Investigation of flow stress behavior of AISI 4340 steel in thermomechanical process

In this study, flow stress behavior of AISI 4340 steel in thermomechanical process was investigated under temperature and strain rate ranges of 1173 to 1373 K and 0.01 to 1 s-1, respectively. In flow curves, mechanisms such as work hardening (WH), dynamic recovery (DRV) and dynamic recrystallization (DRX) occurred. It was also discovered that the flow stress decreases with the increase of deformation temperature and the decrease of strain rate. Flow stress curves declared that in low-strain rate and high temperature, dynamic recrystallization overcome work hardening. Also, decreasing temperature led to dynamic recovery and incomplete dynamic recrystallization. Work hardening rate-stress curves depicted that the presence of a turning point expresses dynamic recrystallization mechanism and sub-boundaries are formed at the beginning of where a turning point occurs. In partial dynamic recrystallization, the microstructure was consisted of long grains reshaped because of deformation and some recrystallized grains that nucleated around those reshaped long grains. The results also indicated that at temperature of 1373 K, stress value of σsf, for strain rate of 0.01 s-1 was increased from 27.8 MPa to 96.5 MPa and also for strain rate of 1 s-1 and stress of σc was increased from 32.3 MPa to 105 MPa. The significance of the approach used in this work was any increase in strain rate leads to accelerating dislocation movements. Therefore, dislocations will hit the barriers sooner and will be stopped and also, as a result of delayed dynamic recovery due to dislocations movements, dynamic recrystallization is also delayed

Effects of nanopowder addition on rheological properties of feedstock for micropowder injection moulding process

Micropowder injection moulding (μPIM) is an ideal alternative for miniaturization of parts because of its ability to produce complex micro-geometries at low manufacturing cost. Utilizing bimodal powder mixtures in feedstock can increase packing density and densification of parts fabricated via μPIM. This study investigated the feedstock consists of nano-micro 316L stainless steel powder-and polyethylene glycol-based binder system. The flowability of different feedstocks was evaluated using rheological parameters, including critical powder volume concentration (CPVC), melt viscosity, activation energy, and rheological index. Results showed that mixing nanopowders with micropowders increases CPVC from 67.66 vol.% (pure micropowder) to 78.33 vol.%. The nano-micropowder feedstock showed viscosity below 45 Pa·s and shear rate in the range of 102 s−1 to 105 s−1, which are suitable for the μPIM process. The determined flow index values ranged from 0.25 to 0.76, and the reduced n values at high temperature with the addition of nanopowder indicated a possible increase in shear-thinning behavior. A defect-free microsample was obtained at an injection temperature of 85°C with sintering at 1200°C. Using the nano–micro bimodal powders, the hardness of the obtained samples also increased from 182 HV to 221 HV, with strength of 501 MPa, which is higher than that of the sample obtained with the use of micropowder only (435 MPa)

Flow behavior of 1.4841 steel in hot compression process

Hot compression experiments using a dilatometer were carried out in order to study the effects of hot compression parameters on the flow behaviour of 1.4841 steel. Specifically, the effects of the strain rate and the deformation temperature within a temperature range of 950 – 1100 oC, strain rate of 0.001-0.5 s-1and strain value of 0.5 were studied among all the effective hot compression parameters. The results were shown in the actual strain–stress curve. Embedded in the work hardening, recrystallization and recovery theories, the hot compression mechanism was determined by focusing on the flow behaviour patterns of this steel. The sensitivity to strain rate and temperature, activation energy and the Zener – Holloman parameter were also investigated. Critical strains (εc) of 0.2 and 0.35 were calculated for strain rates of 0.001 and 0.01 s-1, respectively. The findings showed that the recrystallization and flow stress fell when a deformation was imposed at a low strain rate and high temperature. A further increase in the strain rate and a decrease in the temperature resulted in a dynamic recovery mechanism as the dominant process. With an increase in the temperature, the strain rate sensitivity increased, and the rise in the strain rate resulted in a decrease in the temperature sensitivity. The temperature sensitivity (ηa) for various strain rates was estimated more precisely to be within the range of 5.3 to 11.2. The QHW was measured and the value was 459.186 kJ/mol

Topical Anti-Inflammatory and Analgesic Activities of Citrullus colocynthis Extract Cream in Rats.

