Generalized 3D high cycle fatigue criteria for multiscale bridging‐based progressive damage analysis of multilayer composite parts under random loads and material deterioration

Two frameworks are employed to develop two distinct categories of multiaxial high cycle fatigue life assessment models for composite components experiencing general and random loading conditions. In this regard, the decay in the material properties with cycles is also taken into account. It is obvious that in multilayer components, the fatigue failure is a progressive process that may be accompanied by gradual or sudden changes in the material properties and, consequently, the resulting stresses. In addition to using the traditional progressive damage analyses, a new concept is proposed for tracing of the localized fatigue failures more accurately. It is postulated that generally, the stress components have distinct frequencies, phase shifts, and mean values that all vary with time in a random manner. The proposed fatigue criteria, especially, the equivalent‐stress–based ones, are capable of predicting various fatigue failure modes, such as the fibre breakage, matrix cracking, and interfacial debonding. A special and comprehensive fatigue failure tracking and cycle counting algorithms that are capable of handling the mentioned general peculiarities are proposed. The proposed HCF criteria and the relevant fatigue life assessment algorithm are then implemented on a composite multilayer mono‐leaf spring of a realistic vehicle under a random field‐measured loading condition, as a typical component, and the results are compared and the experimental results conducted by the authors, for accuracy investigations. The considered stochastic road inputs have been chosen on the basis of the consumption times and field measurements.     

Pricing and ordering decisions in a supply chain with imperfect quality items and inspection under buyback of defective items

In this article, the economic production and inventory model in a three-layer supply chain including one distributor, one manufacturer and one retailer for a single-product and general demand functions under three scenarios is developed. We assume that during the production process, both healthy and defective items are generated. As the first scenario, we develop the first model, in which the defective items are not reworked and all considered as scrape, while in the second model, we assume that the defective items are reworked and are sold as perfect item. In the second scenario, we assume that defective item can be sold with lower price than the selling price. Moreover, raw materials with imperfect quality are sent back from a distributor to outside supplier under a lower price. Determining the order quantity of the distributor and the selling prices of the distributor and the manufacturer as well as the retailer was the goal of this article such that the total profit of each member is maximised. In order to solve the models, the Stackelberg approach is employed between the members, and the concavity of the profit functions is proved using several theorems. Then, closed form solutions are derived for the decision variables and a solution algorithm is proposed to determine the optimal solutions. Finally, a numerical example is presented to illustrate the applicability of the model.     

Nonlocal and surface effects on the buckling behavior of flexoelectric sandwich nanobeams

In this article, an analytical approach is presented to study the surface and flexoelectric effects on the buckling characteristics of an embedded piezoelectric sandwich nanobeam. According to the nonlocal elasticity theory, the flexoelectricity is believed to be authentic for size-dependent properties in nanostructures. The boundary conditions and the governing equations are derived by Hamilton's principle and are solved by Navier method. The results obtained from the present work show that the nonlocal term has an important reduction on the critical load and also the flexoelectricity shows an increasing influence on the buckling loads of the sandwich nanobeam, especially at lower thicknesses.     

Preparation and Antibacterial Activity of Three-component NiFe204@PANI@Ag Nanocomposite

A new three-component and magnetically responsive NiFe2O4@PANI@Ag nanocomposite has been fabricated by coating of nickel ferrite, NiFe2O4, nanoparticles with polyaniline （PANI） and subsequent immobilization of silver nanoparticles onto the surface of polyaniline shell. The as-prepared nanocomposite has been characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FT-IR）, scanning electron microscopy （SEM）, and vibrating sample magnetometer （VSM）. The saturation magnetization of the NiFe2O4 core decreases dramatically after coating with polyaniline and silver nanoparticles, however, the nanocomposite NiFe2O4@PANI@Ag can be still separated from solution media through magnetic decantation. The antibacterial activity of the synthesized nanocomposite was studied and compared with those of naked NiFe2O4, NiFe2O4@PANI and some standard antibacterial drugs.     

Local Insulin-Derived Amyloidosis Model Confronted with Silymarin: Histological Insights and Gene Expression of MMP,TNF-α, and IL-6

Amyloidosis is a heterogeneous group of protein deposition diseases associated with the presence of amyloid fibrils in tissues. Analogs of insulin that are used for treating diabetic patients (including regular insulin) can form amyloid fibrils, both in vitro and in vivo as reported in patients. The main purpose of this study was the induction of localized insulin-generated amyloidosis and the observation of silymarin effects on this process. In order to obtain amyloid structures, regular insulin was incubated at 37 °C for 24 h. Congo red absorbance and transmission electron microscopy images validated the formation of amyloid fibrils. Those fibrils were then injected subcutaneously into rats once per day for 6, 12 or 18 consecutive days in the presence or absence of silymarin, and caused development of firm waxy masses. These masses were excised and stained with Hematoxylin and Eosin, Congo red and Thioflavin S. Histological examination showed adipose cells and connective tissue in which amyloid deposition was visible. Amyloids decreased in the presence of silymarin, and the same effect was observed when silymarin was added to normal insulin and injected subsequently. Furthermore, plasma concentrations of MMP2, TNF-α, and IL-6 inflammatory factors were measured, and their gene expression was locally assessed in the masses by immunohistochemistry. All three factors increased in the amyloidosis state, while silymarin had an attenuating effect on their plasma levels and gene expression. In conclusion, we believe that silymarin could be effective in counteracting insulin-generated local amyloidosis.     

