Development of a Control Strategy for Monitoring the Delaminating Damage in Drilling Of Carbon Composite Laminates

Composite materials have attractive features, such as high strength to weight ratio and high stiffness to weight ratio. However, they are easily damaged during machining operations. A typical damage is delamination, which can occur when fiber reinforced composite laminates are drilled. Control of delamination is critical for the utilization of composite materials. This research seeks to develop a technique to control inter-ply delaminations during the drilling of laminated composites. A statistical factorial design technique is used to develop a model that relates the feed rate, cutting speed, and tool size to the acoustic parameters. A control algorithm is built from the model. The algorithm is used to modify the instantaneous feed rate in order to maintain the acoustic energy below a threshold value. This control strategy is effective in limiting the area of delamination. However, using high cutting speeds avoid the delamination of materials, but leads to high production costs due to excessive tool wear.Keywords: Composite Laminates, Drilling, Damage, Acoustic Emission

Prevalence of red blood cell antibodies among transfused patients at Komfo Anokye teaching (Kath) hospital, Ghana

Red blood cell (RBC) alloimmunisation is a common problem in transfused patients because of the possibility of haemolytic reaction and limited availability of compatible blood. In highincome countries, pre-transfusion antibody screening is performed routinely. In Ghana, patients are transfused with ABO Rh ‘D’ compatible blood without screening for immune antibodies. We therefore studied the prevalence and specificities of RBC antibodies in transfused patients at Komfo Anokye Teaching hospital, Ghana. The study was cross-sectional, involving previously transfused patients who required another transfusion. Participants’ basic data on demography and transfusion history were recorded. Blood samples were screened and subsequently typed for RBC antibodies using a column gel agglutination test. A total of 106 transfused patients, 52 male and 54 females were enrolled. The patients had previously received a median of 4 RBC units (range 1-14). Of these, ten patients (9.4%) had 11 RBC alloantibodies, whose specificities were 2 anti-K; 2 anti-C; one each of anti-D, -E, -M, and -S; and 3 were pan-reactive. The number of transfusion episodes was significantly associated with the rate of alloimmunisation (p=0.000). In conclusion the overall alloimmunisation rate in the study was 9.4% and this was significantly associated with increasing number of transfusion episodes. Antibodies were mainly directed against antigens in the Rhesus system and K antigen. We recommend that antibody screening be incorporated into routine pre-transfusion testing procedures in Ghana. Keywords: Alloimmunisation, multi transfusion, Alloantibod

Quasi-Automatic Monitoring System For Turning Operation Using Acoustic Emission Signal Response And Factorial Design Method

This work discusses the generation of a quasi monitoring system intended for an operator to change cutting tool during turning operation. The monitoring system uses the effects of turning va riables on acoustic emission signal responses and factorial experimental design approach. In cutting operations, acoustic emission provides useful information concerning the tool wear condition because of the fundamental differences between its source mechanisms in the rubbing friction on the wear land of the single point tool. In this study, effects of cutting speed, feed and tool condition on the acoustic emission signal are investigated using acoustic emission's energy, amplitude, and frequency response and 23 factorial design for turning operation. Cutting tests were performed using high-speed steel under dry conditions. Calculated effects, standard errors at 95% confidence level, and models governing the acoustic emission response to the cutting conditions have been generated from the acoustic emission signal responses. The generated models revealed that acoustic energy response is affected by significant interactions between cutting speed and feed, and insignificant interactions between cutting speed and tool condition, while the acoustic amplitude response is affected by insignificant interactions among cutting speed, feed, and tool condition. These results suggest that acoustic emission's energy and amplitude responses could be used to control the cutting speed and feed during turning operation, thus prolonging the life of the cutting tool.Journal of Science & Technology (Ghana) Vol. 27 (2) 2007: pp. 107-12

