Dynamic instability analysis of U-shaped electromechanical nano-sensor operated in vdW regime

U-shape nanoelectromechanical systems (NEMS) are potential for developing miniature sensors. While the electro-mechanical performance of conventional beam-type NEMS has been exclusively addressed in the literature, few works have considered this phenomenon in U-shaped systems. Herein, the static and dynamic pull-in instability of the U-shaped NEMS is investigated under the presence of vdW force. Based on the recently developed consistent couple stress theory (CCST), the size-dependent constitutive equation is derived. Two types of the beam cross-sections including rectangular and circular geometries are considered. The nonlinear equations are solved by employing Ray-leigh-Ritz solution method. The developed model is validated by comparison with the results presented in literature. The effect of various parameters on the static and dynamic pull-in parameters, phase plans and stability threshold of the system is discussed. The obtained results reveal that the vdW attraction decreases the pull-in voltage while the size dependency enhances the instability voltage. On the other hand, the presented model demonstrates that characteristics of the tip-plate can change the pull-in parameters significantly

Fuzzy Least Squares Twin Support Vector Machines

Least Squares Twin Support Vector Machine (LST-SVM) has been shown to be an efficient and fast algorithm for binary classification. It combines the operating principles of Least Squares SVM (LS-SVM) and Twin SVM (T-SVM); it constructs two non-parallel hyperplanes (as in T-SVM) by solving two systems of linear equations (as in LS-SVM). Despite its efficiency, LST-SVM is still unable to cope with two features of real-world problems. First, in many real-world applications, labels of samples are not deterministic; they come naturally with their associated membership degrees. Second, samples in real-world applications may not be equally important and their importance degrees affect the classification. In this paper, we propose Fuzzy LST-SVM (FLST-SVM) to deal with these two characteristics of real-world data. Two models are introduced for FLST-SVM: the first model builds up crisp hyperplanes using training samples and their corresponding membership degrees. The second model, on the other hand, constructs fuzzy hyperplanes using training samples and their membership degrees. Numerical evaluation of the proposed method with synthetic and real datasets demonstrate significant improvement in the classification accuracy of FLST-SVM when compared to well-known existing versions of SVM

Modeling the effect of microstructure on the coupled torsion/bending instability of rotational nano-mirror in Casimir regime

t has been well-established that the physical performance of nano-devices might be affected by the microstructure. Herein, a 2-degree-of-freedom model based on the modified couple stress elasticity is developed to incorporate the impact of microstructure in the torsion/bending coupled instability of rotational nano-electromechanical mirror. The governing equation of the mirror is derived incorporating the effects of electrostatic Coulomb and corrected Casimir forces with the consideration of the finite conductivity of interacting surfaces. Effect of microstructure-dependency on the instability parameters are determined as a function of the microstructure parameter, bending/torsion coupling ratio, vacuum fluctuation parameter and geometrical dimensions. It is found that the bending/torsion coupling substantially affects the stable behavior of the mirrors especially those with long rotational beam elements. Depending on the geometry and material characteristics, the presented model is able to simulate both hardening behavior (due to microstructure) and softening behavior (due to torsion/bending coupling) of the nano-mirror

A 2-DOF microstructure-dependent model for the coupled torsion/bending instability of rotational nanoscanner

It has been well established that the physical performance of nanodevices might be affected by the microstructure. Herein, a two-degree-of-freedom model base on the modified couple stress theory is developed to incorporate the impact of microstructure in the torsion/bending coupled instability of rotational nanoscanner. Effect of microstructure dependency on the instability parameters is determined as a function of the microstructure parameter, bending/torsion coupling ratio, van der Waals force parameter and geometrical dimensions. It is found that the bending/torsion coupling substantially affects the stable behavior of the scanners especially those with long rotational beam elements. Impact of microstructure on instability voltage of the nanoscanner depends on coupling ratio and the conquering bending mode over torsion mode. This effect is more highlighted for higher values of coupling ratio. Depending on the geometry and material characteristics, the presented model is able to simulate both hardening behavior (due to microstructure) and softening behavior (due to torsion/bending coupling) of the nanoscanners. © 2016, Springer-Verlag Berlin Heidelberg

