Comprehensive Characterization of Polymeric Composites Reinforced with Silica Microparticles Using Leftover Materials of Fused Filament Fabrication 3D Printing

Silica exhibits properties such that its addition into polymeric materials can result in an enhanced overall quality and improved characteristics and as a result silica has been widely used as a filler material for improving the rheological properties of polymeric materials. The usage of polymers in three-dimensional printing technology has grown exponentially, which has increased the amount of waste produced during this process. Several polymers, such as polypropylene (PP), polyvinyl alcohol (PVA), polylactic acid (PLA), and nylon, are applied in this emerging technology. In this study, the effect of the addition of silica as a filler on the mechanical, thermal, and bulk density properties of the composites prepared from the aforementioned polymeric waste was studied. In addition, the morphology of the composite materials was characterized via scanning electron microscopy. The composite samples were prepared with various silica concentrations using a twin extruder followed by hot compression. Generally, the addition of silica increased the tensile strength of the polymers. For instance, the tensile strength of PVA with 5 wt% filler increased by 76 MPa, whereas those of PP and PLA with 10 wt% filler increased by 7.15 and 121.03 MPa, respectively. The crystallinity of the prepared composite samples ranged from 14% to 35%, which is expected in a composite system. Morphological analysis revealed the random dispersion of silica particles and agglomerate formation at high silica concentrations. The bulk density of the samples decreased with increased amount of filler addition. The addition of silica influenced the changes in the characteristics of the polymeric materials. Furthermore, the properties presented in this study can be used to further study the engineering design, transportation, and production processes, promoting the recycling and reuse of such waste in the same technology with the desired properties.

Ectoparasites infecting Mugil curema (Mugiliformes: Mugilidae) in Amapá state estuary, in the northern Brazilian coast region

In fish, one of the most important interactions is that occur between parasite species and environment. Wild fish interactions with parasites of different taxa can result in diseases for fish and consequently damages to the fishing industry. This study investigated the ectoparasite fauna in Mugil curema in Amapá state estuary, in Brazilian coast region. The parasite prevalence was 51.4%, and a total of 282 parasites were collected among Ligophorus brasiliensis (Dactylogyridae), Excorallana longicornis (Corallanidae), larvae of Gnathia sp. (Gnathiidae) and Ergasilus atafonensis (Ergasilidae), but the dominance was of L. brasiliensis. The parasites presented highly aggregated dispersion, except for Gnathia sp. that had a random dispersion. There was a predominance of hosts parasitized by zero and one species. The relative condition factor did not differ between parasitized and non-parasitized fish. The body size of hosts did not influence the parasite abundance. The community of ectoparasites consisted of low species richness with low infection levels. This is the first study on parasites of fish from the coast of the State of Amapá and is the first report of Gnathia sp. for M. curema.

Effect of Steel Fiber Reinforced in FRP Confined Concrete by Using Numerical Analysis

The models are predicting and analyzing on compressive and flexural testing by considering fiber reinforcement embedded in confinement concrete. In this work, steel 4340 fiber with high aspect ratio was developed in unique random spline shape and randomly disperse in confinement concrete. Fibers designed in 15.5mm of average length and amount were varied in range of 50 to 200 and 250 to 1000 for compressive and flexural testing, respectively. Both varied orientation and random dispersion of fiber were developed using MATLAB before embedded and analyzed in Ansys Workbench. The finite element model was validated in initial results on plain concrete prior study in influence of confining and fibers to structure. The model proposed showed that confining reinforcement increasing ductility and large deflections in structure testing. In addition, fibers as reinforcement slightly increases in strength for both compressive and flexural in certain number. These method reinforcement was help warning of failure prior to complete failure that use in construction material.

Community and infracommunities of metazoan parasites in Hemiodus unimaculatus (Hemiodontidae) from Jari River basin, a tributary of Amazon River (Brazil)

