Effect of Semi-Rigid Connection on Post-Buckling Behaviour of Frames Using Finite Element Method

It is very important task to estimate the post buckling for structures that have slender elements, since post-buckling state means loss the structures stability related with large displacement and that lead to demolition the structures. On the other hand, in the design and analysis of steel frame, the beam-columns connection is assumed perfect pin or fully rigid, this assumption leads to incorrect estimation of the structural behaviour. Practically, beam-column connection is between these two assumptions and this type of connection is called semi-rigid. This study presents a numerical analysis using finite element method to investigate the effect of semi-rigid connections on post-buckling behaviour of two-dimensional frames with different supporting types and different lateral loading cases. The semi-rigid connections are modelled as rotational spring in linear elastic stage, using COMBIN14 element which has rotational stiffness value.  The numerical results showed that; the effect of changing the beam-column connections from rigid to semi rigid for toggle frame with rotational joint stiffness 25EI/L to 15EI/L and 10EI/L led to decrease the initial peak load of the frames of fixed-fixed supports with percentages 3.36 %, 5.6% and 8.95% respectively as compared with that of the rigid connection frame, While, the frames with fixed-pin and pin-pin supports cases did not affected by this changing. The fixed-fixed support case is more affected by changing the joint stiffness from other cases and the effect of changing the joint stiffness in pin-pin support model is less significant from others. This can be attributed to that, the fixed-fixed supports is restrained in all degree of freedom and will be affected by any rotation and presence the pin in other cases makes the frame less affected by the rotation of semi-rigid connection. The effect of changing the beam-column connection from rigid to semi rigid decreases with presence the lateral load. Thus, the semi-rigid connection should be considered in analysis and design of steel frames to obtain more realistic results

New Concrete Technology Negates Traditional Concrete Placement in Sudan

Self-consolidating concrete, also known as self-compacting concrete (SCC), is an innovative concrete that does not require vibration for placing and compaction. The mixture qualification process of Self Compacting Concrete consists from a small, well controlled laboratory batches are tested, second, the closest mixture/s is tested in production, which includes the use of batch mixing, and placing equipment, and finally a quality assurance/control plan for the fresh and hardened properties is developed. However, this paper presents a full research addressed only a small, well controlled laboratory batches and the laboratory testing phase of the mixture qualification process. For the purpose of study, a small, well controlled laboratory batches are tested using available locally aggregates in Sudan. Therefore, Slumpflow, V-funnel, L-box shape, J-ring, and Sieve stability tests of concrete mixtures were used to determine the flowability, passing ability and segregation resistance of SCC mixtures. The produced self compacting concrete is successfully confirmed the fresh properties of SCC with Slumpflow in range of 650 to 850 mm with high viscosity and excellent segregation resistance. The hardened properties of concrete were also considered and tested. The strength of SCC was found to be same or higher than that of normally vibrated concrete with the same constituent materials. SCC has relatively higher dynamic modulus of elasticity ranged between 38 to 42 GPa, in comparison to normally vibrated concrete for the same strength range of 50 to 60 MPa. Whereas the Spilt Tensile and Flexural strength of SCC are of 2.5 MPa and 10 MPa respectively. The major difficulty which was faced in development of SCC was on account of contradictory factors that the concrete should be fully flowable but without bleeding or segregation. It is required that the cement mortar of the SCC should have higher viscosity to ensure flowability while maintaining non-sedimentation of aggregates and that was achieved by using high content of powder (fine materials less than 0.15 mm includes cementitious materials). Achievement of durable concrete structures independent of the quality of construction work by using Self Compacting Concrete (SCC) has been proposed to solve the problem of the durability of concrete structures due to the gradual reduction of adequate compaction and skilled workers and for complex shape for the prestressed and precast industries in Sudan. The features of high benefit of fluidity and self consolidation will result in a variety of potential benefits for the end-user. Other benefits of the application of this new concrete technology require effort to be achieved. Moreover, areas such as quality control, mixture development, and logistics may need modification or expand resources when develop self-compacting concrete in Sudan. Keywords: Self Compacting Concrete (SCC), Sudan, Flowability, Passing ability, Segregation Resistance Slumpflow, V-funnel, L-box shape, J-ring, and Sieve stability, Powder conten

Investigating the Time-dependent and the Mechanical Behavior of Wood Plastic Composite Lumber Made from Thermally Modified Wood in the Use of Marine Aquacultural Structures

