Low Stress Research Articles

Contrasting magma chemistry in the Candelaria IOCG district caused by changing tectonic regimes

Iron oxide-copper-gold (IOCG) deposits are a vital source of copper and critical elements for emerging clean technologies. Andean-type IOCG deposits form in continental arcs undergoing extension, and they have a temporal relationship with magmatism although they do not exhibit a close spatial relation with the causative intrusions. The processes required to form IOCG deposits and their potential connections to iron oxide–apatite (IOA)-type mineralization remain poorly constrained, as well as the characteristics of magmatism linked to both deposit types. Here we combine zircon U–Pb geochronology with zircon trace element geochemistry of intrusive rocks associated with the Candelaria deposit, one of the world’s largest IOCG deposits, to unravel distinctive signatures diagnostic of magmatic fertility. Our results reveal a marked transition in the geochemistry of intrusions in the Candelaria district, characterized by changes in the redox state, water content and temperature of magmas over time. The oldest magmatic stage (~ 128–125 Ma), prior to the formation of the Candelaria deposit, was characterized by zircon Eu/Eu* ratios of 0.20–0.42, and redox conditions of ΔFMQ − 0.4 to + 1.0. The earliest magmatic stage related to the formation of Fe-rich mineralization at Candelaria (118–115 Ma) exhibits low zircon Eu/Eu* ratios (0.09–0.18), low oxygen fugacity values (ΔFMQ ~− 1.8 to + 0.2) and relatively high crystallization temperatures. In contrast, the youngest stage at ~ 111–108 Ma shows higher zircon Eu/Eu* (~ 0.37–0.69), higher oxygen fugacity values (ΔFMQ ~ + 0.4 to + 1.3) and a decrease in crystallization temperatures, conditions that are favorable for the transport and precipitation of sulfur and chalcophile elements. We conclude that Candelaria was formed through two distinct ore-forming stages: the first associated with a reduced, high temperature, water-poor magma developed under a low tectonic stress, followed by a more oxidized, water-rich, and low temperature magmatic event related to a compressional regime. The first event led to Fe-rich and S-poor IOA-type mineralization, while the second event with geochemical signatures similar to those of porphyry copper systems, generated the Cu- and S-rich mineralization. This late stage overprinted preexisting IOA mineralization resulting in the formation of the giant Candelaria IOCG deposit.

OPN, BSP, and Bone Quality-Structural, Biochemical, and Biomechanical Assessment in OPN-/-, BSP-/-, and DKO Mice.

Osteopontin (OPN) and Bone Sialoprotein (BSP), abundantly expressed by osteoblasts and osteoclasts, appear to have important, partly overlapping functions in bone. In gene-knockout (KO, -/-) models of either protein and their double (D)KO in the same CD1/129sv genetic background, we analyzed the morphology, matrix characteristics, and biomechanical properties of femur bone in 2 and 4month old, male and female mice. OPN-/- mice display inconsistent, perhaps localized hypermineralization, while the BSP-/- are hypomineralized throughout ages and sexes, and the low mineralization of young DKO mice recovers with age. The higher contribution of primary bone remnants in OPN-/- shafts suggests a slow turnover, while their lower percentage in BSP-/- indicates rapid remodeling, despite FTIR-based evidence in this genotype of a high maturity of the mineralized matrix. In 3-point bending assays, OPN-/- bones consistently display higher Maximal Load, Work to Max. Load and in young mice Ultimate Stress, an intrinsic characteristic of the matrix. Young male and old female BSP-/- also display high Work to Max. Load along with low Ultimate Stress. Principal Component Analysis confirms the major role of morphological traits in mechanical competence, and evidences a grouping of the WT phenotype with the OPN-/- and of BSP-/- with DKO, driven by both structural and matrix parameters, suggesting that the presence or absence of BSP has the most profound effects on skeletal properties. Single or double gene KO of OPN and BSP thus have multiple distinct effects on skeletal phenotypes, confirming their importance in bone biology and their interplay in its regulation.