Parasites are an important part of biodiversity, and knowledge of species and their relationship with their hosts helps in monitoring an ecosystem over time. The aim of this study was to investigate the fauna of metazoan parasites in Hemiodus unimaculatus from the Jari River, in the eastern Amazon region, northern Brazil. Of the fish examined, 96.7% were parasitized by one or more species, and a total of 336 parasites such as Dactylogyridae gen. sp.1, Dactylogyridae gen. sp.2, Dactylogyridae gen. sp.3, Dactylogyridae gen. sp.4, Gyrodactilydae gen. sp., Urocleidoides sp.1, Urocleidoides sp.2, Urocleidoides sp.3, metacercariae of Digenea gen. sp., Procamallanus (Spirocamallanus) inopinatus, Contracaecum sp., Neoechinorhynchus sp. and Acarina gen. sp. The parasite community showed low Brillouin diversity (0.58 ± 0.29), low evenness (0.44 ± 0.21) and low species richness (7.40 ± 3.83). There was a predominance of ectoparasites, mainly monogeneans and digeneans. The parasites showed an aggregate dispersion, except for P. (S.) inopinatus, which had a random dispersion. The size of the hosts had no effect on diversity, species richness and abundance of parasites, but other factors structured the parasite community. This is the first study on the parasite community and infracommunities in H. unimaculatus.

Diversity of metazoan parasites in fish Triportheus angulatus and Triportheus auritus living in sympatry in the Brazilian Amazon

The aim of this study was to compare the diversity and community structure of metazoan parasites in sympatric populations of Triportheus angulatus and Triportheus auritus in the Jari River basin, in the eastern Brazilian Amazon. All the specimens of T. angulatus and T. auritus examined were infected by Anacanthorus furculus, Anacanthorus pithophallus, Digenea gen. sp., Procamallanus (Spirocamallanus) inopinatus, Rhabdochona acuminata, Contracaecum sp., Ergasilus sp. and Acarina gen. sp. These parasites displayed aggregated or random dispersion. The parasite community in T. angulatus and T. auritus presented a similarity of 78%. The diversity indice and richness of parasite species were greater in T. auritus and there were differences in levels of host parasite infection for some infracommunities. Phyllodistomum spatula occurred only in T. angulatus, while metacercariae of Clinostomum marginatum and Digenea gen. sp.2 occurred only in T. auritus. The species richness of the parasites was influenced by host size, as well as the abundance of some parasite infracommunities. This is the first report of these parasites for T. angulatus and T. auritus, except for P. (S.) inopinatus and Contracaecum sp. for T. angulatus.

Shooting Simulator «Inhibitor»: Mathematical Support for Ballistics of 7.62 Caliber Weapons

The software for support of external ballistics calculation for weapons of 7.62 mm caliber is described taking into account external factors for the optical-electronic tactical exercise machine for small arms "Inhibitor" developed at the Institute of Mechanics UdmFRC UB RAS and at Computer facilities department of Kalashnikov ISTU jointly with JSC «Kalashnikov» Concern». A tactical and technical task is given for ballistic calculation of the trajectory up to 2 km of range of weapon simulators with a laser emitter of the targeting point taking into account external factors: types of sights, especially optical, ballistic scattering of bullets, deflection of the bullet from the side wind and derivation, which have a significant impact on the ballistic trajectory. The implemented differential mathematical model of external ballistics relying on the aiming angle of the weapon simulator depending on the sight readings, the initial speed and ballistic coefficient of various types of ammunition in real time builds a ballistic trajectory with adjustments for the air temperature and pressure and dependence on lateral wind and random dispersion of bullets to further solve the "problem of meeting" with obstacles. The given results of software tests for the error in calculating the coordinates of the ballistic trajectory showed full compliance with the requirements and adequacy of mathematical models. It was concluded that further research and development of electronic shooting simulators were promising thanks to the improvement of computing tools and the development of software libraries in order to increase the accuracy of simulating external ballistics of simulators taking into account many external factors, expand functional networks and reduce cost and, therefore, increase competitiveness.

Development of Alfa Fiber-Based Mortar with Improved Thermo-Mechanical Properties

This work deals with the development of a new composite based on mortar reinforced with optimally sized alfa fiber (AF). Experimental investigations of physical and thermo-mechanical properties of the new AF mortar composite are performed for AF weight fraction varying from 0% to 5%. This simple material preparation process is described and scanning electron microscopy (SEM) is undertaken to analyze the morphology of this composite. It shows a random dispersion of the AF into the mortar matrix. Physical properties such as open porosity, water absorption, and bulk density fluctuations with AF mass content are measured. Measured thermal conductivity is compared to the values generated by different prediction models. Good agreement, within 9.6%, is obtained with data predicted by Woodside–Messmer’s method. It is demonstrated that this simple blending of AF into mortar improves significantly the thermo-mechanical behavior of the new composite. An addition of 5% of AF weight content makes composite material lighter by about 15%, enhances its insulating thermal capabilities by about 57% and increases its heat diffusion damping rate by about 49%. Moreover, the composite mechanical (flexural and compressive) strength increases by up to 10% for an AF weight content of 1%.