Single Point Research Articles

Loneliness Trajectories Predict Risks of Cardiovascular Diseases in Chinese Middle-Aged and Older Adults.

Loneliness is considered a risk factor for cardiovascular diseases (CVD), but related evidence is mixed. Examining trajectories of loneliness over time, as compared to the assessment of loneliness at a single time point, can be useful to better understand the risks for CVD. The present study aimed to examine loneliness trajectories and their impacts on CVD in Chinese middle-aged and older adults. The sample included 9,235 adults aged 45 years and older from 4 waves of the China Health and Retirement Longitudinal Survey from 2011 to 2018. Loneliness was assessed by a single-item question with a 4-point scale. CVD events were measured by self-reports of heart diseases and strokes in 2018. Group-based trajectory modeling showed that 3 loneliness trajectories emerged: stable low, moderate increasing, and high increasing loneliness. Binary logistic regression showed that loneliness trajectories were significantly associated with the risk of having CVD after controlling for all covariates. Specifically, compared to the group with stable low loneliness, people with moderate increasing loneliness had a higher risk of having stroke, and people with high increasing loneliness had higher risks of having both heart diseases and stroke. In contrast, loneliness at a single time point was not independently associated with the risk of having CVD. The present study identified groups of people vulnerable to CVD from the perspective of social connections in terms of loneliness trajectories. Middle-aged and older adults showing increasing loneliness may need social and emotional support to protect their cardiovascular health.

The influence of segmental and suprasegmental phonological awareness on word and pseudoword reading-A comparison between native English speakers and native Chinese speakers of English.

Segmental and suprasegmental phonological awareness (PA) are closely related to word reading skills in native speakers learning to read an alphabetic script as used in English. However, their roles in English word and pseudoword reading among native Chinese (NC) speakers, and how English proficiency might affect these relationships, remain less clear. This study examined the links between English segmental/suprasegmental PA and word/pseudoword reading in NC and native English (NE) speakers. Both child and adult participants were assessed on English segmental and suprasegmental PA, alongside vocabulary, at a single time point. The results showed that both segmental PA (elision and segmenting nonwords) and suprasegmental PA (aural suffix judgment and written suffix judgment) were significantly correlated with English real word and pseudoword reading of both NE and NC children, and NC adults, but not NE adults. Moreover, for NE and NC children, segmental PA correlated stronger with real word reading than suprasegmental PA after controlling for vocabulary. Among NC adults, both segmental and suprasegmental PA significantly contributed to real word reading. For pseudoword reading, after controlling for vocabulary, segmental PA had a stronger correlation among NC children and adults, while suprasegmental PA was more influential for NE children. This research gives insights into factors influencing NC speakers' English word reading ability, bearing essential implications for enhancing second language literacy in learners from a logographic background.

Enhancing Contraceptive Utilization among Females of Reproductive Age: Factors, Challenges, and Strategies at Jinja Regional Referral Hospital

The research aimed to assess the factors influencing the utilization of contraceptives among females of reproductive age seeking health services at Jinja Regional Referral Hospital. Specifically, it sought to establish socio-demographic characteristics, examine health service factors affecting contraceptive utilization, and determine its prevalence. A cross-sectional and descriptive research design employing both quantitative and qualitative methodologies was utilized to ensure the gathered information was representative of the population and captured at a single point in time. The study discovered a prevalence of contraceptive use among females of 55.7%, with short-term hormonal methods being the most common at 57.1%. Key findings revealed that females aged 18 to 30 years (57.1%) were significantly more likely to use contraception (p-value = 0.036), and multiparous individuals (98.2%) were more inclined to utilize contraception compared to para-one individuals (50.6%) (p-value = 0.024). Moreover, prior counseling (73.2%) significantly promoted contraceptive usage (p-value = 0.015). In conclusion, despite the observed prevalence, contraceptive utilization remained relatively low. Recommendations include increasing the availability of contraceptive services at lower-level health care centers to enhance accessibility, educating mothers visiting health facilities about contraceptive services, and addressing contraception-related phobias through counseling to encourage uptake among females. Keywords: Contraceptives, Females, Reproductive age, Health services, Health facility.

