Temperatures For Various Durations Research Articles

Analysis of the Impact of Environmental Conditions on the Reliability in 5G PCB Assemblies

The designs of integrated systems are increasingly compact while the requirements of application, especially in the automotive sector, remain demanding. One main challenge is posed by the environmental conditions. In the present study, their impact on mmWave 5G PCB assemblies is evaluated with respect to both mechanical and highfrequency properties. To that end, material samples were stored at three temperatures for various durations in order to accelerate the ageing effects. Afterwards, the samples were tested by use of mechanical, dielectric and high-frequency test methods. Thermo-oxidative ageing processes were observed and lead to significant changes in mechanical and dielectric properties, with simultaneous changes of sample color. The combined approach of mechanical and high-frequency analysis allows for three innovative advantages: First, a correlation of the degradation in performance with other parameters, e.g. sample change of color, which is much easier to detect. Second, the definition of a Safe Area of Operation and a methodology to estimate the behaviour of a mmWave 5G PCB assembly over its lifetime. Finally, the study opens the pathway to a design for robustness of mmWave communication system in automotive applications.

Comparative efficacy of priming treatments and storage periods in overcoming seed dormancy in round gourd (Praecitrullus fistulosus (Stocks) Pangalo)

Owing to its hard seed coat, the seeds of Praecitrullus fistulosus exhibit dormancy which impairs the germinability and subsequent seed establishment. To overcome this dormancy, the seeds are required to be stored for a minimum of 45 days after harvest (DAH). In north Indian plains, round gourd seeds are harvested in mid-June and are required to be sown immediately in June-July. Therefore, priming treatments were employed to overcome seed dormancy in a short interval. To assess the effect of various priming treatments in overcoming dormancy, the seeds were stored at room temperature for various durations and at the end of the storage period, the seeds were primed by soaking in solutions of GA3 (150 µgmL-1, 500 µgmL-1,1000 µgmL-1 gibberellic acid), cytokinin (150 µgmL-1, 500 µgmL-1,1000 µgmL-1kinetin), ethylene (150, 500, 1000 ethrel), KNO3 (150 and 500 µgmL-1), HNO3 (150 and 500 µlL-1) and water, at 250C for 12 hours and 24 hours, respectively. Among all the priming treatments, 500 µgmL-1 KNO3 for 24 h enhanced percentage germination to more than 60 per cent in freshly harvested seeds to more than 80 per cent in seeds stored for 15 DAH. It also enhanced the length of seedling, vigour index (SVI-I and SVI-II), and coefficient of rate of germination (CRG) with a reduction in the mean days taken for germination (MDG).

Thermal cracking of Al-Dora asphalt for the simultaneous production of light fuel and activated carbon for desulfurization process

Thermal cracking of an Iraqi asphalt, namely Al-Dora asphalt, at multiple temperatures for various durations was first achieved. The main target of this investigation was to produce an upgraded liquid fuel and microporous activated carbon. The thermal pyrolysis of asphalt was carried out in the temperature range of 400–600 °C for different durations (30–150 min) at a 20 °C/min heating rate. The maximum liquid fuel yield (51.55%) was produced at 450 °C for 1 h. This treatment process raised the American Petroleum Institute (API) gravity of the original asphalt from 3.26 to 34.54, while its viscosity was reduced from 422.0 mm2.s−1 to 3.76 mm2.s−1. Analysis of the produced liquid fuel by 1H NMR spectroscopy,13C NMR spectroscopy, and GC-MS disclosed that it was a mixture of n-paraffins (57.05%), isoparaffins (12.68%), and alkenes (30.27%) with a C6 and C19 carbon distribution. The physical and chemical features of the liquid were also determined following ASTM procedures, and the outcomes revealed that the produced liquid fuel had preferable properties to that of the authentic asphalt, suggesting its suitability as an alternative to diesel fuel. The coke produced after thermal pyrolysis of Al-Dora asphalt was successfully converted into active carbon (AC) via the optimized KOH-activation route, and the selected AC was prepared using a 2:1 KOH: coke impregnation ratio at 750 °C for 1 h. The AC was characterized by various techniques, including BET surface area and pore volume, X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis (EDX), and infrared spectroscopy (FTIR). The total acid and basic surface groups besides the pHPZC of the AC were also determined. The adsorption efficiency of the as-obtained AC was tested in the adsorptive desulfurization process. For this target, dibenzothiophene (DBT) in n-hexane was selected as a model fuel. The AC showed an excellent efficiency of 99.33% for eliminating DBT from a model fuel containing 500 mg/L DBT using 0.35 g of AC at 40 °C for 30 min. Moreover, the removal of S- compounds from commercial gasoline using the AC under typical experimental conditions reached 65.12%. The adsorption of DBT by the produced AC offered an excellent fitting for Freundlich isotherm and the pseudo-2nd-order kinetics model. Finally, the regenerated AC demonstrated its ability to eliminate DBT up to the 6th reuse cycle efficiently.

