Increasing Speed (increasing + speed)

Distribution by Scientific Domains

Selected Abstracts

Numerical simulation of heat transfer and fluid flow over two rotating circular cylinders at low Reynolds number

Nikolay Pavlovich Moshkin
Abstract This paper presents a numerical investigation of the characteristics of two-dimensional heat transfer in a steady laminar flow around two rotating circular cylinders in a side-by-side arrangement. The simulation is validated by comparing our computational results for the large gap-spacing between cylinder surfaces with the available numerical and experimental data for a single cylinder. Numerical simulations were carried out for the Reynolds number range 10,Re ,40, for the Prandtl number range 0.7,Pr ,50, and for a variety of absolute rotational speeds (|,|,2.5) at different gap spacings. The study revealed that for the range of parameters considered the rate of heat transfer decreases with the increasing speed of rotation. An increase of the Prandtl number resulted in an increase in the average Nusselt number. The streamlines and isotherms are plotted for a numbers of cases to show the details of the velocity and thermal fields. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( DOI 10.1002/htj.20293 [source]

Evolutionary relationships of sprint speed in Australian varanid lizards

C. J. Clemente
Abstract Ecomorphological studies often seek to link morphology and performance to relevant ecological characteristics. Varanid lizards are unique in that species can vary in body size by almost four orders of magnitude within a single genus, and a question of considerable interest is whether similar ecomorphological relationships exist when constraints on body size are reduced. We studied sprint speed in relation to size, shape and ecology for 18 species of varanid lizards. Maximal speed scaled positively with mass0.166 using least squares regression, and mass0.21 using reduced major-axis regression. However, a curvilinear trend better described this relationship, suggesting an optimal mass of 2.83 kg with respect to speed. Including data for the komodo dragon Varanus komodoensis moves the optimum mass to 2.23 kg. We use this relationship to predict the sprint speed of the Komodo's giant extinct relative Varanus (Megalania) prisca to be 2.6,3 m s,1 similar to that of extant freshwater crocodiles Crocodylus johnstoni. When differences in speed were compared to ecological characteristics, species from open habitats were significantly faster than species from semi-open or closed habitat types, and remained so after correction for size and phylogeny. Thus, despite large variation in body size, varanids appear to share similar associations between performance and ecology as seen in other lizard groups. Varanids did, however, differ in morphological relationships with sprint speed. Differences in relative speed were not related to relative hindlimb length, as is commonly reported for other lizard groups. Instead, size-free forefoot length was negatively related to speed as was the size-free thorax,abdomen length. While shorter forefeet were thought to be an adaptation to burrowing, and thus open habitats, rather than speed per se, the reduction in the thorax,abdomen length may have significant advantages to increasing speed. Biomechanical models predicting this advantage are discussed in relation to a trade-off between speed and manoeuvrability. [source]

3D ultrasound in robotic surgery: performance evaluation with stereo displays,

Paul M. Novotny
Abstract Background The recent advent of real-time 3D ultrasound (3DUS) imaging enables a variety of new surgical procedures. These procedures are hampered by the difficulty of manipulating tissue guided by the distorted, low-resolution 3DUS images. To lessen the effects of these limitations, we investigated stereo displays and surgical robots for 3DUS-guided procedures. Methods By integrating real-time stereo rendering of 3DUS with the binocular display of a surgical robot, we compared stereo-displayed 3DUS with normally displayed 3DUS. To test the efficacy of stereo-displayed 3DUS, eight surgeons and eight non-surgeons performed in vitro tasks with the surgical robot. Results Error rates dropped by 50% with a stereo display. In addition, subjects completed tasks faster with the stereo-displayed 3DUS as compared to normal-displayed 3DUS. A 28% decrease in task time was seen across all subjects. Conclusions The results highlight the importance of using a stereo display. By reducing errors and increasing speed, it is an important enhancement to 3DUS-guided robotics procedures. Copyright © 2006 John Wiley & Sons, Ltd. [source]

The Impact of Product Innovativeness on the Link between Development Speed and New Product Profitability,

