High Temperature Variation Research Articles

Effect of various fin geometries on heat dissipation of traction motors used in Electric vehicles

The traction motor is one of the major component in an electric vehicle subjected to high temperature variations and thermal stresses. In order to cool the motor, fins are proposed on the housing. Present study investigates effect of various fin geometries such as rectangular fin, rectangular fin with a rectangular protrusion, tapered pin fin integrated with rectangular fin, step fin and wavy fin on heat dissipation of an electric motor by developing numerical model and the comparative study is presented. 3D geometrical model of the motor housing is developed using CATIA V5 and analyzed using ANSYS Workbench 2019 R3. Steady-state temperature distribution in the housing cross section is obtained. The obtained results were found in satisfactory quantitative agreement with the published literature results and deviated not more than 7 percent. Research confirmed that rectangular fin with rectangular protrusions gives the greatest heat transfer comparatively and it is concluded that the life of an electric motor increases as there is decrease in temperature of the motor.

Influence of ambient temperature and diurnal temperature variation on the premature rupture of membranes in East China: A distributed lag nonlinear time series analysis

BackgroundExtreme ambient temperature has an adverse effect on pregnancy outcomes, but the conclusions have been inconsistent. The influence of ambient temperature and diurnal temperature variation on the premature rupture of membranes (PROM) needs further study. Methods and findingsThe daily data of PROMs, daily meteorological and air pollutant were obtained. After controlling for potential confounding factors, the quasi-Poisson generalized additive model (GAM) combined with the distributed lag nonlinear model (DLNM) was used to analyze the association between temperature or diurnal temperature variation and PROM, including preterm premature rupture of membranes (PPROM) and term premature rupture of membranes (term PROM).Compared with the median temperature(18.7 °C), the mean temperature of 5–7 days lagging beyond 31.5 °C and below −1.5 °C was positively correlated with PROM; the mean temperature had more sensitive effect on the term PROM. Exposure to extremely high temperatures (97.5th percentile, 32 °C) had a 6-day lagging relative risk (RR) (95% CI: 1.005–1.160) of 1.08 for PROM and a 6-day lagging RR of 1.079 (95% CI: 1.005–1.159) for term PROM; Exposure to a high diurnal temperature variation (diurnal temperature variation greater than 16 °C) was positively correlated with the term PROM. Compared with the 2.5th percentile diurnal temperature variation (2 °C), exposure to the 95th percentile diurnal temperature variation (17 °C) significantly increased the risk of term PROM (RR: 1.229, 95% CI: 1.029–1.467). ConclusionsExposure to a high-temperature and a high diurnal temperature variation environment will increase the relative risks of PROM. For pregnant women in the 3rd trimester, it is important to reduce exposure to extremely high-temperatures and greater diurnal temperature changes.

A novel two-step method to prepare fine-grained SiC/Al-Mg-Sc-Zr nanocomposite: Processing, microstructure and mechanical properties

In this study, a novel two-step method consisting of powder metallurgy (PM) and subsequent friction stir processing (FSP) was used for preparing SiC/Al-Mg-Sc-Zr nanocomposites integrating multiple beneficial microstructural factors, including high densification, uniform distribution of SiC nanoparticles, good SiC/Al interfacial bonding and recrystallized fine Al grains. These favorable microstructure factors enables the resultant AMCs to overshadow the classical ductility loss in the particle reinforced AMCs, and achieve good strength-ductility synergy. At room temperature, with increasing the SiC nanoparticle content, the strength of the FSPed samples increases, and the corresponding ductility decreases, but still maintains at a high level. The FSPed AMC with 10 wt% SiC nanoparticles has a highest YS and UTS of about 227 MPa and 329 MPa respectively while maintaining a uniform elongation of nearly 20%. At high temperature (523 K), the strength and ductility variation of the FSPed samples with SiC nanoparticle content is similar to that at room temperature. The YS and UTS of the FSPed AMC with 10 wt% SiC nanoparticles reach about 148 MPa and 166 MPa respectively while the fracture elongation approaches 0.3. The fracture of the FSPed samples shows ductile fracture characteristics at both room and elevated temperatures caused by the microvoid coalescence mechanism. The novel two-step preparation method will assist the development of particle reinforced AMCs with balanced strength and ductility.