Selection of long-term shear strength parameters for strain softening geosynthetic interfaces (2023 IGS Rowe Lecture)

The behavior of strain-softening geosynthetic interfaces that can lead to progressive failures in lined containment facilities has been a source of confusion in slope stability evaluations for over 30 years. The paper presents fifteen mechanisms that can potentially induce displacements along strain-softening interfaces, along with measures that can be considered to reduce strain-softening displacement. New quantifications of shear strength variability that can be caused by manufacturing, installation, and construction practices are introduced. Guidance and recommendations are given that are applicable to numerical continuum as well as limit-equilibrium approaches to assist in selecting appropriate geosynthetic shear strength parameters for containment facilities that have strain-softening interfaces. While most of the paper focuses on deep-seated critical interfaces for high normal stress bottom liners, low normal stress veneer covers are also addressed.

Analysis of cartilage loading and injury correlation in knee varus deformity.

Knee varus (KV) deformity leads to abnormal forces in the different compartments of the joint cavity and abnormal mechanical loading thus leading to knee osteoarthritis (KOA). This study used computer-aided design to create 3-dimensional simulation models of KOA with varying varus angles to analyze stress distribution within the knee joint cavity using finite element analysis for different varus KOA models and to compare intra-articular loads among these models. Additionally, we developed a cartilage loading model of static KV deformity to correlate with dynamic clinical cases of cartilage injury. Different KV angle models were accurately simulated with computer-aided design, and the KV angles were divided into (0°, 3°, 6°, 9°, 12°, 15°, and 18°) 7 knee models, and then processed with finite element software, and the Von-Mises stress distribution and peak values of the cartilage of the femoral condyles, medial tibial plateau, and lateral plateau were obtained by simulating the human body weight in axial loading while performing the static extension position. Finally, intraoperative endoscopy visualization of cartilage injuries in clinical cases corresponding to KV deformity subgroups was combined to find cartilage loading and injury correlations. With increasing varus angle, there was a significant increase in lower limb mechanical axial inward excursion and peak Von-Mises stress in the medial interstitial compartment. Analysis of patients' clinical data demonstrated a significant correlation between varus deformity angle and cartilage damage in the knee, medial plateau, and patellofemoral intercompartment. Larger varus deformity angles could be associated with higher medial cartilage stress loads and increased cartilage damage in the corresponding peak stress area. When the varus angle exceeds 6°, there is an increased risk of cartilage damage, emphasizing the importance of early surgical correction to prevent further deformity and restore knee function.

Better emotion regulation mediates gratitude and increased stress in undergraduate students across a university semester.

It is well established that university students are vulnerable to poor mental health. Although increased gratitude has been shown to reduce stress among students, a clearer understanding of key mechanisms underpinning this relationship are needed to better inform theoretical models and potential interventions targeted at improving well-being in university students. The present study provides the first direct test of whether capacity for emotion regulation mediates the relationship of gratitude with stress at the beginning and middle of the academic semester. This study is also the first to assess this relationship in a cross-lagged panel mediation model. We used a repeated measures design and a total of 343 undergraduate students completed two online surveys with validated measures of gratitude, stress, and emotion regulation-one at the beginning and the second in the middle of the academic semester. Results showed that emotion regulation mediated the relationship between gratitude and stress at the beginning of semester, and again 6weeks later. A Clogg's z-score test suggested that the strength of the indirect effect significantly increased across the two time points. A post-hoc cross-lagged panel model found that high gratitude at the beginning of the semester predicted low stress in the middle of the semester via emotion regulation. These data provide novel evidence that emotion regulation may serve as a key protective factor against undergraduate stress. The results provide evidence to support leading theories on how gratitude can reduce stress and promote well-being in university students. They also highlight the practical importance of strengthening emotion regulation abilities in university students and can be used to inform future targeted interventions to improve well-being in university students.