Wood Plastic Composite (WPC) lumber based on a patent-pending formulation is being explored for use in the manufacture of an aquaculture fish cage structure (Aquapod net pen cage), as an alternative to the current high density polyethylene (HDPE) lumber. The use of WPC lumber in structural applications in marine environments requires a comprehensive effort to understand the material viscoelastic behavior and the structural performance of the WPC lumber in marine environments where the WPC lumber is exposed to the combined effect of saltwater immersion and temperature (hygrothermal). The evaluation of the viscoelastic behavior of WPC lumber in marine environments was conducted through series of short-term of dynamic mechanical and thermal analysis (DMTA) creep and creep-recovery experiments, where the WPC specimens were preconditioned and tested under the combined effect of temperature and water immersion at different target levels of stress. Long-term creep experiments of WPC and HDPE lumber under the same controlled conditions and stress levels are necessary to evaluate and compare the viscoelastic behavior of WPC and HDPE lumber. An understanding of the structural behavior of WPC lumber in an aquaculture structure was advanced through testing components (triangular panels) from a spherical shape geodesic frame (Aquapod) structure made from WPC and HDPE lumber, respectively. The hygrothermal viscoelastic response of WPC lumber was characterized and modeled. The experiments included measuring 30 minutes of creep and 30 minutes of creep-recovery on the specimens immersed in saltwater and distilled water at two different levels of flexural stresses (9% and 14% of the ultimate flexural strength, Fb) and three temperature values (25, 35, and 45°C). The creep strain fractional increment (CSFI) of the WPC in this study under all conditions was 86% lower than the CSFI of the WPCs reported in previous studies. The WPC material in this study exhibited linear viscoelastic and nonlinear viscoelastic behavior based on the effect of temperature only, and the combined temperature and water immerstion effect, respectively. The 180-day creep behavior of the WPC and HDPE lumber in flexure was characterized and compared for WPC and HDPE lumber (with 853 mm support span) subjected to three levels of creep stress: 7.5, 15, and 30% of the ultimate flexural strength (Fb). The 180-day creep deformation of HDPE specimens was six times higher than the creep deformation of WPC specimens at the 30% creep stress level. A power law model was used to describe 180-day creep deflection of WPC lumber beams. Modeling results predicted that the strain to failure in the HDPE and WPC lumber would occur in 1.5 years and 150 years at a flexural stress of 30% Fb, respectively. A pair of connected triangular panels of the Aquapod structure with and without wire mesh made from WPC and HDPE lumber were tested in compression to evaluate and compare the buckling capacity of the panels, respectively

Entropy generation minimization for enhancing the fluid recovery and energy efficiency in petroleum reservoirs

Hydrocarbon reservoir fluids usually contain a significant amount of mechanical energy that depends on the distribution of temperature and pressure throughout the reservoir. A fraction of the fluid's useful energy is lost during the irreversible processes that occur throughout the production life of the reservoir. Entropy generation (or production) can characterize this loss of useful energy in petroleum reservoirs. A petroleum engineer can develop an appropriate production strategy that minimizes entropy production in a reservoir to promote the efficient use of the reservoir energy. The design of a poor reservoir production system might result in a short-lived production well, low reservoir recovery factor, and inefficient use of available resources. Such an issue would not only result in the loss of a valuable portion of the reservoir's useful energy but also financial benefits. Various forms of energy exchange occur during hydrocarbon production in reservoirs, e.g., fluid and rock expansion, fluid flow, gravity drainage, and compaction of poorly consolidated rocks. During a reservoir's production lifetime, irreversible processes (e.g., fluid friction and heat transfer) lead to waste of energy, reducing the overall system's operational efficiency. Therefore, there is a desire to select an appropriate design that minimizes the entropy generation. In this thesis, we investigate the effect of essential factors such as reservoir formation, reservoir fluids, and production rate on entropy generation. The ultimate goal is to design a reservoir production strategy using the entropy generation analysis such that the production efficiency can be maximized. To simulate the fluid flow behavior of a reservoir system, a pseudo-steady flow state is developed in this thesis for single-phase (dry gas) and two-phase (oil-water) flow models in both the wellbore and reservoir. The effect of the wellbore conditions on the single-phase models is investigated and analyzed. One-dimensional flow is assumed in the wellbore, whereas radial flow occurs in the reservoir. Mass, momentum, energy, and entropy balance equations, including a method of Entropy Generation Minimization (EGM), are used to address the fluid flow behavior and energy loss in wellbore and reservoir systems. For a single-phase flow, the near-wellbore region is investigated and considered to be a separate zone for model development, which allows flexibility in modelling skin effects near the wellbore. Numerical methods are used to solve the fluid flow and entropy equations. The models are solved by a numerical scheme programmed in the MATLAB environment with an appropriate algorithm. For validation purposes, a commercial simulator, Computer Modeling Group (CMG), is used to verify the predicted results. A new production performance criterion called the Coefficient Of Performance (COP) is introduced. The COP integrates the recovery factor with entropy generation and provides a quantitative measure to optimize reservoir production. The models are used to conduct a parametric sensitivity analysis that includes the effects of fluid and rock parameters, such as permeability, porosity, viscosity, skin factor, Bottom Hole Pressure (BHP), wettability, and temperature on the total entropy production. The COP is used to optimize the operating conditions of the reservoir, such as the production rates and BHP. It is found that permeability and BHP have the most impact on the total entropy production for single-phase models. Concurrently, temperature and wettability are essential factors for two-phase flow models. This thesis enhances the understanding of reservoir energy analysis and provides more accurate models for calculating the optimum production rate of a given reservoir. In particular, the results presented in this thesis will impact production history calculations and reservoir simulation results. Furthermore, this research provides practitioners and engineers in the petroleum industry with a useful alternative approach for maximizing recovery efficiency by minimizing entropy generation

