Deg Cone Research Articles

MantisBot successfully mimics prey tracking

The praying mantis is a notorious insect, known for its calm, motionless stance while waiting for prey to draw near, followed by a swift and powerful strike. Mantises track moving prey using rapid turning head movements to keep their target in the foveal region of the eyes, where the highest resolution images are produced. Though much is known about insect motion and control, exactly how mantises use visual information to produce these sharp head turns remains unclear. What makes this insect especially interesting is that numerous studies have found that once a turn is initiated, it cannot be stopped – meaning that the mantis must predict the future position of its prey. So, what information does the brain send to the nerve clusters controlling locomotion in order to produce these precise movements?This is the question that an interdisciplinary team of researchers attempted to answer with their mantis-inspired robot, MantisBot. Based on previous studies of praying mantis head movements and insect locomotion in the literature, the team – led by Nicholas Szczecinski from Case Western Reserve University in Ohio, USA – hypothesised that commands to the nerve centres that control locomotion are relatively simple. To test this, they designed a simple nervous network with commands inspired from those biological results, and incorporated it into MantisBot, a 13.3:1 scale robot model of a praying mantis. Based on information provided by the ‘eyes’ – five solar cells arranged around the front of the head – a bioinspired brain-like controller gave simple instructions to the unit controlling the robot's movements: either move or stand still, and which direction to orient the body.To test how well the proposed network directed the robot, the team shone a 1600 lumen LED at it to simulate prey; the difference in voltage of the solar cells told the robot which direction the prey was in. If the prey moved outside a 20 deg cone from the centre of its vision, the controller told the robot to move its head, and if it moved even further (30 deg outside), the robot also used its body and legs too, just like real praying mantises do. But could it track prey accurately?MantisBot's control network was a success, allowing the robot to track prey to within 30 deg of its centre of vision, even when moving its legs and body. Switching direction mid-step was no problem either, and the robot successfully used its legs to help rotate its body while standing still. The robot's high accuracy in tracking prey demonstrates that simple commands – which direction, and whether or not to move – are capable of producing tracking behaviour comparable to that of the praying mantis, and provides plausible evidence that the information sent to the animal's own locomotion control centre could be just as simple.Bioinspired robotic models are not just great precursors to more advanced robots; studies like this demonstrate that they can also supply meaningful feedback, helping us to understand the underlying biology to answer questions that current biological experiments cannot address. Continuing such interdisciplinary work is therefore essential for both fields to progress, and could potentially provide answers to many biological conundrums.

Boundary-Layer Stability Analysis for Stetson’s Mach 6 Blunt-Cone Experiments

The results of a seminal experimental study of the effects of bluntness and swallowing length on transition on an 8 deg cone at zero angle of attack in Mach 6 high-Reynolds-number flow are analyzed with the STABL-2D computational fluid dynamics code package. Mean flow solutions and parabolized stability analyses for a total of 11 different nose-tip bluntnesses, ranging from sharp to a 15.24 mm radius, are obtained. For the sharpest cases, the factor at transition is approximately seven; but, as bluntness increases and the calculated swallowing distance lengthens, the computed factor at the experimentally observed transition location drops below the level at which Mack’s second mode would be expected to lead to transition. These results indicate that the dominant instability mechanism for the bluntest cases is not the second mode, and oblique mode analysis also excludes these modes as the dominant instability mechanism.

The Herschel and Planck Space Telescopes

The European Space Agency launches in 2009 two flagship missions in the domain of submillimeter space astronomy. The Herschel Space Observatory is a common user facility featuring a 3.5 m aperture Cassegrain telescope passively cooled to 80 K. The Planck survey mission includes a 1.5 m unobscured aperture off-axis aplanatic telescope passively cooled to 40 K. Herschel will make pointed target observations of astrophysical objects and phenomena in the frequency range 448 GHz to 5.3 THz (or 672 to 55 mum wavelength). Planck, on the other hand, will map the entire sky by strip scanning at a spin rate of one revolution per minute covering a frequency bandwidth of 30-857 GHz (or wavelength from 10 to 0.35 mm). Its spin axis is pointed antisunward and can be oriented within a 10deg cone around that direction. The telescope line of sight is fixed at an angle of 85 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> to the spacecraft spin-axis. This paper describes briefly the specific telescopes developed for each mission; their design characteristics, the development process for each, their achieved performances (from on ground testing) and their expected performances in flight.