Distribution, abundance, and life history traits of the blue swimming crab Portunus segnis (Forskål, 1775) in the Saudi waters of the Arabian Gulf

The blue swimming crab, Portunus segnis (Forskål, 1775), formerly known as P. pelagicus (Linnaeus, 1758) has become a major fishery resource in the Gulf. Yet, there are no regional studies on the stock population dynamics and life history processes of this species. Considering the extreme oceanographic features of the Gulf (high salinity and high temperature variations), which is hypothesized to cause fast growth of P. segnis, a study was conducted to determine the abundance/biomass distribution of its stocks, growth rates, and sexual maturation in the territorial Saudi waters in the Arabian Gulf. The study was based on trawling surveys, landing sites monitoring, and records of fisheries catch and efforts and juvenile habitat surveys. The spatial distribution patterns supported by generalized linear model indicated the occurrence of P. segnis in the nearshore shallow waters, and its absence from the offshore deeper waters, attributed to the variability of environmental conditions including salinity, temperature, and trophic resources. Manifa, one of the productive areas in the northern Saudi waters of the Gulf, had high abundance of the crab. In agreement with the hypothesis, the growth rate of the Saudi P. segnis was found to be the higher (2.12 K year −1) compared to other parts of the Gulf (1.1–1.7 K year −1) or other sea areas of tropical regions (0.95–1.68 K year −1). The study shows that P. segnis can spawn throughout the year, with at least three peaks: winter, late spring–early summer, and autumn. The L50% record obtained in this study with females (127 mm) and males (125 mm) are larger than those reported with the same species from other parts of the Gulf (113 mm) or with other congeneric blue species crabs reported from other tropical regions (61–113 mm). The present study provided basic data to develop a management strategy for the fishery of P. segnis in the region.

Design and Implementation of a Photovoltaic Characterization Platform at FaST

The site that houses the FaST faces high dusty winds and considerable temperature variation. Weather conditions such as solar radiation, temperature, and wind speed greatly affect the performance of PV modules. But the data from PV equipment manufacturers do not allow for proper sizing. Therefore, a rigorous study is needed to find the most suitable PV module technology for the study area. For this purpose, platforms for the acquisition of meteorological parameters and module characterization are indispensable. This platform project at FaST will serve training and pedagogy because its configuration will allow master and bachelor students to carry out practical work, to carry out studies on new cell technologies under the influence of external factors specific to the sub-Saharan zone and will bring an added value by providing additional information on real conditions and especially the influence of local external factors. Our study consisted first of all in the realization of the platform on the roof of the FaST, then in the design and the programming of a module of acquisition of the measured parameters on the basis of the Arduino microcontroller card and finally in the test of characterization of the modules used for the platform thanks to an electronic load on the basis of MOSFET of power controlled by a microcontroller that we realized.

Autumn cold acclimation of shoots does not explain the northern distribution limit of three southern exotic tree species in Finland

Frost hardiness (FH) is one of the key traits that limits the distribution of tree species in the north. Different species and ecotypes respond differently to the drivers of frost hardening and may therefore have different survival capacities, especially in their northern distribution range. Several southern tree species such as pedunculate oak (Quercus robur L.), Norway maple (Acer platanoides L.), and mountain elm (Ulmus glabra Hudson) have their natural northern distribution limit in Southern Finland. Here, we examined whether insufficient frost hardening in the autumn limits the northwards distribution of these three species. To that end, we monitored phenological events and frost hardening in the autumn in these exotic species in Central Finland, further north from the natural distribution range of the three exotic species, and for the sake of comparison, in the native silver birch (Betula pendula Roth.). In all species, a timely growth cessation was observed. The water content of the stem decreased, and its dry mass content increased rapidly in August before the onset of frost hardening, after which no major changes were observed in these two traits. In the early phase of hardening, there were differences in leaf colouring between the four species. The values of the electrical impedance parameters of the stem changed during frost hardening, with a clear turning point after the first night frosts at the end of September. Depending on the species and hardening phase, the high temperature exotherm (HTE) of the stem was observed between -3 °C and -10 °C, but HTE did not indicate differences between the species in frost hardening. In all four species, frost hardening started at the beginning of September and proceeded first at equal rates, but the hardening was more rapid later in birch than in the other species. The damaging temperature range assessed by the controlled freezing tests became wider with increasing FH. The occurrence rate of the low temperature exotherm (LTE) varied between the species, and the LTE was observed at around -35 °C in the last sampling at the beginning of December (no LTE was observed in birch). We conclude that the hardening of all four species took place in a timely manner so that in each, the frost hardiness was sufficient to survive the autumn frosts at the experimental site in Central Finland. Further studies are needed to examine whether the exotic three species also tolerate temporarily occurring extreme winter conditions such as temperatures below -35 °C, and the high short-term temperature variations in winter and especially in spring.

