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Shotcrete, a pneumatically sprayed concrete mixture, has gained significant popularity in the construction industry due to its versatility and adaptability. However, the demand for high-strength shotcrete has intensified, driven by advancements in equipment and admixtures. Fiber-reinforced high-strength shotcrete (FRHSS) offers enhanced quality, adhesion, and construction speed, making it ideal for stabilizing excavations and slopes, strengthening masonry and concrete structures, and reinforcing underground structures. Additionally, the increased strength allows for reduced section dimensions, leading to more economical designs.

This research investigates the effects of aggregate gradation and admixtures, including micro silica, superplasticizer, accelerator, and micro recycled steel fibers (MRSFs), on the strength and performance of FRHSS. The study employs wet-mix and dry-mix shotcrete methods, examining the properties through laboratory and field experiments.

The results demonstrate that achieving high-strength shotcrete is more feasible with the wet-mix method. Fiber-reinforced wet-mix shotcrete attained a 28-day compressive strength of 987 kg/cm², representing an 80% and 77% increase in compressive strength and energy absorption, respectively, compared to conventional fiber-reinforced wet-mix shotcrete. Furthermore, fracture toughness tests revealed that MRSFs effectively prevent microcrack propagation and control deformations. FRHSS incorporating MRSFs exhibited a 28% and 97% increase in compressive strength and energy absorption, respectively, compared to the corresponding mix without fibers.
 

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Backgrounds: The primary goal of this study was to identify the potential association between COVID-19 prognosis and demographic and clinical features, underlying diseases, and drug and supplement use in patients admitted to Amir al-Momenin hospital in Zabol.

Materials & Methods: This retrospective study surveyed the electronic health records of 848 COVID-19 patients hospitalized in a tertiary referral hospital in southeastern Iran from the beginning of the COVID-19 outbreak until the end of February 2021. Univariate and multiple analytical tests including unconditional and penalized logistic regressions were used for statistical analysis.

Findings: Out of a total of 848 patients, 371 (43.75%) patients were female, and 477 (56.25%) patients were male. Age, underlying pulmonary and cardiovascular diseases, and loss of consciousness predicted a higher mortality rate. On the contrary, a negative chest X-ray was associated with a lower risk of death.

Conclusion: Identifying predisposing factors of mortality in COVID-19 patients will help physicians provide more intensive care to those at higher risk of death by classifying patients based on risk factors and underlying diseases.

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Size dependent behavior of materials appears for a structure when the characteristic size such as thickness or diameter is close to its internal length-scale parameter. In these cases, ignoring this behavior in modeling may leads to incorrect results. In this paper, strong effects of the size dependence on the static and dynamic behavior of the electrostatically actuated micro-beams have been studied. The equilibrium positions or fixed points of the gold and nickel micro-beams have been determined and shown that for a given DC voltage, there is a considerable difference between the fixed points gained using the classic beam theory and the modified couple stress theory. In addition, it has been shown that the static and dynamic pull-in voltages gained using the couple stress theory are several times higher than those gained using the classic beam theory. Some previous studies have applied the classic beam theory in their models and introduced a considerable hypothetical value of residual stress to match their experimental and incorrect theoretical results. It has been shown that using the modified couple stress theory decreases considerably the difference with the experimental results.

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Electrostatic micro-sensors as a part of microelectromechanical systems (MEMS) play an important role in modern technology. So, precise modeling and suitable solutions for solving the governing mechanical and vibrational equations of them are of great importance. Due to the nonlinear nature of the electrostatic excitation, numerical methods are used to solve the governing equations. This paper presents a comparison between two Galerkin-based approaches to solve them. In the first approach, as used by many researchers in the literature, both sides of the equations are multiplied with the denominator of the electrical force term and then the Galerkin method is applied, whereas in the second approach, we apply direct Galerkin method to solve the equation. As a case study the nonlocal elasticity theory has been used to obtain the governing equation. The results show that for a given beam, although the both approaches predict same pull-in voltage in most cases, but the first approach cannot predict the pull-in instability in some cases and also misses some fixed points. So, the bifurcation diagrams and phase portraits have different quality in the two approaches. Also, the results show that the singular point which is the position of the substrate plate, acts as a strong attractor in the phase diagrams which the first approach is unable to predict it.

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In this paper, the fluid- solid interaction in an electrostatic microbeam by using three- dimensional aerodynamic theory has been studied. Modified couple stress theory is used to model the elasticity depends on the size of the microbeam. The proposed model can be used as a mass micro- sensor. To analyze the dynamic behavior of the microbeam a DC voltage applied to the system and then by applying an AC voltage dynamic characteristics of the system around static deformed condition is analyzed. Because of non-linear nature of the governing equations to solve them reduced order model based on Galerkin is used. Results have shown that considering the couple stress and also increase the size of the length characteristic parameter reduces the size of the fluid pressure differential created between the two sides of the microbeam. However, according to the three- dimensional aerodynamic theory for fluid-solid interaction, change of the pressure difference created does not lead to creation difference in predicting the size of the added mass between the classical and modified couple stress theories. In another part of the results has been shown that the presence of added mass to what extent can makes changes in the frequency response curves drawn for the system. Also applied the couple stress theory and increase the size of the length characteristic parameter makes the system more rigid and consequently reduce the amplitude of the vibration and frequency response curves shift to the right.

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Today, consumption of milk and its products is one of the signs of development of human societies. Milk is a healthy, nutritious, delicious and thirsty drink that is consumed by a large group of people, especially children. Therefore, the aim of this study was using grape syrup as a flavoring in probiotic milk containing Bacillus coagulants and investigating effects of grape syrup on physicochemical and microbial properties of probiotic milk. For this purpose, two quantitative factors including grape syrup concentrations (0.17, 1, 3, 5 and 5.83 %) and storage time (0.96, 2, 4.5, 7 and 8.04 days) in five levels were evaluated by using a central composite design. The results showed that different concentrations of grape syrup and storage time on pH, acidity, dry matter, fat and viability of B. coagulation of probiotic flavored milk were significant (P<0.05). The optimum condition was obtained based on maximum pH and viability of B. coagulation and minimum acidity. The optimum condition was 1% grape syrup and 2 days’ storage time, which its total desirability was 95%.

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Economic security is one of the most important aspects of national security. It is a basic pillar of the economies for achieving economic development and improving social welfare, too. The demographic changes may widely affect the development and trend of target variables of the economy. The identification of the effects of demographic changes on economic security can help policy-making and planning of economic development. The purpose of this paper is to investigate the effect of age structure of the population on economic security in Iran during the period 1981-2016. In this regard, the economic security index (ESI) is firstly estimated using fuzzy logic. The findings indicate the instability of this index. Then, the impact of demographic model of Iran along with other variables affecting Iran's economic security is evaluated using generalized method of moments (GMM). The results show that age structure of the population has a negative and significant effect on Iran's economic security. Population growth, capital stock, financial development, trade openness, and saving rates have positive and significant impacts on the ESI. However, the inflation rate has no significant effect on the ESI. Iran’s population is rapidly aging, and if the current trend continues, the limited economic resources should be assigned to meet the needs of the elderly instead of investing in productive sectors. Therefore, there is a need for planning to tackle this problem.