Application of bending under tension test to determine the effect of tool radius and the contact pressure on the coefficient of friction in sheet metal forming

To quantify the frictional behaviour in sheet forming operations, several laboratory experiments which simulate the real forming conditions are performed. The Bending Under Tension Test is one such experiment which is often used to represent the frictional flow of sheet material around a die or a punch radius. Different mathematical representations are used to determine the coefficient of friction in the Bending Under Tension Test. In general the change in the strip thickness in passing over the die radius is neglected and the radius of curvature to thickness ratio is assumed to be constant in these equations. However, the effect of roller radius, sheet thickness and the surface pressure are also omitted in some of these equations. This work quantitatively determined the effect of roller radius and the tooling pressure on the coefficient of friction. The Bending Under Tension Test was performed using rollers with different radii and also lubricants with different properties. The tool radii were found to have a direct influence in the contact pressure. The effect of roller radius on friction was considerable and it was observed that there is a clear relationship between the contact pressure and the coefficient of friction.

Variation of fibre diameter coefficient of variation and fibre curvature across mohair fleeces: Implications for animal selection, genetic selection and fleece evaluation

The presentwork aimed to determine howthe average fibre diameter coefficient of variation (CVD) and fibre curvature (FC) differences between nine sampling sites vary between sex and flock, to identify differences in variability between sampling sites as a result of between animal and between sire variability and to determine correlations between sampling sites in between animal and between sire variability. Australian Angoras (n = 313) from two farms in southern Australia were sampled at 12 and 18 months of age at nine sites (mid side, belly, brisket, hind flank, hip, hock, mid back, neck, shoulder). Staples were taken prior to shearing at skin level and CVD and FC determined. For each shearing, differences in CVD and FC between sampling sites, how these differences were affected by farm, sex, and sire, and the covariance between sites for sire and individual animal effects were investigated by restricted maximum likelihood (REML) analyses. The median mid side CVD at 12 and 18 months of age ranged from 23.6 to 25.1% but the actual range was 16.8–34.2%. The median mid side FC at 12 and 18 months of age ranged from 14.4 to 18.6◦/mm but the actual range was 10.5–26.3◦/mm. The general pattern for CVDwas for the mid back, hip and neck sites to have similar CVD, the brisket, hind flank and hock sites to have larger CVD and the belly to have smaller CVD than the mid side site. The between animal variation for CVD was lowest at the mid back site. This implies that the mid back would be the most effective site for between animal selection for CVD. Heritabilities for CVD (range at 18 months 0.18–0.30) were only about half the heritabilities for mean fibre diameter in the same study. There was a marked anterior–posterior increase in FC at both farms and with both ages. The results give no clear indication of the best site for between animal selection for FC, other than that the hock should be avoided. Heritabilities for FC are moderate to high (range at 18 months 0.44–0.77) and the genetic correlations are high except for the hock. Thus genetic selection for FC at any site, other than the hock, should be effective for changing FC over the entire fleece. There was more variability between animals than between sites and sires. These results are put into context with associated research on variation in mean fibre diameter and staple length.

Evaluation of electrochemical methods for determination of the seebeck coefficient of redox electrolytes

Recent advances in thermoelectrochemical cells, which are being developed for harvesting low grade waste heat, have shown the promise of cobalt bipyridyl salts as the active redox couple. The Seebeck coefficient, Se, of a redox couple determines the open circuit voltage achievable, for a given temperature gradient, across the thermoelectrochemical cell. Thus, the accurate determination of this thermodynamic parameter is key to the development and study of new redox electrolytes. Further, techniques for accurate determination of Se using only one half of the redox couple reduces the synthetic requirements. Here, we compare three different experimental techniques for measuring Se of a cobalt tris(bipyridyl) redox couple in ionic liquid electrolytes. The use of temperature dependent cyclic voltammetry (CV) in isothermal and non-isothermal cells was investigated in depth, and the Se values compared to those from thermo-electromotive force measurements. Within experimental error, the Se values derived from CV methods were found to be in accordance with those obtained from electromotive force (emf) measurements. The applicability of cyclic voltammetry techniques for determining Se when employing only one part of the redox couple was demonstrated.

