Wide Blade Research Articles

Morphological Trait and Maturity Group Relations with Digestibility of Orchardgrass

Time and labor could be saved in initial screenings if plant breeders had better information on the relationship of morphological traits and of maturity groups to forage quality. This study was conducted to investigate these relations in orchardgrass (>Dactylis glomerata L.). Fifty clones from two maturity groups (anthesis differed by 8 d) were selected divergently for leaf‐blade width, leaf‐blade length, tiller number, growth habit, and seed weight. Space‐planted clones were harvested on a common date in spring (near anthesis of the late group) and summer (after 5 wk of regrowth), and were separated into plant parts before determining in vitro digestible dry matter (IVDDM). Anatomical characteristics were examined for narrow‐ and wide‐blade clones from the two maturity groups. Samples were stained with safranin to identify lignified cell walls, and cross‐sectional areas were quantified by image analysis. Leaf‐blade width was most consistently associated with IVDDM. Wide‐blade clones of the late group were more digestible than narrow‐blade clones during spring growth, but little difference existed during summer regrowth. Differences in digestibility were greatest in stems of reproductive tillers (≈8%). Wide‐blade clones had the same or morelignin in stems than did narrow‐blade clones, but wide‐blade clones had less lignin as a percentage of cross‐sectional area than did narrow‐blade clones. Differences in IVDDM between maturity groups were also most evident during spring growth, when stems of reproductive tillers in the late group were 16% more digestible than those in the early group. Thus, selecting for wide blades and late maturity can be an effective method for initial screening for high digestibility in orchardgrass germplasm.

Characterization of helical impellers by circulation times

AbstractMeasurements of the circulation time during batch mixing of Newtonian and non‐Newtonian fluids were used to analyse and compare the performance of six different helical‐ribbon impellers and a screw impeller inside a draft coil. The distribution of circulation times obtained from two hundred repeated measurements is shown to depend markedly on the impeller geometry. Mixing time data with the helical‐ribbon impellers are correlated with the mean value and the reduced standard deviation of the circulation times. Effective (rapid) mixing corresponds to a large circulation capacity and a wide distribution of the circulation times. The mixing mechanism of Newtonian fluids with the helical‐ribbon impellers is qualitatively described by the Voncken model.The helical impellers' circulation capacities are not affected by the shear‐thinning properties of non‐Newtonian fluids. However, in highly shear‐thinning fluids, the presence of important stagnant zones is responsible for much longer mixing times which consequently do not correlate with the circulation parameters.The relative efficiencies of the different impellers in Newtonian fluids are compared using a criterion based on the the total energy required to achieve a certain degree of mixing. The wide blade impeller is the most efficient of the helical‐ribbon impellers but is considerably less efficient than the screw impeller in a draft coil.

DISTRIBUTIONAL ECOLOGY OF AMPHIPODS AND TANAIDACEANS ASSOCIATED WITH THREE SEA GRASS SPECIES

A one-year survey of amphipods and tanaidaceans associated with monospecific sea grass meadows and a bare sand substratum, under similar physical-chemical conditions, showed that the magnozosterid Thalassia testudinum supported higher numbers of peracarids per square meter than the parvozosterid Halodule wrightii and the bare sand substratum as predicted by Kikuchi and Peres (1977). However, when examined in terms of numbers of individuals per unit sea grass biomass or surface area, Thalassia and Halodule supported nearly equal numbers ofepifauna. Syringodiumfiliforme, a syringodiid, consistently supported highest surface area-standardized abundances of epifauna. The previously reported significance of sea grass biomass in structuring crustacean assemblages held within, but not across, sea grass species. Although the amphipods and tanaids showed no species-specific association with sea grasses, the relative abundance of crustaceans was a function of both sea grass species and biomass. Relative abundance of infaunal types decreased from bare sand to Halodule to Syringodium to Thalassia sites and from low to high biomass sites. The abundance of peracarid crustaceans on sea grass meadows is a complex function of sea grass growth form and biomass which appear to mediate the distribution and foraging behavior of important predators. Despite evidence for strong parallelism among the animal communities of sea grass beds in different geographic regions (Ledoyer, 1964, 1969; Kikuchi, 1966, 1974; Nagle, 1968), Kikuchi and Peres (1977) pointed out that different sea grass species take distinct growth forms which affect the quality and nature of the habitat for small animals. Using the classification system of den Hartog (1967), the abundant sea grasses of the eastern United States are divided into magnozosterids (Zostera marina and Thalassia testudinum) with long, wide blades, parvozosterids (Halodule wrightil) with narrow blades, and syringodiids (Syringodium filiforme) with subulate blades. Because of high microhabitat diversity created by the wide blades, Kikuchi and Peres hypothesized that magnozosterids would support animal communities with higher biomass and species diversity than parvozosterids. Few studies have been designed to test for the role of sea grass species in the organization of associated fauna. Such a study requires closely spaced sites in monotypic beds of different sea grass species, all of which are characterized by similar physical-chemical conditions. In cases where conditions of station similarity have been met, significant differences were found in abundance, species composition, and species richness ofpolychaetes (Santos and Simon, 1974), crustaceans (Lewis, 1982), and fishes (Young, 1981; Stoner, in press) associated with different sea grass species. To test the hypothesis that various sea grass growth forms support different abundance and diversity of resident epifaunal organisms, peracaridan crustaceans were collected at seven closely spaced stations in Indian River lagoon, Florida. Three species of sea grass, Thalassia testudinum, Syringodiumfiliforme, and Halodule wrightii, represent the primary growth forms and are abundant in large beds in the lagoon. With care, it was possible to sample monospecific beds and bare sand substrata with similar depth and water conditions. Seasonal collections at the sites allowed an analysis of differences in species composition, faunal abun

