AN ANALYTICAL APPROACH FOR FATIGUE LIFE ESTIMATION OF COPPER TRACES FOR DESIGN OPTIMIZATION IN ELECTRONIC ASSEMBLIES

This dissertation investigates the durability of the copper traces using experimental results from a fully reversed four point bend test and finite element analysis. The durability data collected from the experiment was used in conjunction with the finite element based critical trace strain, to develop a set of compatible fatigue model constants that best fit the failure behavior observed in the tests. Experimental studies were also conducted in order to determine the impact of assembly variations on the trace fatigue failures including the presence of a surface finish, solder mask as well as the presence of assembled components. In order to validate the established fatigue life model constants further testing was conducted at a different load level. The model was able to predict the test out come with an error of less than 5 % Parametric studies using finite element analysis were also conducted in order to determine the relationship between the various geometric and loading conditions and the critical trace strain in the copper traces. Based on these relationships as well as the experiments to determine the impact of assembly variations of failure of the traces, an analytical model was developed in order to approximate the copper trace strain which is used as the input to the trace fatigue model. To understand the crack initiation and crack propagation process in copper traces, experiments were conducted where the crack growth was periodically monitored. Based on these experiments, the constants for the fatigue crack propagation in copper traces based on Paris’s Law were also determined in this study. Finally the analytical model for trace strain developed was also validated by comparing the copper trace strain evaluated using finite element modeling for the test vehicle used in the experiments. The strains estimated based on the analytical model match well with the strains based on the finite element modeling

Greenways for a Greater Good- An Indian Perspective

Cities have developed on the banks of rivers from the dawn of civilizations. The urban fabric of Indian cities is an intricate tapestry composed of settlements that span almost 4000 years of urban history. Cities as old as 2500 B.C co-exist sometimes in harmony and sometimes in conflict with cities that are still being conceived. The pace of urbanization in India is unprecedented and the country hosts some of the most populous cities in the world. According to the 2011 census, urbanization in India has increased faster than expected reversing the declining trends of the earlier decades. (Census of India, 2011) This boom presents its own set of challenges and opportunities. The role of a Landscape Planner becomes prominent since ensuring the balance of ecological processes and the components of Master Plans are imperative to ensure a sustainable future

Ameliorative effects of waste decomposer and effective microorganisms on composting of paddy straw

Composting is one of the most eco-friendly methods to manage paddy straw and reduce environmental pollution with added value to the soil. The present work aimed to investigate the effects of different treatments on composting paddy straw and identify the most effective method for managing paddy straw while also reducing environmental pollution and adding value to the soil. The study used a split plot design with ten treatment and three replications over two years, and measured various parameters such as total organic carbon, total nitrogen, total phosphorus, total potassium, and water-soluble carbon to evaluate the quality of the compost produced by each treatment. From the pooled data of the experiment, the lowest total organic carbon of the compost was obtained in M1 (2.58%) and S8 (15.58%). The highest total nitrogen was acquired in M1 (12.04%) and S8 (26.04%). The highest total phosphorus was recorded in M1 (1.23%) and S8 (33.75%). The highest potassium was observed in M1 (25.67 %) and S8 (55.61%). The least water-soluble carbon was recorded in M1 (14.28%) and S8 (14.92%). The results of the study provide insights into the effectiveness of various composting methods and can help inform best practices for managing paddy straw in an eco-friendly manner

Real work experiences, practices and adverse events associated with long term usage of N95 respirators during the COVID-19 pandemic – A cross-sectional survey amongst Indian physicians

Introduction: Doctors are at increased risk of exposure to SARS-CoV-2 virus, and use of N95 respirators has emerged as a key preventive measure. This study aimed to study the real-world experiences, practices and adverse effects of N95 respirator usage amongst doctors of India. Methods: An analytical, cross-sectional online survey was conducted between November 2020 and January 2021. Real-world usage characteristics of N-95 respirators were collected via a pre-validated questionnaire (use, reuse, wearing and disposal practices) and compared amongst different sub-cohorts. Results: 453 responses from physicians were analyzed. The most important adjunct to the N95 respirator perceived by the respondents was the full-face shield (81.9%). Most doctors had to purchase extra mask per month (median = 5) and this was more amongst the medical specialties (p = 0.006). Highest mean VAS scores for adverse events were reported for breathing on exertion (6.62 ± 2.25) and ear pain (6.34 ± 2.69). VAS ear pain was higher in ages < 40 and doctors working in the public sector (p = 0.017 and p = 0.019 respectively). Conclusion: There are many inadequacies with regard to proper mask removal and doffing techniques among doctors in India. The major adverse effects faced by the doctors on prolonged mask usage were ear pain and breathing on exertion. However, it can be noted in spite of these deficiencies; there is generally good adherence to protocols and good practices of mask usage in hospital setting

