65 research outputs found
Response of a liquid bridge to an acceleration varying sinusoidally with time
The response of a long cylindrical liquid column subjected to an axial microgravity field has been experimentally studied on a TEXUS sounding rocket flight to check with theoretical predictions. The expected response of the liquid bridge was a quasi-static amphora-type deformation of the cylindrical shape. However, the experimental results showed a more complex behaviour. Nevertheless it has been possible to find out the reasons of this discrepancy except for a mysterious 0.5% uncertainty in the stimuli
Stability of Long Liquid Columns
The aim is to measure the outer shape deformation of long liquid bridges under microgravity when subjected to mechanical disturbances, namely change of geometry, rotation and vibration. This configuration has, aside of its own relevance in fluid mechanics and interface science, a well-known application in materials processing, particularly in Ore floating zone technique of crystal growth in the semiconductor industry. As a spin-off of this research, this configuration has proved to be a unique accelerometer at very low frequencies
Stability of Long Liquid Columns
A description at this experiment, the data analysis performed and tlie results obtained are presented. Three successful runs v/ere executed: the first one included a detailed oscillation test around a low eigenlrequency of the liquid column, the second was a stretching at constant volume until breakage, and the third one included an unexplained instability of an unequal-discs liquid column. The main diagnostic is the image analysis of the recorded videotape, and the most important result is that a residual axial acceleration of less than 5 ]±g is deduced from this SL-D-2 experiment, in contrast to the 70 ,ug deduced from the SL-D1 experiment in 19S5
Spacecraft thermal control design data
This paper shows the actual state of a compilation work on Thermal Control Design Data being done at Madrid (Lamf-ETSIA) under several ESTEC contracts, introducing a Handbook already issued, its additions and updatings
Freezing of a Long Liquid Column on the Texus-18 Sounding Rocket Flight
A free-surface cylindrical column of water (86 mm long by 30 mm diameter) was established during the first minute of microgravity on a sounding-rocket flight. Cooling was applied at one of the supporting discs to permit the advance of the solidification front and free-surface deformation to be observed during the ensuing 5 min of microgravity. The solidification front remained planar and the free surface remained cylindrical throughout, until affected by re-entry deceleration
Digital Optical Ballistocardiographic System for Activity, Heart Rate, and Breath Rate Determination during Sleep
In this work, we present a ballistocardiographic (BCG) system for the determination
of heart and breath rates and activity of a user lying in bed. Our primary goal was to simplify
the analog and digital processing usually required in these kinds of systems while retaining high
performance. A novel sensing approach is proposed consisting of a white LED facing a digital light
detector. This detector provides precise measurements of the variations of the light intensity of
the incident light due to the vibrations of the bed produced by the subject’s breathing, heartbeat,
or activity. Four small springs, acting as a bandpass filter, connect the boards where the LED and
the detector are mounted. Owing to the mechanical bandpass filtering caused by the compressed
springs, the proposed system generates a BCG signal that reflects the main frequencies of the
heartbeat, breathing, and movement of the lying subject. Without requiring any analog signal
processing, this device continuously transmits the measurements to a microcontroller through a twowire
communication protocol, where they are processed to provide an estimation of the parameters of
interest in configurable time intervals. The final information of interest is wirelessly sent to the user’s
smartphone by means of a Bluetooth connection. For evaluation purposes, the proposed system
has been compared with typical BCG systems showing excellent performance for different subject
positions. Moreover, applied postprocessing methods have shown good behavior for information
separation from a single-channel signal. Therefore, the determination of the heart rate, breathing rate,
and activity of the patient is achieved through a highly simplified signal processing without any need
for analog signal conditioning.Junta de Andalucia
European Commission PYC20-RE-040 UGR
MCIN/AEI/10.13039/501100011033/with
PID2019-103938RB-I00European Commissio
The variable geometry central receiver system concept. First results and comparison with conventional central receiver systems
In line with the global trend for improving efficiency of existing solar power plants, the CTAER has
developed and built a variable geometry central receiver facility, in which the solar field rotates around
the tower axis following the sun's position during the day. The goal of this new approach is to increase the
optical efficiency of the field by significantly reducing the angle of incidence of the Sun on the heliostats.
This paper presents the advantages of this new variable geometry design and describes the main features
of the experimental facility based on this approach as built by CTAER in Almeria. It also compares a
conventional solar central receiver plant (i.e., with stationary heliostats and receiver) and an equivalent
variable geometry power plant. For this study we employed published data from a real solar central
receiver plant with known production (Abengoa’s PS10). The results of the study show an increase in
annual energy collection and distribution by the variable geometry plant, leading to a potential reduction
in the number of heliostats required compared to a conventional central receiver plant for the same annual
energy collection
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