Triangular Section Research Articles

Autorotation of many-sided bodies in an airstream

AUTOROTATION is the rotation of an object in an airstream in the absence of any other driving force1. It is important in the fall characteristics of some tree fruits, the growth of hailstones, and the trajectories of objects separating from aircraft and spacecraft. Previous studies have concentrated on thin, flat plates rotating about an axis normal to the airstream, but in many applications— those relating to the free fall of bodies through air—the behaviour of bodies of more complex geometry is of interest. When these autorotate, a lift force is generated which can significantly alter the body's trajectory. Here I examine the autorotation of prisms whose cross-sections are regular polygons. Prisms of triangular section rotate fastest, but generate less lift than a flat plate. Only bodies with less than eight sides are found to show autorotational behaviour. In all of these cases, the lift forces generated are larger than those obtained from a spinning cylinder driven externally at the same rotation speed. Many devices have been proposed in the past that use as a propulsion mechanism the lift force developed on a driven rotating cylinder, perhaps the most spectacular being the Flettner rotorship which crossed the Atlantic in 19262. The use of polygonal bodies would have application in these cases, not only because of the higher lift generated but also because the energy required may be derived simply from the relative wind. There are thus also clear implications for wind-power devices.

Crystal structure of Rb 2Fe 5F 17

Fine, whisker-like crystals of Rb 2Fe 5F 17 have been obtained from solid state stoichiometric mixtures of RbF and FeF 3. A structural model has been determined from single crystal diffractometer data in the Fmmm orthorhombic space group : a = 14.887(2) A ̊ , b = 25.814(3) A ̊ , c = 7.560(1) A ̊ ; z = 8; ϱ exp. = 3.529 g cm −3; ϱ calc.=3.535 g cm −3; λ Co Ka =1.7903 A ̊ ; R = 0.068; R ω = 0.096 for 175 reflections with I σ( I) > 6 . The structure has been compared with that of HTB. Rb 2Fe 5F 17 exhibits layers of (Fe 5F 17) 2n− n composition containing FeF 6 corned-shared octahedra forming tunnels of hexagonal and triangular sections. Rubidium atoms are located between the layers and within the hexagonal tunnels with statistical occupancy. The structure has been roughly confirmed by TEM. The observed lowering in symmetry from Fmmm may be explained by partial ordering of rubidium and by possible bridging of (Fe 5F 17) sheets by FeF 6 octahedra.

Phagodrilus gen.nov. (Lumbriculidae): systematics and biology of a predaceous oligochaete from western North America

The genus Phagodrilus (Lumbriculidae) is erected for Phagodrilus macnabi sp.nov., a predaceous worm with a paryngeo-esophageal region resembling that of Agriodrilus, a monotypic genus from Lake Baikal, often cited as a potential progenitor of the leeches. The pharynx or gizzard of Phagodrilus has the opposite dorsoventral orientation of its triangular section to that of Agriodrilus (apex dorsad in Phagodrilus, ventrad in Agriodrilus). While the latter appears closely related to Lamprodrilus in terms of its reproductive system, Phagodrilus resembles the Stylodrilus–Hrabea complex. These characteristics clearly indicate separate origins of the predatory habit and convergence of these two taxa, which suggests reexamination of the relationship between them and the leeches and branchiobdellids.

ASLO Special Symposium on Regional Effects of Acid Deposition on Surface Waters

Of the 10 papers presented in the ASLO special symposium, Regional Effects of Acid Deposition on Surface Waters, seven were regional case studies of lakes (four papers) or streams (three papers). These papers stressed the importance of hydrologic settings and flow paths in regulating pH and the acid neutralizing capacity (ANC). Three papers dealt with special topics: fishery models, paleolimnological reconstructions, and an overview of lake‐watershed‐airshed interactions. Geographically, data were derived primarily from a triangular section of the eastern and central United States (from Maine to Minnesota and Florida) corresponding to regions 1, 2, and 3 of the National Surface Water Survey.

