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Mechanical properties of 100% polyester and polyester-viscose (P/V) blended yarns produced from polyester fibres which vary in denier and cross-sectional shape have been…
Mechanical properties of 100% polyester and polyester-viscose (P/V) blended yarns produced from polyester fibres which vary in denier and cross-sectional shape have been analyzed. It is observed that fibre fineness and cross-sectional shape play a significant role in the translation of fibre properties to the respective yarn properties. As the fibre linear density decreases, fibre strength translation efficiency increases. In the case of trilobal fibre, translation efficiency is observed to be lower, but yarn breaking elongation is higher in comparison to the corresponding circular fibre. Scalloped oval fibre contributes more towards yarn strength and elongation versus the equivalent circular and tetraskelion fibres. In the P/V blended form, a decrease in yarn tenacity does not affect fibre fineness, but is substantially influenced by changes in the fibre profile. Contribution of broken viscose fibres (comparatively weaker component) at the point of actual breaking of yarn, i.e. Z-value, is altered depending on the polyester fibre profile, which is higher in trilobal and scalloped oval fibres in comparison to the corresponding circular ones, but the role of fibre linear density in this regard is rendered insignificant.
The purpose of this paper is to investigate the effect of fullerene (FNS) reinforcements on the microstructure and mechanical properties of 96.5Sn3Ag0.5Cu (SAC305…
The purpose of this paper is to investigate the effect of fullerene (FNS) reinforcements on the microstructure and mechanical properties of 96.5Sn3Ag0.5Cu (SAC305) lead-free solder joints under isothermal ageing and electrical-migration (EM) stressing.
In this paper, SAC305 solder alloy doped with 0.1 Wt.% FNS was prepared via the powder metallurgy method. A sandwich-like sample and a U-shaped sample were designed and prepared to conduct an isothermal ageing test and an EM test. The isothermal ageing test was implemented under vacuum atmosphere at 150°C, whereas the EM experiment was carried out with a current density of 1.5 × 104 A/cm2. The microstructural and mechanical evolutions of both plain and composite solder joints after thermal ageing and EM stressing were comparatively studied.
A growth of Ag3Sn intermetallic compounds (IMCs) in solder matrix and Cu-Sn interfacial IMCs in composite solder joints was notably suppressed under isothermal ageing condition, whereas the hardness and shear strength of composite solder joints significantly outperformed those of non-reinforced solder joints throughout the ageing period. The EM experimental results showed that for the SAC305 solder, the interfacial IMCs formulated a protrusion at the anode after 360 h of EM stressing, whereas the surface of the composite solder joint was relatively smooth. During the stressing period, the interfacial IMC on the anode side of the plain SAC305 solder showed a continuous increasing trend, whereas the IMC at the cathode presented a decreasing trend for its thickness as the stressing time increased; after 360 h of stressing, some cracks and voids had formed on the cathode side. For the SAC305/FNS composite solder, a continuous increase in the thickness of the interfacial IMC was found on both the anode and cathode sides; the growth rate of the interfacial IMC at the anode was higher than that at the cathode. The nanoindentation results showed that the hardness of the SAC305 solder joint presented a gradient distribution after EM stressing, whereas the hardness data showed a relatively homogeneous distribution in the SAC305/FNS solder joint.
The experimental results showed that the FNS reinforcement could effectively mitigate the failure risk in solder joints under isothermal ageing and high-current stressing. Specifically, the FNS particles in solder joints can work as a barrier to suppress the diffusion and migration of Sn and Cu atoms. In addition, the nanoidentation results also indicated that the addition of the FNS reinforcement was very helpful in maintaining the mechanical stability of the solder joint. These findings have provided a theoretical and experimental basis for the practical application of this novel composite solder with high-current densities.
At the Royal Society of Health annual conference, no less a person than the editor of the B.M.A.'s “Family Doctor” publications, speaking of the failure of the anti‐smoking campaign, said we “had to accept that health education did not work”; viewing the difficulties in food hygiene, there are many enthusiasts in public health who must be thinking the same thing. Dr Trevor Weston said people read and believed what the health educationists propounded, but this did not make them change their behaviour. In the early days of its conception, too much was undoubtedly expected from health education. It was one of those plans and schemes, part of the bright, new world which emerged in the heady period which followed the carnage of the Great War; perhaps one form of expressing relief that at long last it was all over. It was a time for rebuilding—housing, nutritional and living standards; as the politicians of the day were saying, you cannot build democracy—hadn't the world just been made “safe for democracy?”—on an empty belly and life in a hovel. People knew little or nothing about health or how to safeguard it; health education seemed right and proper at this time. There were few such conceptions in France which had suffered appalling losses; the poilu who had survived wanted only to return to his fields and womenfolk, satisfied that Marianne would take revenge and exact massive retribution from the Boche!
