Degradation modeling and degradation-aware control of power electronic systems

The power electronics market is valued at $23.25 billion in 2019 and is projected to reach$ 36.64 billion by 2027. Power electronic systems (PES) have been extensively used in a wide range of critical applications, including automotive, renewable energy, industrial variable-frequency drive, etc. Thus, the PESs\u27 reliability and robustness are immensely important for the smooth operation of mission-critical applications. Power semiconductor switches are one of the most vulnerable components in the PES. The vulnerability of these switches impacts the reliability and robustness of the PES. Thus, switch-health monitoring and prognosis are critical for avoiding unexpected shutdowns and preventing catastrophic failures. The importance of the prognosis study increases dramatically with the growing popularity of the next-generation power semiconductor switches, wide bandgap switches. These switches show immense promise in the high-power high-frequency operations due to their higher breakdown voltage and lower switch loss. But their wide adaptation is limited by the inadequate reliability study. A thorough prognosis study comprising switch degradation modeling, remaining useful life (RUL) estimation, and degradation-aware controller development, is important to enhance the PESs\u27 robustness, especially with wide bandgap switches. In this dissertation, three studies are conducted to achieve these objectives- 1) Insulated Gate Bipolar Transistor (IGBT) degradation modeling and RUL estimation, 2) cascode Gallium Nitride (GaN) Field-Effect Transistor (FET) degradation modeling and RUL estimation, and 3) Degradation-aware controller design for a PES, solid-state transformer (SST). The first two studies have addressed the significant variation in RUL estimation and proposed degradation identification methods for IGBT and cascode GaN FET. In the third study, a system-level integration of the switch degradation model is implemented in the SST. The insight into the switch\u27s degradation pattern from the first two studies is integrated into developing a degradation-aware controller for the SST. State-of-the-art controllers do not consider the switch degradation that results in premature system failure. The proposed low-complexity degradation-aware and adaptive SST controller ensures optimal degradation-aware power transfer and robust operation over the lifetime

Loop antenna over a conducting cone with a spherical cap

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163889/1/mia2bf01314.pd

Managing Engagement in an Emerging Economy Service

© 2019, Emerald Publishing Limited. Purpose: The purpose of this paper is to offer a better understanding of managing engagement in an emerging economy service. It explores the role of organisational climates for initiative and psychological safety as the key drivers of employee engagement (EE). It also examines the effects of EE on customer engagement (CE) and, in turn, on relationship commitment and switching intention. Design/methodology/approach: Data were collected through a structured survey of service employees and customers of 69 bank branches in Bangladesh using two survey instruments. Responses were collected from 156 employees and 316 customers. A dyadic data set was created by matching customer data with the corresponding employee data collected from each bank branch. Structural equation modelling using AMOS (version 22.0) was employed for data analysis. Findings: Organisational climates for initiative and psychological safety positively influence EE. In turn, EE significantly influences CE which has a significant impact on customer relationship commitment and switching intention. Research limitations/implications: Future research could consider actual customer behaviour, such as repeat purchase, as the key outcome variable. Practical implications: The findings emphasise that investment by service managers in organisational resources to facilitate favourable climates for initiative and psychological safety would engage employees at work, which would ultimately help to attain CE and commitment, and reduce switching intention. Originality/value: This research extends the existing engagement literature with empirical evidence supporting two new EE drivers and two new CE outcomes. It offers a better understanding of managing engagement in the financial services industry of an emerging economy, focussing on the relationship chain from organisational climate to EE, CE and customer-based outcomes

