201 research outputs found
Effect of Nose Length, Fuselage Length, and Nose Fineness Ratio on the Longitudinal Aerodynamic Characteristics of Two Complete Models at High Subsonic Speeds
An investigation has been made of the effects of nose length, fuselage length, and nose fineness ratio on the static longitudinal aerodynamic characteristics of an airplane model with a swept wing and low tail and of a second model with a highly tapered wing of moderate sweep and a T-tail. The tests were conducted in the Langley high-speed 7- by 10-foot tunnel at Mach numbers from 0.60 to 0.92. The nose and body cross sections were circular. For either the model with the swept wing and low tail or the model with the highly tapered wing of moderate sweep and the T-tail, the effects of forebody changes amounted primarily to rotations of the pitching-moment curves (changes in static margin) over the test ranges of angle of attack and Mach number. For the range of body shapes investigated the longitudinal stability at low lift is decreased by an increase in nose length or in fuselage length or by a reduction in nose fineness ratio when the fuselage length is held constant. In general, the stability for all model configurations showed substantially the same variation with changes in forebody area moment. The forebody changes did not alter the angle of attack at which an unstable break occurred in the moment contribution of the T-tail but did alter somewhat the magnitude of the instability
Some effects of ailerons on the variation of aerodynamic characteristics with sideslip at low speed
Static Longitudinal Characteristics at High Subsonic Speeds of a Complete Airplane Model with a Highly Tapered Wing having the 0.80 Chord Line Unswept and with Several Tail Configurations
An investigation was made at high subsonic speeds of a complete model having a highly tapered wing and several tail configurations. The basic aspect-ratio-4.00 wing had zero taper and an unswept 0.80 chord line. Several aspect-ratio modifications to the basic wing were made by clipping off portions of the wing tips. The complete model was tested with a chord-plane tail, a T-tail, and a biplane tail (combined T-tail and chord-plane tail). The model was tested in the Langley high-speed 7- by 10-foot tunnel at Mach numbers from 0.60 to 0.92. The data show that, when reduced to the same static margin, all the tail configurations tested on the model provided fairly good stability characteristics, the biplane tail giving the.best overall characteristics as regards pitching-moment linearity. Changes in static margin at zero lift coefficient with Mach number were small for the model with these tails over the Mach number range investigated
Static Longitudinal Characteristics at High Subsonic Speeds of a Complete Airplane Model with a Highly Tapered Wing Having the 0.80 Chord Line Unswept and with Several Tail Configurations
Static Lateral Characteristics at High Subsonic Speeds of a Complete Airplane Model with a Highly Tapered Wing Having the 0.80 Chord Line Unswept and with Several Tail Configurations
Thermal Conductance of an Individual Single-Wall Carbon Nanotube above Room Temperature
The thermal properties of a suspended metallic single-wall carbon nanotube
(SWNT) are extracted from its high-bias (I-V) electrical characteristics over
the 300-800 K temperature range, achieved by Joule self-heating. The thermal
conductance is approximately 2.4 nW/K and the thermal conductivity is nearly
3500 W/m/K at room temperature for a SWNT of length 2.6 um and diameter 1.7 nm.
A subtle decrease in thermal conductivity steeper than 1/T is observed at the
upper end of the temperature range, which is attributed to second order
three-phonon scattering between two acoustic modes and one optical mode. We
discuss sources of uncertainty and propose a simple analytical model for the
SWNT thermal conductivity including length and temperature dependence.Comment: Nano Letters, vol. 6, no. 1, 200
Wind-tunnel investigation at high subsonic speeds of the effects on static stability characteristics of various modifications to a swept-wing fighter-type airplane model
Electro-Thermal Transport in Metallic Single-Wall Carbon Nanotubes for Interconnect Applications
This work represents the first electro-thermal study of metallic single-wall
carbon nanotubes (SWNTs) for interconnect applications. Experimental data and
careful modeling reveal that self-heating is of significance in short (1 < L <
10 um) nanotubes under high-bias. The low-bias resistance of micron scale SWNTs
is also found to be affected by optical phonon absorption (a scattering
mechanism previously neglected) above 250 K. We also explore length-dependent
electrical breakdown of SWNTs in ambient air. Significant self-heating in SWNT
interconnects can be avoided if power densities per unit length are limited to
less than 5 uW/um.Comment: IEEE Intl. Electron Devices Meeting (IEDM), Dec. 2005, Washington D
Strongly Tunable Anisotropic Thermal Transport in MoS2 by Strain and Lithium Intercalation: First--Principles Calculations
The possibility of tuning the vibrational properties and the thermal
conductivity of layered van der Waals materials either chemically or
mechanically paves the way to significant advances in nanoscale heat
management. Using first-principles calculations we investigate the modulation
of heat transport in MoS2 by lithium intercalation and cross-plane strain. We
find that both the in-plane and cross-plane thermal conductivity (kr, kz) of
MoS2 are extremely sensitive to both strain and electrochemical intercalation.
Combining lithium intercalation and strain, the in-plane and cross-plane
thermal conductivity can be tuned over one and two orders of magnitude,
respectively. Furthermore, since kr and kz respond in different ways to
intercalation and strain, the thermal conductivity anisotropy can be modulated
by two orders of magnitude. The underlying mechanisms for such large tunability
of the anisotropic thermal conductivity of \Mos are explored by computing and
analyzing the dispersion relations, group velocities, relaxation times and mean
free paths of phonons. Since both intercalation and strain can be applied
reversibly, their stark effect on thermal conductivity can be exploited to
design novel phononic devices, as well as for thermal management in MoS2-based
electronic and optoelectronic systems
- …