High temperature and pressure study on structural and thermophysical properties of Co2XAl (X = Zr, Nb, Hf) Heusler materials by density functional theory calculations

ABSTRACT Heusler compounds exhibit a wide range of properties for both fundamental and potential technological interests. The extensive tunability of the Heusler compounds, through chemical substitutions and structural motifs, makes the family specifically interesting. As the maturity of these materials grows and commercial applications become more near-term, the properties of these materials become an important factor to both their processing and their final use. Here, we have investigated elasto-mechanical, transport and thermodynamics of Co2XAl (X = Zr, Nb, Hf) Heuslers. The exchange correlation potentials are figured out by GGA, GGA + U eff and GGA + mBJ methods to obtain more precise results of these materials. The continuity in the P–V plot indicates the absence of any structural phase transition from highly symmetric cubic structure to other structural phase. The magnetic interactions were taken into consideration, among which ferromagnetic configuration was found to be stable. The calculated elastic parameters recommend that these alloys are mechanically stable and possess ductile character. The efficient transport parameters with half-metallic and ductile nature suggest the likelihood applications of these alloys to design hard spintronic devices or potential thermoelectric materials. Furthermore, the high temperature and pressure variation of thermodynamic properties were calculated using the quasi-harmonic Debye approximation to descript its stability.

Analysis and precision of the Terrestrial Surface Temperature using Landsat 8 and Sentinel 3 images: Study applied to the city of Granada (Spain)

The use of Landsat 8 and Sentinel 3 satellite images to calculate the land surface temperature (LST) has become one of the most common methods in urban areas. Knowing its precision and seasonal variability will affect future studies of urban climate alteration, such as Urban Heat Island (UHI) that allow sustainable decisions that increase the resilience of cities. In this research, the LST of a medium-sized city, Granada (Spain), was determined using six split window (SW) algorithms: three for Landsat 8 and another three for Sentinel 3A and 3B. Data were validated by measurements in situ at different parts of the city, chosen to represent the different land covers established in the Corine Land Cover inventory (2020). This city has a unique geographical situation, substantial pollution and high daily temperature variations, making it very suitable for study. The data validation by means of statistical analysis gave R2 linear fitting coefficients, the mean square error (RMSE), the mean bias error (MBE) and standard deviation. Our results reveal that the methods based on Landsat 8 SW algorithms present higher mean values (8.16 K) than Sentinel 3 (5.07 K) and Sentinel 3B (2.21 K), the differences being even greater during dry periods. Still, the SWs analyzed can be considered effective and reliable for determining the city’s LST. The use of a Convolutional Neural Network (CNN) in improving the quality of satellite images has reported significant improvements in the LST results obtained.

GaAs electro-optic absorption modulators performance evaluation, under high-temperature variations

Abstract This work presents the gallium arsenide (GaAs) electro-optic absorption (EA) modulators performance evaluation compared to the previous models with SiGe EA modulators under high-temperature variations. The average switching speed is studied and analyzed for both EAs. The consumed energy or power per bit is taken into account for both modulators. The modulation depth and transmission coefficient are studied for both previous and proposed EAs with 250 Gb/s at room temperature. The technical performance parameters are also analyzed such as insertion loss, modulation depth, output power, contrast ratio, transmission coefficient, and power length product for both previous and proposed EAs under high-temperature variations. The study assured that to get the optimum GaAs EAs performance efficiency, the modulator length and the thickness should be values of 50 and 5 mm, respectively at room temperature.

