Modelling residual stresses and environmental degradation in adhesively bonded joints

The aim of this research was to develop predictive models for residual stresses and environmental degradation in adhesively bonded joints exposed to hot/wet environments. Different single lap joint configurations and a hybrid double lap joint with dissimilar adherends (CFRP/AIIFM73 double lap joint), were exposed to different ageing environments in order to determine the durability of the joints and the effects of ageing on the failure load. Thermal residual stresses in bonded joints were investigated with analytical solutions and finite element modelling, first with a bimaterial curved beam to validate the modelling process and determine the most suitable method for calculating thermal stresses in bonded joints. It was found that none of the analytical solutions and 2D geometric approximations was fully able to describe the 3D stress state in the strip. The incorporation of geometric and material non-linearity into the models was necessary to obtain accurate results. The validated methods were then used predict the thermal residual stresses in bonded lap joints. The thermal stresses were found to be highest in joints with dissimilar adherends. Moisture uptake in bonded joints was investigated using Fickian diffusion modelling. Gravimetric experiments were used to determine the Fickian diffusion parameters for the bulk adhesive and composite adherends. Transient diffusion modelling was used to predict the uptake in bonded joints. It was seen that moisture diffusion is a fully three dimensional process, and the effects of moisture absorption can only be adequately studied using 3D FEA. The effects of swelling from moisture absorption in bonded joints were investigated using coupled stress-diffusion FEA models. Coupled stress-diffusion 3D FEA was used to predict the transient and residual hygroscopic stresses that develop in bonded lap joints as a function of exposure time in accelerated ageing environments, taking into account the effects of moisture on the expansion and mechanical properties of the adhesive and CFRP substrate. It was seen that moisture absorption induces significant stresses in the joints and markedly different behaviour was seen in the cases of absorbent and non-absorbent adherends. Hygro-thermo-mechanical stresses arising from the exposure of single and double lap joints with thermal residual stresses to hot/wet environments were investigated. In the single lap joints, a reduction in the stresses present in the adhesive was predicted, owing to swelling of the adhesive from moisture absorption. In the double lap joint with dissimilar adherends, exposure to hot/wet environments initially reduced the stresses in the joint when dry, followed by an increase in the magnitude of some stress components and reductions in others with increasing levels of moisture absorption. This led to a higher equivalent stress state in the adhesive than when dry. Thermal residual and mechanical strains predictions were validated with internal strains measured by neutron diffraction and surface strains measured by moire interferometry. Comparisons of predicted and measured thermal residual strains showed low levels of strain in joints with similar adherends. The magnitude of strains in the CFRP/AI double lap joint was significant, with the same spatial distribution and magnitude in both measured and predicted strains. The comparison of mechanical strains predicted by FEA and measured strains by moire interferometry showed good agreement. High magnification moire interferometry also confirmed the location of strain concentrations predicted by FEA. A path independent cohesive zone model (CZM) and a coupled continuum damage model were used to predict and characterise damage and failure initiation in bonded joints. Progressive failure prediction was calibrated in the cohesive zone model using the moisture dependent cohesive fracture energy of FM73. There was a reasonably good agreement with the experimental failure loads. This implementation of the cohesive zone model is limited by the ability of the interface elements used, thereby creating mesh dependency. The Gurson-Tvergaard-Needleman (GTN) coupled damage model was used to predict the effects of residual stresses on failure loads. However, this method is difficult to implement, given the numerous parameters required. The failure loads predicted by the GTN model were comparable with the experimental data when the joints were dry or wet. The damage models were capable of predicting the sudden crack growth and propagation seen experimentally

Ex-ante Evaluation of Cassava Research for Development in Malawi: A Farm Household and Random Utility Modeling Approach

Ex ante evaluation of agricultural research for development projects has become important in recent years for priority setting, ex post impact assessment and learning about generalizability to other populations and contexts. We apply farm household and random utility modeling to baseline survey data and evaluate the impact of a cassava research for development project in Malawi prior to its implementation. The project is being implemented to unlock the potential of cassava in response to the global food crisis. We find that a high proportion of farm households are not self-sufficient in food production and can be assisted by increasing the productivity of land and labor in production, processing and marketing of cassava to reduce deficits and increase marketed surplus. The research for development embeds research in an innovation systems network and speeds up exposure, awareness, adoption and diffusion. This increases the likelihood that incremental benefits will be generated and accrue earlier compared to the counterfactual without the project.Resource /Energy Economics and Policy,