Antireflection effect in ultrahigh spatial-frequency holographic relief gratings

An interpretation model for low reflectivity in ultrahigh spatial-frequency holographic relief gratings is proposed. The model is based on the concept that the grating effective index, caused by grating ultrahigh spatial frequency, is graded in the depth direction and forms an antireflective constitution similar to the multilayer coating. Numerical results show that a sinusoidal grating is antireflective over wide groove depth, wavelength and incident angle ranges, and a grating with nearly triangular section, having a circle arc index distribution, has a very low reflectivity, >10(-4)%. Reflectivity vs groove depth, obtained experimentally for a holographically recorded photoresist grating, agrees fairly well with the numerical results.

Development of appropriate mechanization for the ‘W’-form soil management system

The ‘W’-form soil management system consists of shaping the soil surface in the form of a ‘W’ with alternate wide and narrow ridges following the contour. The triangular section wide ridges serve as a rainwater harvesting zone, the trapezoidal section narrow ridges as the planting zone and the furrows as water-storage zones and pathways for animals and wheels. The system, which was designed to improve ‘in-situ’ rainwater harvesting and control of run-off and erosion, has also shown promising results in: (1) facilitating separate and selective tillage operations for different zones, (2) decreasing the animal and tractor hours requirement, (3) reducing compaction in the planting zone and (4) permitting localized application of soil conditioners, thus resulting in higher yield and ensured crop production. The operational requirements for implementing and reshaping the system are described in detail for two types of mechanization, one for animal traction and another for tractor traction. Implementation of the system requires 6–8 h ha −1 with animal traction and 2–3 h ha −1 with tractor traction as compared to 20–22 h ha −1 and 6–8 h ha −1 required in the traditional system of flat cultivation with animal and tractor traction, respectively.

Wave Breaking Phenomena in Self-Similar Flow

Mechanism of the occurrence of wave breaking with vortex sheets is discussed by thinking the self-similar flow in strict consideration of the gravitational effect. Approximate realization of the self-similar flow with wave breaking was experimentally confirmed by using a ship model with triangular similar sections whose keel line varies as AX2, where X is the longitudinal length. It is shown that the zonal breadth of wave breaking is proportional to ε X2/F2 and it is related to the zone of the existence of longitudinal waves as a result of applying a linearized theory under the assumption that ε<<1 and F<<1, where ε is an appex angle and F is defined as U∞√A/g. Examinations of local solutions under the nonlinear free surface conditions showed an existence of the singular solution with a vortex sheet on the production of folded wave surface into two. Its solution explains the mechanism of the initiation of wave breaking phenomena.