Survival of murine norovirus and hepatitis A virus in bottled drinking water, strawberries, and oysters

The survival of murine norovirus (MNV) and hepatitis A virus (HAV) in bottled drinking water, strawberries, and oysters stored at different temperatures for various durations was investigated. In drinking water, over 6.4 and 1.6 log 10 plaque-forming units (PFU/mL) reductions of viable MNV and HAV were observed after 20 days of incubation at 35 °C. After 160 days of incubation at 20 °C, there was a sharp decrease in the MNV (>6.4 log 10 PFU/mL) and HAV (>2.9 log 10 PFU/mL) load but only a slight reduction at 4 °C. In fresh strawberry, the MNV and HAV titers reduced by 1.0 and 0.9 log 10 PFU/g after incubation for 2 days at 25 °C, by 0.85 and 1.22 log 10 PFU/g after 3 days of incubation at 15 °C, and by 0.7 and 1.1 log 10 PFU/g after 7 days of incubation at 4 °C, respectively. After 3 days of incubation at 4, 15, and 25 °C in oyster reductions of over 0.3, 0.4, and 0.6 log 10 PFU/mL in the MNV load and 0.16, 0.28, and 0.52 log 10 PFU/mL in the HAV load were observed, respectively. Even though, survival of the two viruses fluctuated with temperature and food commodity. Therefore, our results indicate that major enteric foodborne viruses such as MNV and HAV can survive for long periods, with only a partial reduction in their titers. Owing to the persistence of foodborne viruses, preventive measures need to be taken to prevent food contamination. • MNV and HAV survival in drinking water, strawberries, and oysters was investigated. • MNV and HAV survivability varies with temperature and food type. • Enteric foodborne viruses can persist for a long time at 4 °C. • Study results could lay the foundation for the development of food hazard assessment models.

Residual stresses of heat-treated and hot-dip galvanized RHS cold-formed by different methods

Rectangular hollow sections (RHS) are produced in diverse locations internationally to various specifications, predominantly by cold-forming. RHS cold-formed by different techniques have different material and residual stress properties. Hot-dip galvanizing and heat treatment are commonly applied post-cold-forming processes. A comprehensive literature review showed that dedicated research on the effects of these processes on the performances of tubular steel members and connections is insufficient. Also, there is no definitive published guidance on this topic from structural steel associations. In particular, further research on the effects of heat treatment at various temperatures for various durations is needed to ensure a fit-for-purpose process (e.g. improvement of compressive member behaviour) which consumes less energy. This paper reports a comprehensive experimental investigation on the residual stress properties of 26 RHS specimens with different grades (nominal yield strengths from 350 to 690 MPa), cold-formed by different techniques, and subsequently subjected to post-production galvanizing and heat treatments to different degrees.

Linking chemical to rheological properties of asphalt binder with oxidative aging effect

ABSTRACT This study aimed to establish the chemical-rheological property relationships of asphalt binders subjected to oxidative aging. Five asphalt binders were aged in the oven at several different temperatures for various durations. The chemical characteristic in terms of carbonyl index and rheological characteristic in terms of complex shear modulus and phase angle. The aged asphalt binders were measured using the Fourier Transform infrared spectroscopy (FTIR) and Dynamic Shear Rheometer (DSR) techniques, respectively. During oxidative aging process, the carbonyl index was predicted using the Glover’s aging kinetic model. Crossover frequency and rheological index generated from the aging mastercurves, correlates well with the carbonyl index of asphalt binders, and the correlations are independent of aging temperature and time. Christensen-Anderson model is used in combination with crossover frequency-carbonyl index and rheological index-carbonyl index relationships to predict complex shear modulus and phase angle master curves of the binder with respect to aging.