Investigation into soil ratcheting behind integral bridges using centrifuge modelling

U.K. integral bridges are commonly designed according to PD 6694-1, with guidance on backfill ratcheting based on experimental data that is limited by: testing at a small-scale low stress state, a lack of abutment foundation and soil below, and a limited range of soil-structure configurations. As integral bridge use increases, there is a need for further understanding of the strain ratcheting mechanism which can lead to smarter designs that minimise material usage and lifetime maintenance. This research presents the suitability of modern centrifuge techniques to simulate ratcheting of the soil behind an integral bridge abutment over a design life of thermal loading. A high accuracy actuation system was developed and used in centrifuge testing, with test data provided to demonstrate its capabilities. This is followed by a comparison of surface settlements, deck axial forces and abutment bending moment distributions recorded for various soil-structure combinations, highlighting the sensitivity of soil ratcheting. The paper concludes that centrifuge modelling can successfully simulate backfill strain ratcheting behind integral abutments over a range of soil-structure configurations. Furthermore, results suggest that global rotations and base sliding are significant to the overall response, clarifying the importance of modelling at an appropriate stress state with a foundation and the soil below.

Combined associations of regular exercise and work-related moderate-to-vigorous physical activity with occupational stress responses: a cross-sectional study

ObjectiveThe association between work-related moderate-to-vigorous physical activity (MVPA) and higher levels of stress response is recognized, but whether this association is moderated by regular exercise remains unclear. This cross-sectional study investigated whether exercise-based physical activity (PA) associates with lower levels of stress responses moderated by work-related MVPA.MethodsThe study participants comprised 863 workers from 35 small and medium-sized enterprises in Shimane prefecture, Japan, collected through convenient sampling from April 2021 to August 2022. The Brief Job Stress Questionnaire was used to assess stress responses. Work-related MVPA and exercise-based PA were measured using questionnaires. Multiple linear regression was used to analyze the combined variables of work-related MVPA and exercise-based PA. The reference group had no weekly exercise-based PA and >60 min of work-related MVPA.ResultsWhen work-related MVPA exceeded 60 min/day, flexibility activity or walking for ≥5 days/week (B = −3.53, 95% CI = −5.96, −1.11; B = −2.53, 95% CI = −4.90, −0.16) and muscle-strengthening activity 1–3 times/week (B = −3.52, 95% CI = −6.91, −0.12) were significantly associated with lower psychological stress response. Flexibility activity (B = −1.74, 95% CI = −3.01, −0.46) showed a similar link with physical stress response. When work-related MVPA was below 60 min/day, flexibility activity (B = −3.23, 95% CI = −6.01, −0.44; B = −3.29, 95% CI = −5.94, −0.63) or walking (B = −4.03, 95% CI = −6.62, −1.45; B = −3.10, 95% CI = −5.76, −0.44) practice 1–4 times/week and ≥5 times/week was significantly associated with lower psychological stress response.ConclusionExercise-based PA greatly and consistently associates with a lower level of stress responses moderated by work-related MVPA.

Interleaved High Voltage Gain DC-DC Converter with Winding-Cross-Coupled Inductors and Voltage Multiplier Cells for Photovoltaic Systems

An interleaved high voltage gain DC-DC converter with winding-cross-coupled inductors (WCCIs) and voltage multiplier cells is proposed for photovoltaic systems. The converter configuration is based on the interleaved boost converter integrating the diode-capacitor clamp circuits, the winding-cross-coupled inductors, and voltage multiplier cells to increase the voltage gain and reduce the semiconductor voltage stresses. The equal current sharing of two phases is achieved with the help of the winding-cross-coupled inductors. The converter achieves high voltage gain while operating at a proper duty ratio. The low-voltage-rated MOSFETs with low on-resistance are available to reduce the conduction losses due to the low switch voltage stress. The leakage energy of the coupled inductors is recycled such that the voltage spikes on the power switches are avoided. The input current ripple is decreased due to the interleaved operation. The operating principle and steady-state analysis of the proposed converter are proposed in detail. The design guidelines of the proposed converter are given. In addition, the closed-loop controlled system of the proposed converter is designed to diminish the effect of the variations in input voltage and load on the output voltage. Finally, the experimental results of a 1000 W converter prototype with 36 V input and 400 V output are given to validate the theoretical analysis and the converter performance.

