Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transformation temperature

One of the ongoing challenges of the aerospace industry is to develop more efficient turbine engines. Greater efficiency entails reduced specific strength and larger temperature gradients, the latter of which means higher operating temperatures and increased thermal conductivity. Continued development of nickel-based superalloys has provided steady increases in engine efficiency and the limits of superalloys have probably not been realized. However, other material systems are under intense investigation for possible use in high temperature engines. Ceramic, intermetallic, and various composite systems are being explored in an effort to exploit the much higher melting temperatures of these systems. NiAl is considered a potential alternative to conventional superalloys due to its excellent oxidation resistance, low density, and high melting temperature. The fact that NiAl is the most common coating for current superalloy turbine blades is a tribute to its oxidation resistance. Its density is one-third that of typical superalloys and in most temperature ranges its thermal conductivity is twice that of common superalloys. Despite these many advantages, NiAl requires more investigation before it is ready to be used in engines. Binary NiAl in general has poor high-temperature strength and low-temperature ductility. On-going research in alloy design continues to make improvements in the high-temperature strength of NiAl. The factors controlling low temperature ductility have been identified in the last few years. Small, but reproducible ductility can now be achieved at room temperature through careful control of chemical purity and processing. But the mechanisms controlling the transition from brittle to ductile behavior are not fully understood. Research in the area of fatigue deformation can aid the development of the NiAl system in two ways. Fatigue properties must be documented and optimized before NiAl can be applied to engineering systems. More importantly though, probing the deformation mechanisms operating in fatigue will lead to a better understanding of NiAl's unique characteristics. Low cycle fatigue properties have been reported on binary NiAl in the past year, yet those studies were limited to two temperature ranges: room temperature and near 1000 K. Eventually, fatigue property data will be needed for a wide range of temperatures and compositions. The intermediate temperature range near the brittle-to-ductile transition was chosen for this study to ascertain whether the sharp change occurring in monotonic behavior also occurs under cyclic conditions. An effort was made to characterize the dislocation structures which evolved during fatigue testing and comment on their role in the deformation process

An UML+Z Framework For Validating And Verifying the Static Aspect of Safety Critical System

AbstractThe aim of this paper is to propose an augmented framework for verifying and validating the static aspect of safety critical systems by analysing the UML class diagrams and the relationship between them. Since UML is a semi formal language which is provn to ambiguities due to its various graphical notations, hence Formal analysis of UML class diagram is required. Moreover, class diagram play an important role in system designing phase especially in safety critical systems. Any ambiguity or inconsistency in design can result in potential failure. Formal methods are the mathematical tools and methodology which are sandwiched at various stages of software development process to ensure the correctness, consistency and completeness of software artifacts such as requirement specifications, design etc. In this article, Z notation is used for the purpose of analysis formally and later on verified by the Z/EVES tool

A genetic based neuro-fuzzy controller for thermal processes

This paper presents a neuro-fuzzy network where all its parameters can be tuned simultaneously using Genetic Algorithms. The approach combines the merits of fuzzy logic theory, neural networks and genetic algorithms. The proposed neuro-fuzzy network does not require a priori knowledge about the system and eliminates the need for complicated design steps like manual tuning of input-output membership functions, and selection of fuzzy rule base. Although, only conventional genetic algorithms have been used, convergence results are very encouraging. A well known numerical example derived from literature is used to evaluate and compare the performance of the network with other modelling approaches. The network is further implemented as controller for two simulated thermal processes and their performances are compared with other existing controllers. Simulation results show that the proposed neuro-fuzzy controller whose all parameters have been tuned simultaneously using GAs, offers advantages over existing controllers and has improved performance.Facultad de Informátic

Techniques for using oxide thickness measurements for predicting crack formation and growth history in high-temperature metallic components

A method and system to develop the age and history of a crack by exposing a specimen or component to varying predetermined temperature range that covers the designated service temperatures and measuring the thickness of the oxide across the specimen along the thickness direction

Anti-Apoptotic Genes in the Survival of Monocytic Cells During Infection

Macrophages are cells of the immune system that protect organisms against invading pathogens by fulfilling critical roles in innate and adaptive immunity and inflammation. They originate from circulating monocytes and show a high degree of heterogeneity, which reflects the specialization of function given by different anatomical locations. Differentiation of monocytes towards a macrophage phenotype is also accompanied by an increase of resistance against various apoptotic stimuli, a required characteristic that allows macrophages to accomplish their function in a stressful environment

Clinico-morphological patterns of breast cancer including family history in a New Delhi hospital, India-A cross-sectional study

BACKGROUND: Breast cancer is the second most common malignancy among women, next to cervix cancer. Understanding its pathogenesis, morphological features and various risk-factors, including family history holds a great promise for the treatment, early detection and prevention of this cancer. PATIENTS AND METHODS: In an attempt to evaluate the clinico-morphological patterns of breast cancer patients, including their family history of breast and/or other cancers, a detailed analysis of 569 breast cancer cases diagnosed during the years 1989–2003 was carried out. Mean and standard deviation and Odds ratios along with 95% confidence intervals were estimated. χ(2)/Fisher's exact test were employed to test for proportions. RESULTS: Mean age of the patient at presentation was 47.8 years, ranging from 13–82 years. Among the various histo-morphological types, Infiltrating duct carcinoma (IDC) was found to be commonest type i.e. in 502 cases (88.2%), followed by infiltrating lobular carcinoma (ILC) in 21 cases (3.7%) and other types forming 9(1%). Out of 369 cases where TNM staging was available, stage IIIB (35.2%) was the commonest. Lymph node positivity was observed in 296 cases (80.2%). Out of 226 cases evaluated for presence of family history, 47 cases (20.7%) revealed positive family history of cancer, among which breast or ovarian cancer were the commonest type (72.0%). Patients below 45 years of age had more frequent occurrence of family history as compared to above 45 years. Amongst familial cases, Infiltrating duct carcinoma was the commonest form accounting for 68.8% cases while ILC was found to be in a higher proportion (12.5%) as compared to non- familial cases (5.4%). CONCLUSION: Among the various determining factors for development of breast cancer and for its early detection, family history of cancer forms one of the major risk factor. It is important to take an appropriate history for eliciting information pertaining to occurrence of cancers amongst the patients' relatives there by identifying the high risk group. Educating the population about the risk factors would be helpful in early detection of breast cancer

Knowledge, attitude, and practices of nursing mothers toward breastfeeding in a tertiary care center in Navi Mumbai

Objective: Breastfeeding (BF) has been accepted as the most vital intervention for reducing infant mortality and ensuring optimal growth and development of a child. A major barrier to successful BF is inconsistency in information and improper cultural practices. To assess the knowledge, attitude, and practices toward BF among nursing mothers following up in a tertiary care center in Navi Mumbai, Maharashtra. Methods: A community-based cross-sectional study was conducted among 512 mothers in Navi Mumbai in the state of Maharashtra, India, between January 2016 and June 2016 using a pre-set questionnaire. The mothers with children under the age of 2 years were interviewed following which descriptive statistics were obtained. Results: Our study highlights the growing awareness of the advantages of BF. Of the 512 mothers enrolled in our study, 78.9% believed in exclusive BF (EBF) till 6 months while 51% actually practiced EBF. Nearly 78% mothers felt shy to feed in public places. BF was initiated <1 h of delivery in 35.9% mothers while insufficient milk was the predominant reason (41.4%) in mothers to stop BF before 2 years. Conclusion: The majority of our participants had adequate knowledge and a positive attitude toward EBF, with right posture practiced while feeding