Trace-element systematics and isotopic characteristics of sphalerite-pyrite from volcanogenic massive sulfide deposits of Betul belt, central Indian Tectonic Zone: Insight of ore genesis to exploration

• Co/Ni ratio of pyrite characterized submarine-magmatic hydrothermal ore process. • High-temperature VMS system > 300 °C formed from multiple sulfur sources. • Geochemical trends in sphalerite and pyrite by LA-ICP-MS suggest VMS-type deposits in the Betul belt. • PCA on pyrite and sphalerite helps in the reconstruction of the metallogeny and exploration prospectivity. • Chalcopyrite disease in sphalerite reflect high-temperature ore fluid and metamorphism . The Paleoproterozoic volcanogenic massive sulfide (VMS) deposits in the Betul belt (BB) (ca.1.7 Ga) in central India are well-known for their low-grade Zn-Cu-Pb sulfide mineralization. The physicochemical conditions of ore formation, size, grade, extent, and nature of mineralization are the ongoing debates and concerns to the exploration agencies for the last two decades. Field examination, drill core analysis, petrography, and scanning electron microscopic studies reveal the occurrence of chalcopyrite, sphalerite, pyrite, galena with minor pyrrhotite in the form of dissemination, stringers, and semi-massive sulfide veins. We present the minor-trace element contents in sphalerite and pyrite from drill core samples of four deposits (Banskhapa, Jangaldehri, Biskhan, and Bhuyari), analyzed by electron probe microanalyzer (EPMA) and in-situ laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) for determining ore-forming temperature, ore genesis and exploration prospectivity. The EPMA and LA-ICP-MS studies of sphalerite display a slightly high concentration of trace elements like Mn, In with a mean value of 3533 ppm and 33 ppm, respectively. On the other hand, Ga, Ge, and Ag content are low in abundance along with a low concentration of Bi, Pb, and Sb in all four deposits. Pyrites show low Ni and high Co/Ni (mostly > 1) ratios and variable Ti, Se, As, and Mn. Multivariate statistical analysis, especially the principal component analysis (PCA) of these trace elements, defines the geochemical variations among the Betul belt deposits. The ore-forming temperature is estimated using sphalerite thermometry (374 °C to 402 °C) and pyrite thermometry (225 °C to 484 °C). The geochemical discrepancies occur due to magmatic-hydrothermal activities caused by the sub-volcanic intrusions, followed by recrystallization and remobilization of the sub-microscopic inclusions during subsequent metamorphism. Additionally, sulfur isotope analysis provides insights into the sulfur source variations, metals, and mineralization. Carbon and Oxygen isotopes are used to understand the physicochemical conditions of the ore-forming environment. Sphalerite, pyrite, and chalcopyrite from Banskhapa deposit suggest a broad range of δ 34 S values (7.27–7.79‰, 8.37–8.61‰, and 6.58–6.72‰ respectively, n = 7), which advocate sulfur mostly derived by thermochemical reduction (TSR) of seawater sulfate with some input of magmatic sulfur leaching from the igneous basement. Carbon and oxygen isotope studies of carbonates from Jangaldehri and Bhuyari deposits (δ 13 C: −6.0 to −13.45‰ with an average value of −9.51‰, n = 7; δ 18 O: 7.32‰ to 20.58‰ with an average value of 15.65‰, n = 7) indicate that the carbonates formed from a hydrothermal fluid (seawater with an insignificant magmatic input), the mixing of hydrothermal fluid with ingressing seawater, or both in the mineralized zone. These processes collectively led to Zn-Cu and Zn-Cu-Pb mineralization in the Betul belt. High temperature, strong isotopic and trace element geochemical variations in sphalerites (Ag-Mn, In/Cd-Mn, In/Cd-Fe, Mn-In/Ge, Fe-In/Ge, Fe-In) and pyrite (Ni-Co, As-Cu, Ag-Au, and Se-Te) attest to the mineralization as being volcanogenic massive sulfide (VMS) deposits in Betul belt and differentiated from other genetic types like Mississippi Valley-type (MVT), sedimentary-exhalative (SEDEX), skarn, porphyry, and epithermal hydrothermal deposits.

