A Review of State-of-the-Art Large Sized Foam Cutting Rapid Prototyping and Manufacturing Technologies.

Purpose – Current additive rapid prototyping (RP) technologies fail to efficiently produce objects greater than 0.5?m3 due to restrictions in build size, build time and cost. A need exists to develop RP and manufacturing technologies capable of producing large objects in a rapid manner directly from computer-aided design data. Foam cutting RP is a relatively new technology capable of producing large complex objects using inexpensive materials. The purpose of this paper is to describe nine such technologies that have been developed or are currently being developed at institutions around the world. The relative merits of each system are discussed. Recommendations are given with the aim of enhancing the performance of existing and future foam cutting RP systems. Design/methodology/approach – The review is based on an extensive literature review covering academic publications, company documents and web site information. Findings – The paper provides insights into the different machine configurations and cutting strategies. The most successful machines and cutting strategies are identified. Research limitations/implications – Most of the foam cutting RP systems described have not been developed to the commercial level, thus a benchmark study directly comparing the nine systems was not possible. Originality/value – This paper provides the first overview of foam cutting RP technology, a field which is over a decade old. The information contained in this paper will help improve future developments in foam cutting RP systems

Using the Finite Element Method to Determine the Temperature Distributions in Hot-wire Cutting.

Hot-wire cutting is a common material removal process used to shape and sculpt plastic foam materials, such as expanded polystyrene (EPS). Due to the low cost and sculpt-ability of plastic foams they are popular materials for large sized (> 1 m³) prototypes and bespoke visual artefacts. Recent developments in robotic foam sculpting machines have greatly increased the ability of hot-tools to sculpt complex geometrical surfaces bringing the subject into the realm of subtractive rapid prototyping/manufacturing. Nevertheless foam cut objects are not being exploited to their full potential due to the common perception that hot-wires are a low accuracy cutting tool. If greater accuracy for hot-wires can be obtained, it could provide a low cost method of producing high value functional engineering parts. Polystyrene patterns for lost foam casting are one such possibility. A nonlinear transient thermal finite element model was developed with the purpose of predicting the kerf width of hot-wire cut foams. Accurate predictions of the kerfwidth during cutting will allow the tool paths to be corrected off-line at the tool definition stage of the CAM process. Finite element analysis software (ANSYS) was used to simulate the hot-wire plastic foam cutting. The material property models were compiled from experimental data and commonly accepted values found in literature. The simulations showed good agreement with the experimental data and thus the model is thought to be reliable. The simulations provide an effective method of predicting kerf widths, under steady state cutting conditions. Limitations and further developments to the model are described

A Comparison of five radiographic systems to D-speed film in the detection of artificial bone lesions

The purpose of this study was to compare three direct digital sensors (Kodak 6100, Schick CDR, and Dexis PerfectSize), a phosphor plate system (OpTime), and F-speed film to standard D-speed film in the detection of artificial bone lesions prepared in mandible bone sections. Multiple artificial bone lesions were prepared at varying depths in the cortical bone. Specimens were imaged with six different radiographic systems. Radiographs were randomly presented to nine different observers. A logistic regression analysis indicated that the ability of the different radiographic systems to detect the bone lesions was significantly different at the mean percentage of cortical bone remaining. The Kodak filtered, Schick filtered, OpTime unfiltered, Schick unfiltered, and Dexis filtered images were significantly better at lesion detection compared to D-speed film. Also, all filtered digital images were significantly better at lesion detection than D-speed film

Featured Piece

This year the General Editors continued the tradition started last year by creating a feature piece to show our appreciation for the History Department. We selected four professors from the faculty to answer a question about history: what figure/event/idea inspires your interest in history? Reading their responses helped give us insight into the thoughts of these brilliant minds and further help us understand their passion for the subject we all share a common love and interest in. We hope that you enjoy reading their responses as much as we did. The four members of the faculty we spoke with are Dr. Abou Bamba, Dr. William Bowman, Dr. David Hadley, and Magdalena Sánchez

Recent seismicity in the San Fernando region and tectonics in the west-central transverse ranges, California

Since the San Fernando earthquake, February 1971, the density of the southern California seismic array has increased by an order of magnitude. The enhanced coverage provides an ideal setting for the study of the long-term seismicity of the San Fernando aftershock zone and adjacent regions. Most of the recent activity within the San Fernando zone has been thrust faulting at depths shallower than and south of the main shock. One event located slightly deeper than and several kilometers north of the main event suggests shear along a flat plane. Transport of the upper block is south. This event is very similar to another deep, M_L = 4.5, earthquake 30 km west of San Fernando. If these events are typical of midcrustal deformation, the west-central Transverse Ranges may be a form of decollement. A rapid increase in seismicity (M_L ≧ 3.0) in the region south of San Fernando suggests an increase in regional strain that either was contemporaneous with or immediately followed the San Fernando earthquake

Food insecurity and linear growth of adolescents in Jimma Zone, Southwest Ethiopia

Background: Although many studies showed that adolescent food insecurity is a pervasive phenomenon in Southwest Ethiopia, its effect on the linear growth of adolescents has not been documented so far. This study therefore aimed to longitudinally examine the association between food insecurity and linear growth among adolescents. Methods: Data for this study were obtained from a longitudinal survey of adolescents conducted in Jimma Zone, which followed an initial sample of 2084 randomly selected adolescents aged 13-17 years. We used linear mixed effects model for 1431 adolescents who were interviewed in three survey rounds one year apart to compare the effect of food insecurity on linear growth of adolescents. Results: Overall, 15.9% of the girls and 12.2% of the boys (P=0.018) were food insecure both at baseline and on the year 1 survey, while 5.5% of the girls and 4.4% of the boys (P=0.331) were food insecure in all the three rounds of the survey. In general, a significantly higher proportion of girls (40%) experienced food insecurity at least in one of the survey rounds compared with boys (36.6%) (P=0.045). The trend of food insecurity showed a very sharp increase over the follow period from the baseline 20.5% to 48.4% on the year 1 survey, which again came down to 27.1% during the year 2 survey. In the linear mixed effects model, after adjusting for other covariates, the mean height of food insecure girls was shorter by 0.87 cm (P<0.001) compared with food secure girls at baseline. However, during the follow up period on average, the heights of food insecure girls increased by 0.38 cm more per year compared with food secure girls (P<0.066). However, the mean height of food insecure boys was not significantly different from food secure boys both at baseline and over the follow up period. Over the follow-up period, adolescents who live in rural and semi-urban areas grew significantly more per year than those who live in the urban areas both for girls (P<0.01) and for boys (P<0.01). Conclusions: Food insecurity is negatively associated with the linear growth of adolescents, especially on girls. High rate of childhood stunting in Ethiopia compounded with lower height of food insecure adolescents compared with their food secure peers calls for the development of direct nutrition interventions targeting adolescents to promote catch-up growth and break the intergenerational cycle of malnutrition