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  Partner: UNT Libraries Government Documents Department
 Collection: National Advisory Committee for Aeronautics Collection
Icing properties of noncyclonic winter stratus clouds
No Description digital.library.unt.edu/ark:/67531/metadc53551/
Icing Frequencies Experienced During Climb and Descent by Fighter-Interceptor Aircraft
Data and analyses are presented on the relative frequencies of occurrence and severity of icing cloud layers encountered by jet aircraft in the climb and descent phases of flights to high altitudes. Fighter-interceptor aircraft operated by the Air Defense Command (USAF) at bases in the Duluth and Seattle areas collected the data with icing meters installed for a l-year period. The project was part of an extensive program conducted by the NACA to collect Icing cloud data for evaluating the icing problem relevant to routine operations. The average frequency of occurrence of icing was found to be about 5 percent of the number of climbs and descents during 1 year of operations The icing encounters were predominantly in the low and middle cloud layers, decreasing above 15,000 feet to practically none above 25,000 feet. The greatest thickness of ice that would accumulate on any aircraft component (as indicated by the accretion on a small object) was measured with the icing meters. The ice thicknesses on a small sensing probe averaged less than 1/32 inch and did not exceed 1/2 inch. Such accumulations are relatively small when compared with those that can form during horizontal flight in icing clouds. The light accretions resulted from relatively steep angles of flight through generally thin cloud layers. Because of the limited statistical reliability of the results, an analysis was made using previous statistics on icing clouds below an altitude of 20,000 feet to determine the general icing severity probabilities. The calculations were made using adiabatic lifting as a basis to establish the liquid-water content. Probabilities of over-all ice accretions on a small object as a function of airspeed and rate of climb were computed from the derived water contents. These results were then combined with the probability of occurrence of icing in order to give the icing severity that can be expected for routine aircraft operations. digital.library.unt.edu/ark:/67531/metadc53557/
Meteorological Analysis of Icing Conditions Encountered in Low-Altitude Stratiform Clouds
Liquid-water content, droplet size, and temperature data measured during 22 flights in predominatly stratiform clouds through the 1948-49 and the 1949-50 winters are presented. Several icing encounters were of greater severity than those previously measured over the same geographical area, but were within the limits of similar measurements obtained over different terrain within the United States. An analysis of meteorological conditions existing during the 74 flights conducted for four winters indicated an inverse relation of liquid-water concentration to maximum horizontal extent of icing clouds. Data on the vertical extent of supercooled clouds are also presented. Icing conditions were most likely to occur in the southwest and northwest quadrants of a cyclone area, and least likely to occur in the southeast and northeast quadrants where convergent air flow and lifting over the associated warm frontal surface usually cause precipitation. Additional data indicated that, icing conditions were usually encountered in nonprecipitating clouds existing at subfreezing temperatures and were unlikely over areas where most weather observing stations reported the existence of precipitation. Measurements of liquid-water content obtained during 12 flights near the time and location of radiosonde observations were compared with theoretical values. The average liquid-water content of a cloud layer, as measured by the multicylinder technique, seldom exceeded two-thirds of that which could be released by adiabatic lifting. Local areas near the cloud tops equaled or occasionally exceeded the calculated maximum quantity of liquid water. digital.library.unt.edu/ark:/67531/metadc53550/
Analysis of Meteorological Data Obtained During Flight in a Supercooled Stratiform Cloud of High Liquid-Water Content
Flight icing-rate data obtained in a dense and. abnormally deep supercooled stratiform cloud system indicated the existence of liquid-water contents generally exceeding values in amount and extent previously reported over the midwestern sections of the United States. Additional information obtained during descent through a part of the cloud system indicated liquid-water contents that significantly exceeded theoretical values, especially near the middle of the cloud layer.. The growth of cloud droplets to sizes that resulted in sedimentation from the upper portions of the cloud is considered to be a possible cause of the high water contents near the center of the cloud layer. Flight measurements of the vertical temperature distribution in the cloud layer indicated a rate of change of temperature with altitude exceeding that of the moist adiabatic lapse rate. This excessive rate of change is considered to have contributed to the severity of the condition. digital.library.unt.edu/ark:/67531/metadc53558/
