Daniel Pupazan

Microplastic pollution in aquatic ecosystems represents a major environmental concern, and understanding the mechanisms governing transport, dispersion, and accumulation requires methodologies capable of describing particle – turbulence interactions. This study proposes an integrated methodology for investigating microplastic transport in the confluence area of the East Jiu River and the Maleia Stream, combining experimental data on polymer typology (reported in a previous study) with Computational Fluid Dynamics (CFD) numerical simulations. The numerical modelling was performed in ANSYS Fluent over a representative river reach, employing the Reynolds-Averaged Navier – Stokes (RANS) equations to describe the continuous phase and the Discrete Phase Model (DPM) within a Euler – Lagrange framework to track microplastic particles. Turbulence effects on particle trajectories were incorporated using stochastic tracking methods, enabling a realistic representation of particle dispersion within the flow field. The numerical model consistency was verified through hydrostatic pressure distribution analysis, velocity field evaluation, mass balance closure, and residual convergence assessment. Simulations were conducted for commonly encountered polymers in aquatic environments (PET, HDPE, LDPE, and PVC) with particle diameters ranging from 25 to 250 μm. The results reveal distinct transport behaviors governed by material density and particle size. Polymers with densities lower than water (HDPE, LDPE) are predominantly transported within the upper flow layers, polyethylene terephthalate (PET) exhibits turbulence-controlled dispersion, while polyvinyl chloride (PVC) demonstrates rapid and stable sedimentation. The proposed CFD – DPM approach proves effective in identifying potential accumulation zones and supporting monitoring and mitigation strategies for microplastic pollution in riverine systems, providing a transferable methodological framework for similar studies in other hydrological contexts.

While polyurethane acoustic foam is widely used in entertainment settings for sound absorption, it poses a considerable fire risk when exposed to sparks from pyrotechnic devices. Even though fountain-type pyrotechnic devices are often perceived as producing “cold sparks”, the ignition potential of a single incandescent particle remains insufficiently quantified. This study experimentally investigates the ignition capacity of a fountain-type pyrotechnic article on pyramidal polyurethane acoustic foam under controlled conditions. Three dedicated experimental configurations were developed: (i) ignition probability tests at various distances, (ii) scaled configuration tests reproducing realistic installation geometry, and (iii) high-speed visualization of single incandescent particle interaction with the foam surface. For the first two configurations, ignition probabilities of 20% and 22.2% were obtained. High-speed recordings showed two distinct interaction mechanisms: particle fragmentation and ricochet, which did not result in ignition; partial penetration with localized melting, volatile release, and gas-phase ignition when residual thermal energy (about 0.5–1 J) was retained. The results demonstrate that even isolated single incandescent particles generated under realistic conditions can initiate the combustion of polyurethane acoustic foam. These findings challenge the “cold spark” safety perception and provide quantitative evidence that particle–induced ignition represents a significant fire hazard in enclosed environments where combustible acoustic materials and pyrotechnic effects coexist. The findings in this paper have direct implications for safety regulations in entertainment venues.

On 2021, in the intensive care unit of a County Emergency Hospital where oxygen therapy treatment was applied to COVID patients, located in the municipality of Ploiesti, Prahova County, a fire occurred that resulted in the destruction by burning of the ICU room, the death of two people, and the injury of a medical professional. In order to elucidate the accelerating causes of the combustion phenomenon of materials in the ICU room, a combustion stand was designed whose atmosphere can be controlled in terms of achieving high oxygen concentrations of 40% vol., in accordance with the treatment schemes applied to the patients and with the configuration of the room and the frequency of use of the access door. In this experimental stand, a series of combustion tests of flexible polyurethane foam samples were performed, which highlighted the acceleration of combustion and the complete consumption of the mass. The purpose of this work is to explain the rapidity of the fire in a hospital ward, both with experimental methods and with the help of FDS.