A glimpse of the world through the voice of the echolocating bat.

Bats echolocating in the natural environment face the formidable task of sorting echoes from closely spaced obstacles and prey, which may be mixed with sonar signals of nearby conspecifics. This talk will review behavioral strategies used by the big brown bat, Eptesicus fuscus, to solve such auditory scene analysis tasks. The sonar beam emission pattern of the big brown bat is directional, but broad enough to collect echo information from objects within a 60–90 deg cone, which would enable simultaneous inspection of adjacent objects. Data show, however, that bats shift their sonar gaze to inspect closely spaced objects sequentially and analyze sounds source direction and distance to track auditory objects as they fly. When bats forage in groups, they face the challenge of sorting echoes from their own calls from echoes and calls of neighboring bats. Research findings demonstrate that bats make adjustments in the spectral characteristics of calls when flying with conspecifics, and the magnitude of these changes depend on the baseline similarity of calls produced by individual bats when flying alone. These recent discoveries from studies of bat echolocation point to the general importance of an animal’s action to its analysis of natural scenes.

Neutral interstellar hydrogen in the inner heliosphere under the influence of wavelength-dependent solar radiation pressure

We study the influence of the non-flat shape of the solar Lyman-alpha line on the distribution of neutral interstellar hydrogen in the inner heliosphere and assess importance of this effect for interpretation of heliospheric in situ measurements. Based on available data, construct a model of evolution of the solar Lyman-alpha line profile with solar activity. Modify an existing test-particle code calculating distribution of neutral interstellar hydrogen in the inner heliosphere to take into account the dependence of radiation pressure on radial velocity. Discrepancies between the classical and Doppler models appear at ~ 5 AU and increase towards the Sun from a few percent to a factor of 1.5 at 1 AU. The classical model overestimates density everywhere except a ~ 60 deg cone around the downwind direction, where a density deficit appears. The magnitude of discrepancies depends appreciably on the phase of solar cycle, but only weakly on the parameters of the gas at the termination shock. For in situ measurements of neutral atoms performed at ~ 1 AU, as those planned for IBEX, the Doppler correction will need to be taken into account, because the modifications include both the magnitude and direction of the local flux by a few km/s and degree, which, when unaccounted for, would bring an error of a few degrees and a few km/s in determination of the bulk velocity vector at the termination shock. The Doppler correction is appreciable for in situ observations of neutral H populations and their derivatives performed a few AU from the Sun.

Nose Blowing for Side Force Control on Slender Cones at High Incidence

Vortex asymmetry on axisymmetric pointed forebodies at high angles of incidence results in side forces and adverse yawing moments even in symmetric flight. An experimental investigation has been carried out at low speeds to study the effectiveness of axial nose blowing against the oncoming flow for side force control on two slender cones. Tests were made on the 8 and 12 deg cone models with (circular)jet flow over a Reynolds number range of $0.4\times10^6$ to $5.4\times10^6$. Jet-to-freestream velocity ratio was varied up to 2.0, and the blowing diameter was varied as well. Force measurements were carried over the incidence range of 0 to 45 deg, and limited surface pressure distributions were obtained on the 12 deg cone model. The results explicitly show the effectiveness of nose blowing for side force control over a wide range of Reynolds numbers, and minimum side force was reached around a jet velocity ratio of 1.0. An important result is that the side force reduction correlates with jet velocity ratio in the range of parameters studied. Broad similarities in the trend of side force reduction with the nose blowing and the nose bluntness suggest that the interaction of axial jet with freestream flow results, possibly, in what we may call fluid dynamic blunting.