Preliminary Survey of Icing Conditions Measured During Routine Transcontinental Airline Operation
Icing data collected on routine operations by four DC-4-type aircraft equipped with NACA pressure-type icing-rate meters are presented as preliminary information obtained from a statistical icing data program sponsored by the NACA with the cooperation of many airline companies and the United States Air Force. The program is continuing on a much greater scale to provide large quantities of data from many air routes in the United States and overseas. Areas not covered by established air routes are also being included in the survey. The four aircraft which collected the data presented in this report were operated by United Air Lines over a transcontinental route from January through May, 1951. An analysis of the pressure-type icing-rate meter was satisfactory for collecting statistical data during routine operations. Data obtained on routine flight icing encounters from.these four instrumented aircraft, although insufficient for a conclusive statistical analysis, provide a greater quantity and considerably more realistic information than that obtained from random research flights. A summary of statistical data will be published when the information obtained daring the 1951-52 icing season and that to be obtained during the 1952-53 season can be analyzed and assembled. The 1951-52 data already analyzed indicate that the quantity, quality, and range of icing information being provided by this expanded program should afford a sound basis for ice-protection-system design by defining the important meteorological parameters of the icing cloud. digital.library.unt.edu/ark:/67531/metadc53554/
Observations of icing conditions encountered in flight during 1948
No Description digital.library.unt.edu/ark:/67531/metadc53553/
Pressure distribution on wing ribs of the VE-7 and TS airplanes in flight
This paper is the first of a series of notes, each of which presents the complete results of pressure distribution tests made by the National Advisory Committee for Aeronautics, on single-wing ribs of the VE-7 and TS airplanes for a particular condition of flight. The level flight results are presented here in the form of curves and show the comparison between the pressure distribution over a representative thin wing, R.A.F.-15, and a moderately thick wing, U.S.A.-27, throughout the range of angle of attack. digital.library.unt.edu/ark:/67531/metadc53915/
Note on the air forces on a wing caused by pitching.
The following contains information on the air forces on a wing produced by it's pitching at a finite rate of angular velocity. The condition of smooth flow at the region of the trailing edge is maintained. The wing then experiences the same lift as if moving with the momentary velocity of the rear edge. digital.library.unt.edu/ark:/67531/metadc53912/
Airfoil lift with changing angle of attack
Tests have been made in the atmospheric wind tunnel of the National Advisory Committee for Aeronautics to determine the effects of pitching oscillations upon the lift of an airfoil. It has been found that the lift of an airfoil, while pitching, is usually less than that which would exist at the same angle of attack in the stationary condition, although exceptions may occur when the lift is small or if the angle of attack is being rapidly reduced. It is also shown that the behavior of a pitching airfoil may be qualitatively explained on the basis of accepted aerodynamic theory. digital.library.unt.edu/ark:/67531/metadc53911/
Mass distribution and performance of free flight models
This note deals with the mass distribution and performance of free flight models. An airplane model which is to be used in free flight tests must be balanced dynamically as well as statically, e.g., it must not only have a given weight and the proper center of gravity but also a given ellipsoid of inertia. Equations which relate the motions of an airplane and its model are given. Neglecting scale effect, these equations may be used to predict the performance of an airplane, under the action of gravity alone, from data obtained in making dropping tests of a correctly balanced model. digital.library.unt.edu/ark:/67531/metadc53917/
Experiments with fabrics for covering airplane wings
No Description digital.library.unt.edu/ark:/67531/metadc53910/
The comparison of well-known and new wing sections tested in the variable density wind tunnel
Three groups of airfoils have been tested in the variable density wind tunnel. The first group contains three airfoils. The second group is a systematic series of twenty-seven airfoils. The third group consists of several frequently used wing sections. digital.library.unt.edu/ark:/67531/metadc53918/
The estimation of airplane performance from wind tunnel tests on conventional airplane models