Background and objectives:Citrullus colocynthis (CC), known as bitter apple, is used to treat diabetes in Iranian traditional medicine. The aim of this study is to evaluate the anti-inflammatory and analgesic activities of CC cream in rats. Materials and Methods: The carrageenan-induced edema in a rat hind paw was carried out to evaluate the topical anti-inflammatory effect of the CC fruit extract cream (2⁻8%) and the tissue levels of IL-6 and TNF-α were estimated by using a commercial ELISA kit. The topical antinociceptive activity of CC cream (2⁻8%) was evaluated in the rat formalin test. To determine the role of opioid receptors in the local antinociceptive effect of the CC cream, naloxone (20 μg/paw, i.pl.), a non-selective opioid antagonist, was used. Results: The results showed that the CC cream (2⁻8%) dose-dependently reduced the carrageenan-induced paw edema and reversed the changes in the level of TNF-α and IL-6 due to carrageenan-induced edema (p < 0.01). The anti-inflammatory effect of CC cream 8% was comparable to that of hydrocortisone ointment 1%. Furthermore, the application of CC cream (2⁻8%) dose-dependently inhibited both first and second phases of the formalin test (p < 0.05). The antinociceptive effect of the CC cream (8%) was comparable to that of methyl salicylate cream 30%. Moreover, the administration of naloxone significantly reversed the topical antinociceptive effect of the CC cream (p < 0.05). Conclusions: For the first time, this study indicated that the topical application of CC cream possesses significant anti-inflammatory and antinociceptive activities in animal models, which were probably mediated by opioid receptors and the suppression of pro-inflammatory cytokines (TNF-α and IL-6). Thus, the CC cream can be used to treat inflammatory pain and inflammatory diseases

Mitigating Bias: Enhancing Image Classification by Improving Model Explanations

Deep learning models have demonstrated remarkable capabilities in learning complex patterns and concepts from training data. However, recent findings indicate that these models tend to rely heavily on simple and easily discernible features present in the background of images rather than the main concepts or objects they are intended to classify. This phenomenon poses a challenge to image classifiers as the crucial elements of interest in images may be overshadowed. In this paper, we propose a novel approach to address this issue and improve the learning of main concepts by image classifiers. Our central idea revolves around concurrently guiding the model's attention toward the foreground during the classification task. By emphasizing the foreground, which encapsulates the primary objects of interest, we aim to shift the focus of the model away from the dominant influence of the background. To accomplish this, we introduce a mechanism that encourages the model to allocate sufficient attention to the foreground. We investigate various strategies, including modifying the loss function or incorporating additional architectural components, to enable the classifier to effectively capture the primary concept within an image. Additionally, we explore the impact of different foreground attention mechanisms on model performance and provide insights into their effectiveness. Through extensive experimentation on benchmark datasets, we demonstrate the efficacy of our proposed approach in improving the classification accuracy of image classifiers. Our findings highlight the importance of foreground attention in enhancing model understanding and representation of the main concepts within images. The results of this study contribute to advancing the field of image classification and provide valuable insights for developing more robust and accurate deep-learning models

The Effects of Coronavirus Pandemic on the Iranian Labor Market

The aim of this study is to investigate the impacts of the coronavirus outbreak on Iran’s labor market. To do so, we analyzed changes in key indicators of the labor market in the first four months of the outbreak. In addition, the dynamic effects of COVID-19 are estimated using a vector autoregression model (VAR). Results show that spread of the pandemic has led to an increase innumber of discouraged workers. The participation rate has fallen by 3.7 percentage points, compared to the same period last year. Considering seasonal variations in the labor market, nearly 1.5 million people have lost their jobs due to the coronavirus contagion. Also, around 750 thousand people applied for unemployment benefits which are 60 percent of the claims filed by former service sector employees. The results indicate that during the study period, the increase in confirmed cases of infections increased the number of jobless claims and the number of unemployed persons. Our findings confirm rapid and substantial changes in the Iranian labor market caused by the coronavirus and highlight the necessity of improving the social welfare system for supporting vulnerable groups in the current crisis and future crises. Supporting businesses, especially credit, insurance, etc., can also reduce the problems of businesses and reduce the number of unemployed