Determination of discharge coefficient for flow over one cycle compound trapezoidal plan form labyrinth weir

Weirs are common structure to regulate discharge and flow control inwater conveyance channels and hydraulic structures. Labyrinth weirsconsidered one of economical and effective methods to increase the efficiency of weirs that crest length of weirs increase without a related increase in structure width. Therefore, flow discharge will be increased. Compared to use compound weir, there are some benefits including the simultaneous passage of floating materials such as wood, ice, etc. Also, sedimentations are pass through compound weir. The trapezoidal Labyrinth weir is one of the combined models. In present study 15 physical models that discussion effect changes sidewall angle of labyrinth weir on discharge coefficient of flow over and through the compound trapezoidal one cycle Labyrinth weir. Also, it is developed design curves with various shapes and configurations. The researchshowed here mainly objectives at determining the coefficient of discharge for flow-over trapezoidal labyrinth weir by performing tests at wide range of values of side wall angles (α) from 6° to 35° and compound linear weir to be compared.

Correlating the fineness and residual gum content of degummed hemp fibres

It is well known residual gum exists in degummed or retted hemp fibres. Gum removal results in improvement in fibre fineness and the properties of the resultant hemp yarns. However, it is not known what correlation if any exists between the residual gum content in retted hemp fibres and the fibre fineness, described in terms of fibre width in this paper. This study examined the mean width and coefficient of variation (CV) of fibre width of seventeen chemically retted hemp samples with reference to residual gum content. The mean and CV of fibre width were obtained from an Optical fibre diameter analyser (OFDA 100). The linear regression analysis results show that the mean fibre width is directly proportional to the residual gum content. A slightly weaker linear correlation also exists between the coefficient of variation of fibre width and the residual gum content. The strong linear co-relation between the mean of fibre width and the residual gum content is a significant outcome, since testing for fibre width using the OFDA is a much simpler and quicker process than testing the residual gum content. Scanning Electron Microscopy (SEM) reinforces the OFDA findings. SEM micrographs show a flat ribbon like fibre cross-section hence the term “fibre width” is used instead of fibre diameter. Spectral differences in the untreated dry decorticated skin samples and chemically treated and subsequently carded samples indicate delignification. The peaks at 1370 cm⁻¹, 1325 cm⁻¹, 1733 cm⁻¹, and 1600 cm⁻¹ attributed to lignin in the untreated samples are missing from the spectra of the treated samples. The spectra of the treated samples are more amine-dominated with some of the OH character lost.

A finite element simulation of micro-mechanical frictional behaviour in metal forming

Friction is a critical factor for sheet metal forming (SMF). The Coulomb friction model is usually used in most finite element (FE) simulation for SMF. However, friction is a function of the local contact deformation conditions, such as local pressure, roughness and relative velocity. Frictional behaviour between contact surfaces can be based on three cases: boundary, hydrodynamic and mixed lubrication. In our microscopic friction model based on the finite element method (FEM), the case of dry contact between sheet and tool has been considered. In the view of microscopic geometry, roughness depends upon amplitude and wavelength of surface asperities of sheet and tool. The mean pressure applied on the surface differs from the pressure over the actual contact area. The effect of roughness (microscopic geometric condition) and relative speed of contact surfaces on friction coefficient was examined in the FE model for the microscopic friction behaviour. The analysis was performed using an explicit FE formulation. In this study, it was found that the roughness of deformable sheet decreases during sliding and the coefficient of friction increases with increasing roughness of contact surfaces. Also, the coefficient of friction increases with the increase of relative velocity and adhesive friction coefficient between contact surfaces.