LONG-TERM TEMPERATURE VARIABILITY AND THE INCIDENCE OF CARDIOVASCULAR DISEASES: A LARGE, REPRESENTATIVE COHORT STUDY IN CHINA

Objective: In the context of global climate change, far less is known about the impact of long-term temperature variability (TV), especially in developing countries. The current study was aimed to estimate the effect of long-term TV on cardiovascular disease in China. Design and method: The current study enrolled 23,721 individuals with mean age of 56.15 years in China from 2012–2016 and followed up during 2017 and 2019. TV was defined as the standard deviation of daily temperatures during survey years. The Cox regression was used to estimate the multivariable-adjusted hazard ratio (HR) between TV and cardiovascular diseases (CVD). Results: During the follow-up time, we ascertained 836 cases of incident of CVD. A significant positive trend was observed between CVD risk and increasing levels of TV comparing to the lowest tertile with an HR = 1.343 (95% CI: 1.133–1.591) for the medium tertile and an OR = 1.717(95% CI: 1.347–2.189) for the highest tertile (ptrend < 0.001). The HR per 1°C increase in TV was 1.062 (95% CI:1.014–1.112) for CVD. We also estimated that exposure to high TV would lost 2.11 years disease-free years for population aged 35 to 65 years, and was attributable to 2.93 million CVD cases (or 12.14% cases) in China. Conclusions: Long-term TV was associated with higher risk of incident CVD. Our findings will be valuable for future efforts assessing health risks related to the climate change and developing related policies to reduce TV related adverse health effect.

Temperature, not salinity, drives impact of an emerging invasive species

Biological invasions are a growing ecological and socioeconomic problem worldwide. While robust predictions of impactful future invaders are urgently needed, understandings of invader impacts have been challenged by context-dependencies. In aquatic systems in particular, future climate change could alter the impacts of invasive non-native species. Widespread warming coupled with sea freshening may exacerbate ecological impacts of invaders in marine environments, compromising ecosystem structure, function and stability. We examined how multiple abiotic changes affect the potential ecological impact of an emerging invasive non-native species from the Ponto-Caspian region - a notorious origin hotspot for invaders, characterised by high salinity and temperature variation. Using a comparative functional response (feeding rates across prey densities) approach, the potential ecological impacts of the gammarid Pontogammarus maeoticus towards native chironomid prey were examined across a range of current and future temperature (18, 22°C) and salinity (14, 10, 6, 2ppt) regimes in a factorial design. Feeding rates of P. maeoticus on prey significantly increased with temperature (by 60%), but were not significantly affected by salinity regime. Gammarids displayed significant Type II functional responses, with attack rates not significantly affected by warming across all salinities. Handling times were, however, shortened by warming, and thus maximum feeding rates significantly increased, irrespective of salinity regime. Functional responses were significantly different following warming at high prey densities under all salinities, except under the ambient 10ppt. Euryhalinity of invasive non-native species from the Ponto-Caspian region thus could allow sustained ecological impacts across a range of salinity regimes. These results corroborate high invasion success and field impacts of Ponto-Caspian gammarids in brackish through to freshwater ecosystems. Climate warming will likely worsen the potential ecological impact of P. maeoticus. With invasions growing worldwide, quantifications of how combined elements of climate change will alter the impacts of emerging invasive non-native species are needed.

A complete analytical solution for axial pipeline walking considering seabed resistance as rigid plastic behaviour

Offshore pipelines are important infrastructure for transporting oil and gas. They are subjected to cycles of high temperature and pressure variation during operation and shutdown periods, and are therefore susceptible to the stability problem of axial walking due to the asymmetry between the expansion and contraction. Axial walking can cause damage to subsea pipeline systems, for instance to the connected manifolds and steel catenary risers. This paper provides a complete analytical solution to examine the process of pipeline walking based on underlying principles of mechanics, considering the pipeline–seabed sliding response as rigid plastic. The analytical solution allows calculation of the cumulative displacement, strain, axial force and soil resistance along the pipeline under arbitrary temperature or internal pressure change histories, accounting for the coupled contributions from seabed slopes and end tension forces. A dimensionless parameter η is proposed to explain the triggering mechanism for walking by comparing the activating force to the soil resistance. New criteria are established to judge whether pipeline axial walking is possible. Calculation examples are presented in the final part of this paper to demonstrate the analytical solution. This study can be used as a rigorous benchmark and a simple practical tool to evaluate pipeline walking under arbitrary loading histories of temperature and internal pressure variations.