The Anti-Inflammatory Cytokine, Interleukin-10, Inhibits Inflammatory Mediators in Human Epithelial Cells and Mouse Macrophages Exposed to Live and UV-Inactivated Chlamydia trachomatis

Chlamydia trachomatis infects macrophages and epithelial cells evoking acute and chronic inflammatory conditions, which, if not controlled, may put patients at risk for major health issues such as pelvic inflammatory disease, chronic abdominal pain, and infertility. Here we hypothesized that IL-10, with anti-inflammatory properties, will inhibit inflammatory mediators that are produced by innate immune cells exposed to C. trachomatis. We used human epithelial (HeLa) cells and mouse J774 macrophages as target cells along with live and UV-inactivated C. trachomatis mouse pneumonitis (MoPn) as stimulants. Confocal microscopy employing an anti-Chlamydia antibody confirmed cells infectivity by day 1, which persisted up to day 3. Kinetics studies revealed that live C. trachomatis induced TNF, IL-6, and IL-8, as a function of time, with day-2 infection inducing the highest cytokine levels. Exogenous IL-10 inhibited TNF, IL-6, and IL-8 as secreted by day-2 infected cells. Similarly, IL-10 diminished cytokine levels as produced by macrophages exposed to UV-inactivated Chlamydia, suggesting the IL-10-mediated inhibition of cytokines is not restricted to live organisms. Our data imply that IL-10 is an important regulator of the initial inflammatory response to C. trachomatis infection and that further investigations be made into IL-10 use to combat inflammation induced by this bacterium

Excessive adventitial stress drives inflammation-mediated fibrosis in hypertensive aortic remodelling in mice

Hypertension induces significant aortic remodeling, often adaptive but sometimes not. To identify immuno-mechanical mechanisms responsible for differential remodeling, we studied thoracic aortas from 129S6/SvEvTac and C57BL/6J mice before and after continuous 14-day angiotensin II infusion, which elevated blood pressure similarly in both strains. Histological and biomechanical assessments of excised vessels were similar at baseline, suggesting a common homeostatic set-point for mean wall stress. Histology further revealed near mechano-adaptive remodeling of the hypertensive 129S6/SvEvTac aortas, but grossly maladaptive remodeling of C57BL/6J aortas. Bulk RNA sequencing suggested that increased smooth muscle contractile processes promoted mechano-adaptation of 129S6/SvEvTac aortas while immune processes prevented adaptation of C57BL/6J aortas. Functional studies confirmed an increased vasoconstrictive capacity of the former while immunohistochemistry demonstrated marked increases in inflammatory cells in the latter. We then used multiple computational biomechanical models to test the hypothesis that excessive adventitial wall stress correlates with inflammatory cell infiltration. These models consistently predicted that increased vasoconstriction against an increased pressure coupled with modest deposition of new matrix thickens the wall appropriately, restoring wall stress toward homeostatic consistent with adaptive remodeling. In contrast, insufficient vasoconstriction permits high wall stresses and exuberant inflammation-driven matrix deposition, especially in the adventitia, reflecting compromised homeostasis and gross maladaptation

