid nanofluids” has swapped the usual nanofluid flows to further augment the heat transfer capabilities. The objective of this envisaged model is to compare the performance of two renowned hybrid nanofluid models namely Hamilton–Crosser and Yamada–Ota. The hybrid nanoliquid (TiO2-SiC/DO) flow model is comprised of Titanium oxide (TiO2) and Silicon carbide (SiC) nanoparticles submerged into Diathermic oil (DO). The subject flow is considered over a stretched surface and is influenced by the magnetic dipole. The uniqueness of the fluid model is augmented by considering the modified Fourier law instead of the traditional Fourier law and slip conditions at the boundary. By applying the suitable similarity transformations, the system of ordinary differential equations obtained from the leading partial differential equations is handled by the MATLAB solver bvp4c package to determine the numerical solution. It is divulged that the Yamada–Ota model performs considerably better than the Hamilton–Crosser flow model as far as heat transfer capabilities are concerned. Further, the velocity reduces on increasing hydrodynamic interaction and slip parameters. It is also noted that both temperature profiles increase for higher hydrodynamic interaction and viscous dissipation parameters. The envisioned model is authenticated when compared with an already published result in a limiting case.


2022 ◽  
Vol 9 ◽  
Author(s):  
Gerald Kuchling ◽  
Margaretha D. Hofmeyr

In a captive colony of Chersina angulata in Cape Town, South Africa, we observed in 2015/16 retention of the last egg clutch inside the female until the hatching stage was reached, conforming to the generally accepted definition of viviparity. Retrospective climatic analysis indicates egg retention until the hatching stage co-occurred with unusually hot summer weather: the average air temperatures in December 2015 and January and February 2016 were higher than during the preceding five and the following 5 years when facultative viviparity could not be observed. Late December and January appears to be the critical period for females to either deposit their last clutch of the nesting season into a nest, or to retain the last clutch for embryonic development inside the female. Over the 28 December to 24 January period the minimum, average and maximum air temperatures in 2015–16 were about 3°C higher than in the five following years. This association of facultative viviparity with unusual summer heat suggests that hot ambient temperatures at the end of the nesting season may cue females to switch from oviposition to facultative viviparity. Compared to incubation in a nest this phenotypic plasticity of the reproductive mode—to retain during hot summers the season’s last clutch inside the female—may buffer the developing embryos from excessive heat exposure: females can thermo-regulate by moving among microhabitats whereas sun exposed shallow nests cannot escape high ground temperatures. This novel reproductive strategy has the potential to enhance the resilience of species to global warming.


Metals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 60
Author(s):  
Josef Hlinka ◽  
Kamila Dostalova ◽  
Katerina Peterek Dedkova ◽  
Roman Madeja ◽  
Karel Frydrysek ◽  
...  

Nickel-based austenitic stainless steels are still common for manufacture of implants intended for acute hard tissue reinforcement or stabilization, but the risk of negative reactions due to soluble nickel-rich corrosion products must be considered seriously. Corrosion processes may even be accelerated by the evolution of microstructure caused by excessive heat during machining, etc. Therefore, this study also deals with the investigation of microstructure and microhardness changes near the threaded holes of the anterolateral distal tibial plate containing approx. 14wt.% Ni by composition. There were only insignificant changes of microhardness, grain size, or microstructure orientation found close to the area of machining. In addition, wettability measurements of surface energy demonstrated only minor differences for bulk material and areas close to machining. The cyclic potentiodynamic polarization tests were performed in isotonic physiological solution. The first cycle was used for the determination of corrosion characteristics of the implant after chemical passivation, the second cycle was used to simulate real material behavior under the condition of previous surface damage by excessive pitting corrosion occurring during previous polarization. It was found that the damaged and spontaneously repassived surface showed a three-time higher standard corrosion rate than the “as received” chemically passivated surface. One may conclude that previous surface damage may decrease the lifetime of the implant significantly and increase the amount of nickel-based corrosion products distributed into surrounding tissues.


Author(s):  
Ranjith R ◽  
Manoj Prabhakar ◽  
Giridharan Pytenkar ◽  
M Ramu

Abstract In this research work, an attempt was made to machine Ti6Al4V titanium alloy utilizing AA6061/10Gr composite tool. The composite tool was fabricated using stir casting technique and Al2O3 particles of size 5µm were incorporated in the dielectric fluid to enhance the machining performance. Experiments were conducted by varying Al203 concentration, pulse on time, current, and pulse off time, and the responses Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (Ra) were recorded. Experiments runs were planned using Taguchi orthogonal array. The results revealed that adding powder increases MRR and TWR owing to the excessive heat generation and bridging effect respectively. The best surface finish was attained due to the increase in spark gap and complete flushing of machined debris. Coating of materials over the machined specimen was observed when the parametric value of Ton was higher than 60s under PMEDM conditions. Pits, craters and cracks were observed on the machined topography which was eliminated when 5g/l of Al2O3 particles were added to dielectric fluid. MEIOT technique was utilized for optimization and it was observed that Ton 15µs, Toff 4µs and current 7A and powder concentration of 10g/l results in best machining performance.