Calculations of the magnitude of the correction factors and the range of their variations for wind tunnel models used in making aircraft performance predictions were made for 23 wind tunnel models. Calculated performances were compared with those actually determined for such airplanes as have been built and put through flight test. Except as otherwise noted, all the models have interplane struts and diagonal struts formed to streamwise shape. Wires were omitted in all cases. All the models were about 18 inches in span and were tested in a 4-foot wind tunnel. Results are given in tabular form. digital.library.unt.edu/ark:/67531/metadc53914/
The drift of an aircraft guided towards it's destination by directional receiving of radio signals transmitted from the ground
Following a curved path increases the distance to be flown, and a type of radio navigation that forces the adoption of such a path is therefore less efficient than one that marks out a definite straight line between the point of departure and the intended destination, and holds the airplane to that line. To determine the loss of efficiency resulting from curvature of the path, calculations were made for two particular cases by the method of step-by-step integration. The calculations were based on the assumption that the pilot makes straightforward use of his radio for navigation and makes no allowance for drift. Results are given in tabular form for two airplanes flying 200 miles at 100 mph, one with a cross wind of 50 mph wind across course, and the other with a 20 mph wind across course. It is shown that the following of the curved path increases the time of flight and the air distance flown by 17 percent and 2.5 percent in the two cases. digital.library.unt.edu/ark:/67531/metadc53919/
Propeller design: extension of test data on a family of model propellers by means of the modified blade element theory II
This report is the second of a series of four on propeller design, and describes the method used to extend the data obtained from tests on a family of thirteen model propellers to include all propellers of the same form likely to be met in practice. This necessitates the development of a method of propeller analysis which when used to calculate the powers and efficiencies gives results which check the tests throughout their range. digital.library.unt.edu/ark:/67531/metadc53916/
Determination of the value of wood for structural purposes
No Description digital.library.unt.edu/ark:/67531/metadc53913/
Droplet Impingement and Ingestion by Supersonic Nose Inlet in Subsonic Tunnel Conditions
The amount of water in cloud droplet form ingested by a full-scale supersonic nose inlet with conical centerbody was measured in the NACA Lewis icing tunnel. Local and total water impingement rates on the cowl and centerbody surfaces were also obtained. All measurements were made with a dye-tracer technique. The range of operating and meteorological conditions studied was: angles of attack of 0 deg and 4.2 deg, volume-median droplet diameters from about 11 to 20 microns, and ratios of inlet to free-stream velocity from about 0.4 to 1.8. Although the inlet was designed for supersonic (Mach 2.0) operation of the aircraft, the tunnel measurements were confined to a free-stream velocity of 156 knots (Mach 0.237). The data are extendable to other subsonic speeds and droplet sizes by dimensionless impingement parameters. Impingement and ingestion efficiencies are functions of the ratio of inlet to free-stream velocity as well as droplet size. For the model and range of conditions studied, progressively increasing the inlet velocity ratio from less than to greater than 1.0 increased the centerbody impingement efficiency and shifted the cowl impingement region from the inner- to outer-cowl surfaces, respectively. The ratio of water ingested by the inlet plane to that contained in a free-stream tube of cross section equal to that at the inlet plane also increased with increasing inlet velocity ratio. Theoretically calculated values of inlet water (or droplet) ingestion are in good agreement with experiment for annular inlet configurations. digital.library.unt.edu/ark:/67531/metadc53501/
Impingement of Cloud Droplets on a Cylinder and Procedure for Measuring Liquid-Water Content and Droplet Sizes in Supercooled Clouds by Rotating Multicylinder Method
No abstract available. digital.library.unt.edu/ark:/67531/metadc53500/
Impingement of Cloud Droplets on 36.5-Percent-Thick Joukowski Airfoil at Zero Angle of Attack and Discussion of Use as Cloud Measuring Instrument in Dye-Tracer Technique
The trajectories of droplets i n the air flowing past a 36.5-percent-thick Joukowski airfoil at zero angle of attack were determined. The amount of water i n droplet form impinging on the airfoil, the area of droplet impingement, and the rate of droplet impingement per unit area on the airfoil surface were calculated from the trajectories and cover a large range of flight and atmospheric conditions. With the detailed impingement information available, the 36.5-percent-thick Joukowski airfoil can serve the dual purpose of use as the principal element in instruments for making measurements in clouds and of a basic shape for estimating impingement on a thick streamlined body. Methods and examples are presented for illustrating some limitations when the airfoil is used as the principal element in the dye-tracer technique. digital.library.unt.edu/ark:/67531/metadc53508/
