Fluoroelastomer pyrotechnic time delay compositions

Pyrotechnic compositions are usually employed in time delay detonators to facilitate controlled initiation of explosive charges in mining and quarrying operations. Traditional slow-burning formulat...

This paper is concerned with the shock ignition of pyrotechnic-composition, boron ‐potassium nitrate (B‐KNO3) by means of a one-stage gas gun that is used as a shock-loading device. The pressure ‐time curves on the surface of a sample with different projectile velocities are measured by manganin gauges. Other Hugoniot parameters such as shock-wave velocity, particle velocity, and the approximate values of local sound velocity C0 and coefe cient l related to its property for the B ‐KNO3 samples are also determined. It is shown that the critical shock pressure of the sample with its chemical reaction is about 1.52 GPa with a 3.45- ms time delay. I. Introduction P YROTECHNIC compositions are usually ignited by means of heat, friction, and e ame. However, in modern applications, high requirements on the accuracy of ignition delay and the safety and reliability of the composition are the major considerations in the design of pyrotechnic elements. At the same time, insensitive pyrotechnic compositions are developed in some applications, and ignitions by heat and e ame are avoided by designing regulation. Therefore, shock initiations, which are used to evaluate the shock sensitivity of high explosives in the explosive e eld, are also involved in the study of pyrotechnics. Among the earlier research projects on the shock ignition of pyrotechnics was the work by Hardt and Martinson. 1 The method was used to induce foil vapor or explosion to drive the e ying plate to impact the sample. The velocity threshold of shock ignition was the major parameter measured. Later work includes Lee and Schwarz 2 ; they studied the response of titanium subhydride ‐potassium perchlorate TiH‐KClO4 (33/67) to the shock. The pressures on the impact surface were measured. Shefe eld and Schwarz

Pyrotechnic ignition is one of the important parts of the delay timing devices found in fuses and rockets to provide operational reliability according to technical requirements. In this study, the burning rate and some energy characteristics of the pyrotechnic ignition were described. The research results showed that pyrotechnic compositions containing 85.0% Pb3O4, 15.0% Si, and 1.0% NC (over 100%) had a high and stable burning rate (109.0 mm/s) and good ignition ability.

Pyrotechnic delays are used to provide a time interval between two successive explosive events. The burning performance of delay compositions is evaluated by inverse burn rate (IBR s/cm). At present, several pyrotechnic delay compositions consist of oxidizer, which are toxic. This paper reports a less toxic, green delay composition with a higher IBR value, which provides more delay time. The stoichiometry's effect on density, heat of combustion, particle size and crystallite size of composition, and the effect of all these parameters on IBR and delay time have been studied. Results revealed that (B/BaCrO 4 /NC) composition supported combustion and smooth burning propagation in the range of 3%–10% of boron, with an IBR ranging from 0.22–1.59 s/cm. The (B/BaSO 4 /NC) composition supported combustion with smooth burning propagation in the range of 10%–40% of boron with an inverse burn rate ranging from 0.84–2.04 s/cm. The use of green oxidizer barium sulfate as a replacement for barium chromate in (B/BaCrO 4 /NC) binary delay system significantly increases the IBR and produces more delay time in the same column length hardware.

With the development of international cooperation, South Africa (SA) has been China’s largest trading partner in Africa for several consecutive years. China and SA can build the digital “Belt and Road” to modernize the manufacturing system locally and optimize process control by benchmarking with the best-in-class manufacturers in each country. In this research, an evaluation technology of manufacturer intelligence regarding the selection of decision support system (DSS) of smart manufacturing technologies, analyzing China–South Africa relations, is described. Firstly, the three keys aspects that enable the technologies of DSS are discussed in detail. Then, one key technology, the manufacturers’ intelligent evaluation system with 15 indexes, was built. The indexes and their measurements are also proposed. Finally, a fusion method based on boosting with multi-kernel function (online sequential extreme learning machine based on boosting, Boosting-OSELM) is introduced. The purpose of Boosting-OSKELM is to combine several weak learners into a strong learner (lower mean square error, MSE) through an acceptable time delay. Finally, the case study is presented to demonstrate the improvement on the MSE and process time, showing a relative MSE improvement of 96.19% and a relative time delay ratio of 31.46%. Totally, the largest contribution of the proposed evaluation method in this study is the conversion of the history data saved by the manual scoring method into knowledge in accessible MES and resealable time delay, which will free up the expert workforce in the entire process. We expect this paper will help future research in this field.

