Effect of methyl methacrylate (MMA) as a binder and heating treatment were investigated to improve green alumina compacts machinability. Properties of green compacts and their corresponding sintered samples prepared with and without MMA were compared. Investigation of green and sintered properties was performed on samples compacted at applied pressures up to 150 MPa. After pressing, samples with MMA were thermally treated at 115oC. The intention was to enhance the polymerization of MMA at a temperature a little higher than the glass transition temperature (Tg = 103oC) of poly (methyl methacrylate). Green compacts with MMA had higher green density values than those without MMA. Sintered samples with MMA had lower values of sintered density and higher values of total porosity; after sintering, relative linear shrinkage was around 15 % for the whole range of applied pressures. The possibility of easily machining the green compacts with MMA produces great possibilities for application in many fields
Background: A laboratory professional concerned with the quality of work in medical-biochemical laboratories ensures the accuracy and precision of laboratory analyses through the implementation of international and European guidelines for working with hazardous substances, through the availability and implementation of Standard Operating Procedures (SOPs). Laboratory hazards that affect the concentration and safety of workers arise from laboratory deficiencies such as: lack of preventive measures, knowledge and skills implemented through SOPs and good laboratory practice. Biophysical hazards in medical laboratories are manifested by needles and sharp objects, infectious materials, noise, vibration, radiation, poor air quality, temperature inversions. Objective: The aim of the research was to raise awareness of the quality of work in medical-biochemical laboratories in order to ensure the safety of workers. Methods: A cross-sectional questionnaire-based study was conducted among 100 laboratory professionals from Bosnia and Herzegovina (BiH) and Croatia. The research was conducted over a period of three months. Results: A higher percentage of exposure to infectious agents and needles and sharp objects was found among respondents from BiH compared to CRO (p=0.018 and p=0.001, respectively). We found that respondents employed in accredited laboratories are aware of exposure to hazards in a high percentage related to infectious agents, toxins (p=0.0012 and p=0.0046, respectively). A significant statistical difference was found between respondents with BiH and respondents with CRO in terms of knowledge of accreditation standards of medical-biochemical laboratories (p=0.0155). Respondents who have standard operating procedures available are aware of the hazards of infectious agents (p=0.0001), toxins (p=0.0466), needles and sharp objects (p=0.0052), noise (p=0.0030), vibration (p=0.0007) and extreme temperatures (p=0.0014). Conclusion: Efficient implementation and continuous compliance with the ISO 15189: 2018 standard requires constant commitment and active participation of laboratory staff. Laboratories must have standard operating procedures in place and actively monitor their use.
The main MoR discussion led to further suggestions on KE terminology, including ensuring coherence to directionality in terms of the KE descriptions (e.g., specifying increase, decrease, altered, no direction, etc.) and clarifying differences in ROS and reactive oxygen and nitrogen species (RONS), and enzymatic and non-enzymatic events. The consortium highlighted the importance of the role of ROS as a KE and an associative event in the AOP framework. Additionally, participants highlighted modification to macromolecules from the resultant RONS generation (e.g., lipid peroxidation) as a relevant endpoint to include in the KE. The possibility of grouping ROS-related KEs in the AOP framework needs to be discussed further.
Nowadays, in order to maintain cleanliness in our houses, as well as to maintain personal hygiene, numerous chemical agents are used every day. Dishwashing detergents are used the most, followed by laundry detergents, various soaps and hair sham?poos, and not infrequently descaling agents, for cleaning ovens, unclogging drainage and sewage pipes, neutralizing unpleasant odours, etc. Although their number is growing day by day, most people do not realize the consequences, or at least not enough, and especially not about their potentially toxic effects. In fact, a great deal of the population do not consider household chemicals a particular problem, which is true, if they are used in the pre?scribed manner. However, the fact that these agents can cause harmful effects in humans and animals, and even participate in environmental pollution, is more than a sufficient reason to pay more attention to these agents, that is, to talk about them more and obtain more information for that matter. Particularly since there are authors who believe that some of the mentioned agents can even cause cancer, asthma or birth defects, i.e. infertility. Household chemicals can be divided in several ways, and one of the classifications is the one made according to the place of use. According to this division, the products we use every day at home can be roughly divided into those used for cleaning and maintaining hygiene in kitch?ens, used for the same purposes in bathrooms (including those used for personal hygiene ), and the products used in rooms and on terraces (flower protection).
Introduction/purpose: The hydraulic buffering valve has the greatest influence on the dynamic characteristics of power-shift transmission. The hydraulic buffering valve is a transmission element that controls increase in pressure in friction assemblies during the gear shifting process. By choosing the optimal control of pressure increase during shifting, reduction of dynamic loads in gear transmissions and thermal loads in friction assemblies is achieved. Methods: The paper analyzes the principle of one of hydraulic buffering valve solutions as well as the influence of certain parameters on the control of pressure increase. After the analysis of the working principle of the hydraulic buffering valve, a simulation model was developed in the MATLAB/Simulink software package. Results: The results obtained using the simulation model were compared with the experimental results of the selected pressure modulator solution. The selected hydraulic buffering valve was developed as part of the development of a device for power-shift transmission. The simulation results showed a satisfactory match with the experimental results. Conclusion: The developed simulation model enables a relatively easy and quick change of the parameters of the hydraulic buffering valve as well as a possibility of a faster and better understanding of the influence of individual parameters on pressure increase during the gear shifting process.
