Gheorghe Asachi Technical University of Iași

This paper presents an experimental and numerical investigation of the axial compression behavior of perforated cold-formed steel upright profiles commonly used in pallet racking systems. The primary objective is to examine how slenderness influences the failure modes and load-bearing capacity of these structural elements. Three column lengths, representative of typical vertical spacing in industrial rack systems, were tested under pin-ended boundary conditions. All specimens were fabricated from 2 mm thick S355 steel sheets, incorporating web perforations and a central longitudinal stiffener. Experimental results highlighted three distinct failure mechanisms dependent on slenderness: local buckling for short columns (SS-340), combined distortional–flexural buckling for medium-length columns (MS-990), and global flexural buckling for slender columns (TS-1990). Finite Element Method (FEM) models developed using ANSYS Workbench 2021 R1 software accurately replicated the observed deformation patterns, stress concentrations, and load–displacement curves, with numerical results differing by less than 5% from experimental peak loads. Analytical evaluations performed using the Effective Width Method (EWM) and Direct Strength Method (DSM), following EN 1993-1-3 and AISI S100 specifications, indicated that EWM tends to underestimate the ultimate strength by up to 15%, whereas DSM provided results within 2–7% of experimental values, especially when the entire net cross-sectional area was considered fully effective. The originality of the study is the comprehensive evaluation of full-scale, perforated, stiffened cold-formed steel uprights, supported by robust experimental validation and detailed comparative analyses between FEM, EWM, and DSM methodologies. Findings demonstrate that DSM can be reliably applied to perforated sections with moderate slenderness and adequate web stiffening, without requiring further local reduction in the net cross-sectional area.

Using the geometry of the zero-norm vectors, it is shown that at the cosmological scale resolution, the removing of the singularity of the Schwarzchild metric implies, based on the Kruskal coordinates, Rindler-type dynamics, while at the microscopic scale resolution it implies the Yamamoto form of the spin coordinates and implicitly an egalitarian relationship of uncertainly relationships.

We consider biconservative surfaces in $\text {Sol}_3$ Sol 3 , find their local equations, and then show that all biharmonic surfaces in this space are minimal.

Despite improvements in therapeutic approaches like immunotherapy and gene therapy, cancer still remains a serious threat to world health due to its high incidence and mortality rates. Limitations of conventional therapy include suboptimal targeting, multidrug resistance, and systemic toxicity. A major challenge in current oncology therapies is the development of new delivery methods for antineoplastic drugs that act directly on target. One approach involves the complexation of antitumor drugs with cyclodextrins (CDs) and chitosan (CS) as an attempt to counteract their primary limitations: low water solubility and bioavailability, diminished in vitro and in vivo stability, and high dose-dependent toxicity. All those drawbacks may potentially exclude some therapeutic candidates from clinical trials, thus their integration into smart delivery systems or drug-targeting technologies must be implemented. We intended to overview new drug delivery systems based on chitosan or cyclodextrins with regard to the current diagnosis and cancer management. This narrative review encompasses full-length articles published in English between 2019 and 2025 (including online ahead of print versions) in PubMed-indexed journals, focusing on recent research on the encapsulation of diverse antitumor drugs within those nanosystems that exhibit responsiveness to various stimuli such as pH, redox potential, and folate receptor levels, thereby enhancing the release of bioactive compounds at tumor sites. The majority of the cited references focus on the most notable research, studies of novel applications, and scientific advancements in the field of nanostructures and functional materials employed in oncological therapies over the last six years. Certainly, there are additional stimuli with research potential that can facilitate the drug’s release upon activation, such as reactive oxygen species (ROS), various enzymes, ATP level, or hypoxia; however, our review exclusively addresses the aforementioned stimuli presented in a comprehensive manner.

Solid state Cross-Polarization/Magic-Angle-Spinning ¹³C CP/MAS Nuclear Magnetic Resonance (NMR) spectra were obtained for cellulose and α-cellulose isolated from rapeseed stalks. This study provides the first characterization of the rapeseed stalk cellulose, revealing that native cellulose occurs as cellulose I allomorph, while α-cellulose exhibits distinct crystalline structures similar to those found in cellulose II. Additionally, Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Microanalysis (EDX) were employed to further investigate and unveil the structural properties of cellulose extracted from rapeseed stalks. These complementary techniques offered a more comprehensive understanding of the cellulose morphology, crystallinity, and chemical composition, providing valuable insights into the potential utilization of rapeseed stalks as a renewable biomass resource for various industrial applications.

