Military Technical Institute

Impact toughness of three different samples was evaluated using an instrumented Charpy pendulum combined with fractography performed using scanning electron microscopy (SEM) to analyze the effects of heat treatment and vanadium as alloying element. Samples were made from Mn16V with water quenching and aging (WQA), as well as from Mn16V and Mn16 with WQA and additional aging (WQAA). It was concluded that vanadium reduced impact toughness, whereas the additional aging had practically no effect.

This study investigates the effect of loading density on the performance of 40-mm and 80-mm diameter shaped charges equipped with trumpet-shaped liners of 1-2 mm thickness, respectively. The main charge composition based on nitrotiazolone (NTO), 2,4-dinitroanisole (DNAN), and 1,3,5-trinitro-1,3,5-triazinane (RDX) was synthesized in the laboratory and characterized using differential scanning calorimetry (DSC). Numerical simulations were conducted using Autodyn hydrocode (AD) to analyze jet characteristics and calculate penetration depth. The JWL parameters for the IMX Composition were derived using the Explo5 code and implemented into the simulation. The virtual origin (VO) and effective jet length were tracked using the back-projection method. Analytical equations were also applied to estimate jet breakup time and penetration depth. Some penetration measurements were performed using static firing against RHA targets. Increasing the density from 1.6 g/cm³ to 1.8 g/cm³ increased detonation velocity from 6900 to 8040 m/s, theoretically based on Explo5 (version 5.04). Jet velocity improved by 25 % (40 mm) and 22 % (80 mm), while penetration depth increased by 39 % (40 mm) and 36 % (80 mm) based on AD predictions. The experimental penetration testing exhibited only 5.5 % (40 mm) and 10 % (80 mm) differences compared to numerical predictions. In comparison, the maximum deviation between numerical and analytical predictions of penetration depths was only 9 % (40 mm) and 11 % (80 mm).

Angola has taken steps to deepen its democracy, modernize its goods and services and bring its public administration into line with international best practices. In this context, the need to understand the phenomenon of “leadership” motivated this study, given the diversity of perspectives. To guide the study, the following review question was defined: How is leadership characterized from 2018 to 2023? Taking into account that there are recent literature review publications about the phenomenon under study, we opted for a systematic review of systematic literature reviews, with a qualitative approach, providing a global analysis of the body of information available, according to the objectives of the study and the selection criteria. The evidence from the study revealed that several fields of knowledge are interested in studying leadership, with different approaches, which are developing over time, highlighting its situational and dynamic nature. In general, they also revealed that studies on leadership revolve around its nature, the conditions of its emergence and/or its consequences. On the other hand, they highlight the scarcity of publications on the phenomenon in Angola where any study was founded addressing those questions according to those selection’ criteria. Evidences contributes to the understanding that leadership is not an administrative and/or hierarchical phenomenon, but rather a dynamic psychosocial one, to which several factors other than the leader contribute. Leadership encompasses human relationships and in the organizational context is expressed in an environment of constant change and risk management, and is subject to development.

The present paper evaluates the performance of grid topologies and RANS turbulence models in predicting the aerodynamic drag coefficient of a 155mm artillery projectile by conducting steady-state computational research. The research is performed for Mach numbers from 0.5 to 3.0, assuming axisymmetric flow. Four distinct combinations of grid topology and turbulence model are investigated, where the O- and C-grid topologies are each paired with both the realizable k-ε and the SST k-ω models. Compared to the experimental data across the Mach number range, the combination of O-grid with k-ε model showed the smallest mean deviation of 1.64%, while the combination of O-grid with k-ω exhibited the largest mean deviation of 5.54%. In terms of drag component results, both turbulence models and grid topologies performed equally in predicting pressure and friction drag, with differences less than 6% in all Mach number cases. However, significant discrepancies were obtained in base drag prediction, especially between the two turbulence models, with differences reaching around 60% in the transonic regime. This was identified as the main contributor to the discrepancies in aerodynamic drag coefficient results among the four combinations. Furthermore, the findings indicate that the turbulence model selection impacts the zero-yaw drag prediction more than the grid topology, especially in the transonic and low supersonic cases.

