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The high content of organic matter of surface waters represents a real danger for aquatic fauna, even if their toxicity is low. Such a high rate of biodegradation leads to oxygen depletion of the waters in question and thus the suffocation of aquatic fauna. The elimination of these disadvantages by using purge technologies of catalytic oxidation may be a viable solution. The oxidation process of pollutants in wastewater that contain glycerol or molasses was performed on nanostructured catalysts based on Fe, Mn and Fe-Mn mixed. The catalysts were prepared by precipitation-coprecipitation of selected precursors and they were characterized by determination of particle size distribution. Measurements for the determination of particle size distribution were carried out using the method of dynamic light scattering. The oxidation process was conducted in a batch reactor equipped with air bubbling system, in suspension of catalysts. Efficiency of oxidation process of wastewater loaded with glycerol or molasses is expressed by biochemical oxygen demand. Compared to Mn or Fe catalyst, the Fe-Mn catalyst favors an advanced treatment of wastewater that contain glycerol or molasses by oxidation with air.

Adhesive cements (that chemically adhere to both the tooth and the restoration material) are considered to be a highly specialised group of composite cements. They involve a three-step procedure (acid etching, bonding agents or silane and composite resin), like cements using acid etching technique and have similar physical properties as the latest. The purpose of this study was to statistically analyse the values of the adhesive bond between dental tissue and ceramic, using three types of cements (both commercial products and a product from Romania) and one type of ceramic. The separate combinations were studied in order to identify the weakest link of the interface of dental-tissue-ceramic in terms of shear bond strength. The adhesion values recorded at the interface of cement-enamel for Dualcim and Nexus cements were significantly different from those recorded for Variolink cement. The highest resistance to adhesion was recorded to the interface cement Variolink – dentin, the average being 16.19 MPa.

This paper presents a model for the numerical simulation of Charpy test, using together Smoothed Particle Hydrodynamics (SPH) Method and Finite Element Method. Numerical simulation of the mechanical tests require the use of special material models, so the material fracture to be also simulated. The new numerical method, SPH Method, in fact a version of the Free Particle Method, presents some important advantages among which no material failure criterion to be used. Our proposed model is a model combining the FEM and SPH Model: only the specimen is modeled only by particles. The numerical results are compared with the results using only FEM and finally with the experimental data. Avoiding the material models, in fact the failure criterion, by SPH method presents a great advantages because any material model (Plastic-kinematic, Johnson-Cook, Modified Johnson-Cook, Picewise linear plasticity etc.) involves knowledge about some material constants. This aspect is very important and in the same time, very difficult. The numerical model together with some theoretical fundamentals of the SPH Method could be more then an invitation for using the SPH Method, it could be an available model able to inspire the researchers in their work. The paper is finished after some conclusions.

PETG (polyethylene terephthalate) is a very popular plastic material when it comes to manufacturing invisible orthodontic appliances. These devices are very common nowadays because they provide an esthetic treatment alternative to braces. This type of plastic material has several indications in orthodontics: manufacturing night guards, positioners, orthodontic aligners, invisible single-layer/multi-layer thermoplastic retainers, bite splints, space maintainers, mini trays, fluoride trays, growth guiding splints, etc. The polyethylene foils provide resistant wear and rigid devices, with no substantial elastic deformation, capable of assuring a reliable orthodontic treatment.

The paper presents the development of a cross-ply composite material reinforced with carbon fibers and epoxy matrix (CFRP). Specimens cut from composite plate have been tested in tensile, using a testing machine with hydraulic grips, assisted by full-field strain measurements equipment. Using tensile tests and ultrasounds technique, were determined the nine elastic characteristics of the orthotropic material. During tensile test, at a certain level of stress, inside the specimen, small cracks appear. These cracks become more numerous and larger with increasing of stress. A portion of a specimen without cracks and with cracks respectively, subjected to tensile, were simulated by Finite Elements Analysis (FEA). For this analysis, the composite material was considered homogeneous and orthotropic. The simulation of cracks presented inside the specimens at different stress levels has been realized using X-ray pictures. Based on the FEA determinations, the stress state in the vicinity of the cracks was determined.

