In today's world, engineering materials have changed dramatically. Traditional materials are failing to satisfy the demands of present applications, so several composites are being used to address these issues. Drilling is the most vital manufacturing process in most applications, and the drilled holes serve as maximum stress areas that need to be treated with extreme caution. The issue of selecting optimal parameters for drilling novel composite materials has fascinated researchers and professional engineers for a long time. In this work, LM5/ZrO2 composites are manufactured by stir casting using 3, 6, and 9 wt% zirconium dioxide (ZrO2) as reinforcement and LM5 aluminium alloy as matrix. Fabricated composites were drilled using the L27 OA to determine the optimum machining parameters by varying the input parameters. The purpose of this research is to find the optimal cutting parameters while simultaneously addressing the thrust force (TF), surface roughness (SR), and burr height (BH) of drilled holes for the novel composite LM5/ZrO2 using grey relational analysis (GRA). The significance of machining variables on the standard characteristics of the drilling as well as the contribution of machining parameters were found using GRA. However, to obtain the optimum values, a confirmation experiment was conducted as a last step. The experimental results and GRA reveal that a feed rate (F) of 50 m/s, a spindle speed (S) of 3000 rpm, Carbide drill material, and 6% reinforcement are the optimum process parameters for accomplishing maximum grey relational grade (GRG). Analysis of variance (ANOVA) reveals that drill material (29.08%) has the highest influence on GRG, followed by feed rate (24.24%) and spindle speed (19.52%). The interaction of feed rate and drill material has a minor impact on GRG; the variable reinforcement percentage and its interactions with all other variables were pooled up to the error term. The predicted GRG is 0.824, and the experimental value is 0.856. The predicted and experimental values match each other well. The error is 3.7%, which is very minimal. Mathematical models were also developed for all responses based on the drill bits used.

• Klíčová slova
• ANOVA, composites, design of experiments, drilling, grey relational analysis,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: Aluminium based composites with hybrid reinforcement hold significant potential to replace Al-alloys in a variety of automotive sectors where cheap cost, a significant ratio of strength to weight, and better wear resistance are required. METHODS: Stir casting was utilized to make aluminium matrix composites (AMCs) with 3%, 6%, and 9% of B4C/Fly ash particles. The wear was examined with various Sliding Speed, S (1 m/s, 1.5 m/s and 2 m/s), Sliding Distance, D (500 m, 1000 m and 1500 m), applied load, L (15 N, 30N and 45 N) and reinforcement %, R (3, 6 and 9%). Grey Relational Analysis was used to optimise the wear variables. Taguchi's L27 Orthogonal array (OA) was selected for this statistical approach in order to analyse responses like Specific wear rate (SWR) and Coefficient of Friction (CoF). Furthermore, analysis of variance (ANOVA) was utilized to investigate the influence of input parameters on wear behavior by choosing "smaller is better" feature. RESULTS: Based on this study, the optimal values of S - 1.5 m/s, D - 500 m, L - 30 N, and R% - 9 wt% Hybrid (4.5% Fly ash and 4.5% B4C) are found to yield the lowest SWR and CoF. Wear rate of composite decreased with an increase in reinforcement particles. Increase in hardness was also the reason for decrease in wear rate. The responses have a narrow margin of error, according to confirmation studies. There exists a good agreement between them. DISCUSSION: The research on LM6/B4C/fly ash composite fabrication using Grey Relational Analysis (GRA) has significantly contributed to the development of high-performance materials for wear-related applications. Through the optimization of wear parameters, GRA allows for the improvement of wear resistance, strength, and sustainability.

