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Failure Behavior Analysis of Crack Propagation in Ship Sandwich Structures
Get PDFDamage to ship structures leads to a reduction in strength, which increases the risk of structural failure. The vulnerability of damage in sandwich panel structures made of low-density steelpolyurethane elastomer needs to be evaluated and predictions made regarding failure modes, particularly crack propagation through the core thickness. Variations in structure thickness and the size of the initial crack are evaluated to determine the impact of structural design on damage under the ship’s operational loads. Finite element analysis, validated with experimental data, is used to simulate the dynamics of crack propagation. It was found that a thicker core and a smaller initial crack length result in slower crack propagation rates and shorter crack extensions. Increasing the core thickness from 15 mm to 24 mm reduced the crack propagation rate by up to 28% and improved crack extension resistance by as much as 54%. Thicker face and bottom plates further contributed an additional reduction in crack growth rate, providing an extra margin of structural toughness. Shorter initial cracks also proved significant, with propagation rates decreasing by about 73% when comparing a 25 mm crack to a 75 mm crack. These factors lowered the strength reduction factor (SRF ) and extended crack growth times, confirming that thicker cores and smaller initial cracks improve damage resistance in ship sandwich structures
Efficient Fixation of CO2 at Atmospheric Pressure to N-propargylamines: Facile Method Promoted by Cu(I)-salts to Obtain 4-substituted-3-alkylideneoxazolidin-2-ones
No full textThe development of efficient methodologies for carbon dioxide (CO2) incorporation into value-added compounds remains a key objective in sustainable organic synthesis. Herein, we report the copper(I)-promoted synthesis of (Z)-3-benzyl-5-benzylidene-4,4-dimethyloxazolidin-2-one via coupling of propargyl amines with CO2 under mild conditions. Optimization studies revealed that CuI (1.0 equiv.) in DMF with NaOtBu as base affords the highest yield (90%) of the desired oxazolidinone while combination with palladium additives or using alternative copper sources such as CuBr or CuOAc proved ineffective. This example underscores the significant potential of copper in CO2 fixation chemistry and emphasizes the crucial role that both the nature and stoichiometry of the metal promoter play in governing the efficiency and selectivity of the transformation
Effect of Thermal Aging Parameters on Microstructure and Properties of 6061 Aluminum Alloy in Roller-Skating shoe Tool Holder
No full textAs an important load-bearing structure of roller-skating shoes, the tool holder is mostly made of metal. 6061 aluminum alloy is widely used in the manufacture of roller-skating shoe tool holders because of its high strength, good formability, and strong corrosion resistance. To achieve higher strength after plastic forming, heat treatment, such as solution treatment and aging is usually required. In this study, 6061 solution-treated aluminum alloy was used as the research material. It was found that during the thermal aging process, the hardness of the alloy first in-creased to a peak value and then decreased to a stable value. At an aging temper-ature of 170 °C, the peak hardness reached 128.4 HV after 120 min. The average re-sidual stress release rate at three positions of the 6061 aluminum alloy was about 37 %. After 180 min, the hardness decreased again to its lowest value and tended to stabilize, while the average residual stress release rate increased to 50 %. The experimental results provide theoretical guidance for optimizing the processing of 6061 aluminum alloy in the manufacture of roller-skating shoe tool holders
Managing Economic Leakages for Building Resilient and Sustainable Tourism Destination Performance
No full textTourism yields substantial economic benefits to destinations. However, economic leakages often undermine these benefits, weakening local value chains and hindering long-term economic sustainability. While existing research predominantly emphasises supply-side interventions to address leakages, limited attention has been given to demand-side determinants and to tourists' behaviour in exacerbating or mitigating leakages. This study develops a conceptual framework integrating economic leakages, particularly demand-side determinants, behavioural nudges and destination resilience, to investigate how nudging interventions can influence tourists’ choices and preferences toward local products and services. By synthesising insights from economic leakages, behavioural economics and sustainable tourism, this study highlights both theoretical contributions and practical implications for policymakers and tourism stakeholders. Additionally, it identifies key implementation challenges of behavioural interventions and proposes strategic measures to address them. The study concludes by outlining future research directions, emphasising empirical validation and policy-driven applications to foster sustainable tourism development and economic resilience
Explicating the Conditions for (Un)sustainable Tourists’ Behaviour in a Cultural Heritage Destination: A Mixed-Method Approach Based on the Theory of Planned Behaviour
No full textThe study examines sustainable tourism behaviour at the historic city of Rothenburg ob der Tauber. The research aims to explain tourists' sustainable behaviour and to uncover configurations that lead to sustainable or unsustainable behaviour. The present study is based on the Theory of Planned Behaviour (TPB) as its theoretical framework. A mixed-method design is then employed, integrating quantitative and qualitative research methodologies. The quantitative arm of the study employs regression analysis, while the qualitative research uses the fuzzy-set Qualitative Comparative Analysis (fsQCA).