Effect of creatine supplementation on housekeeping genes in human skeletal muscle using real-time RT-PCR

The present study examined the validity and reliability of measuring the expression of various genes in human skeletal muscle using quantitative real-time RT-PCR on a GeneAmp 5700 sequence detection system with SYBR Green 1 chemistry. In addition, the validity of using some of these genes as endogenous controls (i.e., housekeeping genes) when human skeletal muscle was exposed to elevated total creatine levels and exercise was also examined. For all except 28S, linear relationships between the logarithm of the starting RNA concentrations and the cycle threshold (C_T) values were established for ß-actin, ß2-microglobulin (ß₂M), cyclophilin (CYC), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). We found a linear response between C_T values and the logarithm of a given amount of starting cDNA for all the genes tested. The overall intra-assay coefficient of variance for these genes was 1.3% and 21% for raw C_T values and the linear value of 2^-C_T, respectively. Interassay variability was 2.3% for raw C_T values and 34% for the linear value of 2^-C_T. We also examined the expression of various housekeeping genes in human skeletal muscle at days 0, 1, and 5 following oral supplementation with either creatine or a placebo employing a double-blind crossover study design. Treatments were separated by a 5-wk washout period. Immediately following each muscle sampling, subjects performed two 30-s all-out bouts on a cycle ergometer. Creatine supplementation increased (P < 0.05) muscle total creatine content above placebo levels; however, there were no changes (P > 0.05) in C_T values across the supplementation periods for any of the genes. Nevertheless, 95% confidence intervals showed that GAPDH was variable, whereas ß-actin, ß₂M, and CYC were the least varying genes. Normalization of the data to these housekeeping genes revealed variable behavior for ß₂M with more stable expressions for both ß-actin and CYC. We conclude that, using real-time RT-PCR, ß-actin or CYC may be used as housekeeping genes to study gene expression in human muscle in experiments employing short-term creatine supplementation combined with high-intensity exercise.

Evaluation of the fineness of degummed bast fibers

Fiber fineness characteristics are important for yarn production and quality. In this paper, degummed bast fibers such as hemp, flax and ramie have been examined with the Optical Fiber Diameter Analyzer (OFDA100 and OFDA2000) systems for fiber fineness, in comparison with the conventional image analysis and the Wira airflow tester. The correlation between the results from these measurements was analysed. The results indicate that there is a significant linear co-relation between the fiber fineness measurement results obtained from those different systems. In addition, the mean fiber width and its coefficient of variation obtained from the OFDA100 system are smaller than those obtained from the OFDA2000 system, due to the difference in sample preparation methods. The OFDA2000 system can also measure the fiber fineness profile along the bast fiber plants, which can be useful for plant breeding.

Frictional and tensile properties of conducting polymer coated wool and alpaca fibers

Wool and alpaca fibers were coated with polypyrrole by vapor-phase polymerisation method. The changes in frictional and tensile properties of the single fibers upon coating with the conductive polymer are presented. Coating a thin layer of polypyrrole on the alpaca and wool fibers results in a significant reduction in the fiber coefficient of friction, as the conducting polymer layer smooths the protruding edges of the fiber scales. It also reduces the directional friction effect of the fibers. Depending on the type of fiber, the coating may slightly enhance the tensile properties of the coated fibers.

Modification of tissue fatty acid composition in Murray cod (Maccullochella peelii peelii, Mitchell) resulting from a shift from vegetable oil diets to a fish oil diet.

The dynamics of fatty acid composition modifications were examined in tissues of Murray cod fed diets containing fish oil (FO), canola oil (CO) and linseed oil (LO) for a 25-week period and subsequently transferred to a FO (finishing/wash-out) diet for a further 16 weeks. At the commencement of the wash-out period, following 25 weeks of vegetable oil substitution diets, the fatty acid compositions of Murray cod fillets were reflective of the respective diets. After transfer to the FO diet, differences decreased in quantity and in numerousness, resulting in a revert to the FO fatty acid composition. Changes in percentages of the fatty acids and total accumulation in the fillet could be described by exponential equations and demonstrated that major modifications occurred in the first days of the finishing period. A dilution model was tested to predict fatty acid composition. In spite of a general reliability of the model (Y=0.9234X+0.4260, R²=0.957, P<0.001, where X is the predicted percentage of fatty acid; Y the observed percentage of fatty acid), in some instances the regression comparing observed and predicted values was markedly different from the line of equity, indicating that the rate of change was higher than predicted (i.e. Y=0.4205X+1.191, R²=0.974, P<0.001, where X is the predicted percentage of α-linolenic acid; Y the observed percentage of α-linolenic acid). Ultimately, using the coefficient of distance (D), it was shown that the fatty acid composition of fish previously fed the vegetable oil diets returned to the average variability of the fillet fatty acid composition of Murray cod after 70 or 97 days (LO and CO respectively).