READ a current Government publication, and you work study technicians can draw the inference that you are feared by managements of the Central Electricity Authority. Those managements have declined to apply work study technique because, the report says: “it is known that it will be difficult to deal with that redundancy when ascertained”. It goes on to say: “In consequence we find that work study, operational research and investigations into restrictive practices are undertaken without enthusiasm.”
The breakdown of laminar flow in the clearance space of a journal is considered, and the point of transition is considered in relation to experiments carried out with ‘bearings’ of large clearance. Experiments involving flow visualization with very large clearance ratios of 0.05 to 0.3 show that the laminar regime gives way to cellular or ring vertices at the critical Reynolds number predicted by G. I. Taylor for concentric cylinders even in the presence of an axial flow and at a rather higher Reynolds number in the case of eccentric cylinders. The effect of the transition on the axial flow between the cylinders is small. The critical speed for transition as deduced by Taylor, is little affected by moderate axial flows and is increased by eccentricity. The effect of critical condition on the axial‐flow characteristics of the bearing system appears to be negligible, again for moderate axial flows. Assuming that the results can be extrapolated to clearances applicable to bearing operation, the main conclusion of this paper is that the breakdown of laminar flow, which is a practical possibility in very high‐speed bearings, is delayed by eccentric operation.
Food—national dietary standards—is a sensitive index of socio‐economic conditions generally; there are others, reflecting different aspects, but none more sensitive. A country that eats well has healthy, robust people; the housewife who cooks hearty, nourishing meals has a lusty, virile family. It is not surprising, therefore, that all governments of the world have a food policy, ranking high in its priorities and are usually prepared to sacrifice other national policies to preserve it. Before the last war, when food was much less of an instrument of government policy than now—there were not the shortages or the price vagaries—in France, any government, whatever its colour, which could not keep down the price of food so that the poor man ate his fill, never survived long; it was—to make use of the call sign of those untidy, shambling columns from our streets which seem to monopolize the television news screens—“out!” Lovers of the Old France would say that the country had been without stable government since 1870, but the explanation for the many changes in power in France in those pre‐war days could be expressed in one word—food!
The initial shock of devaluing the currency, after so many promises that it would not take place, has passed; only the uncertainty and apprehension remain. It seems an idle exercise to compare the present state of the country's economy with other periods in recent history, such as when in the first Labour Government, we went off the gold standard; at that time, shock was indeed profound and again, the French were cock‐a‐hoop, but the position was complicated by the huge inter‐indebtedness of the Allies in the First War. Or the first devaluation after the Second World War, but both periods were also characterized by public waste and profligate spending. Now, we have to obtain foreign loans and financial backing to keep going, and it is this aspect of the present devaluation which will probably far outweigh any positive advantages. The country's massive external debts were increased by approximately one‐seventh overnight, probably wiping out completely all the repayments made at such great effort since the War. Devaluation of the currency cannot be seen as anything but a grievous blow to the country, presaging hard times ahead for everyone. When promises were being made that devaluation would not take place, there can be little doubt that these were honestly made and, at the time, believed in, for no Government of a country with imports always exceeding exports, would impose such a burden on its people willingly. It must then have been forced upon them.
Describes a study to measure the quality of service provided by food‐poisoning surveillance agencies in England and Wales in terms of the requirements of a representative…
Describes a study to measure the quality of service provided by food‐poisoning surveillance agencies in England and Wales in terms of the requirements of a representative consumer ‐ the egg producing industry ‐ adopting “egg associated” outbreak investigation reports as the reference output. Defines and makes use of four primary performance indicators: accessibility of information; completeness of evidence supplied in food‐poisoning outbreak investigation reports as to the sources of infection in “egg‐associated” outbreaks; timeliness of information published; and utility of information and advice aimed at preventing or controlling food poisoning. Finds that quality expectations in each parameter measured are not met. Examines reasons why surveillance agencies have not delivered the quality demanded. Makes use of detailed case studies to illustrate inadequacies of current practice. Attributes failure to deliver “accessibility” to a lack of recognition on the status or nature of “consumers”, combined with a self‐maintenance motivation of the part of the surveillance agencies. Finds that failures to deliver “completeness” and “utility” may result from the same defects which give rise to the lack of “accessibility” in that, failing to recognize the consumers of a public service for what they are, the agencies feel no need to provide them with the data they require. The research indicates that self‐maintenance by scientific epidemiologists may introduce biases which when combined with a politically inspired need to transfer responsibility for food‐poisoning outbreaks, skew the conduct of investigations and their conclusions. Contends that this is compounded by serious and multiple inadequacies in the conduct of investigations, arising at least in part from the lack of training and relative inexperience of investigators, the whole conditioned by interdisciplinary rivalry between the professional groups staffing the different agencies. Finds that in addition failures to exploit or develop epidemiological technologies has affected the ability of investigators to resolve the uncertainties identified. Makes recommendations directed at improving the performance of the surveillance agencies which, if adopted will substantially enhance food poisoning control efforts.