Efficient load balancing stands out as a crucial challenge in multi-cloud environments, particularly for applications that demand ultra-reliable, low-latency communications (URLLC). This paper proposes a novel approach integrating Decision Functions with Normal Distributions (DFND) for precise probabilistic modeling of task-to-cloud compatibility. Multivariate normal distributions capture interdependencies between resource features such as CPU, memory, bandwidth, and latency, ensuring accurate resource compatibility evaluation. Additionally, the Tasmanian Devil Optimization (TDO) algorithm employs dynamic exploration and exploitation strategies inspired by natural behaviors, providing rigorous optimization to improve task assignment in dynamic, multi-cloud environments. It uses flexible methods to ensure the optimization process is both efficient and scalable. Simulation results using CloudSim demonstrate significant improvements over state-of-the-art methods in terms of makespan reduction, response time minimization, resource utilization, and cost efficiency. The proposed framework effectively supports latency-sensitive, large-scale applications in dynamic, heterogeneous multi-cloud environments.

The CoCrFeMnNi high-entropy alloy (HEA) thin film has been investigated to understand the impact of vacuum annealing on surface morphology, electrical property, and work function. The thin films were sputtered at room temperature and at 300°C, followed by vacuum annealing at 600°C. Grazing incidence X-ray diffraction analysis demonstrated a transformation from an amorphous to a crystalline structure upon vacuum annealing due to increased thermal energy, accompanied by new MnO peaks. This structural change was corroborated by field-emission scanning electron microscopy, which revealed distinct morphological variations in the films due to MnO formation with increased white spots in H300-A600 and coarser grains. The annealed film lost its conductivity due to oxide formation; however, it gave the highest work function of 4.59 eV. The findings show that vacuum annealing modifies the surface morphology of the thin films by affecting the grain size, electrical properties, and work function compared to as-deposited films. The oxide formation enhanced the thin-film properties and can be used in advanced high-temperature coating applications.

Background: Rheumatoid arthritis is a chronic autoimmune disease that leads to severe disability and requires improved therapeutic strategies to optimize anti-inflammatory treatment. This study aimed to address this challenge by developing and characterizing an extended-release polymer matrix tablet containing ketoprofen and a ketoprofen–β-cyclodextrin complex with enhanced therapeutic properties. The objective was to improve inflammation management and therapeutic outcomes using a novel delivery system based on the inclusion of the active substance in cyclodextrin complexes. Methods: Tablets were formulated using ketoprofen and ketoprofen–β-cyclodextrin complexes combined with hydrophilic polymers such as Carbopol® 971P NF, Kollidon® VA 64, and MethocelTM K4M. The complexes were obtained via the coprecipitation method to improve bioavailability. The kinetics of the release of ketoprofen, ketoprofen–β-cyclodextrin complex (2:1), and ketoprofen–β-cyclodextrin complex (1:1) from the tablets were investigated in vitro in artificial gastric and intestinal fluids, and drug release profiles were established. Advanced mathematical models were used to describe the nonlinear behavior of the drug–polymer systems. Results: The inclusion of ketoprofen in the β-cyclodextrin complexes was confirmed, revealing distinct release profiles. Tablets (K-3 F-3) containing the 1:1 complex showed rapid release (96.2% in 4–7 h), while tablets (K-1 F-4) containing free ketoprofen released 76% over 9–11 h. Higher polymer concentrations slowed the release due to gel barrier formation. Pharmacotechnical and stability tests supported their suitability as extended-release forms. A multifractal modeling approach described the release dynamics, treating the polymer–drug matrix as a complex system, with release curves characterized by variations in the fractal dimension and resolution. Conclusions: Specific hydrophilic polymer combinations effectively prolonged ketoprofen release. The developed matrix tablets, which were evaluated via in vitro studies and mathematical modeling, show promise for improving therapeutic outcomes and patient compliance during rheumatoid arthritis treatment.

This article outlines the method of creating electrodes for electrochemical sensors using hybrid nanostructures composed of graphene and conducting polymers with insertion of gold nanoparticles. The technology employed for graphene dispersion and support stabilization was based on the chemical vapor deposition technique followed by electrochemical delamination. The method used to obtain hybrid nanostructures from graphene and conductive polymers was drop-casting, utilizing solutions of P3HT, PANI-EB, and F8T2. Additionally, the insertion of gold nanoparticles utilized an innovative dip-coating technique, with the graphene-conducting polymer frameworks submerged in a HAuCl4/2-propanol solution and subsequently subjected to controlled heating. The integration of gold nanoparticles differs notably, with P3HT showing the least adhesion of gold nanoparticles, while PANI-EB exhibits the highest. An inkjet printer was employed to create electrodes with metallization accomplished through the use of commercial silver ink. Notable variations in roughness (grain size) result in unique behaviors of these structures, and therefore, any potential differences in the sensitivity of the generated sensing structures can be more thoroughly understood through this spatial arrangement. The electrochemical experiments utilized a diluted sulfuric acid solution at three different scan rates. The oxidation and reduction potentials of the structures seem fairly alike. Nevertheless, a notable difference is seen in the anodic and cathodic current densities, which appear to be largely influenced by the active surface of gold nanoparticles linked to the polymeric grains. The graphene–PANI-EB structure with Au nanoparticles showed the highest responsiveness and will be further evaluated for biomedical applications.