Changing snow water storage in natural snow reservoirs

Abstract. This work introduces a novel snow metric, snow water storage (SwS), defined as the integrated area under the snow water equivalent (SWE) curve (units: length-time, e.g., m d). Unlike other widely used snow metrics that capture snow variables at a single point in time (e.g., maximum SWE) or describe temporal snow characteristics (e.g., length of snow season), SwS is applicable at numerous spatial and temporal scales. This flexibility in the SwS metric enables us to characterize the inherent reservoir function of snowpacks and quantify how this function has changed in recent decades. In this research, changes in the SwS metric are evaluated at point, gridded and aggregated scales across the conterminous United States (hereafter US), with a particular focus on 16 mountainous Environmental Protection Agency (EPA) Level III Ecoregions (ER3s). These ER3s account for 72 % of the annual SwS (SwSA) in the US, despite these ER3s only covering 16 % of the US land area. Since 1982, spatially variable changes in SwSA have been observed across the US with notable decreasing SwSA trends in the western US and in the 16 mountainous ER3s. All mountainous ER3 (except for the Northeastern Highlands in New England) exhibit decreasing trends in SwSA resulting in a 22 % overall decline in SwSA across mountainous ER3s. The peak monthly SwS (SwSM) occurs in March at all spatial scales, while the greatest percentage loss of SwSM occurs early in the snow season, particularly in November. Unsurprisingly, the highest elevations contribute most to SwSA in all mountain ranges, but the specific elevations that have experienced loss or gain in SwSA over the 39-year study period vary between mountain ranges. Comparisons of SwS with other snow metrics underscore the utility of SwS, providing insights into the natural reservoir function of snowpacks, irrespective of SWE curve variability or type (e.g., ephemeral, mountain, permanent). As we anticipate a future marked by increased climate variability and greater variability in mountain snowpacks, the spatial and temporal flexibility of snow metrics such as SwS may become increasingly valuable for monitoring and predicting snow water resources.

Remote Sensing-Based Water Quality Parameters Retrieval Methods: A Review

Water quality is a sensitive global environmental issue, as it is important for long-term economic development and environmental sustainability. It is a general descriptor of water properties in terms of physical, chemical, thermal, and/or biological characteristics. Laboratory analysis is used to measure and analyze water quality parameter, however, it is a conventional, time-consuming, and expensive approach often providing discrete data at a single point in space and time and making it difficult to characterize a larger waterbody, while remote sensing methods is a cost effective and accurate methods of water quality monitoring with a high spatial and temporal resolution for large area of waterbodies. To this end, this review focused on novel findings in the field of water quality estimation using remote sensing techniques, and the result revealed that remote sensing method has used to retrieve water quality parameters which are optically active (Chlorophyll-a, Secchi Disk depth, Water temperature, Turbidity, Total Suspended Matter, Electrical conductivity, Sea Surface Salinity and Colored Dissolved Organic Matter), and optically non active (Dissolved Oxygen, Chemical Oxygen Demand, Biochemical Oxygen Demand, Total Nitrogen, Ammonia Nitrogen and Total Phosphorus). Various properties (spectral, spatial and temporal, etc.) of the more commonly employed multi spectral and hyper spectral sensors of both satellite and non-satellite-born data sources are tabulated to be used as a sensor selection guide. Furthermore, this paper summarizes the commonly used different retrieval algorisms (analytical, empirical, and artificial intelligence/machine learning (AI/ML)) employed in evaluating and quantifying the water quality parameters. As a whole, remote sensing technology is a permissible method for water quality monitoring across the world in its spatio-temporal coverage, accuracy, and its cost effectiveness