Tibial vibration transmission—The effects of incremental osteotomy

s 229 exercise. Fatigue reduced the total stiffness at any given level of initial torque in proportion to the degree of muscle gain reduction. This indicated that reflexes did not preserve the mechanical properties at the joint in the face of fatigue. Furthermore, the stiffness was also reduced when compared at the same level of initial EMG before and after fatigue, without obvious changes in the reflex EMG response. Thus, stilfness was not uniquely related to the motor neuron pool output and was relatively insensitive to feedback from muscle force receptors. TIBIAL VIBRATIOS TRANSMISSIOS-THE EFFECTS OF INCREMENTAL OSTEOTOMY W. J. MINTOWT-CZYZ, J. A. FAIRCLOUGH, I. G. MACKIE and L. D. M. NOKES (Cardiff Royal Infirmary, Cardiff, U.K.) The human tibia will transmit vibration along its length in response to an impulse at one end. Accelerometers positioned proximally and distally detect the vibration and can measure its magnitude. The ratio of the distal to the proximal measurements yields a measure of the attenuation of the vibration as it passes along the bone. This ‘attenuation factor’ (AF) has been shown to change predictably during fracture union and has been used as a measure of bone healing. This cadaver study was performed to investigate the changes in vibration attenuation consequent upon the making of an osteotomy in stages through the tibia with the intention of discovering what was the influence of the residual intact bone in allowing vibration transmission to occur. Five tibiae were studied. Incremental osteotomies were made with a gigli saw in five stages through each bone and the attenuation factor measured at each stage. The depth of the cut was used as an assessment of the residual intact bone. Standard transmission theory suggests that energy transmission along an object is proportional to its cross sectional area. The results of this study show that the attenuation factor is proportional to the calculated residual area of intact bone, making the assumption that the tibia at the point ofdivision has a triangular cross-section with a triangular section to its medullary cavity. The results imply that measurement of the attenuation factor might be a useful technique for the assessment of the mechanical integrity of bone and support the finding that in life attenuation factor changes in parallel with fracture healing. VARIABLE FORCE COIL SPRING HAND SPLINT J. DANOFF, W. SCHNEIDERWIND, B. MOY, B. THORNTON, L. GERBER, A. RICH and J. LEDERMANN (Department of Rehabilitation Medicine, National Institutes of Health, Bethesda, MD, U?S.A.) Medical conditions such as rheumatoid arthritis can cause severe disfigurement and pain in the joints of the fingers with significant functional loss. In recent years surgical intervention has been applied to regain function of these joints. Hand splints as components of post-operative management have been used to apply low forces to the affected digits in such a manner to ensure that functional alignment will be retained after healing has been completed. Dynamic hand splints allow for digit movement, and forces are usually generated by appropriately positioned elastic bands. Several problems are associated with these splints including non-linearity of forces, deterioration of elastic elements, and inability to perform functional movements. For these reasons a new hand splint was developed using stainless steel linear coil springs to provide variable, but easily adjustable, forces to each of the fingers. This splint can also be adjusted in length, flexion/extension angle, and radial/ulnar orientation. Three units are currently being used on post-surgical patients as needed. ASSESSMENT OF FOOTPAD DEPENDABILITY J. DANOFF, T. WAGGONER and G. HUNT (Department of Rehabilitation Medicine, National Institutes of Health, Bethesda, MD) Commercially manufactured switched footpads are available for monitoring foot-surface contact patterns. These are used in many clinical settings to provide information on gait analysis. Testing procedures are necessary to assure the consistency of these pads. In this study footpads were evaluated by mounting each in a rig under a Chatillon Pressure Gauge. The rig was manipulated to determine switch closing force at nine marked points on each pad. Ten pads were tested twice. Five of these were retested additionally to reach ten trials. Correlated r-test and linear correlations (r) were used to compare the paired data, and coefficients of variation (CV) were

Finite element method for unsteady MHD flow through pipes with arbitrary wall conductivity

AbstractA finite element method is given to obtain the numerical solution of the coupled equations in velocity and magnetic field for unsteady MHD flow through a pipe having arbitrarily conducting walls. Pipes of rectangular, circular and triangular sections have been taken for illustration. Computations have been carried out for different Hartmann numbers and wall conductivity at various time levels. It is found that if the wall conductivity increases, the flux through a section decreases. The same is the effect of increasing the Hartmann number. It is also observed that the steady state is approached at a faster rate for larger Hartmann numbers or larger wall conductivity. Selected graphs are given showing the behaviour of velocity, induced magnetic field and flux across a section.

Sparing for repairable, redundant systems : Harold L. Platzer. Proc. A. Reliab. Maintainab. Symp. 394 (1983)

A system has been developed to efficiently test the selection and calibration of a multicomponent model for a solution phase. SPIN14 is a BASIC computer program which calculates the spinodal surface for a line or triangular compositional section through an n-component Kohler or regular solution. The geometry of immiscibility can be approximated from this spinodal thereby providing trial values for a second BASIC program QUATG1 (n ≲ 4) which uses an activity matching algorithm to calculate coexisting phases on the solvus. The output from QUATG1 is designed for contouring the compositional locus of one side of the solvus with isopleths from the other side, thereby eliminating the need for tie lines. QUATG1 also calculates ternary spinodals for Kohler, Wohl, and regular solutions and calibrates a ternary correction free energy model. 6 short programs have been written for a T159 programmable calculator and these prepare data for the two BASIC programs, convert the spinodal geometry to an approximate solvus geometry and vice versa.