Correlation of CA19-9 and P57 (KiP2) Expression with Tumor Grade and Invasive Front in Oral Squamous Cell Carcinoma

Statement of the Problem: Oral squamous cell carcinoma (OSCC) is one of the most widely occurring cancers worldwide. Early diagnosis of primary tumors is the key to improve treatment outcome. Detecting cancer, determining prognosis, and monitoring disease progression or treatment response can be done based on molecular markers. CA19-9 is an isolated form of Lewis antigen. It is widely used for detecting pancreatic cancer in the clinical setting. P57 (KiP2) is a tumor suppressor gene. It is a positive regulator of cell proliferation, regulating proliferation through G1 phase by inhibiting cyclin dependent kinases. Its expression decreases in most malignancies. OSCC has variable differentiation grades and local invasion potential. Purpose: The aim of this study was to evaluate and assess the correlation of CA19-9 and P57 expression with invasive front and grade of OSCC. Materials and Method: This cross-sectional study was performed on forty paraffin blocks in three histologic grades; well, moderate, and poorly differentiated SCC. The two markers were assessed by immunohistochemistry methods (En vision). Proportional and total scores and staining intensity were measured for all samples. Results: CA19-9 staining was low in all three grades. The Kruskal Wallis test showed no significant correlation between tumor grade and CA19-9 expression; however, there was a significant difference between tumor intensity and margin intensity (p= 0.003). P57 staining was high in all three grades. The Kruskal Wallis test showed no significant correlation between tumor grade and P57 expression. There were no significant differences in total intensity of staining in margins of tumor (p= 0.85). Conclusion: Within the limitations of this study, it may be concluded that expression of CA19-9 and P57 cannot be used as determinants of tumor grade. Higher expression of CA19-9 in invasive front of SCC can be representative of local invasion and higher activity of tumor cells in the margins

The Relationship of Body Mass Index and Blood Pressure with Corneal Biomechanical Parameters in Healthy Subjects

This study aimed to assess the possible relationship of body mass index (BMI) and blood pressure (BP) with corneal biomechanical parameters in healthy subjects. The study included 88 eyes of 88 healthy subjects aged 20–40 years. After a thorough medical history, a digital sphygmomanometer was used to measure the systolic blood pressure (SBP) and diastolic blood pressure (DBP). In addition, several hematological and biochemical parameters were determined to assess general health. Before the ophthalmic examination, the body height and weight were measured; then, the BMI was calculated. Finally, after comprehensive ophthalmic examination, all cases were evaluated with Pentacam (Oculus) in order to rule out corneal ectasia; then, the corneal biomechanical parameters of all individuals were measured using the Scheimpflug-based Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany). If the measurements of the hematological and biochemical parameters were within normal range, the results of the Corvis ST, BMI, and BP were included in the analysis carried out with SPSS software. The mean (± standard deviation [SD]) BMI, SBP, DBP, intraocular pressure (IOP), central corneal thickness (CCT), deformation amplitude, radius, and peak distance was 27.24 ± 4.80 kg/m2, 116.47 ± 11.21 mmHg, 80.51 ± 5.68 mmHg, 15.10 ± 1.70 mmHg, 533.10 ± 30.97 ï­m, 1.03 ± 0.11 mm, 7.51 ± 0.86 mm, and 5.03 ± 0.30 mm, respectively. According to the World Health Organization’s classification of BMI, the results showed no significant difference in IOP, CCT, peak distance, radius, and deformation amplitude between different BMI subcategories (all P &gt; 0.05). The results of the Corvis ST showed that corneal biomechanical parameters had no significant correlation with BMI, SBP, and DBP in three subgroups of BMI and all participants (all P &gt; 0.05) but the results showed a positive correlation between CCT and IOP (P &lt; 0.001, r = 0.504) in all participants. CCT and IOP had no correlation with BMI, SBP, and DBP (all P &gt; 0.05). This study showed that BMI and BP had no correlation with corneal biomechanical parameters in healthy subjects using the Corvis ST. Our results can be used in clinical practice.Â