Natural formation of linear defect structures in MoS2

Near surface defects can significantly impact the quality of metallic interconnects and other interfaces necessary to create device structures incorporating two-dimensional materials. Furthermore, the impact of such defects can strongly depend on their organization. In this study, we present scanning tunneling microscopy images and tunneling spectroscopy of point and linear defects near the surface of natural MoS2. The point defects share similar structural and electronic characteristics and occur with comparable frequency as subsurface sulfur vacancies observed previously on natural MoS2. The linear defects observed here occur less frequently than the point defects but share the same depth profile and electronic structure. These data indicate that the linear defects are actually a one-dimensional organization of subsurface sulfur vacancies. Our density functional calculations agree with this assessment in that, for sufficient local defect concentrations, it is energetically more favorable for the defects to be organized in a linear fashion rather than as clusters or even isolated single point defects. Given these measurements were taken from naturally formed MoS2, this organization likely occurs during crystal formation. Considering the impact of one-dimensional organization on the local properties of layered materials, and the potential for them to be introduced purposefully during crystal formation, research into the formation mechanism and properties of these defects could enable new paths for defect engineering in MoS2-based systems.

Carbon storage units and carbon storage obligations: A review of policy approaches

Policies that incentivize the capture and geological storage of CO2 from large point sources (‘CCS’; and more recently, atmospheric removals), have so far tended to reward the resultant avoided CO2 emissions (or CO2 removals) achieved by operators at the point of capture. The expectation has been that geological CO2 storage sites, as well as the connecting infrastructure, will be developed and operated based upon the funding delivered from the single point of incentive (e.g. under an emissions trading system or a carbon tax, only CO2 capture installation operators are absolved of the obligation to acquire and surrender CO2 emission rights or to pay the tax). Project-based crediting mechanisms (e.g. in the voluntary carbon market) tend to treat the entire chain of operations as a single entity to be supplied with emission reduction or removal credits. Consequently, there has been minimal explicit financial incentive to store CO2. Yet a multiple gigaton-per-year scale capture and storage industry requires complex CO2 networks to evolve, with multiple sources connecting to multiple sinks, with installations owned by different operators with different technical expertise, climate mitigation goals and obligations. This multiplicity of goals and incentives can create agency problems and cross-chain risks, which impact negatively upon investment decisions. In this paper, we review the history, evolution and potential of geological net zero (GNZ) and carbon storage (or takeback) obligation concepts applied to fossil carbon producers and suppliers as a means to address these risks alongside policies aimed at atmospheric net zero (ANZ) and fossil carbon emitters.

The impact of sampling scale: A comparison of methods for estimating external contaminant exposure in free-ranging wildlife

The impacts of contaminants on wildlife are dose dependent, and thus being able to track or predict exposure following contamination events is important for monitoring ecosystem health. However, the ability to track exposure in free-ranging wildlife is often severely limited. Consequently, researchers have predominantly relied on simple methods for estimating contaminant exposures in wildlife with little regard for spatial contaminant heterogeneity or an animal's use of diverse habitats. We evaluated the influence sampling scale (i.e., how finely contaminant distribution and organism's spatial use of the landscape is mapped) has on (1) realism and (2) conservativeness of exposure estimates. To do this, we monitored the actual exposure of wild boar (Sus scrofa) in Fukushima, Japan to radioactive contamination using GPS-coupled contaminant monitors placed on individual animals. We compared empirical exposures to estimates generated by combining varying amounts of information about an individual boar's location and/or movement, with the distribution of contamination on the landscape. We found that the most realistic exposure estimates were produced when finer-scale contaminant distribution surveys (e.g., airborne surveys) were combined with more accurate estimates of an individual's space use (e.g., home ranges or core areas). Importantly, estimates of exposure based on single point surveys at a trap site (a simple method commonly used in the literature), did not correlate with actual exposure rates, suggesting dose-effects studies using this method may result in spurious conclusions. These results suggest that researchers seeking realistic estimates of exposure, such as in dose-effect studies, should ensure they have adequately accounted for fine-scale contaminant distribution patterns and areas of higher use by study organisms. However, conservative estimates of exposure (i.e., intentionally over-predicting exposure as is done in initial tiers of ecological risk analyses) were not as scale sensitive and could be achieved with a single known location and coarse contaminant distribution maps.