Automatic Home Appliance Switching Using Speech Recognition Software and Embedded System

In most homes, electrical appliances are controlled and operated manually, this could be difficult and challenging to do when tiredness, handicap, morphological variations (height, aging etc.) and inadequate skill stands in the way as impediment. This study aims to implement a better and more flexible means of controlling home appliances by means of an automated switching mechanism using speech recognition technique. Acoustic signals picked by a microphone controlled by a speech recognition application generate digital signals that are passed to a microcontroller, which in turn dispatches commands that operate the relays to which the appliances in the home are connected. The goal of using speech command to automate the switching of home appliances was achieved and proved to be a more convenient means of switching home appliances

Selfmonitoring of blood glucose practices by people living with diabetes who use their personal glucometers in Port Harcourt, Niger Delta Region, Nigeria

Self-monitoring of blood glucose (SMBG) assists persons living with diabetes with the day-to-day behavioral and therapeutic adjustments to their diabetes care. It is a cheaper and more available alternative to glycated haemoglobin (HbA1c) in Nigeria for monitoring glycaemic control. Information on SMBG practices of Nigerians living with diabetes using their personal glucometers is scanty. The aim of the study is to assess the intensity and frequency of SMBG by glucometer owners, and the extent the patients and/or the health care providers (HCP) utilize SMBG to achieve personalized treatment goals via behavioral/treatment adjustments. This was a cross sectional study carried out among persons living with diabetes that accessed diabetes care at the diabetes clinic of the University of Port Harcourt Teaching Hospital (UPTH) and using their personal glucometers. They were consecutively recruited. Data obtained by using intervieweradministered questionnaires were analyzed using SPSS version 20.0, and pvalue <0.05 was considered significant. A total of 128 persons living with diabetes participated in the study of which 40 (31%) were males and 88 (69%) were females; the mean age of the subjects was 52.05 ± 11.24 years with a range of 26–70 years. The majority of the study subjects (72%) were in the active working age group (25–60years). The highest frequency of glucometer use was in the 26 subjects (20%) who checked their blood glucose every morning while 62 (48%) of the subjects checked their blood glucose any morning they felt like. Most of the subjects (60%) did not have any recording device. Glucometer owners were not just the insulin-requiring people living with diabetes as more than half of the subjects, 66 (52%) were on oral anti diabetic drugs (OAD) only. Glucometer ownership was mainly by those that were in the working age group. SMBG protocol (frequency) was variable and SMBG data were not maximally utilized.Keywords: Self-monitoring of blood glucose; Personal glucometer; Diabetes; Blood glucos

Reproducibility: reliability and agreement parameters of the Revised Short McGill Pain Questionnaire Version-2 for use in patients with musculoskeletal shoulder pain

© 2020, The Author(s). Background: The Revised Short McGill Pain Questionnaire Version-2 (SF-MPQ-2) is a multidimensional outcome measure designed to capture, evaluate and discriminate pain from neuropathic and non-neuropathic sources. A recent systematic review found insufficient psychometric data with respect to musculoskeletal (MSK) health conditions. This study aimed to describe the reproducibility (test–retest reliability and agreement) and internal consistency of the SF-MPQ-2 for use among patients with musculoskeletal shoulder pain. Methods: Eligible patients with shoulder pain from MSK sources completed the SF-MPQ-2: at baseline (n = 195), and a subset did so again after 3–7 days (n = 48), if their response to the Global Rating of Change (GROC) scale remained unchanged. Cronbach alpha (α) and intraclass correlation coefficient (ICC2,1), and their related 95% CI were calculated. Standard error of measurement (SEM), group and individual minimal detectable change (MDC90), and Bland–Altman (BA) plots were used to assess agreement. Results: Cronbach α ranged from 0.83 to 0.95 suggesting very satisfactory internal consistency across the SF-MPQ-2 domains. Excellent ICC2,1 scores were found in support of the total scale (0.95) and continuous subscale (0.92) scores; the remaining subscales displayed good ICC2,1 scores (0.78–0.88). Bland–Altman analysis revealed no systematic bias between the test and retest scores (mean difference = 0.13–0.19). While the best agreement coefficients were seen on the total scale (SEM = 0.5; MDC90individual = 1.2 and MDC90group = 0.3), they were acceptable for the SF-MPQ-2 subscales (SEM: range 0.7–1; MDC90individual: range 1.7–2.3; MDC90group: range 0.4–0.5). Conclusion: Good reproducibility supports the SF-MPQ-2 domains for augmented or independent use in MSK-related shoulder pain assessment, with the total scale displaying the best reproducibility coefficients. Additional research on the validity and responsiveness of the SF-MPQ-2 is still required in this population

