This paper describes a parametric study of the mechanical behaviour of self-pierced riveted (SPR) joints of steel sheets in two loading conditions (lap-shear and cross-tension). Higher strength was ...always observed in lap-shear testing than in cross-tension. In both loading conditions, the strength of a joint was greatly influenced by the hardness and thickness of sheet materials and die depth. An empirical model was developed to predict the joint strength in cross-tension loading using characteristic joint data determined directly from the SPR process (force-displacement) curve. All predictions of joint strength fell within 10% of the measured joint strength. Finally, a relationship was established between the joint strength in lap shear and cross-tension with <8% error. The developed relationship provides a useful tool for further studies especially for different rivet and die geometry.
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•Influence of sheet material, rivet hardness and die depth variation on strength of SPR joints were studied.•An analytical model to estimate SPR joint strength directly from force-displacement curve was developed.•A relationship between cross-tension and lap-shear loading conditions was established.
Due to increasing penetration of renewable distributed generation (DG), conventional distribution networks have been gradually transforming into their active form, where microgrids may serve as ...fundamental building blocks. As the primary step towards microgrid planning, optimal DGs placement and sizing can reduce the total energy losses by localizing power supply to loads. In this paper, a DG optimal placement method by minimizing the total energy losses is proposed, where the planning is formulated as a non-linear programming (NLP) problem. AC optimal power flow (OPF) is used to solve this planning problem by considering operational constraints and uncertainties in load and renewable power generation of the network. IEEE 33-bus test system and a real 404-bus distribution system operated by Saskatoon Light and Power in Saskatoon, Canada are used to validate the proposed method. The proposed method also shows superior performance compared to existing methods.
Microgrids are fundamental building blocks of smart grids. With increasing penetration of renewable energy-based distributed generation (DG) in distribution systems, microgrid formation is an ...effective way to improve reliability and resiliency by transforming a conventional distribution network into its active form. In this paper, a new microgrid planning method through optimal microgrid formation in distribution networks is proposed through a two-stage performance optimization: in Stage 1, the total power losses, the adequacy and reliability of the whole system are optimized; in Stage 2, isolating switches are optimally allocated at judicious locations to improve the reliability of the system. Brute Force search algorithm and Backward Forward sweep method are used to solve the optimization and load flow problems, respectively. Case studies are conducted using the IEEE 33-node test system and a real 404-node distribution system to validate the proposed method.
Due to the increasing penetration of renewable energy sources, microgrids with the self-adequacy feature becomes a promising platform in distribution systems to interconnect geographically closed ...distributed generation units and load. Micogrids enable faster service restoration during disturbances and natural disasters, and offer improved system reliability. In this article, an extensive literature review is conducted by focusing on several important aspects of the distribution network modernization: planning and service restoration using microgrid formation and soft open points (SOPs) to achieve the improved system performance. The SOP is an emerging power electronic device in distribution systems by connecting feeders or networked microgrids to realize voltage regulation and service restoration. The future research directions in these important areas are recommended in the article.
Approximately, half of the population in the world including tropical and sub-tropical climates region is at risk of dengue. Being an endemic country, Bangladesh has experienced the largest dengue ...epidemic in 2019. The present study aimed at evaluating the clinical and laboratory profile of dengue patients in northern Bangladesh during the epidemic.
This cross-sectional study included 319 serologically confirmed dengue patients admitted in Shaheed Ziaur Rahman Medical College Hospital in Bogra district. It is one of the main tertiary care hospitals in northern Bangladesh. Data were collected from July to September 2019. Patients' clinical and laboratory data were extracted from clinical records. Patients were classified into two classes according to the WHO 2009 dengue classification such as (i) non-severe dengue and (ii) severe dengue. Chi-square test and independent t-test were used in this study.
Of the 319 patients, 94.1% had non-severe dengue and the remaining 5.9% had severe dengue (severe plasma leakage 68.4%, severe organ involvement 68.4%, and severe clinical bleeding 10.5%). Most of the patients were suffering from primary dengue infection. The most common clinical presentation was fever followed by headache and myalgia. Vomiting and abdominal pain were the most prevalent warning signs. The common hematological findings on admission were leukopenia (63.3%), thrombocytopenia (30.4%) and increased hematocrit (26.6%). Raised serum ALT or AST was observed in 14.1% cases whereas raised serum creatinine was observed in 6.6% cases. Signs of plasma leakage (pleural effusion, respiratory distress, and ascites, rise of hematocrit >20% during hospital stay) and hepatic or renal involvement (serum ALT >42UI/L or serum creatinine >1.2 mg/dL) on admission were mostly associated with severe dengue.
The study provides clinical evidence on presentation as well as hematological and biochemical profile of dengue patients in northern Bangladesh that should be implicated in effective patient management.
Self-piercing riveting (SPR) is a method used for joining sheet materials by creating a mechanical interlock between the sheets. SPR is of increasing interest in automobile industries due to its ...suitability for joining lightweight, high strength and dissimilar materials. The quality of an SPR joint from cross-sectional perspective is primarily characterized by the amount of mechanical interlock known as rivet flaring. Other parameters, such as rivet head height, bottom thickness and effective length of the rivet in the bottom sheet are also considered as quality parameters. However, the many factors that determine the quality of an SPR joint are poorly described in the literature and, as a consequence, the opportunities to develop new product and optimize the process are limited. In this paper, several of the key parameters that affect the quality of an SPR joint are described and some assistive technologies that have the potential of improving the quality of a joint are discussed. This is a zone in the field of SPR joining which has plenty of research opportunities. Innovative progress will be achieved by a combination of techniques, together with industrial trials and laboratory simulations.