The echolocating bat controls the direction and distance of its acoustic gaze

Echolocation is an active sensing system that depends upon the dynamic interplay between auditory information processing and adaptive motor control. The echolocating bat produces ultrasonic vocalizations and uses information contained in the returning echoes to build a three-dimensional auditory representation of its surroundings. The timing, bandwidth, and duration of echolocation signals used to probe the environment directly impact the information available to the bat's acoustic imaging system. In turn, the bat's auditory representation of space guides its actions--ear movements, head aim, flight path, and the features of subsequent sonar vocalizations. This talk will summarize the bat's adaptive vocal behavior as it engaged in complex spatial tasks. The bat's 3D flight path was recorded with high-speed stereo IR video; its sonar signals were recorded with a microphone array that permitted reconstruction of the emission pattern. The sonar emission pattern of the big brown bat, Eptesicus fuscus, is directional, but broad enough to collect echo information from objects within a 60-90 deg cone, which would enable simultaneous inspection of objects in the frontal plane. Here, we report that bats encountering a complex environment shifted the direction and distance of their sonar gaze to inspect closely spaced obstacles and targets sequentially.

Study of the Thin-Film GaN-Based LEDs with TiO2/SiO2 Omnidirectional Reflectors and PEC Roughened Surfaces

A novel GaN-based thin-film vertical injection light emitting diode (LED) structure with a TiO2 and SiO2 omnidirectional reflector (ODR) and an n-GaN rough surface is designed and fabricated. At a driving current of 350 mA and with chip size of 1 mm x 1 mm, the light output power and the external quantum efficiency of the LED with a TiO2/SiO2 ODR reaches 330 mW and 26.7%; increasing by 18% and 16%, respectively. The optical output power mainly increased within the 120 deg cone due to the higher reflectance of the TiO2/SiO2 ODR within the blue regime.

Fabrication and characteristics of thin-film InGaN–GaN light-emitting diodes with TiO2/SiO2 omnidirectional reflectors

In this paper, a novel GaN-based thin-film vertical injection light-emitting diode (LED) structure with a TiO2 and SiO2 omnidirectional reflector (ODR) and an n-GaN rough surface is designed and fabricated. The designed ODR, consisting of alternating TiO2 and SiO2, layers possesses a complete photonic band gap within the blue region of interest. The arrays of the conducting channels are integrated into the TiO2/SiO2 ODR structure for vertically spreading the current. Assisted by the laser lift-off and photo-enhanced chemically etched surface roughening process, the light output power and the external quantum efficiency of our thin-film LED with a TiO2/SiO2 ODR (at a driving current of 350 mA and with chip size of 1 mm × 1 mm) reached 330 mW and 26.7%, increased by 18% and 16%, respectively, compared with the results from the thin-film LED with an Al mirror. By examining the radiation patterns of the LEDs, the optical output power mainly increased within the 120 deg cone due to the higher reflectance of the TiO2/SiO2 ODR within the blue regime.

Tensile Behavior of Cast-in-Place and Undercut Anchors in High-Strength Concrete

This paper deals with the pullout capacity, the failure cone geometry, and the load deformation behavior for both cast-in-place and post installed undercut anchors embedded in high-strength concretes with compressive strengths of 7500 and 12000 psi. Cast-in-place anchors where embedded at depths of 4, 6, and 8 in., whereas the undercut anchors were only embedded at a depth of 8 in.. Shallow cone failure angles, ranging from 21 to 28 deg, occurred consistently for all cases regardless of embedment depth, contradicting the 45 deg cone assumed in many design methods. For cast-in-place anchors, current design methods (such as CCD, ACI 349, TVA, TRW-Nelson) over predicted anchor pullout capacity. Over prediction of pullout capacity increased with increasing concrete compressive strength. For the post-installed anchors, the CCD model under predicted anchor pullout capacity, whereas the ACI model over predicted anchor pullout capacity.

Evidence in Human Subjects for Independent Coding of Azimuth and Elevation for Direction of Heading from Optic Flow

We studied the accuracy of human subjects in perceiving the direction of self-motion from optic flow, over a range of directions contained in a 45 deg cone whose vertex was at the viewpoint. Translational optic flow fields were generated by displaying brief sequences (<1.0 sec) of randomly positioned dots expanding in a radial fashion. Subjects were asked to indicate the direction of perceived self-motion at the end of the display. The data were analyzed by factoring out the constant component of the error by means of a linear regression analysis performed on the azimuthal and elevational components of the settings. The analysis of the variable error revealed that: a) the variance of the settings is 3–45% greater along elevation than azimuth for five observers; b) azimuth and elevation correspond, on average, to the principal components of the error in the settings; c) there are differences in the variances of azimuthal and elevational errors between upper and lower visual fields. Moreover, the distribution of the errors for azimuth and elevation in the upper and lower hemifields is not the same. All of the above evidence supports the hypothesis that heading information is represented centrally in terms of its azimuthal and elevational components. Copyright © 1996 Elsevier Science Ltd.