Validation of a food-frequency questionnaire assessment of carotenoid and vitamin E intake using weighed food records and plasma biomarkers: the method of triads model.

Background: Reliability or validity studies are important for the evaluation of measurement error in dietary assessment methods. An approach to validation known as the method of triads uses triangulation techniques to calculate the validity coefficient of a food-frequency questionnaire (FFQ).

Objective: To assess the validity of an FFQ estimates of carotenoid and vitamin E intake against serum biomarker measurements and weighed food records (WFRs), by applying the method of triads. Design: The study population was a sub-sample of adult participants in a randomised controlled trial of b-carotene and sunscreen in the prevention of skin cancer. Dietary intake was assessed by a self-administered FFQ and a WFR. Nonfasting blood samples were collected and plasma analysed for five carotenoids (a-carotene, b-carotene, b-cryptoxanthin, lutein, lycopene) and vitamin E. Correlation coefficients were calculated between each of the dietary methods and the validity coefficient was calculated using
the method of triads. The 95% confidence intervals for the validity coefficients were estimated using bootstrap sampling.

Results: The validity coefficients of the FFQ were highest for a-carotene (0.85) and lycopene (0.62), followed by b-carotene (0.55) and total carotenoids (0.55), while the lowest validity coefficient was for lutein (0.19). The method of triads could not be used for b-cryptoxanthin and vitamin E, as one of the three underlying correlations was negative.

Conclusions: Results were similar to other studies of validity using biomarkers and the method of triads. For many dietary factors, the upper limit of the validity coefficients was less than 0.5 and therefore only strong relationships between dietary exposure and disease will be detected.

Performance of statistical inference for block classification in reducing blocking artefact in video coded images

This paper presents a performance study of four statistical test algorithms used to identify smooth image blocks in order to filter the reconstructed image of a video coded image. The four algorithms considered are the Coefficient of Variation (CV), Exponential Entropy of Pal and Pal (E), Shannon's (Logarithmic) Entropy (H), and Quadratic Entropy (Q). These statistical algorithms are employed to distinguish between smooth and textured blocks in a reconstructed image. The linear filtering is carried out on the smooth blocks of the image to reduce the blocking artefact. The rationale behind applying the filter on the smooth blocks only is that the blocking artefact is visually more prominent in the smooth region of an image rather than in the textured region.

Distribution of an alien aquatic snail in relation to flow variability, human activities and water quality

1. Disturbance and anthropogenic land use changes are usually considered to be key factors facilitating biological invasions. However, specific comparisons of invasion success between sites affected to different degrees by these factors are rare.

2. In this study we related the large-scale distribution of the invading New Zealand mud snail (Potamopyrgus antipodarum) in southern Victorian streams, Australia, to anthropogenic land use, flow variability, water quality and distance from the site to the sea along the stream channel.

3. The presence of P. antipodarum was positively related to an index of flow-driven disturbance, the coefficient of variability of mean daily flows for the year prior to the study.

4. Furthermore, we found that the invader was more likely to occur at sites with multiple land uses in the catchment, in the forms of grazing, forestry and anthropogenic developments (e.g. towns and dams), compared with sites with low-impact activities in the catchment. However, this relationship was confounded by a higher likelihood of finding this snail in lowland sites close to the sea.

5. We conclude that P. antipodarum could potentially be found worldwide at sites with similar ecological characteristics. We hypothesise that its success as an invader may be related to an ability to quickly re-colonise denuded areas and that population abundances may respond to increased food resources. Disturbances could facilitate this invader by creating spaces for colonisation (e.g. a possible consequence of floods) or changing resource levels (e.g. increased nutrient levels in streams with intense human land use in their catchments).