A new compact silicon grating coupler enabling fibre-to-chip light coupling at a minimized taper length is proposed. The proposed coupler, which incorporates a hollow tapered waveguide, converts the ...spot-size of optical modes from micro- to nano-scales by reducing the lateral dimension from 15 µm to 300 nm at a length equals to 60 µm. The incorporation of such a coupler in photonic integrated circuit causes a physical footprint as small as 81 µm × 15 µm with coupling efficiency and 3-dB coupling bandwidth as high as 72% and 69 nm respectively.
Background Obesity prevalence is increasing in many countries in the world, including Asia. Maternal obesity is highly associated with fetal and neonatal deaths. This study investigated whether ...maternal obesity is a risk factor of fetal death (measured in terms of miscarriage and stillbirth) and neonatal mortality in South and South-East Asian countries. Methods This cross-sectional study pooled the most recent Demographic and Health Surveys (DHS) from eight South and South-East Asian countries (2014-2018). Multivariate logistic regression was deployed to check the relationships between maternal obesity with fetal and neonatal deaths. Finally, multilevel logistic regression model was employed since the DHS data has a hierarchical structure. Results The pooled logistic regression model illustrated that maternal obesity is associated with higher odds of miscarriage (adjusted odds ratio aOR: 1.26, 95% CI: 1.20-1.33) and stillbirths (aOR: 1.46, 95% CI: 1.27-1.67) after adjustment of confounders. Children of obese mothers were at 1.18 (aOR: 1.18, 95% CI: 1.08-1.28) times greater risk of dying during the early neonatal period than mothers with a healthy weight. However, whether maternal obesity is statistically a significant risk factor for the offspring's late neonatal deaths was not confirmed. The significant association between maternal obesity with miscarriage, stillbirth and early neonatal mortality was further confirmed by multilevel logistic regression results. Conclusion Maternal obesity in South and South-East Asian countries is associated with a greater risk of fetal and early neonatal deaths. This finding has substantial public health implications. Strategies to prevent and reduce obesity should be developed before planning pregnancy to reduce the fetal and neonatal death burden. Obese women need to deliver at the institutional facility centre that can offer obstetrics and early neonatal care.
Any form of long-term physical or mental impairment might negatively influence health-related quality of life (HRQoL). HRQoL, as an independent concept, covers a wide range of characteristics that ...includes physical, mental, social, and spiritual functions. People with disabilities are continuously exposed to multiple barriers that deteriorate their HRQoL. It also creates impairment in performing physical activities. However, experts opine regular physical exercise as an intervention to help disabled people. This research aims to investigate the association between disability and physical activity with HRQoL among the adult population in Australia.
A retrospective cohort study.
This study utilized the most recent 19 waves of data (2002-2020) from the nationally representative Household, Income and Labour Dynamics in Australia (HILDA) survey. Component summary scores such as physical component summary (PCS) and mental component summary (MCS), and SF-6D utility scores were utilized to measure HRQoL. Random-effects GLS regression technique was fitted to estimate the association between disability and physical activity with HRQoL, after adjusting for a range of socio-demographic and health-related characteristics.
Disability was negatively associated with the PCS (-5.95), MCS (-2.70) and SF-6D (-0.060) compared with non-disabled counterparts. However, respondents engaged in the recommended level of physical activity had substantial gain in PCS (b = 0.96), MCS (1.57), and SF-6D (0.021) scores. Besides, the results showed that performing the recommended level of physical activity in the presence of disability has lessen the negative effect of disability/ positive moderating effect of physical activity on PCS, MCS, and SF-6D scores by 1.84 points, 0.82 points, and 0.013 percentage points, respectively.
This study found an inverse association between disability and HRQoL among Australian adults. However, physical activity was associated with improved HRQoL. Therefore, public health interventions, such as the orientation of physical activities, have a higher potential to dwindle the burden regarding HRQoL.
ObjectiveWomen’s empowerment and its association with fertility preference are vital for central-level promotional health policy strategies. This study examines the association between women’s ...empowerment and fertility decision-making in low and middle resource countries (LMRCs).DesignThis cross-sectional study uses the Demographic and Health Survey database.Settings53 LMRCs from six different regions for the period ranging from 2006 to 2018.ParticipantsThe data of women-only aged 35 years and above is used as a unit of analysis. The final sample consists of 91 070 married women.MethodsWe considered two outcome variables: women’s perceived ideal number of children and their ability to achieve preferred fertility desire and the association with women empowerment. Women empowerment was measured by their participation in household decision-making and attitude towards wife-beating. The negative binomial regression model was used to assess women’s perceived ideal number of children, and multivariable logistic regression was used to evaluate women’s ability to achieve their preferred fertility desire.ResultsOur study found that empowered women have a relatively low ideal number of children irrespective of the measures used to assess women empowerment. In this study, the measures were participation in household decision-making (incidence rate ratio (IRR): 0.92, 95% CI: 0.91 to 0.93) and attitude towards wife-beating (IRR: 0.96, 95% CI: 0.95 to 0.97). In the LMRCs, household decision-making and negative attitude towards wife-beating have been found associated with 1.12 and 1.08 times greater odds of having more than their ideal number of children.ConclusionOur findings suggest that women’s perceived fertility desire can be achieved by enhancing their empowerment. Therefore, a modified community-based family planning programme at the national level is required, highlighting the importance of women’s empowerment on reproductive healthcare as a part of the mission to assist women and couples to have only the number of children they desire.
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