Method of forming a skeletal dome structure in situ

A skeletal dome structure composed of a plurality of arcuate support beams joined at their upper ends to a central hub and radiating outwardly and downwardly to terminate at points of engagement with a support surface. Each support beam is composed of an elongated lightweight core sandwiched between upper and lower strips of a material having high tensile and compressive strength. In making the dome, each beam is first preassembled to the extent that the core thereof is secured to a first strip, that strip is then attached at one end to the central hub, the first strip and core are then longitudinally flexed to develop a convex curvature along the side of the core opposite from the strip, and a second flexible strip is then secured to the convex side of the core. A plurality of such beams may be simultaneously formed into buckled or arcuate shape by connecting a plurality of the first strips to a single hub and then raising the hub to impart a curvature into each of the partially-finished beams, followed by the final step of securing the outer strips or skins to the convex upper surfaces of all of the outwardly-radiating arcuate members

Selected heavy metals in some vegetables produced through wastewater irrigation and their toxicological implications in eastern Ethiopia

Vegetables widely consumed in some areas of eastern Ethiopia such as cabbage (Brassica oleraceae var. capitata L.), potato (Solanum tuberosum L.), and khat (Catha edulis Forsk.) are cultivated through irrigation with wastewater. The purpose of this study was to analyse the contents of selected toxic heavy metal (Cr, Co, Cd and Pb) of the vegetables, the effluents used to irrigate the crops, and the soils on which the crops were grown, using flame atomic absorption spectrometry (FAAS). The optimized wet digestion procedure was employed to solubilise the metals from the samples. The validation was performed by spiking the samples with a standard solution of each metal having a known concentration and the percentage recovery values in the range of 91.0–98.3% for soil, 92.0–102% for effluent, and 89.0–101% for vegetable samples. The following concentrations (mg kg-1) of the metals were found in the edible parts of the cabbage, potato, and khat plants, respectively: Cr [less than method detection limit (<MDL)- 17.13], (11.96-14.21), and (9.04-15.54); Co (5.72-9.72), (5.15-8.72), and (<MDL-8.87); Cd (1.15-2.46), (1.22-1.46), and (0.38-3.22); Pb (5.48-11.95), (5.43-7.78), and (4.49-11). The concentrations in the effluent samples (mg kg-1) ranged from 0.17-0.26, 0.57-1.02, 0.04-0.08, and 0.82-2.52 for Cr, Co, Cd, and Pb, respectively. Similarly, concentrations (mg kg-1) of the metals in the soil samples were in the ranges of 25.71-41.45, 17.69-23.59, 0.79-2.56, and 26.04-47.29 for Cr, Co, and Cd, and Pb, respectively. The study revealed that the concentrations of all metals in the vegetables, except Co, were found to be above the safe limits set by different international organizations for consumption, posing a serious health hazard to humans. Therefore, regular monitoring of effluents, soils, and vegetables are essential to prevent excessive build-up of the toxic heavy metals in food. Thus, the health risk and the extent of heavy metal contamination can be reduced.Keywords: Vegetables, wastewater, safe limits, irrigatio

The politics and practice of initiating a public health postgraduate programme in three universities in sub-Saharan Africa: The challenges of alignment and coherence

In-country postgraduate training programme in low and middle income countries are widely considered to strengthen institutional and national capacity. There exists dearth of research about how new training initiatives in public health training institutions come about. This paper examines a south-south collaborative initiative wherein three universities based in Ethiopia, Rwanda and Mozambique set out to develop a local based postgraduate programme on health workforce development/management through partnership with a university in South Africa. Methods: We used a qualitative case study design. We conducted semi-structured interviews with 36 key informants, who were purposively recruited based on their association or proximity to the programme, and their involvement in the development, review, approval and implementation of the programme. We gathered supplementary data through document reviews and observation. Thematic analysis was used and themes were generated inductively from the data and deductively from literature on capacity development. Results: University A successfully initiated a postgraduate training programme in health workforce development/management

Assessment of capacity for Health Policy and Systems Research and Analysis in seven African universities: results from the CHEPSAA project