Green Building Rating of High-Rise Buildings in Sri Lanka


 
 
 As a result of urbanization, constructions of high-rise buildings become a major component of urban development. Constructing high-rise buildings contributes to social, economic and environmental development as well. There are many stages of construction including planning, designing, procurement and implementation. There is a wide range of sustainability practices which can be implemented in each stage of construction. In leading Sri Lanka to Sustainable Development, the green building rating system was introduced by National Green Building Council of Sri Lanka in 2002. This rating system has 100 total points and minimum of 40 points is required for green building certification. The rating system has different components. Among them sustainable sites category includes 25% of total points in green building rating system. This research study highlights the significance of sustainable sites category in order to award the green certification in green building rating system. For this research five major high-rise building construction sites in Colombo were selected and existing site selection practices of each site were investigated. Each site was visited and in-depth discussions were carried out with the planning engineer and other people in the construction site. The structured questionnaire was filled and scores were given accordingly where they have met the sustainable sites criteria. Two sites out of five could not earn single point as they did not fulfill the prerequisites of the site section category. The rest of the sites (three) earned 20, 19, and 18 respectively out of 25 points. In this study, lack of awareness in sustainable site selection practices has dropped the chances of being eligible for the green building certification. Since the minimum points required for green building certification is 40, buildings which are under planning or pre-construction stage have higher chances of obtaining silver, gold and platinum awards for green building certification. Therefore, sustainable sites category of the green building rating system contributes significantly to increase the score and therefore it is highly important in green certification & sustainable construction.
 Keywords: Green concept, High-rise buildings, Sustainable development, Sustainable site selection
 
 

How to make a SPE resolution strategy work in the EU

Abstract When dealing with the resolution of a banking group under EU regulation there are two different approaches: Single point of entry (SPE) versus Multiple Point of Entry (MPE). In a MPE strategy, the resolution authority is taking separate resolution actions at the level of individual legal entities of the group. In a SPE strategy, the resolution authority is taking a resolution action at the level of a single entity, usually the parent undertaking, which, consequently, becomes the so called “resolution entity” building together with its subsidiaries the “resolution group”. The general idea in a SPE strategy is, that losses at subsidiary level are first streamed up to the parent undertaking (resolution entity), i. e. capital is streamed down from the parent undertaking to the subsidiary to cover its losses and ensure its recapitalisation. This leads to losses at the resolution entity level, which, if the resolution entity meets the conditions for resolution, are taken care of by applying resolution tools to the resolution entity. This procedure is not necessarily a two-step approach but could also be completed in one go. In the following, we focus on different ways to upstream losses from the subsidiary to the parent undertaking and to recapitalise the subsidiary.

ПРЕДОПЕРАЦИОННАЯ ДИАГНОСТИКА У ПАЦИЕНТОВ С ЗАБОЛЕВАНИЯМИ СЕРДЕЧНО-СОСУДИСТОЙ СИСТЕМЫ ПЕРЕД ОПЕРАЦИЕЙ ДЕНТАЛЬНОЙ ИМПЛАНТАЦИИ (ОБЗОР ЛИТЕРАТУРЫ)

