a.h. karimi

This research explores the stabilization of clay soil through the application of geopolymer binder derived from silicomanganese slag (SiMnS) and activated by sodium hydroxide (NaOH). This research aims to evaluate the effects of key parameters, including the percentage of slag, the activator-to-stabilizer ratio, and curing conditions (time and temperature), on the mechanical properties of the stabilized soil. Unconfined compressive strength (UCS) tests were conducted to assess improvements in soil strength, while scanning electron microscopy (SEM) was employed to analyze the microstructural changes and stabilization mechanisms. The results demonstrated that clay soil stabilized with SiMnS-based geopolymers exhibited significant strength enhancement. Specifically, the sample stabilized with 20% SiMnS and an activator-to-slag ratio of 1.6, cured at room temperature for 90 days, achieved a UCS of 27.03  kg⁄(cm^2 ). The uniaxial strength was found to be positively correlated with the SiMnS content, activator ratio, curing time, and temperature. Additionally, the strain at failure remained below 1.5% for all samples, indicating a marked improvement in soil stiffness. SEM analysis revealed that geopolymerization led to the formation of a dense matrix, enhancing soil particle bonding and overall durability. These results emphasize the potential of SiMnS-based geopolymers as a sustainable and effective soil stabilizer for geotechnical applications.

Most industrial-practical projects deal with nonlinearity phenomena. Therefore, it is vital to implement a nonlinear method to analyze their behavior. The Finite Element Method (FEM) is one of the most powerful and popular numerical methods for either linear or nonlinear analysis. Although this method is absolutely robust, it suffers from some drawbacks. One of them is convergency issues, especially in large deformation problems. Prevalent iterative methods such as the Newton-Raphson algorithm and its various modified versions cannot converge in certain problems including some cases such as snap-back or through-back. There are some appropriate methods to overcome this issue such as the arc-length method. However, these methods are difficult to implement. In this paper, a computational framework is presented based on meta-heuristic algorithms to improve nonlinear finite element analysis, especially in large deformation problems. The proposed method is verified via different benchmark problems solved by commercial software. Finally, the robustness of the proposed algorithm is discussed compared to the classic methods.

Most industrial-practical projects deal with nonlinearity phenomena. Therefore, it is vital to implement a nonlinear method to analyze their behavior. The Finite Element Method (FEM) is one of the most powerful and popular numerical methods for either linear or nonlinear analysis. Although this method is absolutely robust, it suffers from some drawbacks. One of them is convergency issues, especially in large deformation problems. Prevalent iterative methods such as the Newton-Raphson algorithm and its various modified versions cannot converge in certain problems including some cases such as snap-back or through-back. There are some appropriate methods to overcome this issue such as the arc-length method. However, these methods are difficult to implement. In this paper, a computational framework is presented based on meta-heuristic algorithms to improve nonlinear finite element analysis, especially in large deformation problems. The proposed method is verified via different benchmark problems solved by commercial software. Finally, the robustness of the proposed algorithm is discussed compared to the classic methods.

In breast radiotherapy, enhanced dynamic wedge (EDW) and physical wedges are used to improve the homogeneity of the dose. Scattered photons are the major factor in the off-field organs' unwanted dose. In breast radiotherapy, the thyroid is a critical off-field organ at risk for scattered photons. This study was performed to compare the unwanted dose and the secondary fatal cancer risk to the thyroid in breast radiotherapy between EDW and physical wedge.

The 6-MV Varian 2100 C/D linac was used to irradiate the breast of a thorax phantom under two opposite tangential fields. The unwanted dose that reached the thyroid was estimated using Eclipse Treatment Planning System and Gafchromic film dosimetry. Corresponding fatal secondary cancer risks were also assessed according to the NCRP report 116 recommendations.

The measured dose for thyroid using a physical wedge and enhanced dynamic wedge were measured as 2.1 and 0.735 cGy, which are approximately 1% and 0.37% of the prescribed dose to the breast (2 Gy), respectively. In the case of radiotherapy with the physical wedge, the lifetime risk of secondary fatal cancer attributed to the thyroid is 0.0480 and 0.0504 % using TPS and measured data, respectively. In the case of the dynamic wedge, the above values were reduced to 0.0168 and 0.0176 %, respectively.

Using an enhanced dynamic wedge in breast radiotherapy reduced the thyroid dose by about 65% compared to the physical wedge technique. As a result, it was concluded that the application of EDW is safer than the physical wedge in breast radiotherapy.

One of the common problems in the implementation of concrete structures is seam or cold joint. The discontinuity in concrete body can cause structural weakness, increased permeability, reduced durability, corrosion of the rebar, and bad appearance of concrete. In this study, in order to evaluate the effect of cold joint on compressive strength of concrete, 192 cubic samples by national method of mix design in 4 modes, in which 48 samples without cold joint, 48 samples with horizontal cold joint, 48 samples with vertical cold joint, and 48 samples with diagonal cold joints were concreted in a 24-hour time interval. After 28 days of treatment with standard conditions by pressure cylinder device, the compressive strength of the samples was evaluated. After evaluating the results of the experiments, the values of the effect of cold joint on the compressive strength of the samples, the uncertainty and the probability of failure of the samples have been investigated. The results of analyzes indicate that, generally, the creation of a cold joint in concrete reduces the compressive strength of concrete. However, the reduction in compressive strength depends on the degree of cold joint to its angle. Also, the size of surface angle of the cold joint is also affected by the probability of failure.

A new hydroxylamine sensor has been fabricated by immobilizing oxadiazol denvative at the surface ol aglassy carbon electrode (GCE) modified by multi-wall carbon nanotube (MIVCNT). The adsorbed thin Illms oroxadiazol derivative on the MWCNT modified GCE show a pair of peaks with surface confined characierisnus.The oxadiazol derivative MWCNI (OMWCNT) modified GCE shows highly catalytic activity togurdelectrooxidation of hydroxylamine. The results show that the peak potential of hydroxylamine at OMWCNTmodified GCE surface shifted by about 331 and 346 my toward nevative values compared with those orMIVCNT and activated OCE surface. respectively. In addition. the sensitivity of hydroxylamine determinationis improved remarkably by OMWCNT modified electrode. The kinetic parameters, such as the electron transfercoefficient, a. the standard heterogencouq rate constant, kg and exchange current. i0, for oxidation orhydroxylamtne at the OMWCNT modified GCE (041WCH1-GCE) were determined by cyclic voltainmcirymeasurements. Also &fusion coefficient of hydroxylamine was determined as 4.05 g l0 ctn2 s I by usiagchronoamperometry technique. Furthermore, the linear dynamic range (2 0-600.0 pM), sensitivity and detectionlimit (0.61 pM) for hydroxylamine determination was evaluated using differential pulse voltammary. Excellentelectrochemical reverkibility of the redox couple. technical simplicity, good electrocatalytic activity forhydros ylamine and good reproducibility are the advantages of this modified electrode. ginally. the activi” ofOAIWCNT-UCE ...as also investigated for hydroxylamine determinatm on in two natural water samples.