Acoustic Emission and Guided Wave Modeling and Experiments for Structural Health Monitoring and Non-Destructive Evaluation

This dissertation is organized into major parts. In Part I of the dissertation, plate guided waves due to an acoustic emission (AE) event are analytically studied in the context of seismic moment tensor sources. The guided wave propagation elastodynamic equation corresponding to a point source applied to the plate in an arbitrary direction is modified in order to describe the case when the source is a seismic moment tensor of various tensor components. This part of the dissertation also discusses the analytical modeling of AE test sources such as pencil lead break, hammer hit excitation, etc. In Part II of the dissertation, in situ experimental investigation and predictive modeling of AE from fatigue crack is discussed. The fatigue-crack growth-related AE needs to be separated from crack rubbing/clapping AE to understand the signals originating from the crack and to comprehend the situation of the crack in real-time. Novel SIF-controlled fatigue-crack growth experiment and vibration-induced crack rubbing/clapping experiment was invented for this purpose. The fatigue AE signals were recorded using piezoelectric wafer active sensors (PWAS). The AE source due to fatigue crack growth and rubbing/clapping was assumed as components of the moment tensor source discussed in Part-I, and the simulation was performed. The simulation results were compared with experimental observations, and a good agreement of simulation and experiment was observed. Part III focuses on guided modeling of wave propagation in hollow cylinders. Normal mode expansion (NME) of hollow cylinder guided wave modes for a radial point source excitation is derived analytically. Mutually orthogonal guided wave modes in the hollow cylinder are used for NME, and the modal participation factors are determined analytically. Part IV focuses on the experimental and analytical investigation of health monitoring of hollow cylinders using the passive and active health monitoring techniques discussed in Part III. Both passive and active structural health monitoring experiments are done on the TN32 dry cask storage scaled-down model. Then, the SAFE-NME method discussed in Part III was also used for the predictive simulation in a ‘6-inch schedule-40’ pipe

Effect of Processing on Antinutritional factors in food : A Review

63-69Foods in general are abundant in metabolizable nutrients however some minor amounts of secondary metabolites exert effects contrary to optimum nutrition, Processing by means of dehulling, cooking, autoclaving, roasting or extrusion is meant to decrease the anti-nutritional activity. However certain anti-nutritional factors are generated in-situ on processing or in some cases, their contents might increase on primary processing like milling, de-fatting. The effect of processing on decreasing the levels of specific anti-nutrients like trypsin inhibitors, tannins, phytic acid, uricogenic nucleobases, anti-vitamin factors has been elaborated. Besides the anti-nutrients generated during processing of certain food matrices are also highlighted. These include maillard reaction products, acrylamide,protein-bound D-amino acids and lysine-alanine (LAL), trans-fatty acids etc. Since processing is inevitable to modify food to metabolizable forms, know how on mitigation or generation of these anti-nutrients is important to design food processes to provide optimum nutrition

Recent Advances in Piezoelectric Wafer Active Sensors for Structural Health Monitoring Applications

In this paper, some recent piezoelectric wafer active sensors (PWAS) progress achieved in our laboratory for active materials and smart structures (LAMSS) at the University of South Carolina: http: //www.me.sc.edu/research/lamss/ group is presented. First, the characterization of the PWAS materials shows that no significant change in the microstructure after exposure to high temperature and nuclear radiation, and the PWAS transducer can be used in harsh environments for structural health monitoring (SHM) applications. Next, PWAS active sensing of various damage types in aluminum and composite structures are explored. PWAS transducers can successfully detect the simulated crack and corrosion damage in aluminum plates through the wavefield analysis, and the simulated delamination damage in composite plates through the damage imaging method. Finally, the novel use of PWAS transducers as acoustic emission (AE) sensors for in situ AE detection during fatigue crack growth is presented. The time of arrival of AE signals at multiple PWAS transducers confirms that the AE signals are originating from the crack, and that the amplitude decay due to geometric spreading is observed

Feasibility of implementing public-private mix approach for tuberculosis case management in Pokhara Metropolitan City of western Nepal: a qualitative study

BackgroundThe Public-Private Mix (PPM) approach is a strategic initiative that involves engaging all private and public health care providers in the fight against tuberculosis using international health care standards. For tuberculosis control in Nepal, the PPM approach could be a milestone. This study aimed to explore the barriers to a public-private mix approach in the management of tuberculosis cases in Nepal.MethodsWe conducted key informant interviews with 20 participants, 14 of whom were from private clinics, polyclinics, and hospitals where the PPM approach was used, two from government hospitals, and four from policymakers. All data were audio-recorded, transcribed, and translated into English. The transcripts of the interviews were manually organized, and themes were generated and categorized into 1. TB case detection, 2. patient-related barriers, and 3. health-system-related barriers.ResultsA total of 20 respondents participated in the study. Barriers to PPM were identified into following three themes: (1) Obstacles related to TB case detection, (2) Obstacles related to patients, and (3) Obstacles related to health-care system. PPM implementation was challenged by following sub-themes that included staff turnover, low private sector participation in workshops, a lack of trainings, poor recording and reporting, insufficient joint monitoring and supervision, poor financial benefit, lack of coordination and collaboration, and non-supportive TB-related policies and strategies.ConclusionGovernment stakeholders can significantly benefit by applying a proactive role working with the private in monitoring and supervision. The joint efforts with private sector can then enable all stakeholders to follow the government policy, practice and protocols in case finding, holding and other preventive approaches. Future research are essential in exploring how PPM could be optimized

Early life child micronutrient status, maternal reasoning, and a nurturing household environment have persistent influences on child cognitive development at age 5 years: Results from MAL-ED

Background: Child cognitive development is influenced by early-life insults and protective factors. To what extent these factors have a long-term legacy on child development and hence fulfillment of cognitive potential is unknown. Objective: The aim of this study was to examine the relation between early-life factors (birth to 2 y) and cognitive development at 5 y. Methods: Observational follow-up visits were made of children at 5 y, previously enrolled in the community-based MAL-ED longitudinal cohort. The burden of enteropathogens, prevalence of illness, complementary diet intake, micronutrient status, and household and maternal factors from birth to 2 y were extensively measured and their relation with the Wechsler Preschool Primary Scales of Intelligence at 5 y was examined through use of linear regression. Results: Cognitive T-scores from 813 of 1198 (68%) children were examined and 5 variables had significant associations in multivariable models: mean child plasma transferrin receptor concentration (β: −1.81, 95% CI: −2.75, −0.86), number of years of maternal education (β: 0.27, 95% CI: 0.08, 0.45), maternal cognitive reasoning score (β: 0.09, 95% CI: 0.03, 0.15), household assets score (β: 0.64, 95% CI: 0.24, 1.04), and HOME child cleanliness factor (β: 0.60, 95% CI: 0.05, 1.15). In multivariable models, the mean rate of enteropathogen detections, burden of illness, and complementary food intakes between birth and 2 y were not significantly related to 5-y cognition. Conclusions: A nurturing home context in terms of a healthy/clean environment and household wealth, provision of adequate micronutrients, maternal education, and cognitive reasoning have a strong and persistent influence on child cognitive development. Efforts addressing aspects of poverty around micronutrient status, nurturing caregiving, and enabling home environments are likely to have lasting positive impacts on child cognitive development.publishedVersio