Polyurethane foam (PF) is a versatile polymer widely used in various applications. By changing the composition of polyol and isocyanate, these foams can be classified into rigid polyurethane foams (PUFRs) and flexible polyurethane foams (PUFFs). The flexible polyurethane foam (PUFFs) is well known for its sound absorption capacities; nevertheless, its flammability poses significant safety hazards. The purpose of this study is to look into how flexible polyurethane foam reacts to fire, specifically its combustion properties, and the risks that come with them. The study aims to find out the rates of horizontal and vertical burning, the make-up of the reaction products, and the temperatures that build up inside the polyurethane foam mass when a support pole is placed in front of the stage and sound-absorbing material is added to stop stage sounds from reverberating. There were performed experiments to determine the fire behavior of the samples in contact with an ignition source in the form of a small flame and experiments to determine the ignition temperature of the sound-absorbing sponge, where it was found that vertical position accelerates combustion, and in practical applications, this aspect must be considered for fire prevention. To determine the combustion gases, several methods were used, namely spectrophotometric, ion chromatography, and gas-chromatographic methods. Analysis of the gases resulting from the combustion of the sound-absorbing sponge indicates the presence of dangerous toxic compounds (hydrogen cyanide, carbon monoxide, and hydrochloric acid), which can endanger human health in the event of a fire.

In the present paper, the use of programmable microprocessors to develop a computerized stand for the preparation of a mixture of flammable/toxic/explosive gases in order to obtain mixtures at concentrations in explosive range is presented. The operating principle of the stand is based on the mixing of two volumetric flows, controlled with the help of microprocessors, where gases are stored and circulated at atmospheric pressure through cylindrical injectors, driven by stepper motors so that the gas circuit does not require valves. The exit of the stand is a homogenization chamber, with agitator and sensor to confirm the desired concentration of the mixture. This automated stand eliminates mechanical, electric or pneumatic valves from the gas circuits, avoiding elements with high mechanical resistance suitable for high pressures/depressions, removing the possibility of the return of the gas flow, without sensitivity to sudden pressures variations.

Managing emergencies is a complex task, which involves precise coordination of many activities and people, as well as fast decision-making in environments in which critical, vital information can often be lacking. From a technical and technological point of view, in spite of all advances encountered in most industrial branches, accidents with human casualties and material damage can still occur. For this reason, the presence of special intervention and rescue teams within certain industrial/ economic units is essential, because they can ensure a quick and efficient response to limit or eliminate damage that generates aggressive toxic or chemical environments and rescue people affected by such events. Research to date has shown that in the event of an explosion or fire, its management by the economic/industrial operator, in the first phase, is difficult because there is no available structure, capable of ensuring an effective and fast response to such situations. In this context, the paper aims to highlight the serious consequences that may occur in the event that response time is delayed and to establish activities such as theoretical and practical training, equipment, intervention procedures, which must be completed by economic agents in order to increase the degree of resilience to damage in dangerous environments.

In recent years, virtual reality developers have managed to create an artificial environment that can simulate reality so that the user has the impression of an almost real physical presence in the virtual world. By overlapping and synchronizing projected images with spatial sounds and even with forces that interact with the user, the user is detached from the real environment and an all-encompassing involvement in the virtual world occurs. Virtual reality is frequently present in aviation, medicine, military training and other top fields. Advantages of using a virtual environment are obvious for areas where inexperience can cause loss of life and material loss. Although participants are immersed in the virtual environment scenario, errors produced allow an assessment of mistakes made and their correction, the experience gained being then used in the realworld professional activity. Through experiencing the virtual environment, fear of various dangers can be overcome, dangers that cannot be simulated in reality can easily be simulated, so that objectives of training can be met. The aim of the paper is to provide rescuers with certain training scenarios which create opportunities to interact with elements of the virtual space to fulfil the purpose of training.

Noise from industrial activities is a major problem because of its noxious and its presence in all technological activities. The coal preparation activity from industry, in the presence of risks of exposure to noise, is affecting the health and safety of workers. Occupational hearing loss and deafness caused by exposure to noise at work are the most encountered illnesses occurring in the European Union. This paper examines the main sources of noise in coal preparation technological process and their effects on the human factor.