There is increasing adoption of framework contracts (FC) for construction project delivery in South Africa, but it is not yet clear what the performance of the approach is in accomplishing client's expected outcomes of projects being delivered on time, within budget and to required quality and satisfaction. In this study, the performance of FC and the variables that influences the performance is investigated empirically. A qualitative research methodology was adopted for the study. Data were collected via semi-structured interviews with key informants of eight purposively selected client organizations employing FC in South Africa. From the findings, FC is indicated to have performed spectacularly in dealing with unnecessary cost overruns, time delays, and improvement in the quality of delivery. However, it was reported that the approach work best for repetitive works and when a client has the intention of a long-term programme of work. In which case, clients also have to take care to avoid complacency from the contractors. The results provide substantial evidence that FC can perform better than the conventional approaches to short-term relationships and contracts. The result of the study provides insights that can encourage construction stakeholders to appreciate and adopt FC as a viable alternative approach for construction project delivery.

Background. Intussusception remains the most common cause of bowel obstruction in infants and toddlers and can result in considerable morbidity and mortality if not properly treated. The aim of this study was to determine the success rate of air intussesception reduction (AIR), and to identify factors predicting an unsuccessful procedure, among paediatric patients diagnosed with idiopathic intussusception at the Bloemfontein Academic Hospital Complex, Free State, South Africa. Methods. This retrospective analytic cohort study assessed data from the records of all paediatric patients with the diagnosis of idiopathic intussusception discharged from the Department of Paediatric Surgery between 1 January 2003 and 30 September 2011. Results. Thirty-five children with intussusception were identified. AIR enemas were performed in 18 children (51.4%), with successful reduction in 2 (11.1%). Seventeen children (48.6%) were primarily treated surgically without attempting radiological reduction. Successful AIR was more likely if the duration of symptoms was <48 hours. Sixteen patients in whom AIR was attempted eventually required surgical intervention, either due to perforation during AIR or irreducibility. Approximately 94% of children required bowel resection at surgery. In 37.5% of cases AIR was complicated by perforation, making surgical treatment mandatory. Nine patients (56.3%) had unsuccessful AIR without perforation, but needed bowel resection at surgery. One patient (6.3 %) required manual reduction only, without the need for bowel resection at surgery. No deaths were recorded during the period covered by this audit. Conclusions. Our institution’s radiological reduction outcomes were not comparable to international standards. The only statistically significant predictor of poor outcome of AIR was time delay before attempted reduction.