Impingement of Droplets in 60 Deg Elbows with Potential Flow
Trajectories were determined for water droplets or other aerosol particles in air flowing through 600 elbows especially designed for two-dimensional potential motion. The elbows were established by selecting as walls of each elbow two streamlines of a flow field produced by a complex potential function that establishes a two-dimensional flow around. a 600 bend. An unlimited number of elbows with slightly different shapes can be established by selecting different pairs of streamlines as walls. Some of these have a pocket on the outside wall. The elbows produced by the complex potential function are suitable for use in aircraft air-inlet ducts and have the following characteristics: (1) The resultant velocity at any point inside the elbow is always greater than zero but never exceeds the velocity at the entrance. (2) The air flow field at the entrance and exit is almost uniform and rectilinear. (3) The elbows are symmetrical with respect to the bisector of the angle of bend. These elbows should have lower pressure losses than bends of constant cross-sectional area. The droplet impingement data derived from the trajectories are presented along with equations so that collection efficiency, area, rate, and distribution of droplet impingement can be determined for any elbow defined by any pair of streamlines within a portion of the flow field established by the complex potential function. Coordinates for some typical streamlines of the flow field and velocity components for several points along these streamlines are presented in tabular form. A comparison of the 600 elbow with previous calculations for a comparable 90 elbow indicated that the impingement characteristics of the two elbows were very similar. digital.library.unt.edu/ark:/67531/metadc53504/
Comparison of Three Multicylinder Icing Meters and Critique of Multicylinder Method
Three multicylinder cloud meters, fundamentally similar but differing in important details, were compared in use at the Mount Washington Observatory. Determinations of liquid water content were found to agree within the limits of the probable error, but the two instruments designed by the National Advisory Committee for Aeronautics indicated larger drop sizes than did the Observatory's instrument, apparently because of spurious ice catch on the rather rough surface of the larger cylinders. Comparisons of drop-size distribution were largely indeterminate., In a critique of the method, the probable error of determination of liquid water content was found to be +/-8 percent; of drop size, +/-6 percent; and of drop-size distribution, about +/-0.7 unit of the modulus of distribution. Of the systematic errors, run-off of unfrozen water is most important, blow-off and erosion seldom being hampering. Revision of collection-efficiency computations for cylinders in clouds with distributed drop sizes was found necessary and also revision of one of the correction-factor graphs heretofore used. The assumption of constant ice density in deriving cylinder size was found to be permissible for cylinders 1 inch or more in diameter. digital.library.unt.edu/ark:/67531/metadc53540/
A probability analysis of the meteorological factors conducive to aircraft icing in the United States
No Description digital.library.unt.edu/ark:/67531/metadc53548/
Experimental Droplet Impingement on Four Bodies of Revolution
The rate and. area of cloud droplet impingement on four bodies of revolution were obtained experimentally in the NACA Lewis icing tunnel with a dye-tracer technique. The study included spheres, ellipsoidal forebodies of fineness ratios of 2.5 and 3.0, and a conical forebody of 300 included angle and covered a range of angles of attack from 0? to 60 and rotational speeds up to 1200 rpm. The data were obtained at an airspeed of 157 knots and are correlated by dimensionless impingement parameters. In general, the experimental data show that the local and total impingement rates and impingement limits of bodies of revolution are primarily functions of the modified inertia parameters, the body shape, and fineness ratio. Both the local impingement rate and impingement limits depend upon the angle of attack. Rotation of the bodies had a negligible effect on the impingement characteristics except for an averaging effect at angle of attack. For comparable diameters the bluffer bodies had the largest total impingement efficiency, but the finer and sharper bodies had the largest values of maximum local impingement efficiency and, in most cases, the largest limits of impingement. In most cases, the impingement characteristics were less than those calculated from theoretical trajectories; in general, however, fairly good agreement was obtained between the experimental and theoretical impingement characteristics. digital.library.unt.edu/ark:/67531/metadc53506/
Experimental Droplet Impingement on Several Two-Dimensional Airfoils with Thickness Ratios of 6 to 16 Percent