In vivo and ex vivo regulation of visfatin production by leptin in human and murine adipose tissue : role of mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling pathways

Visfatin is an adipogenic adipokine with increased levels in obesity, properties common to leptin. Thus, leptin may modulate visfatin production in adipose tissue (AT). Therefore, we investigated the effects of leptin on visfatin levels in 3T3-L1 adipocytes and human/murine AT, with or without a leptin antagonist. The potential signaling pathways and mechanisms regulating visfatin production in AT was also studied. Real-time RT-PCR and Western blotting were used to assess the relative mRNA and protein expression of visfatin. ELISA was performed to measure visfatin levels in conditioned media of AT explants, and small interfering RNA technology was used to reduce leptin receptor expression. Leptin significantly (P < 0.01) increased visfatin levels in human and murine AT with a maximal response at leptin 10–9 M, returning to baseline at leptin 10–7 M. Importantly, ip leptin administration to C57BL/6 ob/ob mice further supported leptin-induced visfatin protein production in omental AT (P < 0.05). Additionally, soluble leptin receptor levels rose with concentration dependency to a maximal response at leptin 10–7 M (P < 0.01). The use of a leptin antagonist negated the induction of visfatin and soluble leptin receptor by leptin. Furthermore, leptin-induced visfatin production was significantly decreased in the presence of MAPK and phosphatidylinositol 3-kinase inhibitors. Also, when the leptin receptor gene was knocked down using small interfering RNA, leptin-induced visfatin expression was significantly decreased. Thus, leptin increases visfatin production in AT in vivo and ex vivo via pathways involving MAPK and phosphatidylinositol 3-kinase signaling. The pleiotropic effects of leptin may be partially mediated by visfatin

On model selections for repeated measurement data in clinical studies: On model selections for repeated measurement data in clinical studies

Repeated measurement designs have been widely used in various randomized controlled trials for evaluating long term intervention efficacies. For some clinical trials, the primary research question is to compare two treatments at a fixed time, using a t-test. Though simple, robust, and convenient, this type of analysis fails to utilize a large amount of collected information. Alternatively, the mixed effects model is commonly used for repeated measurement data. It models all available data jointly and allows explicit assessment of the overall treatment effects across the entire time spectrum. In this paper, we propose an analytic strategy for longitudinal clinical trial data where the mixed effects model is coupled with a model selection scheme. The proposed test statistics not only make full use of all available data but also utilize the information from the optimal model deemed for the data. The performance of the proposed method under various setups, including different data missing mechanisms, is evaluated via extensive Monte Carlo simulations. Our numerical results demonstrate that the proposed analytic procedure is more powerful than the t-test when the primary interest is to test for the treatment effect at the last time point. Simulations also reveal that the proposed method outperforms the usual mixed effects model for testing the overall treatment effects across time. In addition, the proposed framework is more robust and flexible in dealing with missing data compared to several competing methods. The utility of the proposed method is demonstrated by analyzing a clinical trial on the cognitive effect of testosterone in geriatric men with low baseline testosterone levels

Effects of columnar disorder on flux-lattice melting in high-temperature superconductors

The effect of columnar pins on the flux-lines melting transition in high-temperature superconductors is studied using Path Integral Monte Carlo simulations. We highlight the similarities and differences in the effects of columnar disorder on the melting transition in YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) and the highly anisotropic Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (BSCCO) at magnetic fields such that the mean separation between flux-lines is smaller than the penetration length. For pure systems, a first order transition from a flux-line solid to a liquid phase is seen as the temperature is increased. When adding columnar defects to the system, the transition temperature is not affected in both materials as long as the strength of an individual columnar defect (expressed as a flux-line defect interaction) is less than a certain threshold for a given density of randomly distributed columnar pins. This threshold strength is lower for YBCO than for BSCCO. For higher strengths the transition line is shifted for both materials towards higher temperatures, and the sharp jump in energy, characteristic of a first order transition, gives way to a smoother and gradual rise of the energy, characteristic of a second order transition. Also, when columnar defects are present, the vortex solid phase is replaced by a pinned Bose glass phase and this is manifested by a marked decrease in translational order and orientational order as measured by the appropriate structure factors. For BSCCO, we report an unusual rise of the translational order and the hexatic order just before the melting transition. No such rise is observed in YBCO.Comment: 32 pages, 13 figures, revte