Psychrometric chart for physiological research

Chart facilitates use of graphical techniques for solving problems involving thermodynamic properties of moist air. The properties are presented, and their units of measurement are listed. Chart presenting conditions at standard atmosphere pressure at sea level is most useful

A single-layer tuneable microwave absorber using an active FSS

An experimental single-layer active microwave absorber in described. The absorber is a planar structure based upon the topology of a Salisbury screen, but in which the conventional resistive layer is replaced by an active frequency selective surface (FSS) controlled by pin diodes. The resulting structure has superior reflectivity-bandwidth characteristics compared to conventional passive absorbers of corresponding thickness. Measured data are presented and show that the reflectivity response of the absorber can be controlled over the frequency band from 9 to 13 GHz

The phase-switched screen

Conventional (passive) radar-absorbent materials operate either by phase cancellation or by absorbing incident electromagnetic energy and converting it into heat. This paper examines a new type of active "absorber," called the phase-switched screen (PSS). The PSS operates quite differently from passive absorbers in that it exhibits an apparently low value of reflectivity by redistributing the electromagnetic energy incident upon it over a bandwidth that is wide enough to ensure that little reflected energy falls within the pass-band of the receiver. The discussion considers the basic temporal and spectral properties of several PSS topologies, and includes measured data on both planar and cylindrical PSS structures

A smart radar absorber based on the phase-switched screen

Although conventional (i.e., passive) radar absorbers are widely used for modifying the radar cross-section (RCS) of current military platforms, such absorbers may not have adequate performance to satisfy future requirements. Active absorbers, however, offer the potential to overcome the so-called Rozanov performance limit and to enable additional smart functionality such as monitoring damage, adaptive control of RCS or target appearance, identification-friend-or-foe, and absorb-while-scan. This paper outlines the concept and basic properties of a novel type of active radar absorber, the so-called phase-switched screen (PSS). The basic PSS topology is then modified so as to enable it to operate as a smart radar absorber when used together with an external sensor and feedback control loop. System implementation issues and the optimum choice of design parameters for a range of operational scenarios are discussed, and theoretical predictions are supported by measured performance data

Influence of switching-waveform characteristics on the performance of a single-layer-phase switched screen

Conventional microwave-absorbing materials rely on the absorption and conversion into heat, of the electromagnetic energy incident upon them. In an alternative approach, the phase-switched screen (PSS) applies phase modulation to the reflected signal so that the energy is redistributed into sidebands with, ideally, none remaining at the original incident carrier frequency f/sub c/. Hence, by adjusting the frequency and shape of the waveform that controls the PSS reflection coefficient, these sidebands may be positioned outside the pass-band of a receiver tuned to f/sub c/. An investigation has been carried out to determine how the choice of control waveform and switching frequency influence the PSS performanc

A liquid cooled garment temperature controller based on sweat rate

An automatic controller for liquid cooled space suits is reported that utilizes human sweat rate as the primary input signal. The controller is so designed that the coolant inlet temperature is inversely proportional to the subject's latent heat loss as evidenced by evaporative water loss

Temperature controller for a fluid cooled garment

An automatic controller for controlling the inlet temperature of the coolant to a fluid cooled garment without requiring skin sensors is described. Temperature is controlled by the wearer's evaporative water loss rate

A study of the thermoregulatory characteristics of a liquid-cooled garment with automatic temperature control based on sweat rate: Experimental investigation and biothermal man-model development

Experimental results for three subjects walking on a treadmill at exercise rates of up to 590 watts showed that thermal comfort could be maintained in a liquid cooled garment by using an automatic temperature controller based on sweat rate. The addition of head- and neck-cooling to an Apollo type liquid cooled garment increased its effectiveness and resulted in greater subjective comfort. The biothermal model of man developed in the second portion of the study utilized heat rates and exchange coefficients based on the experimental data, and included the cooling provisions of a liquid-cooled garment with automatic temperature control based on sweat rate. Simulation results were good approximations of the experimental results

Letter from A.B. Chambers to George Sibley, May 12, 1840

Transcript of Letter from A.B. Chambers to George Sibley, May 12, 1840. Chambers discusses Whig politics in Missouri