High sensitivity sapphire FBG temperature sensors for the signal processing of data communications technology

<p>This study has outlined the fiber bragg grating (FBG) temperature sensors signal processing for data communications by using OptiGrating simulation software. The reflectivity of the silica and sapphire fiber grating spectrum is reported against the grating wavelength for internal and external temperature variations. As well as apodized Gaussian reflectivity of the silica and sapphire fiber grating spectrum is simulated and clarified against the grating wavelength for high temperature variations. The temperature sensitivity of sapphire FBG nearly 0.11 pm/<sup>0</sup>C, where its value is three times higher than silica FBG. It is observed that silica and Sapphire FBG sensors were tested up to 1000 <sup>0</sup>C by using Gaussian apodization type, side lobes in reflectivity spectrum are totally suppressed.</p>

Spatial and Multi-Temporal Analysis of Land Surface Temperature through Landsat 8 Images: Comparison of Algorithms in a Highly Polluted City (Granada)

Over the past decade, satellite imaging has become a habitual way to determine the land surface temperature (LST). One means entails the use of Landsat 8 images, for which mono window (MW), single channel (SC) and split window (SW) algorithms are needed. Knowing the precision and seasonal variability of the LST can improve urban climate alteration studies, which ultimately help make sustainable decisions in terms of the greater resilience of cities. In this study we determine the LST of a mid-sized city, Granada (Spain), applying six Landsat 8 algorithms that are validated using ambient temperatures. In addition to having a unique geographical location, this city has high pollution and high daily temperature variations, so that it is a very appropriate site for study. Altogether, 11 images with very low cloudiness were taken into account, distributed between November 2019 and October 2020. After data validation by means of R2 statistical analysis, the root mean square error (RMSE), mean bias error (MBE) and standard deviation (SD) were determined to obtain the coefficients of correlation. Panel data analysis is presented as a novel element with respect to the methods usually used. Results reveal that the SC algorithms prove more effective and reliable in determining the LST of the city studied here.

Analysis of extreme rains through climate indicators in the context of climate change in southern Benin

The recurrence of flooding in recent years in West Africa is dramatically affecting the socio-economic system of most countries in the region. This work is devoted to the analysis of the heavy rains of its last years in the context of global warming in subequatorial Benin through eight rainfall indicators. For this purpose, the daily rains collected at seventeen stations in the south of Benin between 1960 and 2018, the maximum and minimum daily temperatures of the two synoptic stations in the study area between 1970 and 2018 are used. Analysis of the results shows a non-uniform trend in rainfall indicators over the entire study period. The monthly trend is in accordance with the bimodal rain regime of southern Benin for each of the climatic indicators studied. After the break in the downward trend in rainfall in the 1980s or 1990s at the various stations, the last three decades have been marked above all by ten-year averages of the various indicators that are higher than those obtained over the entire study period. Despite the low proportion of extreme rains, their frequency has increased since the resumption of rainfall in the 1980s or 1990s, especially compared to the 1970s and 1980s. The highest heights are observed for the most part in the towns close to the sea Atlantic Ocean. Global warming in southern Benin is characterized above all by high decadal temperature variation rates in the 1990s. This significant global warming in this pivotal decade is accompanied by relatively large growth in all indicators in southern Benin.

Thermal analysis of fin materials for engine cylinder heat transfer enhancement

In automobiles the internal combustion engine cylinder is one of the major component which is subjected to high thermal stresses and temperature variations. Engine cylinders come up with fins or extended surfaces. The heat transfer enhancement from engine cylinder is mainly depends on fin material and shape. We can use different fin materials and fin geometries in order to increase heat transfer rate. In this work heat transfer rate through fins with different materials was evaluated. The fin geometries such as the rectangular fins attached to the cylinder block. In this analysis different physical and thermal properties along with cost associated with the fin materials are considered. The 3D model of geometries are created using CATIA-V5, and thermal properties are analyzed using commercial software ANSYS FLUENT 2020 R1. From the results of steady state thermal analysis of engine cylinder it is found that the value of heat flux increased through cylinder block to the surroundings. The weighted point method applied to find performance of fins based on material that is best suited for manufacturing of fins.