Tensile Capacity of Single Anchors in Concrete: Evaluation of Existing Formulas on an LRFD Basis

This study concerns the prediction of tensile capacity as governed by concrete cone failure of single anchors placed in uncracked, unreinforced concrete and located far from a free edge and far from other anchors. A total of approximately 801 data points is available from tests on such anchors. A total of 31 data points consisting of data on high-strength anchors previously compiled by Klingner et al., 1 Collins et al., 2 and Cannon is accessible from tests on single anchors failing by fracture of anchor steel. Using common definitions and nomenclature for all variables and material properties, each data set is placed in a database using SI units and concrete cube strengths. The concrete cone failure data are then plotted against capacities predicted by three existing methods: 1) the 45 deg cone method of ACI 349-90, Appendix B; 2) a variable angle cone method (VAC); and 3) the concrete capacity method (CC method). Observed data are compared against these existing methods in terms of average square error and load and resistance factor design (LRFD). Finally, using the principles of load and resistance factor design (LRFD) and following the design procedure of ACI 349-90, Appendix B, the probability of steel or concrete failure under known loads and the probability of concrete failure under unlimited loads are calculated. Based on those comparisons, each approach is evaluated with respect to accuracy and suitability for use in design. For single tension anchors with embedment depths less than 8 in., all three capacity prediction methods fit most of the data relatively well. However, the CC method is more accurate and has a distinctly lower probability offailure when the embedment depth is greater than 8 in.

Analysis of ghost numerical solutions of differential equation caused by nonlinear instability

Jaffe, N. A., Okamura, T. T., and Smith, A. M. O., Determination of Spatial Amplification Factors and Their Application to Predicting Transition, AIAA Journal, Vol. 8, 1970, pp. 301-308. Malik, M. R., and Control of in Supersonic and Hypersonic Boundary Layers, AIAA Journal, Vol. 27, No. 11, 1989, pp. 1487-1493. Fisher, D. F., and Dougherty, N. S., Jr., In-Flight Measurement on a 10 deg Cone at Mach Numbers from 0.5 to 2.0, NASA TP 1971, June 1982. Masad, J. A., and Malik, M. R., Transition Correlation in Subsonic Flow over a Flat Plate, AIAA Journal, Vol. 31, No. 10, 1993, pp. 1953-1955. Masad, J. A., and lyer, V, Transition Prediction and Control in Subsonic Flow over a Hump, Physics of Fluids, Vol. 6, No. 1, 1994, pp. 313327. Mack, L. M., Boundary-Layer Stability Theory, Jet Propulsion Lab., Document 900-277, Rev. A., California Inst. of Technology, Pasadena, CA, May 1969. Chen, F.-J., Malik, M. R., and Beckwith, I. E., Boundary-Layer on a Cone and Flat Plate at Mach 3.5, AIAA Journal, Vol. 27, No. 6, 1989, pp. 687-693. difference schemes are applied

Tensile Capacity of Anchors with Partial or Overlapping Failure Surfaces: Evaluation of Existing Formulas on an LRFD Basis