Preventive effects of Allium hirtifolium Boiss methanolic and aqueous extracts on renal injury induced by lead in rats

Introduction: In this study the kidney protective effects of methanolic and aqueous extracts of Allium hirtifolium Boiss (shallot) were evaluated on kidney toxicity induced by lead (Pb) in Wistar rats. Methods: Eighty adult female Wistar rats of 3–5 months of age and weighing 200–250 g were allocated randomly into 10 groups and treated for 15 and 30 days as follows: control group, Pb (10 mg/L), methanolic extract of shallot (12.5 mg/kg and 25 mg/kg), Pb plus methanolic extract of shallot (12.5 mg/kg and 25 mg/kg), aqueous extract of shallot (12.5 mg/kg and 25 mg/kg), Pb plus aqueous extract of shallot (12.5 mg/kg and 25 mg/kg). Serum concentrations of glucose as well as renal parameters were measured at 15 days and 30 days in the studied groups. Results: Analysis showed a significant reduction in the mean of urea in the methanolic extract group with a concentration of 12.5 mg/kg, compared to the lead group. Consumption of 25 mg/kg methanolic extract of shallot showed a significantly reduction of uric acid, creatinine and total protein in comparison with control group and lead group. Consumption of 25 mg/kg methanolic extract of shallot+lead was able to reduce the mean of urea uric acid, creatinine and total protein in comparison with lead group. Also, the results showed that methanolic extract of shallot+lead at a dose of 12.5 mg/kg could reduce the mean of urea uric acid, creatinine and total protein in comparison with lead group. There was no significant difference in the rest groups. Conclusion: The results of the study showed that shallot extract can dose dependently reduce the factors related to lead induced renal damages

Effect of glycyrrhetinic acid and glycyrrhizic acid on the expression of CXCR4 in epithelial cells of gastric carcinoma

Background and purpose: Gastric cancer is one of the most common cancers and the second common cause of cancer death worldwide. Surgery is the only treatment for gastric cancer but about 50% percent of patients have inoperable tumors. For these patients, combined chemotherapy is the primary treatment which has some side effects. CXCR4 that is expressed on the surface of tumor cells plays a role in metastasis and chemotaxis of tumor cells to different tissues. Licorice compounds are known to have anticancer properties, so this study aimed at investigating their effects on the expression of CXCR4 receptor in gastric cancer AGS cells. Materials and methods: In this experimental study, 106 cells were poured in all wells of 6 pieces plates and exposed to various concentrations of Glycyrrhetinic acid and Glycyrrhizic acid for 24 hours. The CXCR4 gene expression levels were determined by Real−Time PCR and the level of expression in the groups was compared using ANOVA and Dunntt's post hoc test in prism software. P <0.05 was considered as statistically significant. Results: The results showed a significant decrease in CXCR4 gene expression in cells exposed to acid Glycyrrhizic and acid Glycyrrhetinic at 24 hours compared with that of the control group. In fact, decreased expressions of CXCR4 reduced the rates of metastasis and chemotaxis Conclusion: The compounds used in this study reduced the CXCR4 gene expression, so, they could be used as effective treatments for gastric cancer

Effect of the centrifugal force on the electromechanical instability of U-shaped and double-sided sensors made of cylindrical nanowires

The U-shaped and double-sided nanostructures are promising for developing miniature angular speed sensors. While the electromechanical instability of conventional beam-type nanostructures has been extensively addressed in the literature, few researchers have investigated this phenomenon in the double-sided and U-shaped sensors. In this regard, the present work demonstrates the effect of the centrifugal force on the pull-in performance of the double-sided and U-shaped sensors fabricated from cylindrical nanowire and operated in the van der Waals (vdW) regime. Based on the modified couple stress theory, the size-dependent constitutive equations of the sensors are derived. The governing equations are solved by two different approaches, i.e. the analytic Duan–Adomian method and the numerical differential quadrature method. The influences of the vdW and centrifugal forces, geometric parameters and the size phenomenon on the pull-in parameters are demonstrated