Recent experience has shown that test results of standard wind tunnel models under off-design conditions could be a useful aid in preparations of some nonstandard wind tunnel tests. However, reference data for such conditions do not exist, or they are scarce. Therefore, off-design transonic wind tunnel tests of the HB-2 standard models were executed in the VTI T-38 wind tunnel as a supplement to the supersonic tests of the same models under design-intent conditions, for which reference results were available. New tests were conducted so that test envelopes partially overlapped with those from available supersonic reference data. Good agreements of results with references were confirmed in the overlapped ranges, so it was assumed that, by implication, the obtained results were also valid in the transonic range of conditions, with an observation that the effects of sting diameter were much more pronounced in the transonic range than in the supersonic one. HB-2 models were tested in two sizes, using two different wind tunnel balances for each model, so that the results can be used with more confidence.

Introduction/Objective. Severe acute respiratory syn-drome caused by the coronavirus (SARS-CoV-2) mani-fested with an unpredictable clinical course that could rapidly progress, leading to serious and often fatal com-plications. The identification of effective laboratory bi-omarkers that could stratify patients at risk of developing severe forms of the disease is imperative to ensure they receive prompt medical treatment. The aim of our study is to compare baricitinib and tocilizumab in clinical out-come among hospitalized patients with severe COVID- 19. Methods. A retrospective study included the analysis of data from 82 patients of both genders who were treated with biological immunosuppressive therapy at the Mili-tary COVID Hospital Karaburma. All patients who met the criteria for its application according to the guidelines of the national protocol for the treatment of COVID-19 version XIII had a consultative decision made for the ap-plication of biological immunosuppressive therapy. Half were treated with tocilizumab, and the other half with baricitinib. Results. The results of our study show that the mortality rate is lower in the group treated with tocilizumab com-pared to the group treated with baricitinib - 17.1% vs 26.8%, but without statistical significance (p = 0.286). Additionally, the use of tocilizumab reduces the need for mechanical ventilation compared to baricitinib - 53.6% vs 68.3%, without statistical significance (p = 0.454). Conclusion. The results obtained in our study indicate that both drugs are equally clinically effective.

Nowadays, renewable energy sources represent threats to conventional power systems. These threats undermine these systems' stability and threaten their inertia. The present article proposes the intended study's single-area and multi-area traditional power systems. Power systems under study will be modelled using block diagrams, as seen in the article. Renewable energy sources, such as wind farms and solar fields, will present a penetration to these conventional power systems. A dynamic dual-input controller will be used as a virtual inertia controller. The effectiveness of the dual-input controller on the power systems' frequency stability is verified. Simulation results will be carried out using the Matlab/Simulink package. The performance curves are focused on analysing the proposed controller's dynamic effects on the power system frequency stability.

Hospitals are considered a place for people to recover and protect themselves from diseases and epidemics that have spread recently, and perhaps the internal environment plays an important role in the hospitalization process by preventing infection from the patient or to him in order to protect others, and one of the most important of those spaces in hospitals, the importance of which has been demonstrated in this last period is the isolation rooms for patients, and their internal environment constitutes an important focus in the process of recovery and controlling of infection fight, which forces this matter to search for finishing materials and raw materials that do not interact with viruses and do not stimulate their reproduction or spread, and perhaps the matter may require the intervention of the highest limits of intelligence in materials. One of the most important technological revolutions is nanomaterials and raw materials, which have sparked widespread controversy and spread in various fields, and finishing materials have witnessed a large part of this intelligent development in the composition of these. Special Issue of AEIC 2024 (Sustainable Architecture and Urban Design Session)

The surface temperatures of several commercial chargers for contemporary mobile phones with nominal power outputs from 10 W to 120 W were compared in this paper. Using a thermal imaging camera, the charger's surface temperature was recorded while it was connected to the main power source. To determine how the temperature on the charger's surface depended on the phone's charge level, an analysis of the thermograms that were captured was done. In this manner, the impact of the phone's charging speed on the charger's heating and, consequently, the safety factor concerning the charger's overheating, are ascertained. The battery charge range that was observed was 10% to 90%.

In this study corrosion properties of welded joint of low carbon steel were tested. The welded joint was made using S355JR steel by the metal inert gas technique (MIG welding process). Corrosion properties of used base metal (BM) and welded joint were investigated by the electrochemical techniques including open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization. All tests were conducted in 3.5 wt.% NaCl solution. The obtained results show that the lowest corrosion rate is present on the welded joint surface. This interesting result may be explained by the difference in the chemical composition of welded joint and base metals. Namely, the carbon content is the lowest in the welded joint, and consequently, the density of cathodic sites is the lowest in this area, as compared to the base metal parts.