The subject of the study. Dental implantation for patients with cardiovascular diseases is an urgent and important area, but requires special attention from doctors and patients. Cardiovascular diseases can be a risk factor for implant rejection due to the fact that they often have a direct effect on blood flow to tissues. A review of literature sources in the period from 2017 to 2023 showed that there is no common point of view in the scientific community regarding the implementation of implantation in patients with hypertension and coronary heart disease. 
 Objectives. To study the specifics of preoperative diagnosis in patients with cardiovascular diseases before dental implantation surgery, reflected in the scientific literature. 
 Methodology. Currently, the article analyzes sources from databases: Pub Med, Cyberleninka, eLibrary, ResearchGate, CohraneOral Health. The search for scientific literature on the problem under consideration was carried out using keywords. The key criteria for reviewing the scientific publications available in the databases were the availability of indications for dental implantation in the studied individuals.
 Results. An analysis of the scientific literature on the use of dental implantation in patients with diseases of the cardiovascular system did not reveal a single point of view. The authors agree that patients with cardiac pathology need to hold a consultation with a cardiologist, an anesthesiologist, and a surgeon before elective surgery in order to make a joint decision. At that time, there are different points of view regarding the criteria for assessing the risk and scope of preoperative diagnosis of patients with cardiovascular diseases, there is no systematization and classification of complications, as well as criteria for evaluating the complications of dental implantation surgery in cardiac patients. 
 Conclusions. It seems advisable to identify criteria that determine the general condition and dental status of patients with diseases of the cardiovascular system, which will allow assessing the possibility of using dental implants for them.

Controlling Monoterpene Isomerization by Guiding Challenging Carbocation Rearrangement Reactions in Engineered Squalene-Hopene Cyclases.

The interconversion of monoterpenes is facilitated by a complex network of carbocation rearrangement pathways. Controlling these isomerization pathways is challenging when using common Brønsted and Lewis acid catalysts, which often produce product mixtures that are difficult to separate. In contrast, natural monoterpene cyclases exhibit high control over the carbocation rearrangement reactions but are reliant on phosphorylated substrates. In this study, we present engineered squalene-hopene cyclases from Alicyclobacillus acidocaldarius (AacSHC) that catalyze the challenging isomerization of monoterpenes with unprecedented precision. Starting from a promiscuous isomerization of (+)-β-pinene, we first demonstrate noticeable shifts in the product distribution solely by introducing single point mutations. Furthermore, we showcase the tuneable cation steering by enhancing (+)-borneol selectivity from 1 % to >90 % (>99 % de) aided by iterative saturation mutagenesis. Our combined experimental and computational data suggest that the reorganization of key aromatic residues leads to the restructuring of the water network that facilitates the selective termination of the secondary isobornyl cation. This work expands our mechanistic understanding of carbocation rearrangements and sets the stage for target-oriented skeletal reorganization of broadly abundant terpenes.

Efficient method for modeling large-scale arrays of optical nanoresonators based on the coupling theory of quasinormal mode.

We propose an efficient method for calculating the electromagnetic field of a large-scale array of optical nanoresonators based on the coupling theory of quasinormal mode (QNM). In this method, two approaches of the scattered-field reconstruction and stationary-phase-principle calculated plane-wave expansion are developed to obtain the regularized QNM (RQNM) in different regions. This accurate and efficient calculation of RQNM resolves the far-field divergence issue of QNMs in the QNM-coupling theory, thus enabling a rapid computation of the electromagnetic field of a large-scale array of optical nanoresonators, which is a challenging task for full-wave numerical methods. Using this method, we consider the numerical example of the radiation problem of a single point source in a large-scale periodic array of optical nanoantennas. In comparison to full-wave numerical methods, this method significantly reduces the computation time by 1∼2 orders of magnitude while maintaining accuracy. The high computational efficiency and physical intuitiveness of the method enables to clarify the impact of array size (exceeding 50 × 50 wavelengths), period and field-coupling range (far beyond the tight-binding approximation) on the optical response. The proposed method and results can provide an efficient tool and guidance for the design of large-scale arrays of optical nanoresonators.