Microstructure evolution, grain morphology variation and mechanical property change of Cu-Sn intermetallic joints subjected to high-temperature aging

In this work, the aging treatment was carried out on full Cu3Sn joints at different temperatures for various durations, the microstructure evolution, grain morphology variation and mechanical property change of joints were investigated. The temperature effects on the growth rate and grain morphology of Cu41Sn11 phase were found: The complete transformation from Cu3Sn phase to Cu41Sn11 phase in joints needed 300h at 400°C, but 4h at 500°C. The Cu41Sn11 phase formed at 400°C consisted of columnar grains with an average width of 23.5μm, while the Cu41Sn11 phase formed at 500°C consisted columnar grains with an average width of 8.5μm. The average hardness and shear strength values of the Cu41Sn11 joints formed at 400°C were 432.5HV and 62MPa, while the joints formed at 500°C exhibited higher hardness and shear strength (451.5HV and 65MPa). Besides, the Cu41Sn11 joint was found to exhibit a combination of transgranular and intergranular fracture during shear test.

Crystallite growth and optical properties of cadmium oxide thin films annealed at various temperatures for various durations

Abstract The crystallite growth and optical properties of cadmium oxide (CdO) thin films annealed at various temperatures and for various durations have been investigated using grazing incident X-ray diffraction (GID), high-resolution transmittance electron microscopy (HR-TEM), selected area electron diffraction, and ultraviolet-visible spectrometry. All the thin films were annealed between 573 and 773 K for 10 to 60 min, respectively. GID results showed that all thin films contain only a single phase of CdO with (111) preferential orientation. The crystallite size of CdO increases with increases in annealing temperature and duration. It was found that the CdO crystallites followed a normal growth with an average activation energy of 13.04 ± 1.34 kJ/mol when annealed at 573–773 K for 10–60 min. The transmission spectra showed that the band gap energies of CdO thin films decreased from 2.474 to 2.050 eV as the annealing temperature increased, while the thin films maintained highly transparent in the visible spectral range.

Impacts of the annealing profile on AIC thin film solar cell characteristics fabricated by magnetron sputtering

Two different layer orders of p-Si/Al (as structure #1) and Al/p-Si (as structure #2) thin films were deposited on n-type mono-crystalline Silicon wafer and quartz glass by magnetron sputtering at 200 °C. The fabricated films were annealed at different temperatures for various durations. Then, they were analyzed by XRD, Raman and SEM methods. According to XRD results the largest grain size of both structures was smaller than 20 nm. The Raman spectra of the samples annealed at 1000 °C determined a crystallization ratio of 98% and 75% of structures #1 and #2 respectively. SEM images confirmed that the crystallization happened for structure #1 at lower temperatures than for structure #2. The impact of annealing on electrical and photovoltaic performance of the samples were studied after the fabrication of metal contact by sputtering of a few hundred nanometers of aluminium. The highest measured Voc were 360 and 402 mV, and the best Jsc were 2.2 and 0.12 mA/cm2, for structure #1 and #2 respectively.

W/Cu thin film infrared reflector for TiNxOy based selective solar absorber with high thermal stability

The W/Cu thin film structure is deposited by magnetron sputtering to form the infrared reflector for the TiNxOy based selective solar absorber (SSA) that can be used in the low- and middle-temperature applications. The structural, chemical, and optical properties of the SSA layers that experienced thermal annealing at different temperatures for various durations have been investigated with the characterization techniques, including X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, spectroscopic ellipsometry, and spectrophotometry. Without a W layer, the reflectance in both visible and infrared ranges of the SSA increases as a result of the crystallization of the Cu layer at elevated temperatures. With a W layer with appropriate film thickness, the increase of the reflectance in the visible range can be suppressed to maintain a high solar absorptance, whereas a high infrared reflectance can be maintained to achieve a low thermal emittance. It is shown that for the SiO2-TiNxOy-W-Cu-Glass SSA with a 15 nm W thin film, thermal annealing can significantly reduce the thermal emittance to a low value (e.g., 4.4% at the temperature of 400 °C for annealing at 400 °C for 6 h), whereas the solar absorptance can be maintained at a high value (e.g., 92.2% for the annealing at 400 °C for 6 h).