BackgroundPregnancy-associated haemorrhage (PAH) is a leading contributor to maternal mortality in KwaZulu-Natal (KZN) and the fourth most common cause in South Africa. Delays in treating PAH increase maternal mortality; prompt prehospital response is therefore critical to improve outcomes. The aim of this study was to analyse response times and clinical management of PAH by public sector Emergency Care Providers in KZN, looking specifically at postpartum haemorrhage (PPH).MethodsA retrospective cross-sectional study was conducted in two phases. Phase 1 involved analysis of emergency call centre records (n = 4779) assessing response time patterns. Phase 2 analysed randomly selected PPH cases (n = 61) to assess clinical management practices. Descriptive statistics summarised demographics, response patterns, and clinical practice, Pearson correlation examined the relationships between time variables, and chi-square tests assessed associations between clinical variables (p < 0.05).ResultsMore than half (51.5 %) of PAH cases had ambulance response times >60 min. Median pre-response time was 30 min; overall response time was 63.5 min but both were positively skewed by extreme delays, with higher trimmed means(50.9 min and 85.7 min respectively). Most cases (81.6 %, n = 3899) were transported from primary healthcare facilities to hospitals, with Intermediate Life Support Providers managing 75.7 % of the cases. In the sampled PPH patients, compliance with vital signs monitoring was initially high (91.8 %) but declined in transit (42.6 %). Providers were largely non-compliant in documenting blood loss and patient history. Despite almost all patients showing clinical signs of shock 44.3 % of PPH cases received no intravenous fluids.ConclusionSignificant time delays in EMS response and inconsistencies in PAH clinical management by EMS providers were identified. Improved resource allocation, focused training and adherence to clinical and departmental guidelines are vital to strengthening maternal emergency care in KZN.

BackgroundThe measurement of serum creatinine is a standard requirement of the medical management of people living with HIV. Renal dysfunction is common, both as a complication of HIV-infection and as a result of its treatment. The detection of abnormal renal function before the start of antiretroviral therapy will impact patient management and the outcome of treatment.ObjectivesThis study aimed to determine if a time delay in the centrifugation of serum samples affected the creatinine level and the estimated glomerular filtration rate as recorded on the analytical platforms used in the laboratory.MethodsTwenty-two (n = 22) HIV-positive, newly diagnosed and treatment-naïve patients were randomly recruited from Alexandra Health Clinic, Johannesburg, South Africa. Serum samples were centrifuged at six time intervals following receipt of the sample viz. < 4 h (baseline), 6 h, 24 h, 48 h, 72 h and 96 h. Creatinine concentrations were measured on the Roche platform utilising the enzymatic and kinetic Jaffe methods. Whole blood samples were also analysed with the Abbott i-STAT point-of-care instrument. The estimated glomerular filtration rate was calculated using the Cockcroft Gault, CKD–Epidemiology Collaboration and Modified Diet and Renal Disease v3/4 equations.ResultsAt baseline (< 4 h) there was good agreement between the enzymatic and kinetic Jaffe methods: bias 1.7 µmol/l. The enzymatic and i-STAT creatinine concentrations were stable over 96 h viz. changes of 1.8% and 5.7%. However, from 24 h onwards agreement between the enzymatic and kinetic Jaffe methods was poor with the latter measuring 43.7 µmol/l higher than the enzymatic method at 96 h. Creatinine concentrations measured with the kinetic Jaffe method increased significantly in samples centrifuged after 6 h (p < 0.001, 61.7% change), and resulted in a 95% decline in eGFR at 96 h as determined with the CKD–Epidemiology Collaboration equation.ConclusionThe analysis of serum creatinine using the isotope dilution mass spectrometry traceable kinetic Jaffe method is unreliable if performed on samples centrifuged ≥ 6 h after collection. The raised creatinine concentration can affect clinical decisions such as renal functional assessment, choice of antiretroviral drug or regimen, and the dose and frequency of medication.

Challenges relating to the inter-facility transport of high acuity paediatric cases.

This study compares planned repeat laparotomy (PR) with on-demand repeat laparotomy (OD) in a developing world setting. This study was conducted over a 30-month study period (December 2012-May 2015) at Greys Hospital, Pietermaritzburg, South Africa. All trauma and general surgery adult patients requiring a single relaparotomy were included in this study. Prospectively gathered data entered into an established electronic registry were retrospectively analysed. Full ethical approval for the registry and this study was granted by the University of KwaZulu-Natal Biomedical Ethics Committee. A total of 162 patients were included, with an average age of 36years (standard deviation 17) and 69% male predominance. Appendicitis and stab abdomen were the most common underlying diagnoses. PR strategy was used in 46% and an OD approach in 54%. Patients selected for the PR strategy had higher admission pulse rates, higher Modified Early Warning System (MEWS) scores and significantly higher rates of diffuse intra-abdominal sepsis at initial laparotomy. However, findings at relaparotomy were similar in both groups. The PR group had a much shorter time between operations, but much higher need for intensive care unit (ICU) admission. There was no difference between the groups in terms of open abdomen at discharge, length of hospital stay, morbidity or mortality. In our environment, a planned approach to relaparotomy shows no major outcome advantages over an on-demand approach. There is however increased need for ICU admission with the PR approach. This is in keeping with international literature. Of concern is the much longer time delay between index procedure and repeat operation in the OD group. Improved post-operative decision making may help address this.

