Experimental and FE Study on Impact Strength of Toughened Glass–Retrospective Approach

Due to the high cost of experiments commonly performed to verify the resistance of glass elements to impact loads, numerical models are used as an alternative to physical testing. In these, accurate material parameters are crucial for a realistic prediction of the behaviour of glass panels subjected to impact loads. This applies in particular to the glass’s strength, which is strictly dependent on the strain rate. The article reports the results of an extensive experimental campaign, in which 185 simply supported toughened glass samples were subjected to hard-body impacts. The study covers a wide range of glass thicknesses (from 5 to 15 mm), and it aims to determine a critical drop height causing fracture of the glass. Moreover, a 3D numerical model of the experimental set-up was developed to reproduce the experiments numerically and retrospectively to determine the peak stress in glass that developed during the impact. Based on the results of numerical simulations, a load duration factor of 1.40 for toughened glass for impact loads is proposed. In addition, the paper includes a case study to demonstrate the use of the modelling methodology and results of the work on a practical example of an internal glass partition wall.

Calculation of transient temperature and rated capacity of three-phase induction motor under different working systems

This paper aims to propose a method to determine the temperature rise and rated capacity of induction motors under different working systems. A dynamic mathematical model, a 3D temperature field model, and finite element method are used to analyze the electromagnetic loss and transient temperature rise, respectively. The influence of the motor starting process on the temperature rise is taken into account, which resolves the complex loading of transient heat source. The maximum allowable running times for the motor operating with different overloads are determined. The relationship between the motor output power and the allowable running time is obtained, and it provides a basis to determine the rated capacity of motor under S2 working system. The relationship between the motor output power and the temperature rise under different load duration rates is also obtained and provides reasonable evidence to determine the rated capacity of the motor under S3-working system.

Evaluation of Linear Deformation and Unloading Stiffness Characteristics of Asphalt Mixtures Incorporating Various Aggregate Gradations

Optimum stiffness and linear deformation in the unloading phase are fundamental properties of asphalt mixtures required for the durability of flexible pavements. In this research, blends of six different aggregate gradations were used for two base course (BC) and four wearing course (WC) asphalt mixtures. Stability and indirect tensile strength of resulting asphalt mixtures were evaluated to relate to viscoelastic unloading deformation and resilient moduli (instantaneous (MRI) and total (MRT)) at 25 °C using a 40/50 binder for 0.1 and 0.3 s load durations. Results indicated that an increase in coarse aggregate proportion from 48 to 70% for BC has shown a 12% and 14% increase in MRT for 0.1 and 0.3 s load durations, respectively, and an increase in coarse aggregate proportion from 41 to 57.5% for WC has caused a 26% and 20% increase in MRI for 0.1 and 0.3 s load durations, respectively. The same coarse aggregate proportions showed an increase in linear viscoelastic deformation at 0.1 s load duration from 54.6 to 68.2% for WC and from 53.0 to 62.7% for BC, whereas for 0.3 s load duration linear viscoelastic deformation increased from 58.1 to 69.1% for WC and 64.3 to 69.2% for BC. The findings of this study will assist in the selection of aggregate gradations to be used in wearing and base course asphalt mixtures for pavement design, construction and maintenance.

Effect of Lopinavir/Ritonavir Treatment On COVID-2019 Transmissibility: A Possible Option To Reduce Isolation Time

Owing to the coronavirus disease 2019 (COVID-19) pandemic, there is a shortage of hospital wards to accommodate the increasing number of patients, especially in intensive care units. Healthcare systems are collapsing in many countries. Therefore, it is necessary to reduce isolation time. We examined the effect of lopinavir/ritonavir administration in patients with SARS-CoV-2. To assess the viral load, duration and clearance of viable virus; cell culture and RT-PCR were performed in parallel. No viable SARS-CoV-2 could be detected after administration of lopinavir/ritonavir with median time of viable viral clearance being one day after administration. The mean viral load in both upper and lower respiratory tract samples of lopinavir/ritonavir administered group was significantly lower than the group who were not treated with any antiviral agent. The duration of viable viral shedding was shorter in patients with lopinavir/ritonavir treatment compared with those without treatment. This study suggests that lopinavir/ritonavir treatment offers a possible method to reduce isolation time of patients infected with the SARS-CoV-2.