Solid-state transformations of ribavirin as a result of high-shear mechanical processing

Ribavirin (C8H12N4O5; anti-viral agent) was crystallized as two unique, phase-pure polymorphs (R-I and R-II). Calorimetrically determined isobaric heat capacities and heat of transition data were utilized to determine the solid-state transition temperature (Ttr), confirming enantiotropism, while R-I was determined to be kinetically stable at ambient temperature. Unprocessed samples of the low Tm polymorph, R-II, did not convert into R-I when held isothermally well above Ttr for 7days. In contrast milled R-II completely transformed to R-I after 15min at the same storage conditions, indicating that defects sustained during processing reduced the energy barrier for transformation, allowing it to occur. R-II was subjected to both cryogenic milling and impact milling at ambient temperature for various durations. Cryomilling resulted in an in situ progressive reduction of crystallinity, with complete conversion to amorphous ribavirin after 2h. Limited molecular mobility attributable to the low milling temperature (Texp=−196°C) likely inhibited recrystallization, allowing the amorphous solid to persist. In contrast, continuous impact milling at ambient temperature resulted in complete in situ conversion from R-II to R-I after 3h. The data suggested rapid conversion to R-I from highly disordered regions during extended milling, facilitated by localized heat buildup that likely exceeded Tg and/or Ttr.

Cryopreservation of Prunus padus seeds: emphasising the significance of Bayesian methods for data analysis

Conservation of Prunus padus L., a tree of high ecological and pharmacological importance, has been evaluated by storing seeds at subzero (−20 °C and −80 °C) and cryogenic (−196 °C) temperatures for various durations. The effect of the seed’s water content (WC) ranging from 3.5% to 21.1%, fresh weight basis, and the effect of cooling and rewarming procedures on seed viability was investigated. Emergence of seedlings was observed for 40%–55% of the noncryopreserved seeds, with no significant effect of WC. The same seedling emergence was recorded for seeds cryopreserved by direct immersion in liquid nitrogen within the WC range of 3.5%–15.0%. Seeds rehydrated above 17% WC were unable to tolerate cryopreservation. Seedling emergence was not affected by cooling regime but decreased by 10% after stepwise rewarming compared with rapid rewarming in a water bath or on air. No reduction in seedling emergence was recorded after storage at −20 °C, −80 °C, and −196 °C for 1 h, 1 week, and 1 month. We recommend seed storage at subzero or cryogenic temperatures as an effective conservation option for P. padus and possibly other Prunus species. We also demonstrated high effectiveness and reliability of Bayesian statistical methods for analyzing binomial data such as the data obtained in seed conservation experiments.

Effect of SrO addition on the growth behavior of ZrO2–3Y2O3 precursor powders synthesized by a coprecipitation process

Effect of SrO addition on the crystalline growth behavior of ZrO2–3Y2O3 precursor powders using a coprecipitation process has been studied. Zirconium nitrate (Zr(NO3)4·xH2O), yttrium nitrate (Y(NO3)3·6H2O) and strontium nitrate (Sr(NO3)2) were used as the initial materials. Crystalline growth behavior was investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), nano beam electron diffraction (NBED) and high-resolution TEM (HRTEM). The XRD results showed the ZrO2–3Y2O3–xSrO only contained single phase of tetragonal ZrO2 (t-ZrO2) when the precursor powders were calcined at different temperatures for various durations. The crystallite size increased from 22.91 to 27.44nm when the ZrO2–3Y2O3–1SrO precursor powders after calcination at 823K from 15 to 120min. The activation energy values obtained are 9.98, 9.04 and 7.43kJ/mol for SrO addition amount of 1, 2 and 3mol%, respectively, and the kinetics equations of t-ZrO2 crystalline growth with SrO addition are also expressed as follows: D1SrO2=6.00×t0.13exp(−9.98×103RT),D2SrO2=6.02×t0.11exp(−9.04×103RT) and D3SrO2=6.13×t0.10exp(−7.43×103RT) with SrO content for 1, 2 and 3mol%, respectively, for 15≤t≤120min and 773≤T≤923K.