The rate and area of cloud droplet impingement on several two-dimensional swept and unswept airfoils were obtained experimentally in the NACA Lewis icing tunnel with a dye-tracer technique. Airfoil thickness ratios of 6 to 16 percent; angles of attack from 0 deg to 12 deg, and chord sizes from 13 to 96 inches were included in the study. The data were obtained at 152 knots and are extended to other conditions by dimensionless impingement parameters. In general, the data show that the total and local collection efficiencies and impingement limits are primary functions of the modified inertia parameter (in which airspeed, droplet size, and body size are the most significant variables) and the airfoil thickness ratio. Local collection efficiencies and impingement limits also depend on angle of attack. Secondary factors affecting impingement characteristics are airfoil shape, camber, and sweep angle. The impingement characteristics obtained experimentally for the airfoils were within +/-10 percent on the average of the characteristics calculated from theoretical trajectories. Over the range of conditions studied, the experimental data demonstrate that a specific method can be used to predict the impingement characteristics of swept airfoils with large aspect ratios from the data for unswept airfoils of the same series. digital.library.unt.edu/ark:/67531/metadc53503/
An Electric Thrust Meter Suitable for Flight Investigation of Propellers
A lightweight instrument that utilizes resistance-wire electric strain gases to measure propeller-shaft thrust has been developed. A wind-tunnel investigation on a propeller installed, on a single-engine pursuit airplane showed that the instrument gave a reliable indication of propeller-shaft thrust to an accuracy of +/-2 percent within its calibrated range. No attempt was made to determine the relation of indicated shaft thrust to net propeller thrust. digital.library.unt.edu/ark:/67531/metadc53545/
A review of instruments developed for the measurement of the meteorological factors conductive to aircraft icing
No Description digital.library.unt.edu/ark:/67531/metadc53542/
A heated-wire liquid-water-content instrument and results of initial flight tests in icing conditions
No Description digital.library.unt.edu/ark:/67531/metadc53543/
Measurement of distortion in second experimental control rod for argonne naval reactor with constant transverse temperature gradient and uniform longitudinal temperature distribution
No Description digital.library.unt.edu/ark:/67531/metadc53115/
Model tests of a wing-duct system for auxiliary air supply
No Description digital.library.unt.edu/ark:/67531/metadc53112/
Low-speed wind-tunnel tests of a 1/8-scale model of the bell d-188a vtol airplane
No Description digital.library.unt.edu/ark:/67531/metadc53111/
An investigation of supersonic store interference in the vicinity of a 22 deg swept wing fuselage configuration at Mach numbers of 1.61 and 2.01
Pressure tunnel investigation of supersonic store interference in vicinity of 22 deg swept wing fuselage configuration at mach numbers 1.61 and 2.01. digital.library.unt.edu/ark:/67531/metadc53117/
Transonic aerodynamic and trim characteristics of 1/15-scale models of the convair mx-1964 airplane with indented fuselage
No Description digital.library.unt.edu/ark:/67531/metadc53110/
A comparison of flight-measured carrier- approach speeds with values predicted by several different criteria for 41 fighter-type airplane configurations
Comparison of flight measured carrier-approach speeds with values predicted by several different criteria for 41 fighter aircraft configurations. digital.library.unt.edu/ark:/67531/metadc53118/
Chemical and physical properties of a boron-carbon-hydrogen fuel z-244 /naca 55z8/
No Description digital.library.unt.edu/ark:/67531/metadc53114/
Experimental Behavior of Pentaborane-Air Combustion Products During Expansion in a Convergent Divergent Nozzle
In order to evaluate the post combustion behavior of boric oxide, pentaborane-air mixtures, burned to completion at a combustor pressure of 3 atmospheres, were expanded through a 7.1-inch-long convergent-divergent nozzle having a 4-inch-diameter throat and an exit-to-throat area ratio of 1.68. The experimentally determined thrust performance was in good agreement with the ideal equilibrium performance at stagnation temperatures of 3300 deg R and lower. The boric oxide vapor at the combustor exit required about 400 F deg supercooling before any condensed phase was observed. For a given thrust, fuel consumption was as much as 20 percent greater than predicted from vapor-pressure data for combustor outlet temperatures i n the vicinity of 3600 deg R. A similar result could be expected in full-scale engines, since the test combustor provided an unusually long dwell time and a highly turbulent environment. During the expansion process, the vapor (when present) did not condense to the extent predicted for an equilibrium expansion process. Moreover, condensation was observed only i n the form of small, abrupt phase changes i n the subsonic flow near the throat. Friction, due to liquid boric oxide films on the nozzle surfaces, was negligible when the surface temperature was above 800 F. digital.library.unt.edu/ark:/67531/metadc53119/