Improving the UV transmittance of synthetic quartz through defect repair methods

Synthetic quartz materials with high ultraviolet transmittance are widely used in lenses and other optical devices. However, the relatively insufficient transmittance limits the application. In this paper, method of Defect Compensation is proposed to reduce the content of ODC, E'center and NBOHC and synthetic quartz glass with UV high transmittance was prepared successfully. The glass has high transmittance with internal transmittance of 99.9%@193nm, low stress birefringence with 0.9nm/cm @632.8nm and good optical homogeneity with 0.78ppm @ 632.8nm.

Prenatal maternal stress, sleep quality, and neonatal birth weight: A prospective cohort study.

To assess if the impacts of prenatal maternal stress (PNMS) on neonatal physical development including birth weight and body length vary by trimesters, and to explore the mediating effect of sleep quality in the relationships. A total of 2778 pregnant women were included from the Shanghai Maternal-Child Pairs Cohort. PNMS and sleep quality were measured in the first trimester (12-16 gestational weeks) and third trimester (32-36 gestational weeks) using the Life Event Scale for Pregnant Women (LESPW) and Pittsburgh Sleep Quality Index, respectively. And total LESPW scores were classified into three groups: high stress (≥75th percentile), medium stress (≥25th and <75th percentile), and low stress (<25th percentile). Multiple linear and logistic regressions were employed to examine the associations between PNMS and birth weight, and bootstrap were utilized to explore the mediating effects of maternal sleep. Higher (adjusted odds ratio, aOR=1.521; 95% confidence interval (CI), 1.104-2.096) and medium (aOR=1.421; 95% CI, 1.071-1.885) PNMS and stress from subjective events (aOR=1.334; 95% CI, 1.076-1.654) in the first trimester were significantly associated with elevated risk for large for gestational age. Maternal severe negative objective events stress (OE3) in the third trimester were negatively associated with birth weight (β=-0.667; 95% CI, -1.047∼-0.287), and maternal sleep latency during this period acted as a mediator in the association (indirect effect: β=-0.0144; 95% CI, -0.0427∼-0.0003). Besides, a significant negative correlation between total LESPW score (β=-0.022; 95% CI, -0.038∼-0.006; per 100 score) and body length in the third trimester was also observed. The impact of PNMS on neonatal birth weight varies by stress types and exposure timing. Prolonged maternal sleep latency in the third trimester correlated with lower birth weight, and mediating the link of OE3 and birth weight, which might indicate a critical period of vulnerability to the effects of PNMS on neonatal physical development.

Genome-wide identification, molecular evolution and gene expression of P450 gene family in Cyrtotrachelus buqueti

BackgroundInsect Cytochrome P450 monooxygenase (CYPs or P450s) plays an important role in detoxifying insecticides, causing insect populations to develop resistance. However, the molecular functions of P450 gene family in Cyrtotrachelus buqueti genome are still lacking.ResultsIn this study, 71 CbuP450 genes have been identified. The amino acids length of CbuP450 proteins was between 183 aa ~ 1041 aa. They are proteins with transmembrane domains. The main component of their secondary structure is α-helix and random coils. Phylogenetic analysis showed that C. buqueti and Rhynchophorus ferrugineus were the most closely related. This gene family has 29 high-frequency codons, which tend to use A/T bases and A/T ending codons. Gene expression analysis showed that CbuP450_23 in the female adult may play an important role on high temperature resistance, and CbuP450_17 in the larval may play an important role on low temperature tolerance. CbuP450_10, CbuP450_17, CbuP450_23, CbuP450_10, CbuP450_16, CbuP450_20, CbuP450_23 and CbuP450_ 29 may be related to the regulation of bamboo fiber degradation genes in C. buqueti. Protein interaction analysis indicates that most CbuP450 proteins are mainly divided into three aspects: encoding the biosynthesis of ecdysteroids, participating in the decomposition of synthetic insecticides, metabolizing insect hormones, and participating in the detoxification of compounds.ConclusionsWe systematically analyzed the gene and protein characteristics, gene expression, and protein interactions of CbuP450 gene family, revealing the key genes involved in the stress response of CbuP450 gene family in the resistance of C. buqueti to high or low temperature stress, and identified the key CbuP450 proteins involved in important life activity metabolism. These results provided a reference for further research on the function of P450 gene family in C. buqueti.