Compression force variability in mammography in Ghana – a baseline study

Introduction: Breast compression during mammographic examinations improves image quality and patient management. Several studies have been conducted to assess compression force variability among practitioners in order to establish compression guidelines. However, no such study has been conducted in Ghana. This study aims to investigate the compression force variability in mammography in Ghana. Methods: This retrospective study used data gathered from 1071 screening and diagnostic mammography patients from January, 2018–December, 2019. Data were gathered by seven radiographers at three centers. Compression force, breast thickness and practitioners' years of work experience were recorded. Compression force variability among practitioners and the correlation between compression force and breast thickness were investigated. Results: Mean compression force values recorded for craniocaudal (CC) (17.2 daN) and mediolateral oblique (MLO) (18.2 daN), were within the recommended values used by western countries. Most of the mammograms performed – 80% – were within the National Health Service Breast Screening Programme (NHSBSP) range. However, 65% were above the Norwegian Breast Cancer Screening Programme (NBCSP) range. Compression forces varied significantly (p = 0.0001) among practitioners. Compression forces increased significantly (p = 0.0001) with the years of work experience. A weak negative correlation (r = −0.144) and a weak positive correlation (r = 0.142) were established between compression force and breast thickness for CC and MLO projections respectively. Conclusion: This initial study confirmed that although wide variations in compression force exist among practitioners in Ghana, most practitioners used compression forces broadly within the range set by the NHSBSP. As no national guidelines for compression force currently exist in Ghana, provision of these may help to reduce the range of variations recorded. Implications for practice: Confirmation of variations in compression will guide future practice to minimize image quality disparities and improve quality of care

Randomized Controlled Trial of RTS,S/AS02D and RTS,S/AS01E Malaria Candidate Vaccines Given According to Different Schedules in Ghanaian Children

Background:The target delivery channel of RTS,S candidate malaria vaccines in malaria-endemic countries in Africa is the World Health Organisation Expanded Program on Immunization. As an Adjuvant System, age de-escalation and schedule selection step, this study assessed 3 schedules of RTS,S/AS01E and RTS,S/AS02D in infants and young children 5–17 months of age in Ghana.Methodology:A Phase II, partially-blind randomized controlled study (blind to vaccine, not to schedule), of 19 months duration was conducted in two (2) centres in Ghana between August 2006 and May 2008. Subjects were allocated randomly (1:1:1:1:1:1) to one of six study groups at each study site, each defining which vaccine should be given and by which schedule (0,1-, 0,1,2- or 0,1,7-months). For the 0,1,2-month schedule participants received RTS,S/AS01E or rabies vaccine at one center and RTS,S/AS01E or RTS,S/AS02D at the other. For the other schedules at both study sites, they received RTS,S/AS01E or RTS,S/AS02D. The primary outcome measure was the occurrence of serious adverse events until 10 months post dose 1.Results:The number of serious adverse events reported across groups was balanced. One child had a simple febrile convulsion, which evolved favourably without sequelae, considered to be related to RTS,S/AS01E vaccination. Low grade reactions occurred slightly more frequently in recipients of RTS,S/AS than rabies vaccines; grade 3 reactions were infrequent. Less local reactogenicity occurred with RTS,S/AS01E than RTS,S/AS02D. Both candidate vaccines were highly immunogenic for anti-circumsporozoite and anti-Hepatitis B Virus surface antigen antibodies. Recipients of RTS,S/AS01E compared to RTS,S/AS02D had higher peak anti-circumsporozoite antibody responses for all 3 schedules. Three dose schedules were more immunogenic than 2 dose schedules. Area under the curve analyses for anti-circumsporozoite antibodies were comparable between the 0,1,2- and 0,1,7-month RTS,S/AS01E schedules.Conclusions:Both candidate malaria vaccines were well tolerated. Anti-circumsporozoite responses were greater with RTS,S/AS01E than RTS,S/AS02D and when 3 rather than 2 doses were given. This study supports the selection of RTS,S/AS01E and a 3 dose schedule for further development in children and infants