Fred Langerak
A review of the literature reveals that the relationship between development speed and new product profitability is not as strong and straightforward as conventional wisdom suggests. A number of studies show positive results, others show mixed results, and some present no evidence of a relationship. In other words, the valence of the link between development speed and new product profitability is unclear at this time. Therefore, this study investigates whether or not speeding new products to market has positive or negative effects on new product profitability. Prior research shows that product innovativeness influences both development speed and new product profitability. This raises the question of whether increasing speed is equally successful in improving profitability across new products that differ in their degree of innovativeness. Therefore, this study also investigates the moderating effect of product innovativeness on the relationship between development speed and new product profitability. The results from a survey-based study of 233 manufacturers of industrial products in the Netherlands reveal an inverted U-shaped relationship between development speed and new product profitability. The findings also show that the optimal point is different for two new product types,product improvements and line additions,that vary in their innovativeness. These results provide an onset for the development of a decision tool that helps managers to determine how much to spend on accelerating the development of individual new products and how they should allocate that spending across products in their new product portfolio. [source]

Shear Deactivation of Cellulase, Exoglucanase, Endoglucanase, and ,-Glucosidase in a Mechanically Agitated Reactor

Tejas P. Gunjikar
Shear deactivation of cellulase and its major component enzymes, viz., exoglucanase (exo -1,4-,- D -glucan-4-cellobiohydrolase), endoglucanase (endo -1,4-,- D -glucanhydrolase), and 1,4-,-glucosidase, was carried out by exposing cellulase to shear in a mechanically agitated reactor in the presence as well as in the absence of the substrate cellulose. Cellulase was found to undergo deactivation when subjected to shear, and the extent of deactivation increased with increasing speed of agitation. Among the three major component enzymes of cellulase, exoglucanase showed rapid deactivation and contributed the most to cellulase deactivation. The presence of a substrate did not affect the deactivation of cellulase. [source]

Intensity of Nordic Walking in young females with different peak O2 consumption

Toivo Jürimäe
Summary The purpose of this cross - sectional study was to determine the physiological reaction to the different intensity Nordic Walking exercise in young females with different aerobic capacity values. Twenty-eight 19,24-year-old female university students participated in the study. Their peak O2 consumption (VO2 peak kg,1) and individual ventilatory threshold (IVT) were measured using a continuous incremental protocol until volitional exhaustion on treadmill. The subjects were analysed as a whole group (n = 28) and were also divided into three groups based on the measured VO2 peak kg,1 (Difference between groups is 1 SD) as follows: 1. >46 ml min,1 kg,1 (n = 8), 2. 41,46 ml min,1 kg,1 (n = 12) and 3. <41 ml min,1 kg,1 (n = 8). The second test consisted of four times 1 km Nordic Walking with increasing speed on the 200 m indoor track, performed as a continuous study (Step 1 , slow walking, Step 2 , usual speed walking, Step 3 , faster speed walking and Step 4 , maximal speed walking). During the walking test expired gas was sampled breath-by-breath and heart rate (HR) was recorded continuously. Ratings of perceived exertion (RPE) were asked using the Borg RPE scale separately for every 1 km of the walking test. No significant differences emerged between groups in HR of IVT (172·4 ± 10·3,176·4 ± 4·9 beats min,1) or maximal HR (190·1 ± 7·3,191·6 ± 7·8 beats min,1) during the treadmill test. During maximal speed walking the speed (7·4 ± 0·4,7·5 ± 0·6 km h,1) and O2 consumption (30·4 ± 3·9,34·0 ± 4·5 ml min,1 kg,1) were relatively similar between groups (P > 0·05). However, during maximal speed walking, the O2 consumption in the second and third groups was similar with the IVT (94·9 ± 17·5% and 99·4 ± 15·5%, respectively) but in the first group it was only 75·5 ± 8·0% from IVT. Mean HR during the maximal speed walking was in the first group 151·6 ± 12·5 beats min,1, in the second (169·7 ± 10·3 beats min,1) and the third (173·1 ± 15·8 beats min,1) groups it was comparable with the calculated IVT level. The Borg RPE was very low in every group (11·9 ± 2·0,14·4 ± 2·3) and the relationship with VO2and HR was not significant during maximal speed Nordic Walking. In summary, the present study indicated that walking is an acceptable exercise for young females independent of their initial VO2 peak level. However, females with low initial VO2 peak can be recommended to exercise with the subjective ,faster speed walking'. In contrast, females with high initial VO2 peak should exercise with maximal speed. [source]