This study concerns the prediction of tensile capacity, as governed by concrete cone failure, of single anchors located close to a free edge and multiple anchor groups located far from a free edge and installed in uncracked, unreinforced concrete. A total of 160 data points is available for single anchors close to a free edge, while 185 data points are available for multiple anchors. A total of 31 data points consisting of data on high-strength anchors (previously compiled) is accessible from tests on single anchors failing by fracture of the anchor steel. Using common definitions and nomenclature for all variables and material properties, each data set is placed in a database using SI units and concrete cube strengths. The concrete failure data are then compared with capacities predicted by the three existing methods: the 45 deg cone method; a variable angle cone (VAC) method; and the concrete capacity (CC) method. Obsered data are compared against these existing methods in terms of average square error and load and resistance factor design (LRFD). Finally, using the principles of LRFD, and following the design procedure of American Concrete Institute (ACI) 349-90, the probability of steel failure or concrete cone failure under known loads and concrete cone failure under unlimited loads is computed. Based on those comparisons, each procedure is evaluated in terms of accuracy and suitability for use in design. For single anchors located near a free edge and for multiple closely spaced anchors, the CC method fits most of the data better than either the ACI 349-90 method or the VAC method, and gives lower and more consistent probabilities of failure. This is very apparent at very shallow and very deep embedments.

High-speed aerodynamics of several blunt-cone configurations

The experimental techniques and results from NASA Ames research into the aerodynamics of blunt shapes are described. Two facilities are used: the Hypersonic Free Flight Aerodynamic Facility (HFFAF) and the Pressurized Ballistic Range (PBR). The HFFAF features a 23 m test section through which projectiles can be fired by light-gas guns to achieve velocities up to 9 km/sec in pressures from 1 atm down to 20 microns Mg. Aerodynamic flight data are recorded with shadowgraphs. The 62 m long PBR, with 24 orthogonal spark shadowgraph stations, allows testing in up to 6 atm pressures but with only half the velocity of the HFFAF. Tests have been performed on the Galileo probe to be dropped into the Jovian atmosphere. The Galileo data for a 45 deg cone probe have been similar to Pioneer Venus probe data. Ballistic data are presently being obtained for the probe at Re below 1000, when the drag coefficients are expected to increase dramatically as the probe enters the Jovian atmosphere and begins braking from 4700 m/s speed. Sample test data from an OTV which can change orbits through aerodynamic maneuvers and for several asymmetric configurations ae also provided.

Effect of Elevated Temperature and Pressure on Sprays From Simplex Swirl Atomizers

The effects of air temperature and air pressure on spray quality of a moderately high capacity pressure swirl atomizer (127 kg/h MPa or 23.3 lbm/h psid) spraying jet-A and No. 2 diesel fuel have been examined. Drop-size distributions, in terms of both Sauter mean diameter (SMD) and the width of the distribution as given by the Rosin-Rammler N parameter, and cone angle as measured close to the nozzle (10-mm distance) have been determined over a variety of air conditions. A new correction procedure was developed to extend diffraction-based drop-size measurements in dense sprays from maximum optical opacities of 50% to maximum opacities of 96%, equivalent to an increase in spray density of a factor of five. Drop-size measurements are reported for a temperature range of room temperature (297K) to 589K and air pressures of atmospheric (101 kPa) to 597 kPa. Cone angle data are reported for temperatures to 589K and pressures to 1318 kPa. The maximum operating temperature was limited to the occurrence of autoignition. Close to the nozzle (25 mm), limited data suggest that the SMD’s were a strong function of air density, SMD ∼ ρ−0.53, but independent of air temperature (which affects air viscosity). The width of the distribution narrowed slightly with increasing density, N ∼ ρ0.15, at 25-mm distance. Trends of SMD and N are also shown as a function of distance from the nozzle at all conditions. These trends indicate some of the evaporation characteristics of fuel sprays. Pressure drop across the nozzle had an unusually large effect on SMD with SMD ∼ (ΔP)−0.86. At 10 mm from the nozzle exit, the cone angle of the nominal 80 deg cone angle nozzle was φ = 79.8–0.918 (ρ/ρ0) where ρ is the air density at the test condition and ρ0 the density at atmospheric conditions.