Conversion of De-oiled Castor Seed Cake into Bio-oil and Carbon Adsorbents

Castor seed cake is the byproduct of castor seeds with cold pressing. This bio-waste was used as a raw material for the production of bio-oil and activated carbons through pyrolysis. De-oiled castor seed cake was pyrolyzed at various temperatures for various durations to find out the optimal temperature and duration for the pyrolysis. The highest bio-oil yield (63% w/w) was obtained at 400°C for 60 min. The ultimate analysis and the fuel properties for the produced bio-oil were determined. Fourier transform infra-red spectroscopy and fractionation using column adsorption chromatography for bio-oil were also conducted. The results showed that the properties of bio-oil were similar to those reported in the literature. The pyrolysis char was converted into activated carbons of micro-porous structure.

Storage Fading Mechanism of a Commercial 18650 Cell Comprised with Composite NMC/LMO Cathode and Graphite Anode

In this study, the capacities and electrochemical impedances at various states of charge (SOC) are measured after the screened commercial 18650 lithium ion cells assembled with composite cathode of layered mixed oxide (NMC) and spinel lithium manganite (LMO) and graphite anode were stored at various states of depth-of-discharge (DOD) at various temperatures for various durations. The results manifest that the capacity fading is strongly affected by the storage temperature and becomes prominent at temperatures higher than 45oC. Incremental capacity analyses (ICA) for the charge/discharge curves before and after storage were performed for the qualitative mechanism study. It demonstrates that the capacity fade of the cell stored at 60oC and 0% DOD can be attributed to the loss of active materials, and the loss of graphite anode is higher than that of composite cathode. The capacity fade of the cell stored at 60oC and 25% DOD can be caused by the lithium inventory loss, the loss of NMC, and the loss due to the morphology change of LMO. Cell stored at 50% DOD manifests similar fading behavior as that of the cell stored at 0% DOD, however, the ICA plots demonstrate that the capacity loss of the cell comes from losses of lithium inventory and NMC caused by the dissolution of transition metals with additional losses of LMO and graphite anode occur after 10 months of accumulated storage. For cell stored at 75% DOD, most the capacity loss can be due to the loss of NMC with minor contribution of lithium inventory loss, while cell stored at 100% DOD shows almost no change after storage for 12 accumulated months. These results revealed from the ICA study are consistent with those determined from the post mortem study of the electrodes obtained from cells before and after storage.

Thermal conductivity of β-FeSi2/Si endogenous composites formed by the eutectoid decomposition of α-Fe2Si5

Thermoelectric properties of semiconducting β-FeSi2 containing a homogeneous distribution of Si secondary phase have been studied. The synthesis was carried out using arc melting followed by the densification by uniaxial hot pressing. Endogenous β-FeSi2/Si composites were produced by the eutectoid decomposition of high-temperature α-Fe2Si5 phase. The aging heat treatments have been carried out at various temperatures below the equilibrium eutectoid temperature for various durations in order to tune the size of the eutectoid product. Thermal properties of the samples were studied in the temperature range of 100–350 °C. The microstructural investigations support the fact that the finest microstructure generated through the eutectoid decomposition of the α-Fe2Si5 metastable phase is responsible of the phonon scattering. The results suggest an opportunity to produce bulk iron silicide alloys with reduced thermal conductivity in order to enhance its thermoelectric performance.

