A comparative study assessing the wear behaviour of different ceramic die materials during superplastic forming

Superplastic forming (SPF) is an advanced manufacturing process where metallic sheets are heated to their superplastic region to be blow formed within a die set. The process allows for the forming of complex parts but it is typically restricted to low volume and high value products. Ceramic dies are a developing technology in the SPF domain as they offer lower production costs and shorter lead times than conventional metallic dies, thus reducing process costs. Ceramic dies, however, are limited for SPF applications due to their brittle nature. This paper presents a method to assess ceramic die wear which is based on a novel test rig developed at the Advanced Forming Research Centre (AFRC) where SPF die-blank interaction was replicated at laboratory scale. Controllable normal load and twist compression tests on different ceramic materials were carried out with a view to understanding their wear mechanisms and to ultimately identify methods to improve their wear resistance

Strategic management of population programs

Formal strategic planning and management appear to contribute to organizational effectiveness. The author surveys the literature on strategic management in private/for-profit organizations and applies lessons from that literature to population programs. Few would argue that population programs would not benefit from strategic planning and management, but it would be inadvisable to initiate the process when the organization is faced with a short-term crisis; during or immediately before a change in leadership; or when implementation is unlikely. Public sector programs seem to have the latitude to manage strategically. Models available for adoption include life-cycle models, strategic issues management, stakeholder analysis, and portfolio analysis. The model selected may be a function of: (1) who will use it (life-cycle/evolutionary models may be well-suited to the planning needs of donors); (2) the presence of challenges to the survival of the program or to key components of it (stakeholder analysis would find ready application in those circumstances); and (3) the relative success and stability of the program (portfolio analysis may help a program balance its activities in a stable environment whereas strategic issues management is useful in responding to a dynamic environment.) It is important to marshall top-level support, designatewho will do the leg work, analyze the organization's history and current situation, assess internal strengths and weaknesses and external threats and opportunities, and summarize critical issues facing the program. Then a strategy may be developed. Among the available approaches are: (1) scenario developments (useful for a program that senses a need to change its approach to clients); (2) critical issues analysis (useful for refining successful programs); and (3) a goal approach (useful for programs with diffuse, ill-defined objectives). There are no short-cuts, it is argued. A strategic plan typically contains: (1) a mission statement that describes the social need to be addressed, what is unique about the organization, what its values are, and who the principal stakeholders are; (2) a statement of the population to be served and goals for service delivery and quality standards; (3) a service delivery strategy; (4) a financial strategy; (5) a marketing strategy; and (6) support strategies. Most organizations will find that there is no ideal structure - all require tradeoffs - and that attention should focus on eliminating patently dysfunctional aspects of the structure.Health Monitoring&Evaluation,ICT Policy and Strategies,Agricultural Knowledge&Information Systems,Educational Sciences,Enterprise Development&Reform

Oxidation resistance of ODS alloy PM2000 from 880°C to 1400°C

Oxidation resistance of ODS alloy PM2000 from 880°C to 1400°

Coupled visco-mechanical and diffusion void growth modelling during composite curing

Most critical processing step during long fiber reinforced epoxy matrix composite laminate manufacturing is the polymerization stage. If not optimized, it gives birth to defects in the bulk material, such as voids. These defects are considered as possible sources of damage in the composite parts. The aim of this work is to model the evolution of void growth in thermoset composite laminates after ply collation (autoclave processes) or resin impregnation (RTM, LCM process). A coupled mechanical and diffusion model is presented to better predict the final void size at the end of polymerization. Amongst the parameter investigated, onset of pressure application and diffusive species concentration where found to have a major effect on void size evolution during curing process

Quaternary diatomaceous sediments and the geological evolution of lakes, Turkana, Baringo and Bogoria Kenya Rift Valley.