• MeSH
• hliník * chemie   MeSH
• popel uhelný * chemie   MeSH
• slitiny chemie   MeSH
• testování materiálů * metody   MeSH
• tření MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• hliník * MeSH
• popel uhelný * MeSH
• slitiny MeSH

This research investigates the machinability of Inconel 718 under conventional machining speeds using three different tool coatings in comparison with uncoated tool during milling operation. Cutting speed, feed rate and depth of cut were selected as variable machining parameters to analyze output responses including surface roughness, burr formation and tool wear. It was found that uncoated and AlTiN coated tools resulted in lower tool wear than nACo and TiSiN coated tools. On the other hand, TiSiN coated tools resulted in highest surface roughness and burr formation. Among the three machining parameters, feed was identified as the most influential parameter affecting burr formation. Grey relational analysis identified the most optimal experimental run with a speed of 14 m/min, feed of 1 μm/tooth, and depth of cut of 70 μm using an AlTiN coated tool. ANOVA of the regression model identified the tool coating parameter as most effective, with a contribution ratio of 41.64%, whereas cutting speed and depth of cut were found to have contribution ratios of 18.82% and 8.10%, respectively. Experimental run at response surface optimized conditions resulted in reduced surface roughness and tool wear by 18% and 20%, respectively.

• Klíčová slova
• Inconel 718, grey relational analysis, machining, multi-objective optimization,
• Publikační typ
• časopisecké články MeSH

Objectives: Body composition (BC) analysis is a routine part of comprehensive public health care. Assessment of BC is more important source of information than BMI. Adherence to the standard measurement conditions is essential for the correct results. Our study aimed to examine the effect of acute fluid consumption on measures of body mass (BM), percentage of body fat (%BF), visceral fat (VF), percentage of body water (%BW), and impedance at 100 kHz (I100) and 20 kHz (I20) using segmental multi-frequency bioelectrical impedance analysis (SMF-BIA) in a general healthy population. Methods: 95 consecutive healthy normal-weight adults (42 men; 53 women) were involved in the study (mean ± s.d.; age 23.9±1.6 years; body mass 68.3±14.1 kg). All subjects underwent two separate series of body composition (BC) measurements at 0 (BASELINE), 30, 60, 90 min (POST): the first series after drinking 600 ml of isotonic carbohydrate/electrolyte drink (IST) and the second after no fluid administration (CON). Individual measurements were performed in the morning on two consecutive days. Results: In the IST group, BM, VF (both P<0.001), and %BF (P<0.05) increased significantly at 30 min POST compared to BASELINE. BM and VF remained elevated at 90 min POST (both P<0.001). %BW decreased significantly at 30 min POST (P<0.01) then increased at 60 min (P<0.001) and 90 min (P<0.01) POST. There were no significant changes in I100. I20 increased significantly at 30 min POST (P<0.001) then decreased at 60 min (P<0.001) and 90 min POST (P<0.01) compared to BASELINE. In the CON group, BM and VF decreased below BASELINE at 90 min POST (P<0.001), %BF, %BW and I100 did not change significantly. The difference between IST and CON was statistically significant for all POST measurement times only in BM and VF (both P<0.001). The VF results are also underlined by the detected impedance changes in the trunk area at 20 kHz (B20) and 100 kHz (B100) at 60 min and 90 min (both P<0.001). Conclusions: Our study suggests that segmental impedances and BC measurement in healthy young normal-weight adults requires strict adherence to fluid restriction at least 90 min before the measurement to avoid false impedance values and overestimation of BM and VF.

• Klíčová slova
• acute fluid consumption, adults, body composition changes, percentage of body fat, segmental multi-frequency bioelectrical impedance analysis, visceral fat,
• MeSH
• absorpční fotometrie MeSH
• dospělí MeSH
• elektrická impedance MeSH
• elektrolyty MeSH
• index tělesné hmotnosti MeSH
• lidé MeSH
• mladý dospělý MeSH
• potraviny MeSH
• složení těla * MeSH
• tuková tkáň * metabolismus   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• elektrolyty MeSH