Buckling of magneto-electro-hygro-thermal piezoelectric nanoplates system embedded in a visco-Pasternak medium based on nonlocal theory

Microsystem Technologies - In this present work the critical loading of magneto-electro-viscoelastic-hygro-thermal (MEVHT) piezoelectric nanoplates embedded in a viscoelastic foundation are...     

Combined chronic low dose radiation-caloric restriction: a model for regression of spontaneous mammary tumor

PURPOSE: This study was carried out to determine whether chronic low dose radiation can act alone or in synergy with restricted diet in down-regulating spontaneously occurring mammary tumor in tumor-susceptible female C3H/He mice and whether immune cells are involved. METHODS AND MATERIALS: At 7 months of age, one-half of the experimental mice were maintained on an ad lib diet, and the other half was adapted over a period of 1 month to a diet of 70% of the daily amount of food consumed by the ad lib-fed mice. The food of the restricted diet was enriched such that the vitamin and mineral intake was the same for both groups. Half of the mice in each group was then subjected to chronic low dose radiation (0.04 Gy per exposure from a 60Co source, 3 x-per-week for 4 weeks) and the other half was sham irradiated. The 70% calorically restricted diet was maintained throughout the study. RESULTS: Chronic low dose radiation alone was ineffective in down-regulating spontaneous mammary tumor, unlike caloric restriction. However, chronic low dose radiation when combined with caloric restriction promoted regression of mammary tumors, which were infiltrated with massive numbers of CD8+ T cells. These phenomena were not seen in mice subjected to caloric restriction alone. CONCLUSION: Combined chronic low dose radiation-caloric restriction appears to be a useful model for promoting spontaneous mammary tumor regression.     

Optimizing nanoencapsulation of Heracleum lasiopetalum by response surface methodology

This study was carried out to optimize formulation for Heracleum lasiopetalum (golpar) extract nanoencapsulation by response surface methodology (RSM). The primary water-in-oil emulsion was fabricated by (5%–10%) golpar extract (GE), (40%–35%) emulsifier span 80 (EM), and (50%–60%) sunflower oil (SO). The coating materials were the mixture of Lepidium sativum seed gum (LSG) and whey protein concentrate (WPC) at different ratios (1:0, 1:1, and 0:1). The yield of nanoencapsulation of GE, particle size, and zeta potential was investigated as responses of RSM. The optimal formulation for water-in-oil-in-water emulsion of GE were SO: 50.46%, GE 9.52%, and EM: 36.30% in LSG, SO: 57.07%, GE: 7.12%, and EM: 30.85% in LSG:WPC, and SO: 54.98%, GE: 9.05%, and EM: 39.87% in WPC coating. In conclusion, the nanoencapsulation of GE prepared with the optimized formulation by RSM ensures the gradual release and higher stability to sedimentation during storage with nanometric size and high yield of encapsulation. The nanocapsules of GE can be used as a natural antioxidant in food systems.     

Effect of management strategies on reducing negative impacts of climate change on water resources of the Isfahan–Borkhar aquifer using MODFLOW

Recently, many studies have investigated the effect of climate change on groundwater resources in semiarid and arid areas and have shown adverse effects on groundwater recharge and water level. However, only a few studies have shown suitable strategies for reducing these adverse effects. In this study, climate conditions were predicted for the future period of 2020–2044, under the emission scenarios of RCP2.6, RCP4.5, and RCP8.5, for Isfahan–Borkhar aquifer, Isfahan, Iran, using MODFLOW‐2000 (MODFLOW is United States Geological Survey product). Results showed that the average groundwater level of the aquifer would decrease to 13, 15, and 16 m in 2012 to 2044 approximately under RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. Then, three groundwater sustainability management scenarios were defined that included 10%, 30%, and 50% reduction in groundwater extraction. These strategies simulated the reduced negative effects of climate change on the aquifer. The results showed that decreases in water withdrawal rates of 10%, 30%, and 50% under RCP8.5 scenario (critical scenario) could decrease the mean groundwater level by 14, 11, and 7 m, respectively. The main result of the study showed that 50% reduction in groundwater withdrawal may increase the groundwater levels significantly in order to restore the aquifer sustainability in the study area. In this study, with assuming that the current harvest of wells in the future period is constant, so the results of studies showed that for the aquifer's sustainability management, the water abstraction from the aquifer should reduce up to 50% of the existing wells. Changing the irrigation method from surface to subdroplet irrigation plays an important role in reducing the withdrawal from the aquifer. The results of a study in Iran have shown that the change in the irrigation method from surface to subdroplet irrigation causes a 40% reduction in water use for agriculture.