The Annals of “Dunarea de Jos” University of Galati. Fascicle IX, Metallurgy and Materials Science

Some Aspects Regarding the Action of Vibrations on the Human Knee Joint

Marina Gabriela DOGARU — 2025-03-15

Machines that use vibrations in the work process are found in various activities, on construction sites or within the premises of some constructions. Their operators are affected over time by mechanical oscillations. Entering the body through the hand-arm assembly, through the legs, or while sitting, the vibrations affect the human body, usually in a negative way. The positive effects are currently being studied in order to be able to improve various human joint conditions or to improve physical condition, but exposure must be done in a controlled environment and under well-established conditions defined by specialists.
Over time, various studies have been carried out and solutions have been sought to reduce the effects of vibrations on the human body. The difficulty of performing in vivo experiments on people has led to the use of increasingly complex theoretical models to study the problem. By comparing the results obtained from modeling with experimental results collected through measurements under different conditions on the construction site or in the laboratory, useful information was obtained, which can be used to improve the working conditions of workers.
The search for a theoretical model as efficient as possible, and for methods as fast as possible to obtain information about the vibrations that affect the human body, is ongoing, the human body being very complex and difficult to model.
This article investigates the effect of mechanical oscillations on the knee joint of rotary hammer operators, comparing results obtained through laboratory measurements with those obtained from modeling.

Challenges Regarding Digitalization in Construction

Simona STANCA — 2025-03-15

In an era marked by rapid change and accelerated technological progress, the construction industry is already experiencing significant transformations due to the implementation of automation and digitalization. Digitalization in construction is an essential process for increasing efficiency, reducing costs, and improving sustainability. However, this transition faces multiple challenges. Among the main obstacles are the resistance to change by traditional firms, the lack of digital skills
among employees, and the high costs of implementing advanced technologies. The difficult integration of digital solutions into existing processes, the lack of interoperability between platforms, and cybersecurity concerns are other major barriers. Overcoming these challenges can facilitate a sustainable digital transformation with significant benefits for productivity and building quality. Thus, digitalization becomes not only an opportunity, but also a necessity for the future of the construction industry. The paper analyses how digital technology is revolutionizing the construction sector, highlighting both the advantages and challenges generated by this technological change.

Packaging Waste Management and the Main Challenges in Recycling Processes

Carmelia Mariana BĂLĂNICĂ DRAGOMIR — 2025-03-15

Separate collection of packaging is an important step towards a circular economy. Setting a mandatory collection rate is an incentive for the development of efficient and well-targeted collection systems at national level, thus increasing the amount of waste sorted and potentially recycled. This article presents a comparative analysis, by waste type, of the evolution of packaging waste recycling, during the period 2008-2022. While in the period 2013-2022 the average recycling rate of packaging waste in EU member states was 65.74%, in Romania the rate was 50.31%, which requires a series of additional efforts. At the national level, during the period 2013-2022, the highest percentage of packaging waste recycling was represented by paper and cardboard (74.35%) and metal (56.02%), with wood waste ranking last, at 23.77%.

Interrelations Between the Enthalpies of Formation of the Sulfur-Containing Amino Acids L-Cystine, L-Cysteine and L-Methionine

Stefan PERISANU — 2025-03-15

L-Cystine, L-cysteine, and L-methionine are among the twenty-two L-α-amino acids from which all proteins are composed. With their unique sulphur atoms, Lcystine, L-cysteine, and L-methionine have been particularly problematic with regard to both qualitative and quantitative understanding of their energetics, most notably their enthalpies of formation. Using thermochemical quantities from calorimetric experiments (enthalpies of combustion, hydrogenolysis, vaporization, and sublimation), high level quantum chemical calculations, and idealized chemical reactions, these enthalpies of formation are derived and interrelated. In a brief epilogue, the conceptual trichotomy of “convenience, anthropocentrism, and folksonomy” is employed to enhance our thermochemical understanding of these species.

Automated Processing of Mechanical Test Data for Various Composite Materials Using MATLAB

Vasile BRIA — 2025-03-15

The behaviour of composite materials during the mechanical testing process might exhibit, in some situations, very different patterns compared to those of conventional materials. This is why the eventual automation of data processing might require additional steps towards obtaining realistic results from mechanical testing. The present work addresses this issue by proposing an algorithm written using MATLAB software and applying it in processing data from mechanical testing of selected composite materials with various compositions and behaviours.

Pulmonary Trauma and Patient Accommodation with Mechanical Ventilation - Rise Time Settings

Dumitru Adrian DRAGHICI — 2025-03-15

The inspiratory rise time in mechanical ventilation refers to the rate at which airway pressure reaches the set target during inspiration. When appropriately adjusted, it enhances patient-ventilator synchrony and improves comfort by increasing the tolerance of ventilator support. However, an excessively rapid rise time may result in elevated airway pressures and abrupt gas delivery, potentially contributing to lung injury or increased patient effort. An inverse correlation exists between rise time and the mechanical work of breathing, such that a shorter rise time is associated with a disproportionately increased in respiratory workload. As the intensity of respiratory effort and duration of mechanical ventilation increase, so does the risk of ventilator-associated lung injury (VALI). It is therefore imperative that ventilator manufacturers incorporate adjustable rise time parameters and corresponding time intervals into their devices to allow precise, individualized ventilator settings that minimize the risk of iatrogenic lung injury.

Evaluating the Sustainability of Municipal Waste Management in Romania

Carmelia Mariana BĂLĂNICĂ DRAGOMIR — 2025-03-15

The study examines the municipal waste generation per capita trends in Romania from 1995 to 2022 compared to other EU countries using Eurostat data. The analysis divides the period into two phases: pre-accession (1995-2008) and post-accession (2008-2022). In the first period, Romania maintained a low and stable waste generation rate, below 300 kg per capita per year, due to low consumption levels, incomplete waste collection, and limited waste management capacity. After joining the EU, there was a slight increase in waste generation, accompanied by improved data reporting and infrastructure, but Romania still had one of the lowest waste generation rates in the EU. Challenges remained in waste monitoring, rural collection, and public awareness. By contrasting Romania's data with high waste generating countries like Denmark and Germany, the study suggests that factors such as waste monitoring and public awareness contribute to lower waste per capita figures.

The Impact of Pressure Angle and Tooth Root on the Modified Elliptical Gears Bending Stress and Fatigue Life

Paul-Adrian PASCU — 2025-03-15

Noncircular gears are receiving growing attention due to their ability to deliver variable transmission ratios and to optimize motions in specialized mechanical and industrial applications. Unlike circular gears, noncircular gears experience continuous variation in pressure angle and load distribution throughout the meshing cycle, leading to non-uniform stress states among teeth. This study explores the impact of pressure angle and tooth root radius on the bending stress and fatigue life of modified elliptical gears. Finite Element Analysis (FEA) is conducted on three representative teeth positioned at varying distances from the gear centre, highlighting the asymmetric loading characteristic of specific profiles. The tooth root radius is varied, showing a clear reduction in maximum stress with the increased fillet radius size. Then, by varying the rack cutter angle, it is shown that higher angles reduce stress concentration. The results reveal the critical influence of tooth position and geometry on the fatigue vulnerability in noncircular gear design.