Growth and yield performance of hybrid rice varieties under varying zinc levels

Zinc deficiency in soil is currently a widespread problem in Bangladesh that significantly reduces the yield of a variety of crops, including rice. Despite the fact that many farmers started applying zinc fertilizer, many are unaware of the right amount and application technique. For this reason, to determine the impact of variety and zinc treatment on the performance of hybrid rice, a field experiment was carried out between November 2019 and May 2020 at the Sher-e-Bangla Agricultural University's experimental field in Sher-e-Bangla Nagar, Dhaka-1207. The experiment consisted of two factors as variety (3 types) viz., V1 – BRRI hybrid dhan2, V2 – BRRI hybrid dhan3 and V3 – BRRI hybrid dhan5 and, Zinc management (4 levels) viz., Zn0 – 0 kg ha-1 (control), Zn1 – 2 kg ha-1, Zn2 – 4 kg ha-1 and Zn3 – 6 kg ha-1. The experiment was laid out in a Randomized Complete Block Design (Factorial) with three replications. Data on different growth and yield parameter of rice were recorded and significant variation was found for different treatments. Regarding varietal performance, the maximum panicle number hill-1 (17.10), panicle length (28.03 cm), grain number panicle-1 (109.45), 1000-grain weight (26.50 g), grain yield ha-1 (6.94 t), straw yield ha-1 (8.58 t), biological yield ha-1 (15.51 t) and harvest index (44.62%) were found from the variety BRRI hybrid dhan5. Considering Zn effect, the maximum panicle number hill-1 (16.33), panicle length (27.14 cm), grain number panicle-1 (108.11), 1000-grain weight (25.38 g), grain yield ha-1 (6.81 t), straw yield ha-1 (8.34 t), biological yield ha-1 (15.15 t) and harvest index (44.88%) were found from 6 kg Zn ha-1. In the case of treatment combination of variety and zinc, the maximum panicle number hill-1 (20.17), panicle length (29.45 cm), number of grains panicle-1 (117.74), 1000-seed weight (27.43 g), grain yield (7.80 t ha-1), straw yield (9.20 t ha-1), biological yield (17.00 t ha-1) and harvest index (45.78%) were found from BRRI hybrid dhan5 along with 6 kg Zn ha-1. Therefore, the hybrid rice variety BRRI hybrid dhan5 with a Zn application of 6 kg ha-1 yielded considerably more grain than the other treatment combinations under evaluation

Influence of seedling age and integrated nutrient management on growth and yield of aromatic rice (cv. BRRI dhan34)

To investigate the performance of aromatic rice (cv. BRRI dhan34) in response to seedling age and nutrient management, an experiment was carried out at the Sher-e-Bangla Agricultural University, Dhaka from July to December 2021. The experiment includes three different ages of seedlings to be transplanted viz., 30, 45 and 60 days old and six nutrient management practice viz. control (no manures and fertilizers), recommended dose of inorganic fertilizers (RDF), 50% of RDF + cow dung @ 5 t ha-1, 75% of RDF + cow dung @ 5 t ha-1, 50% of RDF + poultry manure @ 2.5 t ha-1 and, 75% of RDF + poultry manure @ 2.5 t ha-1. The experiment was laid out in a randomized complete block design with three replications. The results revealed that in the case of transplanting of different aged seedlings, the highest leaf area index (5.74), dry matter hill-1 (32.86 g), number of tillers hill-1 (13.17), number of effective tillers hill-1 (11.53), plant height (113.34 cm), total grains panicle-1 (135.14), 1000-grain weight (12.45 g), grain yield (3.29 t ha-1), straw yield (4.01 t ha-1), biological yield (7.30 t ha-1) and were recorded from transplanting 30 days old seedlings. Different levels of nutrient management showed a significant impact on most of the parameters under study. The highest total dry matter hill-1 (34.02 g), the maximum LAI (5.35), plant height (115.70 cm), chlorophyll content (42.87), number of effective tillers hill-1 (12.99), panicle length (24.63 cm), total grains panicle-1 (140.17), 1000-grain weight (12.54 g), grain yield (3.27 t ha-1), straw yield (4.15 t ha-1), biological yield (7.42 t ha-1) and harvest index (43.03%)  were also recorded in F5 (75% of RDF + poultry manure @ 2.5 t ha-1) treatment. While considering the interaction effects between the age of seedlings and nutrient management, transplanting 30 days old seedlings along with the nutrient management of 75% of RDF + poultry manure @ 2.5 t ha-1 treatment improved yield contributing parameters and provided the highest yield (3.76 t ha-1) of BRRI dhan34 compared to other treatment combination. So, the application of 75% of RDF + poultry manure @ 2.5 t ha-1 along with 30 days old seedlings appeared as a promising practice to obtain better performance of fine aromatic rice (cv. BRRI dhan34)

Comparative Performance of Hybrid and Elite Inbred Rice Varieties with respect to Their Source-Sink Relationship

