Finite Strain Elastoplasticity: Consistent Eulerian and Lagrangian Approaches

Infinitesimal strain approximation and its additive decomposition into elastic and plastic parts used in phenomenological plasticity models are incapable of predicting the hardening behavior of materials for large strain loading paths. Experimentally observed second-order effect in finite torsional loading of cylindrical bars, known as the Swift effect, as well as deformations involving significant amount of rotations are examples for which infinitesimal models fail to predict the material response accurately. Several different Eulerian and Lagrangian formulations for finite strain elastoplasticity have been proposed based on different decompositions of deformation and their corresponding flow rules. However, issues such as spurious shear oscillation in finite simple shear and elastic dissipation in closed-path loadings as well as elastic ratchetting under cyclic loading have been identified with the classical formulations for finite strain analysis. A unified framework of Eulerian rate-type constitutive models for large strain elastoplasticity is developed here which assigns no preference to the choice of objective corotational rates. A general additive decomposition of arbitrary corotational rate of the Eulerian strain tensor is proposed. Integrability of the model for the elastic part of the deformation is investigated and it is shown that the proposed unified model is consistent with the notion of hyperelasticity for its elastic part. Based on this, the stress power is physically separable into its reversible and irreversible parts using the proposed constitutive model irrespective of the objective rate used in the model. As a result, all of the issues of finite strain elastoplasticity are resolved using the proposed Eulerian rate model for arbitrary corotational rate of stress. A modified multiplicative decomposition of the right stretch tensor is proposed and used to set up a new Lagrangian framework for finite strain elastoplasticity. Decomposition of the deformation is solely defined by the multiplicative decomposition of the total right stretch tensor into its elastic and plastic parts. The flow rule and evolution of the plastic internal variables are based on the Hencky measure of the plastic right stretch tensor instead of the strain rate tensor. As a result, the issue of mismatch between the elastic and plastic parts of the deformation which mostly exists in the classical multiplicative models does not exist in the proposed Lagrangian model. The problem of back stress oscillation observed in the classical Lagrangian models is also resolved using the proposed Lagrangian model and results are identical to those of the proposed unified Eulerian rate model for finite strain elastoplasticity. In the context of nonlinear elasticity, no preference for either Lagrangian or Eulerian formulations exists since the two formulations can be related through proper transformations and are equivalent form of each other in different backgrounds. However, classical Eulerian and Lagrangian models of elastoplasticity do not provide such an equivalency under the same loading path. This is due to different definitions used for the elastic and plastic parts of the deformation and different flow rules used in the classical Eulerian and Lagrangian models. In this research it is shown that both the proposed Lagrangian and unified Eulerian rate models are equivalent and results obtained from both models are identical for the same finite strain loading path. Such an equivalency verifies that the proposed Eulerian and Lagrangian models are unified and transformable to each other. The unified Eulerian and Lagrangian models are extended to mixed nonlinear hardening material behavior. Predicted results for the second-order effect (the well-known Swift effect) are in good agreement with experimental data for fixed-end finite torsional loading of SUS 304 stainless steel tubes. The proposed models are therefore good candidates to be implemented in the displacement-based formulation of the finite element method for the Lagrangian and Eulerian frameworks of finite strain elastoplasticity

Lead Contamination of Opium, Opium Tincture, and Methadone Oral Solution, in Iran

Background: The present study is conducted with the aim to assess the lead contamination in opium tincture,methadone oral solution, and opium.Methods: 10 samples from each of the matters of opium tinctures, methadone oral solutions, and opium(provided by the Law Enforcement Force of the Islamic Republic of Iran) were collected. Then, an atomicabsorption spectrophotometer (AAS) was used to measure lead concentration in each of the samples. Datawere analyzed using the SPSS software. A P value of 0.05 or less was considered to be statistically significant(Two-tailed).Findings: In this study, the amount of lead measured in all samples was equal or less than 5 parts per million(ppm) and the only exception was the lead level of 5.6 ppm in one of the opium tincture samples, which wasslightly higher than the standard lead level.Conclusion: The results of the current study showed that lead was present in opium tincture, methadone oralsolution, and opium, but it was not in toxic levels. It is reasonable for opium derived medicinal products, butthe low levels of lead in opium may need to be addressed at different times in different regions of the countr

Determining the elderly’s level of satisfaction with the provided services in select NAJA hospital and providing solutions to improve it

Aims: Elderly satisfaction is considered as a tool to measure the productivity and effectiveness of hospital services. Any decision and planning in relation to the elderly, requires accurate knowledge and based on objective and scientific observations of their problems. The aim of this study was to determine the status of geriatric services in two NAJA selected hospitals. Materials and Methods: This was an applied study, in terms of purpose, and a mixed exploratory study, in terms of data, using unstructured in-depth interviews (qualitative part) and a questionnaire with five-point Likert scale (after evaluating validity and reliability (quantitative part)). To determine the level of satisfaction and problems, from 300 elderly clients of two NAJA hospitals in Tehran city, were performed between February 21, 2019 and November 22, 2019. Findings: The results showed that the level of satisfaction was with physicians (90%), emergency (75.6%), para clinic (83%). Also, the most mentioned problems of the clients regarding the costs (10.7%), such as the free cost of some drugs (5.7%), the problem of absentee appointments (10.2%), the high volume of clients (6.4%), the problems of parking space (6%). The solutions provided by clients were insurance expansion and supplementary insurance (17.5%), work conscience (13.4%) and disease prevention services (12.4%), and dental expansion (8.2%). Quantitative analysis showed the favorable condition in terms of employee satisfaction and the need for measures to control costs, expand insurance services, NAJA and hospital services. Conclusion: Different parts of hospital according to the percentage and analysis, have acceptable situation but there are defects about equipment, electronic services, staff encounter and the aging services community system in NAJA hospitals, despite of being at the suitable therapeutic level, need to serious practical actions to increase the level of satisfaction