Deep-learning based recommenders for the improved user navigation in VR

Virtual reality (VR) has become a popular choice for education, industrial simulation, entertainment and healthcare applications. User navigation is an essential propriety of virtual applications. However, novice audiences often face the difficulty of engaging with the virtual surrounding environment. This work presents a novel design of a deep learning-based navigation solution to improve the quality of user experience and the engagement with virtual content. We compare two navigation methods avatar-based and arrows-based guidance, both of which are driven by a recurrent neural network (RNN) model. We capture participants’ mobility and eye-gaze to compare the impact of different navigation affects on users’ engagement in VR applications

Paradoxical aortic stiffening and subsequent cardiac dysfunction in Hutchinson-Gilford progeria syndrome

[EN] Hutchinson-Gilford progeria syndrome (HGPS) is an ultra-rare disorder with devastating sequelae resulting in early death, presently thought to stem primarily from cardiovascular events. We analyse novel longitudinal cardiovascular data from a mouse model of HGPS (Lmna(G609G/G609G)) using allometric scaling, biomechanical phenotyping, and advanced computational modelling and show that late-stage diastolic dysfunction, with preserved systolic function, emerges with an increase in the pulse wave velocity and an associated loss of aortic function, independent of sex. Specifically, there is a dramatic late-stage loss of smooth muscle function and cells and an excessive accumulation of proteoglycans along the aorta, which result in a loss of biomechanical function (contractility and elastic energy storage) and a marked structural stiffening despite a distinctly low intrinsic material stiffness that is consistent with the lack of functional lamin A. Importantly, the vascular function appears to arise normally from the low-stress environment of development, only to succumb progressively to pressure-related effects of the lamin A mutation and become extreme in the peri-morbid period. Because the dramatic life-threatening aortic phenotype manifests during the last third of life there may be a therapeutic window in maturity that could alleviate concerns with therapies administered during early periods of arterial development.This work was supported, in part, by grants from the US National Institutes of Health: R01 HL105297 (J.D.H.) and P01 HL134605 (Dan Rifkin) and R01 AG047632 and R33 ES025636 (G.S.S.)Murtada, SI.; Kawamura, Y.; Caulk, AW.; Ahmadzadeh, H.; Mikush, N.; Zimmerman, K.; Kavanagh, D.... (2020). Paradoxical aortic stiffening and subsequent cardiac dysfunction in Hutchinson-Gilford progeria syndrome. Journal of The Royal Society Interface. 17(166):1-12. https://doi.org/10.1098/rsif.2020.00661121716

The prevalence of polypharmacy and hyper-polypharmacy among middle-aged vs. older patients in Saudi Arabia: a cross-sectional study

IntroductionPolypharmacy, the use of multiple medications, is a growing concern among middle-aged and older patients, posing potential risks and challenges in healthcare management.AimThis study aimed to identify the prevalence of polypharmacy and hyper-polypharmacy among populations of middle-aged vs. older patients and identify its associated common comorbidities and prescribed medications in Qatif Central Hospital (QCH), Saudi Arabia.MethodsPatients aged 40 years or older who presented to an outpatient medical care clinic at QCH, Saudi Arabia, between 1 January and 31 December 2021 were included, and their comorbidities, prescribed medications, and recent clinical laboratory test results were collected. The Charlson comorbidity index (CCI) score was calculated to predict the risk of mortality. Logistic regression was used to compute the association between the prevalence of polypharmacy and patient characteristics. The results were presented as odds ratios (ORs) and 95% confidence intervals (95% CIs).ResultsA total of 14,081 patients were included; 31% of the cohort comprised older patients, and 66% of the cohort was identified with polypharmacy. The majority of the polymedicated patients were presented to an internal medicine care unit (34%). The prevalence of polypharmacy was positively associated with CCI (OR = 3.4, 95% CI 3.3–3.6), having a disease related to the musculoskeletal system (MSD) (OR = 4.2, 95% CI 3.8–4.7), and alimentary tract and metabolism (ATM) (OR = 3.8, 95% CI 3.4–4.2). Conversely, the prevalence of polypharmacy was negatively associated with age (OR = 0.9, 95% CI 0.89–0.91) and patients with cardiovascular diseases (OR = 0.6, 95% CI 0.5–0.7).ConclusionPolypharmacy is still an ongoing concern. Patients, particularly those with diseases related to MSD or ATM, should be considered for reviewing prescriptions by pharmacists to reduce the risk of adverse drug reactions and future consequences of polypharmacy