Hybrid rice varieties have higher yield potential over inbred varieties. This improvement is not always translated to the grain yield and its physiological causes are still unclear. In order to clarify it, two field experiments were conducted including two popular indica hybrids (BRRI hybrid dhan2 and Heera2) and one elite inbred (BRRI dhan45) rice varieties. Leaf area index, chlorophyll status, and photosynthetic rate of flag leaf, postheading crop growth rate, shoot reserve translocation, source-sink relation and yield, and its attributes of each variety were comprehensively analyzed. Both hybrid varieties outyielded the inbred. However, the hybrids and inbred varieties exhibited statistically identical yield in late planting. Both hybrids accumulated higher amount of biomass before heading and exhibited greater remobilization of assimilates to the grain in early plantings compared to the inbred variety. Filled grain (%) declined significantly at delayed planting in the hybrids compared to elite inbred due to increased temperature impaired-inefficient transport of assimilates. Flag leaf photosynthesis parameters were higher in the hybrid varieties than those of the inbred variety. Results suggest that greater remobilization of shoot reserves to the grain rendered higher yield of hybrid rice varieties

The association of maternal serum CRP level with gestational diabetes mellitus

Gestational diabetes mellitus is a common medical condition during pregnancy that has detrimental effects on maternal health and fetal well-being. Many serum markers are known to be associated with gestational diabetes, a subclinical inflammatory state that liberates inflammatory mediators, acute phase proteins like CRP into the maternal circulation. This phenomenon has invited many researchers to study inflammatory mediators and acute phase proteins as markers of gestational diabetes mellitus.This case-control study was conducted in the Department of Obstetrics and Gynecology of Bangabandhu Sheikh Mujib Medical Univer- sity, Dhaka, between July 2016 and June 2017. The objective of the study was to evaluate the association of serum CRP level with gestational diabetes mellitus. A total of 140 pregnant women who attended the out-patients antenatal clinic at their 2nd and 3rd trimester (13-40 weeks) of pregnancy were enlisted for the study. The case group consisted of 70 pregnant women who were diagnosed with GDM. Similar number of healthy pregnant women were recruited as control. GDM was diagnosed using standard 75 g OGTT. Blood sample was taken from study subjects to estimate the serum CRP level. CRP level up to 5mg/L was taken as normal. Data analysis was done by utilizing SPSS version 16. The mean BMI of the case group women was significantly higher than the mean BMI of the control (p=0.001). The mean CRP level in case was 13.87±10.19 and the mean for CRP for control group was 4.59±2.41. There was an association of raised level of CRP with GDM. Pregnant mothers with raised level of CRP (& gt; 5 mg/L) were 6.1 times more likely to have GDM than mothers with normal level of CRP. The study concluded that a significant association was found between the raised level of CRP and gestational diabetes mellitus. BSMMU J 2022; 15(2): 96-10

Realizability of tropical lines in the fan tropical plane

textIn this thesis we construct an analogue in tropical geometry for a class of Schubert varieties from classical geometry. In particular, we look at the collection of tropical lines contained in the fan tropical plane. We call these tropical spaces "tropical Schubert prevarieties", and develop them after creating a tropical analogue for flag varieties that we call the "flag Dressian". Having constructed this tropical analogue of Schubert varieties we then determine that the 2-skeleton of these tropical Schubert prevarieties is realizable. In fact, as long as the lift of the fan tropical plane is in general position, only the 2-skeleton of the tropical Schubert prevariety is realizable.Mathematic

Drying and Denaturation Kinetics of Beta-Lactoglobulin during Convective Drying

Beta-Lactoglobulin (β-Lg) is the major fraction of whey protein that comprises more than 65%. Therefore, denaturation of β-Lg during drying can affect the protein functionality where the whey protein is used as an ingredient in food products. This study was carried out to understand the drying and denaturation kinetics of β-Lg during the drying process. A convective drying environment was used to predict the moisture content and temperature kinetics of the drying droplets of β-Lg using Reaction Engineering Approach (REA) models. The predicted values were then coupled with the first order reaction equation to determine the denaturation kinetics. Single droplets of β-Lg (10% w/v; 1.5 ± 0.1 mm initial diameter) were dried at two different temperatures (65 °C and 80 °C) at a constant air velocity (0.5 m/s) for 10 min. The real time denaturation of β-Lg protein was quantified at different drying stages using a reversed phase HPLC. These experimental data from single droplet drier, and HPLC were used to validate the model predictions. The REA model predictions fitted well with the experimental data for moisture-time (±5.70% error) and temperature-time (±3.50% error) profiles. Similarly, the first order kinetics model was also able to predict the denaturation kinetics of β-Lg protein with an average error of 6.00%. The conformation study by FTIR observed that the drying stress increased the secondary structural properties random coil and β-sheet which was compensated by uncoiling of α-helix and transformation of β-turn into β-sheet. The morphology study found that initially β-Lg droplet showed flexible nature but formed firm skin with increasing drying time