The cluster technique involves the creation of clusters and the selection of a cluster head (CH), which connects sensor nodes, known as cluster members (CM), to the CH. The CH receives data from the CM and collects data from sensor nodes, removing unnecessary data to conserve energy. It compresses the data and transmits them to base stations through multi-hop to reduce network load. Since CMs only communicate with their CH and have a limited range, they avoid redundant information. However, the CH's routing, compression, and aggregation functions consume power quickly compared to other protocols, like TPGF, LQEAR, MPRM, and P-LQCLR. To address energy usage in wireless sensor networks (WSNs), heterogeneous high-power nodes (HPN) are used to balance energy consumption. CHs close to the base station require effective algorithms for improvement. The cluster-based glow-worm optimization technique utilizes random clustering, distributed cluster leader selection, and link-based routing. The cluster head routes data to the next group leader, balancing energy utilization in the WSN. This algorithm reduces energy consumption through multi-hop communication, cluster construction, and cluster head election. The glow-worm optimization technique allows for faster convergence and improved multi-parameter selection. By combining these methods, a new routing scheme is proposed to extend the network's lifetime and balance energy in various environments. However, the proposed model consumes more energy than TPGF, and other protocols for packets with 0 or 1 retransmission count in a 260-node network. This is mainly due to the short INFO packets during the neighbor discovery period and the increased hop count of the proposed derived pathways. Herein, simulations are conducted to evaluate the technique's throughput and energy efficiency.

• Klíčová slova
• cluster head, glow-worm, multi-parameters, optimization and heterogeneous, retransmission ratio,
• Publikační typ
• časopisecké články MeSH

Aluminum is a widely popular material due to its low cost, low weight, good formability and capability to be machined easily. When a non-metal such as ceramic is added to aluminum alloy, it forms a composite. Metal Matrix Composites (MMCs) are emerging as alternatives to conventional metals due to their ability to withstand heavy load, excellent resistance to corrosion and wear, and comparatively high hardness and toughness. Aluminum Matrix Composites (AMCs), the most popular category in MMCs, have innumerable applications in various fields such as scientific research, structural, automobile, marine, aerospace, domestic and construction. Their attractive properties such as high strength-to-weight ratio, high hardness, high impact strength and superior tribological behavior enable them to be used in automobile components, aviation structures and parts of ships. Thus, in this research work an attempt has been made to fabricate Aluminum Alloys and Aluminum Matrix Composites (AMCs) using the popular synthesis technique called stir casting and join them by friction stir welding (FSW). Dissimilar grades of aluminum alloy, i.e., Al 6061 and Al 1100, are used for the experimental work. Alumina and Silicon Carbide are used as reinforcement with the aluminum matrix. Mechanical and corrosion properties are experimentally evaluated. The FSW process is analyzed by experimentally comparing the welded alloys and welded composites. Finally, the best suitable FSW combination is selected with the help of a Multi-Attribute Decision Making (MADM)-based numerical optimization technique called Weighted Aggregated Sum Product Assessment (WASPAS).

• Klíčová slova
• alloys, aluminum, composites, friction stir welding, multi-attribute decision making, optimization, parameters, properties, stir casting,
• Publikační typ
• časopisecké články MeSH

Substantial knowledge is available on the association of the indoor school environment and its effect among schoolchildren. In the same context, the SINPHONIE (School indoor pollution and health: Observatory network in Europe) conducted a study to collect data and determine the distribution of several indoor air pollutants (IAPs), physical and thermal parameters and their association with eye, skin, upper-, lower respiratory and systemic disorder symptoms during the previous three months. Finally, data from 115 schools in 54 European cities from 23 countries were collected and included 5175 schoolchildren using a harmonized and standardized protocol. The association between exposures and the health outcomes were examined using logistic regression models on the environmental stressors assessed in classroom while adjusting for several confounding factors; a VOC (volatile organic compound) score defined as the sum of the number of pollutants to which the children were highly exposed (concentration > median of the distribution) in classroom was also introduced to evaluate the multiexposure - outcome association. Schoolchildren while adjusting for several confounding factors. Schoolchildren exposed to above or equal median concentration of PM2.5, benzene, limonene, ozone and radon were at significantly higher odds of suffering from upper, lower airways, eye and systemic disorders. Increased odds were also observed for any symptom (sick school syndrome) among schoolchildren exposed to concentrations of limonene and ozone above median values. Furthermore, the risks for upper and lower airways and systemic disorders significantly increased with the VOCs score. Results also showed that increased ventilation rate was significantly associated with decreased odds of suffering from eye and skin disorders whereas similar association was observed between temperature and upper airways symptoms. The present study provides evidence that exposure to IAPs in schools is associated with various health problems in children. Further investigations are needed to confirm our findings.