Effect of Lopinavir/ritonavir Treatment on COVID-2019 Transmissibility: a Possible Option to Reduce Isolation Time

Background: Owing to the coronavirus disease 2019 (COVID-19) pandemic, there is a shortage of hospital wards to accommodate the increasing number of patients, especially in intensive care units. Healthcare systems are collapsing in many countries. Therefore, it is necessary to reduce isolation time.Methods: We examined the effect of lopinavir/ritonavir administration in patients with SARS-CoV-2. To assess the viral load, duration and clearance of viable virus; cell culture and RT-PCR were performed in parallel. Results: No viable SARS-CoV-2 could be detected after administration of lopinavir/ritonavir with median time of viable viral clearance being one day after administration. The mean viral load in both upper and lower respiratory tract samples of lopinavir/ritonavir administered group was significantly lower than the group who were not treated with any antiviral agent. The duration of viable viral shedding was shorter in patients with lopinavir/ritonavir treatment compared with those without treatment. Conclusion: This study suggests that lopinavir/ritonavir treatment offers a possible method to reduce isolation time of patients infected with the SARS-CoV-2.

Belarus Power Engineering System Modeling Taking into Account the Nuclear Power Plant Commissioning

The article presents the analysis of the specific features of modeling the operation of energy systems with a large share of nuclear power plants (NPP). The study of operating conditions and characteristics of different power units showed that a power engineering system with a large share of NPP and CHPP requires more detailed modeling of operating modes of generating equipment. Besides, with an increase in the share of installations using renewable energy sources, these requirements are becoming tougher. A review of the literature revealed that most often the curve of the load duration and its distribution between blocks are used for modeling energy systems. However, since this method does not reflect a chronological sequence, it can only be used if there are no difficulties with ensuring power balance. Along with this, when the share of CHP and nuclear power plants is high, to maintain a balance of power one must know the parameters and a set of powered equipment not only currently but, also, in the previous period. But this is impossible if a curve of load duration is used. For modeling, it is necessary to use an hourly load curve and to calculate the state of the energy system for each subsequent hour in chronological order. In the course of a comparative analysis of available computer programs, it was not possible to identify a suitable model among the existing ones. The article presents a mathematical model developed by the authors, which makes us possible to simulate the operation of a power engineering system with a large share of NPP and CHPP while maintaining the power balance for each hour of the forecast period. Verification of the proposed model showed good accuracy of the methods used.

Revisiting Relaxation Model towards Prediction of Longterm Mechanical Behavior of Semicrystalline Fibers?

<p>Tensile testing is a well-established method to assess the maximum strength of a material, while relaxation tests are used to evaluate the viscoelastic behaviour of a polymer. Because of slow viscoelastic changes, significant measurement times are required for reliable descriptions. Therefore the relaxation tests are usually combined with lifetime prediction models to reduce the experimental load. Various traditional models use the time-temperature superposition principle while modificated relaxation models are e.g. based on the time-strain superposition principle (TSSP). Both variations require several measurement series to set up a relaxation master curve (RMC). The basic assumption is that a higher strain corresponds to a higher temperature and a longer load duration, respectively. The paper describes a new model approach which allows to predict the longterm behaviour by using a reduced number of measurements as compared to widely models. The new model is based on the well-known Maxwell model and assumes a mean relaxation time in combination with a relaxation coecient. These parameters account for the inhomogeneity of the individual polymer chains. A dimensionless number, similar to the relaxation coecient, has been successfully introduced for the Weibull distribution and the particle size distribution. The new model allows to derive master curve from one measurement series at a single strain by fitting the data to the model equation.<br></p>