Stable PDE Solution Methods for Large Multiquadric Shape Parameters

We present a new method based upon the paper of Volokh and Vilney (2000) that produces highly accurate and stable solutions to very ill-conditioned multiquadric (MQ) radial basis function (RBF) asymmetric collocation methods for partial differential equations (PDEs). We demonstrate that the modified Volokh-Vilney algorithm that we name the improved truncated singular value decomposition (IT-SVD) produces highly accurate and stable numerical solutions for large values of a constant MQ shape parameter, c, that exceeds the critical value of c based upon Gaussian elimination

A Fast Adaptive Wavelet Scheme in RBF Collocation for Nearly Singular Potential PDEs

We present a wavelet based adaptive scheme and investigate the efficiency of this scheme for solving nearly singular potential PDEs. Multiresolution wavelet analysis (MRWA) provides a firm mathematical foundation by projecting the solution of PDE onto a nested sequence of approximation spaces. The wavelet coefficients then were used as an estimation of the sensible regions for node adaptation. The proposed adaptation scheme requires negligible calculation time due to the existence of the fast DiscreteWavelet Transform (DWT). Certain aspects of the proposed adaptive scheme are discussed through numerical examples. It has been shown that the proposed adaptive scheme can detect the singularities both in the domain and near the boundaries. Moreover, the proposed adaptive scheme can be utilized for capturing the regions with high gradient both in the solution and its spatial derivatives. Due to the simplicity of the proposed method, it can be efficiently applied to large scale nearly singular engineering problems

Wavelet based Adaptive RBF Method for Nearly Singular Poisson-Type Problems on Irregular Domains

We present a wavelet based adaptive scheme and investigate the efficiency of this scheme for solving nearly singular potential PDEs over irregularly shaped domains. For a problem defined over Ω ∈ ℜd, the boundary of an irregularly shaped domain, Γ, is defined as a boundary curve that is a product of a Heaviside function along the normal direction and a piecewise continuous tangential curve. The link between the original wavelet based adaptive method presented in Libre, Emdadi, Kansa, Shekarchi, and Rahimian (2008, 2009) or LEKSR method and the generalized one is given through the use of simple Heaviside masking procedure. In addition level dependent thresholding were introduced to improve the efficiency and convergence rate of the solution. We will show how the generalized wavelet based adaptive method can be applied for detecting nearly singularities in Poisson type PDEs over irregular domains. The numerical examples have illustrated that the proposed method is powerful to analyze the Poisson type PDEs with rapid changes in gradients and nearly singularities

A Stabilized RBF Collocation Scheme for Neumann Type Boundary Value Problems

The numerical solution of partial differential equations (PDEs) with Neumann boundary conditions (BCs) resulted from strong form collocation scheme are typically much poorer in accuracy compared to those with pure Dirichlet BCs. In this paper, we show numerically that the reason of the reduced accuracy is that Neumann BC requires the approximation of the spatial derivatives at Neumann boundaries which are significantly less accurate than approximation of main function. Therefore, we utilize boundary treatment schemes that based upon increasing the accuracy of spatial derivatives at boundaries. Increased accuracy of the spatial derivative approximation can be achieved by h-refmement reducing the spacing between discretization points or by increasing the multiquadric shape parameter, c. Increasing the MQ shape parameter is very computationally cost effective, but leads to increased ill-conditioning. We have implemented an improved version of the truncated singular value decomposition (IT-SVD) originated by Volokh and Vilnay (2000) that projects very small singular values into the null space, producing a well conditioned system of equations. To assess the proposed refinement scheme, elliptic PDEs with different boundary conditions are analyzed. Comparisons that made with analytical solution reveal superior accuracy and computational efficiency of the IT-SVD solutions

Investigation of Traffic Load on the Buried Pipeline by Using of Real Scale Experiment and Plaxis-3D Software

Abstract: In some cases, traffic load are effected pipelines so in this study, effects of truckload on the buried pipeline were done with numerical and experimental methods. In numerical method, model is assumed half extreme and length of them are considered extreme, mathematically. For performing of numerical method, 3D model were used in Plaxis-3D software. For comparison and checking of results, Experimental model was prepared and with using of electrical strain gages and computer, results of experimental model were recorded. Results show experimental and finite element models are compatible. In continue, effects of other parameters are studied with Plaxis-3D software

Is prior use of renin-angiotensin system (RAS) inhibitors associated with more favourable outcome in COVID-19 hospitalized patients?