Controlling Monoterpene Isomerization by Guiding Challenging Carbocation Rearrangement Reactions in Engineered Squalene‐Hopene Cyclases

AbstractThe interconversion of monoterpenes is facilitated by a complex network of carbocation rearrangement pathways. Controlling these isomerization pathways is challenging when using common Brønsted and Lewis acid catalysts, which often produce product mixtures that are difficult to separate. In contrast, natural monoterpene cyclases exhibit high control over the carbocation rearrangement reactions but are reliant on phosphorylated substrates. In this study, we present engineered squalene‐hopene cyclases from Alicyclobacillus acidocaldarius (AacSHC) that catalyze the challenging isomerization of monoterpenes with unprecedented precision. Starting from a promiscuous isomerization of (+)‐β‐pinene, we first demonstrate noticeable shifts in the product distribution solely by introducing single point mutations. Furthermore, we showcase the tuneable cation steering by enhancing (+)‐borneol selectivity from 1 % to >90 % (>99 % de) aided by iterative saturation mutagenesis. Our combined experimental and computational data suggest that the reorganization of key aromatic residues leads to the restructuring of the water network that facilitates the selective termination of the secondary isobornyl cation. This work expands our mechanistic understanding of carbocation rearrangements and sets the stage for target‐oriented skeletal reorganization of broadly abundant terpenes.

Concentration performance evaluation of sunlight concentrators: Fresnel lens, plano-convex lens, and parabolic mirrors for daylighting application

ABSTRACT This study investigates the concentration performance of three concentrator types – Fresnel lens, plano-convex lens, and parabolic mirrors in focusing sunlight onto a 1.5 mm diameter plastic optical fiber. The evaluation uses TracePro ray tracing software for simulation and analysis, considering visible light and infrared bands. Results show that parabolic mirrors achieved the highest concentration ratio at 7720 suns, followed by the Fresnel lens at 6400 suns, and the plano-convex lens at 2750 suns for a wavelength of 535 nm, surpassing geometric concentration values of 1202 suns. Efficiency measurements revealed that the Fresnel lens achieved 86% efficiency, the parabolic mirrors reached 97% efficiency, and the plano-convex lens achieved 93% efficiency. Additionally, the parabolic mirror demonstrated potential for creating the smallest concentration spot size due to its ability to focus light on a single point. This study highlights potential applications of sunlight concentrators in enhancing natural lighting in buildings and promoting energy efficiency. The comparative analysis of these concentrators offers insights into their performance characteristics, aiding in the selection and optimization of concentrators for daylighting applications. Moreover, this research supports the concept of green and sustainable energy by demonstrating the potential of solar energy to meet building energy demand and promote daylighting as a means to reduce reliance on conventional energy sources.

Intersection Properties of Finite Disk Collections

In this article, we study the intersection of a finite collection of disks in Euclidean space by examining spheres of various dimensions and their poles (extreme values with respect to canonical projections) contained within the intersection’s boundary. We derive explicit formulae for computing these extreme values and present two applications. The first application involves computing the smallest common rescaling factor for the radii of the disk system, which brings the system to a single point of intersection. This calculation allows us to compute the generalized Čech filtration, a crucial tool for the topological data analysis of weighted point clouds. The second application focuses on determining the minimal Axis-Aligned Bounding Box (AABB) for the intersection of a finite collection of disks in Euclidean space, addressing a significant problem in computational geometry. We consider that this work aims to contribute to the fields of topological data analysis and computational geometry by providing new tools for analyzing complex geometric structures.

