Optimum design of reinforced concrete rectangular columns subjected to axial compression and biaxial bending moments

This study investigates the optimum design in terms of minimum cost of reinforced concrete rectangular columns subjected to axial compression force and biaxial bending moments about x and y axes. For the optimisation process, the Generalised Reduced Gradient (GRG) technique was implemented which is embedded within Excel Solver add-in tool. GRG method was adopted because of its robustness and efficiency in dealing with a wide range of engineering problems as demonstrated by several works available in the literature. GRG is regarded as one of the best deterministic local optimisation methods. Equally important, the GRG is part and parcel of Microsoft Excel which means that there is no need to pay for extra licence to run any optimisation problem. The formulated models for the design of reinforced concrete columns and the imposed constraints were based on the provisions of Eurocode 2 (EC2). The design variables were the cross sectional dimensions (width and depth) and reinforcing steel area. It is worthwhile to mention that the position and orientation of neutral axis were also considered as design variables in order to avoid solving the highly nonlinear simultaneous equations which is time consuming and not necessarily leading to a convergent solution. Several design parameters, such as materials cost ratios and depth to width ratios were tested. Consequently, optimum design charts were developed for a wide range of practical combination of axial compression forces and eccentricities in both x and y directions. Following a comprehensive investigation of the minimum cost problems carried out for different cases, one can conclude that variation of depth to width ratio may have noticeable effect on the optimum width, depth and area of steel only when the eccentricity in y direction (ey) is much greater than the eccentricity in x direction (ex). Furthermore, the effect of steel to concrete unit cost ratio (Cs/Cc) is more obvious at larger loads and higher eccentricities

Modeling and Experimental Validation of the VARTM Process for Thin-Walled Preforms

In this paper, recent shell model is advanced towards the calibration and validation of the Vacuum-assisted Resin Transfer Molding (VARTM) process in a novel way. The model solves the nonlinear and strongly coupled resin flow and preform deformation when the 3-D flow and stress problem is simplified to a corresponding 2-D problem. In this way, the computational efficiency is enhanced dramatically, which allows for simulations of the VARTM process of large scale thin-walled structures. The main novelty is that the assumptions of the neglected through-thickness flow and the restricted preform deformation along the normal of preform surface suffice well for the thin-walled VARTM process. The model shows excellent agreement with the VARTM process experiment. With good accuracy and high computational efficiency, the shell model provides an insight into the simulation-based optimization of the VARTM process. It can be applied to either determine locations of the gate and vents or optimize process parameters to reduce the deformation

Exploring Security Practices in Infrastructure as Code: An Empirical Study

Cloud computing has become popular thanks to the widespread use of Infrastructure as Code (IaC) tools, allowing the community to conveniently manage and configure cloud infrastructure using scripts. However, the scripting process itself does not automatically prevent practitioners from introducing misconfigurations, vulnerabilities, or privacy risks. As a result, ensuring security relies on practitioners understanding and the adoption of explicit policies, guidelines, or best practices. In order to understand how practitioners deal with this problem, in this work, we perform an empirical study analyzing the adoption of IaC scripted security best practices. First, we select and categorize widely recognized Terraform security practices promulgated in the industry for popular cloud providers such as AWS, Azure, and Google Cloud. Next, we assess the adoption of these practices by each cloud provider, analyzing a sample of 812 open-source projects hosted on GitHub. For that, we scan each project configuration files, looking for policy implementation through static analysis (checkov). Additionally, we investigate GitHub measures that might be correlated with adopting these best practices. The category Access policy emerges as the most widely adopted in all providers, while Encryption in rest are the most neglected policies. Regarding GitHub measures correlated with best practice adoption, we observe a positive, strong correlation between a repository number of stars and adopting practices in its cloud infrastructure. Based on our findings, we provide guidelines for cloud practitioners to limit infrastructure vulnerability and discuss further aspects associated with policies that have yet to be extensively embraced within the industry.Comment: 50 pages, 13 figures, 10 table

Models for conductor size selection in single wire earth return distribution networks

The use of the ground as the current return path often presents planning and operational challenges in power distribution networks. This study presents optimization-based models for the optimal selection of conductor sizes in Single Wire Earth Return (SWER) power distribution networks. By using mixed integer non-linear programming (MINLP), models are developed for both branch-wise and primary-lateral feeder selections from a discrete set of overhead conductor sizes. The models are based on a mathematical formulation of the SWER line, where the objective function is to minimize fixed and variable costs subject to constraints specific to SWER power flow. Load growth over different time periods is considered. The practical application is tested using a case study extracted from an existing SWER distribution line in Namibia. The results were consistent for different network operating scenarios

Coiling of elastic rods on rigid substrates

We investigate the deployment of a thin elastic rod onto a rigid substrate and study the resulting coiling patterns. In our approach, we combine precision model experiments, scaling analyses, and computer simulations toward developing predictive understanding of the coiling process. Both cases of deposition onto static and moving substrates are considered. We construct phase diagrams for the possible coiling patterns and characterize them as a function of the geometric and material properties of the rod, as well as the height and relative speeds of deployment. The modes selected and their characteristic length scales are found to arise from a complex interplay between gravitational, bending, and twisting energies of the rod, coupled to the geometric nonlinearities intrinsic to the large deformations. We give particular emphasis to the first sinusoidal mode of instability, which we find to be consistent with a Hopf bifurcation, and analyze the meandering wavelength and amplitude. Throughout, we systematically vary natural curvature of the rod as a control parameter, which has a qualitative and quantitative effect on the pattern formation, above a critical value that we determine. The universality conferred by the prominent role of geometry in the deformation modes of the rod suggests using the gained understanding as design guidelines, in the original applications that motivated the study.National Science Foundation (U.S.) (CMMI-1129894