The findings from the regression analysis revealed that sustainability-oriented attitudes, social norms, and behavioural control have a statistically significant impact on tourists' sustainability-oriented behavioural intention, in descending order of importance. The fsQCA results showed that strong attitudes are a necessary condition for strong behavioural intention toward sustainable tourism activities. Weak social norms are an essential condition for weak behavioural intention toward sustainable tourism activities. Furthermore, the study identified the following sufficient conditions for a strong intention to engage in sustainable tourism activities: strong social norms paired with weak behavioural control, or strong attitudes in conjunction with strong social norms
Investigating Sustainability: A Comprehensive Approach to Understanding Intentional Pro-environmental Behaviour Through Awareness, Religious Beliefs, and Environmental Attitudes
No full textThis paper investigates the psychological and cultural elements that influence pilgrims' pro-environmental activity. By combining the Theory of Planned Behaviour (TPB) with insights from the religious studies literature, a conceptual framework was developed that identified religious beliefs, environmental knowledge, pro-environmental attitudes, and normative perspectives as the main determinants of pilgrims' intentions to engage in sustainable practices during their journey. Using Structural Equation Modelling (SEM) via SmartPLS and data collected from a sample of 201 pilgrims, the study demonstrates complex interactions among these variables. A person's degree of environmental awareness is influenced by their religious beliefs and values; thus, their pro-environmental attitudes and intentions to act also alter. Moreover, the data showed how these aspirations change in keeping with society's expectations. Though there was no clear direct link between pro-environmental views and behavioural intentions, our results suggest that religious beliefs and values—formed by environmental knowledge—are crucial in shaping pilgrims' pro-environmental activities. We advise that projects that aim to support sustainability in pilgrimage settings focus on raising environmental awareness through shared values and religious doctrines. This strategy could effectively use the psychological and cultural settings of pilgrims to encourage more environmentally responsible travel habits
A Novel Approach for Diabetes Mellitus Detection Using a Modified Binary Multi- Neighbourhood Artificial Bee Colony Algorithm with Mahalanobis-Based Feature Selection (MBMNABC-Ma) and an Optimized Decision Forest Framework
No full textDiabetes is a critical global health issue caused by high blood sugar (hyperglycemia), leading to complications like cardiovascular disease, blindness, neuropathy, and kidney failure. Machine learning (ML) algorithms improve both the accuracy and efficiency of medical diagnoses. This study applies a Modified Binary Multi-Neighbourhood Artificial Bee Colony with Mahalanobis- based (MBMNABC-Ma) for a feature selection algorithm, combined with diverse ML models for diabetes identification. Compared to the conventional Binary Multi-Neighbourhood Artificial Bee Colony (BMNABC), MBMNABC-Ma improves classification accuracy and reduces computational complexity. Five diabetes datasets were analyzed using a 70-30% holdout cross-validation. The MBMNABC- Ma model, trained on Optimal Decision Forest (ODF) with Random Forest Ensemble (RFE), demonstrated high effectiveness. It achieved 97.23% accuracy on the Merged Datasets (comprising 130 US and PIMA datasets), 97.93% on the Iranian Ministry of Health Dataset, 96.05% on the Questionnaire Dataset, 98.39% on the Hospital of Sylhet Dataset, and 80.98% on the PIMA Dataset, with high specificity and sensitivity scores across all cases
Some physical laws of exponential decay