The importance of health policy and systems research and analysis (HPSR+A) is widely recognised. Universities are central to strengthening and sustaining the HPSR+A capacity as they teach the next generation of decision-makers and health professionals. However, little is known about the capacity of universities, specifically, to develop the field. In this paper we report results of capacity self-assessments by seven universities within five African countries, conducted through the Consortium for Health Policy and Systems Analysis in Africa (CHEPSAA). The capacity assessments focused on both capacity assets and needs, and covered the wider context, as well as organisational and individual capacity levels. Six thematic areas of capacity were examined: leadership and governance, organisation’s resources, scope of HPSR+A teaching and research, communication, networking and GRIPP, demand for HPRS+A, and resource environment. The self-assessments by each university used combinations of document reviews, semi-structured interviews and staff surveys, followed by comparative analysis. A Framework Approach, guided by the six thematic areas, was used to analyse data. We found that HPSR+A is an international priority, and an existing activity in Africa, though still neglected field with challenges including its reliance on unpredictable international funding. All universities have capacity assets, such as on-going HPSR+A teaching and research. There are, however, varying levels of assets (such as differences in staff numbers, group sizes and amount of HPSR+A teaching and research), which, combined with different capacity needs at all three levels (such as individual training, improvement in systems for quality assurance and fostering demand for HPSR+A work), can shape a future agenda for HPSR+A capacity strengthening. Capacity assets and needs at different levels appear related. Possible integrated strategies for strengthening universities’ capacity include: refining HPSR+A vision, mainstreaming the subject into under- and post-graduate teaching, developing emerging leaders and aligning HPSR+A capacity strengthening within the wider organisational development

Effects Of Fabrication Process On Prestressed Composite Arches

Previous studies suggest that intentional buckling of wide shallow members as a fabrication method for arches and domes could result in buckling loads much lower than the conventional rigid (i.e., nonprestressed) structures of the same shape and weight. A modified prestressing technique is discussed in which single-layer struts are separately but simultaneously buckled into arch shape, and then attached to each other and to the supports to form a sandwich composite section. A nonlinear finite-element model is developed to study the effects of this technique on the stability behavior of prestressed sandwich arches. Equivalent rigid arches of elastica shape are studied by initializing the residual stresses prior to loading. A prestressed homogeneous arch that is twice as thick as each face layer of the sandwich section is used for comparison. Prestressing forces that were known to reduce the buckling loads of homogeneous arches by as much as 25%. are shown to have negligible effect on the stability of sandwich arches. Those negative effects almost completely vanish as the thickness of the core layer is increased relative to the overall thickness of the sandwich section. © ASCE

Nonlinear Transient Finite Element Of Stressed Sandwich Composite Arches

Dynamic stability of prestressed sandwich composite arches subjected to impulsive loads is investigated. The complexity of the problem rises from sequential fabrication of the arch. A nonlinear finite element model is developed that traces the stress path in the composite stressed-arch as it undergoes the fabrication process. Upon erection of the arch, its stability under dynamic loads is studied and compared with that of the conventional rigid arch. A convected corotational formulation is developed to represent the large displacements and large rotations of the finite elements, and Wilson-θ method is used for dynamic analysis

Local damage assessment of turbine missile impact on composite and multiple barriers

Fracture of rotary machines could result in turbine missiles, which are the irregularly shaped projectiles travelling at high velocities. The impact of such missiles on barriers in nuclear power plants has the potential to cause severe damages to the facilities, and endanger public safety. This paper applies the available damage assessment models for composite and multiple barriers to test data from experimental works of the past 2 decades. A method of analysis is used in which the missile\u27s residual velocity after perforating each layer becomes the impact velocity for the next layer. The study indicates that composite action of dissimilar materials acting as a single unit improves the efficiency of the barrier. Recommendations are made as to the most accurate models and most appropriate parameters for barriers made of concrete and steel layers. © 1997 Elsevier Science S.A

Local Damage Assessment Of Metal Barriers Under Turbine Missile Impacts

Turbine missiles resulting from the failure of rotary machines in nuclear-power plants could cause severe damages and endanger public safety. This paper presents the current state of the art on models and methodologies for predicting the magnitude of damages and the possibility of the missile leaving the casing structure. Eight empirical methods for the perforation of steel by rigid missiles were collected and analyzed using over 30 test data from experimental works of the past two decades. Based upon the analyses, several modifications of the empirical and semiempirical formulas are proposed to evaluate the problem of containment and to better reflect the amount of damage resulting from turbine missile impact. The modified formulas are shown to be accurate for over 90% of the test results. It was also found that use of an equivalent missile diameter was helpful in accounting for the piercing impacts in the experimental works. It further reduced the nonconservative nature of the predictions

Automating the design of an asynchronous DLX microprocessor

In this paper the automated design of an asynchronous DLX microprocessor is presented. The microprocessor has been designed beginning with a standard RTL-like Verilog specification and the Pipefitter design flow has been used to automatically generate both the specification for the direct implementation of the Control Unit and a synthesisable Verilog specification of the Data Path. The architecture of the DLX is locally synchronous and globally asynchronous and the delay elements for the generation of the local clock signal are automatically produced by Pipefitter as well. The following steps of the design flows (i.e., logic synthesis, technology mapping, placement and routing) have been completed using standard tools leading to the final layout of the circuit. The final microprocessor implements all the functionality of a standard DLX (with the exception of the floating point unit) and supports its whole set of instructions. Some considerations on the area occupation of the microcontroller will be presented in the last section of this paper