Lifting and nonlifting kernel functions for cascade and isolated airfoils

References 1 East, R. A., Qasrawi, A. M., and Khalid, M., An Experimental Study of the Stability of Pitching Blunt Conical and Hyperballistic Shapes in a Short Running Time Facility, AGARD Conference Proceedings, No. 235, Nov. 1978. Khalid, M. and East, R. A., ''Stability Derivatives of Blunt Slender Cones at High Mach Numbers, Aeronautical Quarterly, Vol. 30, Nov. 1979, pp. 559-590. Eggers, A. J. and Savin, R. C., A Unified Two-Dimensional Approach to the Calculation of Three-Dimensional Flows with Application to Bodies of Revolution, NACA Rept. 1249, 1955. Stone, A. H., On Supersonic Flow Past a Slightly Yawing Cone, II, Journal of Math & Physics, Vol. 30, 1951, pp. 200-213. Kopal, Z., Tables of Supersonic Flow around Cones at Large Yaw, M.I.T. TR. No. 5, 1949. Taylor, G. I. and Maccoll, J. W., Air Pressure on a Cone Moving at High Speeds, Proceedings of the Royal Society of London, Series A, Vol. 139, Feb. 1933, pp. 278-311. Khalid, M., A Theoretical and Experimental Study of the Stability of Blunt Axisymmetric Conical and Power Law Shapes, Ph.D. Thesis, University of Southampton, Hants, England, 1977. Schueler, C. J., Dynamic Stability Results for a 10 deg Cone at Mach Numbers 0.8 to 20, AEDC-TDR 64-226, Dec. 1964. Marshall, L. A., Hypersonic Stability Summary, Pt. 1, Tech. Rept. AFFDL-TDR 66-149, Jan. 1967. Qasrawi, A. M., Unpublished data, University of Southampton, Hants, England, 1978. Ericsson, L. E., Effect of Nose Bluntness, Angle of Attack, and Oscillation Amplitude on Unsteady Aerodynamics of Slender Cones, AIAA Journal, Vol. 9, Feb. 1971, pp. 297-304.

Viscous Interaction or Support Interference-The Dynamicst's Dilemma

In hypersonic low-density flows, slender vehicle dynamics are affected by various viscous flow phenomena. The true viscid-inviscid interaction is often difficult to extract from the background of support interference in wind tunnel tests and nonlinear six-degree-of-freedom motion effects in ballistic range tests, as was demonstrated by Welsh, Winchenbach, and Madagan several years ago. The range data and wind tunnel results for a 10-deg cone were shown to give completely different M^ trends for the pitch damping derivative. The aim of the present paper is to resolve this ambiguity and to help the vehicle designer decide how to obtain the best possible information about the full-scale vehicle dynamics using subscale dynamic test data.

Comment on "Flutter of Flat Finite Element Panels in a Supersonic Potential Flow"

about Mach 3, cone angle and bluntness ratio are equally important; and above Mach 3, bluntness is the relatively stronger parameter in establishing the base pressure level. The validity of the correlation is demonstrated by comparison with specific 9 and 10 deg cone data for sharp and 0.3 bluntness ratio noses which are given in Fig. 4. Data for other cone angles and bluntness ratios exhibit an equally good agreement with the prediction as would be expected based on Fig. 2; however, all of these data are not given in Fig. 4 for clarity. Also, total drag measurements obtained in an aeroballistics range on sharp 10-deg semiangle cones during the course of the transition experiments reported in Ref. 4 were analyzed. A sting free, flight base pressure was extracted from these data by subtracting a calculated forebody drag (pressure and skin friction) from the measured total drag. This calculations can be made with great precision for the sharp slender cone in question since the location of transition was measured. The relatively precise free-flight base pressure results obtained in this manner are given in Fig. 4 and further confirm both the absence of sting effects and the validity of the correlation. Even at Mach numbers in excess of eight, base pressure predictions utilizing this technique are in good qualitative agreement with the available turbulent data for sharp or small bluntness cones (up to Mach ~ 20). Summary At supersonic speeds, the base drag of sharp or blunt conical bodies represents a significant fraction of the total

Transmission of isotropic light across a dielectric surface in two and three dimensions*

Average transmittance of polarized diffuse light across a dielectric surface is calculated in both two and three dimensions. The incident light in both cases is confined to an angular range measured from the surface normal. Limiting values in three dimensions correspond to known results for two cases, (1) normal incidence, and (2) diffuse light incident from a 180 deg cone. The two-dimensional formulation is solvable in terms of elliptic functions and incomplete elliptic integrals of the first, second, and third kinds. Results are displayed graphically for values of transmittances in excess of 0.9 associated with relative indices of refraction in the range m = 1.0 to m = 2.6.