Objective: We aimed to investigate the extent of pulmonary involvement and adverse outcomes in patients receiving angiotensin-converting enzyme inhibitor (ACEI)/ angiotensin II receptor blocker (ARB) versus who did not, in hospitalized coronavirus infectious disease 2019 (COVID-19) patients. Methods: All COVID-19 patients with a positive polymerase chain reaction (PCR) test, who were admitted to our tertiary referral hospitals in Tehran, Iran between January 2021 and May 2021, and had an on-admission chest computed tomography (CT) scan, were included. The patients were divided into two groups (receiving ACEI/ARB and who did not) for further analysis. The outcomes of interest in our study were the extent of pulmonary involvement, intensive care unit (ICU) admission, and death. Results: A total of 893 participants (mean age of 58.6±15.4 years; female, 522 (58.4%)) were enrolled. Among them, 368 (41.2%) participants had hypertension, and use of ACEI/ARB was reported in 183 (20.5%) participants. Of all, 409 (45.8%) participants required ICU admission, and 259 (29%) participants succumbed to death. We found that participants who received ACEI/ARB were less likely to progress critical disease and experienced significantly lower ICU admission (P=0.022) and death (P<0.001). On multivariable analysis adjusting for age, sex, and comorbidities, this relationship remained statistically significant for death [OR: 0.23 (0.14-0.38); P<0.001] and ICU admission [OR: 0.49 (0.32-0.73); P=0.001]. Conclusion: Our findings showed that COVID-19 patients who receiving ACEI/ARB prior to hospitalization vs. those who did not, had more favorable outcomes

Radioprotective effects of Silymarin on the sperm arameters of NMRI mice irradiated with γ-rays.

Free radicals and reactive oxygen species (ROS) are generated using various endogenous systems or from external sources such as exposure to different physiochemicals. Ionizing radiation damage to the cell can be caused by the direct or indirect effects of radiotherapy processes. Silymarin (SM), a flavanolignan compound, has been identified as a natural potent antioxidant with cytoprotection activities due to scavenging free radicals. The aim of the present study was to evaluate the radioprotective effect of SM on sperm parameters of mice induced by γ-rays. A total number of 40 adult, male NMRI mice were randomly divided into four equal groups. The control group was neither treated with SM nor irradiated by γ-rays. The second group was only irradiated with 2Gy of γ-rays. The third group was firstly treated with 50mg/kg of SM for 7 consecutive days, and one day later, last injections were irradiated by 2Gy of γ-rays. The fourth groups received only 50mg/kg of SM for 7 consecutive days. All the animals were treated intraperitoneally. Histopathological and morphometrical examinations were performed. The data were analyzed using ANOVA and Tukey post hoc test. A value of p<0.05 was considered significant. The results showed that in the radiation-only group when compared with those treated with SM and irradiated, a significant different was observed in testicular parameters and DNA damage (p<0.05). In conclusion, SM can be considered as a promising herbal radioprotective agent in complementary medicine which may play an important role to protect normal spermatocytes against possible effects of γ-radiation-induced cellular damage

Application of the oxycodone templated molecular imprinted polymer in adsorption of the drug from human blood plasma as the real biological environment; a joint experimental and density functional theory study

In this project, we have synthesized and used a molecular imprinted polymer (MIP) for adsorption of oxycodone residue from the biological samples. Indeed, this study aims to develop a suitable method for determination of oxycodone drug residue in the human plasma using the common analysis methods. Therefore, the MIP was used for the solid phase extraction (MIP-SPE) approach in order to collect the oxycodone opioid and to concentrate it in the blood plasma samples. The extraction parameters such as adsorption time, pH, and the amount of sorbent in blood plasma were optimized and the capacity of loading amount (LA) for adsorbing it was determined. Moreover, a high performance liquid chromatography (HPLC)-UV detector method was validated and used for analyzing of the mentioned opioid extracted from plasma. The results showed that the limit of detection (LOD), and the limit of quantization (LOQ) for the developed MIP-SPE method were 1.24 ppb, and 3.76 ppb, respectively. Moreover, both of the MIP-, and non-imprinted polymers (NIP)-drug complexes were designed and were then optimized by the density functional theory (DFT) method. The results showed that the theoretical calculations supported the experimental data, confirming the favorability of adsorption of the drug by MIP compared to NIP

Linking Stability Characteristics to Material Performance of Self-consolidating Concrete-equivalent-mortar Incorporating Fly Ash and Metakaolin

Properly designed self-consolidating concrete (SCC) should have high deformability while maintaining high stability to secure homogeneous properties of hardened concrete. This paper aims at correlating the stability characteristics to material performance of self-consolidating concrete-equivalent-mortars (SCCEMs) made with various binary and ternary cement blends of fly ash (FA) and metakaolin (MK). The stability characteristics of the mixtures were determined using mini-column segregation, mini V-funnel flow time, visual stability index (VSI), and hardened visual stability index (HVSI) to assess both static and dynamic stability. A response surface method (RSM) was conducted to mathematically evaluate the level of significance of mixture parameters and their coupled interactions on the performance of SCCEMs. Trade-off contour diagrams between investigated mixture constituents and the modeled responses were illustrated. Test results indicate that binder composition have substantial influence on dynamic and static stability. Based on the established correlation between stability and overall performance, SCCEMs with a higher segregation index (SI) values are expected to have lower fresh and hardened properties. A ternary combination of 25% FA and 25% MK with a SI value of 5 achieved the highest overall material performance among the tested binary and ternary cementitious systems. The slump flow and V-funnel flow time tests are shown to be an efficient tool for controlling static segregation of mixtures. Mixtures with higher level of fluidity and lower flow time exhibited lower segregation resistance