Preliminary report on experimental investigation of engine dynamics and controls for a 48-inch ramjet engine
Experimental investigation of engine dynamics and controls for 48-inch ramjet engine in free jet facility at Mach number 2.76 and altitudes 68,000 to 82,000 feet. digital.library.unt.edu/ark:/67531/metadc53116/
Surge-inception study in a two-spool turbojet engine
No Description digital.library.unt.edu/ark:/67531/metadc53113/
Preliminary investigation of reflections of oblique waves from a porous wall
No Description digital.library.unt.edu/ark:/67531/metadc53288/
Comparison of various heat exchangers for liquid-metal nuclear turbojet over range of flight and operating conditions
No Description digital.library.unt.edu/ark:/67531/metadc53284/
Measurement and analysis of turbulent flow containing periodic flow fluctuations
No Description digital.library.unt.edu/ark:/67531/metadc53289/
Analysis of rocket, ramjet, and turbojet engines for supersonic propulsion of long-range missiles. 3: Ramjet engine performance
No Description digital.library.unt.edu/ark:/67531/metadc53286/
Some notes on the probable damage to an intercontinental-ballistic-missile warhead following puncture of the heat shield
No Description digital.library.unt.edu/ark:/67531/metadc53283/
Chemical and physical properties of modified Hi-Cal-2
No Description digital.library.unt.edu/ark:/67531/metadc53245/
Flight investigation of a liquid hydrogen fuel system
No Description digital.library.unt.edu/ark:/67531/metadc53242/
Design and performance of fuel control for aircraft hydrogen fuel system
No Description digital.library.unt.edu/ark:/67531/metadc53241/
An Oil-Stream Photomicrographic Aeroscope for Obtaining Cloud Liquid-Water Content and Droplet Size Distributions in Flight
An airborne cloud aeroscope by which droplet size, size distribution, and liquid-water content of clouds can be determined has been developed and tested in flight and in wind tunnels with water sprays. In this aeroscope the cloud droplets are continuously captured in a stream of oil, which Is then photographed by a photomicrographic camera. The droplet size and size distribution can be determined directly from the photographs. With the droplet size distribution known, the liquid-water content of the cloud can be computed from the geometry of the aeroscope, the airspeed, and the oil-flow rate. The aeroscope has the following features: Data are obtained semi-automatically, and permanent data are taken in the form of photographs. A single picture usually contains a sufficient number of droplets to establish the droplet size distribution. Cloud droplets are continuously captured in the stream of oil, but pictures are taken at Intervals. The aeroscope can be operated in icing and non-icing conditions. Because of mixing of oil in the instrument, the droplet-distribution patterns and liquid-water content values from a single picture are exponentially weighted average values over a path length of about 3/4 mile at 150 miles per hour. The liquid-water contents, volume-median diameters, and distribution patterns obtained on test flights and in the Lewis icing tunnel are similar to previously published data. digital.library.unt.edu/ark:/67531/metadc53544/
A summary of meteorological conditions associated with aircraft icing and a proposed method of selecting design criterions for ice-protection equipment
No Description digital.library.unt.edu/ark:/67531/metadc53549/
Pressure Distribution on Joukowski Wings
The hydrodynamics and mathematical models as applied to the potential flow about a Joukowski wing are presented. digital.library.unt.edu/ark:/67531/metadc53400/
Elements of the Wing Section Theory and of the Wing Theory
Results are presented of the theory of wings and of wing sections which are of immediate practical value. They are proven and demonstrated by the use of the simple conceptions of kinetic energy and momentum only. digital.library.unt.edu/ark:/67531/metadc53404/
Flow and Force Equations for a Body Revolving in a Fluid
A general method for finding the steady flow velocity relative to a body in plane curvilinear motion, whence the pressure is found by Bernoulli's energy principle is described. Integration of the pressure supplies basic formulas for the zonal forces and moments on the revolving body. The application of the steady flow method for calculating the velocity and pressure at all points of the flow inside and outside an ellipsoid and some of its limiting forms is presented and graphs those quantities for the latter forms. In some useful cases experimental pressures are plotted for comparison with theoretical. The pressure, and thence the zonal force and moment, on hulls in plane curvilinear flight are calculated. General equations for the resultant fluid forces and moments on trisymmetrical bodies moving through a perfect fluid are derived. Formulas for potential coefficients and inertia coefficients for an ellipsoid and its limiting forms are presented. digital.library.unt.edu/ark:/67531/metadc53409/
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