No full textZakoni eksponencijalnog rasta i pada prirodno se pojavljuju u medicini, kemiji, biologiji, geologiji, fizici i brojnim drugim granama znanosti. Matematički je to jedan te isti koncept koji se u osnovi svodi na činjenicu da je brzina kojom se neka veličina mijenja proporcionalno samoj toj veličini, što za posljedicu ima da je ovisnost te veličine o varijabli eksponencijalna. Nakon uvođenja pojma derivacije kao mjere promjene i teorijskog obrazloženja zakona eksponencijalnog rasta i pada, isti je ilustriran na nekoliko poznatih fizikalnih zakona: Newtonovom zakonu hlađenja, zakonu promjene atmosferskog tlaka s nadmorskom visinom te zakonu radioaktivnog raspada.Laws of exponential growth and decay naturally appear in medicine, chemistry, geology, physics, and many other scientific fields. Mathematically, they are all similar and reduce to the statement that the rate of change of a value is proportional to the value itself, meaning this value depends exponentially on its variable. After introducing the notion of the derivative as the rate of change, and describing the problem of exponential growth and decay, we will illustrate this with several well-known physical laws, namely, Newton’s law of cooling, the law of change in atmospheric pressure with respect to altitude, and the law of radioactive decay
Some applications of direct and inverse proportionality functions
No full textU ovom radu opisane su funkcije direktne i obrnute proporcionalnosti te su navedeni primjeri njihove primjene u svakodnevnom životu, ekonomiji i prirodnim znanostima.This paper describes the functions of direct and inverse proportionality and provides examples of their application in everyday life,
economics, and the natural sciences
Mikrobna proizvodnja dvije vrste produkata s pomoću oleaginoznih mikroorganizama: pretvorba otpada od hrane u lipide i biopolimere
No full textThe increasing demand for sustainable alternatives to fossil-derived fuels and plastics has intensified research into microbial platforms that can convert abundant waste resources into valuable products. This review focuses on the emerging field of dual-target bioprocessing using oleaginous microorganisms to produce single-cell oils (SCOs) and polyhydroxyalkanoates (PHAs) from food waste. We discuss key microbial strains, their metabolic pathways, co-production capabilities and substrate preferences. Emphasis is placed on the use of food waste as a low-cost and carbon-rich feedstock, thereby enhancing both economic feasibility and environmental sustainability. We also analyze integrated bioprocess strategies developed to overcome existing challenges, such as yield optimization and metabolic bottlenecks. This dual-production platform addresses the principles of circular economy, facilitating the conversion of waste into high-value bioproducts.Rastuća potražnja za održivim alternativama gorivima i plastici dobivenim iz fosilnih izvora potaknula je intenzivna istraživanja mikrobnih sustava koji mogu pretvarati obilne otpadne resurse u vrijedne proizvode. Ovaj pregledni rad usmjeren je na novo područje mikrobne proizvodnje dvije vrste produkata s pomoću oleaginoznih mikroorganizama, mikrobnih lipida i polihidroksialkanoata (PHA), iz otpada od hrane. Rasprava obuhvaća ključne mikrobne sojeve, njihove metaboličke puteve, mogućnost istodobne proizvodnje, te preferencije prema supstratima. Poseban naglasak stavljen je na uporabu otpada od hrane kao jeftinog i ugljikom bogatog supstrata, čime se povećava ekonomska isplativost i okolišna održivost procesa. Također se analiziraju integrirane bioprocesne strategije razvijene u svrhu prevladavanja postojećih izazova, poput optimiranja prinosa i metaboličkih uskih grla. Ovaj sustav proizvodnje dvije vrste produkata u skladu je s načelima kružnog gospodarstva, jer omogućuje pretvorbu otpada u visokovrijedne bioproizvode