PhdQuaternary lacustrine sediments are described from three contrasting areas within the Kenya Rift Valley. Descriptions are given of the mid-Pleistocene Olorgesailie Formation at Olorgesailie. (southern-, Kenya Rift Valley), a series of lacustrine sediments deposited between the mid-Miocene and present in the Baringo District (central Kenya Rift Valley) and finally of Quaternary'(largely Holocene) deposits at East Turkana (northern Kenya Rift Valley). A wide range of environments are represented by these deposits including offshore and littoral lacustrine, deltaic and alluvial situations. Emphasis is placed on the examination of lacustrine and lake marginal sediments. Diatom assemblages found. in these deposits are described for the first time. These have 'been studied using optical and scanning electron microscopy. The. relationships between diatom assemblages and sedimentary facies are examined and evolutionary trends in certain diatoms are discussed. The contemporary ecology of diatoms at East Turkana is discussed and a review is given of diatom ecology and lake classification in East Africa. Diatoms are used to indicate transgression-regression. cycles during the Holocene, and palaeoecological conditions through the Quaternary. Mapping in conjunction with some altimetric data is used to indicate the location, extent and height of several Holocene lacustrine still-stands. Geochemical and sedimentological data is presented for the Holocene deposits at East Turkana and in the Baringo District. Several erosional and depositional processes operating at East Turkana are briefly discussed. A classification of Holocene environments at East T»rksna is presented. The palaeogeography of the northern Kenya Rift Valley and the development of diatom floras during the Holocene is discussed. Data presented here and in the literature is considered and reviewed from a palaeoclimatic viewpoint. The development of Lakes Turkana, Baringo and Bogoria through the Quaternary are also considered. Conclusions are drawn as to the value of diatoms in palaeoecology and stratigraphy

Flux Density and VLBI Measurements of the IDV Source 0917+624

Extragalactic compact flat spectrum radio sources are known to be highly variable and about 30% of them show intra-day variability (IDV). The quasar 0917+624 was known to show prominent IDV behaviour from the time it was first studied as a short-time variable source. Meanwhile, however, its variability ceased and yet the reason for that is not clear. The working hypothesis for the observations, on which the main part of this thesis is based, was that structural changes of the variable part of the source have caused the variability decline. These changes could be revealed using high resolution observing techniques, namely VLBI. Several epochs of single-dish flux density measurements performed with the Effelsberg 100m radio telescope between 2001 and 2004 as well as several multi-frequency epochs of VLBI observations of 0917+624 over a period of eight years (1999 to 2007) have been analysed concerning particularly kinematic and polarimetric properties and the results are interpreted in terms of Intraday Variability

Electro-impulse de-icing testing analysis and design

Electro-Impulse De-Icing (EIDI) is a method of ice removal by sharp blows delivered by a transient electromagnetic field. Detailed results are given for studies of the electrodynamic phenomena. Structural dynamic tests and computations are described. Also reported are ten sets of tests at NASA's Icing Research Tunnel and flight tests by NASA and Cessna Aircraft Company. Fabrication of system components are described and illustrated. Fatigue and electromagnetic interference tests are reported. Here, the necessary information for the design of an EIDI system for aircraft is provided

Cyclic behaviour and plastic strain memory effect of 55NiCrMoV7 steel under low cycle fatigue

International audienceCyclic plastic behaviour of tempered martensitic tool steel 55NiCrMoV7 with four different initial hardness levels was studied under tensile-compress low cycle fatigue (LCF) in the temperature range from room temperature up to 873 K. Cyclic behavior tests and strain memory effect tests were performed in symmetrical tensile-compression strain loading with a triangular waveform. The results show that steel represents cyclic softening behaviour. The cyclic stress response generally shows an initial exponential softening for the first few cycles, followed by a gradual softening without saturation. Cyclic stress response depends on strain rate. The steel represents cyclic viscoplasticity. The steel shows the plastic strain memory effects at each test temperature, the cyclic stress and cumulated plastic strain depends on the history of cyclic loading. If strain amplitude increases after a previous linear softening is achieved, a new rapid non-linear cyclic softening appears. In the opposite, if strain amplitude decreases from higher one to lower, softening remains linear, and moreover sigma-p curve goes along the previous way at the previous same strain loading level. It was discussed that the influences of initial hardness, fatigue temperature, strain rate and cyclic strain amplitude on cyclic plasticity of the steel