AN INNOVATIVE APPROACH USING TELEROBOTICS FOR INTELLIGENT BLOCK CAVING OPERATIONS

The morphological characteristics of fruit and seed of Syzygium jambos were investigated in this paper. Effects of sowing matrix, illumination conditions, soil cover, storage temperature and duration on seed germination were also investigated. The berry was 4.99 ± 0.45 cm in length, 4.71 ± 0.30 cm in width, 4.42 ± 1.07cm in thickness, 38.96±7.35g in weight, and the seeds were usually 2.28 ± 0.10cm in length, 2.13±0.13cm in width, 2.24±0.15cm in thickness, and 6.67 ± 0.76g in weight. The germination percentage of fresh seeds decreased with delaying of storage time when being preserved at room temperature in sealing condition, and the seeds lost germinability after 6 months, while the seeds could prolong the life of seeds at 3oC and lost germinability after 10 months, so the seeds were likely to be recalcitrant. The seeds could reached higher germination percentage in sand, yellow soil and peat soil, but could not germinate in the nutrient soil used in this experiment. The change of illumination had no significant effect on the seed germination. Soil-buried seeds at a depth of 1 cm had a lower emergence percentage than those with only 2/3 of the volume buried in the soil. Syzygium jambos is an large evergreen tree of Myrtaceae family, typically 6 to 15 meters high, with a tendency to low branching. There are many varieties of it worldwide. In Thailand the commonest cultivated variety bears green berried, but Malaysian variety generally bears red ones. In many regions its fruit is a shade of pale yellow, often with a slight blush[1-3]. There seems to be considerable variation in flavour if such a description has any merit; in South Africa for example, there is no noticeable bitter aftertaste, but the bouquet is decidedly assertive[4-5]. In Southeast Asian countries, its fruit is frequently served with spiced sugar, its wood is dense and accordingly used as a source of charcoal. Because of rich vitamin C, its fruit can be eaten raw or used in various regional recipes. And because of variously rich tannin that are of some antimicrobial interest, it is also used in regional traditional medicine[6-7]. It always grows in all kinds of soil, mostly grow naturally in waterfront and valley wetlands, and can grow well in sand and soil, especially fertile, deep and moist soil. It is native to Southeast Asia and Hainan Province in China, but now widely cultivated in Southern China be cultivated as a windbreak, good fruit and garden greening tree in humid tropics and south subtropics[8-10]. But it has become established and invasive in several regions. Concern has been expressed on the threat to several ecosystems, including those on several Hawaiian islands, Réunion, the Galápagos Islands, parts of Australia and the warmer regions of the Americas. However, in Hawaii, it has been almost wiped out by the introduced rust Puccinia psidii[8-9]. Because this plant have the ornamental and greening value, edible and medicinal value, so it has great research and development potential. Under natural conditions, the plant can be propagated only by seeds. The study on the seed morphology and the germination characteristics of Syzygium jambos under the different environmental conditions will be helpful for the propagation of this tree. An understanding of how different environments affect seed germination will enhance our ability to predict fluctuations in population dynamics in natural habitats. Therefore, we conducted this study to determine the seed germination pattern under different storage conditions, incubation temperatures and light regimes.