Long-term temperature variability and the incidence of cardiovascular diseases: A large, representative cohort study in China.

In the context of global climate change, far less is known about the impact of long-term temperature variability (TV), especially in developing countries. The current study aimed to estimate the effect of long-term TV on the incidence of cardiovascular disease (CVD) in China. A total of 23,721 individuals with a mean age of 56.15 years were enrolled at baseline from 2012 to 2016 and followed up during 2017-2019. TV was defined as the standard deviation of daily temperatures during survey years and was categorized into tertiles (lowest≤ 8.78°C, middle=8.78-10.07°C, highest≥10.07°C). The Cox proportional hazards regression was used to estimate the multivariable-adjusted hazard ratio (HR) between TV and CVD. During the median follow-up of 4.65 years, we ascertained 836 cases of incident CVD. For per 1°C increase in TV, there was a 6% increase of CVD (HR=1.06 [95% confidence interval (CI): 1.01-1.11]). A significant positive trend was observed between CVD risk and increasing levels of TV compared to the lowest tertile [HR=1.34 (95% CI: 1.13-1.59) for the medium tertile, HR=1.72 (95% CI: 1.35-2.19) for the highest tertile, Ptrend<0.001]. Exposure to high TV would lose 2.11 disease-free years for the population aged 35-65 years and 66 CVD cases (or 7.95% cases) could been attributable to TV higher than 8.11°C in the current study. The current findings suggested that long-term TV was associated with a higher risk of CVD incidence, it is needed to reduce the TV-related adverse health effect.

Mixed convection heat transfer of a nanofluid in a closed elbow-shaped cavity (CESC)

The current survey’s primary purpose is to conduct the computational modeling of laminar mixed convection heat transfer of nanofluids inside a CESC using a finite volume method. Water/Cu nanofluid at 0–6% volume fractions was selected as a working fluid. The investigation was done at Grashof numbers of 10,000 < Gr < 100,000 and Richardson numbers of 0.1, 1, and 10. All parameters of the hydrodynamic flow and mixed convection heat transfer are presented as Nusselt number, the coefficient of friction, dimensionless velocity in different sections of the cavity, and entropy generation and temperature contours. Results indicated that nanofluid with higher volume fraction causes heat transfer enhancement. Using nanofluid, applying the gravity domain and the existence of lid driven in studied geometry affect flow behavior. Solid nanoparticles’ existence causes better temperature distribution and better stimulation of buoyancy force, which can be considered another factor for improving buoyancy force. By increasing Grashof number, the circulation mechanism’s improvement is the most significant factor in reducing entropy generation in studied geometry. At the beginning of fluid collision with the surface, the highest temperature variation between the surface and the fluid occurred by considering the fluid temperature. Hence, at the bottom areas of the hot surface, entropy generation is always the least.

High-efficient coupler for thin-film lithium niobate waveguide devices.

Lithium niobate (LN) devices have been widely used in optical communication and nonlinear optics due to its attractive optical properties. The emergence of the thin-film lithium niobate on insulator (LNOI) improves performances of LN-based devices greatly. However, a high-efficient fiber-chip optical coupler is still necessary for the LNOI-based devices for practical applications. In this paper, we demonstrate a highly efficient and polarization-independent edge coupler based on LNOI. The coupler, fabricated by a standard semiconductor process, shows a low fiber-chip coupling loss of 0.54 dB/0.59 dB per facet at 1550 nm for TE/TM light, respectively, when coupled with an ultra-high numerical aperture fiber (UHNAF) of which the mode field diameter is about 3.2 μm. The coupling loss is lower than 1dB/facet for both TE and TM light in the wavelength range of 1527 nm to 1630 nm. A relatively large tolerance for optical misalignment is also proved, due to the coupler's large mode spot size up to 3.2 μm. The coupler shows a promising stability in high optical power and temperature variation.