Rising the persian gulf black-lip pearl oyster to the species level: fragmented habitat and chaotic genetic patchiness in Pinctada persica

Marine organisms with long pelagic larval stages are expected to exhibit low genetic differentiation due to their potential to disperse over large distances. Growing body of evidence, however, suggests that marine populations can differentiate over small spatial scales. Here we focused on black-lip pearl oysters from the Persian Gulf that are thought to belong to the Pinctada margaritifera complex given their morphological affinities. This species complex includes seven lineages that show a wide distribution ranging from the Persian Gulf (Pinctada margaritifera persica) and Indian Ocean (P. m. zanzibarensis) to the French Polynesia (P. m. cumingii) and Hawai'i (P. m. galtsoffi). Despite the long pelagic larval phase of P. m. persica, this lineage is absent from continental locations and can only be found on a few islands of the Persian Gulf. Mitochondrial COI-based analyses indicated that P. m. persica belongs to a clearly divergent ESU and groups with specimens from Mauritius (P. m. zanzibarensis). Microsatellite data, used here to assess the spatial scale of realized dispersal of Persian Gulf black-lip pearl oysters, revealed significant genetic structure among islands distant of only a few dozen kilometres. The scantiness of suitable habitats most likely restricted the distribution of this lineage originating the observed chaotic genetic patchiness. The hatchery-based enhancement performed in one of the sampled islands may also have affected population genetic structure. The long-term accumulation of genetic differences likely resulted from the allopatric divergence between P. m. persica and the neighbouring Indian Ocean black-lip pearl oysters

Cross-Validation of Ratings of Perceived Exertion Derived from Heart Rate Target Ranges Recommended for Pregnant Women

International Journal of Exercise Science 13(3): 1340-1351, 2020. Currently, there are no established evidence-based rating of perceived exertion (RPE) targets for physical activity (PA) in pregnant women. Yet, a set of target heart rate (HR) ranges have been recommended. Using the Borg Scale, we aimed to determine and validate the RPE target ranges for different PA intensities derived from the recommended HR ranges in the 2019 Canadian Guideline for PA throughout pregnancy. We assessed 13 pregnant women (age: 31.2 ± 3.5 years; gestational age: 20.5 ± 5.0 weeks) using the following three phases: 1) the incremental submaximal walking test to develop the linear regression equation; 2) establishment of the RPE targets for light- and moderate-intensity PA; 3) moderate-intensity exercise session aiming to cross-validate RPE targets in women whose HR ranges were within (Step 1; six participants; 36 RPE values) or outside (Step 2; seven participants; 42 RPE values) the guideline. Study Phase 1 showed a strong linear relationship between RPE x HR (RPE = -7.370 + 0.155*HR; R2 = 0.863). RPE targets for pregnant women aged ≤ 29 years are 8-12 (light-intensity) and 12-15 (moderate-intensity), respectively. For women aged ≥ 30 years, RPE targets are 8-11 (light-intensity) and 11-14 (moderate-intensity), respectively. The cross-validation suggested no differences between predicted (13.4 ± 0.7) vs. observed RPE (13.3 ± 1.4; p = 0.703) and a strong % agreement (Step 1 = 80.6%; Step 2 = 73.8%) between observed RPE and its predicted range. Thus, we have determined pregnancy-specific, evidence-based RPE targets. These RPE targets will help exercise professionals, other health care providers, and pregnant women to easily monitor exercise intensity during pregnancy to meet recommended Canadian PA Guideline

High-Methoxyl Apple Pectin Improves Rheological Properties and Storage Stability of the Flavored Probiotic Yogurt Drinks, Compared to Pomegranate Pectin

Background and Objective: Use of pectin has attracted interests in food and nutraceutical industries, owing to its positive effects on stability of dairy drinks and potential health benefits to humans. Furthermore, demands for the production of stable fermented milk drinks during storage period is high. Therefore, the aim of this study was to assess effects of apple and pomegranate pectins as stabilizers on various characteristics of probiotic yogurt drinks. Material and Methods: Apple and pomegranate pectins at concentrations of 0-0.5% (w v-1) were added to the probiotic yogurt drinks containing 2% of inulin and 12% of pomegranate juice. Then, rheological behavior, particle size distribution and stability of probiotic yogurt drinks were studied during storage. Results and Conclusion: Control (treatments with no pectin addition) and probiotic yogurt drinks containing pomegranate pectin (0.1-0.5%) showed Newtonian flow behavior and liquid-like behavior over the frequency range. Probiotic yogurt drinks with apple pectin included shear-thinning flow behavior, gel-like network at low frequencies and mean size particle of 50 mm. The highest G' and G" and stabilities during the storage were achieved in samples containing 0.5% of apple pectin. Results demonstrated that apple pectin included great potentials to be used in industrial production of probiotic yogurt drinks as it improved rheological properties and storage stability of the products. Therefore, use of 0.5% apple pectin is suggested in fermented milk drinks. Conflict of interest: The authors declare no conflict of interest