The conversion of carbon dioxide into platform chemicals such as methanol using copper‐zinc oxide‐alumina (CZA) catalysts is one of the most studied reactions of the past decade. A variety of materials has been tested as catalysts precursors for this reaction, including layered double hydroxides (LDHs). However, the memory effect property of these materials has yet to be fully exploited as a means to maximize their performance. Through successive reconstructions of CuZnAl and CuZnMgAl LDH in Cu(CH3COO)2 aqueous solution, a family of catalysts is developed and thoroughly characterized by means of X‐ray diffraction, electron microscopy and photoelectron spectroscopy. The repeated cycles of calcination, followed by the reconstruction process, lead to the formation of heterostructures combining the recovered LDH structure with CuO nanoparticles (NPs) embedded within the LDH platelets. Each calcination‐reconstruction cycle leads to increasingly smaller and more monodisperse CuO NPs. Catalytic testing reveals the formation of Cu and ZnO NPs during the reductive activation of the LDH material, enabling a large Cu/ZnO interface. This Cu/ZnO synergy is promoted by the consecutive calcination‐reconstruction cycles, such that the third reconstruction of the parent LDH material nearly reaches the performance of the commercially available CZA catalyst.

Water is one of the basic resources for all living things on Earth. From historical studies it can be seen that human settlements appeared near watercourses, because no human activity is possible without water. The Earth’s surface is covered in 78% water, which seems encouraging, but of this amount, only about 2.5% is considered drinkable. This distribution shows us the limiting nature of drinking water resources, which requires efficient management of this resource. Along with the development of mankind, water was used more and more in various domestic, industrial, energetic, and other activities, so that its quality was affected. Under such conditions, it has become absolutely necessary to apply wastewater treatment methods. By applying wastewater treatment methods, the aim is to improve water quality, so that it can be discharged into the emissary without being harmful to various environmental factors. This paper presents the classical methods of wastewater treatment and the possibility of optimizing the technological treatment route in a wastewater treatment plant.

This study aims to develop a mathematical model of the stick-slip phenomenon for various materials employed in sliding tribosystems. Specifically, it focuses on modeling the slip phase of a sliding cylinder, determining its velocity and acceleration. The methodology is illustrated through an example involving the first slip event in a steel-on-steel tribosystem. The modeling framework is based on extensive experimental investigations conducted in the Tribology Laboratory of the IMMR Department at the Faculty of Mechanics. Existing literature provides an overview of different tribosystems and experimental setups used to analyze stick-slip behavior. In this study, a simple sliding tribosystem was utilized, comprising a weight (oscillating mass) on a flat surface moving at a constant translational velocity. The weight was connected to a force sensor via a tensile helical spring. The system was integrated with a CETR UMT-2 Tribometer, enabling controlled variation of translational speed (0.02–8 mm/s) and real-time data acquisition of tangential force, time, velocity, and displacement.

Glass fiber reinforced (GFRP) polymer composites have been prepared by various manufacturing technologies and are widely used for various applications. Fiber glass composites possess good properties such as high strength, flexibility, rigidity, durability, etc. Compared to composite materials reinforced with unidirectional distributed fibers, composites reinforced with fabric have the advantage of the balance achieved between the mechanical and elastic properties in the 0° and 90° directions, although in one of the directions the modulus of elasticity and tensile strength are lower, due to the presence of fiber undulations when reinforcing with fabrics. In this work, a comparison is made between the elastic characteristics of GFRP, determined by tension and by 4 - point bending test.

The stick-slip phenomenon is a frictional instability frequently encountered in mechanical systems, characterized by alternating phases of static adhesion and sudden sliding. This paper presents two experimental methodologies for analyzing this behavior using the CETR UMT-2 Tribometer. The first method employs a unidirectional linear oscillator with a single degree of freedom, while the second follows a methodology based on the VDA 230-206 standard. These approaches enable controlled tribological testing, facilitating precise measurement of frictional forces, displacement, and acceleration data. To support data acquisition, an MMA8451Q accelerometer was integrated with an Arduino Nano 33 BLE development board, allowing real-time monitoring of acceleration variations during stick-slip motion. The collected data was used to evaluate the influence of surface roughness and contact pressure on stick-slip dynamics. By outlining these methodologies, this paper provides a structured framework for studying friction-induced instabilities, contributing to the advancement of tribological research and its applications in mechanical engineering.