The Incidence of Nosocomial Toxigenic Clostridium difficile Associated Diarrhea in Tehran Tertiary Medical Centers

"nClostridium difficile is the most common cause of nosocomial diarrhea. It is usually a consequence of antibiotic treatment, But sporadic cases can occur. This study was aimed to determine the frequency of the nosocomial Clostridium difficile (C. difficile) associated diarrhea in Tehran University of Medical Sciences hospitals and study of antibacterial susceptibility of isolates. In this study a total of 942 stool samples from patients with nosocomial diarrhea that were hospitalized in Imam Khomeini hospital, Shariati hospital and Children clinical center were collected. The samples were cultured on a selective cycloserine cefoxitin fructose agar (CCFA) and incubated in anaerobic conditions, at 37°C for 5 days. Isolates were characterized to species level by conventional biochemical tests. Bacterial cytotoxicity was assayed on tissue culture (vero). Antimicrobial sensitivity of isolated toxigenic C. difficile were investigated by kirby Beuer method (disk diffusion). Our findings show that, of the total patients, 57 toxigenic C. difficile (6.1%) were isolated. Results of statistical analysis show significant differences between the rate of isolated toxigenic C. difficile and age group of patients (P<0.05). Among the wards of selected hospitals, in gastroenterology of Children clinical center, Toxigenic C. difficile was isolated from patients most frequently. The sensitivity of isolates to vancomycin, Chloramphenicol and ceftriaxone were higher than other antibiotics. Toxigenic C. difficile is a common hospital-acquired infection. The organism was found in 6.1% hospitalized patients. Further studies to evaluate the rate and role of toxigenic C. difficile in nosocomial diarrheal processes, ecological and pathogenic terms are suggested

Designing a Model for Handling Losses in Cooperatives of Ilam Province

The present study aims to provide an appropriate model for handling losses in production cooperatives of Ilam province by consulting with experts in the field of cooperation and agriculture. To this aim, 24 experts in the field of agriculture and cooperation were selected based on purposive sampling. The data were collected and analyzed through semi-structured interviews. Then, an appropriate model was presented for handling losses in production cooperatives using grounded theory. Based on the results, this model includes the existence of deficiencies in economic, political, educational, international, infrastructural, socio-cultural, and skill dimensions; losses of companies, along with weak government support, intervening in cooperatives affairs, and strengthening the education-oriented culture of cooperative and collective activities; long inefficient organizational structure of the companies, lack of competitiveness with brokers in a volatile market, and traditional non-scientific management of companies; strengthening government-based organizational communications based on effective market-oriented training; and accelerating the process of rural and agricultural development under promoting the brand value of the companies and their revenue generation and competitiveness. Developing and implementing a model for handling losses in production cooperatives depends on the superior management of their components. The results indicated that the model for handling losses in production cooperatives can be classified into 100 mental concepts, 65 sub-categories, and 6 main categories. In addition, the results can increase the awareness of activists and researchers in the field of cooperative activities regarding the mechanisms, background, causes, interveners, and consequences of designing a model for handling losses in production cooperative

Social network analysis of local water user associations’ actors: evidence from Iran

The purpose of this study was to investigate social network analysis (SNA) indicators of actors among exploiters, members of local water user associations (WUA), and their boards of directors in Ilam Province, Iran. The network analysis method and Ucinet6 software were used to examine the information exchange network and the network of participation among the members of the WUAs across the province. The actors of the local WUAs in the study area included the Water Supply Organization, the Agri-Bank, the Agricultural and Natural Resources Management Organization, the Agriculture Organization, the Department of Cooperatives, Labor and Social Welfare, the Provincial Government, the Village Council and Rural Municipalities, the Agricultural Insurance Fund, and the Regional Water Company of the province. Among the experts, one was selected from each organization or administration via the purposeful sampling method. A questionnaire containing 20 items with a Likert-type scale was designed for data collection, and the actors active in the field of local WUAs were asked to determine the information exchange rate and the participation of their organization/administration with other organizations/administrations. In addition, the relationship between the active actors and local WUAs was examined from the perspective of the actors in the province. The results of the analysis of the density index at the whole level of the information exchange network and the participation network showed that the density of the links to exchange information and participate in the network of actors was low across the provincial WUAs. In total, according to network density indicators, network size, centrality (concentration) of the entire network, and the social cohesion of the information exchange network and the network of participation were ranked to be weak to moderate