Side effects and discontinuation rate of depot medroxyprogesterone acetate in a tertiary hospital, southern Nigeria

Background: Depot medroxyprogesterone acetate (DMPA) also known as depo provera is a highly effective, safe and long-lasting reversible contraceptive with side effects that may cause discontinuation amongst acceptors. Objective was to determine the prevalence rate, side effects, discontinuation rate and indications for discontinuation of DMPA at Rivers State University Teaching Hospital (RSUTH), Port Harcourt.Methods: This was a retrospective study of 874 clients attending family planning clinic at the RSUTH from 1st January, 2015 to 31st December, 2019. Their records were retrieved from the clinic and reviewed. Data was extracted, coded and analyzed using the statistical package for social sciences (SPSS) IBM version 25.0 (Armonk, NY).Results: One hundred and one clients accepted DMPA out of 874 acceptors of contraceptives within the study period giving a prevalence rate of 11.6%. The modal age group was 25-29 years accounting for 31 (30.7%). Age range was 19-47 years and the modal parity was para 2. Majority of the clients had formal education, 100 (99%), married, 94 (93.1%) and multipara 61 (60.4%). The discontinuation rate was 32.7% and the commonest reasons for discontinuation were secondary amenorrhoea and irregular vaginal bleeding with each contributing 24.2%.Conclusions: The prevalence and discontinuation rates of Depo provera were low. Secondary amenorrhoea and irregular vaginal bleeding were the commonest side effects and reasons for discontinuation

Utilisation of new media in communicating insecurity in Southeast Nigeria

  This paper aims to describe how in recent times, the issue of insecurity in the southeast of Nigeria is alarming. People are no longer safe as they have become targets for the perpetrators of insecurity within the region. In all of these cases, people must be fully aware of the level of insecurity in a specific location in order to determine the next course of action. In order to achieve this, this study examined the use of new media to communicate insecurity in Southeast Nigeria. The study was founded on the premise of technological determinism.  In this research, a survey research approach was used. Using the Wimmer and Dominick sample size calculator, a sample of 384 was generated from the study's population of 22,012,828. A questionnaire was utilised as a data collection tool. Meanwhile, the multistage sampling procedure was used. Data was analysed with the use of descriptive statistics and pie chart. The finding showed that 51.0% of respondents had been exposed to insecurity messages via new media to a very large extent. It was also revealed that on an average of 74.8% (N=367), new media has been used in communicating insecurity among residents in southeastern Nigeria to a very large extent. It was recommended that new media users should be sensitized on the need to use the platform appropriately or with a sense of responsibility instead of using it to fuel more security problems within the southeastern region of Nigeria.

Colorimetric Measurement of Triglycerides Cannot Provide an Accurate Measure of Stored Fat Content in Drosophila

Drosophila melanogaster has recently emerged as a useful model system in which to study the genetic basis of regulation of fat storage. One of the most frequently used methods for evaluating the levels of stored fat (triglycerides) in flies is a coupled colorimetric assay available as a kit from several manufacturers. This is an aqueous-based enzymatic assay that is normally used for measurement of mammalian serum triglycerides, which are present in soluble lipoprotein complexes. In this short communication, we show that coupled colorimetric assay kits cannot accurately measure stored triglycerides in Drosophila. First, they fail to give accurate readings when tested on insoluble triglyceride mixtures with compositions like that of stored fat, or on fat extracted from flies with organic solvents. This is probably due to an inability of the lipase used in the kits to efficiently cleave off the glycerol head group from fat molecules in insoluble samples. Second, the measured final products of the kits are quinoneimines, which absorb visible light in the same wavelength range as Drosophila eye pigments. Thus, when extracts from crushed flies are assayed, much of the measured signal is actually due to eye pigments. Finally, the lipoprotein lipases used in colorimetric assays also cleave non-fat glycerides. The glycerol backbones liberated from all classes of glycerides are measured through the remaining reactions in the assay. As a consequence, when these assay kits are used to evaluate tissue extracts, the observed signal actually represents the amount of free glycerols together with all types of glycerides. For these reasons, findings obtained through use of coupled colorimetric assays on Drosophila samples must be interpreted with caution. We also show here that using thin-layer chromatography to measure stored triglycerides in flies eliminates all of these problems