Fused Filament Fabrication (FFF) is an additive process manufacturing based on the deposition of thermoplastic material on a heated plate to produce a three-dimensional part. FFF manufacturing technology creates parts with complex geometries by overlapping material layers. FFF technology is used in various fields to produce physical mock-ups and functional parts. This article focuses on the infill process parameters available in the UltiMaker Cura software. Based on the Ishikawa method, seven parameters directly related to infill were identified. These parameters present other subcategories of parameters, resulting in a total of 41 parameters which can be found in the following slicer’s parameter sections: quality, infill, material, speed, special models, supports, and experimental. These process parameters influence many characteristics of the resulting parts, such as the aesthetic, material consumption, which further influences the production costs and the manufacturing time.

Surface cold deformation is an alternative to traditional machining processes used for finishing and hardening the surfaces of components in mechanical assemblies. One of the key advantages of cold deformation is that it allows for producing high-quality surfaces using tools mounted on conventional machines‒tools commonly found in most mechanical workshops. The resultant surface quality can rival with the one achieved through superfinishing processes, such as finishing grinding or honing. Additionally, this method hardens a sufficiently thick surface layer, enabling the machined parts to function properly without the need for conventional heat treatment. However, specialized tools are necessary for these surface hardening processes, and their proper design is crucial for achieving the desired characteristics in the finished components. This paper proposes an analysis of the different tools utilized for superficial cold plastic deformation of inner cylindrical surfaces, based on logical principles for identifying technical solutions. Using decision support systems (DSS), the adjustment mechanisms for cold surface plastic deformation heads that use roller burnishing have been analyzed. Ultimately, this analysis identified a tool that best meets the specified requirements.

The authors realized reciprocating-sliding friction tests by using different type of contacting surfaces such as steel ball on steel plate, steel cylinder and glass on finger skin in dry and lubricated conditions. The experimental tests put in evidence the transient regime of the tangential force and relative velocity. In case of steel-on-steel contact the transition of tangential force shows almost the same trend as the relative velocity. For the sliding friction between steel-on-skin and glass-on-skin it was observed that the tangential force showed a time delay when pass from positive to negative values compared to velocity. The time period in which tangential force pass through zero is depending on the viscoelastic properties of the finger skin. Experimental results were validated with a simplified model based on Heaviside step function and showed a good correlation, especially for the lubricated sliding contact. The proposed methodology gives satisfactory results only if the tangential friction force is varying symmetrically in the transient sliding friction process.

Modelling and simulation of mechanical systems is very useful to predict the system’s response. Friction is important since it influence the functionality and reliability of the system. Friction force is difficult to model in transient regime when relative velocity is zero and some discontinuity appears in simulation. In this paper the authors presented a literature overview regarding the friction force models used to simulate the transient sliding frictional contact in mechanical systems. Also, the authors have proposed a simplified friction force model based on Heaviside function. Some preliminary simulation results were obtained regarding the transition of friction force from positive to negative values in a sliding frictional process.

This study focuses on the development and characterization of biodegradable polymer composites consisting of a polypropylene (PP) matrix, carbon black pigment, and hybrid fillers. The fillers incorporated into these composites consisted of a blend of fibers and particles derived from natural, biodegradable materials, such as flax fibers (FFs) and wood flour (WF) particles. The compositions of polymer material were expressed as PP/FF/WF weight ratios of 100/0/0, 70/5/25, and 70/10/20. The polymer materials were prepared using conventional plastic processing methods like extrusion to produce composite mixtures, followed by melt injection to manufacture the samples needed for characterization. The structural characterization of the polymer materials was conducted using optical microscopy and X-ray diffraction (XRD) analyses, while thermal, mechanical, and dielectric properties were also evaluated. Additionally, their biodegradation behavior under mold exposure was assessed over six months. The results were analyzed comparatively, and the optimal composition was identified as the polymer composite containing the highest flax fiber content, namely PP + 10 wt.% flax fiber + 20 wt.% wood flour.

This paper explores the critical aspects of designing and manufacturing hydraulic manifold blocks using advanced additive manufacturing techniques. The study focuses on how 3D printing technologies, including stereolithography (SLA), digital light processing (DLP), continuous liquid interface production (CLIP) and direct metal printing (DMP), can influence the manifold performance, the structural integrity and the fluid dynamics. The research highlights the advantages of these technologies in reducing material waste, enabling lightweight structures, and allowing for the construction of complex internal geometries that can improve the circulation of the fluid. By presenting results of Computational Fluid Dynamics (CFD) simulations, this paper demonstrates how 3D-printed manifolds can have reduced pressure losses comparing to the traditionally machined design. Resin-based materials such as epoxy, acrylate, and nanocomposites have good mechanical properties, which make them appropriate for high-pressure applications. The paper also provides information on modern technologies such as post-processing by thermal treatment and hybrid manufacturing. Future research directions regarding smart manifold integration and industrial adoption of 3D-printed hydraulic systems are discussed.