Programs for calculating the geometry of multicomponent exsolution

A system has been developed to efficiently test the selection and calibration of a multicomponent model for a solution phase. SPIN14 is a BASIC computer program which calculates the spinodal surface for a line or triangular compositional section through an n-component Kohler or regular solution. The geometry of immiscibility can be approximated from this spinodal thereby providing trial values for a second BASIC program QUATG1 ( n ≲ 4) which uses an activity matching algorithm to calculate coexisting phases on the solvus. The output from QUATG1 is designed for contouring the compositional locus of one side of the solvus with isopleths from the other side, thereby eliminating the need for tie lines. QUATG1 also calculates ternary spinodals for Kohler, Wohl, and regular solutions and calibrates a ternary correction free energy model. 6 short programs have been written for a T159 programmable calculator and these prepare data for the two BASIC programs, convert the spinodal geometry to an approximate solvus geometry and vice versa.

The V-Shaped Broad-Crested Weir

A discharge measurement structure with a triangular control section and a broad crest provides a rather wide measuring range while the head-discharge relation remains unaffected by tailwater up to a high submergence ratio. Experiments with the V-shaped broad-crested weirs have been carried out in order to investigate the influence of a boundary layer above the crest. The boundary displacement thickness is replaced by a correction height which includes the effects of a non-uniform velocity distribution, non-parallel streamlines and lateral pressure gradients. The experiments have results in a large collection of laboratory data with the aim to derive the head-discharge relations for different shapes under free flow as well as submerged flow conditions. The weir can be constructed with a fixed crest or a movable crest in vertical runways. The maximum discharge depends on the chosen dimensions. The structure is a suitable device for small and moderate discharges. Results of investigation, design rules and limits of application are given.

Accurate estimation of characteristic impedance of coaxial transmission-line problems by the eigenfunction approach

Accurate numerical results are presented for regular polygonal coaxial transmission lines with inner central circular conductor using an eigenfunction approach and a successive integration method of boundary condition satisfaction. Just two-term solutions are found to yield high accuracy. The results for equilateral triangular section are found to be superior to those reported in literature.

Prediction of Fat and Fat Free Live Weight in Broiler Chickens Using Backskin Fat, Abdominal Fat, and Live Body Weight

Data from 100 male and 100 female broiler chickens that were raised on the floor under two lighting regimes (12 and 24 hr light) were combined. Birds were weighed when 58 days old (male data presented first) (2372 g, 1913 g) and then slaughtered at 59 days. Abdominal fat was weighed (2.18%, 2.82%) and fat extracted from ground carcass (12.0%, 13.7% wet basis), intestines (47.6%, 56.2% dry basis), and from a triangular section of backskin (86.1%, 88.0% dry basis). Percent total fat was 10.4 and 12.2 (wet basis). Abdominal fat regressed on live body weight produced negative intercepts, indicating that regressed rather than percent values should be used.Fat from the four locations mentioned above had correlation coefficients of +.45 to +.76 for males and +.47 to +.74 for females. Percent abdominal fat had low nonsignificant correlations with fat free live body weight (r = +.23 male, −.07 female). Abdominal fat weight was a better (higher r2) predictor of total fat, total fat minus abdominal fat, percent carcass fat, and percent intestinal fat, than percent backskin fat. Thirty-three percent (male) and 22% (female) of the variation of percent abdominal fat was accounted for by percent backskin fat. Abdominal fat should be obtained directly and used for predicting fat in the bird rather than backskin fat.Abdominal fat was +20.7% (male) and +22.8% (female) of total fat. Prediction equations for estimating total fat and fat free live weight, given abdominal fat, and live body weight were developed.Selection against percent abdominal fat would probably result in a reduction of fat in other locations and little change in fat free live weight.

Estadio de Kansas City (EE. UU.)