2021 ◽  
pp. 435-442

Background. Excessive heat exposure and dehydration among agricultural workers have been reported to reduce kidney function and lead to chronic kidney disease of unknown etiology (CKDu). Objective. This cross-sectional study aimed to assess heat exposure, factors related to dehydration and the relationship between dehydration and biomarkers of kidney function among sea salt workers in Thailand. Material and methods. Wet bulb globe temperature (WBGT) was used at the time workers started work outdoors on salt farms. Urine-specific gravity, urine osmolarity, and serum creatinine were collected from 50 workers after work. Results. The results showed that more than 50% of the participants were dehydrated after work. The maximum hours spent working per day was 10. The average water intake was 1.51 L. Urine specific gravity was highly significant correlated with urine osmolality (rs = 0.400, p<0.01), and urine osmolality was significantly correlated with the estimated glomerular filtration rate (eGFR) (rs = 0.349, p<0.05). In bivariate analysis adjusted for age, sex, and current alcohol consumption, we found that a WBGTTWA ≥ 30°C (OR = 0.08, 95% CI = 0.01-0.44, p = 0.003) and hours spent working (OR=2.22, 95% CI = 1.42-3.47, p <0.001) were independently associated with dehydration. This suggests that workers should increase their time spent on breaks and increase water consumption. Conclusions. Educational program on heat exposure and heat-related illness prevention strategies should be provided


Author(s):  
Janhavi Mahajan ◽  
Dhruv Talwar ◽  
Sunil Kumar ◽  
Sourya Acharya ◽  
Yogesh Kakde

ECAST Or exercise collapse associated with sickle cell trait is a rare phenomenon associated with sickle cell trait and is an important presentation of sickle cell disease in sports medicine. Collapse is seen following vigorous physical activity, which is due to excessive heat, dehydration and other factors associated with physical exercise. This rare syndrome is often missed by the treating physicians as a result of a lack of knowledge about this rare entity leading to massive underreporting. It is important to identify ECAST as a cause of the collapse in young athletes to prevent mortality and morbidity and in order to provide prompt treatment. We report a case of a 25- year-old young male who was a bodybuilder and reported to the gym after a one-year-long break due to lockdown restrictions of COVID19. After a vigorous exercise session, he collapsed in the gym and was brought to the emergency department. After proper history taking and examination, he was suspected to be a case of ECAST due to a history of a similar episode three years back which was treated as a case of exertional syncope with intravenous fluid therapy and a family history of Sickle cell trait with his mother and father both having sickle cell AS Pattern. Ultimately our patient turned out to be a case of Sickle Cell Trait with evidence of AS pattern on Hb electrophoresis and a small-sized spleen visualized on CT Scan of the abdomen. The patient was managed successfully with intravenous fluids and blood transfusion and was discharged in a stable condition. He was counseled about moderating his exercise and is doing well on follow-up.


Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1397
Author(s):  
Zhuan Bai ◽  
Zonghe Zhang ◽  
Ju Wang ◽  
Xiaoqing Sun ◽  
Wei Hu

Giant magnetostrictive transducer with micro and nano precision has a wide application prospect in the field of remote sensing. However, excessive heat loss of components could generate during the energy conversion and transfer from electric energy to magnetic energy, and magnetic energy to mechanical energy, thereby affecting its long-term service and also reducing energy utilization. In this paper, a new magnetostrictive transducer is proposed and its excitation coil, internal and external magnetic circuit are optimized from the perspective of reducing heat loss. With the help of theoretical and finite element analysis, the response law between key parameters and heat loss of key components are summarized, which provides a basis for reducing heat loss. Finally, according to the optimization scheme, the prototype is processed, and the temperature rise and dynamic output performance of the transducer are tested by constructing an experimental setup. The results show that the transducer has a low temperature rise and good frequency response characteristics, which can provide support for long-time precise actuation on-orbit.


2021 ◽  
Vol 2083 (2) ◽  
pp. 022029
Author(s):  
Yuansong Li ◽  
Bo Gao

Abstract Aiming at a series of issues on traditional boost converter which commonly used in photovoltaic maximum power point tracking (MPPT) devices, such as the limited output voltage, the low boost efficiency, the excessive heat generating, this paper proposed a novel z-source converter. Compared with traditional boost converter, several researches have done among topology structure, operational principle, boost factor. Based on the theoretic analysis, this paper given two schemes of photovoltaic MPPT system which using boost converter and z-source converter, the models of them are established based on Matlab. The simulation results indicate that the duty-ratio of photovoltaic MPPT system based on z-source converter is smaller, the stability of MPPT is better. The novel z-source converter can fundamentally solve the issues caused by traditional boost converter in photovoltaic MPPT devices, and it has incomparable advantages than traditional boost converter in the field of photovoltaic power generation.


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