In the paper, I have brought in a method whereby a body with rheological behaviour is associated to a dynamic-equivalent Kelvin model. The equalization is made so that the forced vibration caused for Kelvin model by a harmonic external impulse is identical to the forced vibration caused in the case of the studied rheological model. It was experimentally determined the elasticity modulus and damping factor for samples with Dammar bio-matrix, reinforced with silk, flax or hemp fabric. Modifying samples dimensions, It was studied the vibrations frequency effect on the studied mechanical properties.

The aim of this research is to develop plastic pyrotechnic compositions with a high level of moldability while maintaining safety and performance features specific to usual plastic bonded pyrotechnic compositions. In this view, theoretical and experimental studies have been performed in order to determine the characteristics of three new plastic pyrotechnic compositions and to establish their agreement with energetic materials safety and performance essential principles. These formulations have been designed to accomplish special requirements, such as processing performances, i.e. good malleability for hand packing or molding at room temperature, and pyrotechnic effects, i.e. illuminating or smoke signaling.

Removable partial dentures (PDs) are an affordable and effective treatment option in patients with partial edentations.This aim of this study is to evaluate the differences, in the terms of patient’s compliance, in restoration of partial edentations through three types of PDs, achieved of Meliodent-Kulzer acrylic resin, Valplast® polyamide resin, respectively of BioDentaplast-Bredent acetal resin. Investigations were carried out on 78 patients (3 groups of 26 patients), to which were performed 101 PDs (35 of Meliodent-Kulzer, 33 of polyamide Valplast®, respectively 33 of BioDentaplast-Bredent) and after the accommodation period with the dentures, six assays of compliance have been conducted. The results of the research have demonstrated that PDs made of flexible materials were far more favourable than those made of Meliodent acrylic resin, and PDs with BioDentaplast framework presented the best impact. The ascertained differences are relevant in the treatment of partial edentation, for choice of the best option for one of these three polymeric denture base materials.

This paper presents the results of the research work performed by the authors aiming at highlighting and quantifying the reinforcement effects (restoring of the mechanical strength) on transmission pipelines, generated by applying composite material sleeves in the areas in which the steel pipes of these lines have local surface defects (metal loss – like flaws). The models proposed to that purpose have been confirmed by performing some experimental programs, the first one consisting of the examination of the behaviour of some full-scale steel pipe specimens, with metal loss – like flaws (made by machining), on which reinforcing wraps made of composite material have been applied (with polymeric matrix and fiberglass fabric), subjected to internal pressure loading, up to bursting, and the second one aiming at the determination of the state of stress and strain in the pipelines on which reinforcing wraps made of composite material have been applied and which are subjected to internal pressure loading, in the elastic range. The items discussed and the results presented in the paper are mainly useful for the development and qualification of the composite materials repair systems for the transmission pipelines, according to the requirements of the standards ASME-PCC2 and ISO 24817.

The growing utilisation of carbon materials increases the waste generation. Therefore, the development of new composites using recycled carbon fiber reinforced polymer (rCFRP) within the present study was driven by environmental and economic factors. Six configurations of new polymeric matrix composites were developed and evaluated by mechanical tests (flexural, compression and interlaminar stress), microscopic and thermal analysis. Four configurations of composites were obtained by filling the matrix with rCFRP powder and fibrous elements mixture, the reinforcement phase being produced by grinding carbon fiber reinforced polymer (CFRP) waste. The new composite configurations showed an increase in mechanical properties with rising the reinforcement fraction. The samples analyzed by stereomicroscopy reveled a fairly homogeneous distribution of the reinforcement in the matrix for 5%wt. up to 30%wt., whereas thermal analysis showed no significant changes in the glass transition temperatures of developed materials. Two configurations of composites were obtained by chemical etching of the matrix and recovering carbon fiber woven, used subsequently as reinforcement phase for new composite configurations. The same method was used for determining the volume fraction of CFRP composite constituents. Initial results demonstrate that recycled carbon remains a highly satisfactory engineering material. These results showed that recycled FRP composites can be used to develop new less demanding composite materials or improve some properties of FRP composites.