Introduction/purpose: Motor vehicles are complex dynamic systems due to spatial displacements, changes in the characteristics of components during their lifetime, a large number of influences and disturbances, the appearance of backlash, friction, hysteresis, etc. The aforementioned dynamic phenomena, especially vibrations, cause driver and passenger fatigue, reduce the lifetime of the vehicle and its systems, etc. Methods: In general, the movement of vehicles is carried out on uneven roads and curvilinear paths in the road. Not only do oscillatory movements cause material fatigue of vehicle parts, but they also have a negative effect on people's health. That is why special attention must be paid to the coordination of the mutual movement of the subsystems, and in particular, the vehicle suspension system, even at the stage of the motor vehicle design. For these purposes, theoretical, experimental or combined methods can be used. Therefore, it is very useful to have the experimental results of the oscillations of the vehicle subsystem in operating conditions, so the aim of this work was to use the movement of the 4x4 drive FAP 1118 vehicle in operating conditions (due to higher speeds - in road conditions) to define the conditions for testing oscillatory loads in laboratory conditions. Results: This is made possible by registering and identifying statistical parameters of registered quantities. Conclusion: Based on the measured data, the research can be programmed on shakers in laboratory conditions, and, at the same time, the size to be reproduced can be chosen as well.
The Regional Skill Councils Blueprint report aims to facilitate understanding, identifying, and developing 21st-century skills through multi-stakeholder collaborative efforts in region-specific and labour-market-relevant contexts. The report details the modalities and aspects of setting up a successful diverse multi-stakeholder constellation tasked with assessing and developing 21st-century skills guided by the labour market needs, technology trends and any differences stemming from gender. A blueprint for stakeholder engagement is a model for cooperation between higher education institutions and employers, provides a clear roadmap of engagement opportunities and potential action for all involved higher education and industry stakeholders.
Energy has an effective role in economic growth and development of societies. This paper is studying the impact of climate factors on performance of solar power plant using machine learning techniques for underlying relationship among factors that impact solar energy production and for forecasting monthly energy production. In this context this work provides two machine learning methods: Artificial Neural Network (ANN) for forecasting energy production and Decision Tree (DC) useful in understanding the relationships in energy production data. Both structures have horizontal irradiation, sunlight duration, average monthly air temperature, average maximal air temperature, average minimal air temperature and average monthly wind speed as inputs parameters and the energy production as output. Results have shown that used machine learning models perform effectively, ANN predicted the energy production of the PV power plant with a correlation coefficient (R) higher than 0.97. The results can help stakeholders in determining energy policy planning in order to overcome uncertainties associated with renewable energy resources.
Multi-material design was developed as a modern design concept for lightweight structures (Lightweight design - LW) which aims to integrate different types of materials into one structure. The main problem when joining sheets made of different, i.e. dissimilar materials, primarily steel and aluminum alloys, are the different mechanical, physical and chemical properties of the materials being joined. Through this paper, the state of the art will be analyzed when it comes to modern technologies for joining steel and aluminum alloys sheets. The term "modern joining technique" refers to all innovative joining technologies that have been developed or have seen significant application in the last few years.
It is known that the temperature of crystallization during the synthesis of zeolite is one of the most important process parameters. However, during the research work on the synthesis of zeolite 13X and the introduction of this material into regular industrial production, it was noticed that the heating rate of the starting reaction suspension can have an equally important influence. This influence can be so pronounced that a difference of just a few minutes in reaching the crystallization temperature can make a significant difference in product quality, affect the presence of other phases in the crystal, or even determine the direction of zeolite crystallization. Therefore, the aim of this work was to show the influence of the heating rate on the quality of the obtained 13X zeolite powders. The obtained samples were analysed in terms of crystallinity (by X-ray diffraction), chemical composition, granulometry and specific surface area (by Brunauer-Emmett-Teller analysis), and regarding water and CO2 adsorption capacities. Additionally, scanning electron microscopy analysis of the samples showed the morphological characteristics of different 13X zeolite powders. The analysis results of the obtained powders confirmed the influence of the heating rate and helped to define the optimal synthesis parameters i.e. the initial temperature and heating time, that resulted in stable product quality.
This paper presents research on hydrodynamics and mass transfer in a packed absorption column. Experimental data on dry column pressure drop, flooding point, and efficiency of absorption of CO2 in water is obtained on a lab-scale absorption column packed with Raschig rings. Auxiliary parts of equipment together with chemical analyses provide simple monitoring and collecting the data. All obtained data were used to test different mathematical models for a given problem, i.e. for determination of the dry column pressure drop, flooding point and the overall gas transfer unit height. For dry column pressure drop, models developed primarily for packed columns described the data the best, with the Billet model generating a 6.54 % mean error, followed by Mackowiak and Stichlmair models. In flooding point calculations, empirical models were tested and models of Lobo, Leva and Takahshi gave the best results. Mass transfer (absorption) experiments gave expected results, since absorption efficiency increased with the increase in the liquid/gas flow rate ratio, i.e. with approaching the flooding point. The Onda?s model was used to calculate partial mass transfer coefficients in liquid and gas phases based on which the height of the overall gas transfer unit was estimated and subsequently compared with the experimental data. Deviation of calculated and experimental results for the height of the overall gas transfer unit is in the expected range of 0-20 %, with mean value of 15.5 %. In conclusion, the available models for determination of the investigated hydrodynamics and mass transfer parameters in packed absorption columns gave adequate results in comparison to the experimental values.
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