The Crosby Kemper stadium, located in the center of an industrial district of Kansas City, was designed for various uses which include activities ranging from music and sports competitions to equestrian sports. It has a capacity for approximately 16 to 18,000 people and parking for 4,000 cars. The outstanding feature of its architectonic conception is the solution adopted for building the roof, by means of enormous metal tubular beams, of triangular section and a height of 8.25 meters with pipe diameters reaching 120 cm.

Molecular flow conductance of long tubes with uniform elliptical cross-section and the effect of different cross-sectional shapes

A formula is derived for the transmission probability (and hence, gas flow conductance) of a long tube, having a uniform elliptical cross-section, valid in the molecular flow regime (long mean free paths). Comparison with long tubes of circular and rectangular section having the same area showed relatively close agreement in transmission probabilities between elliptical and rectangular section tubes for the same ratio of axes or length of sides respectively. Variations from a circular, square (or triangular) section remained within 10% down to axes or side ratios of 0.3. Existing formulae in the literature, applicable to elliptical sections, show deviations increasing with the ellipticity. It is shown that the frequently used relation involving the ratio of cross-sectional area to perimeter for tubes of various shapes (other than circular) may lead to large errors.

Sway Added-Mass of Cylinders in a Canal Using Dual-Extremum Principles

This paper describes a finite-element method based on the dual extremum principles. As an application of the dual-extremum principles, the upper and lower bounds of the added mass of two-dimensional cylinders in a canal are computed for the zero-and infinite-frequency limits. Specifically, the upper and lower bounds of the added mass of a rectangular section, a triangular section, a circular section, and a Lewis-form section at the center of a rectangular canal are computed. The added mass is also computed for a rectangular section at off-center locations in a canal. Present numerical results are compared with previous results obtained by the hypercircle method [1].

Measurements of a Small Near-Bottom Cyclonic Circulation Near the Gulf Stream Axis

Data from near-bottom current meters moored in a small triangular array (25 km/side) plus hydrographic sections reveal the presence of a near-bottom cyclonic circulation with a radius of 50 km and velocity of 10 cm/s just north of the Gulf Stream near 50°W. The circulation extends to at least 1350 m from the ocean floor and was observed over a period of 9 days during which time it moved southward toward the Stream with speeds of 0.5–15 cm/s. The strength of the circulation decreases somewhat with distance from the bottom.

Low frequency vibrations of elastic bars

The method of expansion of three-dimensional displacements in a double power series of the transverse coordinates is employed to find one-dimensional equations applicable to low frequency vibrations of uniform, elastic, isotropic and anisotropic bars. The axial displacements accompanying torsion are chosen specially for each cross-sectional shape of bar—resulting in the correct, or nearly correct, torsional rigidity. Applications are to bars of elliptic, triangular and rectangular sections, illustrating various independent and coupled extensional, flexural and torsional modes of motion.

VI.—Sword Rings and Beads

Alist of ring-swords and beads known to date was published in 1967, and a few more items and observations may now be added. Another jewelled example has just come to my notice in the museum at Laon (Aisne), France (pl. lxiva–c). The basic metal is presumably bronze as it is covered in places with green corrosion products. It is a form which began early, i.e. a triangular middle section with animal head terminals at each end, as in a Snartemo grave. The pommel is hollow and was fastened to the rest of the grip not by lateral rivets, but by the tang of the sword which projects slightly through a hole in the top. Its measurements are 5.1×1.5 cm. and the middle triangular faces are inlaid with garnets in curved cloisons at each corner, and framed in a zigzag border presumably inlaid with silver or niello. From the arced segments each side of this a tongue-shape, also decorated with zigzags, runs up each incurved side towards the apex. At one end is a splayed curved terminal, no longer an animal head but bearing ribbon animal ornament in relief. The corresponding opposite end is not decorated, but on top is a small hollow, and a piece at the extremity is broken off and missing. This end section is a pad for the reception of a missing ring-knob, with the end of the vertical bow fitting into the hollow.