Intervention mechanism of carbide precipitation during tempering and its impact on residual stress and mechanical properties of wear-resistant steels

The production of low-stress, high-performance wear-resistant steels poses a formidable challenge in the steel industry. This article delves into the carbide precipitation behaviour of wear-resistant steel NM300TP during tempering and its subsequent impact on residual stress and mechanical properties. Our findings reveal a crucial aspect: prolonging the holding time can interfere with the precipitation behaviour of carbides, thereby altering the relaxation mechanism of residual stress and its influence on material properties. Remarkably, we discovered that substituting the formation of θ-cementites with the precipitation of ε-transition carbides can yield a steel with significantly lower residual stress while maintaining exceptional mechanical properties. Specifically, when θ-cementites precipitate, the residual stress in the wear-resistant steel diminishes by 54.23%, accompanied by a hardness measurement of 299.58 HV0.5. However, when a substantial quantity of ε-transition carbides is dispersed and precipitated, the residual stress is further diminished by 69.51%, and the hardness reaches 317.2 HV0.5. Furthermore, this precipitation of ε-transition carbides exhibits superior wear resistance compared to θ-cementites. These groundbreaking discoveries offer critical theoretical insights for the development of low-stress, high-performance wear-resistant steels, paving the way for innovative advancements in the steel industry.

The Selah trial: A preference-based partially randomized waitlist control study of three stress management interventions.

Chronic stress undermines psychological and physiological health. We tested three remotely delivered stress management interventions among clergy, accounting for intervention preferences. United Methodist clergy in North Carolina enrolled in a partially randomized, preference-based waitlist control trial. The interventions were: mindfulness-based stress reduction (MBSR), Daily Examen prayer practice, and Stress Proofing (stress inoculation plus breathing skills). Co-primary outcomes were symptoms of stress (Calgary Symptoms of Stress Inventory) and 48-hour ambulatory heart rate variability (HRV) at 12 weeks compared to waitlist control. Survey data were collected at 0, 12, and 24 weeks and 48-hour ambulatory HRV at 0 and 12 weeks. The 255 participants were 91% White and 48% female. Forty-nine participants (22%) without a preference were randomly assigned between the three interventions (n = 40) and waitlist control (n = 9). Two hundred six participants (78%) with a preference were randomly assigned to waitlist control (n = 62) or their preferred intervention (n = 144). Compared to waitlist control, MBSR [mean difference (MD) = -0.30, 95% CI: -0.41, -0.20; P < .001] and Stress Proofing (MD = -0.27, 95% CI: -0.40, -0.14; P < .001) participants had lower stress symptoms at 12 weeks; Daily Examen participants did not until 24 weeks (MD = -0.24, 95% CI: -0.41, -0.08). MBSR participants demonstrated improvement in HRV at 12 weeks (MD = +3.32ms; 95% CI: 0.21, 6.44; P = .036). MBSR demonstrated robust improvement in self-reported and objective physical correlates of stress; Stress Proofing and Daily Examen resulted in improvements in self-reported correlates of stress. These brief practices were sustainable and beneficial for United Methodist clergy during the heightened stressors of the COVID pandemic. ClinicalTrials.gov identifier: NCT04625777.

Comparing the healthy development of youth Australian Rules Footballers across talent development and community settings

ObjectivesThis study aimed to compare talent development athletes to community-level athletes in Australian Rules Football across various markers of healthy youth development.MethodsSurvey data were collected from 363 youth athletes (126...

Subacute cadmium exposure changes different metabolic functions, leading to type 1 and 2 diabetes mellitus features in female rats.