The mechanism of foaming and thermal conductivity of glasses foamed with MnO2

We prepare foam glass from cathode ray tube (CRT) panels using MnO2 as foaming agent at different temperatures for various durations. The reduction of MnO2 to Mn2O3 leads to formation of O2 gas, and hence, causes initial foaming. The Mn2O3 particles dissolve into the glass melt and subsequently reduce, causing further formation of O2 gas and foaming of the glass melt. Increasing the treatment temperature and time enhances foam expansion, Mn2O3 dissolution, and lowers the closed porosity. Once the foam reaches a percolated stage, the foam continues to grow. This is caused by nucleation of new bubbles and subsequent growth. We discuss evolution of pore morphology in terms of pore number density, pore size and closed porosity. The thermal conductivity of the foam glasses is linearly dependent on density. The heat transfer mechanism is revealed by comparing the experimental data with structural data and analytical models. We show that the effect of pore size, presence of crystal inclusions and degree of closed porosity do not affect the overall thermal conductivity.

Characterization of the effects of three Lactobacillus species on the function of chicken macrophages

Lactobacillus acidophilus, Lactobacillus reuteri and Lactobacillus salivarius can influence the adaptive immune responses in chickens but vary in their ability to do so. The present study attempted to identify how these three bacteria alter the innate immune system. A chicken macrophage cell line, MQ-NCSU, was co-cultured with the three live Lactobacillus species, alone or in combination, grown at different temperatures for various durations of time. Late exponential growth phase bacteria were more immunostimulatory, while bacterial growth temperature had little effect. L. acidophilus and L. salivarius significantly increased nitric oxide (NO) production and phagocytosis, while L. reuteri did not. In fact, L reuteri was shown to inhibit NO production of macrophages when co-cultured with the other bacteria or when cells were pre-treated with LPS. The results demonstrate a possible molecular mechanism for the immunomodulatory effects of L. acidophilus and L. salivarius, and a unique immunomodulatory ability of L. reuteri.

Age-induced multi-stage transformation in a Ni-rich NiTiHf alloy

Abnormal multi-stage transformations have already been studied in binary Ni-rich NiTi alloys. In this research, this kind of transformation was investigated in a low supersaturated Ni-rich ternary NiTiHf high-temperature shape memory alloy by aging at intermediate temperatures for various durations. Meticulous examinations of the results of differential scanning calorimetry tests demonstrated the heterogeneous precipitation of (Ti,Hf)3Ni4 particles and the three-stage transformation (one-stage R and two-stage B19′) in the aged alloy. Aging provided a significant rise in transformation temperatures (TTs) until they reached their equilibrium states, corresponding to the equilibrium Ni content at each aging temperature. Equilibrium TTs were higher when aging was performed at a lower temperature. The remarkable increase in TTs was compared with those in aged Ni-rich NiTi alloys, and discussed based on the variation in valence electron concentration. A model was also proposed for the microstructural evolution during aging. Furthermore, aging provided enhanced hardness and strain recovery for the alloy. In particular, aging at a lower temperature resulted in a considerable improvement in hardness and shape recovery, which was discussed based on the microstructural changes in the aged alloy. Equilibrium Ni content at each aging temperature proved to be a crucial parameter in controlling the alloy properties, even in heterogeneous precipitations.

Growth behavior of nanosized ceria powders prepared by coprecipitation routes

Abstract Nanosized ceria (CeO 2 ) powders were obtained by coprecipitation routes of cerium nitrate hexahydrate [Ce(NO 3 ) 3 ·6H 2 O]. The growth behavior of the nanosized CeO 2 powders was investigated by X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The XRD results showed that the dried precursor powders contained a single crystalline phase of CeO 2 , and only a single phase of CeO 2 appeared when the dried precursor powders were calcined at different temperatures for various durations. Moreover, the crystallite size of CeO 2 increased on increasing the calcination temperature and duration. The kinetics equation of the nanosized CeO 2 powders grown between 673 and 1273 K for various durations is described as D t − D 0 = k t m exp ( − 56.42 × 10 3 / R T ) where k =7.5×10 −1 and m =0.20 when t ≤360 min and 673 K≤ T ≤873 K; k =8.46 and m =0.43 when 5 min≤ t ≤30 min and 1073 K≤ T ≤1273 K; and k =3.17×10 and m =0.03 when 30 min≤ t ≤360 min and 1073 K≤ T ≤1273 K.