Piercing All Translates of a Set of Axis-Parallel Rectangles

For a given shape $S$ in the plane, one can ask what is the lowest possible density of a point set $P$ that pierces ("intersects", "hits") all translates of $S$. This is equivalent to determining the covering density of $S$ and as such is well studied. Here we study the analogous question for families of shapes where the connection to covering is altered. That is, we require that a single point set $P$ simultaneously pierces each translate of each shape from some family $\mathcal{F}$. We denote the lowest possible density of such an $\mathcal{F}$-piercing point set by $\pi_T(\mathcal{F})$. Specifically, we focus on families $\mathcal{F}$ consisting of axis-parallel rectangles. When $|\mathcal{F}|=2$ we exactly solve the case when one rectangle is more squarish than $2\times 1$, and give bounds (within $10\,\%$ of each other) for the remaining case when one rectangle is wide and the other one is tall. When $|\mathcal{F}|\ge 2$ we present a linear-time constant-factor approximation algorithm for computing $\pi_T(\mathcal{F})$ (with ratio $1.895$).

Resilient Electricity Load Forecasting Network with Collective Intelligence Predictor for Smart Cities

Accurate electricity forecasting is essential for smart cities to maintain grid stability by allocating resources in advance, ensuring better integration with renewable energies, and lowering operation costs. However, most forecasting models that use machine learning cannot handle the missing values and possess a single point of failure. With rapid technological advancement, smart cities are becoming lucrative targets for cyberattacks to induce packet loss or take down servers offline via distributed denial-of-service attacks, disrupting the forecasting system and inducing missing values in the electricity load data. This paper proposes a collective intelligence predictor, which uses modular three-level forecasting networks to decentralize and strengthen against missing values. Compared to the existing forecasting models, it achieves a coefficient of determination score of 0.98831 with no missing values using the base model in the Level 0 network. As the missing values in the forecasted zone rise to 90% and a single-model forecasting method is no longer effective, it achieves a score of 0.89345 with a meta-model in the Level 1 network to aggregate the results from the base models in Level 0. Finally, as missing values reach 100%, it achieves a score of 0.81445 by reconstructing the forecast from other zones using the meta-model in the Level 2 network.

Development and experimental evaluation of new building air leakage measurement methods: measurement of interior air leaks and comparison to conventional methods

Building air leaks (both through exterior and interior surfaces) can have a significant impact on energy consumption, indoor air quality, fire safety, and moisture accumulation affecting structural durability. Blower door testing has been used to measure leaks in buildings, but commonly used testing methods do not directly measure interior leaks. In this paper, new testing methods (guarded interior test and zonal multipoint pressure testing method) are presented that directly measure these interior leaks, utilizing common blower door equipment for both single and multi-point testing. These new methods are compared to conventional methods in terms of the information provided, limitations and time/effort needed. In addition, building leak measurement results are analyzed to reveal (a) coupling between power law model values (exponent and coefficient) for an ensemble of buildings, (b) the error in using single point testing when estimating low pressure leakage, and (c) how building power law models vary from low to high pressure ranges.

Experimental and Numerical Investigation of Forming Limit Diagrams during Single Point Incremental Forming for Al/Cu Bimetallic Sheets

This article investigated the formability of aluminum/copper bimetal sheets during single-point incremental forming. First, the two-layer sheets were produced by the explosive welding process; then, the rolling process was performed with 50% strain on two-layer samples. Considering the importance of examining the mechanical and metallurgical properties on the formability of the two-layer samples, the mechanical properties were first examined, including the uniaxial tensile and micro-hardness tests. Then, metallurgical tests were performed, including scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDX) to investigate the fracture surface and penetration depth and an X-ray diffraction (XRD) test to check the secondary phase particles in the penetration zone of Al and Cu in five different annealing temperature conditions. Considering that the forming limit diagram (FLD) is dependent on the strain path, to study the effect of the strain path, the two-layer samples were formed by three geometries: pyramid, cone, and straight groove. Simulations of FLD by Abaqus software 6.14-4 with four different methods were studied: FLDCRT, effective strain rate (ESR), second derivation of thinning (SDT), and maximum strain rate (MSR). The results showed that the FLDCRT criterion provided a more accurate estimate of the necking time. In the following, the values of the thickness distribution were carried out by experimental and numerical methods, and the results between the methods were in good agreement.