Cadmium (Cd) is a heavy metal that acts as endocrine disrupting chemical (EDC). Few studies have investigated the effects of Cd exposure on metabolic dysfunctions, such as type 1 and 2 diabetes mellitus (T1DM and T2DM). Thus, we assessed whether subacute Cd exposure at occupational levels causes abnormalities in white adipose tissue (WAT), liver, pancreas, and skeletal muscle. We administered cadmium chloride (CdCl2) (100 ppm in drinking water for 30 days) to female rats and evaluated Cd levels in serum and metabolic organs, morphophysiology, inflammation, oxidative stress, fibrosis, and gene expression. High Cd levels were found in serum, WAT, liver, pancreas, and skeletal muscle. Cd-exposed rats showed low adiposity, dyslipidemia, insulin resistance, systemic inflammation, and oxidative stress compared to controls. Cd exposure reduced adipocyte size, hyperleptinemia, increased cholesterol levels, inflammation, apoptosis and fibrosis in WAT. Cd-exposed rats had increased liver cholesterol levels, insulin receptor beta (IRβ) and peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC1α) expression, karyomegaly, inflammation, and fibrosis. Cd exposure reduced insulin levels and pancreatic islet size and increased inflammation and fibrosis. Cd exposure reduced skeletal muscle fiber diameter and increased IR expression and inflammation. Finally, strong positive correlations were observed between serum, tissue Cd levels, abnormal morphology, tissue inflammation and fibrosis. Thus, these data suggest that subacute Cd exposure impairs WAT, liver, pancreas and skeletal muscle function, leading to T1DM and T2DM features and other complications in female rats.

The Production of Three-Dimensional Metal Objects Using Oscillatory-Strain-Assisted Fine Wire Shaping and Joining

Material shaping and joining are the two fundamental processes that lie at the core of many forms of metal manufacturing techniques, including additive manufacturing. Current metal additive manufacturing processes such as laser/e-beam powder bed fusion and Directed Energy Deposition predominantly use heat and subsequent melt–fusion and solidification to achieve shaping and joining. The energy efficiency of these processes is severely limited due to energy conversion losses before energy is delivered at the point of melt–fusion for shaping and joining, and due to losses through heat transfer to the surrounding environment. This manuscript demonstrates that by using the physical phenomenon of lowered yield stress of metals and enhanced diffusion in the presence of low amplitude high frequency oscillatory strain, metal shaping and joining can be performed in an energy-efficient way. The two performed simultaneously enable a metal additive manufacturing process, namely Resonance-Assisted Deposition (RAD), that has several unique capabilities, like the ability to print net-shape components from hard-to-weld alloys like Al6061 and the ability to print components with a very high aspect ratio. In this study, we show this process’s capabilities by printing solid components using aluminum-based metal alloys.

Pebble to the Metal: A Boulder Approach to Enrichment for Danio rerio.

Zebrafish are an established and widely used animal model, yet there is limited understanding of their welfare needs. Despite an increasing number of studies on zebrafish enrichment, in-tank environmental enrichment remains unpopular among researchers. This is due to perceived concerns over health/hygiene when it comes to introducing enrichment into the tank, although actual evidence for this is sparse. To accommodate this belief, regardless of veracity, we tested the potential benefits of enrichments presented outside the tank. Thus, we investigated the preferences and physiological stress of zebrafish with pictures of pebbles placed underneath the tank. We hypothesized that zebrafish would show a preference for enriched environments and have lower stress levels than barren housed zebrafish. In our first experiment, we housed zebrafish in a standard rack system and recorded their preference for visual access to a pebble picture, with two positive controls: visual access to conspecifics, and group housing. Using a crossover repeated-measures factorial design, we tested if the preference for visual access to pebbles was as strong as the preference for social contact. Zebrafish showed a strong preference for visual access to pebbles, equivalent to that for conspecifics. Then, in a second experiment, tank water cortisol was measured to assess chronic stress levels of zebrafish housed with or without a pebble picture under their tank, with group housing as a positive control. Cortisol levels were significantly reduced in zebrafish housed with pebble pictures, as were cortisol levels in group housed zebrafish. In fact, single housed zebrafish with pebble pictures showed the same cortisol levels as group housed zebrafish without pebble pictures. Thus, the use of an under-tank pebble picture was as beneficial as being group housed, effectively compensating for the stress of single housing. Pebble picture enrichment had an additive effect with group housing, where group housed zebrafish with pebble pictures had the lowest cortisol levels of any treatment group.