Lifting-line Approximation and Calculations of Partially Cavitating Propeller

Lifting-line approximation and calculations are performed to obtain the characteristics of partially cavitating propellers. Main treatments are summarized as follows.(1) Perturbed flow field by the partially cavitating propeller is described by two kinds of singularity-vortex and source distributions. And then a triple integral equation for determining the singularity distributions is derived from pressure constancy condition on cavity and tangential flow condition on foil surface.(2) By application of lifting-line approximation to the triple integral equation, it is denoted that the two dimensionality holds for any blade element of propeller with respect to effective angle of attack corrected by induced one.(3) In order to improve the accuracy of the lifting-line theory of the partially cavitating propeller, curved flow effect, which is of importance in wide blade propellers, is obtained in the form of correction factors to induced angle of attack on the basis of the existing experiments at noncavitating condition.(4) Two partial cavity theories (thin and thick hydrofoil theory) formerly presented are used for obtaining the two dimensional characteristics of any blade element and optimum model at cavity termination formerly proposed is adopted in these theories. The integral equation of lifting-line is solved by application of these two dimensional characteristic data. (5) Numerical calculations are performed for three kinds of MAU propeller-(i) No. 0197 (number of blade 3, pitch ratio 0.4, developed area ratio 0.5) (ii) No. 0.01 (number of blade 4, pitch ratio 0.73, developed area ratio 0.55) (iii) No. 0105 (number of blade 5, pitch ratio 0.679, developed area ratio 0.6) Some notable effects of propeller cavitation numbers on cavity extent, local cavity volume, local lift coefficient, local drag coefficient, thrust coefficient and torque coefficient are clarified concretely.

Studies on bandsawing of aluminum alloys

Bandsawing tests were conducted on plates of 15, 20, 25 and 30 mm in thickness of aluminum alloys, 7N01-T6. 13 mm wide blades of hook-tooth type with 3 or 6 teeth per inch were used for these tests. Blade speed and feed rate were varied over broad ranges, and the 2-component dynamometer was used to measure the cutting and feeding forces simultaneously. The main results obtained were as follows.(1) The cutting resistance increased with the increase of the feeding rate, while in the same feeding rate the cutting resistance decreased in the increase of the blade speed.(2) The variation in the cutting resistance with the slight change of the feeding rate increased as the blade speed decreased. Thus, high blade speed cutting is recommended for aluminum alloys.(3) The cutting force per tooth was approximatly equal to the feeding force per tooth.(4) It is desirable that the cutting force per tooth and the power required for cutting remain unchanged when workpiece thickness varies. From this point of view, the optimum cutting conditions with variations of workpiece thickness were determined as shown in Fig. 11.

Awards of the Institution of Naval Architects

THE Council of the Institution of Naval Architects has awarded the premium of the Institution for the year 1937 to Mr. R. W. L. Gawn, for his paper “Results of Experiments on Model Screw Propellers with Wide Blades”, the Wakeham Prize (1937) to Mr. H. Lackenby, for his paper “Re-analysis of William Froude's Experiments on Surface Friction and their Extension in the Light of Recent Developments”, and the Duke of Northumberland Prize (1937) (awarded by the Council of the Institution in connexion with the award of National Certificates in Naval Architecture) to Mr. D. N. Wallace, of the Royal Technical College, Glasgow.