• Klíčová slova
• Allergy, Indoor air pollution, Multi-pollution, Sick building syndrome, Thermal parameters, VOC,
• MeSH
• dítě MeSH
• látky znečišťující vzduch analýza   MeSH
• lidé MeSH
• školy MeSH
• teplota MeSH
• znečištění ovzduší analýza   MeSH
• znečištění vzduchu ve vnitřním prostředí analýza   MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Evropa MeSH
• Názvy látek
• látky znečišťující vzduch MeSH

Accurate characterization of incident radiation is a fundamental challenge for diagnostic design. Herein, we present an efficient spectral analysis routine that is able to characterize multiple components within the spectral emission by analytically reducing the number of parameters. The technique is presented alongside the design of a hard x-ray linear absorption spectrometer using the example of multiple Boltzmann-like spectral distributions; however, it is generally applicable to all absorption based spectrometer designs and can be adapted to any incident spectral shape. This routine is demonstrated to be tolerable to experimental noise and suitable for real-time data processing at multi-Hz repetition rates.

• Publikační typ
• časopisecké články MeSH

KEY MESSAGE: Climate sensitivity of Pinus sylvestris has changed in minimum density while maximum density remains mostly stable, suggesting the use of additional density parameters could help detect response changes. ABSTRACT: As one of Eurasia's most widely distributed conifer species, Pinus sylvestris L. is frequently used in dendroclimatological reconstructions based on tree-ring width (TRW) and maximum latewood density (MXD). However, the climatic signals of additional parameters such as earlywood/latewood density (EWD/LWD) or minimum density (MND) are often overlooked, leaving their skill unexplored. Here, we investigate the growth responses of multiple P. sylvestris tree-ring parameters to ongoing climate change at two sites with contrasting climatic conditions using well-replicated density data from Scotland and Sweden. Correlations with mean, minimum, and maximum temperatures are strongest for LWD and MXD at both sites, with coefficients ranging from 0.5 to 0.7 for July, August, and the June-August season (p < 0.05). A significant (p < 0.05) negative correlation between MND and July temperatures was identified in the Swedish Torneträsk (TOR) data (p < 0.05), which diminished since the late twentieth century. A comparable inverse MND temperature signal and change into the twenty-first century is not reflected in northern Scotland's overall wetter and warmer site, suggesting a fundamental physiological change in tree-ring formation under global warming. A shift in the sensitivity of tree growth at northern European sites could reduce the effectiveness of proxies from such locations, posing implications for high-resolution climate reconstructions. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00468-025-02681-3.

• Klíčová slova
• Climate change, Pinus sylvestris, Scotland, Sweden, Wood density, X-ray densitometry,
• Publikační typ
• časopisecké články MeSH

The primary objective of this research is to develop a mathematical model, analyze the dynamic occurrence of thermal shock and exploration of how thermal memory with moving line impact of heat transfer within biological tissues. An extended version of the Pennes equation as its foundational framework, a new fractional modelling approach called the Prabhakar fractional operator to investigate and a novel time-fractional interpretation of Fourier's law that incorporates its historical behaviour. This fractional operator has multi parameter generalized Mittag-Leffler kernel. The fractional formulation of heat flow, achieved through a generalized fractional operator with a non-singular type kernel, enables the representation of the finite propagation speed of heat waves. Furthermore, the dynamics of thermal source continually generates a linear thermal shock at predefined locations within the tissue. Introduced the appropriate set of variables to transform the governing equations into dimensionless form. Laplace transform (LT) is operated on the fractional system of equations and results are presented in series form and also expressed the solution in the form of special functions. The article derives analytical solutions for the heat transfer phenomena of both the generalized model, in the Laplace domain, and the ordinary model in the real domain, employing Laplace inverse transformation. The pertinent parameter's influence, such as α, β, γ, a0, b0, to gain insights into the impact of the thermal memory parameter on heat transfer, is brought under consideration to reveal the interesting results with graphical representations of the findings.

• MeSH
• algoritmy * MeSH
• teoretické modely MeSH
• vysoká teplota * MeSH
• Publikační typ
• časopisecké články MeSH