Ultra-stable foam enabled by nano silica engineering for foam concrete improvement

Foam concrete is increasingly applied in construction due to its lightweight, good thermal insulation and fire resistance, and environmental sustainability, while its low strength limits its further popularization and applications. To enhance the stability and performance of foam concrete, amphiphilic nano silica (ANS) was employed in this study to modify the sodium dodecyl sulphate (SDS) based foaming agent. Then, the designed foam was utilized to fabricate foam concrete, of which the micro/macro performance was analysed in detail. The results showed that ANS-modified foam exhibited superior stability with a thicker foam wall thickness, contributing to the enhancement of foam stability within the cement matrix. The foam concrete with ANS exhibited higher strength compared to the control groups. The analysis of pore structures revealed that the ANS modification led to a more rounded and homogeneous pore configuration, characterized by an increased proportion of small and medium-sized pores and a decreased average pore size. The increase in pore roundness was accompanied by a reduction in the number of sharp edges of the pores and therefore a reduction in the stress concentration factor, while the moderately sized pore also was more conducive to increasing strength due to its lower stress concentration. As a result, the strength of the concrete is significantly increased. These findings demonstrate the potential of ANS as an effective foam stabilizer for foam concrete production, leading to enhanced foam stability and improved mechanical properties of concrete.

DESIGN AND ANALYSIS OF PRESSURE VESSEL USING DIFFERENT MATERIALS

This project explores the field of Finite Element Analysis (FEA) in relation to pressure vessels that have different head configurations, while ensuring that the cylindrical volume and thickness remain uniform. The project adheres to ASME standards, specifically Section VIII, Division I, and focuses on designing a pressure vessel that can withstand a pressure of 8 bar within a volume of 24 liters. The main objective of using FEA is to identify areas of stress concentration in each head design. In industrial settings, pressure vessels play a crucial role in containing fluids or gases under varying pressures. The choice of head configuration significantly impacts the distribution of stress and the overall structural strength. This project specifically utilizes ANSYS software for static and thermal analyses to compare stress distribution in pressure vessels with flat heads, elliptical heads, and other common head designs. The goal is to identify configurations that exhibit lower stress levels, with a particular emphasis on practical scenarios that favor elliptical heads. Additionally, the project explores finite element modeling techniques to evaluate pressure vessels made from different materials such as Nimonic 80A and SA516 Gr70 under high-stress conditions

Power flow and reliability analysis of a non-isolated PV/grid connected quasi resonant converter for off-board EV charging station

ABSTRACT Growing awareness of greenhouse gas emissions and exhaustion of fossil fuels leads to the adoption of electric vehicles (EVs). However, the major limitations with respect to EV technology are the driving range and charging time. Also, the proliferation of EVs overloads the power grid and paves the way of incorporating renewable energy sources and energy storage devices. The use of multiple sources necessitates the deployment of compact, low-cost, and high-power electronic converters. This paper proposes a novel configuration of a Multi-Source Non-Isolated Quasi-Resonant Converter (MSNQRC) to overcome the limitations in the charging infrastructure. Due to the presence of a quasi-resonant network, the proposed MSNQRC with a single switch can achieve high voltage gain even at low-duty cycles, provide continuous current and low voltage stress. In addition, this paper elaborates on the parametric design of the converter along with PV modeling based on load ratings and the reliability research of MSNQRC by analysing component failures. A prototype model of 300W is built to verify the efficacy of the designed converter model. The results thus obtained validate the designed model and prove that the proposed system can be used for off-board battery charging systems.