Post-Processing of Selective Laser Sintered Polycarbonate Parts

St\ldies were conducted·to det~rmine the effect of press\lre onpost-prpeessingofpolycarbonate coupons. No significant differences betweencou.pons processed at atmospheric •cQndidons.. andcouponsprpeessedin.vacuum were •observed. However, anisotropic shrinkage .was observedin.thez-directionnormal to thesintering plane. Thisphenomenawasfurtl1erinvestigated usingsYIllmetrical polycarbonatecubespr9(iuced by Selective LaserSintering using yariedlas~rpoweryariedpowderlayer thickness, and varied powder bed temperaturesMechanical Engineerin

Relating Operating Parameters between SLS Machines which have Different Scanner Geometries and Laser Spot Sizes

As the number of SLS machines in operation increases, the opportunities to share operating parameters with other SLS operators also increases. However, if the machines are not identical down to the spot size of the laser beam, the quality of parts made on each machine can be different. The most likely differences between two SLS machines are the laser spot size and the scanning radius of the optics. The total energy flux to the powder surface is a function of the spot size and the scan speed. The algorithms defined to correct for machine differences are verified both experimentally and numerically using a one-dimensional empirical SLS model.McDonald Observator

Laser Sintering Model for Composite Materials

A computer model for the sintering of ceramic/polymer composite materials has been established based on empirical sintering rate data. The model calculates sintering depths which result from variations in the operating parameters which include laser power, beam speed, scan spacing, scan vector length, and initial temperatures of the powder and surroundings. Sintering depths measured in multiple layer parts made of polymer coated ceramic powders are compared to sintering depths calculated by the sintering model.Mechanical Engineerin

The cubic period-distance relation for the Kater reversible pendulum

We describe the correct cubic relation between the mass configuration of a Kater reversible pendulum and its period of oscillation. From an analysis of its solutions we conclude that there could be as many as three distinct mass configurations for which the periods of small oscillations about the two pivots of the pendulum have the same value. We also discuss a real compound Kater pendulum that realizes this property.Comment: 25 pages 4figure

Evaluation of poultry egg marketing in Ikwuano Local Government Area of Abia State, Nigeria

The study focused on evaluation of poultry egg marketing in Ikwuano Local Government Area (LGA) of Abia State. The specific objectives were to describe the socio-economic characteristics of egg marketers in the study area, determine the structure of the egg markets using the market concentration index, determine the costs and return of egg marketing and examine factors that influence the profitability of egg marketing. Two stage sampling technique was adopted for this study. Six communities were purposively selected from the ten communities in the LGA. Ten poultry egg marketers were selected from the six communities using simple random sampling technique. This made the total number of respondents to be sixty. Descriptive statistics, gini coefficient, costs and return analysis as well as multiple regression analysis were used to analyze the data collected. The results showed that majority (55%) of the egg marketers were males who  are still young and agile. They were also married with moderate household size. Many were dominantly farmers and acquired different levels of education. The concentration index showed that egg markets were also highly concentrated with core to perfect equality in size distribution. The result showed a net return of ₦215 and marketing efficiency of 1.035. The coefficient for age, education, sex, and price had positive relationships with amount of sales while household size had a negative relationship with it. Variables that positively influence amount of sales from egg marketing should be considered and strengthened in policy implementation. There is need for guaranteed minimum prices for egg, to reduce price fluctuations and increase consumption of eggs.Keywords: poultry egg, market structure, marketing, Abia Stat

Bose-Glass behaviour in Bi_{2}Sr_{2}Ca_{1-x}Y_{x}Cu_{2}O_{8} crystals with columnar defects: experimental evidence for variable-range hopping

We report on vortex transport in Bi_{2}Sr_{2}Ca_{1-x}Y_{x}Cu_{2}O_{8} crystals irradiated at different doses of heavy ions. We show evidence of a flux-creep resistivity typical of a variable-range vortex hopping mechanism as predicted by Nelson and Vinokur.Comment: 5 pages LaTeX2e (uses elsart.cls), 1 Encapsulated PostScript figur

Economic analysis of beef marketing in Awka North Local Government Area of Anambra State, Nigeria

This study examined the marketing of beef in Awka North Local  Government Area of Anambra State. The objectives of this study were to describe the socio-economic characteristics of beef marketers, ascertain the costs and return of beef marketing, determine the factors affecting revenue derived from beef marketing and examine problems faced by beef  marketers in the study area. Four towns in the local government were  purposively selected because these towns have large markets with many beef marketers. Fifteen beef marketers were randomly selected from each of the four markets giving a total of sixty respondents. Data were analyzed using descriptive statistic, net return analysis and multiple regression analysis. Result showed that 40% of the beef marketers were within the age of 31 – 40 years, 64% were females and a high percentage of them (76%) were married. Majority of the respondents (60%) acquired only primary school education and 70% of the respondents had household size of between 1 -5 persons. A net return of N501.50k per kilogram of beef was obtained showing that beef marketing was profitable in the study area. The multiple regression analysis showed age, educational level, storage cost, marketing experience and cost of purchase were significant variables which affect beef marketing. The major constraints faced by the beef marketers were lack of fund, high transportation cost and inadequate storage facilities. Beef marketers should take advantage of economies of scale to ensure profitability and by extension, improved livelihood and sustainability of the business.Keywords: Beef marketing, economic analysis, net returns, constraints, Awka Nort

Renormalization Group and Decoupling in Curved Space: II. The Standard Model and Beyond

We continue the study of the renormalization group and decoupling of massive fields in curved space, started in the previous article and analyse the higher derivative sector of the vacuum metric-dependent action of the Standard Model. The QCD sector at low-energies is described in terms of the composite effective fields. For fermions and scalars the massless limit shows perfect correspondence with the conformal anomaly, but similar limit in a massive vector case requires an extra compensating scalar. In all three cases the decoupling goes smoothly and monotonic. A particularly interesting case is the renormalization group flow in the theory with broken supersymmetry, where the sign of one of the beta-functions changes on the way from the UV to IR.Comment: 27 pages, 8 figure